Growth inhibition of offspring larvae caused by the maternal transfer effects of tetrabromobisphenol A in zebrafish

Differential developmental effects and its potential mechanism of long-term exposure to TBBPA in two generations of marine medaka (Oryzias melastigma) during early life stages

Tetrabromobisphenol A (TBBPA), a most widely used brominated flame retardant, has been detected in worldwide aquatic environments. However, the effects and mechanisms of TBBPA at environmentally realistic levels have not been well characterized in aquatic organisms. This study aims to investigate the impact of TBBPA on developmental toxicity and endocrine system in two generations of marine medaka (Oryzias melastigma) during early life stages. The results revealed that the embryos under exposure to environmentally relevant concentrations of TBBPA (0, 5, 50, and 500 μg/L) resulted in accelerated hatching and growth development in F0 generation. Conversely, delayed hatching, decreased hatch rate, and growth inhibition were observed in the F1 generation. Moreover, TBBPA disrupted the levels of THs (thyroid hormones), GH (growth hormone), and IGF (insulin growth factor). The gene transcriptional profiling implies modified gene expressions in the HPT axis, GH/IGF axis, and endoplasmic reticulum stress. The molecular docking analysis confirmed the binding affinity of TBBPA to key endocrine-related proteins, which partially elucidates the mechanism of endocrine disruption and developmental abnormalities. Endoplasmic reticulum stress may explain the developmental differences between the two generations. This was the first study to explore the multigenerational developmental toxicity of TBBPA to marine fish, which is essential for ecological risk assessment of this emerging pollutant.

Ecotoxicological impact of the fungicide tebuconazole on fish: a historical review, global trends and challenges

Tebuconazole (TBZ) is a triazole fungicide broadly used to control fungal diseases in agricultural crops, fruit-bearing plants and forestry plantations. However, its increasing use and release into aquatic environments has raised concerns about its hazardous effects on the health of fish. Thus, the aim of the present study was to review the scientific literature on the ecotoxicological effects of TBZ and TBZ-based commercial formulations on fish. Historical review data (publication year and geographical distribution), TBZ type, experimental design, fish species, habitat, life stage, tissue/organ, lethal concentration (LC50), concentration and exposure time, biomarkers and effects were compiled and critically analyzed. Studies were mainly conducted with freshwater species at adult and larval stages, whereas no data were find for marine fish species. Zebrafish, (Danio rerio) was the most assessed species. Both TBZ and TBZ-based commercial formulations induced oxidative stress, endocrine disruption, neurotoxicity, genotoxicity, histopathologies, behavior impairments and mortality on fish. TBZ can induce synergistic and antagonistic effects on fish when it is combined to other pesticides. Overall, the current study has shown the potential hazardous effects of TBZ and TBZ-based commercial formulations on the health of fish.

Olfactory toxicity of tetrabromobisphenol A to the goldfish Carassius auratus

Tetrabromobisphenol A (TBBPA) is one of the most extensively used brominated flame retardants and its increasing use in consumer products has raised concerns about its ecotoxicity. Given the ubiquity of TBBPA in aquatic environments, it is inevitable that these chemicals will enter the olfactory chambers of fish via water currents. Nevertheless, the olfactory toxicity of TBBPA to aquatic organisms and the underlying toxic mechanisms have yet to be elucidated. Therefore, we investigated the olfactory toxicity of TBBPA in the goldfish Carassius auratus, a model organism widely used in sensory biology. Results showed that exposure to TBBPA resulted in abnormal olfactory-mediated behaviors and diminished electro-olfactogram (EOG) responses, indicating reduced olfactory acuity. To uncover the underlying mechanisms of action, we examined the structural integrity of the olfactory epithelium (OE), expression levels of olfactory G protein-coupled receptors (GPCRs), enzymatic activities of ion transporters, and fluctuations in neurotransmitters. Additionally, comparative transcriptomic analysis was employed to investigate the molecular mechanisms further. Our study demonstrates for the first time that TBBPA at environmentally relevant levels can adversely affect the olfactory sensitivity of aquatic organisms by interfering with the transmission of aqueous stimuli to olfactory receptors, impeding the binding of odorants to their receptors, disrupting the olfactory signal transduction pathway, and ultimately affecting the generation of action potentials.

Mechanistic insights into the parental co-exposure of T-2 toxin and epoxiconazole on the F1 generation of zebrafish (Danio rerio)

Mycotoxins and pesticides frequently coexist in agricultural commodities on a global scale. The potential transgenerational consequences induced by these substances pose a significant threat to human health. However, there is a lack of data concerning the effects of co-contamination by these chemicals in the F1 generation following parental exposure. This investigation delved into the mixture effects of T-2 toxin (T-2) and epoxiconazole (EPO) on the offspring of zebrafish (Danio rerio). The findings revealed that exposure across generations to a combination of T-2 and EPO resulted in toxicity in the larvae of the F1 generation. This was demonstrated by a significant increase in the levels or activities of malondialdehyde (MDA), thyroxine (T4), Caspase3, and cas9, along with a decrease in the levels of cyp19a, ERα, and ERβ. These outcomes suggested that cross-generational exposure to T-2 and EPO in D. rerio disrupted oxidative balance, induced cell apoptosis, and affected the endocrine system. Moreover, these effects were magnified when the F1 generation was continuously exposed to these compounds. Notably, these adverse effects could persist in subsequent generations without additional exposure. This study underscored the potential dangers associated with the simultaneous presence of T-2 and EPO on the development of fish offspring and the resulting environmental hazards to aquatic ecosystems. These findings emphasized the significant health risks posed by cross-generational exposure and highlighted the need for additional legislative measures to address these concerns.

