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Background: Estimation of infarction based on computed tomographic perfusion (CTP) remains challenging, mainly due to noise associated with CTP data and variability in reported thresholds ischemic core esstimation. Commercial software companies have attempted to establish CTP thresholds; for example, a relative cerebral blood flow (rCBF) of Methods: Under an approved multi-institutional protocol, patients with acute ischemic stroke of the anterior circulation from three comprehensive stroke centers were included if they met the following criteria: baseline CTP, recanalization achieved (Thrombolysis in cerebral infarction scale ≥ IIb), and follow up MRI (DWI) performed. Perfusion maps were generated from the CTP data by the Bayesian probabilistic model and oscillation singular value decomposition (oSVD). CTP parameters, including time to peak (TTP), rCBF, time to max (Tmax), and Delay (equivalent of Tmax in Bayesian model) were generated. Brain was extracted from CTP and coregistered with the follow up MRI. An infarction mask and non-infarcted masks were drawn on MRI. We used a robust logistic regression to assess the binary outcome of our voxel-based analysis (infarcted vs non-infarcted) by adjusting for intra-subject correlations. Results: Eighty-one patients (42 Male; mean age 67.4 ±17.3) were included. All CTP parameters for the Bayesian and oSVD methods showed significant differences between infarcted and non-infarcted areas (p < 0.001). In the Bayesian model, a combination of rCBF at threshold of Conclusion: Using heterogenous CTP data from three stroke centers, we established thresholds for estimation of ischemic core for Olea software that can be used for both Bayesian and oSVD postprocessing models.

The T-type calcium channel, Cav3.2, is necessary for acute pain perception, as well as mechanical and cold allodynia in mice. Being found throughout sensory pathways, from excitatory primary afferent neurons up to pain matrix structures, it is a promising target for analgesics. In our study, Cav3.2 was detected in ~60% of the lamina II (LII) neurons of the spinal cord, a site for integration of sensory processing. It was co-expressed with Tlx3 and Pax2, markers of excitatory and inhibitory interneurons, as well as nNOS, calretinin, calbindin, PKCγ and not parvalbumin. Non-selective T-type channel blockers slowed the inhibitory but not the excitatory transmission in LII neurons. Furthermore, T-type channel blockers modified the intrinsic properties of LII neurons, abolishing low-threshold activated currents, rebound depolarizations, and blunting excitability. The recording of Cav3.2-positive LII neurons, after intraspinal injection of AAV-DJ-Cav3.2-mcherry, showed that their intrinsic properties resembled those of the global population. However, Cav3.2 ablation in the dorsal horn of Cav3.2GFP-Flox KI mice after intraspinal injection of AAV-DJ-Cav3.2-Cre-IRES-mcherry, had drastic effects. Indeed, it (1) blunted the likelihood of transient firing patterns; (2) blunted the likelihood and the amplitude of rebound depolarizations, (3) eliminated action potential pairing, and (4) remodeled the kinetics of the action potentials. In contrast, the properties of Cav3.2-positive neurons were only marginally modified in Cav3.1 knockout mice. Overall, in addition to their previously established roles in the superficial spinal cord and in primary afferent neurons, Cav3.2 channel appear to be necessary for specific, significant and multiple controls of LII neuron excitability.

International audience; Functional imaging in behaving animals is essential to explore brain functions. Real-time optical imaging of brain functions is limited by light scattering, skull distortion, timing resolution and subcellular precision that altogether, make challenging the rapid acquisition of uncorrupted functional data of cells integrated de novo in the neurogliovascular unit. We report multimodal transcranial in vivo optical imaging for the fast and direct visualization of microcirculation in the perfusion domain where new cells incorporated in the neurogliovascular unit during the progression of a seizure disorder and its treatment. Using this methodology, we explored the performance improvement of cells integrated de novo in the neurogliovascular unit. We report fast transcranial imaging of blood microcirculation at sites of pericyte turnover in the epileptic brain and after treatment with a trophic factor that revealed key features of the regenerating neurogliovascular unit.

International audience; The diversity of actions of the glucocorticoid stress hormones among individuals and within organs, tissues and cells is shaped by age, gender, genetics, metabolism, and the quantity of exposure. However, such factors cannot explain the heterogeneity of responses in the brain within cells of the same lineage, or similar tissue environment, or in the same individual. Here, we argue that the stress response is continuously updated by synchronized neural activity on large-scale brain networks. This occurs at the molecular, cellular and behavioral levels by crosstalk communication between activity-dependent and glucocorticoid signaling pathways, which updates the diversity of responses based on prior experience. Such a Bayesian process determines adaptation to the demands of the body and external world. We propose a framework for understanding how the diversity of glucocorticoid actions throughout brain networks is essential for supporting optimal health, while its disruption may contribute to the pathophysiology of stress-related disorders, such as major depression, and resistance to therapeutic treatments.

