Estrogen reinforces barrier formation and protects against tumor necrosis factor alpha-induced barrier dysfunction in oral epithelial cells

Abstract

Purpose: Epithelial barrier dysfunction is involved in the pathophysiology of periodontitisand oral lichen planus. Estrogens have been shown to enhance the physical barrier functionof intestinal and esophageal epithelia, and we aimed to investigate the effect of estradiol (E2)on the regulation of physical barrier and tight junction (TJ) proteins in human oral epithelialcell monolayers. Methods: HOK-16B cell monolayers cultured on transwells were treated with E2E2, anestrogen receptor (ER) antagonist (ICI 182,780), tumor necrosis factor alpha (TNF alpha), ordexamethasone (Dexa), and the transepithelial electrical resistance (TER) was then measured.Cell proliferation was measured by the cell counting kit (CCK)-8 assay. The levels of TJ proteinsand nuclear translocation of nuclear factor (NF)-kappa B were examined by confocal microscopy. Results: E2 treatment increased the TER and the levels of junctional adhesion molecule(JAM)-A and zonula occludens (ZO)-1 in a dose-dependent manner, without affecting cellproliferation during barrier formation. Treatment of the tight-junctioned cell monolayerswith TNF alpha induced decreases in the TER and the levels of ZO-1 and nuclear translocation ofNF-kappa B. These TNF alpha-induced changes were inhibited by E2, and this effect was completelyreversed by co-treatment with ICI 182,780. Furthermore, E2 and Dexa presented an additiveeffect on the epithelial barrier function. Conclusions: E2 reinforces the physical barrier of oral epithelial cells through the nuclearER-dependent upregulation of TJ proteins. The protective effect of E2 on the TNF alpha-inducedimpairment of the epithelial barrier and its additive effect with Dexa suggest its potential useto treat oral inflammatory diseases involving epithelial barrier dysfunction.