V-ATPase Deficiency Aggravates Hypoxia-induced Spermatogenesis Reduction by Promoting Spermatocyte Apoptosis via the JNK/c-Jun Pathway in Mice

Abstract

Spermatocyte apoptosis is the primary cause of poor outcome after hypoxia-triggered spermatogenesis reduction (HSR). The vacuolar H+-ATPase (V-ATPase) has been found to be involved in the regulation of hypoxia-induced GC-2 cells apoptosis. However, the mechanism of V-ATPase regulating spermatocyte apoptosis after HSR hasnot been well elucidated. In this study, HSRmodel was established by hypoxia exposure in vivo in V-ATPase-knockout (V-ATPase-/-) and wild-type (WT) mice to investigate theeffectof V-ATPase deficiency on spermatocyte apoptosis. GC-2, amouse pachytene spermatocyte-derived cell line, was introduced in vitro experiments. The sperm count and spermatogenic apoptosis were recorded after 60 d of hypoxia exposure in HSR model. The apoptosis of GC-2 cells was detected by flow cytometry and TUNEL staining. The expression of JNK/c-Jun was evaluated by RNA-seq or western blot. The expression of DR5 and caspase-8 was evaluated by RT-qPCR and western blot. The expression of V-ATPase was determined by western blot in the presence and absence ofLenti-transcription factor EB (TFEB).C-Jun interference was used for evaluating the role of JNK in regulating the apoptosis of GC-2 cells byTUNEL and flow cytometry. The in vivo results suggested that hypoxia induced spermatogenesis reduction and downregulation of V-ATPase. Moreover, V-ATPase deficiency resulted in moresevere spermatogenesis reduction after hypoxia exposure. The spermatogenesis reduction was associated with exacerbation of spermatocyte apoptosis. Hypoxia down-regulated the transcription of V-ATPase through inhibiting TFEB and its nuclear translocation. The mRNA and protein expressions of V-ATPaseincreased after TFEB overexpression in GC-2 cells. Moreover, V-ATPase deficiency enhanced JNK/c-Jun activation and related DR-apoptotic pathwayin GC-2 cells.However,inhibition of c-Jun attenuated V-ATPase deficiency-induced GC-2 cells apoptosis in vitro and HSR in vivo. In conclusion, JNK/c-Jun was involved in the enhancement of V-ATPase-mediated HSR in V-ATPase -/- mice. V-ATPase deficiency aggravates spermatocyte apoptosis, which may account forthe poor spermatogenesis outcomes of V-ATPase-/- mice. The discoveredfunction of V-ATPase modulating spermatocyte apoptosis indicates its potential therapeutic effect against HSR.