The cerebellum, a primary brain structure involved in the control of sensorimotor tasks, also contributes to higher cognitive functions including reward, emotion and social interaction. Although the regulation of these behaviors has been largely ascribed to the monoaminergic system in limbic regions, the contribution of cerebellar dopamine signaling in the modulation of these functions remains largely unknown. By combining cell-type-specific transcriptomics, histological analyses, three-dimensional imaging and patch-clamp recordings, we demonstrate that cerebellar dopamine D2 receptors (D2Rs) in mice are preferentially expressed in Purkinje cells (PCs) and regulate synaptic efficacy onto PCs. Moreover, we found that changes in D2R levels in PCs of male mice during adulthood alter sociability and preference for social novelty without affecting motor functions. Altogether, these findings demonstrate novel roles for D2R in PC function and causally link cerebellar D2R levels of expression to social behaviors.

Synaptogenesis is encoded by multiple genes that program the assembly of neural networks in the immature brain during development and later in life, in the experienced brain that must respond to changes of the external world and of proprioception. Processing of neural network activity cannot solely rely on the activity of established synapses as their plasticity can saturate. For this reason, synaptogenesis is reversible. Assembly and disassembly of synapses depend on the exchange of signals between the pre- and postsynaptic terminals. Synaptic trophic factors are paramount for neural network remodeling, homeostasis, and survival because they are present in limited supply. Neurotrophins present the necessary attributes to operate as synaptic trophin. It is speculated that many diverse and pleiotropic actions of neurotrophins on the synapse depend on the sources of neurotrophin ligands, its modes of secretion, and signaling, all influenced by their locations at the synapse. What information is encoded when synaptic neurotrophin signaling is retrograde or anterograde, paracrine or autocrine? Answers emerged from the characterization of the cells that secrete neurotrophins, the cells that respond to neurotrophins, the various modes of secretion, receptor–signaling pathways, and the temporal constraints imposed by synaptic transmission. Failure to communicate the appropriate synaptic trophic signals impairs neuronal networks maintenance and updated wiring.

Background: Pesticide residues have contaminated our environment and nutrition over the last century. Although these compounds are present at very low concentrations, their long-term effects on human health is of concern. The link between pesticide residues and Alzheimer’s disease is not clear and difficult to establish. To date, no in vivo experiments have yet modeled the impact of this chronic contamination on neurodegenerative disorders. Objectives: We investigated the impact of fungicide residues on the pathological markers of Alzheimer’s disease in a transgenic mouse model. Methods: Transgenic (J20, hAPPSw/Ind ) mice were chronically exposed to a cocktail of residues of cyprodinil, mepanipyrim, and pyrimethanil at 0.1μg/L in their drinking water for 9 months. We assessed the effects of fungicide residues on the pathological markers of the disease including Aβ aggregates, neuroinflammation, and neuronal loss. Then, we studied the dynamics of Aβ aggregation in vivo via a longitudinal study using two-photon microscopy. Finally, we investigated the molecular mechanisms involved in the production and clearance of Aβ peptides. Results: We found that a chronic exposure to three fungicide residues exacerbated aggregation, microgliosis, and neuronal loss. These fungicides also increased vascular amyloid aggregates reminiscent of cerebral amyloid angiopathy between 6 and 9 months of treatment. The mechanism of action revealed that fungicides promoted Aβ peptide fibril formation in vitro and involved an in vivo overexpression of the levels of the β-secretase–cleaving enzyme (BACE1) combined with impairment of Aβ clearance through neprylisin (NEP). Conclusions: Chronic exposure of the J20 mouse model of Alzheimer’s disease to a cocktail of fungicides, at the regulatory concentration allowed in tap water (0.1μg/L ), strengthened the preexisting pathological markers: neuroinflammation, Aβ aggregation, and APP β-processing. We hypothesize prevention strategies toward pesticide long-term exposure may be an alternative to counterbalance the lack of treatment and to slow down the worldwide Alzheimer’s epidemic., This project was supported by the French government under the Programme d’investissement d’Avenir, Initiative Sciences Innovation Territoire–MUSE (Montpellier University Site of Excellence) with reference ANR-16-IDEX-0006, I-Site MUSE STEMPest. This project was supported by grants from the French National Research Agency (ANR) under the program Investissement d’Avenir with reference ANR-11-LABX-0021-LipSTIC. W.Y. is the recipient of a fellowship from the China Scholarship Council under the Programme Hubert Curien (PHC) CAI YUANPEI 2014-16–project no. 32106RD and a joint-PhD student from Huazhong University of Science and Technology and University of Montpellier. P.A.L. is the recipient of a fellowship from the French Ministry of Higher Education and Research and from the Center of Excellence for Neurodegenerative diseases of Montpellier (CoEN)–CHU of Montpellier certified by AVIESAN as part of the Plan maladies neuro-dégénératives (2014–2019).

