NMDA receptor dysfunction contributes to impaired brain-derived neurotrophic factor-induced facilitation of hippocampal synaptic transmission in a Tau transgenic model.

While the spatiotemporal development of Tau pathology has been correlated with occurrence of cognitive deficits in Alzheimer's patients, mechanisms underlying these deficits remain unclear. Both brain-derived neurotrophic factor (BDNF) and its tyrosine kinase receptor TrkB play a critical role in hippocampus-dependent synaptic plasticity and memory. When applied on hippocampal slices, BDNF is able to enhance AMPA receptor-dependent hippocampal basal synaptic transmission through a mechanism involving TrkB and N-methyl-d-Aspartate receptors (NMDAR). Using THY-Tau22 transgenic mice, we demonstrated that hippocampal Tau pathology is associated with loss of synaptic enhancement normally induced by exogenous BDNF. This defective response was concomitant to significant memory impairments. We show here that loss of BDNF response was due to impaired NMDAR function. Indeed, we observed a significant reduction of NMDA-induced field excitatory postsynaptic potential depression in the hippocampus of Tau mice together with a reduced phosphorylation of NR2B at the Y1472, known to be critical for NMDAR function. Interestingly, we found that both NR2B and Src, one of the NR2B main kinases, interact with Tau and are mislocalized to the insoluble protein fraction rich in pathological Tau species. Defective response to BDNF was thus likely related to abnormal interaction of Src and NR2B with Tau in THY-Tau22 animals. These are the first data demonstrating a relationship between Tau pathology and synaptic effects of BDNF and supporting a contribution of defective BDNF response and impaired NMDAR function to the cognitive deficits associated with Tauopathies

Encephalopathy induced by Alzheimer brain inoculation in a non-human primate.

Alzheimer's disease is characterized by cognitive alterations, cerebral atrophy and neuropathological lesions including neuronal loss, accumulation of misfolded and aggregated β-amyloid peptides (Aβ) and tau proteins. Iatrogenic induction of Aβ is suspected in patients exposed to pituitary-derived hormones, dural grafts, or surgical instruments, presumably contaminated with Aβ. Induction of Aβ and tau lesions has been demonstrated in transgenic mice after contamination with Alzheimer's disease brain homogenates, with very limited functional consequences. Unlike rodents, primates naturally express Aβ or tau under normal conditions and attempts to transmit Alzheimer pathology to primates have been made for decades. However, none of earlier studies performed any detailed functional assessments. For the first time we demonstrate long term memory and learning impairments in a non-human primate (Microcebus murinus) following intracerebral injections with Alzheimer human brain extracts. Animals inoculated with Alzheimer brain homogenates displayed progressive cognitive impairments (clinical tests assessing cognitive and motor functions), modifications of neuronal activity (detected by electroencephalography), widespread and progressive cerebral atrophy (in vivo MRI assessing cerebral volume loss using automated voxel-based analysis), neuronal loss in the hippocampus and entorhinal cortex (post mortem stereology). They displayed parenchymal and vascular Aβ depositions and tau lesions for some of them, in regions close to the inoculation sites. Although these lesions were sparse, they were never detected in control animals. Tau-positive animals had the lowest performances in a memory task and displayed the greatest neuronal loss. Our study is timely and important as it is the first one to highlight neuronal and clinical dysfunction following inoculation of Alzheimer's disease brain homogenates in a primate. Clinical signs in a chronic disease such as Alzheimer take a long time to be detectable. Documentation of clinical deterioration and/or dysfunction following intracerebral inoculations with Alzheimer human brain extracts could lead to important new insights about Alzheimer initiation processes

Does physical activity associated with chronic food restriction alleviate anxiety like behaviour, in female mice?

