Disease stage-dependent changes in brain levels and neuroprotective effects of neuroactive steroids in Parkinson's disease.

Neuroactive steroids are known neuroprotective agents and neurotransmitter regulators. We previously found that expression of the enzymes synthesizing 5α-dihydroprogesterone (5α-DHP), allopregnanolone (ALLO), and dehydroepiandrosterone sulfate (DHEAS) were reduced in the substantia nigra (SN) of Parkinson's Disease (PD) brain. Here, concentrations of a comprehensive panel of steroids were measured in human post-mortem brains of PD patients and controls. Gas chromatography-mass spectrometry (GC/MS) was used to measure steroid levels in SN (involved in early symptoms) and prefrontal cortex (PFC) (involved later in the disease) of five control (CTR) and nine PD donors, divided into two groups: PD4 (PD-Braak stages 1-4) and PD6 (PD-Braak stages 5-6). In SN, ALLO was increased in PD4 compared to CTR and 5α-DHP and ALLO levels were diminished in PD6 compared to PD4. The ALLO metabolite 3α5α20α-hexahydroprogesterone (3α5α20α-HHP) was higher in PD4 compared to CTR. In PFC, 3α5α20α-HHP was higher in PD4 compared to both CTR and PD6. The effects of 5α-DHP, ALLO and DHEAS were tested on human post-mortem brain slices of patients and controls in culture. RNA expression of genes involved in neuroprotection, neuroinflammation and neurotransmission was analysed after 5 days of incubation with each steroid. In PD6 slices, both 5α-DHP and ALLO induced an increase of the glutamate reuptake effector GLAST1, while 5α-DHP also increased gene expression of the neuroprotective TGFB. In CTR slices, ALLO caused reduced expression of IGF1 and GLS, while DHEAS reduced the expression of p75 and the anti-apoptotic molecule APAF1. Together these data suggest that a potentially protective upregulation of ALLO occurs at early stages of PD, followed by a downregulation of progesterone metabolites at later stages that may exacerbate the pathological changes, especially in SN. Neuroprotective effects of neurosteroids are thus dependent on the neuropathological stage of the disease.

BV-2 Microglial Cells Respond to Rotenone Toxic Insult by Modifying Pregnenolone, 5α-Dihydroprogesterone and Pregnanolone Levels.

Neuroinflammation, whose distinctive sign is the activation of microglia, is supposed to play a key role in the development and progression of neurodegenerative diseases. The aim of this investigation was to determine levels of neurosteroids produced by resting and injured BV-2 microglial cells. BV-2 cells were exposed to increasing concentrations of rotenone to progressively reduce their viability by increasing reactive oxygen species (ROS) production. BV-2 cell viability was significantly reduced 24, 48 and 72 h after rotenone (50-1000 nM) exposure. Concomitantly, rotenone (50-100 nM) determined a dose-independent augmentation of ROS production. Then, BV-2 cells were exposed to a single, threshold dose of rotenone (75 nM) to evaluate the overtime release of neurosteroids. In particular, pregnenolone, pregnenolone sulfate, progesterone, 5α-dihydroprogesterone (5α-DHP), allopregnanolone, and pregnanolone, were quantified in the culture medium by liquid chromatography with tandem mass spectrometry (LC-MS/MS) analysis. BV-2 cells synthesized all the investigated neurosteroids and, after exposure to rotenone, 5αDHP and pregnanolone production was remarkably increased. In conclusion, we found that BV-2 cells not only synthesize several neurosteroids, but further increase this production following oxidative damage. Pregnanolone and 5α-DHP may play a role in modifying the progression of neuroinflammation in neurodegenerative diseases.

Augmentation of endogenous neurosteroid synthesis alters experimental status epilepticus dynamics.

