CHEMOKINE ANTAGONISTS THAT DISCRIMINATE BETWEEN INTERLEUKIN-8 RECEPTORS: SELECTIVE BLOCKERS OF CXCR2

Abstract Human neutrophils express two interleukin (IL)-8 receptors, CXC chemokine receptor (CXCR) 1 and CXCR2. IL-8 with changes to the NH2-terminal ELR motif can block IL-8-induced neutrophil functions (Moser, B., Dewald, B., Barella, L., Schumacher, C., Baggiolini, M., and Clark-Lewis, I. (1993) J. Biol. Chem. 268, 7125–7128). We have now examined the effect of NH2-terminally modified analogs of IL-8, GROα, and PF4 on CXCR1 and CXCR2 independently. Using stable Jurkat transfectants expressing either CXCR1 or CXCR2, it was shown that analogs derived from IL-8 bound both IL-8 receptors with similar affinity and could block IL-8-induced Ca2+ mobilization. By contrast, analogs of GROα and PF4, (R)GROα and (R)PF4, bound only CXCR2 with high affinity and blocked Ca2+ mobilization induced only via CXCR2. The differential effect on CXCR1 and CXCR2 was also demonstrated in studies with isolated neutrophils. Thus (R)GROα and (R)PF4 inhibited only the GROα but not the IL-8-stimulated elastase release, and these two analogs had no effect on IL-8-elicited superoxide generation, a response that is mediated by CXCR1 but not by CXCR2. These results show that CXCR2 selective receptor antagonists can be generated based upon the secondary binding determinants of GROα and PF4. They also highlight the primary importance of CXCR1 in chemokine-mediated release of granule enzymes and superoxide generation. The selective antagonists described may be used in future studies on IL-8 receptor signaling to define distinct steps leading to various functional responses induced in neutrophils via CXCR1 and CXCR2.