Morphological, behavioral and cellular analyses revealed different phenotypes in Wolfram syndrome wfs1a and wfs1b zebrafish mutant lines.

Wolfram syndrome (WS) is a rare genetic disease characterized by diabetes, optic atrophy and deafness. Patients die at 35 years of age, mainly from respiratory failure or dysphagia. Unfortunately, there is no treatment to block the progression of symptoms and there is an urgent need for adequate research models. Here, we report on the phenotypical characterization of two loss-of-function zebrafish mutant lines: wfs1aC825X and wfs1bW493X. We observed that wfs1a deficiency altered the size of the ear and the retina of the fish. We also documented a decrease in the expression level of unfolded protein response (UPR) genes in basal condition and in stress condition, i.e. after tunicamycin treatment. Interestingly, both mutants lead to a decrease in their visual function measured behaviorally. These deficits were associated with a decrease in the expression level of UPR genes in basal and stress conditions. Interestingly, basal, ATP-linked and maximal mitochondrial respirations were transiently decreased in the wfs1b mutant. Taken together, these zebrafish lines highlight the critical role of wfs1a and wfs1b in UPR, mitochondrial function and visual physiology. These models will be useful tools to better understand the cellular function of Wfs1 and to develop novel therapeutic approaches for WS.

Microglial P2X4 receptors promote ApoE degradation and contribute to memory deficits in Alzheimer's disease.

Numerous evidences support that microglia contributes to the progression of Alzheimer's disease. P2X4 receptors are ATP-gated channels with high calcium permeability, which are de novo expressed in a subset of reactive microglia associated with various pathological contexts, contributing to microglial functions. P2X4 receptors are mainly localized in lysosomes and trafficking to the plasma membrane is tightly regulated. Here, we investigated the role of P2X4 in the context of Alzheimer's disease (AD). Using proteomics, we identified Apolipoprotein E (ApoE) as a specific P2X4 interacting protein. We found that P2X4 regulates lysosomal cathepsin B (CatB) activity promoting ApoE degradation; P2rX4 deletion results in higher amounts of intracellular and secreted ApoE in both bone-marrow-derived macrophage (BMDM) and microglia from APPswe/PSEN1dE9 brain. In both human AD brain and APP/PS1 mice, P2X4 and ApoE are almost exclusively expressed in plaque-associated microglia. In 12-month-old APP/PS1 mice, genetic deletion of P2rX4 reverses topographical and spatial memory impairment and reduces amount of soluble small aggregates of Aß1-42 peptide, while no obvious alteration of plaque-associated microglia characteristics is observed. Our results support that microglial P2X4 promotes lysosomal ApoE degradation, indirectly altering Aß peptide clearance, which in turn might promotes synaptic dysfunctions and cognitive deficits. Our findings uncover a specific interplay between purinergic signaling, microglial ApoE, soluble Aß (sAß) species and cognitive deficits associated with AD.

Convolamine, a tropane alkaloid extracted from Convolvulus plauricalis, is a potent sigma-1 receptor-positive modulator with cognitive and neuroprotective properties.

BACKGROUND AND AIM: By using an in vivo phenotypic screening assay in zebrafish, we identified Convolamine, a tropane alkaloid from Convulvus plauricalis, as a positive modulator of the sigma-1 receptor (S1R). The wfs1abKO zebrafish larva, a model of Wolfram syndrome, exhibits an increased visual-motor response due to a mutation in Wolframin, a protein involved in endoplasmic reticulum-mitochondria communication. We previously reported that ligand activating S1R, restored the cellular and behavioral deficits in patient fibroblasts and zebrafish and mouse models. EXPERIMENTAL PROCEDURES: We screened a library of 108 repurposing and natural compounds on zebrafish motor response. KEY RESULTS: One hit, the tropane alkaloid Convolamine, restored normal mobility in wfs1abKO larvae without affecting wfs1abWT controls. They did not bind to the S1R agonist/antagonist binding site nor dissociated S1R from BiP, an S1R activity assay in vitro, but behaved as a positive modulator by shifting the IC50 value of the reference agonist PRE-084 to lower values. Convolamine restored learning in Wfs1∆Exon8 , Dizocilpine-treated, and Aß25-35 -treated mice. These effects were observed at low ~1 mg/kg doses, not shared by Convolvine, the desmethyl metabolite, and blocked by an S1R antagonist. CONCLUSION AND IMPLICATIONS: Convolamine therefore acts as an S1R positive modulator and this pharmacological action is relevant to the traditional use of Shankhpushpi in memory and cognitive protection.

