Effects of amlodipine on gene expression and extracellular matrix formation in human vascular smooth muscle cells and fibroblasts: implications for vascular protection

Amlodipine in hypertension: a first-line agent with efficacy for improving blood pressure and patient outcomes

OBJECTIVES

Hypertension is well established as a major risk factor for cardiovascular disease. Although there is undeniable evidence to support the beneficial effects of antihypertensive therapy on morbidity and mortality, adequate blood pressure management still remains suboptimal. Research into the treatment of hypertension has produced a multitude of drug classes with different efficacy profiles. These agents include β-blockers, diuretics, ACE inhibitors, angiotensin receptor blockers and calcium channel blockers. One of the oldest groups of antihypertensives, the calcium channel blockers are a heterogeneous group of medications.

METHODS

This review paper will focus on amlodipine, a dihydropyridine calcium channel blockers, which has been widely used for 2 decades.

RESULTS

Amlodipine has good efficacy and safety, in addition to strong evidence from large randomised controlled trials for cardiovascular event reduction.

CONCLUSIONS

Amlodipine should be considered a first-line antihypertensive agent.

Treatment with amlodipine and atorvastatin has additive effect on blood and plaque inflammation in hypertensive patients with carotid atherosclerosis

Since previous studies have reported a beneficial effect of amlodipine and atorvastatin treatment in experimental atherosclerosis, we aimed to investigate the effect of the combination of both drugs on blood and plaque inflammation in patients with carotid stenosis. For that purpose, twenty six hypertensive patients undergoing carotid endarterectomy were randomized to receive either atorvastatin 20 mg/day alone (ATV, n=12) or in combination with amlodipine 20 mg/day (ATV+AML, n=14) before scheduled carotid endarterectomy. At the end of follow-up (4-6 weeks), there was a significant decrease in total and LDL-cholesterol levels, but not in blood pressure levels. In contrast, decreased MCP-1 plasma levels, NF-kappaB activation (EMSA) and MCP-1 mRNA expression (quantitative PCR) was only observed in blood from ATV+AML treated-patients. Moreover, carotid atherosclerotic plaques from ATV+AML group demonstrated a significant reduction in macrophage infiltration in relation to ATV group (immunohistochemistry). Our results suggest that combined treatment with atorvastatin and amlodipine decreases inflammatory status of atherosclerotic patients more than atorvastatin treatment alone, suggesting that co-administration of both drugs could have beneficial additive effects.

Effects of RNA interference-induced tryptase down-regulation in P815 cells on IL-6 and TNF-alpha release of endothelial cells

OBJECTIVE

To explore the effects of down-regulated tryptase expression in mast cells on the synthesis and release of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) of vascular endothelial cells.

METHODS

Tryptase-siRNA (small-interfering RNA) vector was constructed to inhibit tryptase expression in P815 cells. The medium of P815 cells treated by the tryptase-siRNA (RNAi-P815 group) or pure vector (P815 group) was collected and used to culture bEnd.3 cells. The messenger RNAs (mRNAs) of IL-6 and TNF-alpha in bEnd.3 cells and their protein levels in the medium were measured by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

IL-6 and TNF-alpha mRNAs in bEnd.3 cells cultured in RNAi-P815-conditioned medium decreased significantly compared to those in P815-conditioned medium. Consistently, IL-6 and TNF-alpha protein levels in the medium of bEnd.3 of RNAi-P815 group were lower than those of P815 group.

CONCLUSION

Reduced tryptase expression significantly inhibited the synthesis and release of IL-6 and TNF-alpha in vascular endothelial cells. RNA interference targeting tryptase expression may be a new anti-inflammatory strategy for vascular diseases.

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.

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.

