MiR-146a upregulates FOXP3 and suppresses inflammation by targeting HIPK3/STAT3 in allergic conjunctivitis

BACKGROUND: Allergic conjunctivitis (AC) is an inflammation caused by a hypersensitive immune reaction of conjunctiva to external allergens. The microRNA (miRNA) miR-146a has been reported to suppress the exacerbation of inflammation. However, the underlying influence and mechanism of miR-146a in AC has not been completely elucidated. METHODS: We first successfully established an AC mouse model and AC cell model. After each model was treated based on the experimental purposes, miR-146a, FOXP3, and homeodomain-interacting protein kinases 3 (HIPK3) expressions were estimated by reverse transcription quantitative polymerase chain reaction (RT-qPCR). The levels of immunoglobulin E (IgE), tumor necrosis factor-α (TNF-α), interleukin-10 (IL-10), interleukin-4 (IL-4), and transforming growth factor-β (TGF-β) were assessed using enzyme-linked immunosorbent assay (ELISA) kits; the related proteins were analyzed by western blot, immunofluorescence, or immunohistochemistry (IHC) assays; the interaction between miR-146a and HIPK3 were validated by a dual-luciferase reporter gene assay; and the inflammatory infiltration was certified by hematoxylin and eosin (H&E) staining. RESULTS: Our results indicated that miR-146a and FOXP3 were downregulated in AC model mice. Meanwhile, miR-146a overexpression could upregulate FOXP3 and inhibit inflammatory response in TGF-β-induced thymocytes. Besides, our results testified that HIPK3, as a target gene of miR-146a, could reverse miR-146a-mediated FOXP3 upregulation and inflammation inhibition. Moreover, we discovered that miR-146a could downregulate p-STAT3 by targeting HIPK3, and activation of STAT3 also could reverse miR-146a-mediated inflammation suppression in TGF-β-induced thymocytes. More importantly, miR-146a could ameliorate inflammatory infiltration and downregulate HIPK3 and p-STAT3 in AC model mice. CONCLUSIONS: We demonstrated a possible protective mechanism by the miR-146a/HIPK3/STAT3 axis, by which decrease of miR-146a could aggravate the inflammation of AC.