BIOCHEMICAL MECHANISM OF BETA-CELL DESTRUCTION

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DESCRIPTION (Adapted from applicant's abstract): This research proposed in this revised submission continues to have the broad goal to elucidate the cellular mechanisms associated with pancreatic islet beta cell destruction in autoimmune diabetes. Important observations relevant to the performance of this research are centered around the well characterized effects of IL-1 on islet beta cell function. IL-1 inhibits insulin secretion and targets iron-sulfur centers of mitochondrial enzymes. NO is an effector molecule produced by IL-1 induced iNOS expression by beta cells. INF gamma reduces the concentration of IL-1 required to stimulate iNOS expression by islets and is associated with an increased stability of iNOS mRNA. In the absence of IL-1 IFN gamma does not modulate beta cell function. Specific aim 1 will elucidate the cellular signaling mechanisms required for IL-1 induced iNOS expression by beta cells and determine the mechanism by which IFN gamma primes for and potentiates IL-1 induced iNOS expression. This aim is based on the observations by the P.I. that IL-1 selectively stimulates inducible nitric oxide synthase (iNOS) expression by beta cells and that IFNgamma primes for and potentiates IL-1 induced iNOS expression. Therefore, cytokine induced iNOS expression and consequent production of high levels of NO is one mechanism of beta cell destruction. Specific aim 2 will determine the cellular source of IL-1, the isoforms of IL-1, the mechanisms controlling intra-islet release of IL-1 and the effects of intra-islet release on beta cell function. This aim is directed to testing the hypothesis that intra-islet macrophage activation mediates the initial events leading to islet beta cell destruction. Specific aim 3 will determine the cellular sources of iNOS and COX-2 (COX catalyzes the first reaction in the biosynthetic pathway responsible for the production of prostaglandins. COX 2 is inducible, IL-1 induces it and iNOS stimulates its activity), whether NO activates COX-2 and whether COX-2 and iNOS participate in islet inflammation and beta cell damage. A major goal of this aim is to test the hypothesis that proinflammatory and destructive actions of NO directly participate in islet inflammation and B cell damage in the NOD mouse model of autoimmune diabetes.