Atheroprotection via Reduced Plasma High Density Lipoprotein-Free Cholesterol Bioavailability

尽管血浆中高浓度的低密度脂蛋白(“坏胆固醇”)与动脉粥样硬化有关 对于心血管疾病(ACVD)，他汀类药物可降低血浆低密度脂蛋白-C，从而降低ACVD。相比之下，高密度 脂蛋白胆固醇(高密度脂蛋白-C；“好胆固醇”)与ACVD的变化相反。然而，试图减少 通过升高血浆高密度脂蛋白胆固醇水平导致的急性脑血管病已经失败。新的证据表明，高密度脂蛋白的质量比 它比数量更重要，而且它从巨噬细胞中清除游离胆固醇(FC)的能力(MΦ)是一个重要的 在ACVD中，细胞类型是其最重要的动脉粥样硬化保护性质。这个过程，MΦ-FC外流，启动FC 转移到肠道进行处理--这是一个防止动脉粥样硬化的过程。矛盾的是，血浆水平非常高的患者 高密度脂蛋白胆固醇水平有很高的心血管疾病风险；其潜在机制尚不清楚，目前还没有 以心脏保护的方式逆转高密度脂蛋白胆固醇水平的干预措施。我们假设潜在的 血浆高密度脂蛋白胆固醇水平非常高的患者发生ACVD的原因是高密度脂蛋白含量过高 Fc，在细胞和脂蛋白之间自由转移。这种状态使FC具有高度的生物利用度，因此 与从动脉壁去除FC相比，富含FC的高密度脂蛋白将FC转移到动脉壁MΦ，这是一个导致动脉粥样硬化的过程。 使用基础高密度脂蛋白-C水平的ACVD小鼠模型(SR-B1-/-小鼠)，我们计划识别高密度脂蛋白-Fc 生物利用度是ACVD的驱动因素，并表明使用降低高密度脂蛋白的细菌蛋白(血清混浊)治疗 因子)，随腺相关病毒提供，预防/逆转ACVD。在这个ACVD-HDL轴上，我们 提出以下具体目标： 目的1-比较野生型、SR-B1-/-高密度脂蛋白-[~3H]Fc和胆固醇酯的血浆清除动力学 (Ce)在野生型和SR-B1-/-小鼠中，同时鉴定[~3H]Fc和[~3H]Ce的组织部位， 以及AAVSOF和AAVGFP对这些动力学和组织分布的影响。 目的2a-验证高密度脂蛋白和J774MΦ之间的FC通量从流出切换到流入的假设 提高高密度脂蛋白胆固醇生物利用度，这是高密度脂蛋白颗粒浓度和高密度脂蛋白胆固醇含量(摩尔%)的函数 Fc)。目标2b-与目标1同时进行，以检验HMGCoA还原酶和ACAT活性的假设 通过提高Φ-FC的生物利用度，分别降低和增加M-HDLFC含量。目标2c- 验证高密度脂蛋白胆固醇生物利用度增加诱导J774MΦ泡沫细胞形成的假说。 目标3-验证AAVSOF与AAVGFP相比降低高密度脂蛋白胆固醇可预防和/或逆转的假设 SR-B1-/-小鼠的动脉粥样硬化。 这些目标的完成将为研究提供一个令人信服的理由来确定高血浆高密度脂蛋白- FC与高密度脂蛋白胆固醇患者的ACVD有关，也与降低高密度脂蛋白胆固醇的药物的开发有关。

Although high plasma concentrations of LDL-C (“bad cholesterol”) are associated with atherosclerotic cardiovascular disease (ACVD), statins reduce plasma LDL-C and with it ACVD. In contrast, high density lipoprotein-cholesterol (HDL-C; “good cholesterol”) varies inversely with ACVD. However attempts to reduce ACVD via increased plasma HDL-C levels have failed. New evidence suggests that HDL quality is more important than quantity and that its ability to remove free cholesterol (FC) from macrophages (MΦ), an important cell type in ACVD, is its most important atheroprotective quality. This process, MΦ-FC efflux, initiates the FC transfer to the intestine for disposal—an atheroprotective process. Paradoxically, patients with very high plasma HDL-C levels are at high ACVD risk; the underlying mechanism is unknown, and currently there are no interventions that reverse high HDL-C levels in a cardioprotective way. We hypothesize that the underlying cause of ACVD in patients with very high plasma HDL-C levels is too much HDL that contains high amounts of FC, which transfers freely among cells and lipoproteins. This state makes FC highly bioavailable so that rather than removing FC from the arterial wall, FC-rich HDL transfers FC to arterial-wall MΦ—an atherogenic process. Using a mouse model of ACVD with underlying high HDL-C levels (SR-B1-/- mouse) we plan to identify HDL-FC bioavailability as a driver of ACVD and show that treatment with an HDL-lowering bacterial protein (serum opacity factor), delivered with an adeno-associated virus prevents/reverses ACVD. Within this ACVD-HDL axis, we propose the following specific aims: Aim 1—To compare the plasma clearance kinetics of wild-type and SR-B1-/- HDL-[3H]FC and cholesteryl ester (CE) in wild-type and SR-B1-/- mice, simultaneously identifying the tissue sites of [3H]FC and [3H]CE accretion, and the effects of AAVSOF vs. AAVGFP on these kinetics and tissue distributions. Aim 2a—To test the hypothesis that FC flux between HDL and J774 MΦ switches from efflux to influx with increasing HDL-FC bioavailability, which is a function of HDL particle concentration and HDL-FC content (mol% FC). Aim 2b—Concurrently with Aim 1, to test the hypothesis that HMGCoA reductase and ACAT activities decrease and increase, respectively, MΦ-FC content as effected by increasing HDL-FC bioavailability. Aim 2c— To test the hypothesis that increased HDL-FC bioavailability induces foam cell formation in J774 MΦ. Aim 3—To test the hypothesis that reduction of HDL-FC by AAVSOF vs. AAVGFP delivery prevents and/or reverses atherosclerosis in SR-B1-/- mice. Completion of these aims will provide a compelling rationale ●for studies to determine whether high plasma HDL- FC is associated with ACVD in patients with high HDL-C and ●for the development of drugs that lower HDL-FC.