Exercise Training Shifts Dependency from NADPH Oxidase 2 to NADPH Oxidase 4 in Endothelium‐Dependent Dilation in Coronary Arterioles Distal to Chronic Occlusion

• Published in: The FASEB journal Vol. 36; no. S1
• Main Authors: Sytha, Sharanee P., Bray, Jeff F., Ramirez, Cristina R., Heaps, Cristine L.
• Format: Journal Article
• Language: English
• Published: United States The Federation of American Societies for Experimental Biology 01-05-2022
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fasebj.2022.36.S1.R3873

Previously, we have reported that exercise training enhances endothelium‐dependent dilation in coronary arterioles distal to chronic occlusion, through increased contribution of the redox signaling molecule, hydrogen peroxide (H2O2). In the present study, we tested the hypothesis that enhanced endothelium‐dependent dilation in collateral‐dependent arterioles after exercise training would be attributable to an increased contribution of NADPH oxidase (NOX) 4‐derived reactive oxygen species. Yucatan miniature swine were surgically instrumented with an ameroid constrictor around the proximal left circumflex artery, which gradually induced occlusion of the artery and created a collateral‐dependent vascular bed. Eight weeks postoperatively, swine were assigned to either a sedentary protocol consisting of normal pen activity or a progressive exercise‐training regimen comprised of treadmill running 5 days a week, for 14 weeks. Coronary arterioles were isolated from the nonoccluded and collateral‐dependent myocardial regions and bradykinin‐mediated dilation via pressure myography was performed in the presence and absence of ML‐171, gp91ds‐tat and GKT136901, inhibiting NOX1, NOX2, and NOX1/4 isoforms, respectively. Additionally, using the superoxide probe, dihydroethidium, HPLC analysis was performed on isolated microvascular endothelial cells, pretreated with NOX inhibitors, to determine candidate sources of superoxide. Inhibition of NOX2 produced a significant rightward shift in EC50 values of arterioles from sedentary animals, independent of occlusion, as well as the nonoccluded arterioles of exercise‐trained pigs. EC50 values of collateral‐dependent arterioles from exercise‐trained swine were not significantly altered by NOX2 inhibition. Contrastingly, collateral‐dependent arterioles from exercise‐trained swine exhibited a significant shift in EC50 values in the presence NOX1/4 inhibition, which was absent in other arteriole treatment groups. Importantly, NOX1 inhibition did not significantly shift EC50 values in any treatment group, suggesting responses to the NOX1/4 inhibitor, GKT136901, reflect the contribution of NOX4. Interestingly, microvascular endothelial cell superoxide levels were not different across arteriole treatment groups. Our present findings suggest that exercise training produces adaptations in collateral‐dependent arterioles that appear to shift dependence from NOX2‐ to NOX4‐derived reactive oxygen species for endothelium‐dependent dilation. Taken together with our previous findings, our data support the assertion that enhanced dilation of collateral‐dependent arterioles after exercise training is driven by enhanced NOX4‐derived H2O2 levels.