Cholesterol, calcium and atherosclerosis: is there a role for calcium channel blockers in atheroprotection?

The Chains of Ferroptosis Interact in the Whole Progression of Atherosclerosis

Atherosclerosis (AS), a category of cardiovascular disease (CVD) that can cause other more severe disabilities, increasingly jeopardizes human health. Owing to its imperceptible and chronic symptoms, it is hard to determine the pathogenesis and precise therapeutics for AS. A novel type of programmed cell death called ferroptosis was discovered in recent years that is distinctively different from other traditional cell death pathways in morphological and biochemical aspects. Characterized by iron overload, redox disequilibrium, and accumulation of lipid hydroperoxides (L-OOH), ferroptosis influences endothelial cells, vascular smooth muscle cells (VSMCs), and macrophages, as well as inflammation, partaking in the pathology of many cardiovascular diseases such as atherosclerosis, stroke, ischemia-reperfusion injury, and heart failure. The mechanisms behind ferroptosis are so sophisticated and interwoven that many molecules involved in this procedure are unknown. This review systematically depicts the initiation and modulation of ferroptosis and summarizes the contribution of ferroptosis to AS, which may open a feasible approach for target treatment in the alleviation of AS progression.

Effects of olmesartan and amlodipine on blood pressure, endothelial function, and vascular inflammation

BACKGROUND

Anti-hypertensive drugs can improve vascular endothelial function. However, the mechanism remains to be elucidated.

OBJECTIVES

This study sought to investigate mechanisms of anti-hypertensive drugs on improvement of vascular endothelial function in patients with essential hypertension.

METHODS

Forty-five patients (mean age 58.5 ± 11.2 years) with uncontrolled essential hypertension were randomly assigned to receive olmesartan, an angiotensin II type 1 receptor blocker (ARB) (N = 23), or amlodipine, a calcium channel blocker (CCB) (N = 22), for 6 months. Endothelial function was evaluated by flow-mediated dilatation (FMD) of the brachial artery. Vascular inflammation was measured by blood-normalized standardized uptake value, known as a target-to-background ratio (TBR) within the carotid arteries using 18F-fluorodeoxyglucose-positron emission tomography combined with computed tomography.

RESULTS

There were no significant differences of baseline clinical data between the ARB and CCB groups. Both anti-hypertensive drugs comparably lowered blood pressure and increased %FMD. TBR values were reduced by olmesartan (P < .001), while blood pressure variability was decreased by amlodipine (P = .004). Changes in %FMD from baseline (Δ%FMD) were inversely associated with ΔTBR in the olmesartan group (r = - .606, P = .003) and with Δsystolic blood pressure variability in the amlodipine group (r = - .434, P = .039).

CONCLUSION

Our study indicated that olmesartan and amlodipine could improve endothelial function in patients with essential hypertension in different manners, suppression of vascular inflammation, and decrease in blood pressure variability, respectively.

Temporal Relationship Between Changes in Serum Calcium and Hypercholesteremia and Its Impact on Future Brachial-Ankle Pulse Wave Velocity Levels

Background: The high levels of serum calcium and cholesterol are the important risk factors of cardiovascular disease (CVD), which frequently influence each other during the development of CVD. However, few studies have examined their temporal relationship to confirm the precursor, and it is still largely unknown whether and how their temporal relationship would influence the development of CVD. This study aimed to establish the temporal relationship between the changes in serum calcium and cholesterol using the longitudinal cohort data, and examine whether this temporal relationship influenced the arterial elasticity indicated by brachial-ankle pulse wave velocity (baPWV). Methods: This is a cohort study with a sample of 3,292 Chinese participants (aged 20-74 years) with 5.7 years follow-up. Serum calcium and cholesterol were measured at baseline and follow-up survey. The cross-lagged path analysis was used to examine their temporal relationship, and mediation analysis was performed to evaluate the potential mediating effect. Results: The cross-lagged path coefficients (β₂ values) from baseline serum calcium to follow-up cholesterol was significantly greater than the path coefficients (β₁ values) from baseline cholesterol to follow-up serum calcium (β₂ = 0.110 vs. β₁ = 0.047; P = 0.010) after adjusting for the multiple covariates. The path coefficients from baseline serum calcium to follow-up cholesterol in the participants with high baPWV was significantly greater than the participants with low baPWV (β₂ = 0.155 for high baPWV and β₂ = 0.077 for low baPWV, P = 0.028 for the difference between the β₂ values). Moreover, cholesterol partially mediated the association between the higher serum calcium and greater subsequent baPWV values, the percentage of the total effect mediated by cholesterol was estimated at 21.7%. Conclusion: Our findings indicate that increased serum calcium precedes increased in serum cholesterol, and this temporal relationship may contribute to the development of higher baPWV levels.

Increased oxidative stress and altered serum macro-minerals and trace elements levels are associated with coronary artery disease

BACKGROUND

This study was designed to evaluate the serum malondialdehyde (MDA), non-enzymatic antioxidants (vitamin A and C), macro-minerals (magnesium and calcium), and trace elements (zinc, copper, and iron) levels in patients with coronary artery disease (CAD) and to explore their role in disease progression.

METHODS

This prospective case-control study was comprised of 40 CAD patients and 40 healthy volunteers as cases and control subjects, respectively. The level of lipid peroxidation was assessed by measuring the serum MDA level using a UV spectrophotometer. The levels of vitamins A and C were determined by high-performance liquid chromatography (HPLC) and UV spectrophotometric method, respectively. Atomic absorption spectroscopy (AAS) was used to measure serum macro-minerals (Mg and Ca) and trace elements (Zn, Cu, and Fe) concentrations.

RESULTS

The mean age of CAD patients and control subjects was 53.90 ± 2.22 and 37.03 ± 1.50 years, respectively. This study revealed significantly higher concentrations of MDA (p < 0.01) and lower concentrations of vitamin A (p < 0.01), and vitamin C (p < 0.05) in the CAD patients than in control subjects. The mean values of Mg, Cu, Zn, Ca, and Fe were 11.67 ± 0.64, 1.17 ± 0.03, 0.43 ± 0.02, 107.38 ± 1.81, and 1.66 ± 0.04 μg/mL, respectively for the CAD patients and 19.38 ± 0.65, 1.07 ± 0.02, 0.87 ± 0.02, 94.29 ± 1.89, and 1.52 ± 0.05 μg/mL, respectively for the controls and the differences were significant (p < 0.05) between the patients and controls.

CONCLUSION

From these findings, we can suggest that there is a strong association of CAD with an elevated level of MDA, depleted levels of antioxidants, and altered macro-minerals and trace elements concentrations.

Six-Gene Signature Associated with Immune Cells in the Progression of Atherosclerosis Discovered by Comprehensive Bioinformatics Analyses

BACKGROUND

As a multifaceted disease, atherosclerosis is often characterized by the formation and accumulation of plaque anchored to the inner wall of the arteries and causes some cardiovascular diseases and vascular embolism. Numerous studies have reported on the pathogenesis of atherosclerosis. However, fewer studies focused on both genes and immune cells, and the correlation of genes and immune cells was evaluated via comprehensive bioinformatics analyses.

METHODS

29 samples of atherosclerosis-related gene expression profiling, including 16 human advanced atherosclerosis plaque (AA) and 13 human early atherosclerosis plaque (EA) samples from the Gene Expression Omnibus (GEO) database, were analyzed to get differentially expressed genes (DEGs) and the construction of protein and protein interaction (PPI) networks. Besides, we detected the relative fraction of 22 immune cell types in atherosclerosis by using the deconvolution algorithm of "cell type identification by estimating relative subsets of RNA transcripts (CIBERSORT)." Ultimately, based on the significantly changed types of immune cells, we executed the correlation analysis between DEGs and immune cells to discover the potential genes and pathways associated with immune cells.

RESULTS

We identified 17 module genes and 6 types of significantly changed immune cells. Correlation analysis showed that the relative percentage of T cell CD8 has negative correlation with the C1QB expression (R = -0.63, p = 0.02), and the relative percentage of macrophage M2 has positive correlation with the CD86 expression (R = 0.57, p = 0.041) in EA. Meanwhile, four gene expressions (CD53, C1QC, NCF2, and ITGAM) have a high correlation with the percentages of T cell CD8 and macrophages (M0 and M2) in AA samples.

CONCLUSIONS

In this study, we suggested that the progression of atherosclerosis might be related to CD86, C1QB, CD53, C1QC, NCF2, and ITGAM and that it plays a role in regulating immune-competent cells such as T cell CD8 and macrophages M0 and M2. These results will enable studies of the potential genes associated with immune cells in the progression of atherosclerosis, as well as provide insight for discovering new treatments and drugs.

Mast cells emerge as mediators of atherosclerosis: Special emphasis on IL-37 inhibition

In atherosclerosis lipoproteins stimulate the innate immune response, leading to the release of inflammatory cytokines and chemokines. Hypercholesterolemia may activate the synthesis and release of inflammatory cytokines such as IL-1, which induces TNF release in mast cells (MCs). IL-1 and IL-1 family members orchestrate a broadening list of inflammatory diseases, including atherosclerosis. MCs are implicated in the pathophysiology of several diseases including allergy and inflammation. Activated MCs, located perivascularly, contribute to inflammation in atherosclerosis by producing inflammatory cytokines. MC IL-1-activation leads to the immediate release of inflammatory chemical mediators and TNF, and late inflammatory compounds such as cytokines. MCs can be activated by exogenous cytokines, antigens, microbial products (LPS) and neurotransmitters and generate IL-1 beta, TNF and several other inflammatory cytokines/chemokines along with PGD2, leukotrienes, histamine and proteases. MCs activated with IL-1 induce selective release of IL-6 without degranulation. TNF emerges as one of the most potent inflammatory cytokines involved in the response due to LDL. Cytokines, such as IL-1, IL-6, IL-33 and TNF, are generated in the inflammatory sites by both macrophages and MCs, mediating atherosclerosis. IL-37 (IL-1 family member 7) binds IL-18Ra chain and acts by an intracellular mechanism down-regulating the expression of pro-inflammatory signals cJun, MAP kinase p38a, STAT transcription factors and p53. Blocking IL-1 with IL-37 alleviates the symptoms in patients with inflammatory diseases including arteriosclerosis. The impact of IL-37 on inflammatory cytokines mediating atherosclerosis is beneficial and protective. However, more studies are needed to better define this mechanism and the safety and tolerability of IL-37.

