RESUMO
Lipoprotein(a) (Lp(a)), an independent, causal cardiovascular risk factor, is a lipoprotein particle that is formed by the interaction of a low-density lipoprotein (LDL) particle and apolipoprotein(a) (apo(a))1,2. Apo(a) first binds to lysine residues of apolipoprotein B-100 (apoB-100) on LDL through the Kringle IV (KIV) 7 and 8 domains, before a disulfide bond forms between apo(a) and apoB-100 to create Lp(a) (refs. 3-7). Here we show that the first step of Lp(a) formation can be inhibited through small-molecule interactions with apo(a) KIV7-8. We identify compounds that bind to apo(a) KIV7-8, and, through chemical optimization and further application of multivalency, we create compounds with subnanomolar potency that inhibit the formation of Lp(a). Oral doses of prototype compounds and a potent, multivalent disruptor, LY3473329 (muvalaplin), reduced the levels of Lp(a) in transgenic mice and in cynomolgus monkeys. Although multivalent molecules bind to the Kringle domains of rat plasminogen and reduce plasmin activity, species-selective differences in plasminogen sequences suggest that inhibitor molecules will reduce the levels of Lp(a), but not those of plasminogen, in humans. These data support the clinical development of LY3473329-which is already in phase 2 studies-as a potent and specific orally administered agent for reducing the levels of Lp(a).
Assuntos
Descoberta de Drogas , Lipoproteína(a) , Macaca fascicularis , Animais , Feminino , Humanos , Masculino , Camundongos , Administração Oral , Kringles , Lipoproteína(a)/antagonistas & inibidores , Lipoproteína(a)/sangue , Lipoproteína(a)/química , Lipoproteína(a)/metabolismo , Camundongos Transgênicos , Bibliotecas de Moléculas Pequenas/farmacologia , Bibliotecas de Moléculas Pequenas/química , Plasminogênio/química , Plasminogênio/metabolismo , Especificidade da Espécie , Ensaios Clínicos Fase II como Assunto , Apolipoproteínas A/química , Apolipoproteínas A/metabolismoRESUMO
SAR in the previously described spirocyclic ROMK inhibitor series was further evolved from lead 4 by modification of the spirocyclic core and identification of novel right-side pharmacophores. In this process, it was discovered that the spiropyrrolidinone core with the carbonyl group α to the spirocenter was preferred for potent ROMK activity. Efforts aimed at decreasing hERG affinity within the series led to the discovery of multiple novel right-hand pharmacophores including 3-methoxythiadiazole, 2-methoxypyrimidine, and pyridazinone. The most promising candidate is pyridazinone analog 32 that showed an improved functional hERG/ROMK potency ratio and preclinical PK profile. In vivo evaluation of 32 demonstrated blood pressure lowering effects in the spontaneously hypertensive rat model.
Assuntos
Canal de Potássio ERG1/metabolismo , Bloqueadores dos Canais de Potássio/química , Canais de Potássio Corretores do Fluxo de Internalização/antagonistas & inibidores , Animais , Modelos Animais de Doenças , Cães , Canal de Potássio ERG1/antagonistas & inibidores , Meia-Vida , Hipertensão/tratamento farmacológico , Bloqueadores dos Canais de Potássio/farmacocinética , Bloqueadores dos Canais de Potássio/uso terapêutico , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Pirimidinas/química , Ratos , Ratos Endogâmicos SHR , Compostos de Espiro/química , Relação Estrutura-Atividade , Tiadiazóis/químicaRESUMO
The renal outer medullary potassium (ROMK) channel, located at the apical surface of epithelial cells in the thick ascending loop of Henle and cortical collecting duct, contributes to salt reabsorption and potassium secretion, and represents a target for the development of new mechanism of action diuretics. This idea is supported by the phenotype of antenatal Bartter's syndrome type II associated with loss-of-function mutations in the human ROMK channel, as well as, by cardiovascular studies of heterozygous carriers of channel mutations associated with type II Bartter's syndrome. Although the pharmacology of ROMK channels is still being developed, channel inhibitors have been identified and shown to cause natriuresis and diuresis, in the absence of any significant kaliuresis, on acute oral dosing to rats or dogs. Improvements in potency and selectivity have led to the discovery of MK-7145 [5,5'-((1R,1'R)-piperazine-1,4-diylbis(1-hydroxyethane-2,1-diyl))bis(4-methylisobenzofuran-1(3H)-one)], a potential clinical development candidate. In spontaneously hypertensive rats, oral dosing of MK-7145 causes dose-dependent lowering of blood pressure that is maintained during the entire treatment period, and that displays additive/synergistic effects when administered in combination with hydrochlorothiazide or candesartan, respectively. Acute or chronic oral administration of MK-7145 to normotensive dogs led to dose-dependent diuresis and natriuresis, without any significant urinary potassium losses or changes in plasma electrolyte levels. Elevations in bicarbonate and aldosterone were found after 6 days of dosing. These data indicate that pharmacological inhibition of ROMK has potential as a new mechanism for the treatment of hypertension and/or congestive heart failure. In addition, Bartter's syndrome type II features are manifested on exposure to ROMK inhibitors.
Assuntos
Síndrome de Bartter/fisiopatologia , Benzofuranos/farmacologia , Pressão Sanguínea/efeitos dos fármacos , Fenótipo , Piperazinas/farmacologia , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio Corretores do Fluxo de Internalização/antagonistas & inibidores , Animais , Síndrome de Bartter/tratamento farmacológico , Benzimidazóis/farmacologia , Benzofuranos/uso terapêutico , Compostos de Bifenilo , Cães , Relação Dose-Resposta a Droga , Sinergismo Farmacológico , Feminino , Células HEK293 , Humanos , Hidroclorotiazida/farmacologia , Masculino , Piperazinas/uso terapêutico , Bloqueadores dos Canais de Potássio/uso terapêutico , Ratos , Tetrazóis/farmacologiaRESUMO
Following the discovery of small molecule acyl piperazine ROMK inhibitors and their initial preclinical validation as a novel diuretic agent, our group set out to discover new ROMK inhibitors with reduced risk for QT effects, suitable for further pharmacological experiments in additional species. Several strategies for decreasing hERG affinity while maintaining ROMK inhibition were investigated and are described herein. The most promising candidate, derived from the newly discovered 4-N-heteroaryl acetyl series, improved functional hERG/ROMK ratio by >10× over the previous lead. In vivo evaluation demonstrated comparable diuretic effects in rat with no detectable QT effects at the doses evaluated in an in vivo dog model.
Assuntos
Canal de Potássio ERG1/fisiologia , Compostos Heterocíclicos/farmacologia , Piperazinas/farmacologia , Compostos Heterocíclicos/química , Piperazinas/química , Relação Estrutura-AtividadeRESUMO
Following the discovery of small molecule acyl piperazine ROMK inhibitors, the acyl octahydropyrazino[2,1-c][1,4]oxazine series was identified. This series displays improved ROMK/hERG selectivity, and as a consequence, the resulting ROMK inhibitors do not evoke QTc prolongation in an in vivo cardiovascular dog model. Further efforts in this series led to the discovery of analogs with improved pharmacokinetic profiles. This new series also retained comparable ROMK potency compared to earlier leads.
Assuntos
Oxazinas/química , Oxazinas/farmacologia , Canais de Potássio Corretores do Fluxo de Internalização/antagonistas & inibidores , Animais , Diurese/efeitos dos fármacos , Cães , Insuficiência Cardíaca/tratamento farmacológico , Humanos , Hipertensão/tratamento farmacológico , Macaca mulatta , Oxazinas/farmacocinética , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Ratos Sprague-Dawley , Regulador Transcricional ERG/antagonistas & inibidores , Regulador Transcricional ERG/metabolismoRESUMO
Resurgent sodium currents contribute to the regeneration of action potentials and enhanced neuronal excitability. Tetrodotoxin-sensitive (TTX-S) resurgent currents have been described in many different neuron populations, including cerebellar and dorsal root ganglia (DRG) neurons. In most cases, sodium channel Nav1.6 is the major contributor to these TTX-S resurgent currents. Here we report a novel TTX-resistant (TTX-R) resurgent current recorded from rat DRG neurons. The TTX-R resurgent currents are similar to classic TTX-S resurgent currents in many respects, but not all. As with TTX-S resurgent currents, they are activated by membrane repolarization, inhibited by lidocaine, and enhanced by a peptide-mimetic of the ß4 sodium channel subunit intracellular domain. However, the TTX-R resurgent currents exhibit much slower kinetics, occur at more depolarized voltages, and are sensitive to the Nav1.8 blocker A803467. Moreover, coimmunoprecipitation experiments from rat DRG lysates indicate the endogenous sodium channel ß4 subunits associate with Nav1.8 in DRG neurons. These results suggest that slow TTX-R resurgent currents in DRG neurons are mediated by Nav1.8 and are generated by the same mechanism underlying TTX-S resurgent currents. We also show that both TTX-S and TTX-R resurgent currents in DRG neurons are enhanced by inflammatory mediators. Furthermore, the ß4 peptide increased excitability of small DRG neurons in the presence of TTX. We propose that these slow TTX-R resurgent currents contribute to the membrane excitability of nociceptive DRG neurons under normal conditions and that enhancement of both types of resurgent currents by inflammatory mediators could contribute to sensory neuronal hyperexcitability associated with inflammatory pain.
Assuntos
Mediadores da Inflamação/farmacologia , Potenciais da Membrana/efeitos dos fármacos , Canal de Sódio Disparado por Voltagem NAV1.8/metabolismo , Células Receptoras Sensoriais/efeitos dos fármacos , Células Receptoras Sensoriais/fisiologia , Bloqueadores dos Canais de Sódio/farmacologia , Tetrodotoxina/farmacologia , Compostos de Anilina/farmacologia , Animais , Biofísica , Células Cultivadas , Estimulação Elétrica , Furanos/farmacologia , Gânglios Espinais/citologia , Imunoprecipitação , Lidocaína/farmacologia , Canal de Sódio Disparado por Voltagem NAV1.8/química , Técnicas de Patch-Clamp , Peptídeos/farmacologia , Subunidades Proteicas/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
The renal outer medullary potassium (ROMK) channel, which is located at the apical membrane of epithelial cells lining the thick ascending loop of Henle and cortical collecting duct, plays an important role in kidney physiology by regulating salt reabsorption. Loss-of-function mutations in the human ROMK channel are associated with antenatal type II Bartter's syndrome, an autosomal recessive life-threatening salt-wasting disorder with mild hypokalemia. Similar observations have been reported from studies with ROMK knockout mice and rats. It is noteworthy that heterozygous carriers of Kir1.1 mutations associated with antenatal Bartter's syndrome have reduced blood pressure and a decreased risk of developing hypertension by age 60. Although selective ROMK inhibitors would be expected to represent a new class of diuretics, this hypothesis has not been pharmacologically tested. Compound A [5-(2-(4-(2-(4-(1H-tetrazol-1-yl)phenyl)acetyl)piperazin-1-yl)ethyl)isobenzofuran-1(3H)-one)], a potent ROMK inhibitor with appropriate selectivity and characteristics for in vivo testing, has been identified. Compound A accesses the channel through the cytoplasmic side and binds to residues lining the pore within the transmembrane region below the selectivity filter. In normotensive rats and dogs, short-term oral administration of compound A caused concentration-dependent diuresis and natriuresis that were comparable to hydrochlorothiazide. Unlike hydrochlorothiazide, however, compound A did not cause any significant urinary potassium losses or changes in plasma electrolyte levels. These data indicate that pharmacologic inhibition of ROMK has the potential for affording diuretic/natriuretic efficacy similar to that of clinically used diuretics but without the dose-limiting hypokalemia associated with the use of loop and thiazide-like diuretics.
