Increased cytochrome P-450 2E1 expression sensitizes hepatocytes to c-Jun-mediated cell death from TNF-α

The mechanisms underlying hepatocyte sensitization to tumor necrosis factor-α (TNF-α)-mediated cell death remain unclear. Increases in hepatocellular oxidant stress such as those that occur with hepatic overexpression of cytochrome P-450 2E1 (CYP2E1) may promote TNF-α death. TNF-α treatment of hepatocyte cell lines with differential CYP2E1 expression demonstrated that overexpression of CYP2E1 converted the hepatocyte TNF-α response from proliferation to apoptotic and necrotic cell death. Death occurred despite the presence of increased levels of nuclear factor-κB transcriptional activity and was associated with increased lipid peroxidation and GSH depletion. CYP2E1-overexpressing hepatocytes had increased basal and TNF-α-induced levels of c-Jun NH₂-terminal kinase (JNK) activity, as well as prolonged JNK activation after TNF-α stimulation. Sensitization to TNF-α-induced cell death by CYP2E1 overexpression was inhibited by antioxidants or adenoviral expression of a dominant-negative c-Jun. Increased CYP2E1 expression sensitized hepatocytes to TNF-α toxicity mediated by c-Jun and overwhelming oxidative stress. The chronic increase in intracellular oxidant stress created by CYP2E1 overexpression may serve as a mechanism by which hepatocytes are sensitized to TNF-α toxicity in liver disease.