Comparison of vasodilatory properties of 14,15-EET analogs: structural requirements for dilation

Abstract

Epoxyeicosatrienoic acids (EETs) are endothelium-derived eicosanoids that activate potassium channels, hyperpolarize the membrane, and cause relaxation. We tested 19 analogs of 14,15-EET on vascular tone to determine the structural features required for activity. 14,15-EET relaxed bovine coronary arterial rings in a concentration-related manner (ED(50) = 10(-6) M). Changing the carboxyl to an alcohol eliminated dilator activity, whereas 14,15-EET-methyl ester and 14,15-EET-methylsulfonimide retained full activity. Shortening the distance between the carboxyl and epoxy groups reduced the agonist potency and activity. Removal of all three double bonds decreased potency. An analog with a Delta8 double bond had full activity and potency. However, the analogs with only a Delta5 or Delta11 double bond had reduced potency. Conversion of the epoxy oxygen to a sulfur or nitrogen resulted in loss of activity. 14(S),15(R)-EET was more potent than 14(R),15(S)-EET, and 14,15-(cis)-EET was more potent than 14,15-(trans)-EET. These studies indicate that the structural features of 14,15-EET required for relaxation of the bovine coronary artery include a carbon-1 acidic group, a Delta8 double bond, and a 14(S),15(R)-(cis)-epoxy group.

14,15-Epoxyeicosa-5(Z)-Enoic-mSI

“…14,15-DHET also induces relaxation of bovine coronary arterial rings, although relaxation is Ϸ5-fold less potent that the EETs. 19,27 Similar to 14,15-EET, 14,15-DHET activates coronary smooth muscle cell BK Ca channels through G-protein-dependent mechanisms. 27 Thus, 14,15-EET and 14,15-DHET appear to induce smooth muscle hyperpolarization and relaxation through similar cellular mechanisms.…”

“…A similar substitution of carbon 1 of 14,15-EET with a methylsulfonimide group (14,15-EET-mSI) did not alter agonist properties. 19 Additionally, 14,15-EET-mSI is not metabolized by smooth muscle cells or incorporated into cellular lipids. 24 Similarly, by using LC/ESI-mass spectrometric analysis of 14,15-EEZE-mSI metabolism in bovine coronary smooth muscle cells, we did not see evidence of ␤-oxidation (data not shown).…”

“…The arterial rings were suspended in a tissue bath containing a Krebs-bicarbonate buffer equilibrated with 95% O 2 -5% CO 2 and maintained at 37°C as previously described. 2,19,20 Tension was measured with a model FT-03C force transducer (Grass Instruments), ETH-400 bridge amplifier, and MacLab 8e A/D converter with MacLab software and a Macintosh computer. The arterial rings were slowly stretched to a basal tension of 3.5 g and equilibrated for 1.5 hours.…”

“…19 Figure 1 compares the chemical structures of 14,15-EET and 14,15-EEZE-mSI. 14,15-EEZE-mSI differs from 14,15-EET in that the double bonds at carbons 8,9 and 11,12 are saturated and the carbon-1 carboxyl was altered to a methylsulfonimide group.…”

“…For 14,15-EET, shortening the distance between the carboxyl and epoxy groups, converting the epoxide oxygen to a sulfur or nitrogen, and changing the carboxyl group at carbon-1 to an alcohol or elimination of the ⌬8 double bond results in loss of agonist potency. 19 Furthermore, the 14,15-EET analogue 14,15-epoxyeicosaenoic acid [14,15-EE-5(Z)-E], with saturated double bonds between carbons 5,6 and 11,12, acts as an EET-specific antagonist. This analogue inhibits relaxation induced by 5,8,11,14,and 14, induced relaxation.…”