Leukocyte Responses to Endotoxin

白细胞对内毒素的反应

• 批准号: 6771261
• 负责人: Thomas M McIntyre
• 金额: $ 31.61万
• 依托单位: CLEVELAND CLINIC LERNER COM-CWRU
• 依托单位国家: 美国
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-06 至 2008-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6771261
• 关键词: anaphylaxis; autocrine; biological signal transduction; biosynthesis; blood lipoprotein; cell surface receptors; clinical research; endotoxins; enzyme activity; human subject; inflammation; leukocyte activation /transformation; leukocyte oxidative burst; leukocytes; lipids; lipopolysaccharides; molecular cloning; neutrophil; oxidation; patient oriented research; platelet activating factor; protein purification; septicemia; shock; transferase

DESCRIPTION (provided by applicant): Platelet-activating factor (PAF), a phospholipid autocoid, was originally defined as a principle that transferred shock from an animal in anaphylactic shock to a naive animal. It is the most powerful inflammatory lipid mediator yet defined: injection of synthetic PAF causes shock with peripheral hypofusion and vasodilation, pulmonary vasoconstriction, compromises cardiac function, and it induces hemoconcentration with tissue edema. All cellular components of the acute inflammatory/innate immune system express the receptor for PAF. PAF recruits, primes, and activates tissue and elicited macrophages, monocytes, and platelets. PAF has a major role in sepsis and the response to endotoxins. Serum levels of PAF are increased in studies of experimental endotoxemia, and blockade of the PAF receptor completely blocks LPS-induced death. PAF is the major injury-promoting mediator released after inhalation of bacterial endotoxin and injection of PAF acetylhydrolase--a phospholipase that specifically inactivates PAF--prevents death in animal models of anaphylactic shock. Decreased PAF acetylhydrolase activity is associated with clinical sepsis. However, models to the contrary, blockade of the single receptor for PAF has not been efficacious in humans, most likely because PAF receptor antagonists are weak relative to PAF. A more efficacious approach, suppression of PAF synthesis, cannot be accomplished because the rate-limiting enzyme for PAF synthesis has not been molecularly characterized. We do not understand how endotoxin might induce PAF synthesis because we do not know of a cell that makes PAF and releases in response to endotoxin stimulation. There are biologically-active PAF analogs formed by unregulated oxidative attack on circulating lipid, and we do not know whether the PAF activity detected in blood and lung lavage after endotoxin exposure is biosynthetic PAF or a chemically produced oxidized phospholipid that also activates the PAF receptor. We propose to purify and molecularly clone the enzyme that synthesizes PAF, to establish the signal transduction path in leukocytes that connects endotoxin receptors to PAF production, determine if PAF synthesis promotes the formation of PAF-like lipid structural mimetics, and to determine how PAF might affect the cell that synthesizes it. We anticipate this work will lead to a new class of anti-inflammatory agents.

描述（申请人提供）：血小板激活因子（PAF）是一种磷脂类自体蛋白，最初被定义为将过敏性休克动物的休克转移到幼稚动物的原理。它是迄今为止定义的最强大的炎症脂质介质：注射合成 PAF 会导致休克，伴有外周血供不足和血管舒张、肺血管收缩、损害心脏功能，并引起血液浓缩和组织水肿。急性炎症/先天免疫系统的所有细胞成分均表达 PAF 受体。 PAF 募集、启动和激活组织并引发巨噬细胞、单核细胞和血小板。 PAF 在败血症和内毒素反应中发挥重要作用。在实验性内毒素血症的研究中，PAF 的血清水平升高，并且阻断 PAF 受体可以完全阻止 LPS 诱导的死亡。 PAF 是吸入细菌内毒素和注射 PAF 乙酰水解酶（一种特异性灭活 PAF 的磷脂酶）后释放的主要损伤促进介质，可防止过敏性休克动物模型死亡。 PAF 乙酰水解酶活性降低与临床脓毒症相关。 然而，模型恰恰相反，阻断 PAF 单一受体在人类中并没有效果，很可能是因为 PAF 受体拮抗剂相对于 PAF 较弱。由于 PAF 合成的限速酶尚未得到分子特征，因此无法实现更有效的方法，即抑制 PAF 合成。我们不了解内毒素如何诱导 PAF 合成，因为我们不知道有一种细胞可以产生 PAF 并响应内毒素刺激而释放。循环脂质受到不受控制的氧化攻击而形成具有生物活性的 PAF 类似物，我们不知道内毒素暴露后在血液和肺灌洗液中检测到的 PAF 活性是生物合成的 PAF 还是化学产生的氧化磷脂（也激活 PAF 受体）。 我们建议纯化并分子克隆合成PAF的酶，建立白细胞中将内毒素受体与PAF产生连接的信号转导路径，确定PAF合成是否促进PAF样脂质结构模拟物的形成，并确定PAF如何可能影响合成它的细胞。我们预计这项工作将产生一类新型抗炎药。