Zebrafish: model for the study of inflammation and the innate immune response to infectious diseases

Immunotoxicity of aristolochic acid I on early zebrafish (Danio rerio) embryos

Aristolochic acids (AAs) are active constituents of many traditional Chinese medicinal herbs. While AAs are known to induce cytotoxicity and pathological changes, such as tissue fibrosis, their specific impact on the immune system remains to be fully elucidated. This investigation used zebrafish as a model animal to evaluate the effects of aristolochic acid I (AAI), the main component of AAs, on the development and function of the early immune system. Our study found that exposure to AAI significantly decreased the numbers of macrophages, neutrophils, and T cells. Moreover, AAI exposure impaired the migratory capacity of immune cells to wound sites and weakened the immune system's response to external stimuli. Further research revealed that AAI exposure induced strong oxidative stress in zebrafish, activated the p53 signaling pathway, and subsequently induced apoptosis of immune cells. Fullerene, a potent antioxidant, is capable of inhibiting the p53 signaling pathway and rescuing the reduction of immune cells induced by AAI. Collectively, our findings indicated that AAI could induce immune cell death and impair immune function during early development via activation of the p53 signaling pathway, thereby uncovering the detrimental effects of AAs on the immune system and their underlying mechanisms. These findings provide a theoretical basis for the rational use of traditional Chinese medicinal herbs containing AAs.

Effects of fulvic acid on zebrafish (Danio rerio) growth, immunity and antioxidant status

This experiment aimed to determine the efficacy of fulvic acid (FLA) on growth performance, innate immune system, antioxidant parameters, and expression of immune and antioxidant-related genes in zebrafish (Danio rerio). To this end, 12 tanks (3 per group), each containing 50 zebrafish (with an average weight of 85.7 ± 10.05 mg) in 72 L, were assigned to diets containing FLA at four levels: 0 (control), 0.25 (FLA1), 0.5 (FLA2), and 1 (FLA3) g/kg diet. Following an eight-week culture period, no significant differences in growth performance were observed among the treatment groups (P > 0.05). However, lysozyme activity, total immunoglobulin (Ig), and total protein concentrations in whole-body extracts were significantly enhanced in the 0.5-1 g FLA/kg diet groups compared to the other treatments (P < 0.05). No significant differences were observed among the groups in catalase (CAT), glutathione peroxidase (GPx), or superoxide dismutase (SOD) activities (P > 0.05). The supplementation of FLA significantly upregulated the gene expression of interferon-α (IFN-α) and tumor necrosis factor-alpha (TNF-α), with the highest expression observed in the 0.5 g FLA/kg diet group (P < 0.05). Additionally, interleukin 1 (IL-1) expression was markedly elevated in this group in comparison to the other treatments (P < 0.05). While there was a significant increase in GPx gene expression with dietary FLA (P < 0.05), no notable differences were observed among FLA treatments (P > 0.05). CAT gene expression remained consistent across all groups (P > 0.05). In contrast, SOD gene expression significantly increased in response to all FLA-supplemented diets, with the highest level observed in the 0.5 g FLA/kg group (P < 0.05). These findings suggest that FLA may serve as an effective dietary supplement to enhance the immune response and antioxidant capacity in zebrafish.

Insights into Virus-Host Interactions: Lessons from Caenorhabditis elegans-Orsay Virus Model

The study of virus-host interactions has been significantly advanced using model organisms, with nematodes being a prominent example. Caenorhabditis elegans (C. elegans) nematodes have provided valuable insights into the mechanisms of viral infections, host defense strategies, and the development of antiviral therapies. With the discovery of natural viral pathogens of nematodes, Orsay virus, Le Blanc virus, Santeuil virus, and Mělník virus, the exploration of the virus-host interaction model based on nematodes has entered a new era. The virus-host interaction network consists of viruses, hosts, and the antagonistic effects of viruses on host immunity. The nematode virus-host interaction model is a concrete manifestation used to study the complex relationships among these three elements. Previous studies have indicated that during the entire process of nematode infection by viruses, antiviral RNA interference (RNAi) plays a crucial role. Additionally, the host's innate immune responses, such as the antiviral-specific intracellular pathogen response (IPR) and certain signaling pathways homologous to those in humans, are particularly important in the natural immune and antiviral processes of nematodes. These processes are regulated by multiple genes in the host. The reverse genetics system for Orsay virus has been successfully developed to study viral gene function and virus-host interactions. Nematodes serve as simple host models for understanding RNA virus replication, related cellular components, and virus-host interaction mechanisms. These findings will likely contribute to the development of antiviral treatment strategies based on novel targets.

Rare earth element erbium induces immune toxicity through the ROS/NF-κB pathway in zebrafish

The large-scale mining and utilization of rare earth elements have significantly increased their concentration in the environment, especially in regions surrounding mining areas. These environmentally-enriched rare earth elements accumulate in agricultural products and organisms through soil and water, potentially impacting in human health through the food chain. Erbium (Er), a rare earth element of the lanthanide series (Group IIIB), plays a crucial role in various modern technological applications. It is primarily utilized in ceramics, glass coloring, optical fibers, laser technology, and the nuclear industry, among others. However, a paucity of information on the health effects and ecotoxicity of erbium is currently available. In this study, we used the zebrafish as experimental animal to investigate the potential impact of the rare earth element erbium on the immune system. We exposed fertilized zebrafish embryos to different concentrations of erbium (0, 4, 8 and 16 mg/L) from 6 hours post-fertilization (hpf) until 72 hpf. We found that with increasing concentrations of erbium exposure, there was an increasing and dispersing trend in the number of zebrafish neutrophils; a decreasing trend in the number of macrophages. Exposure to erbium was demonstrated to impair the phagocytic capability of macrophages, reduce the recruitment of neutrophils to the wound site, and lower the resistance of zebrafish to Escherichia coli infection. Erbium exposure led to macrophage apoptosis and upregulation of oxidative stress in the zebrafish. The individual application of the reactive oxygen species (ROS) scavenger N-acetyl-L-cysteine, the IKBKB inhibitor resveratrol and the NF-κB inhibitor andrographolide were demonstrated to alleviate erbium-induced immune toxicity, as confirmed by assays including acridine orange staining, neutrophils enumeration and recruitment, and real-time quantitative PCR. Therefore, the rare earth element erbium induced immune toxicity in zebrafish through the ROS/NF-κB pathway. The findings of this study provide information for assessing the impact of rare earth elements on human health and ecosystems.

Zebrafish as a model for human epithelial pathology

Zebrafish (Danio rerio) have emerged as an influential model for studying human epithelial pathology, particularly because of their genetic similarity to humans and their unique physiological traits. This review explores the structural and functional homology between zebrafish and human epithelial tissues in organs, such as the gastrointestinal system, liver, and kidneys. Zebrafish possess significant cellular and functional homology with mammals, which facilitates the investigation of various diseases, including inflammatory bowel disease, nonalcoholic fatty liver disease, and polycystic kidney disease. The advantages of using zebrafish as a model organism include rapid external development, ease of genetic manipulation, and advanced imaging capabilities, allowing for the real-time observation of disease processes. However, limitations exist, particularly concerning the lack of organs in zebrafish and the potential for incomplete phenocopy of human conditions. Despite these challenges, ongoing research in adult zebrafish promises to enhance our understanding of the disease mechanisms and regenerative processes. By revealing the similarities and differences in epithelial cell function and disease pathways, this review highlights the value of zebrafish as a translational model for advancing our knowledge of human health and developing targeted therapies.

Peptidoglycan recognition protein PGRP-5 is involved in immune defence and neuro-behavioral disorders in zebrafish embryos

Peptidoglycan recognition proteins (PGRPs) are the evolutionarily highly conserved class of pattern recognition receptors, however, their functions on the innate immune system and neuro-inflammatory response in aquatic organism are still poorly understood. In this study, we systematically investigated the molecular functions of PGRPs in zebrafish embryos. Firstly, we identified three PGRPs in zebrafish and phylogenetic analysis suggested that DrPGRP-5 was a novel member of the PGRP superfamily in evolution. Secondly, the endogenous mRNA levels of DrPGRP-5 were highly expressed in brain and muscle while significantly down-regulated in liver and egg at 72 hpf in zebrafish embryos. Thirdly, the mRNA levels of DrPGRP-5 were greatly elevated after 6 h of E. coli infection but reached its highest value at 24 h after M. luteus stimulation. Moreover, knock-down DrPGRP-5 could significantly reduce the pro-inflammatory cytokines such as TNF-α, IL-1β and IL-6, but increased the expression of anti-inflammatory cytokine TGF-β. On the other hand, the locomotor behavior abilities and the antioxidant enzyme activities such as CAT and SOD were obviously decreased under the DrPGRP-5 KD conditions. Finally, incubation of zebrafish embryos with anti-inflammatory and neuroprotective agents (10 μM Minocycline) can partially rescue the DrPGRP5-regulated locomotor behavior. Taken together, our data suggested that zebrafish PGRP-5 is involved in the innate immune defenses and regulated the neurobehavior and neuro-inflammation, which may provide new strategies for the treatment of neuro-inflammatory diseases in the aquatic organisms.

Methyl 3-Bromo-4,5-dihydroxybenzoate Attenuates Inflammatory Bowel Disease by Regulating TLR/NF-κB Pathways

Inflammatory bowel disease (IBD) is characterized by uncontrolled, chronic relapsing inflammation in the gastrointestinal tract and has become a global healthcare problem. Here, we aimed to illustrate the anti-inflammatory activity and the underlying mechanism of methyl 3-bromo-4,5-dihydroxybenzoate (MBD), a compound derived from marine organisms, especially in IBD, using a zebrafish model. The results indicated that MBD could inhibit the inflammatory responses induced by CuSO4, tail amputation and LPS in zebrafish. Furthermore, MBD notably inhibited the intestinal migration of immune cells, enhanced the integrity of the gut mucosal barrier and improved intestinal peristalsis function in a zebrafish IBD model induced by trinitro-benzene-sulfonic acid (TNBS). In addition, MBD could inhibit ROS elevation induced by TNBS. Network pharmacology analysis, molecular docking, transcriptomics sequencing and RT-PCR were conducted to investigate the potential mechanism. The results showed that MBD could regulate the TLR/NF-κB pathways by inhibiting the mRNA expression of TNF-α, NF-κB, IL-1, IL-1β, IL6, AP1, IFNγ, IKKβ, MyD88, STAT3, TRAF1, TRAF6, NLRP3, NOD2, TLR3 and TLR4, and promoting the mRNA expression of IL4, IκBα and Bcl-2. In conclusion, these findings indicate that MBD could be a potential candidate for the treatment of IBD.

Genetic evidence for the suppressive role of zebrafish vhl targeting mavs in antiviral innate immunity during RNA virus infection

The von Hippel-Lindau (VHL) tumor suppressor gene VHL is a classic tumor suppressor that has been identified in family members with clear cell renal cell carcinomas, central nervous system and retinal hemangioblastomas, phaeochromocytomas, and pancreatic neuroendocrine tumors. The well-defined function of VHL is to mediate proteasomal degradation of hydroxylated hypoxia-inducible factor α proteins, resulting in the downregulation of hypoxia-responsive gene expression. Previously, we reported that VHL inhibits antiviral signaling by targeting mitochondrial antiviral signaling protein (MAVS) for proteasomal degradation. However, due to the lack of a viable animal model, the physiological role and underlying mechanism of VHL in antiviral immunity remains to be elucidated. In this study, we found that heterozygous vhl-deficient zebrafish have normal neutrophils and no gross phenotypic alterations. However, upon spring viremia of carp virus or grass carp reovirus infection, antiviral gene expression is induced in vhl+/- zebrafish compared with wild-type zebrafish. In addition, spring viremia of carp virus replication is suppressed in vhl+/- zebrafish, owing to the enhancement of antiviral ability. Furthermore, by crossing with mavs-/- zebrafish line, we observed that disruption of mavs in vhl+/- zebrafish abrogates the viral resistance exhibited in vhl+/- zebrafish. Thus, we reveal that heterozygous vhl deficiency enhances the antiviral ability of zebrafish against RNA virus infection, and we provide genetic evidence to support that zebrafish mavs serves as a mediator for the suppressive role of vhl in antiviral innate immunity.

Zebrafish as a Model for Investigating Antiviral Innate Immunity

Zebrafish is a widely used model organism in genetics, developmental biology, pathology, and immunology research. Due to their fast reproduction, large numbers, transparent early embryos, and high genetic conservation with the human genome, zebrafish have been used as a model for studying human and fish viral diseases. In particular, the ability to easily perform forward and reverse genetics and lacking a functional adaptive immune response during the early period of development establish the zebrafish as a favored option to assess the functional implication of specific genes in the antiviral innate immune response and the pathogenesis of viral diseases. In this chapter, we detail protocols for the antiviral innate immunity analysis using the zebrafish model, including the generation of gene-overexpression zebrafish, generation of gene-knockout zebrafish by clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9 technology, methods of viral infection in zebrafish larvae, analyzing the expression of antiviral genes in zebrafish larvae using qRT-PCR, Western blotting and transcriptome sequencing, and in vivo antiviral assays. These experimental protocols provide effective references for studying the antiviral immune response in the zebrafish model.

Zebrafish (Danio rerio) as a Model System to Investigate the Role of the Innate Immune Response in Human Infectious Diseases

The zebrafish (Danio rerio) has emerged as a valuable model for studying host-pathogen interactions due to its unique combination of characteristics. These include extensive sequence and functional conservation with the human genome, optical transparency in larvae that allows for high-resolution visualization of host cell-microbe interactions, a fully sequenced and annotated genome, advanced forward and reverse genetic tools, and suitability for chemical screening studies. Despite anatomical differences with humans, the zebrafish model has proven instrumental in investigating immune responses and human infectious diseases. Notably, zebrafish larvae rely exclusively on innate immune responses during the early stages of development, as the adaptive immune system becomes fully functional only after 4-6 weeks post-fertilization. This window provides a unique opportunity to isolate and examine infection and inflammation mechanisms driven by the innate immune response without the confounding effects of adaptive immunity. In this review, we highlight the strengths and limitations of using zebrafish as a powerful vertebrate model to study innate immune responses in infectious diseases. We will particularly focus on host-pathogen interactions in human infections caused by various bacteria (Clostridioides difficile, Staphylococcus aureus, and Pseudomonas aeruginosa), viruses (herpes simplex virus 1, SARS-CoV-2), and fungi (Aspergillus fumigatus and Candida albicans).

Towards an optimized model of food allergy in zebrafish

BACKGROUND

The prevalence of food allergies is on the rise, posing a significant challenge to public health. Rodents serve as the predominant animal model in food allergy research; yet, the application of rodent models proves to be a laborious and time-consuming endeavor. It is imperative to develop novel in vivo models.

METHODS

Ovalbumin (OVA) was administered as the allergen, following the recommended dosage used in other species. During the sensitization phase, a dosage of 0.25 mg per 10 tails per 1 L was administered twice daily, and during the challenge phase, the dosage was increased to 3 times the initial level. The study explored two dimensions of sensitization: the mode of exposure, which can be either continuous or intermittent, and the duration of exposure, which includes 3 days, 5 days, and 7 days. We examined midgut pathological changes, immunoglobulins contents, and mRNA expressions associated to T helper cells (Th) 2 cytokines following exposure.

RESULTS

A significant 109.3 % increase in the number of eosinophils was observed in the midgut histopathology following intermittent 5-day OVA exposure, which emerged as the most effective model. OVA exposure increased concentrations of immunoglobulin M (IgM) (105.2 %), IgZ (312.1 %), and IgD (304.3 %) in this model. The mRNA expressions of Th2-related interleukin (IL)-4 and IL-13 were also elevated by 132.8 % and 421.0 %, respectively.

CONCLUSION

The intermittent 5-day OVA exposure was suggested to be the best constructed zebrafish food allergy model, which may be a potential tool for research into food allergies.

