title: Bcl-2 Regulates Reactive Oxygen Species Signaling and a Redox-Sensitive Mitochondrial Proton Leak in Mouse Pancreatic β-Cells.
abstract: In pancreatic β-cells, controlling the levels of reactive oxygen species (ROS) is critical to counter oxidative stress, dysfunction and death under nutrient excess. Moreover, the fine-tuning of ROS and redox balance is important in the regulation of normal β-cell physiology. We recently demonstrated that Bcl-2 and Bcl-xL, in addition to promoting survival, suppress β-cell glucose metabolism and insulin secretion. Here, we tested the hypothesis that the nonapoptotic roles of endogenous Bcl-2 extend to the regulation of β-cell ROS and redox balance. We exposed mouse islet cells and MIN6 cells to the Bcl-2/Bcl-xL antagonist Compound 6 and the Bcl-2-specific antagonist ABT-199 and evaluated ROS levels, Ca(2+) responses, respiratory control, superoxide dismutase activity and cell death. Both acute glucose stimulation and the inhibition of endogenous Bcl-2 progressively increased peroxides and stimulated superoxide dismutase activity in mouse islets. Importantly, conditional β-cell knockout of Bcl-2 amplified glucose-induced formation of peroxides. Bcl-2 antagonism also induced a mitochondrial proton leak that was prevented by the antioxidant N-acetyl-L-cysteine and, therefore, secondary to redox changes. We further established that the proton leak was independent of uncoupling protein 2 but partly mediated by the mitochondrial permeability transition pore. Acutely, inhibitor-induced peroxides promoted Ca(2+) influx, whereas under prolonged Bcl inhibition, the elevated ROS was required for induction of β-cell apoptosis. In conclusion, our data reveal that endogenous Bcl-2 modulates moment-to-moment ROS signaling and suppresses a redox-regulated mitochondrial proton leak in β-cells. These noncanonical roles of Bcl-2 may be important for β-cell function and survival under conditions of high metabolic demand.
authors.affiliation: Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4.
authors.forename: Michal
authors.initials: M
authors.lastname: Aharoni-Simon
authors.affiliation: Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4.
authors.forename: Rose
authors.initials: R
authors.lastname: Shumiatcher
authors.affiliation: Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4.
authors.forename: Anthony
authors.initials: A
authors.lastname: Yeung
authors.affiliation: Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4.
authors.forename: Alexis Z L
authors.initials: AZ
authors.lastname: Shih
authors.affiliation: Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4.
authors.forename: Vernon W
authors.initials: VW
authors.lastname: Dolinsky
authors.affiliation: Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Doucette
authors.affiliation: Department of Surgery (M.A.-S., R.S., A.Y., A.Z.L.S., D.S.L.), Child & Family Research Institute, University of British Columbia, Vancouver, British Columbia, Canada V5Z 4H4; and Department of Pharmacology and Therapeutics (V.W.D.) and Department of Physiology (C.A.D.), Children's Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, Manitoba, Canada R3E 3P4.
authors.forename: Dan S
authors.initials: DS
authors.lastname: Luciani
mesh_terms: D000818:Animals; D015153:Blotting, Western; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D045744:Cell Line, Tumor; D005260:Female; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D016133:Polymerase Chain Reaction; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011522:Protons; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D013449:Sulfonamides / Q000494:pharmacology; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D019253:Proto-Oncogene Proteins c-bcl-2; D011522:Protons; D017382:Reactive Oxygen Species; D013449:Sulfonamides; D013482:Superoxide Dismutase; C579720:venetoclax