Vascular effects of calcium channel antagonists: new evidence

Preliminary assessment of cardiovascular effects and chemoinformatic analysis of total aqueous extract and fractions from Inula viscosa leaves

Inula viscosa (L.) Aiton [Dittrichia viscosa (L.) Greuter] (Asteraceae) is an evergreen perennial herb that grows in different regions of the Mediterranean Basin. It has been particularly used for the treatment of hypertension and diabetes in the Eastern and South-East regions of Morocco. To assess the cardiovascular effects of total aqueous extract and various fractions of Inula viscosa leaves in rat-isolated hearts and aortic rings, and to investigate the potential mechanisms of action of the most active extract(s). In Langendorff's isolated heart system, heart rate (HR) and left ventricular developed pressure (LVDP) were measured for three increasing concentrations of TAE, DCMF, EAF, BF, and AF (0.003, 0.03, and 0.3 mg/mL). Propranolol (1.5 × 10⁻5 M) and Verapamil (2 × 10⁻7 M) were used to investigate the potential mechanisms of action of both EAF and BF. In isolated intact aortic rings, four cumulative concentrations of EAF and BF (0.0001, 0.001, 0.01, and 1 mg/mL) were tested for their vasorelaxant effects. The role of the endothelium in the vasorelaxant effect of EAF was examined by denuding aortic rings. To explore the involvement of the nitric oxide (NO) pathway, β-adrenergic receptors, calcium channels, and the sarco/endoplasmic reticulum Ca2⁺-ATPase (SERCA) pump, intact aortic rings were preincubated with L-NAME (10⁻4 M), Propranolol hydrochloride (10⁻6 M), Verapamil hydrochloride (10⁻5 M), and Thapsigargin (10⁻7 M), respectively. The hypotensive effects of both BF (125 mg/kg) and EAF (125 mg/kg) were evaluated indirectly using the tail-cuff method in normotensive rats. Additionally, the antioxidant activity, as well as the total phenolic and flavonoid contents of all prepared extracts, were determined. To further investigate the antioxidant properties, computational analysis was conducted to determine the bond dissociation energies of the hydroxyl groups on the B-ring of luteolin and quercetin, which are present in EAF and BF, respectively. Finally, an UHPLC analysis was performed for BF. In isolated perfused hearts, TAE induced a dose-dependent positive inotropic effect, accompanied by mild bradycardia. EAF exhibited both positive inotropic and chronotropic effects in a concentration-dependent manner. BF demonstrated a highly dose-dependent, selective positive inotropic effect (LVDP = 76.5 ± 19.2% vs. control at 0.3 mg/mL) with no significant impact on HR. Our findings suggest that BF acts independently of β-adrenoreceptor-dependent pathways, whereas EAF may exert its effects through β-agonistic activity. Additionally, Ca2⁺ channels may play a role in the effects of both fractions. In phenylephrine-precontracted thoracic arteries, both BF and EAF induced concentration-dependent vasorelaxation, with EAF producing the most potent vasorelaxant effect (Emax = 84.16 ± 3.68%). EAF mediates an endothelium-independent vasodilatory response through inhibition of voltage-dependent Ca2⁺ channels and activation of the SERCA pump. BF also demonstrated a significant hypotensive effect in vivo. Among the various extracts, BF contained the highest total phenolic and flavonoid contents and exhibited the strongest DPPH scavenging activity (IC50 = 7.13 µg/mL). Molecular docking studies supported these findings, indicating that quercetin is more effective at scavenging free radicals than luteolin. Phytochemical study of BF revealed the presence of phenolic compounds such as chlorogenic acid, three isochlorogenic acids (A, B and C), tri-caffeoylhexaric acid, methyl 3,5-dicaffeoylquinic acid, quercetin-3-glucuronide and the new molecule 1,3,4,5-tetracaffeoylaltraric acid. This study revealed a novel and potent selective inotropic effect of the BF fraction from I. viscosa leaves, characterized by the absence of tachycardia and independence from β-adrenergic receptors in isolated rat hearts.

Clinical evidence and rationale of topical nifedipine and lidocaine ointment in the treatment of anal fissure and hemorrhoidal disease

INTRODUCTION

Anorectal conditions such as hemorrhoidal disease and anal fissure are frequently painful and debilitating. Pain after hemorrhoidectomy is also common and distressing. These conditions are at least initially managed conservatively. An ointment formulation containing the calcium channel blocker nifedipine and the local anesthetic lidocaine has an established role in the treatment of rectal conditions, particularly conditions associated with anal sphincter hypertonia such as hemorrhoidal disease and anal fissure. This review aimed to compile the evidence for the use of nifedipine 0.3% and lidocaine 1.5% ointment in treating these common but bothersome anorectal diseases.

EVIDENCE ACQUISITION

A comprehensive literature search was conducted, updated to 07 August 2024, using PubMed and MEDLINE databases to identify studies of lidocaine and nifedipine, alone or in combination, for the topical treatment of anal fissure or hemorrhoidal disease. Articles identified in the literature search were supplemented by ad hoc searches and supplemented by relevant literature known to the authors.

EVIDENCE SYNTHESIS

Nifedipine 0.3% and lidocaine 1.5% ointment is effective in relieving pain and aiding the resolution of thrombosed hemorrhoids, reducing resting anal pressure and healing chronic anal fissures, and controlling pain after hemorrhoidectomy. The ointment was significantly better than controls consisting of topical lidocaine 1.5% alone or in combination with hydrocortisone acetate 1%.

CONCLUSIONS

Although the available literature on the topical application of nifedipine and lidocaine in anorectal diseases is limited, nifedipine 0.3% and lidocaine 1.5% ointment should be considered a valid treatment option for clinicians treating anorectal diseases. Further studies are warranted to confirm and extend the results reported.

