Gorovoy Matvey, Neamu Radu, Niu Jiaxin, Vogel Stephen, Predescu Dan, Miyoshi Jun, Takai Yoshimi, Kini Vidisha, Mehta Dolly, Malik Asrar B, Voyno-Yasenetskaya Tatyana
University of Illinois College of Medicine, Department of Pharmacology, 835 S. Wolcott Ave, Chicago, IL 60612, USA.
Circ Res. 2007 Jul 6;101(1):50-8. doi: 10.1161/CIRCRESAHA.106.145847. Epub 2007 May 24.
Rho family GTPases have been implicated in the regulation of endothelial permeability via their actions on actin cytoskeletal organization and integrity of interendothelial junctions. In cell culture studies, activation of RhoA disrupts interendothelial junctions and increases endothelial permeability, whereas activation of Rac1 and Cdc42 enhances endothelial barrier function by promoting the formation of restrictive junctions. The primary regulators of Rho proteins, guanine nucleotide dissociation inhibitors (GDIs), form a complex with the GDP-bound form of the Rho family of monomeric G proteins, and thus may serve as a nodal point regulating the activation state of RhoGTPases. In the present study, we addressed the in vivo role of RhoGDI-1 in regulating pulmonary microvascular permeability using RhoGDI-1(-/-) mice. We observed that basal endothelial permeability in lungs of RhoGDI-1(-/-) mice was 2-fold greater than wild-type mice. This was the result of opening of interendothelial junctions in lung microvessels which are normally sealed. The activity of RhoA (but not of Rac1 or Cdc42) was significantly increased in RhoGDI-1(-/-) lungs as well as in cultured endothelial cells on downregulation of RhoGDI-1 with siRNA, consistent with RhoGDI-1-mediated modulation RhoA activity. Thus, RhoGDI-1 by repressing RhoA activity regulates lung microvessel endothelial barrier function in vivo. In this regard, therapies augmenting endothelial RhoGDI-1 function may be beneficial in reestablishing the endothelial barrier and lung fluid balance in lung inflammatory diseases such as acute respiratory distress syndrome.
Rho家族GTP酶通过对肌动蛋白细胞骨架组织和内皮细胞间连接完整性的作用，参与内皮通透性的调节。在细胞培养研究中，RhoA的激活会破坏内皮细胞间连接并增加内皮通透性，而Rac1和Cdc42的激活则通过促进紧密连接的形成来增强内皮屏障功能。Rho蛋白的主要调节因子鸟嘌呤核苷酸解离抑制剂（GDI）与单体G蛋白Rho家族的GDP结合形式形成复合物，因此可能作为调节RhoGTP酶激活状态的节点。在本研究中，我们使用RhoGDI-1基因敲除小鼠探讨了RhoGDI-1在调节肺微血管通透性中的体内作用。我们观察到，RhoGDI-1基因敲除小鼠肺组织的基础内皮通透性比野生型小鼠高2倍。这是由于通常封闭的肺微血管内皮细胞间连接开放所致。在RhoGDI-1基因敲除小鼠的肺组织以及用小干扰RNA下调RhoGDI-1后的培养内皮细胞中，RhoA（而非Rac1或Cdc42）的活性显著增加，这与RhoGDI-1介导的对RhoA活性的调节一致。因此，RhoGDI-1通过抑制RhoA活性在体内调节肺微血管内皮屏障功能。在这方面，增强内皮RhoGDI-1功能的疗法可能有助于在急性呼吸窘迫综合征等肺部炎症性疾病中重建内皮屏障和肺液平衡。
