Nicardipine is a putative EED inhibitor and has high selectivity and potency against chemoresistant prostate cancer in preclinical models

BACKGROUND

It is imperative to develop novel therapeutics to overcome chemoresistance, a significant obstacle in the clinical management of prostate cancer (PCa) and other cancers.

METHODS

A phenotypic screen was performed to identify novel inhibitors of chemoresistant PCa cells. The mechanism of action of potential candidate(s) was investigated using in silico docking, and molecular and cellular assays in chemoresistant PCa cells. The in vivo efficacy was evaluated in mouse xenograft models of chemoresistant PCa.

RESULTS

Nicardipine exhibited high selectivity and potency against chemoresistant PCa cells via inducing apoptosis and cell cycle arrest. Computational, molecular, and cellular studies identified nicardipine as a putative inhibitor of embryonic ectoderm development (EED) protein, and the results are consistent with a proposed mechanism of action that nicardipine destabilised enhancer of zeste homologue 2 (EZH2) and inhibited key components of noncanonical EZH2 signalling, including transducer and activator of transcription 3, S-phase kinase-associated protein 2, ATP binding cassette B1, and survivin. As a monotherapy, nicardipine effectively inhibited the skeletal growth of chemoresistant C4-2B-TaxR tumours. As a combination regimen, nicardipine synergistically enhanced the in vivo efficacy of docetaxel against C4-2 xenografts.

CONCLUSION

Our findings provided the first preclinical evidence supporting nicardipine as a novel EED inhibitor that has the potential to be promptly tested in PCa patients to overcome chemoresistance and improve clinical outcomes.

Effects of drug-drug interactions and CYP3A4 variants on alectinib metabolism

In this study, the effects of 17 CYP3A4 variants and drug-drug interactions (DDI) with its mechanism on alectinib metabolism were investigated. In vitro incubation systems of rat liver microsomes (RLM), human liver microsomes (HLM) and recombinant human CYP3A4 variants were established. The formers were used to screen potential drugs that inhibited alectinib metabolism and study the underlying mechanism, and the latter was used to determine the dynamic characteristics of CYP3A4 variants. Alectinib and its main metabolite M4 were quantitatively determined by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). The results showed that compared with CYP3A4.1, only CYP3A4.29 showed higher catalytic activity, while the catalytic activity of CYP3A4.4, .7, .8, .12, .14, .16, .17, .18, .19, .20, .23, and .24 decreased significantly. Among them, the catalytic activity of CYP3A4.20 is the lowest, only 2.63% of that of CYP3A4.1. Based on the RLM incubation system in vitro, 81 drugs that may be combined with alectinib were screened, among which 18 drugs had an inhibition rate higher than 80%. In addition, nicardipine had an inhibition rate of 95.09% with a half-maximum inhibitory concentration (IC50) value of 3.54 ± 0.96 μM in RLM and 1.52 ± 0.038 μM in HLM, respectively. There was a mixture of non-competitive and anti-competitive inhibition of alectinib metabolism in both RLM and HLM. In vivo experiments of Sprague-Dawley (SD) rats, compared with the control group (30 mg/kg alectinib alone), the AUC(0-t), AUC(0-∞), Tmax and Cmax of alectinib administered in combination with 6 mg/kg nicardipine were significantly increased in the experimental group. In conclusion, the metabolism of alectinib was affected by polymorphisms of the CYP3A4 gene and nicardipine. This study provides reference data for clinical individualized administration of alectinib in the future.

Opposing Responses of the Calcium Channel Blocker Nicardipine to Vascular Stiffness in the Elastic and Muscular Arteries in Rabbits

AIM

The cardio-ankle vascular index (CAVI) consists of intrinsic and functional arterial stiffness mainly regulated by vasoactive compounds. A new stiffness index of the aorta (aBeta) and iliac-femoral arteries (ifBeta) was determined by applying the CAVI theory to the whole aorta and iliac-femoral arteries. We investigated the changes in aBeta and ifBeta in response to decreased blood pressure (BP) induced by the Ca2＋ channel blocker nicardipine to elucidate the involvement of Ca2＋ in aBeta and ifBeta.

METHODS

Pressure waves at the origin of the aorta (oA), distal end of the abdominal aorta (dA), and left femoral artery (fA) as well as flow waves at the oA were simultaneously recorded before and after the infusion of nicardipine (50 µg/kg/min) for 2 min in 12 male rabbits under pentobarbital anesthesia. Beta was calculated using the following formula: Beta=2ρ / PP×ln (SBP / DBP)×PWV2, where ρ, SBP, DBP, and PP denote blood density and systolic, diastolic, and pulse pressures, respectively. aBeta, ifBeta, and aortic-iliac-femoral Beta (aifBeta) were calculated using aPWV, ifPWV, and aifPWV, respectively.

RESULTS

SBP, mean arterial pressure (MAP), DBP, and total peripheral vascular resistance significantly decreased during the administration of nicardipine, whereas cardiac output significantly increased. aBeta and ifBeta significantly increased and decreased, respectively, whereas aifBeta did not change despite the decrease in BP. ifBeta and aBeta positively and negatively correlated with BP, respectively, whereas aifBeta did not correlate with SBP.

CONCLUSIONS

There were contradictory arterial responses to nicardipine between the elastic and muscular arteries. Unknown vasoconstriction mechanisms that are not involved in Ca2＋ influx may function in the aorta in response to decreased BP.

An Autophagy Modifier Screen Identifies Small Molecules Capable of Reducing Autophagosome Accumulation in a Model of CLN3-Mediated Neurodegeneration

Alterations in the autophagosomal–lysosomal pathway are a major pathophysiological feature of CLN3 disease, which is the most common form of childhood-onset neurodegeneration. Accumulating autofluorescent lysosomal storage material in CLN3 disease, consisting of dolichols, lipids, biometals, and a protein that normally resides in the mitochondria, subunit c of the mitochondrial ATPase, provides evidence that autophagosomal–lysosomal turnover of cellular components is disrupted upon loss of CLN3 protein function. Using a murine neuronal cell model of the disease, which accurately mimics the major gene defect and the hallmark features of CLN3 disease, we conducted an unbiased search for modifiers of autophagy, extending previous work by further optimizing a GFP-LC3 based assay and performing a high-content screen on a library of ~2000 bioactive compounds. Here we corroborate our earlier screening results and identify expanded, independent sets of autophagy modifiers that increase or decrease the accumulation of autophagosomes in the CLN3 disease cells, highlighting several pathways of interest, including the regulation of calcium signaling, microtubule dynamics, and the mevalonate pathway. Follow-up analysis on fluspirilene, nicardipine, and verapamil, in particular, confirmed activity in reducing GFP-LC3 vesicle burden, while also demonstrating activity in normalizing lysosomal positioning and, for verapamil, in promoting storage material clearance in CLN3 disease neuronal cells. This study demonstrates the potential for cell-based screening studies to identify candidate molecules and pathways for further work to understand CLN3 disease pathogenesis and in drug development efforts.

Relationship between the administration of nicardipine hydrochloride and the development of delirium in patients on mechanical ventilation

A history of hypertension is a known risk factor for delirium in patients in intensive care units, but the effect of antihypertensive agents on delirium development is unclear. Nicardipine, a calcium channel blocker, is widely used in ICU as a treatment agent for hypertensive emergency. This study investigated the relationship between the administration of nicardipine hydrochloride and delirium development in patients under mechanical ventilation. We conducted a medical chart review of 103 patients, who were divided into two groups according to the use of nicardipine hydrochloride. The prevalence of delirium was compared with respect to factors such as age, sex, laboratory data, and medical history, by multivariate analysis. 21 patients (20.4 %) were treated with nicardipine hydrochloride in 103 patients. The treatment and non-treatment groups differed significantly in age (72 vs. 65 years) and history of high blood pressure (57% vs. 11%). Multivariate analysis revealed that patients in the treatment group developed delirium significantly less often than those in the non-treatment group (19% vs. 48%). These results suggested that treatment of high blood pressure with nicardipine hydrochloride is a possible method for preventing the development of delirium.

Role of voltage-gated calcium channels on striatal dopamine release induced by inorganic mercury in freely moving rats

The possible role of voltage-sensitive calcium channels (VSCC) activation on the HgCl₂-induced dopamine release was investigated using selective VSCC blockers and the dopamine levels were measured by HPLC from samples obtained by in vivo brain microdialysis. Infusion of HgCl₂ in nicardipine (10 or 100 μM) or flunaricine (10 μM) pretreated animals had no significant effect on dopamine release induced by HgCl₂. Pretreatment with 100 μM flunaricine, 20 μM ω-conotoxin MVIIC, or ω-conotoxin GVIA significantly decreased the HgCl₂-induced dopamine release over 61%, 88%, and 99%, respectively. HgCl₂-induced dopamine release could be produced, at least in part, by activation of VSCC at dopaminergic terminals, especially N- and P/Q-type.

The effect of nicardipine on the surgical pleth index during thyroidectomy under general anesthesia: A prospective double-blind randomized controlled trial

BACKGROUND

The effectiveness of surgical pleth index (SPI) for managing nociception-antinociception balance during general anesthesia with vasodilators, including nicardipine has not been demonstrated. We aimed to compare the time course during surgery in SPI values in patients receiving nicardipine or remifentanil infusion during thyroidectomy.

METHODS

Forty patients undergoing thyroidectomy were randomly assigned to receive nicardipine (group N; n = 19) or remifentanil (group R; n = 21) along with induction (propofol, fentanyl, and rocuronium) and maintenance (50% desflurane/nitrous oxide in oxygen) anesthesia (goal bispectral index [BIS] ∼50). The infusion of nicardipine or remifentanil was started before the 1st incision and adjusted to keep mean blood pressure (MBP) within ±20% of the preoperative value. SPI, BIS, end-tidal desflurane concentration (EtDes), MBP, and heart rate were recorded at 2.5 minute intervals from the 1st incision to the end of surgery. Extubation and recovery times, pain score/rescue ketorolac consumption, and adverse events in postanesthesia care unit (PACU) were recorded.

RESULTS

The trend of SPI during surgery was comparable between the 2 groups (P = 0.804), although the heart rates in group N were significantly higher than those in group R (P = 0.040). The patient characteristics, trends of BIS, EtDes, and MBP during surgery, extubation and recovery times, and incidence of nausea/vomiting were comparable between the groups. Group N had significantly lower pain scores and rescue ketorolac consumption at PACU.

CONCLUSION

SPI was comparable between patients receiving nicardipine or remifentanil infusion during thyroidectomy under general anesthesia, which suggests that the administration of nicardipine may confound the interpretation of SPI values during general anesthesia.

CLINICAL TRIAL REGISTRATION

This trial was registered in the UMIN clinical trials registry (unique trial number: UMIN000019058; registration number: R000022028; principal investigator's name: Young Ju Won; date of registration: September 17, 2015).

Effect of Angelica acutiloba Extract on Blood flow Regulation in Stroke-prone Spontaneously Hypertensive Rats

Angelica acutiloba Kitagawa (Yamato Toki) is a herbal medicine known to exhibit various health effects. In this study, we used a rat model to examine the effects of two different Yamato Toki extracts on the blood flow response of the instep of the hind paw. Twelve-week- old male stroke-prone spontaneously hypertensive rats (SHRSP) were orally given 200 mg of a water extract of Yamato Toki (n=6), 200 mg of an ethanol extract of Yamato Toki (n = 6), 30 mg/kg of nicardipine (n = 6) as a positive control and saline (n = 6) as a negative control. Blood flow was monitored continuously for 0, 1, 3, 6 and 24 hours after treatment. Rats given 200 mg of the ethanol extract of Yamato Toki demonstrated significantly greater blood flow compared with control rats at I hour after treatment. An ethanol extract of Yamato Toki from Nara administrated orally can increase blood flow in SHRSP.

Effect of Nicardipine on Haemodynamic and Bispectral Index Changes following Endotracheal Intubation

We investigated the effect of IV nicardipine on haemodynamic and bispectral index responses to the induction of general anaesthesia and intubation. Forty patients were randomly allocated to two groups of 20 to receive normal saline or nicardipine 15 μg/kg IV 30 s after induction. Ninety seconds later, tracheal intubation was performed. Systolic blood pressure, heart rate and bispectral index were measured at baseline, 1 min after induction, pre-intubation, and every minute until 5 min after endotracheal intubation. Rate–pressure product values were calculated. In the nicardipine group, systolic blood pressure decreased compared with the control group, and heart rate increased compared with the control group. Bispectral index and rate–pressure product showed no differences between the two groups. In conclusion, the administration of 15 μg/kg nicardipine IV does not affect anaesthetic depth in response to the induction of general anaesthesia and intubation.

Ca2+ influx through L-type Ca2+ channels and Ca2+-induced Ca2+ release regulate cAMP accumulation and Epac1-dependent ERK 1/2 activation in INS-1 cells

We previously reported that INS-1 cells expressing the intracellular II-III loop of the L-type Ca(2+) channel Cav1.2 (Cav1.2/II-III cells) are deficient in Ca(2+)-induced Ca(2+) release (CICR). Here we show that glucose-stimulated ERK 1/2 phosphorylation (GSEP) is slowed and reduced in Cav1.2/II-III cells compared to INS-1 cells. This parallels a decrease in glucose-stimulated cAMP accumulation (GS-cAMP) in Cav1.2/II-III cells. Influx of Ca(2+) via L-type Ca(2+) channels and CICR play roles in both GSEP and GS-cAMP in INS-1 cells since both are inhibited by nicardipine or ryanodine. Further, the Epac1-selective inhibitor CE3F4 abolishes glucose-stimulated ERK activation in INS-1 cells, as measured using the FRET-based sensor EKAR. The non-selective Epac antagonist ESI-09 but not the Epac2-selective antagonist ESI-05 nor the PKA antagonist Rp-cAMPs inhibits GSEP in both INS-1 and Cav1.2/II-III cells. We conclude that L-type Ca(2+) channel-dependent cAMP accumulation, that's amplified by CICR, activates Epac1 and drives GSEP in INS-1 cells.

Mechanisms of the antihypertensive effects of Nigella sativa oil in L-NAME-induced hypertensive rats

OBJECTIVES

This study was conducted to determine whether the blood pressure-lowering effect of Nigella sativa might be mediated by its effects on nitric oxide, angiotensin-converting enzyme, heme oxygenase and oxidative stress markers.

METHODS

Twenty-four adult male Sprague-Dawley rats were divided equally into 4 groups. One group served as the control (group 1), whereas the other three groups (groups 2-4) were administered L-NAME (25 mg/kg, intraperitoneally). Groups 3 and 4 were given oral nicardipine daily at a dose of 3 mg/kg and Nigella sativa oil at a dose of 2.5 mg/kg for 8 weeks, respectively, concomitantly with L-NAME administration.

RESULTS

Nigella sativa oil prevented the increase in systolic blood pressure in the L-NAME-treated rats. The blood pressure reduction was associated with a reduction in cardiac lipid peroxidation product, NADPH oxidase, angiotensin-converting enzyme activity and plasma nitric oxide, as well as with an increase in heme oxygenase-1 activity in the heart. The effects of Nigella sativa on blood pressure, lipid peroxidation product, nicotinamide adenine dinucleotide phosphate oxidase and angiotensin-converting enzyme were similar to those of nicardipine. In contrast, L-NAME had opposite effects on lipid peroxidation, angiotensin-converting enzyme and NO.

CONCLUSION

The antihypertensive effect of Nigella sativa oil appears to be mediated by a reduction in cardiac oxidative stress and angiotensin-converting enzyme activity, an increase in cardiac heme oxygenase-1 activity and a prevention of plasma nitric oxide loss. Thus, Nigella sativa oil might be beneficial for controlling hypertension.

Effects of the calcium channel antagonist nicardipine on renal action of endothelin in dogs

Endothelin is a potent vasoconstrictor peptide isolated from cultured vascular endothelial cells. Interaction between endothelin and calcium channel antagonist on the renal hemodynamics and urine formation was studied in anesthetized dogs. Intrarenal arterial administration of the peptide progressively reduced renal blood flow from 139 +/- 22 to 85 +/- 12 ml/min at 20 min after the start of continuous infusion, with no change in systemic blood pressure. Glomerular filtration rate, urine flow and urinary sodium and calcium excretion decreased significantly by 30-50% from the preinfusion control values. An endothelin-induced reduction in renal blood flow was markedly attenuated by pretreatment with the calcium antagonist nicardipine (100 ng/kg/min intrarenally). Changes in glomerular filtration rate and antinatriuretic and anticalciuretic actions by the peptide was not affected by nicardipine treatment. It is suggested that the renal vasoconstrictor action, but not the tubular action, of endothelin is functionally coupled with the activation of dihydropyridine-sensitive calcium channels.

