Keywords: 
• air pollution /
• PM_2.5 /
• microRNA /
• bioinformatics analysis

Abstract: MicroRNAs can be regarded as new biomarkers for the early diagnosis of clinical diseases, which has been paid more and more attentions. In order to investigate the pathogenic mechanism of air pollution, BALB/c mice were treated with noninvasive tracheal instillation of PM_2.5 suspension to construct experimental animal model. Differentially expressed microRNAs in mouse lung tissues were screened by Agilent chip, and the results were verified by real-time quantitative PCR. Target genes prediction of differential miRNAs was performed using TargetScan, PITA, and microRNAorg. Then, target gene enrichment, gene function (GO) and signal pathway (KEGG) analysis were performed, and differentially expressed miRNAs were detected after exposed to particulate matter for 2 weeks. 4 miRNAs were up-regulated in high dose exposure group compared to control group, 2 miRNAs were up-regulated in low dose exposure group compared to control group, and 4 miRNAs were up-regulated in high dose exposure group compared to low dose exposure group (standard value > = 2 and the P value < = 0.05). The expression of miR-139-5p, miR-691 and miR-340-3p detected by qRT-PCR exhibited similar patterns of up-regulation to those shown in microarray results. Bioinformatics analysis revealed that the target genes of miRNAs were significantly enriched in 34 GOs (including transcription from RNA polymerase II promoter, RNA splicing, DNA-templated, protein binding, RNA binding, DNA binding) and 32 signal pathways (including mainly axon guidance and pathways in cancer). In conclusion, the expression levels of miR-139-5p, miR-691 and miR-340-3p in mice lung tissues were up-regulated remarkably after exposure to particulate matter. Bioinformatics analysis suggested that central nervous system development and cancer pathway may be the major pathogenic pathway mediated by differentially expressed miRNAs related to target genes.