RESUMEN
Heparan Sulfate (HS) mimetics are able to block crucial interactions of the components of the extracellular matrix in angiogenic processes and as such, represent a valuable class of original candidates for cancer therapy. Here we first report the synthesis and in vitro angiogenic inhibition properties of a conjugated, novel and rationally-designed octasaccharide-based HS mimetic. We also herein report its labeling with fluorine-18 and present the preliminary in vivo Positron Emission Tomography imaging data in rats. This constitutes one of the rare examples of labeling and in vivo evaluation of a synthetic, polysaccharide-based, macromolecule.
Asunto(s)
Inhibidores Enzimáticos/farmacología , Inhibidores Enzimáticos/uso terapéutico , Glucuronidasa/antagonistas & inhibidores , Heparitina Sulfato/química , Neoplasias/tratamiento farmacológico , Neovascularización Patológica/diagnóstico , Neovascularización Patológica/tratamiento farmacológico , Animales , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Ensayos de Selección de Medicamentos Antitumorales , Inhibidores Enzimáticos/síntesis química , Inhibidores Enzimáticos/química , Radioisótopos de Flúor , Glucuronidasa/metabolismo , Humanos , Masculino , Estructura Molecular , Neoplasias/irrigación sanguínea , Neoplasias/patología , Neovascularización Patológica/patología , Polisacáridos/química , Tomografía de Emisión de Positrones , Ratas , Ratas Wistar , Relación Estructura-ActividadRESUMEN
Positron emission tomography (PET) coupled to 6-[18F]Fluoro-L-Dopa (18F-Dopa) remains the gold standard for assessing dysfunctionality concerning the dopaminergic nigrostriatal pathway in Parkinson's disease and related disorders. The use of ligands of the dopamine transporters (DAT) is an attractive alternative target; consequently, the current aim was to validate one of them, 11C-PE2I, using a multiinjection modeling approach allowing accurate quantitation of DAT densities in the striatum. Experiments were performed in three controls, three MPTP-treated (parkinsonian) baboons, and one reserpine-treated baboon. 11C-PE2I B'max values obtained with this approach were compared with 18F-Dopa input rate constant values (Ki), in vitro Bmax binding of 125I-PE2I, and the number of dopaminergic neurons in the substantia nigra estimated postmortem by stereology. In the caudate nucleus and putamen, control values for 11C-PE2I B'max were 673 and 658 pmol/mL, respectively, whereas it was strongly reduced in the MPTP-treated (B'max = 26 and 36 pmol/mL) and reserpine-treated animals (B'max = 338 and 483 pmol/mL). In vivo 11C-PE2I B'max values correlated with 18F-Dopa Ki values and in vitro 125I-PE2I Bmax values in the striatum and with the number of nigral dopaminergic neurons. Altogether, these data support the use of 11C-PE2I for monitoring striatal dopaminergic disorders and the effect of potential neuroprotective strategies.
