Pawel M. Kaminski

Aging-Induced Phenotypic Changes and Oxidative Stress Impair Coronary Arteriolar Function

We aimed to elucidate the possible role of phenotypic alterations and oxidative stress in age-related endothelial dysfunction of coronary arterioles. Arterioles were isolated from the hearts of young adult (Y, 14 weeks) and aged (A, 80 weeks) male Sprague-Dawley rats. For videomicroscopy, pressure-induced tone of Y and A arterioles and their passive diameter did not differ significantly. In A, arterioles L-NAME (a NO synthase blocker)–sensitive flow-induced dilations were significantly impaired (Y: 41±8% versus A: 3±2%), which could be augmented by superoxide dismutase (SOD) or Tiron (but not l-arginine or the TXA2 receptor antagonist SQ29,548). For lucigenin chemiluminescence, O2·− generation was significantly greater in A than Y vessels and could be inhibited with SOD and diphenyliodonium. NADH-driven O2·− generation was also greater in A vessels. Both endothelial and smooth muscle cells of A vessels produced O2·− (shown with ethidium bromide fluorescence). For Western blotting, expression of eNOS and COX-1 was decreased in A compared with Y arterioles, whereas expressions of COX-2, Cu/Zn-SOD, Mn-SOD, xanthine oxidase, and the NAD(P)H oxidase subunits p47phox, p67phox, Mox-1, and p22phox did not differ. Aged arterioles showed an increased expression of iNOS, confined to the endothelium. Decreased eNOS mRNA and increased iNOS mRNA expression in A vessels was shown by quantitative RT-PCR. In vivo formation of peroxynitrite was evidenced by Western blotting, and immunohistochemistry showing increased 3-nitrotyrosine content in A vessels. Thus, aging induces changes in the phenotype of coronary arterioles that could contribute to the development of oxidative stress, which impairs NO-mediated dilations.

Increased Superoxide Production in Coronary Arteries in Hyperhomocysteinemia Role of Tumor Necrosis Factor-α, NAD(P)H Oxidase, and Inducible Nitric Oxide Synthase

Objective—In coronary arteries, hyperhomocysteinemia (HHcy, a known risk factor for coronary heart disease) impairs flow-induced dilations, which can be reversed by superoxide dismutase (SOD). To evidence increased O2.− generation and elucidate its source, we characterized changes in activity (lucigenin chemiluminescence, hydroethidine staining) and expression of arterial pro- and antioxidant systems (Western blotting, immunohistochemistry, cDNA microarray, reverse-transcription polymerase chain reaction) in the coronary arteries of rats by using methionine diet-induced HHcy. Methods and Results—The increased generation of O2.− by HHcy coronary arteries was inhibited by SOD, diphenyleneiodonium, apocynin, and apocynin plus amino guanidine but was unaffected by allopurinol and rotenone. Also, diphenyleneiodonium-sensitive NADPH-driven O2.− generation was increased in HHcy vessels. In HHcy arteries expression of the smooth muscle-confined NAD(P)H oxidase subunit nox1 and that of iNOS was increased. Expression of p67phox, p22phox, and p47phox subunits and that of endothelial nitric oxide synthase, Cu,Zn-SOD, Mn-SOD, extracellular SOD (mRNA), and xanthine oxidase was unchanged. Microarray analysis showed increased expression of tumor necrosis factor (TNF)-&agr; (confirmed by reverse-transcription polymerase chain reaction, Western blotting, and immunohistochemistry) that was localized in smooth muscle. In vitro incubation (18 hours) of HHcy arteries with anti-TNF-&agr; antibody decreased O2.− production, whereas incubation of control vessels with TNF-&agr; increased O2.− generation and nox1 expression. Conclusions—In coronary arteries, HHcy increases TNF-&agr; expression, which enhances oxidative stress through upregulating a nox1-based NAD(P)H oxidase and inducible nitric oxide synthase. Thus, TNF-&agr; induces a proinflammatory vascular phenotype in HHcy that potentially contributes to the development of coronary atherosclerosis.

Potent Metalloporphyrin Peroxynitrite Decomposition Catalyst Protects Against the Development of Doxorubicin-Induced Cardiac Dysfunction

Background—Increased oxidative stress and dysregulation of nitric oxide have been implicated in the cardiotoxicity of doxorubicin (DOX), a commonly used antitumor agent. Peroxynitrite is a reactive oxidant produced from nitric oxide and superoxide in various forms of cardiac injury. Using a novel metalloporphyrinic peroxynitrite decomposition catalyst, FP15, and nitric oxide synthase inhibitors or knockout mice, we now delineate the pathogenetic role of peroxynitrite in rodent models of DOX-induced cardiac dysfunction. Methods and Results—Mice received a single injection of DOX (25 mg/kg IP). Five days after DOX administration, left ventricular performance was significantly depressed, and high mortality was noted. Treatment with FP15 and an inducible nitric oxide synthase inhibitor, aminoguanidine, reduced DOX-induced mortality and improved cardiac function. Genetic deletion of the inducible nitric oxide synthase gene was also accompanied by better preservation of cardiac performance. In contrast, inhibition of the endothelial isoform of nitric oxide synthase with N-nitro-l-arginine methyl ester increased DOX-induced mortality. FP15 reduced the DOX-induced increase in serum LDH and creatine kinase activities. Furthermore, FP15 prevented the DOX-induced increase in lipid peroxidation, nitrotyrosine formation, and metalloproteinase activation in the heart but not NAD(P)H-driven superoxide generation. Peroxynitrite neutralization did not interfere with the antitumor effect of DOX. FP15 also decreased ischemic injury in rats and improved cardiac function and survival of mice in a chronic model of DOX-induced cardiotoxicity. Conclusions—Thus, peroxynitrite plays a key role in the pathogenesis of DOX-induced cardiac failure. Targeting peroxynitrite formation may represent a new cardioprotective strategy after DOX exposure or in other conditions associated with peroxynitrite formation, including myocardial ischemia/reperfusion injury.

Pharmacodynamics of Plasma Nitrate/Nitrite as an Indication of Nitric Oxide Formation in Conscious Dogs

BACKGROUND The present investigation was undertaken to better understand the production of nitric oxide (NO) in vivo as measured by alterations in plasma nitrite or nitrate in blood samples from studies in experimental animals or clinical studies in humans. METHODS AND RESULTS Plasma samples were taken from the aorta, the coronary sinus, a peripheral vein in the leg (skeletal muscle), or the right ventricle (mixed venous) in chronically instrumented conscious dogs. Plasma nitrite was converted to NO gas in an argon environment by use of hydrochloric acid, and plasma nitrate was converted first to nitrite with nitrate reductase and then to NO gas with acid. Standard curves were constructed, and the amount of nitrite and nitrate in plasma was determined. The primary metabolite was nitrate, whereas nitrate was approximately 10% of the total and remained constant. In the resting dog, the only vascular bed with a positive arterial-venous nitrate difference, evidence for production of NO, was the heart. Nitrate infusion into quietly resting dogs resulted in increases in plasma nitrate up to 38 +/- 3.4 mmol/L, increases in systemic arterial pressure, and a marked diuresis. The plasma half-life was calculated as 3.8 hours. The volume of distribution was calculated as 0.215 L/kg, or equivalent to the extracellular volume. CONCLUSIONS These studies indicate that nitrate is a reliable measure of NO metabolism in vivo but that because of the long half-life, nitrate will accumulate in plasma once it is produced. Because of the large volume of distribution (21% of body weight versus the 4% of body weight usually attributed to plasma volume, the compartment in which nitrate is measured), simple measures of plasma nitrate underestimate by a factor of 4 to 6 the actual production of nitrate or NO by the body. In disease states, such as heart failure, in which renal function and extracellular volume are altered, caution should be exercised when increases in nitrate in plasma as an index of NO formation are evaluated.

