Respiratory uncoupling by increased H+ or K+ flux is beneficial for heart mitochondrial turnover of reactive oxygen species but not for permeability transition
説明
<jats:title>Abstract</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>Ischemic preconditioning has been proposed to involve changes in mitochondrial H<jats:sup>+</jats:sup> and K<jats:sup>+</jats:sup> fluxes, in particular through activation of uncoupling proteins and ATP-sensitive K<jats:sup>+</jats:sup> channels (MitoK<jats:sub>ATP</jats:sub>). The objectives of the present study were to explore how increased H<jats:sup>+</jats:sup> and K<jats:sup>+</jats:sup> fluxes influence heart mitochondrial physiology with regard to production and scavenging of reactive oxygen species (ROS), volume changes and resistance to calcium-induced mitochondrial permeability transition (mPT).</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>Isolated rat heart mitochondria were exposed to a wide concentration range of the protonophore CCCP or the potassium ionophore valinomycin to induce increased H<jats:sup>+</jats:sup> and K<jats:sup>+</jats:sup> conductance, respectively. Simultaneous monitoring of mitochondrial respiration and calcium retention capacity (CRC) demonstrated that the relative increase in respiration caused by valinomycin or CCCP correlated with a decrease in CRC, and that no level of respiratory uncoupling was associated with enhanced resistance to mPT. Mitochondria suspended in hyperosmolar buffer demonstrated a dose-dependent reduction in CRC with increasing osmolarity. However, mitochondria in hypoosmolar buffer to increase matrix volume did not display increased CRC. ROS generation was reduced by both K<jats:sup>+</jats:sup>- and H<jats:sup>+</jats:sup>-mediated respiratory uncoupling. The ability of heart mitochondria to detoxify H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> was substantially greater than the production rate. The H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub> detoxification was dependent on respiratory substrates and was dramatically decreased following calcium-induced mPT, but was unaffected by uncoupling via increased K<jats:sup>+</jats:sup> and H<jats:sup>+</jats:sup> conductance.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusion</jats:title> <jats:p>It is concluded that respiratory uncoupling is not directly beneficial to rat heart mitochondrial resistance to calcium overload irrespective of whether H<jats:sup>+</jats:sup> or K<jats:sup>+</jats:sup> conductance is increased. The negative effects of respiratory uncoupling thus probably outweigh the reduction in ROS generation and a potential positive effect by increased matrix volume, resulting in a net sensitization of heart mitochondria to mPT activation.</jats:p> </jats:sec>
収録刊行物
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- BMC Cell Biology
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BMC Cell Biology 14 2013-09-22
Springer Science and Business Media LLC
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キーワード
- Carbonyl Cyanide m-Chlorophenyl Hydrazone
- Potassium Channels
- Respiratory Medicine and Allergy
- Mitochondrial Membrane Transport Proteins
- Mitochondria, Heart
- Oxidative Phosphorylation
- Permeability
- Potassium channels
- Animals
- Cardiac and Cardiovascular Systems
- Mitochondrial permeability transition
- Ischemic preconditioning
- Valinomycin
- Mitochondrial Permeability Transition Pore
- Uncoupling Agents
- Diazoxide
- Osmolar Concentration
- Cell Biology
- Hydrogen Peroxide
- Cations, Monovalent
- Rats
- Oxygen
- Neurology
- Respiratory uncoupling
- Cyclosporine
- Potassium
- Proton Ionophores
- Calcium
- Protons
- Reactive oxygen species
- Mitochondrial Swelling
- Reactive Oxygen Species
- Research Article