Analysis of Lethality and Malformations During Zebrafish (Danio rerio) Development

Biological Response Following the Systemic Injection of PEG-PAMAM-Rhodamine Conjugates in Zebrafish

Numerous therapeutic and diagnostic approaches used within a clinical setting depend on the administration of compounds via systemic delivery. Biomaterials at the nanometer scale, as dendrimers, act as delivery systems by improving cargo bioavailability, circulation time, and the targeting of specific tissues. Although evaluating the efficacy of pharmacological agents based on nanobiomaterials is crucial, conducting toxicological assessments of biomaterials is essential for advancing clinical translation. Here, a zebrafish larvae model was explored to assess the biocompatibility of poly(amido amine) (PAMAM), one of the most exploited dendrimers for drug delivery. We report the impact of a systemic injection of polyethylene glycol (PEG)-modified G4 PAMAM conjugated with rhodamine (Rho) as a mimetic drug (PEG-PAMAM-Rho) on survival, animal development, inflammation, and neurotoxicity. A concentration- and time-dependent effect was observed on mortality, developmental morphology, and innate immune system activation (macrophages). Significant effects in toxicological indicators were reported in the highest tested concentration (50 mg/mL PEG-PAMAM-Rho) as early as 48 h post-injection. Additionally, a lower concentration of PEG-PAMAM-Rho (5 mg/mL) was found to be safe and subsequently tested for neurotoxicity through behavioral assays. In accordance, no significative signs of toxicity were detected. In conclusion, the dose response of the animal was assessed, and the safe dosage for future use in theragnostics was defined. Additionally, new methodologies were established that can be adapted to further studies in toxicology using other nanosystems for systemic delivery.

Enzymatic and transcriptional level changes induced by the co-presence of lead and procymidone in hook snout carp (Opsariichthys bidens)

Understanding the interactions between different environmental pollutants is necessary in ecotoxicology since environmental contaminants never appear as single components but rather in combination with other substances. Heavy metals and pesticides are commonly detected in the environment, but the characterization of their mixture toxicity has been inadequately explored. This research aimed to elucidate the mixture impacts of the heavy metal lead (Pb) and the pesticide procymidone (PCM) on the hook snout carp (Opsariichthys bidens) using an array of biomarkers. The data showed that Pb and PCM possessed almost equivalent acute toxicity to the animals, with 4-days LC50 values of 120.9 and 85.15 mg L-1, respectively. Combinations of Pb and PCM generated acute synergistic effects on O. bidens. The contents of malondialdehyde (MDA), antioxidative (SOD), apoptotic (caspase-9), and detoxifying enzymes glutathione S-transferase (GST) and cytochrome P450 (CYP450) significantly changed after most of the mixture exposures compared with the baseline level and the corresponding individual exposures. This suggests the induction of oxidative stress, cell damage, and detoxification dysfunction. The expressions of eight genes (mn-sod, cu-sod, p53, cas3, erβ1, esr, ap, and klf2α) associated with oxidative stress, cell apoptosis, immune response, and hormonal functions exhibited pronounced changes when challenged with the mixture compared to the individual treatments. This indicates the occurrence of immune dysregulation and endocrine disorder. These findings provide an overall understanding of fish upon the challenge of sublethal toxicity between Pb and PCM and can be adopted to evaluate the complicated toxic mechanisms in aquatic vertebrates when exposed to heavy metal and pesticide mixtures. Additionally, these results might guide environmental regulation tactics to protect the population of aquatic vertebrates in natural ecosystems.

The posterity of Zebrafish in paradigm of in vivo molecular toxicological profiling

The aggrandised advancement in utility of advanced day-to-day materials and nanomaterials has raised serious concern on their biocompatibility with human and other biotic members. In last few decades, understanding of toxicity of these materials has been given the centre stage of research using many in vitro and in vivo models. Zebrafish (Danio rerio), a freshwater fish and a member of the minnow family has garnered much attention due to its distinct features, which make it an important and frequently used animal model in various fields of embryology and toxicological studies. Given that fertilization and development of zebrafish eggs take place externally, they serve as an excellent model organism for studying early developmental stages. Moreover, zebrafish possess a comparable genetic composition to humans and share almost 70% of their genes with mammals. This particular model organism has become increasingly popular, especially for developmental research. Moreover, it serves as a link between in vitro studies and in vivo analysis in mammals. It is an appealing choice for vertebrate research, when employing high-throughput methods, due to their small size, swift development, and relatively affordable laboratory setup. This small vertebrate has enhanced comprehension of pathobiology and drug toxicity. This review emphasizes on the recent developments in toxicity screening and assays, and the new insights gained about the toxicity of drugs through these assays. Specifically, the cardio, neural, and, hepatic toxicology studies inferred by applications of nanoparticles have been highlighted.

Angiogenesis Assay for Live and Fixed Zebrafish Embryos/Larvae

Angiogenesis is the process of new blood vessel formation from preexisting vasculature. It is an integral component in normal embryonic development and tissue repair. Dysregulation of angiogenesis might lead to tissue ischemia (resulting from reduced blood vessel formation) or major diseases such as cancer (abnormal vascular growth). This makes angiogenesis an excellent area of research for cancer therapeutics, and various animal models including zebrafish are used to study blood vessel development. As most of the techniques used to study angiogenesis are complex and cumbersome, in this chapter, we provide two simple assays to study angiogenesis with live and fixed zebrafish embryos/larvae.

Acute exposure to tenorite nanoparticles induces phenotypic and behavior alterations in zebrafish larvae

Tenorite or copper oxide nanoparticles (CuO NPs) are extensively used in biomedical fields due to their unique physicochemical properties. Increased usage of these NPs leads to release in the environment, affecting varied ecosystems and the biota within them, including humans. The effect of these NPs can be evaluated with zebrafish, an excellent complementary model for nanotoxicity studies. Previous reports focusing on CuO NPs-induced teratogenicity in zebrafish development have not elucidated the phenotypical changes in detail. In most of the studies, embryos at 3 hpf with a protective chorion layer were exposed to CuO NPs, and their effect on the overall developmental process is studied. Hence, in this study, we focused on the effect of acute exposure to CuO NPs (96-120 hpf) and its impact on zebrafish larvae. Larvae were exposed to commercially available CuO NPs (<50 nm) at various concentrations to obtain the LC50 value (52.556 ppm). Based on the LC50, three groups (10, 20, and 40 ppm) were taken for further analysis. Upon treatment, bradycardia, and impaired swim bladder (reduced/absence of inflation) were found in the treated groups along with alterations in the erythrocyte levels. Also, the angles and distance between the cartilages varied in the treated larvae affecting their craniofacial structures. There was a significant behavior change, as evidenced by the reduced touch escape response and locomotion (speed, distance, time mobile, time frozen, and absolute turn angle). Further, the acetylcholinesterase activity was reduced. Overall, our results suggest that acute exposure to CuO NPs elicits morphological defects in zebrafish larvae.

Zn-regulated GTPase metalloprotein activator 1 modulates vertebrate zinc homeostasis

Zinc (Zn) is an essential micronutrient and cofactor for up to 10% of proteins in living organisms. During Zn limitation, specialized enzymes called metallochaperones are predicted to allocate Zn to specific metalloproteins. This function has been putatively assigned to G3E GTPase COG0523 proteins, yet no Zn metallochaperone has been experimentally identified in any organism. Here, we functionally characterize a family of COG0523 proteins that is conserved across vertebrates. We identify Zn metalloprotease methionine aminopeptidase 1 (METAP1) as a COG0523 client, leading to the redesignation of this group of COG0523 proteins as the Zn-regulated GTPase metalloprotein activator (ZNG1) family. Using biochemical, structural, genetic, and pharmacological approaches across evolutionarily divergent models, including zebrafish and mice, we demonstrate a critical role for ZNG1 proteins in regulating cellular Zn homeostasis. Collectively, these data reveal the existence of a family of Zn metallochaperones and assign ZNG1 an important role for intracellular Zn trafficking.