Vasoprotective effects of resveratrol and SIRT1: attenuation of cigarette smoke-induced oxidative stress and proinflammatory phenotypic alterations

The dietary polyphenolic compound resveratrol, by activating the protein deacetylase enzyme silent information regulator 2/sirtuin 1 (SIRT1), prolongs life span in evolutionarily distant organisms and may mimic the cytoprotective effects of dietary restriction. The present study was designed to elucidate the effects of resveratrol on cigarette smoke-induced vascular oxidative stress and inflammation, which is a clinically highly relevant model of accelerated vascular aging. Cigarette smoke exposure of rats impaired the acetylcholine-induced relaxation of carotid arteries, which could be prevented by resveratrol treatment. Smoking and in vitro treatment with cigarette smoke extract (CSE) increased reactive oxygen species production in rat arteries and cultured coronary arterial endothelial cells (CAECs), respectively, which was attenuated by resveratrol treatment. The smoking-induced upregulation of inflammatory markers (ICAM-1, inducible nitric oxide synthase, IL-6, and TNF-alpha) in rat arteries was also abrogated by resveratrol treatment. Resveratrol also inhibited CSE-induced NF-kappaB activation and inflammatory gene expression in CAECs. In CAECs, the aforementioned protective effects of resveratrol were abolished by knockdown of SIRT1, whereas the overexpression of SIRT1 mimicked the effects of resveratrol. Resveratrol treatment of rats protected aortic endothelial cells against cigarette smoking-induced apoptotic cell death. Resveratrol also exerted antiapoptotic effects in CSE-treated CAECs, which could be abrogated by knockdown of SIRT1. Resveratrol treatment also attenuated CSE-induced DNA damage in CAECs (comet assay). Thus resveratrol and SIRT1 exert antioxidant, anti-inflammatory, and antiapoptotic effects, which protect the endothelial cells against the adverse effects of cigarette smoking-induced oxidative stress. The vasoprotective effects of resveratrol will likely contribute to its antiaging action in mammals and may be especially beneficial in pathophysiological conditions associated with accelerated vascular aging.

High Pressure Induces Superoxide Production in Isolated Arteries Via Protein Kinase C–Dependent Activation of NAD(P)H Oxidase

Background—Oxidative stress seems to be present in all forms of hypertension. Thus, we tested the hypothesis that high intraluminal pressure (Pi) itself, by activating vascular oxidases, elicits increased superoxide (O2·−) production interfering with flow-induced dilation. Methods and Results—Isolated, cannulated rat femoral arterial branches were exposed in vitro (for 30 minutes) to normal Pi (80 mm Hg) or high Pi (160 mm Hg). High Pi significantly increased vascular O2·− production (as measured by lucigenin chemiluminescence and ethidium bromide fluorescence) and impaired endothelium-dependent dilations to flow; these effects could be reversed by superoxide dismutase. Administration of the NAD(P)H oxidase inhibitor diphenyleneiodonium, apocynin, the protein kinase C (PKC) inhibitor chelerythrine or staurosporin or the removal of extracellular Ca2+ during high Pi treatment prevented the increases in O2·− production, whereas administration of losartan or captopril had no effect. High Pi resulted in significant increases in intracellular Ca2+ ([Ca2+]i) in the vascular wall (fura 2 fluorescence) and phosphorylation of PKC&agr; (Western blotting). The PKC activator phorbol myristate acetate significantly increased vascular O2·− production, which was inhibited by superoxide dismutase, diphenyleneiodonium, chelerythrine, or removal of extracellular Ca2+. Both high Pi and phorbol myristate acetate increased the phosphorylation of the NAD(P)H oxidase subunit p47phox. Conclusion—High Pi itself elicits arterial O2·− production, most likely by PKC-dependent activation of NAD(P)H oxidase, thus providing a potential explanation for the presence of oxidative stress and endothelial dysfunction in various forms of hypertension and the vasculoprotective effect of antihypertensive agents of different mechanisms of action.

