Elsevier

Pharmacology & Therapeutics

Volume 111, Issue 3, September 2006, Pages 584-595
Pharmacology & Therapeutics

Associate editor: R.M. Wadsworth
From endothelium-derived hyperpolarizing factor (EDHF) to angiogenesis: Epoxyeicosatrienoic acids (EETs) and cell signaling

https://doi.org/10.1016/j.pharmthera.2005.11.003Get rights and content

Abstract

Epoxyeicosatrienoic acids (EETs) are generated from arachidonic acid by cytochrome P450 (CYP) epoxygenases. The expression of CYP epoxygenases in endothelial cells is determined by a number of physical (fluid shear stress and cyclic stretch) and pharmacological stimuli as well as by hypoxia.

The activation of CYP epoxygenases in endothelial cells is an important step in the nitric oxide and prostacyclin (PGI2)-independent vasodilatation of several vascular beds and EETs have been identified as endothelium-derived hyperpolarizing factors (EDHFs). However, in addition to regulating vascular tone, EETs modulate several signaling cascades and affect cell proliferation, cell migration, and angiogenesis. Signaling molecules modulated by EETs include tyrosine kinases and phosphatases, mitogen-activated protein kinases, protein kinase A (PKA), cyclooxygenase (COX)-2, and several transcription factors. This review summarizes the role of CYP-derived EETs in cell signaling and focuses particularly on their role as intracellular amplifiers of endothelial cell hyperpolarization as well as in cell proliferation and angiogenesis. The angiogenic properties of CYP epoxygenases and CYP-derived EETs implicate that these enzymes may well be accessible targets for anti-angiogenic as well as angiogenic therapies.

Introduction

Cytochrome P450 (CYP) enzymes are membrane-bound, heme-containing terminal oxidases in a multi-enzyme complex that also includes a FAD/FMN-containing NADPH-cytochrome P450 reductase and cytochrome b5. CYP enzymes oxidize, peroxidise, and/or reduce cholesterol, vitamins, steroids, xenobiotics, and numerous pharmacological substances in an oxygen- and NADPH-dependent manner. Some isoforms are fairly specific in their choice of substrates but many catalyse a large number of chemical reactions and can use an almost unlimited number of biologically occurring and synthetic compounds. Hepatic CYP enzymes are responsible for the metabolism of xenobiotica and many pharmaceuticals, but they also utilize endogenous compounds as substrates, such as cholesterol and fatty acids. Because many CYP enzymes metabolize arachidonic acid, they have been referred to as the third pathway of arachidonic acid metabolism, that is, in addition to cyclooxygenases (COX) and lipoxygenases. Among the CYP enzymes that metabolize arachidonic acid, it is possible to distinguish hydroxylases that form vasoconstrictor hydroxyeicosatetraenoic acids (HETEs) and epoxygenases, which generate vasodilator epoxyeicosatrienoic acids (EETs).

Section snippets

What are epoxyeicosatrienoic acids?

EETs are arachidonic acid epoxides, and in mammals the epoxidation of polyunsaturated fatty acids to cis-epoxides is unique to the CYP enzyme system. Multiple mammalian CYP enzymes are capable of generating EETs including members of the CYP 1A, CYP 2B, CYP 2C, CYP 2D, CYP 2J, and CYP 4A subfamilies (for a review, see Fleming, 2001, Zeldin, 2001), whereas the catalytic efficiency as well as the regio- and enantio-selectivity of EET formation is isoform specific. Of the 5,6-, 8,9-, 11,12-, and

Epoxyeicosatrienoic acid receptors

EETs are now recognized as important modulators of intracellular signaling cascades, but it is unclear how they initiate their effects. Several modes of cell activation by EETs have been proposed. One of them involves the activation of a putative extracellular receptor on guinea pig monocytes (Wong et al., 2000). Competition studies showed a specific high affinity binding of 14,15- and 11,12-EET to a receptor that seems to be protein in nature. Another proposed mechanism involves the

Endothelial cells

The first hint that EETs may affect cell signaling and proliferation was obtained in renal epithelial cells (Chen et al., 1998, Chen et al., 1999) and soon afterwards “authentic EDHF” recovered from the luminal incubate of rhythmically stretched coronary arteries was found to activate a number of kinases, whose function was closely linked with endothelial cell proliferation (Fleming et al., 2001a). The activation of these MAP kinases could be inhibited by the treatment with CYP inhibitors as

Cytochrome P450 epoxygenases/epoxyeicosatrienoic acids and angiogenesis

The first link between EETs and angiogenesis was obtained in co-cultures of astrocytes and endothelial cells. EETs released from astrocytes increased thymidine incorporation into endothelial cells and elicited the formation of capillary like structures (Munzenmaier & Harder, 2000, Zhang & Harder, 2002). Moreover, the overexpression of CYP 2C9 in and/or the application of 11,12- or 14,15-EET to monocultures of endothelial cells was associated with angiogenesis (Medhora et al., 2003, Michaelis et

