Circ-OSBPL2 promotes apoptosis, inflammation, and oxidative stress in HBECs in smoking-associated COPD through the miR-193a-5p/BRD4 axis, indicating that the potential of circ-OSBPL2 to act as a diagnostic biomarker for smoking-induced COPD (Zheng et al., 2021). Here, BRD4 is linked to chronic obstructive pulmonary disease.