Exploration On Molecular Mechanism Of Fenvalerate-induced Testicular Germ Cell Apoptosis In Male Mice

Objective Study the effects of fenvalerate exposure on testicular germ cell apoptosis in male mice. To explore the mechanisms on Fas/FasL signaling pathway and mitochondrial signaling pathway of fenvalerate- induced testicular germ cell apoptosis in male mice.Methods Thirty-six male mice at postnatal day (PND) 42 were randomly divided into three groups. Male mice in fenvalerate groups were administered with fenvalerate (15 or 60 mg/kg) by gavage for 28 days. The controls received corn oil only. At 24 h after the last treatment with fenvalerate, the testes were excised, dissected, weighted, histopathological changes were also observed in testes; Germ cell apoptosis was determined by terminal deoxynucleotidyl transferase TdT-mediated dUTP nick-end labeling (TUNEL); Protein expression of cell apoptosis signaling pathway in mice testes was determined using immunoblotting.Results The results showed that compared with the control group, fenvalerate(15 mg/kg, 60 mg/kg) exposed induced the decrease in the weights and organ coefficients of testes. Fenvalerate exposure markedly decreased the layers of spermatogenic cells, increased the inside diameter of seminiferous tubules, and disturbed the array of spermatogenic cells in testicular sections. The number of TUNEL+ germ cells per tubule was significantly increased in a dose-dependent manner. In addition, the percentage of tubules with TUNEL+ germ cells was significantly increased in fenvalerate-treated mice when compared with controls. In addition, TUNEL+ germ cells were observed mainly in stages VII–VIII seminiferous tubules and also stages IX–XII seminiferous tubules in testes of mice treated with fenvalerate. Immunoblotting showed that fenvalerate increased the level of cleaved Caspase-3 in testes. Additional experiments showed that fenvalerate exposure not only upregulated testicular Fas and FasL in a dose-dependent manner, but also the level of cleaved Caspase-8 was significantly increased in testes of mice treated with fenvalerate. Proapoptotic factors Bax and antiapoptotic proteins Bcl-2 of the Bcl-2 family in testicular tissue were analyzed. Results showed that no significant difference on the expression of testicular Bax and Bcl-2 in whole homogenates was observed between fenvalerate-treated mice and controls. In addition, fenvalerate exposure did not affect the distribution of Bax in mitochondria and cytoplasm. To investigate whether fenvalerate exposure induces germ cell apoptosis through mitochondrial pathway, mitochondrial and cytosolic cytochrome c abundance and cleaved Caspase-9 level were analyzed. The results showed that, no significant difference on the level of cytosolic and mitochondrial cytochrome c was observed between fenvalerate-treated mice and controls. In addition, fenvalerate exposure had no effect on the level of cleaved Caspase-9 in mouse testes.Conclusion Fenvalerate have a significant reproductive damage role and induced germ cell apoptosis in male mice; Fenvalerate may be through activation of Fas/FasL signaling pathway induced testicular germ cell apoptosis.