Peroxynitrite Causes Endoplasmic Reticulum Stress and Apoptosis in Human Vascular Endothelium: Implications in Atherogenesis (original) (raw)
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Nitric oxide and peroxynitrite in health and disease
Physiological reviews
The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.
Nitric oxide, peroxynitrite and lipoxygenase in atherogenesis: mechanistic insights
Toxicology, 2005
Nitric oxide (*NO) is a free radical species that diffuses and concentrates in the hydrophobic core of low-density lipoprotein (LDL) to serve as a potent antioxidant. Peroxynitrite, the product of the diffusion-limited reaction between *NO and superoxide anion, as well as lipoxygenase, represent relevant mediators of oxidative modifications in LDL. The focus of this review is the analysis of interactions between *NO, peroxynitrite and lipoxygenase during LDL oxidation, which are relevant in the development of the early steps as well as progression of atherosclerosis. The role of CO2 to redirect peroxynitrite reactivity in LDL, as well as the lipophilic antioxidant sparing actions of *NO, ascorbate and CO2 is also analyzed. In this context, the effects of novel potential pharmacological strategies against atherosclerosis such as Mn(III)porphyrins will be discussed.
Seminars in Perinatology, 1997
Since the discovery that at least one form of endothefium derived relaxing factor is nitric oxide (NO), numerous studies have uncovered diverse roles for this free radical in a variety of physiological and pathophysiological processes. NO production, a process mediated by a family of enzymes termed NO synthases, has been detected in most cell types. Many of the effects of NO are thought to be mediated through its direct interaction with specific and defined cell signaling pathways. The nature of such interactions are highly dependent on the concentration of NO and cell type. Furthermore, specific NO derived reaction products, such as peroxynitrite, also have the potential to effect cell signal transduction events. As with NO, this can occur through diverse mechanisms and depends on concentration and cell type. It is perhaps not surprising that the reported effects of NO in different disease states are often conflicting. In this brief overview, a framework for placing these apparently disparate properties of NO will be described and Hill focus on the effects of NO and peroxynitrite on signaling pathways.
CARDIOVASCULAR EFFECTS OF PEROXYNITRITE
Clinical and Experimental Pharmacology and Physiology, 2007
both exist as free radicals. By itself, PN is not a free radical, but it can generate nitrogen dioxide (·NO 2 ) and carbonate radical ( ·) upon reaction with CO 2 . 2. The reaction of CO 2 constitutes a major pathway for the disposition of PN produced in vivo and this is based on the rapid reaction of PN anion with CO 2 and the availability of CO 2 in both intra-and extracellular fluids. The free radicals ·NO 2 and ·, in combination with ·NO, generated from nitric oxide synthase, can bring about oxidation of critical biological targets resulting in tissue injury. However, the reactions of ·NO 2 , · and ·NO with carbohydrates, protein and non-protein thiols, phenols, indoles and uric acid could result in the formation of a number of nitration and nitrosation products in the vasculature. These products serve as long-acting ·NO donors and, therefore, contribute to vasorelaxant properties, protective effects on the heart, inhibition of leucocyte-endothelial cell interactions and reduction of reperfusion injury.
Biochemistry, 2010
Endothelial nitric oxide synthase (eNOS) is an important regulator of vascular and cardiac function. Peroxynitrite (ONOO − ) inactivates eNOS, but questions remain regarding the mechanisms of this process. It has been reported that inactivation is due to oxidation of the eNOS zinc-thiolate cluster, rather than the cofactor tetrahydrobiopterin (BH 4 ); however, this remains highly controversial. Therefore, we investigated the mechanisms of ONOO − -induced eNOS dysfunction and their dosedependence. Exposure of human eNOS to ONOO − resulted in a dose-dependent loss of activity with a marked destabilization of the eNOS dimer. HPLC analysis indicated that both free and eNOSbound BH 4 were oxidized during exposure to ONOO − ; however, full oxidation of protein bound biopterin required higher ONOO − levels. Additionally, ONOO − triggered changes in UV/Visible spectrum and heme content of the enzyme. Pre-incubation of eNOS with BH 4 decreased dimer destabilization and heme alteration. Addition of BH 4 to the ONOO − -destabilized eNOS dimer only partially rescued enzyme function. In contrast to ONOO − treatment, incubation with the zinc chelator TPEN with removal of enzyme-bound zinc did not change the eNOS activity or stability of the SDSresistant eNOS dimer, demonstrating that the dimer stabilization induced by BH 4 does not require zinc occupancy of the zinc-thiolate cluster. While ONOO − treatment was observed to induce loss of Zn-binding this can not account for the loss of enzyme activity. Therefore, ONOO − -induced eNOS inactivation is primarily due to oxidation of BH 4 and irreversible destruction of the heme/hemecenter.
