Abstract
Elevated H2O2 is implicated in many cardiovascular diseases. We previously demonstrated that H2O2‐induced endothelial nitric oxide synthase (eNOS) activation and excessive NO production contribute to vascular cell injury and increases in microvessel permeability. However, the mechanisms of excessive NO‐mediated vascular injury and hyperpermeability remain unknown. This study aims to examine the functional role of NO‐derived peroxynitrite (ONOO−) in H2O2‐induced vascular barrier dysfunction by elucidating the interrelationships between H2O2‐induced NO, superoxide, ONOO−, and changes in endothelial [Ca2+]i and microvessel permeability. Experiments were conducted on intact rat mesenteric venules. Microvessel permeability was determined by measuring hydraulic conductivity (Lp). Endothelial [Ca2+]i, NO, and O2 − were assessed with fluorescence imaging. Perfusion of vessels with H2O2 (10 µmol/L) induced marked productions of NO and O2 −, resulting in extensive protein tyrosine nitration, a biomarker of ONOO−. The formation of ONOO− was abolished by inhibition of NOS with NG‐Methyl‐L‐arginine. Blocking NO production or scavenging ONOO− by uric acid prevented H2O2‐induced increases in endothelial [Ca2+]i and Lp. Additionally, the application of exogenous ONOO− to microvessels induced delayed and progressive increases in endothelial [Ca2+]i and microvessel Lp, a pattern similar to that observed in H2O2‐perfused vessels. Importantly, ONOO− caused further activation of eNOS with amplified NO production. We conclude that the augmentation of NO‐derived ONOO− is essential for H2O2‐induced endothelial Ca2+ overload and progressively increased microvessel permeability, which is achieved by self‐promoted amplifications of NO‐dependent signaling cascades. This novel mechanism provides new insight into the reactive oxygen and/or reactive nitrogen species‐mediated vascular dysfunction in cardiovascular diseases.
Highlights
Increased production of reactive oxygen species (ROS) has been demonstrated to cause impaired vascular barrier function, resulting in tissue damage and organ dysfunction (Del Maestro et al, 1981; Cai and Harrison, 2000; Zhu and He, 2006; Zhou et al, 2009; Di et al, 2016; Mundi et al, 2017)
We previously demonstrated that H2O2 at pathologically relevant concentrations induced delayed and progressive increases in microvessel Lp, which was initiated by the activation of endothelial nitric oxide synthase (eNOS) and excessive nitric oxide (NO) production (Zhou et al, 2009; Zhou et al, 2013)
Instead of causing an immediate increase in microvessel permeability that occurred in PAF or other inflammatory mediator-stimulated microvessels (He et al, 1996; Zhu and He, 2005; Zhou and He, 2010), this large amount of NO (~10 times the amount of NO detected in PAF-perfused microvessels) was shown to be responsible for intracellular Ca2+ accumulation, subsequent cell apoptosis, and the delayed and progressive increases in microvessel permeability ( Zhou et al, 2013)
Summary
Increased production of reactive oxygen species (ROS) has been demonstrated to cause impaired vascular barrier function, resulting in tissue damage and organ dysfunction (Del Maestro et al, 1981; Cai and Harrison, 2000; Zhu and He, 2006; Zhou et al, 2009; Di et al, 2016; Mundi et al, 2017). Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
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