Calcium Channel Blocking Properties Research Articles

Antihypertensive Property of Celery: A Narrative Review on Current Knowledge.

The incidence of hypertension is increasing significantly on a global scale, and it is considered the leading cause of heart disease and death. Despite the availability of hypotensive drugs, they have many side effects that decrease adherence to treatments and lead to uncontrolled blood pressure. Studies have revealed that celery contains bioactive compounds that oppose hypotensive effect. A thorough literature review was conducted using Scopus, PubMed, and Google Scholar databases. To identify relevant studies on the topic, our search strategy employed keywords such as "celery," "Apium gravenols L," "hypertension," "high blood pressure," "apigenin," "antihypertensive," and "hypotensive." The search was limited to articles published between January 2013 and December 2023. The inclusion criteria were original research articles that involved both animal and human subjects, published in English, and reported results applicable to the subject of this review. Review articles or articles in the form of theses or books were excluded. The available evidence revealed that celery enhances blood pressure parameters. Clinical trials clarified that celery possesses its effect through many bioactive compounds, specifically 3-n-butylphthalide and apigenin. Based on animal and human studies, celery seems to elicit blood pressure regulation mainly by the vasodilatory, diuretic, and calcium channel-blocking properties. Furthermore, celery seed extract seems to exert a bradycardia effect. The current literature review showed a considerable number of studies on the hypertensive models, which confirmed that celery and its extracts are effective hypotensive agents. Some limitations in comparing published data should be considered, including differences in doses, extracts, species of celery, and administration form.

Novel neuroactive steroid with hypnotic and T-type calcium channel blocking properties exerts effective analgesia in a rodent model of post-surgical pain.

Neuroactive steroid (3β,5β,17β)-3-hydroxyandrostane-17-carbonitrile (3β-OH) is a novel hypnotic and voltage-dependent blocker of T-type calcium channels. Here, we examine its potential analgesic effects and adjuvant anaesthetic properties using a post-surgical pain model in rodents. Analgesic properties of 3β-OH were investigated in thermal and mechanical nociceptive tests in sham or surgically incised rats and mice, with drug injected either systemically (intraperitoneal) or locally via intrathecal or intraplantar routes. Hypnotic properties of 3β-OH and its use as an adjuvant anaesthetic in combination with isoflurane were investigated using behavioural experiments and in vivo EEG recordings in adolescent rats. A combination of 1% isoflurane with 3β-OH (60 mg·kg-1 , i.p.) induced suppression of cortical EEG and stronger thermal and mechanical anti-hyperalgesia during 3 days post-surgery, when compared to isoflurane alone and isoflurane with morphine. 3β-OH exerted prominent enantioselective thermal and mechanical antinociception in healthy rats and reduced T-channel-dependent excitability of primary sensory neurons. Intrathecal injection of 3β-OH alleviated mechanical hyperalgesia, while repeated intraplantar application alleviated both thermal and mechanical hyperalgesia in the rats after incision. Using mouse genetics, we found that CaV 3.2 T-calcium channels are important for anti-hyperalgesic effect of 3β-OH and are contributing to its hypnotic effect. Our study identifies 3β-OH as a novel analgesic for surgical procedures. 3β-OH can be used to reduce T-channel-dependent excitability of peripheral sensory neurons as an adjuvant for induction and maintenance of general anaesthesia while improving analgesia and lowering the amount of volatile anaesthetic needed for surgery.

Calcium and potassium channels are involved in curcumin relaxant effect on tracheal smooth muscles

Context Curcumin, the active component of Curcuma longa L. (Zingiberaceae), exhibits a wide variety of biological activities including vasodilation and anti-inflammation. Objective The relaxant effect of curcumin in tracheal smooth muscle (TSM) was not examined so far, thus, this study was designed to assess the relaxant effect of curcumin on rat TSM and examine the underlying mechanism(s) responsible for this effect. Materials and methods TSM was contracted by KCl (60 mM) or methacholine (10 μM), and cumulative concentrations of curcumin (12.5, 25, 50, and 100 mg/mL) or theophylline (0.2, 0.4, 0.6, and 0.8 mM, as positive control) were added to organ bath. The relaxant effect of curcumin was examined in non-incubated or incubated tissues with atropine (1 μM), chlorpheniramine (1 μM), indomethacin (1 μM), and papaverine (100 μM). Results In non-incubated TSM, curcumin showed significant relaxant effects on KCl-induced contraction in a concentration-dependent manner (p < 0.001 for all concentrations). The relaxant effects of curcumin 12.5, 25, and 50 mg/mL were significantly lower in atropine-incubated tissue compared to non-incubated TSM (p < 0.05 to p < 0.001). A significant difference was observed in EC50 between atropine-incubated (48.10 ± 2.55) and non-incubated (41.65 ± 1.81) tissues (p < 0.05). Theophylline showed a significant relaxant effect on both KCl and methacholine-induced contraction in a concentration-dependent manner (p < 0.001 for all cases). Conclusions The results indicated a relatively potent relaxant effect of curcumin on TSM, which was less marked than the effect of theophylline. Calcium channel blocking and/or potassium channel opening properties of curcumin may be responsible for TSM relaxation.

A neurosteroid analogue with T-type calcium channel blocking properties is an effective hypnotic, but is not harmful to neonatal rat brain

BackgroundMore than 4 million children are exposed annually to sedatives and general anaesthetics (GAs) in the USA alone. Recent data suggest that common GAs can be detrimental to brain development causing neurodegeneration and long-term cognitive impairments. Challenged by a recent US Food and Drug Administration (FDA) warning about potentially neurotoxic effects of GAs in children, there is an urgent need to develop safer GAs. MethodsPostnatal Day 7 (P7) rat pups of both sexes were exposed to six (repeated every 2 h) injections of equipotent hypnotic doses of ketamine or the neuroactive steroid (3β,5β,17β)-3-hydroxyandrostane-17-carbonitrile (3β-OH) for 12 h. Loss of righting reflex was used to assess hypnotic properties and therapeutic index; quantitative caspase-3 immunohistochemistry was used to assess developmental neuroapoptosis; patch-clamp recordings in acute brain slices were used to assess the effects of 3β-OH on neuronal excitability and synaptic transmission. Cognitive abilities of rats exposed to ketamine, 3β-OH, or vehicle at P7 were assessed in young adulthood using the radial arm maze. ResultsThe neuroactive steroid 3β-OH has a therapeutic index similar to ketamine, a commonly used clinical GA. We report that 3β-OH is safe and, unlike ketamine, does not cause neuroapoptosis or impair cognitive development when administered to P7 rat pups. Interestingly, 3β-OH blocks T-type calcium channels and presynaptically dampens synaptic transmission at hypnotically-relevant brain concentrations, but it lacks a direct effect on γ-aminobutyric acid A or glutamate-gated ion channels. ConclusionsThe neurosteroid 3β-OH is a relatively safe hypnotic that warrants further consideration for paediatric anaesthesia.

Suicide attempt with self-made Taxus baccata leaf capsules: survival following the application of extracorporeal membrane oxygenation for ventricular arrythmia and refractory cardiogenic shock

Context: Yew intoxication has been known for many years; high dose ingestion of Taxus baccata leads to cardiac toxicity mediated by calcium and sodium channel blocking properties. We present a case report of a patient who attempted suicide after T. baccata ingestion, causing refractory cardiogenic shock requiring temporary circulatory assistance by veno-arterial extra corporeal membrane oxygenation (VA ECMO).Case details: A 28-year-old man was admitted to the critical care unit of a university hospital for arrhythmia after ingestion of self-made T. baccata leaf capsules. He rapidly developed cardiovascular collapse requiring mechanical ventilation, high dose intravenous catecholamines and electrical cardioversion. A femoro-femoral VA ECMO was implanted due to severe biventricular dysfunction and ventricular arrhythmia, associated with continuous renal replacement therapy. Taxol A, taxol B and baccatin III were detected and measured in both blood and urine samples by high-performance liquid chromatography tandem mass spectrometry, and kinetics suggested urinary excretion. Two days after hospital admission, VA ECMO and continuous renal replacement therapy were removed with full recovery of cardiac function.Discussion: Our experience suggests that circulatory assistance by VA ECMO and continuous renal replacement therapy seem to be effective safe second-line therapeutic options in critically ill cases of severe yew intoxication with refractory cardiogenic shock due to arrhythmia.

Amlodipine, an L-type calcium channel blocker, protects against chlorpromazine-induced neurobehavioural deficits in mice.

This study investigated the modulatory and chemopreventive benefit of amlodipine (AML), a dihydropyridine calcium channel antagonist, against neurobehavioural abnormalities (NAs) associated with chlorpromazine (CPZ) toxicity in mice. Adult mice were divided into five groups of six animals/group. Group 1 (control) was administered saline (10 mL/kg i.p.). Group 2 received CPZ (2 mg/kg i.p.). Groups 3 and 4 received bromocriptine (BMC, 2.5 mg/kg s.c.) and AML (1 mg/kg s.c.), respectively, while group 5 received their combination. Groups 3-5 later received CPZ 30 min after initial treatments. Animals were subjected to neurobehavioural tests and euthanized 18 h later. CPZ-induced NAs were characterized by significant increase (P < 0.001) in cataleptic behaviour and lowered (P < 0.05) spontaneous activity reaction time in mice. There were also significant (P < 0.001) increases in malondialdehyde levels and decreased locomotion plus learning and memory parameters (P < 0.05-0.001). AML pretreatment alone did not alleviate CPZ-induced motor deficits in the mice. While pretreatment with BMC alone attenuated CPZ-associated catalepsy, its combination with AML further protected mice against NAs. Furthermore, BMC pretreatment did not affect CPZ-induced increase in malondialdehyde level, but AML or BMC+AML significantly (P < 0.05) decreased malondialdehyde in the CPZ-treated rats. Reduced glutathione levels and activities of superoxide dismutase and catalase remained elevated in all treatment groups. In conclusion, data from this study suggest possible chemopreventive benefit of AML alone or in combination with BMC against CPZ-associated neurobehavioural deficits. The ameliorative effect of AML may be related to its antioxidant and/or calcium channel blocking property.

Clonazepam-associated Bradycardia in a Disabled Elderly Woman with Multiple Complications.

We herein report an 87-year-old woman who was taking clonazepam at 1.5 mg/day. She was hospitalized with an old cerebral infarction complicated with symptomatic epilepsy, dementia, dyslipidemia, and chronic cholecystitis. Electrocardiogram revealed severe bradycardia at 31 beats/min. The bradycardia disappeared on day 3 after clonazepam withdrawal, although the serum clonazepam level had been within normal limits. She was diagnosed with clonazepam-associated bradycardia, which was likely related to the potential calcium channel-blocking properties of clonazepam. Because of age-related pharmacokinetic and pharmacodynamic changes, the adverse effects of clonazepam should be considered, especially in disabled elderly individuals with multiple comorbidities.

Tetrandrine, an alkaloid from S. tetrandra exhibits anti-hypertensive and sleep-enhancing effects in SHR via different mechanisms

BackgroundSleep disorders have been found to be associated with hypertension in both cross-sectional and longitudinal epidemiological studies. Tetrandrine, a major component of Stephania tetrandra, is well known as an antihypertensive agent. The anti-hypertension mechanism mainly relies on its L-type calcium channel blocking property. In the previous study, tetrandrine revealed both anti-hypertension and hypnotic effects in spontaneously hypertensive rats (SHRs). PurposeThis study aims to elucidate whether the antihypertensive mechanism of tetrandrine in SHRs is relevant to its hypnotic effect. Design/MethodsSleep-wake behavior of the SHRs was detected by electroencephalography (EEG) and electromyography (EMG) recordings. Blood pressure was measured by noninvasive blood pressure tail cuff test. Immunohistochemistry was performed to evaluate the noradrenergic neuronal activity. The level of norepinephrine (NE) was detected by HPLC-ECD. ResultsAmlodipine (100mg/kg, i.g.), the well-known L-type Ca2+ channel blockers (CCBs) exhibited remarkable antihypertensive activities in SHRs, but did not show effects on sleep of SHRs. Tetrandrine (30 and 60mg/kg/day, i.g.) significantly suppressed blood pressure of SHRs. Meanwhile, tetrandrine (60mg/kg/day, i.g.) remarkably increased non-rapid eye movement sleep (NREMS) time, bouts and mean duration. The hypnotic effect of tetrandrine was potentiated by prazosin (0.5mg/kg, i.p.) but attenuated by yohimbine (2mg/kg, i.p.). Administration of tetrandrine (60mg/kg/day, i.g.) not only significantly decreased c-Fos positive ratio of noradrenergic neurons in the locus coeruleus (LC), but also significantly decrease NE in the endogenous sleep-wake regulating pathways including LC, hypothalamus and ventrolateral preoptic nucleus (VLPO). ConclusionIn spite of a good potency in blocking L-type Ca2+ channel, the hypnotic effects of tetrandrine may be related to its suppressing effects on the noradrenergic system other than to block calcium channels. As a multi-targets drug, tetrandrine might be favorable to the hypertension patients who suffered poor sleep.

The Nitric Oxide/Soluble Cyclic Guanylase/Cyclic Guanosine Monophosphate Pathway Is Involved in the Cardiovascular Effects of a Novel α1- and β-Adrenoceptor Antagonist

The compound MH-78 ((+/-)-1-(2,6-dimethylphenoxy)-3-{4-[2-(2-methoxyphenoxy)ethyl]-piperazin-1-yl}propan-2-ol dihydrochloride) contains structural elements that are typical for α₁- and β-blockers. This study aimed to investigate the hypotensive activity as well as the in vitro and in vivo cardiovascular effects of a novel α₁- and β-adrenoceptor antagonist (MH-78) and compare it with carvedilol and urapidil. The procedures were performed on aortic rings of normotensive anesthetized rats. MH-78 decreased the blood pressure and heart rate after intravenous and oral administration. MH-78 possesses both α₁- and β-adrenoceptor blocking activity, which was confirmed in the in vivo study. In biofunctional assays, MH-78 displayed vasorelaxant activity due to α₁-adrenoceptor antagonism and calcium channel blocking properties. Moreover, in endothelium-intact aortic rings, pretreatment with N_ω-nitro-L-arginine methyl ester (L-NAME) and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) reduced the MH-78-induced vasorelaxation to a level that is characteristic for MH-78 affinity to α₁-adrenoceptors. Our results demonstrated that MH-78 possesses α₁- and β-adrenoceptor blocking properties and induces potent hypotensive and vasorelaxant effects. Moreover, it relaxes vascular smooth muscle not only due to α₁-adrenoceptor blocking activity, but also via the endothelium-dependent nitric oxide/soluble guanylyl cyclase/cyclic guanosine monophosphate signalling pathway.

The Effect of Carvedilol on Blood Glucose Levels In Normal Albino Rats

Carvedilol is a commonly used drug in hypertension, congestive heart failure in diabetics. It has moderate calcium channel blocking property in addition to α1 and non selective β antagonistic activity. Though some studies bring forth the beneficial effects of Carvedilol in cardiovascular comorbidities in diabetes, there is no consensus on its effects on glycaemic levels. To evaluate the effect of oral Carvedilol administration for 5 days on blood glucose levels in normal albino rats through Oral Glucose Tolerance Test. Twelve adult albino rats of either sex weighing between 150 - 200 g were selected from central animal facility and randomly divided into 2 groups - Control [Distilled water (1ml/rat orally)] and Test (0.8mg/kg body weight orally) and the respective drugs were administered over 5 days. Following overnight fasting, on the fifth day 1 hour after the last dose of the respective drug, OGTT was performed. The CBG (Capillary Blood Glucose) levels were measured at 0 min, glucose (2g/kg body weight) dissolved in water was administered to all the rats orally. The blood sample from tail vein (obtained by tail snipping) at 60 and 150 minutes were analysed for CBG levels using a standardized glucometer. Data was presented as Mean ± SEM. One way ANOVA, independent samples t-test, non-parametric tests, percentages and cross tabs were used in the analysis of data within the same group and between different groups when required. Carvedilol group showed higher CBG levels at all time intervals of OGTT as compared to the Control group i.e., 0, 60 and 150 minutes, the highest being (103.8±5.029 )mg/dl at 60 minutes and was statistically significant. Carvedilol group however showed lesser inter-interval variation compared to the Control group at the same time intervals respectively but was statistically insignificant. Carvedilol has hyperglycaemic potential when given orally for 5 days in normal albino rats. Though it may be beneficial in diabetics for various comorbid conditions, the glycaemic control may worsen during its use in subjects with prediabetes, diabetes, high risk diabetes.

Simultaneous Determination of Dofetilide and Amlodipine in Plasma by HPLC

Dofetilide is a Class III antiarrhythmic drug useful in the management of atrial fibrillation but also known to prolong the QT interval on the ECG and to induce malignant ventricular tachyarrhythmias such as torsades de pointes (TDP). Drugs with calcium channel-blocking properties contribute to decrease the incidence of TDP. Amlodipine is a dihydropyridine calcium channel antagonist. Considering the potentially safe and useful combined use of dofetilide and amlodipine, we undertook drug biotransformation studies. To perform studies aiming to evaluate the possible pharmacokinetic interaction between these drugs, a unique sensitive HPLC assay able to quantify both drugs simultaneously was required. A sensitive and specific HPLC method using a tandem of UV/fluorescence detection was described for the analysis of amlodipine and dofetilide in plasma. The within-day and between-day precision studies showed good reproducibility with coefficients of variation less than 10% for all the analytes. The limits of detection were 0.5 ng/mL and 0.25 ng/mL and the limit of quantification were 1.7 ng/mL and 0.8 ng/mL for dofetilide and amlodipine respectively. This new method could be of great value in many applications such as in vitro and in vivo pharmacokinetic and drug-drug interactions studies, as well as therapeutic drug monitoring.

Synthesis of 4‐(Carbonyloxyphenyl)‐1,4‐Dihydropyridines as Potential Antihypertensive Agents

Abstract Preclinical Research A series of novel symmetric and asymmetric 4‐(carbonyloxyphenyl)‐1,4‐dihydropyridines (DHPs) was synthesized and evaluated for calcium channel blocking, vasodilatory and antihypertensive properties. Some of these new DHPs displayed potent calcium channel blocking and good vasodilatory activities. Heart rate remained relatively constant in comparison with blood pressure changes in the case of these newly synthesized compounds, thereby decreasing the probability of reflex tachycardia, a major side effect of nifedipine. The most potent compound, ethyl methyl 4‐(3‐isopropylcarbonyloxyphenyl)‐2,6‐dimethyl‐1,4‐dihydropyridine‐3,5‐dicarboxylate (14c) exhibited antihypertensive activity comparable with the standard drug—nifedipine.

Action Potential Peak Shape Analysis As A New Tool For Antiarrhythmic Drug Development

Cardiac arrhythmia is a critical heart condition characterized by abnormal electrical activity of the heart. There are a wide variety of drugs which are approved for the treatment of arrhythmia; many of them are acting on voltage dependent sodium, potassium or calcium channels. One of the problems concerning determination of the major mechanism of action of antiarrhythmics is that measurement of their effects on the different ion channels is time-consuming and usually done utilizing different experimental conditions. In order to counter this problem, in this study we applied a novel method, action potential shape analysis, to determine the effect of selected antiarrhythmics on voltage dependent sodium, potassium and calcium channels without performing time-consuming voltage-clamp experiments on each ion channel. Our method is based on fitting ion channel parameters to intracellularly or extracellularly recorded action potentials in a realistic model of NG108-15 cells and quantifying drug effects through their action on the shape of the action potentials and consequently on the fitted ion channel parameters. For this study we selected four drugs, quinidine, lidocaine, encanide, and amidarone, representing Class Ia, Ib, Ic and Class III antiarrhythmics, respectively. Quinidine, encanide and amidarone blocked both sodium and potassium channels, while lidocaine, at the measured membrane potential, shifted the activation of sodium channels in a depolarizing direction. Amidarone showed profound calcium channel blocking properties. Our work is a first step towards establishing a new assay system, based on the analysis of the shape of intracellularly and eventually extracellularly recorded action potentials, which can be used for fast quantitative analysis of drug effects on ion channel currents and classification of antiarrhythmics, and also for measurement of possible cardiac side effects of drug candidates

