Gene expression profiling of primary human type I alveolar epithelial cells exposed to Bacillus anthracis spores reveals induction of neutrophil and monocyte chemokines

• Published in: Microbial pathogenesis 2018-08, Vol.121, p.9-21
• Main Authors: Booth, J. Leland, Duggan, Elizabeth S., Patel, Vineet I., Wu, Wenxin, Burian, Dennis M., Hutchings, David C., White, Vicky L., Coggeshall, K. Mark, Dozmorov, Mikhail G., Metcalf, Jordan P.
• Format: Article
• Language: English
• Subjects: Alveolar Epithelial Cells - microbiology; Anthrax; Anthrax - genetics; Anthrax - metabolism; Bacillus anthracis; Bacillus anthracis - pathogenicity; Chemokine CCL20 - genetics; Chemokine CCL20 - metabolism; Chemokine CXCL5 - genetics; Chemokine CXCL5 - metabolism; Chemokines - genetics; Chemokines - metabolism; Chemotaxis; Gene Expression Profiling; Humans; Interleukin-8 - genetics; Interleukin-8 - metabolism; Monocytes - metabolism; Monocytes - microbiology; Neutrophils - metabolism; Neutrophils - microbiology; Platelet Factor 4 - genetics; Platelet Factor 4 - metabolism; Respiratory Tract Infections - genetics; Respiratory Tract Infections - metabolism; Spores, Bacterial - pathogenicity; Transcriptome microarray analysis; Type I alveolar epithelial cells; Up-Regulation
• ISSN: 0882-4010; 1096-1208
• DOI: 10.1016/j.micpath.2018.04.039

The lung is the entry site for Bacillus anthracis in inhalation anthrax, the most deadly form of the disease. Spores must escape through the alveolar epithelial cell (AEC) barrier and migrate to regional lymph nodes, germinate and enter the circulatory system to cause disease. Several mechanisms to explain alveolar escape have been postulated, and all these tacitly involve the AEC barrier. In this study, we incorporate our primary human type I AEC model, microarray and gene enrichment analysis, qRT-PCR, multiplex ELISA, and neutrophil and monocyte chemotaxis assays to study the response of AEC to B. anthracis, (Sterne) spores at 4 and 24 h post-exposure. Spore exposure altered gene expression in AEC after 4 and 24 h and differentially expressed genes (±1.3 fold, p ≤ 0.05) included CCL4/MIP-1β (4 h), CXCL8/IL-8 (4 and 24 h) and CXCL5/ENA-78 (24 h). Gene enrichment analysis revealed that pathways involving cytokine or chemokine activity, receptor binding, and innate immune responses to infection were prominent. Microarray results were confirmed by qRT-PCR and multiplex ELISA assays. Chemotaxis assays demonstrated that spores induced the release of biologically active neutrophil and monocyte chemokines, and that CXCL8/IL-8 was the major neutrophil chemokine. The small or sub-chemotactic doses of CXCL5/ENA-78, CXCL2/GROβ and CCL20/MIP-3α may contribute to chemotaxis by priming effects. These data provide the first whole transcriptomic description of the human type I AEC initial response to B. anthracis spore exposure. Taken together, our findings contribute to an increased understanding of the role of AEC in the pathogenesis of inhalational anthrax. •Human type I alveolar epithelial cells exposed to Bacillus anthracis, Sterne spores display altered gene expression.•Genes for the chemokines CCL4/MIP-1β, CXCL8/IL-8, and CXCL5/ENA-78 are among the most highly upregulated DEGs.•Pathways involving cytokine or chemokine activity, receptor binding, and innate immune response to infection are prominent.•Spores induce release of neutrophil and monocyte chemokines from AEC I, and CXCL8/IL-8 is the major neutrophil chemokine.•Our results provide the first transcriptomic description of the initial response of AEC I to B. anthracis spore exposure.