Élaboration de nouveaux biopolyesters bactériens fonctionnalisés pour des applications dans le domaine biomédical

Les poly(3-hydroxyalcanoate)s ou PHAs sont des biopolyesters linéaires biodégradables et biocompatibles synthétisés par des microorganismes bactériens en tant que réserve de carbone et d'énergie. Ils sont synthétisés par des bactéries à partir de ressources renouvelables et la diversité de leurs structures possibles se traduit par un large éventail de polymères ayant des propriétés mécaniques très différentes. Nous avons tout d'abord testé les capacités de production de PHAs de nouvelles souches bactériennes marines provenant de tapis microbiens de Polynésie française, en utilisant, entre autres, des substrats naturels comme l'huile de coprah, le glucose et l'acide oléique. Nous avons notamment montré que la souche Pseudomonas guezennei est capable de produire des PHAs avec des taux d'insaturation contrôlés et de masse molaire très élevée. Puis, des oligomères de PHAs fonctionnalisés de structures contrôlées portant des fonctions terminales alcynes ou alcènes ont été préparés par transestérification. Ces oligomères ont ensuite été utilisés pour l'élaboration par chimie click de copolymères amphiphiles greffés EPS-g-PHA avec des exopolysaccharides (EPS) bactériens. Enfin la dernière partie de ces travaux a consisté en la réalisation d'un support de croissance pour le développement de cellules souches pour l'ingénierie tissulaire combinant les propriétés mécaniques des PHAs et les propriétés hydrophiles et bioactives des EPSPoly(3-hydroxyalkanoate)s, or PHAs, are linear biodegradable and biocompatible biopolyesters synthesized by bacterial microorganisms as energy and carbon supply. They are synthesized by bacteria from renewable resources and the diversity of the achievable structures leads to a large range of mechanical properties. First, we studied the PHAs production ability of several new marine bacteria strains, isolated from microbial mats from French Polynesia, using, among others, natural substrates such as coprah oil, glucose and oleic acid. We showed particularly that the strain Pseudomonas guezennei was able to produce PHAs with controlled amounts of insaturations and high molar masses. Then, we prepared functionalized PHAs oligomers with controlled structure and bearing a terminal alkyne or alkene function. Following that, these oligomers were used to elaborate amphiphilic by click chemistry graft copolymers EPS-g-PHA with bacterial exopolysaccharide (EPS). Finally, the last part of this work was the making of a scaffold for stem cell culture for tissue engineering which combined the mechanical properties of PHAs and the hydrophilicity and bioactive properties of EPSPARIS-EST-Université (770839901) / SudocSudocFranceF

Élaboration de copolymères amphiphiles à base de poly (3-hydroxyalcanoate)s

Les poly (3-hydroxyalcanoates) (PHAs) sont des polyesters aliphatiques produits et accumulés par des bactéries en tant que réserve de carbone et d'énergie. Ils sont constitués d'unités b-hydroxyesters et possèdent des chaînes latérales de longueur variable, pouvant être fonctionnalisées. Ils possèdent des propriétés de biodégradabilité et de biocompatibilité; ceci leur confère de vastes possibilités d'utilisation dans le domaine biomédical, notamment pour la mise au point de systèmes de libération contrôlée de principes actifs. Dans cette optique, nous nous sommes intéressés à la synthèse de copolymères amphiphiles de différentes architectures à base de PHAs, ainsi qu'à l'étude de leurs propriétés d'auto-association en milieu aqueux. Une méthode simple et efficace permettant le greffage d'oligomères de poly (éthylène glycol) (PEG) a tout d'abord été mise au point grâce à l'utilisation de la chimie click . Une série de copolymères diblocs bien définis PHA-b-PEG a ainsi pu être synthétisée par cycloaddition de Huisgen catalysée par le cuivre (CuAAC). Les copolymères diblocs à base de PHAs à moyennes chaînes latérales (PHA-mcl) ont montré leur capacité à s'auto-associer en milieu aqueux et à former des micelles monodisperses présentant une concentration micellaire critique très faible. Par la suite des copolymères de type greffés PHOU-g-PEG ont été synthétisés par addition thiol-ène. Les analyses par cryo microscopie électronique à transmission (cryo-TEM) ont montré que dans ce cas les copolymères s'auto-associaient en structures vésiculaires, ou polymersomes. Enfin, la synthèse de copolymères amphiphiles greffés porteurs de chaînes perfluorées PHOU-g-(F;PEG) a permis l'obtention de structures auto-associées plus complexes. Le cryo-TEM a en effet révélé la formation de micelles multicompartimentées, c'est à dire possédant un coeur présentant une séparation de phase entre les domaines hydrophobes et les domaines fluorés. Des tests biologiques préliminaires ont montré la cytocompatibilité de ces micellesPoly (3-hydroxyalkanoates) are natural aliphatic polyesters produced and accumulated by many bacteria as carbon and energy supply. They consist of b-hydroxy ester units, with pendant side chains of different lengths that can be functionalized. Thanks to their biodegradability and biocompatibility, they are promising polymers for biomedical applications, especially for controlled drug delivery systems. In this context, we aimed to synthesize PHA-based amphiphilic copolymers with different molecular architectures, and to study their self-assembly in water. First, a simple and straightforward method using click chemistry has been used to graft poly(ethylene glycol) (PEG) oligomers. A series of well-defined diblock copolymers PHA-b-PEG has thus been synthesized using copper-catalyzed azide-alkyne cycloaddition (CuAAC). Medium chain length PHA-based diblock copolymers have shown their ability to self-assemble into stable micelles having very low critical micelle concentrations. Afterwards, amphiphilic graft copolymers PHOU-g-PEG have been synthesized using thiol-ene addition. In this case, cryo-electron microscopy (cryo-TEM) analysis revealed that graft copolymers self-assembled into vesicular morphologies, i.e. in polymersomes. Finally, the synthesis of amphiphilic graft copolymers bearing perfluorinated chains PHOU-g-(F;PEG) was performed. After aqueous self-assembly, cryo-TEM shown the formation of multicompartment micelles, i.e. with a core displaying segregated hydrophobic and fluorophilic domains. Moreover, these multicompartment micelles have shown their cytocompatibilityPARIS-EST-Université (770839901) / SudocSudocFranceF

Memory for public events in mild cognitive impairment and Alzheimer’s disease : the importance of rehearsal

Ribot’s law refers to the better preservation of remote memories compared with recent ones that presumably characterizes retrograde amnesia. Even if Ribot-type temporal gradient has been extensively studied in retrograde amnesia, particularly in Alzheimer’s disease (AD), this pattern has not been consistently found. One explanation for these results may be that rehearsal frequency rather than remoteness accounts for the better preservation of these memories. Thus, the aim of present study was to address this question by studying retrograde semantic memory in subjects with amnestic mild cognitive impairment (aMCI) (n = 20), mild AD (n = 20) and in healthy older controls (HC; n = 19). In order to evaluate the impact of repetition as well as the impact of remoteness, we used a test assessing memory for enduring and transient public events that occurred in the recent and remote past. Results show no clear temporal gradient across time periods (1960–1975; 1976–1990; 1991–2005; 2006–2011), but a better performance was observed in all three groups for enduring compared with transient events. Moreover, although deficits were globally found in both patients groups compared with HC, more specific analyses revealed that aMCI patients were only impaired on transient events while AD patients were impaired on both transient and enduring events. Exploratory analyses also revealed a tendency suggesting preservation of remote transient events in aMCI. These findings are discussed with regards to memory consolidation models

Expression of Viral Antigen by the Liver Leads to Chronic Infection Through the Generation of Regulatory T Cells

