Nongenomic androgen activation of phosphatidylinositol 3-kinase/Akt signaling pathway in MC3T3-E1 osteoblasts

Testosterone and aging male, a perspective from a developing country

PURPOSE

Hypogonadism is associated with a wide range of physical and psychological symptoms that can affect the overall health of men. However, in a developing country, there are several imposing challenges in the diagnosis and treatment of hypogonadism, including a lack of awareness and understanding of the condition among healthcare providers and patients, limited resources and the high cost of treatment. This review aimed to examine the potential benefits and risks of testosterone replacement therapy (TRT) and provides a perspective of a developing country on the topic.

MATERIALS AND METHODS

A comprehensive literature review was conducted to gather relevant information on the impact of testosterone deficiency on ageing males and the effectiveness of TRT for treating hypogonadism. Published peer-reviewed articles were analyzed to evaluate the benefits and risks of TRT. Additionally, the unique challenges faced in the diagnosis and treatment of hypogonadism in a developing country were considered.

RESULTS

Testosterone replacement therapy has been shown to be an effective treatment for hypogonadism, particularly in symptomatic men with low testosterone levels. It offers potential benefits such as improvements in symptoms and overall quality of life. However, there are associated risks and side effects that need to be considered. In a developing country, challenges such as limited awareness and understanding of hypogonadism, resource constraints, and high treatment costs pose additional barriers to accessing TRT and comprehensive care.

CONCLUSION

In conclusion, TRT holds promise as a treatment for hypogonadism, but its implementation and accessibility face significant challenges in a developing country. Addressing these challenges, including raising awareness, allocating resources, and finding cost-effective solutions, is crucial for ensuring that men with hypogonadism in such settings receive appropriate diagnosis and treatment. Further research and efforts are needed to improve the management of hypogonadism in developing countries and optimize the potential benefits of TRT for affected individuals.

The role of androgens in pressure overload myocardial hypertrophy

Pressure overload hypertrophy of the left ventricle is a common result of many cardiovascular diseases. Androgens show anabolic effects in skeletal muscles, but also in myocardial hypertrophy. We carefully reviewed literature regarding possible effects of androgens on specific left ventricular hypertrophy in pressure overload conditions excluding volume overload conditions or generel sex differences.

The Similarities and Differences between the Effects of Testosterone and DHEA on the Innate and Adaptive Immune Response

Androgens are steroids that modulate various processes in the body, ranging from reproduction, metabolism, and even immune response. The main androgens are testosterone, dihydrotestosterone (DHT) and dehydroepiandrosterone (DHEA). These steroids modulate the development and function of immune response cells. Androgens are generally attributed to immunosuppressive effects; however, this is not always the case. Variations in the concentrations of these hormones induce differences in the innate, humoral, and cell-mediated immune response, which is concentration dependent. The androgens at the highest concentration in the organism that bind to the androgen receptor (AR) are DHEA and testosterone. Therefore, in this work, we review the effects of DHEA and testosterone on the immune response. The main findings of this review are that DHEA and testosterone induce similar but also opposite effects on the immune response. Both steroids promote the activation of regulatory T cells, which suppresses the Th17-type response. However, while testosterone suppresses the inflammatory response, DHEA promotes it, and this modulation is important for understanding the involvement of androgens in infectious (bacterial, viral and parasitic) and autoimmune diseases, as well as in the sexual dimorphism that occurs in these diseases.

Comorbidity of osteoporosis and Alzheimer's disease: Is `AKT `-ing on cellular glucose uptake the missing link?

Osteoporosis and Alzheimer's disease (AD) are both degenerative diseases. Osteoporosis often proceeds cognitive deficits, and multiple studies have revealed common triggers that lead to energy deficits in brain and bone. Risk factors for osteoporosis and AD, such as obesity, type 2 diabetes, aging, chemotherapy, vitamin deficiency, alcohol abuse, and apolipoprotein Eε4 and/or Il-6 gene variants, reduce cellular glucose uptake, and protective factors, such as estrogen, insulin, exercise, mammalian target of rapamycin inhibitors, hydrogen sulfide, and most phytochemicals, increase uptake. Glucose uptake is a fine-tuned process that depends on an abundance of glucose transporters (Gluts) on the cell surface. Gluts are stored in vesicles under the plasma membrane, and protective factors cause these vesicles to fuse with the membrane, resulting in presentation of Gluts on the cell surface. This translocation depends mainly on AKT kinase signaling and can be affected by a range of factors. Reduced AKT kinase signaling results in intracellular glucose deprivation, which causes endoplasmic reticulum stress and iron depletion, leading to activation of HIF-1α, the transcription factor necessary for higher Glut expression. The link between diseases and aging is a topic of growing interest. Here, we show that diseases that affect the same biochemical pathways tend to co-occur, which may explain why osteoporosis and/or diabetes are often associated with AD.

The Role of Testosterone in the Elderly: What Do We Know?

Testosterone is the most important hormone in male health. Aging is characterized by testosterone deficiency due to decreasing testosterone levels associated with low testicular production, genetic factors, adiposity, and illness. Low testosterone levels in men are associated with sexual dysfunction (low sexual desire, erectile dysfunction), reduced skeletal muscle mass and strength, decreased bone mineral density, increased cardiovascular risk and alterations of the glycometabolic profile. Testosterone replacement therapy (TRT) shows several therapeutic effects while maintaining a good safety profile in hypogonadal men. TRT restores normal levels of serum testosterone in men, increasing libido and energy level and producing beneficial effects on bone density, strength and muscle as well as yielding cardioprotective effects. Nevertheless, TRT could be contraindicated in men with untreated prostate cancer, although poor findings are reported in the literature. In addition, different potential side effects, such as polycythemia, cardiac events and obstructive sleep apnea, should be monitored. The aim of our review is to provide an updated background regarding the pros and cons of TRT, evaluating its role and its clinical applicability in different domains.

The Role of Testosterone in the Elderly: What Do We Know?

Testosterone is the most important hormone in male health. Aging is characterized by testosterone deficiency due to decreasing testosterone levels associated with low testicular production, genetic factors, adiposity, and illness. Low testosterone levels in men are associated with sexual dysfunction (low sexual desire, erectile dysfunction), reduced skeletal muscle mass and strength, decreased bone mineral density, increased cardiovascular risk and alterations of the glycometabolic profile. Testosterone replacement therapy (TRT) shows several therapeutic effects while maintaining a good safety profile in hypogonadal men. TRT restores normal levels of serum testosterone in men, increasing libido and energy level and producing beneficial effects on bone density, strength and muscle as well as yielding cardioprotective effects. Nevertheless, TRT could be contraindicated in men with untreated prostate cancer, although poor findings are reported in the literature. In addition, different potential side effects, such as polycythemia, cardiac events and obstructive sleep apnea, should be monitored. The aim of our review is to provide an updated background regarding the pros and cons of TRT, evaluating its role and its clinical applicability in different domains.