Effects of antihypertensives with and without IL-6 lowering properties on long-term blood pressure control: The prospective HELIUS cohort

Background

Chronic inflammation is a well-recognized contributor to hypertension pathogenesis. However, the role of targeting inflammation in hypertension treatment, particularly through modulation of inflammatory markers like interleukin-6 (IL-6), remains less understood. We investigated the effects of antihypertensive medications with and without IL-6-lowering properties on long-term blood pressure (BP) control in a multi-ethnic cohort in the Netherlands.

Methods

Participants from HELIUS cohort receiving hypertension treatment were followed over six years. BP control at follow-up was determined using WHO criteria. Due to unavailability of IL-6 data, a literature review was conducted to classify antihypertensives based on their IL-6-lowering properties - a proxy approach. Logistic regression models were used to assess associations between the IL-6-lowering potential of antihypertensives and BP control, both within and between antihypertensive classes. Effect modification by ethnicity was explored.

Results

A total of 1510 participants were included (mean age 57 years, 62 % women). Within the calcium channel blocker (CCB) class, medications with IL-6-lowering properties (amlodipine and barnidipine) were associated with superior BP control (aOR 1.41, 95 % confidence interval 1.05-1.90) compared to other CCBs (lercanidipine, nifedipine, verapamil, clevidipine, diltiazem). No significant associations were observed within angiotensin receptor blockers (ARBs) or angiotensin-converting enzyme inhibitors (ACEIs), between different antihypertensive drug classes, nor across ethnic groups.

Conclusion

Amlodipine and barnidipine were associated with better BP control compared to other CCBs. Our findings provide an important starting point for understanding the role of IL-6 in hypertension management. Further studies are warranted to confirm these observations by directly measuring IL-6 levels and investigating underlying mechanisms.

The Effect of Oral Nimodipine on Cerebral Metabolism and Hemodynamic Parameters in Patients Suffering Aneurysmal Subarachnoid Hemorrhage

INTRODUCTION

Nimodipine is routinely administered to aneurysmal subarachnoid hemorrhage patients to improve functional outcomes. Nimodipine can induce marked systemic hypotension, which might impair cerebral perfusion and brain metabolism.

METHODS

Twenty-seven aneurysmal subarachnoid hemorrhage patients having multimodality neuromonitoring and oral nimodipine treatment as standard of care were included in this retrospective study. Alterations in mean arterial blood pressure (MAP), cerebral perfusion pressure (CPP), brain tissue oxygen tension (pbtO2), and brain metabolism (cerebral microdialysis), were investigated up to 120 minutes after oral administration of nimodipine (60 mg or 30 mg), using mixed linear models.

RESULTS

Three thousand four hundred twenty-five oral nimodipine administrations were investigated (126±59 administrations/patient). After 60 mg of oral nimodipine, there was an immediate statistically significant (but clinically irrelevant) drop in MAP (relative change, 0.97; P<0.001) and CPP (relative change: 0.97; P<0.001) compared with baseline, which lasted for the whole 120 minutes observation period (P<0.001). Subsequently, pbtO2 significantly decreased 50 minutes after administration (P=0.04) for the rest of the observation period; the maximum decrease was -0.6 mmHg after 100 minutes (P<0.001). None of the investigated cerebral metabolites (glucose, lactate, pyruvate, lactate/pyruvate ratio, glutamate, glycerol) changed after 60 mg nimodipine. Compared with 60 mg nimodipine, 30 mg induced a lower reduction in MAP (relative change, 1.01; P=0.02) and CPP (relative change, 1.01; P=0.03) but had similar effects on pbtO2 and cerebral metabolism (P>0.05).

CONCLUSIONS

Oral nimodipine reduced MAP, which translated into a reduction in cerebral perfusion and oxygenation. However, these changes are unlikely to be clinically relevant, as the absolute changes were minimal and did not impact cerebral metabolism.

Molecular Modeling and Potential Ca2+ Channel Blocker Activity of Diphenylmethoxypiperidine Derivatives

Molecular interactions of 4-diphenylmethoxy-1-methylpiperidine derivatives with the calcium channel CaV1.1 (pdb:6JP5) are described. All the compounds tested, previously shown to inhibit adrenergic vascular contractions, display similar binding energetics and interactions with the trans-membrane domain of 6JP5 on the opposite side relative to the channel pore, where nifedipine, a known dihydropyridine Ca2+ channel blocker binds. Additionally, the compounds tested inhibit Ca2+-dependent contractions in isolated mouse mesenteric arteries. Thus, diphenylpyraline analogs may exert their anticontractile effects, at least partially, by blocking vascular Ca2+ channels.

Chemical composition, vasorelaxant, antioxidant and antiplatelet effects of essential oil of Artemisia campestris L. from Oriental Morocco

BACKGROUND

Artemisia campestris L. (Asteraceae) is a medicinal herb traditionally used to treat hypertension and many other diseases. Hence, this study is aimed to analyze the essential oil of A. campestris L (AcEO) and to investigate the antiplatelet, antioxidant effects and the mechanisms of its vasorelaxant effect.

METHODS

The chemical composition of AcEO was elucidated using GC/MS analysis. Then, the antioxidant effect was tested on DPPH radical scavenging and on the prevention of β-carotene bleaching. The antiplatelet effect was performed on the presence of the platelet agonists: thrombin and ADP. The mechanism of action of the vasorelaxant effect was studied by using the cellular blockers specified to explore the involvement of NO/GC pathway and in the presence of calcium channels blockers and potassium channels blockers.

RESULTS

AcEO is predominated by the volatiles: spathulenol, ß-eudesmol and p-cymene. The maximal antioxidant effect was obtained with the dose 2 mg/ml of AcEO. The dose 1 mg/ml of AcEO showed a maximum antiplatelet effect of, respectively 49.73% ±9.54 and 48.20% ±8.49 on thrombin and ADP. The vasorelaxation seems not to be mediated via NOS/GC pathway neither via the potassium channels. However, pretreatment with calcium channels blockers attenuated this effect, suggesting that the vasorelaxation is mediated via inhibition of L-type Ca2+ channels and the activation of SERCA pumps of reticulum plasma.

