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211 ARCHIVES OF ANDROLOGY 47:211–216 (2001) Copyright ã 2001 Taylor & Francis 0148-5016/01 $12.00 + .00 STRESS AND TESTICULAR GERM CELL APOPTOSIS I. SASAGAWA H. YAZAWA Y. SUZUKI T. NAKADA Department of Urology, Yamagata University School of Medicine, Yamagata, Japan Chronic immobilization stress provokes an increase in serum corticosterone, which causes the decline in testosterone concentration. The stress and glucocorticoid administration induce germ cell apoptosis in rat testes. The cell type that has been shown to undergo apoptosis is spermatogonia. Since a potent glucocorticoid receptor agonist completely suppressed glucocorticoid induced germ cell apoptosis, the regulation of transcription of gene mediated by the glucocorticoid receptor may enhance apoptosis of testicular germ cells. The apoptosis of testicular germ cells would involve certain specific gene activi- ties and proteins, including Bc1-2 family, p53, and Fas. Molecular investigations may help to determine whether the different pathways possess mechanisms of germ cell apoptosis induced by somatic stress and glucocorticoids. Keywords apoptosis, germ cell, glucocorticoid, stress, testis Apoptosis is a rapid, physiologically programmed cell death [13]. It is characterized mor- phologically by a shrinkage of total cell volume, increased cell densities, and compaction of cell organelles [3, 36]. During apoptosis there is often a double-strand, endonuclease-specific cleavage of nuclear DNA at the linker regions between nucleosomes, leading to the production of oligonucleosomal fragments that are multiples of 180 DNA base pairs [36]. Apoptosis of testicular germ cells appears to be a constant feature of normal spermatogen- esis in a variety of mammalian species [1, 11]. It is usually influenced by various kinds of somatic stress [31, 34]. In this review, we discuss testicular germ cell apoptosis with special reference to somatic stress. STRESS AND HORMONES Acute immobilization stress provokes an increase in the concentration of serum cortico- sterone and a reduction in serum testosterone concentration [31]. However, corticosterone and Address correspondence to Isoji Sasagawa, MD, Department of Urology, Yamagata University School of Medicine, 2-2-2 Iidanishi, Yamagata-shi, Yamagata 990-9585, Japan. E-mail: [email protected] Syst Biol Reprod Med Downloaded from informahealthcare.com by Universitat de Girona on 11/20/14 For personal use only.

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Page 1: STRESS AND TESTICULAR GERM CELL APOPTOSIS

211

ARCHIVES OF ANDROLOGY 47:211–216 (2001)Copyright ã 2001 Taylor & Francis0148-5016/01 $12.00 + .00

STRESS AND TESTICULAR GERMCELL APOPTOSIS

I. SASAGAWAH. YAZAWAY. SUZUKIT. NAKADA

Department of Urology, Yamagata UniversitySchool of Medicine, Yamagata, Japan

Chronic immobilization stress provokes an increase in serum corticosterone, which causes the declinein testosterone concentration. The stress and glucocorticoid administration induce germ cell apoptosis inrat testes. The cell type that has been shown to undergo apoptosis is spermatogonia. Since a potentglucocorticoid receptor agonist completely suppressed glucocorticoid induced germ cell apoptosis, theregulation of transcription of gene mediated by the glucocorticoid receptor may enhance apoptosis oftesticular germ cells. The apoptosis of testicular germ cells would involve certain specific gene activi-ties and proteins, including Bc1-2 family, p53, and Fas. Molecular investigations may help to determinewhether the different pathways possess mechanisms of germ cell apoptosis induced by somatic stressand glucocorticoids.

Keywords apoptosis, germ cell, glucocorticoid, stress, testis

Apoptosis is a rapid, physiologically programmed cell death [13]. It is characterized mor-phologically by a shrinkage of total cell volume, increased cell densities, and compaction ofcell organelles [3, 36]. During apoptosis there is often a double-strand, endonuclease-specificcleavage of nuclear DNA at the linker regions between nucleosomes, leading to the productionof oligonucleosomal fragments that are multiples of 180 DNA base pairs [36].

