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AIMS: Cerebral hypometabolism occurs years prior to a diagnosis of neurodegenerative diseases and coincides with reduced cerebral perfusion and declining noradrenergic transmission from the locus coeruleus. In pre-clinical models, ß-adrenoceptor (ß-AR) agonists increase cerebrocortical glucose metabolism, and may have therapeutic potential for neurodegenerative diseases. This study investigated the safety and effects on regional cerebral blood flow (rCBF) of the oral, brain-penetrant ß2-AR agonist, clenbuterol, in healthy volunteers (HV) and patients with mild cognitive impairment (MCI) or Parkinson's disease (PD). METHODS: This study evaluated the safety and effects on cerebral activity of the oral, brain-penetrant, ß2-AR agonist clenbuterol (20-160 µg) in healthy volunteers and patients with MCI or PD. Regional CBF, which is tightly coupled to glucose metabolism, was measured by arterial spin labelling MRI in 32 subjects (25 HV and 8 MCI or PD) across five cohorts. In some cohorts, low doses of nadolol (1-5 mg), a ß-AR antagonist with minimal brain penetration, were administered with clenbuterol to control peripheral ß2-AR responses. RESULTS: Significant, dose-dependent increases in rCBF were seen in multiple brain regions, including hippocampus, amygdala and thalamus, following the administration of clenbuterol to HVs (mean changes from baseline in hippocampal rCBF of -1.7%, 7.3%, 22.9%, 28.4% 3 h after 20, 40, 80 and 160 µg clenbuterol, respectively). In patients with MCI or PD, increases in rCBF following 80 µg clenbuterol were observed both without and with 5 mg nadolol (in hippocampus, 18.6%/13.7% without/with nadolol). Clenbuterol was safe and well-tolerated in all subjects; known side effects of ß2-agonists, including increased heart rate and tremor, were mild in intensity and were blocked by low-dose nadolol. CONCLUSIONS: The effects of clenbuterol on rCBF were evident both in the absence and presence of low-dose nadolol, suggesting central nervous system (CNS) involvement. Concomitant inhibition of the peripheral effects of clenbuterol by nadolol confirms that meaningful ß2-AR antagonism in the periphery was achieved without interrupting the central effects of clenbuterol on rCBF.
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Adrenoceptors (ARs) throughout the brain are stimulated by noradrenaline originating mostly from neurons of the locus coeruleus, a brainstem nucleus that is ostensibly the earliest to show detectable pathology in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. The α1-AR, α2-AR, and ß-AR subtypes expressed in target brain regions and on a range of cell populations define the physiological responses to noradrenaline, which includes activation of cognitive function in addition to modulation of neurometabolism, cerebral blood flow, and neuroinflammation. As these heterocellular functions are critical for maintaining brain homeostasis and neuronal health, combating the loss of noradrenergic tone from locus coeruleus degeneration may therefore be an effective treatment for both cognitive symptoms and disease modification in neurodegenerative indications. Two pharmacologic approaches are receiving attention in recent clinical studies: preserving noradrenaline levels (e.g., via reuptake inhibition) and direct activation of target adrenoceptors. Here, we review the expression and role of adrenoceptors in the brain, the preclinical studies which demonstrate that adrenergic stimulation can support cognitive function and cerebral health by reversing the effects of noradrenaline depletion, and the human data provided by pharmacoepidemiologic analyses and clinical trials which together identify adrenoceptors as promising targets for the treatment of neurodegenerative disease.
