Review Article

REDOX-MODULATED PATHWAYS IN INFLAMMATORY SKIN DISEASES

J. FUCHS, T. M. ZOLLNER, R. KAUFMANN, and M. PODDA

Department of Dermatology, Medical School, J. W. Goethe University, Frankfurt, Germany

(Received14 August2000;Accepted9 November2000)

Abstract—Inflammatory skin diseases account for a large proportion of all skin disorders and constitute a major healthproblem worldwide. Contact dermatitis, atopic dermatitis, and psoriasis represent the most prevalent inflammatory skindisorders and share a common efferent T-lymphocyte mediated response. Oxidative stress and inflammation haverecently been linked to cutaneous damage in T-lymphocyte mediated skin diseases, particularly in contact dermatitis.Insights into the pathophysiology responsible for contact dermatitis can be used to better understand the mechanism ofother T-lymphocyte mediated inflammatory skin diseases, and may help to develop novel therapeutic approaches. Thisreview focuses on redox sensitive events in the inflammatory scenario of contact dermatitis, which comprise forexample, several kinases, transcription factors, cytokines, adhesion molecules, dendritic cell surface markers, theT-lymphocyte receptor, and the cutaneous lymphocyte-associated antigen (CLA). In vitro and animal studies clearlypoint to a central role of several distinct but interconnected redox-sensitive pathways in the pathogenesis of contactdermatitis. However, clinical evidence that modulation of the skin’s redox state can be used therapeutically to modulatethe inflammatory response in contact dermatitis is presently not convincing. The rational for this discrepancy seems tobe multi-faceted and complex and will be discussed. © 2001 Elsevier Science Inc.

Keywords—Skin inflammation, Redox, Reactive oxygen species, Free radicals

INTRODUCTION

It becomes more and more evident that the redox statusof the cell is importantly involved in several basic cel-lular processes, such as signal transduction, gene expres-sion, inflammation, and apoptosis. Scientific informa-tions on redox-modulated molecular and cellular eventsin skin inflammation have increased dramatically duringthe last decade. Although contact dermatitis, psoriasis,and atopic dermatitis are different in nature and patho-genetically unrelated, these T-lymphocyte-mediateddisorders share common features in the inflammatorypathways [1,2]. Insight into the basic mechanisms re-sponsible for contact dermatitis can be used to betterunderstand the pathophysiology of T-lymphocyte-medi-ated inflammatory skin diseases. Oxidative stress andinflammation have been linked to psoriasis [3–7], atopicdermatitis [8–11], and contact dermatitis [12–24]. Forinstance, oxidizing species released during skin infiltra-tion with inflammatory cells, or produced by keratino-

cytes in response to chemical exposure, play an impor-tant role as second messengers in redox-sensitive signaltransduction processes and in gene expression leading toinflammation [25]. The modulation of redox-sensitiveprotein kinases and transcription factors by reactive ox-ygen species (ROS) has been suggested to be a centraland early event in the induction of inflammatory reac-tions [26–28]. The purpose of this review is to providethe reader with current information on the pathophysiol-ogy of T-lymphocyte-mediated skin inflammation, ex-emplified by contact dermatitis, and to identify and char-acterize redox-sensitive steps in this scenario.

IRRITANT AND ALLERGIC CONTACT DERMATITIS

Both irritant contact dermatitis (ICD) and allergiccontact dermatitis (ACD) are very common and impor-tant conditions in clinical and occupational dermatology,with ICD accounting for 50–80% of all cases. Contactdermatitis can be classified by its etiology into irritantcontact dermatitis (ICD) and allergic contact dermatitis(ACD). ICD is a nonimmunological, local inflammatoryskin reaction in response to chemical exposure, while

Address correspondence to: Dr. Jurgen Fuchs, J. W. Goethe Univer-sity, Medical School, Department of Dermatology, Heinsestrasse 8,63739 Aschaffenburg, Germany; Fax:149(6021)219746.

Free Radical Biology & Medicine, Vol. 30, No. 4, pp. 337–353, 2001Copyright © 2001 Elsevier Science Inc.Printed in the USA. All rights reserved

0891-5849/01/$–see front matter

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ACD is a cell-mediated immune type IV hypersensitivityreaction. In contrast to ICD, in ACD the proliferation ofantigen-specific memory T-lymphocytes allows second-ary immune response upon reexposure to the antigen.ACD requires preexisting genetic susceptibility, an im-munocompetent individual, and a chemical antigen ca-pable of transepidermal absorption [29]. Although ICDand ACD have different pathogenetic mechanisms, themolecular, histologic, and clinical features of ICD andACD are strikingly similar. Both types of reaction arecharacterized by an almost identical infiltrate after 48–72h consisting mainly of CD41 T-lymphocytes, most ofwhich are activated [30]. Moreover, some CD81T-lymphocytes, polymorphonuclear leukocytes (PMNs),eosinophilic leukocytes, and monocytes are present inthe infiltrate. There are several thousand chemicals thatcan cause ICD, for example, acids, alkalis, solvents, andoxidizing agents, while allergens are less abundant. Themajority of skin irritants and allergens are redox inactivecompounds, while only a few can generate free radicalsand ROS directly through metabolic activation, redoxcycling, or other mechanisms.

Examples of oxidizing irritants and allergens are hy-droperoxides and peroxides [31–37], metal salts such aschromium (VI) [38–44] and nickel (II) [45–54], phenols[55–60], quinones [61–66], anthranoles [13,67–75], andprimary amines [76–80]. Skin irritation is a complexphenomenon that involves resident epidermal cells, der-mal fibroblasts, and endothelial cells as well as invadingleukocytes, particularly T-lymphocytes, interacting witheach other under the control of a network of cytokines,neuropeptides, and eicosanoids. Keratinocytes presum-ably play an important role in the pathophysiology ofICD as well as ACD via generation of signals leading toattraction of leukocytes. They respond to irritants orsensitizers by the synthesis and release of proinflamma-tory cytokines such as IL-1 and TNFa, which induceendothelial cells to express adhesion molecules neces-sary for accumulation of inflammatory cells [81,82]. Aslittle as 2 h after contact with irritants or allergens,human skin activates cellular mechanisms to increaseT-lymphocyte infiltration. These mechanisms are not de-pendent upon specific immune sensitivity, and reflect acapacity of skin cells to respond to chemical provocationfor the presumed purpose of immune surveillance [83].

THE INTRACELLULAR REDOX STATE AND OXIDIZING

SPECIES

The intracellular redox state is a tightly regulatedparameter that provides the cell with an optimal ability tocounteract the highly oxidizing extracellular environ-ment. Intracellular redox homeostasis is regulated byantioxidants, particularly by thiol-containing molecules

such as glutathione and thioredoxin [84]. Key contribu-tors to altered redox state are ROS, which are formed by,for example, inflammatory cytokines and toxic xenobi-otics [85]. Small variations in the basal level of ROShave been shown to modulate the cell metabolism, geneexpression, as well as posttranslational modification ofproteins.

Reactive oxygen species

ROS are constitutively produced in epidermal kera-tinocytes by specific processes such as enzymatic oxida-tions and aerobic respiration, and can be induced byseveral cytokines, growth factors, and other physiologicstimuli [86–90]. Constitutively generated ROS regulatelevels and activity of phosphorylated proteins and pro-tein kinases within the keratinocytes [91]. ROS genera-tion can be induced in keratinocytes for example, byxenobiotics through various mechanisms and if producedin large amounts dysregulate redox-sensitive signaltransduction pathways, trigger cytotoxicity and apopto-sis. The proinflammatory action of ROS is exemplifiedby induction of ICD through intradermal injection of freeradical and ROS generating systems, such as glucoseoxidase attached to polyethylene glycol, xanthine-oxi-dase/hypoxanthine, and cumene hydroperoxide, respec-tively [16,92,93].

Nitric oxide

NO plays a role in both the vasodilatory component ofthe inflammatory response and in the modulation ofimmune responses in the skin [94]. In high concentra-tions peroxynitrite (ONOO2), the reaction product ofnitric oxide and superoxide anion radical, has the poten-tial to cause cytotoxic effects [95,96], whereas low con-centrations may modulate immune responses. For in-stance, NO has a selective suppressive effect on the Th1subset of helper T-lymphocytes, leading to a predomi-nantly Th2 type response [97]. Epidermal sources ofRNS are keratinocytes, Langerhans cells, fibroblasts, andendothelial cells [98–102]. In a human keratinocyte cellline (HaCaT) the copper/zinc superoxide dismutase genewas found to be upregulated by NO [103], implicating anauto-protective regulatory mechanism. NO is generatedfrom L-arginine by nitric oxide synthase (NOS). Epider-mal keratinocytes in normal human skin contain consti-tutive NOS and inducible-type NOS (iNOS) [104]. Re-cent studies have demonstrated an induction ofexpression of iNOS that is associated with several in-flammatory diseases of the skin. In human skin a signif-icant increase in iNOS was found immunohistochemi-cally in both ICD and ACD [105]. iNOS expression is

338 J. FUCHS et al.

mediated by the activation of transcriptional factors,especially NFkB [106]. IL-2 is a potent inducer of NOsynthesis in mice and humans [107]. A combination ofIL-8 and IFN-g induced the expression of iNOS-specificmRNA and of the functional enzyme in cultured humankeratinocytes [102]. In guinea pig skin the inhibition ofthe production of endogenous NO inhibits both leuko-cyte accumulation and edema formation induced by dif-ferent mediators of inflammation [108], indicating thatNO plays a central role as neutrophil chemoattractant.iNOS mRNA is expressed by keratinocytes and Langer-hans cells at basal levels, which is induced by the contactallergen 2.4-dinitrofluorobenzene (DNFB). Aminoguani-dine, a preferential iNOS blocking compound reducedear swelling response in mice treated with DNFB, sug-gesting that epidermal cell-derived NO contributes to theinflammatory response [101]. Topical application of aNO-releasing cream on human skin resulted in a depletionof epidermal Langerhans cells, in an increase in CD41T-lymphocytes, neutrophil eleastase, apoptotic cells, andincreased expression of ICAM-1 and VCAM-1, clearlydemonstrating the proinflammatory and cytotoxic effects ofNO in human skin in vivo [109]. Experimental clinicalstudies implicate that specific NO trapping agents may beuseful as topical modulators of contact dermatitis (Fuchs,unpublished). However, many inhibitors of NO have potentvasoconstricting effects [110,111]. Since a reduction ofblood flow by itself may be associated with an antiinflam-matory effect [112], studies based solely on NO inhibitorsshould not be overinterpreted as indirect evidence for aninflammatory action of NO.

Reactive halogen species

RHS can be produced and released into skin by invadingmacrophages, polymorphonuclear and eosinophilic leuko-cytes [90], thus contributing to and perpetuating skin in-flammation. The PMN-derived oxidant HOC1 inactivatedspecific tissue inhibitors of matrix metalloproteinase(TIMP-1) at concentrations achieved at sites of inflamma-tion [113], implicating a proinflammatory effect. Taurinechloramine, the major chloramine generated in activatedPMNs, inhibited the release of proinflammatory cytokines,RNS and ROS from activated murine dendritic cells [114],suggesting that PMN-derived RHS may also play an inhib-itory role in the inflammatory response. RHS may be in-volved in maintaining the balance between the inflamma-tory response and the induction of an antigen-specificimmune response.

STRESS SENSITIVE PROTEIN KINASES

Exposure of keratinocytes to chemical irritants andallergens triggers activation of several stress-sensitive

protein kinases, involving ROS as mediators, leading toenhanced synthesis of cytokines. ROS directly alter ki-nases, phosphatases, and transcription factors, or modu-late cysteine-rich redox-sensitive proteins [25,85,115].For instance, ROS act as second messengers to activatetyrosine and serine-threonine kinases, such as the mito-gen-activated protein (MAP) kinase family in humanmesangial cells [116]. MAP kinases are important me-diators of the cellular stress response and can be acti-vated by IL-1 and TNF-aa. Different forms of cellularstress triggered distinct signaling cascades involving ei-ther oxidative stress or GTPase-coupled pathways inMAP kinase activation [117], suggesting that antioxi-dants may only influence MAP kinase activation trig-gered by oxidative stress. In human keratinocytes ROS-enhanced epidermal growth factor (EGF) receptorphosphorylation and activated extracellular regulated ki-nase (ERK) and c-jun N-terminal kinase (JNK) activities[118,119]. Protein Kinase C (PKC) regulates a variety ofsignal transduction events implicated in differentiation,proliferation, and inflammation, including the biosynthe-sis of inflammatory cytokines, superoxide anion radicals,and the activation of phospholipase A2 [120]. The activ-ity of PKC is sensitive to the intracellular redox state[121], and PKC activity is modulated by antioxidantssuch as alpha tocopherol in vitro [122]. In mouse epi-dermal keratinocytes six different isoforms of PKC areexpressed and it was demonstrated that overexpressionof PKCalpha increases the expression of specific proin-flammatory mediators such as COX-2, the neutrophilchemotactic factor, macrophage inflammatory protein,and TNF-a [123]. In human keratinocytes PKC regulatesthe production of the neutrophil chemotactic cytokineIL-8 [124].

CYCLOOXYGENASE

Chemicals can directly or indirectly trigger release ofarachidonic acid (AA) from the plasma membrane by theaction of phospholipase A2 (PLA2), which translocatesfrom the cytosol to the membrane upon activation byCa21 and phosphorylation by the MAP kinase cascade[125]. Subsequently AA undergoes oxygenation by dif-ferent enzymatic pathways, for example, via lipoxygen-ase and cyclooxygenase (COX), and is converted intobiologically active eicosanoids. COX exists as two dis-tinct but similar isoenzymes, COX-1 and COX-2.COX-1 is mainly expressed constitutively, while COX-2is predominantly the inducible form. Prostaglandins(PGs) formed by the enzymatic activity of COX-1 areprimarily involved in the regulation of homeostatic func-tions throughout the body, whereas PGs formed byCOX-2 principally mediate inflammation [126,127].However, there is strong evidence that COX-1 also con-

339Redox modulated pathways

tributes, but presumably to a minor extent, to inflamma-tion [128]. A key process linking PG synthesis with ROSis the modulation of NF-kB by ROS [129,130], becauseactivation of NF-kB regulates the endoperoxide-synthaseof the PG pathway [131]. Increased oxidative stressresulting in the activation of NF-kB is thought to play acrucial role in the expression of COX-2 [132]. Proin-flammatory and pro-oxidant cytokines, such as IL-1 andTNF-a rapidly induce COX-2 activity in many cell typesincluding keratinocytes [133,134]. Leukotriene LTB4,which is a powerful chemotactic agent for PMNs, hasbeen established as a clinically important mediator ofskin inflammation [135]. In contrast to earlier reports,proinflammatory PGs do not seem to play a central rolein the cause of inflammatory skin diseases, because non-steroidal anti-inflammatory drugs, which inhibit bothCOX-1 and COX-2 activity, are clinically not very ef-fective in the treatment of inflammatory skin diseases,including contact dermatitis [136]. It remains to be seenwhether selective COX-2 inhibitors are more potent anti-inflammatory agents in skin in comparison to the con-ventional nonsteroidal anti-inflammatory agents. An invivo study indicated that GSH levels play a major role inthe regulation of PG biosynthesis in mice, showing thatelevated GSH levels inhibited PG production in perito-neal macrophages [137]. The AA cascade can be mod-ulated by antioxidants such asa-tocopherol [138], butthe tocopherol dosage seems to be critical for an anti-inflammatory effect. ROS have been demonstrated toactivate cytosolic and membrane-bound PLA2 activities[139]. Activation of PLA2 also stimulates extracellularregulated kinase (ERK) and c-jun N-terminal kinase(JNK) activities, leading to the activation of transcrip-tional factors and the ultimate stimulation of the tran-scription of several mitogen-stress-responsive genes[139].

TRANSCRIPTION FACTOR NF- KB

The NF-kB transcription factor complex is tightlyregulated through its cytoplasmic retention inhibitoryproteins known as IkB, which includes a group of relatedproteins, IkB-a being the best characterized example.Associated with its inhibitor NFkB resides as an inactiveform in the cytoplasma of most cells. One intriguingcharacteristic of NF-kB regulation is its extreme sensi-tivity to cellular redox status. Most agents activatingNF-kB tend to be either modulated by ROS, or arepro-oxidants themselves [25–27,141,142]. Upon stimu-lation by various agents, for example, singlet oxygen,peroxides, IL-1, and TNF-a, IkB-a undergoes phosphor-ylation, ubiquitination, and is finally proteolyzed. Re-moval of IkB-a allows the complex to rapidly translocateinto the nucleus, where it activates its target genes [143].

The ultimate transduction pathways that lead to IkB-ainactivation remain poorly understood [144]. The targetgenes for NF-kB comprise a list of genes intrinsicallylinked to a coordinate inflammatory response, includinggenes encoding TNF-a, IL-1, IL-6, IL-8, iNOS, MHCclass I antigens, E-selectin, and VCAM-1 [26,145–147].Some of the cytokines whose genes are switched on byNF-kB, such as TNF-a and IL-1, are themselves activa-tors of NF-kB, giving them the potential for a positivefeedback loop. TNF-a-mediated activation of NF-kB indermal fibroblasts was clearly shown to involve ROS[148]. The activation of NF-kB by ROS has been sug-gested to be an early event in the induction of inflam-matory reactions [149]. Even if the initial cellular stim-ulus for NF-kB activation is not ROS, the apparentmerging of all the pathways of signal transduction in-volving NF-kB on a ROS-dependent step suggests apossible therapeutic target [28]. A ROS-independentpathway of NF-kB activation has also been described[150–152], and it is believed that activation of NF-kBcan occur through redox-sensitive as well as throughredox-insensitive pathways [153], similar to what hasbeen described for the MAP-kinase pathway. It is be-coming clear that certain cell types, but certainly not all,respond to oxidative stress by upregulation of NF-kBactivity [154]. Furthermore, if ROS do not directly acti-vate NF-kB, they at least provide costimulatory signalstowards activation of NF-kB [155]. The effect of oxi-dants and reductants on any given signal transductionpathway can be highly tissue- and cell-type-specific. Inparticular, the activation of NF-kB by oxidative stressprovides numerous examples of cell and tissue specific-ity [25]. Several examples listed below have demon-strated NF-kB activation in skin induced by irritants andallergens. NF-kB is activated in human keratinocytes anddermal fibroblasts by oxidizing agents such as ozone[156], hydrogen peroxide [157], UVA [158], and UVB[159,160]. The skin irritant anthralin induced NF-kB inmurine keratinocytes [161], and in BALB-c mouse skinvia a mechanism involving ROS [162]. The corrosiveirritant and potent allergen Cr(VI) and its lower oxida-tion state Cr(IV) activated NF-kB and enhanced NF-kB-DNA binding in Jurkat cells via free-radical-mediatedreactions [43,163]. The irritant and allergen Ni(II) acti-vated NF-kB and subsequently triggered the productionof IL-1, IL-6, TNF-a and the expression of adhesionmolecules in human endothelial cells and keratinocytes.Ni(II) caused a strong increase of NF-kB-DNA bindingand subsequently induced gene transcription of ICAM-1,VCAM-1, and E-selectin as well as mRNA productionand protein secretion of IL-6 in endothelial cells in aredox-dependent mechanism [164]. In cultured humanvascular endothelial cells (HUVECs) Ni(II) activated the

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translocation of NF-kB into the nucleus and enhancedNF-kB-DNA binding [165].

CYTOKINES

Almost every kind of cytokine known so far can bedetected in skin under certain physiological or patholog-ical conditions. While resting epidermal keratinocytesproduce some cytokines constitutively, a variety ofchemicals can induce epidermal keratinocytes to synthe-size and to release proinflammatory cytokines. This isaccomplished by activation of several stress-sensitiveprotein kinases, involving ROS as mediators [166]. Inhuman and animal skin proinflammatory cytokines in-duced by irritants and allergens comprise TNF-a, IL-1,IL-2, and IL-6, chemotactic cytokines such as IL-8,growth-promoting cytokines such as IL-6, IL-7, IL-15,granulocyte macrophage colony stimulating factor (GM-CSF), transforming growth factor (TGF-a), and cyto-kines regulating humoral vs. cellular immunity such asIL-10, IL-12, IL-18, and anti-inflammatory cytokinesIL-4, IL-10 [167–170]. IL-1 and TNF-a have been con-sidered as primary proinflammatory cytokines [171,172],whereas others such as IL-6 and IL-8 are secondary,because they are insufficient to induce an inflammatoryresponse in absence of other stimuli or primary cyto-kines. The expression of IL-8, which is a polymorpho-nuclear leukocyte chemoattractant, is upregulated in hu-man hepatoma cell line Hep-Gby, and in human gastricepithelial cells MKN28 by oxidative stress, respectively[173,174]. IL-1 exists in two different forms, IL-1a andIL-1b, and IL-1a is predominantly produced and storedin keratinocytes, while IL-1b is primarily synthesized bymacrophages and monocytes. IL-1 and TNF-a areknown to induce cellular production of ROS, therebyperpetuating their own formation and action [175–177].In particular, IL-1 is considered an extraordinarily im-portant cytokine, which links innate and acquired immu-nity in human skin [172]. IL-1 stimulates the prolifera-tion and activation of various cells and the production ofother cytokines such as IL-6, IL-8, and GM-CSF, and ischemotactic for monocytes, lymphocytes, and polymor-phonuclear leukocytes. Many allergens and irritants havebeen shown to induce keratinocyte activation with cyto-kine synthesis and secretion. In the mouse, TNF-a isinduced in epidermal keratinocytes and in the dermalinfiltrate after induction of contact hypersensitivity reac-tions and irritant reaction [178]. Seemingly, TNF-a playsa key role in these two types of reactions, and adminis-tration of antibodies to TNF-a or soluble TNF receptorsblocked irritant reactions and contact hypersensitivity inthe mouse [178]. Allergens such as nickel and DNFB, aswell as irritants such as sodium lauryl sulfate, inducedTNF-a expression in the epidermis of sensitized mice

and in isolated keratinocytes, respectively [179,180]. Theirritant anthralin induced expression of IL-6, IL-8, andTNF-a in skin of BALB-c mice [18], and in humankeratinocytes via a mechanism involving ROS [160].The irritant sulfur mustard, which is an alkylating agentand depletes cellular thiols [181], induced the synthesisand release of IL-1, IL-6, IL-8, and TNF-a in isolatedkeratinocytes [182–184]. Noncytotoxic concentrations ofphenol, which is an irritant and induces oxidative stressin human keratinocytes via redox cycling [185], pro-moted the expression of TNF-a, IL-8, and IL-1a incultured human keratinocytes [186]. Ni(II) and Cr(VI)are both potent generators of ROS in noncellular andcellular systems, induced in noncytotoxic concentrationsTNF-a production in cultured human keratinocytes[187]. Topical application of the thiol antioxidant N-ace-tylcysteine reduced Ni(II)-induced cutaneous expressionof mRNA for TNF-a in mice and inhibited Ni(II)-in-duced ACD in these animals [16]. It is controversialwhether the cytokine profile induced by irritants differsfrom that induced by allergens. It was not possible toidentify specific cytokine profiles for different classes ofdermatotoxic agents such as sensitizers, irritants, corro-sives, and carcinogens, but nonsensitizing contact irri-tants produce relative increases in the synthesis andsecretion of the cytokines IL-1, IL-8, and TNF-a, com-pared to the other chemical agents [188]. However, inreconstructed human epidermis it was possible to clas-sify and to discriminate between irritant (Tween 80,Triton 3100 and benzalkonium chloride) and sensitizingagents (1-chloro-2,4-dinitrobenzene [DNCB]) as a func-tion of induced cytokine production patterns and of cellviability measurements [189]. These results currentlyneed confirmation by the introduction of more numerousknown irritants and sensitizers in the tests used in thepresent study.

MATRIX METALLOPROTEINASES

Matrix metalloproteinases (MMP) and specific tissueinhibitors of matrix metalloproteinase (TIMP) play animportant role in physiologic as well as in inflammatoryprocesses, particularly in prolonged skin inflammation[190,191]. These enzymes are produced by fibroblasts,keratinocytes, mast cells, endothelial cells, and leuko-cytes. MMPs are not constitutively expressed in skin butare induced in response to for example, cytokines andgrowth factors. The genes that code for MMP and TIMPare modulated by the redox-sensitive transcription factorAP-1 [192]. TIMPs should be susceptible to redox mod-ulation because their complex tertiary structure is depen-dent upon six disulphide bonds. It was demonstrated thatthe neutrophil-derived oxidant HOCl inactivated TIMP-1at concentrations achieved at sites of inflammation [113].

341Redox modulated pathways

ROS are known to activate MMP in human dermalfibroblasts [193–195]. ROS-activated MMPs can de-grade and inactivate alpha-1-protease inhibitor (alpha1-PI) by proteolysis. Thus, the activation of MMPs, ac-companied by the inactivation of alpha1-PI, will bringabout enhanced proteolytic damage to the tissue sitesinfiltrated with polymorphous leukocytes by both MMPsand elastase [196]. In MMP-3 (stromelysin)-deficientmice the contact hypersensitivity response to the allergenDNFB was significantly impaired, while the irritant re-action to phenol remained unaffected [197]. This mayindicate that MMP-3 serves an important function inACD.

THIOREDOXIN

Thioredoxin and thioredoxin reductase are redox-ac-tive proteins that participate in multiple cellular events,including growth promotion, apoptosis, and cytoprotec-tion. Thioredoxin reductase is believed to function as acellular redox sensor, being involved in redox signaling[198]. Thioredoxin can be released by various cell typesin inflammation and function as a unique chemoattrac-tant for PMNs, monocytes, and T-lymphocytes in in-flammed tissues [199]. ROS induced the release of thi-oredoxin from isolated human keratinocytes [200], andthioredoxin expression was negatively regulated throughPKC in human umbilical-vein endothelial cells [201].The potent allergen DNCB irreversibly inhibits mamma-lian thioredoxin reductase. In this reaction ROS areformed and both events were suggested to be involved inthe inflammatory reactions provoked by some dinitroha-lobenzenes [202].

ADHESION MOLECULES

Application of contact allergens and irritants initiatekeratinocyte cytokine production such as TNF-a [81].These cytokines induce endothelial expression of adhe-sion molecules such as E-selectin, ICAM-1, andVCAM-1, resulting in the recruitment of skin-specificmemory T-lymphocytes. Vascular cell adhesion mole-cule-1 (VCAM-1) and intercellular adhesion molecule-1(ICAM-1) are important for the recruitment of leuko-cytes into inflammed tissues by promoting their strongadhesion. Induction of E-selectin by cytokines or ROS isvital to the initial tethering and rolling of T-lymphocyteson endothelial cells, which is followed by strong adhe-sion mediated for example, by ICAM-1 and VCAM-1expressed on endothelial cells. Therefore, upregulationof these adhesion molecules by IL-1, TNF-a, and byROS plays an important role in cutaneous inflammation[203,204]. ICAM-1, VCAM-1, and E-selectin are ex-

pressed on endothelial cells of inflammed skin in bothICD and ACD [205]. Allergens and irritants can inducethese adhesion molecules either by direct action orthrough induction of proinflammatory keratinocyte-de-rived cytokines [206,207]. The expression of endotheli-al-leukocyte adhesion molecules has been postulated tobe regulated by redox-sensitive events. Expression ofE-selectin, ICAM-1, and VCAM-1 appear in large part tobe controlled by the actions of cytokines, such as TNF-aand IL-1, and ROS via activation of NF-kB [26,208,209]. Ni(II) either promoted or suppressed the expressionof ICAM-1 on endothelial cells depending on its con-centration, subtoxic concentrations inhibiting and toxicconcentrations stimulating ICAM-1 expression [210].Chemical irritants [anthralin] as well as allergens [Ni(II)]induced the expression of E-selectin, VCAM-1, andICAM-1 in human skin and increased the number ofCLA positive T-lymphocytes [211]. N-acetylcysteine in-hibited IL-1-induced mRNA and cell surface expressionof both E-selectin and VCAM-1 in endothelial cells, andreduced NF-kB binding to the NF-kB binding site of theVCAM-1 gene, but not of the E-selectin gene [212].Thus, NF-kB binding to its consensus sequences in theVCAM-1 and E-selectin gene exhibits marked differ-ences in redox sensitivity [212]. TNF-a and IL-1-in-duced E-selectin expression in human vascular endothe-lial cells is regulated by a mechanism involving vicinalthiols. These thiols must be in the reduced state; oxida-tion attenuates the cells’ response to the cytokines [213].

Keratinocytes can express ICAM-1 [22], and IFN-g, aTh1-lymphocyte derived cytokine, induced ICAM-1 ex-pression on the keratinocyte cell surface [206]. ICAM-1expression has been shown to be induced in humankeratinocytes also by oxidative signals such as singletoxygen [214], and is suppressed by antioxidants [215].The regulated expression of ICAM-1 is of key impor-tance to the initiation and evolution of localized inflam-matory processes in the skin as it facilitates recruitmentof T-lymphocytes at sites of inflammation and interac-tion of keratinocytes with T-lymphocytes. However,studies on the involvement of oxidative stress in theinduction of ICAM-1 expression in transformed humankeratinocytes (HaCaT) were inconclusive, showing thatoxidizing agents such as ferric chloride and hydrogenperoxide upregulated ICAM-1 expression, but there wasno clear relationship between the ability of the agents toinduce ICAM-1 expression and their ability to alter thelevels of reduced glutathione [216].