Apoptosis of testicular germ cells appears to be a constant feature of normal spermatogen-esis in a variety of mammalian species [1, 11]. It is usually influenced by various kinds ofsomatic stress [31, 34]. In this review, we discuss testicular germ cell apoptosis with specialreference to somatic stress.

STRESS AND HORMONES

Acute immobilization stress provokes an increase in the concentration of serum cortico-sterone and a reduction in serum testosterone concentration [31]. However, corticosterone and

Address correspondence to Isoji Sasagawa, MD, Department of Urology, Yamagata University School of Medicine,2-2-2 Iidanishi, Yamagata-shi, Yamagata 990-9585, Japan. E-mail: [email protected]

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testosterone concentrations return to the control level 90 and 60 min after the start of the stress,respectively. Similarly, 2 h of immobilization stress for 12 consecutive days could not enhancebasal levels of serum corticosterone [26]. Acute stress causes a transient change in serumcorticosterone and testosterone.

Chronic immobilization stress markedly decreases serum testosterone concentrations [22].This stress provokes an elevated level of serum corticosterone, which causes the decline intestosterone concentrations [25]. During the stress, increased corticosterone have been postu-lated to suppress gonadotropins [4] and to suppress directly gonadal function [22]. Further-more, stress-mediated increases in corticotropin-releasing factor (CRF) have been shown toreduce gonadotropin-releasing hormone (GnRH) [10, 12]. CRF may act directly in suppressingGnRH or indirectly by increasing opioid release [10, 21]. In addition, glucocorticoids releasein response to CRF could suppress secretion of GnRH [28]. Thus, glucocorticoid is consideredto be a stress-induced hormone.

APOPTOSIS OF TESTICULAR GERM CELLS

Rat and hamster testes exhibit spontaneous occurrence of germ cell apoptosis involving afew differentiating spermatogonia, in particular, type A spermatogonia, and spermatocytes dur-ing their meiotic divisions [15, 24]. In mice, spontaneous apoptosis was most commonly ob-served in spermatocytes, including the dividing spermatocytes, and less frequently in sper-matogonia and seldom in spermatids.

Androgen withdrawal as a result of hypophysectomy and administration of anti-LH antibod-ies or gonadotropin-releasing hormone (GnRH) antagonists enhanced testicular germ cell apoptosisin rats [7, 16, 29]. In response to androgen withdrawal, the cell types that have been shown toundergo apoptosis are primary spermatocytes and spermatids. Similarly, primary spermatocytesand spermatids are most vulnerable to heat exposure [34]. Immobilization stress and adminis-tration of glucocorticoid also enhanced germ cell apoptosis in rat testes [31, 32]. However, thepredominant germ cell types undergoing apoptosis included spermatogonia (Table 1, Figure 1).Thus, the mechanism of germ cell apoptosis after androgen withdrawal and heat exposure isdifferent from that after immobilization stress and glucocorticoid administration.

Table 1. Predominant germ cell types undergoing apoptosis in response to various typesof stress

Germ cell typesTypes of stress undergoing apoptosis References

Androgen withdrawal Primary spermatocytes [7, 29]Spermatids

Heat exposure Primary spermatocytes [34]Spermatids

Cryptorchidism Primary spermatocytes [33]

Immobilization Spermatogonia [36]

Glucocorticoid administration Spermatogonia [32]

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Testicular germ cell apoptosis showed age-dependent changes in testis of developing rats.These changes were observed only in germ cells of selected phases of spermatogenesis. Sup-pression of gonadotropin secretion by administration of GnRH antagonist increased germ cellapoptosis in 16- to 32-day-old rats, but not in younger or adult rats, and showed an age-dependent difference of germ cell survival [5]. The predominant germ cell types undergoingapoptosis as a result of immobilization stress and glucocorticoid treatment may differ accord-ing to age.

ROLE OF GLUCOCORTICOID HORMONES IN APOPTOSIS

Steroid hormones have a major role in the regulation of growth development, homeostatis,and programmed cell death [2]. Glucocorticoid hormones bind to the glucocorticoid receptor inthe cytoplasm of target cells, and the formation of a complex between the ligand and thereceptor regulates gene expression of the glucocorticoid response element, a specific DNAsequence in the chromosome [9]. Glucocorticoid hormones induce apoptotic cell death inimmature thymocytes and mature T cells through an active process, characterized by extensiveDNA fragmentation. This process is inhibited by interleukins IL-2 and -4 [17]. According toYazawa et al. [32], a potent glucocorticoid receptor agonist completely inhibited Dex inductionof testicular germ cell apoptosis. Therefore, the regulation of transcription of genes mediatedby the glucocorticoid receptor may enhance apoptosis of testicular germ cells.

Figure 1. In situ end labeling of DNA fragmentation on testis after glucocorticoid administration. Posi-tivity is mainly observed in spermatogonia. ×400.

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MOLECULAR MECHANISMS OF GERM CELL APOPTOSIS

The regulation of apoptosis is dependent on specific gene products. One of the best studiedsurvival genes is Bc1-2, the first member identified of a growing family of genes that regulatesprogrammed cell death in either a positive or a negative fashion. Bc1-2, as well as its structuralhomologue, the long form of Bcl-x (Bcl-xl), promotes cell survival by inhibiting apoptosis [6].Other members of the Bc1-2 family, including Bax, Bak, Bcl-xs, and Bad, can block the abilityof Bc1-2 to inhibit apoptosis and subsequently promote cell death [30]. The ratio of pro-apoptotic to anti-apoptotic Bc1-2 family proteins is the critical determinant of cell fate, with anexcess of anti-apoptotic proteins resulting in cell survival, but an excess of pro-apoptotic pro-tein resulting in cell death. After androgen withdrawal, the concentrations of the apoptosis-related gene products, such as Bcl-xl, Bak, and Bad, do not change. However, the expressionof Bc1-2 and Bax is up-regulated [35]. The induction of Bax may play a role in germ cellapoptosis following androgen withdrawal.

The tumor suppressor p53 is a potent inducer of apoptosis [8]. High levels of testicular p53protein are detected in germ cells, with greatest expression in primary spermatocytes [23].According to Yin et al. [33], the abdominal heat stress induced by experimental cryptorchidismresulted in germ cell apoptosis by both p53-dependent and p53-independent pathways. A p53-dependent pathway is responsible for the initial phase of germ cell apoptosis, whereas otherbiochemical triggers of apoptosis are involved in a later phase of cell death. Recently, Oda etal. [20] have isolated a novel gene, designated p53AIP1 (p53-related Apoptosis-Inducing Pro-tein 1), which is localized within mitochondria. Upon severe DNA damage, Ser-46 on p53 isphosphorylated and apoptosis is induced. p53AIP1 is thought to play an important role inmediating p53-dependent apoptosis, and phosphorylation of Ser-46 regulates the transcrip-tional activation of this apoptosis-inducing gene.

Fas is a transmembrane receptor protein that belongs to the tumor necrosis factor (TNF)/nerve growth factor receptor family [19]. It contains a death domain and is capable of initiatingapoptosis when stimulated by receptor cross-linking or binding to its ligand, FasL [19]. FasL isa TNF-related type II transmembrane protein [27]. Binding of FasL to Fas activates the cyto-plasmic death domain of Fas, which initiates a cascade of interleukin-1 b -converting enzymefamily protease (caspase) activity [18]. The activated caspases cleave various cellular sub-stances, such as actin, fodrin, lamin, poly(ADP-ribose) polymerase, and DNA-dependent pro-tein kinase, resulting in apoptosis. The Fas system in the testis has been identified as oneparacrine signaling system by which Sertoli cells, expressing FasL, can initiate killing of Fas-expressing germ cells [14].

Since the apoptosis of testicular germ cells would involve certain specific gene activity andproteins, molecular investigations may help to determine whether the different pathways pos-sess mechanisms of germ cell apoptosis induced by various types of stress.

