RESUMO
We report SAR studies on a novel non-peptidic bombesin receptor subtype-3 (BRS-3) agonist lead series derived from high-throughput screening hit RY-337. This effort led to the discovery of compound 22e with significantly improved potency at both rodent and human BRS-3.
Assuntos
Descoberta de Drogas , Imidazóis/química , Imidazóis/farmacologia , Receptores da Bombesina/agonistas , Animais , Disponibilidade Biológica , Humanos , Imidazóis/farmacocinética , Ratos , Relação Estrutura-AtividadeRESUMO
This Letter describes optimization of ghrelin receptor antagonists and inverse agonists starting from a screening hit.
Assuntos
Fármacos Antiobesidade/química , Receptores de Grelina/antagonistas & inibidores , Sulfonamidas/química , Animais , Fármacos Antiobesidade/síntese química , Fármacos Antiobesidade/farmacologia , Linhagem Celular , Desenho de Fármacos , Agonismo Inverso de Drogas , Humanos , Masculino , Obesidade/tratamento farmacológico , Ratos , Ratos Sprague-Dawley , Receptores de Grelina/metabolismo , Relação Estrutura-Atividade , Sulfonamidas/síntese química , Sulfonamidas/farmacologia , BenzenossulfonamidasRESUMO
Melanin-concentrating hormone (MCH) exerts a positive regulation on appetite and binds to the G protein-coupled receptors, MCH1R and MCH2R. In rodents, MCH is produced by neurons in the lateral hypothalamus with projections to various hypothalamic and other brain sites. In the present study, MCH1R was shown, by immunocytochemistry, to be present in the human infundibular nucleus/median eminence, paraventricular nucleus, lateral hypothalamic area, and perifornical area, although in the latter two regions, only a few MCH1R-containing cells were found. In addition, MCH1R staining was found in nerve fibers in the periventricular nucleus, dorsomedial and ventromedial nucleus, suprachiasmatic nucleus, and tuberomammillary nucleus. A significant 1.6 times increase in the number of MCH1R cell body staining was found in the infundibular nucleus in postmortem brain material of cachectic patients, compared with matched controls, supporting a role for this receptor in energy homeostasis in the human.
Assuntos
Núcleo Arqueado do Hipotálamo/química , Caquexia/metabolismo , Receptores de Somatostatina/análise , Idoso , Idoso de 80 Anos ou mais , Animais , Feminino , Humanos , Hipotálamo/química , Imuno-Histoquímica , Masculino , Pessoa de Meia-Idade , Coelhos , RatosRESUMO
In mammals, bombesin-like peptides mediate a broad range of physiological functions through binding to three highly conserved G-protein-coupled receptors: the neuromedin B-preferring, the gastrin-releasing peptide-preferring, and the bombesin-receptor subtype 3. Selective modulation of these receptors presents opportunities for the development of novel therapeutics. To ascertain if rhesus monkey could serve as a surrogate animal model for the development of modulators of bombesin-like receptor function, we undertook a search for additional receptor family members and studied the expression profiles of the three known bombesin-related receptors. We found no evidence for additional receptor family members in mammals, suggesting that the expression of the previously described bombesin-receptor subtype 4 is limited to amphibians. We studied the distribution of the three receptors in a broad array of human and rhesus monkey tissues. Based on the similarity between the human and the rhesus expression profiles, we conclude that the rhesus monkey may be a suitable animal model to evaluate the clinical efficacy and potential side effects of bombesin-like peptide ligands.
