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Ischemic tolerance and lipid peroxidation in the brain
1Department of Pharmacology, Faculty of Medicine, National University of Singapore, Singapore.
Abstract:
Using a modified method of focal ischemic preconditioning (FIP) followed by permanent middle cerebral artery occlusion (MCAO), we studied the effects of ischemic tolerance on infarct volume. The FIP was achieved by obstructing the blood flow into the MCA using miniature clamps at two points simultaneously. The first point was proximal to its origin and the second was where it intersects the middle cerebral vein. In rats subjected to three short conditioning periods (3 x 3 min with 7 min reperfusion between occlusions), there were significant reductions in the infarct volume in the cerebral cortex induced by the subsequent MCAO in FIP-treated rats compared with sham-operated controls. This rapid FIP-induced ischemic tolerance to subsequent MCAO occurred within 1 day and lasted for 5 days. Tissue lipid peroxidation in the cortex was significantly reduced for up to 2 days after FIP. In contrast, lipid peroxidation increased rapidly after MCAO. A significant reduction in this increase was observed in FIP-treated rats, suggesting a correlation with the subsequent reduction in the infarct volume.
Insights
Focal ischemic preconditioning (FIP) in rats significantly reduces brain infarct volume after middle cerebral artery occlusion (MCAO). This protective effect, observed within one day, lasts for five days, correlating with reduced lipid peroxidation.
Area of Science:
- Neuroscience
- Ischemic Stroke Research
- Cerebrovascular Biology
Background:
- Ischemic tolerance is a neuroprotective phenomenon that can be induced by brief periods of ischemia.
- Understanding the mechanisms and duration of ischemic tolerance is crucial for developing therapeutic strategies against stroke.
Purpose of the Study:
- To investigate the efficacy of a modified focal ischemic preconditioning (FIP) method in reducing infarct volume following permanent middle cerebral artery occlusion (MCAO) in a rat model.
- To determine the time course and duration of FIP-induced ischemic tolerance.
- To assess the role of lipid peroxidation in FIP-mediated neuroprotection.
Main Methods:
- A modified FIP protocol involving temporary occlusion of the middle cerebral artery (MCA) at two points was applied to rats.
- Permanent MCAO was induced to create an ischemic stroke model.
- Infarct volume in the cerebral cortex was measured and compared between FIP-treated rats and sham-operated controls.
- Tissue lipid peroxidation levels were assessed at various time points post-FIP and post-MCAO.
Main Results:
- FIP treatment resulted in a significant reduction in cerebral infarct volume following permanent MCAO compared to controls.
- The neuroprotective effect of FIP was observed within 1 day and persisted for up to 5 days.
- FIP significantly reduced cortical lipid peroxidation for up to 2 days post-procedure, and attenuated the rapid increase in lipid peroxidation following MCAO.
Conclusions:
- A modified FIP protocol can rapidly induce a robust and sustained ischemic tolerance against focal cerebral ischemia in rats.
- Reduced lipid peroxidation appears to be a key mechanism contributing to FIP-induced neuroprotection.
- This study highlights the potential of FIP as a pre-stroke therapeutic intervention.