Stretch Enhances Contraction of Bovine Coronary Arteries via an NAD(P)H Oxidase–Mediated Activation of the Extracellular Signal–Regulated Kinase Mitogen-Activated Protein Kinase Cascade

Abstract— This study examines the effects of an increase in passive stretch in endothelium-removed bovine coronary artery on oxidant-induced changes in force generation. Increasing passive stretch on the arterial segments from 5 to 20 g for 20 minutes caused a subsequent increase (P <0.05) in force generation to 30 mmol/L KCl or 0.1 &mgr;mol/L serotonin compared with the prestretch control response. Also associated with the passive stretch were increases in superoxide detection by lucigenin and a selective increase in extracellular signal–regulated kinase (ERK) mitogen-activated protein (MAP) kinase phosphorylation measured by Western analysis. The stretch-induced increase in force generation was eliminated by inhibition of the ERK pathway by the MEK inhibitor PD98059 but not by inhibitors of the p38 MAP kinase pathway (SB202190) or c-Jun N-terminal protein kinase pathway (SP200169). Additionally, stretch-induced increases in both ERK phosphorylation and force generation were attenuated by inhibition of tyrosine kinases (genistein), src (PP2), and specific sites on the epidermal growth factor receptor (EGFR) (AG1478). Probes for oxidant signaling, including NAD(P)H oxidase inhibitors (diphenyliodonium and apocynin) or enhancement of peroxide consumption (ebselen) but not inhibition of xanthine oxidase (allopurinol), attenuated the effects of stretch on both ERK phosphorylation and force generation. Furthermore, stretch caused an increase in EGFR phosphorylation and cytosolic to membrane translocation of the p47phox NAD(P)H oxidase subunit. Hydrogen peroxide also elicited contraction through EGFR phosphorylation and ERK. In summary, stretch seems to enhance force generation via ERK signaling through an EGFR/src-dependent mechanism activated by peroxide derived from a stretch-mediated activation of the NAD(P)H oxidase, a response that may contribute to hypertensive alterations in vascular reactivity.

D-4F Induces Heme Oxygenase-1 and Extracellular Superoxide Dismutase, Decreases Endothelial Cell Sloughing, and Improves Vascular Reactivity in Rat Model of Diabetes

Background—Apolipoprotein A1 mimetic peptide, synthesized from D-amino acid (D-4F), enhances the ability of HDL to protect LDL against oxidation in atherosclerotic animals. Methods and Results—We investigated the mechanisms by which D-4F provides antioxidant effects in a diabetic model. Sprague-Dawley rats developed diabetes with administration of streptozotocin (STZ). We examined the effects of daily D-4F (100 &mgr;g/100 g of body weight, intraperitoneal injection) on superoxide (O2−), extracellular superoxide dismutase (EC-SOD), vascular heme oxygenase (HO-1 and HO-2) levels, and circulating endothelial cells in diabetic rats. In response to D-4F, both the quantity and activity of HO-1 were increased. O2− levels were elevated in diabetic rats (74.8±8×103 cpm/10 mg protein) compared with controls (38.1±8×103 cpm/10 mg protein; P<0.01). D-4F decreased O2− levels to 13.23±1×103 (P<0.05 compared with untreated diabetics). The average number of circulating endothelial cells was higher in diabetics (50±6 cells/mL) than in controls (5±1 cells/mL) and was significantly decreased in diabetics treated with D-4F (20±3 cells/mL; P<0.005). D-4F also decreased endothelial cell fragmentation in diabetic rats. The impaired relaxation typical of blood vessels in diabetic rats was prevented by administration of D-4F (85.0±2.0% relaxation). Western blot analysis showed decreased EC-SOD in the diabetic rats, whereas D-4F restored the EC-SOD level. Conclusions—We conclude that an increase in circulating endothelial cell sloughing, superoxide anion, and vasoconstriction in diabetic rats can be prevented by administration of D-4F, which is associated with an increase in 2 antioxidant proteins, HO-1 and EC-SOD.

