Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 202
Filtrar
1.
Nat Commun ; 11(1): 6295, 2020 12 08.
Artigo em Inglês | MEDLINE | ID: mdl-33293550

RESUMO

The central melanocortin system plays a fundamental role in the control of feeding and body weight. Proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC) also regulate overall glucose homeostasis via insulin-dependent and -independent pathways. Here, we report that a subset of ARC POMC neurons innervate the liver via preganglionic parasympathetic acetylcholine (ACh) neurons in the dorsal motor nucleus of the vagus (DMV). Optogenetic stimulation of this liver-projecting melanocortinergic pathway elevates blood glucose levels that is associated with increased expression of hepatic gluconeogenic enzymes in female and male mice. Pharmacological blockade and knockdown of the melanocortin-4 receptor gene in the DMV abolish this stimulation-induced effect. Activation of melanocortin-4 receptors inhibits DMV cholinergic neurons and optogenetic inhibition of liver-projecting parasympathetic cholinergic fibers increases blood glucose levels. This elevated blood glucose is not due to altered pancreatic hormone release. Interestingly, insulin-induced hypoglycemia increases ARC POMC neuron activity. Hence, this liver-projecting melanocortinergic circuit that we identified may play a critical role in the counterregulatory response to hypoglycemia.


Assuntos
Glicemia/metabolismo , Hipoglicemia/etiologia , Fígado/inervação , Pró-Opiomelanocortina/metabolismo , Nervo Vago/metabolismo , Acetilcolina/metabolismo , Potenciais de Ação/fisiologia , Animais , Núcleo Arqueado do Hipotálamo/citologia , Núcleo Arqueado do Hipotálamo/metabolismo , Glicemia/análise , Neurônios Colinérgicos/metabolismo , Corticosterona/sangue , Corticosterona/metabolismo , Modelos Animais de Doenças , Vias Eferentes/fisiologia , Feminino , Técnicas de Silenciamento de Genes , Glucagon/sangue , Glucagon/metabolismo , Gluconeogênese/genética , Humanos , Hipoglicemia/sangue , Hipoglicemia/diagnóstico , Insulina/sangue , Insulina/metabolismo , Fígado/enzimologia , Masculino , Camundongos , Optogenética , RNA Mensageiro/metabolismo , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/genética , Receptor Tipo 4 de Melanocortina/metabolismo , Regulação para Cima , Nervo Vago/citologia
2.
Science ; 368(6489): 428-433, 2020 04 24.
Artigo em Inglês | MEDLINE | ID: mdl-32327598

RESUMO

The melanocortin-4 receptor (MC4R) is involved in energy homeostasis and is an important drug target for syndromic obesity. We report the structure of the antagonist SHU9119-bound human MC4R at 2.8-angstrom resolution. Ca2+ is identified as a cofactor that is complexed with residues from both the receptor and peptide ligand. Extracellular Ca2+ increases the affinity and potency of the endogenous agonist α-melanocyte-stimulating hormone at the MC4R by 37- and 600-fold, respectively. The ability of the MC4R crystallized construct to couple to ion channel Kir7.1, while lacking cyclic adenosine monophosphate stimulation, highlights a heterotrimeric GTP-binding protein (G protein)-independent mechanism for this signaling modality. MC4R is revealed as a structurally divergent G protein-coupled receptor (GPCR), with more similarity to lipidic GPCRs than to the homologous peptidic GPCRs.


Assuntos
Cálcio/química , Receptor Tipo 4 de Melanocortina/química , Receptores Acoplados a Proteínas-G/química , Cristalografia por Raios X , AMP Cíclico/química , Humanos , Ligantes , Hormônios Estimuladores de Melanócitos/química , Hormônios Estimuladores de Melanócitos/farmacologia , Mutação , Canais de Potássio Corretores do Fluxo de Internalização/química , Ligação Proteica , Multimerização Proteica , Estrutura Secundária de Proteína , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/genética , Receptores Acoplados a Proteínas-G/antagonistas & inibidores , Receptores Acoplados a Proteínas-G/genética , Transdução de Sinais
3.
PLoS One ; 15(2): e0229617, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32109250

RESUMO

An increasing prevalence of overweight and obesity in people living with HIV has been associated with initiation of antiretroviral therapy with integrase strand transfer inhibitors (INSTIs). An off-target inhibition of the endogenous ligand binding to the human melanocortin 4 receptor (MC4R) has been suggested as a potential mechanism for clinical body weight gain following initiation of dolutegravir, an INSTI. In this study, we interrogated several INSTIs for their capacity for antagonism or agonism of MC4R in an in vitro cell-based assays including at concentrations far exceeding plasma concentrations reached at the recommended dosages. Our results indicate that while INSTIs do exhibit the capacity to antagonize MC4R, this occurs at concentrations well above predicted clinical exposure and is thus an implausible explanation for INSTI-associated weight gain.


