Effect of oxygen free radicals on cardiovascular function at organ and cellular levels

Network Meta-Analysis of Drug Therapies for Lowering Uric Acid and Mortality Risk in Patients with Heart Failure

PURPOSE

This network meta-analysis aimed to assess the current efficacy of decreasing the uric acid (UA) level with drugs to reduce mortality in patients with heart failure (HF).

METHODS

Electronic literature searches using EMBASE and MEDLINE of studies published from 1 Jan 1950 to 26 Dec 2019 were conducted for randomized controlled trials or non-randomized cohort studies that included at least one group of patients who took UA-lowering drugs and with a study outcome of all-cause mortality. A random-effects network meta-analysis was performed within a frequentist framework. Hierarchy of treatments was expressed as the surface under the cumulative ranking curve (SUCRA) value, which is in proportion to mean rank (best is 100%).

RESULTS

Nine studies, which included seven different types of groups, were eligible for analysis. The "untreated uricemia" group in which patients had hyperuricemia but without treatment had a significantly higher risk of mortality than the "no uricemia" group in which patients had no hyperuricemia (relative risk (RR)(95% confidence interval (CI), 1.43 (1.08-1.89)). The "start-allo" group wherein patients started to take allopurinol did not have a significantly lower risk of mortality than the "untreated uricemia" group (RR (95% CI), 0.68 (0.45-1.01)). However, in the "start-allo" group the SUCRA value was comparable to that in the "no uricemia" group (SUCRA: 65.4% for "start-allo"; 64.1% for "no uricemia").

CONCLUSIONS

Results suggested that allopurinol therapy was not associated with a significantly improved prognosis in terms of mortality but could potentially counteract the adverse effects associated with longstanding hyperuricemia in HF patients.

Hyperuricemia treatment in acute heart failure patients does not improve their long-term prognosis: A propensity score matched analysis from the AHEAD registry

BACKGROUND

Hyperuricemia is associated with a poorer prognosis in heart failure (HF) patients. Benefits of hyperuricemia treatment with allopurinol have not yet been confirmed in clinical practice. The aim of our work was to assess the benefit of allopurinol treatment in a large cohort of HF patients.

METHODS

The prospective acute heart failure registry (AHEAD) was used to select 3160 hospitalized patients with a known level of uric acid (UA) who were discharged in a stable condition. Hyperuricemia was defined as UA ≥500 μmoL/L and/or allopurinol treatment at admission. The patients were classified into three groups: without hyperuricemia, with treated hyperuricemia, and with untreated hyperuricemia at discharge. Two- and five-year all-cause mortality were defined as endpoints. Patients without hyperuricemia, unlike those with hyperuricemia, had a higher left ventricular ejection fraction, a better renal function, and higher hemoglobin levels, had less frequently diabetes mellitus and atrial fibrillation, and showed better tolerance to treatment with angiotensin-converting enzyme inhibitors/angiotensin receptor blockers and/or beta-blockers.

RESULTS

In a primary analysis, the patients without hyperuricemia had the highest survival rate. After using the propensity score to set up comparable groups, the patients without hyperuricemia had a similar 5-year survival rate as those with untreated hyperuricemia (42.0% vs 39.7%, P = 0.362) whereas those with treated hyperuricemia had a poorer prognosis (32.4% survival rate, P = 0.006 vs non-hyperuricemia group and P = 0.073 vs untreated group).

CONCLUSION

Hyperuricemia was associated with an unfavorable cardiovascular risk profile in HF patients. Treatment with low doses of allopurinol did not improve the prognosis of HF patients.

AGE-RAGE Stress in the Pathophysiology of Pulmonary Hypertension and its Treatment

Pulmonary hypertension (PH) is a rare and fatal disease characterized by elevation of pulmonary artery pressure ≥ 25 mm Hg. There are five groups of PH: (1) pulmonary artery (PA) hypertension (PAH), (2) PH due to heart diseases, (3) PH associated with lung diseases/hypoxia, (4) PH associated with chronic obstruction of PA, and (5) PH due to unclear and/or multifactorial mechanisms. The pathophysiologic mechanisms of group 1 have been studied in detail; however, those for groups 2 to 5 are not that well known. PH pathology is characterized by smooth muscle cells (SMC) proliferation, muscularization of peripheral PA, accumulation of extracellular matrix (ECM), plexiform lesions, thromboembolism, and recanalization of thrombi. Advanced glycation end products (AGE) and its receptor (RAGE) and soluble RAGE (sRAGE) appear to be involved in the pathogenesis of PH. AGE and its interaction with RAGE induce vascular hypertrophy through proliferation of vascular SMC, accumulation of ECM, and suppression of apoptosis. Reactive oxygen species (ROS) generated by interaction of AGE and RAGE modulates SMC proliferation, attenuate apoptosis, and constricts PA. Increased stiffness in the artery due to vascular hypertrophy, and vasoconstriction due to ROS resulted in PH. The data also suggest that reduction in consumption and formation of AGE, suppression of RAGE expression, blockage of RAGE ligand binding, elevation of sRAGE levels, and antioxidants may be novel therapeutic targets for prevention, regression, and slowing of progression of PH. In conclusion, AGE-RAGE stress may be involved in the pathogenesis of PH and the therapeutic targets should be the AGE-RAGE axis.

Do Advanced Glycation End Products and Its Receptor Play a Role in Pathophysiology of Hypertension?

There is a close relationship between arterial stiffness and blood pressure. The studies suggest that the advanced glycation end products (AGEs) and its cell receptor (RAGE) are involved in the arterial stiffness in two ways: changes in arterial structure and vascular function. Plasma levels of AGEs and expression of RAGE are elevated, while the levels of soluble RAGE (sRAGE) and endogenous secretory RAGE (esRAGE) are lowered in patients with hypertension (HTN). There is a positive correlation between plasma levels of AGEs and arterial stiffness, and an inverse association between arterial stiffness/HTN, and serum levels of sRAGE and esRAGE. Various measures can reduce the levels of AGEs and expression of RAGE, and elevate sRAGE. Arterial stiffness and blood pressure could be reduced by lowering the serum levels of AGEs, and increasing the levels of sRAGE. Levels of AGEs can be lowered by reducing the consumption of AGE-rich diet, short duration of cooking in moist heat at low temperature, and cessation of cigarette smoking. Drugs such as aminoguanidine, vitamins, angiotensin-converting enzyme (ACE) inhibitors, angiotensin-II receptor blockers, statins, and metformin inhibit AGE formation. Alagebrium, an AGE breakers reduces levels of AGEs. Clinical trials with some drugs tend to reduce stiffness. Systemic administration of sRAGE has beneficial effect in animal studies. In conclusion, AGE-RAGE axis is involved in arterial stiffness and HTN. The studies suggest that inhibition of AGEs formation, reduction of AGE consumption, blockade of AGE-RAGE interaction, suppression of RAGE expression, and exogenous administration of sRAGE may be novel therapeutic strategies for treatment of arterial stiffness and HTN.

