フジサワ　アキオ   藤沢　章雄    所属   応用生物学部 応用生物学科    職種   教授
言語種別	英語
発行・発表の年月	2025/07
形態種別	学術論文
査読	査読あり
標題	Formation of singlet oxygen in addition to hydroxyl radical via the Fenton reaction
執筆形態	共著
掲載誌名	Redox Biology
掲載区分	国外
出版社・発行元	Elsevier
巻・号・頁	84,pp.103687
総ページ数	11
担当区分	責任著者
著者・共著者	Rino Shimizu, Haruki Watanabe, Sayaka Iida, Yorihiro Yamamoto, Akio Fujisawa
概要	We established an LC-MS/MS method for detecting uric acid oxidation metabolites to evaluate reactive oxygen and nitrogen species, as uric acid gives specific products. Parabanic acid was identified during attempts to detect hydroxyl radical-specific products in the Fenton reaction. As parabanic acid is a singlet oxygen-specific product of uric acid, this indicates the Fenton system, which is known for the generation of hydroxyl radicals, also forms singlet oxygen products. This notion was confirmed by replacing uric acid with tryptophan, which resulted in the formation of singlet oxygen-specific oxidation products (cis- and trans-WOOH) and their reductants, cis- and trans-WOH. Product amounts were reduced in a dose-dependent manner by the addition of the singlet oxygen quenchers sodium azide or 1,4-diazabicyclo[2.2.2]octane. Surprisingly, the estimated amount of singlet oxygen produced was 50- to 70-fold greater than that of hydroxyl radical, considering the quantum yield of the reaction between uric acid and singlet oxygen. The formation of singlet oxygen under anaerobic conditions suggested it was derived from hydrogen peroxide. The production of non-labeled parabanic acid, even in an 18O2 atmosphere or the presence of H218O, supported this hypothesis. These results confirmed that singlet oxygen was derived from hydrogen peroxide. The proposed mechanism of singlet oxygen formation is as follows. Two hydrogen peroxyl radicals formed by the reaction of hydrogen peroxide and ferric ion or hydroxyl radical are coupled to form a hydrogen tetraoxide, which subsequently decomposes to form singlet oxygen and hydrogen peroxide via a Russell-like mechanism. Finally, it was observed that significantly more singlet oxygen was generated in whole human blood compared with red blood cell-depleted blood during pseudo-inflammation initiated by lipopolysaccharide addition, suggesting that singlet oxygen formation was due to the Fenton reaction. Thus, the Fenton reaction may be a novel pathway for singlet oxygen production.
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