Nodularin induced oxidative stress contributes to developmental toxicity in zebrafish embryos

Physico-chemical treatments for the removal of cyanotoxins from drinking water: Current challenges and future trends

Cyanobacteria are highly prevalent blue-green algae that grow in stagnant and nutrient-rich water bodies. Environmental conditions, such as eutrophication and human activities, increased the cyanobacterial blooms in freshwater resources worldwide. The excessive bloom formation has also resulted in an alarming surge of cyanobacterial toxins. Prolonged exposure to cyanotoxins is a potential threat to natural ecosystems, animal and human health by the spoilage of the quality of bathing and drinking water. Various molecular and analytical methods have been proposed to monitor their occurrence and understand their global distribution. Moreover, different physical, chemical, and biological approaches have been employed to control cyanobacterial blooms and their toxins to mitigate their occurrence. Numerous strategies have been engaged in drinking water treatment plants (DWTPs). However, the degree of treatment varies greatly and is primarily determined by the source, water properties, and operating parameters such as temperature, pH, and cyanotoxin variants and levels. A comprehensive compilation of methods, from traditional approaches to more advanced oxidation processes (AOPs), are presented for the removal of intracellular and extracellular cyanotoxins. This review discusses the effectiveness of various physicochemical operations and their limitations in a DWTP, for the removal of various cyanotoxins. These operations span from simple to advanced treatment levels with varying degrees of effectiveness and differing costs of implementation. Furthermore, mitigation measures applied in other toxin systems have been considered as alternative strategies.

Vitamin A ameliorates valproic acid-induced autism-like symptoms in developing zebrafish larvae by attenuating oxidative stress and apoptosis

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social deficits and repetitive/stereotyped behaviors. Prenatal exposure to valproic acid (VPA) has been reported to induce ASD-like symptoms in human and rodents. However, the etiology and pathogenesis of ASD have not been well elucidated. This study aimed to explore the mechanisms underlying VPA-induced ASD-like behaviors using zebrafish model and investigated whether vitamin A could prevent VPA-induced neurotoxicity. Here, zebrafish embryos were exposed to 0, 25 and 50 μM VPA from 4 to 96 h post fertilization (hpf) and the neurotoxicity was assessed. Our results showed that VPA affected the normal development of zebrafish larvae and induced ASD-like behaviors, including reduced locomotor activity, decreased distance near conspecifics, impaired social interaction and repetitive swimming behaviors. Exposure to VPA decreased the GFP signal in transgenic HuC:egfp zebrafish according to the negative effect of VPA on the expression of neurodevelopmental genes. In addition, VPA enhanced oxidative stress by promoting the production of reactive oxygen species (ROS) and hydrogen peroxide (H2O2) and inhibiting the activity of superoxide dismutase, then triggered apoptosis by upregulation of apoptotic genes. These adverse outcomes were mitigated by vitamin A, suggesting that vitamin A rescued VPA-induced ASD-like symptoms by inhibiting oxidative stress and apoptosis. Overall, this study identified vitamin A as a promising strategy for future therapeutic regulator of VPA-induced ASD-like behaviors.

TMBPF-induced neurotoxicity and oxidative stress in zebrafish larvae: impacts on central nervous system development and dopamine neurons

Bisphenol A (BPA), a common bisphenol molecule, is well known in the environment as an endocrine disruptor. Furthermore, BPs (BPA, BPS, BPF, and BPAF) have been shown in recent years to be neurotoxic to zebrafish. Tetramethyl bisphenol F (TMBPF) has recently been introduced as a substitute for bisphenol A (BPA) in various industries, including plastics and food contact coatings. However, a growing number of studies have demonstrated that the toxicity of some BPA substitutes is similar to or even stronger than BPA, posing potential harm to human health and the environment. In this study, we used zebrafish larvae as a model to investigate the neurodevelopmental effects of TMBPF at different concentrations (0, 0.25, 0.5, 1, 2, 4 and 8 mg/L). Our results showed that exposure to TMBPF at concentrations higher than 4 mg/L for 72 h post-fertilization (hpf) resulted in zebrafish mortality, whereas exposure to 2 mg/L for 144 hpf caused deformities. Furthermore, TMBPF exposure inhibited the development of the central nervous system, motor nerves, and dopamine neurons in zebrafish. Real-time polymerase chain reaction (PCR) analysis revealed that TMBPF exposure significantly down-regulated the expression of oxidative stress-related genes (Cu/Zn-SOD, Mn-SOD, and CAT) and neurodevelopmental genes (mbp, gafp, and syn2a), while up-regulated the expression of dopamine-related genes (th1, th2, and dat). Notably, treatment with the antioxidant N-acetylcysteine (NAC) alleviated TMBPF-induced toxicity. NAC can regulate the expression of genes related to oxidative stress, neurodevelopment and dopamine development, and make the nerve development of zebrafish normal. Overall, our research suggested that TMBPF may disrupt the development of the early central nervous system and dopamine neurons, leading to abnormal motor behavior in zebrafish larvae. These results highlight the potential risks associated with the use of TMBPF in various industries and the importance to evaluate its potential risks to human health and the environment.

Nano-selenium Antagonizes Heat Stress-Induced Apoptosis of Rainbow Trout (Oncorhynchus mykiss) Hepatocytes by Activating the PI3K/AKT Pathway

The cold-water fish rainbow trout (Oncorhynchus mykiss) shows poor resistance to heat, which is the main factor restricting their survival and yield. With the advancement of nanotechnology, nano-selenium (nano-Se) has emerged as a key nano-trace element, showing unique advantages, including high biological activity and low toxicity, for studying the response of animals to adverse environmental conditions. However, little is still known regarding the potential protective mechanisms of nano-Se against heat stress-induced cellular damage. Herein, we aimed to investigate the mechanism underlying the antagonistic effects of nano-Se on heat stress. Four groups were assessed: CG18 (0 μg/mL nano-Se, 18 °C), Se18 (5.0 μg/mL nano-Se, 18 °C), CG24 (0 μg/mL nano-Se, incubated at 18 °C for 24 h and then transferred to 24 °C culture), and Se24 (5.0 μg/mL nano-Se, incubated at 18 °C for 24 h and then transferred to 24 °C culture). We found that after heat treatment (CG24 group), T-AOC, GPx, and CAT activities in rainbow trout hepatocytes showed a decrease of 36%, 33%, and 19%, respectively, while ROS and MDA levels showed an increase of 67% and 93%, respectively (P < 0.05). Meanwhile, the mRNA levels of the apoptosis-related genes caspase3, caspase9, Cyt-c, Bax, and Bax/Bcl-2 in the CG24 group were 41%, 47%, 285%, 65%, and 151% higher than those in the CG18 group, respectively, while those of PI3K and AKT were 31% and 17% lower, respectively (P < 0.05). Besides, flow cytometry analysis showed an increase in the level of apoptotic cells after heat exposure. More importantly, we observed that nano-Se cotreatment (Se24 group) remarkably attenuated heat stress-induced effects (P < 0.05). We conclude that heat stress induces oxidative stress and apoptosis in rainbow trout hepatocytes. Nano-Se ameliorates heat stress-induced apoptosis by activating the PI3K/AKT pathway. Our results provide a new perspective to improve our understanding of the ability of nano-Se to confer heat stress resistance.

PFOS-induced dyslipidemia and impaired cholinergic neurotransmission in developing zebrafish: Insight into its mechanisms

Perfluorooctane sulfonate (PFOS) is a persistent organic pollutant that has been widely detected in the environment and is known to accumulate in organisms, including humans. The study investigated dose-dependent mortality, hatching rates, malformations, lipid accumulation, lipid metabolism alterations, and impacts on cholinergic neurotransmission. Increasing PFOS concentration led to higher mortality, hindered hatching, and caused concentration-dependent malformations, indicating severe abnormalities in developing zebrafish. The results also demonstrated that PFOS exposure led to a significant increase in total lipids, triglycerides, total cholesterol, and LDL in a concentration-dependent manner, while HDL cholesterol levels were significantly decreased. Additionally, PFOS exposure led to a significant decrease in glucose levels. The study identified TGs, TCHO, and glucose as the most sensitive biomarkers in assessing lipid metabolism alterations. The study also revealed altered expression of genes involved in lipid metabolism, including upregulation of fasn, acaca, and hmgcr and downregulation of ldlr, pparα, and abca1, as well as decreased lipoprotein lipase (LPL) and increased fatty acid synthase (FAS) activity,suggesting an impact on fatty acid synthesis, cholesterol uptake, and lipid transport. Additionally, PFOS exposure led to impaired cholinergic neurotransmission, evidenced by a concentration-dependent inhibition of acetylcholinesterase activity, altered gene expressions related to neural development and function, and reduced Na+/K+-ATPase activity. STRING network analysis highlighted two distinct gene clusters related to lipid metabolism and cholinergic neurotransmission, with potential interactions through the pparα-creb1 pathway. Overall, this study provide important insights into the potential health risks associated with PFOS exposure, including dyslipidemia, cardiovascular disease, impaired glucose metabolism, and neurotoxicity. Further research is needed to fully elucidate the underlying mechanisms and potential long-term effects of PFOS exposure.

Silver Nanoparticles Cause Neural and Vascular Disruption by Affecting Key Neuroactive Ligand-Receptor Interaction and VEGF Signaling Pathways

Introduction

Silver nanoparticles (AgNP) are widely used as coating materials. However, the potential risks of AgNP to human health, especially for neural and vascular systems, are still poorly understood.

Methods

The vascular and neurotoxicity of various concentrations of AgNP in zebrafish were examined using fluorescence microscopy. In addition, Illumina high-throughput global transcriptome analysis was performed to explore the transcriptome profiles of zebrafish embryos after exposure to AgNP. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted to elucidate the top 3000 differentially expressed genes (DEGs) between AgNP-exposed and control groups.

Results

We systematically investigated the neural and vascular developmental toxicities of AgNP exposure in zebrafish. The results demonstrated that AgNP exposure could cause neurodevelopmental anomalies, including a small-eye phenotype, neuronal morphology defects, and inhibition of athletic abilities. In addition, we found that AgNP exposure induces angiogenesis malformation in zebrafish embryos. Further RNA-seq revealed that DEGs were mainly enriched in the neuroactive ligand-receptor interaction and vascular endothelial growth factor (Vegf) signaling pathways in AgNP-treated zebrafish embryos. Specifically, the mRNA levels of the neuroactive ligand-receptor interaction pathway and Vegf signaling pathway-related genes, including si:ch73-55i23.1, nfatc2a, prkcg, si:ch211-132p1.2, lepa, mchr1b, pla2g4aa, rac1b, p2ry6, adrb2, chrnb1, and chrm1b, were significantly regulated in AgNP-treated zebrafish embryos.