C-Reactive Protein Increases Oxygen Radical Generation by Neutrophils

C-reactive protein (CRP) has been suggested to play a role in the pathogenesis of atherosclerosis. Neutrophil respiratory burst and levels of CRP are increased during infection. The increase in the neutrophil respiratory burst may be due to factors that are elevated in infection, such as cytokines, tumor necrosis factor, platelet-activating factor, and CRP. The direct effect of CRP on the release of oxygen radicals by neutrophils is not known. This investigation was made to determine if CRP affects the generation of oxygen radicals by neutrophils and if this effect is blocked by antioxidants. The effect of various concentrations (1 to 200 µg/mL blood) of CRP on the generation of oxygen radicals by neutrophils was measured as luminol-dependent chemiluminescence (chemiluminescent activity) on a luminometer (Auto Lumat LB953, EG & G Berthold, Gaithersburg, MD). The unit of chemiluminescent activity is the relative light unit and was expressed as relative light unit/white blood cell (RLU/WBC). Chemiluminescent activity of blood without CRP was slightly higher than that of buffer with or without CRP. CRP markedly increased the chemiluminescent activity of blood. There was no significant change in the chemiluminescent activity of WBCs with 1 µg/mL of CRP. The chemiluminescent activity increased significantly with higher concentrations of CRP. The percent increases in the chemiluminescent activity with 2, 5, 10, 25, 50, 100 and 200 µg/mL of CRP were 45%, 72%, 50%, 70%, 52%, 67%, and 68% respectively. Antioxidants (superoxide dismutase, catalase, and dimethylthiourea) blocked CRP-induced oxygen radicals by WBCs. These results suggest that CRP increases the generation of oxygen radicals from the WBCs. CRP-induced atherosclerosis may be mediated through generation of oxygen radicals by neutrophils.

Oxidative stress as a mechanism of added sugar-induced cardiovascular disease

Added sugars comprising of table sugar, brown sugar, corn syrup, maple syrup, honey, molasses, and other sweeteners in the prepared processed foods and beverages have been implicated in the pathophysiology of cardiovascular diseases. This article deals with the reactive oxygen species (ROS) as a mechanism of sugar-induced cardiovascular diseases. There is an association between the consumption of high levels of serum glucose with cardiovascular diseases. Various sources of sugar-induced generation of ROS, including mitochondria, nicotinamide adenine dinucleotide phosphate-oxidase, advanced glycation end products, insulin, and uric acid have been discussed. The mechanism by which ROS induce the development of atherosclerosis, hypertension, peripheral vascular disease, coronary artery disease, cardiomyopathy, heart failure, and cardiac arrhythmias have been discussed in detail. In conclusion, the data suggest that added sugars induce atherosclerosis, hypertension, peripheral vascular disease, coronary artery disease, cardiomyopathy, heart failure, and cardiac arrhythmias and that these effects of added sugars are mediated through ROS.

Uric acid and gamma-glutamyl transferase activity are associated with left ventricular remodeling indices in patients with chronic heart failure

INTRODUCTION AND OBJECTIVES

Uric acid and gamma-glutamyl transferase are prognostic indicators in chronic heart failure. Nevertheless, the mechanism underlying the association between uric acid, gamma-glutamyl transferase, and chronic heart failure progression and prognosis remains largely unknown.

METHODS

The association of uric acid and gamma-glutamyl transferase with flow-mediated dilation and echocardiographic indices of cardiac remodeling was addressed in 120 patients with chronic ischemic heart failure. To determine the independent contribution of uric acid and gamma-glutamyl transferase to the flow-mediated dilation and echocardiographic indices of remodeling, a series of multiple linear regression models, based on traditional and nontraditional risk factors impacting upon these parameters, were constructed.

RESULTS

Uric acid, but not gamma-glutamyl transferase, was an independent predictor of flow-mediated dilation. Uric acid was associated with all the echocardiographic indices of left ventricular dysfunction tested in 3 multiple-regression models. Uric acid correlated with left ventricular end-systolic diameter, left ventricular end-diastolic diameter, left ventricular end-systolic volume, and left ventricular end-diastolic volume (r = 0.337; r = 0.340; r = 0.321; r = 0.294; P = .001, respectively). Gamma-glutamyl transferase was an independent predictor of left ventricular end-systolic volume and left ventricular end-diastolic volume, after adjustment for all variables. Gamma-glutamyl transferase correlated with left ventricular end-systolic diameter, left ventricular end-diastolic diameter, left ventricular end-systolic volume, and left ventricular end-diastolic volume (r = 0.238, P = .009; r = 0.219, P = .016; r = 0.359, P < .001; r = 0.369, P = .001, respectively).

CONCLUSIONS

Serum uric acid and gamma-glutamyl transferase levels are associated with left ventricular remodeling in patients with chronic ischemic heart failure.

Inverse Association between Cardiac Troponin-I and Soluble Receptor for Advanced Glycation End Products in Patients with Non-ST-Segment Elevation Myocardial Infarction

Interaction of advanced glycation end products (AGEs) with the receptor for advanced AGEs (RAGE) results in activation of nuclear factor kappa-B, release of cytokines, expression of adhesion molecules, and induction of oxidative stress. Oxygen radicals are involved in plaque rupture contributing to thromboembolism, resulting in acute coronary syndrome (ACS). Thromboembolism and the direct effect of oxygen radicals on myocardial cells cause cardiac damage that results in the release of cardiac troponin-I (cTnI) and other biochemical markers. The soluble RAGE (sRAGE) compete with RAGE for binding with AGE, thus functioning as a decoy and exerting a cytoprotective effect. Low levels of serum sRAGE would allow unopposed serum AGE availability for binding with RAGE, resulting in the generation of oxygen radicals and proinflammatory molecules that have deleterious consequences and promote myocardial damage. sRAGE may stabilize atherosclerotic plaques. It is hypothesized that low levels of sRAGE are associated with high levels of serum cTnI in patients with ACS. The main objective of the study was to determine whether low levels of serum sRAGE are associated with high levels of serum cTnI in ACS patients. The serum levels of sRAGE and cTnI were measured in 36 patients with non-ST-segment elevation myocardial infarction (NSTEMI) and 30 control subjects. Serum levels of sRAGE were lower in NSTEMI patients (802.56 ± 39.32 pg/mL) as compared with control subjects (1311.43 ± 66.92 pg/mL). The levels of cTnI were higher in NSTEMI patients (2.18 ± 0.33 μg/mL) as compared with control subjects (0.012 ± 0.001 μg/mL). Serum sRAGE levels were negatively correlated with the levels of cTnI. In conclusion, the data suggest that low levels of serum sRAGE are associated with high serum levels of cTnI and that there is a negative correlation between sRAGE and cTnI.

