Transcriptome profiling of the newborn mouse lung after hypoxia and reoxygenation: hyperoxic reoxygenation affects mTOR signaling pathway, DNA repair, and JNK-pathway regulation.

Background: The use of oxygen in acute treatment of asphyxiated term newborns is associated with increased mortality. It is unclear how hyperoxic reoxygenation after hypoxia affects transcriptional changes in the newborn lung.
Methods: On postnatal day 7, C57BL/6 mice (n = 62) were randomized to 120-min hypoxia (fraction of inspired oxygen (FiO2) 0.08) or normoxia. The hypoxia group was further randomized to reoxygenation for 30 min with FiO2 0.21, 0.40, 0.60, or 1.00, and the normoxia group to FiO2 0.21 or 1.00. Transcriptome profiling was performed on homogenized lung tissue using the Affymetrix 750k expression array, and validation was carried out by real-time polymerase chain reaction and enzyme-linked immunosorbent assay.
Results: The hypoxia-reoxygenation model induced hypoxia-inducible factor 1 (HIF-1) targets like Vegfc, Adm, and Aqp1. In total, ~70% of the significantly differentially expressed genes were detected in the two high hyperoxic groups (FiO2 0.60 and 1.00). Reoxygenation with 100% oxygen after hypoxia uniquely upregulated Gadd45g, Dusp1, Peg3, and Tgm2. Pathway analysis identified mammalian target of rapamycin (mTOR) signaling pathway, DNA repair, c-jun N-terminal kinase (JNK)-pathway regulation, and cell cycle after hyperoxic reoxygenation was applied.
Conclusion: Acute hypoxia induces HIF-1 targets independent of the reoxygenation regime applied. Hyperoxic reoxygenation affects pathways regulating cell growth and survival. DNA-damage-responsive genes are restricted to reoxygenation with 100% oxygen.