IS GLUTATHIONE TRANSFERASE (GST) ACTIVITY IN POSIDONIA OCEANICA A STRESS RESPONSE TO MERCURY EXPOSURE?

International audienceToday, efficient monitoring of the environment is increasingly depend on the use of bio-indicator species. Marine phanerogams, and in particular Posidonia oceanica, would appear to be potentially valuable bioindicators of metal pollutants. Although correlations have been found between the mercury levels accumulated in the plant tissue and the concentrations of this metal in the water column, it would be of interest to identify early signs of the stress response induced by this xenobiotic. Thus, mercury concentrations and GST activity in Posidonia oceanica (L.) Delile from contaminated and pristine sites were measured. These results demonstrate that an increase in mercury level is correlated with an increase in GST activity, particularly in the sheaths of P. oceanica shoots. The sites contaminated by mercury were also those sites for which the highest enzyme activity was recorded. An even better correlation was found between the mercury levels and GST activity, if a 2 mo lag in the effect of mercury on GST activity is assumed

TRIM33 switches off Ifnb1 gene transcription during the late phase of macrophage activation

Despite its importance during viral or bacterial infections, transcriptional regulation of the interferon-β gene (Ifnb1) in activated macrophages is only partially understood. Here we report that TRIM33 deficiency results in high, sustained expression of Ifnb1 at late stages of toll-like receptor-mediated activation in macrophages but not in fibroblasts. In macrophages, TRIM33 is recruited by PU.1 to a conserved region, the Ifnb1 Control Element (ICE), located 15 kb upstream of the Ifnb1 transcription start site. ICE constitutively interacts with Ifnb1 through a TRIM33-independent chromatin loop. At late phases of lipopolysaccharide activation of macrophages, TRIM33 is bound to ICE, regulates Ifnb1 enhanceosome loading, controls Ifnb1 chromatin structure and represses Ifnb1 gene transcription by preventing recruitment of CBP/p300. These results characterize a previously unknown mechanism of macrophage-specific regulation of Ifnb1 transcription whereby TRIM33 is critical for Ifnb1 gene transcription shutdown

Identification of an RNA Polymerase III Regulator Linked to Disease-Associated Protein Aggregation.

Protein aggregation is associated with age-related neurodegenerative disorders, such as Alzheimer's and polyglutamine diseases. As a causal relationship between protein aggregation and neurodegeneration remains elusive, understanding the cellular mechanisms regulating protein aggregation will help develop future treatments. To identify such mechanisms, we conducted a forward genetic screen in a C. elegans model of polyglutamine aggregation and identified the protein MOAG-2/LIR-3 as a driver of protein aggregation. In the absence of polyglutamine, MOAG-2/LIR-3 regulates the RNA polymerase III-associated transcription of small non-coding RNAs. This regulation is lost in the presence of polyglutamine, which mislocalizes MOAG-2/LIR-3 from the nucleus to the cytosol. We then show biochemically that MOAG-2/LIR-3 can also catalyze the aggregation of polyglutamine-expanded huntingtin. These results suggest that polyglutamine can induce an aggregation-promoting activity of MOAG-2/LIR-3 in the cytosol. The concept that certain aggregation-prone proteins can convert other endogenous proteins into drivers of aggregation and toxicity adds to the understanding of how cellular homeostasis can be deteriorated in protein misfolding diseases

Stabilisation des métaux et dégradation biologique des polluants organiques dans un sédiment portuaire contaminé

The management of dredged sediments is problematic in some French regions due to their significant contamination by organic and/or mineral pollutants. In this study, dredged sediment from a seaport was treated by composting and chemical stabilization. Sediment contamination (organic and mineral pollutants) was characterized, and samples (control and stabilized samples) weighing 6 kg were treated with different mineral additives in a small scale pilot. Results show that (i) total flux of pollutants is reduced by half in samples treated with hematite and zero-valent iron, (ii) fine zeolite (clinoptilolite) is unsuitable to stabilize pollutants in the sediment, (iii) composting reduces organotin concentrations between 38 and 91%, and total PAH level at 15%.Le devenir des sédiments est problématique dans certaines régions françaises en raison d’une contamination significative en polluants organiques et/ou minéraux. Dans cette étude, un sédiment de dragage portuaire a été traité par compostage et stabilisation chimique. Après caractérisation de la contamination (teneurs totales en polluants organiques et minéraux), des andains de 6 kg de sédiment ont été traités par différents additifs minéraux en présence d’un sédiment témoin en milieu extérieur. Les résultats montrent que (i) les flux de polluants sont réduits de moitié dans les sédiments traités à l’hématite et au fer zéro, (ii) la zéolithe fine (clinoptilolite) est peu efficace pour la rétention des polluants dans le sédiment, (iii) le compostage permet de réduire entre 38 et 91 % des teneurs en organoétains et 15% des HAPs

Comparison of mineral-based amendments for ex-situ stabilization of trace elements (As, Cd, Cu, Mo, Ni, Zn) in marine dredged sediments: A pilot-scale experiment

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Ex situ remediation of contaminated sediments using mineral additives: Assessment of pollutant bioavailability with the Microtox solid phase test

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Arsenic in marine sediments from French Mediterranean ports: Geochemical partitioning, bioavailability and ecotoxicology

International audienceThis work investigates arsenic mobility, bioavailability and toxicity in marine port sediments using chemical sequential extraction and laboratory toxicity tests. Sediment samples were collected from two different Mediterranean ports, one highly polluted with arsenic and other inorganic and organic pollutants (Estaque port (EST)), and the other one, less polluted, with a low arsenic content (Saint Mandrier port (SM)). Arsenic distribution in the solid phase was studied using a sequential extraction procedure specifically developed for appraising arsenic mobility in sediments. Toxicity assessment was performed on sediment elutriates, solid phases and aqueous arsenic species as single substance using the embryotoxicity test on oyster larvae (Crassostrea gigas) and the Microtox test with Vibrio fischeri. Toxicity results showed that all sediment samples presented acute and sub-chronic toxic effects on oyster larvae and bacteria, respectively. The Microtox solid phase test allow to discriminate As-contaminated samples from the less contaminated ones, suggesting that toxicity of whole sediment samples is related to arsenic content. Toxicity of dissolved arsenic species as single substance showed that Vibrio fischeri and oyster larvae are most sensitive to As(V) than As(III). The distribution coefficient (Kd) of arsenic in sediment samples was estimated using results obtained in chemical sequential extractions. The Kd value is greater in SM (450 L kg(-1)) than in EST (55 L kg(-1)), indicating that arsenic availability is higher for the most toxic sediment sample (Estaque port). This study demonstrates that arsenic speciation play an important role on arsenic mobility and its bioavailability in marine port sediment

The toxicity of composted sediments from Mediterranean ports evaluated by several bioassays

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