Cigarette Smoking Induced Oxidative Stress may Impair Endothelial Function and Coronary Blood Flow in Angiographically Normal Coronary Arteries

Association of paraoxonase activity and coronary blood flow

BACKGROUND

Paraoxonase (PON) is a high-density lipoprotein-bound anti-oxidant enzyme that inhibits atherosclerosis and endothelial dysfunction. Slow coronary flow (SCF) has long been identified and endothelial dysfunction and atherosclerosis of epicardial coronary arteries and microvasculature were reported to be associated with SCF. Consequently, we aimed to investigate the association between coronary blood flow by means of Thrombolysis in Myocardial Infarction frame count (TFC) and serum PON activity and other laboratory parameters in patients with SCF compared to control cases.

METHODS

Twenty-four patients with SCF and 110 control cases with normal coronary flow were studied after quantifying coronary blood flow according to TFC. Serum PON activity was evaluated by measuring the rate of paraoxon hydrolysis. The association between TFC and serum PON activity and other clinical and laboratory parameters were evaluated.

RESULTS

There were statistically significant differences between SCF and control groups in respect to serum uric acid (p=0.001), high sensitive C-reactive protein (p=0.03) levels and serum PON activity (p<0.001). The mean TFC was correlated with male gender (r=0.263, p=0.002), serum uric acid level (r=0.287, p=0.001), hemoglobin concentration (r=0.192, p=0.032) and serum PON activity (r=-0.306, p<0.001). Serum uric acid level (chi(2)=10.08, beta=0.362, p=0.009) and serum PON activity (chi(2)=16.73, beta=-0.005, p=0.001) were independent predictors of SCF whereas the only independent predictor of mean TFC was serum PON activity (beta=-0.318, p<0.001).

CONCLUSION

These findings suggest that serum PON activity is independently associated with mean TFC and reduced serum PON activity might represent a biochemical marker of SCF.

VEGFR-2 inhibition augments cigarette smoke-induced oxidative stress and inflammatory responses leading to endothelial dysfunction

Vascular endothelial growth factor (VEGF) induces phosphorylation of VEGF receptor-2 (VEGFR-2) and activates the downstream signaling pathway resulting in endothelial cell migration, proliferation, and survival. Cigarette smoking is associated with abnormal vascular and endothelial function, leading to airspace enlargement. Herein, we investigated the mechanism of cigarette smoke (CS) -induced endothelial dysfunction by studying the VEGF-VEGFR-2 signaling in mouse lung and human endothelial cells. CS exposure caused oxidative stress, as shown by increased levels of 4-hydroxy-2-nonenal-adducts in mouse lung and reactive oxygen species generation in human lung microvascular endothelial cells (HMVEC-Ls). Inhibition of VEGFR-2 by a specific kinase inhibitor (NVP-AAD777) enhanced the CS-induced oxidative stress, causing augmented inflammatory cell influx and proinflammatory mediators release in mouse lung. The levels of endothelial nitric oxide synthase (eNOS) and phosphorylated (p) -eNOS in the lungs of mice exposed to CS and/or treated with VEGFR-2 inhibitor were decreased. CS down-regulated VEGFR-2 expression, eNOS levels, and VEGF-induced VEGFR-2 phosphorylation in HMVEC-Ls, resulting in impaired VEGF-induced endothelial cell migration and angiogenesis. Overall, these data show that inhibition of VEGFR-2 augmented CS-induced oxidative stress and inflammatory responses leading to endothelial dysfunction. This explains the mechanism of endothelial dysfunction in smokers and has implications in understanding the pathogenesis of pulmonary and cardiovascular diseases.

Myocardial infarction in adolescents

OBJECTIVES

To determine the incidence, characteristics, and outcomes for adolescents diagnosed with acute myocardial infarction (AMI).

STUDY DESIGN

We analyzed data from the Nationwide Inpatient Sample to determine the incidence of AMI in adolescents (age 13 to 18 years). Data from 1998 to 2001 were analyzed. Patients with primary cardiomyopathies, congenital heart lesions, and previous heart transplantation were excluded.

RESULTS

The estimated incidence of AMI admissions of adolescents in the United States is 157 per year, or 6.6 events per 1 million patient-years. AMI occurs predominantly in males (80%). Reported incidences of substance abuse and smoking are significantly higher in the adolescents with AMI than in adolescents admitted to the hospital for other conditions (P < .001 for both). Of the 123 subjects with AMI that we studied, 36 underwent coronary angiography (29%) and 2 underwent coronary artery bypass graft surgery (1%). The hospital mortality rate was 0.8%.

