Characteristics of circular RNA expression of pulmonary macrophages in mice with sepsis-induced acute lung injury.

Circular RNAs (circRNAs) make up a large class of non-coding RNAs and play important roles in the pathology of a variety of diseases. However, their roles in pulmonary macrophage polarization after sepsisinduced lung injury is unknown. In this study, mice were divided into two groups: Sham control group and cecal ligation and puncture (CLP)-induced ALI group. Macrophages were isolated from lung homogenates 24 hours after SCLP/CLP. We started with RNA-seq of circRNA changes in macrophages and validated by RT-PCR in the following experiments. A total of 4318 circRNAs were detected in the two groups. Of these, 11 and 126 circRNAs were found to be significantly upregulated and downregulated, respectively, compared to the control (p≤0.05, Fold Change ≥2). Differentially expressed circRNAs with a high foldchange (fold-change >4, P<0.05) were selected for validation by qRT-PCR, 10 of which were verified. Furthermore, the most differentially expressed circRNAs within all the comparisons were annotated in detail with circRNA/miRNA interaction information using miRNA target prediction software. The network of circRNA-miRNA-mRNA was illustrated by cytoscape software. Gene ontology analyses indicated the upregulated circRNAs were involved in the multiple biological functions such as regulation of mitochondrion distribution and Notch binding, while the down-regulated circRNAs mainly involved in the biological process as histone H3K27 methylation. KEGG pathway analysis revealed TGF-beta signaling pathway was related to the upregulated circRNAs. The present study provides a novel insight into the roles of circRNAs in pulmonary macrophage differentiation and polarization post septic lung injury.