CONCLUSION

This study confirms the antioxidant, antiplatelet and vasorelaxant effects of A.campestris L essential oil. However, the antihypertensive use of this oil should be further confirmed by the chemical fractionation and subsequent bio-guided assays.

Antihypertensive effects of new dihydropyridine derivatives on phenylephrine-raised blood pressure in rats

Changes in the substitutions at C-3 and C-5 positions of 4-(1-methyl-5-nitro-2-imidazolyl) dihydropyridine analogs of nifedipine have led to changes in potency of the compounds. The objective of the present study was to examine the hypotensive effects of 5 newly synthesized dihydropyridine derivatives of nifedipine in rats with phenylephrine-raised blood pressure. Anesthetized Sprague-Dawley rats were randomly assigned to 19 groups of 7 animals each. Control group received the vehicle dimethylsulfoxide (0.05 mL), 3 groups were given nifedipine at 100, 300, or 1000 μg/kg, and 5 other groups each composed of 3 subgroups administered one of the 5 new dihydropyridine compound at 100, 300, or 1000 μg/kg. All animals were initially infused with 20 µg/kg/min phenylephrine for 45 min, and were then given a bolus of either dimethylsulfoxide, nifedipine, or new dihydropyridine compounds 20 min after the commencement of phenylephrine infusion. Blood pressure and heart rate (HR) of the animals were measured before and at the end of phenylephrine infusion, or 25 min after injection of vehicle or compounds. Compared to dimethylsulfoxide, nifedipine, and new 1, 4-dihydropyridine derivatives caused significant reductions in MBP. Moreover, cyclohexyl propyl, phenyl butyl, and cyclohexyl methyl analogs of 1, 4-dihydro-2,6-dimethyl-4-(1-methyl-5-nitro-2-imidazoyl)-3,5-pyridinedicarboxylase at 100 μg/kg, phenyl butyl, and cyclohexyl methyl analogs at 300 μg/kg, and cyclohexyl methyl analogs at 1000 μg/kg reduced MBP similar to nifedipine. There was no significant difference between HR of all groups before and after administration of the compounds. The findings indicated that changes in substitution at C-3 and C-5 positions of 2-(1-methyl-5-nitro-2-imidazolyl) dihydropyridine analogs of nifedipine were associated with changes in hypotensive activity of the compounds.

Exercise preconditioning of myocardial infarct size in dogs is triggered by calcium

We showed that exercise induces early and late myocardial preconditioning in dogs and that these effects are mediated through nicotinamide adenine dinucleotide phosphate reduced form (NADPH) oxidase activation. As the intracoronary administration of calcium induces preconditioning and exercise enhances the calcium inflow to the cell, we studied if this effect of exercise triggers exercise preconditioning independently of its hemodynamic effects. We analyzed in 81 dogs the effect of blocking sarcolemmal L-type Ca channels with a low dose of verapamil on early and late preconditioning by exercise, and in other 50 dogs, we studied the effect of verapamil on NADPH oxidase activation in early exercise preconditioning. Exercise reduced myocardial infarct size by 76% and 52% (early and late windows respectively; P < 0.001 both), and these effects were abolished by a single low dose of verapamil given before exercise. This dose of verapamil did not modify the effect of exercise on metabolic and hemodynamic parameters. In addition, verapamil blocked the activation of NADPH oxidase during early preconditioning. The protective effect of exercise preconditioning on myocardial infarct size is triggered, at least in part, by calcium inflow increase to the cell during exercise and, during the early window, is mediated by NADPH oxidase activation.

The effect of mepivacaine on swine lingual, pulmonary and coronary arteries

Background

Although mepivacaine has a known biphasic action on the aortic and coronary artery in several animal species, its effects on the lingual and pulmonary artery are not well understood and it is not yet known whether mepivacaine produces vasoconstriction in these vessels. The present study aims to investigate the direct effects of mepivacaine on swine lingual, pulmonary and coronary arterial endothelium-denuded rings.

Methods

Artery rings were perfused with isotonic 40 mM KCl until a stable constricted plateau was reached. The rings were then perfused with isotonic 40 mM KCl plus a particular concentration of mepivacaine (0.4 μM, 4.0 μM, 40 μM, 0.4 mM and 4.0 mM). The isometric tension strengths in each experiment were normalized to the strength of the isometric tension immediately before mepivacaine perfusion and expressed as a percentage.

Results

Mepivacaine at 0.4 to 40 μM did not significantly alter 40 mM KCl-induced contraction in the lingual, pulmonary and coronary arterial rings. In contrast, mepivacaine at 4 mM produced attenuated vasoconstriction in the lingual, pulmonary and coronary arterial compared with isotonic 40 mM KCl.

Conclusions

Mepivacaine produced vasoconstriction at lower concentrations, followed by attenuated vasoconstriction at higher concentrations on swine lingual, pulmonary and coronary arterial endothelium-denuded rings. Mepivacaine (4 μM) appeared to increase isotonic 40 mM KCl-induced contraction, followed by attenuated vasoconstriction at 4 mM. Dentists using 3 % mepivacaine should take into consideration that the risk of complications may be increased if more than six mepivacaine cartridges are used in dental treatment or minor surgery, or if over 15 ml of mepivacaine is administered to a patient with cardiovascular complications during general anesthesia for oral maxillofacial surgery.

