Inhibition of Prostaglandin E2 Receptors EP2 and EP4 Inhibits Adhesion of Human Endometriotic Epithelial and Stromal Cells Through Deregulated Integrin-Mediated Mechanisms.

BACKGROUND: Endometriosis is a chronic inflammatory disease of reproductive-age women. Adhesion of endometriotic epithelial and stromal cells to peritoneum is mediated through integrin and extracellular matrix (ECM) protein interactions. In endometriosis patients, concentrations of PGE2 in the peritoneal fluid are higher compared to that of endometriosis-free women, and this increased PGE2 is thought to promote invasion and proliferation of endometriotic cells through multiple signaling-cross talk involving ERK, AKT, NFkB and b-catenin pathways. However, PGE2 mediated molecular and cellular mechanisms that control of expression and activity of integrins and their interactions with ECM proteins of peritoneum are not known in the pathogenesis of endometriosis. OBJECTIVES: The objective of the present study was to determine functional interaction between PGE2-EP2-EP4 signaling and adhesion of human endometriotic epithelial cells (12Z) and stromal cells (22B) to ECM and to unravel the underlying molecular and cellular mechanisms. METHODS: The 12Z and 22B cells used in this study were derived from active red peritoneal endometriosis lesions from women. EP2 and EP4 receptors were inhibited using pharmacological inhibitors (EP2: AH6809-75 uM and EP4: AH23848-uM) and siRNA. Effects of inhibition of EP2 and EP4 on adhesion of 12Z and 22B cells to ECM substrates were evaluated using cell adhesion assays. Effects of inhibition of EP2 and EP4 expression and activation of integrins and their signaling interactions were determined by western blot and immunoprecipitation. RESULTS: Selective inhibition of PGE2 receptors EP2 and EP4: i) decreased expression of integrin receptor subunits b1 and b3 but not expression of a2, a3, a5, and av; ii) decreased expression of focal adhesion kinase (FAK397) and talin proteins; iii) inhibited interactions among b1/b3, FAK, talin, and EP2/EP4 through b-arrestin-1 and Src kinase protein complex; and iv) decreased adhesion of 12Z and 22B cells to collagen I, collagen IV, fibronectin, and vitronectin in an epithelial-stromal cell specific manner. CONCLUSIONS: Data from the present study for the first time provide a direct molecular link between PGE2 signaling and adhesion of endometriotic cells in human. It suggests that inhibition of EP2/EP4 could be a potential non-steroidal treatment option for endometriosis in child-bearing age women.