Mitochondrial Sources of H ₂ O ₂ Generation Play a Key Role in Flow-Mediated Dilation in Human Coronary Resistance Arteries

Abstract

Abstract-We previously showed that hydrogen peroxide (H 2 O 2 ) contributes to flow-induced dilation in human coronary resistance arteries (HCRAs); however, the source of this H 2 O 2 is not known. We hypothesized that the H 2 O 2 is derived from superoxide (O 2 •Ϫ ) generated by mitochondrial respiration. HCRAs were dissected from right atrial appendages obtained from patients during cardiac surgery and cannulated with micropipettes. H 2 O 2 -derived radicals and O 2•Ϫ were detected by electron spin resonance (ESR) using BMPO as the spin trap and by histofluorescence using hydroethidine (HE, 5 mol/L) and dichlorodihydrofluorescein (DCFH, 5 mol/L). Diameter changes to increases in pressure gradients (20 and 100 cm H 2 O) were examined in the absence and the presence of rotenone (1 mol/L), myxothiazol (100 nmol/L), cyanide (1 mol/L), mitochondrial complex I, III, and IV inhibitors, respectively, and apocynin (3 mmol/L), a NADPH oxidase inhibitor. At a pressure gradient of 100 cm H 2 O, ubisemiquinone and hydroxyl radicals were detected from effluents of vessels. Including superoxide dismutase and catalase in the perfusate reduced the ESR signals. Relative ethidium and DCFH fluorescence intensities in HCRAs exposed to flow were enhanced (1.45Ϯ0.15 and 1.57Ϯ0.12, respectively compared with no-flow) and were inhibited by rotenone (0.87Ϯ0.17 and 0.95Ϯ0.07). Videomicroscopic studies showed that rotenone and myxothiazol blocked flow-induced dilation (% max. dilation at 100 cm H 2 O: rotenone, 74Ϯ3% versus 3Ϯ13%; myxothiazol, 67Ϯ3% versus 28Ϯ4%; PϽ0.05). Neither cyanide nor apocynin altered flow-induced dilation. These results suggest that shear stress induced H 2 O 2 formation, and flow-induced dilation is derived from O 2•Ϫ originating from mitochondrial respiration.

Endothelial cell respiration is affected by the oxygen tension during shear exposure: role of mitochondrial peroxynitrite

“…Although the functional significance of mitochondria-derived ROS in ECs has received little attention, it is well documented that EC mitochondrial O 2 ⅐ Ϫ production from ETC complexes I and III is responsible for the shear-induced dilation in human coronary arterioles (46,82). It is also known that, during EC exposure to cyclic strain, mitochondrial ROS mediate the activation of nuclear factor-B and upregulation of vascular cell adhesion molecule-1 (1).…”

Local production of O2− by NAD(P)H oxidase in the sarcoplasmic reticulum of coronary arterial myocytes: cADPR-mediated Ca2+ regulation

“…These results suggest that this confocal microscopic local assay does detect O 2 .− production from the SR of intact CAMs. Although O 2 .− or other ROS production was reported in different cellular compartments [3,40], many of previous studies used isolated organelles such as mitochondria and SR to analyze related ROS or enzyme activity [3,40]. The confocal microscopic analysis of local production of ROS has been reported only in studies of mitochondrial redox status or ROS release from this organelles in intact cells [39,41,42].…”

Reactive oxygen species and vascular biology: implications in human hypertension

“…[30][31][32] This review will focus on ROS, the vascular system and hypertension, specifically relating to the clinical significance. All vascular cell types produce ROS, including endothelial, smooth muscle, adventitial fibroblasts and perivascular adipocytes, and can be formed by many enzymes, including xanthine oxidoreductase, uncoupled nitric oxide synthase, mitochondrial respiratory enzymes and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase [37][38][39][40][41][42][43][44] (Figure 1). Of these mitochondrial enzymes and NADPH oxidase seem to be particularly important in hypertension.…”