IFN-α induces a preferential long-lasting expression of MHC class I in human pancreatic beta cells

Aims/hypothesis IFN-α, a cytokine expressed in human islets from individuals affected by type 1 diabetes, plays a key role in the pathogenesis of diabetes by upregulating inflammation, endoplasmic reticulum (ER) stress and MHC class I overexpression, three hallmarks of islet histology in early type 1 diabetes. We tested whether expression of these mediators of beta cell loss is reversible upon IFN-α withdrawal or IFN-α pathway inhibition. Methods IFN-α-induced MHC class I overexpression, ER stress and inflammation were evaluated by flow cytometry, immunofluorescence and real-time PCR in human EndoC-βH1 cells or human islets exposed to IFN-α with or without the presence of Janus kinase (JAK) inhibitors. Protein expression was evaluated by western blot. Results IFN-α-induced expression of inflammatory and ER stress markers returned to baseline after 24–48 h following cytokine removal. In contrast, MHC class I overexpression at the cell surface persisted for at least 7 days. Treatment with JAK inhibitors, when added with IFN-α, prevented MHC class I overexpression, but when added 24 h after IFN-α exposure these inhibitors failed to accelerate MHC class I return to baseline. Conclusions/interpretation IFN-α mediates a long-lasting and preferential MHC class I overexpression in human beta cells, which is not affected by the subsequent addition of JAK inhibitors. These observations suggest that IFN-α-stimulated long-lasting MHC class I expression may amplify beta cell antigen presentation during the early phase of type 1 diabetes and that IFN-α inhibitors might need to be used at very early stages of the disease to be effective

Les interventions de l'Union européenne en matière de protection des enfants face aux contenus préjudiciables et à la pédopornographie sur Internet

L'évolution des technologies et plus particulièrement d'Internet, bien que bénéfique, n'est pas sans comporter de nombreux risques pour les enfants. Ce mémoire est dédié à l'étude de la gestion de certains de ces risques au niveau de l'Union européenne. Un premier titre sera consacré à des généralités. Nous nous attacherons à délimiter certaines notions clés, dont celles de « contenu illicite » et « contenu préjudiciable » qui structureront l’ensemble de notre mémoire. Un chapitre sera également consacré à l’étude de certains préalables à une action efficace de l’Union européenne en matière de protection des enfants, à savoir le rapprochement progressif des droits pénaux matériels et l’implication croissante de l’Union dans la protection des droits de l’enfant. En outre, le cadre européen actuel en la matière est le fruit de nombreuses initiatives, dont un bref aperçu sera dressé au sein de ce titre. Nous nous pencherons dans un second titre sur la problématique des contenus préjudiciables. Les actions menées par l’Union européenne en la matière sont questionnables au regard, d’une part, du droit à la liberté d’expression et d’autre part, du principe de la libre circulation des services de la société de l’information. L’Union européenne a ainsi adopté une approche peu contraignante, fondée sur l’éducation aux médias, la mise en place de dispositifs technologiques et enfin, l’autorégulation et la corégulation. Ces deux formes de réglementation alternatives ont été fortement promues par l’Union dans le cadre de la lutte contre les contenus préjudiciables. Nous analyserons dans ce cadre les « Safer Social Networking Principles for the EU », accord issu de l’autorégulation conclu dans le cadre des réseaux sociaux. Ces derniers soulèvent des problèmes nouveaux, issus de l’avènement du web 2.0. Notre troisième et dernier titre sera consacré à la pédopornographie. Nous commencerons par définir cette notion, dont les contours varient selon que l’on se trouve au niveau international, du Conseil de l’Europe ou de l’Union européenne. Tout comme s’agissant des contenus préjudiciables, la lutte contre la pédopornographie présente certaines tensions avec le droit à la liberté d’expression tel que consacré par l’article 10 de la Convention européenne des droits de l’Homme. Nous analyserons à cet égard les enseignements et les limites de l’arrêt Karttunen c.Finlande de la Cour européenne des droits de l’Homme. Un chapitre sera également consacré à la directive du 13 décembre 2011 relative à la lutte contre les abus sexuels et l’exploitation sexuelle des enfants, dont les innovations en termes notamment d’incriminations, de sanctions, ou encore de procédure sont importantes. Nous aurons l’occasion d’y aborder entre autres les mesures de blocage et le débat suscité par celles-ci quant à leur compatibilité avec le droit à la liberté d’expression. Cette problématique est intrinsèquement liée à celle de la responsabilité des prestataires intermédiaires de services Internet, qui fera l’objet de notre troisième chapitre. L’instrument européen réglant cette question est la directive du 8 juin 2000 sur le commerce électronique, qui instaure un régime de responsabilité particulièrement favorable à l’égard de ces intermédiaires. Nous en analyserons les principes et les faiblesses, avant de clôturer ce titre en abordant les mécanismes de coopération internationale mis en place pour lutter contre la pédopornographie.Master [120] en droit, Université catholique de Louvain, 201