CONCLUSIONS

AMI is extremely rare in adolescents. Patient characteristics associated with AMI include substance abuse, tobacco use, and male sex. The hospital survival for AMI in adolescents is excellent, and the need for catheter or surgical coronary artery intervention is uncommon.

Relationship between endothelial function and coronary risk factors in patients with stable coronary artery disease

BACKGROUND

Results of experimental and clinical studies suggest that both coronary artery disease (CAD) itself and its traditional risk factors lead to endothelial dysfunction. The aim of the present study was to determine which CAD risk factors sustain their contribution to endothelial dysfunction despite the presence of established CAD.

METHODS AND RESULTS

The study group comprised 150 patients with CAD. Using a high-resolution ultrasound, the diameter of the brachial artery at rest and during reactive hyperemia (flow-mediated dilatation, FMD%: endothelial-dependent stimulus to vasodilatation), as well as after sublingual administration of nitroglycerin (NTG%: endothelium-independent vasodilatation), was measured. The relationship between FMD% and coronary risk factors [diabetes mellitus (DM), total cholesterol, high-density lipoprotein-cholesterol, low-density lipoprotein-cholesterol, triglycerides, age, family history of premature atherosclerosis, smoking, hypertension (HT), body mass index (BMI)] was investigated. In univariate analysis there was an inverse relationship between FMD% and age (r=-0.300, p<0.001), and BMI (r=-0.230, p<0.005) and FMD% was significantly lower in diabetic patients when compared to non-diabetic patients (p<0.001). In stepwise multivariate regression analysis; FMD still correlated with DM and advanced age, but not with BMI (beta=0.065, p<0.001, beta=-0.001 p=0.002, beta=-0.087, p<0.284, respectively). FMD% was found to be not associated with hypercholesterolemia, family history of premature atherosclerosis, HT and smoking.

CONCLUSION

Only aging and DM were independently associated with endothelial dysfunction in patients with established CAD.

Malondialdehyde as biomarker of oxidative damage to lipids caused by smoking

Thiobarbituric acid reactive substances (TBARS) and malondialdehyde (MDA) have been used as biomarkers of lipid oxidation for more than thirty years. The validity of these biomarkers has been rightfully criticized for a lack of specificity and problems with post sampling formation. Numerous assays have been published for their analysis giving rise to reference intervals for healthy non-smoking humans varying more than to orders of magnitude. In spite of these problems, these biomarkers remain among the most commonly reported indices of oxidative damage and the present review focuses on the problems associated with MDA/TBARS analysis, their potential as biomarkers of oxidative stress and the effect of smoking on MDA status.

Oxidants in the Gas Phase of Cigarette Smoke Pass Through the Lung Alveolar Wall and Raise Systemic Oxidative Stress

Cigarette smoking-induced oxidative stress plays a key role in the pathogenesis of atherosclerosis in smokers. Aqueous cigarette smoke extract (CSE) contains stable oxidants, peroxynitrite-like reactants, which have the ability to oxidize and nitrate low-density lipoprotein (LDL). We examined whether oxidants in CSE can penetrate into the blood through the lung alveolar wall and cause oxidative vascular injury. The oxidants in CSE and sodium peroxynitrite could easily pass through the reconstituted basement membrane. When CSE or sodium peroxynitrite solution was infused into the alveolar air space of an isolated rat lung mounted in tyrosine solution, CSE gradually increased the 3-nitrotyrosine levels in the external tyrosine solution while sodium peroxynitrite caused a rapid increase. CSE did not activate the rat alveolar macrophages. When rats were acutely exposed to the gas phase of cigarette smoke from which tar and nicotine had been removed, both serum levels of 3-nitrotyrosine and 8-hydroxy-2'-deoxyguanine, oxidative stress markers, rapidly increased. Our results demonstrate that relatively stable oxidants in CSE can pass through the pulmonary alveolar wall into the blood and induce systemic oxidative stress, which most likely facilitates oxidative modification of LDL and endothelial dysfunction, explaining early key events in the development of atherosclerosis.

