Channel Blockade Research Articles

Ectopic burst induced by blockade of axonal potassium channels on the mouse hippocampal mossy fiber.

A potassium channel blocker 4-AP has been shown to exert pronounced convulsive action to generate burst firings when applied to hippocampal slices. However, it remains unclear how the blockade of potassium channels leads to the generation of burst firings. One possibility is ectopic spiking from the sites different from those for physiological spike initiation at the axon initial segment, as suggested for several experimental models of epileptogenesis in vitro. To test for possible ectopic spiking at the distal axon by 4-AP application, direct recordings from large mossy fiber terminals were made with the loose-patch clamp technique in mouse hippocampal slices. To localize the action of 4-AP on the distal axon, focal perfusion, as well as micro-cut to disconnect soma and distal axons, were adopted. Focal application of 4-AP on the distal portion of mossy fibers reliably induced burst discharges of the mossy fiber terminals. Photochemical blockade of potassium channels at distal axons, by the application of RuBi-4-AP, a visible wavelength blue light-sensitive caged compound, and the illumination of blue light caused robust bursting activity originating from distal axons. Computer simulation suggested that local blockade of axonal potassium channels prolongs the duration of action potentials and thereby causes reverberating spiking activities at distal axons and subsequent antidromic propagation toward the soma. Taken together, it was suggested that local blockade of voltage-dependent potassium channels in distal axons by application of 4-AP is sufficient to cause a hyperexcitable state of hippocampal mossy fiber axons.

Advancements in understanding cardiotoxicity of EGFR- TKIs in non-small cell lung cancer treatment and beyond.

Epidermal Growth Factor Receptor-Tyrosine Kinase Inhibitors (EGFR-TKIs) are a class of oral targeted anticancer drugs that have been demonstrated to significantly inhibit tumor progression and improve clinical prognosis in patients diagnosed with EGFR-mutated tumors, particularly in those with non-small cell lung cancer. However, the sustained usage of EGFR-TKIs may cause potential cardiotoxicity, thus limiting their applicability. The primary objective of this review is to systematically analyze the evolving landscape of research pertaining to EGFR-TKI-induced cardiotoxicity and elucidate its underlying mechanisms, such as PI3K signaling pathway inhibition, ion channel blockade, oxidative stress, inflammatory responses, and apoptosis. Additionally, the review includes an exploration of risk assessment for cardiotoxicity induced by EGFR-TKIs, along with management and response strategies. Prospective research directions are outlined, emphasizing the need for more accurate predictors of cardiotoxicity and the development of innovative intervention strategies. In summation, this review consolidates recent research advances, illuminates the risks associated with EGFR-TKI-induced cardiac toxicity and presents crucial insights for refining clinical dosage protocols, optimizing patient management strategies, and unraveling the intricate mechanisms governing EGFR-TKI-induced cardiotoxicity.

The Promise of Cilnidipine in Hypertension with Comorbidities: National Consensus Statement: National Consensus Group Comprises Cardiologists, Nephrologists, and Diabetologists from India in a National Meet at New Delhi held on 22nd May 2022.

The rapidly increasing burden of hypertension is responsible for premature deaths from cardiovascular disease (CVD), renal disease, and stroke, with a tremendous public health and financial burden. Hypertension detection, treatment, and control vary worldwide; it is still low, particularly in low- and middle-income countries (LMICs). High blood pressure (BP) and CVD risk have a strong, linear, and independent association. They contribute to alarming numbers of all-cause and CVD deaths. A major culprit for increased hypertension is sympathetic activity, and further complications of hypertension are heart failure, ischemic heart disease (IHD), stroke, and renal failure. Now, antihypertensive interventions have emerged as a global public health priority to reduce BP-related morbidity and mortality. Calcium channel blockers (CCB) are highly effective vasodilators. and the most common drugs used for managing hypertension and CVD. Cilnidipine, with both L- and N-type calcium channel blocking activity, is a promising 4th generation CCB. It causes vasodilation via L-type calcium channel blockade and inhibits the sympathetic nervous system (SNS) via N-type calcium channel blockade. Cilnidipine, which acts as a dual L/N-type CCB, is linked to a reduced occurrence of pedal edema compared to amlodipine, which solely blocks L-type calcium channels. The antihypertensive properties of cilnidipine are very substantial, with low BP variability and long-acting properties. It is beneficial for hypertensive patients to deal with morning hypertension and for patients with abnormal nocturnal BP due to exaggerated sympathetic nerve activation. Besides its BP-lowering effect, it also exhibits organ protection via sympathetic nerve inhibition and renin-angiotensin-aldosterone system inhibition; it controls heart rate and proteinuria. Reno-protective, neuroprotective, and cardioprotective effects of cilnidipine have been well-documented and demonstrated.

