A Potent and Selective Nonpeptide Antagonist of CXCR2 Inhibits Acute and Chronic Models of Arthritis in the Rabbit

Abstract

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.

Small Molecule Disruption of G Protein βγ Subunit Signaling Inhibits Neutrophil Chemotaxis and Inflammation

“…The inflammatory process involves complex signaling cascades partly coordinated by chemokines, which recruit leukocytes, including large numbers of neutrophils, to sites of inflammation . Targeting chemokines with antibodies or binding proteins as well as targeting chemokine receptors has been attempted as a therapeutic strategy (Gong et al, 1997;Ogata et al, 1997;Plater-Zyberk et al, 1997;Barnes et al, 1998;Halloran et al, 1999;Matthys et al, 2001;Podolin et al, 2002;Yang et al, 2002) However, the overwhelming complexity of these signaling molecules (multiple chemokines, chemokine receptors, and redundancy) is a significant hurdle. Polychemokine (Carter, 2002) or combinations of different chemokine (al Mughales et al, 1996) antagonists have been suggested, but there may be chemokines that act as an agonist at one receptor and an antagonist at another (Xanthou et al, 2003).…”

CXC Chemokine Ligand 2 Induced by Receptor Activator of NF-κB Ligand Enhances Osteoclastogenesis

“…Therapies targeting CXCL2/CXCR2 have been tested in animal models of arthritis with concomitant reduction in neutrophil recruitment and TNF-a production (20), and immunization against CXCL2 was efficient in delaying the onset of arthritis and reducing the disease severity in a murine collagen-induced arthritis model (21). In addition, an antagonist of CXCR2 inhibited arthritis in rabbits (22). Our results imply that targeting CXCL2 as a strategy to treat RA would be beneficial in protection from bone destruction by directly inhibiting bone resorption, in addition to the already suggested antiinflammatory effects.…”

Chemokines and their receptors in rheumatoid arthritis: Future targets?

“…Similarly, an antibody to IL-8/CXCL8 inhibited LPS-or monosodium urate crystal-induced leukocyte infiltration into rabbit knee joints (99,100). A nonpeptide oral antagonist of the IL-8/CXCL8 receptor, CXCR2, inhibited acute IL-8/CXCL8-or LPS-induced arthritis and chronic antigen (ovalbumen)-induced arthritis in rabbits (101). In LPS-induced rabbit arthritis, elevated SF GRO levels preceded knee joint leukocyte infiltration, which was inhibited 54% by GRO-specific neutralizing antibody, 48% by anti-IL-8, and 70% by a combination of both antibodies (102).…”