GUT BARRIER DYSFUNCTION: THE TRIGGER FOR CACHEXIA IN APCMIN/+ MICE

肠道屏障功能障碍：APCMIN/小鼠恶病质的触发因素

• 批准号: 7959766
• 负责人: James A Carson
• 金额: $ 3.7万
• 依托单位: UNIVERSITY OF SOUTH CAROLINA AT COLUMBIA
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-06-01 至 2010-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7959766
• 关键词: Accounting; Address; Analytical Biochemistry; Animal Model; Bacteria; Biochemistry; Blood; Cachexia; Cancer Patient; Cell Wall; Cell secretion; Cessation of life; Chronic; Clinical; Colon Carcinoma; Colonic Neoplasms; Colorectal Cancer; Computer Retrieval of Information on Scientific Projects Database; Data; Development; Endotoxemia; Endotoxins; Epithelial Cells; Extravasation; Functional disorder; Funding; Gastrointestinal tract structure; Grant; Hemorrhage; Immune response; Infiltration; Inflammation; Inflammatory; Institution; Interleukin-6; Intestines; Knock-out; Knowledge; Lead; Lipopolysaccharides; Malignant Neoplasms; Malignant neoplasm of lung; Mesentery; Metabolism; Mitochondria; Modeling; Multiple Organ Failure; Mus; Muscle; Muscle Proteins; Muscularis Mucosa; National Cancer Institute; Outcome; Physiology; Prevention; Protein Biosynthesis; Proteolysis; Rattus; Regulation; Research; Research Personnel; Resources; Role; Sepsis; Shock; Signal Transduction; Source; South Carolina; Submucosa; Testing; Tight Junctions; Tumor Burden; Ubiquitin; United States National Institutes of Health; Universities; Work; anticancer research; cytokine; experience; gastrointestinal; lymph nodes; muscle form; neoplastic cell; new therapeutic target; novel; prevent; protein degradation; skeletal muscle wasting; tumor growth; tumorigenesis; wasting

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Cancer cachexia is a condition of whole body wasting that is more common with gastrointestinal tract and lung cancers; cachexia accounts for 30-50% deaths with colon cancer. Thus, the prevention of cachexia is an important objective for the improvement of clinical outcomes in colon cancer patients. Studies on cellular mechanisms involved in muscle wasting indicate that cachexia is initiated by inflammatory signaling, which then activates ATP-dependent ubiquitin-dependent proteasomal degradation of protein, causing loss of muscle mass. Understanding the regulatory mechanisms that integrate inflammatory signaling and muscle proteolysis is critical for understanding cachexia. The PI currently has a RO1 grant funded through the National Cancer Institute to examine inflammatory cytokine IL-6 regulation of muscle protein synthesis and degradation, and muscle mitochondrial function in cachectic ApcMin/+ mice. The source of chronic low level inflammation in ApcMin/+ mice is not well established, but is thought to be related to the immune response to intestinal and colon tumors, and may also involve direct tumor cell secretion of cytokines. A question not addressed by our current funding is the cause of the systemic inflammation that is thought to initiate the skeletal muscle wasting in ApcMin/+ mice. Gut barrier dysfunction (GBD) is a condition where tight junctions between intestinal epithelial cells no longer form an impermeable barrier against bacterial infiltration into the submucosa and muscularis mucosa of the intestine.8 This can lead to endotoxemia (bacterial cell wall fragments in blood) or sepsis (viable bacteria in blood), leading to multiple organ dysfunction syndrome (MODS).7, 21 GBD has been well documented in hemorrhage shock models, and is associated with, and dependent on, increased circulating IL-6 levels; rats with knock-out of IL-6 do not develop GBD.27 We have recently shown that knockout of IL-6 also inhibits development of cachexia and that IL-6 over-expression induces cachexia in ApcMin/+ mice.5 Our preliminary studies demonstrate that a subset of 30 week old ApcMin/+ mice test positive for circulating endotoxin in the blood, and bacteria in the mesenteric lymph nodes. It is not known if GBD with low-level endotoxemia or sepsis, combined with increased expression of IL-6, is a significant source of inflammation that promotes tumorigenesis, tumor growth, and/or cachexia in ApcMin/+ mice. The overall purpose of the current proposal is to determine if gut barrier dysfunction is the primary cause of cachexia in ApcMin/+ mice. To the best of our knowledge the working hypothesis is completely novel. We hypothesize that cachexia is initiated by increased inflammation that results from endotoxin (bacterial lipopolysaccharide or intact bacteria) leakage across the gastrointestinal barrier in ApcMin/+ mice. Additionally, we hypothesize that elevated circulating IL-6 will be necessary to induce endotoxin leakage across the gastrointestinal barrier in ApcMin/+ and ApcMin/+ x Il-6-/- mice. This proposal merges Dr. John Baynes experience in analytical biochemistry, clinical biochemistry, and metabolism with Dr. Carson's understanding of physiology using whole animal models, including the ApcMin/+ mouse. This proposal also servers as a novel project that can bring Dr. Baynes's research expertise closer to the colorectal cancer research group at the University of South Carolina. Completion of this work will lead to a better understanding of the role of GBD and IL-6 signaling in regulation on cachexia, and identify potential novel therapeutic targets to both treat and prevent the cachectic condition. This proposal will provide essential preliminary data for further study in a multi-year RO1 application. Aim 1. Determine if gut barrier dysfunction increases with tumor burden and cachexia in the ApcMin/+ mouse. Aim 2. Determine if inflammatory cytokine IL-6 induces gut barrier dysfunction, in concert with the development of cachexia, in ApcMin/+ and ApcMin/+ x IL-6 -/- mice.

