Interaction Between P450 Eicosanoids and Nitric Oxide in the Control of Arterial Tone in Mice

Abstract

Objective-Epoxyeicosatrienoic acids (EETs) serve as endothelial-derived hyperpolarizing factors (EDHF), but may also affect vascular function by other mechanisms. We identified a novel interaction between EETs and endothelial NO release using soluble epoxide hydrolase (sEH) Ϫ/Ϫ and ϩ/ϩ mice. Methods and Results-EDHF responses to acetylcholine in pressurized isolated mesenteric arteries were neither affected by the sEH inhibitor, N-adamantyl-NЈ-dodecylurea (ADU), nor by sEH gene deletion. However, the EDHF responses were abolished by catalase and by apamin/charybdotoxin (ChTx), but not by iberiotoxin, nor by the cytochrome P450 inhibitor PPOH. All four EETs (order of potency: 8,9-EET Ͼ14,15-EETϷ5,6-EET Ͼ11,12-EET) and all 4 dihydroxy derivatives (14,15-DHETϷ8,9-DHETϷ11,12-DHET Ͼ5,6-DHET) produced dose-dependent vasodilation. Endothelial removal or L-NAME blocked 8,9-EET and 14,15-DHET-dependent dilations. The effects of apamin/ChTx were minimal. 8,9-EET and 14,15-DHET induced NO production in endothelial cells. ADU (100 g/mL in drinking water) lowered blood pressure in angiotensin II-infused hypertension, but not in L-NAME-induced hypertension. Blood pressure and EDHF responses were similar in L-NAME-treated sEH ϩ/ϩ and Ϫ/Ϫ mice. Conclusions-Our data indicate that the EDHF response in mice is caused by hydrogen peroxide, but not by P450 eicosanoids. Moreover, P450 eicosanoids are vasodilatory, largely through their ability to activate endothelial NO synthase (eNOS) and NO release. Key Words: eicosanoids Ⅲ soluble epoxide hydrolase Ⅲ NO synthase Ⅲ L-NAME Ⅲ EDRF T he endothelium releases nitric oxide (NO), prostacyclin, and endothelium-derived hyperpolarizing factor (EDHF). 1,2 Epoxyeicosatrienoic acids (EETs) are cytochrome P450 epoxygenase (CYP)-derived metabolites of arachidonic acid (AA) that may be EDHFs. 3,4 Other candidates include K ϩ ions and hydrogen peroxide (H 2 O 2 ). [5][6][7] Endothelial cell hyperpolarization spreads to adjacent vascular smooth muscle cells (VSMCs) through myo-endothelial gap junctions. 8,9 Calcium-activated potassium channels, most probably the SK4 (IK Ca ) and SK3 (SK Ca ) expressed on the endothelium, are the end-cellular gateway mediating hyperpolarization, and subsequent EDHF relaxation. 2,4,10 -13 EETs convincingly cause hyperpolarization. 14 -16 They can induce vasodilation in certain vascular beds by increasing the open-state probability of calcium-activated potassium (BK) channels. 4,15,17 The soluble epoxide hydrolase (sEH) metabolizes EETs to dihydroxy derivatives (DHET). sEH inhibition could enhance EET activity. 18 Blood pressure decreased in spontaneously hypertensive rats (SHR) given an sEH inhibitor. 19 sEH inhibition also lowered blood pressure in rats given angiotensin II (Ang II). 20 Thus, sEH could contribute to Ang IIinduced hypertension 21 and salt-sensitivity. 22 Even desoxycorticosterone acetate (DOCA)-salt hypertension was ameliorated with sEH inhibition. 23 Finally, male sEH genedeleted (Ϫ/Ϫ) mice had lower blood pressures than sEH ϩ/ϩ mice. 24 EETs coul...

11,12-Epoxyeicosatrienoic acid induces vasodilator response in the rat perfused mesenteric vasculature

“…Incubation with specific calcium‐activated potassium channel inhibitors failed to attenuate the vasodilator effect of 11, 12‐EET in. This finding was similar to the results demonstrated by Hercule et al 34. in which the dilator responses to 5, 6‐EET, 11, 12‐EET and 14, 15‐EET were not changed due to apamin/ChTx in mouse mesenteric arteries.…”

“…Therefore, it was proposed that stimulation of BK ca channel in vascular smooth muscle cells are not linked to the direct effects of EETs 33. Hercule et al 34. also reported that EDHF‐dependent relaxation in mouse mesenteric arteries was not prevented by iberiotoxin.…”

Flaxseed Consumption Reduces Blood Pressure in Patients With Hypertension by Altering Circulating Oxylipins via an α-Linolenic Acid–Induced Inhibition of Soluble Epoxide Hydrolase

“…10 In contrast, the epoxyeicosatrienoic acids (EETs) produced from arachidonic acid are endothelial-derived hyperpolarizing factors that are associated with vasodilation and natriuresis 11,12 and may indirectly propagate vasodilation [13][14][15] by activating endothelial nitric oxide synthase. 16,17 EETs can be rapidly metabolized to dihydroxyeicosatrienoic acids (DHETs) by the enzyme soluble epoxide hydrolase (sEH), resulting in a concomitant loss of vasodilation. 18,19 sEH also converts the protoxins, epoxyoctadecenoic acids, to the dihydroxyoctadecenoic acids, which are potent cytotoxic and proinflammatory metabolites.…”

“…The sEH substrates, EETs, have known vasodilatory actions. [12][13][14][15][16][17][18][19]23 However, because of the short half-life of EETs, 33 these sEH substrates were below the level of detection and it was not . Schematic of proposed α-linolenic acid-induced alterations in the oxylipin profile.…”

Role of KCNQ Channels in Skeletal Muscle Arteries and Periadventitial Vascular Dysfunction

“…We performed radiotelemetry on adult male C57Bl6 and NZO mice (34 weeks) as outlined elsewhere. 28 BP devices were implanted in mice. After 10 days, mice had recovered from surgery and exhibited regular diurnal rhythms of activity.…”