Retinoic Acid Protects and Rescues the Development of Zebrafish Embryonic Retinal Photoreceptor Cells from Exposure to Paclobutrazol

Toxicological mechanism of cannabidiol (CBD) exposure on zebrafish embryonic development

Cannabidiol (CBD) is the main component of plant Cannabis (Cannabis sativa), which exhibits strong antioxidant and anti-inflammatory activities. With the legalization of CBD in the United States, it is an inevitable tendency for its global legalization in the future. Therefore, it has become an urgent task to conduct the toxicological evaluation of CBD before clinical application. In this study, the developmental toxicities of CBD on zebrafish embryos were systematically evaluated, and the mechanisms were revealed. The results showed that the phenotype of liver degeneration was observed in 96 hpf zebrafish embryos after 0.1-5 μmol/L CBD exposure, further RT-qPCR experiments indicated that the above result may attributed by the alterations of FABP10A, GCLC, and GSR. Besides, 1 and 5 μmol/L CBD contributed to the developmental toxicities of heart and eye in zebrafish embryos, characterizing by the decrease in heart rate, the phenotype of pericardial edema, and the reduce of eye area. Compared to other organs, the liver of zebrafish displayed the most sensitive characteristic to CBD exposure, as 0.1 μmol/L CBD already led to the phenotype of liver degeneration. In summary, this paper provided theoretical supports for CBD toxicology research, and laid the foundation for its future clinical application.

Construction of a physiologically based pharmacokinetic model of paclobutrazol and exposure estimation in the human body

Paclobutrazol (PBZ) is a plant growth regulator that can delay plant growth and improve plant resistance and yield. Although it has been widely used in the growth of medicinal plants, human beings may take it by taking traditional Chinese medicine. There are no published studies on PBZ exposure in humans or standardized limits for PBZ in medicinal plants. We measured the solubility, oil-water partition coefficient (logP), and pharmacokinetics of PBZ in rats and established a physiologically based pharmacokinetic (PBPK) model of PBZ in rats. This was followed by extrapolation to healthy Chinese adult males as a theoretical foundation for future risk assessment of PBZ. The results showed that PBZ had low solubility and high fat solubility. Pharmacokinetic experiments showed that PBZ was absorbed rapidly but eliminated slowly in rats. On this basis, the rat PBPK model was successfully constructed and extrapolated to healthy Chinese adult males to predict the plasma concentration-time curve and exposure of PBZ in humans. The construction of the PBPK model of PBZ in this study facilitates the determination of the standard formulation limits and risk assessment of PBZ residues in medicinal plants.

Quality variation of maidong (Ophiopogon japonicus and Liriope spicata) - A HPTLC-based approach

The tuberous roots of Ophiopogon japonicus and Liriope spicata are used for the same therapeutic purpose in traditional Chinese medicine and are collectively referred to as maidong medicine. Interestingly, it was observed that the price of tuberous roots varies depending on their location on the plant, and fibrous roots are usually discarded post-harvest. Mislabeling might be of concern due to similarities in morphological features between the two species. Moreover, paclobutrazol has been observed to be heavily applied during the production, and therefore might be of health concern. Overall, maidong might suffer from quality inconsistencies while its metabolomic complexity is influenced by growing region and cultivation practices, botanical species, and plant parts. To address these challenges, this study employed High-Performance Thin Layer Chromatography (HPTLC) approach, in which sample preparation and derivatization procedure were optimized to enable to capture more detailed and comprehensive metabolomic fingerprints. By integrating with rTLC algorithm and Multivariate Data Analysis (MVDA), an improved quality assessment was achieved. Samples were collected from four production regions and supplemented with commercial products from markets. The optimized HPTLC analysis recognized species- and region-specific metabolomic patterns of maidong, uncovering a 4% of mislabelled cases. Moreover, findings highlight the underexplored therapeutic potential of fibrous roots, and comparable therapeutic efficacy between different root types. Additionally, complemented by Liquid Chromatography-Mass Spectrometry (LC-MS) for paclobutrazol residue evaluation, 24.66% of the commercial maidong samples surpassed maximum residue limits of paclobutrazol, raising safety concerns. This research represents a significant analytical advancement, offering a robust, cost-effective, and comprehensive method for maidong quality control, and paving the way for more strict residue regulation and updates to herbal pharmacopoeias and monographs.