The effects of nicardipine or esmolol on the onset time of rocuronium and intubation conditions during rapid sequence induction: a randomized double-blind trial

PURPOSE

The main aims of rapid sequence induction (RSI) are prompt and adequate muscle relaxation for tracheal intubation and hemodynamic stability during and after intubation. The purpose of the present study was to investigate the effects of nicardipine and esmolol on the action of rocuronium and intubation conditions during RSI.

METHODS

Adult patients (n = 82) were randomly allocated to one of three groups. One minute prior to the induction of sevoflurane-based general anesthesia, patients received 20 μg/kg of nicardipine (N group; n = 27) or 0.5 mg/kg of esmolol (E group; n = 27), or 5 ml of saline (C group; n = 28). Patients were assessed according to intubation conditions, the onset time of rocuronium, mean arterial pressure (MAP), and heart rate (HR) during RSI.

RESULTS

The intubation conditions and score were significantly better in the C and N groups than in the E group (P < 0.001). The onset time of rocuronium was shortened in the N group and prolonged in the E group when compared to the C group (P < 0.001). A significant attenuation in the increase of MAP immediately after intubation was observed in the N group as compared with the C and E groups (P < 0.008). HR was significantly lower in the E group than in the N and C groups (P < 0.01).

CONCLUSION

Pretreatment with nicardipine for RSI improved intubation conditions and shortened the onset time of rocuronium and attenuated changes in MAP after intubation. Esmolol may disturb intubation conditions and the onset of action of rocuronium, despite being effective in alleviating responses of HR after RSI.

Anti-neuroinflammatory effects of the calcium channel blocker nicardipine on microglial cells: implications for neuroprotection

BACKGROUND/OBJECTIVE

Nicardipine is a calcium channel blocker that has been widely used to control blood pressure in severe hypertension following events such as ischemic stroke, traumatic brain injury, and intracerebral hemorrhage. However, accumulating evidence suggests that inflammatory processes in the central nervous system that are mediated by microglial activation play important roles in neurodegeneration, and the effect of nicardipine on microglial activation remains unresolved.

METHODOLOGY/PRINCIPAL FINDINGS

In the present study, using murine BV-2 microglia, we demonstrated that nicardipine significantly inhibits microglia-related neuroinflammatory responses. Treatment with nicardipine inhibited microglial cell migration. Nicardipine also significantly inhibited LPS plus IFN-γ-induced release of nitric oxide (NO), and the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, nicardipine also inhibited microglial activation by peptidoglycan, the major component of the Gram-positive bacterium cell wall. Notably, nicardipine also showed significant anti-neuroinflammatory effects on microglial activation in mice in vivo.

CONCLUSION/SIGNIFICANCE

The present study is the first to report a novel inhibitory role of nicardipine on neuroinflammation and provides a new candidate agent for the development of therapies for inflammation-related neurodegenerative diseases.

Detection of dihydropyridine- and voltage-sensitive intracellular Ca(2+) signals in normal human parathyroid cells

We recently showed dihydropyridine- and voltage-sensitive Ca(2+) entry in cultured parathyroid cells from patients with secondary hyperparathyroidism. To determine whether normal parathyroid cells have a similar extracellular Ca(2+) entry system, cells were isolated from normal (non-hyperplastic) human parathyroid glands. Fluorescence signals related to the cytoplasmic Ca(2+) concentration ([Ca(2+)]I) were examined in these cells. Cells loaded with fluo-3/AM showed a transient increase in fluorescence (Ca(2+) transient) following a 10-s exposure to a 150 mM K(+) solution in the presence of millimolar concentrations of external Ca(2+). The Ca(2+) transient was reduced by dihydropyridine antagonists or 0.5 mM Cd(2+), but enhanced by FPL-64176, an L-type Ca(2+)-channel agonist. Ca(2+) transients induced by the 10-s exposure to 3.0 mM extracellular Ca(2+) ([Ca(2+)]o) were also inhibited by dihydropyridine antagonists or 0.5 mM Cd(2+). These results provide the first evidence that normal human parathyroid cells express a dihydropyridine-sensitive Ca(2+) entry system that may be involved in the [Ca(2+)]o-induced change in [Ca(2+)]I. This system might provide a compensatory pathway for negative feedback regulation of parathyroid hormone secretion under physiological conditions.

Contractile signaling pathways in mouse prostate smooth muscle

BACKGROUND

Prostate smooth muscle plays an important role in the physiological ejection of prostatic fluid and also in the pathogenesis of benign prostate hyperplasia. Although mouse is the best genetically engineered animal model to identify potential molecular targets for human diseases, only fragmentary information is available for basic mechanism of mouse prostate contraction.

METHODS

Small smooth muscle tubular rings were excised from four mouse prostate lobes to measure their isometric contractions. High K(+) , noradrenaline (NA), or acetylcholine (ACh) was applied with and without various antagonists and/or inhibitors to examine the contractile signaling pathways.

RESULTS

Maximum amplitude of agonist-induced contractions varied greatly with different lobes but not with different locations or orientations within each lobe. Both NA and ACh produced large contractions in ventral and dorsal rings, whereas only small contractions were elicited in lateral and anterior rings. Combination of alpha-1 and muscarinic antagonists suppressed K(+) depolarization-induced contraction potently in ventral rings, but slightly in anterior rings. Blocking of either Ca(2+) -release or Ca(2+) -influx reduced agonist-induced contraction of ventral rings, however, a considerable amount of contractility remained even with both blockers. Inhibitors of ROCK and PKC partially inhibited NA-induced contractions, whereas a combination of Ca(2+) -blockers and Ca(2+) -sensitization inhibitors strongly suppressed the contraction.

CONCLUSIONS

The ejection of prostatic fluid is differentially regulated in each prostate lobe. In ventral prostate smooth muscle, Ca(2+) -release, Ca(2+) -influx, and ROCK- and PKC-mediated Ca(2+) -sensitizations are all involved in NA-induced contractions. This finding is a useful step toward the understanding of the phenotypic changes in the smooth muscle of BPH prostate.

Intercellular communication within the rat anterior pituitary gland. XV. Properties of spontaneous and LHRH-induced Ca2+ transients in the transitional zone of the rat anterior pituitary in situ

In the transitional zone of the rat anterior pituitary, spontaneous and LHRH-induced Ca(2+) dynamics were visualized using fluo-4 fluorescence Ca(2+) imaging. A majority of cells exhibited spontaneous Ca(2+) transients, while small populations of cells remained quiescent. Approximately 70% of spontaneously active cells generated fast, oscillatory Ca(2+) transients that were inhibited by cyclopiazonic acid (10 μm) but not nicardipine (1 μm), suggesting that Ca(2+) handling by endoplasmic reticulum, but not Ca(2+) influx through voltage-dependent L-type Ca(2+) channels, plays a fundamental role in their generation. In the adult rat anterior pituitary, LHRH (100 μg/ml) caused a transient increase in the Ca(2+) level in a majority of preparations taken from the morning group rats killed between 0930 h and 1030 h. However, the second application of LHRH invariably failed to elevate Ca(2+) levels, suggesting that the long-lasting refractoriness to LHRH stimulation was developed upon the first challenge of LHRH. In contrast, LHRH had no effect in most preparations taken from the afternoon group rats euthanized between 1200 h and 1400 h. In the neonatal rat anterior pituitary, LHRH caused a suppression of spontaneous Ca(2+) transients. Strikingly, the second application of LHRH was capable of reproducing the suppression of Ca(2+) signals, indicating that the refractoriness to LHRH had not been established in neonatal rats. These results suggest that responsiveness to LHRH has a long-term refractoriness in adult rats, and that the physiological LHRH surge may be clocked in the morning. Moreover, LHRH-induced excitation and associated refractoriness appear to be incomplete in neonatal rats and may be acquired during development.

Effect of allyl sulfides from garlic essential oil on intracellular ca2+ levels in renal tubular cells

Diallyl sulfide (1), diallyl disulfide (2), and diallyl trisulfide (3), which are major organosulfur compounds of garlic (Allium sativum), are recognized as a group of potential chemopreventive compounds. In this study, the early signaling effects of 3 were examined on Madin-Darby canine kidney (MDCK) cells loaded with the Ca(2+)-sensitive dye fura-2. It was found that 3 caused an immediate and sustained increase of [Ca(2+)](i) in a concentration-dependent manner (EC(50) = 40 μM). Compound 3 also induced a [Ca(2+)](i) elevation when extracellular Ca(2+) was removed, but the magnitude was reduced by 45%. In Ca(2+)-free medium, the 3-induced [Ca(2+)](i) level was abolished by depleting stored Ca(2+) with 1 μM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor). Elevation of [Ca(2+)](i) caused by 3 in the Ca(2+)-containing medium was not affected by modulation of protein kinase C activity. The 3-induced Ca(2+) influx was inhibited by nifedipine and nicardipine (1 μM). U73122, an inhibitor of phospholipase C, abolished ATP (but not the 3-induced [Ca(2+)](i) level). These findings suggest that 3 induced a significant [Ca(2+)](i) elevation in MDCK renal tubular cells by stimulating both extracellular Ca(2+) influx and thapsigargin-sensitive intracellular Ca(2+) release via as yet unidentified mechanisms. Furthermore, the order of the allyl sulfide-induced [Ca(2+)](i) elevation and cell viability was 1 < 2 < 3. The differential effect of allyl sulfides on Ca(2+) signaling and cell death appears to correlate with the number of sulfur atoms in the structure of these allyl sulfides.

