Glutathione, macrophages and unstable atherosclerosis

描述(申请人提供)：动脉粥样硬化斑块内巨噬细胞的死亡可能在斑块转化为不稳定斑块的过程中发挥重要作用，这种斑块容易破裂和出血。目前尚不清楚是什么确切地杀死了斑块内的巨噬细胞。一种可能的可能性是氧化的脂类和来自脂蛋白的游离胆固醇的积累，这些脂蛋白已经被细胞外基质捕获和保留。巨噬细胞在体外积累氧化的低密度脂蛋白，伴随着谷胱甘肽的消耗，谷胱甘肽是大多数细胞类型的主要内源性抗氧化剂。药物刺激谷胱甘肽合成可保护巨噬细胞免受氧化低密度脂蛋白的细胞毒作用。我们的初步数据表明，谷胱甘肽合成的限速酶谷氨酸半胱氨酸连接酶催化亚单位的过度表达也可以保护巨噬细胞免受氧化低密度脂蛋白、氧化脂质部分和其他促氧化剂的死亡。氧化低密度脂蛋白也是谷氨酸半胱氨酸连接酶催化和调节亚基表达的有效诱导剂。因此，我们假设增加谷氨酸半胱氨酸连接酶在巨噬细胞中的稳定表达将保护细胞免受促氧化剂诱导的死亡，并增加动脉粥样硬化斑块的稳定性。为了验证这一假说，并进一步研究氧化脂质部分如何在巨噬细胞中调节谷氨酸半胱氨酸连接酶基因的表达，我们提出了以下三个具体目标。 1.探讨氧化型低密度脂蛋白氧化脂质成分在调节巨噬细胞谷氨酸半胱氨酸连接酶亚单位基因表达中的作用。 2.确定原代细胞表达GCL-c的增加是否抑制促氧化和游离胆固醇诱导的死亡。 3.观察GCL-c高表达细胞(GCL-c)和GCL-m缺乏细胞(GCL-m)骨髓移植对老年载脂蛋白E-L小鼠巨噬细胞死亡和动脉粥样硬化的影响。 本提案中包括的旨在防止巨噬细胞死亡的策略具有很高的成功稳定动脉粥样硬化斑块的可能性，应有助于减少斑块破裂、闭塞性血栓形成、心肌梗死和中风。

DESCRIPTION (provided by applicant): The death of macrophages within an atherosclerotic plaque may play a fundamental role in conversion of the plaque to an unstable plaque, one that is vulnerable to rupture and hemorrhage. It is currently unknown precisely what kills macrophages within the plaque. One likely possibility is accumulation of oxidized lipids and free cholesterol derived from lipoproteins that have been trapped and retained by the extra-cellular matrix. Accumulation of oxidized LDL by macrophages in vitro is accompanied by depletion of glutathione, the major endogenous antioxidant for most cell types. Pharmacological stimulation of glutathione synthesis protects macrophages from the cytotoxic effects of oxidized LDL. Our preliminary data suggests that overexpression of the catalytic subunit of glutamate cysteine ligase, the rate-limiting enzyme for glutathione synthesis also protects macrophages from death due to oxidized LDL, oxidized lipid moieties and other prooxidants. Oxidized LDL is also a potent inducer of the expression of both the catalytic and regulatory subunits of glutamate cysteine ligase. Thus, we hypothesize that increased stable expression of glutamate cysteine ligase in macrophages will protect the cells from pro-oxidant induced death and increase the stability of atherosclerotic plaques. To test this hypothesis and to further investigate how oxidized lipid moieties contribute to the regulation of expression of the glutamate cysteine ligase genes in macrophages, we propose the following three specific aims. 1.To determine the role of oxidized lipid components of oxidized LDL in the regulation of macrophage expression of the glutamate cysteine ligase subunit genes. 2.To determine whether ad how increased expression of GCL-c by RAW cells inhibits pro-oxidant and free cholesterol induced death. 3.To determine the effects of bone marrow transplantation of cells over-expressing GCL-c (increased capacity to make glutathione) or deficient in GCL-m (decreased capacity to make glutathione) on macrophage death and atherosclerosis in older apo E-l- mice with established lesions. Strategies such as those included in the present proposal that are designed to prevent macrophage death have a high probability of successfully stabilizing atherosclerotic plaques and should help reduce plaque rupture, occlusive thrombosis, myocardial infarction and stroke.