Progesterone,administered before kainic acid,prevents decrements in cognitive performance in the Morris Water Maze

The nature of progesterone (P₄)'s neuroprotective effects is of interest. We investigated effects of P₄ when administered before, or after, kainic acid, which produces ictal activity and damage to the hippocampus, to mediate effects on spatial performance. The hypothesis was that P₄, compared with vehicle, would reduce decrements in Morris Water Maze performance induced by kainic acid. Experiment 1: We examined the effects of kainic acid on plasma stress hormone, corticosterone, and progestogen (P₄ and its metabolites) levels in plasma and the hippocampus after subcutaneous (s.c.) P₄ administration to ovariectomized rats. Rats administered kainic acid had the highest corticosterone levels immediately following injection. P₄ is 5α‐reduced to dihydroprogesterone (DHP) and subsequently metabolized to 5α‐pregnan‐3α‐ol‐20‐one (3α,5α‐THP) by 3α‐hydroxysteroid dehydrogenase. The regimen of P₄ used produced circulating and hippocampal levels of P₄, DHP, and 3α,5α‐THP within a physiological range, which declined at 14 hours postinjection and were not altered by kainic acid. Experiment 2: The physiological P₄ regimen was administered to rats before, or after, kainic acid‐induced seizures, and later effects on water maze performance were compared with that of rats administered vehicle. Rats administered kainic acid had significantly poorer performance in the water maze (i.e., increased latencies and distances to the hidden platform) than did rats administered vehicle. Administration of P₄ before, but not after, kainic acid prevented these performance deficits. Thus, these data suggest that a physiological regimen of P₄ can prevent some of the deficits in water maze performance produced by kainic acid. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 71: 142‐152, 2011     

Medroxyprogesterone acetate: receptor binding and correlated effects on steroidogenesis in rat granulosa cells

Medroxyprogesterone acetate (MPA), a widely used synthetic steroid, was studied to determine both its effects on steroid receptors and steroidogenesis in the well-characterized rat ovarian granulosa cell model. Initial receptor binding studies showed MPA was as potent as progesterone and 10-fold less potent than R-5020 (an active synthetic progestin) in binding to progesterone cytosolic receptors in rat ovarian granulosa cells. MPA was 20-fold less potent than testosterone, and 10-fold less potent than dexamethasone in binding to the androgen and glucocorticoid cytosolic receptors, respectively. The binding of MPA to progestrone, androgen and glucocorticoid receptors predicted direct effects of MPA on FSH-stimulated estrogen (E), progesterone (P), and 20 alpha-dihydroprogesterone (DHP) production by cultured rat ovarian granulosa cells. MPA at 10(-7) to 10(-6) M significantly augmented FSH-stimulated P and DHP production (a previously documented progestin, androgen and glucocorticoid effect). This augmentation was blocked by the concurrent addition to cell culture of 10-fold excess RU-486 (a potent anti-progestin and anti-glucocorticoid). At concentrations greater than 10(-6) M, MPA inhibited the production of P and DHP (a progestin effect), and the production of E (a progestin and glucocorticoid effect). MPA, structurally a progestin, has complex steroid hormone effects predicted by its interaction with progesterone, androgen and glucocorticoid receptors.     

Time-studies of the changes in the sex-dependent activities of enzymes of hepatic steroid metabolism in the rat during oestrogen administration.

This investigation was undertaken to elucidate the amount of oestradiol and duration of its administration necessary to cause complete feminization of the activities of cytoplasmic 3 alpha- and 17 beta-hydroxysteroid dehydrogenase, microsomal 3 alpha- and 3 beta-hydroxysteroid dehydrogenase and microsomal 5 alpha-reductase in male rat liver. With the exception of cytoplasmic 3 alpha-hydroxysteroid dehydrogenase, 5 microgram oestradiol/d for 8 days and less was sufficient to cause complete feminization. The order of oestrogen sensitivity was cytoplasmic 3 alpha-hydroxysteroid dehydrogenase greater than microsomal 3 beta-hydroxysteroid dehydrogenase greater than microsomal 3 alpha-hydroxysteroid dehydrogenase greater than microsomal 5 alpha-reductase greater than cytoplasmic 17 beta-hydroxysteroid dehydrogenase. Although the changes occurring after oestradiol administration are qualitatively the same as after testectomy, they occur more rapidly. This rules out the possibility that oestradiol exerts its effect via androgen deprivation. Diethylstilboestrol administration causes the same changes in cytoplasmic 17 beta- and microsomal 3 beta-hydroxysteroid dehydrogenase activity as oestradiol, although the dosage must be increased 100 fold. The effect of diethylstilboestrol on 5 alpha-reductase activity changes with the dose applied. Doses up to 100 microgram/d partially feminize the activity, but at higher doses the enzyme activity is repressed.     

