A mutation that causes lability of the androgen receptor under conditions that normally promote transformation to the DNA-binding state

Inhibitory Activities of Dimeric Ellagitannins Isolated from Cornus alba on Benign Prostatic Hypertrophy

Benign prostatic hypertrophy (BPH) is an intractable chronic inflammatory disease. We studied the efficacy of two ellagitannins, namely camptothin B (1) and cornusiin A (2) that were isolated from Cornus alba (CA) for the treatment of BPH, which is a common health issue in older men. The ellagitannins (1 and 2) were evaluated on its inhibitory activities of the enzyme 5α-reductase and tumor necrosis factor (TNF)-α, its interleukin (IL)-1β, IL-6, and IL-8 production, and its anti-proliferation and apoptosis induction in prostate cells that show hypertrophy (RWPE-1 cell). In inhibition of 5α-reductase, the ellagitannins (1 and 2) showed potential effects, compared to the positive control, finasteride. In the case of IL-1β, IL-6, IL-8, and TNF-α, 1 and 2 showed good inhibitory effects as compared to the control group treated with LPS. The ellagitannins (1 and 2) were also shown to inhibit proliferation of, and induce apoptosis in, the RWPE-1 cell. These results suggest that the ellagitannins (1 and 2) may be good candidates for the treatment of BPH.

The Chalice Sign : Characteristic Morphology of the Cervical Carotid Bifurcation in Patients with Loeys-Dietz Syndrome

BACKGROUND AND PURPOSE

Loeys-Dietz syndrome (LDS) is a connective tissue disorder characterized by arterial aneurysms and dissections. This study sought to assess and describe the arterial changes of the cervical arterial vasculature of such patients, with an emphasis on the carotid bifurcation.

MATERIAL AND METHODS

A retrospective review of patients with a known diagnosis of LDS was carried out. The maximum diameters of the external carotid artery (ECA) and internal carotid artery (ICA) origins, common carotid artery (CCA) terminus, maximum transverse and craniocaudal dimensions of the carotid bulb, and bifurcation angle were measured. The presence of a chalice sign was defined as a carotid bifurcation angle of ≥80°. A semi-quantified analysis of vertebral artery tortuosity was completed as well. All measurements were compared to a cohort of age-matched controls.

RESULTS

A total of 21 patients with LDS were included. Compared to normal controls, the presence of a chalice sign had 61.9% sensitivity and 100.0% specificity for LDS if present bilaterally; the sensitivity and specificity of a unilateral chalice sign were 66.7% and 82.3%, respectively. Patients with LDS also had significantly higher rates of a bilateral chalice sign compared to patients with vascular Ehlers-Danlos syndrome (vEDS) (61.9% versus 0%, P <0.0001) and patients with Marfan syndrome (61.9% versus 14.3%, P = 0.001).

CONCLUSION

Patients with LDS have characteristic findings of the cervical arterial vasculature that enables them to be distinguished from normal controls as well as patients with connective tissue diseases, such as Marfan syndrome and vEDS; most notably including marked widening of the carotid bifurcation angle in what is proposed to be named the chalice sign.

Steroid 5α-reductase 2 deficiency leads to reduced dominance-related and impulse-control behaviors

The enzyme steroid 5α-reductase 2 (5αR2) catalyzes the conversion of testosterone into the potent androgen 5α-dihydrotestosterone. Previous investigations showed that 5αR2 is expressed in key brain areas for emotional and socio-affective reactivity, yet the role of this enzyme in behavioral regulation remains mostly unknown. Here, we profiled the behavioral characteristics of 5αR2 heterozygous (HZ) and knockout (KO) mice, as compared with their wild-type (WT) littermates. While male 5αR2 KO mice displayed no overt alterations in motoric, sensory, information-processing and anxiety-related behaviors, they exhibited deficits in neurobehavioral correlates of dominance (including aggression against intruders, mating, and tube dominance) as well as novelty-seeking and risk-taking responses. Furthermore, male 5αR2 KO mice exhibited reduced D₂-like dopamine receptor binding in the shell of the nucleus accumbens - a well-recognized molecular signature of social dominance. Collectively, these results suggest that 5αR2 is involved in the establishment of social dominance and its behavioral manifestations. Further studies are warranted to understand how the metabolic actions of 5αR2 on steroid profile may be implicated in social ranking, impulse control, and the modulation of dopamine receptor expression in the nucleus accumbens.

Dihydrotestosterone: Biochemistry, Physiology, and Clinical Implications of Elevated Blood Levels

Benefits associated with lowered serum DHT levels after 5α-reductase inhibitor (5AR-I) therapy in men have contributed to a misconception that circulating DHT levels are an important stimulus for androgenic action in target tissues (e.g., prostate). Yet evidence from clinical studies indicates that intracellular concentrations of androgens (particularly in androgen-sensitive tissues) are essentially independent of circulating levels. To assess the clinical significance of modest elevations in serum DHT and the DHT/testosterone (T) ratio observed in response to common T replacement therapy, a comprehensive review of the published literature was performed to identify relevant data. Although the primary focus of this review is about DHT in men, we also provide a brief overview of DHT in women. The available published data are limited by the lack of large, well-controlled studies of long duration that are sufficiently powered to expose subtle safety signals. Nonetheless, the preponderance of available clinical data indicates that modest elevations in circulating levels of DHT in response to androgen therapy should not be of concern in clinical practice. Elevated DHT has not been associated with increased risk of prostate disease (e.g., cancer or benign hyperplasia) nor does it appear to have any systemic effects on cardiovascular disease safety parameters (including increased risk of polycythemia) beyond those commonly observed with available T preparations. Well-controlled, long-term studies of transdermal DHT preparations have failed to identify safety signals unique to markedly elevated circulating DHT concentrations or signals materially different from T.

