Cachexia in ApcMin/+ mice: The role of IL-6

描述(申请人提供)：恶病质是一种全身衰弱的状况，占所有癌症相关死亡的20%-40%，特别是胃肠道和肺癌。炎性细胞因子是骨骼肌丢失的重要效应因子，而细胞因子IL-6作为与恶病质有关的信号分子而臭名昭著。突变APC基因杂合子(ApcMin/+)的小鼠在10周龄时出现显著的肠息肉负担，并在18至26周龄时变得恶病质。利用这种小鼠研究恶病质的调节是新颖的，与其他恶病质动物模型相比，它具有优势，包括消瘦速度较慢和缺乏厌食症。PI表明，炎性细胞因子IL-6是ApcMin/+小鼠恶病质的调节器。IL-6基因敲除可预防恶病质，而IL-6过度表达则加速恶病质。目前尚不清楚IL-6是对肌肉产生直接影响，还是通过影响肿瘤生长或肿瘤起源的恶病质介质的分泌而间接影响。然而，了解IL-6消融的有益效果将清楚地提供对癌症期间炎症和恶病质之间的关系的洞察。本应用程序的总体目的是解决ApcMin/+小鼠中恶病质的潜在机制。这些机制将在最初和严重的消耗阶段以及肌肉的氧化代谢能力方面进行研究。目的1研究恶病质ApcMin/+小鼠早期和严重消瘦过程中肌肉蛋白质合成和蛋白酶体降解的调节。在恶病质进展过程中，这些过程在糖酵解和氧化肌肉中的不同调节将被检验。实验还将检验循环中IL-6对肌肉蛋白质合成和降解的逐步增加。目的2研究ApcMin/+小鼠早期和严重消瘦过程中肌肉线粒体功能和肌核细胞凋亡的调控。在恶病质的进展和IL-6的分级过表达过程中，将评估肌肉氧化应激、蛋白质化学修饰、线粒体解偶联、线粒体数量和糖酵解和氧化肌肉中的凋亡指数等生物标志物。目的3将确定通过肌肉gp130受体的直接信号是否调节ApcMin/+小鼠的肌肉蛋白质周转、线粒体功能和细胞凋亡。这些研究将使用肌肉特异性的cre-lox系统，以组织特异性的方式降低gp130受体的表达，以确定IL-6对恶病质的允许作用是对肌肉代谢的直接影响，还是总体上由肿瘤生长或炎症引起的间接影响。与公共卫生相关。这项工作的完成将有助于更好地理解系统性IL-6信号在调节恶病质严重肌肉萎缩中的作用。确定治疗对策的潜在目标，以治疗和预防严重的消瘦阶段，应使患者能够更好地耐受和应对潜在癌症状况的治疗，从而提高死亡率和发病率。

DESCRIPTION (provided by applicant): Cachexia is a condition of whole body wasting that accounts for 20-40% of all cancer-related deaths, particularly GI tract and lung cancers. Inflammatory cytokines are significant effectors of skeletal muscle loss, and the cytokine IL-6 has gained notoriety as a signaling molecule involved in cachexia. Mice heterozygous for a mutated Apc gene (ApcMin/+) develop a significant intestinal polyp burden by 10 weeks of age and become cachexic between 18 and 26 weeks of age. The use of this mouse for studying the regulation of cachexia is novel, and has advantages compared to other animal models of cachexia, including a slower rate of wasting and lack of anorexia. The PI has shown that the inflammatory cytokine IL-6 is a modulator of cachexia in the ApcMin/+ mouse. Knockout of IL-6 prevents cachexia, while over-expression of IL-6 accelerates cachexia. It is not yet clear whether IL-6 exerts a direct effect on muscle or an indirect affect, by affecting tumor growth or secretion of a cachexic mediator of tumor origin. However, understanding the beneficial effects of IL-6 ablation will clearly provide insight into the relationships between inflammation and cachexia during cancer. The overall purpose of this application is to address mechanisms underlying cachexia in the ApcMin/+ mouse. These mechanisms will be examined in respect to the initial and severe stages of wasting and the muscle's oxidative metabolism capacity. Aim 1 will characterize the regulation of muscle protein synthesis and proteasomal degradation during the early and severe stages of wasting in the cachexic ApcMin/+ mouse. Differential regulation of these processes in glycolytic and oxidative muscle during the progression of cachexia will be examined. Experiments also will examine graded increases in circulating IL-6 on muscle protein synthesis and degradation. Aim 2 will characterize the regulation of muscle mitochondrial function, and myonuclear apoptosis during the early and severe stages of wasting in the ApcMin/+ mouse. Biomarkers of muscle oxidative stress, protein chemical modification, mitochondria uncoupling, mitochondrial number, and indices of apoptosis in glycolytic and oxidative muscle will be assessed during the progression of cachexia and with graded IL-6 over- expression. Aim 3 will determine if direct signaling through the muscle gp130 receptor regulates muscle protein turnover, mitochondrial function and apoptosis in the ApcMin/+ mouse. These studies will use a muscle-specific cre-lox system to decrease gp130 receptor expression in a tissue-specific manner in order to determine whether the permissive effect of IL-6 on cachexia is a direct effect on muscle metabolism or an indirect effect resulting from tumor growth or inflammation, in general. PUBLIC HEALTH RELEVANCE. Completion of this work will lead to a better understanding of the role of systemic IL-6 signaling for the regulation of severe muscle wasting with cachexia. The identification of potential targets for therapeutic countermeasures to both treat and prevent the severe stages of wasting should allow patients to better tolerate and respond to treatments for the underlying cancer condition, thus improving mortality and morbidity