TNFalpha and IFNgamma potentiate IL-1beta induced mitogen activated protein kinase activity in rat pancreatic islets of Langerhans.
OBJECTIVE
Interleukin-1 beta (IL-1beta) in synergy with tumour necrosis factor alpha (TNFalpha) and interferon gamma (IFNgamma) is cytotoxic to pancreatic beta cells. Mitogen-activated protein kinase (MAPK) activity that is induced by interleukin-1 beta has been suggested to signal nitric oxide-dependent as well as nitric oxide-independent beta-cell destructive pathways. The aim of this study was to investigate if TNFalpha and IFNgamma signal through mitogen-activated protein kinases in isolated rat islets of Langerhans and if they potentiate mitogen-activated protein kinase activity induced by IL-1beta.


METHODS
Islets of Langerhans were isolated from 5- to 7-day-old Wistar rats and precultured for 7 days before stimulation with IL-1beta, TNFalpha and/or IFNgamma for 20 min followed by lysis. Kinase activity was measured with a whole cell lysate kinase assay and after immunoprecipitation of the kinase using immunocomplex kinase assay.


RESULTS
Exposure to IL-1beta or TNFalpha significantly increased mitogen-activated protein kinase activity, whereas IFNgamma tended to decrease extracellular-signal-regulated kinase activity. Further, TNFalpha and IFNgamma were found to synergistically increase mitogen-activated protein kinase activity induced by IL-1beta.


CONCLUSIONS
We hypothesise that the synergistic effect of IL-1beta, TNFalpha and IFNgamma in the functional inhibition and induction of cell death in pancreatic beta cells is signalled through a synergistic activation of mitogen-activated protein kinase activity.
Andersen
N A
NA
Steno Diabetes Center, Gentofte, Denmark.
Larsen
C M
CM
Mandrup-Poulsen
T
T
D051698:Activating Transcription Factor 2; D000818:Animals; D016923:Cell Death; D046508:Culture Techniques; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004268:DNA-Binding Proteins; D004357:Drug Synergism; D004790:Enzyme Induction; D055551:HSP27 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D006801:Humans; D007163:Immunosorbent Techniques; D007371:Interferon-gamma / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000201:enzymology*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018832:Molecular Chaperones; D009363:Neoplasm Proteins / Q000378:metabolism; D010766:Phosphorylation; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051381:Rats; D011920:Rats, Inbred WF; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D050807:ets-Domain Protein Elk-1
D051698:Activating Transcription Factor 2; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; C494114:Elk1 protein, rat; D055551:HSP27 Heat-Shock Proteins; C057725:HSPB1 protein, human; D006360:Heat-Shock Proteins; C486114:Hspb1 protein, rat; D007375:Interleukin-1; D018832:Molecular Chaperones; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D050807:ets-Domain Protein Elk-1; D007371:Interferon-gamma; D020928:Mitogen-Activated Protein Kinases