Chlorpyrifos-induced biomarkers in Japanese medaka (Oryzias latipes)

Ecological risk assessment of pesticides in sediments of Pampean streams, Argentina

After their application in agricultural areas, pesticides are dispersed throughout the environment, causing contamination problems. In Argentina, the main promoter of transgenic biotechnology in the region, the total consumption of agrochemicals has increased significantly in recent years. Most chemicals dumped near surface waters eventually end up in bottom sediments and can be toxic to the organisms that live there. However, published data on the mixing of pesticides in this compartment is still scarce. The objective of this work was to detect and quantify pesticide residues in the sediment of rural streams in the Pampas region and to carry out acute and chronic risk assessment in these aquatic ecosystems. The study area comprises the mountainous system of Tandilia, located in one of the most productive agricultural areas in the country. The concentration of atrazine, acetochlor, chlorpyrifos, cypermethrin, and 2,4-D in the sediment of four rural streams was determined in three different seasons, and the toxic units (TU) and the risk ratios (RQ) were calculated. All the compounds analyzed were detected in most of the sampling seasons and study sites, at concentrations higher than those established in the national and international quality guidelines for the protection of aquatic biota in surface waters and for human consumption. Chlorpyrifos, cypermethrin, and acetochlor were the main pesticides contributing to the TU and RQ values, representing a medium or high ecological risk in most of the sites. Therefore, the evaluation of these pesticides in the bottom sediments could be a decisive factor in assessing the risk to the aquatic environment.

Toxicity effects of hydrophilic algal lysates from Coolia tropicalis on marine medaka larvae (Oryzias melastigma)

Coolia tropicalis is a species of benthic and epiphytic toxic algae, which can produce phycotoxins that intoxicate marine fauna. In this study, the potential toxic effects of C. tropicalis on fish were investigated using larval marine medaka (Oryzias melastigma) as a model to evaluate fish behavior, physiological performance, and stress-induced molecular responses to exposure to two sublethal concentrations (LC₁₀ and LC₂₀) of hydrophilic algal lysates. Exposure to C. tropicalis lysates inhibited swimming activity, activated spontaneous undirected locomotion, altered nerve length ration, and induced early development abnormalities, such as shorter eye diameter, body as well as axon length. Consistent with these abnormalities, changes in the expression of genes associated with apoptosis (CASPASE-3 and BCL-2), the inflammatory response (IL-1β and COX-2), oxidative stress (SOD), and energy metabolism (ACHE and VHA), were also observed. This study advances our understanding of the mechanisms of C. tropicalis toxicity in marine fish in the early life stages and contributes to future ecological risk assessments of toxic benthic dinoflagellates.

Ecotoxico-lipidomics: An emerging concept to understand chemical-metabolic relationships in comparative fish models

Lipids play an essential role in development, homeostatic functions, immune signaling, reproduction, and growth. Although it is evident that changes in lipid biosynthesis and metabolism can affect organismal physiology, few studies have determined how environmental stressors affect lipid pathways, let alone alter global lipid profiles in fish. This is a significant research gap, as a number of environmental contaminants interact with lipid signaling and metabolic pathways. In this review, we highlight the utility of lipidomics as a tool in environmental toxicology, discussing the current state of knowledge regarding chemical-lipidomic perturbations. As with most oviparous animals, the processing and storage of lipids during oocyte development is also particularly important for embryogenesis in fish. Using largemouth bass (Micropterus salmoides) as an example, transcriptomics data suggest that various chemicals alter lipid metabolism and regulation, highlighting the need for more sophisticated investigations into how toxicants impact lipid responses. We also point out the challenges ahead; these include a lack of understanding about lipid processing and signaling in fish, tissue and species-specific lipid composition, and extraneous factors (e.g., nutrition, temperature) that confound interpretation. For example, toxicant exposure can lead to oxidative stress and lipid peroxidation, resulting in complex lipid byproducts that are challenging to measure. With the emergence of lipidomics in systems toxicology, multi-omics approaches are expected to more clearly define effects on physiology, creating stronger linkages between multiple molecular entities (gene-protein-lipid/metabolite). The development and implementation of novel technologies such as ion mobility-mass spectrometry and ozone-induced dissociation support the complete structural elucidation of lipid molecules. This has implications in the adverse outcome pathway framework, which will enhance the application of lipidomics in toxicology by linking these molecular changes to effects at higher levels of biological organization.

Ecotoxicity of chlorpyrifos to aquatic organisms: A review

Pesticides play an important role in promoting agricultural development, while their unreasonable use has led to environmental problems. Chlorpyrifos (CPF), a typical organophosphate pesticide, is used globally as an insecticide in agriculture. The extensive application of CPF has resulted in water contamination, and CPF has been detected in rivers, lakes, seawater, and even in rain. In the present review, CPF was selected due to its extensive use in agriculture and higher detection rate in surface waters. In this review we summarised the evidence related to CPF pollution and focused on discussing the ecotoxicity of CPF to aquatic systems and revealed the mechanism of action of CPF. The aim of this literature review was to summarise the knowledge of the toxicity to marine and freshwater organisms of CPF as well as try to select a series of sensitive biomarkers, which are suitable for ecotoxicological assessment and environmental monitoring in aquatic systems.

Effects of Agricultural Pesticides in Aquafeeds on Wild Fish Feeding on Leftover Pellets Near Fish Farms

Screening has revealed that modern-day feeds used in Atlantic salmon aquaculture might contain trace amounts of agricultural pesticides. To reach slaughter size, salmon are produced in open net pens in the sea. Uneaten feed pellets and undigested feces deposited beneath the net pens represent a source of contamination for marine organisms. To examine the impacts of long-term and continuous dietary exposure to an organophosphorus pesticide found in Atlantic salmon feed, we fed juvenile Atlantic cod (Gadus morhua), an abundant species around North Atlantic fish farms, three concentrations (0.5, 4.2, and 23.2 mg/kg) of chlorpyrifos-methyl (CPM) for 30 days. Endpoints included liver and bile bioaccumulation, liver transcriptomics and metabolomics, as well as plasma cholinesterase activity, cortisol, liver 7-ethoxyresor-ufin-O-deethylase activity, and hypoxia tolerance. The results show that Atlantic cod can accumulate relatively high levels of CPM in liver after continuous exposure, which is then metabolized and excreted via the bile. All three exposure concentrations lead to significant inhibition of plasma cholinesterase activity, the primary target of CPM. Transcriptomics profiling pointed to effects on cholesterol and steroid biosynthesis. Metabolite profiling revealed that CPM induced responses reflecting detoxification by glutathione-S-transferase, inhibition of monoacylglycerol lipase, potential inhibition of carboxylesterase, and increased demand for ATP, followed by secondary inflammatory responses. A gradual hypoxia challenge test showed that all groups of exposed fish were less tolerant to low oxygen saturation than the controls. In conclusion, this study suggests that wild fish continuously feeding on leftover pellets near fish farms over time may be vulnerable to organophosphorus pesticides.

Neurophysiological responses in the brain tissues of rainbow trout (Oncorhynchus mykiss) treated with bio-pesticide

The aim of this study was to investigate neurophysiological responses in rainbow trout brain tissue exposed to natural/botanical pesticides. Fish were exposed to botanical and synthetic pesticides over a 21-day period. At the end of the treatment period, oxidative DNA damage (indicated by 8-OHdG (8-hydroxy-2'-deoxyguanosine), AChE activity (acetylcholinesterase) and transcriptional parameters (gpx (glutathione peroxidase), sod (superoxide dismutase), cat (catalase), HSP70 (heat shock protein 70) and CYP1A (cytochromes P450)) was investigated in control and application groups. Our results indicated that brain AChE activities decreased very significantly in fish treated with both insecticide types when compared with control (p < 0.05). 8-OHdG activity increased in a dose/time-dependent situation in the brain tissues of Oncorhynchus mykiss (p < 0.05). In addition, with regards to gene expression, gpx sod and, cat expressions were down-regulated, whereas CYP1A and HSP70 gene expression were up-regulated in fish treated with both insecticides when compared to the control group (p < 0.05). The data for this study suggests that bio-pesticides can cause neurophysiological changes in fish brain tissue.

Neuroprotective effects of dietary borax in the brain tissue of rainbow trout (Oncorhynchus mykiss) exposed to copper-induced toxicity

We aimed to investigate the modulating effects of dietary borax on the pathways in rainbow trout brain exposed to copper. For this aim, a comprehensive assessment was performed including biochemical (acetylcholinesterase (AChE), malondialdehyde (MDA), oxidative DNA damage (8-hydroxy-2'-deoxyguanosine (8-OHdG), and caspase-3 levels) and transcriptional parameters (heat shock protein 70 (HSP70) and cytochromes P450 (CYP1A), glutathione peroxidase (gpx), superoxide dismutase (sod), and catalase (cat)) parameters and immunohistochemically staining of 8-OHdG. Special fish feed diets were prepared for the trial. These diets contained different concentrations of borax (1.25, 2.5, and 5 mg/kg) and/or copper (500 and 1000 mg/kg) at the period of pre- and co-treatment strategies for 21 days. At the end of the treatment periods, brain tissue was sampled for each experimental group. As a result, the biochemical parameters were increased and AChE activity decreased in the copper and copper-combined groups in comparison with the control group and also with only borax applications (p < 0.05). We observed an increase or decrease in particular biochemical parameters for the borax group in every application and we established that borax had protective effect against copper toxicity by decreasing and/or increasing the relevant biochemical parameters in brain tissue of fish. The biochemical results of borax and its combinations corresponded to the observations of gene expression data, which similarly concluded that HSP70 and CYP1A genes were strongly induced by copper (p < 0.05). In addition, the expression levels of the sod, cat, and gpx genes in the fish brains exposed to borax and the borax combination groups were significantly higher than the only copper-treated groups. In conclusion, borax supplementation provided significant protection against copper-induced neurotoxicity in trout.

Stage-dependent effects of chlorpyrifos on medaka (Oryzias latipes) swimming behavior using a miniaturized swim flume

By considering chlorpyrifos (CPF), an organophosphorus pesticide with known mechanisms of action that affect neurobehavioral development, we assessed the validity and sensitivity of a miniaturized swim flume by investigating the effects of the insecticide on swimming behavior in medaka (Oryzias latipes) fish growing stages. Medaka in three developmental periods, namely 0, 20 and 40 day-old post-hatch (i.e. time points 0, 20 and 40, respectively), were exposed to CPF (12.5, 25, 50 and 100 μg/L) for 48 h under semi-static conditions. The CPF half-lives during exposures were evaluated and the swimming patterns in a flume section (arena) were presented on two-dimensional gradient maps of forced movement of fish against water current. A comparative numerical analysis of fish residence times between each time point control and the corresponding CPF groups was performed by dividing arenas into 15 proportional areas. The time point 0 control group gradient map showed a noticeably different swim pattern from those of the ≥12.5 μg CPF/L groups, which was statistically supported by the differences for residence times seen in ≥12 corresponding areas. The control group gradient maps for time points 20 and 40 differed from those of the respective ≥12.5 μg CPF/L groups. The comparative analysis of the residence times in the corresponding 15 areas revealed differences in ≥5 areas for time point 20 and in ≥3 areas for time point 40. The integrative analysis of the gradient maps and the numerical statistics revealed stage-specific effects and a concentration-response relationship between CPF and alterations on forced medaka swimming despite the dissipation of CPF from the water column. These results indicate the validity of the miniaturized swim flume toward a more environmentally realistic scenario for the evaluation of neurodevelopmental and behavioral toxicity in small fish models.

The single and joint toxicity effects of chlorpyrifos and beta-cypermethrin in zebrafish (Danio rerio) early life stages

Water environment pollution caused by the widespread application of beta-cypermethrin (BCP) and chlorpyrifos (CPF) in agriculture has attracted extensive concern of the world. In this study, zebrafish was used as a model to investigate the individual and joint toxicity of BCP and CPF. In the acute toxicity test, 3 hpf embryos were exposed to various concentrations of CPF, BCP and their binary mixtures (MIX) for 96h. The results indicated that these two pesticides and mixtures induced malformation and death in larvae, and affected hatchability. These two pesticides in mixtures were verified to act together in a synergistic manner under experimental conditions. Oxidative stress assaying manifested that CPF, BCP and MIX altered CAT, SOD and GST activities and MDA content, resulting in oxidative damage in larvae. By pathology analysis, CPF (236μg/L), BCP (5.9μg/L) and MIX (236μg/L CPF+5.9μg/L BCP) were found to trigger liver lesions and promote apoptosis in tissues. The transcriptome sequencing suggested that ECM- receptor interaction, focal adhesion, cell cycle, DNA replication, phototransduction and adherens junction pathways were closely associated with the toxicity of these two pesticides.

Integrated biomarkers induced by chlorpyrifos in two different life stages of zebrafish (Danio rerio) for environmental risk assessment

This study was performed to understand how chlorpyrifos (CHL) affects zebrafish (Danio rerio) embryos and adults, by exposing this model organism to various concentrations of the insecticide. The 96-h acute toxicity test to determine the effect of CHL on adult zebrafish yielded a LC50 of 709.43μg/L(-1). Small molecular weight proteins less than 25kDa and phospholipids were analyzed with MALDI-TOF MS/MS in order to compare expression patterns, revealing that some peaks were dramatically altered after CHL treatment. Whereas no acute toxicity was detected in the embryo toxicity test, malformation of zebrafish larvae was observed, with many individuals harboring curved spines. In an angiogenesis test on larvae of transgenic zebrafish, CHL did not have an inhibitory effect. Relative gene expression analyses using real-time polymerase chain reaction (RT-PCR) of DNA from zebrafish embryos revealed that different subtypes of cytochrome P450 (CYP450), such as CYP1A and CYP3A, were significantly up-regulated in response to CHL at a concentration of 400μg/L(-1) compared to the control. The expression level of NR1I2, a CYP gene transcriptional regulator, UGT1a1, and MDR1 were all up-regulated in the CHL-treated embryos. Finally, the expression level of acetylcholinesterase (AChE) and catalase (CAT) decreased, whereas that of superoxide dismutase (SOD) did not differ significantly. Our results suggest that the up-regulation of metabolic enzymes including CYP450 and MDR1 may be involved in CHL resistance in zebrafish.