HDL Modulation of monocyte function in endotoxemia

描述(申请人提供)：败血症是住院患者死亡的主要原因。内毒素(LPS)是革兰氏阴性菌的内毒素成分，可引起炎症级联反应，导致多器官损伤。在炎症条件下，单核细胞渗入动脉壁并分化为树突状细胞(DC)或巨噬细胞(MF)。脓毒症导致天然免疫反应失调和脂代谢改变，导致富含甘油三酯(TG)的脂蛋白增加，血浆高密度脂蛋白(HDL)水平降低。高密度脂蛋白及其主要蛋白质组分载脂蛋白(Apo)A-I具有显著的抗炎和抗氧化作用，并可降低白细胞与血管壁黏附相关的损伤反应。最近，人们对使用高密度脂蛋白作为一种新的炎症性疾病如败血症的治疗剂有相当大的兴趣。虽然高密度脂蛋白的作用机制尚不清楚，但提高高密度脂蛋白的质量/功能可能会有利地影响对脓毒症的致病反应。本实验室最近的研究表明，根据apoA-I的结构特征设计的一种新型18个残基的多肽(4F)可以将高密度脂蛋白从功能失调的高密度脂蛋白转化为功能高密度脂蛋白。4F有利于富含apoA-I和对氧磷酶-1(PON1)/PAF-乙酰水解酶(PAF-AH)的高密度脂蛋白颗粒的形成，这两种酶清除氧化脂质和PAF。令人振奋的初步数据显示，在脓毒症的啮齿动物模型(盲肠结扎和穿孔模型)和细胞培养系统中，4F都能抑制炎症和细胞毒性。此外，它还在单核细胞向DC分化过程中发挥作用。4F(如apoA-I)调节单核细胞/MF功能，具有较强的抗炎活性。根据实验数据，我们假设4F：(1)通过抑制单核细胞与内皮细胞的结合/结合和/或其细胞毒作用来减少血管损伤；(2)通过优先诱导单核细胞/MF向DC分化来提高免疫应答。进一步提出，这些作用既由多肽直接介导，也通过提高高密度脂蛋白的质量/功能间接介导。为了验证这些假说，我们提出了以下具体目标：(1)评估4F对脓毒症啮齿动物模型载脂蛋白A-I和载脂蛋白B质量/功能的影响；(2)确定4F在细胞培养模型中的抗炎机制是否归因于脂蛋白质量/功能的改善和/或多肽的直接保护作用；(3)确定4F是否通过促进抗原提呈树突状细胞的形成来改善脓毒症的免疫反应。本研究旨在探讨apoA-I/高密度脂蛋白在脓毒症中单核细胞/MF功能调节中的作用。建议的研究结果将为脓毒症和其他以血浆高密度脂蛋白降低为特征的病理状态的治疗提供新的药理学策略。与公共卫生相关的败血症是住院患者死亡的主要原因。死亡在很大程度上是由于内毒素(LPS)引起的细胞损伤，内毒素是革兰氏阴性细菌外膜的一种成分。在这项应用中，我们建议研究模拟高密度脂蛋白胆固醇保护作用的合成肽4F是否可以减少与脓毒症相关的炎性损伤。我们推测，这种多肽通过刺激新的高密度脂蛋白颗粒的形成和对细胞的直接作用而发挥保护作用。总而言之，这些作用有助于减少脓毒症引起的细胞损伤。

DESCRIPTION (provided by applicant): Sepsis is a major cause of death in hospitalized patients. Lipopolysaccharide (LPS), an endotoxic component of gram negative bacteria, initiates an inflammatory cascade that contributes to multiple organ injury. Under inflammatory conditions, monocytes infiltrate the artery wall and differentiate to either dendritic cells (DCs) or macrophages (MF). Sepsis induces dysregulation of the innate immune response and changes in lipid metabolism leading to an increase in triglyceride (TG)-rich lipoproteins and a decrease in high density lipoprotein (HDL) levels in plasma. HDL and its major protein component apolipoprotein (apo) A-I exert prominent anti-inflammatory and anti-oxidant effects, and reduces injury responses associated with leukocyte adhesion to the vessel wall. Recently, there has been considerable interest in using HDL as a novel therapeutic agent for inflammatory diseases like sepsis. Although the mechanism of HDL action is not well understood, improving HDL quality/function may favorably influence the pathogenic response to sepsis. Recent studies from our laboratory show that a novel 18-residue peptide (4F), whose design is based on the structural features of apoA-I converts HDL from a dysfunctional to functional HDL form. 4F favors the formation of HDL particles enriched in apoA-I and paraoxanase-1 (PON1)/PAF-acetyl hydrolase (PAF-AH), enzymes that scavenge oxidized lipids and PAF. Exciting preliminary data show that 4F inhibits inflammation and cytotoxicity in both a rodent model of sepsis (cecal ligation and puncture model) and cell culture systems. In addition, it also plays a role in the differentiation of monocytes to DCs. 4F (like apoA-I) modulates monocyte/MF function and has potent anti-inflammatory activity. Based on pilot data, we hypothesize that 4F: (1) reduces vascular injury by inhibiting the association/binding of monocytes to ECs and/or their cytotoxic actions; and (2) improves the immune response by preferentially inducing the differentiation of monocyte/MF to DCs. It is further proposed that these effects are mediated both directly by the peptide and indirectly by improving HDL quality/function. To test these hypotheses, we propose the following specific aims: (1) to assess 4F-mediated changes in the quality/function of apo A-I and apoB-containing lipoproteins in a rodent model of sepsis (2) to determine whether anti-inflammatory mechanisms of 4F action in cell culture models are due to improvement in lipoprotein quality/function and/or direct protective effects of the peptide and (3) to determine whether 4F improves the immune response to sepsis by enhancing the formation of antigen-presenting dendritic cells. This proposal explores the role of apoA-I/HDL in the modulation of monocyte/MF function in the context of sepsis. Results of the proposed studies will provide new pharmacologic strategies for the treatment of sepsis and other pathological states characterized by reduced plasma HDL. PUBLIC HEALTH RELEVANCE Sepsis is a major cause of death in hospitalized patients. Mortality is due, in large part, to the cellular injury induced by lipopolysaccharide (LPS), a component of the outer membrane of Gram-negative bacteria. In this application, we propose to investigate whether the synthetic peptide 4F, which mimics the protective effects of HDL cholesterol, reduces inflammatory injury associated with sepsis. We hypothesize that this peptide exerts protective effects by stimulating the formation of new HDL particles with improved function and by direct effects on cells. Collectively, these effects serve to reduce cell injury induced by sepsis.