Antioxidants and atherosclerotic heart disease

Dietary cosupplementation with vitamin E and coenzyme Q(10) inhibits atherosclerosis in apolipoprotein E gene knockout mice

Intimal oxidation of LDL is considered an important early event in atherogenesis, and certain antioxidants are antiatherogenic. Dietary coenrichment with vitamin E (VitE) plus ubiquinone-10 (CoQ(10), which is reduced during intestinal uptake to the antioxidant ubiquinol-10, CoQ(10)H(2)) protects, whereas enrichment with VitE alone can increase oxidizability of LDL lipid against ex vivo oxidation. In the present study, we tested whether VitE plus CoQ(10) cosupplementation is more antiatherogenic than either antioxidant alone, by use of apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet without (control) or with 0.2% (wt/wt) VitE, 0.5% CoQ(10), or 0.2% VitE plus 0.5% CoQ(10) (VitE+CoQ(10)) for 24 weeks. None of the supplements affected plasma cholesterol concentrations, whereas in the VitE and CoQ(10) groups, plasma level of the respective supplement increased. Compared with control, plasma from CoQ(10) or VitE+CoQ(10) but not VitE-supplemented animals was more resistant to ex vivo lipid peroxidation induced by peroxyl radicals. VitE supplementation increased VitE levels in aorta, heart, brain, and skeletal muscle, whereas CoQ(10) supplementation increased CoQ(10) only in plasma and aorta and lowered tissue VITE: All treatments significantly lowered aortic cholesterol compared with control, but only VitE+CoQ(10) supplementation significantly decreased tissue lipid hydroperoxides when expressed per parent lipid. In contrast, none of the treatments affected aortic ratios of 7-ketocholesterol to cholesterol. Compared with controls, VitE+CoQ(10) supplementation decreased atherosclerosis at the aortic root and arch and descending thoracic aorta to an extent that increased with increasing distance from the aortic root. CoQ(10) significantly inhibited atherosclerosis at aortic root and arch, whereas VitE decreased disease at aortic root only. Thus, in apoE-/- mice, VitE+CoQ(10) supplements are more antiatherogenic than CoQ(10) or VitE supplements alone and disease inhibition is associated with a decrease in aortic lipid hydroperoxides but not 7-ketocholesterol.

Phenolic antioxidants trolox and caffeic acid modulate the oxidized LDL-induced EGF-receptor activation

Oxidized low density lipoproteins (oxLDL) are thought to play a major role in atherosclerosis. OxLDL act in part through alteration of intracellular signalling pathways in cells of the vascular wall. We recently reported that the EGF receptor (EGFR) signalling pathway is activated by lipid peroxidation products (among them 4-hydroxynonenal, 4-HNE) contained in oxLDL. The use of phenolic antioxidants, such as trolox, alpha-tocopherol, caffeic acid and tyrphostins A-25, A-46 or A-1478, showed that the oxLDL-induced EGFR activation is constituted by two separate components, the first (early) one being antioxidant-insensitive, the second (late) being antioxidant-sensitive. 4-HNE derivatization of EGFR and EGFR activation induced by exogenous 4-HNE, suggest that the early (0.5 - 3 h) component of oxLDL-induced EGFR activation is mediated (at least in part) by 4-HNE (and possibly by other oxidized lipids). This early component is antioxidant-insensitive. The second component (4 - 5 h) of the oxLDL-induced EGFR activation is antioxidant-sensitive, since it is blocked by antioxidants such as trolox, caffeic acid or PDTC, which act by blocking the cellular oxidative stress (H(2)O(2) generation) evoked by oxLDL. Conversely, exogenous H(2)O(2) induced EGFR autophosphorylation (thus mimicking the second component) and was also inhibited by antioxidants. This effect is mediated in part through inhibition by oxidative stress of protein tyrosine phosphatases involved in EGFR dephosphorylation.

Dietary habits and cardiovascular risk in the Spanish population: the DRECE study (II) micronutrient intake. Dieta y Riesgo de Enfermedades Cardiovasculares en España

OBJECTIVE

To evaluate the dietary micronutrient intake in the adult Spanish population participating in the DRECE study.

METHODS

The cross-sectional study was performed in two stages in 1991 and 1996 in 43 primary care clinics. One thousand two hundred people 'with cardiovascular risk' and 600 'without risk' answered a food frequency questionnaire.

RESULTS

Significant increases in vitamin C, retinol, lycopenes, beta-cryptoxanthin and vitamin E intakes were found. Vitamin A, alpha-carotenoid and lutein intakes decreased. Vitamin B(12), B(6) and folic acid intakes increased in people with cardiovascular risk, whereas only the last two increased in the control group. Nearly 100% of the people consumed the recommended dietary allowances for vitamins B(12) and B(6) and >70% for folic acid. Calcium, iron, and zinc intake increased in both groups, but magnesium and selenium intake increased only in people at risk. Vitamin A, B(1) and zinc intakes have decreased, and >50% of the people do not consume the recommended dietary allowance.

CONCLUSION

Antioxidant vitamins and vitamin B(12), B(6) and folic acid intakes seem to be adequate in the adult Spanish population, no significant differences appear regarding their cardiovascular risk status. Vitamin A, B(1) and zinc intakes are not appropriate.

The role of protein kinase C in the development of the complications of diabetes

Diabetes mellitus produces a state of chronic hyperglycemia which in turn leads to the development of severe complications including retinopathy, nephropathy, neuropathy, and atherosclerosis. Many different mechanisms have been put forward to attempt to explain how glucose elevations can damage these various organ systems. Protein kinase C activation is one of the sequelae of hyperglycemia and is thought to play a role in the development of diabetic complications. There are multiple mechanisms for its activation in the diabetic state and multiple downstream effects attributable to that activation. The role of protein kinase C activation in the development of the above-mentioned complications of diabetes is discussed in this chapter. In addition, the potential use of isoform-specific inhibitors of protein kinase C for the treatment of diabetic complications is proposed.

Vitamin E and macrophage cyclooxygenase regulation in the aged

Aging is associated with increased evidence of cardiovascular disease (CVD). Atherosclerosis, a major cause of CVD, is an inflammatory process whose development is influenced by several proinflammatory mediators. Products of arachidonic acid metabolism, in particular, prostaglandin (PG) E(2) and thromboxane (TX) A(2), play an important role in the development of atherosclerosis. We showed previously that the aged have higher PGE(2) production compared with their young counterparts. This age-associated increase in PGE(2) production is mainly a consequence of increased cyclooxygenase (COX) activity. We demonstrated further that increased COX activity in old mice is due to the increased expression of mRNA and protein for the inducible form of COX, COX-2. Vitamin E has been shown to reduce PGE(2) production and risk of CVD. In aged mice, we showed that a vitamin E-induced decrease in PGE(2) production is due to decreased COX activity. However, vitamin E had no effect on COX mRNA and protein levels, indicating a post-translational regulation of COX by vitamin E. Further experiments indicated that vitamin E decreases COX activity through reducing formation of peroxynitrite, a hydroperoxide shown to be involved in the activation of COX-2. Other homologues of tocopherols were also effective in inhibiting COX activity, but their degree of inhibition varied. The varied potency to inhibit COX activity was not explained totally by differences in their antioxidant capacity. Vitamin E-induced inhibition of COX activity might contribute to its effect of reducing CVD risk.

Free radical production by antibiotic-killed bacteria in the guinea pig middle ear

OBJECTIVES

Oxygen free radicals are implicated in the pathogenesis of otitis media Recent investigations with animal models have demonstrated that free radical-mediated damage of the middle ear mucosa, measured as lipid hydroperoxide, occurs when the middle ear cavity is inoculated with Streptococcus pneumoniae. The present study was conducted to examine the effect of antibiotics on free radical-mediated damage in pneumococcal acute otitis media.

STUDY DESIGN

Animal model of acute otitis media.

METHODS

Seventy-eight guinea pigs underwent bilateral middle ear inoculation with 100 microl of 1) sterile saline as a control, 2) 50 microg/mL amoxicillin, 3) 10(7) colony forming units (CFU)/mL Streptococcus pneumoniae killed with 50 microg/mL amoxicillin, or 4) 10(7) CFU/mL S. pneumoniae. Animals were killed on postoperative day 1 or 5, and the middle ear mucosa was examined for lipid peroxidation as evidence of free radical damage.

RESULTS

Mucosal lipid hydroperoxide was significantly elevated compared with control subjects on day 1 in both the antibiotic-killed S. pneumoniae group and the S. pneumoniae-infected group. On day 5, the S. pneumoniae-infected mucosa had significantly higher lipid hydroperoxide levels compared with the antibiotic-killed group and the control subjects. Histological studies confirmed mucosal edema and the presence of inflammatory cells in the infected groups.

CONCLUSIONS

Antibiotic-killed bacteria seem to produce free radical-mediated damage to the middle ear mucosa in the early phase of acute otitis media. The clinical implication of this study is that free radical damage to the middle ear mucosa may occur in otitis media despite appropriate antibiotic therapy.

The effect of alpha-tocopherol on monocyte proatherogenic activity

Atherosclerosis is the leading cause of morbidity and mortality in Westernized populations. The monocyte is a crucial cell in the genesis of the atherosclerotic lesion and is present during all stages of atherosclerosis. alpha-Tocopherol (AT) is the most active component of the vitamin E family and is the principal and most potent lipid-soluble antioxidant in plasma and LDL. With regard to monocyte function, AT supplementation (1200 IU/d) has been shown to decrease release of reactive oxygen species, lipid oxidation, release of cytokines such as interleukin-1ss (IL-1ss) and tumor necrosis factor-alpha (TNF-alpha) and decrease adhesion of monocytes to human endothelium. The mechanism of inhibition of superoxide and lipid oxidation by monocytes appears to be via inhibition of protein kinase C (PKC), the decrease in IL-1ss and TNF-alpha release by inhibition of 5-lipoxygenase and the inhibition of monocyte-endothelial cell adhesion via decrease in adhesion molecules on monocytes, CD11b and VLA-4 and by decreasing DNA-binding activity of nuclear transcription factor kappaB. Thus, in addition to the decrease in oxidative stress resulting from AT supplementation, as evidenced by decreased F(2)-isoprostanes and LDL oxidizability, AT is anti-inflammatory and exerts beneficial antiatherogenic effects on cells crucial in atherogenesis such as monocytes.

Vitamin E inhibition of platelet aggregation is independent of antioxidant activity

Vitamin E is the principal lipid-soluble antioxidant in human plasma, and some studies indicate that it may provide cardiovascular protection. To investigate putative mechanisms for vitamin E in this regard, the effect of vitamin E on vascular function and platelet aggregation was examined. In animal models of endothelial dysfunction, vitamin E improved the activity of endothelium-derived nitric oxide, and this effect was not dependent upon the antioxidant protection of LDL. In fact, vitamin E improved endothelial function in part due to the inhibition of protein kinase C (PKC) stimulation. This activity of vitamin E was examined in platelets, and vitamin E inhibited platelet aggregation in part through a mechanism that involves PKC. Moreover, the platelet inhibitory activity of vitamin E was independent of its antioxidant action because platelet inhibition was still observed with isoforms of vitamin E that were devoid of antioxidant activity.

The effect of pharmacological doses of different antioxidants on oxidation parameters and atherogenesis in hyperlipidaemic rabbits

The oxidation hypothesis of atherosclerosis implies that antioxidants are able to inhibit lipoprotein oxidation in the arterial wall and thereby retard atherogenesis. Since most of the animal studies performed have used very high doses of antioxidants, it is to date unknown whether antioxidants are effective antiatherosclerotic agents when given in pharmacological doses. Here we addressed this question using homozygous Watanabe heritable hyperlipidaemic (WHHL) rabbits as an animal model of atherosclerosis. The rabbits were divided into four groups, each consisting of ten animals. They received either a standard diet or a diet containing 4.3 mg ubiquinone-10, or 4.3 mg vitamin E or 15 mg probucol/kg body weight daily. After 12 months, the extent of aortic atherosclerosis was assessed as the intima thickness, media thickness and intima-to-media ratio in 14 cross sections equally distributed over the whole aorta. To evaluate the antioxidant effects of the diet, lipophilic and hydrophilic antioxidants, lipids, fatty acids and plasma oxidizability were measured after 0, 3 and 6 months of feeding. We found that supplementation with probucol significantly decreased aortic intima-to-media ratio compared to controls. The antiatherosclerotic action of probucol was accompanied by its beneficial action on plasma oxidizability and some plasma antioxidants. No decrease in aortic atherosclerosis was measured in ubiquinone-10- and vitamin E-supplemented rabbits, despite the fact that both antioxidants decreased plasma oxidizability and ubiquinone-10 increased the plasma levels of antioxidants. Taken together, these data suggest that pharmacological doses of probucol retard atherogenesis in WHHL rabbits by an antioxidant mechanism, while ubiquinone-10 and vitamin E at these dosages are ineffective in this highly hyperlipidaemic model. The measurement of some oxidation-related parameters in plasma, such as lipophilic antioxidants, polyunsaturated fatty acids and lipoprotein oxidizability, may be useful in assessing the risk of atherogenesis in humans.

The recognition, assessment and management of dementing disorders: conclusions from the Canadian Consensus Conference on Dementia

OBJECTIVE

i) To develop evidence based consensus statements on which to build clinical practice guidelines for primary care physicians towards the recognition, assessment and management of dementing disorders; ii) to disseminate and evaluate the impact of these statements and guidelines built on these statements.

OPTIONS

Structured approach to assessment, including recommended laboratory tests, choices for neuroimaging and referral; management of complications (especially behaviour problems and depression) and use of cognitive enhancing agents. POTENTIAL OUTCOMES: Consistent and improved clinical care of persons with dementia; cost containment by more selective use of laboratory investigations, neuroimaging and referrals; appropriate use of cognitive enhancing agents.

EVIDENCE

Authors of each background paper were entrusted to: perform a literature search, discover additional relevant material including references cited in retrieved articles; consult with other experts in the field and then synthesize information. Standard rules of evidence were applied. Based upon this evidence, consensus statements were developed by a group of experts, guided by a steering committee of eight individuals from the areas of Neurology, Geriatric Medicine, Psychiatry, Family Medicine, Preventive Health Care and Health Care Systems.

VALUES

Recommendations have been developed with particular attention to the context of primary care and are intended to support family physicians in their ongoing assessment and care of patients with dementia.

BENEFITS, HARMS AND COSTS

Potential for improved clinical care of individuals with dementia. A dissemination and evaluation strategy will attempt to measure the impact of the recommendations.

RECOMMENDATIONS

See text.

VALIDATION

Four other sets of consensus statements and/or guidelines have been published recently. These recommendations are generally congruent with our own consensus statements. The consensus statements have been endorsed by relevant bodies in Canada.

Induced cytoskeletal changes in bovine pulmonary artery endothelial cells by resveratrol and the accompanying modified responses to arterial shear stress

BACKGROUND

Atherosclerosis and coronary heart disease (CHD) are significant contributors to morbidity and mortality in developed countries. A noted exception is the low mortality of CHD in France, particularly the southwest region. This phenomenon, commonly referred to as the French paradox, may be associated with high consumption of red wine. We investigate whether the cardioprotective activity of red wine may involve the grape skin-derived polyphenol, resveratrol. We further test the possibility that resveratrol acts by modulating structural and functional changes in endothelial cells lining the blood vessel wall.

RESULTS

Bovine pulmonary artery endothelial cells (BPAEC) were incubated with resveratrol, with and without concurrent exposure to simulated arterial shear stress. Resveratrol significantly affected proliferation and shape of BPAEC; growth was suppressed and cells became elongated, based on morphologic analysis of rhodamine-conjugated phalloidin stained F-actin by confocal microscopy. Using selective signaling inhibitors, we showed that the resveratrol-induced cellular phenotype was dependent on intracellular calcium and tyrosine kinase activities, and assembly of actin microfilaments and microtubules, but was unrelated to PKC activity. Exposure to simulated arterial flow revealed that, whereas controls cells easily detached from the culture support in a time-dependent manner, resulting in total cell loss after a 5 min challenge with simulated arterial flow conditions, a significant percentage of the treated cells remained attached to the cultured plastic coverslips under identical experimental conditions, suggesting that they adhered more strongly to the surface. Western blot analysis shows that whereas cells treated with 25 microM and 100 microM resveratrol had no change in total ERK1/2, treatment did result in an increase in phosphorylated ERK1/2, which probably involved stabilization of the active enzyme. An increase in nitric oxide synthase expression was detected as early as 6 h and persisted for up to 4 days of treatment.

CONCLUSIONS

Results of our studies show that resveratrol interacts with endothelial cells in vitro to elicit morphological and structural changes; the observed changes support the interpretation that resveratrol acts as a cardioprotective agent.

Lipid oxidation enhances the function of activated protein C

Although lipid oxidation products are usually associated with tissue injury, it is now recognized that they can also contribute to cell activation and elicit anti-inflammatory lipid mediators. In this study, we report that membrane phospholipid oxidation can modulate the hemostatic balance. Oxidation of natural phospholipids results in an increased ability of the membrane surface to support the function of the natural anticoagulant, activated protein C (APC), without significantly altering the ability to support thrombin generation. Lipid oxidation also potentiated the ability of protein S to enhance APC-mediated factor Va inactivation. Phosphatidylethanolamine, phosphatidylserine, and polyunsaturation of the fatty acids were all required for the oxidation-dependent enhancement of APC function. A subgroup of thrombotic patients with anti-phospholipid antibodies specifically blocked the oxidation-dependent enhancement of APC function. Since leukocytes are recruited and activated at the thrombus or sites of vessel injury, our findings suggest that after the initial thrombus formation, lipid oxidation can remodel the membrane surface resulting in increased anticoagulant function, thereby reducing the thrombogenicity of the thrombus or injured vessel surface. Anti-phospholipid antibodies that block this process would therefore be expected to contribute to thrombus growth and disease.

Evaluation of a novel vitamin E coated cellulosic membrane hollow fiber dialyzer

Adverse physiologic effects accompany hemodialysis. Biocompatible dialyzer membranes may both limit oxidative stress and decrease beta2-microglobulin production, thereby reducing patient morbidity. We compared standard solute clearance, lipid, and antioxidant effects of a novel cellulosic membrane dialyzer modified with covalently bonded vitamin E (Excebrane Clirans E15, Terumo Australia) with standard cellulosic and polysulphone membrane dialyzers. Stable adult hemodialysis patients taking no lipid lowering or antioxidant therapy (n = 17; 9 male, 8 female) were recruited into a 10 week, prospective, unblinded study. Measurements were made at baseline on their usual dialyzer and after 2, 4, and 10 weeks of Excebrane use. Excebrane demonstrated good in vivo clearance of standard solutes relative to surface area. Predialysis beta2-microglobulin levels were unchanged with time and were significantly lower postdialysis than with cellulose acetate (p < 0.05). Oxidized low density lipoprotein levels as measured by nitrotyrosine residues were high predialysis, but tended to decrease with both membranes (p > 0.05). Total antioxidant status fell during dialysis (p < 0.0005), but plasma vitamin A and E concentrations increased (p = 0.007 and p = 0.02, respectively). Baseline vitamin A levels were high in all patients and, along with vitamin E, total antioxidant status and lipid profiles did not change over time with Excebrane use. Excebrane is an efficient, biocompatible membrane with no deleterious effects on beta2-microglobulin or lipids. More long-term study is merited.

Antioxidant supplements to prevent heart disease. Real hope or empty hype?

Antioxidants in foods and supplements are being widely promoted for their health benefits. Protection from heart disease is one claim that seems compelling in light of scientific evidence and large-scale observational studies. But will antioxidant supplements help your patients? To examine this question, Dr Tran reviews numerous clinical studies and evaluates the discrepancies between observational and clinical results.

Pluripotential mechanisms of cardioprotection with HMG-CoA reductase inhibitor therapy

Treatment with hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors has been accompanied by a reduced risk of cardiovascular events. Rapid onset of clinical benefit and weak correlations between plasma low density lipoprotein-cholesterol levels and coronary lumen change or cardiovascular events indicates that nonlipid mechanisms are involved in this beneficial effects with HMG-CoA reductase inhibitors. Furthermore, more rapid onset of clinical benefit with HMG-CoA reductase inhibitors in patients with acute coronary syndromes or acute myocardial infarction than in those with stable coronary heart disease suggest that HMG-CoA reductase inhibitors facilitate repair of ruptured or ulcerated atherosclerotic plaque, facilitate plaque stabilization and/or reduce thrombus formation on ruptured plaques. Treatment with HMG-CoA reductase inhibitors improved endothelial dysfunction in patients with hypercholesterolemia and this improvement in endothelial function was not correlated with reduction in total serum cholesterol levels. Similarly, reduction in endothelial pre-proendothelin mRNA expression and endothelin synthesis and blood pressure lowering with HMG-CoA reductase inhibitors occurred independent of lipid-lowering. Finally, HMG-CoA reductase inhibitors increased endothelial nitric oxide levels i.e. upregulated endothelial nitric oxide synthetase expression via post-transcriptional mechanisms and prevented its down-regulation by oxidized LDL-C. HMG-CoA reductase inhibitors have been shown to modulate the immune response by inhibiting activation of immune-competent cells such as macrophages, and antigen presentation to macrophages by T cells. Treatment with HMG-CoA reductase inhibitors can reduce expression, production and circulating levels of chemokines (monocyte chemoattractant protein-1) and proinflammatory cytokines [tumor necrosis factoralpha, interleukin (IL)-6 and IL-1beta]. HMG-CoA reductase inhibitors reduced inflammation in human atheroma: significantly fewer macrophages and T cells, less oxidized LDL-C and higher collagen content. In addition, treatment with HMG-CoA reductase inhibitor led to decreased cell death within the atheroma. Treatment with these agents also reduced expression of inducible cellular adhesion molecules, decreased secretion of metalloproteinases by macrophages, reduced vascular smooth muscle cell apoptosis. Lastly, HMG-CoA reductase inhibitors appear to have important effects on the thrombogenesis: reduced expression of tissue factor production and activity; increased production of tissue factor package inhibitor; decreased platelet thrombus formation and improved fibrinolysis as a result of lowered plasminogen activator inhibitor-1 levels. As the pluripotential cardioprotective mechanisms of HMG-CoA reductase inhibitors are further elucidated, it is envisaged that treatment with HMG-CoA reductase inhibitors will be initiated earlier and more frequently in patients with hypercholesterolemia.

17Beta-estradiol inhibits proliferation of cultured vascular smooth muscle cells induced by lysophosphatidylcholine via a nongenomic antioxidant mechanism

OBJECTIVE

Lysophosphatidylcholine (lysoPC), an active component of oxidized low-density lipoprotein, stimulates proliferation of vascular smooth muscle cells (VSMC). We investigated the direct impact of 17beta-estradiol (E2) on the proliferation of VSMC from rat aorta.

RESULTS

VSMC derived from both female and male rats expressed estrogen receptors alpha and beta. Treatments with 1% fetal bovine serum or 5 microM lysoPC increased the incorporation of [3H]-thymidine in VSMC obtained from female rats. 17Beta-E2 did not alter the response to fetal bovine serum, but significantly suppressed the enhanced deoxyribonucleic acid synthesis which had been induced by lysoPC in a dose-dependent manner (10(-4)-10(-6) M). Estrogen also inhibited the proliferation of VSMC from male animals. ICI 182,780, a specific estrogen receptor antagonist, and 17alpha-E2, an inactive form of estradiol, also decreased the mitogenic response to lysoPC in VSMC. In addition, N-acetyl-L-cysteine, a potent antioxidant, inhibited the lysoPC effect. Flow cytometric analysis using the oxidation-sensitive probe 2',7'-dichlorofluorescin diacetate revealed that elevated intracellular formation of reactive oxygen species elicited with lysoPC was depressed significantly by 17beta-E2, ICI 182,780, or 17alpha-E2 as well as by N-acetyl-L-cysteine.

CONCLUSION

17Beta-E2 inhibits in vitro VSMC proliferation induced by lysoPC via a nongenomic antioxidant mechanism.

Direct Evidence for apo B-100-Mediated Copper Reduction: Studies with Purified apo B-100 and Detection of Tryptophanyl Radicals

Copper binding to apolipoprotein B-100 (apo B-100) and its reduction by endogenous components of low-density lipoprotein (LDL) represent critical steps in copper-mediated LDL oxidation, where cuprous ion (Cu(I)) generated from cupric ion (Cu(II)) reduction is the real trigger for lipid peroxidation. Although the copper-reducing capacity of the lipid components of LDL has been studied extensively, we developed a model to specifically analyze the potential copper reducing activity of its protein moiety (apo B-100). Apo B-100 was isolated after solubilization and extraction from size exclusion-HPLC purified LDL. We obtained, for the first time, direct evidence for apo B-100-mediated copper reduction in a process that involves protein-derived radical formation. Kinetics of copper reduction by isolated apo B-100 was different from that of LDL, mainly because apo B-100 showed a single phase-exponential kinetic, instead of the already described biphasic kinetics for LDL (namely alpha-tocopherol-dependent and independent phases). While at early time points, the LDL copper reducing activity was higher due to the presence of alpha-tocopherol, at longer time points kinetics of copper reduction was similar in both LDL and apo B-100 samples. Electron paramagnetic resonance studies of either LDL or apo B-100 incubated with Cu(II), in the presence of the spin trap 2-methyl-2-nitroso propane (MNP), indicated the formation of protein-tryptophanyl radicals. Our results supports that apo B-100 plays a critical role in copper-dependent LDL oxidation, due to its lipid-independent-copper reductive ability.

Beneficial effects of statins in coronary artery disease--beyond lowering cholesterol

OBJECTIVE

To review the benefits of statins in coronary artery disease management beyond their cholesterol-lowering effects.

DATA SOURCES

A MEDLINE search (1966-May 2000) was conducted using the following terms: lovastatin, pravastatin, simvastatin, atorvastatin, fluvastatin, cerivastatin, endothelium, plaque stabilization, antithrombotic effects.

STUDY SELECTION

English-language human studies and case reports.

DATA EXTRACTION

Studies published demonstrating other mechanisms of statins' clinical beneficial effects were evaluated and reviewed.

DATA SYNTHESIS

The understanding of the pharmacologic effects of statins has led to the realization that the benefits of these agents extend beyond simply lowering cholesterol. These properties include beneficial effects on vessel endothelial tissue; decreased low-density lipoprotein oxidation and inflammation; ability to stabilize atherosclerotic plaques and perhaps promote regression; proliferative effects on smooth-muscle growths, possibly strengthening atherosclerotic plaques; antithrombotic effects by inhibiting platelet aggregation and stimulation of fibrinolytic factors; and improvement of blood viscosity and flow. With these actions, statins may benefit the situation of long-term atherosclerotic plaque formation and the setting of acute coronary syndrome.

CONCLUSIONS

Further large-scale studies are needed to determine the clinical importance and validity of these postulated beneficial effects of statins.

Lipophilic antioxidants and iron status in ESRD patients on hemodialysis

Cardiovascular disease remains the major cause of mortality in hemodialysis patients. Abnormal oxidative stress and impaired antioxidant defense may contribute to accelerated atherogenesis associated with uremia. As oxidative modification of lipids appears to be a prerequisite for the development of atherosclerotic lesions, lipophilic antioxidants may be protective. The aim of this study was to determine the plasma levels of lipophilic antioxidants in 82 hemodialysis patients and 30 controls and to investigate the influence of body iron status on the levels of lipophilic antioxidants. The patients were categorized into 3 groups according to their serum ferritin levels. We found that the plasma levels of lycopene, delta-tocopherol, gamma-tocopherol and retinol of hemodialysis patients were lower than those of controls. On the other hand, both absolute and lipid-normalized plasma lycopene levels were significantly reduced in those patients in the groups with higher ferritin levels as compared to those with lower ferritin levels. In addition, our study showed that the lipid-normalized plasma levels of beta-carotene and alpha-carotene of hemodialysis patients with higher ferritin levels were lower than those of the patients with lower levels. These data suggest that the plasma levels of lipophilic antioxidants are altered in end-stage renal disease on hemodialysis and may be considered as markers of oxidative stress in these patients. Most importantly, elevated serum ferritin levels may affect the levels of these lipophilic antioxidants.

Genetic polymorphism in paraoxonase is a risk factor for childhood focal segmental glomerulosclerosis

Focal segmental glomerulosclerosis (FSGS) is an important cause of end-stage renal failure (ESRF) in children. Our previous studies have shown that Arab children in Israel have a worse prognosis compared with Jewish patients despite similar clinical presentation and management. Progression of proteinuric glomerular diseases has been associated with alterations in lipid metabolism, and similarities have been drawn between the mechanisms underlying atherosclerosis and glomerulosclerosis. Paraoxonase (PON) is a high-density lipoprotein (HDL)-associated enzyme involved in preventing the oxidation of low-density lipoprotein (LDL), and an association has been shown between two genetic polymorphisms in PON1 and the risk of coronary artery disease. The aim of this study was to determine the frequency of these genetic polymorphisms in PON1 in Arab and Jewish children with FSGS and to determine any association with severity of outcome. Forty-seven children (21 Arab and 26 Jewish) with biopsy-proven FSGS and 274 healthy controls of matching ethnic origin were studied. The glutamine (A)-192-arginine (B) and the methionine (M)-55-leucine (L) polymorphisms were analyzed. The frequency of the A allele was similar in patients and controls (0.68 versus 0.71), as was that of the L allele (0.63 versus 0.6). When subgroups were analyzed, the prevalence of the LL genotype in Arab patients was significantly greater than in Jewish patients (57.1% versus 26.9%, P: < 0.05) and Arab controls (57.1% versus 28.9%, P: < 0.03). A trend in association was found between homozygosity for the L allele and progression of renal disease in Arab children. Homozygosity for the L allele is a risk factor for developing FSGS in Arab children and may be associated with a worse prognosis.

Low plasma lycopene concentration is associated with increased intima-media thickness of the carotid artery wall

Although a number of epidemiological studies have evaluated the association between ss-carotene and the risk of cardiovascular diseases, there has been little research on the role of lycopene, an acyclic form of ss-carotene, with regard to the risk of cardiovascular disease. We investigated the relationship between plasma concentrations of lycopene and intima-media thickness of the common carotid artery wall (CCA-IMT) in 520 middle-aged men and women (aged 45 to 69 years) in eastern Finland. They were examined from 1994 to 1995 at the baseline of the Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) study, a randomized trial concerning the effect of vitamin E and C supplementation on atherosclerotic progression. The subjects were classified into 2 categories according to the median concentration of plasma lycopene (0.12 micromol/L in men and 0.15 micromol/L in women). Mean CCA-IMT of the right and left common carotid arteries was 1.18 mm in men and 0.95 mm in women with plasma lycopene levels lower than the median and 0.97 mm in men (P:<0.001 for difference) and 0.89 mm in women (P:=0.027 for difference) with higher levels of plasma lycopene. In ANCOVA adjusting for cardiovascular risk factors and intake of nutrients, in men, low levels of plasma lycopene were associated with a 17.8% increment in CCA-IMT (P:=0.003 for difference). In women, the difference did not remain significant after the adjustments. We conclude that low plasma lycopene concentrations are associated with early atherosclerosis, manifested as increased CCA-IMT, in middle-aged men living in eastern Finland.

Olive oils rich in natural catecholic phenols decrease isoprostane excretion in humans

This study was undertaken to evaluate, in humans, the antioxidant activity of olive oil phenolics, namely hydroxytyrosol and oleuropein aglycone that share an orthodiphenolic (catecholic) structure. Human volunteers were administered olive oil samples containing increasing amounts of an olive oil phenolic extract that was characterized by gas-chromatography/mass spectrometry. The administration of phenol-rich oils was dose-dependently associated with a decreased urinary excretion of 8-iso-PGF(2alpha), a biomarker of oxidative stress. Also, a statistically significant negative correlation between homovanillyl alcohol (HValc, hydroxytyrosol's major metabolite, formed through the COMT system) and F(2)-isoprostanes excretion was found. Thus, the administration of oil samples with increasing, albeit low, concentrations of orthodiphenolic compounds, namely hydroxytyrosol and oleuropein aglycone, results in a dose-dependent reduction in the urinary excretion of 8-iso-PGF(2alpha). The statistically significant negative correlation between 8-iso-PGF(2alpha) and HValc urinary concentrations suggests that this metabolite better reflects the in vivo activities of hydroxytyrosol.

Pathogenesis of vascular disease

Only recently are we beginning to understand the complex interplay of factors involved in vascular disease and diabetes. Insulin resistance provides a starting point to explain the many factors that lead to the more severe vascular disease characteristic of diabetes. Insulin resistance syndrome comprises insulin resistance and compensatory hyperinsulinaemia as well as hypertension, dyslipidaemia, macrovascular disease, and increased plasminogen activator inhibitor-1 activity. The development of type 2 diabetes may be viewed as the inability of the pancreas to continue to overcome insulin resistance, even with excessive insulin production.

Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) study: a randomized trial of the effect of vitamins E and C on 3-year progression of carotid atherosclerosis

OBJECTIVES

To study the efficacy of vitamin E and C supplementation on the progression of carotid atherosclerosis, hypothesizing an enhanced preventive effect in men and in smokers and synergism between vitamins.

DESIGN AND SUBJECTS

Double-masked two-by-two factorial trial, randomization in four strata (by gender and smoking status) to receive twice daily either 91 mg (136 IU) of d-alpha-tocopherol, 250 mg of slow-release vitamin C, a combination of these or placebo for three years. A randomized sample of 520 smoking and nonsmoking men and postmenopausal women aged 45-69 years with serum cholesterol >/= 5.0 mmol L-1 were studied.

SETTING

The population of the city of Kuopio in Eastern Finland.

INTERVENTION

Twice daily either a special formulation of 91 mg of d-alpha-tocopherol, 250 mg of slow-release vitamin C, a combination of these (CellaVie(R)) or placebo for three years.

MEASUREMENTS

Atherosclerotic progression, defined as the linear regression slope of ultrasonographically assessed common carotid artery mean intima-media thickness (IMT), was calculated over semi-annual assessments.

RESULTS

The average increase of the mean IMT was 0.020 mm year-1 amongst men randomized to placebo and 0.018 mm year-1 in vitamin E, 0.017 mm year-1 in vitamin C and 0.011 mm year-1 in the vitamin combination group (P = 0.008 for E + C vs. placebo). The respective means in women were 0.016, 0.015, 0.017 and 0.016 mm year-1. The proportion of men with progression was reduced by 74% (95% CI 36-89%, P = 0.003) by supplementation with the formulation containing both vitamins, as compared with placebo.

CONCLUSIONS

Our study shows that a combined supplementation with reasonable doses of both vitamin E and slow-release vitamin C can retard the progression of common carotid atherosclerosis in men. This may imply benefits with regard to other atherosclerosis-based events.

Inhibition of lipoprotein oxidation by prenylated xanthones derived from mangostin

Oxidative damage is thought to play a critical role in cardiovascular and other chronic diseases. This has led to considerable interest in the antioxidant activity of dietary compounds. Flavonoids have received the most attention and much is known about the structural requirements for antioxidant activity. However, little is known about the antioxidant activity of other plant derived phenolic compounds such as the xanthones. We have previously shown that the prenylated xanthone, mangostin, can inhibit the oxidation of low density lipoprotein. In order to examine the effects of structure modification on antioxidant activity of this class of compound we have prepared a number of derivatives of mangostin and tested antioxidant activity in an isolated LDL and plasma assay. The results of this study show that structural modification of mangostin can have a profound effect on antioxidant activity. Derivatisation of the C-3 and C-6 hydroxyl groups with either methyl, acetate, propane diol or nitrile substantially reduces antioxidant activity. In contrast, derivatisation of C-3 and C-6 with aminoethyl derivatives enhanced antioxidant activity, which may be related to changes in solubility. Cyclisation of the prenyl chains had little influence on antioxidant activity.

Secondary prevention with antioxidants of cardiovascular disease in endstage renal disease (SPACE): randomised placebo-controlled trial

BACKGROUND

Excess cardiovascular mortality has been documented in chronic haemodialysis patients. Oxidative stress is greater in haemodialysis patients with prevalent cardiovascular disease than in those without, suggesting a role for oxidative stress in excess cardiovascular disease in haemodialysis. We investigated the effect of high-dose vitamin E supplementation on cardiovascular disease outcomes in haemodialysis patients with pre-existing cardiovascular disease.

METHODS

Haemodialysis patients with pre-existing cardiovascular disease (n=196) aged 40-75 years at baseline from six dialysis centres were enrolled and randomised to receive 800 IU/day vitamin E or matching placebo. Patients were followed for a median 519 days. The primary endpoint was a composite variable consisting of: myocardial infarction (fatal and non-fatal), ischaemic stroke, peripheral vascular disease (excluding the arteriovenous fistula), and unstable angina. Secondary outcomes included each of the component outcomes, total mortality, and cardiovascular-disease mortality.

FINDINGS

A total of 15 (16%) of the 97 patients assigned to vitamin E and 33 (33%) of the 99 patients assigned to placebo had a primary endpoint (relative risk 0.46 [95% CI 0.27-0.78], p=0.014). Five (5.1%) patients assigned to vitamin E and 17 (17.2%) patients assigned to placebo had myocardial infarction (0.3 [0.11-0.78], p=0.016). No significant differences in other secondary endpoints, cardiovascular disease, or total mortality were detected.

INTERPRETATION

In haemodialysis patients with prevalent cardiovascular disease, supplementation with 800 IU/day vitamin E reduces composite cardiovascular disease endpoints and myocardial infarction.

Why hemodialysis patients are in a prooxidant state? What could be done to correct the pro/antioxidant imbalance

Oxidative stress which results from an imbalance between reactive oxygen species production and antioxidant defense mechanisms is now well recognized in hemodialysis (HD) patients and could be involved in dialysis-related pathologies such as accelerated atherosclerosis, amyloidosis and anemia. In order to evaluate the rationale for preventive intervention against oxidative damage during HD, we review the factors that are implied and may be responsible for the imbalance between pro- and antioxidative mechanisms. The inflammatory state mainly due to hemobioincompatibility of the dialysis system plays a critical role in the production of free oxygen radical species contributing by this way to worsen the prooxidant status of uremic patients. Two factors largely contribute to the stimulation of the NADPH oxidase: hemoreactivity of the membrane and trace amounts of endotoxins. The antioxidant system is severely impaired in uremic patients and gradually altered with the degree of renal failure. HD could further impair this antioxidant system mainly by losses of (a) hydrophilic unbound small-molecular-weight substances such as vitamin C, (b) trace elements and (c) enzyme-regulatory compounds. Two main axes may be proposed in order to prevent and/or to decrease oxidative stress in HD patients. One consists in improving the hemocompatibility of the dialysis system mainly by using a dialyzer with low hemoreactivity and ultrapure, sterile, nonpyrogenic dialysate. The other consists in supplementing the deficiency patients with antioxidants. This could be achieved by oral or perdialytic supplementation. Vitamin E could be bound on dialyzer membrane. Alternatively, hemolipodialysis consists in loading HD patients with vitamin C or E via an ancillary circuit made of vitamin E-rich liposomes. The presence of liposomes could also facilitate the removal of hydrophobic prooxidative substances.

Telomere attrition of the human abdominal aorta: relationships with age and atherosclerosis

Little is known about the turnover rate (i.e. the rate of replication and death) of cells in the intima and media of human arteries as a function of age and atherosclerosis. One indicator of the replicative history of cells is telomere length. In this work we explored the rate of telomere attrition as a function of age and atherosclerosis in cells of the human abdominal aorta. Telomere length, measured by the terminal restriction fragment using Southern analysis, was determined in the intima and media of the distal (infrarenal) versus proximal (suprarenal) segments of the abdominal aorta. Telomere length was then correlated with age and atherosclerotic grade. The rate of age-dependent telomere attrition was higher in both the intima and media of the distal versus proximal abdominal aorta. In addition, telomere length was negatively correlated with atherosclerotic grade. However, after adjustment for age, this relationship was not statistically significant. The high rate of age-dependent telomere attrition in the distal abdominal aorta probably reflects enhanced cellular turnover rate due to local factors such as an increase in shear wall stress in this vascular segment.

Non-traditional cardiovascular disease risk factors in end-stage renal disease: oxidate stress and hyperhomocysteinemia

Studies in experimental animals have shown that oxidative stress and hyperhomocyst(e)inemia culminate in abnormal vascular and endothelial regulation, functional nitric oxide deficiency, vascular hypertrophy, and atherosclerosis. Oxidative stress is accompanied by increased advanced glycation endproducts and oxidized low density lipoproteins. Studies of patients with end-stage renal disease provide extensive indirect, evidence of increased oxidative stress and more than ninety percent are hyperhomocyt(e)inemic. Presently, only uncontrolled or observational studies are available to assess the effects of anti-oxidant therapy for oxidative stress or folate therapy for hyperhomocyst(e)inemia in these patients. Promising developments include the reports of beneficial effects of a vitamin E coated dialyzer, and the reduction in homocyst(e)ine levels in patients with end-stage renal disease given an intravenous folate metabolite. However, there is presently no therapy available to reverse fully oxidative stress or hyperhomocyst(e)inemia. Therefore, the causative role of these nontraditional risk factors of cardiovascular disease remains untested.

Detection of superoxide anion released extracellularly by endothelial cells using cytochrome c reduction, ESR, fluorescence and lucigenin-enhanced chemiluminescence techniques

Endothelium produces oxygen-derived free radicals (nitric oxide, NO&z.rad;; superoxide anion, O(2)(*-)) which play a major role in physiology and pathology of the vessel wall. However, little is known about endothelium-derived O(2)(*-) production, particularly due to the difficulty in assessing O(2)(*-) when its production is low and to controversies recently raised about the use of lucigenin-enhanced chemiluminescence. We compared four techniques of O(2)(*-) assessment when its production is low. In the present study, we have compared ferricytochrome c reduction, electron spin resonance (ESR) spectroscopy using DMPO as spin trap, hydroethidine fluorescence, and lucigenin-enhanced chemiluminescence to assess O(2)(*-) production in cultured bovine aortic endothelial cells (BAEC). We focused our study on extracellular O(2)(*-) production because the specificity of the signal is provided by the use of superoxide dismutase, and this control cannot be obtained intracellularly. We found that the calcium ionophore A23187 dose-dependently stimulated O(2)(*-) production, with a good correlation between all four techniques. The signals evoked by postconfluent BAEC were increased 2- to 7-fold in comparison to just-confluent BAEC, according to the technique used. Ferricytochrome c 20 microm rather than at 100 microm appears more suitable to detect O(2)(*-). However, in the presence of electron donors such as NADH or NADPH, lucigenin-enhanced chemiluminescence generated high amounts of O(2)(*-). Thus, ferricytochrome c reduction, electron spin resonance (ESR), and hydroethidine fluorescence appear as adequate tools for the detection of extracellular endothelium-derived O(2)(*-) production, whereas lucigenin may be artifactual, even when a low concentration of lucigenin is employed.

Moderate intervention with carotenoid-rich vegetable products reduces lipid peroxidation in men

Because of their antioxidant properties, carotenoids may have beneficial effects in preventing cancer and cardiovascular disease. However, in humans consuming carotenoid-rich vegetables, data concerning the antioxidant effects of carotenoids are rather scarce. A human intervention trial was conducted, therefore, to determine whether a moderately increased consumption of carotenoid-rich vegetables would influence the antioxidant status in 23 healthy men. This short-term feeding study lasted 8 wk during which the men consumed a low carotenoid diet. A 2-wk low carotenoid period was followed by daily consumption of 330 mL tomato juice, then by 330 mL carrot juice and then by 10 g of spinach powder, each for 2 wk. Antioxidant status [water-soluble antioxidants in serum, ferric reducing ability of plasma (FRAP) and antioxidant enzyme activities] and lipid peroxidation (plasma malondialdehyde and ex vivo oxidation of LDL) were determined. In a subgroup of 10 men, lipoprotein carotenoids were measured. The consumption of carotenoid-rich vegetables significantly increased selected carotenoids in lipoproteins but had only minor effects on their relative distribution pattern. Tomato juice consumption reduced plasma thiobarbituric acid reactive substances (TBARS) by 12% (P: < 0.05) and lipoprotein oxidizability in terms of an increased lag time (18%, P: < 0.05). Carrot juice and spinach powder had no effect on lipid peroxidation. Water-soluble antioxidants, FRAP, glutathione peroxidase and reductase activities did not change during any study period. In evaluating the low carotenoid diet, we conclude that the additional consumption of carotenoid-rich vegetable products enhanced lipoprotein carotenoid concentrations, but only tomato juice reduced LDL oxidation in healthy men.

Peripheral vascular disease and type 2 diabetes mellitus

Patients with Type 2 diabetes mellitus frequently have peripheral vascular disease, with a predilection for the lower legs. In this review potential mechanisms for this high prevalence and altered distribution are explored. It is hypothesised that the metabolic abnormalities in the prediabetic phase predispose to a more distal and aggressive atherosclerosis. Once diabetes has developed this process is accelerated due to chronic hyperglycaemia. Furthermore, endothelial damage, non-enzymatic glycosylation and polyneuropathy could lead to impaired vascular remodelling and collateral formation.

Long-term effects of vitamin E, vitamin C, and combined supplementation on urinary 7-hydro-8-oxo-2'-deoxyguanosine, serum cholesterol oxidation products, and oxidation resistance of lipids in nondepleted men

We studied the long-term effects of vitamins E and C and their combination on lipid peroxidation in vivo and in vitro. The Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) trial is a double-masked placebo-controlled randomized clinical trial to study the effects of vitamin C (500 mg of slow release ascorbate per day), vitamin E (182 mg of RRR-alpha-tocopherol acetate per day), and the combination of both antioxidants. Lipid peroxidation measurements were carried out for 48 male participants at entry and at 12 and 36 months. Compared with placebo, vitamin E and the vitamin combination increased plasma lipid-standardized alpha-tocopherol during the first 12 months by 68.2% and 65.2% (P:<0. 001 for both), respectively, and reduced serum 7beta-hydroxycholesterol by 50.4% (P:=0.013) and 44.0% (P:=0.041), respectively. The net change of lipid standardized alpha-tocopherol was 63.8% after 36 months of vitamin E supplementation and 43.3% for the combination. Vitamin C supplementation elevated plasma total ascorbate level by 30.1% (P:=0.043) in 12 months and by 91.1% (P:=0. 001) in 36 months. Neither vitamin E, vitamin C, nor the combination influenced the urinary excretion rate of 7-hydro-8-oxo-2'-deoxyguanosine or the antioxidative capacity of plasma. Vitamin E and the combination of vitamins E and C enhanced the oxidation resistance of isolated lipoproteins and total serum lipids. Our data indicate that long-term supplementation of nondepleted men with a reasonable dose of vitamin E alone or in combination with slow release vitamin C reduces lipid peroxidation in vitro and in vivo, whereas a relatively high dose of vitamin C alone does not.

Potential antiatherogenic mechanisms of ascorbate (vitamin C) and alpha-tocopherol (vitamin E)

The premise that oxidative stress, among several other factors, plays an important role in atherogenesis implies that the development and progression of atherosclerosis can be inhibited by antioxidants. In this minireview we discuss several mechanisms by which the antioxidants ascorbate (vitamin C) and alpha-tocopherol (vitamin E) may protect against atherosclerosis. These mechanisms include inhibition of LDL oxidation and inhibition of leukocyte adhesion to the endothelium and vascular endothelial dysfunction. Overall, ascorbate appears to be more effective than alpha-tocopherol in mitigating these pathophysiological processes, most likely as a result of its abilities to effectively scavenge a wide range of reactive oxygen and nitrogen species and to regenerate alpha-tocopherol, and possibly tetrahydrobiopterin, from its radical species. In contrast, alpha-tocopherol can act either as an antioxidant or a pro-oxidant to inhibit or facilitate, respectively, lipid peroxidation in LDL. However, this pro-oxidant activity of alpha-tocopherol is prevented by ascorbate acting as a coantioxidant. Therefore, an optimum vitamin C intake or body status may help protect against atherosclerosis and its clinical sequelae, whereas vitamin E may only be effective in combination with vitamin C.

Noradrenergic vascular hyper-responsiveness in human hypertension is dependent on oxygen free radical impairment of nitric oxide activity

BACKGROUND

Noradrenergic vascular hyper-responsiveness is a hallmark of essential hypertension. To evaluate whether nitric oxide plays a role in the enhanced vascular response to norepinephrine in hypertension, we examined 32 hypertensives and 28 normotensives who were distributed in 3 experimental series.

METHODS AND RESULTS

In the first series, we measured the forearm blood flow (FBF) response to a norepinephrine infusion under control conditions and during the infusion of L-N-monomethylarginine (L-NMMA). Norepinephrine evoked dose-dependent vasoconstriction that was greater in hypertensives than in normotensives (maximum FBF, -61+/-1 versus -51+/-1%; P<0.01). During L-NMMA infusion, norepinephrine vasoconstriction was not modified in hypertensives; however, it was potentiated in normotensives (maximum FBF, -64+/-2%; P<0.01). In the second series, we tested whether norepinephrine vasoconstriction could be affected by an antioxidant such as ascorbic acid. Norepinephrine vasoconstriction was blunted by ascorbic acid administration only in hypertensives (maximum FBF, -49+/-3 versus -63+/-2%; P<0.01); the vasoconstriction became similar to that observed in normotensives. During ascorbic acid plus L-NMMA administration, the vascular response to norepinephrine increased to a similar extent in both study groups. To rule out the possibility that the effect of ascorbic acid on norepinephrine vasoconstriction could depend on adrenergic receptor-induced nitric oxide release, in the last series we inhibited endogenous nitric oxide and replaced it with an exogenous nitric oxide donor (sodium nitroprusside). Even in these conditions, ascorbic acid attenuated norepinephrine vasoconstriction only in hypertensives (maximum FBF, -50+/-2 versus -62+/-1%; P<0.01).

CONCLUSIONS

Our data demonstrate that noradrenergic vascular hyper-responsiveness in hypertension is dependent on an impairment of nitric oxide activity that is realized through norepinephrine-induced oxygen free radical production.

Simvastatin inhibits the monocyte expression of proinflammatory cytokines in patients with hypercholesterolemia

OBJECTIVE

The purpose of this study was to assess if simvastatin has an anti-inflammatory activity in patients with hypercholesterolemia.

BACKGROUND

Simvastatin, an inhibitor of 3-hydroxy-methyl-glutaryl coenzyme A (HMG-CoA) reductase, reduced cardiovascular events in patients with myocardial infarction and hypercholesterolemia.

METHODS

Sixteen patients with polygenic hypercholesterolemia were randomly allocated to diet (n = 8) or diet plus 20 mg/day simvastatin (n = 8) for eight weeks. Before and at the end of treatment period, lipid profile and monocyte expression of tumor necrosis factor-alpha (TNF) and interleukin-1beta (IL-1beta) were measured.

RESULTS

At baseline no difference in lipid profile and monocyte expression of TNF and IL-1beta were observed between the two groups. In patients allocated to diet alone, no change in lipid profile and monocyte expression of TNF and IL-1beta was seen. In patients with diet plus simvastatin, significant decreases of total cholesterol (-27%, p<0.02), low density lipoprotein-cholesterol (-33%, p<0.02), and monocyte expression of TNF (-49%, p<0.02) and IL-1beta (-35%, p<0.02) were observed. At the end of treatment period, patients treated with simvastatin had lower cholesterol and monocyte TNF and IL-1beta than did patients assigned to diet alone.

CONCLUSION

This study suggests that simvastatin possesses anti-inflammatory activity via the inhibition of pro-inflammatory cytokines TNF and IL-1beta expressed by monocytes.

Epicatechin in human plasma: in vivo determination and effect of chocolate consumption on plasma oxidation status

Diets that are rich in plant foods have been associated with a decreased risk for specific disease processes and certain chronic diseases. In addition to essential macronutrients and micronutrients, the flavonoids in a variety of plant foods may have health-enhancing properties. Chocolate is a food that is known to be rich in the flavan-3-ol epicatechin and procyanidin oligomers. However, the bioavailability and the biological effects of the chocolate flavonoids are poorly understood. To begin to address these issues, we developed a method based on HPLC coupled with electrochemical (coulometric) detection to determine the physiological levels of epicatechin, catechin and epicatechin dimers. This method allows for the determination of 20 pg (69 fmol) of epicatechin, which translates to plasma concentrations as low as 1 nmol/L. We next evaluated the absorption of epicatechin, from an 80-g semisweet chocolate (procyanidin-rich chocolate) bolus. By 2 h after ingestion, there was a 12-fold increase in plasma epicatechin, from 22 to 257 nmol/L (P < 0.01). Consistent with the antioxidant properties of epicatechin, within the same 2-h period, there was a significant increase of 31% in plasma total antioxidant capacity (P < 0.04) and a decrease of 40% in plasma 2-thiobarbituric acid reactive substances (P < 0.01). Plasma epicatechin and plasma antioxidant capacity approached baseline values by 6 h after ingestion. These results show that it is possible to determine basal levels of epicatechin in plasma. The data support the concept that the consumption of chocolate can result in significant increases in plasma epicatechin concentrations and decreases in plasma baseline oxidation products.

Measurement of oxidative stress in human liver by EPR spin-probe technique

A method for the measurement of reactive oxygen species (ROS) in human hepatic tissue has been developed. The method is based on the EPR detection of the nitroxide radical produced by reaction of the hydroxylamine spin-probe bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)decandioate with ROS generated under pseudo-physiologic conditions in fine needle biopsies of healthy (10 controls) and diseased (22 patients) human liver. Measures of malonaldehyde in 9 liver biopsies (3 controls and 6 patients) have also been obtained by high pressure liquid chromatography and values parallel those obtained by the spin-probe technique. The amount of ROS found in healthy human liver (median = 1.8 x 10(-11) mol/mg) was significantly lower than values found in liver affected by hepatitis B (median=5.8 x 10(-10) mol/mg; p < 0.02) or by hepatitis C (median = 2.7 x 10(-9) mol/mg; p < 0.003) as well as compared to some other non-viral liver diseases (NVLD): autoimmune hepatitis, primary biliary cirrhosis, primary schlerosing cholangitis (median = 9.8 x 10(-9) mol/mg; p < 0.005). NVLD also showed significantly higher ROS levels compared to hepatitis B (p < 0.04) and hepatitis C (p < 0.04). The mechanism, potentiality and limitations of our method are discussed.

Nonpharmacologic treatment of heart failure in the elderly

Nonpharmacologic therapy is an integral part of the management of elderly patients with heart failure. Reinforcement of dietary sodium restriction and other nutritional concerns are critical features of therapy. Quality standards for the management of patients with heart failure are being developed, and the implementation of these standards is a goal of clinicians. A multidisciplinary approach to elderly patients with heart failure is beneficial.

Antioxidants and vitamins to reduce cardiovascular disease

Cardiovascular disease is the leading cause of morbidity and mortality in Western populations. Several lines of evidence support the role of oxidative stress in atherogenesis. Dietary micronutrients with antioxidant properties and vitamins have also been shown to have a benefit with regards to cardiovascular disease. The most persuasive evidence relates to alpha tocopherol and folate and vitamin B(12). Although the evidence is mounting for supplementation with alpha tocopherol and folate and B(12) for secondary prevention of cardiovascular disease, no clear consensus can be reached for primary prevention of cardiovascular disease. This will have to await results of ongoing clinical trials.

Physiologic concentrations of homocysteine inhibit the human plasma GSH peroxidase that reduces organic hydroperoxides

The plasma reduced glutathione (GSH) selenoperoxidase is a highly conserved enzyme. Furthermore, a small clinical study reported that patients with severe atherosclerosis had low peroxidase activities. Together these observations suggest that the peroxidase is important in preventing atherosclerosis. Yet others have reported that when the assay was run in Tris buffer, it was inactive with the concentrations of GSH found in the plasma. Second, it is known that hyperhomocysteinemia increases the rate of atherogenesis. Because there is some homology between homocysteine and the cysteine in GSH, the question is whether the hyperhomocysteinemia effect may be due to inhibition of the peroxidase. We purified the peroxidase from human plasma and determined its activity by a coupled spectrophotometric assay and a substrate disappearance chemiluminescence assay. When the peroxidase activity was determined in phosphate-buffered saline solution (PBS), there was significant activity with the reported plasma GSH concentrations (5 to 20 micromol/L). The peroxidase was exclusively in the HDL fraction. There was no correlation between the peroxidase activity and the HDL or LDL cholesterol concentrations. Finally, at physiologic concentrations of GSH (9 micromol/L), the peroxidase was inhibited by physiologic, free homocysteine concentrations (1 to 5 micromol/L). These data suggest that the peroxidase is active in vivo and may be important in protecting the endothelium from atherosclerosis by preventing oxidant injury. The homocysteine inhibition of the peroxidase suggests a possible biochemical basis for the observed association between hyperhomocysteinemia and cardiovascular disease. Our studies imply that low concentrations of this peroxidase may be an independent risk factor for atherosclerosis.

Smoking characteristics, antioxidant vitamins, and carotid artery wall thickness among life-long smokers

We studied the associations between the common carotid-intima-media thickness (IMT), as a marker of atherosclerosis, and smoking characteristics and antioxidant vitamins among 158 male life-long cardiovascular disease (CVD)-free smokers. An "increased" carotid IMT was defined as the upper 25%. The prevalence of increased IMT was 2.5 times (odds ratio (OR) = 2.5; 95% CI: 1.1, 5.6) higher among smokers inhaling smoke deeply into the lungs than among moderate and non-inhalers. This association decreased when adjusted for other CVD risk factors. Smokers with an increased carotid IMT did not differ significantly in mean antioxidant vitamin intake and status with the remaining group. However, classical CVD risk factors contributed importantly to increased carotid IMT. In our study, depth of inhalation was the only smoking characteristic associated with carotid IMT although attenuated after adjustment for traditional risk factors for CVD. Furthermore, in these life-long smokers not using any vitamin supplements, no associations were found for antioxidant vitamins.

Oxidative stress, acute and regular exercise: are they really harmful in the diabetic patient?

Oxidative stress has been involved in the pathogenic process of a variety of diseases including diabetes mellitus. The production of oxidative reactive products has been involved in biochemical changes in bio-molecules that might produce tissue damage directly related to some of the main vascular complications in the diabetic patient. On the other hand, exercise, paradoxically, is a well-recognized model of oxidative stress and also an important therapeutic tool in diabetes management. Therefore, the relationship between oxidative stress and exercise in diabetic patients implies an interesting biochemical paradox due to some of the negative effects of exercise principally by the increase of oxidative species in plasma. The effect of oxidative stress during an acute exercise and after an aerobic training period on those patients remains unknown and needs to be studied.

Oxidation of LDL by myeloperoxidase and reactive nitrogen species: reaction pathways and antioxidant protection

Oxidative modification of low density lipoprotein (LDL) appears to play an important role in atherogenesis. Although the precise mechanisms of LDL oxidation in vivo are unknown, several lines of evidence implicate myeloperoxidase and reactive nitrogen species, in addition to ceruloplasmin and 15-lipoxygenase. Myeloperoxidase generates a number of reactive species, including hypochlorous acid, chloramines, tyrosyl radicals, and nitrogen dioxide. These reactive species oxidize the protein, lipid, and antioxidant components of LDL. Modification of apolipoprotein B results in enhanced uptake of LDL by macrophages with subsequent formation of lipid-laden foam cells. Nitric oxide synthases produce nitric oxide and, under certain conditions, superoxide radicals. Numerous other sources of superoxide radicals have been identified in the arterial wall, including NAD(P)H oxidases and xanthine oxidase. Nitric oxide and superoxide readily combine to form peroxynitrite, a reactive nitrogen species capable of modifying LDL. In this review, we examine the reaction pathways involved in LDL oxidation by myeloperoxidase and reactive nitrogen species and the potential protective effects of the antioxidant vitamins C and E.