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      Effect of Ascorbic Acid on Endothelial Dysfunction of Epicardial Coronary Arteries in Chronic Smokers Assessed by Cold Pressor Testing

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          Abstract

          Background: In chronic smokers there is evidence for increased formation of oxygen-derived free radicals within the vessel wall impairing endothelial function. It has been suggested that the inactivation of endothelium-derived nitric oxide by oxygen free radicals contributes to endothelial dysfunction. Hence, we tested the hypothesis that in chronic smokers the antioxidant ascorbic acid could improve abnormal endothelial function of epicardial coronary arteries. Methods and Results: Thirty-one patients (mean age 57 ± 9 years) referred for routine diagnostic catheterization for evaluation of chest pain and without angiographically significant coronary artery stenoses were randomly assigned to one of the study groups to assess vasomotor response of epicardial coronary arteries due to cold pressor testing (CPT) before and after intravenous infusion of 3 g of ascorbic acid or 100 ml × 0.9% saline infusion. In 6 controls (mean age 55 ± 3 years) CPT led to a similar increase in luminal area before and after ascorbic acid administration (26.5 ± 15.0 vs. 28.4 ± 17.7%, p = NS). In 15 chronic smokers (mean age 55 ± 9 years), CPT induced a decrease in the luminal area of –18.5 ± 6.3%. This flow-dependent vasoconstriction was significantly reversed to 7.7 ± 6.2% (p ≤ 0.03) vasodilation after intravenous ascorbic acid administration. In 10 chronic smokers (mean age 57 ± 11 years) saline infusion (placebo) did not have a significant effect on CPT-induced vasoconstriction (–12.7 ± 5.1 vs. –13.1 ± 5.1%, p = NS). The CPT-induced increase in luminal area in chronic smokers after ascorbic acid infusion was significant compared to controls and placebo (each p ≤ 0.05). Our assessment of endothelium-independent responses to nitroglycerin revealed no significant differences between the single study groups (p = NS). Conclusion: In chronic smokers acute intravenous administration of ascorbic acid significantly improves CPT-induced coronary endothelium-dependent dysfunction. According to the current understanding, this effect is due to improved cellular redox imbalance and prevention of nitric oxide inactivation in the endothelium and subendothelial space.

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          Most cited references 7

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          Vascular endothelial cells synthesize nitric oxide from L-arginine.

          Nitric oxide (NO) released by vascular endothelial cells accounts for the relaxation of strips of vascular tissue and for the inhibition of platelet aggregation and platelet adhesion attributed to endothelium-derived relaxing factor. We now demonstrate that NO can be synthesized from L-arginine by porcine aortic endothelial cells in culture. Nitric oxide was detected by bioassay, chemiluminescence or by mass spectrometry. Release of NO from the endothelial cells induced by bradykinin and the calcium ionophore A23187 was reversibly enhanced by infusions of L-arginine and L-citrulline, but not D-arginine or other close structural analogues. Mass spectrometry studies using 15N-labelled L-arginine indicated that this enhancement was due to the formation of NO from the terminal guanidino nitrogen atom(s) of L-arginine. The strict substrate specificity of this reaction suggests that L-arginine is the precursor for NO synthesis in vascular endothelial cells.
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            Increase in circulating products of lipid peroxidation (F2-isoprostanes) in smokers. Smoking as a cause of oxidative damage.

            It has been hypothesized that the pathogenesis of diseases induced by cigarette smoking involves oxidative damage by free radicals. However, definitive evidence that smoking causes the oxidative modification of target molecules in vivo is lacking. We conducted a study to determine whether the production of F2-isoprostanes, which are novel products of lipid peroxidation, is enhanced in persons who smoke. We measured the levels of free F2-isoprostanes in plasma, the levels of F2-isoprostanes esterified to plasma lipids, and the urinary excretion of metabolites of F2-isoprostanes in 10 smokers and 10 nonsmokers matched for age and sex. The short-term effects of smoking (three cigarettes smoked over 30 minutes) and the effects of two weeks of abstinence from smoking on levels of F2-isoprostanes in the circulation were also determined in the smokers. Plasma levels of free and esterified F2-isoprostanes were significantly higher in the smokers (242 +/- 147 and 574 +/- 217 pmol per liter, respectively) than in the nonsmokers (103 +/- 19 and 345 +/- 65 pmol per liter; P = 0.02 for free F2-isoprostanes and P = 0.03 for esterified F2-isoprostanes). Smoking had no short-term effects on the circulating levels of F2-isoprostanes. However, the levels of free and esterified F2-isoprostanes fell significantly after two weeks of abstinence from smoking (250 +/- 156 and 624 +/- 214 pmol per liter, respectively, before the cessation of smoking, as compared with 156 +/- 67 and 469 +/- 108 pmol per liter after two weeks' cessation; P = 0.03 for free F2-isoprostanes and P = 0.02 for esterified F2-isoprostanes). The increased levels of F2-isoprostanes in the circulation of persons who smoke support the hypothesis that smoking can cause the oxidative modification of important biologic molecules in vivo.
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              Passive smoking and impaired endothelium-dependent arterial dilatation in healthy young adults.

              Passive smoking has been linked to an increased risk of dying from atherosclerotic heart disease. Since endothelial dysfunction is an early feature of atherogenesis and occurs in young adults who actively smoke cigarettes, we hypothesized that passive smoking might also be associated with endothelial damage in healthy young-adult nonsmokers. We studied 78 healthy subjects (39 men and 39 women) 15 to 30 years of age (mean +/- SD, 22 +/- 4): 26 control subjects who had never smoked or had regular exposure to environmental tobacco smoke, 26 who had never smoked but had been exposed to environmental tobacco smoke for at least one hour daily for three or more years, and 26 active smokers. Using ultrasonography, we measured the brachial-artery diameter under base-line conditions, during reactive hyperemia (with flow increase causing endothelium-dependent dilatation), and after sublingual administration of nitroglycerin (an endothelium-independent dilator). Flow-mediated dilatation was observed in all control subjects (8.2 +/- 3.1 percent; range, 2.1 to 16.7) but was significantly impaired in the passive smokers (3.1 +/- 2.7 percent; range, 0 to 9; P < 0.001 for the comparison with the controls) and in the active smokers (4.4 +/- 3.1 percent; range, 0 to 10; P < 0.001 for the comparison with the controls; P = 0.48 for the comparison with the passive smokers). In the passive smokers, there was an inverse relation between the intensity of exposure to tobacco smoke and flow-mediated dilatation (r = -0.67, P < 0.001). In contrast, dilatation induced by nitroglycerin was similar in all groups. Passive smoking is associated with dose-related impairment of endothelium-dependent dilatation in healthy young adults, suggesting early arterial damage.
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                Author and article information

                Journal
                CRD
                Cardiology
                10.1159/issn.0008-6312
                Cardiology
                S. Karger AG
                0008-6312
                1421-9751
                2000
                April 2001
                26 April 2001
                : 94
                : 4
                : 239-246
                Affiliations
                aMedical Clinic, Department of Cardiology and Angiology, and bInstitute for Biometry and Informatics, University of Freiburg, Germany
                Article
                47324 Cardiology 2000;94:239–246
                10.1159/000047324
                11326145
                © 2001 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 3, Tables: 3, References: 46, Pages: 8
                Categories
                Interventional Cardiology

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