A large-scale volumetric correlated light and electron microscopy study localizes Alzheimer's disease-related molecules in the hippocampus.

Connectomics is a nascent neuroscience field to map and analyze neuronal networks. It provides a new way to investigate abnormalities in brain tissue, including in models of Alzheimer's disease (AD). This age-related disease is associated with alterations in amyloid-ß (Aß) and phosphorylated tau (pTau). These alterations correlate with AD's clinical manifestations, but causal links remain unclear. Therefore, studying these molecular alterations within the context of the local neuronal and glial milieu may provide insight into disease mechanisms. Volume electron microscopy (vEM) is an ideal tool for performing connectomics studies at the ultrastructural level, but localizing specific biomolecules within large-volume vEM data has been challenging. Here we report a volumetric correlated light and electron microscopy (vCLEM) approach using fluorescent nanobodies as immuno-probes to localize Alzheimer's disease-related molecules in a large vEM volume. Three molecules (pTau, Aß, and a marker for activated microglia (CD11b)) were labeled without the need for detergents by three nanobody probes in a sample of the hippocampus of the 3xTg Alzheimer's disease model mouse. Confocal microscopy followed by vEM imaging of the same sample allowed for registration of the location of the molecules within the volume. This dataset revealed several ultrastructural abnormalities regarding the localizations of Aß and pTau in novel locations. For example, two pTau-positive post-synaptic spine-like protrusions innervated by axon terminals were found projecting from the axon initial segment of a pyramidal cell. Three pyramidal neurons with intracellular Aß or pTau were 3D reconstructed. Automatic synapse detection, which is necessary for connectomics analysis, revealed the changes in density and volume of synapses at different distances from an Aß plaque. This vCLEM approach is useful to uncover molecular alterations within large-scale volume electron microscopy data, opening a new connectomics pathway to study Alzheimer's disease and other types of dementia.

Effects of Low-Intensity Pulsed Ultrasound-Induced Blood-Brain Barrier Opening in P301S Mice Modeling Alzheimer's Disease Tauopathies.

Alzheimer's disease (AD) is the leading cause of dementia. No treatments have led to clinically meaningful impacts. A major obstacle for peripherally administered therapeutics targeting the central nervous system is related to the blood-brain barrier (BBB). Ultrasounds associated with microbubbles have been shown to transiently and safely open the BBB. In AD mouse models, the sole BBB opening with no adjunct drugs may be sufficient to reduce lesions and mitigate cognitive decline. However, these therapeutic effects are for now mainly assessed in preclinical mouse models of amyloidosis and remain less documented in tau lesions. The aim of the present study was therefore to evaluate the effects of repeated BBB opening using low-intensity pulsed ultrasounds (LIPU) in tau transgenic P301S mice with two main readouts: tau-positive lesions and microglial cells. Our results show that LIPU-induced BBB opening does not decrease tau pathology and may even potentiate the accumulation of pathological tau in selected brain regions. In addition, LIPU-BBB opening in P301S mice strongly reduced microglia densities in brain parenchyma, suggesting an anti-inflammatory action. These results provide a baseline for future studies using LIPU-BBB opening, such as adjunct drug therapies, in animal models and in AD patients.

Huntingtin recruits KIF1A to transport synaptic vesicle precursors along the mouse axon to support synaptic transmission and motor skill learning.

Neurotransmitters are released at synapses by synaptic vesicles (SVs), which originate from SV precursors (SVPs) that have traveled along the axon. Because each synapse maintains a pool of SVs, only a small fraction of which are released, it has been thought that axonal transport of SVPs does not affect synaptic function. Here, studying the corticostriatal network both in microfluidic devices and in mice, we find that phosphorylation of the Huntingtin protein (HTT) increases axonal transport of SVPs and synaptic glutamate release by recruiting the kinesin motor KIF1A. In mice, constitutive HTT phosphorylation causes SV over-accumulation at synapses, increases the probability of SV release, and impairs motor skill learning on the rotating rod. Silencing KIF1A in these mice restored SV transport and motor skill learning to wild-type levels. Axonal SVP transport within the corticostriatal network thus influences synaptic plasticity and motor skill learning.

