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

Abstract

Adenosine increases coronary flow mainly through the activation of A 2A and A 2B adenosine receptors (ARs). However, the mechanisms for the regulation of coronary flow are not fully understood. We previously demonstrated that adenosine-induced increase in coronary flow is in part through NADPH oxidase (Nox) activation, which is independent of activation of either A 1 or A 3 ARs. In this study, we hypothesize that adenosine-mediated increase in coronary flow through Nox activation depends on A 2A but not A 2B ARs. Functional studies were conducted using isolated Langendorff-perfused mouse hearts. Hydrogen peroxide (H 2 O 2 ) production was measured in isolated coronary arteries from WT, A 2A AR k n o c k o u t ( K O ) , a n d A 2 B A R K O m i c e u s i n g dichlorofluorescein immunofluorescence. Adenosineinduced concentration-dependent increase in coronary flow was attenuated by the specific Nox2 inhibitor gp91 ds-tat or reactive oxygen species (ROS) scavenger EUK134 in both WT and A 2B but not A 2A AR KO isolated hearts. Similarly, the A 2A AR selective agonist CGS-21680-induced increase in coronary flow was significantly blunted by Nox2 inhibition in both WT and A 2B AR KO, while the A 2B AR selective agonist BAY 60-6583-induced increase in coronary flow was not affected by Nox2 inhibition in WT. In intact isolated coronary arteries, adenosine-induced (10 μM) increase in H 2 O 2 formation in both WT and A 2B AR KO mice was attenuated by Nox2 inhibition, whereas adenosine failed to increase H 2 O 2 production in A 2A AR KO mice. In conclusion, adenosine-induced increase in coronary flow is partially mediated by Nox2-derived H 2 O 2 , which critically depends upon the presence of A 2A AR.

Adenosine Production by Biomaterial‐Supported Mesenchymal Stromal Cells Reduces the Innate Inflammatory Response in Myocardial Ischemia/Reperfusion Injury

“…Many adenine nucleotides including ATP and AMP are potent vasodilators, yet they serve no benefit in regulating MI/R injury 16. Furthermore, the vasodilation seen in coronary blood flow with adenosine has been previously reported to be dependent on upregulation of NADPH‐oxidase–mediated ROS formation in coronary endothelial cells 57, 58. In light of our findings that MSCs are capable of increasing adenosine levels while simultaneously preventing significant increases in ROS formation, it seems unlikely that vasodilation is the primary therapeutic mechanism at play.…”

Requisite Role of Kv1.5 Channels in Coronary Metabolic Dilation

“…71-73 One advantage of this technique is the ability to measure blood flow in vivo under minimally invasive conditions (intravenous catheter for contrast infusion). Previous measurements of myocardial blood flow in the mouse heart were confined to buffer-perfused isolated heart models, 74-77 which impact a variety of control mechanisms for coronary blood flow causing concerns about physiological relevance of the observations. In our study we used contrast echocardiography to measure myocardial blood flow in anesthetized mice, and these values were about 40% higher compared to the flows measured with microspheres.…”

Kv1.3 channels facilitate the connection between metabolism and blood flow in the heart

“…Most previous efforts directed at understanding the links between metabolism and flow in the heart focused on specific metabolites, for example, adenosine 5,6 , which signal through G-protein-coupled receptors to produce vasodilation [7][8][9][10] . Although a large body of work supports the role of metabolites such as adenosine in coronary regulation, some observations have challenged this hypothesis 11,12 .…”