Embed Size (px)
Citation preview
REVIEW
New Perspectives for Mucolytic, Anti-inflammatoryand Adjunctive Therapy with 1,8-Cineole in COPDand Asthma: Review on the New TherapeuticApproach
Lisa Joy Juergens . Heinrich Worth . Uwe R. Juergens
Received: January 8, 2020 / Published online: March 21, 2020� The Author(s) 2020
ABSTRACT
The mucolytic monoterpene 1,8-cineole (euca-lyptol), the major constituent of eucalyptusspecies, is well known for its anti-inflammatory,antioxidant, bronchodilatory, antiviral andantimicrobial effects. The main protectiveantiviral, anti-inflammatory and mucolyticmechanisms of 1,8-cineole are the induction ofinterferon regulatory factor 3 (IRF3), the controlof nuclear factor kappa-light-chain-enhancer ofactivated B cells (NF-jB) along with decreasingmucin genes (MUC2, MUC19). In normalhuman monocytes direct inhibition was shownof reactive oxygen species (ROS)-mediatedmucus hypersecretion and of steroid resistenceinducing superoxides (O2
�-) and pro-inflamma-tory hydrogen peroxides (H2O2) with partial
control of superoxide dismutase (SOD), whichenzymatically metabolizes O2
�- into H2O2. Byinhibition of NF-jB, 1,8-cineole, at relevantplasma concentrations (1.5 lg/ml), strongly andsignificantly inhibited in normal humanmonocyte lipopolysaccharide (LPS)-stimulatedcytokines relevant for exacerbation (tumournecrosis factor alpha (TNFa), interleukin (IL)-1band systemic inflammation (IL-6, IL-8). Infec-tious agents and environmental noxa haveaccess via TNFa and IL-1b to the immune sys-tem with induction of bronchitis complaintsand exacerbations of chronic obstructive pul-monary disease (COPD), asthma and asthma–-COPD overlap. In lymphocytes from healthyhuman donors 1,8-cineole inhibited TNFa, IL-1b, IL-4 and IL-5 and demonstrated for the firsttime control of Th1/2-type inflammation. 1,8-Cineole at relevant plasma levels increasedadditively in vitro the efficacy of inhaledguideline medications of budesonide (BUD) andbudesonide ? formoterol ,and preliminary dataalso showed increased efficacy of long-actingmuscarinic receptor antagonist (LAMA)-medi-ated cytokine inhibition in vitro. On the basis ofthe preclinical data, earlier randomised con-trolled studies with adjunctive therapy of 1,8-cineole (3 9 200 mg/day) for 6 months showedimprovement of uncontrolled asthma by sig-nificant improvement of lung function, noc-turnal asthma and quality of life scores and inCOPD decrease of exacerbations (- 38.5%)(during wintertime). This review reports an
Digital Features To view digital features for this articlego to https://doi.org/10.6084/m9.figshare.11876436.
U. R. Juergens (&)Department of Pulmonary Rehabilitation, AsklepiosNordseeklinik Westerland, Norderstraße 81, 25980Sylt, Germanye-mail: [email protected];[email protected]
L. J. JuergensMedical University of Tubingen, Medical School,72070 Tubingen, Germanye-mail: [email protected]
H. WorthSpecialist Forum Furth, 90762 Furth, Germany
Adv Ther (2020) 37:1737–1753
https://doi.org/10.1007/s12325-020-01279-0
update with reference to the literature of 1,8-cineole, also as adjunctive therapy, as a thera-peutic agent for the protection and control ofinflammatory airway diseases.
Keywords: Asthma; Chronic obstructivepulmonary disease (COPD); Mucolytics;Sinusitis; 1,8-Cineole
Key Summary Points
This new review focuses on the currentstatus of the monoterpene 1,8-cineole tosuggest therapy and adjunctive therapywith 1,8-cineole for inflammatory airwaydiseases.
It is the first review of the current status ofthe known pathogenetic mechanisms ofinflammatory airway diseases to discuss,in comparison to current guidelinerecommendations for asthma and COPD,the underlying mechanisms of action andclinical benefits of recommendedmedications compared to 1,8-cineolealone and as adjunctive therapy for thetreatment of COPD, asthma and sinusitis.
Therefore, this is the first review to reporton the potential advances in therapy with1,8-cineole.
INTRODUCTION
The monoterpene 1,8-cineole (eucalyptol) ischemicallya terpenoidoxide that iswell knownasthe major constituent (77–84%) of various euca-lyptus species and also the component of otheressential oils with a relevant meaning for clinicaleffect. Eucalyptus oil is well known for its biolog-ical activities, including anti-inflammatory,antioxidant, free radical scavenging, mucolytic/secretolytic, bronchodilatory, antiviral andantimicrobial effects, as reviewed elsewhere [1].These effectswill be of relevance for the treatment
of airway diseases in addition to having antifun-gal, antiseptic, antispasmodic, analgetic andantitumour properties. Essential oils may vary intheir plant concentrations depending on variousregional influences, such as agroclimatic condi-tions [2]; however, 1,8-cineole can be madeavailable in a standardized form for clinical usefollowing extraction from eucalyptus oil.
A further review evaluated the potentialbiological effects of 1,8-cineole on the mostpromising targets in the treatment of chronicobstructive pulmonary disease (COPD) in ani-mal experimental models [3]. In this report, 1,8-cineole interacted with relevant mediators ofpathophysiological pathways of COPD andidentified receivers and membrane channels,oxidative stress, transcription molecules andexpression of cytokines, cell adhesion mole-cules and neutrophil chemotaxis, pro-inflam-matory cells, proteases and remodelling aspotential therapeutic targets. The authors con-cluded from these findings that eucalyptol (1,8-cineole) showed a relevant additional treatmentoption to the use of anti-inflammatory drugs inasthma and COPD.
Former and current conventional treatmentshave long been geared toward relieving symp-toms, preventing recurrent exacerbations, pre-serving optimal lung function and enhancingthe overall quality of life [4]. Because asthmaand COPD are chronic inflammatory diseases, itis essential to determine whether new approa-ches with anti-inflammatory and antioxidantagents can halt or slow the decline in lungfunction that occurs in response to the diseasewhen selecting candidate drugs. In this regard,the consensus of a group of Chinese pulmonaryphysicians [5] and a collaborative task forcebetween the European Respiratory Society andthe American Thoracic Society (ERS/ATS guide-lines) [6] was focused on the prevention ofexcerbations in COPD by mucolytics, macro-lides, long-acting muscarinic receptor antago-nists (LAMAs)/long-acting b2-agonists (LABAs)in stable COPD and the phosphodiesterase(PDE)-IV inhibitor roflumilast in COPD withassociated bronchitis. Selected thresholds by thetask force for clinically important differencesincluded relative risk reductions of mortality(15%), exacerbations (20%), adverse events
1738 Adv Ther (2020) 37:1737–1753
(15%) and a four-point reduction on theSt. George’s Respiratory Questionnaire (SGRQ)with complete medications for COPD to deter-mine the add-on effect. A review and six ran-domized studies of at least 1 year with N-acetylcysteine (NAC), carbocysteine andambroxol in patients with COPD (forced expi-ratory volume in 1 s (FEV1) 30–79%), with atleast two exacerbations per year during theprevious 2 years, were evaluated. Hospitaliza-tions and COPD exacerbations were reduced(rate ratio 0.79) with a stronger effect of high-dose (e.g. NAC 600 mg twice daily) mucolytictherapy (rate ratio 0.69, 95% CI 0.50–0.94),compared to low-dose mucolytic therapy withno significant reduction (rate ratio 0.87, 95% CI0.66–1.14) and no increase of adverse effects.
This article is based on previously conductedstudies and does not contain any studies withhuman participants or animals performed byany of the authors. It is the first review to reporton the current knowledge of the known muco-lytic agent 1,8-cineole (eucalyptol) with regardto its anti-inflammatory, antioxidant andantimicrobial activities for the treatment ofinflammatory airway diseases. In particular, theimportance of 1,8-cineole as adjunctive therapyto control systemic inflammation and to inter-act with guideline medications for COPD andasthma by its exhaled availability via theperipheral airways will be discussed.
APPROVED EFFICACY OF 1,8-CINEOLE IN RANDOMIZED,PLACEBO-CONTROLLED TRIALS
Chronic rhinosinusitis is a well-known riskfactor (hazard ratio 3.7) for 30-day readmissiondue to frequent exacerbations of asthma andCOPD and outpatient management of theupper and lower airways is recommended [7, 8].
The highest odds ratios (OR) for exacerbatedasthma were reported for symptoms of chronicbronchitis (2.70) and sinusitis (1.5) besidesother comorbidities. In perennial allergicrhinitis with seasonal exacerbations (PARSEstudy), symptoms of rhinitis were reportedlyworse in difficult-to-control vs. easy-to-controlasthma, and seasonal patterns also partially
corresponded to those of difficult-to-controlasthma [9]. The first placebo-controlled studywith 1,8-cineole (two 100 mg capsules threetimes daily for 7 days) in acute non-purulentsinusitis showed significant reduction of themean symptoms sum-score after 4 and 7 daysand amelioration of headache of secondary endpoints [10]. The effect of 1,8-cineole on con-trolling mucus hypersecretion was studied in amodel of experimental rhinosinusitis onlipopolysaccharide (LPS)-stimulated nasal slicecultures ex vivo and showed for the first timesignificant decrease in the number of mucin-filled goblet cells with reduction of the mucingenes MUC2 and MUC19 in association withsignificantly attenuated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-jB) activity [11]. Since the common cold isknown as the most frequent reason for virus-exacerbated upper and lower inflammatory air-way diseases, such as acute and chronic rhi-nosinusitis in the context of frequentexacerbations of COPD and asthma, the samegroup also found that 1,8-cineole inducedactivity of the antiviral transcription factorinterferon regulatory factor 3 (IRF3) in thepresence of its inhibitory effect on pro-inflam-matory NF-jB signalling [12].
At this stage of our knowledge, seasonal orpermanent daily adjunctive therapy with 1,8-cineole for the protection of exacerbated airwaydisease of the upper and lower airways is to berecommended, especially in the presence ofincreased risks of sinusitis with existing asthma,asthma–COPD overlap and COPD.
In the first preliminary placebo-controlledstudy in severe steroid-dependent asthma (n =32), following a run-in phase of 2 months todetermine the minimal effective dose of dailyprednisolone, patients were randomly allocatedto receive either 1,8-cineole (3 9 200 mg/day)(Soledum� forte capsules, registered in variousEuropean countries, also available as Soledumaddicur capsules registered in Germany since1 November 2019), or placebo, while dailyprednisolone was reduced by 2.5 mg every3 weeks [13]. Results showed for the first timesignificant prednisolone reduction of 36% withactive treatment (range 2.5–10 mg, mean 3.75)vs. a decrease of only 7% (2.5–5 mg, mean
Adv Ther (2020) 37:1737–1753 1739
0.91 mg) in the placebo group. These resultssuggested a prednisolone equivalent potency of1,8-cineole 600 mg of around 2.8 mg that waswell tolerated following steroid reduction. In afirst double-blind, placebo-controlled multi-centre study of patients (n = 247) with well-controlled asthma (FEV1 82%) on inhaledmedication guidelines, the effects of adjunctivetherapy with 1,8-cineole (3 9 200 mg/day) onimprovement of lung function and AsthmaQuality of Life Questionnaire (AQLQ) werestudied for 6 months [14]. FEV1 increased sig-nificantly in the cineole group (310 ml) com-pared to the placebo group (200 ml), and alsosome scores of nightly asthma and AQLQimproved significantly. Caution is advised inasthmatics with severe perfume incompatibilitysince 1,8-cineole is exhaled.
A randomized study in acute bronchitis (n =242) with 1,8-cineole over 10 days showed sig-nificant improvements after 4 days of thebronchitis severity-sum score compared to pla-cebo [15]. Concomitant therapy with 1,8-cine-ole (two capsules of 100 mg three times daily)was also studied in a placebo-controlled study(n = 242) in COPD (Global Initiative for ChronicObstructive Lung Disease (GOLD) II–III) with aprimary outcome of reduction of exacerbations,and a secondary outcome of changes in lungfunction, respiratory symptoms and quality oflife scores during 6 months [16]. Basic medica-tion consisted of LABA, inhaled corticosteroids(ICS), anticholinergics and theophylline. Allpatients were current smokers or ex-smokerswith at least 10 pack-years. In the group treatedwith 1,8-cineole, the number of exacerbationswas significantly (p\0.036) reduced by 38.5%,as were the severity and duration, FEV1increased by 78 ml in the range of clinical sig-nificance and the improvement in SGRQ scoresalmost reached significance (p = 0.063). Resultsof this first controlled study in COPD suggestnew evidence of the superior therapeutic effi-cacy of adjunctive therapy with 1,8-cineole tocontrol COPD exacerbations compared tocombined inhaled therapies with LABA ? ICSalone.
According to the German Guideline forCOPD [17], 1,8-cineole is recommended inaddition to other mucolytics for its expectorant
activity in dyscrinemic mucus. The guidelinealso recommends that substances with anti-in-flammatory and antioxidant effects can be usedto reduce exacerbations in patients with COPDand frequent exacerbations and points out that1,8-cineole has been shown to significantlyreduce exacerbations in patients with COPDand frequent exacerbations.
ANTI-INFLAMMATORY PROFILEAND MODE OF ACTION OF 1,8-CINEOLE
Inflammation is well known as a protectiveresponse to airway injury due to infections andvarious inhaled agents and to induce airwayrepair by the activation of many pathways, withthe release of multiple inflammatory mediatorsthat may often be excessive to induce chronicairway inflammation [18] characteristic ofCOPD, asthma and sinusitis. The acute andoften chronic persisting clinical symptoms areairway hypersecretion and breathing symptomsthat are caused by various mediators, such asmatrix metalloproteinases (MMP-9), vascularcell adhesion molecules (VCAM-1), cyclooxy-genase-2 (COX-2), cytosolic phospholipase A2
(cPLA2) and LPS [19]. Various pro-inflammatorystimuli such as reactive oxygen species (ROS)from cigarette smoke [20], airway infections andinflammatory processes are linked withincreased release of cytokines/chemokines (tu-mour necrosis factor alpha (TNFa), interleukin(IL)-1b, IL-6, IL-8). These cytokines, as clinicalmarkers of increased mucus production, exac-erbations and steroid resistance, induce NF-jB[21], which is also produced by activation of NF-jB in response to oxidative stress [22]. Theseprocesses promote induction of airway hyper-responsiveness and the expression of inflam-matory genes with relevance in airway diseases.Beyond these interactions, overprotectionagainst ROS by cytokine-induced excessivestimulation or mitochondrial activation and ofthe nicotinamide adenine dinucleotide phos-phate (NADPH oxidase) system in phagocytes isimportant for bacterial killing. In this regard, itis of interest that current guidelines for inhaled
1740 Adv Ther (2020) 37:1737–1753
therapies do not directly control ROSproduction.
Original articles on natural products andreviews on plant species of different herbs con-taining the monoterpene 1,8-cineole besidesother terpenes report on the anti-inflammatoryand antioxidant activities in various models[23–25]. Pro-inflammatory cytokines, such asTNFa, IL-1b, IL-6, IL-8, and COX-2, are knownto be expressed following the dissociation of theinhibitory protein kappa-light-chain-enhancerof activated B cells (Ijba) from the NF-jB sub-units p65 and its translocation from the cyto-plasm to the nucleus, which is controlled byvarious essential oils and their major com-pounds as promising agents for the treatment ofchronic inflammation [26, 27]. The central,anti-inflammatory mechanism of action of 1,8-cineole and potentially various other terpenes isthe induction of Ijba and the prevention of NF-jB translocation with the consequent control ofpro-inflammatory mediator production [28]. Inaddition, in an animal model of LPS-inducedpulmonary inflammation, 1,8-cineole increasedthe anti-inflammatory cytokine IL-10 in lungtissues besides inhibiting TNFa, IL-1b andreducing expression of NF-kB’s subunit p65[29]. Therefore, preventing NF-jB nucleartranslocation is recommended as the potentialtherapeutic target of the antioxidant and anti-inflammatory monoterpene 1,8-cineole. Thereis further evidence that 1,8-cineole also acts asan analgesic and anti-inflammatory agent bystimulating the thermosensitive, cool tempera-ture-detecting transient receptor (TRP) cationchannels (TRPM8) and by inhibiting the humantransient receptor potential cation channel,subfamily A, member 1 (TRPA1), a known sen-sor of noxious cold [30].
