RESUMO
The formation of extracellular amyloid-ß (Aß) plaques is a common molecular change that underlies several debilitating human conditions, including Alzheimer's disease (AD); however, the existing near-infrared (NIR) fluorescent probes for the in vivo detection of Aß plaques are limited by undesirable fluorescent properties and poor brain kinetics. In this work, we designed, synthesized, and evaluated a new family of efficient NIR probes that target Aß plaques by incorporating hydroxyethyl groups into the ligand structure. Among these probes, DANIR 8c showed excellent fluorescent properties with an emission maximum above 670 nm upon binding to Aß aggregates and also displayed a high sensitivity (a 629-fold increase in fluorescence intensity) and affinity (Kd = 14.5 nM). Because of the improved hydrophilicity that was induced by hydroxyls, 8c displayed increased initial brain uptake and a fast washout from the brain, as well as an acceptable biostability in the brain. In vivo NIR fluorescent imaging revealed that 8c could efficiently distinguish between AD transgenic model mice and normal controls. Overall, 8c is an efficient and veritable NIR fluorescent probe for the in vivo detection of Aß plaques in the brain.
Assuntos
Peptídeos beta-Amiloides/análise , Encéfalo/metabolismo , Corantes Fluorescentes/química , Raios Infravermelhos , Imagem Molecular/métodos , Idoso , Doença de Alzheimer/diagnóstico , Doença de Alzheimer/metabolismo , Animais , Encéfalo/patologia , Feminino , Corantes Fluorescentes/síntese química , Humanos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Pessoa de Meia-Idade , Estrutura MolecularRESUMO
A series of 2-arylbenzothiazole derivatives conjugated with bis(aminoethanethiol) (BAT) chelating groups were designed and synthesized. A competitive binding assay-based screening was used to select seven rhenium complexes with potent binding affinity toward Aß1-42 aggregates (Ki < 50 nM) for 99mTc labeling and further evaluation. The 99mTc-labeled probes showed good affinity and specificity to Aß plaques in Tg mouse brain tissue in in vitro autoradiography studies. Moreover, [99mTc]14b exhibited favorable brain pharmacokinetics in normal mice (2.11% ID/g at 2 min and 0.62% ID/g at 60 min). Ex vivo autoradiography revealed extensive labeling of Aß plaques by [99mTc]14b in the brain of Tg mice. Furthermore, we performed the first single-photon emission computed tomography (SPECT) imaging study in nonhuman primates with 99mTc-labeled Aß probes. The semiquantitative data showed that [99mTc]14b penetrated the brains of rhesus monkeys. These results indicate that [99mTc]14b could be utilized as a SPECT imaging probe for Aß plaques.
RESUMO
Cerebral amyloid angiopathy (CAA) is a disorder affecting the elderly that is characterized by amyloid-ß (Aß) deposition in blood vessel walls of the brain. A series of 99mTc(CO)3-labeled benzothiazole derivatives as potential SPECT imaging probes for cerebrovascular Aß deposition is reported. Rhenium surrogate displayed high affinities to Aß aggregates with Ki values ranging from 106 to 42 nM, and they strongly stained Aß deposits in transgenic mice (Tg) and Alzheimer's disease (AD) patients. In vitro autoradiography on brain sections of Tg and AD patients confirmed that [99mTc]24 possessed sufficient affinity for Aß plaques, and [99mTc]24 could only label Aß deposition in blood vessels but not Aß plaques in the parenchyma of the brain of AD patients. Moreover, [99mTc]24 possessed favorable initial uptake (1.21% ID/g) and fast blood washout (blood2 min/blood60 min=23) in normal mice. These preliminary results suggest that [99mTc]24 may be used as an Aß imaging probe for the detection of CAA.
Assuntos
Doença de Alzheimer/diagnóstico por imagem , Benzotiazóis/química , Benzotiazóis/metabolismo , Angiopatia Amiloide Cerebral/diagnóstico por imagem , Placa Amiloide/patologia , Compostos Radiofarmacêuticos/farmacocinética , Compostos de Tecnécio/química , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Animais , Autorradiografia , Encéfalo/metabolismo , Encéfalo/patologia , Encéfalo/efeitos da radiação , Angiopatia Amiloide Cerebral/metabolismo , Angiopatia Amiloide Cerebral/patologia , Feminino , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Pessoa de Meia-Idade , Placa Amiloide/metabolismo , Distribuição Tecidual , Tomografia Computadorizada de Emissão de Fóton ÚnicoRESUMO
The deposition of ß-amyloid (Aß) plaques in the parenchymal and cortical brain is accepted as the main pathological hallmark of Alzheimer's disease (AD); however, early detection of AD still presents a challenge. With the assistance of molecular imaging techniques, imaging agents specifically targeting Aß plaques in the brain may lead to the early diagnosis of AD. Herein, we report the design, synthesis, and evaluation of a series of smart near-infrared fluorescence (NIRF) imaging probes with donor-acceptor architecture bridged by a conjugated π-electron chain for Aß plaques. The chemical structure of these NIRF probes is completely different from Congo Red and Thioflavin-T. Probes with a longer conjugated π system (carbon-carbon double bond) displayed maximum emission in PBS (>650 nm), which falls in the best range for NIRF probes. These probes were proved to have affinity to Aß plaques in fluorescent staining of brain sections from an AD patient and double transgenic mice, as well as in an in vitro binding assay using Aß(1-42) aggregates. One probe with high affinity (K(i) = 37 nM, K(d) = 27 nM) was selected for in vivo imaging. It can penetrate the blood-brain barrier of nude mice efficiently and is quickly washed out of the normal brain. Moreover, after intravenous injection of this probe, 22-month-old APPswe/PSEN1 mice exhibited a higher relative signal than control mice over the same period of time, and ex vivo fluorescent observations confirmed the existence of Aß plaques. In summary, this probe meets most of the requirements for a NIRF contrast agent for the detection of Aß plaques both in vitro and in vivo.
Assuntos
Peptídeos beta-Amiloides/química , Corantes Fluorescentes/química , Raios Infravermelhos , Imagem Óptica/métodos , Fragmentos de Peptídeos/química , Animais , Linhagem Celular , Sobrevivência Celular/efeitos dos fármacos , Desenho de Fármacos , Corantes Fluorescentes/síntese química , Corantes Fluorescentes/toxicidade , Humanos , Camundongos , Multimerização Proteica , Estrutura Secundária de ProteínaRESUMO
Several spirocyclic piperidine derivatives were designed and synthesized as σ1 receptor ligands. In vitro competition binding assays showed that the fluoroalkoxy analogues with small substituents possessed high affinity towards σ1 receptors and subtype selectivity. Particularly for ligand 1'-((6-(2-fluoroethoxy)pyridin-3-yl)methyl)-3H-spiro[2-benzofuran-1,4'-piperidine] (2), high σ1 receptor affinity (Ki=2.30 nM) and high σ1/σ2 subtype selectivity (142-fold) as well as high σ1/VAChT selectivity (234-fold) were observed. [18F]2 was synthesized using an efficient one-pot, two-step reaction method in a home-made automated synthesis module, with an overall isolated radiochemical yield of 8-10%, a radiochemical purity of higher than 99%, and specific activity of 56-78GBq/µmol. Biodistribution studies of [18F]2 in ICR mice indicated high initial brain uptake and a relatively fast washout. Administration of haloperidol, compound 1 and different concentrations of SA4503 (3, 5, or 10 µmol/kg) 5 min prior to injection of [18F]2 significantly decreased the accumulation of radiotracer in organs known to contain σ1 receptors. Ex vivo autoradiography in Sprague-Dawley rats demonstrated high accumulation of radiotracer in brain areas with high expression of σ1 receptors. These encouraging results prove that [18F]2 is a suitable candidate for σ1 receptor imaging with PET in humans.
Assuntos
Imagem Molecular , Piperidinas/síntese química , Piperidinas/metabolismo , Compostos Radiofarmacêuticos/metabolismo , Receptores sigma/análise , Receptores sigma/metabolismo , Compostos de Espiro/química , Animais , Autorradiografia , Ligação Competitiva , Encéfalo/metabolismo , Radioisótopos de Flúor/química , Humanos , Masculino , Camundongos , Camundongos Endogâmicos ICR , Estrutura Molecular , Tomografia por Emissão de Pósitrons , Ensaio Radioligante , Compostos Radiofarmacêuticos/síntese química , Ratos , Ratos Sprague-DawleyRESUMO
A novel series of fluorinated 2-phenylindole derivatives were synthesized and evaluated as ß-amyloid imaging probes for PET. The in vitro inhibition assay demonstrated that their binding affinities for Aß(1-42) aggregates ranged from 28.4 to 1097.8 nM. One ligand was labeled with (18)F ([(18)F]1a) for its high affinity (K(i)=28.4 nM), which was also confirmed by in vitro autoradiography experiments on brain sections of transgenic mouse (C57BL6, APPswe/PSEN1, 11 months old, male). In vivo biodistribution experiments in normal mice showed that this radiotracer displayed high initial uptake (5.82±0.51% ID/g at 2 min) into and moderate washout (2.77±0.31% ID/g at 60 min) from the brain. [(18)F]1a could be developed as a promising new PET imaging probe for Aß plaques although necessary modifications are still needed.
Assuntos
Peptídeos beta-Amiloides/análise , Encéfalo/diagnóstico por imagem , Radioisótopos de Flúor , Indóis , Fragmentos de Peptídeos/análise , Placa Amiloide/diagnóstico , Peptídeos beta-Amiloides/metabolismo , Animais , Encéfalo/metabolismo , Radioisótopos de Flúor/química , Radioisótopos de Flúor/metabolismo , Indóis/síntese química , Indóis/química , Indóis/metabolismo , Masculino , Camundongos , Camundongos Transgênicos , Fragmentos de Peptídeos/metabolismo , Tomografia por Emissão de Pósitrons/métodos , Ligação Proteica , Distribuição TecidualRESUMO
We report the synthesis and evaluation of a series of fluoro-oligo-ethoxylated 4-benzylpiperazine derivatives as potential σ(1) receptor ligands. In vitro competition binding assays showed that 1-(1,3-benzodioxol-5-ylmethyl)-4-(4-(2-fluoroethoxy)benzyl)piperazine (6) exhibits low nanomolar affinity for σ(1) receptors (K(i)=1.85 ± 1.59 nM) and high subtype selectivity (σ(2) receptor: K(i)=291 ± 111 nM; K(i)σ(2)/K(i)σ(1)=157). [(18)F]6 was prepared in 30-50% isolated radiochemical yield, with radiochemical purity of >99% by HPLC analysis after purification, via nucleophilic (18)F(-) substitution of the corresponding tosylate precursor. The logD(pH 7.4) value of [(18)F]6 was found to be 2.57 ± 0.10, which is within the range expected to give high brain uptake. Biodistribution studies in mice demonstrated relatively high concentration of radiotracers in organs known to contain σ(1) receptors, including the brain, lungs, kidneys, heart, and spleen. Administration of haloperidol 5 min prior to injection of [(18)F]6 significantly reduced the concentration of radiotracers in the above-mentioned organs. The accumulation of radiotracers in the bone was quite low suggesting that [(18)F]6 is relatively stable to in vivo defluorination. The ex vivo autoradiography in rat brain showed high accumulation of radiotracers in the brain areas known to possess high expression of σ(1) receptors. These findings suggest that [(18)F]6 is a suitable radiotracer for imaging σ(1) receptors with PET in vivo.
Assuntos
Radioisótopos de Flúor/química , Radioisótopos de Flúor/farmacocinética , Imagem Molecular , Piperazinas/química , Piperazinas/farmacocinética , Receptores sigma/análise , Animais , Autorradiografia , Radioisótopos de Flúor/metabolismo , Masculino , Camundongos , Piperazinas/metabolismo , Ensaio Radioligante , Ratos , Ratos Sprague-Dawley , Receptores sigma/metabolismo , Distribuição Tecidual , Receptor Sigma-1RESUMO
Two uncharged (99m)Tc-labeled phenylbenzoxazole derivatives were biologically evaluated as potential imaging probes for ß-amyloid plaques. The (99m)Tc and corresponding rhenium complexes were synthesized by coupling monoamine-monoamide dithiol (MAMA) and bis(aminoethanethiol) (BAT) chelating ligand via a pentyloxy spacer to phenylbenzoxazole. The fluorescent rhenium complexes 6 and 9 selectively stainined the ß-amyloid plaques on the sections of transgenic mouse, and showed high affinity for Aß((1-42)) aggregates (K(i)=11.1 nM and 14.3 nM, respectively). Autoradiography in vitro indicated that [(99m)Tc]6 clearly labeled ß-amyloid plaques on the sections of transgenic mouse. Biodistribution experiments in normal mice revealed that [(99m)Tc]6 displayed moderate initial brain uptake (0.81% ID/g at 2 min), and quickly washed out from the brain (0.25% ID/g at 60 min). The preliminary results indicate that the properties of [(99m)Tc]6 are promising, although additional refinements are needed to improve the ability to cross the blood-brain barrier.
Assuntos
Peptídeos beta-Amiloides/química , Benzoxazóis/química , Encéfalo/diagnóstico por imagem , Fragmentos de Peptídeos/química , Compostos Radiofarmacêuticos/síntese química , Peptídeos beta-Amiloides/metabolismo , Animais , Benzoxazóis/síntese química , Benzoxazóis/farmacocinética , Complexos de Coordenação/síntese química , Complexos de Coordenação/química , Complexos de Coordenação/farmacocinética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fragmentos de Peptídeos/metabolismo , Compostos Radiofarmacêuticos/química , Compostos Radiofarmacêuticos/farmacocinética , Rênio/química , Tecnécio/química , Distribuição Tecidual , Tomografia Computadorizada de Emissão de Fóton ÚnicoRESUMO
We report the design, synthesis and biological evaluation of a novel (99m)Tc 4-(4-cyclohexylpiperazine-1-yl)-butan-1-one-1-cyclopentadienyltricarbonyl technetium ([(99m)Tc]5) as a potential SPECT tracer for imaging of σ(2) receptors in tumors. [(99m)Tc]5 was prepared in 25±5% isolated radiochemical yield with radiochemical purity of >99% via double-ligand transfer (DLT) reaction from the ferrocene precursor 2b (4-(4-cyclohexylpiperazine-1-yl)-1-ferrocenylbutan-1-one). The corresponding Re-complex 4 and the ferrocenyl complex 2b showed relatively high affinity towards σ(2) receptors in in vitro competition binding assay (K(i) values of 4 and 2b were 64.4±18.5 nM and 43.6±21.3 nM, respectively) and moderate to high selectivity versus σ(1) receptors (K(i)σ(1)/K(i)σ(2) ratios were 12.5 and 95.5, respectively). The logD value of [(99m)Tc]5 was determined to be 2.52±0.33. Biodistribution studies in mice revealed comparably high initial brain uptake of [(99m)Tc]5 and slow washout. Administration of haloperidol 5 min prior to injection of [(99m)Tc]5 significantly reduced the radiotracer uptake in brain, heart, lung, and spleen by 40-50% at 2h p.i.. Moreover, [(99m)Tc]5 showed high uptake in C6 glioma cell lines (8.6%) after incubation for 1h. Blocking with haloperidol to compete with [(99m)Tc]5 significantly reduced the cell uptake. Preliminary blocking study in C6-brain-tumor bearing rats showed that [(99m)Tc]5 binds to σ receptors in the brain-tumor specifically. These results are encouraging for further exploration of (99m)Tc-labeled probes for σ(2) receptor tumor imaging in vivo.
Assuntos
Neoplasias Encefálicas/diagnóstico , Glioma/diagnóstico , Compostos de Organotecnécio , Receptores sigma/análise , Tecnécio , Animais , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Neoplasias Encefálicas/diagnóstico por imagem , Neoplasias Encefálicas/metabolismo , Linhagem Celular Tumoral , Glioma/diagnóstico por imagem , Glioma/metabolismo , Masculino , Camundongos , Compostos de Organotecnécio/química , Compostos de Organotecnécio/metabolismo , Compostos de Organotecnécio/farmacocinética , Cintilografia , Ratos , Ratos Sprague-Dawley , Receptores sigma/metabolismo , Tecnécio/química , Tecnécio/metabolismo , Tecnécio/farmacocinéticaRESUMO
We report the synthesis and biological evaluation of novel (E)-5-styryl-1H-indole and (E)-6-styrylquinoline derivatives as probes for imaging ß-amyloid (Aß) plaques. These derivatives showed binding affinities for Aß1â40 aggregates with K(i) values varying from 4.1 to 288.4 nM. (E)-5-(4-iodostyryl)-1H-indole (8) clearly stained Aß plaques in the brain sections of Alzheimer's disease (AD) model mice (APP/PS1). Furthermore, autoradiography for [¹²5I]8 displayed intense and specific labeling of Aß plaques in the brain sections mentioned above with low background. In biodistribution experiments using normal mice [¹²5I]8 showed high initial brain uptake followed by rapid washout (4.27 and 0.64% ID/g at 2 and 30 min post injection, respectively). These findings suggests that [¹²³I]8 may be a potential SPECT imaging agent for detecting Aß plaques in AD brain.
Assuntos
Encéfalo/patologia , Indóis , Sondas Moleculares , Placa Amiloide/diagnóstico , Quinolinas , Doença de Alzheimer/diagnóstico por imagem , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Animais , Autorradiografia , Feminino , Indóis/química , Indóis/metabolismo , Radioisótopos do Iodo/metabolismo , Camundongos , Camundongos Transgênicos , Sondas Moleculares/química , Sondas Moleculares/metabolismo , Placa Amiloide/metabolismo , Ligação Proteica , Quinolinas/química , Quinolinas/metabolismo , Cintilografia , Coloração e RotulagemRESUMO
Based on the conjugate strategy, two neutral (99m)Tc labeled 2-(1-(6-(dialkylamino)naphthalen-2-yl)ethylidene)malononitrile (DDNP) and 1-(6-(dialkylamino)naphthalen-2-yl)ethanone (ENE) derivatives, and their corresponding rhenium complexes were synthesized. In vitro fluorescent staining indicated that the corresponding rhenium derivatives selectively stained the ß-amyloid (Aß) plaques in the brain sections of AD model mice with low background. Compared with FDDNP and FENE, the affinities of the corresponding rhenium derivatives to Aß aggregates decreased about 10-14-fold. In vivo biodistribution experiments in normal mice showed that (99m)Tc-MAMA-ENE displayed medium initial brain uptake (0.65%ID/g at 2min) with a reasonable washout from the brain (0.19%ID/g at 2h) while (99m)Tc-MAMA-DDNP showed a low brain uptake (0.28%ID/g at 2 min). Further optimize these (99m)Tc-labeled tracers in order to improve their binding affinities to Aß plaques and diffusion through the blood brain barrier may generate useful imaging agents for SPECT.
Assuntos
Peptídeos beta-Amiloides/química , Complexos de Coordenação/química , Naftalenos/química , Compostos de Organotecnécio/química , Compostos Radiofarmacêuticos/química , Rênio/química , Doença de Alzheimer/diagnóstico por imagem , Peptídeos beta-Amiloides/metabolismo , Animais , Encéfalo/metabolismo , Complexos de Coordenação/síntese química , Camundongos , Naftalenos/síntese química , Naftalenos/farmacologia , Compostos Radiofarmacêuticos/síntese química , Distribuição Tecidual , Tomografia Computadorizada de Emissão de Fóton ÚnicoRESUMO
In a search for new probes to detect ß-amyloid plaques in the brain of patients with Alzheimer's disease (AD), we have synthesized and evaluated a series of quinoxaline derivatives containing a '6+6-6' ring system. These quinoxaline derivatives showed excellent affinity for Aß(1-42) aggregates with K(i) values ranging from 2.6 to 10.7nM. Autoradiography with sections of brain tissue from an animal model of AD mice (APP/PS1) and AD patients revealed that [(125)I]5 labeled ß-amyloid plaques specifically. In biodistribution experiments using normal mice, [(125)I]5 displayed high uptake (6.03% ID/g at 2min) into and a moderately fast washout from the brain. Although additional refinements are needed to decrease the lipophilicity and improve the washout rate, the quinoxaline scaffold may be useful as a backbone structure to develop novel ß-amyloid imaging agents.
Assuntos
Peptídeos beta-Amiloides/química , Encéfalo/patologia , Fragmentos de Peptídeos/química , Placa Amiloide/diagnóstico por imagem , Quinoxalinas/química , Compostos Radiofarmacêuticos/química , Doença de Alzheimer/diagnóstico , Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Animais , Autorradiografia , Encéfalo/diagnóstico por imagem , Modelos Animais de Doenças , Humanos , Radioisótopos do Iodo/química , Camundongos , Camundongos Transgênicos , Fragmentos de Peptídeos/metabolismo , Ligação Proteica , Quinoxalinas/farmacocinética , Radiografia , Compostos Radiofarmacêuticos/farmacocinética , Distribuição TecidualRESUMO
We report the synthesis and evaluation of a series of N-benzoylindole derivatives as novel potential imaging agents for ß-amyloid plaques. In vitro binding studies using Aß(1-40) aggregates versus [(125)I]TZDM showed that all these derivatives demonstrated high binding affinities (K(i) values ranged from 8.4 to 121.6 nM). Moreover, two radioiodinated compounds [(125)I]7 and [(125)I]14 were prepared. Autoradiography for [(125)I]14 displayed intense and specific labeling of Aß plaques in the brain sections of AD model mice (C57, APP/PS1) with low background. In vivo biodistribution in normal mice exhibited sufficient initial brain uptake for imaging (2.19% and 2.00%ID/g at 2 min postinjection for [(125)I]7 and [(125)I]14, respectively). Although additional modifications are necessary to improve brain uptake and clearance from the brain, the N-benzoylindole may be served as a backbone structure to develop novel ß-amyloid imaging probes.
Assuntos
Peptídeos beta-Amiloides/metabolismo , Indóis/farmacocinética , Sondas Moleculares/farmacocinética , Placa Amiloide/metabolismo , Animais , Encéfalo/metabolismo , Relação Dose-Resposta a Droga , Indóis/química , Indóis/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Sondas Moleculares/química , Sondas Moleculares/metabolismo , Estrutura Molecular , Estereoisomerismo , Relação Estrutura-Atividade , Distribuição TecidualRESUMO
A series of benzofuran-2-yl(phenyl)methanone derivatives were synthesized and evaluated as novel probes for ß-amyloid plaques. These derivatives were produced by a Rap-Stoermer condensation reaction. Compounds with a N,N-dimethylamino group displayed high affinity for Aß(1-42) aggregates with K(i) values in the nanomolar range. Autoradiography with brain sections of AD model mice (APP/PS1) revealed that a radioiodinated probe, [(125)I]10, labeled ß-amyloid plaques selectively and displayed good brain uptake (3.53% ID/g) at 2 min. The results suggest that benzofuran-2-yl(phenyl)methanone derivatives should be investigated further as potential probes for detecting ß-amyloid plaques in the AD brain.
Assuntos
Doença de Alzheimer/diagnóstico por imagem , Peptídeos beta-Amiloides/análise , Compostos de Anilina/química , Benzofuranos/química , Fragmentos de Peptídeos/análise , Placa Amiloide/diagnóstico por imagem , Compostos Radiofarmacêuticos/química , Compostos de Anilina/síntese química , Compostos de Anilina/farmacocinética , Animais , Autorradiografia , Benzofuranos/síntese química , Benzofuranos/farmacocinética , Encéfalo/metabolismo , Encéfalo/patologia , Radioisótopos do Iodo/química , Ligantes , Camundongos , Ligação Proteica , Cintilografia , Compostos Radiofarmacêuticos/síntese química , Compostos Radiofarmacêuticos/metabolismo , Distribuição TecidualRESUMO
We report the synthesis and evaluation of 4-benzylpiperazine ligands (BP-CH(3), BP-F, BP-Br, BP-I, and BP-NO(2)) as potential σ(1) receptor ligands. The X-ray crystal structure of BP-Br, which crystallized with monoclinic space group P2(1)/c, has been determined. In vitro competition binding assays showed that all the five ligands exhibit low nanomolar affinity for σ(1) receptors (K(i)=0.43-0.91nM) and high subtype selectivity (σ(2) receptor: K(i)=40-61nM; K(i)σ(2)/K(i)σ(1)=52-94). [(125)I]BP-I (1-(1,3-benzodioxol-5-ylmethyl)-4-(4-iodobenzyl)piperazine) was prepared in 53±10% isolated radiochemical yield, with radiochemical purity of >99% by HPLC analysis after purification, via iododestannylation of the corresponding tributyltin precursor. The logD value of [(125)I]BP-I was found to be 2.98±0.17, which is within the range expected to give high brain uptake. Biodistribution studies in mice demonstrated relatively high concentration of radiolabeled substances in organs known to contain σ(1) receptors, including the brain, lung, kidney, heart, and spleen. Administration of haloperidol 5min prior to injection of [(125)I]BP-I significantly reduced the concentration of radioactivity in the above-mentioned organs. The accumulation of radiolabeled substance in the thyroid was quite low suggesting that [(125)I]BP-I is relatively stable to in vivo deiodination. These findings suggest that the binding of [(125)I]BP-I to σ(1) receptors in vivo is specific.
Assuntos
Piperazinas/química , Compostos Radiofarmacêuticos/síntese química , Receptores sigma/química , Animais , Cristalografia por Raios X , Feminino , Haloperidol/farmacologia , Ligantes , Camundongos , Camundongos Endogâmicos ICR , Conformação Molecular , Piperazina , Piperazinas/síntese química , Piperazinas/metabolismo , Compostos Radiofarmacêuticos/química , Compostos Radiofarmacêuticos/metabolismo , Receptores sigma/metabolismo , Distribuição Tecidual , Compostos de Trialquitina/química , Receptor Sigma-1RESUMO
Galactosylated chitosan (GC) was prepared by reacting lactobionic acid with water-soluble chitosan. GC was labeled with fluorine-18 by conjugation with N-succinimidyl-4-(18)F-fluorobenzoate ([(18)F]SFB) under a slightly basic condition. After rapid purification with HiTrap desalting column, [(18)F]FB-GC was obtained with high radiochemical purity (>97%) determined by radio-HPLC. The total reaction time for [(18)F]FB-GC was about 150 min. Typical decay-corrected radiochemical yield was about 4-8%. Ex vivo biodistribution in normal mice showed that [(18)F]FB-GC had moderate activity accumulation in liver with very good retention (11.13+/-1.63, 10.97+/-1.90 and 10.77+/-0.95%ID/g at 10, 60, 120 min after injection, respectively). The other tissues except kidney showed relative low radioactivity accumulation. The high liver/background ratio affords promising biological properties to get clear images. The specific binding of this radiotracer to the ASGP receptor was confirmed by blocking experiment in mice. Compared with the non-blocking group the hepatic uptake of [(18)F]FB-GC significantly declined in all selected time points. The better liver retention properties of [(18)F]FB-GC than that of albumin based imaging agents may improve imaging quality and simplify pharmacokinetic model of liver function in the future application with PET imaging.
Assuntos
Receptor de Asialoglicoproteína/metabolismo , Quitosana/análogos & derivados , Quitosana/química , Fígado/metabolismo , Compostos Radiofarmacêuticos/química , Animais , Radioisótopos de Flúor/química , Glicosilação , Hepatócitos/metabolismo , Fígado/diagnóstico por imagem , Camundongos , Tomografia por Emissão de Pósitrons , Compostos Radiofarmacêuticos/síntese química , Compostos Radiofarmacêuticos/farmacocinética , Distribuição TecidualRESUMO
In this study, six novel benzothiazole derivatives based on the bithiophene structure were developed as potential beta-amyloid probes. In vitro binding studies using Abeta aggregates showed that all of them demonstrated high binding affinities with K(i) values ranged from 0.11 to 4.64nM. In vitro fluorescent staining results showed that these compounds can intensely stained Abeta plaques within brain sections of APP/PS1 transgenic mice, animal model for AD. Two radioiodinated compounds [(125)I]-2-(5'-iodo-2,2'-bithiophen-5-yl)-6-methoxybenzo[d]thiazole [(125)I]10 and [(125)I]-2-(2,2'-bithiophen-5-yl)-6-iodobenzo[d]thiazole [(125)I]13 were successfully prepared through an iododestannylation reaction. Furthermore, in vitro autoradiography of the AD model mice brain sections showed that both [(125)I]10 and [(125)I]13 labeled the Abeta plaques specifically with low background. In vivo biodistribution studies in normal mice indicated that [(125)I]13 exhibited high brain uptake (3.42% ID/g at 2min) and rapid clearance from the brain (0.53% ID/g at 60min), while [(125)I]10 showed lower brain uptake (0.87% ID/g at 2min). In conclusion, these preliminary results of this study suggest that the novel radioiodinated benzothiazole derivative [(125)I]13 may be a candidate as an in vivo imaging agent for detecting beta-amyloid plaques in the brain of AD patients.
Assuntos
Doença de Alzheimer/diagnóstico por imagem , Peptídeos beta-Amiloides/fisiologia , Benzotiazóis/síntese química , Placa Amiloide/diagnóstico por imagem , Compostos Radiofarmacêuticos/síntese química , Tiofenos/química , Peptídeos beta-Amiloides/genética , Animais , Autorradiografia , Benzotiazóis/farmacocinética , Encéfalo/diagnóstico por imagem , Cromatografia Líquida de Alta Pressão , Feminino , Injeções Intravenosas , Radioisótopos do Iodo , Ligantes , Camundongos , Camundongos Transgênicos , Cintilografia , Compostos Radiofarmacêuticos/farmacocinética , Solubilidade , Distribuição TecidualRESUMO
A group of novel 4,5-dianilinophthalimide derivatives has been synthesized in this study for potential use as beta-amyloid (Abeta) plaque probes. Staining of hippocampus tissue sections from Alzheimer's disease (AD) brain with the representative compound 9 indicated selective labeling of it to Abeta plaques. The binding affinity of radioiodinated [(125)I]9 for AD brain homogenates was 0.21 nM (K(d)), and of other derivatives ranged from 0.9 to 19.7 nM, except for N-methyl-4,5-dianilinophthalimide (K(i)>1000 nM). [(125)I]9 possessed the optimal lipophilicity with LogP value of 2.16, and its in vivo biodistribution in normal mice exhibited excellent initial brain uptake (5.16% ID/g at 2 min after injection) and a fast washout rate (0.56% ID/g at 60 min). The encouraging results suggest that this novel derivative of [(123)I]9 may have potential as an in vivo SPECT probe for detecting amyloid plaques in the brain.
Assuntos
Doença de Alzheimer/diagnóstico por imagem , Peptídeos beta-Amiloides/metabolismo , Compostos de Anilina , Encéfalo/diagnóstico por imagem , Ftalimidas , Tomografia Computadorizada de Emissão de Fóton Único/métodos , Compostos de Anilina/química , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Humanos , Camundongos , Ftalimidas/químicaRESUMO
The interaction of human serum albumin and folic acid was studied using fluorescence spectroscopy, UV absorption and synchronous fluorescence spectroscopy in the pH 7.4 Tris-HCl buffer system at different temperatures. The research shows that these interactions result in the endogenous fluorescence quenching of HSA, which belongs to a static quenching mechanism. The quenching rate constants, the binding constants and the binding sites of the static quenching were calculated. The distance between the body (HSA) and receptor (folic acid) and the efficiency of energy transfer were obtained to be 1.77 nm and 0. 052 65 respectively, based on the theory of Forster nonradiative energy transfer. And according to the thermodynamic parameters calculated the binding of HSA and folic acid is mainly attributed to the hydrophobic interaction, partly static force. Further more the synchronous fluorescence spectrum was utilized to investigate the conformational transformation; The decline result of the hydrophobic nature around Trp demonstrates that the folic acid is in the hydrophobic cavity of HSA.
Assuntos
Ácido Fólico/química , Ácido Fólico/metabolismo , Albumina Sérica/química , Albumina Sérica/metabolismo , Transferência de Energia , Humanos , Ligação Proteica , Espectrometria de Fluorescência , Espectrofotometria UltravioletaRESUMO
The benzothiazole aniline (BTA) conjugated with monoamine-monoamide (MAMA) was synthesized and then labeled with (99m)Tc. Its corresponding rhenium analogue was synthesized, and the fluorescent staining was performed in brain sections of both Tg mouse and Alzheimer's disease (AD) patient. The fluorescent rhenium complex Re-MAMA-BTA selectively bound to the amyloid aggregates in the brain sections of both APP Tg mouse and AD patient. The analogous (99m)Tc-MAMA-BTA complex could enter the normal mouse brain with high initial uptake. These results are encouraging for further exploration of their derivatives as imaging agents for Abeta plaques in the brain.