Search Results (785)

Anthropogenic noise pollution is a significant global environmental issue that adversely affects the behavior, physiology, and auditory functions of aquatic species. However, studies on the effects of underwater noise on early developmental stages of fish remain scarce, particularly regarding the differential impacts of daytime versus nighttime noise exposure. In this study, zebrafish (Danio rerio) embryos were exposed to control group (no additional noise), daytime noise (100–1000 Hz, 130 dB, from 08:00 to 20:00) or nighttime noise (100–1000 Hz, 130 dB, from 20:00 to 08:00) for 5 days, and their embryonic development and oxidative stress levels were analyzed. Compared to the control group, the results indicated that exposure to both daytime and nighttime noise led to delays in embryo hatching time and a significant decrease in larval heart rate. Notably, exposure to nighttime noise significantly increased the larval deformity rate. Noise exposure, particularly at night, elevated the activities of catalase (CAT) and glutathione peroxidase (GPX), as well as the concentration of malondialdehyde (MDA), accompanied by upregulation of antioxidant-related gene expression levels. Nighttime noise exposure significantly increased the abnormality rate of otolith development in larvae and markedly downregulated the expression levels of otop1 related to otolith development regulation, while daytime noise exposure only induced a slight increase in the otolith abnormality rate. After noise exposure, the number of lateral neuromasts in larvae decreased slightly, yet genes (slc17a8 and capgb) related to hair cell development were significantly upregulated. Overall, this study demonstrates that both daytime and nighttime noise can induce oxidative stress and impair embryonic development of zebrafish, with nighttime noise causing more severe damage. Full article

Eriobotrya japonica (Thunb.) Lindl. leaves are rich in polyphenolic compounds, yet their toxicological effects in aquatic models remain poorly understood. This study evaluated the impact of a hydroethanolic E. japonica leaf extract on zebrafish embryos through the use of morphological, behavioral, and biochemical parameters. The 96 h LC₅₀ was determined as 189.8 ± 4.5 mg/L, classifying the extract as practically non-toxic, according to OECD guidelines. Thereby, embryos were exposed for 90 h to 75 and 150 mg/L concentrations of the E. japonica leaf extract. While no significant effects were noted at the lowest concentration of 150 mg/L, significant developmental effects were observed, including reduced survival, delayed hatching, underdevelopment of the swim bladder, and retention of the yolk sac. These malformations were accompanied by marked behavioral impairments. Biochemical analysis revealed a concentration-dependent increase in superoxide dismutase (SOD) and catalase (CAT) activity, suggesting the activation of antioxidant defenses, despite no significant change in reactive oxygen species (ROS) levels. This indicates a potential compensatory redox response to a pro-oxidant signal. Additionally, the acetylcholinesterase (AChE) activity was significantly reduced at the highest concentration, which may have contributed to the observed neurobehavioral changes. While AChE inhibition is commonly associated with neurotoxicity, it is also a known therapeutic target in neurodegenerative diseases, suggesting concentration-dependent dual effects. In summary, the E. japonica leaf extract induced concentration-dependent developmental and behavioral effects in zebrafish embryos, while activating antioxidant responses without triggering oxidative damage. These findings highlight the extract’s potential bioactivity and underscore the need for further studies to explore its safety and therapeutic relevance. Full article

Background: Toxoplasma gondii is a globally widespread parasite responsible for toxoplasmosis, a zoonotic disease with significant impact on both human and animal health. The current lack of safe and effective treatments underscores the need for new drugs. Earlier, thiosemicarbazones (TSCs) and their metal complexes have shown promising activities against T. gondii. This study evaluated a gold (III) complex C3 and its TSC ligand C4 for safety in host immune cells and zebrafish embryos, followed by efficacy assessment in a murine model for chronic toxoplasmosis. Methods: The effects on viability and proliferation of murine splenocytes were determined using Alamar Blue assay and BrdU ELISA, and potential effects of the drugs on zebrafish (Danio rerio) embryos were detected through daily light microscopical inspection within the first 96 h of embryo development. The parasite burden in treated versus non-treated mice was measured by quantitative real-time PCR in the brain, eyes and the heart. Results: Neither compound showed immunosuppressive effects on the host immune cells but displayed dose-dependent toxicity on early zebrafish embryo development, suggesting that these compounds should not be applied in pregnant animals. In the murine model of chronic toxoplasmosis, C4 treatment significantly reduced the parasite load in the heart but not in the brain or eyes, while C3 did not have any impact on the parasite load. Conclusions: These results highlight the potential of C4 for further exploration but also the limitations of current approaches in effectively reducing parasite burden in vivo. Full article

