Oleanolic acid induces relaxation and calcium-independent release of endothelium-derived nitric oxide.
OBJECTIVE
The present study investigated the mechanisms by which oleanolic acid, a component of olive oil, increases release of nitric oxide (NO).


METHODS
Measurements of isometric tension, NO concentration, or endothelial cell calcium were made in rat isolated mesenteric arteries. Immunoblotting for endothelial NOS (eNOS) and Akt kinase were performed in primary cultures of human umbilical vein endothelial cells (HUVECs).


RESULTS
Oleanolic acid (3-30 microM) evoked endothelium-dependent relaxations in noradrenaline-contracted rat superior and small mesenteric arteries. In rat superior mesenteric arteries, oleanolic acid induced simultaneous increases in NO concentration and relaxation, and these responses were inhibited by an inhibitor of NOS, asymmetric dimethyl-L-arginine (300 microM) and by the NO scavenger, oxyhaemoglobin (10 microM). Oleanolic acid-evoked NO increases were not reduced in Ca(2+)-free solution and in the presence of an inhibitor of endoplasmic reticulum calcium-ATPase, thapsigargin (1 microM). Oleanolic acid evoked relaxation without changes in endothelial cell calcium, but decreased smooth muscle calcium in arterial segments. Oleanolic acid failed to increase calcium in HUVECs, but increased time-dependently phosphorylation of Akt kinase at Serine(473) (Akt-Ser(473)) and eNOS at Serine(1177) (eNOS-Ser(1177)), which was attenuated by inhibitors of phosphoinositide-3-kinase.


CONCLUSIONS
This study provides direct evidence that a component of olive oil, oleanolic acid, activated endothelium-dependent release of NO and decreased smooth muscle cell calcium followed by relaxation. The oleanolic acid-evoked endothelium-derived NO release was independent of endothelial cell calcium and involved phosphoinositide-3-kinase-dependent phosphorylation of Akt-Ser(473) followed by phosphorylation of eNOS-Ser(1177).
Rodriguez-Rodriguez
R
R
Department of Pharmacology, Faculty of Health Sciences, University of Aarhus, Aarhus C, Denmark.
Stankevicius
E
E
Herrera
M D
MD
Ostergaard
L
L
Andersen
M R
MR
Ruiz-Gutierrez
V
V
Simonsen
U
U
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000187:drug effects / Q000378:metabolism; D009828:Oleanolic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D000069463:Olive Oil; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D010938:Plant Oils / Q000737:chemistry; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014471:Umbilical Veins
D000069463:Olive Oil; D010938:Plant Oils; D009569:Nitric Oxide; D009828:Oleanolic Acid; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D002118:Calcium