Immunology and zebrafish: spawning new models of human disease

Assessment of the hepatoprotective effects of Bicyclol's forced degradation products using a zebrafish model

Bicyclol (BIC), a synthetic hepatoprotective agent widely prescribed in China, lacks comprehensive safety and activity profiles for its degradation products (DPs). Here, we systematically investigated BIC's forced degradation behavior using ultra-high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS). Three hydrolytic degradation products (DP1-DP3) were isolated via HPLC and structurally characterized, revealing methylenedioxy group hydrolysis as the primary degradation pathway. Molecular docking simulations demonstrated enhanced target binding affinities of DPs compared to BIC, supported by absorption, distribution, metabolism, and excretion (ADME) predictions showing improved drug-likeness. In an alcohol-induced fatty liver zebrafish model, both BIC and its DPs attenuated hepatic macrovesicular steatosis and inflammatory responses. Mechanistically, treatment normalized lipid metabolism by downregulating alcohol-induced expression of FASN, SREBP1, PPARα, and PPARγ, while reduced IL-6 and TNF-α levels confirmed anti-inflammatory efficacy. These findings demonstrate that BIC DPs exhibit dual pharmacological activity through lipid homeostasis modulation and inflammation suppression, providing critical insights for quality control and therapeutic applications.

Role of UBC9 in the inflammatory response and pathogen susceptibility in zebrafish

UBC9 is a key enzyme involved in SUMOylation, a post-translational modification that targets protein function, stability, transcriptional regulation, and localization to affect biological processes in host cells. Pathogens often target UBC9 by exploiting the host's SUMO system to modify their proteins with altered functionality, which in turn favors the pathogens' survival or invasion. Herein, we investigated the critical role of UBC9 in regulating the inflammatory response and susceptibility to Mycobacterium marinum (Mm) infection in zebrafish. We effectively knocked down the UBC9 expression using morpholino antisense oligonucleotides, which showed significant developmental abnormalities in zebrafish, particularly in cartilage formation. Our results indicated that UBC9 is essential for immune cell migration, as its knockdown led to impaired macrophage and neutrophil responses during inflammation. Furthermore, we investigated the impact of UBC9 on the zebrafish response to Mm, a close relative of the tuberculosis-causing bacterium. Our results showed that UBC9-knocked-down zebrafish displayed a slight increase in bacterial proliferation, suggesting a potential role of UBC9 in host's ability to control pathogen replication and spread. The study explores the complex interplay between UBC9 and the immune system and provides insights into the important role of UBC9 in immune regulation and pathogen defence.

Single-cell RNA sequencing reveals tissue-specific transcriptomic changes induced by perfluorooctanesulfonic acid (PFOS) in larval zebrafish (Danio rerio)

Perfluorooctanesulfonic acid (PFOS) elicits adverse effects on numerous organs and developmental processes but the mechanisms underlying these effects are not well understood. Here, we use single-cell RNA-sequencing to assess tissue-specific transcriptomic changes in zebrafish (Danio rerio) larvae exposed to 16 µM PFOS or dimethylsulfoxide (0.01 %) from 3-72 h post fertilization (hpf). Data analysis was multi-pronged and included pseudo-bulk, untargeted clustering, informed pathway queries, and a cluster curated for hepatocyte biomarkers (fabp10a, and apoa2). Overall, 8.63 % (2390/27698) genes were significantly differentially expressed. Results from untargeted analysis revealed 22 distinct clusters that were manually annotated to specific tissues using a weight-of-evidence approach. The clusters with the highest number of significant differentially expressed genes (DEGs) were digestive organs, muscle, and otolith. Additionally, we assessed the distribution of pathway-specific genes known to be involved in PFOS toxicity: the PPAR pathway, β-oxidation of fatty acids, the Nfe2l2 pathway, and epigenetic modifications by DNA methylation, across clusters and identified the blood-related tissue to be the most sensitive. The curated hepatocyte cluster showed 220 significant DEGs and was enriched for the Notch signaling pathway. These findings provide insights into both established and novel sensitive target tissues and molecular mechanisms of developmental toxicity of PFOS.

Equipotent bisphenol S and bisphenol F with widely differing modes of action exhibit additive effects in immunotoxicity: insights based on intrinsic immunity, apoptosis and regeneration, and oxidative stress

Bisphenol S (BPS) and Bisphenol F (BPF), as alternatives to bisphenol A (BPA), are recognized for their endocrine-disrupting properties, but their combined immune toxicity mechanisms remain poorly understood. This study systematically evaluates the individual and joint immune toxicity effects of BPS and BPF through ADMET predictions, transgenic zebrafish models, and molecular docking analyses. The results indicate that equal effect concentration BPS and BPF act through distinct immune pathways: BPS primarily targets macrophages to mediate immune responses, while BPF significantly stimulates neutrophil proliferation and induces a stronger inflammatory response through chemokine signaling. Molecular docking studies show that BPF binds more stably to pro-apoptotic protein Mapk8 and oxidative stress-related protein Hsp90aa1, leading to significantly higher levels of apoptosis and reactive oxygen species (ROS) compared to BPS. The similarity of modes of action (MOA)between BPS and BPF based on relevant immune indicators calculated and experimentally is about 0.3; this quantitative result also proves that modes of action differ widely. Nonetheless, most of the indicators showed superimposed effects in the combined experiments, and it is noteworthy that the oxidative stress indicators (SOD, MDA) showed synergistic effects, suggesting that BPS and BPF, which have very different modes of action, are able to be risk assessed using an additive model with respect to immunity, but may exhibit synergistic risks with respect to oxidative stress. This research demonstrates that BPS and BPF induce immune toxicity via different molecular targets and pathways and highlights the need to account for their synergistic effects in risk assessments. These findings provide important insights into the immune toxicity mechanisms of BPA substitutes and the potential risks of combined exposures.

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.

Novel nerve regeneration assessment method using adult zebrafish with crush spinal cord injury

Zebrafish (Danio rerio), an alternative to rodents, are widely used in neurological, genetic, and toxicology research. The zebrafish larval spinal cord injury model has been used in neural mechanistic analyses owing to its high regenerative capacity and throughput; however, it also had several limitations in imitating rodents. Therefore, we investigated the use of adult zebrafish as an alternative model to rodents for evaluating nerve regeneration. Here, we established a novel spinal cord regeneration evaluation method, which was based on the maximum swimming speed of adult zebrafish in a custom-built hydrodynamic-based aquarium. The spinal cords of adult male zebrafish were crushed using forceps, and maximum swimming speed and histological spinal cord regeneration were evaluated. Spinal cord-injured zebrafish showed a significant decline in motor function, followed by recovery at 3 weeks postoperatively, accompanied by histological regeneration. Spinal cord regeneration can be indirectly assessed by monitoring maximum swimming speed. They were also fed a diet containing fig extract, which can promote peripheral nerve regeneration; they were fed daily starting 1 week before the operation. Maximum swimming speed was measured time-dependently until 3 weeks postoperatively. Fig-consuming fish showed improved recovery of maximum swimming speed compared to the controls, which was consistent with the histological analysis. In summary, we established a spinal cord regeneration assessment system using adult zebrafish in a customized aquarium, which enables researchers to evaluate spinal cord regeneration in adult zebrafish similar to that of rodent experiments, contributing to faster and easier screening of neuroregenerative technology.

Intracellular Pseudomonas aeruginosa persist and evade antibiotic treatment in a wound infection model

Persistent bacterial infections evade host immunity and resist antibiotic treatments through various mechanisms that are difficult to evaluate in a living host. Pseudomonas aeruginosa is a main cause of chronic infections in patients with cystic fibrosis (CF) and wounds. Here, by immersing wounded zebrafish embryos in a suspension of P. aeruginosa isolates from CF patients, we established a model of persistent infection that mimics a murine chronic skin infection model. Live and electron microscopy revealed persisting aggregated P. aeruginosa inside zebrafish cells, including macrophages, at unprecedented resolution. Persistent P. aeruginosa exhibited adaptive resistance to several antibiotics, host cell permeable drugs being the most efficient. Moreover, persistent bacteria could be partly re-sensitized to antibiotics upon addition of anti-biofilm molecules that dispersed the bacterial aggregates in vivo. Collectively, this study demonstrates that an intracellular location protects persistent P. aeruginosa in vivo in wounded zebrafish embryos from host innate immunity and antibiotics, and provides new insights into efficient treatments against chronic infections.

Zebrafish Larvae Microinjection and Automated Fluorescence Microscopy for Studying Klebsiella pneumoniae Infection and the Host Immune Response

Studying host-pathogen interactions is essential for understanding infectious diseases and developing possible treatments, especially for priority pathogens with increased virulence and antibiotic resistance, such as Klebsiella pneumoniae. Over time, this subject has been approached from different perspectives, often using mammal host models and invasive endpoint measurements (e.g., sacrifice and organ extraction). However, taking advantage of technological advances, it is now possible to follow the infective process by noninvasive visualization in real time, using optically amenable surrogate hosts. In this line, this chapter describes a live-cell imaging approach to monitor the interaction of K. pneumoniae and potentially other bacterial pathogens with zebrafish larvae in vivo. This methodology is based on the microinjection of fluorescent bacteria into the otic vesicle, followed by time-lapse observation by automated fluorescence microscopy with environmental control, monitoring the dynamics of immune cell recruitment, bacterial load, and larvae survival.

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).