Targeted activation of androgen receptor signaling in the periosteum improves bone fracture repair

Low testosterone level is an independent predictor of osteoporotic fracture in elderly men as well as increased fracture risk in men undergoing androgen deprivation. Androgens and androgen receptor (AR) actions are essential for bone development and homeostasis but their linkage to fracture repair remains unclear. Here we found that AR is highly expressed in the periosteum cells and is co-localized with a mesenchymal progenitor cell marker, paired-related homeobox protein 1 (Prrx1), during bone fracture repair. Mice lacking the AR gene in the periosteum expressing Prrx1-cre (AR^-/Y;Prrx1::Cre) but not in the chondrocytes (AR^-/Y;Col-2::Cre) exhibits reduced callus size and new bone volume. Gene expression data analysis revealed that the expression of several collagens, integrins and cell adhesion molecules were downregulated in periosteum-derived progenitor cells (PDCs) from AR^-/Y;Prrx1::Cre mice. Mechanistically, androgens-AR signaling activates the AR/ARA55/FAK complex and induces the collagen-integrin α2β1 gene expression that is required for promoting the AR-mediated PDCs migration. Using mouse cortical-defect and femoral graft transplantation models, we proved that elimination of AR in periosteum of host mice impairs fracture healing, regardless of AR existence of transplanted donor graft. While testosterone implanted scaffolds failed to complete callus bridging across the fracture gap in AR^-/Y;Prrx1::Cre mice, cell-based transplantation using DPCs re-expressing AR could lead to rescue bone repair. In conclusion, targeting androgen/AR axis in the periosteum may provide a novel therapy approach to improve fracture healing.

Interaction between Non-Coding RNAs and Androgen Receptor with an Especial Focus on Prostate Cancer

The androgen receptor (AR) is a member of the nuclear receptor superfamily and has three functional domains, namely the N-terminal, DNA binding, and C-terminal domain. The N-terminal domain harbors potent transactivation functions, whereas the C-terminal domain binds to androgens and antiandrogens used to treat prostate cancer. AR has genomic activity being DNA binding-dependent or through interaction with other DNA-bound transcription factors, as well as a number of non-genomic, non-canonical functions, such as the activation of the ERK, AKT, and MAPK pathways. A bulk of evidence indicates that non-coding RNAs have functional interactions with AR. This type of interaction is implicated in the pathogenesis of human malignancies, particularly prostate cancer. In the current review, we summarize the available data on the role of microRNAs, long non-coding RNAs, and circular RNAs on the expression of AR and modulation of AR signaling, as well as the effects of AR on their expression. Recognition of the complicated interaction between non-coding RNAs and AR has practical importance in the design of novel treatment options, as well as modulation of response to conventional therapeutics.

Androgen-induced epigenetic modulations in the ovary

In recent years, androgens have emerged as critical regulators of female reproduction and women's health in general. While high levels of androgens in women are associated with polycystic ovary syndrome (PCOS), recent evidence suggests that a certain amount of direct androgen action through androgen receptor is also essential for normal ovarian function. Moreover, prenatal androgen exposure has been reported to cause developmental reprogramming of the fetus that manifests into adult pathologies, supporting the Developmental Origins of Health and Disease (DOHaD) hypothesis. Therefore, it has become imperative to understand the underlying mechanism of androgen actions and its downstream effects under normal and pathophysiological conditions. Over the years, there has been a lot of studies on androgen receptor function as a transcriptional regulator in the nucleus as well as androgen-induced rapid extra-nuclear signaling. Conversely, new evidence suggests that androgen actions may also be mediated through epigenetic modulation involving both the nuclear and extra-nuclear androgen signaling. This review focuses on androgen-induced epigenetic modifications in female reproduction, specifically in the ovary, and discusses emerging concepts, latest perceptions, and highlight the areas that need further investigation.

Role of androgen and microRNA in triple-negative breast cancer

Breast cancer (BC) is the most frequent type of malignancy affecting females worldwide. Molecular-based studies resulted in an identification of at least four subtypes of breast carcinoma, including luminal A and luminal B, Human growth factor receptor (HER-2)-enriched and triple-negative tumors (basal-like and normal breast-like). A proportion of BC cases are of the triple-negative breast cancer (TNBC) type. TNBC lacks the expression of estrogen receptor (ER), progesterone receptor (PR), and HER-2, and is known to express androgen receptor (AR) at considerable levels. AR has been shown to promote the progression of TNBC. However, the exact mechanisms have yet to be unraveled. One of these mechanisms could be through regulating the expression of microRNA (miRNA) molecules, which play an important regulatory role in BC through post-transcriptional gene silencing. Activation of AR controls the expression of miRNA molecules, which target selective mRNAs, consequently, affecting protein expression. In this review we attempt to elucidate the relations between AR and miRNA in TNBC.

Activation of GPR56, a novel adhesion GPCR, is necessary for nuclear androgen receptor signaling in prostate cells

The androgen receptor (AR) is activated in patients with castration resistant prostate cancer (CRPC) despite low circulating levels of androgen, suggesting that intracellular signaling pathways and non-androgenic factors may contribute to AR activation. Many G-protein coupled receptors (GPCR) and their ligands are also activated in these cells indicating that they may play a role in development of Prostate Cancer (PCa) and CRPC. Although a cross talk has been suggested between the two pathways, yet, the identity of GPCRs which may play a role in androgen signaling, is not established yet. By using blast analysis of 826 GPCRs, we identified a GPCR, GPCR 205, which exhibited maximum similarity with the ligand binding domain of the AR. We demonstrate that adhesion GPCR 205, also known as GPR56, can be activated by androgens to stimulate the Rho signaling pathway, a pathway that plays an important role in prostate tumor cell metastasis. Testosterone stimulation of GPR56 also activates the cAMP/ Protein kinase A (PKA) pathway, that is necessary for AR signaling. Knocking down the expression of GPR56 using siRNA, disrupts nuclear translocation of AR and transcription of prototypic AR target genes such as PSA. GPR56 expression is higher in all twenty-five prostate tumor patient’s samples tested and cells expressing GPR56 exhibit increased proliferation. These findings provide new insights about androgen signaling and identify GPR56 as a possible therapeutic target in advanced prostate cancer patients.

