Aberrant mucin assembly in mice causes endoplasmic reticulum stress and spontaneous inflammation resembling ulcerative colitis.
Aberrant mucin assembly in mice causes endoplasmic reticulum stress and spontaneous inflammation resembling ulcerative colitis.
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DOI：
10.1371/journal.pmed.0050054
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发表时间：
2008-03-04
期刊：
影响因子：
15.8
通讯作者：
McGuckin MA
中科院分区：
文献类型：
--
作者：
Heazlewood CK;Cook MC;Eri R;Price GR;Tauro SB;Taupin D;Thornton DJ;Png CW;Crockford TL;Cornall RJ;Adams R;Kato M;Nelms KA;Hong NA;Florin TH;Goodnow CC;McGuckin MA
肠道杯状细胞产生的MUC2粘蛋白是肠道粘液屏障的主要组成部分。炎症性肠病溃疡性结肠炎的特点是杯状细胞减少和黏液层减少，但病因尚不清楚。在这项研究中，我们采用随机诱变的方法产生了两种炎症性肠病的小鼠模型，描述了这些小鼠炎症的基础和性质，并将其与人类溃疡性结肠炎的病理进行了比较。通过小鼠n -乙基-n -亚硝基脲诱变，我们在Muc2中发现了两种不同的非互补错义突变，导致溃疡性结肠炎样表型。6周时，两种菌株的小鼠100%出现轻度自发性远端肠道炎症（组织学结肠炎评分与野生型小鼠相比，p < 0.01）和慢性腹泻。对每种菌株300多只小鼠的监测表明，每种菌株中分别有25%和40%的小鼠在1岁时出现严重的结肠炎临床症状。突变小鼠表现出Muc2生物合成异常，杯状细胞中储存的粘蛋白减少，粘液屏障减少，并且对腔内毒素诱导的结肠炎易感性增加。结肠远端IL-1β、TNF-α和IFN-γ的局部生成增强，肠通透性增加2倍。肠系膜淋巴结内白细胞数量增加5倍，体外培养的白细胞产生更多的Th1和Th2细胞因子（IFN-γ、TNF-α和IL-13）。这种病理伴随着Muc2前体的积累，杯状细胞内质网（ER）应激的超微结构和生化证据，未折叠蛋白反应的激活，以及参与内质网应激、炎症、细胞凋亡和伤口修复的肠道基因表达的改变。体外Muc2寡聚化域的突变表达表明，异常的Muc2寡聚化是内质网应激的基础。在人类溃疡性结肠炎中，我们在杯状细胞中发现了类似的非糖基化MUC2前体的积累，并在未发炎的肠道组织中发现了内质网应激的超微结构和生化证据。虽然我们的研究表明粘蛋白错误折叠和内质网应激引发小鼠结肠炎，但它并没有确定人类结肠炎内质网应激的遗传或环境驱动因素。我们创建的小鼠模型的特征以及与人类疾病的比较表明，内质网应激相关的粘蛋白耗竭可能是人类结肠炎发病机制的一个基本组成部分，结合遗传学、内质网应激相关病理学和相关环境流行病学的临床研究是有必要的。Michael McGuckin和他的同事们在老鼠身上发现了两种导致黏液蛋白寡聚化异常的突变。由此产生的表型，包括内质网应激，类似于人类溃疡性结肠炎的临床和病理特征。炎症性肠病（IBD）是消化道部分发炎的常见疾病。IBD的两种主要类型是主要影响小肠的克罗恩病和主要影响大肠（结肠）的溃疡性结肠炎（UC）。这两种类型都倾向于在家族中遗传，通常在15到35岁之间发病。他们的症状包括腹泻、腹部痉挛和无意中体重减轻。这些症状的严重程度各不相同，可能是慢性的（持续的）或间歇性的，可能是逐渐或突然开始的。目前还没有治愈IBD的方法（除了切除受影响的消化道部分），但调节免疫系统的药物（例如皮质类固醇）或抑制“促炎细胞因子”（由免疫系统产生的刺激炎症的蛋白质）有时会有所帮助。虽然克罗恩病和UC的临床和病理（疾病相关）特征有所不同，但这两种疾病都可能是由免疫系统失衡引起的。正常情况下，免疫系统保护身体免受肠道中潜在有害微生物的侵害，但不会对生活在肠道中的许多无害细菌或通过消化道的食物做出反应。在IBD中，免疫系统由于未知的原因变得过度活跃，淋巴细胞（免疫系统细胞）积聚在肠内壁并引起炎症。在这项研究中，研究人员使用了一种称为随机诱变的技术（使用一种破坏DNA的化学物质随机引入微小的变化，称为突变，进入生物体的基因）来开发两个类似人类UC的小鼠模型，并为这种疾病的发展提供了新的线索。研究人员建立了两种突变小鼠——winnie和Eeyore小鼠——它们会出现轻微的自发性结肠炎症和慢性腹泻，并且在它们的结肠中比正常小鼠有更多的促炎细胞因子和淋巴细胞。25%和40%的Winnie和Eeyore小鼠在1岁时分别出现严重的结肠炎临床症状。这两种菌株都有Muc2基因突变，该基因编码Muc2粘蛋白，Muc2粘蛋白是粘液中的主要蛋白质。这种黏性物质（覆盖在肠道内部）是由肠道“杯状”细胞产生并储存的。粘液有助于维持肠道的免疫平衡，但在UC中被耗尽。研究人员表明，在Winnie和Eeyore小鼠中，Muc2分子的制造和组装是异常的，它们的杯状细胞中储存的粘蛋白比正常小鼠少，而且它们的肠道粘液屏障也减少了。此外，一种被称为Muc2前体的不完全组装的分子在杯状细胞的内质网（内质网是为释放新制造的蛋白质而准备的细胞装置）中积累，导致异常蛋白质超载，并引起一种被称为“内质网应激反应”的细胞窘迫状态。最后，研究人员报告说，MUC2前体也在UC患者的杯状细胞中积累，甚至这些患者的非炎症肠道组织也显示出内质网应激的迹象。这些发现表明粘蛋白异常和内质网应激可引发小鼠结肠炎。动物研究的结果并不总是反映在人类身上发生的情况，但这些发现，以及在人类身上进行的小型研究的结果，表明内质网应激相关的粘蛋白耗竭可能是人类结肠炎发展的一个组成部分。研究结果没有确定可能引发人类结肠炎内质网应激的遗传变化和/或环境因素，但表明内质网应激一旦启动，可能会干扰MUC2的产生，从而导致粘液屏障减少，使肠道内膜暴露于更多的毒素和外来物质，并引发局部粘膜炎症。然后，炎症细胞因子的释放会损害肠道内壁，加剧内质网应激，从而形成肠道损伤和炎症的循环。现在应该进行临床研究，寻找能够触发内质网应激的遗传变化和环境因素，以及人类UC中内质网应激相关的变化，以验证这一假设。请通过本摘要的在线版本http://dx.doi.org/10.1371/journal.pmed.0050054访问这些网站。MedlinePlus百科全书有关于克罗恩病和溃疡性结肠炎的页面（英语和西班牙语），美国国家糖尿病、消化和肾脏疾病研究所提供关于克罗恩病和溃疡性结肠炎的信息，炎性肠病患者及其护理人员的信息和支持由美国克罗恩病和结肠炎基金会和英国国家结肠炎和克罗恩病协会提供维基百科有粘蛋白等页面（请注意，维基百科是一个免费的在线百科全书，任何人都可以编辑；有多种语言版本）
MUC2 mucin produced by intestinal goblet cells is the major component of the intestinal mucus barrier. The inflammatory bowel disease ulcerative colitis is characterized by depleted goblet cells and a reduced mucus layer, but the aetiology remains obscure. In this study we used random mutagenesis to produce two murine models of inflammatory bowel disease, characterised the basis and nature of the inflammation in these mice, and compared the pathology with human ulcerative colitis. By murine N-ethyl-N-nitrosourea mutagenesis we identified two distinct noncomplementing missense mutations in Muc2 causing an ulcerative colitis-like phenotype. 100% of mice of both strains developed mild spontaneous distal intestinal inflammation by 6 wk (histological colitis scores versus wild-type mice, p < 0.01) and chronic diarrhoea. Monitoring over 300 mice of each strain demonstrated that 25% and 40% of each strain, respectively, developed severe clinical signs of colitis by age 1 y. Mutant mice showed aberrant Muc2 biosynthesis, less stored mucin in goblet cells, a diminished mucus barrier, and increased susceptibility to colitis induced by a luminal toxin. Enhanced local production of IL-1β, TNF-α, and IFN-γ was seen in the distal colon, and intestinal permeability increased 2-fold. The number of leukocytes within mesenteric lymph nodes increased 5-fold and leukocytes cultured in vitro produced more Th1 and Th2 cytokines (IFN-γ, TNF-α, and IL-13). This pathology was accompanied by accumulation of the Muc2 precursor and ultrastructural and biochemical evidence of endoplasmic reticulum (ER) stress in goblet cells, activation of the unfolded protein response, and altered intestinal expression of genes involved in ER stress, inflammation, apoptosis, and wound repair. Expression of mutated Muc2 oligomerisation domains in vitro demonstrated that aberrant Muc2 oligomerisation underlies the ER stress. In human ulcerative colitis we demonstrate similar accumulation of nonglycosylated MUC2 precursor in goblet cells together with ultrastructural and biochemical evidence of ER stress even in noninflamed intestinal tissue. Although our study demonstrates that mucin misfolding and ER stress initiate colitis in mice, it does not ascertain the genetic or environmental drivers of ER stress in human colitis. Characterisation of the mouse models we created and comparison with human disease suggest that ER stress-related mucin depletion could be a fundamental component of the pathogenesis of human colitis and that clinical studies combining genetics, ER stress-related pathology and relevant environmental epidemiology are warranted. Michael McGuckin and colleagues identify two mutations that cause aberrant mucin oligomerization in mice. The resulting phenotype, including endoplasmic reticulum stress, resembles clinical and pathologic features of human ulcerative colitis. Inflammatory bowel diseases (IBD) are common disorders in which parts of the digestive tract become inflamed. The two main types of IBD are Crohn's disease, which mainly affects the small bowel, and ulcerative colitis (UC), which mainly affects the large bowel (colon). Both types tend to run in families and usually develop between 15 and 35 years old. Their symptoms include diarrhea, abdominal cramps, and unintentional weight loss. These symptoms can vary in severity, can be chronic (persistent) or intermittent, and may start gradually or suddenly. There is no cure for IBD (except removal of the affected part of the digestive tract), but drugs that modulate the immune system (for example, corticosteroids) or that inhibit “proinflammatory cytokines” (proteins made by the immune system that stimulate inflammation) can sometimes help. Although the clinical and pathological (disease-associated) features of Crohn's disease and UC are somewhat different, both disorders are probably caused by an immune system imbalance. Normally, the immune system protects the body from potentially harmful microbes in the gut but does not react to the many harmless bacteria that live there or to the food that passes along the digestive tract. In IBD, the immune system becomes overactive for unknown reasons, and lymphocytes (immune system cells) accumulate in the lining of the bowel and cause inflammation. In this study, the researchers use a technique called random mutagenesis (the random introduction of small changes, called mutations, into the genes of an organism using