Exposure to pyrazosulfuron-ethyl induces immunotoxicity and behavioral abnormalities in zebrafish embryos

Perfluorodecanoic acid induces the increase of innate cells in zebrafish embryos by upregulating oxidative stress levels

Several studies reported that the widespread use of perfluoroalkyl and polyfluoroalkyl substances (PFASs) causes increased environmental pollution, subsequently impacting aquatic organisms. Perfluoroalkyl substances such as perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) reportedly cause cardiotoxicity, neurotoxicity, and developmental toxicity in different organisms. However, whether perfluorodecanoic acid (PFDA), a widely used perfluoroalkyl substance, induces animal embryos developmental toxicity remain unknown. Here, we explored the immunotoxicity and associated mechanisms of PFDA in zebrafish embryos via RNA sequencing, morphological assessment and behavioral alteration detection following exposure to 0.5, 1 and 2 mg/L of PFDA. Interestingly, We found that with the increase of PFDA to drug concentration, including neutrophils and macrophages, significantly increased the number of inherent cells, immune related genes expression. Furthermore, oxidative stress increased in the PFDA-treated embryos in a dose-dependent manner and inhibition of oxidative stress levels effectively rescued the number of neutrophils. Changes in embryonic behavior were observed after exposure to PFDA. Overall, our results suggest that PFDA may induce innate immune response by accumulation of oxidative stress in zebrafish at early developmental stages, and concern is needed about its environmental exposure risks for animals embryos development. ENVIRONMENTAL IMPLICATION: Perfluorinated and polyfluorinated alkyl substances (PFASs) are a class of synthetic organic compounds containing fluorine widely used as lubricants, surfactants, insecticides, etc. The PFDA, a typical perfluorinated compound, is often used as a wetting agent and flame retardant in industries. Several studies showed that PFASs can cause serious environmental pollution, leading to developmental toxicity to various animals, including reproductive toxicity, liver toxicity, heart toxicity, neurotoxicity, and immunotoxicity. However, there are still limited studies on the effects and mechanisms of PFDA on aquatic organisms. Therefore, there is a need to evaluate the ecological risks of PFDA in animals.

Effects of pyrazosulfuron-ethyl on caudal fin regeneration in zebrafish larvae

With the widespread application of pesticides, water pollution problems are becoming more and more serious, which is very likely to cause harm to fish. Lower vertebrates, including fish, have the ability to repair damaged tissues. The spread of pesticides in the water may affect their regeneration process after injury, leading to their death, thereby affecting the survival rate of the population. Therefore, we used zebrafish as a model animal to evaluate the effect of the pesticide pyrazosulfuron-ethyl on caudal fin regeneration in zebrafish larvae. We exposed zebrafish larvae to 0, 5, 15, and 25 mg/L pyrazosulfuron-ethyl at 3 days after caudal fin amputation. It was found that exposure to pyrazosulfuron-ethyl significantly inhibited caudal fin regeneration and affected the behavior of zebrafish larvae. After exposure to pyrazosulfuron-ethyl, proliferating cells decreased and apoptotic cells increased in the caudal fin of zebrafish larvae. Pyrazosulfuron-ethyl exposure resulted in the decreased number of neutrophils and macrophages, and the downregulation of immune related gene expression levels during caudal fin. Using LPS to activate inflammation can effectively rescue the fin regeneration defects induced by pyrazosulfuron-ethyl. However, inhibiting the Notch signaling pathway and inhibiting reactive oxygen cannot rescue the fin regeneration defects induced by pyrazosulfuron-ethyl. Our results indicate that pyrazosulfuron-ethyl can inhibit zebrafish caudal fin regeneration by reducing the number of innate immune cells and affecting the normal process of inflammation, thereby inhibiting caudal fin regeneration. This study expands our understanding of the potential effects of the pesticide pyrazosulfuron-ethyl on injured fish, highlights the link between the immune system and the regeneration process, and demonstrates the potential application of fin regeneration in risk assessments of environmental toxicology to assess drug toxicity.

Integration of transcriptomics, gut microbiota, and physiology reveals the toxic response of bensulfuron-methyl in Procambarus clarkii

Bensulfuron-methyl (BSM) enters the environment through agricultural practices, posing a threat to the health of aquatic organisms. Currently, the toxic mechanisms of BSM on crayfish (Procambarus clarkii) have not been thoroughly investigated. In this study, crayfish were exposed to BSM solutions at concentrations of 0, 5, and 10 mg/L for 48 h. The study integrated physiological, gut microbiota, and transcriptomic analyses to investigate the mechanisms of action. BSM exposure induced oxidative stress responses in crayfish, resulting in changes in superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GSH) activity, and malondialdehyde (MDA) levels. Exposure to BSM caused damage to the intestinal tissues, reduced gut microbiota diversity, increased the abundance of harmful bacteria, and led to intestinal dysfunction. Analysis of the hepatopancreas revealed significant tissue damage. Transcriptomic data indicated that BSM affects the growth of crayfish through genes related to immune response (SLC17A5, CTSD, CTSB, NFKBIA, Mincle). The lysosomal pathway and NF-κB pathway were notably affected. This study analyzed the negative impacts of BSM on crayfish from various levels and provided detailed data to enhance our understanding of the toxic mechanisms of BSM in aquatic organisms.