Evaluation of Maghemite Nanoparticles-Induced Developmental Toxicity and Oxidative Stress in Zebrafish Embryos/Larvae

Maghemite nanoparticles ([Formula: see text] NPs) have a wide array of applications in various industries including biomedical field. There is an absence of legislation globally for the regulation of the production, use, and disposal of such NPs as they are eventually dumped into the environment where these NPs might affect the living systems. This study evaluates the effect of the [Formula: see text] NP-induced developmental toxicity in zebrafish embryos/larvae. The commercially available Fe₂O₃ NPs were purchased, and zebrafish embryos toxicity test was done by exposing embryos to various concentrations of [Formula: see text] NPs at 1 hpf and analyzed at 96 hpf. Based on the LC₅₀ value (60.17 ppm), the sub-lethal concentrations of 40 and 60 ppm were used for further experiments. Hatching, lethality, developmental malformations, and heartbeat rate were measured in the control and treated embryos/larvae. The ionic Fe content in the media, and the larvae was quantified using ICP-MS and AAS. The biomolecular alterations in the control and treated groups were analyzed using FT-IR. The Fe ions present in the larvae were visualized using SEM-EDXS. In situ detection of AChE and apoptotic bodies was done using staining techniques. Biochemical markers (total protein content, AChE, and Na⁺ K⁺-ATPase) along with oxidants and antioxidants were assessed. A significant decrease in the heartbeat rate and hatching delay was observed in the treated groups affecting the developmental processes. Teratogenic analysis showed increased developmental deformity incidence in treated groups in a dose-dependent manner. The accumulation of Fe was evidenced from the ICP-MS, AAS, and SEM-EDXS. Alterations in AChE and Na⁺ K⁺-ATPase activity were observed along with an increment in the oxidants level with a concomitant decrease in antioxidant enzymes. These results show [Formula: see text] NP exposure leads to developmental malformation and results in the alteration of redox homeostasis.

Acute exposure to environmentally relevant concentrations of phenytoin damages early development and induces oxidative stress in zebrafish embryos

Phenytoin (PHE) is an antiepileptic drug that has been widely used in clinical practice for about 80 years. It is mainly used in the treatment of tonic-clonic and partial seizures. The widespread consumption of this drug around the world has led to PHE being introduced into water bodies through municipal, hospital, and industrial effluent discharges. Since the toxic effects of this drug on aquatic species has been scarcely explored, the aim of this work was to investigate the influence of low (25-400 ngL^-1) and high (500-1500 ngL^-1) environmentally relevant concentrations of PHE on the development and oxidative status of zebrafish (Danio rerio) embryos. The toxicity of PHE was evaluated from 12 to 96 h after fertilization in D. rerio at concentrations between 25 and 1500 ngL^-1. In both the control group and the 0.05% DMSO system, no malformations were observed, all embryos developed normally after 96 h. The severity and frequency of malformations increased with increasing PHE concentration compared to embryos in the control group. Malformations observed included developmental delay, hypopigmentation, miscellaneous (more than one malformation in the same embryo), modified chorda structure, tail malformation, and yolk deformation. Concerning the biomarkers of oxidative stress, an increase in the degree of lipid peroxidation, protein carbonylation, and hydroperoxide content was observed (p < 0.05) concerning the control. In addition, a significant increase (p < 0.05) in antioxidant enzymes (SOD, CAT, and GPx) was observed at low exposure concentrations (25-400 ngL^-1), with a decrease in enzyme activity at high concentrations (500-1500 ngL^-1). Our IBR analysis demonstrated that oxidative damage biomarkers got more influence at 500ngL^-1 of PHE. The results demonstrated that PHE may affect the embryonic development of zebrafish and that oxidative stress may be involved in the generation of this embryotoxic process.

