INTESTINAL MUCOSAL PROTECTION BY EPIDERMAL GROWTH FACTOR

异常高的上皮渗透性和氧化剂诱导的上皮 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。 我们最近已经证明， 生理相关浓度的氧化剂增加 Caco-2和T84细胞单层中的细胞旁渗透性。 的 氧化剂诱导的通透性增加依赖于蛋白质 酪氨酸磷酸化，它被抑制的存在， 表皮生长因子（EGF），一种公认的粘膜保护因子， 因子 根据初步研究，假设， a）氧化剂诱导的细胞旁渗透性增加与 与改变的酪氨酸磷酸化的封闭和E- 在特定位点的钙粘蛋白（连接蛋白），B）氧化剂诱导的 封闭蛋白和E-钙粘蛋白磷酸化的改变是由 pp 125 FAK和pp 60-c-src的活化和膜转位，以及 c）EGF延迟氧化剂诱导的pp 125 FAK和pp 60-c-src的活化 封闭蛋白和E-钙粘蛋白的酪氨酸磷酸化的改变，和 连接复合物的解离。 利用上述模型 氧化损伤，我们建议确定，1）的具体网站， occludin中的酪氨酸磷酸化， 在氧化剂处理期间，2）氧化剂是否诱导活化， pp 125 FAK和pp 60-c-src从胞质溶胶易位到胞质中， 膜，3）如果在Caco-2细胞中调节pp 60-c-src基因表达 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 抑制氧化剂诱导的pp 125 FAK活化和易位 和pp 60-c-src，酪氨酸磷酸化状态的改变， 闭合蛋白和E-钙粘蛋白，以及闭合蛋白/ZO-1和E-钙粘蛋白的解离。 钙粘蛋白/β-连环蛋白复合物。 从这些研究中获得的信息 有可能扩大我们对氧化剂诱导损伤的理解 在肠上皮细胞中，通过识别一些 氧化剂诱导的细胞旁连接复合物的破坏， EGF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.