SummaryThe cerebellum, a primary center involved in the control of sensorimotor tasks, also contributes to higher cognitive functions including reward, emotion and social interaction. The regulation of these behaviors has been largely ascribed to the monoaminergic system in limbic regions. However, the contribution of cerebellar dopamine signaling in the modulation of these functions remains largely unknown due to the lack of precise characterization of cerebellar dopaminoceptive neurons. By combining cell type-specific transcriptomic and histological analyses, 3D imaging and electrophysiology we demonstrate that cerebellar dopamine D2 receptors (D2R) in mice are preferentially expressed in Purkinje cells (PCs). While activation of D2R regulate synaptic efficacy onto PCs, their deletion or overexpression in PCs bidirectionally controls preference for social novelty without affecting motor functions. Altogether, these findings demonstrate novel D2R’s roles in PC function and causally link cerebellar D2R levels of expression to social behaviors.

Summary: Reorganization of the neurovascular unit has been suggested in the epileptic brain, although the dynamics and functional significance remain unclear. Here, we tracked the in vivo dynamics of perivascular mural cells as a function of electroencephalogram (EEG) activity following status epilepticus. We segmented the cortical vascular bed to provide a size- and type-specific analysis of mural cell plasticity topologically. We find that mural cells are added and removed from veins, arterioles, and capillaries after seizure induction. Loss of mural cells is proportional to seizure severity and vascular pathology (e.g., rigidity, perfusion, and permeability). Treatment with platelet-derived growth factor subunits BB (PDGF-BB) reduced mural cell loss, vascular pathology, and epileptiform EEG activity. We propose that perivascular mural cells play a pivotal role in seizures and are potential targets for reducing pathophysiology. : Arango-Lievano et al. follow how status epilepticus changes the dynamics of mural cell turnover at the cortical vasculature, causing vessel damage. PDGF-BB, a growth factor promoting the assembly of mural cells at the vascular unit, ameliorates vessel function and reduces spontaneous epileptiform activity. Keywords: neurovascular, epilepsy, pericyte, blood flow, PDGF-BB, PDGFR-B, in vivo microscopy

Metabolic adaptation is a critical feature of synaptic plasticity. Indeed, synaptic plasticity requires the utilization and resupply of metabolites, in particular when the turnover is high and fast such as in stress conditions. What accounts for the localized energy burden of the post-synaptic compartment to the build up of chronic stress is currently not understood. We used in vivo microscopy of genetically encoded fluorescent probes to track changes of mitochondria, dendritic spines, ATP and H2O2 levels in pyramidal neurons of cortex before and after chronic unpredictable mild stress. Data revealed hotspots of postsynaptic mitochondria and dendritic spine turnover. Pharmacogenetic approach to force expression of the metabolic stress gene NR4A1 caused the fragmentation of postsynaptic mitochondria and loss of proximal dendritic spine clusters, whereas a dominant-negative mutant counteracted the effect of chronic stress. When fragmented, dendritic mitochondria produced lesser ATP at resting state and more on acute demand. This corresponded with significant production of mitochondrial H2O2 oxidative species in the dendritic compartment. Together, data indicate that pyramidal neurons adjust proximal dendritic spine turnover and mitochondria functions in keeping with synaptic demands., Highlights • Addition of dendritic spine clusters match with more proximal mitochondria coverage. • Loss of dendritic spine clusters match with less proximal mitochondria coverage. • Dendrites alter spine dynamics, ATP and H202 production in keeping with excitation. • In excess, the transcription factor NR4A1 promotes cross-clustering losses. • Blocking NR4A1 prevents net cross-clustering losses mediated by chronic stress.

