Effects of triclosan in the freshwater mussel Dreissena polymorpha: a proteomic investigation

Effects of triclosan on the detoxification system in the yellow catfish (Pelteobagrus fulvidraco): expressions of CYP and GST genes and corresponding enzyme activity in phase I, II and antioxidant system

Triclosan (TCS), a broad-spectrum antibacterial agent widely used in pharmaceuticals and personal case products (PPCPs), has been universally detected in aquatic ecosystem in recent years. Unfortunately, there is limited information about its potential impacts on responses of genes and enzymes related to fish detoxification. In the present work, we cloned CYP3A and alpha-GST of yellow catfish (Pelteobagrus fulvidraco) and tested the transcriptional expression of CYP1A, CYP3A and GST as well as the alterations of their corresponding enzymes, including ethoxyresorufin-O-deethylase (EROD), aminopyrine N-demethylase (APND), erythromycin N-demethylase (ERND), glutathione S-transferase (GST) and catalase (CAT), and also the oxidative product malondialdehyde (MDA) content in the liver of P. fulvidraco exposed to TCS. Amino acids of CYP3A and GST were deduced and phylogenetic tree was constructed respectively. High identity percent was exhibited between P. fulvidraco and other species, such as other fish, birds and mammals. Results indicated that TCS significantly elevated CYP1A and GST but decreased CYP3A expression, EROD activity and MDA content at lower concentrations of TCS at 24h. Moreover, CYP3A and GST were significantly inhibited at 72 h but induced at 168 h at lower concentrations. However, CYP3A was always induced at the highest concentration during the exposure period. Furthermore, CYP3A, GST, GST enzyme and MDA content exhibited a dose-effect relationship to some extent, but no significant responses were observed in ERND, APND and CAT except for individual treatments. Taken together, EROD was the most sensitive to TCS exposure as compared to other enzymes. Meanwhile, mRNA responses were more sensitive in yellow catfish.

Diversity of the molecular responses to separate wastewater effluents in freshwater mussels

The environmental safety of pharmaceutical and personal care products (PPCPs) requires a crucial examination. The aim of this study was to evaluate the responses of biomarkers of stress and toxicity in freshwater mussels to the effect of commonly found PPCPs in wastewater. We treated male mussels Unio tumidus, from an undisturbed site with ibuprofen (IBU, 250 ng L(-1)), triclosan (TCS, 500 ng L(-1)), or estrone (E1, 100 ng L(-1)) for 14 days. Untreated mussels from this site (C) and mussels inhabiting a polluted area (P) were also examined after a similar time of being kept in the laboratory. The consequences of chronic exposure of the mussels in the P-group were reflected in elevated concentrations of oxyradicals (1.4 times), oxidized glutathione (4.3 times), lipofuscin (2.2 times), and DNA-strand breaks in the digestive gland (DG) in comparison to the C-group, higher levels of caspase-3 activity in the DG, and vitellogenin-like proteins in gonads among all studied groups. Exposed mussels demonstrated some common responses with mussels in the P-group: elevated levels of lactate/pyruvate ratio, lipofuscin (IBU and E1), DNA fragmentation (TCS and E1), and caspase-3 activity (TCS and E1). Exposed to PPCPs mussels also showed elevation of ethoxyresorufin-O-deethylase and/or glutathione-S-transferase activity in the DG and a decrease in lysosomal stability in hemocytes (TCS and E1). The TCS group was distinguished by having the highest level of DNA-fragmentation and the lowest concentrations of total glutathione, oxyradicals, lipofuscin, pyruvate, and lactate, reflecting total metabolic depression. These results show that selected PPCPs at low concentrations alter a variety of physiological processes in this animal model system.

Environmental pollutants and lifestyle factors induce oxidative stress and poor prenatal development

Developmental toxicity caused by exposure to a mixture of environmental pollutants has become a major health concern. Human-made chemicals, including xenoestrogens, pesticides and heavy metals, as well as unhealthy lifestyle behaviours, mainly tobacco smoking, alcohol consumption and medical drug abuse, are major factors that adversely influence prenatal development and increase susceptibility of offspring to diseases. There is evidence to suggest that the developmental toxicological mechanisms of chemicals and lifestyle factors involve the generation of reactive oxygen species (ROS) and cellular oxidative damage. Overproduction of ROS induces oxidative stress, a state where increased ROS generation overwhelms antioxidant protection and subsequently leads to oxidative damage of cellular macromolecules. Data on the involvement of oxidative stress in the mechanism of developmental toxicity following exposure to environmental pollutants are reviewed in an attempt to provide an updated basis for future studies on the toxic effect of such pollutants, particularly the notion of increased risk for developmental toxicity due to combined and cumulative exposure to various environmental pollutants. The aims of such studies are to better understand the mechanisms by which environmental pollutants adversely affect conceptus development and to elucidate the impact of cumulative exposures to multiple pollutants on post-natal development and health outcomes. Developmental toxicity caused by exposure to mixture of environmental pollutants has become a major health concern. Human-made chemicals, including xenoestrogens, pesticides and heavy metals, as well as unhealthy lifestyle behaviors, mainly tobacco smoking, alcohol consumption and medical drug abuse, are major factors that adversely influence prenatal development and increase the susceptibility of offspring to development complications and diseases. There is evidence to suggest that the developmental toxicological mechanisms of human-made chemicals and unhealthy lifestyle factors involve the generation of reactive oxygen species (ROS) and cellular oxidative damage. Overproduction of ROS induces oxidative stress, a state where increased generation of ROS overwhelms antioxidant protection and subsequently leads to oxidative damage of cellular macromolecules. Exposure to various environmental pollutants induces synergic and cumulative dose-additive adverse effects on prenatal development, pregnancy outcomes and neonate health. Data from the literature on the involvement of oxidative stress in the mechanism of developmental toxicity following in vivo exposure to environmental pollutants will be reviewed in an attempt to provide an updated basis for future studies on the toxic effect of such pollutants, particularly the notion of increased risk for developmental toxicity due to combined and cumulative exposure to various environmental pollutants. The aims of such studies are to better understand the mechanisms by which environmental pollutants adversely affect conceptus development and to elucidate the impact of cumulative exposures to multiple pollutants on postnatal development and health outcomes.

Analysis of the Dreissena polymorpha gill proteome following exposure to dioxin-like PCBs: mechanism of action and the role of gender

PCBs are a persistent environmental problem due to their high stability and lipophilicity. The non-ortho- and the mono-ortho-substituted PCBs (dioxin-like-PCBs) share a common and well-described toxicity mechanism in vertebrates, initially involving binding to cytosolic AhRs. Invertebrate AhRs, however, show a lack of dioxin binding, and little information is available regarding the mechanism of toxicity of dl-PCBs in invertebrates. In this study, a proteomic approach was applied to analyse the variations in the pattern of the gill proteome of the freshwater mussel Dreissena polymorpha. Mussels were exposed to a mixture of dl-PCBs, and to perform a more in-depth evaluation, we chose to investigate the role of gender in the proteome response by analysing male and female mussels separately. The results revealed significant modulation of the gill tissue proteome: glycolysis and Ca(2+) homeostasis appear to be the main pathways targeted by dl-PCBs. In light of the differences between the male and female gill proteome profiles following exposure to dl-PCBs, further in-depth investigations of the role of gender in the protein expression profiles of a selected biological model are required.

Effect of deltamethrin (pyrethroid insecticide) on two clones of Daphnia magna (Crustacea, Cladocera): a proteomic investigation

Deltamethrin is a class II pyrethroid insecticide commonly used in agriculture. It is hazardous to freshwater ecosystems, especially for the cladoceran Daphnia magna (Straus 1820). The results of our previous studies based on acute and chronic ecotoxicity experiments revealed differences in the sensitivity between two different clones. In this work, to investigate deltamethrin toxicity mechanisms in two clones of D. magna, we used a proteomic approach in order to analyze changes in protein expression profiles after 48 h of exposure. We detected 1339 spots; then applying statistical criteria (ANOVA p<0.001 and minimum fold change 1.5), only 128 spots were significantly different in the normalized volume. Among the preselected proteins there were 88 up-regulated and 40 down-regulated proteins. Results showed differences in sensitivities after deltamethrin exposure between the clones. Moreover, using the 2-DIGE method, proteomic investigation for deltamethrin exposure proved to be a reliable and powerful approach to investigate effects of deltamethrin as part of research for new metabolic and cellular biomarkers. After identification by mass spectrometry, there were 39 proteins recognized and identified, in which 21 and 18 were up- and down-regulated, respectively, in deltamethrin-exposed clone A compared to three other conditions (controls of each clone and deltamethrin-exposed clone 2). Up- and down-regulated proteins belonged to 12 biological processes (i.e. metabolic processes, apoptosis and stimulus response) and 5 molecular functions (i.e. catalytic activity, binding, structural molecular activity, antioxidant and receptor activities). Identification of these deregulated proteins opens a new way in discovering new molecular targets and putative biomarkers in daphnids exposed to deltamethrin.

The added value of proteomics for toxicological studies

Proteomics has the potential to elucidate complex patterns of toxic action attributed to its unique holistic a posteriori approach. In the case of toxic compounds for which the mechanism of action is not completely understood, a proteomic approach may provide valuable mechanistic insight. This review provides an overview of currently available proteomic techniques, including examples of their application in toxicological in vivo and in vitro studies. Future perspectives for a wider application of state-of-the-art proteomic techniques in the field of toxicology are discussed. The examples concern experiments with dioxins, polychlorinated biphenyls, and polybrominated diphenyl ethers as model compounds, as they exhibit a plethora of sublethal effects, of which some mechanisms were revealed via successful proteomic studies. Generally, this review shows the added value of including proteomics in a modern tool box for toxicological studies.

Toxic effects of triclosan on the detoxification system and breeding of Daphnia magna

The toxic effects of different concentrations of Triclosan (TCS) (1-128 μg/L) on Daphnia magna (D. magna) were investigated by acute (48 h) and chronic (21-day) toxicity tests. The response of antioxidase system and Phase I metabolism process of D. magna exposed to TCS were investigated by measuring a series of biomarkers including glutathione S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), malondialdehyde (MDA), 7-ethoxyresorufin O-deethylase (EROD), Erythromycin N-demethylase (ERND) and Aminopyrine N-demethylase (APND). The 48 h LC50 of TCS was 330 μg/L for D. magna. In the chronic test, total number of neonates per female, body length and the intrinsic rate of natural increase (r) of D. magna increased at the low exposure concentrations (1-16 μg/L) and decreased at the high concentrations (64-128 μg/L), while the total number of molting per adult decreased continually. The GST and CAT activities showed no significant increase in all treatments, and SOD activities were induced after 24-h exposure and inhibited after 48-h exposure at 4-128 μg/L of concentrations. The MDA content increased after 6-h exposure but decreased after 48-h exposure at 4-128 μg/L. EROD activities initially increased after 6-h exposure, but decreased after 24 and 48-h exposure, ERND and APND activities showed a similar temporal pattern among different treatments groups. SOD, MDA and APND were sensitive to TCS, thus they are suitable as potential biomarkers for the exposure to TCS.