Oxidative stress is a feature of many chronic neurodegenerative diseases as well as a contributing factor in acute disorders including stroke. Fork head class of transcription factors (Foxos) play a key role in promoting oxidative stress-induced apoptosis in neurons through the upregulation of a number of pro-apoptotic genes. Here I demonstrate that synaptic NMDA receptor activity not only promotes Foxos nuclear exclusion but also suppresses the expression of Foxo1 in a PI3K-dependent fashion. I also found that Foxo1 is in fact, a Foxo target gene and that it is subject to a feed-forward inhibition by synaptic activity, which is thought to result in longerterm suppression of Foxo downstream gene expression than previously thought. The nuclear factor (erythroid 2-related) factor 2 (Nrf2) is another transcription factor involved in oxidative stress and the key regulator of many genes, whose products form important intrinsic antioxidant systems. In the CNS, artificial activation of Nrf2 in astrocytes has been shown to protect nearby neurons from oxidative insults. However, the extent to which Nrf2 in astrocytes could respond to endogenous signals such as mild oxidative stress is less clear. The data presented herein, demonstrate for the first time that endogenous Nrf2 could be activated by mild oxidative stress and that this activation is restricted to astrocytes. Contrary to the established dogma, I found that mild oxidative stress induces the astrocytic Nrf2 pathway in a manner distinct from the classical Keap1 antagonism employed by prototypical Nrf2 inducers. The mechanism was found to involve direct regulation of Nrf2's transactivation properties. Overall these results advance our knowledge of the molecular mechanism(s) associated with the control of endogenous antioxidant defences by physiological signals.

Les capillaires sanguins sont des éléments essentiels pour le maintien des fonctions du tissu adipeux comme du muscle squelettique. L’obésité induit une raréfaction capillaire intense dans ces tissus, altérant leur microenvironnement et aboutissant en définitif à des dysfonctions métaboliques systémiques. Malgré l’importance de la microcirculation adipeuse, les mécanismes moléculaires régulant la plasticité de ce réseau capillaire, processus appelé angio-adaptation, restent méconnus. L’activité physique exerce de multiples effets bénéfices chez l’obèse, stimulant notamment la croissance vasculaire dans le muscle squelettique. Dans ce tissu, la réponse angio-adaptative au cours de l’obésité et à l’exercice est sous le contrôle de l’axe Mdm2/FoxOs. Ces facteurs régulent la balance entre le signal pro-angiogénique du VEGF-A et anti-angiogénique de la TSP-1, équilibrant ainsi les processus de croissance et régression capillaire. Nous proposons l’existence d’un mécanisme de signalisation similaire, impliqué dans la régulation du processus angio-adaptatif des tissus adipeux et musculaires. Nous avons alors étudié les effets de 7 semaines d’exercice physique volontaire, chez des souris C57Bl/6 rendues obèses par un régime riche en graisses et en sucre, sur la microcirculation et le microenvironnement du tissu adipeux blanc viscéral et sous-cutané, ainsi que du brun interscapulaire. Il a été retrouvé chez les souris obèses un puissant frein angiostatique, exercé par FoxOs et conduisant à une raréfaction capillaire dans les tissus adipeux. Les 7 semaines d’exercice physique ont conduit à l’augmentation de Mdm2, la levée de ce frein et une croissance vasculaire au sein des différents tissus adipeux, associés à l’amélioration du microenvironnement adipocytaire, avec une baisse de l’hypoxie, de la fibrose et une redistribution des cellules inflammatoires. De plus, la stimulation de l’angiogenèse adipeuse chez l’obèse, via l’exercice et l’action pro-angiogénique de Mdm2, a permis d’améliorer l’insulino-sensibilité du tissu adipeux viscéral, d’activer le processus de browning au sein du tissu adipeux sous-cutané et de réduire le whitening du tissu adipeux brun. Il en résulte une amélioration de l’ensemble des paramètres cardiométaboliques systémiques. Ces données démontrent l’efficacité thérapeutique de l’exercice physique dans la lutte contre l’obésité et ses pathologies associées, mais offrent également de nouvelles perspectives de thérapies moléculaires ciblant l’angio-adaptation du tissu adipeux chez l’Homme obèse. / Blood capillaries are essential elements for maintaining adipose tissue and skeletal muscle