INTESTINAL MUCOSAL PROTECTION BY EPIDERMAL GROWTH FACTOR

异常高的上皮通透性与氧化剂诱导的上皮 损伤与多种疾病的发病机制有关。 肠炎性疾病，包括坏死性小肠结肠炎 和炎症性肠病。我们最近证明了 生理相关浓度的氧化剂增加 Caco-2和T84细胞单层的细胞旁通透性。这个 氧化剂引起的通透性增加依赖于蛋白质 酪氨酸磷酸化，它的存在被抑制 表皮生长因子(EGF)--公认的粘膜保护因子 因素。根据初步研究，假设， A)氧化剂引起的细胞旁通透性增加与 随着阻滞素和E-蛋白酪氨酸磷酸化的改变 钙粘附素(结合蛋白)在特定部位，b)氧化剂诱导 阻滞素和E-钙粘素磷酸化的改变是由 Pp125FAK和pp60-c-src的激活和膜转位，以及 C)EGF延缓氧化剂诱导的pp125FAK和pp60-c-src的激活 阻滞素和E-钙粘蛋白酪氨酸磷酸化的改变 连接复合体的解离。使用上述模型 对于氧化损伤，我们建议确定，1)特定的位置 阻塞素中酪氨酸磷酸化的去磷酸化 在氧化剂处理过程中，2)氧化剂是否诱导活化和 Pp125FAK和pp60-c-src的胞浆转位 膜，3)IF对Caco-2细胞pp60-c-src基因表达的调控 改变氧化剂破坏屏障功能的能力，以及4) EGF介导的上皮保护机制是否包括 防止氧化剂诱导的pp125FAK的激活和转位 和pp60-c-src，酪氨酸磷酸化状态的改变 阻滞素和E-钙粘附素，以及阻滞素/ZO-L和E-钙粘附素的解离 钙粘附素/β-连环蛋白复合体。从这些研究中获得的信息 有可能扩大我们对氧化剂诱导的损伤的理解 在肠上皮细胞中，通过鉴定一些机制， 氧化剂诱导的细胞旁连接复合体的破坏和 表皮生长因子对上皮细胞的保护作用。

Abnormally high epithelial permeability and oxidant-induced epithelial injury have been implicated in the pathogenesis of a wide spectrum of intestinal inflammatory disorders, including necrotizing enterocolitis and inflammatory bowel disease. We have recently demonstrated that oxidants at physiologically relevant concentrations increase paracellular permeability in Caco-2 and T84 cell monolayers. The oxidant induced increase in permeability was dependent on protein tyrosine phosphorylation, and it was inhibited by the presence of epidermal growth factor (EGF), a well recognized mucosal protective factor. On the basis of preliminary studies it is hypothesized that, a) oxidant induced increase in paracellular permeability is associated with an alteration of the tyrosine phosphorylation of occludin and E- cadherin (junctional proteins) at specific sites, b) oxidant induced alterations of occludin and E-cadherin phosphorylation is caused by the activation and membrane translocation of pp125FAK and pp60-c-src, and c) EGF delays oxidant-induced activation of pp125FAK and pp60-c-src alteration of tyrosine phosphorylation of occludin and E-cadherin, and dissociation of junctional complexes. Using the above mentioned model of oxidant injury, we propose to determine, 1) the specific site of tyrosine phosphorylation in occludin which undergoes dephosphorylation during oxidant treatment, 2) whether oxidants induce activation and translocation of pp125FAK and pp60-c-src from the cytosol to the membrane, 3) if modulation of pp60-c-src gene expression in Caco-2 cells alter the ability of oxidants to disrupt the barrier function, and 4) whether the mechanisms of EGF-mediated epithelial protection include a prevention of oxidant-induced activation and translocation of pp125FAK and pp60-c-src, alteration of the tyrosine phosphorylation status of occludin and E-cadherin, and dissociation of occludin/ZO-l and E- cadherin/beta-catenin complexes. Information derived from these studies has the potential to expand our understanding of oxidant-induced injury in intestinal epithelium, by identifying some of the mechanisms of oxidant-induced disruption of paracellular junctional complexes and epithelial protection by EGF.