| Summary: | Wen Shen,1,* Jia Liu,2,* Guohou Zhao,1 Minjuan Fan,1 Gao Song,3 Yang Zhang,1 Zhiying Weng,3 You Zhang4 1Department of Respiratory Medicine, 2Department of Experimental Zoology, The Second Affiliated Hospital of Kunming Medical University, 3School of Pharmaceutical Science, Kunming Medical University, 4Department of Hematology, The Second Affiliated Hospital of Kunming Medical University, Kunming, Yunnan Province, People’s Republic of China *These authors contributed equally to this work Background: Smoking is the leading cause of COPD. Exploring molecular markers and understanding the pathogenic mechanisms of smoking-related COPD are helpful for early clinical diagnosis and treatment of the disease. This study aims to identify specific circulating microRNAs (miRNAs) from the blood of COPD patients with a long history of smoking.Methods: Blood samples from four different groups were collected, and miRNA microarray was performed. Differential expression of miRNAs was verified by quantitative polymerase chain reaction. In vitro, THP-1 cells were cultured and stimulated with cigarette smoke extract (CSE) or transfected with miR-149-3p inhibitor/mimics. Protein levels of Toll-like receptor 4 (TLR-4) and nuclear factor κB (NF-κB) were detected using Western blot and immunofluorescence. Interleukin (IL)-1β and tumor necrosis factor (TNF)-α levels were determined by an enzyme-linked immunosorbent assay.Results: miRNA profiling revealed that the expression of 56 miRNAs was changed between the four groups. Expression of miR-149-3p in group C (non-smoker non-COPD) was higher than in group S (smoker non-COPD), S-COPD (smoker with stable COPD) and AE-COPD (smoker with acute exacerbation COPD). CSE stimulation down-regulated the expression of miR-149-3p and up-regulated the TLR-4 and NF-κB levels in THP-1 cells. Transfecting miR-149-3p inhibitors in THP-1 cells also increased the expression of its target genes. Furthermore, overexpression of miR-149-3p inhibited the TLR-4/NF-κB signaling pathways and reduced the secretion of IL-1β and TNF-α.Conclusion: This study found that smoking can induce differential expression of circulating miRNAs, such as down-regulation of miR-149-3p. Reducing miR-149-3p may increase the inflammatory response in COPD patients through the regulation of the TLR-4/NF-κB signaling pathway. Keywords: smoking, COPD, microRNA-149-3p, Toll-like receptor 4, nuclear factor κB
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