Exposure to particulate matter (PM) associated with air pollution remains a major public health concern, as it has been linked to significant increase in cardiopulmonary morbidity and mortality. Lung endothelial cell (EC) dysfunction is one of the hallmarks of cardiovascular events of lung exposure to PM. However, the role of PM in acute lung injury (ALI) exacerbation and delayed recovery remains incompletely understood. This study tested a hypothesis that PM augments lung injury and EC barrier dysfunction via microtubule-dependent mechanisms. Our data demonstrate that in pulmonary EC PM caused time- and dose-dependent remodeling of actin cytoskeleton and considerable destabilization of the microtubule (MT) network. These events led to the weakening of cell junctions and formation of actin stress fibers, resulting in disruption of lung EC monolayer and increased permeability. PM also caused ROS-dependent activation of MT-specific deacetylase, HDAC6. Suppression of HDAC6 activity by pharmacological inhibitors or siRNA-based depletion of HDAC6 abolished PM-induced EC permeability increase, which was accompanied by reduced activation of stress kinase signaling, inhibition of Rho cascade, decreased IL-6 production and suppressed activation of its downstream target STAT3. Pretreatment of pulmonary EC with IL-6 inhibitor led to inhibition of STAT3 activity and decreased PM-induced hyper-permeability. Because one of the major activators of Rho-GTPase, GEFH1, is localized on the MT, we examined its involvement in PM-caused EC barrier compromise. Inhibition of GEF-H1 activation significantly attenuated PM-induced permeability increase. Moreover, combined inhibition of IL-6 and GEF-H1 signaling exhibited additive protective effect. Taken together, these results demonstrate a critical involvement of MT-associated signaling in the PM-induced exacerbation of lung EC barrier compromise and inflammatory response.

中文翻译：

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由微粒物质引起的微管失稳导致肺内皮屏障功能障碍和炎症。

暴露于与空气污染相关的颗粒物（PM）仍然是一个主要的公共卫生问题，因为它与心肺疾病的发病率和死亡率的显着增加有关。肺内皮细胞（EC）功能障碍是肺部暴露于PM的心血管事件的标志之一。但是，关于PM在急性肺损伤（ALI）加重和恢复延迟中的作用仍未完全了解。这项研究检验了一种假设，即PM通过微管依赖性机制加剧了肺损伤和EC屏障功能障碍。我们的数据表明，在肺EC中，PM引起肌动蛋白细胞骨架的时间和剂量依赖性重塑以及微管（MT）网络的显着失稳。这些事件导致细胞连接的减弱和肌动蛋白应激纤维的形成，导致肺EC单层破坏并增加通透性。PM还引起MT特异性脱乙酰基酶HDAC6的ROS依赖性活化。通过药理抑制剂抑制HDAC6活性或基于siRNA的HDAC6消耗消除了PM诱导的EC渗透性增加，并伴随着应激激酶信号传导的减少，Rho级联的抑制，IL-6生成的减少以及下游靶标的激活的抑制。 STAT3。用IL-6抑制剂预处理肺EC可以抑制STAT3活性，并降低PM诱导的通透性过高。因为Rho-GTPase的主要激活因子之一GEFH1位于MT上，所以我们检查了它在PM引起的EC屏障折衷中的参与。抑制GEF-H1激活显着减弱了PM诱导的通透性增加。而且，IL-6和GEF-H1信号的联合抑制表现出附加的保护作用。综上所述，这些结果证明了MT相关信号在PM诱导的肺EC屏障损害和炎症反应加重中的重要参与。