Downregulation of CCL2 induced by the upregulation of microRNA-206 is associated with the severity of HEV71 encephalitis

MicroRNAs (miRNAs) have been investigated widely as key regulators of gene expression in different diseases by affecting the miRNA-mediated regulatory function. Human enterovirus 71 (HEV71) can cause a series of human diseases, including encephalitis. Chemokine (C-C motif) ligand 2 (CCL2) is one of the important genes involved in regulating inflammation. However, the mechanisms underlying HEV71 encephalitis mediated by CCL2 remain to be elucidated. In the present study, reverse transcription-quantitative polymerase chain reaction analysis was used to determine the expression level of miR-206 and the mRNA expression of CCL2 in samples. Western blot analysis was used to detect the protein levels of CCL2. A luciferase assay was used to verify the miR-206 target site in CCL2. A CCK-8 assay and flow cytometry were used to determine cell proliferation and apoptosis. The results demonstrated that miR-206 was downregulated in severe HEV71 encephalitis. Using bioinformatics analysis, miR-206 was predicted to target the human CCL2 3′-untranslated region (3′-UTR). A dual-luciferase assay demonstrated that miR-206 downregulated the expression of CCL2 by directly targeting its 3′-UTR, whereas CCL2 3′-UTR mutations completely eliminated its interaction with miR-206. The expression levels of miR-206 and CCL2 were inversely correlated in cerebrospinal fluid. The expression of exogenous miRNA, which mimicked miR-206 miRNA, decreased the protein and mRNA levels of CCL2, whereas the suppression of endogenous miR-206 resulted in an increase of the protein and mRNA levels of CCL2. The present study also found that miR-206 promoted NPC cell proliferation and reduced the apoptosis of NPC cells via CCL2. The mechanism is likely to involve suppression of the expression of miR-206 and upregulation of the expression of CCL2, important in regulating the progress of HEV71 encephalitis. In conclusion, miR-206 may be useful in the prognosis and treatment of HEV71 encephalitis.