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Les rétinopathies ischémiques prolifératives telles que la rétinopathie diabétique proliférative et la rétinopathie du prématuré sont les principales causes de la perte de la vision dans la population active et pédiatrique des pays industrialisés. Malgré le fait que les événements initiateurs sont différents et propres à chacune des pathologies, les rétinopathies ischémiques prolifératives sont le résultat d’un processus biphasique. On a d’abord une phase initiale de dégénérescence microvasculaire suivie d’une néovascularisation excessive et pathologique de la rétine hypoxique qui tente de réinstaurer l’apport en nutriments et en énergie. Mais au lieu d’aller revasculariser les zones avasculaires de la rétine, ces nouveaux vaisseaux sanguins sont mal orientés et se dirigent plutôt vers le vitré normalement avasculaire. Ceci provoque des tensions physiques dans la rétine et mène à long terme à son détachement et une perte de vision conséquente. Les traitements actuels ne viennent pas sans effets secondaires majeurs. Par exemple, la formation de la cataracte et l’augmentation de la pression intraoculaire avec l’utilisation des corticostéroïdes ou la perte de la vision partielle dans le cas du traitement au laser sont fréquemment observées. De même, la thérapie anti-VEGF (Vascular endothelial growth factor) apporte aussi son lot de complications, telles que la thromboembolie veineuse et l’augmentation de la neurotoxicité après un long usage, vu les propriétés neuro- et vaso-protectrices du VEGF. Le développement d’une nouvelle approche thérapeutique pour les rétinopathies ischémiques prolifératives est donc nécessaire afin de contrer ces limitations thérapeutiques. Dans notre première étude, nous mettons en évidence un nouveau mécanisme par lequel les cellules neuronales sous stress diabétique sont à l’origine d’une forte inflammation oculaire. Nos résultats démontrent que le co-récepteur multi-ligand Neuropiline-1, le VEGF et la Sémaphorine-3A agissent de concert afin d’attirer une sous-population particulière de phagocytes mononucléaires susceptibles d’activer le processus de croissance vasculaire pathologique dans la rétine diabétique. De plus, notre étude propose une base pour de futures recherches sur l’impact des phagocytes mononucléaires exprimant Neuropiline-1 dans les pathologies du système nerveux central caractérisées par une inflammation excessive. Nos résultats permettent aussi de mettre en lumière le caractère anti-inflammatoire potentiel des thérapies actuelles anti-VEGF (à cause du rôle de VEGF dans la mobilisation des phagocytes mononucléaires via Neuropiline-1) au niveau oculaire. Dans notre deuxième étude, nous mettons en évidence l’activation du facteur HIF1α dans les phagocytes mononucléaires présents dans la rétine hypoxique. L’utilisation d’une approche protéomique non biaisée de spectrométrie de masse en tandem nous a permis d’identifier les partenaires interagissant avec HIF1α dans un milieu déficient en oxygène. Nous avons pu ainsi déterminer pour la première fois l’association entre la voie d’HIF1α et celle d’IRE1α (un des trois senseurs de la voie de l’UPR « unfolded protein response ») dans le processus d’adaptation à l’oxygène des phagocytes mononucléaires. Nos résultats révèlent ensuite l’importance d’IRE1α (plus principalement son activité kinase) dans la production d’HIF1α. Nous démontrons finalement que la synergie entre les signalisations d’IRE1α et HIF1α pourrait être responsable du comportement pathogénique des phagocytes mononucléaires via leur libération de cytokines inflammatoires; ce qui participerait ainsi à la progression des rétinopathies. Collectivement, nos travaux ont permis d’identifier d’importants régulateurs de l’activité pathogénique des phagocytes mononucléaires. Nous montrons : 1) le rôle de Neuropiline-1 dans l’infiltration des phagocytes mononucléaires au niveau des zones endommagées de la rétine et 2) l’impact