Molecular action of norgestimate: new developments.

BACKGROUND: Acne occurs because the sebaceous glands are overstimulated by high levels of androgens or are hypersensitive to normal levels of testosterone. In women with mild or moderate acne, the association of norgestimate (NG), and ethinyl estradiol (EE) is an effective treatment. This is related to the effect of oral contraceptives on androgen production and transport and the antiandrogenic properties of NG itself. DESIGN: The present work was undertaken to find out whether NG and its derivative, 17-deacetylnorgestimate(dNG), present steroid activities other than antiandrogen activities, using human progesterone receptor(PR), estrogen receptor α(ERα) and ß(ERß), glucocorticoid receptor(GR) and mineralocorticoid receptor(MR)-responsive cell lines. RESULTS: We confirmed that NG and its metabolite were progestogen partial agonists (EC50 of 13 and 11.1 nM) and ERα selective agonists (EC50 of 30.4 and 43.4 nM), as well as full antagonists of low affinity for GR (IC50 of 325 and 255 nM) and moderate affinity for MR (IC50 of 81.2 and 83.7). CONCLUSION: We demonstrated that NG and dNG have full progestogen and weak estrogenic (through ERα) properties, which could explain in part the efficacy of NG in association with EE for the treatment of moderate acne in women. Moreover, their antagonist MR activity might have a favorable impact on cardiovascular risk, atherosclerosis and lipid profiles.

Classical membrane progesterone receptors in murine mammary carcinomas: agonistic effects of progestins and RU-486 mediating rapid non-genomic effects.

In this article, we demonstrate the expression of functional progesterone binding sites at the cell membrane in murine mammary carcinomas that are stimulated by progestins and inhibited by antiprogestins. Using confocal immunofluorescence, ligand binding and cell compartment-specific western blots, we were able to identify the presence of the classical progesterone receptors. Medroxyprogesterone acetate (MPA) and RU-486 (1 × 10(-11) and 1 × 10(-8) M) behaved as agonists activating extracellular signal-regulated kinases (ERKs) and progestin-regulated proteins, except for Cyclin D1 and Tissue factor which failed to increase with 1 × 10(-8) M RU-486, an experimental condition that allows PR to bind DNA. These results predicted a full agonist effect at low concentrations of RU-486. Accordingly, at concentrations lower than 1 × 10(-11) M, RU-486 increased cell proliferation in vitro. This effect was abolished by incubation with the ERK kinase inhibitor PD 98059 or by OH-tamoxifen. In vivo, at a daily dose of 1.2 µg/kg body weight RU-486 increased tumor growth, whereas at 12 mg/kg induces tumor regression. Our results indicate that low concentrations of MPA and RU-486 induce similar agonistic non-genomic effects, whereas RU-486 at higher concentrations may inhibit cell proliferation by genomic-induced effects. This suggests that RU-486 should be therapeutically administered at doses high enough to guarantee its genomic inhibitory effect.

Danazol regulates the functions of normal human endometrial stromal cell subpopulations by modifying endometrial cytokine networks.

Local danazol therapy can improve endometriotic signs and symptoms without causing any menstrual disorders. As a consequence, certain direct actions of danazol on endometriotic tissues have been proposed, but the mechanisms of these actions have not been clarified. In the present study, the direct effects of danazol on normal human endometrial stromal cells (ESCs) were examined using in vitro decidualization assays. Danazol did not affect the viable cell numbers of unstimulated ESCs or 8Br-cAMP-stimulated decidualized ESCs, but significantly enhanced the viable cell numbers of 8-Br-cAMP-stimulated ESCs during decidualization in a dose-dependent manner. Danazol had no effect on PRL secretion by 8-Br-cAMP-stimulated decidualized ESCs. Danazol, as well as progesterone and medroxyprogesterone acetate (MPA), induced ESC decidualization. Danazol synergistically enhanced the differentiation process of 8-Br-cAMP-stimulated ESCs during decidualization. Although progesterone and MPA increased G-CSF and IL-8 secretion by ESCs in similar manner to 8-Br-cAMP, danazol had no such effects. Moreover, remarkable increases in G-CSF and IL-8 secretions by 8-Br-cAMP-stimulated ESCs during decidualization were completely inhibited by cotreatment with danazol. These results indicate that danazol has specific pharmacological effects on ESCs, rather than progesterone-like effects or similar effects to those reported for endometrial cytokines. According to the results, normal human ESCs can be classified into at least four functional subpopulations. Therefore, under certain circumstances, danazol has similar or opposite effects on ESCs to certain endometrial cytokines, suggesting that it regulates functional cellular subpopulation ratios of normal human ESCs by modifying the endometrial cytokine network in endometrial stromal tissues.

11 beta-substituted 13 beta-ethyl gonane derivatives exhibit reversal of antiprogestational activity.