Brain aromatase is neuroprotective

The expression of aromatase, the enzyme that catalyzes the biosynthesis of estrogens from precursor androgens, is increased in the brain after injury, suggesting that aromatase may be involved in neuroprotection. In the present study, the effect of inactivating aromatase has been assessed in a model of neurodegeneration induced by the systemic administration of neurotoxins. Domoic acid, at a dose that is not neurotoxic in intact male mice, induced significant neuronal loss in the hilus of the hippocampal formation of mice with reduced levels of aromatase substrates as a result of gonadectomy. Furthermore, the aromatase substrate testosterone, as well as its metabolite estradiol, the product of aromatase, were able to protect hilar neurons from domoic acid. In contrast, dihydrotestosterone, the 5 alpha-reduced metabolite of testosterone and a nonaromatizable androgen, was not. These findings suggest that aromatization of testosterone to estradiol may be involved in the neuroprotective action of testosterone in this experimental model. In addition, aromatase knock-out mice showed significant neuronal loss after injection of a low dose of domoic acid, while control littermates did not, indicating that aromatase deficiency increases the vulnerability of hilar neurons to neurotoxic degeneration. The effect of aromatase on neuroprotection was also tested in male rats treated systemically with the specific aromatase inhibitor fadrozole and injected with kainic acid, a well characterized neurotoxin for hilar neurons in the rat. Fadrozole enhanced the neurodegenerative effect of kainic acid in intact male rats and this effect was counterbalanced by the administration of estradiol. Furthermore, the neuroprotective effect of testosterone against kainic acid in castrated male rats was blocked by fadrozole. These findings suggest that neuroprotection by aromatase is due to the formation of estradiol from its precursor testosterone. Finally, a role for local cerebral aromatase in neuroprotection is indicated by the fact that intracerebral administration of fadrozole enhanced kainic acid induced neurodegeneration in the hippocampus of intact male rats. These findings indicate that aromatase deficiency decreases the threshold for neurodegeneration and that local cerebral aromatase is neuroprotective. Brain aromatase may therefore represent a new target for therapeutic approaches to neurodegenerative diseases.     

Effects of unilateral orchidectomy on rat epididymal delta 4-5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase

The effects of unilateral orchidectomy on the adult rat epidiymal testosterone metabolizing enzymes, delta 4-5 alpha-reductase and 3 alpha-hydroxysteroid dehydrogenase, are investigated. Five weeks following unilateral orchidectomy, it is found that the activity of 3 alpha-hydroxysteroid dehydrogenase per organ is not altered, whereas delta 4-5 alpha-reductase activity decreased by more than 80% on the side of the orchidectomy. Neither accessory sex tissue weights, ventral prostate and seminal vesicles, nor the concentration of circulating testosterone, luteinizing hormone, follicle-stimulating hormone, or prolactin is altered by unilateral orchidectomy. These data indicate that (1) epididymal 3 alpha-hydroxysteroid dehydrogenase activity can be maintained by circulating androgens and that (2) the major factor regulating delta 4-5 alpha-reductase activity is not a substance secreted by the testes into the peripheral circulation. It is suggested that a substance directly secreted into the epididymis by the testis regulates epididymal delta 4-5 alpha-reductase activity.     