Plasma levels of active extracellular matrix metalloproteinases 2 and 9 in patients with essential hypertension before and after antihypertensive treatment

This study was designed to test the hypothesis that plasma concentrations of matrix metallo-proteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9), two enzymes that share similar substrate specificity (collagen type IV and V), possibly related to vascular remodelling, are altered in essential hypertension. The second aim of the study was to assess whether chronic antihypertensive treatment with the calcium channel blocker amlodipine would normalize these alterations. To test this hypothesis, we measured plasma concentrations of active MMP-2 and MMP-9 in 42 patients with never-treated essential hypertension and in 25 normotensive control subjects. Measurements were repeated after 6 months of treatment with the calcium channel blocker amlodipine. Baseline values of MMP-2 and MMP-9 were decreased (P=0.01 and 0.002, respectively) in hypertensive patients compared with normotensives. Hypertensive patients with systemic vascular resistances <1440 dyn s/cm(5) exhibited higher values of MMP-2 (P=0.005) and MMP-9 (P=0.001) than hypertensive patients with systemic vascular resistances >1440 dyn s/cm(5). Treated patients attained a nonsignificant increase in MMP-2 plasma concentrations, but a significant increase in MMP-9 plasma concentrations (P=0.01) compared to respective values before treatment. In conclusion, these findings suggest that plasma concentrations of active MMP-2 and MMP-9, mainly related to vascular extracellular matrix metabolism, are depressed in patients with essential hypertension. A 6 month treatment with amlodipine can normalize MMP-9 but not MMP-2 plasma concentrations. The hypothesis that antihypertensive treatment may modulate collagen metabolism remains to be determined by further studies.

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.

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.

Substantial elevation of interleukin-6 concentration in peritendinous tissue, in contrast to muscle, following prolonged exercise in humans

Plasma interleukin-6 (IL-6) concentration has been shown to increase with exercise and various cell types and tissues have been suggested to be responsible for this increase. At present no studies have measured the interstitial concentration of IL-6 in skeletal muscle and connective tissue. The present study represents the first attempt to simultaneously measure IL-6 in plasma, skeletal muscle and peritendinous connective tissue in response to prolonged exercise. Six healthy well-trained volunteers completed a 36 km run (flat, 12 km h(-1)). IL-6 was measured before, 2 h post-exercise and 24 h, 48 h, 72 h and 96 h post-exercise in both the medial gastrocnemius muscle (not measured at rest due to risk of disabling the subsequent exercise, and 24 h and 72 h post-exercise) and the peritendinous tissue around the Achilles tendon using microdialysis catheters with a high molecular mass cut-off value (3000 kDa). The plasma concentration of IL-6 was measured simultaneously, and in addition every hour during the exercise, by enzyme-linked immunosorbent assay (ELISA). The plasma concentration of IL-6 was found to increase throughout the exercise, reaching peak values immediately after completion of the run (50-fold increase). Using the microdialysis technique, the interstitial concentration of IL-6 was found to increase dramatically from 0 +/- 0 pg ml(-1) to 3618 +/- 1239 pg ml(-1) in the peritendinous tissue in the hours following the exercise. The pattern of changes was similar in plasma and peritendinous tissue, although approximately 100-fold higher in the latter. For comparison the interstitial muscle concentration was found to be 465 +/- 176 pg ml(-1) when measured 2 h post-exercise and 223 +/- 113 pg ml(-1) and 198 +/- 96 pg ml(-1) 48 h and 96 h post-exercise, respectively. The present study demonstrates that the connective tissue around the human Achilles tendon produces significant amounts of IL-6 in response to prolonged physical activity, which might contribute to the exercise-induced increase in IL-6 found in plasma.

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.

Effects of the L- and N-type calcium channel blocker cilnidipine on growth of vascular smooth muscle cells from spontaneously hypertensive rats

