Mechanisms of H2O2-Induced Oxidative Stress in Endothelial Cells Exposed to Physiologic Shear Stress

Abstract

Hydrogen peroxide (H2O2) is produced by inflammatory and vascular cells and induces oxidative stress, which may contribute to vascular disease and endothelial cell dysfunction. In smooth muscle cells, H2O2 induces production of O2 by activating NADPH oxidase. However, the mechanisms whereby H2O2 induces oxidative stress in endothelial cells are not well understood, although O2 may play a role. Recent studies have documented increased O2 in endothelial cells exposed to H2O2 via uncoupled nitric oxide synthase (NOS) and NADPH oxidase under static conditions. To assess responses to H2O2 in porcine aortic endothelial cells (PAEC) under shearing conditions, a constant flow rate of 24. 4 ml/min was applied to produce physiologically relevant shear stress (8. 2 dynes/cm). Here we demonstrate that treatment with 100 muM H2O2 increases intracellular O2 levels in PAEC. In addition, we demonstrate that l-NAME, an inhibitor of NOS, and apocynin, an inhibitor of NADPH oxidase, reduced O2 levels in PAEC treated with H2O2 under physiologic shear suggesting that both NOS and NADPH oxidase contribute to H2O2-induced O2 in PAEC. Co-inhibition of NOS and NADPH oxidase also reduced intracellular O2 levels under shear. We conclude that H2O2-induced oxidative stress in endothelial cells exhibits increased intracellular O2 levels through NOS and NADPH oxidase under shear. The inhibition of NOS and NADPH with H2O2 exposure is nonlinear, suggesting some interdependent or compensating system within endothelial cells. These findings suggest a complex interaction between H2O2 and oxidant-generating enzymes that may contribute to endothelial dysfunction in cardiovascular diseases.

Cocoa polyphenols attenuate hydrogen peroxide-induced inhibition of gap-junction intercellular communication by blocking phosphorylation of connexin 43 via the MEK/ERK signaling pathway☆

“…Additionally, H 2 O 2 can activate other intracellular ROS. Recent studies have reported that H 2 O 2 induced superoxide anion production by stimulation of NAD(P)H oxidase activity in nonphagocytic cell [24] and smooth muscle cells [25]. On the other hand, under stress conditions, an excess of superoxide releases free iron from iron-containing molecules.…”

“…We suggest that CPE is not only a natural dietary antioxidant but also a potent direct inhibitor of MEK, which may contribute to its chemopreventive effects. (10,25 or 50 μg/ml) for 30 min before being exposed to 100 μM H 2 O 2 for 30 min. Cells were harvested, and immunoprecipitation and MEK1 activity assays were performed as described in Materials and methods.…”

Radiation–Induced Signaling Results in Mitochondrial Impairment in Mouse Heart at 4 Weeks after Exposure to X-Rays

“…Such an excess of ROS is capable of causing damage to many cellular components including lipids, proteins, and DNA [35], [36]. Oxidative stress is also known to contribute to vascular disease and endothelial cell dysfunction potentially leading to further cardiovascular damage [37]. Conversely, lower ROS concentrations stimulate cellular signaling and gene expression modulating vascular function [38] and playing an important role in cardioprotection [39], [40].…”

Sperm viability, apoptosis, and intracellular reactive oxygen species levels in human spermatozoa before and after induction of oxidative stress

“…Sperm have a limited amount of cellular cytoplasm in which scavenging enzymes are found, making sperm highly susceptible to ROS damage (10,12,13). As ROS are able to readily permeate the membranes, they can cause DNA, proteins, and lipid molecules peroxidative damage within the cell (7,8,14). Motile sperm have been shown to be activated by excessive ROS formation and undergo apoptosis-like changes (15)(16)(17).…”

“…Superoxide (O 2 À ) and hydrogen peroxide (H 2 O 2 ) are common reactive oxygen species (ROS), which are highly reactive and can interact with nearby molecules, inducing oxidative stress damage in cellular organelles and molecules (6)(7)(8).…”