du mécanisme convergent entre les voies d’IRE1α et HIF1α sur leur sécrétion de facteurs pro-inflammatoires durant les rétinopathies. Nos résultats offrent une base pour le développement de nouvelles stratégies thérapeutiques (ciblant Neuropiline-1, IRE1α et HIF1α) dans le traitement de maladies oculaires et d’autres pathologies caractérisées par une inflammation excessive. / Proliferative ischemic retinopathies such as proliferative diabetic retinopathy (PDR) and retinopathy of prematurity (ROP) are the principal causes of vision loss in working age and pediatric populations of industrialized countries. Although they display different initial triggers, proliferative ischemic retinopathies are biphasic ocular diseases that affect retinal vessels. There is an initial degeneration of the microvasculature, followed by a hypoxic stress on the retina. This triggers a second phase of deregulated and destructive blood vessel growth within the retina. Given this sequence of events and prominent clinical features, the currently most widely used local ocular therapeutic interventions directly target pathological blood vessel growth, yet present a number of non-desirable off-target effects such as the destruction of the retina itself. In fact, currently available treatments for proliferative ischemic retinopathies present non-negligible side effects, such as cataract formation with intravitreal use of corticosteroid or reduced visual field with laser-based photocoagulation surgery. Similarly, the anti-VEGF (Vascular endothelial growth factor) therapy may be associated with thromboembolic events, neuronal toxicity and atrophy when used as frequent long-term treatment given the fact that VEGF serves a vaso- and neuro-protective factor in the retina. Overcoming these therapeutic limitations and exploring novel pharmacological avenues are therefore required to ameliorate the safety profiles of current interventions. In our first study, we describe a novel mechanism by which severely stressed neuronal cells in the diabetic retina provoke destructive inflammation in the eye. We demonstrate that the multi-ligand co-receptor Neuropilin-1, VEGF and Semaphorin3A act as potent attractants for a specialized population of immune cells (mononuclear phagocytes) that later promote the exaggerated pathological vessel growth associated with the disease progression. Importantly, we provide evidence for a novel pharmacological intervention that reduces the inflammation associated with pathological retinal vessel growth. Our findings also suggest that current anti-VEGF therapies (a popular treatment for ocular vascular diseases) may in part be effective by reducing destructive ocular inflammation. In our second study, we provide evidence that those mononuclear phagocytes activate HIF1α in the hypoxic and inflamed retina. After using the unbiased proteomic approach of tandem mass spectrometry, we were able to identify HIF1α partners and found a novel link between HIF1α and the UPR (unfolded protein response) sensor IRE1α. Our data next established the crucial role of IRE1α (precisely via its kinase activity) in HIF1α production. We also suggested that the synergy between IRE1α and HIF1α pathways may be responsible of the pathogenic activity of the hypoxic mononuclear phagocytes via their secretion of inflammatory cytokines, thus contributing to the progression of the retinopathy. Collectively, our work identifies important regulators of the pathogenic activity of mononuclear phagocytes. We show that: 1) Neuropilin-1 promotes the infiltration of mononuclear phagocytes in the retina and 2) the convergent mechanism between IRE1α and HIF1α pathways is responsible for their release of pro-inflammatory factors during retinopathy. Our results could be used as a basis for the development of alternative therapeutic strategies (targeting Neuropilin-1, IRE1α and HIF1α) to treat ocular diseases or other pathologies characterized by an excessive inflammation.

