[Upregulation of miR-498 suppresses Th17 cell differentiation by targeting STAT3 in rheumatoid arthritis patients].

To investigate the effect and mechanism of miR-498 on Th17 cell differentiation of peripheral blood mononuclear cells (PMBCs) in rheumatoid arthritis (RA) patients, peripheral blood samples were collected from RA patients and healthy controls, respectively. The proportion of CD4+IL-17+ T cells (Th17 cells) or CD4+FOXP3+ T cells (Tregs) in T cells and the Th17/Treg ratio were identified by the flow cytometer. The STAT3 and miR-498 expression were measured by Western blot and real-time PCR, respectively. ELISA was used to detect IL-17 concentrations. Luciferase assay was performed to confirm that miR-498 directly targeted the 3' untranslated region (3'UTR) of STAT3 in CD4+ T cells. The effect of miR-498 on Th17 cell differentiation was explored by transfection of miR-498 mimic and/or pcDNA-STAT3 into CD4+ T cells. In PMBCs of RA patients, the Th17/CD4+ T cell ratio was significantly increased, while the Tregs/CD4+ T cell ratio was obviously decreased, leading to a higher Th17/Treg ratio. The results showed a reduced miR-498 expression and an increased STAT3 protein expression in PMBCs, and an increased IL-17 concentration in serum of RA patients. In cells transfected with wild-type-STAT3-LU, miR-498 mimic significantly reduced the luciferase activity, STAT3 gene and protein expression, and miR-498 inhibitor had an opposite function. While the miR-498 mimic/inhibitor had no effect on the luciferase activity and STAT3 expression in cells transfected with mutant-STAT3-LU. CD4+ T cells transfected with miR-498 mimic had a lower Th17/CD4+ T cell ratio and IL-17 concentration, however, transfection of pcDNA-STAT3 reversed the effect of miR-498 mimic on Th17/CD4+ T cell ratio and IL-17 concentration. These results suggest that overexpression of miR-498 suppresses Th17 cell differentiation by targeting STAT3 in RA patients.

A20 overexpression inhibits lipopolysaccharide-induced NF-κB activation, TRAF6 and CD40 expression in rat peritoneal mesothelial cells.

Zinc finger protein A20 is a key negative regulator of inflammation. However, whether A20 may affect inflammation during peritoneal dialysis (PD)-associated peritonitis is still unclear. This study was aimed to investigate the effect of A20 overexpression on lipopolysaccharide (LPS)-induced inflammatory response in rat peritoneal mesothelial cells (RPMCs). Isolated and cultured RPMCs in vitro. Plasmid pGEM-T easy-A20 was transfected into RPMCs by Lipofectamine™2000. The protein expression of A20, phospho-IκBα, IκBα, TNF receptor-associated factor (TRAF) 6 and CD40 were analyzed by Western blot. The mRNA expression of TRAF6, CD40, interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were determined by real time-PCR. NF-κB p65 DNA binding activity, IL-6 and TNF-α levels in cells culture supernatant were determined by ELISA. Our results revealed that RPMCs overexpression of A20 lead to significant decrease of LPS-induced IκBα phosphorylation and NF-κB DNA binding activity (all p<0.01). In addition, A20 also attenuated the expression of TRAF6, CD40, IL-6 and TNF-α as well as levels of IL-6 and TNF-α in cells culture supernatant (all p<0.05). However, A20 only partly inhibited CD40 expression. Our study indicated that A20 overexpression may depress the inflammatory response induced by LPS in cultured RPMCs through negatively regulated the relevant function of adaptors in LPS signaling pathway.