MicroRNA-20a-3p regulates the host immune response to facilitate the mycobacterium tuberculosis infection by targeting IKKβ/NF-κB pathway

Abstract

Background: Mycobacterium tuberculosis (M.tb) has evolved to utilize different mechanisms to evade the host immune response. Several microRNAs (miRNAs) have been found to regulate innate immune response in M.tb replication and infection, but the roles and detailed molecular mechanisms of miRNAs in M.tb infection remain to be clarified.

Methods: Previously published dataset GSE94007 from GEO database was used for screening differential-expressed miRNAs, and a significant up-regulated miR-20a-3p was chosen for further investigation. Cells were transfected with miR-20a-3p mimics, inhibitors, IKKβ siRNA, or their controls to verify the role of miR-20a-3p and IKKβ in M.tb infection and host immune response. IL-β, IL-6 and TNF-α contents in supernatant were measured by ELISA kits. The expression level of IKKβ/NF-κB pathway were also detected by western blot.

Results: We found that miR-20a-3p was dose-and time-dependently increased during M.tb infection. Subsequently, our results demonstrated that upregulation of miR-20a-3p promoted intracellular growth of bacterial, and suppressed the release of proinflammatory cytokines in both M.tb-infected RAW264.7 and BMDM cells, while downregulation of miR-20a-3p had an opposite effect. Moreover, miR-20a-3p suppressed the activity of NF-κB pathway by directly targeting IKKβ, resulting in the suppression of pro-inflammatory cytokines, attenuation of immune response and promotion of M.tb survival.

Conclusion: Our findings uncover a role of miR-20a-3p and its target IKKβ in regulating M.tb induced immune responses and provide a better understanding of pathogenesis of M.tb infection.

Keywords: IKKβ/NF-κB signaling; Immune response; Mycobacterium tuberculosis; miR-20a-3p.