The collection of perivitelline fluid (PVF) from early-stage post-activation zebrafish (Danio rerio) eggs/embryos poses a significant challenge owing to the liability of the egg/embryo to sustain damage and rupture during handling. Rupture of the blastoderm and/or yolk presents a major risk of PVF sample contamination. Previous efforts to extract PVF at such early stages have employed formalin fixation to enhance the structural integrity of the blastoderm and yolk syncytial layer, thereby reducing the likelihood of contamination. While this approach successfully mitigates blastoderm and yolk rupture, formaldehyde fixation may cause issues with downstream proteomic analyses. Recent findings indicate that zebrafish PVF contains a range of maternally inherited proteins involved in innate immune defence. However, current extraction methods compromise the reliability of downstream protein analyses, raising concerns that fixation-induced protein crosslinking may obscure the presence of maternally inherited proteins during the earliest stages of development. The micro-aspiration technique described here allows for the precise extraction of PVF from living, water-activated eggs with minimal disruption to the blastodisc and yolk. This method reduces the risk of contamination from other non-target proteinaceous egg sources and eliminates the need for formalin fixation, thereby improving the integrity of PVF samples and enhancing the reliability of subsequent downstream analyses. Full article

Olive mill wastewaters (OMWWs) are an environmental problem in the Mediterranean region, and it is crucial to explore strategies for their treatment and repurposing. The chemical precipitation technique (CPT) has been presented as a cost-effective wastewater treatment solution that might be applied to OMWW. The CPT-resulting precipitant subproducts (sludge) may be reprocessed (e.g., agricultural fertilizer and/or soil amendment), while the treated wastewater may be repurposed or reused (e.g., irrigation, aquaponic, or industrial processes). This study aimed to evaluate the efficacy of CPT in treating wastewater from the olive oil industry from an ecotoxicological perspective. Additionally, to assess the safe use of the obtained sludge in CPT treatment, its effects on soil biota were assessed. For this, a set of ecotoxicological assays using freshwater (Raphidocelis subcapitata, Daphnia magna and Danio rerio), terrestrial invertebrates (Folsomia candida and Enchytraeus crypticus), and plants (Brassica oleracea and Lolium perenne) were used as model organisms. Results demonstrated that CPT reduced OMWW toxicity to freshwater organisms, offering a favorable outlook on CPT’s potential as a wastewater treatment method. Increasing application rates of sludge in soil reduced the shoot biomass and the hydric content of both plants compared to the control. Survival of F. candida and E. crypticus was not affected by sludge in soil at any tested application rate, yet sludge application negatively affected the reproduction of both species, even at relevant sludge application rates (2%) of sludge in soils. Overall, the applicability of this sludge obtained by the CPT treatment in soils should be carefully evaluated due to the observed adverse effects on soil biota. Although the results of CPT were promising in reducing the toxicity of OMWW for these aquatic species, some adjustments/improvements should be performed to improve this technique and use all the obtained resources (treated water and sludge) in a fully circular perspective. Full article

Background/Objectives: The incorporation of bioactive molecules into mesoporous carriers is a promising strategy to improve stability, solubility, and therapeutic efficacy. In this study, we report for the first time the encapsulation of the synthetic chalcone 4-Cl into KIT-6 mesoporous silica and evaluate its cytotoxicity, toxicological profile, and pharmacological activities (antinociceptive, anti-inflammatory, and anxiolytic) using an in vivo zebrafish (Danio rerio) model. Methods: Zebrafish were orally dosed with 4-Cl, 4-Cl/KIT-6, or KIT-6 (4, 20, 40 mg/kg) and mortality was recorded for 96 h. For analgesia, zebrafish pretreated with 4-Cl, 4-Cl/KIT-6, KIT-6, or morphine received a tail stimulus (0.1% formalin). Locomotor activity (quadrant crossings) was monitored for 30 min to assess analgesia (neurogenic: 0–5 min; inflammatory: 15–30 min). For inflammation, abdominal edema and weight gain were assessed 4 h after intraperitoneal carrageenan (1.5%). Zebrafish (n = 6/group) received 4-Cl, 4-Cl/KIT-6, or KIT-6 (4, 20, 40 mg/kg, p.o.). Controls received ibuprofen (100 mg/kg, p.o.) or 3% DMSO. Weight was measured hourly for 4 h post-carrageenan (difference between baseline and hourly weights). Results: Physicochemical characterizations confirmed successful encapsulation without compromising the ordered structure of KIT-6, as evidenced by a significant reduction in surface area and pore volume, indicating efficient drug incorporation. In vivo assays demonstrated that the 4-Cl/KIT-6 formulation maintained the pharmacological activities of the free chalcone, reduced toxicity, and, notably, revealed a significant anxiolytic effect for the first time. Conclusions: These findings highlight KIT-6 as a promising platform for chalcone delivery systems and provide a solid basis for future preclinical investigations. Full article

Nano- (NPs) and microplastics (MPs) are ubiquitous and raising concerns about their toxicity. A popular model for studying acute toxicity is Danio rerio. This study investigated the acute toxicity in FET test of polystyrene nanoparticles (500 nm, nanoPS) at different concentrations (0.01, 0.1, and 0.2 mg/mL), with different surface groups (non-modified, amine, carboxyl) and discuss the toxicological contribution of commercially added compounds. Different behavioural tests were used to investigate the neurotoxicity of nanoPS and sodium azide: coiling assay test, light–dark preference test, and colour preference test. Sodium azide and other preservatives are often present in commercially available NP and MP solutions frequently used in microplastic toxicity tests, but their effects on the results remain largely unknown. In the FET test, nanoPS did not increase mortality or affect the heart rate or body length. A higher hatching rate was observed at 48 hpf. Although nanoPS showed no acute toxicity, behavioural tests revealed subtle neurotoxic effects (changes in colour preference), suggesting a potential impact on neurological function. Additionally, sodium azide exhibited toxicity, indicating that additives may confound toxicity assessments. This highlights the need for careful consideration of preservatives in nanoparticle research to avoid misleading conclusions. Full article

Strobilurins are a prominent class of fungicides capable of entering aquatic environments via runoff and leaching from the soil. Findings from previous studies suggest that strobilurins are highly toxic in aquatic environments, and evidence of acute developmental toxicity and altered behavioral responses have been emphasized. The objective here was to determine the effects of a new strobilurin, metyltetraprole (MTP), on zebrafish using developmental endpoints, gene expression, and behavioral locomotor assays. We hypothesized that MTP would cause developmental toxicity and induce hyperactivity in zebrafish (Danio rerio). To test this, developing zebrafish embryos/larvae were exposed to environmentally relevant levels of MTP (0.1, 1, 10, and 100 µg/L) until 7 days post-fertilization. Survival percentages did not differ among the treatment groups. No change in reactive oxygen species production was detected, but two genes involved in the mitochondrial electron transport chain (mt-nd3 and uqcrc2) were altered in abundance following MTP exposure. Moreover, the highest concentration (100 µg/L) of MTP caused notable hyperactivity in the zebrafish in the visual motor response test. Overall, results from this study increase our knowledge regarding sub-lethal effects of MTP, helping inform risk assessment for aquatic environments. Full article

The zebrafish (Danio rerio) has emerged as a powerful model organism for investigating the mechanisms of post-traumatic stress disorder (PTSD), offering unique advantages in translational relevance, genetic trackability, and cost-effectiveness. As a logical continuation of our recent systematic review, this manuscript critically examines the spectrum of experimental strategies used to model PTSD in zebrafish, with a focus on the comparative efficacy and validity of acute, chronic, and complex stress paradigms. Among these, 14–15-day chronic unpredictable stress (CUS/UCS) protocols are identified as the gold standard, reliably inducing core PTSD-like phenotypes—such as anxiety-like behavior, cortisol dysregulation, and neuroinflammatory gene activation. We discuss the influence of environmental, developmental, and genetic factors on stress responses, and highlight the importance of standardized behavioral and molecular endpoints for model validation. While alternative paradigms—including acute, social, pharmacological, and predator-based models—offer mechanistic insights, their translational relevance remains limited without further refinement. We conclude by outlining future directions for zebrafish-based PTSD research, emphasizing the need for protocol harmonization, integration of multi-modal readouts, and exploration of individual variability to enhance the translational value of this model system. Full article