S-Glutathiolation by peroxynitrite activates SERCA during arterial relaxation by nitric oxide
Nature Medicine, 2004
Nitric oxide (NO) physiologically stimulates the sarco/endoplasmic reticulum calcium (Ca 2+ ) ATPase (SERCA) to decrease intracellular Ca 2+ concentration and relax cardiac, skeletal and vascular smooth muscle. Here, we show that NO-derived peroxynitrite (ONOO -) directly increases SERCA activity by S-glutathiolation and that this modification of SERCA is blocked by irreversible oxidation of the relevant cysteine thiols during atherosclerosis. Purified SERCA was S-glutathiolated by ONOOand the increase in Ca 2+ -uptake activity of SERCA reconstituted in phospholipid vesicles required the presence of glutathione. Mutation of the SERCA-reactive Cys674 to serine abolished these effects. Because superoxide scavengers decreased Sglutathiolation of SERCA and arterial relaxation by NO, ONOOis implicated as the intracellular mediator. NO-dependent relaxation as well as S-glutathiolation and activation of SERCA were decreased by atherosclerosis and Cys674 was found to be oxidized to sulfonic acid. Thus, irreversible oxidation of key thiol(s) in disease impairs NO-induced relaxation by preventing reversible S-glutathiolation and activation of SERCA by NO/ONOO -.
Peroxynitrite induces haem oxygenase-1 in vascular endothelial cells: a link to apoptosis
Biochemical Journal, 1999
Peroxynitrite (ONOO − ) is a potent oxidizing agent generated by the interaction of nitric oxide (NO) and the superoxide anion. In physiological solution, ONOO − rapidly decomposes to a hydroxyl radical, one of the most reactive free radicals, and nitrogen dioxide, another species able to cause oxidative damage. In the present study we investigated the effect of ONOO − on the expression of haem oxygenase-1 (HO-1), an inducible protein that is highly up-regulated by oxidative stress. Exposure of bovine aortic endothelial cells to ONOO − (250-1000 µM) produced a concentration-dependent increase in haem oxygenase activity and HO-1 protein expression. This effect was completely abolished by the ONOO − scavengers uric acid and N-acetylcysteine, and partly attenuated by 1,3-dimethyl-2-thiourea, a scavenger of hydroxyl radicals. ONOO − also produced a concentration-dependent increase in apoptosis and cytotoxicity, which were considerably decreased by uric acid and N-acetylcysteine. A
Experimental Diabetes Research, 2010
Endothelial dysfunction is characterized by reduced bioavailability of NO due to its inactivation to form peroxynitrite or reduced expression of eNOS. Here, we examine the causal role of peroxynitrite in mediating diabetes-induced endothelial dysfunction. Diabetes was induced by STZ-injection, and rats received the peroxynitrite decomposition catalyst (FeTTPs, 15 mg/Kg/day) for 4 weeks. Vasorelaxation to acetylcholine, oxidative-stress markers, RhoA activity, and eNOS expression were determined. Diabetic coronary arteries showed significant reduction in ACh-mediated maximal relaxation compared to controls. Diabetic vessels showed also significant increases in lipid-peroxides, nitrotyrosine, and active RhoA and 50% reduction in eNOS mRNA expression. Treatment of diabetic animals with FeTTPS blocked these effects. Studies in aortic endothelial cells show that high glucose or peroxynitrite increases the active RhoA kinase levels and decreases eNOS expression and NO levels, which were reversed with blocking peroxynitrite or Rho kinase. Together, peroxynitrite can suppress eNOS expression via activation of RhoA and hence cause vascular dysfunction.
Role of peroxynitrite in the redox regulation of cell signal transduction pathways
Frontiers in Bioscience, 2009
Peroxynitrite is a potent oxidant and nitrating species formed from the reaction between the free radicals nitric oxide and superoxide. An excessive formation of peroxynitrite represents an important mechanism contributing to cell death and dysfunction in multiple cardiovascular pathologies, such as myocardial infarction, heart failure and atherosclerosis. Whereas initial works focused on direct oxidative biomolecular damage as the main route of peroxynitrite toxicity, more recent evidence, mainly obtained in vitro, indicates that peroxynitrite also behaves as a potent modulator of various cell signal transduction pathways. Due to its ability to nitrate tyrosine residues, peroxynitrite affects cellular processes dependent on tyrosine phosphorylation. Peroxynitrite also exerts complex effects on the activity of various kinases and phosphatases, resulting in the up-or downregulation of signalling cascades, in a concentration-and celldependent manner. Such roles of peroxynitrite in the redox regulation of key signalling pathways for cardiovascular homeostasis, including protein kinase B and C, the MAP kinases, Nuclear Factor Kappa B, as well as signalling dependent on insulin and the sympatho-adrenergic system are presented in detail in this review.