Expression And Regulation Of Membrane-Associated Prostaglandin E Synthase-2 In Mouse Oviduct

Prostaglandin E synthase (PGES) is the terminal rate-limiting enzyme for PGE2 synthesis, which catalyzes the conversion of PGH2 into PGE2. There are at least three isoforms of PGES, glutathione-dependent membrane-associated PGES (mPGES-1), glutathione-independent membrane-associated PGES (mPGES-2) and glutathione-dependent cytosolic PGES (cPGES). PGES has been proved to be important for implantation, decidualization, follicle development, formation and regression of corpus luteum, and ovulation. The aim of this study was to investigate the expression of mPGES-2 protein in mouse oviduct during the early pregnancy, pseudopregnancy, and estrous cycle by immunohistochemistry and Western blot. The regulation of mPGES-2 protein in mouse oviducts was also studied under delayed implantation, steroid hormonal treatments and oviductal ligation. mPGES-2 protein was located in the cilial cells in the luminal epithelium of infundibulum and ampulla at different stages. No signal was seen in the myometrium of infundibulum and ampulla, as well as the epithelium and myometrium of isthmus and uterotubal junction. mPGES-2 immunostaining was at a strong level in infundibulum during early pregnancy. mPGES-2 immunostaining remained a strong level from day 1 morning to day 2 evening, slightly increased from days 3 to 4, and dropped to a low level from days 5 and 6. During early pregnancy, mPGES-2 expression pattern shown by Western blot was similar to that of infundibulum by immunohistochemistry. mPGES-2 immunostaining in ampulla was slightly weaker than that in infundibulum. During pseudopregnancy, the level of mPGES-2 protein in infundibulum was a little weaker than that during early pregnancy, and remained a strong level at all stages. mPGES-2 protein in ampulla during pseudopregnancy was weaker than that in infundibulum. After tubal ligation at uterotubal junction during early pregnancy, mPGES-2 protein was expressed much weaker in infundibulum and ampulla than that during normal early pregnancy. In infundibulum and ampulla, the mPGES-2 staining from days 3 to 5 was very weak. During estrous cycle, mPGES-2 immunostaining in infundibulum was weak at diestrus and comparatively stronger at estrus. In ampulla, the immunostaining was nagtive in diestrus and weak in estrus. During estrous cycle, the result from Western blot was similar to immunostaining. In the ovariectomized mice, estrogen had no effects on mPGES-2 expression, whearas progesterone down-regulated mPGES-2 expression dramatically. Under delayed implantation, mPGES-2 immunostaining in infundibulum and ampulla was at a strong level and remained unchanged following the activation of delayed implantation. In conclusion, our results showed that mPGES-2 might be involved in the processes of fertilization, oocyte/early embryo transport and early embryo development by catalyzing PGE2 synthesis in oviductal epithelium.