HDL Metabolism Influence of Extracellular Phospholipases

描述（由申请人提供）：血浆高密度脂蛋白（HDL）胆固醇及其主要HDL载脂蛋白apoA-I水平与动脉粥样硬化性心血管疾病呈负相关。血浆HDL胆固醇和apoA-I水平部分取决于它们被分解代谢的速率，但调节它们在体内分解代谢的机制仍不完全清楚。急性炎症状态如脓毒症和慢性炎症状态如代谢综合征都与低水平的HDL胆固醇和apoA-I相关，主要是由于增加的catabolism。该项目的一个主要基本假设是细胞外磷脂酶在炎症反应中上调，并通过HDL磷脂的水解调节全身HDL代谢。我们克隆并鉴定了脂肪酶基因家族的一个新成员，我们称之为内皮脂肪酶（EL）。在该项目的当前周期中，我们已经证明，小鼠中EL的过表达由于catalase增加而导致HDL显著降低，并且小鼠中EL的抗体抑制由于catalase减少而导致HDL增加。在这个竞争性的更新提案中，我们将把我们的努力集中在EL上，以更好地理解其结构-功能关系，与影响HDL的其他基因的代谢相互作用，与动脉粥样硬化的关系，以及与人体生理学和病理生理学的关系。 具体目标1：研究EL与其高度同源的亲缘种LPL和HL之间在脂质和脂蛋白偏好性的分子基础方面的差异。 具体目标二：为了检验在肝脏中，EL与HL和SR-BI相互作用以影响HDL代谢、胆固醇的选择性摄取和胆固醇逆向转运的假设。 具体目的3：确定慢性肝特异性EL表达对小鼠动脉粥样硬化形成的影响。将这些结果与内皮特异性EL表达对动脉粥样硬化的影响进行比较。验证内皮细胞EL表达影响内皮细胞生理学的假设。 具体目标4：检验以下假设：人类炎症性疾病中EL增加，可能导致与这些疾病相关的HDL-C水平降低。 最近的一篇社论指出：“也许关于内皮脂肪酶最重要的问题是：a）它在人类HDL代谢中是否起重要作用，以及B）它在动脉粥样硬化形成中是否起重要作用？“这项建议解决了这两个问题，也解决了关键的结构-功能问题和潜在的基因-基因相互作用方面的EL及其对HDL代谢的影响。这些研究的结果应提供重要的新的见解EL在HDL代谢和动脉粥样硬化的作用。

DESCRIPTION (provided by applicant): Plasma levels of high-density lipoprotein (HDL) cholesterol and its major HDL apolipoprotein, apoA-I, are inversely associated with atherosclerotic cardiovascular disease. Plasma HDL cholesterol and apoA-I levels are determined in part by the rate at which they are catabolized, but the mechanisms that modulate their catabolism in vivo remain incompletely understood. Both acute inflammatory states, such as sepsis, and chronic inflammatory states, such as the metabolic syndrome, are associated with low levels of HDL cholesterol and apoA-I, primarily due to increased catabolism. A major underlying hypothesis of this project has been that extracellular phospholipases are upregulated in response to inflammation and modulate systemic HDL metabolism through hydrolysis of HDL phospholipids. We cloned and characterized a new member of the lipase gene family that we termed endothelial lipase (EL). In the current cycle of this project, we have demonstrated that overexpression of EL in mice causes markedly reduced HDL due to increased catabolism, and antibody inhibition of EL in mice causes increased HDL due to reduced catabolism. In this competing renewal proposal, we will focus our efforts on EL toward achieving a greater understanding of its structure-function relationships, metabolic interactions with other genes that influence HDL, association with atherosclerosis, and its relationship to human physiology and pathophysiology. Specific Aim 1: To investigate the differences between EL and its highly homologous relatives LPL and HL with regard to the molecular basis of the lipid and lipoprotein preferences of EL compared with LPL and HL. Specific Aim 2: To test the hypothesis that in the liver, EL interacts with HL and SR-BI to influence HDL metabolism, selective uptake of cholesterol, and reverse cholesterol transport. Specific Aim 3: To determine the effects of chronic hepatic-specific EL expression on atherogenesis in mice. To compare these results with the effects of endothelial-specific EL expression on atherosclerosis. To test the hypotheses that endothelial EL expression influences endothelial physiology. Specific Aim 4: To test the hypothesis that EL is increased in inflammatory conditions in humans and may contribute to the reduced HDL-C levels associated with these conditions. A recent editorial stated: "Perhaps the most important questions concerning endothelial lipase are: a) does it play an important role in HDL metabolism in humans, and b) does it play a significant role in atherogenesis?" This proposal addresses both of these issues and also addresses key structure-function questions and potential gene-gene interactions with regard to EL and its effects on HDL metabolism. The results of these studies should provide important new insight into the role of EL in HDL metabolism and atherogenesis.