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Astrocytes crucially contribute to synaptic physiology and information processing. One of their key characteristics is to express high levels of connexins (Cxs), the gap junction-forming protein. Among them, Cx30 displays specific properties since it is postnatally expressed and dynamically upregulated by neuronal activity and modulates cognitive processes by shaping synaptic and network activities, as recently shown in knockout mice. However, it remains unknown whether local and selective upregulation of Cx30 in postnatal astrocytes within a physiological range modulates neuronal activities in the hippocampus. We here show in mice that, whereas Cx30 upregulation increases the connectivity of astroglial networks, it decreases spontaneous and evoked synaptic transmission. This effect results from a reduced neuronal excitability and translates into an alteration in the induction of synaptic plasticity and an in vivo impairment in learning processes. Altogether, these results suggest that astroglial networks have a physiologically optimized size to appropriately regulate neuronal functions.
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Astrocitos , Conexina 43 , Ratones , Animales , Conexina 30/metabolismo , Astrocitos/metabolismo , Conexina 43/genética , Conexina 43/metabolismo , Regulación hacia Arriba , Conexinas/genética , Conexinas/metabolismo , Ratones Noqueados , Hipocampo/metabolismoRESUMEN
Generation of relevant and robust models for neurological disorders is of main importance for both target identification and drug discovery. The non-cell autonomous effects of glial cells on neurons have been described in a broad range of neurodegenerative and neurodevelopmental disorders, pointing to neuroglial interactions as novel alternative targets for therapeutics development. Interestingly, the recent breakthrough discovery of human induced pluripotent stem cells (hiPSCs) has opened a new road for studying neurological and neurodevelopmental disorders "in a dish". Here, we provide an overview of the generation and modeling of both neuronal and glial cells from human iPSCs and a brief synthesis of recent work investigating neuroglial interactions using hiPSCs in a pathophysiological context.
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Diferenciación Celular , Células Madre Pluripotentes Inducidas/trasplante , Enfermedades Neurodegenerativas , Trastornos del Neurodesarrollo , Neuroglía/metabolismo , Humanos , Células Madre Pluripotentes Inducidas/metabolismo , Enfermedades Neurodegenerativas/metabolismo , Enfermedades Neurodegenerativas/terapia , Trastornos del Neurodesarrollo/metabolismo , Trastornos del Neurodesarrollo/terapiaRESUMEN
Background: Modafinil, a nonamphetaminic wake-promoting compound, is prescribed as first line therapy in narcolepsy, an invalidating disorder characterized by excessive daytime sleepiness and cataplexy. Although its mode of action remains incompletely known, recent studies indicated that modafinil modulates astroglial connexin-based gap junctional communication as administration of a low dose of flecainide, an astroglial connexin inhibitor, enhanced the wake-promoting and procognitive activity of modafinil in rodents and healthy volunteers. The aim of this study is to investigate changes in glucose cerebral metabolism in rodents, induced by the combination of modafinil+flecainide low dose (called THN102). Methods: The impact of THN102 on brain glucose metabolism was noninvasively investigated using 18F-2-fluoro-2-deoxy-D-glucose Positron Emission Tomography imaging in Sprague-Dawley male rats. Animals were injected with vehicle, flecainide, modafinil, or THN102 and further injected with 18F-2-fluoro-2-deoxy-D-glucose followed by 60-minute Positron Emission Tomography acquisition. 18F-2-fluoro-2-deoxy-D-glucose Positron Emission Tomography images were coregistered to a rat brain template and normalized from the total brain Positron Emission Tomography signal. Voxel-to-voxel analysis was performed using SPM8 software. Comparison of brain glucose metabolism between groups was then performed. Results: THN102 significantly increased regional brain glucose metabolism as it resulted in large clusters of 18F-2-fluoro-2-deoxy-D-glucose uptake localized in the cortex, striatum, and amygdala compared with control or drugs administered alone. These regions, highly involved in the regulation of sleep-wake cycle, emotions, and cognitive functions were hence quantitatively modulated by THN102. Conclusion: Data presented here provide the first evidence of a regional brain activation induced by THN102, currently being tested in a phase II clinical trial in narcoleptic patients.
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Amígdala del Cerebelo/efectos de los fármacos , Corteza Cerebral/efectos de los fármacos , Cuerpo Estriado/efectos de los fármacos , Flecainida/farmacología , Fluorodesoxiglucosa F18/farmacocinética , Modafinilo/farmacología , Tomografía de Emisión de Positrones/métodos , Bloqueadores del Canal de Sodio Activado por Voltaje/farmacología , Promotores de la Vigilia/farmacología , Amígdala del Cerebelo/diagnóstico por imagen , Amígdala del Cerebelo/metabolismo , Animales , Corteza Cerebral/diagnóstico por imagen , Corteza Cerebral/metabolismo , Cuerpo Estriado/diagnóstico por imagen , Cuerpo Estriado/metabolismo , Combinación de Medicamentos , Flecainida/administración & dosificación , Masculino , Modafinilo/administración & dosificación , Ratas , Ratas Sprague-Dawley , Bloqueadores del Canal de Sodio Activado por Voltaje/administración & dosificación , Promotores de la Vigilia/administración & dosificaciónRESUMEN
AIMS: THN102 is a novel combination of modafinil and low-dose flecainide, targeting glial connexin activity to modulate modafinil effects. We investigated THN102 efficacy compared to modafinil and to placebo on vigilance and cognitive function during 40-hour total sleep deprivation (TSD). METHODS: Twenty healthy men participated in a double-blind, randomized, incomplete-block 3-period cross-over trial with 5 treatments (n = 12 per group): placebo (PBO), modafinil 100 mg (MOD100), THN102 100/1, 100/3, 100/9 (modafinil 100 mg and flecainide 1, 3 or 9 mg). Each period included a baseline day and a TSD day with treatments administered 3 times (01:00, 09:00 and 19:00). Reaction time in psychomotor vigilance test, subjective somnolence and vital signs were assessed before and during treatment. Working memory (2-Back) and executive processes (Go/noGo for vigilance and inhibition, Wisconsin card sorting task for mental flexibility, and Tower of London test for planning) were evaluated at 16:30. RESULTS: At 5 hours postdose−1 (after 23 hours TSD, primary endpoint), THN102 100/1 resulted in statistically higher psychomotor vigilance test speed vs MOD100 (3.97 ± 0.09 vs 3.74 ± 0.14, P < .05). No increase in effect was observed with higher flecainide doses in combinations. Most THN102 doses vs MOD100 also improved the number of correct responses in 2-Back and Go errors in Go/noGo (P < .05 for all doses), and perseverative responses in Wisconsin card sorting task (for 100/1 and 100/9). No impact on cardiac conduction was noted with THN102, and safety was similar to MOD100. CONCLUSIONS: THN102 seems more efficient than modafinil on vigilance, working memory and executive functions, opening new perspectives in management of hypersomnolence disorders.
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Flecainida/farmacología , Modafinilo/farmacología , Neuroglía/efectos de los fármacos , Privación de Sueño/tratamiento farmacológico , Promotores de la Vigilia/farmacología , Adulto , Nivel de Alerta/efectos de los fármacos , Cognición/efectos de los fármacos , Conexinas/antagonistas & inhibidores , Estudios Cruzados , Combinación de Medicamentos , Flecainida/uso terapéutico , Voluntarios Sanos , Humanos , Masculino , Memoria a Corto Plazo/efectos de los fármacos , Modafinilo/uso terapéutico , Neuroglía/metabolismo , Desempeño Psicomotor/efectos de los fármacos , Tiempo de Reacción/efectos de los fármacos , Resultado del Tratamiento , Vigilia/efectos de los fármacos , Promotores de la Vigilia/uso terapéutico , Adulto JovenRESUMEN
Misfolding of the prion protein (PrP) is the central feature of prion diseases. The conversion of the normal α-helical PrP(C) into a pathological ß-enriched PrP(Sc) constitutes an early event in the infectious process. Several hypotheses, involving different regions of the protein, endeavor to delineate the structural mechanism underlying this change of conformation. All current working hypotheses, however, are based on biophysical and modeling studies, the biological relevance of which still needs to be assessed. We have studied the effect of positively charged polymers on the conversion, using polylysine as a model system, and have investigated a possible mechanism of structural stabilization. We have shown that poly-D-lysine removes proteinase K-resistant PrP from prion-infected SN56 neuroblastoma cells without affecting PrP(C). The effect is enantiospecific since the levorotary isomer, poly-L-lysine, has a markedly weaker effect, likely because of its higher susceptibility to degradation. In vitro cross-linking and NMR studies confirm a direct interaction between polylysine and PrP, which mainly maps to the PrP region containing helices 2 and 3 (H2H3). Interaction prevents conformational conversion and protein aggregation. Our results establish a central role of H2H3 in PrP(Sc) amyloidogenesis and replication and provide biological relevance for the pathological misfolding of this domain.
