Xavier Michel

Polycyclic aromatic hydrocarbon (PAH) burden of mussels (Mytilus sp.) in different marine environments in relation with sediment PAH contamination, and bioavailability

Abstract Sediments and mussels (Mytilus edulis, Mytilus galloprovincialis) were sampled in different European coastal environments (Germany, France, Spain) and analysed for their polycyclic aromatic hydrocarbon (PAH) content by Gas Chromatography/Mass Spectrometry (GC-MS). Bioaccumulation factors of individual compounds from the sediment were calculated and discussed according to the compound solubility. The mussels showed different accumulation patterns according to the pollution source they were exposed to (dissolved fraction of PAHs, particulate fraction, petroleum present in the water column). The exposure source also depends on the geographical location of the mussels. In the Mediterranean Sea, the bivalves were mainly exposed to the dissolved fraction of PAHs, while in the Baltic Sea and in the Atlantic Ocean, the PAHs associated to the particles were significant sources.

Benzo(a)pyrene hydroxylase activity in the marine mussel Mytilus galloprovincialis: a potential marker of contamination by polycyclic aromatic hydrocarbon-type compounds

Abstract The aim of this work is to optimize and standardize the incubation conditions necessary to determine benzo(a)pyrene hydroxylase (BPH) activity in mussel microsomes. Evidence is presented that the reaction is dependent on NADPH and linear with time, at least up to the incubation time used. To measure BPH activity with the highest efficiency, the concentrations of benzo(a)pyrene (70 μM) microsomal proteins (0–75 mg/0–8 ml) and NADPH (0.74 mM), and the incubation time (10 min) were optimized to avoid plateauing of the activity due to a lack of substrate or NADPH. The best compromise between signal/noise ratio and linearity of the reaction with time was considered. BPH induction in mussels treated with 3-methylcholanthrene or exposed to field contamination by polycyclic aromatic hydrocarbons (PAH)-type compounds demonstrated the ability of this technique to be a potential marker of exposure to PAH type compound.

Responses of antioxidants and lipid peroxidation in mussels to oxidative damage exposure.

1. The aim of this work was to evaluate the relationships between free radical scavengers and lipid peroxidation in the common mussel Mytilus edulis. 2. Mussels were exposed to compounds known for their ability to produce free radicals (carbon tetrachloride, CCl4) and reactive oxygen species via redox cycling (menadione) and the effects on digestive gland, gills and remaining tissues were studied. 3. Lipid peroxidation parameters and the status of free radical scavengers (glutathione, vitamins A, E and C) were affected more by exposure to menadione than to CCl4. 4. The observed changes in the free radical scavengers content are indicative of a role in detoxication of damaging reactive species.

Metabolism and mutagenic activation of benzo(a)pyrene by subcellular fractions from mussel (Mytilus galloprovincialis) digestive gland and sea bass (Discenthrarcus labrax) liver

Abstract 1. The formation of B(a)P diols, phenols and bacterial mutagens by mussel subcellular fractions is dependent on NADPH whereas B(a)P quinones, the major metabolites, appear to be produced by radical reactions and chiefly in the absence of NADPH. 2. B(a)P metabolism in sea bass liver fractions is totally dependent on NADPH and insensitive to radical scavengers excepted tocopherol inhibition of B(a)P mutagenesis. 3. The 9–10 and 7–8 epoxides formed by sea bass microsomes have a high affinity for EH which readily metabolized all those epoxides to diols. 4. Alpha-naphtoflavone inhibits sea bass B(a)P metabolism at high concentration (100 μM) whereas it increases it at low concentration (20 μM).

Characterisation, tissue distribution and sexual differences of some parameters related to lipid peroxidation in mussels

Abstract The aim of this work is to provide a baseline study of the lipid peroxidation mechanisms on five tissues (digestive gland, gills, mantle, feet and adductor muscle) of the mussel, Mytilus galloprovincialis collected at the entry of the Arcachon Bay in October (spawning season). We measured (1) enzymatic activities (cytochrome P-450, NADPH-cytochrome c reductase) that act as initiators of the peroxidative chain in the lipid membranes in producing damaging free radicals, (2) scavengers of these reactive compounds (glutathione, vitamins A, E and C) and (3) the resulting lipid peroxidation in vitro (malonaldehyde production). Results presented here show that small differences exist in the tissue distribution of these systems between males and females. Moreover, the sensitivity to lipid peroxidation is lower in gills and muscles (feet and adductor muscles) than in digestive gland and mantle. We observe too, that vitamin levels are higher in gills and digestive gland than in muscle. In comparison with the rat liver, digestive gland microsomes of mussels present more polyunsaturated fatty acids and the rate of lipid peroxidation is lower. In conclusion, we found that the systems controlling lipid peroxidation were present in the mussel tissues; their efficiency led to a rate of lipid peroxidation reaching the level measured in rat tissues.

Cytochrome P450 Dependent Activities in Mussel and Fish from Coastal Marine Environment: Field Studies on the French Coast of the Mediterranean Sea

Abstract Hepatic cytochrome P450 monooxygenase activities including Benzo(a)pyrene hydroxylase (BPH), biomarker of exposure to polycyclic hydrocarbons (PAH) and other organic contaminants like polychlorobiphenyls (PCB) was measured in the microsomal fraction from the fish, Serranus cabrilla (sea comber) liver, and the mussel, Mytilus galloprovincialis, digestive gland. Additionally, ethoxyresorufin-O-deethylase (EROD) activity measurements were made on the same fish samples. The animals were collected from multiple sites on the French Mediterranean coast, exhibiting various degrees of sediment contamination by urban/industrial wastes quantified in term of PAH and PCB sediment content. Mussel BPH, fish BPH and to a lower extent fish EROD activities were tentatively correlated to sediment PAH/PCB content. The presence of low concentration (20 μM) of α-naphthoflavone (ANF) in the assay mixture increased hepatic BPH activity of sea comber. Statistical correlation of hepatic BPH with PAH level in sediment was greater with the presence of ANF. This work demonstrates the potential of mussel to be used in biomonitoring programmes for coastal pollution survey.

Regio-Selective Metabolism of Benzo(a)pyrene by Microsomes from Rat and Sea Bass: Evidences for the Occurrence of the 1-Hydroxybenzo(a)pyrene as a Major Metabolite

Abstract The aim of the study was (i) to improve benzo(a)pyrene (BaP) metabolite analysis, (ii) and to establish that 1-hydroxybenzo(a)pyrene (1-phenol) is a major BaP metabolite produced by vertebrate xenobiotic metabolism. The species studied were sea bass (Discentrarcus labrax) and male wistar rat treated with 3-methylcholanthrene (MC). Comparison of the different conditions concerning the oxidized positions in the BaP molecule, was performed and supported by statistical calculations. BaP 9,10-, 4,5-, 7,8-diols, 1,6-, 3,6-, 6,12-quinones and 9-, 1-, 3-phenols in the elution order are the major BaP metabolites detected with both species. This was confirmed by the retention time of cold standards and by the measurement of the UV spectrum of the 9-, 1- and 3-phenols of BaP extracted from incubations of MC treated rat microsomes in the presence of 1,1,1-trichloro-2-propeneoxide (TCPO), an epoxide hydrolase inhibitor. These results support that cytochrome P450 is able to oxidize BaP in six positions, the 3≫...