Neurosteroids can modulate γ-aminobutyric acid type A receptor-mediated inhibitory currents. Recently, we discovered that the neurosteroids progesterone, 5α-dihydroprogesterone, allopregnanolone, and pregnanolone are reduced in the cerebrospinal fluid of patients with status epilepticus (SE). However, it is undetermined whether neurosteroids influence SE. For this reason, first we evaluated whether the inhibitor of adrenocortical steroid production trilostane (50 mg/kg) could modify the levels of neurosteroids in the hippocampus and neocortex, and we found a remarkable increase in pregnenolone, progesterone, 5α-dihydroprogesterone, and allopregnanolone levels using liquid chromatography tandem mass spectrometry. Second, we characterized the dynamics of SE in the presence of the varied neurosteroidal milieu by a single intraperitoneal kainic acid (KA; 15 mg/kg) injection in trilostane-treated rats and their controls. Convulsions started in advance in the trilostane group, already appearing 90 minutes after the KA injection. In contrast to controls, convulsions prevalently developed as generalized seizures with loss of posture in the trilostane group. However, this effect was transient, and convulsions waned 2 hours before the control group. Moreover, electrocorticographic traces of convulsions were shorter in trilostane-treated rats, especially at the 180-minute (P < .001) and 210-minute (P < .01) time points. These findings indicate that endogenous neurosteroids remarkably modulate SE dynamics.

Steroid profiles in quail brain and serum: Sex and regional differences and effects of castration with steroid replacement.

Both systemic and local production contribute to the concentration of steroids measured in the brain. This idea was originally based on rodent studies and was later extended to other species, including humans and birds. In quail, a widely used model in behavioural neuroendocrinology, it was demonstrated that all enzymes needed to produce sex steroids from cholesterol are expressed and active in the brain, although the actual concentrations of steroids produced were never investigated. We carried out a steroid profiling in multiple brain regions and serum of sexually mature male and female quail by gas chromatography coupled with mass spectrometry. The concentrations of some steroids (eg, corticosterone, progesterone and testosterone) were in equilibrium between the brain and periphery, whereas other steroids (eg, pregnenolone (PREG), 5α/ß-dihydroprogesterone and oestrogens) were more concentrated in the brain. In the brain regions investigated, PREG sulphate, progesterone and oestrogen concentrations were higher in the hypothalamus-preoptic area. Progesterone and its metabolites were more concentrated in the female than the male brain, whereas testosterone, its metabolites and dehydroepiandrosterone were more concentrated in males, suggesting that sex steroids present in quail brain mainly depend on their specific steroidogenic pathways in the ovaries and testes. However, the results of castration experiments suggested that sex steroids could also be produced in the brain independently of the peripheral source. Treatment with testosterone or oestradiol restored the concentrations of most androgens or oestrogens, respectively, although penetration of oestradiol in the brain appeared to be more limited. These studies illustrate the complex interaction between local brain synthesis and the supply from the periphery for the steroids present in the brain that are either directly active or represent the substrate of centrally located enzymes.

Identification of steroidal derivatives inhibiting the transformations of allopregnanolone and estradiol by 17ß-hydroxysteroid dehydrogenase type 10.

17ß-Hydroxysteroid dehydrogenase type 10 (17ß-HSD10) is a mitochondrial enzyme known for its potential role in Alzheimer's Disease (AD). 17ß-HSD10, by its oxidative activity, could decrease the concentration of two important neurosteroids, allopregnanolone (ALLOP) and 17ß-estradiol (E2), respectively preventing their neurogenesis and neuroprotective effects. Since the inhibition of 17ß-HSD10 could lead to a new treatment for AD, we developed two biological assays using labeled ALLOP or E2 as substrates to measure the inhibitory activity of compounds against pure 17ß-HSD10 protein. After the optimization of different parameters (time, concentration of enzyme, substrate and cofactor), analogs of the first reported steroidal inhibitor of 17ß-HSD10 in intact cells were screened to determine their inhibitory potency for the ALLOP or the E2 oxidation. One compound, androstane derivative 5, possesses the best dual inhibition against both transformations (ALLOP, IC50 = 235 µM and E2, IC50 = 610 µM). Some compounds are dual inhibitors to a lesser extent, and others seem selective for one of the transformations in particular. By developing two reliable assays and by identifying a first generation of steroidal inhibitors of pure 17ß-HSD10, this preliminary study opens the door to new and more potent inhibitors.

PTSD in women is associated with a block in conversion of progesterone to the GABAergic neurosteroids allopregnanolone and pregnanolone measured in plasma.

