Birukova Anna A, Zagranichnaya Tatiana, Alekseeva Elena, Bokoch Gary M, Birukov Konstantin G
Section of Pulmonary and Critical Care Medicine, Department of Medicine, University of Chicago, Chicago, Illinois 60637, USA.
J Cell Physiol. 2008 Jun;215(3):715-24. doi: 10.1002/jcp.21354.
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 the modulation of lung injury. Besides well recognized physiological effects on vascular tone, plasma volume, and renal function, ANP may exhibit protective effects in models of lung vascular endothelial cell (EC) barrier dysfunction. However, the molecular mechanisms of ANP protective effects are not well understood. The recently described cAMP-dependent guanine nucleotide exchange factor (GEF) Epac activates small GTPase Rap1, which results in activation of small GTPase Rac-specific GEFs Tiam1 and Vav2 and Rac-mediated EC barrier protective responses. Our results show that ANP stimulated protein kinase A and the Epac/Rap1/Tiam/Vav/Rac cascade dramatically attenuated thrombin-induced pulmonary EC permeability and the disruption of EC monolayer integrity. Using pharmacological and molecular activation and inhibition of cAMP-and cGMP-dependent protein kinases (PKA and PKG), Epac, Rap1, Tiam1, Vav2, and Rac we linked ANP-mediated protective effects to the activation of Epac/Rap and PKA signaling cascades, which dramatically inhibited the Rho pathway of thrombin-induced EC hyper-permeability. These results suggest a novel mechanism of ANP protective effects against agonist-induced pulmonary EC barrier dysfunction via inhibition of Rho signaling by Epac/Rap1-Rac and PKA signaling cascades.
急性肺损伤、脓毒症、肺部炎症以及呼吸机诱发的肺损伤都是与肺血管屏障功能障碍相关的危及生命的病症，这可能会导致肺水肿。在这些病理状况下，肺循环中的心钠素（ANP）水平升高，提示其在调节肺损伤中可能发挥的作用。除了对血管张力、血浆容量和肾功能具有公认的生理作用外，ANP在肺血管内皮细胞（EC）屏障功能障碍模型中可能具有保护作用。然而，ANP保护作用的分子机制尚未完全明确。最近描述的cAMP依赖性鸟嘌呤核苷酸交换因子（GEF）Epac可激活小GTP酶Rap1，这会导致小GTP酶Rac特异性GEF Tiam1和Vav2的激活以及Rac介导的EC屏障保护反应。我们的结果表明，ANP刺激蛋白激酶A以及Epac/Rap1/Tiam/Vav/Rac级联反应可显著减弱凝血酶诱导的肺EC通透性以及EC单层完整性的破坏。通过对cAMP和cGMP依赖性蛋白激酶（PKA和PKG）、Epac、Rap1、Tiam1、Vav2和Rac进行药理学和分子激活及抑制，我们将ANP介导的保护作用与Epac/Rap和PKA信号级联反应的激活联系起来，这显著抑制了凝血酶诱导的EC高通透性的Rho途径。这些结果提示了ANP通过Epac/Rap1-Rac和PKA信号级联反应抑制Rho信号，从而对激动剂诱导的肺EC屏障功能障碍产生保护作用的新机制。