Osteopontin is involved in urotensin II-induced migration of rat aortic adventitial fibroblasts

Recent studies suggest that both osteopontin and urotensin II (UII) play critical roles in vascular remodeling. We previously showed that UII could stimulate the migration of aortic adventitial fibroblasts. In this study, we examined whether osteopontin is involved in UII-induced migration of rat aortic adventitial fibroblasts and examined the effects and mechanisms of UII on osteopontin expression in adventitial fibroblasts. Migration of adventitial fibroblasts induced by UII could be inhibited significantly by osteopontin antisense oligonucleotide (P<0.01) but not sense or mismatch oligonucleotides (P>0.05). Moreover, UII dose- and time-dependently promoted osteopontin mRNA expression and protein secretion in the cells, with maximal effect at 10(-8)mol/l at 3h for mRNA expression or at 12h for protein secretion (both P<0.01). Furthermore, the UII effects were significantly inhibited by its receptor antagonist SB710411 (10(-6)mol/l), and Ca(2+) channel blocker nicardipine (10(-5)mol/l), protein kinase C (PKC) inhibitor H7 (10(-5)mol/l), calcineurin inhibitor cyclosporine A (10(-5)mol/l), mitogen-activated protein kinase (MAPK) inhibitor PD98059 (10(-5)mol/l) and Rho kinase inhibitor Y-27632 (10(-5)mol/l). Thus, osteopontin is involved in the UII-induced migration of adventitial fibroblasts, and UII could upregulate osteopontin gene expression and protein synthesis in rat aortic adventitial fibroblasts by activating its receptor and the Ca(2+) channel, PKC, calcineurin, MAPK and Rho kinase signal transduction pathways.

Contractile Response of Human Omental Arteries to Endothelin

The effects of endothelin have been studied in isolated arterial segments (0·8–1 mm in external diam.) of human omental arteries obtained during the course of abdominal operations (15 patients, 7 men and 8 women). Paired segments, one normal and the other de-endothelized, were mounted for isometric recording of tension in organ baths. Endothelin produced concentration-dependent contractions with an EC50 value of 5·4 × 10−9  m. Removal of endothelium did not affect significantly endothelin-induced contractions (EC50, 6·7 × 10−9  m). Removal of extracellular calcium or addition of the calcium channel blocker nicardipine (10−6  m) diminished but did not abolish responses to endothelin. These results indicate that endothelin exerts powerful contractile effects on human isolated omental arteries which are independent of the presence of an intact endothelial cell layer; this contraction cannot be explained solely by voltage-dependent calcium channels.

Cardiovascular pharmacology: an update

Cardiovascular diseases are a leading cause of hospitalizations and death in the United States and elsewhere in the world. Developing new therapeutic agents for cardiovascular diseases has always been the priority for the pharmaceutical industry because of the huge potential market for these drugs. Some of these newer drugs are frequently used in the practice of cardiovascular anesthesiology. This article reviews the recent advances in cardiovascular medications related to the practice of cardiac anesthesia.

Screening for calcium channel modulators in CLN3 siRNA knock down SH-SY5Y neuroblastoma cells reveals a significant decrease of intracellular calcium levels by selected L-type calcium channel blockers

BACKGROUND

Defects of the CLN3 gene on chromosome 16p12.1 lead to the juvenile form of neuronal ceroid-lipofuscinosis (JNCL, Batten Disease), the most common recessive inherited neurodegenerative disorder in children. Dysregulation of intracellular calcium homeostasis in the absence of a functional CLN3 protein (CLN3P, Battenin) has been linked to synaptic dysfunction and accelerated apoptosis in vulnerable neuronal cells. Prolonged increase of intracellular calcium concentration is considered to be a significant trigger for neuronal apoptosis and cellular loss in JNCL.

METHODS

We examined the potential effect of 41 different calcium channel modulators on intracellular calcium concentration in CLN3 siRNA knock down SH-SY5Y neuroblastoma cells.

RESULTS

Six drugs belonging to the group of voltage dependent L-type channel blockers show significant lowering of the increased intracellular calcium levels in CLN3 siRNA knock down cells.

CONCLUSIONS

Our studies provide important new data suggesting possible beneficial effects of the tested drugs on calcium flux regulated pathways in neuronal cell death. Therapeutic intervention in this untreatable disease will likely require drugs that cross the blood-brain barrier as did all of the positively screened drugs in this study.

GENERAL SIGNIFICANCE

Better comprehension of the mechanism of neurodegeneration in rare recessive disorders, such as neuronal ceroid-lipofuscinoses, is likely to help to better understand mechanisms involved in more complex genetic neurodegenerative conditions, such as those associated with aging.

Isoflurane enhances spontaneous Ca(2+) oscillations in developing rat hippocampal neurons in vitro

BACKGROUND

During the nervous system development, spontaneous synchronized Ca(2+) oscillations are thought to possess integrative properties because their amplitude and frequency can influence the patterning of neuronal connection, neuronal differentiation, axon outgrowth, and long-distance wiring. Accumulating studies have confirmed that some drugs such as volatile anesthetic isoflurane produced histopathologic changes in the central nervous system in juvenile animal models. Because the hippocampus plays an important role in learning and memory, the present work was designed to characterize the Ca(2+) oscillations regulated by volatile anesthetic isoflurane in primary cultures of developing hippocampal neurons (5-day-cultured).

METHODS

Primary cultures of rat hippocampal neurons (5-day-cultured) were loaded with the Ca(2+) indicator Fluo-4AM (4 microM) and were studied with a confocal laser microscope.

RESULTS

Approximately 22% of 5-day-cultured hippocampal neurons exhibited typical Ca(2+) oscillations. These oscillations were dose-dependently enhanced by isoflurane (EC50 0.5 MAC, minimum alveolar concentration) and this effect could be reverted by bicuculline (50 microM), a specific gamma-aminobutyric acid (GABA(A)) receptor antagonist.

CONCLUSION

Unlike its depressant effect on the Ca(2+) oscillations in adult neurons in previous researches, isoflurane dose-dependently enhanced calcium oscillations in developing hippocampal neurons by activating GABA(A) receptors, a major excitatory receptor in synergy with N-methyl-d-aspartate receptors at the early stages of development. It may be involved in the mechanism of an isoflurane-induced neurotoxic effect in the developing rodent brain.

[Effects of modulators of calcium metabolism on mesenteric artery contractions during activation of P2X receptors in guinea-pig]

ATP evokes changes in the vascular tone through the activation of P2X and P2Y purinoceptors. To evaluate relative contribution of Ca2+ entry through the L-type voltage-gated calcium channels and Ca2+ -induced Ca2+ -release (CICR) mechanisms in initiation of vascular smooth muscle contraction induced by P2XRs activation, we have applied P2X receptor agonist -meATP (10 microM) and measured changes in phasic isometric tension of endothelium-denuded mesenteric artery rings in the presence of antagonists IP3Rs (60 mcmol/l APB) or RyRs (100 mcmol/l tetracaine) combined with on-off modulation of the L-type calcium channels by nicardipine (5 microM). We found that activation of P2XRs results in Ca2+ release from SR through both IP3Rs and RyRs. In addition, Ca2+ entry via L-type Ca2+ channels also participates in Ca2+ release from SR presumably through CICR mechanism. However, the phasic contractions in the presence of nicardipine were found to be less sensitive to inhibition of IP3Rs than RyRs (47.1 +/- 9.5% and 22.9 +/- 1.4% comparing to 38.3 +/- 9.6% and 518 +/- 7.8% in control solution for IP3R and RyR inhibition, respectively). This finding suggests that Ca2+ entered the cell through L-type Ca2+ channels, has easier access to IP3Rs than to RyRs. This suggestion is further supported by immunostaining IP3Rs and RyRs. Confocal imaging revealed that sub-PM SR elements are enriched with IP3Rs, while RyRs are predominantly located in the central/perinuclear SR elements.

