An orally available Cav2.2 calcium channel inhibitor for the treatment of neuropathic pain.

BACKGROUND AND PURPOSE: Neuropathic pain affects up to 10% of the global population and is caused by an injury or a disease affecting the somatosensory, peripheral, or central nervous system. NP is characterized by chronic, severe and opioid-resistant properties. Therefore, its clinical management remains very challenging. The N-type voltage-gated calcium channel, Cav2.2, is a validated target for therapeutic intervention in chronic and neuropathic pain. The conotoxin ziconotide (Prialt®) is an FDA-approved drug that blocks Cav2.2 channel but needs to be administered intrathecally. Thus, although being principally efficient, the required application route is very much in disfavour. EXPERIMENTAL APPROACH AND KEY RESULTS: Here, we describe an orally available drug candidate, RD2, which competes with ziconotide binding to Cav2.2 at nanomolar concentrations and inhibits Cav2.2 almost completely reversible. Other voltage-gated calcium channel subtypes, like Cav1.2 and Cav3.2, were affected by RD2 only at concentrations higher than 10 µM. Data from sciatic inflammatory neuritis rat model demonstrated the in vivo proof of concept, as low-dose RD2 (5 mg·kg-1) administered orally alleviated neuropathic pain compared with vehicle controls. High-dose RD2 (50 mg·kg-1) was necessary to reduce pain sensation in acute thermal response assessed by the tail flick test. CONCLUSIONS AND IMPLICATIONS: Taken together, these results demonstrate that RD2 has antiallodynic properties. RD2 is orally available, which is the most convenient application form for patients and caregivers. The surprising and novel result from standard receptor screens opens the room for further optimization into new promising drug candidates, which address an unmet medical need.

ɑO-Conotoxin GeXIVA isomers modulate N-type calcium (CaV 2.2) channels and inwardly-rectifying potassium (GIRK) channels via GABAB receptor activation.

αO-Conotoxin GeXIVA is a 28 amino acid peptide derived from the venom of the marine snail Conus generalis. The presence of four cysteine residues in the structure of GeXIVA allows it to have three different disulfide isomers, that is, the globular, ribbon or bead isomer. All three isomers are active at α9α10 nicotinic acetylcholine receptors, with the bead isomer, GeXIVA[1,2], being the most potent and exhibiting analgesic activity in animal models of neuropathic pain. The original report of GeXIVA activity failed to observe any effect of the isomers on high voltage-activated (HVA) calcium channel currents in rat dorsal root ganglion (DRG) neurons. In this study, we report, for the first time, the activity of globular GeXIVA[1,3] at G protein-coupled GABAB receptors (GABAB R) inhibiting HVA N-type calcium (Cav2.2) channels and reducing membrane excitability in mouse DRG neurons. The inhibition of HVA Ba2+ currents and neuroexcitability by GeXIVA[1,3] was partially reversed by the selective GABAB R antagonist CGP 55845. In transfected HEK293T cells co-expressing human GABAB R1 and R2 subunits and Cav2.2 channels, both GeXIVA[1,3] and GeXIVA[1,4] inhibited depolarization-activated Ba2+ currents mediated by Cav2.2 channels, whereas GeXIVA[1,2] had no effect. The effects of three cyclized GeXIVA[1,4] ribbon isomers were also tested, with cGeXIVA GAG being the most potent at human GABAB R-coupled Cav2.2 channels. Interestingly, globular GeXIVA[1,3] also reversibly potentiated inwardly-rectifying K+ currents mediated by human GIRK1/2 channels co-expressed with GABAB R in HEK293T cells. This study highlights GABAB R as a potentially important receptor target for the activity of αO-conotoxin GeXIVA to mediate analgesia.

Closed-state inactivation and pore-blocker modulation mechanisms of human CaV2.2.

N-type voltage-gated calcium (CaV) channels mediate Ca2+ influx at presynaptic terminals in response to action potentials and play vital roles in synaptogenesis, release of neurotransmitters, and nociceptive transmission. Here, we elucidate a cryo-electron microscopy (cryo-EM) structure of the human CaV2.2 complex in apo, ziconotide-bound, and two CaV2.2-specific pore blockers-bound states. The second voltage-sensing domain (VSD) is captured in a resting-state conformation, trapped by a phosphatidylinositol 4,5-bisphosphate (PIP2) molecule, which is distinct from the other three VSDs of CaV2.2, as well as activated VSDs observed in previous structures of CaV channels. This structure reveals the molecular basis for the unique inactivation process of CaV2.2 channels, in which the intracellular gate formed by S6 helices is closed and a W-helix from the domain II-III linker stabilizes closed-state inactivation. The structures of this inactivated, drug-bound complex lay a solid foundation for developing new state-dependent blockers for treatment of chronic pain.