Current status of 5α-reductase inhibitors in prostate disease management

The key enzyme in the androgen synthesis and androgen receptor pathways is 5α-reductase (5-AR), which occurs as three isoenzymes. Types I and II 5-ARs the most important clinically, and two different 5-AR inhibitors (5-ARIs), finasteride and dutasteride, have been developed. Several urology associations have recommended and upgraded the use of 5-ARIs for an enlarged prostate with lower urinary tract symptoms. In the Prostate Cancer Prevention Trial and the Reduction by Dutasteride of Prostate Cancer Events Trial, 5-ARIs reduced the incidence of low-grade prostate cancer. However, despite the documented reductions in the overall incidence of prostate cancer, 5-ARIs are at the center of a dispute. The American Society of Clinical Oncology (ASCO) and the American Urology Association (AUA) presented clinical guidelines for the use of 5-ARIs for chemoprevention of prostate cancer in 2008. However, ASCO/AUA has eliminated these from the main "Clinical Guidelines" in 2012, because the U.S. Food and Drug Administration denied a supplemental New Drug Application for the use of dutasteride for prostate cancer chemoprevention. The 5-ARIs can also be used to manage hemospermia and prostatic hematuria, and to prevent intraoperative bleeding, although there is insufficient evidence for a standard strategy. This review summarizes the current use of 5-ARIs for prostate disease, including benign prostate hyperplasia, prostate cancer, prostate-related bleeding, and hemospermia.

Reduced bone mass and muscle strength in male 5α-reductase type 1 inactivated mice

Androgens are important regulators of bone mass but the relative importance of testosterone (T) versus dihydrotestosterone (DHT) for the activation of the androgen receptor (AR) in bone is unknown. 5α-reductase is responsible for the irreversible conversion of T to the more potent AR activator DHT. There are two well established isoenzymes of 5α-reductase (type 1 and type 2), encoded by separate genes (Srd5a1 and Srd5a2). 5α-reductase type 2 is predominantly expressed in male reproductive tissues whereas 5α-reductase type 1 is highly expressed in liver and moderately expressed in several other tissues including bone. The aim of the present study was to investigate the role of 5α-reductase type 1 for bone mass using Srd5a1^−/− mice. Four-month-old male Srd5a1^−/− mice had reduced trabecular bone mineral density (−36%, p<0.05) and cortical bone mineral content (−15%, p<0.05) but unchanged serum androgen levels compared with wild type (WT) mice. The cortical bone dimensions were reduced in the male Srd5a1^−/− mice as a result of a reduced cortical periosteal circumference compared with WT mice. T treatment increased the cortical periosteal circumference (p<0.05) in orchidectomized WT mice but not in orchidectomized Srd5a1^−/− mice. Male Srd5a1^−/− mice demonstrated a reduced forelimb muscle grip strength compared with WT mice (p<0.05). Female Srd5a1^−/− mice had slightly increased cortical bone mass associated with elevated circulating levels of androgens. In conclusion, 5α-reductase type 1 inactivated male mice have reduced bone mass and forelimb muscle grip strength and we propose that these effects are due to lack of 5α-reductase type 1 expression in bone and muscle. In contrast, the increased cortical bone mass in female Srd5a1^−/− mice, is an indirect effect mediated by elevated circulating androgen levels.

Fetal hormones and sexual differentiation

The process of fetal sexual differentiation, which involves establishment of genetic sex, differentiation of the gonads, and development of phenotypic sex, is summarized. The morphologic changes that occur in utero that lead to development of the male and female gonads, germ cells, reproductive tracts, and external genitalia are described. Most of the article focuses on the hormones that regulate sexual differentiation and development in utero. The genetic factors that regulate sexual differentiation, which constitute a new and emerging field, also are discussed.

5α-Reductase Isozymes in the Prostate

5α-reductases convert testosterone to dihydrotestosterone (DHT). There are two 5α-reductase isozymes, type 1 and type 2 in humans and animals. Mutations in type 2 isozyme with decreased enzymatic activity cause male pseudohermaphroditism. The affected 46XY individuals have high normal or elevated plasma testosterone levels with low normal or decreased DHT levels, resulting in an elevated testosterone/DHT ratios. They are born with ambiguous external genitalia and normal Wolffian differentiation. Their prostate is small and rudimentary, and plasma levels of prostate specific antigen (PSA) are low or undetectable in adulthood. Prostate cancer and benign prostate hyperplasia (BPH) have never been reported in these patients. Similar defects in prostate development are observed in animals with either 5α-reductase-2 or 5α-reductase-2 plus 5α-reductase-1 gene knockout, and in animals treated with specific 5α-reductase inhibitor. 5α-reductase isozymes are expressed in multiple tissues, and the predominant isozyme in human prostate is 5α-reductase-2. The expression of 5α-reductase-2 gene in prostate cells is regulated by various factors. A high dietary fat intake, a risk factor of prostate cancer, induces prostate 5α-reductase-2 gene expression and subsequently stimulates prostate growth, which is blocked by genistein, a phytoestrogen. Inhibition of 5α-reductase activity by medication is used in the treatment of BPH and male-pattern baldness, while its use in prostate cancer prevention is still controversial although it can decrease the incidence of prostate cancer. The analyses of 5α-reductases in humans and animals highlight the differences between testosterone and DHT, and the significance of DHT in male sexual differentiation and prostate physiology and pathophysiology.

