New strategies in the modulation of fatty acid oxidation as a treatment for obesity

Strategies that enhance fat degradation or reduce caloricfood intake could be considered therapeutic interventions to reduce notonly obesity, but also its associated disorders. The enzyme carnitinepalmitoyltransferase 1 (CPT1) is the critical rate-determining regulatorof fatty acid oxidation (FAO) and might play a key role in increasingenergy expenditure and controlling food intake. Our group has shownthat mice overexpressing CPT1 in liver are protected from weight gain,the development of obesity and insulin resistance. Regarding foodintake control, we observed that the pharmacological inhibition ofCPT1 in rat hypothalamus decreased food intake and body weight.This suggests that modulation of CPT1 activity and the oxidation offatty acids in various tissues can be crucial for the potential treatmentof obesity and associated pathologies.

LIGHT/HVEM/LTβR interaction as a target for the modulation of the allogeneic immune response in transplantation.

The exchange of information during interactions of T cells with dendritic cells, B cells or other T cells regulates the course of T, B and DC-cell activation and their differentiation into effector cells. The tumor necrosis factor superfamily member LIGHT (homologous to lymphotoxin, exhibits inducible expression and competes with HSV glycoprotein D for binding to herpesvirus entry mediator, a receptor expressed on T lymphocytes) is transiently expressed upon T cell activation and modulates CD8 T cell-mediated alloreactive responses upon herpes virus entry mediator (HVEM) and lymphotoxin β receptor (LTβR) engagement. LIGHT-deficient mice, or WT mice treated with LIGHT-targeting decoy receptors HVEM-Ig, LTβR-Ig or sDcR3-Ig, exhibit prolonged graft survival compared to untreated controls, suggesting that LIGHT modulates the course and severity of graft rejection. Therefore, targeting the interaction of LIGHT with HVEM and/or LTβR using recombinant soluble decoy receptors or monoclonal antibodies represent an innovative therapeutic strategy for the prevention and treatment of allograft rejection and for the promotion of donor-specific tolerance.

Silencing of both beta-TrCP1 and HOS (beta-TrCP2) is required to suppress human immunodeficiency virus type 1 Vpu-mediated CD4 down-modulation.

The human immunodeficiency virus type 1 (HIV-1) Vpu protein interacts with CD4 within the endoplasmic reticula of infected cells and targets CD4 for degradation through interaction with beta-TrCP1. Mammals possess a homologue of beta-TrCP1, HOS, which is also named beta-TrCP2. We show by coimmunoprecipitation experiments that beta-TrCP2 binds Vpu and is able to induce CD4 down-modulation as efficiently as beta-TrCP1. In two different cell lines, HeLa CD4+ and Jurkat, Vpu-mediated CD4 down-modulation could not be reversed through the individual silencing of endogenous beta-TrCP1 or beta-TrCP2 but instead required the two genes to be silenced simultaneously.

Local Ca(2+) detection and modulation of synaptic release by astrocytes.

Astrocytes communicate with synapses by means of intracellular calcium ([Ca(2+)](i)) elevations, but local calcium dynamics in astrocytic processes have never been thoroughly investigated. By taking advantage of high-resolution two-photon microscopy, we identify the characteristics of local astrocyte calcium activity in the adult mouse hippocampus. Astrocytic processes showed intense activity, triggered by physiological transmission at neighboring synapses. They encoded synchronous synaptic events generated by sparse action potentials into robust regional (∼12 μm) [Ca(2+)](i) elevations. Unexpectedly, they also sensed spontaneous synaptic events, producing highly confined (∼4 μm), fast (millisecond-scale) miniature Ca(2+) responses. This Ca(2+) activity in astrocytic processes is generated through GTP- and inositol-1,4,5-trisphosphate-dependent signaling and is relevant for basal synaptic function. Thus, buffering astrocyte [Ca(2+)](i) or blocking a receptor mediating local astrocyte Ca(2+) signals decreased synaptic transmission reliability in minimal stimulation experiments. These data provide direct evidence that astrocytes are integrated in local synaptic functioning in adult brain.

