Screening of anti-progestins using in vitro human uterine progesterone receptor assay system

The nitric oxide pathway participates in estrous behavior induced by progesterone and some of its ring A-reduced metabolites

Intracerebral and intravenous administration of progesterone (P) and its ring A-reduced metabolites induces intense sexual behavior (lordosis and proceptivity) in estrogen-primed rats. The present study tested the hypothesis that the nitric oxide-cGMP-protein kinase G pathway is involved in the facilitation of sexual behavior induced by the intracerebroventricular (i.c.v.) administration of P (130 ng) and its ring A-reduced metabolites 5alpha-dihydroprogesterone (5alpha-DHP; 13 ng) and 5alpha,3alpha-pregnanolone (5alpha,3alpha-Pgl; 13 ng). In Experiment 1, we tested the relevance of the nitric oxide/cGMP pathway by infusing a nitric oxide synthase inhibitor or a nitric oxide-dependent, soluble guanylyl cyclase inhibitor icv before progestin administration. The lordosis induced by P, 5alpha-DHP and 5alpha,3alpha-Pgl was significantly reduced at 2 h after progestin infusion by the previous injection of either a nitric oxide synthase inhibitor or by a soluble guanylyl cyclase inhibitor. Lordosis behavior returned to control values by 4 h. In Experiment 2, i.c.v. infusion of the protein kinase G inhibitor KT5823 significantly inhibited the lordosis behavior induced by all three progestins at 2 h. These data support the hypothesis that the nitric oxide/cGMP/protein kinase G pathway is involved in the lordosis induced by P and some of its ring A-reduced metabolites.

Indomethacin inhibits lordosis induced by ring A-reduced progestins: possible role of 3alpha-oxoreduction in progestin-facilitated lordosis

Progestins with a delta-4-3-keto configuration bind to the progestin receptor (PR) and facilitate estrous behavior in estrogen-primed rats. Some ring A-reduced progestins [5alpha-dihydroprogesterone (alphaDHP), allopregnanolone, and epipregnanolone] are more potent estrus-inducing agents than progesterone when iv injected despite their lower affinity for the PR. Yet the estrus-inducing action of such progestins is reduced by the antiprogestin RU486, suggesting that binding to the PR is required for this effect. Because allo- and epi-pregnanolone are oxidized to alpha- and betaDHP, respectively, by 3alpha-hydroxysteroid oxo-reductase (3alphaHSOR), part of their estrus-inducing action may occur through the binding of such DHPs to the PR. Conversely, because 3alphaHSOR reduces alpha- and betaDHP to allo- or epi-pregnanolone, both of which exert membrane effects, the estrus-inducing effect of DHPs may involve actions independent of the PR. To test these possibilities we assessed the effect of indomethacin, a blocker of 3alphaHSOR, on the estrus-inducing action of such progestins. Because indomethacin also inhibits cyclooxygenases, we selected a dose and treatment schedule that does not interfere with prostaglandin-mediated brain processes (e.g., LHRH release). Indomethacin did not significantly modify the effect of progesterone or megestrol acetate on lordosis. Yet, it significantly reduced the action of all ring A-reduced progestins. Results suggest that: (a) oxidation is essential for lordosis facilitation by 3alpha-pregnanolones and (b) reduction of 3-keto progestins generates 3alpha-hydroxy metabolites which synergize with processes triggered by occupation of the PR by 3-keto progestins. The possible participation in this response of other events influenced by indomethacin (e.g., prostaglandin or melatonin synthesis) is discussed.

Ring A reductions of progestins are not essential for estrous behavior facilitation in estrogen-primed rats