The syntheses of three 17 alpha-acetoxy-13 beta-ethyl-11 beta-aryl-18,19-dinorpregna-4,9-diene-3,20 diones from levonorgestrel are described. Despite their close structural similarity to the antiprogesterone CDB-2914, one of the compounds exhibits agonistic progestational activity, and the other two compounds are totally inactive.

Inhibition of ovulation by progestin analogs (agonists vs antagonists): preliminary evidence for different sites and mechanisms of actions.

Continuous administration of the antiprogesterone RU486 inhibits ovulation in women and in monkeys; in this regard RU486 may act as a progestin agonist rather than as an antagonist. We compared the site(s) and mechanism(s) of RU486-induced ovulation inhibition with those of levonorgestrel (LNG). Six regularly menstruating cynomolgus monkeys each received placebo, RU486 (1 mg/kg/d) or LNG (2 g/kg/d) i.m. between days (cd) 2-22 of three separate menstrual cycles. Serum levels of estradiol (E2), progesterone (P4), androstenedione, LH and FSH were analyzed by RIAs in daily blood samples. Basal and GnRH-stimulated (1 and 50 g of GnRH i.v. 2 h apart) secretion of LH and FSH was assessed using serial blood samples collected for 12 h on cd 10. Mean cycle length was prolonged by RU486 and LNG treatments from 32 d to 70 d and 52 d, respectively (p < 0.02). Ovulation was inhibited in five of the six primates during RU486, and in all six during LNG treatment. During RU486 treatment, serum E2 levels were similar to those of the control cycle; despite peaks of E2 secretion, no LH peaks were seen. In contrast, E2 concentrations were profoundly suppressed during LNG treatment (p < 0.005). The reduction in serum E2 was accompanied by lower levels of androstenedione, and suppressed ratio of E2/androstenedione (p < 0.02) suggesting both reduced synthesis and aromatization of androgen precursors during administration of LNG. Consequently, LNG treatment was associated with higher levels of serum FSH and LH (p < 0.001; 1-way ANOVA). Similarly, as during the luteal phase of the menstrual cycle, the amplitude of basal LH-pulses was increased during LNG treatment (p < 0.05), whereas RU486 treatment did not affect basal LH secretion. The GnRH-stimulated release of LH was similar during the placebo, RU486 and LNG cycles; enhanced release of FSH was seen during administration of LNG. Thus, in the present model system, RU486 seems to inhibit ovulation mainly at the level of hypothalamus, possibly by interfering with the steroidal positive feedback signals from the ovary. However, LNG inhibits ovulation differently, most likely via direct progesterone-like effects on folliculogenesis and the hypothalamus. The pituitary does not appear to be the major site of action(s) of RU486 or LNG. Thus, the differential mechanisms of ovulation inhibition by RU486 and LNG seem to result from lesser intraovarian impact of RU486 as well as dissimilar influences on tonic gonadotropin secretory levels. We conclude that when inhibiting ovulation, RU486 does not act as a progestin agonist, but rather, functions through a hypothalamic mechanism(s), which might be unique to RU486 as a progesterone antagonist.

PIP: Researchers administered a placebo, 1 mg/kg/day of RU-486, and 2 g/kg/day of levonorgestrel (LNG) to six regularly cycling cynomolgus monkeys (Macaca fascicularis) during days 2-22 of three separate treatment cycles in order to compare the site(s) and mechanism(s) of ovulation inhibition of RU-486 with those of LNG. One rest cycle separated the placebo and RU-486 cycles and at least two menstrual cycles separated the RU-486 and LNG cycles to ensure complete clearance of RU-486. Both RU-486 and LNG significantly prolonged the mean cycle length (from 32 days to 70 days and 52 days, respectively; p 0.02). During RU-486 treatment, five of the six monkeys did not ovulate, while during LNG treatment all six monkeys did not ovulate. Serum estradiol (E2) levels during RU-486 corresponded with those during the control cycle. There were peaks of E2 secretion during RU-486, but no peaks of luteinizing hormone (LH). E2 levels fell significantly during LNG treatment (p 0.005). Androstenedione levels also decreased significantly (p = 0.001) during LNG treatment, as well as the ratio of E2/androstenedione (p 0.02), suggesting that LNG inhibits aromatase activity. LNG treatment increased serum follicle stimulating hormone (FSH) and LH (p 0.001). Just like during the luteal phase of the menstrual cycle, the amplitude of basal LH pulses increased during LNG treatment (p 0.05). RU-486 did not alter basal LH secretion. LNG treatment amplified release of FSH. Neither RU-486 nor LNG affected the gonadotropin-releasing hormone stimulated release of FSH. These findings suggest that RU-486 inhibits ovulation largely at the hypothalamus level, perhaps by obstructing the steroidal positive feedback signals from the ovary. LNG likely inhibits ovulation through direct progesterone-like effects on folliculogenesis and the hypothalamus. Neither progestin analog seems to act at the pituitary level. In conclusion, RU-486 does not function as a typical progestin agonist but through a hypothalamic mechanism or mechanisms that are probably unique to RU-486.