Toxic effects of copper sulfate on diploid and triploid fin cell lines in Misgurnus anguillicaudatus

Copper exposure induces mitochondrial dysfunction and hepatotoxicity via the induction of oxidative stress and PERK/ATF4 -mediated endoplasmic reticulum stress

Copper is an essential trace element, and excessive exposure could result in hepatoxicity, however, the underlying molecular mechanisms remain incompletely understood. The present study is aimed to investigate the molecular mechanisms of copper sulfate (CuSO4) exposure-induced hepatoxicity both in vivo and in vitro. In vitro, HepG2 and L02 cells were exposed to various doses of CuSO4 for 24 h. Cell viability, ROS production, oxidative stress biomarkers, mitochondrial functions, ultrastructure, intracellular calcium (Ca2+) concentration, and the expression of proteins related to mitochondrial apoptosis and endoplasmic reticulum (ER) stress were assessed. In vivo, C57BL/6 mice were treated with CuSO4 at doses of 10 and 30 mg/kg BW/day and co-treated with 4-PBA at 100 mg/kg BW/day for 35 days. Subsequently, liver function, histopathological features, and protein expression were evaluated. Results found that exposure to CuSO4 at concentrations of 100-400 μM for 24 h significantly decreased the viabilities of HepG2 and L02 cells and it was in a dose-dependent manner. Additionally, CuSO4 exposure induced significant oxidative stress and mitochondrial dysfunction in HepG2 cells, which were partially ameliorated by the antioxidant N-acetylcysteine (NAC). Furthermore, CuSO4 exposure prominently triggered ER stress, as evidenced by the upregulation of GRP94, GRP78, phosphorylated forms of PERK and eIF2α, and CHOP proteins in livers of mice and HepG2 cells. NAC treatment significantly inhibited CuSO4 exposure -induced ER stress in HepG2 cells. Pharmacological inhibition of ER stress through co-treatment with 4-PBA and the PERK inhibitor GSK2606414, as well as genetic knockdown of ATF4, partially mitigated CuSO4-induced cytotoxicity in HepG2 cells by reducing mitochondrial dysfunction and inhibiting the mitochondrial apoptotic pathway. Moreover, 4-PBA treatment significantly attenuated CuSO4-induced caspase activation and hepatoxicity in mice. In conclusion, these results reveal that CuSO4-induced hepatotoxicity involves mitochondrial dysfunction and ER stress by activating oxidative stress induction and PERK/ATF4 pathway.

Proposing Effective Ecotoxicity Test Species for Chemical Safety Assessment in East Asia: A Review

East Asia leads the global chemical industry, but environmental chemical risk in these countries is an emerging concern. Despite this, only a few native species that are representative of East Asian environments are listed as test species in international guidelines compared with those native to Europe and America. This review suggests that Zacco platypus, Misgurnus anguillicaudatus, Hydrilla verticillata, Neocaridina denticulata spp., and Scenedesmus obliquus, all resident to East Asia, are promising test species for ecotoxicity tests. The utility of these five species in environmental risk assessment (ERA) varies depending on their individual traits and the state of ecotoxicity research, indicating a need for different applications of each species according to ERA objectives. Furthermore, the traits of these five species can complement each other when assessing chemical effects under diverse exposure scenarios, suggesting they can form a versatile battery for ERA. This review also analyzes recent trends in ecotoxicity studies and proposes emerging research issues, such as the application of alternative test methods, comparative studies using model species, the identification of specific markers for test species, and performance of toxicity tests under environmentally relevant conditions. The information provided on the utility of the five species and alternative issues in toxicity tests could assist in selecting test species suited to study objectives for more effective ERA.

Effect of copper sulphate on Cryptocaryon irritans based on metabolome analysis

Cryptocaryon irritans is one of the most harmful marine parasites in mariculture. Copper sulphate is often used to kill parasites and the influence of copper sulphate on the tomont stage of C. irritans was explored in this study. The results showed that excystment rate was not significantly affected when tomonts were exposed to 5 mg/L (76.7%) and 10 mg/L (78.9%) of copper sulphate for 3 h. However, excystment rate was significantly inhibited when exposed to 15 mg/L (33.3%) for 3 h and 5 mg/L (28.9%), 10 mg/L (33.3%) and 15 mg/L (33.3%) for 6 h. After treatment with high concentrations of copper sulphate, the interior of the tomonts was fuzzy under the microscope, and the division process could not be observed. Metabolomic results combined with preliminary transcriptome analysis results showed that the tomonts were induced to produce linoleate, riboflavin, inositol and other substances under the stress of Cu²⁺ , which affected the antioxidant mechanism of the body. Using MDA content determination and antioxidant enzyme activity analysis, copper sulphate was found to cause oxidative damage to tomonts by affecting the generation of metabolites, leading to the death of tomonts.

