Inhibition of substance P-induced histamine release from rat peritoneal mast cells by ultraviolet light B irradiation: Decreased intracellular calcium as a partial mechanism

Background Ultraviolet light irradiation has been shown to suppress immunological reactions of irradiated individuals, however, less attention has been paid to the effects on neurogenic inflammation. Objective We have investigated the effect of ultraviolet light B (UVB) irradiation on substance P (SP)-induced histamine release from rat mast cells. Methods Rat peritoneal mast cells were treated with UVB irradiation and challenged by SP. Histamine release from the cells and intracellular calcium concentrations ([Ca2+](i)) in the cells were measured. Results UVB Irradiation at doses used in the present study did not induce histamine release from mast cells. UVB irradiation at doses from 25 to 200 mJ/cm(2) inhibited 10(-5) mol/L SP-induced histamine release in a dose-dependent manner. On the other hand, SP-induced increase of [Ca2+](i) was inhibited by UVB Irradiation only at doses of 100 and 200 mJ/cm(2). Conclusion These data suggest that UVB irradiation inhibits histamine release from SP-activated rat peritoneal mast cells partially through the suppression of an increase in [Ca2+](i).