Cellular, humoral and molecular responses in rainbow trout (Oncorhynchus mykiss) exposed to a herbicide and subsequently infected with infectious hematopoietic necrosis virus.

Aquatic ecosystems are now chronically polluted by a cocktail of many chemical substances. There is now clear evidence of associations between exposure to pollutants and greater susceptibility to pathogens. The aim of the present study was to characterize the defense capacities of rainbow trout (Oncorhynchus mykiss), chronically exposed to pendimethalin (PD), to subsequent experimental challenge with the infectious hematopoietic necrosis virus (IHNV). Immunological responses were examined at different organizational levels, from individuals to gene expression. No negative effects of PD were noted on the Fulton index nor on the liver or spleen somatic indices (LSI; SSI) before viral infection, but the infectious stress seems to generate a weak but significant decrease in Fulton and LSI values, which could be associated with consumption of energy reserves. During the viral challenges, the distribution of cumulative mortality was slightly different between infected groups. The impact of the virus on fish previously contaminated by PD started earlier and lasted longer than controls. The proportion of seropositive fish was lower in the fish group exposed to PD than in the control group, with similar quantities of anti-IHNV antibodies secreted in positive fish, regardless of the treatment. While no significant differences in C3-1 expression levels were detected throughout the experiment, TNF1&2, TLR3, Il-1ß and IFN expression levels were increased in all infected fish, but the difference was more significant in fish groups previously exposed to herbicide. On the other hand, ß-def expression was decreased in the pendimethalin-IHNV group compared to that in fish only infected by the virus (control-IHNV group).

Proteomic analysis of the European flounder Platichthys flesus response to experimental PAH-PCB contamination.

Platichthys flesus is often used as a sentinel species to monitor the estuarine water quality. In this study, we carried out an experimental contamination of fish using a PAHs/PCBs mixture, which was designed to mimic the concentrations found in the Seine estuary (C1) and 10 times these concentrations (C2). We used a proteomic approach to understand the molecular mechanisms implied in the response of P. flesus to these xenobiotics. We showed that 54 proteins were differentially accumulated in one or several conditions, which 34 displayed accumulation factors higher than two. 18 of these proteins were identified by MALDI TOF-TOF mass spectrometry. The results indicated the deregulation of oxidative stress- and glutathione metabolism-(GST, GPx) proteins as well as of several proteins belonging to the betaine demethylation pathway and the methionine cycle (BHMT, SHMT, SAHH), suggesting a role for these different pathways in the P. flesus response to chemical contamination.

Assessment of the European flounder responses to chemical stress in the English Channel, considering biomarkers and life history traits.

A multi-biomarker approach was developed to evaluate responses of European flounder (Platichthys flesus) in three contrasted estuaries over the English Channel: the Canche (pristine site), Tamar (heavy metals and PAHs contamination) and Seine (heavily pollution with a complex cocktail of contaminants). The condition factor and several biomarkers of the immune system, antioxidant enzymes, energetic metabolism and detoxification processes were investigated in young-of-the-year (0+) and one-year-old (1+) flounder. Results underlined the difference between the pristine site and the Seine estuary which showed a lower condition factor, a modulation of the immune system, a higher Cytochrome C oxidase activity, and an up-regulation of BHMT expression. The moderate biomarker responses in the Tamar fish could be linked to the specific contamination context of this estuary. Flounder life history traits were analyzed by otolith microchemistry, in order to depict how the fish use their habitat and thus respond to chemical stress in estuaries.

Responses of the European flounder (Platichthys flesus) to a mixture of PAHs and PCBs in experimental conditions.

A multibiomarker approach was developed to evaluate the juvenile European flounder responses to a complex mixture of 9 polycyclic aromatic hydrocarbons (PAHs) and 12 polychlorinated biphenyls (PCBs). Exposure was performed through contaminated food pellets displaying: (1) PAH and PCB levels similar to those detected in the heavily polluted Seine estuary, respectively in sediments and in flatfish and (2) ten times these concentrations. Several biomarkers of the immune system (e.g., lysozyme concentration and gene expression of complement component C3 and TNF-receptor), DNA damage (e.g., Comet assay), energetic metabolism (e.g., activity of cytochrome C oxidase), detoxification process (e.g., cytochrome P450 1A1 expression level: CYP1A1; betaine homocysteine methyl transferase expression level: BHMT) were investigated after 14 and 29 days of contamination, followed by a 14-days recovery period. After 29 days of contamination, the detoxification activity (CYP1A1 expression level) was positively correlated with DNA damages; the increase of the BHMT expression level could also be related to the detoxification process. Furthermore, after the recovery period, some biomarkers were still upregulated (i.e., CYP1A1 and BHMT expression levels). The immune system was significantly modulated by the chemical stress at the two concentration levels, and the lysozyme appeared to be the most sensitive marker of the mixture impact.

A multibiomarker approach on the Atlantic tomcod (Microgadus tomcod) in the St. Lawrence Estuary.

A multibiomarker approach was developed on juvenile Atlantic tomcod (Microgadus tomcod) to evaluate the pertinence of this approach for low-cost screening assessment of the environmental quality of various coastal sites within estuaries. Several biometric indices and biomarkers (ethoxyresorufin-O-deethylase (EROD) activity, metallothionein concentration, and immune responses) were investigated on immature and maturing tomcods (≤ 31 months) collected in four environmentally contrasted sites in the St. Lawrence Estuary (SLE). Simultaneous examination of various age classes provides the opportunity to detect short-term responses in sensitive young-of-the-year fish (e.g., EROD induction) and longer-time effects associated with chronic exposure and bioaccumulation (e.g., metallothionein induction). Principal component analysis was helpful to discriminate between responses possibly related to contaminant exposure (EROD, metallothionein) and responses that could be affected by upstream-downstream gradient (immune response, biometric indices). Measurement of a battery of biomarkers in young tomcods at several sites along the shore of the SLE is a low-cost screening investigation useful to identify hot spots requiring further investigation with chemical analysis and additional reference sites.

Phenotypic and genetic differentiation in young-of-the-year common sole (Solea solea) at differentially contaminated nursery grounds.

Growth-related characters, condition factor, and genetic differentiation were investigated for a single cohort of young-of-the-year (YOY) sole within and among nurseries with differing levels of heavy metals (Cd, Cu and Zn) contamination in the two Charentais Straits, Bay of Biscay, France. Analyses were performed when individuals recruited (May), then after a full summer spent in each nursery (October). Levels of phenotypic and genetic diversity were compared, together with genetic differentiation at a candidate metallothionein (MT) locus and three putatively neutral microsatellite loci. No phenotypic or genetic differentiation was detected among nurseries in May, but significant variation at each phenotypic trait and at the multilocus level in October (P < 0.001). Single locus analysis demonstrated that only the MT locus was significantly differentiated among nurseries, whether corrected for null alleles or not (θ=0.0401 and θ(corr.FreeNA)=0.0326, respectively; P < 0.001). Results indicate that phenotypic differences among YOY sole nurseries present a molecular correlate acting at identical spatio-temporal scales among nurseries, potentially reflecting differential selective pressure among nurseries in response to contamination.