Stress can either promote or impair learning and memory. Such opposing effects depend on whether synapses persist or decay after learning. Maintenance of new synapses formed at the time of learning upon neuronal network activation depends on the stress hormone activated glucocorticoid receptor (GR) and neurotrophic factor release. Whether and how concurrent GR and neurotrophin signaling integrate to modulate synaptic plasticity and learning is unknown. Here we show that deletion of the neurotrophin BDNF-dependent GR phosphorylation sites (GR-PO4) impairs long-term memory retention and maintenance of newly formed postsynaptic dendritic spines in the mouse cortex after motor skills training. Chronic stress and the BDNF polymorphism Val66Met disrupt the BDNF-dependent GR-PO4 pathway necessary for preserving training-induced spines and previously acquired memories. Conversely, enrichment living promotes spine formation but fails to salvage training-related spines in mice lacking BDNF-dependent GR-PO4 sites, suggesting it is essential for spine consolidation and memory retention. Mechanistically, spine maturation and persistence in the motor cortex depend on synaptic mobilization of the glutamate receptor GluA1 mediated by GR-PO4. Together, these findings indicate that regulation of GR-PO4 via activity-dependent BDNF signaling is important for learning-dependent synapses formation and maintenance. They also define a new signaling mechanism underlying these effects.SIGNIFICANCE STATEMENTSignal transduction of receptors tyrosine kinase and nuclear receptors is essential for homeostasis. Phosphorylation is one of the currencies used by these receptors to support homeostatic reactions in learning and memory. Here we show that consolidation of learning-induced neuroplasticity is made possible via stress activated glucocorticoid nuclear receptor phosphorylation through the brain-derived neurotrophic tyrosine kinase pathway. Crosstalk between these pathways is specific of cell types and behavioral experience (e.g. learning, stress and enrichment living). Disruption of this response may contribute to the pathophysiology of stress-related disorders and treatment resistance.

International audience; Glucocorticoid actions are tailored to the organs and cells responding thanks to complex integration with ongoing signaling mediated by cytokines, hormones, neurotransmitters, and growth factors. Disruption of: (1) the amount of signaling molecules available locally; (2) the timing with other signaling pathways; (3) the post-translational modifications on glucocorticoid receptors; and (4) the receptors-interacting proteins within cellular organelles and functional compartments, can modify the sensitivity and efficacy of glucocorticoid responses with implications in physiology, diseases and treatments. Tissue sensitivity to glucocorticoids is sustained by multiple systems that do not operate in isolation. We take the example of the interplay between the glucocorticoid and brain-derived neurotrophic factor signaling pathways to deconstruct context-dependent glucocorticoid responses that play key roles in physiology, diseases and therapies.

Complications of dopamine replacement for Parkinson's disease (PD) can limit therapeutic options, leading to interest in identifying novel pathways that can be exploited to improve treatment. p11 (S100A10) is a cellular scaffold protein that binds to and potentiates the activity of various ion channels and neurotransmitter receptors. We have previously reported that p11 can influence ventral striatal function in models of depression and drug addiction, and thus we hypothesized that dorsal striatal p11 might mediate motor function and drug responses in parkinsonian mice. To focally inhibit p11 expression in the dorsal striatum, we injected an adeno-associated virus (AAV) vector producing a short hairpin RNA (AAV.sh.p11). This intervention reduced the impairment in motor function on forced tasks, such as rotarod and treadmill tests, caused by substantia nigra lesioning in mice. Measures of spontaneous movement and gait in an open-field test declined as expected in control lesioned mice, whereas AAV.sh.p11 mice remained at or near normal baseline. Mice with unilateral lesions were then challenged with l-dopa (levodopa) and various dopamine receptor agonists, and resulting rotational behaviors were significantly reduced after ipsilateral inhibition of dorsal striatal p11 expression. Finally, p11 knockdown in the dorsal striatum dramatically reduced l-dopa-induced abnormal involuntary movements compared with control mice. These data indicate that focal inhibition of p11 action in the dorsal striatum could be a promising PD therapeutic target to improve motor function while reducing l-dopa-induced dyskinesias.

The comorbidity of depression and cocaine addiction suggests shared mechanisms and anatomical pathways. Specifically, the limbic structures, such as the nucleus accumbens (NAc), play a crucial role in both disorders. P11 (S100A10) is a promising target for manipulating depression and addiction in mice. We summarized the recent genetic and viral strategies used to determine how the titration of p11 levels within the NAc affects hedonic behavior and cocaine reward learning in mice. In particular, p11 in the ChAT+ cells or DRD1+ MSN of the NAc, controls depressive-like behavior or cocaine reward, respectively. Treatments to counter maladaptation of p11 levels in the NAc could provide novel therapeutic opportunities for depression and cocaine addiction in humans.

Remodeling of the brain vasculature is a common trait of brain pathologies. In vivo imaging techniques are fundamental to detect cerebrovascular plasticity or damage occurring overtime and in relation to neuronal activity or blood flow. In vivo two-photon microscopy allows the study of the structural and functional plasticity of large cellular units in the living brain. In particular, the thinned-skull window preparation allows the visualization of cortical regions of interest (ROI) without inducing significant brain inflammation. Repetitive imaging sessions of cortical ROI are feasible, providing the characterization of disease hallmarks over time during the progression of numerous CNS diseases. This technique accessing the pial structures within 250 μm of the brain relies on the detection of fluorescent probes encoded by genetic cellular markers and/or vital dyes. The latter (e.g., fluorescent dextrans) are used to map the luminal compartment of cerebrovascular structures. Germane to the protocol described herein is the use of an in vivo marker of amyloid deposits, Methoxy-O4, to assess Alzheimer's disease (AD) progression. We also describe the post-acquisition image processing used to track vascular changes and amyloid depositions. While focusing presently on a model of AD, the described protocol is relevant to other CNS disorders where pathological cerebrovascular changes occur.

Glucocorticoid resistance is a risk factor for Alzheimer’s disease (AD). Molecular and cellular mechanisms of glucocorticoid resistance in the brain have remained unknown and are potential therapeutic targets. Phosphorylation of glucocorticoid receptors (GR) by brain-derived neurotrophic factor (BDNF) signaling integrates both pathways for remodeling synaptic structure and plasticity. The goal of this study is to test the role of the BDNF-dependent pathway on glucocorticoid signaling in a mouse model of glucocorticoid resistance. We report that deletion of GR phosphorylation at BDNF-responding sites and downstream signaling via the MAPK-phosphatase DUSP1 triggers tau phosphorylation and dendritic spine atrophy in mouse cortex. In human cortex, DUSP1 protein expression correlates with tau phosphorylation, synaptic defects and cognitive decline in subjects diagnosed with AD. These findings provide evidence for a causal role of BDNF-dependent GR signaling in tau neuropathology and indicate that DUSP1 is a potential target for therapeutic interventions.

WOS: 000372330700014 PubMed ID: 26787837 Palmitoylation is involved in several neuropsychiatric and movement disorders for which a dysfunctional signaling of the dopamine D3 receptor (Drd3) is hypothesized. Computational modeling of Drd3's homologue, Drd2, has shed some light on the putative role of palmitoylation as a reversible switch for dopaminergic receptor signaling. Drd3 is presumed to be palmitoylated, based on sequence homology with Drd2, but the functional attributes afforded by Drd3 palmitoylation have not been studied. Since these receptors are major targets of antipsychotic and anti-Parkinsonian drugs, a better characterization of Drd3 signaling and posttranslational modifications, like palmitoylation, may improve the prospects for drug development. Using molecular dynamics simulations, we evaluated in silico how Drd3 palmitoylation could elicit significant remodeling of the C-terminal cytoplasmic domain to expose docking sites for signaling proteins. We tested this model in cellulo by using the interaction of Drd3 with the G-alpha interacting protein (GAIP) C terminus 1 (GIPC1) as a template. From a series of biochemical studies, live imaging, and analyses of mutant proteins, we propose that Drd3 palmitoylation acts as a molecular switch for Drd3-biased signaling via a GIPC1-dependent route, which is likely to affect the mode of action of antipsychotic drugs. Fondation pour la recherche medicale; French ministry of research; Fondation de France Fondation pour la recherche medicale provided funding to Pierre Sokoloff and Freddy Jeanneteau. French ministry of research provided funding to Freddy Jeanneteau. Fondation de France provided funding to Margarita Arango-Lievano and Freddy Jeanneteau.

The brain evolved cellular mechanisms for adapting synaptic function to energy supply. This is particularly evident when homeostasis is challenged by stress. Signaling loops between the mitochondria and synapses scale neuronal connectivity with bioenergetics capacity. A biphasic “inverted U shape” response to the stress hormone glucocorticoids is demonstrated in mitochondria and at synapses, modulating neural plasticity and physiological responses. Low dose enhances neurotransmission, synaptic growth, mitochondrial functions, learning, and memory whereas chronic, higher doses produce inhibition of these functions. The range of physiological effects by stress and glucocorticoid depends on the dose, duration, and context at exposure. These criteria are met by neuronal activity and the circadian, stress-sensitive and ultradian, stress-insensitive modes of glucocorticoid secretion. A major hallmark of stress-related neuropsychiatric disorders is the disrupted glucocorticoid rhythms and tissue resistance to signaling with the glucocorticoid receptor (GR). GR resistance could result from the loss of context-dependent glucocorticoid signaling mediated by the downregulation of the activity-dependent neurotrophin BDNF. The coincidence of BDNF and GR signaling changes glucocorticoid signaling output with consequences on mitochondrial respiration efficiency, synaptic plasticity, and adaptive trajectories.

