Identification of the classical androgen receptor in male rat liver and prostate cell plasma membranes

Steroid hormone signaling: multifaceted support of testicular function

Embryonic development and adult physiology are dependent on the action of steroid hormones. In particular, the reproductive system is reliant on hormonal signaling to promote gonadal function and to ensure fertility. Here we will describe hormone receptor functions and their impacts on testicular function, focusing on a specific group of essential hormones: androgens, estrogens, progesterone, cortisol, and aldosterone. In addition to focusing on hormone receptor function and localization within the testis, we will highlight the effects of altered receptor signaling, including the consequences of reduced and excess signaling activity. These hormones act through various cellular pathways and receptor types, emphasizing the need for a multifaceted research approach to understand their critical roles in testicular function. Hormones exhibit intricate interactions with each other, as evidenced, for example, by the antagonistic effects of progesterone on mineralocorticoid receptors and cortisol's impact on androgens. In light of research findings in the field demonstrating an intricate interplay between hormones, a systems biology approach is crucial for a nuanced understanding of this complex hormonal network. This review can serve as a resource for further investigation into hormonal support of male reproductive health.

The Role of Androgen Signaling in Male Sexual Development at Puberty

Puberty is characterized by major changes in the anatomy and function of reproductive organs. Androgen activity is low before puberty, but during pubertal development, the testes resume the production of androgens. Major physiological changes occur in the testicular cell compartments in response to the increase in intratesticular testosterone concentrations and androgen receptor expression. Androgen activity also impacts on the internal and external genitalia. In target cells, androgens signal through a classical and a nonclassical pathway. This review addresses the most recent advances in the knowledge of the role of androgen signaling in postnatal male sexual development, with a special emphasis on human puberty.

Importance of the Androgen Receptor Signaling in Gene Transactivation and Transrepression for Pubertal Maturation of the Testis

Androgens are key for pubertal development of the mammalian testis, a phenomenon that is tightly linked to Sertoli cell maturation. In this review, we discuss how androgen signaling affects Sertoli cell function and morphology by concomitantly inhibiting some processes and promoting others that contribute jointly to the completion of spermatogenesis. We focus on the molecular mechanisms that underlie anti-Müllerian hormone (AMH) inhibition by androgens at puberty, as well as on the role androgens have on Sertoli cell tight junction formation and maintenance and, consequently, on its effect on proper germ cell differentiation and meiotic onset during spermatogenesis.

Calcineurin is involved in retrieval of passive avoidance memory and synaptic plasticity impairment induced by Nandrolone administration in adolescent male rats

In spite of evidence about negative effects of Nandrolone Decanoate (ND) on cognitive and memory performance, the underlying mechanisms are complex and have remained unclear. This research examines the role of Calcineurin in synaptic plasticity and memory storage impairment in ND administrated adolescent male rats. For behavioral study by passive avoidance learning and memory (PAL), adolescent male rats were treated with ND or ND plus selective Calcineurin antagonist (Tacrolimus), before retention test. ND significantly decreased the retrieval of PAL, whereas Tacrolimus plus ND had no significant effect on PAL. For electrophysiological study hippocampal slices were perfused by ND or ND plus Tacrolimus. The magnitude of fEPSP-LTP of ND perfused slices was less than the control and a reduction of fEPSP-PS (E-S) coupling was observed, while pre-administration of Tacrolimus abolished the ND impairment effect on fEPSP-LTP and E-S coupling. This study showed that ND may induce impairing effects on hippocampal area CA1 activity and plasticity and PAL memory storage through changes in the function of the Calcineurin.

Role of Androgens in Female Genitourinary Tissue Structure and Function: Implications in the Genitourinary Syndrome of Menopause

INTRODUCTION

Genitourinary conditions in women increase in prevalence with age. Androgens are prerequisite hormones of estrogen biosynthesis, are produced in larger amounts than estrogens in women, and decrease throughout adulthood. However, research and treatment for genitourinary complaints have traditionally focused on estrogens to the exclusion of other potential hormonal influences.

AIM

To summarize and evaluate the evidence that androgens are important for maintaining genitourinary health in women and that lack of androgenic activity can contribute to the development of symptoms of the genitourinary syndrome of menopause.

METHODS

The role of androgens in the pathophysiology, diagnosis, and treatment of genitourinary syndrome of menopause was discussed by an international and multidisciplinary panel during a consensus conference organized by the International Society for the Study of Women's Sexual Health. A subgroup further examined publications from the PubMed database, giving preference to clinical studies or to basic science studies in human tissues.

MAIN OUTCOME MEASURES

Expert opinion evaluating trophic and functional effects of androgens, their differences from estrogenic effects, and regulation of androgen and estrogen receptor expression in female genitourinary tissues.

RESULTS

Androgen receptors have been detected throughout the genitourinary system using immunohistochemical, western blot, ligand binding, and gene expression analyses. Lower circulating testosterone and estradiol concentrations and various genitourinary conditions have been associated with differential expression of androgen and estrogen receptors. Supplementation of androgen and/or estrogen in postmenopausal women (local administration) or in ovariectomized animals (systemic administration) induces tissue-specific responses that include changes in androgen and estrogen receptor expression, cell growth, mucin production, collagen turnover, increased perfusion, and neurotransmitter synthesis.

CONCLUSION

Androgens contribute to the maintenance of genitourinary tissue structure and function. The effects of androgens can be distinct from those of estrogens or can complement estrogenic action. Androgen-mediated processes might be involved in the full or partial resolution of genitourinary syndrome of menopause symptoms in women. Traish AM, Vignozzi L, Simon JA, et al. Role of Androgens in Female Genitourinary Tissue Structure and Function: Implications in the Genitourinary Syndrome of Menopause. Sex Med Rev 2018;6:558-571.

Membrane androgen receptor characteristics of human ZIP9 (SLC39A) zinc transporter in prostate cancer cells: Androgen-specific activation and involvement of an inhibitory G protein in zinc and MAP kinase signaling

Characteristics of novel human membrane androgen receptor (mAR), ZIP9 (SLC39A9), were investigated in ZIP9-transfected PC-3 cells (PC3-ZIP9). Ligand blot analysis showed plasma membrane [³H]-T binding corresponds to the position of ZIP9 on Western blots which suggests ZIP9 can bind [³H]-T alone, without a protein partner. Progesterone antagonized testosterone actions, blocking increases in zinc, Erk phosphorylation and apoptosis, further evidence that ZIP9 is specifically activated by androgens. Pre-treatment with GTPγS and pertussis toxin decreased plasma membrane [³H]-T binding and blocked testosterone-induced increases in Erk phosphorylation and intracellular zinc, indicating ZIP9 is coupled to an inhibitory G protein (Gi) that mediates both MAP kinase and zinc signaling. Testosterone treatment of nuclei and mitochondria which express ZIP9 decreased their zinc contents, suggesting ZIP9 also regulates free zinc through releasing it from these intracellular organelles. The results show ZIP9 is a specific Gi coupled-mAR mediating testosterone-induced MAP kinase and zinc signaling in PC3-ZIP9 cells.

Androgen receptor-mediated non-genomic regulation of prostate cancer cell proliferation

Androgen receptor (AR)-mediated signaling is necessary for prostate cancer cell proliferation and an important target for therapeutic drug development. Canonically, AR signals through a genomic or transcriptional pathway, involving the translocation of androgen-bound AR to the nucleus, its binding to cognate androgen response elements on promoter, with ensuing modulation of target gene expression, leading to cell proliferation. However, prostate cancer cells can show dose-dependent proliferation responses to androgen within minutes, without the need for genomic AR signaling. This proliferation response known as the non-genomic AR signaling is mediated by cytoplasmic AR, which facilitates the activation of kinase-signaling cascades, including the Ras-Raf-1, phosphatidyl-inositol 3-kinase (PI3K)/Akt and protein kinase C (PKC), which in turn converge on mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) activation, leading to cell proliferation. Further, since activated ERK may also phosphorylate AR and its coactivators, the non-genomic AR signaling may enhance AR genomic activity. Non-genomic AR signaling may occur in an ERK-independent manner, via activation of mammalian target of rapamycin (mTOR) pathway, or modulation of intracellular Ca²⁺ concentration through plasma membrane G protein-coupled receptors (GPCRs). These data suggest that therapeutic strategies aimed at preventing AR nuclear translocation and genomic AR signaling alone may not completely abrogate AR signaling. Thus, elucidation of mechanisms that underlie non-genomic AR signaling may identify potential mechanisms of resistance to current anti-androgens and help developing novel therapies that abolish all AR signaling in prostate cancer.

Identification and characterization of membrane androgen receptors in the ZIP9 zinc transporter subfamily: I. Discovery in female atlantic croaker and evidence ZIP9 mediates testosterone-induced apoptosis of ovarian follicle cells

Rapid, cell surface-initiated, pregenomic androgen actions have been described in various vertebrate cells, but the receptors mediating these actions remain unidentified. We report here the cloning and expression of a cDNA from Atlantic croaker (Micropogonias undulatus) ovaries encoding a 33-kDa, seven-transmembrane protein with binding and signaling characteristics of a membrane androgen receptor that is unrelated to any previously described steroid receptor. Instead, croaker membrane androgen receptor has 81-93% amino acid sequence identity with zinc transporter ZIP9 (SLC39A9) subfamily members, indicating it is a ZIP9 protein. Croaker ZIP9 is expressed in gonadal tissues and in brain and is up-regulated in the ovary by reproductive hormones. Croaker ZIP9 protein is localized to plasma membranes of croaker granulosa cells and human breast cancer (SKBR-3) cells stably transfected with ZIP9. Recombinant croaker ZIP9 has a high affinity (dissociation constant, Kd, 12.7 nM), limited capacity (maximal binding capacity 2.8 nM/mg protein), displaceable, single binding site-specific for androgens, characteristic of steroid receptors. Testosterone activates a stimulatory G protein coupled to ZIP9, resulting in increased cAMP production. Testosterone promotes serum starvation-induced cell death and apoptosis in transfected cells and in croaker ovarian follicle cells that is associated with rapid increases in intracellular free zinc concentrations, suggesting an involvement of zinc in this nonclassical androgen action to promote apoptosis. These responses to testosterone are abrogated by treatment with ZIP9 small interfering RNA. The results provide the first evidence that zinc transporter proteins can function as specific steroid membrane receptors and indicate a previously unrecognized signaling pathway mediated by steroid receptors involving alterations in intracellular zinc.

Androgens in pregnancy: roles in parturition

BACKGROUND

Understanding the physiology of pregnancy enables effective management of pregnancy complications that could otherwise be life threatening for both mother and fetus. A functional uterus (i) retains the fetus in utero during pregnancy without initiating stretch-induced contractions and (ii) is able to dilate the cervix and contract the myometrium at term to deliver the fetus. The onset of labour is associated with successful cervical remodelling and contraction of myometrium, arising from concomitant activation of uterine immune and endocrine systems. A large body of evidence suggests that actions of local steroid hormones may drive changes occurring in the uterine microenvironment at term. Although there have been a number of studies considering the potential role(s) played by progesterone and estrogen at the time of parturition, the bio-availability and effects of androgens during pregnancy have received less scrutiny. The aim of this review is to highlight potential roles of androgens in the biology of pregnancy and parturition.

METHODS

A review of published literature was performed to address (i) androgen concentrations, including biosynthesis and clearance, in maternal and fetal compartments throughout gestation, (ii) associations of androgen concentrations with adverse pregnancy outcomes, (iii) the role of androgens in the physiology of cervical remodelling and finally (iv) the role of androgens in the physiology of myometrial function including any impact on contractility.

RESULTS

Some, but not all, androgens increase throughout gestation in maternal circulation. The effects of this increase are not fully understood; however, evidence suggests that increased androgens might regulate key processes during pregnancy and parturition. For example, androgens are believed to be critical for cervical remodelling at term, in particular cervical ripening, via regulation of cervical collagen fibril organization. Additionally, a number of studies highlight potential roles for androgens in myometrial relaxation via non-genomic, AR-independent pathways critical for the pregnancy reaching term. Understanding of the molecular events leading to myometrial relaxation is an important step towards development of novel targeted tocolytic drugs.

CONCLUSIONS

The increase in androgen levels throughout gestation is likely to be important for establishment and maintenance of pregnancy and initiation of parturition. Further investigation of the underlying mechanisms of androgen action on cervical remodelling and myometrial contractility is needed. The insights gained may facilitate the development of new therapeutic approaches to manage pregnancy complications such as preterm birth.

The low dose gamma ionising radiation impact upon cooperativity of androgen-specific proteins

The paper deals with effects of the ionising radiation (γ-IR, 0.5 Gy) upon serum testosterone (T), characteristics of testosterone-binding globulin (TeBG) and androgen receptor (AR) in parallel with observation of androgen (A) responsive enzyme activity - hexokinase (HK). The interdependence or relationships of T-levels with parameters of the proteins that provide androgenic regulation are consequently analyzed in post-IR dynamics. The IR-stress adjustment data reveal expediency of TeBG- and AR-cooperativity measurements for more precise assessments of endocrine A-control at appropriate emergencies.

Sex-specific effect of the anabolic steroid, 17α-methyltestosterone, on inhibitory avoidance learning in periadolescent rats

The illicit use of anabolic androgenic steroids (AAS) has gained popularity among adolescents in the last decade. However, although it is known that exposure to AAS impairs cognition in adult animal models, the cognitive effects during adolescence remain undetermined. An inhibitory avoidance task (IAT) was used to assess the effect of AAS (17α-methyltestosterone; 17α-meT--7.5 mg/kg) in male and female periadolescent rats. A single injection of 17α-meT immediately before the footshock produced significant impairment of inhibitory avoidance learning in males but not females. Generalized anxiety, locomotion, and risk assessment behaviors (RAB) were not affected. Our results show that exposure to a single pharmacological dose of 17α-meT during periadolescence exerts sex-specific cognitive effects without affecting anxiety. Thus, disruption of the hormonal milieu during this early developmental period might have negative impact on learning and memory.

Rapid membrane responses to dihydrotestosterone are sex dependent in growth plate chondrocytes

Sex steroids are important regulators for longitudinal growth, bone mass accrual, and sexual dimorphism of the skeleton. 17β-Estradiol regulates proliferation and differentiation of female chondrocytes via a membrane-associated signaling pathway in addition to its estrogen receptor (ER) mediated effects. In contrast, testosterone does not elicit a similar membrane response, either in male or female cells. Whereas female rat growth plate chondrocytes convert testosterone to 17β-estradiol, male chondrocytes produce 5α-dihydrotestosterone (DHT). Previously DHT was found to mediate sex-specific effects of testosterone in male cells, but it is not known if a membrane-signaling pathway is involved. In this study, we hypothesized that DHT can induce sex-specific rapid membrane effects similar to other steroid hormones. Confluent cultures of chondrocytes isolated from resting zones of growth plates of both male and female rats were treated with 10(-10)-10(-7)M testosterone or DHT for 3, 9, 90 and 270min and protein kinase C (PKC) and phospholipase A2 (PLA2) activities were measured. To examine potential signaling pathways involved in PKC activation, male chondrocytes were treated with 10(-7)M DHT for 9min in the presence or absence of the phospholipase C (PLC) inhibitor U73122, the secretory PLA2 inhibitor quinacrine or the cytosolic PLA2 inhibitor AACOCF3; the Gαi inhibitor pertussis toxin (PTX) or Gαs activator cholera toxin (CTX), and the general G-protein inhibitor GDPβS; thapsigargin, an inhibitor of a Ca-ATPase pump in the endoplasmic reticulum; verapamil and nifedipine, inhibitors of specific L type Ca2+ channels on the cell membrane; and cyproterone acetate (CPA), which is an inhibitor of the classical androgen receptor (AR); as well as the transcription inhibitor actinomycin D, or the translation inhibitor cycloheximide. DHT induced a dose-dependent increase in PKC and PLA2 activity in male cells with the highest increase at 10(-7)M DHT (p<0.05), whereas testosterone had no effect. PKC activity was augmented at 9 and 90 min, and then decreased to baseline at 270min. Neither testosterone nor DHT affected PKC in female cells. U73122, quinacrine, and AACOCF3 inhibited DHT-induced activation of PKC. DHT treatment for 9 min had no effect in [(3)H]-thymidine incorporation in quiescent confluent cultures but caused a dose dependent increase in alkaline phosphatase specific activity. Inhibition of PLC reduced the response of to DHT in a dose dependent manner, indicating that PLC is involved. In conclusion, our study indicates that DHT, but not testosterone, has sex-specific rapid membrane effects in male growth plate chondrocytes involving PLC and PLA2-mediated PKC signaling pathways. Together with previous observations showing that male cells convert testosterone to DHT, these results suggest that DHT might act in the membrane through an autocrine/paracrine mechanism.