Induction of hepatic Cyp2b and Cyp3a subfamily enzymes by nicardipine and nifedipine in mice

1. Nicardipine (Nic) or nifedipine (Nif) was given to male and female C57BL/6J mice by a single gavage at doses of 100, 200 and 400 micromolkg(-1), and changes in the levels of mRNA and apoprotein of hepatic cytochrome P450 (P450) enzymes, including Cyp2b9, Cyp2b10, Cyp3a11 and Cyp3a41, were examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting, respectively. Furthermore, hepatic microsomal activities for pentoxyresorufin O-dealkylation (PROD) and nifedipine oxidation, which are mainly mediated by Cyp2b and Cyp3a subfamily enzymes, respectively, were measured. 2. Results from RT-PCR analysis revealed that Nic, but not Nif, showed a capacity for activating the Cyp3a11 gene in either sex of mice and that both chemicals could induce a male-selective activation of Cyp2b10 gene, although they had no capacity for activating the Cyp2b9 and Cyp3a41 genes in either sex. 3. Increased levels of the mRNAs of Cyp2b10 and Cyp3a11 were closely correlated with those of apoprotein and activity of the corresponding P450 subfamily enzymes. 4. The study demonstrated for the first time that Nic, but not Nif, showed the ability to induce Cyp3a11 in both sexes of mice, although both Nif and Nic led to a male-selective induction of Cyp2b10, and that Nic and Nif had no ability to induce Cyp2b9 and Cyp3a41 in either sex.

Evidence for postsynaptic modulation of muscle contraction by a Drosophila neuropeptide

DPKQDFMRFamide, the most abundant FMRFamide-like peptide in Drosophila melanogaster, has been shown previously to enhance contractions of larval body wall muscles elicited by nerve stimulation and to increase excitatory junction potentials (EJPs). The present work investigated the possibility that this peptide can also stimulate muscle contraction by a direct action on muscle fibers. DPKQDFMRFamide induced slow contractions and increased tonus in body wall muscles of Drosophila larvae from which the central nervous system had been removed. The threshold for this effect was approximately 10(-8)M. The increase in tonus persisted in the presence of 7x10(-3)M glutamate, which desensitized postsynaptic glutamate receptors. Thus, the effect on tonus could not be explained by enhanced release of glutamate from synaptic terminals and, thus, may represent a postsynaptic effect. The effect on tonus was abolished in calcium-free saline and by treatment with L-type calcium channel blockers, nifedipine and nicardipine, but not by T-type blockers, amiloride and flunarizine. The present results provide evidence that this Drosophila peptide can act postsynaptically in addition to its apparent presynaptic effects, and that the postsynaptic effect requires influx through L-type calcium channels.

[Effects of sulfur dioxide on cardiac function of isolated perfusion heart of rat]

OBJECTIVE

To observe the effects of sulfur dioxide (SO2) on cardiac function of isolated perfused heart of rat and to explore the physiological regulation of endogenous SO2 on myocardial action.

METHODS

The hearts of 64 Wistar rats were isolated, perfused with Krebs-Henseleit (KH) solution through Langendorff apparatus, and randomly divided into 8 equal groups: Four groups underwent perfusion of SO2 of the concentrations 1, 10, 100, 1000 micromol/L respectively for 5 min and then perfused with KH solution for 15 min. Eight hearts underwent perfusion of SO2 of the physiological concentration (10 micromol/L) for 20 min. The control group underwent perfusion of KH solution for 20 min. Eight hearts of the nicardipine group underwent perfusion of nicardipine, a L-type calcium channel blocker, 2.5 micromol/L for 5 min, SO2 10 micromol/L for 5 min, and then KH solution for 10 min. The heart in the hydroxamate (HDX) group underwent perfusion of HDX, an inhibitor of SO2 endogenous generating enzymes, for 5 min, and then perfused by KH solution for 15 min. The heart rate (HR), difference of left ventricular pressure (LVP), left ventricular peak rate of contraction (+ dp/dtmax), peak rate of relaxation (- dp/dtmax), and coronary flow (CF) were measured. Then transmission electron microscopy was conducted.

RESULTS

SO2 concentration-dependently inhibited the left ventricular +/- dp/dtmax, LVP, HR, and CF (all P < 0.01). The left ventricular +/- dp/dtmax, LVP, and HR were inhibited (P < 0.05) by the physiological concentration (10 micromol/L) SO2 donor continuous perfusion for 20 min. During perfusion 20 min, the LVP, + dp/dtmax, - dp/dtmax, and HR after perfusion for 20 min of the physiological concentration (10 micromol/L) SO2 donor continuous perfusion group were (15 +/- 3) mm Hg, (485 +/- 74) mm Hg/s, (339 +/- 64) mm Hg/s, and (114 +/- 26)/min respectively, all significantly lower than those 5 min after perfusion [(23 +/- 7) mm Hg, (595 +/- 93)mm Hg/s, (436 +/- 83) mm Hg/s, and (159 +/- 31)/min, all P < 0.05]. The LVP, + dp/ dtmax, -dp/dtmax, and HR of the nicardipine group were(37 +/- l0)mm Hg, (1025 +/- 287)mm Hg/s, (570 +/- 181)mm Hg/s, and (139 +/- 48)/min respectively, all not significantly different from those of the control group. The LVP, + dp/dtmax, - dp/dtmax, and CF after perfusion of the HDX group were (50 +/- 11)mm Hg, (1167 +/- 270) mm Hg/s, (889 +/- 72) mm Hg/s, and (6.3 +/- 1.9) ml/min respectively, all significantly lower than those before perfusion [(69 +/- 16) mm Hg, (1579 +/- 315) mm Hg/s, (1186 +/- 263) mm Hg/s, and (9.5 +/- 1.3) ml/min, all P < 0.05].

CONCLUSION

Exogenous SO2 has negative inotropic effect on myocardium. by the mechanism related to voltage-gated calcium channel. Nicardipine blocks the inhibitory effect of SO2 at physiological concentration.

[6]-gingerol induces Ca2+ mobilization in Madin-Darby canine kidney cells

[6]-gingerol, a major phenolic compound derived from ginger (Zingiber officinale), is a potential chemopreventive compound that can induce stress in cancer cells and cause apoptotic cell death. This study examines the early signaling effects of [6]-gingerol on renal cells. It was found that [6]-gingerol caused a slow and sustained rise of [Ca2+]i in a concentration-dependent manner. [6]-gingerol also induced a [Ca2+]i rise when extracellular Ca2+ was removed, but the magnitude was reduced by 80%. Depletion of intracellular Ca2+ stores with CCCP, a mitochondrial uncoupler, did not affect the action of [6]-gingerol. In a Ca2+-free medium, the [6]-gingerol-induced [Ca2+]i rise was partially abolished by depleting stored Ca2+ with thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor). The elevation of [6]-gingerol-caused [Ca2+]i in a Ca2+-containing medium was not affected by modulation of protein kinase C activity. The [6]-gingerol-induced Ca2+ influx was blocked by nicardipine. U73122, an inhibitor of phospholipase C, abolished ATP (but not [6]-gingerol)-induced [Ca2+]i rise. These findings suggest that [6]-gingerol induces a significant rise in [Ca2+]i in MDCK renal tubular cells by stimulating both extracellular Ca2+ influx and thapsigargin-sensitive intracellular Ca2+ release via as yet unidentified mechanisms.

Perioperative hypertension management

Perioperative hypertension is commonly encountered in patients that undergo surgery. While attempts have been made to standardize the method to characterize the intraoperative hemodynamics, these methods still vary widely. In addition, there is a lack of consensus concerning treatment thresholds and appropriate therapeutic targets, making absolute recommendations about treatment difficult. Nevertheless, perioperative hypertension requires careful management. When treatment is necessary, therapy should be individualized for the patient. This paper reviews the pharmacologic agents and strategies commonly used in the management of perioperative hypertension.

Effect of chemosensitizers on minimum inhibitory concentrations of fluconazole in Candida albicans

OBJECTIVE

To evaluate the effect of chemosensitizers on the in vitro activity of fluconazole against Candida albicans strains.

