Background--Heparin, used clinically as an anticoagulant, also has antiinflammatory properties and has been described to inhibit interferon (IFN)- responses in endothelial cells. We investigated the effects of heparin on the IFN--inducible chemokines IP-10/CXCL10, I-TAC/CXCL11, and Mig/CXCL9, which play important roles in the vascular recruitment of IFN--producing Th1 cells through interactions with their cognate receptor, CXCR3.

Methods and Results--Patients undergoing coronary artery bypass grafting were studied because coronary atherosclerosis is recognized as a Th1-type inflammatory disease and the subjects required systemic heparinization. Plasma levels of IP-10, I-TAC, and Mig increased immediately after heparin administration and diminished promptly after heparin antagonism with protamine. These effects were independent of detectable circulating IFN- or the IFN- inducer interleukin-12. We confirmed previous reports that heparin inhibits the IFN--dependent production of CXCR3 chemokine ligands using atherosclerotic coronary arteries in organ culture. In addition to prolonged treatment decreasing chemokine secretion, heparin rapidly displaced membrane-associated IP-10 from cultured endothelial cells that did not express CXCR3 and reduced the IP-10-dependent transendothelial migration of T helper cells under conditions of venular shear stress. Finally, heparin administration to immunodeficient mouse hosts decreased both the recruitment and accumulation of memory T cells within allogeneic human coronary arteries.

Conclusions--Besides inhibiting IFN- responses, heparin has further immunomodulatory effects by competing for binding with IP-10, I-TAC, and Mig on endothelial cells. Disruption of CXCR3⁺ Th1 cell trafficking to arteriosclerotic arteries may contribute to the therapeutic efficacy of heparin in inflammatory arterial diseases, and nonanticoagulant heparin derivatives may represent a novel antiinflammatory strategy.