A review of cumulative toxic effects of environmental endocrine disruptors on the zebrafish immune system: Characterization methods, toxic effects and mechanisms

Environmental endocrine disrupting chemicals (EDCs), are a type of exogenous organic pollutants, are ubiquitous in natural aquatic environments. Currently, in addition to neurological, endocrine, developmental and reproductive toxicity, ecotoxicology studies on immunotoxicity are receiving increasing attention. In this review, the composition of immune system of zebrafish, the common indicators of immunotoxicity, the immunotoxicity of EDCs and their molecular mechanism were summarized. We reviewed the immunotoxicity of EDCs on zebrafish mainly in terms of immune organs, immunocytes, immune molecules and immune functions, meanwhile, the possible molecular mechanisms driving these effects were elucidated in terms of endocrine disruption, dysregulation of signaling pathways, and oxidative damage. Hopefully, this review will provide a reference for further investigation of the immunotoxicity of EDCs.

Immunotoxicity and transcriptome analysis of zebrafish embryos exposure to Nitazoxanide

Nitazoxanide (NTZ) is a broad-spectrum immunomodulatory drug, and little information is about the immunotoxicity of aquatic organisms induced by NTZ. In the present study, reduced body length and decreased yolk sac absorption in the NTZ-treated group were observed. Meanwhile, the number of innate immune cells and adaptive immune cells was substantially reduced upon NTZ exposure, and the migration and retention of macrophages and neutrophils in the injured area were inhibited. Following NTZ stimulation, oxidative stress levels in the zebrafish increased obviously. Mechanistically, RNA-seq, a high-throughput method, was performed to analyze the global expression of differentially expressed genes (DEGs) in zebrafish embryos treated with NTZ. 531 DEGs were identified by comparative transcriptome analysis, including 121 up-regulated and 420 down-regulated genes in zebrafish embryos after NTZ exposure. The transcriptome sequences were further subjected to the Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene ontology (GO) and analysis, showing phototransduction and metabolic pathway, respectively, and were most enriched. In addition, some immune-related genes were inhibited after NTZ exposure. RNA-seq results confirmed by qRT-PCR were used to verify the expression of the 6 selected genes. The other immune-related genes such as two pro-inflammatory cytokines (IL-1β, tnfα) and two chemokines (CXCL8b.3, CXCL-c1c) were further confirmed and were differentially regulated after NTZ exposure. In summary, NTZ exposure could lead to immunotoxicity and increased ROS in zebrafish embryos, this study provides valuable information for future elucidating the molecular mechanism of exogenous stimuli-induced immunotoxicity in aquatic ecosystems.

Developmental toxicity, immunotoxicity and cardiotoxicity induced by methidathion in early life stages of zebrafish

Methidathion is a highly effective organophosphorus pesticide and is extensively utilized for the control of insects in agricultural production. However, there is little information on the adverse effects and underlying mechanisms of methidathion on aquatic organisms. In this work, embryonic zebrafish were exposed to methidathion at concentrations of 4, 10, and 25 mg/L for 96 h, and morphological changes and activities of antioxidant indicators alterations were detected. In addition, the locomotor behavioral abilities of zebrafish exposed to methidathion were also measured. To further explore the mechanism of the toxic effects of methidathion, gene expression levels associated with cardiac development, cell apoptosis, and the immune system were tested through qPCR assays. The findings revealed that methidathion exposure could induce a decrease in survival rate, hatchability, length of body, and increase in abnormality of zebrafish, as well as cardiac developmental toxicity. The LC50 value of methidathion in zebrafish embryos was determined to be about 30.72 mg/L at 96 hpf. Additionally, methidathion exposure triggered oxidative stress in zebrafish by increasing SOD activity, ROS, and MDA content. Acridine orange (AO) staining indicated that methidathion exposure led to apoptosis, which was mainly distributed in the pericardial region. Furthermore, significant impairments of locomotor activity in zebrafish larvae were induced by methidathion exposure. Lastly, the expression of pro-inflammatory factors including IFN-γ, IL-6, IL-8, CXCL-clc, TLR4, and MYD88 significantly up-regulated in exposed zebrafish. Taken together, the results in this work illustrated that methidathion caused developmental toxicity, cardiotoxicity, and immunotoxicity in embryogenetic zebrafish.