Role of superoxide generation and degradation system of mast cells in allergic inflammation

Abstract

Rat peritoneal mast cells are stimulated to generate superxide anion (O₂^-) by the addition of compound 48/80 and A23187. Recently, we demonstrated by immunohistochemical and Western blot analysis that the mast cells contained the p47phox protein, which was one of cytosolic component of the NADPH oxidase system. In the present study, it was demonstrated that the mast cells contained the p47phox mRNA, much similar to that of mouse leukocyte. The permeabilized mast cells were stimulated to generate O₂^- by the addition of Ca²⁺, phospholipase A₂(PLA₂) and arachidonic acid. Our data suggest the following: (1) cytosolic PLA₂ may be activated by the elevation of [Ca²⁺]i; (2) the conjugation of membrane component with cytosolic component may be stimulated by the released arachidonic acid. The mast cell granules contained superoxide dismutase (SOD)-like enzyme, which degradated O₂^-, generated in xanthine-xanthinoxidase system. SOD-like enzyme was released from the granules by the treatment with Ca²⁺ and trapped by the treatment with heparin. In conclusion, our studies suggest that the disorder of the degradation system of O₂^- may contribute to the development of allergic inflammation.