title: Monochloramine produces reactive oxygen species in liver by converting xanthine dehydrogenase into xanthine oxidase.
abstract: In the present study, we assessed the influence of monochloramine (NH(2)Cl) on the conversion of xanthine dehydrogenase (XD) into xanthine oxidase (XO) in rat liver in vitro. When incubated with the partially purified cytosolic fraction from rat liver, NH(2)Cl (2.5-20 microM) dose-dependently enhanced XO activity concomitant with a decrease in XD activity, implying that NH(2)Cl can convert XD into the reactive oxygen species (ROS) producing form XO. The NH(2)Cl (5 microM)-induced XD/XO interconversion in the rat liver cytosol was completely inhibited when added in combination with an inhibitor of NH(2)Cl methionine (25 microM). A sulfhydryl reducing agent, dithiothreitol at concentrations of 0.1, 1 and 5 mM also dose-dependently reversed the NH(2)Cl (5 microM)-induced XD/XO interconversion. These imply that NH(2)Cl itself acts on the XD/XO interconversion, and that this conversion occurs at the cysteine residues in XD. Furthermore, using the fluorescent probe 2',7'-dichlorodihydrofluorescein diacetate, it was found that NH(2)Cl could increase ROS generation in the cytoplasm of rat primary hepatocyte cultures, and that this increase might be reversed by an XO inhibitor, allopurinol. These results suggest that NH(2)Cl has the potential to convert XD into XO in the liver, which in turn may induce the ROS generation in this region.
authors.affiliation: Laboratory of Physiological Chemistry, Osaka University of Pharmaceutical Sciences, 4-20-1 Nasahara, Takatsuki, Osaka 569-1094, Japan. sakuma@gly.oups.ac.jp
authors.forename: Satoru
authors.initials: S
authors.lastname: Sakuma
authors.forename: Emi
authors.initials: E
authors.lastname: Miyoshi
authors.forename: Namiko
authors.initials: N
authors.lastname: Sadatoku
authors.forename: Junko
authors.initials: J
authors.lastname: Fujita
authors.forename: Miki
authors.initials: M
authors.lastname: Negoro
authors.forename: Yukio
authors.initials: Y
authors.lastname: Arakawa
authors.forename: Yohko
authors.initials: Y
authors.lastname: Fujimoto
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D002700:Chloramines / Q000633:toxicity*; D003600:Cytosol / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D022781:Hepatocytes / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism; D066298:In Vitro Techniques; D008099:Liver / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D008297:Male; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014968:Xanthine Dehydrogenase / Q000378:metabolism*; D014969:Xanthine Oxidase / Q000378:metabolism*
chemical_list: D002700:Chloramines; D017382:Reactive Oxygen Species; D014968:Xanthine Dehydrogenase; D014969:Xanthine Oxidase; C030816:chloramine