Inhibitory effect of neopterin on NADPH-dependent superoxide-generating oxidase of rat peritoneal macrophages.
The effect of the oxidized form of neopterin (NP) on the NADPH-dependent superoxide-generating oxidase (NADPH-oxidase) was investigated in both whole-cell and cell-free activation systems by using peritoneal macrophages of rats which had received an intraperitoneal injection of mineral oil. In the whole-cell system, NP remarkably inhibited the generation of superoxides in macrophages stimulated with phorbol myristate acetate (PMA). NP also showed an significant suppression of the activation of superoxide-generating NADPH-oxidase in the cell-free system using solubilized membranes and sodium dodecyl sulfate (SDS) as a stimulant. The 50%-inhibitory concentration (IC50) of NP was about 1 microM in both assay systems. In a kinetic study, competitive inhibition of the NADPH-oxidase by NP was observed in the cell-free system with a calculated inhibition constant (Ki) of 6.50 microM. These findings suggest that NP may play an important role in the suppression of superoxide generation via the inhibition of the NADPH-oxidase in phagocytes.
Kojima
S
S
Research Institute for Biosciences, Science University of Tokyo, Chiba, Japan.
Nomura
T
T
Icho
T
T
Kajiwara
Y
Y
Kitabatake
K
K
Kubota
K
K
D000818:Animals; D001667:Binding, Competitive; D001708:Biopterins / Q000031:analogs & derivatives* / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002474:Cell-Free System; D008264:Macrophages / Q000201:enzymology*; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009249:NADP / Q000494:pharmacology*; D019255:NADPH Oxidases; D019798:Neopterin; D010529:Peritoneal Cavity / Q000166:cytology; D011493:Protein Kinase C / Q000378:metabolism; D051381:Rats; D012967:Sodium Dodecyl Sulfate / Q000494:pharmacology; D013481:Superoxides / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019820:Xanthine; D014969:Xanthine Oxidase / Q000378:metabolism; D014970:Xanthines / Q000378:metabolism
D014970:Xanthines; D013481:Superoxides; D019820:Xanthine; D001708:Biopterins; D012967:Sodium Dodecyl Sulfate; D009249:NADP; D019798:Neopterin; D014969:Xanthine Oxidase; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium