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

Cholesterol crystals and atherosclerotic plaque instability: Therapeutic potential of Eicosapentaenoic acid

Atherosclerotic plaques associated with acute coronary syndromes (ACS), i.e. culprit lesions, frequently feature a ruptured fibrous cap with thrombotic complications. On imaging, these plaques exhibit a low attenuation, lipid-rich, necrotic core containing cholesterol crystals and are inherently unstable. Indeed, cholesterol crystals are causally associated with plaque vulnerability in vivo; their formation results from spontaneous self-assembly of cholesterol molecules. Cholesterol homeostasis is a central determinant of the physicochemical conditions leading to crystal formation, which are favored by elevated membrane free cholesterol content in plaque endothelial cells, smooth muscle cells, monocyte-derived macrophages, and foam cells, and equally by lipid oxidation. Emerging evidence from imaging trials in patients with coronary heart disease has highlighted the impact of intervention involving the omega-3 fatty acid, eicosapentaenoic acid (EPA), on vulnerable, low attenuation atherosclerotic plaques. Thus, EPA decreased features associated with unstable plaque by increasing fibrous cap thickness in statin-treated patients, by reducing lipid volume and equally attenuating intraplaque inflammation. Importantly, atherosclerotic plaques rapidly incorporate EPA; indeed, a high content of EPA in plaque tissue is associated with decreased plaque inflammation and increased stability. These findings are entirely consistent with the major reduction seen in cardiovascular events in the REDUCE-IT trial, in which high dose EPA was administered as its esterified precursor, icosapent ethyl (IPE); moreover, clinical benefit was proportional to circulating EPA levels. Eicosapentaenoic acid is efficiently incorporated into phospholipids, where it modulates cholesterol-enriched domains in cell membranes through physicochemical lipid interactions and changes in rates of lipid oxidation. Indeed, biophysical analyses indicate that EPA exists in an extended conformation in membranes, thereby enhancing normal cholesterol distribution while reducing propagation of free radicals. Such effects mitigate cholesterol aggregation and crystal formation. In addition to its favorable effect on cholesterol domain structure, EPA/IPE exerts pleiotropic actions, including antithrombotic, antiplatelet, anti-inflammatory, and proresolving effects, whose plaque-stabilizing potential cannot be excluded. Docosahexaenoic acid is distinguished from EPA by a higher degree of unsaturation and longer carbon chain length; DHA is thus predisposed to changes in its conformation with ensuing increase in membrane lipid fluidity and promotion of cholesterol aggregation into discrete domains. Such distinct molecular effects between EPA and DHA are pronounced under conditions of high cellular cholesterol content and oxidative stress. This review will focus on the formation and role of cholesterol monohydrate crystals in destabilizing atherosclerotic plaques, and on the potential of EPA as a therapeutic agent to attenuate the formation of deleterious cholesterol membrane domains and of cholesterol crystals. Such a therapeutic approach may translate to enhanced plaque stability and ultimately to reduction in cardiovascular risk.

Clinical roles of calcium channel blockers in ischemic heart diseases

Calcium (Ca) channel blockers (CCBs) inhibit Ca²⁺ channels in the myocardium or vascular smooth muscle cells, inhibit myocardium contraction, inhibit the impulse conduction system (anti-arrhythmias) and cause vasodilation. New classifications based on subtypes of Ca channels and α1 subunits have been proposed. Moreover, CCBs have pleiotropic effects on coronary spastic angina (CSA), including variant angina, myocardial infarction (MI) and stent thrombosis (ST). Although the roles of CCBs in clinical situations remain unknown, further studies in this field are expected to broaden our understanding. In this article, we explain the clinical roles of CCBs in ischemic heart diseases, such as CSA, MI and ST, based on previous knowledge and as demonstrated in representative clinical trials.

Lercanidipine effect on polymorphonuclear leukocyte-related inflammation and insulin resistance in essential hypertension patients

INTRODUCTION

Inflammation, insulin resistance, and oxidative stress (OS) are among the mechanisms that have been implicated in the pathogenesis of essential hypertension (EH). Peripheral polymorphonuclear leukocytes (PMNLs) are primed in EH patients, releasing uncontrolled superoxide anions contributing to OS in these patients. PMNL priming correlates with insulin resistance and PMNL intracellular calcium ([Ca(2+)]i). Recent studies have attributed additional anti-ischemic and antioxidative characteristics to the antihypertensive drug, lercanidipine, a third-generation calcium-channel blocker. The purpose of this study was to evaluate the possible nontraditional effect of 2 months of lercanidipine treatment on insulin resistance and on PMNL-related inflammation in EH patients.

METHODS

Non-smoking EH patients with untreated mild-to-moderate high blood pressure (BP) were included. Low-grade inflammation was reflected by PMNL apoptosis and by white blood cell (WBC) and PMNL counts. Systemic inflammation was measured by plasma fibrinogen, C-reactive protein (CRP), and transferrin and albumin levels. Fasting serum insulin levels served as a marker of insulin resistance.

RESULTS

Two months of lercanidipine treatment showed a significant decrease in BP, WBC, and PMNL counts, PMNL apoptosis, CRP, and serum insulin levels, and a significant increase in serum albumin levels. Rates of superoxide release from PMNLs, WBC and PMNL counts, and insulin levels positively correlated with mean arterial BP values.

CONCLUSION

The use of lercanidipine can be favorable in EH patients due to its combined anti-PMNL priming and anti-inflammatory effects, in addition to its antihypertensive characteristics.

Large conductance, calcium- and voltage-gated potassium (BK) channels: regulation by cholesterol

Cholesterol (CLR) is an essential component of eukaryotic plasma membranes. CLR regulates the membrane physical state, microdomain formation and the activity of membrane-spanning proteins, including ion channels. Large conductance, voltage- and Ca²⁺-gated K⁺ (BK) channels link membrane potential to cell Ca²⁺ homeostasis. Thus, they control many physiological processes and participate in pathophysiological mechanisms leading to human disease. Because plasmalemma BK channels cluster in CLR-rich membrane microdomains, a major driving force for studying BK channel-CLR interactions is determining how membrane CLR controls the BK current phenotype, including its pharmacology, channel sorting, distribution, and role in cell physiology. Since both BK channels and CLR tissue levels play a pathophysiological role in human disease, identifying functional and structural aspects of the CLR-BK channel interaction may open new avenues for therapeutic intervention. Here, we review the studies documenting membrane CLR-BK channel interactions, dissecting out the many factors that determine the final BK current response to changes in membrane CLR content. We also summarize work in reductionist systems where recombinant BK protein is studied in artificial lipid bilayers, which documents a direct inhibition of BK channel activity by CLR and builds a strong case for a direct interaction between CLR and the BK channel-forming protein. Bilayer lipid-mediated mechanisms in CLR action are also discussed. Finally, we review studies of BK channel function during hypercholesterolemia, and underscore the many consequences that the CLR-BK channel interaction brings to cell physiology and human disease.

Concentration dependency of modulatory effect of amlodipine on P-glycoprotein efflux activity of doxorubicin — a comparison with tamoxifen

Modulators of P-glycoprotein (P-gp) can enhance or limit the permeability of a number of therapeutic agents that are considered substrates of this efflux pump protein. The modulatory effect of amlodipine (4-dihydropyridine calcium antagonist) on P-gp efflux activity has not been fully elucidated. We have studied the concentration dependency of its modulatory effect and compared it qualitatively with tamoxifen (a non-esteroid anti-estrogen). The investigation was conducted on transmembrane efflux of doxorubicin at a fixed concentration of 5 μm across a Caco-2 monolayer in the presence of various concentrations of amlodipine or tamoxifen. The maximum flux of doxorubicin from basolateral to apical (ba) occurred at 4.5 μm amlodipine and at 0.02 μm tamoxifen. At higher concentrations, the apical to basolateral (ab) flux and the net flux of doxorubicin (ba — ab) declined steadily in a concentration-dependent manner. We analysed the observed net flux data by fitting different mathematical models to the data. A composite sigmoidal Emax/Imax (stimulatory/inhibitory) model was found to be the most appropriate to define the system. The observed and calculated parameters supported the modulatory role of both compounds and clearly indicated that the stimulation and inhibition of transmembrane efflux occurred simultaneously in the presence of amlodipine or tamoxifen. It was concluded that amlodipine, similar to tamoxifen, modulated the transporter-dependent transmembrane flux of the P-gp substrate in a concentration-dependent manner.

