Eicosanoids and Lung Macrophage Antimicrobial Mechanisms

描述(由申请人提供)：调节先天肺防御机制以获得治疗优势，需要更好地了解介导吞噬细胞抗微生物作用的分子。虽然这一领域的大部分研究都集中在多肽介质上，但我们的实验室已经确定了花生四烯酸衍生的二十烷基类脂质介质的重要作用。我们的工作表明，白三烯(Lts)B4和D4促进免疫球蛋白G(Ig G)调理的微生物的肺泡巨噬细胞(AM)吞噬，而前列腺素E2(PGE2)则抑制这一过程，这一过程是通过FcGamma受体(FCR)介导的结合和信号传递进行的。此外，内源性LTS：PGE2比率的降低可能导致在艾滋病毒感染、营养不良和老龄化等情况下观察到的感染易感性增加。FCR或G蛋白偶联二十烷基硫酸酯受体的结扎反应在原发AM中的信号转导机制知之甚少。本研究的重点在于LTS和PGE2如何调节FCR下游的信号转导事件，包括Syk、磷脂酰肌醇3-激酶、Akt、粘着斑激酶和细胞外信号相关激酶。假设二十烷类化合物对AM吞噬功能的调节作用分别反映了LTS和PGE2对这些信号的放大或抑制，这在一定程度上是通过改变细胞内环磷酸腺苷来实现的。这一假设将在一系列体外实验中得到验证，该实验利用培养的AM挑战包被免疫球蛋白的红细胞。外源性和内源性二十烷基类化合物调节吞噬作用的受体、G蛋白和信号靶点将通过结合遗传和药理学工具来确定。通过提供对AM中FCR信号的新见解以及二十烷类化合物调节这一过程的机制，这些研究将增强我们对肺固有免疫这一未被充分研究但具有临床相关性的分支的了解。

DESCRIPTION (provided by applicant): Modulating innate pulmonary defense mechanisms for therapeutic advantage requires a better understanding of the molecules that mediate the antimicrobial actions of phagocytic cells. Although most research in this area has focused on peptide mediators, our laboratory has established an important role for eicosanoid lipid mediators derived from arachidonic acid. Our work has demonstrated that leukotrienes (LTs) B4 and D4 enhance, while prostaglandin E2 (PGE2) inhibits, alveolar macrophage (AM) phagocytosis of immunoglobulin G (IgG)-opsonized microbes, a process that proceeds via Fcgamma receptor (FcR)-mediated binding and signaling. Moreover, decreases in the ratio of endogenously generated LTs:PGE2 may contribute to the increased susceptibility to infection observed in such conditions as HIV infection, malnutrition, and aging. Little is known about signal transduction in primary AMs in response to ligation of either FcR or G protein-coupled eicosanoid receptors. This proposal focuses on how LTs and PGE2 modulate the cascade of signal transduction events downstream from FcR which includes Syk, phosphoinositide 3-kinase, Akt, focal adhesion kinase, and extracellular signal-related kinase. The hypothesis is that the modulatory effects of eicosanoids on AM phagocytosis reflect the amplification or suppression of these signals by LTs and PGE2, respectively, which occur in part via alteration in intracellular cyclic adenosine monophosphate. The hypothesis will be tested in a series of in vitro experiments utilizing cultured AMs challenged with IgG-coated erythrocytes. The receptors, G proteins, and signaling targets through which exogenous and endogenous eicosanoids act to modulate phagocytosis will be defined by employing a combination of genetic and pharmacologic tools. By providing new insight into FcR signaling in AMs and the mechanisms by which eicosanoids modulate this process, these studies will enhance our knowledge of an understudied but clinically relevant arm of pulmonary innate immunity.