Circ-OSBPL2 Contributes to Smoke-Related Chronic Obstructive Pulmonary Disease by Targeting miR-193a-5p/BRD4 Axis

Abstract

Background Circular RNAs (circRNAs) have been identified to play roles in the respiratory diseases. Here, this study aimed to elucidate the function of circRNA oxysterol binding protein like 2 (circOSBPL2) in the development of smoke-related chronic obstructive pulmonary diseases (COPD). Methods The expression of circ-OSBPL2, microRNA (miR)-193a-5p, and bromodomain-containing protein 4 (BRD4) was detected using qRT-PCR and Western blot assays. Cigarette smoke extract (CSE)-induced human bronchial epithelial cells (HBECs) was applied to mimic smoke-related COPD in vitro. Flow cytometric analysis of cell apoptosis and ELISA analysis of interleukins (IL)-6, IL-8, tumor necrosis factor-α (TNF-α) levels were performed. The malondialdehyde (MDA) and superoxide dismutase (SOD) production levels were analyzed according to the kit instructions. The binding interaction between miR-193a-5p and circ-OSBPL2 or BRD4 was confirmed by dual-luciferase reporter assay and RNA immunoprecipitation assays. Results Circ-OSBPL2 was highly expressed in lung tissues of smokers without or with COPD, particularly in smokers with COPD. Also, the expression of circ-OSBPL2 was dose and time-dependently elevated in CSE-induced HBECs. Circ-OSBPL2 down-regulation in HBECs attenuated CSE-evoked cell proliferation arrest, and cell apoptosis, inflammation and oxidative stress promotion. Mechanistically, circ-OSBPL2 served as a sponge for miR-193a-5p, and miR-193a-5p inhibition reversed the effects of circ-OSBPL2 knockdown on CSE-mediated HBECs. Besides that, miR-193a-5p directly targeted BRD4, and miR-193a-5p re-expression in HBECs abolished CSE-induced HBEC injury, which was reverted by BRD4 up-regulation. Additionally, we also found circ-OSBPL2 could indirectly regulate BRD4 via miR-193a-5p. Conclusion Circ-OSBPL2 contributed to the apoptosis, inflammation, and oxidative stress of HBECs in smoke-related COPD by miR-193a-5p/BRD4 axis, suggesting a novel insight on the pathogenesis of COPD and a potential therapeutic strategy for future clinic intervention in COPD.

Cellular and Molecular Signatures of Oxidative Stress in Bronchial Epithelial Cell Models Injured by Cigarette Smoke Extract

“…Oxidative stress can also be measured indirectly, by analyzing the degree of lipid peroxidation, a phenomenon that occurs in the presence of elevated concentrations of oxidants. Malondialdehyde (MDA) is one of the products of lipid peroxidation, and can be easily detected by colorimetric or fluorometric analysis [28,29,33,39,70,71]. Alternatively, it is possible to measure the levels of 4-hydroxynonenale (4-HNE) protein adducts by ELISA [22,24].…”

“…TLR4 expression is increased in response to CSE [84], and its activation triggers most of the CSE-induced proinflammatory pathways in HBE cells. In HBEs, NF-κB, the master regulator of transcriptional reprogramming during inflammation, was widely demonstrated to regulate the inflammatory response to CSE [17,22,24,27,32,36,42,45,70,77,78,98,99,112].…”

“…As is well known, the activation of these pathways leads to increased levels of pro-inflammatory cytokines such as TNF-α, IL-1β, IL-6, and IL-8. Of note, these cytokines are key mediators of CS-induced lung inflammation as well [17,19,22,24,25,[27][28][29][30]32,33,36,37,40,42,[44][45][46][69][70][71]74,75,[77][78][79][80][81]83,90,98,99,102,104,112,113]. ROS, increased by CS, enhance the activation of the IκB kinase (IKK) complex (IKKβ, IKKα, and NF-κB essential modulator (NEMO), leading to the phosphorylation, ubiquitination and proteasomal degradation of IκB, in particular IκBα.…”

“…This promotes the activation of the NF-κB/p65 complex, a process which requires a number of PTMs (phosphorylation, acetylation, glycosylation). Active NF-κB translocates to the nucleus, where it induces the transcription of inflammatory genes [17,22,24,27,32,36,42,45,70,77,78,98,99,112]. It has been reported that treatment of BEAS-2B with CSE 2.5% for 24 h increased NF-κB expression with a higher level of nuclear phospho-p65, and activation of JNK, p38 and ERK1/2.…”

Circular RNAs: Novel Players in the Oxidative Stress‐Mediated Pathologies, Biomarkers, and Therapeutic Targets

“…Similarly, the other group found circRNA oxysterol binding protein like 2 (circOSBPL2) to induce apoptosis, inflammation, and oxidative stress in response to CSE. This effect was mediated by the ceRNA axis and circOSBPL2/miR-193a-5p/BRD4 [ 80 ]. This work indicates an important role of circRNAs in OxS-mediated pathology of the lung, a phenomenon that needs further investigation to elucidate novel markers for diagnosis and targets for control of such conditions.…”