Assuntos
Regulação da Expressão Gênica , Macaca mulatta/genética , Neurocinina B/análogos & derivados , Receptores da Bombesina/genética , Sequência de Aminoácidos , Proteínas de Anfíbios/genética , Proteínas de Anfíbios/metabolismo , Anfíbios/genética , Anfíbios/metabolismo , Animais , Peptídeo Liberador de Gastrina/metabolismo , Regulação da Expressão Gênica/genética , Regulação da Expressão Gênica/fisiologia , Humanos , Macaca mulatta/metabolismo , Dados de Sequência Molecular , Neurocinina B/metabolismo , Especificidade de Órgãos/genética , Receptores da Bombesina/metabolismo , Especificidade da EspécieRESUMO
Central administration of the neuropeptide melanin-concentrating hormone (MCH) stimulates feeding in rodents. We studied the effects of intracerebroventricular (i.c.v.) administration of an MCH-1 receptor agonist (Compound A) and an MCH-1 receptor antagonist (Compound B) on feeding in satiated rats. Compound B (10 microg, i.c.v.) blocked the acute orexigenic effect of Compound A (5 microg, i.c.v.). In an experiment designed to either stimulate or inhibit MCH-1 receptor signaling over an extended period, rats received continuous i.c.v. infusions of vehicle (saline), Compound A (30 microg/day), Compound B (30 or 48 microg/day) or neuropeptide Y (24 microg/day, as positive control) via implantable infusion pumps. Continuous MCH-1 receptor activation recapitulated the obese phenotype of MCH-over-expressor mice, manifest as enhanced feeding (+23%, P<0.001), caloric efficiency and body weight gain (+38%, P<0.005) over the 14-day period relative to controls. Chronic MCH-1 receptor activation also elevated plasma insulin and leptin levels significantly. Conversely, continuous MCH-1 receptor antagonism led to sustained reductions in food intake (-16%, P<0.001), body weight gain (-35%, P<0.01), and body fat gain relative to controls, without an effect on lean mass. Antagonism of the MCH-1 receptor may be an effective approach for the treatment of obesity.
Assuntos
Tecido Adiposo/fisiologia , Apetite/fisiologia , Peso Corporal/fisiologia , Receptores do Hormônio Hipofisário/fisiologia , Tecido Adiposo/efeitos dos fármacos , Sequência de Aminoácidos/fisiologia , Animais , Apetite/efeitos dos fármacos , Peso Corporal/efeitos dos fármacos , Relação Dose-Resposta a Droga , Ingestão de Alimentos/efeitos dos fármacos , Ingestão de Alimentos/fisiologia , Éteres/administração & dosagem , Éteres/química , Hidrocarbonetos Fluorados/administração & dosagem , Hidrocarbonetos Fluorados/química , Masculino , Dados de Sequência Molecular , Ratos , Ratos Sprague-Dawley , Receptores do Hormônio Hipofisário/agonistas , Receptores do Hormônio Hipofisário/antagonistas & inibidores , Receptores do Hormônio Hipofisário/químicaRESUMO
Human melanin-concentrating hormone (hMCH) and many of its analogues are potent but nonspecific ligands for human melanin-concentrating hormone receptors 1 and 2 (hMCH-1R and hMCH-2R). To differentiate between the physiological functions of these receptors, selective antagonists are needed. In this study, analogues of Ac-Arg(6)-cyclo(S-S)(Cys(7)-Met(8)-Leu(9)-Gly(10)-Arg(11)-Val(12)-Tyr(13)-Arg(14)-Pro(15)-Cys(16))-NH(2), a high affinity but nonselective agonist at hMCH-1R and hMCH-2R, were prepared and tested in binding and functional assays on cells expressing these receptors. In the new analogues, 5-aminovaleric acid (Ava) was incorporated in place of the Leu(9)-Gly(10) and/or Arg(14)-Pro(15) segments of the disulfide ring. Several of these compounds turned out to be high affinity antagonists selective for hMCH-1R. Moreover, even at micromolar concentrations, they were devoid of agonist potency at both hMCH receptors and not effective as hMCH-2R antagonists. For example, peptide 14, Gva(6)- cyclo(S-S)(Cys(7)-Met(8)-Leu(9)-Gly(10)-Arg(11)-Val(12)-Tyr(13)-Ava(14,15)-Cys(16))-NH(2), (Gva = 5-guanidinovaleric acid), was a full competitive hMCH-1R antagonist (IC(50) = 14 nM, K(B) = 0.9 nM) with more than 1000-fold selectivity over hMCH-2R. Examination of various compounds with Ava in positions 9,10 and/or 14,15 revealed that the Leu(9)-Gly(10) and Arg(14)-Pro(15) segments of the disulfide ring are the principal structural elements determining hMCH-1R selectivity and ability to act as a hMCH-1R antagonist.
