MiR-20b inhibits mycobacterium tuberculosis induced inflammation in the lung of mice through targeting NLRP3.

Tuberculosis (TB) is one of immune-related disorders. Although dysregulation of miRNAs has been implicated in innate and adaptive immune response, the specific effect of miR-20b on TB has not been documented. In this study, downregulation of miR-20b and upregulation of NLRP3 were observed in macrophages of TB patients, increased levels of inflammatory factors secretion were observed in serum of TB patients. Next, we established a TB mice model by using M. tuberculosis infection and intravenous injection of miR-20b mimic. HE staining showed a denser lymphocytic infiltration and extensive tissue necrosis in the lung of TB mice. Lesions in the TB mice displayed a higher bacterial load by plating of lung homogenates. At the same time, lessened miR-20b and activated NLRP3/caspase-1/IL-1β pathway were observed in TB mice. MiR-20b mimic alleviated the inflammatory response and deactivated the NLRP3/caspase-1/IL-1β pathway in TB mice. Subsequently, we found that miR-20b induced M2 macrophage polarization by using flow cytometry. In addition, luciferase reporter assay confirmed that miR-20b directly bind to the 3'-UTR of NLRP3 and regulated its expression negatively. Further, we found that miR-20b mitigated the inflammation and pyroptosis in alveolar epithelial cells co-cultured with macrophages. Our results indicate that miR-20b could alleviate the inflammatory response in TB mice via targeting the NLRP3/caspase-1/IL-1β pathway, which provides a novel potential molecular mechanism of miR-20b therapy for TB.