The inhibitory effect of ambroxol on respiratory burst, degranulation and cytosolic Ca2+ change in degraded immunoglobulin G-activated neutrophils

Superoxide and H2O2 production by neutrophils stimulated by 0.5 mg/ml degraded immunoglobulin G (IgG) and 1 mu M N-formyl-methionyl-leucyl-phenylalanine (fMLP) was inhibited by ambroxol in a dose-dependent fashion, and at the concentration of 100 mu M, 43.3% to 64.3% of inhibitions were detected. The inhibitory effect of ambroxol on H2O2 production by neutrophils was greater than that on superoxide production. The production of nitrite by lipopolysaccharide-activated murine peritoneal macrophages was significantly attenuated by ambroxol in a dose-dependent fashion and NG-monomethyl-L-arginine (NMMA). Ambroxol decreased the release of myeloperoxidase and lysozyme evoked by 0.5 mg/ml degraded immunoglobulin G and 1 mu M fMLP in a dose-dependent fashion, and at the concentration of 100 mu M, 37.1% to 64.2% of inhibitions were observed. The stimulatory effect of phorbol 12-myristate 13-acetate (PMA) (0.1 mu g/ml) on superoxide production and myeloperoxidase, which is inhibited by 100 nM staurosporine, was not affected by 100 mu M ambroxol. Degraded immunoglobulin G (0.5 mg/ml) caused an immediate elevation of [Ca2+](i) in fura-2 load neutrophils in 1.23 mM Ca2+-containing medium. Preincubation of neutrophils with 10 mu M to 100 mu M ambroxol, 5 mM EGTA and 100 mu M verapamil depressed the elevation of [Ca2+](i) elicited by 0.5 mg/ml degraded immunoglobulin G. In conclusion, the inhibitory action of ambroxol on stimulated neutrophil responses, including respiratory burst and lysosomal enzyme release, appears to be attributed to its depressant action on the activation process, including the change in intracellular Ca2+ level, in which the role of protein kinase C is uncertain.