Assuntos
Hormônios Hipotalâmicos/antagonistas & inibidores , Hormônios Hipotalâmicos/metabolismo , Melaninas/antagonistas & inibidores , Melaninas/metabolismo , Peptídeos Cíclicos/síntese química , Peptídeos Cíclicos/metabolismo , Hormônios Hipofisários/antagonistas & inibidores , Hormônios Hipofisários/metabolismo , Receptores do Hormônio Hipofisário/metabolismo , Equorina/metabolismo , Substituição de Aminoácidos , Aminoácidos Neutros/química , Aminoácidos Neutros/metabolismo , Animais , Ligação Competitiva , Células COS , Linhagem Celular , Dissulfetos/química , Humanos , Hormônios Hipotalâmicos/química , Ligantes , Medições Luminescentes , Melaninas/química , Peptídeos Cíclicos/farmacologia , Hormônios Hipofisários/química , Conformação Proteica , Ensaio Radioligante , Receptores Acoplados a Proteínas G , Receptores do Hormônio Hipofisário/química , TransfecçãoRESUMO
To assess the contribution of potential central nervous system pathways implicated in the control of appetite regulation and energy metabolism, it is essential to first identify appropriate animal models. Melanin-concentrating hormone (MCH), a conserved cyclic neuropeptide implicated in the modulation of food intake, has been shown to bind and activate two G-protein-coupled receptors, called GPR24 and MCHR2, expressed in human brain and other tissues. Here we show that several non-human species (rat, mouse, hamster, guinea pig, and rabbit) do not have functional MCHR2 receptors, or encode a nonfunctional MCHR2 pseudogene while retaining GPR24 expression. We identified three species for further evaluation that express both MCH receptor subtypes. We cloned and functionally characterized dog, ferret, and rhesus GPR24 and MCHR2 in mammalian cells and studied their brain distribution patterns by in situ hybridization. The homology, expression profile, and functional similarity of the receptors in the dog, ferret, and rhesus to that of human support the potential use of these species as preclinical animal models in the development of therapeutic agents for obesity or other MCH-mediated disorders.
Assuntos
Mamíferos/genética , Receptores do Hormônio Hipofisário/genética , Receptores de Somatostatina/genética , Sequência de Aminoácidos , Animais , Regulação da Expressão Gênica , Humanos , Dados de Sequência Molecular , Especificidade de Órgãos , Receptores Acoplados a Proteínas G , Alinhamento de Sequência , Especificidade da EspécieRESUMO
Human melanin-concentrating hormone (hMCH) is a nonselective natural ligand for the human melanin-concentrating hormone receptors: hMCH-1R and hMCH-2R. Similarly, the smaller peptide encompassing the disulfide ring and Arg(6) of hMCH, Ac-Arg(6)-cyclo(S-S)(Cys(7)-Met(8)-Leu(9)-Gly(10)-Arg(11)-Val(12)-Tyr(13)-Arg(14)-Pro(15)-Cys(16))-NH(2), Ac-hMCH(6-16)-NH(2), binds to and activates equally well both human MCH receptors present in the brain. To separate the physiological functions of hMCH-1R from those of hMCH-2R, new potent and hMCH-1R selective agonists are necessary. In the present study, analogs of Ac-hMCH(6-16)-NH(2) were prepared and tested in binding and functional assays on cells expressing the MCH receptors. In these peptides, Arg in position 6 was replaced with various d-amino acids and/or Gly in position 10 was substituted with various L-amino acids. Several of the new compounds turned out to be potent agonists at hMCH-1R with improved selectivity over hMCH-2R. For example, peptide 26 with d-Arg in place of L-Arg in position 6 and Asn in place of Gly in position 10, Ac-dArg(6)-cyclo(S-S)(Cys(7)-Met(8)-Leu(9)-Asn(10)-Arg(11)-Val(12)-Tyr(13)-Arg(14)-Pro(15)-Cys(16))-NH(2), was a potent hMCH-1R agonist (IC(50) = 0.5 nm, EC(50) = 47 nm) with more than 200-fold selectivity with respect to hMCH-2R. Apparently, these structural changes in positions 6 and 10 results in peptide conformations that allow for efficient interactions with hMCH-1R but are unfavorable for molecular recognition at hMCH-2R.