Diabetes and Obesity Research Program, Garvan Institute of Medical Research, St Vincent's Hospital, 384 Victoria St, Darlinghurst, NSW 2010, Australia.
Diabetologia. 2012 Nov;55(11):2999-3009. doi: 10.1007/s00125-012-2657-3. Epub 2012 Jul 28.
AIMS/HYPOTHESIS: Pancreatic beta cell destruction in type 1 diabetes may be mediated by cytokines such as IL-1β, IFN-γ and TNF-α. Endoplasmic reticulum (ER) stress and nuclear factor-κB (NFκB) signalling are activated by cytokines, but their significance in beta cells remains unclear. Here, we investigated the role of cytokine-induced ER stress and NFκB signalling in beta cell destruction.
Isolated mouse islets and MIN6 beta cells were incubated with IL-1β, IFN-γ and TNF-α. The chemical chaperone 4-phenylbutyric acid (PBA) was used to inhibit ER stress. Protein production and gene expression were assessed by western blot and real-time RT-PCR.
We found in beta cells that inhibition of cytokine-induced ER stress with PBA unexpectedly potentiated cell death and NFκB-regulated gene expression. These responses were dependent on NFκB activation and were associated with a prolonged decrease in the inhibitor of κB-α (IκBα) protein, resulting from increased IκBα protein degradation. Cytokine-mediated NFκB-regulated gene expression was also potentiated after pre-induction of ER stress with thapsigargin, but not tunicamycin. Both PBA and thapsigargin treatments led to preferential upregulation of ER degradation genes over ER-resident chaperones as part of the adaptive unfolded protein response (UPR). In contrast, tunicamycin activated a balanced adaptive UPR in association with the maintenance of Xbp1 splicing.
CONCLUSIONS/INTERPRETATION: These data suggest a novel mechanism by which cytokine-mediated ER stress interacts with NFκB signalling in beta cells, by regulating IκBα degradation. The cross-talk between the UPR and NFκB signalling pathways may be important in the regulation of cytokine-mediated beta cell death.
目的/假设：1 型糖尿病中胰岛β细胞的破坏可能是由细胞因子如 IL-1β、IFN-γ 和 TNF-α介导的。细胞因子激活内质网 (ER) 应激和核因子-κB (NFκB) 信号通路，但它们在β细胞中的意义尚不清楚。在这里，我们研究了细胞因子诱导的 ER 应激和 NFκB 信号通路在β细胞破坏中的作用。
用 IL-1β、IFN-γ 和 TNF-α孵育分离的小鼠胰岛和 MIN6β细胞。用化学伴侣 4-苯基丁酸 (PBA) 抑制 ER 应激。通过 Western blot 和实时 RT-PCR 评估蛋白产生和基因表达。
我们发现，用 PBA 抑制细胞因子诱导的 ER 应激出人意料地增强了细胞死亡和 NFκB 调节的基因表达。这些反应依赖于 NFκB 的激活，并与 IκBα 蛋白的延长减少有关，这是由于 IκBα 蛋白降解增加所致。细胞因子介导的 NFκB 调节的基因表达在使用 thapsigargin 预先诱导 ER 应激后也得到增强，但 tunicamycin 则不然。PBA 和 thapsigargin 处理都导致 ER 降解基因的优先上调，而不是 ER 驻留伴侣，这是适应性未折叠蛋白反应 (UPR) 的一部分。相比之下，tunicamycin 激活了平衡的适应性 UPR，同时保持 Xbp1 剪接。
结论/解释：这些数据表明，细胞因子介导的 ER 应激通过调节 IκBα 降解与β细胞中的 NFκB 信号通路相互作用的一种新机制。UPR 和 NFκB 信号通路之间的串扰可能在调节细胞因子介导的β细胞死亡中很重要。
