NF-κB and androgen receptor variant 7 induce expression of SRD5A isoforms and confer 5ARI resistance.

BACKGROUND: Benign prostatic hyperplasia (BPH) is treated with 5α-reductase inhibitors (5ARI). These drugs inhibit the conversion of testosterone to dihydrotestosterone resulting in apoptosis and prostate shrinkage. Most patients initially respond to 5ARIs; however, failure is common especially in inflamed prostates, and often results in surgery. This communication examines a link between activation of NF-κB and increased expression of SRD5A2 as a potential mechanism by which patients fail 5ARI therapy. METHODS: Tissue was collected from "Surgical" patients, treated specifically for lower urinary tract symptoms secondary to advanced BPH; and, cancer free transition zone from "Incidental" patients treated for low grade, localized peripheral zone prostate cancer. Clinical, molecular and histopathological profiles were analyzed. Human prostatic stromal and epithelial cell lines were genetically modified to regulate NF-κB activity, androgen receptor (AR) full length (AR-FL), and AR variant 7 (AR-V7) expression. RESULTS: SRD5A2 is upregulated in advanced BPH. SRD5A2 was significantly associated with prostate volume determined by Transrectal Ultrasound (TRUS), and with more severe lower urinary tract symptoms (LUTS) determined by American Urological Association Symptom Score (AUASS). Synthesis of androgens was seen in cells in which NF-κB was activated. AR-FL and AR-V7 expression increased SRD5A2 expression while forced activation of NF-κB increased all three SRD5A isoforms. Knockdown of SRD5A2 in the epithelial cells resulted in significant reduction in proliferation, AR target gene expression, and response to testosterone (T). In tissue recombinants, canonical NF-κB activation in prostatic epithelium elevated all three SRD5A isoforms and resulted in in vivo growth under castrated conditions. CONCLUSION: Increased BPH severity in patients correlates with SRD5A2 expression. We demonstrate that NF-κB and AR-V7 upregulate SRD5A expression providing a mechanism to explain failure of 5ARI therapy in BPH patients. Prostate 76:1004-1018, 2016. © 2016 Wiley Periodicals, Inc.

5α-Reductase Type 2 Regulates Glucocorticoid Action and Metabolic Phenotype in Human Hepatocytes.

Glucocorticoids and androgens have both been implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD); androgen deficiency in males, androgen excess in females, and glucocorticoid excess in both sexes are associated with NAFLD. Glucocorticoid and androgen action are regulated at a prereceptor level by the enzyme 5α-reductase type 2 (SRD5A2), which inactivates glucocorticoids to their dihydrometabolites and converts T to DHT. We have therefore explored the role of androgens and glucocorticoids and their metabolism by SRD5A2 upon lipid homeostasis in human hepatocytes. In both primary human hepatocytes and human hepatoma cell lines, glucocorticoids decreased de novo lipogenesis in a dose-dependent manner. Whereas androgen treatment (T and DHT) increased lipogenesis in cell lines and in primary cultures of human hepatocytes from female donors, it was without effect in primary hepatocyte cultures from men. SRD5A2 overexpression reduced the effects of cortisol to suppress lipogenesis and this effect was lost following transfection with an inactive mutant construct. Conversely, pharmacological inhibition using the 5α-reductase inhibitors finasteride and dutasteride augmented cortisol action. We have demonstrated that manipulation of SRD5A2 activity can regulate lipogenesis in human hepatocytes in vitro. This may have significant clinical implications for those patients prescribed 5α-reductase inhibitors, in particular augmenting the actions of glucocorticoids to modulate hepatic lipid flux.

Hamster SRD5A3 lacks steroid 5α-reductase activity in vitro.

