2-DIMENSIONAL GEL-ELECTROPHORESIS OF RAT ISLET PROTEINS - INTERLEUKIN1-BETA-INDUCED CHANGES IN PROTEIN EXPRESSION ARE REDUCED BY L-ARGININE DEPLETION AND NICOTINAMIDE

Interleukin (IL)-1 beta-mediated damage to beta-cells in isolated isle ts of Langerhans depends upon de novo synthesis of proteins that have not been fully identified. Further, IL-1 beta-induced and tumor necros is factor alpha-induced islet damage partly depends on the intracellul ar production of the nitric oxide (NO) radical. IL-1 beta has also bee n reported to induce the synthesis of cellular defense proteins, e.g., heme-oxygenase and heat shock proteins 70 and 90. Nicotinamide, while in itself inactive, inhibited IL-1 beta-induced NO production in a ti me- and dose-dependent manner. To enable the identification of IL-1 be ta-induced proteins with possible protective and deleterious effects, we characterized the effects of IL-1 beta, nicotinamide, and NO synthe sis inhibition by L-arginine depletion on rat islet protein expression detected by high-resolution two-dimensional gel electrophoresis. More than 1,600 proteins were reproducibly detected in control rat islets. Incubation with IL-1 beta-, nicotinamide-, or L-arginine-depleted con trol medium upregulated 29, 3, and 1 protein, respectively, and downre gulated 4, 0, and 1 protein, respectively. Addition of nicotinamide an d L-arginine depletion reduced the upregulation of 16 and 20 IL-1 beta -induced proteins, respectively. The identity of these proteins is und er study. The demonstrated changes in protein expression caused by IL- 1 beta +/- nicotinamide and L-arginine depletion may form the basis fo r identification of proteins with possible protective and deleterious roles in the initial beta-cell destruction in insulin-dependent diabet es mellitus.