Pancreatic beta-cell damage mediated by beta-cell production of interleukin-1. A novel mechanism for virus-induced diabetes.

Viral infection is one environmental factor that may initiate beta-cell damage during the development of autoimmune diabetes. Formed during viral replication, double-stranded RNA (dsRNA) activates the antiviral response in infected cells. In combination, synthetic dsRNA (polyinosinic-polycytidylic acid, poly(I-C)) and interferon (IFN)-gamma stimulate inducible nitric-oxide synthase (iNOS) expression, inhibit insulin secretion, and induce islet degeneration. Interleukin-1 (IL-1) appears to mediate dsRNA + IFN-gamma-induced islet damage in a nitric oxide-dependent manner, as the interleukin-1 receptor antagonist protein prevents dsRNA + IFN-gamma-induced iNOS expression, inhibition of insulin secretion, and islet degeneration. IL-1beta is synthesized as an inactive precursor protein that requires cleavage by the IL-1beta-converting enzyme (ICE) for activation. dsRNA and IFN-gamma stimulate IL-1beta expression and ICE activation in primary beta-cells, respectively. Selective ICE inhibition attenuates dsRNA + IFN-gamma-induced iNOS expression by primary beta-cells. In addition, poly(I-C) + IFN-gamma-induced iNOS expression and nitric oxide production by human islets are prevented by interleukin-1 receptor antagonist protein, indicating that human islets respond to dsRNA and IFN-gamma in a manner similar to rat islets. These studies provide biochemical evidence for a novel mechanism by which viral infection may initiate beta-cell damage during the development of autoimmune diabetes. The viral replicative intermediate dsRNA stimulates beta-cell production of pro-IL-1beta, and following cleavage to its mature form by IFN-gamma-activated ICE, IL-1 then initiates beta-cell damage in a nitric oxide-dependent fashion.