Vitamin A ameliorates valproic acid-induced autism-like symptoms in developing zebrafish larvae by attenuating oxidative stress and apoptosis

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by social deficits and repetitive/stereotyped behaviors. Prenatal exposure to valproic acid (VPA) has been reported to induce ASD-like symptoms in human and rodents. However, the etiology and pathogenesis of ASD have not been well elucidated. This study aimed to explore the mechanisms underlying VPA-induced ASD-like behaviors using zebrafish model and investigated whether vitamin A could prevent VPA-induced neurotoxicity. Here, zebrafish embryos were exposed to 0, 25 and 50 μM VPA from 4 to 96 h post fertilization (hpf) and the neurotoxicity was assessed. Our results showed that VPA affected the normal development of zebrafish larvae and induced ASD-like behaviors, including reduced locomotor activity, decreased distance near conspecifics, impaired social interaction and repetitive swimming behaviors. Exposure to VPA decreased the GFP signal in transgenic HuC:egfp zebrafish according to the negative effect of VPA on the expression of neurodevelopmental genes. In addition, VPA enhanced oxidative stress by promoting the production of reactive oxygen species (ROS) and hydrogen peroxide (H2O2) and inhibiting the activity of superoxide dismutase, then triggered apoptosis by upregulation of apoptotic genes. These adverse outcomes were mitigated by vitamin A, suggesting that vitamin A rescued VPA-induced ASD-like symptoms by inhibiting oxidative stress and apoptosis. Overall, this study identified vitamin A as a promising strategy for future therapeutic regulator of VPA-induced ASD-like behaviors.

2,4-Dichlorophenoxyacetic acid (2,4-D) affects DNA integrity and retina structure in zebrafish larvae

Monitoring the potential risk of herbicides in non-target organisms is a crucial issue for environmental safety. 2,4-D is an herbicide of high environmental relevance that has been shown to exert toxic effects to soil and aquatic biota. In the present study, we investigated the possible genotoxic and retinal development effects of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide in early life stages zebrafish (Danio rerio). Genotoxicity was evaluated by measuring DNA damage using the comet assay and also by the mRNA expression of genes implicated in apoptosis and/or DNA repair. Retinal development toxicity was evaluated with histological approach. The results obtained revealed that 2,4-D alters DNA integrity of zebrafish larvae. Moreover, transcriptomic data showed a significant induction of p-53 and casp-3 genes and a significant decrease of lig-4 in larvae exposed to the highest tested concentration of 2,4-D (0.8 mg/L). This suggested that p-53 gene regulates the process of DNA repair and apoptosis with increased levels of 2,4-D. The histopathological analysis revealed that early exposure to 2,4-D damaged the structure of larvae retina. Overall, this study is the first to report the DNA damage, casp-3, lig-4 and p-53 regulation, as well as the ocular developmental toxicity in zebrafish larvae at environmentally relevant concentrations of 2,4-D herbicide.

Azole-Induced Color Vision Deficiency Associated with Thyroid Hormone Signaling: An Integrated In Vivo, In Vitro, and In Silico Study

Azoles that are used in pesticides, pharmaceuticals, and personal care products can have toxic effects on fish. However, there is no information regarding azole-induced visual disorder associated with thyroid disruption. We evaluated changes in retinal morphology, optokinetic response, transcript abundance of the genes involved in color perception and hypothalamic-pituitary-thyroid (HPT) axis, and thyroid hormone (TH) levels in zebrafish larvae exposed to common azoles, such as climbazole (CBZ, 0.1 and 10 μg/L) and triadimefon (TDF, 50 and 500 μg/L), at environmentally relevant and predicted worst-case environmental concentrations. Subsequently, the effect of azoles on TH-dependent GH3 cell proliferation and thyroid receptor (TR)-regulated transcriptional activity, as well as the in silico binding affinity between azoles and TR isoforms, was investigated. Azole exposure decreased cell densities of the ganglion cell layer, inner nuclear layer, and photoreceptor layer. Zebrafish larvae exposed to environmentally relevant concentrations of CBZ and TDF showed a decrease in optokinetic response to green-white and red-white stripes but not blue-white stripes, consistent with disturbance in the corresponding opsin gene expression. Azole exposure also reduced triiodothyronine levels and concomitantly increased HPT-related gene expression. Molecular docking analysis combined with in vitro TR-mediated transactivation and dual-luciferase reporter assays demonstrated that CBZ and TDF exhibited TR antagonism. These results are comparable to those obtained from a known TR antagonist, namely, TR antagonist 1, as a positive control. Therefore, damage to specific color perception by azoles appears to result from lowered TH signaling, indicating the potential threat of environmental TH disruptors to the visual function of fish.

Retinal Transcriptomics Analysis Reveals the Underlying Mechanism of Disturbed Emmetropization Induced by Wavelength Defocus

PURPOSE

Wavelength signals play a vital role in refractive development. This study aimed to explore the retinal transcriptome signature in these processes.

METHODS

Guinea pigs were randomly divided into three groups exposed to white, blue, or green environmental light for eight weeks. Refraction and axial length were evaluated every 4 weeks, and the retinal transcriptome was profiled at 8 weeks.

RESULTS

Compared with the white group, ocular refraction significantly decreased and ocular axial length significantly extended in the green group whereas these parameters showed opposite trends in the blue group. RNA-sequencing showed that, compared with the white group, 184 and 171 differentially expressed genes (DEGs) were found in the blue and green groups, respectively. Among these DEGs, only 31 overlapped. These two sets of DEGs were enriched in distinct biological processes and pathways. There were 268 DEGs between the blue and green groups, which were primarily enriched in the extracellular matrix, and metabolism, receptor activity, and ion binding processes. In addition, nine human genes, including ECEL1, CHRND, SHBG, PRSS56, OVOL1, RDH5, WNT7B, PEBP4, CA12, were identified to be related to myopia development and wavelength response, indicating the potential role of these genes in human wavelength-induced myopia.

CONCLUSIONS

In this study, we identified retinal targets and pathways involved in the response to wavelength signals in emmetropization.

Study on endocrine disruption effect of paclobutrazol and uniconazole on the thyroid of male and female rats based on lipidomics

The present study investigated the effects of paclobutrazol and uniconazole on thyroid endocrine system in rats. Lipidomic analysis was performed to obtain the biomarkers of thyroid endocrine disruption induced by paclobutrazol and uniconazole. Network pharmacology was further used to discover potential targets of biomarkers related to drugs and diseases. After paclobutrazol and uniconazole administration, seven and four common biomarkers related to thyroid endocrine disruption for female and male rats were obtained, respectively. Paclobutrazol and uniconazole significantly increased the biomarker levels of PG (12:0/15:0), PS (14:0/16:0), PA (20:1/15:0) and PG (13:0/17:0) in both sexes of rats. Exposure to paclobutrazol additionally caused a significant decrease of PG (22:6/20:2), PE (24:1/18:1) and PE (24:0/18:0) in female rats, while an increase in male rats. Changes of the common biomarkers for paclobutrazol and uniconazole revealed similar endocrine disruption effect, which was higher in the females. Network pharmacology and KEGG pathway analysis indicated that the thyroid endocrine disrupting effects of paclobutrazol and uniconazole may be related to V-akt murine thymoma viral oncogene homolog (Akts), mitogen-activated protein kinase (MAPKs), epidermal growth factor receptor (EGFR), Insulin-like growth factor (IGF-1), IGF-IR and V-Raf murine sarcoma viral oncogene homolog B1 (BRAF). The results demonstrated that paclobutrazol and uniconazole could cause thyroid endocrine disorders in male and female rats, which were sex-specific, thus highlighting the importance of safe and effective application of these plant growth regulators.

