The Inflammatory Chemokine CXCL16 Triggers Platelet Activation and Adhesion via CXCR6-Dependent PI3K/Akt Signaling
Rationale: The recently discovered chemokine CXCL16 is highly expressed in atherosclerotic lesions and a potential pathogenic mediator in coronary artery disease.
Objective: To test the role of CXCL16 on platelet activation and vascular adhesion as well as the underlying mechanism and signaling pathway.
Methods and Results: RT-PCR, western blotting, confocal microscopy and flow cytometry revealed that CXCL16-specific receptor CXCR6 is highly expressed on platelets. According to flow cytometry and confocal microscopy stimulation of platelets with CXCL16 induced platelet degranulation, integrin αIIbβ3activation and shape change. CXCL16 increased Akt phosphorylation (Thr308/Ser473), an effect abrogated by phosphatidylinositide 3-kinase (PI3K) inhibitors wortmannin (100nM) and LY294002 (25 µM). The PI3K inhibitors and Akt inhibitor SH-6 (20 µM) further diminished CXCL16-induced platelet activation. CXCL16-mediated platelet degranulation, integrin αIIbβ3 activation and Akt phosphorylation were blunted in platelets lacking CXCL16-specific receptor CXCR6. CXCL16-induced platelet activation was abrogated in Akt1- or Akt2-deficient platelets. CXCL16 enhanced platelet adhesion to endothelium in vitro following high arterial shear stress (2000-s) and to injured vascular wall in vivo following carotis ligation. CXCL16-induced stimulation of platelet adhesion was again prevented by PI3K and Akt inhibitors. Apyrase and antagonists of platelet purinergic receptors P2Y1 (MRS2179, 100µM) and especially P2Y12 (Cangrelor, 10µM) blunted CXCL16-triggered platelet activation as well as CXCL16-induced platelet adhesion under high arterial shear stress in vitro and after carotis ligation in vivo.
Conclusions: The inflammatory chemokine CXCL16 triggers platelet activation and adhesion via CXCR6-dependent PI3K/Akt signaling and paracrine activation suggesting a decisive role for CXCL16 in linking vascular inflammation and thrombo-occlusive diseases.
- Received June 26, 2012.
- Accepted August 27, 2012.
- Copyright © 2012, American Heart Association