Channel Blocker Nifedipine Research Articles

Detection of TRPV4 channel current-like activity in Fawn Hooded hypertensive (FHH) rat cerebral arterial muscle cells.

The transient receptor potential vallinoid type 4 (TRPV4) is a calcium entry channel known to modulate vascular function by mediating endothelium–dependent vasodilation. The present study investigated if isolated cerebral arterial myocytes of the Fawn Hooded hypertensive (FHH) rat, known to display exaggerated KCa channel current activity and impaired myogenic tone, express TRPV4 channels at the transcript and protein level and exhibit TRPV4-like single-channel cationic current activity. Reverse transcription polymerase chain reaction (RT-PCR), Western blot, and immunostaining analysis detected the expression of mRNA transcript and translated protein of TRPV4 channel in FHH rat cerebral arterial myocytes. Patch clamp recording of single-channel current activity identified the presence of a single-channel cationic current with unitary conductance of ~85 pS and ~96 pS at hyperpolarizing and depolarizing potentials, respectively, that was inhibited by the TRPV4 channel antagonist RN 1734 or HC 067074 and activated by the potent TRPV4 channel agonist GSK1016790A. Application of negative pressure via the interior of the patch pipette increased the NPo of the TRPV4-like single-channel cationic current recorded in cell-attached patches at a patch potential of 60 mV that was inhibited by prior application of the TRPV4 channel antagonist RN 1734 or HC 067047. Treatment with the TRPV4 channel agonist GSK1016790A caused concentration-dependent increase in the NPo of KCa single-channel current recorded in cell-attached patches of cerebral arterial myocytes at a patch potential of 40 mV, which was not influenced by pretreatment with the voltage-gated L-type Ca2+ channel blocker nifedipine or the T-type Ca2+ channel blocker Ni2+. These findings demonstrate that FHH rat cerebral arterial myocytes express mRNA transcript and translated protein for TRPV4 channel and display TRPV4-like single-channel cationic current activity that was stretch-sensitive and activation of which increased the open state probability of KCa single-channel current in these arterial myocytes.

Mechanism of endothelial nitric oxide synthase phosphorylation and activation by tentacle extract from the jellyfish Cyanea capillata.

Our previous study demonstrated that tentacle extract (TE) from the jellyfish Cyanea capillata (C. capillata) could cause a weak relaxation response mediated by nitric oxide (NO) using isolated aorta rings. However, the intracellular mechanisms of TE-induced vasodilation remain unclear. Thus, this study was conducted to examine the role of TE on Akt/eNOS/NO and Ca2+ signaling pathways in human umbilical vein endothelial cells (HUVECs). Our results showed that TE induced dose- and time-dependent increases of eNOS activity and NO production. And TE also induced Akt and eNOS phosphorylation in HUVECs. However, treatment with specific PI3-kinase inhibitor (Wortmannin) significantly inhibited the increases in NO production and Akt/eNOS phosphorylation. In addition, TE also stimulated an increase in the intracellular Ca2+ concentration ([Ca2+]i), which was significantly attenuated by either IP3 receptor blocker (Heparin) or PKC inhibitor (PKC 412). In contrast, extracellular Ca2+-free, L-type calcium channel blocker (Nifedipine), or PKA inhibitor (H89) had no influence on the [Ca2+]i elevation. Since calcium ions also play a critical role in stimulating eNOS activity, we next explored the role of Ca2+ in TE-induced Akt/eNOS activation. In consistent with the attenuation of [Ca2+]i elevation, we found that Akt/eNOS phosphorylation was also dramatically decreased by Heparin or PKC 412, but not affected by Nifedipine or H89. However, the phosphorylation level could also be decreased by the removal of extracellular calcium. Taken together, our findings indicated that TE-induced eNOS phosphorylation and activation were mainly through PI3K/Akt-dependent, PKC/IP3R-sensitive and Ca2+-dependent pathways.

Nongenomic action of cortisol in rainbow trout hepatocytes

Cortisol rapidly activates cell signalling in trout hepatocytes; however, the mechanisms are far from clear. We tested the hypothesis that rapid action of cortisol involves modulation of intracellular Ca2+ levels in trout hepatocytes. Stress level of cortisol reported in fish plasma elicits a rapid increase in intracellular Ca2+ level as determined by Fura‐2AM ratiometric imaging. The increase in intracellular Ca2+ level in trout hepatocytes was also seen with the membrane impermeable form of the steroid (cortisol‐BSA), and this response was not affected by mifepristone (glucocorticoid receptor antagonist). We determined the role of extracellular and intracellular stores of calcium in affecting cortisol‐induced elevation in Ca2+ levels by using EGTA (a chelator) and BAPTA‐AM (inhibitor), respectively. Furthermore, we determined if IP3R pathway was involved in the activation of intracellular stores by using various inhibitors, including PLC inhibitor (U73122), thapsigargin (SERCA blocker) and Rynodine (RyR blocker). Also, L‐type calcium channel blocker Nifedipine and Ca2+release‐activated Ca2+ (CRAC) channel blocker Cpd5J‐4 were utilized to determine the mode of entry of extracellular calcium in response to cortisol stimulation. Overall, our results suggest that cortisol rapidly increases intracellular calcium levels and this may be mediated by the activation of CRAC channel in trout hepatocytes.Support or Funding InformationThis study was supported by the Natural Sciences and Engineering Research Council of Canada Discovery Grant to MMV.

AMPA receptor-mediated rapid EPSCs in vestibular calyx afferents.

In the vestibular periphery neurotransmission between hair cells and primary afferent nerves occurs via specialized ribbon synapses. Type I vestibular hair cells (HCIs) make synaptic contacts with calyx terminals, which enclose most of the HCI basolateral surface. To probe synaptic transmission, whole cell patch-clamp recordings were made from calyx afferent terminals isolated together with their mature HCIs from gerbil crista. Neurotransmitter release was measured as excitatory postsynaptic currents (EPSCs) in voltage clamp. Spontaneous EPSCs were classified as simple or complex. Simple events exhibited a rapid rise time and a fast monoexponential decay (time constant < 1 ms). The remaining events, constituting ~40% of EPSCs, showed more complex characteristics. Extracellular Sr2+ greatly increased EPSC frequency, and EPSCs were blocked by the AMPA receptor blocker NBQX. The role of presynaptic Ca2+ channels was assessed by application of the L-type Ca2+ channel blocker nifedipine (20 µM), which reduced EPSC frequency. In contrast, the L-type Ca2+ channel opener BAY K 8644 increased EPSC frequency. Cyclothiazide increased the decay time constant of averaged simple EPSCs by approximately twofold. The low-affinity AMPA receptor antagonist γ-d-glutamylglycine (2 mM) reduced the proportion of simple EPSCs relative to complex events, indicating glutamate accumulation in the restricted cleft between HCI and calyx. In crista slices EPSC frequency was greater in central compared with peripheral calyces, which may be due to greater numbers of presynaptic ribbons in central hair cells. Our data support a role for L-type Ca2+ channels in spontaneous release and demonstrate regional variations in AMPA-mediated quantal transmission at the calyx synapse.NEW & NOTEWORTHY In vestibular calyx terminals of mature cristae we find that the majority of excitatory postsynaptic currents (EPSCs) are rapid monophasic events mediated by AMPA receptors. Spontaneous EPSCs are reduced by an L-type Ca2+ channel blocker and notably enhanced in extracellular Sr2+ EPSC frequency is greater in central areas of the crista compared with peripheral areas and may be associated with more numerous presynaptic ribbons in central hair cells.

Low pHo boosts burst firing and catecholamine release by blocking TASK-1 and BK channels while preserving Cav1 channels in mouse chromaffin cells.

Mouse chromaffin cells (MCCs) generate spontaneous burst-firing that causes large increases of Ca2+ -dependent catecholamine release, and is thus a key mechanism for regulating the functions of MCCs. With the aim to uncover a physiological role for burst-firing we investigated the effects of acidosis on MCC activity. Lowering the extracellular pH (pHo ) from 7.4 to 6.6 induces cell depolarizations of 10-15 mV that generate bursts of ∼330ms at 1-2Hz and a 7.4-fold increase of cumulative catecholamine-release. Burst-firing originates from the inhibition of the pH-sensitive TASK-1-channels and a 60% reduction of BK-channel conductance at pHo 6.6. Blockers of the two channels (A1899 and paxilline) mimic the effects of pHo 6.6, and this is reverted by the Cav1 channel blocker nifedipine. MCCs act as pH-sensors. At low pHo , they depolarize, undergo burst-firing and increase catecholamine-secretion, generating an effective physiological response that may compensate for the acute acidosis and hyperkalaemia generated during heavy exercise and muscle fatigue. Mouse chromaffin cells (MCCs) generate action potential (AP) firing that regulates the Ca2+ -dependent release of catecholamines (CAs). Recent findings indicate that MCCs possess a variety of spontaneous firing modes that span from the common 'tonic-irregular' to the less frequent 'burst' firing. This latter is evident in a small fraction of MCCs but occurs regularly when Nav1.3/1.7 channels are made less available or when the Slo1β2-subunit responsible for BK channel inactivation is deleted. Burst firing causes large increases of Ca2+ -entry and potentiates CA release by ∼3.5-fold and thus may be a key mechanism for regulating MCC function. With the aim to uncover a physiological role for burst-firing we investigated the effects of acidosis on MCC activity. Lowering the extracellular pH (pHo ) from 7.4 to 7.0 and 6.6 induces cell depolarizations of 10-15mV that generate repeated bursts. Bursts at pHo 6.6 lasted ∼330ms, occurred at 1-2Hz and caused an ∼7-fold increase of CA cumulative release. Burst firing originates from the inhibition of the pH-sensitive TASK-1/TASK-3 channels and from a 40% BK channel conductance reduction at pHo 7.0. The same pHo had little or no effect on Nav, Cav, Kv and SK channels that support AP firing in MCCs. Burst firing of pHo 6.6 could be mimicked by mixtures of the TASK-1 blocker A1899 (300nm) and BK blocker paxilline (300nm) and could be prevented by blocking L-type channels by adding 3μm nifedipine. Mixtures of the two blockers raised cumulative CA-secretion even more than low pHo (∼12-fold), showing that the action of protons on vesicle release is mainly a result of the ionic conductance changes that increase Ca2+ -entry during bursts. Our data provide direct evidence suggesting that MCCs respond to low pHo with sustained depolarization, burst firing and enhanced CA-secretion, thus mimicking the physiological response of CCs to acute acidosis and hyperkalaemia generated during heavy exercise and muscle fatigue.

