Pharmacological blockade of CCR1 ameliorates murine arthritis and alters cytokine networksin vivo

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Abstract
Background and purpose: The chemokine receptor CCR1 is a potential target for the treatment of rheumatoid arthritis. To explore the impact of CCR1 blockade in experimental arthritis and the underlying mechanisms, we used J‐113863, a non‐peptide antagonist of the mouse receptor.Experimental approach: Compound J‐113863 was tested in collagen‐induced arthritis (CIA) and three models of acute inflammation;Staphylococcusenterotoxin B (SEB)‐induced interleukin‐2 (IL‐2), delayed‐type hypersensitivity (DTH) response, and lipopolysaccharide (LPS)‐induced tumour necrosis factorα (TNFα) production. In the LPS model, CCR1 knockout, adrenalectomised, or IL‐10‐depleted mice were also used. Production of TNFα by mouse macrophages and human synovial membrane samples in vitro were also studied.Key results: Treatment of arthritic mice with J‐113863 improved paw inflammation and joint damage, and dramatically decreased cell infiltration into joints. The compound did not inhibit IL‐2 or DTH, but reduced plasma TNFα levels in LPS‐treated mice. Surprisingly, CCR1 knockout mice produced more TNFα than controls in response to LPS, and J‐113863 decreased TNFα also in CCR1 null mice, indicating that its effect was unrelated to CCR1. Adrenalectomy or neutralisation of IL‐10 did not prevent inhibition of TNFα production by J‐113863. The compound did not inhibit mouse TNFα in vitro, but did induce a trend towards increased TNFα release in cells from synovial membranes of rheumatoid arthritis patients.Conclusions and implications: CCR1 blockade improves the development of CIA, probably via inhibition of inflammatory cell recruitment. However, results from both CCR1‐deficient mice and human synovial membranes suggest that, in some experimental settings, blocking CCR1 could enhance TNF production.British Journal of Pharmacology(2006)149, 666–675. doi:10.1038/sj.bjp.0706912