Network Pharmacology Combined with Metabolomics Approach to Investigate the Toxicity Mechanism of Paclobutrazol

Paclobutrazol (PBZ) is a commonly used plant growth regulator (PGR) with good antibacterial activity. It has widespread applications in agricultural production. However, there is limited research reported on the potential risks of human health resulting from PBZ residues. In this study, using Sprague-Dawley rats, we carried out a systematic study on the hepatotoxicity and nephrotoxicity of PBZ in different doses (0.2, 0.5, and 1.0 g/kg). The metabolic profiles and network pharmacology were combined to construct a PBZ-endogenous substances-gene-hepatorenal diseases network to elucidate the underlying mechanism of PBZ's hepatorenal toxicity. At first, metabolomics analysis was done to investigate the metabolites and the related metabolic pathways associated with PBZ. Secondly, the network pharmacology approach was used in further exploration of the toxic targets. Additionally, molecular docking was carried out to investigate the interactions between PBZ and potential targets. The results indicated that PBZ showed obvious toxicity towards the liver and kidney of rats. The metabolomics analysis showed that PBZ mainly affected 4 metabolic pathways, including tryptophan metabolism, arachidonic acid metabolism, linoleic acid metabolism, and purine metabolism. Network pharmacology and molecular docking revealed that CYP1A2, CYP2A6, CYP2E1, MAOA, PLA2G2A, PTGS1, and XDH were critical targets for PBZ hepatorenal toxicity. This preliminary study revealed PBZ's hepatorenal toxicity and provided a theoretical basis for the rational and safe use of PBZ. Furthermore, it provided possible intervention targets for further research on how to avoid or reduce the damage caused by pesticides to the human body.

Restoring the oxidative balance in age-related diseases - An approach in glaucoma

As human life expectancy increases, age-related health issues including neurodegenerative diseases continue to rise. Regardless of genetic or environmental factors, many neurodegenerative conditions share common pathological mechanisms, such as oxidative stress, a hallmark of many age-related health burdens. In this review, we describe oxidative damage and mitochondrial dysfunction in glaucoma, an age-related neurodegenerative eye disease affecting 80 million people worldwide. We consider therapeutic approaches used to counteract oxidative stress in glaucoma, including untapped treatment options such as novel plant-derived antioxidant compounds that can reduce oxidative stress and prevent neuronal loss. We summarize the current pre-clinical models and clinical work exploring the therapeutic potential of a range of candidate plant-derived antioxidant compounds. Finally, we explore advances in drug delivery systems, particular those employing nanotechnology-based carriers which hold significant promise as a carrier for antioxidants to treat age-related disease, thus reviewing the key current state of all of the aspects required towards translation.

Retinoic acid and taurine enhance differentiation of the human bone marrow stem cells into cone photoreceptor cells and retinal ganglion cells

