Faculty Collaboration Database

5,6-δ-DHTL, a stable metabolite of arachidonic acid, is a potential EDHF that mediates microvascular dilation. Free Radic Biol Med 2017 Feb;103:87-94

Date

12/23/2016

Pubmed ID

28007573

DOI

10.1016/j.freeradbiomed.2016.12.022

Scopus ID

2-s2.0-85006860846 (requires institutional sign-in at Scopus site)   18 Citations

Abstract

OBJECTIVE: Prominent among the endothelium-derived hyperpolarizing factors (EDHFs) are the Cytochrome P450 (CYP) epoxygenase-derived arachidonic acid metabolites-the epoxyeicosatrienoic acids (EETs), that are known as vasodilators in the microcirculation. Among the EET isomers, 5,6-EET undergoes rapid lactonization in aqueous solution to the more stable 5,6-δ DHTL (5,6-dihydroxytrienoic lactone) isomer. It is unclear whether this metabolic transformation maintains its vasodilator potential and what is the mechanism of action. Thus, the aim of this study was to investigate the capacity of the lactone isomer, 5,6- δ DHTL, to induce dilation of arterioles and explore the endothelial Ca²⁺ response mechanism.

APPROACH AND RESULTS: In isolated human microvessels 5,6- δ DHTL induced a dose dependent vasodilation, that was inhibited by mechanical denudation of the endothelial layer. This 5,6- δ DHTL -dependent dilation was partially reduced in the presence of L-NAME (NOS inhibitor) or the NO-scavenger, cPTIO (by 19.7%, which was not statistically significantly). In human endothelial cells, 5,6- δ DHTL induced an increase in intracellular Ca²⁺([Ca²⁺]i) in a dose dependent manner. This increase in [Ca²⁺]i was similar to that induced by the 5,6-EET isomer, and significantly higher than observed by administering the hydrolytic dihydroxy isomer, 5,6-DHET. Further experiments aimed to investigate the mechanism of action revealed, that the 5,6-δ DHTL-mediated ([Ca²⁺]i elevation was reduced by IP3 and ryanodine antagonists, but not by antagonists to the TRPV4 membrane channel. Similar to their effect on the dilation response in the arteries, NO inhibitors reduced the 5,6-δ DHTL-mediated ([Ca²⁺]i elevation by 20%. Subsequent 5,6-δ DHTL -dependent K⁺ ion efflux from endothelial cells, was abolished by the inhibition of small and intermediate conductance K_Ca.

CONCLUSIONS: The present study shows that 5,6-δ DHTL is a potential EDHF, that dilates microvessels through a mechanism that involves endothelial dependent Ca²⁺ entry, requiring endothelial hyperpolarization. These results suggest the existence of additional lactone-containing metabolites that can be derived from the PUFA metabolism and which may function as novel EDHFs.

Author List

Levi-Rosenzvig R, Beyer AM, Hockenberry J, Ben-Shushan RS, Chuyun D, Atiya S, Tamir S, Gutterman DD, Szuchman-Sapir A

Author

Andreas M. Beyer PhD Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Arterioles
Calcium Signaling
Cells, Cultured
Drug Evaluation, Preclinical
Endothelial Cells
Endothelium, Vascular
Enzyme Activation
Humans
Hydroxyeicosatetraenoic Acids
Membrane Potentials
Nitric Oxide Synthase Type III
Vasodilation
Vasodilator Agents