Related Experiment Videos
Hyperoxia causes inducible nitric oxide synthase-mediated cellular damage to the immature rat brain
Thomas Hoehn1, Ursula Felderhoff-Mueser, Katja Maschewski
1Neonatology and Pediatric Intensive Care, University Children's Hospital, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany. thomas.hoehn@uni-duesseldorf.de
Insights
Relative hyperoxia increases inducible nitric oxide synthase (iNOS) in premature rat brains, particularly in microglial cells. This suggests potential cellular damage via peroxynitrite formation in the developing neonatal brain.
Area of Science:
- Neuroscience
- Neonatal Physiology
- Cellular Biology
Background:
- Relative hyperoxia is common in premature infants, impacting neonatal intensive care unit (NICU) treatments.
- The effects of high oxygen on immature brain cells and signaling pathways remain largely unknown.
Purpose of the Study:
- To investigate hyperoxia's impact on inducible nitric oxide synthase (iNOS) expression in immature rat brains.
- To map the distribution of iNOS and peroxynitrite formation, a marker of cellular damage, in immature cerebral structures.
Main Methods:
- Seven-day-old Wistar rat pups exposed to >80% oxygen for 24 hours.
- Immunohistochemical staining for iNOS and nitrotyrosine, Western blot for iNOS protein, and RT-PCR for iNOS mRNA.
- Analysis of total brain iNOS mRNA, protein expression, and topographic distribution of iNOS and nitrotyrosine.
Main Results:
- Hyperoxia significantly up-regulated iNOS mRNA and protein in the immature rat brain.
- iNOS expression was primarily localized in microglial cells of the hippocampus and frontal cortex.
- Positive neuronal nitrotyrosine staining in the frontal cortex indicated peroxynitrite formation.
Conclusions:
- Hyperoxia induces iNOS up-regulation in microglial cells of the immature rat brain.
- Neuronal nitrotyrosine staining suggests peroxynitrite formation, potentially causing deleterious effects on immature brain structures.
- Findings highlight the risks of hyperoxia in neonatal brain development.
Abstract:
Relative hyperoxia is a condition frequently encountered in premature infants, either spontaneously or during treatment in the Neonatal Intensive Care Unit. The effects of high inspiratory oxygen concentrations on immature brain cells and their signaling cascades are largely unknown. The aim of the study was to investigate the effect of hyperoxia on the amount and topographic distribution of iNOS-expression (inducible nitric oxide synthase) in the immature rat brain, and to localize hyperoxia-induced formation of peroxynitrite as a potential marker of cellular damage to immature cerebral structures. Seven-day-old Wistar rat pups were exposed to >80% oxygen for 24 h and were then transcardially perfused. Following paraformaldehyde fixation, brains were paraffin-embedded and immunohistochemically stained for iNOS and nitrotyrosine. iNOS protein was quantified by Western blot; iNOS mRNA expression was studied by RT-PCR. Total brain iNOS mRNA was up-regulated, demonstrating a peak at 6 h following the onset of hyperoxia. Immunohistochemical staining was predominantly observed in microglial cells of hippocampus and frontal cortex with some iNOS reactivity in endothelial and perivascular cells. Nitrotyrosine staining was positive in apical dendrites of neurons in the frontal cortex. There was no positive staining for iNOS or nitrotyrosine in control animals. Hyperoxia causes iNOS mRNA and protein up-regulation in microglial cells of the immature rat brain. Positive neuronal nitrotyrosine staining indicates formation of peroxynitrite with potential deleterious effects for immature cellular structures in the neonatal brain.