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Depolarization of In Situ Mitochondria Due to Hydrogen Peroxide‐Induced Oxidative Stress in Nerve Terminals
Author(s) -
Chinopoulos Christos,
Tretter Laszlo,
AdamVizi Vera
Publication year - 1999
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1999.0730220.x
Subject(s) - oligomycin , rotenone , hydrogen peroxide , depolarization , membrane potential , respiratory chain , chemistry , mitochondrion , oxidative stress , biophysics , oxidative phosphorylation , atpase , biochemistry , biology , enzyme
Mitochondrial membrane potential (Δ? m ) was determined in intact isolated nerve terminals using the membrane potential‐sensitive probe JC‐1. Oxidative stress induced by H 2 O 2 (0.1‐1 m M ) caused only a minor decrease in Δ? m . When complex I of the respiratory chain was inhibited by rotenone (2 μ M ), Δ? m was unaltered, but on subsequent addition of H 2 O 2 , Δ? m started to decrease and collapsed during incubation with 0.5 m M H 2 O 2 for 12 min. The ATP level and [ATP]/[ADP] ratio were greatly reduced in the simultaneous presence of rotenone and H 2 O 2 . H 2 O 2 also induced a marked reduction in Δ? m when added after oligomycin (10 μ M ), an inhibitor of F 0 F 1 ‐ATPase. H 2 O 2 (0.1 or 0.5 m M ) inhibited α‐ketoglutarate dehydrogenase and decreased the steady‐state NAD(P)H level in nerve terminals. It is concluded that there are at least two factors that determine Δ? m in the presence of H 2 O 2 : (a) The NADH level reduced owing to inhibition of α‐ketoglutarate dehydrogenase is insufficient to ensure an optimal rate of respiration, which is reflected in a fall of Δ? m when the F 0 F 1 ‐ATPase is not functional. (b) The greatly reduced ATP level in the presence of rotenone and H 2 O 2 prevents maintenance of Δ? m by F 0 F 1 ‐ATPase. The results indicate that to maintain Δ? m in the nerve terminal during H 2 O 2 ‐induced oxidative stress, both complex I and F 0 F 1 ‐ATPase must be functional. Collapse of Δ? m could be a critical event in neuronal injury in ischemia or Parkinson’s disease when H 2 O 2 is generated in excess and complex I of the respiratory chain is simultaneously impaired.