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

项目概要/摘要 临床研究表明，随着年龄的增长，呼吸功能明显丧失。这导致降低 生活质量，增加其他疾病的倾向，和无效的气雾剂药物输送治疗 阻塞性呼吸道疾病然而，年龄依赖性的细胞和分子基础的损失， 呼吸尚未建立。气道平滑肌（ASM）在调节气道炎症中起着重要作用。 由于其机械（收缩和舒张）特性，通过影响支气管张力来控制呼吸。 在此，我们提出建立分子变化，发生在ASM由于老化，占损失的 老年人的呼吸功能。初步研究表明， 与“年轻”大鼠相比，老年（“老年”）大鼠中气道和ASM细胞的反应。其他数据显示， 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现象， 其中平滑肌收缩表型改变为增殖/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 与年轻大鼠相比，从老年大鼠获得的ASM中。此外，全球基因表达谱分析 在ASM细胞中发现肌生长抑制素表达减少，肌生长抑制素是TGF-β家族的一员，已知可以抑制平滑肌细胞的生长。 肌细胞的生长和增殖。最后，ASM细胞的初步数据表明，细胞内 随着年龄的增长，收缩剂和舒张剂都能激活G蛋白偶联受体（GPCR） 关于ASM基于这些研究，我们假设ASM随着年龄的增长而经历表型调节， 导致收缩和舒张反应性降低; GPCR信号传导能力的丧失是这一结果的基础。 反应性丧失，部分由随年龄增长发生的TGF-β通路活化丧失介导。在 具体目标1我们建议使用大鼠和人建立ASM表型的年龄依赖性变化 气道和ASM细胞，通过采用新的工具，如肌描记器，光学磁扭转细胞术， 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， 随着年龄的增长而发生的ASM，详细描述了第二信使的表达和活性的变化， 调节ASM功能的GPCR信号传导的效应子和调节子。在具体目标3中，我们提出研究 表征肌生长抑制素和TGF- B对气道和ASM表型的作用，并确定 TGF- B信号转导逆转与年龄相关的合成/增殖表型的能力。总的来说， 这些研究试图确定ASM功能中与年龄相关的分子变化， 与老年人群呼吸功能下降相关。我们的发现可能有助于开发工具， 改善呼吸功能，改进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.