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

Abstract

Objective: 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.

Methods: 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.

Results: 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).

Conclusion: 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.