RESUMEN
Three series of substituted anti-1,2,3-triazoles (IND, PPRD, and QND), synthesized by cycloaddition from azide and alkyne building blocks, were designed to enhance selectivity and potency profiles of a lead α7 nicotinic acetylcholine receptor (α7-nAChR) agonist, TTIn-1. Designed compounds were synthesized and screened for affinity by a radioligand binding assay. Their functional characterization as agonists and antagonists was performed by fluorescence resonance energy transfer assay using cell lines expressing transfected cDNAs, α7-nAChRs, α4ß2-nAChRs, and 5HT3A receptors, and a fluorescence cell reporter. In the IND series, a tropane ring of TTIn-1, substituted at N1, was replaced by mono- and bicyclic amines to vary length and conformational flexibility of a carbon linker between nitrogen atom and N1 of the triazole. Compounds with a two-carbon atom linker optimized binding with Kd's at the submicromolar level. Further modification at the hydrophobic indole of TTIn-1 was made in PPRD and QND series by fixing the amine center with the highest affinity building blocks in the IND series. Compounds from IND and PPRD series are selective as agonists for the α7-nAChRs over α4ß2-nAChRs and 5HT3A receptors. Lead compounds in the three series have EC50's between 28 and 260 nM. Based on the EC50, affinity, and selectivity determined from the binding and cellular responses, two of the leads have been advanced to behavioral studies described in the companion article (DOI: 10.1021/acschemneuro.5b00059).
Asunto(s)
Agonistas Nicotínicos/farmacología , Triazoles/farmacología , Receptor Nicotínico de Acetilcolina alfa 7/agonistas , Relación Dosis-Respuesta a Droga , Diseño de Fármacos , Evaluación Preclínica de Medicamentos , Transferencia Resonante de Energía de Fluorescencia , Células HEK293 , Humanos , Modelos Químicos , Estructura Molecular , Agonistas Nicotínicos/síntesis química , Agonistas Nicotínicos/química , Antagonistas Nicotínicos/síntesis química , Antagonistas Nicotínicos/química , Antagonistas Nicotínicos/farmacología , Ensayo de Unión Radioligante , Receptores Nicotínicos/genética , Receptores Nicotínicos/metabolismo , Receptores de Serotonina 5-HT3/genética , Receptores de Serotonina 5-HT3/metabolismo , Transfección , Triazoles/síntesis química , Triazoles/química , Receptor Nicotínico de Acetilcolina alfa 7/antagonistas & inhibidores , Receptor Nicotínico de Acetilcolina alfa 7/genética , Receptor Nicotínico de Acetilcolina alfa 7/metabolismoRESUMEN
α-Conotoxins are disulfide-rich peptide neurotoxins that selectively inhibit neuronal nicotinic acetylcholine receptors (nAChRs). The α3ß4 nAChR subtype has been identified as a novel target for managing nicotine addiction. Using a mixture-based positional-scanning synthetic combinatorial library (PS-SCL) with the α4/4-conotoxin BuIA framework, we discovered a highly potent and selective α3ß4 nAChR antagonist. The initial PS-SCL consisted of a total of 113 379 904 sequences that were screened for α3ß4 nAChR inhibition, which facilitated the design and synthesis of a second generation library of 64 individual α-conotoxin derivatives. Eleven analogues were identified as α3ß4 nAChR antagonists, with TP-2212-59 exhibiting the most potent antagonistic activity and selectivity over the α3ß2 and α4ß2 nAChR subtypes. Final electrophysiological characterization demonstrated that TP-2212-59 inhibited acetylcholine evoked currents in α3ß4 nAChRs heterogeneously expressed in Xenopus laevis oocytes with a calculated IC50 of 2.3 nM and exhibited more than 1000-fold selectivity over the α3ß2 and α7 nAChR subtypes. As such, TP-2212-59 is among the most potent α3ß4 nAChRs antagonists identified to date and further demonstrates the utility of mixture-based combinatorial libraries in the discovery of novel α-conotoxin derivatives with refined pharmacological activity.
Asunto(s)
Técnicas Químicas Combinatorias/métodos , Conotoxinas/farmacología , Antagonistas Nicotínicos/síntesis química , Receptores Nicotínicos/efectos de los fármacos , Descubrimiento de Drogas , Evaluación Preclínica de Medicamentos , Células HEK293 , Humanos , Potenciales de la Membrana/efectos de los fármacos , Antagonistas Nicotínicos/farmacología , Receptores Nicotínicos/química , Relación Estructura-ActividadRESUMEN
A series of azaaromatic quaternary ammonium analogs has been discovered as potent and selective α9α10 nicotinic acetylcholine receptor (nAChR) antagonists. The preliminary structure-activity relationships of these analogs suggest that increased rigidity in the linker units results in higher potency in inhibition of α9α10 nAChRs and greater selectivity over α7 nAChRs. These analogs represent a new class of analgesic for the treatment of neuropathic and tonic inflammatory pain.
Asunto(s)
Analgésicos/química , Antagonistas Nicotínicos/química , Dolor/tratamiento farmacológico , Receptores Nicotínicos/química , Analgésicos/síntesis química , Analgésicos/uso terapéutico , Animales , Evaluación Preclínica de Medicamentos , Antagonistas Nicotínicos/síntesis química , Antagonistas Nicotínicos/uso terapéutico , Compuestos de Amonio Cuaternario/síntesis química , Compuestos de Amonio Cuaternario/química , Compuestos de Amonio Cuaternario/uso terapéutico , Ratas , Receptores Nicotínicos/metabolismo , Relación Estructura-ActividadRESUMEN
Using positron emission tomography (PET) with a specific and selective radioligand targeting nicotinic acetylcholine receptor (nAChR) would allow us to better understand various nAChR related CNS disorders. The use of radiolabeled nAChR antagonists would provide a much safer pharmacological profile, avoiding most peripheral side effects that might be generated from radiolabeled nAChR agonists even at the tracer level; thus, PET imaging with nAChR antagonists would facilitate clinical application. A potent and selective nAChR antagonist was labeled and characterized with PET in non-human primates. Its high brain uptake, high signal-to-noise ratio, and high specific binding strongly suggest a great potential to carry out imaging studies in humans. In addition, the use of a C-11 radiotracer would allow us to perform multiple PET studies in the same individual within a short time frame. The presence of an iodine atom in the molecule also allows the possibility to label with radioiodine for SPECT studies.
Asunto(s)
Encéfalo/diagnóstico por imagen , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacocinética , Antagonistas Nicotínicos/farmacocinética , Tomografía de Emisión de Positrones/métodos , Receptores Nicotínicos/efectos de los fármacos , Animales , Unión Competitiva/efectos de los fármacos , Encéfalo/efectos de los fármacos , Compuestos Bicíclicos Heterocíclicos con Puentes/síntesis química , Compuestos Bicíclicos Heterocíclicos con Puentes/química , Radioisótopos de Carbono , Evaluación Preclínica de Medicamentos , Ligandos , Estructura Molecular , Nicotina/farmacocinética , Antagonistas Nicotínicos/síntesis química , Antagonistas Nicotínicos/química , Papio , Relación Estructura-Actividad , Factores de TiempoRESUMEN
Enantioselective synthesis of the poison-frog alkaloids 237D, 207A, and two congeners of 235B' has been achieved. The absolute stereochemistry of 237D was determined to be 5S, 8S, 9R by the present synthesis.
Asunto(s)
Alcaloides/síntesis química , Antagonistas Nicotínicos/síntesis química , Receptores Nicotínicos/fisiología , Alcaloides/aislamiento & purificación , Alcaloides/farmacología , Animales , Anuros , Evaluación Preclínica de Medicamentos/métodos , Antagonistas Nicotínicos/aislamiento & purificación , Antagonistas Nicotínicos/farmacologíaRESUMEN
Philanthotoxin-12 (PhTX-12) is a novel potent and selective, noncompetitive antagonist of nicotinic acetylcholine receptors (nAChRs). Homologues of PhTX-12 with 7-11 methylene groups between the primary amino group and the aromatic head-group were synthesized using solid-phase methodology. In vitro electrophysiological studies of nAChR demonstrated that decreasing the number of methylene groups from 12 to 11 significantly increased potency. Antagonism by PhTX-11, like that of PhTX-12, was only weakly voltage-dependent. When the methylene spacer was reduced further, antagonism was decreased below that of PhTX-12, and in some cases potentiation of ACh responses by up to 60% was observed.