Different CaV1.3 Channel Isoforms Control Distinct Components of the Synaptic Vesicle Cycle in Auditory Inner Hair Cells.

The mechanisms orchestrating transient and sustained exocytosis in auditory inner hair cells (IHCs) remain largely unknown. These exocytotic responses are believed to mobilize sequentially a readily releasable pool of vesicles (RRP) underneath the synaptic ribbons and a slowly releasable pool of vesicles (SRP) at farther distance from them. They are both governed by Cav1.3 channels and require otoferlin as Ca2+ sensor, but whether they use the same Cav1.3 isoforms is still unknown. Using whole-cell patch-clamp recordings in posthearing mice, we show that only a proportion (∼25%) of the total Ca2+ current in IHCs displaying fast inactivation and resistance to 20 μm nifedipine, a l-type Ca2+ channel blocker, is sufficient to trigger RRP but not SRP exocytosis. This Ca2+ current is likely conducted by short C-terminal isoforms of Cav1.3 channels, notably Cav1.342A and Cav1.343S, because their mRNA is highly expressed in wild-type IHCs but poorly expressed in Otof-/- IHCs, the latter having Ca2+ currents with considerably reduced inactivation. Nifedipine-resistant RRP exocytosis was poorly affected by 5 mm intracellular EGTA, suggesting that the Cav1.3 short isoforms are closely associated with the release site at the synaptic ribbons. Conversely, our results suggest that Cav1.3 long isoforms, which carry ∼75% of the total IHC Ca2+ current with slow inactivation and confer high sensitivity to nifedipine and to internal EGTA, are essentially involved in recruiting SRP vesicles. Intracellular Ca2+ imaging showed that Cav1.3 long isoforms support a deep intracellular diffusion of Ca2+SIGNIFICANCE STATEMENT Auditory inner hair cells (IHCs) encode sounds into nerve impulses through fast and indefatigable Ca2+-dependent exocytosis at their ribbon synapses. We show that this synaptic process involves long and short C-terminal isoforms of the Cav1.3 Ca2+ channel that differ in the kinetics of their Ca2+-dependent inactivation and their relative sensitivity to the l-type Ca2+ channel blocker nifedipine. The short C-terminal isoforms, having fast inactivation and low sensitivity to nifedipine, mainly control the fast fusion of the readily releasable pool (RRP); that is, they encode the phasic exocytotic component. The long isoforms, with slow inactivation and great sensitivity to nifedipine, mainly regulate the vesicular replenishment of the RRP; that is, the sustained or tonic exocytosis.

Pharmacological Identification of an L-Type Calcium Channel Impedance Signal in Human Induced Pluripotent Stem-Cell Derived Cardiomyocytes

Impedance recordings of contractile human induced pluripotent stem-cell derived cardiomyocytes hold significant potential for drug discovery and cardiac safety given their easy implementation in medium throughput systems. However, the mechanisms underlying the complex impedance signal remain to be elucidated. The main component of the signal is the impedance twitch, a transient increase in electrode resistance that is obliterated by the myosin kinase inhibitor blebbistatin. Three additional small peaks (two initial negative deflections and one positive during relaxation) complete the complex impedance waveform. This work focuses on the pharmacological dissection of the first negative deflection that occurs after the sodium spike subsides and before the beginning of contraction. To test the hypothesis that the signal parallels the activation of calcium channels and not contraction, we investigated the effect of a calcium channel blocker (nifedipine), an agonist (FPL64176), and blebbistatin. Impedance recordings of iCell cardiomyocytes2 (CDI) were measured at 37°C using a CardioECR instrument (ACEA Biosciences) with pacing at 0.67 Hz. The impedance signal of iCell cardiomyocytes2 shows two initial negative deflections of −0.38±0.02 Ω and −0.78±0.03 Ω followed by a 4.05±0.12 Ω positive peak (mean ± sem, n=20).FPL64176 at 10 and 30 nM increased the first negative peak amplitude by 14.9±4.2% (p>0.05) and 31.0±6.8% (p<0.05), respectively (paired t-test, n=4). In 10 µM blebbistatin FPL64176-activated peaks were smaller (10 nM: 8.8±2.8%, p<0.05) or not affected (30 nM: 1.0±3.7%, p>0.05). Nifedipine at 30 nM and 100 nM significantly decreased the first negative peak amplitude by 26.7±6.9% and 32.7±2.5% respectively, and no peak was observed in 10 µM blebbistatin. The data suggests that the first negative impedance deflection is determined by the opening of calcium channels and thus may be used as marker for excitation-contraction coupling.