Neuronal expression of the ubiquitin ligase Nedd4-2 in rat dorsal root ganglia: modulation in the SNI model of neuropathic pain

La douleur neuropathique est une forme de douleur chronique apparaissant suite à des lésions du système nerveux somato-sensoriel. Caractérisée par une plasticité neuronale inadapté, elle est très souvent intense, invalidante, associe des symptômes comme l'allodynie ou l' hyperalgésie et reste difficile à traiter avec les agents thérapeutiques actuels. Le thème de mon travail de thèse se concentre sur des mécanismes moléculaires de modulation des canaux sodiques voltage-dépendants suite à une lésion du nerf périphérique. Dans l'article présenté en annexe, j'ai focalisé mon travail sur une protéine, Nedd4-2, qui est une ligase ubiquitine. Elle a pour rôle de réguler et d'internaliser dans la cellule des protéines membranaires dont les canaux sodiques. Suite aux lésions du système nerveux périphérique, il existe une hyperexcitabilité neuronale engendrée notamment par un surplus et une dysrégulation des canaux sodiques à la membrane cellulaire. Dans 1 'hypothèse que l'ubiquitine ligase Nedd4-2 soit présente dans les neurones sensitifs primaires et ait un rôle dans la régulation des canaux sodiques, nous avons identifié cette protéine dans les neurones nociceptifs primaires du rat. En utilisant des techniques de Western Blot et d'immunohistochimie, j'ai trouvé que Nedd4-2 est présente dans presque 50% des neurones du ganglion spinal et ces neurones sont principalement des neurones nociceptifs. Dans un modèle expérimental de douleur neuropathique (SN I, pour spared nerve injury), Nedd4-2 se retrouve significativement diminuée dans le tissu du ganglion spinal. J'ai également investigué 1' expression de 2 isoformes des canaux sodiques connues pour leur implication dans la douleur, Navl.7 et Navl.8, et ces 2 isoformes se retrouvent dans les mêmes neurones que Nedd4-2. La caractérisation détaillée est décrite dans le manuscrit: «Neuronal expression of the ubiquitin ligase Nedd4-2 in rat dorsal root ganglia: modulation in the SNI model of neuropathic pain; Cachemaille M, Laedermann CJ, Pertin M, Abriel H, Gasselin RD, Decosterd 1.» Les résultats obtenus indiquent que Nedd4-2, en étant downrégulé après une lésion nerveuse, pourrait ainsi contribuer à une augmentation des canaux sodiques fonctionnels à la membrane. Ainsi Nedd4-2 pourrait être proposée comme cible thérapeutique de manière alternative aux bloqueurs de canaux sodiques. Ce travail a permis l'initiation d'autres expériences. J'ai contribué activement à la construction de vecteurs viraux type adéno-associé recombinant (rAA V2/6) et surexprimé la protéine in vivo dans les ganglions spinaux. Cette partie de mon travail se trouve intégrée dans d'autres travaux de mon laboratoire d'accueil qui a pu démontrer les effets fonctionnels de cette approche sur les courants sodiques enregistrés par électrophysiologie et une diminution de la douleur neuropathique chez la souris. - Abstract-Neuronal hyperexcitability following peripheral nerve lesions may stem from altered activity of voltagegated sodium channels (VGSCs), which gives rise toallodynia or hyperalgesia. In vitro, the ubiquitin ligase Nedd4-2 is a negative regulator of VGSC a-subunits (Nav), in particular Nav1.7, a key actor in nociceptor excitability. We therefore studied Nedd4-2 in rat nociceptors, its co-expression with Nav1.7 and Nav1.8, and its regulation in pathology. Adult rats were submitted to the spared nerve injury (SNI) model of neuropathic pain or injected with complete Freund's adjuvant (CFA), a model of inflammatory pain. L4 dorsal root ganglia (DRG) were analyzed in shamoperated animals, seven days after SNI and 48 h after CFA with immunofluorescence and Western blot. We observed Nedd4-2 expression in almost 50% of DRG neurons, mostly small and medium-sized. A preponderant localization is found in the non-peptidergic sub-population. Additionally, 55.7± 2.7% and 55.0 ±3.6% of Nedd4-2-positive cells are co-labeled with Nav1.7 and Nav1.8 respectively. SNI significantly decreases the proportion of Nedd4-2-positive neurons from 45.9± 1.9% to 33.5± 0.7% (p < 0.01) and the total Nedd4-2 protein to 44%± 0.13% of its basal level (p <0.01, n = 4 animals in each group, mean± SEM). In contrast, no change in Nedd4-2 was found after peripheral inflammation induced by CFA. These results indicate that Nedd4-2 is present in nociceptive neurons, is downregulated after peripheral nerve injury, and might therefore contribute to the dysregulation of Navs involved in the hyperexcitability associated with peripheral nerve injuries.

