Lacidipine prevents endothelial dysfunction in salt-loaded stroke-prone hypertensive rats

Lacidipine Ameliorates the Endothelial Senescence and Inflammatory Injury Through CXCR7/P38/C/EBP-β Signaling Pathway

Background: Lacidipine, a third-generation calcium channel blocker, exerts beneficial effects on the endothelium of hypertensive patients in addition to blood pressure lowering. However, the detailed mechanism underlying Lacidipine-related endothelial protection is still elusive.

Methods: Sixteen spontaneous hypertensive rats (SHRs) were randomly divided into two groups: Lacidipine-treated SHR group and saline-treated control group. Tail systolic blood pressure was monitored for four consecutive weeks. Endothelial cells (ECs) were pretreated with Lacidipine prior to being stimulated with H₂O₂, bleomycin, or Lipopolysaccharides (LPS) in vitro. Then, cell activity, migration, and senescence were measured by Cell Counting Kit-8 assay, transwell assay, and β-galactosidase staining, respectively. The fluorescent probe 2′, 7′-dichlorofluorescein diacetate (DCFH-DA) was used to assess the intracellular reactive oxygen species (ROS). Related protein expression was detected by Western blotting and immunofluorescence.

Results: Our data showed that Lacidipine treatment lowered the blood pressure of SHRs accompanied by the elevation of CXCR7 expression and suppression of P38 and CCAAT/enhancer-binding protein beta (C/EBP-β) compared with the control group. In vitro experiments further demonstrated that Lacidipine increased the cell viability and function of ECs under oxidative stress, cell senescence, and inflammatory activation via the CXCR7/P38/signaling pathway.

Conclusions: Our results suggested that Lacidipine plays a protective role in EC senescence, oxidative stress, and inflammatory injury through the regulation of CXCR7/P38/C/EBP-β signaling pathway.

Cerebral Small Vessel Disease (CSVD) - Lessons From the Animal Models

Cerebral small vessel disease (CSVD) refers to a spectrum of clinical and imaging findings resulting from pathological processes of various etiologies affecting cerebral arterioles, perforating arteries, capillaries, and venules. Unlike large vessels, it is a challenge to visualize small vessels in vivo, hence the difficulty to directly monitor the natural progression of the disease. CSVD might progress for many years during the early stage of the disease as it remains asymptomatic. Prevalent among elderly individuals, CSVD has been alarmingly reported as an important precursor of full-blown stroke and vascular dementia. Growing evidence has also shown a significant association between CSVD's radiological manifestation with dementia and Alzheimer's disease (AD) pathology. Although it remains contentious as to whether CSVD is a cause or sequelae of AD, it is not far-fetched to posit that effective therapeutic measures of CSVD would mitigate the overall burden of dementia. Nevertheless, the unifying theory on the pathomechanism of the disease remains elusive, hence the lack of effective therapeutic approaches. Thus, this chapter consolidates the contemporary insights from numerous experimental animal models of CSVD, to date: from the available experimental animal models of CSVD and its translational research value; the pathomechanical aspects of the disease; relevant aspects on systems biology; opportunities for early disease biomarkers; and finally, converging approaches for future therapeutic directions of CSVD.

Beneficial effects of combined therapy with lacidipine and candesartan in obese hypertensive patients

INTRODUCTION

Obesity is becoming one of the leading risk factors of coronary heart disease, hypertension, cerebrovascular disease. Despite the presence of a large number of antihypertensive agents and scientific substantiation of antihypertensive treatment principles it would be wrong to assume that the problem is completely solved. Development of endothelial dysfunction is one of the key pathogenic mechanisms in hypertension. This process is proven to have contributed by immune inflammation activation which is mediated by pro-inflammatory cytokines and oxidative stress.

AIMS

To investigate the additional benefits of the combined antihypertensive therapy with lacidipine and candesartan on the basis of studying their antioxidant properties, impact on endothelial function and pro-inflammatory cytokines activity in hypertensive patients with overweight and obesity.

METHODS

A combination of a calcium channel blocker and angiotensin receptor blocker (lacidipine 2 mg, 4 mg, and candesartan 4mg, 8mg, 16mg) was prescribed to 30 patients with essential hypertension of grades 1-3, 30 to 65 years old (mean age - 54.7 ± 5.8 years), who previously have not been receiving regular antihypertensive therapy.

RESULTS

During the course of combined antihypertensive therapy with lacidipine and candesartan, a significant reduction in i-NOS activity, TNF-α to its type I soluble receptor ratio (TNF- α/sTNF-αRI), and oxidative stress marker - 8-iso-PgF2α has been observed. Activity of e-NOS, levels of SOD and catalase, in contrast, have increased by the end of observation period.

CONCLUSION

The improvement of endothelial function due to lower level of oxidative stress and a significant decrease of immune activation has been observed in hypertensive patients with overweight and obesity under the influence of combined antihypertensive therapy with lacidipine and candesartan.

Discovery and Development of Calcium Channel Blockers

In the mid 1960s, experimental work on molecules under screening as coronary dilators allowed the discovery of the mechanism of calcium entry blockade by drugs later named calcium channel blockers. This paper summarizes scientific research on these small molecules interacting directly with L-type voltage-operated calcium channels. It also reports on experimental approaches translated into understanding of their therapeutic actions. The importance of calcium in muscle contraction was discovered by Sidney Ringer who reported this fact in 1883. Interest in the intracellular role of calcium arose 60 years later out of Kamada (Japan) and Heibrunn (USA) experiments in the early 1940s. Studies on pharmacology of calcium function were initiated in the mid 1960s and their therapeutic applications globally occurred in the the 1980s. The first part of this report deals with basic pharmacology in the cardiovascular system particularly in isolated arteries. In the section entitled from calcium antagonists to calcium channel blockers, it is recalled that drugs of a series of diphenylpiperazines screened in vivo on coronary bed precontracted by angiotensin were initially named calcium antagonists on the basis of their effect in depolarized arteries contracted by calcium. Studies on arteries contracted by catecholamines showed that the vasorelaxation resulted from blockade of calcium entry. Radiochemical and electrophysiological studies performed with dihydropyridines allowed their cellular targets to be identified with L-type voltage-operated calcium channels. The modulated receptor theory helped the understanding of their variation in affinity dependent on arterial cell membrane potential and promoted the terminology calcium channel blocker (CCB) of which the various chemical families are introduced in the paper. In the section entitled tissue selectivity of CCBs, it is shown that characteristics of the drug, properties of the tissue, and of the stimuli are important factors of their action. The high sensitivity of hypertensive animals is explained by the partial depolarization of their arteries. It is noted that they are arteriolar dilators and that they cannot be simply considered as vasodilators. The second part of this report provides key information about clinical usefulness of CCBs. A section is devoted to the controversy on their safety closed by the Allhat trial (2002). Sections are dedicated to their effect in cardiac ischemia, in cardiac arrhythmias, in atherosclerosis, in hypertension, and its complications. CCBs appear as the most commonly used for the treatment of cardiovascular diseases. As far as hypertension is concerned, globally the prevalence in adults aged 25 years and over was around 40% in 2008. Usefulness of CCBs is discussed on the basis of large clinical trials. At therapeutic dosage, they reduce the elevated blood pressure of hypertensive patients but don't change blood pressure of normotensive subjects, as was observed in animals. Those active on both L- and T-type channels are efficient in nephropathy. Alteration of cognitive function is a complication of hypertension recognized nowadays as eventually leading to dementia. This question is discussed together with the efficacy of CCBs in cognitive pathology. In the section entitled beyond the cardiovascular system, CCBs actions in migraine, neuropathic pain, and subarachnoid hemorrhage are reported. The final conclusions refer to long-term effects discovered in experimental animals that have not yet been clearly reported as being important in human pharmacotherapy.

Calcium channel blockers in cardiovascular pharmacotherapy

This paper summarizes the pharmacological properties of calcium channel blockers (CCBs), their established therapeutic uses for cardiovascular disorders and the current improvement of their clinical effects through drug combinations. Their identification resulted from study of small molecules including coronary dilators, which were named calcium antagonists. Further experiments showed that they reduced contraction of arteries by inhibiting calcium entry and by interacting with binding sites identified on voltage-dependent calcium channels. This led to the denomination calcium channel blockers. In short-term studies, by decreasing total peripheral resistance, CCBs lower arterial pressure. By unloading the heart and increasing coronary blood flow, CCBs improve myocardial oxygenation. In long-term treatment, the decrease in blood pressure is more pronounced in hypertensive than in normotensive patients. A controversy on the safety of CCBs ended after a large antihypertensive trial (ALLHAT) sponsored by the National Heart, Lung, and Blood Institute. There are two main types of CCBs: dihydopyridine and non-dihydropyridine; the first type is vascular selective. Dihydropyrines are indicated for hypertension, chronic, stable and vasospastic angina. Non-dihydropyridines have the same indications plus antiarrythmic effects in atrial fibrillation or flutter and paroxysmal supraventricular tachycardia. In addition, CCBs reduced newly formed coronary lesions in atherosclerosis. In order to reach recommended blood pressure goals, there is a recent therapeutic move by combination of CCBs with other antihypertensive agents particularly with inhibitors acting at the level of the renin-angiotensin system. They are also combined with statins. Prevention of dementia has been reported in hypertensive patients treated with nitrendipine, opening a way for further studies on CCBs' beneficial effect in cognitive deterioration associated with aging.

Lacidipine improves endothelial repair capacity of endothelial progenitor cells from patients with essential hypertension

BACKGROUND

Endothelial progenitor cells (EPCs) play a critical role in maintaining the integrity of vascular endothelium following arterial injury. Lacidipine has a beneficial effect on endothelium of hypertensive patients, but limited data are available on EPCs-mediated endothelial protection. This study tests the hypothesis that lacidipine treatment can improve endothelial repair capacity of EPCs from hypertensive patients through increasing CXC chemokine receptor four (CXCR4) signaling.

METHODS

In vivo reendothelialization capacity of EPCs from hypertensive patients with or without in vitro lacidipine treatment was examined in a nude mouse model of carotid artery injury. Expression of CXCR4 and alteration in migration and adhesion functions of EPCs were evaluated.

RESULTS

Basal CXCR4 expression was markedly reduced in EPCs from hypertensive patients compared with normal subjects. In parallel, the phosphorylation of Janus kinase-2 (JAK-2) of EPCs, a CXCR4 downstream signaling, was also significantly decreased. Lacidipine promoted CXCR4/JAK-2 signaling expression of in vitro EPCs. Transplantation of EPCs pretreated with lacidipine significantly accelerated in vivo reendothelialization. The enhanced in vitro function and in vivo reendothelialization capacity of EPCs were inhibited by shRNA-mediated knockdown of CXCR4 expression or pretreatment with JAK-2 inhibitor AG490, respectively. In hypertensive patients, lacidipine treatment for 4 weeks also resulted in an upregulation of CXCR4/JAK-2 signaling of EPCs, which was associated with augmented EPCs-mediated reendothelialization and improved endothelial function.

CONCLUSION

Deterioration of CXCR4 signaling may lead to impaired EPCs-mediated reendothelialization of hypertensive patients. Lacidipine-modified EPCs via a partially CXCR4 signaling contribute to enhanced endothelial repair capacity in hypertension.

Discrepant regulation of QT (QTc) interval duration by calcium channel blockade and angiotensin converting enzyme inhibition in experimental hypertension

Antihypertensive treatment may reduce prolonged QT duration in hypertension. Generally, the reductions of blood pressure and/or of cardiac mass are believed to be the responsible factors. However, drugs are not equivalent in QT modulation despite similar antihypertensive and antihypertrophic action. We investigated the effect of a calcium channel blocker, lacidipine and an angiotensin-converting enzyme inhibitor, enalapril on QT duration in rats. Normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were treated with lacidipine (at the dose of 1.5 mg/kg per day for WKY and 3 mg/kg per day for SHR) or enalapril (5 mg/kg per day for WKY and 10 mg/kg per day for SHR) during 8 weeks. Tail-cuff systolic blood pressure (sBP), left ventricular weight (LVW), vascular function of isolated aorta and mesenteric artery and duration of QT (and QTc) interval on Frank electrocardiograms were evaluated. As expected, untreated SHR showed elevated sBP, impaired vascular reactivity, increased LVW and prolonged QT when compared with WKY (p < 0.05). After treatment, both agents markedly improved vascular reactivity and reduced sBP in SHR (p < 0.05). Additionally, enalapril reduced LVW in both hypertensive (by 17%; p < 0.05) and normotensive rats (by 13%; p < 0.05) and, consequently, corrected QT duration in SHR. Interestingly, lacidipine also reduced LVW in SHR (by 9%; p < 0.05), but without influence on prolonged QT. Moreover, lacidipine had no effect on LVW in WKYs but prolonged their QT interval (by 10%; p < 0.05). In conclusion, lacidipine did not reverse a progressive prolongation of QT in SHR, despite sBP lowering and LVW reduction. Thus, the lowering of blood pressure and/or reduction of LVW are not sufficient per se to normalize ventricular repolarization in hypertensive cardiac disease. More likely, modulation of QT prolongation by antihypertensive drugs is a function of their complex action on blood pressure, vascular function, cardiac mass and on reflex neurohumoral activation.

Salt-induced hemodynamic regulation mediated by nitric oxide

Excess daily salt intake impairs vasodilatation and enhances vasoconstriction, resulting in reduction of regional blood flow and elevation of blood pressure in healthy individuals and hypertensive patients with either salt sensitivity or not tested for salt sensitivity or not evaluated for salt sensitivity. The mechanism may involve decreased production of nitric oxide via endothelial nitric oxide synthase (eNOS), impaired bioavailability of nitric oxide, and elevated plasma levels of asymmetric dimethylarginine (ADMA). Experimental animals, irrespective of salt sensitivity, although less extensive in those with salt-resistance, fed a high-salt diet have deteriorated endothelial functions; the mechanisms involved include an impairment of eNOS activation, a decrease in eNOS expression, and an increase in oxidative stress and ADMA. The imbalance of interactions between nitric oxide and angiotensin II is also involved in salt sensitivity. Deficiency of nitric oxide formed via neuronal NOS and inducible NOS may contribute to salt-induced hypertension. Reduced daily salt intake, therefore, would be the most rational prophylactic measure against the development of hypertension.

Lacidipine has antiatherosclerotic effects independent of its actions on lipid metabolism and blood pressure

The antiatherosclerotic effect of lacidipine has been attributed to its actions on cholesterol levels, lipid metabolism or oxidant stress in advanced disease. The purpose of the present experiments was to examine whether lacidipine is protective of intimal thickening and vascular dysfunction in early atherosclerosis in the absence of the hypertension and hypercholesterolemia. A second goal was to determine whether and to what extent MMP-9 and oxidant stress are involved in possible beneficial effects of lacidipine. Lacidipine treatment (5 mg/kg/day, p.o. for 3 weeks) significantly prevented the collar-induced intimal thickening. MMP-9 expressions were increased by collar but not effected by lacidipine treatment. Nitrotyrosine staining, a marker for oxidant stress was not changed neither by collar nor lacidipine treatment in early atherosclerosis. The enhanced sensitivity to serotonine and diminished sensitivity to acetylcholine in collared arteries were restored to normal levels with treatment. These results demonstrate that the lacidipine treatment prevents the collar-induced intimal thickening and accompanying vascular dysfunction in early atherosclerosis without cholesterol loading. These beneficial effects of lacidipine were not associated with changes in either MMP-9 expression or oxidant stress. However, enhanced endothelium-dependent relaxations by lacidipine, suggest that vascular protective effects of nitric oxide may be at least partly, responsible from antiatherosclerotic effects of lacidipine.

Nephroprotection of lacidipine against gentamycin-induced nephrotoxicity in albino rats

AIM

Gentamycin, a widely-used aminoglycoside antibiotic, is recognized as possessing significant nephrotoxic potential in human beings. Gentamycin-induced nephrotoxicity is suggested to be mediated via reactive oxygen species. The present study investigated the possible antioxidant nephroprotective effect of lacidipine as a calcium-channel blocker in a gentamycin-induced nephrotoxicity model in albino rats.

METHODS

Albino rats were divided into 3 groups. Group 1 received normal saline. Group 2 received gentamycin 80 mg/kg intraperitoneally for 14 days. Group 3 received lacidipine 1 mg/kg intraperitoneally 3 days before and 14 days concurrently with gentamycin. This dose does not affect the blood pressure of rats, as evidenced in the pilot study.

RESULTS

Gentamycin-induced nephrotoxicity was evidenced by a marked reduction in creatinine clearance. Treatment with lacidipine improved creatinine clearance compared to the gentamycin-treated group. In addition, it reduced thiobarbituric acid reactive substance, as an index of lipid peroxidation, with significant increases in superoxide dismutase enzyme in erythrocyte lysates and kidney catalase enzyme activities.

CONCLUSION

This study recommends the use of lacidipine in prophylaxis against gentamycin-induced nephrotoxicity.

Effects of antihypertensive drugs on alcohol-induced functional responses of cultured human endothelial cells

Alcohol-induced endothelial changes might contribute to an increase in blood pressure in regular alcohol consumers. Some antihypertensive drugs affect oxidative stress and endothelial function and might counteract the effects of alcohol at the cellular level. The aim of this study was to investigate in vitro the effects of three different types of antihypertensive agents on alcohol-induced endothelial responses and oxidative stress. Cultured human endothelial cells were exposed to increasing concentrations (1, 10, 60 micromol/L) of zofenoprilat, carvedilol, and lacidipine in the absence and in the presence of ethanol (140 mmol/L). Concentrations of endothelin (ET) and nitric oxide (NO) were measured in the culture media as markers of endothelial function, and malondialdehyde (MDA) and intracellular glutathione (GSHi) were measured as markers of oxidative stress. Exposure to alcohol increased the levels of ET, NO, and MDA, and decreased GSHi. Carvedilol and zofenoprilat were more effective than lacidipine in counteracting the effects of alcohol on ET production. Alcohol-induced NO production was enhanced by carvedilol, whereas zofenoprilat and lacidipine did not have a significant effect. The alcohol-induced increase in MDA concentrations was blunted by all three drugs, but only carvedilol restored a normal response. All three drugs increased GSHi levels, with the effect being greater for carvedilol and lacidipine than zofenoprilat. Carvedilol is more effective than zofenoprilat and lacidipine in counteracting alcohol-induced endothelial responses in vitro and in decreasing oxidative stress. These effects might be particularly beneficial in patients with alcohol-related hypertension.

Increased expression of endothelial nitric oxide synthase and caveolin-1 in the aorta of rats with isoproterenol-induced cardiac hypertrophy

Isoproterenol-induced cardiac hypertrophy is associated with increased expression of endothelial nitric oxide synthase in the aorta but without signs of improved endothelial function. The aim was to examine the hypothesis that increased expression of eNOS allosteric inhibitor caveolin-1 could be associated with unimproved endothelium-dependent relaxations. Rats received isoproterenol (5 mg/kg body mass, i.p., n = 13) or its vehicle (n = 14) during 1 week. Systolic blood pressure (SBP) and heart rate (HR) were measured by the tail-cuff method. Expression of eNOS and caveolin-1 was measured using immunoblotting analysis. Relaxations of isolated aorta to acetylcholine and sodium nitroprusside were evaluated ex vivo. After 1 week of isoproterenol administration, basal SBP and HR were decreased (SBP 110 +/- 3 vs. 126 +/- 3 mmHg, p < 0.05; HR 342 +/- 8 vs. 366 +/- 6 beats/min, p < 0.05). Isoproterenol increased the mass of the left ventricle (+33% +/- 4% vs. control; p < 0.05) and right ventricle (+40% +/- 9%; p < 0.05). Isoproterenol administration increased the expression of eNOS (+53% +/- 12%; p < 0.05) and caveolin-1 (+54% +/- 20%, p < 0.05) in the aorta. Relaxation of isolated aorta to acetylcholine and sodium nitroprusside showed a trend towards a worsened endothelial function and a lower sensitivity to exogenous NO. Thus, 1 week of isoproterenol administration led to increased eNOS expression in the aorta without amelioration of endothelial vasorelaxation function. Concomitant increase in caveolin-1 expression may be responsible for this paradox.

Impaired effect of salt loading on nitric oxide-mediated relaxation in aortas from stroke-prone spontaneously hypertensive rats

1. The present study was designed to characterize the effects of salt on vasorelaxation via the nitric oxide (NO)/cGMP pathway in stroke-prone spontaneously hypertensive rats (SHRSP), which are highly salt sensitive. 2. Male 8-week-old SHRSP were given 1% NaCl solution as drinking water for 4 weeks, whereas control animals were given water only. 3. In aortic rings from salt-loaded SHRSP, relaxations in response to acetylcholine and sodium nitroprusside were significantly impaired compared with those in the control. In the presence of zaprinast, a cGMP-specific cyclic nucleotide phosphodiesterase (PDE)-5 inhibitor, the cGMP levels induced by these drugs were significantly reduced by salt loading, but remained unchanged in the absence of zaprinast. The protein levels of endothelial NO synthase, soluble guanylate cyclase (sGC) and cGMP-dependent protein kinase (PKG) remained unchanged with salt loading, but those of PDE-5 decreased significantly and those of phosphorylated PKG tended to decrease, although the change was not statistically significant. Salt loading significantly impaired the relaxation in response to 8-bromo-cGMP. 4. These results indicate that, in aortas from SHRSP, salt loading causes impairment of relaxation in response to NO, which may be due to a decrease in cGMP production by sGC and impairment of the relaxation pathway downstream of cGMP, which, in turn, probably causes a decrease in PKG activity. Reduced PDE-5 protein expression may act, in part, as a compensatory response to impairment of cGMP-mediated relaxation.

Cilnidipine, a slow-acting Ca2+ channel blocker, induces relaxation in porcine coronary artery: role of endothelial nitric oxide and [Ca2+]i

Cilnidipine is a dual blocker of L-type voltage-gated Ca(2+) channels in vascular smooth muscle and N-type Ca(2+) channels in sympathetic nerve terminals that supply blood vessels. However, the clinical benefits of cilnidipine and underlying mechanisms are incompletely understood. This study was designed to compare the time course of relaxant responses to cilnidipine and nifedipine, and to examine the role of endothelial NO and [Ca(2+)](i) in the vasorelaxation. Porcine left circumflex coronary arteries were isolated and isometric tension was measured with Grass force transducers. Endothelial [Ca(2+)](i) in intact arteries was determined by a calcium fluorescence imaging technique. The free radical scavenging capacity was also assayed. Cilnidipine and nifedipine induced concentration-dependent relaxations in high KCl-precontracted artery rings, while the former-induced relaxation was slower as compared to the latter. Treatment with L-NAME or ODQ reduced relaxations to cilnidipine or nifedipine to the same extent as in rings without endothelium. Indomethacin or omega-conotoxin had no effects. L-Arginine antagonized the effect of L-NAME on cilnidipine-induced relaxations. Cilnidipine did not affect sodium nitroprusside-induced relaxation in rings with and without endothelium. Cilnidipine and nifedipine caused extracellular Ca(2+)-dependent increases in endothelial [Ca(2+)](i) in intact arteries and cilnidipine's action had a slower onset, similar to that of cilnidipine-induced relaxation. Neither cilnidipine nor nifedipine exhibited a free radical scavenging property. The present results demonstrate that cilnidipine can produce endothelium-dependent relaxation in porcine coronary arteries in vitro in addition to blocking Ca(2+) channels. Like short-acting nifedipine, cilnidipine-dependent relaxation, albeit to a slower onset, is partly mediated by endothelial NO but not by prostacyclin. The increased release or bioavailability of NO may causally result from elevated endothelial [Ca(2+)](i) in arteries. The Ca(2+) channel-independent effect suggests the usefulness of cilnidipine in the treatment of cardiovascular diseases associated with diminished NO release, such as atherosclerosis.

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.

Antioxidant effects and the therapeutic mode of action of calcium channel blockers in hypertension and atherosclerosis

Drugs currently known as calcium channel blockers (CCB) were initially called calcium antagonists because of their ability to inhibit calcium-evoked contractions in depolarized smooth muscles. Blocking the entry of calcium reduces the active tone of vascular smooth muscle and produces vasodilatation. This pharmacological property has been the basis for the use of CCBs in the management of hypertension and coronary heart disease. A major question is whether drugs reducing blood pressure have other effects that help prevent the main complications of hypertension, such as atherosclerosis, stroke, peripheral arterial disease, heart failure and end-state renal disease. Experimental studies that focus on this question are reviewed in the present paper.

The vasorelaxing action of labedipinedilol-A involves endothelial cell-derived NO and eNOS expression caused by calcium influx

Labedipinedilol-A, a novel dihydropyridine-type calcium antagonist, has been shown to induce hypotension and vasorelaxation. The objective of the present study was to investigate the effect of labedipinedilol-A on vascular function of rat aortic rings and cultured human umbilical vein endothelial cells (HUVECs). Labedipinedilol-A induced vasorelaxation in rat aortic rings that had been precontracted with phenylephrine in a concentration-dependent manner. This labedipinedilol-A-induced relaxation was significantly reduced by endothelium removal and by exposure to L-NG-nitroarginine methyl ester (L-NAME), methylene blue, or 1H-[1,2,4]oxadiazolol[4,3,a]quinoxalin-1-one (ODQ). In addition, the cyclic GMP content was significantly increased by labedipinedilol-A, which was inhibited by L-NAME in aorta. In cultured HUVECs, labedipinedilol-A induced concentration-dependent formation of NO and Ca2+ influx, and it increased the abundance of endothelial NO synthase (eNOS) protein. Furthermore, labedipinedilol-A suppressed basal, 10% FBS- and thrombin-stimulated endothelin-1 production, which were reversed by pretreatment with L-NAME, demonstrating that NO was able to inhibit production of ET-1 in HUVECs. Labedipinedilol-A significantly protected cultured HUVECs against dihydroxyfumarate/iron ion-induced decrease of glutathione and cell death. Moreover, labedipinedilol-A also inhibited iron-induced lipid peroxidation in rat brain homogenate and scavenged 2,2'-azobis (2-amidinopropane) dihydrochloride-derived peroxy radicals. Labedipinedilol-A acts as lacidipine with additional antioxidant effects and can protect endothelial cells against free radical-induced lipid peroxidation and cell injury. Our results indicate that the endothelium-dependent vasorelaxation by labedipinedilol-A is mediated through Ca2+-dependent activation of NO synthase and stimulation of NO/cyclic GMP pathway.

Effect of high-salt diet on NO release and superoxide production in rat aorta

Sprague-Dawley rats were fed either a high-salt (HS) diet (4.0% NaCl) or a low-salt (LS) diet (0.4% NaCl) for 3 days. Nitric oxide (NO) and superoxide production were assessed in the thoracic aorta by evaluating the fluorescence signal intensity from 4,5-diaminofluorescein (DAF-2DA) and dihydroethidine, respectively. Methacholine caused increased NO release in the aortas from rats on a LS but not HS diet. The SOD mimetic tempol restored methacholine-induced NO release in aortas from rats on a HS diet. Methacholine also caused superoxide production in the aortas of rats on a HS diet but not in the aortas of rats on a LS diet. Tempol and NG-monomethyl-l-arginine eliminated methacholine-induced superoxide production in the aortas of rats on a HS diet. Aortic rings from rats on the HS diet showed impaired methacholine-induced relaxation, which was improved by tempol. Tempol alone caused a NO-dependent relaxation of norepinephrine-precontracted aortas that was significantly greater in the aortas of rats on the HS diet than in vessels from rats on the LS diet. These data suggest that a HS diet impairs endothelium-dependent relaxation via reduced NO levels and increased superoxide production.

Are antihypertensive agents protective against dementia? A review of clinical and preclinical data

In the United States, the size of the population of persons aged 65 years or older is expected to double within the next 30 years, resulting in a marked increase in the prevalence of dementia. Hypertension is a risk factor for cognitive impairment and dementia in addition to cerebrovascular morbidity and mortality. The evidence for a connection between high blood pressure in midlife and dementia in late life comes from numerous longitudinal studies. A placebo-controlled, double-blind, randomized trial involving 2,418 patients aged 60 years or older with isolated systolic hypertension demonstrated that active treatment based on the dihydropyridine calcium antagonist nitrendipine with the addition of enalapril, hydrochlorothiazide, or both if needed to control systolic blood pressure to <150 mmHg, significantly reduced not only stroke and cardiovascular complications but also the incidence of vascular dementia and Alzheimer's disease. Several trials of antihypertensive treatment are ongoing to confirm this important finding. The newer dihydropyridine calcium antagonists lacidipine and lercanidipine are effective and well tolerated in the treatment of hypertension. In animal models, these newer agents also have been shown to prevent the progression of hypertensive microvascular damage. Their neuroprotective effects offer possible unique advantages in the management of hypertension.