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 癌症恶病质是一种全身消瘦的病症，在胃肠道癌和肺癌中更常见;恶病质占结肠癌死亡的30-50%。因此，恶病质的预防是改善结肠癌患者临床结局的重要目标。 对肌肉萎缩中涉及的细胞机制的研究表明，恶病质是由炎症信号传导引发的，其然后激活ATP依赖性泛素依赖性蛋白酶体的蛋白降解，导致肌肉质量损失。 了解整合炎症信号和肌肉蛋白水解的调节机制对于理解恶病质是至关重要的。PI目前通过国家癌症研究所获得了RO 1资助，用于检查炎性细胞因子IL-6对恶病质ApcMin/+小鼠肌肉蛋白合成和降解以及肌肉线粒体功能的调节。ApcMin/+小鼠中慢性低水平炎症的来源尚未完全确定，但认为与对肠和结肠肿瘤的免疫应答有关，还可能涉及细胞因子的直接肿瘤细胞分泌。我们目前的资金没有解决的一个问题是全身性炎症的原因，这被认为是引发ApcMin/+小鼠骨骼肌萎缩的原因。 肠屏障功能障碍（GBD）是指肠上皮细胞之间的紧密连接不再形成不可渗透的屏障，阻止细菌渗入肠粘膜下层和粘膜肌层。8这可能导致内毒素血症（血液中的细菌细胞壁碎片）或败血症（血液中的活菌），导致多器官功能障碍综合征（MODS）。7，21 GBD已在出血性休克模型中得到很好的证明，并且与增加循环IL-6水平;敲除IL-6的大鼠不发展GBD。27我们最近已经表明敲除IL-6也抑制恶病质的发展，并且IL-6过表达诱导ApcMin/+小鼠中的恶病质。5我们的初步研究表明30周龄的ApcMin/+小鼠的一个亚组对血液中的循环内毒素测试呈阳性，肠系膜淋巴结中的细菌目前尚不清楚GBD伴低水平内毒素血症或脓毒症以及IL-6表达增加是否是促进ApcMin/+小鼠肿瘤发生、肿瘤生长和/或恶病质的重要炎症来源。 当前提案的总体目的是确定肠道屏障功能障碍是否是ApcMin/+小鼠恶病质的主要原因。据我们所知，这个工作假设是完全新颖的。我们假设恶病质是由ApcMin/+小鼠中内毒素（细菌脂多糖或完整细菌）穿过胃肠屏障渗漏引起的炎症增加引发的。此外，我们假设升高的循环IL-6对于诱导ApcMin/+和ApcMin/+ x IL-6-/-小鼠中内毒素穿过胃肠屏障渗漏是必要的。该提案将John Baynes博士在分析生物化学、临床生物化学和代谢方面的经验与卡森博士对使用整个动物模型（包括ApcMin/+小鼠）的生理学的理解相结合。这项建议也是一个新颖的项目，可以使贝恩斯博士的研究专业知识更接近于结肠直肠癌研究小组， 南卡罗来纳州大学。这项工作的完成将导致更好地理解GBD和IL-6信号在恶病质调节中的作用，并确定潜在的新的治疗靶点，以治疗和预防恶病质。该提案将为多年RO 1应用的进一步研究提供必要的初步数据。 目标1.确定ApcMin/+小鼠中肠道屏障功能障碍是否随肿瘤负荷和恶病质增加而增加。 目标2.在ApcMin/+和ApcMin/+ x IL-6 -/-小鼠中确定炎性细胞因子IL-6是否诱导肠道屏障功能障碍，以及恶病质的发展。