PM2.5-induced lung injury in rats: Identification of differential circRNAs and analysis of circRNA-miRNA-mRNA regulatory networks.

Exposure to high levels of fine particulate matter (PM) over a long period is strongly associated with an increased risk of morbidity and mortality from respiratory diseases. Although PM2.5 has been demonstrated to cause lung damage, the exact mechanisms are not fully understood. In this study, six-week-old SPF-grade SD rats were used as an experimental model for PM2.5 exposure via the endotracheal drip method. A library of circRNAs in rat lung tissues was constructed, and 16,020 circRNAs were successfully predicted, with the highest percentage being of the all-exon type. Validation of the screened differentially expressed circRNAs (DEcircRNAs) was performed using an RNase R digestion assay, Sanger sequencing, and RT-qPCR. In addition, bioinformatics analyses were used to predict the potential miRNA binding sites of the circRNAs and the target genes of miRNAs. A circRNA-miRNA-mRNA regulatory network was constructed and validated through miRNA pull-down experiments. The results showed that exposure to PM2.5 significantly altered the expression profile of circRNAs in rat lung tissue. The DEcircRNAs and their host genes were found to be primarily associated with physiological processes such as neuromuscular regulation. The constructed circRNA-miRNA-mRNA regulatory network indicated that circRNA4503, circRNA4511, and ciRNA131 (asso-type circRNA131) can adsorb miR-340-5p via the ceRNA mechanism. This process regulates the expression of the target genes DMD, HECW2, and SGIP1, which play a role in the pathological processes of lung diseases. In conclusion, this study establishes a new theoretical foundation for understanding the molecular mechanisms underlying PM2.5-induced lung injury.