Temporal Patterns of Gene Expression Profiles in the Neonatal Mouse Lung after Hypoxia-Reoxygenation

Abstract

Background: One out of four children with neonatal asphyxia has lung involvement. Still, there has been little research on injury mechanisms of hypoxia-reoxygenation in the neonatal lung. Objectives: To make a temporal profile of the gene expression changes of 44 a priori selected genes after hypoxia-reoxygenation in the newborn mouse lung, and to compare the changes after hyperoxic and normoxic reoxygenation. Methods: Postnatal day 7 mice were randomized to 2-hour hypoxia (8% O₂) and 30-min reoxygenation in either 60% O₂ or air. After 0-72 h of observation, gene expression changes and protein concentrations in whole lung homogenates were examined. Results: Immediately after completed reoxygenation, 7 genes of mediators of inflammation were downregulated, and there was an antiapoptotic gene expression pattern. Three DNA glycosylases were downregulated, while genes involved in cell cycle renewal indicated both increased and decreased cell cycle arrest. Sod1 (T2.5h median H60: 1.01, H21: 0.88, p = 0.005; T5h median H60: 1.04, H21: 0.85, p = 0.038) and Il1b (T0h median H60: 0.86, H21: 1.08, p = 0.021) were significantly differentially expressed when comparing hyperoxic and normoxic reoxygenation. Conclusion: In this newborn mouse lung hypoxia-reoxygenation model, we found downregulation of genes of mediators of inflammation, an antiapoptotic gene expression pattern, and downregulation of DNA glycosylases. Sod1 and Il1b were significantly differentially expressed when comparing reoxygenation using 60% O₂ with air.

Oxygen therapy of the newborn from molecular understanding to clinical practice

“…An indication of DNA-damage response includes the up-regulation of nucleotide excision repair mechanisms after hyperoxic (60% O 2 ) reoxygenation. Conversely, DNA polymerase is down-regulated by hyperoxia, leading to reduction of DNA replication 78 and hyperoxic reoxygenation induces a stronger brain inflammatory gene response than reoxygenation with air. 79 Chen et al 80 studied epigenetic changes in the lungs of newborn rats breathing either air or 85% O 2 from day 1 to 14.…”

Neonatal Ogg1/Mutyh knockout mice have altered inflammatory gene response compared to wildtype mice in the brain and lung after hypoxia-reoxygenation

“…One hundred and twenty-four pups were used in the experiments [OM n = 44, WT n = 63, mortality OM n = 6 (12%), WT n = 11 (15%)]. For 42 of the WT mice, the gene expression changes in the brain and the lungs have been reported previously [16,17].…”

“…Total RNA was extracted from the hippocampus/striatum or whole lung homogenates, reverse transcribed to cDNA and amplified as described previously [20]. Polr2a and Ubc were chosen as reference genes in the brain samples and Actb and Ubc in the lung samples, based on an endogenous control pilot [16,17]. Custom TaqMan array microfluidic cards (Thermo Fisher Scientific, Waltham, MA, USA) were designed with 44 target genes suitable for brain and lung tissue [list of assays in Supplementary Methods (online)], three reference genes and one manufacturer control.…”

“…The brain and the lung are frequently affected after neonatal asphyxia [14], and the hippocampus and striatum are especially vulnerable to hypoxia-reoxygenation insults [15]. We have previously reported the temporal patterns of gene expression in the hippocampus/striatum and lung of WT mice subjected to hypoxia-reoxygenation [16,17]. In the brain, hyperoxic reoxygenation resulted in an augmented stress and inflammatory gene response, and decreased downregulation of the DNA glycosylase Neil3 [16].…”

“…In the brain, hyperoxic reoxygenation resulted in an augmented stress and inflammatory gene response, and decreased downregulation of the DNA glycosylase Neil3 [16]. In the lung, hypoxia-reoxygenation showed an early downregulation of inflammatory and BER pathway genes and an antiapoptotic gene expression pattern [17]. To explore the effect of oxidative DNA damage after hypoxia-reoxygenation, we studied the differences in gene expression in the hippocampus/striatum and lung after hypoxia-reoxygenation in OM mice compared to WT.…”