Endogenous pathology in tauopathy mice progresses via brain networks.

Neurodegenerative tauopathies are hypothesized to propagate via brain networks. This is uncertain because we have lacked precise network resolution of pathology. We therefore developed whole-brain staining methods with anti-p-tau nanobodies and imaged in 3D PS19 tauopathy mice, which have pan-neuronal expression of full-length human tau containing the P301S mutation. We analyzed patterns of p-tau deposition across established brain networks at multiple ages, testing the relationship between structural connectivity and patterns of progressive pathology. We identified core regions with early tau deposition, and used network propagation modeling to determine the link between tau pathology and connectivity strength. We discovered a bias towards retrograde network-based propagation of tau. This novel approach establishes a fundamental role for brain networks in tau propagation, with implications for human disease.

Golgi localization of SARS-CoV-2 spike protein and interaction with furin in cerebral COVID-19 microangiopathy: a clue to the central nervous system involvement?

In a neuropathological series of 20 COVID-19 cases, we analyzed six cases (three biopsies and three autopsies) with multiple foci predominantly affecting the white matter as shown by MRI. The cases presented with microhemorrhages evocative of small artery diseases. This COVID-19 associated cerebral microangiopathy (CCM) was characterized by perivascular changes: arterioles were surrounded by vacuolized tissue, clustered macrophages, large axonal swellings and a crown arrangement of aquaporin-4 immunoreactivity. There was evidence of blood-brain-barrier leakage. Fibrinoid necrosis, vascular occlusion, perivascular cuffing and demyelination were absent. While no viral particle or viral RNA was found in the brain, the SARS-CoV-2 spike protein was detected in the Golgi apparatus of brain endothelial cells where it closely associated with furin, a host protease known to play a key role in virus replication. Endothelial cells in culture were not permissive to SARS-CoV-2 replication. The distribution of the spike protein in brain endothelial cells differed from that observed in pneumocytes. In the latter, the diffuse cytoplasmic labeling suggested a complete replication cycle with viral release, notably through the lysosomal pathway. In contrast, in cerebral endothelial cells the excretion cycle was blocked in the Golgi apparatus. Interruption of the excretion cycle could explain the difficulty of SARS-CoV-2 to infect endothelial cells in vitro and to produce viral RNA in the brain. Specific metabolism of the virus in brain endothelial cells could weaken the cell walls and eventually lead to the characteristic lesions of COVID-19 associated cerebral microangiopathy. Furin as a modulator of vascular permeability could provide some clues for the control of late effects of microangiopathy.

Alterations of Neuronal Lysosomes in Alzheimer's Disease and in APPxPS1-KI Mice.

BACKGROUND: The cellular and molecular alterations associated with synapse and neuron loss in Alzheimer's disease (AD) remain unclear. In transgenic mouse models that express mutations responsible for familial AD, neuronal and synaptic losses occur in populations that accumulate fibrillar amyloid-ß 42 (Aß42) intracellularly. OBJECTIVE: We aimed to study the subcellular localization of these fibrillar accumulations and whether such intraneuronal assemblies could be observed in the human pathology. METHODS: We used immunolabeling and various electron microscopy techniques on APP x presenilin1 - knock-in mice and on human cortical biopsies and postmortem samples. RESULTS: We found an accumulation of Aß fibrils in lipofuscin granule-like organelles in APP x presenilin1 - knock-in mice. Electron microscopy of human cortical biopsies also showed an accumulation of undigested material in enlarged lipofuscin granules in neurons from AD compared to age-matched non-AD patients. However, in those biopsies or in postmortem samples we could not detect intraneuronal accumulations of Aß fibrils, neither in the lipofuscin granules nor in other intraneuronal compartments. CONCLUSION: The intralysosomal accumulation of Aß fibrils in specific neuronal populations in APPxPS1-KI mice likely results from a high concentration of Aß42 in the endosome-lysosome system due to the high expression of the transgene in these neurons.

Pilot study of repeated blood-brain barrier disruption in patients with mild Alzheimer's disease with an implantable ultrasound device.

BACKGROUND: Temporary disruption of the blood-brain barrier (BBB) using pulsed ultrasound leads to the clearance of both amyloid and tau from the brain, increased neurogenesis, and mitigation of cognitive decline in pre-clinical models of Alzheimer's disease (AD) while also increasing BBB penetration of therapeutic antibodies. The goal of this pilot clinical trial was to investigate the safety and efficacy of this approach in patients with mild AD using an implantable ultrasound device. METHODS: An implantable, 1-MHz ultrasound device (SonoCloud-1) was implanted under local anesthesia in the skull (extradural) of 10 mild AD patients to target the left supra-marginal gyrus. Over 3.5 months, seven ultrasound sessions in combination with intravenous infusion of microbubbles were performed twice per month to temporarily disrupt the BBB. 18F-florbetapir and 18F-fluorodeoxyglucose positron emission tomography (PET) imaging were performed on a combined PET/MRI scanner at inclusion and at 4 and 8 months after the initiation of sonications to monitor the brain metabolism and amyloid levels along with cognitive evaluations. The evolution of cognitive and neuroimaging features was compared to that of a matched sample of control participants taken from the Alzheimer's Disease Neuroimaging Initiative (ADNI). RESULTS: A total of 63 BBB opening procedures were performed in nine subjects. The procedure was well-tolerated. A non-significant decrease in amyloid accumulation at 4 months of - 6.6% (SD = 7.2%) on 18F-florbetapir PET imaging in the sonicated gray matter targeted by the ultrasound transducer was observed compared to baseline in six subjects that completed treatments and who had evaluable imaging scans. No differences in the longitudinal change in the glucose metabolism were observed compared to the neighboring or contralateral regions or to the change observed in the same region in ADNI participants. No significant effect on cognition evolution was observed in comparison with the ADNI participants as expected due to the small sample size and duration of the trial. CONCLUSIONS: These results demonstrate the safety of ultrasound-based BBB disruption and the potential of this technology to be used as a therapy for AD patients. Research of this technique in a larger clinical trial with a device designed to sonicate larger volumes of tissue and in combination with disease-modifying drugs may further enhance the effects observed. TRIAL REGISTRATION: ClinicalTrials.gov, NCT03119961.

P2X7-deficiency improves plasticity and cognitive abilities in a mouse model of Tauopathy.

Alzheimer's disease is the most common form of dementia characterized by intracellular aggregates of hyperphosphorylated Tau protein and extracellular accumulation of amyloid ß (Aß) peptides. We previously demonstrated that the purinergic receptor P2X7 (P2X7) plays a major role in Aß-mediated neurodegeneration but the relationship between P2X7 and Tau remained overlooked. Such a link was supported by cortical upregulation of P2X7 in patients with various type of frontotemporal lobar degeneration, including mutation in the Tau-coding gene, MAPT, as well as in the brain of a Tauopathy mouse model (THY-Tau22). Subsequent phenotype analysis of P2X7-deficient Tau mice revealed the instrumental impact of this purinergic receptor. Indeed, while P2X7-deficiency had a moderate effect on Tau pathology itself, we observed a significant reduction of microglia activation and of Tau-related inflammatory mediators, particularly CCL4. Importantly, P2X7 deletion ultimately rescued synaptic plasticity and memory impairments of Tau mice. Altogether, the present data support a contributory role of P2X7 dysregulation on processes governing Tau-induced brain anomalies. Due to the convergent role of P2X7 blockade in both Aß and Tau background, P2X7 inhibitors might prove to be ideal candidate drugs to curb the devastating cognitive decline in Alzheimer's disease and Tauopathies.