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Encéfalo/metabolismo , Proteínas Portadoras/análisis , Dihidroxifenilalanina/metabolismo , Glicoproteínas de Membrana , Proteínas de Transporte de Membrana , Proteínas del Tejido Nervioso , Nortropanos/metabolismo , Enfermedad de Parkinson Secundaria/metabolismo , 1-Metil-4-fenil-1,2,3,6-Tetrahidropiridina/administración & dosificación , Animales , Química Encefálica , Radioisótopos de Carbono , Proteínas Portadoras/metabolismo , Núcleo Caudado/química , Núcleo Caudado/metabolismo , Cerebelo/química , Cerebelo/metabolismo , Cuerpo Estriado/química , Dihidroxifenilalanina/análogos & derivados , Proteínas de Transporte de Dopamina a través de la Membrana Plasmática , Radioisótopos de Flúor , Cinética , Ligandos , Papio , Enfermedad de Parkinson Secundaria/inducido químicamente , Enfermedad de Parkinson Secundaria/patología , Putamen/química , Putamen/metabolismo , Reserpina/administración & dosificación , Sustancia Negra/química , Sustancia Negra/metabolismo , Tomografía Computarizada de Emisión , Tirosina 3-Monooxigenasa/análisisRESUMEN
UNLABELLED: Ca(2+) channels play a key role in the basic working of the heart. There is one particular type of Ca(2+) channel in cardiac cells (L-type) whose gating is affected in different ways by beta-adrenoceptors and 1,4-dihydropyridines. In this study, we used ex vivo studies and PET to evaluate and compare the myocardial kinetics of the enantiomers labeled with (11)C (the more active: S12968, absolute configuration S; the less active: S12967, absolute configuration R) of the L-type Ca(2+) channel antagonist S11568 (3-ethyl 5-methyl (+/-)-2-[(2-(2-aminoethoxy)ethoxy) methyl]-4-(2,3-dichlorophenyl)-6-methyl-1,4-dihydropyridine-3,5-dicarboxylate). METHODS: [(11)C]S12968 was injected into the tail vein of rats (0.22 kBq--5.92 MBq) to assess the relationship between injected dose and myocardial uptake. A series of 5 rats was pretreated with 4 micromol unlabeled S12968 5 min before injection of 2.2 kBq [(11)C]S12968. In another series of 5 rats, unlabeled S12698 (4 micromol) was injected 5 min after injection of 2.2 kBq [(11)C]S12968. The animals were killed 15 min later, and the myocardial radioactivity was assessed in a gamma well counter. Beagle dogs received injections of 5-15 nmol [(11)C]S12968 or [(11)C]S12967 and were imaged with PET. Presaturation and displacement experiments using 2 micromol/kg unlabeled S12968 or 6 mol/kg S12967 were performed. RESULTS: In rats, a statistically significant relationship between myocardial uptake and injected dose of S12968 was observed. Pretreatment or displacement with unlabeled S12968 reduced myocardial radioactivity by 75% and 70%, respectively. In dogs, after injection of 5 nmol of each enantiomer, myocardial radioactivity plateaued within 3 min and the clearance from blood was rapid. Injection of 13--15 nmol [(11)C]S12968 led to a higher myocardial uptake and a more rapid washout, which were related to an increased coronary blood flow as shown by the linear relationship between k(1)--an estimate of coronary blood flow--and the mass of S12968 injected. Presaturation and displacement experiments showed that 70%--80% of S12968 binding was specific. This specificity was not observed with S12967. Plasma metabolite analysis showed that 70% of the compound was unchanged 20 min after injection. CONCLUSION: These results show the feasibility of imaging myocardial L-type Ca(2+) channels in vivo using [(11)C]S12968.
Asunto(s)
Bloqueadores de los Canales de Calcio , Radioisótopos de Carbono , Dihidropiridinas , Corazón/diagnóstico por imagen , Tomografía Computarizada de Emisión , Animales , Bloqueadores de los Canales de Calcio/farmacocinética , Radioisótopos de Carbono/farmacocinética , Circulación Coronaria , Dihidropiridinas/farmacocinética , Perros , Femenino , Masculino , Miocardio/metabolismo , Ratas , Ratas Sprague-Dawley , Distribución TisularRESUMEN
OBJECTIVE: The study assessed striatal presynaptic dopamine function in patients with different subtypes of depression. METHOD: Magnetic resonance imaging and positron emission tomography with [(18)F]fluorodopa ([(18)F]DOPA) were used to compare six depressed patients with marked affective flattening and psychomotor retardation, six depressed patients with marked impulsivity and anxiety, and 10 healthy comparison subjects. Depressed patient groups were matched for severity of depression. RESULTS: [(18)F]DOPA uptake K(i) values in the left caudate were significantly lower in patients with psychomotor retardation than in patients with high impulsivity and in comparison subjects. CONCLUSIONS: These results suggest that left caudate dopamine function differs between depressed patients with psychomotor retardation and those with impulsivity and provide direct evidence of a link between dopamine hypofunction and psychomotor retardation in depression.