Modulation of calcification of vascular smooth muscle cells in culture by calcium antagonists, statins, and their combination

Background Vascular calcification is an organized process in which vascular smooth muscle cells (VSMCs) are implicated primarily. The purpose of the present study was to assess the effects of calcium antagonists and statins on VSMC calcification in vitro. Methods VSMC calcification was stimulated by incubation in growth medium supplemented with 10 mmol/l β-glycerophosphate, 8 mmol/l CaCl₂, 10 mmol/l sodium pyruvate, 1 μmol/l insulin, 50 μg/ml ascorbic acid, and 100 nmol/l dexamethasone (calcification medium). Calcification, proliferation, and apoptosis of VSMCs were quantified. Results Calcium deposition was stimulated dose-dependently by β-glycerophosphate, CaCl₂, and ascorbic acid (all P < 0.01). Addition of amlodipine (0.01–1 μmol/l) to the calcification medium did not affect VSMC calcification. However, atorvastatin (2–50 μmol/l) stimulated calcium deposition dose-dependently. Combining treatments stimulated calcification to a degree similar to that observed with atorvastatin alone. Both atorvastatin and amlodipine inhibited VSMC proliferation at the highest concentration used. Only atorvastatin (50 μmol/l) induced considerable apoptosis of VSMCs. Conclusion In vitro calcification of VSMCs is not affected by amlodipine, but is stimulated by atorvastatin at concentrations ≥10 μmol/l, which could contribute to the plaque-stabilizing effect reported for statins.

Calcium-channel modulators for cardiovascular disease

It is generally accepted that hypertension doubles the risk of cardiovascular disease, of which coronary heart disease is the most common and lethal. Hypertension is a predisposing factor for the development of stroke, peripheral arterial disease, heart failure and end-state renal disease. Atherosclerosis-causing coronary heart disease is related to the severity of hypertension. Inhibition of calcium entry reduces the active tone of vascular smooth muscle and produces vasodilatation. This pharmacological action has been the basis for the use of calcium-channel blockers (CCBs) for the management of hypertension. Other drug families may achieve this: diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, angiotensin-receptor antagonists. Cardiovascular hypertrophy and atherosclerosis are major complications related to high blood pressure. Cardiac hypertrophy is considered as an independent risk factor associated with abnormalities of diastolic function and can result in heart failure. Atherosclerosis is associated with activation of innate immunity. Atherosclerosis is expressing itself not only as coronary heart disease, but as a cerebrovascular and peripheral arterial disease. By impairing physiological vasomotor function, atherosclerosis includes ultimately necrosis of myocardium. CCBs reduce blood pressure. Do they prevent the progress of the main complications of hypertension? This major question is the matter of the present paper.

Lipid headgroup superlattice modulates the activity of surface-acting cholesterol oxidase in ternary phospholipid/cholesterol bilayers

The relationship between the molecular organization of lipid headgroups and the activity of surface-acting enzyme was examined using a bacterial cholesterol oxidase (COD) as a model. The initial rate of cholesterol oxidation by COD in fluid state 1-palmitoyl-2-oleoyl-phosphatidylethanolamine/1-palmitoyl-2-oleoyl-phosphatidylcholine/cholesterol (POPE/POPC/CHOL) bilayers was measured as a function of POPE-to-phospholipid mole ratio (X(PE)) and cholesterol-to-lipid mole ratio (X(CHOL)) at 37 degrees C. At X(PE) = 0, the COD activity changed abruptly at X(CHOL) approximately 0.40, whereas major activity peaks were detected at X(PE) approximately 0.18, 0.32, 0.50, 0.64, and 0.73 when X(CHOL) was fixed to 0.33 or 0.40. At a fixed X(CHOL) of 0.50, the COD activity increased progressively with PE content and exhibited small peaks or kinks at X(PE) approximately 0.40, 0.50, 0.58, 0.69, and 0.81. When X(PE) and X(CHOL) were systematically varied within a narrow 2-D lipid composition window, an onset of COD activity at X(CHOL) approximately 0.40 and the elimination of the activity peak at X(PE) approximately 0.64 for X(CHOL) >0.40 were clearly observed. Except for X(PE) approximately 0.40 and 0.58, the observed critical PE mole ratios agree closely (+/-0.03) with those predicted by a headgroup superlattice model (Virtanen, J.A., et al. (1998) Proc. Natl. Acad. Sci. U.S.A. 95, 4964-4969; Cannon, B., et al. (2006) J. Phys. Chem. B 110, 6339-6350), which proposes that lipids with headgroups of different sizes tend to adopt regular, superlattice-like distributions at discrete and predictable compositions in fluid lipid bilayers. Our results indicate that headgroup superlattice domains exist in lipid bilayers and that they may play a crucial role in modulating the activity of enzymes acting on the cell membrane surface.

Anti-Atherosclerotic Effect of Amlodipine, Alone and in Combination With Atorvastatin, in APOE*3-Leiden/hCRP Transgenic Mice

We investigated the pleiotropic effects of a calcium antagonist (amlodipine) on early atherosclerosis development in the presence and absence of an HMG-CoA-reductase inhibitor (atorvastatin) in apolipoprotein E*3-Leiden/human C-reactive protein (E3L/CRP) transgenic mice. Male E3L/CRP transgenic mice were fed a cholesterol-containing diet either with or without amlodipine and/or atorvastatin. After 31 weeks, atherosclerosis in the aortic root area was quantified. Treatment with amlodipine did not significantly lower blood pressure, but resulted in a 43% reduction (P < 0.03) of lesion area as compared with the untreated group. Treatment with atorvastatin resulted in an 80% reduction of lesion area as compared with the untreated group (P < 0.001). Combined treatment with amlodipine and atorvastatin decreased the lesion area by 93%, significantly more than either treatment alone (P < 0.008). Plasma C-reactive protein levels were mildly elevated, on average 10 +/- 6 mg/L, and did not differ between groups, neither on baseline nor during treatment. Treatment with amlodipine, independently of blood pressure lowering, reduced atherosclerosis development in E3L/CRP mice. Atorvastatin had a strong anti-atherosclerotic effect, whereas co-treatment with amlodipine enhanced this effect significantly. Plasma C-reactive protein levels were not affected by any of the three treatments.

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.

Benidipine, a long-acting calcium channel blocker, inhibits oxidative stress in polymorphonuclear cells in patients with essential hypertension

To study the relationship between blood pressure and oxidative stress in leukocytes, the effect of benidipine on these variables was compared with that of a placebo. Hypertensive patients were randomly assigned benidipine 4 mg (n=40) or placebo (n=40), and treated for 6 months. Oxidative stress in polymorphonuclear cells (PMNs) was measured by gated flow cytometry. There was a significant relationship between systolic or diastolic arterial pressure and reactive oxygen species (ROS) formation by PMNs in the benidipine group (r=0.61, p<0.01) and in the placebo group (r=0.58, p<0.01). After administration of 4 mg benidipine, ROS formation by PMNs fell by 32 arbitrary units (n=40, p<0.01). After administration of placebo, ROS formation by PMNs decreased by 0.6 arbitrary units (n=40, p=0.31) (p<0.01 for differing treatment effects). There was a significant relationship between the decrease in systolic arterial pressure and the decrease in ROS formation by PMNs in the benidipine group (r=0.52, p<0.01), but not in the placebo group (r=-0.08, p=0.61). There was also a significant relationship between the decrease in diastolic arterial pressure and decrease in ROS formation by PMNs in the benidipine group (r=0.65, p<0.01) but not in the placebo group (r=-0.09, p=0.59). In hypertensive patients, we observed a significant relationship between systolic or diastolic blood pressure and ROS formation by PMNs, and found that benidipine decreased oxidative stress in PMNs of hypertensive patients, at least in part by decreasing blood pressure.