There is a need to identify new and more effective treatments for posttraumatic stress disorder (PTSD). Allopregnanolone and its stereoisomer pregnanolone (together termed ALLO) are metabolites of progesterone that positively and allosterically modulate GABA effects at GABAA receptors, thereby reducing anxiety and depression. Previous research revealed that women with PTSD had low cerebrospinal fluid (CSF) ALLO levels and a low ratio of ALLO to the allopregnanolone precursor 5α-DHP, consistent with deficient activity of the ALLO synthetic enzyme 3α-hydroxysteroid dehydrogenase (3α-HSD). The current study examined ALLO and the ratio of ALLO to 5α-DHP in plasma at rest and in response to psychophysiological stressors in trauma-exposed, medication-free women with and without PTSD. Participants were examined twice in random order during the early follicular phase (eFP) and mid-luteal phase (mLP) of the menstrual cycle. Plasma neurosteroids were measured using gas chromatography-mass spectrometry. Results indicate that the ALLO to 5α-DHP ratio in plasma increases between the eFP and mLP. In addition, women with PTSD have a lower ratio of ALLO to 5α-DHP than trauma-exposed healthy women, as well as blunted increases in this ratio in response to a moderately stressful laboratory procedure, i.e., differential fear conditioning, across the menstrual cycle. Clinically feasible testing for 3α-HSD dysfunction is critical to translating this line of research into clinical care. Measurement of this ratio in plasma could facilitate patient stratification in clinical treatment trials, as well as precision medicine targeting of treatments that address ALLO synthesis deficits in women with PTSD.

Sex Hormones Protect Against Amyloid-ß Induced Oxidative Stress in the Choroid Plexus Cell Line Z310.

The choroid plexus (CP) epithelium is a unique structure in the brain that forms an interface between the peripheral blood on the basal side and the cerebrospinal fluid (CSF) on the apical side. It is a relevant source of many polypeptides secreted to the CSF with neuroprotective functions and also participates in the elimination and detoxification of brain metabolites, such as ß-amyloid (Aß) removal from the CSF through transporter-mediated influx. The CP is also a target tissue for sex hormones (SHs) that have recognised neuroprotective effects against a variety of insults, including Aß toxicity and oxidative stress in the central nervous system. The present study aimed to understand how SHs modulate Aß-induced oxidative stress in a CP cell line (Z310 cell line) by analysing the effects of Aß1-42 on oxidative stress, mitochondrial function and apoptosis, as well as by assessing how 17ß-oestradiol (E2 ) and 5α-dihydrotestosterone (DHT) modulated these effects and the cellular uptake of Aß1-42 by CP cells. Our findings show that E2 and DHT treatment reduce Aß1-42 -induced oxidative stress and the internalisation of Aß1-42 by CP epithelial cells, highlighting the importance of considering the background of SHs and therefore sex-related differences in Aß metabolism and clearance by CP cells.

Mechanism of action of the breast cancer-promoter hormone, 5α-dihydroprogesterone (5αP), involves plasma membrane-associated receptors and MAPK activation.

Previous studies have shown that breast tissues and breast cell lines can convert progesterone to 5α-pregnane-3,20-dione (5aP), and that 5αP stimulates breast cell proliferation and detachment in vitro, and tumor formation in vivo, regardless of presence or absence of receptors for progesterone (PR) or estrogen (ER). Recently it was demonstrated, both in vitro and in vivo, that pro-cancer actions attributed to administered progesterone are due to the in situ produced 5αP. Because of the significant role of 5αP in breast cancers, it is important to understand its molecular mechanisms of action. The aims of the current studies were to identify 5αP binding sites and to determine if the mechanisms of action of 5αP involve the mitogen-activated protein kinase (MAPK), extracellular signal-regulated protein kinases (ERK1/2) pathway. Binding studies, using tritium-labeled 5αP ([(3)H]5αP), carried out on membrane, cytosol and nuclear fractions from human breast cells (MCF-7, PR/ER-positive; MDA-MB-231, PR/ER-negative) and on highly enriched membrane fractions, identified the plasma membrane as the site of ligand specific 5αP receptors. Localization of 5αP receptors to the cell membrane was confirmed visually with fluorescently labeled conjugate (5αP-BSA-FITC). Treatment of cells with either 5αP or membrane-impermeable 5αP-BSA resulted in significant increases in cell proliferation and detachment. 5αP and 5αP-BSA equally activated the MAPK/ERK1/2 pathway as evidenced by phosphorylation of ERK1/2. Inhibitors (PD98059, mevastatin and genistein) of specific sites along the Ras/Raf/MEK/ERK signaling pathway, blocked the phosphorylation and concomitantly inhibited 5αP-induced stimulation of cell proliferation and detachment. The study has identified high affinity, stereo-specific binding sites for 5αP that have the characteristics of a functional membrane 5αP receptor, and has shown that the cancer-promoter actions of 5αP are mediated from the liganded receptor via the MAPK/ERK1/2 signaling cascade. The findings enhance our understanding of the role of the progesterone metabolite 5αP in breast cancer and should promote new approaches to the development of breast cancer diagnostics and therapeutics.

