Age-related changes in the concentration of cytosolic androgen receptors in the epididymis, vas deferens and seminal vesicle of maturing male mice

Aging and sexual health: getting to the problem

Erectile dysfunction (ED) is one of the most common disorders in male and is often associated with other age-related comorbidities. The aging process affects the structural organization and function of penile erectile components such as smooth muscle cell and vascular architecture. These modifications affect penile hemodynamics by impairing cavernosal smooth muscle cell relaxation, reducing penile elasticity, compliance and promoting fibrosis. This review aims to identify the mechanisms of ED in the penile aging process in experimental and clinical data. It also highlights areas that are in need of more research. The search strategies yielded total records screened from PubMed. Clarification of the molecular mechanisms that accompanies corpus cavernosum aging and aging-associated ED will aid new perspectives in the development of novel mechanism-based therapeutic approaches. Age is not a limiting factor for ED medical management, and it is never too late to treat. Hypogonadism should be managed regardless of age, and synergistic effects have been found during testosterone (T) replacement therapy when used along with oral phosphodiesterase-5 (PDE-5) inhibitors. Therefore, the clinical management of ED related to aging can be done by therapeutic interventions that include PDE-5 inhibitors, and other pharmacological treatments.

The testosterone conundrum: The putative relationship between testosterone levels and prostate cancer

BACKGROUND

The controversy surrounding the relationship between testosterone and prostate cancer has existed for decades. The literature surrounding this topic is confusing and at times contradictory. There is no level-one quality evidence that confirms or refutes the relationship between either high or low serum testosterone levels and the subsequent development of prostate cancer. This commentary aims to review the issues involved and to provide an interpretation as to the causes of the confusion and to provide a framework for ongoing discussion and investigation.

MATERIALS AND METHODS

A Medline and PubMed search was conducted using search terms: testosterone levels and prostate cancer to identify pertinent literature.

RESULTS

There is no consistent evidence that a single testosterone level is predictive of prostate cancer risk.

CONCLUSION

The development of prostate cancer is a complex biologic process potentially involving genetics,dietary, life style and hormonal factors. Serum testosterone levels do not accurately reflect the internal prostatic milieu. Finally, if testosterone levels are to be considered in the etiology of prostate cancer they should be measured and interpreted on a chronic basis with multiple measurements over a period of years.

Characterisation of Lyzls in mice and antibacterial properties of human LYZL6

C-type lysozyme genes (Lyzls) belong to the class of lysozymes and are highly expressed in the testis and epididymis. The members Lyzl4 and Spaca3 have been reported to play a role in sperm-egg binding and fertilisation in mice. However, the function of the remaining two mouse c-type lysozyme genes, Lyzl1 and Lyzl6, is still not clear. In the present study, we analysed the tissue expression and androgen-dependent expression of mouse c-type lysozyme genes and the possible contribution of human recombinant LYZL6 (rLYZL6) to immunity. The expression of Lyzls was detected by RT-PCR, Western blots, immunohistochemistry and immunofluorescence. The bacteriolytic activity of rLYZL6 was analysed by a colony-forming assay. In mice, the expression of Lyzl genes was mainly in the testis and epididymis in a developmentally regulated manner and androgen- or testicular factor-regulated manner. Immunodetection revealed the presence of LYZL6 protein in primary spermatocytes and round spermatids of the testis and on the post-acrosomal area and midpiece of mature epididymal spermatozoa. The rLYZL6 protein exhibited antibacterial activity. From the results, Lyzls may play a role in mitochondrial function of spermatozoa and LYZL6 may contribute to the innate immunity of the male genital tract.

Localization and androgen regulation of metastasis-associated protein 1 in mouse epididymis

BACKGROUND

Metastasis-associated protein 1 (MTA1), the founding member of the MTA family of genes, can modulate transcription by influencing the status of chromatin remodeling. Despite its strong correlation with the metastatic potential of cancer cells, MTA1 can also regulate crucial cellular pathways by modifying the acetylation status. We have previously reported the presence of MTA1/MTA1 in human and mouse testes, providing the evidence for its involvement in the regulation of testicular function during murine spermatogenesis. The objective of present study was to further assess the localization of MTA1 in mouse epididymis on both transcriptional and translational level, and then to explore whether MTA1 expression is regulated by androgens and postnatal epididymal development.

METHODOLOGY/PRINCIPAL FINDINGS

Mice were deprived of circulating androgen by bilaterally castration and were then supplemented with exogenous testosterone propionate for one week. MTA1 was immunolocalized in the epithelium of the entire epididymis with the maximal expression in the nuclei of principal cells and of clear cells in proximal region. Its expression decreased gradually after castration, whereas testosterone treatment could restore the expression, indicating that the expression of this gene is dependent on androgen. During postnatal development, the protein expression in the epididymis began to appear from day 7 to day 14, increased dramatically from postnatal day 28, and peaked at adulthood onwards, coinciding with both the well differentiated status of epididymis and the mature levels of circulating androgens. This region- and cell-specific pattern was also conservative in normal human epididymis.

CONCLUSIONS

Our data suggest that the expression of MTA1 protein could be regulated by androgen pathway and its expression level is closely associated with the postnatal development of the epididymis, giving rise to the possibility that this gene plays a potential role in sperm maturation and fertility.

Testosterone for the aging male; current evidence and recommended practice

An international consensus document was recently published and provides guidance on the diagnosis, treatment and monitoring of late-onset hypogonadism (LOH) in men. The diagnosis of LOH requires biochemical and clinical components. Controversy in defining the clinical syndrome continues due to the high prevalence of hypogonadal symptoms in the aging male population and the non-specific nature of these symptoms. Further controversy surrounds setting a lower limit of normal testosterone, the limitations of the commonly available total testosterone result in assessing some patients and the unavailability of reliable measures of bioavailable or free testosterone for general clinical use. As with any clinical intervention testosterone treatment should be judged on a balance of risk versus benefit. The traditional benefits of testosterone on sexual function, mood, strength and quality of life remain the primary goals of treatment but possible beneficial effects on other parameters such as bone density, obesity, insulin resistance and angina are emerging and will be reviewed. Potential concerns regarding the effects of testosterone on prostate disease, aggression and polycythaemia will also be addressed. The options available for treatment have increased in recent years with the availability of a number of testosterone preparations which can reliably produce physiological serum concentrations.

Pem homeobox gene regulatory sequences that direct androgen-dependent developmentally regulated gene expression in different subregions of the epididymis

The epididymis is a useful model system to understand the mechanisms that govern region-specific gene expression, as many gene products display spatially restricted expression within this organ. However, surprisingly little is known about how this regulation is achieved. Here, we report regulatory sequences from the Pem homeobox gene that drive expression in different subregions of the mouse epididymis in vivo. We found that the 0.3-kb 5'-flanking sequence (region I) from the Pem proximal promoter (Pem Pp) was sufficient to confer androgen-dependent and developmentally regulated expression in the caput region of the epididymis. Expression was restricted to the normal regions of expression of Pem in the caput (segments 2-4), but there was also aberrant expression in the corpus region. This corpus misexpression was extinguished when 0.6 kb of Pem Pp 5'-flanking sequence was included in the transgene, indicating that one or more negative regulatory elements exist between 0.6 and 0.3 kb upstream of the Pem Pp start site (region II). When heterologous sequences were introduced upstream of the Pem Pp, expression was further restricted, mainly to caput segment 3, implying that the Pem Pp has segment-specific regulatory elements. To our knowledge, the regulatory regions we have identified are the shortest so far defined that dictate regionally localized expression in the epididymis in vivo. They may be useful for identifying the factors that regulate region-specific expression in the epididymis, for expressing and conditionally knocking out genes in different subregions of the epididymis, for treating male infertility, and for generating novel methods of male contraception.

A 5-kilobase pair promoter fragment of the murine epididymal retinoic acid-binding protein gene drives the tissue-specific, cell-specific, and androgen-regulated expression of a foreign gene in the epididymis of transgenic mice

The murine epididymis synthesizes and secretes a retinoic acid-binding protein (mE-RABP) that belongs to the lipocalin superfamily. The gene encoding mE-RABP is specifically expressed in the mouse mid/distal caput epididymidis under androgen control. In transgenic mice, a 5-kilobase pair (kb) promoter fragment, but not a 0.6-kb fragment, of the mE-RABP gene driving the chloramphenicol acetyltransferase (CAT) reporter gene restricted high level of transgene expression to the caput epididymidis. No transgene expression was detected in any other male or female tissues. Immunolocalization of the CAT protein and in situ hybridization of the corresponding CAT mRNA indicated that transgene expression occurred in the principal cells of the mid/distal caput epididymidis, thereby mimicking the spatial endogenous mE-RABP gene expression. Transgene and mE-RABP gene expression was detected from 30 days and progressively increased until 60 days of age. Castration, efferent duct ligation, and hormone replacement studies demonstrated that transgene expression was specifically regulated by androgen but not by any other testicular factors. Altogether, our results demonstrate that the 5-kb promoter fragment of the mE-RABP gene contains all of the information required for the hormonal regulation and the spatial and temporal expression of the mE-RABP gene in the epididymis.

Differential androgen regulation of the murine genes for cysteine-rich secretory proteins (CRISP)

The androgen dependency of the genes coding for the cysteine-rich secretory proteins (CRISP) was analysed in their main sites of expression. Male mice were treated with the gonadotropin-releasing hormone antagonist Ac-DNapAla-DClPhAla-DPyrAla-Ser-Tyr-DCtl-Leu-Lys (Mor)-Pro-DAla-NH2 [DNapAla, D-2-naphthyl-Ala; DClPhAla, D-4-chlorphenyl-Ala; DPyrAla, D-pyridyn-3-yl-Ala; DCtl, D-citrulline; Lys(Mor), L-2-amino-6-(morpholin-4-yl)-hexanoic acid], and CRISP RNA levels were assessed by northern blot and competitive reverse transcriptase-mediated (RT)-PCR. In the salivary gland, CRISP-1 and to a lesser extent CRISP-3 expression was markedly reduced, in spite of an up-regulation of androgen receptor transcript levels. A down-regulation of CRISP-1 expression was also observed in the epididymis. Conversely, the levels of the testicular CRISP-2 transcripts were hardly affected at all. Female mice were ovariectomised and treated with testosterone propionate, and their salivary gland RNAs analysed. CRISP-1 and CRISP-3 RNA levels were significantly increased, and these effects were prevented by a concomitant treatment with the antiandrogen flutamide. Androgen receptor transcript levels were not affected by androgen administration but increased following antiandrogen treatment. CRISP expression during postnatal development was monitored by northern blot analysis. CRISP-1 and CRISP-2 transcripts were detected as early as 22 days after birth in the epididymis and testis, respectively, whereas CRISP-3 mRNA was visible only from day 30 in the salivary gland. A sharp increase of all CRISP levels was noted on day 40, coincident with the onset of sexual maturity. Altogether these results indicate that despite their high similarity, the CRISP genes are differentially regulated by androgens.

Immunolocalization of androgen receptor and estrogen receptor in the developing testis and excurrent ducts of goats

BACKGROUND

Because of the significance of androgens and estrogens in prenatal and postanatal differentiation of the testis and excurrent ducts, it is important to understand the developmental pattern of androgen receptor (AR) and estrogen receptor (ER) in these organs.

METHODS

Tissues from 1-23-week-old goats were fixed in 4% paraformaldehyde and embedded in Paraplast-plus. Antigenic sites for AR and ER were immunolocalized using the PG-21 rabbit anti-rat/human antibody and the H-222 rat anti-human monoclonal antibody, respectively. The avidin-biotin horseradish peroxidase procedure was used to identify positive immunoreactivity. Controls included incubation of sections with irrelevant IgG in place of primary antibody.

RESULTS

Within the testis, immunostaining for AR in the nuclei of Sertoli cells increased gradually from mild at week 1 to strong at week > or = 19. In contrast, nuclei of peritubular myoid cells and Leydig cells exhibited moderate to strong reaction for AR in all animals. Germ cells were negative. Within the rete testis, efferent ductules, regions I-V of the epididymis, and ductus deferens, nuclei of all epithelial cells, peritubular myoid cells, and intertubular connective tissue cells expressed moderate to strong staining for AR at all ages. ER were confined to nonciliated cells of the efferent ductules, which displayed moderate staining in all animals, beginning from week 1.

CONCLUSIONS

Nuclear AR staining, found in all testicular cells (except germ cells) and excurrent duct cells examined, was observed to change in an age-related manner only in Sertoli cells, where staining intensity increased between week 1 and week 19. Staining for ER, confined to nonciliated epithelial cells of the efferent ductules, was not affected by postnatal age.

The receptor, metabolism and effects of androgen in osteoblastic MC3T3-E1 cells

We investigated the androgen receptor (AR), metabolism and effects of androgens in osteoblastic MC3T3-E1 cells. AR was proved as a transcript of a 10-kb mRNA and as a 110-kDa protein. An immunocytochemical study showed that AR was located mainly in the nuclei. Specific binding of [3H]DHT was observed in both the nuclear and cytosol fractions. MC3T3-E1 cells possessed approximately 1190 binding sites per cell and most of the sites (1150 sites) situated in the nucleus. The apparent Kd value in the nuclear fraction was 1.35 nM for [3H]DHT binding, and it was similar to that for [3H]testosterone. In the competition analysis, there was not much difference in the displacement of the [3H]DHT binding from AR between the addition of radioinert DHT and testosterone. In studies of 5 alpha-reductase activity and aromatase activity of the cells, both activities were lower than the respective values in classical androgen target tissues. Androgens stimulated the incorporation of [3H]thymidine into the cell, and DHT and testosterone had a similar potency on the cell proliferation. Thus, these results suggest testosterone itself acts mainly on the osteoblasts without conversion to DHT.

Histophysiological and morphometric studies of the post-natal development of rat vas deferens

The post-natal growth and differentiation of the vas deferens was studied in rats aged 1-180 d by light, and with transmission electron microscopy in parallel with a radioimmunoassay of serum testosterone. During the first week and the major part of the second week of the post-natal life the vas deferens presented embryological features. Differentiation of the proximal and distal segments of the vas started 12 d after birth. At 25 d, the epithelium of the mucosa in the distal segment already showed some adult histologic characteristics. The weight notably increased between 1 and 45 d and the higher rates of growth of their histologic components occurred until 45 or 60 d, in parallel to testosterone serum levels. These results suggest that growth and differentiation of the vas deferens are androgen-dependent events and precede the end of the first spermatogenic cycle, assuring the viability of spermatozoa that will enter the duct.

Quantitative characterization of hormone receptors by a nonlinear regression approach

This paper describes a mathematical model for the quantification of receptors based only upon the total bound values as a function of the total ligand concentration. In contrast to methods relying on linearization transformations, this nonlinear model requires more sophisticated computation, however, avoids loss of material for determination of nonspecific binding in competed tubes. Monte-Carlo simulation indicated high stability of this model against random experimental error. The androgen receptor of the male gerbil (Meriones unguiculatus) ventral prostate is characterized using the described nonlinear computation.

Androgen dependence during development of the mouse vas deferens protein mRNA

The mRNA encoding a major protein of the mouse vas deferens (MVDP) was first detected in 10-day-old males and its concentration increased sharply between 10 and 20 days, reaching adult levels at 40 days. This increase was not associated with an increase in tissular androgen concentrations. In 30-day-old mice castrated at birth or treated with cyproterone acetate over 29 days, MVDP mRNA levels were not abolished and were similar to those measured in 10- and 20-day-old controls. These results suggest that the neonatal expression of MVDP gene is independent of androgens. In addition, precocious accumulation of MVDP mRNA could be induced by injection of excess amounts of androgens in 20- but not in 10-day-old animals. The prepubertal increase in MVDP mRNA levels is androgen-dependent but other factors may be necessary for MVDP expression.