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This Article Full Text Full Text (PDF) All Versions of this Article: 295/5/H2068    most recent 01333.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Nayeem, M. A. Articles by Mustafa, S. J. PubMed PubMed Citation Articles by Nayeem, M. A. Articles by Mustafa, S. J.

Role of CYP epoxygenases in A_2AAR-mediated relaxation using A_2AAR-null and wild-type mice

¹Department of Physiology and Pharmacology, Center for Interdisciplinary Research in Cardiovascular Sciences, West Virginia Univeristy, Morgantown, West Virginia; ²Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, Texas; ³Université Libre de Bruxelles, Brussels, Belgium; ⁴University of Pittsburgh School of Pharmacy, Pittsburgh, Pennslyvania; and ⁵Division of Intramural Research, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina

Submitted 13 November 2007 ; accepted in final form 12 September 2008

We hypothesized that A_2A adenosine receptor (A_2AAR) activation causes vasorelaxation through cytochrome P-450 (CYP) epoxygenases and endothelium-derived hyperpolarizing factors, whereas lack of A_2AAR 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 A_2AAR (A_2AAR^+/+; +33.99 ± 4.70%, P < 0.05) versus contraction in A_2AAR knockout (A_2AAR^–/–; –27.52 ± 4.11%) mouse aortae. An A_2AAR-specific antagonist (SCH-58261; 1µM) changed the NECA (10^–6 M) relaxation response to contraction (–35.82 ± 4.69%, P < 0.05) in A_2AAR^+/+ aortae, whereas no effect was noted in A_2AAR^–/– aortae. Significant contraction was seen in the absence of the endothelium in A_2AAR^+/+ (–2.58 ± 2.25%) aortae compared with endothelium-intact aortae. An endothelial nitric oxide synthase inhibitor (N-nitro-L-arginine methyl ester; 100 µM) and a cyclooxygenase inhibitor (indomethacin; 10 µM) failed to block NECA-induced relaxation in A_2AAR^+/+ 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 A_2AAR^+/+ aortae, whereas no response was noted in A_2AAR^–/– aortae. Furthermore, an epoxyeicosatrienoic acid (EET) antagonist [14,15-epoxyeicosa-5(Z)-enoic acid; 10 µM] was able to block NECA-induced relaxation in A_2AAR^+/+ aortae, whereas -hydroxylase inhibitors (10 µM dibromo-dodecenyl-methylsulfimide and 10 µM HET-0016) changed contraction into relaxation in A_2AAR^–/– aorta. Cyp2c29 protein was upregulated in A_2AAR^+/+ aortae, whereas Cyp4a was upregulated in A_2AAR^–/– aortae. Higher levels of dihydroxyeicosatrienoic acids (DHETs; 14,15-DHET, 11,12-DHET, and 8,9-DHET, P < 0.05) were found in A_2AAR^+/+ versus A_2AAR^–/– aortae. EET levels were not significantly different between A_2AAR^+/+ and A_2AAR^–/– aortae. It is concluded that CYP epoxygenases play an important role in A_2AAR-mediated relaxation, and the deletion of the A_2AAR leads to contraction through Cyp4a.

epoxyeicosatrienoic acids; dihydroxyeicosatrienoic acids; vasodilation; vasoconstriction; adenosine; cytochrome P-450s