Cross-talk between the unfolded protein response and nuclear factor-κB signalling pathways regulates cytokine-mediated beta cell death in MIN6 cells and isolated mouse islets.
OBJECTIVE
Pancreatic beta cell destruction in type 1 diabetes may be mediated by cytokines such as IL-1β, IFN-γ and TNF-α. Endoplasmic reticulum (ER) stress and nuclear factor-κB (NFκB) signalling are activated by cytokines, but their significance in beta cells remains unclear. Here, we investigated the role of cytokine-induced ER stress and NFκB signalling in beta cell destruction.


METHODS
Isolated mouse islets and MIN6 beta cells were incubated with IL-1β, IFN-γ and TNF-α. The chemical chaperone 4-phenylbutyric acid (PBA) was used to inhibit ER stress. Protein production and gene expression were assessed by western blot and real-time RT-PCR.


RESULTS
We found in beta cells that inhibition of cytokine-induced ER stress with PBA unexpectedly potentiated cell death and NFκB-regulated gene expression. These responses were dependent on NFκB activation and were associated with a prolonged decrease in the inhibitor of κB-α (IκBα) protein, resulting from increased IκBα protein degradation. Cytokine-mediated NFκB-regulated gene expression was also potentiated after pre-induction of ER stress with thapsigargin, but not tunicamycin. Both PBA and thapsigargin treatments led to preferential upregulation of ER degradation genes over ER-resident chaperones as part of the adaptive unfolded protein response (UPR). In contrast, tunicamycin activated a balanced adaptive UPR in association with the maintenance of Xbp1 splicing.


CONCLUSIONS
These data suggest a novel mechanism by which cytokine-mediated ER stress interacts with NFκB signalling in beta cells, by regulating IκBα degradation. The cross-talk between the UPR and NFκB signalling pathways may be important in the regulation of cytokine-mediated beta cell death.
Diabetes and Obesity Research Program, Garvan Institute of Medical Research, St Vincent's Hospital, 384 Victoria St, Darlinghurst, NSW 2010, Australia.
J Y
JY
Chan
T J
TJ
Biden
D R
DR
Laybutt
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects / Q000502:physiology*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D016207:Cytokines / Q000378:metabolism* / Q000494:pharmacology; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism* / Q000473:pathology; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D007371:Interferon-gamma / Q000378:metabolism / Q000494:pharmacology; D053583:Interleukin-1beta / Q000378:metabolism / Q000494:pharmacology; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism*; D010190:Pancreatic Neoplasms; D010654:Phenylbutyrates / Q000494:pharmacology; D034741:RNA, Small Interfering / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D019284:Thapsigargin / Q000494:pharmacology; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology; D014415:Tunicamycin / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000502:physiology*
D000970:Antineoplastic Agents; D016207:Cytokines; C497250:Ddit3 protein, mouse; D004791:Enzyme Inhibitors; D053583:Interleukin-1beta; D016328:NF-kappa B; D010654:Phenylbutyrates; D034741:RNA, Small Interfering; D014409:Tumor Necrosis Factor-alpha; D014415:Tunicamycin; D051742:Transcription Factor CHOP; D019284:Thapsigargin; C075773:4-phenylbutyric acid; D007371:Interferon-gamma