Assuntos
Inibidores de Integrase de HIV/efeitos adversos , Receptor Tipo 4 de Melanocortina/efeitos dos fármacos , Ganho de Peso/efeitos dos fármacos , Peso Corporal , Infecções por HIV/tratamento farmacológico , Inibidores de Integrase de HIV/farmacologia , Inibidores de Integrase de HIV/uso terapêutico , Humanos , Receptor Tipo 4 de Melanocortina/agonistas , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores
4.
J Med Chem ; 63(5): 2194-2208, 2020 03 12.
Artigo em Inglês | MEDLINE | ID: mdl-31845801

RESUMO

While the melanocortin receptors (MCRs) are known to be involved in numerous biological pathways, the potential roles of the MC5R have not been clearly elucidated in humans. Agouti-related protein (AgRP), an MC3R/MC4R antagonist and MC4R inverse agonist, contains an exposed ß-hairpin loop composed of six residues (Arg-Phe-Phe-Asn-Ala-Phe) that is imperative for binding and function. Within this active loop of AgRP, four human missense polymorphisms were deposited into the NIH Variation Viewer database. These polymorphisms, Arg111Cys, Arg111His, Phe112Tyr, and Ala115Val (AgRP full-length numbering), were incorporated into the peptide macrocycles c[Pro1-Arg2-Phe3-Phe4-Xaa5-Ala6-Phe7-dPro8], where Xaa was Dap5 or Asn5, to explore the functional effects of these naturally occurring substitutions in a simplified AgRP scaffold. All peptides lowered potency at least 10-fold in a cAMP accumulation assay compared to the parent sequences at the MC4Rs. Compounds MDE 6-82-3c, ZMK 2-82, MDE 6-82-1c, ZMK 2-85, and ZMK 2-112 are also the first AgRP-based chemotypes that antagonize the MC5R.


Assuntos
Proteína Relacionada com Agouti/farmacologia , Compostos Macrocíclicos/farmacologia , Peptídeos Cíclicos/farmacologia , Receptores de Melanocortina/antagonistas & inibidores , Proteína Relacionada com Agouti/química , Proteína Relacionada com Agouti/genética , Descoberta de Drogas , Humanos , Compostos Macrocíclicos/química , Simulação de Acoplamento Molecular , Peptídeos Cíclicos/química , Polimorfismo de Nucleotídeo Único , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores
5.
Pharmacol Biochem Behav ; 181: 28-36, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30991059

RESUMO

A fixed dose combination of bupropion (BPP) and naltrexone (NTX), Contrave®, is an FDA approved pharmacotherapy for the treatment of obesity. A recent study found that combining BPP with low-dose NTX reduced alcohol drinking in alcohol-preferring male rats. To explore potential pharmacological effects of the BPP + NTX combination on alcohol drinking, both male and female C57Bl/6J mice were tested on one-week drinking-in-the dark (DID) and three-week intermittent access (IA) models. Neuronal proopiomelanocortin (POMC) enhancer knockout (nPE-/-) mice with hypothalamic-specific deficiency of POMC, and its bioactive peptides melanocyte stimulating hormone and beta-endorphin, were used as a genetic control for the effects of the BPP + NTX. A single administration of BPP + NTX (10 mg/kg + 1 mg/kg) decreased alcohol intake after DID in C57Bl/6J males, but not females. Also in C57Bl/6J males, BPP + NTX reduced intake of the caloric reinforcer sucrose, but not the non-caloric reinforcer saccharin. In contrast, BPP + NTX had no effect on alcohol DID in nPE-/- males. Pretreatment with the selective melanocortin 4 receptor (MC4R) antagonist HS014 reversed the anti-dipsogenic effect of BPP + NTX on alcohol DID in C57Bl/6J males. In the 3-week chronic IA model, single or repeated administrations for four days of BPP + NTX reduced alcohol intake and preference in C57Bl/6J males only. The behavioral measures observed in C57Bl/6J mice provide clear evidence that BPP + NTX profoundly reduced alcohol drinking in males, but the doses tested were not effective in females. Furthermore, our results suggest a hypothalamic POMC/MC4R-dependent mechanism for the observed BPP + NTX effects on alcohol drinking in male mice.


Assuntos
Consumo de Bebidas Alcoólicas/tratamento farmacológico , Alcoolismo/tratamento farmacológico , Bupropiona/farmacologia , Bupropiona/uso terapêutico , Avaliação Pré-Clínica de Medicamentos/métodos , Naltrexona/farmacologia , Naltrexona/uso terapêutico , Animais , Comportamento Animal/efeitos dos fármacos , Bupropiona/administração & dosagem , Combinação de Medicamentos , Sinergismo Farmacológico , Etanol/administração & dosagem , Feminino , Técnicas de Inativação de Genes , Hipotálamo/metabolismo , Injeções Intraperitoneais , Locomoção/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Naltrexona/administração & dosagem , Peptídeos Cíclicos/farmacologia , Peptídeos Cíclicos/uso terapêutico , Fotoperíodo , Pró-Opiomelanocortina/genética , Pró-Opiomelanocortina/metabolismo , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/metabolismo , Sacarina/farmacologia , Fatores Sexuais , Sacarose/farmacologia
6.
J Med Chem ; 62(1): 141-143, 2019 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-29863866

RESUMO

The determination of the potential value of receptor trafficking at melanocortin receptors has been hampered by the absence of known biased ligands. Heterobivalent MC4R ligands linking agonist to antagonist small peptidic moieties were designed and found to act as Gαs enhancers while minimally activating ß-arrestin recruitment. The strategy invoked offers intriguing promise as a surprising approach that is possibly broadly applicable to the challenge of designing biased ligands at other GPCRs.