Conclusion

Our findings indicate that AgNP exposure transcriptionally induces developmental toxicity in neural and vascular development by disturbing neuroactive ligand-receptor interactions and the Vegf signaling pathway in zebrafish embryos.

Resveratrol ameliorates penconazole-induced cardiotoxicity by inhibition of oxidative stress and apoptosis in zebrafish larvae

Penconazole (PEN) is a typical systemic triazole fungicide with cardiac toxic effects. Resveratrol (RES) is a natural polyphenolic phytochemical with antioxidation properties. This study aimed to investigate if RES could protect against PEN-induced cardiotoxicity and to determine the underlying mechanisms. Zebrafish embryos were exposed to 0, 0.5, 1 and 2 mg/L of PEN from 4 to 96 h post fertilization (hpf) and cardiac developmental toxicity was assessed. Our results showed that PEN decreased hatching rate, survival rate, heart rate and body length, with increased malformation rate and spontaneous movement. PEN induced pericardial edema and abnormal cardiac structure in myl7:egfp transgenic zebrafish, as well as downregulation of cardiac development related genes (nkx2.5, tbx2.5, gata4, noto, and vmhc). In addition, PEN elevated oxidative stress via reactive oxygen species (ROS) accumulation and triggered cardiomyocytic apoptosis by upregulation of p53, bcl-2, bax and caspase 3. These adverse outcomes were counteracted by RES, indicating that RES ameliorated PEN-induced cardiotoxicity by inhibiting oxidative stress and apoptosis in zebrafish. Taken together, this study revealed the important role of oxidative stress in PEN-induced cardiotoxicity and identified dietary RES supplementation as a novel strategy to mitigate its toxicity.

Effects of cyanobacterial metabolites: Aeruginosin 98A, microginin-FR1, anabaenopeptin-A, cylindrospermopsin in binary and quadruple mixtures on the survival and oxidative stress biomarkers of Daphnia magna

The aim of our study was to determine the effects of aeruginosin 98 A (ARE-A), microginin-FR1 (MG-FR1), anabaenopeptin-A (ANA-A) cylindrospermopsin (CYL) and their binary and quadruple mixtures on the survival and the levels of oxidative stress biomarkers in Daphnia magna: total glutathione (GSH), catalase (CAT), dismutase (SOD) and malondialdehyde (MDA). The biochemical indicators were measured with ELISA kits and the interactive effects were determined by isobole and polygonal analysis with Compusyn® computer software. The study revealed that oligopeptides did not decrease daphnid survival, only CYL inhibited this parameter, with synergistic effects when it was used as a component. The single metabolites at the two highest concentrations and all the binary and quadruple mixtures at all concentrations diminished GSH level, however both in the binary and in the quadruple mixtures most of the interactions between the metabolites were antagonistic. Nearly additive effects were found only in AER-A + CYL and MG-FR1+CYL. On the other hand, CAT activity was slightly increased in daphnids exposed to the binary mixtures with antagonistic interactions, however nearly addivive effects were found in animals exposed to the mixture of AER-A + ANA-A and synergistic in the quadruple mixture. SOD was elevated in daphnids exposed to single AER-A and MG-FR1, however it was diminished in the animals exposed to ANA-A and CYL. Binary mixtures in which CYL was present as a component decreased the level of this enzyme with nearly additive interactions in ANA-A + CYL. The quadruple mixture increased SOD level, with antagonistic interactions. Both single cyanobacterial metabolites, their binary and quadruple mixtures induced lipid peroxidation measured by MDA level and most of interactions in the binary mixtures were synergistic. The study suggested that antioxidative system of Daphnia magna responded to the tested metabolites and the real exposure to mixtures of these products may lead to various interactive effects with varied total toxicity.

Acute exposure of Isopyrazam damages the developed cardiovascular system of zebrafish (Danio rerio)

Isopyrazam (IPZ) is one of the broad-spectrum succinate dehydrogenase inhibitor fungicides (SDHIs). Although the potential bio-toxicity of SDHIs has been reported hourly, the specific effects focused on the cardiovascular system have remained unclear and piecemeal. Thus, we chose IPZ as a representative to observe the cardiovascular toxicity of SDHIs in zebrafish. Two types of transgenic zebrafish, Tg (cmlc2:GFP) and Tg (flk1:GFP) were used in this study. Healthy embryos at 6 hpf were exposed to IPZ solutions. The statistical data including survival rate, hatching rate, malformed rate, and morphological and functional parameters of the cardiovascular system at 48 hpf and 72 hpf demonstrated that IPZ could cause abnormalities and cardiovascular defects such as spinal curvature, dysmotility, pericardial edema, pericardial hemorrhage, and slowed heart rate, etc. At the same time, the activity of enzymes related to oxidative stress was altered with IPZ. Our results revealed that IPZ-induced cardiovascular toxicity and oxidative stress might be one of the underlying toxic mechanisms.

