Aims

Airways and alveoli abnormalities in COPD are mainly caused by inflammatory damage resulting from significant exposure to toxic particles such as cigarette smoke (CS). Small airways are a key target of injury in COPD. Here, we explored CS-induced transcriptome and chromatin accessibility changes in primary human small airway epithelial cells (HSAECs).

Methods

RNA-seq and ATAC-seq were performed on HSAECs after exposure to cigarette smoke extract (CSE) for 72h. RT-PCR was used for gene expression validation. Histone modifications were analyzed using CUT&RUN assay.

Results

RNA-seq revealed an enrichment of differentially expressed genes that regulate inflammatory signaling pathways and the rhythmic process in response to CSE. ATAC-seq showed that CSE decreased the overall chromatin accessibility. The combined analysis identified a total of 398 downregulated genes which were located within closed chromatin regions after CSE stimulation. Functional enrichment analysis of these genes identified significant regulation in circadian gene expression. RT-PCR confirmed that circadian genes PER2&CRY2 were significantly downregulated, whereas Bmal1 was upregulated in CSE-treated HSAECs. CUT&RUN showed that CSE reduced Histone 3 acetylation at the promoter region of PER2.

Conclusions

CS may cause both transcriptomic and epigenomic reprogramming in HSAECs. CS-induced dysregulation of circadian genes was likely due to chromatin structure remodeling via histone modifications.Given the essential role of molecular circadian rhythms in inflammation, targeting epigenetic regulation may serve as a potential strategy for COPD.