Ambivalent effects of diazoxide on mitochondrial ROS production at respiratory chain complexes I and III

• Published in: Biochimica et biophysica acta Vol. 1790; no. 6; pp. 558 - 565
• Main Authors: Dröse, Stefan, Hanley, Peter J., Brandt, Ulrich
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2009
• Subjects: Animals; Cattle; Diazoxide; Diazoxide - pharmacology; Electron Transport Complex I - drug effects; Electron Transport Complex I - metabolism; Electron Transport Complex II - drug effects; Electron Transport Complex II - metabolism; Electron Transport Complex III - drug effects; Electron Transport Complex III - metabolism; Hydrogen Peroxide - metabolism; Mitochondria; Mitochondria, Heart - drug effects; Mitochondria, Heart - metabolism; Mitochondria, Heart - ultrastructure; Oxidants - metabolism; Pharmacological preconditioning; Rats; Reactive oxygen species; Reactive Oxygen Species - metabolism; Redox signaling; Respiratory chain; Submitochondrial Particles - drug effects; Submitochondrial Particles - metabolism; Vasodilator Agents - pharmacology; Reactive oxygen species; TCA cycle; HRP; SOD; FCCP; DBH; Diazoxide; 5-HD; Redox signaling; (mito)KATP channel; DBQ; Mitochondria; Respiratory chain; RCF; DQA; Pharmacological preconditioning; RHM; ROS; SMPs; Q-pool
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2009.01.011

Reactive oxygen species (ROS) are among the main determinants of cellular damage during ischemia and reperfusion. There is also ample evidence that mitochondrial ROS production is involved in signaling during ischemic and pharmacological preconditioning. In a previous study we analyzed the mitochondrial effects of the efficient preconditioning drug diazoxide and found that it increased the mitochondrial oxidation of the ROS-sensitive fluorescent dye 2′,7′-dichlorodihydrofluorescein (H2DCF) but had no direct impact on the H2O2 production of submitochondrial particles (SMP) or intact rat heart mitochondria (RHM). H2O2 generation of bovine SMP and tightly coupled RHM was monitored under different conditions using the amplex red/horseradish peroxidase assay in response to diazoxide and a number of inhibitors. We show that diazoxide reduces ROS production by mitochondrial complex I under conditions of reverse electron transfer in tightly coupled RHM, but stimulates mitochondrial ROS production at the Qo site of complex III under conditions of oxidant-induced reduction; this stimulation is greatly enhanced by uncoupling. These opposing effects can both be explained by inhibition of complex II by diazoxide. 5-Hydroxydecanoate had no effect, and the results were essentially identical in the presence of Na+ or K+ excluding a role for putative mitochondrial KATP-channels. A straightforward rationale is presented to mechanistically explain the ambivalent effects of diazoxide reported in the literature. Depending on the metabolic state and the membrane potential of mitochondria, diazoxide-mediated inhibition of complex II promotes transient generation of signaling ROS at complex III (during preconditioning) or attenuates the production of deleterious ROS at complex I (during ischemia and reperfusion).