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1.
Neuroimage ; : 120778, 2024 Aug 07.
Artículo en Inglés | MEDLINE | ID: mdl-39122057

RESUMEN

BACKGROUND: Clinical and translational research has identified deficits in the dopaminergic neurotransmission in the striatum in Alzheimer's disease (AD) and this could be related to the pathophysiology of psychiatric symptoms appearing even at early stages of the pathology. HYPOTHESIS: We hypothesized that AD pathology in the hippocampus may influence dopaminergic neurotransmission even in the absence of AD-related lesion in the mesostriatal circuit. METHODS: We chemogenetically manipulated the activity of hippocampal neurons and astrocytes in wild-type and hemizygous TgF344-AD (Tg) rats, an animal model of AD pathology. We assessed the brain-wide functional output of this manipulation using in vivo Single Photon Emission Computed Tomography to measure cerebral blood flow and D2/3 receptor binding, in response to acute (3mg/kg i.p.) and chronic (0.015 mg/ml in drinking water, 28 days) stimulation of neurons or astrocytes with clozapine N-oxide. We also assessed the effects of the chronic chemogenetic manipulations on D2 receptor density, low or high aggregated forms of amyloid Aß40 and Aß42, astrocytes and microglial reactivity, and the capacity of astrocytes and microglia to surround and phagocytize Aß both locally and in the striatum. RESULTS: We showed that acute and chronic neuronal and astrocytic stimulation induces widespread effects on the brain regional activation pattern, notably with an inhibition of striatal activation. In the Tg rats, both these effects were blunted. Chemogenetic stimulation in the hippocampus increased microglial density and its capacity to limit AD pathology, whereas these effects were absent in the striatum perhaps as a consequence of the altered connectivity between the hippocampus and the striatum. CONCLUSIONS: Our work suggests that hippocampal AD pathology may alter mesostriatal signalling and induce widespread alterations of brain activity. Neuronal and astrocytic activation may induce a protective, Aß-limiting phenotype of microglia, which surrounds Aß plaques and limits Αß concentration more efficiently.

2.
Neurobiol Dis ; 200: 106623, 2024 Aug 03.
Artículo en Inglés | MEDLINE | ID: mdl-39103022

RESUMEN

Alzheimer's Disease (AD) is characterized by an accumulation of pathologic amyloid-beta (Aß) and Tau proteins, neuroinflammation, metabolic changes and neuronal death. Reactive astrocytes participate in these pathophysiological processes by releasing pro-inflammatory molecules and recruiting the immune system, which further reinforces inflammation and contributes to neuronal death. Besides these neurotoxic effects, astrocytes can protect neurons by providing them with high amounts of lactate as energy fuel. Astrocytes rely on aerobic glycolysis to generate lactate by reducing pyruvate, the end product of glycolysis, through lactate dehydrogenase. Consequently, limited amounts of pyruvate enter astrocytic mitochondria through the Mitochondrial Pyruvate Carrier (MPC) to be oxidized. The MPC is a heterodimer composed of two subunits MPC1 and MPC2, the function of which in astrocytes has been poorly investigated. Here, we analyzed the role of the MPC in the pathogeny of AD, knowing that a reduction in overall glucose metabolism has been associated with a drop in cognitive performances and an accumulation of Aß and Tau. We generated 3xTgAD mice in which MPC1 was knocked-out in astrocytes specifically and focused our study on the biochemical hallmarks of the disease, mainly Aß and neurofibrillary tangle production. We show that inhibition of the MPC before the onset of the disease significantly reduces the quantity of Aß and Tau aggregates in the brain of 3xTgAD mice, suggesting that acting on astrocytic glucose metabolism early on could hinder the progression of the disease.

3.
J Transl Med ; 22(1): 163, 2024 02 16.
Artículo en Inglés | MEDLINE | ID: mdl-38365700

RESUMEN

BACKGROUND: Soluble oligomeric forms of Tau protein have emerged as crucial players in the propagation of Tau pathology in Alzheimer's disease (AD). Our objective is to introduce a single-domain antibody (sdAb) named 2C5 as a novel radiotracer for the efficient detection and longitudinal monitoring of oligomeric Tau species in the human brain. METHODS: The development and production of 2C5 involved llama immunization with the largest human Tau isoform oligomers of different maturation states. Subsequently, 2C5 underwent comprehensive in vitro characterization for affinity and specificity via Enzyme-Linked Immunosorbent Assay and immunohistochemistry on human brain slices. Technetium-99m was employed to radiolabel 2C5, followed by its administration to healthy mice for biodistribution analysis. RESULTS: 2C5 exhibited robust binding affinity towards Tau oligomers (Kd = 6.280 nM ± 0.557) and to Tau fibers (Kd = 5.024 nM ± 0.453), with relatively weaker binding observed for native Tau protein (Kd = 1791 nM ± 8.714) and amyloid peptide (Kd > 10,000 nM). Remarkably, this SdAb facilitated immuno-histological labeling of pathological forms of Tau in neurons and neuritic plaques, yielding a high-contrast outcome in AD patients, closely mirroring the performance of reference antibodies AT8 and T22. Furthermore, 2C5 SdAb was successfully radiolabeled with 99mTc, preserving stability for up to 6 h post-radiolabeling (radiochemical purity > 93%). However, following intravenous injection into healthy mice, the predominant uptake occurred in kidneys, amounting to 115.32 ± 3.67, 97.70 ± 43.14 and 168.20 ± 34.52% of injected dose per gram (% ID/g) at 5, 10 and 45 min respectively. Conversely, brain uptake remained minimal at all measured time points, registering at 0.17 ± 0.03, 0.12 ± 0.07 and 0.02 ± 0.01% ID/g at 5, 10 and 45 min post-injection respectively. CONCLUSION: 2C5 demonstrates excellent affinity and specificity for pathological Tau oligomers, particularly in their early stages of oligomerization. However, the current limitation of insufficient blood-brain barrier penetration necessitates further modifications before considering its application in nuclear medicine imaging for humans.