Summary/outlook

Since the first proposal that CYP-derived metabolites of arachidonic acid may be linked to vascular smooth muscle hyperpolarization and relaxation, it has become clear that the arachidonic acid epoxides (5,6-, 8,9-, 11,12-, and 14,15-EET) are important intracellular signaling molecules that modulate much more than membrane potential. The vasodilator and anti-inflammatory actions of EETs mean that therapies that increase their generation or prevent their degradation may prove beneficial in the

Acknowledgments

Work performed in the author's laboratory was supported by the Deutsche Forschungsgemeinschaft (SFB-TR 23, A6).

References (135)

  • E. Eliasson et al.

    Hormone- and substrate-regulated intracellular degradation of cytochrome P450 (2E1) involving MgATP-activated rapid proteolysis in the endoplasmic reticulum membranes

    J Biol Chem

    (1992)
  • M. Faehling et al.

    Vascular endothelial growth factor-A activates Ca2+-activated K+ channels in human endothelial cells in culture

    Int J Biochem Cell Biol

    (2001)
  • X. Fang et al.

    Epoxyeicosatrienoic acid metabolism in arterial smooth muscle cells

    J Lipid Res

    (1995)
  • X. Fang et al.

    Differences in positional esterification of 14,15-epoxyeicosatrienoic acid in phosphatidylcholine of porcine coronary artery endothelial and smooth muscle cells

    Prostaglandins Other Lipid Mediat

    (2003)
  • I. Fleming

    Cytochrome P450 epoxygenases as EDHF-synthase(s)

    Pharmacol Res

    (2004)
  • C. Ged et al.

    Isolation of the human cytochrome P-450 IIC8 gene: multiple glucocorticoid responsive elements in the 5′ region

    Biochim Biophys Acta

    (1991)
  • S. Gerbal-Chaloin et al.

    Transcriptional Regulation of CYP2C9 Gene. Role of glucocorticoid receptor and constitutive androstane receptor

    J Biol Chem

    (2002)
  • B.G. Hoebel et al.

    11,12-Epoxyeicosatrienoic acid stimulates tyrosine kinase activity in porcine aortic endothelial cells

    Eur J Pharmacol

    (1998)
  • A. Karara et al.

    Arachidonic acid epoxygenase. Stereochemical analysis of the endogenous epoxyeicosatrienoic acids of human kidney cortex

    FEBS Lett

    (1990)
  • A. Karara et al.

    Arachidonic acid epoxygenase: structural characterization and quantification of epoxyeicosatrienoates in plasma

    Biochem Biophys Res Commun

    (1992)
  • K.K. Korsmeyer et al.

    Proteolytic degradation of heme-modified hepatic cytochromes P450: a role for phosphorylation, ubiquitination, and the 26S proteasome?

    Arch Biochem Biophys

    (1999)
  • T. Matoba et al.

    Hydrogen peroxide is an endothelium-derived hyperpolarizing factor in human mesenteric arteries

    Biochem Biophys Res Commun

    (2002)
  • H.S. Park et al.

    Akt (protein kinase B) negatively regulates SEK1 by means of protein phosphorylation

    J Biol Chem

    (2002)
  • M. Potente et al.

    Cytochrome P450 2C9-induced endothelial cell proliferation involves induction of mitogen-activated protein (MAP) kinase phosphatase-1, inhibition of the c-Jun N-terminal kinase, and up-regulation of cyclin D1

    J Biol Chem

    (2002)
  • M. Potente et al.

    11,12-Epoxyeicosatrienoic acid-induced inhibition of FOXO factors promotes endothelial proliferation by down-regulating p27Kip1

    J Biol Chem

    (2003)
  • A. Pozzi et al.

    Charaterization of 5,6- and 8,9-Epoxyeicosatrienoic acids (5,6- and 8,9-EET) as potent in vivo angiogenic lipids

    J Biol Chem

    (2005)
  • N.J. Alkayed et al.

    Neuroprotection and P450 2C11 up-regulation after experimental transient ischemic attack

    Stroke

    (2002)
  • H.K. Anandatheerthavarada et al.

    Dual targeting of cytochrome P4502B1 to endoplasmic reticulum and mitochondria involves a novel signal activation by cyclic AMP-dependent phosphorylation at Ser128

    EMBO J

    (1999)
  • S.L. Archer et al.

    Endothelium-derived hyperpolarizing factor in human internal mammary artery is 11,12-epoxyeicosatrienoic acid and causes relaxation by activating smooth muscle BKCa channels

    Circulation

    (2003)
  • A. Baron et al.

