Hydrogen sulfide protects testicular germ cells against heat-induced injury

•CBS, CSE and 3MST are all expressed in mouse testicular germ cells.•Heat stress caused CBS and CSE down-regulation and decreased H2S level in mouse testis.•Heat stress promoted germ cells apoptosis via an intrinsic pathway.•H2S ameliorates heat-induced germ cells apoptosis through an antioxidant mechanism. The present study was designed to investigate whether H2S can protect testicular germ cells against heat exposure induced injury and the underlying mechanisms. It was found that all three H2S generating enzymes, cystathionine β-synthase (CBS), cystathionine γ-lysase (CSE), and 3-mercaptopyruvate sulfurtransferase (3MST), were expressed in mouse testicular tissue. Three episodes of heat exposure (42 °C, 30 min/day, 3 days) significantly decreased endogenous H2S production and down-regulated the expression of CBS and CSE in testes. In primary cultured testicular germ cells, exogenous application of NaHS (an H2S donor) attenuated heat stress (42 °C, 30 min) induced cell death and apoptosis. This was mediated by the inhibitory effects of H2S on cytochrome C release and the ratio of the Bax/Bcl-2. NaHS also improved mitochondrial function by decreasing oxygen consumption and increasing ATP production. NaHS treatment also stimulated SOD activity and reduced ROS production. Our results revealed both physiological and pharmacological roles of H2S in testicular germ cells. Exogenous application of H2S may protect germ cells by preservation of mitochondrial function and stimulation of anti-oxidant activity.