title: Thioredoxin reductase-2 is essential for keeping low levels of H(2)O(2) emission from isolated heart mitochondria.
abstract: Respiring mitochondria produce H(2)O(2) continuously. When production exceeds scavenging, H(2)O(2) emission occurs, endangering cell functions. The mitochondrial peroxidase peroxiredoxin-3 reduces H(2)O(2) to water using reducing equivalents from NADPH supplied by thioredoxin-2 (Trx2) and, ultimately, thioredoxin reductase-2 (TrxR2). Here, the contribution of this mitochondrial thioredoxin system to the control of H(2)O(2) emission was studied in isolated mitochondria and cardiomyocytes from mouse or guinea pig heart. Energization of mitochondria by the addition of glutamate/malate resulted in a 10-fold decrease in the ratio of oxidized to reduced Trx2. This shift in redox state was accompanied by an increase in NAD(P)H and was dependent on TrxR2 activity. Inhibition of TrxR2 in isolated mitochondria by auranofin resulted in increased H(2)O(2) emission, an effect that was seen under both forward and reverse electron transport. This effect was independent of changes in NAD(P)H or membrane potential. The effects of auranofin were reproduced in cardiomyocytes; superoxide and H(2)O(2) levels increased, but similarly, there was no effect on NAD(P)H or membrane potential. These data show that energization of mitochondria increases the antioxidant potential of the TrxR2/Trx2 system and that inhibition of TrxR2 results in increased H(2)O(2) emission through a mechanism that is independent of changes in other redox couples.
authors.affiliation: Division of Cardiology, Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.
authors.forename: Brian A
authors.initials: BA
authors.lastname: Stanley
authors.forename: Vidhya
authors.initials: V
authors.lastname: Sivakumaran
authors.forename: Sa
authors.initials: S
authors.lastname: Shi
authors.forename: Iain
authors.initials: I
authors.lastname: McDonald
authors.forename: David
authors.initials: D
authors.lastname: Lloyd
authors.forename: Walter H
authors.initials: WH
authors.lastname: Watson
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Aon
authors.forename: Nazareno
authors.initials: N
authors.lastname: Paolocci
mesh_terms: D000818:Animals; D001310:Auranofin / Q000494:pharmacology; D004137:Dinitrochlorobenzene / Q000494:pharmacology; D004579:Electron Transport / Q000187:drug effects; D004734:Energy Metabolism / Q000187:drug effects; D057075:Enzyme Assays; D005978:Glutathione / Q000378:metabolism; D006168:Guinea Pigs; D006861:Hydrogen Peroxide / Q000378:metabolism*; D051379:Mice; D008929:Mitochondria, Heart / Q000187:drug effects / Q000201:enzymology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D061105:Peroxiredoxin III / Q000378:metabolism; D054482:Thioredoxin Reductase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013879:Thioredoxins / Q000378:metabolism
chemical_list: D004137:Dinitrochlorobenzene; D001310:Auranofin; D013879:Thioredoxins; D006861:Hydrogen Peroxide; D061105:Peroxiredoxin III; D054482:Thioredoxin Reductase 2; D005978:Glutathione