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H2O2-induced endothelial NO production contributes to vascular cell apoptosis and increased permeability in rat venules.

ABSTRACT: Although elevated levels of H(2)O(2) have been implicated to play important roles in the pathogenesis of various cardiovascular diseases, the underlying mechanisms remain unclear. This study aims to examine the effect of H(2)O(2) on endothelial nitric oxide (NO) production in intact venules, and elucidate the role and mechanisms of NO in H(2)O(2)-induced increases in microvessel permeability. Experiments were conducted on individually perfused rat mesenteric venules. Microvessel permeability was determined by measuring hydraulic conductivity (Lp), and endothelial [Ca(2+)](i) was measured on fura-2-loaded vessels. Perfusion of H(2)O(2) (10 ?M) caused a delayed and progressively increased endothelial [Ca(2+)](i) and Lp, a pattern different from inflammatory mediator-induced immediate and transient response. Under the same experimental conditions, measuring endothelial NO via DAF-2 and the spatial detection of cell apoptosis by fluorescent markers revealed that H(2)O(2) induced two phases of NO production followed by caspase activation, intracellular Ca(2+) accumulation, and vascular cell apoptosis. The initial NO production was correlated with increased endothelial NO synthase (eNOS) Ser(1177) phosphorylation in the absence of elevated endothelial [Ca(2+)](i), whereas the second phase of NO depended on increased [Ca(2+)](i) and was associated with Thr(495) dephosphorylation without increased Ser(1177) phosphorylation. Inhibition of NOS prevented H(2)O(2)-induced caspase activation, cell apoptosis, and increases in endothelial [Ca(2+)](i) and Lp. Our results indicate that H(2)O(2) at micromolar concentration is able to induce a large magnitude of NO in intact venules, causing caspase activation-mediated endothelial Ca(2+) accumulation, cell apoptosis, and increases in permeability. The mechanisms revealed from intact microvessels may contribute to the pathogenesis of oxidant-related cardiovascular diseases.

SUBMITTER: Zhou X

PROVIDER: S-EPMC3543683 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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H2O2-induced endothelial NO production contributes to vascular cell apoptosis and increased permeability in rat venules.

Zhou Xueping X Yuan Dong D Wang Mingxia M He Pingnian P

American journal of physiology. Heart and circulatory physiology 20121019 1

Although elevated levels of H(2)O(2) have been implicated to play important roles in the pathogenesis of various cardiovascular diseases, the underlying mechanisms remain unclear. This study aims to examine the effect of H(2)O(2) on endothelial nitric oxide (NO) production in intact venules, and elucidate the role and mechanisms of NO in H(2)O(2)-induced increases in microvessel permeability. Experiments were conducted on individually perfused rat mesenteric venules. Microvessel permeability was ...[more]

PMID: 23086988

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Project description:Vascular remodeling has been implicated in many inflammation-involved diseases. This study aims to investigate the microvascular remodeling-associated alterations in cell-cell adhesion and cytoskeleton reactions to inflammatory stimuli and their impact on microvessel permeability. Experiments were conducted in individually perfused rat mesenteric venules. Microvessel permeability was determined by measuring hydraulic conductivity (Lp), and endothelial intracellular calcium concentration, [Ca(2+)](i), was measured in fura-2-perfused vessels. Alterations in VE-cadherin and F-actin arrangement were examined by confocal imaging. Vascular wall cellular composition and structural changes were evaluated by electron microscopy. Vessels exposed to platelet activating factor (PAF) on day 1 were reevaluated 3 days later in rats that had undergone survival surgery. Initial PAF exposure and surgical disturbance increased microvascular wall thickness along with perivascular cell proliferation and altered F-actin arrangement. Although basal permeability was not changed, upon reexposure to PAF, peak endothelial [Ca(2+)](i) was augmented and the peak Lp was 9.3 ± 1.7 times higher than that of day 1. In contrast to patterns of PAF-induced stress fiber formation and VE-cadherin redistribution observed in day 1 vessels, the day 4 vessels at the potentiated Lp peak exhibited wide separations of VE-cadherin between endothelial cells and striking stress fibers throughout the vascular walls. Confocal images and ultrastructural micrographs also revealed that the largely separated VE-cadherin and endothelial gaps were completely covered by F-actin bundles in extended pericyte processes at the PAF-induced Lp peak. These results indicate that inflammation-induced vascular remodeling increased endothelial susceptibility to inflammatory stimuli with augmented Ca(2+) response resulting in upregulated contractility and potentiated permeability increase. Weakened adhesions between the endothelial cells and contractile mechanisms are both involved in increasing permeability in the intact microvessels and are aggravated during remodeling. The perivascular cells play important roles in stabilizing the microvessel wall, while lessening an otherwise much greater magnitude of leakage during cytoskeletal contraction.

Dataset Information

H2O2-induced endothelial NO production contributes to vascular cell apoptosis and increased permeability in rat venules.

Publications

H2O2-induced endothelial NO production contributes to vascular cell apoptosis and increased permeability in rat venules.

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