The unique target specificity of a nonpeptide chemokine receptor antagonist: selective blockade of two Th1 chemokine receptors CCR5 and CXCR3

CC chemokine receptor (CCR) 5 and CXC chemokine receptor (CXCR)3 are expressed on T helper cell type 1 cells and have been implicated in their migration to sites of inflammation. Our preceding study demonstrated that a nonpeptide synthetic CCR5 antagonist, TAK‐779 {N, N‐dimethyl‐N‐[4‐[[[2‐(4‐methylphenyl)‐6, 7‐dihydro‐5H‐benzocyclohepten‐8‐yl]carbon‐yl]amino]benzyl]‐tetrahydro‐2H‐pyran4‐aminium chloride, inhibits the development of experimentally induced arthritis by modulating the migration of CCR5+/CXCR3+ T cells to joints. The present study investigated the functional properties of TAK‐779, including the effect of this antagonist on CXCR3 function. For this purpose, transfectants expressing mouse CCR5 (mCCR5) or mCXCR3 and expressing mCCR4 or mCXCR4 as controls were established by introducing each relevant gene into 2B4 T cells and were subjected to the following assays. First, the ligand binding to chemokine receptors was assayed by incubating transfectants with [125I]‐labeled relevant ligand or with the unlabeled relevant ligand followed by staining with anti‐ligand antibody. Second, chemokine‐induced lymphocyte function‐associated antigen‐1 (LFA‐1) activation was assayed by measuring the adhesion of cells to microculture plates coated with purified intercellular adhesion molecule‐1. Third, chemokine‐stimulated chemotaxis was assayed by observing the cell migration through transwells. In these assays, TAK‐779 blocked the ligand binding as well as LFA‐1 up‐regulating and chemotactic function of mCXCR3 and mCCR5 but did not elicit a biologically significant inhibition of those functions of mCCR4 and mCXCR4. These observations indicate the unique target specificity of TAK‐779 and explain why this antagonist efficiently blocks the migration of T cells expressing CCR5 and CXCR3 to sites of inflammation.