Mechanisms for Dysfunctional HDL Formation in Familial Hypercholesterolemia

描述（由申请方提供）：HDL的抗动脉粥样硬化功能包括介导胆固醇逆向转运以及抗氧化和抗炎作用。越来越多的证据支持HDL功能可能受损或丧失的概念，并且功能失调的HDL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疾病，与LDL水平严重升高和早发冠状动脉疾病（CAD）风险增加相关。杂合子和纯合子FH均具有低HDL，但这一发现并未受到太多关注，并且CAD风险增加归因于LDL水平升高。我们最近发现FH患者的HDL具有显著的促炎性。本提案的目标（具体目标1）是检查FH患者的HDL功能失调（促炎、促氧化和/或与外排能力降低相关）的假设。异前列烷是由脂蛋白和细胞膜磷脂中花生四烯酸的非酶促氧化形成的。F2-异前列烷的血浆水平是脂质过氧化和氧化应激的体内标志物。有趣的是，人血浆中的酯化异前列烷（EI）主要定位于HDL，与LDL和VLDL相关的量较少。几条证据支持脂质过氧化和/或F2-异前列烷在动脉粥样硬化病变发展中的直接作用。在 目前尚不清楚EI在HDL中的积累是否影响其动脉粥样硬化保护功能。有趣的是，我们已经发现，与正常血浆相比，接受LDL单采术的FH受试者的血浆具有两倍的EI量，并且在LDL单采术后EI水平降低了45%。异evuglandins（isoLG）是一组g-酮醛（isoketals），是与异前列腺素平行形成的氧化损伤的高反应性介质。我们将研究这些生物活性脂质是否在FH患者中HDL的促炎症特性中发挥直接的机制作用。在具体目标2中，我们将研究HDL中生物活性脂质（F2-异前列腺素和异evuglandins）的积累导致抗炎功能丧失的假设。已显示异前列烷与动脉粥样硬化形成中涉及的类二十烷酸受体结合，包括血栓烷（TP）和前列腺素（PG）E2（EP 2）的受体。因此，我们将检验TP和EP 2受体对富含F2-异前列烷的HDL的炎症作用有贡献的假设。异缩酮快速加合到蛋白质上赖氨酸的e-氨基基团，促进蛋白质交联和功能障碍。因此，我们将检验异evuglandins介导HDL相关蛋白的氧化损伤导致HDL胆固醇功能受损的假设。我们的研究结果可能会导致HDL功能的新标志物的发展，提供新的药理学目标，改善HDL功能，并确定HDL作为FH患者的治疗目标。

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.