Androgen and Androgen Receptors as Regulators of Monocyte and Macrophage Biology in the Healthy and Diseased Lung

Androgens, the predominant male sex hormones, drive the development and maintenance of male characteristics by binding to androgen receptor (AR). As androgens are systemically distributed throughout the whole organism, they affect many tissues and cell types in addition to those in male sexual organs. It is now clear that the immune system is a target of androgen action. In the lungs, many immune cells express ARs and are responsive to androgens. In this review, we describe the effects of androgens and ARs on lung myeloid immune cells-monocytes and macrophages-as they relate to health and disease. In particular, we highlight the effect of androgens on lung diseases, such as asthma, chronic obstructive pulmonary disease and lung fibrosis. We also discuss the therapeutic use of androgens and how circulating androgens correlate with lung disease. In addition to human studies, we also discuss how mouse models have helped to uncover the effect of androgens on monocytes and macrophages in lung disease. Although the role of estrogen and other female hormones has been broadly analyzed in the literature, we focus on the new perspectives of androgens as modulators of the immune system that target myeloid cells during lung inflammation.

Lack of influence of sex hormones on Brugada syndrome-associated mutant Nav1.5 sodium channel

Brugada syndrome (BS) is an autosomal dominant disease. The most common causes of BS are loss-of-function mutations occur in the SCN5A gene which encodes the sodium channel protein Nav1.5. BS has a higher incidence rate in males and the underlying mechanisms of the gender inequality are not yet fully understood. Considering sex hormones are among the most important factors behind gender differences and have previously been shown to regulate the activity of multiple cardiac ion channels, we hypothesized that sex hormones also affect Nav1.5 function which lead to BS predominantly affecting males. In this study, we investigate the protein expression level and current of Nav1.5 in the HEK293 cells cotransfected with SCN5A and sex hormone receptor plasmids using both wild-type SCN5A and BS-associated SCN5A channel mutants R878C and R104W. Our findings showed that sex hormones have no effects on the protein expression level and current of the wild-type Nav1.5, neither does it affect the protein expression level and current of BS-associated Nav1.5 mutants R878C and R104W, regardless of homozygous or heterozygous state. Our results suggest that the male preponderance of BS does not arise from the effects of the sex hormones on Nav1.5. Further studies are needed to explain the male preponderance of this disease.

Development of selective androgen receptor modulators (SARMs)

The Androgen Receptor (AR), a member of the steroid hormone receptor family, plays important roles in the physiology and pathology of diverse tissues. AR ligands, which include circulating testosterone and locally synthesized dihydrotestosterone, bind to and activate the AR to elicit their effects. Ubiquitous expression of the AR, metabolism and cross reactivity with other receptors limit broad therapeutic utilization of steroidal androgens. However, the discovery of selective androgen receptor modulators (SARMs) and other tissue-selective nuclear hormone receptor modulators that activate their cognate receptors in a tissue-selective manner provides an opportunity to promote the beneficial effects of androgens and other hormones in target tissues with greatly reduced unwanted side-effects. In the last two decades, significant resources have been dedicated to the discovery and biological characterization of SARMs in an effort to harness the untapped potential of the AR. SARMs have been proposed as treatments of choice for various diseases, including muscle-wasting, breast cancer, and osteoporosis. This review provides insight into the evolution of SARMs from proof-of-concept agents to the cusp of therapeutic use in less than two decades, while covering contemporary views of their mechanisms of action and therapeutic benefits.

Dihydrotestosterone, a robust promoter of osteoblastic proliferation and differentiation: understanding of time-mannered and dose-dependent control of bone forming cells

Objective(s):

The present study was aimed to evaluate the time-mannered and dose-dependent effects of 5α-dihydrotestosterone (5α-DHT) on the proliferation and differentiation of bone forming cells using MC3T3-E1 cells.

Materials and Methods:

Cell proliferation was analyzed using MTS and phase contrast microscopic assays. Osteogenic differentiation was assessed through a series of in vitro experiments including crystal violet staining, alkaline phosphatase (ALP) activity, and Van Gieson (VG) staining. Taken together, the efficiency of bone mineralization was examined by using alizarin red s (ARS) staining, Von Kossa staining, scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) analysis.

Results:

The resulting data revealed that 5α-DHT exhibits promising potential particularly at a dose of 0.1 ng/ml, in promoting the growth of MC3T3-E1 cells compared to the control group (CN). Moreover, a significantly higher ALP activity was evident in the experimental group treated with 5α-DHT compared to the CN group at various time intervals. MC3T3-E1 cells treated with 5α-DHT also expressed a remarkably higher collagen deposition and mineralization (calcium and phosphate contents) compared to the CN group at various time intervals.

Conclusion:

Conclusively, we suggest that 5α-DHT exhibits outstanding potential of promoting proliferation and differentiation in osteoblasts which could be the in vitro basis for the efficacy of 5α-DHT in the treatment of androgen-deficient male osteoporosis.

The RhoGAP Myo9b Promotes Bone Growth by Mediating Osteoblastic Responsiveness to IGF-1

The Ras homolog A (RhoA) subfamily of Rho guanosine triphosphatases (GTPases) regulates actin-based cellular functions in bone such as differentiation, migration, and mechanotransduction. Polymorphisms or genetic ablation of RHOA and some of its regulatory guanine exchange factors (GEFs) have been linked to poor bone health in humans and mice, but the effects of RhoA-specific GTPase-activating proteins (GAPs) on bone quality have not yet been identified. Therefore, we examined the consequences of RhoGAP Myo9b gene knockout on bone growth, phenotype, and cellular activity. Male and female mice lacking both alleles demonstrated growth retardation and decreased bone formation rates during early puberty. These mice had smaller, weaker bones by 4 weeks of age, but only female KOs had altered cellular numbers, with fewer osteoblasts and more osteoclasts. By 12 weeks of age, bone quality in KOs worsened. In contrast, 4-week-old heterozygotes demonstrated bone defects that resolved by 12 weeks of age. Throughout, Myo9b ablation affected females more than males. Osteoclast activity appeared unaffected. In primary osteogenic cells, Myo9b was distributed in stress fibers and focal adhesions, and its absence resulted in poor spreading and eventual detachment from culture dishes. Similarly, MC3T3-E1 preosteoblasts with transiently suppressed Myo9b levels spread poorly and contained decreased numbers of focal adhesions. These cells also demonstrated reduced ability to undergo IGF-1-induced spreading or chemotaxis toward IGF-1, though responses to PDGF and BMP-2 were unaffected. IGF-1 receptor (IGF1R) activation was normal in cells with diminished Myo9b levels, but the activated receptor was redistributed from stress fibers and focal adhesions into nuclei, potentially affecting receptor accessibility and gene expression. These results demonstrate that Myo9b regulates a subset of RhoA-activated processes necessary for IGF-1 responsiveness in osteogenic cells, and is critical for normal bone formation in growing mice. © 2017 American Society for Bone and Mineral Research.

