Synergistic activation of JNK/SAPK induced by TNF-α and IFN-γ: Apoptosis of pancreatic β-cells via the p53 and ROS pathway

• Published in: Cellular signalling 2005-12, Vol.17 (12), p.1516-1532
• Main Authors: Kim, Won Ho, Lee, June Woo, Gao, Bin, Jung, Myeong Ho
• Format: Article
• Language: English
• Subjects: Animals; Anthracenes - pharmacology; Apoptosis; bcl-X Protein - metabolism; Caspase 3; Caspases - metabolism; Cell Culture Techniques; Cell Line, Tumor; Cytokines; Insulin-Secreting Cells - metabolism; Interferon-gamma - physiology; Islet cells; JNK Mitogen-Activated Protein Kinases - metabolism; JNK/SAPK; MAP Kinase Signaling System; Membrane Potentials; Mice; Mice, Inbred ICR; Mice, Inbred NOD; Mitochondria - metabolism; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-bcl-2; Reactive oxygen species; Reactive Oxygen Species - metabolism; Transfection; Tumor Necrosis Factor-alpha - physiology; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Protein p53 - metabolism
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/j.cellsig.2005.03.020

IFN-γ and TNF-α are major proinflammatory cytokines implicated in islet β-cell destruction, which results in type-1 diabetes; however, the underlying mechanism is not clear. Using pancreatic β-cell line MIN6N8 cells, co-treatment with TNF-α and IFN-γ, 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 (ΔΨm). Additionally, cells transfected with wild-type JNK1 became more susceptible to apoptosis induced by TNF-α/IFN-γ through ROS production and loss of Δψm, 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-α/IFN-γ, an additional pathway was considered to be involved. The level of p53 was significantly increased through synergistic activation of JNK by TNF-α/IFN-γ. Furthermore, the synergistic effect of TNF-α/IFN-γ 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-α/IFN-γ 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-α/IFN-γ synergistically activates JNK/SAPK, playing an important role in promoting apoptosis of pancreatic β-cell via activation of p53 pathway together with ROS.