Nitric oxide (NO), generated from L-arginine by endothelial nitric oxide synthase (eNOS), is a key endothelial-derived factor whose bioavailability is essential to the normal function of the endothelium. Endothelium dysfunction is characterized by loss of NO bioavailability because of either reduced formation or accelerated degradation of NO. We have recently reported that overexpression of vascular cytochrome P-450 (CYP) 4A in rats caused hypertension and endothelial dysfunction driven by increased production of 20-hydroxyeicosatetraenoic acid (20-HETE), a major vasoconstrictor eicosanoid in the microcirculation. To further explore cellular mechanisms underlying CYP4A-20-HETE-driven endothelial dysfunction, the interactions between 20-HETE and the eNOS-NO system were examined in vitro. Addition of 20-HETE to endothelial cells at concentrations as low as 1 nM reduced calcium ionophore-stimulated NO release by 50%. This reduction was associated with a significant increase in superoxide production. The increase in superoxide in response to 20-HETE was prevented by N(G)-nitro-L-arginine methyl ester, suggesting that uncoupled eNOS is a source of this superoxide. The response to 20-HETE was specific in that 19-HETE did not affect NO or superoxide production, and, in fact, the response to 20-HETE could be competitively antagonized by 19(R)-HETE. 20-HETE had no effect on phosphorylation of eNOS protein at serine-1179 or threonine-497 following addition of calcium ionophore; however, 20-HETE inhibited association of eNOS with 90-kDa heat shock protein (HSP90). In vivo, impaired acetylcholine-induced relaxation in arteries overexpressing CYP4A was associated with a marked reduction in the levels of phosphorylated vasodilator-stimulated phosphoprotein, an indicator of bioactive NO, that was reversed by inhibition of 20-HETE synthesis or action. Because association of HSP90 with eNOS is critical for eNOS activation and coupled enzyme activity, inhibition of this association by 20-HETE may underlie the mechanism, at least in part, by which increased CYP4A expression and activity cause endothelial dysfunction.

All-cis-14,15-epoxyeicosa-5,8,11-trienoic acid (14,15-EET) is a labile, vasodilatory eicosanoid generated from arachidonic acid by cytochrome P450 epoxygenases. A series of robust, partially saturated analogs containing epoxide bioisosteres were synthesized and evaluated for relaxation of precontracted bovine coronary artery rings and for in vitro inhibition of soluble epoxide hydrolase (sEH). Depending upon the bioisostere and its position along the carbon chain, varying levels of vascular relaxation and/or sEH inhibition were observed. For example, oxamide 16 and N-iPr-amide 20 were comparable (ED50 1.7 μM) to 14,15-EET as vasorelaxants, but were approx. 10–35 times less potent as sEH inhibitors (IC50 59 and 19 μM, respectively); unsubstituted urea 12 showed useful activity in both assays (ED50 3.5 μM, IC50 16 nM). These data reveal differential structural parameters for the two pharmacophores that could assist the development of potent and specific in vivo drug candidates.

Endothelial dysfunction and activation occur in the vasculature and are believed to contribute to the pathogenesis of cardiovascular diseases. We have shown that 8,11,, a cytochrome P450 4A-derived eicosanoid that promotes vasoconstriction in the microcirculation, uncouples endothelial nitric-oxide synthase (eNOS) and reduces nitric oxide (NO) levels via the dissociation of the 90-kDa heat shock protein (HSP90) from eNOS. It also causes endothelial activation by stimulating nuclear factor-B (NF-B) and increasing levels of proinflammatory cytokines. In this study, we examined signaling mechanisms that may link 20-HETE-induced endothelial dysfunction and activation. Under conditions in which 20-HETE inhibited NO production, it also stimulated inhibitor of NF-B (IB) phosphorylation. Both effects were prevented by inhibition of tyrosine kinases and mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK). It is noteworthy that inhibitor of IB kinase (IKK) activity negated the 20-HETE-mediated inhibition of NO production. Immunoprecipitation experiments revealed that treatment of ionophore-stimulated cells with 20-HETE brings about a decrease in HSP90-eNOS association and an increase in HSP90-IKK␤ association, suggesting that the activation by 20-HETE of NF-B is linked to its action on eNOS. Furthermore, addition of inhibitors of tyrosine kinase MAPK and IKK restored the 20-HETE-mediated impairment of acetylcholine-induced relaxation in rat renal interlobar arteries. The results indicate that 20-HETE mediates eNOS uncoupling and endothelial dysfunction via the activation of tyrosine kinase, MAPK, and IKK, and these effects are linked to 20-HETE-mediated endothelial activation.The integrity of the vascular endothelium is vital to the regulation of the cardiovascular system. The endothelium serves as a protective barrier between tissues and circulating blood and functions to maintain vascular homeostasis by releasing bioactive factors in response to hemodynamic changes and blood-borne signals. An uncontrolled endothelial cell response is involved in many disease processes, including hypertension, atherosclerosis, and diabetes. These diseases are related to endothelial injury, dysfunction and activation. Nitric oxide (NO), generated from L-arginine by endothelial nitric-oxide synthase (eNOS), is a key endothelial-derived factor, the bioavailability of which is essential to the integrity and function of the endothelium. Endothelial dysfunction occurs as a result of a loss of NO bioavailability that is due to either reduced formation or accelerated degradation of NO, and it is often associated with endothelial activation. NO actively mediates many functions of the endothelium. In addition to its Article, publication date, and citation information can be found at http://jpet.aspetjournals.org. doi:10.1124/jpet.109.159863.ABBREVIATIONS: NO, nitric oxide; eNOS, endothelial nitric-oxide synthase; SMC, smooth muscle cell; 20-HETE, 20-hydroxyeicosatetraenoic acid; HSP90, 90-kDa heat shock prot...