Bay w 9798, a Dihydropyridine Structurally Related to Nifedipine with No Calcium Channel-blocking Properties, Inhibits Tumour Necrosis Factor-α-induced Vascular Cell Adhesion Molecule-1 Expression in Endothelial Cells by Suppressing Reactive Oxygen Species Generation

Dihydropyridine-based calcium antagonists (DHPs) are widely used to treat hypertension. We have previously shown that nifedipine, one of the most popular DHPs, blocks tumour necrosis factor-alpha (TNF-alpha)-induced monocyte chemoattractant protein-1 as well as vascular cell adhesion molecule-1 (VCAM-1) expression in endothelial cells by suppressing reactive oxygen species generation (ROS). The molecular mechanism is still to be elucidated, however, because endothelial cells do not possess voltage-operated L-type calcium channels. The aim of this study was to determine in TNF-alpha-exposed human umbilical vein endothelial cells (HUVECs) whether and how Bay w 9798, a dihydropyridine structurally related to nifedipine with no calcium antagonistic properties, may suppress VCAM-1 expression, a key molecule which mediates the adhesion of monocytes to vasculature in the early stages of atherosclerosis. In HUVECs, 10 ng/ml TNF-alpha for 4 h stimulated ROS generation and subsequently upregulated VCAM-1 mRNA levels, both of which were dose-dependently blocked by Bay w 9798. The results demonstrated that Bay w 9798 inhibited VCAM-1 expression in TNF-alpha-exposed cells by suppressing ROS generation. They suggest that the anti-inflammatory and anti-oxidative properties of nifedipine and Bay w 9798 may be ascribed to the dihydropyridine structure, which is common to both molecules and has no calcium antagonistic ability.

Allodynia and hyperalgesia suppression by a novel analgesic in experimental neuropathic pain

SCP-1, n-[α-(benzisothiazol-3(2ho-ona,1-dioxide-2yl)-acetyl]- p-aminophenol (100 nmol), when intrathecally injected, suppressed tactile allodynia and thermal hyperalgesia in a rat neuropathic pain model. The tactile allodynia suppression lasted for at least 4 h and SCP-M1 (100 nmol), the main metabolite of SCP-1, displayed similar suppression as SCP-1, but shorter latency, indicating SCP-M1 may be the bioactive component of SCP-1. Acetaminophen was less potent than SCP-1 and SCP-M1. To study mechanisms underlying SCP-1 action, we recorded voltage-gated Ca 2+ channel currents in acutely isolated dorsal root ganglion neurons using the whole-cell patch-clamp technique. SCP-1 and SCP-M1 inhibited non-L-type calcium channel currents up to 23.0 ± 2.3% and 23.1 ± 3.5%, respectively, at a depolarized pulse to −10 mV from a holding potential of −80 mV. Acetaminophen only induced 6.8 ± 1.0% inhibition. The results suggest SCP-1 possesses anti-nociceptive activity in the rat model involving calcium channel blocking properties.

Pediatric Cinnarizine Overdose and Toxicokinetics

Cinnarizine, a piperazine derivative, is a widely prescribed medication for the treatment of vestibular disorders and motion sickness. Cinnarizine has antihistaminic, antiserotoninergic, antidopaminergic, and calcium channel-blocking properties. We present the first report in the English literature of cinnarizine poisoning and toxicokinetics. A 30-month-old toddler ingested 225 mg of cinnarizine, 18 times the recommended dose for older children. Four hours later, she became jittery with a wide-based gait and vomited 3 times. She was examined by her family physician, who reported stupor and twitching in both hands. On admission to the hospital, 6 hours after the ingestion, she was stuporous and had 3 short, generalized tonic-clonic convulsions that were controlled with a single dose of midazolam. Full clinical recovery was seen 10 hours after ingestion. Serum cinnarizine levels were 7407, 2629, and 711 ng/mL on admission and at 4 and 12 hours thereafter, respectively, 26.9 times higher than the therapeutic levels in adults. Elimination rate constant, calculated by linear regression of the ln concentrations of the 3 data points, was 0.19. Half-life, calculated from the equation t(1/2) = 0.693/kel, where kel is the elimination rate constant, was 3.65 hours. The manufacturing company revealed that their database contains 23 reports of cinnarizine overdose (adult and children), received between 1972 and 2004. Clinically, these cases reflect mainly symptoms of alterations in consciousness ranging from somnolence to stupor and coma, vomiting, extrapyramidal symptoms, and hypotonia. In a small number of young children, convulsions developed; recovery was uneventful in 4 cases and not reported in 1. The neurologic complication may be explained by the antihistaminic effect of cinnarizine because central nervous system depression and convulsions are known complications of antihistaminic overdose. It is hypothesized that cinnarizine-induced convulsions also are related to the antidopaminergic effect of the drug. Apart from the convulsions, no other adverse effects related to calcium channel-blocking properties, such as bradycardia or hemodynamic instability, were observed. Pediatric patients with cinnarizine overdose need to be observed in a health care facility for potential neurologic complications and be treated symptomatically. The delay to onset of clinical effect should be considered in the observation period.

Carvedilol Inhibits Proliferation of Cultured Pulmonary Artery Smooth Muscle Cells of Patients with Idiopathic Pulmonary Arterial Hypertension

Idiopathic pulmonary arterial hypertension (IPAH) is associated with proliferation of smooth muscle cells (SMCs) in small pulmonary arteries. Inhibition of proliferation of pulmonary artery smooth muscle cells (PASMCs) may be an effective treatment of patients with idiopathic pulmonary arterial hypertension. Recent studies have shown that carvedilol, an alpha- and beta-blocker with antioxidant and calcium channel blocking properties, inhibits the proliferation of cultured normal human pulmonary artery smooth muscle cells. In this study, we tested the hypothesis that carvedilol has antiproliferative effects on pulmonary artery smooth muscle cells of patients with idiopathic pulmonary arterial hypertension. Pulmonary artery smooth muscle cells from six idiopathic pulmonary arterial hypertension patients who had undergone lung transplantation were cultured. To determine cell proliferation, H-thymidine incorporation was measured. Platelet-derived growth factor-induced proliferation of IPAH-PASMCs was significantly greater than that of normal control pulmonary artery smooth muscle cells. Carvedilol (0.1 microM to 10 microM) inhibited the proliferation of idiopathic pulmonary arterial hypertension-pulmonary artery smooth muscle cells in a concentration-dependent manner. Prazosin (an alpha-blocker) and N-acetyl L cysteine (an antioxidant agent) (0.1 microM to 10 microM) did not inhibit their proliferation, but the high concentration of propranolol (a beta-blocker) and nifedipine (a calcium channel blocker) (10 microM) inhibited the proliferation. The combination of propranolol and nifedipine inhibited the proliferation but only at a high concentration (10 microM) combination. Cell cycle analysis revealed that carvedilol (10 microM) significantly decreased the number of cells in S and G2/M phases. These results indicate that carvedilol inhibits the exaggerated proliferation of pulmonary artery smooth muscle cells of patients with idiopathic pulmonary arterial hypertension partially via its beta-blocking [corrected] and calcium channel blocking effects in vitro.

14-Deoxyandrographolide as a Platelet Activating Factor Antagonist in Bovine Neutrophils

14-Deoxyandrographolide (14-DAP) is a labdane diterpene isolated from Andrographis paniculata with previously reported calcium channel blocking activity. Its potential platelet activating factor (PAF) antagonistic activity in bovine neutrophils was assessed. 14-DAP, in concentrations between 10-100 microM, reduced the extracellular acidification rate and the intracellular alkalinization in a dose-dependent manner. In addition, 14-DAP reduced PAF-induced calcium flux in the presence of extracellular calcium, and tyrosine phosphorylation of a 44 kDa protein corresponding to the MAPK(ERK1). However, 14-DAP reduced the 3H-PAF binding with a Ki of 7.8 x 10 (- 9)M, and a Hill slope of 0.63, suggesting that there is more than one binding site for 14-DAP. We concluded that 14-DAP is an effective antagonist of PAF-mediated processes in bovine neutrophils, probably by virtue of its calcium channel blocking property.

