Lung Injury Center, Section of Pulmonary and Critical Medicine, Department of Medicine, University of Chicago, Chicago, IL 60637, USA.
Am J Respir Cell Mol Biol. 2012 Nov;47(5):688-97. doi: 10.1165/rcmb.2012-0161OC. Epub 2012 Jul 27.
Oxidative stress is an important part of host innate immune response to foreign pathogens, such as bacterial LPS, but excessive activation of redox signaling may lead to pathologic endothelial cell (EC) activation and barrier dysfunction. Microtubules (MTs) play an important role in agonist-induced regulation of vascular endothelial permeability, but their impact in modulation of inflammation and EC barrier has not been yet investigated. This study examined the effects of LPS-induced oxidative stress on MT dynamics and the involvement of MTs in the LPS-induced mechanisms of Rho activation, EC permeability, and lung injury. LPS treatment of pulmonary vascular EC induced elevation of reactive oxygen species (ROS) and caused oxidative stress associated with EC hyperpermeability, cytoskeletal remodeling, and formation of paracellular gaps, as well as activation of Rho, p38 stress kinase, and NF-κB signaling, the hallmarks of endothelial barrier dysfunction. LPS also triggered ROS-dependent disassembly of the MT network, leading to activation of MT-dependent signaling. Stabilization of MTs with epothilone B, or inhibition of MT-associated guanine nucleotide exchange factor (GEF)-H1 activity by silencing RNA-mediated knockdown, suppressed LPS-induced EC barrier dysfunction in vitro, and attenuated vascular leak and lung inflammation in vivo. LPS disruptive effects were linked to activation of Rho signaling caused by LPS-induced MT disassembly and release of Rho-specific GEF-H1 from MTs. These studies demonstrate, for the first time, the mechanism of ROS-induced Rho activation via destabilization of MTs and GEF-H1-dependent activation of Rho signaling, leading to pulmonary EC barrier dysfunction and exacerbation of LPS-induced inflammation.
氧化应激是宿主固有免疫对外来病原体（如细菌 LPS）反应的重要组成部分，但氧化还原信号的过度激活可能导致病理性内皮细胞（EC）激活和屏障功能障碍。微管（MTs）在激动剂诱导的血管内皮通透性调节中发挥重要作用，但它们在炎症和 EC 屏障调节中的作用尚未得到研究。本研究探讨了 LPS 诱导的氧化应激对 MT 动力学的影响，以及 MT 在 LPS 诱导的 Rho 激活、EC 通透性和肺损伤机制中的作用。LPS 处理肺血管 EC 诱导活性氧（ROS）的升高，并导致与 EC 高通透性、细胞骨架重塑和形成细胞旁间隙以及 Rho、p38 应激激酶和 NF-κB 信号转导相关的氧化应激，这些都是内皮屏障功能障碍的特征。LPS 还触发 ROS 依赖性 MT 网络解聚，导致 MT 依赖性信号转导激活。用表鬼臼毒素 B 稳定 MT，或通过 RNA 介导的沉默抑制 MT 相关鸟嘌呤核苷酸交换因子（GEF）-H1 的活性，抑制 LPS 诱导的体外 EC 屏障功能障碍，并减轻体内血管渗漏和肺炎症。LPS 的破坏作用与 LPS 诱导的 MT 解聚引起的 Rho 信号激活以及 MT 从 MT 释放的 Rho 特异性 GEF-H1 有关。这些研究首次证明了 ROS 诱导的 Rho 激活的机制，即通过破坏 MT 和 GEF-H1 依赖性 Rho 信号转导的稳定性，导致肺 EC 屏障功能障碍和 LPS 诱导的炎症加重。
