Aldehydes in Alcohol-Induced Organ Injury

描述（申请人提供）：饮酒对身体有毒性作用，以肝脏和大脑为主要靶器官。最近的研究表明，酒精引起的器官损伤可能涉及器官间的相互作用。最著名的器官-器官相互作用的机制是肠道产生的内毒素（脂多糖，LPS）信号。饮酒会破坏肠道屏障，导致内毒素血症，而内毒素血症反过来又会刺激细胞因子的产生，从而导致肝脑轴的组织损伤。醛生成是酒精中毒的一个特征。酒精代谢产生乙醛，脂质过氧化产生脂质醛，如4-羟基壬烯醛（4-HNE）和丙二醛（MDA）。酒精中毒后，在肠内容物、肝脏、血液和大脑中发现了醛的积累。醛类具有细胞毒性，可能介导酒精在肠-肝-脑轴的作用。首先，肠道菌群产生的乙醛介导酒精诱导的肠道屏障破坏和LPS信号的产生。其次，由肝脏产生的醛已被证明通过使蛋白质失活介导酒精诱导的肝损伤。第三，乙醛清除的肝功能障碍导致全身性乙醛升高，这可能是一个全身性因素，介导酒精性脑损伤。醛主要通过肝脏中的ALDH解毒，然而，我们的研究表明，尽管慢性酒精暴露后醛积累，但肝脏中的线粒体ALDH （ALDH2）并未上调。我们还发现补充锌可以减轻酒精诱导的肝损伤，这与ALDH2的上调有关。ALDH2的过度表达已被证明可以减轻线粒体和内质网（ER）应激，从而防止酒精诱导的器官损伤，包括肝和脑。该项目将验证我们的假设，即醛在肠-肝-脑轴上介导酒精诱导的细胞毒性，从而成为酒精诱导的发病机制中的一个系统性因素。目的1是确定微生物群醛生成在酒精诱导的肠道屏障破坏和LPS信号生成中的作用。确定肠腔醛对肠紧密连接、血脂多糖和肝脑损伤的影响。肠道内容物和上皮的代谢变化也将被测量。目的2：探讨肝醛生成在酒精性肝损伤中的意义。醛类对肝脂质稳态和促炎细胞因子产生的影响将被确定。醛和脂多糖在促炎细胞因子生产中的相互作用也将被测量。将确定醛与酒精诱导的肝脏代谢组学和蛋白质组学改变的机制联系。目的3：探讨肝生成醛信号在酒精性脑损伤中的意义。肝功能障碍和全身性醛升高之间的联系将被确定。肝生成的醛信号在酒精性脑损伤中的作用将被确定。目的四是探讨乙醛毒性的分子机制和脱醛治疗。醛蛋白加合物在肠-肝-脑轴的形成将被确定。确定aldh2重组嗜酸乳杆菌、锌和白藜芦醇对醛清除和酒精性器官损伤的影响。小灵通398/2590 （Rev. 06/09）页延续格式页

DESCRIPTION (provided by applicant): Alcohol consumption exerts toxic effects on the body with liver and brain as the major target organs. Recent studies suggest that alcohol-induced organ injury may involve organ-organ interactions. The most well-known mechanism underlying organ-organ interactions is gut-generated endotoxin (lipopolysaccharide, LPS) signal. Alcohol consumption causes gut barrier disruption, leading to endotoxemia, which, in turn, causes tissue injury at the liver-brain axis by stimulating cytokine production. Aldehyde generation is a feature of alcohol intoxication. While alcohol metabolism generates acetaldehyde, lipid peroxidation produces lipid aldehydes such as 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA). Accumulation of aldehydes has been detected in intestinal contents, liver, blood and brain after alcohol intoxication. Aldehydes are cytotoxic, and may mediate alcohol actions at the gut-liver-brain axis. First, acetaldehyde generation from the gut microflora critically mediate alcohol-induced gut barrier disruption and generation of LPS signal. Second, aldehydes generated from the liver have shown to mediate alcohol-induced liver injury by inactivating proteins. Third, liver dysfunction in aldehyde clearance results in systemic aldehyde elevation, which may act as a systemic factor and mediate alcohol-induced brain damage. Aldehydes can be detoxified primarily by ALDH in the liver, however, our studies showed that mitochondrial ALDH (ALDH2) was not up-regulated in the liver despite aldehyde accumulation after chronic alcohol exposure. We also found that zinc supplementation attenuated alcohol-induced liver injury in association with up-regulation of ALDH2. Over-expression of ALDH2 has been shown to attenuate mitochondrial and endoplasmic reticulum (ER) stress, thereby preventing alcohol-induced organs injury including liver and brain. This project will test our hypothesis that aldehydes critically mediate alcohol-induced cytotoxicity at the gut-liver-brain axis, thereby being a systemic factor in alcohol-induced pathogenesis. Aim 1 is to define the role of microbiota aldehyde generation in alcohol-induced gut barrier disruption and generation of LPS signal. Effects of gut luminal aldehydes on gut tight junctions, blood LPS and liver-brain injury will be determined. Metabolic alterations in the gut luminal contents and epithelium will also be measured. Aim 2 is to determine the significance of hepatic aldehyde generation in alcohol-induced liver injury. Effects of aldehydes on hepatic lipid homeostasis and pro-inflammatory cytokine production will be determined. Interaction between aldehydes and LPS in pro-inflammatory cytokine production will also be measured. Mechanistic link of aldehydes with alcohol-induced metabolomic and proteomic alterations in the liver will be identified. Aim 3 is to determine the significance of liver-generated aldehyde signal in alcohol-induced brain injury. The link between liver dysfunction and systemic aldehyde elevation will be defined. The role of liver- generated aldehyde signal in alcohol-induced brain injury will be determined. Aim 4 is to explore the molecular mechanism of aldehyde toxicity and aldehyde removal therapies. Formation of aldehyde-protein adducts at the gut-liver-brain axis will be identified. Effects of ALDH2-recombinant L. acidophilus, zinc and resveratrol on aldehyde clearance and alcohol-induced organ injury will be determined. PHS 398/2590 (Rev. 06/09) Page Continuation Format Page