Prostaglandin G/H Synthase (PGHS)-2 Expression in Bovine Myometrium: Influence of Steroid Hormones and PGHS Inhibitors1

Abstract

Prostaglandins (PGs) are important mediators regulating uterine functions during the reproductive process. The objective of this study was to examine, in myocytes from the circular and longitudinal layers of bovine myometrium, the relative levels of mRNA and proteins corresponding to the gene expression of key enzymes (phospholipase A2; prostaglandin G/H synthase-1 [PGHS-1]; prostaglandin G/H synthase-2 [PGHS-2]; prostaglandin I2 synthase) involved in PG biosynthesis. We examined the influence of estradiol-17beta and progesterone on the expression and activity of these enzymes. Treatment of myocytes with progesterone (P4: 10 nM, 24 h) in the absence or presence of estradiol-17beta (E2: 1 nM, 72 h) suppressed PG biosynthesis by approximately 60% in both myometrial layers. No significant effect was observed after E2 treatment. The combined effect of E2 and P4 on PG accumulation was correlated with the modulation of PGHS-2 protein and mRNA levels in the two myometrial layers without affecting other enzymes of the PG cascade. Selective or nonselective inhibition of PGHS activity with CGP 28238 (PGHS-2-specific; a product from Ciba-Geigy: 6-[2, 4-difluorophenoxy]-5-methyl-sulfonylamino-1-indanone) or indomethacin (PGHS-1 and -2) reduced prostacyclin accumulation (measured as 6-keto-PGF1alpha in the culture medium) in a dose-dependent manner in the two myometrial layers. A significant inhibitory effect was obtained at a low concentration of indomethacin (1 nM, p < 0.05) compared to CGP 28238 (10 nM, p < 0. 05). In both myometrial layers, the maximal effect of indomethacin and/or CGP 28238 on PG accumulation was observed at 100 nM and represented 85% and 65% inhibition, respectively. In the presence of phorbol 12-myristate (100 nM), CGP 28238 (10 nM) significantly suppressed PGHS-2 mRNA level by 44.80 +/- 7.67% (p < 0.01) and 27.83 +/- 7.62% (p < 0.05) in the longitudinal and circular layer, respectively. In contrast, indomethacin did not have any significant effect. These data constitute the first quantitative analysis of key enzymes involved in PG biosynthesis in separated myometrial layers. Furthermore, the results provide interesting information on the CGP 28238 drug modulating both enzymatic activity and mRNA expression of PGHS-2.

Detrimental effects of hyperandrogenism on uterine functions

“…In addition, COX1 and COX2 are independently regulated [51]. Our data demonstrate that DHEA generates a pro-inflammatory status shown not only by the modulation of PG synthesis but also by increased uterine oxidative stress, as discussed in the following paragraph.…”

“…The enzyme catalyzing the rate-limiting steps in PG synthesis exists in two isoforms; COX1 which is normally constitutively expressed and COX2 which is generally inducible in response to inflammatory stimuli [51]. In addition, COX1 and COX2 are independently regulated [51].…”

An Antiprogesterone, Onapristone, Enhances the Gene Expression of Promatrix Metalloproteinase 3/Prostromelysin-1 in the Uterine Cervix of Pregnant Rabbit.

“…34) Very similar regulation by steroid hormones of prostaglandin G/H synthase-2 has been observed in bovine myometrium. 35) In contrast, there have been few reports that describe the effects of antiprogesterone on connective-tissue metabolism; mifepristone suppresses the production of metalloproteinase inhibitors in cultured human and rat granulosa cells. 36) In addition, the administration of mifepristone to pregnant rats has been found to accelerate the decrease in collagen concentration in the uterine cervix.…”

Luteinising hormone receptor kinetic and LH-induced prostaglandin production throughout the oestrous cycle in porcine endometrium

“…The key-enzyme in prostaglandin production is prostaglandin G/H synthase (PGHS), also known as cyclo-oxygenase (COX) [5,8,15,16,18].…”