Lysosomal phospholipase A2 in autoimmune disease

溶酶体磷脂酶 A2 在自身免疫性疾病中的作用

• 批准号: 8017485
• 负责人: JAMES ALAN SHAYMAN
• 金额: $ 32.59万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-02-01 至 2014-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8017485
• 关键词: Apoptotic; Autoimmune Diseases; Autoimmune Process; Bacteriophages; Binding; Cells; Ceramides; Clinical Research; Defect; Digestion; Disease; EGF gene; Eating; Electrostatics; Enzymes; Exhibits; Family; Gene Mutation; Genes; Glomerulonephritis; Hepatosplenomegaly; Human; Hydralazine; Immunoglobulins; Immunotherapy; Impairment; Kidney Failure; Knockout Mice; Laboratories; Lecithin; Lupus; Membrane Lipids; Modeling; Molecular; Mus; Names; Pathogenesis; Pharmaceutical Preparations; Phenocopy; Phenotype; Phospholipase; Phospholipase A2; Phospholipid Degradation Pathway; Phospholipids; Procainamide; Quinidine; Reporting; Secondary to; Signal Transduction; Spleen; Stimulus; Systemic Lupus Erythematosus; Testing; Zymosan; base; drug induced lupus; enzyme activity; human MERTK protein; insight; lymph nodes; macrophage; milk fat globule; novel; public health relevance; receptor; research study; response; uptake; wasting

DESCRIPTION (provided by applicant): Systemic lupus erythematosus historically has been and still remains a poorly understood autoimmune disorder. Recent advances have been made in identifying lupus promoting single gene alterations that phenocopy many aspects of lupus in humans. Despite these advances there remains no unifying hypothesis and no new mechanism based, directed immunotherapy for this disease. In recent years several clinical and experimental studies have pointed to the impairment in the clearance of apoptotic cells as a common feature of lupus. As the molecular basis for the recognition, binding, and uptake of apoptotic cells by macrophages has become better defined, gene alterations associated with the impaired expression of phagocytic receptors for "eat me" signals are associated with murine models of lupus. Examples include the milk fat globule-EGF factor 8 and the c-mer proto-oncogene tyrosine kinase. The phospholipid lyso- phosphatidylcholine has been identified as an important "find me" signal for the recruitment of macrophages involved in the clearance of apoptotic cells. However, how lyso-phosphatidylcholine is generated as a find me signal is unknown and the identification of comparable alterations in the genes encoding the enzyme or enzymes involved in lyso-PC formation that would result in a lupus phenotype have not been reported. Our laboratory discovered, cloned, and characterized a novel phospholipase A2 named lysosomal phospholipase A2. This enzyme is distinct among the family of phospholipase A2s. Lysosomal phospholipase A2 is characterized by an acidic pH optimum, the ability to transacylate ceramide, and it secretion from macrophages in response to phagocytic stimuli such as zymosan. A knockout mouse, lacking the expression of lysosomal phospholipase A2 is characterized by a late onset autoimmune phenotype that mimics most aspects of lupus. These mice develop lymphoproliferation with hepatosplenomegaly, wasting, and renal failure. The mice exhibit markedly positive ANAs, anti-dsDNA titers, high circulating immunoglobulin levels, and glomerulonephritis. The spleens and lymph nodes are characterized by the persistence of high levels of apoptotic bodies in association with resident macrophages, consistent with a defect in the clearance of apoptotic cells. Based on these observations, the following primary hypothesis is proposed. Lysosomal phospholipase A2 is necessary for the digestion and clearance of apoptotic cells by macrophages. The following specific aims are proposed to test this hypothesis: 1) To immunologically phenotype LPLA2 null mice. 2) To determine the mechanism by which the absence of lysosomal phospholipase A2 inhibits or eliminates the clearance of apoptotic cells by macrophages. 3) To determine lysosomal phospholipase A2 is either sufficient or necessary to rescue the lupus phenotype in the LPLA2 null mice. 4) To determine whether inhibition of lysosomal phospholipase A2 by hydralazine, quinidine, and procainamide is the basis for drug induced lupus. PUBLIC HEALTH RELEVANCE: We have discovered and characterized a new lysosomal phospholipase A2. Knockout mice, deficient in the activity of this enzyme, develop a late onset autoimmune phenotype with features similar to systemic lupus erythematosus. Understanding the mechanisms whereby impaired degradation of phospholipids result in the autoimmune phenotype may provide new insights into the pathogenesis of lupus and potential new targets for therapy.

描述(由申请人提供)：系统性红斑狼疮历史上一直是一种知之甚少的自身免疫性疾病。最近在识别狼疮方面取得了进展，促进了人类狼疮许多方面的单基因改变。尽管取得了这些进展，但仍然没有统一的假说，也没有新的基于机制的、定向的免疫疗法来治疗这种疾病。近年来，一些临床和实验研究表明，狼疮的一个共同特征是对凋亡细胞的清除障碍。随着巨噬细胞识别、结合和摄取凋亡细胞的分子基础得到更好的确定，与吞噬细胞受体“Eat Me”信号表达受损相关的基因改变与狼疮小鼠模型有关。例子包括乳脂球-EGF因子8和原癌基因c-mer酪氨酸激酶。磷脂溶解磷脂酰胆碱已被确认为一个重要的“找到我”的信号，以招募参与清除凋亡细胞的巨噬细胞。然而，Lyso-磷脂酰胆碱是如何作为Find Me信号产生的尚不清楚，而且编码Lyso-PC形成的一个或多个酶的基因中类似的变化将导致狼疮表型还没有报道。本实验室发现、克隆并鉴定了一种新的磷脂酶A2，命名为溶酶体磷脂酶A2。这种酶在磷脂酶A2家族中是不同的。溶酶体磷脂酶A2具有最适的酸性、转酰化神经酰胺的能力以及巨噬细胞对酵母多糖等吞噬刺激的反应能力。缺乏溶酶体磷脂酶A2表达的基因敲除小鼠的特征是一种迟发的自身免疫表型，模仿狼疮的大部分方面。这些小鼠出现淋巴组织增生并伴有肝脾肿大、消瘦和肾功能衰竭。小鼠表现出显著的ANAS阳性、抗dsDNA滴度、高循环免疫球蛋白水平和肾小球肾炎。脾和淋巴结的特点是持续存在高水平的凋亡小体，与滞留的巨噬细胞有关，这与凋亡细胞的清除缺陷相一致。基于这些观察，提出了以下主要假设。溶酶体磷脂酶A2是巨噬细胞消化和清除凋亡细胞所必需的。为了验证这一假说，提出了以下具体目标：1)免疫表型LPLA2缺失小鼠。2)探讨溶酶体磷脂酶A2缺失抑制或消除巨噬细胞清除凋亡细胞的机制。3)测定溶酶体磷脂酶A2对于挽救LPLA2缺失小鼠的狼疮表型是充分的还是必要的。4)明确肼、奎尼丁、普鲁卡因胺对溶酶体磷脂酶A2的抑制是否为药物性狼疮的发病基础。 公共卫生相关性：我们发现并鉴定了一种新的溶酶体磷脂酶A2。基因敲除小鼠缺乏这种酶的活性，会发展出一种迟发的自身免疫表型，其特征类似于系统性红斑狼疮。了解磷脂降解受损导致自身免疫表型的机制可能为狼疮的发病机制提供新的见解，并为治疗提供新的靶点。