Assuntos
Desenho de Fármacos , Ligantes , Arrestina/química , Arrestina/metabolismo , Humanos , Modelos Moleculares , Receptor Tipo 4 de Melanocortina/agonistas , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/metabolismo , Receptores Acoplados a Proteínas-G/química , Receptores Acoplados a Proteínas-G/metabolismo
7.
J Med Chem ; 61(17): 7729-7740, 2018 09 13.
Artigo em Inglês | MEDLINE | ID: mdl-30035543

RESUMO

Antagonist ligands of the melanocortin-3 and -4 receptors (MC3R, MC4R), including agouti-related protein (AGRP), are postulated to be targets for the treatment of diseases of negative energy balance. Previous studies reported the macrocyclic MC3R/MC4R antagonist c[Pro1-Arg2-Phe3-Phe4-Asn5-Ala6-Phe7-dPro8], which is 250-fold less potent at the mouse (m) mMC3R and 3-fold less potent at the mMC4R than AGRP. Previous studies explored the structure-activity relationships around individual positions in this template. Herein, a multiresidue substitution strategy is utilized, combining the lead sequence with hPhe4, Dap5, Arg5, Ser6, and Nle7 substitutions previously reported. Two compounds from this study (16, 20) contain an hPhe4/Ser6/Nle7 substitution pattern, are 3-6-fold more potent than AGRP at the mMC4R and are 600-800-fold selective for the mMC4R over the mMC3R. Another lead compound (21), possessing the hPhe4/Arg5 substitutions, is only 5-fold less potent than AGRP at the mMC3R and is equipotent to AGRP at the mMC4R.


Assuntos
Proteína Relacionada com Agouti/metabolismo , Sinergismo Farmacológico , Fragmentos de Peptídeos/química , Fragmentos de Peptídeos/farmacologia , Receptor Tipo 3 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Substituição de Aminoácidos , Animais , Células HEK293 , Humanos , Ligantes , Camundongos , Modelos Moleculares , Biblioteca de Peptídeos , Conformação Proteica , Receptor Tipo 3 de Melanocortina/metabolismo , Receptor Tipo 4 de Melanocortina/metabolismo , Relação Estrutura-Atividade
8.
Mil Med ; 183(suppl_1): 408-412, 2018 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-29635611

RESUMO

There is a great need for effective treatment options for post-traumatic stress disorder (PTSD). Neuropeptide Y (NPY) is associated with resilience to traumatic stress. MC4R antagonists, such as HS014, also reduce response to stress. Both regulate stress-responsive systems - the hypothalamic-pituitary-axis (HPA) and the noradrenergic nervous system and their associated behaviors. Therefore, we examined if their intranasal delivery to brain could attenuate development of PTSD-related symptoms in single prolonged stress (SPS) rodent PTSD model. Three regimens were used: (1) prophylactic treatment 30 min before SPS stressors, (2) early intervention right after SPS stressors, (3) therapeutic treatment when PTSD behaviors are manifested 1 wk or more after the traumatic stress. NPY delivered by regimen 1 or 2 prevented SPS-triggered elevation in anxiety, depressive-like behavior, and hyperarousal and reduced dysregulation of HPA axis. Hypothalamic CRH mRNA and GR in ventral hippocampus were significantly induced in vehicle- but not NPY-treated group. NPY also prevented hypersensitivity of LC/NE system to novel mild stressor and induction of CRH in amygdala. Some of these impairments were also reduced with HS014, alone or together with NPY. When given after symptoms were manifested (regiment 3), NPY attenuated anxiety and depressive behaviors. This demonstrates strong preclinical proof of concept for intranasal NPY, and perhaps MC4R antagonists, for non-invasive early pharmacological interventions for PTSD and comorbid disorders and possibly also as therapeutic strategy.


Assuntos
Neuropeptídeo Y/administração & dosagem , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Transtornos de Estresse Pós-Traumáticos/tratamento farmacológico , Administração Intranasal , Animais , Terapia Comportamental/métodos , Masculino , Neuropeptídeo Y/uso terapêutico , Ratos , Ratos Sprague-Dawley/psicologia , Receptor Tipo 4 de Melanocortina/administração & dosagem , Transtornos de Estresse Pós-Traumáticos/prevenção & controle
9.
ACS Chem Neurosci ; 9(2): 320-327, 2018 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-28968061

RESUMO

Central administration of melanocortin ligands has been used as a critical technique to study energy homeostasis. While intracerebroventricular (ICV) injection is the most commonly used method during these investigations, intrathecal (IT) injection can be equally efficacious for the central delivery of ligands. Importantly, intrathecal administration can optimize exploration of melanocortin receptors in the spinal cord. Herein, we investigate comparative IT and ICV administration of two melanocortin ligands, the synthetic MTII (Ac-Nle-c[Asp-His-DPhe-Arg-Trp-Lys]-NH2) MC4R agonist and agouti-related peptide [AGRP(87-132)] MC4R inverse agonist/antagonist, on the same batch of age-matched mice in TSE metabolic cages undergoing a nocturnal satiated paradigm. To our knowledge, this is the first study to test how central administration of these ligands directly to the spinal cord affects energy homeostasis. Results showed, as expected, that MTII IT administration caused a decrease in food and water intake and an overall negative energy balance without affecting activity. As anticipated, IT administration of AGRP caused weight gain, increase of food/water intake, and increase respiratory exchange ratio (RER). Unexpectantly, the prolonged activity of AGRP was notably shorter (2 days) compared to mice given ICV injections of the same concentrations in previous studies (7 days or more).1-4 It appears that IT administration results in a more sensitive response that may be a good approach for testing synthetic compound potency values ranging in nanomolar to high micromolar in vitro EC50 values. Indeed, our investigation reveals that the spine influences a different melanocortin response compared to the brain for the AGRP ligand. This study indicates that IT administration can be a useful technique for future metabolic studies using melanocortin ligands and highlights the importance of exploring the role of melanocortin receptors in the spinal cord.


