Protective role of ANP in the models of acute lung injury

描述（由申请方提供）：急性肺损伤、脓毒症、肺部炎症和呼吸机诱导的肺损伤是与肺血管屏障功能障碍相关的危及生命的疾病，可能导致肺水肿。在这些病理中报告的肺循环中心房钠尿肽（ANP）水平升高表明其在肺损伤过程中的调节作用。虽然ANP对血管张力、血浆容量和肾功能的生理作用是众所周知的，但最近的研究发现了新的ANP生物活性，包括对内皮屏障功能的影响，并且ANP对肺EC保护作用的分子机制仍有待阐明。我们以前的研究表明，小GTP酶Rac和Rho之间的相互关系，在调节内皮细胞的通透性和特定的肌动蛋白细胞骨架和细胞接触的重塑。我们的初步研究表明，ANP对内皮细胞模型和急性肺损伤动物模型中炎性激动剂诱导的肺EC屏障功能障碍具有屏障保护作用，并将其与ANP诱导的Rho信号转导下调和cAMP依赖性蛋白激酶（PKA）介导的细胞骨架重塑以及新的Epac-Rap 1-Tiam 1/Vav 2- Rac机制联系起来。我们推测，ANP可能通过抑制内皮细胞高通透性的Rho依赖性途径来减轻与急性肺损伤相关的急性肺内皮功能障碍。我们还推测，ANP可能通过触发PKA和新的Epac/Rap介导的信号传导，激活Rac依赖的EC屏障保护通路，从而增强受损肺的血管屏障功能。具体目标1将研究Epac/Rap和PKA介导的机制在激活与ANP屏障保护作用相关的Rac依赖性信号传导中的作用。具体目标2将集中在ANP诱导的Rho下调的分子机制，通过Rac/PAK依赖的微管稳定和调控微管相关的Rho特异性鸟嘌呤核苷酸交换因子GEF-H1。具体目标3将使用siRNA转染、ANP敲除小鼠和在脓毒性和无菌性肺损伤动物模型中的拯救方法来描绘ANP在减轻体内急性肺损伤中的潜在作用。我们相信，这些研究可能会发现新的蛋白质靶点，并提出新的治疗方法，用于预防与急性肺部炎症和损伤相关的肺血管屏障功能障碍。

DESCRIPTION (provided by applicant): Acute lung injury, sepsis, lung inflammation, and ventilator-induced lung injury are life-threatening conditions associated with lung vascular barrier dysfunction, which may lead to pulmonary edema. Increased levels of atrial natriuretic peptide (ANP) in lung circulation reported in these pathologies suggest its potential role in modulation of lung injury process. Although physiological effects of ANP on the vascular tone, plasma volume, and renal function are well known, recent studies discovered novel ANP biological activities including effects on endothelial barrier function, and molecular mechanisms of ANP protective effects on pulmonary EC remain to be elucidated. Our previous studies demonstrated reciprocal relations between small GTPases Rac and Rho in the regulation of endothelial permeability and specific remodeling of actin cytoskeleton and cell contacts. Our preliminary studies strongly suggest the barrier protective effects of ANP against lung EC barrier dysfunction induced by inflammatory agonists in endothelial cell models and animal models of acute lung injury and link them to the ANP-induced downregulation of Rho signaling and cytoskeletal remodeling mediated via cAMP-dependent protein kinase (PKA) and novel Epac-Rap1-Tiam1/Vav2- Rac mechanism. We hypothesize that ANP may attenuate acute pulmonary endothelial dysfunction associated with acute lung injury via inhibition of Rho-dependent pathways of endothelial hyper-permeability. We also hypothesize that ANP may enhance the vascular barrier function in the injured lung by triggering PKA and novel Epac/Rap-mediated signaling leading to activation of Rac-dependent pathways of EC barrier protection. Specific Aim 1 will investigate a role of Epac/Rap and PKA-mediated mechanisms in the activation of Rac-dependent signaling associated with ANP barrier protective effects. Specific Aim 2 will focus on molecular mechanisms of ANP-induced Rho downregulation via Rac/PAK-dependent microtubule stabilization and regulation of microtubule-associated Rho-specific guanine nucleotide exchange factor GEF-H1. Specific Aim 3 will use siRNA transfections, ANP knockout mice and rescue approaches in the animal models of septic and aseptic lung injury to delineate potential role of ANP in the alleviation of acute lung injury in vivo. We believe that these studies may identify novel protein targets and propose new therapies for prevention of pulmonary vascular barrier dysfunction associated with acute lung inflammation and injury.