According to current knowledge, two steroid 5α-reductases, designated type 1 (SRD5A1) and type 2 (SRD5A2), are present in all species examined to date. These isozymes play a central role in steroid hormone physiology by catalyzing the reduction of 3-keto-4-ene-steroids into more active 5α-reduced derivatives, including the conversion of testosterone (T) to dihydrotestosterone (DHT). A third 5α-reductase (SRD5A3, -type 3), which is overexpressed in hormone-refractory prostate cancer cells, has been identified; however, its enzymatic characteristics are practically unknown. Here, we isolated a cDNA encoding hamster Srd5a3 (hSrd5a3) and performed functional metabolic assays to investigate its biochemical properties. The cloned cDNA encodes a 330 amino acid protein that is 87% identical to the homologous protein in mice and 78% to that in humans. However, hSrd5a3 exhibits low sequence homology with its counterparts hSrd5a1 (19%) and hSrd5a2 (17%). A fusion protein consisting of hSrd5a3 and green fluorescent protein provided evidence for cytoplasmic localization in transfected mammalian cells. Real-time PCR analysis revealed that, Srd5a3 mRNA was present in nearly all hamster tissues, with high expression in the cerebellum, Harderian gland and testis. Functional assays expressing hSrd5a3 cDNA in HEK-293 cells revealed that this isozyme is unable to reduce T into DHT. Further expression assays confirmed that similar to testosterone, progesterone, androstenedione and corticosterone are not reduced by hSrd5a3 or human SRD5A3. Together, these results indicate that hSrd5a3 lacks the catalytic activity to transform 3-keto-4-ene-compounds; therefore 5α-reductase type 3 may not be involved in 5α-reduction of steroids.

5α-reductase type 1 modulates insulin sensitivity in men.

CONTEXT: 5α-Reductase (5αR) types 1 and 2 catalyze the A-ring reduction of steroids, including androgens and glucocorticoids. 5α-R inhibitors lower dihydrotestosterone in benign prostatic hyperplasia; finasteride inhibits 5αR2, and dutasteride inhibits both 5αR2 and 5αR1. In rodents, loss of 5αR1 promotes fatty liver. OBJECTIVE: Our objective was to test the hypothesis that inhibition of 5αR1 causes metabolic dysfunction in humans. DESIGN, SETTING, AND PARTICIPANTS: This double-blind randomized controlled parallel group study at a clinical research facility included 46 men (20-85 years) studied before and after intervention. INTERVENTION: Oral dutasteride (0.5 mg daily; n = 16), finasteride (5 mg daily; n = 16), or control (tamsulosin; 0.4 mg daily; n = 14) was administered for 3 months. MAIN OUTCOME MEASURE: Glucose disposal was measured during a stepwise hyperinsulinemic-euglycemic clamp. Data are mean (SEM). RESULTS: Dutasteride and finasteride had similar effects on steroid profiles, with reduced urinary androgen and glucocorticoid metabolites and reduced circulating DHT but no change in plasma or salivary cortisol. Dutasteride, but not finasteride, reduced stimulation of glucose disposal by high-dose insulin (dutasteride by -5.7 [3.2] µmol/kg fat-free mass/min, versus finasteride +7.2 [3.0], and tamsulosin +7.0 [2.0]). Dutasteride also reduced suppression of nonesterified fatty acids by insulin and increased body fat (by 1.6% [0.6%]). Glucose production and glycerol turnover were unchanged. Consistent with metabolic effects of dutasteride being mediated in peripheral tissues, mRNA for 5αR1 but not 5αR2 was detected in human adipose tissue. CONCLUSION: Dual inhibition of 5αRs, but not inhibition of 5αR2 alone, modulates insulin sensitivity in human peripheral tissues rather than liver. This may have important implications for patients prescribed dutasteride for prostatic disease.

Neuroactive steroids in pregnancy: key regulatory and protective roles in the foetal brain.

Neuroactive steroid concentrations are remarkably high in the foetal brain during late gestation. These concentrations are maintained by placental progesterone synthesis and the interaction of enzymes in the placenta and foetal brain. 5α-Pregnane-3α-ol-20-one (allopregnanolone) is a key neuroactive steroid during foetal life, although other 3α-hydroxy-pregnanes may make an additional contribution to neuroactive steroid action. Allopregnanolone modulates GABAergic inhibition to maintain a suppressive action on the foetal brain during late gestation. This action suppresses foetal behaviour and maintains the appropriate balance of foetal sleep-like behaviours, which in turn are important to normal neurodevelopment. Neuroactive steroid-induced suppression of excitability has a key role in protecting the foetal brain from acute hypoxia/ischaemia insults. Hypoxia-induced brain injury is markedly increased if neuroactive steroid levels are suppressed and there is increased seizure activity. There is also a rapid increase in allopregnanolone synthesis and hence levels in response to acute stress that acts as an endogenous protective mechanism. Allopregnanolone has a trophic role in regulating development, maintaining normal levels of apoptosis and increasing myelination during late gestation in the brain. In contrast, chronic foetal stressors, including intrauterine growth restriction, do not increase neuroactive steroid levels in the brain and exposure to repeated synthetic corticosteroids reduce neuroactive steroid levels. The reduced availability of neuroactive steroids may contribute to the adverse effects of chronic stressors on the foetal and newborn brain. Preterm birth also deprives the foetus of neuroactive steroid mediated protection and may increase vulnerability to brain injury and suboptimal development. These finding suggest replacement therapies should be explored. This article is part of a Special Issue entitled 'Pregnancy and steroids'.