LANGERHANS CELLS

In the development of ACD the sensitization phase isdistinguished from the elicitation phase. Langerhanscells are fundamental components of the sensitization

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phase. For sensitization a low molecular weight contactallergen (hapten) has to penetrate the skin and, in mostinstances, to combine with a protein carrier. Haptens canbe classified by their chemical reactivity. They can bindto proteins by nucleophilic, electrophilic, or free radicalreactions. Free radical reactions are important for hapten-protein binding involving hydroperoxides [217], alkylphenols and alkyl resorcinols [14], quinones [218], dini-trohalo (chloro, bromo, iodo) benzenes [219], azo com-pounds such as 2,2-azobis (2-aminopropane) (AAPH)[220], and primary aromatic amines such as p-phenylen-diamine [221,222]. The determinants of antigenicity aremultifactorial, including the type of binding that thehapten undergoes with the carrier and the final three-dimensional configuration of the conjugate [223]. Lang-erhans cells (LC) serve as the primary antigen-presentingcell of the epidermis. They belong to the dendritic cellfamily and are derived from hematopoietic stem cells.The hapten-protein complex will be taken up and pro-cessed by epidermal Langerhans cells, which leads topresentation of the hapten-peptide complexe via consti-tutively expressed cell surface major histocompatibilitycomplex (MHC) class II molecules. In some instancesthe hapten directly binds to MHC bound peptides on theLC surface [224,225]. Upon interaction with a hapten viathe MHC molecules, LC become activated and migratevia the afferent lymph into the paracortical region oflocal lymph nodes [226], where they meet naiveT-lymphocytes with hapten-specific T-lymphocyte re-ceptors. It was recently reported that ROS induce up-regulation of dendritic cell surface markers involved ininteraction with T-lymphocytes, including MHC class IImolecules [227], suggesting that ROS may play an im-portant role in activation of sentinel dendritic cells, link-ing tissue damage to the initiation of an immune re-sponse. Almost all allergens are irritants and thus maystimulate MHC class II molecule expression on LCs viainduction of oxidative stress in the epidermis. Hydrogenperoxide upregulated TNF-a and IL-8 synthesis by hu-man dendritic cells [228], suggesting that dendritic cellscould contribute to innate immunity through the en-hanced production of inflammatory cytokines in re-sponse to oxidative stress. Furthermore, LC can alsorelease nitric oxide upon stimulation [101].

T-LYMPHOCYTES

Lymphocytes are antigen-specific cells whose effectorfunction is acquired through complex differentiationpathways. This implies, firstly, antigen encounter andrecognition at specific sites, and, subsequently, the tran-sition from a naive to a memory/effector phenotype.Clonotypically expanded cells must then be capable ofrecirculating to the tissue where their effector function is

needed. To this aim, defined receptor-counter receptorpairs are expressed on lymphocytes versus endothelialcells. Naive lymphocytes preferentially migrate into sec-ondary lymphoid organs, where all the requirements foreffective antigen presentation and differentiation areavailable, while memory/effector lymphocytes preferen-tially migrate to peripheral tissues, such as skin andmucosa [229]. The transition from a naive to a memory/effector T-lymphocyte requires the tyrosine phosphory-lation of a number of cellular substrates including theantigen receptor itself, and the membrane recruitment ofsignalling effectors mediating the activation of Ras andeventually ERK kinases. A parallel chain of signallingevents leads to activation of the JNKs, whose activity, inconcert with the Ras/ERK pathway signalling compo-nents is required for full response of T-lymphocytes toantigenic stimulation [230]. T-lymphocytes are a classi-cal target for oxidative stress, for example, ROS areinvolved in T-lymphocytes apoptosis [231], and hydro-gen peroxide induces a number of signalling events,including tyrosine phosphorylation and the activation ofNF-kB [232,233]. The T-lymphocyte receptor (TCR)responsible for T-lymphocyte recognition of foreign an-tigen in association with molecules by the MHC is adisulfide-linked 90 kD heterodimer consisting of twopolypeptide chains expressed on the surface of the ma-jority of T-lymphocytes. TCRs are members of the im-munoglobulin family restricted to T-lymphocytes thatshare three-dimensional structural features, sequence ho-mology, antigenic cross-reactivity, and common mecha-nisms of diversification with conventional immuno-globulins, allowing them to recognize and to respond toany foreign antigen [234,235]. In T-lymphocytes theengagement of CD28, a molecule involved in T-lympho-cyte costimulation by antigen presenting cells, has beenshown to activate NF-kB in a ROS-dependent fashion[236]. ROS were recently identified as important stimu-lators of the signalling cascade, including proteine ty-rosine phosphorylation and c-Jun N-terminal kinase ac-tivation, initiated by mitogenic lectins in thymocytesand, by extension, as a novel class of mediators down-stream of the TCR [237]. These findings demonstrate arole for ROS in the T-lymphocyte response to antigens,with important implications for the understanding of theredox regulation of immune functions.

Cutaneous lymphocyte-associated antigen (CLA)

Memory T-lymphocytes that infiltrate the skin expressa unique skin-homing receptor called cutaneous lympho-cyte-associated antigen (CLA), a carbohydrate epitopethat facilitates the targeting of T-lymphocytes to in-flamed skin [238,239]. Although the molecular nature ofthe signals required for the induction of CLA is not yet

343Redox modulated pathways

known in detail, several factors seem to be involved:antigen, cytokines, and possibly ROS/RNS [240]. CLAbinds specifically to E-selectin and CLA is present onmost T-lymphocytes at sites of cutaneous immune re-sponse. Antioxidants such as N-acetylcysteine, alpha to-copherol, and ascorbate blocked the expression and func-tional activity of CLA in isolated human T-lymphocytes[241], implicating a possible site of redox modulation.

Differentiation into Th1 and Th2-lymphocytes

On first encounter with antigen, memory T-lympho-cytes differentiate into cytokine-producing effector cells.Two types of effector cells characterized by their distinctexpression of cytokine profiles have been described.Th1-lymphocytes produce IL-2 and IFNg, whereas Th2-lymphocytes produce IL-4, IL-5, IL-6, IL-10, and IL-13[242]. In general, Th1-lymphocytes activate proinflam-matory effector mechanisms involved in protection andautoimmunity, whereas Th2-lymphocytes induce hu-moral and allergic responses and downregulate localinflammation [243,244]. ACD is mainly associated withthe activation of Th1-lymphocytes, but Th2-lymphocytesare also involved in the development of ACD [245–250].Current thinking attributes the balance between Th1 andTh2 response patterns in immune responses to the natureof the antigen, its concentration, the genetic compositionof the host, and the cytokines involved in the earlyinteraction between T lymphocytes and antigen-present-ing cells. In barrier-disrupted skin, allergens induced aTh2-dominant immunological response, while in intactskin they triggered a Th1 response [251]. Barrier disrup-tion has been shown to induce the release and synthesisof proinflammatory cytokines, including IL-1a andTNF-a [252–254], implicating that epidermal cytokinesmay regulate the selective stimulation of distinct Thsubpopulations. This is in good agreement with the find-ing that the specific cytokine pattern in the microenvi-ronment modulated the differentiation of T-lymphocytesinto Th1 or Th2 effector cells [255,256]. Accordingly,the production of distinct cytokines by epidermal cells inresponse to topical antigen exposure governed the devel-opment of Th1 or Th2-like immune responses, depend-ing on the type of antigen [257,258]. The concentrationof the antigen also influences whether ACD is regulatedby Th1 or Th2 lymphocytes [259]. It is presently notknown what role ROS and RNS may play in the differ-entiation of antigen-specific memory T-lymphocytes, butrecently glutathione levels were found to modulate Th1versus Th2 response patterns in antigen-presenting cell[260].

The ultimate T-lymphocyte response

Following homing to skin, activated T-lymphocytes(Th1 and Th2) can induce pathology in the dermis andepidermis. In ACD the proportion of T-lymphocytesspecific for the provoking antigen is less than 1:1000[261], indicating that T-lymphocytes are extremely po-tent and must provoke significant amplification [262].This is further demonstrated because the transfer of onesingle [263], or a few antigen specific T-lymphocytes[264], into a naive recipient animal is sufficient to pro-voke contact dermatitis. Antigen-specific CD41 T-lym-phocytes have many potential mechanisms for inducinginflammation, including cell-mediated cytotoxicity, re-cruitment of other inflammatory cells, direct effects ofcytokines, and they may cause a specific B-cell mediatedreaction. In addition, antigens can trigger an oxidativeburst in T-lymphocytes releasing ROS and AA metabo-lites [265,266]. Several studies indicate that keratino-cytes apoptosis may be initiated by ROS [267–269] andit was reported that antigen-specific CD41 T-lympho-cytes can induce keratinocyte apoptosis [270,271]. How-ever, it is presently unknown whether oxidative eventsare involved in T-lymphocyte-mediated epidermal dam-age.

POLYMORPHONUCLEAR LEUKOCYTES

Polymorphonuclear leukocytes (PMNs) have the po-tential to damage surrounding tissue by releasing ROSproduced via NADPH oxidase/myeloperoxidase and pro-teolytic enzymes before self-necrosis. PMN necrosis fur-ther exacerbates inflammation and promotes chemotaxisand PMN recruitment. ROS are known to inactivateprotease inhibitors, thus enhancing the destructive effectsof PMN. Furthermore, PMN recruitment is stimulated byoxidative stress because ROS increase adhesion of PMNand monocytes to the endothelium [272,273]. The move-ment of PMN from the mainstream of blood to theextravascular space is triggered by several proinflamma-tory molecules, including histamine, LTB4, and platelet-activating factor. In particular, proinflammatory cyto-kines in concert with other mediators augment PMNcytotoxicity. This is illustrated by two examples. IL-6 atpathophysiologically relevant concentrations enhancedboth basal and formyl-Met-Leu-Phe-stimulated elastaserelease by human PMNs [274]. Incubation of humanPMN with TNF-a, or a mixture of TNF-a and IFN-gresulted in a dose-dependent enhancement of ROS pro-duction in response to phorbol myristate acetate. Theincubation with both IFN-g and TNF-a caused a signif-icantly higher increase of ROS production than withTNF-a alone [275]. NO regulates PMN function [276],

344 J. FUCHS et al.

but whether or not human PMNs express NOS activity iscontroversial [277–279].

EOSINOPHILIC LEUKOCYTES

Eosinophilic leukocytes are attracted by several hu-moral and cellular factors such as products of the com-plement cascade and AA metabolism, as well as byfactors derived from lymphocytes, mast cells, and PMNs[280,281]. The chemokines RANTES and eotaxin wereidentified as the most important eosinophil-attractingchemokines [282], RANTES representing a potent eosi-nophil-specific activator of oxidative metabolism [280,281]. At sites of inflammation, eosinophils release toxicproteins such as eosinophilic cation protein, major basicprotein, eosinophil-derived neurotoxin, ROS, and RHSleading to tissue damage [280,281]. They are able toproduce two to three times as much superoxide anionradicals as PMNs. Eosinophilic leukocytes play a criticalrole in the late-phase reaction of allergic inflammatoryresponses. Eosinophilic infiltration in susceptible indi-viduals was identified to be a specific property of theallergen [283].

MACROPHAGES

Macrophages are considered to be very important activeinflammatory cells in secretion of degrading enzymes,such as metalloproteinases, and production of ROS[284–286]. The production of ROS in macrophages de-pends significantly on the specific stimulus, site of mac-rophage isolation, and the extent of differentiation of thecells. The ability of cultured monocytes to produce ROSdecreases with their differentiation into macrophages,histiocytes, epitheloid cells, and giant cells. The order ofdeclining potency is: monocyte. histiocyte (tissue mac-rophage). epitheloid cell. giant cell [287].

SYNOPSIS

As outlined in this review cell culture experiments andanimal studies have clearly identified several cellularkinases, phosphatases, the arachidonic acid cascade,transcription factor NF-kB, ICAM-1 expression on en-dothelial cells, dendritic cell surface markers such asMHC class II molecules, the lymphocyte receptor, andthe cutaneous lymphocyte-associated antigen (CLA) asredox-sensitive sites, responsive to modulation by anti-oxidants. In the patent literature antioxidants such asascorbic acid and alpha tocopherol have been consideredfor topical therapy of contact dermatitis [288–291].However, in contrast to several animal studies [16–21],clinical trials have failed to show significant inhibition of

contact dermatitis by topical or systemic redox-modulat-ing antioxidants. For example, topical N-acetylcysteinefailed to inhibit ICD induced by either sodium laurylsulfate or dimethylsulfoxide in human skin [292]. Thecontact hypersensitivity response to nickel in nickel-sensitized patients was not significantly inhibited by highdoses of systemic alpha tocopherol and ascorbate [293].High concentrations of topical alpha tocopherol andascorbate only slightly inhibited (10%) the contact hy-persensitivity reaction caused by nickel sulfate in nickel-sensitive subjects, while chelating agents such as clio-quinol and EDTA caused 100 or 40% inhibition,respectively [294]. The rational for this discrepancyseems to be multi-faceted and complex. (i) Althoughexperimental evidence of redox-sensitive molecular andcellular events in contact dermatitis is accumulating, itmay be of limited clinical significance. (ii) Oxidizing orreducing conditions may have opposite effects in differ-ent pathways, for example, oxidizing conditions activateNF-kB in human keratinocytes and stimulate MHC classII molecule expression on dendritic cells, but triggerT-lymphocyte apoptosis and inhibit cytokine/ROS pro-duction in dendritic cells. (iii) Bioavailability of systemicor topical antioxidants may be insufficient to modulateredox-sensitive sites in cutaneous microenvironments.(iv) The cellular redox state is influenced by a variety ofelectron-donating (antioxidants) and electron-acceptingagents (oxidants), which interact with each other in dis-tinct microenvironments and with different specificities.The redox-modulating activity of antioxidants is quali-tatively and quantitatively different, and is restricted tospecific cellular hydrophilic/lipophilic sites. (v) Irritantsand sensitizers may stimulate cellular production of ox-idizing species and mediators in a qualitatively and quan-titatively different manner, trigger different cytokine pro-files, and attract different subsets of inflammatory cells,thus resulting in disparate molecular and cellular patternsof inflammatory reactions. (vi) The redundancies of theinflammatory cell populations, the cytokines, the oxidiz-ing species and other metabolites produced by the skinpredictably limit the effectiveness of any single agentand make clinical evaluation of such agents difficult.These complexities may limit the feasibility of antioxi-dant therapy. It remains to be seen whether antioxidantsor combinations of antioxidants will be clinically effec-tive in treatment of T-lymphocyte-mediated inflamma-tory skin diseases. The skin as the most readily accessi-ble organ of the human body invites antioxidant/redoxintervention trials.