Gene regulation by PDGF via the PI3-kinase pathway : focus on HBP1 and stearoyl-coenzyme A desaturase

Our laboratory is interested in the study of growth factors and in particular the platelet-derived growth factor (PDGF) and its receptor (PDGFR). Many signaling pathways, including the phosphatidylinositol 3-kinase (PI3K) pathway, are activated downstream of PDGFR, leading to cell proliferation, survival, migration and differentiation. In line with this, the objective of this thesis was to characterize the regulation and the function of two mediators of the PDGFR-PI3K pathway. We focused on the HMG-box protein 1 (HBP1) and the stearoyl-coenzyme A desaturase (SCD). In our first study, we identified the transcription factor HBP1 as a negative target of the growth factor-PI3K-AKT pathway, up-regulated by FOXO via a direct transcriptional regulation. These regulations were observed in different cellular models including normal and cancer cells from human and mice origin. Using small-hairpin RNA (shRNA), we found that HBP1 knockdown increased cell proliferation and potentiated the proliferative effect of growth factors. Finally, we observed that HBP1 and FOXO1 were down-regulated in breast cancer tissues compared to normal breast tissues. In addition, breast tumors with a lower expression of FOXO also presented a lower expression of HBP1, which suggests that, in these tumors, FOXO loss could explain HBP1 down-regulation, at least partially. Our second study started from published data from our laboratory showing that PDGF strongly induces SCD expression via PI3K, mTORC1 and SREBP and stimulates lipid synthesis, in particular unsaturated fatty acids. SCD is a Δ9 desaturase that converts saturated fatty acids (SFA), such as palmitoyl-CoA and stearoyl-CoA, into mono-unsaturated fatty acids (MUFA), such as palmitoleoyl-CoA and oleyl-CoA. By increasing SCD expression, PDGF increased the MUFA / SFA ratio in the total cellular lipids. Using shRNA targeting SCD, we showed that SCD was essential for the proliferation and the survival of human fibroblasts in response to PDGF. The proliferative effect was confirmed with an inhibitor of SCD. Interestingly, the treatment of cells with palmitate, but not oleate, also blocked cell proliferation in response to PDGF, and the addition of oleate to palmitate suppressed this effect. In addition, SCD knockdown and palmitate induced endoplasmic reticulum stress (ER stress), which could explain the observed effects. Together, our results strongly suggest that SCD is necessary for PDGF-mediated cell proliferation by supplying an increased amount of MUFA. It also protects cells from SFA accumulation-induced lipotoxicity and ER stress. To conclude, PDGF activates many signaling pathways that allow the regulation of plenty of genes involved in PDGF functions. Among them, we identified HBP1 and SCD as downstream targets of the PI3K pathway, both involved in the control of cell proliferation by PDGF: HBP1 blocked cell proliferation whereas SCD favored it.(BIFA - Sciences biomédicales et pharmaceutiques) -- UCL, 201

FOXO transcription factors in cancer development and therapy.

The forkhead box O (FOXO) transcription factors are considered as tumor suppressors that limit cell proliferation and induce apoptosis. FOXO gene alterations have been described in a limited number of human cancers, such as rhabdomyosarcoma, leukemia and lymphoma. In addition, FOXO proteins are inactivated by major oncogenic signals such as the phosphatidylinositol-3 kinase pathway and MAP kinases. Their expression is also repressed by micro-RNAs in multiple cancer types. FOXOs are mediators of the tumor response to various therapies. However, paradoxical roles of FOXOs in cancer progression were recently described. FOXOs contribute to the maintenance of leukemia-initiating cells in acute and chronic myeloid leukemia. These factors may also promote invasion and metastasis of subsets of colon and breast cancers. Resistance to treatment was also ascribed to FOXO activation in multiple cases, including targeted therapies. In this review, we discuss the complex role of FOXOs in cancer development and response to therapy

Isotope fractionation during root water uptake by Acacia caven is enhanced by arbuscular mycorrhizas

Aim: A growing number of studies show a discrepancy between the isotopic composition of xylem water and plant water sources. We tested the effect of arbuscular mycorrhizal fungi (AMF) on the isotopic composition of Acacia caven xylem water. As the most common plant-fungal association, AMF might explain this isotopic mismatch. Methods: Seedlings were grown with and without AMF and irrigated with the same water. After 120 days, stem and soil samples were collected and following cryogenic distillation, H and O isotopic composition of xylem and soil water, as well as irrigation water, was measured. Results: Xylem water of non-mycorrhizal seedlings was significantly depleted in H-2 compared to soil water (differences up to -15.6 parts per thousand). When AMF were present, the depletion was significantly higher and appeared for both H and O (differences up to -24.6 parts per thousand for delta H-2 and - 2.9 parts per thousand for delta O-18 between soil and xylem water). Conclusions: Results suggest that isotopic fractionation occurred during water uptake in this xerophytic species. To explain this, we propose an aquaporin-driven mechanism mediating water transport via transmembrane passage. Furthermore, we show for the first time, that AMF enhance the observed discrimination against heavy isotopes, probably by enforcing water passage through aquaporins. Given their ubiquity, AMF could question the fractionation-free assumption during root water uptake

Interferon-α mediates human beta cell HLA class I overexpression, endoplasmic reticulum stress and apoptosis, three hallmarks of early human type 1 diabetes

Aims/hypothesis: Three hallmarks of the pancreatic islets in early human type 1 diabetes are overexpression of HLA class I, endoplasmic reticulum (ER) stress and beta cell apoptosis. The mediators of these phenomena remain to be defined. The type I interferon IFNα is expressed in human islets from type 1 diabetes patients and mediates HLA class I overexpression. We presently evaluated the mechanisms involved in IFNα-induced HLA class I expression in human beta cells and determined whether this cytokine contributes to ER stress and apoptosis. Methods: IFNα-induced inflammation, ER stress and apoptosis were evaluated by RT-PCR, western blot, immunofluorescence and nuclear dyes, and proteins involved in type I interferon signalling were inhibited by small interfering RNAs. All experiments were performed in human islets or human EndoC-βH1 cells. Results: IFNα upregulates HLA class I, inflammation and ER stress markers in human beta cells via activation of the candidate gene TYK2, and the transcription factors signal transducer and activator of transcription 2 and IFN regulatory factor 9. Furthermore, it acts synergistically with IL-1β to induce beta cell apoptosis. Conclusions/interpretation: The innate immune effects induced by IFNα may induce and amplify the adaptive immune response against human beta cells, indicating that IFNα has a central role in the early phases of diabetes

PDGF-D expression is down-regulated by TGFβ in fibroblasts

Transforming growth factor-β (TGFβ) is a key mediator of fibrogenesis. TGFβ is overexpressed and activated in fibrotic diseases, regulates fibroblast differentiation into myofibroblasts and induces extracellular matrix deposition. Platelet-derived growth factor (PDGF) is also a regulator of fibrogenesis. Some studies showed a link between TGFβ and PDGF in certain fibrotic diseases. TGFβ induces PDGF receptor alpha expression in scleroderma fibroblasts. PDGF-C and -D are the most recently discovered ligands and also play a role in fibrosis. In this study, we report the first link between TGFβ and PDGF-D and -C ligands. In normal fibroblasts, TGFβ down-regulated PDGF-D expression and up-regulated PDGF-C expression at the mRNA and protein levels. This phenomenon is not limited to TGFβ since other growth factors implicated in fibrosis, such as FGF, EGF and PDGF-B, also regulated PDGF-D and PDGF-C expression. Among different kinase inhibitors, only TGFβ receptor inhibitors and the IκB kinase (IKK) inhibitor BMS-345541 blocked the effect of TGFβ. However, activation of the classical NF-κB pathway was not involved. Interestingly, in a model of lung fibrosis induced by either bleomycin or silica, PDGF-D was down-regulated, which correlates with the production of TGFβ and other fibrotic growth factors. In conclusion, the down-regulation of PDGF-D by TGFβ and other growth factors may serve as a negative feedback in the network of cytokines that control fibrosis