Association between VDAC1 mRNA expression and intracellular ATP levels of cultured L-02 hepatocytes during hexavalent chromium toxicity

Abstract

One way in which xenobiotics induce apoptotic cell death is to alter the selective permeability of the intracellular voltage-dependent anion channel (VDAC1) in the mitochondrial membrane. In this study, we explored the association between VDAC1 mRNA expression and mitochondrial function during hexavalent chromium compounds [Cr(VI)] treatment. Cultured L-02 hepatocytes were treated with 2, 4, 8, 16, or 32 μmol/L Cr(VI) for 12, 24, or 36 h. Expression of VDAC1 mRNA was measured by qualitative reverse transcription polymerase chain reaction (RT-PCR), whereas intracellular adenosine triphosphate (ATP) levels were determined by an ATP-specific bioluminescence assay. Over this range of Cr(VI) concentrations, average VDAC1 mRNA expression decreased by 84% after 12 h treatment and by 40% after 24 h of treatment, but it increased 2.33-fold at 36 h when compared with the control cultures. Treatment with Cr(VI) disrupted cellular metabolism as evidenced by changes in ATP levels. Cr(VI) treatment caused ATP levels to increase at 12 h, decrease at 24 h, and increase again at 36 h, resulting in a slant V-shaped curve. Correlation analysis revealed a moderate negative relationship between VDAC1 mRNA expression and intracellular ATP levels during Cr(VI) treatment (r = -0.557, P < 0.05). The negative association seemed to be more obvious in 32 μmol/L Cr(VI) group. Based on these results, heavy metal toxicity may induce over-expression of VDAC1 mRNA, which causes a decrease in ATP levels.

Key words: Heavy metal toxicity, VDAC1 mRNA expression, ATP, relationship.