Fig. 5

Tristetraprolin (TTP) silencing in rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) and murine fibroblasts induces cytokine expression. a RA FLS (n = 4) were left untransfected or were transfected with control non-targeting siRNA (siCtrl) or specific siRNA targeting TTP (siTTP). Knockdown efficiency was verified at the mRNA level by qPCR (left panel) and by immunoblotting (right panel). For immunoblot samples, cells were stimulated with IL-1β for 2 h. Protein lysate was analyzed with antibodies recognizing TTP or control H3: **p < 0.01, ratio t-test. b RA FLS (n = 7) were transfected as in a, and further left untreated or treated with ITF2357, prior to stimulation with IL-1β for 8 h. Gene expression was determined by qPCR. Data are presented as fold change in mRNA expression compared to siCtrl conditions. c RA FLS were processed as in b, IL6, IL8, CXCL2 and PTGS2 (n = 7) and TTP expression (n = 3) was determined by qPCR. Data presented as fold change in mRNA expression compared to siCtrl-IL-1β stimulated conditions. d Wild-type (ZFP36^+/+) or TTP knockout (ZFP36^−/−) murine fibroblasts (n = 4) were either left untreated or treated with ITF2357 and were further stimulated with IL-1β. Gene expression was determined by qPCR. Results are presented as 2^{^(-ΔCT)}× 100 of the target of interest normalized to ACTB housekeeping gene. b-d *p < 0.05, **p < 0.01, one-way analysis of variance with Greenhouse-Geisser correction followed by Fisher’s least significant difference test