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Receptor-interacting serine/threonine protein kinase 1 (RIPK1) has emerged as an important regulator of pathologic cell death and inflammation and is implicated in the pathologies of various central nervous system diseases. In this study, we reported the development of three potent dihydropyrazole-cored RIPK1 positron emission tomography (PET) ligands [18F]WL1-3. Among these, [18F]WL1 showed specific binding to RIPK1 in mouse brain sections in vitro through autoradiography and exhibited favorable brain kinetics in mice, characterized by a high initial uptake (brain2â¯min = 4.89% ID/g) and rapid washout (brain60â¯min = 0.21% ID/g). PET studies in rat brains revealed that [18F]WL1 could readily penetrate the brain with specific binding confirmed by inhibition effects of unlabeled WL1 and GSK'547. Notably, [18F]WL1 showed significant potential in imaging the alterations of RIPK1 in a rat brain of tumor necrosis factor α-induced systemic inflammatory response syndrome model. These findings may pave the way for the future design of potent RIPK1 PET ligands.
Assuntos
Encéfalo , Tomografia por Emissão de Pósitrons , Pirazóis , Proteína Serina-Treonina Quinases de Interação com Receptores , Animais , Tomografia por Emissão de Pósitrons/métodos , Proteína Serina-Treonina Quinases de Interação com Receptores/metabolismo , Encéfalo/metabolismo , Encéfalo/diagnóstico por imagem , Pirazóis/química , Pirazóis/síntese química , Pirazóis/farmacocinética , Pirazóis/farmacologia , Pirazóis/metabolismo , Ligantes , Camundongos , Ratos , Masculino , Radioisótopos de Flúor/química , Compostos Radiofarmacêuticos/química , Compostos Radiofarmacêuticos/farmacocinética , Compostos Radiofarmacêuticos/síntese química , Ratos Sprague-Dawley , Camundongos Endogâmicos C57BL , Humanos , Síndrome de Resposta Inflamatória Sistêmica/diagnóstico por imagem , Síndrome de Resposta Inflamatória Sistêmica/metabolismo , Distribuição TecidualRESUMO
Receptor-interacting serine/threonine-protein kinase 1 (RIPK1) regulates programmed cell death and inflammation, contributing to a wide range of human pathologies, including inflammatory disorders, neurodegenerative conditions, and cancer. Despite this, no RIPK1 positron emission tomography (PET) ligand with significant in vivo specificity has been reported to date. In this work, we designed and synthesized a new family of dihydropyrazole-cored ligands suitable for 18F-labeling at the late stage. Among these, WL8 showed a strong binding affinity to RIPK1 (EC50 = 19.9 nM, Kd = 25 nM) and was successfully labeled with 18F in the 6-position of pyridine ring, yielding a high radiochemistry yield of 27.9 % (decay-corrected) and a high molar activity of 18.8-31.2 GBq/µmol. In in vitro autoradiography, [18F]WL8 showed some specific binding in the brain sections of rats and lipopolysaccharide (LPS) model mice. Preliminary PET studies in rat brains revealed that [18F]WL8 could efficiently penetrate the blood-brain barrier and was rapidly washed out. As anticipated, [18F]WL8 exhibited a high initial uptake (brain2min = 4.80 % ID/g) in mouse brains, followed by a rapid washout (brain60min = 0.14 % ID/g), although no clear specific binding to RIPK1 was observed. Moderate in vivo stability was noted for [18F]WL8 in mouse brains with 35.2 % of the parent fraction remaining after 30 min post-administration. Altogether, our work broadens the landscape and offers a new chemotype for RIPK1 PET ligand development.
Assuntos
Encéfalo , Tomografia por Emissão de Pósitrons , Pirazóis , Proteína Serina-Treonina Quinases de Interação com Receptores , Animais , Ligantes , Encéfalo/metabolismo , Encéfalo/diagnóstico por imagem , Proteína Serina-Treonina Quinases de Interação com Receptores/metabolismo , Ratos , Camundongos , Pirazóis/química , Pirazóis/síntese química , Pirazóis/farmacologia , Estrutura Molecular , Masculino , Humanos , Relação Estrutura-Atividade , Radioisótopos de Flúor/química , Compostos Radiofarmacêuticos/química , Compostos Radiofarmacêuticos/síntese química , Descoberta de Drogas , Ratos Sprague-Dawley , Lipopolissacarídeos/farmacologia , Relação Dose-Resposta a DrogaRESUMO
In vivo bioimaging using shortwave infrared (SWIR) (1000-2000 nm) molecular dyes enables deeper penetration and higher contrast compared to visible and near-infrared-I (NIR-I, 700-900 nm) dyes. Developing new SWIR molecules is still quite challenging. This study developed SRHCYs, a panel of fluorescent dyes based on hemicyanine, with adjustable absorbance (830-1144 nm) and emission (886-1217 nm) wavelength. The photophysical attributes of these dyes are precisely tailored by strengthening the donor parts and extending polymethine chains. SRHCY-3, with its clickable azido group, was chosen for high-performance imaging of blood vessels in living mice, enabling the precise detection of brain and lung cancer. The combination of these probes achieved in vivo multicolor imaging with negligible optical crosstalk. This report presents a series of SWIR hemicyanine dyes with promising spectroscopic properties for high-contrast bioimaging and multiplexing detection.
Assuntos
Carbocianinas , Corantes Fluorescentes , Imagem Óptica , Animais , Corantes Fluorescentes/química , Corantes Fluorescentes/síntese química , Carbocianinas/química , Carbocianinas/síntese química , Camundongos , Humanos , Raios Infravermelhos , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Encefálicas/diagnóstico por imagem , Camundongos Nus , Estrutura MolecularRESUMO
Cholinergic receptors represent a promising class of diagnostic and therapeutic targets due to their significant involvement in cognitive decline associated with neurological disorders and neurodegenerative diseases as well as cardiovascular impairment. Positron emission tomography (PET) is a noninvasive molecular imaging tool that has helped to shed light on the roles these receptors play in disease development and their diverse functions throughout the central nervous system (CNS). In recent years, there has been a notable advancement in the development of PET probes targeting cholinergic receptors. The purpose of this review is to provide a comprehensive overview of the recent progress in the development of these PET probes for cholinergic receptors with a specific focus on ligand structure, radiochemistry, and pharmacology as well as in vivo performance and applications in neuroimaging. The review covers the structural design, pharmacological properties, radiosynthesis approaches, and preclinical and clinical evaluations of current state-of-the-art PET probes for cholinergic receptors.
Assuntos
Compostos Radiofarmacêuticos , Receptores Colinérgicos , Compostos Radiofarmacêuticos/química , Tomografia por Emissão de Pósitrons/métodos , Encéfalo/diagnóstico por imagem , Sistema Nervoso CentralRESUMO
We report the design, synthesis and evaluation of five oaminopyridyl alkynyl derivatives as colony-stimulating factor 1 receptor (CSF-1R) ligands. Compounds 4 and 5 with the fluoroethoxy group at the meta- or para-position of the phenyl ring possessed nanomolar inhibitory potency against CSF-1R with IC50 values of 7.6 nM and 2.3 nM, respectively. Radioligands [18F]4 and [18F]5 were obtained in radiochemical yields of 17.2 ± 5.3% (n = 5, decay-corrected) and 14.0 ± 4.3% (n = 4, decay-corrected), with radiochemical purity of > 99% and molar activity of 9-12 GBq/µmol (n = 5) and 6-8 GBq/µmol (n = 4), respectively. In biodistribution studies, radioligands [18F]4 and [18F]5 showed moderate brain uptake in male ICR mice with 1.52 ± 0.15 and 0.91 ± 0.07% ID/g, respectively, at 15 min. Metabolic stability studies in mouse brain revealed that [18F]4 exhibited high stability while [18F]5 suffered from low stability. Higher accumulation of [18F]4 in the brain of lipopolysaccharide (LPS)-treated mice was observed, and further pretreatment of BLZ945 or CPPC led to remarkable reduction, indicating specific binding of [18F]4 to CSF-1R.
Assuntos
Aminopiridinas , Radioisótopos de Flúor , Doenças Neuroinflamatórias , Tomografia por Emissão de Pósitrons , Receptores de Fator Estimulador das Colônias de Granulócitos e Macrófagos , Animais , Masculino , Camundongos , Radioisótopos de Flúor/química , Camundongos Endogâmicos ICR , Doenças Neuroinflamatórias/diagnóstico por imagem , Tomografia por Emissão de Pósitrons/métodos , Distribuição Tecidual , Aminopiridinas/química , Aminopiridinas/farmacologia , Receptores de Fator Estimulador das Colônias de Granulócitos e Macrófagos/químicaRESUMO
Leucine-rich repeat kinase 2 (LRRK2) has been demonstrated to be closely involved in the pathogenesis of Parkinson's disease (PD), and pharmacological blockade of LRRK2 represents a new opportunity for therapeutical treatment of PD and other related neurodegenerative conditions. The development of an LRRK2-specific positron emission tomography (PET) ligand would enable a target occupancy study in vivo and greatly facilitate LRRK2 drug discovery and clinical translation as well as provide a molecular imaging tool for studying physiopathological changes in neurodegenerative diseases. In this work, we present the design and development of compound 8 (PF-06455943) as a promising PET radioligand through a PET-specific structure-activity relationship optimization, followed by comprehensive pharmacology and ADME/neuroPK characterization. Following an efficient 18F-labeling method, we have confirmed high brain penetration of [18F]8 in nonhuman primates (NHPs) and validated its specific binding in vitro by autoradiography in postmortem NHP brain tissues and in vivo by PET imaging studies.
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Doença de Parkinson , Tomografia por Emissão de Pósitrons , Animais , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Leucina/metabolismo , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina/genética , Serina-Treonina Proteína Quinase-2 com Repetições Ricas em Leucina/metabolismo , Ligantes , Doença de Parkinson/metabolismo , Tomografia por Emissão de Pósitrons/métodosRESUMO
Lewy pathologies, which mainly consist of insoluble α-synuclein (α-syn) aggregates, are the hallmarks of Parkinson's disease and many other neurodegenerative diseases termed "synucleinopathies". Detection of Lewy pathologies with optical methods is of interest for preclinical studies, while the α-syn fluorescent probe is still in great demand. By rational design, we obtained a series of D-π-A-based trisubstituted alkenes with acceptable optical properties and high binding affinities to α-syn fibrils. Among these probes, FPQXN and TQXN-2 exhibited high binding affinities (6 and 8 nM, respectively), significant fluorescence enhancements (17.2- and 26.6-fold, respectively), and satisfying quantum yields (36.5% and 10.4%, respectively), which met the need for the in vitro neuropathological staining of Lewy pathologies in the PD brain sections. In addition, TQXN-2 showed great potential in fluorescent discrimination of Lewy pathologies and Aß plaques. Our research provides flexible tools for in vitro detection of α-syn aggregates and offers new structural frameworks for the further development of α-syn fluorescent probes.
Assuntos
Corantes Fluorescentes , Doença de Parkinson , Humanos , Corantes Fluorescentes/metabolismo , Alcenos/metabolismo , alfa-Sinucleína/química , Doença de Parkinson/metabolismo , Placa Amiloide/metabolismo , Encéfalo/metabolismoRESUMO
The presence of Aß plaques in the brain is a hallmark of Alzheimer's disease. Here, we designed and synthesized a series of molecular rotors with various bi-aromatic rings and investigated their applications as near-infrared (NIR) probes for Aß plaques. We found that the interaction with Aß aggregates hindered the rotational freedom of the molecular rotors, which brought about a noticeable enhancement in fluorescence intensity. Among them, probe 4b (Kd = 8.5 nM) with a phenyl-pyridine ring showed a 98-fold increase in fluorescence intensity upon binding with Aß aggregates. In addition, 4b could identify Aß plaques in brain sections of both a transgenic (Tg) mouse and AD patients. Furthermore, 4b could readily penetrate the mouse blood-brain barrier (brain2min = 10.11% ID/g) and washed out rapidly. Finally, the NIR imaging with Tg mice confirmed the practical application of 4b in detecting Aß plaques in vivo. Altogether, our work widens the landscape of Aß NIR probes and offers a new tool for Aß detection.
Assuntos
Doença de Alzheimer , Animais , Camundongos , Doença de Alzheimer/diagnóstico por imagem , Doença de Alzheimer/metabolismo , Corantes Fluorescentes/química , Sondas Moleculares/metabolismo , Placa Amiloide/diagnóstico por imagem , Placa Amiloide/metabolismo , Peptídeos beta-Amiloides/metabolismo , Camundongos Transgênicos , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismoRESUMO
Serotonin (5-hydroxytryptamine, 5-HT) and 5-HT receptors (5-HTRs) have crucial roles in various neuropsychiatric disorders and neurodegenerative diseases, making them attractive diagnostic and therapeutic targets. Positron emission tomography (PET) is a noninvasive nuclear molecular imaging technique and is an essential tool in clinical diagnosis and drug discovery. In this context, numerous PET ligands have been developed for "visualizing" 5-HTRs in the brain and translated into human use to study disease mechanisms and/or support drug development. Herein, we present a comprehensive repertoire of 5-HTR PET ligands by focusing on their chemotypes and performance in PET imaging studies. Furthermore, this Perspective summarizes recent 5-HTR-focused drug discovery, including biased agonists and allosteric modulators, which would stimulate the development of more potent and subtype-selective 5-HTR PET ligands and thus further our understanding of 5-HTR biology.
Assuntos
Tomografia por Emissão de Pósitrons , Receptores de Serotonina , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Humanos , Ligantes , Tomografia por Emissão de Pósitrons/métodos , Compostos Radiofarmacêuticos , Receptores de Serotonina/metabolismoRESUMO
We have discovered and synthesized a series of indole-based derivatives as novel sigma-2 (σ 2) receptor ligands. Two ligands with high σ 2 receptor affinity and subtype selectivity were then radiolabeled with F-18 in good radiochemical yields and purities, and evaluated in rodents. In biodistribution studies in male ICR mice, radioligand [18F]9, or 1-(4-(5,6-dimethoxyisoindolin-2-yl)butyl)-4-(2-[18F]fluoroethoxy)-1H-indole, was found to display high brain uptake and high brain-to-blood ratio. Pretreatment of animals with the selective σ 2 receptor ligand CM398 led to significant reductions in both brain uptake (29%-54%) and brain-to-blood ratio (60%-88%) of the radioligand in a dose-dependent manner, indicating high and saturable specific binding of [18F]9 to σ 2 receptors in the brain. Further, ex vivo autoradiography in male ICR mice demonstrated regionally heterogeneous specific binding of [18F]9 in the brain that is consistent with the distribution pattern of σ 2 receptors. Dynamic positron emission tomography imaging confirmed regionally distinct distribution and high levels of specific binding for [18F]9 in the rat brain, along with appropriate tissue kinetics. Taken together, results from our current study indicated the novel radioligand [18F]9 as the first highly specific and promising imaging agent for σ 2 receptors in the brain.
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Monoacylglycerol lipase (MAGL) is a pivotal enzyme in the endocannabinoid system, which metabolizes 2-arachidonoylglycerol (2-AG) into the proinflammatory eicosanoid precursor arachidonic acid (AA). MAGL and other endogenous cannabinoid (EC) degrading enzymes are involved in the fibrogenic signaling pathways that induce hepatic stellate cell (HSC) activation and ECM accumulation during chronic liver disease. Our group recently developed an 18F-labeled MAGL inhibitor ([18F]MAGL-4-11) for PET imaging and demonstrated highly specific binding in vitro and in vivo. In this study, we determined [18F]MAGL-4-11 PET enabled imaging MAGL levels in the bile duct ligation (BDL) and carbon tetrachloride (CCl4) models of liver cirrhosis; we also assessed the hepatic gene expression of the enzymes involved with EC system including MAGL, NAPE-PLD, FAAH and DAGL that as a function of disease severity in these models; [18F]MAGL-4-11 autoradiography was performed to assess tracer binding in frozen liver sections both in animal and human. [18F]MAGL-4-11 demonstrated reduced PET signals in early stages of fibrosis and further significantly decreased with disease progression compared with control mice. We confirmed MAGL and FAAH expression decreases with fibrosis severity, while its levels in normal liver tissue are high; in contrast, the EC synthetic enzymes NAPE-PLD and DAGL are enhanced in these different fibrosis models. In vitro autoradiography further supported that [18F]MAGL-4-11 bound specifically to MAGL in both animal and human fibrotic liver tissues. Our PET ligand [18F]MAGL-4-11 shows excellent sensitivity and specificity for MAGL visualization in vivo and accurately reflects the histological stages of liver fibrosis in preclinical models and human liver tissues.
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Owing to the complex anatomical structure, precise resection of a tumor while maintaining adjacent tissue is a challenge in radical prostatectomy for prostate cancer (PCa). Optical imaging in near-infrared window II (NIR-II) is a promising technology for intraoperative guidance, whereas there is no available probe for PCa yet. In this article, a novel probe (PSMA-1092) bearing two prostate-specific membrane antigen (PSMA) binding motifs was developed, displaying excellent optical properties (λmax = 1092 nm) and ultrahigh affinity (Ki = 80 pM) toward PSMA. The tumor was visualized with high resolution (tissue-to-normal tissue ratio = 7.62 ± 1.05) and clear margin by NIR-II imaging using PSMA-1092 in a mouse model. During the tumor resection, residual tumors missed by visible inspection were detected by the real-time imaging. Overall, PSMA-1092 displayed excellent performance in delineating the tumor margin and detecting residual tumors, demonstrating promising potential for precise PCa tumor resection in clinical practice.
Assuntos
Corantes Fluorescentes/química , Antígeno Prostático Específico/metabolismo , Neoplasias da Próstata/diagnóstico por imagem , Animais , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Modelos Animais de Doenças , Estabilidade de Medicamentos , Corantes Fluorescentes/metabolismo , Corantes Fluorescentes/farmacologia , Humanos , Concentração de Íons de Hidrogênio , Masculino , Camundongos , Camundongos Nus , Antígeno Prostático Específico/química , Prostatectomia , Neoplasias da Próstata/cirurgia , Espectroscopia de Luz Próxima ao Infravermelho , Transplante HeterólogoRESUMO
The plaques of accumulated ß-amyloid (Aß) in the parenchymal brain are accepted as an important biomarker for the early diagnosis of Alzheimer's disease (AD). Many near-infrared (NIR) probes, which were based on the D-π-A structure and bridged by conjugated double bonds, had been reported and displayed a high affinity to Aß plaques. Considering the isomerization caused by the polyethylene chain, however, the conjugated polyacetylene chain is a better choice for developing new NIR Aß probes. Hence, in this report, a new series of NIR probes with naphthyl or phenyl rings and different numbers of conjugated triple bonds were designed, synthesized, and evaluated as NIR probes for Aß plaques. Upon interaction with Aß aggregates, these probes displayed a significant increase in fluorescence intensity (45- to 360-fold) and a high to moderate affinity (6.05-56.62 nM). Among them, probe 22b displayed excellent fluorescent properties with a 183-fold increase in fluorescence intensity and an emission maximum at 650 nm after incubated with Aß aggregates. Furthermore, 22b had a high affinity to Aß aggregates (Kd = 12.96 nM) and could efficiently detect the Aß plaques in brain sections from both transgenic mice and AD patients in vitro. In summary, this work may lead to a new direction in the development of novel NIR probes for the detection of Aß plaques.
Assuntos
Doença de Alzheimer , Corantes Fluorescentes , Doença de Alzheimer/diagnóstico por imagem , Peptídeos beta-Amiloides/metabolismo , Animais , Encéfalo/diagnóstico por imagem , Humanos , Camundongos , Placa Amiloide/diagnóstico por imagem , Polímero PoliacetilênicoRESUMO
N-methyl-D-aspartate receptors (NMDARs) play critical roles in the physiological function of the mammalian central nervous system (CNS), including learning, memory, and synaptic plasticity, through modulating excitatory neurotransmission. Attributed to etiopathology of various CNS disorders and neurodegenerative diseases, GluN2B is one of the most well-studied subtypes in preclinical and clinical studies on NMDARs. Herein, we report the synthesis and preclinical evaluation of two 11C-labeled GluN2B-selective negative allosteric modulators (NAMs) containing N,N-dimethyl-2-(1H-pyrrolo[3,2-b]pyridin-1-yl)acetamides for positron emission tomography (PET) imaging. Two PET ligands, namely [11C]31 and [11C]37 (also called N2B-1810 and N2B-1903, respectively) were labeled with [11C]CH3I in good radiochemical yields (decay-corrected 28% and 32% relative to starting [11C]CO2, respectively), high radiochemical purity (>99%) and high molar activity (>74 GBq/µmol). In particular, PET ligand [11C]31 demonstrated moderate specific binding to GluN2B subtype by in vitro autoradiography studies. However, because in vivo PET imaging studies showed limited brain uptake of [11C]31 (up to 0.5 SUV), further medicinal chemistry and ADME optimization are necessary for this chemotype attributed to low binding specificity and rapid metabolism in vivo.
Assuntos
Acetamidas/metabolismo , Pirimidinas/metabolismo , Pirróis/metabolismo , Compostos Radiofarmacêuticos/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Acetamidas/síntese química , Acetamidas/farmacocinética , Animais , Encéfalo/metabolismo , Radioisótopos de Carbono/química , Feminino , Ligantes , Masculino , Metilação , Camundongos Endogâmicos ICR , Tomografia por Emissão de Pósitrons , Pirimidinas/síntese química , Pirimidinas/farmacocinética , Pirróis/síntese química , Pirróis/farmacocinética , Compostos Radiofarmacêuticos/síntese química , Compostos Radiofarmacêuticos/farmacocinética , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/antagonistas & inibidoresRESUMO
Selective modulation of metabotropic glutamate receptor 2 (mGlu2) represents a novel therapeutic approach for treating brain disorders, including schizophrenia, depression, Parkinson's disease (PD), Alzheimer's disease (AD), drug abuse and addiction. Imaging mGlu2 using positron emission tomography (PET) would allow for in vivo quantification under physiological and pathological conditions and facilitate drug discovery by enabling target engagement studies. In this paper, we aimed to develop a novel specific radioligand derived from negative allosteric modulators (NAMs) for PET imaging of mGlu2. Methods. A focused small molecule library of mGlu2 NAMs with tetrahydro naphthyridine scaffold was synthesized for pharmacology and physicochemical evaluation. GIRK dose-response assays and CNS panel binding selectivity assays were performed to study the affinity and selectivity of mGlu2 NAMs, among which compounds 14a and 14b were selected as PET ligand candidates. Autoradiography in SD rat brain sections was used to confirm the in vitro binding specificity and selectivity of [11C]14a and [11C]14b towards mGlu2. In vivo binding specificity was then studied by PET imaging. Whole body biodistribution study and radiometabolite analysis were conducted to demonstrate the pharmacokinetic properties of [11C]14b as most promising PET mGlu2 PET ligand. Results. mGlu2 NAMs 14a-14g were synthesized in 14%-20% yields in five steps. NAMs 14a and 14b were selected to be the most promising ligands due to their high affinity in GIRK dose-response assays. [11C]14a and [11C]14b displayed similar heterogeneous distribution by autoradiography, consistent with mGlu2 expression in the brain. While PET imaging study showed good brain permeability for both tracers, compound [11C]14b demonstrated superior binding specificity compared to [11C]14a. Further radiometabolite analysis of [11C]14b showed excellent stability in the brain. Conclusions. Compound 14b exhibited high affinity and excellent subtype selectivity, which was then evaluated by in vitro autoradiography and in vivo PET imaging study after labeling with carbon-11. Ligand [11C]14b, which we named [11C]MG2-1904, demonstrated high brain uptake and excellent in vitro/in vivo specific binding towards mGlu2 with high metabolic stability in the brain. As proof-of-concept, our preliminary work demonstrated a successful example of visualizing mGlu2in vivo derived from NAMs, which represents a promising chemotype for further development and optimization aimed for clinical translation.
Assuntos
Naftiridinas/administração & dosagem , Tomografia por Emissão de Pósitrons/métodos , Ensaio Radioligante/métodos , Compostos Radiofarmacêuticos/administração & dosagem , Receptores de Glutamato Metabotrópico/análise , Regulação Alostérica , Animais , Autorradiografia , Encéfalo/diagnóstico por imagem , Radioisótopos de Carbono , Ligantes , Masculino , Modelos Animais , Naftiridinas/química , Naftiridinas/farmacocinética , Compostos Radiofarmacêuticos/química , Compostos Radiofarmacêuticos/farmacocinética , Ratos , Receptores de Glutamato Metabotrópico/metabolismo , Distribuição TecidualRESUMO
We report the design, synthesis, and evaluation of a series of 1-oxa-8-azaspiro[4.5]decane and 1,5-dioxa-9-azaspiro[5.5]undecane derivatives as selective σ1 receptor ligands. All seven ligands exhibited nanomolar affinity for σ1 receptors (Ki(σ1) = 0.47 - 12.1 nM) and moderate selectivity over σ2 receptors (Ki(σ2)/ Ki(σ1) = 2 - 44). Compound 8, with the best selectivity among these ligands, was selected for radiolabeling and further evaluation. Radioligand [18F]8 was prepared via nucleophilic 18F-substitution of the corresponding tosylate precursor, with an overall isolated radiochemical yield of 12-35%, a radiochemical purity of greater than 99%, and molar activity of 94 - 121 GBq/µmol. Biodistribution studies of [18F]8 in mice demonstrated high initial brain uptake at 2 min. Pretreatment with SA4503 resulted in significantly reduced brain-to-blood ratio (70% - 75% at 30 min). Ex vivo autoradiography in ICR mice demonstrated high accumulation of the radiotracer in σ1 receptor-rich brain areas. These findings suggest that [18F]8 could be a lead compound for further structural modifications to develop potential brain imaging agents for σ1 receptors.
Assuntos
Compostos Aza/farmacocinética , Receptores sigma/análise , Compostos de Espiro/farmacocinética , Animais , Compostos Aza/síntese química , Compostos Aza/química , Encéfalo/diagnóstico por imagem , Relação Dose-Resposta a Droga , Radioisótopos de Flúor/química , Ligantes , Masculino , Camundongos , Camundongos Endogâmicos ICR , Estrutura Molecular , Ensaio Radioligante , Compostos de Espiro/síntese química , Compostos de Espiro/química , Relação Estrutura-Atividade , Distribuição Tecidual , Receptor Sigma-1RESUMO
BACKGROUND & AIMS: The vitronectin receptor integrin αvß3 drives fibrogenic activation of hepatic stellate cells (HSCs). Molecular imaging targeting the integrin αvß3 could provide a non-invasive method for evaluating the expression and the function of the integrin αvß3 on activated HSCs (aHSCs) in the injured liver. In this study, we sought to compare differences in the uptake of [18F]-Alfatide between normal and injured liver to evaluate its utility for assessment of hepatic fibrogenesis. METHODS: PET with [18F]-Alfatide, non-enhanced CT, histopathology, immunofluorescence staining, immunoblotting and gene analysis were performed to evaluate and quantify hepatic integrin αvß3 levels and liver fibrosis progression in mouse models of fibrosis (carbon tetrachloride [CCl4] and bile duct ligation [BDL]). The liver AUC divided by the blood AUC over 30 min was used as an integrin αvß3-PET index to quantify fibrosis progression. Ex vivo analysis of frozen liver tissue from patients with fibrosis and cirrhosis verified the animal findings. RESULTS: Fibrotic mouse livers showed enhanced [18F]-Alfatide uptake and retention compared to control livers. The radiotracer was demonstrated to bind specifically with integrin αvß3, which is mainly expressed on aHSCs. Autoradiography and histopathology confirmed the PET imaging results. Further, the mRNA and protein level of integrin αvß3 and its signaling complex were higher in CCl4 and BDL models than controls. The results obtained from analyses on human fibrotic liver sections supported the animal findings. CONCLUSIONS: Imaging hepatic integrin αvß3 with PET and [18F]-Alfatide offers a potential non-invasive method for monitoring the progression of liver fibrosis. LAY SUMMARY: Integrin αvß3 expression on activated hepatic stellate cells (aHSCs) is associated with HSC proliferation during hepatic fibrogenesis. Herein, we show that a radioactive tracer, [18F]-Alfatide, binds to integrin αvß3 with high affinity and specificity. [18F]-Alfatide could thus be used as a non-invasive imaging biomarker to track hepatic fibrosis progression.
Assuntos
Células Estreladas do Fígado/metabolismo , Integrina alfaVbeta3/metabolismo , Cirrose Hepática , Peptídeos Cíclicos/farmacologia , Tomografia por Emissão de Pósitrons/métodos , Animais , Progressão da Doença , Imunofluorescência/métodos , Radioisótopos de Flúor/farmacologia , Perfilação da Expressão Gênica/métodos , Cirrose Hepática/diagnóstico por imagem , Cirrose Hepática/metabolismo , Cirrose Hepática/patologia , Camundongos , Imagem Molecular/métodos , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) belong to the family of ionotropic transmembrane receptors for glutamate (iGluRs) that are implicated in the pathology of neurological disorders and neurodegenerative diseases. Inspired by a recently developed positive allosteric modulator of AMPARs, 4-cyclopropyl-7-(3-methoxyphenoxy)-3,4-dihydro-2H-benzo[ e ][1,2,4]thiadiazine 1,1-dioxide (16; EC50 = 2.0 nM), we designed a new synthetic route for N-protected phenolic precursor 13 and efficiently radiolabeled a PET ligand [11C]AMPA-1905 ([11C]16) using a modified one-pot two-step strategy in high radiochemical yield and high molar activity. Preliminary in vivo evaluation was carried out to investigate the suitability of [11C]16 as a potential PET probe for AMPAR imaging.
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Cholesterol 24-hydroxylase, also known as CYP46A1 (EC 1.14.13.98), is a monooxygenase and a member of the cytochrome P450 family. CYP46A1 is specifically expressed in the brain where it controls cholesterol elimination by producing 24S-hydroxylcholesterol (24-HC) as the major metabolite. Modulation of CYP46A1 activity may affect Aß deposition and p-tau accumulation by changing 24-HC formation, which thereafter serves as potential therapeutic pathway for Alzheimer's disease. In this work, we showcase the efficient synthesis and preliminary pharmacokinetic evaluation of a novel cholesterol 24-hydroxylase inhibitor 1 for use in positron emission tomography.
Assuntos
Dióxido de Carbono/química , Isótopos de Carbono , Colesterol 24-Hidroxilase/antagonistas & inibidores , Inibidores Enzimáticos/síntese química , Compostos Radiofarmacêuticos/síntese química , Animais , Inibidores Enzimáticos/química , Inibidores Enzimáticos/farmacocinética , Camundongos , Estrutura Molecular , Neuroimagem , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos/química , Compostos Radiofarmacêuticos/farmacocinética , Distribuição TecidualRESUMO
Dysfunction of monoacylglycerol lipase (MAGL) is associated with several psychopathological disorders, including drug addiction and neurodegenerative diseases. Herein we design, synthesize, and evaluate several irreversible fluorine-containing MAGL inhibitors for positron emission tomography (PET) ligand development. Compound 6 (identified from a therapeutic agent) was advanced for 18F-labeling via a novel spirocyclic iodonium ylide (SCIDY) strategy, which demonstrated high brain permeability and excellent specific binding. This work supports further development of novel 18F-labeled MAGL PET probes.