title: Akt downregulation by flavin oxidase-induced ROS generation mediates dose-dependent endothelial cell damage elicited by natural antioxidants.
abstract: High intake of natural antioxidants (NA) from plant-derived foods and beverages is thought to provide cardiovascular benefits. The endothelium plays a pivotal role in cardiovascular homeostasis, and for this reason, the molecular events resulting from NA actions on endothelial cells (ECs) are actively investigated. Here, we show the direct impact of two NA, coumaric acid and resveratrol, on intracellular reactive oxygen species levels, protein carbonylation, and cell physiology in human ECs. While at lower doses, both NA promoted antioxidant effects, at moderately high doses, NA elicited a dose-dependent pro-oxidant effect, which was followed by apoptosis, cell damage, and phospho-Akt downregulation. NA-induced pro-oxidant effects were counteracted by N-acetyl cysteine and diphenyleneiodonium (DPI), suggesting a role for flavin oxidases in NA-induced toxicity. DPI also prevented NA-induced phospho-Akt downregulation indicating that Akt can work downstream of flavin oxidases in mediating cellular responses to NA. Stimulation of phospho-Akt by insulin dramatically counteracted NA-induced cell death, an effect abolished by Akt inhibition further suggesting that mechanistically Akt regulates cell survival in response to NA-induced stress. Although further studies are required to better characterize the molecular mechanism of NA-induced cell toxicity, our study is the first to show in a human vascular model that moderately high doses of NA can induce cell damage mediated by flavoproteins and the Akt pathway.
authors.affiliation: Department of Biomedical Sciences, University of Sassari, 07100 Sassari, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Pasciu
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Posadino
authors.forename: Annalisa
authors.initials: A
authors.lastname: Cossu
authors.forename: Bastiano
authors.initials: B
authors.lastname: Sanna
authors.forename: Bruna
authors.initials: B
authors.lastname: Tadolini
authors.forename: Leonardo
authors.initials: L
authors.lastname: Gaspa
authors.forename: Andrea
authors.initials: A
authors.lastname: Marchisio
authors.forename: Salvatore
authors.initials: S
authors.lastname: Dessole
authors.forename: Giampiero
authors.initials: G
authors.lastname: Capobianco
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Pintus
mesh_terms: D000975:Antioxidants / Q000633:toxicity*; D003373:Coumaric Acids / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects; D042783:Endothelial Cells / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D005415:Flavins / Q000378:metabolism*; D006801:Humans; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D050050:Protein Carbonylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D000077185:Resveratrol; D013267:Stilbenes / Q000633:toxicity
chemical_list: D000975:Antioxidants; D003373:Coumaric Acids; D005415:Flavins; D017382:Reactive Oxygen Species; D013267:Stilbenes; D010088:Oxidoreductases; D051057:Proto-Oncogene Proteins c-akt; D000077185:Resveratrol