Targeting N-Methyl-d-Aspartate Receptors in Neurodegenerative Diseases.

N-methyl-d-aspartate receptors (NMDARs) are the main class of ionotropic receptors for the excitatory neurotransmitter glutamate. They play a crucial role in the permeability of Ca2+ ions and excitatory neurotransmission in the brain. Being heteromeric receptors, they are composed of several subunits, including two obligatory GluN1 subunits (eight splice variants) and regulatory GluN2 (GluN2A~D) or GluN3 (GluN3A~B) subunits. Widely distributed in the brain, they regulate other neurotransmission systems and are therefore involved in essential functions such as synaptic transmission, learning and memory, plasticity, and excitotoxicity. The present review will detail the structure, composition, and localization of NMDARs, their role and regulation at the glutamatergic synapse, and their impact on cognitive processes and in neurodegenerative diseases (Alzheimer's, Huntington's, and Parkinson's disease). The pharmacology of different NMDAR antagonists and their therapeutic potentialities will be presented. In particular, a focus will be given on fluoroethylnormemantine (FENM), an investigational drug with very promising development as a neuroprotective agent in Alzheimer's disease, in complement to its reported efficacy as a tomography radiotracer for NMDARs and an anxiolytic drug in post-traumatic stress disorder.

Variants in USP48 encoding ubiquitin hydrolase are associated with autosomal dominant non-syndromic hereditary hearing loss.

Non-Syndromic Hereditary Hearing Loss (NSHHL) is a genetically heterogeneous sensory disorder with about 120 genes already associated. Through exome sequencing (ES) and data aggregation, we identified a family with six affected individuals and one unrelated NSHHL patient with predicted-to-be deleterious missense variants in USP48. We also uncovered an eighth patient presenting unilateral cochlear nerve aplasia and a de novo splice variant in the same gene. USP48 encodes a ubiquitin carboxyl-terminal hydrolase under evolutionary constraint. Pathogenicity of the variants is supported by in vitro assays that showed that the mutated proteins are unable to hydrolyze tetra-ubiquitin. Correspondingly, three-dimensional representation of the protein containing the familial missense variant is situated in a loop that might influence the binding to ubiquitin. Consistent with a contribution of USP48 to auditory function, immunohistology showed that the encoded protein is expressed in the developing human inner ear, specifically in the spiral ganglion neurons, outer sulcus, interdental cells of the spiral limbus, stria vascularis, Reissner's membrane and in the transient Kolliker's organ that is essential for auditory development. Engineered zebrafish knocked-down for usp48, the USP48 ortholog, presented with a delayed development of primary motor neurons, less developed statoacoustic neurons innervating the ears, decreased swimming velocity and circling swimming behavior indicative of vestibular dysfunction and hearing impairment. Corroboratingly, acoustic startle response assays revealed a significant decrease of auditory response of zebrafish lacking usp48 at 600 and 800 Hz wavelengths. In conclusion, we describe a novel autosomal dominant NSHHL gene through a multipronged approach combining ES, animal modeling, immunohistology and molecular assays.

The Intriguing Sigma-1 and Sigma-2 Receptors and Their Potential Therapeutic Roles 2.0.

For some time now, the research on sigma receptors has been at a high level of maturity but, despite everything that has already been achieved, further work in this field still holds huge appeal, with vast possibilities for original discoveries [...].

Photoswitchable Pseudoirreversible Butyrylcholinesterase Inhibitors Allow Optical Control of Inhibition in Vitro and Enable Restoration of Cognition in an Alzheimer's Disease Mouse Model upon Irradiation.