Progesterone-induced stimulation of mammary tumorigenesis is due to the progesterone metabolite, 5α-dihydroprogesterone (5αP) and can be suppressed by the 5α-reductase inhibitor, finasteride.

Progesterone has long been linked to breast cancer but its actual role as a cancer promoter has remained in dispute. Previous in vitro studies have shown that progesterone is converted to 5α-dihydroprogesterone (5αP) in breast tissue and human breast cell lines by the action of 5α-reductase, and that 5αP acts as a cancer-promoter hormone. Also studies with human breast cell lines in which the conversion of progesterone to 5αP is blocked by a 5α-reductase inhibitor, have shown that the in vitro stimulation in cell proliferation with progesterone treatments are not due to progesterone itself but to the metabolite 5αP. No similar in vivo study has been previously reported. The objective of the current studies was to determine in an in vivo mouse model if the presumptive progesterone-induced mammary tumorigenesis is due to the progesterone metabolite, 5αP. BALB/c mice were challenged with C4HD murine mammary cells, which have been shown to form tumors when treated with progesterone or the progestin, medroxyprogesterone acetate. Cells and mice were treated with various doses and combinations of progesterone, 5αP and/or the 5α-reductase inhibitor, finasteride, and the effects on cell proliferation and induction and growth of tumors were monitored. Hormone levels in serum and tumors were measured by specific RIA and ELISA tests. Proliferation of C4HD cells and induction and growth of tumors was stimulated by treatment with either progesterone or 5αP. The progesterone-induced stimulation was blocked by finasteride and reinstated by concomitant treatment with 5αP. The 5αP-induced tumors expressed high levels of ER, PR and ErbB-2. Hormone measurements showed significantly higher levels of 5αP in serum from mice with tumors than from mice without tumors, regardless of treatments, and 5αP levels were significantly higher (about 4-fold) in tumors than in respective sera, while progesterone levels did not differ between the compartments. The results indicate that the stimulation of C4HD tumor growth in BALB/c mice treated with progesterone is due to the progesterone metabolite 5αP formed at elevated levels in mammary cells as a result of the 5α-reductase action on progesterone. The results provide the first in vivo demonstration that stimulation of breast cell tumorigenesis and tumor growth accompanying progesterone treatment is due to the progesterone metabolite 5αP, and that breast tumorigenesis can be blocked with the 5α-reductase inhibitor, finasteride.

Fluoxetine elevates allopregnanolone in female rat brain but inhibits a steroid microsomal dehydrogenase rather than activating an aldo-keto reductase.

BACKGROUND AND PURPOSE: Fluoxetine, a selective serotonin reuptake inhibitor, elevates brain concentrations of the neuroactive progesterone metabolite allopregnanolone, an effect suggested to underlie its use in the treatment of premenstrual dysphoria. One report showed fluoxetine to activate the aldo-keto reductase (AKR) component of 3α-hydroxysteroid dehydrogenase (3α-HSD), which catalyses production of allopregnanolone from 5α-dihydroprogesterone. However, this action was not observed by others. The present study sought to clarify the site of action for fluoxetine in elevating brain allopregnanolone. EXPERIMENTAL APPROACH: Adult male rats and female rats in dioestrus were treated with fluoxetine and their brains assayed for allopregnanolone and its precursors, progesterone and 5α-dihydroprogesterone. Subcellular fractions of rat brain were also used to investigate the actions of fluoxetine on 3α-HSD activity in both the reductive direction, producing allopregnanolone from 5α-dihydroprogesterone, and the reverse oxidative direction. Fluoxetine was also tested on these recombinant enzyme activities expressed in HEK cells. KEY RESULTS: Short-term treatment with fluoxetine increased brain allopregnanolone concentrations in female, but not male, rats. Enzyme assays on native rat brain fractions and on activities expressed in HEK cells showed fluoxetine did not affect the AKR producing allopregnanolone from 5α-dihydroprogesterone but did inhibit the microsomal dehydrogenase oxidizing allopregnanolone to 5α-dihydroprogesterone. CONCLUSIONS AND IMPLICATIONS: Fluoxetine elevated allopregnanolone in female rat brain by inhibiting its oxidation to 5α-dihydroprogesterone by a microsomal dehydrogenase. This is a novel site of action for fluoxetine, with implications for the development of new agents and/or dosing regimens to raise brain allopregnanolone.

