NADPH Oxidase Pathway Is Involved in Aortic Contraction Induced by A₃ Adenosine Receptor in Mice

Abstract

The NADPH oxidase (Nox) subunits 1, 2 (gp91 phox), and 4 are the major sources for reactive oxygen species (ROS) in vascular tissues. In conditions such as ischemia-reperfusion and hypoxia, both ROS and adenosine are released, suggesting a possible interaction. Our aim in this study was to examine the A 3 adenosine receptor (A 3 AR)-induced vascular effects and its relation to ROS and Nox1, 2, and 4 using aortic tissues from wild-type (WT) andϪ5 M) induced contraction of the aorta from WT but not from A 3 KO mice, and this contraction was inhibited by the Nox inhibitor apocynin (10 Ϫ5 M) and the ROS scavengers superoxide dismutase-polyethylene glycol and catalase-polyethylene glycol (100 U/ml each). Cl-IBMECA-induced contraction was not affected by the mast cell degranulator compound 48/80 (100 g/ml) or the stabilizer cromolyn sodium (10 Ϫ4 M). In addition, Cl-IBMECA (10 Ϫ7 M) increased intracellular ROS generation by 35 Ϯ 14% in WT but not in A 3 KO aorta, and this increase was inhibited by apocynin (10 Ϫ5 M), diphenyleneiodonium chloride (10 Ϫ5 M), and the A 3 AR antagonist 3-propyl-6-ethyl-5-[(ethylthio)carbonyl]-2 phenyl-4-propyl-3-pyridine carboxylate (MRS1523) (10 Ϫ5 M). Furthermore, Cl-IBMECA selectively increased the protein expression of the Nox2 subunit by 150 Ϯ 15% in WT but not in A 3 KO mice without affecting either Nox1 or 4, and this increase was inhibited by apocynin. The mRNA of Nox2 was unchanged by Cl-IBMECA in either WT or A 3 KO aortas. In conclusion, A 3 AR enhances ROS generation, possibly through activation of Nox2, with subsequent contraction of the mouse aorta.

Involvement of NADPH oxidase in A2A adenosine receptor-mediated increase in coronary flow in isolated mouse hearts

“…In contrast, Nox2 inhibition or ROS scavenging blunted the adenosine-induced vasodilation in cerebral arteries [35] and coronary circulation [37], both of which suggest that adenosine is capable of generating ROS in these vasculatures. Consistent with our previous findings in the coronary circulation but in contrast to those in other vascular beds [33,34,37], Nox2 inhibition or ROS scavenging significantly attenuated the adenosine-mediated increase in coronary flow, suggesting that adenosine-mediated coronary vasodilation is in part attributed to Nox2-derived ROS. This heterogeneity might be due to vasoconstrictor ROS vs. vasodilator ROS [29,31] generated from different vascular beds (coronary vs. renal artery) [34,37].…”

“…Given the fact that Nox has been suggested to be the major source of ROS in coronary vasculature [32,52], it is not clear whether this leads to the generation of ROS by adenosine. We recently found that activation of A 3 AR enhances Nox2-derived ROS contributing to vascular contraction in mouse aorta [33], suggesting a role of A 3 AR in relation to ROS production. In contrast, in the coronary circulation, we have already excluded the involvement of A 1 and A 3 ARs in increased flow that is coupled to the activation of Nox2 [37].…”

“…However, little is known about the involvement of Nox2-derived ROS in adenosine-mediated flow response in the coronary circulation. Although activation of A 1 and A 3 AR has been shown to have vascular effects through ROS [33,36], our recent studies have already excluded the involvement of A 1 and A 3 ARs in ROS-mediated regulation of coronary flow [37]. Therefore, with the focus on the adenosine signaling, the first aim of the present study was to further investigate whether A 2A and/or A 2B AR are involved in Nox2-derived ROS-mediated coronary vasodilation.…”

“…Among Nox isoforms, Nox2 has been extensively studied in various vascular beds. Nox2 inhibition or deletion attenuated the adenosine-mediated vasoconstriction in aortas [33] and renal arterioles [34]. In contrast, Nox2 inhibition or ROS scavenging blunted the adenosine-induced vasodilation in cerebral arteries [35] and coronary circulation [37], both of which suggest that adenosine is capable of generating ROS in these vasculatures.…”

“…Several recent studies have shown the interaction between adenosine and ROS via the regulation of Nox activity. For instance, inhibition or deletion of Nox2 leads to the attenuation of adenosine vasoconstrictor responses in aortas [33] and renal arterioles [34] and adenosine vasodilator responses in cerebral arteries [35]. However, little is known about the involvement of Nox2-derived ROS in adenosine-mediated flow response in the coronary circulation.…”