Androgens, estrogens, and bone loss in males

男性雄激素、雌激素和骨质流失

• 批准号: 10254219
• 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 2021-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10254219
• 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; Funding; Generations; Hematopoietic; Homing; Hormones; Hydrogen Peroxide; In Vitro; Life; Longevity; Maintenance; Malignant neoplasm of prostate; Mediating; Mesenchymal; Mesenchymal Stem Cells; 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; osteoporosis with pathological fracture; 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 这些效应的靶点和分子机制仍然知之甚少。在之前的资助期间 期间，我们发现雄激素对松质骨的影响是由细胞中的AR信号引起的。 间充质系导致破骨细胞减少；切除(ORX)增加可溶性RANKL 小鼠骨髓中B淋巴细胞的水平和数量。RANKL来源于骨细胞 松质骨重建的关键因素和B淋巴细胞来源的RANKL在松质骨丢失中的作用 去卵巢(OVX)小鼠骨量。然而，在皮质骨中，雄激素的作用不需要AR 在间充质系的任何细胞类型中的信号，也不需要ERα信号下游 在破骨细胞谱系中，以OSX1-Cre或AR或ERα信号为靶点的承诺成骨祖细胞。 然而，雌激素通过ERα信号传递未承诺的信号来减弱女性的皮质内吸收 PrX1-Cre靶向的间充质祖细胞。此外，SDF1-a的mRNA和分泌蛋白水平 CXC家族的趋化细胞因子，在PRX1-Cre靶向细胞中大量表达并促进 破骨细胞生成-在绿色荧光蛋白标记的ERα零细胞以及女性骨髓细胞培养中更高 Erαf/f；Prx1-Cre小鼠与产仔对照的相同培养物比较；破骨细胞的形成也是如此 ER、α缺失的骨髓基质细胞或颅骨细胞与巨噬细胞共培养。此外，OVX和ORX都是 增加骨髓血浆中的SDF1，给ORX小鼠注射E2可阻止这种增加，而E2， 但不是DHT，可以防止ORX小鼠的皮质骨丢失。最后，我们发现OVX或ORX诱导的大脑皮层 通过抑制破骨细胞线粒体中过氧化氢的生成和皮质骨的丢失来防止骨丢失 17β-E2树状大分子偶联物可防止去卵巢小鼠的肿块，但不能刺激核- 启动了ERα的行动。基于这些进展，我们将检验相关的假设：在男性中， 雄激素对松质骨的保护作用是通过骨细胞、B淋巴细胞或 两者都有。这些作用导致RANKL的衰减，从而导致松质细胞数量的衰减 破骨细胞。雄激素对皮质内吸收的保护作用至少部分是由ER-α- 靶向PRX1-Cre的中介作用(在雄激素芳构化为雌激素时) 间充质祖细胞。这些作用抑制SDF1的产生，从而减少破骨细胞的形成 和归巢于骨内膜表面。雌激素对SDF1产生的抑制作用最终导致 抑制破骨细胞中H_2O_2蓄积及非核启动信号转导的结果 呃α。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。 通过测定骨细胞和B淋巴细胞来源的RANKL在松质骨中的作用及作用 B淋巴细胞AR在这些效应中的作用。为了做到这一点，我们将研究：i)RANKL从成熟小鼠中缺失 成骨细胞/骨细胞(RANKLf/f；Dmp1-Cre)，ii)AR和RANKL均缺失的小鼠 成骨细胞/骨细胞(RANKLf/f；ARF/y；Dmp1-Cre)，III)B淋巴细胞中RANKL缺失的小鼠 (RANKLf/f；CD19-Cre)和iv)B淋巴细胞AR缺失的小鼠(ARF/y；CD19-Cre)。此外，我们 将通过以下研究阐明雄激素对皮质骨保护作用的机制：a) SDF1在未分化间充质祖细胞中的下调是造成这些效应的部分原因 使用：i)其中在PrX1-Cre靶向细胞中SDF1缺失的小鼠，以及ii)其中SDF1受体， CXCR4在LysM-Cre靶向细胞中缺失；以及b)雄激素的作用是否源于ERα介导 ERαf/f；Prx1-Cre小鼠对雄激素芳构化为雌激素的作用。使用基质和基质细胞的混合培养 我们还将研究SDF1是否通过过氧化氢促进破骨细胞的生成；以及 雌激素对SDF1的影响是由非核启动的ERα信号转导所致。