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Polilisina/química , Proteínas PrPSc/química , Animales , Línea Celular Tumoral , Ratones , Modelos Moleculares , Unión Proteica , Pliegue de Proteína , Estructura Terciaria de ProteínaRESUMEN
Autophagy is a process leading to the degradation of cellular material, in organelles called lysosomes, to supply energy or generate building blocks for the synthesis of new materials. Over the past decades, its role has been evidenced in several indications, notably in neurodegenerative disorders and orphan diseases called lysosomal storage disorders and its modulation is largely envisioned as a therapeutic avenue to alleviate the symptoms and reverse the clinical courses of these indications. Identifying new chemical classes and drugs is, hence, of huge importance. In this study, we developed automated assays to assess the potential efficacy of chemical compounds on different steps of autophagy, notably its induction through the localization of a largely involved transcription factor, transcription factor EB (TFEB). These assays were then used to screen a collection of 1,520 approved drugs. This study led to the identification of five candidate hits modulating autophagy and TFEB subcellular localization. Our results suggest the repurposing potential of already approved drugs in central nervous system disorders with lysosomal storage impairments.
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Autofagia , Lisosomas , Autofagia/fisiología , Lisosomas/metabolismoRESUMEN
Attention-Deficit hyperactivity disorder (ADHD) is a central nervous system (CNS) disorder frequently associated with other psychiatric disorders. Pathophysiology processes at stake in ADHD are still under investigation and interestingly neuroimaging data points to modulated brain connectivity in patients. The genetic spontaneously hypertensive rat (SHR) model has been widely used to study pathophysiological underpinnings of ADHD and resting-state brain connectivity using functional magnetic resonance imaging. Here, functional ultrasound imaging, a new technique enabling fast measurement of cerebral blood volume (CBV), was used to further characterize resting-state functional connectivity - at both local and long-range - and visual response in SHR. We demonstrated that response to visual stimulation was increased in SHR in the visual cortex and the superior colliculus. They displayed altered long-range functional connectivity between spatially distinct regions. SHR also displayed modulated local connectivity, with strong increases of regional homogeneity in parts of the motor and visual cortex, along with decreases in the secondary cingulate cortex, the superior colliculus and the pretectal area. As CBV is intricately coupled to cerebral activity, these results suggest an abnormal neural activity in the SHR animal model, consistent with previous clinical studies and demonstrate the potential of functional ultrasound imaging as a translational tool in ADHD.
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Real-world evidence (RWE) refers to observational data gathered outside the formalism of randomized controlled trials, in real life situations, on marketed drugs. While clinical trials are the gold standards to demonstrate the efficacy and tolerability of a medicinal product, the generalizability of their results to actual use in real-life is limited by the biases induced by the very nature of clinical trials; indeed, the patients included in the trials may differ from actual users because of their concomitant diseases or treatments, or other factors excluding them from the trials. Clinical researchers and pharmaceutical industries have hence become increasingly interested in expanding and integrating RWE into clinical research, by capitalizing on the exponential growth in access to data from electronic health records, claims databases, electronic devices, software or mobile applications, registries embedded in clinical practice and social media. Meanwhile, applications of RWE may also be used for drug discovery and repurposing, for clinical developments and post-marketing studies. The aim of this review is to provide our opinion regarding the use of RWE in translational research, including non-clinical and clinical pharmacology research, at the different step of drugs development use.
