Mechanism of Endotoxin absorption in alcoholism

酒精中毒时内毒素吸收机制

• 批准号: 8504885
• 负责人: RADHAKRISHNA RAO
• 金额: $ 31.42万
• 依托单位: UNIVERSITY OF TENNESSEE HEALTH SCI CTR
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-05-01 至 2015-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8504885
• 关键词: Acetaldehyde; Actomyosin; Adherens Junction; Alcohol consumption; Alcohol dehydrogenase; Alcoholic Liver Diseases; Alcoholism; Alcohols; Biopsy; Calcium; Cell Culture Techniques; Clinical Research; Colon; Complex; Data; Development; Endotoxemia; Endotoxins; Enterobacteriaceae; Epidermal Growth Factor; Epidermal Growth Factor Receptor; Epithelial; Ethanol; Ethanol Metabolism; Event; Functional disorder; Future; Glutamine; Goals; Human; Injury; Intercellular Junctions; Intestines; Knowledge; Kupffer Cells; Lactobacillus plantarum; Lung; Mediating; Metabolic; Methylation; Mitogen-Activated Protein Kinases; Modeling; Molecular; Mucous Membrane; Mus; Myosin Light Chain Kinase; Outcome Study; PTPN1 gene; Pancreas; Pancreatic Diseases; Pathogenesis; Permeability; Phosphorylation; Phosphotransferases; Plasma; Play; Prevention; Probiotics; Process; Protein Dephosphorylation; Protein Tyrosine Phosphatase; Protein phosphatase; Proteins; Research; Role; SRC gene; Site; Testing; Tight Junctions; Tissues; Tyrosine Phosphorylation; absorption; alcohol effect; aldehyde dehydrogenases; base; citrate carrier; claudin 4; feeding; gastrointestinal epithelium; gut microflora; intestinal epithelium; liver injury; loss of function; novel therapeutics; occludin; prevent; public health relevance; research study; response; src-Family Kinases

DESCRIPTION (provided by applicant): Evidence from clinical and experimental studies indicates that elevated intestinal permeability to endotoxins and the resulting endotoxemia play a crucial role in the pathogenesis of alcoholic liver disease. Our studies conducted so far have shown that acetaldehyde, the metabolic product of ethanol, disrupts the intestinal epithelial barrier function and increases the permeability to endotoxins. The mechanism of this acetaldehyde-induced disruption of epithelial barrier function involves inhibition of a protein tyrosine phosphatase, PTP1B, tyrosine phosphorylation of junctional proteins, disruption of the interactions among the junctional proteins (that determine the barrier function), and loss of integrity of the junctional complexes. Furthermore, our studies demonstrated that epidermal growth factor (EGF) and L-glutamine prevent acetaldehyde-mediated increase in permeability to endotoxins by a PLC?, PKC?, PKC?I and calcium-dependent mechanism. Our preliminary studies indicate that acetaldehyde induces translocation of PP2A leading to dephosphorylation of occludin and claudin-4, ethanol amplifies the effect of acetaldehyde by a Src kinase and MLCK-dependent mechanism and that probiotic, L. plantarum prevents acetaldehyde- induced barrier disruption. On the basis of these results it is further hypothesized that: a) ethanol metabolism and gut microflora play crucial roles in ethanol-induced intestinal barrier dysfunction, b) PP2A-dependent dephosphorylation of occludin and Cldn-4 is involved in acetaldehyde-induced disruption of intestinal barrier function, c) ethanol synergizes acetaldehyde-induced barrier disruption by c-Src-mediated MLCK activation, and d) probiotic, L. plantarum, prevents ethanol and acetaldehyde-induced disruption of barrier function by a EGF receptor, p38MAPK and Rac1- dependent mechanism. Using a cell culture model of the intestinal epithelium and human colonic biopsies we will determine that: 1) ADH1B and ALDH2 modulate ethanol-induced disruption of TJs and barrier function. 2) ALDH2 deficient mice are more sensitive to ethanol-induced barrier dysfunction. 3) Gut microflora play a role in ethanol metabolism and ethanol-induced disruption of TJs. 4) Acetaldehyde-induced PP2A methylation and translocation leads to dephosphorylation of TJ proteins and disruption of barrier function. 5) Dephosphorylation of occludin and Cldn-4 on specific Ser and Thr residues is associated with acetaldehyde-induced disruption of TJs and barrier dysfunction. 6) PP2A translocation plays a role in acetaldehyde-induced TJ disruption in mouse intestine. 7) Ethanol-mediated c-Src activation synergizes acetaldehyde-induced TJ disruption. 8) MLCK mediates synergization of acetaldehyde-induced TJ disruption by ethanol. 9) Ethanol sensitizes mouse colon for acetaldehyde-induced barrier dysfunction by a c-Src and MLCK- dependent mechanism. 10) L. plantarum prevents ethanol/acetaldehyde-induced disruption of junctions by p38MAPK-dependent mechanism. 11) Rac1 activation and stabilization of actomyosin ring are involved in the L. plantarum-mediated prevention of ethanol/acetaldehyde-induced tight junction disruption. 12) L. plantarum ameliorates ethanol/acetaldehyde-induced intestinal barrier dysfunction in mice and human colonic mucosa. The outcome of these studies has a direct relevance to our understanding of the pathogenesis of alcoholic liver and pancreatic diseases, and has the potential to contribute to the future development of new therapeutic strategies. PUBLIC HEALTH RELEVANCE: On the basis of our research during the past several years we hypothesized that ethanol metabolism by gut microflora into acetaldehyde disrupts intestinal epithelial barrier function by inducing phosphorylation of proteins of intercellular junctions, and the probiotic L. plantarum prevents such cellular damage by acetaldehyde. We propose to conduct studies to uncover the cellular and molecular mechanisms involved in these processes and determine the protective role of a probiotic in alleviating the alcohol- induced tissue injury. The outcome of these studies is expected to provide knowledge to develop new therapies in the treatment of alcoholic liver disease and alcohol-induced tissue injury in pancreas and lung.

