IFN-α induces a preferential long-lasting expression of MHC class I in human pancreatic beta cells

Aims/hypothesis IFN-α, a cytokine expressed in human islets from individuals affected by type 1 diabetes, plays a key role in the pathogenesis of diabetes by upregulating inflammation, endoplasmic reticulum (ER) stress and MHC class I overexpression, three hallmarks of islet histology in early type 1 diabetes. We tested whether expression of these mediators of beta cell loss is reversible upon IFN-α withdrawal or IFN-α pathway inhibition. Methods IFN-α-induced MHC class I overexpression, ER stress and inflammation were evaluated by flow cytometry, immunofluorescence and real-time PCR in human EndoC-βH1 cells or human islets exposed to IFN-α with or without the presence of Janus kinase (JAK) inhibitors. Protein expression was evaluated by western blot. Results IFN-α-induced expression of inflammatory and ER stress markers returned to baseline after 24–48 h following cytokine removal. In contrast, MHC class I overexpression at the cell surface persisted for at least 7 days. Treatment with JAK inhibitors, when added with IFN-α, prevented MHC class I overexpression, but when added 24 h after IFN-α exposure these inhibitors failed to accelerate MHC class I return to baseline. Conclusions/interpretation IFN-α mediates a long-lasting and preferential MHC class I overexpression in human beta cells, which is not affected by the subsequent addition of JAK inhibitors. These observations suggest that IFN-α-stimulated long-lasting MHC class I expression may amplify beta cell antigen presentation during the early phase of type 1 diabetes and that IFN-α inhibitors might need to be used at very early stages of the disease to be effective

Cytokines Interleukin-1β and Tumor Necrosis Factor-α Regulate Different Transcriptional and Alternative Splicing Networks in Primary β-Cells

OBJECTIVE: Cytokines contribute to pancreatic beta-cell death in type 1 diabetes. This effect is mediated by complex gene networks that remain to be characterized. We presently utilized array analysis to define the global expression pattern of genes, including spliced variants, modified by the cytokines interleukin (IL)-1beta + interferon (IFN)-gamma and tumor necrosis factor (TNF)-alpha + IFN-gamma in primary rat beta-cells. RESEARCH DESIGN AND METHODS: Fluorescence-activated cell sorter-purified rat beta-cells were exposed to IL-1beta + IFN-gamma or TNF-alpha + IFN-gamma for 6 or 24 h, and global gene expression was analyzed by microarray. Key results were confirmed by RT-PCR, and small-interfering RNAs were used to investigate the mechanistic role of novel and relevant transcription factors identified by pathway analysis. RESULTS Nearly 16,000 transcripts were detected as present in beta-cells, with temporal differences in the number of genes modulated by IL-1beta + IFNgamma or TNF-alpha + IFN-gamma. These cytokine combinations induced differential expression of inflammatory response genes, which is related to differential induction of IFN regulatory factor-7. Both treatments decreased the expression of genes involved in the maintenance of beta-cell phenotype and growth/regeneration. Cytokines induced hypoxia-inducible factor-alpha, which in this context has a proapoptotic role. Cytokines also modified the expression of >20 genes involved in RNA splicing, and exon array analysis showed cytokine-induced changes in alternative splicing of >50% of the cytokine-modified genes. CONCLUSIONS: The present study doubles the number of known genes expressed in primary beta-cells, modified or not by cytokines, and indicates the biological role for several novel cytokine-modified pathways in beta-cells. It also shows that cytokines modify alternative splicing in beta-cells, opening a new avenue of research for the field.Journal ArticleResearch Support, Non-U.S. Gov'tinfo:eu-repo/semantics/publishe

MDA5 and PTPN2, two candidate genes for type 1 diabetes, modify pancreatic β-cell responses to the viral by-product double-stranded RNA

β-Cell destruction in type 1 diabetes (T1D) is at least in part consequence of a ‘dialog’ between β-cells and immune system. This dialog may be affected by the individual's genetic background. We presently evaluated whether modulation of MDA5 and PTPN2, two candidate genes for T1D, affects β-cell responses to double-stranded RNA (dsRNA), a by-product of viral replication. These genes were selected following comparison between known candidate genes for T1D and genes expressed in pancreatic β-cells, as identified in previous array analysis. INS-1E cells and primary fluorescence-activated cell sorting-purified rat β-cells were transfected with small interference RNAs (siRNAs) targeting MDA5 or PTPN2 and subsequently exposed to intracellular synthetic dsRNA (polyinosinic–polycitidilic acid—PIC). Real-time RT–PCR, western blot and viability assays were performed to characterize gene/protein expression and viability. PIC increased MDA5 and PTPN2 mRNA expression, which was inhibited by the specific siRNAs. PIC triggered apoptosis in INS-1E and primary β-cells and this was augmented by PTPN2 knockdown (KD), although inhibition of MDA5 did not modify PIC-induced apoptosis. In contrast, MDA5 silencing decreased PIC-induced cytokine and chemokine expression, although inhibition of PTPN2 induced minor or no changes in these inflammatory mediators. These findings indicate that changes in MDA5 and PTPN2 expression modify β-cell responses to dsRNA. MDA5 regulates inflammatory signals, whereas PTPN2 may function as a defence mechanism against pro-apoptotic signals generated by dsRNA. These two candidate genes for T1D may thus modulate β-cell apoptosis and/or local release of inflammatory mediators in the course of a viral infection by acting, at least in part, at the pancreatic β-cell level

Mutation H63D in the HFE gene confers risk for the development of type 2 diabetes mellitus but not for chronic complications

info:eu-repo/semantics/publishe

Molecular Footprints of the Immune Assault on Pancreatic Beta Cells in Type 1 Diabetes

info:eu-repo/semantics/publishe

PTPN2 and MDA5, two candidate genes for type 1 diabetes, modify beta cell responses to double-stranded RNA

info:eu-repo/semantics/publishe

Abscesso hipofisário simulando apoplexia

O abscesso hipofisário representa uma patologia rara, que, contudo, deve ser considerada na avaliação das massas selares, uma vez que o seu prognóstico depende da drenagem cirúrgica e do uso de antibióticos específicos. A principal manifestação clínica é cefaléia crônica e nem sempre está associada à identificação de um foco infeccioso, o que diminui a probabilidade da sua inclusão nas hipóteses diagnósticas. Apresenta-se o caso de um paciente com abscesso de hipófise e história pregressa de adenoma operado, cefaléia de início recente e hipopituitarismo adquirido, cujo diagnóstico inicial foi de apoplexia pituitária.info:eu-repo/semantics/publishe

Endoplasmic reticulum stress sensitizes pancreatic beta cells to interleukin-1b-induced apoptosis via Bim/A1 imbalance

info:eu-repo/semantics/publishe