RESUMO
Im-3 was isolated from the venom of the scorpion Isometrus maculatus through several steps of HPLC fractionation based on the insect paralytic activity. Injecting Im-3 into crickets induced paralysis, but no toxicity was apparent in mice after an intracerebroventricular injection. Im-3 shares sequence similarity to scorpion ß-toxins that specifically affect insect sodium channels.
Assuntos
Venenos de Artrópodes/química , Gryllidae/efeitos dos fármacos , Neurotoxinas/química , Escorpiões/química , Bloqueadores dos Canais de Sódio/química , Sequência de Aminoácidos , Animais , Venenos de Artrópodes/classificação , Venenos de Artrópodes/isolamento & purificação , Venenos de Artrópodes/farmacologia , Cromatografia Líquida de Alta Pressão , Gryllidae/fisiologia , Injeções Intraventriculares , Masculino , Camundongos , Camundongos Endogâmicos ICR , Dados de Sequência Molecular , Neurotoxinas/classificação , Neurotoxinas/isolamento & purificação , Neurotoxinas/farmacologia , Filogenia , Escorpiões/patogenicidade , Alinhamento de Sequência , Análise de Sequência de Proteína , Homologia de Sequência de Aminoácidos , Bloqueadores dos Canais de Sódio/classificação , Bloqueadores dos Canais de Sódio/isolamento & purificação , Bloqueadores dos Canais de Sódio/farmacologia , Canais de Sódio/metabolismo , Especificidade da EspécieRESUMO
The voltage-gated sodium (Na(v)) channel is a target for a number of drugs, insecticides and neurotoxins. These bind to at least seven identified neurotoxin binding sites and either block conductance or modulate Na(v) channel gating. A number of peptide neurotoxins from the venoms of araneomorph and mygalomorph spiders have been isolated and characterized and determined to interact with several of these sites. These all conform to an 'inhibitor cystine-knot' motif with structural, but not sequence homology, to a variety of other spider and marine snail toxins. Of these, spider toxins several show phyla-specificity and are being considered as lead compounds for the development of biopesticides. Hainantoxin-I appears to target site-1 to block Na(v) channel conductance. Magi 2 and Tx4(6-1) slow Na(v) channel inactivation via an interaction with site-3. The delta-palutoxins, and most likely mu-agatoxins and curtatoxins, target site-4. However, their action is complex with the mu-agatoxins causing a hyperpolarizing shift in the voltage-dependence of activation, an action analogous to scorpion beta-toxins, but with both delta-palutoxins and mu-agatoxins slowing Na(v) channel inactivation, a site-3-like action. In addition, several other spider neurotoxins, such as delta-atracotoxins, are known to target both insect and vertebrate Na(v) channels most likely as a result of the conserved structures within domains of voltage-gated ion channels across phyla. These toxins may provide tools to establish the molecular determinants of invertebrate selectivity. These studies are being greatly assisted by the determination of the pharmacophore of these toxins, but without precise identification of their binding site and mode of action their potential in the above areas remains underdeveloped.
Assuntos
Proteínas de Insetos/farmacologia , Neurotoxinas/farmacologia , Controle Biológico de Vetores , Bloqueadores dos Canais de Sódio/farmacologia , Canais de Sódio/efeitos dos fármacos , Venenos de Aranha/farmacologia , Aranhas/fisiologia , Sequência de Aminoácidos , Animais , Proteínas de Insetos/química , Proteínas de Insetos/classificação , Ativação do Canal Iônico , Dados de Sequência Molecular , Neurotoxinas/química , Neurotoxinas/classificação , Conformação Proteica , Bloqueadores dos Canais de Sódio/química , Bloqueadores dos Canais de Sódio/classificação , Canais de Sódio/química , Canais de Sódio/metabolismo , Venenos de Aranha/química , Venenos de Aranha/classificaçãoRESUMO
ISSUE: Anticonvulsants are not a single therapeutic class, but are composed of multiple distinct subclasses with different mechanisms of action, efficacies, and side effects.