Androgens and male physiology the syndrome of 5alpha-reductase-2 deficiency

Dihydrotestosterone (DHT), a potent androgen, is converted from testosterone by 5alpha-reductase isozymes. There are two 5alpha-reductase isozymes, type 1 and type 2 in humans and animals. These two isozymes have differential biochemical and molecular features. Mutations in type 2 isozyme cause male pseudohermaphroditism, and many mutations have been reported from various ethnic groups. The affected 46XY individuals have high normal to elevated plasma testosterone levels with decreased DHT levels and elevated testosterone/DHT ratios. They have ambiguous external genitalia at birth so that they are believed to be girls and are often raised as such. However, Wolffian differentiation occurs normally and they have epididymides, vas deferens and seminal vesicles. Virilization occurs at puberty frequently with a gender role change. The prostate in adulthood is small and rudimentary, and facial and body hair is absent or decreased. Balding has not been reported. Spermatogenesis is normal if the testes are descended. The clinical, biochemical and molecular genetic analyses of 5alpha-reductase-2 deficiency highlight the significance of DHT in male sexual differentiation and male pathophysiology.

Discovery of potent, nonsteroidal, and highly selective glucocorticoid receptor antagonists

An approach to the computer-assisted, pharmacophore design of nonsteroidal templates for the glucocorticoid receptor (GR) that contained an element of pseudo-C2 symmetry was developed. The enatiomer of the initial design, 1Ra, and not the designed molecule, 1S, showed the desired ligand binding to the GR. The pseudo-C2 symmetry of the template allowed for rapid improvements in GR activity resulting in potent, selective, nonsteroidal GR antagonists, CP-394531 and CP-409069.

Unexpected virilization in male mice lacking steroid 5 alpha-reductase enzymes

Mice lacking steroid 5 alpha-reductase 1 and 2 were produced by gene targeting and breeding. Male mice without 5 alpha-reductase 2 or without both enzymes had fully formed internal and external genitalia and were fertile, but had smaller prostates and seminal vesicles than controls. T accumulated to high levels in the reproductive tissues of the mutant mice. DHT administration increased seminal vesicle and coagulating gland weights in mice deficient in 5 alpha-reductase 2 and increased the weights of the prostate, seminal vesicle, and coagulating gland in animals deficient in both enzymes. An inhibitor of both 5 alpha-reductases (GI 208335X) decreased prostate and coagulating gland weights of control mice, but had no effect in those lacking 5 alpha-reductase 1 and 2. Castration reduced the sizes of these tissues in animals of all genotypes. Androgen-dependent gene expression was decreased in the seminal vesicles of mice lacking one or more 5 alpha-reductases and was restored by administration of T or DHT. Female mice missing both enzymes exhibited parturition and fecundity defects similar to those of animals without 5 alpha-reductase 1. We conclude that T is the only androgen required for differentiation of the male urogenital tract in mice and that the synthesis of DHT serves largely as a signal amplification mechanism.

Androgen-activating enzymes in the central nervous system

In the rat brain, several steroids can be converted by specific enzymes to either more potent compounds or to derivatives showing new biological effects. One of the most studied enzyme is the 5alpha-reductase (5alpha-R), which acts on 3keto-delta4 steroids. In males, testosterone is the main substrate and gives rise to the most potent natural androgen dihydrotestosterone. In females, progesterone is reduced to dihydroprogesterone, a precursor of allopregnanolone, a natural anxiolytic/anesthetic steroid. Other substrates are some gluco- and minero-corticoids. Two isoforms of the 5alpha-R, with limited degree of homology, have been cloned: 5alpha-R type 1 and type 2. The 5alpha-R type 1 possesses low affinity for the various substrates and is widely distributed in the body, with the highest levels in the liver; in the brain, this isoform is expressed throughout life and does not appear to be controlled by androgens. 5Alpha-R type 1 in the rat brain is mainly concentrated in myelin membranes, where it might be involved in the catabolism of potentially neurotoxic steroids. The 5alpha-R type 2 shows high affinity for the various substrates, a peculiar pH optimum at acidic values and is localized in androgen-dependent structures. In the rat brain, the type 2 isoform is expressed at high levels only in the perinatal period and is controlled by androgens, at least in males. In adulthood, the type 2 gene appears to be specifically expressed in localised brain regions, like the hypothalamus and the hippocampus. The 5alpha-R type 2 is present in the GT1 cells, a model of LHRH-secreting neurons. These cells also contain the androgen receptor, which is probably involved in the central negative feedback effect exerted by androgens on the hypothalamic-pituitary-gonadal axis. The physiological significance of these and additional data will be discussed.