Dissecting the long-term neurobehavioral impact of embryonic benz[a]anthracene exposure on zebrafish: Social dysfunction and molecular pathway activation

Benz[a]anthracene (BaA), a prevalent environmental contaminant within the polycyclic aromatic hydrocarbon class, poses risks to both human health and aquatic ecosystems. The impact of BaA on neural development and subsequent social behavior patterns remains inadequately explored. In this investigation, we employed the zebrafish as a model to examine the persisting effects of BaA exposure on social behaviors across various developmental stages, from larvae, juveniles to adults, following embryonic exposure. Our findings indicate that BaA exposure during embryogenesis yields lasting neurobehavioral deficits into adulthood. Proteomic analysis highlights that BaA may impair neuro-immune crosstalk in zebrafish larvae. Remarkably, our proteomic data also hint at the activation of the aryl hydrocarbon receptor (AHR) and cytochrome P450 1A (CYP1A) pathway by BaA, leading to the hypothesis that this pathway may be implicated in the disruption of neuro-immune interactions, contributing to observable behavioral disruptions. In summary, our findings suggest that early exposure to BaA disrupts social behaviors, such as social ability and shoaling behaviors, from the larval stage through to maturity in zebrafish, potentially through the detrimental effects on neuro-immune processes mediated by the AHR-CYP1A pathway.

A review on current advancement in zebrafish models to study chronic inflammatory diseases and their therapeutic targets

Chronic inflammatory diseases are caused due to prolonged inflammation at a specific site of the body. Among other inflammatory diseases, bacterial meningitis, chronic obstructive pulmonary disease (COPD), atherosclerosis and inflammatory bowel diseases (IBD) are primarily focused on because of their adverse effects and fatality rates around the globe in recent times. In order to come up with novel strategies to eradicate these diseases, a clear understanding of the mechanisms of the diseases is needed. Similarly, detailed insight into the mechanisms of commercially available drugs and potent lead compounds from natural sources are also important to establish efficient therapeutic effects. Zebrafish is widely accepted as a model to study drug toxicity and the pharmacokinetic effects of the drug. Moreover, researchers use various inducers to trigger inflammatory cascades and stimulate physiological changes in zebrafish. The effect of these inducers contrasts with the type of zebrafish used in the investigation. Hence, a thorough analysis is required to study the current advancements in the zebrafish model for chronic inflammatory disease suppression. This review presents the most common inflammatory diseases, commercially available drugs, novel therapeutics, and their mechanisms of action for disease suppression. The review also provides a detailed description of various zebrafish models for these diseases. Finally, the future prospects and challenges for the same are described, which can help the researchers understand the potency of the zebrafish model and its further exploration for disease attenuation.

Deficiency of P2RY11 causes narcolepsy and attenuates the recruitment of neutrophils and macrophages in the inflammatory response in zebrafish

Purinergic receptor P2Y11, a G protein-coupled receptor that is stimulated by extracellular ATP, has been demonstrated to be related to the chemotaxis of granulocytes, apoptosis of neutrophils, and secretion of cytokines in vitro. P2Y11 mutations were associated with narcolepsy. However, little is known about the roles of P2RY11 in the occurrence of narcolepsy and inflammatory response in vivo. In this study, we generated a zebrafish P2Y11 mutant using CRISPR/Cas9 genome editing and demonstrated that the P2Y11 mutant replicated the narcolepsy-like features including reduced HCRT expression and excessive daytime sleepiness, suggesting that P2Y11 is essential for HCRT expression. Furthermore, we accessed the cytokine expression in the mutant and revealed that the P2RY11 mutation disrupted the systemic inflammatory balance by reducing il4, il10 and tgfb, and increasing il6, tnfa, and il1b. In addition, the P2RY11-deficient larvae with caudal fin injuries exhibited significantly slower migration and less recruitment of neutrophils and macrophages at damaged site, and lower expression of anti-inflammatory cytokines during tissue damage. All these findings highlight the vital roles of P2RY11 in maintaining HCRT production and secreting anti-inflammatory cytokines in the native environment, and suggested that P2RY11-deficient zebrafish can serve as a reliable and unique model to further explore narcolepsy and inflammatory-related diseases with impaired neutrophil and macrophage responses.

Psoralen and Isopsoralen, Estrogen Natural Products from , Induced Cholestasis via Activation of ERK1/2

With the increasing use of oral contraceptives and estrogen replacement therapy, the incidence of estrogen-induced cholestasis (EC) has tended to rise. Psoralen (P) and isopsoralen (IP) are the major bioactive components in Psoraleae Fructus, and their estrogen-like activities have already been recognized. Recent studies have also reported that ERK1/2 plays a critical role in EC in mice. This study aimed to investigate whether P and IP induce EC and reveal specific mechanisms. It was found that P and IP increased the expression of esr1, cyp19a1b and the levels of E2 and VTG at 80 μM in zebrafish larvae. Exemestane (Exe), an aromatase antagonist, blocked estrogen-like activities of P and IP. At the same time, P and IP induced cholestatic hepatotoxicity in zebrafish larvae with increasing liver fluorescence areas and bile flow inhibition rates. Further mechanistic analysis revealed that P and IP significantly decreased the expression of bile acids (BAs) synthesis genes cyp7a1 and cyp8b1, BAs transport genes abcb11b and slc10a1, and BAs receptor genes nr1h4 and nr0b2a. In addition, P and IP caused EC by increasing the level of phosphorylation of ERK1/2. The ERK1/2 antagonists GDC0994 and Exe both showed significant rescue effects in terms of cholestatic liver injury. In conclusion, we comprehensively studied the specific mechanisms of P- and IP-induced EC and speculated that ERK1/2 may represent an important therapeutic target for EC induced by phytoestrogens.

Utility of zebrafish-based models in understanding molecular mechanisms of neurotoxicity mediated by the gut-brain axis

The gut microbes perform several beneficial functions which impact the periphery and central nervous systems of the host. Gut microbiota dysbiosis is acknowledged as a major contributor to the development of several neuropsychiatric and neurological disorders including bipolar disorder, depression, anxiety, Parkinson's disease, Alzheimer's disease, attention deficit hyperactivity disorder, and autism spectrum disorder. Thus, elucidation of how the gut microbiota-brain axis plays a role in health and disease conditions is a potential novel approach to prevent and treat brain disorders. The zebrafish (Danio rerio) is an invaluable vertebrate model that possesses conserved brain and intestinal features with those of humans, thus making zebrafish a valued model to investigate the interplay between the gut microbiota and host health. This chapter describes current findings on the utility of zebrafish in understanding molecular mechanisms of neurotoxicity mediated via the gut microbiota-brain axis. Specifically, it highlights the utility of zebrafish as a model organism for understanding how anthropogenic chemicals, pharmaceuticals and bacteria exposure affect animals and human health via the gut-brain axis.

Short-term exposure to fine particulate matter exposure impairs innate immune and inflammatory responses to a pathogen stimulus: A functional study in the zebrafish model

Short-term exposure to fine particulate matter (PM2.5) is associated with the activation of adverse inflammatory responses, increasing the risk of developing acute respiratory diseases, such as those caused by pathogen infections. However, the functional mechanisms underlying this evidence remain unclear. In the present study, we generated a zebrafish model of short-term exposure to a specific PM2.5, collected in the northern metropolitan area of Milan, Italy. First, we assessed the immunomodulatory effects of short-term PM2.5 exposure and observed that it elicited pro-inflammatory effects by inducing the expression of cytokines and triggering hyper-activation of both neutrophil and macrophage cell populations. Moreover, we examined the impact of a secondary infectious pro-inflammatory stimulus induced through the injection of Pseudomonas aeruginosa lipopolysaccharide (Pa-LPS) molecules after exposure to short-term PM2.5. In this model, we demonstrated that the innate immune response was less responsive to a second pro-inflammatory infectious stimulus. Indeed, larvae exhibited dampened leukocyte activation and impaired production of reactive oxygen species. The obtained results indicate that short-term PM2.5 exposure alters the immune microenvironment and affects the inflammatory processes, thus potentially weakening the resistance to pathogen infections.

