Kazuhito Tsuboi

The prostaglandin receptor EP4 suppresses colitis, mucosal damage and CD4 cell activation in the gut

We used mice deficient in each of the eight types and subtypes of prostanoid receptors and examined the roles of prostanoids in dextran sodium sulfate-induced (DSS-induced) colitis. Among the prostanoid receptor-deficient mice, only EP4-deficient mice and not mice deficient in either DP, EP1, EP2, EP3, FP, IP, or TP developed severe colitis with 3% DSS treatment, which induced only marginal colitis in wild-type mice. This phenotype was mimicked in wild-type mice by administration of an EP4-selective antagonist (AE3-208). The EP4 deficiency impaired mucosal barrier function and induced epithelial loss, crypt damage, and aggregation of neutrophils and lymphocytes in the colon. Conversely, administration of an EP4-selective agonist (AE1-734) to wild-type mice ameliorated severe colitis normally induced with 7% DSS, while that of AE3-208 suppressed recovery from colitis and induced significant proliferation of CD4+ T cells. In vitro AE3-208 enhanced and AE1-734 suppressed the proliferation and Th1 cytokine production of lamina propria mononuclear cells from the colon. DNA microarray analysis revealed elevated expression of genes associated with immune response and reduced expression of genes with mucosal repair and remodeling in the colon of EP4-deficient mice. We conclude that EP4 maintains intestinal homeostasis by keeping mucosal integrity and downregulating immune response.

Prostanoid receptor subtypes

Prostanoids are a group of lipid mediators that include the prostaglandins (PG) and thromboxanes (TX). Upon cell stimulation, prostanoids are synthesized from arachidonic acid via the cyclooxygenase (COX) pathway and released outside the cells to exert various physiological and pathological actions in a variety of tissues and cells. The activities of prostanoids are mediated by specific G protein-coupled receptors, which have been classified on the basis of pharmacological experiments into eight types and subtypes according to their responsiveness to selective agonists and antagonists. These prostanoid receptors have been cloned from various species including human, and their distinct binding properties and signal transduction pathways have been characterized by analyses of cells expressing each receptor. Furthermore, the distribution patterns of prostanoid receptor mRNAs have been determined in tissues and cells for various species. This information is useful for understanding the molecular basis of the pathophysiological actions of prostanoids.

Uterine expression of prostaglandin H2 synthase in late pregnancy and during parturition in prostaglandin F receptor-deficient mice.

PG production in uterine tissues is important for many physiological processes in late pregnancy, including parturition. We examined the expression of the PGH2 synthases, cyclooxygenase-1 (COX-1) and COX-2, in uterine tissues during late pregnancy, using PGF receptor-deficient (FP−/−) mice. Female FP−/− mice are unable to deliver normal fetuses at term, as they do not undergo luteolysis necessary for parturition. In wild-type mice, COX-1 messenger RNA (mRNA) was expressed in the endometrial epithelium, myometrium, and decidua throughout late pregnancy. The expression of COX-1 mRNA in the endometrial epithelium and myometrium decreased both in wild-type mice undergoing natural parturition and in FP−/− mice undergoing ovariectomy-induced parturition, but expression of COX-1 mRNA was enhanced in FP−/− mice at the expected term. In wild-type mice, COX-2 mRNA was not expressed in the myometrium before parturition, but was markedly induced during parturition. This induction of COX-2 was absent in FP−/− mice at ...

Expression of Messenger RNA for Prostaglandin E Receptor Subtypes EP4/EP2 and Cyclooxygenase Isozymes in Mouse Periovulatory Follicles and Oviducts During Superovulation

