RESUMO
The binding site for DETQ [2-(2,6-dichlorophenyl)-1-((1S,3R)-3-(hydroxymethyl)-5-(2-hydroxypropan-2-yl)-1-methyl-3,4-dihydroisoquinolin-2(1H)-yl)ethan-1-one], a positive allosteric modulator (PAM) of the dopamine D1 receptor, was identified and compared with the binding site for CID 2886111 [N-(6-tert-butyl-3-carbamoyl-4,5,6,7-tetrahydro-1-benzothiophen-2-yl)pyridine-4-carboxamide], a reference D1 PAM. From D1/D5 chimeras, the site responsible for potentiation by DETQ of the increase in cAMP in response to dopamine was narrowed down to the N-terminal intracellular quadrant of the receptor; arginine-130 in intracellular loop 2 (IC2) was then identified as a critical amino acid based on a human/rat species difference. Confirming the importance of IC2, a ß2-adrenergic receptor construct in which the IC2 region was replaced with its D1 counterpart gained the ability to respond to DETQ. A homology model was built from the agonist-state ß2-receptor structure, and DETQ was found to dock to a cleft created by IC2 and adjacent portions of transmembrane helices 3 and 4 (TM3 and TM4). When residues modeled as pointing into the cleft were mutated to alanine, large reductions in the potency of DETQ were found for Val119 and Trp123 (flanking the conserved DRY sequence in TM3), Arg130 (located in IC2), and Leu143 (TM4). The D1/D5 difference was found to reside in Ala139; changing this residue to methionine as in the D5 receptor reduced the potency of DETQ by approximately 1000-fold. None of these mutations affected the activity of CID 2886111, indicating that it binds to a different allosteric site. When combined, DETQ and CID 2886111 elicited a supra-additive response in the absence of dopamine, implying that both PAMs can bind to the D1 receptor simultaneously.
Assuntos
Regulação Alostérica/fisiologia , Sítio Alostérico/fisiologia , Receptores de Dopamina D1/metabolismo , Regulação Alostérica/efeitos dos fármacos , Sítio Alostérico/efeitos dos fármacos , Aminoácidos/metabolismo , Animais , Linhagem Celular , Sequência Conservada/efeitos dos fármacos , Sequência Conservada/fisiologia , Dopamina/metabolismo , Células HEK293 , Humanos , Isoquinolinas/farmacologia , RatosRESUMO
Allosteric potentiators amplify the sensitivity of physiologic control circuits, a mode of action that could provide therapeutic advantages. This hypothesis was tested with the dopamine D1 receptor potentiator DETQ [2-(2,6-dichlorophenyl)-1-((1S,3R)-3-(hydroxymethyl)-5-(2-hydroxypropan-2-yl)-1-methyl-3,4-dihydroisoquinolin-2(1H)-yl)ethan-1-one]. In human embryonic kidney 293 (HEK293) cells expressing the human D1 receptor, DETQ induced a 21-fold leftward shift in the cAMP response to dopamine, with a Kb of 26 nM. The maximum response to DETQ alone was â¼12% of the maximum response to dopamine, suggesting weak allosteric agonist activity. DETQ was â¼30-fold less potent at rat and mouse D1 receptors and was inactive at the human D5 receptor. To enable studies in rodents, an hD1 knock-in mouse was generated. DETQ (3-20 mg/kg orally) caused a robust (â¼10-fold) increase in locomotor activity (LMA) in habituated hD1 mice but was inactive in wild-type mice. The LMA response to DETQ was blocked by the D1 antagonist SCH39166 and was dependent on endogenous dopamine. LMA reached a plateau at higher doses (30-240 mg/kg) even though free brain levels of DETQ continued to increase over the entire dose range. In contrast, the D1 agonists SKF 82958, A-77636, and dihydrexidine showed bell-shaped dose-response curves with a profound reduction in LMA at higher doses; video-tracking confirmed that the reduction in LMA caused by SKF 82958 was due to competing stereotyped behaviors. When dosed daily for 4 days, DETQ continued to elicit an increase in LMA, whereas the D1 agonist A-77636 showed complete tachyphylaxis by day 2. These results confirm that allosteric potentiators may have advantages compared with direct-acting agonists.
Assuntos
Comportamento Animal/efeitos dos fármacos , Técnicas de Introdução de Genes , Isoquinolinas/farmacologia , Locomoção/efeitos dos fármacos , Receptores de Dopamina D1/genética , Receptores de Dopamina D1/metabolismo , Taquifilaxia , Adamantano/análogos & derivados , Adamantano/farmacologia , Regulação Alostérica/efeitos dos fármacos , Animais , Benzopiranos/farmacologia , Relação Dose-Resposta a Droga , Feminino , Células HEK293 , Humanos , Isoquinolinas/efeitos adversos , Masculino , Camundongos , Transporte Proteico/efeitos dos fármacos , Receptores de Dopamina D1/agonistasRESUMO
Preclinical experiments and clinical observations suggest the potential effectiveness of selective 5-HT1F receptor agonists in migraine. Identifying compounds with enhanced selectivity is crucial to assess its therapeutic value. Replacement of the indole nucleus in 2 (LY334370) with a monocyclic phenyl ketone moiety generated potent and more selective 5-HT1F receptor agonists. Focused SAR studies around this central phenyl ring demonstrated that the electrostatic and steric interactions of the substituent with both the amide CONH group and the ketone CO group play pivotal roles in affecting the adopted conformation and thus the 5-HT1F receptor selectivity. Computational studies confirmed the observed results and provide a useful tool in the understanding of the conformational requirements for 5-HT1F receptor agonist activity and selectivity. Through this effort, the 2-F-phenyl and N-2-pyridyl series were also identified as potent and selective 5-HT1F receptor agonists.