Progesterone facilitates exploration, affective and social behaviors among wildtype, but not 5α-reductase Type 1 mutant, mice.

Progesterone (P4) facilitates exploration, anxiety and social behaviors in estrogen (E2)-primed mice. Some of these effects may be due to actions of its 5α-reduced metabolite, 5α-pregnan-3α-ol-20-one (3α,5α-THP). In order to address the role of P4 and its metabolite, 3α,5α-THP, a mouse model was utilized. We hypothesized that if P4's metabolism to 3α,5α-THP is essential to facilitate exploratory, anti-anxiety and social behaviors of mice, then wildtype, but not 5α-reductase knockout (5α-RKO), mice will have greater expression of these behaviors. Experiment 1: Mice were ovariectomized (ovx), E2-primed and administered P4 (0, 125, 250, or 500µg) subcutaneously and then tested 4h later in a battery of tasks: open field, elevated plus maze, and social interaction. Experiment 2: Ovx, E2-primed mice were administered P4 (4mg/kg), 3α,5α-THP (4mg/kg), medroxyprogesterone acetate (MPA, which does not convert to 3α,5α-THP; 4mg/kg), or vehicle subcutaneously and tested 4h later. There was a dose-dependent effect of P4 to wildtype, but not 5α-RKO, mice. Neither wildtype, nor 5α-RKO, mice had increased exploration, anti-anxiety or pro-social behavior with MPA administration. Progesterone only exerted effects on anti-anxiety behavior, and increased 3α,5α-THP in the prefrontal cortex and hippocampus, when administered to wildtype mice. 3α,5α-THP to both WT and 5α-RKO mice increased exploration, anti-anxiety and social interaction and 3α,5α-THP levels in the hippocampus and prefrontal cortex. Thus, metabolism of P4 by the 5α-reductase enzyme may be essential for enhancement of these behaviors.

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.

5alphaDH-DOC (5alpha-dihydro-deoxycorticosterone) activates androgen receptor in castration-resistant prostate cancer.

Prostate cancer often relapses during androgen-depletion therapy, even under the castration condition in which circulating androgens are drastically reduced. High expressions of androgen receptor (AR) and genes involved in androgen metabolism indicate a continued role for AR in castration-resistant prostate cancers (CRPCs). There is increasing evidence that some amounts of 5alpha-dihydrotestosterone (DHT) and other androgens are present sufficiently to activate AR within CRPC tissues, and enzymes involved in the androgen and steroid metabolism, such as 5alpha-steroid reductases, are activated in CRPCs. In this report, we screened eight natural 5alphaDH-steroids to search for novel products of 5alpha-steroid reductases, and identified 11-deoxycorticosterone (DOC) as a novel substrate for 5alpha-steroid reductases in CRPCs. 11-Deoxycorticosterone (DOC) and 5alpha-dihydro-deoxycorticosterone (5alphaDH-DOC) could promote prostate cancer cell proliferation through AR activation, and type 1 5alpha-steroid reductase (SRD5A1) could convert from DOC to 5alphaDH-DOC. Sensitive liquid chromatography-tandem mass spectrometric analysis detected 5alphaDH-DOC in some clinical CRPC tissues. These findings implicated that under an extremely low level of DHT, 5alphaDH-DOC and other products of 5alpha-steroid reductases within CRPC tissues might activate the AR pathway for prostate cancer cell proliferation and survival under castration.

Understanding the epidemiology, natural history, and key pathways involved in prostate cancer.

