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/或信号连接断裂。在该资助的第一个资助期，我们专注于确定肌肉萎缩症特定模型骨骼肌的机械，结构和功能完整性的改变。在即将到来的这一项目期间，我们的目标是了解与可能异常激活的促炎信号通路在特定的小鼠模型的肌营养不良症的呼吸泵的机制。我们将使用2个互补的小鼠模型的肌营养不良症，mdx和阿尔法？整合素缺失小鼠。我们的具体目标是：具体目标1：探讨Rho家族小分子GT3蛋白RhoA、Racl和cdc 42在正常骨骼肌牵张性信号转导中的作用。假设1：小的GT3蛋白RhoA，Racl和Cdc 42参与隔膜中的机械信号转导;这些蛋白质中的每一个具有不同的信号传导作用，这可能取决于施加的机械应力的方向。每种蛋白质都参与启动影响骨骼肌细胞增殖、分化和基因表达的特定信号转导途径。具体目标#2;为了检查在缺乏肌营养不良蛋白或α 7整联蛋白的肌纤维中，机械拉伸诱导的机械敏感性转录因子如AP-1、C/EBP、NF κ B的活化和Rho家族GTP酶的活性是否改变，假设2：营养不良小鼠骨骼肌的机械拉伸导致MAP激酶和机械敏感性转录因子的异常激活，这可能与Rho家族GTP结合蛋白的异常调节有关。具体目标3：为了测试肌营养不良蛋白或α 7整联蛋白的损失是否导致机械敏感性转导途径的激活，从而导致肌肉消耗细胞因子如TNF-α、IL-1 β和蛋白酶如基质金属蛋白酶MMP 9的表达改变。假设三：机械应力诱导的mdx和α 7整合素缺失小鼠骨骼肌中NF-κ B和AP-1的活化可能导致肌肉消耗细胞因子和组织降解蛋白酶水平的增加。这些促炎分子的更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;确定机械敏感性转录因子NF-κ B、C/EBP和AP-1在mdx和α 7整合素缺失小鼠中肌肉变性发病机制中的作用。假设4：NF-κ B和/或AP-1的抑制将减少炎性基因如TNF-α、IL-6、IL-1B和MMP的表达，因此可以减少mdx和α 7整联蛋白缺失小鼠的骨骼肌中结构完整性的损失并引起可能的功能增加。这些目标的完成将大大有助于呼吸泵中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.