Pregnancy without progesterone in horses defines a second endogenous biopotent progesterone receptor agonist, 5α-dihydroprogesterone.

One of the most widely accepted axioms of mammalian reproductive biology is that pregnancy requires the (sole) support of progesterone, acting in large measure through nuclear progesterone receptors (PRs) in uterine and cervical tissues, without which pregnancy cannot be established or maintained. However, mares lack detectable progesterone in the latter half of pregnancy. Instead of progesterone, several (mainly 5α-reduced) pregnanes are elevated and have long been speculated to provide progestational support in lieu of progesterone itself. To the authors' knowledge, evidence for the bioactivity of a second potent endogenously synthesized pregnane able to support pregnancy in the absence of progesterone has never before been reported. The 5α-reduced progesterone metabolite dihydroprogesterone (DHP) was shown in vivo to stimulate endometrial growth and progesterone-dependent gene expression in the horse at subphysiological concentrations and to maintain equine pregnancy in the absence of luteal progesterone in the third and fourth weeks postbreeding. Results of in vitro studies indicate that DHP is an equally potent and efficacious endogenous progestin in the horse but that the PR evolved with increased agonistic potency for DHP at the expense of potency toward progesterone based on comparisons with human PR responses. Sequence analysis and available literature indicate that the enzyme responsible for DHP synthesis, 5α-reductase type 1, also adapted primarily to metabolize progesterone and thereby to serve diverse roles in the physiology of pregnancy in mammals. Our confirmation that endogenously synthesized DHP is a biopotent progestin in the horse ends decades of speculation, explaining how equine pregnancies survive without measurable circulating progesterone in the last 4 to 5 mo of gestation.

Neuroprotection by steroids after neurotrauma in organotypic spinal cord cultures: a key role for progesterone receptors and steroidal modulators of GABA(A) receptors.

Progesterone is neuroprotective after spinal cord injury, however its mechanism of action remains unexplored. Here we used organotypic spinal cord slice cultures from 3 weeks-old mice to evaluate the mechanisms of neuroprotection by progesterone and its 5α-reduced metabolites. In vitro spinal cord injury, using a weight drop model, induced a decrease in the number of motoneurons. This was correlated with an increase in the number of dying cells (PI⁺ cells) and in LDH release. Addition of 10 µM of progesterone, 5α-dihydroprogesterone (5α-DHP) or allopregnanolone (3α, 5α-tetrahydroprogesterone) to the medium at the time of injury rescued the spinal cord slices from the effects of damage. Progesterone prevented membrane cell damage, motoneuron loss and cell death. These effects were not due to its bioconversion to 5α-DHP nor to allopregnanolone, as supported by the finasteride, an inhibitor of 5α-reductase enzymes, and by the absence of 5α-reduced progesterone metabolites in the slices analyzed by gas chromatography-mass spectrometry. The neuroprotective effects of progesterone required PR as they could not be observed in slices from homozygous knockout PR(-/-) mice. Allopregnanolone treatment was also neuroprotective. Its effects were not due to its bioconversion back to 5α-DHP, which can activate gene transcription via PR, because they were still observed in slices from knockout PR(-/-) mice. Allopregnanolone effects involved GABA(A) receptors, as they were inhibited by the selective GABA(A) receptor antagonist Gabazine, in both PR(+/+) and PR(-/-) mice. Altogether, these findings identify both PR and GABA(A) receptors as important targets for neuroprotection by progestagens after spinal cord injury.

A single glycine-alanine exchange directs ligand specificity of the elephant progestin receptor.

