Expression of Dicer in rheumatoid arthritis is associated with disease activity and balances the production of TNF­α.

Gene expression can be altered through RNA interference (RNAi), including microRNA (miRNA) or small interfering RNA. Alterations of miRNAs in rheumatoid arthritis (RA) have been reported, however, the components of the RNAi machinery in RA remain to be fully elucidated. The aim of the present study was to detect the levels of Dicer, Argonaute2 and Drosha, components of the RNAi machinery, in the peripheral blood mononuclear cells of patients with RAusingreverse transcription­quantitative polymerase chain reaction, and to compare the results with disease activity and clinical features. Disease activity was assessed using the Disease Activity Score 28 (DAS28). Transfection and stimulation of cultured cells were conducted to determine the biological function of Dicer. ELISA was used to test tumor necrosis factor (TNF)­α protein levels. It was found that the mRNA expression levels of Dicer and Drosha were upregulated in patients with RA, and that the increased level of Dicer was correlated with disease activity in patients with RA. Dicer and TNF­α were activated in the serum of patients with RA. The activation of Dicer suppressed the production of TNF­α. These results suggested that Dicer can balance the production of TNF­α, and thus may serve as a regulator of the immune response in patients with RA.