Cadmium impairs zebrafish swim bladder development via ROS mediated inhibition of the Wnt / Hedgehog pathway

Sensitivity Variations in Developmental Toxicity of Imidacloprid to Zebrafish Embryos at Different Neurodevelopmental Stages

Neonicotinoids are ubiquitous in global surface waters and pose a significant risk to aquatic organisms. However, information is lacking on the variations in sensitivity of organisms at different developmental stages to the neurotoxic neonicotinoids. We established a spectrum of toxicity to zebrafish embryos at four neurodevelopmental stages (1, 3, 6, and 8 h post fertilization [hpf]) and dechorionated embryos at 6 hpf based on external and internal exposure to imidacloprid as a representative neonicotinoid. Embryos at the gastrula stage (6 and 8 hpf) were more sensitive to imidacloprid than embryos at earlier developmental stages. Dechorionated embryos were more sensitive to imidacloprid than embryos with a chorion, suggesting that the chorion offers protection against pollutants. Nine sublethal effects were induced by imidacloprid exposure, among which uninflated swim bladder (USB) was the most sensitive. Water depth and air availability in the exposure chambers were critical factors influencing the occurrence of USB in zebrafish larvae. Internal residues of metabolites accounted for <10% of imidacloprid, indicating that imidacloprid was metabolized in a limited fashion in the embryos. In addition, acute toxicity of the main metabolite 5-hydroxy-imidacloprid was significantly lower than that of imidacloprid, indicating that the observed toxicity in embryos exposed to imidacloprid was mainly induced by the parent compound. Our research offers a fresh perspective on choosing the initial exposure time in zebrafish embryo toxicity tests, particularly for neurotoxicants. Environ Toxicol Chem 2024;00:1-11. © 2024 SETAC.

Parental exposure to Cypermethrin causes intergenerational toxicity in zebrafish offspring

Cypermethrin (CYP), a synthetic pyrethroid pesticide, has been detected in agriculture and aquaculture. However, there is limited knowledge about the transgenerational impacts. This study aimed to investigate the developmental toxicity of CYP on F1 larvae offspring of adult zebrafish exposed to various CYP concentrations (5, 10, and 20 μg/L) for 28 days. The results indicated that CYP accumulated in parental zebrafish, and CYP was below the limit of quantification in offspring. Paternal exposure impacted the hatching rate and heart rate of the F1 generation. Furthermore, CYP significantly impacted the development of swim bladders in progeny and dysregulated the genes relevant to swim bladder development. The neutrophil migrated to the swim bladder. The mRNA levels of the inflammatory factors were also significantly elevated. According to network toxicology, PI3-AKT may be the signaling pathway for CYP-influenced bladder development. Subsequent molecular docking and Western blot analysis showed CYP affected the PI3-AKT signaling pathway. Notably, MK-2206, a specific Akt inhibitor, rescued the CYP-induced damage of swim bladder development in offspring. The present study highlights the potential risks of CYP on the development of offspring and lasting impact in aquatic environments.

Polluted water from a storage dam (Villa Victoria, méxico) induces oxidative damage, AChE activity, embryotoxicity, and behavioral changes in Cyprinus carpio larvae

The Villa Victoria dam is one of the most important storage reservoirs in Mexico since it distributes water to more than 20 million inhabitants in the Metropolitan Zone of Mexico City. In this dam, the common carp (Cyprinus carpio) is an important food resource for the inhabitants, so the aim of this work was to evaluate the oxidative damage (lipoperoxidation, oxidized proteins, antioxidant enzymes activity and gene expression), AChE, embryotoxicity and behavioral changes in C. carpio embryos and larvae exposed to water from Villa Victoria dam for 24, 48, 72 and 96 h. The embryotoxicity was evaluated trough the General Morphology Score (GMS) and the teratogenic index. Behavioral changes in basal locomotor activity and thigmotaxis were evaluated in a DanioVision, Noldus ™. An increase in lipid and protein oxidation as well as modification of CAT, SOD and GPx enzymatic activity was observed during the exposure times. The GMS indicated a low development in the embryos, the teratogenic index was less than 1, however teratogenic effects as yolk edema, fin malformation, head malformation and scoliosis were observed. In parallel, an increase in AChE activity and gene expression was observed reflecting changes in distance traveled of the basal locomotor activity and thigmotaxis at the sampling points. In conclusion, pollutants in water from Villa Victoria dam caused oxidative damage, changes in SOD, CAT, GPx and AChE activity as well as embryotoxicity and modifications in the behavior of C. carpio larvae. This study demonstrates the need to implement restoration programs for this reservoir since, contamination in the Villa Victoria dam could eventually endanger aquatic life and human health.

