title: Mitochondrial respiratory complex I probed by delayed luminescence spectroscopy.
abstract: The role of mitochondrial complex I in ultraweak photon-induced delayed photon emission [delayed luminescence (DL)] of human leukemia Jurkat T cells was probed by using complex I targeting agents like rotenone, menadione, and quercetin. Rotenone, a complex I-specific inhibitor, dose-dependently increased the mitochondrial level of reduced nicotinamide adenine dinucleotide (NADH), decreased clonogenic survival, and induced apoptosis. A strong correlation was found between the mitochondrial levels of NADH and oxidized flavin mononucleotide (FMNox) in rotenone-, menadione- and quercetin-treated cells. Rotenone enhanced DL dose-dependently, whereas quercetin and menadione inhibited DL as well as NADH or FMNox. Collectively, the data suggest that DL of Jurkat cells originates mainly from mitochondrial complex I, which functions predominantly as a dimer and less frequently as a tetramer. In individual monomers, both pairs of pyridine nucleotide (NADH/reduced nicotinamide adenine dinucleotide phosphate) sites and flavin (FMN-a/FMN-b) sites appear to bind cooperatively their specific ligands. Enhancement of delayed red-light emission by rotenone suggests that the mean time for one-electron reduction of ubiquinone or FMN-a by the terminal Fe/S center (N2) is 20 or 284 μs, respectively. All these findings suggest that DL spectroscopy could be used as a reliable, sensitive, and robust technique to probe electron flow within complex I in situ.
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Irina
authors.initials: I
authors.lastname: Baran
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Diana
authors.initials: D
authors.lastname: Ionescu
authors.affiliation: Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud, 62 via S. Sofia, 95125 Catania, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Privitera
authors.affiliation: Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud, 62 via S. Sofia, 95125 Catania, ItalycUniversità di Catania, Dipartimento di Fisica e Astronomia, 6 v.le Andrea Doria, I-95125 Catania, Italy.
authors.forename: Agata
authors.initials: A
authors.lastname: Scordino
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Maria Magdalena
authors.initials: MM
authors.lastname: Mocanu
authors.affiliation: Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud, 62 via S. Sofia, 95125 Catania, ItalycUniversità di Catania, Dipartimento di Fisica e Astronomia, 6 v.le Andrea Doria, I-95125 Catania, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Musumeci
authors.affiliation: Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud, 62 via S. Sofia, 95125 Catania, Italy.
authors.forename: Rosaria
authors.initials: R
authors.lastname: Grasso
authors.affiliation: Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali del Sud, 62 via S. Sofia, 95125 Catania, ItalydUniversità degli Studi di Enna "Kore," Facoltà di Ingegneria, Architettura e delle Scienze Motorie, Cittadella Universitaria, 94100 Enna, Italia.
authors.forename: Marisa
authors.initials: M
authors.lastname: Gulino
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Adrian
authors.initials: A
authors.lastname: Iftime
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Ioana Teodora
authors.initials: IT
authors.lastname: Tofolean
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Alexandru
authors.initials: A
authors.lastname: Garaiman
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Alexandru
authors.initials: A
authors.lastname: Goicea
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Ruxandra
authors.initials: R
authors.lastname: Irimia
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Alexandru
authors.initials: A
authors.lastname: Dimancea
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Department of Biophysics, 8 Eroii Sanitari, 050474 Bucharest, Romania.
authors.forename: Constanta
authors.initials: C
authors.lastname: Ganea
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D042967:Electron Transport Complex I / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism; D005456:Fluorescent Dyes / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D019169:Jurkat Cells; D007700:Kinetics; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D009249:NADP / Q000737:chemistry / Q000378:metabolism; D012402:Rotenone / Q000494:pharmacology; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D005456:Fluorescent Dyes; D014475:Uncoupling Agents; D012402:Rotenone; D009243:NAD; D009249:NADP; D006861:Hydrogen Peroxide; D042967:Electron Transport Complex I