Prostate cancer accounts for about 25% of all the newly diagnosed cancers in American men and was projected to cause >28,000 deaths in 2008. Black men are disproportionately affected; their incidence rate is about 1.6 times greater than the rate for white men. As the population ages, the number of new cases per year is expected to increase by >60% and reach 300,000 by 2015. This high incidence, coupled with the protracted onset of the disease, makes PCa a particularly appropriate candidate for prevention and early intervention strategies. Potential disease precursors, particularly high-grade prostatic intraepithelial neoplasia, might help identify men at high risk of developing PCa. Dihydrotestosterone, a product converted from testosterone by 5alpha-reductases, plays an important role in normal prostate growth and in the development of PCa. The 5alpha-reductase levels, particularly type 1, appear to increase during the disease course of prostatic intraepithelial neoplasia and PCa, with greater expression occurring as the disease progresses. Therefore, the inhibition of 5alpha-reductase could potentially reduce the risk of PCa development, slow or prevent disease progression, and/or treat existing disease. A substantial research effort has recently focused on understanding the pathways involved in the disease's emergence and progression, particularly the 5alpha-reductase pathway.

Long-term inhibition of 5-alpha reductase and aromatase changes the cellular and extracellular compartments in gerbil ventral prostate at different postnatal ages.

As local steroid metabolism controls the bioavailability of active steroidal hormones in the prostate, the aim of this study, was to investigate the effects of absence of 5-alpha reductase (5alpha-r) and aromatase (Aro) enzymes on prostatic cellular and extracellular components after long-term inhibition. Young, adult and old male Mongolian gerbils were treated orally, once a day, for 30 consecutive days, with Finasteride (10.0 mg/kg) and Letrozole (1.0 mg/kg) (5alpha-r and Aro enzymes inhibitors respectively) simultaneously or separately. Animals were killed on 1, 7, 14 and 21 days post-treatment. Data obtained after double or single enzymatic inhibition with Finasteride and Letrozole demonstrated marked remodelling of epithelial and stromal compartments. During the post-treatment period, particularly on the first and the last analysed days, prostatic epithelial cells showed decreased cytoplasmic volume and secretory activity. In the stroma, collagen fibres had accumulated in the epithelial base and among smooth muscle cells, which showed reduced diameter and condensed cytoplasm, and some of them had a highly irregular external contour. Also in the sub-epithelial area, some fibroblasts acquired an activated phenotype besides increased deposits of amorphous granular material. In conclusion, the inhibition of 5alpha-r and Aro enzymes affected, in a persistent manner, the structural and ultrastructural morphology of the prostate, irrespective of the gerbil's age. Hence these enzymes appear to be crucial in the maintenance of this gland during postnatal development. Also, these data bring more light to the complex issue of the mechanisms of local steroid metabolism and prostatic histology. Thus, the blockade of the steroid-metabolizing enzymes provided an important novel tool to study the relationship between sex steroids and normal physiology and diseases of the prostate.

Possible involvement of 5alpha-reduced neurosteroids in adrenergic and serotonergic stimulation of GFAP gene expression in rat C6 glioma cells.

Influence of adrenergic and serotonergic stimulation on glial fibrillary acidic protein (GFAP) gene expression in rat C6 glioma cells was first examined as an in vitro model experiment for investigating the neuronal regulation of glial cell differentiation. Stimulation of these cells with isoproterenol and serotonin elevated GFAP mRNA levels followed by an increase in its protein contents, thus suggesting that both adrenergic and serotonergic stimulation might induce the differentiation of the glioma cells. In addition, progesterone and its 5alpha-reduced metabolite dihydroprogesterone also elevated GFAP mRNA levels in rat C6 glioma cells, consistent with their stimulatory actions on GFAP gene expression observed in rat astrocytes. Further studies showed that the elevation of GFAP mRNA levels induced by isoproterenol and serotonin as well as progesterone was abolished by pretreatment of the glioma cells with finasteride, an inhibitor of 5alpha-reduced steroid production. Moreover, the stimulatory actions of isoproterenol and serotonin on GFAP gene expression were inhibited by pretreatment with a GABA(A) receptor antagonist bicuculline and a progesterone receptor antagonist RU486. These findings suggest that both adrenergic and serotonergic stimulation may indirectly activate GFAP gene expression probably through the production of 5alpha-reduced steroid metabolites in rat C6 glioma cells, proposing the possibility that 5alpha-reduced neurosteroids may play a potential role in the neuronal regulation of glial cell differentiation.

