Ambient Pollution-related Reprogramming of the Human Small Airway Epithelial Transcriptome

Rationale: Epidemiologic studies have demonstrated that exposure to particulate matter ambient pollution has adverse effects on lung health, exacerbated by cigarette smoking. Particulate matter less than or equal to 2.5 mu m in aerodynamic diameter (PM2.5) is among the most harmful urban pollutants and is closely linked to respiratory disease. Objectives: Based on the knowledge that the small airway epithelium (SAE) plays a central role in the pathogenesis of smoking-related lung disease, we hypothesized that elevated PM2.5 levels are associated with dysregulation of SAE gene expression, which may contribute to the development of respiratory disease. Methods: From 2009 to 2012, healthy nonsmoker (n = 29) and smoker (n = 129) residents of New York City underwent bronchoscopy with SAE brushing (2.6 +/- 1.3 samples/subject; total of 405 samples). SAE gene expression was assessed by Affymetrix HG-U133 Plus 2.0 microarray. New York City PM2.5 levels (Environmental Protection Agency data) were averaged for the 30 days before bronchoscopy. A linear mixed model was used to assess PM2.5-related gene dysregulation accounting for multiple clinical and methodologic variables. Measurements and Main Results: Thirty-day mean PM 25 levels varied from 6.2 to 18 mu g/m(3). In nonsmokers, there was no dysregulation of SAE gene expression associated with ambient PM2.5 levels. In marked contrast, n = 219 genes were significantly dysregulated in association with PM2.5 levels in the SAE of smokers. Many of these genes relate to cell growth and transcription regulation. Interestingly, 11% of genes were mitochondria associated. Conclusions: PM2.5 exposure contributes to significant dysregulation of the SAE transcriptome of smokers, linking pollution and airway epithelial biology in the risk of development of respiratory disease in susceptible individuals.