High NaCl Concentrations in Water Are Associated with Developmental Abnormalities and Altered Gene Expression in Zebrafish

Salt is frequently introduced in ecosystems, where it acts as a pollutant. This study examined how changes in salinity affect the survival and development of zebrafish from the two-cell to the blastocyst stage and from the blastocyst to the larval stage. Control zebrafish embryos were cultured in E3 medium containing 5 mM Sodium Chloride (NaCl), 0.17 mM Potassium Chloride (KCL), 0.33 mM Calcium Chloride (CaCl2), and 0.33 mM Magnesium Sulfade (MgSO4). Experiments were conducted using increasing concentrations of each individual salt at 5×, 10×, 50×, and 100× the concentration found in E3 medium. KCL, CaCl2, and MgSO4 did not result in lethal abnormalities and did not affect early embryo growth at any of the concentrations tested. Concentrations of 50× and 100× NaCl caused embryonic death in both stages of development. Concentrations of 5× and 10× NaCl resulted in uninflated swim bladders in 12% and 65% of larvae, compared to 4.2% of controls, and caused 1654 and 2628 genes to be differentially expressed in blastocysts, respectively. The ATM signaling pathway was affected, and the Sonic Hedgehog pathway genes Shh and Ptc1 implicated in swim bladder development were downregulated. Our findings suggest that increased NaCl concentrations may alter gene expression and cause developmental abnormalities in animals found in affected ecosystems.

Co-exposure to sodium hypochlorite and cadmium induced locomotor behavior disorder by influencing neurotransmitter secretion and cardiac function in larval zebrafish

Sodium hypochlorite (NaClO) and cadmium (Cd) are widely co-occurring in natural aquatic environment; however, no study has been conducted on effects of their combined exposure on aquatic organisms. To assess effects of exposure to NaClO and Cd in zebrafish larvae, we designed six treatment groups, as follows: control group, NaClO group (300 μg/L), 1/100 Cd group (48 μg/L), 1/30 Cd group (160 μg/L), NaClO+1/100 Cd group, and NaClO+1/30 Cd group analyzed behavior, neurological function and cardiac function. Results revealed that exposure to 1/30 Cd and NaClO+1/30 Cd caused abnormal embryonic development in larvae by altering body morphology and physiological indicators. Combined exposure to NaClO and 1/30 Cd affected the free-swimming activity and behavior of larvae in response to light-dark transition stimuli. Moreover, exposure to 1/30 Cd or NaClO+1/30 Cd resulted in a significant increase in tyrosine hydroxylase and acetylcholinesterase activities, as well as significant changes of various neurotransmitters. Lastly, exposure to 1/30 Cd or NaClO+1/30 Cd influenced the transcription of cardiac myosin-related genes and disturbed the myocardial contractile function. Altogether, our results suggested that combined exposure to NaClO and Cd induced oxidative damage in larvae, resulting in detrimental effects on nervous system and cardiac function, thus altering their swimming behavior.