5 alpha-reductase isozymes in the central nervous system

The enzyme 5 alpha-reductase (5 alpha-R) activates several delta 4-3keto steroids to more potent derivatives which may also acquire new biological actions. Testosterone gives rise to the most potent natural androgen dihydrotestosterone (DHT), and progesterone to dihydroprogesterone (DHP), a precursor of the endogenous anxiolytic/anesthetic steroid tetrahydroprogesterone (THP). Two isoforms of 5 alpha-R, with a limited degree of homology, different biochemical properties and distinct tissue distribution have been cloned: 5 alpha-R type 1 and type 2. In androgen-dependent structures DHT is almost exclusively formed by 5 alpha-R type 2; 5 alpha-R type 1 is widely distributed in the body, with the highest levels in the liver, and may be involved in steroid catabolism. In the brain, the roles of the two isozymes are still largely unknown. This brief review will summarize recent experimental data from our laboratory which try to assign possible functional roles to the process of 5 alpha-reduction, and to the two 5 alpha-R isoforms in the CNS.

Insulin-like growth factor-I and -II in human benign prostatic hyperplasia: relationship with binding proteins 2 and 3 and androgens

In prostatic tissue, androgen action may be mediated by growth factors such as insulin-like growth factor-I (IGF-I) and II (IGF-II), which are mitogenic for prostatic cells and modulate the stroma-epithelium interaction. IGF-binding proteins (IGFBPs) have an autocrine and/or paracrine role in regulating the local actions of the IGFs. In this study, testosterone, dihydrotestosterone (DHT), 3 alpha androstanediol (3 alpha diol), IGF-I, IGF-II, IGFBP2, and IGFBP3 concentrations were evaluated in human benign prostatic hyperplasia (BPH) tissue. Samples of prostate tissue were removed by suprapubic prostatectomy from twelve BPH patients. Androgen tissue levels were determined by radioimmunoassay after purification on celite microcolumns. IGF-I, IGFBP2, and IGFBP3 were measured by radioimmunoassay, and IGF-II by immunoradio metric assay, after acidification and chromatography on Sep-pak C18 Cartridges for IGF-I and IGF-II. Androgen concentrations, expressed in ng/g tissue (mean +/- SE), were 0.51 +/- 0.05 for testosterone, 5.3 +/- 0.16 for DHT, and 1.1 +/- 0.07 for 3 alpha diol. IGF-I, IGF-II, IGFBP2, and IGFBP3 levels were 24 +/- 3.7, 121 +/- 14 ng/g tissue and 0.44 +/- 0.05 and 1.2 +/- 0.17 micrograms/g tissue, respectively. No correlation between IGF-I, androgens, and IGFBPs was found. IGF-II was positively correlated with DHT (r = 0.78; p = 0.003) and 3 alpha diol (r = 0.66; p = 0.021) but not with IGFBPs. These data suggest that in BPH, DHT modulates the IGF system by increasing IGF-II without modifying IGFBPs. Therefore, the stroma-epithelium interaction, which plays an important role in prostatic growth, may be regulated by DHT through IGF-II.

Natural potent androgens: lessons from human genetic models

Male pseudohermaphroditism due to 17 beta-hydroxysteroid dehydrogenase-3 (17 beta-HSD-3) deficiency and 5 alpha-reductase-2 (5 alpha-RD-2) deficiency provides natural human genetic models to elucidate androgen actions. To date, five 17 beta-HSD isozymes have been cloned that catalyse the oxidoreduction of androstenedione and testosterone and dihydrotestosterone (DHT), oestrone and oestradiol. Mutations in the isozyme 17 beta-HSD-3 gene are responsible for male pseudohermaphroditism due to 17 beta-HSD deficiency. The type 3 isozyme preferentially catalyses the reduction of androstenedione to testosterone and is primarily expressed in the testes. Fourteen mutations in the 17 beta-HSD-3 gene have been identified from different ethnic groups. Affected males with the 17 beta-HSD-3 gene defect have normal wolffian structures but ambiguous external genitalia at birth. Many are raised as girls but virilize at the time of puberty and adopt a male gender role. Some develop gynaecomastia at puberty, which appears to be related to the testosterone/oestradiol ratio. Two 5 alpha-reductase (5 alpha-RD) isozymes, types 1 and 2, have been identified, which convert testosterone to the more potent androgen DHT. Mutations in the 5 alpha-RD-2 gene cause male pseudohermaphroditism, and 31 mutations in the 5 alpha-RD-2 gene have been reported from various ethnic groups. Such individuals also have normal wolffian structure but ambiguous external genitalia at birth and are raised as girls. Virilization occurs at puberty, often with a gender role change. The prostate remains infantile and facial hair is decreased. Balding has not been reported.

Evidence of heterogeneity and quantitative differences of the type 1 5alpha-reductase expression in cultured human skin cells--evidence of its presence in melanocytes

Steroid 5alpha-reductase is of crucial importance in androgen physiology because it catalyzes the conversion of testosterone into the more potent 5alpha-dihydrotestosterone in androgen-regulated target tissues. The enzyme occurs in two isoforms, whereby type 1 isozyme exists mainly in the skin and type 2 in the prostate. By using human cell cultures, we examined cutaneous expression and subcellular localization of type 1 5alpha-reductase in vitro. In immunocytochemistry, type 1 5alpha-reductase was detected in the cytoplasm of cultured human sebocytes, keratinocytes, fibroblasts, dermal microvascular endothelial cells, hair dermal papilla cells, and melanocytes. In western blot studies, two closely lying bands of 21-27 kDa were detected, possibly indicating heterogeneity of the type 1 5alpha-reductase in all the cell types tested, with the exception of beard dermal papilla cells. Northern blot studies revealed most abundant type 1 mRNA in neonatal foreskin keratinocytes, followed by adult facial sebocytes. Occipital hair dermal papilla cells presented higher levels of type 1 5alpha-reductase mRNA than those of beard. These findings were confirmed by semiquantitative reverse transcriptase polymerase chain reaction coupled with high performance liquid chromatography analysis. Taken together, it seems likely that in cultured human skin cells there exist (i) heterogeneity of type 1 5alpha-reductase protein and (ii) quantitative differences in its transcriptional and translational expression levels.