Regulation of endothelial-type NO synthase expression in pathophysiology and in response to drugs

In many types of cardiovascular pathophysiology such as hypercholesterolemia and atherosclerosis, diabetes, cigarette smoking, or hypertension (with its sequelae stroke and heart failure) the expression of endothelial NO synthase (eNOS) is altered. Both up- and downregulation of eNOS have been observed, depending on the underlying disease. When eNOS is upregulated, the upregulation is often futile and goes along with a reduction in bioactive NO. This is due to an increased production of superoxide generated by NAD(P)H oxidase and by an uncoupled eNOS. A number of drugs with favorable effects on cardiovascular disease upregulate eNOS expression. The resulting increase in vascular NO production may contribute to their beneficial effects. These compounds include statins, angiotensin-converting enzyme inhibitors, AT1 receptor antagonists, calcium channel blockers, and some antioxidants. Other drugs such as glucocorticoids, whose administration is associated with cardiovascular side effects, downregulate eNOS expression. Stills others such as the immunosuppressants cyclosporine A and FK506/tacrolimus or erythropoietin have inconsistent effects on eNOS. Thus regulation of eNOS expression and activity contributes to the overall action of several classes of drugs, and the development of compounds that specifically upregulate this protective enzyme appears as a desirable target for drug development.

High salt intake impairs vascular nitric oxide/cyclic guanosine monophosphate system in spontaneously hypertensive rats

In aortas of spontaneously hypertensive rats (SHRs), excessive dietary salt causes down-regulation of soluble guanylate cyclase (sGC) followed by decreased cyclic GMP production, which leads to impairment of the vascular relaxation response to nitric oxide (NO). The present study aimed to elucidate whether this impaired NO/cyclic GMP system results secondarily from increased blood pressure or from an effect of the salt itself. The antihypertensive drug nifedipine was used on 4-week-old SHRs that received a normal-salt diet or a high-salt diet for 4 weeks. Treatment with nifedipine (30 mg/kg/day, p.o.) reduced the increased blood pressure of SHRs fed the high-salt diet to the level of SHRs fed the normal-salt diet. In aortic rings from SHRs fed the high-salt diet, not only endothelium-dependent relaxations but also endothelium-independent relaxations were significantly impaired. However, these impairments were not alleviated by treatment with nifedipine. Furthermore, nifedipine did not prevent the increase in protein levels of endothelial NO synthase and the decrease in the protein levels of sGC in aortas from SHRs fed the high-salt diet. These alterations by high salt intake were restored after replacement with the normal-salt diet for 4 additional weeks. These results indicate that in SHRs given excessive dietary salt, normalization of salt intake but not blood pressure reduction can ameliorate alterations in the NO/cyclic GMP system. High salt intake may directly affect the vascular smooth muscle and cause impairment of the relaxation response to NO.

Effects of amlodipine and lacidipine on cardiac remodelling and renin production in salt-loaded stroke-prone hypertensive rats

1. Calcium channel blockers (CCBs) are anti-hypertensive drugs that are usually considered to act mainly as vasodilators. We investigated the relation between the reduction of blood pressure evoked by two long-acting CCBs and their protective effect against cardiac and renal damage in salt-loaded stroke-prone spontaneously hypertensive rats (SHRSP). 2. SHRSP were exposed to high dietary salt intake (1% NaCl in drinking solution) from 8 to 14 weeks of age, with or without amlodipine or lacidipine at three dosage regimens producing similar effects on blood pressure. 3. The lowest dosages of both drugs had non-significant effects on blood pressure but inhibited the paradoxical increases in plasma renin activity (PRA) and in renin mRNA in kidney that were found in salt-loaded SHRSP. The lowest dosage of lacidipine (but not of amlodipine) restored the physiological downregulation of renin production by high salt and reduced left ventricular hypertrophy and mRNA levels of atrial natriuretic factor and transforming growth factor-beta1. 4. The intermediate dosages reduced blood pressure and PRA in a comparable manner, but cardiac hypertrophy was more reduced by lacidipine than by amlodipine. 5. Although the highest doses exhibited a further action on blood pressure, they had no additional effect on cardiac hypertrophy, and they increased PRA and kidney levels of renin mRNA even more than in the absence of drug treatment. 6. We conclude that reduction of blood pressure is not the sole mechanism involved in the prevention of cardiac remodelling by CCBs, and that protection against kidney damage and excessive renin production by low and intermediate dosages of these drugs contributes to their beneficial cardiovascular effects.