Estrogen receptor beta dependent attenuation of cytokine-induced cyclooxygenase-2 by androgens in human brain vascular smooth muscle cells and rat mesenteric arteries

Androgens may provide protective effects in the vasculature under pathophysiological conditions. Our past studies have shown that dihydrotestosterone (DHT) decreases expression of cyclooxygenase-2 (COX-2) during cytokine, endotoxin, or hypoxic stimulation in human vascular smooth muscle cells, in an androgen receptor (AR)-independent fashion. Classically DHT is regarded as a pure AR agonist; however, it can be endogenously metabolized to 5α-androstane-3β, 17β-diol (3β-diol), which has recently been shown to be a selective estrogen receptor (ERβ) agonist. Therefore, we hypothesized that DHT's anti-inflammatory properties following cytokine stimulation are mediated through ERβ. Using primary human brain vascular smooth muscle cells (HBVSMC), we tested whether DHT's effect on IL-1β induced COX-2 expression was mediated via AR or ERβ. The metabolism of DHT to 3β-diol is a viable pathway in HBVSMC since mRNA for enzymes necessary for the synthesis and metabolism of 3β-diol [3alpha-hydroxysteroid dehydrogenase (HSD), 3β-HSD, 17β-HSD, CYP7B1] was detected. In addition, the expression of AR, ERα, and ERβ mRNA was detected. When applied to HBVSMC, DHT (10nM; 18 h) attenuated IL-1β-induced increases in COX-2 protein expression. The AR antagonist bicalutamide did not block DHT's ability to reduce COX-2. Both the non-selective estrogen receptor antagonist ICI 182,780 (1 μM) and the selective ERβ antagonist PHTPP (1 μM) inhibited the effect of DHT, suggesting that DHT actions are ERβ-mediated. In HBVSMC and in rat mesenteric arteries, 3β-diol, similar to DHT, reduced cytokine-induced COX-2 levels. In conclusion, DHT appears to be protective against the progression of vascular inflammation through metabolism to 3β-diol and activation of ERβ.

Non-classic androgen actions in Sertoli cell membrane in whole seminiferous tubules: effects of nandrolone decanoate and catechin

Studies show a mechanism of action of testosterone, nandrolone and catechin as agonists of the membrane androgen receptor. The aim of this work is to investigate the non-classical effect of androgens and catechin in Sertoli cells from immature rats. The membrane potential of Sertoli cells in whole seminiferous tubules was recorded using a standard single microelectrode technique. It was performed a topical application of testosterone (1 μM), nandrolone (0.1, 0.5 and 1 μM) and the flavonoid catechin (0.1, 0.5 and 1 μM) alone and also after infusion with flutamide (1 μM), diazoxide (100 μM) or U73122 (1 μM). The immature testes were incubated for 5 min in KRb with (45)Ca(2+), with or without nandrolone (1 μM). The results were given as mean±SEM. The data were analyzed using ANOVA for repeated measures with Bonferroni post-test. Testosterone produces a depolarization in the membrane potential at 120 s after application. Catechin (1 μM) and nandrolone (1 μM) have shown a similar response to testosterone: depolarization at 120 s after the application. The same response of catechin and nandrolone was observed at different doses. The effects of testosterone, catechin and nandrolone were not affected after perfusion with flutamide. Perfusion with diazoxide and U73122 nullified the effect of nandrolone (1 μM) and catechin (1 μM). Nandrolone and testosterone increased (45)Ca(2+) uptake with or without flutamide within 5min. These results indicate that nandrolone and catechin act through a receptor on the plasmatic membrane, as well as testosterone, showing a non-classical pathway in Sertoli cells from immature rat testes.

Dihydrotestosterone alters cyclooxygenase-2 levels in human coronary artery smooth muscle cells

Both protective and nonprotective effects of androgens on the cardiovascular system have been reported. Our previous studies show that the potent androgen receptor (AR) agonist dihydrotestosterone (DHT) increases levels of the vascular inflammatory mediator cyclooxygenase (COX)-2 in rodent cerebral arteries independent of an inflammatory stimulus. Little is known about the effects of androgens on inflammation in human vascular tissues. Therefore, we tested the hypothesis that DHT alters COX-2 levels in the absence and presence of induced inflammation in primary human coronary artery smooth muscle cells (HCASMC). Furthermore, we tested the ancillary hypothesis that DHT's effects on COX-2 levels are AR-dependent. Cells were treated with DHT (10 nM) or vehicle for 6 h in the presence or absence of LPS or IL-1beta. Similar to previous observations in rodent arteries, in HCASMC, DHT alone increased COX-2 levels compared with vehicle. This effect of DHT was attenuated in the presence of the AR antagonist bicalutamide. Conversely, in the presence of LPS or IL-1beta, increases in COX-2 were attenuated by cotreatment with DHT. Bicalutamide did not affect this response, suggesting that DHT-induced decreases in COX-2 levels occur independent of AR stimulation. Thus we conclude that DHT differentially influences COX-2 levels under physiological and pathophysiological conditions in HCASMC. This effect of DHT on COX-2 involves AR-dependent and- independent mechanisms, depending on the physiological state of the cell.

In vitro screening of environmental chemicals for targeted testing prioritization: the ToxCast project

BACKGROUND

Chemical toxicity testing is being transformed by advances in biology and computer modeling, concerns over animal use, and the thousands of environmental chemicals lacking toxicity data. The U.S. Environmental Protection Agency's ToxCast program aims to address these concerns by screening and prioritizing chemicals for potential human toxicity using in vitro assays and in silico approaches.

OBJECTIVES

This project aims to evaluate the use of in vitro assays for understanding the types of molecular and pathway perturbations caused by environmental chemicals and to build initial prioritization models of in vivo toxicity.

METHODS

We tested 309 mostly pesticide active chemicals in 467 assays across nine technologies, including high-throughput cell-free assays and cell-based assays, in multiple human primary cells and cell lines plus rat primary hepatocytes. Both individual and composite scores for effects on genes and pathways were analyzed.

RESULTS

Chemicals displayed a broad spectrum of activity at the molecular and pathway levels. We saw many expected interactions, including endocrine and xenobiotic metabolism enzyme activity. Chemicals ranged in promiscuity across pathways, from no activity to affecting dozens of pathways. We found a statistically significant inverse association between the number of pathways perturbed by a chemical at low in vitro concentrations and the lowest in vivo dose at which a chemical causes toxicity. We also found associations between a small set of in vitro assays and rodent liver lesion formation.

CONCLUSIONS

This approach promises to provide meaningful data on the thousands of untested environmental chemicals and to guide targeted testing of environmental contaminants.

Androgens induce nongenomic stimulation of colonic contractile activity through induction of calcium sensitization and phosphorylation of LC20 and CPI-17

We show that androgens, testosterone and 5alpha-dihydrotestosterone (DHT), acutely (approximately 40 min) provoke the mechanical potentiation of spontaneous and agonist-induced contractile activity in mouse colonic longitudinal smooth muscle. The results using flutamide, finasteride, cycloheximide, and actinomycin D indicate that androgen-induced potentiation is dependent on androgen receptors, requires reduction of testosterone to DHT, and occurs independently of transcriptional and translational events. Using permeabilized colonic smooth muscle preparations, we could demonstrate that mechanical potentiation is entirely due to calcium sensitization of contractile machinery. In addition, DHT (10 nm) increased phosphorylation of both 20-kDa myosin light chain (LC(20)) [regulatory myosin light chain, (MLC)] and CPI-17 (an endogenous inhibitor of MLC phosphatase). Paralleling these findings, inhibition of Rho-associated Rho kinase (ROK) and/or protein kinase C (PKC) with, respectively, Y27632 and chelerythrine, prevented LC(20) phosphorylation and abolished calcium sensitization. In addition, inhibition of ROK prevents CPI-17 phosphorylation, indicating that ROK is located upstream PKC-mediated CPI-17 modulation in the signalling cascade. Additionally, androgens induce a rapid activation of RhoA and its translocation to the plasma membrane to activate ROK. The results demonstrate that androgens induce sensitization of colonic smooth muscle to calcium through activation of ROK, which in turn, activates PKC to induce CPI-17 phosphorylation. Activation of this pathway induces a potent steady stimulation of LC(20) by inhibiting MLC phosphatase and displacing the equilibrium of the regulatory subunit towards its phosphorylated state. This is the first demonstration that colonic smooth muscle is a physiological target for androgen hormones, and that androgens modulate force generation of smooth muscle contractile machinery through nongenomic calcium sensitization pathways.

Sex hormones, their receptors and bone health

Sex steroids regulate skeletal maturation and preservation in both men and women, as already recognized in the 1940s by Albright and Reifenstein. The impact of gonadal insufficiency on skeletal integrity has been widely recognized in adult men and women ever since. In the context of their skeletal actions, androgens and estrogens are no longer considered as just male and female hormones, respectively. Androgens can be converted into estrogens within the gonads and peripheral tissues and both are present in men and women, albeit in different concentrations. In the late 1980s, sex steroid receptors were discovered in bone cells. However, the understanding of sex steroid receptor activation and translation into biological skeletal actions is still incomplete. Due to the complex metabolism, sex steroids may have not only endocrine but also paracrine and/or autocrine actions. Also, circulating sex steroid concentrations do not necessarily reflect their biological activity due to strong binding to sex hormone binding globulin (SHBG). Finally, sex steroid signaling may include genomic and non-genomic effects in bone and non-bone cells. This review will focus on our current understanding of gonadal steroid metabolism, receptor activation, and their most relevant cellular and biological actions on bone.

