Exp Mol Med.  2007 Aug;39(4):556-563.

Ischemic preconditioning in the rat hippocampus increases antioxidant activities but does not affect the level of hydroxyl radicals during subsequent severe ischemia

• Choi YS
• Cho KO
• Kim EJ
• Sung KW
• Kim SY

Abstract

Several studies have demonstrated that ischemic preconditioning increases superoxide dismutase activity, but it is unclear how ischemic preconditioning affects events downstream of hydrogen peroxide production during subsequent severe ischemia and reperfusion in the hippocampus. To answer this question, we investigated whether ischemic preconditioning in the hippocampal CA1 region increases the activities of antioxidant enzymes glutathione peroxidase and catalase, resulting in a decrease in the level of hydroxyl radicals during subsequent severe ischemia-reperfusion. Transient forebrain ischemia was induced by four-vessel occlusion in rats. Ischemic preconditioning for 3 min or a sham operation was performed and a 15-min severe ischemia was induced three days later. Ischemic preconditioning preserved the CA1 hippocampal neurons following severe ischemia. The concentration of 2,3-dihydroxybenzoic acid, an indicator of hydroxyl radical, was measured using in vivo microdialysis technique combined with HPLC. The ischemia-induced increase in the ratio of 2,3-dihydroxybenzoic acid concentration relative to baseline did not differ significantly between preconditioned and control groups. On the other hand, activities of the antioxidant enzymes glutathione peroxidase-1 and catalase were significantly increased at 3 days after ischemic preconditioning in the hippocampus. Our results suggest that, in preconditioned rats, while hydrogen peroxide is generated from severe ischemia, the activity of catalase and glutathione peroxidase-1 is correspondingly increased to eliminate the excessive hydrogen peroxide. However, our results show that the enhanced activity of these antioxidant enzymes in preconditioned rats is not sufficient to decrease hydroxyl radical levels during subsequent severe ischemia-reperfusion.

Keyword

brain ischemia; catalase; glutathione peroxidase; hippocampus; hydroxyl radical; ischemic preconditioning

MeSH Terms

Animals
Antioxidants/*metabolism
Catalase/metabolism
Enzyme Activation
Glutathione Peroxidase/metabolism
Hippocampus/*blood supply
Hydrogen Peroxide/metabolism
Hydroxybenzoic Acids/metabolism
Hydroxyl Radical/*metabolism
Ischemic Attack, Transient/*metabolism/physiopathology/prevention & control
*Ischemic Preconditioning
Male
*Prosencephalon
Rats
Rats, Sprague-Dawley
Reperfusion Injury/metabolism/prevention & control