Molecular basis of age-dependent changes in airway smooth muscle functions

项目摘要/摘要 临床研究表明，随着年龄的增长，呼吸功能显著丧失。这将导致减少 生活质量，其他疾病的倾向增加，以及用于治疗的气雾剂药物输送无效 阻塞性呼吸道疾病。然而，年龄相关性丢失的细胞和分子基础 呼吸作用尚未建立。气道平滑肌(ASM)在肺功能的调节中起重要作用。 由于机械(收缩和松弛)特性而影响支气管张力的呼吸作用。 在这里，我们建议建立由于衰老而在ASM中发生的分子变化，该变化解释了 老年人的呼吸功能。初步研究显示收缩和松弛减弱 老年大鼠与年轻大鼠的呼吸道和ASM细胞的反应。更多数据表明 衰老促进ASM的“表型可塑性”或“转换”，这是在某些疾病中观察到的一种现象 由平滑肌收缩表型转变为增殖/合成表型的过程。 肌球蛋白重链和平滑肌α-肌动蛋白(收缩表型标志蛋白)的表达较低 老年大鼠与青年大鼠ASM的比较。此外，全球基因表达谱分析 ASM细胞中的Myostatin的表达减少，Myostatin是转化生长因子-b家族的成员之一，已知的抑制 心肌细胞的生长和增殖。最后，来自ASM细胞的初步数据表明，细胞内的 随着年龄的增长，向激活G蛋白偶联受体(GPCRs)的收缩和舒张剂发出信号 在ASM上。基于这些研究，我们假设ASM随着年龄的增长而经历表型调整 导致收缩和松弛反应性降低；GPCR信号能力的丧失是这一现象的基础 反应性的丧失，部分是由随着年龄增长而发生的转化生长因子-b途径激活的丧失所介导的。在……里面 具体目标1我们建议用大鼠和人建立ASM表型随年龄变化的模型 呼吸道和ASM细胞通过使用新的工具，如肌图仪，光磁扭曲细胞仪和 牵引显微镜。在具体目标2中，我们建议建立表型转换的机制基础。 通过详细描述第二信使的表达和活动的变化，随着年龄的增长而发生的ASM， 调节ASM功能的GPCR信号的效应者和调节者。在具体目标3中，我们建议进行研究 [目的]研究肌肉生长抑素和转化生长因子-β对呼吸道和ASM表型的影响，并探讨其对ASM表型的影响 转化生长因子-b信号逆转与年龄相关的合成/增殖表型的能力。总而言之， 这些研究试图确定ASM功能中与年龄相关的分子变化，这些变化有助于年龄- 老年人口中呼吸功能的相关下降。我们的发现可能有助于开发工具来 改善呼吸功能，修改阻塞性肺疾病的诊断和治疗方案 老年人的疾病。

Project Summary/Abstract Clinical studies have demonstrated a significant loss of respiratory function with age. This results in reduced quality of life, increased propensity for other diseases, and ineffective aerosol drug delivery for the treatment of obstructive respiratory diseases. However, the cellular and molecular basis for age-dependent loss of respiration has not been established. Airway smooth muscle (ASM) plays a significant role in the regulation of respiration by influencing the bronchial tone due to its mechanical (contraction and relaxation) properties. Herein we propose to establish molecular changes that occur in the ASM due to aging that account for loss of respiratory function in the elderly. Preliminary studies demonstrate diminished contractile and relaxation responses of airways and ASM cells in aged ("Old") rats compared to "Young" rats. Additional data suggest aging promotes "phenotype plasticity" or "switching" in ASM, a phenomenon observed in certain disease processes in which the smooth muscle contractile phenotype is changed to a proliferative/synthetic phenotype. Expression of myosin heavy chain and smooth muscle a-actin (contractile phenotype marker proteins) is lower in ASM obtained from Old rats compared to Young rats. Furthermore, global gene expression profile analysis in ASM cells revealed decreased expression of myostatin, a member of the TGF-b family, known to inhibit the growth and proliferation of myocytes. Lastly, preliminary data from ASM cells suggest diminished intracellular signaling with age to both contractile and relaxant agents that activate G protein-coupled receptors (GPCRs) on ASM. Based on these studies we hypothesize that ASM undergoes phenotype modulation with age that results in decreased contractile and relaxant responsiveness; a loss of GPCR signaling capacity underlies this loss of responsiveness, mediated in part by a loss of TGF-b pathway activation that occurs with age. In Specific Aim 1 we propose to establish age-dependent changes in ASM phenotype using rat and human airways and ASM cells by employing novel tools such as myograph, optical magnetic twisting cytometry and traction microscopy. In Specific Aim 2, we propose to establish the mechanistic basis for a phenotype switch in the ASM that occurs with age by detailing changes in the expression and activity of second messengers, effectors and regulators of GPCR signaling that regulate ASM function. In Specific Aim 3, we propose studies to characterize the effects of myostatin and TGF- b on airways and ASM phenotype, and determine the capacity of TGF- b signaling to reverse the synthetic/proliferative phenotype associated with age. Collectively, these studies seek to identify age-dependent molecular changes in ASM function that contribute to the age- associated decline in respiratory function in the elderly population. Our findings may help develop tools to improve respiratory functions, and modify diagnostic and treatment regimens for obstructive pulmonary diseases in the elderly.