Role of CYP epoxygenases in A2AAR-mediated relaxation using A2AAR-null and wild-type mice

Mohammed A. Nayeem, Samuel M. Poloyac, John R. Falck, Darryl C. Zeldin, Catherine Ledent, Dovenia S. Ponnoth, Habib R. Ansari, S. Jamal Mustafa

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

We hypothesized that A2A adenosine receptor (A2AAR) activation causes vasorelaxation through cytochrome P-450 (CYP) epoxygenases and endothelium-derived hyperpolarizing factors, whereas lack of A2AAR activation promotes vasoconstriction through Cyp4a in the mouse aorta. Adenosine 5′-N-ethylcarboxamide (NECA; 10-6 M), an adenosine analog, caused relaxation in wild-type A2AAR (A2AAR+/+; +33.99 ± 4.70%, P < 0.05) versus contraction in A2AAR knockout (A2AAR-/-; -27.52 ± 4.11%) mouse aortae. An A2AAR-specific antagonist (SCH-58261; 1μ-M) changed the NECA (10-6 M) relaxation response to contraction (-35.82 ± 4.69%, P < 0.05) in A2AAR+/+ aortae, whereas no effect was noted in A2AAR-/- aortae. Significant contraction was seen in the absence of the endothelium in A2AAR+/+ (-2.58 ± 2.25%) aortae compared with endothelium-intact aortae. An endothelial nitric oxide synthase inhibitor (N-nitro-L-arginine methyl ester; 100 μ-M) and a cyclooxygenase inhibitor (indomethacin; 10 μ-M) failed to block NECA-induced relaxation in A2AAR+/+ aortae. A selective inhibitor of CYP epoxygenases (methylsulfonyl-propargyloxyphenylhexanamide; 10 -μM) changed NECA-mediated relaxation (-22.74 ± 5.11% at 10 -6 M) and CGS-21680-mediated relaxation (-18.54 ± 6.06% at 10-6 M) to contraction in A2AAR+/+ aortae, whereas no response was noted in A2AAR-/- aortae. Furthermore, an epoxyeicosatrienoic acid (EET) antagonist [14,15-epoxyeicosa- 5(Z)-enoic acid; 10 μ-M] was able to block NECA-induced relaxation in A 2AAR+/+ aortae, whereas ω-hydroxylase inhibitors (10 μ-M dibromo-dodecenyl-methylsulfimide and 10 -μM HET-0016) changed contraction into relaxation in A2AAR-/- aorta. Cyp2c29 protein was upregulated in A2AAR+/+ aortae, whereas Cyp4a was upregulated in A2AAR-/- aortae. Higher levels of dihydroxyeicosatrienoic acids (DHETs; 14,15-DHET, 11,12-DHET, and 8,9-DHET, P < 0.05) were found in A2AAR+/+ versus A 2AAR-/- aortae. EET levels were not significantly different between A2AAR+/+ and A2AAR -/- aortae. It is concluded that CYP epoxygenases play an important role in A2AAR-mediated relaxation, and the deletion of the A 2AAR leads to contraction through Cyp4a.

Original languageEnglish (US)
Pages (from-to)H2068-H2078
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume295
Issue number5
DOIs
StatePublished - Nov 2008

Keywords

  • Adenosine
  • Cytochrome P-450s
  • Dihydroxyeicosatrienoic acids
  • Epoxyeicosatrienoic acids
  • Vasoconstriction
  • Vasodilation

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)

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