Identified molecular mechanism of interaction between environmental risk factors and differential expression genes in cartilage of Kashin-Beck disease

As environmental risk factors (ERFs) play an important role in the pathogenesis of Kashin-Beck disease (KBD), it is important to identify the interaction between ERFs and differentially expression genes (DEGs) in KBD. The environmental response genes (ERGs) were analyzed in cartilage of KBD in comparison to normal controls.We searched 5 English and 3 Chinese databases from inception to September 2015, to identify case-control studies that examined ERFs for KBD using integrative meta-analysis and systematic review. Total RNA was isolated from articular cartilage of KBD patients and healthy controls. Human whole genome microarray chip (Agilent) was used to analyze the amplified, labeled, and hybridized total RNA, and the validated microarray data were partially verified using real-time quantitative polymerase chain reaction (qRT-PCR). The ERGs were derived from the Comparative Toxicogenomics Database. The identified ERGs were subjected to KEGG pathway enrichment, biological process (BP), and interaction network analyses using the Database for Annotation, Visualization and Integrated Discovery (DAVID) v6.7, and STRING.The trace elements (selenium and iodine), vitamin E, and polluted grains (T-2 toxin/HT-2 toxin, deoxynivalenol, and nivalenol) were identified as the ERFs for KBD using meta-analysis and review. We identified 21 upregulated ERGs and 7 downregulated ERGs in cartilage with KBD compared with healthy controls, which involved in apoptosis, metabolism, and growth and development. KEGG pathway enrichment analysis found that 2 significant pathways were involved with PI3K-Akt signaling pathway and P53 signaling pathway, and gene ontology function analysis found 3 BPs involved with apoptosis, death, and cell death in KBD cartilage.According to previous results and our own research, we suggest that the trace element selenium and vitamin E induce PI3K-Akt signaling pathway and the mycotoxins (T-2 toxin/HT-2 toxin and DON) induce P53 signaling pathway, contributing to the development of KBD, and chondrocyte apoptosis and cell death.

Androgen receptor (AR) in cardiovascular diseases

Cardiovascular diseases (CVDs) are still the highest leading cause of death worldwide. Several risk factors have been linked to CVDs, including smoking, diabetes, hyperlipidemia, and gender among others. Sex hormones, especially the androgen and its receptor, androgen receptor (AR), have been linked to many diseases with a clear gender difference. Here, we summarize the effects of androgen/AR on CVDs, including hypertension, stroke, atherosclerosis, abdominal aortic aneurysm (AAA), myocardial hypertrophy, and heart failure, as well as the metabolic syndrome/diabetes and their impacts on CVDs. Androgen/AR signaling exacerbates hypertension, and anti-androgens may suppress hypertension. Androgen/AR signaling plays dual roles in strokes, depending on different kinds of factors; however, generally males have a higher incidence of strokes than females. Androgen and AR differentially modulate atherosclerosis. Androgen deficiency causes elevated lipid accumulation to enhance atherosclerosis; however, targeting AR in selective cells without altering serum androgen levels would suppress atherosclerosis progression. Androgen/AR signaling is crucial in AAA development and progression, and targeting androgen/AR profoundly restricts AAA progression. Men have increased cardiac hypertrophy compared with age-matched women that may be due to androgens. Finally, androgen/AR plays important roles in contributing to obesity and insulin/leptin resistance to increase the metabolic syndrome.

Genetic influence on the association between bone mineral density and testosterone in Korean men

Low bone mineral density (BMD) leads to an increased risk of osteoporotic fracture. Total testosterone and free testosterone were positively associated with BMD, which was significantly influenced by the additive genetic effects.

INTRODUCTION

This cross-sectional study aimed to evaluate an association between testosterone and BMD and the influence of genetic factors on the association.

METHODS

Study subjects were 1070 Korean men including 144 pairs of monozygotic twins and their family members. Levels of serum total testosterone and sex hormone binding globulin (SHBG) were measured by chemiluminescence immunoassay. Calculated free testosterone (cFT) was then determined using Vermeulen's method. BMDs of the whole body and specific regions were measured using dual-energy X-ray absorptiometry.

RESULTS

Linear mixed regression analyses showed that total testosterone and cFT were positively associated with BMD at most regions, after considering intra-familial relationship and covariates including fat mass, lean mass, and SHBG. SHBG had an inverse association with BMD at the pelvis but not with the BMD at other regions after adjusting for all covariates and cFT. Co-twin control analysis in monozygotic twins found no association between pairwise difference of testosterone and pairwise difference of BMD. Bivariate variance component analysis showed that both total testosterone and cFT had a significant positive additive genetic correlation with BMD at rib, spine, and arm, whereas SHBG had no significant genetic correlation with BMD. Inverse environmental correlations were seen between total testosterone and BMDs at the lumbar spine and arm.

CONCLUSIONS

This Korean twin and family study showed that both total testosterone and free testosterone were positively associated with BMD and that genetic effects were significant on the association between testosterone and BMD.

Androgen receptor non-nuclear regulation of prostate cancer cell invasion mediated by Src and matriptase

Castration-resistant prostate cancers still depend on nuclear androgen receptor (AR) function despite their lack of dependence on exogenous androgen. Second generation anti-androgen therapies are more efficient at blocking nuclear AR; however resistant tumors still develop. Recent studies indicate Src is highly active in these resistant tumors. By manipulating AR activity in several different prostate cancer cell lines through RNAi, drug treatment, and the use of a nuclear-deficient AR mutant, we demonstrate that androgen acting on cytoplasmic AR rapidly stimulates Src tyrosine kinase via a non-genomic mechanism. Cytoplasmic AR, acting through Src enhances laminin integrin-dependent invasion. Active Matriptase, which cleaves laminin, is elevated within minutes after androgen stimulation, and is subsequently shed into the medium. Matriptase activation and shedding induced by cytoplasmic AR is dependent on Src. Concomitantly, CDCP1/gp140, a Matriptase and Src substrate that controls integrin-based migration, is activated. However, only inhibition of Matriptase, but not CDCP1, suppresses the AR/Src-dependent increase in invasion. Matriptase, present in conditioned medium from AR-stimulated cells, is sufficient to enhance invasion in the absence of androgen. Thus, invasion is stimulated by a rapid but sustained increase in Src activity, mediated non-genomically by cytoplasmic AR, leading to rapid activation and shedding of the laminin protease Matriptase.

