The circular RNA circTXNRD1 promoted ambient particulate matter-induced inflammation in human bronchial epithelial cells by regulating miR-892a/COX-2 axis

Particulate matter (PM)-induced airway inflammation contributes to the development and exacerbation of chronic airway diseases. Circular RNA (circRNA) is a new class of non-coding RNA that participates in gene regulation in various respiratory diseases, but the regulatory role of circRNA in PM-induced airway inflammation has not been fully elucidated. In this study, we performed the human circRNA microarray to reveal differentially expressed circRNAs in PM-induced human bronchial epithelial cells (HBECs). A total of 176 upregulated and 15 downregulated circRNAs were identified. Of these, a new circRNA termed circTXNRD1 was upregulated by PM exposure in a dose- and time-dependent manner. Knockdown of circTXNRD1 significantly attenuated PM-induced expression of proinflammatory cytokine interleukin 6 (IL-6). CircRNA pull-down, dual-luciferase reporter assay and fluorescence in situ hybridization showed that circTXNRD1 acted as an endogenous sponge to decrease miR-892a levels in HBECs. Downregulation of miR-892a could increase cyclooxygenase-2 (COX-2) expression and eventually promote IL-6 secretion in PM-induced HBECs. Taken together, our findings reveal circTXNRD1 as a novel inflammatory mediator in PM-induced inflammation in HBECs via regulating miR-892a/COX-2 axis. These results provide new insight into the biological mechanism underlying PM-induced inflammation in chronic airway diseases.