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Double-Stranded Ribonucleic Acid (RNA) Induces ß-Cell Fas Messenger RNA Expression and Increases Cytokine-Induced ß-Cell Apoptosis¹

Gene Expression Unit, Diabetes Research Center, Vrije Universiteit Brussel, B-1090 Brussels, Belgium

Address all correspondence and requests for reprints to: Dr. D. L. Eizirik, Gene Expression Unit, Diabetes Research Center, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium. E-mail: deizirik{at}mebo.vub.ac.be

Type 1 diabetes mellitus (T1DM) is an autoimmune disease caused by progressive destruction of insulin-producing pancreatic ß-cells. Both viral infections and the cytokines interleukin-1ß (IL-1ß) and interferon- (IFN-) have been suggested as potential mediators of ß-cell death in early T1DM. We presently investigated whether the viral replicative intermediate double stranded RNA [here used as synthetic polyinosinic-polycytidylic acid (PIC)] modifies the effects of IL-1ß and IFN- on gene expression and viability of rat pancreatic ß-cells. For this purpose, fluorescence-activated cell sorting-purified rat ß-cells were exposed for 6–16 h (study of gene expression by RT-PCR) or 6–9 days (study of viability by nuclear dyes) to PIC and/or IL-1ß and IFN-. PIC increased the expression of Fas and Mn superoxide dismutase messenger RNAs by 5- to 10-fold. IL-1ß and a combination of PIC and IFN- (but not PIC or IFN- alone) induced expression of inducible nitric oxide (NO) synthase (iNOS) and consequent NO production. Induction of iNOS expression by PIC and IFN- requires nuclear factor-B activation, as suggested by transfection experiments with iNOS promoter-luciferase reporter constructs into primary ß-cells. Combinations of IL-1ß plus IFN-, PIC plus IFN-, or PIC plus IL-1ß induced a 2- to 3-fold increase in the number of apoptotic ß-cells. Blocking of iNOS activity significantly decreased PIC- plus IL-1ß-induced, but not PIC- plus IFN--induced, apoptosis.

In conclusion, PIC alone or in combination with cytokines modifies the expression of several genes in pancreatic ß-cells. Two of these genes, Fas and iNOS, may contribute to ß-cell death. The transcription factor nuclear factor-B is required for PIC-induced iNOS expression. PIC has an additive effect on cytokine-induced ß-cell death by both NO-dependent (in the case of IL-1ß) and NO-independent (in the case of IFN-) mechanisms. These findings suggest that viral intermediates in synergism with local cytokine production may play an important role in ß-cell apoptosis in early T1DM.