Estrogen modulates intestinal mucus physiochemical properties and protects against oxidant injury

The intestinal epithelial barrier and the intestinal mucus layer may be protective against trauma/hemorrhage shock-induced injury in females. This effect is related to estradiol (E₂) concentrations and varies with the menstrual cycle. We examined the ability of E₂ to impact the physiochemical properties of intestinal mucus and to protect against oxidant-related injury to the mucus and underlying intestinal epithelial barrier in an in vitro model. Non-mucus-producing (HT29) and mucus-producing (HT29-MTX) intestinal epithelial cells (IECs) were exposed to E₂ or no E₂ for 3 days and then grown to confluence on transwell plates. Nonadherent and adherent mucus content was indexed by analysis of mucin using an enzyme-linked immunosorbent assay and mucus viscosity (cp) and elasticity (G') were determined by rheometry. In additional experiments, IEC groups were exposed to hydrogen peroxide and IEC apoptosis as well as permeability (fluorescein isothiocyanate-dextran) and oxidative damage determined by measuring lipid hydroperoxide and protein carbonyl content. There were nearly 50% increases in the mucin content of both the nonadherent and adherent mucus layer(s) in HT29-MTX cells exposed to estrogen. Estrogen treatment also resulted in a twofold and eightfold increase in mucus viscosity and elasticity versus HT29-MTX cells with no estrogen exposure, respectively. Oxygen radical damage to the mucus layer caused by H₂O₂ was significantly reduced by E₂ compared with HT29-MTX + H₂O₂ without estrogen. Estrogen treatment resulted in significant reductions in both apoptosis and permeability seen after H₂O₂ challenge. The results of this study suggest that sex differences in gut barrier function following trauma/hemorrhage shock may in part be related to differences in intestinal mucus content and the resultant physiochemical and oxidant-resistant properties of the mucus layer.