International audienceAnorexia nervosa (AN) is an eating disorder characterized by excessive weight loss, persistent food restriction and inappropriate physical activity relative to declining energy balance. The comorbidity with depression and/ or anxiety disorders might contribute to the "chronicization" of the disease. We aimed here to question first the link between physical activity and anxiety from a clinical investigation of AN patients (n = 206). Then, using a rodent model mimicking numerous physiological and metabolic alterations commonly seen in AN patients, we examined whether 1) chronic food restriction increased anxiety-like behaviour and 2) physical activity plays a role in regulating anxiety levels. To this end, we exposed young female mice to a chronic food restriction (FR, n = 8) paradigm combined or not with access to a running wheel (FRW, n = 8) for two weeks. The mice were compared to a group of mice fed ad libitum without (AL, n = 6) or with running wheel access (ALW, n = 8). We explored anxiety-like behaviour of all mice in the following tests: hyponeophagia, marble burying, elevated plus maze, open field, and the light and dark box. On the last day, we used a restraint test of 30 min duration and measured their stress reactivity by assaying plasma corticosterone. In the open field and the elevated plus-maze, we found that FRW mice behaved similarly to AL and ALW mice whereas FR mice did not express anxiety-like behaviour. The FRW mice displayed the lowest latency to reach the food in the hyponeophagia test. Regarding stress reactivity, FRW mice exhibited corticosterone reactivity after acute stress that was similar to the control mice, while FR mice did not fully return to basal corticosterone at one hour after the restraint stress. Taken together, these data demonstrate a differential reactivity to acute stress in FR conditions and a beneficial effect of running wheel activity in ALW and FRW conditions. Moreover, we report the absence of a typical anxiety-like behaviour associated with the food restriction (FR and FRW groups). We conclude that this model (FR and FRW mice) did not express typical anxiety-like behaviour, but that physical activity linked to food restriction improved coping strategies in an anxiogenic context

La protéine TMEM240, mutée dans la SCA21, est exprimée dans les cellules de Purkinje et ses terminaisons synaptiques: Localisation de TMEM240 dans le cervelet

International audienceA variety of missense mutations and a stop mutation in the gene coding for transmembrane protein 240 (TMEM240) have been reported to be the causative mutations of spinocerebellar ataxia 21 (SCA21). We aimed to investigate the expression of TMEM240 protein in mouse brain at the tissue, cellular, and subcellular levels. Immunofluorescence labeling showed TMEM240 to be expressed in various areas of the brain, with the highest levels in the hippocampus, isocortex, and cerebellum. In the cerebellum, TMEM240 was detected in the deep nuclei and the cerebellar cortex. The protein was expressed in all three layers of the cortex and various cerebellar neurons. TMEM240 was localized to climbing, mossy, and parallel fiber afferents projecting to Purkinje cells, as shown by coimmunostaining with VGLUT1 and VGLUT2. Co-immunostaining with synaptophysin, post-synaptic fractionation, and confirmatory electron microscopy showed TMEM240 to be localized to the post-synaptic side of synapses near the Purkinje-cell soma. Similar results were obtained in human cerebellar sections. These data suggest that TMEM240 may be involved in the organization of the cerebellar network, particularly in synaptic inputs converging on Purkinje cells. This study is the first to describe TMEM240 expression in the normal mouse brain

Gel electrophoresis of human sperm: a simple method for evaluating sperm protein quality

