title: Isoflurane modulates cardiac mitochondrial bioenergetics by selectively attenuating respiratory complexes.
abstract: Mitochondrial dysfunction contributes to cardiac ischemia-reperfusion (IR) injury but volatile anesthetics (VA) may alter mitochondrial function to trigger cardioprotection. We hypothesized that the VA isoflurane (ISO) mediates cardioprotection in part by altering the function of several respiratory and transport proteins involved in oxidative phosphorylation (OxPhos). To test this we used fluorescence spectrophotometry to measure the effects of ISO (0, 0.5, 1, 2mM) on the time-course of interlinked mitochondrial bioenergetic variables during states 2, 3 and 4 respiration in the presence of either complex I substrate K(+)-pyruvate/malate (PM) or complex II substrate K(+)-succinate (SUC) at physiological levels of extra-matrix free Ca(2+) (~200nM) and Na(+) (10mM). To mimic ISO effects on mitochondrial functions and to clearly delineate the possible ISO targets, the observed actions of ISO were interpreted by comparing effects of ISO to those elicited by low concentrations of inhibitors that act at each respiratory complex, e.g. rotenone (ROT) at complex I or antimycin A (AA) at complex III. Our conclusions are based primarily on the similar responses of ISO and titrated concentrations of ETC. inhibitors during state 3. We found that with the substrate PM, ISO and ROT similarly decreased the magnitude of state 3 NADH oxidation and increased the duration of state 3 NADH oxidation, ΔΨm depolarization, and respiration in a concentration-dependent manner, whereas with substrate SUC, ISO and ROT decreased the duration of state 3 NADH oxidation, ΔΨm depolarization and respiration. Unlike AA, ISO reduced the magnitude of state 3 NADH oxidation with PM or SUC as substrate. With substrate SUC, after complete block of complex I with ROT, ISO and AA similarly increased the duration of state 3 ΔΨm depolarization and respiration. This study provides a mechanistic understanding in how ISO alters mitochondrial function in a way that may lead to cardioprotection.
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Bhawana
authors.initials: B
authors.lastname: Agarwal
authors.affiliation: Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA; Biotechnology and Bioengineering Center, Medical College of Wisconsin, Milwaukee, WI, USA; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Ranjan K
authors.initials: RK
authors.lastname: Dash
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, USA; Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI, USA; Research Service, Zablocki VA Medical Center, Milwaukee, WI, USA; Department of Biomedical Engineering, Marquette University, Milwaukee, WI, USA.
authors.forename: David F
authors.initials: DF
authors.lastname: Stowe
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, USA; Department of Physiology, Medical College of Wisconsin, Milwaukee, WI, USA; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Zeljko J
authors.initials: ZJ
authors.lastname: Bosnjak
authors.affiliation: Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, USA; Cardiovascular Research Center, Medical College of Wisconsin, Milwaukee, WI, USA.
authors.forename: Amadou K S
authors.initials: AK
authors.lastname: Camara
mesh_terms: D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D004579:Electron Transport / Q000187:drug effects; D042967:Electron Transport Complex I / Q000378:metabolism*; D042963:Electron Transport Complex II / Q000378:metabolism*; D014450:Electron Transport Complex III / Q000378:metabolism*; D004734:Energy Metabolism / Q000187:drug effects*; D007530:Isoflurane / Q000494:pharmacology*; D008293:Malates / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D008929:Mitochondria, Heart / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D008954:Models, Biological; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D019289:Pyruvic Acid / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012402:Rotenone / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D019802:Succinic Acid / Q000378:metabolism; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D008293:Malates; D014475:Uncoupling Agents; D012402:Rotenone; D009243:NAD; D000968:Antimycin A; C030298:malic acid; D019289:Pyruvic Acid; D019802:Succinic Acid; D007530:Isoflurane; D042963:Electron Transport Complex II; D042967:Electron Transport Complex I; D014450:Electron Transport Complex III
keywords: Cardiac IR injury; Cardioprotection; Electron transport chain; Isoflurane; Mitochondrial bioenergetics; Volatile anesthetic