Mechanisms of Neurotensin in Intestinal Inflammation

描述(申请人提供)：炎症性肠病(IBD)的病理生理学尚未完全了解，IBD是一种发病率和死亡率都很高的临床实体。越来越多的证据表明神经肽在结肠炎的发病机制中起着重要作用。我们发现神经肽神经降压素(NT)在结肠炎急性期起到促炎介质的作用。我们的初步证据还表明，NT缺陷小鼠降低了肠道炎症反应，为这种多肽在肠道炎症中的重要性提供了直接证据。然而，NT还通过激活EGF受体(EGFR)和磷酸化抗凋亡信号分子Akt来促进炎症修复阶段的愈合。因此，我们对这一修订后的更新应用的目标1的假设是，NT通过减少细胞凋亡和增加细胞增殖参与结肠炎的愈合阶段。目的1在分离的结肠细胞和实验性结肠炎模型中，研究NT-NT受体1(NTR1)诱导Akt和EGFR相关的抗凋亡和增殖反应的信号机制。我们还发现在结肠炎期间肠系膜脂肪库中NT和NTR1的表达增加，并证实了NT和NTR1在小鼠前脂肪细胞中的表达，这是对NT BE释放细胞因子和促进增殖的反应。这些发现首次将结肠炎期间肠系膜脂肪中依赖NT-NTR1的炎症变化联系在一起，并可能在IBD中具有重要意义，因为在IBD患者的手术中，肠道脂肪包裹是常见的发现。因此，在目标2中，将通过比较肠系膜脂肪中NT和NTR1的表达与IBD相关模型中粘膜和脂肪组织的炎症程度，来研究急慢性实验性结肠炎中NT介导的结肠粘膜和肠系膜之间的串扰。在分离的前脂肪细胞中的实验将检验NT刺激促炎细胞因子和脂肪因子的释放，改变黏附分子的表达，以及刺激巨噬细胞向这些细胞迁移的机制。目标1和目标2中的实验还将比较NT缺陷小鼠和野生型小鼠的结肠炎和脂肪库炎症变化。目标3中的研究将确定NT诱导的前脂肪细胞IGF-1R磷酸化所涉及的信号转导途径，并研究NT-NTR1相互作用导致细胞增殖和迁移的机制。我们的结果将为了解NT及其受体在结肠炎中的作用，以及它在IBD和实验性结肠炎动物模型中观察到的肠系膜脂肪组织的激活和炎症中的扩展作用提供重要的见解。本项目将研究神经肽神经降压素参与肠炎和炎症性肠病发病的病理生理机制。这个项目的一部分还研究了这种神经肽如何在结肠炎症变化后影响邻近脂肪组织的炎症发展。

DESCRIPTION (provided by applicant): The pathophysiology of Inflammatory Bowel Disease (IBD), a clinical entity with significant morbidity and mortality, is not completely understood. Emerging evidence indicates that neuropeptides are major participants in the pathogenesis of colonic inflammation. We showed that the neuropeptide neurotensin (NT) acts as a proinflammatory mediator in the acute phase of colitis. Our preliminary evidence also indicates that NT deficient mice have reduced intestinal inflammatory responses, providing direct evidence for the importance of this peptide in intestinal inflammation. However, NT also promotes healing during the repair phase of inflammation by activating the EGF receptor (EGFR) and phosphorylating the anti-apoptotic signaling molecule Akt. Thus, our hypothesis for aim 1 of this revised renewal application is that NT participates in the healing phase of colitis by reducing apoptosis and increasing cell proliferation. Aim 1 therefore will examine the signaling mechanisms involved in NT-NT receptor 1 (NTR1)-induced Akt-and EGFR-related anti-apoptotic and proliferative responses in isolated colonocytes and models of experimental colitis. We also found increased NT and NTR1 expression in the mesenteric fat depots during colitis and identified expression of NT and NTR1 in mouse preadipocytes that respond to NT be release of cytokines and increased proliferation. These findings link for the first time NT-NTR1-dependent inflammatory changes in mesenteric fat during colitis and may be of major importance in IBD where fat wrapping of the bowel is a common finding during surgery of IBD patients. Thus, in aim 2 will examine the NT-mediated cross talk between the colonic mucosa and mesenteric depots in acute and chronic experimental colitis by comparing NT and NTR1 expression in mesenteric fat to the degree of mucosal and adipose tissue inflammation in IBD-related models. Experiments in isolated preadipocytes will examine the mechanisms by which NT stimulates release of proinflammatory cytokines and adipokines, alters expression of adhesion molecules, and stimulates macrophage migration to these cells. Experiments in aim 1 and 2 will also compare colitis and inflammatory changes in fat depots between NT deficient and wild type mice. Studies in aim 3 will determine the signal transduction pathways involved in NT-induced IGF-1R phosphorylation in preadipocytes and examine the mechanisms by which NT-NTR1 interactions lead to cell proliferation and migration. Our results will provide important insights on the role of NT and its receptor in colonic inflammation and its expanded role in activation and inflammation of mesenteric adipose tissue observed in IBD and animal models of experimental colitis. PUBLIC HEALTH REVELVANCE This project will examine the pathophysiologic mechanisms by which the neuropeptide neurotensin participates in the pathogenesis of intestinal inflammation and Inflammatory Bowel Disease. Part of this project also examines how this neuropeptide influences development of inflammation in the adjacent fat tissue following colonic inflammatory changes.