Chlorothalonil as a potential endocrine disruptor in male zebrafish (Danio rerio): Impact on the hypothalamus-pituitary-gonad axis and sperm quality.

Chlorothalonil is a broad-spectrum organochlorine fungicide widely employed in agriculture to control fungal foliar diseases. This fungicide enters aquatic environments through the leaching process, leading to toxicity in non-target organisms. Organic contaminants can impact organism reproduction as they have the potential to interact with the neuroendocrine system. Although there are reports of toxic effects of chlorothalonil, information regarding its impact on reproduction is limited. The aim of the present study was to evaluate the influence of chlorothalonil on male reproductive physiology using the zebrafish (Danio rerio) as ecotoxicological model. Zebrafish were exposed for 7 days to two concentrations of chlorothalonil (0.1 and 10 µg/L) along with a control group (with DMSO - 0.001%). Gene expression of hypothalamus-pituitary-gonad axis components (gnrh2, gnrh3, lhr, fshr, star, hsd17b1, hsd17b3, and cyp19a1), as well as hepatic vitellogenin concentration were assessed. In sperm cells, reactive oxygen species (ROS) content, lipid peroxidation (LPO), mitochondrial functionality, and membrane integrity and fluidity were evaluated. Results indicate that exposure to the higher concentration of chlorothalonil led to a reduction in brain gnr2 expression. In gonads, mRNA levels of lhr, star, and hsd17b1 were decreased at both chlorothalonil concentrations tested. Similarly, hepatic vitellogenin concentration was reduced. Regarding sperm cells, a decreased ROS level was observed, without significant difference in LPO level. Additionally, a higher mitochondrial potential and lower membrane fluidity were observed in zebrafish exposed to chlorothalonil. These findings demonstrate that chlorothalonil acts as an endocrine disruptor, influencing reproductive control mechanisms, as evidenced by changes in expression of genes HPG axis, as well as hepatic vitellogenin concentration. Furthermore, our findings reveal that exposure to this contaminant may compromise the reproductive success of the species, as it affected sperm quality parameters.

Preclinical toxicological assessment of polydatin in zebrafish model.

Polydatin (3,4',5-trihydroxystilbene-3-ß-D-glucoside, piceid), a natural stilbenoid found in different plant sources, has gained increasing attention for its potential health benefits. However, prior to its widespread adoption in human therapeutics and consumer products, a comprehensive investigation of its toxicological effects is crucial. In this study, the toxicity of polydatin was investigated in a developmental toxicity test using zebrafish (Danio rerio) as a valuable model for preclinical assessments. We employed the Fish Embryo Test (FET test - OECD n°236) to investigate the effects of polydatin on survival, hatchability, development, and behavior of zebrafish embryo-larval stage. Remarkably, the results demonstrated that polydatin up to 435 µM showed no toxicity. Throughout the exposure period, zebrafish embryos exposed to polydatin exhibited normal development, with no significant mortality observed. Furthermore, hatching success and heartbeat rate were unaffected, and no morphological abnormalities were identified, signifying a lack of teratogenic effects and cardiotoxicity. Locomotion activity assessment revealed normal swimming patterns and response to stimuli, indicating no neurotoxic effects. Our study provides valuable insights into the toxicological profile of polydatin, suggesting that it may offer potential therapeutic benefits under a considerable concentration range. In addition, zebrafish model proves to be an efficient system for early-stage toxicological screening, guiding further investigations into the secure utilization of polydatin for human health and wellness.

N-acetylcysteine inhibits Mancozeb-induced impairments to the normal development of zebrafish embryos.

Mancozeb (MZ), a manganese/zinc-containing ethylene-bis-dithiocarbamate (EBCD) fungicide has been claimed to present low acute toxicity and short environmental persistence, however, its effects on embryogenesis in non-target organisms is unclear. Here, we used zebrafish embryos (5 hpf) to assess the potential embryotoxic effects induced by MZ (up to 72 hpf) as well as the role of reactive oxygen species (ROS) in this process by pre-treatment with a classical antioxidant (N-acetylcysteine, NAC). Markers of reactive oxygen species production (ROS), glutathione (GSH) levels and glutathione S-transferase (GST) activity were measured along with genotoxicity (comet assay), cell death (Acridine Orange) and behavioral parameters (spontaneous movement, touch stimulation and swimming response), in order to determine potential mechanisms of embryotoxicity. According to results, MZ was able to induce morphological abnormalities such as body axis distortion, DNA damage, cell death, increased ROS generation and changes in behavioral endpoints during zebrafish development. All these toxic effects were inhibited by the pre-treatment with NAC indicating a key role of redox unbalance during MZ-induced embryotoxicity. At least in our knowledge, this is the first report on the deleterious effect of MZ to the normal embryogenesis of zebrafish. In addition, the importance of ROS generation during this pathophysiological condition was highlighted.

Senecio brasiliensis impairs eclosion rate and induces apoptotic cell death in larvae of Drosophila melanogaster.

Senecio brasilienis (Spreng) Less., is a species native from Brazil, popularly known as "Maria mole", and known to induce hepatotoxicity due to its high content of Pyrrolizidine alkaloids. Despite its toxicity, this plant is widely used in Brazilian folk medicine. Considering the antagonizing effects described for S. brasiliensis, we describe here molecular markers involved in the toxicity of hydroalcoholic extract from leaves of S. brasiliensis (HESB) in Drosophila melanogaster. Phytochemical analysis of HESB revealed the presence of phenolic acids and flavonoids. A significant antioxidant potential against ABTS+ and DPPH radical was found in parallel. Ingestion of extract did not alter the survival and locomotor activity of adult flies. However when ingested along the larval developmental phase, the eclosion rate of flies was interrupted at higher concentration of extract. To comprehend this phenomenon several analysis were conducted in larvae. HESB stimulated activity of antioxidant enzymes SOD and GST, and increased GSH/GSSG ratio and ROS production. Additionally, HESB caused a significant decrease of cell viability. The mRNA expression of Nrf2, TrxR, CAT, Drice and Dilp6 were also significantly up-regulated. HESB caused significant decrease on the phosphorylation of MAPKs and AKT. In parallel, PARP cleavage and caspases 3/7 activity were stimulated. In addition, glucose, glycogen and triglycerides levels were decreased. Taken together our study depicts a disruption in the eclosion of D. melanogaster possibly attributed to the inhibition of kinases implied in developmental process, energetic demand and induction of apoptotic cell death process.