Gut Dysbiosis and Cardiac Remodeling in IBD

项目总结/摘要 炎症性肠病（IBD）是一种使人衰弱且难以控制的消化道慢性炎症， 肠道，引起腹泻等胃肠道症状。它与终身发病率，更大的医疗 注意力和生活质量下降。大约有300万美国人患有IBD及其巨大的经济负担。 IBD的肠外表现（EIM）很常见，尤其是在儿童中，甚至使IBD的临床表现黯然失色。 肠道症状越来越多的证据表明，IBD与以下疾病的发病率增加有关： 心血管事件。然而，IBD使患者易患 心血管疾病（CVD）仍然难以捉摸。除了慢性炎症，IBD的一个特征是 肠道微生物群的生态失调，其特征是专性厌氧菌的显著减少和 兼性厌氧菌虽然炎症可以通过药物治疗或手术得到很好的控制，但肠道微生物 生态失调持续存在，可能在IBD相关的心血管疾病中发挥关键作用。我们在小鼠中证实了这一现象 结肠炎模型，其概括了人类IBD的一些常见EIM。我们的初步发现表明， 肠道微生物群失调通过上调miR-155和下调脑- 衍生的神经营养因子（BDNF），两者都被认为是心脏系统的关键参与者。我们假设 结肠炎引起的微生物群失调通过表观遗传触发成人心脏的分子重塑 机制等我们将通过追求三个具体目标来检验这一假设。目标1将把生态失调作为一个关键 通过移植IBD患者的生态失调粪便微生物群， 从患有结肠炎的小鼠到细菌耗尽的小鼠。我们还将确定是否可以通过以下方法消除疾病信号： 移植正常粪便微生物群和/或益生菌。目标2将集中于表征外泌体miR- 155作为IBD诱导的分子重塑的关键参与者。我们预见，外泌体miR-155衍生 特别是来自肠上皮细胞（IEC）的功能是肠道之间串扰的主要介质， 微生物群和心脏使用新型IEC特异性miR-155敲除（Mir155 Δ IEC）和Mir155 Δ IEC/IL10-/-小鼠， 我们的目的是显示肠源性的外泌体miR-155在存在下表观遗传地下调心脏BDNF。 慢性结肠炎我们还将确定miR-155抑制剂是否减轻IBD诱导的心脏病。在目标3中， 心肌细胞中BDNF减少的表观遗传机制将通过体内、体外和 蛋白质组学方法。我们将描述BDNF在成人心脏中的功能和表型作用。 使用新的他莫昔芬诱导的心脏特异性BDNF敲除小鼠模型。我们亦会探讨 BDNF对IBD相关CVD的预防和治疗潜力。我们的研究结果应该有助于建立一个新的 结肠炎通过微生物群失调→外泌体miR-155 → BDNF诱导心脏重塑的范例 信号轴，导致心脏功能障碍。

PROJECT SUMMARY/ABSTRACT Inflammatory bowel disease (IBD) is a debilitating and difficult to manage chronic inflammation in the digestive tract, causing gastrointestinal symptoms such as diarrhea. It is associated with lifelong morbidity, greater medical attention, and diminished quality of life. About 3 million Americans suffer from IBD and its huge financial burden. Extraintestinal manifestations (EIM) of IBD are common, especially in children, and even overshadow the intestinal symptoms. Accumulating evidence suggests that IBD is associated with an increased incidence of cardiovascular events. However, the molecular mechanisms by which IBD predisposes patients to cardiovascular diseases (CVD) remain elusive. In addition to chronic inflammation, a signature of IBD is dysbiosis of the gut microbiota marked by a significant reduction of obligate anaerobes and a sharp increase in facultative anaerobes. While inflammation could be well controlled by drug therapy or surgery, gut microbial dysbiosis persists and may play a key role in IBD-associated CVD. We confirmed this phenomenon in murine models of colitis, which recapitulate some common EIM of human IBD. Our preliminary findings suggest that dysbiotic gut microbiota contributes to cardiac dysfunction by up-regulating miR-155 and down-regulating brain- derived neurotrophic factor (BDNF), both identified as crucial players in cardiac system. We hypothesize that colitis-induced microbiota dysbiosis triggers molecular remodeling in the adult heart through epigenetic mechanisms. We will test the hypothesis by pursuing three specific aims. Aim 1 will establish dysbiosis as a key player in colitis-induced heart dysfunction by transplanting dysbiotic fecal microbiota from patients with IBD and mice with colitis to bacteria-depleted mice. We will also determine whether the disease signal can be ablated by transplantation of normal fecal microbiota and/or probiotics. Aim 2 will focus on characterizing exosomal miR- 155 as a key player in IBD-induced molecular remodeling. We foresee that exosomal miR-155 derived specifically from the intestinal epithelial cells (IEC) functions as a major mediator of the crosstalk between gut microbiota and the heart. Using novel IEC-specific miR-155-knockout (Mir155ΔIEC) and Mir155ΔIEC/IL10-/- mice, we aim to show that exosomal miR-155 of gut origin epigenetically down-regulates cardiac BDNF in the presence of chronic colitis. We will also determine if miR-155 inhibitors mitigate IBD-induced heart diseases. In Aim 3, epigenetic mechanisms of BDNF reduction in cardiomyocytes will be elucidated using in vivo, in vitro, and proteomics approaches. We will characterize the functional and phenotypic roles of BDNF in the adult heart using a novel tamoxifen-inducible, cardiac-specific BDNF knockout mouse model. We will also explore the preventive and therapeutic potential of BDNF for IBD-associated CVD. Our results should help establish a novel paradigm that colitis induces cardiac remodeling through microbiota dysbiosis→exosomal miR-155→BDNF signaling axis, resulting in heart dysfunction.