Effects of Ca-antagonists on oxidative susceptibility of low density lipoprotein (LDL)

L-type calcium channel blockers and Parkinson disease in Denmark

OBJECTIVE

This study was undertaken to investigate L-type calcium channel blockers of the dihydropyridine class for association with Parkinson disease (PD), because some of these drugs traverse the blood-brain barrier, are potentially neuroprotective, and have previously been evaluated for impact on PD risk.

METHODS

We identified 1,931 patients with a first-time diagnosis for PD between 2001 and 2006 as reported in the Danish national hospital/outpatient database and density matched them by birth year and sex to 9,651 controls from the population register. The index date for cases and their corresponding controls was advanced to the date of first recorded prescription for anti-Parkinson drugs, if prior to first PD diagnosis in the hospital records. Prescriptions were determined from the national pharmacy database. In our primary analyses, we excluded all calcium channel blocker prescriptions 2 years before index date/PD diagnosis.

RESULTS

Employing logistic regression analysis adjusting for age, sex, diagnosis of chronic pulmonary obstructive disorder, and Charlson comorbidity score, we found that subjects prescribed dihydropyridines (excludes amlodipine) between 1995 and 2 years prior to the index date were less likely to develop PD (odds ratio, 0.73; 95% confidence interval, 0.54-0.97); this 27% risk reduction did not differ with length or intensity of use. Risk estimates were close to null for the peripherally acting drug amlodipine and for other antihypertensive medications.

INTERPRETATION

Our data suggest a potential neuroprotective role for centrally acting L-type calcium channel blockers of the dihydropyridine class in PD that should be further investigated in studies that can distinguish between types of L-type channel blockers.

Cardiac hypertrophy during hypercholesterolemia and its amelioration with rosuvastatin and amlodipine

Hypercholesterolemia is a common accompaniment of atherosclerosis and may be associated with cardiac hypertrophy. To define the mechanistic basis of cardiac hypertrophy in hypercholesterolemia, we fed low-density lipoprotein receptor knockout (LDLR KO) mice regular diet or high cholesterol (HC) diet for 26 weeks. There was clear evidence of cardiomyocyte hypertrophy and collagen deposition in the hearts of LDLR KO mice fed with HC diet, confirmed by histopathology (hematoxylin and eosin and Picrosirius staining) and upregulation of genes for brain natriuretic peptide, alpha-tubulin, transforming growth factor beta1, and connective tissue growth factor (CTGF). These changes were independent of change in blood pressure. The hypercholesterolemic mice hearts showed an upregulation of LOX-1, an oxidized low-density lipoprotein receptor, and angiotensin II type 1 receptor (AT1R) at messenger RNA level. In addition, there was a marked upregulation of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and nuclear factor kappaB (NF-kappaB) messenger RNA, indicating overexpression of markers of oxidant stress. A separate group of LDLR KO mice were fed HC diet along with a potent 3-hydroxy-3-methylglutarylcoenzyme A reductase inhibitor rosuvastatin or a dihydropyridine calcium channel blocker amlodipine. Administration of rosuvastatin or amlodipine reduced the overexpression of genes for LOX-1 and AT1R and associated NADPH oxidase and NF-kappaB. These phenomena were associated with a marked decrease in cardiomyocyte hypertrophy and collagen deposits in and around the cardiomyocytes. In conclusion, this study provides evidence of cardiac hypertrophy and fibrosis in hypercholesterolemia independent of blood pressure change LOX-1 and AT1R act as possible signals for oxidant stress leading to alterations in cardiac structure during hypercholesterolemia. Most importantly, rosuvastatin and amlodipine ameliorate cardiomyocyte hypertrophy and fibrosis.

Treatment of hypertension in metabolic syndrome subjects with amlodipine and olmesartan-effects on oxidized non-esterified free fatty acids and cytokine production

PURPOSE

Angiotensin II increases activation of oxidative signaling and vascular inflammatory gene expression, and interruption of the renin-angiotensin system has been considered more vasculoprotective than use of calcium channel antagonists and other anti-hypertensive therapies. Despite these putative mechanisms, amlodipine is equally efficacious as other therapies in reducing cardiovascular events.

METHODS

Double-blind, controlled trial, designed to investigate the effects of 2-months treatment with amlodipine and olmesartan on oxidized non-esterified fatty acids (ox-NEFA), and lipopolysaccharide-stimulated cytokine production in whole blood among 23 hypertensive subjects with the metabolic syndrome.

RESULTS

Treatment with olmesartan was no different than amlodipine in changing concentrations of total oxidized fatty acids (p = 0.37), total ox-NEFA (p = 0.43) and 9, 10, 11, 12, 13, 14, 15 and 16 ox-NEFA concentrations. In contrast, 8 ox-NEFA increased (median [interquartile ranges] by 45.2% [5.3 to 50.0] in olmesartan-treated subjects) compared with a decrease of 18.4% (-45.1-13.9) in amlodipine-treated subjects (p = 0.03). Lipopolysaccharide-stimulated cytokine production and levels of soluble cellular adhesion molecules did not change with either treatment.

CONCLUSION

Despite experimental data that demonstrates that angiotensin receptor antagonists reduce cellular oxidant stress and inflammation, olmesartan was not different than amlodipine in changing ox-NEFA and inflammatory markers in hypertensive subjects with the metabolic syndrome.

Neuroprotective effect of the angiotensin-converting enzyme inhibitor perindopril in MPTP-treated mice

The angiotensin -converting enzyme (ACE) inhibitor perindopril has been shown to exert beneficial effects on the dopaminergic system. Here, we investigated the effects of perindopril on the dopaminergic system in mice after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment, in comparison with a Ca(2+) antagonist, amlodipine. Administration of perindopril showed dose-dependent neuroprotective effects against MPTP-induced striatal dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) depletion. However, administration of amlodipine showed no significant effects on striatal dopamine depletion after MPTP treatment. In our immunohistochemical studies with antibodies against tyrosine hydroxylase (TH), microtubule-associated protein 2a, b (MAP2), dopamine transporter (DAT), parvalbumin (PV), glial fibrillary acidic protein (GFAP) and Cu/Zn-superoxide dismutase (Cu/Zn-SOD), the administration of perindopril significantly attenuated MPTP-induced substantia nigra and striatal damage. This drug also blocked the increases in GFAP-positive astrocytes in the striatum and substantia nigra after MPTP treatment. Furthermore, the administration of perindopril showed a protective effect against the intense Cu/Zn-SOD immunoreactivity in the neurons and glial cells in both the striatum and substantia nigra after MPTP treatment. These results indicated that the ACE inhibitor perindopril can protect against MPTP-induced striatal dopamine and DOPAC depletion in mice. The protective effect may be, at least in part, caused by the reduction of free radicals caused by MPTP. The present study also demonstrated that perindopril is effective against MPTP-induced neurodegeneration of the nigro-striatal dopaminergic pathway. Furthermore, our results provided further evidence that free radical scavengers may be effective in the treatment of neurodegenerative diseases such as Parkinson's disease.

Synergistic effect of Nicorandil and Amlodipine on tissue defense system during experimental myocardial infarction in rats

The synergistic protective effect of Nicorandil (K(ATP) channel opener) and Amlodipine (calcium channel blocker) on heart tissue antioxidant defense system and lipid profile were examined on isoproterenol induced myocardial infarction in rats. The rats given isoproterenol (150 mg kg(-1) daily, i.p.) for 2 days showed significant changes in antioxidant defense system and lipid profile levels. Pretreatment with Nicorandil (2.5 mg kg(-1) daily, p.o.) and Amlodipine (5.0 mg kg(-1) daily, p.o.) for 3 days significantly prevented these alterations and restored the enzyme activities to near normal. These findings indicate the synergistic protective effect of Nicorandil and Amlodipine on tissue defense system and lipid metabolism during isoproterenol induced cardiac damage.

Effect of oxidation of low-density lipoprotein on drug binding affinity studied by high performance frontal analysis-capillary electrophoresis

The effect of oxidation of low-density lipoprotein (LDL) on the enantioselective drug binding affinity was investigated using high performance frontal analysis--capillary electrophoresis (HPFA-CE). Verapamil and nilvadipine enantiomers were used as the chiral model drugs. LDL was oxidized with copper sulfate for 0, 0.5, 1, 2, and 12 h at 37 degrees C. The HPFA-CE method enabled microdetermination of unbound drug concentrations in native and oxidized LDL solutions. It was found that the bindings between LDL and the model drugs were not enantioselective at any oxidation stage. The total binding affinity (nK) between LDL and verapamil enantiomers was increased by 3.3-, 4.6-, 7.0-, and 19-fold after 0.5, 1, 2, and 12 h oxidation, respectively, whereas the nK value between nilvadipine and LDLwas increased by 1.3-, 1.4-, 1.4-, and 1.7-fold in the same reaction times, respectively. These results indicate that the LDL oxidation enhances the drug binding affinity, and the affinity of verapamil is increased more sensitively than that of nilvadipine. The nK value of each model drug increased steeply after the first 2 h oxidation, followed by the gradual increase after the next 10 h oxidation. It is considered that the net increase in the negative charges and/or the formation of hydroperoxides in the first 2 h oxidation enhances the drug-LDL binding more significantly than the formation of aldehydes or Schiff bases in the following 10 h oxidation.

Effective blood pressure treatment improves LDL-cholesterol susceptibility to oxidation in patients with essential hypertension

OBJECTIVES

LDL-cholesterol particles from hypertensive patients exhibit enhanced susceptibility to in vitro oxidation, an abnormality thought to increase cardiovascular risk. We tested whether blood pressure (BP) normalization can reverse this abnormality.

DESIGN

Double-blind, randomized pharmacological intervention trial.

SETTING

Clinical research centre. Subjects. A total of 29 nondiabetic, normolipidaemic patients with essential hypertension (BP= 151 +/- 3/99 +/- 1 mmHg) and 11 normotensive controls (BP=125 +/- 3/85 +/- 1 mmHg) matched for gender, age, obesity, glucose tolerance and lipid profile. Intervention. Anti-hypertensive treatment for 3 months with a calcium-antagonist in randomized combination with either an ACE inhibitor or a beta-blocker.

MAIN OUTCOME MEASURES

Lag phase of copper-induced LDL oxidation, cell-mediated (human umbilical vein endothelium) generation of malondialdehyde (MDA) by LDL and vitamin E content in LDL.

RESULTS

At baseline in hypertensives versus controls, lag phase was shorter (89 +/- 3 vs. 107 +/- 6 min, P < 0.04), MDA generation was higher (5.8 +/- 0.1 vs. 5.1 +/- 0.2 nmol L(-1), P=0.002), and vitamin E was reduced (6.40 +/- 0.05 vs. 6.67 +/- 0.11 microg mg(-1), P=0.03). At 3 months, BP was normalized (124 +/- 3/81 +/- 1, P < 0.0001 vs. baseline, P=ns versus controls), lag phase was prolonged (to 98 +/- 3 min, P=0.0005), MDA generation was reduced (5.6 +/- 0.1 nmol L-1, P = 0.001), and vitamin E was increased (6.53 +/- 0.05 microg mg(-1), P=0.003), with no significant differences between the randomized groups.

CONCLUSIONS

In nondiabetic, nonobese, normolipidaemic patients with essential hypertension, LDL susceptibility to copper- and cell-mediated oxidation is increased. BP normalization is associated with a significant improvement, but not a full reversal, of this abnormality.

Calcium antagonists as inhibitors of in vitro low density lipoprotein oxidation and glycation

The peroxidation step in lipid transformation is considered to be essential in the pathogenesis of atherosclerosis. Calcium antagonists (CA) appear to have antioxidant effects in addition to their potent vasorelaxant properties. In the present study, we compared the antioxidative efficacy of CA (amlodipine, lacidipine, nifedipine, isradipine, diltiazem, and semotiadil) in the copper-catalysed oxidation of low-density lipoprotein (LDL) with that of glycated(g)/glycoxidated(go) LDL. This issue is of great importance when considering the potential therapeutic use of antioxidant drugs in diabetes-associated vasculopathy. Oxidation of native LDL was inhibited most efficiently (>90%) by lacidipine and semotiadil in the concentration range 10(-4)-10(-3) M. We found, however, a dramatic decrease in antioxidant activity towards g/goLDL as compared to native LDL in all the CA tested. Only lacidipine significantly inhibited copper-mediated oxidation of g/goLDL in the whole concentration range tested (10(-5) M-10(-3) M). This probably resulted from the increased auto-oxidative potential introduced by early and advanced glycation end products (AGE) into the g/goLDL. We noted that coincubation of LDL with 10(-3) M CA and 0.5 M glucose under oxidative/non-oxidative conditions partially or fully restored the antioxidant capacity of the different CA to inhibit the subsequent copper-catalysed oxidation of the modified LDL. This is a clear indication that CA inhibit glycative or glycoxidative LDL changes during the preceding long-term glycation period. The notion that both oxidative changes and long-term glycation effects were reduced by CA was corroborated by fluorescence analysis, AGE-ELISA, quantitation of lipid peroxidation, and thiobarbituric acid reactive substance (TBARS) measurement of long-term g/goLDL. The strongest antioxidative effects during long-term glycation of LDL were seen with isradipine, lacidipine, nifedipine, and semotiadil. Diltiazem was the only CA that could not prevent TBARS formation in LDL during the long-term glycation period. In contrast, Amadori product formation, as measured by the generation of fructosamines, was not significantly reduced by any CA tested. Thus CA, like other antioxidants, significantly retard AGE formation, while initial glycation reactions, such as Amadori product formation, are only weakly inhibited.

Inhibition of LDL oxidation and oxidized LDL-induced cytotoxicity by dihydropyridine calcium antagonists

PURPOSE

The antioxidant activity of dihydropyridine calcium channel antagonists was evaluated based on LDL oxidation kinetics, oxidative cell injury associated with reactive species generation, and increases in free intracellular calcium (Ca2+) levels. Interactions with ascorbic acid were studied under conditions representative of LDL oxidation in plasma and tissue.

METHODS

Analysis of antioxidant activity utilized measurements of one-electron oxidation potentials and scavenging of peroxy radical-mediated oxidation. LDL antioxidant potency was determined spectrophotometrically using copper-mediated oxidation kinetics in the absence and presence of 100 microM ascorbic acid. Prevention of oxidant-induced endothelial cell injury was determined from the formation of reactive oxygen species generation and increases in intracellular free calcium concentrations following addition of oxidized LDL or linoleic acid hydroperoxide.

RESULTS

Felodipine and amlodipine effectively inhibit peroxyl radical-mediated oxidation in lipoproteins and cells that is markedly enhanced in the presence of ascorbic acid. In the presence of ascorbic acid, inhibition of LDL oxidation is over four times greater than in LDL treated without antioxidants, and oxidized LDL and linoleic acid hydroperoxide-induced reactive oxygen species formation is effectively suppressed in cells. Inhibition of intracellular calcium increases was achieved using nM concentrations of felodipine or amlodipine.

CONCLUSIONS

The additive effect for ascorbic acid and the calcium channel antagonist is postulated to involve a combination of peroxide-degrading and peroxyl radical scavenging reactions, demonstrating the importance of lipid peroxides during LDL oxidation and oxidized LDL-induced cytotoxicity. Cytoprotection is associated with inhibition of oxidant-induced increases in intracellular free calcium. Both the cytoprotective and LDL antioxidant activity for these compounds is manifested at concentrations approaching the therapeutic levels found in plasma.

Binding analysis of nilvadipine to plasma lipoproteins by capillary electrophoresis-frontal analysis

Capillary electrophoresis coupled with frontal analysis (HPCE/FA) was applied to the ultramicro analysis of enantioselective binding of nilvadipine (NV), a calcium channel blocker, to plasma lipoproteins. The drug lipoprotein mixed solution was hydrodynamically introduced into a non-coated fused silica capillary for capillary electrophoresis. Since NV has no electric charge in the run buffer (pH 7.4), the unbound NV moved towards the cathodic end by electroosmotic flow, which was faster than the electrophoretic migrations of negatively charged lipoproteins and the bound NV. Once unbound NV migrated apart from lipoprotein, and bound NV was quickly released from the protein to maintain the binding equilibrium. Thus, NV migrated as a zone with a plateau region. The concentration of NV in this plateau region appearing on the electrophorogram was the same as the unbound NV concentration in the initial sample solution. It was found that the binding of NV to high-density lipoprotein (HDL), low-density lipoprotein (LDL) and oxidized LDL was non-specific and not enantioselective. Partition-like binding to the lipid part of these lipoproteins seemed to occur dominantly. The total binding affinities of NV to LDL were about seven times stronger than those to HDL, and the oxidation of LDL enhanced the binding affinity significantly.

