The effects of a primary-treated municipal effluent on the immune system of rainbow trout (Oncorhynchus mykiss): exposure duration and contribution of suspended particles

Assessing Fish Immunotoxicity by Means of In Vitro Assays: Are We There Yet?

There is growing awareness that a range of environmental chemicals target the immune system of fish and may compromise the resistance towards infectious pathogens. Existing concepts to assess chemical hazards to fish, however, do not consider immunotoxicity. Over recent years, the application of in vitro assays for ecotoxicological hazard assessment has gained momentum, what leads to the question whether in vitro assays using piscine immune cells might be suitable to evaluate immunotoxic potentials of environmental chemicals to fish. In vitro systems using primary immune cells or immune cells lines have been established from a wide array of fish species and basically from all immune tissues, and in principal these assays should be able to detect chemical impacts on diverse immune functions. In fact, in vitro assays were found to be a valuable tool in investigating the mechanisms and modes of action through which environmental agents interfere with immune cell functions. However, at the current state of knowledge the usefulness of these assays for immunotoxicity screening in the context of chemical hazard assessment appears questionable. This is mainly due to a lack of assay standardization, and an insufficient knowledge of assay performance with respect to false positive or false negative signals for the different toxicant groups and different immune functions. Also the predictivity of the in vitro immunotoxicity assays for the in vivo immunotoxic response of fishes is uncertain. In conclusion, the currently available database is too limited to support the routine application of piscine in vitro assays as screening tool for assessing immunotoxic potentials of environmental chemicals to fish.

Toxicity of the pharmaceuticals finasteride and melengestrol acetate to benthic invertebrates

The toxicity of endocrinologically active pharmaceuticals finasteride (FIN) and melengestrol acetate (MGA) was assessed in freshwater mussels, including acute (48 h) aqueous tests with glochidia from Lampsilis siliquoidea, sub-chronic (14 days) sediment tests with gravid female Lampsilis fasciola, and chronic (28 days) sediment tests with juvenile L. siliquoidea, and in chronic (42 days) sediment tests with the amphipod Hyalella azteca and the mayfly Hexagenia spp. Finasteride was not toxic in acute aqueous tests with L. siliquoidea glochidia (up to 23 mg/L), whereas significant toxicity to survival and burial ability was detected in chronic sediment tests with juvenile L. siliquoidea (chronic value (ChV, the geometric mean of LOEC and NOEC) = 58 mg/kg (1 mg/L)). Amphipods (survival, growth, reproduction, and sex ratio) and mayflies (growth) were similarly sensitive (ChV = 58 mg/kg (1 mg/L)). Melengestrol acetate was acutely toxic to L. siliquoidea glochidia at 4 mg/L in aqueous tests; in sediment tests, mayflies were the most sensitive species, with significant growth effects observed at 37 mg/kg (0.25 mg/L) (ChV = 21 mg/kg (0.1 mg/L)). Exposure to sublethal concentrations of FIN and MGA had no effect on the (luring and filtering) behaviour of gravid L. fasciola, or the viability of their brooding glochidia. Based on the limited number of measured environmental concentrations of both chemicals, and their projected concentrations, no direct effects are expected by these compounds individually on the invertebrates tested. However, organisms are exposed to contaminant mixtures in the aquatic environment, and thus, the effects of FIN and MGA as components of these mixtures require further investigation.

Genotoxicity and Oxidative Stress in Experimental Hybrid Catfish Exposed to Heavy Metals in a Municipal Landfill Reservoir

This study aimed to investigate the concentrations of Cr, Cd and Pb in the water, sediment and experimental hybrid catfish muscles, and to compare the genetic differentiation and the levels of oxidative stress biomarkers (malondialdehyde and protein carbonyl) between the catfish from the contaminated reservoir near a municipal landfill and the reference area after chronic exposure. The concentrations of all metals in the water and the concentration of Cd in the sediment exceeded Thailand's surface water quality and soil quality standards, respectively, whereas the concentrations of these metals in fish muscles did not exceed Thailand's food quality standards. Dendrogram results in terms of genetic similarity values of the catfish from the reference and the landfill areas were 0.90 to 0.96 and 0.79 to 0.86, respectively, implying that the genetic differentiation of the fish from the landfill was greater than of those from the reference area. The fish in the landfill reservoir had slightly increased protein carbonyl levels. The results indicate that chronic heavy metal exposure can cause genotoxicity of the hybrid catfish and induce protein carbonyl as an oxidative stress biomarker in the reservoir near a municipal landfill.

20 Years of fish immunotoxicology - what we know and where we are

Despite frequent field observations of impaired immune response and increased disease incidence in contaminant-exposed wildlife populations, immunotoxic effects are rarely considered in ecotoxicological risk assessment. The aim of this study was to review the literature on immunotoxic effects of chemicals in fish to quantitatively evaluate (i) which experimental approaches were used to assess immunotoxic effects, (ii) whether immune markers exist to screen for potential immunotoxic activities of chemicals, and (iii) how predictive those parameters are for adverse alterations of fish immunocompetence and disease resistance. A total of 241 publications on fish immunotoxicity were quantitatively analyzed. The main conclusions included: (i) To date, fish immunotoxicology focused mainly on innate immune responses and immunosuppressive effects. (ii) In numerous studies, the experimental conditions are poorly documented, as for instance age or sex of the fish or the rationale for the selected exposure conditions is often missing. (iii) Although a broad variety of parameters were used to assess immunotoxicity, the rationale for the choice of measured parameters was often not given, remaining unclear how they link to the suspected immunotoxic mode of action of the chemicals. (iv) At the current state of knowledge, it is impossible to identify a set of immune parameters that could reliably screen for immunotoxic potentials of chemicals. (v) Similarly, in fish immunotoxicology there is insufficient understanding of how and when chemical-induced modulations of molecular/cellular immune changes relate to adverse alterations of fish immunocompetence, although this would be crucial to include immunotoxicity in ecotoxicological risk assessment.

Are combined AOPs effective for toxicity reduction in receiving marine environment? Suitability of battery of bioassays for wastewater treatment plant (WWTP) effluent as an ecotoxicological assessment

Ecotoxicological assessment of three different wastewater treatment plant (WWTP) effluents D1, D2 and D3 was performed before and after tertiary treatment using combination of advanced oxidation processes (AOPs). A multibarrier treatment (MBT) consisting of microfiltration (MF), hydrogen peroxide photolysis (H2O2/UVC) and catalytic wet peroxide oxidation (CWPO) was applied for all effluents. Sparus aurata, Paracentrotus lividus, Isochrysis galbana and Vibrio fischeri, representing different trophic levels, constituted the battery of bioassays. Different acute toxicity effects were observed in each WWTP effluents tested. The percentage of sea urchin larval development and mortality fish larvae were the most sensitive endpoints. Significant reduction (p < 0.05) of effluent's toxicity was observed using a classification pT-method after MBT process. Base on obtained results, tested battery of bioassays in pT-method framework can be recommended for acute toxicity preliminary evaluation of WWTP effluents for the marine environment.

Exposure of fathead minnows to municipal wastewater effluent affects intracellular signaling pathways in the liver

Municipal wastewater effluent can impact its receiving environment. In the St. Lawrence River, male fish living downstream from Montreal exhibit increased hepatic vitellogenin, intersex, delayed spermatogenesis and altered immune function. Few studies have examined genome-wide effects associated with municipal effluent exposure in fish to decipher the mechanisms of toxicity. The present objective was to identify hepatic cellular signaling pathways in fathead minnows following exposure to municipal wastewater effluent. Immature minnows were exposed for 21 days to either 0% (Control) or 20% municipal effluent, the highest concentration in the St. Lawrence River. Hepatic RNA was extracted and used to hybridize a fathead minnow oligonucleotide microarray containing approximately 15k gene sequences. A total of 1300 genes were differentially expressed, of which 309 genes had more than 2-fold change in expression level between control and MWWE-exposed fish. Of those, 118 were up-regulated and 191 were down-regulated. Altered genes grouped according to function, indicated effects on various signaling pathways, apoptosis, immune responses, and cellular metabolism. Pathway analysis software predicted at least 5 signaling pathways that were altered by treatment: cell adhesion, inflammation, various kinases, estrogen receptor signaling and WNT signaling. Various components of the canonical Wnt pathway were dramatically down-regulated, while several other genes involved in the non-canonical Wnt pathway, such as Wnt4, LRP6, and PPP2R5E, which are known to inhibit the canonical Wnt pathway, were increased. These results indicate that municipal wastewater effluent from Montreal can target and inhibit various signaling including those implicated in hepatic Wnt signaling pathway in fathead minnows.

In vitro immunotoxicity of untreated and treated urban wastewaters using various treatment processes to rainbow trout leucocytes

Municipal effluents are known to impede the immune system of aquatic organisms. The purpose of this study was to examine the immunotoxicity of urban wastewaters before and after 6 treatment processes from 12 cities toward trout leucocytes. Freshly prepared trout leucocytes were exposed to increasing concentrations of solid phase (C18) extracts of wastewaters for 24 hr at 150C. Immunocompetence was determined by following changes in leucocyte viability and the proportion of cells able to ingest at least one (immunoactivity) and at least three (immunoefficiency) fluorescent beads. The influents were treated by six different treatment strategies consisting of facultative aerated lagoons, activated sludge, biological aerated filter, biological nutrient removal, chemically-assisted physical treatment and trickling filter/solid contact. Water quality parameters of the wastewaters revealed that the plants effectively removed total suspended solids and reduced the chemical oxygen demand. The results revealed that the effluents' immunotoxic properties were generally more influenced by the properties of the untreated wastewaters than by the treatment processes. About half of the incoming influents decreased leucocyte viability while 4 treatment plants were able to reduce toxicity. The influents readily increased phagocytosis activity for 8/12 influents while it was decreased in 4/12 influents. This increase was abolished for 4/12 of the effluents using treatments involving biological and oxidative processes. In conclusion, municipal effluents have the potential to alter the immune system in fish and more research will be needed to improve the treatments of wastewaters to better protect the quality of the aquatic environment.

In vitro immunotoxicity of environmentally representative antibiotics to the freshwater mussel Elliptio complanata

The separate and combined in vitro toxic effects of antibiotics (ciprofloxacin, erythromycin, novobiocin, oxytetracycline, sulfamethazole and trimethoprim) commonly found in urban wastewater effluents were assessed on the immune parameters of Elliptio complanata at environmentally relevant concentrations. The observed responses were then compared to those produced by the physicochemical-treated wastewater effluent of a major city before and after the removal of microorganisms. Most of the selected antibiotics, separately and as mixture, induced changes in immune responses. The removal of microorganisms and fine particles from the effluent increased or decreased the resulting immunotoxic effects, depending of the observed parameter. The immunotoxic effects of erythromycin, sulfamethoxazole and trimethoprim were closely associated to the antibiotic mixture and the filtered effluent. In conclusion, the data revealed that the removal of fine particles and microorganisms from municipal effluents can alter the toxic nature of the effluent that is closely associated with the cumulative effects of antibiotics.

Effects of in vivo chronic hydrocarbons pollution on sanitary status and immune system in sea bass (Dicentrarchus labrax L.)

Following the development of an experimental system to expose adult fish to low and stable concentration of pollutant over a prolonged period, the in vivo effects of hydrocarbons on sanitary status, i.e. the health status of fish with regard to chemical pollution, and immune system in sea bass, Dicentrarchus labrax were assessed. A total of 90 fish were acclimated for 15 days, then 45 fish were exposed to the water soluble fraction (WSF) of Arabian crude oil, similar to a complex pollution by hydrocarbons chronically observed in situ in estuaries, while the 45 other control fish sustained the same experimental conditions in clean seawater. After 21 days of exposure, 30 contaminated and control fish were sampled, then 30 other fish were collected after a 15 day recovery period in clean sea water. PAH concentrations in crude oil, WSF, muscles and bile were measured by gas chromatography coupled with mass spectrometry analysis. White blood cell counts and differential leucocyte counts were determined by classical haematology methods. Cell mortality and phagocytosis activity of leucocytes were analyzed by flow cytometry. Haemolytic alternative complement activity and stress parameters were analyzed in blood plasma by spectrophotometry. After a 21 day exposure period to a mixture of 41 parent/alkylated-PAHs (835 ± 52/85 ± 1 5 ng L(-1)). Fish flesh was contaminated by a bioconcentration of naphthalene very closed to the Reference Dose for Oral Exposure estimated by US-EPA's Integrated Risk Information System, causing a potential risk for human consumers. A leucopenia due to a lymphopenia, a rise in leucocyte mortality and a decrease in phagocytosis activity were noted in contaminated fish compared to controls. All these results may be explained by the damage to membrane cells integrity by uptake of PAHs and suggested an impairment of specific and nonspecific immune systems. After a 15 day recovery period, effects were reversible for sanitary status and an offset in immunity was noted by a significant increase in leucocytes in contaminated fish compared to controls.