RESUMO
Human ghrelin receptor (GHSR) is a recognized prospective target in the diagnosis and therapy of multiple cancer types. To gain a better understanding of this receptor signaling system, we have synthesized a novel full-length ghrelin analog that is fluorescently labeled at the side-chain of a C-terminal cysteine extension. This analog exhibited nanomolar affinity and potency for the ghrelin receptor. It shows comparable efficacy with that of endogenous ghrelin. The fluorescently-labeled ghrelin analog is a valuable tool for in vitro imaging of cell lines that express ghrelin receptor.
Assuntos
Grelina/análogos & derivados , Grelina/síntese química , Proteínas Luminescentes/síntese química , Proteínas Luminescentes/metabolismo , Fluorescência , Células HEK293 , Humanos , Proteínas Luminescentes/química , Receptores de Grelina/metabolismoRESUMO
A new fluorine-containing azadibenzocyclooctyne (ADIBO-F) was designed using a synthetically accessible pathway. The fluorine-18 prosthetic group was prepared from its toluenesulfonate precursor and isolated in 21-35 % radiochemical yield in 30â minutes of synthetic time. ADIBO-F has been incorporated into azide-functionalized, cancer-targeting peptides through a strain-promoted alkyne-azide cycloaddition with high radiochemical yields and purities. The final products are novel peptide-based positron emission tomography (PET) imaging agents that possess high affinities for their targets, growth hormone secretagogue receptorâ 1a (GHSR-1a) and gastrin-releasing peptide receptor (GRPR), with IC50 values of 9.7 and 0.50â nm, respectively. This is a new and rapid labelling option for the incorporation of fluorine-18 into biomolecules for PET imaging.
Assuntos
Bombesina/análogos & derivados , Ciclo-Octanos/química , Grelina/análogos & derivados , Compostos Heterocíclicos com 3 Anéis/química , Compostos Radiofarmacêuticos/química , Alcinos/síntese química , Alcinos/química , Bombesina/síntese química , Química Click , Reação de Cicloadição , Ciclo-Octanos/síntese química , Radioisótopos de Flúor , Grelina/síntese química , Compostos Heterocíclicos com 3 Anéis/síntese química , Marcação por Isótopo/métodos , Estrutura Molecular , Tomografia por Emissão de Pósitrons/métodos , Estudo de Prova de Conceito , Compostos Radiofarmacêuticos/síntese químicaRESUMO
The nose-to-brain delivery of ghrelin loaded in liposomes is a promising approach for the management of cachexia. It could limit the plasmatic degradation of ghrelin and provide direct access to the brain, where ghrelin's specific receptors are located. Anionic liposomes coated with chitosan in either a liquid or a dry-powder formulation were compared. The powder formulation showed stronger adhesion to mucins (89⯱â¯4% vs 61⯱â¯4%), higher ghrelin entrapment efficiency (64⯱â¯2% vs 55⯱â¯4%), higher enzymatic protection against trypsin (26⯱â¯2% vs 20⯱â¯3%) and lower ghrelin storage degradation at 25⯰C (2.67⯱â¯1.1% vs 95.64⯱â¯0.85% after 4â¯weeks). The powder formulation was also placed in unit-dose system devices that were able to generate an appropriate aerosol characterized by a Dv50 of 38⯱â¯6⯵m, a limited percentage of particles smaller than 10⯵m of 4⯱â¯1% and a reproducible mass delivery (CV: 1.49%). In addition, the device was able to deposit a large amount of powder (52.04% w/w) in the olfactory zone of a 3D-printed nasal cast. The evaluated combination of the powder formulation and the device could provide a promising treatment for cachexia.
Assuntos
Encéfalo/metabolismo , Caquexia/tratamento farmacológico , Sistemas de Liberação de Medicamentos/métodos , Grelina/administração & dosagem , Administração por Inalação , Administração Intranasal/métodos , Linhagem Celular Tumoral , Quitosana/química , Inaladores de Pó Seco , Grelina/síntese química , Grelina/metabolismo , Grelina/uso terapêutico , Humanos , Lipossomos/química , Mucinas/metabolismo , Sprays Nasais , Tamanho da Partícula , Permeabilidade , PósRESUMO
The discovery of ghrelin has resulted in the development of potential therapeutics for cachexia caused by multiple underlying diseases. When chronic respiratory diseases progress to their advanced stages, cachexia often occurs, thereby worsening the patient's prognosis. A small clinical trial that enrolled cachectic patients with chronic respiratory disease revealed that administration of ghrelin improved their nutritional status and exercise tolerance. Short-term administration of ghrelin was found to be safe and tolerated with adverse events, including suffusion, sleepiness, peristalsis, hunger, and sweating. Further large-scale and long-term clinical trials are needed.
Assuntos
Caquexia/tratamento farmacológico , Grelina/uso terapêutico , Transtornos Respiratórios/tratamento farmacológico , Acilação , Apetite/efeitos dos fármacos , Caprilatos/administração & dosagem , Caprilatos/farmacologia , Doença Crônica/tratamento farmacológico , Ensaios Clínicos como Assunto , Esquema de Medicação , Teste de Esforço/métodos , Alimentos Formulados , Grelina/administração & dosagem , Grelina/síntese química , Humanos , Peristaltismo , Sudorese , Resultado do TratamentoRESUMO
Ghrelin, the only known peripherally produced and centrally acting peptide that stimulates food intake, is synthesized primarily in the stomach and acts through the growth hormone secretagogue receptor (GHS-R1a). In addition to its orexigenic effect, ghrelin stimulates the release of growth hormone (GH). In this study, we investigated the biological properties of full-length and shortened ghrelin analogs in which octanoylated Ser(3) is replaced with an octanoic acid moiety coupled to diaminopropionic acid (Dpr). Ghrelin analogs stabilized with Dpr(N-octanoyl) in position 3 and noncoded amino acids in position 1 (sarcosine) and/or position 4 (naphthylalanine or cyclohexylalanine) were found to possess affinities similar to those of ghrelin for cell membranes with transfected GHS-R1a. In vivo, the prolonged orexigenic effects of analogs containing Dpr(N-octanoyl)(3) compared with that of ghrelin in adult mice and a similar impact on GH secretion in young mice were found. Full-length [Dpr(N-octanoyl)(3)]ghrelin and its analogs with a noncoded amino acid in position 1 and/or 4 showed significantly prolonged stability in blood plasma compared with that of ghrelin. Ghrelin analogs with a prolonged orexigenic effect are potential treatments for GH deficiency or cachexia that accompanies chronic diseases. Desoctanoylated ghrelin analogs and N-terminal penta- and octapeptides of ghrelin did not show any biological activity.
Assuntos
Ingestão de Alimentos/efeitos dos fármacos , Grelina/análogos & derivados , Sequência de Aminoácidos , Animais , Grelina/síntese química , Grelina/metabolismo , Hormônio do Crescimento/sangue , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Dados de Sequência Molecular , Receptores de Grelina/metabolismo , Relação Estrutura-AtividadeRESUMO
In our effort to create imaging probes targeting the growth hormone secretagogue receptor (GHSR), we now report on the design and synthesis of fluorine and rhenium containing ghrelin analogues through modification of the n-octanoyl Ser-3 side chain. Fluorine analogues were designed whereby the fluorine atom is situated at the terminus of an aliphatic chain using diaminopropionic acid (Dpr) as residue-3. Truncated ghrelin(1-5) and ghrelin(1-14) fluorine-bearing analogues were prepared, the best of which had a 28 nM IC(50) for GHSR. Ghrelin(1-14) analogues were also prepared containing rhenium, as a surrogate metal for technetium-99m, with a cyclopentadienylrhenium tricarbonyl being situated at the terminus of the residue-3 side chain, yielding compounds the best of which had a 35 nM IC(50). This represents a rare case of incorporating rhenium into a peptide structure where the metal complex is required for biological activity. These fluorine and rhenium derivatives demonstrate the ability to modify the Ser-3 side chain of ghrelin in order to create imaging probes for the GHSR.