Development of Epoxyeicosatrienoic Acid Analogs with in Vivo Anti-Hypertensive Actions

Epoxyeicosatrienoic acids (EETs) contribute importantly to the regulation of vascular tone and blood pressure control. The purpose of this study was to develop stable EET analogs and test their in vivo blood pressure lowering effects in hypertensive rats. Using the pharmacophoric moiety of EETs, ether EET analogs were designed with improved solubility and resistance to auto-oxidation and metabolism by soluble epoxide hydrolase. Ether EET analogs were chosen based on their ability to dilate afferent arterioles and subsequently tested for blood pressure lowering effects in rodent models of hypertension. Initially, 11,12-ether-EET-8-ZE failed to lower blood pressure in angiotensin hypertension or spontaneously hypertensive rats (SHR). Esterification of the carboxylic group of 11,12-ether-EET-8-ZE prevented blood pressure increase in SHR when injected at 2 mg/day for 12 days (MAP Δ change at day 8 of injection was −0.3 ± 2 for treated and 12 ± 1 mmHg for control SHR). Amidation of the carboxylic group with aspartic acid produced another EET analog (NUDSA) with a blood pressure lowering effect when injected at 3 mg/day in SHR for 5 days. Amidation of the carboxylic group with lysine amino acid produced another analog with minimal blood pressure lowering effect. These data suggest that esterification of the carboxylic group of 11,12-ether-EET-8-ZE produced the most effective ether-EET analog in lowering blood pressure in SHR and provide the first evidence to support the use of EET analogs in treatment of cardiovascular diseases

14,15-Dihydroxy-eicosa-5(Z)-enoic Acid Selectively Inhibits 14,15-Epoxyeicosatrienoic Acid-Induced Relaxations in Bovine Coronary Arteries

Cytochrome P-450 epoxygenases metabolize arachidonic acid (AA) to epoxyeicosatrienoic acids (EETs). EETs relax vascular smooth muscle by membrane hyperpolarization. 14,15-Epoxyeicosa-5(Z)-enoic acid (14,15-EE5ZE) antagonizes many vascular actions of EETs. EETs are converted to the corresponding dihydroxyeicosatrienoic acids by soluble epoxide hydrolase (sEH). sEH activity in the bovine arterial endothelium and smooth muscle regulates endogenous EETs. This study examined sEH metabolism of 14,15-EE5ZE to 14,15-dihydroxy-eicosa-5(Z)-enoic acid (14,15-DHE5ZE) and the resultant consequences on EET relaxations of bovine coronary arteries (BCAs). BCAs converted 14,15-EE5ZE to 14,15-DHE5ZE. This conversion was blocked by the sEH inhibitor 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA). 14,15-EET relaxations (maximal relaxation, 83.4 ± 4.5%) were inhibited by 14,15-DHE5ZE (10 μM; maximal relaxation, 36.1 ± 9.0%; p < 0.001). In sharp contrast with 14,15-EE5ZE, 14,15-DHE5ZE is a 14,15-EET-selective inhibitor and did not inhibit 5,6-, 8,9-, or 11,12-EET relaxations. 14,15-EET and 11,12-EET relaxations were similar in the presence and absence of AUDA (1 μM). 14,15-EE5ZE inhibited 14,15-EET relaxations to a similar extent with and without AUDA pretreatment. However, 14,15-EE5ZE inhibited 11,12-EET relaxations to a greater extent with than without AUDA pretreatment. These observations indicate that sEH converts 14,15-EE5ZE to 14,15-DHE5ZE, and this alteration influences antagonist selectivity against EET-regioisomers. 14,15-DHE5ZE inhibited endothelium-dependent relaxations to AA but not endothelium-independent relaxations to sodium nitroprusside. A series of sEH-resistant ether analogs of 14,15-EE5ZE was developed, and analogs with agonist and antagonist properties were identified. The present study indicates that conversion of 14,15-EE5ZE to 14,15-DHE5ZE produces a 14,15-EET-selective antagonist that will be a useful pharmacological tool to identify EET receptor(s) and EET function in the cardiovascular system