Androgens, estrogens, and bone loss in males

男性雄激素、雌激素和骨质流失

• 批准号: 9240823
• 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
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9240823
• 关键词: Adult; Androgen Receptor; Androgens; Apoptosis; Apoptotic; Applications Grants; Attenuated; B-Lymphocytes; Bone Marrow; Bone Marrow Cells; Bone remodeling; CD19 gene; CXCL12 gene; CXCR4 gene; Calvaria; Cell Culture Techniques; Cells; Coculture Techniques; Dendrimers; Development; Down-Regulation; Estradiol; Estrogen Receptor alpha; Estrogens; Family; Female; Fracture; Funding; Generations; Hematopoietic; Homing; Hormones; Hydrogen Peroxide; In Vitro; Life; Longevity; Maintenance; Malignant neoplasm of prostate; Mediating; Mesenchymal; Messenger RNA; Mitochondria; Molecular; Mus; Nuclear; Null Lymphocytes; Orchiectomy; Osteoblasts; Osteoclasts; Osteocytes; Osteoporosis; Pharmaceutical Preparations; Plasma; Production; Proteins; Receptor Signaling; Research; Role; Signal Transduction; Surface; TNFSF11 gene; Testing; Testosterone; Veterans; Woman; Work; attenuation; base; bone; bone loss; bone mass; cell type; chemokine; cortical bone; dentin matrix protein 1; gonad function; insight; macrophage; male; malignant breast neoplasm; men; mouse model; novel; novel therapeutics; osteoclastogenesis; prevent; progenitor; protective effect; receptor; reproductive organ; sex; substantia spongiosa

Both androgens and estrogens contribute to the maintenance of bone mass during adult life in men, but the cell targets and molecular mechanisms of these effects remain poorly understood. During the preceding funding period, we found that the effects of androgens on cancellous bone result from AR signaling in cells of the mesenchymal lineage leading to a decrease in osteoclasts; and orchidectomy (ORX) increases soluble RANKL levels as well as the number of B-lymphocytes in the murine bone marrow. RANKL derived from osteocytes is critical for cancellous bone remodeling and B-lymphocyte-derived RANKL contributes to the loss of cancellous bone mass in ovariectomized (OVX) mice. In cortical bone, however, the effects of androgens do not require AR signaling in any cell type of the mesenchymal lineage, nor do they require ERα signaling downstream of committed osteoblast progenitors targeted by Osx1-Cre, or AR or ERα signaling in the osteoclast lineage. Estrogens, nonetheless, attenuate endocortical resorption in females by ERα signaling in uncommitted mesenchymal progenitors targeted by Prx1-Cre. In addition, the mRNA and secreted protein levels of SDF1 – a chemotactic cytokine of the CXC family that is abundantly expressed in Prx1-Cre targeted cells and promotes osteoclast generation – are higher in GFP-tagged ERα null cells as well as bone marrow cell cultures from female ERαf/f;Prx1-Cre mice as compared to identical cultures from littermate controls; and so is osteoclastogenesis in co-cultures of ERα null BM stromal or calvaria cells with macrophages. Furthermore, both OVX and ORX increase SDF1 in the bone marrow plasma, administration of E2 to ORX mice prevents this increase, and E2, but not DHT, prevents cortical bone loss in ORX mice. Finally, we found that the OVX- or ORX-induced cortical bone loss is prevented by restraining H2O2 generation in osteoclast mitochondria; and the loss of cortical bone mass in OVX mice is prevented by a 17β-E2 dendrimer conjugate (EDC), incapable of stimulating nuclear- initiated actions of ERα. Based on these advances, we will test the interrelated hypotheses that: in males, the protective effects of androgens on cancellous bone result from AR signaling in osteocytes, B-lymphocytes, or both. These actions result in the attenuation of RANKL and thereby attenuation of the number of cancellous osteoclasts. The protective effects of androgens against endocortical resorption result, at least in part, from ERα- mediated actions (upon aromatization of androgens to estrogens) on Prx1-Cre targeted uncommitted mesenchymal progenitors. These actions repress SDF1 production, thereby attenuating osteoclast formation and homing at the endosteal surfaces. The suppressive effect of estrogens on SDF1 production ultimately leads to the restraining of H2O2 accumulation in osteoclasts and results from non-nuclear-initiated signaling of the ERα. To advance these hypotheses we will try to elucidate the mechanism of the protective effects of androgens on cancellous bone by determining the role of osteocyte- and B-lymphocyte-derived RANKL as well as the role of the B lymphocyte AR in these effects. To do this we will study: i) mice in which RANKL is deleted from mature osteoblasts/osteocytes (RANKLf/f;Dmp1-Cre), ii) mice in which both AR and RANKL are deleted from osteoblasts/osteocytes (RANKLf/f;ARf/y;Dmp1-Cre), iii) mice in which RANKL is deleted from B-lymphocytes (RANKLf/f;CD19-Cre), and iv) mice in which AR is deleted from B-lymphocytes (ARf/y;CD19-Cre). In addition, we will elucidate the mechanism of the protective effects of androgens on cortical bone by investigating: a) whether down-regulation of SDF1 in uncommited mesenchymal progenitors is responsible for some of these effects using: i) mice in which SDF1 is deleted in Prx1-Cre targeted cells, and ii) mice in which the SDF1 receptor, CXCR4, is deleted in LysM-Cre targeted cells; and b) whether the effect of androgens results from ERα-mediated actions upon androgen aromatization to estrogens using ERαf/f;Prx1-Cre mice. Using co-cultures of stromal and hematopoietic cells, we will also examine whether SDF1 promotes osteoclastogenesis via H2O2; and whether the effect of estrogens on SDF1 results from non-nuclear-initiated signaling of the ERα.

