title: (-)-Epicatechin-induced calcium independent eNOS activation: roles of HSP90 and AKT.
abstract: Cardiovascular disease (CVD) is a leading determinant of mortality and morbidity in the world. Epidemiologic studies suggest that flavonoid intake plays a role in the prevention of CVD. Consumption of cocoa products rich in flavonoids lowers blood pressure and improves endothelial function in healthy subjects as well as in subjects with vascular dysfunction such as smokers and diabetics. The vascular actions of cocoa follow the stimulation of nitric oxide (NO). These actions can be reproduced by the administration of the cocoa flavanol (-)-epicatechin (EPI). Previously, using human endothelial cells cultured in calcium-free media, we documented EPI effects on eNOS independently of its translocation from the plasmalemma. To further define the mechanisms behind EPI-eNOS activation in Ca(2+) -deprived endothelial cells, we evaluated the effects of EPI on the eNOS/AKT/HSP90 signaling pathway. Results document an EPI-induced phosphorylation/activation of eNOS, AKT, and HSP90. We also demonstrate that EPI induces a partial AKT/HSP90 migration from the cytoplasm to the caveolar membrane fraction. Immunoprecipitation assays of caveolar fractions demonstrate a physical association between HSP90, AKT, and eNOS. Thus, under Ca(2+)-free conditions, EPI stimulates NO synthesis via the formation of an active complex between eNOS, AKT, and HSP90.
authors.affiliation: Department of Medicine, University of California, San Diego, San Diego, CA 92093, USA.
authors.forename: Israel
authors.initials: I
authors.lastname: Ramirez-Sanchez
authors.forename: Hugo
authors.initials: H
authors.lastname: Aguilar
authors.forename: Guillermo
authors.initials: G
authors.lastname: Ceballos
authors.forename: Francisco
authors.initials: F
authors.lastname: Villarreal
mesh_terms: D002118:Calcium / Q000378:metabolism; D002392:Catechin / Q000494:pharmacology*; D021941:Caveolae / Q000187:drug effects / Q000378:metabolism; D051242:Caveolin 1 / Q000378:metabolism; D003331:Coronary Vessels / Q000166:cytology; D003902:Detergents / Q000494:pharmacology; D042783:Endothelial Cells / Q000187:drug effects / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D018841:HSP90 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D021962:Membrane Microdomains / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000096:biosynthesis; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D051242:Caveolin 1; D003902:Detergents; D018841:HSP90 Heat-Shock Proteins; D009569:Nitric Oxide; D002392:Catechin; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D051057:Proto-Oncogene Proteins c-akt; D002118:Calcium