functions. Obesity induces intense capillary rarefaction in these tissues, altering their microenvironment and ultimately resulting in systemic metabolic dysfunction. Despite the importance of adipose microcirculation, molecular mechanisms regulating adipose capillary network plasticity, a process called angio-adaptation, remains unknown. Physical exercise exerts multiple beneficial effects in obese patient, including skeletal muscle vascular growth stimulation. In this tissue, angio-adaptive response during obesity and exercise is under the control of the Mdm2/FoxOs axis. These factors regulate harmonization between VEGF-A pro-angiogenic signal and TSP-1 anti-angiogenic, thus balancing growth and capillary regression processes. We made the hypothesis of the existence of a similar signaling mechanism, involved in the angio-adaptive process regulation of adipose and muscular tissues. Therefore, we studied the effects of 7 weeks-voluntary physical exercise in C57Bl/6 obese mice induced by a diet rich in fats and sugar, on microcirculation and microenvironment of visceral and subcutaneous white adipose tissue, as well as interscapular brown adipose tissue. Obese mice presented a powerful angiostatic control in all adipose tissues, under FoxOs protein regulation, leading to capillary rarefaction. Physical exercise led to the increase of Mdm2 expression, repressing the angiostatic control in favor of adipose vascular regrowth. This phenomenon was also associated with adipocytes microenvironment improvement, a decrease in hypoxia, fibrosis and redistribution of inflammatory cells. In addition, adipose angiogenesis stimulation in obese mice, through exercise and the Mdm2 pro-angiogenic action, improved visceral adipose tissue insulin sensitivity, activated browning process within subcutaneous adipose tissue and reducing whitening of brown adipose tissue. The overall result is an improvement of all systemic cardiometabolic parameters. These data demonstrate the therapeutic efficacy of physical exercise against obesity and its associated pathologies, but also offer new prospects for molecular therapies targeting the adipose angio-adaptation in obese humans.

Wnt proteins are crucial for development/homeostasis by controlling cell fate including apoptosis (Moon RT et al. 1997). Three humanWnt13 isoforms were identified: the secreted Wnt13A, mitochondrial Wnt13B, and nuclear Wnt13C forms; and nuclear Wnt13 had an increased sensitivity to LPS/TNF-induced apoptosis in primary endothelial cells (EC); both Wnt13B and C mRNA contain two start codons (AUG+1 and +74), but the same protein encoded from AUG+74 by Wnt13C was expressed lower than Wnt13B (Struewing IT et al.2006). We hypothesize that during EC apoptosis, the nuclear Wnt13C expression is regulated translationally; nuclear Wnt13 favors apoptosis through regulating the activity/expression of apoptosis-related factors; Wnt13 isoforms may have differential effects on EC apoptosis and apoptosis-related factors. 1. The protein levels, but not the mRNA levels of Wnt13C were induced by apoptosis-inducers. And the Myc-tag insertion at the AUG+1 in Wnt13C mRNA inhibited its expression, indicating the RNA sequences/structures are critical. Therefore, nuclear Wnt13C is regulated during apoptosis at translational levels. 2. Nuclear Wnt13 increased caspase-3/7 expression with/without LPS, followed by an increase in LPS-induced caspase-3/7 cleavage; and nuclear Wnt13 upregulated the pro-apoptotic Bcl-2 family member Bim expression, suggesting that nuclear Wnt13 increased caspase activation through upregulating caspase and Bim expression. Wnt13 isoforms increased EC apoptosis with different strengths: nuclear > mitochondrial > secreted forms. 3. Both caspase-3 and Bim are FOXO target genes; and nuclear Wnt13 increased the nuclear localization of FOXOs, suggesting increased FOXO activity. Nuclear Wnt13 also upregulated SOD2, another FOXO target gene related to oxidative stress-resistance. Nuclear Wnt13 did not increase FOXO activity at the SOD2 promoter, but increased the SOD2-intron 2 element luciferase activity upon LPS, where a novel putative FOXO site was found, implying intron 2 may be responsible for enhanced SOD2 transcription by nuclear Wnt13. Altogether, our results pinpoint the interplay between the expression and functions of Wnt13 forms during EC apoptosis, forming a positive cycle further facilitating the apoptotic program completion, which is important for EC homeostasis.