Global profiling of double stranded RNA- and IFN-gamma-induced genes in rat pancreatic beta cells.

AIMS/HYPOTHESIS Viral infections and local production of IFN-gamma might contribute to beta-cell dysfunction/death in Type 1 Diabetes. Double stranded RNA (dsRNA) accumulates in the cytosol of viral-infected cells, and exposure of purified rat beta cells to dsRNA (tested in the form of polyinosinic-polycytidylic acid, PIC) in combination with IFN-gamma results in beta-cell dysfunction and apoptosis. To elucidate the molecular mechanisms involved in PIC + IFN-gamma-effects, we determined the global profile of genes modified by these agents in primary rat beta cells. METHODS FACS-purified rat beta cells were cultured for 6 or 24 h in control condition or with IFN-gamma, PIC or a combination of both agents. The gene expression profile was analysed in duplicate by high-density oligonucleotide arrays representing 5000 full-length genes and 3000 EST's. Changes of greater than or equal to 2.5-fold were considered as relevant. RESULTS Following a 6- or 24-h treatment with IFN-gamma, PIC or IFN-gamma and PIC, we observed changes in the expression of 51 to 189 genes. IFN-gamma modified the expression of MHC-related genes, and also of genes involved in beta-cell metabolism, protein processing, cytokines and signal transduction. PIC affected preferentially the expression of genes related to cell adhesion, cytokines and dsRNA signal transduction, transcription factors and MHC. PIC and/or IFN-gamma up-regulated the expression of several chemokines and cytokines that could contribute to mononuclear cell homing and activation during viral infection, while IFN-gamma induced a positive feedback on its own signal transduction. PIC + IFN-gamma inhibited insulin and GLUT-2 expression without modifying pdx-1 mRNA expression. CONCLUSION/INTERPRETATION This study provides the first comprehensive characterization of the molecular responses of primary beta cells to dsRNA + IFN-gamma, two agents that are probably present in the beta cell milieu during the course of virally-induced insulitis and Type 1 Diabetes. Based on these findings, we propose an integrated model for the molecular mechanisms involved in dsRNA + IFN-gamma induced beta-cell dysfunction and death.