Les associations potentielles de gènes KIR avec la susceptibilité/résistance au développement de la maladie de Crohn

La famille des gènes KIR « Killer-cell Immunoglobulin-like Receptor » comprend six gènes activateurs, d'autres étant des gènes inhibiteurs. En raison des différences haplotypiques, les humains diffèrent entre eux par le nombre des gènes KIR activateurs hérités. Ils peuvent hériter de zéro à un nombre complet de six de ces gènes. Dans cette étude, nous voulons investiguer si cette variation du nombre de ces gènes KIR activateurs est impliquée avec une association à la maladie de Crohn (MC), qui est une maladie inflammatoire chronique du tractus gastro-intestinal dans laquelle des facteurs génétiques jouent un rôle important. L'approche du" candidate gene" a été utilisée pour génotyper six gènes KIR activateurs des cas et des contrôles dans trois cohortes indépendantes (Montréal, Ottawa et Winnipeg) par PCR en utilisant des amorces spécifiques, l’usage de la régression logistique inconditionnelle nous permet de déterminer la présence de cette association. Notre étude démontre une forte association entre la plupart des gènes et la MC dans les trois cohortes. Après une analyse globale pour toutes les cohortes quatre des gènes démontrent une forte association avec la maladie. Nous avons également étudié l'expression des récepteurs KIR et non-KIR et des différentes intégrines sur les cellules NK du sang périphérique chez les patients atteints de la maladie vis-à-vis des sujets témoins en bonne santé. De plus, nous avons également déterminé l'historique de la dégranulation et le potentiel cytotoxique des cellules NK en utilisant du sang périphérique fraîchement isolé provenant des patients MC et des sujets témoins sains. Nos résultats montrent que les cellules NK des patients atteints de la MC expriment des niveaux plus élevés des KIR activateurs ainsi que d'autres récepteurs activateurs non-KIR. Les cellules NK provenant des patients également expriment des niveaux accrus de différentes « gut-homing » intégrines. De plus, les cellules NK de ces patients ont démontré une dégranulation et un potentiel cytotoxique plus élevé. En générale, cette étude montre que les gènes KIR activateurs confèrent un risque de développer la MC chez les enfants et les adultes et que les cellules NK du sang périphérique chez les patients sont plus actives et plus cytotoxiques comparées aux individus sains. Nos résultats nous offrent de nouvelles perspectives sur l'immuno-pathogenèse de la maladie et pourraient être utiles dans le traitement en développant de nouvelles immunothérapies.The KIR (Killer-cell Immunoglobulin-like Receptor) gene family comprises six activating genes, others being inhibitory ones. Due to the existence of different KIR haplotypes, humans differ from one another in the number of inherited activating KIR genes. They may inherit zero to a full complement of six of these genes. The KIR gene variations have been shown to affect human’s susceptibility to a wide variety of human diseases. In this study, we sought to determine whether variations in the numbers of activating KIR gene in humans bear any associations with Crohn disease (CD), a chronic inflammatory disease of the gastrointestinal tract in which genetic factors have been shown to play an important role. We used the candidate gene approach, whereby we genotyped cases and controls for all six activating KIR genes by PCR using gene-specific primers in three independent cohorts (Montreal, Ottawa and Winnipeg) of Canadian Caucasian CD patients and determined associations using unconditional logistic regression. We observed strong associations between most of the genes and CD in all the three cohorts of the patients. An overall analysis for all the cohorts showed strong associations with four of the genes. We also investigated the expression of KIR and non-KIR receptors and different integrins on peripheral blood NK cells in Crohn disease (CD) patients vis-a-vis healthy control subjects. Furthermore, we also determined recent degranulation history and cytotoxic potential of NK cells using freshly isolated peripheral blood from both CD patients and healthy control subjects. Our results show that NK cells from CD patients expressed higher levels of activating KIR as well as other non-KIR activating receptors. They also showed increased frequencies of the cells expressing these receptors. NK cells from the patients also expressed increased levels of different gut-homing integrin molecules. Furthermore, NK cells from CD patients showed a recent history of increased cytotoxic events and exhibited higher cytotoxicity. Collectively, this study shows that activating KIR genes confer risk for CD in both children and adults and peripheral blood NK cells in CD patients are more activated and more cytotoxic compared with their counterparts from healthy individuals. Our results provide novel insights on the immuno-pathogenesis of the disease and bear implications for devising novel immunotherapies

CELL DAMAGE INDUCED BY LYSOSOMAL IMPAIRMENT: STUDY OF THE ROLE OF PLASMA MEMBRANE SPHINGOLIPIDS

Lysosomes are the principal site of the catabolism of sphingolipids, a class of bioactive lipids mainly associated with the external leaflet of cell plasma membrane. Several lines of evidence support a direct correlation between modifications in sphingolipid pattern and the activation of specific signaling pathways, including apoptosis and autophagy. Loss-of-function mutations in genes coding for lysosomal enzymes involved in sphingolipid catabolism result in severe clinical manifestations called sphingolipidoses. These pathologies belong to the group of Lysosomal Storage Diseases and are characterized by the accumulation of undegraded materials leading to lysosomal impairment and consequent cell damage. Until now, the molecular mechanisms by which the perturbation of lysosomal homeostasis affects cell functionality and viability are unknown. To investigate this issue, I used an artificial in vitro model of lysosomal impairment obtained by loading human fibroblasts with 88 mM sucrose for 14 days. In these experimental conditions, the absence of invertase induces sucrose accumulation into lysosomes. I found that sucrose loaded fibroblasts are characterized by a growth slowdown and by the activation of both apoptosis and autophagy. By RNA-sequencing, approximately a thousand of genes were found to be dysregulated after sucrose loading. In particular, 56 cell cycle-related genes are downregulated, whereas 37 lysosomal-related genes are upregulated. Using biochemical approaches, I found that sucrose loading activates lysosomal biogenesis although sucrose storage inhibits lysosomal functionality. In particular, in sucrose loaded cells lipid catabolism is blocked and complex lipids, such as phospholipids, cholesterol, glycosphingolipids, and gangliosides are accumulated. Moreover, I found that sucrose loading induces the nuclear translocation of the Transcription Factor EB (TFEB), a master-gene regulator of lysosomal function, which in turn promotes the increased fusion between lysosomes and the plasma membrane. This last event leads to higher levels of sphingolipid hydrolases at the cell surface resulting in the alteration of the plasma membrane sphingolipid composition and the consequent ectopic production of pro-apoptotic and pro-autophagic ceramide. Interestingly, in sucrose loaded fibroblasts the blocking of glycosphingolipid hydrolysis at the plasma membrane results in a reduction of autophagy and apoptosis. Similar results were also obtained in response to sphingomyelin accumulation in Niemann-Pick Type A disease (NPA). NPA is a sphingolipidosis caused by acid sphingomyelinase deficiency which leads to sphingomyelin storage. Interestingly, using NPA-derived human fibroblasts loaded with 50 \ub5M exogenous sphingomyelin for 30 days, I found that the lysosomal impairment caused by sphingomyelin accumulation activates the same molecular pathways described in healthy fibroblasts subjected to sucrose loading. A pathogenic role of TFEB has also been suggested by biochemical analysis on brains from Acid Sphingomyelinase Knockout (ASMKO) mice. In fact, ASMKO mouse brains are characterized by TFEB nuclear translocation, increased lysosomal biogenesis, increased glycohydrolytic activities and onset of apoptosis and autophagy. Collectively, these data suggest the existence of a cross-talk among lysosomes and the cell plasma membrane. In this context, the lysosomal impairment caused by the accumulation of uncatabolized substrates leads to an altered composition of plasma membrane sphingolipids resulting in the ectopic production of ceramide which in turn is responsible for the onset of cell damage

