title: High Ca2+ load promotes hydrogen peroxide generation via activation of α-glycerophosphate dehydrogenase in brain mitochondria.
abstract: H(2)O(2) generation associated with α-glycerophosphate (α-GP) oxidation was addressed in guinea pig brain mitochondria challenged with high Ca(2+) load (10 μM). Exposure to 10 μM Ca(2+) induced an abrupt 2.5-fold increase in H(2)O(2) release compared to that measured in the presence of a physiological cytosolic Ca(2+) concentration (100 nM) from mitochondria respiring on 5 mM α-GP in the presence of ADP (2 mM). The Ca(2+)-induced stimulation of H(2)O(2) generation was reversible and unaltered by the uniporter blocker Ru 360, indicating that it did not require Ca(2+) uptake into mitochondria. Enhanced H(2)O(2) generation by Ca(2+) was also observed in the absence of ADP when mitochondria exhibited permeability transition pore opening with a decrease in the NAD(P)H level, dissipation of membrane potential, and mitochondrial swelling. Furthermore, mitochondria treated with the pore-forming peptide alamethicin also responded with an elevated H(2)O(2) generation to a challenge with 10 μM Ca(2+). Ca(2+)-induced promotion of H(2)O(2) formation was further enhanced by the complex III inhibitor myxothiazol. With 20 mM α-GP concentration, stimulation of H(2)O(2) formation by Ca(2+) was detected only in the presence, not in the absence, of ADP. It is concluded that α-glycerophosphate dehydrogenase, which is accessible to and could be activated by a rise in the level of cytosolic Ca(2+), makes a major contribution to Ca(2+)-stimulated H(2)O(2) generation. This work highlights a unique high-Ca(2+)-stimulated reactive oxygen species-forming mechanism in association with oxidation of α-GP, which is largely independent of the bioenergetic state and can proceed even in damaged, functionally incompetent mitochondria.
authors.affiliation: Department of Medical Biochemistry, Semmelweis University, Budapest H-1444, Hungary.
authors.forename: Laszlo
authors.initials: L
authors.lastname: Tretter
authors.forename: Vera
authors.initials: V
authors.lastname: Adam-Vizi
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism / Q000502:physiology; D000408:Alamethicin / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000378:metabolism; D002118:Calcium / Q000502:physiology*; D014450:Electron Transport Complex III / Q000037:antagonists & inhibitors / Q000378:metabolism; D004734:Energy Metabolism; D004789:Enzyme Activation; D005993:Glycerolphosphate Dehydrogenase / Q000378:metabolism*; D005994:Glycerophosphates / Q000378:metabolism / Q000502:physiology; D006168:Guinea Pigs; D006861:Hydrogen Peroxide / Q000378:metabolism*; D008297:Male; D053078:Membrane Potential, Mitochondrial; D008689:Methacrylates / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D010101:Oxygen Consumption; D013844:Thiazoles / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
chemical_list: D005994:Glycerophosphates; D008689:Methacrylates; D013844:Thiazoles; D014475:Uncoupling Agents; D000408:Alamethicin; D000244:Adenosine Diphosphate; C030517:myxothiazol; C029620:alpha-glycerophosphoric acid; D006861:Hydrogen Peroxide; D005993:Glycerolphosphate Dehydrogenase; D014450:Electron Transport Complex III; D002118:Calcium