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Estrogens, androgens, aging, and bone loss in males

男性雌激素、雄激素、衰老和骨质流失

基本信息

批准号：
8244288
负责人：
STAVROS C. MANOLAGAS
金额：
--
依托单位：
CENTRAL ARKANSAS VETERANS HLTHCARE SYS
依托单位国家：
美国
项目类别：
财政年份：
2012
资助国家：
美国
起止时间：
2012-01-01 至 2015-12-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/8244288
关键词：
Adult Adverse effects Affect Aging Agreement Anabolism Androgens Antioxidants Apoptosis Attenuated Cell Survival Cells Chemosensitization Commit DNA Binding Defense Mechanisms Dendrimers Development Disease Enzymes Equilibrium Estradiol Estrogen Receptors Estrogens Excision Female Generations Genetic Transcription Gonadal Steroid Hormones Growth Homeostasis Longevity Maintenance Mediating Mesenchymal Molecular Muramidase Mus NF-kappa B Nuclear Organ Osteoblasts Osteoclasts Osteocytes Osteoporosis Ovarian Ovariectomy Oxidation-Reduction Oxidative Stress Pathway interactions Phosphorylation Production Reactive Oxygen Species Secondary to Seminal Vesicles Signal Transduction Skeleton Thick Weight Work attenuation base bone bone cell bone loss bone mass cathepsin K cell type dentin matrix protein 1 gain of function in vivo male osteoclastogenesis overexpression p66(ShcA) protein prevent progenitor protective effect receptor reproductive sex skeletal substantia spongiosa transcription factor

项目摘要

DESCRIPTION (provided by applicant): Gonadectomy increases the generation of reactive oxygen species (ROS) in the murine skeleton and the adverse effects of the loss of ovarian or testicular function on bone can be prevented by anti-oxidants. Conversely, estrogens or non-aromatizable androgens decrease oxidative stress. The effects of estrogens result from DNA-binding independent actions of the ER1. In full agreement with such a mechanism, an estradiol dendrimer conjugate (EDC) that is not capable of stimulating the nuclear- initiated actions of ER1 reproduces the effects of estradiol on osteoclasts and osteoblasts ; and is as potent as estradiol in preventing oxidative stress and ovariectomy-induced bone loss, without affecting uterine weight. ER1 deletion in cells of the osteoclast lineage (expressing Lys-M) causes loss of cancellous, but not cortical, bone in female mice; while ER1 deletion from mesenchymal progenitors (Prx1 expressing cells) decreases cortical thickness in both females and males. Consistent with the above, ROS attenuate osteoblastogenesis and shorten the lifespan of osteoblasts and osteocytes. On the other hand ROS are required for osteoclast generation, function, and survival. Moreover, loss or gain of function of FoxOs - transcription factors that are an important defense mechanism against oxidative stress (OS) -dramatically alters skeletal homeostasis. Based on these findings it is hypothesized that similar to ER1-mediated effects of estrogens, AR-mediated effects of androgens decrease ROS generation in both osteoblasts and osteoclasts via cell autonomous mechanisms. Conversely, androgen deficiency increases ROS production in either cell type, and in the adult male skeleton this leads to loss of both cancellous and cortical bone. The protective effect of androgens on cancellous bone is mediated primarily via the osteoclast AR and results from decreased osteoclastogenesis and shortened osteoclast lifespan secondary to increased apoptosis. The protective effect of androgens on cortical bone is mediated via both the AR and the ER1 and is caused by attenuation of ROS-induced FoxO activation and the resulting potentiation of Wnt signaling and osteoblastogenesis. The EDC will be protective of cortical bone in gonadectomised males, as it is in females, without affecting male reproductive organs such as seminal vesicles. To advance these interrelated hypotheses, the contribution of cell autonomous effects of androgens on osteoblasts to skeletal homeostasis will be investigated by determining the effects of AR deletion from Prx1, Osx, or DMP1 expressing cells in the skeleton of male mice; and the effects of AR-mediated androgen signaling on ROS and FoxO-activated pathways in vivo and in osteoblastic cells isolated from these mice. Further, the contribution of cell autonomous effects of androgens on osteoclasts to skeletal homeostasis will be studied by determining the effects of AR deletion from LysM and Cathepsin K expressing cells in the skeleton of male mice; and the effects of AR-mediated androgen signaling on ROS-activated pathways in vivo and in osteoclastic cells isolated from these mice. Lastly, the contribution of the ER1 deletion from osteoblastic cells to skeletal homeostasis in the male and the bone sparing efficacy of the EDC in androgen deficient wild type adult male mice will be determined. PUBLIC HEALTH RELEVANCE: A deficiency of estrogens in females or both androgens and estrogens in males contributes to the development of osteoporosis in either sex. However, the mechanism(s) responsible for the adverse effects of the deficiency of either class of sex steroid on the male or female skeleton are not well understood; nor is the molecular mechanism(s) by which estrogens contribute to the maintenance of the male skeleton. The work proposed in this application will investigate how loss of androgens influences oxidative stress on bone cells and how it contributes to the development of this disease.

描述（由申请人提供）：