Early diagnosis is critical for the effective management of neurodegenerative disorders, and retinal alterations have emerged as promising early biomarkers due to the retina’s close developmental and functional link to the brain. The zebrafish (Danio rerio), with its rapid development, transparent embryos, and evolutionarily conserved visual system, represents a powerful and versatile model for studying retinal degeneration. This review discusses a range of behavioral assays—including visual adaptation, motion detection, and color discrimination—that are employed to evaluate retinal function in zebrafish. These methods enable the detection of subtle visual deficits that may precede overt anatomical damage, providing a non-invasive, efficient strategy for early diagnosis and high-throughput drug screening. Importantly, these behavioral tests also serve as sensitive functional readouts to evaluate the efficacy of pharmacological treatments over time. Compared to traditional murine models, zebrafish offer advantages such as lower maintenance costs, faster development, optical transparency for live imaging, and ethical benefits due to reduced use of higher vertebrates. However, variability in experimental protocols highlights the need for standardization to ensure reliability and reproducibility. Full article

Background/Objectives: Haloperidol is a typical antipsychotic drug widely used for acute confusional state, psychotic disorders, agitation, delirium, and aggressive behavior. Methods: The toxicity of haloperidol was studied using zebrafish (ZF) embryos as a model organism. Dechorionated embryos were exposed to various concentrations of haloperidol (0.5–6.0 mg/L). The lethal dose concentration was estimated and was found to be 1.941 mg/L. Results: The impact of haloperidol was dose-dependent and significant from 0.25 mg/L. Haloperidol induced several deformities at sublethal doses, including abnormal somites, yolk sac edema, and skeletal deformities. Haloperidol significantly affected heart rate and blood flow and induced pericardial edema and hyperemia in a dose-dependent manner, suggesting its influence on heart development and function. Embryos exposed to haloperidol during their ontogenetic development had smaller body length and eye surface area than non-exposed ones in a dose-dependent manner. Conclusions: It was found that haloperidol significantly affects the behavior of the experimental organisms in terms of mobility, reflexes to stimuli, and adaptation to dark/light conditions. Full article

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exposure has long been associated with reproductive dysfunction in males and females even at miniscule levels, which can persist across generations. Given the continued industrial use and detection of other aryl hydrocarbon receptor (AhR) agonists in the general population and the demonstrated heritable phenotypes of TCDD exposure, further work is justified to elucidate reproductive pathologies and minimize exposure risk. In females, multi- and transgenerational subfertility has been demonstrated in a zebrafish (Danio rerio) model exposed to 50 pg/mL TCDD once at 3 and 7 weeks post fertilization (wpf). We further characterize the histopathologic, hormonal and transcriptomic outcomes of the mature female zebrafish ovary following early-life TCDD exposure. Exposure was associated with significantly increased ovarian atresia in the F0 and F1, but not F2 generation. Other oocyte staging and vitellogenesis were unaffected in all generations. Exposed F0 females showed increased levels of whole-body triiodothyronine (T3) and 17β-estradiol (E2) levels, but not vitellogenin (Vtg), 11-ketotestosterone (11-KT), cortisol, thyroxine (T4), or testosterone (T). Ovarian transcriptomics were most dysregulated in the F2. Both F0 and F2, but not F1, showed changes in epigenetic-related gene expression. Rho signaling was the top pathway for both F0 and F2. Full article

Epilepsy remains a widespread neurological disorder, with approximately 30% of patients showing resistance to current antiepileptic therapies. To address this unmet need, a series of 2-(isoindolin-2-yl) esters derived from natural amino acids were designed and evaluated for their potential interaction with the GABA_A receptor. Sixteen derivatives were subjected to in silico assessments, including physicochemical and ADMET profiling, virtual screening–ensemble docking, and enhanced sampling molecular dynamics simulations (metadynamics calculations). Among these, compounds derived from the aromatic amino acids, phenylalanine, tyrosine, tryptophan, and histidine, exhibited superior predicted affinity, attributed to π–π stacking interactions at the benzodiazepine binding site of the GABA_A receptor. Based on computational performance, the tyrosine and tryptophan derivatives were synthesized and further assessed in vivo using the pentylenetetrazole-induced seizure model in zebrafish (Danio rerio). The tryptophan derivative produced comparable behavioral seizure reduction to the reference drug diazepam at the tested concentrations. The results implies that aromatic amino acid-derived isoindoline esters are promising anticonvulsant candidates and support the hypothesis that π–π interactions may play a critical role in modulating GABA_A receptor binding affinity. Full article

Silver nanoparticles (AgNPs), lauded for their unique antibacterial and physicochemical attributes, are proliferating across industrial sectors, raising concerns about their environmental fate, in aquatic systems. While “green” synthesis offers a sustainable production route with reduced chemical byproducts, the safety of these AgNPs for aquatic fauna remains uncertain due to nanoparticle-specific effects. Conversely, mast cells play crucial roles in fish immunity, orchestrating innate and adaptive immune responses by releasing diverse mediators and recognizing danger signals. Goblet cells are vital for mucosal immunity and engaging in immune surveillance, regulation, and microbiota interactions. The interplay between these two cell types is critical for maintaining mucosal homeostasis, is central to defending against fish diseases and is highly responsive to environmental cues. This study investigates the acute dermatotoxicity of environmentally relevant AgNP concentrations (0, 0.031, 0.250, and 5.000 μg/L) on zebrafish epidermis. A 96 h assay revealed a biphasic response: initial mucin hypersecretion at lower AgNP levels, suggesting an early stress response, followed by a concentration-dependent collapse of mucosal integrity at higher exposures, with mucus degradation and alarm cell depletion. A rapid and generalized increase in epidermal mucus production was observed across all AgNP exposure groups within two hours of exposure. Further mechanistic insights into AgNP-induced toxicity were revealed by concentration-dependent alterations in goblet cell dynamics. Lower AgNP concentrations initially led to an increase in both goblet cell number and size. However, at the highest concentration, this trend reversed, with a significant decrease in goblet cell numbers and size evident between 48 and 96 h post-exposure. The simultaneous presence of neutral and acidic mucins indicates a dynamic epidermal response suggesting a primary physical barrier function, with acidic mucins specifically upregulated early on to enhance mucus viscosity, trap AgNPs, and inhibit pathogen invasion, a clear defense mechanism. The subsequent reduction in mucin-producing cells at higher concentrations signifies a critical breakdown of this protective strategy, leaving the epidermis highly vulnerable to damage and secondary infections. These findings highlight the vulnerability of fish epidermal defenses to AgNP contamination, which can potentially compromise osmoregulation and increase susceptibility to threats. Further mechanistic research is crucial to understand AgNP-induced epithelial damage to guide sustainable nanotechnology. Full article

Zebrafish (Danio rerio) combine accessible behavioral phenotypes with conserved neurochemical pathways and molecular features of vertebrate brain function, positioning them as a powerful model for investigating early neurodegenerative processes and screening neuroprotective strategies. In this context, integrated behavioral and proteomic analyses provide valuable insights into the initial pathophysiological events shared by conditions such as Parkinson’s disease and related disorders—including mitochondrial dysfunction, oxidative stress, and synaptic impairment—which emerge before overt neuronal loss and offer a crucial window to understand disease progression and evaluate therapeutic candidates prior to irreversible damage. To investigate this early window of dysfunction, zebrafish larvae were exposed to 500 μM 1-methyl-4-phenylpyridinium (MPP⁺) from 1 to 5 days post-fertilization and evaluated through integrated behavioral and label-free proteomic analyses. MPP⁺-treated larvae exhibited hypokinesia, characterized by significantly reduced total distance traveled, fewer movement bursts, prolonged immobility, and a near-complete absence of light-evoked responses—mirroring features of early Parkinsonian-like motor dysfunction. Label-free proteomic profiling revealed 40 differentially expressed proteins related to mitochondrial metabolism, redox regulation, proteasomal activity, and synaptic organization. Enrichment analysis indicated broad molecular alterations, including pathways such as mitochondrial translation and vesicle-mediated transport. A focused subset of Parkinsonism-related proteins—such as DJ-1 (PARK7), succinate dehydrogenase (SDHA), and multiple 26S proteasome subunits—exhibited coordinated dysregulation, as visualized through protein–protein interaction mapping. The upregulation of proteasome components and antioxidant proteins suggests an early-stage stress response, while the downregulation of mitochondrial enzymes and synaptic regulators reflects canonical PD-related neurodegeneration. Together, these findings provide a comprehensive functional and molecular characterization of MPP⁺-induced neurotoxicity in zebrafish larvae, supporting its use as a relevant in vivo system to investigate early-stage Parkinson’s disease mechanisms and shared neurodegenerative pathways, as well as for screening candidate therapeutics in a developmentally responsive context. Full article