BACKGROUND: The extent to which ambient benzo[a]pyrene (B[a]P) contributes to mechanistically distinct de novo asthma remains unknown. OBJECTIVES: To identify molecular signatures and regulatory networks underlying childhood exposure to ambient B[a]P and asthma, using robust and unbiased systems biology approaches. METHODS: Clinically confirmed asthmatic (n = 191) vs. control (n = 194) children (aged, 7-15) were enrolled from a polluted urban center and semi-rural region in Czech Republic. Contemporaneous B[a]P concentration, gene expressions, DNA methylation data were analyzed against asthma diagnosis, as well as a modified prognostic index of asthma, using integrative multiscale co-expression network analysis. Sample-wise cell type compositions were inferred by a machine learning approach (i.e. CIBERSORT) with reference gene expressions of purified 38 distinct hematopoietic cell states from umbilical cord (i.e. stem cell/progenitors) or peripheral blood (i.e. lymphocytes). RESULTS: The median outdoor B[a]P was increased near the homes of the urban children with 'moderate' or 'severe' prognostic markers of asthma, but not in the urban controls. An elevated B[a]P induced epigenetic suppression of NF-κB inflammation, decreased Natural Killer T (NKT) cells and activated anti-inflammatory IL10-secreting CD8+ T effective memory cells. B[a]P was positively correlated with an increased expression of a heme biosynthesis gene, ALAS2, which in turn, appears to promote concurrent increase of neutrophilic metamyelocyte and mature CD71low erythroid cells. Furthermore, erythroid-specific master transcription regulator gene (GATA1), glutathione transferase genes (GSTM1 and GSTM3) and Eosinophil marker (IL5RA) were simultaneously activated in the urban asthma cases. CONCLUSIONS: B[a]P might contribute to concurrent suppression of pro-inflammatory (e.g. NF-κB mediated NKT cells), and activation of anti-inflammatory pathways (e.g. IL10-secreting CD8+ T cells) in the urban asthmatic children. In addition, B[a]P appears to elevate heme biosynthesis, which in turn, promotes neutrophilic metamyelocyte expansion and reduction of CD71+ erythroids.

Department of Genetic Toxicology and Nanotoxicology Institute of Experimental Medicine Academy of Sciences of the Czech Republic v v i Vídeňská 1083 142 20 Prague 4 Czech Republic

Departments of Environmental Health Sciences Epidemiology and Biostatistics State University of New York at Albany School of Public Health Rensselaer NY USA

Icahn Institute of Genomics and Multiscale Biology Icahn School of Medicine at Mount Sinai New York NY USA

University of Chemistry and Technology Prague Faculty of Food and Biochemical Technology Department of Food Analysis and Nutrition Technicka 3 166 28 Prague Czech Republic

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