Asunto(s)
Enfermedad de Alzheimer , Anticuerpos de Dominio Único , Animales , Humanos , Ratones , Enfermedad de Alzheimer/diagnóstico por imagen , Encéfalo/patología , Anticuerpos de Dominio Único/química , Anticuerpos de Dominio Único/metabolismo , Proteínas tau/química , Proteínas tau/inmunología , Distribución Tisular
4.
J Neuroinflammation ; 19(1): 311, 2022 Dec 22.
Artículo en Inglés | MEDLINE | ID: mdl-36550510

RESUMEN

Preclinical studies have recently evaluated the impact of low-dose brain radiation therapy (LD-RT) in animal models of Alzheimer's disease (AD) showing anti-amyloid and anti-inflammatory effects of this treatment. Its effectiveness varied, however, depending on the LD-RT protocol used and the stage when the treatment was applied. In this study, we aimed to evaluate the therapeutic potential of 10 Gy delivered in five daily fractions of 2 Gy (a protocol previously shown to induce an improvement of cognitive performances) in 9-month-old TgF344-AD rats, modeling at a pre-symptomatic stage of the disease. We showed that at an early stage, LD-RT was able to lower levels of the 18-kDa translocator protein (TSPO)-mediated neuroinflammation to normal ranges in addition to the secreted CLUSTERIN, another inflammatory protein also involved in Aß aggregation. In addition, we demonstrated that LD-RT reduces all amyloid forms (~ - 60 to - 80%, P < 0.01; soluble and aggregated forms of Aß40, Aß42, and Aßoligomers). Interestingly, we showed for the first time that sAPPα levels were improved by the treatment, showing a higher activation of the non-amyloidogenic pathway, that could favor neuronal survival. The current evidence confirms the capacity of LD-RT to successfully modulate two pathological hallmarks of AD, namely amyloid and neuroinflammation, when applied before symptoms onset.


Asunto(s)
Enfermedad de Alzheimer , Péptidos beta-Amiloides , Ratas , Animales , Péptidos beta-Amiloides/metabolismo , Clusterina/metabolismo , Clusterina/farmacología , Enfermedades Neuroinflamatorias , Enfermedad de Alzheimer/metabolismo , Encéfalo/metabolismo , Amiloide/metabolismo , Modelos Animales de Enfermedad , Proteínas Portadoras/metabolismo , Receptores de GABA-A
5.
Int J Neuropsychopharmacol ; 24(3): 239-251, 2021 03 17.
Artículo en Inglés | MEDLINE | ID: mdl-33151278

RESUMEN

BACKGROUND: Impulsivity and novelty preference are both associated with an increased propensity to develop addiction-like behaviors, but their relationship and respective underlying dopamine (DA) underpinnings are not fully elucidated. METHODS: We evaluated a large cohort (n = 49) of Roman high- and low-avoidance rats using single photon emission computed tomography to concurrently measure in vivo striatal D2/3 receptor (D2/3R) availability and amphetamine (AMPH)-induced DA release in relation to impulsivity and novelty preference using a within-subject design. To further examine the DA-dependent processes related to these traits, midbrain D2/3-autoreceptor levels were measured using ex vivo autoradiography in the same animals. RESULTS: We replicated a robust inverse relationship between impulsivity, as measured with the 5-choice serial reaction time task, and D2/3R availability in ventral striatum and extended this relationship to D2/3R levels measured in dorsal striatum. Novelty preference was positively related to impulsivity and showed inverse associations with D2/3R availability in dorsal striatum and ventral striatum. A high magnitude of AMPH-induced DA release in striatum predicted both impulsivity and novelty preference, perhaps owing to the diminished midbrain D2/3-autoreceptor availability measured in high-impulsive/novelty-preferring Roman high-avoidance animals that may amplify AMPH effect on DA transmission. Mediation analyses revealed that while D2/3R availability and AMPH-induced DA release in striatum are both significant predictors of impulsivity, the effect of striatal D2/3R availability on novelty preference is fully mediated by evoked striatal DA release. CONCLUSIONS: Impulsivity and novelty preference are related but mediated by overlapping, yet dissociable, DA-dependent mechanisms in striatum that may interact to promote the emergence of an addiction-prone phenotype.


Asunto(s)
Dopamina/metabolismo , Conducta Exploratoria/fisiología , Conducta Impulsiva/fisiología , Neostriado/metabolismo , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D3/metabolismo , Estriado Ventral/metabolismo , Anfetamina/farmacología , Animales , Autorreceptores/efectos de los fármacos , Autorreceptores/metabolismo , Conducta Animal/efectos de los fármacos , Conducta Animal/fisiología , Dopaminérgicos/farmacología , Conducta Exploratoria/efectos de los fármacos , Conducta Impulsiva/efectos de los fármacos , Masculino , Neostriado/efectos de los fármacos , Ratas , Receptores de Dopamina D2/efectos de los fármacos , Receptores de Dopamina D3/efectos de los fármacos , Tomografía Computarizada de Emisión de Fotón Único , Estriado Ventral/efectos de los fármacos
6.
Eur J Nucl Med Mol Imaging ; 49(1): 146-163, 2021 12.
Artículo en Inglés | MEDLINE | ID: mdl-33433698

RESUMEN

The 18 kDa translocator protein (TSPO) is a highly conserved protein located in the outer mitochondrial membrane. TSPO binding, as measured with positron emission tomography (PET), is considered an in vivo marker of neuroinflammation. Indeed, TSPO expression is altered in neurodegenerative, neuroinflammatory, and neuropsychiatric diseases. In PET studies, the TSPO signal is often viewed as a marker of microglial cell activity. However, there is little evidence in support of a microglia-specific TSPO expression. This review describes the cellular sources and functions of TSPO in animal models of disease and human studies, in health, and in central nervous system diseases. A discussion of methods of analysis and of quantification of TSPO is also presented. Overall, it appears that the alterations of TSPO binding, their cellular underpinnings, and the functional significance of such alterations depend on many factors, notably the pathology or the animal model under study, the disease stage, and the involved brain regions. Thus, further studies are needed to fully determine how changes in TSPO binding occur at the cellular level with the ultimate goal of revealing potential therapeutic pathways.


Asunto(s)
Receptores de GABA , Tomografía Computarizada por Rayos X , Animales , Encéfalo/diagnóstico por imagen , Encéfalo/metabolismo , Humanos , Microglía/metabolismo , Tomografía de Emisión de Positrones , Receptores de GABA/genética , Receptores de GABA/metabolismo
7.
Bioorg Chem ; 96: 103582, 2020 03.
Artículo en Inglés | MEDLINE | ID: mdl-31978687

RESUMEN

A series of iodinated ligands for the SPECT imaging of 5-HT4 receptors was designed starting from the previously reported hit MR-26132. We focused on the modulation of the piperidine-containing lateral chain by introducing hydrophilic groups in order to decrease the liphophilicity of the new ligands. All the synthesized compounds were tested for their binding affinities on 5-HT4Rs and based on the Ligand Lipophilicity Efficiency approach, compound 13 was further selected for radioiodination with iodine-125 and imaging experiments. Compound 13 showed its ability to displace the specific signal of the reference compound [125I]SB-207710 but no significant detection of [125I]13 was observed in vivo in SPECT experiments.


Asunto(s)
Radioisótopos de Yodo/química , Piperidinas/química , Receptores de Serotonina 5-HT4/análisis , Tomografía Computarizada de Emisión de Fotón Único/métodos , Animales , Química Encefálica , Células CHO , Cricetulus , Dioxanos/química , Humanos , Ligandos , Ratas
8.
Neurobiol Dis ; 121: 95-105, 2019 01.
Artículo en Inglés | MEDLINE | ID: mdl-30261283

RESUMEN

The involvement of the 18kDa translocator protein (TSPO), a marker of neuroinflammation, in Alzheimer's disease (AD) remains controversial. In the present report, we used [125I]-CLINDE, a SPECT TSPO radiotracer never before used in AD, and we investigated the relationship between TSPO and amyloid plaque density (using [125I]-DRM106) in a triple transgenic mouse model of AD (3xTgAD, APPSWE, PS1M146V and TauP301L). Our results show that TSPO increases appear before those of amyloid deposits. Moreover, the different parts of the hippocampus are differentially affected. Indeed, for both TSPO and amyloid, the subiculum is affected earlier and the ventral hippocampus later than the dorsal hippocampus. In the subiculum and the dorsal hippocampus of 3xTgAD mice, a positive correlation between TSPO and of amyloid deposit levels is observed. This data supports the hypothesis that TSPO could be used as a predictive marker of amyloid pathology. In addition, our immunohistochemical data shows a segregation of TSPO in the hippocampus and immunofluorescence imaging revealed a mainly microglial origin of the TSPO expression. Thus, imaging TSPO with CLINDE may be a good alternative to PET radiotracers.


Asunto(s)
Enfermedad de Alzheimer/metabolismo , Hipocampo/metabolismo , Placa Amiloide/metabolismo , Receptores de GABA/metabolismo , Enfermedad de Alzheimer/complicaciones , Enfermedad de Alzheimer/diagnóstico por imagen , Animales , Plexo Coroideo/metabolismo , Modelos Animales de Enfermedad , Encefalitis/complicaciones , Encefalitis/metabolismo , Femenino , Hipocampo/diagnóstico por imagen , Humanos , Ratones Endogámicos C57BL , Ratones Transgénicos , Tomografía Computarizada de Emisión de Fotón Único/métodos
9.
Neuroimage ; 176: 528-540, 2018 08 01.
Artículo en Inglés | MEDLINE | ID: mdl-29723640