Non-invasive diagnosis of bacterial and non-bacterial inflammations using a dual-enzyme-responsive fluorescent indicator

Bacterial infections, as the second leading cause of global death, are commonly treated with antibiotics. However, the improper use of antibiotics contributes to the development of bacterial resistance. Therefore, the accurate differentiation between bacterial and non-bacterial inflammations is of utmost importance in the judicious administration of clinical antibiotics and the prevention of bacterial resistance. However, as of now, no fluorescent probes have yet been designed for the relevant assessments. To this end, the present study reports the development of a novel fluorescence probe (CyQ) that exhibits dual-enzyme responsiveness. The designed probe demonstrated excellent sensitivity in detecting NTR and NAD(P)H, which served as critical indicators for bacterial and non-bacterial inflammations. The utilization of CyQ enabled the efficient detection of NTR and NAD(P)H in distinct channels, exhibiting impressive detection limits of 0.26 μg mL-1 for NTR and 5.54 μM for NAD(P)H, respectively. Experimental trials conducted on living cells demonstrated CyQ's ability to differentiate the variations in NTR and NAD(P)H levels between A. baumannii, S. aureus, E. faecium, and P. aeruginosa-infected as well as LPS-stimulated HUVEC cells. Furthermore, in vivo zebrafish experiments demonstrated the efficacy of CyQ in accurately discerning variations in NTR and NAD(P)H levels resulting from bacterial infection or LPS stimulation, thereby facilitating non-invasive detection of both bacterial and non-bacterial inflammations. The outstanding discriminatory ability of CyQ between bacterial and non-bacterial inflammation positions it as a promising clinical diagnostic tool for acute inflammations.

BPA induces hepatotoxicity in zebrafish through oxidative stress and apoptosis pathways

BPA is so ubiquitous that 27 million tons of BPA-containing plastic, including mineral water bottles and baby bottles, is produced worldwide each year. The potential toxicity of BPA to humans and aquatic organisms has been the subject of intense research. In this study, a zebrafish model system was used to assess BPA-mediated hepatotoxicity. Zebrafish larvae at 72-144 hpf were exposed to BPA at different concentrations (0,1, 3 and 5mg/L). For example, BPA-treated zebrafish larvae showed increased mortality, delayed uptake of nutrients in yolk sac, shortened body length, smaller liver area, abnormal expression of genes related to liver development, and pathological changes in the liver tissue. Mechanistically, BPA exposure induced excessive oxidative stress in the liver of zebrafish and increased the level of hepatocyte apoptosis in zebrafish larvae, and the antioxidant astaxanthin could rescue the BPA-mediated liver toxicity.

Single-cell transcriptome landscape of zebrafish liver reveals hepatocytes and immune cell interactions in understanding nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is becoming the most common chronic liver disease in the world. Immunity is the major contributing factor in NAFLD; however, the interaction of immune cells and hepatocytes in disease progression has not been fully elucidated. As a popular species for studying NAFLD, zebrafish, whose liver is a complex immune system mediated by immune cells and non-immune cells in maintaining immune tolerance and homeostasis. Understanding the cellular composition and immune environment of zebrafish liver is of great significance for its application in NAFLD. Here, we established a liver atlas that consists of 10 cell types using single-cell RNA sequencing (scRNA-seq). By examining the heterogeneity of hepatocytes and analyzing the expression of NAFLD-associated genes in the specific cluster, we provide a potential target cell model to study NAFLD. Additionally, our analysis identified two subtypes of distinct resident macrophages with inflammatory and non-inflammatory functions and characterized the successive stepwise development of T cell subclusters in the liver. Importantly, we uncovered the possible regulation of macrophages and T cells on target cells of fatty liver by analyzing the cellular interaction between hepatocytes and immune cells. Our data provide valuable information for an in-depth study of immune cells targeting hepatocytes to regulate the immune balance in NAFLD.

Integrated histopathology and transcriptome metabolome profiling reveal the toxicity mechanism of phenazine-1-carboxylic acid in zebrafish

Phenazine-1-carboxylic acid (PCA) is a new type of agrochemical used to prevent plant diseases, but its effects on aquatic organisms are unclear. To comprehensively assess the impacts of PCA for aquatic organisms and its associated environmental risks, this study investigated, taking zebrafish as the research object, the toxicological mechanism of PCA by means of optical microscopy, hematoxylin and eosin (HE) staining, ultrastructural observation, physiological and biochemical testing, transcriptome sequencing, metabolome analysis, fluorescence quantitative PCR and molecular simulation. The results indicated that PCA was detrimental to zebrafish embryos, larvae and adults, with LC50 values at 96 h of 3.9093 mg/L, 8.5075 mg/L, and 13.6388 mg/L, respectively. PCA caused abnormal spontaneous movement, slowed the heart rate, delayed hatching, shortened the body length, slowed growth, and caused malformations. PCA mainly affected the brain, liver, heart, and ovaries. PCA distorted cell morphology, damaged mitochondrial membranes, disintegrated mitochondrial ridges, and dissociated nuclear membranes. PCA inhibited the enzyme activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX), decreased the malondialdehyde (MDA) content and disrupted antioxidant effects. The results of omics studies confirmed that PCA interfered with the transcriptional and metabolic network of zebrafish, downregulating most genes and metabolites. PCA mainly affected functions related to mitochondrial steroids, lipids, sterols, oxidoreductase activity and pathways involving cofactors, steroids, porphyrin, cytochromes, which specifically bound to targets such as panx3, agmat, and ace2. PCA was moderately toxic to zebrafish, and its usage should be strictly controlled to reduce toxic effects on aquatic organisms. The results of this study provide a new insights for ecotoxicology research.

Modelling 3D Tumour Microenvironment In Vivo: A Tool to Predict Cancer Fate

Recently, many studies demonstrated the fundamental role of the tumour microenvironment (TME) in cancer progression. Here, we describe a method to visualize in 3D the behaviour of tumours in zebrafish embryos. We highlight two major actors of the TME, macrophages and vessels. This valuable tool is transposable to Patient-Derived Xenograft imaging in order to predict the fate of malignant tumours according to the dynamics of their TME.

Zebrafish nos2a benefits bacterial proliferation via suppressing ROS and inducing NO production to impair the expressions of inflammatory cytokines and antibacterial genes

The enzyme nitric oxide synthase 2 or inducible NOS (NOS2), reactive oxygen species (ROS) and nitric oxide (NO) are important participants in various inflammatory and immune responses. However, the functional significances of the correlations among piscine NOS2, ROS and NO during pathogen infection remain unclear. In teleost, there are two nos2 genes (nos2a and nos2b). It has been previously reported that zebrafish nos2a behaves as a classical inducible NOS, and nos2b exerts some functions similar to mammalian NOS3. In the present study, we reported the functional characterization of zebrafish nos2a during bacterial infection. We found that zebrafish nos2a promoted bacterial proliferation, accompanied by an increased susceptibility to Edwardsiella piscicida infection. The nagative regulation of zebrafish nos2a during E. piscicida infection was characterized by the impaired ROS levels, the induced NO production and the decreased expressions of proinflammatory cytokines, antibacterial genes and oxidant factors. Furthermore, although both inducing ROS and inhibiting NO production significantly inhibited bacterial proliferation, only inhibiting NO production but not inducing ROS significantly increased resistance to E. piscicida infection. More importantly, ROS supplementation and inhibition of NO completely abolished this detrimental consequence mediated by zebrafish nos2a during E. piscicida infection. All together, these results firstly demonstrate that the innate response mediated by zebrafish nos2a in promoting bacterial proliferation is dependent on the lower ROS level and higher NO production. The present study also reveals that inhibition of NO can be effective in the protection against E. piscicida infection.

Choosing the right animal model for osteomyelitis research: Considerations and challenges

Osteomyelitis is a debilitating bone disorder characterized by an inflammatory process involving the bone marrow, bone cortex, periosteum, and surrounding soft tissue, which can ultimately result in bone destruction. The etiology of osteomyelitis can be infectious, caused by various microorganisms, or noninfectious, such as chronic nonbacterial osteomyelitis (CNO) and chronic recurrent multifocal osteomyelitis (CRMO). Researchers have turned to animal models to study the pathophysiology of osteomyelitis. However, selecting an appropriate animal model that accurately recapitulates the human pathology of osteomyelitis while controlling for multiple variables that influence different clinical presentations remains a significant challenge. In this review, we present an overview of various animal models used in osteomyelitis research, including rodent, rabbit, avian/chicken, porcine, minipig, canine, sheep, and goat models. We discuss the characteristics of each animal model and the corresponding clinical scenarios that can provide a basic rationale for experimental selection. This review highlights the importance of selecting an appropriate animal model for osteomyelitis research to improve the accuracy of the results and facilitate the development of novel treatment and management strategies.