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Registros Electrónicos de Salud , Investigación Biomédica Traslacional , Bases de Datos Factuales , Humanos , Sistema de RegistrosRESUMEN
BACKGROUND: There is an urgent need to understand and reverse cognitive impairment. The lack of appropriate animal models combined with the limited knowledge of pathophysiological mechanisms makes the development of new cognition-enhancing drugs complex. Scopolamine is a pharmacologic agent which impairs cognition and functional imaging in a wide range of animal species, similarly to what is seen in cognitive impairment in humans. METHODS: In this study, using a functional ultrasound (fUS) neuroimaging technique, we monitored the impact of donepezil (DPZ), a potent acetylcholinesterase inhibitor and first-line treatment in patients with mild to moderate Alzheimer's disease, in a scopolamine-induced mouse model. RESULTS: We demonstrated that despite its low impact on the cerebral blood volume (CBV) signal, scopolamine injection produced an overall decrease in functional connectivity between various brain areas. In addition, we revealed that DPZ induced a strong decrease in CBV signal without causing a difference in functional connectivity. CONCLUSION: Finally, our work highlighted that DPZ counteracted the impact of scopolamine on functional connectivity changes and confirmed the interest of using pharmaco-fUS imaging on cognitive disorders, both in frequent and rare neurological disorders.
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Enfermedad de Alzheimer , Disfunción Cognitiva , Animales , Ratones , Humanos , Indanos/farmacología , Acetilcolinesterasa/uso terapéutico , Piperidinas/farmacología , Donepezilo/farmacología , Donepezilo/uso terapéutico , Disfunción Cognitiva/inducido químicamente , Disfunción Cognitiva/tratamiento farmacológico , Escopolamina/farmacología , Enfermedad de Alzheimer/tratamiento farmacológico , Proteína FUS de Unión a ARNRESUMEN
Ten years after the launch of the Future Investment Program (Programme d'Investissement d'Avenir, PIA) and the implementation of these tools, one of Giens' roundtable workshop wanted to further explore the impact of PIA on health research and innovation with the aim of preparing action reports (bibliometrics, valuation, reputation) based on 2019 findings and the history of PIA deployment in relation to the healthcare sector; to analyze the development of the industrial sector vis-a-vis the PIA actions and to examine how the specific actions and the healthcare sector in general were able to duly articulate themselves, or, take form, given existing structures or organizations and contribute to site policies through Idex/Isite. Five success keys have been identified, which should serve as a strategic compass for future action plans to develop health innovation: Full trust governance between the project manager and the institution, driven by project objectives; An increased role of universities in the steering of PIA objects, joining together in a federation, in a site policy with the Hospital University Centres and Public Scientific and Technological Establishments; A simplification of public/private partnership schemes, in the nature of the Assessment and Action Plans, and in the responsiveness of the institutions; help with the development of local ecosystems, the fostering and support of young researchers; early cross-fertilization between the academic and industrial worlds.
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Ecosistema , Universidades , Humanos , InvestigadoresRESUMEN
Central nervous system disorders remain the leading causes of mortality and morbidity worldwide, affecting more than 1 billion patients. This therapeutic area suffers from high unmet medical needs and the search for innovative approaches to identify therapeutic strategies is urgent in the field. This review will first cover the challenges and opportunities of drug discovery in neurology, and then as well as the new models, such as human model stem cells and animal models under development in the field. In addition, innovative and translational neuroimaging techniques will be discussed, as the use of big data and artificial intelligence to discovery new drugs in neurological and neuropsychiatric disorders.
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Inteligencia Artificial , Descubrimiento de Drogas , Animales , Macrodatos , Fármacos del Sistema Nervioso Central , HumanosRESUMEN
TFEB is a mammalian transcription factor that binds directly to the CLEAR consensus sequence (5'-GTCACGTGAC-3') present in the regulatory regions of genes inducing autophagosome formation, autophagosome-lysosome fusion, hydrolase enzyme expression, and lysosomal exocytosis. By modulating these activities, TFEB coordinates on-demand control over each cell's degradation pathway. Thus, a nuclear signaling pathway regulates cellular energy metabolism through TFEB. Our growing understanding of the role of TFEB and CLEAR in the promotion of healthy clearance together with in vitro and in vivo preclinical findings in various animal models of disease supports the conclusion that the pharmacological activation of TFEB could clear toxic proteins to treat both rare and common forms of neurodegenerative disease.