Assuntos
Diurese/efeitos dos fármacos , Diurese/fisiologia , Natriurese/efeitos dos fármacos , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio Corretores do Fluxo de Internalização/antagonistas & inibidores , Canais de Potássio Corretores do Fluxo de Internalização/fisiologia , Animais , Células CHO , Cricetinae , Cricetulus , Cães , Relação Dose-Resposta a Droga , Feminino , Células HEK293 , Humanos , Células Madin Darby de Rim Canino , Masculino , Natriurese/fisiologia , Ratos , Ratos Sprague-DawleyRESUMO
A series of benzazepinones were synthesized and evaluated for block of Nav1.7 sodium channels. Compound 30 from this series displayed potent channel block, good selectivity versus other targets, and dose-dependent oral efficacy in a rat model of neuropathic pain.
Assuntos
Benzazepinas/farmacologia , Neuralgia/tratamento farmacológico , Bloqueadores dos Canais de Sódio/farmacologia , Animais , Modelos Animais de Doenças , RatosRESUMO
A sub-class of distinct small molecule ROMK inhibitors were developed from the original lead 1. Medicinal chemistry endeavors led to novel ROMK inhibitors with good ROMK functional potency and improved hERG selectivity. Two of the described ROMK inhibitors were characterized for the first in vivo proof-of-concept biology studies, and results from an acute rat diuresis model confirmed the hypothesis that ROMK inhibitors represent new mechanism diuretic and natriuretic agents.
Assuntos
Benzofuranos/química , Benzofuranos/farmacologia , Canais de Potássio Corretores do Fluxo de Internalização/antagonistas & inibidores , Animais , Benzofuranos/farmacocinética , Diurese/efeitos dos fármacos , Descoberta de Drogas , Canais de Potássio Éter-A-Go-Go/antagonistas & inibidores , Canais de Potássio Éter-A-Go-Go/metabolismo , Humanos , Canais de Potássio Corretores do Fluxo de Internalização/metabolismo , Ratos , Ratos Sprague-Dawley , Tetrazóis/química , Tetrazóis/farmacocinética , Tetrazóis/farmacologiaRESUMO
Voltage-gated sodium channels have been shown to play a critical role in neuropathic pain. A series of low molecular weight biaryl substituted pyrazole carboxamides were identified with good in-vitro potency and in-vivo efficacy. Compound 26, a Nav1.7 blocker has excellent efficacy in the Chung model of neuropathic pain.
Assuntos
Neuralgia/tratamento farmacológico , Pirazóis/química , Pirazóis/uso terapêutico , Bloqueadores dos Canais de Sódio/química , Bloqueadores dos Canais de Sódio/uso terapêutico , Canais de Sódio/metabolismo , Animais , Cães , Haplorrinos , Humanos , Microssomos Hepáticos/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.7 , Pirazóis/farmacocinética , Pirazóis/farmacologia , Ratos , Bloqueadores dos Canais de Sódio/farmacocinética , Bloqueadores dos Canais de Sódio/farmacologia , Relação Estrutura-AtividadeRESUMO
Voltage-gated sodium channels have been shown to play a critical role in neuropathic pain. With a goal to develop potent peripherally active sodium channel blockers, a series of low molecular weight biaryl substituted imidazoles, oxazoles, and thiazole carboxamides were identified with good in vitro and in vivo potency.
Assuntos
Neuralgia/tratamento farmacológico , Oxazóis/uso terapêutico , Bloqueadores dos Canais de Sódio/uso terapêutico , Canais de Sódio/metabolismo , Tiazóis/uso terapêutico , Animais , Cães , Humanos , Imidazóis/química , Imidazóis/metabolismo , Imidazóis/farmacologia , Imidazóis/uso terapêutico , Microssomos Hepáticos/metabolismo , Canal de Sódio Disparado por Voltagem NAV1.7 , Oxazóis/química , Oxazóis/metabolismo , Oxazóis/farmacologia , Ratos , Bloqueadores dos Canais de Sódio/química , Bloqueadores dos Canais de Sódio/metabolismo , Bloqueadores dos Canais de Sódio/farmacologia , Tiazóis/química , Tiazóis/metabolismo , Tiazóis/farmacologiaRESUMO
A series of novel biphenyl pyrazole dicarboxamides were identified as potential sodium channel blockers for treatment of neuropathic pain. Compound 20 had outstanding efficacy in the Chung rat spinal nerve ligation (SNL) model of neuropathic pain.