Role of sex steroid receptors in pathobiology of hepatocellular carcinoma

The striking gender disparity observed in the incidence of hepatocellular carcinoma (HCC) suggests an important role of sex hormones in HCC pathogenesis. Though the studies began as early as in 1980s, the precise role of sex hormones and the significance of their receptors in HCC still remain poorly understood and perhaps contribute to current controversies about the potential use of hormonal therapy in HCC. A comprehensive review of the existing literature revealed several shortcomings associated with the studies on estrogen receptor (ER) and androgen receptor (AR) in normal liver and HCC. These shortcomings include the use of less sensitive receptor ligand binding assays and immunohistochemistry studies for ERα alone until 1996 when ERβ isoform was identified. The animal models of HCC utilized for studies were primarily based on chemical-induced hepatocarcinogenesis with less similarity to virus-induced HCC pathogenesis. However, recent in vitro studies in hepatoma cells provide newer insights for hormonal regulation of key cellular processes including interaction of ER and AR with viral proteins. In light of the above facts, there is an urgent need for a detailed investigation of sex hormones and their receptors in normal liver and HCC. In this review, we systematically present the information currently available on androgens, estrogens and their receptors in normal liver and HCC obtained from in vitro, in vivo experimental models and clinical studies. This information will direct future basic and clinical research to bridge the gap in knowledge to explore the therapeutic potential of hormonal therapy in HCC.

Flutamide protects against trauma-hemorrhage-induced liver injury via attenuation of the inflammatory response, oxidative stress, and apopotosis

Although studies have shown that administration of testosterone receptor antagonist, flutamide, following trauma-hemorrhage, improves hepatic, cardiovascular, and immune functions, the precise cellular/molecular mechanisms responsible for producing these salutary effects remain largely unknown. To study this, male C3H/HeN mice were subjected to a midline laparotomy and hemorrhagic shock (35+/-5 mmHg for approximately 90 min), followed by resuscitation with Ringer lactate. Flutamide (25 mg/kg) or vehicle was administered subcutaneously at the onset of resuscitation, and animals were killed 2 h thereafter. Hepatic injury was assessed by plasma alpha-glutathione S-transferase concentration, liver myeloperoxidase activity, and nitrotyrosine formation. Hepatic malondialdehyde and 4-hydroxyalkenals (lipid peroxidation indicators), cellular DNA fragmentation, and the expression of inducible nitric oxide synthase and hypoxia-inducible factor-1alpha were also evaluated. Cytokines (TNF-alpha, IL-6) and chemokines (keratinocyte-derived chemokine and monocyte chemoattractant protein-1) levels were determined by cytometric bead array. The results indicate that flutamide administration after trauma-hemorrhage reduced liver injury, which was associated with decreased levels of alpha-glutathione S-transferase, myeloperoxidase activity, nitrotyrosine formation, lipid peroxidation, and cytokines/chemokines (systemic, liver tissue, and intracellular cytokines/chemokines). Cellular apoptosis, hepatocyte hypoxia-inducible factor-1alpha, and inducible nitric oxide synthase expression were also decreased under such conditions. Thus administration of flutamide following trauma-hemorrhage protects against liver injury via reduced inflammation, cellular oxidative stress, and apoptosis.

Non-genomic actions of androgens

Previous work in the endocrine and neuroendocrine fields has viewed the androgen receptor (AR) as a transcription factor activated by testosterone or one of its many metabolites. The bound AR acts as transcription regulatory element by binding to specific DNA response elements in target gene promoters, causing activation or repression of transcription and subsequently protein synthesis. Over the past two decades evidence at the cellular and organismal level has accumulated to implicate rapid responses to androgens, dependent or independent of the AR. Androgen's rapid time course of action; its effects in the absence or inhibition of the cellular machinery necessary for transcription/translation; and in the absence of translocation to the nucleus suggest a method of androgen action not initially dependent on genomic mechanisms (i.e. non-genomic in nature). In the present paper, the non-genomic effects of androgens are reviewed, along with a discussion of the possible role non-genomic androgen actions have on animal physiology and behavior.

The androgen receptor of the prostate plasma membrane – an hypothesis

The hypothesis that the prostatic plasma membrane sodium pump apparatus functions as a non-genomic androgen receptor is based upon a number of its properties: (1) Androgen enhances the uptake of K(+) into minced rat prostate. (2) Ouabain, a specific inhibitor of Na/K-ATPase activity, strongly opposes the androgenic effect. (3) In non-genomic microsomes, ouabain sensitivity of the enzyme is enhanced by androgen. (4) Kinetic studies show that androgen significantly increases Vmax, Km and energy of activation of the enzyme. (5) Enzyme, treated with [gamma-(32)P]-ATP and then subjected to SDS-PAGE electrophoresis, binds only to its alpha-subunit, but, if treated with [(3)H]-DHT, shows isotope binding to the beta-subunit. (6) [(3)H]-ouabain binding to androgenized enzyme is 5.5 times greater than to the non-androgenized enzyme. (7) Treatment of the enzyme with 10(-9) M DHT enhances by 40% the binding of the ouabain derivative, anthroyl ouabain (AO). (8) Fluorescent spectra appears to show that, upon phosphorylation of the androgenized enzyme, there is a 14% approximation of the two subunits to each other. (9) Except for neuroepithelium, only the epithelium of the prostate has apically located Na/K-ATPase. Preliminary work in other labs suggests that the beta-subunit of the Na/K-ATPase may be required for establishing the polarity of some epithelial cells.

