Two-Dimensional Gel Electrophoresis of Rat Islet Proteins: Interleukin 1β-Induced Changes in Protein Expression are Reduced by L-Arginine Depletion and Nicotinamide

Abstract

Interleukin (IL)-1 β-mediated damage to β-cells in isolated islets of Langerhans depends upon de novo synthesis of proteins that have not been fully identified. Further, IL-1 β-induced and tumor necrosis factor alpha-induced islet damage partly depends on the intracellular production of the nitric oxide (NO) radical. IL-1 β has also been 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 β-induced NO production in a time- and dose-dependent manner. To enable the identification of IL-1 β-induced proteins with possible protective and deleterious effects, we characterized the effects of IL-1 β, nicotinamide, and NO synthesis 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 β–, nicotinamide-, or L-arginine-depleted control medium upregulated 29, 3, and 1 protein, respectively, and downregulated 4, 0, and 1 protein, respectively. Addition of nicotinamide and L-arginine depletion reduced the upregulation of 16 and 20 IL-1 β-induced proteins, respectively. The identity of these proteins is under study. The demonstrated changes in protein expression caused by IL-1 β ± nicotinamide and L-arginine depletion may form the basis for identification of proteins with possible protective and deleterious roles in the initial β-cell destruction in insulin-dependent diabetes mellitus.