Estrogen Stimulates Female Biliary Epithelial Cell Interleukin-6 Expression in Mice and Humans

Females are more susceptible than males to several biliary tract diseases. Interleukin-6 (IL-6) is critical to triggering autoimmune reactions and contributes substantially to biliary epithelial cell (BEC) barrier function and wound repair, and estrogen differentially regulates IL-6 expression in various cell types. We hypothesized that estrogen might stimulate BEC IL-6 production. Exposure to physiologic levels of estradiol, in vitro, increased female mouse BEC (mBEC) IL-6 messenger RNA (mRNA) and protein expression, but either inhibited or had no effect on male mBECs. Female mBECs expressed higher concentrations of estrogen receptor-alpha (ER alpha) mRNA and protein and were also more dependent on estradiol for survival, in vitro. In vivo, elevated estrogen during estrous cycling in mice, and estrogen treatment of mice harboring an ER alpha(+) human cholangiocarcinoma resulted in increased BEC IL-6 mRNA and tumor viability, respectively. Both responses could be blocked by an ERa antagonist. Human cholangiocarcinoma cell tines differentially expressing ER alpha were treated with specific ER alpha and ER beta agonists/antagonists to further test the relationship between estrogen stimulation, ER alpha expression, and IL-6 production. Results show that ER alpha, and not the underlying BEC sex, was responsible for estrogen-induced IL-6 production. Estrogen-induced proliferation of ER alpha-expressing cholangiocarcinoma was blocked by anti-IL-6 antibodies, indicating that at least some of the estrogen-trophic effects are mediated via IL-6. Finally, an association between ER alpha, IL-6, and phosphorylated signal transducer and activator of transcription 3 (pSTAT3) signaling was shown in female-predominant polycystic livers using immunohistochemical analyses, including multiplex quantum dot labeling. Conclusion: Estrogens stimulate IL-6 production in non-neoplastic female BECs and in neoplastic BECs expressing ER alpha. An association between these signaling pathways was demonstrated for female-predominant polycystic livers and might also influence autoimmune hepatitis, primary biliary cirrhosis, and cholangiocarcinogenesis. (HEPATOLOGY 2010;51:869-880.)