The opioid agonist ethylketocyclazocine reverts the rapid, non-genomic effects of membrane testosterone receptors in the human prostate LNCaP cell line

Neuropeptides influence cancer cell replication and growth. Opioid peptides, and opiergic neurons are found in the prostate gland, and they are proposed to exert a role in tumor regulation, influencing cancer cell growth, as opioid agonists inhibit cell growth in several systems, including the human prostate cancer cell line LNCaP. In the same cell line, the existence of membrane testosterone receptors was recently reported, which increase, in a non-genomic manner, the secretion of PSA, and modify actin cytoskeleton dynamics, through the signaling cascade FAK-->PI-3 kinase-->Cdc42/Rac1. In the present work, we present data supporting that the general opioid agonist Ethylketocyclazocine (EKC) decreases testosterone-BSA (a non-internalizable testosterone analog) induced PSA secretion. Furthermore, we report that this opioid affects this non-genomic testosterone action, by modifying the distribution of the actin cytoskeleton in the cells, disrupting the above signaling cascade. In addition, after long (>24 h) incubation, opioids decrease the number of membrane testosterone receptors, and reverse their effect on the signaling molecules. In conclusion, our results provide some new insights of a possible action of opioids in prostate cancer control by interfering with the action and the expression of membrane testosterone receptors and signaling.

Biochemical characterization of a membrane androgen receptor in the ovary of the atlantic croaker (Micropogonias undulatus)

Membrane androgen receptors have been biochemically characterized in only a few vertebrate species to date. Therefore, the purpose of the current study was to comprehensively investigate the binding characteristics of a putative membrane androgen receptor in the ovary of the teleost, Atlantic croaker (Micropogonias undulatus). Specific androgen binding to an ovarian plasma membrane fraction was demonstrated using a radioreceptor assay protocol consisting of a short-term incubation with [(3)H]testosterone (T) and subsequent filtration of bound steroid from free steroid. Saturation and Scatchard analyses of T binding to an ovarian plasma membrane fraction indicated the presence of a single, high-affinity (K(d) = 15.32 +/- 2.68 nM [mean +/- SEM]), low-capacity (B(max) = 2.81 +/- 0.31 pmol/mg protein), androgen-binding site. Specific androgen binding to the receptor was readily displaceable, and the association and dissociation kinetics were rapid (half-time = 3.7 +/- 1.7 and 4.7 +/- 0.2 min, respectively). Competitive binding assays showed that 5alpha-dihydrotestosterone, T, and 11-ketotestosterone had relative binding affinities (RBAs) of 193%, 100%, and 13%, respectively, whereas none of the C(18) or C(21) steroids tested bound with high affinity except for progesterone (RBA = 191%). This androgen-binding moiety with high affinity for progesterone is unlikely to mediate the physiological actions of progestins in croaker, because it has low binding affinity for fish progestin hormones. Androgen-binding sites were also detected in membrane fractions of the brain, liver, kidney, and drumming muscle, whereas little or no binding was detected in the trunk muscle, heart, gills, or intestine. Receptor levels increased 10-fold during ovarian recrudescence, reaching maximum levels in fully mature ovaries, which suggests a likely physiological role for this receptor during the reproductive cycle of female croaker. It is concluded that the androgen-binding moiety identified in the plasma membrane fraction of Atlantic croaker ovarian tissue fulfils all the criteria for its designation as a steroid receptor.

Androgens inhibit estradiol-17beta synthesis in Atlantic croaker (Micropogonias undulatus) ovaries by a nongenomic mechanism initiated at the cell surface

The presence of androgen receptors in the ovaries of several vertebrate species, including Atlantic croaker, suggests that androgens may have important roles in ovarian function. In the current study the effects of androgens on ovarian steroidogenesis in Atlantic croaker were investigated. Addition of 17beta-hydroxy-5alpha-androstan-3-one (DHT), 11-ketotestosterone (11-KT), or Mibolerone to ovarian incubations caused dose-dependent decreases in gonadotropin-stimulated in vitro estradiol production, which was not reversed by cotreatment with the antiandrogens, cyproterone acetate or 1,1-dichloro-2,2-bis(p-chlorophenyl) ethylene. Androgen treatment also caused significant decreases in estradiol production in the presence of 17-hydroxyprogesterone, which suggests that the site of androgen action is downstream of this steroid in the steroidogenic pathway. The mechanism of androgen action on ovarian steroidogenesis was also investigated. Coincubation with actinomycin D did not reverse the inhibitory effect of the androgens, which suggests that the mechanism of androgen action is nongenomic. An androgen conjugated to bovine serum albumin (DHT-BSA), which does not enter the cell, also caused inhibition of estradiol production in vitro, indicating that the androgen is acting at the cell surface. In addition, time course experiments revealed that the androgen action is rapid; 5-min exposure to DHT was sufficient to cause a significant reduction in estradiol production. Finally, preliminary evidence was obtained for the existence of a high-affinity, low-capacity androgen binding site in croaker ovarian plasma membranes. These studies suggest that androgens can down-regulate estrogen production in croaker ovaries via a rapid, cell surface-mediated, nongenomic mechanism.

The roles of androgen receptors and androgen-binding proteins in nongenomic androgen actions

The biological activity of testosterone and dihydrotestosterone is thought to occur predominantly through binding to the androgen receptor (AR), a member of the nuclear receptor superfamily that functions as a ligand-activated transcription factor. However, androgens have also been reported to induce the rapid activation of kinase-signaling cascades and modulate intracellular calcium levels. These effects are considered to be nongenomic because they occur in cell types that lack a functional AR, in the presence of inhibitors of transcription and translation, or are observed to occur too rapidly to involve changes in gene transcription. Such nongenomic effects of androgens may occur through AR functioning in the cytoplasm to induce the MAPK signal cascade. In addition, androgens may function through the sex hormone binding globulin receptor and possibly a distinct G protein-coupled receptor to activate second messenger signaling mechanisms. The physiological effect of nongenomic androgen action has yet to be determined. However, it may ultimately contribute to regulation of transcription factor activity, including mediation of the transcriptional activity of AR.