Effects of Chronic Masitinib Treatment in APPswe/PSEN1dE9 Transgenic Mice Modeling Alzheimer's Disease.

BACKGROUND: Masitinib is a selective tyrosine kinase inhibitor that modulates mast cells activity. A previous phase II study reported a cognitive effect of masitinib in patients with Alzheimer's disease. OBJECTIVE: We aimed to shed light on the mode of action of masitinib in Alzheimer's disease. METHODS/RESULTS: We demonstrated here that chronic oral treatment of APPswe/PSEN1dE9 transgenic mice modeling Alzheimer's disease restored normal spatial learning performance while having no impacts on amyloid-ß loads nor on neuroinflammation. However, masitinib promoted a recovery of synaptic markers. Complete genetic depletion of mast cells in APPswe/PSEN1dE9 mice similarly rescued synaptic impairments. CONCLUSION: These results underline that masitinib therapeutic efficacy might primarily be associated with a synapto-protective action in relation with mast cells inhibition.

The lipid phosphatase Synaptojanin 1 undergoes a significant alteration in expression and solubility and is associated with brain lesions in Alzheimer's disease.

Synaptojanin 1 (SYNJ1) is a brain-enriched lipid phosphatase critically involved in autophagosomal/endosomal trafficking, synaptic vesicle recycling and metabolism of phosphoinositides. Previous studies suggest that SYNJ1 polymorphisms have significant impact on the age of onset of Alzheimer's disease (AD) and that SYNJ1 is involved in amyloid-induced toxicity. Yet SYNJ1 protein level and cellular localization in post-mortem human AD brain tissues have remained elusive. This study aimed to examine whether SYNJ1 localization and expression are altered in post-mortem AD brains. We found that SYNJ1 is accumulated in Hirano bodies, plaque-associated dystrophic neurites and some neurofibrillary tangles (NFTs). SYNJ1 immunoreactivity was higher in neurons and in the senile plaques in AD patients carrying one or two ApolipoproteinE (APOE) ε4 allele(s). In two large cohorts of APOE-genotyped controls and AD patients, SYNJ1 transcripts were significantly increased in AD temporal isocortex compared to control. There was a significant increase in SYNJ1 transcript in APOEε4 carriers compared to non-carriers in AD cohort. SYNJ1 was systematically co-enriched with PHF-tau in the sarkosyl-insoluble fraction of AD brain. In the RIPA-insoluble fraction containing protein aggregates, SYNJ1 proteins were significantly increased and observed as a smear containing full-length and cleaved fragments in AD brains. In vitro cleavage assay showed that SYNJ1 is a substrate of calpain, which is highly activated in AD brains. Our study provides evidence of alterations in SYNJ1 mRNA level and SYNJ1 protein degradation, solubility and localization in AD brains.

Presynaptic APP levels and synaptic homeostasis are regulated by Akt phosphorylation of huntingtin.

Studies have suggested that amyloid precursor protein (APP) regulates synaptic homeostasis, but the evidence has not been consistent. In particular, signaling pathways controlling APP transport to the synapse in axons and dendrites remain to be identified. Having previously shown that Huntingtin (HTT), the scaffolding protein involved in Huntington's disease, regulates neuritic transport of APP, we used a microfluidic corticocortical neuronal network-on-a-chip to examine APP transport and localization to the pre- and post-synaptic compartments. We found that HTT, upon phosphorylation by the Ser/Thr kinase Akt, regulates APP transport in axons but not dendrites. Expression of an unphosphorylatable HTT decreased axonal anterograde transport of APP, reduced presynaptic APP levels, and increased synaptic density. Ablating in vivo HTT phosphorylation in APPPS1 mice, which overexpress APP, reduced presynaptic APP levels, restored synapse number and improved learning and memory. The Akt-HTT pathway and axonal transport of APP thus regulate APP presynaptic levels and synapse homeostasis.