Études sur le rôle d’IL-18 dans l’immunopathogénèse du SIDA

Le virus de l’immunodéficience humaine ou VIH est l’agent qui cause le SIDA. Le VIH donne lieu à une dérégulation dans la production de certaines cytokines qui ont un rôle immunologique très important chez les patients infectés. L’IL-18, autrement nommé facteur inducteur d’IFN-γ, est une cytokine pro-inflammatoire qui affecte le système immunitaire de façon importante. Son activité est régulée par l’"IL-18 Binding Protein" (IL-18BP), une autre cytokine qui se lie avec l’IL-18 et inhibe son activité biologique. Des études ultérieures ont montré des niveaux élevés d’Il-18 chez les patients infectés par le VIH par rapport aux personnes saines. Cependant, aucune étude n’a été réalisée concernant la production d’IL-18BP chez ces patients. Due à sa relevance dans la régulation de l’IL-18, nous avons étudié l’effet de l’infection par le VIH sur l’équilibre entre ces deux facteurs et l’impact de cet équilibre sur l’homéostasie des cellules NK. Nous avons mesuré les taux de l’IL-18 et de l’IL-18BP circulantes dans les sérums des patients infectés par le VIH en les comparants avec le même nombre de personnes saines et séronégatives. Nous avons aussi déterminé le nombre total des différents sous-types de cellules NK et analysé l’activité des cellules NK (Natural Killer). Finalement nous avons cherché à déterminer si l’IL-18 pouvait induire l’apoptose des cellules NK en activant l’expression de Fas ligand. Nos résultats nous démontrent que les patients infectés par le VIH ont trois fois plus d’IL-18 que les donneurs sains. Cependant les niveaux d’IL-18BP sont plus bas chez les patients infectés comparés aux donneurs sains. Alors, le ratio IL-18/IL-18BP est augmenté chez les patients infectés, ce qui entraîne une grande quantité d’IL-18 libre et biologiquement active circulante dans leur organisme. Nos études démontrent que chez ces patients, les concentrations d’IL-18 sont en corrélation négative avec l’activité cytotoxique de leurs cellules NK. Nos études in vitro démontrent que le traitement des cellules NK par l’IL-18 induit de façon fratricide leur apoptose en augmentant l’expression de Fas ligand. Finalement, cette production non coordonnée de ces deux facteurs pourrait contribuer à une immunopathologie induite par l’IL-18 en entraînant une apoptose fratricide des cellules NK qui possèdent un rôle important dans la réponse antivirale. Le dérèglement de l’homéostasie des cellules NK pourrait donc contribuer à la pathogenèse induite par le VIH.HIV-1, the causative agent of AIDS, induces a deregulated production of several immunologically important cytokines in the infected persons. One of these cytokines is IL-18: a powerful proinflammatory cytokine that can regulate both innate and adaptive immune responses. In vivo, its activity is tightly regulated by IL-18 Binding Protein (IL-18BP), another cytokine that specifically binds and neutralizes IL-18 with high affinity. Previous studies have shown that IL-18 concentrations are significantly increased in the circulation of HIV-infected AIDS patients compared to those in healthy people. However, it is not yet clear how the increased levels of this cytokine affect the development of AIDS in HIV infected persons. Furthermore, little is known concerning the production of IL-18 antagonist (IL-18BP) in these patients. These issues were addressed in the studies presented in this thesis. We measured levels of IL-18 and IL-18BP in the sera of HIV-infected patients by using commercial ELISA kits and compared them with the values obtained from a similar number of healthy HIV-seronegative persons. We also determined the absolute and total number of different NK cell subsets and NK cell activity in the peripheral blood mononuclear cells (PBMC) of these individuals. Finally we determined the effects of recombinant human IL-18 as well as of IL-18-rich sera from AIDS patients on cytolytic activity and survival of human NK cells. Our results show that sera from HIV- infected patients contain up to 3 fold higher levels of IL-18 compared to the sera from healthy people. However, levels of IL-18BP were lower in the infected individuals compared to the healthy ones. Consequently, IL-18/IL-18BP ratio is increased in the patients resulting in a further increase in the concentrations of biologically active IL-18 in the circulation of these patients. Our results show that the concentrations of IL-18 correlated inversely with NK cell numbers as well as with their cytolytic activity in the infected persons. These results suggested the involvement of IL-18 in the disappearance of NK cells that prompted us to determine the potential cytocidal effects of this cytokine on human NK cells. The results from our in vitro experiments show that recombinant human IL-18 and IL-18-rich sera from AIDS patients caused apoptosis in a human NK cell line as well as in primary human NK cells. Anti-FasL antagonist antibodies inhibited this cell death. In a series of experiments, we found that IL-18 enhances expression of FasL but does not affect the expression of Fas on human NK cells. In vitro IL-18 also stimulated transcription from human FasL promoter. Furthermore, the cytokine also enhanced susceptibility of NK cells to Fas-mediated death, as it decreased the expression of an anti-apoptotic protein Bcl-XL. Our study shows that enhanced IL-18 bioactivity in HIV-infected patients may contribute to the pathogenesis of AIDS by disrupting NK cell homoeostasis

Il Partito comunista cinese e il Comintern (1921-1927)

Le relazioni tra Pcc e Comintern tra il 1921 e il 192

State of Art about water uses and wastewater management in Lebanon

12 p.International audienceThis paper shows the real situation about management of water and wastewater in Lebanon and focuses on problems related to urban water pollution released in environment. Water and wastewater infrastructures have been rebuilt since 1992. However, wastewater management still remains one of the greatest challenges facing Lebanese people, since water supply projects have been given priority over wastewater projects. As a consequence of an increased demand of water by agricultural, industrial and household sectors in the last decade, wastewater flows have been increased. In this paper, the existing wastewater treatment plants (WWTP) operating in Lebanon are presented. Most of them are small-scale community-based ones, only two large-scale plants, constructed by the government, are currently operational. Lebanese aquatic ecosystems are suffering from the deterioration of water quality because of an insufficient treatment of wastewater, which is limited mostly to pre-treatment processes. In fact, domestic and industrial effluents are mainly conducted together in the sewer pipes to the WWTP before being discharged, without adequate treatment into the rivers or directly into the Mediterranean Sea. Such discharges are threatening the coastal marine ecosystem in the Mediterranean basin. This paper aims at giving the current state of knowledge about water uses and wastewater management in Lebanon. The main conclusion drawn from this state of art is a lack of data. In fact, the available data are limited to academic researches without being representative on a national scale

Chiang Kai-shek and His Time. New Historical and Historiographical Perspectives

The essays collected in this book were originally presented at the international workshop Chiang Kai-shek and His Time. New Historical and Historiographical Perspectives, held at the Department of Asian and African Studies of Ca' Foscari University of Venice on October 18th, 2013 and jointly funded by the Ministry of Culture of the Republic of China at Taiwan (Taiwan Spotlight Project) and Ca' Foscari University. The contributions of scholars from Europe, China, Taiwan and Japan collected in the volume illustrate the major trends in recent international research on Chiang Kai-shek, not only enriching the understanding of Chiang's personality and life but also placing Chiang and his historical experience in the broader framework of China's domestic and international context