REFERENCES

1. Allan DJ, Harmon BV, Roberts SA (1992): Spermatogonial apoptosis has three morphologicallyrecognizable phases and shows no circadian rhythm during normal spermatogenesis in the rat. CellProlif 25:241–250.

2. Amsterdam A, Dantes A, Selvaraj N, Aharoni D (1997): Apoptosis in steroidogenic cells: structure–function analysis. Steroids 62:207–211.

Syst

Bio

l Rep

rod

Med

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

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20/1

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al u

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Page 5: STRESS AND TESTICULAR GERM CELL APOPTOSIS

Testis/Stress/Apoptosis 215

3. Arends MJ, Morris RG, Wyllie AH (1990): Apoptosis: the role of endonuclease. Am J Pathol 136:593–608.

4. Bambino T, Hsueh A (1981): Direct inhibitory effect of glucocorticoids upon testicular luteinizinghormone receptors and steroidogenesis in vivo and in vitro. Endocrinology 108:2142–2148.

5. Billig H, Furuta I, Rivier C, Tapanainen J, Parvinen M, Hsueh AJ (1995): Apoptosis in testis germcells: developmental changes in gonadotropin dependence and localization to selective tubule stages.Endocrinology 136:5–12.

6. Boise LH, Gonzalez-Garcia M, Postema CE, Ding L, Lindsten T, Turka LA, Mao X, Nunez G,Thompson C (1993): Bcl-x, a bc1-2 related gene that functions as dominant regulator of apoptoticdeath. Cell 74:597–608.

7. Brinkworth MH, Weinbauer GF, Schlatt S, Nieschlog E (1995): Identification of male germ cellsundergoing apoptosis in adult rats. J Reprod Fertil 105:25–33.

8. Clarke PGH (1990): Developmental cell death: morphological diversity and multiple mechanisms.Anat Embryol 181:195–213.

9. DeGroot LJ (1989): Endocrinology, 2 ed. Philadelphia: Saunders.10. Gindoff RR, Ferin M (1987): Endogenous opioid peptides modulate the effect of corticosterone-

releasing factor on gonadotrophin release in the primate. Endocrinology 121:837–842.11. Huckins C (1978): The morphology and kinetics of spermatogonial degeneration in normal adult rats:

an analysis using a simplified classification of the germinal epithelium. Anat Rec 190:905–926.12. Hulse GK, Coleman GJ (1983): The role of endogenous opioids in the blockade of reproductive

function in the rat following exposure to acute stress. Pharmacol Biochem Behav 19:795–799.13. Kerr JFR, Wyllie AH, Currie AR (1992): Apoptosis: a basic biological phenomenon with wide-

ranging implications in tissue kinetics. Br J Cancer 26:239–257.14. Lee J, Richburg JH, Younkin SC, Boekelheide K (1997): The Fas system is a key regulator of germ

cell apoptosis in the testis. Endocrinology 138:2081–2088.15. Lue Y, Sinha-Hikim AP, Wang C, Bonavera JJ, Baravarian S, Leung A, Swerdloff RS (1997): Early

effect of vasectomy on testicular structure and on germ cell and macrophage apoptosis. J Androl18:166–173.

16. Marathe GK, Shetty J, Dighe RR (1995): Selective immunoneutralization of luteinizing hormoneresults in the apoptotic cell death of pachytene spermatocytes and spermatids in the rat testis. EndocrRev 3:705–709.

17. Migliorati G, Nicoletti I, D’Adamio F, Spreca A, Pagliacci MC, Riccardi C (1994): Dexamethasoneinduces apoptosis in mouse natural killer cells and cytotoxic T lymphocytes. Immunology 81:21–26.

18. Nagata S (1997): Apoptosis by death factor. Cell 88:355–365.19. Nagata S, Golstein P (1995): The Fas death factor. Science 267:1449–1456.20. Oda K, Arakawa H, Tanaka T, Matsuda K, Tanikawa C, Mori T, Nishimori H, Tamai K, Tokino T,

Nakamura Y, Taya Y (2000): p53AIP1, a potential mediator of p53-dependent apoptosis, and itsregulation by Ser-46-phosphorylated p53. Cell 102:849–862.

21. Rasmussen DD, Liu JH, Wolf PL, Yen SS (1983): Endogenous opioid regulation of gonadotropin-releasing hormone release from the human fetal hypothalamus in vitro. J Clin Endocrinol Metab57:881–884.

22. Sapolski RM (1985): Stress-induced suppression of testicular function in the wild baboon: role ofglucocorticoids. Endocrinology 116:2273–2278.

23. Schwartz D, Goldfinger N, Rotter V (1993): Expression of p53 protein in spermatogenesis is con-fined to the tetraploid pachytene primary spermatocytes. Oncogene 8:1487–1494.

24. Sinha-Hikim AP, Wang C, Leung A, Swerdloff RS (1995): Involvement of apoptosis in the inductionof germ cell degeneration in adult rats after gonadotropin-releasing hormone antagonist treatment.Endocrinology 136:2770–2775.

Syst

Bio

l Rep

rod

Med

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Uni

vers

itat d

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11/

20/1

4Fo

r pe

rson

al u

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Page 6: STRESS AND TESTICULAR GERM CELL APOPTOSIS

216 I. Sasagawa et al.

25. Srivastava RK, Taylor MF, Mann DR (1993): Effect of immobilization stress on plasma luteinizinghormone, testosterone, and corticosterone concentrations and on 3 b -hydroxysteroid dehydrogeneseactivity in the testes of adult rats. Proc Soc Exp Biol Med 204:231–235.

26. Suarez M, Fiol de Cuneo M, Vincenti L, Ruiz RD (1996): Changes in corticosterone levels and spermfunctional activity by chronic stress in rats. Arch Physiol Biochem 104:351–356.

27. Suda T, Takahashi T, Golstein P, Nagata S (1993): Molecular cloning and expression of the Fasligand, a novel member of the tumor necrosis factor family. Cell 75:1169–1178.

28. Suter DE, Schwartz NB, Ringstrom SJ (1988): Dual role of glucocorticoids in regulation of pituitarycontent and secretion of gonadotropin. Am J Physiol 254:E595–E600.

29. Tapanainen JS, Tilly JL, Vihko KK, Hsuch AJ (1993): Hormonal control of apoptotic cell death in thetestis: gonadotropins and androgens as testicular cell survival factors. Mol Endocrinol 7:643–650.

30. Yang E, Zha J, Jokel J, Boise LH, Thompson CB, Korsmeyer SJ (1995): Bad, a heterodimeric partnerfor Bcl-xL and Bc1-2, displaces Bax and promotes cell death. Cell 80:285–291.

31. Yazawa H, Sasagawa I, Nakada T (1999): Effect of immobilization stress on testicular germ cellapoptosis in rats. Hum Reprod 14:1806–1810.

32. Yazawa H, Sasagawa I, Nakada T (2000): Apoptosis of testicular germ cells induced by exogenousglucocorticoid in rats. Hum Reprod 15:1917–1920.

33. Yin Y, DeWolf WC, Morgentaler A (1998): Experimental cryptorchidism induces testicular germ cellapoptosis by pS3-dependent and -independent pathways in mice. Biol Reprod 58:492–496.

34. Yin Y, Hawkins KL, DeWolf WC, Morgentaler A (1997): Heat stress causes testicular germ cellapoptosis in adult mice. J Androl 18:159–165.

35. Woolveridge I, de Boer-Brouwer M, Taylor MF, Teerds KJ, Wu FCW, Morris ID (1999): Apoptosis inthe rat spermatogenic epithelium following androgen withdrawal: changes in apoptosis related genes.Biol Reprod 60:461–470.

36. Wyllie AH, Kerr FJR, Currie AR (1980): Cell death: the significance of apoptosis. Int Rev Cytol68:251–306.

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