Assuntos
Benzamidas/farmacologia , Descoberta de Drogas , Piperidinas/farmacologia , Receptores 5-HT1 de Serotonina/metabolismo , Agonistas do Receptor 5-HT1 de Serotonina/farmacologia , Benzamidas/síntese química , Benzamidas/química , Relação Dose-Resposta a Droga , Humanos , Estrutura Molecular , Piperidinas/síntese química , Piperidinas/química , Teoria Quântica , Agonistas do Receptor 5-HT1 de Serotonina/síntese química , Agonistas do Receptor 5-HT1 de Serotonina/química , Relação Estrutura-AtividadeRESUMO
The in-vitro potency and selectivity, in-vivo binding affinity and effect of the 5-HT(6)R antagonist Lu AE58054 ([2-(6-fluoro-1H-indol-3-yl)-ethyl]-[3-(2,2,3,3-tetrafluoropropoxy)-benzyl]-amine) on impaired cognition were evaluated. Lu AE58054 displayed high affinity to the human 5-HT(6) receptor (5-HT(6)R) with a Ki of 0.83 nm. In a 5-HT(6) GTPgammaS efficacy assay Lu AE58054 showed no agonist activity, but demonstrated potent inhibition of 5-HT-mediated activation. Besides medium affinity to adrenergic alpha(1A)- and alpha(1B)-adrenoreceptors, Lu AE58054 demonstrated >50-fold selectivity for more than 70 targets examined. Orally administered Lu AE58054 potently inhibited striatal in-vivo binding of the 5-HT(6) antagonist radioligand [(3)H]Lu AE60157 ([(3)H]8-(4-methylpiperazin-1-yl)-3-phenylsulfonylquinoline), with an ED(50) of 2.7 mg/kg. Steady-state modelling of an acute pharmacokinetic/5-HT(6)R occupancy time-course experiment indicated a plasma EC(50) value of 20 ng/ml. Administration of Lu AE58054 in a dose range (5-20 mg/kg p.o.) leading to above 65% striatal 5-HT(6)R binding occupancy in vivo, reversed cognitive impairment in a rat novel object recognition task induced after subchronic treatment for 7 d with phencyclidine (PCP 2 mg/kg b.i.d., i.p. for 7 d, followed by 7 d drug free). The results indicate that Lu AE58054 is a selective antagonist of 5-HT(6)Rs with good oral bioavailability and robust efficacy in a rat model of cognitive impairment in schizophrenia. Lu AE58054 may be useful for the pharmacotherapy of cognitive dysfunction in disease states such as schizophrenia and Alzheimer's disease.
Assuntos
Benzilaminas/química , Benzilaminas/uso terapêutico , Transtornos Cognitivos/tratamento farmacológico , Transtornos Cognitivos/metabolismo , Indóis/química , Indóis/uso terapêutico , Fenciclidina/toxicidade , Receptores de Serotonina/metabolismo , Reconhecimento Psicológico/fisiologia , Antagonistas da Serotonina/uso terapêutico , Animais , Benzilaminas/metabolismo , Células Cultivadas , Transtornos Cognitivos/induzido quimicamente , Cricetinae , Relação Dose-Resposta a Droga , Células HEK293 , Humanos , Indóis/metabolismo , Masculino , Fenciclidina/administração & dosagem , Ratos , Ratos Sprague-Dawley , Reconhecimento Psicológico/efeitos dos fármacos , Antagonistas da Serotonina/química , Antagonistas da Serotonina/metabolismoRESUMO
PURPOSE: Cannabinoid subtype 1 (CB(1)) receptors are found in nearly every organ in the body, may be involved in several neuropsychiatric and metabolic disorders, and are therefore an active target for pharmacotherapy and biomarker development. We recently reported brain imaging of CB(1) receptors with two PET radioligands: (11)C-MePPEP and (18)F-FMPEP-d (2). Here we describe the biodistribution and dosimetry estimates for these two radioligands. METHODS: Seven healthy subjects (four men and three women) underwent whole-body PET scans for 120 min after injection with (11)C-MePPEP. Another seven healthy subjects (two men and five women) underwent whole-body PET scans for 300 min after injection with (18)F-FMPEP-d (2). Residence times were acquired from regions of interest drawn on tomographic images of visually identifiable organs for both radioligands and from radioactivity excreted in urine for (18)F-FMPEP-d (2). RESULTS: The effective doses of (11)C-MePPEP and (18)F-FMPEP-d (2) are 4.6 and 19.7 microSv/MBq, respectively. Both radioligands demonstrated high uptake of radioactivity in liver, lung, and brain shortly after injection and accumulated radioactivity in bone marrow towards the end of the scan. After injection of (11)C-MePPEP, radioactivity apparently underwent hepatobiliary excretion only, while radioactivity from (18)F-FMPEP-d (2) showed both hepatobiliary and urinary excretion. CONCLUSION: (11)C-MePPEP and (18)F-FMPEP-d (2) yield an effective dose similar to other PET radioligands labeled with either (11)C or (18)F. The high uptake in brain confirms the utility of these two radioligands to image CB(1) receptors in brain, and both may also be useful to image CB(1) receptors in the periphery.
Assuntos
Agonismo Inverso de Drogas , Tomografia por Emissão de Pósitrons/métodos , Pirrolidinonas/farmacologia , Pirrolidinonas/farmacocinética , Receptor CB1 de Canabinoide/metabolismo , Adulto , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Feminino , Humanos , Masculino , RadiometriaRESUMO
[11C]MePPEP is a high affinity, CB1 receptor-selective, inverse agonist that has been studied in rodents and monkeys. We examined the ability of [11C]MePPEP to quantify CB1 receptors in human brain as distribution volume calculated with the "gold standard" method of compartmental modeling and compared results with the simple measure of brain uptake. A total of 17 healthy subjects participated in 26 positron emission tomography (PET) scans, with 8 having two PET scans to assess retest variability. After injection of [11C]MePPEP, brain uptake of radioactivity was high (e.g., 3.6 SUV in putamen at approximately 60 min) and washed out very slowly. A two-tissue compartment model yielded values of distribution volume (which is proportional to receptor density) that were both well identified (SE 5%) and stable between 60 and 210 min. The simple measure of brain uptake (average concentration of radioactivity between 40 and 80 min) had good retest variability ( approximately 8%) and moderate intersubject variability (16%, coefficient of variation). In contrast, distribution volume had two-fold greater retest variability ( approximately 15%) and, thus, less precision. In addition, distribution volume had three-fold greater intersubject variability ( approximately 52%). The decreased precision of distribution volume compared to brain uptake was likely due to the slow washout of radioactivity from brain and to noise in measurements of the low concentrations of [11C]MePPEP in plasma. These results suggest that brain uptake can be used for within subject studies (e.g., to measure receptor occupancy by medications) but that distribution volume remains the gold standard for accurate measurements between groups.
Assuntos
Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Pirrolidinonas , Receptor CB1 de Canabinoide/agonistas , Receptor CB1 de Canabinoide/metabolismo , Adulto , Simulação por Computador , Feminino , Humanos , Cinética , Imageamento por Ressonância Magnética , Masculino , Modelos Neurológicos , Tomografia por Emissão de Pósitrons , Pirrolidinonas/sangue , Pirrolidinonas/farmacocinética , Reprodutibilidade dos TestesRESUMO
Clinical development of catechol-based orthosteric agonists of the dopamine D1 receptor has thus far been unsuccessful due to multiple challenges. To address these issues, we identified LY3154207 (3) as a novel, potent, and subtype selective human D1 positive allosteric modulator (PAM) with minimal allosteric agonist activity. Conformational studies showed LY3154207 adopts an unusual boat conformation, and a binding pose with the human D1 receptor was proposed based on this observation. In contrast to orthosteric agonists, LY3154207 showed a distinct pharmacological profile without a bell-shaped dose-response relationship or tachyphylaxis in preclinical models. Identification of a crystalline form of free LY3154207 from the discovery lots was not successful. Instead, a novel cocrystal form with superior solubility was discovered and determined to be suitable for development. This cocrystal form was advanced to clinical development as a potential first-in-class D1 PAM and is now in phase 2 studies for Lewy body dementia.
Assuntos
Isoquinolinas/farmacologia , Receptores de Dopamina D1/agonistas , Acetilcolina/metabolismo , Administração Oral , Regulação Alostérica/efeitos dos fármacos , Animais , Sítios de Ligação , Cristalografia por Raios X , AMP Cíclico/metabolismo , Células HEK293 , Meia-Vida , Humanos , Isoquinolinas/química , Isoquinolinas/farmacocinética , Rim/efeitos dos fármacos , Rim/metabolismo , Locomoção/efeitos dos fármacos , Camundongos , Conformação Molecular , Isoformas de Proteínas/agonistas , Isoformas de Proteínas/metabolismo , Ratos , Receptores de Dopamina D1/metabolismo , Bibliotecas de Moléculas Pequenas/química , Bibliotecas de Moléculas Pequenas/metabolismo , Bibliotecas de Moléculas Pequenas/farmacologia , Relação Estrutura-AtividadeRESUMO
The cannabinoid CB(1) receptor is one of the most abundant G protein-coupled receptors in the brain and is a promising target of therapeutic drug development. Success of drug development for neuropsychiatric indications is significantly enhanced with the ability to directly measure spatial and temporal binding of compounds to receptors in central compartments. We assessed the utility of a new positron emission tomography (PET) radioligand to image CB(1) receptors in monkey brain. [(11)C]MePPEP ((3R,5R)-5-(3-methoxy-phenyl)-3-((R)-1-phenyl-ethylamino)-1-(4-trifluoromethyl-phenyl)-pyrrolidin-2-one) has high CB(1) affinity (K(b)=0.574+/-0.207 nM) but also moderately high lipophilicity (measured LogD(7.4)=4.8). After intravenous injection of [(11)C]MePPEP, brain activity reached high levels of almost 600% standardized uptake value (SUV) within 10-20 min. The regional uptake was consistent with the distribution of CB(1) receptors, with high radioactivity in striatum and cerebellum and low in thalamus and pons. Injection of pharmacological doses of CB(1)-selective agents confirmed that the tracer doses of [(11)C]MePPEP reversibly labeled CB(1) receptors. Preblockade or displacement with two CB(1) selective agents (ISPB; (4-(3-cyclopentyl-indole-1-sulfonyl)-N-(tetrahydro-pyran-4-ylmethyl)-benzamide) and rimonabant) showed that the majority (>89%) of brain uptake in regions with high receptor densities was specific and reversibly bound to CB(1) receptors in the high binding regions. [(11)C]MePPEP was rapidly removed from arterial plasma. Regional brain uptake could be quantified as distribution volume relative to the concentration of parent radiotracer in plasma. The P-glycoprotein (P-gp) inhibitor DCPQ ((R)-4-[(1a,6,10b)-1,1-dichloro-1,1a,6,10b-tetrahydrodibenzo[a,e]cyclopropa[c]cyclohepten-6-yl]-[(5-quinolinyloxy)methyl]-1-piperazineethanol) did not significantly increase brain uptake of [(11)C]MePPEP, suggesting it is not a substrate for this efflux transporter at the blood-brain barrier. [(11)C]MePPEP is a radioligand with high brain uptake, high specific signal to CB(1) receptors, and adequately fast washout from brain that allows quantification with (11)C (half-life=20 min). These promising results in monkey justify studying this radioligand in human subjects.
Assuntos
Encéfalo/diagnóstico por imagem , Pirrolidinonas/farmacocinética , Receptor CB1 de Canabinoide/fisiologia , Animais , Transporte Biológico , Encéfalo/metabolismo , Radioisótopos de Carbono , Processamento de Imagem Assistida por Computador , Cinética , Análise dos Mínimos Quadrados , Macaca mulatta , Masculino , Tomografia por Emissão de Pósitrons , Pirrolidinonas/sangue , Radiografia , Ensaio RadioliganteRESUMO
The ability to rapidly assess the preferred conformation of key fragments in a structure "by visual inspection" is a very useful starting point in the process of drug design. With the ability to do so, one could address questions like: "How could we avoid planarity in a molecule?", "Will a molecule change its conformational preference if we make it more or less basic?" or "How does this electronic repulsion affect the conformational preference in the system?" in timely fashion. In this paper, we describe how the conformational energy profile (CEP, plot of energy as a function of dihedral bond angle) of a fragment can be interpreted through the understanding the interplay between resonance stabilization, steric effects and electrostatic interactions. Fifty-nine biaryl and aryl carbonyl fragments present in oral drugs or which are close derivatives thereof were selected. Calculation of their CEPs using ab initio methodology allowed us to conclude the relative importance of these factors in the conformational preference of these fragments as follows: "steric repulsion > lone pair-lone pair repulsion > lone pair-fluorine repulsion > resonance stabilization" and to formulate "rules of thumb" that the practicing medicinal/organic chemist can apply when analysing molecules that contain these fragments.
Assuntos
Desenho de Fármacos , Modelos Moleculares , Software , Eletricidade EstáticaRESUMO
DETQ, an allosteric potentiator of the dopamine D1 receptor, was tested in therapeutic models that were known to respond to D1 agonists. Because of a species difference in affinity for DETQ, all rodent experiments used transgenic mice expressing the human D1 receptor (hD1 mice). When given alone, DETQ reversed the locomotor depression caused by a low dose of reserpine. DETQ also acted synergistically with L-DOPA to reverse the strong hypokinesia seen with a higher dose of reserpine. These results indicate potential as both monotherapy and adjunct treatment in Parkinson's disease. DETQ markedly increased release of both acetylcholine and histamine in the prefrontal cortex, and increased levels of histamine metabolites in the striatum. In the hippocampus, the combination of DETQ and the cholinesterase inhibitor rivastigmine increased ACh to a greater degree than either agent alone. DETQ also increased phosphorylation of the AMPA receptor (GluR1) and the transcription factor CREB in the striatum, consistent with enhanced synaptic plasticity. In the Y-maze, DETQ increased arm entries but (unlike a D1 agonist) did not reduce spontaneous alternation between arms at high doses. DETQ enhanced wakefulness in EEG studies in hD1 mice and decreased immobility in the forced-swim test, a model for antidepressant-like activity. In rhesus monkeys, DETQ increased spontaneous eye-blink rate, a measure that is known to be depressed in Parkinson's disease. Together, these results provide support for potential utility of D1 potentiators in the treatment of several neuropsychiatric disorders, including Parkinson's disease, Alzheimer's disease, cognitive impairment in schizophrenia, and major depressive disorder.
Assuntos
Doenças do Sistema Nervoso/metabolismo , Transtornos Psicóticos/metabolismo , Receptores de Dopamina D1/metabolismo , Animais , Antipsicóticos/uso terapêutico , Piscadela/efeitos dos fármacos , Corpo Estriado/efeitos dos fármacos , Corpo Estriado/metabolismo , Modelos Animais de Doenças , Dopaminérgicos/uso terapêutico , Isoquinolinas/uso terapêutico , Levodopa/uso terapêutico , Macaca mulatta , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Doenças do Sistema Nervoso/tratamento farmacológico , Córtex Pré-Frontal/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , Transtornos Psicóticos/tratamento farmacológico , Receptores de Dopamina D1/genética , Reserpina/uso terapêutico , Sono/efeitos dos fármacos , Vigília/efeitos dos fármacosRESUMO
LY334370 is a high affinity, selective agonist at the 5-HT(1F) receptor. On this basis, the tritiated compound was examined for its utility in autoradiography to localize the 5-HT(1F) receptor in rat and guinea pig brain regions. Specific 5-HT(1F) receptor binding in rat brain was found in layers 4-5 of all cortical regions examined, as well as olfactory bulb and tubercle, nucleus accumbens, caudate putamen, parafascicular nucleus of the thalamus, medial mammillary nucleus, the CA3 region of the hippocampus, subiculum, and several amygdaloid nuclei. In guinea pig brain, the [(3)H]LY334370 binding sites were found at highest density in claustrum, but also in a layer of the cortex, caudate putamen, nucleus accumbens, thalamus, and medial mammillary nucleus. Some species differences in the distribution of the 5-HT(1F) receptor were noted. Side by side comparison of rat brain autoradiography with [(3)H]LY334370 and [(3)H]sumatriptan showed labeling in the same brain regions. Preliminary binding studies in rhesus monkey and human brain sections showed [(3)H]LY334370 binding in cortical layers 4-5, subiculum (in the monkey), and the granule cell layer of the cerebellum. These findings suggest a discrete localization of the 5-HT(1F) receptor in the rat, guinea pig, monkey and human brain, and confirms the utility of [(3)H]LY334370 as a potential tool to explore further the localization and possible functions of the 5-HT(1F) receptor.
Assuntos
Benzamidas/farmacologia , Encéfalo/metabolismo , Indóis/farmacologia , Receptores de Serotonina/análise , Agonistas do Receptor de Serotonina/farmacologia , Animais , Autorradiografia , Encéfalo/efeitos dos fármacos , Cobaias , Humanos , Ligantes , Macaca mulatta , Masculino , Ratos , Ratos Sprague-Dawley , Receptores de Serotonina/efeitos dos fármacos , Especificidade da Espécie , Sumatriptana/farmacologia , Trítio , Receptor 5-HT1F de SerotoninaRESUMO
[(3)H]LY334370 was developed as a radioligand to study the characteristics of this compound's interaction with the 5-HT(1F) receptor. Monovalent or divalent cations did not enhance the binding of [(3)H]LY334370 to the cloned human 5-HT(1F) receptor. In the presence of MgCl(2), the time to reach equilibrium was approximately 2 h, while in its absence equilibrium was reached in less than 1 h. [(3)H]LY334370 had high affinity for the cloned human 5-HT(1F) receptor (K(d)=0.446 nM) and the 5-HT(1F) receptor in rat brain (K(d)=0.388 nM). The expression density of 5-HT(1F) receptors, as determined by binding to homogenates of cortical regions from rat, was low (B(max)=79.1 fmol/mg protein). There was a statistically significant correlation between the apparent pK(i) for inhibition of [(3)H]LY334370 binding and the pEC(50) for stimulation of [(35)S]GTPgammaS binding to homogenates of cells expressing the cloned human 5-HT(1F) receptor. In addition, there was a statistically significant correlation between the apparent pK(i) for inhibition of [(3)H]LY334370 binding to the cloned human 5-HT(1F) receptor and the pID(50) for inhibition of trigeminal nerve stimulated dural plasma protein extravasation in the guinea pig. The conclusion from these studies is that [(3)H]LY334370 is a high affinity radioligand which can be used for the study of the 5-HT(1F) receptor in rat brain or in cells transformed with the human 5-HT(1F) receptor.
Assuntos
Benzamidas/farmacologia , Indóis/farmacologia , Receptores de Serotonina/análise , Agonistas do Receptor de Serotonina/farmacologia , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Células Cultivadas , Guanosina 5'-O-(3-Tiotrifosfato)/farmacologia , Cobaias , Humanos , Técnicas In Vitro , Ligantes , Ensaio Radioligante , Ratos , Receptores de Serotonina/efeitos dos fármacos , Receptores de Serotonina/genética , Transfecção , Trítio , Receptor 5-HT1F de SerotoninaRESUMO
Compound 1a (LY334370), a selective 5-HT(1F) receptor agonist (SSOFRA), inhibited dural inflammation in the neurogenic plasma protein extravasation model of migraine and demonstrated clinical efficacy for the acute treatment of migraine. Although 1a was greater than 100-fold selective over both the 5-HT(1B) and 5-HT(1D) receptors, it exhibited appreciable 5-HT(1A) receptor affinity. Described here is the synthesis and evaluation of a series of pyrrolo[2,3-c]pyridine and pyrrolo[3,2-b]pyridine (2a and 3a) as well as pyrrolo[3,2-d]pyrimidine (4a) analogues of 1a, compounds prepared in an effort to identify SSOFRAs with improved selectivity over other 5-HT(1) receptor subtypes. The pyrrolo[3,2-b]pyridine analogue 3a showed high 5-HT(1F) receptor affinity but offered no improvement in selectivity compared to 1a. However, the C-5 acetamide derivative, 3b, was greater than 100-fold selective over the 5-HT(1A), 5-HT(1B), and 5-HT(1D) receptors. SAR studies of this series determined that alkylamides in particular exhibited high selectivity for the 5-HT(1F) receptor. Replacement at C-5 with other substituents decreased affinity or selectivity. These SAR studies identified SSOFRAs that demonstrated oral activity in the neurogenic plasma protein extravasation model, a model indicative of antimigraine activity.
