A role for the
antioxidants vitamin E and
idebenone in decreasing
retinal cell injury, after metabolic inhibition induced by chemical
ischemia and
hypoglycemia, was investigated and compared with oxidative stress conditions. Preincubation of the
antioxidants,
vitamin E (20 microM) and
idebenone (10 microM), effectively protected from
retinal cell injury after oxidative stress or
hypoglycemia, whereas the protection afforded after postincubation of both
antioxidants was decreased. Delayed
retinal cell damage, mediated by chemical
ischemia, was attenuated
at 10 or 12 h postischemia, only after exposure to the
antioxidants during all the experimental procedure. An antagonist of the
N-methyl-D-aspartate (
NMDA) receptors, an inhibitor of
nitric oxide synthase (NOS) or a blocker of L-type Ca2+ channels were ineffective in reducing cell injury induced by chemical
ischemia,
hypoglycemia or oxidative stress. Oxidative stress and
hypoglycemia increased (about 1.2-fold) significantly the fluorescence of the probe DCFH2-DA, that is indicative of intracellular ROS formation.
Free radical generation detected with the probe
dihydrorhodamine 123 (DHR 123) was enhanced after oxidative stress, chemical
ischemia or
hypoglycemia (about 2-fold). Nevertheless, the
antioxidants vitamin E or
idebenone were ineffective against intracellular ROS generation. Cellular energy charge decreased greatly after chemical
ischemia, was moderately affected after
hypoglycemia, but no significant changes were observed after oxidative stress. Preincubation with
vitamin E prevented the changes in energy charge upon 6 h posthypoglycemia. We can conclude that irreversible changes occurring during chemical
ischemia mainly reflect the alterations taking place at the ischemic core, whereas
hypoglycemia situations may reflect changes occurring at the penumbra area, whereby
vitamin E or
idebenone may help to increase cell survival, exerting a beneficial
neuroprotective effect.