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）：来自临床和实验研究的证据表明，肠道通透性升高，内毒素的肠道渗透性升高，而所得的内毒素血症在酒精性肝病的发病机理中起着至关重要的作用。到目前为止，我们进行的研究表明，乙醇的代谢产物乙醛破坏了肠上皮屏障功能，并增加了对内毒素的渗透性。这种乙醛诱导的上皮屏障功能的破坏的机制包括抑制蛋白酪氨酸磷酸酶，PTP1B，连接蛋白的酪氨酸磷酸化，破坏连接蛋白之间相互作用的相互作用（确定屏障功能）和整合性复杂性的损失。此外，我们的研究表明，表皮生长因子（EGF）和l-谷氨酰胺可预防乙醛介导的乙醛介导的plc？，pkc？，pkc？i和钙依赖性机制的渗透性增加。 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 C-SRC介导的MLCK激活和d）益生菌，plantarum l. plantarum诱导的屏障破坏，可防止乙醇和乙醛诱导的EGF受体，P38MAPK和RAC1-依赖机制通过EGF受体诱导的屏障功能。使用肠上皮和人类结肠活检的细胞培养模型，我们将确定：1）ADH1B和ALDH2调节乙醇诱导的TJ和屏障功能的破坏。 2）ALDH2缺乏小鼠对乙醇诱导的屏障功能障碍更敏感。 3）肠道菌群在乙醇代谢和乙醇引起的TJ中的破坏中起作用。 4）乙醛诱导的PP2A甲基化和易位导致TJ蛋白的去磷酸化和屏障功能的破坏。 5）在特定的Ser和Thr残基上，occludin和cldn-4的去磷酸化与乙醛诱导的TJS和屏障功能障碍的破坏有关。 6）PP2A易位在小鼠肠中乙醛诱导的TJ破坏中起作用。 7）乙醇介导的C-SRC激活协同乙醛诱导的TJ破坏。 8）MLCK介导乙醇诱导乙醇的TJ破坏的协同化。 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。 10）L. plantarum可防止乙醇/乙醛诱导的p38mapk依赖机制对结的破坏。 11）Rac1激活和肌球蛋白环的激活和稳定涉及l. plantarum介导的预防乙醇/乙醛诱导的紧密连接破坏。 12）L。plantarum可改善小鼠和人类结肠粘膜中乙醇/乙醛诱导的肠屏障功能障碍。这些研究的结果与我们对酒精性肝脏和胰腺疾病的发病机理的理解直接相关，并有可能为新的治疗策略的未来发展做出贡献。 公共卫生相关性：根据过去几年的研究，我们假设肠道菌群将乙醇代谢成乙醛中的乙醇代谢破坏了肠上皮屏障的功能，通过诱导细胞间连接的蛋白质磷酸化，而植物学的植物植物会损害这种细胞的损害，并通过AcetaldeDecectectecte。我们建议进行研究，以发现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诱导的组织损伤中的保护作用。这些研究的结果有望提供知识，以开发用于胰腺和肺中酒精肝病治疗的新疗法和酒精诱导的组织损伤。