Platelet Activating Factor and Epidermal Cytoxicity

乙醇使用可能是世界范围内发病率和死亡率的重要来源。据了解，有一半的人 严重烧伤需要住院治疗的患者乙醇（EtOH）呈阳性。从统计学上讲， 这些人中的大多数是偶尔酗酒者，而不是酗酒者。受伤时的乙醇使用 还导致烧伤患者的发病率和死亡率增加（> 2倍）。经验证的鼠模型 联合EtOH +热烧伤已显示大量急性全身性细胞因子释放和毒性 这些涉及肺、小肠和肝脏的联合药剂，模拟人类病理学。过程 乙醇通过何种途径增强热烧伤损伤介导的毒性尚不清楚，然而，我们已经证明， 涉及脂质介质血小板活化因子（1-烷基-2-乙酰基）的新机制 甘油磷酸胆碱; PAF）。这项提案是对一项长期赠款的延续， 描述PAF效应，重点关注皮肤病理生理学。通过一种特异性G蛋白偶联 受体（PAFR）广泛表达，急性PAF暴露导致全身促炎反应， 类似感染性休克我们正在进行的和已发表的研究，在此赠款的最后一个周期完成， 发现体外角质形成细胞或体内小鼠急性暴露于EtOH，然后发生热烧伤 导致PAF产生的巨大增加，由增强的胞质磷脂酶A2（cPLA 2）介导 activation.重要的是，PAFR KO小鼠完全免受中毒性热烧伤- 引起多器官炎症。此外，我们发现PAF通过亚细胞途径离开角质形成细胞， 微泡颗粒（MVP）在依赖于PAFR活化和酶酸的过程中 鞘磷脂酶（aSMase）。我们假设在MVP中旅行可以保护PAF免受PAF降解- 乙酰基水解酶，并以最佳形式为PAFR提供脂质配体。计划的总体目标 在这次更新的研究是解决知识差距，如何PAF填充MVP的生产，以及究竟如何， 产生广泛的多器官系统性炎症，以响应EtOH +热烧伤的组合。 设计了三个目的来检验急性EtOH暴露绕过严格调节的PAF的假设 合成和降解途径导致热烧伤后PAF产生增加， 并且PAFR激活通过aSMase产生PAF填充的MVP。填充PAF的Burn-MVP系统性旅行 以诱导肠道细菌移位，导致“败血性休克”。第一个目标将定义EtOH的机制- 介导MVP和PAF产生的增加。第二个目标将确定MVP是否用于保护PAF 并通过提供嵌入膜中的配体来增加PAF的效力。第三个目标 将明确Burn-MVP中PAF产生全身毒性的确切机制。这一目标将建立在 我们的机制研究旨在测试中毒性热烧伤的潜在治疗策略。这些研究 将填补知识空白，并为环境伤害产生新的治疗方法。

Ethanol use can be an important source of morbidity and mortality worldwide. It is known that half of individuals with significant burn injuries necessitating hospitalization were positive for ethanol (EtOH). Statistically speaking, the majority of these individuals were occasional binge drinkers, not alcoholics. Ethanol use at the time of injury also results in increased morbidity and mortality (> 2-fold) in the burned patients. Validated murine models combining EtOH + thermal burn injury have demonstrated massive acute systemic cytokine release with toxicity of these combined agents involving lung, small intestine and liver, which mimics human pathology. The process by which EtOH augments thermal burn injury-mediated toxicity has been unknown, yet, we have demonstrated a novel mechanism involving the lipid mediator Platelet-activating Factor (1-alkyl-2-acetyl glycerophosphocholine; PAF). This proposal is the renewal of a long-standing grant that has served to characterize PAF effects, focusing on skin pathophysiology. Exerting its effects via a specific G-protein coupled receptor (PAFR) widely expressed, acute PAF exposure results in a systemic pro-inflammatory response that mimics septic shock. Our ongoing and published studies accomplished in the last cycle of this grant have discovered that acute exposure of keratinocytes in vitro or mice in vivo with EtOH followed by thermal burn injury results in a tremendous increase in PAF production, mediated by augmented cytosolic phospholipase A2 (cPLA2) activation. Of importance, PAFR KO mice were completely protected from intoxicated thermal burn injury- induced multi-organ inflammation. Moreover, we discovered that PAF leaves the keratinocyte via subcellular microvesicle particles (MVP) in a process dependent upon PAFR activation and the enzyme acid sphingomyelinase (aSMase). We hypothesize that traveling in MVP protects PAF from degradation from PAF- acetyl hydrolases, and provides the lipid ligand to the PAFR in optimal form. The overall objective of the planned studies in this renewal is to address knowledge gaps in how PAF-filled MVPs are produced and exactly how they generate widespread multi-organ systemic inflammation in response to combining EtOH + thermal burn injury. Three aims are designed to test the hypothesis that acute EtOH exposure bypasses the tightly regulated PAF synthetic and degradation pathways resulting in exaggerated PAF production in response to thermal burn injury, and that PAFR activation generates PAF-filled MVP via aSMase. The PAF-filled Burn-MVP travel systemically to induce gut bacterial translocation resulting in “septic shock”. The first aim will define the mechanisms for EtOH- mediated augmentation of MVP and PAF production. The second aim will define if MVP serve to protect PAF from degradation and increases PAF's potency by providing the ligand embedded in membrane. The third aim will define the exact mechanisms by which PAF in Burn-MVP generate systemic toxicity. This aim will build upon our mechanistic studies to test potential treatment strategies for intoxicated thermal burn injury. These studies will address knowledge gaps and generate new therapeutic approaches for environmental injuries.