C. Giulivi et E. Cadenas, THE ROLE OF MITOCHONDRIAL GLUTATHIONE IN DNA-BASE OXIDATION, Biochimica et biophysica acta. Bioenergetics, 1366(3), 1998, pp. 265-274
The objective of this study was to elucidate the role of mitochondrial
GSH in the reactions leading to mitochondrial DNA oxidative damage in
terms of 8-hydroxy-desoxyguanosine (8-HOdG) accumulation. With this p
urpose, tightly coupled mitochondria depleted of matrix GSH were used
and the effects of H2O2 (generated during the oxidation of substrates)
on 8-HOdG levels were investigated. Mitochondrial integrity, assessed
by Oz uptake, respiratory control and P/O ratios, was conserved upon
depletion of GSH up to 95%. The rates of H2O2 production linked to the
oxidation of endogenous substrates by control and GSH-depleted mitoch
ondria were similar. Succinate (in the absence or presence of antimyci
n A) enhanced the rate H2O2 production to a similar extent in both con
trol and GSH-depleted mitochondria. These rates of H2O2 production acc
ounted for 1.5-2.5% of the rate of O-2 uptake. The levels of 8-HOdG in
GSH-depleted mitochondria were 35-50% lower than those in control mit
ochondria, when measured at different H2O2 production rates. Conversel
y, in experiments carried out with calf thymus DNA with different Cu/F
e content, GSH increased 1.4-2.4-fold the accumulation of 8-HOdG. Thes
e values were further enhanced (44-50%) by superoxide dismutase and de
creased by catalase. The lower levels of s-HOdG in GSH-depleted mitoch
ondria and the higher levels in GSH-supplemented calf thymus DNA sugge
st a role for the non-protein thiol in the reactions leading to mtDNA
oxidative damage. These findings are interpreted in terms of the redox
transitions involving O-2, GSH, and metal catalysts bound to DNA. A m
echanism is proposed by which GSH plays a critical role in the reducti
on of DNA-Cu complexes and decays by free radical pathways kinetically
regulated by superoxide dismutase. (C) 1998 Elsevier Science B.V. All
rights reserved.