IRREVERSIBLE INHIBITION OF METABOLIC FUNCTION AND ISLET DESTRUCTION AFTER A 36-HOUR EXPOSURE TO INTERLEUKIN-1-BETA

The purpose of this study was to identify the duration of exposure of islets to interleukin 1 beta (IL-1 beta) that results in irreversible damage. Treatment of rat islets for 18 h with IL-1 beta results in an inhibition of glucose-stimulated insulin secretion, mitochondrial acon itase activity, and total protein synthesis. The addition of N-G-monom ethyl-L-arginine (NMMA) or aminoguanidine to islets preincubated for 1 8 h with IL-1 beta, followed by continued culture for 8 h (with both N MMA and IL-1 beta), results in the recovery of islet secretory functio n, aconitase activity, and protein synthesis. However, islet metabolic function is irreversibly inhibited after a 36-h incubation with IL-1 beta, as an additional 8-h incubation with NMMA or aminoguanidine does not stimulate the recovery of insulin secretion, aconitase activity, or protein synthesis. The irreversible inhibition of metabolic functio n correlates with the commitment of islets to destruction. Treatment o f islets for 96 h with IL-1 beta results in islet degeneration. NMMA, added to islets 24 h after the addition of IL-1 beta, followed by cont inued culture for 72 h (with NMMA and IL-1 beta), prevents islet degen eration. However, NMMA added to islets 36 h or 48 h after the addition of IL-1 beta, followed by continued culture for a total of 96 h, does not prevent islet degeneration. New messenger RNA expression appears to be required for islet recovery from IL-1 beta-induced damage as act inomycin D prevents the recovery of islet aconitase activity. Lastly, treatment of human islets with a combination of IL-1 beta and interfer on-gamma (IFN gamma) results in a potent inhibition of mitochondrial a conitase activity. NMMA, when cocultured with IL-1 beta + IFN gamma, c ompletely prevents cytokine-induced inhibition of human islet aconitas e activity. NMMA, when added to human islets pretreated for 18 h with IL-1 beta + IFN gamma, stimulates the recovery of mitochondrial aconit ase activity after an additional 8 h incubation. These findings indica te that nitric oxide-induced islet damage is reversible; however, prol onged production of nitric oxide (after a 36-h exposure to IL-1 beta) results in the irreversible inhibition of islet metabolic and secretor y function.