The interaction of buccal mucosal epithelial cells with E. coli bacteria enhances the intraepithelial calcium flux and the release of prostaglandin E2 (PgE2)

Abstract

Mucosal epithelial cells contribute significantly to host defense mechanisms. Uroepithelial cells (UEC) from healthy donors suppress bacterial growth in vitro. Bacterial adherence to UEC has been shown to be a prerequisite. Similar results have been shown for buccal epithelial cells (BEC). The host response triggered by the host-parasite interaction seems to involve signal transduction and intracellular activation of second messengers. In this study the intraepithelial calcium flux was analyzed in individual BEC after bacterial contact. BEC were derived from scrapes of the buccal mucosa and labelled with fluo-3 (a calcium indicator). Thereafter the cells were analyzed immediately with a FACscan flowcytometer. The intracellular events were evaluated before and after the addition of viable E. coli bacteria (strain 4389, K1O1H7, pili II pos.). For control, the influence of prostaglandins, histamine, PMA, LPS and opsonized avital E. coli on the epithelial calcium flux was investigated. Additionally, supernatants of BEC-E. coli cocultures were analyzed with respect to their PgE2 content. PgE2 concentrations in supernatants of BEC, cultured alone or together with E. coli, were measured by a commercial PgE2 ELISA kit. The addition of vital E. coli to BEC was promptly answered by a significant intracellular calcium flux. PgE2, histamine and PMA, but not PgF2alpha, PgE1, LPS and opsonized E. coli, increased intracellular calcium. BEC alone did not release PgE2. After coculture with E. coli increased levels of PgE2 were measured in the supernatants. PgE2 release was still enhanced by coactivation of the BEC with phorbolester (PMA). Our results confirm that calcium flux in mucosal epithelial cells is stimulated by the cell-bacteria contact. We suggest that the increased PgE2 release amplifies the stimulation of intraepithelial second messengers. The resulting cell activation may lead to the secretion of antimicrobial peptides, thereby contributing to the regulation of mucosal host resistance to bacterial infections.