Glutathione, macrophages and unstable atherosclerosis

描述（由申请人提供）：动脉粥样硬化斑块内巨噬细胞的死亡可能在斑块转变为不稳定斑块（易破裂和出血）的过程中起着重要作用。目前还不清楚是什么杀死了斑块内的巨噬细胞。一种可能是氧化脂质和游离胆固醇的积累，这些脂质和游离胆固醇来源于被细胞外基质捕获和保留的脂蛋白。体外巨噬细胞氧化LDL的积累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。谷胱甘肽合成的药理刺激保护巨噬细胞免受氧化LDL的细胞毒性作用。我们的初步数据表明，谷氨酸半胱氨酸连接酶（谷胱甘肽合成的限速酶）的催化亚基的过度表达也可以保护巨噬细胞免受氧化LDL、氧化脂质部分和其他促氧化剂导致的死亡。氧化LDL也是谷氨酸半胱氨酸连接酶的催化和调节亚基表达的有效诱导剂。因此，我们假设增加巨噬细胞中谷氨酸半胱氨酸连接酶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。为了验证这一假设，并进一步研究氧化脂质部分如何参与巨噬细胞中谷氨酸半胱氨酸连接酶基因的表达调节，我们提出以下三个具体目标。

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.