To develop tools to investigate the biological functions of butyrylcholinesterase (BChE) and the mechanisms by which BChE affects Alzheimer's disease (AD), we synthesized several selective, nanomolar active, pseudoirreversible photoswitchable BChE inhibitors. The compounds were able to specifically influence different kinetic parameters of the inhibition process by light. For one compound, a 10-fold difference in the IC50-values (44.6 nM cis, 424 nM trans) in vitro was translated to an "all or nothing" response with complete recovery in a murine cognition-deficit AD model at dosages as low as 0.3 mg/kg.

Sigma-1 receptor is a key genetic modulator in amyotrophic lateral sclerosis.

Sigma-1 receptor (S1R) is an endoplasmic reticulum (ER) chaperone that not only regulates mitochondrial respiration but also controls cellular defense against ER and oxidative stress. This makes S1R a potential therapeutic target in amyotrophic lateral sclerosis (ALS). Especially, as a missense mutation E102Q in S1R has been reported in few familial ALS cases. However, the pathogenicity of S1RE102Q and the beneficial impact of S1R in the ALS context remain to be demonstrated in vivo. To address this, we generated transgenic Drosophila that expresses human wild-type S1R or S1RE102Q. Expression of mutant S1R in fly neurons induces abnormal eye morphology and locomotor defects in a dose-dependent manner. This was accompanied by abnormal mitochondrial fragmentation, reduced adenosine triphosphate (ATP) levels and a higher fatigability at the neuromuscular junction during high energy demand. Overexpressing IP3 receptor or glucose transporter mitigates the S1RE102Q-induced eye phenotype, further highlighting the role of calcium and energy metabolism in its toxicity. More importantly, we showed that wild-type S1R rescues locomotor activity and ATP levels of flies expressing the key ALS protein, TDP43. Moreover, overexpressing wild-type S1R enhances resistance of flies to oxidative stress. Therefore, our data provide the first genetic evidence that mutant S1R recapitulates ALS pathology in vivo while increasing S1R confers neuroprotection against TDP43 toxicity.

Synthesis and Biological Evaluation of Flavonoid-Cinnamic Acid Amide Hybrids with Distinct Activity against Neurodegeneration in Vitro and in Vivo.

Flavonoids are polyphenolic natural products and have shown significant potential as disease-modifying agents against neurodegenerative disorders like Alzheimer's disease (AD), with activities even in vivo. Hybridization of the natural products taxifolin and silibinin with cinnamic acid led to an overadditive effect of these compounds in several phenotypic screening assays related to neurodegeneration and AD. Therefore, we have exchanged the flavonoid part of the hybrids with different flavonoids, which show higher efficacy than taxifolin or silibinin, to improve the activity of the respective hybrids. Chemical connection between the flavonoid and cinnamic acid was realized by an amide instead of a labile ester bond to improve stability towards hydrolysis. To investigate the influence of a double bond at the C-ring of the flavonoid, the dehydro analogues of the respective hybrids were also synthesized. All compounds obtained show neuroprotection against oxytosis, ferroptosis and ATP-depletion, respectively, in the murine hippocampal cell line HT22. Interestingly, the taxifolin and the quercetin derivatives are the most active compounds, whereby the quercetin derivate shows even more pronounced activity than the taxifolin one in all assays applied. As aimed for, no hydrolysis product was found in cellular uptake experiments after 4 h whereas different metabolites were detected. Furthermore, the quercetin-cinnamic acid amide showed pronounced activity in an in vivo AD mouse model at a remarkably low dose of 0.3 mg/kg.

Restoring glutamate receptosome dynamics at synapses rescues autism-like deficits in Shank3-deficient mice.

Shank3 monogenic mutations lead to autism spectrum disorders (ASD). Shank3 is part of the glutamate receptosome that physically links ionotropic NMDA receptors to metabotropic mGlu5 receptors through interactions with scaffolding proteins PSD95-GKAP-Shank3-Homer. A main physiological function of the glutamate receptosome is to control NMDA synaptic function that is required for plasticity induction. Intact glutamate receptosome supports glutamate receptors activation and plasticity induction, while glutamate receptosome disruption blocks receptors activity, preventing the induction of subsequent plasticity. Despite possible impact on metaplasticity and cognitive behaviors, scaffold interaction dynamics and their consequences are poorly defined. Here, we used mGlu5-Homer interaction as a biosensor of glutamate receptosome integrity to report changes in synapse availability for plasticity induction. Combining BRET imaging and electrophysiology, we show that a transient neuronal depolarization inducing NMDA-dependent plasticity disrupts glutamate receptosome in a long-lasting manner at synapses and activates signaling pathways required for the expression of the initiated neuronal plasticity, such as ERK and mTOR pathways. Glutamate receptosome disruption also decreases the NMDA/AMPA ratio, freezing the sensitivity of the synapse to subsequent changes of neuronal activity. These data show the importance of a fine-tuning of protein-protein interactions within glutamate receptosome, driven by changes of neuronal activity, to control plasticity. In a mouse model of ASD, a truncated mutant form of Shank3 prevents the integrity of the glutamate receptosome. These mice display altered plasticity, anxiety-like, and stereotyped behaviors. Interestingly, repairing the integrity of glutamate receptosome and its sensitivity to the neuronal activity rescued synaptic transmission, plasticity, and some behavioral traits of Shank3∆C mice. Altogether, our findings characterize mechanisms by which Shank3 mutations cause ASD and highlight scaffold dynamics as new therapeutic target.

Fenfluramine modulates the anti-amnesic effects induced by sigma-1 receptor agonists and neuro(active)steroids in vivo.

Fenfluramine (N-ethyl-α-methl-3-(trifluoromethyl)phenethylamine) is an anti-seizure medication (ASM) particularly effective in patients with Dravet syndrome, a severe treatment-resistant epileptic encephalopathy. Fenfluramine acts not only as neuronal serotonin (5-HT) releaser but also as a positive modulator of the sigma-1 receptor (S1R). We here examined the modulatory activity of Fenfluramine on the S1R-mediated anti-amnesic response in mice using combination analyses. Fenfluramine and Norfenfluramine, racemate and isomers, were combined with either the S1R agonist (PRE-084) or the S1R-acting neuro(active)steroids, pregnenolone sulfate (PREGS), Dehydroepiandrosterone sulfate (DHEAS), or progesterone. We report that Fenfluramine racemate or (+)-Fenfluramine, in the 0.1-1 mg/kg dose range, attenuated the dizocilpine-induced learning deficits in spontaneous alternation and passive avoidance, and showed low-dose synergies in combination with PRE-084. These effects were blocked by the S1R antagonist NE-100. Dehydroepiandrosterone sulfate or PREGS attenuated dizocilpine-induced learning deficits in the 5-20 mg/kg dose range. Co-treatments at low dose between steroids and Fenfluramine or (+)-Fenfluramine were synergistic. Progesterone blocked Fenfluramine effect. Finally, Fenfluramine and (+)-Fenfluramine effects were prevented by the 5-HT1A receptor antagonist WAY-100635 or 5-HT2A antagonist RS-127445, but not by the 5-HT1B/1D antagonist GR 127935 or the 5-HT2C antagonist SB 242084, confirming a 5-HT1A and 5-HT2A receptor involvement in the drug effect on memory. We therefore confirmed the positive modulation of Fenfluramine racemate or dextroisomer on S1R and showed that, in physiological conditions, the drug potentiated the low dose effects of neuro(active)steroids, endogenous S1R modulators. The latter are potent modulators of the excitatory/inhibitory balance in the brain, and their levels must be considered in the antiepileptic action of Fenfluramine.

Defective tubulin detyrosination causes structural brain abnormalities with cognitive deficiency in humans and mice.

Reversible detyrosination of tubulin, the building block of microtubules, is crucial for neuronal physiology. Enzymes responsible for detyrosination were recently identified as complexes of vasohibins (VASHs) one or two with small VASH-binding protein (SVBP). Here we report three consanguineous families, each containing multiple individuals with biallelic inactivation of SVBP caused by truncating variants (p.Q28* and p.K13Nfs*18). Affected individuals show brain abnormalities with microcephaly, intellectual disability and delayed gross motor and speech development. Immunoblot testing in cells with pathogenic SVBP variants demonstrated that the encoded proteins were unstable and non-functional, resulting in a complete loss of VASH detyrosination activity. Svbp knockout mice exhibit drastic accumulation of tyrosinated tubulin and a reduction of detyrosinated tubulin in brain tissue. Similar alterations in tubulin tyrosination levels were observed in cultured neurons and associated with defects in axonal differentiation and architecture. Morphological analysis of the Svbp knockout mouse brains by anatomical magnetic resonance imaging showed a broad impact of SVBP loss, with a 7% brain volume decrease, numerous structural defects and a 30% reduction of some white matter tracts. Svbp knockout mice display behavioural defects, including mild hyperactivity, lower anxiety and impaired social behaviour. They do not, however, show prominent memory defects. Thus, SVBP-deficient mice recapitulate several features observed in human patients. Altogether, our data demonstrate that deleterious variants in SVBP cause this neurodevelopmental pathology, by leading to a major change in brain tubulin tyrosination and alteration of microtubule dynamics and neuron physiology.

Anti-Amnesic and Neuroprotective Effects of Fluoroethylnormemantine in a Pharmacological Mouse Model of Alzheimer's Disease.

BACKGROUND: Current therapies in Alzheimer's disease (AD), including Memantine, have proven to be only symptomatic but not curative or disease modifying. Fluoroethylnormemantine (FENM) is a structural analogue of Memantine, functionalized with a fluorine group that allowed its use as a positron emission tomography tracer. We here analyzed FENM neuroprotective potential in a pharmacological model of AD compared with Memantine. METHODS: Swiss mice were treated intracerebroventricularly with aggregated Aß 25-35 peptide and examined after 1 week in a battery of memory tests (spontaneous alternation, passive avoidance, object recognition, place learning in the water-maze, topographic memory in the Hamlet). Toxicity induced in the mouse hippocampus or cortex was analyzed biochemically or morphologically. RESULTS: Both Memantine and FENM showed symptomatic anti-amnesic effects in Aß 25-35-treated mice. Interestingly, FENM was not amnesic when tested alone at 10 mg/kg, contrarily to Memantine. Drugs injected once per day prevented Aß 25-35-induced memory deficits, oxidative stress (lipid peroxidation, cytochrome c release), inflammation (interleukin-6, tumor necrosis factor-α increases; glial fibrillary acidic protein and Iba1 immunoreactivity in the hippocampus and cortex), and apoptosis and cell loss (Bcl-2-associated X/B-cell lymphoma 2 ratio; cell loss in the hippocampus CA1 area). However, FENM effects were more robust than observed with Memantine, with significant attenuations vs the Aß 25-35-treated group. CONCLUSIONS: FENM therefore appeared as a potent neuroprotective drug in an AD model, with a superior efficacy compared with Memantine and an absence of direct amnesic effect at higher doses. These results open the possibility to use the compound at more relevant dosages than those actually proposed in Memantine treatment for AD.

Analysis of CX3CR1 haplodeficiency in male and female APPswe/PSEN1dE9 mice along Alzheimer disease progression.

Microglia, the resident immune cells of the brain, have recently emerged as key players in Alzheimer Disease (AD) pathogenesis, but their roles in AD remain largely elusive and require further investigation. Microglia functions are readily altered when isolated from their brain environment, and microglia reporter mice thus represent valuable tools to study the contribution of these cells to neurodegenerative diseases such as AD. The CX3CR1+/eGFP mice is one of the most popular microglia reporter mice, and has been used in numerous studies to investigate in vivo microglial functions, including in the context of AD research. However, until now, the impact of CX3CR1 haplodeficiency on the typical features of Alzheimer Disease has not been studied in depth. To fill this gap, we generated APPswe/PSEN1dE9:CX3CR1+/eGFP mice and analyzed these mice for Alzheimer's like pathology and neuroinflammation hallmarks. More specifically, using robust multifactorial statistical and multivariate analyses, we investigated the impact of CX3CR1 deficiency in both males and females, at three typical stages of the pathology progression: at early stage when Amyloid-ß (Aß) deposition just starts, at intermediate stage during Aß accumulation phase and at more advanced stages when Aß plaque number stabilizes. We found that CX3CR1 haplodeficiency had little impact on the progression of the pathology in the APPswe/PSEN1dE9 model and demonstrated that the APPswe/PSEN1dE9:CX3CR1+/eGFP line is a relevant and useful model to study the role of microglia in Alzheimer Disease. In addition, although Aß plaques density is higher in females compared to age-matched males, we show that their glial reaction, inflammation status and memory deficits are not different.

