References of "Heurtaux, Tony 50001978"
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See detailMicrogliosis: a double-edged sword in the control of food intake
Salvi, Juliette; Andreoletti, Pierre; Audinat, Etienne et al

in FEBS Journal (2022)

Maintaining energy balance is essential for survival and health. This physiological function is controlled by the brain, which adapts food intake to energy needs. Indeed, the brain constantly receives a ... [more ▼]

Maintaining energy balance is essential for survival and health. This physiological function is controlled by the brain, which adapts food intake to energy needs. Indeed, the brain constantly receives a multitude of biological signals that are derived from digested foods or that originate from the gastrointestinal tract, energy stores (liver and adipose tissues) and other metabolically active organs (muscles). These signals, which include circulating nutrients, hormones and neuronal inputs from the periphery, collectively provide information on the overall energy status of the body. In the brain, several neuronal populations can specifically detect these signals. Nutrient-sensing neurons are found in discrete brain areas and are highly enriched in the hypothalamus. In turn, specialized brain circuits coordinate homeostatic responses acting mainly on appetite, peripheral metabolism, activity and arousal. Accumulating evidence shows that hypothalamic microglial cells located at the vicinity of these circuits can influence the brain control of energy balance. However, microglial cells could have opposite effects on energy balance, that is homeostatic or detrimental, and the conditions for this shift are not totally understood yet. One hypothesis relies on the extent of microglial activation, and nutritional lipids can considerably change it. [less ▲]

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See detailSingle-cell transcriptional profiling and gene regulatory network modeling in Tg2576 mice reveal gender-dependent molecular features preceding Alzheimer-like pathologies
Ali, Muhammad UL; Huarte, Oihane; Heurtaux, Tony UL et al

in Molecular Neurobiology (2022), in press (doi:10.1007/s12035-022-02985-2)(in press),

Alzheimer’s disease (AD) onset and progression is influenced by a complex interplay of several environmental and genetic factors, one of them gender. Pronounced gender differences have been observed both ... [more ▼]

Alzheimer’s disease (AD) onset and progression is influenced by a complex interplay of several environmental and genetic factors, one of them gender. Pronounced gender differences have been observed both in the relative risk of developing AD and in clinical disease manifestations. A molecular level understanding of these gender disparities is still missing, but could provide important clues on cellular mechanisms modulating the disease and reveal new targets for gender-oriented disease-modifying precision therapies. We therefore present here a comprehensive single-cell analysis of disease-associated molecular gender differences in transcriptomics data from the neocortex, one of the brain regions most susceptible to AD, in one of the most widely used AD mouse models, the Tg2576 model. Cortical areas are also most commonly used in studies of post-mortem AD brains. To identify disease-linked molecular processes that occur before the onset of detectable neuropathology, we focused our analyses on an age with no detectable plaques and microgliosis. Cell-type specific alterations were investigated at the level of individual genes, pathways, and gene regulatory networks. The number of differentially expressed genes (DEGs) was not large enough to build context-specific gene regulatory networks for each individual cell type, and thus, we focused on the study of cell types with dominant changes and included analyses of changes across the combination of cell types. We observed significant disease-associated gender differences in cellular processes related to synapse organization and axonogenesis, and identified a limited set of transcription factors, including Egr1 and Klf6, as key regulators of many of the disease-associated and gender-dependent gene expression changes in the model. Overall, our analyses revealed significant celltype-specific gene expression changes in individual genes, pathways and subnetworks, including gender-specific and gender-dimorphic changes in both upstream transcription factors and their downstream targets, in the Tg2576 AD model before the onset of overt disease. This opens a window into molecular events that could determine gender-susceptibility to AD, and uncovers tractable target candidates for potential gender-specific precision medicine for AD. [less ▲]

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See detailNeurodegeneration and neuroinflammation are linked, but independent of a-synuclein inclusions, in a seeding/spreading mouse model of Parkinson's disease
Garcia, Pierre UL; Wemheuer, W.; Uriarte, O. et al

in Glia (2022)

A key pathological process in Parkinson's disease (PD) is the transneuronal spreading of α-synuclein. Alpha-synuclein (α-syn) is a presynaptic protein that, in PD, forms pathological inclusions. Other ... [more ▼]

A key pathological process in Parkinson's disease (PD) is the transneuronal spreading of α-synuclein. Alpha-synuclein (α-syn) is a presynaptic protein that, in PD, forms pathological inclusions. Other hallmarks of PD include neurodegeneration and microgliosis in susceptible brain regions. Whether it is primarily transneuronal spreading of α-syn particles, inclusion formation, or other mechanisms, such as inflammation, that cause neurodegeneration in PD is unclear. We used a model of spreading of α-syn induced by striatal injection of α-syn preformed fibrils into the mouse striatum to address this question. We performed quantitative analysis for α-syn inclusions, neurodegeneration, and microgliosis in different brain regions, and generated gene expression profiles of the ventral midbrain, at two different timepoints after disease induction. We observed significant neurodegeneration and microgliosis in brain regions not only with, but also without α-syn inclusions. We also observed prominent microgliosis in injured brain regions that did not correlate with neurodegeneration nor with inclusion load. Using longitudinal gene expression profiling, we observed early gene expression changes, linked to neuroinflammation, that preceded neurodegeneration, indicating an active role of microglia in this process. Altered gene pathways overlapped with those typical of PD. Our observations indicate that α-syn inclusion formation is not the major driver in the early phases of PD-like neurodegeneration, but that microglia, activated by diffusible, oligomeric α-syn, may play a key role in this process. Our findings uncover new features of α-syn induced pathologies, in particular microgliosis, and point to the necessity for a broader view of the process of α-syn spreading. [less ▲]

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See detailAn archaeal compound as a driver of Parkinson’s disease pathogenesis
Trezzi, Jean-Pierre; Aho, Velma UL; Jäger, Christian UL et al

E-print/Working paper (2022)

Patients with Parkinson’s disease (PD) exhibit differences in their gut microbiomes compared to healthy individuals. Although differences have most commonly been described in the abundances of bacterial ... [more ▼]

Patients with Parkinson’s disease (PD) exhibit differences in their gut microbiomes compared to healthy individuals. Although differences have most commonly been described in the abundances of bacterial taxa, changes to viral and archaeal populations have also been observed. Mechanistic links between gut microbes and PD pathogenesis remain elusive but could involve molecules that promote α-synuclein aggregation. Here, we show that 2-hydroxypyridine (2-HP) represents a key molecule for the pathogenesis of PD. We observe significantly elevated 2-HP levels in faecal samples from patients with PD or its prodrome, idiopathic REM sleep behaviour disorder (iRBD), compared to healthy controls. 2-HP is correlated with the archaeal species Methanobrevibacter smithii and with genes involved in methane metabolism, and it is detectable in isolate cultures of M. smithii. We demonstrate that 2-HP is selectively toxic to transgenic α-synuclein overexpressing yeast and increases α-synuclein aggregation in a yeast model as well as in human induced pluripotent stem cell derived enteric neurons. It also exacerbates PD-related motor symptoms, α-synuclein aggregation, and striatal degeneration when injected intrastriatally in transgenic mice overexpressing human α-synuclein. Our results highlight the effect of an archaeal molecule in relation to the gut-brain axis, which is critical for the diagnosis, prognosis, and treatment of PD. [less ▲]

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See detailPostprandial hyperglycemia stimulates neuroglial plasticity in hypothalamic POMC neurons after a balanced meal
Nuzzaci, Danaé; Cansell, Céline; Liénard, Fabienne et al

in Cell Reports (2020), 30

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See detailAlpha-Synuclein Proteins Promote Pro-Inflammatory Cascades in Microglia: Stronger Effects of the A53T Mutant.
Hoenen, Claire; Gustin, Audrey; Birck, Cindy et al

in PLoS ONE (2016)

Parkinson’s disease (PD) is histologically described by the deposition of α-synuclein, whose accumulation in Lewy bodies causes dopaminergic neuronal death. Although most of PD cases are sporadic, point ... [more ▼]

Parkinson’s disease (PD) is histologically described by the deposition of α-synuclein, whose accumulation in Lewy bodies causes dopaminergic neuronal death. Although most of PD cases are sporadic, point mutations of the gene encoding the α-synuclein protein cause inherited forms of PD. There are currently six known point mutations that result in familial PD. Oxidative stress and neuroinflammation have also been described as early events associated with dopaminergic neuronal degeneration in PD. Though it is known that microglia are activated by wild-type α-synuclein, little is known about its mutated forms and the signaling cascades responsible for this microglial activation. The present study was designed to investigate consequences of wild-type and mutant α-synuclein (A53T, A30P and E46K) exposure on microglial reactivity. Interestingly, we described that α-synuclein-induced microglial reactivity appeared to be peptide-dependent. Indeed, the A53T protein activated more strongly microglia than the wild-type α-synuclein and other mutants. This A53T-induced microglial reactivity mechanism was found to depend on phosphorylation mechanisms mediated by MAPKs and on successive NFkB/AP-1/Nrf2 pathways activation. These results suggest that the microgliosis intensity during PD might depend on the type of α-synuclein protein implicated. Indeed, mutated forms are more potent microglial stimulators than wild-type α-synuclein. Based on these data, anti-inflammatory and antioxidant therapeutic strategies may be valid in order to reduce microgliosis but also to subsequently slow down PD progression, especially in familial cases. [less ▲]

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See detailTranscriptomic analyses of primary astrocytes under TNFα treatment
Birck, Cindy UL; Koncina, Eric UL; Heurtaux, Tony UL et al

in Genomics Data (2015), 7

Astrocytes, the most abundant glial cell population in the central nervous system, have important functional roles in the brain as blood brain barrier maintenance, synaptic transmission or intercellular ... [more ▼]

Astrocytes, the most abundant glial cell population in the central nervous system, have important functional roles in the brain as blood brain barrier maintenance, synaptic transmission or intercellular communications. Numerous studies suggested that astrocytes exhibit a functional and morphological high degree of plasticity. For example, following any brain injury, astrocytes become reactive and hypertrophic. This phenomenon, also called reactive gliosis, is characterized by a set of progressive gene expression and cellular changes. Interestingly, in this context, astrocytes can re-acquire neurogenic properties. It has been shown that astrocytes can undergo dedifferentiation upon injury and inflammation, and may re-acquire the potentiality of neural progenitors. To assess the effect of inflammation on astrocytes, primary mouse astrocytes were treated with tumor necrosis factor α (TNFα), one of the main pro-inflammatory cytokines. The strength of this study is that pure primary astrocytes were used. As microglia are highly reactive immune cells, we used a magnetic cell sorting separation (MACS) method to further obtain highly pure astrocyte cultures devoid of microglia. Here, we provide details of the microarray data, which have been deposited in the Gene Expression Omnibus (GEO) under the series accession number GSE73022. The analysis and interpretation of these data are included in Gabel et al. (2015). Analysis of gene expression indicated that the NFκB pathway-associated genes were induced after a TNFα treatment. We have shown that primary astrocytes devoid of microglia can respond to a TNFα treatment with the re-expression of genes implicated in the glial cell development. [less ▲]

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See detailInflammation Promotes a Conversion of Astrocytes into Neural Progenitor Cells via NF-κB Activation
Gabel, Sebastien; Koncina, Eric UL; Dorban, Gauthier et al

in Molecular Neurobiology (2015), 53(8), 5041-5055

Brain inflammation, a common feature in neurodegenerative diseases, is a complex series of events, which can be detrimental and even lead to neuronal death. Nonetheless, several studies suggest that ... [more ▼]

Brain inflammation, a common feature in neurodegenerative diseases, is a complex series of events, which can be detrimental and even lead to neuronal death. Nonetheless, several studies suggest that inflammatory signals are also positively influencing neural cell proliferation, survival, migration, and differentiation. Recently, correlative studies suggested that astrocytes are able to dedifferentiate upon injury and may thereby re-acquire neural stem cell (NSC) potential. However, the mechanism underlying this dedifferentiation process upon injury remains unclear. Here, we report that during the early response of reactive gliosis, inflammation induces a conversion of mature astrocytes into neural progenitors. A TNF treatment induces the decrease of specific astrocyte markers, such as glial fibrillary acidic protein (GFAP) or genes related to glycogen metabolism, while a subset of these cells re-expresses immaturity markers, such as CD44, Musashi-1, and Oct4. Thus, TNF treatment results in the appearance of cells that exhibit a neural progenitor phenotype and are able to proliferate and differentiate into neurons and/or astrocytes. This dedifferentiation process is maintained as long as TNF is present in the culture medium. In addition, we highlight a role for Oct4 in this process, since the TNF-induced dedifferentiation can be prevented by inhibiting Oct4 expression. Our results show that activation of the NF-κB pathway through TNF plays an important role in the dedifferentiation of astrocytes via the re-expression of Oct4. These findings indicate that the first step of reactive gliosis is in fact a dedifferentiation process of resident astrocytes mediated by the NF-κB pathway. [less ▲]

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See detailNLRP3 Inflammasome Is Expressed and Functional in Mouse Brain Microglia but Not in Astrocytes.
Gustin, Audrey; Kirchmeyer, Mélanie UL; Koncina, Eric UL et al

in PLoS ONE (2015), 10(6),

Neuroinflammation is the local reaction of the brain to infection, trauma, toxic molecules or protein aggregates. The brain resident macrophages, microglia, are able to trigger an appropriate response ... [more ▼]

Neuroinflammation is the local reaction of the brain to infection, trauma, toxic molecules or protein aggregates. The brain resident macrophages, microglia, are able to trigger an appropriate response involving secretion of cytokines and chemokines, resulting in the activation of astrocytes and recruitment of peripheral immune cells. IL-1β plays an important role in this response; yet its production and mode of action in the brain are not fully understood and its precise implication in neurodegenerative diseases needs further characterization. Our results indicate that the capacity to form a functional NLRP3 inflammasome and secretion of IL-1β is limited to the microglial compartment in the mouse brain. We were not able to observe IL-1β secretion from astrocytes, nor do they express all NLRP3 inflammasome components. Microglia were able to produce IL-1β in response to different classical inflammasome activators, such as ATP, Nigericin or Alum. Similarly, microglia secreted IL-18 and IL-1α, two other inflammasome-linked pro-inflammatory factors. Cell stimulation with α-synuclein, a neurodegenerative disease-related peptide, did not result in the release of active IL-1β by microglia, despite a weak pro-inflammatory effect. Amyloid-β peptides were able to activate the NLRP3 inflammasome in microglia and IL-1β secretion occurred in a P2X7 receptor-independent manner. Thus microglia-dependent inflammasome activation can play an important role in the brain and especially in neuroinflammatory conditions. [less ▲]

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See detailTocopherol derivative TFA-12 promotes myelin repair in experimental models of multiple sclerosis.
Blanchard, Benoit; Heurtaux, Tony UL; Nait Oumesmar, Brahim

in Journal of Neuroscience (2013), 33(28), 11633-42

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See detailAn efficient method to limit microglia-dependent effects in astroglial cultures.
Losciuto, Sophie; Dorban, Gauthier; Gabel, Sébastien et al

in Journal of Neuroscience Methods (2012), 207(1), 59-71

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See detailMicroglial activation depends on beta-amyloid conformation: role of the formylpeptide receptor 2
Heurtaux, Tony UL; Michelucci, Alessandro UL; Losciuto, Sophie UL et al

in Journal of Neurochemistry (2010), 114(2), 576-586

Alzheimer's disease (AD) is characterized by the presence of extracellular deposits referred to beta-amyloid (Abeta) complexes or senile plaques. Abeta peptide is firstly produced as monomers, readily ... [more ▼]

Alzheimer's disease (AD) is characterized by the presence of extracellular deposits referred to beta-amyloid (Abeta) complexes or senile plaques. Abeta peptide is firstly produced as monomers, readily aggregating to form multimeric complexes, of which the smallest aggregates are known to be the most neurotoxic. In AD patients, abundant reactive microglia migrate to and surround the Abeta plaques. Though it is well known that microglia are activated by Abeta, little is known about the peptide conformation and the signaling cascades responsible for this activation. In this study, we have stimulated murine microglia with different Abeta(1-42) forms, inducing an inflammatory state, which was peptide conformation-dependent. The lightest oligomeric forms induced a more violent inflammatory response, whereas the heaviest oligomers and the fibrillar conformation were less potent inducers. BocMLF, a formylpeptide chemotactic receptor 2 antagonist, decreased the oligomeric Abeta-induced inflammatory response. The Abeta-induced signal transduction was found to depend on phosphorylation mechanisms mediated by MAPKs and on activator protein 1/nuclear factor kappa-light-chain-enhancer of activated B cells pathways activation. These results suggest that the reactive microgliosis intensity during AD might depend on the disease progression and consequently on the Abeta conformation production. The recognition of Abeta by the formylpeptide chemotactic receptor 2 seems to be a starting point of the signaling cascade inducing an inflammatory state. [less ▲]

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See detailCharacterization of the microglial phenotype under specific pro-inflammatory and anti-inflammatory conditions: Effects of oligomeric and fibrillar amyloid-beta
Michelucci, Alessandro UL; Heurtaux, Tony UL; Grandbarbe, Luc UL et al

in Journal of Neuroimmunology (2009), 210(1-2), 3-12

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 ... [more ▼]

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. [less ▲]

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See detailNotch signaling modulates the activation of microglial cells
Grandbarbe, Luc UL; Michelucci, Alessandro UL; Heurtaux, Tony UL et al

in Glia (2007), 55(15), 1519-30

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 ... [more ▼]

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. [less ▲]

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