Subcutaneous ω-Conotoxins Alleviate Mechanical Pain in Rodent Models of Acute Peripheral Neuropathy.

The peripheral effects of ω-conotoxins, selective blockers of N-type voltage-gated calcium channels (CaV2.2), have not been characterised across different clinically relevant pain models. This study examines the effects of locally administered ω-conotoxin MVIIA, GVIA, and CVIF on mechanical and thermal paw withdrawal threshold (PWT) in postsurgical pain (PSP), cisplatin-induced neuropathy (CisIPN), and oxaliplatin-induced neuropathy (OIPN) rodent models. Intraplantar injection of 300, 100 and 30 nM MVIIA significantly (p < 0.0001, p < 0.0001, and p < 0.05, respectively) alleviated mechanical allodynia of mice in PSP model compared to vehicle control group. Similarly, intraplantar injection of 300, 100, and 30 nM MVIIA (p < 0.0001, p < 0.01, and p < 0.05, respectively), and 300 nM and 100 nM GVIA (p < 0.0001 and p < 0.05, respectively) significantly increased mechanical thresholds of mice in OIPN model. The ED50 of GVIA and MVIIA in OIPN was found to be 1.8 pmol/paw and 0.8 pmol/paw, respectively. However, none of the ω-conotoxins were effective in a mouse model of CisIPN. The intraplantar administration of 300 nM GVIA, MVIIA, and CVIF did not cause any locomotor side effects. The intraplantar administration of MVIIA can alleviate incision-induced mechanical allodynia, and GVIA and MVIIA effectively reduce OIPN associated mechanical pain, without locomotor side effects, in rodent models. In contrast, CVIF was inactive in these pain models, suggesting it is unable to block a subset of N-type voltage-gated calcium channels associated with nociceptors in the skin.

Low oxygen microenvironment and cardiovascular remodeling: Role of dual L/N.type Ca2+ channel blocker.

OBJECTIVE: Patients exposed to chronic sustained hypoxia frequently develop cardiovascular disease risk factors to ultimately succumb to adverse cardiovascular events. In this context, the present study intends to assess the role of cilnidipine (Cil), a unique calcium channel blocker that blocks both L-type and N-type calcium channels, on cardiovascular pathophysiology in face of chronic sustained hypoxia exposure. MATERIALS AND METHODS: The study involved Wistar strain albino rats. The group-wise allocation of the experimental animals is as follows - Group 1, control (21% O2); Group 2, chronic hypoxia (CH) (10% O2, 90% N); Group 3, Cil + 21% O2; and Group 4, CH (10% O2, 90% N) + Cil (CH + Cil). Cardiovascular hemodynamics, heart rate variability, and endothelial functions (serum nitric oxide [NO], serum endothelial nitric oxide synthase [NOS3], and serum vascular endothelial growth factor [VEGF]) were assessed. Cardiovascular remodeling was studied by histopathological examination of the ventricular tissues, coronary artery (intramyocardial), and elastic and muscular arteries. Normalized wall index of the coronary artery was also calculated. RESULTS AND CONCLUSION: The results demonstrated altered cardiovascular hemodynamics, disturbed cardiovascular autonomic balance, increased levels of VEGF and NOS3, and decreased bioavailability of NO on exposure to chronic sustained hypoxia. The histopathological examination further pointed toward cardiovascular remodeling. Treatment with Cil ameliorated the cardiovascular remodeling and endothelial dysfunction induced by CH exposure, which may be due to its blocking actions on L/N-type of calcium channels, indicating the possible therapeutic role of Cil against CH-induced cardiovascular pathophysiology.

Modulation of intracellular calcium concentration by D2-like DA receptor agonists in non-peptidergic DRG neurons is mediated mainly by D4 receptor activation.

