[Urolithin A alleviates respiratory syncytial virus-induced lung infection in neonatal mice by activating miR-136-mediated Sirt1 signaling].

OBJECTIVE

To observe the therapeutic effects of urolithin A (UA) on respiratory syncytial virus (RSV)-induced lung infection in neonatal mice and explore the underlying mechanisms.

METHODS

Babl/c mice (5-7 days old) were subjected to nasal instillation of RSV and received intraperitoneal injection of saline or 2.5, 5 and 10 mg/kg UA 2 h after the infection and then once daily for 2 weeks. Bronchoalveolar lavage fluid (BALF) was then collected for detection of inflammatory cells and mediators, and lung pathology was evaluated with HE staining. RSV-infected BEAS-2B cells were treated with 2.5, 5 or 10 µmol/ L UA. Inflammatory factors, cell viability, apoptosis and autophagy were analyzed using ELISA, CCK-8 assay, TUNEL staining, flow cytometry, Western blotting and immunofluorescence staining. The cellular expressions of miR-136 and Sirt1 mRNAs were detected using qRT-PCR. A dual-luciferase reporter system was used to verify the binding between miR-136 and Sirt1.

RESULTS

In neonatal Babl/c mice, RSV infection caused obvious lung pathologies, promoted pulmonary cell apoptosis and LC3-Ⅱ/Ⅰ, Beclin-1 and miR-136 expressions, and increased the total cell number, inflammatory cells and factors in the BALF and decreased p62 and Sirt1 expressions. All these changes were alleviated dose-dependently by UA. In BEAS-2B cells, RSV infection significantly increased cell apoptosis, LC3B-positive cells and miR-136 expression and reduced Sirt1 expression (<0.01), which were dose-dependently attenuated by UA. Dual-luciferase reporter assay confirmed the binding between miR-136 and Sirt1. In RSV-infected BEAS-2B cells with UA treatment, overexpression of miR-136 and Ex527 treatment both significantly increased the inflammatory factors and cell apoptosis but decreased LC3B expression, and these changes were further enhanced by their combined treatment.

CONCLUSION

UA ameliorates RSV-induced lung infection in neonatal mice by activating miR-136-mediated Sirt1 signaling pathway.