Downregulated MiR-203 Attenuates IL-β, IL-6, and TNF-α Activation in TRAF6-treated Human Renal Mesangial and Tubular Epithelial Cells

Circulating microRNAs (miRNAs) are attracting major interest as novel non-invasive biomarkers for human autoimmune diseases including lupus nephritis (LN). A previous study showed that altered miR-203 expression may provide highly diagnostic for systemic lupus erythematosus. However, whether miR-203 is a diagnostic biomarker for LN is still unknown. In the present research, serum samples from 35 cases of active LN patients, 58 cases of inactive LN patients, and 74 cases of healthy volunteers were collected to analyze the expression profiles of miR-203 by qRT-PCR. The serum concentration of complement component 3 (C3) and complement component 4 (C4) was detected using nephelometry method. The expression of inflammatory cytokines, including interleukin 1 beta (IL-1β), interleukin 6 (IL-6), and tumor necrosis factor α (TNF-α), were analyzed using enzyme-linked immunosorbent assay (ELISA). The effect of miR-203 overexpression on the TNF receptor associated factor 6 (TRAF6)-induced inflammation of human renal mesangial cells (HRMCs) and human renal tubular epithelial cell line (HK-2) were evaluated. Results showed that miR-203 in serum of active LN patients was significantly down-regulated when compared with serum from inactive LN patients and healthy volunteers. Receiver operating curve (ROC) showed that decreased circulating miR-203 was a significant diagnostic biomarker for active LN patients, with an area under curve (AUC) of 0.974; sensitivity was 85.79%, and specificity was 89.40%. Significant downregulation of C3 and C4, and obvious upregulation of IL-β, IL-6, and TNF-α, was observed in serum of active LN patients. Furthermore, circulating miR-203 expression was positively correlated with the serum concentrations of C3 and C4, and negatively correlated with the serum expression of IL-1β, IL-6, and TNF-α in active LN patients. In addition, transfection of HRMCs and HK-2 cells with miR-203 mimics could suppress TRAF6-induced IL-β, IL-6, or TNF-α expression compared to cells treated with the mimics control group. In summary, decreased circulating miR-203 might be a candidate diagnostic biomarker for human active LN, and it attenuated IL-β, IL-6, and TNF-α activation in TRAF6-treated HRMCs and HK-2 cells.