Cottet Sandra, Dupraz Philippe, Hamburger Fabienne, Dolci Wanda, Jaquet Muriel, Thorens Bernard
Institute of Pharmacology and Toxicology, University of Lausanne, Lausanne, Switzerland.
Diabetes. 2002 Jun;51(6):1805-14. doi: 10.2337/diabetes.51.6.1805.
Type 1 diabetes is characterized by the infiltration of activated leukocytes within the pancreatic islets, leading to beta-cell dysfunction and destruction. The exact role played by interferon-gamma, tumor necrosis factor (TNF)-alpha, and interleukin-1beta in this pathogenic process is still only partially understood. To study cytokine action at the cellular level, we are working with the highly differentiated insulin-secreting cell line, betaTc-Tet. We previously reported that it was susceptible to apoptosis induced by TNF-alpha, in combination with interleukin-1beta and interferon-gamma. Here, we report that cytokine-induced apoptosis was correlated with the activation of caspase-8. We show that in betaTc-Tet cells, overexpression of cFLIP, the cellular FLICE (FADD-like IL-1beta-converting enzyme)-inhibitory protein, completely abolished cytokine-dependent activation of caspase-8 and protected the cells against apoptosis. Furthermore, cFLIP overexpression increased the basal and interleukin-1beta-mediated transcriptional activity of nuclear factor (NF)-kappaB, whereas it did not change cytokine-induced inducible nitric oxide synthase gene transcription and nitric oxide secretion. The presence of cFLIP prevented the weak TNF-alpha-induced reduction in cellular insulin content and secretion; however, it did not prevent the decrease in glucose-stimulated insulin secretion induced by the combined cytokines, in agreement with our previous data demonstrating that interferon-gamma alone could induce these beta-cell dysfunctions. Together, our data demonstrate that overexpression of cFLIP protects mouse beta-cells against TNF-alpha-induced caspase-8 activation and apoptosis and is correlated with enhanced NF-kappaB transcriptional activity, suggesting that cFLIP may have an impact on the outcome of death receptor-triggered responses by directing the intracellular signals from beta-cell death to beta-cell survival.
1型糖尿病的特征是活化的白细胞浸润胰岛，导致β细胞功能障碍和破坏。干扰素-γ、肿瘤坏死因子（TNF）-α和白细胞介素-1β在这一致病过程中的确切作用仍仅被部分了解。为了在细胞水平研究细胞因子的作用，我们正在使用高度分化的胰岛素分泌细胞系βTc-Tet。我们之前报道过，它对TNF-α联合白细胞介素-1β和干扰素-γ诱导的凋亡敏感。在此，我们报道细胞因子诱导的凋亡与半胱天冬酶-8的激活相关。我们表明，在βTc-Tet细胞中，细胞FLICE（FADD样白细胞介素-1β转化酶）抑制蛋白cFLIP的过表达完全消除了细胞因子依赖性半胱天冬酶-8的激活，并保护细胞免受凋亡。此外，cFLIP过表达增加了核因子（NF）-κB的基础和白细胞介素-1β介导的转录活性，而它并未改变细胞因子诱导的诱导型一氧化氮合酶基因转录和一氧化氮分泌。cFLIP的存在阻止了TNF-α诱导的细胞胰岛素含量和分泌的轻微降低；然而，它并未阻止联合细胞因子诱导的葡萄糖刺激的胰岛素分泌的减少，这与我们之前的数据一致，即单独的干扰素-γ可诱导这些β细胞功能障碍。总之，我们的数据表明，cFLIP的过表达保护小鼠β细胞免受TNF-α诱导的半胱天冬酶-8激活和凋亡，并与增强的NF-κB转录活性相关，提示cFLIP可能通过将细胞内信号从β细胞死亡导向β细胞存活，对死亡受体触发的反应结果产生影响。