Effects of two calcium channel blockers on messenger RNA expression of endothelin-1 and nitric oxide synthase in cardiovascular tissue of hypertensive rats

OBJECTIVE

The aim of this study was to investigate the effects of calcium channel blockers on messenger RNA expression of endothelin-1 and endothelial-type nitric oxide synthase in the cardiovascular tissue of stroke-prone spontaneously hypertensive rats (SHRSP).

MATERIALS AND METHODS

The calcium channel blocker nilvadipine (1.0 or 3.2 mg/kg per day) was subcutaneously administered to two groups of SHRSP, from 4 or 8 weeks of age, for 8 weeks and 4 weeks, respectively. For comparison, nifedipine (3.2 mg/kg per day) was similarly administered to SHRSP from 4 weeks of age for 8 weeks. Kidney, heart, aorta and brain tissue samples were obtained when the rats were 12 weeks old. Messenger RNA expression of endothelin-1 and endothelial-type nitric oxide synthase was determined by reverse transcription-polymerase chain reaction followed by Southern blotting and a ribonuclease protection assay, respectively. Results were compared with those in untreated SHRSP and Wistar-Kyoto rats at 12 weeks of age.

RESULTS

Both nilvadipine and nifedipine significantly decreased blood pressure in SHRSP. Although there were no changes in the weights of the kidney and brain, there was a significant decrease in the weight of the left ventricle of the groups treated with nilvadipine (1.0 mg/kg per day: mean +/- SEM 0.282 +/- 0.003 g; 3.2 mg/kg per day: 0.269 +/- 0.005 g) and nifedipine (1 mg/kg/day: 0.281 +/- 0.012 g) for 8 weeks compared with untreated SHRSP (0.301 +/- 0.004 g). Endothelin-1 messenger RNA expression, which was significantly increased by about twofold in the kidney, heart and brain of SHRSP compared with Wistar-Kyoto rats, was normalized by both calcium blockers. Endothelin-1 messenger RNA expression, which was decreased in the aorta of SHRSP, was further decreased by both calcium blockers. While there was no significant difference in endothelial-type nitric oxide synthase messenger RNA expression in the kidney, heart and aorta between the untreated SHRSP and Wistar-Kyoto rats, expression in the aorta was significantly increased in the group treated with these calcium blockers for 8 weeks from 4 weeks of age.

CONCLUSIONS

These results suggest that, in addition to their potent antihypertensive effects, calcium channel blockers may exhibit cardiovasculoprotective and renoprotective effects by modifying mRNA expression of endothelin-1 and endothelial-type nitric oxide synthase in tissue.

Effect of low-dose simvastatin on cholesterol levels, oxidative susceptibility, and antioxidant levels of low-density lipoproteins in patients with hypercholesterolemia: a pilot study

In this pilot study, 12 patients (6 men, 6 postmenopausal women) with hypercholesterolemia were treated with low-dose (5 mg/d) simvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, for 4 weeks. Low-density lipoprotein (LDL) samples were isolated at the beginning (week 0) and at the end (week 4) of the treatment regimen. Simvastatin caused significant decreases of total cholesterol (-18.1%), LDL cholesterol (-27.6%), and apolipoprotein B (-21.8%), and significantly reduced total cholesterol, free cholesterol, cholesterol esters, phospholipids, and protein in LDL without significantly changing the component ratios and fatty acid levels of LDL. However, simvastatin therapy had no major effects on either antioxidant levels in LDL or the oxidative susceptibility of LDL. We conclude that low-dose simvastatin significantly reduces LDL cholesterol levels without increasing the oxidative susceptibility of LDL or decreasing the antioxidant levels of LDL, and thus may reduce the risk of coronary artery disease.