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Autofagia/fisiología , Factores de Transcripción Básicos con Cremalleras de Leucinas y Motivos Hélice-Asa-Hélice/metabolismo , Lisosomas/metabolismo , Enfermedades Neurodegenerativas/fisiopatología , Animales , Línea Celular , Modelos Animales de Enfermedad , Evaluación Preclínica de Medicamentos , Regulación de la Expresión Génica , Humanos , Enfermedades por Almacenamiento Lisosomal , Estrés Oxidativo/fisiología , Fosforilación/fisiología , Transducción de SeñalRESUMEN
BACKGROUND: Recent advances using functional ultrasound (fUS) imaging have opened new avenues to evaluate brain activity through the regional monitoring of cerebral blood volume (CBV) dynamics. In particular, this technology paves the way for understanding physiological or pathological cerebral processes or exploring the pharmacological profiles of new drugs targeting brain disorders. One of the main difficulties of this technology is the lack of standardized and validated tools, in particular relevant brain atlases, to help improving the accuracy, automation and reproducibility of fUS data analysis. NEW METHOD: Here, we demonstrate the possibility to use the MRI-validated SIGMA brain atlas in rat to perform fast and precise analysis of CBV changes in numerous functionally relevant regions of interest using fUS imaging. We applied this atlas to a dataset obtained in anesthetized rats evaluating the cerebral effects of atomoxetine, a norepinephrine reuptake inhibitor currently marketed in attention-deficit/hyperactivity-disorder. RESULTS: This approach enabled to show the subregional effects of atomoxetine in the rat with very few inter-individual differences in some areas, such as the dentate gyrus. CONCLUSIONS: We show the feasibility of inter-individual registration of 2D pharmaco-fUS data and subsequent detailed analysis using the SIGMA atlas.
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Encéfalo , Imagen por Resonancia Magnética , Animales , Encéfalo/diagnóstico por imagen , Neuroimagen , Ratas , Reproducibilidad de los Resultados , UltrasonografíaRESUMEN
In vertebrates, intercellular communication is largely mediated by connexins (Cx), a family of structurally related transmembrane proteins that assemble to form hemichannels (HCs) at the plasma membrane. HCs are upregulated in different brain disorders and represent innovative therapeutic targets. Identifying modulators of Cx-based HCs is of great interest to better understand their function and define new treatments. In this study, we developed automated versions of two different cell-based assays to identify new pharmacological modulators of Cx43-HCs. As HCs remain mostly closed under physiological conditions in cell culture, depletion of extracellular Ca2+ was used to increase the probability of opening of HCs. The first assay follows the incorporation of a fluorescent dye, Yo-Pro, by real-time imaging, while the second is based on the quenching of a fluorescent protein, YFPQL, by iodide after iodide uptake. These assays were then used to screen a collection of 2242 approved drugs and compounds under development. This study led to the identification of 11 candidate hits blocking Cx43-HC, active in the two assays, with 5 drugs active on HC but not on gap junction (GJ) activities. To our knowledge, this is the first screening on HC activity and our results suggest the potential of a new use of already approved drugs in central nervous system disorders with HC impairments.