RESUMEN

PURPOSE: SPECT imaging with two radiotracers at the same time is feasible if two different radioisotopes are employed, given their distinct energy emission spectra. In the case of 123I and 125I, dual SPECT imaging is not straightforward: 123I emits photons at a principal energy emission spectrum of 143.1-179.9 keV. However, it also emits at a secondary energy spectrum (15-45 keV) that overlaps with the one of 125I and the resulting cross-talk of emissions impedes the accurate quantification of 125I. In this paper, we describe three different methods for the correction of this cross-talk and the simultaneous in vivo [123I]IBZM and [125I]R91150 imaging of D2/3 and 5-HT2A receptors in the rat brain. METHODS: Three methods were evaluated for the correction of the effect of cross-talk in a series of simultaneous, [123I]IBZM and [125I]R91150 in vivo and phantom SPECT scans. Method 1 employs a dual-energy window (DEW) approach, in which the cross-talk on 125I is considered a stable fraction of the energy emitted from 123I at the principal emission spectrum. The coefficient describing the relationship between the emission of 123I at the principal and the secondary spectrum was estimated from a series of single-radiotracer [123I]IBZM SPECT studies. In Method 2, spectral factor analysis (FA) is applied to separate the radioactivity from 123I and 125I on the basis of their distinct emission patterns across the energy spectrum. Method 3 uses a modified simplified reference tissue model (SRTMC) to describe the kinetics of [125I]R91150. It includes the coefficient describing the cross-talk on 125I from 123I in the model parameters. The results of the correction of cross-talk on [125I]R91150 binding potential (BPND) with each of the three methods, using cerebellum as the reference region, were validated against the results of a series of single-radiotracer [123I]R91150 SPECT studies. In addition, the DEW approach (Method 1), considered to be the most straightforward to apply of the three, was further applied in a dual-radiotracer SPECT study of the relationship between D2/3 and 5-HT2A receptor binding in the striatum, both at the voxel and at the regional level. RESULTS: Average regional BPND values of [125I]R91150, estimated on the cross-talk corrected dual-radiotracer SPECT studies provided satisfactory correlations with the BPND values for [123I]R91150 from single-radiotracer studies: r = 0.92, p < 0.001 for Method 1, r = 0.92, p < 0.001 for Method 2, r = 0.92, p < 0.001, for Method 3. The coefficient describing the ratio of the 123I-emitted radioactivity at the 125I-emission spectrum to the radioactivity that it emits at its principal emission spectrum was 0.34 in vivo. Dual-radiotracer in vivo SPECT studies corrected with Method 1 demonstrated a positive correlation between D2/3 and 5-HT2A receptor binding in the rat nucleus accumbens at the voxel level. At the VOI-level, a positive correlation was confirmed in the same region (r = 0.78, p < 0.01). CONCLUSION: Dual-radiotracer SPECT imaging using 123I and 125I-labeled radiotracers is feasible if the cross-talk of 123I on the 125I emission spectrum is properly corrected. The most straightforward approach is Method 1, in which a fraction (34%) of the radioactivity emitted from 123I at its principal energy spectrum is subtracted from the measured radioactivity at the spectrum of 125I. With this method, a positive correlation between the binding of [123I]IBZM and [125I]R91150 was demonstrated in the rat nucleus accumbens. This result highlights the interest of dual-radiotracer SPECT imaging to study multiple neurotransmitter systems at the same time and under the same biological conditions.


Asunto(s)
Encéfalo/metabolismo , Radioisótopos de Yodo/farmacocinética , Neuroimagen/métodos , Núcleo Accumbens/metabolismo , Fantasmas de Imagen , Radiofármacos/farmacocinética , Receptor de Serotonina 5-HT2A/metabolismo , Receptores de Dopamina D2/metabolismo , Tomografía Computarizada de Emisión de Fotón Único/métodos , Animales , Benzamidas/farmacocinética , Encéfalo/diagnóstico por imagen , Estudios de Factibilidad , Humanos , Núcleo Accumbens/diagnóstico por imagen , Piperidinas/farmacocinética , Pirrolidinas/farmacocinética , Receptores de Dopamina D3/metabolismo
10.
Synapse ; 72(4)2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-29265497

RESUMEN

The Roman high (RHA)- and low (RLA)-avoidance rat sublines have been identified as an addiction-prone and addiction-resistant phenotype based on their high vs. low locomotor responsiveness to novelty and high vs. low ability to develop neurochemical and behavioral sensitization to psychostimulants, respectively. Most studies though have focused on psychostimulants and little is known about the neuroadaptive response of these two lines to cannabinoids. This study investigated the effects of chronic exposure to Δ9 -tetrahydrocannabinol (THC) on dopamine D2/3 receptor (D2/3 R) availabilities and functional sensitivity in the mesostriatal system of RHA and RLA rats. At baseline, RLA rats exhibited higher densities of mesostriatal D2/3R but lower levels of striatal CB1 R mRNA and displayed a lower locomotor response to acute THC as compared to RHAs. Following chronic THC treatment, striking changes in D2/3 R signaling were observed in RLA but not in RHA rats, namely an increased availability and functional supersensitivity of striatal D2/3 R, as evidenced by a supersensitive psychomotor response to the D2/3 R agonist quinpirole. Moreover, in RLA rats, the lower was the locomotor response to acute THC, the higher was the psychomotor response to quinpirole following chronic THC. These results showing a greater neuroadaptive response of RLA vs. RHA rats to chronic THC thus contrast with previous studies showing a resistance to neuroadaptive response of RLAs to psychostimulants, This suggests that, contrasting with their low proneness to psychostimulant drug-seeking, RLAs may exhibit a heightened proneness to cannabinoid drug-seeking as compared to RHA rats.


Asunto(s)
Encéfalo/efectos de los fármacos , Dronabinol/farmacología , Psicotrópicos/farmacología , Receptores de Dopamina D2/metabolismo , Receptores de Dopamina D3/metabolismo , Trastornos Relacionados con Sustancias/metabolismo , Animales , Encéfalo/metabolismo , Modelos Animales de Enfermedad , Dopaminérgicos/farmacología , Comportamiento de Búsqueda de Drogas/fisiología , Predisposición Genética a la Enfermedad , Masculino , Actividad Motora/efectos de los fármacos , Actividad Motora/fisiología , Quinpirol/farmacología , ARN Mensajero/metabolismo , Receptor Cannabinoide CB1/metabolismo
11.
Neuroimage ; 147: 461-472, 2017 02 15.
Artículo en Inglés | MEDLINE | ID: mdl-28011253