Na+/H+ exchange inhibition and antioxidants lack additive protective effects after reperfusion injury in the working heterotopic rat heart isograft

BACKGROUND

The utility of combining strategies of myocardial protection was studied in intact rat hearts subjected to 1 hour of ischemia and 40 minutes blood reperfusion.

METHODS

Lewis rats (n = 48) were divided into 4 transplant groups. Twenty-four hearts were arrested by coronary perfusion with hypothermic Celsior solution at 60 mm Hg. The aortic valve was punctured to introduce volume into the left ventricle (LV), and the hearts were abdominally isografted. Animals were either given both the antioxidant probucol (300 mg/kg) and the sodium-hydrogen exchange inhibitor cariporide (5 mg/kg) (CP; n = 6), just cariporide (CAR; n = 6), just probucol (PROB; n = 6), or neither drug (CON; n = 6). After 40 minutes of blood reperfusion, transplanted hearts were rearrested. The control recipients' native hearts (native; n = 6) were also arrested. Postmortem LV compliance relations and myocardial water content (MWC) were measured.

RESULTS

Grafts protected by probucol were significantly more compliant than controls and significantly less compliant than grafts protected by cariporide alone and with both cariporide and probucol (p = 0.0001, analysis of variance). Compliance relations for CP overlapped those for CAR. All grafts were less compliant than natives. MWC was significantly greater in controls and PROB than in natives.

CONCLUSIONS

Pretreatment with cariporide in the setting of ischemia-reperfusion injury provides greater protection against the development of diastolic abnormalities than probucol when Celsior solution is used for both arrest and preservation. In this model, there is no advantage to combining the drugs, supporting the hypothesis that there is an overlapping mechanism of protection.

Effect of amlodipine on vascular responses after coronary stenting compared with an angiotensin-converting enzyme inhibitor

BACKGROUND

Prevention of restenosis after coronary stenting is clinically important. We compared amlodipine and quinapril to determine which is more effective in preventing restenosis after stenting.

METHODS AND RESULTS

Immediately after successful coronary stenting of 101 lesions in 63 consecutive patients, the patients were randomly divided into 2 groups: 32 patients with 48 lesions were administered amlodipine 5 mg/day (group A), and 31 patients with 53 lesions were administered quinapril 10 mg/day (group Q). Lesions were assessed by quantitative coronary angiography (QCA) before and immediately after stenting and in the follow-up phase. Intravascular ultrasound (IVUS) could only be performed on 20 lesions in group A and 16 lesions in group Q throughout the follow-up period. We analyzed each lesion at 5 sites. In the follow-up phase, the minimal lumen diameter in group A was significantly larger than that in group Q (1.88 +/- 0.64 mm vs 1.52 +/- 0.53 mm, p<0.01). In the follow-up phase, the neointimal area (stent area-lumen area) in group A was significantly smaller than that in group Q (1.9 +/- 0.5 mm2 vs 2.7 +/- 0.8 mm2 at the middle portion of stent, p<0.01).

CONCLUSION

These QCA and IVUS findings suggest that amlodipine has beneficial effects in inhibiting neointimal hyperplasia in stented lesions compared with quinapril.

Influence of serum cholesterol on atherogenesis and intimal hyperplasia after angioplasty: inhibition by amlodipine

The objectives of the present study were to determine whether serum hypercholesterolemia (HC) promotes the development of spontaneous and angioplasty-induced lesions and whether amlodipine inhibits these lesions and cellular processes underlying their genesis. Rabbits were fed normal, 0.5%, or 2% cholesterol diets for 9 wk, which resulted in the development of increasing HC. After week one, balloon dilation of the abdominal aorta was performed while the thoracic aorta was not disturbed and monitored for the development of spontaneous lesions. Lesion size increased with the degree of HC and was accompanied by increased collagen synthesis and smooth muscle cell (SMC) proliferation at each site. Amlodipine (5 mg/kg p.o.) inhibited lesion size by 50% (P < 0.01) at both sites in cholesterol-fed animals but not at angioplasty sites in animals on a normal diet. Local collagen synthesis was inhibited at both sites by amlodipine in the diet animals. The increase in HC was accompanied by a 1.7-fold increase in basal Ca2+ uptake in SMCs in the thoracic aorta, which was not altered by amlodipine, nifedipine, Ni2+, or La3+, revealing an uninhibitable calcium leak during atherogenesis. In culture, cholesterol enrichment increased SMC proliferation, collagen synthesis, and the secretion of a soluble SMC mitogen, which were inhibited by amlodipine (10(-9) M). Finally, in SMC membranes, amlodipine uniquely restored the cholesterol-expanded membrane bilayer width without any effect on membrane fluidity. This study establishes a causal role between serum HC and the development of spontaneous and angioplasty-induced lesions and the ability of amlodipine to disrupt this action by a novel remodelling action on the SMC membrane.

Ambulatory blood pressure monitoring and active renin in menopausal women treated with amlodipine and hormone replacement therapy

The aim of this study was to follow up the effect of an 8-week treatment with amlodipine given alone or in combination with hormone replacement therapy (HRT) on blood pressure and active renin in postmenopausal women with mild to moderate arterial hypertension using both conventional clinical blood pressure measurements and ambulatory blood pressure monitoring. Twenty-nine hypertensive menopausal women were divided randomly into two groups according to the treatment regimens: amlodipine and amlodipine plus HRT. The combination with HRT led to normalization of 24-h and daytime systolic and diastolic blood pressure. In contrast to the group treated with amlodipine alone, where a significant fall only of systolic night-time blood pressure was observed, in the group treated with amlodipine plus HRT both systolic and diastolic night-time blood pressure decreased significantly. Active renin did not change significantly after treatment in both groups. Triglycerides decreased significantly and high-density lipoprotein-cholesterol increased significantly only after amlodipine treatment. There were no significant differences in serum total cholesterol and low-density lipoprotein-cholesterol after HRT plus amlodipine. In conclusion, amlodipine is effective in reducing blood pressure in postmenopausal women. The maintenance of a normal circadian blood pressure pattern was influenced by HRT.

[Effects of angiotensin II receptor blockers, angiotensin converting enzyme inhibitors, 3-hydroxy-3-methyl glutaryl (HMG) CoA reductase inhibitors, amlodipine and epalrestat on cultured basilar artery smooth muscle cell proliferation]

Proliferation of vascular smooth muscle cells (VSMC) stimulated by oxidative stresses and reactive oxygen species (ROS) may play a pivotal role in the pathogenesis of atherosclerosis. Antiatherosclerotic effects of angiotensin II receptor blockers, angiotensin converting enzyme inhibitors, HMG CoA reductase inhibitors, calcium channel blocker and epalrestat were studied with an in vitro guinea-pig basilar artery smooth muscle cell (GBa-SM3) culture system over 3 days incubated with 0 to 10% of fetal bovine serum. Results demonstrated that simvastatin (0.1 mM), fluvastatin (0.3 mM), amlodipine (0.2 mM) and epalrestat (1 mM) elicited significant (p < 0.05 or 0.01) antiproliferative effects, whereas losartan (1 mM), valsartan (1 mM), enalapril (0.1 mM), captopril (1 mM), trandolapril (0.01 mM), pravastatin (0.7 mM) did not. In conclusion, the present in vitro VSMC culture system may serve as a comprehensive screening method for pleiotropic effects of commonly used therapeutic agents.