Impact of gabapentin on neuronal high voltage-activated Ca2+ channel properties of injured-side axotomized and adjacent uninjured dorsal root ganglions in a rat model of spinal nerve ligation.

The density and properties of ion channels in the injured axon and dorsal root ganglion (DRG) neuronal soma membrane change following nerve injury, which may result in the development of neuropathic pain. Gabapentin (GBP) is a drug for the first-line treatment of neuropathic pain. One of its therapeutic targets is the voltage-activated calcium channel (VACC). In the present study, the whole-cell patch clamp technique was used to examine the changes of high voltage-activated Ca2+ (HVA-Ca2+) channels in DRG neurons from sham and neuropathic rats in the absence and presence of GBP. The results demonstrated a reduction in peak current density and the ‘window current’ between activation and inactivation in adjacent and axotomized neurons from rats that had undergone L5 spinal nerve ligation, thus attenuating the total inward Ca2+ current. Following the use of the specific channel blockers nifedipine, ω-conotoxin MVIIC and ω-conotoxin MVIIA, increased HVA-Ca2+ channels as well as an increased proportion of N-type Ca2+ currents were observed in axotomized neurons. GBP inhibited HVA calcium channel currents in a dose-dependent manner. The activation and steady-state inactivation curves for HVA channels were shifted in a hyperpolarizing direction by 100 µmol/l GBP. Following the application of GBP, a reduction in the ‘window current’ was observed in control and axotomized neurons, whereas the ‘window current’ was unchanged in adjacent neurons. This indicates that the inhibitory effects of GBP may be dependent on particular neuropathological or inflammatory conditions. The proportion of N-type Ca2+ currents and sensitivity to GBP were increased in axotomized neurons, which indicated the involvement of N-type Ca2+ currents in the inhibitory effect of GBP.

Medium throughput biochemical compound screening identifies novel agents for pharmacotherapy of neurofibromatosis type 1

The variable manifestation of phenotypes that occur in patients with neurofibromatosis type 1 (NF1) includes benign and malignant neurocutaneous tumors for which no adequate treatment exists. Cell-based screening of known bioactive compounds library identified the protein phosphatase 2A (PP2A) inhibitor Cantharidin and the L-type calcium channel blocker Nifedipine as potential candidates for NF1 pharmacotherapy. Validation of screening results using human NF1-associated malignant peripheral nerve sheath tumor (MPNST) cells showed that Cantharidin effectively impeded MPNST cell growth, while Nifedipine treatment significantly decreased local tumor growth in an MPNST xenograft animal model. These data suggest that inhibitors of PP2A, as well as calcium channel blockers, might be used in broader MPNST preclinical studies as single agents or in combinatorial therapeutic strategies.

Antiepileptic effect of calcium channel blockers alone and in combination with phenytoin on MES induced epilepsy in rats

Background: The currently available antiepileptic drugs have a low therapeutic index, and provide satisfactory seizure control in only 60-70% of patients. Calcium channel blocker has shown potentials of a useful add-on drug for the existing antiepileptic drugs. Objectives: To study the effect of calcium channel blockers (CCBs) nifedipine and verapamil on maximal electroshock (MES)-induced convulsions and also to evaluate their effect in combination with Phenytoin. Methods: For this study, Male Wistar rats were used. Effects of nifedipine (5 mg/kg), verapamil (20mg/kg) alone and in combination with phenytoin (25mg/kg) were studied in MES model. Abolition of hind limb tonic extension and reduction of duration of tonic extension was considered as the index for antiepileptic activity in MES. Results: Verapamil and nifedipine produced significant antiepileptic effect alone. Verapamil and nifedipine potentiated the antiepileptic effect of phenytoin sodium. Conclusion: Dose of phenytoin sodium can be reduced in epileptic patients receiving verapamil or nifedipine for some other clinical conditions. Verapamil and nifedipine can also be used alone in the treatment of generalized tonic clonic seizures. However it needs further confirmation to establish clinical utility of calcium channel blockers. KEY WORDS: Nifedipine, verapamil, phenytoin, MES seizure rats.

Biphasic augmentation of alpha-adrenergic contraction by plumbagin in rat systemic arteries.

Plumbagin, a hydroxy 1,4-naphthoquinone compound from plant metabolites, exhibits anticancer, antibacterial, and antifungal activities via modulating various signaling molecules. However, its effects on vascular functions are rarely studied except in pulmonary and coronary arteries where NADPH oxidase (NOX) inhibition was suggested as a mechanism. Here we investigate the effects of plumbagin on the contractility of skeletal artery (deep femoral artery, DFA), mesenteric artery (MA) and renal artery (RA) in rats. Although plumbagin alone had no effect on the isometric tone of DFA, 1 µM phenylephrine (PhE)-induced partial contraction was largely augmented by plumbagin (ΔTPlum, 125% of 80 mM KCl-induced contraction at 1 µM). With relatively higher concentrations (>5 µM), plumbagin induced a transient contraction followed by tonic relaxation of DFA. Similar biphasic augmentation of the PhE-induced contraction was observed in MA and RA. VAS2870 and GKT137831, specific NOX4 inhibitors, neither mimicked nor inhibited ΔTPlum in DFA. Also, pretreatment with tiron or catalase did not affect ΔTPlum of DFA. Under the inhibition of PhE-contraction with L-type Ca2+ channel blocker (nifedipine, 1 µM), plumbagin still induced tonic contraction, suggesting Ca2+-sensitization mechanism of smooth muscle. Although ΔTPlum was consistently observed under pretreatment with Rho A-kinase inhibitor (Y27632, 1 µM), a PKC inhibitor (GF 109203X, 10 µM) largely suppressed ΔTPlum. Taken together, it is suggested that plumbagin facilitates the PKC activation in the presence of vasoactive agonists in skeletal arteries. The biphasic contractile effects on the systemic arteries should be considered in the pharmacological studies of plumbagin and 1,4-naphthoquinones.

A Simple and Efficient Methodology for the Study of Cardioprotective Drugs in Animal Model of Cardiac Ischemia-Reperfusion

To study cardioprotective drugs, we developed a simple and efficient methodology to evaluate effects of drugs on cardiac electrical activity using electrocardiogram (ECG) in rats submitted to cardiac ischemia-reperfusion (I/R). Using adult male Wistar rats (14 - 16-week-old) anesthetized (urethane 1.25 g/kg, i.p.) and kept under mechanical ventilation, we used surgical procedures to induce cardiac I/R by means mechanical occlusion of left anterior descendent coronary artery for 10 min (ischemia) with silk suture (tourniquet) followed by its removal to allow coronary recirculation (reperfusion). To evaluate the effects of surgical process, a group of rats (SHAM-operated) was submitted to surgical procedures previously described, but without coronary occlusion. To evaluate cardiac electrical activity in rats submitted to cardiac I/R and SHAM-operated, the ECG system was coupled to animal body to determine the incidence of ventricular arrhythmia (VA), atrio-ventricular blockade (AVB) and lethality (LET). To evaluate injury biomarkers production in rats submitted to cardiac I/R and SHAM-operated, serum concentrations of creatine kinase fraction (MB/CK-MB) and troponin I were determined by biochemical techniques. Using the methodology proposed in this work, we observed that VA, AVB and LET incidence was significantly higher in cardiac I/R group (85%, 79% and 70%, respectively) than in SHAM-operated group (0%, 0% and 0%, respectively). Serum levels of CK-MB and troponin I were also significantly higher in cardiac I/R (1,850 ± 222 U/L and 0.031 ± 0.009 ng/mL, respectively) compared to SHAM-operated group (808 ± 72 U/L and 0.200 ± 0.027 ng/mL). To evaluate efficiency of methodology proposed in this work to study the effect of cardioprotective drugs, the effects of the L-type Ca2+ channel blocker (CCB) nifedipine (30 mg/kg, intravenously - IV) in rats submitted to cardiac I/R were studied. The treatment with nifedipine (before ischemia) significantly reduced the incidence of VA (from 85% to 28%), AVB (from 79% to 14%), and LET (from 70% to 14%). These results indicate that the methodology described in the present work is simple, and efficient, to evaluate cardiac functional and biochemical alterations induced by cardiac I/R, and also the study of cardioprotective drugs in rats. This methodology could contribute to the development of new pharmacological cardioprotective strategies for to treatment of ischemic cardiac diseases in humans, such as myocardial infarction.

Ponatinib Exerts Multiple Effects on Vascular Endothelial Cells: Possible Mechanisms and Explanations for the Adverse Vascular Events Seen in CML Patients Treated with Ponatinib

The potent BCR-ABL1-targeting tyrosine kinase inhibitor (TKI) ponatinib is used for the treatment of patients with drug-resistant chronic myeloid leukemia (CML). However, an increased risk of development of cardiovascular events has been described in CML patients treated with ponatinib. The etiology of these adverse events is currently unknown. In an attempt to discover mechanisms underlying ponatinib-induced adverse vascular events, we have evaluated the effects of ponatinib in vitro on human vascular endothelial cells and on contraction of explanted mice aortic rings. In addition, we examined the effects of ponatinib on angiogenesis in vivo in a mouse model of hind limb ischemia. Ponatinib dose-dependently induced apoptosis in human coronary artery endothelial cells (HCAEC) in a caspase assay (relative apoptosis vs. 1% DMSO: ponatinib 50 nM: 1.79±0.38, p<0.001; ponatinib 100 nM: 2.13±0.42, p<0.001) and this drug effect could partially be blocked by addition of insulin (ponatinib 100 nM + insulin 5 µg/ml: 1.70±0.18, p<0.05). In addition, ponatinib was found to inhibit the proliferation of human umbilical vein endothelial cells (HUVEC) and the human microvascular endothelial cell line HMEC-1, with IC50 values ranging between 100 and 250 nM (p<0.05) as determined by thymidine-incorporation assay. Using a phospho-receptor tyrosine kinase assay in HCAEC, we found that ponatinib also inhibits fetal bovine serum-induced phosphorylation of the VEGF receptor KDR as well as phosphorylation of MER and insulin receptors, which play a role in angiogenesis, vascular homeostasis, and vessel protection. We also found that ponatinib (1 µM, 4 hours) increases adhesion of HUVEC to a plastic-surface compared to DMSO control (Figure). Based on clinical observations of vasoconstriction in ponatinib-treated patients, we also applied ponatinib on aortic rings harvested from C57BL/6 mice. Ponatinib (100 nM, overnight) enhanced norepinephrine-induced vasoconstriction (log EC50: control -7.76±0.06 vs. ponatinib -7.96±0.05, p<0.05, n=6) and inhibited acetylcholine-mediated vasodilatation (log IC50: control -7.45±0.05 vs. ponatinib -7.06±0.1, p<0.001) as shown by myography. These drug effects were blocked by inhibition of nitric oxide (using nitric oxide synthase inhibitor L-NNA, 100 µM) or COX (by applying diclofenac, 3 mg/l), suggesting that ponatinib promotes the generation of vasoconstricting prostanoids. Ponatinib effects were also blocked by the calcium channel blocker nifedipine (1 µM). In C57BL/6 mice, ponatinib (5 mg/kg/day for 35 days) was found to inhibit blood flow recovery in a hind limb ischemia model as shown by Laser-Doppler perfusion imaging after femoral artery ligation. The blood perfusion ratios of the ischemic limb vs. non-ischemic limb at week 5 were: control group: 0.67±0.07 vs. ponatinib: 0.56±0.1; p<0.05). Ponatinib-treated mice also developed toe and foot necrosis more frequently than control mice (necrosis score: control: 0.3 vs. ponatinib: 1.3). In summary, ponatinib affects endothelial cell growth and vasomotor function in-vitro as well as blood flow recovery in a mouse model. These findings might help explain the occurrence of vascular events in CML patients treated with ponatinib and may lead to development of therapeutic strategies for prevention and treatment of ponatinib-induced adverse events. [Display omitted] DisclosuresKirchmair:Ariad: Research Funding. Valent:Ariad: Honoraria, Research Funding; Amgen: Honoraria; Deciphera Pharmaceuticals: Research Funding; Novartis: Honoraria, Research Funding; Celgene: Honoraria, Research Funding.

AB313. SPR-40 Spontaneous Ca2+ waves in mouse urethral smooth muscle visualized with a genetically encoded Ca2+ indicator in situ

ObjectiveThe urethra generates myogenic tone during bladder filling to maintain continence. There are few visual studies of urethra motor activity and the specific Ca2+ signalling of urethral smooth muscle is relatively unknown. In the present study, we sought to characterize the pattern of smooth muscle cell activation in urethra utilizing Ca2+ imaging with a genetically encoded Ca2+ reporter, GCaMP3.MethodsCa2+ signals in mouse urethra were imaged using GCaMP3, activated by a smooth muscle heavy chain promoter. The urethra was excised and urothelium layer removed by sharp dissection. Ca2+ signals were recorded in situ using an upright fluorescent microscope. Enzymatically dispersed mouse urethral smooth muscle cells with an eGFP tag were purified for qPCR analysis using fluorescence-activated cell sorting.ResultsUrethral smooth muscle cells fired spontaneous intracellular Ca2+ waves. Ca2+ waves did not propagate from cell to cell and activity in individual cells was not correlated with adjacent cells. Ca2+ waves were significantly increased in frequency, amplitude, duration and spatial spread by the α1a agonist phenylephrine and abolished by the guanylate cyclase donor NONATE. Ca2+ waves originated from both Ca2+ influx and Ca2+ release from intracellular stores as removal of extracellular Ca2+ and blocking the sarcoplasmic Ca2+-ATPase abolished Ca2+ waves. Ca2+ waves were insensitive to the L-type Ca2+ channel blocker nifedipine but were inhibited by blockers of T-type Ca2+ channels (NNC 55-0396 and TTA-A2) as well as blockers of ryanodine and IP3 receptors (tetracaine and 2-APB). qPCR revealed that urethral smooth muscle cells expressed the ER Ca2+ release channels IP3R1,2 and RyR1-3 as well as the voltage dependent Ca2+ influx channels Cacna1s, Cacna1c, Cacna1d, Cacna1f and Cacna1h.ConclusionsUrethral smooth muscle cells fire spontaneous Ca2+ waves which are modulated by both adrenergic and nitrergic inputs. These Ca2+ waves rely on Ca2+ influx from a non-L type Ca2+ influx mechanism and release of Ca2+ from intracellular stores for their generation.Funding Source(s)R01 DK-091336, P01 DK41315

Calcineurin/NFAT Activation-Dependence of Leptin Synthesis and Vascular Growth in Response to Mechanical Stretch.

Background and Aims: Hypertension and obesity are important risk factors of cardiovascular disease. They are both associated with high leptin levels and have been shown to promote vascular hypertrophy, through the RhoA/ROCK and ERK1/2 phosphorylation. Calcineurin/NFAT activation also induces vascular hypertrophy by upregulating various genes. This study aimed to decipher whether a crosstalk exists between the RhoA/ROCK pathway, Ca2+/calcineurin/NFAT pathway, and ERK1/2 phosphorylation in the process of mechanical stretch-induced vascular smooth muscle cell (VSMC) hypertrophy and leptin synthesis.Methods and Results: Rat portal vein (RPV) organ culture was used to investigate the effect of mechanical stretch and exogenous leptin (3.1 nM) on VSMC hypertrophy and leptin synthesis. Results showed that stretching the RPV significantly upregulated leptin secretion, mRNA, and protein expression, which were inhibited by the calcium channel blocker nifedipine (10 μM), the selective calcineurin inhibitor FK506 (1 nM), and the ERK1/2 inhibitor PD98059 (1 μM). The transcription inhibitor actinomycin D (0.1 μM) and the translation inhibitor cycloheximide (1 mM) significantly decreased stretch-induced leptin protein expression. Mechanical stretch or leptin caused an increase in wet weight changes and protein synthesis, considered as hypertrophic markers, while they were inhibited by FK506 (0.1 nM; 1 nM). In addition, stretch or exogenous leptin significantly increased calcineurin activity and MCIP1 expression whereas leptin induced NFAT nuclear translocation in VSMCs. Moreover, in response to stretch or exogenous leptin, the Rho inhibitor C3 exoenzyme (30 ng/mL), the ROCK inhibitor Y-27632 (10 μM), and the actin depolymerization agents Latrunculin B (50 nM) and cytochalasin D (1 μM) reduced calcineurin activation and NFAT nuclear translocation. ERK1/2 phosphorylation was inhibited by FK506 and C3.Conclusions: Mechanical stretch-induced VSMC hypertrophy and leptin synthesis and secretion are mediated by Ca2+/calcineurin/NFAT activation. RhoA/ROCK and ERK1/2 activation are critical for mechanical stretch-induced calcineurin activation.

Design, synthesis, and negative inotropic evaluation of 4-phenyl-1H-1,2,4-triazol-5(4H)-one derivatives containing triazole or piperazine moieties.

In this study, four novel series of 4-phenyl-1H-1,2,4-triazol-5(4H)-one derivatives containing triazole or piperazine moieties were designed, synthesized, and evaluated for negative inotropic activity by measuring the left atrium stroke volume in isolated rabbit heart preparations. Almost all of the compounds showed an ability to moderate the cardiac workload by decreasing the heart rate and contractility. Among them, 7h was found to be the most potent with a change in stroke volume of -48.22±0.36% at a concentration of 3×10-5 mol/L (metoprolol: -9.74±0.14%). The cytotoxicity of these compounds was evaluated using the human cervical cancer cell line HeLa, the liver cancer cell line Hep3B, and the human normal hepatic cell line LO2. A preliminary study of the mechanism of action for the compound 7h on the regulation of atrial dynamics with ATP-sensitive K+ channel and L-type Ca2+ channel blockers glibenclamide and nifedipine was performed in the isolated perfused beating rabbit atria.

The L-type Ca(2+) Channel Blocker Nifedipine Inhibits Mycelial Growth, Sporulation, and Virulence of Phytophthora capsici.

The oomycete vegetable pathogen Phytophthora capsici causes significant losses of important vegetable crops worldwide. Calcium and other plant nutrients have been used in disease management of oomycete pathogens. Calcium homeostasis and signaling is essential for numerous biological processes, and Ca2+ channel blockers prevent excessive Ca2+ influx into the fungal cell. However, it is not known whether voltage-gated Ca2+ channel blockers improve control over oomycete pathogens. In the present study, we compared the inhibitory effects of CaCl2 and the extracellular Ca2+ chelator EDTA on mycelial growth and found that calcium assimilation plays a key role in P. capsici mycelial growth. Next, we involved the voltage-gated Ca2+ channel blockers verapamil (VP) and nifedipine (NFD) to analyze the effect of Ca2+ channel blockers on mycelial growth and sporulation; the results suggested that NFD, but not VP, caused significant inhibition. Ion rescue in an NFD-induced inhibition assay suggested that NFD-induced inhibition is calcium-dependent. In addition, NFD increased P. capsici sensitivity to H2O2 in a calcium-dependent manner, and extracellular calcium rescued it. Furthermore, NFD inhibited the virulence and gene expression related to its pathogenicity. These results suggest that NFD inhibits mycelial growth, sporulation, and virulence of P. capsici.

Abstract 234A: Aberrant sodium current contributes to constitutive mTOR activity in malignant melanoma cells

Abstract Transformation from disciplined melanocytes to untamed melanoma cells remains an enigma. Our previous studies have demonstrated that melanoma cells are more resistant to oxidative stress and melanoma cells exhibit constitutive mTOR activity. Surprisingly, further studies have failed to present the expression and activity of EGFR using conventional anti-EGFR antibodies. We hypothesized that constitutive mTOR activity in melanoma cells may be due to mutated EGFR variants and membrane channel activities. Using patch clamping technique, we have shown that melanoma cells (WM 266-4) but not human skin melanocytes exhibit Na+ current which is blocked by TTX. Interestingly, mTOR inhibitor, rapamycin, blocks Na+ current. Western blot and confocal microscopy data further revealed that Na+/Ca2+ exchanger blocker KB-R7943 (KBR), and L-type Ca2+ channel blocker Nifedipine (NIF) inhibits mTOR activity in melanoma cells in a dose dependent manner. To further characterize Na+ channels, we used commercially available channel antibodies. Western blot analysis data showed that melanoma cells but not human melanocytes express Na+ v1.5 and Na+ v1.6 and NCX3. Functional studies also indicated that KBR and NIF inhibit melanoma cell proliferation and migration. Taken all together, our data suggest that aberrant Na+ current contributes to constitutive mTOR activity in melanoma cells and channel blockers may be potential for the treatment of melanoma. Citation Format: Benjamin Gallant, Nicole Lizza, Ryan Garrity, Audrey Madigan, Zachary Jost, Alfredo Gonzalez, Jeanine Justiniano, An Xie, Yinsheng Wan. Aberrant sodium current contributes to constitutive mTOR activity in malignant melanoma cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 234A.

The signaling of amitriptyline-induced inhibitory effect on electrical field stimulation response in colon smooth muscle.

Amitriptyline, a well-known antidepressant, exerts inhibitory effect on electrically stimulated rat colon smooth muscle contraction. In this study, we investigated the signaling pathway of amitriptyline-induced inhibitory effect. Changes in isometric force of colon muscle were recorded on polygraph, and data were analyzed by measuring the inhibitory extent induced by amitriptyline. Firstly, muscles were contracted by stimulation with electric field stimulation (EFS), and then, amitriptyline was added cumulatively to determine its influence effect on EFS. Amitriptyline significantly inhibited EFS-induced contraction dose dependently. Then, the mechanism of inhibitory effect of amitriptyline was evaluated by pretreating with various antagonists such as L-NAME, methylene blue, atropine, 5-HT receptors blockers, guanethidine, prazosin, guanabenz, isoprenaline, Y27632 (Rho-kinase inhibitor), ML9 (myosin light chain kinase (MLCK) inhibitor), U73122 (PLC inhibitor), and chelerythrine (PKC inhibitor). Then, Ca(2+) channel blocker (nifedipine) and K(+)channel blockers, tetraethylammonium (TEA), 4-aminopyridine (4-AP), and glybenclamide, were used to determine the involvement of ion channels. L-NAME, guanabenz, 5HT4 receptor blocker, ML9, and Y27632 enhanced the effect of amitriptyline. Meanwhile, methylene blue, atropine, guanethidine, prazosin, methylsergide, ondansetron, U73122, and chelerythrine blocked its effect. It was also shown that nifedipine enhanced but TEA and glybenclamide blocked amitriptyline-induced inhibitory effect on EFS. Our results indicated that amitriptyline may exert inhibitory effect in response to EFS by inhibiting muscarinic receptors and then PLC-mediated PKC pathway leading to opening of ATP-sensitive potassium channel.

Cyclopiazonic acid, an inhibitor of calcium-dependent ATPases with antiviral activity against human respiratory syncytial virus

Human respiratory syncytial virus (RSV) is a common cause of lower respiratory tract infections in infants and young children worldwide, yet no vaccine or effective antiviral treatment is available. To search for new anti-RSV agents, we developed a cell-based assay that measures inhibition of RSV-induced cytopathic effect (CPE) and identified cyclopiazonic acid (CPA), an intracellular calcium ATPase inhibitor as a RSV inhibitor (EC50 values 4.13 μM) by screening of natural product library. CPA inhibited the replication of RSV strains belonging to both A and B subgroups and human parainfluenza virus type 3, but not Enterovirus 71. Mechanism of action study by time-of-addition assay and minigenome assay revealed that CPA acts at the step of virus genome replication and/or transcription. Moreover, two other calcium ATPase inhibitors (Thapsigargin and BHQ) and calcium ionophores (A23187 and ionomycin), but not calcium channel blockers (nifedipine, nimodipine, and tetrandrine), also had similar effect. These results indicate that an increase in intracellular calcium concentration is detrimental to RSV replication. Thus, our findings provide a new strategy for anti-RSV therapy via increasing intracellular calcium concentration.