miR-155-5p/FOXO3a promotes pulmonary fibrosis in rats by mediating NLRP3 inflammasome activation.

OBJECTIVE: Pulmonary fibrosis (PF) is regarded as progressive lung disease. miR-155-5p depletion exerts anti-fibrotic effects in silicotic mice. This study explored the effect and possible mechanism of miR-155-5p in PF rats, hoping to find a new target for PF management. METHODS: Bleomycin-induced PF rat model was established. Alveolar structure and collagen fiber deposition were observed by HE and Elastica-Masson staining. Alveolitis and PF scores were evaluated using the method of Szapiel. Total collagen content was detected using the Sircol method. PF rats were intraperitoneally injected with NLRP3 inhibitor MCC950 or intravenously injected with miR-155-5p antagomir and si-FOXO3a lentivirus plasmids. Binding sites of miR-155-5p and FOXO3a were predicted using bioinformatics analysis and dual-luciferase reporter assay. The expressions of miR-155-5p, NLRP3, ASC, caspase-1, IL-1ß, IL-18, and FOXO3a were detected by RT-qPCR, Western blot, and ELISA. RESULTS: MCC950 treatment inhibited NLRP3 inflammasome, alleviated alveolar hemorrhage and alveolitis, and reduced blue collagen fiber deposition, scores of alveolitis and PF, and levels of NLRP3, ASC, caspase-1, IL-1ß, and IL-18 in PF rats. miR-155-5p was elevated in lung tissues of PF rats. Inhibition of miR-155-5p downregulated levels of NLRP3, ASC, caspase-1, IL-1ß, and IL-18 in lung tissues of PF rats. miR-155-5p targeted FOXO3a. miR-155-5p inhibition and silencing FOXO3a exacerbated alveolitis and PF in rats and increased levels of NLRP3, ASC, caspase-1, IL-1ß, and IL-18. CONCLUSIONS: miR-155-5p aggravated alveolitis and promoted PF by targeting FOXO3a and prompting the activation of NLRP3 inflammasome and then inducing IL-1ß and IL-18 release.

Anti-asthmatic miR-224-5p inhibits the FHL1/MAPK pathway to repress airway smooth muscle cell proliferation in a murine model of asthma-like airway inflammation.

BACKGROUND: The proliferation of airway smooth muscle cells (ASMCs) contributes to the contractility and inflammation in the pathophysiology of asthma. This intrigued us to clarify the effect of microRNA (miR)-224-5p on biological characteristics of ASMCs in mice with asthma-like airway inflammation and responses through the FHL1-dependent MAPK pathway. METHODS: An ovalbumin (OVA)-induced asthma mouse model was established, where ASMCs were isolated. The expression of FHL1 was determined in asthmatic mice. Artificial modulation of FHL1 expression was performed to explore its effect on airway inflammation of asthmatic mice and ASMC proliferation and apoptosis. Afterwards, we analyzed the interaction among miR-224-5p, FHL1 and the MAPK pathway, and explored their combined impacts on airway inflammation of asthmatic mice and ASMC proliferation and apoptosis. RESULTS: FHL1 was highly expressed and miR-224-5p was poorly expressed in asthmatic mice. FHL1 was verified to be a target of miR-224-5p. Loss of FHL1 function reduced airway inflammation in asthmatic mice and proliferation of ASMCs while inducing their apoptosis. Besides, miR-224-5p inhibited the MAPK pathway by binding to FHL1. Overexpression of miR-224-5p relieved airway inflammation, inhibited ASMC proliferation, and increased apoptosis, which could be reversed by overexpression of FHL1. CONCLUSION: Altogether, miR-224-5p inhibited airway inflammation in asthmatic mice and ASMC proliferation through blocking the MAPK pathway by down-regulating FHL1.