Aim: 

Fractalkine/CX₃CL1 (FR) is a membrane-bound chemokine and an adhesion molecule. It has been implicated in atherosclerosis. Since angiotensin-II (AII) exerts vascular inflammation, we have investigated whether AII cause FR expression on human umbilical arterial and vein endothelial cells (HUAECs and HUVECs) and the underlying mechanisms involved in this response.

Methods: 

HUAECs and HUVECs were stimulated with AII (1 mM). Semiquantitative RT-PCR and immunofluorescence were employed to detect FR mRNA and protein expression. Flow chamber was used to evaluate the functional role of FR on mononuclear cell arrest under dynamic conditions. Intravital microscopy was used for in vivo experiments.

Results: 

Increased FR mRNA expression on AII-stimulated HUAECs and HUVECs was detected at 12 h being greater in HUAECs than in HUVECs. Immunofluorescence revealed a clear expression of FR in both cell types after 24 h stimulation with AII. AII-induced FR expression was inhibited by losartan (AT1 receptor antagonist) or by a NF-kB inhibitor. HUAECs showed 5 fold greater mononuclear cell arrest than HUVECs when they were stimulated with AII. These responses were clearly inhibited by pre-treatment of the cells with a NF-kB inhibitor or with neutralizing antibodies against FR and vascular cell adhesion molecule-1 (VCAM-1). KO mice in FR receptor (CX₃CR1) had less leukocyte adhesion to AII-stimulated arterioles than wild type animals.

Conclusions: 

These results suggest that AII induces FR expression and mononuclear cell recruitment through NF-kB activation. Therefore, FR may be a key chemokine in the selective adhesion of mononuclear leukocytes to the arterial endothelium elicited by AII.