Allopurinol as a cardiovascular drug

Cardiovascular disease (CVD) remains the leading cause of death in the United States. There is evidence that shows a direct relationship between an elevated uric acid level and an increased risk of cardiovascular (CV) events, which has set the foundation for the investigation of uric acid-lowering drugs for the treatment of CVD. Although traditionally the cornerstone therapy for gout, allopurinol's ability to be a competitive inhibitor of the key enzyme, xanthine oxidase, needed for uric acid formation, has prompted recent clinical research evaluating allopurinol as a CV drug. Epidemiologic and biochemical studies on uric acid formation have shown that it is not only uric acid itself that leads to worsening prognosis and increased CV events, but also the free radicals and superoxides formed during xanthine oxidase activity. The combination of uric acid formation and formed free radicals could ultimately lead to coronary endothelial dysfunction and worsening of myocardial oxidative stress. Along with preventing uric acid formation, allopurinol also has the ability to behave as a free radical scavenger of the superoxide anions and free radicals released during uric acid formation.Clinical studies have shown that allopurinol improves endothelial dysfunction and subsequently improves the exercise capacity in patients diagnosed with angina pectoris. Allopurinol has also been shown to decrease oxidative stress and ameliorate the morbidity and mortality of congestive heart failure patients by possibly improving mechanoenergetic uncoupling, with the enhancement of myocardial contractility and the left ventricular ejection fraction. This review presents the pharmacologic action of allopurinol on the CV system and describes the effectiveness of allopurinol as a potential drug to treat 2 CVD morbidities: ischemic heart disease and congestive heart failure.

Oxidative stress and hyperuricaemia: pathophysiology, clinical relevance, and therapeutic implications in chronic heart failure

Heart failure (HF) is a state of chronic deterioration of oxidative mechanisms due to enhanced oxidative stress and consequent subcellular alterations. In this condition, oxidant-producing enzymes, in particular xanthine oxidase (XO), the major cardiovascular source of reactive oxygen species (ROS), are up-regulated. Growing evidence shows that this impaired oxidative metabolism due to enhanced ROS release is implicated in the development of cardiac hypertrophy, myocardial fibrosis, left ventricular remodelling, and contractility impairment responsible for worsening of cardiac function in CHF. Uric acid (UA) has long been linked with cardiovascular diseases, and hyperuricaemia is a common finding in patients with CHF. Hyperuricaemia is associated with impairment of peripheral blood flow and reduced vasodilator capacity, which relate closely to clinical status and reduced exercise capacity. Recent studies also suggest an association between UA levels and parameters of diastolic function; more importantly, UA has emerged as a strong independent prognostic factor in patients with CHF. In this review, we describe the up-to-date experimental and clinical studies that have begun to test whether the inhibition of XO translates into meaningful beneficial pathophysiological changes. This treatment gives evidence that myocardial energy, endothelial dysfunction, and vasodilator reactivity to exercise are improved by reducing markers of oxidative stress responsible for vascular dysfunction, so it represents an interesting therapeutic alternative for better outcome in CHF patients.

Potential role and mechanisms of subcellular remodeling in cardiac dysfunction due to ischemic heart disease

Several studies have revealed varying degrees of changes in sarcoplasmic reticular and myofibrillar activities, protein content, gene expression and intracellular Ca-handling during cardiac dysfunction due to ischemia-reperfusion (I/R); however, relatively little is known about the sarcolemmal and mitochondrial alterations, as well as their mechanisms in the I/R hearts. Because I/R is associated with oxidative stress and intracellular Ca-overload, it has been indicated that changes in subcellular activities, protein content and gene expression due to I/R are related to both oxidative stress and Ca-overload. Intracellular Ca-overload appears to induce changes in subcellular activities, protein contents and gene expression (subcellular remodeling) by activation of proteases and phospholipases, as well as by affecting the genetic apparatus, whereas oxidative stress is considered to cause oxidation of functional groups of different subcellular proteins in addition to modifying the genetic machinery. Ischemic preconditioning, which is known to depress the development of both intracellular Ca-overload and oxidative stress due to I/R, was observed to attenuate the I/R-induced subcellular remodeling and improve cardiac performance. It is suggested that a combination therapy with antioxidants and interventions, which reduce the development of intracellular Ca-overload, may improve cardiac function by preventing or attenuating the occurrence of subcellular remodeling due to ischemic heart disease. It is proposed that defects in the activities of subcellular organelles may serve as underlying mechanisms for I/R-induced cardiac dysfunction under acute conditions, whereas subcellular remodeling due to alterations in gene expression may explain the impaired cardiac performance under chronic conditions of I/R.

C-reactive protein (CRP)-lowering agents

C-reactive protein (CRP) plays a role in the pathogenesis of cardiovascular disease. It is a marker and predictor of cardiovascular disease. CRP possesses numerous cardiovascular effects (clotting, generation of oxygen radicals, increase in the expression of adhesion molecules and plasminogen activator inhibitor-1, plaque destabilization) that could result in cardiovascular disease. This review describes the effects of various cardiovascular drugs on the levels of CRP in health and disease. Cyclooxygenase inhibitors (aspirin, rofecoxib, celecoxib), platelet aggregation inhibitors (clopidogrel, abciximab), lipid lowering agents (statins, ezetimibe, fenofibrate, niacin, diets), beta-adrenoreceptor antagonists and antioxidants (vitamin E), as well as angiotensin converting enzyme (ACE) inhibitors (ramipril, captopril, fosinopril), reduce serum levels of CRP; while enalapril and trandolapril have not been shown to have the same effect. Angiotensin receptor blockers (ARBs) (valsartan, irbesartan, olmesartan, telmisartan) markedly reduce serum levels of CRP. The findings with other ARBs (losartan and candesartan) were inconsistent. Antidiabetic agents (rosiglitazone and pioglitazone) reduce CRP levels, while insulin is ineffective. Calcium channel antagonists have variable effects on CRP levels. Hydrochlorothiazide and oral estrogen do not affect CRP. The CRP-lowering effect of statins is more pronounced than their lipid lowering effect and is not dependent on their hypolipemic activity. The effect of atorvastatin on CRP seems to be dose-dependent. CRP-lowering effect of statins is likely to contribute to the favorable outcome of statin therapy. The data suggest that lipid lowering agents, ACE inhibitors, ARBs, antidiabetic agents, antiinflammatory and antiplatelet agents, vitamin E, and beta-adrenoreceptor antagonists lower serum or plasma levels of CRP, while vitamin C, oral estrogen and hydrochlorothiazide do not affect CRP levels.

Serum level of uric acid, partly secreted from the failing heart, is a prognostic marker in patients with congestive heart failure

BACKGROUND

A recent study suggested that xanthine oxidase is activated in congestive heart failure (CHF). However, whether uric acid (UA) is secreted from the failing heart remains unknown, so it is currently unclear whether serum UA can provide prognostic information independent of brain natriuretic peptide (BNP).

METHODS AND RESULTS

Serum UA was measured in the aortic root (AO) and the coronary sinus (CS) of 74 patients with CHF. The serum UA level was significantly higher in the CS than in the AO. The transcardiac gradient of UA (CS-AO) increased with the severity of CHF, inversely correlated with left ventricular ejection fraction (LVEF) and positively correlated with left ventricular end-diastolic volume index. The plasma levels of norepinephrine, BNP, UA, and LVEF were monitored prospectively in 150 CHF patients for a mean follow-up of 3 years. High plasma levels of UA (p<0.001) and BNP (p<0.001) were shown by multivariate stepwise analysis to be independent predictors of mortality.

CONCLUSIONS

High plasma UA level, partly secreted from the failing heart, is a prognostic predictor independent of BNP in patients with CHF. Monitoring a combination of BNP and UA may be useful for the management of patients with CHF.

Relaxant effect of oxygen free radicals on rabbit tracheal smooth muscle

We investigated the effect of exogenously generated superoxide anions (O(2)(-)), hydrogen peroxide (H(2)O(2)) and hydroxyl radicals (.OH) on isolated rabbit tracheal smooth muscle suspended in Krebs-Ringer solution. The ability of oxygen free radicals (OFRs) to affect acetyicholine (Ach)-induced contraction in these muscles was also investigated. OFRs, in general, produced a concentration-dependent relaxation of the tracheal smooth muscle in the doses used. However, in large concentrations, O(2)(-) and H(2)O(2) produced effects which were smaller than those obtained with lower concentrations. The relaxant effects of these oxyradicals were progressive and lasted throughout the 20min observation period. At all concentrations used, the OFRs tended to abolish or reduce Ach-induced contraction in a concentration-dependent manner. O(2)(-) was more potent than H(2)O(2) or DHF in relaxing the Ach-precontracted muscle and in inhibiting the response of the muscle to Ach. OFR-induced relaxation of the Ach-contracted muscle was not due to inactivation of the Ach by OFRs. Relaxation produced by OFRs was greater in preparations with intact epithelium than in those denuded of epithelium. The relaxant effects were blocked by indomethacin, a cyclooxygenase inhibitor. OFRs in the presence of indomethacin produced contraction only in the preparations with intact epithelium, suggesting a release of contractile factor(s) from epithelium. These results suggest that OFRs relax rabbit tracheal smooth muscle. The relaxation appears to be mediated through the synthesis and release of prostaglandins from the epithelium and smooth muscles.

Allopurinol improves endothelial dysfunction in chronic heart failure

BACKGROUND

Increased oxidative stress in chronic heart failure is thought to contribute to endothelial dysfunction. Xanthine oxidase produces oxidative stress and therefore we examined whether allopurinol improved endothelial dysfunction in chronic heart failure.

METHODS AND RESULTS

We performed a randomized, placebo-controlled, double-blind crossover study on 11 patients with New York Heart Association class II-III chronic heart failure, comparing 300 mg allopurinol daily (1 month) versus placebo. Endothelial function was assessed by standard forearm venous occlusion plethysmography with acetylcholine, nitroprusside, and verapamil. Plasma malondialdehyde levels were also compared to assess significant changes in oxidative stress. Allopurinol significantly increased the forearm blood flow response to acetylcholine (percentage change in forearm blood flow [mean+/-SEM]: 181+/-19% versus 120+/-22% allopurinol versus placebo; P=0.003). There were no significant differences in the forearm blood flow changes between the placebo and allopurinol treatment arms with regard to sodium nitroprusside or verapamil. Plasma malondialdehyde was significantly reduced with allopurinol treatment (346+/-128 nmol/L versus 461+/-101 nmol/L, allopurinol versus placebo; P=0.03), consistent with reduced oxidative stress with allopurinol therapy.

CONCLUSIONS

We have shown that allopurinol improves endothelial dysfunction in chronic heart failure. This raises the distinct possibility that allopurinol might reduce cardiovascular events and even improve exercise capacity in chronic heart failure.

Plasma oxidized low-density lipoprotein as a prognostic predictor in patients with chronic congestive heart failure

OBJECTIVES

The aim of this study was to evaluate the relationship between plasma oxidized low-density lipoprotein (oxLDL), a marker of oxidative stress, and the prognosis of patients with chronic congestive heart failure (CHF).

BACKGROUND

Oxidative stress appears to play a role in the pathophysiology of CHF. We have recently reported the usefulness of plasma oxLDL as a marker of oxidative stress in CHF patients with dilated cardiomyopathy.

METHODS

We measured the plasma level of oxLDL by sandwich enzyme-linked immunosorbent assay using a specific monoclonal antibody against oxLDL in 18 age-matched normal subjects and in 84 patients with chronic CHF (New York Heart Association functional class II to IV) and monitored them prospectively for a mean follow-up period of 780 days.

RESULTS

Plasma oxLDL level was significantly higher in severe CHF patients than in control subjects and mild CHF patients. A significant negative correlation existed between the plasma level of oxLDL and left ventricular ejection fraction (LVEF) and a significant positive correlation between the plasma level of oxLDL and plasma norepinephrine level. Twenty-six patients had cardiac events; 14 had cardiac death and 12 were hospitalized for heart failure or other cardiovascular events. Among 10 variables including LVEF and neurohumoral factors, only high plasma levels of brain natriuretic peptide and oxLDL were shown to be independent predictors of mortality.

CONCLUSIONS

These results indicate that the plasma level of oxLDL is a useful predictor of mortality in patients with CHF, suggesting that oxidative stress plays an important role in the pathophysiology of CHF.

Reactive oxygen species and endotoxic shock: effect of dimethylthiourea

The effects of endotoxemia on the cardiac function and contractility, oxygen radical production by polymorphonuclear leukocytes (PMNL-CL), cardiac antioxidant reserve (LV-CL), antioxidant enzymes (superoxide dismutase [SOD], catalase, glutathione peroxidase [GSH-P(X)]) and malondialdehyde (MDA); and plasma creatine kinase (CK) and lactate in the absence or presence of dimethylthiourea (DMTU), an antioxidant, in anesthetized dogs were studied. Dogs were assigned to three groups: group 1, control; group II, endotoxin (ET) (5 mg/kg body wt intravenously), and group III, ET + DMTU (500 mg/kg intravenously). ET produced decreases in the cardiac function and contractility, antioxidant reserve, antioxidant enzymes; and increases in PMNL-CL, cardiac MDA, plasma CK, and lactate. Pretreatment with DMTU attenuated the ET-induced cardiac dysfunction and changes in the cardiac MDA, antioxidant reserve, and antioxidant enzymes, PMNL-CL, and plasma CK and lactate levels. These results suggest that reactive oxygen species may be involved in the deterioration of cardiac function and contractility, and cellular injury during endotoxic shock and that antioxidants may be of value in the treatment of endotoxic shock.

Relationship between tumor necrosis factor-alpha production and oxidative stress in the failing hearts of patients with dilated cardiomyopathy

OBJECTIVES

This study evaluated oxidative stress in the failing ventricle in patients with dilated cardiomyopathy (DCM).

BACKGROUND

Oxidative stress appears to increase in the failing myocardium and may contribute to ventricular dysfunction in patients with DCM. Tumor necrosis factor-alpha (TNF-alpha), which is expressed in the failing heart, may stimulate oxidative stress.

METHODS

We measured plasma oxidized low density lipoprotein (oxLDL) by sandwich enzyme-linked immunosorbent assay using specific antibodies against oxLDL in the aortic root (AO) and the coronary sinus (CS) in control subjects (n = 8) and in 22 patients with DCM and mild congestive heart failure. We also measured the plasma levels of TNF-alpha and angiotensin II.

RESULTS

There was no difference in oxLDL between the AO and CS in control subjects. In contrast, plasma oxLDL was significantly higher in the CS than the AO in patients with DCM, suggesting that the transcardiac gradient ofoxLDL reflects oxidative stress in the failing heart in these patients. Plasma TNF-alpha levels were significantly higher in the CS than the AO with a significant positive correlation of the transcardiac gradient of TNF-alpha and the transcardiac gradient of oxLDL. Moreover, a significant negative correlation existed between the transcardiac gradient of oxLDL and left ventricular ejection fraction. The transcardiac gradient of plasma oxLDL was significantly lower in 6 patients who received carvedilol than in 16 patients who did not receive carvedilol.

CONCLUSIONS

These findings indicate that the transcardiac gradient of oxLDL may be a marker of oxidative stress in the heart and that left ventricular dysfunction may be partly due to the oxidative stress in patients with DCM. In addition, TNF-alpha may stimulate oxidative stress in the failing heart in patients with DCM.

The effects of trimetazidine on heart rate variability and signal-averaged electrocardiography in early period of acute myocardial infarction

BACKGROUND

Acute myocardial infarction (AMI) is accompanied by electrophysiological changes in cardiovascular system as well as those in autonomic cardiac control. Heart rate variability (HRV) is depressed due to increased sympathetic activity and/or decreased parasympathetic activity following AMI. Moreover, the frequency of ventricular late potentials (VLP) is increased due to the electrophysiological changes. Based on the hypothesis that the treatments increasing HRV and decreasing the frequency of VLP can improve the prognosis of AMI, we investigated the short-term effects of trimetazidine (TMZ) on HRV and VLP in patients with AMI.

METHODS

The study group consisted of 64 patients (men 49, mean age 55+/-12 years, range 26-70) suffering from first Q-wave AMI. Thirty-one of them were treated with conventional therapy (thrombolytic therapy, aspirin, beta-blocker, heparin and intravenous nitroglycerin) plus TMZ 20 mg tid. The remaining 33 patients served as controls. Holter monitorization between 24 and 48 h, echocardiography at average day 6 (range 4-7 days) and SAECG and sub-maximal exercise at average day 7 (range 6-9 days) were performed to all patients.

RESULTS

While HRV parameters reflecting parasympathetic activity (SDSD: 43+/-16 ms-35+/-13 ms, RMSSD: 34+/-14 ms-27+/-8 ms, HF: 7.8+/-5 ms(2) -4.3+/-4 ms(2), P<0.05) were of significantly higher levels in TMZ group, the low frequency component mainly reflecting sympathetic activity (LF: 10+/-6 ms(2)-10+/-5 ms(2), P>0.05) was similar in both groups. In addition, LF/HF ratio showing sympatho-vagal balance was significantly decreased in TMZ group (1.5-3.0, P=0.005). About VLP, the mean FQRS (105+/-8 ms-107+/-10 ms), LAS (28+/-10 ms-30+/-11 ms) and RMS-40 (34+/-15 microV-41+/-12 microV) were not different in both two groups (P>0.05).

CONCLUSION

Our results suggest that TMZ treatment causes changes in sympatho-vagal balance in favor of vagal activity by increasing parasympathetic activity in AMI at early period; however, no effect on VLP was observed.

Changes in cardiac dimensions and indices of cardiac function during deconditioning in horses

OBJECTIVE

To investigate the effects of deconditioning on cardiac dimensions and indices of cardiac function in horses.

ANIMALS

Thirteen 3-to 4-year-old Standardbred geldings.

PROCEDURE

All horses had echocardiographic measurements performed at the conclusion of 9 months of intense training and at weeks 1.5, 4, 8, and 12 of deconditioning. Direct echocardiographic measurements included interventricular septal thickness, left ventricular internal dimensions, left ventricular freewall thickness, left atrial dimension, aortic diameter, diameter of the pulmonary artery, slopes of the mitral valve, heart rate, preejection period, and ejection time. Derived indices of cardiac function included fractional shortening, fractional area change, and cardiac output.

RESULTS

Cardiac dimensions did not change significantly for the first 4 weeks of deconditioning but decreased significantly by week 8 and continued to decrease until week 12. Indices of cardiac function increased significantly during the first 10 days of deconditioning, remaining stable until week 4 of deconditioning. After week 4, indices of cardiac function decreased significantly until week 12.

CONCLUSIONS AND CLINICAL RELEVANCE

Deconditioning resulted in a general reduction in cardiac dimensions and indices of cardiac function over 12 weeks. However, results of the study reported here indicate that following an intense period of training, cardiac function may be maintained during the first 4 weeks of deconditioning. Results indicate that trained horses may rest for up to 4 weeks without a substantial reduction in cardiac capacity as reflected by echocardiographic indices.

Oxidative stress and the pathogenesis of heart failure

There is strong evidence for an adverse role of oxidative stress in CHF in both animals and humans. Antioxidant supplement have been very effective in the treatment of animal paradigms; however, the data for the possible benefits of treatment for patients with CHF is either retrospective or inferential. Such information is important and should be the subject of prospective randomized trials.

Association of high plasma antioxidant capacity with new lesion formation in carotid atherosclerosis: a prospective study

BACKGROUND

In atherosclerosis, both reductions and elevations in plasma levels of antioxidants have been reported. This study investigated total antioxidant capacity of plasma from subjects with atherosclerotic disease.

MATERIALS AND METHODS

The study population consisted of 48 men with or without carotid atherosclerosis. At baseline (1990) carotid arteries were evaluated by duplex sonography and plasma samples were obtained for testing antioxidant capacity by two different test systems. One assay system used neutrophils from healthy volunteers as a source of oxygen free radicals activating the non-fluorescent dichlorofluorescin diacetate in the presence of antioxidant containing plasma from study subjects. In the other test system, total plasma antioxidants were detected colorimetrically by using 2,2'-azino-di-(3-ethylbenzthiazoline sulphonate), metmyoglobin and superoxide in the presence of plasma. Carotid arteries were re-evaluated for the development of new plaques 5 years later (1995).

RESULTS

Increased baseline total antioxidant capacity of plasma was significantly associated with the development of new atherosclerotic lesions during a period of 5 years.

CONCLUSIONS

Endogenous antioxidant capacity of plasma is increased in patients with active atherosclerotic disease. As scavenging of oxygen free radicals is thought to protect from atherogenesis, elevated antioxidative capacity may represent an adaptive mechanism.

Oxygen Free Radicals and Endotoxic Shock: Effect of Flaxseed

BACKGROUND: Cardiac dysfunction and tissue injury during endotoxemia may be caused by increased levels of oxygen free radicals. METHODS AND RESULTS: We therefore investigated the effects of endotoxic shock on cardiac function and contractility, plasma creatine kinase (CK) activity and lactate concentration, oxyradical-producing activity of polymorphonuclear leukocytes (PMNL-CL) and white blood corpuscles, antioxidant reserve (cardiac chemiluminescence [LV-CL]), antioxidant enzyme activity (superoxide dismutase, catalase, glutathione peroxidase), cardiac malondialdehyde (MDA) concentration, a lipid peroxidation product, and hemodynamics in the absence or presence of flaxseed treatment in anesthetized dogs. Flaxseed contains lignans that have antioxidant activites and inhibit platelet-activating factor (PAF). The dogs were assigned to three groups: group I, sham control; group II, endotoxin (ET) treated (5 mg/kg intravenously); group III, ET + flaxseed (2 gm/kg/day orally) for 6 days. ET produced a decrease in cardiac function and contractility and antioxidant enzyme levels, and an increase in cardiac MDA and LV-CL, PMNL-CL, and plasma CK and lactate. Pretreatment with flaxseed attenuated the ET-induced cardiac dysfunction and cellular damage. Protection was incomplete for cardiovascular function, plasma CK, and lactate. CONCLUSIONS: These results suggest that oxyradicals and/or PAF may be involved in the deterioration of cardiovascular function and cellular integrity during ET shock and that antioxidant and anti-PAF agents may be effective in the treatment of ET shock.

