Mechanisms for Dysfunctional HDL Formation in Familial Hypercholesterolemia

描述(申请人提供)：高密度脂蛋白的抗动脉粥样硬化功能包括调节胆固醇逆向运输，以及抗氧化和抗炎作用。越来越多的证据支持这一概念，即高密度脂蛋白功能可能受损或丢失，高密度脂蛋白功能障碍有助于动脉粥样硬化的发展。家族性高胆固醇血症(FH)是一种常染色体显性遗传性疾病，与严重的低密度脂蛋白水平升高和早发冠状动脉疾病(CAD)的风险增加有关。杂合子和纯合子FH都有低的高密度脂蛋白，但这一发现没有得到太多的关注，而冠心病风险的增加归因于低密度脂蛋白水平的升高。我们最近发现，FH患者的高密度脂蛋白具有显著的促炎作用。这项建议的一个目标(具体目标1)是检验FH患者高密度脂蛋白功能失调的假设(促炎、促氧化和/或与外排能力降低相关)。异前列腺素是由脂蛋白和细胞膜的磷脂中的花生四烯酸非酶氧化而形成的。血浆中F2-异前列腺素水平是体内脂质过氧化和氧化应激的标志物。有趣的是，人体血浆中的酯化异前列腺素(EIS)主要定位于高密度脂蛋白，少量与低密度脂蛋白和极低密度脂蛋白有关。一些证据支持脂质过氧化和/或F2-异前列腺素在动脉粥样硬化病变发展中的直接作用。在… 目前尚不清楚EIS在高密度脂蛋白中的积聚是否影响其动脉粥样硬化的保护功能。有趣的是，我们发现接受低密度脂蛋白分离的FH患者的血浆中EIS的数量是正常血浆的两倍，并且在低密度脂蛋白分离后EI水平下降了45%。异丙肾上腺素(Isolevuglandins，Isoevuglandins，Isoevuglandins)是一组与异前列腺素平行形成的高活性氧化损伤介质。我们将研究这些生物活性脂质是否在FH患者的高密度脂蛋白的促炎特性中发挥直接的机制作用。在特定的目标2中，我们将检验生物活性脂类(F2-异前列腺素和异丙肾上腺素)在高密度脂蛋白中积累导致抗炎功能丧失的假说。研究表明，异前列腺素可与二十烷类受体结合，包括血栓烷(TP)和前列腺素(PG)E2受体(EP2)。因此，我们将验证这样的假设，即TP和EP2受体参与了F2-异前列腺素强化的高密度脂蛋白的炎症效应。异酮醛迅速加成到蛋白质上赖氨酸的e-氨基上，促进蛋白质的交联和功能障碍。因此，我们将检验这一假说，即异紫甘油素介导高密度脂蛋白相关蛋白的氧化损伤，导致高密度脂蛋白胆固醇功能受损。我们的结果可能导致开发新的高密度脂蛋白功能标志物，为改善高密度脂蛋白功能提供新的药理靶点，并确定高密度脂蛋白作为FH患者的治疗靶点。

DESCRIPTION (provided by applicant): Anti-atherogenic functions of HDL include mediation of reverse cholesterol transport, and anti-oxidative and anti- inflammatory effects. Mounting evidence supports the concept that HDL function can be impaired or lost, and that dysfunctional HDL contributes to the development of atherosclerosis. Familial hypercholesterolemia (FH) is an autosomal dominant disorder associated with severely elevated LDL levels and increased risk of premature coronary artery disease (CAD). Both heterozygous and homozygous FH have low HDL, but this finding has not received much attention, and the increased CAD risk is attributed to the elevated LDL levels. We have recently discovered that the HDL from patients with FH is dramatically pro-inflammatory. A goal of this proposal (Specific Aim 1) is to examine the hypothesis that HDL of FH patients is dysfunctional (pro-inflammatory, pro- oxidant, and/or associated with reduced efflux capacity). Isoprostanes are formed from the non-enzymatic oxidation of arachidonic acid in phospholipids of lipoproteins and cell membranes. Plasma levels of F2- isoprostanes are established in vivo markers of lipid peroxidation and oxidant stress. Interestingly, the esterified isosprostanes, (EIs) in human plasma are mainly localized to HDL, with lesser amounts associated with LDL and VLDL. Several lines of evidence support a direct role for lipid peroxidation and/or F2-isoprostanes in atherosclerotic lesion development. At present it is unknown whether the accumulation of EIs in HDL affects its atheroprotective functions. Interestingly, we have found that plasma from subjects with FH undergoing LDL apheresis has twice the amount of EIs compared to normal plasma, and that after LDL apheresis EI levels decrease by 45%. Isolevuglandins (isoLGs) are a group of g-ketoaldehydes (isoketals) that are highly reactive mediators of oxidative damage formed in parallel with isoprostanes. We will investigate whether these bioactive lipids play direct mechanistic roles in the pro-inflammatory properties of HDL in FH patients. In Specific Aim 2, we will examine the hypothesis that accumulation of bioactive lipids (F2-isoprostanes and Isolevuglandins) in HDL results in loss of anti-inflammatory function. Isoprostanes have been shown to bind to eicosanoid receptors implicated in atherogenesis, including receptors for thromboxane (TP) and prostaglandin (PG)E2 (EP2). Therefore, we will examine the hypothesis that the TP and EP2 receptors contribute to the inflammatory effects of F2-isoprostane enriched HDL. Isoketals rapidly adduct to the e-amino groups of lysines on proteins, promoting protein cross-linking and dysfunction. Therefore, we will examine the hypothesis that isolevuglandins mediate oxidative damage of HDL associated proteins resulting in impaired function of HDL cholesterol. Our results may lead to the development of new markers of HDL function, provide new pharmacologic targets for improving HDL function, and identify HDL as a target of therapy in FH patients.