Fig. 1

Effects of ER stress on RA FLS inflammatory gene expression and cellular viability. a, b Expression of ER stress markers (a) and XBP1 splice variants (b) was measured in three FLS lines after exposure to increasing concentrations of TG (a) or constant 10 nM TG (b). The significance of changes relative to unstimulated controls was assessed by analysis of variance with post hoc Dunnett’s test. * p < 0.05; ** p < 0.01; *** p < 0.001. c, d Apoptosis induction and cellular viability were measured using a cell death ELISA (c) and an MTT assay (d), respectively, after stimulation with 10 nM TG for 8, 16, or 24 h or with increasing concentrations of TG for 24 h. e IL-6 and IL-8 in cell culture supernatants (n = 3) were measured by ELISA after 24-h incubation with 10 nM TG. f FLS (n = 3) were incubated with 10 nM TG for 2 h, and expression of 84 inflammatory genes was analyzed by qPCR-based array. Shown are the top 20 genes ranked by mean fold change relative to unstimulated cells. BiP Binding immunoglobulin protein, CHOP C/EBP homologous protein, ELISA Enzyme-linked immunosorbent assay, ER Endoplasmic reticulum, FLS Fibroblast-like synoviocytes, GAPDH Glyceraldehyde 3-phosphate dehydrogenase, IL Interleukin, MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, N.D. Not detectable, OD Optical density, qPCR Quantitative polymerase chain reaction, RA Rheumatoid arthritis, TG Thapsigargin, TLR Toll-like receptor, TNF Tumor necrosis factor, XBP1 X-box binding protein 1