Role of Natural Antibodies Against Oxidation Specific Epitopes in Bone Homeostasis

抗氧化特异性表位的天然抗体在骨稳态中的作用

• 批准号: 9974993
• 负责人: Elena Ambrogini
• 金额: --
• 依托单位: CENTRAL ARKANSAS VETERANS HLTHCARE SYS
• 依托单位国家: 美国
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-07-01 至 2023-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/9974993
• 关键词: Adverse effects; Age; Age-Months; Age-Related Bone Loss; Anabolism; Antibodies; Antibody Therapy; Apoptosis; Apoptotic; Atherosclerosis; Binding; Bone Density; Bone Marrow; Calvaria; Cardiovascular Diseases; Cells; Chronic; Data; Defense Mechanisms; Development; Diet; Disease; Epidemiology; Epitopes; Female; Genes; High Fat Diet; Homeostasis; Human; Immunoglobulin M; In Vitro; Incidence; Inflammation; Inflammatory; Inflammatory Response; Innate Immune System; Knockout Mice; Lipid Peroxidation; Lipids; Longevity; Lymphocyte; Measures; Mediating; Mus; Osteoblasts; Osteocytes; Osteogenesis; Osteoporosis; Oxidative Stress; Oxides; Pathogenesis; Pathway interactions; Phenotype; Phospholipids; Phosphorylcholine; Play; Population; Prevention; Production; Proteins; Receptor Activation; Roentgen Rays; Role; Site; Skeleton; Surface; Testing; Therapeutic; Tissues; Transgenes; Transgenic Mice; Veterans; Virulence Factors; Work; adduct; age related; aged; amino group; antigen binding; base; bone; bone loss; bone mass; cell injury; cell type; cohort; cortical bone; cytokine; in vivo; macrophage; male; natural antibodies; novel therapeutic intervention; osteogenic; overexpression; oxidation; oxidized low density lipoprotein; prevent; scavenger receptor; skeletal; substantia spongiosa

Lipid peroxidation forms highly reactive molecules that generate adducts with amino groups of proteins and lipids, known as oxidation specific epitopes (OSEs). OSEs are ubiquitous pro-inflammatory moieties that cause extensive cell damage if not promptly eliminated. Natural antibodies of the innate immune system, recognize OSEs and block their adverse effects. Scavenger receptors (SRs) expressed in macrophages and other cell types recognize OSEs and dispose of oxidatively-modified endogenous molecules. Persistence and/or excessive amounts of OSEs overwhelm these defense mechanisms, and the inflammatory response initiated by scavenger receptor/toll-receptor activation causes tissue damage and the development of disease. Phosphocholine-containing oxidized phospholipids (PC-OxPLs) form OSEs on oxidized low density lipoproteins (OxLDLs) and on the surface of apoptotic cells. The IgM E06 is a natural antibody that recognizes PC-OxPL. Transgenic mice expressing a single chain (scFv) form of the antigen-binding domain of E06 IgM (E06-scFv) are protected against atherosclerosis and have increased lifespan. This effect results from the prevention of OSE binding to macrophages and the subsequent activation of inflammatory pathways. In humans, low levels of natural antibodies are associated with increased incidence of cardiovascular disease. Epidemiologic evidence in humans as well as mechanistic studies in mice indicate that the OSE-rich OxLDL is a pathogenic factor for osteoporosis as well. Remarkably, we found that the E06-scFv transgene prevents the cortical bone loss caused by HFD by increasing endosteal osteoblast number and bone formation. In addition, E06-scFv increases cancellous and cortical bone in male and female C57Bl/6J mice fed a normal diet by increasing bone formation and osteoblast number. Mechanistic studies showed that E06 IgM prevents the negative effects of OxLDL on proliferation, differentiation, and survival of cultured osteoblastic cells suggesting that anti-OSE antibodies promote bone anabolism by preventing the negative effects of OSEs on osteoblasts. Consistently, the production of anti-osteogenic cytokines by macrophages was not affected in E06-scFv transgenic mice. Deletion of the scavenger receptor ScrB1, the most abundant scavenger receptor for PC- OxPL in cells of the osteoblast lineage, prevents the adverse effects of OxLDL on apoptosis and differentiation. Moreover, anti-PC IgM (which includes E06) decline with age in mice, in association with a decline in bone mass. Therefore, we hypothesize that anti PC-OxPLs antibodies play a beneficial role in skeletal homeostasis by protecting against deleterious effects of PC-OxPLs on bone formation, that are transmitted by ScrB1 on osteoblasts. Increased production of OSEs due to accelerated apoptosis, oxidative stress, or chronic inflammation, in concert with declining levels of anti PC-OxPLs antibodies with age, contributes to the pathogenesis of osteoporosis in both mice and humans. Studies proposed in this application will establish whether ScrB1 mediates the negative effects of PC-OxPLs on osteoblasts in vivo by characterizing the bone phenotype of mice in which the ScrB1 gene has been deleted in cells of the osteoblast lineage. We will also determine if E06-scFv prevents the reduction in bone formation caused by old age. Additionally, we will investigate whether endogenous anti-PC IgM levels correlate with bone mineral density in humans by measuring the levels of anti-PC IgM in a cohort of eligible Veterans who had a bone mineral density (BMD) assessment by dual X-ray absorptiometry (DXA). Successful completion of this work may may suggest a novel therapeutic approach for the management of osteoporosis and atherosclerosis simultaneously.