The primary gestagen of elephants is 5α-dihydroprogesterone (DHP), which is unlike all other mammals studied until now. The level of DHP in elephants equals that of progesterone in other mammals, and elephants are able to bind DHP with similar affinity to progesterone indicating a unique ligand-binding specificity of the elephant progestin receptor (PR). Using site-directed mutagenesis in combination with in vitro binding studies we here report that this change in specificity is due to a single glycine to alanine exchange at position 722 (G722A) of PR, which specifically increases DHP affinity while not affecting binding of progesterone. By conducting molecular dynamics simulations comparing human and elephant PR ligand-binding domains (LBD), we observed that the alanine methyl group at position 722 is able to push the DHP A-ring into a position similar to progesterone. In the human PR, the DHP A-ring position is twisted towards helix 3 of PR thereby disturbing the hydrogen bond pattern around the C3-keto group, resulting in a lower binding affinity. Furthermore, we observed that the elephant PR ligand-binding pocket is more rigid than the human analogue, which probably explains the higher affinity towards both progesterone and DHP. Interestingly, the G722A substitution is not elephant-specific, rather it is also present in five independent lineages of mammalian evolution, suggesting a special role of the substitution for the development of distinct mammalian gestagen systems.

Type 1 5α-reductase may be required for estrous cycle changes in affective behaviors of female mice.

There are estrous cycle differences in affective behaviors of rodents that are generally attributed to cyclic variations in estradiol, progesterone (P) and its metabolites. A question is the role of the steroid metabolism enzyme, 5α-reductase, for these estrous cycle differences. To address the requirement of 5α-reductase, estrous cycle variations in the behavior of wildtype mice and their littermates that are deficient in the 5α-reductase type 1 enzyme (5αRKO mice) were examined. The hypothesis was that if some of the estrous cycle differences in exploratory (open field) and anxiety (elevated plus maze) are due to P's 5α-reduction to 5α-pregnan-3α-ol-20-one (3α,5α-THP), then wildtype mice will have estrous cycle differences in the expression of these behaviors, but 5αRKO mice will not. Mice were tested in these tasks and then had plasma and brains collected so that steroid levels (estradiol, P, 3α,5α-THP, corticosterone) could be measured in these tissues. Results supported this hypothesis. There were estrous cycle differences among wildtype, but not 5αRKO, mice. Proestrous wildtype mice made more central entries in the open field and spent more time on the open arms of the plus maze, coincident with higher 3α,5α-THP levels in plasma and brain regions important for these behaviors, such as the hippocampus and cortex, compared to their diestrous counterparts. Variability in the open field and elevated plus maze could be explained by circulating and hippocampus levels of 3α,5α-THP, respectively. Thus, 5α-reductase may be required for the estrous cycle variations in affective behavior and 3α,5α-THP levels of female mice.

I. Levels of 5α-reduced progesterone metabolite in the midbrain account for variability in reproductive behavior of middle-aged female rats.

At middle-age, the reproductive capacity of female rats begins to decline. Whether there are consequences for social and reproductive behaviors related to changes in estradiol (E(2)), progesterone (P(4)) and its 5α-reduced metabolites, dihydroprogesterone (DHP) and 5α-pregnan-3α-ol-20-one (3α,5α-THP), is of interest. In Experiment 1, 1-year-old female breeder rats that had "maintained their reproductive status" (having 4-5 days estrous cycles, > 60% successful pregnancies after mating, > 10 pups/litter) or their age-matched counterparts with "declining reproductive status" were assessed in social interaction, standard mating, and paced mating when in proestrus. Rats that maintained reproductive status tended to have higher levels of proceptivity, and significantly reduced aggression, towards males, compared to rats with declining reproductive status. Basal midbrain E(2) and DHP levels accounted for a significant proportion of variance in lordosis. In Experiment 2, 1-year-old, age-matched, female breeders that had maintained reproductive status or were in reproductive decline were compared to three-month old, nulliparous females that had regular (4-5 days) or irregular estrous cycles. Age did not influence paced mating but younger rats had greater diencephalon E(2) than did middle-aged rats. After mating, rats with declining/irregular reproductive status had higher P(4) and DHP levels in midbrain than did rats with maintaining/regular reproductive status, albeit differences in midbrain 3α,5α-THP were not seen. Middle-aged rats that maintained reproductive function had greater 3α,5α-THP formation in diencephalon compared to other groups. Thus, age-related changes in central progestogen formation in midbrain or diencephalon may contribute to some variability in expression of reproductive behaviors.

BTG2 is an LXXLL-dependent co-repressor for androgen receptor transcriptional activity.

