Abstract

Hepatic cytochrome P450 (P450) enzymes are down-regulated during inflammation. In this study, an animal model of inflammatory bowel disease was subjected to characterization of hepatic P450 expression under inflammatory conditions. Rats were treated intracolonically with 100 mg/kg trinitrobenzene sulfonic acid (TNBS) dissolved in 30% ethanol, and homogenates of colonic mucosa and hepatic microsomes of the rats were prepared. The colitis was accompanied by appearance of higher levels of portal endotoxin, interleukin-6, and nitric oxide metabolites and decreases in contents and activities for hepatic CYP3A2, CYP2C11, and, to a lesser extent, CYP1A2 and CYP2E1. Nimesulide, a preferential COX-2 inhibitor, protected rats with TNBS-induced colitis (TNBS-colitis) against the down-regulation of hepatic CYP3A2. Polymyxin B, which neutralizes endotoxin, curcumin, which has anti-inflammatory properties, and gadolinium chloride, which inactivates macrophages, attenuated the down-regulation of CYP3A2. Similar effects were observed in other P450s such as CYP2C11, but the agents were less effective in attenuating the down-regulation. Our data suggest that endogenous substances leaked from damaged colon in the rats with TNBS-colitis activate Kupffer cells, leading to down-regulation of hepatic P450s with differential susceptibility to the inflammatory stimuli. The colitis model, instead of exogenous administration of lipopolysaccharide or cytokines, could be applied to the study on mechanisms for altered hepatic P450 expression and other liver functions under mild inflammatory conditions.