Nitric oxide contributes to cytokine-induced apoptosis in pancreatic beta cells via potentiation of JNK activity and inhibition of Akt

Diabetologia. 2005 Oct;48(10):2039-50. doi: 10.1007/s00125-005-1912-2. Epub 2005 Aug 25.

Abstract

Aims/hypothesis: Pro-inflammatory cytokines cause beta cell secretory dysfunction and apoptosis--a process implicated in the pathogenesis of type 1 diabetes. Cytokines induce the expression of inducible nitric oxide (NO) synthase (iNOS) leading to NO production. NO contributes to cytokine-induced apoptosis, but the underlying mechanisms are unclear. The aim of this study was to investigate whether NO modulates signalling via mitogen-activated protein kinases (MAPKs) and Akt.

Materials and methods: MAPK activities in INS-1 cells and isolated islets were determined by immunoblotting and in vitro kinase assay. Apoptosis was determined by ELISA measurement of histone-DNA complexes present in cytoplasm.

Results: Apoptosis in INS-1 cells induced by IL-1beta plus IFNgamma was dependent on NO production as demonstrated by the use of the NOS blocker NG-methyl-L-arginine. Accordingly, an NO donor (S-nitroso-N-acetyl-D, L-penicillamine, SNAP) dose-dependently caused apoptosis in INS-1 cells. SNAP activated c-Jun N-terminal kinase (JNK) and p38 MAPK, but suppressed the activity of extracellular signal-regulated kinase MAPK. In rat islets, NOS inhibition decreased JNK and p38 activities induced by a 6-h exposure to IL-1beta. Likewise, IL-1beta-induced JNK and p38 activities were lower in iNOS(-/-) mouse islets than in wild-type islets. In human islets, SNAP potentiated IL-1beta-induced JNK activation. The constitutive level of active, Ser473-phosphorylated Akt in INS-1 cells was suppressed by SNAP. IGF-I activated Akt and protected against SNAP-induced apoptosis. The anti-apoptotic effect of IGF-I was not associated with reduced JNK activation.

Conclusions/interpretation: We suggest that NO contributes to cytokine-induced apoptosis via potentiation of JNK activity and suppression of Akt.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis / drug effects*
  • Blotting, Western
  • Cell Separation
  • Cells, Cultured
  • Cytokines / pharmacology*
  • Dose-Response Relationship, Drug
  • Enzyme Activation / drug effects
  • Enzyme Inhibitors / pharmacology
  • Humans
  • Insulin / metabolism
  • Insulin Secretion
  • Insulin-Secreting Cells / drug effects*
  • Insulin-Secreting Cells / metabolism
  • MAP Kinase Kinase 4 / genetics*
  • Mice
  • Mitogen-Activated Protein Kinases / metabolism
  • NG-Nitroarginine Methyl Ester / pharmacology
  • Nitric Oxide / physiology*
  • Nitric Oxide Donors / pharmacology
  • Nitric Oxide Synthase Type II / antagonists & inhibitors
  • Oncogene Protein v-akt / genetics*
  • S-Nitroso-N-Acetylpenicillamine / pharmacology
  • Signal Transduction
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Cytokines
  • Enzyme Inhibitors
  • Insulin
  • Nitric Oxide Donors
  • Nitric Oxide
  • S-Nitroso-N-Acetylpenicillamine
  • Nitric Oxide Synthase Type II
  • Oncogene Protein v-akt
  • Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 4
  • NG-Nitroarginine Methyl Ester