The anti-inflammatory activity of 1,8-ci-neole was studied in various preclinical stud-ies using in vitro and ex vivo models fromnormal human subjects and in patients withasthma and in animal models. We reportedfor the first time in healthy subjects and inpatients with asthma the inhibition ofarachidonic metabolism of leukotriene B4
(LTB4) and prostaglandin E2 (PGE2) of ex vivocultured monocytes as the first hint of theanti-inflammatory mode of action of 1,8-
cineole (Soledum� forte capsules) taken orallyfor 4 days, with a regression 4 days aftercompletion of therapy [31]. These results alsoshowed for the first time a relevant systemicanti-inflammatory effect of 1,8-cineole afteroral ingestion of 3 9 200 mg/day of Soledum�
forte capsules for 4 days. Early in vitro studiesfurther reported that 1,8-cineole decreased(by more than 60%) the production of TNFa,IL-1b, IL-6 and IL-8 in monocytes [32] and ofTNFa, IL-1b, IL-4 and IL-5 in lymphocytes[32] from healthy human donors and controlsTh2-type inflammation and Th1/Th2 balance,which is now controlled downstream ineosinophilic asthma by IL-5 inhibitors andreceptor antagonists [33]. In these studies,1,8-cineole showed for the first time a steroid-like inhibitory effect on stimulated cellsin vitro at the relevant concentration of10-5 M (1.5 lg/ml) equivalent to the plasmalevel after taking 3 9 200 mg of 1,8-cineolefor 14 days [34] [Pidgeon AW. Expert reporton the pharmacokinetics (phase I) of cineole.1993 (not published)]. This should be takeninto account regarding several animal studiesusing much higher concentrations in relationto body weight. Furthermore, a previousstudy evaluated that around 20% of orallytaken 1,8-cineole reaches the peripheral air-ways and is then exhaled [35]. Besides theknown systemic anti-inflammatory effects inthe blood as a volatile organic compound,1,8-cineole also reaches the peripheral lung,which is not possible by currently availableinhaled therapies for asthma and COPD.When 1,8-cineole is exhaled it also reachesthe paranasal sinuses, which can benefit onlyto a limited extent from low blood circulationof orally administered medications. In arecent study on a house dust mite (HDM)-stimulated in vitro model of bronchialepithelial cells and an HDM-induced murineasthma model of inhaled 1,8-cineole, Der-matophagoides pteronyssinus stimulated IL-8,IL-6, granulocyte macrophage-colony stimu-lating factor (GM-CSF) and induced airwayhyper-responsiveness (AHR). In this approach,the numbers of eosinophils in bronchoalveo-lar lavage fluid (BAL) and of IL-4, IL-13 andIL-17A were significantly reduced by 1,8-
Adv Ther (2020) 37:1737–1753 1741
cineole [36]. A recent study that investigatedBAL cytokine profiles in healthy subjectscompared to those in controlled and uncon-trolled asthma showed increased productionof various cytokines (IL-1b, IL-5, IL-6, IL-8etc.) and of eosinophils and granulocytes inpatients with asthma as compared to patientswithout asthma, whereas non-controlledasthma was distinguished from controlledasthma only by neutrophil percentage and IL-8 levels, which correlated with FEV1 [37]. Ineosinophils, high asthma levels of IL-5, IL-13,IL-16 etc. were higher in the presence of thesame neutrophil percentage, IL-8 and ofFEV1, indicating the role of neutrophils andIL-8 in uncontrolled asthma with inversecorrelation to lung function [38]. In smokerswith COPD and preserved spirometry (post-bronchodilator FEV1/forced vital capacity(FVC)[ 0.70), systemic inflammatory markersof IL-6-induced C-reactive protein (CRP) wereassociated with a greater number of exacer-bations and increased symptom burden(CAT), while increased TNFa correlated withan elevated CAT score and CRP and werenegatively correlated with 6-min walkingdistance (6MWD) [39]. These data underlineagain the important correlation, even in earlystages COPD, of TNFa and IL-6 (CRP), asmarkers of systemic inflammation, for theprogressive symptomatic burden of theCOPD.
In this regard a recently published in vitrostudy of cultured human monocytes from nor-mal, non-smoking subjects showed, at relevantsystemic concentrations of 1,8-cineole(0.15–1.5 lM), dose-dependent inhibition of IL6[IL1b[IL-8 C TNFa, with complete inhibitionat therapeutic concentration (1.5 lM) and par-tial inhibition (20–40%) of IL-1b and IL-6 at theexhaled concentration (0.3 lM) [40]. These datashowed for the first time dose-dependent anti-inflammatory activities of 1,8-cineole at clini-cally relevant systemic and also exhaled con-centrations, since in LPS-stimulated culturedhuman monocytes 1,8-cineole demonstratedthe strongest inhibitory effect of 100% on IL-6at the lowest and almost half the plasma con-centration (0.6 lM) [40].
A new study reports the importance ofepithelial IL-6 trans-signalling, in the absence ofsystemic inflammation, as a new asthma phe-notype with frequent exacerbations, bloodeosinophilia and increased airway inflamma-tion with infiltration of T cells and macro-phages [41].
In summary, this current knowledge repor-ted 1,8-cineole as a Th1/Th2 cytokineimmunomodulator by its anti-inflammatoryand antioxidant activities to control systemicinflammation, disease progression, the rate ofexacerbations, steroid resistance and potentiallyprotective effects against increasing develop-ment of lung emphysema in inflammatory air-way diseases. So far, the current state ofknowledge suggests that not only as a mucoly-tic/secretolytic drug but also by its multifunc-tional mechanisms 1,8-cineole controls thecause of mucus production with a peripheraland systemic availability as compared toinhaled medications, suggesting the adjunctivetherapy with 1,8-cineole for COPD, asthma andsinusitis [42] (Fig. 1).
Fig. 1 Various inhalable pollutants as well as viruses andbacteria induce or intensify pre-existing airway inflamma-tion. The result is the release of oxygen radicals andinflammatory mediators, which cause bronchitis withhypersecretion and acute respiratory distress, dependingon the type of inflammation and genetic determinism. As aresult of the at least bifunctional anti-inflammatory andantioxidant efficacy profile of 1,8-cineole, this is not only asymptomatic but also a causative therapy for the treatmentof bronchial complaints. Through this approach, mucushypersecretion and recurrent exacerbations are directlycontrolled with the aim to reduce the progression ofchronic respiratory diseases
1742 Adv Ther (2020) 37:1737–1753
ANTIOXIDANT ACTIVITY OF 1,8-CINEOLE AND CONTROLOF REDOX BALANCEFOR ADJUNCTIVE THERAPYIN COPD AND ASTHMA
Oxidative stress and oxidant/antioxidant, pro-tease/antiprotease imbalance have a majorimpact on the severity of symptoms and diseaseprogression [43]. Oxidative stress is caused byvarious ROS, in particular by O2
�- from cigarettesmoke or by the degree of pulmonary and sys-temic inflammation responses as produced bymacrophages and neutrophils [44]. O2
�- is fur-ther metabolized by superoxide dismutases(SOD) to H2O2, with a further breakdown bycatalases [45]. Since H2O2 is also inhaled withcigarette smoke and is increased when exhaled,control of H2O2 would be desirable in COPD[46], which promotes inflammatory airwayresponses by the initiation of cytokine produc-tion. Furthermore, a controlled clinical study(n = 182) reported decreased levels of ascorbicacid in smokers and a considerable recovery by25% after 4 weeks of smoking cessation [47]. Acompleted European survey (n = 680) followedthe effect of dietary antioxidants for 10 years onlung function according to documented foodand vitamin intake and smoking status, andreports improvements in lung function decline(FEV1 - 3.7 ml/year; FVC - 4.5 ml/year), par-ticularly in ex-smokers [48]. Since current stan-dard guideline medications of LABA, ICS and ofLAMA only have at most very limited antioxi-dant effects, it would be of interest to explorethe potential antioxidant activity of themonoterpene 1,8-cineole for further potentialco-medication.
Recent in vitro studies on the antioxidantactivity of essential oils reported scavengingactivity against ROS [49], ROS effects onantioxidant enzymes (catalases, SOD, glu-tathione reductase (GR), heme oxygenase 1(HO1), glutathione peroxidase (GPx)) inducedby H2O2 [50], nitrogen oxide (NO) andmyeloperoxidase (MPO) production by H2O2-stimulated neutrophils [51]. One publicationshowed for the first time the antioxidant profileof 1,8-cineole, at relevant plasma
concentrations (B 1.5 lg/ml; 10-5 M) in foetalcalf serum (FCS)-stimulated normal humanmonocytes in vitro, with significant inhibitionof O2
�- (10-5 M: - 53%), SOD (concentrationindependent: - 28%) and of H2O2 (10-10 M:- 48%) [52] (Fig. 2). These data showed for thefirst time control of O2
�- production withoutcomplete inhibition, by virtue of necessaryantibacterial activity with only partial controlof SOD to allow the controlled metabolism ofO2
�- into pro-oxidant and pro-inflammatoryH2O2, which is also directly controlled at verylow concentrations of systemic and exhaledconcentrations of 1,8-cineole.