Huntingtin phosphorylation governs BDNF homeostasis and improves the phenotype of Mecp2 knockout mice.

Mutations in the X-linked MECP2 gene are responsible for Rett syndrome (RTT), a severe neurological disorder for which there is no treatment. Several studies have linked the loss of MeCP2 function to alterations of brain-derived neurotrophic factor (BDNF) levels, but non-specific overexpression of BDNF only partially improves the phenotype of Mecp2-deficient mice. We and others have previously shown that huntingtin (HTT) scaffolds molecular motor complexes, transports BDNF-containing vesicles, and is under-expressed in Mecp2 knockout brains. Here, we demonstrate that promoting HTT phosphorylation at Ser421, either by a phospho-mimetic mutation or inhibition of the phosphatase calcineurin, restores endogenous BDNF axonal transport in vitro in the corticostriatal pathway, increases striatal BDNF availability and synaptic connectivity in vivo, and improves the phenotype and the survival of Mecp2 knockout mice-even though treatments were initiated only after the mice had already developed symptoms. Stimulation of endogenous cellular pathways may thus be a promising approach for the treatment of RTT patients.

Long-lasting correction of in vivo LTP and cognitive deficits of mice modelling Down syndrome with an α5-selective GABAA inverse agonist.

BACKGROUND AND PURPOSE: Excessive GABAergic inhibition contributes to cognitive dysfunctions in Down syndrome (DS). Selective negative allosteric modulators (NAMs) of α5-containing GABAA receptors such as the α5 inverse agonist (α5IA) restore learning and memory deficits in Ts65Dn mice, a model of DS. In this study we have assessed the long-lasting effects of α5IA on in vivo LTP and behaviour in Ts65Dn mice. EXPERIMENTAL APPROACH: We made in vivo LTP recordings for six consecutive days in freely moving Ts65Dn mice and their wild-type littermates, treated with vehicle or α5IA. In parallel, Ts65Dn mice were assessed by various learning and memory tests (Y maze, Morris water maze, or the novel object recognition) for up to 7 days, following one single injection of α5IA or vehicle. KEY RESULTS: LTP was not evoked in vivo in Ts65Dn mice at hippocampal CA3-CA1 synapses. However, this deficit was sustainably reversed for at least six consecutive days following a single injection of α5IA. This long-lasting effect of α5IA was also observed when assessing working and long-term memory deficits in Ts65Dn mice. CONCLUSION AND IMPLICATIONS: We show for the first time in vivo LTP deficits in Ts65Dn mice. These deficits were restored for at least 6 days following acute treatment with α5IA and might be the substrate for the long-lasting pharmacological effects of α5IA on spatial working and long-term recognition and spatial memory tasks. Our results demonstrate the relevance of negative allosteric modulators of α5-containing GABAA receptors to the treatment of cognitive deficits associated with DS.

Human subiculo-fornico-mamillary system in Alzheimer's disease: Tau seeding by the pillar of the fornix.

