Cr(VI) induces the decrease of ATP level and the increase of apoptosis rate mediated by ROS or VDAC1 in L-02 hepatocytes

The present study explored the ability of the voltage-dependent anion channel 1 (VDAC1) mRNA and ROS levels to modulate the effects of hexavalent chromium Cr(VI) on the adenosine triphosphate (ATP) level and the rate of apoptotic cell death. Cultured L-02 cells were pretreated with 20 mM N-acetyl-cysteine (NAC) for 24 h or transiently transfected with small interfering RNAs targeting VDAC1 (siVDAC1) for 48 h; cells that were not pretreated were used as the control. The cells were subsequently treated with 0, 2, 8, or 32 mu M Cr(VI) for 24 h. Then, levels of VDAC1 mRNA, ROS, and ATP and the apoptosis rate were measured by reverse-transcription quantitative PCR, fluorometry, a bioluminescence assay, and flow cytometry, respectively. The results showed that Cr(VI) at 32 mu M led to increase in the ROS level, VDAC1 mRNA expression, and the apoptosis rate and a decrease in the ATP level; pretreatment with NAC led to the down-regulation in the levels of ROS, VDAC1 mRNA and apoptosis and the significant up-regulation in the ATP levels. Interestingly, after the pretreatment with siVDAC1 to inhibit VDAC1 mRNA expression, the increased apoptosis rates and decreased ATP levels were reversed as well. These results suggested that changes in the ROS or VDAC1 mRNA levels were associated with changes in the ATP level and apoptosis rate. Furthermore, correlation analysis confirmed the association between both the ROS and VDAC1 levels and both the ATP level and the apoptosis rate. In conclusion, Cr(VI) induced ROS- and VDAC1-mediated decreases in ATP levels and increases in the apoptosis rate. (C) 2012 Elsevier BM. All rights reserved.