The potential for hormonal prevention trials

Breast and prostate cancer are significant causes of morbidity and mortality and are very similar in etiology, epidemiology, and modalities of treatment. Investigational strategies in the prevention of these malignancies also have strong parallels. The National Cancer Institute is sponsoring several large scale clinical trials involving hormonal manipulation and cancer prevention. In the Breast Cancer Prevention Trial, 16,000 women at high risk for breast cancer are being randomized to receive the antiestrogen agent tamoxifen or placebo for 5 years in an effort to determine if breast cancer development can be inhibited. In a similar trial, the Prostate Cancer Prevention Trial, 18,000 men older than 55 years of age will be randomized to receive finasteride, a 5-alpha-reductase inhibitor, or placebo to determine if inhibition of dihydrotestosterone synthesis in the prostate over a prolonged period will lead to a decreased incidence of prostate cancer. Both clinical trials offer the possibility of demonstrating that a hormonal intervention can decrease an individual's risk of developing breast or prostate cancer. They also have the potential of providing critical information about cancer risk, etiology, screening, and genetics, as well as quantifying the risks and benefits of specific preventive interventions.

Role of 5 alpha-reductase in health and disease

The mechanism of androgen action varies in different tissues, but in the majority of androgen target tissues either testosterone or 5 alpha-dihydrotestosterone (DHT) binds to a specific androgen receptor to form a complex that can regulate gene expression. Testosterone is metabolized to DHT by the enzyme 5 alpha-reductase. The autosomal recessive genetic disorder of 5 alpha-reductase deficiency has clearly shown that the requirement for DHT formation varies with different tissues. In this syndrome genetic males contain normal male internal structures including testes, but exhibit ambiguous or female external genitalia at birth; at puberty they undergo partial virilization which includes development of a male gender identity even if brought up as females. Their development suggests that testosterone itself is able to stimulate psychosexual behaviour, development of the embryonic wolffian duct, muscle development, voice deepening, spermatogenesis, and axillary and pubic hair growth; DHT seems to be essential for prostate development and growth, the development of the external genitalia and male patterns of facial and body hair growth or male-pattern baldness. How different hormones operate to regulate genes via the same receptor is currently unknown, but appears to involve cell-specific factors. The 5-alpha-reductase enzyme has proved difficult to isolate biochemically, but recently at least two human isoenzymes have been identified using molecular biological methods. All the various 5 alpha-reductase-deficient kindreds have been shown to have mutations in 5 alpha-reductase 2, the predominant form in the prostate. The biological role of 5 alpha-reductase 1 has not yet been ascertained, but at present it cannot be ruled out that some of the actions ascribed to testosterone are indeed in cells producing DHT via this enzyme. The activity of 5 alpha-reductase is also implicated in benign prostatic hypertrophy, hirsutism and possibly male-pattern baldness; recent evidence discounts the role of 5 alpha reductase 2 in sebaceous glands and acne. Specific inhibitors of both enzymes are now available and finasteride, a 5 alpha-reductase 2 inhibitor, has been used successfully in clinical trials of benign prostatic hypertrophy. Knowledge of 5 alpha-reductase is expanding dramatically at the moment with the application of molecular biological methods. The advent of antibodies to the isoenzymes should herald further understanding of their biological and clinical roles.

Local implants of testosterone metabolites regulate vasopressin mRNA in sexually dimorphic nuclei of the rat brain

Biosynthesis of the neuropeptide vasopressin (VP) in extrahypothalamic neurons is dependent on circulating levels of testosterone (T). However, the mechanism by which endogenous or peripherally administered T induces VP gene expression in the brain has not been established. This study investigated the effects of androgens and estrogen in the steroid-dependent expression of VP mRNA in the bed nucleus of the stria terminalis (BNST). Testosterone, estrogen, and the T metabolite, dihydrotestosterone (DHT), were either peripherally administered or locally implanted in cannula into the BNST of castrated male rats to determine whether these steroids influence VP gene expression through a local effect within the nucleus itself. The results indicate that T does act locally within the BNST, since complete restoration of VP mRNA levels occurred in BNST neurons in the vicinity of T-containing cannulas but not on the contralateral side. In addition, both DHT and estrogen were partially effective in stimulating VP gene expression in the BNST, and in combination, synergized to produce the full complement of VP gene expression induced by T itself.

The androgen resistance syndromes: clinical and biochemical aspects

The genetic, biochemical, clinical and endocrinological features of syndromes associated with androgen resistance (insensitivity) are described. The clinical appearance of these syndromes covers the whole spectrum of phenotypically female patients to normal appearing men with infertility. In these disorders testosterone formation and regression of the Müllerian duct derivates are normal, but male development is absent or impaired as a result of total or partial resistance to androgen action in the target cell. Based on studies with cultured genital skin fibroblasts three defects on the level of the androgen target organ can be differentiated in these syndromes: 1. Defective testosterone metabolism, 2. anomalies of the androgen receptor and 3. a postreceptor defect.

Mutations in the ligand-binding domain of the androgen receptor gene cluster in two regions of the gene

We have analyzed the nucleotide sequence of the androgen receptor from 22 unrelated subjects with substitution mutations of the hormone-binding domain. Eleven had the phenotype of complete testicular feminization, four had incomplete testicular feminization, and seven had Reifenstein syndrome. The underlying functional defect in cultured skin fibroblasts included individuals with absent, qualitative, or quantitative defects in ligand binding. 19 of the 21 substitution mutations (90%) cluster in two regions that account for approximately 35% of the hormone-binding domain, namely, between amino acids 726 and 772 and between amino acids 826 and 864. The fact that one of these regions is homologous to a region of the human thyroid hormone receptor (hTR-beta) which is a known cluster site for mutations that cause thyroid hormone resistance implies that this localization of mutations is not a coincidence. These regions of the androgen receptor may be of particular importance for the formation and function of the hormone-receptor complex.

The state transitions of normal and mutant androgen-receptor complexes in human genital skin fibroblasts

We have incubated cells from controls and subjects with receptor-defective androgen resistance with 3H-labelled testosterone (T), methyltrienolone (MT), dihydrotestosterone (DHT) or mibolerone (MB) and studied the temperature dependence of the dissociation rate constants of these various androgen-receptor (A-R) complexes both within cells and after they were extracted from them. In control cells, Arrhenius plots for T-, MT-, DHT- and MB-R complexes were linear and formed a hierarchy of dissociation states with energies of state IV greater than III greater than II, greater than I, respectively. Relative to this hierarchy, the dissociation states of the MB-, DHT- and MT-R complexes in mutant cells were displaced to higher, androgen-inappropriate energies in a mutant-distinctive pattern. When extracted from cells control or mutant T- or MT-R complexes, and mutant (but not control) DHT- or MB-R complexes lowered their respective dissociation rates by undergoing state transitions in conformity with the hierarchy. Hence we propose that different A-R complexes reach different dissociative states by undergoing sequential transitions along a common pathway, and that these transitions are co-regulated both by the chemical characteristics of the bound androgen and by other cellular non-receptor factors.

Androgen resistance due to decreased amounts of androgen receptor: a reinvestigation

To provide insight into the pathogenesis of the androgen resistance in a previously described family with X-linked Reifenstein syndrome, we have systematically assessed a variety of parameters of androgen receptor function in fibroblasts cultured from scrotal skin biopsies. We assessed the amount of high affinity binding, the affinity of ligand binding to the receptor, the upregulation of androgen receptor levels by androgen, the stability of ligand binding in intact fibroblasts at high temperature, the dissociation of ligand from the receptor, the intranuclear localization and salt elution profiles of ligand-receptor complexes, and the ultracentrifugation characteristics of the ligand-receptor complexes. Since the only parameter found to be abnormal is a decreased amount of receptor, we conclude that the underlying mutation in this family influences the amount rather than the structure of the androgen receptor protein.

Inhibitors of steroid 5 alpha-reductase in benign prostatic hyperplasia, male pattern baldness and acne

Benign prostatic hyperplasia is an androgen-dependent disease which afflicts a large percentage of males over the age of fifty, and is usually treated by surgery. Dihydrotestosterone, a 5 alpha-reduced metabolite of testosterone, has been implicated as a causative factor in the progression of the disease, largely through the clinical study of males who are genetically deficient in the dihydrotestosterone-producing enzyme, steroid 5 alpha-reductase. As a result, inhibition of this enzyme has become a pharmacological strategy for the treatment of benign prostatic hyperplasia as well as other dihydrotestosterone-related disorders such as acne and male pattern baldness. In this review, Brian Metcalf and colleagues focus on the chemical and kinetic mechanisms of steroid 5 alpha-reductase, and known inhibitors of this enzyme, and discuss the rationale behind the design of a mechanistically distinct class of steroid 5 alpha-reductase inhibitors.

Partial purification and characterisation of the human skin fibroblast androgen receptor: detection of abnormal receptor complexes in cells from patients with androgen insensitivity syndromes

After incubation of hGSF with [3H]5 alpha-dihydrotestosterone, 17 beta-hydroxy-7 alpha, 17 alpha-dimethyl-4-estrene-3-one, or 17 beta-hydroxy-17 alpha-methyl-4,9,11-estrien-3-one, androgen-receptor complexes were extracted with 0.5 M KCl and precipitated by 35% ammonium sulphate. Receptor complexes from control hGSF sedimented at approximately 4S on linear 5-20% sucrose gradients. The 4S peak was diminished or absent in cells from androgen insensitive patients exhibiting absent, deficient or unstable binding of androgens in intact hGSF. This procedure may be a useful means of distinguishing quantitative and qualitative defects in androgen binding to receptor, since one cell line found to have normal levels of androgen receptor complexes in whole cell assays had a profile resembling that of receptor negative cells on sucrose gradients. The complexes from one patient with complete androgen insensitivity having normal androgen binding in intact hGSF were indistinguishable from control complexes after sucrose gradient analysis and ADP-Sepharose chromatography. Receptor complexes were eluted from the ADP-Sepharose between 0.5-1.0 M KCl. HPLC-gel filtration of androgen receptor complexes at 22 degrees C revealed two peaks, the larger had a Mr of 60-65K, Stokes radius of 3.16 nm and a frictional ratio between 1.21 and 1.43. The second peak, Mr of 15K, was believed to represent a fragment of the receptor containing the steroid binding domain. On gel filtration at 22 degrees C the complexes from a patient with partial androgen insensitivity, who showed a diminished 4S receptor peak on sucrose gradients, revealed only the small "meroreceptor" fragment, suggesting that the mutation in this individual might render the androgen receptor more susceptible to proteolysis in vitro.