REFERENCES

[1] Robert, C.; Kupper, T. S. Inflammatory skin diseases, T cells,and immune surveillance.N. Engl. J. Med.341:1817–1828;1999.

345Redox modulated pathways

[2] Shiohara, T.; Moriya, N. Epidermal T cells: their functional roleand disease relevance for dermatologists.J. Invest. Dermatol.109:271–275; 1997.

[3] Lontz, W.; Sirsjo, A.; Liu, W.; Lindberg, M.; Rollman, O.;Torma, H. Increased mRNA expression of manganese superox-ide dismutase in psoriasis skin lesions and in cultured humankeratinocytes exposed to IL-1-beta and TNF-a. Free Radic. Biol.Med.18:349–355; 1995.

[4] Filipe, P.; Emerit, I.; Youssefi, A.; Alaoui, M.; Levy, A.; Cern-javski, L.; Freitas, J.; de Castro, J. L. Oxyradical-mediatedclastogenic plasma factors in psoriasis: Increase in clastogenicactivity after PUVA.Photochem. Photobiol.66:497–501; 1997.

[5] Maresca, V.; Mussi, A.; Carducci, M.; Bonifati, C.; Ameglio, F.;Fazio, M.; Picardo, M. Involvement of antioxidants in psoriasis.Int. J. Immunopathol. Pharmacol.10:77–80; 1997.

[6] Kokcam, I.; Naziroglu, M. Antioxidants and lipid peroxidationstatus in the blood of patients with psoriasis.Clin. Chim. Acta289:23–31; 1999.

[7] Pereira, P.; Rocha, R. L.; Santos-Silva, A.; Figueiredo, A.; Ferra,M. I. A.; Quintanilha, A.; Teixeira, F. Leukocyte activation andoxidative stress in psoriasis.Br. J. Pharmacol.127(ProceedingsSuppl.):83P; 1999.

[8] Wolber, R.; Staeb, F.; Abeck, D.; Bleck, O.; Schreiner, V.;Untiedt, S.; Sauermann, G.; Hoppe, U. Antioxidant status androle of oxidative stress in atopic dermatitis.J. Invest. Dermatol.106:888; 1996.

[9] De Luca, C.; Stancato, A.; Carbone, S.; Guarnieri, D.; Passi, S.Blood oxidative stress in children with atopic dermatitis.J. In-vest. Dermatol.110:534; 1998.

[10] Mundt, C.; Blatt, T.; Wolber, R.; Gercken, G.; Foelster-Holst,H.; Schachtschabel, D.; Staeb, F. Oxidative stress response innormal human skin versus noninvolved atopic dermatitic skin.J. Invest. Dermatol.112:572; 1999.

[11] Niwa, Y.; Iizawa, O. Abnormalities in serum lipids and leuco-cyte superoxide dismutase and associated cataract formation inpatients with atopic dermatitis.Arch. Dermatol.130:1387–1392;1994.

[12] Miyachi, Y.; Uchida, K.; Komura, J.; Asada, Y.; Niwa, Y. Autooxidative damage in cement dermatitis.Arch. Dermatol. Res.277:288–292; 1985.

[13] Sharkey, P.; Eedy, D. J.; Burrows, D.; McCaigue, M. D.; Bell,A. L. A possible role for superoxide production in the patho-genesis of contact dermatitis. Acta Derm. Venereol.71:156–159; 1991.

[14] Finnen, M. J.; Lawrence, C. M.; Shuster, S. Inhibition of dithra-nol inflammation by free radical scavengers.Lancet217:1129–1130; 1984.

[15] Schmidt, R. J.; Khan, L.; Chung, L. Y. Are free radicals and notquinones the haptenic species derived from urushiols and othercontact allergenic mono- and dihydric alkylbenzenes? The sig-nificance of NADH, glutathione, and redox cycling in the skin.Arch. Dermatol. Res.282:56–64; 1990.

[16] Senaldi, G.; Pointaire, P.; Piguet, P. F.; Grau, G. E. Protectiveeffect of N-acetylcysteine in haptene-induced irritant and contacthypersensitivity reactions.J. Invest. Dermatol.102:934–937;1994.

[17] Fuchs, J.; Milbradt, R. Antioxidant inhibition of skin inflamma-tion induced by reactive oxidants: evaluation of the redox coupledihydrolipoate/lipoate.Skin Pharmacol.7:278–284; 1994.

[18] Hirai, A.; Minamiyama, Y.; Hamada, T.; Ishii, M.; Inoue, M.Glutathione metabolism in mice is enhanced more with hapteneinduced allergic contact dermatitis than with irritant contactdermatitis.J. Invest. Dermatol.109:314–318; 1997.

[19] Lange, R. W.; Germolec, D. R.; Foley, J. F.; Luster, M. I.Antioxidants attenuate anthralin-induced skin inflammation inBALB-c mice: role of specific proinflammatory cytokines.J. Leukoc. Biol.64:170–176; 1998.

[20] Somani, S. M.; Babu, S. R. Toxicodynamics of sulfur mustard.Int. J. Clin. Pharmacol. Ther. Toxicol.27:419–435; 1989.

[21] Camera, E.; Jensen, C.; Stab, L. S.; Scala, G.; Baadsgaard, O.;

Picardo, M. Correlation between antioxidant levels and skinreactivity to irritants.J. Dermatol. Sci.16(Suppl.1):S193; 1998.

[22] Willis, C. M.; Reiche, L.; Wilkinson, J. D. Immunocytochemicaldemonstration of reduced Cu, Zn-superoxide dismutase levelsfollowing topical application of dithranol and sodium laurylsulphate: an indication of the role of oxidative stress in acuteirritant contact dermatitis.Eur. J. Dermatol.8:8–12; 1998.

[23] Kimura, J.; Hayakari, M.; Kumano, T.; Nakano, H.; Satoh, K.;Tsuchida, S. Altered glutathione transferase levels in rat skininflamed due to contact hypersensitivity: induction of the alpha-class subunit 1.Biochem. J.335:605–610; 1998.

[24] Sarnstrand, B.; Jansson, A. H.; Matuseviciene, G.; Scheynius,A.; Pierrou, S.; Bergstrand, H. N,N9-Diacetyl-L-cystine-the di-sulfide dimer of N-acetylcysteine is a potent modulator of con-tact sensitivity/delayed type hypersensitivity reactions in ro-dents.J. Pharmacol. Exp. Ther.288:1174–1184; 1999.

[25] Allen, R. G.; Tresini, M. Oxidative stress and gene regulation.Free Radic. Biol. Med.28:463–499; 2000.

[26] Bauerle, P. A.; Henkel, T. Function and activation of NFkB inthe immune system.Annu. Rev. Immunol.12:141–179; 1994.

[27] Sen, C. K.; Packer, L. Antioxidant and redox regulation of genetranscription.FASEB J.10:709–720; 1996.

[28] Winyard, P. G.; Blake, D. R. Antioxidants, redox-regulatedtranscription factors, and inflammation. In: Sies, H., ed.Ad-vances in pharmacology: antioxidants in disease mechanism andtherapy. San Diego, CA: Academic Press; 1997:403–421.

[29] Wakem, P.; Gaspari, A. A. Mechanisms of allergic and irritantcontact dermatitis. In: Kydonieus, A. F.; Wille, J. J., eds.Bio-chemical modulations of skin reactions. Boca Raton, FL: CRCPress; 2000:83–106.

[30] Brasch, J.; Burgard, J.; Sterry, W. Common pathogenic path-ways in allergic and irritant contact dermatitis.J. Invest. Der-matol.98:166–170; 1992.

[31] Vessey, D. A.; Lee, K. W.; Blacker, K. L. Characterization of theoxidative stress initiated in cultured human keratinocytes bytreatment with peroxides.J. Invest. Dermatol.99:859–863;1992.

[32] Vessey, D. A.; Lee, K. H. Inactivation of enzymes of theglutathione antioxidant system by treatment of cultured humankeratinocytes with peroxides.J. Invest. Dermatol.100:829–833;1993.

[33] Iannone, A.; Marconi, A.; Zambruno, G.; Gianetti, A.; Vannini,V.; Tomasi, A. Free radical production during metabolism oforganic hydroperoxides by normal human keratinocytes.J. In-vest. Dermatol.101:59–63; 1993.

[34] Timmins, G. S.; Davies, M. J. Free radical formation in isolatedmurine keratinocytes treated with organic peroxides and itsmodulation by antioxidants.Carcinogenesis14:1615–1620;1993.

[35] Kensler, T.; Guyton, K.; Egner, P.; McCarthy, T.; Lesko, S.;Akman, S. Role of reactive intermediates in tumor promotionand progression.Prog. Clin. Biol. Res.391:103–116; 1995.

[36] Taffe, B. G.; Takahashi, N.; Kensler, T. W.; Mason, R. P.Generation of free radicals from organic hydroperoxide tumorpromoters in isolated mouse keratinocytes.J. Biol. Chem.262:12143–12149; 1987.

[37] Athar, M.; Mukhtar, H.; Bickers, D. R.; Khan, I. U.; Kalyanara-man, B. Evidence for the metabolism of tumor promoter organichydroperoxides into free radicals by human carcinoma skinkeratinocytes: an ESR-spin trapping study.Carcinogenesis10:1499–1503; 1989.

[38] Sugiyama, M. Role of physiological antioxidants in chromium(VI)-induced cellular injury.Free Radic. Biol. Med.12:397–407; 1992.

[39] Shi, X.; Dalal, N. S. The role of superoxide radical in chromium(VI)-generated hydroxyl radical: the Cr(VI) Haber-Weiss cycle.Arch. Biochem. Biophys.292:323–327; 1992.

[40] Shi, X.; Dalal, N. S.; Kasprzak, K. S. Generation of free radicalsfrom hydrogen peroxide and lipid hydroperoxides in the pres-ence of Cr(III).Arch. Biochem. Biophys.302:294–299; 1993.

[41] Mao, Y.; Zang, L.; Shi, X. Generation of free radicals by Cr(IV)

346 J. FUCHS et al.

from lipid hydroperoxides and its inhibition by chelators.Bio-chem. Mol. Biol. Int.36:327–337; 1995.

[42] Tsou, T. C.; Yang, J. L. Formation of reactive oxygen speciesand DNA strand breakage during interaction of chromium (III)and hydrogen peroxide in vitro: evidence for a chromium (III)-mediated Fenton-like reaction.Chem. Biol. Interact.102:133–153; 1996.

[43] Ye, J.; Zhang, X.; Young, H. A.; Mao, Y.; Shi, X. Chromi-um(VI)-induced nuclear factor-kappaB activation in intact cellsvia free radical reactions.Carcinogenesis16:2401–2405; 1995.

[44] Kadiiska, M. B.; Xiang, Q. H.; Mason, R. P. In vivo free radicalgeneration by chromium(VI): An electron spin resonance spin-trapping investigation.Chem. Res. Toxicol.7:800–805; 1994.

[45] Athar, M.; Hasan, S. K.; Srivastav, R. C. Evidence for theinvolvement of hydroxyl radicals in nickel mediated enhance-ment of lipid peroxidation: implications for nickel carcinogene-sis.Biochem. Biophys. Res. Commun.147:1276–1281; 1987.

[46] Chen, C. Y.; Huang, Y. L.; Lin, T. H. Association betweenoxidative stress and cytokine production in nickel-treated rats.Arch. Biochem. Biophys.356:127–132; 1998.

[47] Huang, X.; Frenkel, K.; Klein, C. B.; Costa, M. Nickel inducesincreased oxidants in intact cultured mammalian cells as de-tected by dichlorofluorescein fluorescence.Toxicol. Appl. Phar-macol.120:29–36; 1993.

[48] Huang, X.; Zhuang, Z.; Frenkel, K.; Klein, C. B.; Costa, M. Therole of nickel and nickel-mediated reactive oxygen species in themechanism of nickel carcinogenesis.Environ. Health Perspect.102:281–284; 1994.

[49] Shi, X.; Dalal, N. S.; Kasprzak, K. S. Generation of free radicalsin reactions of nickel-thiol complexes with molecular oxygenand model lipid hydroperoxides.J. Inorgan. Biochem.50:211–225; 1993.

[50] Tkeshelashvili, L. K.; Reid, T. M.; McBride, T. J.; Loeb, L. A.Nickel induces a signature mutation for oxygen free radicaldamage.Cancer Res.53:4172–4174; 1993.

[51] Novelli, E. L.; Rodrigues, N. L.; Ribas, B. O. Superoxide radicaland toxicity of environmental nickel exposure.Hum. Exp. Toxi-col. 14:248–251; 1995.

[52] Lynn, S.; Yew, F. H.; Chen, K. S.; Jan, K. Y. Reactive oxygenspecies are involved in nickel inhibition of DNA repair.Environ.Mol. Mutagen.29:208–216; 1997.

[53] Misra, M.; Rodriguez, R. E.; Kasprzak, K. Nickel-induced lipidperoxidation in the rat: correlation with nickel effect on antiox-idant defense systems.Toxicology64:1–17; 1990.

[54] Misra, M.; Rodriguez, R. E.; North, S. L.; Kasprzak, K. Nickel-induced renal lipid peroxidation in different strains of mice:concurrence with nickel effect on antioxidant defense systems.Toxicol. Lett.58:121–133; 1991.

[55] Hess, J. A.; Molinari, J. A.; Gleason, M. J.; Radecki, C. Epider-mal toxicity of disinfectants.Am. J. Dent.4:51–56; 1991.

[56] Thompson, D. C.; Perera, K., London, R. Quinone methideformation from para isomers of methylphenol (cresol), ethylphe-nol, and isopropylphenol: relationship to toxicity.Chem. Res.Toxicol.8:55–60; 1995.

[57] Stoyanovsky, D. A.; Goldman, R.; Claycamp, H. G.; Kagan,V. E. Phenoxyl radical-induced thiol-dependent generation ofreactive oxygen species: Implications for benzene toxicity.Arch.Biochem. Biophys.317:315–323; 1995.

[58] Stoyanovsky, D. A.; Goldman, R.; Jonnalagadda, S. S.; Day,B. W.; Claycamp, H. G.; Kagan, V. E. Detection and character-ization of the electron paramagnetic resonance-silent glutathio-nyl-5,5-dimethyl-1-pyrroline N-oxide adduct derived from re-dox cycling of phenoxyl radicals in model systems.Arch.Biochem. Biophys.330:3–11; 1996.

[59] Bogadi-Sare, A.; Brumen, V.; Turk, R.; Karacic, V.; Zavalic, M.Genotoxic effects in workers exposed to benzene: with specialreference to exposure biomarkers and confounding factors.Ind.Health 35:367–373; 1997.

