Figure 5.

Live/Dead assays determined calcium dependency and extracellular signal-regulated kinase (ERK) contribution to cell death induced by pH 6.0 with IL-1β. The number of dead fibroblast-like synoviocytes (FLS) and the number of live FLS were counted to obtain the percent dead. (A-F) Representative images from FLS stained using a Live/Dead Viability/Cytotoxicity kit. Live cells were stained with calcein AM (green), dead cells were stained with ethidium homodimer (red). (A and B) Show images of FLS treated by pH 7.4 without or with IL-1β, respectively. (C and D) Show images of FLS treated by pH 6.0 and IL-1β without or with intracellular calcium chelating agent (BAPTA, 1 μM), respectively; (E and F) show images of FLS treated by pH 6.0 and IL-1β without or with inhibitor of ERK (PD98059,10 μM), respectively. (G) Quantitative analysis shows approximately 30% dead FLS after treatment with pH 6.0 and IL-1β, which was significantly greater than FLS treated with pH 6.0 and IL-1β with BAPTA, and pH 7.4 and IL-1β with and without BAPTA (*P <0.01). (H) Quantitative analysis shows approximately 30% dead FLS after treatment with pH 6.0 and IL-1β, which was significantly greater than FLS treated with pH 6.0 and IL-1β with PD98059 (10 μM), and FLS with or without IL-1β and pH 7.4 (*P <0.001). Data are mean ± standard error of the mean.

Gong et al. Arthritis Research & Therapy 2014 16:R121   doi:10.1186/ar4577
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