Oxidative stress, autophagy, and apoptosis induced by doxycycline in loach fin cells in vitro

Cytotoxicity, molecular function disorder, mitophagy, and apoptosis were studied in loach fin cells in vitro after exposure to doxycycline (DOX). The semi-lethal concentration of DOX in loach cells was calculated as 668.96 ± 2.83 mol/L. Loss of cell viability and increases in vacuoles and autolysosomes were evident in cells exposed to DOX at 200 and 400 μmol/L, and apoptotic bodies occurred at 600 μmol/L. In addition, Superoxide Dismutase (SOD), catalase (CAT), Na⁺-K⁺-ATPase, and Ca²⁺-ATPase activities increased significantly in cells exposed to 200 μmol/L DOX, and dose-dependent inhibitory effects on activities were observed in cells exposed to 400 and 600 μmol/L DOX. Quantitative gene expression showed that 400 and 600 μmol/L DOX could induce caspase-3- and caspase-8-mediated apoptosis as well as caspase-activated DNase in loach cells. Transcriptome sequencing in DOX vs. control groups found 16,288 differentially expressed genes, among which protein binding (2633, 31.91%) was the most significant in Gene Ontology terms. Furthermore, 11,930 genes were enriched in 298 Kyoto Encyclopedia of Genes and Genomes (KEGG)pathways. The top three upregulated pathways included "lysosome", "protein processing in endoplasmic reticulum", and "proteasome". FPKM analysis indicated that most genes associated with autophagy and in "protein processing in the endoplasmic reticulum", "TNF signaling pathway", and "NF-kappa B signaling pathway" were upregulated. This suggests that at lower concentrations, DOX induces reactive oxidative species (ROS) in loach fin cells to reduce cell proliferation. ROS in turn stimulate oxidant stress, ion excretion capability and mitophagy to maintain cell homeostasis. Apoptosis was induced in cells subjected to higher concentrations of DOX. The transcriptome data and pathways determined in this study will provide a foundation for the analysis of DOX toxicity in loach cells, which must be examined thoroughly to further understand the cytotoxic mechanism of antibiotics in fish cells.

Cytotoxicity and apoptosis induced by enrofloxacin in loach fin cells in vitro

The cytotoxic effect and cell death were studied in loach fin cells in vitro after enrofloxacin (ENR) exposure. The semi-lethal concentration of ENR for loach cells was calculated as 1296.2 ± 3.11 mol/L (about 512.5 mg/L). Loss of cell viability, increase in vacuoles, disappearance of microvilli, and apoptotic bodies were evident in cells exposed to 400, 800, and 1200 μmol/L ENR. Besides, dose-dependent inhibitory effects on SOD, CAT, Na⁺-K⁺-ATPase, and Ca²⁺-ATPase activities were also observed in loach cells exposed to ENR. Quantitative gene expression results showed that ENR induced caspase-3- and caspase-8-mediated apoptosis as well as caspase-activated DNase in loach cells. The findings also indicated a role of JNK pathway in ENR-induced apoptosis in loach cells. Transcriptome sequencing results showed 10,016 differentially expressed genes in ENR vs. control groups, which were all enriched in "Molecular Function" process in GO term. Furthermore, 6763 genes were enriched in 291 KEEG pathways, with most of them belonging to immune and material metabolic pathways. The large number of transcriptome data and pathways determined in this study provide a database foundation for the toxicity analysis of ENR in loach cells, which must be thoroughly examined to further investigate the cytotoxic mechanism of antibiotics in fish cells.

Metabolic responses of golden trout (Oncorhynchus mykiss aguabonita) after acute exposure to waterborne copper

Despite the broad knowledge of copper-induced stress and toxicity, data on the physiological responses to acute copper exposure and the correlation of those activities to a generalized stress response are still limited. The present study aimed to assess the physiological responses of golden trout to overcome copper stress at concentrations of 60 µg/L and 120 µg/L after 96 h, respectively. The activities of glucose-6-phosphate dehydrogenase (G6PD) phosphoenolpyruvate carboxykinase (PEPCK) and NADPH/NADP⁺ ratio were significantly increased, and metabolites including glucose 6-phosphate, fructose 1-phosphate and fatty acids significantly accumulated in fish liver, indicating that gluconeogenesis, the pentose-phosphate pathway, as well as alteration of the membrane fatty acid composition were activated to serve as a defense mechanism against 60 µg/L of copper after 96 h. After exposure to 120 µg/L of copper for 96 h, the NAD⁺ and ATP contents, the activities of enzymes in the glycolytic pathway (phosphofructokinase, PFK and pyruvate kinase, PK) and mitochondrial respiratory chain complex I decreased significantly in fish liver. In addition, carbohydrates and MDA accumulated in golden trout after 120 µg/L copper treatment. These results indicated that 120 µg/L of copper exposure may induce a metabolic stress in golden trout after 96 h. The multi-marker approach allows us to reach a greater understanding of the effects of copper on physiological responses of golden trout.

The specification of zebrafish (Danio rerio) heart electrocardiogram index characteristic responses to different types of pollutants

Water quality was highly affected by common pollutants. Metals, pesticides and small molecules are ubiquitous pollutants. Advancement in engineering technology (computer-based monitoring systems) increased the efficiency of quantifying toxicity of different chemicals in an organism. The cardiovascular system reflects internal and external stress of an organism, and electrocardiogram (ECG) data reliably measure external stress. As ECG data can accurately reflect the physiological conditions of organisms, and zebrafish (Danio rerio) are considered to be good models for cardiovascular research, it is hypothesized that ECG parameters of zebrafish could indicate the toxicity of water-borne chemicals. To achieve this, we treated zebrafish with different concentrations of target chemicals (CuSO₄, C₁₀H₁₉O₆PS₂ and NH₄Cl) for 48 h and ECG data were measured. P-wave, R-wave, T-wave, PR-interval, QRS-complex and QT-interval data were the focus of this study. The results of self-organizing maps and Pearson correlation analysis indicate that the QRS-complex can be used as an indicator for CuSO₄ stress. The QT-interval could be used to assess the C₁₀H₁₉O₆PS₂ stress. The QT-interval and P-wave can be used to evaluate the NH₄Cl stress. Responses of zebrafish ECG parameters were identical with other vertebrate model, and were specific to toxicant types. It is proved that zebrafish heart ECG index could be used as a potential indicator in early detection of environmental stress.

Editorial of the VSI "Antibiotics and heavy metals in the environment: Facing the challenge"

The Virtual Special Issue (VSI) "Antibiotics and Heavy Metals in the Environment: Facing the Challenge" received more than 100 submissions from research teams around the world. Finally, more than 50 papers were accepted and published. These very interesting research papers allow going ahead in the knowledge of different aspects which determine the fate of antibiotics and heavy metals in the environmental. The success of the VSI, as well as reports from scientific databases, indicate that this field of research is clearly growing, which is expected to continue, especially considering emerging pollutants as a whole.

MAVS of triploid hybrid of red crucian carp and allotetraploid possesses the improved antiviral activity compared with the counterparts of its parents

Triploid hybrid (3n = 150) of red crucian carp (♀, 2n = 100) and allotetraploid (♂, 4n = 200) presents the obviously stronger disease resistance than its parents. To elucidate the innate immunity of triploid hybrid, the MAVS homologues of triploid hybrid (3nMAVS), red crucian carp (2nMAVS) and allotetraploid (4nMAVS) have been identified and characterized separately in this study. 2nMAVS and 4nMAVS were evolutionarily conserved; however, 3nMAVS showed lower amino acid similarity and differently predicted structure to 2nMAVS or 4nMAVS. 3nMAVS transcription increase rate in host cells were obviously higher than 2nMAVS or 4nMAVS in response to different stimuli, which included spring viraemia of carp virus (SVCV), grass carp reovirus (GCRV) and poly (I:C). The reporter assay in EPC cells showed that 3nMAVS owned much stronger ability to induce the production of DrIFNφ1 and eIFN than either 2nMAVS or 4nMAVS. Accordingly, EPC cells transfected with 3nMAVS presented obviously stronger antiviral activity against both GCRV and SVCV than the cells expressing 2nMAVS or 4nMAVS. All the data support the conclusion that 3nMAVS-mediated antiviral signaling during innate immune activation was stronger than those of 2nMAVS and 4nMAVS, which provided us the new insight on the innate immune system of triploid hybrid.