雄激素和雌激素都有助于维持成年男性的骨量，但细胞 这些作用的靶点和分子机制仍然知之甚少。在前期融资中 在此期间，我们发现雄激素对松质骨的作用是由肾上腺皮质细胞中的AR信号引起的。 间充质谱系导致破骨细胞减少;而类骨质增生切除术（ORX）增加可溶性RANKL 水平以及小鼠骨髓中B淋巴细胞的数量。来源于骨细胞的RANKL是 对于松质骨重塑至关重要，B淋巴细胞来源的RANKL有助于松质骨的丢失。 卵巢切除（OVX）小鼠的骨量。然而，在皮质骨中，雄激素的作用不需要AR 在间充质谱系的任何细胞类型中，它们也不需要ERα信号传导， 破骨细胞谱系中Osx 1-Cre或AR或ERα信号转导靶向的定向成骨细胞祖细胞。 然而，雌激素通过雌激素受体α信号减弱女性皮质内吸收， Prx 1-Cre靶向的间充质祖细胞。此外，SDF 1- a的mRNA和分泌蛋白水平 CXC家族的趋化细胞因子，在Prx 1-Cre靶向细胞中大量表达，并促进 破骨细胞生成-在GFP标记的ERα无效细胞以及来自女性的骨髓细胞培养物中较高 ERαf/f; Prx 1-Cre小鼠与同窝对照的相同培养物相比; ERα无效BM基质或颅骨细胞与巨噬细胞的共培养物。OVX和ORX 增加骨髓血浆中的SDF 1，给予ORX小鼠E2可防止这种增加，而E2， 而不是DHT，防止ORX小鼠的皮质骨丢失。最后，我们发现OVX或ORX诱导的皮质 通过抑制破骨细胞线粒体中H2 O2的产生来防止骨丢失; 通过17β-E2树枝状聚合物缀合物（EDC）防止OVX小鼠中的肿块，该缀合物不能刺激核- 启动ERα的作用。基于这些进展，我们将测试相互关联的假设，即：在男性中， 雄激素对松质骨的保护作用来自骨细胞、B淋巴细胞或 两者这些作用导致RANKL的衰减，从而减少松质骨的数量。 破骨细胞雄激素对皮质内吸收的保护作用至少部分是由于ERα- 介导的作用（在雄激素芳构化为雌激素后）对Prx 1-Cre靶向的非定向作用 间充质祖细胞这些作用抑制SDF 1的产生，从而减弱破骨细胞的形成 并在骨内膜表面归巢。雌激素对SDF 1产生的抑制作用最终导致 抑制H2 O2在破骨细胞中的积累，并由非核启动的信号传导引起。 ERα。为了推进这些假设，我们将试图阐明雄激素保护作用的机制 通过确定骨细胞和B淋巴细胞源性RANKL的作用以及 B淋巴细胞AR在这些效应中的作用。为此，我们将研究：i）RANKL从成熟RANKL缺失的小鼠 成骨细胞/骨细胞（RANKLf/f; Dmp 1-Cre），ii）AR和RANKL均缺失的小鼠， 成骨细胞/骨细胞（RANKLf/f;ARf/y; Dmp 1-Cre），iii）B淋巴细胞中RANKL缺失的小鼠 （RANKLf/f; CD 19-Cre），和iv）AR从B淋巴细胞中缺失的小鼠（ARf/y; CD 19-Cre）。另外我们 将通过研究阐明雄激素对皮质骨保护作用的机制：a）是否 未定型间充质祖细胞中SDF 1的下调是造成这些效应的原因之一 使用：i）在Prx 1-Cre靶向细胞中SDF 1缺失的小鼠，和ii）SDF 1受体， B）雄激素的作用是否是由ERα介导的 使用ERαf/f; Prx 1-Cre小鼠对雄激素芳构化为雌激素的作用。使用基质和 造血细胞，我们还将研究SDF 1是否通过H2 O2促进破骨细胞生成; 雌激素对SDF 1的作用是由ERα的非核启动信号传导引起的。