Attenuation of ischemia--reperfusion injury by enalapril maleat

1. The aim of this study was to investigate the effects of enalapril maleate on ischemia-reperfusion injury of the myocardium, after cardioplegic arrest in isolated guinea pig hearts, in a modified Langendorff model. 2. Animals were subjected to 90 min of normothermic global ischemia, followed by 30 min of reperfusion. Cardioplegic arrest was achieved by administering St. Thomas Hospital cardioplegic solution (STHCS). 3. The hearts were randomly allocated into four groups (n=8 in each group). The first group was utilized as control. In the second group, oral pretreatment was made (0.2 mg/kg enalapril maleat was given twice a day for 10 days). In the third group, enalapril maleat (1 micromol/l) was added to STHCS. In the fourth group, hearts were arrested with enalapril maleat-enriched STHCS, and enalapril maleat-enriched (1 micromol/l) Krebs-Henseleit solution was applied during the reperfusion period. 4. Although the study groups showed better recovery of contractility than did the control group, in the last group, the hearts had the best recovery of left ventricular systolic function, where dp/dt maximum was 89.7+/-6.9% of the preischemic values. Group 1, group 2 and group 3 achieved 44.2+/-4.5%, 79.4+/-5.8% and 68.1+/-6.7% of their preischemic dp/dt values. A similar observation was found for left ventricular developed pressure (LVDP); LVDP values were 52.4+/-2.1% (in group 1), 79.6+/-2.8% (in group 2), 72.8+/-4.6% (in group 3) and 86.7+/-5.8% (in group 4) of control after reperfusion. Creatine kinase leakage was significantly lower and postischemic coronary flows were significantly higher in group 4. 5. We concluded that usage of enalapril maleat in the reperfusion period was more effective for improving myocardial recovery after cardioplegic arrest. The additional protective effects of enalapril maleat not only were by angiotensin-converting-enzyme-inhibition-dependent coronary vasodilation and thiol-dependent limitation of oxidative injury, but could also be related to an oxygen-free-radical-scavenging effect.

Cardiac protein phosphorylation: functional and pathophysiological correlates

Protein phosphorylation acts a pivotal mechanism in regulating the contractile state of the heart by modulating particular levels of autonomic control on cardiac force/length relationships. Early studies of changes in cardiac protein phosphorylation focused on key components of the excitation-coupling process, namely phospholamban of the sarcoplasmic reticulum and myofibrillar troponin I. In more recent years the emphasis has shifted towards the identification of other phosphoproteins, and more importantly, the delineation of the mechanistic and signaling pathways regulating the various known phosphoproteins. In addition to cAMP- and Ca(2+)-calmodulin-dependent kinase processes, these have included regulation by protein kinase C and the ever-emerging family of growth factor-related kinases such as the tyrosine-, mitogen- and stress-activated protein kinases. Similarly, the role of protein dephosphorylation by protein phosphatases has been recognized as integral in modulating normal cardiac cellular function. Recent studies involving a variety of cardiovascular pathologies have demonstrated that changes in the phosphorylation states of key cardiac regulatory proteins may underlie cardiac dysfunction in disease states. The emphasis of this comprehensive review will be on discussing the role of cardiac phosphoproteins in regulating myocardial function and pathophysiology based not only on in vitro data, but more importantly, from ex vivo experiments with corroborative physiological and biochemical evidence.

Beneficial effect of captopril against ischaemia-reperfusion injury in isolated guinea pig hearts

The study was designed to clarify whether captopril, an angiotensin-coverting enzyme inhibitor, will reduce the injury of global ischaemia and reperfusion after cardioplegic arrest in isolated guinea pig hearts, in a modified Langendorff model. The hearts were randomly allocated into four groups (n = 10 in each) and subjected to 90 min of normothermic global ischemia, followed by 30 min of reperfusion; in all groups, cardioplegic arrest was achieved by administering St. Thomas's Hospital cardioplegic solution (STHCS). The first group was utilized as the control group. In the second group, captopril (200 mumol/L) was added to STHCS. In the third group, oral pretreatment was carried out (0.3 mg/kg captopril was given twice a day for 10 days). In the fourth group, oral pretreatment was achieved and captopril-enriched solution was applied in the first 5 min of reperfusion. Although the study groups showed better recovery of contractility than the control group, in the fourth group the hearts had the best left ventricular contractile function, where contractile force (g contractility/g heart weight) was 55.4% +/- 3.8% of the preischameic values. Groups I, II, and III achieved 31.0% +/- 3.2%, 41.6% +/- 3.8%, and 48.3% +/- 3.9% of their preischaemic contractile force values. Creatine kinase leakage was significantly lower and postischaemic coronary flows, too, were significantly higher in the fourth group. Coronary flow after reperfusion increased from 48.5 +/- 6.7 to 65.2 +/- 7.1 ml/min g heart in group 4 (p < 0.05). Myocardial lipid peroxides and glutathione contents showed that there was a correlation between the depletion of myocardial glutathione content and increased lipid peroxidation. These preliminary results showed that: the addition of captopril to reperfusion solution and oral preconditioning improved post-ischameic myocardial function and decreased myocardial injury.

