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(Arteriosclerosis, Thrombosis, and Vascular Biology. 2009;29:394.)
© 2009 American Heart Association, Inc.

Cell Biology/Signaling

Fibrinogen- C-Terminal Fragments Induce Endothelial Barrier Dysfunction and Microvascular Leak via Integrin-Mediated and RhoA-Dependent Mechanism

Mingzhang Guo; Dayle Daines; Jing Tang; Qiang Shen; Rachel M. Perrin; Yoshikazu Takada; Sarah Y. Yuan; Mack H. Wu

From the Division of Research, Department of Surgery, University of California Davis School of Medicine, Sacramento.

Correspondence to Sarah Yuan, MD, PhD, Professor and Director of Research, Department of Surgery, University of California Davis School of Medicine, 4625 2nd Avenue, Room 3006, Sacramento, CA 95817. E-mail sarahyuan{at}ucdavis.edu

Objectives— The purposes of this study were to characterize the direct effect of the C-terminal fragment of fibrinogen chain (C) on microvascular endothelial permeability and to examine its molecular mechanism of action.

Methods and Results— Intravital microscopy was performed to measure albumin extravasation in intact mesenteric microvasculature, followed by quantification of hydraulic conductivity in single perfused microvessels. Transendothelial electric resistance was measured in microvascular endothelial cells in combination with immunoblotting and immunocytochemistry. The results show that C induced time- and concentration-dependent increases in protein transvascular flux and water permeability and decreases in endothelial barrier function, coupled with Rho GTPase activation, myosin light chain phosphorylation, and stress fiber formation. Depletion of RhoA via siRNA knockdown or pharmacological inhibition of RhoA signaling attenuated C-induced barrier dysfunction. Imaging analyses demonstrated binding of C to endothelial cells; the interaction was inhibited during blockage of the vβ3 integrin. Furthermore, in vivo experiments showed that the microvascular leak response to C was attenuated in integrin β3^–/– animals.

Conclusion— Fibrinogen- C terminus directly interacts with the microvascular endothelium causing fluid and protein leak. The endothelial response to C involves an integrin receptor-mediated RhoA-dependent signaling pathway that leads to paracellular hyperpermeability.

The effect of fibrinogen- C-terminal fragment (C) on microvascular endothelial permeability was assessed by measuring albumin flux and hydraulic conductivity in mesenteric microvessels and transcellular electric resistance in endothelial monolayers. The results suggest that C induces an integrin-mediated RhoA-dependent endothelial response leading to microvascular leakage.

Key Words: fibrinogen degradation products • microvascular permeability • signal transduction • Rho-GTPase • thrombosis