Hydrogen Peroxide Promotes Endothelial Dysfunction by Stimulating Multiple Sources of Superoxide Anion Radical Production and Decreasing Nitric Oxide Bioavailability

Abstract

Hydrogen peroxide (H₂O₂) is an oxidant implicated in cell signalling and various pathologies, yet relatively little is known about its impact on endothelial cell function. Herein we studied the functional and biochemical changes in aortic vessels and cultured porcine aortic endothelial cells (PAEC) exposed to H₂O₂. Exposure of aortic rings to 25 or 50 µM, but not 10 µM, H₂O₂ for 60 min prior to constriction significantly decreased subsequent relaxation in response to acetylcholine (ACh), but not the nitric oxide (^·NO) donor sodium nitroprusside. Treatment of PAEC with 50 µM H₂O₂ significantly decreased ACh-induced accumulation of ^·NO, as measured with a ^·NO-selective electrode, yet such treatment increased nitric oxide synthase activity ∼3-fold, as assessed by conversion of L-arginine to L-citrulline. Decreased ^·NO bioavailability was reflected in decreased cellular cGMP content, associated with increased superoxide anion radical (O₂^–·), and overcome by addition of polyethylene glycol superoxide dismutase. Increased cellular O₂^–· production was inhibited by allopurinol, diphenyliodonium and rotenone in an additive manner. The results show that exposure of endothelial cells to H₂O₂ decreases the bioavailability of agonist-induced ^·NO as a result of increased production of O₂^–· likely derived from xanthine oxidase, NADPH-oxidasse and mitochondria. These processes could contribute to H₂O₂-induced vascular dysfunction that may be relevant under conditions of oxidative stress such as inflammation.

Role and regulation of ferritin H in rotenone-mediated mitochondrial oxidative stress

“…4), suggesting that oxidative stress is a necessary cue in ferritin H activation by rotenone. Several recent studies have reported that in some conditions, especially hypoxia, rotenone reduces mitochondrial ROS generation [34][35][36]. To date there is no clear consensus about the effect of rotenone on mitochondrial ROS generation under various conditions; however, such contradictory reports support the need for further investigation into the intricacies of mechanisms of mitochondrial ROS generation and suppression.…”

Sustained Contraction and Endothelial Dysfunction Induced by Reactive Oxygen Species in Porcine Coronary Artery

“…Among the various biological effects attributed to ROS, vascular endothelial dysfunction has consistently been noted, irrespective of the preparations used. 2,18) In addition, ROS generated by the XϩXOD system caused contraction of rat pulmonary artery 19) and canine basilar artery, 20) whereas it relaxed canine coronary artery, 21) implying the existence of species or tissue differences in response to ROS. Furthermore, the responses of arteries to ROS are well-known to be influenced by the presence of endothelium.…”

Association of HLA Class I and II Antigens with Vitiligo in Egyptian Population

“…It is known that under diabetic conditions there are increased oxidative stress levels [68]. Increased ROS prompts the EPCs to produce pathologic cytokines such as monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), NF-κB, interleukin-8 (IL-8), elevated levels of iNOS, and decreased eNOS.…”

“…In disease states such as diabetes, vascular production of reactive oxygen metabolites can increase substantially [68]. Increased production of the superoxide anion can lead to decreased tissue bioavailability of nitric oxide (NO) via a facile radical/radical reaction that occurs more rapidly than the reaction of with superoxide dismutase (SOD) [71].…”

“…Importantly, this endothelial dysfunction is due to vascular production of superoxide. There are several enzymes that involve generating ROS such as NADPH oxidase, aldehyde oxidase, xanthine oxidase, and glucose oxidase [68]. Decreased endothelium-dependent vasodilation in diabetic subjects is associated with the impaired action of NO secondary to its inactivation resulting from increased oxidative stress, rather than decreased NO production from vascular endothelium and that abnormal NO metabolism is related to advanced diabetic microvascular complications [72].…”