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

Abstract

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

Adenosine A2A receptor modulates vascular response in soluble epoxide hydrolase-null mice through CYP-epoxygenases and PPARγ

“…Similarly, the EDHF response in bovine coronary arteries was inhibited by the EET antagonist, 14,15-epoxyeicosa-5(Z)-enoic acid (14). Recently, a report from our laboratory also showed that in A 2A AR ϩ/ϩ mouse aorta, the adenosine-induced vascular relaxation was inhibited by the EET antagonist, 14,15-epoxyeicosa-5(Z)-enoic acid (36). In the present study, we also found an upregulation of CYP2J5 proteins in sEH Ϫ/Ϫ compared with sEH ϩ/ϩ mouse aortas ( Fig.…”

“…In blood vessels, vasodilation is primarily caused by the activation of A 2A AR (36 -39). Moreover, A 2A AR-mediated relaxation was found to be dependent on the presence of a functional endothelium (1,25,36,42).…”

“…Endothelial cells express CYP2C and CYP2J, which are the main source of EETs generation in the vascular system (13,41,46). The most potent biological effects of EETs occur in small-resistance vessels, as well as in the aorta (9,36). For example, 14,15-EET has been observed to produce relaxation of isolated coronary microvessels at concentrations as low as 10 pM (9).…”

“…For example, 14,15-EET has been observed to produce relaxation of isolated coronary microvessels at concentrations as low as 10 pM (9). This process occurs through hyperpolarization and suggests that the EETs function as an endothelium-derived hyperpolarizing factor (EDHF) in a number of vascular beds, including the coronary artery and aorta (3,4,13,36,37). The EDHF response in bovine coronary arteries and mouse aorta is inhibited by the EET antagonist, 14,15-epoxyeicosa-5(Z)-enoic acid (14,36).…”

“…This process occurs through hyperpolarization and suggests that the EETs function as an endothelium-derived hyperpolarizing factor (EDHF) in a number of vascular beds, including the coronary artery and aorta (3,4,13,36,37). The EDHF response in bovine coronary arteries and mouse aorta is inhibited by the EET antagonist, 14,15-epoxyeicosa-5(Z)-enoic acid (14,36). The peroxisome proliferator-activated receptor (PPAR) transcription factors are members of the nuclear receptor superfamily that are activated by fatty acids and fatty acid derivatives (11).…”