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。我们的实验室已经证明，通过FC诱导的磷脂酰胆碱（PC）生物合成上调和阻断FC向外周细胞部位（如质膜和线粒体）的运输，可以阻止培养细胞的游离胆固醇（FC）负荷。在此背景下，本提案的总体目标是通过对脂质代谢和死亡信号通路进行基因操纵的小鼠，测试有关动脉粥样硬化中Mphi死亡的特定假设。假设是，Mphi可能(a)通过在病变发展过程中限制Mphi的数量和“安全”处理晚期病变中死亡的Mphi来起到保护作用；和/或(b)通过促进从死亡的Mphi中释放有害分子来促进脂质核心的发育。当Mphi细胞以“凋亡”的方式死亡时，可能会产生保护作用，而当Mphi细胞以更“坏死”的方式死亡时，可能会产生有害作用。在Aim I中，我们将使用载脂蛋白E敲除（动脉粥样硬化）小鼠，这些小鼠的PC生物合成发生mphi特异性改变（通过CTP：磷脂酰酰基转移酶的遗传操作）或FC转运到外周细胞部位有缺陷（Niemann-Pick C小鼠）。目的是在体内测试PC和FC代谢在Mphi死亡中的作用，并在我们的假设背景下评估Mphi死亡改变对动脉粥样硬化和脂质核心发展的影响。在Aim II中，我们将专门研究Mphi细胞凋亡应该被阻断的小鼠模型。鉴于初步数据显示，在缺乏Fas死亡受体的Mphi中，fc介导的细胞凋亡被阻止，我们将主要关注在Mphi中缺乏Fas的小鼠身上。Fas通路在衰老诱导剂（如氧化脂蛋白和生长因子退出）引起的Mphi死亡中的作用也将被探讨。此外，考虑到bcl- 2家族蛋白在某些类型的fas介导的细胞凋亡以及其他原因导致的死亡中的关键作用，Mphi过表达抗凋亡蛋白bcl- 2和bcl- xl的小鼠将被检查动脉粥样硬化和脂质核心的发展。根据上述状态假说，当坏死样变化不受抑制时，病变Mphi细胞凋亡的阻断可能会对动脉粥样硬化产生不利影响。总之，该项目将有助于阐明基于脂质机制和Mphi死亡在动脉粥样硬化和脂质核心发展中的生理后果。

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.