Cognitive impairments are common in depression and involve dysfunctional serotonin neurotransmission. The 5-HT1B receptor (5-HT(1B)R) regulates serotonin transmission, via presynaptic receptors, but can also affect transmitter release at heterosynaptic sites. This study aimed at investigating the roles of the 5-HT(1B)R, and its adapter protein p11, in emotional memory and object recognition memory processes by the use of p11 knockout (p11KO) mice, a genetic model for aspects of depression-related states. 5-HT(1B)R agonist treatment induced an impairing effect on emotional memory in wild type (WT) mice. In comparison, p11KO mice displayed reduced long-term emotional memory performance. Unexpectedly, 5-HT(1B)R agonist stimulation enhanced memory in p11KO mice, and this atypical switch was reversed after hippocampal adeno-associated virus mediated gene transfer of p11. Notably, 5-HT(1B)R stimulation increased glutamatergic neurotransmission in the hippocampus in p11KO mice, but not in WT mice, as measured by both pre- and postsynaptic criteria. Magnetic resonance spectroscopy demonstrated global hippocampal reductions of inhibitory GABA, which may contribute to the memory enhancement and potentiation of pre- and post-synaptic measures of glutamate transmission by a 5-HT(1B)R agonist in p11KO mice. It is concluded that the level of hippocampal p11 determines the directionality of 5-HT(1B)R action on emotional memory processing and modulates hippocampal functionality. These results emphasize the importance of using relevant disease models when evaluating the role of serotonin neurotransmission in cognitive deficits related to psychiatric disorders.

A large number of studies have demonstrated that the nucleus accumbens (NAC) is a critical site in the neuronal circuits controlling reward responses, motivation, and mood, but the neuronal cell type(s) underlying these processes are not yet known. Identification of the neuronal cell types that regulate depression-like states will guide us in understanding the biological basis of mood and its regulation by diseases like major depressive disorder. Taking advantage of recent findings demonstrating that the serotonin receptor chaperone, p11, is an important molecular regulator of depression-like states, here we identify cholinergic interneurons (CINs) as a primary site of action for p11 in the NAC. Depression-like behavior is observed in mice after decrease of p11 levels in NAC CINs. This phenotype is recapitulated by silencing neuronal transmission in these cells, demonstrating that accumbal cholinergic neuronal activity regulates depression-like behaviors and suggesting that accumbal CIN activity is crucial for the regulation of mood and motivation.

Neurotrophins and glucocorticoids are robust synaptic modifiers, and deregulation of their activities is a risk factor for developing stress-related disorders. Low levels of brain-derived neurotrophic factor (BDNF) increase the desensitization of glucocorticoid receptors (GR) and vulnerability to stress, whereas higher levels of BDNF facilitate GR-mediated signaling and the response to antidepressants. However, the molecular mechanism underlying neurotrophic-priming of GR function is poorly understood. Here we provide evidence that activation of a TrkB-MAPK pathway, when paired with the deactivation of a GR-protein phosphatase 5 pathway, resulted in sustained GR phosphorylation at BDNF-sensitive sites that is essential for the transcription of neuronal plasticity genes. Genetic strategies that disrupted GR phosphorylation or TrkB signaling in vivo impaired the neuroplasticity to chronic stress and the effects of the antidepressant fluoxetine. Our findings reveal that the coordinated actions of BDNF and glucocorticoids promote neuronal plasticity and that disruption in either pathway could set the stage for the development of stress-induced psychiatric diseases.

Well-defined as signaling hormones for the programming of cell type-specific and context-dependent gene expression signatures, glucocorticoids control experience-driven allostasis. One unifying model is that glucocorticoids help maintaining the integrity and plasticity of cellular networks in changing environments through the mobilization of cellular energy stores, profiling of gene expression, and changes in the electrical and morphological properties of cells. The nucleus is their primary site of action, yet recent discoveries point to additional gene transcription-independent functions at the plasma membrane of neuronal synapses. Glucocorticoids are secreted factors that reflect intrinsically the changes coming from the external world, temporally and regionally, during development and adulthood. In this review, we will enumerate the properties and signaling attributes of glucocorticoids and their receptors that characterize them as allostatic modulators. The molecular mechanisms used to support their role at the synapse will be highlighted.

The comorbidity of depression and cocaine addiction suggests shared mechanisms and anatomical pathways. Specifically, the limbic structures, such as the nucleus accumbens (NAc), play a crucial role in both disorders. P11 (S100A10) is a promising target for manipulating depression and addiction in mice. We summarized the recent genetic and viral strategies used to determine how the titration of p11 levels within the NAc affects hedonic behavior and cocaine reward learning in mice. In particular, p11 in the ChAT+ cells or DRD1+ MSN of the NAc, controls depressive-like behavior or cocaine reward, respectively. Treatments to counter maladaptation of p11 levels in the NAc could provide novel therapeutic opportunities for depression and cocaine addiction in humans.

Introduction: Neuro-vascular rearrangement occurs in brain disorders, including epilepsy. Platelet-derived growth factor receptor beta (PDGFRβ) is used as a marker of perivascular pericytes. Whether PDGFRβ + cell reorganization occurs in regions of neuro-vascular dysplasia associated with seizures is unknown. Methods : We used brain specimens derived from epileptic subjects affected by intractable seizures associated with focal cortical dysplasia (FCD) or temporal lobe epilepsy with hippocampal sclerosis (TLE-HS). Tissues from cryptogenic epilepsy, non-sclerotic hippocampi or peritumoral were used for comparison. An in vivo rat model of neuro-vascular dysplasia was obtained by pre-natal exposure to methyl-axozy methanoic acid (MAM). Status epilepticus (SE) was induced in adult MAM rats by intraperitoneal pilocarpine. MAM tissues were also used to establish organotypic hippocampal cultures (OHC) to further assess pericytes positioning at the dysplastic microvasculature. PDGFRβ and its colocalization with RECA-1 or CD34 were used to segregate perivascular pericytes. PDGFRβ and NG2 or IBA1 colocalization were performed. Rat cortices and hippocampi were used for PDGFRβ western blot analysis. Results: Human FCD displayed the highest perivascular PDGFRβ immunoreactivity, indicating pericytes, and presence of ramified PDGFRβ + cells in the parenchyma and proximal to microvessels. Tissues deriving from human cryptogenic epilepsy displayed a similar pattern of immunoreactivity, although to a lesser extent compared to FCD. In TLE-HS, CD34 vascular proliferation was paralleled by increased perivascular PDGFRβ + pericytes, as compared to non-HS. Parenchymal PDGFRβ immunoreactivity co-localized with NG2 but was distinct from IBA1 + microglia. In MAM rats, we found pericyte-vascular changes in regions characterized by neuronal heterotopias. PDGFRβ immunoreactivity was differentially distributed in the heterotopic and adjacent normal CA1 region. The use of MAM OHC revealed microvascular-pericyte dysplasia at the capillary tree lining the dentate gyrus (DG) molecular layer as compared to control OHC. Severe SE induced PDGFRβ + immunoreactivity mostly in the CA1 region of MAM rats. Conclusion: Our descriptive study points to microvascular-pericyte changes in the epileptic pathology. The possible link between PDGFRβ + cells, neuro-vascular dysplasia and remodeling during seizures is discussed.

Well-defined as signaling hormones for the programming of cell type-specific and context-dependent gene expression signatures, glucocorticoids control experience-driven allostasis. One unifying model is that glucocorticoids help maintaining the integrity and plasticity of cellular networks in changing environments through the mobilization of cellular energy stores, profiling of gene expression, and changes in the electrical and morphological properties of cells. The nucleus is their primary site of action, yet recent discoveries point to additional gene transcription-independent functions at the plasma membrane of neuronal synapses. Glucocorticoids are secreted factors that reflect intrinsically the changes coming from the external world, temporally and regionally, during development and adulthood. In this review, we will enumerate the properties and signaling attributes of glucocorticoids and their receptors that characterize them as allostatic modulators. The molecular mechanisms used to support their role at the synapse will be highlighted.

Background The high rate of comorbidity between depression and cocaine addiction suggests shared molecular mechanisms and anatomical pathways. Limbic structures, such as the nucleus accumbens (NAc), play a crucial role in both disorders, yet how different cell types within these structures contribute to the pathogenesis remains elusive. Downregulation of p11 (S100A10), specifically in the NAc, elicits depressive-like behaviors in mice, but its role in drug addiction is unknown. Methods We combined mouse genetics and viral strategies to determine how the titration of p11 levels within the entire NAc affects the rewarding actions of cocaine on behavior (six to eight mice per group) and molecular correlates (three experiments, five to eight mice per group). Finally, the manipulation of p11 expression in distinct NAc dopaminoceptive neuronal subsets distinguished cell-type specific effects of p11 on cocaine reward (five to eight mice per group). Results We demonstrated that p11 knockout mice have enhanced cocaine conditioned place preference, which is reproduced by the focal downregulation of p11 in the NAc of wild-type mice. In wild-type mice, cocaine reduced p11 expression in the NAc, while p11 overexpression exclusively in the NAc reduced cocaine conditioned place preference. Finally, we identified dopamine receptor-1 expressing medium spiny neurons as key mediators of the effects of p11 on cocaine reward. Conclusions Our data provide evidence that disruption of p11 homeostasis in the NAc, particularly in dopamine receptor-1 expressing medium spiny neurons, may underlie pathophysiological mechanisms of cocaine rewarding action. Treatments to counter maladaptation of p11 levels may provide novel therapeutic opportunities for cocaine addiction.

Despite much progress in the study and treatment of depression, the mechanisms underlying this debilitating disease are still unclear. Altered activity of several major neurotransmitters in the brain including serotonin is involved, but pinpointing the parts of the brain affected in depression has proved challenging. Alexander and colleagues now implicate a brain region called the nucleus accumbens and a protein called p11 expressed in this region as important mediators of depression in humans and mice. The authors were alerted to the potential importance of p11 in depression because mice that lack this protein show depressive-like behavior. This protein is involved in the activation of two receptors for serotonin, 5-HT1B and 5-HT4. Alexander et al . decided to down-regulate expression of p11 specifically in the nucleus accumbens by injecting a viral vector containing a small interfering RNA against p11 directly into this brain region in healthy mice. They then tested the treated mice to see if they exhibited depressive-like behaviors in response to two stress tests (suspension by the tail and swimming in a water tank). In both tests, treated mice showed greater immobility compared with control animals, a sign of depressive-like behavior. To show that these depressive symptoms were indeed caused by loss of p11 in the nucleus accumbens, the investigators overexpressed p11 in the nucleus accumbens of mice that completely lacked this protein. They demonstrated restoration of normal immobility times on the two stress tests and an increased desire to sip sucrose solution (a treat that rodents normally enjoy but depressed animals do not). They also showed increased activity of 5-HT1B serotonin receptors expressed by striatal neurons in the nucleus accumbens of mice overexpressing p11. But do these results have any relevance to depression in humans? Alexander and colleagues tackled this question by comparing postmortem nucleus accumbens brain tissue from individuals with and without depression at the time of death. They discovered that expression of p11 was much lower in the nucleus accumbens of depressed individuals compared with healthy persons. These new findings pinpoint the nucleus accumbens and the p11 protein as important mediators of depression and provide new therapeutic targets for drug development.

It has been postulated that brain tumor stem cells (TSCs) may be the population of cells responsible for the maintenance and recurrence of glioblastoma multiforme (GBM). The purpose of this study was to optimize a reproducible protocol for generating TSCs for their subsequent transfection or transduction. Patient GBMs were enzymatically and mechanically dissociated and tumor spheres were resuspended in appropriate media and analyzed to ensure they met stem cell criteria. These cells were then transfected with a plasmid or transduced with a viral vector to introduce a previously absent gene and then allowed to form tumor spheres. Tumor spheres were generated from patient GBMs without contamination. These cells met stringent criteria as stem cells, including multipotentiality and self-renewal. High efficiency transfection and transduction of tumor spheres was possible, even at the core of the sphere. This allowed for the introduction of new genes to the TSCs, as evidenced by fluorescent microscopy and Western blot analysis. This study is a guide to optimize the generation of patient derived GBM tumor spheres without RBC and dead cell contamination. GBM TSCs within tumor spheres can easily be transfected with plasmids or transduced with a virus. This is important from a therapeutic perspective if gene replacement is to be successful in replacing genes lost in GBM progression or to knock down or silence genes that are over-expressed in malignant brain tumors.

International audience; Neurotrophins are synthetized as precursors (proneurotrophins) with a N-terminal prodomain and a C-terminal mature domain. Classically, neurotrophins must be cleaved off their prodomains to be operational. That is to promote neuronal and non-neuronal cell survival, growth and differentiation via rapid signaling routes and long lasting changes in gene transcription. This view came with the assumption that the proforms of all neurotrophins are inactive. But since the early 2000s, several laboratories driven by the group of Dr. Barbara L. Hempstead revealed that the proforms are signaling molecules as well. Proneurotrophins can be secreted and bind specifically and with high affinity to the p75 neurotrophin receptor (p75 NTR) as receptor. Recent studies on Brain Derived Neurotrophic Factor (BDNF) demonstrated that proBDNF effects via p75 NTR opposes the functions of mature BDNF through its cognate tropomyosin related kinase B (TrkB) receptor. These antagonistic effects include synaptic plasticity (depression versus potentiation), dendritic spine maintenance (elimination versus growth) and cell fate (death versus survival). In this chapter we will review proBDNF intracellular and extracellular processing, transport, signaling mechanisms, as well as its biological function in health and disease. We will focus on the effect of a common human polymorphism in the BDNF gene inducing a Val66Met substitution that causes structural remodeling of the prodomain promoting a gain of function of this peptide independently of mature BDNF. Given their features, neurotrophins have been implicated in numerous neurodegenerative diseases and psychiatric disorders in which the Met66 allele human carriers are more vulnerable than the Val66 carriers.