title: Does NAD(P)H oxidase-derived H2O2 participate in hypotonicity-induced insulin release by activating VRAC in β-cells?
abstract: NAD(P)H oxidase (NOX)-derived H(2)O(2) was recently proposed to act, in several cells, as the signal mediating the activation of volume-regulated anion channels (VRAC) under a variety of physiological conditions. The present study aims at investigating whether a similar situation prevails in insulin-secreting BRIN-BD11 and rat β-cells. Exogenous H(2)O(2) (100 to 200 μM) at basal glucose concentration (1.1 to 2.8 mM) stimulated insulin secretion. The inhibitor of VRAC, 5-nitro-2-(3-phenylpropylamino)-benzoate (NPPB) inhibited the secretory response to exogenous H(2)O(2). In patch clamp experiments, exogenous H(2)O(2) was observed to stimulate NPPB-sensitive anion channel activity, which induced cell membrane depolarization. Exposure of the BRIN-BD11 cells to a hypotonic medium caused a detectable increase in intracellular level of reactive oxygen species (ROS) that was abolished by diphenyleneiodonium chloride (DPI), a universal NOX inhibitor. NOX inhibitors such as DPI and plumbagin nearly totally inhibited insulin release provoked by exposure of the BRIN-BD11 cells to a hypotonic medium. Preincubation with two other drugs also abolished hypotonicity-induced insulin release and reduced basal insulin output: 1) N-acetyl-L-cysteine (NAC), a glutathione precursor that serves as general antioxidant and 2) betulinic acid a compound that almost totally abolished NOX4 expression. As NPPB, each of these inhibitors (DPI, plumbagin, preincubation with NAC or betulinic acid) strongly reduced the volume regulatory decrease observed following a hypotonic shock, providing an independent proof that VRAC activation is mediated by H(2)O(2). Taken together, these data suggest that NOX-derived H(2)O(2) plays a key role in the insulin secretory response of BRIN-BD11 and native β-cells to extracellular hypotonicity.
authors.affiliation: Laboratory of Cell and Molecular Physiology, Université Libre de Bruxelles, Campus Erasme, CP 611. Room E1.6.214, Route de Lennik, 808, 1070, Bruxelles, Belgium.
authors.forename: R
authors.initials: R
authors.lastname: Crutzen
authors.forename: V
authors.initials: V
authors.lastname: Shlyonsky
authors.forename: K
authors.initials: K
authors.lastname: Louchami
authors.forename: M
authors.initials: M
authors.lastname: Virreira
authors.forename: E
authors.initials: E
authors.lastname: Hupkens
authors.forename: A
authors.initials: A
authors.lastname: Boom
authors.forename: A
authors.initials: A
authors.lastname: Sener
authors.forename: W J
authors.initials: WJ
authors.lastname: Malaisse
authors.forename: R
authors.initials: R
authors.lastname: Beauwens
mesh_terms: D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D005947:Glucose / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism* / Q000494:pharmacology*; D007038:Hypotonic Solutions; D007328:Insulin / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D023421:Models, Animal; D019255:NADPH Oxidases / Q000378:metabolism*; D009579:Nitrobenzoates / Q000494:pharmacology; D009861:Onium Compounds / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D053978:Pentacyclic Triterpenes; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D014315:Triterpenes / Q000494:pharmacology; D050994:Voltage-Dependent Anion Channels / Q000378:metabolism*; D000094062:Betulinic Acid
chemical_list: D007038:Hypotonic Solutions; D007328:Insulin; D009579:Nitrobenzoates; D009861:Onium Compounds; D053978:Pentacyclic Triterpenes; D017382:Reactive Oxygen Species; D014315:Triterpenes; D050994:Voltage-Dependent Anion Channels; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; C007517:diphenyleneiodonium; D006861:Hydrogen Peroxide; D019255:NADPH Oxidases; D005947:Glucose; D000111:Acetylcysteine; D000094062:Betulinic Acid
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