SYP-3343 drives abnormal vascularization in zebrafish through regulating endothelial cell behavior

SYP-3343 is a novel strobilurin fungicide with excellent and broad-spectrum antifungal activity, and its potential toxicity raises public health concerns. However, the vascular toxicity of SYP-3343 to zebrafish embryos is still not well understood. In the present study, we investigated the effects of SYP-3343 on vascular growth and its potential mechanism of action. SYP-3343 inhibited zebrafish endothelial cell (zEC) migration, altered nuclear morphology, and triggered abnormal vasculogenesis and zEC sprouting angiogenesis, resulting in angiodysplasia. RNA sequencing showed that SYP-3343 exposure altered the transcriptional levels of vascular development-related biological processes in zebrafish embryos including angiogenesis, sprouting angiogenesis, blood vessel morphogenesis, blood vessel development, and vasculature development. Whereas, the addition of NAC exerted an improvement effect on zebrafish vascular defects owing to SYP-3343 exposure. Additionally, SYP-3343 altered cell cytoskeleton and morphology, obstructed migration and viability, disrupted cell cycle progression, and depolarized mitochondrial membrane potential, as well as promoted apoptosis and reactive oxygen species (ROS) in HUVEC. SYP-3343 also caused an imbalance of the oxidation and antioxidant systems and irritated the alterations in the cell cycle- and apoptosis-related genes in HUVECs. Collectively, SYP-3343 has high cytotoxicity, possibly by up-regulating p53 and caspase3 expressions and bax/bcl-2 ratio via ROS, leading to malformed vascular development.

Environmentally relevant concentrations of butyl benzyl phthalate triggered oxidative stress and apoptosis in adult zebrafish (Danio rerio) liver: Combined analysis at physiological and molecular levels

Butyl benzyl phthalate (BBP), a typical phthalate plasticizer, is frequently detected in aquatic environments, but its possible effects on fish liver are unknown. In this study, adult zebrafish were exposed to 5-500 μg/L BBP and cultured for 28 days. The toxicity mechanism of environmentally relevant concentrations of BBP in the liver was explored using integrated biomarker response (IBR), molecular docking, and histopathological analysis, based on the tests of oxidative stress, apoptosis, and tissue damage, respectively. The results revealed that exposure to 500 μg/L BBP caused lipid peroxidation and DNA damage and induced inflammatory responses in the liver and intestinal tissues. The accumulation of reactive oxygen species (ROS) is the primary manifestation of BBP toxicity and is accompanied by changes in the activities of antioxidant and detoxification enzymes. Notably, the pro-apoptotic genes (p53 and caspase-3) were still significantly upregulated in the 50 μg/L and 500 μg/L treatment groups on day 28. Moreover, BBP interfered with apoptosis by forming a stable complex with apoptosis proteins (P53 and Caspase-3). Our findings are helpful for understanding the toxicity mechanisms of BBP, which could further promote the assessment of the potential environmental risks of BBP.

Sublethal effect of the toxic dinoflagellate Karlodinium veneficum on early life stages of zebrafish (Danio rerio)

Dinoflagellates of the genus Karlodinium are ichthyotoxic species that produce toxins including karlotoxins and karmitoxins. Karlotoxins show hemolytic and cytotoxic activities and have been associated with fish mortality. This study evaluated the effect of toxins released into the environment of Karlodinium veneficum strain K10 (Ebro Delta, NW Mediterranean) on the early stages of Danio rerio (zebrafish). Extracts of the supernatant of K10 contained the mono-sulfated KmTx-10, KmTx-11, KmTx-12, KmTx-13, and a di-sulfated form of KmTx-10. Total egg mortality was observed for karlotoxin concentration higher than 2.69 μg L^-1. For 1.35 μg L^-1, 87% of development anomalies were evidenced (all concentrations were expressed as KmTx-2 equivalent). Larvae of 8 days postfertilization exposed to 1.35 µg L^-1 presented epithelial damage with 80% of cells in the early apoptotic stage. Our results indicate that supernatants with low concentration of KmTxs produce both lethal and sublethal effects in early fish stages. Moreover, apoptosis was induced at concentrations as low as 0.01 μg L^-1. This is of great relevance since detrimental long-term effects due to exposure to low concentrations of these substances could affect wild and cultured fish.

In silico and in vivo assessment of developmental toxicity, oxidative stress response & Na+/K+-ATPase activity in zebrafish embryos exposed to cypermethrin

Cypermethrin (CYP), a synthetic type II pyrethroid pesticide, is extensively used to control pests in industrial, domestic, and agricultural environments. However, its indiscriminate use leads to a potential threat to aquatic organisms. Although several reports focussed on developmental toxicity effects, a concise study combining cardiotoxicity along with Na⁺/K⁺-ATPase activity and molecular docking of developmental proteins with CYP was lacking. This present study was designed to address this gap to comprehend the impact of CYP exposure (0, 25, 100 and 200 µg/L) on embryonic zebrafish. As a result, CYP delayed the hatching rate, reduced heart rate, increased mortality rate and induced numerous morphological abnormalities. Subsequently, CYP induced oxidative stress in treated zebrafish embryos with the concomitant increase in antioxidant enzymes (SOD and CAT) and malondialdehyde production. In addition, an alteration in AChE, NO content and Na⁺/K⁺-ATPase activity was observed, suggesting a disruption in cardiac development and ion regulation. Furthermore, AO staining showed notable apoptotic cells which are supported by alteration in apoptosis-related gene expressions. Moreover, to explore the putative targets of CYP, computational docking with developmental proteins (WNT3A, WNT8A, GATA-4, Nkx 2-5 and ZHE1) showed strong interactions and binding. Taken together, our findings provide a better understanding of assessing the ecotoxicological risk information and the mode of action underlying the development of teleost fishes following CYP exposure. Meanwhile, the pioneering nature of this study is to emphasize the future use of Na⁺/K⁺-ATPase activity as a potential toxicity biomarker and in silico molecular docking studies to complement developmental toxicity findings.

