Abstract
Cytokines contribute to pancreatic islet inflammation, leading to impaired glucose homeostasis and diabetic diseases. A plethora of data shows that proinflammatory cytokines are produced in pancreatic islets by infiltrating mononuclear immune cells. Here, we show that pancreatic islet α cells and β cells express tumor necrosis factor-α (TNF-α) and other cytokines capable of promoting islet inflammation when exposed to interleukin-1β (IL-1β). Cytokine expression by β cells was dependent on calcineurin (CN)/nuclear factor of activated T cells (NFAT) and MAPK signaling. NFAT associated with the TNF-α promoter in response to stimuli and synergistically activated promoter activity with ATF2 and c-Jun. In contrast, the β-cell-specific transcriptional activator MafA could repress NFAT-mediated TNF-α gene expression whenever C/EBP-β was bound to the promoter. NFAT differentially regulated the TNF-α gene depending upon the expression and MAPK-dependent activation of interacting basic leucine zipper partners in β cells. Both p38 and JNK were required for induction of TNF-α mRNA and protein expression. Collectively, the data show that glucose and IL-1β can activate signaling pathways, which control induction and repression of cytokines in pancreatic endocrine cells. Thus, by these mechanisms, pancreatic β cells themselves may contribute to islet inflammation and their own immunological destruction in the pathogenesis of diabetes.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Animals
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Basic-Leucine Zipper Transcription Factors / immunology
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Basic-Leucine Zipper Transcription Factors / metabolism
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CCAAT-Enhancer-Binding Protein-beta / immunology
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CCAAT-Enhancer-Binding Protein-beta / metabolism
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Calcineurin / immunology*
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Calcineurin / metabolism
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Cells, Cultured
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Diabetes Mellitus, Type 1 / immunology
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Diabetes Mellitus, Type 1 / metabolism
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Diabetes Mellitus, Type 2 / immunology
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Diabetes Mellitus, Type 2 / metabolism
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Gene Expression Regulation / drug effects
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Gene Expression Regulation / immunology
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Glucagon-Secreting Cells / immunology*
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Glucagon-Secreting Cells / metabolism
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Glucaric Acid / pharmacology
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Insulin-Secreting Cells / immunology*
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Insulin-Secreting Cells / metabolism
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Interleukin-1beta / immunology
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Interleukin-1beta / pharmacology
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JNK Mitogen-Activated Protein Kinases / immunology
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JNK Mitogen-Activated Protein Kinases / metabolism
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Lectins, C-Type / immunology
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Lectins, C-Type / metabolism
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MAP Kinase Signaling System / drug effects
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MAP Kinase Signaling System / immunology*
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Membrane Glycoproteins / immunology
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Membrane Glycoproteins / metabolism
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Mice
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NFATC Transcription Factors / immunology*
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NFATC Transcription Factors / metabolism
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Promoter Regions, Genetic / immunology
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Tumor Necrosis Factor-alpha / genetics*
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Tumor Necrosis Factor-alpha / immunology
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p38 Mitogen-Activated Protein Kinases / immunology
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p38 Mitogen-Activated Protein Kinases / metabolism
Substances
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Basic-Leucine Zipper Transcription Factors
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CCAAT-Enhancer-Binding Protein-beta
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Interleukin-1beta
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Klrg1 protein, rat
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Lectins, C-Type
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Membrane Glycoproteins
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NFATC Transcription Factors
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Tumor Necrosis Factor-alpha
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JNK Mitogen-Activated Protein Kinases
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p38 Mitogen-Activated Protein Kinases
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Calcineurin
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Glucaric Acid