Synergistic activation of JNK/SAPK induced by TNF-alpha and IFN-gamma: apoptosis of pancreatic beta-cells via the p53 and ROS pathway.
IFN-gamma and TNF-alpha are major proinflammatory cytokines implicated in islet beta-cell destruction, which results in type-1 diabetes; however, the underlying mechanism is not clear. Using pancreatic beta-cell line MIN6N8 cells, co-treatment with TNF-alpha and IFN-gamma, but neither cytokine alone, synergistically induced apoptosis, correlated with the activation of the JNK/SAPK, which resulted in the production of reactive oxidative species (ROS) and loss of mitochondrial transmembrane potential (delta psi m). Additionally, cells transfected with wild-type JNK1 became more susceptible to apoptosis induced by TNF-alpha/IFN-gamma through ROS production and loss of delta psi m, while cascading apoptotic events were prevented in dominant-negative JNK1-transfected or JNK inhibitor SP600125-treated cells. As the antioxidant, N-acetyl-cysteine, failed to completely suppress apoptosis induced by TNF-alpha/IFN-gamma, an additional pathway was considered to be involved. The level of p53 was significantly increased through synergistic activation of JNK by TNF-alpha/IFN-gamma. Furthermore, the synergistic effect of TNF-alpha/IFN-gamma on apoptosis and ROS production was further potentiated by the overexpression of wild-type p53, but not with mutant p53. This synergistic activation of JNK/SAPK by TNF-alpha/IFN-gamma was also induced in insulin-expressing pancreatic islet cells, and increased ROS production and p53 level, which was significantly inhibited by SP600125. Collectively, these data demonstrate that TNF-alpha/IFN-gamma synergistically activates JNK/SAPK, playing an important role in promoting apoptosis of pancreatic beta-cell via activation of p53 pathway together with ROS.
Kim
Won Ho
WH
Division of Metabolic Disease, Department of Biomedical Science, National Institutes of Health, #5 Nokbun-dong, Eunpyung-gu, Seoul 122-701, South Korea.
Lee
June Woo
JW
Gao
Bin
B
Jung
Myeong Ho
MH
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D018929:Cell Culture Techniques; D045744:Cell Line, Tumor; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D007371:Interferon-gamma / Q000502:physiology*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008564:Membrane Potentials; D051379:Mice; D008813:Mice, Inbred ICR; D016688:Mice, Inbred NOD; D008928:Mitochondria / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism
D000873:Anthracenes; C494812:Bcl2l1 protein, mouse; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D014409:Tumor Necrosis Factor-alpha; D016159:Tumor Suppressor Protein p53; D051020:bcl-X Protein; C052617:Bcl2 protein, mouse; C432165:pyrazolanthrone; D007371:Interferon-gamma; D048031:JNK Mitogen-Activated Protein Kinases; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases