Activation of 12-lipoxygenase in proinflammatory cytokine-mediated beta cell toxicity

Diabetologia. 2005 Mar;48(3):486-95. doi: 10.1007/s00125-005-1673-y. Epub 2005 Feb 24.


Aims/hypothesis: Beta cell inflammation and cytokine-induced toxicity are central to autoimmune diabetes development. Lipid mediators generated upon lipoxygenase (LO) activation can participate in inflammatory pathways. 12LO-deficient mice are resistant to streptozotocin-induced diabetes. This study sought to characterise the cellular processes involving 12LO-activation lipid inflammatory mediator production in cytokine-treated pancreatic beta cells.

Methods: Islets and beta cell lines were treated with a combination of IL-1beta, IFN-gamma and TNF-alpha, or the 12LO product 12(S)-hydroxyeicosatetraenoic acid (HETE). Insulin secretion was measured using an enzyme immunoassay, and cell viability was evaluated using an in situ terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling assay. 12LO activity was evaluated and 12LO protein levels were determined using immunoblotting with a selective leucocyte type 12LO antibody. Cellular localisation of 12LO was evaluated using immunocytochemistry.

Results: Basal expression of leucocyte type 12LO protein was found in human and mouse islets and in several rodent beta cell lines. In mouse beta-TC3 cells, and in human islets, cytokines induced release of 12-HETE within 30 min. Cytokine addition also induced a rapid translocation of 12LO protein from the cytosol to the nucleus of beta-TC3 cells as shown by subcellular fractionation and immunostaining. Cytokine-induced cell death and inhibition of insulin secretion were partially reversed by baicalein, a 12LO inhibitor. 12(S)-HETE inhibited beta-TC3 cell insulin release in a time- and concentration-dependent manner. Incubating beta-TC3 cells with 100 nmol/l of 12(S)-HETE resulted in a 57% reduction in basal insulin release (6 h), and a 17% increase in cell death (18 h) as compared with untreated cells. 12(S)-HETE activated the stress-activated protein kinase c-Jun N-terminal kinase and p38 within 15 min, as judged by increased kinase protein phosphorylation.

Conclusions/interpretation: The data suggest that inflammatory cytokines rapidly activate 12LO and show for the first time that cytokines induce 12LO translocation. The effects of 12-HETE on insulin secretion, cytotoxicity and kinase activation were similar to the effects seen with cytokines. The results provide mechanistic information of cytokine-induced toxic effects on pancreatic beta cells and support the hypothesis that blocking 12LO activation could provide a new therapeutic way to protect pancreatic beta cells from autoimmune injury.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid / pharmacology
  • Arachidonate 12-Lipoxygenase / metabolism*
  • Cell Line
  • Cytokines / toxicity*
  • Humans
  • Interferon-gamma / pharmacology
  • Interleukin-1 / pharmacology
  • Islets of Langerhans / drug effects
  • Islets of Langerhans / enzymology*
  • Islets of Langerhans / pathology
  • Protein Transport / drug effects
  • Tumor Necrosis Factor-alpha / pharmacology


  • Cytokines
  • Interleukin-1
  • Tumor Necrosis Factor-alpha
  • 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid
  • Interferon-gamma
  • Arachidonate 12-Lipoxygenase