Biological mechanisms underlying RU 486 clinical effects: inhibition of endometrial stromal cell tissue factor content

Despite the pronounced hemorrhagic effects of RU 486 administration on luteal phase and early gestational endometrium, no information is available on the effect of RU 486 on endometrial hemostatic potential. The expression of endometrial stromal cell tissue factor (TF), the primary initiator of hemostasis, has been shown to be progestationally regulated in vivo and in vitro. To evaluate the effects of RU 486 on progestin-enhanced TF expression, confluent stromal cell cultures derived from proliferative phase endometria were exposed to vehicle control, 10(-8) mol/L estradiol (E2), 10(-6) mol/L dexamethasone, 10(-7) mol/L medroxyprogesterone acetate (MPA), E2 plus MPA, E2 plus 10(-6) mol/L progesterone (P), or 10(-6) mol/L RU 486 alone or with E2 plus MPA or E2 plus P for 3-4 days. Compared to the vehicle control, E2, dexamethasone, and RU 486 alone had no effect on the content of immunoreactive and functionally active TF protein, whereas MPA increased and the combination of E2 and MPA further increased TF protein content. Similarly, E2 and P enhanced the stromal cell TF content. These progestin effects were blocked by RU 486. Similar results were obtained for steady state TF messenger ribonucleic acid (mRNA) levels. Possible RU 486-mediated reversal of progestin-enhanced stromal cell TF expression was assessed by incubating confluent cultures in E2 plus MPA for 3-10 days to enhance TF content, then washing the cultures and reexposing them to either E2 plus MPA or to RU 486 alone or with E2 plus MPA for 3, 4, or 7 days. Exposure to RU 486 alone or with E2 plus MPA greatly reduced levels of stromal cell TF protein and mRNA expression compared to those in cultures maintained in E2 plus MPA. These findings demonstrate that RU 486 not only blocks but also reverses in vitro progestin-enhanced stromal cell TF protein and mRNA expression, suggesting an additional mechanism for RU 486-induced menses and early abortion.

The expression of the placental anticoagulant protein, annexin V, by villous trophoblasts: immunolocalization and in vitro regulation

We evaluated the histological and ultrastructural localization of the potent anticoagulant protein, annexin V, at the light and electron microscopic levels, using immunohistochemistry and an immunogold method. Annexin V was found to localize to the microvillar surface of the villous syncytiotrophoblasts. Isolated villous-derived trophoblasts were then utilized to evaluate the expression of annexin 1 protein mRNA in response to syncytialization in vitro, as well as to exposure to adenylate cyclase and protein kinase C agonists. Levels of immunoreactive annexin V released into the conditioned media and associated with cell protein were assessed by ELISA while levels of annexin V mRNA were evaluated by Northern analysis. No significant change in either media or cell-associated annexin V concentrations were detected over time in culture or in response to 1.5 mM 8-bromo-cyclic-adenosine-monophosphate (8-b-cAMP) or 0.15 nM phorbol ester myristic acid (PMA). These results indicate that annexin V is ideally positioned to inhibit intervillous thrombosis and maintain the fluidity of the intervillous circulation. Moreover, the absence of trophoblast annexin V regulation by intracellular second messenger regulators suggests that this crucial placental anticoagulant factor is constitutively produced.

Steroid-modulated stromal cell tissue factor expression: a model for the regulation of endometrial hemostasis and menstruation

This study examined steroidal regulation of tissue factor expression by cultured endometrial stromal cells. Confluent stromal cell cultures derived from cycling human endometria were exposed to vehicle control, 10(-8) mol/L estradiol (E2), 10(-8)-10(-6) mol/L medroxyprogesterone acetate (MPA), or both E2 and MPA for 2-24 days in serum-containing medium. The progestin enhanced immunoreactive and functionally active stromal cell tissue factor content, achieving peak effects by 8-12 days of culture. Although E2 alone was ineffective, it augmented MPA-enhanced tissue factor content by 8 days of culture, with continued increases beyond 20 days. Dose-dependent effects on tissue factor protein content were observed between 10(-8)-10(-6) mol/L MPA added alone or together with E2. The content of tissue factor mRNA was also increased by MPA and synergistically increased by E2 plus MPA. Similar steroidal effects on stromal cell tissue factor protein and mRNA content were observed using a defined medium. After optimal induction of tissue factor expression by E2 plus MPA, removal of these steroids reduced levels of stromal cell tissue factor mRNA and protein, with virtually complete reversal by day 7 of withdrawal. These time-course and dose-response relationships establish in vitro conditions with which to dissect factors controlling endometrial hemostasis, whereas the observed effects of steroid withdrawal establish a novel model for the study of mechanisms regulating normal and abnormal uterine bleeding.

