Étude de l’effet du cadmium et du benzo[a]pyrène sur des enzymes de phase I et phase II de biotransformation chez le polychète Nereisdiversicolor

Le présent travail reporte l’effet du cadmium (Cd), du benzo[a]pyrène (B[a]P) ainsi que leur mélange (Cd/B[a]P), à 1 µM, sur les activités d’enzymes impliqués dans la phase I et la phase II de biotransformation chez le polychète Nereis diversicolor en fonction du temps (après 12, 24, 36 et 48 h).L’effet d’une contamination aiguë par du cadmium à une dose de 1 µM après 12, 24 et 36 h montre une inhibition de l’activité NADPH cytochrome C réductase chez les individus contaminés comparés à leurs témoins relatifs, alors que le seul effet du cadmium sur l’activité glutathion-S-transférase n’est enregistré qu’après 36 h d’exposition. Quant au benzo[a]pyrène, les résultats montrent une augmentation significative de l’activité NADPH cytochrome C réductase après 12, 24 et 36 h d’exposition, alors que pour l’activité glutathion-S‑transférase, la variation significative entre les animaux témoins et traités n’est enregistrée qu’à 36 h d’exposition. Le mélange (Cd/B[a]P) inhibe l’activité NADPH cytochrome C réductase chez les individus traités par comparaison aux témoins relatifs et montre un effet inducteur sur l’activité GST sauf après 36 h d’exposition. Ces résultats montrent ainsi les interactions entre les polluants ainsi que leurs effets sur les organismes.The acute effects of cadmium and benzo[a]pyrene, individually and as a mixture, were evaluated on the phase I and phase II biotransformation enzymes of Nereis diversicolor (Polychaeta) collected from unpolluted sites. In the acute assay (1 µM) after 12, 24, 36 and 48 h, the comparison between worms exposed to cadmium and their controls showed an inhibited activity of NADPH cytochrome C reductase after 12, 24 and 36 h. For the activity of glutathione-S-transferase (GST), however, inhibition in the presence of Cd was only noted after 36 h of exposure. Although exposure to benzo[a]pyrene resulted in a significant increase in NADPH cytochrome C reductase activity after 12, 24 and 36 h, a significant difference in glutathione-S-transferase (GST) activity between treated and control animals was only observed after 36 h. The mixture (Cd/B[a]P) seemed to inhibit the activity of NADPH cytochrome C reductase and to induce the activity of GST in individuals but only up until 36 h of exposure. These findings illustrate the interactions between pollutants and their effects on organisms

Cholinesterase activity as biomarker of neurotoxicity: utility in the assessment of aquatic environment contamination * Actividade da colinesterase como biomarcador de neurotoxicidade: avaliação da contaminação em ambientes aquáticos ** ** Portuguese Titl

AbstrAct Cholinesterase can take place in aquatic organisms under a series of environmental adverse conditions. The study of cholinesterases in these organisms can give important information about their physiological status and about environmental health. However, it is very important to know how the environmental factors such as fluctuation of physicochemical parameters associated to the presence of pollutants might affect these cholinesterase activities. We studied the response of cholinesterase activity in the caged cockle Cerastoderma glaucum. In addition, we evaluated the potential uses of cholinesterase activity in the common sole, which inhabit the Tunisian coast, subjected to different stress conditions, such as the exposure to different contaminants. This review summarizes the data obtained in some studies carried out in organisms from the Tunisian aquatic environment. Keyword

Metallothionein induction by Cu, Cd and Hg in liver: assessment by RP-HPLC with fluorescent detection and spectrophotometry

International audienc

Dietary supplementation with Aloe vera induces hepatic steatosis and oxidative stress together with a disruption of cellular signaling pathways and lipid metabolism related genes' expression in gilthead sea bream (Sparus aurata).

This study aimed to assess the effects of dietary increasing concentrations of Aloe vera (AV) powder of 0.5%, 2.5% and 5% on the growth performance, hepatic oxidative status, histology, and lipid metabolism and cellular signaling pathways-related genes' expression in gilthead sea bream (Sparus aurata). The preliminary phytochemical analysis revealed the richness of the dried AV extract on total phenol content, total flavonoid content, and condensed tannins when compared to the lyophilized sample. The dried extract showed a good DPPH-radical scavenging activity and its profiling by HPLC-DAD-ESI-MS revealed the presence of anthraquinones namely aloin A, aloin B and their hydroxyl (7-hydroxyaloin A and 7-hydroxyaloin B) and methyl-hydroxy (8-O-methyl-7-hydroxyaloin A and 8-O-methyl-7-hydroxyaloin B) derivatives as well as aloeresin A and B. The AV supplementation in fish diet did not affect growth performance (WG, WGR, and SGR) and feed utilization (FI, FCR, FER), and HSI indexes. However, the hepatic insulin-like growth factors (IGF-I and II) levels were significantly enhanced. Genes' expression levels of enzymes or transcription factors involved in lipolysis (lpl, hsl, and atgl), beta-oxidation (pparα, hadh), fatty acid transporters (cd36, fabp11) and lxrα were significantly down-regulated by the two high concentrations of AV powder. In contrast, fatty acid synthase (fas), a key gene of lipogenesis was significantly up regulated by dietary AV 5% powder supplementation. The induction of fas together with the down-regulation of peroxisome proliferator-activated receptor (pparα) and hydroxyacyl-coenzyme A dehydrogenase (hadh) could explain the lipid accumulation resulting in hepatic steatosis, which was confirmed by histological analysis, since the diets at the two higher concentrations (AV 2.5% and AV 5%) induced a significant increase in the number and diameter of hepatic lipid vacuoles in a dose dependent manner. Moreover, the mRNA levels of protein kinase B named (akt), mammalian target of rapamycin (mtor) and extracellular regulated kinase (erk1/2) involved in cell survival and proliferation were decreased by all AV powder supplemented diets. AV 5% increased catalase and glutathione S transferase activities suggesting a cellular strategy to fight against reactive oxygen species (ROS) accumulation. In conclusion, dietary supplementation with AV 0.5% is recommended for gilthead sea bream feed formulation, as it stimulates the igf-i expression. However, higher levels of AV should be avoided as they might cause lipid metabolism disruption, oxidative stress and liver steatosis