Intracellular and nuclear binding of [3H]dihydrotestosterone in cultured genital skin fibroblasts of patients with severe hypospadias

Androgens stimulate the development and growth of the male external genitalia. Because hypospadias is the most common congenital defect of the male urethra and because in most cases the cause of this malformation is unknown, we examined the hypothesis that the etiology of the severe forms of this disorder, which is frequently associated with other genital anomalies, might be explained by receptor abnormalities. Intracellular and nuclear binding of androgens were determined in cultured genital skin fibroblasts from 10 males who underwent circumcision for phimosis (controls A), 2 patients with 5 alpha-reductase deficiency (controls B), and 11 patients with severe forms of hypospadias of unknown etiology. Genital skin fibroblast monolayers were incubated for 60 min at 37 degrees C with varying concentrations of [3H]-dihydrotestosterone ([3H]DHT), and specific binding in whole cells and nuclei was measured. Maximum binding (Bmax) in the whole cell assay averaged 0.88 +/- 0.15 fmol . microgram DNA-1 (mean +/- SD) in the control group (controls A, 0.89 +/- 0.16 fmol . microgram DNA-1; controls B, 0.85 fmol . microgram DNA-1) and 0.7 +/- 0.25 fmol . microgram DNA-1 in the patients with hypospadias. In the latter group, Bmax in six patients was below the minimum values determined in the controls. Maximum specific nuclear binding in the control groups averaged 43% (range, 30-55%) of the corresponding intracellular binding. In contrast, nuclear binding in strains from patients with hypospadias was lower (range, 0-12% of whole cell Bmax). In particular, no high affinity saturable nuclear [3H]DHT binding could be measured in 6 of the 11 patients. We interpret these data to suggest that defective intracellular and/or nuclear binding might be the cause of defective genital development in some patients with severe hypospadias.

A single-site allosteric model of intracellular androgen-receptor interaction

We present a single-site, two-state model for analyzing the effect of time and ligand concentration on the extent and character of 5 alpha-dihydrotestosterone, methyltrienolone or mibolerone binding to the specific androgen receptor within cultured human genital skin fibroblasts. The model has three basic attributes: formation of the initial low-affinity androgen-receptor complex, and its transformation to a higher affinity state are irreversible, first-order processes; and receptors released from complexes in each state not only differ from each other and from their pre-liganded progenitor, but can also reassociate with androgen to yield complexes in their respective parental states. The rate constants of dissociation and apparent equilibrium binding constants of the two affinity states were determined for each of the three androgens within normal cells and those of a transformation-defective mutant. When these values are combined with estimates of the rate constants at which the complexes are formed and transformed, the model accurately simulates time-dependent changes in the slopes and character of experimental Scatchard plots. It can also generate Scatchard plots that are concave, convex or sigmoidal simply by making sequential changes in its formation or transformation constants. Thus, our model can explain complex ligand-receptor binding kinetics that have heretofore been interpreted according to alternate models of transformation and binding-site multiplicity with or without properties of cooperativity, and it supports the notion that receptor recycling involves intermediate receptor states.

Characterization and expression of a cDNA encoding the human androgen receptor

We report the isolation of a cDNA that encodes the complete human androgen receptor. The cDNA predicts a protein of 917 amino acids with a molecular weight of 98,918. Introduction of the cDNA into heterologous mammalian cells caused expression of high levels of a protein that binds dihydrotestosterone with the affinity, specificity, and sedimentation properties characteristic of the native human androgen receptor. Comparisons with the amino acid sequence of previously cloned steroid hormone receptors revealed a high degree of sequence conservation with the progesterone, glucocorticoid, and mineralocorticoid receptors in the putative hormone and DNA-binding domain regions.

Androgen receptors: structures, mutations, antibodies and cellular dynamics

An overview of recent studies from this and other laboratories on the structures and intracellular dynamics of androgen receptors is presented. Human and rat androgen receptors are unique in that, aside from their DNA and androgen binding domains, they have amino terminal regions rich in oligo- and poly(amino acids) motifs as in some regulatory and homeotic genes. Point mutations that cause sequence changes or deletion of regions of androgen receptors appear to be responsible for some cases of androgen-insensitivity. Monoclonal antibodies produced against specific regions of the androgen receptor bind to androgen receptors but not other major steroid receptors. Androgen receptors in the human and rat prostate, and monkey seminal vesicle were localized to the nucleus of target cells in these tissues with these antibodies; androgen receptors also were found in the cytoplasm of some target cells. Actinomycin D and 3'-deoxyadenosine, inhibitors of transcription, RNA processing and nucleo-cytoplasmic transport of RNA, interfere with the intracellular dynamics of androgen receptors, suggesting as we have proposed previously that androgen receptors may function not only at the site of transcription but also are involved in posttranscriptional regulation of mRNA stability and utilization.