A common polymorphism within the steroid 5-alpha-reductase type 2 gene and timing of menopause in Caucasian women.

OBJECTIVE: Androgens are thought to play an important role in various reproductive functions. We evaluated the association between a common polymorphism of the steroid 5-alpha-reductase type 2 gene (SRD5A2) involved in androgen metabolism and the timing of menopause. STUDY DESIGN: Three hundred and twenty-three consecutive women were included in this cross-sectional study. The common exon 1 Valine/Leucin polymorphism of the SRD5A2 gene was analyzed using a microarray-based system. RESULTS: No significant association between the SRD5A2 polymorphism and age (years) at natural menopause was ascertained. There were no significant differences in the background characteristics of the subjects among SDR5A2 genotypes including the number of full term pregnancies, age at first delivery, BMI, personal or family history of breast cancer, smoking status and personal history of recurrent abortion. A multivariate regression analysis showed that the number of full term pregnancies, but not smoking, an increased body mass index, or a history of breast cancer significantly influenced timing of natural menopause. CONCLUSION: In the present study the number of full term pregnancies, but not the common V89L SRD5A2 polymorphism, is the only significant predictor for the timing of natural menopause in Caucasian women.

Steroid 5alpha-reductase 1 promotes 5alpha-androstane-3alpha,17beta-diol synthesis in immature mouse testes by two pathways.

5alpha-Androstane-3alpha,17beta-diol (androstanediol) is the predominant androgen in immature mouse testes, and studies were designed to investigate its pathway of synthesis, the steroid 5alpha-reductase isoenzyme involved in its formation, and whether testicular androstanediol is formed in embryonic mouse testes at the time of male phenotypic development. In 24-26-day-old immature testes, androstanediol is formed by two pathways; the predominant one involves testosterone --> dihydrotestosterone --> androstanediol, and a second utilizes the pathway progesterone --> 5alpha-dihydroprogesterone --> 5alpha-pregnane-3alpha-ol-20-one --> 5alpha-pregnane-3alpha,17alpha-diol-20-one --> androsterone --> androstanediol. Formation of androstanediol was normal in testes from mice deficient in steroid 5alpha-reductase 2 but absent in testes from mice deficient in steroid 5alpha-reductase 1, indicating that isoenzyme 2 is not expressed in day 24-26 testes. The fact that androstenedione and testosterone were the only androgens identified after incubation of day 16 and 17 embryonic testes with [3H]progesterone implies that androstanediol formation in the testis plays no role in male phenotypic differentiation in the mouse.

[Dihydrotestosterone and the role of 5 alpha-reductase inhibitors in benign prostatic hyperplasia]. / Dihydrotestosteron und die Rolle der 5 alpha-Reduktasehemmer bei der benignen Prostatahyperplasie.

The genesis of benign prostate hyperplasia (BPH) depends on two factors: testicular androgen and the aging process. The most important androgen in the prostate is dihydrotestosterone (DHT). In the aging male the level of DHT in the prostate remains largely constant although the plasma level of testosterone decreases. DHT is formed by the reduction of testosterone by the enzyme 5-alpha-reductase, which has two isoenzymes. The 5-alpha-reductase type 2 is the predominant isoenzyme in genital tissue and thus also in the prostate. Finasteride is a 5-alpha-reductase inhibitor, which is applied in the treatment of BHP and male baldness. In the doses used finasteride acts mainly by inhibiting the 5-alpha-reductase type 2, thereby reducing the serum level of DHT by approximately 70% and by about 85-90% in the prostate. Indeed the effect of finasteride in BPH was proven in clinical studies. However, the circulating and intraprostatic DHT could be further reduced by a more effective dual 5-alpha-reductase inhibitor, which would be efficacious in the treatment of benign prostate hyperplasia and other DHT-related disorders.

5alpha-reductase activity in the prostate.

