Molecular Impact of Electronic Cigarette Aerosol Exposure in Human Bronchial Epithelium.

Little evidence is available regarding the physiological effects of exposure to electronic cigarette (ECIG) aerosol. We sought to determine the molecular impact of ECIG aerosol exposure in human bronchial epithelial cells (HBECs). Gene-expression profiling was conducted in primary grown at air liquid interface and exposed to 1 of 4 different ECIG aerosols, traditional tobacco cigarette (TCIG) smoke, or clean air. Findings were validated experimentally with quantitative polymerase chain reaction and a reactive oxygen species immunoassay. Using gene set enrichment analysis, signatures of in vitro ECIG exposure were compared with those generated from bronchial epithelial brushings of current TCIG smokers and former TCIG smokers currently using ECIGs. We found 546 genes differentially expressed across the ECIG, TCIG, and air-exposed groups of HBECs (ANOVA; FDR q < .05; fold change > 1.5). A subset of these changes were shared between TCIG- and ECIG-exposed HBECs. ECIG exposure induced genes involved in oxidative and xenobiotic stress pathways and increased a marker of reactive oxygen species production in a dose-dependent manner. ECIG exposure decreased expression of genes involved in cilia assembly and movement. Furthermore, gene-expression differences observed in vitro were concordant with differences observed in airway epithelium collected from ECIG users (q < .01). In summary, our data suggest that ECIG aerosol can induce gene-expression changes in bronchial airway epithelium in vitro, some of which are shared with TCIG smoke. These changes were generally less pronounced than the effects of TCIG exposure and were more pronounced in ECIG products containing nicotine than those without nicotine. Our data further suggest that the gene-expression alterations seen with the in vitro exposure system reflects the physiological effects experienced in vivo by ECIG users.

MicroRNA 4423 is a primate-specific regulator of airway epithelial cell differentiation and lung carcinogenesis.

Smoking is a significant risk factor for lung cancer, the leading cause of cancer-related deaths worldwide. Although microRNAs are regulators of many airway gene-expression changes induced by smoking, their role in modulating changes associated with lung cancer in these cells remains unknown. Here, we use next-generation sequencing of small RNAs in the airway to identify microRNA 4423 (miR-4423) as a primate-specific microRNA associated with lung cancer and expressed primarily in mucociliary epithelium. The endogenous expression of miR-4423 increases as bronchial epithelial cells undergo differentiation into mucociliary epithelium in vitro, and its overexpression during this process causes an increase in the number of ciliated cells. Furthermore, expression of miR-4423 is reduced in most lung tumors and in cytologically normal epithelium of the mainstem bronchus of smokers with lung cancer. In addition, ectopic expression of miR-4423 in a subset of lung cancer cell lines reduces their anchorage-independent growth and significantly decreases the size of the tumors formed in a mouse xenograft model. Consistent with these phenotypes, overexpression of miR-4423 induces a differentiated-like pattern of airway epithelium gene expression and reverses the expression of many genes that are altered in lung cancer. Together, our results indicate that miR-4423 is a regulator of airway epithelium differentiation and that the abrogation of its function contributes to lung carcinogenesis.

A dynamic bronchial airway gene expression signature of chronic obstructive pulmonary disease and lung function impairment.

RATIONALE: Molecular phenotyping of chronic obstructive pulmonary disease (COPD) has been impeded in part by the difficulty in obtaining lung tissue samples from individuals with impaired lung function. OBJECTIVES: We sought to determine whether COPD-associated processes are reflected in gene expression profiles of bronchial airway epithelial cells obtained by bronchoscopy. METHODS: Gene expression profiling of bronchial brushings obtained from 238 current and former smokers with and without COPD was performed using Affymetrix Human Gene 1.0 ST Arrays. MEASUREMENTS AND MAIN RESULTS: We identified 98 genes whose expression levels were associated with COPD status, FEV1% predicted, and FEV1/FVC. In silico analysis identified activating transcription factor 4 (ATF4) as a potential transcriptional regulator of genes with COPD-associated airway expression, and ATF4 overexpression in airway epithelial cells in vitro recapitulates COPD-associated gene expression changes. Genes with COPD-associated expression in the bronchial airway epithelium had similarly altered expression profiles in prior studies performed on small-airway epithelium and lung parenchyma, suggesting that transcriptomic alterations in the bronchial airway epithelium reflect molecular events found at more distal sites of disease activity. Many of the airway COPD-associated gene expression changes revert toward baseline after therapy with the inhaled corticosteroid fluticasone in independent cohorts. CONCLUSIONS: Our findings demonstrate a molecular field of injury throughout the bronchial airway of active and former smokers with COPD that may be driven in part by ATF4 and is modifiable with therapy. Bronchial airway epithelium may ultimately serve as a relatively accessible tissue in which to measure biomarkers of disease activity for guiding clinical management of COPD.

Chlamydia pneumoniae-specific IgE is prevalent in asthma and is associated with disease severity.

BACKGROUND: Several Chlamydia pneumoniae (Cp) biomarkers have been associated with asthma but Cp-specific IgE (Cp IgE) has not been investigated extensively. Our objective was to investigate Cp IgE in community adult asthma patients. METHODS: (1) Prevalence of Cp IgE (measured by immunoblotting) and Cp DNA (by polymerase chain reaction) in peripheral blood, and biomarker associations with asthma severity. (2) Case-control studies of Cp IgE association with asthma using healthy blood donor (study 1) and non-asthmatic clinic patient (study 2) controls. RESULTS: Of 66 asthma subjects (mean age 40.9 years, range 5-75, 59% male, 45% ever-smokers) 33 (50%) were Cp IgE positive and 16 (24%) were Cp DNA positive (P = 0.001 for association of Cp IgE and DNA). Cp IgE was detected in 21% of mild intermittent asthma v 79% of severe persistent asthma (test for trend over severity categories, P = 0.002). Cp IgE detection was significantly (P = 0.001) associated with asthma when compared to healthy blood donor controls but not when compared to clinic controls. CONCLUSIONS: Half of this sample of community asthma patients had detectable IgE against C. pneumoniae. Cp IgE was strongly and positively associated with asthma severity and with asthma when healthy blood donor controls were used. These results support the inclusion of Cp IgE as a biomarker in future studies of infectious contributions to asthma pathogenesis.