Microarray analysis of drug metabolizing enzyme induction in primary hepatocyte cultures

We used cDNA expression arrays to measure the global pattern of drug metabolizing enzyme induction in primary human hepatocytes. We validated our results by generating specific riboprobes suitable for RNase protection assay for 8 clinically relevant cytochrome P450 enzymes: CYP1A2, 2D6, 2E1, 2C8, 2C9, 2C18, 2C19 and 3A4. The primary hepatocytes were isolated from human liver or purchased from commercial sources. Cells were treated for 3 days with 33μM rifampin, total RNA isolated and mRNA expression levels compared to control cells. In one hepatocyte preparation the results from cDNA expression arrays show rifampin caused a greater than 15 fold induction in CYP2A6 and a greater than 2 fold increase in CYP1A2 and CYP2C family while having no effect on CYP2E1 and CYP2D6. Many non-P450 enzymes, including phase II enzymes, were also induced by rifampin. Furthermore, rifampin caused a decrease in mRNA expression for several enzymes including ∼2 fold decrease in superoxide dismutase. RNase protection validated the results for CYP2C, CYP1A2, CYP2E1 and CYP2D6. And as a control for rifampin induction, CYP3A4 mRNA expression was measured by RNase protection. Variability in the level of induction was seen between cultures but the general pattern of enzymes involved remained similar. The results of this study show that microarray analysis is a useful tool for studying the effects of drugs on enzyme induction in primary human hepatocytes.