New strategies in the modulation of fatty acid oxidation as a treatment for obesity

Strategies that enhance fat degradation or reduce caloricfood intake could be considered therapeutic interventions to reduce notonly obesity, but also its associated disorders. The enzyme carnitinepalmitoyltransferase 1 (CPT1) is the critical rate-determining regulatorof fatty acid oxidation (FAO) and might play a key role in increasingenergy expenditure and controlling food intake. Our group has shownthat mice overexpressing CPT1 in liver are protected from weight gain,the development of obesity and insulin resistance. Regarding foodintake control, we observed that the pharmacological inhibition ofCPT1 in rat hypothalamus decreased food intake and body weight.This suggests that modulation of CPT1 activity and the oxidation offatty acids in various tissues can be crucial for the potential treatmentof obesity and associated pathologies.

Stimulus-induced rhythmic, periodic or ictal discharges (SIRPIDs) in comatose survivors of cardiac arrest: Characteristics and prognostic value.

OBJECTIVES: To analyze the prevalence of stimulus-induced rhythmic, periodic or ictal discharges (SIRPIDs) in patients with coma after cardiac arrest (CA) and therapeutic hypothermia (TH) and to examine their potential association with outcome. METHODS: We studied our prospective cohort of adult survivors of CA treated with TH, assessing SIRPIDs occurrence and their association with 3-month outcome. Only univariated analyses were performed. RESULTS: 105 patients with coma after CA who underwent electroencephalogram (EEG) during TH and normothermia (NT) were studied. Fifty-nine patients (56%) survived, and 48 (46%) had good neurological recovery. The prevalence of SIRPIDs was 13.3% (14/105 patients), of whom 6 occurred during TH (all died), and 8 in NT (3 survived, 1 with good neurological outcome); none had SIRPIDs at both time-points. SIRPIDs were associated with discontinuous or non-reactive EEG background and were a robustly related to poor neurological outcome (p<0.001). CONCLUSION: This small series provides preliminary univariate evidence that in patients with coma after CA, SIRPIDs are associated with poor outcome, particularly when occurring during in therapeutic hypothermia. However, survival with good neurological recovery may be observed when SIRPIDs arise in the post-rewarming normothermic phase. SIGNIFICANCE: This study provides clinicians with new information regarding the SIRPIDs prognostic role in patients with coma after cardiac arrest.

Extrasynaptic neurotransmission in the modulation of brain function. Focus on the striatal neuronal glial networks

Extrasynaptic neurotransmission is an important short distance form of volume transmission (VT) and describes the extracellular diffusion of transmitters and modulators after synaptic spillover or extrasynaptic release in the local circuit regions binding to and activating mainly extrasynaptic neuronal and glial receptors in the neuroglial networks of the brain. Receptor-receptor interactions in G protein-coupled receptor (GPCR) heteromers play a major role, on dendritic spines and nerve terminals including glutamate synapses, in the integrative processes of the extrasynaptic signaling. Heteromeric complexes between GPCR and ion-channel receptors play a special role in the integration of the synaptic and extrasynaptic signals. Changes in extracellular concentrations of the classical synaptic neurotransmitters glutamate and GABA found with microdialysis is likely an expression of the activity of the neuron-astrocyte unit of the brain and can be used as an index of VT-mediated actions of these two neurotransmitters in the brain. Thus, the activity of neurons may be functionally linked to the activity of astrocytes, which may release glutamate and GABA to the extracellular space where extrasynaptic glutamate and GABA receptors do exist. Wiring transmission (WT) and VT are fundamental properties of all neurons of the CNS but the balance between WT and VT varies from one nerve cell population to the other. The focus is on the striatal cellular networks, and the WT and VT and their integration via receptor heteromers are described in the GABA projection neurons, the glutamate, dopamine, 5-hydroxytryptamine (5-HT) and histamine striatal afferents, the cholinergic interneurons, and different types of GABA interneurons. In addition, the role in these networks of VT signaling of the energy-dependent modulator adenosine and of endocannabinoids mainly formed in the striatal projection neurons will be underlined to understand the communication in the striatal cellular networks