Toxicological findings about an anticancer fraction with casearins described by traditional and alternative techniques as support to the Brazilian Unified Health System (SUS)

ETHNOPHARMACOLOGICAL RELEVANCE

Extracts, essential oils and molecules from Casearia sylvestris have popularly shown pharmacological actions against chronic diseases, as anxiety, inflammation, cancer and dyslipidemia. In the context of antitumoral therapy, we investigated in vitro, ex vivo and in vivo toxicological changes induced by a Fraction with Casearins (FC) and its component Casearin X isolated from C. sylvestris on animal and vegetal cells, and upon invertebrates and mammals.

MATERIAL AND METHODS

Cytotoxicity was carried out using normal lines and absorbance and flow cytometry techniques, Artemia salina nauplii, Danio rerio embryos and meristematic cells from Allium cepa roots. Acute and 30 days-mice analysis were done by behavioral, hematological and histological investigations and DNA/chromosomal damages detected by alkaline Cometa and micronucleus assays.

RESULTS

FC was cytotoxic against lung and fibroblasts cells and caused DNA breaks, loss of integrity and mitochondrial depolarization on ex vivo human leukocytes. It revealed 24 h-LC₅₀ values of 48.8 and 36.7 μg/mL on A. salina nauplii and D. rerio embryos, reduced mitotic index of A. cepa roots, leading to cell cycle arrest at metaphase and anaphase and micronuclei. FC showed i.p. and oral LD₅₀ values of 80.9 and 267.1 mg/kg body weight. Subacute i.p. injections induced loss of weight, swelling of hepatocytes and tubules, tubular and glomerular hemorrhage, microvesicular steatosis, lung inflammatory infiltration, augment of GPT, decrease of albumin, alkaline phosphatase, glucose, erythrocytes, and lymphocytes, and neutrophilia (p > 0.05). FC-treated animals at 10 mg/kg/day i.p. caused micronuclei in bone marrow and DNA strand breaks in peripheral leukocytes.

CONCLUSIONS

This research postulated suggestive side effects after use of FC-related drugs, demonstrating FC as antiproliferative and genotoxic on mammal and meristematic cells, including human leukocytes, teratogenicity upon zebrafish embryos, myelosuppression, clastogenicity, and morphological and biochemical markers indicating liver as main target for FC-induced systemic toxicity.

Synthesis, characterization and biological evaluation of cationic organoruthenium(ii) fluorene complexes: influence of the nature of the counteranion

In this study, five ruthenium arene complexes with fluorene-bearing N,N-(1) and N,O-(2) donor Schiff base ligands were synthesized and fully characterized. Cationic ruthenium complexes 3[X], ([Ru(η⁶-C₆H₆)(Cl)(fluorene-N[double bond, length as m-dash]CH-pyridine)][X] (where X = BF₄, PF₆, BPh₄), were obtained by reacting ligand 1 with [Ru(η⁶-C₆H₆)Cl₂]₂ in the presence of NH₄X salts, whereas neutral complex 4, Ru(η⁶-C₆H₆)(Cl)(fluorene-N[double bond, length as m-dash]CH-naphtholate), was isolated by reacting ligand 2 with the same precursor. It was possible to obtain a cationic version of the latter, 5[BF₄], by reacting 4 with AgBF₄ in the presence of pyridine. All compounds were fully characterized by NMR and HR-ESI-MS whereas some of them were also analyzed by single crystal X-ray analysis. Their in vitro antiproliferative activity was also assessed in human breast cancer cell lines, notably MCF-7 and T47D. Complex 4 and its cationic counterpart 5[BF₄] were found to be the most cytotoxic compounds of the series (IC₅₀ = 6.2-16.2 μM) and displayed higher antiproliferative activities than cisplatin in both cell lines. It was found that 5[BF₄] undergoes a ligand exchange reaction and readily converts to 4 in the presence of 0.1 M NaCl, explaining the similarity in their observed cytotoxicities. Whereas 3[BF₄] and 3[PF₆] were found inactive at the tested concentrations, 3[BPh₄] displayed a considerable cytotoxicity (IC₅₀ = 16.7-27.8 μM). Notably, 3[BPh₄], 4 (and 5[BF₄]) were active against T47D, a cisplatin resistant cell line. Interestingly, 4 (16.4 μM) was found to be less cytotoxic than 3[BPh₄] and cisplatin (6.6 and 7.9 μM, respectively) in breast healthy cells (MCF-12A). However, in comparison to 4 and cisplatin (at 10 μM), a lower in vivo toxicity was observed for complex 3[BPh₄] on the development of zebrafish (Danio rerio) embryos.

