Insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease characterized by the selective destruction of insulin producing beta-cells found in pancreatic islets of Langerhans. Environmental factors, such as viral infections, are believed to trigger or initiate this autoimmune reaction directed against beta cells. Studies in animal models of viral-induced diabetes have implicated a primary role for macrophages and macrophage-derived cytokines in mediating beta-cell damage during the development of diabetes. The broad goal of this research is to determine the biochemical mechanisms by which viral infection of islets mediates beta-cell dysfunction and destruction. Double stranded RNA (dsRNA) is the active component of a viral infection that stimulates antiviral responses. In preliminary data, it is shown that dsRNA, in combination with the T-cell cytokine interferon-gamma (IFN-gamma), stimulates the activation of macrophages and induces islet dysfunction and destruction. This proposal focuses on determining the biochemical mechanisms by which dsRNA stimulates macrophage activation and induces beta-cell damage. There are two specific aims.
Specific aim 1 will elucidate the cellular signaling mechanisms by which dsRNA stimulates macrophage activation. Proposed experiments will focus on the role of dsRNA-dependent protein kinase (PKR) in mediating dsRNA-induced: (1) inducible nitric oxide synthase (iNOS) expression and nitric oxide production; and (2) cytokine expression and release by primary macrophages.
Aim 2 will test the hypothesis that viral infection of islets stimulates beta-cell damage by inducing the expression and release of interleukin-1 (IL-1) by beta cells (as suggested by our preliminary data). Proposed experiments will determine (1) the mechanism by which dsRNA stimulates IL-1 and iNOS expression by beta cells; and (2) the role of PKR in dsRNA-induced beta-cell destruction. A number of biochemical, molecular biological, immunological, histochemical, and transgenic techniques will be utilized to investigate the cellular pathways through which viral infection stimulates macrophage activation and induces islet destruction. It is hoped that insights into the molecular mechanisms of viral-mediated beta-cell damage gained from the proposed studies will influence the design of novel therapeutic strategies aimed at the prevention of this debilitating disorder.
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