Transcriptome profiling of the newborn mouse lung response to acute ozone exposure

Ozone is a major air pollutant in highly populated areas. High levels of ambient ozone have been associated with decreased lung function and increased exacerbations of asthma in children and adults. However, the effects of ozone on the newborn’s lung are largely unknown. This study was aimed at profiling the newborn lung response to ozone at the transcriptome level to define the impact of ozone pollutant on the developing postnatal lung. Newborn mice were exposed to ozone or filtered normal air for 3 h. Total RNA was isolated from lung tissues at 6 and 24 h after completion of exposure and was subjected to gene expression analysis using Whole Mouse Genome Gene Expression 4X44K Microarrays (G2519F-014868, Agilent Technologies). Transcriptome analysis of the postnatal lung indicated that 455 genes were down-regulated and 166 genes were up-regulated by at least 1.5 fold at 6 h post-ozone exposure (t-test, p<0.05). At 24 h post exposure, 543 genes were down-regulated and 323 genes were up-regulated in the lungs of ozone-exposed newborn mice, compared to filtered air-exposed newborn mice (t-test, p<0.05). After controlling for false discovery rate, 50 genes were significantly down-regulated and only 4 genes were up-regulated at 24 h post ozone-exposure (q<0.05). Gene ontology enrichment analysis revealed that cell cycle-associated functions including cell division/proliferation, cellular assembly and organization were the predominant pathways negatively regulated by ozone exposure. These findings suggest that elevated ozone pollution may interfere with lung development and growth in the early age. Three-day old BALB/c mice were exposed for 3 h to ozone (1000 parts per billion). Age-matching littermate controls were exposed for 3 h to filtered normal air. Whole lung tissue was collected 6 and 24 h after completion of exposure to ozone or filtered air and was subjected to microarray analysis. Each time point was performed separately with its own filtered air littermate controls. Pups were cross-fostered during exposure so that all pups were with a dam during exposure. A total of 6-8 mice were initially included in each group and time point. Of these, n=4 mouse lungs were randomly selected for use in gene expression analysis.