Surgical Studies of Gut Permeability

描述(由申请人提供)： 肠上皮屏障的破坏通常发生在各种危重的手术条件下，包括败血症、出血、大手术、创伤和烧伤，并导致细菌和内毒素移位到血流中。调节肠上皮屏障功能的确切机制和制剂仍不清楚，预防屏障功能障碍的有效治疗方法有限，导致合并肠屏障功能障碍的外科危重患者死亡。天然多胺在维持肠上皮细胞完整性方面起着关键作用，而细胞多胺的调节是驱动上皮细胞功能的多个信号通路的中心汇聚点。富含钙粘附素的黏附连接介导了细胞与细胞之间的强接触，并在形成和调节上皮屏障方面起着功能作用。我们最近发现多胺可调节肠上皮细胞间的连接，而多胺的耗竭会减少黏附连接的表达，尤其是E-钙粘蛋白，这与肠道细胞旁通透性的增加有关。初步研究进一步表明：a)多胺主要在转录水平调节E-cadherin基因的表达，b)反义siRNA抑制E-cadherin可破坏肠上皮屏障功能。基于这些观察，我们假设多胺通过改变E-eherin的表达在调节肠上皮屏障功能中发挥重要作用。将追求三个具体目标来检验这一假设。1)明确多胺调控肠上皮细胞Ecadherin基因转录的分子机制。2)探讨多胺介导的Ecadherin在肠上皮细胞旁通透性调节中的作用及机制。3)探讨多胺在手术应激过程中对E-钙粘蛋白表达和屏障功能的影响，进一步阐明肠屏障功能障碍患者E-钙粘蛋白的变化。这些特定目标的完成将提供有关肠道屏障调节的新信息，这可能导致新的治疗策略的发展。由于屏障功能障碍常见于外科危重患者，并导致死亡，因此本提案的主题是及时的、重要的，并具有直接的临床应用。

DESCRIPTION (provided by applicant): Disruption of intestinal epithelial barrier occurs commonly in various critical surgical conditions, including sepsis, hemorrhage, massive surgical operation, trauma, and burns, and results in the translocation of bacteria and endotoxin into the blood stream. The exact mechanisms and agents that regulate intestinal epithelial barrier function are still obscure and effective therapies to prevent the barrier dysfunction are limited, contributing to death in critical surgical patients with gut barrier dysfunction. Natural polyamines are shown to play a critical role in maintenance of intestinal epithelial integrity, and the regulation of cellular polyamines is a central convergence point for the multiple signaling pathways driving epithelial cell functions. The cadherin-rich adherens junctions mediate strong cell-cell contacts and have functional role in forming and regulating epithelial barrier. We have recently demonstrated that polyamines modulate intercellular junctions in intestinal epithelial cells and that polyamine depletion decreases expression of adherens junctions, especially E-cadherin, which is associated with an increase in intestinal paracellular permeability. Preliminary studies further indicate that a) polyamines regulate expression of the E-cadherin gene primarily at the transcriptional level and b) inhibition of E-cadherin by SiRNA antisense disrupts intestinal epithelial barrier function. Based on these observations, we hypothesize that polyamines play an important role in regulation of intestinal epithelial barrier function by altering E-eadherin expression. Three specific aims will be pursued to test the hypothesis. 1) To define the molecular mechanism by which polyamines regulate transcription of the Ecadherin gene in intestinal epithelial ceils. 2) To determine the role and mechanisms of polyamine-mediated Ecadherin in the regulation of intestinal epithelial paracellular permeability. 3) To determine the role polyamines in E-cadherin expression and barrier function during surgical stress in vivo and further elucidate changes in Ecadherin in patients with gut barrier dysfunction. Completion of these specific aims will provide novel information regarding the regulation of intestinal barrier, which may lead to the development of new therapeutic strategies. Because barrier dysfunction occurs commonly in critical surgical patients and contributes to death, the subject matter of this proposal is timely, important, and has direct clinical application.