. 20-HETE-induced nitric oxide production in pulmonary artery endothelial cells is mediated by NADPH oxidase, H2O2, and PI3-kinase/Akt. Am J Physiol Lung Cell Mol Physiol 298: L564 -L574, 2010. First published January 8, 2010 doi:10.1152/ajplung.00298.2009We have shown that 20-hydroxyeicosatetraenoic acid (20-HETE) increases both superoxide and nitric oxide (NO) production in bovine pulmonary artery endothelial cells (BPAECs). The current study was designed to determine mechanisms underlying 20-HETE-stimulated NO release, and particularly the role of NADPH oxidase, reactive oxygen species, and PI3-kinase in stimulated NO release. Intracellular hydrogen peroxide (H2O2) and NO production were detected by dichlorofluorescein or dihydrorhodamine and diaminofluorescein fluorescence, respectively. Activation of endothelial nitric oxide synthase (eNOS) (Ser1179) and Akt (Ser473) was assessed by comparing the ratio of phosphorylated to total protein expression by Western blotting. Addition of 20-HETE to BPAECs caused an increase in superoxide and hydrogen peroxide, but not peroxynitrite. 20-HETE-evoked activation of Akt and eNOS, as well as enhanced NO release, are dependent on H2O2 as opposed to superoxide in that these endpoints are blocked by PEG-catalase and not PEG-superoxide dismutase. Similarly, 20-HETE-stimulated NO production in BPAECs is blocked by NADPH oxidase inhibitors apocynin or gp91 blocking peptide, and by PI3-kinase/Akt blockers wortmannin, LY-294002, or Akt inhibitor, implicating NADPH oxidase, PI3-kinase, and Akt signaling pathways, respectively, in this process. Together, these data suggest the following scheme: 20-HETE stimulates NADPH oxidase-dependent formation of superoxide. Superoxide is rapidly dismutated to hydrogen peroxide, which then mediates activation of PI3-kinase/Akt, phosphorylation of eNOS, and enhanced release of NO from eNOS in response to 20-HETE in BPAECs. pulmonary endothelium; superoxide; hydrogen peroxide; endothelial nitric oxide synthase WE HAVE PREVIOUSLY DEMONSTRATED that 20-HETE, a product of arachidonic acid catalyzed by CYP4, induces activation of nitric oxide synthase (NOS) from pulmonary artery endothelial cells in a [Ca 2ϩ ] i -dependent manner (9,23,36). Furthermore, 20-HETE releases NO, which contributes to endotheliumdependent vasodilation in pulmonary arteries (9, 19). Growing evidence from our own work as well as that from others indicates that 20-HETE activates the vascular NADPH oxidase, leading to increased production of superoxide anion (O 2•Ϫ ) and hydrogen peroxide (2,23,32 /calmodulin-dependent protein kinase II/Janus-kinase 2-dependent pathway in bovine aortic endothelial cells (6, 12). Furthermore, it has been shown that exogenous H 2 O 2 in micromolar concentrations activates eNOS from porcine aortic endothelial cells to cause endothelial NO release (7,28). Superoxide may also react with NO in a diffusion-limited fashion to form peroxynitrite. This species is believed to result in the loss of many of the beneficial effects of NO, including vasodila...

Arachidonic acid (AA) is metabolized by endothelial 15-lipoxygenase (15-LO) to several vasodilatory eicosanoids such as 11,12,15-trihydroxyeicosatrienoic acid (11,12,15-THETA) and its proposed unstable precursor 15-hydroxy-11,12-epoxyeicosatrienoic acid (15-H-11,12-EETA). In the present study, the acid-stable 13-hydroxy-trans-14,15-epoxy-eicosatrienoic acid (13-H-14,15-EETA) was identified and its vascular activities characterized. Rabbit aorta, mesenteric arteries, and the combination of 15-LO and cytochrome P450 2J2 converted AA to two distinct HEETA metabolites. The HEETA metabolites were resistant to acidic hydrolysis but were hydrolyzed by recombinant sEH to a more polar metabolite identified by mass spectrometry as 13,14,15-THETA.