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NMDA blockade attenuates caspase-3 activation and DNA fragmentation after neonatal hypoxia-ischemia
M Puka-Sundvall1, U Hallin, C Zhu
1Perinatal Center, Department of Physiology, Göteborg University, Sweden.
Abstract:
The aim was to study the effects of an NMDA receptor antagonist on caspase-3 activation and DNA fragmentation after hypoxia-ischemia (HI) in 7-day-old rats. Animals were treated with vehicle or MK-801 (0.5 mg/kg) directly after HI and sacrificed 8, 24 or 72h later. MK-801 reduced injury (by 53%), cells positive for active caspase-3 (by 39%) and DNA fragmentation (by 79%) in the cerebral cortex. Furthermore, MK-801 significantly decreased caspase-3 activity, and Western blots revealed a tendency towards decreased proteolytic cleavage of the caspase-3 proform. The data imply that NMDA receptors are involved in the activation of apoptotic processes in the immature brain after HI.
Insights
MK-801, an NMDA receptor antagonist, significantly reduced brain injury, caspase-3 activation, and DNA fragmentation in immature rats following hypoxia-ischemia (HI). This suggests NMDA receptors play a key role in apoptosis after HI in the developing brain.
Area of Science:
- Neuroscience
- Cellular Biology
- Developmental Biology
Background:
- Hypoxia-ischemia (HI) is a major cause of brain injury in newborns.
- Apoptosis, or programmed cell death, contributes significantly to neuronal loss after HI.
- NMDA receptors are implicated in excitotoxicity and neuronal damage.
Purpose of the Study:
- To investigate the neuroprotective effects of an NMDA receptor antagonist, MK-801, on apoptosis markers after HI in immature rats.
- To determine the role of NMDA receptors in caspase-3 activation and DNA fragmentation following HI.
Main Methods:
- Neonatal rats (7-day-old) were subjected to a hypoxia-ischemia (HI) model.
- Animals received either vehicle or MK-801 (0.5 mg/kg) post-HI.
- Cerebral cortex was analyzed 8, 24, and 72 hours after HI for injury, active caspase-3, and DNA fragmentation.
- Caspase-3 activity and procaspase-3 cleavage were assessed via Western blot.
Main Results:
- MK-801 treatment reduced overall brain injury by 53%.
- The number of cells positive for active caspase-3 decreased by 39% in MK-801 treated rats.
- DNA fragmentation was significantly reduced by 79% with MK-801 administration.
- MK-801 also decreased caspase-3 activity and showed a trend towards reduced procaspase-3 cleavage.
Conclusions:
- NMDA receptor antagonism with MK-801 confers significant neuroprotection against HI-induced brain injury in immature rats.
- NMDA receptor activation is critically involved in the apoptotic cascade, including caspase-3 activation and DNA fragmentation, in the developing brain post-HI.