The tumor suppressor gene, BTG2 has been down-regulated in prostate cancer and the ectopic expression of this gene has been shown to inhibit prostate cancer cell growth. Sequence analysis revealed that the BTG2 protein contains two leucine-rich motifs ((20)LxxLL(24) and (92)LxxLL(96)), which are usually found in nuclear receptor co-factors. Based on this, we postulated that there will be an association between BTG2 and AR. In this study, we discovered that BTG2 directly bound to the androgen receptor (AR) in the absence of 5α-dihydrotestosterone (DHT), and in the presence of the androgen, this interaction was increased. BTG2 bearing the mutant (20)LxxLL(24) motif bound to AR equally efficient as the wild-type BTG2, while BTG2 bearing the mutant (92)LxxLL(96) motif failed to interact with AR. Functional studies indicated that ectopic expression of BTG2 caused a significant inhibition of AR-mediated transcriptional activity and a decreased growth of prostate cancer cells. Androgen-induced promoter activation and expression of prostate-specific antigen (PSA) are significantly attenuated by BTG2. The intact (92)LxxLL(96) motif is required for these activities. These findings, for the first time, demonstrate that BTG2 complexes with AR via an LxxLL-dependent mechanism and may play a role in prostate cancer via modulating the AR signaling pathway.

Corticosteroid and neurosteroid dysregulation in an animal model of autism, BTBR mice.

Autism spectrum disorders (ASD) are a constellation of neurodevelopmental disorders associated with disruptions in social, cognitive, and/or motor behaviors. ASD are more prevalent among males than females and characterized by aberrant social and language development, and a dysregulation in stress-responding. Levels of progesterone (P(4)) and its metabolite 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) are higher and more variable in females compared to males. 3alpha,5alpha-THP is also a neurosteroid, which can be rapidly produced de novo in the brain, independent of peripheral gland secretion, and can exert homeostatic effects to modulate stress-responding. An inbred mouse strain that has demonstrated an ASD-like behavioral and neuroendocrine phenotype is BTBR T +tf/J (BTBR). BTBR mice have deficits in cognitive and social behaviors and have high circulating levels of the stress hormone, corticosterone. We hypothesized that central 3alpha,5alpha-THP levels would be different among BTBR mice compared to mice on a similar background C57BL/6J (C57/J) and 129S1/SvlmJ (129S1). Tissues were collected from BTBR, C57/J and 129S1 male mice and levels of corticosterone, P(4), and 3alpha,5alpha-THP in plasma and in the hypothalamus, midbrain, hippocampus, and cerebellum were measured by radioimmunoassay. Circulating levels of corticosterone, P(4), and 3alpha,5alpha-THP were significantly higher among BTBR, than C57/J and 129S1, mice. Levels of P(4) in the cerebellum were significantly higher than other brain regions among all mouse strains. Levels of 3alpha,5alpha-THP in the hypothalamus of BTBR mice were significantly higher compared to C57/J and 129S1 mice. These findings suggest that neuroendocrine dysregulation among BTBR mice extends to 3alpha,5alpha-THP.

A role for Src kinase in progestin facilitation of estrous behavior in estradiol-primed female rats.

This study tested the hypothesis that the Src/Raf/MAPK signaling pathway is involved in the facilitation of the lordosis and proceptive behaviors induced by progesterone (P) and its ring A-reduced metabolites in ovariectomized, estradiol-primed rats. Intraventricular (icv) infusion of PP2 (7.5, 15 and 30 microg), a Src kinase inhibitor, significantly depressed P-dependent estrous behavior (lordosis and proceptivity) in estradiol-primed rats. Icv infusion of 30 microg of PP2 also significantly attenuated estrous behavior induced by the ring A-reduced P metabolites 5 alpha-dihydroprogesterone (5 alpha-DHP) and 5 alpha-pregnan-3alpha-ol-20-one (allopregnanolone). PP2 did not inhibit estrous behavior induced by administration of high doses of estradiol alone to ovariectomized rats. We also assessed if the ventromedial hypothalamus (VMH) is one of the neural sites at which progestins activate Src signaling to facilitate estrous behavior. Bilateral administration of 15 microg of PP2 into the VMH inhibited the stimulation of both lordosis and proceptive behaviors elicited by subcutaneous P administration to estradiol-primed rats. These results suggest that progestins act through Src/Raf/MAPK signaling to initiate estrous behaviors in estrogen-primed rats. This event is one component of the cellular pathways leading to the display of estrous behaviors induced by P and its ring A-reduced metabolites in female rats.