Abstract Prostaglandin (PG) E2 is synthesized from arachidonic acid by cyclooxygenase (COX) and acts as a regulator in ovulation and fertilization reactions. We present the temporal and regional expression patterns of mRNAs for the two Gs-coupled PGE receptors, EP2 and EP4, and for COX-1 and COX-2 in mouse periovulatory follicles and oviducts during superovulation. Analysis using reverse transcription polymerase chain reaction revealed that the mouse ovaries express a significant amount of EP4 mRNA in addition to EP2 mRNA during superovulation. In situ hybridization results revealed that the signals for EP4 mRNA were localized mostly to oocytes in the preantral follicles. Three hours after hCG injection, the signals for EP4 and EP2 mRNA were present in both granulosa and cumulus cells. However, 9 h after hCG injection, just before ovulation, the signals for EP4 mRNA were still detectable in both cell types, whereas those for EP2 mRNA were found only in cumulus cells. COX-2 mRNA expression was present in both granulosa and cumulus cells at 3 h but was present only in cumulus cells at 9 h. COX-1 mRNA expression was not found in granulosa cells at 3 h but was found in these cells at 9 h. In the oviduct, the expression of EP4 and COX-1 mRNA was localized to epithelial cells, whereas expression of EP2 mRNA was localized to the smooth muscle layer. The tightly regulated expression of both EP2 and EP4 in the preovulatory follicles may reflect the essential role of PGE2 in the ovulation process.

Role of Prostaglandin H2 Synthase 2 in Murine Parturition: Study on Ovariectomy-Induced Parturition in Prostaglandin F Receptor-Deficient Mice

Abstract To determine the prostaglandin (PG) H2 synthase (generally referred to as cyclooxygenase [COX]) isozyme responsible for producing uterotonic PGs during parturition, we used PGF2α receptor-deficient mice, which exhibit parturition failure due to impaired withdrawal of serum progesterone at term. On ovariectomy-induced parturition in these mice, uterine COX-2 mRNA expression was drastically induced in the myometrium, whereas COX-1 mRNA expression in the endometrial epithelium decreased. The concomitant administration of progesterone with ovariectomy resulted in a delay in parturition and the disappearance of both the increase in COX-2 mRNA and the decrease in COX-1 mRNA. Thus, the expression of myometrial COX-2 and the occurrence of parturition are closely associated in this model. Furthermore, administration of the COX-nonselective inhibitor, indomethacin, or the COX-2-selective inhibitor, Dup-697 or JTE-522, effectively delayed ovariectomy-induced parturition in these mice. These findings suggest that COX-2-derived PGs contribute to the onset of parturition after the decrease in serum progesterone level.

Female Reproduction in Mice Lacking the Prostaglandin F Receptor

Female mice lacking the receptor for prostaglandin F2 alpha (FP) do not deliver fetuses at term, although these can be successfully rescued by cesarean section. No induction of oxytocin receptor mRNA is found in the uterus of these mice, and they show no uterine contraction on intravenous administration of oxytocin. Furthermore, a decline in serum progesterone levels during the periparturition period is not observed in these animals. Ovariectomy at day 19 of pregnancy restored induction of the oxytocin receptor and caused successful delivery in these animals. These results indicate not only the essential role of luteolytic PGF 2 alpha action in natural parturition but also the importance of oxytocin receptor induction in this process.

Prostaglandin E2 and F2α in mouse reproduction

Abstract The prostaglandins (PGs) are involved in various mammalian female reproductive processes including ovulation, fertilization, luteolysis, and uterine contraction. To determine which specific PG and receptor subtype are crucial for each of the reproductive processes, we generated PG receptor-deficient mice. Among the eight types of PG receptors, only the PGF2α receptor FP-deficient and PGE2 receptor subtype EP2-deficient mice exhibited a failure of parturition and a decrease in litter size, respectively. FP-deficient mice failed to show both the up-regulation of the oxytocin receptor in uterine tissues at term and the prepartum decline in serum progesterone levels, indicating that PGF2α is essential for the induction of parturition via its luteolytic activity. Furthermore, expression analyses of the cyclooxygenases (COXs) suggested that the COX-2 isozyme in the myometrium at term is responsible for producing uterotonic PGs. On the other hand, EP2-deficient female mice consistently delivered fewer pups than their wild-type counterparts. They showed phenotypes of slightly impaired ovulation and a dramatic reduction in fertilization due to impaired expansion of the cumulus cells, indicating that PGE2 plays a role in ovulation and fertilization by inducing cumulus expansion via the EP2 receptor. These results show that PGE2 and PGF2α play important roles in the mouse physiological reproduction processes.