Asunto(s)
Antagonistas Nicotínicos/síntesis química , Antagonistas Nicotínicos/farmacología , Poliaminas , Tirosina/síntesis química , Tirosina/farmacología , Cromatografía Líquida de Alta Presión , Evaluación Preclínica de Medicamentos , Espectrometría de Masas , Antagonistas Nicotínicos/química , Técnicas de Placa-Clamp , Tirosina/análogos & derivados , Tirosina/químicaRESUMEN
In this work we report the synthesis and evaluation of the analgesic properties of new isosteric heterocyclic derivatives, presenting the isoxazole nucleus, designed as nicotinic acetylcholine receptor ligand candidates, analogues to alkaloid epibatidine. Compound 2-(3-methyl-5-isoxazolyl)pyridine (3) presented the best analgesic profile of this series in hot plate test, which was partially prevented by pretreatment with nicotinic receptor antagonist mecamylamine.
Asunto(s)
Analgésicos/química , Analgésicos/farmacología , Isoxazoles/química , Isoxazoles/farmacología , Antagonistas Nicotínicos/química , Antagonistas Nicotínicos/farmacología , Receptores Nicotínicos/metabolismo , Analgésicos/síntesis química , Analgésicos/metabolismo , Animales , Evaluación Preclínica de Medicamentos , Femenino , Isoxazoles/síntesis química , Isoxazoles/metabolismo , Ligandos , Masculino , Ratones , Estructura Molecular , Antagonistas Nicotínicos/síntesis química , Antagonistas Nicotínicos/metabolismo , Relación Estructura-ActividadRESUMEN
The universal template approach to drug design foresees that a polyamine can be modified in such a way to recognize any neurotransmitter receptor. Thus, hybrids of polymethylene tetraamines and philanthotoxins, exemplified by methoctramine (1) and PhTX-343 (2), respectively, were synthesized to produce novel inhibitors of muscular nicotinic acetylcholine receptors. Polyamines 3-25 were synthesized and their biological profiles were evaluated at frog rectus abdominis muscle nicotinic receptors and guinea pig left atria (M(2)) and ileum longitudinal muscle (M(3)) muscarinic acetylcholine receptors. All of the compounds, like prototypes 1 and 2, were noncompetitive antagonists of nicotinic receptors while being, like 1, competitive antagonists at muscarinic M(2) and M(3) receptor subtypes. Interestingly, polyamines bearing a low number of methylenes between the nitrogen atoms, as in 3, 6, and 7, displayed a biological profile similar to that of 2: a noncompetitive antagonism at nicotinic receptors in the 7-25 microM range while not showing any antagonism for muscarinic receptors up to 10 microM. Increasing the number of methylenes separating these nitrogen atoms in methoctramine-related tetraamines resulted in a significant improvement in potency at nicotinic receptors. The most potent tetraamine was 19, bearing a 12 methylene spacer between the nitrogen atoms, which was 12-fold and 250-fold more potent than prototypes 1 and 2, respectively. Tetraamines 9-11, bearing a rather rigid spacer between the nitrogen atoms instead of the very flexible polymethylene chain, displayed a profile similar to that of 1 at nicotinic receptors, whereas a significant decrease in potency was observed at muscarinic M(2) receptors. This finding may have relevance in understanding the mode of interaction with these receptors. Similarly, the constrained analogue 12 of methoctramine showed a decrease in potency at nicotinic and muscarinic M(2) receptors, revealing that the tricyclic system, which incorporates the 2-methoxybenzylamine moiety of 1, does not represent a good pharmacophore for activity at these sites. A most intriguing finding was the observation that the photolabile tetraamine 22 was more potent than methoctramine at nicotinic receptors and, what is more important, it inhibited a closed state of the receptor.
Asunto(s)
Diaminas/química , Atrios Cardíacos/efectos de los fármacos , Músculo Esquelético/efectos de los fármacos , Antagonistas Nicotínicos/farmacología , Poliaminas/farmacología , Animales , Anuros , Diseño de Fármacos , Evaluación Preclínica de Medicamentos , Estimulación Eléctrica , Cobayas , Atrios Cardíacos/metabolismo , Espectroscopía de Resonancia Magnética , Músculo Esquelético/metabolismo , Antagonistas Nicotínicos/síntesis química , Antagonistas Nicotínicos/química , Etiquetas de Fotoafinidad , Poliaminas/síntesis química , Poliaminas/química , Receptores Muscarínicos/clasificación , Receptores Muscarínicos/efectos de los fármacosRESUMEN
Snakes and cone snails produce toxins which block muscular and/or neuronal nicotinic acetylcholine receptors (AChRs). This paper mostly focuses on the determinants by which a snake long chain curaremimetic toxin and the cone snail toxin ImI bind specifically to the alpha 7 neuronal receptor. In both cases, the site involves a small turn-like structure constrained by two half-cystines.