Focal adhesion kinase and Src mediate microvascular hyperpermeability caused by fibrinogen- ?C- terminal fragments.

ABSTRACT:

Objectives

We previously reported microvascular leakage resulting from fibrinogen-? chain C-terminal products (?C) occurred via a RhoA-dependent mechanism. The objective of this study was to further elucidate the signaling mechanism by which ?C induces endothelial hyperpermeability. Since it is known that ?C binds and activates endothelial ?v?3, a transmembrane integrin receptor involved in intracellular signaling mediated by the tyrosine kinases FAK and Src, we hypothesized that ?C alters endothelial barrier function by activating the FAK-Src pathway leading to junction dissociation and RhoA driven cytoskeletal stress-fiber formation.

Methods and results

Using intravital microscopy of rat mesenteric microvessels, we show increased extravasation of plasma protein (albumin) resulting from ?C administration. In addition, capillary fluid filtration coefficient (Kfc) indicated ?C-induced elevated lung vascular permeability. Furthermore, ?C decreased transendothelial barrier resistance in a time-dependent and dose-related fashion in cultured rat lung microvascular endothelial cells (RLMVECs), accompanied by increased FAK/Src phosphorylation detection by western blot. Experiments with pharmacological inhibition or gene silencing of FAK showed significantly reduced ?C-induced albumin and fluid leakage across microvessels, stress-fiber formation, VE-cadherin tyrosine phosphorylation, and improved ?C-induced endothelial barrier dysfunction, indicating the involvement of FAK in ?C mediated hyperpermeability. Comparable results were found when Src was targeted in a similar manner, however inhibition of FAK prevented Src activation, suggesting that FAK is upstream of Src in ?C-mediated hyperpermeability. In addition, ?C-induced cytoskeletal stress-fiber formation was attenuated during inhibition or silencing of these tyrosine kinases, concomitantly with RhoA inhibition.

Conclusion

The FAK-Src pathway contributes to ?C-induced microvascular barrier dysfunction, junction protein phosphorylation and disorganization in a manner that involves RhoA and stress-fiber formation.

SUBMITTER: Guo X 

PROVIDER: S-EPMC7192500 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature