LPS Efflux from Host Cells to Plasma Lipoproteins

描述(申请人提供)：细菌脂多糖(脂多糖或内毒素)的刺激作用可以增强动物宿主有益的先天免疫反应，而其潜在的毒性被认为在脓毒症的病理生理中起重要作用。血浆脂蛋白结合和中和内毒素，并通过促进这些细胞的内毒素外流来帮助控制单核细胞的激活。与循环单核细胞相比，我们发现分化的巨噬细胞可以促进内毒素的快速外流，而不需要任何血浆成分。ATP结合盒转运体A1(ABCA1)和内源性合成的载脂蛋白E(ApoE)可以清除巨噬细胞相关的内毒素，其机制类似于从巨噬细胞中清除炎性宿主脂类，帮助减轻动脉粥样硬化。由于已知载脂蛋白E可增强对内毒素毒性和细菌感染的抵抗力，我们推测巨噬细胞来源的载脂蛋白和ABC转运蛋白通过降低内毒素的生物活性和防止内毒素在组织中积聚来帮助控制局部炎症。我们的具体目标是：(1)巨噬细胞内毒素外流的分子机制，特别是ABCA1和巨噬细胞来源的载脂蛋白(apoE和apoC-L)的作用。(Ii)巨噬细胞释放的内毒素的处置和生物活性，主要是它与载脂蛋白E和载脂蛋白C-L的联系。我们还将研究脂多糖-载脂蛋白E与载脂蛋白E受体的相互作用。(ILL)小鼠炎症和脓毒症过程中载脂蛋白及相关基因的调节，以及巨噬细胞特异性表达或体内apoE缺陷的影响，以确定巨噬细胞来源的apoE对局部炎症、先天免疫反应和对细菌感染的抵抗力的影响。希望这些研究将确定巨噬细胞和载脂蛋白控制局部炎症的新机制，这些研究将导致脓毒症治疗的改善。

DESCRIPTION (provided by applicant): The stimulatory effects of bacterial lipopolysaccharide (LPS or endotoxin) can enhance beneficial innate immune responses in animal hosts, whereas its potential toxicity is thought to contribute importantly to the pathophysiology of sepsis. Plasma lipoproteins bind and neutralize LPS and help to control monocyte activation by promoting LPS efflux from these cells. In contrast to circulating monocytes, we found that differentiated macrophages can promote rapid LPS efflux without a requirement for any plasma constituent. ATP-binding cassette transporter A1 (ABCA1) and endogenously synthesized apolipoprotein E (apoE) can remove macrophage-associated LPS by mechanisms that are similar to those that remove inflammatory host lipids from macrophages and help reduce atherosclerosis. Since apoE is known to increase resistance to LPS toxicity and bacterial infection, we hypothesize that macrophage-derived apolipoproteins and ABC transporters help control local inflammation by decreasing LPS bioactivity and preventing LPS accumulation in tissues. Our Specific Aims are to determine: (I) The molecular mechanisms of LPS efflux from macrophages, specifically the roles of ABCA1 and macrophage-derived apolipoproteins (apoE and apoC-l). (II) The disposition and bioactivity of the LPS that is released from macrophages, primarily in terms of its association with apoE and apoC-l. We will also study LPS-apoE interactions with apoE receptors. (Ill) The regulation of apolipoproteins and related genes during inflammation and sepsis in mice, and the effects of macrophage specific expression or deficiency of apoE in vivo to determine the impact of macrophage-derived apoE on local inflammation, innate immune responses, and resistance to bacterial infection. It is hoped that these studies will define novel mechanisms for the control of local inflammation by macrophages and apolipoproteins and that these studies will lead to improvements in the management of sepsis.