Abstract

Cytochromes P450 (P450s) are down-regulated in hepatocytes in response to inflammation and infection. This effect has been extensively studied in animal models, but significantly less is known about responses in humans and even less about responses in the absence of inducing agents. This article focuses on the effects of bacterial lipopolysaccaride (LPS), interleukin-6 (IL-6), tumor necrosis factor-α (TNF), interferon γ (IFN), transforming growth factor-β (TGF) and interleukin-1β (IL-1) on expression of CYP2B6 and the CYP2C mRNAs in human hepatocytes. These effects were compared with responses of the better studied and more abundant CYP3A4. CYP3A4 and CYP2C8 were down-regulated by all cytokine treatments. CYP2C18, which is expressed at very low levels in liver, was unaffected by cytokine treatments. The other CYP2Cs and CYP2B6 showed cytokine-specific effects. CYP2C9 and CYP2C19 showed almost identical response patterns, being down-regulated by IL-6 and TGF but not significantly affected by LPS, TNF, IFN, or IL-1. CYP2B6 mRNA responded only to IL-6 and IFN. IL-6 down-regulated the mRNAs of all P450s studied. Western blot analysis of P450 protein expression supported the mRNA data to a large extent, although some inconsistencies were observed. Our results show that human CYP2C8, 2C9, 2C18, 2C19, 2B6, and 3A4 responses to inflammation are independently regulated and indicate that this fine control may have a critical effect on human drug responses in disease states.