Amlodipine, but not verapamil or nifedipine, dilates rabbit femoral artery largely through a nitric oxide- and kinin-dependent mechanism

The wHole Story About Fenestrations in LSEC

The porosity of liver sinusoidal endothelial cells (LSEC) ensures bidirectional passive transport of lipoproteins, drugs and solutes between the liver capillaries and the liver parenchyma. This porosity is realized via fenestrations - transcellular pores with diameters in the range of 50-300 nm - typically grouped together in sieve plates. Aging and several liver disorders severely reduce LSEC porosity, decreasing their filtration properties. Over the years, a variety of drugs, stimulants, and toxins have been investigated in the context of altered diameter or frequency of fenestrations. In fact, any change in the porosity, connected with the change in number and/or size of fenestrations is reflected in the overall liver-vascular system crosstalk. Recently, several commonly used medicines have been proposed to have a beneficial effect on LSEC re-fenestration in aging. These findings may be important for the aging populations of the world. In this review we collate the literature on medicines, recreational drugs, hormones and laboratory tools (including toxins) where the effect LSEC morphology was quantitatively analyzed. Moreover, different experimental models of liver pathology are discussed in the context of fenestrations. The second part of this review covers the cellular mechanisms of action to enable physicians and researchers to predict the effect of newly developed drugs on LSEC porosity. To achieve this, we discuss four existing hypotheses of regulation of fenestrations. Finally, we provide a summary of the cellular mechanisms which are demonstrated to tune the porosity of LSEC.

Risk Factors Associated with Intubation and Readmissions in patients with Angioedema: A Single Center Experience

BACKGROUND

Given the heterogeneity of etiologies, pathophysiology and presentation of angioedema, variations in clinical outcomes, such as intubation and hospital readmissions, need further clarification.

OBJECTIVE

To determine factors associated with intubation and hospital readmissions in patients with angioedema.

METHODS

Retrospective study of patients evaluated with a diagnosis of angioedema over a 6year period. Demographic and clinical data such as medication use, family history, comorbidities, and symptoms were recorded. Multivariable logistic regression was used to analyze factors associated with intubation, while Cox regression was used to analyze readmissions.

RESULTS

From 636 patients, the most common etiology of angioedema was angiotensin converting enzyme inhibitor (ACEI) induced at 58%. The overall mortality was 0.5%. After adjusting for gender, race, comorbidities, and type of angioedema, smoking (OR=1.79, 95% CI=1.10-2.93, p=0.02), calcium channel blocker (CCB) therapy (OR=1.91, 95% CI=1.18-3.10, p=0.009), histaminergic symptoms (OR=3.21, 95% CI=1.93-5.33, p<0.001) and age (OR=1.02, 95% CI=1.00-1.04, p=0.023) were independently associated with increased odds of intubation. Involvement of either the pharynx, larynx or tongue was associated with higher odds of intubation (OR=20.96, 95% CI=10.63-41.33, p<0.001). 10% of patients had a readmission for angioedema within 90 days and 75% occurred within 30 days. After Multivariable Cox Regression analysis, only COPD/asthma (OR=2.13, 95% CI=1.12-4.07, p=0.022) and ACEI related angioedema (OR=2.93, 95% CI=1.33-6.47, p=0.008) were significantly associated with readmissions.

CONCLUSION

Smoking, CCB use, histaminergic symptoms, age, and upper airway involvement were significantly associated with intubation. Presence of COPD/asthma and ACEI related angioedema were independently associated with increased odds of readmission.

Vasopressin for persistent hypotension due to amlodipine and olmesartan overdose: A case report

Background

While there are consensus recommendations for managing calcium channel blocker (CCB) toxicity, reports on angiotensin II receptor blocker (ARB) toxicity and management are limited. Herein, we report a case of catecholamine-refractory hypotension due to CCB and ARB overdose.

Case presentation

A 54-year-old woman with underlying hypertension was brought to the emergency department after she attempted suicide by ingesting 345 mg of amlodipine, a CCB, and 340 mg of olmesartan, an ARB. She was hypotensive, which was considered vasodilatory because of high cardiac and low systemic vascular resistance indices. Hypotension persisted despite the administration of norepinephrine and epinephrine. Intravenous calcium gluconate, glucagon, and high-dose insulin euglycemia therapy, which were initiated because CCB toxicity was suspected, failed to raise her blood pressure. The presence of normal anion-gap metabolic acidosis and the fact that the patient remained hypotensive suggested that the hypotension might have been due to the effect of ARB. Vasopressin was finally administered, which improved her hemodynamic status. She was weaned off all vasopressors on day 3.

Discussion

There is no consensus recommendation for ARB toxicity. Since chronic use of ARBs at conventional doses can block the sympathetic nervous and renin–angiotensin systems, catecholamines may not effectively increase blood pressure in cases of hypotension due to ARB overdose, for which vasopressin could be indicated.

Conclusions

Vasopressin could be an option for treating hypotension secondary to ARB and CCB toxicity when catecholamines and treatment for CCB toxicity fail.

•

Chronic use of ARBs blocks the sympathetic nervous and renin–angiotensin systems.

•

There is no consensus recommendation for angiotensin II receptor blocker (ARB) toxicity.

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Catecholamines may not effectively raise blood pressure in hypotension due to ARB toxicity.

