Mislocalization of the exitatory amino-acid transporters (EAATs) in human astrocytoma and non-astrocytoma cancer cells: effect of the cell confluence

<p>Abstract</p> <p>Background</p> <p>Astrocytomas are cancers of the brain in which high levels of extracellular glutamate plays a critical role in tumor growth and resistance to conventional treatments. This is due for part to a decrease in the activity of the glutamate transporters, i.e. the Excitatory Amino Acid Transporters or EAATs, in relation to their nuclear mislocalization in astrocytoma cells. Although non-astrocytoma cancers express EAATs, the localization of EAATs and the handling of L-glutamate in that case have not been investigated.</p> <p>Methods</p> <p>We looked at the cellular localization and activity of EAATs in human astrocytoma and non-astrocytoma cancer cells by immunofluorescence, cell fractionation and L-glutamate transport studies.</p> <p>Results</p> <p>We demonstrated that the nuclear mislocalization of EAATs was not restricted to astrocytoma and happened in all sub-confluent non-astrocytoma cancer cells we tested. In addition, we found that cell-cell contact caused the relocalization of EAATs from the nuclei to the plasma membrane in all human cancer cells tested, except astrocytoma.</p> <p>Conclusions</p> <p>Taken together, our results demonstrated that the mislocalization of the EAATs and its associated altered handling of glutamate are not restricted to astrocytomas but were also found in human non-astrocytoma cancers. Importantly, we found that a cell contact-dependent signal caused the relocalization of EAATs at the plasma membrane at least in human non-astrocytoma cancer cells, resulting in the correction of the altered transport of glutamate in such cancer cells but not in astrocytoma.</p

Etude biochimique et nutritionnelle de l\u27effet immunomodulateur des huiles de poisson, d\u27olive et d\u27argan. Effets comparés de leurs acides gras

L\u27huile d\u27argan est caractérisée par sa composition lipidique unique et sa richesse en acides oléique et linoléique. Alors qu\u27elle suscite un intérêt croissant pour ses effets bénéfiques dans la prévention des maladies cardiovasculaires, son rôle potentiel sur les fonctions immunitaires n\u27est pas connu. C\u27est pourquoi, nous avons réalisé une étude nutritionnelle visant à comparer l\u27effet immunomodulateur d\u27un régime enrichi en huile d\u27argan à ceux de régimes riches en huiles de poisson, d\u27olive, de noix de coco et de tournesol, administrés pendant quatre semaines chez le rat. Nos résultats ont montré que les différents régimes induisent des changements dans la composition en acides gras des triglycérides et des phospholipides plasmatiques, et à un degré moindre dans les phospholipides des thymocytes. Une corrélation positive a été établie entre la réponse proliférative aux mitogènes et la proportion de 18 :2n-6 dans les phospholipides cellulaires, quel que soit le régime administré. La réponse proliférative est aussi corrélée négativement avec l\u27activité phospholipase D (PLD) thymocytaire. Parallèlement des travaux ont été réalisés in vitro afin de vérifier les effets des acides gras majeurs des différentes huiles sur la prolifération et l\u27activité PLD. L\u27ensemble de nos résultats indique que le profil immunomodulateur de l\u27huile d\u27argan est proche de celui de l\u27huile d\u27olive. L\u27huile d\u27argan s\u27étant montrée par ailleurs plus efficace dans la prévention des maladies cardiovasculaires, sa consommation peut être recommandée sans restriction puisqu\u27elle est dépourvue d(effets secondaires au niveau du système immunitaire

Etude biochimique et nutritionnelle de l'effet immunomodulateur des huiles d'argan, de poisson et d'olive (effets comparés de leurs acides gras)

L'huile d'argan est extraite de l'arganier "Argania spinosa". Cette huile est caractérisée par sa composition lipidique unique et sa richesse en acides oléique et linoléique. Alors qu'elle suscite un intérêt croissant pour ses effets bénéfiques dans la prévention des maladies cardiovasculaires, son rôle potentiel sur les fonctions immunitaires n'est pas connu. C'est pourquoi, nous avons réalisé une étude nutritionnelle visant à comparer l'effet immunomodulateur d'un régime enrichi en huile d'argan (HA) à ceux des régimes riches enhuiles de poisson (HP), d'olive (HO), de noix de coco (HC) et de tournesol (HT), administrés pendant quatre semaines chez le rat. Nos résultats ont montré que les différents régimes induisent des changements dans la composition en acides gras des triglycérides et des phospholipides plasmatiques, et à un degré moindre dans les phospholipides des thymocytes. Les thymocytes des rats nourris avec un régime enrichi en huile de coco ont une réponse proliférative significativement diminuée par rapport aux autres groupes, alors que les réponses les plus fortes sont observées chez les animaux des groupes poisson et tournesol. De plus, une corrélation positive a été établie entre la réponse proliférative aux mitogènes et la proportion de 18:2n-6 dans les phospholipides cellulaires, quel que soit le régime. Cette réponse proliférative est aussi corrélée négativement avec l'activité phospholipase D (PLD) thymocytaire. Les résultats de Western blotting indiquent que les variations d'activités PLD induites par les différents régimes reflètent essentiellemnt les variations d'expression de la protéine PLD2. Parallèlement, des travaux ont été réalisés in vitro afin de vérifier les effets des acides gras majeurs des différentes huiles sur la prolifération et l'activité PLD. Nous avons mis en évidence une corrélation négative entre la réponse proliférative aux mitogènes et l'activité PLD. L'ensemble de nos résultats indique que l'huile d'argan est dépourvue d'effets majeurs sur la prolifération lymphocytaire et que son profil immunomodulateur est proche de celui de l'huile d'olive. L'huile d'argan s'étant montrée par ailleurs plus efficace dans la prévention des maladies cardiovasculaires, sa consommation peut être recommandée sans restriction puisqu'elle est dépourvue d'effets secondaires au niveau du sytème immunitaire.Argan oil is rich in unsaturated fatty acids especially oleic acids. This oil is receiving increasing attention due to its potential health benefits in the prevention of cardiovascular risk, but no information to date about its possible effect on immune cells and functions. To address this issue male rats were fed one of five diets that contained either fish oil, olive oil, coconut oil or sunflower oil for 4 wk. Our results showed that the various diets induced significant changes in the fatty acid composition of plasma triacylglycerols and phospholips and thymocyte phosphlipids. Furthermore, a significant positive linear relationship was found between thymocyte proliferation and the 18:2n-6 proportion of thymocyte phospholipids whatever the diet. The proliferation response of thymcytes to mitogenic activation was also inversely correlated to the phospholipase D (PLD) activity measured in intact thymocytes. In parallel, an in vitro study was performed to investigate the effects of the major fatty acids of the various oils on the proliferation and PLD activity of rat thymocytes. On the whole, the present study shows that the effects of argan oil on immune cells are very are very similar to those of olive, and that, as a consequence, argan oil can be used as a balanced dietary supply without marked adverse effects on immune cell function.VILLEURBANNE-DOC'INSA LYON (692662301) / SudocSudocFranceMoroccoFRM

Staphylococcal enterotoxin A: Partial unfolding caused by high pressure or denaturing agents enhances superantigenicity

Contact: fax: +334 6714 3352. E-mail address: [email protected] audienceThe effect of transient exposure of Staphylococcus aureus enterotoxin A (SEA) to high pressure and/or denaturing agents was examined by assessing the toxin superantigenicity and immunoreactivity, and by monitoring pressure-induced changes in fluorescence emission spectra. Pressurization of SEA at 600 MPa and 45 °C in Tris–HCl buffer (20 mM, pH 7.4) resulted in a marked increase in both T-cell proliferation (superantigenicity) and immunoreactivity. In opposite, pressurization at 20 °C did not change significantly SEA superantigenicity and immunoreactivity, indicating some toxin baro-resistance. Exposure of SEA to 8 M urea at atmospheric pressure or at 600 MPa and 20 °C, also led to a marked increase of superantigenicity (but not of immunoreactivity). In contrast, exposure of SEA to sodium-dodecylsulfate (30 mM) led to an increase of immunoreactivity with some effect on superantigenicity after pressurization at 45 °C only. High pressure up to 600 MPa induced spectral changes which at 20 °C were fully reversible upon decompression. At 45 °C, however, a sharp break of the centre of spectral mass mainly due to tryptophan residues was observed at 300 MPa, and irreversible spectral changes mainly related to tyrosine residues subsisted after pressure release, indicating a marked protein conformational transition. Urea 8 M further increased SEA structural changes at 600 MPa and 20 °C. These results indicate that SEA, under a combination of high pressure and mild temperature, as well as in the presence of urea, partly unfolds to a structure of strongly increased T-cell proliferative ability

The ribotoxin deoxynivalenol affects the viability and functions of glial cells.

International audienceGlial cells are responsible for maintaining brain homeostasis. Modification of the viability and functions of glial cells, including astrocytes and microglia, are associated with neuronal death and neurological diseases. Many toxins (heavy metals, pesticides, bacterial or viral toxins) are known to impact on brain cell viability and functions. Although recent publications suggest a potential link between environmental exposure of humans to mycotoxins and neurological diseases, data regarding the effects of fungal toxins on brain cells are scarce. In the present study, we looked at the impact of deoxynivalenol (DON), a fungal ribotoxin, on glial cells from animal and human origin. We found that DON decreased the viability of glial cells with a higher toxicity against microglial cells compared with astrocytes. In addition to cellular toxicity, DON affected key functions of glial cells. Thus, DON caused a biphasic effect on the neuroinflammatory response of microglia to lipopolysaccharide (LPS), while sublethal doses of DON increased the LPS-induced secretion of TNF-α and nitric oxide, toxic doses inhibited it. In addition to affecting microglial functions, sublethal doses of DON also suppressed the uptake of L-glutamate by astrocytes. This inhibition was associated with a modification of the expression of the glutamate transporters at the plasma membrane. Our results suggest that environmental ribotoxins such as DON could, at low doses, cause modifications of brain homeostasis and possibly participate in the etiology of neurological diseases in which alterations of the glia are involved. © 2011 Wiley-Liss, Inc

UHPH-processed O/W submicron emulsions stabilised with a lipid-based surfactant: Physicochemical characteristics and behaviour on in vitro TC7-cell monolayers and ex vivo pig's ear skin

International audienceSubmicron O/W emulsions formulated with sesame oil plus a lipid-base surfactant, and with or without retinyl acetate (RAC) as a model hydrophobic biomolecule, were prepared by single-pass homogenisation at ≥ 200 MPa (UHPH) and an initial fluid temperature (Tin) of 24°C. These emulsions were characterised by a monomodal distribution (peak maximum at 260 nm) and a 2-year potential physical stability at ambient temperature. Submicron droplets were investigated in term of (i) physicochemical characteristics (size distribution curves; ζ-potential value), and (ii) impact on TC7-cell monolayers (MTT-assay and cell LDH-leakage). Submicron droplets ± RAC did not affect or increased significantly (p=0.05) TC7-cell metabolic activity after 4-24h of exposure indicating absence of cellular impairment, except when high amounts of droplets were deposed on TC7-cells. Indeed, the lipid-based surfactant deposed alone on TC7-cells at high concentration, induced some significant (p=0.05) cell LDH-leakage, and therefore cell-membrane damage. Cellular uptake experiments revealed a significant (p=0.05) time-dependent internalisation of RAC from submicron droplets, and cellular transformation of RAC into retinol. The turnover of RAC into retinol and therefore RAC bioaccessibility appeared faster for RAC-micelles of similar size-range and prepared at atmospheric pressure with polysorbate 80, than for submicron O/W emulsions. Permeation experiments using pig's ear skin mounted on Franz-type diffusion cells, revealed RAC in dermis-epidermis, in significantly (p=0.05) higher amounts for submicron than coarse pre-emulsions. However, RAC amounts remained low for both emulsion-types and RAC was not detected in the receptor medium of Franz-type diffusion cells

: DHA supplementation and immune function

International audienceDietary intake of long-chain n-3 PUFA has been reported to decrease several markers of lymphocyte activation and modulate monocyte susceptibility to apoptosis. However, most human studies examined the combined effect of DHA and EPA using relatively high daily amounts of n-3 PUFA. The present study investigated the effects of increasing doses of DHA added to the regular diet of human healthy volunteers on lymphocyte response to tetradecanoylphorbol acetate plus ionomycin activation, and on monocyte apoptosis induced by oxidized LDL. Eight subjects were supplemented with increasing daily doses of DHA (200, 400, 800, 1600 mg) in a TAG form containing DHA as the only PUFA, for 2 weeks each dose. DHA intake dose-dependently increased the proportion of DHA in mononuclear cell phospholipids, the augmentation being significant after 400 mg DHA/d. The tetradecanoylphorbol acetate plus ionomycin-stimulated IL-2 mRNA level started to increase after ingestion of 400 mg DHA/d, with a maximum after 800 mg intake, and was positively correlated (P < 0.003) with DHA enrichment in cell phospholipids. The treatment of monocytes by oxidized LDL before DHA supplementation drastically reduced mitochondrial membrane potential as compared with native LDL treatment. Oxidized LDL apoptotic effect was significantly attenuated after 400 mg DHA/d and the protective effect was maintained throughout the experiment, although to a lesser extent at higher doses. The present results show that supplementation of the human diet with low DHA dosages improves lymphocyte activability. It also increases monocyte resistance to oxidized LDL-induced apoptosis, which may be beneficial in the prevention of atherosclerosis