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Reduction and restoration of mitochondrial dna content after focal cerebral ischemia/reperfusion
1Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St Louis, MO 63110, USA.
Background And Purpose:
Oxidative damage of mitochondrial DNA (mtDNA) in the ischemic brain is expected after ischemia/reperfusion injury. A recent study demonstrated limited patterns of mtDNA deletion in the brain after ischemia/reperfusion. We studied the ischemia/reperfusion-induced global changes of mtDNA integrity and its restoration in a rat model of transient focal ischemia in vivo.
Methods:
Changes in mtDNA content in the ischemic brain were assessed with the use of a rat stroke model featuring transient severe ischemia confined to the cerebral cortex of the right middle cerebral artery territory for 30 or 90 minutes. A new long polymerase chain reaction method, using mouse DNA as an internal standard, was applied to measure the relative content of intact rat mtDNA. Southern hybridization following alkaline gel electrophoresis was conducted in a parallel study to confirm long polymerase chain reaction results.
Results:
A reduction in mtDNA content was found after ischemia for 30 and 90 minutes. The mtDNA was restored to near nonischemic levels 24 hours after 30- but not 90-minute ischemia.
Conclusions:
These results confirm that ischemia/reperfusion causes mtDNA damages. Restoration of the mtDNA content to nonischemic levels after 30-minute ischemia raises the possibility that mtDNA repair or repletion occurs after brief ischemia.
Insights
Ischemia/reperfusion injury reduces mitochondrial DNA (mtDNA) content in the brain. Following brief ischemia, mtDNA levels restored, suggesting potential repair mechanisms after stroke.
Area of Science:
- Neuroscience
- Mitochondrial Biology
- Stroke Research
Background:
- Ischemia/reperfusion injury in the brain is known to cause oxidative damage to mitochondrial DNA (mtDNA).
- Previous studies indicated limited mtDNA deletion patterns post-ischemia/reperfusion.
- The current study investigates global changes and restoration of mtDNA integrity following transient focal ischemia.
Purpose of the Study:
- To examine ischemia/reperfusion-induced global changes in mtDNA integrity.
- To assess the restoration of mtDNA content after transient focal cerebral ischemia in a rat model.
- To investigate the potential for mtDNA repair or repletion after brief ischemic events.
Main Methods:
- Utilized a rat stroke model with transient focal cerebral ischemia (30 or 90 minutes).
- Employed a novel long polymerase chain reaction (PCR) method with a mouse DNA internal standard to quantify intact rat mtDNA.
- Confirmed PCR findings using Southern hybridization following alkaline gel electrophoresis.
Main Results:
- A significant reduction in mtDNA content was observed in the ischemic brain after both 30 and 90 minutes of ischemia.
- mtDNA levels were restored to near non-ischemic levels 24 hours after 30-minute ischemia.
- However, mtDNA content did not recover to baseline levels after 90-minute ischemia.
Conclusions:
- The findings confirm that ischemia/reperfusion injury leads to damage and reduction of mtDNA.
- The restoration of mtDNA content after 30-minute ischemia suggests a potential for endogenous repair or repletion mechanisms.
- Prolonged ischemia (90 minutes) impaired the recovery of mtDNA integrity, highlighting the impact of ischemic duration.
