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...

A-kinase anchoring proteins (AKAPs) tether protein kinase A (PKA) and other signaling proteins to defined intracellular sites, thereby establishing compartmentalized cAMP signaling. AKAP-PKA interactions play key roles in various cellular processes, including the regulation of cardiac myocyte contractility. We discovered small molecules, 3,3′-diamino-4,4′-dihydroxydiphenylmethane (FMP-API-1) and its derivatives, which inhibit AKAP-PKA interactions in vitro and in cultured cardiac myocytes. The molecules bind to an allosteric site of regulatory subunits of PKA identifying a hitherto unrecognized region that controls AKAP-PKA interactions. FMP-API-1 also activates PKA. The net effect of FMP-API-1 is a selective interference with compartmentalized cAMP signaling. In cardiac myocytes, FMP-API-1 reveals a novel mechanism involved in terminating β-adrenoreceptor-induced cAMP synthesis. In addition, FMP-API-1 leads to an increase in contractility of cultured rat cardiac myocytes and intact hearts. Thus, FMP-API-1 represents not only a novel means to study compartmentalized cAMP/PKA signaling but, due to its effects on cardiac myocytes and intact hearts, provides the basis for a new concept in the treatment of chronic heart failure.