Assuntos
Compostos de Bifenilo/química , Neuralgia/tratamento farmacológico , Pirazóis/química , Bloqueadores dos Canais de Sódio/química , Canais de Sódio/química , Animais , Compostos de Bifenilo/síntese química , Compostos de Bifenilo/uso terapêutico , Cães , Avaliação Pré-Clínica de Medicamentos , Humanos , Camundongos , Microssomos Hepáticos/metabolismo , Atividade Motora/efeitos dos fármacos , Pirazóis/farmacocinética , Pirazóis/uso terapêutico , Ratos , Bloqueadores dos Canais de Sódio/farmacocinética , Bloqueadores dos Canais de Sódio/uso terapêutico , Canais de Sódio/metabolismoRESUMO
A series of novel isoxazole voltage gated sodium channel blockers have been synthesized and evaluated. Substitutions on the benzylic position of benzamide were investigated to determine their effect on Na(v)1.7 inhibitory potency. The spirocyclobutyl substitution had the most significant enhancement on Na(v)1.7 inhibitory activity.
Assuntos
Isoxazóis/uso terapêutico , Dor/tratamento farmacológico , Bloqueadores dos Canais de Sódio/uso terapêutico , Canais de Sódio/metabolismo , Animais , Linhagem Celular , Doença Crônica , Humanos , Isoxazóis/química , Isoxazóis/farmacologia , Dor/imunologia , Ratos , Bloqueadores dos Canais de Sódio/química , Bloqueadores dos Canais de Sódio/farmacologia , Nervos Espinhais/efeitos dos fármacos , Relação Estrutura-AtividadeRESUMO
Analogs of the previously reported voltage gated sodium channel blocker CDA54 were prepared in which one of the amide functions was replaced with aromatic and non-aromatic heterocycles. Replacement of the amide with an aromatic heterocycle resulted in significant loss of sodium channel blocking activity, while non-aromatic heterocycle replacements were well tolerated.
Assuntos
Isoxazóis/química , Isoxazóis/farmacologia , Bloqueadores dos Canais de Sódio/química , Bloqueadores dos Canais de Sódio/farmacologia , Animais , Isoxazóis/uso terapêutico , Modelos Moleculares , Estrutura Molecular , Dor/tratamento farmacológico , Ratos , Ratos Sprague-Dawley , Bloqueadores dos Canais de Sódio/uso terapêutico , Nervos Espinhais/efeitos dos fármacos , Relação Estrutura-AtividadeRESUMO
Relief from chronic pain continues to represent a large unmet need. The voltage-gated potassium channel Kv7.2/7.3, also known as KCNQ2/3, is a key contributor to the control of resting membrane potential and excitability in nociceptive neurons and represents a promising target for potential therapeutics. In this study, we present a medium throughput electrophysiological assay for the identification and characterization of modulators of Kv7.2/7.3 channels, using the IonWorks Barracuda™ automated voltage clamp platform. The assay combines a family of voltage steps used to construct conductance curves with a unique analysis method. Kv7.2/7.3 modulators shift the activation voltage and/or change the maximal conductance of the current, and both parameters have been used to quantify compound mediated effects. Both effects are expected to modulate neuronal excitability in vivo. The analysis method described assigns a single potency value that combines changes in activation voltage and maximal conductance and is expected to predict compound mediated changes in excitability.