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Bioensayo , Conexina 43/genética , Drogas en Investigación/farmacología , Neuroglía/efectos de los fármacos , Medicamentos bajo Prescripción/farmacología , Automatización de Laboratorios , Proteínas Bacterianas/genética , Proteínas Bacterianas/metabolismo , Benzoxazoles/química , Calcio/metabolismo , Carbenoxolona/farmacología , Línea Celular Tumoral , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Conexina 43/antagonistas & inhibidores , Conexina 43/metabolismo , Colorantes Fluorescentes/química , Expresión Génica , Humanos , Yoduros/farmacología , Proteínas Luminiscentes/genética , Proteínas Luminiscentes/metabolismo , Ácido Meclofenámico/farmacología , Neuroglía/citología , Neuroglía/metabolismo , Compuestos de Quinolinio/química , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Imagen de Lapso de TiempoRESUMEN
ABSTRACT: Tricyclic antidepressants that inhibit serotonin and noradrenaline reuptake, such as amitriptyline, are among the first-line treatments for neuropathic pain, which is caused by a lesion or disease affecting the somatosensory nervous system. These treatments are, however, partially efficient to alleviate neuropathic pain symptoms, and better treatments are still highly required. Interactions between neurons and glial cells participate in neuropathic pain processes, and importantly, connexins-transmembrane proteins involved in cell-cell communication-contribute to these interactions. In a neuropathic pain model in rats, mefloquine, a connexin inhibitor, has been shown to potentiate the antihyperalgesic effect of amitriptyline, a widely used antidepressant. In this study, we further investigated this improvement of amitriptyline action by mefloquine, using the cuff model of neuropathic pain in mice. We first observed that oral mefloquine co-treatment prolonged the effect of amitriptyline on mechanical hypersensitivity by 12 hours after administration. In addition, we showed that this potentiation was not due to pharmacokinetic interactions between the 2 drugs. Besides, lesional and pharmacological approaches showed that the prolonged effect was induced through noradrenergic descending pathways and the recruitment of α2 adrenoceptors. Another connexin blocker, carbenoxolone, also improved amitriptyline action. Additional in vitro studies suggested that mefloquine may also directly act on serotonin transporters and on adenosine A1 and A2A receptors, but drugs acting on these other targets failed to amplify amitriptyline action. Together, our data indicate that pharmacological blockade of connexins potentiates the therapeutic effect of amitriptyline in neuropathic pain.
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Amitriptilina , Neuralgia , Amitriptilina/uso terapéutico , Animales , Antidepresivos/uso terapéutico , Antidepresivos Tricíclicos , Mefloquina/uso terapéutico , Ratones , Neuralgia/tratamiento farmacológico , RatasRESUMEN
Donepezil is a potent acetylcholinesterase inhibitor, largely used worldwide to alleviate cognitive symptoms in Alzheimer's disease (AD). Beyond the widely described neuronal impact of donepezil, it was recently shown that targeting connexins, the proteins involved in astrocyte network organization, potentiates donepezil efficacy profile using behavioral tests in AD rodent models. We herein present data demonstrating the potential of functional ultrasound imaging to monitor cerebral activity changes after pharmacological challenge in mice. As an example, we showed that although administration of donepezil or mefloquine alone at low dose had only very limited effects on the signal compared to the baseline, their combination produced marked hemodynamic effects in the hippocampus, in line with previously published behavioral data demonstrating a synergic interaction between both drugs. Thus, the present study provides new perspectives, (i) through the use of pharmaco-fUS, a new non-clinical imaging modality, to move forward drug discovery in AD and (ii) by the profiling of two drug treatments on brain dynamics, one used in AD: donepezil, and the other in development: donepezil combined with mefloquine (THN201) as a modulator of astrocyte network.
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Functional ultrasound (fUS) is a new tool enabling the imaging of brain activity through the regional monitoring of cerebral blood volume (CBV) dynamics. This innovative technique has not yet demonstrated its full potential in pharmacological applications and drug development. In the current proof-of-concept study, the impact of atomoxetine (ATX), a potent norepinephrine reuptake inhibitor and non-stimulant treatment marketed in attention-deficit/hyperactivity-disorder, was evaluated in anesthetized rat using pharmacological functional ultrasound (pharmaco-fUS) at increasing doses (0.3, 1 and 3 mg/kg). Using regions of interest (acute changes of CBV and functional connectivity) or pixel-based (general linear modeling and independent component analysis) analysis, we here demonstrated that ATX consistently displayed a hemodynamic effect in the visual cortex, the dentate gyrus and thalamus, especially visual areas such as lateral posterior thalamic nuclei and lateral geniculate nuclei (LGN). The time profile of ATX effects was dose-dependent, with fastest CBV increases at the highest dose, and longer CBV increases at the intermediate dose. Standardizing the use of pharmaco-fUS could improve our understanding of the mechanism of action of drugs active in the brain and might constitute a new step to move forward in drug development for neurological disorders.