Optimizing probucol administration to preserve left ventricular compliance after reperfusion injury in the heterotopic rat heart isograft

BACKGROUND

We investigated the optimal method of administering probucol to attenuate reperfusion-induced diastolic abnormalities in the left ventricle of the heterotopically transplanted rat heart isograft.

METHODS

We assigned Lewis rats (n = 84) to 7 transplant groups. We arrested 42 hearts using coronary perfusion with hypothermic University of Wisconsin (UW) solution at 60 mm Hg and abdominally isografted the hearts. Neither donors nor recipients in the control group (C-C, n = 6) received probucol. Oral probucol (1% by weight in chow) was fed for 1 month before surgery to the donors only (OP-C, n = 6), the recipients only (C-OP, n = 6), or both (OP-OP, n = 6). We administered an intraperitoneal injection of probucol (300 mg/kg) in 3 ml oil 1 hour before surgery to the donors only (IP-C, n = 6), the recipients only (C-IP, n = 6), or both (IP-IP, n = 6). Transplanted hearts were reperfused for 15 minutes and re-arrested. We also arrested the control recipients' native hearts (native, n = 6). We measured post-mortem left ventricular compliance curves and myocardial water content.

RESULTS

The most compliant grafts were in Groups IP-IP, OP-OP, and C-IP. All isograft groups had significantly less left ventricular compliance than did native hearts. Myocardial water content was significantly greater in controls than in natives, OP-OP, and OP-C.

CONCLUSIONS

Pre-treatment with intraperitoneal probucol in cardiac isograft recipients combines optimal protection with simple administration when UW solution is used for both arrest and preservation. Further studies of the protective effect of probucol against reperfusion injury in large-animal models are warranted and should use intraperitoneal or intravenous injection in recipients.

Inhibitory effect of oolong tea on the oxidative state of low density lipoprotein (LDL)

In the present study, we investigated the anti-oxidant activity of oolong tea in an oxidation model using human low-density lipoprotein (LDL). Oolong tea suppressed the oxidation of LDL induced by 2-2'-azobis 4-methoxy-2,4-dimethyvaleronitrile (V70) in a dose-dependent manner, that is, it prolonged the lag time to 114.3%, 138% and 199.9% as compared with the control group at 0.5 microg/ml, 1.0 microg/ml, and 2.5 microg/ml, respectively. We also determined the scavenging effect of oolong tea on active oxygen radicals using the electron spin resonance (ESR) technique with 5,5-dimethyl-1-pyrroline N-oxide (DMPO) as a spin trapping agent. The intensity of the ESR signals for the DMPO-OOH adduct formed by the hypoxanthine/xanthine oxidase reaction system with DMPO decreased in the presence of oolong tea. The IC(50) of oolong tea was 19.9 microg/ml. These findings suggested that oolong tea has beneficial effects on health related to its anti-oxidative action.

Effects of the calcium channel blocker amlodipine on serum and aortic cholesterol, lipid peroxidation, antioxidant status and aortic histology in cholesterol-fed rabbits