[60] Shedova, A. A.; Kommineni, C.; Jeffries, B. A.; Castranova, V.;Tyurina, Y. Y.; Tyurin, V. A.; Serbonova, E.; Fabisiak, J. B.;Kagan, V. Redox cycling of phenol induces oxidative stress in

human epidermal keratinocytes.J. Invest. Dermatol.114:354–364; 2000.

[61] Svingen, B. A.; Powis, G. P.; Appel, P. L.; Scot, M. Protectionagainst adriamycin induced skin necrosis in the rat by dimethylsulfoxide and a-tocopherol.Cancer Res.41:3395–3399; 1981.

[62] Daugherty, J. P.; Khurana, A. Amelioration of doxorubicin in-duced skin necrosis in mice by butylated hydroxytoluene.Can-cer Chemother. Pharmacol.14:243–246; 1985.

[63] Powis, G. Free radical formation by antitumor quinones.FreeRadic. Biol. Med.6:63–101; 1989.

[64] Monks, T. J.; Hanzlik, R. P.; Cohen, G. M.; Ross, D.; Graham,D. G. Quinone chemistry and toxicity.Toxicol. Appl. Pharma-col. 112:2–16; 1992.

[65] Hajarizadeh, H.; Lebredo, L.; Barrie, R.; Woltering, E. A. Pro-tective effect of doxorubicin in vitamin C or dimethyl sulfoxideagainst skin ulceration in the pig.Ann. Surg. Oncol.1:411–414;1994.

[66] Bekerecioglu, M.; Kutluhan, A.; Demirtas, I.; Karaayvaz, M.Prevention of adriamycin-induced skin necrosis with variousfree radical scavengers.J. Surg. Res.75:61–65; 1998.

[67] Viluksela, M. Characteristics and modulation of dithranol (an-thralin) induced skin irritation in the mouse ear model.Arch.Dermatol. Res.283:262–268; 1991.

[68] Muller, K.; Wiegrebe, W.; Younes, M. Formation of activeoxygen species by dithranol III. Dithranol, active oxygen speciesand lipid peroxidation in vivo.Arch. Pharm. (Weinheim)320:59–66; 1987.

[69] Muller, K.; Kappus, H. Hydroxyl radical formation by dithranol.Biochem. Pharmacol.37:4277–4280; 1988.

[70] Muller, K. Antipsoriatic anthrones: aspects of oxygen radicalformation, challenges and prospects.Gen. Pharmacol.27:1325–1335; 1996.

[71] Muller, K. Antipsoriatic and proinflammatory action of anthra-lin. Implications for the role of oxygen radicals.Biochem. Phar-macol.53:1215–1221; 1997.

[72] Shroot, B.; Brown, C. Free radicals in skin exposed to dithranoland its derivatives.Arzneimittelforschung36:1253–1255; 1986.

[73] Fuchs, J.; Packer, L. Investigations on anthralin free radicals inmodel systems and in skin of hairless mice.J. Invest. Dermatol.92:677–682; 1989.

[74] Hayden, P. J.; Free, K. E.; Chignell, C. F. Structure-activityrelationships for the formation of secondary radicals and inhi-bition of keratinocyte proliferation by 9-anthrones.Mol. Phar-macol.46:186–198; 1994.

[75] Mader, K.; Baacic, G.; Swartz, H. M. In vivo detection ofanthralin-derived free radicals in the skin of hairless mice bylow-frequency electron paramagnetic resonance spectroscopy.J. Invest. Dermatol.104:514–517; 1995.

[76] Chignel, C. F. Structure activity relationships in the free radicalmetabolism of xenobiotics.Environ. Health Perspect.61:133–137; 1985.

[77] Cavalieri, E. L.; Rogan, E. Role of radical cations in aromatichydrocarbon carcinogenesis.Environ. Health Perspect.64:69–84; 1985.

[78] Cavalieri, E. L.; Rogan, E. Radical cations in aromatic hydro-carbon carcinogenesis.Free Radic. Res. Commun.11:77–87;1990.

[79] Brennan, R. J.; Schiestl, R. H. Aniline and its metabolitesgenerate free radicals in yeast.Mutagenesis12:215–220; 1997.

[80] Hlavica, P.; Golly, I.; Lehnerer, M.; Schulze, J. Primary aro-matic amines: their N-oxidative bioactivation.Hum. Exp. Toxi-col. 16:441–448; 1997.

[81] Barker, J. N.; Mitra, R. S.; Griffiths, C. E.; Dixit, V. M.;Nickolof, B. J. Keratinocytes as initiators of inflammation.Lan-cet 337:211–214; 1991.

[82] Enk, A. H.; Katz, S. I. Early molecular events in the inductionphase of contact sensitivity.Proc. Natl. Acad. Sci. USA89:1398–1402; 1992.

[83] Friedmann, P. S.; Strickland, I.; Memon, A. A.; Johnson, P. M.Early time course of recruitment of immune surveillance in

347Redox modulated pathways

human skin after chemical provocation.Clin. Exp. Immunol.91:351–356; 1993.

[84] Arrigo, A. P. Gene expression and the thiol redox state.FreeRadic. Biol. Med.27:936–944; 1999.

[85] Adler, V.; Yin, Z.; Tew, K. D.; Ronai, Z. Role of redox potentialand reactive oxygen species in stress signaling.Oncogene18:6104–6111; 1999.

[86] Fuchs, J., ed.Oxidative injury in dermatopathology. Heidelberg,Germany: Springer Verlag; 1992.

[87] Darr, D.; Fridovich, I. Free radicals in cutaneous biology.J. In-vest. Dermatol.102:671–675; 1994.

[88] Maccarrone, M.; Catani, M. V.; Iraci, S.; Melino, G.; Agro, A. F.A survey of reactive oxygen and their role in dermatology.J.Eur. Acad. Dermatol. Venereol.8:185–202; 1997.

[89] Goldman, R.; Moshonov, S.; Zor, U. Generation of reactiveoxygen species in a human keratinocyte cell line: role of cal-cium. Arch. Biochem. Biophys.350:10–18; 1998.

[90] Babior, B. M. NADPH oxidase: an update.Blood 93:1464–1476; 1999.

[91] Coquette, A.; Berna, N.; Poumay, Y.; Pittelkow, M. R. Thekeratinocyte in cutaneous irritation and sensitization. In: Kydo-nieus, A. F.; Wille, J. J., eds.Biochemical modulations of skinreactions. Boca Raton, FL: CRC Press; 2000:125–143.

[92] Yoshioka, A.; Miyachi, Y.; Imamura, S. Mechanism of reactiveoxygen species induced skin erythema and superoxide dismutaseactivities in guinea pigs.J. Dermatol.14:569–575; 1987.

[93] Trenam, C. W.; Dabbagh, A. J.; Morris, C. J.; Blake, D. R. Skininflammation induced by reactive oxygen species (ROS): anin-vivo model.Br. J. Dermatol.125:325–329; 1991.

[94] Bruch-Gerharz, D.; Ruizicka, T.; Kolb-Bachofen, V. Nitric ox-ide in human skin. Current status and future prospects.J. Invest.Dermatol.110:1–7; 1998.

[95] Beckman, J. S.; Tsai, T. S. Reactions and diffusion of nitricoxide and peroxynitrite.Biochemist16:8–10; 1994.

[96] Beckman, J. S.; Koppenol, W. H. Nitric oxide, superoxide, andperoxinitrite. The good, the bad, and the ugly.Am. J. Physiol.271:C1414–C1437; 1996.

[97] Curran, A. D. The role of nitric oxide in the development ofasthma.Int. Arch. Allergy Immunol.111:1–4; 1996.

[98] Sirsjo, A.; Karlsson, M.; Gidlof, A.; Rollman, O.; Torma, H.Increased expression of inducible nitric oxide synthase in pso-riatic skin and cytokine stimulated cultured keratinocytes.Br. J.Dermatol.134:643–648; 1996.

[99] Becherel, P. A.; Le Goff, L.; Ktorza, S.; Quaaz, F.; Mencia-Huerta, J. M.; Dugas, B.; Debre, P.; Mossalayi, M. D.; Arock,M. Interleukin-10 inhibitis IgE-mediated nitrix oxide synthaseinduction and cytokine synthesis in normal human keratinocytes.Eur. J. Immunol.25:2992–2995; 1995.

[100] Deliconstantinos, G.; Villiotou, V.; Stavrides, J. C. Increase ofparticular nitric oxide synthase activity and peroxynitrite syn-thesis in UVB irradiated keratinocyte membranes.Biochem. J.320:997–1003; 1996.

[101] Ross, R.; Gillitzer, C.; Klein, R.; Schwing, J.; Kleinert, H.;Forstermann, U.; Reske-Kunz, A. B. Involvement of NO incontact hypersensitivity.Int. Immunol.10:61–69; 1998.

[102] Bruch-Gerharz, D.; Fehsel, K.; Suschek, C.; Michel, G.;Ruzicka, T.; Kolb-Bachofen, V. A proinflammatory activity ofinterleukin 8 in human skin: expression of the inducible nitricoxide synthase in psoriatic lesions and cultured keratinocytes.J.Exp. Med.184:2007–2012; 1996.

[103] Frank, S.; Kampfer, H.; Podda, M.; Kaufmann, R.; Pfeilschifter,J. Identification of copper/zinc superoxide dismutase as a nitricoxide-regulated gene in human (HaCaT) keratinocytes: implica-tions for keratinocyte proliferation.Biochem. J.346:719–728;2000.

[104] Shimizu, Y.; Sakai, M.; Umemura, Y.; Ueda, H. Immunohisto-chemical localization of nitric oxide synthase in normal humanskin: expression of endothelial-type and inducible-type nitricoxide synthase in keratinocytes.J. Dermatol.24:80–87; 1997.

[105] Ormerod, A. D.; Dwyer, C. M.; Reid, A.; Copeland, P.; Thomp-son, W. D. Inducible nitric oxide synthase demonstrated in

allergic and irritant contact dermatitis.Acta Derm. Venereol.77:436–440; 1997.

[106] Brady, T. C.; Chang, L. Y.; Day, B. J.; Crapo, J. D. Extracellularsuperoxide dismutase is upregulated with inducible nitric oxidesynthase after NF-kB activation.Am. J. Physiol.273:L1002–L1006; 1997.

[107] Yim, C. Y.; McGregor, J. R.; Kwon, O. D.; Bastian, N. R.; Rees,M.; Mori, M.; Hibbs, J. B. Jr.; Samlowski, W. E. Nitric oxidesynthesis contributes to IL-2-induced antitumor responsesagainst intraperitoneal Meth A tumor.J. Immunol.155:4382–4390; 1995.

[108] Teixeira, M. M.; Williams, T. J.; Hellewell, P. G. Role ofprostaglandins and nitric oxide in acute inflammatory reactionsin guinea-pig skin.Br. J. Pharmacol.110:1515–1521; 1993.

[109] Ormerod, A. D.; Copeland, P.; Hay, I.; Husain, A.; Ewen, S. W.The inflammatory and cytotoxic effects of a nitric oxide releas-ing cream on normal skin.J. Invest. Dermatol.113:392–397;1999.

[110] Huang, M.; Manning, R. D. Jr.; LeBlanc, M. H.; Hester, R. L.Overall hemodynamic studies after the chronic inhibition ofendothelial-derived nitric oxide in rats.Am. J. Hypertens.8:358–364; 1995.

[111] Tozer, G. M.; Prise, V. E.; Motterlini, R.; Poole, B. A.; Wilson,J.; Chaplin, D. J. The comparative effects of the NOS inhibitor,Nomega-nitro-L-arginine, and the haemoxygenase inhibitor, zincprotoporphyrin IX, on tumour blood flow.Int. J. Radiat. Oncol.Biol. Phys.42:849–853; 1998.

[112] Fukumura, D.; Yuan, F.; Endo, M.; Jain, R. K. Role of nitricoxide in tumor microcirculation. Blood flow, vascular perme-ability, and leukocyte-endothelial interactions.Am. J. Pathol.150:713–725; 1997.

[113] Shabani, F.; McNeil, J.; Tippett, L. The oxidative inactivation oftissue inhibitor of metalloproteinase-1 (TIMP-1) by hypochlor-ous acid (HOCI) is suppressed by anti-rheumatic drugs.FreeRadic. Res.28:115–123; 1998.

[114] Marcinkiewicz, J.; Nowak, B.; Grabowska, A.; Bobek, M.;Petrovska, L.; Chain, B. Regulation of murine dendritic cellfunctions in vitro by taurine chloramine, a major product of theneutrophil myeloperoxidase-halide system.Immunology98:371–378; 1998.

[115] Monteiro, H. P.; Stern, A. Redox modulation of tyrosine phos-phorylation-dependent signal transduction pathways.FreeRadic. Biol. Med.21:323–333; 1996.

[116] Wilmer, W. A.; Tan, L. C.; Dickerson, J. A.; Danne, M.; Rovin,B. H. Interleukin-1-beta induction of mitogen-activated proteinkinases in human mesangial cells. Role of oxidation.J. Biol.Chem.272:10877–10881; 1997.

[117] Wesselborg, S.; Bauer, M. K. A.; Vogt, M.; Schmitz, M. L.;Schulze-Osthoff, K. Activation of transcription factor NF-kap-pa-B and p38 mitogen-activated protein kinase is mediated bydistinct and separate stress effector pathways.J. Biol. Chem.272:12422–12429; 1997.

[118] Peus, D.; Vasa, R. A.; Beyerle, A.; Meves, A.; Krautmacher, C.;Pittelkow, M. R. UVB activates ERK1/2 and p38 signallingpathways via reactive oxygen species in cultured human kera-tinocytes.J. Invest. Dermatol.112:751–756; 1999.

[119] Peus, D.; Vasa, R. A.; Meves, A.; Pott, M.; Beyerle, A.; Squil-lace, K.; Pittelkow, M. R. H2O2 is an important mediator ofUVB-induced EGF receptor phosphorylation in cultured kera-tinocytes.J. Invest. Dermatol.110:966–972; 1998.

[120] Jacobson, P. B.; Kuchera, S. L.; Metz, A.; Schachtele, C.; Imre,K.; Schrier, D. J. Anti-inflammatory properties of Go 6850: aselective inhibitor of protein kinase C.J. Pharmacol. Exp. Ther.275:995–1002; 1995.

[121] Orrenius, S.; Burkitt, M. J.; Kass, G. E.; Dypbukt, J. M.; Nico-tera, P. Calcium ions and oxidative cell injury.Ann. Neurol.32(Suppl.):S33–S42; 1992.

[122] Azzi, A. M.; Bartoli, G.; Boscoboinik, D.; Hensey, C.; Szew-czyk, A. a-Tocopherol and protein kinase C regulation of intra-cellular signalling. In: Packer, L.; Fuchs, J., eds.Vitamin E in

348 J. FUCHS et al.

health and disease. New York: Marcel Dekker Inc.; 1993:371–383.