Immunoelectron microscope localization of androgen receptors and proliferating cell nuclear antigen in the epithelial cells of albino rat ventral prostate

Androgen receptor (AR) and proliferating cell nuclear antigen (PCNA) play a crucial role in development and progression of various prostatic diseases including prostatic carcinoma that is a leading cause of death in males. Previous studies have evaluated the expression pattern of AR and PCNA in prostate epithelial cells using immunohistochemistry (IHC). However, this technique has limited ability to identify their precise subcellular localization. Therefore, the aim of this study was to localize, subcellularly, AR and PCNA in the secretory epithelial cells of rat ventral prostate using post embedding immunogold-electron microscopy. The ventral lobes were dissected from six adult male albino rats after being perfused with paraformaldehyde. Some specimens were immuno-labeled with AR or PCNA and others were processed for immuno-electron microscope of AR and PCNA using 15-nm gold conjugated secondary antibodies. The results showed that, by immunoperoxidase reaction, AR and PCNA were localized diffusely throughout the nuclei of the epithelial cells of prostatic acini without visible cytoplasmic expression. However, the higher resolution immuno-electron microscopy was able to detect AR and PCNA in the nucleus and some cytoplasmic organelles. In conclusion, this study emphasizes the importance of immuno-electron microscopy in precise localization of AR and PCNA at the subcelullar levels in the secretory epithelial cells of the rat prostatic acini. These findings will help to further understand the mechanism of action of these receptors under normal and pathological conditions that could have future clinical application after careful human investigation.

Human androgen deficiency: insights gained from androgen receptor knockout mouse models

The mechanism of androgen action is complex. Recently, significant advances have been made into our understanding of how androgens act via the androgen receptor (AR) through the use of genetically modified mouse models. A number of global and tissue-specific AR knockout (ARKO) models have been generated using the Cre-loxP system which allows tissue- and/or cell-specific deletion. These ARKO models have examined a number of sites of androgen action including the cardiovascular system, the immune and hemopoetic system, bone, muscle, adipose tissue, the prostate and the brain. This review focuses on the insights that have been gained into human androgen deficiency through the use of ARKO mouse models at each of these sites of action, and highlights the strengths and limitations of these Cre-loxP mouse models that should be considered to ensure accurate interpretation of the phenotype.

Involvement of androgens in ovarian health and disease

In women, ovary and adrenal gland produce androgens. Androgens are essential drivers of the primordial to antral follicle development, prior to serving as substrate for estrogen production in the later stages of folliculogenesis. Androgens play a crucial role in the follicular-stromal intertalk by fine tuning the extracellular matrix and vessel content of the ovarian stroma. Local auto-and paracrine factors regulate androgen synthesis in the pre-antral follicle. Androgen excess is a hallmark of polycystic ovary syndrome and is a key contributor in the exaggerated antral follicle formation, stromal hyperplasia and hypervascularity. Hyperandrogenaemia overrides the follicular-stromal dialog, resulting in follicular arrest and disturbed ovulation. On the other hand, androgen deficiency is likely to have a negative impact on fertility as well, and further research is needed to examine the benefits of androgen-replacement therapy in subfertility.

Androgen receptor (AR) pathophysiological roles in androgen-related diseases in skin, bone/muscle, metabolic syndrome and neuron/immune systems: lessons learned from mice lacking AR in specific cells

The androgen receptor (AR) is expressed ubiquitously and plays a variety of roles in a vast number of physiological and pathophysiological processes. Recent studies of AR knockout (ARKO) mouse models, particularly the cell type- or tissue-specific ARKO models, have uncovered many AR cell type- or tissue-specific pathophysiological roles in mice, which otherwise would not be delineated from conventional castration and androgen insensitivity syndrome studies. Thus, the AR in various specific cell types plays pivotal roles in production and maturation of immune cells, bone mineralization, and muscle growth. In metabolism, the ARs in brain, particularly in the hypothalamus, and the liver appear to participate in regulation of insulin sensitivity and glucose homeostasis. The AR also plays key roles in cutaneous wound healing and cardiovascular diseases, including atherosclerosis and abdominal aortic aneurysm. This article will discuss the results obtained from the total, cell type-, or tissue-specific ARKO models. The understanding of AR cell type- or tissue-specific physiological and pathophysiological roles using these in vivo mouse models will provide useful information in uncovering AR roles in humans and eventually help us to develop better therapies via targeting the AR or its downstream signaling molecules to combat androgen/AR-related diseases.

Testosterone delivered with a scaffold is as effective as bone morphologic protein-2 in promoting the repair of critical-size segmental defect of femoral bone in mice

Loss of large bone segments due to fracture resulting from trauma or tumor removal is a common clinical problem. The goal of this study was to evaluate the use of scaffolds containing testosterone, bone morphogenetic protein-2 (BMP-2), or a combination of both for treatment of critical-size segmental bone defects in mice. A 2.5-mm wide osteotomy was created on the left femur of wildtype and androgen receptor knockout (ARKO) mice. Testosterone, BMP-2, or both were delivered locally using a scaffold that bridged the fracture. Results of X-ray imaging showed that in both wildtype and ARKO mice, BMP-2 treatment induced callus formation within 14 days after initiation of the treatment. Testosterone treatment also induced callus formation within 14 days in wildtype but not in ARKO mice. Micro-computed tomography and histological examinations revealed that testosterone treatment caused similar degrees of callus formation as BMP-2 treatment in wildtype mice, but had no such effect in ARKO mice, suggesting that the androgen receptor is required for testosterone to initiate fracture healing. These results demonstrate that testosterone is as effective as BMP-2 in promoting the healing of critical-size segmental defects and that combination therapy with testosterone and BMP-2 is superior to single therapy. Results of this study may provide a foundation to develop a cost effective and efficient therapeutic modality for treatment of bone fractures with segmental defects.

Androgen receptor decreases the cytotoxic effects of chemotherapeutic drugs in upper urinary tract urothelial carcinoma cells

Upper urinary tract urothelial carcinomas (UUTUCs) represent relatively uncommon yet devastating tumors that affect more males than females. However, the correlation between gender difference and disease progression remains unclear. Androgen and the androgen receptor (AR) were previously hypothesized to account for the gender difference in the incidence of urothelial carcinomas; however, the role of AR in the development and progression of UUTUCs is not well understood. In addition, although UUTUCs are responsive to chemotherapy, various responses are presented among patients. Therefore, the aim of the present study was to determine the role of AR in the response of UUTUC cells to chemotherapeutic drugs. In this study, AR overexpression in UUTUC cells (BFTC 909) was identified to reduce the cytotoxic effect of chemotherapeutic drugs, including doxorubicin, cisplatin and mitomycin C and protected cells from drug-induced death. The expression of ABCG2, an ATP-binding cassette half-transporter associated with multidrug resistance, was increased in AR-overexpressing BFTC cells. In addition, use of the AR degradation enhancer, ASC-J9^®, repressed the AR effect on increasing cell viability under drug treatment. In summary, results of the present study indicate that the status of AR expression levels in UUTUCs may be a significant factor in affecting the efficacy of chemotherapy and classic chemotherapeutic drugs and AR targeted therapy may provide a novel potential therapeutic approach to improve treatment of UUTUCs.