Asunto(s)
Núcleo Caudado/metabolismo , Trastorno Depresivo/diagnóstico , Trastorno Depresivo/metabolismo , Dopamina/metabolismo , Lateralidad Funcional , Adulto , Núcleo Caudado/diagnóstico por imagen , Núcleo Caudado/fisiopatología , Trastorno Depresivo/psicología , Dihidroxifenilalanina/análogos & derivados , Dopamina/fisiología , Femenino , Humanos , Masculino , Persona de Mediana Edad , Terminales Presinápticos/diagnóstico por imagen , Terminales Presinápticos/metabolismo , Escalas de Valoración Psiquiátrica/estadística & datos numéricos , Cintigrafía , Índice de Severidad de la EnfermedadRESUMEN
Evaluation of oligonucleotides for biomedical applications requires different in vivo and in vitro approaches (pharmacokinetics, biodistribution, macro- and microimaging, metabolism,.), that are performed with different radioisotopes according to the temporal and spatial resolution needed. A method to introduce radioactive isotopes of halogens (fluorine, bromine, and iodine) in a small and stable molecule has been developed. Radiosynthons can then be conjugated with any given oligonucleotide in one step to create the appropriate radiotracer. This general radiolabeling procedure for oligonucleotides is efficient to synthesize (18)F-, (76)Br-, and (125)I-oligonucleotides for biological needs. Applications of the method to biodistribution, metabolism, in vivo and ex vivo imaging of (125)I- and (18)F-labeled oligonucleotides are reported.
Asunto(s)
Oligodesoxirribonucleótidos Antisentido/síntesis química , Oligodesoxirribonucleótidos Antisentido/farmacocinética , Animales , Autorradiografía , Secuencia de Bases , Radioisótopos de Bromo/farmacocinética , Cromatografía Líquida de Alta Presión/métodos , Radioisótopos de Flúor/farmacocinética , Humanos , Radioisótopos de Yodo/farmacocinética , Marcaje Isotópico/métodos , Masculino , Ratas , Ratas Sprague-Dawley , Distribución Tisular , Tomografía Computarizada de Emisión/métodosRESUMEN
The lead compound of a new series of 3-pyridyl ethers, the azetidine derivative A-85380 (3-[(S)-2-azetidinylmethoxy]pyridine), is a potent and selective ligand for the human alpha4beta2 nicotinic acetylcholine receptor (nAChR) subtype. In vitro, the fluoro derivative of A-85380 (2-fluoro-3-[(S)-2-azetidinylmethoxy]pyridine or F-A-85380) competitively displaced [3H]cytisine or [3H]epibatidine with Ki values of 48 and 46 pM, respectively. F-A-85380 has been labeled with the positron emitter fluorine-18 (t1/2 (half-life) = 110 min) by no-carrier-added nucleophilic aromatic substitution by K[18F]F-K222 complex with (3-[2(S)-N-(tert-butoxycarbonyl)-2-azetidinylmethoxy]pyridin-2-yl) tri methylammonium trifluoromethanesulfonate as a highly efficient labeling precursor, followed by TFA removal of the Boc protective group. The total synthesis time was 50-53 min from the end of cyclotron fluorine-18 production (EOB). Radiochemical yields, with respect to initial [18F]fluoride ion radioactivity, were 68-72% (decay-corrected) and 49-52% (non-decay-corrected), and the specific radioactivities at EOB were 4-7 Ci/micromol (148-259 GBq/micromol). In vivo characterization of [18F]F-A-85380 showed promising properties for PET imaging of central nAChRs. This compound does not bind in vivo to alpha7 nicotinic or 5HT3 receptors. Moreover, its cerebral uptake can be modulated by the synaptic concentration of the endogenous ligand acetylcholine. The preliminary PET experiments in baboons with [18F]F-A-85380 show an accumulation of the radiotracer in the brain within 60 min. In the thalamus, a nAChR-rich area, uptake of radioactivity reached a maximum at 60 min (4% I.D./100 mL of tissue). [18F]F-A-85380 appears to be a suitable radioligand for brain imaging nAChRs with PET.
Asunto(s)
Azetidinas/síntesis química , Piridinas/síntesis química , Radiofármacos/síntesis química , Receptores Nicotínicos/metabolismo , Animales , Azetidinas/química , Azetidinas/metabolismo , Azetidinas/farmacocinética , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Radioisótopos de Flúor , Humanos , Ligandos , Masculino , Papio , Piridinas/química , Piridinas/metabolismo , Piridinas/farmacocinética , Radiofármacos/química , Radiofármacos/metabolismo , Radiofármacos/farmacocinética , Ratas , Ratas Sprague-Dawley , Distribución Tisular , Tomografía Computarizada de EmisiónRESUMEN
(+/-)-3-[11C]Methyl-2-[4-[3-(tert-butylamino)-2-hydroxypropoxy]phenyl]-6 -methoxy-4(3H) quinazolinone ([+/-]-[11C]HX-CH 44) was labeled with carbon-11 using [11C]iodomethane with the corresponding N-demethylated precursor. Then, 30-90 mCi (1.10-3.33 GBq) of pure [11C]HX-CH 44 were obtained 30 min after end of bombardment with specific radioactivities of 500-1,400 mCi/micromol (18.5-51.8 GBq/micromol). Myocardial uptake in dogs was 0.340+/-0.043 pmol/mL tissue per nanomole injected, 10-15 min postinjection. Heart-to-lung ratio was 3 from the 5th to the 30th minute. Only 35% of the myocardial radioactivity could be displaced. Tissue uptake could not be blocked with appropriate compounds. Therefore, (+/-)-[11C]HX-CH 44 does not appear to be a suitable ligand for the study of myocardial beta1-adrenoceptors in positron emission tomography.
Asunto(s)
Antagonistas Adrenérgicos beta , Corazón/diagnóstico por imagen , Pulmón/diagnóstico por imagen , Propanolaminas , Radiofármacos/síntesis química , Receptores Adrenérgicos beta 1/análisis , Antagonistas Adrenérgicos beta/sangre , Antagonistas Adrenérgicos beta/farmacología , Animales , Radioisótopos de Carbono , Perros , Ligandos , Propanolaminas/sangre , Propanolaminas/farmacología , Quinazolinonas , Ratas , Ratas Sprague-Dawley , Receptores Adrenérgicos beta 1/efectos de los fármacos , Tomografía Computarizada de EmisiónRESUMEN
The biodistribution of the nicotinic acetylcholine receptor (nAChR) radioligand 2-[18F]fluoro-3-[2(S)-2-azetidinylmethoxy]pyridine ([18F]fluoro-A-85380, half-life of fluorine-18 = 110 min) in selected rat brain areas was assessed in vivo. The radiotracer showed a good penetration in the brain. The regional distribution of the radioligand was consistent with the density of nAChRs determined from previous studies in vitro. Sixty minutes post-injection, the highest uptake was observed in the thalamus, (1% I.D./g tissue), an intermediate one in the frontal cortex (0.78% I.D./g tissue), and the lowest in the cerebellum (0.5% I.D./g tissue). Pretreatment with several nAChR ligands (nicotine, cytisine, epibatidine, unlabeled fluoro-A-85380) substantially reduced uptake of the radioligand in the three cerebral areas. Pretreatment with the nAChR channel blocker mecamylamine or with the muscarinic receptor antagonist dexetimide had no appreciable effect on the uptake of fluoro-A-85380. These results support the high in vivo selectivity and specificity of fluoro-A-85380. Therefore, [18F]fluoro-A-85380 may be useful for positron emission tomography study of nAChRs in humans.
Asunto(s)
Azetidinas/farmacocinética , Encéfalo/metabolismo , Receptores Nicotínicos/metabolismo , Alcaloides/farmacología , Animales , Azocinas , Unión Competitiva , Compuestos Bicíclicos Heterocíclicos con Puentes/farmacología , Cerebelo/metabolismo , Radioisótopos de Flúor/farmacocinética , Lóbulo Frontal/metabolismo , Cinética , Ligandos , Masculino , Mecamilamina/farmacología , Nicotina/farmacología , Agonistas Nicotínicos/farmacología , Piridinas/farmacología , Quinolizinas , Ensayo de Unión Radioligante , Ratas , Ratas Sprague-Dawley , Receptores Nicotínicos/análisis , Receptores Nicotínicos/efectos de los fármacos , Tálamo/metabolismo , Distribución TisularRESUMEN
[11C]S11568 (3-ethyl-5-methyl 2-[2-(2-aminoethoxy)ethoxymethyl]-4-(2,3-dichlorophenyl)-6-methyl- 1,4-dihydropyridine-3,5-dicarboxylate) is a powerful ligand for the visualization of the cardiac calcium channel in vivo using PET. The aim of the present study was to synthesize a lipophilic, nonionized derivative of S11568 to facilitate its penetration into the brain. To increase the lipophilicity and to remove simultaneously the ionic nature of our ligand, the N-tert-butoxycarbonyl (N-Boc) derivative of S11568 was synthesized. An IC50 value of 1.7 nM for this derivative confirmed that both the affinity and selectivity for the calcium channel was unaltered by this chemical modification (S11568 with IC50 value of 9.9 nM). The biologically more active enantiomer of S11568, the levogyre isomer S12968, was labelled with 11C using [11C]iodomethane. The lipophilicity of the N-Boc derivative was increased by a factor of three to four when compared to the parent compound (as determined by the measurement of the octanol/buffer partition coefficients). In vivo, this derivative slightly crosses the blood-brain barrier, as demonstrated by a 4-fold increase (with respect to the parent compound S12968) of the radioactivity in the brain using the 11C-labelled N-Boc S12968. This uptake remained too low to be suitable for imaging calcium channels.
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Encéfalo/metabolismo , Bloqueadores de los Canales de Calcio/síntesis química , Bloqueadores de los Canales de Calcio/farmacocinética , Canales de Calcio/metabolismo , Dihidropiridinas/síntesis química , Dihidropiridinas/farmacocinética , Animales , Barrera Hematoencefálica , Bloqueadores de los Canales de Calcio/química , Dihidropiridinas/química , Masculino , Ratas , Ratas Sprague-Dawley , Estereoisomerismo , Relación Estructura-Actividad , Distribución Tisular , Tomografía Computarizada de EmisiónAsunto(s)
Radioisótopos de Flúor/farmacocinética , Oligodesoxirribonucleótidos/farmacocinética , Tomografía Computarizada de Emisión/métodos , Animales , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Corazón/diagnóstico por imagen , Riñón/diagnóstico por imagen , Riñón/metabolismo , Hígado/diagnóstico por imagen , Hígado/metabolismo , Masculino , Miocardio/metabolismo , Oligodesoxirribonucleótidos/síntesis química , Papio , Radiofármacos/farmacocinética , Reproducibilidad de los Resultados , Tionucleótidos , Distribución Tisular , Tomografía Computarizada de Emisión/instrumentaciónRESUMEN
(+/-)-S11568 (1, 3-ethyl-5-methyl-(+/-)-2-[(2-(2-aminoethoxy)ethoxy) methyl]-4-(2,3-dichlorophenyl)-6-methyl-1,4-dihydropyridine-3, 5-dicarboxylate), has an in vitro profile of high potency and of high selectivity for the low-voltage dependent. L-type calcium channel. In in vitro binding studies, it displaced specifically bound (-)-[3H]PN 200-110 (isradipine (2), the reference molecule for in vitro studies) from cardiac and vascular smooth muscle preparations with potencies of 5.6 and 51 nM, respectively. It also appears as a pure pharmacological antagonist acting at a single channel L-type and free of any interaction at the benzothiazepine binding site such as amlodipine (3). Both enantiomers of S11568 have in vitro activities, the dextro isomer S12967 ((+)-1) being 6 to 18-fold less potent than the levo one S12968 ((-)-1). Two couples of optically active labelling precursors of S11568, ((-)-10/(+)-10 and (-)-14/(+)-14) have been synthesized using a modified Hantzsch's dihydropyridine synthesis. In both cases, the enantiomers were separated by preparative chiral HPLC. They both have been independently labelled with carbon-11, using [11C]diazomethane or [11C]iodomethane to give multimilliCurie quantities of (-)-1 (S12968) and (+)-1 (S12967) with high specific activities (500-1000 mCi/mumol, 18.5-37.0 GBq/mumol). Both enantiomers appear suitable for PET experiments: their myocardial concentration increases after a bolus injection to reach a maximum in 2 min and then remains on a plateau with a slight downslope while the blood concentration falls rapidly. Myocardial uptake was threefold higher than lung uptake, leading to a good contrast on PET images. The present preliminary biological results obtained in Beagle dogs showed that both enantiomers have similar myocardial kinetics and in vivo affinity for the left ventricular myocardium.
Asunto(s)
Bloqueadores de los Canales de Calcio/síntesis química , Dihidropiridinas/síntesis química , Corazón/diagnóstico por imagen , Tomografía Computarizada de Emisión/métodos , Amlodipino/química , Amlodipino/metabolismo , Animales , Unión Competitiva , Bloqueadores de los Canales de Calcio/química , Bloqueadores de los Canales de Calcio/metabolismo , Bloqueadores de los Canales de Calcio/farmacología , Radioisótopos de Carbono , Cromatografía Líquida de Alta Presión , Dihidropiridinas/química , Dihidropiridinas/metabolismo , Dihidropiridinas/farmacología , Perros , Corazón/efectos de los fármacos , Cardiopatías/diagnóstico por imagen , Marcaje Isotópico , Isradipino/química , Isradipino/metabolismo , Espectroscopía de Resonancia Magnética , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/metabolismo , Miocardio/metabolismo , Reproducibilidad de los Resultados , EstereoisomerismoRESUMEN
Physostigmine, a powerful cholinesterase inhibitor, has recently been labelled with 11C in view of its potential application for in vivo imaging of cerebral acetylcholinesterase (AChE) using positron emission tomography. Here we carried out autoradiography of the rat brain using [11C]physostigmine in order to characterize the cerebral targets of this ligand. Autoradiograms were obtained using phosphor storage plates which, compared to autoradiographic films, greatly improved the quality of 11C images. Following autoradiography, brain sections were stained for AChE activity, allowing a direct comparison of autoradiographic and histoenzymatic localizations. The distributions of 11C label and of AChE activity were found to be essentially super-imposable, both after in vivo injection of and after in vitro incubation with [11C]physostigmine. Densitometric analysis showed that radioactivity and enzymatic activity distributions were regionally correlated. The fixation of [11C]physostigmine to cerebral tissue was abolished after incubation of the rat brain sections with BW 284C51, a specific AChE inhibitor, but not after incubation with iso-OMPA, a specific inhibitor of butyrylcholinesterase. Unilateral excitotoxic lesions of the striatum that eliminated local AChE expression concomitantly reduced the binding of the ligand in the lesioned area. These results indicate that autoradiographic images of the rat brain obtained with [11C]physostigmine reflect AChE distribution, thus supporting the use of this radioligand to trace cerebral AChE activity in humans with positron emission tomography.