title: Role of superoxide radical anion in the mechanism of apoB100 degradation induced by DHA in hepatic cells.
abstract: VLDL is produced by the liver. Its major protein is apoB100. Docosahexaenoic acid (DHA), a dietary polyunsaturated fatty acid (PUFA), reduces VLDL levels and is used therapeutically for hypertriglyceridemia. In model systems, DHA lowers VLDL secretion by inducing presecretory apoB100 degradation, a process dependent on PUFA-derived lipid peroxides. We hypothesized that superoxide (SO) was a major participant in DHA-induced apoB100 degradation, given its promotion of lipid peroxidation. SO levels in a model of VLDL metabolism, rat hepatoma McArdle cells, were either decreased by a mimetic of superoxide dismutase 1 (SOD1) or by overexpressing SOD1 or increased by SOD1 siRNA. ApoB100 recovery was assessed by immunoprecipitation, SO by 2-hydroxyethidine, and lipid peroxides by thiobarbituric acid reactive substances. The SOD1 mimetic or SOD1 overexpression reduced SO and inhibited apoB100 degradation in DHA-treated cells by up to 100%. Surprisingly, silencing SOD1 did not increase DHA-induced degradation, although levels of SO were higher (+44%); those of lipid peroxides were similar, and their reduction by α-tocopherol decreased degradation by 50%. SO is required for lipid peroxidation in DHA-induced apoB100 degradation, but it is the peroxide level that has a tighter relationship to the level of degradation and the regulation of VLDL production.
authors.affiliation: Department of Medicine, Leon H. Charney Division of Cardiology, Marc and Ruti Bell Program in Vascular Biology, New York University School of Medicine, New York, New York, USA 10016, USA.
authors.forename: Ursula
authors.initials: U
authors.lastname: Andreo
authors.forename: Josh
authors.initials: J
authors.lastname: Elkind
authors.forename: Courtney
authors.initials: C
authors.lastname: Blachford
authors.forename: Arthur I
authors.initials: AI
authors.lastname: Cederbaum
authors.forename: Edward A
authors.initials: EA
authors.lastname: Fisher
mesh_terms: D000818:Animals; D053299:Apolipoprotein B-100 / Q000378:metabolism*; D045744:Cell Line, Tumor; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic; D020868:Gene Silencing; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism*; D015227:Lipid Peroxidation; D008665:Metalloporphyrins; D051379:Mice; D051381:Rats; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism; D000072105:Superoxide Dismutase-1; D013481:Superoxides / Q000378:metabolism*
chemical_list: D053299:Apolipoprotein B-100; D008665:Metalloporphyrins; C097284:manganese(III)-tetrakis(4-benzoic acid)porphyrin; D013481:Superoxides; D004281:Docosahexaenoic Acids; C000606291:Sod1 protein, mouse; C000606292:Sod1 protein, rat; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1