Potent inhibition of the hypothalamic progesterone 5 alpha-reductase by a 5 alpha-dihydroprogesterone analog

The ability of the 5 alpha-dihydroprogesterone analog, 4-aza-4-methyl-5 alpha-pregnane-3,20-dione (AMPD), to inhibit the progesterone 5 alpha-reductase and the two 5 alpha-dihydroprogesterone 3 alpha-hydroxysteroid oxidoreductase activities (NADH- and NADPH-linked) from female rat hypothalamus has been studied. Dose response experiments indicate that AMPD is a potent antagonist of hypothalamic progesterone 5 alpha-reduction but is an ineffective inhibitor of the NADPH- and NADH-linked 3 alpha-hydroxysteroid oxidoreductase activities, even at concentrations up to 10 microM. Kinetic analyses of the interaction of AMPD with the progesterone 5 alpha-reductase show that it is a competitive inhibitor versus progesterone (Ki(slope) = 6.2 +/- 0.5 nM; apparent Km (progesterone) = 130 +/- 12 nM) and an uncompetitive inhibitor versus NADPH (Ki(intercept) = 11.8 +/- 0.8 nM). These inhibition patterns are consistent with the concept that NADPH binding precedes that of either AMPD or progesterone. The inhibition of the progesterone 5 alpha-reductase by AMPD does not appear irreversible since preincubation of the enzymatic activity (at 37 degrees C) with inhibitor and NADPH, for periods of time up to 60 min, does not lead to a time-dependent loss of activity. Furthermore, this inhibition can be easily removed via dilution, even following a 60-min preincubation with AMPD and NADPH. It is postulated that the specific and powerful inhibition of the progesterone 5 alpha-reductase by AMPD may be due to this compound functioning as a transition state analog. This inhibitor should prove valuable in studying the characteristics of the progesterone 5 alpha-reductase and the function of hypothalamic progestin metabolism.     

Effect of flutamide on 5 alpha-reductases, 5 beta-reductases, and 3-hydroxysteroid dehydrogenases in rat liver

Flutamide (0.5 mM) decreased in vitro the activity of NADH-5 alpha-reductase (substrate testosterone) in liver homogenate of male and female rats, whereas no change of activity of NADPH-5 alpha-reductase was observed. NADH- and NADPH-5 beta-reductase activity increased only in liver of female, but not of male rats. NAD+-3 beta-hydroxysteroid dehydrogenase and NAD+-3 alpha-hydroxysteroid dehydrogenase (substrate 5 alpha-dihydro-testosterone) in liver homogenate from female rats were inhibited by flutamide (0.5 mM), whereas the activity of NADP+-3 alpha-hydroxysteroid dehydrogenase (substrate 5 alpha-dihydrotestosterone) and of NAD+-3 alpha-hydroxysteroid dehydrogenase (substrate 5 beta-dihydrotestosterone) increased in presence of flutamide. The activity of NADH- and NADPH-5 alpha-reductase decreased after flutamide administration to female rats at a dose of 5 mg per day for 7 days.     

Interactions between type 1 astrocytes and LHRH-secreting neurons (GT1-1 cells): modification of steroid metabolism and possible role of TGFbeta1

The hypothesis that type 1 astrocytes (A1) might modify the activities of the enzymes 5alpha-reductase (5alpha-R) and 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) present in the GT1-1 cells has been tested. The data obtained indicate that, utilizing a co-culture technique, A1 are able to: (1) decrease the formation of dihydrotestosterone (DHT) from testosterone (T); (2) increase the formation of dihydroprogesterone (DHP) from progesterone (P); (3) decrease the conversion of DHP into tetrahydroprogesterone (THP) in GT1-1 cells. Moreover, GT1-1 cells are able to increase the formation of DHP in A1; that of DHT was unchanged. The present data might suggest the possible existence of a third isoform of the enzyme 5alpha-R; details on this hypothesis are provided in the text. Interestingly, the inhibitory effect exerted by A1 on the formation of DHT in GT1-1 cells can be mimicked by transforming growth factor beta1 (TGFbeta1). Since TGFbeta1 had been previously shown to be directly involved in the stimulatory control of LHRH secretion by GT1-1 cells, acting both on LHRH release [R.C. Melcangi, M. Galbiati, E. Messi, F. Piva, L. Martini, M. Motta, Type 1 astrocytes influence luteinizing hormone-releasing hormone release from the hypothalamic cell line GT1-1: is transforming growth factor-beta the principle involved? Endocrinology 136 (1995) 679-686.] and gene expression [M. Galbiati, M. Zanisi, E. Messi, I. Cavarretta, L. Martini, R.C. Melcangi, Transforming growth factor-beta and astrocytic conditioned medium influence LHRH gene expression in the hypothalamic cell line GT1, Endocrinology 137 (1996) 5605-5609], the present data also show that TGFbeta1 might intervene in modulating feedback signals reaching hypothalamic LHRH producing neurons. The present findings underline once more the importance of the physiological cross-talk between A1 and neurons.     

