NADPH Oxidase 2 and 4 Contribute to Endothelium‐Dependent Dilation in Healthy Human Arterioles

Abstract

NADPH oxidases (NOXs) are a major source of reactive oxygen species (ROS) in the vasculature and play diverse roles in vascular health and disease. We have recently shown that NOX‐derived ROS are involved in flow‐induced dilation of human arterioles from subjects with coronary artery disease (CAD). However, the role of NOXs in non‐diseased human arterioles remains largely unclear. Previous studies indicate that NOXs contribute to endothelium‐dependent vasodilation in normal animal arteries. This study is designed to test whether NOX2 and NOX4 play a role in receptor and non‐receptor mediated endothelium‐dependent vasodilation in human adipose arterioles (HAA). HAAs (~150 μm ID), isolated from fat tissues from patients without coronary artery disease (non‐CAD) or <1 risk factor, were cannulated and pressurized at 60 mmHg for videomicroscopic measurement of vessel diameters. In arterioles constricted with endothelin‐1, acetylcholine (Ach; 10−9 to 10−5 M) elicited concentration‐dependent dilation (maximal dilation at 10−5 M: 95±3%, n=4), and this dilation was reduced in the presence of nitric oxide (NO) synthase inhibitor nitro‐L‐arginine methyl ester (L‐NAME) and cyclooxygenase inhibitor indomethacin (Indo) (maximal dilation: 63±7%, n=4). Ach‐induced dilation was inhibited by NOX2 inhibitor GSK2795039 (10−6 M; maximal dilation: 57±10%, n=5) and to a less extent by NOX4 inhibitor GKT137831 (10−6 M; maximal dilation: 86±4%, n=5). In the presence of L‐NAME and Indo, NOX2 and NOX4 inhibitors largely abolished Ach‐induced vasodilation (maximal dilation: 29±9% and 18±5%, respectively, n=4). We also examined the effect of NOX inhibition on non‐receptor‐mediated concentration‐dependent dilation by the Ca2+ ionophore A23187 (10−11 to 10−7 M). A23187‐induced dilation (maximal dilation at 10−7 M: 68±5%, n=4) was inhibited by NOX2 (maximal dilation: 6±2%, n=4) and NOX4 (maximal dilation: 15±2%, n=5). Unexpectedly, L‐NAME and Indo also inhibited A23187‐dependent dilation (maximal dilation: 7±2%, n=4). Together, these data support our hypothesis that NOX2 and NOX4 are involved in receptor and non‐receptor mediated endothelium‐dependent vasodilation in non‐CAD HAA. While A23187 dilation is largely NO/prostacyclin (PGI2)‐dependent, there is a non‐NO/PGI2 component contributing to NOX inhibitor‐sensitive vasodilator response to Ach.Support or Funding InformationSupport for this research was provided by the National Heart, Lung and Blood Institute Grant R01‐HL 096647. Tissue was supplied by Cardiovascular Surgery Associates, Midwest Heart Surgery Institute, Wisconsin Heart Group, and Froedtert Memorial Lutheran Hospital.