Vascular Research Laboratory, Providence Veterans Affairs Medical Center, 830 Chalkstone Avenue, Providence, RI 02908, USA.
Am J Respir Cell Mol Biol. 2012 May;46(5):623-32. doi: 10.1165/rcmb.2011-0271OC. Epub 2011 Dec 28.
One hallmark of acute lung injury is the disruption of the pulmonary endothelial barrier. Such disruption correlates with increased endothelial permeability, partly through the disruption of cell-cell contacts. Protein tyrosine phosphatases (PTPs) are known to affect the stability of both cell-extracellular matrix adhesions and intercellular adherens junctions (AJs). However, evidence for the role of select PTPs in regulating endothelial permeability is limited. Our investigations noted that the inhibition of PTP1B in cultured pulmonary endothelial cells (ECs), as well as in the vasculature of intact murine lungs via the transient overexpression of a catalytically inactive PTP1B, decreased the baseline resistance of cultured EC monolayers and increased the formation of edema in murine lungs, respectively. In addition, we observed that the overexpression of wild-type PTP1B enhanced basal barrier function in vitro. Immunohistochemical analyses of pulmonary ECs and the coimmunoprecipitation of murine lung homogenates demonstrated the association of PTP1B with the AJ proteins β-catenin, p120-catenin, and VE-cadherin both in vitro and ex vivo. Using LPS in a model of sepsis-induced acute lung injury, we showed that reactive oxygen species were generated in response to LPS, which correlated with enhanced PTP1B oxidation, inhibited phosphatase activity, and attenuation of the interactions between PTP1B and β-catenin, as well as enhanced β-catenin tyrosine phosphorylation. Finally, the overexpression of a cytosolic PTP1B fragment, shown to be resistant to nicotinamide adenine dinucleotide phosphate-reduced oxidase-4 (Nox4)-mediated oxidation, significantly attenuated LPS-induced endothelial barrier dysfunction and the formation of lung edema, and preserved the associations of PTP1B with AJ protein components, independent of PTP1B phosphatase activity. We conclude that PTP1B plays an important role in maintaining the pulmonary endothelial barrier, and PTP1B oxidation appears to contribute to sepsis-induced pulmonary vascular dysfunction, possibly through the disruption of AJs.
急性肺损伤的一个标志是肺内皮屏障的破坏。这种破坏与内皮通透性的增加有关，部分原因是细胞-细胞连接的破坏。已知蛋白酪氨酸磷酸酶（PTPs）会影响细胞-细胞外基质黏附以及细胞间黏附连接（AJs）的稳定性。然而，关于特定 PTP 在调节内皮通透性方面的作用的证据是有限的。我们的研究表明，在培养的肺内皮细胞（ECs）以及通过瞬时过表达无催化活性的 PTP1B 抑制完整鼠肺血管中的 PTP1B，分别降低了培养的 EC 单层的基础阻力并增加了鼠肺水肿的形成。此外，我们观察到野生型 PTP1B 的过表达增强了体外的基础屏障功能。肺 ECs 的免疫组织化学分析和鼠肺匀浆的共免疫沉淀表明，PTP1B 与 AJ 蛋白 β-连环蛋白、p120-连环蛋白和 VE-钙粘蛋白在体外和体内均存在关联。在脓毒症诱导的急性肺损伤模型中使用 LPS，我们表明 LPS 会产生活性氧，这与 PTP1B 氧化增强、磷酸酶活性抑制以及 PTP1B 与 β-连环蛋白相互作用减弱以及增强的 β-连环蛋白酪氨酸磷酸化有关。最后，过表达对烟酰胺腺嘌呤二核苷酸磷酸还原型氧化酶-4（Nox4）介导的氧化具有抗性的细胞质 PTP1B 片段可显著减轻 LPS 诱导的内皮屏障功能障碍和肺水肿的形成，并维持 PTP1B 与 AJ 蛋白成分的关联，而与 PTP1B 磷酸酶活性无关。我们得出结论，PTP1B 在维持肺内皮屏障方面发挥着重要作用，PTP1B 氧化似乎导致了脓毒症引起的肺血管功能障碍，可能是通过破坏 AJs 所致。
