Abstract 13436: The Tyrosine Kinase Arg, But Not c-Abl is the Molecular Target in the Endothelial Barrier Protective Effects of Imatinib
Introduction Endothelial barrier dysfunction and vascular leakage are significant pathogenic phenomena. Although contributing to life-threatening conditions like acute lung injury, they currently lack specific therapy. In a case-report we reported fast resolution of pulmonary edema upon treatment with the tyrosine kinase inhibitor imatinib. Here, we test the hypothesis that imatinib protects against endothelial barrier dysfunction and elucidate its molecular target.
Methods & Results The effects of imatinib on endothelial barrier function were assessed by macromolecule passage and electrical resistance over human endothelial monolayers during endothelial activation with thrombin or histamine. Pretreatment with imatinib (10µM) attenuated the thrombin-induced macromolecule passage over endothelial monolayers (40% reduction, P<0.001, n=4), and reduced the maximal drop in electrical resistance during thrombin and histamine stimulation (24% reduction, P<0.001, n=5, and 37% reduction, P=0.01, n=4, respectively) in macro- and microvascular endothelial cells. In a systematic siRNA knock down of the imatinib-sensitive kinases (c-Abl, Abl-related gene [Arg], PDGFR and c-KIT) only Arg knock down mimicked the barrier protective effects during thrombin stimulation (22% reduction of macromolecule passage, P<0.01, n=4; 22% reduction of the maximal drop in electrical resistance, P=0.01, n=4). Imatinib had no additive protective effect in Arg depleted cells. PDGFR and c-KIT depletion did not affect the thrombin response, whereas depletion of c-Abl impaired endothelial integrity. Arg inhibition impaired F-actin stress fiber formation during endothelial activation with thrombin, which was paralleled by reduced phosphorylation of myosin light chain (MLC). Imatinib did not affect RhoA activation, indicating that Arg mediates endothelial barrier dysfunction via RhoA-independent MLC phosphorylation.
Conclusion Inhibition of Arg and not c-Abl underlies the protective effects of imatinib during endothelial barrier dysfunction. This study identifies the tyrosine kinase Arg as an entirely novel mediator of endothelial barrier dysfunction, and indicates imatinib as a potential candidate for treatment of vascular leakage and edema.
- © 2011 by American Heart Association, Inc.