Expression and Regulation of Prostaglandin Biosynthetic Enzymes Cox-2 and Pges-1 and Receptors EP1, EP2, EP3, and EP4 in Endometriosis in the Nonhuman Primate.

Endometriosis is a debilitating disease where endometrium-like tissue forms lesions outside the uterus that result in chronic pelvic pain and infertility in 10-20% of women of reproductive age. Endometriosis is an estrogen-dependent disease and current medical therapies for the disease include oral contraceptives, aromatase inhibitors, and gonadotropin releasing hormone analogues that act by suppressing estrogen action. These therapies are not ideal in that they frequently produce undesirable menopause-like side effects such as loss of bone density and hot flushes and fail to restore fertility in women of reproductive age. Moreover, cessation of medical therapy results in reestablishment of the disease within a year in ~50-60% of patients. Our broad goal is to investigate new therapies for endometriotic disease. There is growing evidence that prostaglandin E2 (PGE2) can act to mediate the actions of steroid hormones to promote growth and development of endometriotic lesions. PGE2 biosynthesis is limited by cyclooxygenase-2 (COX-2) and prostaglandin E-synthase-1 (PGES-1) and its actions are mediated through G-protein coupled membrane receptors (EP1, EP2, EP3, and EP4). Rhesus macaques can develop endometriosis and provide a useful animal model for testing novel therapies for the disease. However, little is known regarding the PGE2 paracrine system in rhesus macaque endometrium. This study had two objectives. Our first objective was to characterize tissue specific expression on steroid hormone regulation of COX-2, PGES-1, and the EP receptors in eutopic and ectopic endometria from rhesus macaques. Our second objective was to assess the effect of COX-2, EP2 and EP4 on cell proliferation in rhesus macaque endometrial epithelial and stromal cells by pharmacological blockade. Samples were obtained from animals assigned to studies at the Oregon National Primate Research Center (ONPRC). Animal use was reviewed and approved by the ONPRC Institutional Animal Care and Use Committee. The samples included formaldehyde-fixed paraffin-embedded endometrium, spontaneous endometriosis and ectopically grafted endometrium (induced endometriosis) from castrated monkeys under estrogen treatment (n=3 each). Fresh samples of endometrium from spontaneous endometriosis were also used to prepare isolated epithelial and stromal cells cultures for in vitro study. We found that COX-2 and PGES-1 were expressed in glandular epithelia (GLE) and stroma (STR) and were significantly up regulated in ectopic compared to eutopic endometria. EP1 protein was present at similar levels in the GLE and STR of both ectopic and eutopic endometria. However, EP2 and EP4 proteins were expressed at greater levels in GLE and STR of ectopic compared to eutopic endometria. Expression of EP3 protein was very low or undetectable in both eutopic and ectopic macaque endometrium. Functional studies revealed that progesterone down-regulated EP4 but not EP2, COX-2 or PGES-1 in ectopic and eutopic endometria in vivo. Pharmacological blockade of COX-2 or EP2 and EP4 decreased proliferation of primary cultured endometrial GLE and STR. In conclusion, our data suggest that PGE2 may play an important role in the pathogenesis of endometriosis and targeting COX-2 or EP2 and EP4 could develop into novel non-estrogen or non-steroidal therapies for treatment of endometriosis in women. Supported by NIH grants HD18185 and RR000163 to ONPRC.