Transcriptome analysis identifies IL24 as an autophagy modulator in PM2.5 caused lung dysfunction

Background: Evidence suggests that exposure to PM_2.5 increased hospitalization and mortality rates of respiratory diseases. However, the potential biomarkers and targets associated with PM_2.5-induced lung dysfunction are not fully discovered.

Methods: Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and HALLMARK enrichment analysis of the RNA-seq data (Beas-2B cells treated with PM_2.5) were applied. Gene set enrichment analysis (GSEA) was performed to identify the biological processes correlated with Autophagy. Three gene expression profile datasets (GSE158954, GSE155616 and GSE182199) were downloaded from the Gene Expression Omnibus (GEO) database to identify the potential targets. PM_2.5-exposed mice were constructed. Real-time qPCR, siRNA transfection, western blot, immunofluorescence, and pathological staining were applied for validation both in vitro and in vivo studies.

Results: GO, KEGG and HALLMARK enrichment based on RNA-seq data showed that the differentially expressed genes (DEGs) were associated with Autophagy like lysosome and macroautophagy. GSEA analysis revealed that PM_2.5 was positively correlated with autophagy-related biological processes compared with control group. Venn diagrams identified IL24 was upregulated in our data as well as in these three datasets (GSE158954, GSE155616 and GSE182199) after PM_2.5 exposure. Consistent with the analysis, activation of Autophagy by PM_2.5 was validated in vivo and in vitro. In PM_2.5-exposed mice, lung pathological changes were observed, including airway inflammation and mucus secretion. The mRNA and protein levels of the key gene, IL24, were significantly increased. Moreover, Bafilomycin A1, the inhibitor of Autophagy, inhibited the Autophagy and ameliorated lung injury induced by PM2.5. Furthermore, downregulation of IL24 decreased Autophagy activity. Meanwhile, IL24 was regulated by mTOR signaling.

Conclusions: In summary, we discovered a potential relationship between IL24 and Autophagy during PM_2.5 exposure. IL24 might be a novel potential biomarker or therapeutic target in PM_2.5 caused lung dysfunction through regulation of Autophagy.