[Effect of a leukotriene B4 antagonist on substance P-induced granulocyte infiltration in mouse skin]

Substance P causes granulocyte (neutrophil and eosinophil) infiltration in mouse skin by inducing mast cell degranulation. However, the mediator responsible for this granulocyte infiltration has not been determined. In this study, we examined the effect of a leukotriene B4 (LTB4) antagonist ONO-4057 on substance P-induced granulocyte infiltration in the skin of BALB/c mice. Pretreatment with the LTB4 antagonist decreased substance P-induced neutrophil and eosinophil infiltrations in mouse skin at 6 h to the same extent that an inhibitor of mast cell degranulation disodium cromoglycate decreased those responses. The LTB4 antagonist also decreased substance P-induced neutrophil, but not eosinophil, infiltration in mouse skin at 24 h. We conclude that LTB4 is a major mast cell-derived chemotactic mediator for initiating substance P-induced neutrophil and eosinophil infiltrations in mouse skin.