MATERIALS AND METHODS

Using Clinical Laboratory Standard Institute method, antifungal activity of fluconazole was determined alone and in combination with 16 chemosensitizers that included verapamil, reserpine, quinine, quinidine, gemfibrozil, lansoprazole, tamoxifen, diltiazem, desipramine, nicardipine, cyclosporine, chlorpromazine, prochlorperazine, promethazine, thioridazine, and trifluoperazine. Further studies were done using double combinations of selected chemosensitizers with fluconazole (28 combinations). For testing combinations, half of the minimum inhibitory concentration (MIC) of each agent was selected in order to avoid the effect of the drug alone. One reference strain (ATCC90028) and one clinical isolate of C. albicans were used for testing the in vitro activity. Broth dilution method was used to determine the MICs of fluconazole and chemosensitizers.

RESULTS

Of the 16 chemosensitizers tested, 3 exhibited in vitro activity by increasing fluconazole susceptibility to 7-fold. The MICs of the reference strain and clinical isolate for fluconazole were 5.5 and 0.55 microg/ml, respectively, and these were reduced to 0.76 microg/ml by gemfibrozil, 0.83 microg/ml by quinine, and 0.76 microg/ml by chlorpromazine in the reference strain, with MIC reduction to 0.08 microg/ml by all three chemosensitizers in the clinical isolate. Some double combinations reduced the MIC of fluconazole to 10- to 100-fold, even when the chemosensitizers were not effective alone.

CONCLUSION

The most effective double combinations were those of chlorpromazine with either reserpine or nicardipine.

Effect of anabasine on catecholamine secretion from the perfused rat adrenal medulla

OBJECTIVES

The present study was designed to investigate the characteristic effects of anabasine on secretion of catecholamines (CA) from the isolated perfused rat adrenal gland and to establish its mechanism of adrenomedullary secretion.

METHODS

The adrenal gland was isolated by a modification of the Wakade method, and perfused with normal Krebs-bicarbonate solution. The content of CA was measured using fluorometry.

RESULTS

The perfusion of anabasine(30-300 microM) into an adrenal vein for 60 min resulted in great increases in CA secretions in a dose-dependent fashion. Upon repeated injection of anabasine (100 microM) at 120 min-intervals, CA secretion was rapidly decreased after the third injection of anabasine. However, there was no statistical difference between the CA secretory responses of both 1st and 2nd treated groups by the successive administration of anabasine at 120 min-intervals. Tachyphylaxis to the releasing effects of CA evoked by anabasine was observed by repeated administration. Therefore, in all subsequent experiments, anabasine was not administered successively more than twice at only 120 min-intervals. The CA-releasing effects of anabasine were depressed by pretreatment with chlorisondamine (selective neuronal nicotinic receptor antagonist, 1 microM), atropine (muscarinic receptor antagonist, 2 microM), nicardipine (L-type dihydropyridine Ca2+ channel blocker, 1 microM), TMB-8 (anti-releaser of intracellular Ca2 +, 30 microM), and perfusion of EGTA (Ca2+ chelator, 5 mM) plus Ca2+ -free medium. In the presence of anabasine (100 microM), the CA secretory responses induced by acetylcholine (5.32 mM), high K+ (direct membrane-depolarizer, 56 mM), DMPP(selective neuronal nicotinic receptor agonist, 10(-4) M), and McN-A-343 (selective muscarinic M1 receptor agonist, 10(-4) M) were maximally enhanced in the first 4 min. However, as time elapsed, these responses became more inhibited at later periods. Furthermore, the perfusion of nicotine (30 microM) into an adrenal vein for 60 min also caused a great increase in CA secretion, leading to peak response in the first 0-5 min period. In the presence of nicotine (30 microM), the CA secretory responses induced by acetylcholine, high K+, DMPP and McN-A-343 were also enhanced for the first 4min, but later reduced to less than the control release.

CONCLUSIONS

Taken together, these experimental results indicate that anabasine affects rat adrenomedullary CA secretion in a calcium-dependent fashion. This facilitatory effect of anabasine may be mediated by activation of both cholinergic nicotinic and muscarinic receptors, which is relevant to both stimulation of Ca2+ influx into adrenomedullary chromaffin cells and Ca2+ release from cytoplasmic Ca2+ Anabasine may be less potent than nicotine in rat adrenomedullary CA secretion. Anabasine, in addition to nicotine, alkaloids present in tobacco smoke may be a risk factor in causing cardiovascular diseases.

Voltage-gated Ca2+ currents are necessary for slow-wave propagation in the canine gastric antrum

Electrical slow waves determine the timing and force of peristaltic contractions in the stomach. Slow waves originate from a dominant pacemaker in the orad corpus and propagate actively around and down the stomach to the pylorus. The mechanism of slow-wave propagation is controversial. We tested whether Ca(2+) entry via a voltage-dependent, dihydropyridine-resistant Ca(2+) conductance is necessary for active propagation in canine gastric antral muscles. Muscle strips cut parallel to the circular muscle were studied with intracellular electrophysiological techniques using a partitioned-chamber apparatus. Slow-wave upstroke velocity and plateau amplitude decreased from the greater to the lesser curvature, and this corresponded to a decrease in the density of interstitial cells of Cajal in the lesser curvature. Slow-wave propagation velocity between electrodes impaling cells in two regions of muscle and slow-wave upstroke and plateau were measured in response to experimental conditions that reduce the driving force for Ca(2+) entry or block voltage-dependent Ca(2+) currents. Nicardipine (0.1-1 microM) did not affect slow-wave upstroke or propagation velocities. Upstroke velocity, amplitude, and propagation velocity were reduced in a concentration-dependent manner by Ni(2+) (1-100 microM), mibefradil (10-30 microM), and reduced extracellular Ca(2+) (0.5-1.5 mM). Depolarization (by 10-15 mM K(+)) or hyperpolarization (10 microM pinacidil) also reduced upstroke and propagation velocities. The higher concentrations (or lowest Ca(2+)) of these drugs and ionic conditions tested blocked slow-wave propagation. Treatment with cyclopiazonic acid to empty Ca(2+) stores did not affect propagation. These experiments show that voltage-dependent Ca(2+) entry is obligatory for the upstroke phase of slow waves and active propagation.

Vasorelaxant effects of Acer nikoense extract and isolated coumarinolignans on rat aortic rings

The organic extract of the heartwood of Acer nikoense Maxim. (Aceraceae) showed vasorelaxant activity on rat aorta with or without endothelium. Coumarin [scopoletin (1)] and coumarinolignans [cleomiscosin A (2) and aquillochin (3)] were isolated as major constituents from the organic extract of the heartwood of A. nikoense. Compounds 1-3 exhibited moderate vasorelaxant effects on rat aorta, while 2 and 3 showed vasorelaxant effects in the norepinephrine-stimulated and also in high K+-depolarized preparations.

Mechanisms of endothelin-1-induced decrease in contractility in adult mouse ventricular myocytes

BACKGROUND AND PURPOSE

The potent vasoconstrictor polypeptide endothelin-1 (ET-1) plays an important pathophysiological role in progression of cardiovascular diseases and elicits prominent effects on myocardial contractility. Although ET-1 produces a positive inotropy in cardiac muscle of most mammalian species, it induces a sustained negative inotropy in mice. This study was performed to gain an insight into the cellular mechanisms underlying the negative inotropy in adult mouse ventricular myocytes.

EXPERIMENTAL APPROACH

Cell shortening and Ca(2+) transients were simultaneously recorded from isolated mouse ventricular myocytes loaded with the Ca(2+)-sensitive fluorescent dye indo-1.

KEY RESULTS

ET-1 decreased cell shortening in a concentration-dependent manner (pD(2) value of 10.1). The ET-1-induced decrease in cell shortening was associated with a decrease in Ca(2+) transients. In addition, the Ca(2+) transient/cell-shortening relationship was shifted to the right by ET-1, indicating decreased myofilament Ca(2+) sensitivity. The instantaneous relationship of the rising phase of the Ca(2+) transient and cell shortening was shifted to the right by ET-1. Decreased Ca(2+) transients and cell shortening induced by ET-1 were markedly attenuated by the specific Na(+)/Ca(2+) exchange inhibitor SEA0400.

CONCLUSIONS AND IMPLICATIONS

ET-1-induced negative inotropy in mouse ventricular myocytes was mediated by decreased Ca(2+) transients and myofilament Ca(2+) sensitivity. These data are entirely consistent with the involvement of increased Ca(2+) extrusion via the Na(+)/Ca(2+) exchanger in the ET-1-mediated decrease in Ca(2+) transients. Decreased Ca(2+) sensitivity may be due to retardation of cell shortening in response to a rise in Ca(2+) transients.

