MiR-31 aggravates inflammation and apoptosis in COPD rats via activating the NF-κB signaling pathway

OBJECTIVE: To study the effect of micro ribonucleic acid (miR)-31 on rats with chronic obstructive pulmonary disease (COPD) by activating the nuclear factor-kappa B (NF-kappa B) signaling pathway. MATERIALS AND METHODS: A total of 36 Sprague-Dawley rats were randomly divided into normal group (n=12), model group (n=12) and miR-31 mimics group (n=12). The rats were fed normally in normal group. In model group, the COPD model was first established, followed by intervention using normal saline. In miR-31 mimics group, the COPD model was also first established, followed by intervention using miR-31 mimics. The expression of NF-kappa B was detected via immunohistochemistry. Protein expressions of B-cell lymphoma-2 (Bcl-2) and Bcl-2 associated X protein (Bax) were determined through Western blotting. Serum levels of interleukin-6 (IL-6), IL-18 and tumor necrosis factor-alpha (TNF-alpha) were measured via enzyme-linked immunosorbent assay (ELISA). Moreover, the apoptosis was examined via terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay, and the relative expression of miR-31 was detected by means of quantitative polymerase chain reaction (qPCR). RESULTS: The immunohistochemistry results showed that the positive expression of NF-kappa B was significantly higher in the other two groups than that in normal group (p<0.05), while it was also remarkably higher in miR-31 mimics group than that in model group (p<0.05). The results of Western blotting revealed that the relative protein expression of Bax significantly increased, while that of Bcl-2 notably declined in the other two groups compared with those in normal group (p<0.05). Similarly, the relative protein expression of Bax was upregulated, while that of Bcl-2 was distinctly reduced in miR-31 mimics group compared with those in model group (p<0.05). It was found via ELISA that the model group and miR-31 mimics group had evidently higher levels of IL-6, IL-18 and TNF-alpha than those in normal group (p<0.05), while miR-31 mimics group also had prominently higher levels than those in model group (p<0.05). In addition, according to the TUNEL assay, the apoptosis rate remarkably increased in the other two groups in comparison with that in normal group (p<0.05), while it remarkably rose in miR-31 mimics group compared with that in model group (p<0.05). Finally, a significantly higher expression of miR-31 was observed in the other two groups than that in normal group via qPCR (p<0.05), and such a higher expression was also found in miR-31 mimics group than that in model group (p<0.05). CONCLUSIONS: MiR-31 aggravates inflammation and apoptosis in COPD rats by activating the NF-kappa B signaling pathway.