Changes of embryonic development, locomotor activity, and metabolomics in zebrafish co-exposed to chlorpyrifos and deltamethrin

Metabolomics reveals the lipid metabolism disorder in Pelophylax nigromaculatus exposed to environmentally relevant levels of microcystin-LR

Cyanobacterial blooms have emerged as a significant environmental issue worldwide in recent decades. However, the toxic effects of microcystin-LR (MC-LR) on aquatic organisms, such as frogs, have remained poorly understood. In this study, frogs (Pelophylax nigromaculatus) were exposed to environmentally relevant concentrations of MC-LR (0, 1, and 10 μg/L) for 21 days. Subsequently, we assessed the impact of MC-LR on the histomorphology of the frogs' livers and conducted a global MS-based nontarget metabolomics analysis, followed by the determination of substances involved in lipid metabolism. Results showed that MC-LR significantly induced histological alterations in the frogs' hepatopancreas. Over 200 differentially expressed metabolites were identified, primarily enriched in lipid metabolism. Biochemical analysis further confirmed that MC-LR exposure led to a disorder in lipid metabolism in the frogs. This study laid the groundwork for a mechanistic understanding of MC-LR toxicity in frogs and potentially other aquatic organisms.

AOP-Anchored Transcriptome Analysis Catalogue Accelerates the Discovery of Environmental Toxicants in Zebrafish

Current toxicity screening approaches to evaluate the vast number of environmental chemicals that require assessment are hampered due to their significant costs, time requirements, and reliance on live animal testing. The aim of the present study was to develop an adverse outcome pathway (AOP)-anchored transcriptome analysis (AATA) catalogue to expedite the discovery of environmental toxicants. 437 AOPs from the AOPwiki (https://aopwiki.org/) and 2280 transcriptomics data sets from NCBI Gene Expression Omnibus (GEO) and EMBL-EBI ArrayExpress (AE) repositories were comprehensively reviewed and analyzed. By using the differentially expressed molecular key event (mKE) genes as connection nodes, we created a large-scale environmental substance─target gene (mKE)─predicted adverse outcomes (SGAs) network that included 78 substances, 1099 genes, and 354 adverse outcomes (AOs). To validate the reliability of the network, comprehensive literature verification was conducted. We demonstrated that 164 of the 354 AOs identified have been previously characterized in the literature. The results for 136 of these AOs were consistent with the predictions of the AATA catalogue, representing an accuracy rate of 82.9%. Besides, distinct patterns in molecular KEs and AOs among categories of substances, such as biocides and metals, were demonstrated. Some representative substances, including atrazine and copper, pose significant risks to fish at various levels of biological organization. Moreover, experimental verification of the AATA predictions was conducted, including exposures of zebrafish to perfluorooctanesulfonate, cresyl diphenyl phosphate, and lanthanum. Results demonstrated consistency with predictions of the AATA catalogue, with an accuracy rate of 92.3%. Collectively, the present findings support the AATA catalogue as an efficient and promising platform for identifying environmental toxicants to fish and thereby provide novel insights into the understanding of potential risks of environmental contaminants.

Reviewing the use of zebrafish for the detection of neurotoxicity induced by chemical mixtures through the analysis of behaviour

The knowledge and assessment of mixtures of chemical pollutants in the aquatic environment is a complex issue that is often challenging to address. In this review, we focused on the use of zebrafish (Danio rerio), a vertebrate widely used in biomedical research, as a model for detecting the effects of chemical mixtures with a focus on behaviour. Our aim was to summarize the current status of the ecotoxicological research in this sector. Specifically, we limited our research to the period between January 2012 and September 2023, including only those works aimed at detecting neurotoxicity through behavioural endpoints, utilizing zebrafish at one or more developmental stages, from egg to adult. Additionally, we gathered the findings for every group of chemicals involved and summarised data from all the works we included. At the end of the screening process 101 papers were considered eligible for inclusion. Results show a growing interest in zebrafish at all life stages for this kind of research in the last decade. Also, a wide variety of different assays, involving different senses, was used in the works we surveyed, with exposures ranging from acute to chronic. In conclusion, the results of this study show the versatility of zebrafish as a model for the detection of mixture toxicity although, for what concerns behavioural analysis, the lack of standardisation of methods and endpoints might still be limiting.

Long-term tributyltin exposure alters behavior, oocyte maturation, and histomorphology of the ovary due to oxidative stress in adult zebrafish

Tributyltin (TBT), an organotin endocrine-disrupting substance, is recognized as one of the important toxic environmental pollutants. The present study was carried out to investigate the toxic effects of TBT on behavior and the ovary of adult zebrafish with a focus on oxidative stress markers and oocyte maturation. Adult zebrafish were exposed to three different concentrations (125, 250, and 500 ng/L of water) of TBT for 28 days. TBT exposure produced a concentration-dependent negative effect on the body weight and behavior (anxiety-like symptoms) of adult zebrafish. Alterations in the activity of superoxide dismutase (SOD) and catalase (CAT), the total antioxidant capacity of ovarian tissue by the highest exposure level of TBT resulted in lipid peroxidation as indicated by increased malondialdehyde (MDA) level. The numbers of early-vitellogenic oocytes were significantly increased in zebrafish exposed to TBT as low as 125 ng/L. However, the numbers and size of fully-grown (mature) oocytes were significantly reduced in the highest exposure group only. Correlation between the MDA level and pre-vitellogenic oocytes in the 500 ng/L group indicated that lipid peroxidation prevented the maturation of pre-vitellogenic oocytes. TBT exposure produced significant histological changes in the ovary as evidenced by disturbed maturation of oocytes. In conclusion, TBT adversely affected the maturation of oocytes in zebrafish ovary through oxidative stress-mediated mechanisms.

Co-exposure to polystyrene microplastics and cypermethrin enhanced the effects on hepatic phospholipid metabolism and gut microbes in adult zebrafish

Microplastics (MPs) can absorb environmental pollutants from the aquatic environment to cause mixed toxicity, which has received widespread attention. However, studies on the joint effects of MPs and insecticides are limited. As one of the most widely used pyrethroids, there was a large amount of residual cypermethrin (CYP) in water due to insufficient decomposition. Here, adult female zebrafish were exposed to MPs, CYP, and their mixtures for 21 days, respectively. After exposures, the MPs and CYP caused tissue damage to the liver. Hepatic triglyceride (TG) level increased significantly after MPs + CYP exposure, and the expression of genes about glycolipids metabolism was significantly altered. Furthermore, metabolome results suggested that MPs + CYP exposure resulted in increased content of some glycerophospholipid, affecting phospholipid metabolism-related pathways. In addition, through 16 s rDNA sequencing, it was found that MPs + CYP led to significant changes in the proportion of dominant phyla. Interestingly, Cetobacterium which increased in CYP and the co-exposure group was positively correlated with most lipid metabolites. Our results suggested that co-exposure to MPs and CYP enhanced the disturbances in hepatic phospholipid metabolism by affecting the gut microbial composition, while these changes were not observed in separate treatment groups. These results emphasized the importance of studying the joint toxicity of MPs and insecticides.

Lipid metabolic links between serum pyrethroid levels and the risk of incident type 2 diabetes: A mediation study in the prospective design

Emerging evidence revealed that pyrethroids and circulating lipid metabolites are involved in incident type 2 diabetes (T2D). However, the pyrethroid-associated lipid profile and its potential role in the association of pyrethroids with T2D remain unknown. Metabolome-wide association or mediation analyses were performed among 1006 pairs of T2D cases and matched controls nested within the prospective Dongfeng-Tongji cohort. We identified 59 lipid metabolites significantly associated with serum deltamethrin levels, of which eight were also significantly associated with serum fenvalerate (false discovery rate [FDR] < 0.05). Pathway enrichment analysis showed that deltamethrin-associated lipid metabolites were significantly enriched in the glycerophospholipid metabolism pathway (FDR = 0.02). Furthermore, we also found that several deltamethrin-associated lipid metabolites (i.e., phosphatidylcholine [PC] 32:0, PC 34:4, cholesterol ester 20:0, triacylglycerol 52:5 [18:2]), and glycerophosphoethanolamine-enriched latent variable mediated the association between serum deltamethrin levels and T2D risk, with the mediated proportions being 44.81%, 15.92%, 16.85%, 16.66%, and 22.86%, respectively. Serum pyrethroids, particularly deltamethrin, may lead to an altered circulating lipid profile primarily in the glycerophospholipid metabolism pathway represented by PCs and lysophosphatidylcholines, potentially mediating the association between serum deltamethrin and T2D. The study provides a new perspective in elucidating the potential mechanisms through which pyrethroid exposure might induce T2D.

6-Benzylaminopurine causes lipid dyshomeostasis via disruption of glycerophospholipid metabolism in zebrafish

6-Benzylaminopurine (6-BA) is ubiquitous in agricultural production and is accessible to humans through diets. The modulation of lipid metabolism by 6-BA has been previously demonstrated in plants and oleaginous microorganisms. Therefore, whether it alters lipid homeostasis in other living organisms requires further investigation. In this study, doses ≥10 mg 6-BA/L caused malformation of the yolk sac, steatosis, and other hepatopathies in zebrafish larvae. Exposure to 25 mg 6-BA/L resulted in increased levels of triglyceride and total cholesterol. Results of transcriptomic analysis indicated that 6-BA alters genes associated with fatty acid and glycerophospholipid metabolism. Among them, the expression levels of hmgcra, elovl7b, and apobb.2 were downregulated, whereas those of lpcat3, bco1l, cyp7al, fabp1b.1, elp6, pde6ha, apoa4b.2_2, sgk1, dgkaa, and mogat2 were upregulated. Correspondingly, a study of the metabolome identified lysophosphatidylcholine (LPC) as the major differentially expressed metabolite in response to 6-BA treatment. Therefore, abnormal accumulation of LPCs and dyshomeostasis of glycerophospholipid metabolism were identified as potential mechanisms causing the toxicity of 6-BA, which should be assessed to understand the risks of 6-BA and the products contaminated by it. ENVIRONMENTAL IMPLICATION: 6-Benzylaminopurine (6-BA), an important residue in "toxic bean sprouts," is ubiquitous in agricultural production and is common in typical diets. Its regulation of lipid metabolism has been demonstrated in plants and oleaginous microorganisms. Whether it alters lipid homeostasis in other organisms and the underlying mechanisms remain largely unknown. The worldwide use of 6-BA and the potential exposure of humans have aroused public attention owing to its hazardous effects; thus, its hazardous effects, particularly those on lipid homeostasis, deserve careful clarification.