Effects of low-dose testosterone undecanoate treatment on bone mineral density and bone turnover markers in elderly male osteoporosis with low serum testosterone

This prospective 2-year, single-center, randomized, placebo-controlled, open-label clinical trial was performed to evaluate the efficacy of low-dose testosterone undecanoate (TU) treatment on bone mineral density (BMD) and biochemical markers of bone turnover in elderly male osteoporosis with low serum testosterone. A total of 186 elderly male osteoporosis patients with low serum testosterone were randomized into three groups: low-dose TU (20 mg, per day), standard-dose TU (40 mg, per day), and placebo group with a 24-month followup. Since the 6th month in standard-dose TU group or since the 12th month followup in low-dose TU group and throughout the study, lumbar spine and femoral neck BMD and serum levels of free testosterone, estradiol, and bone alkaline phosphatase significantly increased. There were no significant differences between groups of low-dose TU and standard dose TU in the percentage of changes of these data since the 18th month followup and throughout the study. No side effects on prostate glands including prostate specific antigen were found. In conclusion, low-dose TU (20 mg, per day) may be a cost effective and safe protocol for treating elderly male osteoporosis with low serum testosterone.

Exploring the cyclooxygenase 2 (COX2)/15d-Δ(12,14)PGJ(2) system in hamster Sertoli cells: regulation by FSH/testosterone and relevance to glucose uptake

We have previously described a stimulatory effect of testosterone on cyclooxygenase 2 (COX2) expression and prostaglandin (PG) synthesis, and the involvement of PGs in the modulation of testosterone production in Leydig cells of the seasonal breeder Syrian hamster. In this study, we investigated the existence of a COX2/PGs system in hamster Sertoli cells, its regulation by testosterone and FSH, and its effect on glucose uptake. COX2 expression was observed in Sertoli cells of both reproductively active and inactive adult hamsters. Testosterone and the plasma membrane-impermeable testosterone-BSA significantly induced COX2 expression, mitogen activated protein kinases 1/2 (MAPK1/2) phosphorylation and 15d-Δ(12,14)PGJ(2) production in Sertoli cells purified from photoperiodically regressed hamsters. These actions were abolished by the antiandrogen bicalutamide and by the inhibitor of MAPK kinase (MEK1/2) U0126, suggesting that testosterone exerts its stimulatory effect on COX2/PGs through a non-classical mechanism that involves the presence of androgen receptors and MAPK1/2 activation. FSH also stimulated COX2/PGs via MAPK1/2 phosphorylation. FSH and testosterone stimulate, whereas 15d-Δ(12,14)PGJ(2) via PPARγ inhibits, [2,6-(3)H]-2-deoxy-d-glucose ([(3)H]-2-DOG) uptake. Meloxicam, a selective COX2 inhibitor, further increases [(3)H]-2-DOG uptake in the presence of FSH or testosterone. Thus, in addition to their positive effect, FSH and testosterone may also exert an indirect negative regulation on glucose uptake which involves the COX2/15d-Δ(12,14)PGJ(2)/PPARγ system. Overall, these results demonstrate the presence of a COX2/PG system in hamster Sertoli cells which might act as a local modulator of FSH and testosterone actions.

Sex steroids and bone health status in men

Male osteoporosis is a health problem which deserves more attention as nearly 30% of osteoporotic fractures happen in men aged 50 years and above. Although men do not experience an accelerated bone loss phase and testosterone deficiency is not a universal characteristic for aged men, osteoporosis due to age-related testosterone deficiency does have a negative impact on bone health status of men. Observations from epidemiological studies indicate that elderly men with higher testosterone can preserve their BMD better and thus are less prone to fracture. Observations on men with estrogen resistance or aromatase deficiency indicate that estrogen is equally important in the maintenance of bone health status. This had been validated in several epidemiological studies which found that the relationships between estrogen and bone health indices are significant and sometimes stronger than testosterone. Studies on the relationship between quantitative ultrasound and bone remodeling markers suggest that testosterone and estrogen may have differential effects on bone, but further evidence was needed. In conclusion, both testosterone and estrogen are important in the maintenance of bone health in men.

Activation of the PI3K/Akt signaling pathway through P2Y₂ receptors by extracellular ATP is involved in osteoblastic cell proliferation

We studied the PI3K/Akt signaling pathway modulation and its involvement in the stimulation of ROS 17/2.8 osteoblast-like cell proliferation by extracellular ATP. A dose- and time-dependent increase in Akt-Ser 473 phosphorylation (p-Akt) was observed. p-Akt was increased by ATPγS and UTP, but not by ADPβS. Akt activation was abolished by PI3K inhibitors and reduced by inhibitors of PI-PLC, Src, calmodulin (CaM) but not of CaMK. p-Akt was diminished by cell incubation in a Ca²⁺-free medium but not by the use of L-type calcium channel blockers. The rise in intracellular Ca²⁺ induced by ATP was potentiated in the presence of Ro318220, a PKC inhibitor, and attenuated by the TPA, a known activator of PKC. ATP-dependent p-Akt was diminished by TPA and augmented by Ro318220 treatment in a Ca²⁺-containing but not in a Ca²⁺-free medium. ATP stimulated the proliferation of both ROS 17/2.8 cells and rat osteoblasts through PI3K/Akt. In the primary osteoblasts, ATP induces alkaline phosphatase activity via PI3K, suggesting that the nucleotide promotes osteoblast differentiation. These results suggest that ATP stimulates osteoblast proliferation through PI-PLC linked-P2Y₂ receptors and PI3K/Akt pathway activation involving Ca²⁺, CaM and Src. PKC seems to regulate Akt activation through Src and the Ca²⁺ influx/CaM pathway.

The reduced trabecular bone mass of adult ARKO male mice results from the decreased osteogenic differentiation of bone marrow stroma cells

Male mice with androgen receptor knock-out (ARKO) show significant bone loss at a young age. However, the lasting effect of AR inactivation on bone in aging male mice remains unclear. We designed this study to evaluate the effect of AR on bone quality in aging male mice and to find the possible causes of AR inactivation contributing to the bone loss. The mice were grouped according to their ages and AR status and their trabecular bones were examined by micro-CT analysis at 6, 12, 18, and 30 weeks old. We found that bone mass consistently decreased and the bone microarchitectures continuously deteriorated in male ARKO mice at designated time points. To determine the cause of the bone loss in ARKO mice, we further examined the role of AR in bone cell fate decision and differentiation and we conducted experiments on bone marrow stromal cells (BMSC) obtained from wild type (WT) and AR knockout (KO) mice. We found that ARKO mice had higher numbers of colony formation unit-fibroblast (CFU-F), and CD44 and CD34 positive cells in bone marrow than WT mice. Our Q-RT-PCR results showed lower expression of genes linked to osteogenesis in BMSCs isolated from ARKO mice. In conclusion, AR nullification disrupted bone microarchitecture and caused trabecular bone mass loss in male ARKO mice. And the fate of BMSCs was impacted by the loss of AR. Therefore, these findings suggest that AR may accelerate the use of progenitor cells and direct them into osteogenic differentiation to affect bone metabolism.

