Institute of Biomedical and Clinical Sciences, University of Exeter Medical School, RILD Building (Level 4), Barrack Road, Exeter, EX2 5DW, UK.
Diabetologia. 2019 Jan;62(1):87-98. doi: 10.1007/s00125-018-4750-8. Epub 2018 Oct 18.
AIMS/HYPOTHESIS: In type 1 diabetes, selective beta cell loss occurs within the inflamed milieu of insulitic islets. This milieu is generated via the enhanced secretion of proinflammatory cytokines and by the loss of anti-inflammatory molecules such as IL-4 and IL-13. While the actions of proinflammatory cytokines have been well-studied in beta cells, the effects of their anti-inflammatory counterparts have received relatively little attention and we have addressed this.
Clonal beta cells, isolated human islets and pancreas sections from control individuals and those with type 1 diabetes were employed. Gene expression was measured using targeted gene arrays and by quantitative RT-PCR. Protein expression was monitored in cell extracts by western blotting and in tissue sections by immunocytochemistry. Target proteins were knocked down selectively with interference RNA.
Cytoprotection achieved with IL-4 and IL-13 is mediated by the early activation of signal transducer and activator of transcription 6 (STAT6) in beta cells, leading to the upregulation of anti-apoptotic proteins, including myeloid leukaemia-1 (MCL-1) and B cell lymphoma-extra large (BCLXL). We also report the induction of signal regulatory protein-α (SIRPα), and find that knockdown of SIRPα is associated with reduced beta cell viability. These anti-apoptotic proteins and their attendant cytoprotective effects are lost following siRNA-mediated knockdown of STAT6 in beta cells. Importantly, analysis of human pancreas sections revealed that STAT6 is markedly depleted in the beta cells of individuals with type 1 diabetes, implying the loss of cytoprotective responses.
CONCLUSIONS/INTERPRETATION: Selective loss of STAT6 may contribute to beta cell demise during the progression of type 1 diabetes.
目的/假设：在 1 型糖尿病中，胰岛内的炎症环境会导致选择性的β细胞丧失。这种微环境是通过前炎性细胞因子的增强分泌以及抗炎分子如 IL-4 和 IL-13 的丧失而产生的。虽然前炎性细胞因子在β细胞中的作用已经得到了很好的研究，但它们的抗炎对应物的作用却相对较少受到关注，我们已经解决了这个问题。
使用从对照个体和 1 型糖尿病患者中分离的克隆β细胞、人胰岛和胰腺切片进行了研究。使用靶向基因芯片和定量 RT-PCR 测量基因表达。通过 Western 印迹在细胞提取物中监测蛋白质表达，通过免疫细胞化学在组织切片中监测蛋白质表达。使用干扰 RNA 选择性地敲低靶蛋白。
IL-4 和 IL-13 实现的细胞保护作用是通过β细胞中信号转导和转录激活因子 6（STAT6）的早期激活介导的，导致抗凋亡蛋白如髓样白血病-1（MCL-1）和 B 细胞淋巴瘤-额外大（BCLXL）的上调。我们还报告了信号调节蛋白-α（SIRPα）的诱导，并发现 SIRPα 的敲低与β细胞活力降低有关。这些抗凋亡蛋白及其伴随的细胞保护作用在β细胞中 STAT6 的 siRNA 介导敲低后丢失。重要的是，对人胰腺切片的分析表明，1 型糖尿病患者的β细胞中 STAT6 明显耗竭，这意味着细胞保护反应的丧失。
结论/解释：选择性的 STAT6 丧失可能导致 1 型糖尿病进展过程中的β细胞死亡。
