Størling J, Binzer J, Andersson AK, Züllig RA, Tonnesen M, Lehmann R, Spinas GA, Sandler S, Billestrup N, Mandrup-Poulsen T. Nitric oxide contributes to cytokine-induced apoptosis in pancreatic beta cells via potentiation of JNK activity and inhibition of Akt.
Diabetologia 2005;
48:2039-50. [PMID:
16132952 DOI:
10.1007/s00125-005-1912-2]
[Citation(s) in RCA: 97] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/15/2005] [Accepted: 05/19/2005] [Indexed: 10/25/2022]
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.
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