Nitric oxide and cyclic GMP formation induced by interleukin 1β in islets of Langerhans. Evidence for an effector role of nitric oxide in islet dysfunction

Abstract

Treatment of pancreatic islets with interleukin 1 (IL-1) results in a time-dependent inhibition of glucose-stimulated insulin secretion which has recently been demonstrated to be dependent on the metabolism of L-arginine to nitric oxide. In this report IL-1 beta is shown to induce the accumulation of cyclic GMP (cGMP) in a time-dependent fashion that mimics the time-dependent inhibition of insulin secretion by IL-1 beta. The accumulation of cGMP is dependent on nitric oxide synthase activity, since NG-monomethyl-L-arginine (a competitive inhibitor of nitric oxide synthase) prevents IL-1 beta-induced cGMP accumulation. cGMP formation and nitrite production induced by IL-1 beta pretreatment of islets are also blocked by the protein synthesis inhibitor, cycloheximide. The formation of cGMP does not appear to mediate the inhibitory effects of IL-1 beta on insulin secretion since a concentration of cycloheximide (1 microM) that blocks IL-1 beta-induced inhibition of glucose-stimulated insulin secretion and nitric oxide formation does not prevent cGMP accumulation, thus dissociating the two events. By using e.p.r. spectroscopy, IL-1 beta is shown to induce the formation of a g = 2.04 iron-nitrosyl feature in islets which is prevented by cycloheximide, demonstrating the requirement of protein synthesis for IL-1 beta-induced nitric oxide formation. Iron-nitrosyl complex-formation by islets confirms that IL-1 beta induces the generation of nitric oxide by islets, and provides evidence indicating that nitric oxide mediates destruction of iron-sulphur clusters of iron-containing enzymes. Consistent with the destruction of iron-sulphur centres is the finding that pretreatment of islets with IL-1 beta results in an approx. 60% inhibition of mitochondrial oxidation of D-glucose to CO2. Inhibition of islet glucose oxidation appears to be mediated by nitric oxide since both NMMA and cycloheximide prevent IL-1 beta-induced inhibition of glucose oxidation. These results show that IL-1 beta-induced nitric oxide formation parallels the ability of IL-1 beta to inhibit glucose-stimulated insulin secretion by islets, and that protein synthesis is required for IL-1 beta-induced nitric oxide formation. These results also suggest that nitric oxide mediates IL-1 beta-induced inhibitory effects on the pancreatic beta-cell by functioning as an effector molecule responsible for the destruction of iron-sulphur centres of iron-containing proteins, resulting in an impairment of mitochondrial function.

Cytotoxic action of IL‐1β against pancreatic islets is mediated via nitric oxide formation and is inhibited by NG‐monomethyl‐l‐arginine

“…the modulation of insulin secretion after glucose challenge, also have been reported [7,10]. And it was shown very recently that the 1L-1/~-induced inhibition of insulin secretion is also reversible by adding NMA [14,15]. Islets contain a dense capillary network [I 6] and endothelial cells have been shown to be inducible for generating large amounts of nitric oxide by cytokines, eSl~-cially IL-1]~ in synergny with TNF~ and/or IFN-7 [17][18][19][20].…”

Prolongation of islet allograft survival following ex vivo transduction with adenovirus encoding a soluble type 1 TNF receptor–Ig fusion decoy

“…[51][52][53][54][55] In rodents, islet-resident macrophages are important for the initiation of b-cell dysfunction and produce TNFa, resulting in the induction of nitric oxide (NO) production by upregulation of the inducible nitric oxide synthase enzyme (iNOS). [56][57][58][59] Production of these cytokines in transplanted tissue is a key determinant of chronic rejection. [60][61][62] In our studies, the addition of TNFa alone to human cultured islets was not capable of inducing significant apoptosis activation above that observed in untreated islet cultures.…”

Interleukin-1 Reduces the Glycolytic Utilization of Glucose by Pancreatic Islets and Reduces Glucokinase mRNA Content and Protein Synthesis by a Nitric Oxide-dependent Mechanism

“…Nitrite Measurement-Medium nitrite content was measured spectrophotometrically (540 nm, Titertek Multiskan MCC/340 microtiter plate reader) after mixing medium (0.1 ml) with Griess reagent (0.1 ml of a solution of 1 part of 1.32% sulfanilamide in 60% acetic acid and 1 part of 0.1% naphthylethylenediamine-HCl) and incubation (10 min, room temperature), as described previously (1,2).…”

“…induces islet expression of the inducible isoform of nitric oxide synthase and overproduction of nitric oxide (NO) (1)(2)(3)(4)(5)(6). This is associated with inhibition of glucose-induced insulin secretion (7)(8)(9)(10) and impaired islet oxidation of glucose (8 -12), and both of these effects are prevented by the inducible nitric oxide synthase inhibitor N G -monomethylarginine (NMMA) (1, 2, 4), indicating that they occur through NO-dependent mechanisms.…”