Physiology of Respiratory Muscle Micromechanics

描述（由申请人提供）：肌营养不良的发病机制是由于细胞骨架和细胞外基质之间的机械和/或信号联系断裂。在该基金的第一个资助期，我们专注于确定特定肌肉萎缩症模型骨骼肌的机械、结构和功能完整性的改变。在接下来的项目中，我们的目标是了解特定肌肉萎缩症小鼠模型中呼吸泵中促炎信号通路可能异常激活的机制。我们将使用两种互补的肌肉萎缩小鼠模型，mdx和α ？整合素null鼠标。我们的具体目标是：具体目标# 1：评估Rho家族的小GTPase蛋白，如RhoA， Racl和cdc42在正常骨骼肌机械拉伸诱导的信号转导中的作用。假设1:GTPase小蛋白RhoA、Racl和Cdc42参与膈膜的机械信号转导；这些蛋白质中的每一种都有不同的信号作用，这可能取决于施加机械应力的方向。每一种蛋白都参与启动一个特定的信号转导通路，影响骨骼肌细胞的增殖、分化和基因表达。具体目标# 2；研究在缺乏肌营养不良蛋白或a7整合素的肌肉纤维中，机械拉伸诱导的AP-1、C/EBP、NFKB等机械敏感转录因子的激活以及Rho家族gtp酶的活性是否发生改变假设2：来自营养不良小鼠的骨骼肌的机械拉伸导致MAP激酶和机械敏感转录因子的异常激活，可能是通过Rho家族gtp结合蛋白的异常调节。特异性目标# 3：测试肌营养不良蛋白或a7整合素的缺失是否会导致机械敏感转导途径的激活，从而导致肌肉萎缩细胞因子(如TNF-a、IL-1p和蛋白酶（如基质金属蛋白酶MMP9）的表达改变。假设3：机械应力诱导mdx和α 7整合素缺失小鼠骨骼肌nf - kb和AP-1的激活可能导致肌肉萎缩细胞因子和组织降解蛋白酶水平的增加。这些促炎分子的高活化可能导致这些营养不良小鼠的结构完整性丧失和收缩功能障碍。具体目标# 4；探讨机械敏感转录因子NF-KB、C/EBP和AP-1在mdx和a7整合素缺失小鼠肌肉退行性变发病机制中的作用。假设4：抑制NF-KB和/或AP-1将降低炎症基因如TNF-a、IL-6、IL-1B和MMPs的表达，因此可能减少结构完整性的损失，并可能导致mdx和α 7整合素缺失小鼠骨骼肌功能的增加。这些目标的完成将有助于对呼吸泵机械信号转导的基本理解。

DESCRIPTION (provided by applicant): Muscular dystrophy pathogenesis results from a broken mechanical and/or signaling linkage between the cytoskeleton and the extracellular matrix. In the first funding period of this grant we focused on determining the alteration in the mechanical, structural and functional integrity in skeletal muscles of specific models of muscular dystrophies. In the upcoming period of this project our objective is to understand the mechanisms involved with possible aberrant activation of pro-inflammatory signaling pathways in the respiratory pump of specific mouse models of muscular dystrophy. We will use the 2 complementary mouse models of muscular dystrophy, the mdx and alpha? integrin null mouse. Our specific aims are: Specific Aim # 1: To evaluate the role of the small GTPase proteins of Rho family such as RhoA, Racl and cdc42 in the mechanical stretch-induced signal transduction in normal skeletal muscles. Hypothesis 1: The small GTPase proteins RhoA, Racl and Cdc42 are involved in mechanical signal transduction in the diaphragm; each of these proteins has a distinct signaling role, which may depend on the direction of applied mechanical stress. Each of the proteins is involved in the initiation of a specific signal transduction pathway that affects the proliferation, differentiation and the gene expression in skeletal muscle cells. Specific Aim # 2; To examine whether mechanical stretch-induced activation of mechanosensitive transcription factors such as AP-1, C/EBP, NFKB and the activity of the Rho family GTPases are altered in muscle fibers lacking either dystrophin or a7 integrin Hypothesis 2: Mechanical stretching of skeletal muscles from dystrophic mice leads to aberrant activation of MAP kinases and mechanosensitive transcription factors, possibly through the anomalous regulation ofGTP binding proteins of Rho family. Specific Aim # 3: To test whether loss of either dystrophin or a7 integrin results in the activation of mechanosensitive transduction pathways leading to altered expression of muscle wasting cytokines such as TNF-a, IL-1p and proteases such as matrix metalloproteinase MMP9. Hypothesis 3: Mechanical stressinduced activation ofNF-KB and AP-1 in skeletal muscle of the mdx, and alpha7 integrin null mice may lead to an augmented level of muscle wasting cytokines and tissue degrading proteases. Higher activation of these proinflammatory molecules could lead to loss of structural integrity and contractile dysfunction in these dystrophic mice. Specific Aim # 4; To determine the role of mechanosensitive transcription factors NF-KB, C/EBP and AP-1 on the pathogenesis of muscular degeneration in mdx and a7 integrin null mice. Hypothesis 4: Inhibition of NF-KB and/or AP-1 will reduce the expression of inflammatory genes such as TNF-a, IL-6, IL-1B and MMPs, and therefore may reduce loss of structural integrity and cause possible gain in function in skeletal muscles of the mdx, and the alpha7 integrin null mice. The completion of these aims will significantly contribute to the fundamental understanding of mechanical signal transduction in the respiratory pump.