Sequential opening of mitochondrial ion channels as a function of glutathione redox thiol status.

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Aon MA, Cortassa S, Maack C, O'Rourke B

Sequential opening of mitochondrial ion channels as a function of glutathione redox thiol status.

J Biol Chem. 2007 Jul 27;282(30):21889-900. Epub 2007 May 31.

PubMed ID

17540766 [ View in PubMed

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Abstract

Mitochondrial membrane potential (DeltaPsi(m)) depolarization contributes to cell death and electrical and contractile dysfunction in the post-ischemic heart. An imbalance between mitochondrial reactive oxygen species production and scavenging was previously implicated in the activation of an inner membrane anion channel (IMAC), distinct from the permeability transition pore (PTP), as the first response to metabolic stress in cardiomyocytes. The glutathione redox couple, GSH/GSSG, oscillated in parallel with DeltaPsi(m) and the NADH/NAD(+) redox state. Here we show that depletion of reduced glutathione is an alternative trigger of synchronized mitochondrial oscillation in cardiomyocytes and that intermediate GSH/GSSG ratios cause reversible DeltaPsi(m) depolarization, although irreversible PTP activation is induced by extensive thiol oxidation. Mitochondrial dysfunction in response to diamide occurred in stages, progressing from oscillations in DeltaPsi(m) to sustained depolarization, in association with depletion of GSH. Mitochondrial oscillations were abrogated by 4'-chlorodiazepam, an IMAC inhibitor, whereas cyclosporin A was ineffective. In saponin-permeabilized cardiomyocytes, the thiol redox status was systematically clamped at GSH/GSSG ratios ranging from 300:1 to 20:1. At ratios of 150:1-100:1, DeltaPsi(m) depolarized reversibly, and a matrix-localized fluorescent marker was retained; however, decreasing the GSH/GSSG to 50:1 irreversibly depolarized DeltaPsi(m) and induced maximal rates of reactive oxygen species production, NAD(P)H oxidation, and loss of matrix constituents. Mitochondrial GSH sensitivity was altered by inhibiting either GSH uptake, the NADPH-dependent glutathione reductase, or the NADH/NADPH transhydrogenase, indicating that matrix GSH regeneration or replenishment was crucial. The results indicate that GSH/GSSG redox status governs the sequential opening of mitochondrial ion channels (IMAC before PTP) triggered by thiol oxidation in cardiomyocytes.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
NADH	Glutathione reductase, mitochondrial	Protein	Humans	Unknown	Not Available	Details