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BACKGROUND: Targeted inhibitors of B-cell activating factor (BAFF) have been evaluated in phase III trials in over 4000 patients with systemic lupus erythematosus (SLE). Post hoc analyses of these studies identify greater treatment effect in patients entering with higher disease activity, greater corticosteroid doses, anti double-stranded DNA (dsDNA) and low complement C3 or C4. OBJECTIVES: To evaluate the efficacy and safety of blisibimod, a BAFF inhibitor, in a population of patients with SLE enriched for high disease activity. METHODS: 442 patients with SLE with antinuclear antibodies or anti-dsDNA and Safety of Estrogen in Lupus Erythematosus National Assessment - Systemic Lupus Erythematosus Disease Activity Index (SELENA-SLEDAI) score ≥10 on standard-of-care medications were randomised to receive weekly subcutaneous blisibimod (200 mg) or placebo. Corticosteroid taper was encouraged from week 8. The primary end point was the week 52 SLE Responder Index-6 (SRI-6). RESULTS: The SRI-6 primary end point was not met. There was a statistically significant steroid-sparing effect, and significantly more blisibimod-treated subjects achieved corticosteroid taper. Increased blisibimod treatment effect on SRI-6 was observed in subjects who achieved a concomitant decrease in corticosteroid dose from baseline. In subjects with baseline urinary protein:creatinine ratio (UPCR) ≥56.5 mg/mmol, significantly higher proportions of blisibimod subjects achieved >50% reduction in UPCR and/or UPCR <56.5 mg/mmol. Reductions in SLE autoantibodies and B cells, and increases in complement C3 and C4 were observed with blisibimod.Blisibimod was well-tolerated. The most common adverse events were upper respiratory tract infection, urinary tract infection, injection site erythema/reaction and diarrhoea. CONCLUSIONS: Although the SRI-6 end point was not met, blisibimod was associated with successful steroid reduction, decreased proteinuria and biomarker responses. TRIAL REGISTRATION NUMBER: NCT01395745.
Assuntos
Fator Ativador de Células B/antagonistas & inibidores , Fatores Imunológicos/uso terapêutico , Lúpus Eritematoso Sistêmico/tratamento farmacológico , Proteínas Recombinantes de Fusão/uso terapêutico , Adulto , Anticorpos Antinucleares/sangue , Linfócitos B/imunologia , Biomarcadores/sangue , Método Duplo-Cego , Esquema de Medicação , Quimioterapia Combinada , Feminino , Glucocorticoides/administração & dosagem , Glucocorticoides/uso terapêutico , Humanos , Fatores Imunológicos/administração & dosagem , Fatores Imunológicos/efeitos adversos , Injeções Subcutâneas , Lúpus Eritematoso Sistêmico/imunologia , Contagem de Linfócitos , Masculino , Pessoa de Meia-Idade , Prednisona/administração & dosagem , Prednisona/uso terapêutico , Qualidade de Vida , Proteínas Recombinantes de Fusão/administração & dosagem , Proteínas Recombinantes de Fusão/efeitos adversos , Índice de Gravidade de Doença , Resultado do Tratamento , Adulto JovemRESUMO
Background: Noradrenergic signaling declines in Parkinson's disease (PD) following locus coeruleus neurodegeneration. Epidemiologic studies demonstrate that ß-acting drugs slow PD progression. Objective: The primary objective was to compare the safety and effects of 3 ß-adrenoceptor (ß-AR) acting drugs on central nervous system (CNS) function after a single dose in healthy volunteers (HVs) and evaluate the effects of multiple doses of ß-AR acting drugs in HVs and PD-patients. Methods: In Part A, HVs received single doses of 32âmg salbutamol, 160µg clenbuterol, 60âmg pindolol and placebo administered in a randomized, 4-way cross-over study. In Part B (randomized cross-over) and Part C (parallel, 2:1 randomized), placebo and/or clenbuterol (20µg on Day 1, 40µg on Day 2, 80µg on Days 3-7) were administered. CNS functions were assessed using the NeuroCart test battery, including pupillometry, adaptive tracking and recall tests. Results: Twenty-seven HVs and 12 PD-patients completed the study. Clenbuterol improved and pindolol reduced the adaptive tracking and immediate verbal recall performance. Clenbuterol and salbutamol increased and pindolol decreased pupil-to-iris ratios. Clenbuterol was selected for Parts B and C. In Part B, clenbuterol significantly increased performance in adaptive tracking with a tendency toward improved performance in immediate and delayed verbal recall. In Part C trends toward improved performance in immediate and delayed verbal recall were observed in PD-patients. Typical cardiovascular peripheral ß2-AR effects were observed with clenbuterol. Conclusions: This study demonstrates the pro-cognitive effects of clenbuterol in HVs with similar trends in PD-patients. The mechanism of action is likely activation of ß2-ARs in the CNS.
Aims and Purpose of the Research:This research aimed to explore how three different drugs affect brain function. These drugs are salbutamol, clenbuterol, and pindolol and work in the brain by stimulating specific brain cells that can improve aspects like memory and coordination. The main question was to see how safe these drugs were and how they impact the brain function after one dose in healthy people, and after multiple doses in both healthy people and those with Parkinson's disease.Background of the Research:Parkinson's disease is a condition where brain cells start to die, which affects different areas of the brain, including movement function, as well as memory and attention. This research matters because finding drugs that affect the brain function could improve the lives of people with Parkinson's disease.Methods and Research Design:The study was conducted in three parts. In the first part, healthy volunteers took one dose of each of the three drugs salbutamol, clenbuterol, and pindolol as well as a placebo (a harmless pill that has no effect). The researchers tested the participants' brain functions using various tasks including memory tests and eye response measurements. In the second and third part, healthy people and people with Parkinson's disease took the drug that performed best in healthy volunteers for seven days.Results and Importance:In the first part, a single dose of clenbuterol was safe and improved memory and attentions tasks in healthy people, and therefore was chosen for further testing in the second and third part. In these parts, multiple doses of clenbuterol were safe and helped improve memory and attention tasks in healthy people, with similar positive trends seen in people with Parkinson's disease. The study suggests that clenbuterol might help improve brain function by activating specific receptors in the brain.These results are important because they suggest that clenbuterol could be a potential treatment to help improve brain function in people with Parkinson's disease. However, more research is needed to fully understand its effects and to confirm these findings.
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Albuterol , Clembuterol , Estudos Cross-Over , Doença de Parkinson , Pindolol , Humanos , Doença de Parkinson/tratamento farmacológico , Doença de Parkinson/metabolismo , Masculino , Feminino , Pessoa de Meia-Idade , Clembuterol/farmacologia , Clembuterol/administração & dosagem , Clembuterol/efeitos adversos , Idoso , Adulto , Pindolol/farmacologia , Pindolol/administração & dosagem , Albuterol/farmacologia , Albuterol/administração & dosagem , Agonistas Adrenérgicos beta/farmacologia , Agonistas Adrenérgicos beta/administração & dosagem , Voluntários SaudáveisRESUMO
A series of 5-HT(6) ligands derived from (R)-1-(amino)methyl-6-(phenyl)sulfonyltetralin was prepared that yielded several non-basic analogs having sub-nanomolar affinity. Ligand structure-activity relationships, receptor point mutation studies, and molecular modeling of these novel ligands all combined to reveal a new alternative binding mode to 5-HT(6) for antagonism.
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Receptores de Serotonina/metabolismo , Ligantes , Modelos Moleculares , Mutagênese Sítio-Dirigida , Relação Estrutura-AtividadeRESUMO
Although several antidepressants (including fluoxetine, imipramine, citalopram, venlafaxine, and duloxetine) are known to inhibit the serotonin transporter (SERT), whether or not these molecules compete with 5-hydroxytryptamine (serotonin) (5-HT) for binding to SERT has remained controversial. We have performed radioligand competition binding experiments and found that all data can be fitted via a simple competitive interaction model, using Cheng-Prusoff analysis (Biochem Pharmacol 22:3099-3108, 1973). Two different SERT-selective radioligands, [(3)H]N,N-dimethyl-2-(2-amino-4-cyanophenyl thio)-benzylamine (DASB) and [(3)H]S-citalopram, were used to probe competitive binding to recombinantly expressed human SERT or native SERT in rat cortical membranes. All the SERT inhibitors that we tested were able to inhibit [(3)H]DASB and [(3)H]S-citalopram binding in a concentration-dependent manner, with unity Hill coefficient. In accordance with the Cheng-Prusoff relationship for a competitive interaction, we observed that test compound concentrations associated with 50% maximal inhibition of radiotracer binding (IC(50)) increased linearly with increasing radioligand concentration for all ligands: 5-HT, S-citalopram, R-citalopram, paroxetine, clomipramine, fluvoxamine, imipramine venlafaxine, duloxetine, indatraline, cocaine, and 2-beta-carboxy-3-beta-(4-iodophenyl)tropane. The equilibrium dissociation constant of 5-HT and SERT inhibitors were also derived using Scatchard analysis of the data set, and they were found to be comparable with the data obtained using the Cheng-Prusoff relationship. Our studies establish a reference framework that will contribute to ongoing efforts to understand ligand binding modes at SERT by demonstrating that 5-HT and the SERT inhibitors tested bind to the serotonin transporter in a competitive manner.