Résumé Contexte Les limites des analyses conventionnelles du sperme ont mis en évidence la nécessité de moyens supplémentaires d’évaluation de la qualité du sperme. Matériel et Méthodes La méthode d’électrophorèse unidimensionnelle a été utilisée pour évaluer la teneur et la qualité protéique dans des échantillons d’éjaculats individuels de 245 hommes avec des paramètres spermatiques connus. Résultats La teneur en protéines du sperme variait d’un échantillon à l’autre, en particulier dans la gamme des poids moléculaires élevés. L’intensité des bandes de 80–110 kDa était corrélée à la mobilité progressive (r = 0,15, p = 0,015) et était significativement plus élevée (p = 0,0367) dans le groupe des hommes avec des paramètres conventionnels spermatiques supérieurs aux valeurs de référence (OMS, 2010) comparé au groupe d’hommes dont l’éjaculat présentait au moins un paramètre spermatique (volume de sperme, concentration de spermatozoïdes, numération des spermatozoïdes, motilité progressive, formes normales et indice d’anomalies multiples) en deça de la valeur de référence. Les bandes dans la gamme de 80–110 kDa ont été identifiées en spectrométrie de masse et se sont révélées être des protéines de la gaine fibreuse du flagelle: la protéine d’ancrage A-kinase 4, la protéine d’ancrage A-kinase 3 et l’hexokinase de type 1. Conclusion La méthode d’électrophorèse unidimensionnelle constitue une méthode simple, rapide, fiable et peu coûteuse pour analyser la qualité des protéines du sperme dans les éjaculats humains individuels

A ß-Secretase Modulator Decreases Tau Pathology and Preserves Short-Term Memory in a Mouse Model of Neurofibrillary Degeneration

International audienceIdentifying which among several in cellulo pharmacological activities is necessary for the proper in vivo activity is essential for further drug development against Alzheimer’s disease pathophysiological processes. An in-depth structure–activity relationship–based study has been carried out, and two molecules, named MAGS02-14 and PEL24-199, that share a ß-secretase modulatory effect associated or not to a lysosomotropic activity in cellulo have been identified. In terms of chemical formulas, MAGS02-14 and PEL24-199 only differ from each other by a single nitrogen atom. The study aimed to elucidate the in vivo pharmacological effects of lysosomotropic and/or the ß-secretase modulatory activity in a tau pathology mouse model. To address this question, the THY-Tau22 transgenic model of tauopathy was treated with both compounds for 6 weeks in a curative paradigm. Short-term memory, tau burden, and inflammatory processes were analyzed using orthogonal methods, and PEL24-199, but not MAGS02-14, was shown to restore the short-term memory and reduce the neurofibrillary degenerating process. These effects were associated with a reduced phosphorylation of tau, an increased phosphatase expression, and decreased astrogliosis. Our results, therefore, suggest that the lysosomotropic activity may be nonessential for the effect on tau pathology

Microtube Array Membrane Encapsulated Cell Therapy: A Novel Platform Technology Solution for Treatment of Alzheimer’s Disease

International audienceAlzheimer's disease is the most frequent form of dementia in aging population and is presently the world's sixth largest cause of mortality. With the advancement of therapies, several solutions have been developed such as passive immunotherapy against these misfolded proteins, thereby resulting in the clearance. Within this segment, encapsulated cell therapy (ECT) solutions that utilize antibody releasing cells have been proposed with a multitude of techniques under development. Hence, in this study, we utilized our novel and patented Microtube Array Membranes (MTAMs) as an encapsulating platform system with anti-pTau antibody-secreting hybridoma cells to study the impact of it on Alzheimer's disease. In vivo results revealed that in the water maze, the mice implanted with hybridoma cell MTAMs intracranially (IN) and subcutaneously (SC) showed improvement in the time spent the goal quadrant and escape latency. In passive avoidance, hybridoma cell loaded MTAMs (IN and SC) performed significantly well in step-through latency. At the end of treatment, animals with hybridoma cell loaded MTAMs had lower phosphorylated tau (pTau) expression than empty MTAMs had. Combining both experimental results unveiled that the clearance of phosphorylated tau might rescue the cognitive impairment associated with AD

A phenotypic approach to the discovery of compounds that promote non-amyloidogenic processing of the amyloid precursor protein: Toward a new profile of indirect β-secretase inhibitors

