Abstract:Objective: To investigate the effect of cytochrome P450 isozymes on aristolochic acid induced cytotoxicity on renal proximal tubular epithelial cell (cell line HK-2). Method: Human renal tubular cells (cell line HK-2), were treated with aristolochic acid(AA) alone or in combination with cytochrome P450 isozymes inhibitors, including α-naphthoflavone (CYP450 1A1 and 1 A2 inhibitors), ketoconazole (CYP450 3A4 inhibitor), sodium diethyldithiocarbamate (CYP450 2A6 and 2E1 inhibitors), quinidine (CYP450 2D inhibitor), α-lipoic acid (NADPH: P450 reductase inhibitor), sulfaphenazole (CYP450 2C inhibitor) in the presence or absence of liver microsome(S9). The inhibition of cell proliferation rate was studied by MTT assay and the lactate dehydrogenase release rate was determined with continuous monitoring method. Result: AA inhibits cell proliferation and promotes the release of LDH over the range of 12.5-100 mg·L-1, in a dose-dependent manner. Addition of S9 into the culture system reduced AA cytotoxicity, with the cell proliferation inhibition reducing and the release of LDH decreasing (AA+S9 group vs the same concentration of AA alone group, P<0.05). In the absence of S9, ketoconazole or α-naphthoflavone has no obvious effect on AA cytotoxicity, however，under the conditions of adding S9, ketoconazole or α-naphthoflavone enhances AA cytotoxicity. Other inhibitors of CYP450 isozymes has no distinct effect on AA cytotoxicity. Conclusion: The microsomal enzyme of Liver can reduce the AA cytotoxicity， and CYP450 3A, CYP450 1A may be the major cytochrome P450 isozymes which impact AA cytotoxicity.