Referred to by David E. Kaplan " Does Massive Antigen Burden Allow Hepatic Viruses to Induce Regulatory T Cells and Their Tolerance and Persistence?" CMGH Cellular and Molecular Gastroenterology and Hepatology, Volume 1, Issue 3, May 2015, Pages 259-261International audienceThe constant exposure of the liver to food and bacterial antigens through the mesenteric circulation requires it to maintain tolerance while preserving the ability to mount an effective immune response against pathogens. We investigated the contribution of the liver's tolerogenic nature on the establishment of chronic viral infections. Methods: TTR-NP mice, which express the nucleoprotein (NP) of lymphocytic choriomeningitis virus (LCMV) specifically in hepatocytes under control of a modified transthyretin (TTR) promoter, were infected with the Armstrong (Arm) or WE acute strains of LCMV. Results: The infection persisted for at least 147 days in TTR-NP mice. Expression of NP by the liver induced a strong peripheral tolerance against NP that was mediated by interleukin-10-secreting CD4+ regulatory T cells, leading to high PD-1 (programmed death-1) expression and reduced effector function of virus-specific T cells. Despite an active immune response against LCMV, peripheral tolerance against a single viral protein was sufficient to induce T-cell exhaustion and chronic LCMV Armstrong (Arm) or WE infection by limiting the antiviral T-cell response in an otherwise immunocompetent host. Regulatory T-cell depletion of chronically infected TTR-NP mice led to functional restoration of LCMV-specific CD4+ and CD8+ Tcell responses and viral clearance. Conclusions: Expression of a viral antigen by hepatocytes can induce a state of peripheral tolerance mediated by regulatory Tcells that can lead to the establishment of a chronic viral infection. Strategies targeting regulatory T cells in patients chronically infected with hepatotropic viruses could represent a promising approach to restore functional antiviral immunity and clear infection

The impact of time and repeated exposure on famous person knowledge in amnestic Mild cognitive impairment and Alzheimer’s disease

Objective: Famous people knowledge has been shown to be impaired early in Alzheimer’s disease (AD) and amnestic mild cognitive impairment (aMCI). However, the question of whether recently acquired knowledge is more impaired than remotely acquired knowledge remains a matter of debate. The aim of this study was to investigate the patterns of semantic memory impairment in aMCI and AD by investigating two factors that may influence the retrieval of such knowledge, namely remoteness and frequency of repetition of information over time. Method: Three groups (19 controls, 20 aMCI and 20 AD patients) were compared on a test assessing general and specific biographical knowledge about famous people, where the period of acquired fame (remote vs recent) and the type of fame (enduring vs transient) were controlled for. Results: Global performance of aMCI and AD patients was significantly poorer than that of controls. However, different patterns of recall were observed as a function of time and type of fame. A temporal gradient was found in both patient groups for enduring names but not for transient ones, whereby knowledge about remote enduring famous persons was better recalled. Patients were more impaired at questions assessing specific biographical knowledge (unique to an individual) than more general knowledge. Conclusions: Tests of famous people knowledge offer a unique opportunity to investigate semantic deficits in aMCI and AD, because they make it possible to estimate the time at which memories were acquired, as well as the type of fame. Results are discussed in light of memory consolidation models. Keywords

Impact of crude oil and the dispersant CorexitTM EC9500A on capelin (Mallotus villosus) embryo development

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L’évaluation de la mémoire rétrograde dans la population québécoise âgée: Le PUB-40 et le PUB-12

L’évaluation de la mémoire représente une partie importante du travail des neuropsychologues cliniciens œuvrant en gériatrie. En effet, au Canada, environ le tiers des aînés rapporte une plainte mnésique dont les causes sont variées. Selon l’étiologie, différentes composantes du système mnésique peuvent être atteintes, toutefois, l’évaluation de la mémoire rétrograde non autobiographique (publique ou sémantique) n’est souvent effectuée que de manière superficielle, puisqu’aucun outil d’évaluation fiable, valide et standardisé n’est disponible pour la population québécoise vieillissante. Les objectifs de cette recherche étaient donc (1) d’élaborer un protocole d’évaluation de la mémoire rétrograde non autobiographique spécifiquement adapté à cette population, le PUB-40, (2) de recueillir des données de référence auprès de 105 participants âgés sains et (3) de développer une version abrégée à partir des items permettant de discriminer un groupe de 20 patients atteints de troubles cognitifs légers de type amnésique (TCLa) des participants âgés sains

Towards regulation of Endocrine Disrupting chemicals (EDCs) in water resources using bioassays - A guide to developing a testing strategy

Endocrine disrupting chemicals (EDCs) are found in every environmental medium and are chemically diverse. Their presence in water resources can negatively impact the health of both human and wildlife. Currently, there are no mandatory screening mandates or regulations for EDC levels in complex water samples globally. Bioassays, which allow quantifying in vivo or in vitro biological effects of chemicals are used commonly to assess acute toxicity in water. The existing OECD framework to identify single-compound EDCs offers a set of bioassays that are validated for the Estrogen-, Androgen-, and Thyroid hormones, and for Steroidogenesis pathways (EATS). In this review, we discussed bioassays that could be potentially used to screen EDCs in water resources, including in vivo and in vitro bioassays using invertebrates, fish, amphibians, and/or mammalians species. Strengths and weaknesses of samples preparation for complex water samples are discussed. We also review how to calculate the Effect-Based Trigger values, which could serve as thresholds to determine if a given water sample poses a risk based on existing quality standards. This work aims to assist governments and regulatory agencies in developing a testing strategy towards regulation of EDCs in water resources worldwide. The main recommendations include 1) opting for internationally validated cell reporter in vitro bioassays to reduce animal use & cost; 2) testing for cell viability (a critical parameter) when using in vitro bioassays; and 3) evaluating the recovery of the water sample preparation method selected. This review also highlights future research avenues for the EDC screening revolution (e.g., 3D tissue culture, transgenic animals, OMICs, and Adverse Outcome Pathways (AOPs)).This work was supported by the Fonds de recherche du Québec - Nature et technologies (FRQNT-290501) to JR, Natural Sciences and Engineering Research Council (NSERC) of Canada (NSERC-DG-2020-06475), and Canada Research Chairs to VSL (CRC-950-232235). LNM was supported by a H2020-Marie Skłodowska-Curie Action MSCA-IF-RI- 2017 awarded by the European Commission (ref. 797725-EpiSTOX). The authors are grateful to the Intersectorial Centre for Endocrine Disruptor Analysis (ICEDA)'s researcher network that facilitated this Special Issue. We thank Peta Neale that compiled references from the literature for EBT value that can be found in Table 3.Peer reviewe

Élaboration de copolymères à base de biopolyesters pour la libération contrôlée de principes actifs

Les poly(3-hydroxyalcanoate)s ou P(3-HA)s, sont des polyesters aliphatiques d'origine naturelle, comportant des chaînes latérales saturées ou insaturées de différentes longueurs, produits par des bactéries. Les propriétés de biodégradabilité et de biocompatibilité confèrent à ces polymères naturels de vastes possibilités d'utilisation, notamment dans le domaine biomédical. Notre objectif a consisté à élaborer de nouveaux matériaux à base de P(3-HA)s afin d'améliorer leurs propriétés. Pour cela, des copolymères à base de P(3-HA)s et de polymères semi-cristallins (poly( -caprolactone) ou poly(acide lactique)) de structures différentes telles que des copolymères à blocs, greffés et statistiques, ont été synthétisés. La présence d'insaturations sur les chaînes latérales a permis de préparer des copolymères fonctionnalisés. Les copolymères à blocs ont été utilisés pour préparer des nanoparticules par nanoprécipitation. Les nanoparticules obtenues sont susceptibles d'encapsuler et de libérer de manière contrôlée, en fonction du pourcentage de P(3-HA) dans le copolymère, de la doxorubicine, un agent anti-tumoral utilisé lors de thérapies des tumeurs de la vessie. Ces systèmes nanoparticulaires présentent des propriétés de mucoadhésivité particulièrement favorables pour des systèmes de vectorisation endocavitaire.Poly(3-hydroxyalkanoate)s (P(3-HA)s), are aliphatic biopolyesters with saturated and unsaturated side chains of different lengths. They are produced by a wide range of microorganisms. These biopolymers are biodegradable and biocompatible and can be used for biomedical applications. The aim of the study was to investigate and improve the properties of novel materials based on P(3-HA)s. Copolymers based on P(3-HA)s and semi-crystalline polymers (poly( -caprolactone) or poly(lactic acid)) with different structures e.g. block, graft or statistic copolymers, were synthesized. The presence of unsaturated units on side chains affords us the ability to prepare functionalised copolymers. Block copolymers were used to prepare mucoadhesive nanoparticles by nanoprecipitation and encapsulating doxorubicin. Doxorubicin is a chemotherapeutic agent used to treat bladder disease. The amount of P(3-HA) in the copolymers was used to control the release of doxorubicin.PARIS12-CRETEIL BU Multidisc. (940282102) / SudocSudocFranceF