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Vasopressin could be an option for treating hypotension secondary to ARB toxicity.

Angiotensin axis antagonists increase the incidence of haemodynamic instability in dihydropyridine calcium channel blocker poisoning

CONTEXT

Amlodipine, a dihydropyridine calcium channel blocker (CCB), is the leading cause of cardiovascular drug-related overdose deaths in the USA. In contrast, angiotensin-II receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs) cause minimal toxicity in overdose. ACEIs/ARBs are often combined with dihydropyridines in hypertension treatment. Co-ingested ARBs/ACEIs may significantly contribute to the toxicity of dihydropyridine, but this has not been investigated.

OBJECTIVE

To investigate the clinical outcomes from dihydropyridine overdoses with ARBs/ACEIs versus dihydropyridine overdoses alone.

METHODS

This was a retrospective study of patients reported to the New South Wales Poisons Information Centre (NSW PIC) and 3 toxicology units (Jan 2016 to Jun 2019) in Australia. Patients >14 years who took an overdose of dihydropyridines (amlodipine, felodipine, lercanidipine, nifedipine) were included. Concurrent overdoses with non-dihydropyridine CCBs, alpha-blockers and beta-blockers were excluded. Patient demographics, drugs exposure details, serial vital signs, treatments and outcome were collected.

RESULTS

There were 100 patients. 68 took mixed overdoses of dihydropyridines with ARBs/ACEIs and 32 took single overdoses of dihydropyridines without ARBs/ACEIs. The mixed group had lower median nadir mean arterial pressures (62 vs 75 mmHg, p < 0.001), more frequently had hypotension (OR 4.5, 95%CI: 1.7-11.9) or bradycardia (OR 8.8, 95%CI: 1.1-70). Multivariable analysis indicated the mixed overdoses had an 11.5 mmHg (95%CI: 4.9-18.1) lower minimum systolic blood pressure (SBP) compared with the single group; other factors associated with a lower minimum SBP were higher doses [2.3 mmHg (95%CI: 1.1-3.5) lower per 10 defined daily doses] and younger age [2.2 mmHg (95%CI: 0.3-4.2) higher per decade]. A larger proportion of the mixed ingestion group received intravenous fluids (OR 5.7, 95%CI: 1.8-18.6) and antidotes and/or vasopressors (OR 2.9, 95%CI: 1.004-8.6).

CONCLUSION

Combined overdoses of dihydropyridines with ARBs/ACEIs caused more significant hypotension and required more haemodynamic support than overdoses of dihydropyridines alone.

Amlodipine Improves Vessel Function and Remodeling in the Lewis Polycystic Kidney Rat Mesenteric Artery

BACKGROUND

Hypertension is a common comorbidity associated with chronic kidney disease (CKD). Treatment in these patients often involves L-type Ca2+ channel (LTCC) blockers. The effect of chronic LTCC-blockade treatment on resistance vasculature was investigated in a genetic hypertensive rat model of CKD, the Lewis Polycystic Kidney (LPK) rat.

METHODS

Mixed-sex LPK and Lewis control rats (total n = 38) were allocated to treated (amlodipine 20 mg/kg/day p.o. from 4 to 18 weeks) and vehicle groups. Following systolic blood pressure and renal function assessment, animals were euthanized and mesenteric vasculature was collected for functional and structural assessment using pressure myography and histology.

RESULTS

Amlodipine treatment reduced LPK rat blood pressure (untreated vs. treated: 185 ± 5 vs. 165 ± 9 mm Hg; P = 0.019), reduced plasma creatinine (untreated vs. treated: 197 ± 17 vs. 140 ± 16 µmol/l; P = 0.002), and improved some vascular structural parameters (internal and external diameters and wall-lumen ratios); however wall thickness was still increased in LPK relative to Lewis despite treatment (Lewis vs. LPK: 31 ± 2 vs. 41 ± 2 µm, P = 0.047). Treatment improved LPK rats' endothelium dysfunction, and nitric oxide-dependent and endothelium-derived hyperpolarization vasorelaxation components, and downregulated prostanoid contributions. LTCC blockade had no effect on biomechanical properties of compliance and intrinsic stiffness, nor artery wall composition.

CONCLUSIONS

Our results indicate that blockade of LTCCs with amlodipine is effective in improving, to a certain extent, detrimental structural and functional vascular features of resistance arteries in CKD.

Manipulating fenestrations in young and old liver sinusoidal endothelial cells

Fenestrations are pores within liver sinusoidal endothelial cells (LSECs) that enable the transfer of substrates (particularly insulin and lipoproteins) between blood and hepatocytes. With increasing age, there are marked reductions in fenestrations, referred to as pseudocapillarization. Currently, fenestrations are thought to be regulated by vascular endothelial growth factor and nitric oxide (NO) pathways promoting remodeling of the actin cytoskeleton and cell membrane lipid rafts. We investigated the effects of drugs that act on these pathways on fenestrations in old (18-24 mo) and young mice (3-4 mo). Isolated LSECs were incubated with either cytochalasin 7-ketocholesterol, sildenafil, amlodipine, simvastatin, 2, 5-dimethoxy-4-iodoamphetamine (DOI), bosentan, TNF-related apoptosis-inducing ligand (TRAIL) or nicotinamide mononucleotide (NMN). LSECs were visualized under scanning electron microscopy to quantify fenestration porosity, diameter, and frequency, as well as direct stochastic optical reconstruction microscopy to examine actin and NO synthase. In young and old LSECs, fenestration porosity, diameter and frequency were increased by 7-ketocholesterol, while porosity and/or frequency were increased with NMN, sildenafil, amlodipine, TRAIL, and cytochalasin D. In old mice only, bosentan and DOI increased fenestration porosity and/or frequency. Modification of the actin cytoskeleton was observed with all agents that increased fenestrations, while NO synthase was only increased by sildenafil, amlodipine, and TRAIL. In conclusion, agents that target NO, actin, or lipid rafts promote changes in fenestrations in mice LSECs. Regulation of fenestrations occurs via both NO-dependent and independent pathways. This work indicates that age-related defenestration can be reversed pharmacologically, which has potential translational relevance for dyslipidemia and insulin resistance. NEW & NOTEWORTHY We demonstrate the effects of multiple nitric oxide-dependent and -independent pharmaceutical agents on fenestrations of the liver sinusoidal endothelium. Fenestrations are reorganized in response to nicotinamide mononucleotide, sildenafil, amlodipine, and TNF-related apoptosis-inducing ligand. This work indicates that age-related defenestration can be reversed pharmacologically, which has potential translational relevance for dyslipidemia and insulin resistance in old age.

Vasoplegic Shock Treated with Methylene Blue Complicated by Severe Serotonin Syndrome

INTRODUCTION

Management of severe vasoplegic shock in overdose can be very challenging. We describe a case of severe refractory vasodilatory shock in poisoning where methylene blue (MB) was used with success. However, the patient subsequently developed severe Serotonin Syndrome (SS) as a result of an interaction between serotonergic drugs and MB.

CASE REPORT

A 15-year-old male developed severe vasoplegic shock 1.5 hours after overdosing on several different medications including quetiapine slow release, quetiapine immediate release, desvenlafaxine slow release, venlafaxine, amlodipine, ramipril, fluoxetine, promethazine and lithium. His vasoplegic shock was resistant to high doses of noradrenaline and vasopressin. MB was administered 6.5 hours post ingestion and within 1 hour there was an improvement in his hemodynamic status and reduction of catecholamine requirements. Twelve hours post ingestion, he developed severe Serotonin Syndrome that lasted 5 days as a result of interaction between MB, a reversible monoamine oxidase inhibitor (MAO-I), and the antidepressants taken in overdose. MB had a calculated half-life of 38 hours.

CONCLUSION

MB is a useful additional strategy for severe drug induced vasodilatory shock and may be potentially life-saving. Clinicians should be aware that it can interact with other drugs and cause life-threatening Serotonin Syndrome. Lower doses or shorter durations may be wise in patients at risk of this interaction.

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.

Amlodipine Ameliorates Ischemia-Induced Neovascularization in Diabetic Rats through Endothelial Progenitor Cell Mobilization

Objectives. We investigated whether amlodipine could improve angiogenic responses in a diabetic rat model of acute myocardial infarction (AMI) through improving bone marrow endothelial progenitor cell (EPC) mobilization, in the same way as angiotensin converting enzyme inhibitors. Methods. After induction of AMI by coronary artery ligation, diabetic rats were randomly assigned to receive perindopril (2 mgkg⁻¹ day⁻¹), amlodipine (2.5 mgkg⁻¹ day⁻¹), or vehicle by gavage (n = 20 per group). Circulating EPC counts before ligation and on days 1, 3, 5, 7, 14, and 28 after AMI were measured in each group. Microvessel density, cardiac function, and cardiac remodeling were assessed 4 weeks after treatment. The signaling pathway related to EPC mobilization was also measured. Results. Circulating EPC count in amlodipine- and perindopril-treated rats peaked at day 7, to an obvious higher level than the control group peak which was reached earlier (at day 5). Rats treated with amlodipine showed improved postischemia neovascularization and cardiac function, together with reduced cardiac remodeling, decreased interstitial fibrosis, and cardiomyocyte apoptosis. Amlodipine treatment also increased cardiac SDF-1/CXCR4 expression and gave rise to activation of VEGF/Akt/eNOS signaling in bone marrow. Conclusions. Amlodipine promotes neovascularization by improving EPC mobilization from bone marrow in diabetic rats after AMI, and activation of VEGF/Akt/eNOS signaling may in part contribute to this.

Nifedipine attenuation of abdominal aortic aneurysm in hypertensive and non-hypertensive mice: Mechanisms and implications

