title: Cytokines downregulate the sarcoendoplasmic reticulum pump Ca2+ ATPase 2b and deplete endoplasmic reticulum Ca2+, leading to induction of endoplasmic reticulum stress in pancreatic beta-cells.
abstract: Cytokines and free radicals are mediators of beta-cell death in type 1 diabetes. Under in vitro conditions, interleukin-1beta (IL-1beta) + gamma-interferon (IFN-gamma) induce nitric oxide (NO) production and apoptosis in rodent and human pancreatic beta-cells. We have previously shown, by microarray analysis of primary beta-cells, that IL-1beta + IFN-gamma decrease expression of the mRNA encoding for the sarcoendoplasmic reticulum pump Ca(2+) ATPase 2b (SERCA2b) while inducing expression of the endoplasmic reticulum stress-related and proapoptotic gene CHOP (C/EBP [CCAAT/enhancer binding protein] homologous protein). In the present study we show that cytokine-induced apoptosis and necrosis in primary rat beta-cells and INS-1E cells largely depends on NO production. IL-1beta + IFN-gamma, via NO synthesis, markedly decreased SERCA2b protein expression and depleted ER Ca(2+) stores. Of note, beta-cells showed marked sensitivity to apoptosis induced by SERCA blockers, as compared with fibroblasts. Cytokine-induced ER Ca(2+) depletion was paralleled by an NO-dependent induction of CHOP protein and activation of diverse components of the ER stress response, including activation of inositol-requiring ER-to-nucleus signal kinase 1alpha (IRE1alpha) and PRK (RNA-dependent protein kinase)-like ER kinase (PERK)/activating transcription factor 4 (ATF4), but not ATF6. In contrast, the ER stress-inducing agent thapsigargin triggered these four pathways in parallel. In conclusion, our results suggest that the IL-1beta + IFN-gamma-induced decrease in SERCA2b expression, with subsequent depletion of ER Ca(2+) and activation of the ER stress pathway, is a potential contributory mechanism to beta-cell death.
authors.affiliation: Laboratory of Experimental Medicine, Université Libre de Bruxelles, Route de Lennik, 808 CP-618, 1070 Brussels, Belgium. akupperc@ulb.ac.be
authors.forename: Alessandra K
authors.initials: AK
authors.lastname: Cardozo
authors.forename: Fernanda
authors.initials: F
authors.lastname: Ortis
authors.forename: Joachim
authors.initials: J
authors.lastname: Storling
authors.forename: Ying-Mei
authors.initials: YM
authors.lastname: Feng
authors.forename: Joanne
authors.initials: J
authors.lastname: Rasschaert
authors.forename: Morten
authors.initials: M
authors.lastname: Tonnesen
authors.forename: Françoise
authors.initials: F
authors.lastname: Van Eylen
authors.forename: Thomas
authors.initials: T
authors.lastname: Mandrup-Poulsen
authors.forename: André
authors.initials: A
authors.lastname: Herchuelz
authors.forename: Décio L
authors.initials: DL
authors.lastname: Eizirik
mesh_terms: D000818:Animals; D001483:Base Sequence; D002118:Calcium / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000235:genetics*; D016207:Cytokines / Q000494:pharmacology*; D017931:DNA Primers; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000201:enzymology*; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D016207:Cytokines; D017931:DNA Primers; D019284:Thapsigargin; D000252:Calcium-Transporting ATPases; D002118:Calcium