HDL Modulation of monocyte function in endotoxemia

描述（由申请方提供）：脓毒症是住院患者死亡的主要原因。脂多糖（LPS）是革兰氏阴性菌的内毒素成分，其引发炎症级联反应，导致多器官损伤。在炎症条件下，单核细胞浸润动脉壁并分化为树突状细胞（DC）或巨噬细胞（MF）。脓毒症诱导先天免疫应答的失调和脂质代谢的变化，导致血浆中富含甘油三酯（TG）的脂蛋白增加和高密度脂蛋白（HDL）水平降低。HDL及其主要蛋白组分载脂蛋白（apo）A-I发挥显著的抗炎和抗氧化作用，并减少与白细胞粘附到血管壁相关的损伤反应。最近，人们对使用HDL作为炎性疾病如脓毒症的新型治疗剂产生了相当大的兴趣。虽然HDL的作用机制还不清楚，但改善HDL的质量/功能可能会有利地影响脓毒症的致病反应。我们实验室最近的研究表明，一种新的18-残基肽（4F），其设计是基于apoA-I的结构特征，将HDL从功能失调的HDL形式转化为功能正常的HDL形式。4F有利于富含apoA-I和对氧黄酶-1（PON 1）/PAF-乙酰水解酶（PAF-AH）的HDL颗粒的形成，这些酶抑制氧化脂质和PAF。令人兴奋的初步数据显示，4F在败血症啮齿动物模型（盲肠结扎和穿孔模型）和细胞培养系统中抑制炎症和细胞毒性。此外，它还在单核细胞向DC的分化中起作用。4F（如apoA-I）调节单核细胞/MF功能，并具有有效的抗炎活性。基于初步数据，我们假设4F：（1）通过抑制单核细胞与EC的缔合/结合和/或其细胞毒性作用来减少血管损伤;和（2）通过优先诱导单核细胞/MF向DC分化来改善免疫应答。进一步提出，这些作用由肽直接介导，并通过改善HDL质量/功能间接介导。为了检验这些假设，我们提出了以下具体目标：（1）评估4F介导的在败血症啮齿动物模型中含apo A-I和apoB的脂蛋白的质量/功能的变化（2）确定细胞培养模型中4F作用的抗炎机制是否是由于脂蛋白质量/功能的改善和/或肽的直接保护作用，和（3）以确定4F是否通过增强抗原呈递树突状细胞的形成来改善对脓毒症的免疫应答。该建议探讨了apoA-I/HDL在脓毒症背景下调节单核细胞/MF功能中的作用。拟议的研究结果将提供新的药理学策略，用于治疗脓毒症和其他病理状态，其特征在于降低血浆HDL。败血症是住院患者死亡的主要原因。死亡率在很大程度上是由于脂多糖（LPS）诱导的细胞损伤，脂多糖是革兰氏阴性菌外膜的一种成分。在本申请中，我们建议研究模拟HDL胆固醇保护作用的合成肽4F是否减少与脓毒症相关的炎性损伤。我们推测这种肽通过刺激具有改善功能的新HDL颗粒的形成和对细胞的直接作用来发挥保护作用。总的来说，这些作用有助于减少脓毒症诱导的细胞损伤。

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.