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Antidepressivos/farmacologia , Proteínas da Membrana Plasmática de Transporte de Serotonina/efeitos dos fármacos , Animais , Antidepressivos/farmacocinética , Ligação Competitiva , Membrana Celular , Córtex Cerebral , Humanos , Ensaio Radioligante , Ratos , Serotonina/metabolismo , Inibidores Seletivos de Recaptação de Serotonina/farmacologiaRESUMO
Several serotonin reuptake inhibitors are in clinical use for treatment of depression and anxiety disorders. However, to date, reported pharmacological differentiation of these ligands has focused mainly on their equilibrium binding affinities for the serotonin transporter. This study takes a new look at antidepressant binding modes using radioligand binding assays with [(3)H]S-citalopram to determine equilibrium and kinetic rate constants across multiple temperatures. The observed dissociation rate constants at 26 degrees C fall into a narrow range for all molecules. Conversely, association rate constants generally decreased with increasing equilibrium binding affinities. Consistent with this, the measured activation energy for S-citalopram association was relatively large (19.5 kcal . mol(-1)), suggesting conformational change upon ligand binding. For most of the drugs, including citalopram, the enthalpy (DeltaH(O)) and entropy (-TDeltaS(O)) contributions to reaction energetics were determined by van't Hoff analyses to be roughly equivalent (25-75% DeltaG(O)) and to correlate (positively for enthalpy) with the polar surface area of the drug. However, the binding of the drug fluvoxamine was predominantly entropically driven. When these data are considered in the context of the physicochemical properties of these ligands, two distinct binding modes can be proposed. The citalopram-type binding mode probably uses a polar binding pocket that allows charged or polar interactions between ligand and receptor with comparatively small loss in enthalpy due to dehydration. The fluvoxamine-type binding mode is fueled by energy released upon burying hydrophobic ligand moieties into a binding pocket that is flexible enough to suffer minimal loss in entropy from conformational constraint.
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Inibidores Seletivos de Recaptação de Serotonina/farmacocinética , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Antidepressivos/farmacocinética , Citalopram , Entropia , Fluvoxamina , Humanos , Interações Hidrofóbicas e Hidrofílicas , Cinética , Ligação Proteica , Ensaio Radioligante , Proteínas da Membrana Plasmática de Transporte de Serotonina/química , Eletricidade Estática , Temperatura , TermodinâmicaRESUMO
INTRODUCTION: Blisibimod is a potent and selective inhibitor of B cell activating factor (BAFF), a mediator of differentiation, maturation and survival of B cells. It has a unique tetravalent, 'peptibody' structure and resulting high potency, and is currently in clinical evaluation for the treatment of SLE. The importance of BAFF in the pathogenesis of systemic lupus erythematosus (SLE) is under intense investigation. The anti BAFF monoclonal antibody belimumab was approved by the FDA for the treatment of SLE. AREAS COVERED: The general properties of blisibimod are reviewed including pharmacokinetic and pharmacodynamic properties in patients with SLE, efficacy and safety in the phase 2 PEARL-SC and open-label extension trials, and the focus in the ongoing phase 3 trial (CHABLIS-SC1) on the hypothesized 'responder' population. In addition, the rationale for evaluating blisibimod in patients with IgA nephropathy, a common nephritic disease for which there is no approved therapy, is presented. EXPERT OPINION: Blisibimod's unique tetravalent, peptibody structure and resulting high potency, and the deliberate focus of the Phase 3 clinical development program on the 'responder populations' identified in completed trials in SLE raise the possibility that blisibimod will become an important medication for treatment of SLE and IgA nephropathy.
