title: Calcium-Induced Mitochondrial Permeability Transitions: Parameters of Ca2+Ion Interactions with Mitochondria and Effects of Oxidative Agents.
abstract: We evaluated the parameters of Ca2+-induced mitochondrial permeability transition (MPT) pore formations, Ca2+binding constants, stoichiometry, energy of activation, and the effect of oxidative agents, tert-butyl hydroperoxide (tBHP), and hypochlorous acid (HOCl), on Ca2+-mediated process in rat liver mitochondria. From the Hill plot of the dependence of MPT rate on Ca2+concentration, we determined the order of interaction of Ca2+ions with the mitochondrial sites, n = 3, and the apparent Kd= 60 ± 12 µM. We also found the apparent Michaelis-Menten constant, Km, for Ca2+interactions with mitochondria to be equal to 75 ± 20 µM, whereas that in the presence of 300 µM tBHP was 120 ± 20 µM. Using the Arrhenius plots of the temperature dependences of apparent mitochondrial swelling rate at various Ca2+concentrations, we calculated the activation energy of the MPT process. ΔEawas 130 ± 20 kJ/mol at temperatures below the break point of the Arrhenius plot (30-34 °C) and 50 ± 9 kJ/mol at higher temperatures. Ca2+ions induced rapid mitochondrial NADH depletion and membrane depolarization. Prevention of the pore formation by cyclosporin A inhibited Ca2+-dependent mitochondrial depolarization and Mg2+ions attenuated the potential dissipation. tBHP (10-150 µM) dose-dependently enhanced the rate of MPT opening, whereas the effect of HOCl on MPT depended on the ratio of HOCl/Ca2+. The apparent Kmof tBHP interaction with mitochondria in the swelling reaction was found to be Km= 11 ± 3 µM. The present study provides evidence that three calcium ions interact with mitochondrial site with high affinity during MPT. Ca2+-induced MPT pore formations due to mitochondrial membrane protein denaturation resulted in membrane potential dissipation. Oxidants with different mechanisms, tBHP and HOCl, reduced mitochondrial membrane potential and oxidized mitochondrial NADH in EDTA-free medium and had an effect on Ca2+-induced MPT onset.
authors.affiliation: Department of Biochemistry, Yanka Kupala State University of Grodno, Blvd. Len. Kom. - 50, 230030, Grodno, Belarus.
authors.forename: Nina G
authors.initials: NG
authors.lastname: Golovach
authors.affiliation: Department of Biochemistry, Yanka Kupala State University of Grodno, Blvd. Len. Kom. - 50, 230030, Grodno, Belarus.
authors.forename: Vitali T
authors.initials: VT
authors.lastname: Cheshchevik
authors.affiliation: Department of Biochemistry, Yanka Kupala State University of Grodno, Blvd. Len. Kom. - 50, 230030, Grodno, Belarus.
authors.forename: Elena A
authors.initials: EA
authors.lastname: Lapshina
authors.affiliation: Department of Biochemistry, Yanka Kupala State University of Grodno, Blvd. Len. Kom. - 50, 230030, Grodno, Belarus.
authors.forename: Tatsiana V
authors.initials: TV
authors.lastname: Ilyich
authors.affiliation: Department of Biochemistry, Yanka Kupala State University of Grodno, Blvd. Len. Kom. - 50, 230030, Grodno, Belarus. zavodnik_il@mail.ru.
authors.forename: Ilya B
authors.identifier: http://orcid.org/0000-0002-6130-787X
authors.initials: IB
authors.lastname: Zavodnik
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D006997:Hypochlorous Acid / Q000378:metabolism / Q000494:pharmacology*; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000187:drug effects* / Q000378:metabolism*; D000083162:Mitochondrial Permeability Transition Pore; D051381:Rats; D020122:tert-Butylhydroperoxide / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D006997:Hypochlorous Acid; D020122:tert-Butylhydroperoxide; D002118:Calcium
keywords: Calcium; Hypochlorous acid; Liver mitochondria; Mitochondrial permeability transition; Tert-butyl hydroperoxide