LPS-stimulated 8-isoprostane (8-Isop) as amarker of total antioxidant activity was dose-dependently (10-6 M: - 42%; 10-5 M: - 84%)inhibited [52]. This is of interest since exhaled8-Isop became known as an in vivo biomarker oflung oxidative stress in patients with COPD andhealthy smokers [53]. On the basis of theseresults, the most promising approach inrepeatedly exacerbated COPD or steroid-de-pendent asthma is reversal of corticosteroidresistance through increasing histone deacety-lase 2 (HDAC2) activity, where 1,8-cineoleshould be recognized as a more effective
Fig. 2 Cigarette smoke is rich in oxygen radicals thatinduce bronchial hypersecretion and, among other activ-ities, steroid resistance. Oxygen radicals (O2
�-) aredegraded via the activity of superoxide dismutases (SOD)to hydrogen peroxide (H2O2), which induces bronchialinflammation. In vitro studies of foetal calf serum-stimulated human monocytes showed modulating antiox-idant effects of therapeutically relevant concentrations of1,8-cineole with approximately 50% inhibition of O2
�-
and H2O2 and a partial inhibition in this approach ofSOD [52]
Adv Ther (2020) 37:1737–1753 1743
antioxidant with additional anti-inflammatoryactivities [54].
O2�- radicals are inhaled and released from
activated inflammatory cells during exacerba-tions as the most putative risk factors to stim-ulate bronchial hypersecretion andinflammatory airway responses in COPD andasthma, in addition to their pro-carcinogenicactivities. In moderate COPD (GOLD II, n = 23)the antioxidant capacity of the natural thiol-containing antioxidants GPx was reduced andin severe COPD (GOLD III, n = 56) the antioxi-dant lipid peroxidation product malondialde-hyde (MDA) was significantly higher than inmoderate COPD [55]. These results suggested anassociation between oxidative stress andobstructive lung impairment as a measure ofCOPD severity. An earlier controlled study inmice exposed to cigarette smoke (CS) for 5 daysreported for the first time that CS-induced acutelung inflammation of increased metallopro-tease 12, TNFa and NF-jB activation wasreduced by non-thiol compound supplementa-tion with the vitamins ascorbic acid and a-to-copherol [56]. In this regard, recent results froma mouse model of intermittent hypoxia, rele-vant for severe COPD, showed increased ROSproduction and elastase activity that could becontrolled by antioxidative L-glutathione andthe TNFa antagonist infliximab [57]. In variousin vitro and animal studies with essential oils1,8-cineole was reported as the main antioxi-dant compound [58, 59]. Short-term exposureto inhaled eucalyptol (3 mg, 10 mg for 5 days)in a mouse model decreased oxidative stress bythe inhibition of ROS, SOD, catalase and MDA,and showed anti-inflammatory efficacy by theinhibition of NF-kB’s p65 subunit and of IL-1b,IL-6 and of TNFa at the highest concentration of10 mg/day, suggesting relevant antioxidativeand anti-inflammatory activities [60]. In thisreport, 1,8-cineole promoted lung repair athigher doses with de novo formation of alveolias compared to the control group. In this study,lung regeneration by 1,8-cineole resulted in theupregulation of elastin, tissue inhibitor ofmatrix metalloproteinase (TIMP-1) and antiox-idant, anti-inflammatory protective effects bythe reduction of anti-inflammatory (MPO,TNFa, IL-1b, IL-6 etc.) and redox marker levels.
Using a similar design, a further study withinhaled concentrations of eucalyptus oil(10-300 mg/kg) also reports prevention of lunginjury [61]. A new review is focusing on theimportance of controlling various diseasemechanisms of oxidative stress in chronic res-piratory diseases (CRDs) including asthma,COPD, respiratory infections, and also lungcancer, which are not sufficiently controlled byavailable anti-inflammatory therapies, such asICS, LABAs, NF-jB inhibitors, mitogen-activatedprotein kinase p38 (MAPK p38) inhibitors andPDE-IV inhibitors with no effect on diseaseprogression in COPD [62]. Although ICS are thebasic medications for control of airway inflam-mation in asthma, glucocorticosteroids werenot effective in preventing oxidative stress-me-diated airway inflammation by steroid-relatedinterference with anti-inflammatory geneexpression and antioxidant enzymes [63].
To summarize, current knowledge on therole of a balanced ratio of oxidants andantioxidants, especially in the pathophysiologyof COPD and asthma, has suggested theimportance of effective antioxidant therapy ininflammatory airway diseases. Since standardtherapies with LABA ? ICS seem not to provideany antioxidant effects, compensation withadjunctive therapy with 1,8-cineole is an optionfor achieving relevant antioxidant effects ofstandard inhaled therapies for the lungs.
ANTIMICROBIAL AND ANTIVIRALEFFECTS OF 1,8-CINEOLEAND ESSENTIAL OILS
There is increasing knowledge on the role of therespiratory microbiome in lower and upper air-way disease, which may have an impact ondisease severity, in particular with the fre-quency of exacerbations and the underlyingdisease phenotype [64]. Changes to the airwaymicrobiome by external viral and bacterialinfections could potentially induce microbialdysbiosis with clinical relevance of interactionswith inflammatory airway-induced exacerba-tions [65]. In this regard long-term treatment incontrolled clinical studies with the antibioticand anti-inflammatory-acting azithromycin
1744 Adv Ther (2020) 37:1737–1753
showed improvement of exacerbations anddisease severity in severe COPD [66] by thedownregulation of various antigen-regulatinggenes and of inflammatory T cell responses invarious inflammatory pathways [67]. Also Glo-bal Initiative for Asthma (GINA) guidelinesrecommend the use of the antibiotic and anti-inflammatory azithromycin as co-medication(500 mg three times weekly) in Th1-typeinflammation for neutrophilic, uncontrolledasthma, with, however, no significant effect ontotal bacterial load [68]. 1,8-Cineole was alsoreported to protect against influenza viralinfections in mice and virus-induced pul-monary cytokine production of IL-1b, IL-6 andTNFa by the control of NF-kB p65 expression[28] and the induction of the antiviral tran-scription factor inteferon regulatory factor 3(IFR3) [12].
New research directly focusing on theantimicrobial activity of various eucalyptus oilswith the main component of 1,8-cineole,ranging from 66.93% to 97.3%, inhibited orkilled in vitro the majority of microorganisms[69]. Furthermore, both Eucalyptus globulusessential oil and 1,8-cineole prevented biofilmformation by methicillin-resistant Staphylococ-cus aureus (MRSA) and subsequently thespreading of nosocomial infection. A recentstudy reports genetic downregulation of biofilminduction in chronic rhinosinusitis by 1,8-ci-neole with inhibition of relevant microbialpathogens (S. aureus, Escherichia coli, Moraxellacatarrhalis) and pro-inflammatory NF-jB targetgenes at relevant concentrations [70]. This maybe of further relevance, since in another studythe microbiome profile was assessed by usingsequencing of the 16S rRNA gene for the follow-up of hospitalized patients with acute exacer-bated COPD (AECOPD) who did not survivewith higher Staphylococcus levels [71]. A formerstudy of the pharmacokinetics of inhaled 1,8-cineole in humans showed peak plasma con-centrations after 18 min, with a biphasic meandistribution of 6.7 min and an elimination half-life of 104.6 min [72]. Besides the oral route,application of 1,8-cineole by vapour inhalationhas been suggested for exacerbated purulentand non-purulent bronchitis, asthma andCOPD owing to its long history of usage and
good safety record [73]. In a recent compre-hensive in vitro study, the monoterpene 1,8-cineole was demonstrated as the major com-pound (up to 70.4%) of different eucalyptus oilsthat were investigated for the minimal inhibi-tion concentration (MIC) and the minimumbactericidal concentration (MBC) to kill 99.4%of bacterials after incubation for 18-24 h [74].In this study, eucalyptus species with a contentof 1,8-cineole of 42-70.4% showed antibacte-rial activities of 8.1-27.4% against Haemophilusinfluenzae, Klebsiella pneumoniae, Pseudomonasaeruginosa, S. aureus, Streptococcus agalactiae,Streptococcus pneumoniae and Streptococcus pyo-genes compared to various antibiotics(19.9-37.5%). Also antifungal and antiviralactivities were reported for these eucalyptusspecies, however with generally only a minimalchance for the development of resistance com-pared to antibiotics. Such data would be of greatinterest, since 16S ribosomal RNA genesequencing and host gene expression analysesby quantitative real-time PCR actually showedassociations between host gene expression andmicrobiota lung profiles by correlation of theseverity of COPD (GOLD III–IV) and potentiallythe course of the disease. In vitro studies on thesensitivity of microbes to various species ofeucalyptus oils with a major content of 1,8-ci-neole were reviewed [75]. In summary, currentdata suggest a clinical relevant antiviral andantibacterial activity of 1,8-cineole.