[123] Wang, H. Q.; Smart, R. C. Overexpression of protein kinaseC-alpha in the epidermis of transgenic mice results in strikingalterations in phorbol ester-induced inflammation and COX-2,MIP-2 and TNF-a expression but not tumor promotion.J. CellSci.112:3497–3506; 1999.

[124] Chabot-Fletcher, G.; Breton, J.; Lee, J.; Young, P.; Griswold,D. E. Interleukin-8 production is regulated by protein kinase C inhuman keratinocytes.J. Invest. Dermatol.103:509–515; 1994.

[125] Leslie, C. C. Properties and regulation of cytosolic phospho-lipase A2.J. Biol. Chem.272:16709–16714; 1997.

[126] Simon, L. S. Role and regulation of cyclooxygenase-2 duringinflammation.Am. J. Med.106:37S–42S; 1999.

[127] Adelizzi, R. A. COX-1 and COX-2 in health and disease.J. Am.Osteopath. Assoc.99(Suppl. 11):S7–S12; 1999.

[128] Wallace, J. L. Distribution and expression of cyclooxygenase(COX) isoenzymes, their physiological roles, and the categori-zation of nonsteroidal antiinflammatory drugs (NSAIDs).Am. J.Med.107:11S–17S; 1999.

[129] Faux, S. P.; Howden, P. J. Possible role of lipid peroxidation inthe induction of NF-kappa B and AP-1 in RFL-6 cells bycrocidolite asbestos: evidence following protection by vitaminE. Environ. Health Perspect.105:1127–1130; 1997.

[130] Adderley, S. R.; Fitzgerald, D. J. Oxidative damage of cardio-myocytes is limited by extracellular regulated kinase 1/2-medi-ated induction of cyclooxygenase-2.J. Biol. Chem.274:5038–5046; 1999.

[131] Mitchell, J. A.; Larkin, S.; William, T. J. Cyclooxygenase-2regulation and relevance in inflammation.Biochem. Pharmacol.50:1535–1542; 1995.

[132] Sahnoun, Z.; Jamoussi, K.; Zeghal, K. M. Radicaux libres etanti-oxydants: physiologie, pathologie humaine et aspects thera-peutiques (ileme partie).Therapie53:315–339; 1998.

[133] Vane, J. R.; Bakhle, Y. S.; Botting, R. M. Cyclooxygenases 1and 2.Annu. Rev. Pharmacol. Toxicol.38:97–120; 1998.

[134] Crofford, L. J. COX-1 and COX-2 tissue expression: implica-tions and predictions.J. Rheumatol.24(Suppl. 49):15–19; 1997.

[135] Camp, R. D. R.; Jones, R. R.; Brain, S.; Woollard, P. M.;Greaves, M. Production of intraepidermal microabscesses bytopical application of leukotriene B4.J. Invest. Dermatol.82:202–204; 1984.

[136] Ikai, K. Proinflammatory mediators of the arachidonic acidcascade. In: Kydonieus, A. F.; Wille, J. J., eds.Biochemicalmodulations of skin reactions. Boca Raton, FL: CRC Press;2000:189–201.

[137] Margalit, A.; Hauser, S.; Zweifel, B. S.; Anderson, M. A.;Isakson, P. C. Regulation of prostaglandin biosynthesis in vivoby glutathione.Am. J. Physiol.274:R294–R302; 1998.

[138] Cornwell, D. G.; Panganamala, R. V. Vitamin E action inmodulating the arachidonic acid cascade. In: Packer, L.; Fuchs,J., eds.Vitamin E in health and disease. New York: MarcelDekker Inc.; 1993:385–410.

[139] Chakraborti, S.; Chakraborti, T. Oxidant-mediated activation ofmitogen-activated protein kinases and nuclear transcription fac-tors in the cardiovascular system: a brief overview.Cell. Signal.10:675–683; 1998.

[140] Meyer, M.; Pahl, H. L.; Baeuerle, P. A. Regulation of thetranscription factors NFkappa B and AP-1 by redox changes.Chem. Biol. Interact.91:91–100; 1994.

[141] Flohe, L.; Brigelius-Flohe, R.; Saliou, C.; Traber, M. G.; Packer,L. Redox regulation of NF-kappa B activation.Free Radic. Biol.Med.22:1115–1126; 1997.

[142] Gius, D.; Botero, A.; Shah, S.; Curry, H. A. Intracellular oxida-tion/reduction status in the regulation of transcription factorsNF-kappaB and AP-1.Toxicol. Lett.106:93–106; 1999.

[143] Piette, J.; Piret, B.; Bonizzi, G.; Schoonbroodt, S.; Merville,M. P.; Legrand-Poels, S.; Bours, V. Multiple redox regulation inNF-kappaB transcription factor activation.Biol. Chem. 378:1237–1245; 1997.

[144] Courtois, G.; Whiteside, S. T.; Sibley, C. H.; Israel, A. Charac-

terization of a mutant cell line that does not activate NF-kappaBin response to multiple stimuli.Mol. Cell. Biol. 17:1441–1449;1997.

[145] Schreck, R.; Baeuerle, P. A. NF-kB as inducible transcriptionalactivator of the granulocyte macrophage colony stimulating fac-tor gene.Mol. Cell. Biol. 10:1281–1286; 1990.

[146] Schreck, R.; Rieber, P.; Baeuerle, P. A. Reactive oxygen inter-mediates as apparently widely used second messengers in theactivation of the NFkB transcription factor and HIV-1.EMBO J.10:2247–2258; 1991.

[147] Schreck, R.; Albermann, K.; Baeuerle, P. A. Nuclear transcrip-tion factorkB: an oxidative stress responsive transcription factorof eukaryotic cells (a review).Free Radic. Res. Commun.17:221–237; 1992.

[148] Koehler, H. B. K.; Knop, J.; Martin, M.; de Bruin, A.; Huckz-ermeyer, B.; Lehmann, H.; Kiezmann, M.; Meier, B.; Nolte, I.Involvement of reactive oxygen species in TNF-a mediatedactivation of the transcription factor NF-kB in canine dermalfibroblasts.Vet. Immunol. Immunopathol.71:125–142; 1999.

[149] Kaltschmidt, C.; Kaltschmidt, B.; Lannes-Vieira, J.; Kreuzberg,G. W.; Wekerle, H.; Baeuerle, P. A.; Gehrmann, J. Transcriptionfactor NFkB is activated in microglia during experimental au-toimmune encephalomyelitis.J. Neuroimmunol.55:99–106;1994.

[150] Bonizzi, G.; Dejardin, E.; Piret, B.; Piette, J.; Merville, M. P.;Bours, V. Interleukin-1 induces nuclear factorkB in epithelialcells independently of the production of reactive oxygen inter-mediates.Eur. J. Biochem.242:544–549; 1996.

[151] Alonso, K.; Pontiggia, P.; Medenica, R.; Rizzo, S. Cytokinepatterns in adults with AIDS.Immunol. Invest.26:341–350;1997.

[152] Brennan, P.; O’Neill, L. A. J. Effects of oxidants and antioxi-dants on nuclear factorkB activation in three different cell lines:evidence against a universal hypothesis involving oxygen radi-cals.Biochim. Biophys. Acta1260:167–175; 1995.

[153] Legrand-Poels, S.; Zecchinon, L.; Piret, B.; Schoonbroodt, S.;Piette, J. Involvement of different transduction pathways inNF-kB activation by several inducers.Free Radic. Res.27:301–309; 1997.

[154] Li, N.; Karin, M. Is NF-kappaB the sensor of oxidative stress?FASEB J.13:1137–1143; 1999.

[155] Janssen-Heininger, Y. M.; Poynter, M. E.; Baeuerle, P. A. Re-cent advances towards understanding redox mechanisms in theactivation of nuclear factor kappa B.Free Radic. Biol. Med.28:1317–1327; 2000.

[156] Podda, M.; Koh, B.; Thiele, J.; Milbradt, R.; Packer, L. Ozoneactivates the transcription factor NFkB in keratinocytes viareactive oxygen species.Australas. J. Dermatol.38(Suppl. 2):185; 1997.

[157] Ikeda, M.; Miyoshi, K.; Chikazawa, M.; Kodama, H. Activationof nuclar factorkB by hydrogen peroxide in epidermal keratin-ocytes and its inhibition by antioxidants.Australas. J. Dermatol.38(Suppl. 2):190; 1997.

[158] Vile, G. F.; Tanew-Iliitschew, A.; Tyrrell, R. M. Activation ofNF-kappa-B in human skin fibroblasts by the oxidative stressgenerated by UVA radiation.Photochem. Photobiol.62:463–468; 1995.

[159] Devary, Y.; Gottlieb, R. A.; Lau, L. F.; Karin, M. Rapid andpreferential activation of the c-jun gene during the mammalianUV response.Mol. Cell. Biol. 11:2804–2811; 1991.

[160] Radler-Pohl, A.; Sachsenmaier, C.; Gebel, S.; Auer, H.; Bruder,J. T.; Rapp, U.; Angel, P.; Rahmsdorf, H. J.; Herrlich, P. UV-induced activation of AP-1 involves obligatory extranuclearsteps including RAF-1 kinase.EMBO J.12:1005–1012; 1993.

[161] Schmidt, K. N.; Podda, M.; Packer, L.; Baeuerle, P. A. Anti-psoriatic drug anthralin activates transcription factor NF-kap-pa-B in murine keratinocytes.J. Immunol. 156:4514–4519;1996.

[162] Lange, R. W.; Hayden, P. J.; Chignell, C. F., Luster, M. I.Anthralin stimulates keratinocyte-derived proinflammatory cy-

349Redox modulated pathways

tokines via generation of reactive oxygen species.Inflamm. Res.47:174–181; 1998.

[163] Shi, X.; Ding, M.; Ye, J.; Wang, S.; Leonard, S. S.; Zang, L.;Castranova, V.; Vallyathan, V.; Chiu, A.; Dalal, N. Cr (IV)causes activation of nuclear transcription factor-kappaB, DNAstrand breaks and dG hydroxylation via free radical reactions.J. Inorgan. Biochem.75:37–44; 1999.

[164] Goebeler, M.; Roth, J.; Broecker, E. B.; Sorg, C.; Schulze-Osthoff, K. Activation of nuclear factor-kappa-B and gene ex-pression in human endothelial cells by the common haptensnickel and cobalt.J. Immunol.155:2459–2467; 1995.

[165] Wagner, M.; Klein, C. L.; Van Kooten, T. G.; Kirkpatrick, C. J.Mechanisms of cell activation by heavy metal ions.J. Biomed.Mater. Res.42:443–452; 1998.

[166] Koy, A. Initiation of acute phase reponse and synthesis ofcytokines.Biochim. Biophys. Acta1317:84–94; 1996.

[167] Corsini, E.; Galli, C. L. Cytokines and irritant contact dermatitis.Toxicol. Lett.102–103:277–282; 1998.

[168] Hunziker, T.; Brand, C. U.; Kapp, A.; Waelti, E. R.; Braathen,L. R. Increased levels of inflammatory cytokines in human skinlymph derived from sodium lauryl sulphate-induced contactdermatitis.Br. J. Dermatol.127:254–257; 1992.

[169] Larsen, C. G.; Ternowitz, T.; Larsen, F. G.; Zachariae, G.;Thestrup-Pedersen, K. ETAF/interleukin-1 and epidermal lym-phocyte chemotactic factor in epidermal lymphocyte chemotac-tic factor in epidermis overlying an irritant patch test.ConcactDermatitis20:335–340; 1989.

[170] Kimber, I. Epidermal cytokines in contact hypersensitivity: im-munological roles and practical applications.Toxicol. In Vitro7:295–298; 1993.

[171] Luster, M. I.; Simeonova, P. P.; Gallucci, R.; Matheson, J.Tumor necrosis factor alpha and toxicology.Crit. Rev. Toxicol.29:491–511; 1999.

[172] Murphy, J. E.; Robert, C.; Kupper, T. S. Interleukin-1 andcutaneous inflammation: a crucial link between innate and ac-quired immunity.J. Invest. Dermatol.114:602–608; 2000.

[173] Deforge, L. E.; Preston, A. M.; Takeuchi, E.; Kenny, J.; Boxter,L. A.; Remick, D. G. Regulation of interleukin 8 gene expressionby oxidant stress.J. Biol. Chem.268:25568–25576; 1993.

[174] Shimada, T.; Watanabe, N.; Hiraishi, H.; Terano, A. Redoxregulation of interleukin-8 expression in MKN28 cells.Dig. Dis.Sci.44:266–273; 1999.

[175] Adamson, G. M.; Billings, R. E. Tumor necrosis factor inducedoxidative stress in isolated mouse hepatocytes.Arch Biochem.Biophys.294:223–229; 1992.

[176] Lo, Y. Y. C.; Conquer, J. A.; Grinstein, S.; Cruz, T. F. Inter-leukin-1-beta induction of c-fos and collagenase expression inarticular chondrocytes: involvement of reactive oxygen species.J. Cell. Biochem.69:19–29; 1998.

[177] Goucherot-Pocidalo, M. A.; Revillard, J. P. Oxidative stress,cytokines and lymphocyte activation. In: Fuchs, J.; Packer, L.,eds.Oxidative stress in dermatology. New York: Marcel DekkerInc.; 1993:187–205.

[178] Piguet, P. F.; Grau, G. E.; Hauser, C.; Vasalli, P. Tumor necrosisfactor is a critical mediator in hapten induced irritant and contacthypersensitivity reactions.J. Exp. Med.173:673–679; 1991.

[179] Lisby, S.; Muller, K. M.; Jongeneel, C. V.; Saurat, J. H.; Hauser,C. Nickel and skin irritants up-regulate tumor necrosis factor-alpha mRNA in keratinocytes by different but potentially syn-ergistic mechanisms.Int. Immunol.7:343–349; 1995.

[180] Little, M. C.; Gawkrodger, D. J.; MacNeil, S. Chromium- andnickel-induced cytotoxicity in normal and transformed humankeratinocytes: an investigation of pharmacological approaches tothe prevention of Cr(VI) induced cytotoxicity.Br. J. Dermatol.134:199–205; 1996.

[181] Gentilhomme, E.; Neveux, Y.; Hua, A.; Thiriot, C.; Faure, M.;Thivolet, J. Action of bis(betachloro-ethyl)sulphide (BCES) onhuman epidermis reconstituted in culture: morphological alter-ations and biochemical depletion of glutathione.Toxicol. InVitro 6:139–147; 1992.

[182] Kurt, E. M.; Schafer, R. J.; Arroyo, C. M. Effects of sulfur

mustard on cytokines released from cultured human epidermalkeratinocytes.Int. J. Toxicol.17:223–229; 1998.