Actions of LH/hCG on accumulation and catabolism of progestins in cultured rat granulosa cells

Immature hypophysectomized rats were treated with estradiol-17 beta and follicle-stimulating hormone. Granulosa cells were isolated and incubated for 24 h with or without varying doses of ovine luteinizing hormone (NIMADD-oLH-24) or human chorionic gonadotropin (NIADDK CR 125) and accumulations of progesterone and 20 alpha-hydroxy-4-pregnen-3-one were determined. The cells were reincubated for 3 h with [4-14C]progesterone (0.5 nmol/mL) and the radiolabelled metabolites were separated and quantified. Both LH (0.04-1.0 ug/mL) and hCG (0.04-1.0 ug/mL) enhanced the accumulation of endogenous progesterone (by up to 300 and 150%, respectively) and 20 alpha-hydroxy-4-pregnen-3-one (by up to 90 and 85%, respectively) producing dose-dependent increases of the ratio of progesterone to 20 alpha-hydroxy-4-pregnen-3-one (by up to 125 and 70%, respectively). Studies of the metabolism of [1-14C] progesterone have demonstrated that both LH and hCG led to a dose-dependent decrease of the utilization of radiolabelled progesterone (down to 64 and 70%, respectively, of the control value). This effect was associated with an LH- and hCG-dependent inhibition of 20 alpha-hydroxysteroid dehydrogenase activity (down to 60 and 70%, respectively, of the control value) but had no significant effect on 5 alpha-reductase. The present results indicate that LH and hCG stimulate accumulation of progesterone at least in part by decreasing the 20 alpha-hydroxysteroid dehydrogenase activity.     

Regulation of ovarian progestin production by epidermal growth factor in cultured rat granulosa cells

The modulation of ovarian steroidogenesis by epidermal growth factor (EGF) was investigated in cultured rat granulosa cells. Granulosa cells, obtained from ovaries of immature, hypophysectomized, estrogen-treated rats, were incubated for 2 days with EGF, follicle-stimulating hormone (FSH), or EGF plus FSH. Treatment with EGF did not affect estrogen production, but stimulated progestin (i.e. progesterone and 20 alpha-hydroxy-pregn-4-en-3-one) production in a dose-dependent manner. Stimulation of progestin production by EGF appears to be the result of an increase in pregnenolone biosynthesis as well as increases in the activities of 20 alpha-hydroxysteroid dehydrogenase and 3 beta-hydroxysteroid dehydrogenase/isomerase. Treatment with FSH increased both estrogen and progestin production by cultured granulosa cells. When cells were treated concomitantly with EGF, FSH-stimulated estrogen production was inhibited, while progestin production was further enhanced. The EGF enhancement of FSH-stimulated progestin production appears to be the result of synergistic increases in pregnenolone biosynthesis and 20 alpha-hydroxysteroid dehydrogenase activity, resulting in substantial increases in 20 alpha-hydroxypregn-4-en-3-one but not progesterone production. The effects of EGF were shown to be time-dependent. The concept of a direct action of EGF on rat granulosa cells is reinforced by the demonstration of high affinity (Kd approximately 3 X 10(-10) M), low capacity (approximately 5,000 sites/cell) EGF binding sites in these cells. Thus, EGF interacts with specific granulosa cell receptors to stimulate progestin but to inhibit estrogen biosynthesis.     

Effect of allylisopropylacetamide and Sedormid on enzymes of steroid metabolism in rat liver

Female rats, treated with allylisopropylacetamide (AIA) showed a marked decrease of hepatic NADH-5 alpha-reductase, NADPH-5 alpha-reductase, NAD+- and NADP+-3 alpha-hydroxysteroid dehydrogenase activities and an increase of the activity of NADH- and NADPH-5 beta-reductase and NAD+ and NADP+-3 beta-hydroxysteroid dehydrogenase. Administration of Sedormid decreased the activities of 5 alpha-reductases and 3 alpha-hydroxysteroid dehydrogenases (substrate, 5 alpha-dihydrotestosterone) and increased the activity of NADH-5 beta-reductase, whereas no effect was seen on NADPH-5 beta-reductase and 3 beta-hydroxysteroid dehydrogenase.     