SUMMARY: AT LEASTBIFUNCTIONAL ACTIVITIES OF 1,8-CINEOLE TO IMPROVE COPDAND ASTHMA UNDER GUIDELINETHERAPIES
In a previous report 1,8-cineole was shown forthe first time to induce additively the anti-in-flammatory efficacy of ICS and of combinedinhaled therapies of LABA ? ICS in vitro at theapproximate airway concentrations of exhaled1,8-cineole [40]. Additionally, a recent publica-tion reports for the first time on the antioxidanteffects of 1,8-cineole with a highly superiorsuppression of O2
�- (- 53%) at a relevant
Adv Ther (2020) 37:1737–1753 1745
plasma concentration (10-5 M) as compared tothe strongest effects of budesonide (BUD)(10-9 M: - 10.5%) and formoterol (F) (10-10 M:- 10.8%) alone [52]. At increasing concentra-tions (10-8 M), weak inhibitory effects of BUDand F changed into significant small pro-ox-idative activities with at least no pro-oxidativeor antioxidative effects of therapeutically rele-vant combinations of BUD ? F. These resultsshowed that 1,8-cineole has at least two differ-ent pharmacological actions in the same mole-cule as a bifunctional drug besides itbronchodilatory, antimicrobial and otheractivities for the treatment of inflammatoryairway diseases.
Th1-type inflammation in high IL-17 phe-notype very often plays a key role in frequentlyexacerbating neutrophilic asthma and COPD[76], which is also controlled by 1,8-cineole inaddition to its control of Th2-type inflamma-tion [33]. In this regard, adjunctive pulse ther-apies with azithromycin (3 9 500 mg per week)[77] and clarithromycin (2 9 500 mg per week)[78] for 1 year are recommended only for theseantibiotics to control exacerbations besidesknown side effects (evidence A) by the currentTask Force Report of the GOLD ExecutiveSummary [4]. For other mucolytic (mucokinet-ics, mucoregulators) and antioxidant agents(NAC, carbocysteine), however, as a result of thepartial (IL-6) or missing anti-inflammatory (IL-1b, IL-8, TNFa) efficacy of NAC, the antioxi-dant/anti-inflammatory activity of NAC andcarbocysteine seemed to be relevant only inpatients not receiving ICS [79]. Evidence ofvitamin D supplementation was only reportedin patients with COPD and vitamin D defi-ciency (25-hydroxyvitamin D3\ 25 nmol) [80],and oxidative stress in severe asthma exacerba-tions was linked with vitamin D deficiency,increased release of ROS, TNFaNF-jB expression[81] and downregulated expression of gluco-corticoid receptors by H2O2. For this reason,owing to at least a bifunctional anti-inflamma-tory/antioxidant mode of action, the monoter-pene 1,8-cineole seems to be a more promisingadjunctive therapy for COPD and asthma,including the asthma–COPD overlap type(ACO), though clinical studies are still rare.Previous randomised controlled trials on the
exacerbation rates in COPD with therapies ofLABA ? ICS compared to LABA ? ICS ? 1,8-ci-neole have shown an add-on effect of 1,8-cine-ole [14], with a stronger reduction ofexacerbations compared to LABA ? ICS (Fig. 3).In the cineole study, patients with COPD wereenrolled with 80% on LABA and 23% on ICS,suggesting a relevant ICS-like effect of themultifunctional 1,8-cineole in real life thatmight have been even greater in patients withCOPD on currently recommended standardmedications of LAMA ? LABA or LAMA ?
LABA ? ICS. Following antagonism of mus-carinic M1/M3 receptors by tiotropium, inhibi-tion of NF-jB and IL-8 in LPS-stimulatedbronchial epithelial cells and airway fibroblasts[82] was shown in addition to the publishedinhibition of many other cytokines. In a guineapig model of allergic asthma, combined treat-ment with a nebulizer concentration of tio-tropium (0.01 mM) and ciclesonide (0.01 mg/kg) inhibited eosinophilic airway inflammationand remodelling, which was not shown for the
Fig. 3 Previous randomized trials in COPD found adecrease in exacerbation frequency for LABA ? ICS inthe range of 24%, regardless of the amount of ICS used[85–88], with only a slight difference to ICS alone (20%)[89]. Studies with monotherapy of a LAMA [90, 91] orPDE-IV inhibitor [92] showed comparable reductions(14-18%) of exacerbations such as ICS alone. In recentstudies with LAMA ? LABA, however, there a nearlytwofold decrease in exacerbations in the range of 50% hasbeen detected [93, 94]. For the first time, the effect ofadjunctive therapy with the monoterpene 1,8-cineoleshowed a 38% decrease in exacerbations
1746 Adv Ther (2020) 37:1737–1753
two substances when administered alone [83].1,8-Cineole also showed an airway relaxanteffect in a guinea pig model at relevant con-centrations (greater than 6.5 9 10-6 M) with adecreased effect on tracheal hyper-responsive-ness to KCl and carbachol, whereas the effect ofacetylcholine (10-4 M) was only partially con-trolled at higher concentrations of 1,8-cineole(6.5 9 10-3 M), suggesting an additional actionon electromechanical coupling [84]. The clini-cal effect of LAMA, such as that of M1/M3
antagonism by tiotropium, may be improved bythe at least bifunctional anti-inflammatory andantioxidant activity of the mucolytic agent 1,8-cineole. Since 1,8-cineole primarily controls IL-1b and TNFa, adjunctive therapy with 1,8-ci-neole in inflammatory airway diseases is rec-ommended for the protection of virus-inducedM2 receptor dysfunction and to improve theeffects of LAMA alone or in combinations withLABA and/or ICS. With respect to the newguideline recommendation for COPD, prelimi-nary in vitro results now show for the first timethat 1,8-cineole also controls the pro-inflam-matory effects of acetylcholine (ACh), thusimproving the anti-inflammatory effects of iso-lated M1/M3 receptor antagonism of LAMAs(Fig. 4).
These preliminary results suggest that rele-vant respiratory and plasma concentrations of1,8-cineole, at least in the present experimentaldesign, could mediate a comparable or higheranti-inflammatory activity than tiotropiumalone and also additively intensifies its anti-in-flammatory effects. For this reason, adjunctivetherapy with 1,8-cineole is also suggested withLAMA therapy in the early stages of symp-tomatic COPD (GOLD I–IIB) to control exacer-bation and also, potentially, the progression ofcigarette smoke-induced neutrophilic and eosi-nophilic airway inflammation.
LESSONS FOR CLINICIANS
Inflammatory processes, particularly in COPD,are characterized by only partial therapyresponses to ICS, depending on the type ofinflammation, such as the COPD–bronchitistype with exposure to CS, inhaled ROS and/or
by increased production of exacerbation acti-vated airway cells or the degree and mixturewith neutrophilic/eosinophilic Th1/Th2-typeinflammation in asthma and ACO. As previ-ously shown [40, 52] in vitro, anti-inflamma-tory and antioxidant effects increased additivelyby co-incubation of 1,8-cineole ? ICS or 1,8-cineole ? (ICS ? LABA), whereas BUD ? F atleast did not show any pro- or antioxidantactivity as shown for O2
�-. This would suggest atherapeutic value for 1,8-cineole as adjunctivetherapy for partial ICS responders by its controlof Th1-type inflammation in steroid-resistentasthma, independently of eosinophilia or Th2-type inflammation, and of the COPD–bronchi-tis type, with and without sinusitis, by itsbifunctional antioxidant and anti-inflamma-tory activity, or in patients with asthma, COPDand ACO with frequent exacerbations under
Fig. 4 In an in vitro model (105/ml, 2 Expt., n = 6) ofhuman monocytes from healthy volunteers (expressingM1–M5 receptors), the effects of respiratory-relevantconcentrations (2 9 10-6 M) and a relevant plasmaconcentration (4 9 10-6 M) of 1,8-cineole (C), tiotro-pium 15 pg/ml (TIO) alone and of TIO ? C afterincubation for 20 h were investigated for IL-8 in thepresence of LPS (10 lg/ml) (Sigma-Aldrich, Germany).Stimulated IL-8 production was inhibited (p \ 0.0001compared to the LPS control) in a dose-dependentmanner, even comparable to tiotropium (TIO) (15 pg/ml) at a small exhaled and therefore respiratory-relevantconcentration of C (2 9 10-6 M). This inhibitory effectof TIO on IL-8 production increased significantly after co-incubation with the investigated breath-relevant concen-tration of C, and further dose-dependently, at an increas-ing, small systemically relevant concentration(4 9 10-6 M)
Adv Ther (2020) 37:1737–1753 1747
standard triple therapy. In this regard, it may beof interest that the anti-inflammatory in vitroeffect of LAMAs increased in the presence ofanti-inflammatory agents, such as 1,8-cineole orICS, possibly in part by protection againstinfection or inflammation-induced M2 receptordysfunction or by improvement of the effects ofM1/M3 receptor inhibition, though the precisemechanism of action seems so far not to beunderstood. For this reason, a non-steroidalanti-inflammatory substance, such as 1,8-cine-ole, could be recommended in the early COPDstages of groups without (A) or with (B) clinicalsymptoms in the known typical range of indi-cation for 1,8-cineole and as adjunctive therapyto LAMA for symptomatic early COPD.
CONCLUSIONS
Independently of mono- or adjunctive therapywith 1,8-cineole, long-term therapy, because ofits antiviral, antibacterial, antioxidant and anti-inflammatory activity, is to be recommendedbesides its effects to control systemic andperipheral lung inflammation, an area that isnot generally reachable for standard inhalationtherapies.
ACKNOWLEDGEMENTS
We acknowledge the helpful cooperation of DrM. Ploch, Cassella-med Ltd, Cologne, Germanyand Dr H. Greve, Dusseldorf, Germany.
Funding. The study, rapid service fee andthe open access fee was funded by Cassella-medLtd, Cologne, Germany.
Authorship. All named authors meet theInternational Committee of Medical JournalEditors (ICMJE) criteria for authorship for thisarticle, take responsibility for the integrity ofthe work as a whole, and have given theirapproval for this version to be published.
Authorship Contributions. LJ (medical stu-dent) and UJ carried out the literature searchand the interpretation of cited data. UJ
developed the design and conception of thestudy. UJ, LJ and HW were involved in draftingand revising the manuscript.
Disclosures. Uwe Juergens was a member ofthe advisory board at Cassella-med Inc. Lisa JoyJuergens and Heinrich Worth have nothing todisclose.
Compliance with Ethics Guidelines. Thisarticle is based on previously conducted studiesand does not contain any studies with humanparticipants or animals performed by any of theauthors.
Data Availability. Data sharing is notapplicable to this article as no datasets weregenerated or analyzed during the current study.
Open Access. This article is licensed under aCreative Commons Attribution-NonCommer-cial 4.0 International License, which permitsany non-commercial use, sharing, adaptation,distribution and reproduction in any mediumor format, as long as you give appropriate creditto the original author(s) and the source, providea link to the Creative Commons licence, andindicate if changes were made. The images orother third party material in this article areincluded in the article’s Creative Commonslicence, unless indicated otherwise in a creditline to the material. If material is not includedin the article’s Creative Commons licence andyour intended use is not permitted by statutoryregulation or exceeds the permitted use, youwill need to obtain permission directly from thecopyright holder.To view a copy of this licence,visit http://creativecommons.org/licenses/by-nc/4.0/.
REFERENCES
1. Dhakad AK, Pandey VV, Beg S, Rawat JM, Singh A.Biological, medicinal and toxicological significanceof eucalyptus leaf essential oil: a review. J Sci FoodAgric. 2018;98:833–48.
2. Jnanesha AC, Ashish K, Vanitha TK. Variation inthe yield and chemical composition of eucalyptusspecies (Nilagiri) under different agro climatic
1748 Adv Ther (2020) 37:1737–1753
condition of India. Int J Herbal Med. 2019;7(1):04–7.
3. De Lima Gondim F, dos Santos GR, do NascimentoIFMG, Serra DS, Cavalcante FSA. Beneficial effects ofeucalyptol in the pathophysiological changes of therespiratory system: a proposal for alternative phar-macological therapy for individuals with COPD.Eur J Med Plants. 2018;25(1):1–10.
4. Siafakas NM, Vermeire P, Pride NB, et al. Optimalassessment and management of chronic obstructivepulmonary disease (COPD). The European Respira-tory Society Task Force. Eur Respir J. 1995;8(8):398–1420.
5. Yan X, Song Y, Shen C, et al. Mucoactive andantioxidant medicines for COPD: consensus of agroup of Chinese pulmonary physicians. Int JChron Obstruct Pulmon Dis. 2017;12:803–12.
6. Wedzicha JA, Calverley PMA, Albert RK, et al.Prevention of COPD exacerbations: a EuropeanRespiratory Society/American Thoracic Societyguideline. Eur Respir J. 2017. https://doi.org/10.1183/13993003.02265-2016.
7. Singh U, Wangia-Anderson V, Bernstein JA.Chronic rhinitis is a high-risk comorbidity for30-day hospital readmission of patients withasthma and chronic obstructive pulmonary disease.J Allergy Clin Immunol Pract. 2019;7(1):279–285.
8. Kariya S, Okano M, Tachibana T, Rikmaru T, Nish-izaki K. Lund-Mackay computed tomography scoreis associated with obstructive pulmonary functionchanges in chronic cough patients. Am J RhinolAllergy. 2019;33(3):294–301.
9. Togias A, Gergen PJ, Hu JW, et al. Rhinitis in chil-dren and adolescents with asthma: ubiquitous,difficult to control, and associated with asthmaoutcomes. J Allergy Clin Immunol. 2019;143(3):1003–11.e10. https://doi.org/10.1016/j.jaci.2018.07.041.
10. Kehrl W, Sonnemann U, Dethlefsen U. Therapy fornonpurulent rhinosinusitis with cineole: results ofa double-blind, randomized, placebo-controlledtrial. Laryngoscope. 2004;114(4):738–42.
11. Sudhoff H, Klenke C, Greiner JF, et al. 1,8-Cineolereduces mucus-production in a novel humanex vivo model of late rhinosinusitis. PLoS One.2015;10(7):e0133040. https://doi.org/10.1371/journal.phone.0133040.
12. Muller J, Greiner JF, Zeuner M, et al. 1,8-Cineolepotentiates IFR3-mediated antiviral response inhuman stem cells and in ex vivo model of rhinos-inusitis. Clin Sci (Lond). 2016;130(15):1339–52.
13. Juergens UR, Dethlefsen U, Steinkamp G, GillissenA, Repges R, Vetter H. Anti-inflammatory activity of1,8-cineole (eucalyptol) in bronchial asthma: adouble-blind placebo-controlled trial. Respir Med.2003;97(3):250–6.
14. Worth H, Dethlefsen U. Patients with asthma ben-efit from concomitant therapy with cineole: a pla-cebo-controlled, double-blind trial. J Asthma.2012;49(8):849–53.
15. Fischer J, Dethlefsen U. Efficacy of cineole inpatients suffering from acute bronchitis: a placebo-controlled double-blind trial. Cough. 2013;9:25.
16. Worth H, Schacher C, Dethlefsen U. Concomitanttherapy with cineole (eucalyptol) reduces exacer-bations in COPD: a placebo-controlled double-blind trial. Respir Res. 2009;10:69–76.
17. Vogelmeier C, Buhl R, Burghuber O, et al. Guidelinefor the diagnosis and treatment of COPD patients—issued by the German Respiratory Society and theGerman Atemwegsliga in Cooperation with theAustrian Society of Pneumology. Pneumologie.2018;72(4):253–308. https://doi.org/10.1055/s-0043-125031.
18. Onkin D, Medzhitov R. Evolution of inflammatorydiseases. Curr Biol. 2012;22:R733–40.
19. Lee It, Yang CM. Inflammatory signalings involvedin airway and pulmonary diseases. Mediat Inflamm.2013;2013:791231. https://doi.org/10.1155/2013/791231.
20. Luo SF, Chang C, Lee IT, et al. Activation of ROS/NF-jB and Ca2?/CaM kinase II are necessary forVCAM-1 induction in IL-1b-treated human trachealsmooth muscle cells. Toxicol Appl Pharmacol.2009;237(1):8–21.
21. Rider CF, Shah S, Miller-Larsson A, Giembycz MA,Newton R. Inflammatory stimuli inhibit glucocor-ticoid-dependent transactivation in human pul-monary epithelial cells: rescue by long-acting beta2-adrenoceptor agonists. J Pharmacol Exp Ther.2011;338(3):860–9.
22. Lee IT, Yang CM. Role of NADPH oxidase/ROS inpro-inflammatory mediators-induced airway andpulmonary diseases. Biochem Pharmacol.2012;84(5):581–90.
23. Gaofeng Y, Wahlqvist ML, He G, Yang M, Li D.Natural products and anti-inflammatory activity.Asia Pac J Clin Nutr. 2006;15(2):143–52.
24. Borges SR, Ortiz BLS, Pereira ACM, Keita H, Car-valho JCT. Rosmarinus officinalis essential oil: areview of its phytochemistry, anti-inflammatory
Adv Ther (2020) 37:1737–1753 1749
activity, and mechanisms of action involved.J Ethnopharmacol. 2019;229:29–45.
25. Quintans JSS, Shanmugaam S, Heimfarth L, et al.Monoterpenes modulating cytokines: a review.Food Chem Toxicol. 2018;123:233–57.
26. De Lavor EM, Fernandes AWC, de Andrade TelesRB, et al. Essential oils and their major compoundsin the treatment of chronic inflammation: a reviewof antioxidant potential in preclinical studies andmolecular mechanisms. Oxid Med Cell Longev.2018:6468593. https://doi.org/10.1155/2018/6468593.
27. Raha S, KIM SM, Lee SJ, et al. Essential oil fromKorean Chameacyparis obtusa leaf ameliorates res-piratory activity in Sprague-Daley rats and exhibitsprotection from NF-jB-induced inflammation inWI38 fibroblast cells. Int J Mol Med. 2019;43(1):393–403. https://doi.org/10.3892/ijmm.2018.3966.
28. Greiner JF, Muller J, Zeuner MT, et al. 1,8-Cineoleinhibits nuclear translocation of NF-kB p65 and NF-kB-dependent transcriptional activity. BiochimBiophys Acta. 2013;1833(12):2866–78.
29. Zhao C, Sun J, Fang C, Tang F. 1,8-Cineole attenu-ates LPS-induced acute pulmonary inflammation inmice. Inflammation. 2014;37(2):566–72.
30. Takaishi M, Fujita F, Uchida K, et al. 1,8-Cineole, aTRPM8 agonist, is a novel natural antagonist ofhuman TRPA1. Mol Pain. 2012;8:86. https://doi.org/10.1186/1744-8069-8-86.
31. Juergens UR, Stober M, Schmidt-Schilling L, KleuverT, Vetter H. Antiinflammatory effects of eucalyptol(1,8-cineole) in bronchial asthma: inhibition ofarachidonic acid metabolism in human bloodmonocytes ex vivo. Eur J Med Res. 1998;3(9):407–12.
32. Juergens UR, Stober M, Vetter H. Inhibition ofcytokine production and arachidonic acid metabo-lism by eucalyptol (1,8-cineole) in human bloodmonocytes in vitro. Eur J Med Res. 1998;3(11):508–10.
33. Varricchi G, Bagnasco D, Borriello F, Heffler E,Canonica GW. Interleukin-5 pathway inhibition inthe treatment of eosinophilic respiratory disorders:evidence and unmet needs. Curr Opin Allergy ClinImmunol. 2016;16:186–200.
34. Juergens UR, Engelen T, Racke K, Stober M, Gillis-sen A, Vetter H. Inhibitory activity of 1,8-cineole(eucalyptol) on cytokine production in culturedhuman lymphocytes and monocytes. Pulm Phar-macol Ther. 2004;17(5):281–7.
35. Beauchamp J, Kirsch F, Buettner A. Real-time breathgas analysis for pharmacokinetics: monitoringexhaled breath by on-line proton-transfer-reactionmass spectrometry after ingestion of eucalyptol-containing capsules. J Breath Res. 2010;4(2):026006. https://doi.org/10.1088/1752-7155/4/2/026006.
36. Song WJ, Kang HR, Park HW, Sohn SW. Effect of1,8-cineole in Dermatophagoides pteronyssinus-stim-ulated bronchial epithelial cells and mouse modelof asthma. Biol Pharm Bull. 2016;39:946–52.
37. Hosoki K, Ying S, Corrigan C, et al. Analysis of apanel of 48 cytokines in BAL fluids specificallyidentifies IL-8 levels as the only cytokine that dis-tinguishes asthma and correlates inversely withFEV1. PLoS One. 2015. https://doi.org/10.1371/journal.pone.0126035.
38. Ekstedt S, Safholm J, Georen SK, Cardell LO.Dividing neutrophils in subsets reveals a significantrole for activated neutrophils in the development ofairway hyperreactivity. Clin Exp Allergy. 2019;49:285–91.
39. Garudadri S, Woodruff PG, Han MLK, et al. Sys-temic markers of inflammation in smokers withsymptoms despite preserved spirometry in SPIRO-MICS. Chest. 2019;155(5):908–17.
40. Juergens LJ, Racke K, Tuleta I, Stoeber M, JuergensUR. Anti-inflammatory effects of 1,8-cineole (euca-lyptol) improve glucocorticoid effects in vitro: anovel approach of steroid-sparing add-on therapyfor COPD and asthma? Synergy. 2017;5:1–8.
41. Jevnikar Z, Ostling J, Ax E, et al. Epithelial IL-6trans-signaling defines a new asthma phenotypewith increased airway inflammation. J Allergy ClinImmunol.2019;143(2):577–90.
42. Juergens UR. Anti-inflammatory properties of themonoterpene 1,8-cineole: current evidence for co-medication in inflammatory airway diseases. DrugRes. 2014;64(12):638–46.
43. Fischer BM, Voynow JA, Ghio AJ. COPD: balancingoxidants and antioxidants. Int J Chron ObstructPulmon Dis. 2015;10:261–76. https://doi.org/10.2147/COPD.S42414.
44. Rodgman A, Perfetti TA. The chemical componentsof tobacco smoke. Boca Raton: CRC; 2009.
45. Ho SP, Chan-Yeung M, Chow KK, Ip MS, Mak JC.Antioxidant enzyme activities in healthy Chineseadults: influence of age, gender and smoking.Respirology. 2005;10(3):305–9.
46. Dekhuijzen PN, Aben KK, Dekker I, et al. Increasedexhalation of hydrogen peroxide in patients with
1750 Adv Ther (2020) 37:1737–1753
stable and unstable chronic obstructive pulmonarydisease. Am J Respir Crit Care Med. 1996;154:813–6.
47. Lykkesfeldt J, Prieme H, Loft S, Poulsen HE. Effect ofsmoking cessation on plasma ascorbic acid con-centration. BMJ.1996;313(7049):91. https://doi.org/10.1136/bmj.313.7049.91.
48. Garcia-Larsen V, Potts JF, Omenaas E, et al. Dietaryantioxidants and 10-year lung function decline inadults from the ECRHS survey. Eur Respir J.2017;50:1602286.
49. Kang JS, Han MH, Kim CM, et al. Schisandraesemen essential oil attenuates oxidative stress-in-duced cell damage in C2C12 murine skeletal mus-cle-induced cells through Nrf2-mediatedupregulation of HO-1. Int J Mol Med. 2015;35(2):453–9.
50. Porres-Martinez M, Gonzalez-Burgos E, CarreteroME, Gomez-Serranillos MP. Protective properties ofSalvia lavandulifolia Vahl. essential oil againstoxidative stress-induced neuronal injury. FoodChem Toxicol. 2015;80:154–62.
51. Perez-Roses R, Risco E, Vila R, Penalver P, Cani-gueral S. Biological and nonbiological antioxidantactivity of some essential oils. J Agric Food Chem.2016;64(23):4716–24.
52. Juergens LJ, Tuleta I, Stoeber M, Racke K, JuergensUR. Regulation of monocyte redox balance by 1,8-cineole (eucalyptol) controls oxidative stress andpro-inflammatory responses in vitro: a new optionto increase the antioxidant effects of combinedrespiratory therapy with budesonide and for-moterol? Synergy. 2018;7:1–9. https://doi.org/10.1016/j.synres.2018.05.001.
53. Montuschi P, Collins JV, Ciabattoni G, et al.Exhaled 8-isoprostane as an in vivo biomarker oflung oxidative stress in patients with COPD andhealthy smokers. Am J Respir Crit Care Med.2000;162:1175–7.
54. Barnes PJ. Identifying molecular targets for newdrug development for chronic obstructive pul-monary disease: what does the future hold. SeminRespir Crit Care Med. 2015;36(4):508–22.
55. Kluchova Z, Petrasova D, Joppa P, Dorkova Z,Tkavcoa R. The association between oxidative stressand obstructive lung impairment in patients withCOPD. Physiol Res. 2007;56(1):51–6.
56. Bezerra FS, Santos Valenca S, et al. a-Tocopheroland ascorbic acid supplementation reduced acutelung inflammatory response by cigarette smoke inmouse. Nutrition. 2006;22:1192–12001.
57. Tuleta I, Stockigt F, Juergens UR, et al. Intermittenthypoxia contributes to the lung damage byincreased oxidative stress, inflammation, and dis-balance in protease/antiprotease system. Lung.2016;194(6):1015–20. https://doi.org/10.1007/s00408-016-9946-4.
58. Alam A, Majumdar RS. Anitoxidant activity ofessential oil of three cultivars of Amomum subula-tum and standardization of high performance thinlayer chromatography (HPTLC) method for theestimation of 1,8-cineole. Afr J Biotechnol.2016;17(36):1129–37.
59. Ballester-Costa C, Sendra E, Fernandez-Lopez J,Perez-Alvarez JA, Viuda-Martos M. Assessment ofantioxidant and antibacterial properties on meathomogenates of essential oils obtained from fourthymus species achieved from organic growth.Foods. 2017;28;6(8). https://doi.org/10.3390/foods6080059.
60. Kennedy-Feitosa E, Tiemi Okuro R, Pinho Ribeiro V,et al. Eucalyptol attenuates cigarette smoke-in-duced acute lung inflammation and oxidative stressin the mouse. Pulm Pharmacol Ther. 2016;41:11–8.
