Role of NOX enzymes in phagocyte response and signaling upon Chlamydia infection

Les membres de l'ordre des Chlamydiales peuvent infecter un choix étendu d'animaux, insectes, et protistes. Comme toutes bactéries intracellulaires obligatoires, les Chlamydiales ont besoin d'une cellule hôte pour se répliquer. Chaque fois qu'une cellule est infectée une lutte commence entre les mécanismes de défense de la cellule et l'arsenal de facteurs de virulence de la bactérie. Dans cette thèse nous nous sommes intéressés à déterminer le rôle de deux mécanismes de l'immunité innée de l'hôte. En premier, nous avons étudié les NADPH oxidases, une source de molécules superoxydantes (MSO). Leur rôle dans la restriction de la réplication de Waddlia chondrophila et Estrella iausannensis a été étudié dans l'organisme modèle Dictyostelium discoideum et les macrophages humains. Différentes protéines Nox étaient nécessaires pour contrôler la réplication de W. chondrophila ou E. Iausannensis. De plus, nous avons déterminé que parmi les Chlamydiales, cinq espèces possédaient une catalase. Cette enzyme peut dégrader l'eau oxygénée, une MSO. L'activité de la catalase a été démontrée in vitro et dans les corps élémentaires. Avant de pouvoir étudier le rôle de NOX2 dans des macrophages infectés avec E. Iausannensis, nous avons dû établir la capacité de la bactérie à se répliquer clans les macrophages avec son trafic intracellulaire. Le deuxième mécanisme d'immunité innée que nous avons étudié est l'autophagie. Dans les cellules infectées l'autophagie permet de digérer les bactéries envahissantes. Deux protéines de la voie autophagique (Atg1 et Atg8) jouent un rôle dans la restriction de la croissance de W. chondrophila dans D. discoideum. D'avantage d'études sur l'immunité innée et les bactéries apparentés aux Chlamydia sont indispensables, car les réponses paraissent être spécifiques pour chaque espèce. - Members of the Chlamydiales order are able to infect a large variety of animals, insects, and protists. These obligate intracellular bacteria require a host cell for replication. Each time a cell is infected a struggle begins between the virulence arsenal of the bacteria and the defense mechanisms activated by the host. Each bacterial species will exhibit a selection of virulence factors that will allow it to overcome the defense of the host in some species, but not others. In this thesis we were interested in dissecting the role of two host innate immunity mechanisms. First we determined the role of NADPH oxidases, a source of reactive oxygen species (ROS), in restricting replication of Waddlia chondrophila and EstreHa lausannensis in the model organism Dictyostelium discoideum and human macrophages. Different Nox proteins were required to restrict growth of W. chondrophila and E. lausannensis. Additionally, we determined that five Chlamydia- related bacterial species encode for catalase, an enzyme that is able to degrade hydrogen peroxide, a ROS. The activity of the catalase was demonstrated in vitro and in elementary bodies. To study the role of NOX2 in macrophages for E. lausannensis we first had to determine the ability of E. lausannensis to grow in macrophages. Besides demonstrating its replication we also determined the intracellular trafficking of E. lausannensis. The second innate immunity mechanism studied was autophagy. Through autophagy bacteria can be targeted to degradation. Atg1 and Atg8, two autophagic proteins appeared restrict W. chondrophila replication in D. discoideum. More studies on innate immunity and Chlamydia-related bacteria are required. It appears that the responses to innate immunity are species specific and it will be difficult to generalize data obtained for W. chondrophila to the Chlamydiales order.

Theory of mind tasks and executive functions: A systematic review of group studies in neurology.

A growing number of studies have been addressing the relationship between theory of mind (TOM) and executive functions (EF) in patients with acquired neurological pathology. In order to provide a global overview on the main findings, we conducted a systematic review on group studies where we aimed to (1) evaluate the patterns of impaired and preserved abilities of both TOM and EF in groups of patients with acquired neurological pathology and (2) investigate the existence of particular relations between different EF domains and TOM tasks. The search was conducted in Pubmed/Medline. A total of 24 articles met the inclusion criteria. We considered for analysis classical clinically accepted TOM tasks (first- and second-order false belief stories, the Faux Pas test, Happe's stories, the Mind in the Eyes task, and Cartoon's tasks) and EF domains (updating, shifting, inhibition, and access). The review suggests that (1) EF and TOM appear tightly associated. However, the few dissociations observed suggest they cannot be reduced to a single function; (2) no executive subprocess could be specifically associated with TOM performances; (3) the first-order false belief task and the Happe's story task seem to be less sensitive to neurological pathologies and less associated to EF. Even though the analysis of the reviewed studies demonstrates a close relationship between TOM and EF in patients with acquired neurological pathology, the nature of this relationship must be further investigated. Studies investigating ecological consequences of TOM and EF deficits, and intervention researches may bring further contributions to this question.

