Selective and opposing actions of progesterone receptor isoforms in human endometrial stromal cells.

Transcriptional regulation by progesterone is mediated primarily through the two progesterone receptor (PR) isoforms, PR-A and PR-B. Primary human endometrial stromal cell cultures, in which endogenous PR expression was lost, were infected with adenovirus expressing PR-A, PR-B, or both. Global gene expression analysis was conducted on vehicle and 30 nM progesterone (P4) treated cells following 12 h treatment. Interestingly, many genes regulated by PR-B alone or upon PR-A and PR-B co-expression, did not overlap with each other or with the PR-A expression group. Although many genes known to be progestin regulated in the uterus in vivo were also regulated in this study, markedly little overlap with published P4 regulated genes from human breast cancer cells was observed. Progesterone dose response curves were generated for several genes demonstrating gene selective potency and efficacy for each PR isoform. Furthermore, the PR isoforms opposed each other in regulation of tissue factor, with PR-B increasing and PR-A decreasing both mRNA and protein levels. Our data provide a view of global gene expression by PR isoforms in human endometrial cells and a comparison with other cell types. The specific genes and regulation patterns found provide groundwork to revealing the mechanism of PR isoform selectivity, and perhaps ultimately to the tissue selective properties these receptors appear to exhibit.

Evaluation of adenosine agonists as potential analgesics.

Adenosine agonists, N6-cyclohexyladenosine (CHA), N6-cyclopentyladenosine (CPA), N6-phenylisopropyladenosine (PIA), 5'-N-ethylcarboxamidoadenosine (NECA), 5'-N-methylcarboxamidoadenosine (MECA) and 2-chloroadenosine (CADO), produced a dose-related inhibition of acetylcholine (ACh)-induced writhing in mice. The antinociceptive potency of adenosine agonists was comparable to that of morphine. Adenosine agonists were 10-1000 times more potent when given i.c.v. than p.o., suggesting a central site of action. Theophylline antagonized the antinociceptive activity of R-PIA in the writhing assay, suggestive of an adenosine receptor-mediated event. The sedative/ataxic properties of adenosine agonists were evaluated using a rotorod assay. Adenosine agonists impaired performance on the rotorod in doses comparable to and in some cases lower than those active in the ACh writhing assay. The results of the present study suggest that adenosine agonists attenuate nociceptive responding to a chemical stimulus through a central purinergic mechanism. The ability of adenosine agonists to inhibit ACh-induced writhing may be secondary to their sedative/ataxic properties.

In vitro and in vivo characterization of a novel nonsteroidal, species-specific progesterone receptor modulator, PRA-910.

The progesterone receptor (PR) is an important regulator of female reproduction. Consequently, PR modulators have found numerous pharmaceutical utilities in women's reproductive health. In the process of identifying more receptor-specific and tissue-selective PR modulators, we discovered a novel nonsteroidal, 6-aryl benzoxazinone compound, PRA-910, that displays unique in vitro and in vivo activities. In a PR/PRE reporter assay in COS-7 cells, PRA-910 shows potent PR antagonist activity with an IC50 value of approximately 20 nM. In the alkaline phosphatase assay in the human breast cancer cell line T47D, PRA-910 is a partial progesterone antagonist at low concentrations and is also an effective PR agonist at higher concentrations (EC50 value of approximately 700 nM). PRA-910 binds to the human PR with high affinity (Kd = 4 nM) and was previously shown to exhibit greater than 100-fold selectivity for the PR versus other steroid receptors. In the adult ovariectomized rat, PRA-910 is a potent PR antagonist. It inhibits progesterone-induced uterine decidual response with an ED50 value of 0.4 mg/kg, p.o., and reverses progesterone suppression of estradiol-induced complement C3 expression with potency similar to RU-486. In the nonhuman primate, however, PRA-910 is a PR agonist. The effect on endometrial histology strongly resembles that of progesterone. This unique compound also suppresses estradiol-induced epithelial cell proliferation and both estrogen and progesterone receptor expression in the uterine endometrium as a PR agonist would. In summary, PRA-910 is a structurally and biologically novel selective PR modulator with either PR agonist or antagonist activity, depending on context, concentration, and species.