Role of stress-induced reduction in Lactobacillus reuteri on colonic inflammation

描述（由申请人提供）：炎症性肠病（IBD，包括克罗恩病和溃疡性结肠炎）涉及由于多种遗传和环境因素导致的微生物群和粘膜免疫系统之间的稳态相互作用被破坏。公认增加IBD严重程度的主要环境因素是心理社会压力。然而，将压力与微生物群和粘膜免疫系统之间的稳态关系破坏联系起来的生物学机制尚未得到很好的理解。 该提案将测试新的假设，即肠上皮细胞代表应激，肠道微生物群改变和病原体诱导的结肠炎之间的机械联系。我们的初步数据表明，将小鼠暴露于一种被称为社会破坏（SDR）的被充分表征和广泛使用的社会应激源中，可以减少结肠中嗜酸性罗伊氏乳杆菌的丰度。在用鼠结肠病原体啮齿柠檬酸杆菌（Citrobacter rodentium）进行口服攻击后，小鼠暴露于SDR（因此L. reuteri）在病原体诱导的结肠炎中显著增加，如结肠组织病理学，趋化因子（例如，CCL 2）、细胞因子（例如，TNF-α），效应分子（例如，iNOS）和巨噬细胞浸润。重要的是，防止应激诱导的L。reuteri，以L. reuteri在应激暴露期间对小鼠的作用消除了应激对C.啮齿动物引起的结肠炎就像它的人类同源物（即，肠致病性E. coli）、C.啮齿动物通过定居结肠上皮诱导结肠炎症。因此，C.啮齿动物是确定结肠上皮在应激、微生物群和结肠炎恶化之间的联系中是否至关重要的理想模型。这个建议将测试新的假设，当L。由于应激物暴露，结肠上皮细胞过度产生趋化因子（特别是CCL 2），其增加炎性巨噬细胞向结肠的募集，在结肠中它们最终加重结肠炎。 第一个目标是通过评估应激诱导的L. reuteri对结肠上皮细胞和使用CCL 2敲除小鼠产生CCL 2的影响。在第二个目标，我们将使用过继转移实验，以测试是否外周炎性单核细胞，我们表明，增加在循环的压力小鼠，交通结肠在响应升高的CCL 2，在那里他们可以通过过度生产的TNF-？和iNOS。最后，在第三个目标中，我们将确定L。reuteri影响结肠上皮细胞产生趋化因子依赖于L. reuteri定殖结肠，和/或由于免疫调节因子的产生。该提案将确定可能导致IBD治疗中的新治疗靶点的新机制。 公共卫生相关性：在实验动物和炎症性肠病患者中，应激反应加剧了结肠炎，但这种情况发生的生物学机制尚不清楚。我们的研究表明，应激诱导的减少，在肠道罗伊氏乳杆菌参与了观察到的增加结肠组织病理学的小鼠在暴露于一个良好的特点和广泛使用的社会应激过程中与啮齿类柠檬酸杆菌挑战。这一提议将检验新的假设，即应激诱导的L。reuteri导致结肠上皮细胞过度产生趋化因子，特别是CCL 2和细胞因子，最终导致TNF-α的募集。产生炎症巨噬细胞加剧结肠炎

DESCRIPTION (provided by applicant): The inflammatory bowel diseases (IBD, including Crohn's disease and ulcerative colitis) involve disrupted homeostatic interactions between the microbiota and the mucosal immune system as a result of multiple genetic and environmental factors. A major environmental factor that is well recognized to increase the severity of IBD is psychosocial stress. However, the biological mechanisms linking stress to disrupted homeostatic relationships between the microbiota and the mucosal immune system are not well understood. This proposal will test the novel hypothesis that intestinal epithelial cells represent a mechanistic link between stress, alterations of the gut microbiota, and pathogen-induced colitis. Our preliminary data demonstrate that exposing mice to a well characterized and widely used social stressor, called social disruption (SDR) reduces the abundance of commensal Lactobacillus reuteri in the colon. Upon oral challenge with the murine colonic pathogen Citrobacter rodentium, which induces colonic histopathology with similarities to human IBD, mice exposed to SDR (and thus having lower levels of L. reuteri) had a significant increase in pathogen-induced colitis as indicated by a significant increase in colonic histopathology, chemokines (e.g., CCL2), cytokines (e.g., TNF-?), effector molecules (e.g., iNOS), and macrophage infiltration. Importantly, preventing the stressor-induced reduction in L. reuteri by feeding L. reuteri to the mice during stressor exposure abrogated the effects of the stressor on C. rodentium-induced colitis. Like its human homologue (i.e., enteropathogenic E. coli), C. rodentium induces colonic inflammation by colonizing the colonic epithelium. Thus, the use of C. rodentium is an ideal model to determine whether the colonic epithelium is critical in the link between stress, the microbiota, and exacerbation of colitis. This proposal will test the novel hypothesis that when L. reuteri are decreased due to stressor exposure, colonic epithelial cells overproduce chemokines (particularly CCL2) that increase the recruitment of inflammatory macrophages to the colon where they ultimately exacerbate colitis. The first aim will examine the role of CCL2 as a novel primary mechanism (pathway) mediating the effects of stress on colonic inflammation, by assessing the effects of stress-induced alterations of L. reuteri on CCL2 production by colonic epithelial cells and by using CCL2 knockout mice. In the second aim, we will use adoptive transfer experiments to test whether peripheral inflammatory monocytes, which we show are increased in the circulation of stressed mice, traffic to the colon in response to the elevated CCL2, where they can exacerbate colitis through an overproduction of TNF-? and iNOS. Finally, in the third aim, we will determine whether the ability of L. reuteri to affect chemokine production by colonic epithelial cells is dependent upon L. reuteri colonizing the colon, and/or due to the production of immunomodulatory factor(s). This proposal will identify novel mechanism(s) that may lead to new therapeutic targets in the treatment of IBD. PUBLIC HEALTH RELEVANCE: The stress response exacerbates colitis, both in experimental animals and in patients with inflammatory bowel disease, but the biological mechanisms by which this occurs are not well understood. Our studies demonstrate that stressor-induced reduction in commensal Lactobacillus reuteri is involved with the observed increase in colonic histopathology in mice challenged with Citrobacter rodentium during exposure to a well characterized and widely used social stressor. This proposal will test the novel hypothesis that the stressor-induced reduction in L. reuteri leads to an overproduction of chemokines, particularly CCL2, and cytokines by colonic epithelial cells, ultimately resulting in the recruitment of TNF-?-producing inflammatory macrophages that exacerbate colitis.