Introduction Appropriate apoptosis is important for testicular cell homeostasis and disruption of this orderly process may be associated with several male reproductive disorders. The purpose of our study was to evaluate the previously undefined role of glutathione-to-glutathione disulfide (GSH-to-GSSG) redox balance in human male germ cell death. We also investigated the antiapoptotic mechanism(s) of N-acetyl-l-cysteine (NAC), a clinically used compound with multiple mechanisms of action in many nontesticular tissues that include antioxidation, modulation of AP-1 and NF-κB activation, and regulation of death pathways through phosphorylation of stress kinase p38 MAPK.
Results and Methods Incubation of human seminiferous tubule segments under serum- and hormone-free conditions induced germ cell apoptosis as demonstrated by Southern blot analysis of DNA fragmentation, in situ TUNEL, electron microscopy, and Western blot detection of caspase 3 and 9 activation. Apoptosis was associated with increased NF-κB- and AP-1-DNA-binding activities (EMSA) and lowered glutathione levels as well as decreased ratio of reduced (GSH) to oxidized (GSSG) glutathione (HPLC). NAC, while not affecting the NF-κB- or AP-1 binding activities, effectively prevented the germ cell death and fully restored the GSH-to-GSSG ratios. Two inhibitors of p38 MAPK suppressed human male germ cell apoptosis, suggesting a role of the stress kinases in regulating male germ cell death.
Conclusion We conclude that the hormone- and serum-free culture condition disturbs the GSH-to-GSSG balance, indicating oxidative stress, and induces human male germ cell death. NAC prevents these events, which were associated with p38 MAPK activation. The present study may lead to the clinical use of NAC to prevent inappropriate male germ cell death.
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