脂质过氧化形成高反应性分子，与蛋白质的氨基生成加合物， 脂质，称为氧化特异性表位（OSE）。 OSE 是普遍存在的促炎部分，可导致 如果不及时消除，则会造成广泛的细胞损伤。先天免疫系统的天然抗体可识别 OSE 并阻止其不利影响。巨噬细胞和其他细胞中表达的清道夫受体 (SR) 类型识别 OSE 并处理氧化修饰的内源性分子。持久性和/或 过量的 OSE 会压倒这些防御机制，并引发炎症反应 通过清道夫受体/收费受体的激活导致组织损伤和疾病的发展。 含磷酸胆碱的氧化磷脂 (PC-OxPL) 在氧化低密度上形成 OSE 脂蛋白（OxLDL）和凋亡细胞表面。 IgM E06 是一种天然抗体，可识别 PC-OxPL。表达 E06 IgM 抗原结合结构域的单链 (scFv) 形式的转基因小鼠 (E06-scFv) 可以预防动脉粥样硬化并延长寿命。这种效应的结果是 防止 OSE 与巨噬细胞结合以及随后激活炎症通路。在 人类中，低水平的天然抗体与心血管疾病发病率增加有关。 人类流行病学证据以及小鼠机制研究表明，富含 OSE 的 OxLDL 是 也是骨质疏松症的致病因素。值得注意的是，我们发现 E06-scFv 转基因可以防止 HFD 通过增加骨内成骨细胞数量和骨形成引起皮质骨丢失。此外， E06-scFv 增加正常饮食喂养的雄性和雌性 C57Bl/6J 小鼠的松质骨和皮质骨 增加骨形成和成骨细胞数量。机制研究表明 E06 IgM 可预防 OxLDL 对培养的成骨细胞的增殖、分化和存活的负面影响表明 抗 OSE 抗体通过防止 OSE 对成骨细胞的负面影响来促进骨合成代谢。 一致地，E06-scFv 中巨噬细胞产生的抗成骨细胞因子未受到影响 转基因小鼠。删除清道夫受体 ScrB1，这是 PC- 中最丰富的清道夫受体 成骨细胞谱系细胞中的 OxPL 可防止 OxLDL 对细胞凋亡和分化的不利影响。 此外，小鼠中抗 PC IgM（包括 E06）随着年龄的增长而下降，与骨量下降有关 大量的。因此，我们假设抗 PC-OxPLs 抗体在骨骼稳态中发挥有益作用 通过防止 PC-OxPLs 对骨形成的有害影响，这种影响是通过 ScrB1 传播的 成骨细胞。由于细胞凋亡加速、氧化应激或慢性病导致 OSE 产生增加 炎症，以及抗 PC-OxPLs 抗体水平随着年龄的增长而下降，导致 小鼠和人类骨质疏松症的发病机制。本申请中提出的研究将建立 ScrB1 是否通过表征骨介导 PC-OxPLs 对体内成骨细胞的负面影响 成骨细胞谱系细胞中 ScrB1 基因已被删除的小鼠的表型。我们还将 确定 E06-scFv 是否可以防止老年引起的骨形成减少。此外，我们将 研究内源性抗 PC IgM 水平是否与人类骨矿物质密度相关 测量一组具有骨矿物质密度 (BMD) 的合格退伍军人的抗 PC IgM 水平 通过双 X 射线吸收测定法 (DXA) 进行评估。成功完成这项工作可能会推荐一部小说 同时治疗骨质疏松症和动脉粥样硬化的治疗方法。