Aldehydes in Alcohol-Induced Organ Injury

描述（由申请人提供）：酒精消耗对身体产生毒性作用，肝脏和大脑是主要靶器官。最近的研究表明，酒精引起的器官损伤可能涉及器官-器官相互作用。器官-器官相互作用的最著名机制是肠道产生的内毒素（脂多糖，LPS）信号。酒精消耗导致肠道屏障破坏，导致内毒素血症，这反过来又通过刺激细胞因子的产生导致肝-脑轴的组织损伤。乙醛的产生是酒精中毒的一个特征。当酒精代谢产生乙醛时，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、血液和脑中检测到醛类的积累。醛类具有细胞毒性，可介导肠-肝-脑轴的酒精作用。首先，肠道菌群中乙醛的产生决定性地介导了酒精诱导的肠道屏障破坏和LPS信号的产生。第二，从肝脏产生的醛类已被证明通过使蛋白质失活来介导酒精诱导的肝损伤。第三，肝脏醛清除功能障碍导致全身醛水平升高，这可能作为全身因素并介导酒精诱导的脑损伤。醛可以主要通过肝脏中的ALDH解毒，然而，我们的研究表明，尽管慢性酒精暴露后醛积累，但线粒体ALDH（ALDH 2）在肝脏中没有上调。我们还发现，锌补充剂与ALDH 2的上调有关，可减轻酒精诱导的肝损伤。ALDH 2的过表达已经显示出减弱线粒体和内质网（ER）应激，从而防止酒精诱导的器官损伤，包括肝脏和大脑。该项目将检验我们的假设，即醛类在肠-肝-脑轴上关键介导酒精诱导的细胞毒性，从而成为酒精诱导发病机制中的全身因素。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。将确定肠腔醛对肠紧密连接、血液LPS和肝-脑损伤的影响。还将测量肠腔内容物和上皮的代谢变化。目的2探讨肝醛生成在酒精性肝损伤中的意义。将确定醛类对肝脏脂质稳态和促炎细胞因子产生的影响。还将测量醛和LPS在促炎细胞因子产生中的相互作用。醛类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将被确定。目的3探讨肝源性醛信号在酒精性脑损伤中的意义。将定义肝功能障碍和全身醛升高之间的联系。将确定肝脏产生的醛信号在酒精诱导的脑损伤中的作用。目的4探讨乙醛毒性的分子机制及除醛治疗方法。将确定肠-肝-脑轴处的胰蛋白酶-蛋白质加合物的形成。ALDH 2重组L.将测定嗜酸乳杆菌、锌和白藜芦醇对醛清除和酒精诱导的器官损伤的影响。PHS 398/2590（Rev.06/09） 公共卫生相关性：酒精中毒导致多器官损伤，但FDA批准的有效治疗方法尚不可用。酒精代谢产生具有细胞毒性的醛类。肠内产生的醛破坏肠道屏障，导致内毒素血症，引发炎症。肝脏对乙醛的清除功能障碍会引起乙醛在肝脏和血液中蓄积，导致多器官损伤。本项目将确定醛作为介导酒精诱导的肠-肝-脑轴组织损伤的全身因子的作用。这项研究不仅将促进我们对酒精诱导的发病机制的认识，而且还建议将醛类的去除作为治疗酒精诱导疾病的潜在治疗策略。

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 PUBLIC HEALTH RELEVANCE: Alcohol intoxication causes multiple organ injury, but FDA-approved effective therapy is not available. Alcohol metabolism generates aldehydes which are cytotoxic. Aldehyde generation in the intestine disrupts gut barrier, leading to endotoxemia which triggers inflammation. Liver dysfunction in aldehyde clearance will cause aldehyde accumulation in the liver and blood, leading to multiple organ injury. This project will define the role of aldehyde as a systemic factor in mediating alcohol-induced tissue damage at the gut-liver-brain axis. The proposed research will not only advance our knowledge on alcohol-induced pathogenesis, but also suggest the removal of aldehydes as a potential therapeutic strategy for treatment of alcohol-induced diseases.