Dengue Virus Activates Membrane TRAIL Relocalization and IFN-α Production by Human Plasmacytoid Dendritic Cells In Vitro and In Vivo

Background

Dengue displays a broad spectrum of clinical manifestations that may vary from asymptomatic to severe and even fatal features. Plasma leakage/hemorrhages can be caused by a cytokine storm induced by monocytes and dendritic cells during dengue virus (DENV) replication. Plasmacytoid dendritic cells (pDCs) are innate immune cells and in response to virus exposure secrete IFN-α and express membrane TRAIL (mTRAIL). We aimed to characterize pDC activation in dengue patients and their function under DENV-2 stimulation in vitro.

Methods & Findings

Flow cytometry analysis (FCA) revealed that pDCs of mild dengue patients exhibit significantly higher frequencies of mTRAIL compared to severe cases or healthy controls. Plasma levels of IFN-α and soluble TRAIL are increased in mild compared to severe dengue patients, positively correlating with pDC activation. FCA experiments showed that in vitro exposure to DENV-2 induced mTRAIL expression on pDC. Furthermore, three dimension microscopy highlighted that TRAIL was relocalized from intracellular compartment to plasma membrane. Chloroquine treatment inhibited DENV-2-induced mTRAIL relocalization and IFN-α production by pDC. Endosomal viral degradation blockade by chloroquine allowed viral antigens detection inside pDCs. All those data are in favor of endocytosis pathway activation by DENV-2 in pDC. Coculture of pDC/DENV-2-infected monocytes revealed a dramatic decrease of antigen detection by FCA. This viral antigens reduction in monocytes was also observed after exogenous IFN-α treatment. Thus, pDC effect on viral load reduction was mainly dependent on IFN-α production

Conclusions

This investigation characterizes, during DENV-2 infection, activation of pDCs in vivo and their antiviral role in vitro. Thus, we propose TRAIL-expressing pDCs may have an important role in the outcome of disease.     

Cholesterol Depletion Disorganizes Oocyte Membrane Rafts Altering Mouse Fertilization

Drastic membrane reorganization occurs when mammalian sperm binds to and fuses with the oocyte membrane. Two oocyte protein families are essential for fertilization, tetraspanins and glycosylphosphatidylinositol-anchored proteins. The firsts are associated to tetraspanin-enriched microdomains and the seconds to lipid rafts. Here we report membrane raft involvement in mouse fertilization assessed by cholesterol modulation using methyl-β-cyclodextrin. Cholesterol removal induced: (1) a decrease of the fertilization rate and index; and (2) a delay in the extrusion of the second polar body. Cholesterol repletion recovered the fertilization ability of cholesterol-depleted oocytes, indicating reversibility of these effects. In vivo time-lapse analyses using fluorescent cholesterol permitted to identify the time-point at which the probe is mainly located at the plasma membrane enabling the estimation of the extent of the cholesterol depletion. We confirmed that the mouse oocyte is rich in rafts according to the presence of the raft marker lipid, ganglioside GM1 on the membrane of living oocytes and we identified the coexistence of two types of microdomains, planar rafts and caveolae-like structures, by terms of two differential rafts markers, flotillin-2 and caveolin-1, respectively. Moreover, this is the first report that shows characteristic caveolae-like invaginations in the mouse oocyte identified by electron microscopy. Raft disruption by cholesterol depletion disturbed the subcellular localization of the signal molecule c-Src and the inhibition of Src kinase proteins prevented second polar body extrusion, consistent with a role of Src-related kinases in fertilization via signaling complexes. Our data highlight the functional importance of intact membrane rafts for mouse fertilization and its dependence on cholesterol.     

Virulence of Klebsiella pneumoniae Isolates Harboring bla KPC-2 Carbapenemase Gene in a Caenorhabditis elegans Model

Klebsiella pneumoniae carbapenemase (KPC) is a carbapenemase increasingly reported worldwide in Enterobacteriaceae. The aim of this study was to analyze the virulence of several KPC-2-producing K. pneumoniae isolates. The studied strains were (i) five KPC-2 clinical strains from different geographical origins, belonging to different ST-types and possessing plasmids of different incompatibility groups; (ii) seven transformants obtained after electroporation of either these natural KPC plasmids or a recombinant plasmid harboring only the bla _KPC-2 gene into reference strains K. pneumoniae ATCC10031/{"type":"entrez-protein","attrs":{"text":"CIP53153","term_id":"878514309","term_text":"CIP53153"}}CIP53153; and (iii) five clinical strains cured of plasmids. The virulence of K. pneumoniae isolates was evaluated in the Caenorhabditis elegans model. The clinical KPC producers and transformants were significantly less virulent (LT50: 5.5 days) than K. pneumoniae reference strain (LT50: 4.3 days) (p<0.01). However, the worldwide spread KPC-2 positive K. pneumoniae ST258 strains and reference strains containing plasmids extracted from K. pneumoniae ST258 strains had a higher virulence than KPC-2 strains belonging to other ST types (LT50: 5 days vs. 6 days, p<0.01). The increased virulence observed in cured strains confirmed this trend. The bla _KPC-2 gene itself was not associated to increased virulence.     

Morphological and Molecular Characterization of Adult Midgut Compartmentalization in Drosophila

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Characterization of AgMaT2, a plasma membrane mannitol transporter from celery, expressed in phloem cells, including phloem parenchyma cells

A second mannitol transporter, AgMaT2, was identified in celery (Apium graveolens L. var. dulce), a species that synthesizes and transports mannitol. This transporter was successfully expressed in two different heterologous expression systems: baker's yeast (Saccharomyces cerevisiae) cells and tobacco (Nicotiana tabacum) plants (a non-mannitol-producing species). Data indicated that AgMaT2 works as an H(+)/mannitol cotransporter with a weak selectivity toward other polyol molecules. When expressed in tobacco, AgMaT2 decreased the sensitivity to the mannitol-secreting pathogenic fungi Alternaria longipes, suggesting a role for polyol transporters in defense mechanisms. In celery, in situ hybridization showed that AgMaT2 was expressed in the phloem of leaflets, petioles from young and mature leaves, floral stems, and roots. In the phloem of petioles and leaflets, AgMaT2, as localized with specific antibodies, was present in the plasma membrane of three ontologically related cell types: sieve elements, companion cells, and phloem parenchyma cells. These new data are discussed in relation to the physiological role of AgMaT2 in regulating mannitol fluxes in celery petioles.     

Resistance to high-fat diet in the female progeny of obese mice fed a control diet during the periconceptual, gestation, and lactation periods

With the worldwide epidemic of metabolic syndrome (MetS), the proportion of women that are overweight/obese and overfed during pregnancy has increased. The resulting abnormal uterine environment may have deleterious effects on fetal metabolic programming and lead to MetS in adulthood. A balanced/restricted diet and/or physical exercise often improve metabolic abnormalities in individuals with obesity and type 2 diabetes mellitus (T2D). We investigated whether reducing fat intake during the periconceptual/gestation/lactation period in mothers with high-fat diet (HFD)-induced obesity could be used to modify fetal/neonatal MetS programming positively, thereby preventing MetS. First generation (F1) C57BL/6J female mice with HFD-induced obesity and T2D were crossed with F1 males on control diet (CD). These F1 females were switched to a CD during the periconceptual/gestation/lactation period. At weaning, both male and female second generation (F2) mice were fed a HFD. Weight, caloric intake, lipid parameters, glucose, and insulin sensitivity were assessed. Sensitivity/resistance to the HFD differed significantly between generations and sexes. A similar proportion of the F1 and F2 males (80%) developed hyperphagia, obesity, and T2D. In contrast, a significantly higher proportion of the F2 females (43%) than of the previous F1 generation (17%) were resistant (P<0.01). Despite having free access to the HFD, these female mice were no longer hyperphagic and remained lean, with normal insulin sensitivity and glycemia but mild hypercholesterolemia and glucose intolerance, thus displaying a "satiety phenotype." This suggests that an appropriate dietary fatty acid profile and intake during the periconceptual/gestation/lactation period helps the female offspring to cope with deleterious intrauterine conditions.     

Efficiencies of selected biotreatments for the remediation of PAH in diluted bitumen contaminated soil microcosms

Unconventional oils such as diluted bitumen from oil sands differs from most of conventional oils in terms of physiochemical properties and PAHs composition. This raises concerns regarding the effectiveness of current remediation strategies and protocols originally developed for conventional oil. Here we evaluated the efficiency of different biotreatment approaches, such as fungi inoculation (bioaugmentation), sludge addition (bioaugmentation/biostimulation), perennial grasses plantation (phytoremediation) and their combinations as well as natural attenuation (as control condition), for the remediation of soil contaminated by synthetic crude oil (a product of diluted bitumen) in laboratory microcosms. We specifically monitored the PAHs loss percentage (alkylated PAHs and unsubstituted 16 EPA Priority PAHs), the residue of PAHs and evaluated the ecotoxicity of soil after treatment. All treatments were highly efficient with more than?~?80% of ∑PAHs loss after 60 days. Distinctive loss efficiencies between light PAHs (≤?3 rings,?~?96% average loss) and heavy PAHs (4–6 rings,?~?29% average loss) were observed. The lowest average PAHs residue (0.10?±?0.02 mg·kg^?1, for an initial concentration of 0.29?±?0.12 mg·kg^?1) was achieved with the “sludge—plants (grasses)” combination. Sludge addition was the only treatment that achieved significantly lower ecotoxicity (3%?±?4% of growth inhibition of L. sativa) than the control (natural attenuation, 13%?±?4% of inhibition). Sludge addition, grasses plantation and “sludge—fungi combination” treatments could result in lower PAH exposure (than other treatments) in post-treated soil when using the Canadian Soil Quality Guidelines for the protection of environmental and human health for potentially carcinogenic and other PAHs.