Assuntos
Anticonvulsivantes/uso terapêutico , Encéfalo/efeitos dos fármacos , Proteínas de Membrana Transportadoras , Transtornos Mentais/tratamento farmacológico , Transportadores de Ânions Orgânicos , Anticonvulsivantes/efeitos adversos , Anticonvulsivantes/classificação , Bloqueadores dos Canais de Cálcio/efeitos adversos , Bloqueadores dos Canais de Cálcio/classificação , Bloqueadores dos Canais de Cálcio/uso terapêutico , Canais de Cálcio/efeitos dos fármacos , Proteínas de Transporte/antagonistas & inibidores , Moduladores GABAérgicos/efeitos adversos , Moduladores GABAérgicos/classificação , Moduladores GABAérgicos/uso terapêutico , Proteínas da Membrana Plasmática de Transporte de GABA , Humanos , Potenciais da Membrana/efeitos dos fármacos , Proteínas de Membrana/antagonistas & inibidores , Bloqueadores dos Canais de Sódio/efeitos adversos , Bloqueadores dos Canais de Sódio/classificação , Bloqueadores dos Canais de Sódio/uso terapêutico , Canais de Sódio/efeitos dos fármacosRESUMO
BACKGROUND: There is only one established drug binding site on sodium channels. However, drug binding of sodium channels shows extreme promiscuity: â¼25% of investigated drugs have been found to potently inhibit sodium channels. The structural diversity of these molecules suggests that they may not share the binding site, and/or the mode of action. Our goal was to attempt classification of sodium channel inhibitors by measuring multiple properties of inhibition in electrophysiology experiments. We also aimed to investigate if different properties of inhibition correlate with specific chemical properties of the compounds. METHODOLOGY/PRINCIPAL FINDINGS: A comparative electrophysiological study of 35 compounds, including classic sodium channel inhibitors (anticonvulsants, antiarrhythmics and local anesthetics), as well as antidepressants, antipsychotics and neuroprotective agents, was carried out using rNav1.2 expressing HEK-293 cells and the QPatch automatic patch-clamp instrument. In the multi-dimensional space defined by the eight properties of inhibition (resting and inactivated affinity, potency, reversibility, time constants of onset and offset, use-dependence and state-dependence), at least three distinct types of inhibition could be identified; these probably reflect distinct modes of action. The compounds were clustered similarly in the multi-dimensional space defined by relevant chemical properties, including measures of lipophilicity, aromaticity, molecular size, polarity and electric charge. Drugs of the same therapeutic indication typically belonged to the same type. We identified chemical properties, which were important in determining specific properties of inhibition. State-dependence correlated with lipophilicity, the ratio of the neutral form of molecules, and aromaticity: We noticed that the highly state dependent inhibitors had at least two aromatic rings, logP>4.0, and pKa<8.0. CONCLUSIONS/SIGNIFICANCE: The correlations of inhibition properties both with chemical properties and therapeutic profiles would not have been evident through the sole determination of IC(50); therefore, recording multiple properties of inhibition may allow improved prediction of therapeutic usefulness.
Assuntos
Bloqueadores dos Canais de Sódio/classificação , Bloqueadores dos Canais de Sódio/farmacologia , Anestésicos/farmacologia , Anticonvulsivantes/farmacologia , Automação , Química Farmacêutica/métodos , Relação Dose-Resposta a Droga , Eletrofisiologia/métodos , Humanos , Concentração de Íons de Hidrogênio , Concentração Inibidora 50 , Cinética , Técnicas de Patch-Clamp , Sódio/química , Canais de Sódio/químicaRESUMO
Class I antiarrhythmic drugs are sodium channel inhibitors that act by slowing myocardial conduction and, thus, interrupting or preventing reentrant arrhythmia. Due to proarrhythmic effects and the risk of ventricular tachyarrhythmia, class I antiarrhythmics should not be administered in patients with structural heart disease. Nevertheless, there remains a broad spectrum of arrhythmias--among the most common being atrial fibrillation--that can successfully be treated with class I antiarrhythmic drugs. This review gives an overview on the classification, antiarrhythmic mechanisms, indications, side effects, and application modes of class I antiarrhythmic drugs.
Assuntos
Antiarrítmicos/classificação , Antiarrítmicos/uso terapêutico , Arritmias Cardíacas/tratamento farmacológico , Bloqueadores dos Canais de Sódio/classificação , Bloqueadores dos Canais de Sódio/uso terapêutico , Administração Oral , Antagonistas Adrenérgicos beta/uso terapêutico , Antiarrítmicos/efeitos adversos , Arritmias Cardíacas/induzido quimicamente , Arritmias Cardíacas/mortalidade , Fibrilação Atrial/tratamento farmacológico , Fibrilação Atrial/mortalidade , Contraindicações , Relação Dose-Resposta a Droga , Quimioterapia Combinada , Eletrocardiografia/efeitos dos fármacos , Feminino , Insuficiência Cardíaca/complicações , Insuficiência Cardíaca/tratamento farmacológico , Humanos , Infusões Intravenosas , Infarto do Miocárdio/complicações , Infarto do Miocárdio/tratamento farmacológico , Gravidez , Ensaios Clínicos Controlados Aleatórios como Assunto , Bloqueadores dos Canais de Sódio/efeitos adversos , Taquicardia por Reentrada no Nó Atrioventricular/tratamento farmacológico , Taquicardia Supraventricular/tratamento farmacológico , Taquicardia Ventricular/tratamento farmacológicoRESUMO
A series of benzodiazepines and benzazepinones were synthesized and evaluated as potential sodium channel blockers in a functional, membrane potential-based assay. One member of the benzazepinone series, compound 47, displayed potent, state-dependent block of hNa(v)1.7, and was orally efficacious in a rat model of neuropathic pain.