Degeneration and apoptotic death of the photoreceptor cell-layer of retina are a major cause of irreversible blindness in the development era. The stem cell replacement therapy is one of the strategies for the retinal repairing. In addition, exogenous signals critically contribute to the direction of lineage decisions that causes the fate-restricted photoreceptor progenitors from stem cell progeny in culture. It has been found that epidermal growth factor (EGF), taurine, and retinoic acid (RA) initially act in the instructive as well as lineage-restricted way in the progenitor lineage for producing neuroretinal cells or photoreceptor like cells from stem cell. The study aims to investigate the effect of RA and taurine in differentiation of the human bone marrow stem cell into cone photoreceptors cells and retinal ganglion cells. Mesenchymal stem cell was derived from human bone marrow of the term delivery. Therefore, the cultured cells have been treated with Dulbecco's modified Eagle's medium (DMEM)/high glucose (H⁺ ). After the four-cell passage, basal medium was replaced with DMEM/F12 complemented with 50 μmol/L taurine, RA (1 µM) and EGF (1 µg/ml). Subsequently cellular change morphology was detected following 7 and 14 days. Then, gene expression of neuroretinal and photoreceptor cell biomarkers (CRX, OTX2, PKC-α, recoverin, and Rho) were examined by quantitative polymerase chain reaction (Q-PCR). Also, cells were cultured, fixed, and then immunocytochemical analyzed. Primary antibodies included CRX and Rho. Cellular morphology demonstrated spindle elongated morphology. Taurine alone and combination of RA upregulate neuroretinal and photoreceptor cell biomarkers in messenger RNA and protein levels but along with EGF have not significant effect. Our data showed that taurine combination with RA can differentiate bone marrow mesenchymal stem cells into neuroretinal or photoreceptor like cells in vitro that can offer an attractive treatment ground for transplantation in the cell-replacement therapy for some forms of the retinal degeneration.

Paclobutrazol exposure induces apoptosis and impairs autophagy in hepatocytes via the AMPK/mTOR signaling pathway

Paclobutrazol (PBZ), one of the most widely used plant growth retardants in vegetables, fruits, and traditional Chinese medicine ingredients, exposes people to adverse events. In this study, HepaRG hepatocytes were cultured and exposed to PBZ (360 μM) in vitro to determine its mechanism. Results showed that PBZ exposure inhibited cell viability in a time- and dose-dependent manner and increased the oxidative stress and apoptosis ratio in HepaRG cells. These data revealed that the adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) has an important role in PBZ-induced cell apoptosis, which is mediated by impaired autophagy and blocked by the AMPK activator. In conclusion, PBZ exposure induces apoptosis and impairs autophagy in hepatocytes via the AMPK/mTOR signaling pathway.

Neurodegeneration, Neuroprotection and Regeneration in the Zebrafish Retina

Neurodegenerative retinal diseases, such as glaucoma and diabetic retinopathy, involve a gradual loss of neurons in the retina as the disease progresses. Central nervous system neurons are not able to regenerate in mammals, therefore, an often sought after course of treatment for neuronal loss follows a neuroprotective or regenerative strategy. Neuroprotection is the process of preserving the structure and function of the neurons that have survived a harmful insult; while regenerative approaches aim to replace or rewire the neurons and synaptic connections that were lost, or induce regrowth of damaged axons or dendrites. In order to test the neuroprotective effectiveness or the regenerative capacity of a particular agent, a robust experimental model of retinal neuronal damage is essential. Zebrafish are being used more often in this type of study because their eye structure and development is well-conserved between zebrafish and mammals. Zebrafish are robust genetic tools and are relatively inexpensive to maintain. The large array of functional and behavioral tests available in zebrafish makes them an attractive model for neuroprotection studies. Some common insults used to model retinal disease and study neuroprotection in zebrafish include intense light, chemical toxicity and mechanical damage. This review covers the existing retinal neuroprotection and regeneration literature in the zebrafish and highlights their potential for future studies.

Growth Factors as Tools in Photoreceptor Cell Regeneration and Vision Recovery

Photoreceptor loss is a major cause of blindness around the world. Stem cell therapy offers a new strategy in retina degenerative disease. Retinal progenitors can be derived from embryonic stem cells (ESC) in vitro, but cannot be processed to a mature state. In addition, the adult recipient retina presents a very different environment than the photoreceptor precursor donor. It seems that modulation of the recipient environment by ectopic development regulated growth factors for transplanted cells could generate efficient putative photoreceptors. The purpose of this review article was to investigate the signaling pathway of growth factors including: insulin-like growth factors (IGFs), fibroblast growth factors (FGF), Nerve growth factor (NGF), Brain-derived neurotrophic factor (BDNF), Taurin and Retinoic acid (RA) involved in the differentiation of neuroretina cell, like; photoreceptor and retinal progenitor cells. Given the results available in the related literature, the differentiation efficacy of ESCs toward the photoreceptor and retinal neurons and the important role of growth factors in activating signaling pathways such as Akt, Ras/Raf1/ and ERKs also inhibit the ASK1/JNK apoptosis pathway. Manipulating differentiated culture, growth factors can influence photoreceptor transplantation efficiency in retinal degenerative disease.

An inadvertent issue of human retina exposure to endocrine disrupting chemicals: A safety assessment

Endocrine disrupting chemicals (EDCs) are a group of chemical compounds that present a considerable public health problem due to their pervasiveness and associations with chronic diseases. EDCs can interrupt the endocrine system and interfere with hormone homeostasis, leading to abnormalities in human physiology. Much attention has been focused on the adverse effects EDCs have on the reproductive system, neurogenesis, neuroendocrine system, and thyroid dysfunction. The eye is usually directly exposed to the surrounding environment; however, the influences of EDCs on the eye have received comparatively little attention. Ocular diseases, such as ocular surface diseases and retinal diseases, have been implicated in hormone deficiency or excess. Epidemiologic studies have shown that EDC exposure not only causes ocular surface disorders, such as dry eye, but also associates with visual deficits and retinopathy. EDCs can pass through the human blood-retinal barrier and enter the neural retina, and can then accumulate in the retina. The retina is an embryologic extension of the central nervous system, and is extremely sensitive and vulnerable to EDCs that could be passed across the placenta during critical periods of retinal development. Subtle alterations in the retinal development process usually result in profound immediate, long-term, and delayed effects late in life. This review, based on extensive literature survey, briefly summarizes the current knowledge about the impact of representative manufactured EDCs on retinal toxicity, including retinal structure alterations and dysfunction. We also highlight the potential mechanism of action of EDCs on the retina, and the predictive retinal models of EDC exposure.

Zebrafish as an Animal Model for Ocular Toxicity Testing: A Review of Ocular Anatomy and Functional Assays

Xenobiotics make their way into organisms from diverse sources including diet, medication, and pollution. Our understanding of ocular toxicities from xenobiotics in humans, livestock, and wildlife is growing thanks to laboratory animal models. Anatomy and physiology are conserved among vertebrate eyes, and studies with common mammalian preclinical species (rodent, dog) can predict human ocular toxicity. However, since the eye is susceptible to toxicities that may not involve a histological correlate, and these species rely heavily on smell and hearing to navigate their world, discovering visual deficits can be challenging with traditional animal models. Alternative models capable of identifying functional impacts on vision and requiring minimal amounts of chemical are valuable assets to toxicology. Human and zebrafish eyes are anatomically and functionally similar, and it has been reported that several common human ocular toxicants cause comparable toxicity in zebrafish. Vision develops rapidly in zebrafish; the tiny larvae rely on visual cues as early as 4 days, and behavioral responses to those cues can be monitored in high-throughput fashion. This article describes the comparative anatomy of the zebrafish eye, the notable differences from the mammalian eye, and presents practical applications of this underutilized model for assessment of ocular toxicity.

Waterborne Exposure of Paclobutrazol at Environmental Relevant Concentration Induce Locomotion Hyperactivity in Larvae and Anxiolytic Exploratory Behavior in Adult Zebrafish

