Rôle de la protéine LMP1 dans la balance survie/apoptose des cellules infectées par le virus d'Epstein-Barr

Le virus d Epstein-Barr (EBV) est un herpèsvirus humain qui infecte 90% de la population, mais l infection est, le plus souvent, asymptomatique. Après infection, le virus établit une latence virale caractérisée par l expression restreinte de gènes viraux, appelés gènes de latence permettant au virus de persister tout au long de la vie. On définit trois latences virales (I, II et III) selon le profil d expression des gènes de latence codant les antigènes EBNAs (-1, -2, -3 et -LP) et les protéines membranaires LMPs (-1 et -2). L immortalisation in vitro des lymphocytes B aboutit à des lignées cellulaires lymphoblastoïdes (LCL de latence III), exprimant la totalité des gènes de latence. L EBV est associée à des cancers (lymphome de Burkitt, lymphomes liés à un déficit immunitaire innée ou acquis, lymphome de Hodgkin, carcinome du rhinopharynx). Hors dans le lymphome de Burkitt, LMP-1 est exprimée dans toutes les pathologies malignes, et constitue l oncogène majeur du virus. Les propriétés oncogènes de LMP-1 sont liées à sa capacité d activer de façon chronique des voies de signalisation cellulaire telles que les voies NFkB, JNK et p38. Malgré son pouvoir transformant, LMP-1 induit la surexpression du récepteur proapoptotique Fas/CD95 via les facteurs NFkB, p53 et STAT1, sensibilisant les cellules à l action des lymphocytes T cytotoxiques. Des résultats préliminaires ont montré que LMP-1 induit l apoptose des LCLs. Nous avons d abord cherché à déterminer l origine de l expression de LMP-1 lors de la latence II. En effet, la latence II est caractérisée par l absence d EBNA-2, principal transactivateur viral de LMP-1. Nous montrons que LMP-1 autorégule sa propre expression via l induction d une balance entre les voies de signalisation NFkB (répresseur) et JNK (activateur). Ce mode de régulation est également retrouvé au cours de la latence III. Puis, nous avons voulu décrire les bases moléculaires de la cytotoxicité cellulaire de LMP-1 dans les LCLs et déterminer le rôle de Fas/CD95. Nous démontrons que LMP-1 induit l autoactivation de Fas/CD95, indépendamment de son ligand FasL/CD95L et l activation des caspases. Ces résultats suggèrent le caractère ambivalent de LMP-1 qui induit simultanément des signaux de survie et d apoptose, notamment grâce à la voie de signalisation NFkB. L apoptose contribuerait alors à l homéostasie cellulaire du compartiment lymphocytaire B infecté par l EBV.Esptein-Barr Virus (EBV) is a human herpesvirus which infects 90% of worldwide population, but the infection is often asymptomatic. After infection, EBV establishes a viral latency characterized by the expression of viral genes called latency genes, allowing the virus to persist throughout life. Three viral latency are defined (I, II et III) according to the profile of expression of genes coding for EBNAs antigens (-1, -2, -3 et -LP) and latent membrane proteins LMPs (-1 and -2). The immortalization in vitro of B lymphocytes leads to lymphoblastoid cell lines (LCL sharing a latency III), expressing all the latency genes. EBV is associated with cancer (Burkitt's lymphoma, lymphomas linked to an innate immune deficiency or acquired Hodgkin's lymphoma, carcinoma of rhinopharynx). Out in Burkitt's lymphoma, LMP-1 is expressed in all malignant diseases, and is the major viral oncogenic protein. Oncogenic properties of LMP-1 are linked to its ability to activate a chronic cellular signaling pathways such as NFkB, JNK and p38 pathways. Despite its transforming power, LMP-1 induced overexpression of the receptor proapoptotique Fas/CD95 via NFkB, p53, and STAT1 factors, sensitizing cells to action of cytotoxic T lymphocytes. Preliminary results showed that LMP-1 induced apoptosis LCLs. We first sought to determine the origin of the expression of LMP-1 in latency II. Indeed, the latency II is characterized by the absence of EBNA-2, the main viral transactivator of LMP-1. We show that LMP-1 induced its self-expression through induction of a balance between signaling pathways NFkB (repressor) and JNK (activator). This mode of regulation is also found during the latency III. Then, we wanted to describe the molecular basis of cellular cytotoxicity of LMP-1 in LCLs and to determine the role of Fas/CD95. We demonstrate that LMP-1 induced autoactivation of Fas/CD95, regardless of its FasL/CD95L ligand and activation of caspases. These results suggest the ambivalence of LMP-1 which induced simultaneously survival and apoptosis, via the NFkB signaling pathway. Apoptosis would then homeostasis cellular compartment B lymphocyte infected with EBV.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

Cationic porphyrin–xylan conjugate hydrogels for photodynamic antimicrobial chemotherapy

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Xylan–Porphyrin Hydrogels as Light-Triggered Gram-Positive Antibacterial Agents

In the present work, we report on the synthesis of light-triggered antibacterial hydrogels, based on xylan chains covalently bound to meso-tetra(4-carboxyphenyl)porphyrin (TCPP). Not only does TCPP act as a photosensitizer efficient against Gram-positive bacteria, but it also serves as a cross-linking gelator, enabling the simple and easy building of xylan conjugate hydrogels. The hydrogels were characterized by infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), along with swelling and rheological tests. The antimicrobial activity of the hydrogels was tested under visible light irradiation against two Gram-positive bacterial strains, Staphylococcus aureus and Bacillus cereus. The preliminary results showed an interesting activity on these bacteria, indicating that these hydrogels could be of great potential in the treatment of skin bacterial infections with this species by photodynamic antimicrobial chemotherapy (PACT)

Xylan-Porphyrin Hydrogels as Light-Triggered Gram-Positive Antibacterial Agents

International audienceIn the present work, we report on the synthesis of light-triggered antibacterial hydrogels, based on xylan chains covalently bound to meso-tetra(4-carboxyphenyl)porphyrin (TCPP). Not only does TCPP act as a photosensitizer efficient against Gram-positive bacteria, but it also serves as a cross-linking gelator, enabling the simple and easy building of xylan conjugate hydrogels. The hydrogels were characterized by infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), along with swelling and rheological tests. The antimicrobial activity of the hydrogels was tested under visible light irradiation against two Gram-positive bacterial strains, Staphylococcus aureus and Bacillus cereus. The preliminary results showed an interesting activity on these bacteria, indicating that these hydrogels could be of great potential in the treatment of skin bacterial infections with this species by photodynamic antimicrobial chemotherapy (PACT)

Xylan-Based Cross-Linked Hydrogel for Photodynamic Antimicrobial Chemotherapy

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Optimized Single-Step Recovery of Lipophilic and Hydrophilic Compounds from Raspberry, Strawberry and Blackberry Pomaces Using a Simultaneous Ultrasound-Enzyme-Assisted Extraction (UEAE)

International audienceAn ultrasound-enzyme-assisted extraction (UEAE) was optimized to extract, simultaneously, the hydrophilic and lipophilic compounds from three berry pomaces (raspberry, strawberry and blackberry). First, an enzyme screening designated a thermostable alkaline protease as the most suitable enzyme to recover, in an aqueous medium, the highest yields of polyphenols and oil in the most efficient way. Secondly, the selected enzyme was coupled to ultrasounds (US) in sequential and simultaneous combinations. The simultaneous US-alkaline enzyme combination was selected as a one-single-step process and was then optimized by definitive screening design (DSD). The optimized parameters were: US amplitude, 20% (raspberry pomace) or 70% (strawberry and blackberry pomaces); pH, 8; E/S ratio, 1% (w/w); S/L ratio, 6% (w/v); extraction time, 30 min; temperature, 60 • C. Compared to conventional extractions using organic solvents, the UEAE extracted all the polyphenols, with around 75% of the active polyphenols (measured by the DPPH • method) and up to 75% of the initial oil from the berry pomaces. Characterized lipophilic compounds were rich in polyunsaturated fatty acids (PUFAs), tocols and phytosterols. The polyphenolics were analyzed by UPLC-MS/MS; characteristic ellagitannins of the Rosaceae family (sanguiin H-6 or agrimoniin, sanguiin H-10,. . .) and ellagic acid conjugates were found as the major components

Prebiotic Isomaltooligosaccharide Provides an Advantageous Fitness to the Probiotic Bacillus subtilis CU1

International audienceBacillus subtilis CU1 is a probiotic strain with beneficial effects on immune health in elderly subjects and diarrhea. Commercialized under spore form, new strategies to improve the germination, fitness and beneficial effects of the probiotic once in the gut have to be explored. For this purpose, functional food ingredients, such as isomaltooligosaccharides (IMOSs), could improve the fitness of Bacillus probiotics. IMOSs are composed of α(1 → 6)- and α(1 → 4)-linked oligosaccharides and are partially indigestible. Dietary IMOSs stimulate beneficial members of intestinal microbiota, but the effect of a combination of IMOSs with probiotics, such as B. subtilis CU1, is unknown. In this study, we evaluate the potential effect of IMOSs in B. subtilis CU1 and identify the metabolic pathways involved. The biochemical analysis of the commercial IMOSs highlights a degree of polymerization (DP) comprised between 1 and 29. The metabolism of IMOSs in CU1 was attributed to an α-glucosidase, secreted in the extracellular compartment one hundred times more than with glucose, and which seems to hydrolyze high DP IMOSs into shorter oligosaccharides (DP1, DP2 and DP3) in the culture medium. Proteomic analysis of CU1 after growth on IMOSs showed a reshaping of B. subtilis CU1 metabolism and functions, associated with a decreased production of lactic acid and acetic acid by two times. Moreover, we show for the first time that IMOSs could improve the germination of a Bacillus probiotic in the presence of bile salts in vitro, with an 8 h reduced lag-time when compared to a glucose substrate. Moreover, bacterial concentration (CFU/mL) was increased by about 1 log in IMOS liquid cultures after 48 h when compared to glucose. In conclusion, the use of IMOSs in association with probiotic B. subtilis CU1 in a synbiotic product could improve the fitness and benefits of the probiotic