Cellular action of nicardipine

In silico modelling of stroke volume, cardiac output and systemic vascular resistance in cardiovascular safety pharmacology studies by telemetry

The principle of proportionality of the systolic area of the central aortic pressure to stroke volume (SV) has been long known. The aim of the present work was to evaluate an in silico solution derived from this principle for modelling SV (iSV model) in cardiovascular safety pharmacology studies by telemetry. Blood pressure was measured in the abdominal aorta in accordance with standard practice. Central aortic pressure was modelled from the abdominal aortic pressure waveform using the N-point moving average (NPMA) method for beat-to-beat estimation of SV. First, the iSV was compared to the SV measured by ultrasonic flowmetry in the ascending aorta (uSV) after various pharmacological challenges in beagle dogs anaesthetised with etomidate/fentanyl. The iSV showed minimal bias (0.2 mL i.e. 2%) and excellent agreement with uSV. Then, previous telemetry studies including reference vasoactive and inotropic compounds were retrospectively reanalysed to model drug effects on stroke volume (iSV), cardiac output (iCO) and systemic vascular resistance (iSVR). Among them, the examples of nicardipine and isoprenaline highlight risks of erroneous or biased estimation of drug effects from the abdominal aortic pressure due to pulse pressure amplification. Furthermore, the examples of verapamil, quinidine and moxifloxacin show that iSV, iCO and iSVR are earlier biomarkers than blood pressure itself for predicting drug effect on blood pressure. This in silico modelling approach included in vivo telemetry safety pharmacology studies can be considered as a New Approach Methodology (NAM) that provides valuable additional information and contribute to improving non-clinical translational research to the clinic.

Repurposing the Dihydropyridine Calcium Channel Inhibitor Nicardipine as a Nav1.8 Inhibitor In Vivo for Pitt Hopkins Syndrome

PURPOSE

Individuals with the rare genetic disorder Pitt Hopkins Syndrome (PTHS) do not have sufficient expression of the transcription factor 4 (TCF4) which is located on chromosome 18. TCF4 is a basic helix-loop-helix E protein that is critical for the normal development of the nervous system and the brain in humans. PTHS patients lacking sufficient TCF4 frequently display gastrointestinal issues, intellectual disability and breathing problems. PTHS patients also commonly do not speak and display distinctive facial features and seizures. Recent research has proposed that decreased TCF4 expression can lead to the increased translation of the sodium channel Na_v1.8. This in turn results in increased after-hyperpolarization as well as altered firing properties. We have recently identified through a drug repurposing screen an FDA approved dihydropyridine calcium antagonist nicardipine used to treat angina, which inhibited Na_v1.8.

METHODS

We have now performed behavioral testing in groups of 10 male Tcf4(± ) PTHS mice dosing by oral gavage at 3 mg/kg once a day for 3 weeks using standard methods to assess sociability, nesting, fear conditioning, self-grooming, open field and test of force.

RESULTS

Nicardipine returned this spectrum of behavioral deficits in the Tcf4(± ) PTHS mouse model to WT levels and resulted in statistically significant results.

CONCLUSIONS

These in vivo results in the well characterized Tcf4(± ) PTHS mice may suggest the potential to test this already approved drug further in a clinical study with PTHS patients or suggest the potential for use off label under compassionate use with their physician.

Hemodynamic effects of intravenous nicardipine in severely pre-eclamptic women with a hypertensive crisis

OBJECTIVE

Nicardipine permits rapid control of blood pressure in women with severe pre-eclampsia (PE) and hypertensive crisis. Our objective was to investigate its maternal and fetal hemodynamic effects.

METHODS

Ten severely pre-eclamptic pregnant women who required intravenous nicardipine for severe hypertension were included in this prospective observational trial. Maternal macrocirculation was assessed by transthoracic echocardiography. Maternal microcirculatory perfusion was examined sublingually with the sidestream dark field imaging technique. Fetal hemodynamics were assessed by Doppler examinations of the uteroplacental and fetal circulations. Maternal cardiac output, total vascular resistance, mitral E/A ratio and capillary heterogeneity index, uterine artery pulsatility index and fetal cerebroplacental ratio were considered primary outcomes. Paired measurements, obtained before administration of nicardipine infusion and after stabilization of blood pressure, were compared.

RESULTS

Administration of nicardipine significantly reduced the mean arterial blood pressure (median difference, 26 mmHg; P = 0.002) and total vascular resistance (median difference, 791 dynes × s/cm(5) ; P = 0.002) in all included women. This induced a reflex tachycardia with consequent increase in cardiac output of 1.55 L/min (P  =  0.004). There were no significant changes in the other determinants of maternal or fetal hemodynamic parameters.

CONCLUSIONS

Nicardipine effectively reduces blood pressure through selective afterload reduction that triggers an increase in cardiac output, without affecting maternal diastolic function, or microcirculatory, uteroplacental or fetal perfusion. This hemodynamic response is uniform and predictable. Fetomaternal cardiovascular profiling can be achieved by combining transthoracic echocardiography with obstetric Doppler.

Effect of nicardipine prolonged-release implants on cerebral vasospasm and clinical outcome after severe aneurysmal subarachnoid hemorrhage: a prospective, randomized, double-blind phase IIa study

BACKGROUND AND PURPOSE

The purpose of this study was to investigate the effect of nicardipine prolonged-release implants (NPRIs) on cerebral vasospasm and clinical outcome after severe subarachnoid hemorrhage.

METHODS

Thirty-two patients with severe subarachnoid hemorrhage and undergoing aneurysm clipping were included into this single center, randomized, double-blind trial. Sixteen patients received NPRIs implanted into the basal cisterns in direct contact to the exposed proximal blood vessels; in 16 control patients, the basal cisterns were opened and washed out only without leaving implants. Angiography was performed preoperatively and at day 8+/-1. Computed tomography imaging was analyzed for the incidence of territorial infarcts unrelated to surgery. Patient outcome was assessed using the modified Rankin and National Institute of Health Stroke scales.

RESULTS

The incidence of angiographic vasospasm in proximal vessel segments was significantly reduced after implantation of NPRIs (73% control versus 7% NPRIs). Significant differences occurred also for the majority of distal vessel segments. Computed tomography scans revealed a lower incidence of delayed ischemic lesions (47% control versus 14% NPRIs). The NPRI group demonstrated more favorable modified Rankin and National Institute of Health Stroke scales as well as a significantly lower incidence of deaths (38% control versus 6% NPRIs).

CONCLUSIONS

Implantation of NPRIs reduces the incidence of cerebral vasospasm and delayed ischemic deficits and improves clinical outcome after severe subarachnoid hemorrhage.

Intravenous Nicardipine

Nicardipine is a water soluble calcium channel antagonist, with predominantly vasodilatory actions. Intravenous (IV) nicardipine (Cardene IV), which demonstrates a relatively rapid onset/offset of action, is used in situations requiring the rapid control of blood pressure (BP). IV nicardipine was as effective as IV nitroprusside in the short-term reduction of BP in patients with severe or postoperative hypertension. A potential role for IV nicardipine in the intraoperative acute control of BP in patients undergoing various surgical procedures (including cardiovascular, neurovascular and abdominal surgery), and in the deliberate induction of reduced BP in surgical procedures in which haemostasis may be difficult (e.g. surgery involving the hip or spine) was demonstrated in preliminary studies. Preliminary studies also indicated the ability of a bolus dose of IV nicardipine to attenuate the hypertensive response, but not the increase in tachycardia, after laryngoscopy and tracheal intubation in anaesthetised patients. In large, well designed studies, IV nicardipine prevented cerebral vasospasm in patients with recent aneurysmal subarachnoid haemorrhage; however, overall clinical outcomes at 3 months were similar to those in patients who received standard management. Small preliminary studies have investigated the use of IV nicardipine in a variety of other settings, including acute intracerebral haemorrhage, acute ischaemic stroke, pre-eclampsia, acute aortic dissection, premature labour and electroconvulsive therapy.In conclusion, the efficacy of IV nicardipine in the short-term treatment of hypertension in settings for which oral therapy is not feasible or not desirable is well established. The ability to titrate IV nicardipine to the tolerance levels of individual patients makes this agent an attractive option, especially in critically ill patients or those undergoing surgery. Potential exists for further investigation of the use of this agent in clinical settings where a vasodilatory agent with minimal inotropic effects is appropriate.

Effect of nicardipine on pulmonary hypertension after repair of congenital heart defects in early postoperative period

We examined the effect of nicardipine and hyperventilatin on pulmonary arterial pressure (PAP) in four patients with pulmonary hypertension in congenital heart defect especially in the early postoperative period. There was a significant positive correlation between the values of arterial carbon dioxide tension (PaCO2) and the ratio of mean PAP to mean systemic arterial pressure (Pp/Ps) in two patients whose Heath Edwards classification was Grade II; one of them also had 20% reduction of mean PAP by nicardipine without changing mean arterial pressure. In the remaining two patients showing no correlation between the values of PaCO2 and Pp/Ps, nicardipine did not reduce PAP. Although nicardipine reduced PAP without changing systemic arterial pressure in only one out of four patients, these results suggest that nicardipine may be a drug for control of PAP during weaning phase from the ventilator especially in patients whose PAP decreases under hyperventilation.

Inhibition of the Na(+)/H(+) exchanger delays the development of rapid pacing-induced atrial contractile dysfunction

BACKGROUND

Atrial mechanical stunning due to atrial fibrillation may persist after restoration of sinus rhythm. Although the mechanism of rapid rate-related contractile dysfunction remains unknown, ischemia, pH changes, and calcium overload have been postulated as potential mechanisms. We hypothesized that blockade of the Na(+)/H(+) exchanger (NHE) would alter atrial contractile dysfunction from rapid rates.

METHODS AND RESULTS

Twenty-three anesthetized dogs were studied and subjected to 5 hours of rapid right atrial pacing. Ten received an inhibitor of the NHE, 10 received saline, and 3 received nifedipine. All animals underwent placement of 2 sonomicrometers on the left atrium, transesophageal echocardiography, and invasive hemodynamic monitoring. All measurements were made in sinus rhythm. Except for baseline and postdrug measurements, reduction in left atrial fractional shortening was significantly less at all time points in the NHEI group than in the control and nifedipine groups (P:=0.05). The percent change from baseline of left atrial function at all time intervals as assessed by left atrial appendage contraction velocity (LAACV) was significantly less in the NHEI group than in the control (P:=0.05) group. LAACV was significantly preserved at all time intervals (except 300 minutes) in the NHEI group compared with the nifedipine group (P:=0.05). The only significant difference in hemodynamics among the groups was between the control and the nifedipine groups at 30 minutes after drug (P:=0.05).

CONCLUSIONS

Treatment with HOE642 significantly blunts the decline in left atrial mechanical function from rapid atrial rates compared with both control and nifedipine-treated groups.

Extracellular Ca2+ increases cytosolic free Ca2+ in freshly isolated rat odontoblasts

Recent evidence suggests that extracellular Ca2+ may modulate cell function in mineralized tissue. To determine whether dentinogenic cells, in particular, are sensitive to extracellular Ca2+, fura-2 microfluorometry was used to monitor intracellular calcium levels in odontoblasts freshly isolated from rat incisor. In response to applications of 0.5-4.0 mM extracellular calcium (CaCl2), most odontoblasts (84%; 107/128) showed an increase in intracellular calcium. For the majority of these cells (70%; 75/107), the typical response was biphasic; there was an initial, transient increase in intracellular calcium which reached peak levels within 30-50 s and decayed rapidly, followed by a slower (> 300 s) recovery toward basal levels. In general, the response of these cells to calcium was repeatable and the mean calcium concentration for the half-maximal response was approximately 1.3 mM. This effect could be partially blocked by either 200 microM lanthanum, a nonspecific blocker of Ca2+ channels, or 20 microM dantrolene, a potent inhibitor of Ca2+ release from internal stores. Used in combination, lanthanum, and dantrolene nearly abolished the calcium response completely. In addition, this response was sensitive to the dihydropyridine-sensitive calcium channel blocking agent nicardipine (60 microM), indicating a role for voltage-gated calcium channels during these events. These results show that odontoblasts respond to external calcium through mechanisms involving both influx of external calcium as well as release of calcium from internal stores and suggest a role for extracellular calcium in regulating the function of these cells.

Effects of nicardipine and nitroglycerin on perioperative myocardial ischemia in patients undergoing coronary artery bypass surgery

