title: Monoamine-dependent production of reactive oxygen species catalyzed by pseudoperoxidase activity of human hemoglobin.
abstract: Hemoglobin (Hb) solution-based blood substitutes are being developed as oxygen-carrying agents for the prevention of ischemic tissue damage and low blood volume-shock. However, the cell-free Hb molecule has intrinsic toxicity to the tissue since harmful reactive oxygen species (ROS) are readily produced during autoxidation of Hb from the ferrous state to the ferric state, and the cell-free Hb also causes distortion in the oxidant/antioxidant balance in the tissues. There may be further hindering dangers in the use of free Hb as a blood substitute. It has been reported that Hb has peroxidase-like activity oxidizing peroxidase substrates such as aromatic amines. Here we observed the Hb-catalyzed ROS production coupled to oxidation of a neurotransmitter precursor, beta-phenylethylamine (PEA). Addition of PEA to Hb solution resulted in generation of superoxide anion (O2*-). We also observed that PEA increases the Hb-catalyzed monovalent oxidation of ascorbate to ascorbate free radicals (Asc'). The O2*- generation and Asc formation were detected by O2*--specific chemiluminescence of the Cypridina lucigenin analog and electron spin resonance spectroscopy, respectively. PEA-dependent O2*- production and monovalent oxidation of ascorbate in the Hb solution occurred without addition of H2O2, but a trace of H2O2 added to the system greatly increased the production of both O2*- and Asc*. Addition of GSH completely inhibited the PEA-dependent production of O2*- and Asc* in Hb solution. We propose that the O2*- generation and Asc* formation in the Hb solution are due to the pseudoperoxidase activity-dependent oxidation of PEA and resultant ROS may damage tissues rich in monoamines, if the Hb-based blood substitutes were circulated without addition of ROS scavengers such as thiols.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, Hiroshima University, Higashi-Hiroshima, Japan. kawanotom@sci.hiroshima-u.ac.jp
authors.forename: Tomonori
authors.initials: T
authors.lastname: Kawano
authors.forename: Reinhard
authors.initials: R
authors.lastname: Pinontoan
authors.forename: Hishoshi
authors.initials: H
authors.lastname: Hosoya
authors.forename: Shoshi
authors.initials: S
authors.lastname: Muto
mesh_terms: D015306:Biogenic Monoamines / Q000378:metabolism*; D001802:Blood Substitutes; D002384:Catalysis; D016166:Free Radical Scavengers; D006454:Hemoglobins / Q000378:metabolism*; D006801:Humans; D008706:Methemoglobin / Q000378:metabolism; D010084:Oxidation-Reduction; D010544:Peroxidases / Q000378:metabolism*; D010627:Phenethylamines / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D013054:Spectrophotometry, Atomic; D013481:Superoxides / Q000378:metabolism
chemical_list: D015306:Biogenic Monoamines; D001802:Blood Substitutes; D016166:Free Radical Scavengers; D006454:Hemoglobins; D010627:Phenethylamines; D017382:Reactive Oxygen Species; D013481:Superoxides; C029261:phenethylamine; D008706:Methemoglobin; D010544:Peroxidases