Assuntos
Aminopiridinas/análise , Carbamatos/análise , Desenvolvimento de Medicamentos , Ensaios de Triagem em Larga Escala/instrumentação , Técnicas de Patch-Clamp/instrumentação , Fenilenodiaminas/análise , Aminopiridinas/farmacologia , Carbamatos/farmacologia , Células Cultivadas , Fenômenos Eletrofisiológicos , Células HEK293 , Humanos , Canal de Potássio KCNQ2/metabolismo , Canal de Potássio KCNQ3/metabolismo , Fenilenodiaminas/farmacologiaRESUMO
Voltage-gated sodium (Na(V)1) channels play a critical role in modulating the excitability of sensory neurons, and human genetic evidence points to Na(V)1.7 as an essential contributor to pain signaling. Human loss-of-function mutations in SCN9A, the gene encoding Na(V)1.7, cause channelopathy-associated indifference to pain (CIP), whereas gain-of-function mutations are associated with two inherited painful neuropathies. Although the human genetic data make Na(V)1.7 an attractive target for the development of analgesics, pharmacological proof-of-concept in experimental pain models requires Na(V)1.7-selective channel blockers. Here, we show that the tarantula venom peptide ProTx-II selectively interacts with Na(V)1.7 channels, inhibiting Na(V)1.7 with an IC(50) value of 0.3 nM, compared with IC(50) values of 30 to 150 nM for other heterologously expressed Na(V)1 subtypes. This subtype selectivity was abolished by a point mutation in DIIS3. It is interesting that application of ProTx-II to desheathed cutaneous nerves completely blocked the C-fiber compound action potential at concentrations that had little effect on Abeta-fiber conduction. ProTx-II application had little effect on action potential propagation of the intact nerve, which may explain why ProTx-II was not efficacious in rodent models of acute and inflammatory pain. Mono-iodo-ProTx-II ((125)I-ProTx-II) binds with high affinity (K(d) = 0.3 nM) to recombinant hNa(V)1.7 channels. Binding of (125)I-ProTx-II is insensitive to the presence of other well characterized Na(V)1 channel modulators, suggesting that ProTx-II binds to a novel site, which may be more conducive to conferring subtype selectivity than the site occupied by traditional local anesthetics and anticonvulsants. Thus, the (125)I-ProTx-II binding assay, described here, offers a new tool in the search for novel Na(V)1.7-selective blockers.
Assuntos
Potenciais de Ação/efeitos dos fármacos , Nociceptores/efeitos dos fármacos , Bloqueadores dos Canais de Sódio/farmacologia , Canais de Sódio/efeitos dos fármacos , Venenos de Aranha/farmacologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Linhagem Celular , Primers do DNA , Humanos , Ativação do Canal Iônico , Masculino , Modelos Animais , Dados de Sequência Molecular , Mutagênese Sítio-Dirigida , Ensaio Radioligante , Ratos , Ratos Sprague-Dawley , Homologia de Sequência de Aminoácidos , Canais de Sódio/química , Canais de Sódio/genética , Canais de Sódio/fisiologiaRESUMO
A series of 3-amino-1,5-benzodiazepinones were synthesized and evaluated as potential sodium channel blockers in a functional, membrane potential-based assay. One member of this series displayed subnanomolar, state-dependent sodium channel block, and was orally efficacious in a mouse model of epilepsy.
Assuntos
Anticonvulsivantes/farmacologia , Benzodiazepinonas/farmacologia , Epilepsia/tratamento farmacológico , Canais de Potássio Éter-A-Go-Go/antagonistas & inibidores , Bloqueadores dos Canais de Sódio/farmacologia , Animais , Anticonvulsivantes/síntese química , Anticonvulsivantes/farmacocinética , Benzodiazepinonas/síntese química , Benzodiazepinonas/farmacocinética , Eletrofisiologia , Eletrochoque , Epilepsia/metabolismo , Canais de Potássio Éter-A-Go-Go/metabolismo , Transferência Ressonante de Energia de Fluorescência , Humanos , Camundongos , Estrutura Molecular , Ratos , Bloqueadores dos Canais de Sódio/síntese química , Bloqueadores dos Canais de Sódio/farmacocinéticaRESUMO
A series of imidazopyridines were evaluated as potential sodium channel blockers for the treatment of neuropathic pain. Several members were identified with good hNa(v)1.7 potency and excellent rat pharmacokinetic profiles. Compound 4 had good efficacy (52% and 41% reversal of allodynia at 2 and 4h post-dose, respectively) in the Chung rat spinal nerve ligation (SNL) model of neuropathic pain when dosed orally at 10mg/kg.
