Fig. 3

Tristetraprolin (TTP) expression and activity are induced by ITF2357. a, b Rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) were left untreated or were treated with ITF2357 before incubation with IL-1β for either 2 h (a, n = 4) or for 4 and 8 h (b, n = 6). The mRNA expression of the Adenosine uridine-rich elements (ARE) binding proteins (ARE-BP) was analyzed by qPCR. c RA FLS (n = 6) were subject to mRNA stability analysis as specified in Fig. 2a and TTP expression was analyzed by qPCR: *p < 0.05, Wilcoxon matched pairs test. d RA FLS (n = 4) were treated with ITF2357 before incubation with IL-1β for either 2 h, 4 h or 8 h and the expression levels of TTP primary and mature transcript were analyzed by qPCR. Graph shows the 2^{^(-ΔCT)} ratio of the primary/mature transcript normalized to GAPDH housekeeping gene. e RA FLS were left untreated or were treated with ITF2357 before incubation with IL-1β for 2 and 4 h. Protein lysates were processed for immunoblotting with antibodies recognizing TTP and tubulin (left panel) and signal intensity (n = 8) was subsequently quantified by densitometry analysis (right panel). Band with higher apparent molecular mass corresponds to the post-translationally modified protein. d, e *p < 0.05, **p < 0.01, one-way analysis of variance with Greenhouse-Geisser correction followed by Fisher’s least significant difference test. ActD, actinomycin D; AUF, AU-rich binding factor; KHSRP, KH-type splicing regulatory protein; HuR, Hu antigen R