Amyloid Beta Peptide Is an Endogenous Negative Allosteric Modulator of Leptin Receptor.

INTRODUCTION: Metabolic dysfunction is now recognized as a pivotal component of Alzheimer's disease (AD), the most common dementia worldwide. However, the precise molecular mechanisms linking metabolic dysfunction to AD remain elusive. OBJECTIVE: Here, we investigated the direct impact of soluble oligomeric amyloid beta (Aß) peptides, the main molecular hallmark of AD, on the leptin system, a major component of central energy metabolism regulation. METHODS: We developed a new time-resolved fluorescence resonance energy transfer-based Aß binding assay for the leptin receptor (LepR) and studied the effect of Aß on LepR function in several in vitro assays. The in vivo effect of Aß on LepR function was studied in an Aß-specific AD mouse model and in pro-opiomelanocortin (POMC) neurons of the hypothalamic arcuate nucleus. RESULTS: We revealed specific and high-affinity (Ki = 0.1 nM) binding of Aß to LepR. Pharmacological characterization of this interaction showed that Aß binds allosterically to the extracellular domain of LepR and negatively affects receptor function. Negative allosteric modulation of LepR by Aß was detected at the level of signaling pathways (STAT-3, AKT, and ERK) in vitroand in vivo. Importantly, the leptin-induced response of POMC neurons, key players in the regulation of metabolic function, was completely abolished in the presence of Aß. CONCLUSION: Our data indicate that Aß is a negative allosteric modulator of LepR, resulting in impaired leptin action, and qualify LepR as a new and direct target of Aß oligomers. Preventing the interaction of Aß with LepR might improve both the metabolic and cognitive dysfunctions in AD condition.

Zebrafish Models to Study New Pathways in Tauopathies.

Tauopathies represent a vast family of neurodegenerative diseases, the most well-known of which is Alzheimer's disease. The symptoms observed in patients include cognitive deficits and locomotor problems and can lead ultimately to dementia. The common point found in all these pathologies is the accumulation in neural and/or glial cells of abnormal forms of Tau protein, leading to its aggregation and neurofibrillary tangles. Zebrafish transgenic models have been generated with different overexpression strategies of human Tau protein. These transgenic lines have made it possible to highlight Tau interacting factors or factors which may limit the neurotoxicity induced by mutations and hyperphosphorylation of the Tau protein in neurons. Several studies have tested neuroprotective pharmacological approaches. On few-days-old larvae, modulation of various signaling or degradation pathways reversed the deleterious effects of Tau mutations, mainly hTauP301L and hTauA152T. Live imaging and live tracking techniques as well as behavioral follow-up enable the analysis of the wide range of Tau-related phenotypes from synaptic loss to cognitive functional consequences.

Use of Zebrafish Models to Boost Research in Rare Genetic Diseases.

Rare genetic diseases are a group of pathologies with often unmet clinical needs. Even if rare by a single genetic disease (from 1/2000 to 1/more than 1,000,000), the total number of patients concerned account for approximatively 400 million peoples worldwide. Finding treatments remains challenging due to the complexity of these diseases, the small number of patients and the challenge in conducting clinical trials. Therefore, innovative preclinical research strategies are required. The zebrafish has emerged as a powerful animal model for investigating rare diseases. Zebrafish combines conserved vertebrate characteristics with high rate of breeding, limited housing requirements and low costs. More than 84% of human genes responsible for diseases present an orthologue, suggesting that the majority of genetic diseases could be modelized in zebrafish. In this review, we emphasize the unique advantages of zebrafish models over other in vivo models, particularly underlining the high throughput phenotypic capacity for therapeutic screening. We briefly introduce how the generation of zebrafish transgenic lines by gene-modulating technologies can be used to model rare genetic diseases. Then, we describe how zebrafish could be phenotyped using state-of-the-art technologies. Two prototypic examples of rare diseases illustrate how zebrafish models could play a critical role in deciphering the underlying mechanisms of rare genetic diseases and their use to identify innovative therapeutic solutions.

Sigma-1 Receptor Is Critical for Mitochondrial Activity and Unfolded Protein Response in Larval Zebrafish.

The sigma-1 receptor (S1R) is a highly conserved transmembrane protein highly enriched in mitochondria-associated endoplasmic reticulum (ER) membranes, where it interacts with several partners involved in ER-mitochondria Ca2+ transfer, activation of the ER stress pathways, and mitochondria function. We characterized a new S1R deficient zebrafish line and analyzed the impact of S1R deficiency on visual, auditory and locomotor functions. The s1r+25/+25 mutant line showed impairments in visual and locomotor functions compared to s1rWT. The locomotion of the s1r+25/+25 larvae, at 5 days post fertilization, was increased in the light and dark phases of the visual motor response. No deficit was observed in acoustic startle response. A critical role of S1R was shown in ER stress pathways and mitochondrial activity. Using qPCR to analyze the unfolded protein response genes, we observed that loss of S1R led to decreased levels of IRE1 and PERK-related effectors and increased over-expression of most of the effectors after a tunicamycin challenge. Finally, S1R deficiency led to alterations in mitochondria bioenergetics with decreased in basal, ATP-linked and non-mitochondrial respiration and following tunicamycin challenge. In conclusion, this new zebrafish model confirmed the importance of S1R activity on ER-mitochondria communication. It will be a useful tool to further analyze the physiopathological roles of S1R.

Improvement of BDNF signalling by P42 peptide in Huntington's disease.

Huntington's disease (HD) is caused by a mutation in the Huntingtin (HTT) protein. We previously reported that the 23aa peptide of HTT protein, P42, is preventing HD pathological phenotypes, such as aggregation, reduction of motor performances and neurodegeneration. A systemic treatment with P42 during the pre-symptomatic phase of the disease showed therapeutic potential in R6/2 mice. We here tested P42 effects when administered during the post-symptomatic phase. The P42 treatment alleviated deficits in motor performances, even when symptoms have already started. Because changes in the level and activity of brain-derived neurotrophic factor (BDNF) have been shown to play a central role in HD, we analysed the influence of P42 on BDNF deficit and associated phenotypes. Our data suggest that P42 is involved in the spatio-temporal control of bdnf and trkB mRNA and their protein levels. Related to this enhancement of BDNF-TrkB signalling, R6/2 mice treated with P42, exhibit reduced anxiety, better learning and memory performances, and better long-term potentiation (LTP) response. Finally we identified a direct influence of P42 peptide on neuronal plasticity and activity. These results suggest that P42 offers an efficient therapeutic potential not only by preventing aggregation of mutant HTT at early stages of the disease, but also by favouring some physiological functions of normal HTT, as P42 is naturally part of it, at the different stages of the disease. This makes P42 peptide potentially suitable not only to prevent, but also to treat HD.

Sterubin: Enantioresolution and Configurational Stability, Enantiomeric Purity in Nature, and Neuroprotective Activity in Vitro and in Vivo.

Alzheimer's disease (AD) is a neurological disorder with still no preventive or curative treatment. Flavonoids are phytochemicals with potential therapeutic value. Previous studies described the flavanone sterubin isolated from the Californian plant Eriodictyon californicum as a potent neuroprotectant in several in vitro assays. Herein, the resolution of synthetic racemic sterubin (1) into its two enantiomers, (R)-1 and (S)-1, is described, which has been performed on a chiral chromatographic phase, and their stereochemical assignment online by HPLC-ECD coupling. (R)-1 and (S)-1 showed comparable neuroprotection in vitro with no significant differences. While the pure stereoisomers were configurationally stable in methanol, fast racemization was observed in the presence of culture medium. We also established the occurrence of extracted sterubin as its pure (S)-enantiomer. Moreover, the activity of sterubin (1) was investigated for the first time in vivo, in an AD mouse model. Sterubin (1) showed a significant positive impact on short- and long-term memory at low dosages.