title: Resolving Contributions of Oxygen-Consuming and ROS-Generating Enzymes at the Synapse.
abstract: Disruption of cellular redox homeostasis is implicated in a wide variety of pathologic conditions and aging. A fundamental factor that dictates such balance is the ratio between mitochondria-mediated complete oxygen reduction into water and incomplete reduction into superoxide radical by mitochondria and NADPH oxidase (NOX) enzymatic activity. Here we determined mitochondrial as well as NOX-dependent rates of oxygen consumption in parallel with H2O2generation in freshly isolated synaptosomes using high resolution respirometry combined with fluorescence or electrochemical sensory. Our results indicate that although synaptic mitochondria exhibit substantially higher respiratory activities (8-82-fold greater than NOX oxygen consumption depending on mitochondrial respiratory state), NADPH-dependent oxygen consumption is associated with greater H2O2production (6-7-fold higher NOX-H2O2). We also show that, in terms of the consumed oxygen, while synaptic mitochondria "leaked" 0.71% ± 0.12 H2O2during NAD+-linked resting, 0.21% ± 0.04 during NAD+-linked active respiration, and 0.07% ± 0.02 during FAD+-linked active respiration, NOX converted 38% ± 13 of O2into H2O2. Our results indicate that NOX rather than mitochondria is the major source of synaptic H2O2. The present approach may assist in the identification of redox-modulating synaptic factors that underlie a variety of physiological and pathological processes in neurons.
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Engy A
authors.initials: EA
authors.lastname: Abdel-Rahman
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Ali M
authors.initials: AM
authors.lastname: Mahmoud
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Abdullah
authors.initials: A
authors.lastname: Aaliya
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Yasmine
authors.initials: Y
authors.lastname: Radwan
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Basma
authors.initials: B
authors.lastname: Yasseen
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Abdelrahman
authors.initials: A
authors.lastname: Al-Okda
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Ahmed
authors.identifier: 0000-0002-4559-5752
authors.initials: A
authors.lastname: Atwa
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Eslam
authors.initials: E
authors.lastname: Elhanafy
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Moaaz
authors.initials: M
authors.lastname: Habashy
authors.affiliation: Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt.
authors.forename: Sameh S
authors.identifier: 0000-0002-0339-6106
authors.initials: SS
authors.lastname: Ali
mesh_terms: D000818:Animals; D001921:Brain / Q000201:enzymology*; D005470:Fluorometry; D006861:Hydrogen Peroxide / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000201:enzymology; D019255:NADPH Oxidases / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D013569:Synapses / Q000201:enzymology*; D013574:Synaptosomes / Q000201:enzymology
chemical_list: D006861:Hydrogen Peroxide; D019255:NADPH Oxidases