Increased GIRK channel activity prevents arrhythmia in mice with heart failure by enhancing ventricular repolarization

Ventricular arrhythmia causing sudden cardiac death is the leading mode of death in patients with heart failure. Yet, the mechanisms that prevent ventricular arrhythmias in heart failure are not well characterized. Using a mouse model of heart failure created by transverse aorta constriction, we show that GIRK channel, an important regulator of cardiac action potentials, is constitutively active in failing ventricles in contrast to normal cells. Evidence is presented indicating that the tonic activation of M2 muscarinic acetylcholine receptors by endogenously released acetylcholine contributes to the constitutive GIRK activity. This constitutive GIRK activity prevents the action potential prolongation in heart failure ventricles. Consistently, GIRK channel blockade with tertiapin-Q induces QT interval prolongation and increases the incidence of arrhythmia in heart failure, but not in control mice. These results suggest that constitutive GIRK channels comprise a key mechanism to protect against arrhythmia by providing repolarizing currents in heart failure ventricles.

Effectiveness of calcium channel blockade for organophosphorus and carbamate pesticide poisoning – study protocol for an open label, pragmatic, 3-arm RCT repurposing two widely available medicines

Pesticide self-poisoning is one of the three most important global means of suicide, killing an estimated 110–168,000 people each year, mostly in poor rural Asian communities. Organophosphorus (OP) and carbamate anticholinesterase insecticides are responsible for about two-thirds of these deaths. Calcium channel blocking medicines (CCB) may reduce the effect of pesticides and prevent deaths. Two preclinical rodents’ studies and eight clinical studies utilising nimodipine and magnesium sulphate (MgSO4), respectively, showed mixed results. We have established a multi-centre randomised controlled trial (RCT) of patients with OP or carbamate self-poisoning admitted to at least six major hospitals in Bangladesh. The study aims to recruit maximum 3,243 patients over four years. One-third of the patients selected at random will receive standard treatment, while one-third will be treated with additional nimodipine and one-third with additional MgSO4. The additional treatments will be given for 48 h. We will check mortality (currently an estimated 11% die with standard treatment) and need for intensive care for mechanical ventilation across the three groups. This could lead to development of the first novel treatment for anticholinesterase poisoning in 50 years and its introduction into routine hospital practice worldwide.

CaV3.1 channels facilitate calcium wave generation and myogenic tone development in mouse mesenteric arteries

The arterial myogenic response to intraluminal pressure elicits constriction to maintain tissue perfusion. Smooth muscle [Ca2+] is a key determinant of constriction, tied to L-type (CaV1.2) Ca2+ channels. While important, other Ca2+ channels, particularly T-type could contribute to pressure regulation within defined voltage ranges. This study examined the role of one T-type Ca2+ channel (CaV3.1) using C57BL/6 wild type and CaV3.1−/− mice. Patch-clamp electrophysiology, pressure myography, blood pressure and Ca2+ imaging defined the CaV3.1−/− phenotype relative to C57BL/6. CaV3.1−/− mice had absent CaV3.1 expression and whole-cell current, coinciding with lower blood pressure and reduced mesenteric artery myogenic tone, particularly at lower pressures (20–60 mmHg) where membrane potential is hyperpolarized. This reduction coincided with diminished Ca2+ wave generation, asynchronous events of Ca2+ release from the sarcoplasmic reticulum, insensitive to L-type Ca2+ channel blockade (Nifedipine, 0.3 µM). Proximity ligation assay (PLA) confirmed IP3R1/CaV3.1 close physical association. IP3R blockade (2-APB, 50 µM or xestospongin C, 3 µM) in nifedipine-treated C57BL/6 arteries rendered a CaV3.1−/− contractile phenotype. Findings indicate that Ca2+ influx through CaV3.1 contributes to myogenic tone at hyperpolarized voltages through Ca2+-induced Ca2+ release tied to the sarcoplasmic reticulum. This study helps establish CaV3.1 as a potential therapeutic target to control blood pressure.

IK Channel-Independent Effects of Clotrimazole and Senicapoc on Cancer Cells Viability and Migration.

Many studies highlighted the importance of the IK channel for the proliferation and the migration of different types of cancer cells, showing how IK blockers could slow down cancer growth. Based on these data, we wanted to characterize the effects of IK blockers on melanoma metastatic cells and to understand if such effects were exclusively IK-dependent. For this purpose, we employed two different blockers, namely clotrimazole and senicapoc, and two cell lines: metastatic melanoma WM266-4 and pancreatic cancer Panc-1, which is reported to have little or no IK expression. Clotrimazole and senicapoc induced a decrease in viability and the migration of both WM266-4 and Panc-1 cells irrespective of IK expression levels. Patch-clamp experiments on WM266-4 cells revealed Ca2+-dependent, IK-like, clotrimazole- and senicapoc-sensitive currents, which could not be detected in Panc-1 cells. Neither clotrimazole nor senicapoc altered the intracellular Ca2+ concentration. These results suggest that the effects of IK blockers on cancer cells are not strictly dependent on a robust presence of the channel in the plasma membrane, but they might be due to off-target effects on other cellular targets or to the blockade of IK channels localized in intracellular organelles.

Facilitation of hERG Activation by Its Blocker: A Mechanism to Reduce Drug-Induced Proarrhythmic Risk.

Modulation of the human Ether-à-go-go-Related Gene (hERG) channel, a crucial voltage-gated potassium channel in the repolarization of action potentials in ventricular myocytes of the heart, has significant implications on cardiac electrophysiology and can be either antiarrhythmic or proarrhythmic. For example, hERG channel blockade is a leading cause of long QT syndrome and potentially life-threatening arrhythmias, such as torsades de pointes. Conversely, hERG channel blockade is the mechanism of action of Class III antiarrhythmic agents in terminating ventricular tachycardia and fibrillation. In recent years, it has been recognized that less proarrhythmic hERG blockers with clinical potential or Class III antiarrhythmic agents exhibit, in addition to their hERG-blocking activity, a second action that facilitates the voltage-dependent activation of the hERG channel. This facilitation is believed to reduce the proarrhythmic potential by supporting the final repolarizing of action potentials. This review covers the pharmacological characteristics of hERG blockers/facilitators, the molecular mechanisms underlying facilitation, and their clinical significance, as well as unresolved issues and requirements for research in the fields of ion channel pharmacology and drug-induced arrhythmias.

Blockade of L-type calcium channels alters hepatic mitochondrial function in insulin-resistant rats

Mitochondria are central organelles in maintaining energy and oxidative homeostasis. Despite intensive research, the function of mitochondria and the mechanisms of its regulation under physiological conditions and in insulin resistance require detailed investigation. The aim of this study was to investigate the effect of blockade L-type calcium channels in insulin-resistant rats on hepatic mitochondrial oxidative function and changes in its oxidative status. Insulin resistance was modeled in 6-month-old male Wistar rats by 14 days of high-fat feeding. Standard fed animals served as controls. Verapamil was administered intraperitoneally at a dose of 1 mg/kg to block L-type calcium channels. Indicators of pro- and antioxidant systems (active products of tiobarbituric acid, reduced glutathione, catalase, Cu,Zn-superoxide dismutase) were assayed in the liver homogenate extracted from anesthetized animals after 3 h. Mitochondrial function was studied by the Chance polarographic method using different metabolic substrates. It was shown that in intact animals blockade of L-type calcium channels reduced the efficiency of mitochondrial respiration (V3/V4) in liver mitochondria during oxidation of all substrates through an inhibitory effect on the phosphorylation respiration (V3) and a stimulatory effect on the controlled respiration (V4), without affecting the oxidative status of the liver. In rats with insulin resistance the rate of V3 during oxidation of both NAD- and FADdependent substrates was decreased, violations of oxidative status and increased antioxidant protection were detected. However, in insulin-resistant rats blockade of L-type calcium channels significantly enhanced basic respiration (V2) during NAD-dependent substrate oxidation, V3 and V4 during palmitoyl lipid substrate oxidation, reduced the V3/V4 ratio compared to control, and partially or fully restored the violation of the oxidative status. This may indicate the involvement of calcium mechanisms in the disturbance of the oxidative status of the liver and the regulation of energy metabolism in mitochondria during insulin resistance.

An opto-electronic control system for real-time complete (re)shaping of cardiac action potentials on a multicellular scale

Abstract Background Cardiomyocytes maintain a membrane potential (Vm), which fulfills essential regulatory roles in various biological functions, including not only action potential (AP) propagation and mechanical contraction, but also homeostatic regulation. In-depth studies into these roles have been severely hampered by the lack of research methods allowing full control over Vm, especially in multicellular cardiac preparations. Purpose We aimed to unlock new research possibilities by the development of an experimental system (APqr) capable of full Vm control, including instantaneous modulation of AP morphology on a multicellular level. Methods Immortalized human atrial myocytes (hiAMs) grown in monolayer format (n=7) were genetically modified to express the blue light-activatable cation channel Cheriff and the red light-sensitive inward chloride pump Jaws for depolarizing and hyperpolarizing effects, respectively. Real-time Vm readout was obtained by patch clamp electrophysiology. Dynamic Vm control was achieved by a custom closed-coop controller calculating Vm deviations from reference values. A 470-nm and a 617-nm LED were modulated by the controller in a Vm deviation-dependent manner, selectively activating Cheriff and Jaws. To explore the feasibility of AP restoration, electrical disturbances were introduced by non-selective potassium channel blockade (4-aminopyridine, 4AP, 200 µM) or by a preprogrammed blue-light pulse creating abnormal cation influx during the repolarization phase of the hiAM AP. Results 4AP induced a 82.4 ± 27.8 ms increase of AP duration at 90% repolarization (APD90) values in hiAM monolayers. Using APs recorded under control conditions (CTL) as reference, the APqr maneuver reduced this APD90 difference to 1.9 ± 3.1 ms. Similarly, APqr suppressed the effects of light-induced abnormal cation influx on APD90 (CTL: 342.9 ± 51.7 ms, blue-light pulse: 700.8 ± 64.5 ms, APqr: 338.3 ± 68 ms) effectively, with Vm deviation less than 2.5 mV in 96.7% of the time. APqr could also be applied for the enforcement of arbitrary AP shapes. In these experiments, the Vm references consisted of AP shapes of hiAM monolayers exposed to drugs with APD-prolonging (4AP) or shortening (carbachol) effects. APqr was able to enforce these reference APs, that were distinctly different from the endogenous AP shapes, on hiAM monolayers with great accuracy, with Vm deviations less than 2.5 mV in 95.8% and 94.4% of the time, respectively. Conclusions APqr restores AP morphologies in the presence of electrical perturbations of different origin without any prior knowledge about the disturbance and enforces arbitrary AP morphologies with high accuracy in an immediate and self-regulatory manner. Collectively, these results set the stage for in-depth investigations into the regulatory roles of Vm in healthy and diseased cardiomyocytes via the application of such real-time opto-electronic control systems.Real-time (re)shaping of cardiac APs

Abstract 11661: Genotypic and Phenotypic Guided Antiarrhythmic Drug Management of Multifocal Premature Ventricular Contractions

Introduction: Antiarrhythmic selection for progressive and intractable PVCs unresponsive to first and second line regimens can prove challenging. Genetic analysis assists by targeting specific genes, such as the SCN5a gene, which encodes for the alpha subunit of cardiac sodium channel NaV1.5. Mutations are associated with autosomal dominant phenotypes of multifocal ectopic Purkinje-related premature Contractions (MEPPCs). Case: A 38 year old female with a history of syncope and moderate left ventricular systolic dysfunction status post AICD and a family history of SCD presented for follow-up with complaints of frequent palpitations. ECG and a 72 hour Holter monitor had multifocal PVCs of purkinje origin with a burden of 31%. Despite a therapeutic trial with sotalol and amiodarone in various doses, she remained unresponsive with multifocal purkinje-related PVCs. TTE revealed global LV hypokinesia with worsening LVEF, and a cardiac MRI revealed features suggestive of a dilated cardiomyopathy (DCM) phenotype. Whole exome DNA analysis showed a heterozygous missense mutation pArg814Tryp on exon 16 of the SCN5A gene. Her specific variant, R814W, is a gain-of-function variant responsible for the hyperexcitability of the Purkinje fibers, making it amenable to sodium channel blockade with flecainide. After starting gene-directed flecainide, her PVC burden drastically reduced from 31% to 3% on repeat Holter monitor after 2 months. She has remained asymptomatic with an improved LVEF. Discussion: This is a unique case of SCN5A channelopathy with a MEPPC phenotype demonstrating a dramatic response to genotype guided management of multifocal PVCs. Clinicians should include such phenotypes in their differentials for patients that fail first and second line treatment regimens and have significant family history. It is essential to offer genetic testing to patients with a MEPPC phenotype in a DCM setting to choose the appropriate therapy and prevent SCD.

Abstract 16851: Tricyclic Antidepressant Induced Wide Complex Tachycardia With Brugada Pattern

Case Description: A 52-year-old male with bipolar disorder and depression was brought to the ED after he was found confused following an episode of syncope. He reported taking 5 pills of his new dose of Nortriptyline 75mg instead of 5 pills of his previous dose of Nortriptyline 25mg. ECG from the field showed a wide complex tachycardia (WCT) with a rightward axis and a Brugada pattern in V1 and V2 at a rate of 120-130s. Upon arrival in the ED, he continued to have WCT, and was treated with Amiodarone, Magnesium Sulfate, and Sodium Bicarbonate. Following treatment, his heart rate improved and the QRS duration shortened with a gradual loss of Brugada pattern (Figure 1). Six hours from initial presentation, his QRS completely normalized. Transthoracic echocardiogram (TTE) showed normal LV function. His presentation was consistent with tricyclic antidepressant (TCA) overdose. Discussion: The cardiotoxic effects of TCAs are mediated through their behavior as class IA antiarrhythmic drugs. This results in lengthening of both depolarization and repolarization of the cardiac action potential resulting in a widened QRS complex and QT prolongation. Sodium channel blockade can precipitate a Brugada phenotype which resolves after Sodium Bicarbonate administration. Similar to class IA agents, TCAs also exhibit use dependence and in our patient, the Brugada pattern began to resolve soon after presentation, possibly due to slowing of the tachycardia. Recognition of TCA toxicity is important to allow for timely administration of bicarbonate which facilitates prompt reversal.

Abdominal pain syndrome in patients with irritable bowel syndrome: features of selection of therapy

Irritable bowel syndrome (IBS) is an important social problem, since it is often diagnosed in people of young working age, significantly affects the quality of life of patients and causes economic damage to society. IBS is a chronic functional bowel disease, the main manifestation of which is pain combined with changes in bowel movements, frequency and character of stool. The mechanism of formation of abdominal pain syndrome is due to a disruption in the interaction along the brain-gut axis, which leads to changes in the regulation of intestinal motor function and the development of visceral hypersensitivity (VH). Abdominal pain as a manifestation of IBS is primarily associated with spasm of intestinal smooth muscles. The first-line drugs for pain relief are antispasmodics, which reduce the tone and contractility of intestinal smooth muscles, effectively coping with abdominal pain. The domestic pharmaceutical market is represented by different groups of muscle relaxants, among which calcium channel blockers are of particular relevance for patients with IBS. Representative of the latter is the drug Otilonium bromide, which is widely used throughout the world, is effective and safe, well tolerated and superior to placebo in reducing symptoms and preventing relapse of pain in patients with IBS. The effectiveness of otilonium bromide is due to a triple mechanism of action: blockade of calcium channels (relief of spasm), antagonism of tachykinone NK2 receptors (effect on HHV) and inhibition of acetylcholine muscarinic receptors (M3-ChR) (reduction of intestinal secretion). This article presents a short review of the literature on the causes and mechanism of development of pain in IBS, as well as the possibilities of its relief, primarily with the use of smooth muscle relaxants, namely otilonium bromide.

Interaction Between HCN and Slack Channels Regulates mPFC Pyramidal Cell Excitability in Working Memory Circuits.

The ability of monkeys and rats to carry out spatial working memory tasks has been shown to depend on the persistent firing of pyramidal cells in the prefrontal cortex (PFC), arising from recurrent excitatory connections on dendritic spines. These spines express hyperpolarization-activated cyclic nucleotide-gated (HCN) channels whose open state is increased by cAMP signaling, and which markedly alter PFC network connectivity and neuronal firing. In traditional neural circuits, activation of these non-selective cation channels leads to neuronal depolarization and increased firing rate. Paradoxically, cAMP activation of HCN channels in PFC pyramidal cells reduces working memory-related neuronal firing. This suggests that activation of HCN channels may hyperpolarize rather than depolarize these neurons. The current study tested the hypothesis that Na+ influx through HCN channels activates Slack Na+-activated K+ (KNa) channels to hyperpolarize the membrane. We have found that HCN and Slack KNa channels co-immunoprecipitate in cortical extracts and that, by immunoelectron microscopy, they colocalize at postsynaptic spines of PFC pyramidal neurons. A specific blocker of HCN channels, ZD7288, reduces KNa current in pyramidal cells that express both HCN and Slack channels, but has no effect on KNa currents in an HEK cell line expressing Slack without HCN channels, indicating that blockade of HCN channels in neurons reduces K+ current indirectly by lowering Na+ influx. Activation of HCN channels by cAMP in a cell line expressing a Ca2+ reporter results in elevation of cytoplasmic Ca2+, but the effect of cAMP is reversed if the HCN channels are co-expressed with Slack channels. Finally, we used a novel pharmacological blocker of Slack channels to show that inhibition of Slack in rat PFC improves working memory performance, an effect previously demonstrated for blockers of HCN channels. Our results suggest that the regulation of working memory by HCN channels in PFC pyramidal neurons is mediated by an HCN-Slack channel complex that links activation HCN channels to suppression of neuronal excitability.

Rational mucolytic therapy with ambroxol: controversial and indisputable. A review

Many years of experience in the use of ambroxol is based on its ability to regulate the basic mechanisms of physiological production and transport of bronchial mucus. The main indication for ambroxol is the mucolytic therapy of acute and chronic bronchopulmonary diseases associated with hypersecretion and impaired mucus transport. Ambroxol has a number of the following properties: high secretolytic activity (promotes mucus clearance, facilitates expectoration of sputum, reduces productive cough); anti-inflammatory and antioxidant activity; local analgesic (anesthetic) effect through the blockade of sodium channels of cell membranes. The effect of anesthesia of the mucous membranes is attributed to the new pharmacological action of ambroxol, useful in the treatment of acute respiratory tract infections. The efficacy and safety of ambroxol in clinical practice has been confirmed by half a century of experience in its administration. The purpose of this publication was an up-to-date assessment of the controversial and indisputable chemical, pharmacological, clinical data on the properties of ambroxol in the concept of modern recovery mucolytic therapy that can improve the therapy and prognosis of patients with tracheobronchial secretion hypersecretion, impaired mucociliary clearance and unproductive cough.

Discovery of novel multifunctional ligands targeting GABA transporters, butyrylcholinesterase, β-secretase, and amyloid β aggregation as potential treatment of Alzheimer's disease

Alzheimer's disease (AD) is a global health problem in the medical sector that will increase over time. The limited treatment of AD leads to the search for a new clinical candidate. Considering the multifactorial nature of AD, a strategy targeting number of regulatory proteins involved in the development of the disease is an effective approach. Here, we present a discovery of new multi-target-directed ligands (MTDLs), purposely designed as GABA transporter (GAT) inhibitors, that successfully provide the inhibitory activity against butyrylcholinesterase (BuChE), β-secretase (BACE1), amyloid β aggregation and calcium channel blockade activity. The selected GAT inhibitors, 19c and 22a – N-benzylamide derivatives of 4-aminobutyric acid, displayed the most prominent multifunctional profile. Compound 19c (mGAT1 IC50 = 10 μM, mGAT4 IC50 = 12 μM and BuChE IC50 = 559 nM) possessed the highest hBACE1 and Aβ40 aggregation inhibitory activity (IC50 = 1.57 μM and 99 % at 10 μM, respectively). Additionally, it showed a decrease in both the elongation and nucleation constants of the amyloid aggregation process. In contrast compound 22a represented the highest activity and a mixed-type of eqBuChE inhibition (IC50 = 173 nM) with hBACE1 (IC50 = 9.42 μM), Aβ aggregation (79 % at 10 μM) and mGATs (mGAT1 IC50 = 30 μM, mGAT4 IC50 = 25 μM) inhibitory activity. Performed molecular docking studies described the mode of interactions with GATs and enzymatic targets. In ADMET in vitro studies both compounds showed acceptable metabolic stability and low neurotoxicity. Successfully, compounds 19c and 22a at the dose of 30 mg/kg possessed statistically significant antiamnesic properties in a mouse model of amnesia caused by scopolamine and assessed in the novel object recognition (NOR) task or the passive avoidance (PA) task.

Subcellular Effectors of Cocaine Cardiotoxicity: All Roads Lead to Mitochondria-A Systematic Review of the Literature.

Cocaine abuse is a serious public health problem as this drug exerts a plethora of functional and histopathological changes that potentially lead to death. Cocaine causes complex multiorgan toxicity, including in the heart where the blockade of the sodium channels causes increased catecholamine levels and alteration in calcium homeostasis, thus inducing an increased oxygen demand. Moreover, there is evidence to suggest that mitochondria alterations play a crucial role in the development of cocaine cardiotoxicity. We performed a systematic review according to the Preferred Reporting Items for Systemic Reviews and Meta-Analysis (PRISMA) scheme to evaluate the mitochondrial mechanisms determining cocaine cardiotoxicity. Among the initial 106 articles from the Pubmed database and the 17 articles identified through citation searching, 14 final relevant studies were extensively reviewed. Thirteen articles included animal models and reported the alteration of specific mitochondria-dependent mechanisms such as reduced energy production, imbalance of membrane potential, increased oxidative stress, and promotion of apoptosis. However, only one study evaluated human cocaine overdose samples and observed the role of cocaine in oxidative stress and the induction of apoptosis though mitochondria. Understanding the complex processes mediated by mitochondria through forensic analysis and experimental models is crucial for identifying potential therapeutic targets to mitigate or reverse cocaine cardiotoxicity in humans.

LC-MS Fingerprinting Development for Standardized Precipitate from Agastache mexicana, Which Induces Antihypertensive Effect through NO Production and Calcium Channel Blockade.

The aim of this work was to evaluate the vasorelaxant and antihypertensive effects of a standardized precipitate of the hydroalcoholic extract from Agastache mexicana (PPAm), comprising ursolic acid, oleanolic acid, acacetin, luteolin and tilianin, among others. In the ex vivo experiments, preincubation with L-NAME (nonspecific inhibitor of nitric oxide synthases) reduced the relaxation induced by PPAm; nevertheless, preincubation with indomethacin (nonspecific inhibitor of cyclooxygenases) did not generate any change in the vasorelaxation, and an opposed effect was observed to the contraction generated by CaCl2 addition. Oral administration of 100 mg/kg of PPAm induced a significant acute decrease in diastolic (DBP) and systolic (SBP) blood pressure in spontaneously hypertensive rats, without changes in heart rate. Additionally, PPAm showed a sustained antihypertensive subacute effect on both DBP and SBP for 10 days compared to the control group. On the other hand, human umbilical vein cells treated with 10 µg/mL of PPAm showed a significant reduction (p < 0.05) in intracellular adhesion molecule-1, compared to the control, but not on vascular cell adhesion molecule-1. In conclusion, PPAm induces a significant antihypertensive effect in acute- and subacute-period treatments, due to its direct vasorelaxant action on rat aortic rings through NO production and Ca2+ channel blockade.

Selective Inhibition of Pulmonary Vein Excitability by Constitutively Active GIRK Channels Blockade in Rats.

Pulmonary veins (PV) are the main source of ectopy, triggering atrial fibrillation. This study investigated the roles of G protein-coupled inwardly rectifying potassium (GIRK) channels in the PV and the left atrium (LA) of the rat. Simultaneous intracellular microelectrode recording from the LA and the PV of the rat found that in the presence or absence of acetylcholine, the GIRK channel blocker tertiapin-Q induced AP duration elongation in the LA and the loss of over-shooting AP in the PV, suggesting the presence of constitutively active GIRK channels in these tissues. Patch-clamp recordings from isolated myocytes showed that tertiapin-Q inhibited a basal inwardly rectified background current in PV cells with little effect in LA cells. Experiments with ROMK1 and KCa1.1 channel blockers ruled out the possibility of an off-target effect. Western blot showed that GIRK4 subunit expression was greater in PV cardiomyocytes, which may explain the differences observed between PV and LA in response to tertiapin-Q. In conclusion, GIRK channels blockade abolishes AP only in the PV, providing a molecular target to induce electrical disconnection of the PV from the LA.

The effect of calcium channels blockade on slow-wave distribution in the electrophysiological model of human gastric wall smooth muscle cells

The effect of calcium channels blockade on slow-wave distribution in the electrophysiological model of human gastric wall smooth muscle cells