Interferon-α mediates human beta cell HLA class I overexpression, endoplasmic reticulum stress and apoptosis, three hallmarks of early human type 1 diabetes

Abstract

Aims/hypothesis Three hallmarks of the pancreatic islets in early human type 1 diabetes are overexpression of HLA class I, endoplasmic reticulum (ER) stress and beta cell apoptosis. The mediators of these phenomena remain to be defined. The type I interferon IFNα is expressed in human islets from type 1 diabetes patients and mediates HLA class I overexpression. We presently evaluated the mechanisms involved in IFNα-induced HLA class I expression in human beta cells and determined whether this cytokine contributes to ER stress and apoptosis. Methods IFNα-induced inflammation, ER stress and apoptosis were evaluated by RT-PCR, western blot, immunofluorescence and nuclear dyes, and proteins involved in type I interferon signalling were inhibited by small interfering RNAs. All experiments were performed in human islets or human EndoC-βH1 cells.Results IFNα upregulates HLA class I, inflammation and ER stress markers in human beta cells via activation of the candidate gene TYK2, and the transcription factors signal transducer and activator of transcription 2 and IFN regulatory factor 9. Furthermore, it acts synergistically with IL-1β to induce beta cell apoptosis. Conclusions/interpretation The innate immune effects induced by IFNα may induce and amplify the adaptive immune response against human beta cells, indicating that IFNα has a central role in the early phases of diabetes.

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

“…The human beta cell line EndoC-βH1 (kindly provided by Dr. R. Scharfmann, University of Paris, France) was cultured in Matrigel-fibronectin-coated plates as described [4]. These cells are free from mycoplasma infection, as evaluated by MycoAlert Mycoplasma Detection kit (Lonza, Basel, Switzerland).…”

“…After arrival in Brussels, islets were dispersed and cultured as in [4]. All experiments shown with EndoC-βH1 cells or human islet cells (indicated as “n” in the figures) refer to independent biological data (i.e using EndoC-βH1 cells from different passages or human islets from different donors).…”

“…All experiments shown with EndoC-βH1 cells or human islet cells (indicated as “n” in the figures) refer to independent biological data (i.e using EndoC-βH1 cells from different passages or human islets from different donors). Where indicated, cells were treated with human IFNα (PeproTech Inc., Rocky Hill, NJ) 20 or 1000 U/ml [4]. Cells were treated with ruxolitinib (kindly provided by Calibr, CA, USA), cerdulatinib (Selleckchem, Germany), Bayer-18 (Synkinase, UK), or cycloheximide (Sigma-Aldrich, Germany) as indicated.…”

“…These effects are mediated via activation of the Janus kinase (JAK-TYK2)/STAT pathway [4], with a key role for the type 1 diabetes candidate gene TYK2 , whose encoded protein phosphorylates and activates STATs [4, 5]. JAK/TYK2 inhibitors have been recently approved for the treatment of other autoimmune diseases, such as rheumatoid arthritis [6].…”

Autoreactive T cells in type 1 diabetes

“…Along with their epidemiological associations (29,30), enterovirus infections of β cells impair insulin secretion (118), alter mRNA/miRNA expression (119,120), and induce interferon responses (121,122) that promote β cell stress, dysfunction, and apoptosis (123). Enteroviruses may also trigger autoimmunity via presentation of self-molecules in an inflammatory context (bystander activation) (124) and/or by molecular mimicry (125)(126)(127).…”