[Effect of autophagy in cadmium chloride induced apoptosis of mouse spermatogenic cells].

OBJECTIVE: To study the effect of autophagy in cadmium chloride(CdCl_2)-induced apoptosis of mouse spermatocytes(GC-2 spd) cells and explore the underlying molecular mechanisms. METHODS: The cells were treated with different concentrations of CdCl_2(0, 5 and 10 µmol/L) for 24 h. Hoechst33342 staining and monodansylcadaverine(MDC) were performed to explore the formation of autophagosomes and apoptotic bodies. The apoptosis of cadmium-treated cells was examined by TUNEL staining. Autophagy inhibitor 3-methyladenine(3-MA)(60 µmol/L), apoptotic inhibitorCaspase inhibitor Z-VAD-FMK( zVAD-FMK)(50 nmol/L), autophagy inducer rapamycin(RAPA)(50 nmol/L) and lysosomal inhibitor chloroquine(CQ)(10 µmol/L) were added to cell culture in the presence/absence of CdCl_2(10 µmol/L) to treat GC-2 spd cells for 24 h. The expression levels of autophagy-related proteins LC3, P62, and pro-apoptotic proteins cleaved Caspase-3 and cleaved Caspase-9 were examined by Western blot. RESULTS: Autophagosomes aggregated and the number of apoptotic cells increased after exposure to CdCl_2 for 24 h. Western blot result showed that in the 5 and 10 µmol/L CdCl_2 exposure groups, the protein expression levels of LC3II/LC3I increased to 9.23±0.81 and 12.15±0.80 compared with the control group(5.50±0.56)(P<0.05), LC3II protein expression level increased to 3.35±0.14 and 3.47±0.32 compared with the control group(2.35±0.34)(P<0.05), P62 protein expression level increased to 1.48±0.12 and 1.80±0.22 compared with the control group(0.83±0.09)(P<0.05). Compared with the CdCl_2-treated group, the protein expression levels of LC3II/LC3I, LC3II, P62, cleaved Caspase-9 and cleaved Caspase-3 after 3-MA treatment decreased to 0.90±0.07(CdCl_2 group: 1.47±0.06), 1.57±0.14(CdCl_2 group: 2.45±0.29), 0.82±0.05(CdCl_2 group: 1.44±0.18), 0.18±0.01(CdCl_2 group: 0.28±0.01) and 0.61±0.84(CdCl_2 group: 1.15±0.04)(P<0.05). Compared with the CdCl_2-treated group, the protein expression levels of cleaved Caspase-9 and cleaved Caspase-3 after zVAD-FMK treatment decreased to 0.12±0.01(CdCl_2 group: 0.28±0.01) and 0.34±0.01(CdCl_2 group: 1.15±0.04)(P<0.05), while those of LC3II/LC3I, LC3II and P62 had no significant change(P>0.05). Compared with the CdCl_2-treated group, RAPA enhanced cadmium-induced LC3II/LC3I, LC3II and P62 protein expressions to 2.22±0.21(CdCl_2 group: 1.56±0.06), 3.72±0.21(CdCl_2 group: 2.97±0.15) and 2.41±0.19(CdCl_2 group: 1.52±0.35)(P<0.05). Western blot result showed that compared with the CdCl_2 group, the protein expressions of LC3II/LC3I, LC3II, P62 and cleaved Caspase-3 in the CdCl_2 and CQ treatment groups increased to 3.21±0.31(CdCl_2 group: 2.09±0.25), 4.49±0.43(CdCl_2 group: 2.72±0.26), 2.59±0.19(CdCl_2 group: 1.84±0.19) and 2.43±0.23(CdCl_2 group: 1.50±0.27)(P<0.05). CONCLUSION: Cadmium chloride induces apoptosis of mouse spermatocyte cells by inhibiting autophagosome-lysosomal fusion and prompting abnormal aggregation of autophagosomes.

[Effects of down-regulating Spag6L expression on the proliferation and apoptosis of mouse spermatocytes].

OBJECTIVE: To explore the expression of the Spag6L gene during spermatogenesis and the effects of Spag6L silencing on the proliferation and apoptosis of mouse GC-2 spd cells. METHODS: Using reverse-transcription PCR and real-time qPCR, we detected the expression of the Spag6L gene in the testis tissue collected from the mice at 8, 16, 20, 28 and 42 postnatal days. We prepared lentiviral particles inhibiting the expression of Spag6L and transfected them into the GC-2 spd cells. Then we screened the stably transfected cell lines with the Spag6L expression effectively down-regulated by real-time qPCR, analyzed the effects of Spag6L silencing on the proliferation, activity, cell cycle and apoptosis of the GC-2 spd cells by cell counting and flow cytometry, and on the expression levels of pro-apoptotic Bax and anti-apoptotic Bcl-2 by Western blot. RESULTS: The Spag6L gene was slightly expressed in the testis tissue of the mice at 8 postnatal days and gradually up-regulated with the development of the testis. Inhibition of the Spag6Lexpression significantly decreased the activity of the GC-2 spd cells (P < 0.01), leading to cell arrest in the G1 phase. The expression of the Bax protein was dramatically up-regulated (P < 0.01) while that of Bcl-2 remarkably down-regulated (P < 0.01) in the Spag6L shRNA- transfected cells, inducing the apoptosis of the cells. CONCLUSIONS: The Spag6L gene is involved in the spermatogenesis of mice by regulating the cell cycle, proliferation and apoptosis of spermatocytes.