The available arable land is unable to fulfill the food production need of rapidly the exponentially growing human population in the world. Pesticides are one of those different measures taken to meet this demand. As a plant growth regulator to block gibberellin, paclobutrazol (PBZ) is used excessively throughout the world to promote early fruit setting, and to increase seed setting which might be harmful because PBZ is a very stable compound; therefore, it can bioaccumulate into the food chain of an ecosystem. In the present study, we discovered unexpected effects of PBZ on zebrafish larvae and adult behaviors by challenging them with low dose exposure. Zebrafish larvae aged 4 days post-fertilization (dpf) were exposed for 24 h at 10 µg/L (0.01 ppm) and 100 µg/L (0.1 ppm) of PBZ, respectively, and adults were incubated at 100 µg/L (0.1 ppm) and 1000 µg/L (1 ppm) concentrations of PBZ, respectively, for fourteen days. After incubation, the locomotor activity, burst, and rotation movement for the larvae; and multiple behavioral tests such as novel tank exploration, mirror biting, shoaling, predator avoidance, and social interaction for adult zebrafish were evaluated. Brain tissues of the adult fish were dissected and subjected to biochemical analyses of the antioxidant response, oxidative stress, superoxide dismutase (SOD), and neurotransmitter levels. Zebrafish larvae exposed to PBZ exhibited locomotion hyperactivity with a high burst movement and swimming pattern. In adult zebrafish, PBZ resulted in anxiolytic exploratory behavior, while no significant results were found in social interaction, shoal making, and predator avoidance behaviors. Interestingly, high dose PBZ exposure significantly compromised the innate aggressive behavior of the adult fish. Biochemical assays for oxidative stress, antioxidant response, and superoxide dismutase (SOD) showed significant reductions in their relative contents. In conclusion, for the first time, our behavior assays revealed that chronic PBZ exposure induced behavioral alterations in both larvae and the adult zebrafish. Because PBZ is a widely-used plant growth regulator, we suggest that it is necessary to conduct more thorough tests for its biosafety and bioaccumulation.

Toxic Effects of Paclobutrazol on Developing Organs at Different Exposure Times in Zebrafish

To enhance crop productivity and economic profit, farmers often use pesticides that modulate plant growth and prevent disease. However, contamination of ecosystems with agricultural pesticides may impair the health of resident biota. Paclobutrazol (PBZ), an aromatic-containing triazole, is widely applied to many crops in order to promote flowering and fruit setting, while also regulating plant growth and preventing fungus-related diseases. Due to its high mobility, high stability and potential for bioaccumulation, the risks of PBZ to the health of organisms and ecological systems have become a serious concern. In previous studies, we documented the toxicity of PBZ on developing heart, eyes, liver, pancreas and intestine of zebrafish. In this study, we sought to further understand the developmental stage-specific impacts of PBZ on digestive organs and other tissues. Zebrafish were exposed to PBZ beginning at different embryonic stages, and the toxic effects on organs were evaluated at 120 hpf (hours post-fertilization) by in situ hybridization staining with tissue-specific marker genes, such as liver, intestine and pancreas. Unsurprisingly, early-stage embryos exhibited higher sensitivity to PBZ-induced death and developmental hypoplasia of digestive organs. Interestingly, the developing liver and pancreas were more sensitive to PBZ than intestine when embryos were exposed at early stages, but these tissues showed lower sensitivity at later stages. Our delineation of the differential toxic effects of PBZ on developing organs at different exposure timings can serve as a powerful reference for further studies into the mechanisms of PBZ organ toxicity.

mRNA-Sequencing Identifies Liver as a Potential Target Organ for Triphenyl Phosphate in Embryonic Zebrafish