Neuroprotection by the steroids pregnenolone and dehydroepiandrosterone is mediated by the enzyme aromatase

Pregnenolone and dehydroepiandrosterone (DHEA) are sex hormone precursors and neuroprotective steroids. Effects of pregnenolone and DHEA may be in part mediated by their conversion to testosterone and by the consecutive conversion of testosterone to estradiol by the enzyme aromatase. This enzyme is induced in reactive astrocytes after different forms of neurodegenerative lesions and the resultant local production of estradiol in the brain has been shown to be neuroprotective. The participation of aromatase in the neuroprotective effect of pregnenolone and DHEA has been assessed in this study. The protective effect of different doses (12.5, 25, 50, and 100 mg/kg) of pregnenolone or DHEA, against systemic kainic acid (7 mg/kg b.w.), was assessed on hippocampal hilar neurons in gonadectomized Wistar male rats. To determine whether the neuroprotective effect of pregnenolone and DHEA was dependent on their conversion to estradiol, the aromatase inhibitor fadrozole (4.16 mg/ml) was administered using subcutaneous osmotic minipumps. The number of Nissl-stained neurons in the hilus of the dentate gyrus of the hippocampal formation was estimated by the optical disector method. The administration of kainic acid resulted in a significant decrease in the number of hilar neurons compared to rats injected with vehicles. Pregnenolone and DHEA showed a dose-dependent protective effect of hilar neurons against kainic acid. The administration of the aromatase inhibitor fadrozole blocked the neuroprotective effect of pregnenolone and DHEA. These findings suggest that estradiol formation by aromatase mediates neuroprotective effects of pregnenolone and DHEA against excitotoxic-induced neuronal death in the hippocampus.     

Neuroprotective Actions of the Synthetic Estrogen 17α-Ethynylestradiol in the Hippocampus

17α-Ethynylestradiol (EE2), a major constituent of many oral contraceptives, is similar in structure to 17β-estradiol, which has neuroprotective properties in several animal models. This study explored the potential neuroprotective actions of EE2 against kainic and quinolinic acid toxicity in the hippocampus of adult ovariectomized Wistar rats. A decrease in the number of Nissl-stained neurons and the induction of vimentin immunoreactivity in astrocytes was observed in the hilus of the dentate gyrus of the hippocampus after the administration of either kainic acid or quinolinic acid. EE2 prevented the neuronal loss and the induction of vimentin immunoreactivity induced by kainic acid at low (1 μg/rat) and high (10–100 μg/rat) doses and exerted a protection against quinolinic acid toxicity at a low dose (1 μg/rat) only. These observations demonstrate that EE2 exerts neuroprotective actions against excitotoxic insults. This finding is relevant for the design of new neuroprotective estrogenic compounds.     

Evaluation of the neuroprotective activity of stansin 6, a resin glycoside from Ipomoea stans

Stansin 6 a tetrasaccharide resin glycoside isolated from the root of Ipomoea stans was evaluated as anticonvulsant and neuroprotective in kainic acid-induced seizures of rats. Intraperitoneal injection of kainic acid (10 mg/kg) induced typical behavioral seizures such as wet dog shakes and limbic seizures, and histopathological changes in the hippocampus (degeneration and loss of pyramidal cells in CA1 to CA4 areas). Stansin 6 (10–80 mg/kg) had no effect on the behavior of rats and did not induce hippocampal damage. Pretreatment with stansin 6 inhibited convulsions in rats from kainic acid-induced seizures, reduced the degeneration pattern in the CA3 region, decreased astrocytic reactivity, and reduced the expression of IL-1β and TNF-α induced by kainic acid. These results suggest that stansin 6 possesses neuroprotective and anticonvulsant activities.     

Progesterone receptors and ventilatory stimulation by progestin

Progestin is thought to be a ventilatory stimulant but its effectiveness in raising ventilation is variable in humans and other species. We hypothesized that the level of progesterone receptors was an important determinant of the ventilatory response to progestin. Since estradiol induces progesterone receptor formation, we compared the ventilatory effect of the synthetic progestin medroxyprogesterone acetate (MPA) given in combination with estradiol with the effects of estradiol alone, MPA alone, or vehicle (saline) in ovariectomized rats. Animals receiving MPA alone had low numbers of progesterone receptors (2.43 pmol/g uterine wt) and had no change in ventilation, arterial Pco2, or Po2. MPA administration raised ventilation 23 +/- 5%, lowered arterial Pco2 3.2 +/- 0.9 Torr (both P less than 0.01) and tended to raise arterial Po2 when given in combination with estradiol to animals with increased numbers of progesterone receptors (4.85 pmol/g uterine wt). Estradiol alone produced the highest number of progesterone receptors (12.3 pmol/g uterine wt) but had no effect on ventilation or arterial Pco2 and decreased arterial Po2. Combined estradiol plus MPA treatment produced a greater fall in arterial Pco2 than did treatment with MPA alone, estradiol, or saline (all P less than 0.05). These results suggest that both an elevation in progestin levels and progesterone receptor numbers are required to stimulate ventilation.     

A novel neuroprotective agent with antioxidant and nitric oxide synthase inhibitory action

N(alpha)-vanillyl-N(omega)-nitroarginine (N - 1) that combines the active functions of natural antioxidant and nitric oxide synthase inhibitor was developed for its neuroprotective properties. N - 1 exhibited protective effects against hydrogen peroxide-induced cell damage and the inhibitory effect on nitric oxide 'NO' production induced by calcium ionophore in NG 108-15 cells. N - 1 inhibited the constitutive NOS isolated from rat cerebellar in a greater extent than constitutive NOS from human endothelial cells. Low binding energy (-10.2 kcal/mol) obtained from docking N - 1 to nNOS supported the additional mode of action of N - 1 as an nNOS inhibitor. The in vivo neuroprotective effect on kainic acid-induced nitric oxide production and neuronal cell death in rat brain was investigated via microdialysis. Rats were injected intra-peritonially with N - 1 at 75 micromol/kg before kainic acid injection (10 mg/kg). The significant suppression effect on kainic acid-induced NO and significant increase in surviving cells were observed in the hippocampus at 40 min after the induction.     

The influence of oestradiol on androgen- and oestrogen-dependent enzyme activities of hepatic steroid metabolism in rats.

Five sexually differentiated enzyme activities of hepatic steroid metabolism (cytoplasmic 17 beta-hydroxysteroid dehydrogenase, 5 beta-reductase; microsomal 3 alpha- and 3 beta-hydroxysteroid dehydrogenase and 5 alpha-reductase) were investigated in intact, gonadectomized and hypophysectomized rats after administration of a single dose of oestradiol valerate. Oestradiol administration caused a partial or complete feminization of these activities in intact male rats. The influence of oestradiol on these activities in gonadectomized rats was determined by the mode of sex hormone-dependent regulation of the individual activity: the most prominent effects were seen in the oestrogen-dependent activities (17 beta-hydroxysteroid dehydrogenase, 5 beta-reductase); no effect was seen in the completely androgen-dependent 3 alpha-hydroxysteroid dehydrogenase because gonadectomy alone was sufficient to cause complete feminization of the activity. Oestradiol administration had no effect on the activities of hypophysectomized rats. The fact that oestrogen administration to intact male rats caused greater changes than prepuberal gonadectomy demonstrates that oestrogen action is more than simple suppression of testicular function.     

Effects of progesterone and its reduced metabolites, dihydroprogesterone and tetrahydroprogesterone, on the expression and phosphorylation of glycogen synthase kinase-3 and the microtubule-associated protein tau in the rat cerebellum

Progesterone exerts a variety of actions in the brain, where it is rapidly metabolized to 5alpha-dihydroprogesterone (DHP) and 3alpha,5alpha-tetrahydroprogesterone (THP). The effect of progesterone and its metabolites on the expression and phosphorylation of the microtubule-associated protein Tau and glycogen synthase kinase 3beta (GSK3beta), a kinase involved in Tau phosphorylation, were assessed in two progesterone-sensitive brain areas: the hypothalamus and the cerebellum. Administration of progesterone, DHP, and THP to ovariectomized rats did not affect Tau and GSK3beta assessed in whole hypothalamic homogenates. In contrast, progesterone and its metabolites resulted in a significant decrease in the expression of Tau and GSK3beta in the cerebellum. Furthermore, progesterone administration resulted in an increase in the phosphorylation of two epitopes of Tau (Tau-1 and PHF-1) phosphorylated by GSK3beta, but did not affect the phosphorylation of an epitope of Tau (Ser262) that is GSK3beta insensitive. These effects were accompanied by a decrease in the phosphorylation of GSK3beta in serine, which is associated to an increase in its activity, suggesting that the effect of progesterone on Tau-1 and PHF-1 phosphorylation in the cerebellum is mediated by GSK3beta. The regulation of Tau expression and phosphorylation by progesterone may contribute to the hormonal regulation of cerebellar function by the modification of neuronal cytoskeleton.     