The prostate gland depends on androgen stimulation for its development and growth. However, testosterone is not the major androgen responsible for growth of the prostate. Testosterone is converted to dihydrotestosterone (DHT) by the enzyme Delta(4), 3 ketosteroid, 5alpha-reductase in prostatic stromal and basal cells. DHT is primarily responsible for prostate development and the pathogenesis of benign prostatic hyperplasia (BPH). Inhibitors of 5alpha-reductase reduce prostate size by 20% to 30%. This reduction in glandular tissue is achieved by the induction of apoptosis, which is histologically manifested by ductal atrophy. Inhibition also diminishes the number of blood vessels in the prostate because of a reduction in vascular-derived endothelial growth factor. 5alpha-Reductase occurs as 2 isozymes, type 1 and type 2, with the prostate expressing predominantly the type-2 isozyme, and the liver and skin expressing primarily the type-1 isozyme. Patients have been identified with deficiencies in the type-2 5alpha-reductase, but not type 1. Knockout mice with the type-2 5alpha-reductase demonstrate a phenotype similar to that seen in men with 5alpha-reductase deficiency. Type-1 5alpha-reductase knockout male mice are phenotypically normal. Enzymatic activity for 5alpha-reductase or immunohistochemical detection has been noted in other genitourinary tissues, such as the epididymis, testes, gubernaculum, and corporal cavernosal tissue. Preputial skin predominately expresses the type-1 5alpha-reductase, whereas stromal cells in the seminal vesicle also express type-2 isozyme. However, epithelial cells in the epididymis, but not surrounding stroma, express type-1 5alpha-reductase. In addition to influencing prostatic growth, 5alpha-reductase also influences the expression of neuronal nitric-oxide synthase in the corpus cavernosum. The contribution of DHT in the serum, which is partially derived from type-1 5alpha-reductase in the liver and the small amount of type-1 5alpha-reductase in the prostate, may play a role in maintaining prostatic enlargement. Thus, in an effort to increase efficacy of treatment for BPH, clinical trials are under way using new drugs, such as GI-198745 (Glaxo-Wellcome, Research Triangle Park, NC), PNU 157706 (Pharmacia & Upjohn, Peapack, NJ), FR146687 (Fujisawa, Osaka, Japan), and LY 320236 (Lilly, Indianapolis, IN), which inhibit both the type-1 and type-2 5alpha-reductase.

Inhibition of 5alpha-reductase enzyme or GABA(A) receptors in the VMH and the VTA attenuates progesterone-induced sexual behavior in rats and hamsters.

Progesterone (P) to the ventromedial hypothalamus (VMH) and the ventral tegmental area (VTA) of ovariectomized (OVX), estradiol benzoate (EB)-primed rats and hamsters produces female sexual behavior similar to that seen in proestrous, receptive rodents. Because P's 5alpha-reduced metabolites can have facilitative effects on female sexual receptivity through actions at GABA(A)/benzodiazepine receptor complexes (GBRs), the role of 5alpha-reductase and GBRs in the VMH and the VTA was investigated. In Experiment 1, 5alpha-reductase immunoreactivity (5alpha-red-IR) and GBR immunoreactivity (GBR-IR) in the VMH and the VTA of OVX, EB (10 microg) and P (500 microg)-primed rats and hamsters was examined. More 5alpha-red-IR and GBR-IR was seen in the VMH and the VTA of receptive (EB and P-primed) compared to non-receptive (sesame oil vehicle) rodents. In Experiment 2, OVX, EB and P-primed rats and hamsters received implants of finasteride, a 5alpha-reductase inhibitor, or no implants to the VMH and the VTA and were tested for sexual receptivity with a male. Ovariectomized EB and P-primed rats and hamsters receiving finasteride to the VMH and the VTA had decreased lordosis compared to rodents receiving control implants to the VMH and the VTA. In Experiment 3, OVX, EB and P-primed rats and hamsters received infusions of picrotoxin, a GBR antagonist, or vehicle infusion to the VMH and the VTA and were tested for sexual receptivity with a male. Ovariectomized EB and P-primed rats and hamsters receiving picrotoxin to the VMH and the VTA had decreased lordosis compared to rodents receiving vehicle infusions to the VMH and the VTA. These data suggest that 5alpha-reductase and GBRs are present in the VMH and VTA, and that inhibiting 5alpha-reductase activity or blocking GBRs in the VMH and the VTA attenuates EB+P-primed sexual receptivity of OVX rats and hamsters.

GEN GEN: the genomic genetic analysis of androgen-metabolic genes and prostate cancer as a paradigm for the dissection of complex phenotypes.