[183] Tsuruta, J.; Sugisaki, K.; Dannenberg, A. M.; Yoshimura, T.;Abe, Y.; Mounts, P. The cytokines NAP-1 (IL-8), MCP-1 IL-1beta, and GRO in rabbit inflammatory skin lesions produced bythe chemical irritant sulfur mustard.Inflammation20:293–318;1996.

[184] Arroyo, C. M.; Carmichael, A. J.; Broomfield, C. A. Couldnitrosyl chloride be produced by human skin keratinocytes andsulfur mustard? A magnetic resonance study.In Vitro Toxicol.10:253–261; 1997.

[185] Shvedova, A. A.; Kommineni, C.; Jeffries, B. A.; Castranova,V.; Tyurina, Y. Y.; Tyurin, V. A.; Serbinova, E. A.; Fabisiak,J. P.; Kagan, V. E. Redox cycling of phenol induces oxidativestress in human epidermal keratinocytes.J. Invest. Dermatol.114:354–364; 2000.

[186] Wilmer, J. L.; Burleson, F. G.; Kayama, F.; Kanno, J.; Luster,M. I. Cytokine induction in human epidermal keratinocytesexposed to contact irritants and its relation to chemical inducedinflammation in mouse skin.J. Invest. Dermatol.102:915–922;1994.

[187] Gueniche, A.; Viac, J.; Lizard, G.; Charveron, M.; Schmitt, D.Effect of various metals on intercellular adhesion molecule-1expression and tumour necrosis factor alpha production by nor-mal human keratinocytes.Arch. Dermatol. Res.286:466–470;1994.

[188] Luster, M. I.; Wilmer, J. L.; Germolec, D. R.; Spalding, J.;Yoshida, T.; Gaido, K.; Simeonova, P. P.; Burleson, F. G.;Bruccoleri, A. Role of keratinocyte-derived cytokines in chem-ical toxicity. Toxicol. Lett.82–83:471–476; 1995.

[189] Coquette, A.; Berna, N.; Vandenbosch, A.; Rosdy, M.; Poumay,Y. Differential expression and release of cytokines by an in vitroreconstructed human epidermis following exposure to skin irri-tant and sensitizing chemicals.Toxicol. In Vitro 13:867–877;1999.

[190] Maillard, J. L.; Favreau, C.; Reboud-Ravaux, M. Role of mono-cyte/macrophage derived matrix-metalloproteinases (gelati-nases) in prolonged skin inflammation.Clin. Chim. Acta233:61–74; 1995.

[191] Kahari, V. M.; Saarialho-Kere, U. Matrix metalloproteinases inskin. Exp. Dermatol.6:199–213; 1997.

[192] Petersen, M. J.; Hansen, C.; Craig, S. Ultraviolet A irradiationstimulates collagenase production in cultured human fibroblasts.J. Invest. Dermatol.99:440–444; 1992.

[193] Zaw, K. K.; Yokoyama, Y.; Ishikawa, O.; Miyachi, Y. Thereactive oxygen species (ROS) regulate the gene expressionsinvolved in the biosynthesis and biodegradation of collagens inthree-dimensional culture of normal human dermal fibroblasts.J. Invest. Dermatol.112:609; 1999.

[194] Brenneisen, P.; Briviba, K.; Wlaschek, M.; Wenk, J.; Scharffet-ter-Kochanek, K. Hydrogen peroxide (H-2O-2) increases thesteady-state mRNA levels of collagenase/MMP-1 in human der-mal fibroblasts.Free Radic. Biol. Med.22:515–524; 1997.

[195] Kawaguchi, Y.; Tanaka, H.; Okada, T.; Konishi, H.; Takahashi,M.; Ito, M.; Asai, J. The effects of ultraviolet A and reactiveoxygen species on the mRNA expression of 72-kDa type IVcollagenase and its tissue inhibitor in cultured human dermalfibroblasts.Arch. Dermatol. Res.288:39–44; 1996.

[196] Maeda, H.; Okamoto, T.; Akaike, T. Human matrix metallopro-tease activation by insults of bacterial infection involving pro-teases and free radicals.Biol. Chem.379:193–200; 1998.

[197] Wang, M.; Qin, X.; Mudgett, J. S.; Ferguson, T. A.; Senior,R. M.; Welgus, H. G. Matrix metalloproteinase deficienciesaffect contact hypersensitivity: stromelysin-1 deficiency pre-vents the response and gelatinase B deficiency prolongs theresponse.Proc. Natl. Acad. Sci. USA96:6885–6889; 1999.

[198] Sun, Q.; Wu, Y.; Zappacosta, F.; Jeang, K. T.; Lee, B.; Hatfield,D. L.; Gladyshev, V. N. Redox regulation of cell signaling byselenocysteine in mammalian thioredoxin reductases.J. Biol.Chem.274:24522–24530; 1999.

[199] Bertini, R.; Howard, O. M.; Dong, H. F.; Oppenheim, J. J.;

350 J. FUCHS et al.

Bizzarri, C.; Sergi, R.; Caselli, G.; Pagliei, S.; Romines, B.;Wilshire, J. A.; Mengozzi, M.; Nakamura, H.; Yodoi, J.; Pe-kkari, K.; Gurunath, R.; Holmgren, A.; Herzenberg, L. A.;Herzenberg, L. A.; Ghezzi, P. Thioredoxin, a redox enzymereleased in infection and inflammation, is a unique chemoattrac-tant for neutrophils, monocytes, and T cells.J. Exp. Med.189:1783–1789; 1999.

[200] Sachi, Y.; Hirota, K.; Masutani, H.; Toda, K. I.; Okamoto, T.;Takigawa, M.; Yodoi, J. Induction of ADF/TRX by oxidativestress in keratinocytes and lymphoid cells.Immunol. Lett.44:189–193; 1995.

[201] Anema, S. M.; Walker, S. W.; Forbes, H. A.; Arthur, J. R.;Nicol, F.; Beckett, G. J. Thioredoxin reductase is the majorselenoprotein expressed in human umbilical-vein endothelialcells and is regulated by protein kinase C.Biochem. J.342:111–117; 1999.

[202] Nordberg, J.; Zhong, L.; Holmgren, A.; Arner, E. S. Mammalianthioredoxin reductase is irreversibly inhibited by dinitrohaloben-zenes by alkylation of both the redox active selenocysteine andits neighboring cysteine residue.J. Biol. Chem.273:10835–10842; 1998.

[203] Manning, A. M.; Chen, C. C.; Rosenbloom, C. L.; McNab,A. R.; Cruz, R.; Anderson, D. C. Redox and proteolytic signaltransduction events in the activation of E-selectin, VCAM-1 andICAM-1 gene expression.J. Leukoc. Biol.10(Suppl):38; 1994.

[204] Marui, N.; Offermann, M. K.; Swerlick, R.; Kunsch, C.; Rosen,C. A.; Ahmad, M.; Alexander, R. W.; Medford, R. M. Vascularcell adhesion molecule-1 (VCAM-1) gene transcription and ex-pression are regulated through an antioxidant-sensitive mecha-nism in human vascular endothelial cells.J. Clin. Invest.92:1866–1874; 1993.

[205] Das, P. K.; de Boer, O. J.; Visser, A.; Verhagen, C. E.; Bos,J. D.; Pals, S. T. Differential expression of ICAM-1, E-selectinand VCAM-1 by endothelial cells in psoriasis and contact der-matitis.Acta Derm. Venereol.186(Suppl):21–22; 1994.

[206] Griffiths, C. E. M.; Nickoloff, B. J. Keratinocyte intracellularadhesion molecule-1 (ICAM-1) expression preceeds dermal Tlymphocyte infiltration in allergic contact dermatitis (Rhus der-matitis).Am. J. Pathol.135:1045–1053; 1989.

[207] Wildner, O.; Lipkow, T.; Knop, J. Increased expression ofICAM-1, E-selectin, and VCAM-1 by cultured human endothe-lial cells upon exposure to haptens.Exp. Dermatol.1:191–198;1992.

[208] Pober, J. S.; Cotran, R. S. Cytokine and endothelial cell biology.Physiol. Rev.70:427–451; 1990.

[209] Ghosh, S. NF-kappaB and Rel proteins: evolutionarily con-served mediators of immune responses.Annu. Rev. Immunol.16:225–260; 1998.

[210] Wataha, J. C.; Sun, Z. L.; Hanks, C. T.; Fang, D. N. Effect of Niions on expression of intercellular adhesion molecule 1 byendothelial cells.J. Biomed. Mater. Res.36:145–151; 1997.

[211] Jung, K.; Linse, F.; Pals, S. T.; Heller, R.; Moths, C.; Neumann,C. Adhesion molecules in atopic dermatitis: patch tests elicitedby house dust mite.Contact Dermatitis37:163–172; 1997.

[212] Faruqi, R. M.; Poptic, E. J.; Faruqi, T. R.; De La Motte, C.;DiCorleto, P. E. Distinct mechanisms for N-acetylcysteine inhi-bition of cytokine induced E-selectin and VCAM-1 expression.Am. J. Physiol.273:H817–H826; 1997.

[213] Friedrichs, B.; Mueller, C.; Brigelius-Flohe, R. Inhibition oftumor necrosis factor-alpha and interleukin-1 induced endothe-lial E-selectin expression by thiol-modifying agents.Arterio-scler. Thromb. Vasc. Biol.18:1829–1837; 1998.

[214] Grether-Beck, S.; Olaizola-Horn, S.; Schmitt, H.; Grewe, M.;Jahnke, A.; Johnson, J. P.; Briviba, K.; Sies, H.; Krutman, J.Activation of transcription factor AP-2 mediates UVA radiation-and singlet oxygen-induced expression of the human intercellu-lar adhesion molecule-1 gene.Proc. Natl. Acad. Sci. USA93:14586–14591; 1996.

[215] Ikeda, M.; Schroeder, K. K.; Mosher, L. B.; Woods, C. W.;Akeson, A. L. Suppressive effect of antioxidants on intracellular

adhesion molecule-1 (ICAM-1) expression in human epidermalkeratinocytes.J. Invest. Dermatol.103:791–796; 1994.

[216] Little, M. C.; Metcalfe, R. A.; Haycock, J. W.; Healy, J.;Gawkrodger, D. J.; Mac Neil, S. The participation of prolifera-tive keratinocytes in the preimmune response to sensitizingagents.Br. J. Dermatol.138:45–56; 1998.

[217] Gafvert, E.; Shao, L. P.; Karlberg, A. T.; Nilson, U.; Nilson,J. L. G. Contact allergy to resin acid hydroperoxides. Haptenbinding via free radicals and epoxides.Chem. Res. Toxicol.7:260–266; 1994.

[218] Barratt, M. D.; Basketter, D. A. Structure activity relationshipsfor skin sensitization: an expert system. In: Rougier, A.; Gold-berg, A. M.; Maibach, H. I., eds.In vitro toxicology: irritation,phototoxicity, sensitization. New York: Ann Liebert; 1994:293–301.

[219] Schmidt, R. J.; Chung, L. Y. Biochemical responses of skin toallergenic and non-allergenic nitrohalobenzenes. Evidence thatan NADPH dependent reductase in skin may act as a prohaptenactivating enzyme.Arch. Dermatol. Res.284:400–408; 1992.

[220] Takiwaki, H.; Arase, S.; Nakayama, H. Contact dermatitis due to2,29-azobis(2-amidinopropane) dihydrochloride: an outbreak inproduction workers.Contact Dermatitis39:4–7; 1998.

[221] Santucci, B.; Cristaudo, A.; Cannistraci, C.; Amantea, A.;Picardo, M. Hypertrophic allergic contact dermatitis from hairdye.Contact Dermatitis31:169–171; 1994.

[222] Picardo, M.; Zompetta, C.; Marchese, C.; De Luca, C.; Faggioni,A.; Schmidt, R. J.; Santucci, B. Para-phenylenediamine, a con-tact allergen, induces oxidative stress and ICAM-1 expression inhuman keratinocyte.Br. J. Dermatol.126:450–455; 1996.

[223] Lepoittevin, J. P.; Berl, V. Molecular basis of allergic contactdermatitis. In: Marzulli, F. N.; Maibach, H. I., eds.Dermato-toxicology. Washington, DC: Taylor & Francis; 1996:147–160.

[224] Romagnoli, P.; Labhardt, A. M.; Sinigaglia, F. Selective inter-action of Ni with an MHC-bound peptide.EMBO J.10:1303–1306; 1991.

[225] Zanni, M. P.; von Greyerz, S.; Schnyder, B.; Brander, K. A.;Frutig, K.; Hari, Y.; Valitutti, S.; Pichler, W. J. HLA restrictedprocessing and metabolism independent pathway of drug recog-nition by human alpha beta T-lymphocytes.J. Clin. Invest.102:1591–1598; 1998.

[226] Weinlich, G.; Heine, M.; Stossel, H.; Zanella, M.; Stoitzner, P.;Ortner, U.; Smolle, J.; Koch, F.; Sepp, N. T.; Schuler, G. Entryinto afferent lymphatics and maturation in situ of migratingmurine cutaneous dendritic cells.J. Invest. Dermatol.110:441–448; 1998.

[227] Rutault, K.; Alderman, C.; Chain, B. M.; Katz, D. R. Reactiveoxygen species activate human peripheral blood dendritic cells.Free Radic. Biol. Med.26:232–238; 1999.

[228] Verhasselt, V.; Goldman, M.; Willems, F. Oxidative stress up-regulates IL-8 and TNF-a synthesis by human dendritic cells.Eur. J. Immunol.28:3886–3890; 1998.

[229] Fabbri, M.; Bianchi, E.; Fumagalli, L.; Pardi, R. Regulation oflymphocyte traffic by adhesion molecules.Inflamm. Res.48:239–246; 1999.

[230] Su, B.; Jacinto, E.; Masahiko, H.; Tuula, K.; Michael, K.; Yinon,B. N. JNK is involved in signal integration during costimulationof T lymphocytes.Cell 77:727–736; 1994.

[231] Slater, A. F. G.; Nobel, C. S. I.; Maellaro, E.; Bustamant, J.;Kimland, M.; Orrenius, S. Nitrone spin traps and a nitroxideantioxidant inhibit a common pathway of thymocyte apoptosis.Biochem. J.306:771–778; 1995.

[232] Staal, F. J. T.; Anderson, M. T.; Staal, G. E. J.; Herzenberg,L. A.; Gitler, C.; Herzenberg, L. A. Redox regulation of signaltransduction: tyrosine phosphorylation and calcium influx.Proc.Natl. Acad. Sci. USA91:3619–3622; 1994.

[233] Schulze-Osthoff, K.; Los, M.; Baeuerle, P. A. Redox signallingby transcription factors NF-kappa-B and AP-1 in lymphocytes.Biochem. Pharmacol.50:735–741; 1995.

