Benzo[a]pyrene is associated with dysregulated myelo-lymphoid hematopoiesis in asthmatic children

• Main Authors: Hyunok Choi, Won-min Song, Minghui Wang, Radim J. Sram, Bin Zhang
• Format: Article
• Language: English
• Published: Elsevier 2019-07-01
• Series: Environment International
• Online Access: http://www.sciencedirect.com/science/article/pii/S0160412018317215

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. Keywords: Polycyclic aromatic hydrocarbon, Asthma, Air pollution, Gene co-expression network analysis, Multiscale clustering analysis, Environmental systems biology