Activation of extracellular signal-regulated kinase (ERK)1/2 contributes to cytokine-induced apoptosis in purified rat pancreatic beta-cells.
Cytokines may contribute to beta-cell apoptosis in the early stages of type 1 diabetes mellitus. It has been reported recently that interleukin-1 beta (IL-1 beta) induces activation of the mitogen-activated protein kinases (MAPK) p38 and ERK1/2 in neonatal rat islets. Since these kinases may participate in cytokine-induced apoptosis, we evaluated whether cytokines induce activation of MAPKs in FACS-purified primary rat beta-cells, and whether blockers of p38 and/or ERK1/2 prevent beta-cell death. IL-1 beta, but not interferon-gamma (IFN-gamma), caused phosphorylation of the substrates Elk-1, ATF-2 and hsp25, and the phosphorylation of both Elk-1 and hsp25 were decreased by the p38 blocker SB203580 (p38i) and the MAPK/ERK blocker PD 098059 (MEKi). When added together, p38i and MEKi decreased IL-1 beta-induced nitrite production over 24 hours by 60%, but did not affect IL-1 beta-induced manganese superoxide dismutase (MnSOD) mRNA expression. To test the effects of MAPK inhibitors on beta-cell death by necrosis or apoptosis, these cells were exposed for 6 or 9 days to IL-1 beta + IFN-gamma. This treatment induced cell death, mostly by apoptosis. The MEKi, but not the p38i, significantly decreased cytokine-induced apoptosis, thus decreasing the total number of dead cells. This protection was only partial, suggesting that ERK1/2 activation is not the only mechanism by which cytokines induce beta-cell apoptosis. We conclude that IL-1 beta induces activation of both p38 and ERK1/2, and that ERK1/2 contributes to the pro-apoptotic effects of the cytokine in primary beta-cells.
Pavlovic
D
D
Gene Expression Unit, Diabetes Research Center, Vrije Universiteit Brussel, Laarbeeklaan 103, B-1090 Brussels, Belgium. deizirik@mebo.vub.ac.be
Andersen
N A
NA
Mandrup-Poulsen
T
T
Eizirik
D L
DL
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology*; D001483:Base Sequence; D002478:Cells, Cultured; D017931:DNA Primers / Q000235:genetics; D003922:Diabetes Mellitus, Type 1 / Q000201:enzymology / Q000209:etiology / Q000473:pathology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D007371:Interferon-gamma / Q000494:pharmacology*; D007375:Interleukin-1 / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology*; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009573:Nitrites / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins; D013482:Superoxide Dismutase / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases
D017931:DNA Primers; D004791:Enzyme Inhibitors; D007375:Interleukin-1; D009573:Nitrites; D012333:RNA, Messenger; D011994:Recombinant Proteins; D007371:Interferon-gamma; D013482:Superoxide Dismutase; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases