Characterization of the microglial phenotype under specific pro-inflammatory and anti-inflammatory conditions: Effects of oligomeric and fibrillar amyloid-beta

M1 and M2 are the extremes of the differentiation spectrum of activated macrophages. Since microglia are members of the same cell lineage, we have characterized their transcription profile and their phagocytic activity under different conditions. LPS or IFN-gamma induce a M1-like phenotype, while IL-10 or IL-4 differentiate microglia towards a M2-deactivated or M2-alternatively-activated phenotype respectively. These differentiation processes also affect the Notch pathway. In order to study the polarization induced by Abeta, microglia was stimulated with different forms of the peptide. The oligomeric Abeta is a stronger M1-inductor than the fibrillar form. Moreover, a cytokine-induced anti-inflammatory environment reduces the microglial reactivity towards oligomeric Abeta

NF-κB and TNF Affect the Astrocytic Differentiation from Neural Stem Cells

The NF-κB signaling pathway is crucial during development and inflammatory processes. We have previously shown that NF-κB activation induces dedifferentiation of astrocytes into neural progenitor cells (NPCs). Here, we provide evidence  that the NF-κB pathway plays also a fundamental role during the differentiation of NPCs into astrocytes. First, we show that the NF-κB pathway is essential to initiate astrocytic differentiation as its early inhibition induces NPC apoptosis and impedes their differentiation. Second, we demonstrate that persistent NF-κB activation affects NPC-derived astrocyte differentiation. Tumor necrosis factor (TNF)-treated NPCs show NF-κB activation, maintain their multipotential and proliferation properties, display persistent expression of immature markers and inhibit astrocyte markers. Third, we analyze the effect of  NF-κB activation on the main known astrocytic differentiation pathways, such as NOTCH and JAK-STAT. Our findings suggest that the NF-κB pathway plays a dual fundamental role during NPC differentiation into astrocytes: it promotes astrocyte specification, but its persistent activation impedes their differentiation

The epidemiology of mild cognitive impairment (MCI) and Alzheimer’s disease (AD) in community-living seniors: protocol of the MemoVie cohort study, Luxembourg

BACKGROUND: Cognitive impairment and Alzheimer’s disease (AD) are increasingly considered a major public health problem. The MemoVie cohort study aims to investigate the living conditions or risk factors under which the normal cognitive capacities of the senior population in Luxembourg (≥ 65 year-old) evolve (1) to mild cognitive impairment (MCI) – transitory non-clinical stage – and (2) to AD. Identifying MCI and AD predictors undeniably constitutes a challenge in public health in that it would allow interventions which could protect or delay the occurrence of cognitive disorders in elderly people. In addition, the MemoVie study sets out to generate hitherto unavailable data, and a comprehensive view of the elderly population in the country. METHODS/DESIGN: The study has been designed with a view to highlighting the prevalence in Luxembourg of MCI and AD in the first step of the survey, conducted among participants selected from a random sample of the general population. A prospective cohort is consequently set up in the second step, and appropriate follow-up of the non-demented participants allows improving the knowledge of the preclinical stage of MCI. Case-control designs are used for cross-sectional or retrospective comparisons between outcomes and biological or clinical factors. To ensure maximal reliability of the information collected, we decided to opt for structured face to face interviews. Besides health status, medical and family history, demographic and socio-cultural information are explored, as well as education, habitat network, social behavior, leisure and physical activities. As multilingualism is expected to challenge the cognitive alterations associated with pathological ageing, it is additionally investigated. Data relative to motor function, including balance, walk, limits of stability, history of falls and accidents are further detailed. Finally, biological examinations, including ApoE genetic polymorphism are carried out. In addition to standard blood parameters, the lipid status of the participants is subsequently determined from the fatty acid profiles in their red blood cells. The study obtained the legal and ethical authorizations. DISCUSSION: By means of the multidisciplinary MemoVie study, new insights into the onset of cognitive impairment during aging should be put forward, much to the benefit of intervention strategies as a whole

Les interactions neurotrophiques dans le système nerveux central : études par transplantations et cultures cellulaires

Doctorat en sciences biologiques -- UCL, 199

Composés hybrides resvératrol/oméga-alcanols (Modulateurs de l'activation microgliale et inducteurs de la différenciation cellulaire)

Les neuropathologies dégénératives, telles que la maladie d Alzheimer et la sclérose en plaques, sont souvent accompagnées de phénomènes inflammatoires. La microglie, une population de monocytes-macrophages résidant dans le système nerveux central, est en grande partie responsable de la régulation des phénomènes inflammatoires et immunitaires dans le cerveau. Après certains stimuli, la microglie se différencie en cellules immuno-compétentes capables de faire de la phagocytose. Cette activation microgliale se traduit également par une libération de divers radicaux libres, de certaines protéases ainsi que de cytokines pro-inflammatoires. Elle est souvent observée lors de lésions ou infections cérébrales, ainsi q au cours de neuropathies comme la maladie d Alzheimer ou la sclérose en plaques.Une approche thérapeutique intéressante consiste à protéger les cellules des différentes formes de dégénérescence tout en régénérant ou en remplaçant les cellules nerveuses mortes ou lésées à partir de cellules souches neurales. Dans cette optique nous avons synthétisé des molécules hybrides, les RFA (Resveratrol Fatty Alcohols) combinant un noyau anti-oxydant, le resvératrol, pour son effet neuroprotecteur et une chaîne -hydroxylée pour son aspect neurorégénérateur. La synthèse adoptée repose sur un couplage de Sonogashira permettant de greffer la chaîne oméga-alcanol et sur un couplage de Wadsworth-Emmons permettant la création de la double liaison carbone-carbone exclusivement trans et donnant ainsi naissance au noyau stilbène.Les RFA possèdent de bonnes capacités anti-oxydantes. De plus, les RFA et plus particulièrement le RFA12, portant 12 atomes de carbone, est capable d atténuer la réponse inflammatoire en modulant l activation microgliale tout en induisant la différenciation des cellules souches neurales en neurones matures. Des études préliminaires du mécanisme d action permettent de postuler en faveur d une implication du RFA12 dans la voie de signalisation Notch.Inflammatory events are often observed during degenerative neuropathies like Alzheimer s disease or multiple sclerosis. Microglial cells, the brain resident monocyte-macrophage cell population, play an important role during neuro-inflammation processes. Upon appropriate stimulation, these cells continue their previously halted differentiation to become immunocompetent phagocytic cells. This activation is accompanied by the production of numerous free radicals, proteases and pro-inflammatory cytokines. This type of activation is observed after brain injury or infections, as well as during the development of neuropathies, like Alzheimer s disease or multiple sclerosis.A new therapeutic approach consists in protecting cells against degeneration while regenerating nerve cells from existing neural stem cells. So, we investigated the synthesis of compounds presenting neuroprotective as well as neuroregenerative activities. These compounds, Resveratrol Fatty Alcohols (RFAs) bear a neuroprotective moiety, resveratrol, and a neurotrophic omega-alkanol structure. A Sonogashira cross-coupling followed by a Wadsworth-Emmons reaction leads to the RFAs.The different RFAs have good antioxidative capacities. Beside, RFA s, especially RFA12, bearing 12 carbon atoms on the side chain, have a down regulating effect on neuroinflammation by modulating the microglial activation while promoting the differentiation of neural stem cells into mature neurons at 0.1 M. Preliminary mechanistic studies showed that these effects act at least partially through the Notch signalling pathway.STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Composés hybrides oméga-alcanols / vitamine E ou C (Synthèses et études biologiques de modulateurs de l'activation microgliale)

STRASBOURG-Sc. et Techniques (674822102) / SudocSudocFranceF

Transplantation of neural stem cells in a rat model of stroke: assessment of short-term graft survival and acute host immunological response

The use of progenitors and stem cells for neural grafting is promising, as these not only have the potential to be maintained in vitro until use, but may also prove less likely to evoke an immunogenic response in the host, when compared to primary (fetal) grafts. We investigated whether the short-term survival of a grafted conditionally immortalised murine neuroepithelial stem cell line (MHP36) (2 weeks post-implantation, 4 weeks post-ischaemia) is influenced by: (i) immunosuppression (cyclosporin A (CSA) vs. no CSA), (ii) the local (intact vs. lesioned hemisphere), or (iii) global (lesioned vs. sham) brain environment. MHP36 cells were transplanted ipsi- and contralateral to the lesion in rats with middle cerebral artery occlusion (MCAo) or sham controls. Animals were either administered CSA or received no immunosuppressive treatment. A proliferation assay of lymphocytes dissociated from cervical lymph nodes, grading of the survival of the grafted cells, and histological evaluation of the immune response revealed no significant difference between animals treated with or without CSA. There was no difference in survival or immunological response to cells grafted ipsi- or contralateral to the lesion. Although a local upregulation of immunological markers (MHC class I, MHC class II, CD45, CD11b) was detected around the injection site and the ischaemic lesion, these were not specifically upregulated in response to transplanted cells. These results provide evidence for the low immunogenic properties of MHP36 cells during the initial period following implantation, known to be associated with an acute host immune response and ensuing graft rejection

Notch signaling modulates the activation of microglial cells

The Notch signaling pathway plays a crucial role in specifying cellular fate in metazoan development by regulating communication between adjacent cells. Correlative studies suggested an involvement of Notch in hematopoietic cell development. Here, we report that the Notch pathway is expressed and active in microglial cells. During inflammatory activation, the transcription of the Notch down-stream effector Hes1 is downregulated. When Notch1 transcription in microglia is inhibited, an upregulation of the expression of pro-inflammatory cytokines is observed. Notch stimulation in activated microglia, using a soluble form of its ligand Jagged1, induces a decrease in pro-inflammatory cytokines secretion and nitric oxide production as well as an increase in phagocytic activity. Notch-stimulation is accompanied by an increase in the rate of STAT3 phosphorylation and nuclear translocation. Our results show that the Notch pathway plays an important role in the control of inflammatory reactions in the CNS