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Lúpus Eritematoso Sistêmico/tratamento farmacológico , Proteínas Recombinantes de Fusão/uso terapêutico , Fator Ativador de Células B/antagonistas & inibidores , Ensaios Clínicos como Assunto , Glomerulonefrite por IGA/tratamento farmacológico , Humanos , Proteínas Recombinantes de Fusão/farmacocinética , Proteínas Recombinantes de Fusão/farmacologiaRESUMO
The pharmacology of G protein-coupled receptors is widely accepted to depend on the G protein subunit to which the agonist-stimulated receptor couples. In order to investigate whether CB(1) agonist-mediated signal transduction via an engineered G(alpha 16) system is different than that of the G(i/o) coupling normally preferred by the CB(1) receptor, we transfected the human recombinant CB(1) receptor (hCB(1)) or a fusion protein comprising the hCB(1) receptor and G(alpha 16) (hCB(1)-G(alpha 16)) into HEK293 cells. From competition binding studies, the rank order of ligand affinities at the hCB(1)-G(alpha 16) fusion protein was found to be similar to that for hCB(1): HU 210 > CP 55,940 > or = SR 141716A > WIN 55212-2 > anandamide > JWH 015. Agonists increased [(35)S]GTP gamma S binding or inhibited forskolin-stimulated cAMP, presumably by coupling to G(i/o), in cells expressing hCB(1) but not hCB(1)-G(alpha 16). However, an analogous rank order of potencies was observed for these agonists in their ability to evoke increases in intracellular calcium concentration in cells expressing hCB(1)-G(alpha 16) but not hCB(1). These data demonstrate that ligand affinities for the hCB(1) receptor are not affected by fusion to the G(alpha 16) subunit. Furthermore, there is essentially no difference in the function of the hCB(1) receptor when coupled to G(i/o) or G (alpha 16).
Assuntos
Proteínas Heterotriméricas de Ligação ao GTP/farmacologia , Receptores de Droga/metabolismo , Cálcio/metabolismo , AMP Cíclico/análise , Cicloexanóis/metabolismo , Subunidades alfa Gq-G11 de Proteínas de Ligação ao GTP , Guanosina 5'-O-(3-Tiotrifosfato)/metabolismo , Humanos , Receptores de Canabinoides , Proteínas Recombinantes de Fusão/farmacologia , Radioisótopos de Enxofre/metabolismo , Trítio/metabolismoRESUMO
RATIONALE: Marijuana is known to have psychotropic effects in humans. In this study, we used rat models of sensorimotor gating, hyperactivity and stereotypy to explore whether CB(1) receptor stimulation or blockade induces behavioral changes consistent with psychotomimetic or antipsychotic agents, respectively. OBJECTIVES: We determined whether (a) the cannabinoid agonist CP 55940 decreased pre-pulse inhibition (PPI) as might be expected from a psychotomimetic agent, and (b) the selective CB(1) receptor antagonist, SR 141716A, had any effect on PPI on its own or following disruptions by psychotomimetic agents. In addition, we investigated the effects of SR 141716A on elevated levels of hyperactivity and stereotypy elicited by d-amphetamine. METHODS: These studies were conducted in rats using standard methodologies for determination of PPI following acoustic stimuli, and d-amphetamine-induced hyperactivity and stereotypies. RESULTS: Decreased startle responses to 120 dB stimuli were observed in rats treated with CP 55940 (0.1 mg/kg IP) in the absence and presence of a 73 dB pre-pulse. These effects were reversed by SR 141716A (5 and 10 mg/kg, respectively). SR 141716A (0.1, 5, 10 mg/kg) had no effect on PPI on its own or following disruptions by apomorphine, d-amphetamine or MK-801. Conversely, in separate experiments different antipsychotic agents reversed disruptions in PPI induced by d-amphetamine (haloperidol), apomorphine (haloperidol or clozapine) or MK-801 (clozapine or olanzapine). In addition, unlike haloperidol, SR 141716A (5 mg/kg) did not reverse d-amphetamine-mediated increases in hyperactivity or stereotypy. CONCLUSIONS: The CP 55940-mediated decreases in startle amplitude confound assessment of the effects of CB(1) receptor activation on PPI. The failure of SR 141716A to reverse disruptions in PPI, hyperactivity or stereotypy induced by non-cannabinoid psychotomimetic agents suggests that blockade of the CB(1) receptor on its own is not sufficient for antipsychotic therapy.
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Antipsicóticos/farmacologia , Comportamento Animal/efeitos dos fármacos , Cicloexanóis/farmacologia , Dextroanfetamina/farmacologia , Alucinógenos/farmacologia , Piperidinas/farmacologia , Psicoses Induzidas por Substâncias/fisiopatologia , Pirazóis/farmacologia , Receptores de Droga/efeitos dos fármacos , Animais , Apomorfina/farmacologia , Nível de Alerta/efeitos dos fármacos , Nível de Alerta/fisiologia , Atenção/efeitos dos fármacos , Atenção/fisiologia , Comportamento Animal/fisiologia , Maleato de Dizocilpina/farmacologia , Relação Dose-Resposta a Droga , Masculino , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Ratos , Ratos Wistar , Receptores de Canabinoides , Receptores de Droga/fisiologia , Reflexo de Sobressalto/efeitos dos fármacos , Rimonabanto , Comportamento Estereotipado/efeitos dos fármacos , Comportamento Estereotipado/fisiologiaRESUMO
A number of drugs and drug candidates, including fenfluramine and ergot derivatives, are associated with valvulopathy in humans; however, these responses are poorly predicted from animal studies. In vitro and in vivo evidence suggests that these compounds exert their pathological effect through activation of serotonin 2B receptor (5HT2BR) signaling. However, the variable effect of fenfluramine and other 5HT2BR agonists in rodents has cast doubt on the relevance of animal findings to predicting human risk. Herein, a candidate compound, RO3013, induced subendocardial cell proliferation in the mitral and tricuspid valves in rats after only 3 days of daily dosing. Additionally, there was a treatment-related increase in immunostaining of the proliferation marker Ki67, and phosphorylated Smad3 in the heart indicative of TGFß signaling co-localized with 5HT2BR expression. To substantiate the hypothesis that RO3013-induced valvular proliferation is secondary to 5HT2BR activation, the compound was evaluated in vitro and found to bind to the human 5HT2BR with a K(i) of 3.8µM; however, it was virtually devoid of agonist activity in a functional assay in human cells. By contrast, RO3013 bound to the rat 5HT2BR with a K(i) of 1.2µM and activated the receptor with an EC50 of 0.5µM. This agonist potency estimate is in good agreement with the free plasma concentrations of RO3013 at which valvular proliferation was observed. These results suggest that the rat may be susceptible to 5HT2BR-mediated valvular proliferation similar to humans; yet, the significant differences between binding and functional activities can be a possible explanation for the observed species-selective receptor responses.
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Doenças das Valvas Cardíacas/induzido quimicamente , Miocárdio/patologia , Receptor 5-HT2B de Serotonina/fisiologia , Agonistas do Receptor 5-HT2 de Serotonina/farmacologia , Animais , Proliferação de Células/efeitos dos fármacos , Humanos , Antígeno Ki-67/análise , Masculino , Ratos , Ratos Wistar , Agonistas do Receptor 5-HT2 de Serotonina/metabolismo , Proteína Smad3/metabolismo , Fator de Crescimento Transformador beta/fisiologiaRESUMO
BACKGROUND AND PURPOSE: Purinoceptors containing the P2X3 subunit (P2X3 homotrimeric and P2X2/3 heterotrimeric) are members of the P2X family of ion channels gated by ATP and may participate in primary afferent sensitization in a variety of pain-related diseases. The current work describes the in vitro pharmacological characteristics of AF-353, a novel, orally bioavailable, highly potent and selective P2X3/P2X2/3 receptor antagonist. EXPERIMENTAL APPROACH: The antagonistic potencies (pIC(50)) of AF-353 for rat and human P2X3 and human P2X2/3 receptors were determined using methods of radioligand binding, intracellular calcium flux and whole cell voltage-clamp electrophysiology. KEY RESULTS: The pIC(50) estimates for these receptors ranged from 7.3 to 8.5, while concentrations 300-fold higher had little or no effect on other P2X channels or on an assortment of receptors, enzymes and transporter proteins. In contrast to A-317491 and TNP-ATP, competition binding and intracellular calcium flux experiments suggested that AF-353 inhibits activation by ATP in a non-competitive fashion. Favourable pharmacokinetic parameters were observed in rat, with good oral bioavailability (%F = 32.9), reasonable half-life (t(1/2) = 1.63 h) and plasma-free fraction (98.2% protein bound). CONCLUSIONS AND IMPLICATIONS: The combination of a favourable pharmacokinetic profile with the antagonist potency and selectivity for P2X3 and P2X2/3 receptors suggests that AF-353 is an excellent in vivo tool compound for study of these channels in animal models and demonstrates the feasibility of identifying and optimizing molecules into potential clinical candidates, and, ultimately, into a novel class of therapeutics for the treatment of pain-related disorders.
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Trifosfato de Adenosina/metabolismo , Éteres Fenílicos/farmacologia , Antagonistas do Receptor Purinérgico P2 , Pirimidinas/farmacologia , Administração Oral , Animais , Disponibilidade Biológica , Células CHO , Cálcio/metabolismo , Cricetinae , Cricetulus , Meia-Vida , Humanos , Concentração Inibidora 50 , Masculino , Técnicas de Patch-Clamp , Éteres Fenílicos/administração & dosagem , Éteres Fenílicos/farmacocinética , Pirimidinas/administração & dosagem , Pirimidinas/farmacocinética , Ratos , Ratos Wistar , Receptores Purinérgicos P2X2 , Receptores Purinérgicos P2X3RESUMO
A series of novel 3,4-dihydro-2H-benzo[1,4]oxazine derivatives has been designed and synthesized as 5-HT(6) receptor antagonists. Many of the compounds displayed subnanomolar affinities for the 5-HT(6) receptor and good brain penetration in rats. The relationship of structure and lipophilicity to hERG inhibition of this series of compounds is discussed.
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Oxazinas/farmacologia , Receptores de Serotonina/efeitos dos fármacos , Antagonistas da Serotonina/farmacologia , Animais , Modelos Químicos , Oxazinas/síntese química , Ratos , Receptores de Serotonina/metabolismo , Antagonistas da Serotonina/síntese química , Relação Estrutura-AtividadeRESUMO
Activation of G protein-coupled receptors is thought to involve disruption of intramolecular interactions that stabilize their inactive conformation. Such disruptions are induced by agonists or by constitutively active mutations. In the present study, novel potent inverse agonists are described to inhibit the constitutive activity of 5-HT(4) receptors. Using these compounds and specific receptor mutations, we investigated the mechanisms by which inverse agonists may reverse the disruption of intramolecular interactions that causes constitutive activation. Two mutations (D100(3.32)A in transmembrane domain (TMD)-III and F275(6.51)A in TMD-VI) were found to completely block inverse agonist effects without impairing their binding properties nor the molecular activation switches induced by agonists. Based on the rhodopsin model, we propose that these mutated receptors are in equilibrium between two states R and R* but are unable to reach a third "silent" state stabilized by inverse agonists. We also found another mutation in TMD-VI (W272(6.48)A) that stabilized this silent state. This mutant remained fully activated by agonists. Molecular modeling indicated that Asp-100, Phe-275, and Trp-272 might constitute a network required for stabilization of the silent state by the described inverse agonists. However, this network is not necessary for agonist activity.