Cultured vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) show exaggerated growth compared with cells from Wistar-Kyoto (WKY) rats. Calcium antagonists have recently been reported to have an in vivo antiproliferative effect on hypertensive cardiovascular organs. We investigated the effects of the calcium antagonist cilnidipine that blocks both L- and N-type calcium channels on the growth of VSMC from SHR. Cilnidipine (1 and 10 microM) significantly inhibited basal DNA synthesis in VSMC from both rat strains; the inhibition was significantly larger in VSMC from SHR than in cells from WKY rats, and was significantly greater than effects of nifedipine. Cilnidipine (1 microM) significantly inhibited serum-stimulated DNA synthesis in VSMC from both rat strains. The inhibition was more marked in VSMC from SHR than in cells from WKY rats. Angiotensin II, platelet-derived growth factor (PDGF)-AA, and phorbol-12-myristate-13-acetate dose-dependently increased DNA synthesis in VSMC from SHR but not in cells from WKY rats. Cilnidipine (1 microM) significantly suppressed this increase in DNA synthesis in VSMC from SHR. Expression of basic fibroblast growth factor (bFGF), transforming growth factor-beta1, and PDGF A-chain mRNAs was markedly greater in VSMC from SHR than in cells from WKY rats. Cilnidipine (1 microM) significantly inhibited the expression of TGF-beta1 mRNA in VSMC from SHR but not in cells from WKY rats. These findings suggest that cilnidipine exerts its antiproliferative effects through the inhibition of DNA synthesis induced by growth-promoting factors and by inhibiting the expression of TGF-beta1 mRNA in VSMC from SHR.

Amlodipine inhibits expression of matrix metalloproteinase-1 and its inhibitor in human vascular endothelial cells

Matrix metalloproteinase-1 (MMP-1) may play an important role in the pathogenesis of atherosclerosis and atherosclerotic plaque rupture. We investigated the effect of the calcium channel blockers amlodipine and nifedipine on the expression of MMP-1 and tissue inhibitor of metalloproteinase-1 (TIMP-1) in endothelial cells (ECs). MMP-1 and TIMP-1 levels in conditioned media of human vascular ECs were measured by enzyme-linked immunosorbent assay. Collagenolytic activity was determined by fluorescence-labeled collagen digestion. The addition of interleukin-1beta (IL-1beta) increased MMP-1 levels in the culture media of ECs. Amlodipine, but not nifedipine, significantly decreased MMP-1 levels in IL-1beta-stimulated ECs. TIMP-1 levels also were significantly increased by IL-1beta, and its expression was slightly decreased by amlodipine, not by nifedipine. Amlodipine significantly inhibited collagenolytic activity in the culture media of IL-1beta-stimulated ECs, whereas nifedipine showed no significant effect on the activity. Our findings revealed that amlodipine, but not nifedipine, inhibits IL-1beta-induced MMP-1 expression in human ECs.

Nifedipine inhibits pulmonary hypertension but does not prevent decreased lung eNOS in hypoxic newborn pigs

Therapies to prevent the onset or progression of pulmonary hypertension in newborns have received little study compared with those in adult models. We wanted to determine whether nifedipine treatment prevents the increased pulmonary vascular resistance, blunted pulmonary vascular responses to acetylcholine, and reduced lung endothelial nitric oxide synthase (eNOS) amounts that we have found in a newborn model of chronic hypoxia-induced pulmonary hypertension. Studies were performed with 1- to 3-day-old piglets raised in room air (control) or 10% O2 (hypoxia) for 10-12 days. Some piglets from each group were given nifedipine (3-5 mg/kg sublingually three times a day). Pulmonary arterial pressure, pulmonary wedge pressure, and cardiac output were measured in anesthetized animals. Pulmonary vascular responses to acetylcholine and eNOS amounts were assessed in excised lungs. The calculated value of the pulmonary vascular resistance for nifedipine-treated hypoxic piglets (0.09 +/- 0.01 cmH(2)O. ml(-1). min. kg) was almost one-half of the value for untreated hypoxic piglets (0.16 +/- 0.01 cmH(2)O. ml(-1). min. kg) and did not differ from the value for untreated control piglets (0.05 +/- 0.01 cmH(2)O. ml(-1). min. kg). Pulmonary arterial pressure responses to acetylcholine and whole lung homogenate eNOS amounts were less for both nifedipine-treated and untreated hypoxic piglets than for untreated control piglets. Nifedipine treatment attenuated pulmonary hypertension in chronically hypoxic newborn piglets despite the persistence of blunted responses to acetylcholine and reduced lung eNOS amounts.