Assuntos
Proteína Relacionada com Agouti/administração & dosagem , Peso Corporal/efeitos dos fármacos , Ingestão de Alimentos/efeitos dos fármacos , Homeostase/efeitos dos fármacos , Fragmentos de Peptídeos/administração & dosagem , Receptor Tipo 4 de Melanocortina/agonistas , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , alfa-MSH/análogos & derivados , Animais , Cateteres de Demora , Estudos Cross-Over , Injeções Intraventriculares , Injeções Espinhais , Masculino , Camundongos da Linhagem 129 , Camundongos Endogâmicos C57BL , Receptor Tipo 4 de Melanocortina/metabolismo , Fatores de Tempo , alfa-MSH/administração & dosagem
10.
J Med Chem ; 60(19): 8103-8114, 2017 10 12.
Artigo em Inglês | MEDLINE | ID: mdl-28813605

RESUMO

The melanocortin system consists of five reported receptors, agonists from the proopiomelanocortin gene transcript, and two antagonists, agouti-signaling protein (ASP) and agouti-related protein (AGRP). For both ASP and AGRP, the hypothesized Arg-Phe-Phe pharmacophores are on exposed ß-hairpin loops. In this study, the Asn and Ala positions of a reported AGRP macrocyclic scaffold (c[Pro-Arg-Phe-Phe-Asn-Ala-Phe-DPro]) were explored with 14-compound and 8-compound libraries, respectively, to generate more potent, selective melanocortin receptor antagonists. Substituting diaminopropionic acid (Dap), DDap, and His at the Asn position yielded potent MC4R ligands, while replacing Ala with Ser maintained MC4R potency. Since these substitutions correlate to ASP loop residues, an additional Phe to Ala substitution was synthesized and observed to maintain MC4R potency. Seventeen compounds also possessed inverse agonist activity at the MC5R, the first report of this pharmacology. These findings are useful in developing molecular probes to study negative energy balance conditions and unidentified functions of the MC5R.


Assuntos
Proteína Agouti Sinalizadora/química , Proteína Relacionada com Agouti/química , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Receptores de Melanocortina/agonistas , Substituição de Aminoácidos , Animais , AMP Cíclico/metabolismo , Metabolismo Energético/efeitos dos fármacos , Células HEK293 , Humanos , Ligantes , Camundongos , Modelos Moleculares , Relação Estrutura-Atividade
11.
J Med Chem ; 60(10): 4342-4357, 2017 05 25.
Artigo em Inglês | MEDLINE | ID: mdl-28453292

RESUMO

The centrally expressed melanocortin-3 and -4 receptors (MC3R/MC4R) have been studied as possible targets for weight management therapies, with a preponderance of studies focusing on the MC4R. Herein, a novel tetrapeptide scaffold [Ac-Xaa1-Arg-(pI)DPhe-Xaa4-NH2] is reported. The scaffold was derived from results obtained from a MC3R mixture-based positional scanning campaign. From these results, a set of 48 tetrapeptides were designed and pharmacologically characterized at the mouse melanocortin-1, -3, -4, and -5 receptors. This resulted in the serendipitous discovery of nine compounds that were MC3R agonists (EC50 < 1000 nM) and MC4R antagonists (5.7 < pA2 < 7.8). The three most potent MC3R agonists, 18 [Ac-Arg-Arg-(pI)DPhe-Tic-NH2], 1 [Ac-His-Arg-(pI)DPhe-Tic-NH2], and 41 [Ac-Arg-Arg-(pI)DPhe-DNal(2')-NH2] were more potent (EC50 < 73 nM) than the melanocortin tetrapeptide Ac-His-DPhe-Arg-Trp-NH2. This template contains a sequentially reversed "Arg-(pI)DPhe" motif with respect to the classical "Phe-Arg" melanocortin signaling motif, which results in pharmacology that is first-in-class for the central melanocortin receptors.


Assuntos
Oligopeptídeos/química , Oligopeptídeos/farmacologia , Receptor Tipo 3 de Melanocortina/agonistas , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Sequência de Aminoácidos , Animais , Descoberta de Drogas , Camundongos , Biblioteca de Peptídeos , Receptor Tipo 3 de Melanocortina/metabolismo , Receptor Tipo 4 de Melanocortina/metabolismo
12.
Neuropharmacology ; 118: 26-37, 2017 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-28267582

