Context: Exposure to single pollutants e.g. particulate matter (PM) is associated with adverse health effects, but it does not represent a real world scenario that usually involves multiple pollutants. Objectives: Determine if simultaneous exposure to PM and NO₂ results in synergistic interactions. Materials and methods: Healthy young volunteers were exposed to clean air, nitrogen dioxide (NO₂, 0.5 ppm), concentrated fine particles from Chapel Hill air (PM_2.5CAPs, 89.5 ± 10.7 µg/m³), or NO₂+PM_2.5CAPs for 2 h. Each subject performed intermittent exercise during the exposure. Parameters of heart rate variability (HRV), changes in repolarization, peripheral blood endpoints and lung function were measured before and 1 and 18 h after exposure. Bronchoalveolar lavage (BAL) was performed 18 h after exposure. Results: NO₂ exposure alone increased cholesterol and HDL 18 h after exposure, decreased high frequency component of HRV one and 18 h after exposure, decreased QT variability index 1 h after exposure, and increased LDH in BAL fluid. The only significant change with PM_2.5CAPs was an increase in HDL 1 h after exposure, likely due to the low concentrations of PM_2.5CAPs in the exposure chamber. Exposure to both NO₂ and PM_2.5CAPs increased BAL α1-antitrypsin, mean t wave amplitude, the low frequency components of HRV and the LF/HF ratio. These changes were not observed following exposure to NO₂ or PM_2.5CAPs alone, suggesting possible interactions between the two pollutants. Discussion and conclusions: NO₂ exposure may produce and enhance acute cardiovascular effects of PM_2.5CAPs. Assessment of health effects by ambient PM should consider its interactions with gaseous copollutants.

Coarse, fine, and ultrafine particulate matter (PM) fractions possess different physical properties and chemical compositions and may produce different adverse health effects. Studies were undertaken to determine whether or not gene expression patterns may be used to discriminate among the three size fractions. Airway epithelial cells obtained from 6 normal individuals were exposed to Chapel Hill coarse, fine or ultrafine PM (250 μg/ml) for 6 and 24 h (n = 3 different individuals each). RNA was isolated and hybridized to Affymetrix cDNA microarrays. Significant genes were identified and mapped to canonical pathways. Expression of selected genes was confirmed by reverse-transcription polymerase chain reaction (RT-PCR). The numbers of genes altered by coarse, fine, and ultrafine PM increased from 0, 6, and 17 at 6 h to 1281, 302, and 455 at 24 h, respectively. The NRF2-mediated oxidative stress response, cell cycle:G2/M DNA damage checkpoint regulation, and mitotic roles of polo-like kinase were the top three pathways altered by all three fractions. Fine and ultrafine PM displayed more similar gene expression patterns. One example was the increased expression of metallothionein isoforms, reflecting the higher zinc content associated with fine and ultrafine fractions. A set of 10 genes was identified that could discriminate fine and ultrafine PM from coarse PM. These results indicate that common properties shared by the three size fractions as well as size-specific factors, e.g., compositions, may determine the effects on gene expression. Genomic markers may be used to discriminate coarse from fine and ultrafine PM.

Exposure to pollutant particles increased respiratory morbidity and mortality. The alveolar macrophages (AMs) are one cell type in the lung directly exposed to particles. Upon contact with particles, AMs are activated and produce reactive oxygen species, but the scope of this oxidative stress response remains poorly defined. In this study, we determined the gene expression profile in human AMs exposed to particles, and sought to characterize the global response of pro- and antioxidant genes. We exposed AMs obtained by bronchoscopy from normal individuals to Chapel Hill particulate matter of 2.5-μm diameter or smaller (PM2.5; 1 μg/ml) or vehicle for 4 hours (n = 6 independent samples). mRNAs were extracted, amplified, and hybridized to Agilent human 1A microarray. Significant genes were identified by significance analysis of microarrays (false discovery rate, 10%; P ≤ 0.05) and mapped with Gene Ontology in the Database for Annotation, Visualization, and Integrated Discovery. We found 34 and 41 up- and down-regulated genes, respectively; 22 genes (∼30%) were involved in metal binding, and 11 were linked to oxidative stress, including up-regulation of five metallothionein (MT)-1 isoforms. Exogenous MT1 attenuated PM2.5-induced H2O2 release. PM2.5 premixed with MT1 stimulated less H2O2 release. Knockdown of MT1F gene increased PM2.5-induced H2O2 release. PM2.5 at 1 μg/ml did not increase H2O2 release. Mount St. Helens PM2.5 and acid-extracted Chapel Hill PM2.5, both poor in metals, did not induce MT1F or H2O2 release. Our results show that PM2.5 induced a gene expression profile prevalent with genes related to metal binding and oxidative stress in human AMs, independent of oxidative stress. Metals associated with PM may play an important role in particle-induced gene changes.

Respiratory syncytial virus (RSV) infection involves complex virus-host interplay. In this study, we analyzed gene expression in RSV-infected BEAS-2B cells to discover novel signaling pathways and biomarkers. We hybridized RNAs from RSV- or vehicle-treated BEAS-2B to Affymetrix HU133 plus 2.0 microarrays (n = 4). At 4 and 24 h post-infection, 277 and 900 genes (RSV/control ratio ≥2.0 or ≤0.5), and 1 and 12 pathways respectively were significantly altered. Twenty-three and 92 genes at 4 and 24 h respectively matched respiratory disease biomarkers with ARG2 flagged at 24 h and SCNN1G, EPB41L4B, CSF1, PTEN, TUBB1 and ESR2 at both time points. Hierachical clustering showed a cluster containing ARG2 and IL8. In human bronchial epithelial cells, RSV upregulated arginase II protein. Knockdown of ARG2 increased RSV-induced IL-8, LDH and histone release. With microarray, we identified novel proximal airway epithelial cell genes that may be tested in the sputum samples as biomarkers of RSV infection.