[234] Davis, M. M.; Bjorkman, P. J. T-Cell antigen receptor genes andT-cell recognition.Nature334:395–402; 1988.

[235] Marchalonis, J. J.; Schluter, S. F.; Edmundson, A. B. The T-cell

351Redox modulated pathways

receptor as immunoglobulin: paradigm regained.Proc. Soc. Exp.Biol. Med.216:303–318; 1997.

[236] Los, M.; Schenk, H.; Hexel, K.; Baeuerle, P. A.; Droege, W.;Schulze-Osthoff, K. IL-2 gene expression and NF-kappa B ac-tivation through CD28 requires reactive oxygen production by5-lipoxygenase.EMBO J.14:3731–3740; 1995.

[237] Pani, G.; Colavitti, R.; Borrello, S.; Galeotti, T. Endogenousoxygen radicals modulate protein tyrosine phosphorylation andJNK-1 activation in lectin-stimulated thymocytes.Biochem. J.347:173–181; 2000.

[238] Fuhlbrigge, R. C.; Kieffer, J. D.; Armerding, D.; Kupper, T. S.Cutaneous lymphocyte antigen is a specialized form of PSGL-1expressed on skin-homing T cells.Nature389:978–981; 1997.

[239] Santamaria Babi, L. F.; Perez Soler, M. T.; Hauser, C.; Blaser,K. Skin-homing T cells in human cutaneous allergic inflamma-tion. Immunol. Res.14:317–324; 1995.

[240] Podda, M.; Beschmann, H. A.; von Andrian, U. H.; Kaufmann,R.; Zollner, T. M. Peroxynitrite induces the expression of cuta-neous lymphocytes associated antigen (CLA) via alpha (1,3)-fucosyltransferase-7 on human T-cells.J. Invest. Dermatol. Inpress; 2000.

[241] Zollner, T. M.; Diehl, S.; Kaufman, R.; Podda, M. Antioxidantsblock the expression and functional activity of the skin-selectivehoming receptor cutaneous lymphocyte-associated antigen.J. Invest. Dermatol.110:476; 1998.

[242] Viola, J. P. B.; Rao, A. Molecular regulation of cytokine geneexpression during the immune response.J. Clin. Immunol.19:98–108; 1999.

[243] Umetsu, D. T.; Dekruyff, R. H. Th1 and Th2 CD41 cells in thepathogenesis of allergic diseases.Proc. Soc. Exp. Biol. Med.215:11–20; 1997.

[244] Singh, V. K.; Mehrotra, S.; Agarwal, S. S. The paradigm of Th1and Th2 cytokines: its relevance to autoimmunity and allergy.Immunol. Res.20:147–161; 1999.

[245] Xu, H.; DiIulio, N. A.; Fairchild, R. L. T cell populations primedby hapten sensitization in contact sensitivity are distinguished bypolarized patterns of cytokine production: interferon gamma-producing (Tc1) effector CD81 T cells and interleukin (I1)4/I1-10-producing (Th2) negative regulatory CD41 T cells. J.Exp. Med.183:1001–1012; 1996.

[246] Yokozeki, H.; Ghoreishi, M.; Takagawa, S.; Takayama, K.;Takahiro, S.; Ichiro, K.; Kiyoshi, T.; Shizuo, A.; Kiyoshi, N.Signal transducer and activator of transcription 6 is essential inthe induction of contact hypersensitivity.J. Exp. Med.191:995–1004; 2000.

[247] Bour, H.; Peyron, E.; Gaucherand, M.; Garrigue, J. L.; Des-vignes, C.; Kaiserlian, D.; Revillard, J. P.; Nicolas, J. F. Majorhistocompatibility complex class I-restricted CD81 T cells andclass II-restricted CD41 T cells, respectively, mediate and reg-ulate contact sensitivity to dinitrofluorobenzene.Eur. J. Immu-nol. 25:3006–3010; 1995.

[248] Cavani, A.; Mei, D.; Guerra, E.; Corinti, S.; Giani, M.; Pirrotta,L.; Puddu, P.; Girolomoni, G. Patients with allergic contactdermatitis to nickel and nonallergic individuals display differentnickel-specific T cell responses. Evidence for the presence ofeffector CD81 and regulatory CD41 T cells.J. Invest. Derma-tol. 111:621–628; 1998.

[249] Moulon, C.; Wild, D.; Dormoy, A.; Weltzien, H. U. MHC-dependent and -independent activation of human nickel-specificCD81 cytotoxic T cells from allergic donors.J. Invest. Derma-tol. 111:360–366; 1998.

[250] Kalish, R. S.; Askenase, P. W. Molecular mechanisms of CD81T cell-mediated delayed hypersensitivity: implications for aller-gies, asthma, and autoimmunity.J. Allergy Clin. Immunol.103:192–199; 1999.

[251] Kondo, H.; Ichikawa, Y.; Imokawa, G. Percutaneous sensitiza-tion with allergens through barrier-disrupted skin elicits a Th2-dominant cytokine response.Eur. J. Immunol.28:769–779;1998.

[252] Wood, J. C.; Jackson, S. M.; Elias, P. M.; Grunfeld, C.; Fein-gold, K. R. Cutaneous barrier pertubation stimulates cytokine

production in the epidermis of mice.J. Clin. Invest.90:482–487;1992.

[253] Wood, L. C.; Elias, P.; Calhoun, C.; Tsai, J. C.; Grunfeld, C.;Feingold, K. R. Barrier disruption stimulates interleukin-1a ex-pression and release from a pre-formed pool in murine epider-mis. J. Invest. Dermatol.106:397–403; 1996.

[254] Nickoloff, B. J.; Naidu, Y. Perturbation of epidermal barrierfunction correlates with initiation of cytokine cascade in humanskin. J. Am. Acad. Dermatol.30:535–546; 1994.

[255] Asselin, S.; Breban, M.; Fradelizi, D. Action of cytokines IL-12and IL-4 on T helper cells. Cellular immunity or humoral im-munity?Presse Med.26:278–283; 1997.

[256] Teraki, Y.; Picker, L. J. The regulation of skin homing (cutane-ous lymphocyte associated antigen: CLA) T helper 1 and Thelper 2 cells.J. Invest. Dermatol.108:641; 1997.

[257] Dearman, R. J.; Basketter, D. A.; Kimber, I. Characterization ofchemical allergens as a function of divergent cytokine secretionprofiles induced in mice.Toxicol. Appl. Pharmacol.138:308–316; 1996.

[258] Bellinghausen, I.; Brand, U.; Enk, A. H.; Knop, J.; Saloga, J.Signals involved in the early TH1/TH2 polarization of an im-mune response depending on the type of antigen.J. Allergy Clin.Immunol.103:298–306; 1999.

[259] Steinbrink, K.; Sorg, C.; Macher, E. Low zone tolerance tocontact allergens in mice: a functional role for CD81 T helpertype 2 cells.J. Exp. Med.183:759–768; 1996.

[260] Peterson, J. D.; Herzenberg, L. A.; Vasquez, K.; Waltenbaugh,C. Glutathione levels in antigen-presenting cells modulate Th1versus Th2 response patterns.Proc. Natl. Acad. Sci. USA95:3071–3076; 1998.

[261] Kalish, R. S.; Johnson, K. L. Enrichment and function of uru-shiol (poison ivy) specific T-lymphocytes in lesions of allergiccontact dermatitis to urushiol.J. Immunol. 145:3706–3713;1990.

[262] Kalish, R. S. Pathogenesis of allergic contact dermatitis: role ofT cells. In: Kydonieus, A. F.; Wille, J. J., eds.Biochemicalmodulations of skin reactions. Boca Raton, FL: CRC Press;2000:145–156.

[263] Marchal, G.; Seman, M.; Milon, G.; Truffa-Bachi, P.; Zilberfarb,V. Local adoptive transfer of skin delayed-type hypersensitivityinitiated by a single T lymphocyte.J. Immunol.129:954–958;1982.

[264] Bianchi, A. T.; Hooijkaas, H.; Benner, R.; Tees, R.; Nordin,A. A.; Schreier, M. H. Clones of helper T cells mediate antigen-specific, H-2-restricted DTH.Nature290:62–63; 1981.

[265] Benichou, G.; Kanellopoulos, J. M.; Mitenne, F.; Galanaud, P.;Leca, G. T-cell chemiluminescence. A novel aspect of T-cellmembrane activation studied with a Jurkat tumour cell line.Scand. J. Immunol.30:265–269; 1989.

[266] Hou, S.; Hyland, L.; Ryan, K. W.; Portner, A.; Doherty, P. C.Virus specific CD81 T-cll memory determined by clonal burstsize.Nature369:652–654; 1994.

[267] Elegbede, J. A.; Pompillus, M.; Schell, K.; Oberley, T. D.;Verma, A. K. Okadaic acid-induced apoptosis in mouse kera-tinocytes is acompanied by the production of reactive oxygenspecies and release of tumor necrosis factor alpha.Proc. Am.Assoc. Cancer Res.40:223; 1999.

[268] Stewart, M. S.; Spallholz, J. E.; Neldner, K. H.; Pence, B. C.Selenium compounds have disparate abilities to impose oxida-tive stress and induce apoptosis.Free Radic. Biol. Med.26:42–48; 1999.

[269] Fumelli, C.; Marconi, A.; Giannetti, A.; Pincelli, C. The free-radical scavengers carboxyfullerenes protect human keratino-cytes from UVB-induced apoptosis.J. Invest. Dermatol.114:853; 2000.

[270] Schwarz, T. No eczema without keratinocyte death.J. Clin.Invest.106:9–10; 2000.

[271] Trautmann, A. T-cell mediated Fas induced keratinocyte apo-ptosis plays a key pathogenetic role in eczematous dermatitis.J. Clin. Invest.106:25–35; 2000.

[272] Lo, S. K.; Janakidevi, K.; Lai, L.; Malik, A. B. Hydrogen

352 J. FUCHS et al.

peroxide-induced increase in endothelial adhesiveness is depen-dent on ICAM-1 activation.Am. J. Physiol.264:L406–L412;1993.

[273] Rattan, V.; Sultana, C.; Shen, Y.; Kalra, V. K. Oxidant stress-induced transendothelial migration of monocytes is linked to phos-phorylation of PECAM-1.Am. J. Physiol.273:E453–E461; 1997.

[274] Johnson, J. L.; Moore, E. E.; Tamura, D. Y.; Zallen, G.; Biffl,W. L.; Silliman, C. C. Interleukin-6 augments neutrophil cyto-toxic potential via selective enhancement of elastase release.J. Surg. Res.76:91–94; 1998.

[275] Vondracek, J. Effects of recombinant rat tumor necrosis factor-alpha and interferon-gamma on the respiratory burst of rat poly-morphonuclear leukocytes in whole blood.Folia Biol. (Praha)43:115–121; 1997.

[276] Belenky, S. N.; Robbins, R. A.; Rennard, S. I.; Gossman, G. L.;Nelson, K. J.; Rubinstein, I. Inhibitors of nitric oxide synthaseattenuate human neutrophil chemotaxis in vitro.J. Lab. Clin.Med.122:388–394; 1993.

[277] Su, Z.; Ishida, H.; Fukuyama, N.; Todorov, R.; Genka, C.;Nakazawa, H. Peroxynitrite is not a major mediator of endothe-lial cell injury by activated neutrophils in vitro.Cardiovasc. Res.39:485–491; 1998.

[278] Yan, L.; Vandivier, R. W.; Suffredini, A. F.; Danner, R. L.Human polymorphonuclear leukocytes lack detectable nitric ox-ide synthase activity.J. Immunol.153:1825–1834; 1994.

[279] Goode, H. F.; Webster, N. R.; Howdle, P. R.; Walker, B. E.Nitric oxide production by human peripheral blood polymorpho-nuclear leucocytes.Clin. Sci. (Colch.)86:411–415; 1994.

[280] Elsner, J.; Kapp, A. Activation and modulation of eosinophils bychemokines.Allergologie23:59–72; 2000.

[281] Elsner, J.; Kapp, A. Activation of human eosinophils by chemo-kines. In: Marone, G., ed.Human eosinophils: Biologic andclinical aspects (Chemical immunology). Basel, Switzerland:Karger; 2000:177–207.

[282] Schroder, J. M.; Mochizuki, M. The role of chemokines in cutane-ous allergic inflammation.Biol. Chem.380:889–896; 1999.

[283] Litchfield, T. M.; Smith, C. H.; Atkinson, B. A.; Norris, P. G.;Elliott, P.; Haskard, T. H. Eosinophil infiltration into human skinis antigen-dependent in the late-phase reaction.Br. J. Dermatol.134:997–1004; 1996.

[284] Nathan, C. F.; Murray, H. W.; Cohn, Z. A. The macrophage asan effector cell.N. Engl. J. Med.303:622–626; 1980.

[285] Gemsa, D.; Leser, H. G.; Seitz, M.; Debatin, M.; Ba¨rlin, E.;Deimann, W.; Kramer, W. Cells in inflammation. The role ofmacrophages in inflammation.Agents Action (Suppl)11:93–114;1982.

[286] Rittner, H. L.; Kaiser, M.; Brack, A.; Szweda, L. I.; Goronzy,J. J.; Weyand, C. M. Tissue-destructive macrophages in giantcell arteritis.Circ. Res.84:1050–1058; 1999.

[287] Nakagawara, A.; Nathan, C. F.; Cohn, Z. A. Hydrogen peroxidemetabolism in human monocytes during differentiation in-vitro.J. Clin. Invest.68:1243–1252; 1981.

[288] Roshdy, I.; German Patent DE 3,522,572, February 1987.[289] Nagy, C. F.; Quick, T. W.; Shaapiro, S. S. US Patent 5,252,604,

October, 1993.[290] Duffy, J. US Patent 5,516,793, May, 1996.[291] Hall, B. J.; Baur, J. A.; Deckner, G. E. US Patent 5,545,407,

August, 1996.[292] Pasche-Koo, F.; Arechalde, A.; Arrighi, J. F.; Hauser, C. Effect

of N-acetylcysteine, an inhibitor of tumor necrosis factor, onirritant contact dermatitis in the human. In: Elsner, P.; Maibach,H. I., eds.Irritant dermatitis. Freiburg, Germany: Karger; 1995:198–206.

[293] Fuchs, J.; Packer, L. Antioxidant protection from solar-simu-lated radiation induced suppression of contact hypersensitivity tothe recall antigen nickel sulfate in human skin.Free Radic. Biol.Med.27:422–427; 1999.

[294] Memon, A. A.; Molokhia, M. M.; Friedmann, P. S. The inhib-itory effects of topical chelating agents and antioxidants onnickel-induced hypersensitivity reactions.J. Am. Acad. Derma-tol. 30:560–565; 1994.

353Redox modulated pathways