Macrophage death and lipid metabolism in atherosclerosis

巨噬细胞（Mphi）死亡是动脉粥样硬化病变的一个重要特征，但这一事件的生理后果仍不确定。我们的实验室已经表明，培养的游离胆固醇（FC）负荷可以通过FC诱导的磷脂酰胆碱（PC）生物合成的上调和通过阻断FC转运到外周细胞位点（例如，质膜和线粒体）。在这种情况下，这个建议的总体目标是测试特定的假设，Mphi死亡动脉粥样硬化使用小鼠的脂质代谢和死亡信号通路已被遗传操纵。假设是Mphi可能（a）通过限制病变发展期间Mphi的数量并且可能通过“安全地”处置晚期病变中垂死的Mphi而具有保护性;和/或（B）通过促进垂死的Mphi释放有害分子而有助于脂质核心的发展。当Mphi's通过“凋亡”死亡时可能发生保护作用，而当Mphi's通过更多的“坏死”样过程死亡时可能发生有害作用。在目的I中，我们将使用载脂蛋白E敲除（动脉粥样硬化）小鼠，其PC生物合成中具有Mphi特异性改变（通过CTP：磷酸胆碱胞苷酰转移酶的遗传操作）或具有缺陷的FC转运至外周细胞位点（Niemann-Pick C小鼠）。我们的目标是测试PC和FC代谢在体内Mphi死亡中的作用，并在我们的假设的背景下评估改变Mphi死亡对动脉粥样硬化形成和脂质核心发展的后果。在目的II中，我们将专门研究Mphi细胞凋亡应被阻断的小鼠模型。鉴于初步数据显示FC介导的细胞凋亡在缺乏Fas死亡受体的Mphi中被阻止，主要焦点将集中在Mphi中不存在Fas的小鼠上。Fas通路在Mphi死亡中的作用也将被探讨，Mphi死亡是由较老的诱导剂引起的，如氧化脂蛋白和生长因子戒断。此外，考虑到bcl- 2家族蛋白在某些类型的Fas介导的细胞凋亡中以及在由于其它原因导致的死亡中的关键作用，将检查Mphi过表达抗细胞凋亡蛋白Bcl-2和Bcl-xL的小鼠的动脉粥样硬化形成和脂质核心发育。根据上述假设，病变Mphi细胞凋亡的阻断可能对动脉粥样硬化的发生产生不利影响，使坏死样变化不受抑制。总之，该项目将有助于阐明脂质为基础的机制和生理后果的Mphi死亡动脉粥样硬化和脂质核心的发展。

Macrophage (Mphi) death is an important feature of atherosclerotic lesions, yet there are still uncertainties about the physiological consequences of this event. Our laboratory has shown that free cholesterol (FC) loading of cultured can be prevented by FC-induced up-regulation of phosphatidylcholine (PC) biosynthesis and by blockage of FC transport to peripheral cellular sites (e.g., plasma membrane & mitochondria). In this context, the overall objective of this proposal is to test specific hypotheses regarding Mphi death in atherosclerosis using mice in which lipid metabolic and death-signaling pathways have been genetically manipulated. The hypotheses are that Mphi may (a) be protective by limiting the number of Mphi's during lesion development and perhaps by "safely" disposing of dying Mphi's in advanced lesions; and/or (b) contribute to lipid core development by promoting the release of harmful molecules from dying Mphi's. Protective effects may occur when Mphi's die by "apoptosis", whereas harmful effects may occur when Mphi's die by more "necrotic"-like processes. In Aim I, we will use apolipoprotein E knockout (atherosclerotic) mice with Mphi-specific alterations in PC biosynthesis (via; genetic manipulation of CTP: phosphocholine cytidylylyltransferase) or with defective FC transport to peripheral cellular sites (Niemann-Pick C mice). The goal will be to test the role of PC and FC metabolism in Mphi death in vivo and to evaluate, in the context of our hypotheses, the consequences of altered Mphi death on atherogenesis and lipid core development. In Aim II, we will specifically examine mouse models in which Mphi apoptosis should be blocked. In view of preliminary data showing the FC-mediated apoptosis is prevented in Mphi's lacking the Fas death receptor, a major focus will be on mice in which Fas is absent in Mphi's. The role of the Fas pathway in Mphi death caused by older inducers, such as oxidized lipoproteins and growth factor withdrawal, will also be explored. Furthermore, given the key role of bcl- 2 family proteins in certain types of Fas-mediated apoptosis as well as in death due to other causes, mice whose Mphi's over-express the anti- apoptotic proteins Bcl-2 and Bcl-xL will be examined for atherogenesis and lipid core development. Blockage of lesional Mphi apoptosis may, according the above-state hypothesis, adversely affect atherogenesis in necrotic-like changes are left uninhibited. In summary, this project should help elucidate lipid-based mechanisms and physiologic consequences of Mphi death in atherogenesis and lipid core development.