Involvement of endothelium in the vasorelaxant effects of 3,4-DHPEA-EA and 3,4-DHPEA-EDA, two major functional bioactives in olive oil

Abstract

The olive oil polyphenols 3,4-DHPEA-EA and 3,4-DHPEA-EDA displayed an endothelium-dependent vasorelaxant effect in rat aorta, starting at ~1 µM and abolished by NG-nitro-L-arginine (L-NA) or N-acetylcysteine, and an endothelium-independent vasorelaxant effect, starting at ~10 µM. Hydroxytyrosol only presented an endothelium-independent effect at 100 µM. DHPEA-EA and 3,4-DHPEA-EDA, but not hydroxytyrosol, also increased NO generation within endothelial cells. At higher concentrations, the three compounds reduced arginine-vasopressin-induced increase of cytosolic Ca2+ concentration ([Ca2+]c) in vascular myocytes. By UV-visible spectroscopy, we found that these polyphenols undergo autoxidative processes in organ-bath conditions. Thus, 3,4-DHPEA-EA and 3,4-DHPEA-EDA have an endothelium-dependent vasorelaxant effect caused by an enhanced NO production, probably through a redox mechanism within endothelial cells and an endothelium-independent vasorelaxant effect mediated by a reduction of agonist-induced [Ca2+]c increase in vascular myocytes. Bearing in mind the plasmatic concentrations of these polyphenols following dietary intake of olive oil, these effects could modulate vascular tone in vivo.