The effects of bisphenol S exposure on the growth, physiological and biochemical indices, and ecdysteroid receptor gene expression in red swamp crayfish, Procambarus clarkii

The experiment was conducted to investigate the effects of Bisphenol S (BPS) on growth, physiological and biochemical indices, and the expression of ecdysteroid receptor (ECR) of the red swamp crayfish (Procambarus clarkii). The gene encoding ECR was isolated from red swamp crayfish by homologous cloning and rapid amplification of cDNA ends (RACE). The ECR transcripts were 1757 bp long and encoded proteins of 576 amino acids. The quantitative real-time PCR (qRT-PCR) analysis showed that the ECR gene was expressed in various tissues under normal conditions, and the highest level was observed in the ovary and the lowest level was observed in the muscle (P < 0.05). Then, the experiment was designed with four different BPS concentrations (0, 1, 10, and 100 μg/L), BPS exposure for 14 days, three parallel groups, and a total of 240 red swamp crayfish. At 100 μg/L BPS, the survival rate, weight gain rate, and relative length rate were decreased significantly (P < 0.05). Malonaldehyde (MDA) content reached the highest level at 100 μg/L BPS. When BPS concentration was higher than 10 μg/L, the activities of superoxide dismutase (SOD) and catalase (CAT) were significantly lower than those of the control group (P < 0.05). The expression levels of the ECR gene in ovary, intestinal, gill, and hepatopancreas tissues were significantly increased after BPS exposure (P < 0.05). The ECR gene expression in ovaries and Y-organs was significantly higher than other groups in 10 μg/L BPS (P < 0.05). The expressions of the tumor necrosis factor -α (TNF-α) and interleukin-6 (IL-6) genes in the hepatopancreas gradually increased, and the highest expression was observed exposed in 100 μg/L BPS (P < 0.05). This research will provide novel insights into the health risk assessment of BPS in aquatic organisms.

Multigenerational effects and mutagenicity of three flame retardants on germ cells in Caenorhabditis elegans

Flame retardants (FRs) have raised public concerns because of their environmental persistence and negative impacts on human health. Recent evidence has revealed that many FRs exhibit reproductive toxicities and transgenerational impacts, whereas the toxic effects of FRs on germ cells remain barely explored. Here we investigated the multigenerational effects of three flame retardants (TBBPA, TCEP and TCPP) on germ cell development in Caenorhabditis elegans, and examined the germ cell mutagenicity of these FRs by using whole genome sequencing. Parental exposure to three FRs markedly increased germ cell apoptosis, and impeded oogenesis in F1-F6 offspring. In addition, the double-increased mutation frequencies observed in progeny genomes uncover the mutagenic actions of FRs on germ cells. Analysis of mutation spectra revealed that these FRs predominantly induced point mutations at A:T base pairs, whereas both small and large indels were almost unaffected. These results revealed the long-term effects of FRs on development and genomic stability of germ cells, which may pose risks to environmental organisms and human reproductive health. Taken together, our findings suggest that germ cell mutagenicity should be carefully examined for the environmental risk assessment of FRs and other emerging pollutants.

Environmental impacts of chlorpyrifos: Transgenerational toxic effects on aquatic organisms cannot be ignored

Chlorpyrifos (CPF) has been extensively used in the world and frequently found in natural environments, might cause a range of environmental issues and pose a health risk to aquatic species. However, investigation of its toxic effects on offspring after parental exposure has been neglected, especially for aquatic organisms such as fish. In the current study, the effects of chronic CPF exposure (3 and 60 μg/L) on adult zebrafish (F0) was investigated to determine its influence on adult reproductive capacity and offspring (F1 and F2). The results showed the existence of CPF both in F0 ovaries and F1 embryos and larvae, indicating that CPF could be transferred directly from the F0 adult fish to F1 offspring. After 90 d exposure, we observed that F0 female fish showed increased proportion of perinucleolar oocyte in the ovaries, decreased proportion of mature oocyte, and decreased egg production, but not in F1 adult. The transcriptomic analysis revealed that the disruption of metabolism during oocyte maturation in the CPF treatment zebrafish might interfere with F0 oocytes development and quality and ultimately influence offspring survival. For the larvae, the parental CPF exposure distinctly inhibited heart rate at 72 and 120 hpf and increased the mortality of F1 but not F2 larvae. The changes of biochemical indicators confirmed a disturbance in the oxidative balance, induced inflammatory reaction and apoptosis in F1 larvae. Furthermore, the changing profiles of mRNA revealed by RNA-seq confirmed an increased susceptibility in F1 larvae and figured out potential disruptions of ROS metabolism, immune system, apoptosis, and metabolism pathways. Taken together, these results show that chronic CPF treatment can induce reproductive toxicity, and parental transfer of CPF occurs in fish, resulting in transgenerational alters in F1 generation survival and transcription that raising concerns on the ecological risk of CPF in the natural environment.