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Inhibidores de Captación Adrenérgica/metabolismo , Clorhidrato de Atomoxetina/metabolismo , Giro Dentado/metabolismo , Tálamo/metabolismo , Ultrasonografía/métodos , Corteza Visual/metabolismo , Inhibidores de Captación Adrenérgica/farmacología , Animales , Clorhidrato de Atomoxetina/farmacología , Giro Dentado/diagnóstico por imagen , Giro Dentado/efectos de los fármacos , Masculino , Ratas , Ratas Endogámicas WKY , Tálamo/diagnóstico por imagen , Tálamo/efectos de los fármacos , Corteza Visual/diagnóstico por imagen , Corteza Visual/efectos de los fármacosRESUMEN
Donepezil (DPZ) is an acetylcholinesterase inhibitor used in Alzheimer's disease to restore cognitive functions but is endowed with limited efficacy. Recent studies pointed out the implication of astroglial networks in cognitive processes, notably via astrocyte connexins (Cxs), proteins involved in gap junction intercellular communications. Hence, we investigated the impact on cognition of pharmacological or genetic modulations of those astrocyte Cxs during DPZ challenge in two rodent models of Alzheimer's disease-like memory deficits. We demonstrated that the Cx modulator mefloquine (MEF) significantly enhanced the procognitive effect of DPZ in both models. In parallel, we determined that MEF potentiated DPZ-induced release of acetylcholine in hippocampus. Finally, local genetic silencing of astrocyte Cxs in the hippocampus was also found to enhance the procognitive effect of DPZ, pointing out the importance of Cx-dependent astrocyte networks in memory processes.
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We consider a model for the polymerization (fragmentation) process involved in infectious prion self-replication and study both its dynamics and non-zero steady state. We address several issues. Firstly, we extend a previous study of the nucleated polymerization model [M.L. Greer, L. Pujo-Menjouet, G.F. Webb, A mathematical analysis of the dynamics of prion proliferation, J. Theoret. Biol. 242 (2006) 598; H. Engler, J. Pruss, G.F. Webb, Analysis of a model for the dynamics of prions II, J. Math. Anal. Appl. 324 (2006) 98] to take into account size dependent replicative properties of prion aggregates. This is achieved by a choice of coefficients in the model that are not constant. Secondly, we show stability results for this steady state for general coefficients where reduction to a system of differential equations is not possible. We use a duality method based on recent ideas developed for population models. These results confirm the potential influence of the amyloid precursor production rate in promoting amyloidogenic diseases. Finally, we investigate how the converting factor may depend upon the aggregate size. Besides the confirmation that size-independent parameters are unlikely to occur, the present study suggests that the PrPsc aggregate size repartition is amongst the most relevant experimental data in order to investigate this dependence. In terms of prion strain, our results indicate that the PrPsc aggregate repartition could be a constraint during the adaptation mechanism of the species barrier overcoming, that opens experimental perspectives for prion amyloid polymerization and prion strain investigation.
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Modelos Biológicos , Enfermedades por Prión/metabolismo , Priones/metabolismo , Animales , Simulación por Computador , Humanos , Conformación ProteicaRESUMEN
Gap junctions (GJs) are dynamic structures composed of hexamers of connexins (Cxs), a class of transmembrane proteins enabling channel-mediated direct intercellular communication through cell-cell diffusion of ions and small metabolites. In defined conditions, Cxs also work as hemichannels allowing exchanges between the cytoplasm and the extracellular medium. The most common GJ channel is formed by connexin 43 (Cx43) and plays an important role in physiological and pathological processes in excitable tissues, such as heart and brain. Hence, Cx43 has been largely envisioned as a new therapeutic target in cancer, neurological and psychiatric indications, or cardiovascular diseases. Identifying new pharmacological inhibitors of Cx43 GJs with different mechanisms of action and from diverse chemical classes is thus highly challenging. We present here a high-content screening method, based on the evaluation of fluorescent dye transfer rates between adjacent cells to monitor the function of GJs in U251 glioblastoma cells expressing high levels of Cx43. This assay was validated using well-described pharmacological GJ inhibitors such as mefloquine. The method was adapted to screen a library of 1,280 Food and Drug Administration- and European Medicines Agency-approved drugs that led to the selection of both known and new inhibitors of GJ channel function. We further focused on a specific class of microtubule-targeting agents, confirming that a proper tubulin network is required for functional Cx43 GJ channels.