Quantitative reverse transcriptase polymerase chain reaction assay for mouse androgen receptor mRNA

Sexual Differentiation of Circadian Clock Function in the Adrenal Gland

Sex differences in glucocorticoid production are associated with increased responsiveness of the adrenal gland in females. However, the adrenal-intrinsic mechanisms that establish sexual dimorphic function remain ill defined. Glucocorticoid production is gated at the molecular level by the circadian clock, which may contribute to sexual dimorphic adrenal function. Here we examine sex differences in the adrenal gland using an optical reporter of circadian clock function. Adrenal glands were cultured from male and female Period2::Luciferase (PER2::LUC) mice to assess clock function in vitro in real time. We confirm that there is a pronounced sex difference in the intrinsic capacity to sustain PER2::LUC rhythms in vitro, with higher amplitude rhythms in adrenal glands collected from males than from females. Changes in adrenal PER2::LUC rhythms over the reproductive life span implicate T as an important factor in driving sex differences in adrenal clock function. By directly manipulating hormone levels in adult mice in vivo, we demonstrate that T increases the amplitude of PER2::LUC rhythms in adrenal glands of both male and female mice. In contrast, we find little evidence that ovarian hormones modify adrenal clock function. Lastly, we find that T in vitro can increase the amplitude of PER2::LUC rhythms in male adrenals but not female adrenals, which suggests the existence of sex differences in the mechanisms of T action in vivo. Collectively these results reveal that activational effects of T alter circadian timekeeping in the adrenal gland, which may have implications for sex differences in stress reactivity and stress-related disorders.

Sertoli cell-specific expression of metastasis-associated protein 2 (MTA2) is required for transcriptional regulation of the follicle-stimulating hormone receptor (FSHR) gene during spermatogenesis

BACKGROUND

Desensitization of FSH response by down-regulation of FSHR transcription is critical for FSH action.

RESULTS

Chromatin modifier MTA2 participates in the down-regulation of FSHR transcription.

CONCLUSION

The FSH/Ar/MTA2 cascade may serve as an indispensable negative feedback mechanism to modulate FSH transduction events in Sertoli cells.

SIGNIFICANCE

Our findings provide new insights into mechanisms by which FSH is deregulated in male infertile patients. The effect of follicle-stimulating hormone (FSH) on spermatogenesis is modulated at a fundamental level by controlling the number of competent receptors present at the surface of Sertoli cells (SCs). One underlying mechanism is the down-regulation of the expression levels of the FSH receptor (FSHR) gene after exposure to FSH. Here we report that metastasis-associated protein 2 (MTA2), a component of histone deacetylase and nucleosome-remodeling complexes, as a gene product induced directly by testosterone or indirectly by FSH, is exclusively expressed in SCs. Stimulation of SCs with FSH is accompanied by up-regulation of MTA2 expression and enhancement of deacetylase activity. This effect requires the integrity of functional androgen receptor. Furthermore, MTA2 is a potent corepressor of FSHR transcription, because it can recruit histone deacetylase-1 onto the FSHR promoter and participates in the down-regulation of FSHR expression upon FSH treatment. Abolishment of endogenous MTA2 by siRNA treatment disrupted the desensitization of the FSH response and thereafter impaired the FSH-dependent secretory function of SCs. From a clinical standpoint, deregulated expression of MTA2 in SCs of human pathological testes negatively correlates to the deregulated level of serum FSH. Overall, our present results provide the first evidence that the FSH/androgen receptor/MTA2 cascade may serve as an indispensable negative feedback mechanism to modulate the transduction events of SCs in response to FSH. These data also underscore an unexpected reproductive facet of MTA2, which may operate as a novel integrator linking synergistic actions of FSH and androgen signaling in SCs.

High abundance of testosterone and salivary androgen-binding protein in the lateral nasal gland of male mice

To better understand androgen function in the mammalian nose, we have determined the levels of testosterone (T) in the olfactory mucosa (OM, which harbors the olfactory receptor neurons) and the lateral nasal gland (LNG, which is the largest anterior nasal gland) of C57BL/6 mice. The results indicated that, in adult male mice, T levels in the LNG were substantially higher than those in the OM and other non-reproductive or non-endocrine tissues examined, including liver, kidney, and brain. Furthermore, in the LNG, the high T levels were accompanied by high levels of salivary androgen-binding protein (sABP) and low microsomal T-hydroxylase activities. The high abundance of T and sABP in the LNG suggests not only that the LNG is a storage site for androgen, but also the possibility that unusually high T levels may occur in other organs that have abundant expression of sABP but low expression of steroid-metabolizing enzymes. Our findings suggest a critical need to determine androgen levels in various organs, as well as to establish the functional significance of an unusually high T level in the LNG, a gland known for its secretion of biologically active molecules, such as odorant binding proteins and immunoglobulin A, to the nasal cavity.

Androgen receptor gene expression in leucocytes is hormonally regulated: implications for gender differences in disease pathogenesis

OBJECTIVE

There is evidence that male sex hormones influence the rate of progression of inflammatory and cardiovascular diseases. We have previously shown that human leucocytes and arterial cells isolated from male donors express more androgen receptor (AR) than those from female cells, with potentially pro-atherogenic effects. We now investigate whether the gender difference in AR expression is due to genetic or hormonal regulation.

DESIGN AND PATIENTS

The influence of hormones on AR expression were studied in hpg mice (a mouse model of androgen deficiency) treated with testosterone, oestradiol or dihydrotestosterone (DHT). Blood samples were obtained for leucocyte AR expression and hormone levels from 53 subjects, grouped into: 12 male [six young adult (27-45 years), six elderly (71-79 years)] and six female (young adult 25-45 years) healthy controls; six male-to-female transsexuals (M2F; 20-50 years) receiving stable pharmacological oral oestrogen treatment; six female-to-male transsexuals (F2M; 31-51 years) receiving stable androgen replacement therapy; five younger men (18-56 years) who had been receiving long-term androgen replacement therapy for hypogonadal disease; six elderly men (72-88 years) who had undergone medical castration for prostate cancer treatment; and 12 male bone marrow transplant recipients (BMT; 23-65 years) from either male or female donors.

MEASUREMENTS

Serum testosterone and oestradiol concentrations were measured by established immunoflurometric assays from unextracted human serum. AR mRNA levels were measured by RT-PCR and AR protein levels by western blot (cell culture) or immunohistochemistry (mouse arteries).

RESULTS

We found that AR mRNA levels were significantly down-regulated in the leucocytes of hpg mice that were treated with exogenous testosterone, oestradiol or DHT. AR protein levels were also lower in aortic tissue from the same mice. In humans, we found AR expression was significantly down-regulated by exogenous treatment with testosterone in F2M (31 +/- 13%, compared with control) or oestradiol in M2F (22 +/- 5%) but was significantly up-regulated by endogenous testosterone in BMT (128 +/- 17%). Low androgen levels measured in castrated older men were associated with markedly increased AR expression (207 +/- 26%, P < 0.05) compared with age-matched older male controls (100 +/- 2%).

CONCLUSIONS

Our results indicate a regulated ability of vascular cells to respond to sex hormones, with the effects of exogenous therapies differing markedly from those due to endogenous sex hormones. We conclude that the gender difference in AR expression in vascular cells is hormonally, rather than genetically, controlled.

Kinetics of whole serum and prepurified IgG digestion by pepsin for F(ab')2 manufacture

An alternative route for the production of polyclonal F(ab')(2) fragments that might be adopted for the facile preparation of antivenoms is assessed in this work. The method involves the digestion of whole serum by free pepsin, which results in reduction of the number of processing steps commonly in use, because it avoids the initial purification of IgG's prior to their proteolytic cleavage by the enzyme. Digestion kinetics of whole serum and caprylic acid prepurified IgG using free pepsin were monitored with SDS-PAGE followed by densitometric analysis and antigen binding activity assay of the digested samples. It was observed that with equal units of pepsin activity, caprylic acid prepurified IgG was digested more rapidly than whole serum but that the overall retention of antigen binding activity was significantly greater in the latter case. The estimated first-order digestion rate parameters were 11.8 and 4.42 microM min(-)(1) for pure IgG and whole serum, respectively. The K(m) value obtained for whole serum digestion was 33 microM and that for pure IgG digestion was 43.5 microM. Calibration with undigested whole serum and pure IgG samples of known concentrations was performed using SDS-PAGE followed by image analysis. A linear relationship was observed between the protein concentration and the respective band intensity within the range of concentrations investigated (0.63-31.2 microM IgG concentration). This technique proved to be relatively rapid, reproducible, and more precise than size-exclusion chromatography as a result of its F(ab')(2)/IgG resolving power. Staining and destaining protocols were reproduced in terms of staining and destaining times, volumes added, and compositions. Furthermore, all digestion experiments were performed in duplicate sets to monitor the extent of variation of the digestion kinetic parameters measured by this method. The results obtained from this technique confirm and quantify previous observations that pepsin digestion of whole serum is slower and easier to control than digestion of pure IgG and results in higher recovery of antigenic binding activity.