The human prostate cancer cell line LNCaP bears functional membrane testosterone receptors that increase PSA secretion and modify actin cytoskeleton

Recent findings have shown that, in addition to the genomic action of steroids, through intracellular receptors, short-time effects could be mediated through binding to membrane sites. In the present study of prostate cancer LNCaP cells, we report that dihydrotestosterone and the non-internalizable analog testosterone-BSA increase rapidly the release of prostate-specific antigen (PSA) in the culture medium. Membrane testosterone binding sites were identified through ligand binding on membrane preparations, flow cytometry, and confocal laser microscopy of the non-internalizable fluorescent analog testosterone-BSA-FITC, on whole cells. Binding on these sites is time- and concentration-dependent and specific for testosterone, presenting a KD of 10.9 nM and a number of 144 sites/mg protein (approximately 13000 sites/cell). Membrane sites differ immunologically for intracellular androgen receptors. The secretion of PSA after membrane testosterone receptor stimulation was inhibited after pretreatment with the actin cytoskeleton disrupting agent cytochalasin B. In addition, membrane testosterone binding modifies the intracellular dynamic equilibrium of monomeric to filamentous actin and remodels profoundly the actin cytoskeleton organization. These results are discussed in the context of a possible involvement of these sites in cancer chemotherapy.

Functional testosterone receptors in plasma membranes of T cells

T cells are considered to be unresponsive to testosterone due to the absence of androgen receptors (AR). Here, we demonstrate the testosterone responsiveness of murine splenic T cells in vitro as well as the presence of unconventional cell surface receptors for testosterone and classical intracellular AR. Binding sites for testosterone on the surface of both CD4(+) and CD8(+) subsets of T cells are directly revealed with the impeded ligand testosterone-BSA-FITC by confocal laser scanning microscopy (CLSM) and flow cytometry, respectively. Binding of the plasma membrane impermeable testosterone-BSA conjugate induces a rapid rise (<5 s) in [Ca2+]i of Fura-2-loaded T cells. This rise reflects influx of extracellular Ca2+ through non-voltage-gated and Ni2+-blockable Ca2+ channels of the plasma membrane. The testosterone-BSA-induced Ca2+ import is not affected by cyproterone, a blocker of the AR. In addition, AR are not detectable on the surface of intact T cells when using anti-AR antibodies directed against the amino and carboxy terminus of the AR, although T cells contain AR, as revealed by reverse transcription-polymerase chain reactions and Western blotting. AR can be visualized with the anti-AR antibodies in the cytoplasm of permeabilized T cells by using CLSM, though AR are not detectable in cytosol fractions when using the charcoal binding assay with 3H-R1881 as ligand. Cytoplasmic AR do not translocate to the nucleus of T cells in the presence of testosterone, in contrast to cytoplasmic AR in human cancer LNCaP cells. These findings suggest that the classical AR present in splenic T cells are not active in the genomic pathway. By contrast, the cell surface receptors for testosterone are in a functionally active state, enabling T cells a nongenomic response to testosterone.

Purification of a cortisol binding protein from hepatic plasma membrane

A cortisol binding protein from rat liver plasma membranes has been solubilized in active form by using the zwitterionic detergent CHAPS. Two types of binding sites have been characterised in both native and solubilized membranes. The first is of high affinity and low binding capacity (12 nM; 946 fmol/mg) and the other one is of low affinity and high capacity of binding (344 nM; 12677 fmol/mg) for solubilized membranes. The purified material retained a binding activity comparable to that displayed by the original membrane. The specific binding activity was enriched about 12700-fold, with an 8% yield. Analysis of the purified preparation on sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed two protein subunits with molecular mass of 52000 and 57000 Da. The new cortisol-specific binding membrane protein could be related to the nongenomic effects previously described for this hormone.

Steroid hormone signalling system and fungi

Three components of the steroid hormone signalling system, 17 beta-hydroxysteroid dehydrogenase, androgen binding proteins and steroid hormone signalling molecule testosterone were determined in the filamentous fungus Cochliobolus lunatus for the first time in a fungus. Their possible role in C. lunatus is discussed in comparison with their role in mammalian steroid hormone signalling system. The results are in accordance with the hypothesis, that the elements of primordial signal transduction system should exist in present day eukaryotic microorganisms.

Partial purification of a putative membrane bound androgen binding protein in the dog cauda epididymis

1. An androgen binding protein(s) has been partially purified from cell plasma membranes of dog epididymides. 2. The protein(s) has a pI of 5.3 and an association constant of (1.13 x 10(9) M-1). 3. Conclusive demonstration of androgen receptors in epididymal plasma membranes would be of significance in understanding epididymal physiology.

Receptors for mammalian steroid hormones in microbes and plants

Steroids are of universal occurrence, present variously as cell wall constituents and bioregulators. A number of bacteria, fungi, and photosynthetic vascular plants synthesize steroids that are hormonally active in the animal world. The cellular effect of such steroids in microbes and plants appears by and large to be comparable to that in mammals. Available evidence suggests that steroid action in botanical phyla is mediated via receptors organized in a manner similar to that seen in animals. Therefore, the ancestry of ligand induced transactivation via zinc finger proteins appears to date farther back than the early Cambrian burst of metazoan evolution 500 million years ago.