Prostate cancer will be diagnosed in about 179,300 men in the US in 1999 alone. Some 37,000 individuals die of this disease annually. Prostate cancer is characterized by a substantial racial/ethnic variation in risk: highest in African-American men, lowest in Asian men and intermediate in Caucasian and Latino men. We set out to investigate as our central hypothesis that genetic variants of genes involved in androgen metabolism by themselves and in combination significantly contribute to prostate cancer progression and its racial/ethnic variation. Specifically, we examined the hypothesis that DNA sequence (allelic) variations in the type II (or prostatic) steroid 5alpha-reductase (SRD5A2) gene contribute substantially to the risk and progression of prostate cancer particularly across racial/ethnic lines. The "candidate gene", SRD5A2, was chosen because the reaction product [i.e. dihydrotestosterone (DHT)] of the enzyme encoded by this gene modulates directly cell division in the prostate. DHT binds to the androgen receptor (AR) and the DHT-AR complex leads to the transactivation of a variety of genes which ultimately modulates cell division in the prostate. Epidemiologic evidence suggests that variation in DHT levels play an important role in risk of prostate cancer. Thus, steroid 5alpha-reductase activity encoded by SRD5A2 variant alleles may be important in regulating intraprostatic DHT steady state levels by controlling its biosynthesis. A second candidate gene, the type II 3beta-hydroxysteroid dehydrogenase (HSD3B2) gene, encodes the enzyme that initiates the metabolic inactivation of testosterone (T) to DHT. We have identified allelic variants in this gene as well. Here I review our strategy for identifying candidate genes for prostate cancer, a multifactorial disease. I summarize the significant findings, particularly of allelic variants in the HSD3B2 and SRD5A2 genes and discuss how they by themselves, in combination and through interactions with the environment may play a role in prostate cancer predisposition and its progression. Our approach, a multidisciplinary genomic genetic (GEN GEN) attack on the problem, may be useful in the analysis of other complex phenotypes as well.

What knockout mice can tell us about parturition.

Many molecules, including steroid and peptide hormones, prostaglandins and cytokines, regulate the preparation, initiation and progression of parturition in mammals. Gene targeting studies show that, in the knockout mice of steroid 5alpha-reductase type 1 gene, prostaglandin F2alpha receptor gene and cytosolic phospholipase A2 gene, parturition was severely disturbed, although live offspring were delivered by Caesarean section. Relaxin gene-disrupted mice also showed protracted labour. However, most knockout mice in which the steroid hormone, prostaglandin, cytokine or peptide hormone (for example, oxytocin, corticotrophin releasing hormone and endothelin) endocrine-paracrine systems are disrupted are inadequate for analysis of the mechanism of parturition because they die before reaching reproductive age or are infertile, or because they reproduce normally. A conditional knockout strategy, for example, using the Cre-LoxP system, should be considered for investigating the biochemical background of parturition to overcome these problems.

Association of benign prostatic hyperplasia with male pattern baldness.

OBJECTIVES: Both benign prostatic hyperplasia (BPH) and male pattern baldness (androgenic alopecia) share the pathogenesis of an androgen-dependent disorder and afflict a large population of elderly men with chronobiologic progress. However, it is unclear whether these diseases are related epidemiologically. We evaluated the association of frequency and severity of male pattern baldness between patients with BPH and a control group. METHODS: A total of 225 patients with BPH (mean age 69.3 +/- 6.5 years) and 1 60 controls (mean age 68.5 +/- 6.4 years), all over 60 years of age, were included in this study. The estimation of baldness severity was based on Norwood's classification (grade I to VII). The International Prostate Symptom Score (IPSS) and genetic tendency for baldness were also evaluated. The difference between IPSS and grade of baldness between the two groups was analyzed by the Mann-Whitney test and the frequency of inherited baldness was compared by the chi-square test. Correlation between severity of baldness and IPSS in each group was estimated by Spearman's rank correlation method. RESULTS: The patients with BPH had an apparently higher grade of male pattern baldness in comparison with that of controls (median value of grade IV versus III, P <0.001). The proportion of men with male pattern baldness of grade IV or higher in the BPH group was significantly larger than that of controls (53.8% versus 36.9%, P <0.01). There was a greater frequency of inherited baldness in the BPH group than in the controls (31.6% versus 12.5%, P <0.001). No significant correlation was noted between baldness severity and IPSS in either group. CONCLUSIONS: This study demonstrates a strong association of BPH with male pattern baldness.