Icariin induces developmental toxicity via thyroid hormone disruption in zebrafish larvae

Icariin (ICA) is a natural flavonoid isolated from the traditional Chinese medicinal herb, Epimedium brevicornu Maxim. Although previous studies have reported that ICA exhibits various pharmacological activities, little is known about its toxicology. Herein, zebrafish embryos were exposed to ICA at 0, 2.5, 10, and 40 μM. In developmental analysis, reduced hatching rates, decreased body length, and abnormal swim bladder were found after treatment with 10 and 40 μM ICA. In addition, the ability of locomotor behavior was impaired by ICA. Two important thyroid hormones (THs), triiodothyronine (T3) and thyroxine (T4), were tested. The exposure resulted in a remarkable alteration of T4 level and a significant decrease of the T3/T4 ratio in the 40 μM, indicating thyroid endocrine disruption. Furthermore, gene transcription analysis showed that genes involved in thyroid development (nkx2.1) and THs synthesis (tg) were up-regulated after ICA exposure. Significant down-regulation of iodothyronine deiodinase (dio1) was also observed in the 10 and 40 μM groups compared to the control. Taken together, our study first demonstrated that ICA caused developmental toxicity possibly through disrupting thyroid development and hormone synthesis. These results show that it is necessary to perform risk assessments of ICA in clinical practice.

Life-cycle exposure to tris (2-chloroethyl) phosphate (TCEP) causes alterations in antioxidative status, ion regulation and histology of zebrafish gills

Tris (2-chloroethyl) phosphate (TCEP) has been receiving great concerns owing to its ubiquitous occurrence in various environmental compartments and potential risks to wildlife and humans. Gill is structural basis for ion regulation and homeostasis in fish and susceptible to xenobiotics. However, current knowledge on the impacts of long-term exposure to TCEP on the structure and physiological function of fish gills are insufficient. In this work, zebrafish were exposed to environmental realistic concentrations (0.8, 4, 20 and 100 μg/L) of TCEP from 3 h post ferterlization (hpf) till 120 days post ferterlization (dpf). Our results demonstrated that life-cycle exposure to TCEP significantly decreased the activity of glutathione S-transferase (GST), but elevated the activities of antioxidative enzymes including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and increased malondialdehyde (MDA) content in zebrafish gills. Gene transcription analysis implied that the mRNA expressions of antioxidant-related genes (nrf2, cat and nqo1) were induced, while the transcription of gstα1, hmox1, keap1 were down-regulated, indicating that Nrf2-Keap1 pathway might be activated to defend the oxidative stress induced by TCEP. Additionally, the ion homeostasis was disrupted by TCEP exposure, evidenced by reduced activities of Na+/K+-ATPase (NKA), Ca2+-ATPase and Mg2+-ATPase and downregulated transcription levels of ncc, nkcc, cftr and clc-3. Besides, whole-life exposure to TCEP resulted in a series of structural damages to gills, including epithelial lifting, epithelial rupture, telangiectasis, vacuolation, edema and shortened gill lamellae. Overall, our results demonstrated that long-term TCEP exposure could induce oxidative stress, affect ion regulation and cause histological changes in zebrafish gills.

Doxorubicin and erastin co-loaded hydroxyethyl starch-polycaprolactone nanoparticles for synergistic cancer therapy

Cancer stem cells (CSCs), enabled to self-renew, differentiate, and initiate the bulk tumor, are recognized as the culprit of treatment resistance, metastasis, and recurrence. Simultaneously eradicating CSCs and bulk cancer cells is crucial for successful cancer therapy. Herein, we reported that doxorubicin (Dox) and erastin co-loaded hydroxyethyl starch-polycaprolactone nanoparticles (DEPH NPs) eliminated CSCs and cancer cells by regulating redox status. We found that an excellently synergistic effect existed when Dox and erastin were co-delivered by DEPH NPs. Specifically, erastin could deplete intracellular glutathione (GSH), thereby inhibiting the efflux of intracellular Dox and boosting Dox-induced reactive oxygen species (ROS) to amplify redox imbalance and oxidative stress. The high ROS levels restrained CSCs self-renewal via downregulating Hedgehog pathways, promoted CSCs differentiation, and rendered differentiated cancer cells vulnerable to apoptosis. As such, DEPH NPs significantly eliminated not only cancer cells but more importantly CSCs, contributing to suppressed tumor growth, tumor-initiating capacity, and metastasis, in various tumor models of triple negative breast cancer. This study demonstrates that the combination of Dox and erastin is potent in elimination of both cancer cells and CSCs, and that DEPH NPs represent a promising treatment against CSCs-rich solid tumors.

Cumulus Cell Transcriptome after Cumulus-Oocyte Complex Exposure to Nanomolar Cadmium in an In Vitro Animal Model of Prepubertal and Adult Age

Cadmium (Cd), a highly toxic pollutant, impairs oocyte fertilization, through oxidative damage on cumulus cells (CCs). This study analysed the transcriptomic profile of CCs of cumulus-oocyte complexes (COCs) from adult and prepubertal sheep, exposed to Cd nanomolar concentration during in vitro maturation. In both age-groups, CCs of matured oocytes underwent RNA-seq, data analysis and validation. Differentially expressed genes (DEGs) were identified in adult (n = 99 DEGs) and prepubertal (n = 18 DEGs) CCs upon Cd exposure. Transcriptomes of adult CCs clustered separately between Cd-exposed and control samples, whereas prepubertal ones did not as observed by Principal Component Analysis. The transcriptomic signature of Cd-induced CC toxicity was identified by gene annotation and literature search. Genes associated with previous studies on ovarian functions and/or Cd effects were confirmed and new genes were identified, thus implementing the knowledge on their involvement in such processes. Enrichment and validation analysis showed that, in adult CCs, Cd acted as endocrine disruptor on DEGs involved in hormone biosynthesis, cumulus expansion, regulation of cell signalling, growth and differentiation and oocyte maturation, whereas in prepubertal CCs, Cd affected DEGs involved in CC development and viability and CC-oocyte communications. In conclusion, these DEGs could be used as valuable non-invasive biomarkers for oocyte competence.

Cineole regulates Wnt/β-catenin pathway through Nrf2/keap1/ROS to inhibit bisphenol A-induced apoptosis, autophagy inhibition and immunosuppression of grass carp hepatocytes

Bisphenol A (BPA), an environmental pollutant, can cause multiple organ tissue damage by inducing oxidative stress. Cineole (CIN) is a terpene oxide existing in a variety of plant essential oils, which has anti-inflammatory, analgesic, and antioxidant effects. This study examined the effects of 200 nM BPA and 20 μM CIN on apoptosis, autophagy, and immunology in grass carp hepatocytes (L8824). The treatments were categorized as NC, CIN, BPA + CIN, and BPA. The findings demonstrated that BPA exposure could increase ROS levels and oxidative stress-related indicators, decrease the expression of the Nrf2/keap1 pathway and the Wnt/β-catenin pathway, increase the expression of genes involved in the apoptotic pathway (Bax and Caspase3), and decrease the expression of the anti-apoptotic gene Bcl-2 by lowering mitochondrial membrane potential. BPA also reduced the expression of genes linked to autophagy (ATG5, Beclin1, LC3). Changes in immunological function after BPA exposure were also shown by changes in the amounts of antimicrobial peptides (HEPC, β-defensin, LEAP2) and cytokines (INF-γ, IL-1β, IL-2, and TNF-α). After the co-treatment of CIN and BPA, CIN can inhibit BPA-induced apoptosis and recover from autophagy and immune function to a certain extent by binding to keap1 to exert an anti-oxidative regulatory effect of Nrf2 incorporation into the nucleus. Molecular docking provides strong evidence for the interaction of CIN ligands with keap1 receptors. Therefore, these results indicated that CIN could inhibit BPA-induced apoptosis, autophagy inhibition and immunosuppression in grass carp hepatocytes by regulating the Wnt/β-catenin pathway with Nrf2/keap1/ROS. This study provided further information to the risk assessment of the neuroendocrine disruptor BPA on aquatic organisms and offered suggestions and resources for further research into the function of natural extracts in the body's detoxification process.