Cloning of human androgen receptor complementary DNA and localization to the X chromosome

The androgen receptor (AR) mediates the actions of male sex steroids. Human AR genomic DNA was cloned from a flow-sorted human X chromosome library by using a consensus nucleotide sequence from the DNA-binding domain of the family of nuclear receptors. The AR gene was localized on the human X chromosome between the centromere and q13. Cloned complementary DNA, selected with an AR-specific oligonucleotide probe, was expressed in monkey kidney (COS) cells and yielded a high-affinity androgen-binding protein with steroid-binding specificity corresponding to that of native AR. A predominant messenger RNA species of 9.6 kilobases was identified in human, rat, and mouse tissues known to contain AR and was undetectable in tissues lacking AR androgen-binding activity, including kidney and liver from androgen-insensitive mice. The deduced amino acid sequence of AR within the DNA-binding domain has highest sequence identity with the progesterone receptor.

High efficiency covalent radiolabeling of the human androgen receptor. Studies in cultured fibroblasts using dihydrotestosterone 17 beta-bromoacetate

Analysis of mutations affecting the androgen receptor protein in human cells has been limited because of the low abundance and lability of these proteins in target tissues. All methods used to date have been based on the noncovalent interaction of radiolabeled androgens with the receptor's ligand binding site. We report here synthesis and use of the electrophilic affinity label dihydrotestosterone 17 beta-bromoacetate. This ligand, prepared as a radioactive compound of high specific activity, rapidly and covalently binds to a protein of 58,000 daltons in cytosol from normal genital skin fibroblasts. This protein is a high affinity, saturable specific binding site for the ligand and was not detectable in cultured cells from a subject with androgen resistance or in receptor-negative nongenital fibroblasts. The efficiency of incorporation of the covalent radiolabel into the 58-kD protein is greater than 80% based on estimates of receptor content using noncovalent ligands in intact cell assays. These studies demonstrate that dihydrotestosterone 17 beta-bromoacetate is useful for high efficiency covalent labeling of the human androgen receptor in crude cytosolic extracts from cultured cells.

Ligand-specific thermal misbehavior of synthetic androgen-receptor complexes in genital skin fibroblasts of subjects with familial ligand-sensitive androgen resistance

We have used 5 alpha-dihydrotestosterone (DHT) and two synthetic, non-metabolizable androgens, methyltrienolone (MT) and mibolerone (MB), to study intact genital skin fibroblasts from four subjects with familial incomplete androgen resistance. In each, the free androgen receptor has normal binding capacity at 37 degrees C and normal half-lives at 37-43 degrees C. In three the mutant receptor misbehaves in a pattern that is ligand-specific and temperature-dependent. At 37 degrees C the equilibrium (Kd) and non-equilibrium (k) dissociation constants, and the ability to augment binding activity during prolonged exposure to androgen, are impaired with DHT, but not with MT; with MB, only the k is abnormal. Mutant MT-receptor complexes dissociate normally even at 42 degrees C; yet, in cells post-incubated at 42 degrees C with cycloheximide and a saturating concentration of ligand, their pool size decays in the rank order, MT greater than MB greater than normal. This measure of lability is nonlinear as a semilogarithmic function of time; it varies directly with temperature and the concentration of cycloheximide, but inversely with that of ligand. Thus, MT and MB evoke distinct forms of thermal dysfunction from the androgen receptor in ligand-sensitive androgen resistance. This observation will help to elucidate the combinatorial properties of normal androgen-receptor complexes that enable them to regulate gene transcription differentially in various androgen target tissues.

High plasma steroid levels in the squirrel monkey: deficient receptors or metabolism?

Many New World primates such as the squirrel monkey have extraordinarily high plasma steroid hormone levels as compared to humans and Old World primates. To clarify the mechanism(s) underlying this apparent steroid resistance, glucocorticoid and androgen binding to putative receptors in genital skin fibroblasts from several species was investigated. Differences in either affinity and/or number of binding sites were found but these were small compared to the very large differences in total or free plasma steroid concentrations between Old and New World primate species. In contrast, when the ability of fibroblasts to metabolize testosterone was compared, squirrel monkey cells were devoid of 5 alpha-reductase activity which was readily demonstrated in human cells. Together with other data indicating that squirrel monkeys excrete little if any 5 alpha- or 5 beta-reduced urinary steroid metabolites, these results suggest that inefficient metabolism rather than receptor binding abnormalities may account for the elevated plasma hormone levels in the squirrel monkey.

Augmentation of androgen-receptor binding in vitro: studies in normals and patients with androgen insensitivity

Using a simple whole-cell binding assay, the effect of androgens on receptor binding activity was studied in genital skin fibroblasts (GSF) from normals and patients with either androgen insensitivity syndrome (AIS), isolated micropenis or hypospadias. Expressing the response as a ratio of augmented to basal specific dihydrotestosterone (DHT) binding, there was a 2.4 +/- 0.87 (mean +/- SD) increase following 20 h incubation with 2 nmol/l [3H]-DHT in normal GSF. Mibolerone, a synthetic nonmetabolizable androgen, produced a similar response. Augmentation was temperature dependent, independent of androgen metabolism and suppressed by protein and RNA inhibitors. All patients with isolated micropenis and hypospadias demonstrated normal augmentation of receptor binding activity. There was no response in patients with complete AIS who were receptor negative. In the majority of patients with partial AIS, there was an in vitro response to androgens; those reared as males all virilized with androgen therapy. In contrast, a male patient with partial AIS who failed to respond to high-dose androgen therapy, showed no augmentation of specific androgen binding in GSF preincubated with androgens. This technique may be a useful in vitro bioassay to predict androgen responsiveness in vivo in patients with androgen insensitivity, either soon after birth in the short-term, or later at puberty.