International audienceDysregulation of the Amyloid Precursor Protein (APP) processing leading to toxic species of amyloid b peptides (Ab) is central to Alzheimer's disease (AD) etiology. Ab peptides are produced by sequential cleavage of APP by b-secretase (BACE-1) and g-secretase. Lysosomotropic agent, chloroquine (CQ), has been reported to inhibit Ab peptide production. However, this effect is accompanied by an inhibition of lysosome-mediated degradation pathways. Following on from the promising activity of two series of APP metabolism modulators derived from CQ, we sought to develop new series of compounds that would retain the inhibitory effects on Ab production without altering lysosome functions. Herein, we applied a ligand-based pharmacophore modeling approach coupled with de novo design that led to the discovery of a series of biaryl compounds. Structure-activity relationship studies revealed that minor modifications like replacing a piperidine moiety of compound 30 by a cyclohexyl (compound 31) allowed for the identification of compounds with the desired profile. Further studies have demonstrated that compounds 30 and 31 act through an indirect mechanism to inhibit b-secretase activity. This work shows that it is possible to dissociate the inhibitory effect on Ab peptide secretion of CQ-derived compounds from the lysosome-mediated degradation effect, providing a new profile of indirect b-secretase inhibitors

Transmission of amyloid-beta and tau pathologies is associated with cognitive impairments in a primate

International audienceAbstract Amyloid-β (Aβ) pathology transmission has been described in patients following iatrogenic exposure to compounds contaminated with Aβ proteins. It can induce cerebral Aβ angiopathy resulting in brain hemorrhages and devastating clinical impacts. Iatrogenic transmission of tau pathology is also suspected but not experimentally proven. In both scenarios, lesions were detected several decades after the putatively triggering medico-surgical act. There is however little information regarding the cognitive repercussions in individuals who do not develop cerebral hemorrhages. In the current study, we inoculated the posterior cingulate cortex and underlying corpus callosum of young adult primates ( Microcebus murinus ) with either Alzheimer’s disease or control brain extracts. This led to widespread Aβ and tau pathologies in all of the Alzheimer-inoculated animals following a 21-month-long incubation period (n = 12) whereas none of the control brain extract-inoculated animals developed such lesions (n = 6). Aβ deposition affected almost all cortical regions. Tau pathology was also detected in Aβ-deposit-free regions distant from the inoculation sites ( e.g. in the entorhinal cortex), while some regions adjacent, but not connected, to the inoculation sites were spared ( e.g. the occipital cortex). Alzheimer-inoculated animals developed cognitive deficits and cerebral atrophy compared to controls. These pathologies were induced using two different batches of Alzheimer brain extracts. This is the first experimental demonstration that tau can be transmitted by human brain extracts inoculations in a primate. We also showed for the first time that the transmission of widespread Aβ and tau pathologies can be associated with cognitive decline. Our results thus reinforce the need to organize a systematic monitoring of individuals who underwent procedures associated with a risk of Aβ and tau iatrogenic transmission. They also provide support for Alzheimer brain-inoculated primates as relevant models of Alzheimer pathology

Inhibition of Tau seeding by targeting Tau nucleation core within neurons with a single domain antibody fragment

Tau proteins aggregate into filaments in brain cells in Alzheimer’s disease and related disorders referred to as tauopathies. Here, we used fragments of camelid heavy-chain-only antibodies (VHHs or single domain antibody fragments) targeting Tau as immuno-modulators of its pathologic seeding. A VHH issued from the screen against Tau of a synthetic phage-display library of humanized VHHs was selected for its capacity to bind Tau microtubule-binding domain, composing the core of Tau fibrils. This lead VHH was optimized to improve its biochemical properties and to act in the intracellular compartment, resulting in VHH Z70. VHH Z70 was more efficient than the lead to inhibit in vitro Tau aggregation in heparin-induced assays. Expression of VHH Z70 in a cellular model of Tau seeding also decreased the fluorescence-reported aggregation. Finally, intracellular expression of VHH Z70 in the brain of an established tauopathy mouse seeding model demonstrated its capacity to mitigate accumulation of pathological Tau. VHH Z70, by targeting Tau inside brain neurons, where most of the pathological Tau resides, provides a new tool to explore the optimal strategies of immunotherapy in tauopathies