Nociceptive stimuli attributes are codified in the periphery; at this level, D2-like dopamine (DA) receptor activation decreases the high voltage-gated Ca2+ current predominantly in mechanonociceptive neurons, which explains the presynaptic action mechanism of the antinociception produced by quinpirole when it is intrathecally administered in rats. However, the identity of D2-like DA receptor subtype that mediates this effect remains unknown. To answer this question, we used Fluo-4-based Ca2+ microfluorometry to study the depolarization-elicited [Ca2+]i increase in small non-peptidergic DRG neurons (identified by its binding to the Isolectin B4), and to test the effect of D2-like DA receptor activation by quinpirole in presence of selective antagonists for D2, D3, and D4 DA receptors. The results showed a significantly greater contribution of the D4 DA receptor in the down-modulation of depolarization-elicited [Ca2+]i increase in small non-peptidergic DRG neurons compared to the other receptors. Although the D2 and D3 receptor antagonists also slightly inhibited the effect of quinpirole, their effects were significantly weaker than those of the D4 receptor antagonist. Furthermore, we showed that quinpirole selectively inhibits the CaV2.2 Ca2+ channels. Our results suggest that the activation of the D4 DA receptors is a promising strategy for pain management at the spinal cord level.

Antidepressant-like and memory-enhancing effects of the N-type calcium channel blocker ziconotide in rats.

The lack of oral or injectable formulations of ziconotide (ω-conotoxin peptide), a novel analgesic agent, limits research on potential neurobehavioral protective properties of this substance, including antidepressant-like effects. Here we expose rats to a stress paradigm that induces depression and memory impairment to assess the effects of ziconotide treatment. Ziconotide was administered intracerebroventricular (i.c.v.) to rats undergoing stereotaxic surgery at a single dose (1 µg/rat) or in repeated long-term applications (dosage groups: 0.1, 0.3, and 1 µg/rat). The antidepressant activity and memory-enhancing effects of ziconotide were examined via the forced swimming test, the Morris water maze test, and the passive avoidance learning test. Behavioral results showed that long-term i.c.v. ziconotide administration significantly decreased the immobility time and delayed the latency period to immobility in a dose-dependent manner compared to controls. In the passive avoidance learning test, the latency period increased, and in the Morris water maze test, the platform location latency time decreased. A single dose of ziconotide (1 µg/rat) did not show a significant effect on memory function or depression parameters during the same tests. Animals were sacrificed immediately after behavioral testing, and both hippocampi were removed and prepared for BDNF evaluation. Hippocampal BDNF levels were significantly increased in rats receiving long-term i.c.v. ziconotide compared to controls. Our results suggest that long-term consumption of ziconotide may attenuate the severity of depression-like behavior and could be useful for preventing memory impairments in various learning models by elevating BDNF levels.

Effect of ethanolic extract of Solanum virginianum Linn. on neuropathic pain using chronic constriction injury rat model and molecular docking studies.

The present research work was designed to examine the neuroprotective effect of ethanolic extract of Solanum virginianum Linn. (SV) in chronic construction injury (CCI) of sciatic nerve-induced neuropathic pain in rats. The extract was initially standardized by high-performance thin-layer chromatography using solasodine as a biomarker and was then subjected to assess the degree of mechanical allodynia, thermal allodynia, mechanical hyperalgesia, thermal hyperalgesia and biochemical evaluations. Administration of SV (100 and 200 mg/kg; p.o.) and pregabalin (10 mg/kg; p.o.) as a reference standard significantly debilitated hyperalgesia and allodynia and notably restored the altered antioxidant level and pro-inflammatory cytokine (IL-1ß and TNF-α) expression in a dose-dependent manner. Further, to appraise the mechanistic approach of solasodine, docking simulation studies were done on the 3D structure of the voltage-gated N-type calcium channel (Cav 2.2), R-type calcium channel (Cav 2.3) and sodium channel (Nav 1.7), and the results revealed that solasodine properly positioned into Phe 19, Leu 32, Met 51 and Met 71 (FLMM pocket) of Cav 2.2 and Cav 2.3 and being a competitor of Ca2+/N-lobe it may inactivate these calcium channels but did not bind into the desired binding pocket of Nav 1.7. Thus, the study confirmed the role of solasodine as a major biomarker for the observed neuroprotective nature of Solanum virginianum.

Comparison of effects of L/N-type and L-type calcium channel blockers on post-infarct cardiac remodelling in spontaneously hypertensive rats.

Hypertension and coronary events are becoming more prevalent in aging societies, and myocardial infarction usually occurs in calcium channel blocker (CCB)-treated hypertensive patients. We herein compared the effects of cilnidipine, an L/N-type CCB and amlodipine, an L-type CCB, on post-infarct left ventricular (LV) remodelling in spontaneously hypertensive rats (SHRs). Male SHRs were subjected to 30 minutes of left coronary artery occlusion followed by reperfusion (MI group). The administration of cilnidipine (10 mg/kg/d; MI + Cil group) or amlodipine (10 mg/kg/d; MI + Aml group) was initiated one week before surgery and continued for five weeks. Both CCBs decreased blood pressure. Four weeks after surgery, cilnidipine, but not amlodipine, attenuated LV dilatation, fractional shortening impairments, end-diastolic pressure elevations, and tau elongation. In the non-infarct region, myocyte hypertrophy and brain natriuretic peptide (BNP) mRNA levels were similarly attenuated by both CCBs. On the other hand, interstitial fibrosis, the mRNA expression of collagen type III and transforming growth factor (TGF) ß and immunohistological TGF ß protein expression in the non-infarct region were reduced more in the MI + Cil group than in the MI + Aml group. Additionally, elevated angiotensin-converting enzyme activity and interstitial noradrenaline concentrations in the non-infarct region were reduced by cilnidipine. These results suggest that cilnidipine reduced cardiac noradrenaline concentrations and inhibited the renin-angiotensin system, which attenuated post-infarct remodelling more than amlodipine in hypertensive rats.

An N-/L-type calcium channel blocker, cilnidipine, suppresses autonomic, electrical, and structural remodelling associated with atrial fibrillation.

AIMS: Autonomic dysfunction can promote atrial fibrillation (AF) and results from AF-related remodelling. N-type Ca2+-channels (NTCCs) at sympathetic nerve terminals mediate Ca2+-entry that triggers neurotransmitter release. AF-associated remodelling plays an important role in AF pathophysiology but the effects of NTCC inhibition on such remodelling is unknown. Here, we investigated the ability of a clinically available Ca2+-channel blocker (CCB) with NTCC-blocking activity to suppress the arrhythmogenic effects of AF-promoting remodelling in dogs. METHODS AND RESULTS: Mongrel dogs were kept in AF by right atrial tachypacing at 600 bpm. Four groups were studied under short-term AF (7 days): (i) Shams, instrumented but without tachypacing (n = 5); (ii) a placebo group, tachypaced while receiving placebo (n = 6); (iii) a control tachypacing group receiving nifedipine (10 mg orally twice-daily; n = 5), an L-type CCB; and (iv) a cilnidipine group, subjected to tachypacing and treatment with cilnidipine (10 mg orally twice-daily; n = 7), an N-/L-type CCB. With cilnidipine therapy, dogs with 1-week AF showed significantly reduced autonomic changes reflected by heart rate variability (decreases in RMSSD and pNN50) and plasma norepinephrine concentrations. In addition, cilnidipine-treated dogs had decreased extracellular matrix gene expression vs. nifedipine-dogs. As in previous work, atrial fibrosis had not yet developed after 1-week AF, so three additional groups were studied under longer-term AF (21 days): (i) Shams, instrumented without tachypacing or drug therapy (n = 8); (ii) a placebo group, tachypaced while receiving placebo (n = 8); (iii) a cilnidipine group, subjected to tachypacing during treatment with cilnidipine (10 mg twice-daily; n = 8). Cilnidipine attenuated 3-week AF effects on AF duration and atrial conduction, and suppressed AF-induced increases in fibrous-tissue content, decreases in connexin-43 expression and reductions in sodium-channel expression. CONCLUSIONS: Cilnidipine, a commercially available NTCC-blocking drug, prevents AF-induced autonomic, electrical and structural remodelling, along with associated AF promotion.

Reversal of Peripheral Neuropathic Pain by the Small-Molecule Natural Product Physalin F via Block of CaV2.3 (R-Type) and CaV2.2 (N-Type) Voltage-Gated Calcium Channels.

No universally efficacious therapy exists for chronic pain, a disease affecting one-fifth of the global population. An overreliance on the prescription of opioids for chronic pain despite their poor ability to improve function has led to a national opioid crisis. In 2018, the NIH launched a Helping to End Addiction Long-term plan to spur discovery and validation of novel targets and mechanisms to develop alternative nonaddictive treatment options. Phytochemicals with medicinal properties have long been used for various treatments worldwide. The natural product physalin F, isolated from the Physalis acutifolia (family: Solanaceae) herb, demonstrated antinociceptive effects in models of inflammatory pain, consistent with earlier reports of its anti-inflammatory and immunomodulatory activities. However, the target of action of physalin F remained unknown. Here, using whole-cell and slice electrophysiology, competition binding assays, and experimental models of neuropathic pain, we uncovered a molecular target for physalin F's antinociceptive actions. We found that physalin F (i) blocks CaV2.3 (R-type) and CaV2.2 (N-type) voltage-gated calcium channels in dorsal root ganglion (DRG) neurons, (ii) does not affect CaV3 (T-type) voltage-gated calcium channels or voltage-gated sodium or potassium channels, (iii) does not bind G-protein coupled opioid receptors, (iv) inhibits the frequency of spontaneous excitatory postsynaptic currents (EPSCs) in spinal cord slices, and (v) reverses tactile hypersensitivity in models of paclitaxel-induced peripheral neuropathy and spinal nerve ligation. Identifying CaV2.2 as a molecular target of physalin F may spur its use as a tool for mechanistic studies and position it as a structural template for future synthetic compounds.

Targeting the CaVα-CaVß interaction yields an antagonist of the N-type CaV2.2 channel with broad antinociceptive efficacy.

Inhibition of voltage-gated calcium (CaV) channels is a potential therapy for many neurological diseases including chronic pain. Neuronal CaV1/CaV2 channels are composed of α, ß, γ and α2δ subunits. The ß subunits of CaV channels are cytoplasmic proteins that increase the surface expression of the pore-forming α subunit of CaV. We targeted the high-affinity protein-protein interface of CaVß's pocket within the CaVα subunit. Structure-based virtual screening of 50,000 small molecule library docked to the ß subunit led to the identification of 2-(3,5-dimethylisoxazol-4-yl)-N-((4-((3-phenylpropyl)amino)quinazolin-2-yl)methyl)acetamide (IPPQ). This small molecule bound to CaVß and inhibited its coupling with N-type voltage-gated calcium (CaV2.2) channels, leading to a reduction in CaV2.2 currents in rat dorsal root ganglion sensory neurons, decreased presynaptic localization of CaV2.2 in vivo, decreased frequency of spontaneous excitatory postsynaptic potentials and miniature excitatory postsynaptic potentials, and inhibited release of the nociceptive neurotransmitter calcitonin gene-related peptide from spinal cord. IPPQ did not target opioid receptors nor did it engage inhibitory G protein-coupled receptor signaling. IPPQ was antinociceptive in naive animals and reversed allodynia and hyperalgesia in models of acute (postsurgical) and neuropathic (spinal nerve ligation, chemotherapy- and gp120-induced peripheral neuropathy, and genome-edited neuropathy) pain. IPPQ did not cause akinesia or motor impairment, a common adverse effect of CaV2.2 targeting drugs, when injected into the brain. IPPQ, a quinazoline analog, represents a novel class of CaV2.2-targeting compounds that may serve as probes to interrogate CaVα-CaVß function and ultimately be developed as a nonopioid therapeutic for chronic pain.

Discovering the pharmacodynamics of conolidine and cannabidiol using a cultured neuronal network based workflow.

Determining the mechanism of action (MOA) of novel or naturally occurring compounds mostly relies on assays tailored for individual target proteins. Here we explore an alternative approach based on pattern matching response profiles obtained using cultured neuronal networks. Conolidine and cannabidiol are plant-derivatives with known antinociceptive activity but unknown MOA. Application of conolidine/cannabidiol to cultured neuronal networks altered network firing in a highly reproducible manner and created similar impact on network properties suggesting engagement with a common biological target. We used principal component analysis (PCA) and multi-dimensional scaling (MDS) to compare network activity profiles of conolidine/cannabidiol to a series of well-studied compounds with known MOA. Network activity profiles evoked by conolidine and cannabidiol closely matched that of ω-conotoxin CVIE, a potent and selective Cav2.2 calcium channel blocker with proposed antinociceptive action suggesting that they too would block this channel. To verify this, Cav2.2 channels were heterologously expressed, recorded with whole-cell patch clamp and conolidine/cannabidiol was applied. Remarkably, conolidine and cannabidiol both inhibited Cav2.2, providing a glimpse into the MOA that could underlie their antinociceptive action. These data highlight the utility of cultured neuronal network-based workflows to efficiently identify MOA of drugs in a highly scalable assay.

Polycyclic maleimide-based derivatives as first dual modulators of neuronal calcium channels and GSK-3ß for Alzheimer's disease treatment.

Current healthcare has significantly increased the average life expectancy, leading to a consequently greater incidence of age-related diseases, such as Alzheimer's disease. Following a multitarget approach, in this paper a series of polycyclic maleimide-based derivatives were designed and synthesized aimed at simultaneously modulate neuronal calcium channels and glycogen synthase kinase 3-beta (GSK-3ß), validated targets to combat Alzheimer' disease. Different structural modifications were performed on the polycyclic scaffold in order to investigate the structure-activity relationships and compound 10 emerged as a promising non-toxic lead compound, endowed with calcium modulating brain-addressed properties and significant GSK-3ß inhibitory activity. Moreover, the easily affordable polycyclic core appears as a new appealing privileged structure in medicinal chemistry.

Matrine inhibits itching by lowering the activity of calcium channel.

Sophorae Flavescentis Radix (SFR) is a medicinal herb with many functions that are involved in anti-inflammation, antinociception, and anticancer. SFR is also used to treat a variety of itching diseases. Matrine (MT) is one of the main constituents in SFR and also has the effect of relieving itching, but the antipruritic mechanism is still unclear. Here, we investigated the effect of MT on anti-pruritus. In acute and chronic itch models, MT significantly inhibited the scratching behavior not only in acute itching induced by histamine (His), chloroquine (CQ) and compound 48/80 with a dose-depended manner, but also in the chronic pruritus models of atopic dermatitis (AD) and acetone-ether-water (AEW) in mice. Furthermore, MT could be detected in the blood after intraperitoneal injection (i.p.) and subcutaneous injection (s.c.). Finally, electrophysiological and calcium imaging results showed that MT inhibited the excitatory synaptic transmission from dorsal root ganglion (DRG) to the dorsal horn of the spinal cord by suppressing the presynaptic N-type calcium channel. Taken together, we believe that MT is a novel drug candidate in treating pruritus diseases, especially for histamine-independent and chronic pruritus, which might be attributed to inhibition of the presynaptic N-type calcium channel.

Synthesis and evaluation of aminobenzothiazoles as blockers of N- and T-type calcium channels.

Both N- and T-type calcium ion channels have been implicated in pain transmission and the N-type channel is a well-validated target for the treatment of neuropathic pain. An SAR investigation of a series of substituted aminobenzothiazoles identified a subset of five compounds with comparable activity to the positive control Z160 in a FLIPR-based intracellular calcium response assay measuring potency at both CaV2.2 and CaV3.2 channels. These compounds may form the basis for the development of drug leads and tool compounds for assessing in vivo effects of variable modulation of CaV2.2 and CaV3.2 channels.

Comparison between L-type and N/L-type calcium channel blockers in the regulation of home blood-pressure variability in elderly hypertensive patients.

Recent studies suggest that L-type calcium channel blockers (CCBs) contribute to reducing blood pressure (BP) variability. We investigated whether inhibition of the N-type calcium channel has an additional effect on BP variability by comparing the effect of L-type and L/N-type CCBs on home BP variability in elderly hypertensive patients. Twenty-six hypertensive patients (≥65 years) were subjected to repeated changes with the administration of amlodipine (L-type CCB) and cilnidipine (L/N-type CCB) every 2 months. They measured the home BP in the morning and evening, and the coefficient of variation (CV) was calculated. We measured the brachial-ankle pulse wave velocity (baPWV) and urinary catecholamine excretion as an index of the arterial stiffness and sympathetic nerve activity, respectively. There was no difference in the effect of both drugs on the CV in the morning and evening, while amlodipine was associated with a modestly higher pulse rate and lower BP than cilnidipine. By comparing individual patient data for the CV with each drug, we found that higher urinary catecholamine excretion was associated with the effectiveness of cilnidipine over amlodipine in the BP variability in the morning, which was not the case in the evening. In contrast, lower baPWV was associated with the effectiveness of amlodipine over cilnidipine on BP variability in the evening. Lower baPWV was also associated with lower BP variability in the evening. Cilnidipine has a similar capacity as amlodipine in reducing home BP variability, but the underlying mechanisms in reducing BP variability may differ.

Pre-clinical evaluation of voltage-gated calcium channel blockers derived from the spider P. nigriventer in glioma progression.

This study investigated the effects of P/Q- and N-type voltage-gated calcium channel (VGCC) blockers derived from P. nigriventer in glioma progression, by means of in vitro and in vivo experiments. Glioma cells M059J, U-138MG and U-251MG were used to evaluate the antiproliferative effects of P/Q- and N-type VGCC inhibitors PhTx3-3 and Phα1ß from P. nigriventer (0.3-100 pM), in comparison to MVIIC and MVIIA from C. magus (0.3-100 pM), respectively. The toxins were also analyzed in a glioma model induced by implantation of GL261 mouse cells. PhTx3-3, Phα1ß and MVIIA displayed significant inhibitory effects on the proliferation and viability of all tested glioma cell lines, and evoked cell death mainly with apoptosis characteristics, as indicated by Annexin V/propidium iodide (PI) positivity. The antiproliferative effects of toxins were confirmed by flow cytometry using Ki67 staining. None of the tested toxins altered the proliferation rates of the N9 non-tumor glial cell line. Noteworthy, the administration of the preferential N-type VGCC inhibitors, Phα1ß (50 pmol/site; i.c.v.), its recombinant form CTK 01512-2 (50 pmol/site; i.c.v. and i.t.), or MVIIA (10 pmol/site; i.c.v.) caused significant reductions of tumor areas in vivo. N-type VGCC inhibition by Phα1ß, CTK 01512-2, and MVIIA led to a marked increase of GFAP-activated astrocytes, and Iba-1-positive microglia, in the peritumoral region, which might explain, at least in part, the inhibitory effects of the toxins in tumor development. This study provides novel evidence on the potential effects of P. nigriventer-derived P/Q-, and mainly, N-type VGCC inhibitors, in glioma progression.

Phospholipase C-dependent hydrolysis of phosphatidylinositol 4,5-bisphosphate underlies agmatine-induced suppression of N-type Ca2+ channel in rat celiac ganglion neurons.

Agmatine suppresses peripheral sympathetic tone by modulating Cav2.2 channels in peripheral sympathetic neurons. However, the detailed cellular signaling mechanism underlying the agmatine-induced Cav2.2 inhibition remains unclear. Therefore, in the present study, we investigated the electrophysiological mechanism for the agmatine-induced inhibition of Cav2.2 current (ICav2.2) in rat celiac ganglion (CG) neurons. Consistent with previous reports, agmatine inhibited ICav2.2 in a VI manner. The agmatine-induced inhibition of the ICav2.2 current was also almost completely hindered by the blockade of the imidazoline I2 receptor (IR2), and an IR2 agonist mimicked the inhibitory effect of agmatine on ICav2.2, implying involvement of IR2. The agmatine-induced ICav2.2 inhibition was significantly hampered by the blockade of G protein or phospholipase C (PLC), but not by the pretreatment with pertussis toxin. In addition, diC8-phosphatidylinositol 4,5-bisphosphate (PIP2) dialysis nearly completely hampered agmatine-induced inhibition, which became irreversible when PIP2 resynthesis was blocked. These results suggest that in rat peripheral sympathetic neurons, agmatine-induced IR2 activation suppresses Cav2.2 channel voltage-independently, and that the PLC-dependent PIP2 hydrolysis is responsible for the agmatine-induced suppression of the Cav2.2 channel.

[New calcium channel blockers for the treatment of hypertension]. / Nuevos bloqueadores de los canales de calcio en el tratamiento de la hipertensión arterial.

L-type voltage-gated calcium channels play a key role in the regulation of arterial vascular smooth muscle tone and blood pressure levels and L-type calcium channel blockers (CCBs) are widely used antihypertensive drugs. Additionally, T-type channels regulate vascular tone in small-resistance vessels and renin and aldosterone secretion, and N-type channels, expressed in sympathetic nerve terminals, regulate the release of neurotransmitters. As compared with L-type CCBs, L/N-and L/T-type CCBs decreased intraglomerular pressure, improved renal hemodynamics and provided a greater decrease in proteinuria even in patients already treated with renin-angiotensin-aldosterone inhibitors. Thus, dual L/N-and L/T-type CCBs may exhibit therapeutic advantages over L-type blockers in hypertensive patients with chronic kidney disease. However, further large-scale, long-term comparative trials are needed to confirm that these differences translate into an improvement in clinical outcomes. © 2017 SEHLELHA. Published by Elsevier España, S.L.U. All rights reserved.