Assuntos
Piridinas/química , Piridinas/farmacologia , Bloqueadores dos Canais de Sódio/química , Bloqueadores dos Canais de Sódio/farmacologia , Canais de Sódio/metabolismo , Analgésicos/química , Analgésicos/farmacologia , Animais , Inflamação/tratamento farmacológico , Estrutura Molecular , Canal de Sódio Disparado por Voltagem NAV1.7 , Dor/tratamento farmacológico , Ratos , Bloqueadores dos Canais de Sódio/farmacocinética , Relação Estrutura-AtividadeRESUMO
Delayed-rectifier K+ currents (I(DR)) in pancreatic beta-cells are thought to contribute to action potential repolarization and thereby modulate insulin secretion. The voltage-gated K+ channel, K(V)2.1, is expressed in beta-cells, and the biophysical characteristics of heterologously expressed channels are similar to those of I(DR) in rodent beta-cells. A novel peptidyl inhibitor of K(V)2.1/K(V)2.2 channels, guangxitoxin (GxTX)-1 (half-maximal concentration approximately 1 nmol/l), has been purified, characterized, and used to probe the contribution of these channels to beta-cell physiology. In mouse beta-cells, GxTX-1 inhibits 90% of I(DR) and, as for K(V)2.1, shifts the voltage dependence of channel activation to more depolarized potentials, a characteristic of gating-modifier peptides. GxTX-1 broadens the beta-cell action potential, enhances glucose-stimulated intracellular calcium oscillations, and enhances insulin secretion from mouse pancreatic islets in a glucose-dependent manner. These data point to a mechanism for specific enhancement of glucose-dependent insulin secretion by applying blockers of the beta-cell I(DR), which may provide advantages over currently used therapies for the treatment of type 2 diabetes.
Assuntos
Canais de Potássio de Retificação Tardia/fisiologia , Glucose/farmacologia , Insulina/metabolismo , Ilhotas Pancreáticas/fisiologia , Bloqueadores dos Canais de Potássio/farmacologia , Sequência de Aminoácidos , Animais , Canais de Potássio de Retificação Tardia/efeitos dos fármacos , Secreção de Insulina , Ilhotas Pancreáticas/efeitos dos fármacos , Cinética , Potenciais da Membrana/efeitos dos fármacos , Potenciais da Membrana/fisiologia , Camundongos , Dados de Sequência Molecular , Peptídeos/química , Peptídeos/farmacologia , Bloqueadores dos Canais de Potássio/química , Venenos de Aranha/química , Venenos de Aranha/farmacologiaRESUMO
UNLABELLED: Sodium channel blockers such as lidocaine, lamotrigine, and carbamazepine can be effective in the treatment of neuropathic pain. Though not approved for neuropathic pain indications, tricyclic antidepressants are often considered first-line treatment for conditions such as post-herpetic neuralgia and diabetic neuropathy. Several tricyclic antidepressants have been shown to block peripheral nerve sodium channels, which may contribute to their antihyperalgesic efficacy. In this study, we compared the sodium channel-blocking potency of a number of antidepressants, including tricyclic antidepressants and selective serotonin reuptake inhibitors. All compounds tested inhibited Na(V)1.7 in a state- and use-dependent manner, with affinities for the inactivated state ranging from 0.24 micromol/L for amitriptyline to 11.6 micromol/L for zimelidine. The tricyclic antidepressants were more potent blockers of Na(V)1.7. Moreover, IC(50)s for block of the inactivated state for amitriptyline, nortriptyline, imipramine, desipramine, and maprotiline were in the range of therapeutic plasma concentrations for both the treatment of depression as well as neuropathic pain. By contrast, fluoxetine, paroxetine, mianserine, and zimelidine had IC(50)s for Na(V)1.7 outside their therapeutic concentration ranges and generally were not efficacious against post-herpetic neuralgia or diabetic neuropathy. These results suggest that block of peripheral nerve sodium channels may contribute to the antihyperalgesic efficacy of certain antidepressants. PERSPECTIVE: Tricyclic antidepressants are often considered first-line treatment for neuropathic pain. Some tricyclic antidepressants block sodium channels, which may contribute to their antihyperalgesic efficacy. In the current study, we compared the potency of peripheral sodium channel blockade for several tricyclic antidepressants and selective serotonin reuptake inhibitors with their therapeutic efficacy.