Coomans de Brachène Alexandra, Castela Angela, Musuaya Anyïshai E, Marselli Lorella, Marchetti Piero, Eizirik Decio L
ULB Center for Diabetes Research, Medical Faculty, Campus Erasme, Université Libre de Bruxelles (ULB), Route de Lennik, 808-CP618, 1070, Brussels, Belgium.
Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
Auto Immun Highlights. 2021 Mar 27;12(1):6. doi: 10.1186/s13317-021-00148-2.
Type 1 diabetes (T1D) is an autoimmune disease characterized by the progressive destruction of pancreatic beta cells. Interferon-α (IFNα), an antiviral cytokine, is expressed in the pancreatic islets in early T1D, which may be secondary to viral infections. However, not all patients harboring a type I IFN signature present signals of viral infection, suggesting that this response might be initiated by other "danger signals". Accumulation of mitochondrial double-stranded RNA (mtdsRNA; a danger signal), secondary to silencing of members of the mitochondrial degradosome, PNPT1 and SUV3, has been described to activate the innate immune response.
To evaluate whether mtdsRNA represents a "danger signal" for pancreatic beta cells in the context of T1D, we silenced PNPT1 and/or SUV3 in slowly proliferating human insulin-secreting EndoC-βH1 cells and in non-proliferating primary human beta cells and evaluated dsRNA accumulation by immunofluorescence and the type I IFN response by western blotting and RT-qPCR.
Only the simultaneous silencing of PNPT1/SUV3 induced dsRNA accumulation in EndoC-βH1 cells but not in dispersed human islets, and there was no induction of a type I IFN response. By contrast, silencing of these two genes individually was enough to induce dsRNA accumulation in fibroblasts present in the human islet preparations.
These data suggest that accumulation of endogenous mtdsRNA following degradosome knockdown depends on the proliferative capacity of the cells and is not a mediator of the type I IFN response in human pancreatic beta cells.
1型糖尿病（T1D）是一种自身免疫性疾病，其特征是胰腺β细胞进行性破坏。干扰素-α（IFNα）是一种抗病毒细胞因子，在T1D早期的胰岛中表达，这可能继发于病毒感染。然而，并非所有具有I型干扰素特征的患者都有病毒感染信号，这表明这种反应可能由其他“危险信号”引发。线粒体双链RNA（mtdsRNA；一种危险信号）在线粒体降解体成员PNPT1和SUV3沉默后积累，已被描述为可激活先天免疫反应。
为了评估mtdsRNA在T1D背景下是否代表胰腺β细胞的“危险信号”，我们在缓慢增殖的人胰岛素分泌EndoC-βH1细胞和非增殖的原代人β细胞中沉默PNPT1和/或SUV3，并通过免疫荧光评估双链RNA积累，通过蛋白质印迹和逆转录定量聚合酶链反应评估I型干扰素反应。
只有PNPT1/SUV3同时沉默会在EndoC-βH1细胞中诱导双链RNA积累，但在分散的人胰岛中不会，并且没有诱导I型干扰素反应。相比之下，单独沉默这两个基因就足以在人胰岛制剂中的成纤维细胞中诱导双链RNA积累。
这些数据表明，降解体敲低后内源性mtdsRNA的积累取决于细胞的增殖能力，并且不是人胰腺β细胞中I型干扰素反应的介质。
