Epstein-Barr Virus Interferes with the Amplification of IFNα Secretion by Activating Suppressor of Cytokine Signaling 3 in Primary Human Monocytes

Epstein-Barr virus is recognized to cause lymphoproliferative disorders and is also associated with cancer. Evidence suggests that monocytes are likely to be involved in EBV pathogenesis, especially due to a number of cellular functions altered in EBV-infected monocytes, a process that may affect efficient host defense. Because type I interferons (IFNs) are crucial mediators of host defense against viruses, we investigated the effect of EBV infection on the IFNalpha pathway in primary human monocytes.Infection of monocytes with EBV induced IFNalpha secretion but inhibited the positive feedback loop for the amplification of IFNalpha. We showed that EBV infection induced the expression of suppressor of cytokine signaling 3 (SOCS3) and, to a lesser extent, SOCS1, two proteins known to interfere with the amplification of IFNalpha secretion mediated by the JAK/STAT signal transduction pathway. EBV infection correlated with a blockage in the activation of JAK/STAT pathway members and affected the level of phosphorylated IFN regulatory factor 7 (IRF7). Depletion of SOCS3, but not SOCS1, by small interfering RNA (siRNA) abrogated the inhibitory effect of EBV on JAK/STAT pathway activation and significantly restored IFNalpha secretion. Finally, transfection of monocytes with the viral protein Zta caused the upregulation of SOCS3, an event that could not be recapitulated with mutated Zta.We propose that EBV protein Zta activates SOCS3 protein as an immune escape mechanism that both suppresses optimal IFNalpha secretion by human monocytes and favors a state of type I IFN irresponsiveness in these cells. This immunomodulatory effect is important to better understand the aspects of the immune response to EBV

Synthetic Plasmodium-Like Hemozoin Activates the Immune Response: A Morphology - Function Study

Increasing evidence points to an important role for hemozoin (HZ), the malaria pigment, in the immunopathology related to this infection. However, there is no consensus as to whether HZ exerts its immunostimulatory activity in absence of other parasite or host components. Contamination of native HZ preparations and the lack of a unified protocol to produce crystals that mimic those of Plasmodium HZ (PHZ) are major technical limitants when performing functional studies with HZ. In fact, the most commonly used methods generate a heterogeneous nanocrystalline material. Thus, it is likely that such aggregates do not resemble to PHZ and differ in their inflammatory properties. To address this issue, the present study was designed to establish whether synthetic HZ (sHZ) crystals produced by different methods vary in their morphology and in their ability to activate immune responses. We report a new method of HZ synthesis (the precise aqueous acid-catalyzed method) that yields homogeneous sHZ crystals (Plasmodium-like HZ) which are very similar to PHZ in their size and physicochemical properties. Importantly, these crystals are devoid of protein and DNA contamination. Of interest, structure-function studies revealed that the size and shape of the synthetic crystals influences their ability to activate inflammatory responses (e.g. nitric oxide, chemokine and cytokine mRNA) in vitro and in vivo. In summary, our data confirm that sHZ possesses immunostimulatory properties and underline the importance of verifying by electron microscopy both the morphology and homogeneity of the synthetic crystals to ensure that they closely resemble those of the parasite. Periodic quality control experiments and unification of the method of HZ synthesis are key steps to unravel the role of HZ in malaria immunopathology

Implication de l'endocytose du BLT1 et de l'activation de la kinase Yes dans la dégranulation du neutrophile induite par le leucotriène B[indice inférieur 4]

Une des activités biologiques importantes du neutrophile humain est la dégranulation qui peut être induite par le leucotriène B4 (LTB4). Nous avons étudié les voies de signalisation intracellulaires menant à la dégranulation du neutrophile impliquant le récepteur de haute affinité du LTB4, le BLT1. Des neutrophiles humains de même que la lignée cellulaire humaine pro-myéloïde PLB-985 transfectée de façon stable avec l'ADNc du BLT1 et différenciée en type neutrophile ont été utilisés lors de cette étude. Le relâchement de l'enzyme [béta]-hexosaminidase induit par le LTB4 était inhibé de 50-80% lorsque les cellules étaient prétraitées avec les inhibiteurs pharmacologiques d'endocytose, soit le sucrose, la concanavaline A et le NH4C1. De plus, une transfection transitoire d'une forme mutante de type dominant négatif de la dynamine (K44A) a mené à approximativement 70% d'inhibition de la dégranulation induite par le ligand. Un prétraitement de neutrophiles ou de cellules PLB-985 exprimant le BLT1 avec l'inhibiteur de la famille des Src kinases, PP1, diminuait de 30-60% la dégranulation impliquant le BLT1. Yes kinase, mais pas c-Src ou Fgr, présente une activité kinase augmentée après une stimulation avec le LTB4. De plus, la transfection transitoire de la dynamine de type dominant négatif inhibait cette activation, suggérant que l'endocytose du BLT1 est nécessaire à l'activation de Yes. La dégranulation induite par le LTB4 semble de plus être partiellement sensible à l'inhibition de la phosphatidyl inositol 3' (PI-3) kinase. D'un autre côté, la dégranulation n'était pas affectée par l'inhibition des MAP kinases MEKK ou p38, les Janus kinases ou les récepteurs tyrosines kinases epidermal growth factor receptor (EGFR) et platelet-derived growth factor receptor (PDGFR). En résumé, nos résultats démontrent un rôle essentiel de l'endocytose du BLT1 et de l'activation de Yes kinase dans la dégranulation du neutrophile induite par le LTB4

Optimized N-phenyl-N′-(2-chloroethyl)ureas as potential antineoplastic agents: Synthesis and growth inhibition activity

International audienceIn our ongoing research program aimed at the optimization of microtubule-self-assembly disrupting agents, we have prepared three series of phenylurea analogues (CEU), derived from N-(3-omega-hydroxyalkyl or 4-omega-hydroxyalkyl or 3-omega-hydroxyalkynyl)-phenyl-N'-(2-chloroethyl)ureas. Most compounds exhibit potent growth inhibitory activity on human colon carcinoma HT-29, human skin melanoma M21, and human breast carcinoma MCF-7 tumor cell lines, with a GI50 ranging from 250 nM to 8 microM. Among these new molecules, three CEUs exhibit GI50 in the nanomolar range. They are more potent by approximately an order of magnitude than previously described CEU analogues. As such, they are attractive hit compounds for the development of potent new alkylating antitubulin drugs

Novel imidazo[1,2-a]naphthyridinic systems (part 1): Synthesis, antiproliferative and DNA-intercalating activities

International audienceNovel imidazo[1,2-a]naphthyridinic systems 6a-15a and 6b-15b were obtained from Friedländer's reaction in imidazo[1,2-a]pyridine series. Most of the compounds were evaluated for their antitumor activity in the NCIs in vitro human tumor cell line screening panel. Among them, pentacyclic derivatives 13b and 14a exhibited in vitro activity comparable to anticancer agent such as amsacrine. Their mechanism of cytotoxicity action was unrelated to poisoning or inhibiting abilities against topo1. On the contrary, we highlighted a direct intercalation of the drugs into DNA by electrophoresis on agarose gel