Neuroprotective effect of hydrogen peroxide on an in vitro model of brain ischaemia

Reactive oxygen species (ROS) have been postulated to play a crucial role in the pathogenesis of ischaemia-reperfusion injury. Among these, hydrogen peroxide (H(2)O(2)) is known to be a toxic compound responsible for free-radical-dependent neuronal damage. In recent years, however, the 'bad reputation' of H(2)O(2) and other ROS molecules has changed. The aim of this study was to assess the protective role of H(2)O(2) and modification in its endogenous production on the electrophysiological and morphological changes induced by oxygen/glucose deprivation (OGD) on CA1 hippocampal neurons.

Neuroprotective effects of exogenous and endogenous H(2)O(2) were determined using extracellular electrophysiological recordings of field excitatory post synaptic potentials (fEPSPs) and morphological studies in a hippocampal slice preparation. In vitro OGD was delivered by switching to an artificial cerebrospinal fluid solution with no glucose and with oxygen replaced by nitrogen.

Neuroprotection against in vitro OGD was observed in slices treated with H(2)O(2) (3 mM). The rescuing action of H(2)O(2) was mediated by catalase as pre-treatment with the catalase inhibitor 3-amino-1,2,4-triazole blocked this effect. More interestingly, we showed that an increase of the endogenous levels of H(2)O(2), due to a combination of an inhibitor of the glutathione peroxidase enzyme and addition of Cu,Zn-superoxide dismutase in the tissue bath, prevented the OGD-induced irreversible depression of fEPSPs.

Taken together, our results suggest new possible strategies to lessen the damage produced by a transient brain ischaemia by increasing the endogenous tissue level of H(2)O(2).