MECHANISM OF ACTIVATION OF MACROPHAGES BY BACTERIAL LIPOPOLYSACCHARIDES

这项研究的长期目标是理解分子 脂多糖(LPS)启动信号转导机制的模型研究 激活的巨噬细胞在体内的杀瘤能力 癌症的治疗可能会被评估。LP已经被公认为有几个 几十年是最有力的刺激因素之一 巨噬细胞杀灭肿瘤细胞。越来越多的实验证据表明 可能牵涉到几个巨噬细胞膜结构 激活和合成信号转导的重要受体。 其中包括磷脂酰肌醇连接的CD14糖蛋白p73 内毒素结合蛋白和CD11/18粘附素。准确的贡献 这些分子中的每一个到实际的激活事件还没有 已经建立，拟议研究的具体目标#1是 确定这些不同的膜内毒素结合蛋白的相对作用 以及巨噬细胞激活的机制。我们的假设是 激活将取决于内毒素的大分子结构，以及 脂类A结合的内在可及性和先天 环境因素的影响；我们还假设有一个 脂多糖激活事件的中心途径。依赖内毒素的巨噬细胞 激活会导致多种促炎因子的产生 介质，包括肿瘤坏死因子(TNF)和一氧化氮(NO)。 这两种物质都被证明有助于杀死肿瘤细胞，通过 脂多糖激活巨噬细胞。这个实验室最近的研究表明 显示巨噬细胞，在体外用非常低的浓度进行预处理 内毒素(不足以诱导肿瘤坏死因子或一氧化氮的分泌) 仍然可以在这些细胞中引起深刻的变化，从而 随后用内毒素或其他刺激激活会导致明显的 改变了对肿瘤坏死因子和一氧化氮分泌的反应。这些改动 在肿瘤坏死因子和一氧化氮反应是生物相性和互换的，并代表 先前描述的巨噬细胞脱敏和启动的成分。 我们将这一过程称为巨噬细胞“重编程”和第二次 拟议研究的具体目的将是调查 这一现象的生化和细胞基础。特别关注 将关注百日咳毒素敏感型G-杆菌的潜在作用 蛋白质，已被其他人证明有助于内毒素依赖 巨噬细胞的信号和我们平行内毒素的许多方面- 依赖巨噬细胞重新编程。我们还假设 巨噬细胞的重新编程是在体内发生的，这种事件是 在宿主杀死肿瘤的能力中的重要性。在美国的研究 因此，第三个特定目标将寻求建立巨噬细胞 重新编程事件是内毒素诱导的主要解释 耐受性或肿瘤介导的内毒素超敏反应。

The long-term goal of this research is an understanding of molecular mechanisms of lipopolysaccharide (LPS)-initiated signalling as a model system by which the tumoricidal potential of the activated macrophage in treating cancer may be assessed. LPS has been recognized for several decades as among the most potent stimuli for the activation of macrophages for tumor cell killing. Increasing experimental evidence has implicated several macrophage membrane structures as potentially important receptors for activation and resultant signal transduction. These include the phosphatidyl-inositol linked CD14 glycoprotein, the p73 LPS binding protein and the CD11/18 adhesins. The precise contribution of each of these molecules to the actual activation event has not yet been established and Specific Aim #1 of the proposed research is to define the relative role of these various membrane LPS binding proteins and mechanisms of macrophage activation. It is our hypothesis that activation will depend upon the macromolecular structure of the LPS, and the intrinsic accessibility of lipid A for binding and the prior influence of environmental factors; we also hypothesize that there is one central pathway for LPS activation events. LPS-dependent macrophage activation results in the production of multiple proinflammatory mediators, including tumor necrosis factor (TNF) and nitric oxide (NO). Both of these have been shown to contribute to killing of tumor cells by LPS activated macrophages. Recent studies from this laboratory have shown that macrophages, pretreated in vitro with very low concentrations of LPS (which are not sufficient to induce either TNF or NO secretion) can nevertheless induce profound alterations in these cells such that subsequent activation with LPS or other stimuli results in markedly altered responses in terms of TNF and NO secretion. These alterations in TNF and NO responses are biophasic and reciprocal, and represent components of earlier-described macrophage desensitization and priming. We have termed this process macrophage "reprogramming" and a second Specific Aim of the proposed research will be to investigate the biochemical and cellular basis for this phenomenon. Particular attention will focus upon the potential role of a pertussis-toxin sensitive G- protein, which has been shown by others to contribute to LPS-dependent signalling of macrophages and by us to parallel many aspects of LPS- dependent macrophage reprogramming. We also hypothesize that reprogramming of macrophages occurs in vivo and that such events are of importance in the ability of the host to kill tumors. Studies in the third Specific Aim, therefore, will seek to establish macrophage reprogramming events as the primary explanation for induction of LPS tolerance or tumor-mediated LPS hypersensitivity reactions.