Lactate and Po2 Modulate Superoxide Anion Production in Bovine Cardiac Myocytes Potential Role of NADH Oxidase

BACKGROUND Lactate increases lucigenin chemiluminescence (CL)-detectable superoxide anion (O2.-) generation in bovine vascular smooth muscle and endothelium, and a microsomal flavoprotein-containing NADH oxidase whose activity is regulated by PO2 and cytosolic NAD(H) redox appears to be the detected source of O2.- production. Little is known about the importance of this O2.(-)-producing system in cardiac myocytes. METHODS AND RESULTS In isolated bovine cardiac myocytes, lactate (10 mmol/L) increased lucigenin-detectable O2.- levels to approximately 1.8 times baseline, whereas pyruvate (10 mmol/L) and mitochondrial probes did not increase the detection of O2.-. A nonmitochondrial NADH oxidase activity, found in microsomes containing a cytochrome b558, was a major source of O2.- production in the homogenate of myocytes, because NADH (0.1 mmol/L) increased basal lucigenin CL >100-fold. NADPH oxidases, mitochondria, and xanthine oxidase were minor sources of detectable O2.- production. However, mitochondria released H2O2 in the presence of 5 mmol/L succinate and 30 micromol/L antimycin, based on its detection as catalase-inhibitable luminol (+horseradish peroxidase)-elicited CL. Diphenyliodonium (DPI), an inhibitor of flavoprotein-containing oxidases, significantly attenuated basal, lactate, and NADH-elicited lucigenin CL. Hypoxia eliminated myocyte lucigenin CL, and posthypoxic reoxygenation caused an 8.6-fold increase in the detection of O2.- that was potentiated by lactate and inhibited by DPI. CONCLUSIONS NADH oxidase activity linked to cytosolic NAD(H) redox appears to be a key source of O2.- production in cardiac myocytes that could contribute to oxidant signaling mechanisms and injury upon exposure to changes in PO2 and metabolites produced under hypoxia, such as lactate. These processes could contribute to the previously observed potentiation of injury caused by lactate in cardiac ischemia/reperfusion.

S-Nitroglutathione, a Product of the Reaction between Peroxynitrite and Glutathione That Generates Nitric Oxide

Peroxynitrite (ONOO−) has been shown in studies on vascular relaxation and guanylate cyclase activation to react with glutathione (GSH), generating an intermediate product that promotes a time-dependent production of nitric oxide (NO). In this study, reactions of ONOO− with GSH produced a new substance, which was characterized by liquid chromatography, ultraviolet spectroscopy, and electrospray tandem mass spectrometry. The mass spectrometric data provided evidence that the product of this reaction was S-nitroglutathione (GSNO2) and that S-nitrosoglutathione (GSNO) was not a detectable product of this reaction. Further evidence was obtained by comparison of the spectral and chromatographic properties with synthetic standards prepared by reaction of GSH with nitrosonium or nitronium borofluorates. Both the synthetic and ONOO−/GSH-derived GSNO2 generated a protonated ion, GSNO2H+, at m/z 353, which was unusually resistant to decomposition under collision activation, and no fragmentation was observed at collision energy of 25 eV. In contrast, an ion at m/z 337 (GSNOH+), generated from the synthetic GSNO, readily fragmented with the abundant loss of NO at 9 eV. Reactions of ONOO− with GSH resulted in the generation of NO, which was detected by the head space/NO-chemiluminescence analyzer method. The generation of NO was inhibited by the presence of glucose and/or CO2 in the buffers employed. Synthetic GSNO2 spontaneously generated NO in a manner that was not significantly altered by glucose or CO2. Thus, ONOO− reacts with GSH to form GSNO2, and GSNO2 decomposes in a manner that generates NO.