Metabolism of androgens in human hyperplastic prostate: evidence for a differential localization of the enzymes involved in the metabolism

The subcellular distribution of 5 alpha-reductase, 17 beta-hydroxy steroid dehydrogenase, 3 alpha- and 3 beta-hydroxysteroid dehydrogenase activities was studied in human hyperplastic prostate. 5 alpha-reductase and 17 beta-hydroxysteroid dehydrogenase activities are located in the nuclear envelope. 3 alpha-hydroxysteroid dehydrogenase activity was almost equally distributed between cytosol and membranes, 3 beta-hydroxysteroid dehydrogenase activity was linked to all membranes. Direct testosterone metabolism (transformation into its active metabolite 5 alpha-DHT and into androstenedione, an inactive androgen) takes place only in the nucleus whereas indirect metabolism takes place mainly in the cytoplasm. These findings add new evidence for the mechanism of action of testosterone in prostatic tissue. Testosterone diffuses into the cell, migrates toward the nucleus and is transformed at the nuclear envelope level into two metabolites, DHT and androstenedione. After transformation into its active form, the hormone enters the nucleus whereas the inactive form is released into the cytoplasm. This metabolism could be seen as a control of the amount of active hormone entering the nucleus and being able to bind the androgen receptor.     

Alterations of 20 alpha-hydroxysteroid dehydrogenase activity in cultured rat granulosa cells by follicle-stimulating hormone and testosterone

The effect of follicle-stimulating hormone (FSH) and testosterone (T) on rat granulosa cell progestin metabolism was investigated by incubation of the cells for 24 h with FSH and/or T and subsequent reincubation with an appropriate rabiolabeled steroid for 3 h. Exposure to varying concentrations of FSH (8-1000 ng/ml) and T (4-500 nM) decreased overall 4-[14C] progesterone utilization and accumulation of 20 alpha-reduced metabolites of progesterone in a dose-related manner. The accumulation of 5 alpha-reduced metabolites was not markedly changed by FSH and T treatments. Treatments with FSH and/or T decreased utilization of all progestins studied: progesterone by 30-50%, 20 alpha-hydroxy-4-pregnen-3-one by 23-31%, 3 alpha-hydroxy-5 alpha-pregnan-20-one by 41-64%, and 5 alpha-pregnane-3 alpha,20 alpha-diol by 26-34%. The greatest effects were observed following FSH + T treatments. Decreased utilization of substrates was associated with the decrease of 20 alpha-hydroxy-steroid dehydrogenase activity; the conversion of progesterone to 20 alpha-hydroxy-4-pregnen-3-one was decreased by 44-62%, the conversion of 20 alpha-hydroxy-4-pregnen-3-one to progesterone was decreased by 41-61%, the conversion of 3 alpha-hydroxy-5 alpha-pregnan-20-one to 5 alpha-pregnane-3 alpha,20 alpha-diol was decreased by 42-69%, and the conversion of 5 alpha-pregnane-3 alpha,20 alpha-diol to 3 alpha-hydroxy-5 alpha-pregnan-20-one was decreased by 53-60%. The incubation of granulosa cells with cyanoketone (10(-6)M), an inhibitor of delta 5,3 beta-hydroxysteroid dehydrogenase, virtually eliminated de novo progesterone production but did not alter the inhibitory effect of FSH and T on radiolabeled progesterone utilization and accumulation of 20 alpha-reduced metabolites, indicating that the observed effects are not influenced by endogenous production of progesterone. It was concluded from these studies that both FSH and testosterone inhibit the 20 alpha-hydroxysteroid dehydrogenase activity and consequently decrease progesterone catabolism by granulosa cells.