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急的外科状况中，包括败血症、出血、大规模外科手术、创伤和烧伤，并且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药物仍然不清楚，预防屏障功能障碍的有效疗法有限，导致肠屏障功能障碍的危重外科患者死亡。天然多胺在维持肠上皮完整性中起关键作用，并且细胞多胺的调节是驱动上皮细胞功能的多个信号传导途径的中心汇聚点。富含钙粘蛋白的粘附连接介导强的细胞-细胞接触，并且在形成和调节上皮屏障中具有功能性作用。我们最近已经证明，多胺调节肠上皮细胞的细胞间连接，多胺耗竭降低粘附连接的表达，特别是E-钙粘蛋白，这是与肠细胞旁通透性增加。初步研究进一步表明，a）多胺主要在转录水平调节E-钙粘蛋白基因的表达，和B）通过siRNA反义抑制E-钙粘蛋白破坏肠上皮屏障功能。基于这些观察，我们推测，多胺通过改变E-前粘附素的表达在调节肠上皮屏障功能中发挥重要作用。为了检验这一假设，将追求三个具体目标。1)明确多胺调节肠上皮细胞E钙粘蛋白基因转录的分子机制。2)探讨多胺介导的E钙粘蛋白在肠上皮细胞旁通透性调节中的作用及其机制。3)确定体内手术应激过程中多胺在E-钙粘蛋白表达和屏障功能中的作用，进一步阐明肠屏障功能障碍患者E-钙粘蛋白的变化。这些特定目标的实现将提供关于肠屏障调节的新信息，这可能导致新的治疗策略的开发。由于屏障功能障碍常发生在外科危重患者中，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.