Molecular biomarkers of oxidative stress in aquatic organisms in relation to toxic environmental pollutants

Trace element and lipidomic analysis of bottlenose dolphin blubber from the Yucatan coast: Lipid composition relationships

Bottlenose dolphins (Tursiops truncatus) are found in coastal and estuarine ecosystems where they are in continuous contact with multiple abiotic and biotic stressors in the environment. Due to their role as predators, they can bioaccumulate contaminants and are considered sentinel organisms for monitoring the health of coastal marine ecosystems. The northern zonal coast of the Yucatan peninsula of Mexico has a high incidence of anthropogenic activities. The principal objectives of this study were two-fold: 1) to determine the presence of trace metals and their correlation with lipids in bottlenose dolphin blubber, and 2) to use a lipidomics approach to characterize their biological responses. Levels of trace elements (Al, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Pb) were analyzed using ICP-MS and lipids were measured using a targeted lipidomics approach with LC-MS/MS. Spearman correlation analysis was used to identify associations between lipids and trace elements. The influences of gender, stranding codes, presence of stomach content, growth stages and body length were also analyzed. Blubber lipid composition was dominated by triacylglycerols (TAG). Our results demonstrated the presence of heavy-metal elements such as Cd and As, which were correlated with different lipid species, mainly the ceramides and glycerophospholipids, respectively. Organisms with Cd showed lower concentrations of ceramides (CER, HCER and DCER), TAG and cholesteryl esters (CE). Trace elements Cr, Co, As and Cd increased proportionately with body length. This study provides a novel insight of lipidomic characterization and correlations with trace elements in the bottlenose dolphin which might contribute to having a better understanding of the physiological functions and the risks that anthropogenic activities can bring to sentinel organisms from coastal regions.

Impact of Nickel Oxide Nanoparticles (NiO) on Oxidative Stress Biomarkers and Hemocyte Counts of Mytilus galloprovincialis

In this study, the toxic effects of nickel oxide nanoparticles (NiO-NPs) on the model organism Mediterranean mussel (Mytilus galloprovincialis) gill, digestive gland, and hemolymph tissues for 96 h were investigated. Lipid peroxidation (MDA) determination was performed to reveal the oxidative stress generation potential of nanoparticles, and superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), glutathione reductase (GR), and glutathione-S-transferase (GST) enzyme levels were measured to determine antioxidant responses. Lysosomal membrane stability and total hemocyte counts were performed to determine cytotoxic effects. All parameters were altered in different concentrations of NiO-NPs (2, 20, and 200 mg L^-1). The SOD levels increased depending on the concentration (p < 0.05), and the increases in CAT, GPx, and GST levels were lower at 20 mg L^-1 concentration (p < 0.05). There was a slight difference between the exposure and the control groups in terms of GR enzyme. The MDA level increased in parallel with the concentration (p < 0.05), the stability of the cell membrane (p < 0.05), and the number of hemocyte cells decreased as a result of exposure (p < 0.05). The results emphasize that NiO-NPs may have negative effects on the aquatic environment.

Interactive effects of high temperature and pesticide exposure on oxidative status, apoptosis, and renin expression in kidney of goldfish: Molecular and cellular mechanisms of widespread kidney damage and renin attenuation

One of many noteworthy consequences of increasing societal reliance on pesticides is their predominance in aquatic environments. These pernicious chemicals interact with high temperatures from global climate change, heat waves, and natural variations to create unstable environments that negatively impact organisms' health. To understand these conditions, we examined the dose-dependent effects of environmentally relevant pesticide mixtures (metolachlor, linuron, isoproturon, tebuconazole, aclonifen, atrazine, pendimethalin, and azinphos-methyl) combined with elevated temperatures (22 control vs. 32°C for 4-week exposure) on renin, dinitrophenyl protein (DNP, an indicator of reactive oxygen species, ROS), 3-nitrotyrosine protein (NTP, an indicator of reactive nitrogen species, RNS), superoxidase dismutase (SOD, an antioxidant), and catalase (CAT, an antioxidant) expressions in the kidneys of goldfish (Carassius auratus). Histopathological analysis showed widespread damage to kidney tissues in high temperature and pesticide co-exposure groups, including rupture of the epithelial layer, hemorrhaging, and degeneration of tubular epithelium. Quantitative real-time polymerase chain reaction (qRT-PCR) and immunohistochemical analyses demonstrated significant declines in renin receptor-like mRNA and protein expressions in kidney tissues under combined exposure to high temperature and pesticides compared with controls; conversely, expression of DNP, NTP, SOD, and CAT increased in kidney tissues under the same conditions. Apoptotic cells were also increased in co-exposure groups as assessed by in situ terminal deoxynucleotidyl transferase dUTP nick labeling (TUNEL) assay. The enhanced apoptosis in kidneys of heat and pesticides co-exposed fish was associated with increased caspase-3 (a protease enzyme) mRNA levels. Our results demonstrated that high temperature and pesticides induced oxidative/nitrative stress (i.e., ROS/RNS), damaged tissues, increased cellular apoptosis, and suppressed renin expression in kidneys of goldfish.

Difenoconazole causes spleen tissue damage and immune dysfunction of carp through oxidative stress and apoptosis

As the use of pesticides increases year after year, so does the level of residual pesticides in the aquatic environment, posing a serious threat to non-target organisms. Difenoconazole (DFZ), a class of long-lasting fungicides and residues in the marine environment, has been shown to cause damaging effects on different organs of aquatic organisms. However, there is no research on the damage of DFZ to carp spleen tissue. This study aimed to investigate the acute toxic effects of DFZ on the spleen tissue of carp (Cyprinus carpio) by exposing juvenile carp to environmentally relevant concentrations of DFZ. We randomly selected 30 carp, divided them into the Control, Low, and High groups, and then exposed the three groups to 0, 0.488 mg/L DFZ, and 1.953 mg/L DFZ for 96 h respectively. We then investigated the toxic effects caused by DFZ on carp and spleen tissues by detecting changes in spleen histopathologic damage, apoptosis, oxidative stress, inflammation, and blood biochemical parameters. We found that DFZ causes severe histopathology in spleen tissue, including ballooning, structural relaxation, and giant mitochondria. In addition, we found that DFZ caused excessive apoptosis in spleen tissue by TUNEL staining and expression levels of apoptosis-related genes (caspase3, caspase8, caspase9, fas, bax, bcl-2, and p53). The activities and transcript levels of the antioxidant enzymes SOD, CAT, and GSH-Px were significantly down-regulated. In addition, DFZ led to a significant increase in activation of the NF-κB signaling pathway and mRNA levels of pro-inflammatory cytokines il-6, il-1β, and tnf-α, and a substantial decrease in mRNA levels of anti-inflammatory cytokines il-10 and tgf-β1 in spleen tissue. Blood biochemical parameters showed that DFZ exposure significantly reduced erythrocyte, leukocyte, hemoglobin, C3, and IgM levels. Collectively, DFZ exposure induced apoptosis, immunosuppression, oxidative stress, and inflammatory responses in the spleen tissue of carp, resulting in spleen tissue damage.

Effect of sea lice chemotherapeutant hydrogen peroxide on the photosynthetic characteristics and bleaching of the coralline alga Lithothamnion soriferum

The proliferation of sea lice (Lepeophtheirus salmonis) represents a major challenge for the salmonid aquaculture industry in Norway. Hydrogen peroxide (H₂O₂) is a chemotherapeutant frequently used on Norwegian farms, however, its toxicity to non-target benthic species and habitats remains poorly understood. Maerl beds are constructed by the accumulation of non-geniculate coralline algae and provide important ecological functions. Due to the rapid expansion of aquaculture in Norway and the continued use of H₂O₂ as an anti-sea lice treatment, it is crucial to understand the impact of H₂O₂ on the physiology of maerl-forming species. The effects of a 1 h exposure to H₂O₂ on the photophysiology and bleaching of the coralline alga Lithothamnion soriferum were examined here through a controlled time-course experiment. PAM fluorimetry measurements showed that H₂O₂ concentrations ≥ 200 mg l^-1 negatively affected photosystem II (PSII) in thalli immediately after exposure, which was observed through a significant decline in maximum photochemical efficiency (F_v/F_m) and relative electron transport rate (rETR). The negative effects on PSII induced by oxidative stress, however, appear to be reversible, and full recovery of photosynthetic characteristics was observed 48 h to 28 days after exposure to 200 mg H₂O₂ l^-1 and 2000 mg H₂O₂ l^-1, respectively. At 28 days after exposure, there was evidence of two- to four-times more bleaching in thalli treated with concentrations ≥ 200 mg H₂O₂ l^-1 compared to those in the control. This indicates that despite the recovery of PSII, persistent damages can occur on the structural integrity of thalli, which may considerably increase the vulnerability of coralline algae to further exposure to H₂O₂ and other chemical effluents from salmonid farms.

