Abstract 17442: CXCL12 is a Novel Suppressor of Endothelial Permeability
C-X-C chemokine ligand 12 (CXCL12) is well-known to regulate the mobilization of hematopoietic stem cells and endothelial progenitor cells. However, the effects of CXCL12 on pre-existing vascular functions remain unknown. We here investigated the role of CXCL12 signaling in endothelial barrier function. CXCL12 (1-100 ng/ml) dose-dependently increased transendothelial electrical resistance (TER) and inhibited thrombin-induced FITC-dextran hyperpermeability in bovine aortic endothelial cells (BAECs). Both indicate an endothelial barrier enhancement. We next investigated the signaling pathway underlying CXCL12-induced endothelial barrier enhancement. CXCL12 binds to two receptors, C-X-C chemokine receptor types 4 and 7 (CXCR4 and CXCR7). Pretreatment with a CXCR4 antagonist (AMD3100, 1 μM) or CXCR4 gene depletion by siRNA transfection abolished CXCL12-induced endothelial barrier enhancement. In contrast, CXCR7 gene depletion by siRNA did not influence CXCL12-induced barrier enhancement. Pretreatment with a Gi-protein inhibitor (pertussis toxin, 100 ng/ml), a phosphoinositide 3-kinase (PI3K) inhibitor (LY294002, 10 μM) or a PI3Kp110γ subunit inhibitor (AS605240, 10 μM) also significantly inhibited CXCL12-induced barrier enhancement. Consistently, western blot analysis revealed that CXCL12 phosphorylated AktSer473 in endothelial cells indicating PI3K activation. Immune-staining showed that CXCL12 (100 ng/ml) induced cortical actin rim formation of BAECs, which was accompanied by Rac1 activation. In vivo, using a modified Mile’s assay, we revealed that CXCL12 (100 ng/ear) inhibited croton oil-induced vascular leakage. In conclusion, we identified CXCL12 as a novel suppressor of endothelial permeability. Specifically, CXCL12 stimulates the CXCR4/PI3K/Rac1-signaling pathway and the subsequent cytoskeletal rearrangement.
- © 2013 by American Heart Association, Inc.