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Mice Exposed in situ to Urban Air Pollution Exhibit Pulmonary Alterations in Lipid Droplet Synthesis Pathways

ABSTRACT: In the present study, we investigate pulmonary transcriptional responses in mice following exposure in situ to ambient air in a heavily polluted urban environment. Mature C57BL/CBA male mice were caged in sheds located in an urban area near two working steel mills and a major highway in Hamilton, Ontario, Canada. Control mice were housed in the same environment but received only high-efficiency particle-filtered air. Whole lung tissues were collected from mice exposed for 3 weeks, 10 weeks or for 10 weeks followed by 6 weeks in the laboratory (16 weeks total). DNA microarrays were used to explore changes in pulmonary gene expression in mice breathing ambient air versus HEPA-filtered air. Transcriptional profiling revealed changes in the expression of genes implicated in the lipid droplet synthesis pathway (plin, dgat2, lpl, s3-12, agpat2), antioxidants (ucp1). We postulate that exposure to particulate matter adsorbed with polycyclic aromatic hydrocarbons triggers lipid droplet synthesis (holding depots for lipids and malformed/excess proteins tagged for degradation) in the lungs, which act to sequester particulates adsorbed with toxic chemicals. Increased lipid droplet synthesis could potentially lead to endogenous/stressor-induced synthesis of reactive oxygen species and activation of antioxidant mechanisms. Further investigation into the stimulation of lipid droplet synthesis in the lung in response to air pollution is warranted in order to better understand these mechanistic changes and the resulting health implications.

ORGANISM(S): Mus musculus

PROVIDER: GSE41698 | GEO | 2013/09/30

SECONDARY ACCESSION(S): PRJNA178025

REPOSITORIES: GEO

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Project description:In the present study, we investigate pulmonary transcriptional responses in mice following exposure in situ to ambient air in a heavily polluted urban environment. Mature C57BL/CBA male mice were caged in sheds located in an urban area near two working steel mills and a major highway in Hamilton, Ontario, Canada. Control mice were housed in the same environment but received only high-efficiency particle-filtered air. Whole lung tissues were collected from mice exposed for 3 weeks, 10 weeks or for 10 weeks followed by 6 weeks in the laboratory (16 weeks total). DNA microarrays were used to explore changes in pulmonary gene expression in mice breathing ambient air versus HEPA-filtered air. Transcriptional profiling revealed changes in the expression of genes implicated in the lipid droplet synthesis pathway (plin, dgat2, lpl, s3-12, agpat2), antioxidants (ucp1). We postulate that exposure to particulate matter adsorbed with polycyclic aromatic hydrocarbons triggers lipid droplet synthesis (holding depots for lipids and malformed/excess proteins tagged for degradation) in the lungs, which act to sequester particulates adsorbed with toxic chemicals. Increased lipid droplet synthesis could potentially lead to endogenous/stressor-induced synthesis of reactive oxygen species and activation of antioxidant mechanisms. Further investigation into the stimulation of lipid droplet synthesis in the lung in response to air pollution is warranted in order to better understand these mechanistic changes and the resulting health implications. Mature male C57BL/6 x CBA F1 hybrid mice were exposed to either HEPA-filtered or ambient air in Hamilton, ON, Canada. Animals were exposed starting May 14, 2004 for 3 weeks (3wk), 10 weeks (10wk), or for 10 weeks followed by 6 weeks of recovery (16wk). Each treatment group consisted of five mice, for a total of 30 mice. Total RNA was isolated from a random section of the whole lung using TRIzol reagent (Invitrogen) and purified using the RNeasy Mini Kit (Qiagen). RNA quality was confirmed by UV spectrophotometry and using an Agilent Bioanalyzer. Total RNA (200 ng) from HEPA-filtered air or whole air-exposed mice and Universal Mouse Reference RNA (Stratagene) were used to synthesize double-stranded cDNA and cyanine-labelled cRNA according to the manufacturer's instructions (Agilent Linear Amplification Kits, Agilent Technologies). Biological samples were labelled with Cy5 dye while the commercially available Stratagene mouse reference RNA was labelled with Cy3 dye. At each of the three time points, ambient air-exposed samples and HEPA-filtered samples were hybridized to Agilent microarrays. Arrays were washed, and scanned on an Agilent G2505B scanner. Data were acquired using the Agilent Feature Extraction software version 9.5.3.1.

Project description: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 newbornM-bM-^@M-^Ys 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.

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Mice Exposed in situ to Urban Air Pollution Exhibit Pulmonary Alterations in Lipid Droplet Synthesis Pathways

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