Camellia japonica Seed Extract Stimulates Nitric Oxide Production via Activation of Phosphoinositide 3-Kinase/Akt/endothelial Nitric Oxide Synthase Pathway in Endothelial Cells

Endothelial cells are important for the maintenance of endothelial function. Nitric oxide (NO), synthesized by endothelial NO synthase (eNOS), is produced and secreted from these cells and is involved in various physiological functions such as regulation of vascular relaxation, platelet aggregation, inflammation, and oxidation. Camellia japonica seed cake extract contains saponins, which are amphiphilic triterpenes that activate eNOS in endothelial cells. Therefore, we investigated whether defatted C. japonica seed cake extract (CJE) activates eNOS and increases NO production in bovine aortic endothelial cells. CJE increased NO production, eNOS mRNA expression, and eNOS activity in a concentration-dependent manner. CJE-stimulated NO production was reduced by eNOS and phosphoinositide 3-kinase inhibitors, but not by 5'-adenosine monophosphate-activated protein kinase inhibitor. Furthermore, we confirmed that camelliasaponin B was, at least partly, involved in CJE-stimulated NO production. These findings suggest that CJE may help to prevent and treat vascular endothelium-dependent diseases by expanding blood vessels.