In Experiment 1 six dose levels (range 0.66-2000 microg) of progesterone (P) and two synthetic progestins with a double bond at C6: megestrol acetate (MA) and chlormadinone acetate (CA), which cannot be reduced at C5, were injected to estrogen-primed (2 microg estradiol benzoate 42 h earlier) ovariectomized (ovx) rats. The three progestins elicited significant lordosis and proceptive behaviors. Potency analysis showed that MA was the most potent progestin for stimulating estrous behavior, followed by P and CA. These results suggest that ring A reduction of progestins to 5alpha/5beta metabolites is not essential for the facilitation of estrous behavior in ovx estrogen-primed rats. Progestins with the 3-ketone group and a double bond at C4 can also be reduced at C3 to yield 3alpha-hydroxysteroid metabolites potentially capable of stimulating estrous behavior. In Experiment 2, the relevance of the formation of 3alpha-hydroxysteroid metabolites for estrous behavior facilitation was tested by concurrently injecting indomethacin (1.5 mg), a blocker of 3alpha-hydroxysteroid oxidoreductase, with 400 microg of P, MA, or CA to ovx estrogen-primed rats. Indomethacin failed to block the stimulatory effect of these progestins on estrous behavior. These results suggest that 3-ketosteroid reduction is also not essential for estrous behavior facilitation by progestins.

Ring A reduced progestins potently stimulate estrous behavior in rats: paradoxical effect through the progesterone receptor

The effect of ring A reductions at C5 and C3 on the capacity of the progesterone (P) molecule to stimulate estrous behavior was studied in ovariectomized estrogen primed rats (5 micrograms estradiol benzoate, EB, 40 h before progestin administration). Dose-response curves (dose range: 0.75-200 micrograms) for the lordosis quotient (LQ), lordosis score (LS), and proceptivity were constructed for P and all its ring A reduced metabolites: 5 alpha-pregnanedione (alpha DHP), 5 beta-pregnanedione (beta DHP), 3 alpha,5 alpha-pregnanolone (3 alpha,5 alpha-Pgl), 3 alpha,5 beta-pregnanolone (3 alpha,5 beta-Pgl), 3 beta,5 alpha-pregnanolone (3 beta,5 alpha-Pgl), and 3 beta,5 beta-pregnanolone (3 beta,5 beta-Pgl). Progestins were dissolved in propylene glycol and IV injected through an indwelling jugular catheter. Tests for lordosis and proceptivity were made at 5, 30, and 120 min after progestin injection. Weak, though significant lordosis behavior was observed at 5 min following the injection of some of the progestins, particularly the pregnanolones. Maximal responses were obtained at 120 min postinjection for all progestins. Dose response curves of the LQ, LS, and proceptivity were dualistic for alpha DHP and both 3 alpha pregnanolones, smaller responses being observed with high doses. Relative potency analysis revealed that alpha DHP, 3 alpha,5 beta-Pgl, 3 beta,5 alpha-Pgl, and 3 alpha,5 alpha-Pgl were considerably more potent for eliciting lordosis than P (14, 13.7, 9, and 4-fold, respectively). The same order of relative potencies was found for both LS and proceptivity. 3 beta,5 beta-Pgl and beta DHP were only slightly more potent than P (2 and 1.5-fold, respectively). In a second study, the antiprogestin RU486 (5 mg, SC), injected 60 min before one of four selected progestins (alpha DHP, 3 alpha,5 alpha-Pgl, 3 alpha,5 beta-Pgl, and 3 beta,5 beta-Pgl), significantly inhibited their action on estrous behavior (lordosis and proceptivity) when tested at 60 and 120 min postinjection. On the other hand, RU486 failed to inhibit early lordotic responses obtained at 5 and 30 min following 3 alpha,5 alpha-Pgl and 3 alpha,5 beta-Pgl. Similarly RU486 was ineffective in inhibiting lordosis in ovariectomized rats treated only with estradiol (3 micrograms of EB/day for 7 days). Data suggest that: (i) ring A reduction of the P molecule plays an important role in the normal facilitation of estrous behavior in the rat; and (ii) ring A reduced progestins provoke this effect by acting, at least partially, through the progesterone receptor.

Progestin and antiprogestin interactions with progesterone receptors in human myomas

Progesterone receptors (PRs) in human fibromyomata (myomas) and normal myometrium were characterized by gel filtration, sucrose gradient sedimentation analysis, isoelectrofocusing and ligand specificity. The PR population in myoma tissues, 1242 +/- 505 fmol/mg protein, was 3-fold higher than normal myometrial tissues under similar hormonal milieu. The increased PR concentration in myomas appears to be of potential importance in physiopathology of fibromyoma.

