Assessment of the mechanisms of detoxification of chemical compounds and antioxidant enzymes in the digestive gland of mussels, Mytilus galloprovincialis, from Mediterranean coastal sites

Glutathione S-transferase, glutathione peroxidase and acetylcholinesterase activities in mussels transplanted to harbour areas

As part of an integrative monitoring campaign involving water and sediment chemistry, in situ bioassays, and mussel bioaccumulation and biomarkers, Mytilus galloprovincialis mussels of standard size were transplanted from a clean location to five sites in two important harbours from the Atlantic coast of Spain (Vigo and Pasaia). After a 30-day field exposure, the concentrations of major contaminants (trace metals, polychlorinated biphenyls and polycyclic aromatic hydrocarbons) accumulated in mussel tissues were measured at each site, and a mussel bioaccumulation index (MBI) was calculated. The enzymatic activity levels of glutathione S-transferase (GST), glutathione peroxidase (GPx) and acetylcholinesterase (AChE) were quantified in the gills of transplanted mussels (n=12). Mussels from the most polluted sites consistently exhibited significantly higher GST and GPx activities compared to the control site, whereas AChE activity was significantly inhibited. The responses of the GST and GPx activities were related to MBI, trace metals and PAH concentrations in mussels, whereas AChE activity was related to the trace metals concentrations in mussels. The above results suggest that GST and AChE activities can be used as potential biomarkers for active monitoring in marine coastal ecosystems. However, at this moment, GPx activity is not robust enough to be applicable to harbour areas.

Differential ABCB and ABCC gene expression and efflux activities in gills and hemocytes of Mytilus galloprovincialis and their involvement in cadmium response

The aim of the study was to characterize ABC transport proteins gene expression and efflux activities in gills and hemocytes of the Mediterranean mussel and to evaluate their response to Cd. At basal level a higher expression of abcb-like gene was observed in gills than in hemocytes while abcc-like gene showed similar levels. Both P-gp and MRPs inhibitors (cyclosporine and MK571) blocked efflux activities in gills; hemocytes were sensitive only to MK571. After 120 min in vitro pre-exposure to CdCl2, the efflux activity increased significantly in gills and hemocytes. In vivo exposure to CdCl2 (0.4 μM) increased abcb-like gene expression in gills without affecting efflux activity. In hemocytes abcc-like gene resulted up-regulated and Ca-AM efflux resulted enhanced. An increased uptake of Cd in gills biopsies was observed in the presence of both P-gp and MRPs inhibitors. Our results indicate that ABC transporters seem involved in the first protective response to Cd and this response is tissue-specific.

Contamination by hazardous substances in the Gulf of Naples and nearby coastal areas: a review of sources, environmental levels and potential impacts in the MSFD perspective

During the 7th FW EU Programme, a large group of research institutions with a strong tradition in marine science designed PERSEUS, a policy-oriented, marine research project aimed at identifying human-derived pressures and their impacts in the Southern European Seas. PERSEUS is about gathering and analyzing the data on our marine ecosystems and developing recommendations to assist policy makers in the implementation of the Marine Strategy Framework Directive (MSFD). In its initial phase, the project focuses on the analysis and evaluation of human pressures in selected coastal areas across the Mediterranean and Black Seas. This paper reports on the results about the chemical pollution pressure in the Gulf of Naples, one of the sites selected for the analysis, and surrounding waters of the Southern Tyrrhenian Sea. Based on a systematic up-to-date literature review, the paper brings together for the first time the available information on the presence, severity and distribution of contaminants on the site. In spite of methodological and sampling heterogeneity among studies, this review compiles the data in a harmonized and effective way, so that the current status, knowledge gaps and research priorities can be established. Thus, the review wishes not only to provide a contribution to the scientific community, but also to help to extract recommendations for mitigating pollution sources and risks in the area of concern. A similar process of analysis may be carried out for other areas and pressures in order to facilitate policy making at the European level.

Comparative DNA damage and oxidative effects of carcinogenic and non-carcinogenic sediment-bound PAHs in the gills of a bivalve

Polycyclic aromatic hydrocarbons (PAHs) regarded as carcinogenic and non-carcinogenic to humans are ubiquitous hydrophobic pollutants that tend to be trapped in aquatic sediments. As a consequence of their acknowledged toxicity and pro-mutagenic or even carcinogenic potential, PAHs are deemed prioritary in biomonitoring programmes. Still, the differences between the toxicity of carcinogenic and non-carcinogenic PAHs are poorly known especially, when aquatic organisms are exposed to ecologically-relevant concentrations of these compounds in sediments. Laboratory bioassays with sediments spiked with phenanthrene (Phe) and benzo[b]fluoranthene (B[b]F), non-carcinogenic and carcinogenic PAH, respectively, were conducted and the effects of exposure (related to DNA damage and oxidative stress) were analyzed in the gills of a burrowing clam, Ruditapes decussatus (Bivalvia, Veneridae). To ensure ecological relevance, two contaminant concentrations (termed "low" and "high") were selected in accordance with available PAH sediment quality guidelines. The results showed that, even in "low" concentrations, both compounds caused a likely genotoxic effect in the gills, which is in accordance with the link between PAHs in water. Glutathione S-transferase activity and glutathione biosynthesis appear to be associated with limited lipid peroxidation even though they were insufficient to prevent higher and faster genotoxicity induced by exposure to the carcinogenic B[b]F, comparative to Phe. Overall the findings indicate that low concentrations of sediment-bound PAHs, carcinogenic or not, may be rendered significantly bioavailable to benthic filter-feeders as to induce genotoxicity, revealing that even PAHs considered non-carcinogenic to humans detain a latent, albeit significant, pro-mutagenic hazard to bivalve molluscs.

Effects of environmental pollution in caged mussels (Mytilus galloprovincialis)

Biological effects of environmental pollution, mainly related to presence of PAHs, were assessed in mussels Mytilus galloprovincialis caged in Priolo, an anthropogenically-impacted area, and Vendicari, a reference site, both located along the eastern coastline of Sicily (Italy). PAHs concentration and histopathological changes were measured in digestive gland tissues. Expression of cytochrome P4504Y1 (CYP4Y1) and glutathione S-transferase (GST), indicative of xenobiotic detoxification, and activity of catalase (CAT) as oxidative stress index, were evaluated. The results show a direct correlation between the high concentrations of PAHs in digestive glands of mussels from Priolo and the significantly altered activity of phase I (P < 0.001) and phase II (P < 0.0001) biotransformation enzymes, along with increased levels of CAT activity (P < 0.05). These findings show the enhancement of the detoxification and antioxidant defense systems. The mussel caging approach and selected biomarkers demonstrated to be reliable for the assessment of environmental pollution effects on aquatic organisms.

Pseudo-basal levels of and distribution of anti-oxidant enzyme biomarkers in Eisenia fetida and effect of exposure to phenanthrene

In the paper, the pseudo-basal levels of anti-oxidant system in different earthworm life stages (juvenile and adult) and the pseudo-basal distribution in different regions of adult earthworms (pre-clitellum, clitellum and post-clitellum) were studied using filter contact tests. The effects of phenanthrene (PHE) at different exposure levels on anti-oxidant enzymes along the earthworm body were also investigated after 24 and 48h of exposure. The pseudo-basal levels of the anti-oxidant enzymes varied during the different growth phase, and results indicated that earthworm has a low oxidative risk and SOD plays important roles during the development whereas CAT and POD are more important in maintain the low ROS level in adult earthworm. The pseudo-basal distribution of the anti-oxidant enzymes along the earthworms was heterogeneous and MDA mainly located in clitellum. POD in pre-clitellum, SOD in clitellum and CAT in post-clitellum were important to eliminate excess total ROS. Time of exposure impacted the anti-oxidant enzyme activities and their distribution patterns along earthworms, from the viewpoint of which supported that exposure time was an environment stress factors. In a short exposure time (24 h), CAT and SOD in the three regions, POD in pre-clitellum and clitellum might be good indicator to a low PHE stress level (0.0629 μg cm(-2) treatments). In a long exposure time (48 h), only SOD in clitellum is a good indicator to both low and high PHE stress (0.629 μg cm(-2) treatments). Earthworm biomembrane system inflicted no oxidative damage until the stress magnitude reached or exceeds the level of exposure in low PHE concentration condition for 48 h.

Assessment of antioxidant responses and trace metal accumulation by digestive gland of ribbed mussel Aulacomya atra atra from Northern Patagonia

Seasonal and spatial variability of trace metal concentrations and of a battery of antioxidant parameters were evaluated in digestive gland of the ribbed mussel Aulacomya atra atra. Fe, Al and Cu accumulated in tissue exhibited maximum values in winter, coinciding partially with the highest labile concentrations of Fe and Cu in sediment. Metals, as other pollutants, are known to influence the oxidative status of organisms and antioxidant enzymes have been often proposed as biomarkers of contaminant effects. Seasonal variations of trace metals did not appear to influence those of biochemical parameters, which generally showed an opposite trend with higher enzymatic activities in summer when trace metal concentrations were lower. Organisms from Punta Cuevas (control site) showed higher induction of reactive oxygen species production than those from both considered impacted sites, suggesting the possibility of some biochemical adaptation in organisms or a higher modulation of environmental and physiological factors on antioxidant responses than levels of trace metals. This study, which is the first in the area in this matter, showed that seasonal variations of potential biomarkers should be incorporated into interpretation of long-term biomonitoring studies in this marine coastal ecosystem.

Comparative study of biochemical and immunological biomarkers in three marine bivalves exposed at a polluted site

A battery of biochemical and immunological biomarkers used for pollution assessment were measured for first time in the clams Venus verrucosa and Callista chione and were compared with those of the mussel Mytilus galloprovincialis, a well-established indicator organism utilized in numerous environmental monitoring programs. Clams and mussel were transplanted at a polluted and a reference site or maintained at the laboratory. Among biochemical biomarkers, acetylcholinesterase did not differ at the polluted site in all species, but there was a significant difference between the mussel and the clams, glutathione S-transferase showed a clear inhibition at the polluted site in all species and a significant difference between the two clams was also indicated, while catalase activities were increased only in V. verrucosa at the polluted site and not in mussel or the other clam. Immunological biomarkers responses were also pronounced at the polluted site. Lysozyme activity was species-dependent whereas respiratory burst activity measured as luminol-dependent chemiluminescence (CL) was site and stimulus dependent, and it was evident in M. galloprovincialis and V. verrucosa and not in C. chione. Further investigation focused on biochemical and immunological biomarkers related with the oxidative mechanisms in clams will strengthen and expand their use as bioindicators for pollution assessment.