Mechanisms of hydrogen peroxide-induced contraction of rat aorta

It has been suggested that reactive oxygen species may be involved in the regulation of vascular tone. However, the underlying mechanisms remain to be elucidated. The present studies were designed to investigate the contractile effects of hydrogen peroxide (H2O2), one of the reactive oxygen species, on isolated ring segments of rat aorta with and without endothelium. H2O2 induced an endothelium-independent contraction in isolated rat aorta ring segments in a concentration-dependent manner at concentrations from 5 x 10(-6) to 5 x 10(-3) M. H2O2-induced contractions of denuded rat aorta rings were stronger than those on intact rat aorta segments. The contractile effects of H2O2 were inhibited completely by 1200 u/ml catalase. The presence of 1.0 microM Fe2+ or 10 microM proadifen, a cytochrome P450 monooxygenase inhibitor, potentiated the contractile effect of H2O2 on isolated rat aorta segments. 1 mM deferoxamine (a Fe2+ chelator) or 100 microM dimethyl sulfoxide (a hydroxyl radical scavenger) significantly attenuated the vessel contractions induced by hydrogen peroxide plus Fe2+ or hydrogen peroxide itself. Removal of extracellular Ca2+ ([Ca2+]0), addition of 5 microM verapamil, administration of a protein kinase C inhibitor (staurosporine), treatment with an inhibitor of protein tyrosine phosphorylation (genistein) or employment of 5.0 microM indomethacin resulted in a significant attenuation of the contractile responses of the vessels to H2O2. Pharmacological antagonists (e.g. a muscarinic acetylcholine receptor antagonist (atropine), an antagonist of histamine H1 receptors (diphenhydramine), an antagonist of histamine H2 receptors (cimetidine), an alpha-adrenoceptor antagonist (phentolamine), a beta-adrenoceptor antagonist (propranolol) and an antagonist of serotonin receptor (methysergide)) did not inhibit or attenuate the contractions induced by H2O2. Exposure of primary aortic smooth muscle cells to H2O2 (5 x 10(-6) to 5 x 10(-3) M) produced significant rises of intracellular Ca2+ ([Ca2+]i) within 20 s. Employment of 1.0 microM Fe2+ markedly enhanced the increment in [Ca2+]i in the smooth muscle cells. 10 microM proadifen treatment failed to alter the hydrogen peroxide-induced increment in [Ca2+]i of the smooth muscle cells. However, the presence of 5 microM indomethacin significantly attenuated the rise in [Ca2+]i in smooth muscle cells. The present results suggest that H2O2 can induce contractions of rat aorta segments, at pathophysiological concentrations, which are Ca2+-dependent. Hydroxyl radicals (.OH), cyclooxygenase products, protein kinase C and products of protein tyrosine phosphorylation appear to play some role in hydrogen peroxide-induced contractions. Metabolites catalyzed by cytochrome P450-dependent enzymes (upon treatment with hydrogen peroxide) appear to exert a vasodilator effect on rat aorta segments. Lastly, some unidentified mediators, produced by a cytochrome P450 inhibitor (proadifen), during hydrogen peroxide treatment, appear to play some role in contraction of vascular smooth muscle of rat aorta segments in vitro.

Progressive bradycardia, a possible factor in the pathogenesis of ascites in fast growing broiler chickens raised at low altitude

1. The first objective was to evaluate baseline heart rate (HR) responses in fast growing broilers fed ad libitum from 1 to 45d or subjected to a food restriction (85%, 70% and 55% of ad libitum from 7 to 21d) and a refeeding (22 to 45d) regimen in a normal thermal environment. The second was to evaluate HR and haematocrit responses in fast growing broilers reared at a low environmental temperature and fed ad libitum (A-L) from 1 to 42d, subjected to food restriction (70% ad libitum) between 7 to 21d and refed thereafter (R-R), or subjected to food restriction between 7 to 42d (R), and to follow the changes in normal birds and those prone to ascites. 2. The baseline HR in the normal thermal environment at 21 and 45d in birds fed ad libitum was lower (P < 0.001) than at 7d. The food-restricted groups had higher HRs at 21d than at 7d, with the differences significant (P < 0.01) for the 70% and 55% treatments. At 21d the HRs in restricted groups were significantly higher (P < 0.01) than in ad libitum-fed birds. After returning to ad libitum feeding the HRs in these birds tended to decline, with the differences significant (P < 0.05) for the 70% and 55% treatments. 3. In the birds exposed to cold, each feeding regimen produced distinct patterns of change in HR and haematocrit. Both feeding regimen and age had significant (P < 0.001) effects on the changes of both variables. Relative to 7d, on 14d and 21d the HRs decreased and haematocrits increased in all groups, but the rates of change were highest in the A-L and R-R birds. The first fulminant cases of ascites were observed during the third week in the A-L group and during the fourth week in the R-R group. None of the chickens from the R group developed ascites. Altogether, the incidence of ascites was 48% in the A-L group and 28% in the R-R group. 4. Among the birds exposed to cold, the ascitic birds had significantly (P < 0.001) lower HRs and higher haematocrits than normal birds from the same feeding regimen group. The time trends in the rates of change in HR and haematocrit were distinctly different (P < 0.001) for ascitic and normal birds. The change in feeding regimen from restricted to ad libitum in the R-R group resulted in a significant (P < 0.001) decrease in HR and increase in haematocrit. 5. In view of the evidence presented, it appears that hypoxaemia and tissue hypoxia in broiler chickens may be a result of circulatory insufficiency associated with progressive bradycardia rather than, as commonly believed, pulmonary insufficiency. In this situation the pulmonary hypertension may be a secondary symptom.

Effects of trimetazidine on heart rate variability and left ventricular systolic performance in patients with coronary artery disease after percutaneous transluminal angioplasty

Fifty-one patients (mean age 51.6 +/- 7.1 years) with angiographically proven coronary artery disease (CAD) entered the study. In 26 patients (Group I), trimetazidine treatment started twenty-four hours after percutaneous transluminal coronary angioplasty (PTCA). Another 25 patients (Group II) without trimetazidine treatment were kept as controls. The groups were comparable by age, gender, risk factors of CAD, coronary anatomy, left ventricular performance, and heart rate variability indices at baseline state. Power spectral analysis of heart rate variability and two-dimensional and Doppler echocardiographic examinations were performed before PTCA, and twenty-four hours, ten days, thirty days, and three months after PTCA. A statistically significant improvement of left ventricular systolic performance (P < 0.001), augmentation of the parasympathetic band of heart rate variability (P < 0.001), and decline of P1/P2 ratio (P < 0.01) were evident in patients treated with trimetazidine, while no apparent changes were observed in controls. The intergroup analysis also showed marked difference between groups as recorded on the day 30 and month 3 of observation (P < 0.001). During follow-up period recurrences of angina pectoris and ischemia were registered in Group II, while no evidence of ischemia was discerned in Group I patients. In conclusion, trimetazidine modulates the autonomic control of heart rate, ie, reduces sympathetic overactivity and augments vagal influences, improves left ventricular contractility, and diminishes the clinical manifestations of ischemia in patients with CAD after PTCA.

Mechanism of hydroxyl radical-induced modulation of vascular tone

We investigated the effects of hydroxyl radicals (OH) generated by a .OH-generating system (dihydroxyfumarate [DHF], adenosine diphosphate [ADP], and FeCl3) on isolated rabbit aorta suspended in Krebs-Ringer solution. The .OH-generating system produced a concentration-dependent generation of .OH. .OH relaxed rabbit aorta and norepinephrine (NE)-precontracted aorta in a concentration-dependent manner. Mannitol completely prevented this relaxation. Relaxation was completely absent in preparations denuded of endothelium. The relaxant effect was reduced by 62% by an inhibitor of nitric oxide synthesis (NG-monomethyl-L-arginine), by 58% by an inhibitor of guanylate cyclase (methylene blue), by 48% by an inhibitor of cyclooxygenase (indomethacin), and by 83% by an adenosine triphosphate (ATP)-sensitive K+ channel blocker (glyburide). The inhibition of .OH-induced relaxation by a combination of indomethacin, methylene blue, and glyburide was not greater than by each of the individual agents. These results indicate that .OH produces a relaxation of the aorta that is completely endothelium-dependent and is partly mediated by an endothelium-derived relaxing factor (nitric oxide), vasodilatory arachidonic acid metabolites, and an ATP-sensitive K+ channel.

Oxy free radical system in heart failure and therapeutic role of oral vitamin E

Twenty patients of heart failure and ten matched healthy controls were included in the trial. Out of these 20 patients of heart failure, 12 patients were also studied prospectively. Plasma levels of superoxide anion and malonyldialdehyde were increased while the levels of superoxide dismutase, catalase and glutathione reductase were decreased in patients of heart failure as compared to control subjects. The alteration in oxidative stress and antioxidant system did not correlate with the age and sex of patients or the etiology of heart failure. With the increasing severity of heart failure the malonyldialdehyde and superoxide anion increased significantly and catalase, glutathione reductase and superoxide dismutase levels decreased. The group of heart failure patients with ejection fraction < 40% (n = 7) exhibited significantly higher levels of malonyldialdehyde than those with an ejection fraction > 40% (n = 13). The superoxide anion and malonyldialdehyde levels were significantly higher in patients of heart failure in the pre-treatment state as compared to those in post-treatment state. Conversely catalase, glutathione reductase and superoxide dismutase were higher in the post-treatment period as compared to their values before treatment. The addition of vitamin E in doses of 400 mg once a day orally for 4 weeks significantly reduced the malonyldialdehyde and superoxide anion levels and produced an elevation of the antioxidant enzymes. Thus, there is an apparent normalisation of the indices of oxidative stress following treatment of heart failure and a markedly improved response on vitamin E supplementation which may be more beneficial.

Effect of pharmacological interventions in the prevention of lipid peroxidation and respiratory depression induced by oxygen free radicals in anesthetized rats

We have recently reported that in an anesthetized rat model, generation of oxygen free radicals (OFR) via i.v. administration of Xanthine plus Xanthine Oxidase [X + XO] resulted in death of about 90% of the animals within a 120-min observation period. Pretreatment of the rats with endogenous scavengers Superoxide Dismutase and Catalase, or with felodipine, a dihydropyridine calcium channel blocker, and/or with dopexamine, an agonist of beta 2 adrenoceptors as well as dopamine (DA-1) receptors significantly enhanced the survival rate to over 70%. The present study was designed to investigate whether lipid peroxidation and ensuing respiratory depression contributed to the lethal toxicity of the free radicals. In the control group, the death of the rats administered [X + XO] was proceeded by significant increases in the plasma lipid peroxides (PLP) and by a severe hypertensive response characteristic of an intense ischemic state, which was confirmed by the presence of hypercapnia, hypoxemia, and acidosis. Placement of the animals on the positive pressure ventilation prior to the administration of [X + XO] did not prevent increases in PLP but, prevented any adverse alterations in the respiratory markers and significantly enhanced survival rate up to 70%. In contrast, both felodipine as well as dopexamine prevented any increases in PLP, normalized blood gas profile, and significantly increased survival rate to 80 to 90%. These observations suggest that the lethal toxicity produced by oxygen free radical was due to respiratory distress. The relationship between increases in the PLP and respiratory depression and the mechanisms via which two pharmacologically distinct agents, felodipine and dopexamine, facilitated the salutary effects cannot be conclusively stated at this time. It is further suggested that although the doses of these two drugs employed in the present studies are not adequate to function as antioxidants, such a possibility cannot be entirely ruled out.

Mediation of H2O2-induced vascular relaxation by endothelium-derived relaxing factor

We investigated the effects of H2O2 generated by glucose (G) and glucose glucose oxidase (GO) on the isolated rabbit aorta suspended in Krebs-Ringer solution. H2O2 produced contraction in small concentration and relaxation followed by contraction in large concentration. Contraction produced by large concentration was smaller than that produced by small concentration of H2O2. Relaxation was prevented by deendothelialization or NG-monomethyl-L-arginine, an inhibitor of nitric oxide synthesis. These results suggest that H2O2 in large concentrations produces relaxation followed by contraction, and that the relaxation is endothelium-dependent and is mediated by nitric oxide, an endothelium-derived relaxing factor.

Pretreatment with antioxidants and allopurinol diminishes cardiac onset events in coronary artery bypass grafting

Oxygen-derived free radicals constitute one part of the etiologic factors for cardiac onset harmful events. Allopurinol is able to reduce the generation of free radicals. Vitamins E and C scavenge radicals after their formation. Eighty-one patients with coronary artery disease were randomized into four study groups: Group 1 (n = 20) patients had stable disease and received oral vitamin E for 4 weeks, and vitamin C and allopurinol 2 days before and 1 day after coronary artery bypass grafting. Group 2 (n = 25) consisted of their controls. Group 3 patients (n = 17) had more unstable disease and received the same medications as group 1, except that vitamin E was given only 2 days before the operation. Group 4 (n = 19) was their controls. Groups 1 and 3 had fewer ischemic electrocardiographic events and required less dopamine perioperatively than corresponding control groups 2 and 4. Group 3 had fewer perioperative infarctions and less creatine kinase-MB release than the respective controls (group 4). Plasma levels of vitamins E and C, urate, and total free radical trapping ability were considered to support the theory about the role of free radicals in reperfusion injury. Especially the unstable patients, but also patients with stable coronary artery disease requiring coronary artery bypass grafting benefit from perioperative allopurinol and vitamin E and C treatment.

Beneficial effects of antioxidants in hemorrhagic shock

The present study was undertaken to investigate the role of endogenous hydrogen peroxide (H2O2) in cardiac depression and cytotoxicity during hemorrhagic shock and reinfusion. To achieve this objective, the changes in the cardiac function and contractility, plasma creatine kinase (CK) and CK-MB activity and lactate concentration, oxyradical-producing activity of polymorphonuclear leukocytes (PMNL-CL), and cardiac malondialdehyde (MDA) concentration in anesthetized dogs were determined before and during shock and reinfusion in the presence of absence of catalase (a metabolizer of H2O2). The dogs were divided into three groups randomly. Group I: sham, four hour duration; group II: two hours of shock followed by two hours of reinfusion; group III: same as group II but pretreated with catalase. Hemorrhage shock was produced in the dogs by lowering the mean arterial pressure to 50 +/- 5 mm Hg by bleeding into standard blood bank bags containing 63 mL of citrate, phosphate, dextrose, and adenine (CPDA) anticoagulant for 450 mL of blood. The shock was maintained for two hours by bleeding or reinfusing the shed blood as needed. Cardiac function and contractility were depressed while plasma CK, CK-MB, and lactate increased during shock. Reinfusion after two hours of shock tended to return hemodynamic parameters and plasma lactate levels toward control values. Plasma CK and CK-MB and PMNL-CL increased further. Cardiac MDA content also increased after shock and reinfusion, suggesting oxidative damage. Pretreatment with catalase attenuated the deleterious effects of shock and reinfusion on the cardiovascular function and contractility, and the rise in plasma CK, CK-MB, and lactate, PMNL-CL, and cardiac MDA. However, the protection with catalase was not complete. These results suggest that hydrogen peroxide (H2O2) may partly be involved in the deterioration of cardiovascular function and cellular injury during hemorrhagic shock and reinfusion.