CYP2E1 autoantibodies in liver diseases

Autoimmune reactions involving cytochrome P4502E1 (CYP2E1) are a feature of idiosyncratic liver injury induced by halogenated hydrocarbons and isoniazid, but are also detectable in about one third of the patients with advanced alcoholic liver disease (ALD) and chronic hepatitis C (CHC). In these latter the presence of anti-CYP2E1 auto-antibodies is an independent predictor of extensive necro-inflammation and fibrosis and worsens the recurrence of hepatitis following liver transplantation, indicating that CYP2E1-directed autoimmunity can contribute to hepatic injury. The molecular characterization of the antigens recognized by anti-CYP2E1 auto-antibodies in ALD and CHC has shown that the targeted conformational epitopes are located in close proximity on the molecular surface. Furthermore, these epitopes can be recognized on CYP2E1 expressed on hepatocyte plasma membranes where they can trigger antibody-mediated cytotoxicity. This does not exclude that T cell-mediated responses against CYP2E1 might also be involved in causing hepatocyte damage. CYP2E1 structural modifications by reactive metabolites and molecular mimicry represent important factors in the breaking of self-tolerance against CYP2E1 in, respectively, ALD and CHC. However, genetic or acquired interferences with the mechanisms controlling the homeostasis of the immune system are also likely to contribute. More studies are needed to better characterize the impact of anti-CYP2E1 autoimmunity in liver diseases particularly in relation to the fact that common metabolic alterations such as obesity and diabetes stimulates hepatic CYP2E1 expression.