Absorption, elimination and cerebrospinal fluid concentrations of nimodipine in healthy beagle dogs receiving human intravenous and oral formulation

Nimodipine is an L-type calcium channel blocker and is used to treat vasospasm in patients with subarachnoid hemorrhage. Its putative mechanism of action is relaxation of smooth muscle cells in cerebral arteries. In addition, nimodipine may have pleiotropic effects against vasospasm. Systemic hypotension is an adverse effect when patients are treated with oral or intravenous nimodipine. Intracranial administration of nimodipine formulations may produce higher concentration of nimodipine in the cerebrospinal fluid (CSF) than is possible to achieve orally or intravenously, while resulting in lower incidence of systemic hypotension. The aim of this study was to provide information on plasma and CSF levels of nimodipine in beagle dogs as a comparative data for development of experimental intracranial treatment modalities. Plasma levels of nimodipine were measured after current 30 and 60 mg single oral dose of nimodipine (Nimotop(®) 30 mg tablets), a single intravenous bolus 0.72 mg/dog of nimodipine (Nimotop(®) 0.2 mg/ml infusion solution) and CSF levels after 60 mg single oral dose of nimodipine. CSF/Plasma concentration ratio of nimodipine after oral administration of 60 mg at 1 h was 0.013 ± 0.0005. The mean terminal elimination half-life of nimodipine after i.v. bolus dose 0.72 mg was 1.8 h and mean plasma clearance was 40.3 and 3.4 l/h/kg. Absolute bioavailability was 22 %. Maximum plasma concentration and area under the plasma concentration-time curve from time of administration until the last measurable plasma concentration increased in a dose-proportional manner comparing the exposure parameters at oral doses of 30 and 60 mg. Individual variation in the kinetic profile of nimodipine was measured.

Manidipine plus delapril in patients with Type 2 diabetes and hypertension: reducing cardiovascular risk and end-organ damage

In patients with hypertension and diabetes, atherothrombosis is a leading cause of morbidity and mortality, and there is now compelling evidence demonstrating that lowering elevated blood pressure (BP) is one of the most beneficial aims of therapy in this high-risk population. Indeed, major international guidelines have set a target BP goal of 130/80 mmHg in high-risk patients and recommend combination treatment with two or more drug classes to help achieve this objective. Manidipine plus delapril is a fixed-dose combination of a third-generation dihydropyridine calcium antagonist and an angiotensin-converting enzyme inhibitor, which is effective in mild-to-moderately hypertensive patients with an inadequate response to monotherapy. It is also effective in the long-term (50 weeks) management of essential hypertension. Comparative studies have demonstrated that manidipine plus delapril is as effective as enalapril plus hydrochlorothiazide (HCTZ) in patients with hypertension that is unresponsive to monotherapy, and as effective as ramipril plus HCTZ, valsartan plus HCTZ, irbesartan plus HCTZ and olmesartan plus HCTZ in patients with essential hypertension and Type 2 diabetes. In addition, manidipine plus delapril exhibited renoprotective effects in normotensive Type 2 diabetic patients, and improved fibrinolytic function (significantly more than irbesartan plus HCTZ) in hypertensive patients with Type 2 diabetes. Manidipine 10 mg plus delapril 30 mg once daily was generally well tolerated, with no unexpected adverse effects and evidence of a low incidence of ankle edema. Thus, manidipine plus delapril is a fixed-dose combination treatment that significantly reduces elevated BP with once-daily administration. It is well tolerated and has ancillary properties, such as nephroprotective activity and improvement of fibrinolytic balance, which may help reduce cardiovascular morbidity and mortality, particularly in high-risk patients, such as those with Type 2 diabetes mellitus.

Management of hypertension with fixed-dose triple-combination treatments

The objective of this review is to evaluate the role of fixed-dose triple-combination therapy for the management of hypertension. An assessment of clinical trials showed that half the patients with hypertension have uncontrolled blood pressure (BP), with underlying factors including therapeutic inertia and poor patient adherence. Many patients will require three antihypertensive agents to achieve BP goals, and current guidelines recommend combining drugs with complementary mechanisms of action. Three single-pill triple-combination treatments are available and each includes an agent affecting the renin-angiotensin-aldosterone pathway (either a direct renin inhibitor or an angiotensin II receptor blocker) in combination with a calcium channel blocker and diuretic. These triple-combination therapies consistently demonstrated significantly greater BP reduction relative to the component dual combinations, with BP reductions documented across a range of patient populations. Triple-combination treatments were well tolerated in all clinical trials reviewed. The use of single-pill, triple-combination antihypertensive therapy has been shown to be an effective, well-tolerated, and convenient treatment strategy that can help patients achieve BP control.

Metabolic effects of manidipine

The calcium channel antagonists (CCAs) were originally introduced as vasodilators for the treatment of coronary heart disease, but are now also noted for their clinical efficacy in the management of hypertension. Data from large clinical studies have shown that CCAs are not associated with the undesirable metabolic effects (e.g. worsening of dyslipidemia and reduction of insulin sensitivity) seen with older agents such as thiazide diuretics and beta-adrenoceptor antagonists (beta-blockers) that are used to treat hypertension. Indeed, reductions in cardiovascular risk and rates of onset of new cases of diabetes mellitus have been reported in trials in patients with hypertension treated with CCAs. These beneficial effects extend beyond those expected to accompany reductions in BP. Until recently, the biochemical effects underlying these metabolic changes were only poorly understood, but pharmacologic studies have now started to shed more light on these issues. Of particular interest are studies with manidipine, some of which suggest that this agent may be associated with greater improvements in insulin sensitivity and may have better renal protective properties than other CCAs. Confirmation of potential differences among CCAs in terms of the relative magnitude of any beneficial metabolic effects requires further study. Ongoing research is expected to clarify further the action of these agents at the cellular level and to assist with the optimization of antihypertensive therapy, particularly in patients with elevated cardiovascular risk profiles.