Triphenyl phosphate (TPHP) is a commonly used organophosphate flame retardant and plasticizer in the United States. Using zebrafish as a model, the overall objective of this study was to identify potential organs that might be targeted by TPHP during embryonic development. Based on mRNA-sequencing, TPHP exposure from 24 to 30 h post fertilization (hpf) and 24 to 48 hpf significantly affected the abundance of 305 and 274 transcripts, respectively, relative to vehicle (0.1% DMSO) controls. In addition to minor effects on cardiotoxicity- and nephrotoxicity-related pathways, Ingenuity Pathway Analysis (IPA) of significantly affected transcripts within 30- and 48-hpf embryos revealed that hepatotoxicity-related pathways were strongly affected following exposure to TPHP alone. Moreover, while pre-treatment with fenretinide (a retinoic acid receptor agonist) mitigated TPHP-induced pericardial edema and liver enlargement at 72 hpf and 128 hpf, respectively, IPA revealed that fenretinide was unable to block TPHP-induced effects on cardiotoxicity-, nephrotoxicity-, and hepatotoxicity-related pathways at 48 hpf, suggesting that TPHP-induced effects on the transcriptome were not associated with toxicity later in development. In addition, based on Oil Red O staining, we found that exposure to TPHP nearly abolished neutral lipids from the embryonic head and trunk and, based on metabolomics, significantly decreased the total abundance of metabolites - including betaine, a known osmoprotectant - at 48 and 72 hpf. Overall, our data suggest that, in addition to the heart, TPHP exposure during early development results in adverse effects on the liver, lipid utilization, and osmoregulation within embryonic zebrafish.

Acute toxic responses of embryo-larval zebrafish to zinc pyrithione (ZPT) reveal embryological and developmental toxicity

Zinc pyrithione (ZPT) is widely used in industrial and human daily life, due to its broad antimicrobial spectrum activity. Persistent accumulation of ZTP in the aquatic environment and bioaccumulation in the living organisms attracts more and more attention. However, only very limited information is available so far for the evaluation of systematic toxicity effects of ZPT on multiple organs development. This study intends to deepen our knowledge about the potential toxicity elicited by ZPT by assessing its acute effects on zebrafish (Danio rerio) through morphological, histological and molecular investigations. It has been verified that ZPT exhibits a broad spectrum of toxicity which causes growth retardation and tissue pathological and physiology alternations in heart, liver, eye, notochord, kidney and other organisms of zebrafish. The acute toxicity values of LC50 (95% CI) 96-h is calculated as 0.073 μM. Furthermore, the organ toxicity was verified due to up-regulation of expression of biomarker genes related to organ function and development. In sum, this study demonstrats systematic acute embryological and developmental toxicity of the ZPT on zebrafish embryos/larvae.

Coral-Derived Natural Marine Compound GB9 Impairs Vascular Development in Zebrafish

Blood vessels in vertebrates are established and genetically controlled in an evolutionarily-conserved manner during embryogenesis. Disruption of vascular growth by chemical compounds or environmental hormones may cause developmental defects. This study analyzed the vascular impacts of marine compound GB9 in zebrafish. GB9 was isolated from the marine soft coral Capnella imbricata and had shown anti-neuroinflammatory and anti-nociceptive activities. However, the role of GB9 on vascular development has not been reported. We first tested the survival rate of embryos under exogenous 5, 7.5, 10, and 15 μM GB9 added to the medium and determined a sub-lethal dosage of 10 μM GB9 for further assay. Using transgenic Tg(fli:eGFP) fish to examine vascular development, we found that GB9 treatment impaired intersegmental vessel (ISV) growth and caudal vein plexus (CVP) patterning at 25 hours post-fertilization (hpf) and 30 hpf. GB9 exposure caused pericardial edema and impaired circulation at 48–52 hpf, which are common secondary effects of vascular defects and suggest the effects of GB9 on vascular development. Apoptic cell death analysis showed that vascular defects were not caused by cell death, but were likely due to the inhibition of migration and/or proliferation by examining ISV cell numbers. To test the molecular mechanisms of vascular defects in GB9-treated embryos, we examined the expression of vascular markers and found the decreased expression of vascular specific markers ephrinb2, flk, mrc1, and stabilin. In addition, we examined whether GB9 treatment impairs vascular growth due to an imbalance of redox homeostasis. We found an enhanced effect of vascular defects during GB9 and H₂O₂ co-treatment. Moreover, exogenous N-acetyl-cysteine (NAC) treatment rescued the vascular defects in GB9 treated embryos. Our results showed that GB9 exposure causes vascular defects likely mediated by the imbalance of redox homeostasis.