17Beta-estradiol modulates age-dependent binding of 40 kDa nuclear protein to androgen receptor promoter in mouse cerebral cortex

Androgen influences the function of central and peripheral nervous system and plays a crucial role in maintaining reproductive behaviors and neuroendocrine regulation. Such action is mediated by interaction of androgen receptor (AR) promoter with nuclear proteins, which are involved in transcriptional regulation of androgen responsive genes. We have analyzed the binding of AR core promoter to nuclear proteins from the cerebral cortex of adult and old mice of both sexes by electrophoretic mobility shift assay (EMSA) and characterized the bound protein by Southwestern blotting. EMSA showed that the binding of nuclear proteins declined in the cerebral cortex of intact old mice as compared to adult. Following gonadectomy, the binding was reduced in old male and adult female but increased in old female. In contrast, estradiol supplementation increased the binding in old male and adult female but decreased in old female. Southwestern blotting analysis revealed that a 40 kDa nuclear protein bound to the promoter and the binding pattern was similar to that observed in EMSA. Further characterization of this protein may help to explore the intricate mechanism that underlies the transcriptional regulation of androgen responsive genes during aging.

Aging of Brain: Role of Estrogen

The brain undergoes many structural and functional changes during aging. Some of these changes are regulated by estrogens which act mainly through their intracellular receptors, estrogen receptor ERalpha and ERbeta. The expression of these receptors is regulated by several factors including their own ligand estrogen, and others such as growth hormone and thyroid hormone. The levels of these factors decrease during aging which in turn influence estrogen signaling leading to alterations in brain functions. In the present paper, we review the effects of aging on brain structure and function, and estrogen action and signaling during brain aging. The findings suggest key role of estrogen in the maintenance of brain functions during aging.

Expression of estrogen receptor (ER) α and β in mouse cerebral cortex: Effect of age, sex and gonadal steroids

Estrogen receptor (ER), which mediates the multiple effects of estrogen in brain, is regulated by several factors including its own ligand. In the present study, we have examined the effect of age, sex and gonadal steroids (estrogen and testosterone) on the level of ERalpha and ERbeta in the cerebral cortex of AKR mice. Adult and old mice of both sexes were divided into four groups: intact, gonadectomized, 17beta-estradiol treated and testosterone treated. Western blot analysis showed higher level of ERalpha and ERbeta in the cerebral cortex of adult female than male mice. ERbeta level decreased significantly with advancing age in both sexes, whereas 17beta-estradiol supplementation decreased ERalpha level in old male and increased in old female, it also increased ERbeta level in old male and adult female. On the other hand, testosterone treatment decreased ERalpha level significantly in old female and ERbeta level in adult female but increased ERbeta level in male mice of both ages. Thus, these findings showed that the expression of ERalpha and ERbeta protein is differentially influenced by age, sex and gonadal steroids in the mouse cerebral cortex, suggesting differences in ER-mediated brain functions.

Estrogen receptor ? expression in mice kidney shows sex differences during aging

We have used semi quantitative RT-PCR and western blotting for the analysis of expression of estrogen receptor (ER) alpha and beta mRNA and protein in the kidney of adult and old mice of both sexes. Uterus, a well-known target for estrogen action, was used for comparison. As compared to adult, the expression of both ER alpha mRNA and protein of old mice decreased in male but increased in female. However, unlike uterus, neither ERbeta mRNA nor protein could be detected in the kidney of adult or old mice. Thus the present data reveal that the expression of ERalpha in mice kidney shows sex differences during aging.