PROSTAGLANDIN E2 SIGNALING IN PATHOPHYSIOLOGY OF ENDOMETRIOSIS IN HUMAN

Abstract

Endometriosis is a debilitating disease affects up to 20% of reproductive age women characterized by the presence of functional endometrial glandular epithelium and stroma out side the uterine cavity. The pathophysiology of endometriosis remains as enigma in reproductive medicine. Accumulating evidence indicates that steroids, growth factors, and cytokines, and prostaglandins may promote establishment and maintenance of endometriosis. Treatment options include oral contraceptives, aromatase inhibitors, androgenic agents, and gonadotrophin releasing hormone analogues and nonsteroidal anti-inflammatory drugs and surgical removal. But the recurrence rate is up to 70% after cessation of therapy. Prostaglandin E2 (PGE2) promotes cell proliferation, migration, invasion, angiogenesis, anti-apoptosis, pain and immunomodulation. PGE2 mediated effects are primarily mediated through G-protein coupled membrane receptors designated EP that includes EP1, EP2, EP3 and EP4. EP2 and EP4 receptors are coupled to adenyl cyclase generating cAMP that in turn activates the protein kinase A signaling pathway. EP1 receptor is coupled to phospholipase C generating two second messengers, inositol triphosphate (IP3) involved in the liberation of intracellular calcium (Ca2+), and diacyl glycerol an activator of protein kinase C. There are several EP3 isoforms exhibiting a wide range of actions from inhibition of cAMP production to increases in Ca2+ and IP3. In this study, we used immortalized human endometriotic epithelial cells (11-Z, 12-Z, 49-Z, and 108-Z) and stromal cells (22-B) as in vitro models to unravel PGE2 signaling in pathophysiology of endometriosis in human. Normal endometrial epithelial and stromal cells were used as control. We investigated: (1) PGE2 production; (2) expression profiles of EP1, EP2, EP3, and EP4 receptors and (3) role of EP receptors in endometriotic cell proliferation, migration and invasion, and unraveled the underlined mechanisms. We used RT-PCR, western blot, zymography, matrigel migration and invasion assays, and ELISA. Endometriotic cells produced 8–10 fold more PGE2 than normal endometrial cells at basal condition. EP2 and EP4 receptor mRNAs and proteins were abundantly expressed whereas EP1 and EP3 receptor mRNAs and proteins are barely detectable in endometriotic epithelial and stromal cells. Inhibition of either EP2 or EP4 decreased (60%) the endometriotic epithelial and stromal cell proliferation, migration and invasion. Combined inhibition of EP2 and EP4 synergistically decreased (80–85%) endometriotic epithelial and stromal cell proliferation, migration and invasion. Inhibition of EP1 receptor did not have any effect. Inhibition of EP2 and/or EP4 decreased the expression and phosphorylation of Bcl2 protein. Inhibition of EP2 and/or EP4 decreased MMP2 and MMP9 activities. These results suggest that EP2 and/or EP4 mediated cell proliferation and invasion might be mediated respectively through Bcl2 and MMP2 and MMP9 pathways in endometriotic epithelial and stromal cells. Although endometriosis is not a malignancy its pathophysiology seems to be analogous to the mechanisms of cancer metastasis. In conclusion, these endometriotic epithelial and stromal cells can be used as ideal model to study the cellcell communications and interactions in the establishment and maintenance of endometriosis in human. Targeting PGE2 receptors and downstream signaling might be a novel therapy for endometriosis in human. (poster)