Identification of compounds that inhibit the binding of Keap1a/Keap1b Kelch DGR domain with Nrf2 ETGE/DLG motifs in zebrafish

The Keap1-Nrf2-ARE system serves as a premier defence mechanism to curb oxidative stress, which remains as one of the major causes of ageing and pathogenesis in various diseases. Nrf2 is the principal master regulator of the cellular defence system, and its activation remains the prospective therapeutic approach against chronic diseases. One of the recent strategies is to disrupt Keap1-Nrf2 protein-protein interaction (PPI) that alters the docking of Keap1 with Nrf2 by compounds occupying a position in the Keap1 blocking the interface with Nrf2. In this study, we made an attempt to identify the compounds with anticancer, antioxidant and anti-inflammatory properties to disrupt Keap1a/b-Nrf2 PPI through in silico molecular docking in zebrafish. The phylogenetic analysis of Keap1 proteins revealed the existence of orthologous Keap1-Nrf2-ARE system in lower vertebrates that includes zebrafish. The DGR domains of zebrafish Keap1a and Keap1b were modelled with Modeller 9.19 using Keap1 of Mus musculus (PDB ID:5CGJ) as template. Based on the docking calculations, top hit compounds were identified to disrupt both Keap1a and Keap1b interaction with Nrf2 which include quercetin 3,4'-diglucoside, flavin adenine dinucleotide disodium salt hydrate, salvianolic acid A, tunicamycin and esculin. The LC₅₀ of esculin in 3 dpf zebrafish larvae is 5 mmol/L, and the qRT-PCR results showed that esculin significantly increased the transcription of Nrf2 target genes-Gstpi, Nqo1, Hmox1a and Prdx1 in 3 dpf zebrafish larvae. These potential hits could serve as safer Nrf2 activators due to their non-covalent disruption of Keap1-Nrf2 PPI and be developed into efficacious preventive/therapeutic agents for various diseases.

Genome-wide identification and analysis of Nrf2 binding sites - Antioxidant response elements in zebrafish

In the post-genomic era, deciphering the Nrf2 binding sites - antioxidant response elements (AREs) is an essential task that underlies and governs the Keap1-Nrf2-ARE pathway - a cell survival response pathway to environmental stresses in the vertebrate model system. AREs regulate the transcription of a repertoire of phase II detoxifying and/or oxidative-stress responsive genes, offering protection against toxic chemicals, carcinogens, and xenobiotics. In order to identify and analyze AREs in zebrafish, a pattern search algorithm was developed to identify AREs and computational tools available online were utilized to analyze the identified AREs in zebrafish. This study identified the AREs within 30 kb upstream from the transcription start site of antioxidant genes and mitochondrial genes. We report for the first time the AREs of all the known protein coding genes in the zebrafish genome. Western blotting, RT² profiler array PCR, and qRT-PCR were performed to test whether AREs influence the Nrf2 target genes expression in the zebrafish larvae using sulforaphane. This study reveals unique AREs that have not been previously reported in the cytoprotective genes. Nine TGAG/CNNNTC and six TGAG/CNNNGC AREs were observed significantly. Our findings suggest that AREs drive the dynamic transcriptional events of Nrf2 target genes in the zebrafish larvae on exposure to sulforaphane. The identified abundant putative AREs will define the Keap1-Nrf2-ARE network and elucidate the precise regulation of Nrf2-ARE pathway in not only diseases but also in embryonic development, inflammation, and aerobic respiration. Our results help to understand the dynamic complexity of the Nrf2-ARE system in zebrafish.