Perioperative myocardial ischemic episodes are predictive of adverse cardiac outcomes after coronary artery bypass surgery. We compared the efficacy of continuous infusions of nicardipine (group NIC) and nitroglycerin (group NTG) in reducing the frequency and severity of myocardial ischemic episodes. Patients received either a nicardipine infusion, 0.7 to 1.4 microg/kg/min (n = 30), nitroglycerin infusion, 0.5 to 1 microg/kg/min (n = 30), or neither medication (group C; n = 17) after aortic occlusion clamp release and for 24 hours postoperatively. Myocardial ischemic episodes were considered as ST segment depressions or elevations of 1 mm or greater from baseline, each at J + 60 milliseconds and lasting 1 minute or greater, using a two-channel Holter monitor. Only nicardipine significantly decreased the duration (3.2 +/- 1.2 min/h) and the area under the ST time curve (AUC; 5.7 +/- 15.7 AUC/h) of 1-mm or greater myocardial ischemic episodes compared with group C (17.2 +/- 5.6 min/h and 30.1 +/- 49 AUC/h, respectively) during the intraoperative postbypass period. A trend toward lower frequency, duration, and area under the ST time curve of myocardial ischemic episodes was observed in group NIC compared with group NTG. Cardiac indices and mixed venous oxygen saturations were significantly greater, whereas systemic pressures were less in group NIC compared with group NTG for the same period. These results suggest that nicardipine, but not nitroglycerin, decreased the duration and area under the ST time curve of myocardial ischemic episodes shortly after coronary revascularization. Larger studies are required to verify the efficacy of nicardipine in reducing the severity of myocardial ischemia during cardiac surgery.

Hepatotoxicity of ethanol: protective effect of calcium channel blockers in isolated hepatocytes

This study examines the effects of three calcium channel blockers (verapamil, nifedipine and diltiazem) on isolated rat hepatocytes exposed to ethanol. In the first part of our study, hepatocytes were incubated with increasing concentrations of ethanol (100, 300, 500, 1000 mM) for varying times. Alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) release were measured to evaluate the cytotoxic effects of ethanol. The concentration of 300 mM and time of incubation of 45 min were chosen for cytoprotection experiments in which calcium channel blockers, at two different concentrations, were added to the medium 30 min prior to the addition of ethanol. ALT, AST and LDH release as well as lipid peroxidation and cellular reduced glutathione (GSH) were measured. Nifedipine and verapamil (25 microM) reduced ALT, AST and LDH activities. The highest dose of diltiazem (50 microM) was more effective than the lowest one (25 microM). Ethanol caused a significant depletion of cellular GSH content as well as a moderate enhancement of lipid peroxidation. While none of the three calcium channel blockers was able to restore the decrease in GSH levels, diltiazem (25 microM) and nifedipine (50 microM) showed the greatest effect, significantly reducing lipid peroxidation.

Protective effect of various calcium antagonists against an experimentally induced calcium overload in isolated hepatocytes

The effect of the hepatotoxic substance diamidinothionaphthene (98/202) on cytosolic, mitochondrial and extra-mitochondrial calcium distribution was measured in isolated rat hepatocytes. The drastic disturbance of the intracellular calcium homeostasis caused by this substance (increase of the cytosolic and mitochondrial calcium contents and depletion of extra-mitochondrial calcium stores, which at last lead to cell death) gave rise to an investigation of the possible cytoprotective effect of calcium antagonists of various chemical classes: verapamil, diltiazem, and nifedipine on isolated hepatocytes. Our results show that all three calcium antagonists prevented cell death caused by 98/202. The 98/202-induced increase of cytosolic and mitochondrial calcium content was inhibited by all three calcium antagonists. However, only verapamil was able to inhibit the depletion of extra-mitochondrial calcium stores. Since 98/202-induced cell death occurs only in the presence of extracellular calcium, it is concluded that calcium antagonists are also able to inhibit the influx of extracellular calcium in liver cells, which leads to a calcium overload of the cytosol and mitochondria. The various ways of interfering with the calcium homeostasis of liver cells qualifies the hepatotoxic substance 98/202 as a suitable in vitro hepatotoxicity model for testing the hepatoprotective effect of different calcium antagonists.

Preventive effect of nicardipine on hyperplastic changes in venous bypass grafts

Nicardipine is a relatively new calcium channel blocker with important properties that could result in attenuation of the adverse proliferative changes in autogenous vein bypass grafts. In this experimental, randomized, controlled study, the effect of nicardipine on the pathologic findings in aortoaortic bypass graft was assessed. Forty-two male rabbits (Orycytolagus cuniculus) were randomized to three groups: group 1 received nicardipine and groups 2 and 3 placebo for 4 weeks, after which an aortaortic bypass was realized with an autogenous inferior vena cava segment. During the following 4 weeks, groups 1 and 2 received nicardipine, and placebo was continued in group 3. The animals were sacrificed at the end of the study to permit removal and evaluation of the bypass grafts. The mean intimal and medial thickness values for groups 1 and 2 were lower than those for group 3, indicating that nicardipine has a significant preventive effect on the hyperplastic changes in venous bypass grafts compared to placebo. The mean intimal and medial thickness values of group 1 were also lower than those of group 2, and the differences carried statistical relevance, suggesting that the use of nicardipine before grafting could potentiate its protective effect. To provide stimulus for further research, an attempt is made to relate the hyperplasia-preventing effect of nicardipine to possible mechanisms.

Potentiation of the cardiovascular effects of nicardipine by enflurane anesthesia in canine blood-perfused heart preparations

The cardiovascular interaction between nicardipine (N) and enflurae (E) was examined with blood perfused isolated paplillary muscle preparations (PMP) and sinoatrial node preparations (SNP). Blood flow to these preparations was supplied by either conscious or 1.7% E-anesthetized-donor dogs. N was administered continuously at a rate of 2.0 microg.kg(-1).min(-1) into the donor dogs for 60 min. Measurements were as follows: mean arterial blood pressure (MAP), heart rate (DHR), PQ interval (PQ) in the electrocardiogram, developed tension (DT) in PMP, sinoatrial rate (SAR) in SNP and blood flow (BF) to PMP and SNP. There were no significant differences in PQ, SAR and BF between two groups. However, N further decreased MAP, DHR and DT that were already decreased by E significantly. The authors conclude that the cardiovascular interaction between N and E was generally additive but that concerning negative inotropism was synergistic.

Nicardipine prevents calcium loading and "oxygen paradox" in anoxic single rat myocytes by a mechanism independent of calcium channel blockade

The protective effect of nicardipine (1 and 4 microM) against reoxygenation injury was studied in an unstimulated rat single myocyte oxygen paradox model in comparison with control (no drug) or nifedipine (1 microM). Either concentration of nicardipine was strongly protective, approximately doubling the duration of ATP depletion (rigor) that cells could withstand without undergoing hypercontracture when reoxygenated. Nifedipine (1 microM), which matched the negative inotropic effect of nicardipine (4 microM) (as measured by extent of shortening when stimulated), had no protective effect against reoxygenation injury. Neither drug affected the time to rigor, which is a measure of the rate at which the resting cell consumes its endogenous glycogen stores during anaerobic metabolism. Intracellular calcium, measured with the fluorescent probe indo-1, which partitions into both cytosol and mitochondria, rose progressively throughout the rigor period. This rise in calcium was almost totally suppressed by nicardipine (1 microM) but was unaffected by nifedipine. We conclude that nicardipine possesses a direct protective effect on the myocardium not shared by all dihydropyridines. This effect is associated with the prevention of intracellular, and probably mitochondrial, calcium loading but is probably not due to blockade of the L-type calcium channel or reduction of metabolic rate.

Nicardipine suppresses bronchoconstrictor actions of pharmacologic agents in guinea pigs

We investigated the inhibitory effects of nicardipine on airway smooth muscle constriction in the guinea pig via both in vitro and in vivo preparations. In the in vitro studies, we created dose-response curves of the excised tracheal strip. The increase in respiratory overflow produced by leukotriene (LT) D4 was measured in the in vivo preparation. In the organ bath, nicardipine (1-12 micrograms/ml) significantly inhibited constriction of the isolated tracheal spiral strip induced by 7 different agonists, acetylcholine (Ach), histamine (HA), serotonin (5-HT), prostaglandin F2 alpha (PGF2 alpha), slow-reacting substance of anaphylaxis (SRS-A), and LTC4 and LTD4. Compared to nifedipine and verapamil (data in the literature), the inhibitory potency of nicardipine on the constriction of the isolated guinea pig tracheal strip is 100-1,000 times greater. In the in vivo studies, nicardipine (50 and 100 micrograms/kg) significantly attenuated the LTD4-induced increase in respiratory overflow. These results suggest that nicardipine inhibits bronchoconstrictor-induced constriction of airway smooth muscle both in vitro and in vivo, and that it is a potent bronchodilator. The inhibitory characteristics of nicardipine may prove to be applicable clinically.

Cytoprotective effects of calcium channel blockers. Mechanisms and potential applications in hepatocellular injury

Deregulation of calcium homeostasis is strongly implicated in the development of cellular injury, including in hepatocytes, and is thought to be the limiting step in transition to an irreversible stage. Calcium channel blockers appear to exert their cytoprotective effects through several mechanisms. These may involve blockade of L-(long-lasting)-type calcium channels, reduction of oxidative stress, antagonism at inflammatory mediator receptor sites and interaction at other intracellular sites. Studies relating to the liver are few but suggest that calcium channel blockers may have a role to play in limiting hepatocellular damage, especially those arising from exposure to a variety of toxic agents.