The Role Of Micro RNA-29b In The Airway Inflammation In Chronic Obstructive Pulmonary Disease

Background: Chronic obstructive pulmonary disease(COPD)is a common chronic airway inflammatory disease.Micro RNAs(mi RNAs)are a class of non-coding RNA(nc RNAs)molecules,which are involved in many varied pathophysiologic processes including the regulation of inflammation.However,the role of micro RNA-29b(mi R-29b)in the airway inflammation in COPD remains unknown.Objective: To investigate the role of mi R-29 b in the airway inflammation in COPD.Methods: All subjects were recruited into the study,who were patients undergoing surgery for pulmonary lump.Subjects were divided into three groups based on their diagnosis and smoking history: nonsmokers,smokers and patients with COPD.The relative levels of mi R-29 b expression in the lung and plasma were determined by quantitative PCR(q PCR).Correlation analyses were performed to examine the associations of mi R-29 b expression levels with pulmonary function and inflammation.The sites of mi R-29 b expression in human lung tissues were mapped by fluorescence in situ hybridization(FISH).The target of mi R-29 b was predicted by online algorithms and verified in human bronchial epithelial(HBE)cells.The relative levels of the target of mi R-29 b in the lung of subjects were determined by q PCR,and correlation analyses were performed to examine the associations of the target of mi R-29 b with mi R-29 b,pulmonary function and inflammation.Immunohistofluorescence staining showed the sites of the target of mi R-29 b in lung tissues.The mechanism of mi R-29 b involved in the airway inflammation in COPD was investigated using an in vitro model system.Inflammatory cytokine expression was examined after overexpression of mi R-29 b and/or knockdown of the target of mi R-29 b in cigarette smoke extract(CSE)-treated HBE cells.The relative levels of Inflammatory cytokine,mi R-29 b and the target of mi R-29 b were detected in CSE-stimulated HBE cells pretreated with the antioxidant N-acetylcysteine(NAC).Results: In total,60 subjects were recruited,including 10 nonsmokers,24 smokers,and 26 patients with COPD.Both lung and plasma mi R-29 b were decreased in patients with COPD,and mi R-29 b expression levels were correlated with pulmonary function and inflammation.FISH in lung tissues revealed mi R-29 b expressed in bronchial epithelial cells.The target of mi R-29 b,bromodomain protein 4(BRD4),was predicted and verified.BRD4 was increased in the lung of patients with COPD and was correlated with mi R-29 b and interleukin(IL)-8 expression.Immunohistofluorescence staining showed that BRD4 was expressed in bronchial epithelial cells.In vitro,the expression of mi R-29 b was significantly reduced after CSE treatment.Overexpression of mi R-29 b and/or knockdown of BRD4 expression suppressed CSE-induced IL-8 production,which was more pronounced for cotransfection.The antioxidant NAC has been shown to prevent CSE-induced mi R-29 b downregulation and BRD4 and IL-8 upregulation.Conclusion: mi R-29 b may participate in the airway inflammation in COPD by regulating inflammatory cytokine expression through targeting BRD4,plasma mi R-29 b may serve as a biomarker for disease severity in COPD,and oxidative stress may contribute to the decrease of mi R-29 b induced by cigarette smoke.