Hepatic apoptosis and proliferation in male and female rats fed alcohol: role of cytokines

Background: The female liver is more sensitive to the toxic effect of chronic alcohol intake than the male liver. The aim of the study was to compare the influence of gender and sex hormonal status on apoptosis and cell proliferation following chronic ethanol intake. Methods: Male and female rats were pair fed for 8 weeks a liquid diet containing 36% of their total daily calories as ethanol (ETOH group) or sucrose (control group). Liver samples were analyzed for apoptosis and hepatocyte proliferation by immunohistochemistry. The hepatic production of factors able to influence cell death and proliferation, such as tumor necrosis factor alpha (TNFalpha) and interleukin 6 (IL-6) were determined. Results: In both male and female rats, ethanol intake promoted apoptosis in the liver. This effect of ethanol was more evident in female than male rat livers. Hepatic TNFalpha levels, which promote apoptosis, are significantly more elevated in female than in male livers. Hepatic IL-6 production, which promotes hepatocyte proliferation, was induced by ethanol only in males, but not female animals. Conclusion: This observed difference in cytokine responses may contribute to the enhanced sensitivity of female liver to EtOH-induced injury.