Cytosolic phospholipase A2 in rat decidual cells: evidence for its role in decidualization

Prostaglandins F2α and E2 in rat placenta and fetal membrane: a comprehensive immunohistochemistry of their synthetic enzymes and in vivo tissue levels during normal pregnancy

We determined a comprehensive immunohistochemistry of putative isoforms of enzymes for prostaglandin (PG) F₂α and PGE₂ biosynthesis and these PGs levels in placenta and fetal membrane of normal pregnant rats in vivo. Placenta and fetal membrane showed positive immunoreactions for phospholipase A₂ group 4A, but not group 2A, and cyclooxygenase (COX)-1 rather than COX-2. They showed positive immunoreactions for at least one isoform of each of PGF synthase and PGE synthase with tissue-dependent variations. PGF₂α and PGE₂ levels in both tissues were highest on day 12 and declined and remained low thereafter. Obtained data would be the basic information on the primary PGs synthesis in rat placenta and fetal membrane in normal pregnancy.

Decidualized pseudopregnant rat uterus shows marked reduction in Ang II and Ang-(1-7) levels

Previous studies showed that angiotensin (Ang) II and Ang-(1-7) concentrations were reduced in the implantation site at day 7 of pregnancy in Sprague-Dawley rats as compared to the site immediately adjacent to it, which does not have the embryo attached, clearly showing the importance of the blastocyst in the regulation of renin-angiotensin system (RAS).

OBJECTIVE

The objective of this study was to evaluate the regulation of the RAS in the decidualized uterus in the pseudopregnant rat, a model without the presence of a conceptus.

METHODS

Ovariectomized, adult female rats were sensitized for the decidual cell reaction with steroid treatments; decidualization was induced by oil-injection of the right horn; the left horn served as a control. The uterine content of Ang I, Ang II, and Ang-(1-7) was examined in the decidualized and non-decidualized uteri.

RESULTS

Both Ang-(1-7) and Ang II and ACE and ACE2 mRNA were significantly reduced in the decidualized horn as compared to the non-decidualized horn. Immunocytochemical characterization of Ang II, Ang-(1-7), ACE and ACE2 demonstrated that Ang-(1-7), Ang II, and ACE2 polarize to the anti-mesometrial pole with decidualization.

CONCLUSION

The decidualization process elicits marked reduction in uterine Ang II and Ang-(1-7) content as compared to the non-decidualized horn. The differential immunocytochemical expression of Ang II and Ang-(1-7) with ACE2, but not ACE in the anti-mesometrial pole of the decidualized horn may favor the formation and action of Ang-(1-7) in the anti-mesometrial pole, an area which plays a role in triggering the decidualization process.

Phospholipase D1 as a key enzyme for decidualization in human endometrial stromal cells

Using primary cell cultures of human endometrial stromal cells (ES cells), we investigated the role of phospholipase D (PLD) in 8-Br-cAMP-induced decidualization, which involves morphological and biological differentiation processes. When treated with 0.5 mM 8-Br-cAMP for 12 days, ES cells were transformed into a decidualized morphology and produced significant amounts of prolactin (PRL) and insulin-like growth factor-binding protein 1 (IGFBP1). Simultaneously, the activity and expression levels of PLD1 increased. In addition, removal of 8-Br-cAMP from decidualized ES cells restored the undifferentiated state, and this was accompanied by decreases in PLD1 promoter activity and PLD1 expression. Overexpression of dominant negative (DN)-PLD1 inhibited the morphological changes induced by 0.5 mM 8-Br-cAMP, whereas PLD1 overexpression induced morphological changes in the absence of 0.5 mM 8-Br-cAMP treatment. Moreover, knockdown of PLD1 by siRNA and blockage of PLD by treatment with 0.3% 1-butanol decreased PRL/IGFBP1 mRNA expression, whereas PLD1 overexpression increased PRL/IGFBP1 mRNA expression. Treatment of ES cells with phosphatidic acid (PA) for 3 days induced PRL mRNA expression and morphological changes, which implies that PA is an end-product of PLD activation-induced decidualization. In addition, pretreatment of ES cells with mepacrine decreased PRL/IGFBP1 expression and inhibited morphological change, whereas pretreatment with propranolol caused no changes, as compared to cAMP-treated cells, which suggests that PA induces decidualization through phospholipase A2 (PLA2G1B). Taken together, these results suggest that PLD1 regulates 8-Br-cAMP-induced decidualization through PLA2G1B, and that PLD1 upregulation is essential for the decidualization of ES cells.

Expression and regulation of cytosolic prostaglandin E synthase in mouse uterus during the peri-implantation period

Prostaglandin E(2) (PGE(2)) is considered important for blastocyst spacing, implantation, and decidualization in rodent uteri. PGE synthase (PGES) catalyzes the isomerization of PGH(2) to PGE(2). Two isoforms of PGES exist: microsomal PGES (mPGES) and cytosolic PGES (cPGES); however, the expression and regulation of cPGES in the mammalian uterus during early pregnancy are still unknown. The aim of this study was to investigate the differential expression of cPGES in mouse uterus during early pregnancy and its regulation under different conditions using in situ hybridization and immunohistochemistry. A strong level of cPGES mRNA signal was exhibited in the stromal cells at the implantation site on Day 5 of pregnancy, whereas cPGES immunostaining was strongly detected in the luminal epithelium. The signals for both cPGES mRNA and immunostaining were strongly detected in the decidualized cells from Days 6-8 of pregnancy. A basal level of cPGES mRNA signal and immunostaining was exhibited in the uterus in delayed implantation. After delayed implantation was terminated by estrogen treatment and embryo implantation was initiated, cPGES mRNA signal was strongly detected in the stroma underlying the luminal epithelium at the implantation site, and cPGES immunostaining was strongly observed in the luminal epithelium surrounding the implanting blastocyst. A strong cPGES mRNA signal and immunostaining were detected in decidualized cells under artificial decidualization, whereas only a basal level of cPGES mRNA signal and immunostaining were observed in the control horn. Our data suggest that cPGES may play an important role during implantation and decidualization.

Biphasic change in correlation between ovarian lipid peroxides and progestational activity during pseudopregnancy induced in immature rats

We measured ovarian lipid peroxide (LP) levels and plasma progestins, progesterone (P4) and 20alpha-dihydroprogesterone, throughout pseudopregnancy in gonadotropin-primed immature rats. Plasma P4 fluctuated, with two peaks on days 5 (PSP5) and 8 of pseudopregnancy, and then declined to the basal level by PSP12. Ovarian LP increased from PSP1 to PSP4, decreased temporarily until PSP8, and then rose gradually until PSP14. From PSP1 through PSP7, ovarian LP was positively correlated with total progestins according to the Spearman ranked correlation coefficient (r=+0.829, p<0.05). In contrast, a negative correlation between ovarian LP and plasma P4 was apparent (r=-0.816, p<0.05) from PSP8 to PSP14. These results show the biphasic correlation of LP with luteal progestational activity depending on the luteal stage.