title: Production of nitric oxide-derived reactive nitrogen species in human oral cavity and their scavenging by salivary redox components.
abstract: Nitrite is reduced to nitric oxide (NO) in the oral cavity. The NO generated can react with molecular oxygen producing reactive nitrogen species. In this study, reduction of nitrite to NO was observed in bacterial fractions of saliva and whole saliva. Formation of reactive nitrogen species from NO was detected by measuring the transformation of 4,5-diaminofluorescein (DAF-2) to triazolfluorescein (DAF-2T). The transformation was fast in bacterial fractions but slow in whole saliva. Salivary components such as ascorbate, glutathione, uric acid and thiocyanate inhibited the transformation of DAF-2 to DAF-2T in bacterial fractions without affecting nitrite-dependent NO production. The inhibition was deduced to be due to scavenging of reactive nitrogen species, which were formed from NO, by the above reagents. The transformation of DAF-2 to DAF-2T was faster in bacterial fractions and whole saliva which were prepared 1-4 h after tooth brushing than those prepared immediately after toothbrushing. Increase in the rate as a function of time after toothbrushing seemed to be due to the increase in population of bacteria which could reduce nitrite to NO. The results obtained in this study suggest that reactive nitrogen species derived from NO are continuously formed in the oral cavity and that the reactive nitrogen species are effectively scavenged by salivary redox components in saliva but the scavenging is not complete.
authors.affiliation: Department of Bioscience, Kyushu Dental University, Kitakyushu, 803-8580, Japan. takahama@kyu-dent.ac.jp
authors.forename: Umeo
authors.initials: U
authors.lastname: Takahama
authors.forename: Sachiko
authors.initials: S
authors.lastname: Hirota
authors.forename: Takayuki
authors.initials: T
authors.lastname: Oniki
mesh_terms: D000328:Adult; D002851:Chromatography, High Pressure Liquid; D004578:Electron Spin Resonance Spectroscopy; D019793:Fluorescein / Q000737:chemistry; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry; D008875:Middle Aged; D009055:Mouth / Q000201:enzymology / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism*; D010084:Oxidation-Reduction; D026361:Reactive Nitrogen Species / Q000378:metabolism*; D012463:Saliva / Q000201:enzymology / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013997:Time Factors
chemical_list: C111205:4,5-diaminofluorescein; D007202:Indicators and Reagents; D009573:Nitrites; D026361:Reactive Nitrogen Species; D009569:Nitric Oxide; D019793:Fluorescein