Direct transcriptional targets of sex steroid hormones in bone

The sex steroid hormones, androgens and estrogens, via their respective nuclear receptors, regulate bone mineral density in humans and mice. Very little is known about the direct targets of the androgen and estrogen receptors in bone cells. First, models of hormone and receptor deficiency in mouse and human bone are discussed. This review then focuses on the direct targets of the receptors in osteoblasts and osteoclasts. A direct target of a NR is defined here as a gene that is regulated by NR binding to the DNA (either through DNA binding or association with a DNA binding protein) at an enhancer or promoter of that gene. The experimental evidence that illustrates androgen and estrogen gene regulation in osteoblasts and osteoclasts will be summarized and compared with the phenotype of the hormones in vivo.

GPRC6A mediates the non-genomic effects of steroids

The identity of the putative G-protein coupled receptor (GPCR) that mediates the non-genomic effects of androgens is unknown. We present in vitro and in vivo evidence that the orphan GPRC6A receptor, a widely expressed calcium and amino acid sensing GPCR, transduces the non-genomic effects of testosterone and other steroids. Overexpression of GPRC6A imparts the ability of extracellular testosterone to illicit a rapid, non-genomic signaling response in HEK-293 cells lacking the androgen receptor. Conversely, testosterone-stimulated rapid signaling and phosphorylation of ERK is attenuated in bone marrow stromal cells derived from GPRC6A(-/-) mice and in 22Rv1 prostate cancer cells after siRNA-mediated knockdown of GPRC6A. Compared with wild-type controls, GPRC6A(-/-) null mice exhibit significantly less ERK activation and Egr-1 expression in both bone marrow and testis in response to pharmacological doses of testosterone in vivo. In addition, testosterone administration results in suppression of luteinizing hormone in wild-type male mice, but paradoxically stimulates serum luteinizing hormone levels in GPRC6A(-/-) null mice. These results suggest that GPRC6A is functionally important in regulating non-genomic effects of androgens in multiple tissues.

Bisphenol A interferes with synaptic remodeling

The potential adverse effects of Bisphenol A (BPA), a synthetic xenoestrogen, have long been debated. Although standard toxicology tests have revealed no harmful effects, recent research highlighted what was missed so far: BPA-induced alterations in the nervous system. Since 2004, our laboratory has been investigating one of the central effects of BPA, which is interference with gonadal steroid-induced synaptogenesis and the resulting loss of spine synapses. We have shown in both rats and nonhuman primates that BPA completely negates the ∼ 70-100% increase in the number of hippocampal and prefrontal spine synapses induced by both estrogens and androgens. Synaptic loss of this magnitude may have significant consequences, potentially causing cognitive decline, depression, and schizophrenia, to mention those that our laboratory has shown to be associated with synaptic loss. Finally, we discuss why children may particularly be vulnerable to BPA, which represents future direction of research in our laboratory.

Testosterone induces redistribution of forkhead box-3a and down-regulation of growth and differentiation factor 9 messenger ribonucleic acid expression at early stage of mouse folliculogenesis

Increasing evidence has shown that excess androgen may be a main cause of polycystic ovary syndrome (PCOS). However, the molecular mechanism of androgen action on the ovary is unclear. To investigate the possible impacts of androgen on early follicular development, neonatal mouse ovaries mainly containing primordial follicles were cultured with testosterone. We demonstrated that the number of primary follicles was increased after 10 d culture with testosterone treatment via phosphatidylinositol 3-kinase/Akt pathway. Androgen induced Forkhead box (Foxo)-3a activation, and translocation of Foxo3a protein from oocyte nuclei to cytoplasm, which might be a key step for primordial follicle activation. Interestingly, testosterone was also capable of down-regulating growth and differentiation factor-9 expression via its receptor. In summary, we infer that intraovarian excess androgen in PCOS might result in excess early follicles by inducing oocyte Foxo3a translocation and follicular arrest by down-regulating growth and differentiation factor-9 expression.

Specific involvement of glycogen synthase kinase-3 in the function and activity of sex steroid hormone receptors reveals the complexity of their regulation

Protein kinases represent key nodes for the integration of multiple intracellular signalling pathways, resulting in modulation of both ligand-dependent and ligand-independent mechanisms of sex steroid receptor (sSR) signalling cascades. The proline-directed Ser/Thr kinases including mitogen-activated protein kinases and cyclin dependent kinases were especially reported to contribute to the function and activity of sSRs. The relevant effects of these kinases are well-documented but the impact of glycogen synthase kinase-3 (GSK-3), another member of this kinase family, has been underestimated. Indeed, the specific role of GSK-3 regarding the different sSRs will help to understand further the complexity of sSR signalling. So far, AR and ERalpha were identified as GSK-3 substrates. Additionally, the docking properties of GSK-3 were demonstrated to play a crucial role in sSR signal transduction. Reciprocally, GSK-3 was described as a potential target of non-genomic effects of sSRs. Therefore, GSK-3 regulates and is regulated by sSRs. This review focuses on the emerging and promising involvements of GSK-3 regarding the signalling cascade of the respective sSRs. This review represents a necessary complement of information to highlight the importance of GSK-3 regarding sSR function and activity.

Sex steroids deficiency impairs glucose transporter 4 expression and its translocation through defective Akt phosphorylation in target tissues of adult male rat

There is a substantial body of evidence suggesting that altered level of sex steroids in male is associated with insulin resistance and type 2 diabetes mellitus. However, the mechanism of this effect is not apparent. Our recent study indicated that testosterone deprivation decreases insulin receptor expression and glucose oxidation in insulin target tissues. The present study was designed to assess the impact of deficiency of testosterone and estradiol on Akt phosphorylation, glucose transporter expression, and glucose uptake in skeletal muscle, adipose tissue, and liver of adult male rat. Adult male albino rats of Wistar strain were orchidectomized and supplemented with testosterone (100 microg/100 g body weight per day), estradiol (5 microg/100 g body weight per day), and their combination (100 microg testosterone plus 5 microg estradiol per 100 g body weight per day) for 15 days from the 11th day postorchidectomy. On the day after the last treatment, animals were perfused; and blood was collected for the assay of plasma glucose, serum insulin, testosterone, and estradiol. Gastrocnemius muscle, adipose tissue, and liver were dissected out and used for the assay of various parameters such as Akt phosphorylation, glucose transporter (GLUT) 2 and 4 expression, glucose uptake, and glycogenic and glycogenolytic enzymes activity. Castration elevated the blood glucose level, which was accompanied by inhibitory effect on serum insulin, Akt phosphorylation, GLUT4 expression and its plasma membrane population, glucose uptake, glycogen and glycogen synthase activity, and stimulatory effect on GLUT2 expression and glycogen phosphorylase activity in tissues studied. After testosterone and its combination with estradiol supplementation to castrated rats, a normal pattern of all these parameters was restored. Estradiol administration to castrated rats increased the Akt phosphorylation without altering other parameters studied. It is concluded from the present study that sex steroids deficiency-induced defective glucose uptake in skeletal muscle and adipose tissue is mediated through defective Akt phosphorylation and GLUT4 expression in plasma membrane.

DHEA improves impaired activation of Akt and PKC zeta/lambda-GLUT4 pathway in skeletal muscle and improves hyperglycaemia in streptozotocin-induced diabetes rats

AIM

Addition of dehydroepiandrosterone (DHEA) to a cultured skeletal muscle locally synthesizes 5alpha-dihydrotestosterone (DHT). It induced activation of glucose metabolism-related signalling pathway via protein kinase B (Akt) and protein kinase C zeta/lambda (PKC zeta/lambda)-glucose transporter-4 (GLUT4) proteins. However, such an effect of DHEA in vivo remains unclear.

METHODS

Using streptozotocin (STZ)-induced rats with type 1 diabetes mellitus, we tested the hypothesis that a single bout of DHEA injection in the rats improves hyperglycaemia and muscle GLUT4-regulated signalling pathway. After 1 week of STZ injection (55 mg kg(-1)) with male Wistar rats, fasting glucose concentrations were determined in a blood sample taken from the tail vein. Blood glucose levels were then monitored for 180 min after DHEA or sesame oil (control) was injected (n = 10 for each group).

RESULTS

Blood glucose levels decreased significantly for 30-150 min after 2 mg DHEA injection in the STZ rats. In the skeletal muscle, expression and translocation of GLUT4 protein, phosphorylation of Akt and PKC zeta/lambda, and phosphofructokinase and hexokinase enzyme activities increased significantly by DHEA injection. However, DHEA-induced improvements in Akt and PKC zeta/lambda-GLUT4 pathways were blocked by a DHT inhibitor.

CONCLUSION

These results suggest that a single bout of DHEA injection can improve hyperglycaemia and activate the glucose metabolism-related signalling pathway via Akt and PKC zeta/lambda-GLUT4 proteins of skeletal muscles in rats. Moreover, these results show that a DHEA-induced increase in muscle glucose uptake and utilization might contribute to improvement in hyperglycaemia in type 1 diabetes mellitus.

Dihydrotestosterone activates CREB signaling in cultured hippocampal neurons

Although androgens induce numerous actions in brain, relatively little is known about which cell signaling pathways androgens activate in neurons. Recent work in our laboratory showed that the androgens testosterone and dihydrotestosterone (DHT) activate androgen receptor (AR)-dependent mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling. Since the transcription factor cyclic AMP response element binding protein (CREB) is a downstream effector of MAPK/ERK and androgens activate CREB in non-neuronal cells, we investigated whether androgens activate CREB signaling in neurons. First, we observed that DHT rapidly activates CREB in cultured hippocampal neurons, as evidenced by CREB phosphorylation. Further, we observed that DHT-induced CREB phosphorylation is AR-dependent, as it occurs in PC12 cells stably transfected with AR but in neither wild-type nor empty vector-transfected cells. Next, we sought to identify the signal transduction pathways upstream of CREB phosphorylation using pharmacological inhibitors. DHT-induced CREB phosphorylation in neurons was found to be dependent upon protein kinase C (PKC) signaling but independent of MAPK/ERK, phosphatidylinositol 3-kinase, protein kinase A, and Ca(2+)/calmodulin-dependent protein kinase IV. These results demonstrate that DHT induces PKC-dependent CREB signaling, which may contribute to androgen-mediated neural functions.

Lef1 haploinsufficient mice display a low turnover and low bone mass phenotype in a gender- and age-specific manner

We investigated the role of Lef1, one of the four transcription factors that transmit Wnt signaling to the genome, in the regulation of bone mass. Microcomputed tomographic analysis of 13- and 17-week-old mice revealed significantly reduced trabecular bone mass in Lef1(+/-) females compared to littermate wild-type females. This was attributable to decreased osteoblast activity and bone formation as indicated by histomorphometric analysis of bone remodeling. In contrast to females, bone mass was unaffected by Lef1 haploinsufficiency in males. Similarly, females were substantially more responsive than males to haploinsufficiency in Gsk3beta, a negative regulator of the Wnt pathway, displaying in this case a high bone mass phenotype. Lef1 haploinsufficiency also led to low bone mass in males lacking functional androgen receptor (AR) (tfm mutants). The protective skeletal effect of AR against Wnt-related low bone mass is not necessarily a result of direct interaction between the AR and Wnt signaling pathways, because Lef1(+/-) female mice had normal bone mass at the age of 34 weeks. Thus, our results indicate an age- and gender-dependent role for Lef1 in regulating bone formation and bone mass in vivo. The resistance to Lef1 haploinsufficiency in males with active AR and in old females could be due to the reduced bone turnover in these mice.

Testosterone induction of prostaglandin-endoperoxide synthase 2 expression and prostaglandin F(2alpha) production in hamster Leydig cells

We have previously observed expression of prostaglandin-endoperoxide synthase 2 (PTGS2), the key enzyme in the biosynthesis of prostaglandins (PGs), in reproductively active Syrian hamster Leydig cells, and reported an inhibitory role of PGF(2alpha) on hamster testicular steroidogenesis. In this study, we further investigated PTGS2 expression in hamster Leydig cells during sexual development and photoperiodic gonadal regression. Since PTGS2 is mostly expressed in pubertal and reproductively active adult hamsters with high circulating levels of LH and androgens, we studied the role of these hormones in the regulation/maintenance of testicular PTGS2/PGF(2alpha). In active hamster Leydig cells, LH/hCG and testosterone induced PTGS2 and PGF(2alpha) production, and their actions were abolished by the antiandrogen bicalutamide (Bi). These results indicate that LH does not exert a direct effect on PG synthesis. Testosterone also stimulated phosphorylation of the mitogen-activated protein kinase isoforms 3/1 (MAPK3/1) within minutes and hours, but the testosterone metabolite dihydrotestosterone had no effect on PTGS2 and MAPK3/1. Because Bi and U0126, an inhibitor of the MAP kinase kinases 1 and 2 (MAP2K1/2), abolished testosterone actions on MAPK3/1 and PTGS2, our studies suggest that testosterone directly induces PTGS2/PGF(2alpha) in hamster Leydig cells via androgen receptors and a non-classical mechanism that involves MAPK3/1 activation. Since PGF(2alpha) inhibits testosterone production, it might imply the existence of a regulatory loop that is setting a brake on steroidogenesis. Thus, the androgen environment might be crucial for the regulation of testicular PG production at least during sexual development and photoperiodic variations in hamsters.