Rupture of abdominal aortic aneurysm (AAA) is a lethal event. No oral medicine has been available to prevent or treat AAA. We have recently identified a novel mechanism of eNOS uncoupling by which AAA develops, in angiotensin II (Ang II) infused hyperphenylalaninemia 1 (hph-1) mice. Using this unique model we investigated effects on AAA formation of the L-type calcium channel blocker nifedipine, in view of the unclear relationship between hypertension and AAA, and unclear mechanisms of aneurysm protective effects of some blood pressure lowering drugs. Six-month old hph-1 mice were infused with Ang II (0.7 mg/kg/day) for 2 weeks, and fed nifedipine chow at two different doses (5 and 20 mg/kg/day). While the high dose of nifedipine reduced blood pressure, the lower dose had no effect. Interestingly, the incidence rate of AAA dropped from 71% to 7 and 12.5% for low and high dose nifedipine, respectively. Expansion of abdominal aorta, determined by ultrasound imaging, was abolished by both doses of nifedipine, which recoupled eNOS completely to improve NO bioavailability. Both also abrogated aortic superoxide production. Of note, Ang II activation of NADPH oxidase in vascular smooth muscle cells and endothelial cells, known to uncouple eNOS, was also attenuated by nifedipine. Although low dose was a sub-pressor while the high dose reduced blood pressure via inhibition of calcium channels, both doses were highly effective in preventing AAA by preserving eNOS coupling activity to eliminate sustained oxidative stress from uncoupled eNOS. These data demonstrate that oral treatment of nifedipine is highly effective in preserving eNOS function to attenuate AAA formation. Nifedipine may be used for AAA prevention either at low dose in AAA risk group, or at high dose in patients with co-existing hypertension.

Efficacy of methylene blue in an experimental model of calcium channel blocker-induced shock

STUDY OBJECTIVE

Calcium channel blocker poisonings account for a substantial number of reported deaths from cardiovascular drugs. Although supportive care is the mainstay of treatment, experimental therapies such as high-dose insulin-euglycemia and lipid emulsion have been studied in animal models and used in humans. In the most severe cases, even aggressive care is inadequate and deaths occur. In both experimental models and clinical cases of vasodilatory shock, methylene blue improves hemodynamic measures. It acts as a nitric oxide scavenger and inhibits guanylate cyclase that is responsible for the production of cyclic guanosine monophosphate (cGMP). Excessive cGMP production is associated with refractory vasodilatory shock in sepsis and anaphylaxis. The aim of this study is to determine the efficacy of methylene blue in an animal model of amlodipine-induced shock.

METHODS

Sprague-Dawley rats were anesthetized, ventilated, and instrumented for continuous blood pressure and pulse rate monitoring. The dose of amlodipine that produced death within 60 minutes was 17 mg/kg per hour (LD50). Rats were divided into 2 groups: amlodipine followed by methylene blue or amlodipine followed by normal saline solution, with 15 rats in each group. Rats received methylene blue at 2 mg/kg during 5 minutes or an equivalent amount of normal saline solution in 3 intervals from the start of the protocol: minutes 5, 30, and 60. The animals were observed for a total of 2 hours after the start of the protocol. Mortality risk and survival time were analyzed with Fisher's exact test and Kaplan-Meier survival analysis with the log rank test.

RESULTS

Overall, 1 of 15 rats (7%) in the saline solution-treated group survived to 120 minutes compared with 5 of 15 (33%) in the methylene blue-treated group (difference -26%; 95% confidence interval [CI] -54% to 0.3%). The median survival time for the normal saline solution group was 42 minutes (95% CI 28.1 to 55.9 minutes); for the methylene blue group, 109 minutes (95% CI 93.9 to 124.1 minutes). Pulse rate and mean arterial pressure (MAP) differences between groups were analyzed until 60 minutes. Pulse rate was significantly higher in the methylene blue-treated group beginning 25 minutes after the start of the amlodipine infusion (95% CI 30 to 113 minutes) that was analyzed until 60 minutes. MAP was significantly higher in the methylene blue-treated group starting 25 minutes after the amlodipine infusion (95% CI 2 to 30 minutes) that was analyzed until 60 minutes.

CONCLUSION

Methylene blue did not result in a significant difference in mortality risk. There was an increased pulse rate, MAP, and median survival time in the methylene blue group.

Methylene blue for distributive shock: a potential new use of an old antidote

Methylene blue is used primarily in the treatment of patients with methemoglobinemia. Most recently, methylene blue has been used as a treatment for refractory distributive shock from a variety of causes such as sepsis and anaphylaxis. Many studies suggest that the nitric oxide-cyclic guanosine monophosphate (NO-cGMP) pathway plays a significant role in the pathophysiology of distributive shock. There are some experimental and clinical experiences with the use of methylene blue as a selective inhibitor of the NO-cGMP pathway. Methylene blue may play a role in the treatment of distributive shock when standard treatment fails.

Comparison of high-definition oscillometry -- a non-invasive technology for arterial blood pressure measurement -- with a direct invasive method using radio-telemetry in awake healthy cats

This study compared indirect blood pressure measurements using a non-invasive method, high-definition oscillometry (HDO), with direct measurements using a radio-telemetry device in awake cats. Paired measurements partitioned to five sub-ranges were collected in six cats using both methods. The results were analysed for assessment of correlation and agreement between the two methods, taking into account all pressure ranges, and with data separated in three sub-groups, low, normal and high ranges of systolic (SBP) and diastolic (DBP) blood pressure. SBP data displayed a mean correlation coefficient of 0.92 ± 0.02 that was reduced for low SBP. The agreement level evaluated from the whole data set was high and slightly reduced for low SBP values. The mean correlation coefficient of DBP was lower than for SBP (ie, 0.81 ± 0.02). The bias for DBP between the two methods was 22.3 ± 1.6 mmHg, suggesting that HDO produced lower values than telemetry. These results suggest that HDO met the validation criteria defined by the American College of Veterinary Internal Medicine consensus panel and provided a faithful measurement of SBP in conscious cats. For DBP, results suggest that HDO tended to underestimate DBP. This finding is clearly inconsistent with the good agreement reported in dogs, but is similar to outcomes achieved in marmosets and cynomolgus monkeys, suggesting that this is not related to HDO but is species related. The data support that the HDO is the first and only validated non-invasive blood pressure device and, as such, it is the only non-invasive reference technique that should be used in future validation studies.

Aliskiren and amlodipine in the management of essential hypertension: meta-analysis of randomized controlled trials

Background

Aliskiren is a novel renin-angiotensin aldosterone system (RAAS) inhibitor, the combination therapy of aliskiren and amlodipine for blood pressure control have been reported recently. The primary objective of this analysis is to review recently reported randomized controlled trials (RCTs) to compare antihypertensive effects and adverse events between mono (amlodipine or aliskiren alone) and combination therapy of both medicines.

Methods

Databases for the search included Pubmed, Embase and the Cochrane Central Register of Controlled Trials. Revman v5.0 statistical program was used to analyze the data. Weighted mean differences (WMD) with a 95% confidence interval (CI) were used for the calculation of continuous data, and relative risk (RR) with a 95% CI was used for dichotomous data.

Results

We analyzed the data from 7 RCTs for a total of 6074 participants in this meta-analysis. We found that the aliskiren/amlodipine combination therapy had a stronger effect in lowering blood pressure as compared with the monotherapy using aliskiren (SBP: WMD = −10.42, 95% CI −13.03∼−7.82, P<0.00001; DBP: WMD = −6.60, 95% CI −7.22∼−5.97, P<0.00001) or amlodipine (SBP: WMD = −4.85, 95% CI −6.88∼−2.81, P<0.00001; DBP: WMD = −2.91, 95% CI −3.85∼−1.97, P<0.00001). No differences were found in terms of adverse events between combination therapy and monotherapy, except for the rates of peripheral edema and hypokalaemia which were significantly lower in the combination therapy than in the amlodipine monotherapy (RR = 0.78, 0.66∼0.92, P = 0.004; RR = 0.51, 0.27∼0.97, P = 0.04). Similar antihypertensive effects were found in both obese (body mass index > = 30 kg/m²) hypertensive and non-obese (body mass index <30 kg/m²) hypertensive patients. Moreover, there was no difference with the blood pressure lowering or adverse effects with regards to the combination therapy in both subgroups.

Conclusion

We found that aliskiren/amlodipine combination therapy provided a more effective blood pressure reduction than monotherapy with either drug without increase in the occurrence of adverse events.

Modern views on amlodipine and new S-amlodipine medications

The review presents the latest evidence on the calcium antagonist amlodipine, summarizing its mechanisms of action, its pleiotropic, endothelial function-related effects, and its anti-atherogenic activity. Amlodipine suppresses the proliferation of vascular smooth myocytes and extracellular matrix and improves endothelial vasodilatation, despite the absence of L-type calcium channels in these cells. This mechanism is related to an increase in endothelial nitric oxide (NO) release. The results of experimental studies on the role of S and R amlodipine isomers in its hemodynamic and pleiotropic activity are presented. While S-amlodipine is a pharmacologically active blocker of L-type calcium channels, R-amlodipine increases endothelial NO release. New medications have been developed, based on S-amlodipine. It has been shown that S-amlodipine 5 mg/d is bioequivalent to amlodipine 10 mg/d. The pharmacodynamics analysis demonstrated that S-amlodipine 5 mg/d and amlodipine 10 mg/d did not differ significantly in terms of mean levels of systolic and diastolic blood pressure, or mean heart rate. S-amlodipine was better tolerated and characterised by a lower incidence of peripheral edema than amlodipine. However, the effects of S-amlodipine on hard end-points should be investigated in the long-term prospective studies.

Methylene blue in the treatment of refractory shock from an amlodipine overdose

Amlodipine is a potent vasodilator with a long half-life and delayed onset of action that is particularly concerning after an overdose. Vasodilation occurs through stimulation of nitric oxide release with increased cyclic guanosine monophosphate (cGMP) production. Methylene blue inhibits guanylate cyclase. This enzyme is responsible for the production of cGMP. Methylene blue also has the ability to scavenge nitric oxide, as well as inhibit nitric oxide synthase. We report the use of methylene blue for refractory shock in a patient with amlodipine toxicity.

Effect of the two new calcium channel blockers mebudipine and dibudipine in comparison to amlodipine on vascular flow of isolated kidney of diabetic rat

Calcium channel blockers are clinically useful vasodilators, used widely in the treatment of hypertension. These agents are reported to preserve or improve renal function in patients with essential hypertensive renal disease or diabetic renal disease. Among the classes of calcium channel blockers, dihydropyridine derivatives are widely used because of their potent vasodilating activity and weak cardiodepressant action. Mebudipine and dibudipine are two new 1,4-dihydropyridine calcium channel blockers that recently have been synthesized. In previous research mebudipine and dibudipine showed considerable relaxant effects on vascular and ileal smooth muscle cells. In this study we investigated the effects of these new drugs on vascular flow of isolated kidney of diabetic rat and compare their potencies to amlodipine. It is concluded that mebudipine and dibudipine (1-10 μM) are at least as potent as amlodipine in inhibiting PE-induced perfusion pressure in isolated kidney of diabetic rats. These new dihydropyridines improve kidney perfusion of diabetic rat in the setting of PE infusion. Similarly, amlodipine.

Long-term safety, tolerability and efficacy of combination therapy with aliskiren and amlodipine in patients with hypertension

OBJECTIVE

Most patients with hypertension require antihypertensive combination therapy to achieve BP control. This study investigated the safety and efficacy of the direct renin inhibitor aliskiren combined with the calcium channel blocker amlodipine.

METHODS

Overall, 556 patients with hypertension (msDBP > or =95-<110 mmHg) received open-label aliskiren/amlodipine 150/5 mg for 2 weeks, followed by forced titration to aliskiren/amlodipine 300/10 mg for 52 weeks. Add-on hydrochlorothiazide (HCT) was permitted from week 10 to achieve BP control (<140/90 mmHg). The primary objective of the study was to evaluate the long-term safety and tolerability of aliskiren/amlodipine combination therapy; the BP-lowering efficacy of the combination was also assessed (week 54 endpoint; last observation carried forward).

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT00402103.

RESULTS

In total, 452 patients completed 54 weeks' treatment with aliskiren/amlodipine 300/10 mg, with or without add-on HCT. The most frequently reported adverse events (AEs) were peripheral edema, upper respiratory tract infection, headache and bronchitis. Peripheral edema (the most common AE), occurred in 22.7% of treated patients, and was generally mild or moderate in intensity and transient in nature. Few patients exhibited laboratory abnormalities. Aliskiren/amlodipine combination therapy provided a mean BP reduction from baseline to week 54 of 24.2/15.5 mmHg; 74.3% of patients achieved BP control. In the subgroup of patients with stage 2 hypertension (baseline msSBP > or =160 mmHg and/or msDBP > or =100 mmHg), the mean BP reduction at week 54 was 29.1/17.1 mmHg, and 67.0% of patients achieved BP control.

CONCLUSION

In this open-label study, aliskiren/amlodipine 300/10 mg combination therapy, with or without add-on HCT, effectively reduced BP, particularly in patients with stage 2 hypertension. The most common AE was peripheral edema, consistent with the known AE profile of high-dose (10 mg) amlodipine. Further studies comparing the aliskiren/amlodipine combination with the component monotherapies and other antihypertensive combinations are warranted.

Cardioprotective effect of benidipine on cardiac performance and remodeling in failing rat hearts

BACKGROUND

We have known that endothelial nitric-oxide synthase (eNOS) and oxidative stress may play a key role in cardiac performance in failing rat hearts. However, the interactions between eNOS or oxidative stress and bradykinin (BK) under treatment of calcium channel blockers (CCBs) remain unknown. To elucidate the mechanism underlying the cardioprotective effect of long-acting dihydropyridine CCBs, we evaluated the effect of benidipine on the BK-eNOS and NAD(P)H oxidase pathway in Dahl salt-sensitive (DS) rats with heart failure.

METHODS

11-week-old DS rats were treated with one of the following drug combinations for 7 weeks until the onset of the failing stage: vehicle, BK B2 receptor antagonist (FR172357 (FR)) alone, hydralazine, benidipine, and benidipine plus FR. The left ventricular end-systolic pressure-volume relationship (ESPVR) (contractility: Ees) was evaluated using a conductance catheter.

RESULTS

Downregulated Ees and per cent of fractional shortening (%FS) assessed by echocardiography and eNOS expression in the failing stage were both significantly increased by using benidipine; this result was not found, however, when using FR alone or hydralazine or benidipine plus FR. Upregulated expression of NAD(P)H oxidase p22phox and p47phox and lectin-like oxidized low-density lipoprotein receptor-1, and downregulated superoxide dismutase-1 (SOD-1) were significantly ameliorated by benidipine, but not by FR alone or by hydralazine or benidipine plus FR. Benidipine effectively inhibited vascular lesion formation and suppressed atrial natriuretic peptide (ANP) and transforming growth factor-beta1 (TGF-beta1), but this was not the case when using FR alone or hydralazine or benidipine plus FR.

CONCLUSIONS

These results suggest that benidipine may be useful for cardioprotective agents in preventing the cardiac dysfunction and remodeling associated with the BK-eNOS and oxidative stress pathway.

Alteration of nitric oxide production in rats exposed to a prolonged, extremely low-frequency magnetic field

The purpose of this study is to investigate the possible effect of an extremely low-frequency magnetic field (ELF-MF) on nitric oxide (NO) level. In this study, 27 male Sprague-Dawley rats were used. The rats were divided into three groups: two experimental and one control (sham-exposed). The first and second experimental group (n = 10) were exposed to 100 microT and 500 microT ELF-MF during 10 months, 2 h a day, respectively, and the third (n = 7) group was treated like an experimental group except for ELF-MF exposure in methacrylate boxes. After ELF-MF and sham exposure, serum nitrite levels were measured by Griess reaction. A significant reduction was observed in nitrite levels among the first and second experimental groups of rats and sham-exposed rats after exposure for 10 months, 2 h a day, to ELF-MF of 100 and 500 microT (p < 0.01). These results suggest that prolonged ELF-MF exposure at intensities of exposure limits, determined by ICNIRP for public and occupational, may reduce NO production probably affected by NO generation pathways.

