Gene transfer to cultured human endometrial stromal cells: a model to study cyclooxygenase-2 gene regulation

Withdrawal of Ovarian Steroids Stimulates Prostaglandin F2.ALPHA. Production Through Nuclear Factor-.KAPPA.B Activation via Oxygen Radicals in Human Endometrial Stromal Cells: Potential Relevance to Menstruation

The present study was undertaken to investigate whether withdrawal of estrogen and progesterone (EP-withdrawal) stimulates prostaglandin F2alpha (PGF2alpha) production through oxygen radical (ROS)-induced NF-kappaB activation in human endometrial stromal cells (ESC). To study the EP-withdrawal, ESC that had been treated with estradiol (E, 10(-8) M) and medroxyprogesterone acetate (MPA, 10(-6) M) for 12 days were then incubated with or without E+MPA for a further 11 days. PGF2alpha concentrations in the medium and cyclooxygenase-2 (COX-2) mRNA levels were significantly increased after EP-withdrawal, while they were unchanged by the continuous treatment with E+MPA. When ESC were incubated with N-acetyl-L-cysteine (Nac, 50 mM), an antioxidant, during EP-withdrawal, Nac blocked the increases in PGF2alpha production and COX-2 mRNA expression caused by EP-withdrawal. Next, we examined whether ROS generated in response to EP-withdrawal acted through NF-kappaB activation. Electrophoretic mobility shift assay revealed that EP-withdrawal caused marked increases in NF-kappaB DNA binding activity, which was completely suppressed by Nac. Furthermore, when ESC were incubated with MG132 (3 microM), which inhibits NF-kappaB activation, during EP-withdrawal, MG132 blocked the increases in PGF2alpha production and COX-2 mRNA expression caused by EP-withdrawal. In conclusion, EP-withdrawal stimulates COX-2 expression and PGF2alpha production through ROS-induced NF-kappaB activation, suggesting a possible mechanism for menstruation.

Molecular characterization of bovine prostaglandin G/H synthase-2 and regulation in uterine stromal cells

Prostaglandin G/H synthase (PGHS) is a key rate-limiting enzyme in the prostaglandin biosynthetic pathway, and prostaglandins play a central role in the control of the reproductive cycle. The objectives of this study were to clone and characterize the primary structure of bovine PGHS-2 and to study its regulation in uterine stromal cells in vitro. The bovine PGHS-2 cDNA was cloned by a combination of reverse transcription-polymerase chain reaction and cDNA library screening. Results showed that the complete bovine PGHS-2 cDNA is composed of a 5'-untranslated region of 128 bp, an open reading frame of 1815 bp, and a 3'-untranslated region of 1565 bp containing multiple repeats (n = 11) of the Shaw-Kamen sequence 5'-ATTTA-3'. The open reading frame encodes a 604-amino acid protein that is 86-97% identical to other mammalian PGHS-2 homologs. The regulation of PGHS-2 mRNA and protein was studied in primary cultures of bovine uterine stromal cells stimulated with phorbol 12-myristate 13-acetate (PMA; 100 nM). Northern and Western blot analyses reveal a marked induction in PGHS-2 transcript (4.0 kilobases) and protein (M(r) = 72 000) after 3-12 h of PMA stimulation (P < 0.05). However, this induction was transient in nature as levels of PGHS-2 mRNA and protein returned to basal levels after 24 h of PMA stimulation. In contrast, PMA had no effect on levels of PGHS-1 (P > 0.05). The PMA-dependent induction of PGHS-2 was associated with a significant increase in prostaglandin E2 secretion in the culture media (P < 0.05). To study promoter activity of the 5'-flanking DNA region of the bovine PGHS-2 gene, the genomic fragment -1574/-2 (+1 = transcription start site), as well as a series of 5'-deletion mutants, were fused upstream of the firefly luciferase gene and transiently transfected into primary cultures of bovine uterine stromal cells. Results showed that a first promoter region located between -1574 and -492 and a second region between -88 and -39 appear to play important roles in PMA-dependent regulation of PGHS-2 promoter activity in bovine uterine cells. Thus, this study characterizes for the first time the structure of the bovine PGHS-2 transcript and the deduced amino acid sequence of its encoded protein and establishes an in vitro model to study the regulation of PGHS-2 gene expression in bovine uterine tissue.