In Alzheimer's disease (AD), Tau and Aß aggregates involve sequentially connected regions, sometimes distantly separated. These alterations were studied in the pillar of the fornix (PoF), an axonal tract, to analyse the role of axons in their propagation. The PoF axons mainly originate from the subicular neurons and project to the mamillary body. Forty-seven post-mortem cases at various Braak stages (Tau) and Thal phases (Aß) were analysed by immunohistochemistry. The distribution of the lesions showed that the subiculum was affected before the mamillary body, but neither Tau aggregation nor Aß deposition was consistently first. The subiculum and the mamillary body contained Gallyas positive neurofibrillary tangles, immunolabelled by AT8, TG3, PHF1, Alz50 and C3 Tau antibodies. In the PoF, only thin and fragmented threads were observed, exclusively in the cases with neurofibrillary tangles in the subiculum. The threads were made of Gallyas negative, AT8 and TG3 positive Tau. They were intra-axonal and devoid of paired helical filaments at electron microscopy. We tested PoF homogenates containing Tau AT8 positive axons in a Tau P301S biosensor HEK cell line and found a seeding activity. There was no Aß immunoreactivity detected in the PoF. We could follow microcryodissected AT8 positive axons entering the mamillary body; contacts between Tau positive endings and Aß positive diffuse or focal deposits were observed in CLARITY-cleared mamillary body. In conclusion, we show that non-fibrillary, hyperphosphorylated Tau is transported by the axons of the PoF from the subiculum to the mamillary body and has a seeding activity. Either Tau aggregation or Aß accumulation may occur first in this system: this inconstant order is incompatible with a cause-and-effects relationship. However, both pathologies were correlated and intimately associated, indicating an interaction of the two processes, once initiated.

Activity-induced MEMRI cannot detect functional brain anomalies in the APPxPS1-Ki mouse model of Alzheimer's disease.

Alzheimer's disease (AD) is the most common cause of dementia. Aside neuropathological lesions, abnormal neuronal activity and brain metabolism are part of the core symptoms of the disease. Activity-induced Manganese-Enhanced Magnetic Resonance Imaging (MEMRI) has been proposed as a powerful approach to visualize evoked brain activity in rodents. Here, we evaluated the relevance of MEMRI in measuring neuronal (dys-)function in the APPxPS1 knocked-in (KI) mouse model of AD. Brain anomalies were firstly demonstrated in APPxPS1-Ki mice using cognitive testing (memory impairment) and histological mapping of immediate early gene products (decreased density of fos-positive neurons). Paradoxically, MEMRI analyses were not able to confirm the occurrence of neuronal hypoactivities in vivo. We then performed a neuropathological analysis that highlighted an abnormal increased permeability of the blood-brain barrier (BBB) in APPxPS1-Ki mice. We hypothesized that diffuse weakening of the BBB results in an uncontrolled diffusion of the MR contrast agent and a lack of correlation between manganese accumulation and neuronal activity. These results bring to light a limitation of the activity-induced MEMRI approach when applied to the APPxPS1-Ki mouse model as well as other mouse models harboring a compromised BBB.

Mechanisms Associated with Type 2 Diabetes as a Risk Factor for Alzheimer-Related Pathology.

Current evidence suggests dementia and pathology in Alzheimer's Disease (AD) are both dependent and independent of amyloid processing and can be induced by multiple 'hits' on vital neuronal functions. Type 2 diabetes (T2D) poses the most important risk factor for developing AD after ageing and dysfunctional IR/PI3K/Akt signalling is a major contributor in both diseases. We developed a model of T2D, coupling subdiabetogenic doses of streptozotocin (STZ) with a human junk food (HJF) diet to more closely mimic the human condition. Over 35 weeks, this induced classic signs of T2D (hyperglycemia and insulin dysfunction) and a modest, but stable deficit in spatial recognition memory, with very little long-term modification of proteins in or associated with IR/PI3K/Akt signalling in CA1 of the hippocampus. Intracerebroventricular infusion of soluble amyloid beta 42 (Aß42) to mimic the early preclinical rise in Aß alone induced a more severe, but short-lasting deficits in memory and deregulation of proteins. Infusion of Aß on the T2D phenotype exacerbated and prolonged the memory deficits over approximately 4 months, and induced more severe aberrant regulation of proteins associated with autophagy, inflammation and glucose uptake from the periphery. A mild form of environmental enrichment transiently rescued memory deficits and could reverse the regulation of some, but not all protein changes. Together, these data identify mechanisms by which T2D could create a modest dysfunctional neuronal milieu via multiple and parallel inputs that permits the development of pathological events identified in AD and memory deficits when Aß levels are transiently effective in the brain.

