Cellular Lipids and Leukocyte Function

 描述（由申请方提供）：脓毒症的特征是释放细菌结构成分和毒素，激活靶细胞中的炎症级联反应。中性粒细胞的募集及其与血管内皮的结合是脓毒症的重要早期反应。中性粒细胞和常驻巨噬细胞通过分泌细胞因子、趋化因子和消化酶启动修复过程。然而，免疫应答的失调可导致以白细胞增多为特征的广泛且不受控制的炎性损伤（嗜中性粒细胞增多症/单核细胞增多症）。这种失调导致多器官功能障碍综合征（MODS），并转变为明显的感染性休克。呼吸衰竭进展迅速，死亡率约为40- 50%。HDL作为载脂蛋白（apo）A-I和apoE等多种蛋白质的载体，在介导胆固醇逆向转运中发挥作用。几项研究表明，apoE发挥抗炎作用，包括免疫细胞功能的调节，这是独立于其降低血浆胆固醇水平的能力。在这方面，apoE最近显示限制造血干细胞和多能祖细胞（HSPC）的扩增，导致中性粒细胞和单核细胞增殖的减少。apoE对白细胞活化的抑制作用与细胞胆固醇含量本身的降低有关。这表明HDL相关的apoE在减少脓毒症的炎症细胞损伤中起着至关重要的作用。然而，apoE的这种保护作用可能受到HDL水平降低的限制，HDL水平降低是脓毒症的特征。本申请中提供的初步数据显示，模拟天然apoE作用的合成肽（Ac-hE 18 A-NH 2）可防止白细胞活化并改善啮齿动物败血症模型中的存活率。Ac-hE 18 A-NH 2还诱导含有抗氧化剂对氧磷酶和apoE本身的前HDL颗粒的释放。我们的数据还表明，apoE模拟物结合到细胞表面蛋白聚糖和介导胆固醇流出白细胞，这是一种反应，与脂多糖诱导的细胞因子/趋化因子释放减少。在本申请中，我们将测试新的假设，即Ac-hE 18 A-NH 2和相关的apoE模拟肽通过抑制HSPC扩增和白细胞增殖/活化来减轻脓毒症诱导的炎性损伤，所述HSPC扩增和白细胞增殖/活化通过涉及细胞胆固醇含量降低的机制。另外的研究将测试用apoE模拟肽体外治疗是否改变从脓毒症患者分离的白细胞的表型/功能。

 DESCRIPTION (provided by applicant): Sepsis is characterized by the release of bacterial structural components and toxins that activate inflammatory cascades in target cells. The recruitment of neutrophils and their binding to the vascular endothelium is an important, early response to sepsis. Neutrophils and resident macrophages initiate repair processes via the secretion of cytokines, chemokines and digestive enzymes. Dysregulation of the immune response, however, can lead to widespread and uncontrolled inflammatory injury characterized by leukocytosis (neutrophilia/monocytosis). This dysregulation results in multiple organ dysfunction syndrome (MODS) with the transition to overt septic shock. Respiratory failure progresses rapidly and is associated with approximately 40- 50% mortality. HDL serves as a carrier for diverse proteins, including apolipoprotein (apo) A-I and apoE, that play a role in mediating reverse cholesterol transport. Several studies suggest that apoE exerts anti-inflammatory effects, including the modulation of immune cell function, that are independent of its ability to lower plasma cholesterol levels. In this regard, apoE was recently shown to limit th expansion of hematopoietic stem and multipotential progenitor cells (HSPCs), resulting in a decrease in neutrophil and monocyte proliferation. The inhibitory effect of apoE on leukocyte activation was linked to a reduction in cellular cholesterol content per se. It is proposed that HDL-associated apoE plays a critical role in reducing inflammatory cell injury in the context of sepsis. This protective effect of apoE, however, may be limited by reduced levels of HDL that characterize sepsis. Preliminary data presented in the application show that a synthetic peptide (Ac-hE18A-NH2) that mimics effects of native apoE prevents the activation of leukocytes and improves survival in a rodent model of sepsis. Ac-hE18A-NH2 also induces the release of preß-HDL particles containing the antioxidant paraoxonase and apoE itself. Our data also show that apoE mimetics bind to cell surface proteoglycans and mediate cholesterol efflux from leukocytes, a response that is associated with a reduction in lipopolysaccharide-induced cytokine/chemokine release. In this application, we will test the novel hypothesis that Ac-hE18A-NH2 and related apoE mimetic peptides attenuate sepsis-induced inflammatory injury by inhibiting HSPC expansion and leukocyte proliferation/activation by a mechanism involving a reduction in cellular cholesterol content. Additional studies will test whether in vitro treatment with apoE mimetic peptides alters the phenotype/function of leukocytes isolated from septic patients.