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The chemokine fragment CXCL9(74–103) diminishes neutrophil recruitment and joint inflammation in antigen‐induced arthritis

This study investigates if treatment with a peptide corresponding to the 30 C‐terminal amino acids of CXCL9, CXCL9(74–103), ameliorates joint inflammation in a murine model of antigen‐induced arthritis (AIA). AIA was induced in male C57BL/6J mice. Intravenous injection of CXCL9(74–103), simultaneously performed with a tibiofemoral challenge with methylated BSA (mBSA) as antigen in mice immunized with mBSA, diminished the accumulation of leukocytes, in particular neutrophils, in the synovial cavity. The levels of the chemokines CXCL1, CXCL2, and CXCL6 and of the cytokine IL‐6 were decreased in inflamed periarticular tissue of mice treated with the CXCL9‐derived peptide compared to non‐treated AIA mice. In addition, CXCL9(74–103) treatment substantially reduced joint and cartilage damage. CXCL9(74‐103) competes with CXCL6 and CCL3 for binding to the glycosaminoglycans heparan sulfate and chondroitin sulfate in vitro. In vivo, CXCL9(74‐103) quickly binds to blood vessels in joints as observed by confocal microscopy. Next, we evaluated if later treatment with CXCL9(74–103) had a beneficial impact on joint inflammation. CXCL9(74‐103) injection 6 h after mBSA challenge still reduced neutrophil accumulation in the joint, although it did not reduce chemokine and IL‐6 concentrations. However, a delay of treatment until 12 h after challenge had no effect on cell recruitment and chemokine and IL‐6 levels. Taken together, we demonstrated that treatment with a peptide, which interferes with the interaction between chemokines and glycosaminoglycans, from the beginning of the disease controlled the massive accumulation of neutrophils in the joint of AIA mice, greatly impacting on joint inflammation and tissue damage.