Unlocking the Potential of Zebrafish Research with Artificial Intelligence: Advancements in Tracking, Processing, and Visualization

Zebrafish have become a widely accepted model organism for biomedical research due to their strong cortisol stress response, behavioral strain differences, and sensitivity to both drug treatments and predators. However, experimental zebrafish studies generate substantial data that must be analyzed through objective, accurate, and repeatable analysis methods. Recently, advancements in artificial intelligence (AI) have enabled automated tracking, image recognition, and data analysis, leading to more efficient and insightful investigations. In this review, we examine key AI applications in zebrafish research, including behavior analysis, genomics, and neuroscience. With the development of deep learning technology, AI algorithms have been used to precisely analyze and identify images of zebrafish, enabling automated testing and analysis. By applying AI algorithms in genomics research, researchers have elucidated the relationship between genes and biology, providing a better basis for the development of disease treatments and gene therapies. Additionally, the development of more effective neuroscience tools could help researchers better understand the complex neural networks in the zebrafish brain. In the future, further advancements in AI technology are expected to enable more extensive and in-depth medical research applications in zebrafish, improving our understanding of this important animal model. This review highlights the potential of AI technology in achieving the full potential of zebrafish research by enabling researchers to efficiently track, process, and visualize the outcomes of their experiments.

Toxicity effects of pesticides based on zebrafish (Danio rerio) models: Advances and perspectives

Pesticides inevitably enter aquatic environments, posing potential risks to organisms. The common aquatic model organism, zebrafish (Danio rerio), are widely used to evaluate the toxicity of pesticides. In this review, we searched the Web of Science database for articles published between 2012 and 2022, using the keywords "pesticide", "zebrafish", and "toxicity", retrieving 618 publications. Furthermore, we described the main pathways by which pesticides enter aquatic environments and the fate of their residues in these environments. We systematically reviewed the toxicity effects of pesticides on zebrafish, including developmental toxicity, endocrine-disrupting effects, reproductive toxicity, neurotoxicity, immunotoxicity, and genotoxicity. Importantly, we summarized the latest research progress on the toxicity mechanism of pesticides to zebrafish based on omics technologies, including transcriptomics, metabolomics, and microbiomics. Finally, we discussed future research prospects, focusing on the combined exposure of multiple pollutants including pesticides, the risk of multigenerational exposure to pesticides, and the chronic toxicity of aquatic nanopesticides. This review provides essential data support for ecological risk assessments of pesticides in aquatic environments, and has implications for water management in the context of pesticide pollution.

Identification of side effects of COVID-19 drug candidates on embryogenesis using an integrated zebrafish screening platform

Drug repurposing is an important strategy in COVID-19 treatment, but many clinically approved compounds have not been extensively studied in the context of embryogenesis, thus limiting their administration during pregnancy. Here we used the zebrafish embryo model organism to test the effects of 162 marketed drugs on cardiovascular development. Among the compounds used in the clinic for COVD-19 treatment, we found that Remdesivir led to reduced body size and heart functionality at clinically relevant doses. Ritonavir and Baricitinib showed reduced heart functionality and Molnupiravir and Baricitinib showed effects on embryo activity. Sabizabulin was highly toxic at concentrations only 5 times higher than Cmax and led to a mean mortality of 20% at Cmax. Furthermore, we tested if zebrafish could be used as a model to study inflammatory response in response to spike protein treatment and found that Remdesivir, Ritonavir, Molnupiravir, Baricitinib as well as Sabizabulin counteracted the inflammatory response related gene expression upon SARS-CoV-2 spike protein treatment. Our results show that the zebrafish allows to study immune-modulating properties of COVID-19 compounds and highlights the need to rule out secondary defects of compound treatment on embryogenesis. All results are available on a user friendly web-interface https://share.streamlit.io/alernst/covasc_dataapp/main/CoVasc_DataApp.py that provides a comprehensive overview of all observed phenotypic effects and allows personalized search on specific compounds or group of compounds. Furthermore, the presented platform can be expanded for rapid detection of developmental side effects of new compounds for treatment of COVID-19 and further viral infectious diseases.

Immunotoxicity and transcriptome analysis of zebrafish embryos exposure to Nitazoxanide

Nitazoxanide (NTZ) is a broad-spectrum immunomodulatory drug, and little information is about the immunotoxicity of aquatic organisms induced by NTZ. In the present study, reduced body length and decreased yolk sac absorption in the NTZ-treated group were observed. Meanwhile, the number of innate immune cells and adaptive immune cells was substantially reduced upon NTZ exposure, and the migration and retention of macrophages and neutrophils in the injured area were inhibited. Following NTZ stimulation, oxidative stress levels in the zebrafish increased obviously. Mechanistically, RNA-seq, a high-throughput method, was performed to analyze the global expression of differentially expressed genes (DEGs) in zebrafish embryos treated with NTZ. 531 DEGs were identified by comparative transcriptome analysis, including 121 up-regulated and 420 down-regulated genes in zebrafish embryos after NTZ exposure. The transcriptome sequences were further subjected to the Kyoto Encyclopedia of Genes and Genomes (KEGG) and gene ontology (GO) and analysis, showing phototransduction and metabolic pathway, respectively, and were most enriched. In addition, some immune-related genes were inhibited after NTZ exposure. RNA-seq results confirmed by qRT-PCR were used to verify the expression of the 6 selected genes. The other immune-related genes such as two pro-inflammatory cytokines (IL-1β, tnfα) and two chemokines (CXCL8b.3, CXCL-c1c) were further confirmed and were differentially regulated after NTZ exposure. In summary, NTZ exposure could lead to immunotoxicity and increased ROS in zebrafish embryos, this study provides valuable information for future elucidating the molecular mechanism of exogenous stimuli-induced immunotoxicity in aquatic ecosystems.

Identification of histone deacetylase inhibitors as neutrophil recruitment modulators in zebrafish using a chemical library screen

Tissue injury-induced neutrophil recruitment is a prerequisite for the initiation and amplification of inflammatory responses. Although multiple proteases and enzymes involved in post-translational modification (PTM) of proteins regulate leukocyte recruitment, an unbiased functional screen of enzymes regulating inflammatory leukocyte recruitment has yet to be undertaken. Here, using a zebrafish tail fin amputation (TFA) model to screen a chemical library consisting of 295 compounds that target proteases and PTM enzymes, we identified multiple histone deacetylase (HDAC) inhibitors that modulate inflammatory neutrophil recruitment. AR-42, a pan-HDAC inhibitor, was shown to inhibit neutrophil recruitment in three different zebrafish sterile tissue injury models: a TFA model, a copper-induced neuromast damage and mechanical otic vesicle injury (MOVI) model, and a sterile murine peritonitis model. RNA sequencing analysis of AR-42-treated fish embryos revealed downregulation of neutrophil-associated cytokines/chemokines, and exogenous supplementation with recombinant human IL-1β and CXCL8 partially restored the defective neutrophil recruitment in AR-42-treated MOVI model fish embryos. We thus demonstrate that AR-42 non-cell-autonomously modulates neutrophil recruitment by suppressing transcriptional expression of cytokines/chemokines, thereby identifying AR-42 as a promising anti-inflammatory drug for treating sterile tissue injury-associated diseases.

Toxic effects of sirolimus and everolimus on the development and behavior of zebrafish embryos

Sirolimus and everolimus have been widely used in children. These mammalian target of rapamycin (mTOR) inhibitors have shown excellent efficacy not only in organ transplant patients as immunosuppressive agents but also in patients with some other diseases. However, whether mTOR inhibitors can affect the growth and development of children is of great concern. In this study, using zebrafish models, we discovered that sirolimus and everolimus could slow the development of zebrafish, affecting indicators such as survival, hatching, deformities, body length, and movement. In addition to these basic indicators, sirolimus and everolimus had certain slowing effects on the growth and development of the nervous system, blood vessels, and the immune system. These effects were dose dependent. When the drug concentration reached or exceeded 0.5 μM, the impacts of sirolimus and everolimus were very significant. More interestingly, the impact was transient. Over time, the various manifestations of experimental embryos gradually approached those of control embryos. We also compared the effects of sirolimus and everolimus on zebrafish, and we revealed that there was no significant difference between these drugs in terms of their effects. In summary, the dose of sirolimus and everolimus in children should be strictly controlled, and the drug concentration should be monitored over time. Otherwise, drug overdosing may have a certain impact on the growth and development of children.