Abnormalities of Selected Trace Elements in Patients with Coronary Artery Disease

BACKGROUND

Coronary artery diseases are multifactorial, and over the last several decades particular consideration and research have been devoted to investigating the imbalance of patient elemental levels. Our current study aimed to investigate the comparative distribution of Ca, Mg, Fe, Zn, Cu, Co, Mn, Cr, Cd and Pb in the blood of coronary artery disease patients and healthy subjects.

METHODS

Blood samples collected from both groups were digested into a HNO3-HCLO4 (10:1 v/v) mixture in a microwave oven, followed by quantification of the elements by atomic absorption spectrometry.

RESULTS

The average levels of Pb and Cr were markedly higher (p < 0.001) while those of Ca, Fe, Cu and Mn were moderately higher (p < 0.05) in blood of the patients compared to the controls. However, correlation study showed divergent relationships between various elements in the blood of both groups. Multivariate cluster analysis revealed two major clusters of the elements for patients: Ca-Mg-Mn-Co-Cd and Pb-Cu-Fe-Zn-Cr; whereas three common groups were observed for controls: Ca-Mg-Zn-Cu, Cr-Mn-Fe and Co-Cd-Pb. Variations in the elemental levels were also observed to be associated with gender, habitat, food and smoking habits of the subjects.

CONCLUSIONS

Overall, the distribution, correlation and apportionment of elemental data indicated an imbalance of the toxic/essential elements in blood of the patients compared to the controls.

KEY WORDS

AAS; Blood; Cluster analysis; Coronary artery disease; Essential/toxic element.

Comparative Distribution, Correlation, and Chemometric Analyses of Selected Metals in Scalp Hair of Angina Patients and Healthy Subjects

Numerous epidemiological studies are preponderance of evidences intimating development of coronary artery disease caused by metal imbalance. The present study was aimed to analyze Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Pb, Sr, and Zn in the scalp hair of angina patients and healthy subjects/controls employing HNO3-HCLO4-based wet digestion followed by quantification with atomic absorption spectrophotometry. The average concentrations of Cd, Cu, Cr, Fe, Mn, Pb, and Sr revealed significantly higher levels in scalp hair of patients than controls; however, Na and Zn were appreciably higher in healthy subjects. Dissimilarity in the trace metal distribution was also observed with gender, residence, dietary habits, and smoking habits of both donor groups. The correlation study and multivariate analyses revealed diverse mutual relationships and apportionment of the trace metals in the scalp hair of patients and controls.

Efficacy of the combination of amlodipine and candesartan in hypertensive patients with coronary artery disease: a subanalysis of the HIJ-CREATE study

BACKGROUND

The effects of the combination of angiotensin II receptor blocker (ARB) plus dihydropyridine calcium channel blockers (DHP-CCBs), which is known as a potent antihypertensive drug regimen, on cardiovascular events remain unclear.

OBJECTIVE

The purpose of this post hoc subgroup analysis was to compare the incidence of major adverse cardiovascular events (MACE) of patients treated with candesartan and amlodipine with that of those with candesartan and non-amlodipine CCBs in hypertensive patients with coronary artery disease (CAD).

METHODS

HIJ-CREATE was a multicenter, prospective, randomized, controlled study that compared the effects of candesartan-based with those of non-ARB-based standard therapy on MACE in 2049 hypertensive patients with CAD. In the candesartan group, a total of 335 patients were treated with DHP-CCBs (amlodipine: 170 and non-amlodipine-CCBs: 165) at the baseline. In this sub-analysis, we compared, among the participants allocated to candesartan regimen, the long-term effects of amlodipine and non-amlodipine CCBs that were concomitantly given with ARB, although the choice of CCB was not randomized.

RESULTS

The median follow-up was 3.9 years. Treatment using amlodipine with candesartan reduced the risk of MACE by 38% (hazard ratio, 0.62; 95% confidence interval, 0.41-0.94, p=0.025), as compared to patients treated with non-amlodipine-CCBs and candesartan. In a multivariate analysis, combination therapy of candesartan with amlodipine was an independent predictor of reduced risk of MACE.

CONCLUSIONS

The results suggest that the combination of amlodipine and candesartan is more beneficial in reducing MACE in hypertensive patients with CAD compared to non-amlodipine-DHP-CCBs in combination therapy with candesartan. Further investigation in larger-scale prospective randomized studies is required to reach any conclusion as to the superiority of combination therapy of candesartan with amlodipine.

Verapamil stereoisomers induce antiproliferative effects in vascular smooth muscle cells via autophagy

Calcium channel blockers (CCBs) are important in the management of hypertension and limit restenosis. Although CCB efficacy could derive from decreased blood pressure, other mechanisms independent of CCB activity also can contribute to antiproliferative action. To understand mechanisms of CCB-mediated antiproliferation, we studied two structurally dissimilar CCBs, diltiazem and verapamil, in cultured rat vascular smooth muscle cells (VSMC). To elucidate CCB-independent effects, pure stereoisomers of verapamil (R-verapamil, inactive VR; S-verapamil, active, VS) were used. The effects of CCB exposure on cell viability (MTT reduction), cell proliferation ((3)H-thymidine incorporation), VSMC morphology by light and transmission electron microscopy (TEM) and autophagy (LC3I/II, ATG5) were measured. In general, verapamil, VR or VS treatment alone (80 μM) appreciably enhanced MTT absorbance although higher concentrations (VR or VS) slightly decreased MTT absorbance. Diltiazem (140 μM) markedly decreased MTT absorbance (40%) at 120 h. VR or VS treatment inhibited (3)H-thymidine incorporation (24h) and induced cytological alterations (i.e., karyokinesis, enhanced perinuclear MTT deposition, accumulated perinuclear "vacuoles"). TEM revealed perinuclear "vacuoles" to be aggregates of highly laminated and electron-dense vesicles resembling autophagosomes and lysosomes, respectively. Increased autophagosome activity was confirmed by a concentration-dependent increase in LC3-II formation by Western blotting and by increased perinuclear LC3-GFP(+) puncta in verapamil-treated VSMC. Verapamil stereoisomers appeared to decrease perinuclear mitochondrial density. These observations indicate that antiproliferative effects of verapamil stereoisomers are produced by enhanced mitochondrial damage and upregulated autophagy in VSMC. These effects are independent of CCB activity indicating a distinct mechanism of action that could be targeted for more efficacious anti-atherosclerotic and anti-restenosis therapy.

Azelnidipine and amlodipine anti-coronary atherosclerosis trial in hypertensive patients undergoing coronary intervention by serial volumetric intravascular ultrasound analysis in Juntendo University (ALPS-J)

BACKGROUND

A previous study reported that amlodipine retarded coronary plaque progression in patients with coronary artery disease. The goal of this multicenter study was to determine which calcium-channel blockers (CCBs) other than amlodipine attenuated the progression of plaque volume (PV) accessed by intravascular ultrasound (IVUS).

METHODS AND RESULTS

ALPS-J was a prospective, randomized open-label study conducted at 5 centers. Patients who had hypertension and were scheduled for coronary intervention were enrolled. Subjects were randomly assigned to receive 16 mg/day of azelnidipine or 5mg/day of amlodipine administered for 48 weeks. The primary endpoint was the percent change in coronary PV measured by IVUS. Between 2007 and 2009, 199 patients were enrolled; 115 had evaluable IVUS images at both baseline and after 48 weeks of treatment. Blood pressure significantly reduced to 128/68 mmHg at follow-up. The lipid profiles in the 2 groups were comparable (low-density lipoprotein cholesterol: 97 mg/dl). The %change in PV showed a significant regression of 4.67 and 4.85% in the azelnidipine and amlodipine groups, respectively. The upper limit of the 95% confidence interval of the mean difference in %change PV between the 2 groups (0.18%, 95% confidence interval 4.62 to 4.98%) did not exceed the pre-defined non-inferiority margin of 6.525%.

CONCLUSIONS

ALPS-J demonstrated that azelnidipine was not inferior to amlodipine for primary efficacy. In addition to standard medical therapy, dihydropyridine CCBs will retard PV progression in hypertensive patients.

Numerical modeling of stress in stenotic arteries with microcalcifications: a micromechanical approximation

Most finite element models of atherosclerotic arteries do not account for the heterogeneity of the plaque constituents at the microscale. Failure of plaque lesions has been shown to be a local event, linked to stress concentrations caused by cap thinning, inflammation, macroscopic heterogeneity, and recently, the presence of microcalcifications. There is growing evidence that microcalcifications exist in the fibrous cap of plaque lesions. However, their role is not yet fully understood. The goal of the present work is to investigate the effects of localized regions of microcalcifications on the stress field of atherosclerotic plaque caps in a section of carotid artery. This is achieved by performing finite element simulations of three-dimensional fluid-structure interaction models. The material response in the region of microcalcification is modeled using a combination of finite elements, homogenization theory, and a stress concentration function that approximates the average local stresses in the fibrous tissue and microcalcification phases. The results indicate that the circumferential stress in the fibrous tissue phase increases as the volume fraction of microcalcifications is increased, and that the stress exceeds a critical threshold when the fibrous cap thickness is decreased. Furthermore, the presence of the microcalcifications significantly influences the distribution of stress by shifting the maximum circumferential stress away from the cap shoulders, where failure is most common when the effective region of microcalcification is located at the center of the cap. This is a possible explanation of why 40% of plaque ruptures occur away from the shoulder region of the cap.

Effect of amlodipine + candesartan on cardiovascular events in hypertensive patients with coronary artery disease (from The Heart Institute of Japan Candesartan Randomized Trial for Evaluation in Coronary Artery Disease [HIJ-CREATE] Study)

Combination therapy with calcium channel blockers and angiotensin II receptor blockers is recommended as one of the effective therapies for hypertension. However, it remains unclear whether this combination reduces major adverse cardiovascular events (MACEs) in patients with hypertension with coronary artery disease (CAD). The purpose of the present study was to examine the effects of amlodipine plus candesartan on MACEs in patients with hypertension with CAD. The study population was drawn from The Heart Institute of Japan Candesartan Randomized Trial for Evaluation in Coronary Artery Disease (HIJ-CREATE), which was a multicenter, prospective, randomized controlled trial including 2,049 patients with hypertension with angiographically documented CAD. Subgroup analysis was performed in patients treated with amlodipine at baseline (n = 388). The median follow-up period was 4.3 years. Treatment using amlodipine plus candesartan reduced the risk for MACEs by 39% (p = 0.015) compared to that using amlodipine without angiotensin II receptor blockers. Among the individual events constituting MACEs, the incidence of unstable angina pectoris requiring hospitalization was significantly lower, by 52% (p = 0.007). In conclusion, amlodipine plus candesartan demonstrated a more favorable effect on reducing cardiovascular events in patients with hypertension with CAD compared to amlodipine-based therapy without candesartan.

Calcium channel blocker, azelnidipine, reduces lipid hydroperoxides in patients with type 2 diabetes independent of blood pressure

Anti-hypertensive agents with antioxidative effects are potentially useful for diabetic patients with hypertension to prevent the onset and progression of their complication. While dihydropyridine-type calcium antagonists are among the frequently used anti-hypertensive drugs, azelnidipine, a novel calcium antagonist, has been reported to have a unique anti-oxidative effect in vitro and in animals. In this study, we measured lipid hydroperoxides in human sample using diphenyl-1-pyrenylphosphine for the first time, and used the value of lipid hydroperoxides as an index of oxidative stress. Then, we compared the antioxidative properties of azelnidipine and amlodipine, a frequently used calcium antagonist in hypertensive diabetic patients. Administration of vitamin C and E for 8 weeks significantly reduced lipid hydroperoxides in erythrocyte membrane in normal subjects. In hypertensive diabetic patients, azelnidipine treatment for 12 weeks induced a more significant fall in erythrocyte lipid hydroperoxide level than amlodipine, though blood pressure during each treatment was comparable. Our data confirm the usefulness of lipid hydroperoxides in erythrocyte membrane as a marker of oxidative stress in vivo, and indicate that azelnidipine has a unique antioxidative property in human.

Effects of amlodipine-atorvastatin combination on inflammation markers and insulin sensitivity in normocholesterolemic obese hypertensive patients

OBJECTIVE

The objective of this study was to assess the effect of amlodipine-atorvastatin combination on plasma interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-alpha) and insulin sensitivity in normocholesterolemic obese hypertensive patients.

MATERIALS AND METHODS

After a 4-week placebo wash-out period, 50 normocholesterolemic [total cholesterol (TC) <5.2 mmol/L], obese (BMI >/=30 kg/m(2)) hypertensive patients (DBP >90 and <105 mm Hg and SBP >140 and <180 mm Hg) were randomly treated with amlodipine (10 mg) or with amlodipine (10 mg) plus atorvastatin (20 mg) according to a cross-over design; each treatment had a 12-week duration. At the end of the placebo and of each treatment period, blood pressure (BP), TNF-alpha, IL-6, insulin resistance (IR) by homeostasis model assessment of IR index (HOMA-IR) and TC were evaluated.

RESULTS

Amlodipine monotherapy decreased both SBP (-17.1 mm Hg, p=0.008 vs. placebo) and DBP (-14.3 mm Hg, p=0.008) as well as TNF-alpha (from 3.66+/-1.6 to 3.09+/-1.1 pg/ml, p=0.045) and HOMA-IR (from 4.58+/-0.7 to 3.88+/-0.6, p=0.007). The amlodipine-atorvastatin combination produced a decrease in SBP (-22.5 mm Hg, p=0.0007 vs. placebo, p=0.039 vs. amlodipine), DBP (-17.7 mm Hg, p=0.0007 vs. placebo; p=0.04 vs. amlodipine), TNF-alpha (2.59+/-0.9 pg/mL, p=0.007 vs. placebo and p=0.038 vs. amlodipine) and HOMA-IR (2.86+/-0.4, p=0.0008 vs. placebo and p=0.007 vs. amlodipine). The combination reduced IL-6 (from 7.93+/-1.9 to 5.59+/-1.2 pg/mL, p=0.008 vs. placebo and p=0.007 vs. amlodipine) and TC (from 4.3+/-0.5 to 3.6+/-0.4 mmol/L, p=0.008 vs. placebo and vs. amlodipine). HOMA-IR changes significantly correlated with TNF-alpha changes (r=0.38, p<0.05) during combination but not during amlodipine monotherapy. In normocholesterolemic, obese hypertensive patients, the amlodipine-atorvastatin combination decreased inflammatory markers and IR more than amlodipine monotherapy and produced a greater SBP and DBP reduction.

Pharmacological basis of different targets for the treatment of atherosclerosis

The development of atherosclerotic plaque is a highly regulated and complex process which occurs as a result of structural and functional alterations in endothelial cells, smooth muscle cells (SMCs), monocytes/macrophages, T-lymphocytes and platelets. The plaque formation in the coronary arteries or rupture of the plaque in the peripheral vasculature in latter stages of atherosclerosis triggers the onset of acute ischemic events involving myocardium. Although lipid lowering with statins has been established as an important therapy for the treatment of atherosclerosis, partially beneficial effects of statins beyond decreasing lipid levels has shifted the focus to develop newer drugs that can affect directly the process of atherosclerosis. Blockade of renin angiotensin system, augmentation of nitric oxide availability, reduction of Ca(2+) influx, prevention of oxidative stress as well as attenuation of inflammation, platelet activation and SMC proliferation have been recognized as targets for drug treatment to control the development, progression and management of atherosclerosis. A major challenge for future drug development is to formulate a combination therapy affecting different targets to improve the treatment of atherosclerosis.

Voltage-dependent effects of barnidipine in rat vascular smooth muscle

The effects of the dihydropyridine nifedipine and its more lipophilic congener, barnidipine, were investigated in smooth muscle preparations from the rat in resting and depolarizing conditions. Both drugs relaxed precontracted aortic rings more potently in depolarizing conditions, barnidipine being more potent than nifedipine. Currents through Ca2+ channels in rat vascular smooth muscle cells (A7r5) and in isolated rat cardiomyocytes were reduced more potently by both drugs at a holding potential of -40 mV than at -80 mV. However, barnidipine and nifedipine were more effective in reducing the current in A7r5 cells than in cardiomyocytes. The IC(50) obtained in aortic rings and in A7r5 cells were similar for barnidipine but an order of magnitude different for nifedipine. The results show that, in depolarizing conditions, barnidipine was more effective than nifedipine. It is suggested that the higher potency of barnidipine acting in vascular smooth muscle is related to both a higher affinity to the inactivated state of vascular Ca2+ channels and to a more lipophilic property as compared with nifedipine.

Inhibition of oxidized LDL aggregation with the calcium channel blocker amlodipine: role of electrostatic interactions

Atherogenic low-density lipoproteins (LDL) are characterized by elevations in cholesterol content and increased electronegativity, factors that contribute to aggregation and foam cell formation. This study was designed to test the effect of the positively charged calcium channel blocker (CCB) amlodipine on the aggregation properties of oxidized LDL lipids. Large unilamellar vesicles (LUVs) (100 nm diameter) labeled with a non-exchangeable marker [3H]cholesteryl hexadecyl ether were prepared with lipids extracted from human LDL following oxidation. The LUVs were shown to bind, in a reversible fashion, to charged diethylaminoethyl Sephadex columns. The addition of amlodipine inhibited binding of the oxidized LDL lipids in a dose-dependent fashion with an IC(50) in the nanomolar range as a result of its high lipophilicity and positively charged amino group (pK(a) of 9.02). The activity of amlodipine was reproduced in model membranes that contained fixed amounts of charged phospholipid (glycerophospholipid) in a concentration-dependent manner. By contrast, drugs lacking a formal positive charge, including CCBs (felodipine, nifedipine, diltiazem, verapamil) and an angiotensin-converting enzyme-inhibitor (ramiprilate) had no effect on the column binding of the modified, electronegative lipids. These effects of amlodipine on LDL lipid aggregation and electrostatic properties may represent a novel antiatherosclerotic mechanism of action.

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.

Raman spectroscopic investigation of atorvastatin, amlodipine, and both on atherosclerotic plaque development in APOE*3 Leiden transgenic mice

Raman spectroscopy allows quantitative, non-destructive evaluation of entire, intact atherosclerotic plaques. We quantified the anti-atherosclerotic effects of atorvastatin and amlodipine on progression of atherosclerosis using post-mortem Raman spectroscopic plaque imaging in 28 APOE*3 Leiden transgenic mice who were fed a high fat/high cholesterol diet for 28 weeks. Mice were assigned to a control group receiving the diet alone or to groups that received the diet with either 0.01% w/w atorvastatin, 0.002% w/w amlodipine, or the combination. The entire excised aortic arch was scanned with Raman microspectroscopy for quantitation of the distribution of cholesterol and calcification content. When mice had been treated with atorvastatin, cholesterol accumulation and calcification in the aortic arch was reduced by 91 and 98%, respectively, (both P<0.001). Amlodipine did not reduce the cholesterol content but reduced calcification of the aorta by 69% (P<0.05). The combination of amlodipine and atorvastatin was as effective as atorvastatin alone. This study demonstrates the strong atheroprotective potential of atorvastatin. In addition it is demonstrated that amlodipine reduces mineralization of atherosclerotic plaque. No synergistic effect of the combination of amlodipine and atorvastatin on plaque development is demonstrated. This study encourages Raman spectroscopic evaluations of anti-atherosclerotic drugs in larger animals and humans in vivo.

Antiatherosclerotic effects of calcium channel blockers

Over the past 30 years, a considerable body of experimental and clinical evidence has accumulated to support the suggestion that calcium channel blockers (CCBs) have significant antiatherosclerotic effects that are independent of their hypotensive effects. Early research using animal models of atherosclerosis and CCBs in concentrations that exceeded the normal therapeutic dose range showed definite antiatherosclerotic effects, especially in the development of new lesions. Investigations of these effects in humans have used quantitative coronary angiography and B-mode ultrasonography and have demonstrated some antiatherosclerotic effects. This article reviews the currently available evidence of antiatherosclerotic effects of CCBs in animal models and in clinical trials.

Effect of cholesterol liposomes on calcium mobilization in muscle cells from the rabbit sphincter of Oddi

AIM: To analyze the influence of cholesterol liposome on the Ca²⁺ mobilization of cultured muscle cells in rabbit sphincter of Oddi’s.

METHODS: New Zealand rabbit was sacrificed and the sphincter of Oddi (SO) segement was obtained aseptically. The SO segment was cut into pieces and cultured in DMEM solution. Then the smooth muscle cells were subcultured, and the 4th-7th passage cells were used for further investigation. The intracellular Ca²⁺ increase was measured under confocal microscope after the addition of 20 mmol·L^-1 KCl, 10^-7 mol·L^-1 acetylcholine and 10^-7 mol·L^-1 cholecystokinin, and different antagonists were added to analyze the Ca²⁺ mobilization pathway. After the cells were incubated with 1 g·L^-1 cholesterol liposome (CL)(molar ratio was-2:1), the intracellular Ca²⁺ increase was measured again to determine the effect of CL on cellular Ca²⁺ mobilization.

RESULTS: The resting cellular calcium concentration of cultured SO cell was 108 nmol·L^-1± 21 nmol·L^-1. The intracellular Ca²⁺ increases induced by 20 mmol·L^-1 KCl, 10^-7 mol·L^-1 ACh and 10^-7 mol·L^-1 CCK were 183% ± 56%, 161% ± 52% and 130% ± 43%, respectively. When the extracellular Ca²⁺ was eliminated by 2 mmol·L^-1 EGTA and 5 μmol·L^-1 verapamil, the intracellular Ca²⁺ increases induced by KCl, ACh and CCK were 20% ± 14%, 82% ± 21% and 104% ± 23%, respectively. After the preincubation with heparin, the Ca²⁺ increases were 62% ± 23% and 23% ± 19% induced by ACh and CCK, as for preincubation with procaine they were 72% ± 28% and 85% ± 37% induced by ACh and CCK, respectively. Pretreatment with CL for 18 h, the resting cellular Ca²⁺ concentration elevated to 152 nmol·L^-1± 26 nmol·L^-1, however, the cellular Ca²⁺ increase percentages in response to these agonists were 67% ± 32%, 56% ± 33% and 34% ± 15%.

CONCLUSION: KCl elicite the SO cellular Ca²⁺ increase depends on influx of extracellular Ca²⁺, ACh evoked the SO celllular Ca²⁺ increase is through the mobilization of intracellular Ca²⁺ pool and influx of extracellular Ca²⁺ as well, CCK excites the SO cells mainly through mobilization of intracellular IP3-sensitive Ca²⁺ store. After the incorporation with cholesterol liposome, KCl,ACh and CCK induced cellular Ca²⁺ increase percentages decreased.

Effect of lipid-lowering agents, angiotensin-converting enzyme inhibitors, and calcium antagonists on coronary disease risk

Dyslipidemia is a causative, yet modifiable risk factors for the development of adverse outcomes secondary to coronary artery disease. Recent trials have focused on the level of low-density lipoprotein cholesterol (LDL-C) necessary to achieve maximum reduction in clinical events. Data also exist demonstrating that intensive lowering of LDL-C in patients with unstable angina reduces the incidence of adverse clinical events. The statins appear to be fundamental therapy in patients with established coronary disease as well as a mainstay for those with early evidence of atherosclerosis. The angiotensin-converting enzyme (ACE) inhibitors have demonstrated a reduction in ischemic events in patients with heart failure. Recent trials of ACE inhibitors in patients with vascular disease who do not have the traditional indications for ACE inhibition have shown a reversal of endothelial dysfunction and a reduction in adverse clinical endpoints. A role for the use of calcium antagonists in patients with atherosclerosis is less well established, despite the evidence of excellent results in patients with symptomatic coronary disease. A recent clinical trial, using a third-generation dihydropyridine calcium antagonist with novel mechanisms, found promising results with regard to its effects on atherosclerosis

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.

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.

The smooth muscle cell membrane during atherogenesis: a potential target for amlodipine in atheroprotection

BACKGROUND

Atherosclerotic disease has been present in the human population apparently from the beginning of time. However, it has only been in the 20th century that improvements in the control of infectious diseases have allowed the average life span to increase to the point where atherosclerosis has been able to affect the general population. By the middle of the 20th century, atherosclerosis had reached epidemic levels, and it is currently pandemic and increasing worldwide. Despite its growing significance to health care, we still know relatively little about the cellular basis for plaque genesis in the vessel wall. Current thinking holds that atherosclerosis is caused by an unchecked chronic inflammatory process involving the cells of the arterial wall and their interaction with LDL and various inflammatory cells. Considerable evidence suggests that the principal insults underlying atherogenesis are serum dyslipidemias and oxidative stress mediated primarily by oxidized LDL. However, just how these insults alter the cell biology of vascular cells and lead to the atherosclerotic phenotype is still under intense investigation. Moreover, recent clinical trials have provided evidence that certain classes of drugs, including newer calcium channel blockers (CCBs), can remodel the arterial smooth muscle cell (SMC) membrane and inhibit the progression of atherosclerotic disease.

METHODS

This review summarizes our current thinking on atherogenesis in the arterial SMC and considers recent developments regarding alterations in the SMC membrane during the very early period of atherogenesis. We also discuss how certain CCBs might operate to produce atheroprotection.

RESULTS

The SMC membrane becomes enriched in unesterified cholesterol soon after the development of serum hypercholesterolemia. With excess membrane cholesterol, the membrane becomes thicker and develops distinct cholesterol domains. These alterations in the membrane increase the permeability of SMC to calcium and induce a variety of alterations in SMC function that contribute to cellular atherogenic processes during plaque genesis. Amlodipine, a third-generation CCB, markedly inhibits the progression of lesions. The explanation of this novel action may lie in the effects of this drug on various potential cellular targets.

CONCLUSIONS

Evidence is accumulating that excess membrane cholesterol may contribute to the cellular defects responsible for the transformation of the SMC to the atherosclerotic phenotype. Amlodipine, which has membrane-remodeling properties, is emerging as an important atheroprotective drug.

