Interleukin-8 (IL-8The present findings suggest that CXCR2 is responsible for neutrophil chemotaxis and margination induced by IL-8. This selective antagonist will be a useful tool compound to define the role of CXCR2 in inflammatory diseases where neutrophils play a major role.

Much evidence implicates IL-8 as a major mediator of inflammation and joint destruction in rheumatoid arthritis. The effects of IL-8 and its related ligands are mediated via two receptors, CXCR1 and CXCR2. In the present study, we demonstrate that a potent and selective nonpeptide antagonist of human CXCR2 potently inhibits 125I-labeled human IL-8 binding to, and human IL-8-induced calcium mobilization mediated by, rabbit CXCR2 (IC50 = 40.5 and 7.7 nM, respectively), but not rabbit CXCR1 (IC50 = >1000 and 2200 nM, respectively). These data suggest that the rabbit is an appropriate species in which to examine the anti-inflammatory effects of a human CXCR2-selective antagonist. In two acute models of arthritis in the rabbit induced by knee joint injection of human IL-8 or LPS, and a chronic Ag (OVA)-induced arthritis model, administration of the antagonist at 25 mg/kg by mouth twice a day significantly reduced synovial fluid neutrophils, monocytes, and lymphocytes. In addition, in the more robust LPS- and OVA-induced arthritis models, which were characterized by increased levels of proinflammatory mediators in the synovial fluid, TNF-α, IL-8, PGE2, leukotriene B4, and leukotriene C4 levels were significantly reduced, as was erythrocyte sedimentation rate, possibly as a result of the observed decreases in serum TNF-α and IL-8 levels. In vitro, the antagonist potently inhibited human IL-8-induced chemotaxis of rabbit neutrophils (IC50 = 0.75 nM), suggesting that inhibition of leukocyte migration into the knee joint is a likely mechanism by which the CXCR2 antagonist modulates disease.

The recruitment of inflammatory cells into sites of inflammation is a normal physiological response designed to fight infection, remove damaged cells, and stimulate healing. However, the excessive recruitment of such cells often exacerbates tissue damage, slows healing, and in some cases leads to host death. Therefore, inhibition of inflammatory cell recruitment may be an appropriate therapeutic strategy in a number of inflammatory diseases, such as asthma, reperfusion injury, arthritis, and inflammatory bowel disease.Chemokines are a superfamily of approximately 30 distinct small secreted proteins, and additional members continue to be identified (1, 2). They are classified into two major groups, CXC and CC, based on the position of the first two of their four invariant cysteines (3). The actions of chemokines are mediated via interactions with 7-TM 1 G protein-coupled receptors on the surface of immune and inflammatory cells. To date, 18 unique chemokine receptors, including 11 CC chemokine receptors, have been cloned (4, 5).The properties of the chemokines suggest that they are essential for leukocyte trafficking and inflammatory processes and thus are important components in a number of disease states (6, 7). Eosinophils are proinflammatory granulocytes that play a major role in allergic diseases, such as bronchial asthma (8), allergic rhinitis (9), atopic dermatitis (10), and eosinophilic gastroenteritis (11). Upon activation, eosinophils release lipid mediators, cytotoxic proteins, oxygen metabolites, and cytokines, all of which have the potential to produce pathophysiology. Recent studies have clearly demonstrated the presence of eosinophils or eosinophil-specific products in inflamed lung biopsy tissues in human asthma (10).Although the molecular mechanism responsible for the selective infiltration of eosinophils into inflamed tissue has not been elucidated, recently the CC chemokine eotaxin was identified in guinea pig lung following antigen challenge in sensitized guinea pigs (12, 13). Furthermore, neutralizing antibodies to eotaxin in a mouse model of allergy demonstrated inhibition of eosinophil recruitment when administered before the antigen challenge (14). Five CCR3 ligands have been shown to induce eosinophil transendothelial migration using human umbilical vein endothelial cells. This migration is inhibited by pretreatment with anti-CCR3. In addition, a human lung epithelial cell line (BEAS-2B), stimulated with proinflammatory cytokines, has been shown to produce eotaxin and 16). In humans, biopsies obtained from asthmatic lung have shown increased levels of CCR3 and its ligands, eotaxin, eotaxin-2, RANTES, and MCP-4, both at the mRNA and pro-* The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.§ To whom correspondence should be addressed: Dept. of Immunology, SmithKline Beecham Pharmaceuticals, 709 Swedeland Rd., King of ...

N,N'-Diarylureas were prepared, and the structure-activity relationship relative to the CXCR2 receptor was examined. This led to the identification of a potent and highly selective CXCR2 antagonist, which in addition was shown to be functionally active both in vitro against human neutrophils and in vivo in rabbit models of ear edema and neutropenia.

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