Escherichia coli Nissle 1917 ghosts alleviate inflammatory bowel disease in zebrafish

Escherichia coli Nissle 1917 (EcN) has become a research hotspot in inflammatory bowel disease (IBD). It has a strong targeting effect on the colon, and has some therapeutic effect on inflammatory bowel disease. EcN is prepared into EcN ghosts, which also retain EcN's biological characteristics. Consequently, EcN ghosts are used for drug delivery. This study evaluated the safety and efficacy of EcN ghosts as carriers of drugs for treating IBD in zebrafish. Caco-2 cell adhesion experiments and zebrafish intestinal adhesion experiments demonstrated that EcN ghosts was highly adherent to the intestine. Additionally, oral administration of EcN ghosts attenuated dextran sulfate sodium-induced IBD symptoms by inhibiting neutrophil chemotaxis and reactive oxygen species production in larval zebrafish. Because of the unique biological functions of EcN ghosts, it may serve as a strategy for future targeted drug delivery in IBD treatment.

Zebrafish as a Useful Model System for Human Liver Disease

Liver diseases represent a significant global health challenge, thereby necessitating extensive research to understand their intricate complexities and to develop effective treatments. In this context, zebrafish (Danio rerio) have emerged as a valuable model organism for studying various aspects of liver disease. The zebrafish liver has striking similarities to the human liver in terms of structure, function, and regenerative capacity. Researchers have successfully induced liver damage in zebrafish using chemical toxins, genetic manipulation, and other methods, thereby allowing the study of disease mechanisms and the progression of liver disease. Zebrafish embryos or larvae, with their transparency and rapid development, provide a unique opportunity for high-throughput drug screening and the identification of potential therapeutics. This review highlights how research on zebrafish has provided valuable insights into the pathological mechanisms of human liver disease.

Radix Panacis quinquefolii Extract Ameliorates Inflammatory Bowel Disease through Inhibiting Inflammation

OBJECTIVE

To investigate the anti-inflammatory activity of Radix Panacis quinguefolii root extract (RPQE) and its therapeutic effects on inflammatory bowel disease (IBD).

METHODS

The 72-hour post-fertilization zebrafish was used to generate the local and systematic inflammation models through tail-amputation and lipopolysaccharide (LPS)-induction (100 µ g/mL), respectively. The Tg(zlyz:EGFP) zebrafish was induced with 75 µ g/mL 2,4,6-trinitrobenzene sulfonic acid (TNBS) for establishing the IBD model. The tail-amputated, LPS-, and TNBS-induced models were subjected to RPQE (ethanol fraction, 10-20 µ g/mL) administration for 12 and 24 h, respectively. Anti-inflammatory activity of RPQE was evaluated by detecting migration and aggregation of leukocytes and expression of inflammation-related genes. Meanwhile, TNBS-induced fish were immersed in 0.2% (W/V) calcein for 1.5 h and RPQE for 12 h before photographing to analyze the intestinal efflux efficiency (IEE). Moreover, the expression of inflammation-related genes in these fish was detected by quantitative polymerase chain reaction.

RESULTS

Subject to RPQE administration, the migration and aggregation of leukocytes were significantly alleviated in 3 zebrafish models (P<0.01). Herein, RPQE ameliorated TNBS-induced IBD with respect to a significantly reduced number of leukocytes, improved IEE, and inhibited gene expression of pro-inflammatory factors (P<0.05 or P<0.01).

CONCLUSION

RPQE exhibited therapeutic effects on IBD by inhibiting inflammation.

LPS-Induced Mortality in Zebrafish: Preliminary Characterisation of Common Fish Pathogens

Disease outbreaks are a common problem in aquaculture, with serious economic consequences to the sector. Some of the most important bacterial diseases affecting aquaculture are caused by Gram-negative bacteria including Vibrio spp. (vibriosis), Photobacterium damselae (photobacteriosis), Aeromonas spp. (furunculosis; haemorrhagic septicaemia) or Tenacibaculum maritimum (tenacibaculosis). Lipopolysaccharides (LPS) are important components of the outer membrane of Gram-negative bacteria and have been linked to strong immunogenic responses in terrestrial vertebrates, playing a role in disease development. To evaluate LPS effects in fish, we used a hot-phenol procedure to extract LPS from common fish pathogens. A. hydrophila, V. harveyi, T. maritimum and P. damselae purified LPS were tested at different concentrations (50, 100, 250 and 500 µg mL-1) at 3 days post-fertilisation (dpf) Danio rerio larvae, for 5 days. While P. damselae LPS did not cause any mortality under all concentrations tested, A. hydrophila LPS induced 15.5% and V. harveyi LPS induced 58.3% of zebrafish larvae mortality at 500 µg mL-1. LPS from T. maritimum was revealed to be the deadliest, with a zebrafish larvae mortality percentage of 80.6%. Analysis of LPS separated by gel electrophoresis revealed differences in the overall LPS structure between the bacterial species analysed that might be the basis for the different mortalities observed.

Sanguinarine exposure induces immunotoxicity and abnormal locomotor behavior in zebrafish

Sanguinarine (C20H14NO4+), a plant alkaloid and pesticide, works well a fungicidal and insecticidal applications. The prospect that sanguinarine may have potentially toxic effects on aquatic organisms has been brought to light by its use in agriculture. The first evaluation of the immunotoxic and behavioral effects of sanguinarine exposure on larval zebrafish was done in this work. Firstly, zebrafish embryos exposed to sanguinarine had shorter body length, larger yolk sacs, and slower heart rates. Secondly, the number of innate immune cells was significantly reduced. Thirdly, alterations in locomotor behavior were observed as exposure concentrations increased. Total distance travelled, travel time, and mean speed were all reduced. We also found significant changes in oxidative stress-related indicators and a significant increase in apoptosis in the embryos. Further studies revealed aberrant expression of some key genes in the TLR immune signaling pathway including CXCL-c1c, IL8, MYD88, and TLR4. At the same time, the expression of the pro-inflammatory cytokine IFN-γ was upregulated. To sum up, our results suggest that sanguinarine exposure may cause immunotoxicity and aberrant behavior in larval zebrafish.

Sulfoxaflor induces immunotoxicity in zebrafish (Danio rerio) by activating TLR4/NF-κB signaling pathway

Sulfoxaflor is an insecticide that is widely used and affects the nervous system of sucking pests. However, studies on the molecular mechanism of the toxicity of sulfoxaflor to non-target species are limited. Zebrafish (Danio rerio) was used as an experimental subject in this study. Zebrafish embryos were exposed to 20, 25, and 30 mg/L sulfoxaflor solution to detect hatchability, mortality, heart rate, neutrophil count, oxidative stress, and expression of genes related to apoptosis and immune inflammation. The results showed that zebrafish embryos exposed to sulfoxaflor solution increased mortality and growth retardation, and the number of innate immune cells decreased significantly. In addition, the expression levels of apoptotic and proapoptotic genes increased significantly, and oxidative stress-related indexes changed significantly. Toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) signaling pathway was further studied, and the interleukin 6 (IL-6), interleukin 1 beta (IL-1β), cyclooxygenase-2 (COX2), tumor necrosis factor-alpha (TNF-α), TLR4, and myeloid differentiation primary response 88 (MYD88) gene expression levels were significantly up-regulated. We used small molecule inhibitor QNZ for the rescue experiment and detected the expression of relevant target proteins in the QNZ signaling pathway. QNZ reduced the expression of TLR4/NF-κB signaling pathway-related protein NF-κB p65 in the cytoplasm and nucleus and rescued the number of innate immune cells. In summary, sulfoxaflor may induce developmental toxicity and immunotoxicity in zebrafish by activating the TLR4/NF-κB signaling pathway, which provides a basis for further studies on the molecular mechanism of sulfoxaflor action in the aquatic ecosystem and the development and utilization of QNZ.

Anti-Inflammatory and Antioxidant Properties of Squalene in Copper Sulfate-Induced Inflammation in Zebrafish (Danio rerio)

Long-term or excessive oxidative stress can cause serious damage to fish. Squalene can be added to feed as an antioxidant to improve the body constitution of fish. In this study, the antioxidant activity was detected by 2,2-diphenyl-1-acrylhydrazyl (DPPH) test and fluorescent probe (dichloro-dihydro-fluorescein diacetate). Transgenic Tg (lyz: DsRed2) zebrafish were used to evaluate the effect of squalene on CuSO₄-induced inflammatory response. Quantitative real-time reverse transcription polymerase chain reaction was used to examine the expression of immune-related genes. The DPPH assay demonstrated that the highest free radical scavenging exerted by squalene was 32%. The fluorescence intensity of reactive oxygen species (ROS) decreased significantly after 0.7% or 1% squalene treatment, and squalene could exert an antioxidative effect in vivo. The number of migratory neutrophils in vivo was significantly reduced after treatment with different doses of squalene. Moreover, compared with CuSO₄ treatment alone, treatment with 1% squalene upregulated the expression of sod by 2.5-foldand gpx4b by 1.3-fold to protect zebrafish larvae against CuSO₄-induced oxidative damage. Moreover, treatment with 1% squalene significantly downregulated the expression of tnfa and cox2. This study showed that squalene has potential as an aquafeed additive to provide both anti-inflammatory and antioxidative properties.

Restoring airway epithelial homeostasis in Cystic Fibrosis

Cystic fibrosis (CF), the most common life-threatening genetic disorder in Caucasians, is caused by recessive mutations in the Cystic Fibrosis Transmembrane Regulator (CFTR) gene encoding a chloride ion channel. Aberrant function of CFTR involves mucus- and sweat-producing epithelia affecting multiple organs, including airways and lungs. This condition facilitates the colonization of fungi, bacteria, or viruses. Recurrent antibiotic administration is commonly used to treat pathogen infections leading to the insurgence of resistant bacteria and to a chronic inflammatory state that jeopardizes airway epithelium repair. The phenotype of patients carrying CFTR mutations does not always present a strict correlation with their genotype, suggesting that the disease may occur because of multiple additive effects. Among them, the frequent microbiota dysbiosis observed in patients affected by CF, might be one cause of the discrepancy observed in their genotype-phenotype correlation. Interestingly, the abnormal polarity of the CF airway epithelium has been observed also under non-infectious and non-inflammatory conditions, suggesting that CFTR dysfunction "per se" perturbs epithelial homeostasis. New pathogen- or host-directed strategies are thus needed to counteract bacterial infections and restore epithelial homeostasis in individuals with CF. In this review, we summarized alternative cutting-edge approaches to high-efficiency modulator therapy that might be promising for these patients.

Pyrogallol downregulates the expression of virulence-associated proteins in Acinetobacter baumannii and showing anti-infection activity by improving non-specific immune response in zebrafish model

Acinetobacter baumannii, a virulent uropathogen with widespread antibiotic resistance, has arisen as a critical scientific challenge, necessitating the development of innovative therapeutic agents. This is the first study reveal the proteomic changes in A. baumannii upon pyrogallol treatment for understanding the mechanisms using nano-LC-MS/MS-based quantitative proteomics and qPCR analysis. The obtained results found that pyrogallol treatment dramatically downregulated the expression level of several key proteins such as GroEL, DnaK, ClpB, SodB, KatE, Bap, CsuA/B, PgaA, PgaC, BfmR, OmpA, and SecA in A. baumannii, which are involved in chaperone-mediated oxidative stress responses, antioxidant defence system, biofilm formation, virulence enzyme production, bacterial adhesion, capsule formation, and antibiotic resistance. Accordingly, the pyrogallol dramatically enhanced the lifespan of A. baumannii-infected zebrafish by inhibiting bacterial colonization, demonstrating the anti-infective potential of pyrogallol against A. baumannii. Further, the histopathological results also demonstrated the disease protection efficacy of pyrogallol against the pathognomonic sign of A. baumannii infection. In addition, the pyrogallol treatment effectively improved the immune parameters such as serum myeloperoxidase activity, leukocyte respiratory burst activity, and serum lysozyme activity in zebrafish against A. baumannii infection. Based on the results, the present study strongly proposes pyrogallol as a promising therapeutic agent for treating A. baumannii infection.

Understanding CNS Effects of Antimicrobial Drugs Using Zebrafish Models

Antimicrobial drugs represent a diverse group of widely utilized antibiotic, antifungal, antiparasitic and antiviral agents. Their growing use and clinical importance necessitate our improved understanding of physiological effects of antimicrobial drugs, including their potential effects on the central nervous system (CNS), at molecular, cellular, and behavioral levels. In addition, antimicrobial drugs can alter the composition of gut microbiota, and hence affect the gut-microbiota-brain axis, further modulating brain and behavioral processes. Complementing rodent studies, the zebrafish (Danio rerio) emerges as a powerful model system for screening various antimicrobial drugs, including probing their putative CNS effects. Here, we critically discuss recent evidence on the effects of antimicrobial drugs on brain and behavior in zebrafish, and outline future related lines of research using this aquatic model organism.

Mixture toxicity of pyraclostrobine and metiram to the zebrafish (Danio rerio) and its potential mechanism

The interplay between pesticides plays a critical role in ecotoxicology since these chemicals rarely emerge as single substances but rather in mixtures with other chemicals. In the present work, we purposed to clarify the combined toxic impacts of pyraclostrobine (PYR) and metiram (MET) on the zebrafish by using numerous indicators. Results exhibited that the 4-day LC₅₀ value of MET to fish embryos was 0.0025 mg a.i. L^-1, which was lower compared with PYR (0.019 mg a.i. L^-1). Combinations of PYR and MET presented a synergetic impact on fish embryos. Contents of POD, CYP450, and VTG were drastically increased in the plurality of the single and joint treatments relative to the baseline value. Three genes, including vtg1, crh, and il-8, related to the endocrine and immune systems, were also surprisingly up-regulated when fish were challenged by the individual and mixture pesticides compared with the baseline value. These results afforded valuable information on the latent toxicity mechanisms of co-exposure for PYR and MET in the early growth stage of fish. Moreover, our data also revealed that frequent application of these two pesticides might exert a potentially ecotoxicological hazard on aquatic ecosystems. Collectively, the present study provided valuable guidance for the risk evaluation of chemical combinations.

Pre-clinical models for evaluating glioma targeted immunotherapies

Gliomas have an extremely poor prognosis in both adult and pediatric patient populations as these tumors are known to grow aggressively and respond poorly to standard of care treatment. Currently, treatment for gliomas involves surgical resection followed by chemoradiation therapy. However, some gliomas, such as diffuse midline glioma, have more limited treatment options such as radiotherapy alone. Even with these interventions, the prognosis for those diagnosed with a glioma remains poor. Immunotherapy is highly effective for some cancers and there is great interest in the development of effective immunotherapies for the treatment of gliomas. Clinical trials evaluating the efficacy of immunotherapies targeted to gliomas have largely failed to date, and we believe this is partially due to the poor choice in pre-clinical mouse models that are used to evaluate these immunotherapies. A key consideration in evaluating new immunotherapies is the selection of pre-clinical models that mimic the glioma-immune response in humans. Multiple pre-clinical options are currently available, each one with their own benefits and limitations. Informed selection of pre-clinical models for testing can facilitate translation of more promising immunotherapies in the clinical setting. In this review we plan to present glioma cell lines and mouse models, as well as alternatives to mouse models, that are available for pre-clinical glioma immunotherapy studies. We plan to discuss considerations of model selection that should be made for future studies as we hope this review can serve as a guide for investigators as they choose which model is best suited for their study.

Animal Inflammation-Based Models of Neuropsychiatric Disorders

Mounting evidence links psychiatric disorders to central and systemic inflammation. Experimental (animal) models of psychiatric disorders are important tools for translational biopsychiatry research and CNS drug discovery. Current experimental models, most typically involving rodents, continue to reveal shared fundamental pathological pathways and biomarkers underlying the pathogenetic link between brain illnesses and neuroinflammation. Recent data also show that various proinflammatory factors can alter brain neurochemistry, modulating the levels of neurohormones and neurotrophins in neurons and microglia. The role of "active" glia in releasing a wide range of proinflammatory cytokines also implicates glial cells in various psychiatric disorders. Here, we discuss recent animal inflammation-related models of psychiatric disorders, focusing on their translational perspectives and the use of some novel promising model organisms (zebrafish), to better understand the evolutionally conservative role of inflammation in neuropsychiatric conditions.