RESUMEN

PURPOSE: Molecular imaging of the D2/3 receptor is widely used in neuropsychiatric research. Non-displaceable binding potential (BPND) is a very popular quantitative index, defined as the product of the receptor concentration (Bavail) and the radiotracer affinity for the receptor (1/appKd). As the appKd is influenced by parameters such as the endogenous neurotransmitter dynamics, it often constitutes a confounding factor in research studies. A simplified method for absolute quantification of both these parameters would be of great interest in this context. Here, we describe the use of a partial saturation protocol that permits to produce an in vivo Scatchard plot and thus estimate Bavail and appKd separately, through a single dynamic SPECT session. To validate this approach, a multi-injection protocol is used for the full kinetic modeling of [123I]IBZM using a 3-tissue compartment, 7-parameter model (3T-7k). Finally, more "classic" BPND estimation methods are also validated against the results of the 3T-7k. METHODS: Twenty-nine male rats were used. Binding parameters were estimated using the 3T-7k in a multi-injection protocol. A partial saturation protocol was applied at the region- and voxel-level and results were compared to those obtained with the 3T-7k model. The partial saturation protocol was applied after an adenovirus-mediated D2 receptor striatal overexpression and in an amphetamine-induced dopamine release paradigm. The Simplified Reference Tissue Model (SRTM), the Logan's non-invasive graphical analysis (LNIGA) and a simple standardized uptake ratio (SUR) method were equally applied. RESULTS: The partial saturation experiments gave similar values as the 3T-7k both at the regional and voxel-level. After adenoviral-mediated D2-receptor overexpression, an increase in Bavail by approximately 18% was observed in the striatum. After amphetamine administration, a 16.93% decrease in Bavail (p<0.05) and a 39.12% increase (p<0.01) in appKd was observed. BPND derived from SRTM, LNIGA and SUR correlated well with the Bavail values from the 3T-7k (r=0.84, r=0.84 and r=0.83, respectively, p<0.0001 for all correlations). CONCLUSION: A partial saturation protocol permits the non-invasive and time-efficient estimation of Bavail and appKd separately. Given the different biological phenomena that underlie these parameters, this method may be applied for the in-depth study of the dopaminergic system in translational molecular imaging studies. It can detect the biological variations in these parameters, dissociating the variations in receptor density (Bavail) from affinity (1/appKd), which reflects the interactions of the receptor with its endogenous ligand.


Asunto(s)
Benzamidas/farmacocinética , Encéfalo/metabolismo , Antagonistas de Dopamina/farmacocinética , Pirrolidinas/farmacocinética , Receptores de Dopamina D2/metabolismo , Animales , Encéfalo/diagnóstico por imagen , Encéfalo/efectos de los fármacos , Masculino , Unión Proteica , Ratas , Ratas Sprague-Dawley , Receptores de Dopamina D3/metabolismo , Tomografía Computarizada de Emisión de Fotón Único
12.
J Neurochem ; 132(5): 609-18, 2015 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-25258048

RESUMEN

Previous works have shown the interest of naturally fluorescent proflavine derivatives to label Abeta deposits in vitro. This study aimed to further characterize the properties of the proflavine 3-acetylamino-6-[3-(propargylamino)propanoyl]aminoacridine (COB231) derivative as a probe. This compound was therefore evaluated on human post-mortem and mice brain slices and in vivo in 18-month-old triple transgenic mice APPswe, PS1M146V and tauP301L (3xTgAD) mice presenting the main characteristics of Alzheimer's disease (AD). COB231 labelled amyloid plaques on brain slices of AD patients, and 3xTgAD mice at 10 and 0.1 µM respectively. However, no labelling of the neurofibrillary tangle-rich areas was observed either at high concentration or in the brain of fronto-temporal dementia patients. The specificity of this mapping was attested in mice using Thioflavin S and IMPY as positive controls of amyloid deposits. After intravenous injection of COB231 in old 3xTgAD mice, fluorescent amyloid plaques were detected in the cortex and hippocampus, demonstrating COB231 blood­brain barrier permeability. We also controlled the cellular localization of COB231 on primary neuronal cultures and showed that COB231 accumulates into the cytoplasm and not into the nucleus. Finally, using a viability assay, we only detected a slight cytotoxic effect of COB231 (< 10%) for the highest concentration (100 µM).


Asunto(s)
Enfermedad de Alzheimer/patología , Inmunohistoquímica/métodos , Placa Amiloide/diagnóstico , Proflavina/análogos & derivados , Aminacrina/análogos & derivados , Aminacrina/síntesis química , Aminacrina/química , Animales , Autopsia , Encéfalo/patología , Modelos Animales de Enfermedad , Femenino , Colorantes Fluorescentes/síntesis química , Colorantes Fluorescentes/química , Humanos , Procesamiento de Imagen Asistido por Computador , Ratones , Ratones Endogámicos C57BL , Ratones Transgénicos , Microscopía Fluorescente , Sensibilidad y Especificidad , Coloración y Etiquetado/métodos
13.
Mol Imaging ; 142015.
Artículo en Inglés | MEDLINE | ID: mdl-26105563

RESUMEN

Our goal was to identify suitable image quantification methods to image 5-hydroxytryptamine2A (5-HT2A) receptors in vivo in Mdr1a knockout (KO) rats (i.e., P-glycoprotein KO) using 123I-R91150 single-photon emission computed tomography (SPECT). The 123I-R91150 binding parameters estimated with different reference tissue models (simplified reference tissue model [SRTM], Logan reference tissue model, and tissue ratio [TR] method) were compared to the estimates obtained with a comprehensive three-tissue/seven-parameter (3T/7k)-based model. The SRTM and Logan reference tissue model estimates of 5-HT2A receptor (5-HT2AR) nondisplaceable binding potential (BPND) correlated well with the absolute receptor density measured with the 3T/7k gold standard (r > .89). Quantification of 5-HT2AR using the Logan reference tissue model required at least 90 minutes of scanning, whereas the SRTM required at least 110 minutes. The TR method estimates were also highly correlated to the 5-HT2AR density (r > .91) and only required a single 20-minute scan between 100 and 120 minutes postinjection. However, a systematic overestimation of the BPND values was observed. The Logan reference tissue method is more convenient than the SRTM for the quantification of 5-HT2AR in Mdr1a KO rats using 123I-R91150 SPECT. The TR method is an interesting and simple alternative, despite its bias, as it still provides a valid index of 5-HT2AR density.


Asunto(s)
Subfamilia B de Transportador de Casetes de Unión a ATP/metabolismo , Encéfalo/diagnóstico por imagen , Radioisótopos de Yodo/metabolismo , Receptor de Serotonina 5-HT2A/metabolismo , Tomografía Computarizada de Emisión de Fotón Único/métodos , Animales , Encéfalo/metabolismo , Masculino , Metaboloma , Piperidinas , Ratas Sprague-Dawley
14.
J Neurochem ; 128(1): 125-39, 2014 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-24117599

RESUMEN

Astrocytes have recently become a major center of interest in neurochemistry with the discoveries on their major role in brain energy metabolism. An interesting way to probe this glial contribution is given by in vivo (13) C NMR spectroscopy coupled with the infusion labeled glial-specific substrate, such as acetate. In this study, we infused alpha-chloralose anesthetized rats with [2-(13) C]acetate and followed the dynamics of the fractional enrichment (FE) in the positions C4 and C3 of glutamate and glutamine with high sensitivity, using (1) H-[(13) C] magnetic resonance spectroscopy (MRS) at 14.1T. Applying a two-compartment mathematical model to the measured time courses yielded a glial tricarboxylic acid (TCA) cycle rate (Vg ) of 0.27 ± 0.02 µmol/g/min and a glutamatergic neurotransmission rate (VNT ) of 0.15 ± 0.01 µmol/g/min. Glial oxidative ATP metabolism thus accounts for 38% of total oxidative metabolism measured by NMR. Pyruvate carboxylase (VPC ) was 0.09 ± 0.01 µmol/g/min, corresponding to 37% of the glial glutamine synthesis rate. The glial and neuronal transmitochondrial fluxes (Vx (g) and Vx (n) ) were of the same order of magnitude as the respective TCA cycle fluxes. In addition, we estimated a glial glutamate pool size of 0.6 ± 0.1 µmol/g. The effect of spectral data quality on the fluxes estimates was analyzed by Monte Carlo simulations. In this (13) C-acetate labeling study, we propose a refined two-compartment analysis of brain energy metabolism based on (13) C turnover curves of acetate, glutamate and glutamine measured with state of the art in vivo dynamic MRS at high magnetic field in rats, enabling a deeper understanding of the specific role of glial cells in brain oxidative metabolism. In addition, the robustness of the metabolic fluxes determination relative to MRS data quality was carefully studied.


Asunto(s)
Metabolismo Energético/fisiología , Ácido Glutámico/metabolismo , Espectroscopía de Resonancia Magnética/métodos , Neuroglía/metabolismo , Neuronas/metabolismo , Animales , Isótopos de Carbono , Corteza Cerebral/química , Corteza Cerebral/metabolismo , Hidrógeno , Masculino , Simulación de Dinámica Molecular , Método de Montecarlo , Neuroglía/química , Neuronas/química , Ratas , Ratas Sprague-Dawley
15.
Mol Imaging ; 132014.
Artículo en Inglés | MEDLINE | ID: mdl-25248453

RESUMEN

Defluorination of [18F]fallypride and accumulation of 18F in skull and glands leads to the contamination of brain structures with spillover activity due to partial volume effects, leading to considerable errors in binding potential estimations. Here we propose a modification of the simplified reference tissue model (SRTM) to take into account the contribution of skull activity to the radioactivity kinetic pattern in cerebellum and target regions. It consists of the introduction of an additional parameter for each volume of interest (sT) and one for the cerebellum (sR), corresponding to the fraction of skull activity contaminating these structures. Using five rat positron emission tomography experiments, we applied the modified SRTM (SRTMc), which resulted in excellent fits. As a relative means of comparison of results, we applied factor analysis (FA) to decompose dynamic data into images corresponding to brain and skull activity. With the skull factor images, we estimated the "true" sT and sR values, ultimately permitting us to fix the sR value. Parameters obtained with the SRTMc were closely correlated with values obtained from FA-corrected data. In conclusion, we propose an efficient method for reliable quantification of dopamine D2/3 receptors with single-injection [18F]fallypride scans that is potentially applicable to human studies where 18F skull accumulation compromises binding parameter estimation.


Asunto(s)
Benzamidas/farmacocinética , Pirrolidinas/farmacocinética , Radiofármacos/farmacocinética , Receptores de Dopamina D2/análisis , Receptores de Dopamina D3/análisis , Animales , Cerebelo/diagnóstico por imagen , Análisis Factorial , Masculino , Tomografía de Emisión de Positrones , Ratas , Ratas Sprague-Dawley , Cráneo/diagnóstico por imagen
16.
Mol Imaging ; 132014.
Artículo en Inglés | MEDLINE | ID: mdl-24622810