Glucocorticoid suppression of human placental fibronectin expression: implications in uterine-placental adherence

Increased levels of glucocorticoids are associated with human parturition whether occurring before or at term. In the present study we examined the effects of glucocorticoids on placental fibronectin (FN) expression in cytotrophoblasts, isolated from human term placentas, to provide a potential mechanism through which glucocorticoids may influence uterine-placental adherence near parturition. Based on immunoassays, relative to controls, media levels of placental FNs bearing an oncofetal epitope (onfFN) were inhibited 65-80% by treatment with 10(-7) M dexamethasone (DEX) during experiments in which cumulative levels and daily release of onfFN were measured. DEX treatment increased human CG production by cytotrophoblasts approximately 3-fold without affecting the levels of total protein, suggesting that DEX treatment did not reduce placental function. DEX and cortisol inhibited onfFN expression with an EC50 of 2 and 16 nM, respectively. Other steroids were not effective in down-regulating onfFN expression, indicating that this was a glucocorticoid-specific response. In immunoprecipitation studies, treatment of cytotrophoblasts with 10(-7) M DEX for 3 days inhibited both release of labeled FN to the media and its incorporation into cell-associated material by approximately 80%. Results from Northern blotting indicated that DEX treatment suppressed levels of FN messenger RNA approximately 90% relative to controls. Levels of labeled laminin in media were inhibited approximately 80% by a 3-day treatment with 10(-7) M DEX, suggesting that glucocorticoids may coordinately suppress the synthesis of multiple extracellular matrix proteins in cytotrophoblasts. In our model, we propose that glucocorticoids may suppress placental extracellular matrix protein synthesis, which could lead to decreased uterine-placental adherence and be associated with parturition.

Progestational regulation of human endometrial stromal cell tissue factor expression during decidualization

Decidualized endometrial stromal cells from mid- to late secretory phase and decidual cells from gestational human endometrium displayed prominent immunohistochemical staining for tissue factor, a primary initiator of hemostasis. Consistent with the regulation by progesterone of the decidualization process in vivo, medroxy-progesterone acetate elevated the tissue factor content of primary stromal cell cultures 8-fold over basal values. This increase paralleled the release of immunoreactive PRL, a marker of decidualization. The induced, as well as basal, tissue factor displayed full functional activity and the expected electrophoretic mobility (46 kilodaltons). Moreover, Northern analysis of RNA from cultured stromal cells indicated that medroxyprogesterone acetate increased tissue factor mRNA levels approximately 10-fold relative to control levels. In contrast, cultured stromal cell tissue factor protein content and mRNA levels were unaffected by exogenous estradiol. These findings indicate that enhancement of endometrial stromal cell tissue factor content is associated with progesterone induction of the decidualization process. In humans, trophoblastic invasion of the endometrial vasculature during blastocyst implantation risks hemorrhage. Therefore, increases in perivascular decidual cell tissue factor expression could serve to promote periimplantational endometrial hemostasis.

Characterization and identification of a pyrazole-inducible form of cytochrome P-450

In vivo administration of the alcohol dehydrogenase inhibitor pyrazole induces a cytochrome P-450 isozyme. The pyrazole-inducible cytochrome P-450 has been purified from rat livers to electrophoretic homogeneity and its biochemical, spectral, and immunological properties characterized. The final preparation had a specific content of 11 nmol of cytochrome P-450/mg of protein. A single band with an apparent molecular weight of 52,000 was observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The absolute spectrum of the isolated pyrazole cytochrome P-450 displayed peaks at 648 and 396 nm, suggestive of a high spin cytochrome. The ethylisocyanide difference spectrum exhibited two maxima, one at 457 nm, the other at 428 nm. Pyrazole and dimethyl sulfoxide produced binding spectra with the purified P-450, with peaks at 425 or 419 nm and troughs at 390 or 386 nm, respectively. K8 values for dimethyl sulfoxide and pyrazole were 21 and 0.04 mM, respectively. The catalytic activity of the pyrazole cytochrome P-450 was elevated with aniline and dimethylnitrosamine (low Km) but not with aminopyrine, benzphetamine, ethoxycoumarin, or ethoxyresorufin as substrates. An antibody against pyrazole cytochrome P-450 recognized a 52,000 molecular weight protein upon reaction with saline microsomes. The intensity of the immunoblot was increased when microsomes isolated from pyrazole, 4-methylpyrazole-, acetone-, or chronic ethanol-treated rats were utilized, but not after phenobarbital or 3-methylcholanthrene treatment. Homology at the amino terminus of 19 amino acids was observed between pyrazole P-450 and the isoniazid-inducible P-450j. Based upon the above catalytic, spectral, and immunological properties, it appears that pyrazole induces a form of cytochrome P-450 which is identical to that induced by ethanol and isoniazid.

Effect of chronic ethanol consumption on microsomal lipid peroxidation. Role of iron and comparison between controls

Microsomes isolated from chronic ethanol-fed rats displayed elevated rats of malondialdehyde production when compared to pair-fed controls, but lower rates when compared to chow-fed controls. These differences did not correlate with total content of cytochrome P-450 or activity of NADPH-cytochrome c reductase. Titration curves with the potent iron-chelating agent desferrioxamine revealed that the content of iron was greater in microsomes from the chow-fed and lowest in microsomes from the pair-fed control. However, other variables must also exist since even when excess iron was added to the microsomes, the order of malondialdehyde production remained chow-fed greater than chronic ethanol greater than pair-fed control. The variabilities associated with the different controls and the role and content of transition metals such as iron probably contribute towards the divergent effects of ethanol on lipid peroxidation.

Rat liver microsomal induction of the oxidation of drugs and alcohols, and sodium dodecyl sulfate-gel profiles after in vivo treatment with pyrazole or 4-methylpyrazole

Studies were carried out to characterize and compare the effects of pyrazole and 4-methylpyrazole, potent inhibitors of alcohol dehydrogenase, on microsomal oxidation of a variety of drugs and alcohols. Whereas pyrazole treatment of rats (200 mg/kg b.wt./day for 2 days) resulted in an enrichment of a cytochrome P-450 isozyme with a molecular weight of about 52,000 on sodium dodecyl sulfate gels, 4-methylpyrazole treatment resulted in increased amounts of two or three P-450 isozymes, one of which appeared to be similar to the isozyme increased by pyrazole. The qualitative induction of two or three isozymes of P-450 as shown by sodium dodecyl sulfate-gel electrophoresis correlates with a 2-fold increase in total content of P-450 by 4-methylpyrazole. Microsomes from the pyrazole-treated rats displayed increased activity (expressed per milligram of protein or per nanomole of P-450) with aniline, p-nitroanisole, dimethylnitrosamine (low-Km enzyme) and ethanol as substrates, but not with aminopyrine, ethoxycoumarin or dimethylnitrosamine (high-Km enzyme). A stereochemical preference for the (+)-2-butanol isomer over the (-)-isomer was also observed. Kinetic experiments indicated that the pyrazole treatment increased the Vmax for ethanol, aniline and (+)-2-butanol oxidation. These properties are similar to those found with microsomes from chronic ethanol-fed rats and suggest that, in rats, pyrazole and ethanol may induce similar isozymes of P-450, and that the former may serve as a convenient model for the latter. This comparable induction between ethanol and pyrazole is in contrast to results using imidazole, which has been reported by others not to induce an alcohol-preferring P-450 in rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of microsomal pathways of oxidation of alcohols and hydroxyl radical scavenging agents with carbon monoxide and cobalt protoporphyrin IX