Mepivacaine-induced contraction is attenuated by endothelial nitric oxide release in isolated rat aorta

Mepivacaine is an aminoamide-linked local anesthetic with an intermediate duration that intrinsically produces vasoconstriction both in vivo and in vitro. The aims of this in-vitro study were to examine the direct effect of mepivacaine in isolated rat aortic rings and to determine the associated cellular mechanism with a particular focus on endothelium-derived vasodilators, which modulate vascular tone. In the aortic rings with or without endothelium, cumulative mepivacaine concentration-response curves were generated in the presence or absence of the following antagonists: N(ω)-nitro-L-arginine methyl ester [L-NAME], indomethacin, fluconazole, methylene blue, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one [ODQ], verapamil, and calcium-free Krebs solution. Mepivacaine produced vasoconstriction at low concentrations (1 × 10(-3) and 3 × 10(-3) mol/L) followed by vasodilation at a high concentration (1 × 10(-2) mol/L). The mepivacaine-induced contraction was higher in endothelium-denuded aortae than in endothelium-intact aortae. Pretreatment with L-NAME, ODQ, and methylene blue enhanced mepivacaine-induced contraction in the endothelium-intact rings, whereas fluconazole had no effect. Indomethacin slightly attenuated mepivacaine-induced contraction, whereas verapamil and calcium-free Krebs solution more strongly attenuated this contraction. The vasoconstriction induced by mepivacaine is attenuated mainly by the endothelial nitric oxide - cyclic guanosine monophosphate pathway. In addition, mepivacaine-induced contraction involves cyclooxygenase pathway activation and extracellular calcium influx via voltage-operated calcium channels.

Arterial calcification in chronic kidney disease: key roles for calcium and phosphate

Vascular calcification contributes to the high risk of cardiovascular mortality in chronic kidney disease (CKD) patients. Dysregulation of calcium (Ca) and phosphate (P) metabolism is common in CKD patients and drives vascular calcification. In this article, we review the physiological regulatory mechanisms for Ca and P homeostasis and the basis for their dysregulation in CKD. In addition, we highlight recent findings indicating that elevated Ca and P have direct effects on vascular smooth muscle cells (VSMCs) that promote vascular calcification, including stimulation of osteogenic/chondrogenic differentiation, vesicle release, apoptosis, loss of inhibitors, and extracellular matrix degradation. These studies suggest a major role for elevated P in promoting osteogenic/chondrogenic differentiation of VSMC, whereas elevated Ca has a predominant role in promoting VSMC apoptosis and vesicle release. Furthermore, the effects of elevated Ca and P are synergistic, providing a major stimulus for vascular calcification in CKD. Unraveling the complex regulatory pathways that mediate the effects of both Ca and P on VSMCs will ultimately provide novel targets and therapies to limit the destructive effects of vascular calcification in CKD patients.

Identification of quaternary ammonium compounds as potent inhibitors of hERG potassium channels

The human ether-a-go-go-related gene (hERG) channel, a member of a family of voltage-gated potassium (K(+)) channels, plays a critical role in the repolarization of the cardiac action potential. The reduction of hERG channel activity as a result of adverse drug effects or genetic mutations may cause QT interval prolongation and potentially leads to acquired long QT syndrome. Thus, screening for hERG channel activity is important in drug development. Cardiotoxicity associated with the inhibition of hERG channels by environmental chemicals is also a public health concern. To assess the inhibitory effects of environmental chemicals on hERG channel function, we screened the National Toxicology Program (NTP) collection of 1408 compounds by measuring thallium influx into cells through hERG channels. Seventeen compounds with hERG channel inhibition were identified with IC(50) potencies ranging from 0.26 to 22μM. Twelve of these compounds were confirmed as hERG channel blockers in an automated whole cell patch clamp experiment. In addition, we investigated the structure-activity relationship of seven compounds belonging to the quaternary ammonium compound (QAC) series on hERG channel inhibition. Among four active QAC compounds, tetra-n-octylammonium bromide was the most potent with an IC(50) value of 260nM in the thallium influx assay and 80nM in the patch clamp assay. The potency of this class of hERG channel inhibitors appears to depend on the number and length of their aliphatic side-chains surrounding the charged nitrogen. Profiling environmental compound libraries for hERG channel inhibition provides information useful in prioritizing these compounds for cardiotoxicity assessment in vivo.

Endothelin-dependent vasoconstriction in human uterine artery: application to preeclampsia

BACKGROUND

Reduced uteroplacental perfusion, the initiating event in preeclampsia, is associated with enhanced endothelin-1 (ET-1) production which feeds the vasoconstriction of uterine artery. Whether the treatments of preeclampsia were effective on ET-1 induced contraction and could reverse placental ischemia is the question addressed in this study. We investigated the effect of antihypertensive drugs used in preeclampsia and of ET receptor antagonists on the contractile response to ET-1 on human uterine arteries.

METHODOLOGY/PRINCIPAL FINDINGS

Experiments were performed, ex vivo, on human uterine artery samples obtained after hysterectomy. We studied variations in isometric tension of arterial rings in response to the vasoconstrictor ET-1 and evaluated the effects of various vasodilators and ET-receptor antagonists on this response. Among antihypertensive drugs, only dihydropyridines were effective in blocking and reversing the ET-1 contractile response. Their efficiency, independent of the concentration of ET-1, was only partial. Hydralazine, alpha-methyldopa and labetalol had no effect on ET-1 induced contraction which is mediated by both ET(A) and ET(B) receptors in uterine artery. ET receptors antagonists, BQ-123 and BQ-788, slightly reduced the amplitude of the response to ET-1. Combination of both antagonists was more efficient, but it was not possible to reverse the maximal ET-1-induced contraction with antagonists used alone or in combination.

CONCLUSION

Pharmacological drugs currently used in the context of preeclampsia, do not reverse ET-1 induced contraction. Only dihydropyridines, which partially relax uterine artery previously contracted with ET-1, might offer interesting perspectives to improve placental perfusion.

Manidipine treatment in patients with albuminuria not sufficiently reduced with renin-angiotensin system blockers

Microalbuminuria is an issue of great concern in hypertensive patients owing to its close relation with cardiovascular morbidity and mortality. Treatment should aim to reduce microalbuminuria to the normal range. Drugs that block the renin-angiotensin system have specific antiproteinuric properties, but more than one drug is needed to achieve blood pressure control in most cases. The aim of this study was to compare the effects of adding manidipine to the treatment of patients with essential hypertension and persistent albuminuria, despite full-dose treatment with a renin-angiotensin system blocker on urinary albumin excretion (UAE) after 24 weeks of therapy. Patients with diabetes and renal insufficiency were excluded. At baseline, blood pressure and UAE were 155.1 +/- 12/87.76 +/- 11 mmHg and 293.19 +/- 285 mg/g, respectively. At study end, blood pressure was 137.1 +/- 13.1/77.24 +/- 10.4 mmHg (p < 0.001 vs baseline). UAE was reduced by 45% to 161.52 +/- 163 mg/g (p < 0.001 vs baseline). No correlations were found between systolic blood pressure reduction and UAE reduction (Pearson's R = -0.034; p = not significant) nor between estimated glomerular filtration rate and UAE reduction (Pearson's R = -0.0056; p = not significant). No patient withdrew from the study owing to side effects. In conclusion, treatment with manidipine resulted in a large reduction in UAE rates, and this reduction appeared to be independent of the degree of blood pressure reduction or changes in estimated glomerular filtration rate. Our data supports the added value of manidipine in the treatment of patients with hypertension and microalbuminuria.

Effect of blood pressure lowering on markers of kidney disease progression

Hypertension remains a common comorbidity and cause of chronic kidney disease (CKD). As the number of patients with CKD grows, so does the need to identify modifiable risk factors for CKD progression. Data on slowing progression of CKD or preventing end-stage renal disease with aggressive blood pressure control have not yielded definitive conclusions regarding ideal blood pressure targets. Shifting the focus of antihypertensive therapy to alternative markers of end-organ damage, specifically proteinuria, has yielded some promise in preventing the progression of CKD. Nevertheless, proteinuria and decline in estimated GFR may represent an irreversible degree of injury to the kidney that limits the impact of any therapy. The identification and use of novel markers of kidney injury to assess the impact of antihyper-tensive therapy may yield clearer direction with regard to optimal management of hypertension in the setting of CKD.

Role of clevidipine butyrate in the treatment of acute hypertension in the critical care setting: a review

Acutely elevated blood pressure in the critical care setting is associated with a higher risk of acute end-organ damage (eg, myocardial ischemia, stroke, and renal failure) and perioperative bleeding. Urgent treatment and careful blood pressure control are crucial to prevent significant morbidity. Clevidipine butyrate (Cleviprex) is an ultrashort-acting, third-generation intravenous calcium channel blocker. It is an arterial-selective vasodilator with no venodilatory or myocardial depressive effects. Clevidipine has an extremely short half-life of approximately 1 minute as it is rapidly metabolized by blood and tissue esterases. These metabolites are then primarily eliminated through urine and fecal pathways. The rapid onset and the short duration of action permit tighter and closer adjustment of the blood pressure than is possible with other intravenous agents.

The interdependence of endothelin-1 and calcium: a review

The 21-amino-acid peptide ET-1 (endothelin-1) regulates a diverse array of physiological processes, including vasoconstriction, angiogenesis, nociception and cell proliferation. Most of the effects of ET-1 are associated with an increase in intracellular calcium concentration. The calcium influx and mobilization pathways activated by ET-1, however, vary immensely. The present review begins with the basics of calcium signalling and investigates the different ways intracellular calcium concentration can increase in response to a stimulus. The focus then shifts to ET-1, and discusses how ET receptors mobilize calcium. We also examine how disease alters calcium-dependent responses to ET-1 by discussing changes to ET-1-mediated calcium signalling in hypertension, as there is significant interest in the role of ET-1 in this important disease. A list of unanswered questions regarding ET-mediated calcium signals are also presented, as well as perspectives for future research of calcium mobilization by ET-1.

Calcium and calmodulin regulate mercury-induced phospholipase D activation in vascular endothelial cells

Earlier, we reported that mercury, the environmental risk factor for cardiovascular diseases, activates vascular endothelial cell (EC) phospholipase D (PLD). Here, we report the novel and significant finding that calcium and calmodulin regulated mercury-induced PLD activation in bovine pulmonary artery ECs (BPAECs). Mercury (mercury chloride, 25 microM; thimerosal, 25 microM; methylmercury, 10 microM) significantly activated PLD in BPAECs. Calcium chelating agents and calcium depletion of the medium completely attenuated the mercury-induced PLD activation in ECs. Calmodulin inhibitors significantly attenuated mercury-induced PLD activation in BPAECs. Despite the absence of L-type calcium channels in ECs, nifedipine, nimodipine, and diltiazem significantly attenuated mercury-induced PLD activation and cytotoxicity in BPAECs. This study demonstrated the importance of calcium and calmodulin in the regulation of mercury-induced PLD activation and the protective action of L-type calcium channel blockers against mercury cytotoxicity in vascular ECs, suggesting mechanisms of mercury vasculotoxicity and mercury-induced cardiovascular diseases.

Myeloproliferative disorder therapy: assessment and management of adverse events--a cardiologist's perspective

Although some cardiac effects, such as palpitations and tachycardia, occur commonly in healthy people, they have also been shown to be associated with agents used to treat the myeloproliferative disorders. Various strategies exist to prevent and manage cardiac effects and minimise their impact on treatment compliance and persistence. These include pre-therapy cardiac assessment, pharmacological intervention and referral to a cardiologist. Ultimately, treating physicians must use their discretion when deciding which management strategy to use and which cardiac side effects require referral to a cardiologist, but the value of continuous dialogue between specialists should not be ignored.

Add-on manidipine versus amlodipine in diabetic patients with hypertension and microalbuminuria: the AMANDHA study

The aim of this study was to compare the efficacy and safety of adding manidipine 20 mg versus amlodipine 10 mg to the treatment of diabetic patients with uncontrolled hypertension and microalbuminuria despite full-dose treatment with a renin-angiotensin system blocker for at least 6 months. Patients were randomized to receive manidipine (n = 61) or amlodipine (n = 30) in a 2:1 ratio for 6 months and monitored for microalbuminuria for an additional extension phase of 18 months. Manidipine and amlodipine decreased blood pressure values to a similar extent. Urinary albumin excretion was reduced by 65.5% with manidipine versus 20% with amlodipine (p < 0.01) at 6 months and 62.7 versus 16.6% (p < 0.01) at the end of the extension phase. Manidipine was better tolerated than amlodipine. Thus, the addition of manidipine, but not amlodipine, resulted in a large reduction in the urinary albumin excretion rate despite similar blood pressure reductions.

A common NOS1AP genetic polymorphism is associated with increased cardiovascular mortality in users of dihydropyridine calcium channel blockers

AIM

Recently, a polymorphism in the NOS1AP gene (rs10494366), a regulator of neuronal nitric oxide synthase (nNOS), was associated with QTc prolongation. Both nNOS and calcium channel blockers (CCBs) regulate intracellular calcium levels and have an important role in cardiovascular homeostasis. The aim was to investigate whether this polymorphism is associated with cardiovascular mortality in users of CCBs.

METHODS

The data from the Rotterdam study, a population-based closed cohort study of Caucasian individuals of > or =55 years of age, were used. We identified 1113 participants in the Rotterdam Study who were prescribed CCBs for the first time between 1991 and 2005. All-cause and cardiovascular mortality was assessed in participants who were prescribed CCBs with different NOS1AP rs10494366 genotypes using Cox proportional hazard models.

RESULTS

In participants starting on dihydropyridine CCBs (amlodipine, nifedipine and others) all-cause mortality (n = 79) risks were higher in participants with the TG [hazard ratio (HR) 2.57, 95% confidence interval (CI) 1.24, 5.34] or the GG genotype (HR 3.18, 95% CI 1.18, 8.58) than in participants with the referent TT genotype. Cardiovascular mortality (n = 54) risks were 3.51 (95% CI 1.41, 8.78) for the TG genotype and 6.00 (95% CI 1.80, 20.0) for the GG genotype. No differences in all-cause mortality or cardiovascular mortality were seen in participants starting with the nondihydropyridine CCBs verapamil or diltiazem.

CONCLUSION

The minor G allele of rs10494366 in the NOS1AP gene is associated with increased all-cause and cardiovascular mortality in Caucasian users of dihydropyridine CCBs. The mechanism underlying the observed association is unknown.

Synthesis and structure characterization of new 1,2,4-oxadiazolo[4,5-d]-1,5-benzothiazepines derivatives containing 2-phenyl-1,2,3-triazole through 1,3-dipolar cycloaddition reaction

Reaction of 1,5-benzothiazepines, containing 2-phenyl-1,2,3-triazole 2a-d, with aryl nitrile oxides in CH2 Cl2 at room temperature leads to a series of novel 1,2,4-oxadiazolo[4,5-d]-1,5-benzothiazepine derivatives 3a-l in good yields. The products were characterized by IR, 1H NMR, MS, elemental analyses, X-ray and their spectrum characters were discussed.

Drugs for the perioperative control of hypertension: current issues and future directions

The management of hypertension continues to pose important challenges. Recent developments have established the importance of more rigorous blood pressure control in the community. In the perioperative setting, hypertension has long been recognised as undesirable, although the adverse impact of high blood pressure on the acute risks of elective surgery may have been previously overstated.A number of agents and techniques are available to control blood pressure perioperatively. These include principally general and regional anaesthetics, alpha(2)-adrenoceptor agonists, peripheral alpha(1)- and beta-adrenoceptor antagonists, dihydropyridine calcium channel antagonists, dopamine D(1A)-receptor agonists (fenoldopam), and nitric oxide donors. Recent years have seen important developments in the receptor selectivity of new compounds and in pharmacokinetics, particularly esterase metabolism. The future study of genomics may enable us to identify patients at risk for hypertension-related adverse events and target therapies most effectively to these high-risk groups.

Vascular large conductance calcium-activated potassium channels: functional role and therapeutic potential

Large-conductance Ca2+-activated K+ channels (BK Ca or maxiK channels) are expressed in different cell types. They play an essential role in the regulation of various cell functions. In particular, BK Ca channels have been extensively studied in vascular smooth muscle cells, where they contribute to the control of vascular tone. They facilitate the feedback regulation against the rise of intracellular Ca2+, membrane depolarization and vasoconstriction. BK Ca channels promote a K+ outward current and lead to membrane hyperpolarization. In endothelial cells expression and function of BK Ca channels play an important role in the regulation of the vascular smooth muscle activity. Endothelial BK Ca channels modulate the biosyntheses and release of various vasoactive modulators and regulate the membrane potential. Because of their regulatory role in vascular tone, endothelial BK Ca channels have been suggested as therapeutic targets for the treatment of cardiovascular diseases. Hypertension, atherosclerosis, and diabetes are associated with altered current amplitude, open probability, and Ca2+-sensing of BK Ca channels. The properties of BK Ca channels and their role in endothelial and vascular smooth muscle cells would address them as potential therapeutic targets. Further studies are necessary to identify the detailed molecular mechanisms of action and to investigate selective BK Ca channels openers as possible therapeutic agents for clinical use.

Efonidipine reduces proteinuria and plasma aldosterone in patients with chronic glomerulonephritis

Efonidipine, a dihydropirydine calcium channel blocker, has been shown to dilate the efferent glomerular arterioles as effectively as the afferent arterioles. The present study compared the chronic effects of efonidipine and amlodipine on proteinuria in patients with chronic glomerulonephritis. The study subjects were 21 chronic glomerulonephritis patients presenting with spot proteinuria greater than 30 mg/dL and serum creatinine concentrations of <or=1.3 mg/dL in men or <or=1.1 mg/dL in women. All patients were receiving antihypertensive medication or had a blood pressure >or=130/85 mmHg. Efonidipine 20-60 mg twice daily and amlodipine 2.5-7.5 mg once daily were given for 4 months each in a random crossover manner. In both periods, calcium channel blockers were titrated when the BP exceeded 130/85 mmHg. Blood sampling and urinalysis were performed at the end of each treatment period. The average blood pressure was comparable between the efonidipine and the amlodipine periods (133+/-10/86+/-5 vs. 132+/-8/86+/-5 mmHg). Urinary protein excretion was significantly less in the efonidipine period than in the amlodipine period (1.7+/-1.5 vs. 2.0+/-1.6 g/g creatinine, p=0.04). Serum albumin was significantly higher in the efonidipine period than the amlodipine period (4.0+/-0.5 vs. 3.8+/-0.5 mEq/L, p=0.03). Glomerular filtration rate was not significantly different between the two periods. Plasma aldosterone was lower in the efonidipine period than in the amlodipine period (52+/-46 vs. 72+/-48 pg/mL, p=0.009). It may be concluded that efonidipine results in a greater reduction of plasma aldosterone and proteinuria than amlodipine, and that these effects occur by a mechanism independent of blood pressure reduction. A further large-scale clinical trial will be needed in order to apply the findings of this study to the treatment of patients with renal disease.

Benidipine Attenuates Glomerular Hypertension and Reduces Albuminuria in Patients with Metabolic Syndrome

Recent studies have shown that metabolic syndrome is associated with an increased risk for chronic kidney disease. We recently found that the prevalence of sodium-sensitive hypertension in patients with metabolic syndrome was significantly higher than that in patients with essential hypertension but without metabolic syndrome. We therefore assessed the effects of benidipine, a long-acting calcium channel blocker, on the sodium sensitivity of blood pressure and renal hemodymamics in 5 patients with metabolic syndrome. Glomerular hemodynamics were assessed using pressure-natriuresis curves, which were constructed by plotting the urinary excretion of sodium as a function of the mean arterial pressure, which was calculated as the mean of 48 values based on 24-h monitoring, during the intake of low (3 g NaCl daily) and relatively high (10 g NaCl daily) sodium diets. Under the relatively high sodium diet condition, benidipine significantly lowered systolic and diastolic blood pressure. The pressure-natriuresis curve was steeper after the administration of benidipine. Benidipine lowered glomerular capillary hydraulic pressure (P(GC)) levels (from 54.4+/-7.5 to 47.0+/-7.0 mmHg, p=0.0152) and reduced both the resistance of the afferent arterioles (from 10,338+/-2,618 to 9,026+/-2,627 dyn.s/cm5, p=0.047) and the resistance of the efferent arterioles (from 4,649+/-2,039 to 2,419+/-2,081 dyn.s/cm(5), p=0.003). The urinary albumin excretion rate also decreased after the administration of benidipine. These findings indicated that benidipine may be effective for reducing the risk of developing chronic kidney disease in patients with metabolic syndrome.

The effect of nimodipine on calcium homeostasis and pain sensitivity in diabetic rats

1. The pathogenesis of diabetic neuropathy is a complex phenomenon, the mechanisms of which are not fully understood. Our previous studies have shown that the intracellular calcium signaling is impaired in primary and secondary nociceptive neurons in rats with streptozotocin (STZ)-induced diabetes. Here, we investigated the effect of prolonged treatment with the L-type calcium channel blocker nimodipine on diabetes-induced changes in neuronal calcium signaling and pain sensitivity. 2. Diabetes was induced in young rats (21 p.d.) by a streptozotocin injection. After 3 weeks of diabetes development, the rats were treated with nimodipine for another 3 weeks. The effect of nimodipine treatment on calcium homeostasis in nociceptive dorsal root ganglion neurons (DRG) and substantia gelatinosa (SG) neurons of the spinal cord slices was examined with fluorescent imaging technique. 3. Nimodipine treatment was not able to normalize elevated resting intracellular calcium ([Ca(2+)]( i )) levels in small DRG neurons. However, it was able to restore impaired Ca(2+) release from the ER, induced by either activation of ryanodine receptors or by receptor-independent mechanism in both DRG and SG neurons. 4. The beneficiary effects of nimodipine treatment on [Ca(2+)]( i ) signaling were paralleled with the reversal of diabetes-induced thermal hypoalgesia and normalization of the acute phase of the response to formalin injection. Nimodipine treatment was also able to shorten the duration of the tonic phase of formalin response to the control values. 5. To separate vasodilating effect of nimodipine Biessels et al., (Brain Res. 1035:86-93) from its effect on neuronal Ca(2+) channels, a group of STZ-diabetic rats was treated with vasodilator - enalapril. Enalapril treatment also have some beneficial effect on normalizing Ca(2+) release from the ER, however, it was far less explicit than the normalizing effect of nimodipine. Effect of enalapril treatment on nociceptive behavioral responses was also much less pronounced. It partially reversed diabetes-induced thermal hypoalgesia, but did not change the characteristics of the response to formalin injection. 6. The results of this study suggest that chronic nimodipine treatment may be effective in restoring diabetes-impaired neuronal calcium homeostasis as well as reduction of diabetes-induced thermal hypoalgesia and noxious stimuli responses. The nimodipine effect is mediated through a direct neuronal action combined with some vascular mechanism.

Antihypertensive effect of manidipine

Manidipine is a lipophilic, third-generation, highly vasoselective, dihydropyridine (DHP) calcium channel antagonist, which, when given on a once-daily basis, effectively reduces blood pressure (BP) in patients with mild-to-moderate essential hypertension. Manidipine has a gradual onset and a long duration of action, effectively maintaining reduced BP levels throughout the 24-hour dosing period, and is effective in the long term with no evidence of intolerance. The BP-lowering capacity of manidipine is similar to that of other established DHPs and of angiotensin-converting enzyme inhibitors. Diabetic patients and very elderly patients with mild-to-moderate hypertension also respond favourably to treatment with manidipine. Manidipine has neutral effects on glucose and lipid metabolism and is generally well tolerated. Manidipine thus represents a first-line option for lowering BP in patients with mild-to-moderate hypertension.