Reactive oxygen metabolites and oxidized fatty acids are proinflammatory and are involved in the pathophysiology of atherosclerosis. Amlodipine, a unique third-generation dihydropyridine-type calcium channel blocker, seems to exert atheroprotective effects through its antioxidant properties related to its chemical structure and independent of its calcium channel-blocking effect. In this study, the interactions of amlodipine with major cellular antioxidants were investigated in order to elucidate the mechanisms underlying its atheroprotective effects. New Zealand white male rabbits were fed regular chow (group 1), chow with 1% cholesterol (group 2), regular chow plus 5 mg/kg/day amlodipine per os (group 3) and 1% cholesterol plus amlodipine (group 4) for 8 weeks. Total cholesterol, malondialdehyde (MDA) and vitamin E concentrations and catalase and superoxide dismutase (SOD) activities were determined in blood drawn before and after the experimental period. Aortic tissue was examined for atherosclerotic changes and aortic total cholesterol, MDA, catalase and SOD were determined. At the end of the 8-week treatment period, serum total cholesterol and plasma MDA were elevated in groups 2 and 4. In group 2, serum vitamin E and plasma SOD diminished (p < 0.05) and catalase increased (p < 0.05). In group 4, SOD activity increased at the end of treatment. MDA levels were lower and plasma SOD activities were higher in group 4 than in group 2. Aortic tissue investigations revealed higher total cholesterol and MDA concentrations and catalase activities in group 2 than in group 4, and the highest tissue SOD activity was recorded in group 4 (p < 0.05 for all comparisons). Morphological examination of aortic tissues exhibited endothelial disarrangement and lipid deposition in group 2. Histopathological alterations related to atherogenesis were less in group 4 than in group 2. Amlodipine seems to exert atheroprotective effects by reducing aortic cholesterol accumulation and blood and aortic lipid peroxidation, enhancing SOD activity both in blood and aortic tissue and suppressing the consumption of vitamin E. On the other hand, the suppression of catalase activity in blood and the aorta interferes with the drug's well-known antioxidant effects.

Edaravone, a Radical Scavenger, May Enhance or Produce Antiproliferative Effects of Fluvastatin, Amlodipine, Ozagrel, GF109203X, Y27632 on Cultured Basilar Artery Smooth Muscle Cells

Proliferation of vascular smooth muscle cells stimulated by reactive oxygen species (ROS) may play a pivotal role in the pathogenesis of atherosclerosis. To clarify mechanisms by which ROS promote vascular atherogenesis, effects of fluvastatin, amlodipine, ozagrel (thromboxane synthetase inhibitor), GF109203X (a protein kinase C inhibitor) and Y27632 (a ROCK inhibitor) on the proliferation of guinea-pig basilar artery smooth muscle cells (GBa-SM3) in a 5% FBS culture medium were studied over 3 d in the presence or absence of a free radical scavenger, edaravone. Viability of cells at the end of incubation was measured by the 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test. Results demonstrated that fluvastatin and amlodipine by themselves possess antiproliferative effects on the GBa-SM3 cells at 10-100 microM and 0.1-1 microM, respectively. While edaravone possessed no antiproliferative effect by itself at 100 microM, it significantly (p<0.05) augmented the antiproliferative effects of fluvastatin and amlodipine. In addition, ozagrel, GF109203X and Y27632 possessed no appreciable effects on the cell growth by themselves. However, coincubation of edaravone at 100 microM with these agents elicited significant antiproliferative effects for ozagrel, GF109203X and Y27632 at 10-100 microM, 1-10 microM and 0.1-1 microM, respectively. In conclusion, edaravone may have clinically beneficial interactions with fluvastatin, amlodipine and ozagrel regarding the prevention of vascular atherosclerosis. The interactions between edaravone and the inhibitors of protein kinase C and ROCK were suggestive of possible contributions of ROS-triggered intracellular signals associated with these enzymes to vascular atherogenesis, but further studies are required for confirmation.

Analysis of definitions and word misusage in vascular pathology

Science being the search for truth or factual knowledge pertaining to nature and human health, accurate and precise word usage is prerequisite to avoid unintentional misrepresentation in scientific communication. The increasing frequency of word misusage necessitates review of a number of definitions and frequently misused words in vascular pathology. Correction of such errors is essential to foster accurate, standardized definitions. Otherwise scientific progress is delayed, the unwary are misled and fallacious data and concepts are propagated. Adherence to correct word usage facilitates the development of logic and precision so essential in education and in scientific thinking and literature, whereas consistently misused words ultimately become meaningless and unusable.

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.