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<p>  Fetal Alcohol Syndrome (FAS) is the most serious form of Fetal Alcohol Spectrum Disorders (FASD) and the most prevalent neurodevelopmental disorder in North America. Patients with FAS may exhibit cognitive problems with working memory, manipulating information, and reduced executive functioning. Additionally, previous studies exhibited that stress responses are affected by prenatal alcohol consumption Gut microbiota compositions can also influence stress responses and memory, as several studies have shown strong relationships between the enteric gut system and the brain. However, few studies have examined how prenatal alcohol exposure’s effects on the gut microbiome and neuroinflammatory responses. For this study, pregnant HsdBlu:LE Long Evans rats were treated with either a dry diet, liquid diet, or liquid diet with alcohol. On day 28 and 42 after birth, three male and three female adolescent pups from each treatment group had their gut microbiome (fecal samples) analyzed through 16S rRNA amplicon sequencing. Brain histology staining of the cortex and hippocampus regions was also done to evaluate changes in the CNS through microglial counts and morphology analysis. There were no significant differences in alpha diversity of the fecal microbiome between groups of pups based on prenatal alcohol exposure (PAE), sex, age, the interaction of PAE and sex, or in the morphology of cortex microglia. However, analysis of beta diversity using Bray-Curtis dissimilarity and weighted UniFrac suggested distinct microbial communities between the treatment groups based on PAE and the interaction of PAE, sex, and the interaction between PAE and sex. Microglial count comparisons by PAE or sex were only statistically different in the cortex (p ≤ 0.005). The significance of this study suggests that there are some associations between the gut microbiome and CNS inflammation in rats with PAE. Based on these findings, 11 future studies may implement therapeutics such as antibiotics or probiotics to mitigate cognitive or neural symptoms of FASD affected individuals. </p>

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No / Microglial activation and behavioral abnormalities occur before neuronal loss in experimental murine prion disease; the behavioral changes coincide with a reduction in synaptic plasticity. Because synaptic plasticity depends on an intact perineuronal net (PN), a specialized extracellular matrix that surrounds parvalbumin (PV)-positive GABAergic (gamma-aminobutyric acid [GABA]) inhibitory interneurons, we investigated the temporal relationships between microglial activation and loss of PN and PV-positive neurons in ME7 murine prion disease. Anesthetized C57Bl/6J mice received bilateral intracerebral microinjections of ME7-infected or normal brain homogenate into the dorsal hippocampus. Microglial activation, PrP accumulation, the number of PV-positive interneurons, and Wisteria floribunda agglutinin-positive neurons (i.e. those with an intact PN) were assessed in the ventral CA1 and subiculum at 4, 8, 12, 16, and 20 weeks postinjection. Hippocampal areas and total neuron numbers in the ventral CA1 and subiculum were also determined. Loss of PN coincided with early microglial activation and with a reduction in synaptic plasticity. No significant loss of PV-positive interneurons was observed. Our findings suggest that the substrate of the earliest synaptic and behavioral abnormalities in murine prion disease may be inflammatory microglia-mediated degradation of the PN.

Obesidade é fator de risco para a hipertensão arterial e os mecanismos envolvidos nesta doença não são totalmente esclarecidos. Camundongos C57BL/6J e transgênicos com com deleção em neurônios e glia da via inflamatória do receptor toll-like-NF&#954;B foram submetidos à dieta hiperlipídica (HL) por 8 e 15 semanas e avaliados parâmetros metabólicos, pressão arterial, frequência cardíaca, atividade do sistema nervoso autônomo, fatores inflamatórios e neuropeptídeos no hipotálamo e no tronco encefálico. Os camundongos expostos HL desenvolveram hipertensão arterial acompanhada de disfunção autonômica e aumento de CART no DMH. Os animais transgênicos quando submetidos à dieta HL desenvolveram um quadro de obesidade, porém não apresentaram hipertensão arterial e disfunção autonômica. Além disso, o grupo de animais HL aumentou o RNAm de CCL5 no hipotálamo e de CD86 no tronco-encefálico e a densidade de microglia no NTS caudal. Os resultados sugerem novos mecanismos para a hipertensão e disfunção autonômica secundárias à ingestão de dieta hiperlipídica mostrando o papel do CART o DMH e o envolvimento da via inflamatória do TLR-NF&#954;B em neurônios e glia nos mecanismos desta patologia. / Obesity is a risk factor for high blood pressure and the mechanisms involved in this disease are not fully clarified. C57BL/6J and transgenic mice with toll-like-NF&#954;B receptor inflammatory- pathway deletion in neurons and glia were fed with high-fat diet (HL) for 8 or 15 weeks and assessed metabolic parameters, blood pressure, heart rate, autonomic nervous system activity, inflammatory factors and neuropeptides in the hypothalamus and brainstem. The HL mice developed hypertension accompanied with autonomic dysfunction and increased CART in DMH. Transgenic animals when submitted to HL diet developed obesity, but not showed high blood pressure and autonomic dysfunction. In addition, HL animals had increased CCL5 mRNA in hypothalamus, CD86 mRNA in brainstem and micróglia density in caudal NTS. The results suggest new mechanisms for hypertension and autonomic dysfunction secondary to intake of high-fat diet by showing CART role in DMH and the involvement of the inflammatory pathway TLR-NF&#954;B in neurons and glia.