Progress on the toxicity of quantum dots to model organism-zebrafish

In vivo toxicological studies are currently necessary to analyze the probable dangers of quantum dots (QDs) to the environment and human safety, due to the fast expansion of QDs in a range of applications. Because of its high fecundity, cost-effectiveness, well-defined developmental phases, and optical transparency, zebrafish has long been considered the "gold standard" for biosafety assessment of chemical substances and pollutants. In this review, the advantages of using zebrafish in QD toxicity assessment were explored. Then, the target organ toxicities such as developmental toxicity, immunotoxicity, cardiovascular toxicity, neurotoxicity, and hepatotoxicity were summarized. The hazardous effects of different QDs, including cadmium-containing QDs like CdTe, CdSe, and CdSe/ZnS, as well as cadmium-free QDs like graphene QDs (GQDs), graphene oxide QDs (GOQDs), and others, were emphasized and described in detail, as well as the underlying mechanisms of QDs generating these effects. Furthermore, general physicochemical parameters determining QD-induced toxicity in zebrafish were introduced, such as chemical composition and surface coating/modification. The limitations and special concerns of using zebrafish in QD toxicity studies were also mentioned. Finally, we predicted that the utilization of high-throughput screening assays and omics, such as transcriptome sequencing, proteomics, and metabolomics will be popular topic in nanotoxicology.

Neuromasts and Olfactory Organs of Zebrafish Larvae Represent Possible Sites of SARS-CoV-2 Pseudovirus Host Cell Entry

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of the acute respiratory disease coronavirus disease 2019 (COVID-19), which has resulted in millions of deaths globally. Here, we explored the mechanism of host cell entry of a luciferase-ZsGreen spike (SARS-CoV-2)-pseudotyped lentivirus using zebrafish embryos/larvae as an in vivo model. Successful pseudovirus entry was demonstrated via the expression of the luciferase (luc) gene, which was validated by reverse transcription-PCR (RT-PCR). Treatment of larvae with chloroquine (a broad-spectrum viral inhibitor that blocks membrane fusion) or bafilomycin A1 (a specific inhibitor of vacuolar proton ATPases, which blocks endolysosomal trafficking) significantly reduced luc expression, indicating the possible involvement of the endolysosomal system in the viral entry mechanism. The pharmacological inhibition of two-pore channel (TPC) activity or use of the tpcn2^dhkz1a mutant zebrafish line also led to diminished luc expression. The localized expression of ACE2 and TPC2 in the anterior neuromasts and the forming olfactory organs was demonstrated, and the occurrence of endocytosis in both locations was confirmed. Together, our data indicate that zebrafish embryos/larvae are a viable and tractable model to explore the mechanism of SARS-CoV-2 host cell entry, that the peripheral sense organs are a likely site for viral host cell entry, and that TPC2 plays a key role in the translocation of the virus through the endolysosomal system. IMPORTANCE Despite the development of effective vaccines to combat the COVID-19 pandemic, which help prevent the most life-threatening symptoms, full protection cannot be guaranteed, especially with the emergence of new viral variants. Moreover, some resistance to vaccination remains in certain age groups and cultures. As such, there is an urgent need for the development of new strategies and therapies to help combat this deadly disease. Here, we provide compelling evidence that the peripheral sensory organs of zebrafish possess several key components required for SARS-CoV-2 host cell entry. The nearly transparent larvae provide a most amenable complementary platform to investigate the key steps of viral entry into host cells, as well as its spread through the tissues and organs. This will help in the identification of key viral entry steps for therapeutic intervention, provide an inexpensive model for screening novel antiviral compounds, and assist in the development of new and more effective vaccines.

Fenpropathrin exposure induces neurotoxicity in zebrafish embryos

Fenpropathrin has been a commonly used insecticide to control agricultural and household insects over a few decades. Up to now, fenpropathrin residue in soil and water has been often determined due to its widespread use, which poses serious threat to environment and aquatic organisms. The potential of fenpropathrin to affect aquatic lives is still poorly understood. In this study, we used zebrafish (Danio rerio) embryo as an experimental model system to evaluate the toxicity of fenpropathrin to the development of zebrafish nervous system. Zebrafish embryos were separately exposed to fenpropathrin at the dose of 0.016 mg/L, 0.032 mg/L, 0.064 mg/L, starting at 6 h post-fertilizationhpf (hpf) up to 96 hpf. The results showed that fenpropathrin exposure gives rise to physiological, behavioral, and neurodevelopmental impairments in zebrafish embryos, including enhanced acetylcholinesterase (AChE) activity, abnormal swimming behavior, karyopyknosis in brain cells, increased intercellular space, and uneven migration of neuron in brain area. In addition, the expressions of genes concerning neurodevelopment and neurotransmitter system were inhibited following fenpropathrin exposure. We also found that fenpropathrin exposure distinctly induced oxidative stress by increasing reactive oxygen species (ROS) generation and inhibiting the production of antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD). Expectedly, some apoptosis-associated genes were induced and the apoptosis appeared in the brain and heart cells of zebrafish embryos. Moreover, fenpropathrin exposure also inhibited the expressions of genes in Nrf2 signaling pathway, such as heme oxygenase-1 (HO-1) and SOD. In summary, the results of this study indicate that oxidative stress-triggered apoptosis may be an underlying fundamental of fenpropathrin-induced neurotoxicity in zebrafish embryos.

PCSK9 Confers Inflammatory Properties to Extracellular Vesicles Released by Vascular Smooth Muscle Cells

Vascular smooth muscle cells (VSMCs) are key participants in both early- and late-stage atherosclerosis and influence neighbouring cells possibly by means of bioactive molecules, some of which are packed into extracellular vesicles (EVs). Proprotein convertase subtilisin/kexin type 9 (PCSK9) is expressed and secreted by VSMCs. This study aimed to unravel the role of PCSK9 on VSMCs-derived EVs in terms of content and functionality. EVs were isolated from human VSMCs overexpressing human PCSK9 (VSMCPCSK9-EVs) and tested on endothelial cells, monocytes, macrophages and in a model of zebrafish embryos. Compared to EVs released from wild-type VSMCs, VSMCPCSK9-EVs caused a rise in the expression of adhesion molecules in endothelial cells and of pro-inflammatory cytokines in monocytes. These acquired an increased migratory capacity, a reduced oxidative phosphorylation and secreted proteins involved in immune response and immune effector processes. Concerning macrophages, VSMCPCSK9-EVs enhanced inflammatory milieu and uptake of oxidized low-density lipoproteins, whereas the migratory capacity was reduced. When injected into zebrafish embryos, VSMCPCSK9-EVs favoured the recruitment of macrophages toward the site of injection. The results of the present study provide evidence that PCSK9 plays an inflammatory role by means of EVs, at least by those derived from smooth muscle cells of vascular origin.

Evaluation of phages and liposomes as combination therapy to counteract Pseudomonas aeruginosa infection in wild-type and CFTR-null models

Multi drug resistant (MDR) bacteria are insensitive to the most common antibiotics currently in use. The spread of antibiotic-resistant bacteria, if not contained, will represent the main cause of death for humanity in 2050. The situation is even more worrying when considering patients with chronic bacterial infections, such as those with Cystic Fibrosis (CF). The development of alternative approaches is essential and novel therapies that combine exogenous and host-mediated antimicrobial action are promising. In this work, we demonstrate that asymmetric phosphatidylserine/phosphatidic acid (PS/PA) liposomes administrated both in prophylactic and therapeutic treatments, induced a reduction in the bacterial burden both in wild-type and cftr-loss-of-function (cftr-LOF) zebrafish embryos infected with Pseudomonas aeruginosa (Pa) PAO1 strain (PAO1). These effects are elicited through the enhancement of phagocytic activity of macrophages. Moreover, the combined use of liposomes and a phage-cocktail (CKΦ), already validated as a PAO1 “eater”, improves the antimicrobial effects of single treatments, and it is effective also against CKΦ-resistant bacteria. We also address the translational potential of the research, by evaluating the safety of CKΦ and PS/PA liposomes administrations in in vitro model of human bronchial epithelial cells, carrying the homozygous F508del-CFTR mutation, and in THP-1 cells differentiated into a macrophage-like phenotype with pharmacologically inhibited CFTR. Our results open the way to the development of novel pharmacological formulations composed of both phages and liposomes to counteract more efficiently the infections caused by Pa or other bacteria, especially in patients with chronic infections such those with CF.