A crucial role for TNF‐α in mediating neutrophil influx induced by endogenously generated or exogenous chemokines, KC/CXCL1 and LIX/CXCL5

Background and purpose: Chemokines orchestrate neutrophil recruitment to inflammatory foci. In the present study, we evaluated the participation of three chemokines, KC/CXCL1, MIP‐2/CXCL2 and LIX/CXCL5, which are ligands for chemokine receptor 2 (CXCR2), in mediating neutrophil recruitment in immune inflammation induced by antigen in immunized mice. Experimental approach: Neutrophil recruitment was assessed in immunized mice challenged with methylated bovine serum albumin, KC/CXCL1, LIX/CXCL5 or tumour necrosis factor (TNF)‐α. Cytokine and chemokine levels were determined in peritoneal exudates and in supernatants of macrophages and mast cells by elisa. CXCR2 and intercellular adhesion molecule 1 (ICAM‐1) expression was determined using immunohistochemistry and confocal microscopy. Key results: Antigen challenge induced dose‐ and time‐dependent neutrophil recruitment and production of KC/CXCL1, LIX/CXCL5 and TNF‐α, but not MIP‐2/CXCL2, in peritoneal exudates. Neutrophil recruitment was inhibited by treatment with reparixin (CXCR1/2 antagonist), anti‐KC/CXCL1, anti‐LIX/CXCL5 or anti‐TNF‐α antibodies and in tumour necrosis factor receptor 1‐deficient mice. Intraperitoneal injection of KC/CXCL1 and LIX/CXCL5 induced dose‐ and time‐dependent neutrophil recruitment and TNF‐α production, which were inhibited by reparixin or anti‐TNF‐α treatment. Macrophages and mast cells expressed CXCR2 receptors. Increased macrophage numbers enhanced, while cromolyn sodium (mast cell stabilizer) diminished, LIX/CXCL5‐induced neutrophil recruitment. Macrophages and mast cells from immunized mice produced TNF‐α upon LIX/CXCL5 stimulation. Methylated bovine serum albumin induced expression of ICAM‐1 on mesenteric vascular endothelium, which was inhibited by anti‐TNF‐α or anti‐LIX/CXCL5. Conclusion and implications: Following antigen challenge, CXCR2 ligands are produced and act on macrophages and mast cells triggering the production of TNF‐α, which synergistically contribute to neutrophil recruitment through induction of the expression of ICAM‐1.