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The Hypoxic Ischemic Encephalopathy Model of Perinatal Ischemia
Published on: November 19, 2008
Hypoxia-ischemia brain damage disrupts brain cholesterol homeostasis in neonatal rats
1Department of Physiology, Dalian Medical University, Dalian, People's Republic of China.
Insights
Neonatal hypoxia-ischemia (HI) damages white matter development by disrupting brain cholesterol homeostasis and increasing inflammatory cytokines. Maintaining cholesterol balance may aid recovery from this brain injury.
Area of Science:
- Neuroscience
- Developmental Biology
- Biochemistry
Background:
- The initial 3 weeks of life are critical for oligodendrocyte development and a period of rapid central nervous system cholesterol increase in rats.
- Neonatal hypoxia-ischemia (HI) brain damage during this sensitive period can disrupt brain cholesterol balance and impair white matter development.
Purpose of the Study:
- To investigate the impact of neonatal hypoxia-ischemia (HI) on brain cholesterol homeostasis and white matter integrity in developing rats.
- To examine the role of inflammatory cytokines in HI-induced white matter injury.
Main Methods:
- Postnatal day 7 Sprague-Dawley rats were subjected to HI insult.
- Cholesterol levels in brain and plasma were measured.
- White matter integrity was assessed via myelin basic protein (MBP) immunostaining and electron microscopy.
- Brain tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) levels were quantified.
Main Results:
- HI significantly reduced brain cholesterol levels within three days post-insult, while plasma cholesterol remained unaffected.
- Marked reductions in MBP immunostaining and thinner myelinated axons indicated significant hypomyelination.
- Elevated brain TNF-alpha and IL-6 levels were observed 12 hours after HI.
Conclusions:
- Neonatal HI disrupts brain cholesterol homeostasis, contributing to white matter injury.
- Proinflammatory cytokines may play a role in oligodendrocyte damage and cholesterol imbalance.
- Therapeutic strategies aimed at restoring brain cholesterol balance could be beneficial for white matter recovery.
Purpose:
The first 3 weeks of life is the peak time of oligodendrocytes development and also the critical period of cholesterol increasing dramatically in central nervous system in rats. Neonatal hypoxia-ischemia (HI) brain damage happening in this period may disturb the brain cholesterol balance as well as white matter development.
Materials And Methods:
To test this hypothesis, postnatal day 7 (P7) Sprague-Dawley rats were subjected to HI insult. Cholesterol concentrations from brain and plasma were measured. White matter integrity was evaluated by densitometric analysis of myelin basic protein (MBP) immunostaining and electron microscopy. Brain TNF-alpha and IL-6 levels were also measured.
Results:
HI-induced brain cholesterol, but not the plasma cholesterol, levels decreased significantly during the first three days after HI compared with naïve and sham operated rats (p<0.05). Obvious hypomyelination was indicated by marked reductions in MBP immunostaining on both P10 and P14 (p<0.01) and less and thinner myelinated axons were detected on P21 by electron microscopy observation. High expressions of brain TNF-alpha and IL-6 12 h after HI (p<0.05) were also observed.
Discussion:
The present work provides evidence that HI insult destroyed brain cholesterol homeostasis, which might be important in the molecular pathology of hypoxic-ischemic white matter injury. Proinflammatory cytokines insulting oligodendrocytes, may cause cholesterol unbalance. Furthermore, specific therapeutic interventions to maintain brain cholesterol balance may be effective for the recovery of white matter function.
