title: STAT1-mediated down-regulation of Bcl-2 expression is involved in IFN-γ/TNF-α-induced apoptosis in NIT-1 cells.
abstract: Tumor necrosis factor (TNF)-α and interferon (IFN)-γ are the major pro-inflammatory cytokines involved in beta-cell destruction. The fate of islet beta-cells in the cytokine-induced intrinsic mitochondrial apoptotic pathway is determined by the interaction between members of the Bcl-2 family. However, the mechanism through which beta-cell apoptosis is regulated remains unclear. In this study, we treated the murine beta-cell line NIT-1 with TNF-α and IFN-γ and then investigated the regulation of signal transducer and activator of transcription-1 (STAT-1) and expression of the members of the Bcl-2 family in this apoptotic pathway. Results showed that TNF-α and IFN-γ synergistically reduced NIT-1 cell viability. In addition, the decrease in cell growth was due to apoptosis as shown by apoptotic body formation, detected by confocal laser microscope, and a significant increase in Annexin-Vup(+) cell percentage, detected by flow cytometry. Combination treatment with TNF-α and IFN-γ caused a remarkable increase in the release of cytochrome c, and in the activation of caspase-9 and caspase-3, as well as, an obvious enhancement in STAT-1 phosphorylation; the treatment, however, resulted in the down-regulation in Bcl-2 expression. The enhancement in STAT-1 activity and a down-regulation in Bcl-2 expression was also observed in MIN6 cells, another murine beta-cell derived line, after cells exposure to the combination of TNF-α and IFN-γ treatment. Knockdown of STAT-1 gene expression by siRNA or inhibition of STAT-1 activation with fludarabine reversed Bcl-2 down-expression and led to a significant decrease in apoptosis in TNF-α- and IFN-γ-treated NIT-1 cells. Taken together, our results suggest that STAT1-mediated down-regulation of Bcl-2 is involved in NIT-1 cell apoptosis induced by combination treatment with TNF-α and IFN-γ.
authors: Department of Urology, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400042, China; Department of Biochemistry and Molecular Biology, School of Pharmacy and Biological Sciences, School of Public Health, University of South China, Hengyang 421001, China.
authors: Zhao-hui
authors: ZH
authors: Cao
authors: Department of Urology, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400042, China.
authors: Quan-you
authors: QY
authors: Zheng
authors: Department of Immunology, Third Military Medical University, Chongqing 400038, China.
authors: Gui-qing
authors: GQ
authors: Li
authors: Department of Biochemistry and Molecular Biology, School of Pharmacy and Biological Sciences, School of Public Health, University of South China, Hengyang 421001, China.
authors: Xiao-bo
authors: XB
authors: Hu
authors: Department of Health Laboratory Technology, School of Public Health, University of South China, Hengyang 421001, China.
authors: Shao-long
authors: SL
authors: Feng
authors: Department of Immunology, Third Military Medical University, Chongqing 400038, China.
authors: Gui-lian
authors: GL
authors: Xu
authors: Department of Urology, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400042, China.
authors: Ke-qin
authors: KQ
authors: Zhang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects*; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism*; D007371:Interferon-gamma / Q000494:pharmacology*; D051379:Mice; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics* / Q000378:metabolism; D050794:STAT1 Transcription Factor / Q000378:metabolism*; D013312:Stress, Physiological; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
chemical_list: D019253:Proto-Oncogene Proteins c-bcl-2; D050794:STAT1 Transcription Factor; D014409:Tumor Necrosis Factor-alpha; D007371:Interferon-gamma