Oxidative DNA damage and alteration of glutamate transporter expressions in the hippocampal Ca1 area immediately after ischemic insult

Abstract

Although oxidative stress and excitotoxicity may be interdependent mechanisms that are involved in delayed neuronal death, the temporal participation of these events in the early stage after ischemia-reperfusion insult is unclear. Therefore, in the present study, using the gerbil global ischemic model we investigated whether oxidative stress could be correlated with the expression of the glutamate transporters in the hippocampus, and whether these events are related and cooperate in the events that link ischemia to neuronal death in vivo. Thirty minutes after ischemia, the intensities of glutamate transporter-1 (GLT-1), glutamate/aspar-tate transporter (GLAST), and 8-hydroxy2'-deoxy-guanosine (8-OHdG) immunoreactivities were markedly increased in the hippocampal CA1 area. In contrast, excitatory amino acid carrier-1 (EAAC-1) immunoreactivity was 30% lower in the CA1 area than in the sham level. At 3 h post-reperfusion, the EAAC-1 expression began to increase in the CA1 area. Twelve hours after reperfusion, the reduction of both GLT-1 and GLAST immunoreactivity was salient, while the EAAC-1 immunoreactivity level intensified significantly. The 8-OHdG immunoreactivity peaked at this time point. These findings suggest that oxidative stress and alterations in the glutamate transporter expression in the CA1 area may simultaneously trigger neuronal damages very early after ischemia.