[Effect and mechanism of microRNA-155 in chronic obstructive pulmonary disease by targeting PIK3R1]

This study aimed to investigate the effect of microRNA-155 (miR-155) in chronic obstructive pulmonary disease (COPD) and cigarette smoke extract (CSE)-treated airway smooth muscle cells (ASMCs) by targeting phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) to regulate the PTEN/PI3K/Akt signaling pathway. The COPD mouse model was induced by lipopolysaccharide (LPS) combined with passive smoking. After modeling, miR-155 mimics and miR-155 inhibitor were used for intervention treatment. The pulmonary function of each group was detected by an EMKA detector. Hematoxylin-eosin (HE) staining was used to observe the pathological changes and scores of lung tissues. The expression of TNF-α, IL-6, and IL-1β in bronchial alveolar lavage fluid (BALF) was detected by ELISA. Primary ASMCs were isolated and cultured in adherent tissue culture. The proliferation activity was detected by CCK-8 and EdU assays. Transwell and wound healing assays were used to measure the migration of ASMCs. The targeting relationship between miR-155 and PIK3R1 was validated by a double luciferase reporter gene assay. The expression levels of miR-155 and PIK3R1 mRNA in lung tissues of mice in each group were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Western blot was used to detect the expression levels of Ki67, PNCA, PTEN, p-PI3K, PI3K, p85α, p-Akt, and Akt in lung tissues and ASMCs. The results showed that lung function was significantly reduced in the miR-155 mimic group, and the levels of PIK3R1 were significantly increased; while lung function in the miR-155 inhibitor group was significantly improved. The results of HE staining showed that there was obvious inflammatory cell infiltration in the miR-155 mimics group compared to that of the model group. Lung histopathological injury was significantly reduced in the miR-155 inhibitor group, accompanied by decreased expression of Ki67, PNCA, PI3K, p-Akt, increased PTEN and p85α protein levels, and reduced levels of TNF-α, IL-6, and IL-1β in BALF. The results of the double luciferase reporter gene assay showed that miRNA-155 could target bind to PIK3R1. Compared with those in the CSE+miR-155 NC group, the proliferation and migration of ASMCs were significantly increased in the CSE+miR-155 group. The proliferation and migration of ASMCs were significantly attenuated in the CSE+miR-155+pcDNA PIK3R1 group compared with those in the CSE+miR-155 group, accompanied by decreased expression of Ki67, PNCA, p-Akt and increased PTEN and p85α protein levels. These results suggest that miR-155 activates the PTEN/PI3K/Akt signaling pathway by targeting PIK3R1 to promote the occurrence and development of COPD, which provides new evidence for the use of miR-155 in the treatment of COPD.