New role of P2X7 receptor in an Alzheimer's disease mouse model.

Extracellular aggregates of amyloid ß (Aß) peptides, which are characteristic of Alzheimer's disease (AD), act as an essential trigger for glial cell activation and the release of ATP, leading to the stimulation of purinergic receptors, especially the P2X7 receptor (P2X7R). However, the involvement of P2X7R in the development of AD is still ill-defined regarding the dual properties of this receptor. Particularly, P2X7R activates the NLRP3 inflammasome leading to the release of the pro-inflammatory cytokine, IL-1ß; however, P2X7R also induces cleavage of the amyloid precursor protein generating Aß peptides or the neuroprotective fragment sAPPα. We thus explored in detail the functions of P2X7R in AD transgenic mice. Here, we show that P2X7R deficiency reduced Aß lesions, rescued cognitive deficits and improved synaptic plasticity in AD mice. However, the lack of P2X7R did not significantly affect the release of IL-1ß or the levels of non-amyloidogenic fragment, sAPPα, in AD mice. Instead, our results show that P2X7R plays a critical role in Aß peptide-mediated release of chemokines, particularly CCL3, which is associated with pathogenic CD8+ T cell recruitment. In conclusion, our study highlights a novel detrimental function of P2X7R in chemokine release and supports the notion that P2X7R may be a promising therapeutic target for AD.

Evidence for altered dendritic spine compartmentalization in Alzheimer's disease and functional effects in a mouse model.

Alzheimer's disease (AD) is associated with a progressive loss of synapses and neurons. Studies in animal models indicate that morphological alterations of dendritic spines precede synapse loss, increasing the proportion of large and short ("stubby") spines. Whether similar alterations occur in human patients, and what their functional consequences could be, is not known. We analyzed biopsies from AD patients and APP x presenilin 1 knock-in mice that were previously shown to present a loss of pyramidal neurons in the CA1 area of the hippocampus. We observed that the proportion of stubby spines and the width of spine necks are inversely correlated with synapse density in frontal cortical biopsies from non-AD and AD patients. In mice, the reduction in the density of synapses in the stratum radiatum was preceded by an alteration of spine morphology, with a reduction of their length and an enlargement of their neck. Serial sectioning examined with electron microscopy allowed us to precisely measure spine parameters. Mathematical modeling indicated that the shortening and widening of the necks should alter the electrical compartmentalization of the spines, leading to reduced postsynaptic potentials in spine heads, but not in soma. Accordingly, there was no alteration in basal synaptic transmission, but long-term potentiation and spatial memory were impaired. These results indicate that an alteration of spine morphology could be involved in the early cognitive deficits associated with AD.

DYRK1A inhibition and cognitive rescue in a Down syndrome mouse model are induced by new fluoro-DANDY derivatives.

Inhibition of DYRK1A kinase, produced by chromosome 21 and consequently overproduced in trisomy 21 subjects, has been suggested as a therapeutic approach to treating the cognitive deficiencies observed in Down syndrome (DS). We now report the synthesis and potent DYRK1A inhibitory activities of fluoro derivatives of 3,5-di(polyhydroxyaryl)-7-azaindoles (F-DANDYs). One of these compounds (3-(4-fluorophenyl)-5-(3,4-dihydroxyphenyl)-1H-pyrrolo[2,3-b]pyridine, 5a) was selected for in vivo studies of cognitive rescuing effects in a standard mouse model of DS (Ts65Dn line). Using the Morris water maze task, Ts65Dn mice treated i.p. with 20 mg/kg of 5a performed significantly better than Ts65Dn mice treated with placebo, confirming the promnesiant effect of 5a in the trisomic mice. Overall, these results demonstrate for the first time that selective and competitive inhibition of DYRK1A kinase by the F-DANDY derivative 5a may provide a viable treatment strategy for combating the memory and learning deficiencies encountered in DS.