Reprint of: Ubisemiquinone Is the Electron Donor for Superoxide Formation by Complex III of Heart Mitochondria.

Much evidence indicates that superoxide is generated from O in a cyanide-sensitive reaction involving a reduced component of complex III of the mitochondrial respiratory chain, particularly when antimycin A is present. Although it is generally believed that ubisemiquinone is the electron donor to O, little experimental evidence supporting this view has been reported. Experiments with succinate as electron donor in the presence of antimycin A in intact rat heart mitochondria, which contain much superoxide dismutase but little catalase, showed that myxothiazol, which inhibits reduction of the Rieske iron-sulfur center, prevented formation of hydrogen peroxide, determined spectrophotometrically as the HO-peroxidase complex.

Suggested involvement of ketone bodies in the pathogenesis of the metabolic syndrome.

Untreated brain mitochondria are strong producers of H2O2. High peroxide production (in the presence of glutamate and pyruvate) is strictly succinate-dependent. Importantly, it is inhibited by the ketone body acetoacetate (AcAc) starting at 10 μM (maximal effect at 0.

The control of mitochondrial succinate-dependent H2O2 production.

In brain mitochondria succinate activates H(2)O(2) release, concentration dependently (starting at 15 μM), and in the presence of NAD dependent substrates (glutamate, pyruvate, β-hydroxybutyrate). We report that TCA cycle metabolites (citrate, isocitrate, α-ketoglutarate, fumarate, malate) individually and quickly inhibit H(2)O(2) release. When they are present together at physiological concentration (0.

Different effects of SNP and GSNO on mitochondrial O2 .- /H 2O2 production.

Sodium Nitroprusside (SNP) and S-Nitrosoglutathione (GSNO) differently affect mitochondrial H(2)O(2) release at Complex-I. mM SNP increases while GSNO decreases the release induced by succinate alone or added on top of NAD-linked substrates. Stimulation likely depends on Nitric Oxide ((.

Succinate is the controller of O2-/H2O2 release at mitochondrial complex I : negative modulation by malate, positive by cyanide.

Mitochondrial production of H(2)O(2) is low with NAD substrates (glutamate/pyruvate, 3 and 2 mM) (G/P) and increases over ten times upon further addition of succinate, with the formation of a sigmoidal curve (semimaximal value at 290 microM, maximal H(2)O(2) production at 600 microM succinate). Malate counteracts rapidly the succinate induced increased H(2)O(2) release and moves the succinate dependent H(2)O(2) production curve to the right. Nitric oxide (NO) and carbon monoxide (CO) are cytochrome c oxidase inhibitors which increase mitochondrial ROS production.

Clorgyline and other propargylamine derivatives as inhibitors of succinate-dependent H(2)O(2) release at NADH:UBIQUINONE oxidoreductase (Complex I) in brain mitochondria.

Complex I is the main O(2)(-) producer of the mitochondrial respiratory chain. O(2)(-) release is low with NAD-linked substrates and increases strongly during succinate oxidation, which increases the QH(2)/Q ratio and is rotenone sensitive. We show that the succinate dependent O(2)(-) production (measured as H(2)O(2) release) is inhibited by propargylamine containing compounds (clorgyline, CGP 3466B, rasagiline and TVP-1012).

Succinate modulation of H2O2 release at NADH:ubiquinone oxidoreductase (Complex I) in brain mitochondria.

Complex I (NADH:ubiquinone oxidoreductase) is responsible for most of the mitochondrial H2O2 release, both during the oxidation of NAD-linked substrates and during succinate oxidation. The much faster succinate-dependent H2O2 production is ascribed to Complex I, being rotenone-sensitive. In the present paper, we report high-affinity succinate-supported H2O2 generation in the absence as well as in the presence of GM (glutamate/malate) (1 or 2 mM of each).

Dopamine-derived dopaminochrome promotes H(2)O(2) release at mitochondrial complex I: stimulation by rotenone, control by Ca(2+), and relevance to Parkinson disease.

Inhibitors of Complex I of the mitochondrial respiratory chain, such as rotenone, promote Parkinson disease-like symptoms and signs of oxidative stress. Dopamine (DA) oxidation products may be implicated in such a process. We show here that the o-quinone dopaminochrome (DACHR), a relatively stable DA oxidation product, promotes concentration (0.

Respiration-dependent removal of exogenous H2O2 in brain mitochondria: inhibition by Ca2+.

In brain mitochondria, state 4 respiration supported by the NAD-linked substrates glutamate/malate in the presence of EGTA promotes a high rate of exogenous H2O2 removal. Omitting EGTA decreases the H2O2 removal rate by almost 80%. The decrease depends on the influx of contaminating Ca2+, being prevented by the Ca2+ uniporter inhibitor ruthenium red.