High salt diet exacerbates vascular contraction in the absence of adenosine A2A receptor

High salt (4% NaCl, HS) diet modulates adenosine-induced vascular response through adenosine A2A receptor (A2AAR). Evidence suggests that A2AAR stimulates cyp450-epoxygenases, leading to epoxyeicosatrienoic acids (EETs) generation. The aim of this study was to understand the vascular reactivity to HS and underlying signaling mechanism in the presence or absence of A2AAR. Therefore, we hypothesized that HS enhances adenosine-induced relaxation through EETs in A2AAR, but exaggerates contraction in A2AAR. Organ bath and Western blot experiments were conducted in HS and normal salt (NS, 0.18% NaCl)-fed A2AAR and A2AAR mice aorta. HS produced concentration-dependent relaxation to non-selective adenosine analog, NECA in A2AAR, whereas contraction was observed in A2AAR mice and this was attenuated by A1AR antagonist (DPCPX). CGS 21680 (selective A2AAR agonist) enhanced relaxation in HS-A2AAR versus NS-A2AAR, which was blocked by EETs antagonist (14,15-EEZE). Compared with NS, HS significantly upregulated the expression of vasodilators A2AAR and cyp2c29, whereas vasoconstrictors A1AR and cyp4a in A2AAR were downregulated. In A2AAR mice, however, HS significantly downregulated the expression of cyp2c29, whereas A1AR and cyp4a were upregulated compared with A2AAR mice. Hence, our data suggest that in A2AAR, HS enhances A2AAR-induced relaxation through increased cyp-expoxygenases-derived EETs and decreased A1AR levels, whereas in A2AAR, HS exaggerates contraction through decreased cyp-epoxygenases and increased A1AR levels. Copyright ?2013 by Lippincott Williams & Wilkins.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Role of ω-hydroxylase in adenosine-mediated aortic response through MAP kinase using a 2A-receptor knockout mice

Previously, we have shown that A 2A adenosine receptor (A 2AAR) knockout mice (KO) have increased contraction to adenosine. The signaling mechanism(s) for A 2AAR is still not fully understood. In this study, we hypothesize that, in the absence of A 2AAR, ω-hydroxylase (Cyp4a) induces vasoconstriction through mitogen-activated protein kinase (MAPK) via upregulation of adenosine A1 receptor (A 1AR) and protein kinase C (PKC). Organ bath and Western blot experiments were done using isolated aorta from A 2AKO and corresponding wild-type (WT) mice. Isolated aortic rings from WT and A2AKO mice were precontracted with submaximal dose of phenylephrine (10 -6 M), and concentration responses for selective A 1AR, A 2AAR agonists, angiotensin II and cytochrome P-450-epoxygenase, 20-hydroxyeicosatrienoic acid (20- HETE) PKC, PKC-α, and ERK1/2 inhibitors were obtained. 2-p-(2- Carboxyethyl)-phenethylamino-5'-N-ethylcarboxamidoadenosine hydrochloride (CGS-21680, A 2AAR agonist) induced concentration-dependent relaxation in WT, which was blocked by methylsulfonyl-propargyloxyphenylhexanamide (cytochrome P-450-epoxygenase inhibitor; 10 -5 M) and also with removal of endothelium. A 1 agonist, 2-chloro-N 6- cyclopentyladenosine (CCPA) produced higher contraction in A 2AKO aorta than WT (49.2 ± 8.5 vs. 27 ± 5.9% at 10 -6 M, P < 0.05). 20-HETE produced higher contraction in A 2AKO than WT (50.6 ± 8.8 vs. 21.1 ± 3.3% at 10 -7 M, P < 0.05). Contraction to CCPA in WT and A 2AKO aorta was inhibited by PD-98059 (p42/p44 MAPK inhibitor; 10 -6 M), chelerythrine chloride (nonselective PKC blocker; 10 -6 M), Gö-6976 (selective PKC-α inhibitor; 10 -7 M), and HET0016 (20-HETE inhibitor; 10 -5 M). Also, contraction to 20- HETE in WT and A 2AKO aorta was inhibited by PD-98059 and Gö-6976. Western blot analysis indicated the upregulation of A 1AR, Cyp4a, PKC-α, and phosphorylated-ERK1/2 in A 2AKO compared with WT (P < 0.05), while expression of Cyp2c29 was significantly higher in WT. CCPA (10 -6 M) increased the protein expression of PKC-α and phosphorylated-ERK1/2, while HET0016 significantly reduced the CCPA-induced increase in expression of these proteins. These data suggest that, in the absence of A 2AAR, Cyp4a induces vasoconstriction through MAPK via upregulation of A 1AR and PKC-α. © 2012 the American Physiological Society.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Reduced coronary reactive hyperemia in mice was reversed by the soluble epoxide hydrolase inhibitor (t-AUCB): Role of adenosine A2A receptor and plasma oxylipins

Coronary reactive hyperemia (CRH) protects the heart against ischemia. Adenosine A2AAR–deficient (A2AAR−/−) mice have increased expression of soluble epoxide hydrolase (sEH); the enzyme responsible for breaking down the cardioprotective epoxyeicosatrienoic acids (EETs) to dihydroxyeicosatrienoic acids (DHETs). sEH–inhibition enhances CRH, increases EETs, and modulates oxylipin profiles. We investigated the changes of oxylipins and their impact on CRH in A2AAR−/− and wild type (WT) mice. We hypothesized that the attenuated CRH in A2AAR−/− mice is mediated by changes in oxylipin profiles, and that it can be reversed by either sEH- or ω-hydroxylases–inhibition. Compared to WT mice, A2AAR−/− mice had attenuated CRH and changed oxylipin profiles, which were consistent between plasma and heart perfusate samples, including decreased EET/DHET ratios, and increased hydroxyeicosatetraenoic acids (HETEs). Plasma oxylipns in A2AAR−/− mice indicated an increased proinflammatory state including increased ω-terminal HETEs, decreased epoxyoctadecaenoic/dihydroxyoctadecaenoic acids (EpOMEs/DiHOMEs) ratios, increased 9-hydroxyoctadecadienoic acid, and increased prostanoids. Inhibition of either sEH or ω-hydroxylases reversed the reduced CRH in A2AAR−/− mice. In WT and sEH−/− mice, blocking A2AAR decreased CRH. These data demonstrate that A2AAR–deletion was associated with changes in oxylipin profiles, which may contribute to the attenuated CRH. Also, inhibition of sEH and ω-hydroxylases reversed the reduction in CRH.SCOPUS: ar.jinfo:eu-repo/semantics/publishe