Modulation of tumor necrosis factor-alpha production with anti-hypertensive drugs

It is well known that some anti-hypertensive drugs affect insulin sensitivity and that tumor necrosis factor-alpha (TNF-alpha) is a mediator of obesity-associated insulin resistance. In this study, we have investigated the effect of anti-hypertensive drugs, calcium (Ca) channel blockers (amlodipine, manidipine and nicardipine), an alpha(1)-blocker (doxazosin), a beta(1)-blocker (metoprolol), and a thiazide diuretic (hydrochlorothiazide), on lipopolysaccharide (LPS)-induced TNF-alpha production. TNF-alpha production, measured with a bioassay and an immunoassay, was evaluated both in vivo and in vitro, by utilizing mice and a human peripheral blood mononuclear cell culture, respectively. Nicardipine, or amlodipine, manidipine and doxazosin significantly inhibited TNF-alpha production in mice at doses more than one or ten times higher than those used clinically, respectively. On the other hand, metoprolol increased TNF-alpha production at doses of more than 10 times those used clinically, whereas hydrochlorothiazide did not alter production of the cytokine. The in vivo effects of these drugs were not necessary parallel to the in vitro effects. Because high doses of these drugs in mice correspond to clinical doses and effects in human, these actions may be related to beneficial and/or harmful effects of these drugs on TNF-alpha mediated diseases, including insulin resistance.

Calcium channel blockers, apoptosis and cancer: is there a biologic relationship?

Calcium channel blockers (CCBs) represent a chemically and pharmacologically diverse group of agents that are widely used for the treatment of hypertension and angina. A small number of retrospective, observational analyses have raised concern about a potential causal link between CCB use and an increased risk for cancer development. Despite the absence of cancer findings in extensive preclinical studies, it has been proposed that CCBs may work differently in humans by interfering with apoptosis, leading to an increased potential for abnormal cell proliferation and tumor growth. This biologic hypothesis has attracted considerable attention in the medical community but has not been critically evaluated. An analysis of the basic and clinical literature was conducted to examine biologic relationships among cell Ca2+ modulation, apoptosis, and cancer. In addition to a comprehensive review of the cellular and animal data, the results of large observational studies were included in this analysis. Results of this review demonstrated that the effects of CCBs on apoptosis are complex as both increases and decreases in intracellular Ca2+ have been linked to this form of programmed cell death. Most studies show that an effect (either positive or negative) of CCBs on apoptosis requires doses in the supra-pharmacologic range, and are therefore not clinically relevant. Results of large and methodologically robust observational studies fail to provide support for the hypothesis that CCB use is associated with an increased susceptibility for cancer incidence. A comprehensive analysis of the basic and clinical evidence does not support a causal relationship between the therapeutic use of CCBs and an increased incidence of cancer development as a result of interfering with apoptosis.

Atheroprotection with amlodipine: cells to lesions and the PREVENT trial. Prospective Randomized Evaluation of the Vascular Effects of Norvasc Trial

Oxidized lipid and calcium regulatory abnormalities appear to play important roles in early atherogenesis secondary to cholesterol enrichment of the cell membrane in endothelial and arterial smooth muscle cells (SMCs). However, the link between the two is poorly understood. The findings reviewed here demonstrate that amlodipine has membrane-modifying and antioxidant actions at the cell membrane level in addition to its classical calcium channel blocking properties. These multiple pharmacologic actions may explain the cellular mechanisms of the atheroprotective effects of amlodipine in spontaneous atherogenesis and in accelerated atherosclerotic syndromes. Recent animal model studies have demonstrated that amlodipine inhibits the progression of atherosclerotic lesions and protects against restenosis after angioplasty. Amlodipine inhibits the cholesterol-induced increase in calcium permeability in SMCs, and has been shown to repair abnormalities in SMC membrane structure. Recent data have also demonstrated that amlodipine has a marked antioxidant action in membrane bilayers enriched with polyunsaturated fatty acids. However, these findings have been in animal models only; the efficacy of amlodipine in atheroprotection in humans cannot be predicted. The PREVENT trial has therefore been launched to examine the atheroprotective potential of amlodipine in spontaneous lesion development in humans with ischemic heart disease and in the prevention of restenosis after angioplasty.

Abnormal cell calcium homeostasis in type 2 diabetes mellitus: a new look on old disease

Cumulative evidence reveals that diabetes is a condition in which cell Ca2+ homeostasis is impaired. Defects in cell Ca2+ regulation were found in erythrocytes, cardiac muscle, platelets, skeletal muscle, kidney, aorta, adipocytes, liver, osteoblasts, arteries, lens, peripheral nerves, brain synaptosomes, retinal tissue, and pancreatic beta cells, confirming that this defect in cell Ca2+ metabolism is a basic pathology associated with the diabetic state. Though different defects in a variety of functions that regulate cell Ca2+ homeostasis were described in diabetes, the most common finding is an increase in [Ca2+]i levels. However, it is not clear whether the defect in cell Ca2+ metabolism in diabetes precedes or succeeds the overt diabetic condition. It is also not clear which of the multiple functions involved in cell Ca2+ regulation has the primary defect. Defects in cell Ca2+ metabolism may be significant for the observed pathologies in insulin secretion and insulin action in diabetes. They may also play an important role in the vascular complications seen in this condition, such as hypertension, atherosclerosis, and microangiopathy. Therefore, better understanding of the impairment in cell Ca2+ metabolism in diabetes may markedly enhance our understanding of this condition.