Families of periodic orbits for the spatial isosceles 3-body problem

We study the families of periodic orbits of the spatial isosceles 3-body problem (for small enough values of the mass lying on the symmetry axis) coming via the analytic continuation method from periodic orbits of the circular Sitnikov problem. Using the first integral of the angular momentum, we reduce the dimension of the phase space of the problem by two units. Since periodic orbits of the reduced isosceles problem generate invariant two-dimensional tori of the nonreduced problem, the analytic continuation of periodic orbits of the (reduced) circular Sitnikov problem at this level becomes the continuation of invariant two-dimensional tori from the circular Sitnikov problem to the nonreduced isosceles problem, each one filled with periodic or quasi-periodic orbits. These tori are not KAM tori but just isotropic, since we are dealing with a three-degrees-of-freedom system. The continuation of periodic orbits is done in two different ways, the first going directly from the reduced circular Sitnikov problem to the reduced isosceles problem, and the second one using two steps: first we continue the periodic orbits from the reduced circular Sitnikov problem to the reduced elliptic Sitnikov problem, and then we continue those periodic orbits of the reduced elliptic Sitnikov problem to the reduced isosceles problem. The continuation in one or two steps produces different results. This work is merely analytic and uses the variational equations in order to apply Poincar´e’s continuation method.

Infinitely many periodic orbits for the rhomboidal five-body problem

We prove the existence of infinitely many symmetric periodic orbits for a regularized rhomboidal five-body problem with four small masses placed at the vertices of a rhombus centered in the fifth mass. The main tool for proving the existence of such periodic orbits is the analytic continuation method of Poincaré together with the symmetries of the problem. © 2006 American Institute of Physics.

Generation of symmetric periodic orbits by a heteroclinic loop formed by two singular points and their invariant manifolds of dimension 1 and 2 in R3

In this paper we will find a continuous of periodic orbits passing near infinity for a class of polynomial vector fields in R3. We consider polynomial vector fields that are invariant under a symmetry with respect to a plane and that possess a “generalized heteroclinic loop” formed by two singular points e+ and e− at infinity and their invariant manifolds � and . � is an invariant manifold of dimension 1 formed by an orbit going from e− to e+, � is contained in R3 and is transversal to . is an invariant manifold of dimension 2 at infinity. In fact, is the 2–dimensional sphere at infinity in the Poincar´e compactification minus the singular points e+ and e−. The main tool for proving the existence of such periodic orbits is the construction of a Poincar´e map along the generalized heteroclinic loop together with the symmetry with respect to .

Symmetric periodic orbits near heteroclinic loops at infinity for a class of polynomial vector fields

For polynomial vector fields in R3, in general, it is very difficult to detect the existence of an open set of periodic orbits in their phase portraits. Here, we characterize a class of polynomial vector fields of arbitrary even degree having an open set of periodic orbits. The main two tools for proving this result are, first, the existence in the phase portrait of a symmetry with respect to a plane and, second, the existence of two symmetric heteroclinic loops.

Symmetric periodic orbits near a heteroclinic loop in R3 formed by two singular points, a semistable periodic orbit and their invariant manifolds

In this paper we consider C1 vector fields X in R3 having a “generalized heteroclinic loop” L which is topologically homeomorphic to the union of a 2–dimensional sphere S2 and a diameter connecting the north with the south pole. The north pole is an attractor on S2 and a repeller on . The equator of the sphere is a periodic orbit unstable in the north hemisphere and stable in the south one. The full space is topologically homeomorphic to the closed ball having as boundary the sphere S2. We also assume that the flow of X is invariant under a topological straight line symmetry on the equator plane of the ball. For each n ∈ N, by means of a convenient Poincar´e map, we prove the existence of infinitely many symmetric periodic orbits of X near L that gives n turns around L in a period. We also exhibit a class of polynomial vector fields of degree 4 in R3 satisfying this dynamics.