a chemical that damages DNA) to develop two mouse models that resemble human UC and that throw new light on to how this disorder develops. The researchers establish two mutant mouse strains—Winnie and Eeyore mice—that develop mild spontaneous inflammation of the colon and chronic diarrhea and that have more proinflammatory cytokines and more lymphocytes in their colons than normal mice. 25% and 40% of the Winnie and Eeyore mice, respectively, have severe clinical signs of colitis by 1 year of age. Both strains have a mutation in the Muc2 gene, which codes for MUC2 mucin, the main protein in mucus. This viscous substance (which coats the inside of the intestine) is produced by and stored in intestinal “goblet” cells. Mucus helps to maintain the intestine's immunological balance but is depleted in UC. The researchers show that the manufacture and assembly of Muc2 molecules is abnormal in Winnie and Eeyore mice, that less mucin is stored in their goblet cells than in normal mice, and that their intestinal mucus barrier is reduced. In addition, an incompletely assembled version of the molecule, called Muc2 precursor, accumulates in the endoplasmic reticulum (ER; the cellular apparatus that prepares newly manufactured proteins for release) of goblet cells, leading to overload with abnormal protein and causing a state of cellular distress known as the “ER stress response.” Finally, the researchers report that MUC2 precursor also accumulates in the goblet cells of people with UC and that even the noninflamed intestinal tissue of these patients shows signs of ER stress. These findings indicate that mucin abnormalities and ER stress can initiate colitis in mice. Results from animal studies do not always reflect what happens in people, but these findings, together with those from the small study in humans, suggest that ER stress-related mucin depletion could be a component in the development of human colitis. The results do not identify the genetic changes and/or environmental factors that might trigger ER stress in human colitis, but suggest that once initiated, ER stress might interfere with MUC2 production, which would lead to a diminished mucus barrier, expose the lining of the intestine to more toxins and foreign substances, and trigger local mucosal inflammation. The release of inflammatory cytokines would then damage the intestine's lining and exacerbate ER stress, thus setting up a cycle of intestinal damage and inflammation. Clinical studies to look for genetic changes and environmental factors capable of triggering ER stress and for ER-stress related changes in human UC should now be undertaken to test this hypothesis. Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050054. The MedlinePlus Encyclopedia has pages on Crohn's disease and on ulcerative colitis (in English and Spanish) The US National Institute of Diabetes and Digestive and Kidney Diseases provides information on Crohn's disease and ulcerative colitis Information and support for patients with inflammatory bowel disease and their caregivers is provided by the Crohn's and Colitis Foundation of America and by the UK National Association for Colitis and Crohn's Disease Wikipedia has pages on mucins and on mucus (note that Wikipedia is a free online encyclopedia that anyone can edit; available in several languages)
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影响因子：
3.3
作者：
DVORAK, AM;OSAGE, JE;DICKERSIN, GR
通讯作者：
DICKERSIN, GR
影响因子：
14.2
作者：
Hogan, Simon P.;Seidu, Luqman;Rothenberg, Marc E.
通讯作者：
Rothenberg, Marc E.
影响因子：
15.9
作者：
Fuss, IJ;Heller, F;Strober, W
通讯作者：
Strober, W
影响因子：
4.8
作者：
Godl, K;Johansson, MEV;Hansson, GC
通讯作者：
Hansson, GC
影响因子：
24.5
作者：
Bodger, K.;Halfvarson, J.;Rhodes, J. M.
通讯作者：
Rhodes, J. M.