The toxicity of 4-tert-butylphenol in early development of zebrafish: morphological abnormality, cardiotoxicity, and hypopigmentation

Endocrine disrupting effects of 4-tert-butylphenol (4-t-BP) are well described in literature. However, the evidence regarding developmental toxic effect of 4-t-BP is still vague. The present study used zebrafish as a model organism to investigate the toxic effect of 4-t-BP. The results showed that 4-t-BP exposure at 3, 6, and 12 μM induced developmental toxicity in zebrafish, such as reduced embryo hatchability and abnormality morphological. Flow cytometry analysis showed that 4-t-BP also induced intracellular ROS production. 4-t-BP induced changes in the expression of genes related to cardiac development and melanin synthesis, resulting in cardiotoxicity and hypopigmentation. 4-t-BP also caused oxidative stress, and initiated apoptosis through p53-bcl-2/bax-capase3 pathway. Integrative biomarker response analysis showed time- and dose-dependent effects of 4-t-BP on oxidative damage and developmental toxicity in zebrafish embryos. Overall, this study contributed to a comprehensive evaluation of the toxicity of 4-t-BP, and the findings provided new evidence for early warning of residues in aquatic environments.

2,4-Dichlorophenoxyacetic acid (2,4-D) affects DNA integrity and retina structure in zebrafish larvae

Monitoring the potential risk of herbicides in non-target organisms is a crucial issue for environmental safety. 2,4-D is an herbicide of high environmental relevance that has been shown to exert toxic effects to soil and aquatic biota. In the present study, we investigated the possible genotoxic and retinal development effects of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide in early life stages zebrafish (Danio rerio). Genotoxicity was evaluated by measuring DNA damage using the comet assay and also by the mRNA expression of genes implicated in apoptosis and/or DNA repair. Retinal development toxicity was evaluated with histological approach. The results obtained revealed that 2,4-D alters DNA integrity of zebrafish larvae. Moreover, transcriptomic data showed a significant induction of p-53 and casp-3 genes and a significant decrease of lig-4 in larvae exposed to the highest tested concentration of 2,4-D (0.8 mg/L). This suggested that p-53 gene regulates the process of DNA repair and apoptosis with increased levels of 2,4-D. The histopathological analysis revealed that early exposure to 2,4-D damaged the structure of larvae retina. Overall, this study is the first to report the DNA damage, casp-3, lig-4 and p-53 regulation, as well as the ocular developmental toxicity in zebrafish larvae at environmentally relevant concentrations of 2,4-D herbicide.

Spiromesifen contributes vascular developmental toxicity via disrupting endothelial cell proliferation and migration in zebrafish embryos

Spiromesifen (SPF) is a specific contact pesticide, which has been widely used to control the growth of sucking insects like mites and whiteflies on crops. Although its residues in crops and effects on organisms has been extensively reported, its impact on the vasculature is still not being reported. In the present study, using human umbilical vein endothelial cells (HUVECs) and zebrafish embryos, we investigated the effects of SPF on blood vessel development and its mechanism of action. SPF exposure triggered abnormal blood vessel development, including vascular deletions and malformations, inhibition of CCV remodeling, and decrease of SIV areas. SPF exposure also obstructed the migration of endothelial cell from caudal hematopoietic tissue in zebrafish embryos. SPF damaged cytoskeleton, caused cell cycle arrest, inhibited the viability and migration of HUVECs. In addition, SPF also inhibited the expression of the VEGF/VEGFR pathway-related genes (hif1a, vegfa, flt1, and kdrl), cell cycle-related genes (ccnd1, ccne1, cdk2, and pcna), and Rho/ROCK pathway-related genes (itgb1, rho, rock, mlc-1, and vim-1). Taken together, SPF may inhibit the proliferation and migration of vascular endothelial cells through disturbing cytoskeleton via the Rho/ ROCK pathway, resulting in vascular malformation. Our study contributes to potential insight into the mechanism of SPF toxicity in angiocardiopathy.

Spiromesifen conferred abnormal development in zebrafish embryos by inducing embryonic cytotoxicity via causing oxidative stress

Spiromesifen (SPF) is widely used in agriculture to protect against herbivorous mites, whose residues may be harmful to the environment. However, the toxicity assessment of SPF is insufficient. Here, we investigated the toxicological effects of SPF using zebrafish embryos as an animal model. The results showed that SPF exposure solutions at 10, 20, 30, and 40 μM caused cytotoxicity in zebrafish embryos such as reactive oxygen species (ROS) accumulation, mitochondrial membrane potential decrease, cell division arrest, and apoptosis, which further led to developmental toxicity in zebrafish embryos including delayed hatching, decreased survival rate and spontaneous curling rate, and severe morphological deformities. SPF also induced apoptosis via changes in the expressions of apoptosis-related marker genes, caused immunotoxicity by reducing the number of macrophages and the activity of AKP/ALP and increasing inflammatory factors, and disturbed endogenous antioxidant systems via changes SOD, CAT, and GST activities as well as MDA and GSH contents. Therefore, the potential mechanism that caused embryonic developmental toxicity appeared to be related to the generation of oxidative stress by an elevation in ROS and changes in apoptosis-, immune-, antioxidant-related markers. The antioxidant system and inflammatory response simultaneously participated in and resisted the threat of SPF to prevent tissue damage. Taken together, spiromesifen induced oxidative stress to contribute to developmental toxicity in zebrafish embryos by inducing embryonic cytotoxicity. Our study provides new insight into the toxicity assessment of SPF to non-target organisms.

Silver nanoparticles induce developmental toxicity via oxidative stress and mitochondrial dysfunction in zebrafish (Danio rerio)

Sliver nanoparticles (AgNPs) are widely used in industry, agriculture, and medicine, potentially resulting in adverse effects on human health and aquatic environments. Here, we investigated the developmental toxicity of zebrafish embryos with acute exposure to AgNPs. Our results demonstrated developmental defects in 4 hpf zebrafish embryos after exposure to different concentrations of AgNPs for 72 h. In addition, RNA-seq profiling of zebrafish embryos after AgNPs treatment. Further Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that the differentially expressed genes (DEGs) were enriched in DNA replication initiation, oxidoreductase activity, DNA replication, cellular senescence, and oxidative phosphorylation signaling pathways in the AgNPs-treated group. Notably, we also found that AgNPs exposure could result in the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA), the inhibition of superoxide dismutase (SOD), catalase (CAT), and mitochondrial complex I-V activities, and the downregulated expression of SOD, CAT, and mitochondrial complex I-IV chain-related genes. Moreover, the expression of mitochondrion-mediated apoptosis signaling pathway-related genes, such as bax, bcl2, caspase-3, and caspase-9, was significantly regulated after AgNPs exposure in zebrafish. Therefore, these findings demonstrated that AgNPs exposure could cause oxidative stress, induce mitochondrial dysfunction, and ultimately lead to developmental toxicity.

Adverse effects of SYP-3343 on zebrafish development via ROS-mediated mitochondrial dysfunction

As a newly-invented and highly-efficiency strobilurin fungicide, pyraoxystrobin (SYP-3343) has been recognized as a highly poisonous toxin for a variety of aquatic organisms. Nevertheless, the developmental toxicity and potential mechanism of SYP-3343 have not been well-documented. The results showed that SYP-3343 was relatively stable and maintained within the range of 20 % in 24 h, and the LC₅₀ value to embryos at 72 hpf was 17.13 μg/L. The zebrafish embryotoxicity induced by 1, 2, 4, and 8 μg/L SYP-3343 is demonstrated by repressive embryo incubation, enhancive mortality rate, abnormal heart rate, malformed morphological characteristic, and impaired spontaneous coiling, indicating SYP-3343 mostly exerted its toxicity in a dose- and time-dependent manner. Besides SYP-3343 was critically involved in regulating cell cycle, mitochondrial membrane potential, and reactive oxygen species production as well as zebrafish primary cells apoptosis, which can be mitigated using antioxidant N-acetyl-L-cysteine. A significant change occurred in total protein content, the biochemical indices, and antioxidant capacities owing to SYP-3343 exposure. Additionally, SYP-3343 altered the mRNA levels of heart development-, mitochondrial function-, and apoptosis-related genes in zebrafish embryos. These results indicated that SYP-3343 induced apoptosis accompanying reactive oxygen species-initiated mitochondrial dysfunction in zebrafish embryos.

A review and assessment of cyanobacterial toxins as cardiovascular health hazards

Eutrophicated waters frequently support bloom-forming cyanobacteria, many of which produce potent cyanobacterial toxins (cyanotoxins). Cyanotoxins can cause adverse health effects in a wide range of organisms where the toxins may target the liver, other internal organs, mucous surfaces and the skin and nervous system. This review surveyed more than 100 studies concerning the cardiovascular toxicity of cyanotoxins and related topics. Over 60 studies have described various negative effects on the cardiovascular system by seven major types of cyanotoxins, i.e. the microcystin (MC), nodularin (NOD), cylindrospermopsin (CYN), anatoxin (ATX), guanitoxin (GNTX), saxitoxin (STX) and lyngbyatoxin (LTX) groups. Much of the research was done on rodents and fish using high, acutely toxin concentrations and unnatural exposure routes (such as intraperitoneal injection), and it is thus concluded that the emphasis in future studies should be on oral, chronic exposure of mammalian species at environmentally relevant concentrations. It is also suggested that future in vivo studies are conducted in parallel with studies on cells and tissues. In the light of the presented evidence, it is likely that cyanotoxins do not constitute a major risk to cardiovascular health under ordinary conditions met in everyday life. The risk of illnesses in other organs, in particular the liver, is higher under the same exposure conditions. However, adverse cardiovascular effects can be expected due to indirect effects arising from damage in other organs. In addition to risks related to extraordinary concentrations of the cyanotoxins and atypical exposure routes, chronic exposure together with co-existing diseases could make some of the cyanotoxins more dangerous to cardiovascular health.

Enantioselective Ecotoxicity of Venlafaxine in Aquatic Organisms: Daphnia and Zebrafish

Venlafaxine is a chiral antidepressant detected in aquatic compartments. It was recently included in the 3rd Watch List from the European Union. The present study aimed to investigate venlafaxine toxicity effects, targeting possible enantioselective effects, using two aquatic organisms, daphnia (Daphnia magna) and zebrafish (Danio rerio). Specimens were exposed to both racemate, (R,S)-venlafaxine (VEN), and to pure enantiomers. Acute assays with daphnia showed that up to 50 000 μg/L of the (R,S)-VEN induced no toxicity. Organisms were also exposed to sublethal concentrations (25-400 μg/L) of (R,S)-, (R)- and (S)-VEN, for 21 days. No significant effects on mortality, age at first reproduction, and size of the first clutch were observed. However, a decrease in fecundity was observed for both enantiomers at the highest concentration. Regarding zebrafish, the effects of venlafaxine on mortality, embryo development, behavior, biochemistry, and melanin pigmentation were investigated after 96 h of exposure to the range of 0.3-3000 μg/L. (R)-VEN significantly increased the percentage of malformations in comparison with (S)-VEN. Behavior was also enantiomer dependent, with a decrease in the total distance moved and an increase in avoidance behavior observed in organisms exposed to (R)-VEN. Despite the biochemical variations, no changes in redox homeostasis were observed. (R)-VEN also led to an increase in zebrafish pigmentation. The different susceptibility to venlafaxine and enantioselective effects were observed in zebrafish. Our results suggest that at environmental levels (R,S)-VEN and pure enantiomers are not expected to induce harmful effects in both organisms, but (R)-VEN increased malformations in zebrafish larvae, even at reported environmental levels. These results highlight the importance of including enantioselective studies for an accurate risk assessment of chiral pollutants. Environ Toxicol Chem 2022;41:1851-1864. © 2022 SETAC.

Oxidative Stress and AKT-Associated Angiogenesis in a Zebrafish Model and Its Potential Application for Withanolides

Oxidative stress and the AKT serine/threonine kinase (AKT) signaling pathway are essential regulators in cellular migration, metastasis, and angiogenesis. More than 300 withanolides were discovered from the plant family Solanaceae, exhibiting diverse functions. Notably, the relationship between oxidative stress, AKT signaling, and angiogenesis in withanolide treatments lacks comprehensive understanding. Here, we summarize connecting evidence related to oxidative stress, AKT signaling, and angiogenesis in the zebrafish model. A convenient vertebrate model monitored the in vivo effects of developmental and tumor xenograft angiogenesis using zebrafish embryos. The oxidative stress and AKT-signaling-modulating abilities of withanolides were highlighted in cancer treatments, which indicated that further assessments of their angiogenesis-modulating potential are necessary in the future. Moreover, targeting AKT for inhibiting AKT and its AKT signaling shows the potential for anti-migration and anti-angiogenesis purposes for future application to withanolides. This particularly holds for investigating the anti-angiogenetic effects mediated by the oxidative stress and AKT signaling pathways in withanolide-based cancer therapy in the future.

Effects of tralopyril on histological, biochemical and molecular impacts in Pacific oyster, Crassostrea gigas

Recently, the toxic effects of tralopyril, as a new antifouling biocide, on aquatic organisms have aroused widespread attention about the potential toxicity. However, the mechanism of tralopyril on marine mollusks has not been elaborated clearly. In this study, the histological, biochemical and molecular impacts of tralopyril on adult Crassostrea gigas were investigated. The results indicated that the 96 h LC50 of tralopyril to adult Crassostrea gigas was 911 μg/L. After exposure to tralopyril (0, 40, 80 and 160 μg/L) for 6 days, the mantle mucus secretion coverage ratio of Crassostrea gigas was increased with a dose-dependent pattern. Catalase (CAT) activity was significantly increased, amylase (AMS) activity, acid phosphatase (ACP) activity and calcium ion (Ca²⁺) concentration significantly decreased. Meanwhile, integrated biomarker responses (IBR) index suggested that higher concentrations of tralopyril caused severer damage to Crassostrea gigas. In addition, the mRNA expression levels of biomineralization related genes in the mantle were significantly upregulated. Collectively, this study firstly revealed the histological, biochemical and molecular impacts of tralopyril exposure on adult Crassostrea gigas, which provided new insights for understanding the toxicity of tralopyril in marine mollusks.

Developmental toxicity assessment of 4-MBC in Danio rerio embryo-larval stages

Enormous production of cosmetic products and its indiscriminate use tends to discharge into the aquatic environment and might threaten non-target organisms inhabiting aquatic ecosystems. In the present study, developmental toxicity of 4-methylbenzylidene camphor (4-MBC), a widely used organic UV filter in personal care products has been evaluated using zebrafish embryo-larval stages. Waterborne exposure induced developmental toxicity and deduced 2.71 mg/L as 96 h LC₅₀ whereas embryos exposed to sub-lethal concentrations (50 and 500 μg/L) caused a significant delay in hatching rate, heart rate, reduced larval length, and restricted hatchlings motility besides the axial curvature. Chronic exposure to 10 dpf resulted in significant decrease in SOD activity at 500 μg/L with no changes in CAT level besides a significant increase in GST enzyme at 5 μg/L concentration in 5 dpf sampled larvae. However, all the three enzymes were significantly elevated in 10 dpf larvae indicating differential oxidative stress during the stages of development. Similar trend is noticed for acetylcholine esterase enzyme activity. A concentration dependent increase in malondialdehyde content was noted in larvae sampled at 5 and 10 dpf. In addition, multixenobiotic resistance (MXR) activity inhibition, and elevated oxidative tissue damage were noticed at 5 dpf with no significant changes in 10 dpf larvae. Furthermore, immunoblot analysis confirms 4-MBC induced apoptosis in zebrafish larvae with promoted cleaved Caspase-3, Bax and inhibited Bcl-2 proteins expression. Subsequently, docking studies revealed the binding potential of 4-MBC to zebrafish Abcb4 and CYP450 8A1 proteins with the binding energy of -8.1 and -8.5 kcal/mol representing target proteins interaction and toxicity potentiation. Our results showed that 4-MBC exposure triggers oxidative stress at sub-lethal concentrations leading to apoptosis, deformities and locomotion perturbations in developing zebrafish.This is first of its kind in systematically demonstrating developmental toxicity of 4-MBC and the information shall be used for aquatic toxicity risk assessment.

Toxic effects of cyanotoxins in teleost fish: A comprehensive review

The phenomenon of eutrophication leads to the global occurrence of algal blooms. Cyanotoxins as produced by many cyanobacterial species can lead to detrimental effects to the biome due to their stability and potential biomagnification along food webs. Therefore, understanding of the potential risks these toxins pose to the most susceptible organisms is an important prerequisite for ecological risks assessment of cyanobacteria blooms. Fishes are an important component of aquatic ecosystems that are prone to direct exposure to cyanotoxins. However, relatively few investigations have focused on measuring the toxic potentials of cyanotoxins in teleost fishes. This review comprehensively describes the major toxicological impacts (such as hepatotoxicity, neurotoxicity, immune toxicity, reproductive toxicity and cytogenotoxicity) of commonly occurring cyanotoxins in teleost fishes. The present work encompasses recent research progresses with special emphasis on the basic molecular mechanisms by which different cyanotoxins impose their toxicities in teleost fishes. The major research areas, which need to be focused on in future scientific investigations, have also been highlighted. Protein kinase inhibition, transcriptional dysregulation, disruption of redox homeostasis and the induction of apoptotic pathways appear to be the key drivers of the toxicological effects of cyanotoxins in fish. Analyses also showed that the impacts of cyanotoxins on specific reproductive processes are relatively less described in teleosts in comparison to mammalian systems. In fact, as compared to other toxicological effects of cyanotoxins, their reproductive toxicity (such as impacts on oocyte development, maturation and their hormonal regulation) is poorly understood in fish, and thus requires further studies. Furthermore, additonal studies characterizing the molecular mechanisms responsible for the cellular uptake of cyanotoxins need to be investigated.

Anabaenopeptins: What We Know So Far

Cyanobacteria are microorganisms with photosynthetic mechanisms capable of colonizing several distinct environments worldwide. They can produce a vast spectrum of bioactive compounds with different properties, resulting in an improved adaptative capacity. Their richness in secondary metabolites is related to their unique and diverse metabolic apparatus, such as Non-Ribosomal Peptide Synthetases (NRPSs). One important class of peptides produced by the non-ribosomal pathway is anabaenopeptins. These cyclic hexapeptides demonstrated inhibitory activity towards phosphatases and proteases, which could be related to their toxicity and adaptiveness against zooplankters and crustaceans. Thus, this review aims to identify key features related to anabaenopeptins, including the diversity of their structure, occurrence, the biosynthetic steps for their production, ecological roles, and biotechnological applications.

Zebrafish (Danio rerio) using as model for genotoxicity and DNA repair assessments: Historical review, current status and trends

Genotoxic pollutants lead to both DNA damage and changes in cell repair mechanisms. Selecting suitable biomonitors is a fundamental step in genotoxicity studies. Thus, zebrafish have become a popular model used to assess the genotoxicity of different pollutants in recent years. They have orthologous genes with humans and hold almost all genes involved in different repair pathways. Therefore, the aim of the current study is to summarize the existing literature on zebrafish using as model system to assess the genotoxicity of different pollutants. Revised data have shown that comet assay is the main technique adopted in these studies. However, it is necessary standardizing the technique applied to zebrafish in order to enable better result interpretation and comparisons. Overall, pollutants lead to single-strand breaks (SSB), double-strand breaks (DSB), adduct formation, as well as to changes in the expression of genes involved in repair mechanisms. Although analyzing repair mechanisms is essential to better understand the genotoxic effects caused by pollutants, few studies have analyzed repair capacity. The current review reinforces the need of conducting further studies on the role played by repair pathways in zebrafish subjected to DNA damage. Revised data have shown that zebrafish are a suitable model to assess pollutant-induced genotoxicity.

Comprehensive insights into the occurrence and toxicological issues of nodularins

The occurrence of cyanobacterial toxins is being increasingly reported. Nodularins (NODs) are one of the cyanotoxins group mainly produced by Nodularia spumigena throughout the world. NODs may exert adverse effects on animal and human health, and NOD-R variant is the most widely investigated. However, research focused on them is still limited. In order to understand the realistic risk well, the aim of this review is to compile the available information in the scientific literature regarding NODs, including their sources, distribution, structural characteristics, physicochemical properties, biosynthesis and degradation, adverse effects in vitro and vivo, and toxicokinetics. More data is urgently needed to integrate the cumulative or synergistic effects of NODs on different species and various cells to better understand, anticipate and aggressively manage their potential toxicity after both short- and long-term exposure in ecosystem, and to minimize or prevent the adverse effects on human health, environment and the economy.