Notch signaling in hematopoiesis and lymphopoiesis: lessons from Drosophila.

The evolutionarily conserved Notch signaling pathway regulates a broad spectrum of cell fate decisions and differentiation processes during fetal and postnatal life. It is involved in embryonic organogenesis as well as in the maintenance of homeostasis of self-renewing systems. In this article, we review the role of Notch signaling in the hematopoietic system with particular emphasis on lymphocyte development and highlight the similarities in Notch function between Drosophila and mammalian differentiation processes. Recent studies indicating that aberrant NOTCH signaling is frequently linked to the induction of T leukemia in humans will also be discussed.

Redundant Notch1 and Notch2 signaling is necessary for IFNγ secretion by T helper 1 cells during infection with Leishmania major.

The protective immune response to intracellular parasites involves in most cases the differentiation of IFNγ-secreting CD4(+) T helper (Th) 1 cells. Notch receptors regulate cell differentiation during development but their implication in the polarization of peripheral CD4(+) T helper 1 cells is not well understood. Of the four Notch receptors, only Notch1 (N1) and Notch2 (N2) are expressed on activated CD4(+) T cells. To investigate the role of Notch in Th1 cell differentiation following parasite infection, mice with T cell-specific gene ablation of N1, N2 or both (N1N2(ΔCD4Cre)) were infected with the protozoan parasite Leishmania major. N1N2(ΔCD4Cre) mice, on the C57BL/6 L. major-resistant genetic background, developed unhealing lesions and uncontrolled parasitemia. Susceptibility correlated with impaired secretion of IFNγ by draining lymph node CD4(+) T cells and increased secretion of the IL-5 and IL-13 Th2 cytokines. Mice with single inactivation of N1 or N2 in their T cells were resistant to infection and developed a protective Th1 immune response, showing that CD4(+) T cell expression of N1 or N2 is redundant in driving Th1 differentiation. Furthermore, we show that Notch signaling is required for the secretion of IFNγ by Th1 cells. This effect is independent of CSL/RBP-Jκ, the major effector of Notch receptors, since L. major-infected mice with a RBP-Jκ deletion in their T cells were able to develop IFNγ-secreting Th1 cells, kill parasites and heal their lesions. Collectively, we demonstrate here a crucial role for RBP-Jκ-independent Notch signaling in the differentiation of a functional Th1 immune response following L. major infection.

The longitudinal association between social functioning and theory of mind in first episode psychosis

Introduction. There is some cross-sectional evidence that theory of mind ability is associated with social functioning in those with psychosis but the direction of this relationship is unknown. This study investigates the longitudinal association between both theory of mind and psychotic symptoms and social functioning outcome in first-episode psychosis. Methods. Fifty-four people with first-episode psychosis were followed up at 6 and 12 months. Random effects regression models were used to estimate the stability of theory of mind over time and the association between baseline theory of mind and psychotic symptoms and social functioning outcome. Results. Neither baseline theory of mind ability (regression coefficients: Hinting test 1.07 95% CI 0.74, 2.88; Visual Cartoon test 2.91 95% CI 7.32, 1.51) nor baseline symptoms (regression coefficients: positive symptoms 0.04 95% CI 1.24, 1.16; selected negative symptoms 0.15 95% CI 2.63, 2.32) were associated with social functioning outcome. There was evidence that theory of mind ability was stable over time, (regression coefficients: Hinting test 5.92 95% CI 6.66, 8.92; Visual Cartoon test score 0.13 95% CI 0.17, 0.44). Conclusions. Neither baseline theory of mind ability nor psychotic symptoms are associated with social functioning outcome. Further longitudinal work is needed to understand the origin of social functioning deficits in psychosis.

The degradation of HFR1, a putative bHLH class transcription factor involved in light signaling, is regulated by phosphorylation and requires COP1.

All developmental transitions throughout the life cycle of a plant are influenced by light. In Arabidopsis, multiple photoreceptors including the UV-A/blue-sensing cryptochromes (cry1-2) and the red/far-red responsive phytochromes (phyA-E) monitor the ambient light conditions. Light-regulated protein stability is a major control point of photomorphogenesis. The ubiquitin E3 ligase COP1 (constitutively photomorphogenic 1) regulates the stability of several light-signaling components. HFR1 (long hypocotyl in far-red light) is a putative transcription factor with a bHLH domain acting downstream of both phyA and the cryptochromes. HFR1 is closely related to PIF1, PIF3, and PIF4 (phytochrome interacting factor 1, 3 and 4), but in contrast to the latter three, there is no evidence for a direct interaction between HFR1 and the phytochromes. Here, we show that the protein abundance of HFR1 is tightly controlled by light. HFR1 is an unstable phosphoprotein, particularly in the dark. The proteasome and COP1 are required in vivo to degrade phosphorylated HFR1. In addition, HFR1 can interact with COP1, consistent with the idea of COP1 directly mediating HFR1 degradation. We identify a domain, conserved among several bHLH class proteins involved in light signaling , as a determinant of HFR1 stability. Our physiological experiments indicate that the control of HFR1 protein abundance is important for a normal de-etiolation response.

Roles of canonical Wnt/TCF-1 signaling for hematopoiesis, lymphocyte development and function

Summary : The canonical Wnt signaling pathway plays key roles in the maintenance of self-renewing tissues, like the gut or the skin. In contrast, the role of this pathway in hematopoiesis remains poorly defined. Wnt ligands transmit signals through ß-catenin which activates gene transcription upon its association with Lymphoid Cell Enhancer/T Cell Factor (LEF/TCF). Currently, v-catenin is the only alternative factor known to transduce canonical Wnt signals. The ß-/γ-catenin bindiná domain in TCF-1 is required to partly rescue thymopoiesis and NK cell development in TCF-1-deficient mice. However, T cell development and hematopoiesis w-as normal in mice deficient of ß-catenin, or of γ-catenin. Surprisingly we found that hematopoiesis and thymopoiesis was also normal in the combined absence of ß- and γ-catenin. Reporter assays showed that double-deficient lymphocytes were still able to transduce canonical wnt signals. These data provided evidence that hematopoietic cells can transduce canonical Wnt signals in the combined absence of ß- and γ-catenin. There exist numerous TCF-1 isoforrns including those that harbor the N-terminal ß-/y-catenin binding domain or that contains a C-terminal CRARF domain whose role in vivo has not been previously tested. We found that the CRARF domain influences lymphocyte development in conjunction with the N-treminal ß-/γ-catenin binding. The presence of the two domains directs thymocytes to the CD8+ T cell lineage whereas NK cell development is abolished. Roles of the canonical Wnt/TCF-1 pathway for lymphocyte function have not been defined. We demonstrate that TCF-1 deficient CDBT T cells mount a normal primary response to viral infection but these T cells fail to expand upon restimulation. The failure of CD8+ T cells to respond to IL-2 during primary infection seems to account for this phenotype. Thus, TCF-1 is essential for programming functional CD8+ T cell memory. Collectively, these data provide significant new insights into the role of Wnt/TCF-1 pathway for lymphocyte development and function and suggest a novel mechanism of Wnt signal transuction in hematopoietic cells. Résumé : La voie de signalisation canonique Wnt joue un rôle prépondérant dans le renouvellement de tissus, comme l'intestin ou la peau. Son rôle dans l'hématopoïèse est quant à lui mal défini. Le ligand Wnt transmet le signal via la ß-catenin qui active la transcription de gènes cibles quand il est associé avec Lymphoid Cell Enhancer,~T Cell Factor (LEF/TCF). Actuellement, la γ-catenin est le seul autre facteur connu pouvant se substituer à la fonction de la ß-catenin. Un variant de TCF-1 contenant le domaine liant ß-/,~-catenin est capable de restaurer le développement des lymphocytes T et NK en l'absence de TCF-1. Cependant la thymopoïèse et l'hématopoïèse sont normales dans les souris déficientes pour la ß-catenin ou la γ-catenin. De façon surprenante, nous avons trouvé que l'hématopoïèse et le développement des lymphocytes sont normaux lors de l'absence combinée de ß-/γ-catenin. De plus, la transduction des signaux de la voie de signalisation Wnt est maintenue dans des lymphocytes déficients pour ß-/γ-catenin. Ces résultats démontrent que les cellules hématopoïétiques peuvent transmettre les signaux de la voie canonique Wnt lors de l'absence combinée de la ß et la γ -catenin. Il existe de nombreuses isofonnes de TCF-1, y compris certaines qui comprennent un domaine qui lie ß-/γ-catenin du côté N-terminus ou qui contiennent un domaine CRARF du côté C-terminus. Nous montrons ici que le domaine CRARF influence le développement des lymphocytes en conjonction avec le domaine liant ß-/γ-catenin. La présence des deux domaines dirige les thymocytes vers la lignée de cellules T CD8, alors que le développement des cellules NK est aboli. Au-delà de sa fonction sur le développement des lymphocytes, le rôle de la soie de signalisation canonique Wnt/TCF-1 lors d'une infection n'a pas été défini. Nous avons montré que les cellules T CD8, déficientes pour TCF-1, développent une réponse primaire normale à une infection virale, mais qu'elles ne s'accumulent pas après restimulation. L'incapacité des cellules TCD8 à répondre à l'IL-2 durant la réponse primaire peut expliquer ce phénotype. Ainsi; TCF-1 est essentiel pour la programmation de cellules T CD8 mémoires fonctionnelles. L'ensemble de ces résultats fournit de nouveaux aperçus du rôle de la voie de signalisation Wnt/TCF-1 pour le développement et la fonction des lymphocytes et suggèrent un nouveau mécanisme de transduction du signal Wnt dans les cellules hématopoïétiques.

