Abstract 20295: Key Role of Integrin Alpha6/Beta4 in Endothelial Cell Barrier Regulation
The dynamic regulation of lung endothelial cell (EC) barrier integrity is essential in the initiation and resolution of inflammation during acute lung injury (ALI) and ventilator-induced lung injury (VILI). In previous studies, we identified integrin beta β4 (ITGβ4) as a key focal adhesion (FA) component, involved in human lung EC barrier enhancement by simvastatin. The clear functional role and key contribution of ITGβ4 in endothelial barrier regulation vascular permeability is largely unknown. We demonstrated that reduced ITGβ4 expression (siRNA attenuated sphingosine-1-phosphate (S1P, 1 μM) or hepatocyte growth factor (HGF, 25 ng/ml) mediated endothelial barrier enhancement. At the same time, S1P receptor 1 (S1PR1) or HGF receptor cMet knockdown also attenuated S1P- or HGF-mediated endothelial barrier enhancement. Consistent with these findings, in situ proximity ligation assays revealed that ITGβ4, S1PR1, and cMet, translocated together to the cell periphery as co-localized proteins after HGF treatment. We further confirmed that the interaction of c-Met and S1PR1 with ITGβ4 was dependent upon ITGβ4 phosphorylation, which is essential for HGF-mediated barrier enhancement. The selective antibody targeting integrin α6 (ITGα6, 10 μg/ml), the only binding partner of ITGβ4, attenuates S1P-mediated endothelial barrier enhancement. Furthermore, this antibody retarded barrier recovery after thrombin (0.5 U/ml), an EC barrier disruptor. These findings highly suggest ITGβ4 is essential participant in EC barrier regulation and paracellular gap closure. We next exposed genetically-engineered mice expressing a mutant ITGβ4 that lacks the cytoplasmic tail to ventilator-induced lung injury (VILI). The absence of the cytoplasmic tail conferred significant attenuation of inflammatory lung injury compared to wild-type controls with reduced BAL protein and cell counts and lung inflammation. These data suggest that the ITGβ4 cytoplasmic domain is an important participant in both pro- and anti-inflammatory responses to the excessive mechanical stress produced by VILI. In summary, ITGβ4 is a central regulator of endothelial barrier function, and a novel therapeutic target for acute lung inflammation.
Author Disclosures: A.E. Cress: None. W. Chen: None. Y. Epstein: None. J.B. Mascarenhas: None. T. Wang: None. T. Zhou: None. R. Kittles: None. J.G. Garcia: None. J.R. Jacobson: None.
- © 2014 by American Heart Association, Inc.