Endoplasmic reticulum stress and intestinal inflammation

描述（由申请人提供）：内质网（ER）应激是一种古老的保守机制，其允许细胞，特别是具有重要分泌功能的细胞，如肠上皮细胞（IEC），通过称为未折叠蛋白反应（UPR）的机制科普ER内错误折叠或未折叠蛋白的出现。UPR由三个ER相关通路组成，这些通路在细胞核内发出适应性转录程序的信号。最高度保守的途径是与肌醇需要酶1（IRE 1）相关的途径，IRE 1通过其核糖核酸内切酶和激酶活性分别调节X-box结合蛋白1（XBP 1）和Jun相关激酶（JNK）的转录活性。特异性地在IEC内缺失XBP 1基因独特地导致自发性肠炎和对结肠炎诱导剂的敏感性，其与增加的ER应激、潘氏细胞和杯状细胞功能的丧失、不能管理管腔微生物挑战以及IEC对源自细菌和免疫因子的信号的超敏性相关。因此，XBP 1与IEC的功能影响IBD发病机制的两个中心决定因素：微生物群和对微生物群本身的免疫反应。考虑到ER应激在炎症性肠病（IBD）的动物模型和人类疾病中很容易证明，并且XBP 1基因具有多态性，这些多态性赋予IBD发展的风险，因此可以合理地提出，宿主管理IEC内由环境因素（包括炎症本身）引起的ER应激的能力是理解IBD发病机制的重要问题。本提案旨在：（1）通过表征三种主要UPR途径的活性、NF κ B活化的作用、ER应激和自噬途径之间的潜在交叉，XBP 1缺乏对上皮细胞的特定上皮亚型的影响，以及确定NFkB或JNK的阻断是否可以改善XBP 1相关的炎症;（2）通过定义TNFa的作用和对XBP 1缺陷小鼠肠中肠相关淋巴样细胞群的表征，定义来自上皮的参与炎症的炎症介质及其对粘膜免疫细胞群的影响;（3）定义与XBP 1相关的炎症恶化或缓解相关的环境因素-通过表征XBP 1缺陷型小鼠的微生物组和微生物群在诱导自发性肠炎和对结肠炎的易感性中的作用，以及确定降低ER应激的试剂是否可以消除由XBP 1缺陷型上皮细胞引起的肠道炎症，来确定对缺乏XBP 1的研究。这些动物模型和它们的询问提供了鉴定和测试用于治疗和预防IBD的新型治疗方法的独特机会，所述治疗方法通常可扩展至具有广泛表型和遗传谱系的IBD患者。 公共卫生相关性：肠上皮细胞（IEC）内的XBP 1功能与内质网（ER）应激相关，并影响炎症性肠病（IBD）发病机制的两个中心决定因素;胃肠道中发现的细菌和对这些细菌本身的免疫反应。鉴于ER应激在IBD动物模型和人类条件中很容易证明，并且XBP 1基因具有多态性，从而导致IBD的发展风险，我们建议宿主在IEC内管理ER应激的能力是由环境因素（包括炎症本身）引起的，这是理解IBD发病机制的一个重要问题。这些动物模型和它们的询问提供了鉴定和测试用于治疗和预防IBD的新型治疗方法的独特机会，所述治疗方法通常可扩展至具有广泛表型和遗传谱系的IBD患者。

DESCRIPTION (provided by applicant): Endoplasmic reticulum (ER) stress is an ancient conserved mechanism that allows cells, especially those with significant secretory function such as intestinal epithelial cells (IEC), to cope with the emergence of misfolded or unfolded proteins within the ER through a mechanism called the Unfolded Protein Response (UPR). The UPR consists of three ER-associated pathways that signal adaptive transcriptional programs within the nucleus. The most highly conserved pathway is that related to inositol requiring enzyme 1 (IRE1) which, through its endoribonuclease and kinase activities, regulates the transcriptional activity of X-box binding protein 1 (XBP1) and Jun related kinase (JNK), respectively. Deletion of the XBP1 gene specifically within IECs leads, uniquely, to spontaneous enteritis and sensitivity to colitis-inducing agents in association with increased ER stress, loss of Paneth and goblet cell function, an inability to manage luminal microbial challenges and a hypersensitivity of the IEC to signals emanating from bacterial and immune factors. XBP1 function with the IEC thus affects the two central determinants of IBD pathogenesis; the microbiota and immune response to the microbiota itself. Given that ER stress is readily demonstrable in animal models of inflammatory bowel disease (IBD) and the human condition and that the XBP1 gene harbors polymorphisms that confer risk for the development of IBD, it is reasonable to propose that the host's ability to manage ER stress within the IEC that is caused by environmental factors including inflammation itself is an important issue in understanding IBD pathogenesis. The current proposal aims to: (1) Elucidate the molecular pathways that connect unabated ER stress with inflammation that occurs in the presence of hypomorphic XBP1 function within the epithelium by characterizing the activity of the three major UPR pathways, the role NFkB activation, the potential intersection between ER stress and autophagy pathways, the effects of XBP1 deficiency on specific epithelial subtypes of epithelial cells and a determination of whether blockade of NFkB or JNK can ameliorate XBP1-related inflammation; (2) Define the inflammatory mediators derived from the epithelium that are involved in inflammation and their effects on mucosal immune cell populations by defining the role of TNFa and the characterization of the gut associated lymphoid cell populations in the intestines of XBP1-deficient mice, and; (3) Define the environmental factors involved in the exacerbation or alleviation of inflammation associated with XBP1- deficiency by characterizing the microbiome of XBP1-deficient mice and the role of the microbiota in inducing spontaneous enteritis and susceptibility to colitis and establishing whether agents that reduce ER stress can abrogate the intestinal inflammation arising from XBP1-deficient epithelia. These animal models and their interrogation provide a unique opportunity to identify and test novel therapeutic approaches for the treatment and prevention of IBD that may be generally extensible to IBD patients with a wide-range of phenotypic and genetic pedigrees. PUBLIC HEALTH RELEVANCE: XBP1 function within intestinal epithelial cells (IEC) is associated with endoplasmic reticulum (ER) stress and affects the two central determinants of inflammatory bowel disease (IBD) pathogenesis; the bacteria found in the gastro-intestinal tract and immune response to these bacteria itself. Given that ER stress is readily demonstrable in animal models of IBD and the human condition, and that the XBP1 gene harbors polymorphisms that confer risk for the development of IBD, we propose that the host's ability to manage ER stress within the IEC that is caused by environmental factors including inflammation itself is an important issue in understanding IBD pathogenesis. These animal models and their interrogation provide a unique opportunity to identify and test novel therapeutic approaches for the treatment and prevention of IBD that may be generally extensible to IBD patients with a wide-range of phenotypic and genetic pedigrees.