MicroRNA-106b regulates pro-allergic properties of dendritic cells and Th2 polarisation by targeting early growth response-2 in vitro

Recent evidence has suggested that miRNA is implicated in the immune response of allergic and inflammatory diseases. However, little is known about its role in the mechanism that underlies the establishment of pro-allergic DCs in allergic rhinitis is not fully understood. This study assessed whether and how microRNA (miR)-106b regulates the pro-allergic properties of DCs upon allergen stimulation in vitro. Bone marrow-derived dendritic cells (BMDCs) were generated and stimulated with ovalbumin (OVA) to identify the miRNA expression profile. After transfection with miR-106b mimics and inhibitors OVA-activated BMDCs were further evaluated for surface marker expression using flow cytometry, cytokine production using ELISA and subsequent effects on Th2 cell polarisation using flow cytometry. Moreover, the upstream controllers and potential target proteins of miR-106b were examined in a western blot analysis. Results showed that MiR-106b expression was significantly inhibited in activated BMDCs upon OVA stimulation (p < 0.05). Surface marker expression (e.g., MHC class II, CD80 and CD86) was significantly upregulated after the transfection of an miR-106b inhibitor (p < 0.05), and the proportion of GATA-3+ T cells was significantly increased among CD4+ T cells that were cocultured with miR-106b inhibitor-pretreated BMDCs (p < 0.05). Conversely, IL-12 production from OVA-activated BMDCs and the proportion of T-bet+ T cells increased significantly in a coculture of CD4+ T cells and miR-106b mimics-transfected BMDCs (p < 0.05). The early growth response (Egr)-2 was identified via luciferase reporter assays as a target gene of miR-106b, and significant Egr-2 upregulation was observed in OVA-activated BMDCs following transfection with a miR-106b inhibitor (p < 0.05). In conclusion, our results suggest that miR-106b negatively regulates the pro-allergic properties of BMDCs and subsequent Th2 polarisation upon OVA stimulation and might represent a promising therapeutic target for allergic inflammation.