Rat liver microsomes catalyze the oxidation of hydroxyl radical scavenging agents by an iron-dependent process, and can oxidize alcohols by pathways dependent on, as well as independent of, .OH. Experiments were carried out to evaluate which microsomal components participate in the production of .OH, and in the two pathways of oxidation of alcohols. Cobalt protoporphyrin IX treatment of rats resulted in a decrease in microsomal oxidation of aminopyrine, .OH scavengers, and alcohols. However, this treatment not only lowered the content of cytochrome P-450, but also decreased the activity of NADPH-cytochrome P-450 reductase. Carbon monoxide, metyrapone and SKF-525A also inhibited the oxidation of aminopyrine but did not affect oxidation of .OH scavengers. Desferrioxamine, a potent iron chelator, inhibited the oxidation of .OH scavengers but not aminopyrine. The oxidation of alcohols was partly sensitive to desferrioxamine and partly sensitive to carbon monoxide, thus showing similarities to the oxidation of .OH scavengers and drugs. These results suggest that the desferrioxamine-sensitive, .OH-dependent pathway of alcohol oxidation is mediated by the reductase, in analogy to results with .OH scavengers, whereas the desferrioxamine-resistant pathway of alcohol oxidation is mediated by cytochrome P-450, in analogy to results with aminopyrine. By the use of desferrioxamine or carbon monoxide, either of the two alcohol-oxidizing pathways can be inhibited independently of each other.

Stereochemical studies on the cytochrome P-450 and hydroxyl radical dependent pathways of 2-butanol oxidation by microsomes from chow-fed, phenobarbital-treated, and ethanol-treated rats

Microsomes have the potential to oxidize alcohols by two pathways, one dependent on hydroxyl radicals (.OH) and the other dependent on cytochrome P-450 in which .OH does not seem to be involved. The possibility that these two pathways may display differences in stereospecificity was evaluated by comparing the oxidation of (+)-2-butanol, (-)-2-butanol, and racemic 2-butanol. Microsomes oxidized 2-butanol to 2-butanone by a reaction which was partially sensitive to carbon monoxide and to competitive .OH scavengers. Desferrioxamine, which completely blocks the production of .OH by microsomes, inhibited the oxidation of ethanol by about 60%, while the oxidation of 2-butanol and 1-butanol was decreased by only 30%. Vmax values for the oxidation of ethanol, 1-butanol, and 2-butanol were 17.7, 6.2, and 23.8 nmol min-1 (mg of protein)-1, respectively, in the absence of desferrioxamine and 5.9, 4.7, and 13.6 nmol min-1 (mg of protein)-1, respectively, in the presence of desferrioxamine. 2-Butanol appears to be a particularly good alcohol substrate for the cytochrome P-450 dependent pathway of alcohol oxidation. Chronic ethanol consumption, which induces the microsomal alcohol oxidizing system, resulted in a 3-fold increase in the rate of 2-butanol oxidation. Most of this increment reflected an increased rate of metabolism by the cytochrome P-450 pathway. A type 2 binding spectrum was observed for the interaction of 2-butanol with microsomes from ethanol-fed rats, but not with controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased microsomal oxidation of alcohols after pyrazole treatment and its similarities to the induction by ethanol consumption

Microsomes isolated from rats treated for 3 days with 200 mg/kg body wt. per day of pyrazole, a potent inhibitor of alcohol dehydrogenase, catalyzed the oxidation of ethanol and 2-butanol at rates 2-3-fold higher than saline controls. This increase was blocked by carbon monoxide, and was not associated with an increase in the oxidation of aminopyrine or in the content of cytochrome P-450, suggesting the possibility of an induction of an alcohol-preferring cytochrome P-450 by pyrazole. Microsomes from the pyrazole-treated rats displayed a stereochemical preference for the oxidation of the (+)-2-butanol isomer over the (-)-2-butanol isomer, which was blocked by carbon monoxide, and also displayed a type-2 binding spectrum with dimethylsulfoxide or 2-butanol. No such spectrum was found with the saline controls. These properties are similar to those which are observed with microsomes from chronic ethanol-fed rats. These similarities suggest the possibility that pyrazole treatment may induce a cytochrome P-450 isozyme with properties similar to the ethanol-inducible cytochrome P-450.