Functional interaction of neuronal Cav1.3 L-type calcium channel with ryanodine receptor type 2 in the rat hippocampus

Neuronal L-type Ca(2+) channels do not support synaptic transmission, but they play an essential role in synaptic activity-dependent gene expression. Ca(v)1.2 and Ca(v)1.3 are the two most widely expressed L-type Ca(2+) channels in neurons and have different biophysical and subcellular distributions. The function of the Ca(v) 1.3 L-type Ca(2+) channel and its cellular mechanisms in the central nervous system are poorly understood. In this study, using a yeast two-hybrid assay, we found that the N terminus of the rat Ca(v)1.3 alpha(1) subunit interacts with a partial N-terminal amino acid sequence of ryanodine receptor type 2 (RyR2). Reverse transcription-PCR and Western blot assays revealed high expression of both Ca(v)1.3 and RyR2 in the rat hippocampus. We also demonstrate a physical association of Ca(v)1.3 with RyR2 using co-immunoprecipitation assays. Moreover, immunocytochemistry revealed prominent co-localization between Ca(v)1.3 and RyR2 in hippocampal neurons. Depolarizing cells by an acute treatment of a high concentration of KCl (high-K, 60 mm) showed that the activation of L-type Ca(2+) channels induced RyR opening and led to RyR-dependent Ca(2+) release, even in the absence of extracellular Ca(2+). Furthermore, we found that RyR2 mRNA itself is increased by long term treatment of high-K via activation of L-type Ca(2+) channels. These acute and long term effects of high-K on RyRs were selectively blocked by small interfering RNA-mediated silencing of Ca(v)1.3. These results suggest a physical and functional interaction between Ca(v)1.3 and RyR2 and important implications of Ca(v)1.3/RyR2 clusters in translating synaptic activity into alterations in gene expression.

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.

Coronary Blood Flow Responses are Impaired Independent of NO and Endothelial Function in Conscious Dogs with Dilated Cardiomyopathy

BACKGROUND

Dilated cardiomyopathy (DCM) is characterized by nitric oxide (NO) deficiency and endothelial dysfunction. Whether endothelium-independent vasodilation is preserved, particularly in the coronary circulation, remains controversial.

METHODS AND RESULTS

We studied systemic and coronary flow responses to the endothelium-dependent agonist, acetylcholine, the cGMP-dependent NO-donor, nitroglycerin, the predominantly endothelium-independent agonist, adenosine, the beta-adrenergic cAMP-dependent agonist, isoproterenol, and the calcium channel antagonist, nicardipine, in conscious dogs with pacing-induced DCM. Systemic blood flow response was impaired to acetylcholine but preserved to other vasodilators in DCM. In contrast, coronary blood flow response was significantly ( P < .05) depressed to all agonists. (Peak coronary blood flow response, control versus DCM: acetylcholine: 221 +/- 14% versus 156 +/- 11%; nitroglycerin: 220 +/- 17% versus 138 +/- 9%; adenosine: 635 +/- 65% versus 376 +/- 56%; nicardipine: 338 +/- 59% versus 115 +/- 23%; isoproterenol: 219 +/- 18% versus 86 +/- 20%). The attenuation was independent of systemic hemodynamic differences.

CONCLUSION

In contrast to systemic responses, coronary blood flow responses in DCM are impaired dependent or independent of NO or second messenger mechanisms, implying either distal signaling defects or structural abnormalities in the coronary vasculature.

Decreased plasma levels of nitric oxide metabolites, angiotensin II, and aldosterone in spontaneously hypertensive rats exposed to 5 mT static magnetic field

Previously, we found that whole body exposure to static magnetic fields (SMF) at 10 mT (B(max)) and 25 mT (B(max)) for 2-9 weeks suppressed and delayed blood pressure (BP) elevation in young, stroke resistant, spontaneously hypertensive rats (SHR). In this study, we investigated the interrelated antipressor effects of lower field strengths and nitric oxide (NO) metabolites (NO(x) = NO(2)(-) + NO(3)(-)) in SHR. Seven-week-old male rats were exposed to two different ranges of SMF intensity, 0.3-1.0 mT or 1.5-5.0 mT, for 12 weeks. Three experimental groups of 20 animals each were examined: (1) no exposure with intraperitoneal (ip) saline injection (sham-exposed control); (2) 1 mT SMF exposure with ip saline injection (1 mT); (3) 5 mT SMF exposure with ip saline injection (5 mT). Arterial BP, heart rate (HR), skin blood flow (SBF), plasma NO metabolites (NO(x)), and plasma catecholamine levels were monitored. SMF at 5 mT, but not 1 mT, significantly suppressed and retarded the early stage development of hypertension for several weeks, compared with the age matched, unexposed (sham exposed) control. Exposure to 5 mT resulted in reduced plasma NO(x) concentrations together with lower levels of angiotensin II and aldosterone in SHR. These results suggest that SMF may suppress and delay BP elevation via the NO pathways and hormonal regulatory systems.

Implication of steady state concentrations of nitrite and nitrate metabolites of nitric oxide in plasma and whole blood in healthy human subjects

1. The aim of the present study was to determine whether the steady state NOx concentration reflects NOx formation in vivo. 2. A NO3- load study was performed after achieving NOx steady state. Chronological changes in NOx concentrations in plasma and whole blood samples from nine healthy subjects were determined by the HPLC-Griess system and NOx concentrations in erythrocytes were estimated as a possible NOx compartment influential in regulating plasma NOx concentrations. 3. Analysis was performed using the first-order one-compartment open model and the NOx formation rate was subsequently calculated. 4. The mean (+/-SEM) steady state NOx concentration of plasma (15.5 +/- 1.6 micromol/L), whole blood (12.8 +/- 1.2 micromol/L) and erythrocytes (11.9 +/- 0.7 micromol/L) did not correlate with the NOx formation rate in the compartments (0.50 +/- 0.05, 0.61 +/- 0.04 and 0.91 +/- 0.17 micromol/kg per h, respectively), whereas a significant correlation was found between the steady state NOx concentration and NOx elimination rate (Kel) in plasma (r=-0.69; P=0.04) and whole blood (r=-0.79; P=0.01). 5. Although there was no direct correlation between steady state NOx concentrations and serum creatinine levels, the correlation between half-life and serum creatinine levels was significant (plasma: r=0.60, P=0.02; whole blood: r=0.49, P=0.04). 6. Plasma NOx concentrations correlated significantly with erythrocyte NOx concentrations (r=0.92, P <0.01; erythrocyte NOx=0.66 x plasma NOx). 7. The results of the present study indicate that NOx does not accumulate excessively into erythrocytes at steady state and during a NO3- load and that the steady state NOx concentration in whole blood and plasma preferentially implies NOx elimination (mainly depending on renal function) rather than NOx formation.

Antitumor effects of amlodipine, a Ca 2+ channel blocker, on human epidermoid carcinoma A431 cells in vitro and in vivo

Amlodipine, a dihydropyridine Ca(2+) channel blocker, is reported to inhibit proliferation of human epidermoid carcinoma A431 cells, and specifically attenuates Ca(2+) responses evoked by thapsigargin, an inhibitor of endoplasmic reticulum Ca(2+)-ATPases. In this study, we further examined the possible mechanism of the antiproliferative action of amlodipine and its antitumor effect on A431 xenografts in nude mice. Amlodipine reduced BrdU incorporation into nucleic acids in serum-starved A431 cells, and the reduction was diminished by uridine 5'-triphosphate (UTP), a phospholipase C (PLC)-linked agonist. Fluorometric measurement of intracellular free Ca(2+) concentration revealed that amlodipine blunted the UTP-induced Ca(2+) release from the internal Ca(2+) stores and consequently Ca(2+) influx through Ca(2+)-permeable channels on the plasma membrane. Although amlodipine alone caused Ca(2+) release from thapsigargin-sensitive Ca(2+) stores, such an effect was not reproduced by other dihydropyridine Ca(2+) channel blockers, including nicardipine and nimodipine, despite their antiproliferative effects in the cells. Daily intraperitoneal administration of amlodipine (10 mg/kg) for 20 days into mice bearing A431 xenografts retarded tumor growth and prolonged the survival of mice. Our results suggest a potential antitumor action for amlodipine in vitro and in vivo, which may be in part mediated by inhibiting Ca(2+) influx evoked by the passive depletion of internal Ca(2+) stores and by PLC-linked agonist stimulation.

Novel Vascular Biology of Third-Generation L-Type Calcium Channel Antagonists

Calcium channel blockers (CCBs) were developed as vasodilators, and their use in cardiovascular disease treatment remains largely based on that mechanism of action. More recently, with the evolution of second- and third-generation CCBs, pleiotropic effects have been observed, and at least some of CCBs’ benefit is attributable to these mechanisms. Understanding these effects has contributed greatly to elucidating disease mechanisms and the rationale for CCB use. Furthermore, this knowledge might clarify why drugs are useful in some disease states, such as atherosclerosis, but not in others, such as heart failure. Although numerous drugs used in the treatment of vascular disease, including statins and angiotensin-converting–enzyme inhibitors, have well-described pleiotropic effects universally accepted to contribute to their benefit, little attention has been paid to CCBs’ potentially similar effects. Accumulating evidence that at least 1 CCB, amlodipine, has pharmacologic actions distinct from L-type calcium channel blockade prompted us to investigate the pleiotropic actions of amlodipine and CCBs in general. There are several areas of research; foci here are (1) the physicochemical properties of amlodipine and its interaction with cholesterol and oxidants; (2) the mechanism by which amlodipine regulates NO production and implications; and (3) amlodipine’s role in controlling smooth muscle cell proliferation and matrix formation.

Antiarrhythmic drug target choices and screening

Most antiarrhythmic drugs are ion channel blockers, and to date, those tested in large randomized placebo-controlled clinical trials have shown no decrease in mortality outcome. This apparent lack of survival benefit may result from the significant liabilities associated with these agents that offset any long-term benefit. Despite the current success of implantable defibrillators and the future promise of gene therapy, there is still a pressing need for new antiarrhythmic drugs. An improved understanding of cardiac ion channels and novel approaches to target selection and compound screening will provide new opportunities for drug discovery in the near future. Here, we briefly review the multiple mechanisms of arrhythmia, the history of drug failures, and the possibilities that evolving technologies may provide in the search for more efficacious and safer antiarrhythmic drugs.