Female hepatology: Favorable role of estrogen in chronic liver disease with hepatitis B virus infection

Chronic hepatitis B virus (HBV) infection is the most common cause of hepatic fibrosis and hepatocellular carcinoma (HCC), mainly as a result of chronic necroinflammatory liver disease. A characteristic feature of chronic hepatitis B infection, alcoholic liver disease and nonalcoholic fatty liver disease (NAFLD) is hepatic steatosis. Hepatic steatosis leads to an increase in lipid peroxidation in hepatocytes, which, in turn, activates hepatic stellate cells (HSCs). HSCs are the primary target cells for inflammatory and oxidative stimuli, and these cells produce extracellular matrix components. Chronic hepatitis B appears to progress more rapidly in males than in females, and NAFLD, cirrhosis and HCC are predominately diseases that tend to occur in men and postmenopausal women. Premenopausal women have lower hepatic iron stores and a decreased production of proinflammatory cytokines. Hepatic steatosis has been observed in aromatase-deficient mice, and has been shown to decrease in animals after estradiol treatment. Estradiol is a potent endogenous antioxidant which suppresses hepatic fibrosis in animal models, and attenuates induction of redox sensitive transcription factors, hepatocyte apoptosis and HSC activation by inhibiting a generation of reactive oxygen species in primary cultures. Variant estrogen receptors are expressed to a greater extent in male patients with chronic liver disease than in females. These lines of evidence suggest that the greater progression of hepatic fibrosis and HCC in men and postmenopausal women may be due, at least in part, to lower production of estradiol and a reduced response to the action of estradiol. A better understanding of the basic mechanisms underlying the sex-associated differences in hepatic fibrogenesis and carciogenesis may open up new avenues for the prevention and treatment of chronic liver disease.