Systemic oxidative stress is associated with visceral fat accumulation and the metabolic syndrome

BACKGROUND

The metabolic syndrome (MetS) is a major target for prevention of atherosclerotic cardiovascular diseases and visceral fat accumulation is an underlying component of MetS. The aim of this study was to investigate the association of systemic oxidative stress with visceral fat accumulation and MetS.

METHODS AND RESULTS

The study group consisted of Japanese men (n=44; 51.2+/-11.4 years) and women (n=61; 55.4 +/-13.4 years). Urinary 8-epi-prostaglandin F2alpha (8-epi-PGF2 alpha) concentration, a biomarker of systemic oxidative stress, was significantly high in the subjects with MetS. As the urinary concentration of 8-epi-PGF2alpha increased, the number of criteria for MetS were significantly met (abdominal obesity, hypertriglyceridemia, low high-density lipoprotein-cholesterol, hypertension, and high fasting glucose). Among parameters associated with MetS, the correlation coefficient of visceral fat area (VFA) with urinary 8-epi-PGF2alpha concentration was the highest (r=0.636, p<0.0001). In non-obese subjects, the correlation coefficient of VFA with urinary 8-epi-PGF2alpha concentration was higher (r=0.728, p<0.0001), although there was no significant correlation between subcutaneous fat area and urinary 8-epi-PGF2 alpha. Stepwise multiple regression analysis identified VFA as the strongest and independent determinant of urinary 8-epi-PGF2 alpha (p<0.0001) followed by adiponectin (p=0.0212) and, high sensitive C-reactive protein (p=0.0365).

CONCLUSIONS

Systemic oxidative stress, as measured by urinary 8-epi-PGF2alpha , is strongly associated with visceral fat accumulation and MetS.

Trimetazidine reduces oxidative stress in cardiac surgery

BACKGROUND

Trimetazidine is an anti-ischemic agent that is used to treat angina and it has cardioprotective effects without inducing any significant hemodynamic changes. It inhibits the long-chain mitochondrial 3-ketoacyl coenzyme A thiolase enzyme in the myocyte and can improve cardiac mitochondrial metabolism, as well as scavenge free radicals. The aim of this double-blind prospective randomized study was to investigate the effect of preoperative use of trimetazidine on the reduction of oxidative stress during coronary artery bypass grafting (CABG) under cardiopulmonary bypass (CPB).

METHODS AND RESULTS

The study group (group T) and the control group (group C) each comprised 12 patients. Pretreatment began 2 weeks before CABG with trimetazidine (60 mg/day po); the control group did not receive any medication. Serial blood samples were collected before and after CPB for measurement of the serum concentrations of these major endogenous antioxidant enzyme systems, which are markers for oxidative degradation of the cellular membranes; postoperative levels were significantly different between the groups (p<0.05). There were no significant difference in hemodynamic values.

CONCLUSION

The findings suggest that pretreatment with trimetazidine alleviates malondialdehyde production and preserves endogenous antioxidant capacity during CABG with CPB and cardioplegic arrest.

Does the Impact of Smoking on Coronary Heart Disease Differ by Low-Density Lipoprotein Cholesterol Level? The Atherosclerosis Risk in Communities (ARIC) Study

BACKGROUND

The association of smoking with coronary heart disease (CHD) occurrence has been reported to be weaker for populations with lower plasma cholesterol levels. Recent studies suggest that low-density lipoprotein cholesterol (LDL-C) and smoking contribute to different stages of atherosclerosis, so the present study was designed to test the hypothesis that smoking is a stronger risk factor for CHD when LDL-C is high.

METHODS AND RESULTS

The study group of 13,410 middle-aged adults who were initially free of stroke and CHD were followed and over 13.3 years there were 932 incident CHD events. Tests for multiplicative interaction were performed using proportional hazards models. Both smoking and increased LDL-C were risk factors for CHD incidence. The relative hazard (RH) of CHD in relation to smoking tended to be larger among higher LDL-C categories compared with lower LDL-C categories. For example, when the participants were dichotomized into 4 categories, using smoking >or=15 cigarettes per day and LDL-C >or=130 mg/dl as cutoffs, those with high LDL-C and heavier cigarette smoking showed a very high RH of CHD (RH =2.81) compared with that expected from the product of the RHs of high LDL-C (RH =1.15) only x heavy smoking only (RH =1.71) (p for interaction =0.04).

CONCLUSIONS

These results suggest positive multiplicative interactions between smoking and LDL-C for CHD incidence.