Inhibition of free radical generation by biotin.
To assess the inhibitory effect of biotin on free radical generation, we used a spectrophotometric assay of cytochrome c reduction and determined the 2-methyl-6-phenyl-3,7-dihydroimidazo[1,3-a]-pyrazin-3-one (CLA)-dependent chemiluminescence response of human neutrophils or a hypoxanthine-xanthine oxidase (XOD) system. In the spectrophotometric assay of cytochrome c reduction, superoxide (O2-) generation by neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine (f-MLP) was reduced significantly when biotin was added. In the CLA-dependent chemiluminescence test of neutrophils stimulated by f-MLP, biotin significantly reduced the generation of free radical species, including O2-, in a concentration-dependent manner, the concentration corresponding to 50% inhibition (IC50) of biotin for free radical generation was 1.12 x 10(-7) mol. However, biotin did not exert an inhibitory effect on oxidative metabolism by directly scavenging superoxide anion, as shown by the study using the hypoxanthine-XOD system.
Sekiguchi
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First Department of Internal Medicine, Gunma University School of Medicine, Maebashi, Japan.
Nagamine
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D000328:Adult; D001710:Biotin / Q000494:pharmacology*; D003574:Cytochrome c Group / Q000737:chemistry; D005609:Free Radicals; D006801:Humans; D019271:Hypoxanthine; D007042:Hypoxanthines; D008163:Luminescent Measurements; D008297:Male; D009240:N-Formylmethionine Leucyl-Phenylalanine; D009504:Neutrophils / Q000187:drug effects / Q000378:metabolism; D011719:Pyrazines; D013053:Spectrophotometry; D014969:Xanthine Oxidase
D003574:Cytochrome c Group; D005609:Free Radicals; D007042:Hypoxanthines; D011719:Pyrazines; C048193:2-methyl-6-phenyl-3,7-dihydroimidazo(1,2-a)pyrazin-3-one; D019271:Hypoxanthine; D009240:N-Formylmethionine Leucyl-Phenylalanine; D001710:Biotin; D014969:Xanthine Oxidase