Assuntos
Compostos Bicíclicos Heterocíclicos com Pontes/síntese química , Piperidinas/síntese química , Piridinas/síntese química , Pirróis/síntese química , Receptores de Serotonina/efeitos dos fármacos , Agonistas do Receptor de Serotonina/síntese química , Administração Oral , Animais , Proteínas Sanguíneas/metabolismo , Compostos Bicíclicos Heterocíclicos com Pontes/química , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Linhagem Celular , Técnicas In Vitro , Transtornos de Enxaqueca/tratamento farmacológico , Transtornos de Enxaqueca/metabolismo , Piperidinas/química , Piperidinas/farmacologia , Alcamidas Poli-Insaturadas , Piridinas/química , Piridinas/farmacologia , Pirróis/química , Pirróis/farmacologia , Coelhos , Ensaio Radioligante , Veia Safena/efeitos dos fármacos , Veia Safena/fisiologia , Agonistas do Receptor de Serotonina/química , Agonistas do Receptor de Serotonina/farmacologia , Relação Estrutura-Atividade , Nervo Trigêmeo/metabolismo , Vasoconstrição/efeitos dos fármacos , Receptor 5-HT1F de SerotoninaRESUMO
In the present study, the role of 5-HT(1A) receptors in control of lower urinary tract function in cats was examined using 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and 5-methoxy-N,N-dimethyltryptamine (5-MeODMT) as agonists and WAY100635 and LY206130 as antagonists. Bladder function was assessed using cystometric infusion of saline or 0.5% acetic acid to produce bladder irritation. External urethral sphincter (EUS) function was assessed using electromyographic (EMG) recordings of activity recorded during cystometry or by recording electrically evoked pudendal reflexes. Both 5-HT(1A) receptor agonists caused dose-dependent decreases in bladder activity and increases in EUS EMG activity under conditions of acetic acid infusion. 5-HT(1A) receptor antagonists reversed both the bladder-inhibitory and sphincter-facilitatory effects. Thus, 5-HT(1A) receptor activation can have opposite effects on nociceptive afferent processing depending upon the efferent response being measured. During saline infusion of the bladder, 8-OH-DPAT produced moderate inhibition of bladder activity and had no significant effect on sphincter electromyographic (EMG) activity. 8-OH-DPAT either had no effect, or inhibited, low-threshold electrically evoked pudendal reflexes. These findings indicate that 5-HT(1A) receptor stimulation is inhibitory to bladder function in cats, especially under conditions where the bladder is hyperactive due to irritation. Furthermore, these bladder-inhibitory effects are the exact opposite of the bladder-excitatory effects of 8-OH-DPAT reported in rats. 5-HT(1A) receptor stimulation increases EUS motoneuron activity when driven by nociceptive bladder afferent inputs but not when driven by non-nociceptive afferent inputs. In summary, 5-HT(1A) receptor agonists facilitate a nociceptor-driven spinal reflex (sphincter activity) but inhibit a nociceptor-driven supraspinal reflex (micturition). This pattern of activity would facilitate urine storage and may be important under 'fight-or-flight' conditions when serotonergic activity is high.
Assuntos
Receptores de Serotonina/efeitos dos fármacos , Sistema Urinário/efeitos dos fármacos , 8-Hidroxi-2-(di-n-propilamino)tetralina/farmacologia , Ácido Acético , Animais , Gatos , Cistite/fisiopatologia , Relação Dose-Resposta a Droga , Estimulação Elétrica , Eletromiografia , Feminino , Contração Muscular/fisiologia , Músculo Liso/efeitos dos fármacos , Músculo Liso/inervação , Piperazinas/farmacologia , Piridinas/farmacologia , Receptores 5-HT1 de Serotonina , Antagonistas da Serotonina/farmacologia , Agonistas do Receptor de Serotonina/farmacologia , Uretra/efeitos dos fármacos , Uretra/inervação , Uretra/fisiologia , Bexiga Urinária/efeitos dos fármacos , Bexiga Urinária/inervação , Bexiga Urinária/fisiologia , Sistema Urinário/inervaçãoRESUMO
MePPEP ((3R,5R)-5-(3-methoxy-phenyl)-3-((R)-1-phenyl-ethylamino)-1-(4-trifluoromethyl-phenyl)-pyrrolidin-2-one) is an inverse agonist shown to be an effective PET ligand for labeling cannabinoid CB1 receptors in vivo. [¹¹C]MePPEP and structurally related analogs have been reported to specifically and reversibly label cannabinoid CB1 receptors in rat and non-human primate brains, and [¹¹C]MePPEP has been used in human subjects as a PET tracer. We have generated [³H]MePPEP, an ortholog of [¹¹C]MePPEP, to characterize the molecular pharmacology of the cannabinoid CB1 receptor across preclinical and clinical species. [³H]MePPEP demonstrates saturable, reversible, and single-site high affinity binding to cannabinoid CB1 receptors. In cerebellar membranes purified from brains of rat, non-human primate and human, and cells ectopically expressing recombinant human cannabinoid CB1 receptor, [³H]MePPEP binds cannabinoid CB1 receptors with similar affinity with K(d) values of 0.09 nM, 0.19 nM, 0.14 nM and 0.16 nM, respectively. Both agonist and antagonist cannabinoid ligands compete [³H]MePPEP with predicted rank order potency. No specific binding is present in autoradiographic sections from cannabinoid CB1 receptor knockout mouse brains, demonstrating that [³H]MePPEP selectively binds cannabinoid CB1 receptors in native mouse tissue. Furthermore, [³H]MePPEP binding to anatomical sites in mouse and rat brain is comparable to the anatomical profiles of [¹¹C]MePPEP in non-human primate and human brain in vivo, as well as the binding profiles of other previously described cannabinoid CB1 receptor agonist and antagonist radioligands. Therefore, [³H]MePPEP is a promising tool for translation of preclinical cannabinoid CB1 receptor pharmacology to clinical PET ligand and cannabinoid CB1 receptor inverse agonist therapeutic development.
Assuntos
Canabinoides/agonistas , Proteínas do Tecido Nervoso/metabolismo , Pirrolidinonas/metabolismo , Receptor CB1 de Canabinoide/metabolismo , Animais , Ligação Competitiva , Canabinoides/antagonistas & inibidores , Cerebelo/anatomia & histologia , Cerebelo/metabolismo , Agonismo Inverso de Drogas , Humanos , Ligantes , Macaca mulatta , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Neurônios/metabolismo , Tomografia por Emissão de Pósitrons/métodos , Pirrolidinonas/farmacocinética , Traçadores Radioativos , Ratos , Receptor CB1 de Canabinoide/genética , Proteínas Recombinantes/metabolismo , Distribuição Tecidual , TrítioRESUMO
UNLABELLED: We recently demonstrated that (11)C-MePPEP, a PET ligand for CB(1) receptors, has such high uptake in the human brain that it can be imaged for 210 min and that receptor density can be quantified as distribution volume (V(T)) using the gold standard of compartmental modeling. However, (11)C-MePPEP had relatively poor retest and intersubject variabilities, which were likely caused by errors in the measurements of radioligand in plasma at low concentrations by 120 min. We sought to find an analog of (11)C-MePPEP that would provide more accurate plasma measurements. We evaluated several promising analogs in the monkey brain and chose the (18)F-di-deutero fluoromethoxy analog ((18)F-FMPEP-d(2)) to evaluate further in the human brain. METHODS: (11)C-FMePPEP, (18)F-FEPEP, (18)F-FMPEP, and (18)F-FMPEP-d(2) were studied in 5 monkeys with 10 PET scans. We calculated V(T) using compartmental modeling with serial measurements of unchanged parent radioligand in arterial plasma and radioactivity in the brain. Nonspecific binding was determined by administering a receptor-saturating dose of rimonabant, an inverse agonist at the CB(1) receptor. Nine healthy human subjects participated in 17 PET scans using (18)F-FMPEP-d(2), with 8 subjects having 2 PET scans to assess retest variability. To identify sources of error, we compared intersubject and retest variability of brain uptake, arterial plasma measurements, and V(T). RESULTS: (18)F-FMPEP-d(2) had high uptake in the monkey brain, with greater than 80% specific binding, and yielded less radioactivity uptake in bone than did (18)F-FMPEP. High brain uptake with (18)F-FMPEP-d(2) was also observed in humans, in whom V(T) was well identified within approximately 60 min. Retest variability of plasma measurements was good (16%); consequently, V(T) had a good retest variability (14%), intersubject variability (26%), and intraclass correlation coefficient (0.89). V(T) increased after 120 min, suggesting an accumulation of radiometabolites in the brain. Radioactivity accumulated in the skull throughout the entire scan but was thought to be an insignificant source of data contamination. CONCLUSION: Studies in monkeys facilitated our development and selection of (18)F-FMPEP-d(2), compared with (18)F-FMPEP, as a radioligand demonstrating high brain uptake, high percentage of specific binding, and reduced uptake in bone. Retest analysis in human subjects showed that (18)F-FMPEP-d(2) has greater precision and accuracy than (11)C-MePPEP, allowing smaller sample sizes to detect a significant difference between groups.
Assuntos
Encéfalo/diagnóstico por imagem , Fluordesoxiglucose F18 , Pirrolidinonas , Compostos Radiofarmacêuticos , Receptor CB1 de Canabinoide/agonistas , Receptor CB1 de Canabinoide/metabolismo , Adulto , Animais , Área Sob a Curva , Química Encefálica , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Marcação por Isótopo , Macaca mulatta , Masculino , Plasma/diagnóstico por imagem , Cintilografia , Compostos Radiofarmacêuticos/síntese química , Crânio/diagnóstico por imagem , Adulto JovemRESUMO
[11C]MePPEP is an inverse agonist and a radioligand developed to image cannabinoid CB1 receptors with positron emission tomography (PET). It provides reversible, high specific signal in monkey brain. We assessed [11C]MePPEP in rodent brain with regard to receptor selectivity, susceptibility to transport by P-glycoprotein (P-gp), sensitivity to displacement by agonists, and accumulation of radiometabolites. We used CB1 receptor knockout mice and P-gp knockout mice to assess receptor selectivity and sensitivity to efflux transport, respectively. Using serial measurements of PET brain activity and plasma concentrations of [11C]MePPEP, we estimated CB1 receptor density in rat brain as distribution volume. CB1 knockout mice showed only nonspecific brain uptake, and [11C]MePPEP was not a substrate for P-gp. Direct acting agonists anandamide (10 mg/kg), methanandamide (10 mg/kg), CP 55,940 (1 mg/kg), and indirect agonist URB597 (0.3 and 0.6 mg/kg) failed to displace [11C]MePPEP, while the inverse agonist rimonabant (3 and 10 mg/kg) displaced >65% of [11C]MePPEP. Radiometabolites represented ~13% of total radioactivity in brain between 30 and 120 min. [11C]MePPEP was selective for the CB1 receptor, was not a substrate for P-gp, and was more potently displaced by inverse agonists than agonists. The low potency of agonists suggests either a large receptor reserve or non-overlapping binding sites for agonists and inverse agonists. Radiometabolites of [11C]MePPEP in brain caused distribution volume to be overestimated by approximately 13%.
Assuntos
Química Encefálica , Tomografia por Emissão de Pósitrons , Pirrolidinonas/farmacocinética , Compostos Radiofarmacêuticos/farmacocinética , Receptor CB1 de Canabinoide/análise , Animais , Ácidos Araquidônicos/farmacologia , Ligação Competitiva , Moduladores de Receptores de Canabinoides/farmacologia , Radioisótopos de Carbono/farmacocinética , Endocanabinoides , Masculino , Espectrometria de Massas , Camundongos , Alcamidas Poli-Insaturadas/farmacologia , Ratos , Ratos Sprague-DawleyRESUMO
We have reported that [methyl- (11)C] (3 R,5 R)-5-(3-methoxyphenyl)-3-[(R)-1-phenylethylamino]-1-(4-trifluoromethylphenyl)pyrrolidin-2-one ([(11)C] 8, [(11)C]MePPEP) binds with high selectivity to cannabinoid type-1 (CB 1) receptors in monkey brain in vivo. We now describe the synthesis of 8 and four analogues, namely, the 4-fluorophenyl (16, FMePPEP), 3-fluoromethoxy (20, FMPEP), 3-fluoromethoxy- d 2 (21, FMPEP- d 2), and 3-fluoroethoxy analogues (22, FEPEP), and report their activity in an ex vivo model designed to identify compounds suitable for use as positron emission tomography (PET) ligands. These ligands exhibited high, selective potency at CB 1 receptors in vitro (K b < 1 nM). Each ligand (30 microg/kg, iv) was injected into rats under baseline and pretreatment conditions (3, rimonabant, 10 mg/kg, iv) and quantified at later times in frontal cortex ex vivo with liquid chromatography-mass spectrometry (LC-MS) detection. Maximal ligand uptakes were high (22.6-48.0 ng/g). Under pretreatment, maximal brain uptakes were greatly reduced (6.5-17.3 ng/g). Since each ligand readily entered brain and bound with high selectivity to CB 1 receptors, we then established and here describe methods for producing [(11)C] 8, [(11)C] 16, and [(18)F] 20- 22 in adequate activities for evaluation as candidate PET radioligands in vivo.
Assuntos
Pirrolidinonas/síntese química , Pirrolidinonas/metabolismo , Receptor CB1 de Canabinoide/metabolismo , Animais , Cromatografia Líquida , Ligantes , Espectroscopia de Ressonância Magnética , Tomografia por Emissão de Pósitrons , Pirrolidinonas/farmacologia , Ratos , Espectrometria de Massas por Ionização por ElectrosprayRESUMO
Analogues of pindolol, 1-(1H-indol-4-yloxy)-3-isopropylamino-propan-2-ol, were synthesized and evaluated as 5-HT(1A) receptor antagonists. The structural features required for optimal binding to the 5-HT1A receptor are as follows: S-2-propanol linker, 4-indoloxy substituent, and a large lipophilic cyclic amine substituent.
Assuntos
Indóis/química , Propanolaminas/química , Propanolaminas/farmacologia , Receptor 5-HT1A de Serotonina/metabolismo , Antagonistas do Receptor 5-HT1 de Serotonina , Animais , Corticosterona/sangue , Hidroxilação , Isomerismo , Masculino , Estrutura Molecular , Oxirredução , Propanolaminas/síntese química , Ratos , Ratos Sprague-Dawley , Relação Estrutura-AtividadeRESUMO
: 1. The mechanism of anandamide uptake and disposal has been an issue of considerable debate in the cannabinoid field. Several compounds have been reported to inhibit anandamide uptake or fatty acid amide hydrolase (FAAH; the primary catabolic enzyme of anandamide) activity with varying degrees of potency and selectivity. We recently reported the first evidence of a binding site involved in the uptake of endocannabinoids that is independent from FAAH. There are no direct comparisons of purported selective inhibitory compounds in common assay conditions measuring anandamide uptake, FAAH activity and binding activity. 2. A subset of compounds reported in the literature were tested in our laboratory under common assay conditions to measure their ability to (a) inhibit [(14)C]-anandamide uptake in cells containing (RBL-2H3) or cells lacking (HeLa) FAAH, (b) inhibit purified FAAH hydrolytic activity, and (c) inhibit binding to a putative binding site involved in endocannabinoid transport in both RBL and HeLa cell membranes. 3. Under these conditions, nearly all compounds tested inhibited (a) uptake of [(14)C]-anandamide, (b) enzyme activity in purified FAAH preparations, and (c) radioligand binding of [(3)H]-LY2183240 in RBL and HeLa plasma membrane preparations. General rank order potency was preserved within the three assays. However, concentration response curves were right-shifted for functional [(14)C]-anandamide uptake in HeLa (FAAH(-/-)) cells. 4. A more direct comparison of multiple inhibitors could be made in these three assay systems performed in the same laboratory, revealing more information about the selectivity of these compounds and the relationship between the putative endocannabinoid transport protein and FAAH. At least two separate proteins appear to be involved in uptake and degradation of anandamide. The most potent inhibitory compounds were right-shifted when transport was measured in HeLa (FAAH(-/-)) cells suggesting a requirement for a direct interaction with the FAAH protein to maintain high affinity binding of anandamide or inhibitors to the putative anandamide transport protein.