Claudin-3, Gut Dysbiosis and Inflammatory Bowel Disease

炎症性肠病（IBD），主要包括溃疡性结肠炎（UC）和克罗恩病（CD）， 是一组使人衰弱的自身免疫性疾病，它会严重影响一个人的生活方式并具有很高的风险 结肠癌。尽管这些疾病的临床治疗已取得重大进展，但 现役军人和退伍军人的总体发病率和疾病严重程度不断增加 可能是由于压力很大。此外，IBD 显着增加患结肠癌的风险， 因此，这些疾病给我们的退伍军人带来了巨大的身体和经济负担 高。然而，IBD 的病因仍不清楚。总而言之，存在着迫切且未得到满足的需求 提高对促进 IBD 易感性和/或疾病严重程度的分子机制的了解， 因为它可以帮助确定新的治疗靶点。在这方面，上皮极性的破坏和 在紧密连接（TJ）解除管制的协助下，区室化在诱导和促进方面发挥着关键作用 粘膜炎症。值得注意的是，长期以来人们一直认为肠漏与 IBD 之间存在关联。 然而，尽管有这些知识，该领域在治疗方面取得的进展仍然有限，这主要是由于 一般观点认为，构成 TJ 的蛋白质在功能上是静态且冗余的。这个提议 不同意这种普遍观点，并提出 Claudin-3（一种 TJ 整合蛋白）在动态调节中的关键作用 肠道上皮和炎症稳态。我们的工作假设是，claudin-3 的丢失， IBD 患者的特征是，粘膜屏障完整性失调，导致肠道菌群失调和促炎 环境。伴随着 gp130/IL6/Stat3 和 Hippo/Yap 信号级联的放松管制，由于 Par-3 表达失调引起的极性缺陷，使最初的炎症损伤长期存在 失调的粘膜损伤/修复最终导致肿瘤生长。 这项建议建立在强有力的科学前提之上，因为包括我们在内的一系列研究现已证实 确定claudin-3（此处为Cldn3）是维持肠上皮屏障成熟和完整性的关键TJ蛋白。 在这方面，我们发现 Cldn3 是表达最高的细胞间粘附蛋白，主要分布于 正常结肠隐窝顶部分化的结肠细胞。此外，用于建模的 Cldn3KO 小鼠的 IBD 患者的 Cldn3 水平表现出高渗透性肠道和免疫细胞浸润到固有层。 此外，肠道菌群失调以及 gp130/IL6/Stat3 表达的特异性和强劲增加是其特征 Cldn3KO 小鼠。 Cldn3 缺失还会损害结肠上皮细胞 (CEC) 的分化和极性，并且 推广河马/雅普信号。重要的是，Stat-3 和 Yap 信号通路促进过度增殖， 当放松管制时，慢性炎症和恶性生长。因此，DSS 结肠炎攻击 Cldn3KO 小鼠表现出严重的结肠炎和发育不良（与WT小鼠相比）。综上所述，我们的数据支持 Cldn3 的作用 作为调节结肠上皮和免疫信号的变阻器，从而得出以下假设： Cldn3 缺失在促进结肠炎方面是混杂的。为了检验我们的假设，我们提出以下研究：Aim-1。至 确定 Cldn3 表达缺失促进 IBD 的表达动态和背景；目标2。至 确定 IL6/Stat3 和 Hippo/Yap 信号传导在促进结肠炎中的作用和潜在协作 在 Cldn3 表达缺失的条件下；和目标 3。确定 Cldn3 之间的因果整合 损失和肠道菌群失调促进 IBD。总的来说，该提案为解剖电路提供了一个独特的平台 粘膜屏障失调和极性之间在调节结肠炎和相关癌症治疗中的作用 收益。结果对于改善退伍军人的生存和生活质量将具有重要意义。

Inflammatory bowel disease (IBD), consisting primarily of the ulcerative colitis (UC) and Crohn’s disease (CD), is a group of debilitating auto-immune disorders, which significantly affect one’s life-style and carry a high risk of colon cancer. While significant advances have been made in the clinical management of these diseases, the overall incidence rate and disease severity in active duty army personnel and veterans is constantly increasing possibly due to the high level of stress involved. Moreover, IBD significantly increases the risk of colon cancer, and therefore physical and economical burden of these diseases upon our veteran population is significantly high. However, the etiology of IBD remains unclear. Taken together, there is an urgent and unmet need for improved understanding of the molecular mechanisms that promote IBD susceptibility and/or disease severity, as it can help identify novel therapeutic targets. In this regard, disruption of epithelial polarity and compartmentalization, assisted by the tight junction (TJ) deregulation, plays key role in inducing and promoting mucosal inflammation. Notably, an association between the leaky gut and IBD has long been suggested. However, despite this knowledge, progress in this area for therapeutic gains has been limited due primarily to the generic perspective that proteins constituting the TJ are static and redundant in their function. This proposal disagrees with this generic view and proposes key role of claudin-3, a TJ-integral protein, in dynamic regulation of the gut epithelial and inflammatory homeostasis. Our working hypothesis is that the loss of claudin-3, which characterizes IBD patients, deregulates mucosal barrier integrity to induce gut dysbiosis and pro-inflammatory environment. Accompanying deregulations of gp130/IL6/Stat3 and Hippo/Yap signaling cascades, due to the polarity defects ensued by deregulated Par-3 expression, render chronicity to the initial inflammatory insult by deregulating mucosal injury/repair leading ultimately to neoplastic growth. This proposal is built upon a strong scientific premise as a series of studies, including ours, have now identified claudin-3 (hereon Cldn3) as a key TJ-protein in maintaining gut epithelial barrier maturity and integrity. In this regard, we found Cldn3 to be the highest expressed cell-cell adhesion protein localized primarily amongst differentiated colonocyte at the crypt top in normal colon. Furthermore, Cldn3KO mice, used to model decreased Cldn3 levels in IBD patients, exhibited hyper-permeable gut and immune cell infiltration into the lamina propria. In addition, gut dysbiosis along with specific and robust increase in gp130/IL6/Stat3 expression characterized Cldn3KO mice. Cldn3 loss also compromised colonic epithelial cell (CEC) differentiation and polarity, and promoted Hippo/Yap-signaling. Importantly, Stat-3 and Yap-signaling pathways promote hyper-proliferation, chronic inflammation and malignant growth when deregulated. Accordingly, DSS colitis-challenged Cldn3KO mice exhibited severe colitis and dysplasia (versus WT-mice). Taken together, our data support the role of Cldn3 as a rheostat in regulating the colonic epithelial and immune signaling and thereby leading to the hypothesis that Cldn3 loss is promiscuous in promoting colitis. To test our hypothesis, we propose following studies: Aim-1. To determine the expression dynamics and context for the loss of Cldn3 expression in promoting IBD; Aim-2. To determine the role and potential collaboration between IL6/Stat3 and Hippo/Yap signaling in promoting colitis under conditions of the loss of Cldn3 expression; and Aim-3. To determine the causal integration between Cldn3 loss and gut dysbiosis in promoting IBD. Overall, this proposal presents a unique platform for dissecting circuity between mucosal barrier deregulation and polarity in regulating colitis and associated cancer for therapeutic gains. Outcome will be significant in improving survival and quality of life of our Veterans.