61. De Lima Gondim F, Silveira Serra D, Avila S. Effectsof eucalyptol in respiratory system mechanics onacute lung injury after exposure to short-termcigarette smoke. Respir Phsiol Neurobiol.2019;266(8):33–8. https://doi.org/10.1016/j.resp.2019.04.007.
62. Dua K, Malyla V, Singhvi G, et al. Increasing com-plexity and interactions of oxidative stress inchronic respiratory diseases: an emerging need fornovel drug delivery systems. Chem Biol Interact.2019;299:168–78.
63. Dozor AJ. The role of oxidative stress in thepathogenesis and treatment of asthma. Ann N YAcad Sci. 2010;1203:133–7. https://doi.org/10.1111/j.1749-6632.2010.05562.
64. Faner R, Sibila O, Agustı A, et al. The microbiome inrespiratory medicine: current challenges and futureperspectives. Eur Respir J. 2017; 49:1602086.
65. Dickson RP, Martinez FJ, Huffnagle GB. The role ofthe microbiome in exacerbations of chronic lungdiseases. Lancet. 2014;384:691–702.
66. Segal LN, Clemente JC, Wu BG, et al. Randomised,double-blind, placebo-controlled trial with azi-thromycin selects for anti-inflammatory microbialmetabolites in the emphysematous lung. Thorax.2017;72(1):3–22.
67. Baines KJ, Wright TK, Gibson PG, Powell H, Hans-bro PM, Simpson JL. Azithromycin treatmentmodifies airway and blood gene expression
Adv Ther (2020) 37:1737–1753 1751
networks in neutrophilic COPD. ERS Open Res.2018;4:00031–2018. https://doi.org/10.1183/23120541.00031-2018.
68. Leitao Filho FS, Alotaibi NM, Ngan D, et al. Sputummicrobiome is associated with 1-year mortalityfollowing COPD hospitalizations. Am J Respir CritCare Med. 2019;199(10):1205–13.
69. Aldoghaim FS, Flematti GR, Hammer KA. Antimi-crobial activity of several cineole-rich Australianeucalyptus essential oils. Microorganisms 2018.https://doi.org/10.3390/microorganisms6040122.
70. Schurmann M, Oppel F, Gottschalk M, et al. Thetherapeutic effect of 1,8-cineole on pathogenicbacteria species present in chronic rhinosinusitis.Front Microbiol. 2019;10.2325. https://doi.org/10.3389/fmicb.2019.02325.
71. Merghni A, Noumi E, Hadded O, et al. Assessmentof the antibiofilm and antiquorum sensing activi-ties of Eucalyptus globulus essential oil and its maincomponent 1,8-cineole against methicillin-resis-tant Staphylococcus aureus strains. Microb Pathog.2018;118:74–80.
72. Jager W, Nasal B, Nasel C, et al. Pharmacokineticstudies of the fragrance compound 1,8-cineole inhumans during inhalation. Chem Senses. 1996;4:477–80.
73. Sadlon AE, Lamson DW. Immune-modifying andantimicrobial effects of eucalyptus oil and simpleinhalation devices. Altern Med Rev. 2010;15(1):33–47.
74. Elaissi A, Abid NBS, Rouis Z, et al. Chemical com-position of 8 eucalyptus species’ essential oils andthe evaluation of their antibacterial, antifungal andantiviral activities. BMC Complement Altern Med.2012;12:81. https://doi.org/10.1186/1472-6882-12-81.
75. Mika M, Nita I, Morf L, et al. Microbial and hostimmune factors as drivers of COPD. ERJ Open Res.2018;4:00015–2018. https://doi.org/10.1183/23120541.00015-2018.
76. Ostling J, van Geest M, Schofield JPR, et al. IL-17-high asthma with features of a psoriasisimmunophenotype. J Allergy Clin Immunol. 2019.https://doi.org/10.1016/j.jaci.2019.03.027.
77. Uzun S, Djamin RS, Kluytmans JA, et al. Azi-thromycin maintenance treatment in patients withfrequent exacerbations of chronic obstructive pul-monary disease (COLUMBUS): a randomised, dou-ble-blind, placebo-controlled trial. Lancet RespirMed. 2014;2:361–8.
78. Seemungal TA, Wilkinson TM, Hurst JR, Perera WR,Sapsford RJ, Wedzicha JA. Long-term erythromycintherapy is associated with decreased chronicobstructive pulmonary disease exacerbations. Am JRespir Crit Care Med. 2008;178:1139–47.
79. Cazzola M, Calzetta L, Page C, et al. Influence of N-acetylcysteine on chronic bronchitis or COPDexacerbations: a meta-analysis. Eur Respir Rev.2015;24:451–61.
80. JolliffeDA, Greenberg L, Hooper RL, et al. Vitamin Dto prevent exacerbations of COPD: systemic reviewand meta-analysis of individual participant datafrom randomised controlled trials. Thorax2019;74(4):337–345. https://doi.org/10.1136/thoraxjnl-2018-212092.
81. Ian N, Luo G, Yang X, et al. 25-Hydroxyvitamin D3-deficiency enhances oxidative stress and corticoidresistance in severe asthma exacerbations. PLoSOne. 2014;9(11):e111599.
82. Suzaki I, Asano K, Shikama Y, Hamasaki T, Kanel A,Suzaki H. Suppression of IL-8 production from air-way cells by tiotropium bromide in vitro. Int JChron Obstruct Pulmon Dis. 2011;6:439–48.
83. Kistemaker LE, Bos IS, Menzen MH, Maarsingh H,Meurs H, Gosens R. Combination therapy of tio-tropium and ciclesonide attenuates airway inflam-mation and remodeling in a guinea pig model ofchronic asthma. Respir Res. 2016;17:13. https://doi.org/10.1186/s12931-016-0327-6.
84. Bastos VP, Brito TS, Lima FJ. Inhibitory effect of 1,8-cineole on guinea-pig airway challenged withobalbumin involves a preferential action on elec-tromechanical coupling. Clin Exp PharmacolPhysiol. 2009;36(11):1120–6.
85. Singh D, D’Urzo AD, Chuecos F, Munos A, GarciaGil E. Reduction in clinically important deteriora-tion in chronic obstructive pulmonary disease withaclidinium/formoterol. Respir Res. 2017;18(1):106.https://doi.org/10.1186/s12931-017-0583-0.
86. Calverley PM, Anderson JA, Celli B, et al. Salmeteroland fluticasone propionate and survival in chronicobstructive pulmonary disease. N Engl J Med.2007;356(8):775–89.
87. Wedzicha JA, Singh D, Tsiligianni I, et al. Treatmentresponse to indacaterol/glycopyrronium versus sal-meterol/fluticasone in exacerbating COPD patientsby gender: a post hoc analysis in the Flame study.Respir Res. 2019;20(1):4. https://doi.org/10.1186/s12931-019-0972-7.
88. Szafranski W, Cukier A, Ramirez A, et al. Efficacyand safety of budesonide/formoterol in the
1752 Adv Ther (2020) 37:1737–1753
management of chronic obstructive pulmonarydisease. Eur Respir J. 2003;21(1):74–81.
89. Cazzola M, Santus P, Di Marco F, et al. Bron-chodilator effect of an inhaled combination ther-apy with salmeterol ? fluticasone andformoterol ? budesonide in patients with COPD.Respir Med. 2003;97(5):453–7.
90. Burge PS, Calverley PM, Jones PW, Spencer S,Anderson JA, Maslen TK. Randomised, double-blind, placebo-controlled study of fluticasone pro-pionate in patients with moderate to severe chronicobstructive pulmonary disease: the ISOLDE trial.BMJ. 2000;320(7245):1297–303.
91. Niewoehner DE, Rice K, Cote C, et al. Prevention ofexacerbations of chronic obstructive pulmonarydisease with tiotropium, a once-daily inhaled
anticholinergic bronchodilator: a randomized trial.Ann Intern Med. 2005;143(5):317–26.
92. Tashkin DP, Celli B, Senn S, et al. A 4-year trial oftiotropium in chronic obstructive pulmonary dis-ease. N Engl J Med. 2008;359(15):1543–54.
93. Calverly PM, Rabe KF, Goehring UM, Kristiansen S,Fabbri LM, Martinez FJ. Roflumilast in symptomaticchronic obstructive pulmonary disease: two ran-domised clinical trials. Lancet. 2009;374(9691):685–94.
94. Singh D, Maleki-Yazdi MR, Tombs L, Iqbal A, FahyWA, Naya I. Prevention of clinically importantdeteriorations in COPD with umeclidinium/vi-lanterol. Int J Chron Obstruct Pulmon Dis. 2016;11:1413–24.
Adv Ther (2020) 37:1737–1753 1753
