The participation of pyridine nucleotides redox state and reactive oxygen in the fatty acid-induced permeability transition in rat liver mitochondria

Abstract

The ability of low concentrations (5–15 μM) of long-chain fatty acids to open the permeability transition pore (PTP) in Ca 2+-loaded mitochondria has been ascribed to their protonophoric effect mediated by mitochondrial anion carriers, as well as to a direct interaction with the pore assembly [M.R. Wieckowski and L. Wojtczak, FEBS Lett. 423 (1998) 339–342]. Here, we have compared the PTP opening ability of arachidonic acid (AA) with that of carbonyl cyanide- p-trifluoromethoxyphenylhydrazone (FCCP) at concentrations that cause similar quantitative dissipation of the membrane potential (Δ Ψ) in Ca 2+-loaded rat liver mitochondria respiring on succinate. The initial protonophoric effects of AA and FCCP were only slightly modified by carboxyatractyloside and were followed by PTP opening, as indicated by a second phase of Δ Ψ disruption sensitive to EGTA, ADP, dithiothreitol and cyclosporin A. This second phase of Δ Ψ dissipation could also be prevented by rotenone or NAD(P)H-linked substrates which decrease the pyridine nucleotide (PN) oxidation that follows the stimulation of oxygen consumption induced by AA or FCCP. These results suggest that, under the experimental conditions used here, the PTP opening induced by AA or FCCP was a consequence of PN oxidation. Exogenous catalase also inhibited both AA- and FCCP-induced PTP opening. These results indicate that a condition of oxidative stress associated with the oxidized state of PN underlies membrane protein thiol oxidation and PTP opening.