Expressions of miR-21 and programmed cell death factor 4 in alveolar macrophages of bronchoalveolar lavage fluid in patients with chronic obstructive pulmonary disease

  Objective  To investigate the expression levels of miR-21 and programmed cell death factor 4 (PDCD4) in alveolar macrophages (AM) of bronchoalveolar lavage fluid (BALF) in patients with chronic obstructive pulmonary disease (COPD).

  Methods  A total of 135 COPD patients were selected as study objects (COPD group). According to the patients' conditions, they were divided into stable COPD group (62 cases) and acute exacerbation stage of COPD (AECOPD) group (73 cases); a total of 73 healthy people who underwent bronchoscopy due to laryngeal foreign body sensation were selected for control study (normal group). The general data of COPD group and normal group were compared; real-time quantitative polymerase chain reaction (qRT-PCR) was used to detect the relative expression of miR-21 and PDCD4 mRNA in BALF AM; Pearson method was used to analyze the correlations between the expression of miR-21 and PDCD4 mRNA in BALF AM and lung function indexes, and the correlation between miR-21 expression level and PDCD4 mRNA expression level; receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value of miR-21 and PDCD4 mRNA in BALF AM for COPD.

  Results  Compared with the normal group, the percentage of forced expiratory volume in the first second (FEV₁) in expected value (FEV₁%) and FEV₁/forced vital capacity (FVC) level in the COPD group were significantly decreased (P < 0.05); compared with the normal group, the expression levels of miR-21 in BALF AM were significantly higher, and the expression levels of PDCD4 mRNA were significantly lower of patients in the stable COPD group and AECOPD group (P < 0.05); compared with the stable COPD group, the expression level of miR-21 in BALF AM of the AECOPD group was significantly higher, and the expression level of PDCD4 mRNA was significantly lower (P < 0.05); the expression levels of miR-211 in BALF AM of COPD patients were negatively correlated with PDCD4 mRNA level, FEV₁% and FEV₁/FVC (P < 0.05), while PDCD4 mRNA expression was positively correlated with FEV₁% and FEV₁/FVC (P < 0.05); the area under the curve (AUC) of miR-21 and PDCD4 mRNA in BALF AM were 0.844 and 0.849, corresponding cut-off value were 1.54 and 0.70, sensitivity were 70.4% and 77.8%, specificity were 86.3% and 80.8%, respectively; the AUC of the combined diagnosis of COPD was 0.903, and its sensitivity and specificity were 90.4% and 84.9%, respectively.

  Conclusion  The expression of miR-21 in BALF AM of COPD patients is increased, and the expression of PDCD4 is decreased. MiR-21 may interact with PDCD4, and then synergistically affect the pathological process of COPD. Both levels are helpful for clinical screening of COPD patients and evaluation of patients' condition.