Environmentally relevant concentrations of benzophenones triggered DNA damage and apoptosis in male Chinese rare minnows (Gobiocypris rarus)

Benzophenone-type ultraviolet (UV) filters (BPs) are commonly used as sunscreen agents, fragrance enhancers and plastic additives, and are great threats to aquatic organisms due to their high detected concentrations in the aquatic environment. However, few studies on their toxicity and mechanism in fish have been clearly reported. In this study, Chinese rare minnows (Gobiocypris rarus) were exposed to benzophenone (BP), 2,4-dihydroxybenzophenone (BP-1), and 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid (BP-4) at 5, 50, 500 µg/L for 28 d to assess their toxicity. Transcriptomics screening showed that cell cycle, DNA replication and repair were significantly altered pathways (p < 0.05). The altered transcripts were similar to those identified by RNA-seq. DNA damage and 8-OHdG levels were significantly increased at 50 and 500 μg/L groups (p < 0.05). The DNA methylcytosine level was not significantly changed exposure to BP, BP-1 and BP-4. TUNEL assays indicated that hepatic apoptosis was significantly improved at 500 μg/L BP and BP-4 and 50 and 500 μg/L BP-1 (p < 0.05), with the significantly increasing the activity of caspase-3, -8 and -9 (p < 0.05). Molecular docking analysis revealed that BP, BP-1 and BP-4 could bind differently to caspase-3 through different binding interactions. Therefore, BP-1 induced more serious oxidative DNA damage and apoptosis by activating caspase-3 than BP and BP-4, which will provide theoretical basis and data support for ecological evaluation of aquatic organisms induced by BPs.

Commercial Red Food Dyes Preparations Modulate the Oxidative State in Three Model Organisms (Cucumis sativus, Artemia salina, and Danio rerio)

The growing environmental spreading of food synthetic dyes and bio-colors have the potential for altering organisms’ redox states. Here, three model species for aquatic pollution trials, Cucumis sativus seeds, Artemia salina cysts, and Danio rerio embryos, were short-term exposed to a fixed concentration of the artificial red E124, and two red bio-colors, cochineal E120, and vegan red (VEGR). In the animal models, we evaluated the total reactive oxygen species (ROS) and the susceptibility to in vitro oxidative stress, and in C. sativus, H2O2 production and antioxidant capacity. We also measured organismal performance indices (routine oxygen consumption in the animal models, dark oxygen consumption, and photosynthetic efficiency in C. sativus). In C. sativus, only E124 increased ROS and affected dark oxygen consumption and photosynthetic efficiency, while all dyes enhanced the antioxidant defenses. In the A. salina nauplii, all dyes increased ROS, while E120 and E124 reduced the susceptibility to oxidative stress. In D. rerio, treatments did not affect ROS content, and reduced oxidative stress susceptibility. Our data show that red food dyes affect the redox state of the developing organisms, in which ROS plays a significant role. We suggest a potentially toxic role for red food dyes with environmentally relevant consequences.

Odor-producing response pattern by four typical freshwater algae under stress: Acute microplastic exposure as an example

Algae-induced odor problems in water have been repeatedly occurred concerns for drinking water quality. However, present researches mostly focus on the odor-producing pattern of algae in normal growth, and there is scarce discussion on those under stress. Microplastics (MPs) pollution have been global concern for their negative ecological impacts and frequently co-occurs with odor-producing algal bloom in freshwaters. Thus, this study aimed to elucidate the effects and mechanisms of MPs as an environmental stress on algal odorant production for good illustration of odor-producing response pattern under stress. Variation in MP size (polystyrene microspheres; 100 nm, 1000 nm and 10 μm) had significant effects on odorant formation (β-cycloidal, 2-methylisopropanol, 2,4-heptandienal and 2,4-decadienal) by four freshwater algae (Microcystis aeruginosa, Pseudanabaena sp., Cyclotella meneghiniana and Melosira varians). The size ratio of MPs over cells (SRMC) was proposed to categorize the size-ratio dependent effects on the algal odorant production. Interestingly, when SRMC was in the range of 0.1-1, there were always promoting effects; when SRMC < 0.1 or SRMC > 1, there exhibited inhibiting effects, and the inhibiting effects of SRMC < 0.1 were far more severe than those of SRMC > 1. The promotion on odorant production in the SRMC range of 0.1-1 was mainly attributed to the increase in cellular yield, which was related to the increased odorant precursors derived from the oxidation products of reactive oxygen species (ROS). Alternatively, the inhibition of odorant production caused by MPs with SRMC < 0.1 was the results of simultaneously inhibiting cellular density and cellular yield, which might be attributed to the cellular internalization of MPs, inducing the extensive toxic effects. This study illustrated the possibilities of MPs in impairing the esthetics of the source water and provided guidance for the future algal odor issues under stress.

Metabolomic Profile of the Fungus Cryomyces antarcticus Under Simulated Martian and Space Conditions as Support for Life-Detection Missions on Mars

The identification of traces of life beyond Earth (e.g., Mars, icy moons) is a challenging task because terrestrial chemical-based molecules may be destroyed by the harsh conditions experienced on extraterrestrial planetary surfaces. For this reason, studying the effects on biomolecules of extremophilic microorganisms through astrobiological ground-based space simulation experiments is significant to support the interpretation of the data that will be gained and collected during the ongoing and future space exploration missions. Here, the stability of the biomolecules of the cryptoendolithic black fungus Cryomyces antarcticus, grown on two Martian regolith analogues and on Antarctic sandstone, were analysed through a metabolomic approach, after its exposure to Science Verification Tests (SVTs) performed in the frame of the European Space Agency (ESA) Biology and Mars Experiment (BIOMEX) project. These tests are building a set of ground-based experiments performed before the space exposure aboard the International Space Station (ISS). The analysis aimed to investigate the effects of different mineral mixtures on fungal colonies and the stability of the biomolecules synthetised by the fungus under simulated Martian and space conditions. The identification of a specific group of molecules showing good stability after the treatments allow the creation of a molecular database that should support the analysis of future data sets that will be collected in the ongoing and next space exploration missions.

Dietary gamma-aminobutyric acid (GABA) improves non-specific immunity and alleviates lipopolysaccharide (LPS)-induced immune overresponse in juvenile Chinese mitten crab (Eriocheir sinensis)

Inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is an immunomodulator to inhibit immune-mediated pro-inflammatory response and has been used to treat various immune-related diseases in mammals. However, the immunoregulatory effect of GABA in crustaceans has not been reported. This study evaluates the regulatory effect of dietary GABA supplementation on the innate immune status and immunoregulatory potential in lipopolysaccharide (LPS)-induced immune response in juvenile Eriocheir sinensis. Juvenile crabs were fed with six diets supplemented with graded GABA levels (0, 40, 80, 160, 320 and 640 mg/kg dry matter) for 8 weeks and then 24 h LPS challenge test was carried out. The results showed that dietary GABA supplementation significantly decreased mortality at 4 and 8 weeks. Moreover, the hemocyanin content, acid phosphatase, and alkaline phosphatase activities significantly increased in the crabs fed GABA supplementation compared with the control. On the contrary, the alanine aminotransferase and alanine aminotransferase activities in serum decreased significantly in the GABA supplementation groups compared with the control. Similarly, superoxide dismutase activity, glutathione content, and the transcriptional expression of the antioxidant-related genes and immune-related genes were significantly higher in the GABA supplementation groups than in the control. In addition, the mRNA expressions of anti-lipopolysaccharide factors (ALF 1, ALF 2, ALF 3) and inflammatory signaling pathways related genes (TLR, Myd88, Relish, LITAF, P38-MAPK, ADAM17) were significantly up-regulated in LPS stimulation groups compared with PBS treatment. Meanwhile, pro-apoptosis-related genes' mRNA expressions were significantly up-regulated, and anti-apoptosis-related genes were significantly down-regulated under LPS stimulation compared with PBS treatment. However, GABA pretreatment effectively alleviated LPS-induced immune overresponse and apoptosis. Therefore, this study demonstrates that dietary GABA supplementation could be used as an immunomodulator to improve the non-specific immunity and antioxidant capacity and alleviate the immune-mediated immune overresponse of juvenile E. sinensis.

Ferroptosis and Apoptosis Are Involved in the Formation of L-Selenomethionine-Induced Ocular Defects in Zebrafish Embryos

Selenium is an essential trace element for humans and other vertebrates, playing an important role in antioxidant defense, neurobiology and reproduction. However, the toxicity of excessive selenium has not been thoroughly evaluated, especially for the visual system of vertebrates. In this study, fertilized zebrafish embryos were treated with 0.5 µM L-selenomethionine to investigate how excessive selenium alters zebrafish eye development. Selenium-stressed zebrafish embryos showed microphthalmia and altered expression of genes required for retinal neurogenesis. Moreover, ectopic proliferation, disrupted mitochondrial morphology, elevated ROS-induced oxidative stress, apoptosis and ferroptosis were observed in selenium-stressed embryos. Two antioxidants—reduced glutathione (GSH) and N-acetylcysteine (NAC)—and the ferroptosis inhibitor ferrostatin (Fer-1) were unable to rescue selenium-induced eye defects, but the ferroptosis and apoptosis activator cisplatin (CDDP) was able to improve microphthalmia and the expression of retina-specific genes in selenium-stressed embryos. In summary, our results reveal that ferroptosis and apoptosis might play a key role in selenium-induced defects of embryonic eye development. The findings not only provide new insights into selenium-induced cellular damage and death, but also important implications for studying the association between excessive selenium and ocular diseases in the future.

Impact of P-Chloroaniline on Oxidative Stress and Biomacromolecules Damage in the Clam Ruditapes philippinarums: A Simulate Toxicity Test of Spill Incident

As a hazardous chemical, p-chloroaniline (PCA) shows intensive adsorption and accumulation after entering the aquatic ecosystem, which can be enriched in organisms and cause damage. With the objective of achieving an integrated and mechanistic view of the toxic effects of PCA in the marine sentinel organism Ruditapes philippinarum, Manila clams were exposed to different concentration of PCA (0.5, 2 and 5 mg/L) for 15 days. Focusing on the gills, first targeting the toxic and digestive gland, the metabolic detoxification organ, we detected dose- and time-related changes inantioxidase activities and biomacromolecular damages in treated clams. Glutathione S-transferase (GST) activity and glutathione (GSH) contents were significantly induced, and superoxide dismutase (SOD) activity increased at the beginning of exposure and then decreased. The malondialdehyde (MDA) and protein methylation (PC) contents which represent lipid peroxidation and carbonylation of proteins, increased first with exposure time and then decreased in the digestive gland. DNA strand break levels were consistently higher than those in the control group. The digestive gland showed more sensitivity to the stress of PCA than the gills. GST and MDA in the gill and GST, GSH, SOD, DNA strand break level in the digestive gland showed significant correlation with PCA exposure, which indicated that these parameters can be used as sensitive biomarkers to indicate toxic effects from chloraniline leakage.

Enantioselective toxicity, degradation and transformation of the chiral insecticide fipronil in two algae culture

The occurrence of pesticides and their metabolites in the environment can alter the ecological relationships between aquatic food chains. Fipronil is a broad-spectrum insecticide which release in the environment may harm the non-target organisms. However, the toxicity and biotransformation of its two enantiomers are far from fully understood. The present study aimed to investigate the aquatic toxicity and environmental behavior of fipronil at enantiomeric level using two freshwater algae, Scenedesmus quaclricauda (S. quaclricauda), and Chlorella vulgaris (C. vulgaris) through an integrative approach the transformation process of the individual enantiomer isolated and in racemic form. The 72 h-EC₅₀ values of rac-, R-, S-fipronil varied from 3.27 to 7.24 mg L^-1 with R-fipronil posing a more significant effect on algal growth inhibition. Chlorophyll a was more susceptible to fipronil exposure than chlorophyll b and carotenoids. Enantioselective alterations on physiological and biochemical parameters (chlorophyll a, chlorophyll b, carotenoids, and the activities of antioxidant enzyme catalase (CAT) and superoxide dismutase (SOD)) were also observed. The half-lives (T_1/2) of R-fipronil and S-fipronil in algae culture were 3.4-3.5 d and 4.0-4.9 d, respectively. By the end of the 17-d exposure, the enantiomer fractions (EFs) increased to 0.59, indicating a preferential depuration of R-fipronil. The metabolites monitoring showed the fipronil sulfide was the main metabolite followed by fipronil sulfone. The results revealed that the enantiomers of fipronil pose enantiospecific behaviors induced by these two algae, with the R-enantiomer more toxic to algal growth and favorable in degradation. These analyses are beneficial for understanding the ecological effect of chiral pesticide in aquatic environment, and the enantiomeric differences of the toxicity, degradation and the formation of toxic metabolites could be helpful for the eco-environmental risk evaluation.

Protective efficacy of naringenin against cadmium-induced redox imbalance in Labeo rohita: an integrated biomarker approach

The protective efficacy of dietary naringenin (NG) has been investigated against the toxicity caused by cadmium chloride (CdCl₂) using biomarkers of oxidative stress in the liver, gills and kidney of Labeo rohita. The fish were exposed to environmentally relevant concentrations of CdCl₂ (0.37 and 0.62 mg/L) and simultaneously orally administered with NG (50 mg/kg bw/day) for 60 days. Tissue (gills, liver and kidney) samples were collected on days 15, 30 and 60 of the experiment and analysed for endogenous antioxidants and oxidative stress biomarkers. CdCl₂ exposure for 15 and 30 days induced the development of adaptive mechanism as demonstrated by the enhanced activities of superoxide dismutase, catalase, glutathione peroxidase and glutathione-S-transferase in all three tissues. However, on the 60th day, CdCl₂-induced oxidative damage was stipulated by a decline in the enzyme activities and reduced glutathione (GSH) content significantly (p < 0.05) below control levels along with enhanced levels of lipid peroxidation. Oral administration of NG in toxicant exposed fish significantly restored the altered levels of antioxidants, oxidative enzymes and lipid peroxidation. Besides, integrated biomarker response (IBR) analysis was applied by combining all the biomarkers to indicate the overall stress response index. IBR analysis confirmed the altered levels of biomarkers, the oxidative stress induced by CdCl₂ exposure and the ameliorative potential of NG. The present study suggested that NG might have protective role against Cd-induced oxidative insult which might be ascribed to the ability of NG to chelate metals and scavenge free radicals.

Impacts of tailings of Fundão dam (Brazil) rupture on marine fish: Metals bioaccumulation and physiological responses

This study evaluated the impacts of the mining tailings after the rupture of the Fundão dam on fish communities on the Atlantic Ocean southeast coast. Four sample collections were carried out over two years (2018-2020), in seasonal periods. Omnivorous/herbivorous and carnivorous fish were collected for analysis of metal bioaccumulation, multibiomarkers of environmental contamination and histopathology. Metal bioaccumulation was stronger correlated in carnivorous fish in the dry-2018 collection, besides higher activity of antioxidant enzymes, energy metabolism and higher morphological damage; however, there was less oxidative damage and less metallothioneins induction, and these variables were strongly associated with the wet-2020 collection. In a temporal view, it was possible to observe a reduction in metal levels in fish, except in the mouth of the Doce River. These events can be explained by seasonal natural events, which tend the resuspension and boost metal levels, mainly in the mouth region during the rainy season.

Estrogenic mixtures induce alterations in lipidomic profiles in the gonads of female oysters

This study aimed to reveal possible alterations to lipidomic profiles in Sydney rock oysters, Saccostrea glomerata, exposed to estrogenic mixtures (i.e., estrone, E1; 17β-estradiol, E2; estriol, E3; 17α-ethinylestradiol, EE2; bisphenol A, BPA; 4-t-octylphenol, 4-t-OP; and 4-nonylphenol, 4-NP) at "low" and "high" concentrations, typical of those detected in Australian and global receiving waters. A seven-day acute exposure window exhibited significantly lower abundances of many non-polar metabolites in digestive gland, gills, and gonads. Overall, there was a strong effect of the carrier solvent ethanol (despite a low exposure of 0.0002%), with all solvent containing treatments exhibiting lower abundances of lipidic metabolites, especially in the gill and digestive gland. No significant changes of the lipidome were exhibited in the male gonad by estrogenic exposure. However, in the female gonad, significant reductions of phospholipids and phosphatidylcholine were associated with exposure to high estrogenic mixtures. We hypothesise that the decreases in these phospholipids in the female gonad may be attributable to 1) lower algal consumption and thus lower uptake of lipidic building blocks; 2) a reduction of available substrates for phospholipid and phosphatidylcholine synthesis; and/or 3) induction of reactive oxygen species via estrogen metabolism, which may cause lipid peroxidation and lower abundance of phospholipids.

Metabolomic profiles in relation to benchmark polycyclic aromatic compounds (PACs) and trace elements in two seabird species from Arctic Canada

While exposure of birds to oil-related contaminants has been documented, the related adverse effects this exposure has on Arctic marine birds remain unexplored. Metabolomics can play an important role to explore biologically relevant metabolite biomarkers in relation to different stressors, even at benchmark levels of contamination. The aim of this study was to characterize the metabolomics profiles in relation to polycyclic aromatic compounds (PACs) and trace elements in the liver of two seabird species in the Canadian Arctic. In July 2018, black guillemots (Cepphus grylle) and thick-billed murres (Uria lomvia) were collected by hunters from a region where natural oil seeps occur in the seabed near Qikiqtarjuaq, Nunavut, Canada. A total of 121 metabolites were identified in liver tissue samples using reversed phase and hydrophilic interaction liquid chromatography coupled to high resolution mass spectrometry platforms to detect non-polar and polar metabolites, respectively. Sixty-nine metabolites showed excellent repeatability and linearity and were used to examine possible effects of oil-related contaminants exposure (PACs and trace elements). Metabolites including 3-hydroxy anthranilic acid, adenine, adenosine, adenosine mono-phosphate, ascorbic acid, butyrylcarnitine, cholic acid, guanosine, guanosine mono-phosphate, inosine, norepinephrine and threonine showed significant differences (more than two fold) between the two species. Elevated adenine and adenosine, along with decreased reduced/oxidized glutathione ratio, highlighted the potential for oxidative stress in murres. Lipid peroxidation and superoxide dismutase activity assays also confirmed these metabolomic findings. These results will help to characterize the baseline metabolomic profiles of Arctic seabird species with different foraging behaviour and trace element burden.

Possible enzymatic mechanism underlying chemical tolerance and characteristics of tolerant population in Scapholeberis kingi

To determine the potential effects of pesticides on aquatic organisms inhabiting a realistic environment, we explored the characteristics and mechanisms of chemical tolerance in Scapholeberis kingi(Cladocera). We established a chemical-tolerant population via continuous exposure to pirimicarb, an acetylcholinesterase (AChE) inhibitor, and examined the effects of pirimicarb concentration on the intrinsic growth rates (r) of tolerant cladocerans. We also explored the association between r and feeding rate and tested the involvement of antioxidant enzymes [peroxidase (PO) and superoxide dismutase] and AChE in pirimicarb sensitivity. S. kingi was continuously exposed to lethal and sublethal pirimicarb concentrations (0, 2.5, 5, and 10 µg/L) for 15 generations, and changes (half maximal effective concentration at 48 h, 48 h-EC₅₀) in chemical sensitivity were investigated. In the F14 generation, the sensitivity of the 10 µg/L group was three times lower than that of the control group, suggesting the acquisition of chemical tolerance. Moreover, r was significantly and negatively correlated with 48 h-EC₅₀, suggesting a fitness cost for tolerance. Surprisingly, there was no significant correlation between r and feeding rate. There was a weak but significant positive correlation between each enzyme activity and the 48 h-EC₅₀ value (p < 0.05). Thus, oxidative stress regulation and enhanced AChE may be involved in the acquisition of chemical tolerance in cladocerans. These findings will help elucidate the characteristics and mechanisms of chemical tolerance in aquatic organisms.

Effects of chlorobromoisocyanuric acid on embryonic development and immunotoxicity of zebrafish

Although chlorobromoisocyanuric acid has been widely used in agriculture, its deleterious toxicity on aquatic organisms remains rare. In this study, zebrafish were exposed to chlorobromoisocyanuric acid (0, 30, 40, and 50 mg/L) from 10 to 96 h post-fertilization (hpf). We found a significant reduction in immune cell numbers (neutrophils and macrophages) and the area of thymus at 96 hpf. The expression of immune-related genes and pro-inflammatory cytokines genes were upregulated. Besides, chlorobromoisocyanuric acid triggered neutrophils cell apoptosis. The mRNA and protein levels of pro-apoptotic p53 pathway and the Bax/Bcl-2 ratio further indicated the underlying mechanism. Furthermore, the oxidative stress was observed that the accumulation of reactive oxygen species and malondialdehyde significantly increased. Subsequently, the antioxidant agent astaxanthin significantly attenuated the level of oxidative stress and the dysregulation of inflammatory response. In summary, our results showed that chlorobromoisocyanuric acid induced developmental defects and immunotoxicity of zebrafish, partly owing to oxidative stress and cell apoptosis.

Finding Biomarkers in Antioxidant Molecular Mechanisms for Ensuring Food Safety of Bivalves Threatened by Marine Pollution

Aquaculture production as an important source of protein for our diet is sure to continue in the coming years. However, marine pollution will also likely give rise to serious problems for the food safety of molluscs. Seafood is widely recognized for its high nutritional value in our diet, leading to major health benefits. However, the threat of marine pollution including heavy metals, persistent organic pollutants and other emerging pollutants is of ever-growing importance and seafood safety may not be guaranteed. New approaches for the search of biomarkers would help us to monitor pollutants and move towards a more global point of view; protocols for the aquaculture industry would also be improved. Rapid and accurate detection of food safety problems in bivalves could be carried out easily by protein biomarkers. Hence, proteomic technologies could be considered as a useful tool for the discovery of protein biomarkers as a first step to improve the protocols of seafood safety. It has been demonstrated that marine pollutants are altering the bivalve proteome, affecting many biological processes and molecular functions. The main response mechanism of bivalves in a polluted marine environment is based on the antioxidant defense system against oxidative stress. All these proteomic data provided from the literature suggest that alterations in oxidative stress due to marine pollution are closely linked to robust and confident biomarkers for seafood safety.

Assessing the potential toxicity of paint industry effluents to aquatic organisms using the whole effluent testing (WET) approach

Point source effluent discharges from industries are major sources of pollutants in aquatic ecosystems. In this study, the whole effluent testing approach was used to assess the toxicity of paint industry effluents to fish. Effluents were collected from three paint industries at point of discharge into the environment. Bioassay procedures were used to assess the toxicity of the effluents to fish. Effluent B was the most acutely toxic to the fish with a 96 h LC₅₀ value of 3.50% dilution (v/v). The acute toxicity ranking of the effluents to the fish was B > C > A. Analysis of the biochemical parameters of fish exposed to sublethal dilutions of the effluents showed that the three effluents significantly (p < 0.05) enhanced the activities of liver function enzymes and oxidative stress enzymes in exposed fish. The levels of malondialdehyde, a substrate of oxidative stress, was also significantly (p < 0.05) higher in fish exposed to the effluents (3.87 ± 0.40, 4.99 ± 0.45, and 3.22 ± 0.57 U mg^-1 protein for effluents A, B, and C, respectively) compared to levels in control (1.24 ± 0.31 U mg^-1 protein). Results from this study have established that untreated or poorly treated paint industry effluents can be highly toxic to aquatic organisms, having the potential to disrupt normal functioning of organisms at low concentrations. The study highlights the advantages of whole effluent testing as a method that accurately predicts the toxic potentials of industrial effluents. This is vital for the adequate protection aquatic ecosystems.

Nano-insecticides against the black cutworm Agrotis ipsilon (Lepidoptera: Noctuidae): Toxicity, development, enzyme activity, and DNA mutagenicity

Frequent applications of synthetic insecticides might cause environmental pollution due to the high residue. In addition, increasing insecticide resistance in many insect pests requires novel pest control methods. Nanotechnology could be a promising field of modern agriculture, and is receiving considerable attention in the development of novel nano-agrochemicals, such as nanoinsectticides and nanofertilizers. This study assessed the effects of the lethal and sublethal concentrations of chlorantraniliprole, thiocyclam, and their nano-forms on the development, reproductive activity, oxidative stress enzyme activity, and DNA changes in the black cutworm, Agrotis ipsilon, at the molecular level. The results revealed that A. ipsilon larvae were more susceptible to the nano-forms than the regular forms of both nano chlorine and sulfur within the chlorantraniliprole and thiocyclam insecticides, respectively, with higher toxicities than the regular forms (ca. 3.86, and ca.2.06-fold, respectively). Significant differences in biological parameters, including developmental time and reproductive activity (fecundity and hatchability percent) were also observed. Correspondingly, increases in oxidative stress enzyme activities were observed, as were mutagenic effects on the genomic DNA of A. ipsilon after application of the LC50 of the nano-forms of both insecticides compared to the control. These promising results could represent a crucial step toward developing efficient nanoinsecticides for sustainable control of A. ipsilon.

Targeted and non-targeted analysis of young-of-year smallmouth bass using comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry

Smallmouth bass in the Susquehanna River Basin, Chesapeake Bay Watershed, USA, have been exhibiting clinical signs of disease and reproductive endocrine disruption (e.g., intersex, male plasma vitellogenin) for over fifteen years. Previous histological and targeted chemical analyses have identified infectious agents and pollutants in fish tissues including organic contaminants, mercury, and perfluorinated compounds, but a common causative link for the observed signs of disease across this widespread area has not been determined. This study examines 146 young-of-year smallmouth bass collected from 14 sampling sites in the Susquehanna River Basin, Pennsylvania, USA with varying levels of disease prevalence. Whole fish were extracted by a recently developed modification to the quick, easy, cheap, effective, rugged, and safe extraction method and analyzed by comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry. A targeted analysis was conducted to identify the presence and quantity of 127 known contaminants, including polychlorinated biphenyls, brominated diphenyl ethers, organochlorinated pesticides, and pharmaceutical and personal care products. A non-targeted analysis was conducted on the same data set to identify analytes of interest not included on routine target compound lists. Chromatographic alignment through Statistical Compare (ChromaTOF GC) was followed by Fisher ratio and principal component analysis to reduce the data set from thousands of peaks per sample to a final data set of 65 analytes of interest. Comparisons of these 65 compounds between Normal (no observed health anomalies) and Lesioned (observed health anomaly at time of collection) fish revealed increased levels of three chemical families in Lesioned fish including esters, ketones, and nitrogen containing compounds.

Grape seed alleviates lindane-induced oxidative stress and improves growth performance, caecal fermentation and antioxidant capacity in growing rabbits

This study evaluated the protective effect of grape seed on performance, caecal characteristics, blood metabolites and liver antioxidant status in lindane-treated rabbits. Four-week-old New Zealand White rabbits (n = 96) with an initial body weight of 0.750 ± 0.23 g were randomly divided into four groups (n = 24). One group was the control received only corn oil orally, while group L were received lindane daily via gavage in corn oil (4 mg/kg BW; 1/50 LD₅₀ for oral dose), group GS was treated with 50 g grape seed /kg diet, and group LGS treated with a combination of both L and GS for 98 days. Results revealed that final body weight (FBW), average daily gain (ADG), dry matter intake and feed efficiency (FE) were similar between GS and control groups, and achieved the highest FBW and ADG, and the best FE. Caecum pH of the L group increased, while the caecum pH of the GS group decreased sharply. There was a significant increase in the concentration of total VFA, acetic acid, propionic acid and NH₃ -N in the GS group, but butyric acid level decreased. GS treatment resulted in a significant increase in the concentrations of total protein, albumin and AChE. GPx, GST, CAT and SOD activity decreased, but TBARS activity significantly increased in the group L, while GS caused a significant elevation of antioxidant activity in the liver. These results confirm that the antioxidant compounds present in grape seed can alleviate the oxidative stress caused by lindane-induced hepatotoxicity and could be a useful supplement to maintain health and improve performance in rabbits.

Proanthocyanidins Protect Against Cadmium-Induced Diabetic Nephropathy Through p38 MAPK and Keap1/Nrf2 Signaling Pathways

Diabetic nephropathy (DN) is one of the most devastating complications of diabetes mellitus. Although cadmium (Cd) exposure might be involved in the pathogenesis of DN, the underlying mechanism is still unclear. In this study, we explored the protective effects and possible mechanism of proanthocyanidins (OPC) from grape seed using a mouse model of Cd-induced DN. The successful establishment of this model was verified by analyzing the physiological and biochemical indices of mice, including their body weight and tissue ratio; levels of blood glucose, creatinine, microalbumin, total cholesterol, triglycerides, high-density lipoprotein-cholesterol and low-density lipoprotein-cholesterol; and was based on histopathological examination. Oxidative-antioxidative status, elemental analysis, and key signaling pathway analysis were performed to explore the possible protective mechanism of OPC. The protective effects of OPC and its possible mechanism in preventing the progression of DN were investigated using a multidimensional approach, including its ability in regulating oxidative-antioxidative status (lipid peroxidation, protein carbonyl, superoxide dismutase, and glutathione GST, GSH-Px), metal-binding ability (Cd levels in the kidneys and urine and MT content) and mediation of essential elements (Zn, Ca, Cu, and Fe levels in the kidneys), and activation of the p38 MAPK and Keap1/Nrf2 signaling pathways. OPC exhibited a significant renoprotective effect, attributed to the metal-chelating ability, anti-oxidative effect, and mediation of oxidative stress-related signaling pathway. These results highlight the potential of OPC in preventing or treating DN in humans and suggest the dietary intake of grapes, which are rich in polyphenols, for the prevention of type 2 diabetes mellitus and its complications.

Integration of chemical and biological methods: A case study of polycyclic aromatic hydrocarbons pollution monitoring in Shandong Peninsula, China

Polycyclic aromatic hydrocarbons (PAHs), as persistent toxic substances (PTS), have been widely monitored in coastal environment, including seawater and sediment. However, scientific monitoring methods, like ecological risk assessment and integrated biomarker response, still need massive researches to verify their availabilities. This study was performed in March, May, August and October of 2018 at eight sites, Yellow River estuary (S1), Guangli Port (S2), Xiaying (S3), Laizhou (S4), Inner Bay (S5), Outer Bay (S6), Hongdao (S7) and Hongshiya (S8) of Shandong Peninsula, China. The contents of 16 priority PAHs in local seawater and sediment were determined, by which ecological risk assessment risk quotient (RQ) for seawater and sediment quality guidelines (SQGs) were calculated to characterize the PAHs pollution. Meanwhile, multiple biomarkers in the digestive gland of clam Ruditapes philippinarum were measured to represent different biological endpoints, including ethoxyresorufin-O-deethylase (EROD), glutathione S-transferase (GST), sulfotransferase (SULT), superoxide dismutase (SOD) and lipid peroxidation (LPO), by which integrated biomarker response (IBR) was calculated to provide a comprehensive assessment of environmental quality. Taken together, these results revealed the heaviest pollution at S2 as both PAHs concentrations and biomarkers responses reflected, and supported the integrated biomarker response as a useful tool for marine environmental monitoring, through its integration with SQGs.

Circulating exosome level of indigenous fish may be a novel biomarker for the integrated ecotoxicity effect of water environment

The deficiency of effective biomarker for the toxic effects of water pollutants greatly limits the application of biological monitoring. This study aimed to investigate the possibility of circulating exosomes of indigenous fish acting as biomarker for the ecotoxicity effect of water environment. The Helong Reservoir in Guangzhou, China, was chosen as the investigating field, of which the water quality belongs to Class V (2013) (GB 3838-2002, China). The clean drinking water source of the upper reaches of the Liuxihe Reservoir was selected as the control. Indigenous fishes including Oreochromis niloticus (Nile tilapia), Labeo rohita (Rohu), Carassius auratus (Crucian carp) were sampled during the period from July 2020 to April 2021. Circulating exosomes of fish samples were isolated by using ultracentrifugation, characterized with transmission electron microscopy (TEM) and quantified by using bicinchoninic acid (BCA) assay. Oxidative stress, DNA and chromosome damage in liver, kidney, brain, gill and blood of fish samples were measured. The results showed that there were significant differences in superoxide dismutase (SOD) activity, glutathione (GSH) and malondialdehyde (MDA) contents, DNA and chromosome damage in fish samples between the Helong Reservoir and the control. Interestingly, there were also significant differences in circulating exosome levels of fish samples between them. Our data suggested that circulating exosome level of indigenous fish may be a novel biomarker for the ecotoxicity effects of water environment.

Particulate air-borne pollutants in Port Harcourt could contaminate recreational pools; toxicity evaluation and children's health risk assessment

Air pollution in Port Harcourt metropolis exacerbated by ambient air-borne black soot particles in the past 4 years has become a great concern especially for children who indulge in recreational pools' activities. This study was therefore carried out to evaluate the toxicities of recreational pools in Port Harcourt City and hence perform preliminary health risk assessment. Five recreational pools (4 outdoor and 1 indoor) were used out of the randomly selected 8, from 30 that were identified. Toxicity assessment was carried out using "Ostracods-linked mathematical model" while risk assessment was by analysing protein oxidation and hepatotoxicity in the hepatocytes of exposed rats. Questionnaire-based approach was used to elicit relevant information from children (10-13 years) who consistently engaged in recreational pool activities. The pH and temperature and bacteriological examination of the pools were also carried out. Results show that all the pools were in fairly good sanitary conditions based on the highest mean bacterial counts (2.33±0.57/100 ml), while all were slightly acidic and with normal temperature range. The toxicity indices of outdoor pools (SP 1) and (SP 5) are respectively 20.8 and 49.0 units, while that of outdoor pools (SP 2) and (SP 3) are the same (42.5 units). "No-observed-effect-toxicity" (NOET) was observed for the indoor pool (SP 4). Analysis of the structured questionnaires inferred that none of the children traced has or has had any of the recreational water illnesses. However, results of protein oxidation in rats and hepatotoxicity of rats' hepatocytes suggest that the exposed children may be at oxidative stress-related risks in future especially if the children continue, without adequate precaution, in the use of these pools. It is recommended that further monitoring of these children be continued while measures such as frequent changes of the pool water are ensured.

Study on toxicity effects of environmental pollutants based on metabolomics: A review

In the past few decades, the toxic effects of environmental pollutants on non-target organisms have received more and more attention. As a new omics technology, metabolomics can clarify the metabolic homeostasis of the organism at the overall level by studying the changes in the relative contents of endogenous metabolites in the organism. Recently, a large number of studies have used metabolomics technology to study the toxic effects of environmental pollutants on organisms. In this review, we reviewed the analysis processes and data processes of metabolomics and its application in the study of the toxic effects of environmental pollutants including heavy metals, pesticides, polychlorinated biphenyls, polycyclic aromatic hydrocarbons, polybrominated diphenyl ethers and microplastics. In addition, we emphasized that the combination of metabolomics and other omics technologies will help to explore the toxic mechanism of environmental pollutants and provide new research ideas for the toxicological evaluation of environmental pollutants.

Metal–organic-framework-based photocatalysts for microorganism inactivation: a review

A metal–organic framework (MOF) is a porous coordination material composed of multidentate organic ligands and metal ions or metal clusters.

Genome-wide identification and functional analysis of the glutathione S-transferase (GST) family in Pomacea canaliculata

Cold causes oxidative stress in living organisms, mainly caused by the accumulation of reactive oxygen species (ROS). In the antioxidant defense systems, Glutathione S-transferases (GSTs) play a vital role in the regulation of detoxification and redox balance of ROS. In this study, the P. canaliculata GST gene family were characterized using a genome-wide search of the conserved domain. Phylogenetic tree and domain composition analysis revealed that 30 PcGSTs belong to seven classes, including five in MAPEG, two in Mu, nine in Omega, 11 in Sigma, one in Rho, Theta and Alpha class, respectively. RNA-seq analysis revealed that most PcGSTs localized in mitochondria highly expressed in hepatopancreas, and most PcGSTs localized in cytoplasm highly expressed in kidney. A total of 12 PcGST genes were significantly up-regulated and PcGST12 was significantly down-regulated after cold acclimation. Ten PcGSTs were identified as DEGs under cold stress after cold acclimation. qRT-PCR revealed that the expression level of five PcGST genes were significantly varied during the cold acclimation. The present study investigated the characterization of the P. canaliculata GST gene family, extending our understanding of GST mediated cold acclimation and cold stress-response mechanisms in this invasive snail.

Photo-degradation behavior of seven benzoylurea pesticides with C3N4 nanofilm and its aquatic impacts on Scendesmus obliquus

Present concerns on the residual benzoylurea pesticides (BUPs) are rapidly climbing as their market shares increase and now seven typical compounds were picked to study their photo-degradation behavior and ecological impacts. Carbon nitride (C₃N₄) nanofilm at a thickness of 50-80 nm was built on the glass slides and utilized to evaluate the photostability of pesticides under visible light. The results showed that the nano-C₃N₄ can promote the degradation efficiency of BUPs and it follows the first-order dynamic mechanism. They could be divided into three categories with the substituents and their degradations were discriminated in order of chlorofluoro-, chlorofluoroalkoxy- and chlorofluorophenoxy- substituted ones. Analyzing the intermediates by UHPLC-MS, it can be speculated that the similar pathways came to BUPs such as cleavage of urea-bridge, hydroxylation and dehalogenation. It is attractive that they all passed into a same molecule, 2-fluorobenzamide (m/z, 301.14). Moreover Scendesmus obliquus was applied to indicate the ecological impacts of originals and their photoproducts. Exposed to pesticides, the levels of chlorophyll a demonstrated much more inhibition than chlorophyll b. Lufenuron and chlorfuazuron among seven showed the higher toxicity for algal cells and finally the photodegradation products showed the lowest toxicity. The activities of antioxidant enzymes happened to a significant remedy after photodegradation. It can be concluded that the residual BUPs under visible-light irradiation may degrade through similar pathways and reduce the aquatic toxicity with the presence of C₃N₄ nanofilm.

Molecular characterization of superoxide dismutase and catalase genes, and the induction of antioxidant genes under the zinc oxide nanoparticle-induced oxidative stress in air-breathing magur catfish (Clarias magur)

The deduced amino acid sequences from the complete cDNA coding sequences of three antioxidant enzyme genes (sod1, sod2, and cat) demonstrated that phylogenetically the magur catfish (Clarias magur) is very much close to other bony fishes with complete conservation of active site residues among piscine, amphibian, and mammalian species. The three-dimensional structures of three antioxidant enzyme proteins are very much similar to mammalian counterparts, thereby suggesting the functional similarities of these enzymes. Exposure to ZnO NPs resulted in an oxidative stress as evidenced by an initial sharp rise of intracellular concentrations of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) but decreased gradually at later stages. The level of glutathione (GSH) also increased gradually in all the tissues examined after an initial decrease. Biochemical and gene expression analyses indicated that the magur catfish has the ability to defend the ZnO NP-induced oxidative stress by inducing the SOD/CAT enzyme system and also the GSH-related enzymes that are mediated through the activation of various antioxidant-related genes both at the transcriptional and translational levels in various tissues. Furthermore, it appeared that the stimulation of NO, as a consequence of induction nos2 gene, under NP-induced oxidative stress serves as a modulator to induce the SOD/CAT system in various tissues of magur catfish as an antioxidant strategy. Thus, it can be contemplated that the magur catfish possesses a very efficient antioxidant defensive mechanisms to defend against the oxidative stress and also from related cellular damages during exposure to ZnO NPs into their natural environment.

Acute exposition to Roundup Transorb® induces systemic oxidative stress and alterations in the expression of newly sequenced genes in silverside fish (Odontesthes humensis)

Roundup Transorb® (RDT) is a glyphosate-based herbicide commonly used in agricultural practices worldwide. This herbicide exerts negative effects on the aquatic ecosystem and affects bioenergetic and detoxification pathways, oxidative stress, and cell damage in marine organisms. These effects might also occur at the transcriptional level; however, the expression of genes associated with oxidative stress has not been studied well. Odontesthes humensis is a native Brazilian aquatic species naturally distributed in the habitats affected by pesticides, including Roundup Transorb® (RDT). This study evaluated the toxic effects of short-term exposure to RDT on O. humensis. Moreover, the genes related to oxidative stress were sequenced and characterized, and their expressions in the gills, hepatopancreas, kidneys, and brain of the fish were quantified by quantitative reverse transcription-polymerase chain reaction. The animals were exposed to two environmentally relevant concentrations of RDT (2.07 and 3.68 mg L^-1) for 24 h. Lipid peroxidation, reactive oxygen species (ROS), DNA damage, and apoptosis in erythrocytes were quantified by flow cytometry. The expression of the target genes was modulated in most tissues in the presence of the highest tested concentration of RDT. In erythrocytes, the levels of lipid peroxidation, ROS, and DNA damage were increased in the presence of both the concentrations of RDT, whereas cell apoptosis was increased in the group exposed to 3.68 mg L^-1 RDT. In conclusion, acute exposure to RDT caused oxidative stress in the fish, induced negative effects on cells, and modulated the expression of genes related to the enzymatic antioxidant system in O. humensis.

The effects of ammonia-N stress on immune parameters, antioxidant capacity, digestive function, and intestinal microflora of Chinese mitten crab, Eriocheir sinensis, and the protective effect of dietary supplement of melatonin

Ammonia nitrogen pollution seriously affects the economic benefits of Chinese mitten crab (Eriocheir sinensis) farming. In this study, we first evaluated the protective effects of melatonin (MT) on immune parameters, antioxidant capacity, and digestive enzymes of E. sinensis under acute ammonia nitrogen stress. The results showed that ammonia-N stress significantly decreased the antibacterial ability of crabs, nevertheless MT could significantly improve it under ammonia-N stress (P < 0.05). Ammonia-N group hemolymph antioxidant capacity indicators (T-AOC, T-SOD, GSH-Px) were significantly decreased than control (p < 0.05), while the MT ammonia-N group hemolymph T-SOD activity significantly increased than ammonia-N group (p < 0.05). For hepatopancreas, ammonia-N group GSH-PX activity significantly decreased than control group, but MT ammonia-N group was significant increased than ammonia-N (p < 0.05). Ammonia-N stress has significantly increased the content of MDA in hemolymph and hepatopancreas (p < 0.05), but MT ammonia-N treatment significantly decreased than ammonia-N group (p < 0.05). Compared with the control group, ammonia-N significantly reduced the activities of Trypsin in the intestine and hepatopancreas (p < 0.05), while MT ammonia-N group can significantly improve the intestinal trypsin activity than ammonia-N (p < 0.05). The intestinal microbiota of E. sinensis results showed that ammonia-N stress significantly decreased the relative abundance of Bacteroidetes (p < 0.05). Ammonia-N stress significantly decreased the Dysgonomonas and Rubellimicrobium, and the Citrobacter significantly increased. In summary, melatonin has a protective effect on E. sinensis under ammonia-N stress. Acute ammonia-N stress may lead to the decrease of probiotics and the increase of pathogenic bacteria, which may be closely related to the impairment of digestive function and immune function.

Demonstration of the protective effect of ghrelin in the livers of rats with cisplatin toxicity

Despite the various and newly developed chemotherapeutic agents in recent years, cisplatin is still used very frequently as a chemotherapeutic agent, even though cisplatin has toxic effects on many organs. The aim of our study is to show whether ghrelin reduces the liver toxicity of cisplatin in the rat model. Twenty-eight male Sprague Dawley albino mature rats were chosen to be utilized in the study. Group 1 rats (n = 7) were taken as the control group, and no medication was given to them. Group 2 rats (n = 7) received 5 mg/kg/day cisplatin and 1 ml/kg/day of 0.9% NaCl, Group 3 rats (n = 7) received 5 mg/kg/day cisplatin and 10 ng/kg/day ghrelin, Group 4 rats (n = 7) received 5 mg/kg/day cisplatin and 20 ng/kg/day ghrelin for 3 days. Glutathione, malondialdehyde (MDA), superoxide dismutase (SOD), plasma alanine aminotransferase (ALT) levels, and liver biopsy results were measured in rats. It was determined that, especially in the high-dose group, the MDA, plasma ALT, and SOD levels increased less in the ghrelin group as compared to the cisplatin group, and the glutathione level decreased slightly with a low dose of ghrelin, while it increased with a higher dose. In histopathological examination, it was determined that the toxic effect of cisplatin on the liver was reduced with a low dose of ghrelin, and its histopathological appearance was similar to normal liver tissue when given a high dose of ghrelin. These findings show that ghrelin, especially in high doses, can be used to reduce the toxic effect of cisplatin.

Tartrazine exposure results in histological damage, oxidative stress, immune disorders and gut microbiota dysbiosis in juvenile crucian carp (Carassius carassius)

Tartrazine (TZ) is an azo dye widely used in foods, cosmetics, beverages, textile, and leather. In recent years, there are reports on detecting azo dyes in the aquatic environment, so the impact of these compounds on aquatic organisms could not be ignored. In this study, we aimed to evaluate the adverse effects of TZ exposure on teleosts' embryo development and juvenile's health by using crucian carp (Carassius carassius) as the experimental fish. The results showed that embryos exposed to TZ (0.19, 0.76 and 1.5 mM) exhibited a deformity, delayed egg resorption and decreased fertilization and hatching rate. When the juvenile fish were exposed to TZ at a level higher than those present in water for 30 days caused severe histopathological damages of the gill, intestine, kidney and liver. Antioxidant enzymes (CAT, SOD and GSH-Px) activities in the gill, intestine and liver, exhibited a decreasing trend after TZ exposure, while MDA contents elevated. TZ exposure also resulted in the upregulation of pro-inflammatory cytokines (il1 and il6), lysozymes (lyz), complement component 3 (c3), and β-defensin 3 (defb3). In addition, TZ exposure also affected the intestinal microbiota structure. In summary, the data in the present study indicated that TZ exposure  reduce the embryo fertilization and hatching rate; cause histopathological damage of tissues, trigger oxidative stress, innate immune disorders and dysbiosis of gut microbiota in juvenile crucian carp. Therefore, it is necessary to be informed about the hazards of TZ exposure and the discharge of the dye into waters should be strictly administrated to prevent environmental pollution.

Genomic markers for the biological responses of Triclosan stressed hatchlings of Labeo rohita

Triclosan (TCS) used commonly in pharmaceuticals and personal care products has become the most common pollutant in water. Three-day-old hatchlings of an indigenous fish, Labeo rohita, were given 96h exposure to a nonlethal (60 μg L^-1) and two moderately lethal concentrations (67 and 97 μg L^-1) of TCS and kept for 10 days of recovery for recording transcriptomic alterations in antioxidant/detoxification (SOD, GST, CAT, GPx, GR, CYP1a and CYP3a), metabolic (LDH, ALT and AST) and neurological (AchE) genes and DNA damage. The data were subjected to principal component analysis (PCA) for obtaining biomarkers for the toxicity of TCS. Hatchlings were highly sensitive to TCS (96h LC₅₀ = 126 μg L^-1 and risk quotient = 40.95), 96h exposure caused significant induction of CYP3a, AChE and ALT but suppression of all other genes. However, expression of all the genes increased significantly (except for a significant decline in ALT) after recovery. Concentration-dependent increase was also observed in DNA damage [Tail Length (TL), Tail Moment (TM), Olive Tail Moment (OTM) and Percent Tail DNA (TDNA)] after 96 h. The damage declined significantly over 96h values at 60 and 67 μg L^-1 after recovery, but was still several times more than control. TCS elicited genomic alterations resulted in 5-11% mortality of exposed hatchlings during the recovery period. It is evident that hatchlings of L. rohita are a potential model and PCA shows that OTM, TL, TM, TDNA, SOD and GR (association with PC1 during exposure and recovery) are the biomarkers for the toxicity of TCS. Graphical abstract.

Single and binary-combined toxic effects of acetochlor and Cu2+ on goldfish (Carassius auratus) larvae

Acetochlor and copper are common freshwater pollutants and pose a severe threat to aquatic animals. The toxicity of acetochlor (Ac) and Cu²⁺ toward goldfish larvae was investigated by subjecting the larvae to different concentrations of acetochlor, Cu²⁺, and mixed solutions for 1, 3, and 7 days. The length of goldfish larvae exposed to the 100 μg/L Ac + 100 μg/L Cu²⁺ mixed solution was considerably lower than that of the control on day 3, but there were no significant differences among the other groups. The heart rates of the larvae in 100 μg/L Ac + 100 μg/L Cu²⁺ mixed solution were higher than those of the control group on days 3 and 7. Acetochlor and Cu²⁺ also caused severe damage to the liver and intestine of the larvae, especially in the 100 μg/L Ac + 100 μg/L Cu²⁺ mixed solution group. Indicators related to oxidative stress (hydrogen peroxide, catalase, glutathione peroxidase, and total superoxide dismutase) that could potentially be induced by acetochlor or Cu²⁺ began to increase on day 7, and the enzyme activities of the larvae in the mixed groups were significantly lower than those in the control group. In contrast, the expression levels of the genes related to antioxidant stress were rapidly down-regulated in all groups on the 7th day after exposure. Briefly, the combined toxicity of acetochlor and Cu²⁺ was stronger than that of the single toxicity treatments. Furthermore, toxicity toward larvae in the mixed solution group (100 μg/L Ac + 100 μg/L Cu²⁺) was more obvious.

Physiological role of CYP17A1-like in cadmium detoxification and its transcriptional regulation in the Pacific oyster, Crassostrea gigas

Cadmium (Cd) is one of the most harmful heavy metals due to its persistence and bioaccumulation through the food chains, posing health risks to human. Oysters can bioaccumulate and tolerate high concentrations of Cd, providing a great model for studying molecular mechanism of Cd detoxification. In a previous study, we identified two CYP genes, CYP17A1-like and CYP2C50, that were potentially involved in Cd detoxification in the Pacific oyster, Crassostrea gigas. In this work, we performed further investigations on their physiological roles in Cd detoxification through RNA interference (RNAi). After injection of double-stranded RNA (dsRNA) into the adductor muscle of oysters followed by Cd exposure for 7 days, we observed that the expressions of CYP17A1-like and CYP2C50 in interference group were significantly suppressed on day 3 compared with control group injected with PBS. Moreover, the mortality rate and Cd content in the CYP17A1-like dsRNA interference group (dsCYP17A1-like) was significantly higher than those of the control on day 3. Furthermore, the activities of antioxidant enzymes, including SOD, CAT, GST, were significantly increased in dsCYP17A1-like group, while were not changed in dsCYP2C50 group. More significant tissue damage was observed in gill and digestive gland of oysters in RNAi group than control group, demonstrating the critical role of CYP17A1-like in Cd detoxification. Dual luciferase reporter assay revealed three core regulatory elements of MTF-1 within promoter region of CYP17A1-like, suggesting the potential transcriptional regulation of CYP17A1-like by MTF-1 in oysters. This work demonstrated a critical role of CYP17A1-like in Cd detoxification in C. gigas and provided a new perspective toward unravelling detoxification mechanisms of bivalves under heavy metal stress.

Effects of long-term exposure of Mytilus galloprovincialis to thiacloprid: A multibiomarker approach

Thiacloprid is a neonicotinoid insecticide widely exploited in agriculture and easily mobilized towards aquatic environments by atmospheric agents. However, little information about its toxicological effects on aquatic invertebrate bioindicators is available. In this study, specimens of the mussel Mytilus galloprovincialis were exposed to thiacloprid at environmental (4.5 μg L^-1) and 100 times higher than environmental (450 μg L^-1) concentrations for 20 days. Thiacloprid affected haemolymph biochemical parameters, cell viability in the digestive gland, antioxidant biomarkers and lipid peroxidation in the digestive gland and gills at environmentally relevant concentrations (4.5 μg L^-1). In addition, thiacloprid exposure caused histological damage to the digestive gland and gills. Interestingly, the pesticide was detected at levels equal to 0.14 ng g^-1 in the soft tissues of sentinels exposed for 20 days to 450 μg L^-1 thiacloprid in seawaterμ. Due to its harmful potential and cumulative effects after long-term exposure of M. galloprovincialis, thiacloprid may pose a potential risk to nontarget aquatic organisms, as well as to human health. This aspect requires further in-depth investigation.

The mechanism of apoptosis of Chlamys farreri hemocytes under benzopyrene stress in vitro

Hemocytes are critical to the immune defense system of bivalves, and polycyclic aromatic hydrocarbons (PAHs) can mediate the immunity of bivalves by affecting the apoptosis of hemocytes. However, the underlying mechanism is still unclear. Chlamys farreri, as an important economic bivalve, was selected as the research subject for this experimentation. The hemocytes were exposed to typical PAHs-benzopyrene (B[a]P) in vitro to explore the apoptosis mechanism through detecting oxidative stress and oxidative damage-related indicators, apoptosis pathway factors, and apoptosis rate within 24 h. The results showed that the reactive oxygen species (ROS) and benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) content in hemocytes increased significantly under B[a]P exposure, while antioxidant genes, glutathione peroxidase content and total antioxidant capacity all showed a trend of first rising and subsequent falling. B[a]P also caused serious damage to DNA and lysosomal membrane stability. The proapoptotic factors genes in the mitochondrial apoptosis pathway were significantly up-regulated, and the anti-apoptotic gene Bcl-2 was significantly down-regulated. Besides, mitochondrial membrane potential stability was significantly reduced and caspase 9 enzyme activity was significantly improved with the B[a]P stimulation. The factors of death receptor pathway were also significantly up-regulated by B[a]P. Moreover, the expression levels of Mitogen-Activated Protein Kinases were also induced. The gene expression and enzyme activity of the caspase 3 and the apoptosis rate were significantly increased under B[a]P exposure. In conclusion, these results indicated that ROS was induced by B[a]P, and further triggered the oxidative stress and oxidative damage in hemocytes. B[a]P induced hemocyte apoptosis was mediated by both mitochondrial apoptosis pathway and death receptor apoptosis, and the activation of mitochondrial apoptosis pathway was affected by ROS. In addition, BPDE and MAPKs may play important roles in the B[a]P-mediated apoptosis pathway. This study deepens understanding of the apoptosis pathway and the immunotoxicity mechanism in bivalves hemocytes stimulated by persistent organic pollutants.

DNA oxidative damage in pregnant women upon exposure to conventional and alternative phthalates

Exposure to alternative phthalates and related health effects in pregnant women are rarely reported. Nineteen phthalate metabolites and a DNA oxidative damage biomarker 8-hydroxy-2'-deoxyguanosine (8-OHdG) were determined in urine samples of pregnant women recruited in South China. The detection frequencies and concentration of selected alternative phthalates, i.e., diisononyl phthalate (DiNP), diisodecyl phthalate (DiDP) and di-(2-propylheptyl) phthalate (DPHP) were lower than those of conventional phthalates. However, mono-(6-hydroxy-2-propylheptyl) phthalate, a metabolite of DPHP, was detected in 70% of urine samples (median: 0.13 ng/mL). The estimated daily intakes of conventional plasticizers, including dimethyl phthalate, di-n-butyl phthalate, diisobutyl phthalate and di-(2-ethylhexyl) phthalate (median range: 1.0-3.0 μg/kg_bw/day) were significantly higher than those of DiNP (0.08 μg/kg_bw/day) and DPHP (0.03 μg/kg_bw/day) (p < 0.05). Approximately 24% of pregnant women were at high risk when cumulative risk from exposure to several phthalates was considered. The concentrations of phthalate metabolites and urinary 8-OHdG were significantly correlated with each other (r = 0.206-0.772, p < 0.01), which were further conformed by multiple linear regression analysis (β = 0.168-0.639, p < 0.01). In addition, conventional phthalates were more strongly correlated with 8-OHdG than alternative phthalates (i.e., DiNP, DPHP), partly suggesting the relatively smaller health effects of alternatives due to their low exposure doses and toxicities. These findings suggested that alternative phthalates have entered the human body from consumer products in the study area, and exposure-related risk of DNA oxidative stress was comparatively lower.