IDENTIFICATION OF A POTENT, SELECTIVE NONPEPTIDE CXCR2 ANTAGONIST THAT INHIBITS INTERLEUKIN-8-INDUCED NEUTROPHIL MIGRATION

Interleukin-8 (IL-8) and closely related Glu-Leu-Arg (ELR) containing CXC chemokines, including growth-related oncogene (GRO)alpha, GRO beta , GRO gamma,; and epithelial cell-derived neutrophil-activating peptid e-78 (ENA-78), are potent neutrophil chemotactic and activating peptid es, which are proposed to be major mediators of inflammation. IL-8 act ivates neutrophils by binding to two distinct seven-transmembrane (7-T MR) G-protein coupled receptors CXCR1 (IL-8RA) and CXCR2 (IL-8RB), whi le GRO alpha, GRO beta, GRO gamma, and ENA-78 bind to and activate onl y CXCR2. A chemical lead, which selectively inhibited CXCR2 was discov ered by high throughput screening and chemically optimized. SE 225002 -(2-hydroxy-4-nitrophenyl)-N'-(2-bromophenyl)urea) is the first report ed potent and selective non-peptide inhibitor of a chemokine receptor. It is an antagonist of I-125-IL-8 binding to CXCR2 with an IC50,, = 2 2 nM. SE 225002 showed >150-fold selectivity over CXCR1 and four other 7-TMRs tested. In vitro, SE 225002 potently inhibited human and rabbi t neutrophil chemotaxis induced by both IL-8 and GRO alpha. In vivo, S E 225002 selectively blocked IL-8-induced neutrophil margination in ra bbits. The present findings suggest that CXCR2 is responsible for neut rophil chemotaxis and margination induced by IL-8. This selective anta gonist will be a useful tool compound to define the role of CXCR2 in i nflammatory diseases where neutrophils play a major role.