Properties of spontaneous Ca2+ transients recorded from interstitial cells of Cajal-like cells of the rabbit urethra in situ

Interstitial cells of Cajal-like cells (ICC-LCs) in the urethra may act as electrical pacemakers of spontaneous contractions. However, their properties in situ and their interaction with neighbouring urethral smooth muscle cells (USMCs) remain to be elucidated. To further explore the physiological role of ICC-LCs, spontaneous changes in [Ca(2+)](i) (Ca(2+) transients) were visualized in fluo-4 loaded preparations of rabbit urethral smooth muscle. ICC-LCs were sparsely distributed, rather than forming an extensive network. Ca(2+) transients in ICC-LCs had a lower frequency and a longer half-width than those of USMCs. ICC-LCs often exhibited Ca(2+) transients synchronously with each other, but did not often show a close temporal relationship with Ca(2+) transients in USMCs. Nicardipine (1 microm) suppressed Ca(2+) transients in USMCs but not in ICC-LCs. Ca(2+) transients in ICC-LCs were abolished by cyclopiazonic acid (10 microm), ryanodine (50 microm) and caffeine (10 mm) or by removing extracellular Ca(2+), and inhibited by 2-aminoethoxydiphenyl borate (50 microm) and 3-morpholino-sydnonimine (SIN-1; 10 microm), but facilitated by increasing extracellular Ca(2+) or phenylephrine (1-10 microm). These results indicated that Ca(2+) transients in urethral ICC-LCs in situ rely on both Ca(2+) release from intracellular Ca(2+) stores and Ca(2+) influx through non-L-type Ca(2+) channel pathways. ICC-LCs may not act as a coordinated pacemaker electrical network as do ICC in the gastrointestinal (GI) tract. Rather they may randomly increase excitability of USMCs to maintain the tone of urethral smooth muscles.

Sub-plasmalemmal [Ca2+]i upstroke in myocytes of the guinea-pig small intestine evoked by muscarinic stimulation: IP3R-mediated Ca2+ release induced by voltage-gated Ca2+ entry

Membrane depolarization triggers Ca²⁺ release from the sarcoplasmic reticulum (SR) in skeletal muscles via direct interaction between the voltage-gated L-type Ca²⁺ channels (the dihydropyridine receptors; VGCCs) and ryanodine receptors (RyRs), while in cardiac muscles Ca²⁺ entry through VGCCs triggers RyR-mediated Ca²⁺ release via a Ca²⁺-induced Ca²⁺ release (CICR) mechanism. Here we demonstrate that in phasic smooth muscle of the guinea-pig small intestine, excitation evoked by muscarinic receptor activation triggers an abrupt Ca²⁺ release from sub-plasmalemmal (sub-PM) SR elements enriched with inositol 1,4,5-trisphosphate receptors (IP₃Rs) and poor in RyRs. This was followed by a lesser rise, or oscillations in [Ca²⁺]_i. The initial abrupt sub-PM [Ca²⁺]_i upstroke was all but abolished by block of VGCCs (by 5 μM nicardipine), depletion of intracellular Ca²⁺ stores (with 10 μM cyclopiazonic acid) or inhibition of IP₃Rs (by 2 μM xestospongin C or 30 μM 2-APB), but was not affected by block of RyRs (by 50–100 μM tetracaine or 100 μM ryanodine). Inhibition of either IP₃Rs or RyRs attenuated phasic muscarinic contraction by 73%. Thus, in contrast to cardiac muscles, excitation–contraction coupling in this phasic visceral smooth muscle occurs by Ca²⁺ entry through VGCCs which evokes an initial IP₃R-mediated Ca²⁺ release activated via a CICR mechanism.

Quantitative Structure−Activity Relationship Analysis and Molecular Dynamics Simulation To Functionally Validate Nonsynonymous Polymorphisms of Human ABC Transporter ABCB1 (P-Glycoprotein/MDR1)

Several preclinical and clinical studies suggest the importance of naturally occurring polymorphisms of drug transporters in the individual difference of drug response. To functionally validate the nonsynonymous polymorphisms of ABCB1 (P-glycoprotein/MDR1) in vitro, we generated SNP variant forms (i.e., S400N, R492C, R669C, I849M, A893P, A893S, A893T, M986V, A999T, P1051A, and G1063A) and expressed them in Sf9 cells. The kinetic properties (Km and Vmax) of those variants were analyzed by measuring the ATPase activity to obtain the ATPase profile for each variant toward structurally unrelated substrates. On the basis of the experimental data, we determined the substrate specificity of ABCB1 WT and its variants by the quantitative structure-activity relationship (QSAR) analysis method. While several SNP variants appeared to influence the substrate specificity of ABCB1, the nonsynonymous polymorphisms of 2677G > T, A, or C at amino acid position 893 (Ala > Ser, Thr, or Pro) have great impacts on both the activity and the substrate specificity of ABCB1. The A893P variant (2677G > C), a rare mutation, exhibited markedly high activity of ATPase toward different test compounds. Molecular dynamics (MD) simulation based on a three-dimensional structural model of human ABCB1 revealed that multiple kinks are formed in the intracellular loop between transmembrane domains 10 and 11 of the A893P variant (2677G > C) protein. The polymorphisms of 2677G, 2677T, and 2677A exhibit wide ethnic differences in the allele frequency, and these nonsynonymous polymorphisms are suggested to be clinically important because of their altered ATPase activity and substrate specificity toward different drugs.

Effects of nicardipine-induced hypotension on cerebrovascular carbon dioxide reactivity in patients with diabetes mellitus under sevoflurane anesthesia

PURPOSE

The purpose of this study was to examine the effects of nicardipine-induced hypotension on cerebrovascular CO2 reactivity in patients with diabetes mellitus under sevoflurane anesthesia.

METHODS

Nineteen diabetic patients, and 11 nondiabetic patients (serving as controls), undergoing elective orthopedic, cardiovascular, or thoracic surgery were included in the study. The diabetic patients were divided into three groups according to the antidiabetic therapy they were receiving, i.e., diet therapy (n = 6), oral antidiabetic drugs (n = 7), and insulin (n = 6). Anesthesia was maintained with 1.0 minimum alveolar concentration of sevoflurane. Absolute and relative cerebrovascular CO2 reactivity was calculated using a 2.5-MHz pulsed transcranial Doppler (TCD) probe for the continuous measurement of mean blood flow velocity in the middle cerebral artery (Vmca). The cerebrovascular CO2 reactivity was measured both at baseline and during hypotension by increasing the ventilatory frequency by 4 to 7 breaths.min(-1). Nicardipine was used to induce hypotension.

RESULTS

We found that values for the Bispectral index (BSI), baseline mean blood pressure, endtidal CO2 (Pet(CO2)), and Vmca were essentially identical in all patients, irrespective of the type of antidiabetic treatment being taken. Values for absolute and relative CO2 reactivity in insulin-dependent patients, at both baseline blood pressure and during hypotension, were lower than those in patients in the antidiabetic drug, diet, and control groups (during hypotension, absolute CO2 reactivity: diet group: 3.2 +/- 0.9; oral antidiabetic drug group: 3.2 +/- 0.7; insulin group: 1.5 +/- 0.6; control group: 3.4 +/- 0.8 cm.s(-1).mmHg(-1), [P < 0.05 insulin group vs the other groups]; relative CO2 reactivity: diet group, 6.3 +/- 1.0; oral antidiabetic drug group, 6.5 +/- 0.8; insulin group, 3.5 +/- 0.8; control group, 6.5 +/- 0.7%.mmHg(-1), [P < 0.05 insulin group vs the other groups].

CONCLUSION

We concluded that cerebrovascular CO2 reactivity in insulin-dependent patients is impaired during nicardipine-induced hypotension under sevoflurane anesthesia.

The mechanism and spread of pacemaker activity through myenteric interstitial cells of Cajal in human small intestine

BACKGROUND & AIMS

It has been generally assumed that interstitial cells of Cajal (ICC) in the human gastrointestinal tract have similar functions to those in rodents, but no direct experimental evidence exists to date for this assumption. This is an important question because pathologists have noted decreased numbers of ICC in patients with a variety of motility disorders, and some have speculated that loss of ICC could be responsible for motor dysfunction. Our aims were to determine whether myenteric ICC (ICC-MY) in human jejunum are pacemaker cells and whether these cells actively propagate pacemaker activity.

METHODS

The mucosa and submucosa were removed, and strips of longitudinal muscle were peeled away to reveal the ICC-MY network. ICC networks were loaded with the Ca(2+) indicator fluo-4, and pacemaker activity was recorded via high-speed video imaging at 36.5 degrees C +/- 0.5 degrees C.

RESULTS

Rhythmic, biphasic Ca(2+) transients (6.03 +/- 0.33 cycles/min) occurred in Kit-positive ICC-MY. These consisted of a rapidly propagating upstroke phase that initiated a sustained plateau phase, which was associated with Ca(2+) spikes in neighboring smooth muscle. Pacemaker activity was dependent on inositol 1,4,5-triphosphate receptor-operated stores and mitochondrial function. The upstroke phase of Ca(2+) transients in ICC-MY appeared to result from Ca(2+) influx through dihydropyridine-resistant Ca(2+) channels, whereas the plateau phase was attributed to Ca(2+) release from inositol 1,4,5-triphosphate receptor-operated Ca(2+) stores.

CONCLUSIONS

Each ICC-MY in human jejunum generates spontaneous pacemaker activity that actively propagates through the ICC network. Loss of these cells could severely disrupt the normal function of the human small intestine.

The comparative effects of intravenous nicardipine and prostaglandin E1 on the cerebral pial arteriolar constriction seen after unclamping of an aortic cross-clamp in rabbits

BACKGROUND

The potent vasodilators nicardipine and prostaglandin E1 (PGE1) are useful for the treatment of systemic hypertension or pulmonary hypertension during aortic surgery.

METHODS

We measured cerebral pial arteriolar diameters, using a rabbit closed cranial window preparation: before (baseline) and 15 min after the start of an IV infusion (preclamp) (0.9% saline [control group], nicardipine [at 0.1, 1.0, or 10 microg x kg(-1) x min(-1)], or PGE1 [at 0.1 or 1.0 microg x kg(-1) x min(-1)]), just after aortic clamping, 20 min after clamping, and at 0-60 min after unclamping.

RESULTS

In the control group, a significant decrease in diameter persisted for at least 60 min after unclamping (maximum [at 60 min], -16% for large [> or =75 microm], and -27% for small [<75 microm] arterioles versus baseline). Although the aortic unclamping-induced vasoconstriction was unaffected under the smallest dose of nicardipine, it was significantly attenuated under larger doses in both large and small arterioles (residual vasoconstriction, -10% and -6% for large and -18% and -10% for small arterioles; at 60 min). The pial arteriolar constriction observed at 5 min or more after unclamping in the control group was not altered by PGE1 in either large or small arterioles.

CONCLUSIONS

The larger doses of nicardipine, but neither dose of PGE1, attenuated aortic unclamping-induced sustained cerebral pial arteriolar constriction.

Regulation of membrane excitability by intracellular pH (pHi) changers through Ca2+-activated K+ current (BK channel) in single smooth muscle cells from rabbit basilar artery

Employing microfluorometric system and patch clamp technique in rabbit basilar arterial myocytes, regulation mechanisms of vascular excitability were investigated by applying intracellular pH (pH(i)) changers such as sodium acetate (SA) and NH(4)Cl. Applications of caffeine produced transient phasic contractions in a reversible manner. These caffeine-induced contractions were significantly enhanced by SA and suppressed by NH(4)Cl. Intracellular Ca(2+) concentration ([Ca(2+)](i)) was monitored in a single isolated myocyte and based the ratio of fluorescence using Fura-2 AM (R (340/380)). SA (20 mM) increased and NH(4)Cl (20 mM) decreased R (340/380) by 0.2 +/- 0.03 and 0.1 +/- 0.02, respectively, in a reversible manner. Caffeine (10 mM) transiently increased R (340/380) by 0.9 +/- 0.07, and the ratio increment was significantly enhanced by SA and suppressed by NH(4)Cl, implying that SA and NH(4)Cl may affect [Ca(2+)](i) (p < 0.05). Accordingly, we studied the effects of SA and NH(4)Cl on Ca(2+)-activated K(+) current (IK(Ca)) under patch clamp technique. Caffeine produced transient outward current at holding potential (V (h)) of 0 mV, caffeine induced transient outward K(+) current, and the spontaneous transient outward currents were significantly enhanced by SA and suppressed by NH(4)Cl. In addition, IK(Ca) was significantly increased by acidotic condition when pH(i) was lowered by altering the NH(4)Cl gradient across the cell membrane. Finally, the effects of SA and NH(4)Cl on the membrane excitability and basal tension were studied: Under current clamp mode, resting membrane potential (RMP) was -28 +/- 2.3 mV in a single cell level and was depolarized by 13 +/- 2.4 mV with 2 mM tetraethylammonium (TEA). SA hyperpolarized and NH(4)Cl depolarized RMP by 10 +/- 1.9 and 16 +/- 4.7 mV, respectively. SA-induced hyperpolarization and relaxation of basal tension was significantly inhibited by TEA. These results suggest that SA and NH(4)Cl might regulate vascular tone by altering membrane excitability through modulation of [Ca(2+)](i) and Ca(2+)-activated K channels in rabbit basilar artery.

Comparison of Nicardipine Versus Esmolol in Attenuating the Hemodynamic Responses to Anesthesia Emergence and Extubation

OBJECTIVE

The purpose of this study was to compare the effectiveness of intravenous (IV) nicardipine versus esmolol in controlling heart rate (HR) and blood pressure (BP) responses to emergence and extubation.

DESIGN

Prospective, randomized, double blind.

SETTING

University hospital, single institution.

PARTICIPANTS

Twenty-two American Society of Anesthesiologists physical class 1 to 3 adult inpatients scheduled for general anesthesia.

INTERVENTIONS

General endotracheal anesthesia with oxygen/isoflurane and muscle relaxation. At end of surgery, with at least 2 twitches by nerve stimulator and end-tidal isoflurane <0.4%, muscle relaxant reversal was accomplished with neostigmine and glycopyrrolate. Two minutes postreversal, the IV study drug nicardipine, 0.03 mg/kg, or esmolol, 1.5 mg/kg, was administered. HR and BP were measured every minute up to 10 minutes and at minute 15 postreversal.

MEASUREMENTS AND MAIN RESULTS

There were no significant differences between groups in age, weight, gender, American Society of Anesthesiologists physical class or preoperative hemodynamics (HR, BP, mean arterial pressure [MAP]). Compared with nicardipine, 0.03 mg/kg IV, esmolol, 1.5 mg/kg IV, significantly (p < 0.05) attenuated HR more than nicardipine for the 15-minute time period poststudy drug. Compared with esmolol, nicardipine was significantly (p < 0.05) more effective in controlling MAP and systolic BP for the 1- to 3-minute and diastolic BP for the 1- to 2-minute time periods poststudy drug. There were no episodes of hypotension or adverse events.

CONCLUSIONS

Although esmolol, 1.5 mg/kg, IV was more effective than nicardipine, 0.03 mg/kg, IV for attenuating the HR response to extubation, nicardipine was more effective in controlling the BP response.

Intravenously administered vasodilatory prostaglandins increase retinal and choroidal blood flow in rats

We established an experimental system for measuring blood flow in the rat fundus and examined whether intravenously administered vasodilatory prostaglandins (PGE(1), PGE(2), and PGI(2)), 8-(4-chlorophenylthio)-cAMP (a cAMP analogue), and nicardipine (a Ca(2+)-channel blocker) increase fundus blood flow (FBF). Under artificial ventilation, rats were injected with tetrodotoxin (50 microg/kg, i.v.) to eliminate any nerve activity and prevent movement of the eye. After tetrodotoxin, the rats were infused with norepinephrine (0.3 - 0.5 microg . kg(-1) . min(-1)) and epinephrine (2.7 - 4.5 microg . kg(-1) . min(-1)) simultaneously to maintain adequate systemic circulation. We found that intravenous infusion of PGE(1) (2 - 10 microg . kg(-1) . min(-1)), PGE(2) (3 - 30 microg . kg(-1) . min(-1)), and PGI(2) (1 - 10 microg . kg(-1) . min(-1)) increased the FBF in a dose-dependent manner. The vasodilatory PGs decreased arterial pressure, whereas they did not affect heart rate. Like vasodilatory PGs, 8-(4-chlorophenylthio)-cAMP (30 micromol/kg, i.v.) increased FBF and decreased arterial pressure. While infusion of nicardipine (0.3 - 3 microg . kg(-1) . min(-1)) produced comparable depressor responses with those to vasodilatory PGs and the cAMP analogue, it did not increase FBF. These results suggest that vasodilatory PGs and cAMP act more selectively than Ca(2+)-channel blockers on retinal/choroidal blood vessels. Therefore, the vasodilatory PGs might be considered to be possible candidates for the therapeutics to treat disorders of retinal/choroidal circulation.