[Effect of reactive oxygen species in cadmium chloride induced apoptosis of mouse Leydig cells]

To study the effect of reactive oxygen species(ROS) in cadmium chloride-induced apoptosis of mouse Leydig cells(TM3 cells) and explore the underlying molecular mechanisms.

TM3 cells were used as an in vitro model for studying reproductive toxicity induced by cadmium exposure. The cells were treated with different concentrations of CdCl_2(0, 5 and 10 μmol/L) for 24 h. CCK-8 assay was used to detect the effect of CdCl_2 on TM3 cell activity. Hoechst33342 staining was performed to explore the formation of apoptotic bodies. DCFH-DA probe was used to detect the level of ROS in the cells. TM3 cells were pretreated with 1 mmol/L NAC for 1 h and then treated with 10 μmol/L CdCl_2 for 24 h. The protein expression levels of pro-apoptotic proteins Caspase-9 and cleaved Caspase-3 were detected by Western blot; RT-qPCR was used to measure the expression of anti-apoptotic gene Bcl-2 and pro-apoptotic genes Caspase-9 and Caspase-3.

After exposure to CdCl_2 for 24 h, viability of TM3 cells decreased and the number of apoptotic bodies increased. Western blot result showed that the protein level of Caspase-9 in the 10 μmol/L CdCl_2 treatment group was increased to 0.86±0.10(P<0.05) compared with the control group(0.56±0.07). Compared with the control group(0.37±0.11), the protein level of cleaved Caspase-3 in the 5 and 10 μmol/L CdCl_2 treatment groups were increased to 0.65±0.03 and 1.05±0.13(P<0.05). Compared with the control group(46.80±1.24), the intracellular ROS content in the 5 and 10 μmol/L treatment groups increased to 60.47±1.39 and 80.63±1.34(P<0.05). Compared with the cadmium-treated group, NAC inhibited Caspase-9(CdCl_2 group: 0.89±0.07; CdCl_2+NAC group: 0.28±0.02)and cleaved Caspase-3(CdCl_2 group: 1.53±0.21; CdCl_2+NAC group: 0.66 ±0.07), the difference was statistically significant(P<0.05). At the same time, NAC decreased the ROS level(62.64±0.93) in the CdCl_2 exposure group(80.13±0.94)(P<0.05). In addition, RT-qPCR result showed that the Caspase-9 mRNA levels in the 5 and 10 μmol/L CdCl_2 treatment groups were 1.40±0.14 and 1.90±0.12(P<0.05), compared with the control group(0.97±0.10). Compared with the control group(0.88±0.08), the cleaved Caspase-3 mRNA levels in the 5 and 10 μmol/L CdCl_2 treatment groups were increased to 1.42±0.11 and 1.59±0.12(P<0.05). While in the 5 and 10 μmol/L CdCl_2-treated group, compared with the control group(0.94±0.02), the Bcl-2 mRNA level were decreased to 0.60±0.02 and 0.50±0.09(P<0.05). Compared with the cadmium treatment group(0.57±0.06), NAC could significantly improve the cadmium-induced Bcl-2 mRNA expression level(0.92±0.03), and Caspase-9(CdCl_2 group: 1.96±0.07; CdCl_2+NAC group: 1.04±0.02) and Caspase-3(CdCl_2 group: 1.65±0.02; CdCl_2+NAC group: 0.66±0.04) were decreased(P<0.05).

The Caspase cascade in mouse Leydig cells can be activated by excessive ROS induced by CdCl_2, and inhibition of ROS production can significantly reduce the CdCl_2-induced apoptosis of TM3 cells.