A high-performance liquid chromatographic method for determination of the niguldipine analogue DHP-014

A simple and reliable reversed-phase high-performance liquid chromatography method was developed and validated for the determination of DHP-014, a niguldipine analogue with potent P-glycoprotein inhibitory and negligible calcium channel blocking properties, in rat plasma. DHP-014 and niguldipine hydrochloride (the internal standard) were extracted from rat plasma by liquid extraction using hexane. DHP-014 was then separated by HPLC on a C18 column and quantified by ultraviolet detection at 238 nm. The mobile phase consisted of acetonitrile-aqueous 5 mM phosphate buffer (65:35, v/v) containing 0.4% (v/v) triethylamine adjusted to pH 7.0. The mean extraction efficiency of DHP-014 was 109.0 +/- 12.9, 97.7 +/- 8.0 and 102.9 +/- 7.5% for DHP-014 concentrations of 10, 50 and 100 nM, respectively (n = 5). The method was linear over the concentration range 2.5-200 nM with a regression coefficient of 0.998. The limit of detection of DHP-014 in rat plasma was 1.0 nM. The intra- and inter-day coefficients of variation for DHP-014 in rat plasma were 4.7-7.9 and 6.9-9.9%, respectively. The intra- and inter-day accuracy was 98.2-99.5 and 97.9-103%, respectively. The bioanalytical technique was used to determine DHP-014 in plasma samples in a pharmacokinetic study of DHP-014 administered to female Sprague-Dawley rats.

Unique atheroprotective property of azelnidipine, a dihydropyridine-based calcium antagonist

Insulin resistance and central obesity are often associated with hypertension. The metabolic syndrome is a cluster of these common clinical disorders, and is related with an increased risk for cardiovascular diseases. A number of pro-inflammatory cytokines derived from adipose tissues have been thought to contribute to the development of insulin resistance and accelerated atherosclerosis. Among them, TNF-alpha has been most widely studied; it not only suppresses the insulin signaling, but also elicits vascular inflammation. Indeed, inhibition of TNF-alpha was found to improve insulin resistance in obese rats and reduce the progression of atherosclerosis in apolipoprotein E knockout mice, respectively. These observations demonstrate that TNF-alpha could play a central role in the pathogenesis of insulin resistance and accelerated atherosclerosis in the metabolic syndrome. Considering that the primary goals of treatment for hypertensive patients with the metabolic syndrome are prevention of the development of diabetes and cardiovascular events, anti-hypertensive drugs that have abilities to block the TNF-alpha signaling would be desirable as a first-line therapy for these patients. In the process of the search for such a unique anti-hypertensive drug, we have recently found that azelnidipine, a newly developed and commercially used long-acting dihydropyridine-based calcium antagonist (DHP), inhibited TNF-alpha-induced activator protein-1 activation and interleukin-8 expression in human umbilical vein endothelial cells by suppressing NADPH oxidase-mediated reactive oxygen species generation. The concentration of azelnidipine that was found effective in these in vitro-experiments is well within the therapeutic range. Since endothelial cells do not possess voltage-operated L-type calcium channels, these observations suggest that the beneficial effects of azelnidipine are not likely due to calcium channel blocking property, but due to its unique anti-oxidative ability. Furthermore, we have very recently found that serum levels of monocyte chemoattractant protein-1, a biomarker for subclinical atherosclerosis, were significantly decreased by the treatment of azelnidipine in patients with essential hypertension. In this paper, we would like to hypothesize that due to its unique TNF-alpha signal modulatory, anti-oxidative property, azelnidipine may be a promising DHP that targets diabetes and cardiovascular diseases in hypertensive patients with the metabolic syndrome.