Recommandations de pratique clinique dans la schizophrénie: de la théorie à la mise en application = Clinical practice guidelines for the treatment of schizophrenia: from theory to practice

Dans le cadre d'une étude rétrospective au sein d'une unité de réhabilitation, nous avons cherché à examiner le degré de respect de recommandations de pratique clinique (RPC) abordant le traitement pharmacologique au long cours de la schizophrénie, par des médecins qui n'en ont qu'une connaissance indirecte. The Expert Consensus Guideline for the treatment of schizophrenia (ECGTS) a été retenu comme référence sur la base d'une comparaison avec cinq autres RPC principales. Sur un collectif de 20 patients, les recommandations de l'ECGTS sont totalement respectées dans 65 % des cas, partiellement respectées dans 10 % et non respectées dans 25 %, démontrant ainsi que la pratique clinique est clairement perfectible (principalement dans le traitement des symptômes psychotiques et dépressifs). Cependant, le respect des RPC ne garantit pas forcément la résolution de tous les problèmes cliniques rencontrés : 12 patients sur 20 présentent des effets secondaires à l'évaluation clinique et pour huit d'entre eux, les recommandations à ce niveau, sont respectées. Notre étude montre cependant que le choix et l'application d'une RPC ne sont pas simples. Les RPC actuelles donnent peu ou pas d'instruments de mesure, ni de critères précis pour évaluer les problèmes cliniques auxquels elles font référence. L'avenir appartient donc à des RPC qui proposent, outre les recommandations cliniques elles-mêmes, les moyens de leur vérification et de leur application sur le terrain.

The use of the murine model of infection with Leishmania major to reveal the antagonistic effects that IL-4 can exert on T helper cell development and demonstrate that these opposite effects depend upon the nature of the cells targeted for IL-4 signaling.

In contrast to mice from the majority of inbred strains, BALB mice develop aberrant Th2 responses and suffer progressive disease after infection with Leishmania major. These outcomes depend on the production of Interleukin 4, during the first 2 d of infection, by CD4+ T cells that express the Vbeta4-Valpha8 T cell receptors specific for a dominant I-A(d) restricted epitope of the LACK antigen from L. major. In contrast to this well established role of IL-4 in Th2 cell maturation, we have recently shown that, when limited to the initial period of activation of dendritic cells by L. major preceding T cell priming, IL-4 directs DCs to produce IL-12, promotes Th1 cell maturation and resistance to L. major in otherwise susceptible BALB/c mice. Thus, the antagonistic effects that IL-4 can have on Th cell development depend upon the nature of the cells (DCs or primed T cells) targeted for IL-4 signaling.

Diethyldithiocarbamic acid inhibits the octadecanoid signaling pathway for the wound induction of proteinase-inhibitors in tomato leaves

The induction of proteinase inhibitor I synthesis in tomato (Lycopersicon esculentum) leaves in response to wounding is strongly inhibited by diethyldithiocarbamic acid (DIECA). DIECA also inhibits the induction of inhibitor I synthesis by the 18-amino acid polypeptide systemin, polygalacturonic acid (PCA), and linolenic acid, but not by jasmonic acid, suggesting that DIECA interferes with the octadecanoid signaling pathway. DIECA only weakly inhibited tomato lipoxygenase activity, indicating that DIECA action occurred at a step after the conversion of linolenic acid to 13(S)-hydroperoxylinolenic acid (HPOTrE). DIECA was shown to efficiently reduce HPOTrE to 13-hydroxylinolenic acid (HOTrE), which is not a signaling intermediate. Therefore, in vivo, DIECA is likely inhibiting the signaling pathway by shunting HPOTrE to HOTrE, thereby severely reducing the precursor pool leading to cyclization and eventual synthesis of jasmonic acid. Phenidone, an inhibitor of lipoxygenase, inhibited proteinase inhibitor I accumulation in response to wounding, further supporting a role for its substrate, linolenic acid, and its product, HPOTrE, as components of the signal-transduction pathway that induces proteinase inhibitor synthesis in response to wounding, systemin, and PCA.