Role of Krev Interaction Trapped-1 in Prostacyclin-Induced Protection against Lung Vascular Permeability Induced by Excessive Mechanical Forces and Thrombin Receptor Activating Peptide 6

Abstract

Mechanisms of vascular endothelial cell (EC) barrier regulation during acute lung injury (ALI) or other pathologies associated with increased vascular leakiness are an active area of research. Adaptor protein krev interaction trapped-1 (KRIT1) participates in angiogenesis, lumen formation, and stabilization of EC adherens junctions (AJs) in mature vasculature. We tested a role of KRIT1 in the regulation of Rho-GTPase signaling induced by mechanical stimulation and barrier dysfunction relevant to ventilator-induced lung injury and investigated KRIT1 involvement in EC barrier protection by prostacyclin (PC). PC stimulated Ras-related protein 1 (Rap1)-dependent association of KRIT1 with vascular endothelial cadherin at AJs, with KRIT1-dependent cortical cytoskeletal remodeling leading to EC barrier enhancement. KRIT1 knockdown exacerbated Rho-GTPase activation and EC barrier disruption induced by pathologic 18% cyclic stretch and thrombin receptor activating peptide (TRAP) 6 and attenuated the protective effects of PC. In the two-hit model of ALI caused by high tidal volume (HTV) mechanical ventilation and TRAP6 injection, KRIT1 functional deficiency in KRIT1 1/2 mice increased basal lung vascular leak and augmented vascular leak and lung injury caused by exposure to HTV and TRAP6. Down-regulation of KRIT1 also diminished the protective effects of PC against TRAP6/HTV-induced lung injury. These results demonstrate a KRIT1-dependent mechanism of vascular EC barrier control in basal conditions and in the two-hit model of ALI caused by excessive mechanical forces and TRAP6 via negative regulation of Rho activity and enhancement of cell junctions. We also conclude that the stimulation of the Rap1-KRIT1 signaling module is a major mechanism of vascular endothelial barrier protection by PC in the injured lung.

MiR-135a Protects Vascular Endothelial Cells Against Ventilator-Induced Lung Injury by Inhibiting PHLPP2 to Activate PI3K/Akt Pathway

“…After PHLPP2 silencing, we detected apoptotic cells following MS, but whether PHLPP2 silencing alone affects the apoptosis of HUVECs was not investigated, and other parameters were not measured after PHLPP2 silencing in HUVECs following MS. In addition, this study was conducted in HUVECs, and pulmonary endothelial cells are more representative of cells involved in VILI [54,55]. Thus, our results need to be confirmed in pulmonary endothelial cells and in animal models in the future.…”

Oxidative stress and inflammation in cerebral cavernous malformation disease pathogenesis: Two sides of the same coin

“…Existing data points to an anti-inflammatory role for CCM proteins, in which they function to suppress the activation of, or response to, pro-inflammatory signals. As an effector of Rap1, KRIT1 mediates the ability of this GTPase to stabilize endothelial cell-cell contacts, as has been shown in response to thrombin (Glading et al, 2007) and acute lung injury (Meliton et al, 2015), thus limiting the inflammatory response. Less direct evidence is available regarding the ability of CCM2 and PDCD10 to regulate the endothelial inflammatory response.…”

Cerebral Cavernous Malformation Proteins in Barrier Maintenance and Regulation

“…In contrast, histamine-induced vascular permeability increase occurred normally in Krit1 heterozygous knockout mice [101,102]. However, another report suggests KRIT1 is required for preservation of endothelial barrier following stimuli [103]. KRIT1 depletion in cultured endothelial cells attenuated prostacyclin-induced perijunctional F-actin accumulation and tightening of endothelial barrier and enhanced cyclic stretch-induced Rho activation and endothelial barrier disruption [103].…”