Modulation of steroid production in goat ovarian cells: effect of progestins and antiprogestins

Effect of various synthetic progestins and antiprogestational compounds on progesterone (P) and estradiol (E) production by isolated goat ovarian granulosa (G) and corpus luteum (CL) cell types was studied in vitro. Steroid production was studied either under basal conditions or after stimulation with follicle stimulating hormone (FSH) in the presence of aromatase substrate, androstenedione (A). None of the progestins had any significant effect on basal P and E production by either cell types during 48 hour of culture. The FSH and A - induced increase in P and E production was significantly inhibited following concommitant treatment with synthetic progestins at concentrations higher than 10(-7) M. The added progestins had no effect on G and CL cell viability. None of the antiprogestational compounds had any significant effect on basal steroid production in either of the cell types. Furthermore, the higher concentrations of three antiprogestins namely RMI 14156, STS 557 and isomer 201 of RMI 12936, were found to stimulate significantly the basal as well as FSH + A - induced production of estradiol in both the cell types. In contrast, the other two antiprogestins tested were found to stimulate the gonadotropin + A - induced production of P. These results indicate that exogeneous progestins directly inhibit the gonadotropin + androstenedione - induced steroid production by G and CL cells in vitro. Moreover, different antiprogestin had different effect on the modulation of steroid production.

Binding characteristics of progesterone and antiprogestin ZK 98.299 in human endometrial and myometrial cytosol

The binding of ZK 98.299, a synthetic progesterone antagonist, with human endometrium and myometrium cytosol was studied and compared with that of progesterone. Progesterone showed specific saturable binding to its receptors in both endometrium and myometrium. ZK 98.299 and progesterone were mutually competitive for binding to progesterone receptors; however, the relative binding affinity of ZK 98.299 was 16% that of progesterone. ZK 98.299 exchanged the progesterone-labelled receptor sites. [3H]ZK 98.299 showed specific binding which was linearly related to the cytosol protein concentration. The binding was not saturable at 15 nM of ligand. The binding capacity and binding affinity of ZK 98.299 receptor was less than that of progesterone. Progesterone also partially displaced the binding of [3H]ZK 98.299. This study suggest that ZK 98.299 and progesterone both bind to the same protein. However, whether ZK 98.299 binds to progesterone receptors alone or even to other functionally related sites is not known. It appears that ZK 98.299 when present in higher concentration than progesterone would be an effective receptor ligand.

Interaction of antiprogestins with progesterone receptors in rat uterus

Cytosolic and nuclear progesterone receptors (PRc and PRn) under antiprogestin treatment were measured in rat deciduoma and compared with values for contralateral (nondeciduomatous) rat uterine tissue. Uterine PRc and PRn of the progesterone treated group were 101 +/- 8.7 and 4770 +/- 590 fmol/mg DNA respectively. After treatment with antiprogestins STS-557, 5 alpha-DNE, (5 alpha-dihydronorethisterone), 5 alpha-DNG (5 alpha-dihydronorgestrel), RU-22092 and RU-16556, PRc in the nondeciduomatous control horn ranged from 127 to 377 fmol/mg DNA and PRn from 2785 to 17925 fmol/mg DNA. In the decidual tissue, PRc decreased significantly (4.6 +/- 0.8 fmol/mg DNA) on 5 alpha-DNG treatment as compared with the progesterone alone treatment group (147 +/- 3.8). PRn in decidual tissue also decreased maximally on 5 alpha-DNG treatment. These results suggest that the interaction of antiprogestins may not be identical in control uterine tissue and in deciduoma.

Screening of anti-progestagens by receptor studies and bioassays

A large number of potential anti-progestational compounds were screened for their ability to bind to the progesterone (MCF-7 cells) and glucocorticoid (IM-9 cells) receptors and for their activity in the pregnancy interruption test in rats. The anti-glucocorticoid activity was assessed by the effect of the compounds on body weight gain, adrenal weight and thymus weight in dexamethasone-treated rats. Of the compounds tested, two (Org 31167 and Org 31343) with the dimethylaminophenyl group at carbon atom 18 of 17 beta-hydroxy-17 alpha-(2-propenyl)-estra-4-en-3-one are equipotent with RU 38486 in the pregnancy interruption test. Both compounds possess lower anti-glucocorticoid activity than RU 38486. Since these compounds are far more active after oral than subcutaneous administration it is very likely that they become activated in the gastro-intestinal tract.

A chemical classification of nonsteroidal antagonists of sex-steroid hormone action

A highly varied collection of nonsteroids have been reported over the last forty years as being able to exert an antihormonal action versus steroid hormones in vivo. This diversity is partly explained by the manifold molecular targets of these compounds which may be either enzymes or receptors (leading to inhibition of steroid production and action respectively) and by the different possible levels of interference within feedback loops between the central nervous system, pituitary, gonads and other peripheral organs. The present chapter is a chemist's classification of some of these structures often in the absence of detailed biochemical data. Nonsteroid antiestrogens (and estrogens) most often share a common feature with diethylstilbestrol and consequently the effects of structural modifications on biological activities can be studied in a rational manner. This is not the case for non-steroidal antiandrogens that we have only been able to classify into conventional chemical groups. Nor have any true lead compounds nor well-defined chemical classes been identified for nonsteroid antiprogestogens. This is however the only hormonal class where natural products play an important role.

Glucocorticoid receptors in bronchoalveolar lavage fluid in sarcoidosis. A preliminary report

Glucocorticoid receptor (GR) content was measured in bronchoalveolar lavage fluid (BALF) cells of 20 untreated patients with sarcoidosis. A significantly higher (p less than 0.001) lymphocyte count and GR content of BALF cells was noted in patients with sarcoidosis as compared to normal volunteers. The GR content correlated positively with lymphocytes (%) (r = 0.6; p less than 0.01) and was significantly higher (p less than 0.001) in patients who showed roentgenographic improvement, physiologic improvement, and improvement in both parameters compared to those who did not show improvement. Above findings suggest that the GR content of BALF cells is increased in sarcoidosis and a major contribution to this may be made by the lymphocytes.

Relative binding affinity of antiprogestins ZK 98.299 and ZK 98.734 for progesterone receptors in the endometrium and myometrium of bonnet monkeys

Progesterone bound with high affinity to the endometrial and myometrial cytosol of ovariectomized bonnet monkeys pretreated with estradiol benzoate and progesterone. The equilibrium dissociation constant (Kd) of 3H-progesterone was 4.5 nM and 5.5 nM and the binding capacity was 1.7 nM and 1.4 nM for the endometrial and myometrial receptors, respectively. This experimental 'model' was used to assess the relative binding affinity (RBA) of progesterone, ZK 98.299 and ZK 98.734. The tested compounds showed competitive binding to cytoplasmic progesterone receptors. The RBA of progesterone in the endometrium (100) was more than that of ZK 98.299 (25.1) and ZK 98.734 (17.8). A similar RBA pattern was observed in the myometrial cytosol. Both ZK 98.299 and ZK 98.734, like progesterone, displaced the 3H-progesterone bound to the receptors. The administration of ZK 98.299 or ZK 98.734, during the mid-luteal phase, has been reported to shorten the cycle length in bonnet monkeys and marmosets, respectively. These compounds, therefore, appear to intercept the progesterone action by blocking progesterone binding sites in the target tissue. Since ZK 98.299 has higher binding affinity than ZK 98.734, it may be a more potent progesterone antagonist.

Relationship between progesterone receptor binding and progestin biological activity

The binding affinities of a series of steroidal compounds for the hamster uterine progesterone receptor were determined using two sets of incubation conditions. These competitive binding conditions were designed to deduce the relative rates of ligand dissociation from the progesterone receptor. The progestin activity of these compounds was also determined in a bioassay employing the measurement of diamine oxidase in the traumatized hamster uterus. Steroids could be classified into two categories based on either an increase or decrease in relative binding affinity (RBA) with increasing time of competitive incubation. The mean (+/- SEM) progestin biopotency for the compounds having an increase in RBA was 120 +/- 18 (progesterone = 100), while the biopotency for compounds having a decrease in RBA was only 44 +/- 17. This difference was significant (P less than 0.01). Linear regression analyses revealed significant correlations between the RBAs and progestin biopotencies. Compounds showing a decrease in RBA with increasing time of incubation did not have antiprogestin activity. Kinetic studies of this type should be useful for selecting compounds with potent agonistic activity, but cannot unequivocally predict antihormonal activity.