RESUMEN

The pharmacokinetic properties of radiotracers are crucial for successful in vivo single-photon emission computed tomographic (SPECT) imaging. Our goal was to determine if MDR1A-deficient animals could allow better SPECT imaging outcomes than wild-type (WT) animals for a selection of serotoninergic radioligands. Thus, we compared the performances of 123I-p-MPPI, 123I-R91150, 123I-SB207710, and 123I-ADAM radioligands, for imaging of their respective targets (5-hydroxytryptamine [5-HT]1A, 5-HT2A, 5-HT4, and serotonin transporter [SERT]), in WT and Mdr1a knockout (KO) rats. With 123I-SB207710, virtually no SPECT signal was recorded in the brain of WT or KO animals. For 123I-p-MPPI, low nondisplaceable binding potentials (BPND, mean ± SD) were observed in WT (0.49 ± 0.25) and KO (0.89 ± 0.52) animals. For 123I-ADAM, modest imaging contrast was observed in WT (1.27 ± 0.02) and KO (1.31 ± 0.09) animals. For 123I-R91150, the BPND were significantly higher in Mdr1a KO (3.98 ± 0.65) animals compared to WT animals (1.22 ± 0.26). The pharmacokinetics of 123I-SB207710 and 123I-p-MPPI do not make them ideal tracers for preclinical SPECT neuroimaging. 123I-ADAM showed adequate brain uptake regardless of Mdr1a expression and appeared suitable for preclinical SPECT neuroimaging in both animal strains. The use of Mdr1a KO animals significantly improved the brain penetration of 123I-R91150, making this animal strain an interesting option when considering SPECT neuroimaging of 5-HT2A receptors in rat.


Asunto(s)
Subfamilia B de Transportador de Casetes de Unión a ATP/genética , Encéfalo/diagnóstico por imagen , Radioisótopos de Yodo/farmacocinética , Radiofármacos/farmacocinética , Receptores de Serotonina/metabolismo , Inhibidores Selectivos de la Recaptación de Serotonina/farmacocinética , Tomografía Computarizada de Emisión de Fotón Único/métodos , Subfamilia B de Transportador de Casetes de Unión a ATP/metabolismo , Aminopiridinas/farmacocinética , Animales , Encéfalo/metabolismo , Cinanserina/análogos & derivados , Cinanserina/farmacocinética , Técnicas de Inactivación de Genes , Masculino , Especificidad de Órganos , Piperazinas/farmacocinética , Piperidinas/farmacocinética , Ratas , Ratas Sprague-Dawley , Distribución Tisular
17.
J Alzheimers Dis ; 98(3): 1001-1016, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38489181

RESUMEN

Background: Low-dose radiation therapy (LD-RT) has demonstrated in preclinical and clinical studies interesting properties in the perspective of targeting Alzheimer's disease (AD), including anti-amyloid and anti-inflammatory effects. Nevertheless, studies were highly heterogenous with respect to total doses, fractionation protocols, sex, age at the time of treatment and delay post treatment. Recently, we demonstrated that LD-RT reduced amyloid peptides and inflammatory markers in 9-month-old TgF344-AD (TgAD) males. Objective: As multiple studies demonstrated a sex effect in AD, we wanted to validate that LD-RT benefits are also observed in TgAD females analyzed at the same age. Methods: Females were bilaterally treated with 2 Gy×5 daily fractions, 2 Gy×5 weekly fractions, or 10 fractions of 1 Gy delivered twice a week. The effect of each treatment on amyloid load and inflammation was evaluated using immunohistology and biochemistry. Results: A daily treatment did not affect amyloid and reduced only microglial-mediated inflammation markers, the opposite of the results obtained in our previous male study. Moreover, altered fractionations (2 Gy×5 weekly fractions or 10 fractions of 1 Gy delivered twice a week) did not influence the amyloid load or neuroinflammatory response in females. Conclusions: A daily treatment consequently appears to be the most efficient for AD. This study also shows that the anti-amyloid and anti-inflammatory response to LD-RT are, at least partly, two distinct mechanisms. It also emphasizes the necessity to assess the sex impact when evaluating responses in ongoing pilot clinical trials testing LD-RT against AD.


Asunto(s)
Enfermedad de Alzheimer , Ratas , Masculino , Femenino , Animales , Enfermedad de Alzheimer/patología , Microglía/patología , Modelos Animales de Enfermedad , Amiloide , Inflamación/radioterapia , Inflamación/tratamiento farmacológico , Proteínas Amiloidogénicas , Antiinflamatorios/uso terapéutico , Péptidos beta-Amiloides/uso terapéutico
18.
Drug Metab Dispos ; 41(8): 1548-56, 2013 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-23708009

RESUMEN

For drugs with hepatobiliary transport across hepatocytes, the interplay between uptake and efflux transporters determines hepatic concentrations of drugs, but the evolution over time of these concentrations is difficult to measure in humans other than with magnetic resonance imaging contrast agents in the liver. Gadobenate dimeglumine (BOPTA) is a contrast agent used in liver magnetic resonance imaging that enters into human hepatocytes through organic anion transporting polypeptides (OATP) and exits unchanged into bile through the multiple resistance-associated protein 2 (MRP2). Rifampicin (RIF) is transported by the same membrane proteins and may compete with BOPTA for hepatic uptake. Simultaneous drug-drug interactions through uptake and efflux transport systems in hepatocytes according to the cellular concentrations of competing drugs were never investigated. In perfused rat liver preparations, we demonstrate how the drug-drug interactions through transporters determine cellular concentrations of the competing drugs BOPTA and RIF, and we show that the cellular concentrations by modulating transport through membranes regulate the rat Oatp-Mrp2 interplay. Moreover, drug interactions through transporters change greatly over time.