RESUMO

The role of the urocortin 1 (Ucn1) expressing centrally projecting Edinger-Westphal (EWcp) nucleus in energy homeostasis and stress adaptation response has previously been investigated. Morphological and functional studies have proven that orexigenic and anorexigenic peptidergic afferents and receptors for endocrine messengers involved in the energy homeostasis are found in the EWcp. The central role of the hypothalamic melanocortin system in energy homeostasis is well known, however, no data have been published so far on possible crosstalk between melanocortins and EWcp-Ucn1. First, we hypothesized that members of the melanocortin system [i.e. alpha-melanocyte stimulating hormone (alpha-MSH), agouti-related peptide (AgRP), melanocortin 4 receptor (MC4R)] would be expressed in the EWcp. Second, we put forward, that alpha-MSH and AgRP contents as well as neuronal activity and Ucn1 peptide content of the EWcp would be affected by fasting. Third, we assumed that the intra-EWcp injections of exogenous MC4R agonists and antagonist would cause food intake-related and metabolic changes. Ucn1 neurons were found to carry MC4Rs, and they were contacted both by alpha-MSH and AgRP immunoreactive nerve fibers in the rat. The alpha-MSH immunosignal was reduced, while that of AgRP was increased upon starvation. These were associated with the elevation of FosB and Ucn1 expression. The intra-EWcp administration of MC4R blocker (i.e. HS024) had a similar, but enhanced effect on FosB and Ucn1. Furthermore, alpha-MSH injected into the EWcp had anorexigenic effect, increased oxygen consumption and caused peripheral vasodilation. We conclude that the melanocortin system influences the EWcp that contributes to energy-homeostasis.


Assuntos
Núcleo de Edinger-Westphal/citologia , Homeostase/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Consumo de Oxigênio/efeitos dos fármacos , Receptor Tipo 4 de Melanocortina , Urocortinas/metabolismo , Proteína Relacionada com Agouti/metabolismo , Animais , Temperatura Corporal/efeitos dos fármacos , Vias de Administração de Medicamentos , Ingestão de Alimentos/efeitos dos fármacos , Jejum , Ligantes , Masculino , Fibras Nervosas/efeitos dos fármacos , Fibras Nervosas/fisiologia , Proteínas Oncogênicas v-fos/metabolismo , Peptídeos Cíclicos/farmacologia , Ratos , Ratos Wistar , Receptor Tipo 4 de Melanocortina/agonistas , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/metabolismo , alfa-MSH/metabolismo , alfa-MSH/farmacologia
13.
Psychopharmacology (Berl) ; 234(11): 1683-1692, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28243712

RESUMO

RATIONALE AND OBJECTIVES: Alpha-melanocyte stimulating hormone (αMSH) and agouti-related protein (AgRP) are antagonistic neuropeptides that play an important role in the control of feeding and body weight through their central actions on the melanocortin-3 and melanocortin-4 receptors. Increasing evidence indicates that αMSH and AgRP can interact with the mesolimbic dopamine system to regulate feeding as well as other behaviors. For example, we have shown previously that injection of melanocortin receptor agonists and antagonists into the ventral tegmental area (VTA) alters both normal home-cage feeding and the intake of sucrose solutions, but it remains unknown whether αMSH and AgRP can also act in the VTA to affect reward-related feeding. METHODS: We tested whether injection of the melanocortin receptor agonist, MTII, or the melanocortin receptor antagonist, SHU9119, directly into the VTA affected operant responding maintained by sucrose pellets in self-administration assays. RESULTS: Injection of MTII into the VTA decreased operant responding maintained by sucrose pellets on both fixed ratio and progressive ratio schedules of reinforcement, whereas SHU9119 increased operant responding under fixed ratio, but not progressive ratio schedules. MTII also increased and SHU9119 decreased 24-h home-cage food intake. CONCLUSIONS: This study demonstrates that αMSH and AgRP act in the VTA to affect sucrose self-administration. Thus, it adds critical information to the growing literature showing that in addition to their well-characterized role in controlling "need-based" feeding, αMSH and AgRP can also act on the mesolimbic dopamine system to control reward-related behavior.


Assuntos
Receptor Tipo 4 de Melanocortina/agonistas , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Sacarose/administração & dosagem , Área Tegmentar Ventral/efeitos dos fármacos , Animais , Peso Corporal/efeitos dos fármacos , Peso Corporal/fisiologia , Ingestão de Alimentos/efeitos dos fármacos , Ingestão de Alimentos/fisiologia , Injeções Intraventriculares , Masculino , Hormônios Estimuladores de Melanócitos/administração & dosagem , Ratos , Ratos Sprague-Dawley , Recompensa , Autoadministração , Área Tegmentar Ventral/metabolismo , alfa-MSH/administração & dosagem , alfa-MSH/análogos & derivados
14.
J Comp Physiol B ; 187(4): 603-612, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-28197776

RESUMO

Melanocortin-4 receptor (Mc4r) function related to reproduction in fish has not been extensively investigated. Here, we report on gene expression changes by real-time PCR following treatment with Mc4r agonists and antagonists in the spotted scat (Scatophagus argus). Using in vitro incubated hypothalamus, the Mc4r nonselective agonist NDP-MSH ([Nle4, D-Phe7]-α-melanocyte stimulating hormone; 10-6 M) and selective agonist THIQ (N-[(3R)-1, 2, 3, 4-Tetrahydroisoquinolinium-3-ylcarbonyl]- (1R)-1-(4-chlorobenzyl)-2-[4-cyclohexyl-4-(1H-1,2,4-triazol-1-ylmethyl) piperidin-1-yl]-2-oxoethylamine; 10-7 M) significantly increased the expression of gnrh (Gonadotropin releasing hormone), while the Mc4r nonselective antagonist SHU9119 (Ac-Nle-[Asp-His-DPhe/DNal(2')-Arg-Trp-Lys]-NH2; 10-6 M) and selective antagonist Ipsen 5i (compound 5i synthesized in Ipsen Research Laboratories; 10-6 M) significantly inhibited gnrh expression after 3 h of incubation. In incubated pituitary tissue, NDP-MSH and THIQ significantly increased the expression of fshb (Follicle-stimulating hormone beta subunit) and lhb (Luteinizing hormone beta subunit), while SHU9119 and Ipsen 5i significantly decreased fshb and lhb expression after 3 h of incubation. During the in vivo experiment, THIQ (1 mg/kg bw) significantly increased gnrh expression in hypothalamic tissue, as well as the fshb and lhb expression in pituitary tissue 12 h after abdominal injection. Furthermore, Ipsen 5i (1 mg/kg bw) significantly inhibited gnrh expression in hypothalamic tissue, as well as fshb and lhb gene expression in pituitary tissue 12 h after abdominal injection. In summary, Mc4r singling appears to stimulate gnrh expression in the hypothalamus, thereby modulating the synthesis of Fsh and Lh in the pituitary. In addition, Mc4r also appears to directly regulate fshb and lhb levels in the pituitary in spotted scat. Our study suggests that Mc4r, through the hypothalamus and pituitary, participates in reproductive regulation in fish.