Antioxidant/protective effects of carob pod (Ceratonia siliqua L.) water extract against deltamethrin-induced oxidative stress/toxicity in zebrafish larvae

In our study, the antioxidant capacity of carob pods water extract (CPWE) against deltamethrin (DM)-induced oxidative stress, a widely used pesticide around the world, was investigated in vitro and in vivo in a zebrafish model. The in vitro antioxidant capacity of the obtained extract was evaluated with different methods using trolox, BHA and BHT standard antioxidants. For in vivo experiments, 4hpf zebrafish embryos were exposed to 10 ppb and 25 ppb DM for 120 h and the larvae were treated with 1-10 and 100 ppm CPWE for 4 h at 72th hours. According to the results obtained, it has been determined that the exposure of zebrafish to DM during the developmental period causes important body malformations, decrease in survival rate, reduction in eye size, shortening in body length and decrease in locomotor activity in the dark period. In addition, according to the results of whole-mount staining, it was determined that DM caused a significant increase in the amount of free oxygen radicals and apoptotic cells. It was also confirmed by metabolome analysis that CPWE application for 4 h reduced DM-induced toxicity and oxidative stress. As a result, it can be said that CPWE has an important antioxidant capacity in eliminating DM-induced oxidative stress.

Zebrafish: A Pharmacological Model for Learning and Memory Research

Learning and memory are essential to organism survival and are conserved across various species, especially vertebrates. Cognitive studies involving learning and memory require using appropriate model organisms to translate relevant findings to humans. Zebrafish are becoming increasingly popular as one of the animal models for neurodegenerative diseases due to their low maintenance cost, prolific nature and amenability to genetic manipulation. More importantly, zebrafish exhibit a repertoire of neurobehaviors comparable to humans. In this review, we discuss the forms of learning and memory abilities in zebrafish and the tests used to evaluate the neurobehaviors in this species. In addition, the pharmacological studies that used zebrafish as models to screen for the effects of neuroprotective and neurotoxic compounds on cognitive performance will be summarized here. Lastly, we discuss the challenges and perspectives in establishing zebrafish as a robust model for cognitive research involving learning and memory. Zebrafish are becoming an indispensable model in learning and memory research for screening neuroprotective agents against cognitive impairment.

Mass Spectrometry-Based Zebrafish Toxicometabolomics: A Review of Analytical and Data Quality Challenges

Metabolomics has achieved great progress over the last 20 years, and it is currently considered a mature research field. As a result, the number of applications in toxicology, biomarker, and drug discovery has also increased. Toxicometabolomics has emerged as a powerful strategy to provide complementary information to study molecular-level toxic effects, which can be combined with a wide range of toxicological assessments and models. The zebrafish model has gained importance in recent decades as a bridging tool between in vitro assays and mammalian in vivo studies in the field of toxicology. Furthermore, as this vertebrate model is a low-cost system and features highly conserved metabolic pathways found in humans and mammalian models, it is a promising tool for toxicometabolomics. This short review aims to introduce zebrafish researchers interested in understanding the effects of chemical exposure using metabolomics to the challenges and possibilities of the field, with a special focus on toxicometabolomics-based mass spectrometry. The overall goal is to provide insights into analytical strategies to generate and identify high-quality metabolomic experiments focusing on quality management systems (QMS) and the importance of data reporting and sharing.

Screening of Marine Bioactive Antimicrobial Compounds for Plant Pathogens

Plant diseases have been threatening food production. Controlling plant pathogens has become an important strategy to ensure food security. Although chemical control is an effective disease control strategy, its application is limited by many problems, such as environmental impact and pathogen resistance. In order to overcome these problems, it is necessary to develop more chemical reagents with new functional mechanisms. Due to their special living environment, marine organisms have produced a variety of bioactive compounds with novel structures, which have the potential to develop new fungicides. In the past two decades, screening marine bioactive compounds to inhibit plant pathogens has been a hot topic. In this review, we summarize the screening methods of marine active substances from plant pathogens, the identification of marine active substances from different sources, and the structure and antibacterial mechanism of marine active natural products. Finally, the application prospect of marine bioactive substances in plant disease control was prospected.