    Epoxyeicosatrienoic acids activate a high-conductance, Ca2+-dependent K+ channel on pig coronary artery endothelial cells

    J Physiol (Lond)

    (1997)
  • J. Bauersachs et al.

    Nitric oxide attenuates the release of endothelium-derived hyperpolarizing factor

    Circulation

    (1996)
  • J. Bauersachs et al.

    Cytochrome P450 2C expression and EDHF-mediated relaxation in porcine coronary arteries is increased by cortisol

    Cardiovasc Res

    (2002)
  • W.B. Campbell et al.

    Identification of epoxyeicosatrienoic acids as endothelium-derived hyperpolarizing factors

    Circ Res

    (1996)
  • P. Carmeliet

    VEGF gene therapy: stimulating angiogenesis or angioma-genesis?

    Nat Med

    (2000)
  • J.K. Chen et al.

    Heparin-binding EGF-like growth factor mediates the biological effects of P450 arachidonate epoxygenase metabolites in epithelial cells

    Proc Natl Acad Sci U S A

    (2002)
  • Z.M. Chu et al.

    Cytochrome P450 metabolites of arachidonic acid may be important mediators in angiotensin II-induced vasoconstriction in the rat mesentery in vivo

    Clin Sci (Colch)

    (2000)
  • Y.J. Chun et al.

    Discovery of cytochrome P450 1B1 inhibitors as new promising anti-cancer agents

    Med Res Rev

    (2003)
  • P. Coats et al.

    Endothelium-derived hyperpolarizing factor: identification and mechanisms of action in human subcutaneous resistance arteries

    Circulation

    (2001)
  • J.K. Coller

    Oxidative metabolism of tamoxifen to Z-4-hydroxy-tamoxifen by cytochrome P450 isoforms: an appraisal of in vitro studies

    Clin Exp Pharmacol Physiol

    (2003)
  • J.P. Cullen et al.

    Pulsatile flow-induced angiogenesis: role of Gi subunits

    Arterioscler Thromb Vasc Biol

    (2002)
  • B.B. Davis et al.

    Inhibitors of soluble epoxide hydrolase attenuate vascular smooth muscle cell proliferation

    Proc Natl Acad Sci U S A

    (2002)
  • J.F. Desaphy et al.

    Effect of cyclic AMP on the calcium-dependent potassium conductances of rat Leydig cells

    Can J Physiol Pharmacol

    (1998)
  • S. Earley et al.

    Endothelium-dependent blunting of myogenic responsiveness after chronic hypoxia

    Am J Physiol Heart Circ Physiol

    (2002)
  • S. Earley et al.

    Cytochrome P-450 epoxygenase products contribute to attenuated vasoconstriction after chronic hypoxia

    Am J Physiol Heart Circ Physiol

    (2003)
  • B.A. Escalante et al.

    Role of cytochrome P-450 arachidonate metabolites in endothelin signaling in rat proximal tubule

    Am J Physiol Renal Physiol

    (2002)
  • M. Esguerra et al.

    Cloned Ca2+-dependent K+ channel modulated by a functionally associated protein kinase

    Nature

    (1994)
  • X. Fang et al.

    14,15-Epoxyeicosatrienoic acid inhibits prostaglandin E2 production in vascular smooth muscle cells

    Am J Physiol

    (1998)
  • X. Fang et al.

    Human coronary endothelial cells convert 14,15-EET to a biologically active chain-shortened epoxide

    Am J Physiol Heart Circ Physiol

    (2002)
  • X. Fang et al.

    Activation of peroxisome proliferator-activated receptor α by substituted urea-derived soluble epoxide hydrolase inhibitors

    Am J Physiol Heart Circ Physiol

    (2005)
  • Fang, X., Hu, S., Xu, B., Snyder, G., Harmon, S., Yao, J., et al. (in press). 14,15-Dihydroxyeicosatrienoic acid...
  • Cited by (108)

    • The emerging role of PPAR-alpha in breast cancer

      2023, Biomedicine and Pharmacotherapy
    • PD146176 affects human EA.hy926 endothelial cell function by differentially modulating oxylipin production of LOX, COX and CYP epoxygenase

      2022, Biochimica et Biophysica Acta - Molecular and Cell Biology of Lipids
      Citation Excerpt :

      The activation of p38 MAPK by PD at 30 min coincides with a reduced production of anti-inflammatory oxylipins such as 5,6-, 8,9- and 11,12-EpETrEs [52]. EpETrEs also have a pro-angiogenic effect [53] and thus lower levels of these EpETrEs after PD treatment may relate to the reduction in cell proliferation that was observed in this study. 13-HDoHE can be generated non-enzymatically from DHA, and is an indicator of oxidative stress [54].

    View all citing articles on Scopus
    View full text