描述（由申请人提供）：临床和实验研究的证据表明，肠道对内毒素的通透性升高以及由此产生的内毒素血症在酒精性肝病的发病机制中发挥着至关重要的作用。迄今为止我们进行的研究表明，乙醇的代谢产物乙醛会破坏肠上皮屏障功能并增加内毒素的渗透性。乙醛诱导的上皮屏障功能破坏的机制涉及抑制蛋白酪氨酸磷酸酶 PTP1B、连接蛋白的酪氨酸磷酸化、破坏连接蛋白之间的相互作用（决定屏障功能）以及丧失上皮屏障的完整性。连接复合体。此外，我们的研究表明，表皮生长因子 (EGF) 和 L-谷氨酰胺通过 PLC?、PKC?、PKC?I 和钙依赖性机制防止乙醛介导的内毒素渗透性增加。我们的初步研究表明，乙醛诱导 PP2A 易位，导致 Occludin 和 Claudin-4 去磷酸化，乙醇通过 Src 激酶和 MLCK 依赖性机制放大乙醛的作用，而益生菌植物乳杆菌可防止乙醛诱导的屏障破坏。基于这些结果，进一步假设：a) 乙醇代谢和肠道微生物群在乙醇诱导的肠道屏障功能障碍中起着至关重要的作用，b) PP2A 依赖性的 occludin 和 Cldn-4 去磷酸化参与乙醛诱导的肠道屏障功能破坏。肠道屏障功能，c) 乙醇通过 c-Src 介导的 MLCK 激活来协同乙醛诱导的屏障破坏，d) 益生菌植物乳杆菌可预防乙醇和乙醛诱导的屏障破坏EGF 受体、p38MAPK 和 Rac1 依赖性机制破坏屏障功能。使用肠上皮细胞培养模型和人结肠活检，我们将确定：1) ADH1B 和 ALDH2 调节乙醇诱导的 TJ 和屏障功能破坏。 2) ALDH2 缺陷小鼠对乙醇引起的屏障功能障碍更敏感。 3) 肠道菌群在乙醇代谢和乙醇诱导的 TJ 破坏中发挥作用。 4) 乙醛诱导的 PP2A 甲基化和易位导致 TJ 蛋白去磷酸化和屏障功能破坏。 5) occludin 和 Cldn-4 在特定 Ser 和 Thr 残基上的去磷酸化与乙醛诱导的 TJ 破坏和屏障功能障碍有关。 6) PP2A 易位在乙醛诱导的小鼠肠道 TJ 破坏中发挥作用。 7) 乙醇介导的 c-Src 激活可协同乙醛诱导的 TJ 破坏。 8) MLCK 介导乙醇对乙醛诱导的 TJ 破坏的协同作用。 9) 乙醇通过 c-Src 和 MLCK 依赖性机制使小鼠结肠对乙醛诱导的屏障功能障碍敏感。 10) L. plantarum 通过 p38MAPK 依赖性机制防止乙醇/乙醛诱导的连接破坏。 11）Rac1激活和肌动球蛋白环的稳定参与植物乳杆菌介导的乙醇/乙醛诱导的紧密连接破坏的预防。 12) 植物乳杆菌可改善乙醇/乙醛引起的小鼠和人结肠粘膜肠道屏障功能障碍。这些研究的结果与我们对酒精性肝和胰腺疾病发病机制的理解有直接关系，并有可能为未来新治疗策略的发展做出贡献。 公共健康相关性：根据我们过去几年的研究，我们假设肠道微生物群将乙醇代谢为乙醛，通过诱导细胞间连接蛋白磷酸化来破坏肠上皮屏障功能，而益生菌植物乳杆菌通过以下方式防止这种细胞损伤：乙醛。我们建议进行研究，以揭示这些过程中涉及的细胞和分子机制，并确定益生菌在减轻酒精引起的组织损伤中的保护作用。这些研究的结果预计将为开发治疗酒精性肝病以及酒精引起的胰腺和肺组织损伤的新疗法提供知识。