REV-ERBα inhibits the PTGS2 expression in bovine uterus endometrium stromal and epithelial cells exposed to ovarian steroids

The nuclear receptor REV-ERBα (encoded by NR1D1) has a critical role in metabolism and physiology as well as circadian rhythm. Here, we investigated the possible contribution of clock genes including NR1D1 to the secretion of prostaglandin F₂α (PGF₂α) from bovine uterine stromal (USCs) and epithelial cells (UECs) by modulating the expression of PTGS2. The circadian oscillation of clock genes in the cells was weak compared with that reported in rodents, but the expression of BMAL1, PER1, and NR1D1 was changed temporally by treatment with ovarian steroids. Significant expression of clock genes including NR1D1 was detected in USCs exposed to progesterone. NR1D1 was also significantly expressed in UECs exposed to estradiol. The expression of PTGS2 was suppressed in USCs exposed to progesterone, while the expression was initially suppressed in UECs exposed to estradiol and then increased after long-term exposure to estradiol. BMAL1 knockdown with specific siRNA caused a significant decrease in the transcript levels of NR1D1 and PTGS2 in USCs, but not in UECs. The production of PGF₂α also decreased in USCs after BMAL1 knockdown, while its level did not significantly change in UECs. The transcript level of PTGS2 was increased by treatment with the antagonist of REV-ERBα in both cell types, but the agonist was ineffective. In these two cell types treated with the agonist or antagonist, the PGF₂α production coincided well with the PTGS2 expression. Collectively, these results indicate that REV-ERBα plays an inhibitory role in the expression of PTGS2 in both bovine USCs and UECs treated with ovarian steroids.