Double-stranded ribonucleic acid (RNA) induces beta-cell Fas messenger RNAexpression and increases cytokine-induced beta-cell apoptosis

Type 1 diabetes mellitus (T1DM) is an autoimmune disease caused by progress ive destruction of insulin-producing pancreatic beta -cells. Both viral inf ections and the cytokines interleukin-1 beta (IL-1 beta) and interferon-gam ma (IFN-gamma) have been suggested as potential mediators of beta -cell dea th in early T1DM. We presently investigated whether the viral replicative i ntermediate double stranded RNA [here used as synthetic polyinosinic-polycy tidylic acid (PIC)] modifies the effects of IL-1 beta and IFN-gamma on gene expression and viability of rat pancreatic beta -cells. For this purpose, fluorescence-activated cell sorting-purified rat beta -cells were exposed f or 6-16 h (study of gene expression by RT-PCR) or 6-9 days (study of viabil ity by nuclear dyes) to PIC and/or IL-1 beta and IFN-gamma. PIC increased t he expression of Fas and Mn su peroxide dismutase messenger RNAs by 5- to 1 0-fold. IL-1 beta and a combination of PIC and IFN-gamma (but not PIC or IF N-gamma alone) induced expression of inducible nitric oxide (NO) synthase ( iNOS) and consequent NO production. Induction of iNOS expression by PIC and IFN-gamma requires nuclear factor-kappaB activation, as suggested by trans fection experiments with iNOS promoter-luciferase reporter constructs into primary beta -cells. Combinations of IL-1 beta plus IFN-gamma, PIC plus IFN -gamma, or PIG plus IL-1 beta induced a 2- to 3-fold increase in the number of apoptotic P-cells. Blocking of iNOS activity significantly decreased PI C- plus IL-1 beta -induced, but not PIC- plus IFN-gamma -induced, apoptosis . In conclusion, PIC alone or in combination with cytokines modifies the expr ession of several genes in pancreatic beta -cells. Two of these genes, Fas and iNOS, may contribute to beta -cell death. The transcription factor nucl ear factor-kappaB is required for PIG-induced iNOS expression. PIC has an a dditive effect on cytokine-induced beta -cell death by both NO-dependent (i n the case of IL-1 beta) and NO-independent (in the case of IFN-gamma) mech anisms. These findings suggest that viral intermediates in synergism with l ocal cytokine production may play an important role in beta -cell apoptosis in early T1DM.