Figure 8.

Cytokine‐induced heat‐shock protein 90α (hsp90α) release by pancreatic beta cells was mediated by c‐Jun N‐terminal kinase (JNK) and not p38 mitogen‐activated protein (MAP) kinase. Human βLox5 cells were treated with media alone or a JNK inhibitor (SP600125) for 6 hr before 24 hr stimulation with interleukin‐1β (IL‐1β), tumour necrosis factor‐α (TNF‐α) and interferon‐γ (IFN‐γ) (Cyt). Extracellular IL‐6 (a) and hsp90α (b) levels were measured by ELISA. Extracellular hsp90α levels were calculated relative to hsp90α release by control cells cultured without SP600125 or cytokines. Extracellular hsp90α values ranged between 6·8 and 77·1 ng/ml. Human βLox5 cells were transfected for 72 hr with control or JNK siRNA. JNK knockdown was assessed by immunoblotting (c, d). Transfected cells were then treated with media alone or IL‐1β, TNF‐α, and IFN‐γ (Cyt) for 24 hr. Extracellular hsp90α levels were analysed by ELISA (e). Data are presented as relative to control siRNA‐transfected cells treated with media alone. Hsp90α values ranged between 13·1 and 178·5 ng/ml. Human βLox5 cells were treated with media alone or the p38 MAP kinase inhibitor (SB202190) for 6 hr before 24 hr stimulation with IL‐1β, TNF‐α, and IFN‐γ (Cyt). Extracellular IL‐6 (f) and hsp90α (g) levels were measured by ELISA. Extracellular hsp90α levels were indicated relative to control cells treated without SB202190 or cytokines. Extracellular hsp90α values ranged between 2·8 and 34·1 ng/ml. Data are mean + SEM of n = 3 or n = 4 experiments. *P < 0·05, ***P < 0·001, ****P < 0·0001 (NS, not significant).