Aldo-keto reductase 1C3 expression in MCF-7 cells reveals roles in steroid hormone and prostaglandin metabolism that may explain its over-expression in breast cancer.

Aldo-keto reductase (AKR) 1C3 (type 5 17beta-hydroxysteroid dehydrogenase and prostaglandin F synthase), may stimulate proliferation via steroid hormone and prostaglandin (PG) metabolism in the breast. Purified recombinant AKR1C3 reduces PGD(2) to 9alpha,11beta-PGF(2), Delta(4)-androstenedione to testosterone, progesterone to 20alpha-hydroxyprogesterone, and to a lesser extent, estrone to 17beta-estradiol. We established MCF-7 cells that stably express AKR1C3 (MCF-7-AKR1C3 cells) to model its over-expression in breast cancer. AKR1C3 expression increased steroid conversion by MCF-7 cells, leading to a pro-estrogenic state. Unexpectedly, estrone was reduced fastest by MCF-7-AKR1C3 cells when compared to other substrates at 0.1muM. MCF-7-AKR1C3 cells proliferated three times faster than parental cells in response to estrone and 17beta-estradiol. AKR1C3 therefore represents a potential target for attenuating estrogen receptor alpha induced proliferation. MCF-7-AKR1C3 cells also reduced PGD(2), limiting its dehydration to form PGJ(2) products. The AKR1C3 product was confirmed as 9alpha,11beta-PGF(2) and quantified with a stereospecific stable isotope dilution liquid chromatography-mass spectrometry method. This method will allow the examination of the role of AKR1C3 in endogenous prostaglandin formation in response to inflammatory stimuli. Expression of AKR1C3 reduced the anti-proliferative effects of PGD(2) on MCF-7 cells, suggesting that AKR1C3 limits peroxisome proliferator activated receptor gamma (PPARgamma) signaling by reducing formation of 15-deoxy-Delta(12,14)-PGJ(2) (15dPGJ(2)).

Opposing actions of the progesterone metabolites, 5alpha-dihydroprogesterone (5alphaP) and 3alpha-dihydroprogesterone (3alphaHP) on mitosis, apoptosis, and expression of Bcl-2, Bax and p21 in human breast cell lines.

Previous studies have shown that breast tissues and breast cell lines convert progesterone (P) to 5alpha-dihydroprogesterone (5alphaP) and 3alpha-dihydroprogesterone (3alphaHP) and that 3alphaHP suppresses, whereas 5alphaP promotes, cell proliferation and detachment. The objectives of the current studies were to determine if the 5alphaP- and 3alphaHP-induced changes in cell numbers are due to altered rates of mitosis and/or apoptosis, and if 3alphaHP and 5alphaP act on tumorigenic and non-tumorigenic cells, regardless of estrogen (E) and P receptor status. The studies were conducted on tumorigenic (MCF-7, MDA-MB-231, T47D) and non-tumorigenic (MCF-10A) human breast cell lines, employing several methods to assess the effects of the hormones on cell proliferation, mitosis, apoptosis and expression of Bcl-2, Bax and p21. In all four cell lines, 5alphaP increased, whereas 3alphaHP decreased cell numbers, [(3)H]thymidine uptake and mitotic index. Apoptosis was stimulated by 3alphaHP and suppressed by 5alphaP. 5alphaP resulted in increases in Bcl-2/Bax ratio, indicating decreased apoptosis; 3alphaHP resulted in decreases in Bcl-2/Bax ratio, indicating increased apoptosis. The effects of either 3alphaHP or 5alphaP on cell numbers, [(3)H]thymidine uptake, mitosis, apoptosis, and Bcl-2/Bax ratio, were abrogated when cells were treated simultaneously with both hormones. The expression of p21 was increased by 3alphaHP, and was unaffected by 5alphaP. The results provide the first evidence that 5alphaP stimulates mitosis and suppresses apoptosis, whereas 3alphaHP inhibits mitosis and stimulates apoptosis. The opposing effects of 5alphaP and 3alphaHP were observed in all four breast cell lines examined and the data suggest that all breast cancers (estrogen-responsive and unresponsive) might be suppressed by blocking 5alphaP formation and/or increasing 3alphaHP. The findings further support the hypothesis that progesterone metabolites are key regulatory hormones and that changes in their relative concentrations in the breast microenvironment determine whether breast tissues remain normal or become cancerous.