Asunto(s)
Hepatocitos/metabolismo , Meglumina/análogos & derivados , Proteínas Asociadas a Resistencia a Múltiples Medicamentos/fisiología , Transportadores de Anión Orgánico/fisiología , Compuestos Organometálicos/metabolismo , Rifampin/metabolismo , Animales , Transporte Biológico , Interacciones Farmacológicas , Masculino , Meglumina/metabolismo , Proteína 2 Asociada a Resistencia a Múltiples Medicamentos , Ratas , Ratas Sprague-Dawley , Rifampin/farmacología
19.
Int J Neuropsychopharmacol ; 16(8): 1819-34, 2013 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-23574629

RESUMEN

High novelty-seeking has been related to an increased risk for developing addiction, but the neurobiological mechanism underlying this relationship is unclear. We investigated whether differences in dopamine (DA) D2/3-receptor (D2/3R) function underlie phenotypic divergence in novelty-seeking and vulnerability to addiction. Measures of D2/3R availability using the D2R-preferring antagonist [18F]Fallypride, and the D3R-preferring agonist [3H]-(+)-PHNO and of DA-related gene expression and behaviours were used to characterize DA signalling in Roman high- (RHA) and low-avoidance (RLA) rats, which respectively display high and low behavioural responsiveness both to novelty and psychostimulant exposure. When compared to RLA rats, high novelty-responding RHAs had lower levels of D2R, but not D3R, binding and mRNA in substantia nigra/ventral tegmental area (SN/VTA) and showed behavioural evidence of D2-autoreceptor subsensitivity. RHA rats also showed a higher expression of the tyrosine hydroxylase gene in SN/VTA, higher levels of extracellular DA in striatum and augmentation of the DA-releasing effects of amphetamine (Amph), suggesting hyperfunctioning of midbrain DA neurons. RHA rats also exhibited lower availabilities and functional sensitivity of D2R, but not D3R, in striatum, which were inversely correlated with individual scores of novelty-seeking, which, in turn, predicted the magnitude of Amph-induced behavioural sensitization. These results indicate that innately low levels of D2R in SN/VTA and striatum, whether they are a cause or consequence of the concomitantly observed elevated DA tone, result in a specific pattern of DA signalling that may subserve novelty-seeking and vulnerability to drug use. This suggests that D2R deficits in SN/VTA and striatum could both constitute neurochemical markers of an addiction-prone phenotype.


Asunto(s)
Trastornos Relacionados con Anfetaminas/patología , Anfetamina/farmacología , Estimulantes del Sistema Nervioso Central/farmacología , Receptores de Dopamina D2/metabolismo , Área Tegmental Ventral/fisiología , Trastornos Relacionados con Anfetaminas/metabolismo , Análisis de Varianza , Animales , Benzamidas/farmacocinética , Benzopiranos/farmacología , Cuerpo Estriado/efectos de los fármacos , Modelos Animales de Enfermedad , Dopaminérgicos/farmacología , Relación Dosis-Respuesta a Droga , Comportamiento de Búsqueda de Drogas/efectos de los fármacos , Comportamiento de Búsqueda de Drogas/fisiología , Fluorodesoxiglucosa F18 , Masculino , Actividad Motora/efectos de los fármacos , Actividad Motora/fisiología , Oxazinas/farmacología , Ratas , Receptores de Dopamina D2/genética , Reflejo de Sobresalto/efectos de los fármacos , Tritio/farmacocinética , Tirosina 3-Monooxigenasa/genética , Tirosina 3-Monooxigenasa/metabolismo , Área Tegmental Ventral/efectos de los fármacos
20.
Mol Brain ; 16(1): 57, 2023 07 05.
Artículo en Inglés | MEDLINE | ID: mdl-37408083

RESUMEN

The 18 kDa translocator protein (TSPO) is a classical marker of neuroinflammation targeted for in vivo molecular imaging. Microglial cells were originally thought to be the only source of TSPO overexpression but astrocytes, neurons and endothelial cells can also up-regulate TSPO depending on the pathological context. This study aims to determine the cellular origin of TSPO overexpression in a simplified model of neuroinflammation and to identify the molecular pathways involved. This is essential to better interpret TSPO molecular imaging in preclinical and clinical settings. We used lentiviral vectors (LV) to overexpress the ciliary neurotrophic factor (CNTF) in the right striatum of 2-month-old Sprague Dawley rats. A LV encoding for ß-Galactosidase (LV-LacZ) was used as control. One month later, TSPO expression was measured by single-photon emission computed tomography (SPECT) imaging using [125I]CLINDE. The fluorescence-activated cell sorting to radioligand-treated tissue (FACS-RTT) method was used to quantify TSPO levels in acutely sorted astrocytes, microglia, neurons and endothelial cells. A second cohort was injected with LV-CNTF and a LV encoding suppressor of cytokine signaling 3 (SOCS3), to inhibit the JAK-STAT3 pathway specifically in astrocytes. GFAP and TSPO expressions were quantified by immunofluorescence. We measured a significant increase in TSPO signal in response to CNTF by SPECT imaging. Using FACS-RTT, we observed TSPO overexpression in reactive astrocytes (+ 153 ± 62%) but also in microglia (+ 2088 ± 500%) and neurons (+ 369 ± 117%), accompanied by an increase in TSPO binding sites per cell in those three cell populations. Endothelial cells did not contribute to TSPO signal increase. Importantly, LV-SOCS3 reduced CNTF-induced astrocyte reactivity and decreased global TSPO immunoreactivity (-71% ± 30%), suggesting that TSPO overexpression is primarily mediated by reactive astrocytes. Overall, this study reveals that CNTF induces TSPO in multiple cell types in the rat striatum, through the JAK2-STAT3 pathway in astrocytes, identifying this cell type as the primary mediator of CNTF effects neuroinflammatory processes. Our results highlight the difficulty to interpret TSPO imaging in term of cellular origin without addition cellular analysis by FACS-RTT or quantitative immunostainings. Consequently, TSPO should only be used as a global marker of neuroinflammation.


Asunto(s)
Astrocitos , Factor Neurotrófico Ciliar , Animales , Ratas , Astrocitos/metabolismo , Proteínas Portadoras/metabolismo , Factor Neurotrófico Ciliar/metabolismo , Factor Neurotrófico Ciliar/farmacología , Células Endoteliales/metabolismo , Enfermedades Neuroinflamatorias , Ratas Sprague-Dawley
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