Assuntos
Proteínas de Peixes/genética , Perciformes/fisiologia , Receptor Tipo 4 de Melanocortina/agonistas , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Animais , Feminino , Subunidade beta do Hormônio Folículoestimulante/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Hormônio Liberador de Gonadotropina/genética , Hipotálamo/efeitos dos fármacos , Hormônio Luteinizante Subunidade beta/genética , Hormônios Estimuladores de Melanócitos/farmacologia , Técnicas de Cultura de Órgãos/métodos , Receptor Tipo 4 de Melanocortina/genética , Reprodução/efeitos dos fármacos , Reprodução/genética , Tetra-Hidroisoquinolinas/farmacologia , Triazóis/farmacologia , alfa-MSH/análogos & derivados , alfa-MSH/farmacologia
15.
Addict Biol ; 22(3): 692-701, 2017 May.
Artigo em Inglês | MEDLINE | ID: mdl-26804193

RESUMO

Humans diagnosed with alcohol use disorder are more sensitive to painful stimuli during withdrawal, which suggests that excessive alcohol drinking worsens pain outcomes. Alcohol-dependent rats exhibit increases in nociceptive sensitivity during withdrawal. Data from animal models suggest that brain melanocortin-4 receptors (MC4Rs) mediate alcohol drinking and nociception. Here we tested: (1) the effect of alcohol dependence on thermal nociception in rats, and (2) the ability of acute alcohol and (3) MC4R antagonists to reverse hyperalgesia during withdrawal in alcohol-dependent rats. Rats were trained to self-administer operant alcohol and were tested for baseline thermal nociception. Half of the rats were made dependent on alcohol, then all rats were cannulated in the lateral ventricle. We tested the effects of acute alcohol drinking, acute fixed-dose alcohol, intra-ventricular agouti-related protein (endogenous MC4R antagonist), intra-ventricular HS014 (synthetic MC4R antagonist) and intra-nasal HS014 on hyperalgesia during withdrawal in alcohol-dependent rats, relative to non-dependent drinkers and alcohol-naïve controls. Alcohol-dependent rats exhibit thermal hyperalgesia that is abolished by alcohol drinking, bolus alcohol and intra-ventricular and intra-nasal MC4R antagonists. These manipulations did not affect thermal nociception in non-dependent drinkers and alcohol-naïve controls, suggesting that alcohol dependence produces neuroadaptations in brain MC4R systems. These results suggest that brain MC4R systems may be an effective therapeutic target for reducing nociception in the alcohol-dependent organism.


Assuntos
Alcoolismo/complicações , Encéfalo/efeitos dos fármacos , Hiperalgesia/tratamento farmacológico , Peptídeos Cíclicos/farmacologia , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Síndrome de Abstinência a Substâncias/tratamento farmacológico , Administração Intranasal , Animais , Modelos Animais de Doenças , Hiperalgesia/complicações , Masculino , Nociceptividade/efeitos dos fármacos , Ratos Wistar
16.
Am J Physiol Heart Circ Physiol ; 311(2): H433-44, 2016 08 01.
Artigo em Inglês | MEDLINE | ID: mdl-27402666

RESUMO

Hypothalamic arcuate nucleus (ARCN) stimulation elicited increases in sympathetic nerve activity (IBATSNA) and temperature (TBAT) of interscapular brown adipose tissue (IBAT). The role of hypothalamic dorsomedial (DMN) and paraventricular (PVN) nuclei in mediating these responses was studied in urethane-anesthetized, artificially ventilated, male Wistar rats. In different groups of rats, inhibition of neurons in the DMN and PVN by microinjections of muscimol attenuated the increases in IBATSNA and TBAT elicited by microinjections of N-methyl-d-aspartic acid into the ipsilateral ARCN. In other groups of rats, blockade of ionotropic glutamate receptors by combined microinjections of D(-)-2-amino-7-phosphono-heptanoic acid (D-AP7) and NBQX into the DMN and PVN attenuated increases in IBATSNA and TBAT elicited by ARCN stimulation. Blockade of melanocortin 3/4 receptors in the DMN and PVN in other groups of rats resulted in attenuation of increases in IBATSNA and TBAT elicited by ipsilateral ARCN stimulation. Microinjections of Fluoro-Gold into the DMN resulted in retrograde labeling of cells in the ipsilateral ARCN, and some of these cells contained proopiomelanocortin (POMC), α-melanocyte-stimulating hormone (α-MSH), or vesicular glutamate transporter-3. Since similar projections from ARCN to the PVN have been reported by us and others, these results indicate that neurons containing POMC, α-MSH, and glutamate project from the ARCN to the DMN and PVN. Stimulation of ARCN results in the release of α-MSH and glutamate in the DMN and PVN which, in turn, cause increases in IBATSNA and TBAT.


Assuntos
Tecido Adiposo Marrom/efeitos dos fármacos , Núcleo Arqueado do Hipotálamo/efeitos dos fármacos , Núcleo Hipotalâmico Dorsomedial/efeitos dos fármacos , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Sistema Nervoso Simpático/efeitos dos fármacos , Termogênese/efeitos dos fármacos , 2-Amino-5-fosfonovalerato/análogos & derivados , 2-Amino-5-fosfonovalerato/farmacologia , Tecido Adiposo Marrom/inervação , Animais , Núcleo Arqueado do Hipotálamo/fisiologia , Núcleo Hipotalâmico Dorsomedial/fisiologia , Agonistas de Aminoácidos Excitatórios/farmacologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Corantes Fluorescentes , Agonistas de Receptores de GABA-A/farmacologia , Ácido Glutâmico/metabolismo , Imuno-Histoquímica , Masculino , Microinjeções , Muscimol/farmacologia , N-Metilaspartato/farmacologia , Inibição Neural , Núcleo Hipotalâmico Paraventricular/fisiologia , Pró-Opiomelanocortina/metabolismo , Quinoxalinas/farmacologia , Ratos , Ratos Wistar , Receptor Tipo 3 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Estilbamidinas , Sistema Nervoso Simpático/fisiologia , Temperatura , Termogênese/fisiologia , Proteínas Vesiculares de Transporte de Glutamato/metabolismo , alfa-MSH/metabolismo
17.
Sci Rep ; 6: 29424, 2016 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-27405276

RESUMO

Various pathophysiologic mechanisms leading to sickness behaviors have been proposed. For example, an inflammatory process in the hypothalamus has been implicated, but the signaling modalities that involve inflammatory mechanisms and neuronal circuit functions are ill-defined. Here, we show that toll-like receptor 2 (TLR2) activation by intracerebroventricular injection of its ligand, Pam3CSK4, triggered hypothalamic inflammation and activation of arcuate nucleus microglia, resulting in altered input organization and increased activity of proopiomelanocortin (POMC) neurons. These animals developed sickness behavior symptoms, including anorexia, hypoactivity, and hyperthermia. Antagonists of nuclear factor kappa B (NF-κB), cyclooxygenase pathway and melanocortin receptors 3/4 reversed the anorexia and body weight loss induced by TLR2 activation. These results unmask an important role of TLR2 in the development of sickness behaviors via stimulation of hypothalamic microglia to promote POMC neuronal activation in association with hypothalamic inflammation.


Assuntos
Anorexia/patologia , Núcleo Arqueado do Hipotálamo/patologia , Febre/patologia , Lipopeptídeos/farmacologia , Fator 88 de Diferenciação Mieloide/genética , Pró-Opiomelanocortina/metabolismo , Receptor 2 Toll-Like/genética , Receptor 2 Toll-Like/metabolismo , Animais , Inibidores de Ciclo-Oxigenase/farmacologia , Metabolismo Energético/fisiologia , Inflamação/patologia , Masculino , Camundongos , Camundongos Knockout , Microglia/metabolismo , NF-kappa B/antagonistas & inibidores , Ratos , Receptor Tipo 3 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Perda de Peso/efeitos dos fármacos , Perda de Peso/fisiologia
18.
ACS Chem Neurosci ; 7(9): 1283-91, 2016 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-27385405

RESUMO

The melanocortin-4 receptor (MC4R) has been indicated as a therapeutic target for metabolic disorders such as anorexia, cachexia, and obesity. The current study investigates the in vivo effects on energy homeostasis of a 15 nM MC4R antagonist SKY2-23-7, Ac-Trp-DPhe(p-I)-Arg-Trp-NH2, that is a 3700 nM melanocortin-3 receptor (MC3R) antagonist with minimal MC3R and MC4R agonist activity. When monitoring both male and female mice in TSE metabolic cages, sex-specific responses were observed in food intake, respiratory exchange ratio (RER), and energy expenditure. A 7.5 nmol dose of SKY2-23-7 increased food intake, increased RER, and trended toward decreasing energy expenditure in male mice. However, this compound had minimal effect on female mice's food intake and RER at the 7.5 nmol dose. A 2.5 nmol dose of SKY2-23-7 significantly increased female food intake, RER, and energy expenditure while having a minimal effect on male mice at this dose. The observed sex differences of SKY2-23-7 administration result in the discovery of a novel chemical probe for elucidating the molecular mechanisms of the sexual dimorphism present within the melanocortin pathway. To further explore the melanocortin sexual dimorphism, hypothalamic gene expression was examined. The mRNA expression of the MC3R and proopiomelanocortin (POMC) were not significantly different between sexes. However, the expression of agouti-related peptide (AGRP) was significantly higher in female mice which may be a possible mechanism for the sex-specific effects observed with SKY2-23-7.


Assuntos
Metabolismo Energético/efeitos dos fármacos , Receptor Tipo 3 de Melanocortina/antagonistas & inibidores , Receptor Tipo 3 de Melanocortina/metabolismo , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/metabolismo , Animais , Ingestão de Alimentos/efeitos dos fármacos , Feminino , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Oligopeptídeos/farmacologia , Fragmentos de Peptídeos/farmacologia , Peptídeo YY/farmacologia , Perilipina-2/genética , Perilipina-2/metabolismo , Pró-Opiomelanocortina/genética , Pró-Opiomelanocortina/metabolismo , Receptor Tipo 3 de Melanocortina/genética , Receptor Tipo 4 de Melanocortina/genética , Fatores Sexuais , Relação Estrutura-Atividade , Fatores de Tempo
19.
Am J Physiol Regul Integr Comp Physiol ; 311(1): R97-R103, 2016 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-27122366

RESUMO

Following binding to receptors in the arcuate nucleus (ArcN), insulin increases sympathetic nerve activity (SNA) and baroreflex control of SNA via a pathway that includes the paraventricular nucleus of the hypothalamus (PVN). Previous studies in males indicate that the sympathoexcitatory response is mediated by α-melanocyte stimulating hormone (α-MSH), which binds to PVN melanocortin type 3/4 receptors (MC3/4R). The present study was conducted in α-chloralose-anesthetized female rats to test the hypothesis that suppression of inhibitory neuropeptide Y (NPY) inputs to the PVN is also involved. In support of this, blockade of PVN NPY Y1 receptors with BIBO 3304 (NPY1x), ArcN insulin nanoinjections, and PVN NPY1x followed by ArcN insulin each increased lumbar SNA (LSNA) and its baroreflex regulation similarly. Moreover, prior PVN injections of NPY blocked the sympathoexcitatory effects of ArcN insulin. Finally, PVN nanoinjections of the MC3/4R inhibitor SHU9119 prevented both the acute (15 min) and longer, more slowly developing (60 min), increases in LSNA in response to ArcN insulin. In conclusion, in females, ArcN insulin increases LSNA, in part, by suppressing tonic PVN NPY inhibition, which unmasks excitatory α-MSH drive of LSNA. Moreover, the steadily increasing rise in LSNA induced by ArcN insulin is also dependent on PVN MC3/4R.


Assuntos
Hipoglicemiantes/farmacologia , Insulina/farmacologia , Neuropeptídeo Y/antagonistas & inibidores , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Sistema Nervoso Simpático/efeitos dos fármacos , Animais , Arginina/análogos & derivados , Arginina/farmacologia , Barorreflexo/efeitos dos fármacos , Pressão Sanguínea/efeitos dos fármacos , Feminino , Frequência Cardíaca/efeitos dos fármacos , Hipoglicemiantes/administração & dosagem , Insulina/administração & dosagem , Hormônios Estimuladores de Melanócitos/farmacologia , Microinjeções , Ratos , Ratos Sprague-Dawley , Receptor Tipo 3 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Receptores de Neuropeptídeo Y/antagonistas & inibidores
20.
Am J Hypertens ; 29(7): 832-40, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-26584577

RESUMO

BACKGROUND: Hyperandrogenemia in females may be associated with sympathetic nervous system (SNS) activation and increased blood pressure (BP). However the importance of hyperandrogenemia in causing hypertension in females and the mechanisms involved are still unclear. We tested whether chronic hyperandrogenemia exacerbates hypertension in young female spontaneously hypertensive rats (SHR) and whether endogenous melanocortin-3/4 receptor (MC3/4R) activation contributes to the elevated BP. METHODS: Cardiovascular and metabolic effects of chronic MC3/4R antagonism were assessed in female SHR treated with dihydrotestosterone (DHT, beginning at 5 weeks of age) and placebo-treated female SHR. BP and heart rate (HR) were measured by telemetry and an intracerebroventricular (ICV) cannula was placed in the lateral ventricle for infusions. After control measurements, the MC3/4R antagonist (SHU-9119) was infused for 10 days (1 nmol/hour, ICV, at 15 weeks of age) followed by a 5-day recovery period. RESULTS: MC3/4R antagonism increased food intake and body weight in DHT-treated SHR (14±1 to 35±1g/day and 244±3 to 298±8g) and controls (14±1 to 34±2g/day and 207±4 to 269±8g). Compared to untreated SHR, DHT-treated SHR had similar BP but lower HR (146±3 vs. 142±4mm Hg and 316±2 vs. 363±4 bpm). Chronic SHU-9119 infusion reduced BP and HR in DHT-treated SHR (-12±2mm Hg and -14±4 bpm) and control female SHR (-19±2mm Hg and -21±6 bpm). CONCLUSION: These results indicate that hyperandrogenemia does not exacerbate hypertension in female SHR. MC3/4R antagonism reduces BP and HR despite marked increases in food intake and body weight in hyperandrogenemic and control female SHR.


Assuntos
Pressão Sanguínea , Sistema Nervoso Central/metabolismo , Hiperandrogenismo/fisiopatologia , Receptor Tipo 3 de Melanocortina/metabolismo , Receptor Tipo 4 de Melanocortina/metabolismo , Animais , Apetite , Glicemia , Peso Corporal , Di-Hidrotestosterona/sangue , Ingestão de Alimentos , Feminino , Hiperandrogenismo/complicações , Hiperandrogenismo/metabolismo , Insulina/sangue , Leptina/sangue , Ratos Endogâmicos SHR , Receptor Tipo 3 de Melanocortina/antagonistas & inibidores , Receptor Tipo 4 de Melanocortina/antagonistas & inibidores , Respiração
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA