Preservation of endogenous antioxidant activity and inhibition of lipid peroxidation as common mechanisms of antiatherosclerotic effects of vitamin E, lovastatin and amlodipine

Effects of d-003, a new hypocholesterolaemic and antiplatelet compound, on lipid profile and lipid peroxidation in healthy volunteers

BACKGROUND

D-003 is a mixture of long-chain aliphatic primary acids purified from sugarcane wax with hypocholesterolaemic effects proven in rabbits and healthy volunteers; it lowers serum total cholesterol (TC) and low-density lipoprotein-cholesterol (LDL-C) and increases high-density lipoprotein-cholesterol (HDL-C). D-003 also prevents lipoprotein lipid peroxidation in experimental models.

OBJECTIVE

To investigate the effects of D-003 on lipid profile and lipid peroxidation in healthy human volunteers.

PARTICIPANTS

Forty-six healthy volunteers (24 women, 22 men).

METHODS

This double-blind, randomised, placebo-controlled study investigated the effects of D-003 at 5 and 10 mg/day on the susceptibility of LDL to lipid peroxidation induced by copper ions in healthy volunteers. Forty-six individuals were randomised (1 : 2) to placebo or D-003 at 5 or 10 mg/day, the tablets being taken once a day with the evening meal for 8 weeks. Laboratory determinations and physical examination were performed at baseline and after 4 and 8 weeks of therapy, and compliance and adverse experience assessments were performed at weeks 4 and 8.

RESULTS

All groups were well matched at baseline. At study completion, D-003 at 5 and 10 mg/day significantly (p < 0.001) lowered LDL-C, the primary response variable, by 20.8% and 28.8%, respectively. In addition, D-003 at 5 and 10 mg/day reduced (p < 0.001) TC (12.7% and 17.5%, respectively), LDL-C/ HDL-C (25.9% and 36.3%, respectively) and TC/HDL-C (18.6% and 26.3%, respectively), while significantly (p < 0.01) increasing HDL-C (7.7% and 12.4%, respectively). Triglycerides were significantly (p < 0.05) reduced (8.8% and 13.1%, respectively) with respect to baseline, but not versus placebo. Responses assessed at 4 weeks showed significant reductions of LDL-C, TC and atherogenic ratios with both doses of D-003, whereas HDL-C was significantly increased. Triglycerides, however, remained unchanged. No significant changes in any lipid profile variable occurred in the placebo group. D-003 at 5 and 10 mg/day significantly (p < 0.05) increased lag time (18.3% and 32.0%, respectively) and decreased maximum rate of diene propagation (V(max)) [12.7% and 19.1%, respectively] of copper-induced LDL peroxidation. D-003 5 and 10 mg/day attenuated the reduction of the reactivity against 2, 4, 6-trinitrobenzene sulfonic acid (TNBS) by 19.9% and 32.0%, respectively. The treatment was well tolerated. Three subjects (one from each group) discontinued the study. Only one, treated with D-003 5 mg/day, discontinued because of an adverse event (gastritis).

CONCLUSIONS

D-003 at 5 and 10 mg/day demonstrated dose-dependent cholesterol-lowering effects in healthy volunteers characterised by reductions in LDL-C, TC and atherogenic ratios, and increases in HDL-C. Effects on triglycerides were modest and uncertain. As expected from experimental studies, D-003 inhibited the susceptibility of LDL to lipid peroxidation assessed by three indicators lag time V(max) and reactivity versus TNBS. Further studies investigating the effect of larger doses and treatment duration must be conducted to confirm the reproducibility of the present results in different study populations.

Mechanisms of plaque stabilization for the dihydropyridine calcium channel blocker amlodipine: review of the evidence

Coronary artery disease (CAD) is the consequence of atherosclerosis, a vascular disorder that is the leading cause of death and disability throughout much of the developed world. Certain cellular changes in the vulnerable atherosclerotic plaque are characterized by a loss of normal calcium regulation. This observation has led to interest in a potential antiatherogenic role for calcium channel blockers (CCBs), independent of their effects on vasodilation. The Prospective Randomized Evaluation of the Vascular Effects of Norvasc Trial (PREVENT) demonstrated that treatment with amlodipine, a third-generation CCB, in patients with documented CAD produced marked reductions in cardiovascular events as compared with placebo, without a reduction in coronary luminal loss. Amlodipine therapy was also associated with significant slowing in carotid atherosclerosis, an important surrogate marker for CAD, independent of blood pressure changes. The findings from PREVENT were remarkably consistent with another study known as the Coronary Angioplasty Amlodipine Restenosis Study (CAPARES). A reduction in the progression of carotid atherosclerosis has also been recently reported for lacidipine, another third-generation dihydropyridine CCB. These clinical findings have led to a renewed interest in potential plaque stabilization properties of certain CCBs, as will be systematically reviewed in this article. It is also probable that vascular protective agents, such as amlodipine may work in a synergistic fashion with other established treatments, including HMG-CoA reductase inhibitors, to effectively improve outcomes in patients who are at risk for or have established CAD.

Anti-thrombotic effects of atorvastatin--an effect unrelated to lipid lowering

Statins (3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) have been shown to reduce clinical events in excess of what can be explained by altering lipid profile. Statins have been shown to possess modest antioxidant and antiplatelet aggregatory effect. We postulated that statins may accordingly inhibit arterial thrombus formation. To assess the antithrombotic effects of atorvastatin, a commonly used statin, in response to an oxidant stimulus, we fed Sprague-Dawley rats either regular chow, or chow mixed with atorvastatin (1.25 mg/kg) for 10 days (n = 16 in each group). Eight rats in each group were also given oxidized low-density lipoprotein intravenously prior to the induction of thrombus. An occlusive thrombus was created in the abdominal aorta by application of Whatman paper soaked in 35% FeCl3. The time to occlusive thrombus formation was not altered by administration of oxidized low-density lipoprotein in the rats fed regular chow or chow mixed with atorvastatin. However, time to thrombosis was increased in the group given chow mixed with atorvastatin (26 +/- 4 minutes vs. 20 +/- 5 minutes, P < 0.02). To determine the mechanism of atorvastatin's antithrombotic effect, we measured the expression of endothelial constitutive nitric oxide synthase (cNOS) in rat aortas by Western analysis. The cNOS protein expression was enhanced 75% in rats fed chow with atorvastatin (P < 0.01 vs. rats fed regular chow). Plasma levels of total cholesterol and low-density lipoprotein-cholesterol were similar in all groups. This study shows that atorvastatin delays thrombus formation in arterial channels exposed to oxidant stress. This effect of atorvastatin appears to be related to increased expression of cNOS, which is known to inhibit platelet aggregation and induce vasodilatation. The effects of atorvastatin are independent of its effects on plasma cholesterol levels.

Reduction of bFGF-induced smooth muscle cell proliferation and endothelin receptor mRNA expression by mevastatin and atorvastatin

The anti-atherosclerosis mechanisms of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) occur via both cholesterol-dependent and cholesterol-independent mechanisms. The present study used aortic and cerebral vascular smooth muscle cells (SMC) from rat to investigate whether atorvastatin and mevastatin affect basic fibroblast growth factor (bFGF)-induced SMC proliferation and the mRNA expression of endothelin A (ET(A)) and endothelin B (ET(B)) receptors. Cell proliferation was assessed by MTT and real-time PCR was used to quantify ET(A) and ET(B) receptor mRNA. bFGF-induced concentration and time dependent SMC proliferation and up-regulation of the mRNA expression of ET(A) and ET(B) receptors. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors inhibited bFGF-induced proliferation of SMC (P<0.01). In aortic SMC atorvastatin and mevastatin significantly inhibited bFGF-induced mRNA expression of endothelin ET(A) and ET(B) receptors (P<0.05). Although in cerebral SMC the inhibitory effect of the statins was comparable in size with that seen in aortic SMC, only reached borderline significance (P=0.06) for ET(A) receptor mRNA but not for ET(B). The findings suggested a direct effect of statins on the vascular wall beyond their well-known lipid lowering effect in anti-atherosclerosis. Furthermore, the specific antagonists of ET(A) and ET(B) receptors (FR139317 and BQ788, respectively) significantly inhibited bFGF-induced SMC proliferation (P<0.001). The results suggested that endothelin receptors and the mevalonate pathway were involved in bFGF-induced SMC proliferation.

Renin-angiotensin system antagonism and lipid-lowering therapy in cardiovascular risk management

The renin-angiotensin system (RAS) and dyslipidaemia have been shown to be involved in the genesis and progression of atherosclerosis. Manipulation of the RAS has been effective in modifying human coronary artery disease progression. Similarly, the 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors or statins have been shown to reduce cholesterol and lower cardiovascular events in primary and secondary prevention trials in coronary artery disease. In addition to their primary mode of action, statins and blockers of the RAS possess common additional properties that include restoration of endothelial activity and inhibition of cellular proliferation. This article reviews the current data on the common properties of these classes of drugs in which the beneficial effects extend beyond their antihypertensive and lipid-lowering properties.

Simvastatin improves endothelial function in spontaneously hypertensive rats through a superoxide dismutase mediated antioxidant effect

BACKGROUND

Hydroxymethylglutaryl coenzyme A (HMGCoA) reductase inhibitors have beneficial effects beyond their cholesterol-lowering properties. The antioxidant mechanism of HMGCoA reductase inhibitors is not completely understood.

OBJECTIVES

To elucidate the antioxidant effect of simvastatin.

METHODS

We studied the influence of simvastatin treatment on the development of hypertension, modification of antioxidant systems, and reactivity of aortic rings in Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats.

RESULTS

Simvastatin had no effect on blood pressure (BP). Simvastatin treatment (either 1 or 2 mg/kg body weight for 12 or 20 weeks) increased superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities in SHR rats compared with untreated control SHR rats. Carbachol-induced relaxation of aortic rings was impaired in control SHR rats and was restored by simvastatin treatment. Addition of SOD improved the response in control SHR rats and did not have any effect in treated SHR rats. Addition of diethyldithiocarbamic acid, a selective inhibitor of SOD, produced a mild non-significant impairment in carbachol-induced relaxation in control SHR rats, suggesting a deficient antioxidant system in these animals. However, in treated SHR and in WKY rats, impairment of the relaxation was marked, implying that SOD activity in these animals was important to maintain endothelial function. In aortic rings without endothelium from SHR rats, contraction induced by free radicals was substantially higher than in WKY rats. This effect was attenuated in 1-mg-treated rats and abolished in 2-mg-treated rats.

CONCLUSIONS

Simvastatin promotes intracellular antioxidant systems, fundamentally SOD, restoring endothelial function but not having any effect on blood pressure.

Modulation of matrix metalloproteinase-1, its tissue inhibitor, and nuclear factor-kappa B by losartan in hypercholesterolemic rabbits

Upregulation of angiotensin II receptor, may be involved in the initiation and progression of atherosclerosis. To examine the contribution of AT1 receptor in the expression of matrix metalloproteinase-1 (MMP-1) and its tissue inhibitor (TIMP-2) in lipid-deposited arterial tissues, New Zealand white rabbits were given high-cholesterol chow (with losartan 25 mg/d or vehicle) for 10 weeks. Losartan reduced the areas of sudanophilia in the aorta of rabbits fed high-cholesterol diet (p < 0.01 vs. control). Losartan also significantly decreased the enhanced mRNA expression of MMP-1 and TIMP-2 in aortas of rabbits with high-cholesterol diet. Losartan-treated rabbits revealed a reduction in immunohistochemical expression of MMP-1, whereas TIMP-2 expression became localized to the intima. In addition, losartan treatment reduced the activation of NF-kappa B by inhibiting the degradation of its inhibitor I kappa-B alpha. These observations demonstrate that AT1 receptor blockade with losartan reduces lipid deposition and exerts potent inhibitory effects on NF-kappa B activation and modulates the expression of MMP-1 and TIMP-2 in hypercholesterolemic rabbits.

Endothelial dysfunction, angiotensin-converting enzyme inhibitors and calcium antagonists

The endothelium plays a crucial role in the pathogenesis of cardiovascular disease. Endothelial function is attenuated by the presence of different well known cardiovascular risk factors. Evaluation of endothelial vasodilator function serve as an index integrating the overall stress imposed by cardiovascular risk factors and reinforce the suggestion that endothelial dysfunction is an early marker of cardiovascular disease that precedes clinical manifestations. Angiotensin-converting enzyme inhibitors have been shown to reduce the cardiovascular mortality, an effect that could be the consequence of an improvement in the endothelial function. Recent studies have shown that a calcium antagonist might improve the endothelial function, however, there is controversy about this action and also about the potential mechanisms for the effect of a calcium antagonist in the regulation of endothelial function.

Mixed tocopherol preparation is superior to alpha-tocopherol alone against hypoxia-reoxygenation injury

Hypoxia-reoxygenation (H-R) is associated with alterations in oxidant-antioxidant balance and L-arginine-nitric oxide system. Tocopherols decrease the activity of reactive oxygen species (ROS) and yet are not beneficial in clinical trials. It has been proposed that mixed tocopherols as found in nature may be more tissue protective than alpha-tocopherol alone found in commercial preparations. We compared the effect of a mixed tocopherol preparation with that of alpha-tocopherol alone on superoxide dismutase (SOD) activity and iNOS expression in cultured myocytes exposed to H-R. Myocytes from Sprague-Dawley rat hearts were subjected to hypoxia for 24 h followed by reoxygenation for 3 h H-R. Parallel groups of myocytes were pretreated with alpha-tocopherol alone or a mixed-tocopherol preparation (containing alpha-, gamma-, and delta-tocopherols) (50 microM) for 30 min. H-R resulted in myocyte injury (determined by LDH release), a decrease in SOD activity and an upregulation of iNOS expression/activity. Both tocopherol preparations attenuated cell injury and markedly decreased the effects of H-R on SOD activity and iNOS expression/activity (all P < 0.05 vs H-R group, n = 5). However, mixed-tocopherol preparation was much superior to alpha-tocopherol in terms of myocyte protection from the adverse effect of H-R (P < 0.05). Lack of efficacy of commercial tocopherol preparations in clinical trials may reflect absence of gamma- and delta-tocopherols.

The effects of magnesium sulphate and EDTA in the hypercholesterolaemic rabbit

Numerous clinical reports suggest the beneficial effects of chelation therapy for the treatment of atherosclerosis. However, the results of these studies are inconclusive and controversial. The purpose of this present study was to examine the prophylactic and therapeutic effects of chelation liquid (CHL) in experimental atherosclerosis. Twenty New Zealand white rabbits were fed a 1% cholesterol-supplemented diet for 45 days. In the prophylactic phase of the study subcutaneous 300 mg EDTA + 500 mg magnesium sulphate (MgSO4) injections (five rabbits) and isotonic saline (five rabbits) were given to test and control groups, respectively, along with cholesterol rich diet. The CHL treatment ameliorated the rise of serum cholesterol and serum triglyceride concentrations, lowered serum calcium concentrations and reduced the aortic atheroma. In the therapeutic phase of the experiment the cholesterol diet was stopped and the remaining 10 animals were returned to normal diet. Five of these rabbits were given CHL injections and other five animals were given isotonic saline injections for 121 days. Although the level of cholesterol and triglyceride were not significantly different in the two groups, the serum calcium concentration and the percentage of the area of flate aortic specimen occupied by atheroma were significantly lower in the CHL treated rabbits as compared to controls. It is concluded that CHL injections have a definite prophylactic effect on atherogenesis in the cholesterol-fed rabbit, and may have some therapeutic value in the regression phase. Further confirmatory studies are suggested.

Downregulation of angiotensin II type 1 receptor by hydrophobic 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors in vascular smooth muscle cells

3-Hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors, so-called statins, reduce the relative risk of a major coronary event by lowering the serum cholesterol level. In addition, statins may confer beneficial effects by cholesterol-lowering independent mechanisms, which are incompletely characterized. Because angiotensin II (Ang II) plays crucial roles in the pathogenesis of cardiovascular diseases, we examined the effect of statins on the expression of the Ang II type 1 receptor (AT(1)-R) in cultured vascular smooth muscle cells (VSMCs). Cerivastatin and fluvastatin reduced the AT(1)-R mRNA and the AT(1)-R protein levels; however, pravastatin lacked this effect. Cerivastatin and fluvastatin suppressed the AT(1)-R promoter activity measured by luciferase assay but did not affect AT(1)-R mRNA stability, suggesting that the suppression occurs at the transcriptional level. Coincubation of VSMCs with mevalonate or geranylgeranyl pyrophosphate but not with farnesyl pyrophosphate reversed the cerivastatin-induced AT(1)-R downregulation. Overexpression of dominant-negative Rho A also suppressed AT(1)-R mRNA expression. Treatment with cerivastatin for 24 hours reduced the calcium response of VSMCs to Ang II. Taken together, statins downregulate AT(1)-R expression through a mevalonate-dependent, geranylgeranyl pyrophosphate-dependent, and Rho A-dependent manner and attenuate the biological function of Ang II. Downregulation of AT(1)-R may contribute to the cholesterol-independent beneficial effect of statins on the cardiovascular system.

Mechanisms of atherosclerotic plaque stabilization for a lipophilic calcium antagonist amlodipine

Coronary artery disease (CAD) is the result of atherosclerosis, a vascular disorder characterized by abnormalities in vasoconstriction and endothelial function, ultimately leading to partial or complete vessel occlusion. Because the atherosclerotic plaque is marked by changes in calcium regulation, there has been interest in a potential antiatherosclerotic role for calcium antagonists. In support of this hypothesis, a recent clinical study demonstrated in patients with CAD that treatment with the lipophilic dihydropyridine-type calcium antagonist amlodipine resulted in significantly fewer cardiovascular procedures and events. The Prospective Randomized Evaluation of the Vascular Effects of Norvasc Trial (PREVENT) evaluated the effects of amlodipine on the development and progression of atherosclerotic lesions in coronary and carotid arteries in 825 patients with documented CAD. The results of PREVENT showed that patients receiving amlodipine had marked reductions in hospitalization for revascularization and unstable angina compared with placebo in a population consisting of either normotensive or controlled hypertensive patients. Ultrasound approaches determined that amlodipine therapy was also associated with significant slowing in carotid atherosclerosis-an important surrogate marker for CAD-over the 3-year period. This vascular-wall benefit associated with amlodipine treatment was not related to changes in blood pressure. The findings from PREVENT were consistent with a second reported study known as the Coronary Angioplasty Amlodipine Restenosis Study (CAPARES). These clinical results have led to an interest in potential plaque-stabilization properties of this lipophilic calcium antagonist. In this article, cellular and molecular mechanisms of action that may contribute to a beneficial role for a calcium antagonist in the treatment of atherosclerosis will be reviewed.

Do statins afford neuroprotection in patients with cerebral ischaemia and stroke?

An emerging body of evidence indicates that beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, or 'statins', provide neuroprotection in addition to reducing ischaemic stroke. Statins reduce the incidence of ischaemic stroke by stabilising atherosclerotic plaques in the precerebral vasculature and through antithrombotic actions, and the neuroprotective effects of statins may confer significant clinical benefit. Some of these neuroprotective effects are likely to be cholesterol independent and mediated by the interruption of isoprenoid biosynthesis. Therapy with statins may modulate endothelial function and preserve blood flow to regions exposed to an ischaemic insult. In particular, statin-mediated preservation of endothelial nitric oxide synthase activity in cerebral vasculature, especially in the ischaemic penumbra, may limit neurological deficit. Moreover, putative anti-inflammatory and antioxidant properties of statins may confer additional neuroprotection. Further large clinical trials are necessary to address the role of statin therapy in the primary prevention of stroke, small vessel cerebrovascular disease and vascular dementia.

Statins: mechanism of action and effects

The beneficial effects of statins are the result of their capacity to reduce cholesterol biosyntesis, mainly in the liver, where they are selectively distributed, as well as to the modulation of lipid metabolism, derived from their effect of inhibition upon HMG-CoA reductase. Statins have antiatherosclerotic effects, that positively correlate with the percent decrease in LDL cholesterol. In addition, they can exert antiatherosclerotic effects independently of their hypolipidemic action. Because the mevalonate metabolism generates a series of isoprenoids vital for different cellular functions, from cholesterol synthesis to the control of cell growth and differentiation, HMG-CoA reductase inhibition has beneficial pleiotropic effects. Consequently, statins reduce significantly the incidence of coronary events, both in primary and secondary prevention, being the most efficient hypolipidemic compounds that have reduced the rate of mortality in coronary patients. Independent of their hypolipidemic properties, statins interfere with events involved in bone formation and impede tumor cell growth.

Statins and neuroprotection

The beneficial effect of beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) in primary prevention of coronary artery disease in those with hypercholesterolaemia and in secondary prevention in those with established coronary vascular disease are now well known. A growing body of evidence suggests that statins also possess important additional clinical benefits, such as stroke risk reduction. In this article we review the evidence that statins may be neuroprotective, especially in the brain parenchyma during stroke. We also review the observational data that statins may prevent the onset of dementia.

Rationale and design of the St. Francis Heart Study: a randomized clinical trial of atorvastatin plus antioxidants in asymptomatic persons with elevated coronary calcification

Early detection of asymptomatic subjects who are at risk for future cardiovascular events may allow for earlier medical treatment in order to prevent disease progression and future events. Electron-beam computed tomography accurately identifies people with increased coronary calcification, which is correlated with increased coronary plaque mass, increased likelihood of obstructive coronary disease, and increased likelihood of future cardiovascular events. The St. Francis Heart Study is a single-center combination study of men and women 50-70 years old that includes a natural history study of the relation between calcium scores and cardiovascular events (n = 5582), the association of calcium scores with traditional and nontraditional coronary disease risk factors (n = 1160), and a randomized clinical trial designed to assess the benefit of combination treatment with atorvastatin, vitamin C, and vitamin E, as compared to placebos, in subjects with elevated age- and gender-adjusted coronary calcification (n = 1007). Mean follow-up duration will be 4 years. The study is proceeding on schedule with anticipated completion by August 2002. It should provide important information regarding the benefits of treating asymptomatic men and women who have elevated coronary artery calcium, using cholesterol reduction and antioxidant therapy. The article describes the design of the St. Francis Heart Study.

Mechanisms of plaque stabilization for a charged calcium channel blocker in coronary artery disease

Coronary artery disease (CAD) results from atherosclerosis, a systemic vascular disorder that is the leading cause of death and disability throughout much of the developed world. Because cellular changes associated with vulnerable atherosclerotic plaque are characterized by a loss of normal calcium regulation, there is strong interest in a potential antiatherosclerotic role for calcium channel blockers. This hypothesis has been supported by investigational studies conducted in well-defined cellular and animal models of atherosclerosis. In addition, several clinical studies have tested the benefit of calcium channel blockers among patients with mild-to-moderate CAD. More recent trials have shown reductions in cardiovascular events after treatment with amlodipine, a long-acting, dihydropyridine-type calcium channel blocker. The Prospective Randomized Evaluation of the Vascular Effects of Norvasc Trial (PREVENT) demonstrated that patients with documented CAD treated with amlodipine experienced marked reductions in cardiovascular events compared with patients receiving placebo. Amlodipine also was associated with significant slowing of carotid atherosclerosis, an important surrogate marker for CAD, independent of blood pressure modification. These results have renewed interest in potential plaque stabilization properties of third-generation calcium channel blockers and their possible therapeutic role in CAD.

Statin therapy and stroke prevention

Hypercholesterolemia has not traditionally been considered an important risk factor in the pathogenesis of stroke. However, recent studies show that statin therapy significantly reduces ischemic stroke for patients with established coronary artery disease. Statin therapy may reduce stroke through amelioration of precerebral atherosclerosis in the carotid artery and the aorta. Anti-atherosclerotic, anti-inflammatory, and antithrombotic actions of statins occur within the blood and in plaque. Statins may also protect against cerebral ischemia through beneficial modulation of the brain endothelial nitric oxide system. Ongoing studies are exploring the role of statin therapy in the primary prevention of stroke and in the prevention of cognitive decline and multi-infarct cerebrovascular disease.

Use of statins in CNS disorders

It is well established that 3-hydroxy-3-methyglutaryl coenzyme A (HMG-CoA) reductase inhibitors ("statins") reduce cholesterol levels and prevent coronary heart disease (CHD). Although a causal relation between elevated cholesterol levels and stroke has not been well defined, a number of large secondary prevention studies and meta-analyses have shown that statin therapy reduces stroke in patients with CHD and hypercholesterolemia. In addition to the vascular effects of statins (stabilization of atherosclerotic plaques, decreased carotid intimal-medial thickness), there are increasing data to suggest that these agents have additional properties that are potentially neuroprotective. These include endothelial protection via actions on the nitric oxide synthase system, as well as antioxidant, anti-inflammatory and anti-platelet effects. These actions of statins might have potential uses in other neurological disorders such as Alzheimer's disease and certain types of brain tumors.

The hyperlipemic hamster - a model for testing the anti-atherogenic effect of amlodipine

Male Golden Syrian hamsters were subjected to a hyperlipemic diet. At intervals ranging from 2 to 14 weeks, the animals were examined for changes in serum constituents and structural modifications of lesion-prone areas: the cardiac valves, coronary arteries and aortic arch. Serum was characterized by a gradual increase in cholesterol, triglycerides and a decrease in total peroxyl-radical trapping potential. The sequence of modifications of the endothelial cells, smooth muscle cells, and migrating plasma monocytes as well as of the extracellular matrix were established. Amlodipine treatment of hyperlipemic hamster was assessed. Amlodipine exhibited an athero-protective effect, acting as antioxidant, reducing the LDL uptake by the vessel wall and consequently, limiting the size and extent of lesioned areas. The hyperlipemic hamster is a reliable model to unravel the cellular alterations leading to atheroma formation, and for testing the effect of drugs in this process.

Different isoforms of tocopherols enhance nitric oxide synthase phosphorylation and inhibit human platelet aggregation and lipid peroxidation: implications in therapy with vitamin E

BACKGROUND

alpha-Tocopherol has received much attention in the primary and secondary prevention of coronary artery disease. Absence of other isoforms, such as gamma- and delta-tocopherol, in commercial preparations of vitamin E may account for the inconsistent results of clinical trials. Since platelet aggregation is intimately involved in thrombogenesis, the relative effects of alpha-, gamma-, and delta-tocopherol and their combination were examined on human platelet aggregation, lipid peroxidation, and constitutive nitric oxide synthase (cNOS) activity.

METHODS AND RESULTS

Human platelets were incubated with the three different isoforms of tocopherol and their combination for 30 minutes, and then ADP-induced platelet aggregation measured. All three isoforms of tocopherol markedly and similarly decreased platelet aggregation in a concentration (120--480 microM)-dependent manner. All three tocopherols also decreased the level of the lipid peroxidation product, malondialdehyde (MDA), and increased NO release (P < 0.05 vs control). These isoforms of tocopherol did not affect cNOS protein expression, but enhanced cNOS phosphorylation in platelets. The combination of three tocopherols in a concentration found in nature was more potent than alpha-, gamma-, or delta-tocopherol alone in this regard.

CONCLUSION

These observations suggest that all three major isoforms of tocopherol have a similar effect on human platelet aggregation. The three isoforms appear to attenuate platelet aggregation at least in part via a decrease in free radical generation and an increase in platelet cNOS activity. The combination of tocopherols has a synergistic platelet inhibitory effect. Future clinical trials should concentrate on the combination of these three isoforms of tocopherols.

Statins and cerebrovascular disease: plaque attack to prevent brain attack

Stroke is the third leading cause of death in the USA and in the developed world. The beneficial role of cholesterol reduction in decreasing stroke has been uncertain. However, recent data indicate that statin treatment in patients with a history of myocardial infarction not only reduces the risk of a second myocardial infarction, coronary heart disease, revascularization procedures and death, but also significantly reduces the risk of stroke. However, the mechanism(s) by which statins reduce stroke remain uncertain. Thus, the therapeutic armamentarium for the reduction of stroke in secondary prevention now includes cholesterol reduction with statins.

Epinephrine upregulates superoxide dismutase in human coronary artery endothelial cells

Regular exercise resulting in release of catecholamines is an oxidant stress, and yet it protects humans from acute cardiac events. We designed this study to examine the effect of epinephrine on free radical release and endogenous superoxide dismutase (SOD) gene and protein expression in human coronary artery endothelial cells (HCAECs). HCAECs were incubated with epinephrine (10(-9) to 10(-5) M) alone or with the water-soluble analog of vitamin E (trolox) (10(-5) M), the lipid-soluble vitamin E (5 x 10(-5) M), or the beta(1)-adrenergic blocker atenolol (10(-5) M). At 1 and 24 h of incubation with epinephrine, superoxide anion generation increased by 102 and 81% in the HCAECs. There was a marked increase in both MnSOD and Cu/ZnSOD mRNA and protein, as determined by RT-PCR and Western Analysis, respectively. Both MnSOD and Cu/ZnSOD activities were also increased. Pretreatment of HCAECs with trolox and vitamin E decreased superoxide anion generation (p <.05 vs. epinephrine alone) and blocked the subsequent upregulation of SOD mRNA and protein. Treatment of cells with the beta-blocker atenolol also blocked the upregulation of SOD (p <.05 vs. epinephrine alone). These observations suggest that epinephrine via beta(1)-adrenoceptor activation causes superoxide anion generation, and the superoxide subsequently upregulates the endogenous antioxidant species SOD. These observations may be the basis of long-term benefits of exercise.

The effect of amlodipine on endothelial function in young adults with a strong family history of premature coronary artery disease: a randomised double blind study

Endothelial dysfunction, an early event in atherogenesis, has been demonstrated in young asymptomatic subjects with a strong family history of premature coronary artery disease (CAD). In these subjects, preventive measures involving risk factor modification are not appropriate, and strategies employing novel antiatherogenic agents, such as the dihydropyridine calcium channel blocker, amlodipine, may be useful. Ninety-one subjects (mean age, 28.6 years; range, 18-40) with a strong family history of premature CAD and no other identified vascular risk factors were randomised to either 5 mg amlodipine (49 subjects) or placebo (42 subjects). Brachial artery flow mediated dilatation (FMD) (endothelium-dependent response) and response to glyceryltrinitrate (GTN) (direct smooth muscle dilator) were assessed non-invasively at baseline, and after 12 and 24 weeks using high-resolution vascular ultrasound. In those treated with amlodipine, mean FMD increased from 2.32+/-2.23% at baseline to 3.52+/-3.1% at 24 weeks (P<0.005). However, FMD also increased in the placebo group from 1.64+/-2.12 to 3.37+/-2.68% (P<0.002), and the difference between the FMD response in the amlodipine and placebo groups was not significant. Dilatation to GTN did not change in either group. Therefore, impaired endothelial function improved in family history subjects taking both amlodipine and placebo, but there is no difference between the groups.

Simvastatin inhibits noradrenaline-induced hypertrophy of cultured neonatal rat cardiomyocytes

1. Oxidative mechanisms have been implicated in neonatal cardiomyocyte hypertrophy. We and others have shown that a HMG-CoA reductase inhibitor preserves endogenous antioxidant enzyme activity and inhibits cardiac hypertrophy in vivo. We therefore have examined whether noradrenaline (NA) induces the generation of reactive oxygen species (ROS) during its induction of neonatal cardiomyocyte hypertrophy and whether simvastatin, a HMG-CoA reductase inhibitor, attenuates ROS production and thus NA-induced hypertrophy of cardiomyocytes. 2. NA increased the intracellular ROS levels in a concentration-dependent manner. This increase of ROS was significantly inhibited by simvastatin and catalase. Prazosin partially suppressed NA-induced increase of ROS and beating, while preincubation with both prazosin and propranolol completely abolished NA-evoked increase of ROS and beating. Simvastatin did not affect NA-induced increase of beating. 3. The NA-induced increase of protein content was partially suppressed by prazosin and completely abolished by preincubation with both prazosin and propranolol. Simvastatin inhibited the increase of NA-induced increase of RNA content and [(3)H]-leucine incorporation in a concentration-dependent manner. Mevalonic acid (MVA) reversed the inhibition of NA-induced RNA and protein increase by simvastatin. Catalase also inhibited the NA-induced increase of RNA and protein. 4. We conclude that the inhibitory effects of simvastatin on myocyte hypertrophy were associated with its antioxidant effects and inhibition of MVA-metabolism pathway in neonatal rat cardiomyocytes. NA-induced increases of intracellular ROS and cardiomyocyte hypertrophy requires both alpha and beta adrenoceptors activation in neonatal rat cardiomyocytes. The increases of ROS induced by NA is required for hypertrophy.

Upregulation of LOX-1 expression in aorta of hypercholesterolemic rabbits: modulation by losartan

Angiotensin-II (Ang-II) enhances the modification of LDL and the expression of its lectin-like receptor (LOX-1) by activating type 1 (AT(1)) receptors. This study was designed to determine the effect of hypercholesterolemia on LOX-1 expression in aorta and its modulation by the AT(1) receptor blocker losartan. Male New Zealand White rabbits were fed regular chow (Control group), chow with 1% cholesterol and 4% peanut oil (HC-diet group), or 1% cholesterol and 4% peanut oil diet plus losartan (25 mg/kg/day) (Losartan + HC-diet group) for 10 weeks. Animal body weight, serum cholesterol levels, and arterial blood pressure were measured. Aortic intimal thickening was quantitated in H&E-stained segments. LOX-1 expression in aortas was examined by immunohistochemistry and semi-quantitative RT-PCR. High-cholesterol diet did not affect body weight, but induced hypercholesterolemia and extensive intimal thickening. Aortas of rabbits in the control group showed a modest LOX-1 expression in the endothelium. Aortic intimal proliferation in HC-diet group was associated with a marked increase in LOX-1 expression (protein and mRNA) in the endothelium and neointima. Treatment with losartan attenuated aortic intimal proliferation and markedly decreased the enhanced LOX-1 expression. Thus high-cholesterol diet induces the upregulation of LOX-1 expression in neointima of aortas of rabbits. Treatment with losartan, an AT(1) blocker, markedly decreases this enhanced LOX-1 expression.

Effects of the new hydroxy-3-methylglutaryl coenzyme a reductase inhibitor fluvastatin on anti-oxidant enzyme activities and renal function in streptozotocin-induced diabetic rats

1. The effects of 11 week treatments with the new hydroxy3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor fluvastatin on renal intrinsic anti-oxidant enzyme (AOE) activities and renal function were evaluated in streptozotocin (STZ)-induced diabetic rats. 2. Renal intrinsic AOE activities, creatinine clearance and urinary albumin excretion were examined in STZ-induced diabetic rats. The levels of total cholesterol (TC), triglyceride (TG) and phospholipid (PL) were also examined. 3. In general, renal AOE activities and function were lower in diabetic rats than in non-diabetic Sprague-Dawley rats. 4. Decreases in TC, TG and PL levels and urinary albumin excretion by the HMG-CoA reductase inhibitor fluvastatin improved renal function and produced a non-uniform alteration in renal AOE; only glutathione peroxidase (GSH-Px) activity increased significantly with fluvastatin treatment. 5. It appears that the improvement in renal function and albuminuria may be related to increases in GSH-Px activity, but there was no correlation between changes in renal function and changes in the activity of Mn-superoxide dismutase or catalase.

Effects of alpha-tocopherol on ox-LDL-mediated degradation of IkappaB and apoptosis in cultured human coronary artery endothelial cells

Experimental studies have demonstrated that vitamin E (alpha-tocopherol) may provide significant cytoprotection during cell injury. In this study, we examined the effects of alpha-tocopherol on oxidized low-density lipoprotein (ox-LDL)-induced apoptosis in human coronary artery endothelial cells (HCAECs). In addition, we examined the activation of NF-kappaB pathway in this process. Cultured HCAECs were treated with ox-LDL for 24 h. Incubation of HCAECs with ox-LDL resulted in apoptosis of HCAECs in a concentration-dependent manner, as determined by TUNEL and DNA laddering. Ox-LDL degraded IkappaB and activated NF-kappaB in HCAECs, as determined by Western blot analysis. Treatment with alpha-tocopherol (10 and 50 microM) decreased ox-LDL-mediated apoptosis as well as degradation of IkappaB and activation of NF-kappaB in HCAECs. High concentration of alpha-tocopherol (50 microM) was more effective than the low concentration of alpha-tocopherol (10 microM). Thus, ox-LDL induces apoptosis of HCAECs, in concurrence with degradation of IkappaB and activation of NF-kappaB. Alpha-tocopherol markedly decreases ox-LDL-induced effects.

The effect of vitamin E, probucol, and lovastatin on oxidative status and aortic fatty lesions in hyperlipidemic-diabetic hamsters

Diabetes mellitus is associated with an increased risk of premature atherosclerosis, which may be due in part to an increased rate of low density lipoprotein (LDL) oxidation. Previous studies have shown that vitamin E, probucol, and lovastatin can reduce the oxidative susceptibility of LDL in normoglycemic animal models; however, few studies have investigated this in conjunction with aortic fatty streak lesion formation in diabetic hyperlipidemic models. Forty-eight Syrian hamsters were made diabetic by intraperitoneal injection of low dose streptozotocin. Diabetic animals (12 animals/groups) received a high saturated fat and cholesterol diet for 12.5 weeks. At 2.5 week of dietary treatments, the diet was supplemented with either: (1) 500 IU/day vitamin E (D+E); (2) 1% probucol w/w of the diet (D+P); (3) 25 mg/kg lovastatin (D+L); or (4) diabetic control (D). An age-matched group of hamsters (n=6) receiving the same diet but not made diabetic (ND) was used as control. At the end of the study, aortic arch foam cell-rich fatty streak lesion, plasma glucose, total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), non-HDL-C, triglycerides (TG), phospholipids, alpha-tocopherol, plasma lipid peroxide and the susceptibility of LDL to copper-catalyzed oxidation were determined. Diabetes increased plasma glucose, and when combined with an atherogenic diet resulted in a further increase of plasma lipids. Vitamin E, probucol, and lovastatin significantly reduced plasma TG in the diabetic hamsters fed the atherogenic diet. Vitamin E treatment increased TC, probucol reduced HDL-C without affecting TC; whereas lovastatin reduced TC and selectively decreased non-HDL-C, and significantly reduced fatty streak lesion formation in the aortic arch. While vitamin E and probucol were effective in reducing several indices of oxidative stress including plasma lipid peroxides, cholesterol oxidation products and in vitro LDL oxidation, they had no effect on fatty streak lesion formation. Our results indicate that the LDL in diabetic animals is more susceptible to oxidation than in non-diabetic hamsters and that not only vitamin E and probucol but also lovastatin provide antioxidant protection. It appears that in this combined model of diabetes and hypercholesterolemia, progression of fatty streak lesion formation is mainly associated with changes in TC and non-HDL-C as affected by lovastatin, and is less dependent on the extent of LDL oxidation, changes in plasma TG level and oxidative stress status.

Cardiovascular effects of combination of perindopril, candesartan, and amlodipine in hypertensive rats

The combination therapy with ACE inhibitors, angiotensin II type 1 (AT(1)) receptor antagonists, or calcium channel antagonists may exert more beneficial effects on cardiovascular diseases than monotherapy. Perindopril, candesartan cilexetil, or amlodipine alone or the combination of low doses of each agent was administered orally to stroke-prone spontaneously hypertensive rats (SHRSP) for 4 weeks to compare the hypotensive or cardiovascular effects. Although perindopril (2 mg/kg), candesartan cilexetil (2 mg/kg), or amlodipine (3 mg/kg) alone caused comparable hypotensive effects in SHRSP, monotherapy with perindopril or candesartan decreased left ventricular (LV) weight; mRNA levels for atrial natriuretic factor, skeletal alpha-actin, and collagen types I and III; and aortic weight and platelet-derived growth factor-beta receptor tyrosine phosphorylation to a greater extent than monotherapy with amlodipine. Although monotherapy with a low dose (0.2 mg/kg) of perindopril or candesartan cilexetil did not significantly reduce the LV mRNA levels and aortic platelet-derived growth factor-beta receptor phosphorylation of the SHRSP, combination therapy at such a low dose normalized these parameters more potently than the use of amlodipine (3 mg/kg) alone. Although perindopril or candesartan cilexetil alone at 0.05 mg/kg did not decrease the blood pressure of the SHRSP, such a low dose of combination therapy decreased LV weight and atrial natriuretic factor mRNA levels of the SHRSP to a greater extent than amlodipine alone or amlodipine combined with perindopril or candesartan cilexetil. Our results provide evidence that suggests the combination of an ACE inhibitor and an AT(1) receptor antagonist may be more effective in the treatment of cardiac and vascular diseases than the combination of a calcium channel blocker with an ACE inhibitor or an AT(1) receptor antagonist or monotherapy with each agent.

The evolving role of statins in the management of atherosclerosis

Significant advances in the management of cardiovascular disease have been made possible by the development of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors--"statins." Initial studies explored the impact of statin therapy on coronary artery disease (CAD) progression and regression. Although the angiographic changes were small, associated clinical responses appeared significant. Subsequent large prospective placebo-controlled clinical trials with statins demonstrated benefit in the secondary and primary prevention of CAD in subjects with elevated cholesterol levels. More recently, the efficacy of statins has been extended to the primary prevention of CAD in subjects with average cholesterol levels. Recent studies also suggest that statins have benefits beyond the coronary vascular bed and are capable of reducing ischemic stroke risk by approximately one-third in patients with evidence of vascular disease. In addition to lowering low-density lipoprotein (LDL) cholesterol, statin therapy appears to exhibit pleiotropic effects on many components of atherosclerosis including plaque thrombogenicity, cellular migration, endothelial function and thrombotic tendency. Growing clinical and experimental evidence indicates that the beneficial actions of statins occur rapidly and yield potentially clinically important anti-ischemic effects as early as one month after commencement of therapy. Future investigations are warranted to determine threshold LDL values in primary prevention studies, and to elucidate effects of statins other than LDL lowering. Finally, given the rapid and protean effects of statins on determinants of platelet reactivity, coagulation, and endothelial function, further research may establish a role for statin therapy in acute coronary syndromes.

Pranidipine enhances the action of nitric oxide released from endothelial cells

Nitric oxide (NO) synthesis in vascular endothelium of patients with hypertension is altered. Calcium antagonists have been shown to improve endothelial function in hypertensive patients. Here we report that pranidipine, one of the latest long-acting calcium antagonists in the dihydropyridine group, enhances the actions of NO released from endothelial cells (ECs). Pranidipine significantly enhanced cGMP accumulation in vascular smooth muscle cells cocultured with ECs, whereas amlodipine and nifedipine had no significant effects. In addition, pranidipine also suppressed basal and thrombin-stimulated endothelin-1 production from ECs. Pranidipine also enhanced cGMP accumulation in rat aortic segments with endothelium but not in endothelium-denuded vessels. In contrast, pranidipine had no effect in the presence of N(G)-monomethyl-L-arginine, an inhibitor of NO synthesis. Pranidipine did not affect the basal expression of endothelial NO synthase in ECs. However, pranidipine upregulated the activity of superoxide dismutase in ECs. These findings suggest that pranidipine enhances NO action through inhibition of superoxide-induced NO decomposition in the vessel wall. Thus, pranidipine may be useful in the treatment of impaired endothelial function in patients with hypertension.

Comparative study of ACE-inhibition, angiotensin II antagonism, and calcium channel blockade on flow-mediated vasodilation in patients with coronary disease (BANFF study)

OBJECTIVES

To determine the effect of angiotensin-converting enzyme (ACE) inhibition on brachial flow-mediated vasodilation.

BACKGROUND

Quinapril, an ACE inhibitor with high affinity, has been shown to improve coronary endothelial dysfunction in patients with coronary artery disease. The effectiveness of different vasoactive agents to improve human endothelial function is unknown.

METHODS

High resolution ultrasound was used to assess endothelium-dependent brachial artery flow-mediated vasodilation (FMD) in patients with coronary disease. We studied 80 patients (mean age 58 +/- 0.9 years) in a partial-block, cross-over design trial. Patients were randomized to one of four different drug sequences to receive quinapril 20 mg, enalapril 10 mg, losartan 50 mg or amlodipine 5 mg daily. Each patient received three drugs with a two-week washout period between treatments. The primary end point was the absolute difference in FMD after eight weeks of each study drug compared with their respective baselines analyzed in a blinded fashion.

RESULTS

There was mild impairment of FMD at baseline (7.3 +/- 0.6%). The change in FMD from baseline was significant only for quinapril (1.8 +/- 1%, p < 0.02). No change was seen with losartan (0.8 +/- 1.1%, p = 0.57), amlodipine (0.3 +/- 0.9%, p = 0.97) or enalapril (-0.2 +/- 0.8%, p = 0.84). No significant change in nitroglycerin-induced dilation occurred with drug therapy. The improvement in quinapril response was not seen in those with the DD ACE genotype (0.5 +/- 2.1%) but was seen in those with the ID and II genotype (3.3 +/- 1.2 and 3.2 +/- 1.9%, respectively, p = 0.03).

CONCLUSION

Only quinapril was associated with significant improvement in FMD, and this response is related to the presence of the insertion allele of the ACE genotype.

Effects of alacepril and amlodipine on the renal injury induced by a high-cholesterol diet in rats

BACKGROUND

A high-cholesterol (HC) diet increases blood pressure and induces renal injury in rats. We compared the effects of alacepril, an ACE inhibitor, and amlodipine, a Ca antagonist, on the renal injury induced by an HC diet in rats.

DESIGN AND METHODS

Male Sprague-Dawley rats were given either an HC diet only (n = 5), an HC diet and amlodipine (n = 10) or an HC diet and alacepril (n = 10). The control rats (n = 5) were given a normal diet Systolic blood pressure (SBP) was measured by a tail-cuff method. Serum lipids, malondialdehyde (MDA) as a parameter for lipid peroxidation and urinary protein excretion were determined at 0, 4 and 8 weeks. The renal injury was evaluated histologically by the glomeruli sclerosing score.

RESULTS

The HC diet increased SBP. Amlodipine lowered SBP more significantly than alacepril. Serum total cholesterol was increased by the HC diet and was not affected by either anti-hypertensive agent. HDL-cholesterol was similarly decreased in the three HC diet groups. Alacepril, but not amlodipine, completely attenuated the MDA elevation induced by the HC diet. Urinary protein excretion was decreased by the two anti-hypertensive agents at a similar rate. The renal histological injury assessed by the sclerosing score was ameliorated more significantly by alacepril than by amlodipine.

CONCLUSIONS

Both amlodipine and alacepril decreased blood pressure and urinary protein, and ameliorated the renal injury induced by the HC diet in rats. The renal effect of alacepril seems to be mediated by the decrease in oxidative stress as well as by reduction of blood pressure, since alacepril lowered the sclerosing score more than amlodipine and completely attenuated MDA, although the blood pressure reduction by alacepril was less than that by amlodipine.

Dietary and pharmacological antioxidants in atherosclerosis

Antioxidants that inhibit LDL oxidation are thought to be potential anti-atherogenic compounds. The results of major human randomized trials with antioxidants have, however, been disappointing, except for probucol, which consistently inhibits restenosis. Similarly, animal intervention studies show that antioxidants do not generally inhibit atherosclerosis, although some compounds provide protection. Direct evidence for the oxidation of LDL causing atherosclerosis is needed. This article summarizes results from antioxidant intervention studies, and highlights some of the key issues that need to be addressed to link biochemical changes in the arterial wall more directly to the oxidation theory of atherosclerosis.

Comparative effects of different dihydropyridines on the expression of adhesion molecules induced by TNF-alpha on endothelial cells

OBJECTIVE

Lacidipine has already been demonstrated to reduce the expression of some adhesion molecules induced by pro-oxidant signals on endothelial cells. In order to verify if this effect is a peculiarity of this molecule, or belongs to other dihydropyridinic compounds (DHPs), the activity of lacidipine was compared with that of lercanidipine, amlodipine, nimodipine and nifedipine.

DESIGN AND METHODS

The compounds were incorporated in human umbilical vein endothelial cells (HUVECs) using native low-density lipoprotein as a carrier. The drug concentrations in HUVECs were measured by mass spectrometry. Human recombinant tumour necrosis factor-alpha was then incubated with HUVECs for 7 h at 37 degrees C for adhesion molecule expression.

RESULTS

The cellular amount of lacidipine, lercanidipine and amlodipine was similar, while nimodipine and nifedipine were almost undetectable or undetectable, respectively. Lacidipine, at any concentration, determined a dose-dependent significant decrease of the expression of intercellular adhesion molecule-1 (ICAM-1) ICAM-1, vascular cell adhesion molecule-1 (VCAM-1) VCAM-1 and E-selectin (P < 0.01). Lercanidipine and amlodipine determined variable decreases of adhesion molecules at the intermediate and highest concentrations. Nimodipine and nifedipine determined no effect on ICAM-1, VCAM-1 and E-selectin. The lowest IC50, i.e. the concentration determining the 50% reduction of ICAM-1, VCAM-1 and E-selectin expression was obtained with lacidipine for all the adhesion molecules considered (P < 0.01).

CONCLUSIONS

It is concluded that the effect of the DHPs used in this study on adhesion molecule expression is determined first by their lipophilicity and then by their intrinsic antioxidant activity.

Cholesterol lowering and endothelial function

The pathophysiology of the association between cholesterol and atherosclerosis has been thought to involve the deposition, modification, and cellular uptake of cholesterol. We now believe that the process begins with vascular injury and involves inflammation and vessel remodeling. The vascular endothelium actively regulates vascular tone, lipid breakdown, thrombogenesis, inflammation, and vessel growth, all of which are important factors in the development of atherosclerosis. Endothelial dysfunction promotes atherosclerosis through vasoconstriction, monocyte and platelet adhesion, thrombogenesis, and cytokine and growth factor stimulation and release. An important component of endothelial dysfunction is reduced availability of nitric oxide, which is caused by low-density lipoproteins, especially if they are oxidized. This reduced availability appears to occur through a combination of decreased production, abnormal signaling, and increased destruction by oxygen-free radicals. Concurrently, endothelium-mediated vasoconstrictors, adhesion molecules, cytokines, growth factors, and thrombogenic factors, such as endothelin, are increased by oxidized low-density lipoprotein. Several studies have shown improvements in endothelial function with cholesterol lowering, which may explain the early and substantial reductions in major cardiovascular events associated with cholesterol lowering.

Differential effects of alpha- and gamma-tocopherol on low-density lipoprotein oxidation, superoxide activity, platelet aggregation and arterial thrombogenesis

OBJECTIVES

This study was designed to examine the differential effects of alpha- and gamma-tocopherol on parameters of oxidation-antioxidation and thrombogenesis.

BACKGROUND

Experimental studies have shown that antioxidants, such as vitamin E (alpha-tocopherol), improve atherosclerotic plaque stability and vasomotor function, and decrease platelet aggregation and tendency to thrombus formation.

METHODS

Sprague Dawley rats were fed chow mixed with alpha- or gamma-tocopherol (100 mg/kg/day) for 10 days. A filter soaked in 29% FeCl3 was applied around the abdominal aorta to study the patterns of arterial thrombosis. The aortic blood flow was observed and continuously recorded using an ultrasonic Doppler flow probe. ADP-induced platelet aggregation, low-density lipoprotein oxidation induced by phorbol 12-myristate 13-acetate (PMA)-stimulated leukocytes, superoxide anion generation and superoxide dismutase (SOD) activity were also measured.

RESULTS

Both alpha- and gamma-tocopherol decreased platelet aggregation and delayed time to occlusive thrombus (all p < 0.05 vs. control). Both alpha- and gamma-tocopherol decreased arterial superoxide anion generation, lipid peroxidation and LDL oxidation (all p < 0.05 vs. control), and increased endogenous SOD activity (p < 0.05). The effects of gamma-tocopherol were more potent than those of alpha-tocopherol (p < 0.05).

CONCLUSIONS

This study indicates that both alpha- and gamma-tocopherol decrease platelet aggregation and delay intraarterial thrombus formation, perhaps by an increase in endogenous antioxidant activity. Gamma-tocopherol is significantly more potent than alpha-tocopherol in these effects.

Relative Effects of alpha- and gamma-Tocopherol on Low-Density Lipoprotein Oxidation and Superoxide Dismutase and Nitric Oxide Synthase Activity and Protein Expression in Rats

BACKGROUND: Increasing evidence suggests that vitamin E prevents the progression of atherosclerosis by inhibiting platelet aggregation, monocyte adhesion, and improving plaque stability and vasomotor function. Recently, controversy has arisen as to the relative effects of alpha- and gamma-tocopherol in modulating some mediators of atherosclerosis. METHODS AND RESULTS: We examined the effects of alpha- and gamma-tocopherol on constitutive nitric oxide synthase (cNOS) and superoxide dismutase (SOD) activity and protein expression in rats. Sprague-Dawley rats were fed regular chow or chow mixed with alpha- or gamma-tocopherol (100 mg/kg/day) for 7 to 10 days. Plasma alpha- and gamma-tocopherol levels, low-density lipoprotein (LDL) oxidation, and cNOS and SOD activity and protein expression were measured. Plasma alpha-tocopherol levels were significantly increased (eP <.01 vs control), but gamma-tocopherol levels fell (P <.01 vs control) in rats fed alpha-tocopherol. Plasma gamma-tocopherol levels were increased (P <.01 vs control), and alpha-tocopherol levels did not change in rats fed gamma-tocopherol. Both alpha- and gamma-tocopherol feeding decreased the rate of LDL oxidation induced by phorbol 12-myristate 13-acetate (PMA)-stimulated leukocytes (P <.01 vs control). Both alpha- and gamma-tocopherol increased SOD activity in plasma and arterial tissues as well as Mn SOD and Cu/Zn SOD protein expression in arterial tissues (all P <.01 vs control). gamma-Tocopherol was more potent than alpha-tocopherol in all these effects (P <.05). Both a- and gamma-tocopherol increased NO generation and cNOS activity (all P <.05 vs control). However, only gamma-tocopherol increased cNOS protein expression. CONCLUSIONS: These observations indicate that whereas both alpha- and gamma-tocopherol exert important effects on determinants of oxidationand vasomotor function, effects of dietary gamma-tocopherol supplementation in vivo are less pronounced than those of gamma-tocopherol supplementation.

Neuroprotective properties of statins in cerebral ischemia and stroke

BACKGROUND

The atheroma-retarding properties of beta-hydroxy-beta-methylglutaryl coenzyme A reductase (HMG-CoA) inhibitors, or "statins," in both the coronary and carotid arterial beds are well established. However, a growing body of recent data suggests that statins possess important adjunctive properties that may confer additional benefit beyond the retardation of atherosclerosis. In this article, we review the emerging evidence that statins have beneficial effects within the cerebral circulation and brain parenchyma during ischemic stroke and reperfusion.

SUMMARY OF REVIEW

Clinical studies show that statins reduce the incidence of ischemic stroke through probable effects on precerebral atherosclerotic plaque and through antithrombotic mechanisms. Additionally, statins have been shown to reduce infarct size in experimental animal models of stroke. Statins both upregulate endothelial nitric oxide synthase (eNOS) and inhibit inducible nitric oxide synthase (iNOS), effects that are potentially neuroprotective. The preservation of eNOS activity in cerebral vasculature, particularly in the ischemic penumbra, may be especially important in preserving blood flow and limiting neurological loss. Statins may also attenuate the inflammatory cytokine responses that accompany cerebral ischemia, and they possess antioxidant properties that likely ameliorate ischemic oxidative stress in the brain.

CONCLUSIONS

In addition to reducing stroke, the statin class of drugs exhibits a number of important neuroprotective properties that likely attenuate the effects of ischemia on the brain vasculature and parenchyma. Further investigation of the role of statins in human neuroprotection by use of neuroimaging and cognitive studies is warranted to explore these preliminary observations. In addition to reducing ischemic stroke, early evidence indicates that statins may also be neuroprotective.

Regulation of platelet-activating factor (PAF) activity in human diseases by phospholipase A2 inhibitors, PAF acetylhydrolases, PAF receptor antagonists and free radical scavengers

The aim of this review is to present recent findings indicating the likely involvement of platelet-activating factor (PAF) in human diseases, and possible ways of alleviating its harmful effects. PAF is a potent proinflammatory mediator and promotes adhesive interactions between leukocytes and endothelial cells, leading to transendothelial migration of leukocytes, by a process of juxtacrine intercellular signalling. This process leads to activation of leukocytes and the release of reactive oxygen radicals, lipid mediators, cytokines and enzymes. These reaction products subsequently contribute to the pathological features of various inflammatory diseases. The reactive oxygen radicals cause low density lipoprotein (LDL) oxidation which mediates the development of atherosclerosis. Oxidized LDL may damage cellular and subcellular membranes, leading to tissue injury and cell death. Among the therapeutic approaches considered are agents that inhibit/degrade proinflammatory mediators and thereby have anti-inflammatory and/or anti-atherogenic potential. These include inhibitors of phospholipase A2 activity, PAF-acetylhydrolases, PAF antagonists and free radical scavengers/antioxidants, the latter protecting against oxidized LDL-induced cytotoxicity.

Antiatherosclerotic activity of drugs in relation to nitric oxide function

Many studies have shown that loss of endothelium-derived nitric oxide is a major factor of ischemic episodes in patients with coronary artery disease and there is increasing evidence to suggest that nitric oxide might exert antiatherosclerotic actions. Based on these concepts, the results of animal studies on the effects of lipid lowering drugs, antioxidants, angiotensin converting enzyme inhibitors, Ca2+ channel blockers, estrogens and agents which modulate nitric oxide bioavailability are presented and compared to the results of patient studies and clinical trials. In spite of encouraging results obtained with antioxidants in animals, clinical trials could only show a clear positive effect of vitamin E treatment on the outcome of cardiovascular disease. Angiotensin converting enzyme inhibitors can ameliorate endothelial dysfunction in coronary heart disease, but their impact on disease progression remains unclear. There is evidence that estrogen replacement therapy in post-menopausal women may increase the bioavailability of nitric oxide. Finally, improved endothelial function and plaque stability clearly contribute to the clinical benefits of lipid lowering interventions, statins in particular. Taken together, these studies lend support to the concept that improving endothelial function and nitric oxide release might serve as valuable elements in the prevention or therapy of cardiovascular disease.

Effects of lovastatin therapy on susceptibility of LDL to oxidation during alpha-tocopherol supplementation

A randomized, double-masked, crossover clinical trial was carried out to evaluate whether lovastatin therapy (60 mg daily) affects the initiation of oxidation of low density lipoprotein (LDL) in cardiac patients on alpha-tocopherol supplementation therapy (450 IU daily). Twenty-eight men with verified coronary heart disease and hypercholesterolemia received alpha-tocopherol with lovastatin or with dummy tablets in random order. The two 6-week, active-treatment periods were preceded by a washout period of at least 8 weeks. The oxidizability of LDL was determined by 2 methods ex vivo. The depletion times for LDL ubiquinol and LDL alpha-tocopherol were determined in timed samples taken during oxidation induced by 2, 2-azobis(2,4-dimethylvaleronitrile). Copper-mediated oxidation of LDL isolated by rapid density-gradient ultracentrifugation was used to measure the lag time to the propagation phase of conjugated-diene formation. alpha-Tocopherol supplementation led to a 1.9-fold concentration of reduced alpha-tocopherol in LDL (P<0.0001) and to a 2.0-fold longer depletion time (P<0.0001) of alpha-tocopherol compared with determinations after the washout period. A 43% prolongation (P<0.0001) was seen in the lag time of conjugated-diene formation. Lovastatin decreased the depletion time of reduced alpha-tocopherol in metal ion-independent oxidation by 44% and shortened the lag time of conjugated-diene formation in metal ion-dependent oxidation by 7%. In conclusion, alpha-tocopherol supplementation significantly increased the antioxidative capacity of LDL when measured ex vivo, which was partially abolished by concomitant lovastatin therapy.

Vitamins C and E prolong time to arterial thrombosis in rats

To examine the modulation of arterial thrombosis by vitamins C and E, Sprague-Dawley rats were fed nonpurified diet, or diet mixed with vitamin C [100 mg/(kg body weight.d)], vitamin E [100 mg/(kg.d)] or both vitamins C and E [each 100 mg/(kg.d)], for a period of 9-19 d (mean 15 d). An occlusive aortic thrombus was created by application of a Whatman filter soaked in 1 mol/L FeCl3. Both vitamins C and E and their combination decreased platelet aggregation and delayed time to occlusive thrombus formation (P < 0.05 vs. control). Vitamins C and E decreased arterial superoxide generation (P < 0.05 vs. control). Interestingly, vitamin E also increased endogenous superoxide dismutase activity (SOD) and protein expression in aortic tissues (P < 0.05 vs. control). The combination of vitamins C and E was not superior to each vitamin alone with regard to effect on time to thrombus formation, but it was more potent with regard to platelet inhibition. The increase in endogenous antioxidant activity by vitamin E is an intriguing observation. This study shows that the antioxidant vitamins C and E have important effects on platelet aggregation, SOD activity, superoxide generation and thrombus formation.

Involvement of Nitric Oxide in the Inhibition of Aortic Smooth Muscle Cell Proliferation by Calcium Dobesilate

Vascular smooth muscle cell (SMC) proliferation is a key process in the pathogenesis of atherosclerosis. Numerous factors are involved in the regulation of SMC growth. Nitric oxide (NO) induces the inhibition of SMC proliferation whereas oxidized low-density lipoproteins (LDL) have a mitogenic effect. Calcium dobesilate (Doxium) is an angioprotective agent for treating vascular diseases. It has been shown to increase NO production and to have antioxidant properties but its mechanism of action is not yet fully understood. This study investigated the effect of calcium dobesilate on proliferation of rat aortic SMC in culture. Proliferation was evaluated by cell number and DNA synthesis. Orally administered calcium dobesilate (30, 100, or 200 mg/kg/day for 7 days) induced a dose-dependent decrease of proliferation of SMC in primary culture compared with controls. In vitro treatment with calcium dobesilate (0.05-5 mM) inhibited both DNA synthesis and proliferation in a time- and concentration-dependent manner. In both ex vivo and in vitro models, the inhibition was reversible upon removal of the drug. Calcium dobesilate also stimulated NO production and NO synthase activity. Inhibitors of NO synthesis attenuated the inhibitory effect of calcium dobesilate (300 µM) on DNA synthesis. In addition, calcium dobesilate (2.5-40 µM) induced a dose-dependent protection of cooper-induced LDL oxidation. These results showed that calcium dobesilate inhibits SMC proliferation, partly by a NO-dependent mechanism, and suggest that it could be effective in the treatment of pathological disorders associated with vascular SMC proliferation.

HMG-CoA reductase inhibition by atorvastatin reduces neointimal inflammation in a rabbit model of atherosclerosis

OBJECTIVES

To study the effect of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA)-reductase inhibitor atorvastatin on the potential mechanisms involved in the recruitment of monocytic cells into the vessel wall.

BACKGROUND

Inhibitors of HMG-CoA-reductase reduce cardiovascular mortality though the mechanisms yet elucidated. Most ischemic events are secondary to disruption of atherosclerotic plaques highly infiltrated by macrophages.

METHODS

Atherosclerosis was induced in the femoral arteries of rabbits by endothelial damage and atherogenic diet for 4 weeks. Then, animals were switched to standard chow and randomized to receive either no treatment or atorvastatin (5 mg/kg/d) and killed after 4 weeks.

RESULTS

Atorvastatin induced a significant reduction in serum lipids and in lesion size. Arterial macrophage infiltration was abolished by the treatment, and monocyte chemoattractant protein-1 (MCP-1) was significantly diminished in the neointima and in the media. Nuclear factor kappa-B (NF-kappaB) was activated in the 60% of the lesions, both in macrophages and vascular smooth muscle cells (VSMC), of the untreated group while only in 30% of the atorvastatin group. NF-kappaB activity was also lower in the uninjured aorta and liver of treated compared with untreated rabbits. In cultured VSMC, MCP-1 expression and NF-kappaB activity induced by tumor necrosis factor alpha were downregulated by atorvastatin.

CONCLUSIONS

In a rabbit atherosclerosis model, atorvastatin diminishes the neointimal inflammation, and this could contribute to the stabilization of the atherosclerotic plaque. This may be an additional explanation for the reduction of acute ischemic events in patients treated with statins.