Phenotypic Heterogeneity in Pathogens

Pathogen diversity within an infected organism has traditionally been explored through the lens of genetic heterogeneity. Hallmark studies have characterized how genetic diversity within pathogen subpopulations contributes to treatment escape and infectious disease progression. However, recent studies have begun to reveal the mechanisms by which phenotypic heterogeneity is established within genetically identical populations of invading pathogens. Furthermore, exciting new work highlights how these phenotypically heterogeneous subpopulations contribute to a pathogen population better equipped to handle the complex and fluctuating environment of a host organism. In this review, we focus on how bacterial pathogens, including Staphylococcus aureus, Salmonella typhimurium, Pseudomonas aeruginosa, and Mycobacterium tuberculosis, establish and maintain phenotypic heterogeneity, and we explore recent work demonstrating causative links between this heterogeneity and infection outcome.

The role of AbaI quorum sensing molecule synthase in host cell inflammation induced by Acinetobacter baumannii and its effect on zebrafish infection model

Acinetobacter baumannii is currently one of the most important opportunistic pathogens causing severe nosocomial infections worldwide. Quorum Sensing (QS) system is a widespread mechanism in bacteria to coordinate group behavior by sensing the density of bacterial populations and affect eukaryotic host cell. In Acinetobacter baumannii, AbaI protein is used as QS molecule synthetase to synthesize N- acyl homoserine lactones (AHLs). Currently, QS has made great progress in the study of drug resistance, but there is still a lack of complete understanding of its damage to host cells after adhesion and invasion. Thus, in this study, we examined the effects of abaI mutant (ΔabaI) on the functions of adhesion and invasion, cell viability, inflammation, apoptosis in A. baumannii infected A549 cells, to evaluate the effects of ΔabaI in a zebrafish model. We found the group infected with ΔabaI increased cell viability, reduced adhesion and invasion, cell injury, inflammatory cytokine production and apoptosis. By RNA-Seq, we explored the possibility that abaI stimulated A549 cells inflammation by A. baumannii infection via TLR4/MAPK signaling pathway. In addition, the ΔabaI significantly reduced pathogenicity and recruitment to neutrophils in zebrafish. These observations suggest that abaI plays a major role in A. baumannii infection.

Chemical structure and immunomodulatory activity of a polysaccharide from Saposhnikoviae Radix

A new polysaccharide, named SP40015A01, was obtained from Saposhnikoviae Radix by water extraction, isolation and purification. SP40015A01 (9.7 × 105 Da) is composed of Rhamnose (Rha), Galacturonic acid (GalA), Galactose (Gal), and Arabinose (Ara) with the proportion of 1.6:85.6:5.8:7.6. The backbone of SP40015A01 is composed of 3-α-GalAp, 2-α-GalAp, 2,3-β-GalAp and 2,3-β-Galp, and branched at C3 of 2,3-β-GalAp, C3 of 2,3-β-Galp. Zebrafish experiments were used to explore the immunomodulatory activity of SP40015A01. Results showed that SP40015A01 could significantly improve the neutrophils density of immunocompromised zebrafish and reduce the content of nitric oxide (NO) and interleukin-1β (IL-1β). This study demonstrated that SP40015A01 has significant immunomodulatory activity, which can improve the neutrophils density and reduce inflammatory factor content, suggesting SP40015A01 may be a potential immunomodulator in Saposhnikoviae Radix (SR) for treatment of hypoimmunity related disease. This study supplemented the research on the polysaccharide components in traditional Chinese medicine and provided a scientific explanation for the development and clinical applications of SR.

Meningitis caused by Aeromonas hydrophila in Oreochromis niloticus: Proteomics and druggability of virulence factors

Meningitis caused by Gram-negative bacteria is a serious public health problem, causing morbidity and mortality in both children and adults. Here, we propose a novel experimental model using Nile tilapia (Oreochromis niloticus) to study neuroinflammation. The fish were infected with Aeromonas hydrophila, and the course of infection was monitored in the peripheral blood. Septicemia was obvious in the blood, while in the brain tissue, infection of the meninges was present. The histopathological examination showed suppurative meningitis, and the cellular immune response in the brain tissue during infection was mediated by microglia. These cells were morphologically characterized and phenotyped by MHC class II markers and CD68. The increased production of TNF-α, IL-1β and iNOS supported the infiltration of these cells during the neuroinflammatory process. In the proteomic analysis of A. hydrophila isolated from brain tissue, we found chemotactic and transport proteins, proteolytic enzymes and enzymes associated with the dismutation of nitric oxide (NO), as well as motor proteins and those responsible for cell division. After characterizing the most abundant proteins during the course of infection, we investigated the druggability index of these proteins and identified promising peptide sequences as molecular targets that are similar among bacteria. Thus, these findings deepened the understanding of the pathophysiology of meningitis caused by A. hydrophila. Moreover, through the proteomics analysis, important mechanisms and pathways used by the pathogen to subvert the host response were revealed, providing insights for the development of novel antibiotics and vaccines.

Diving into drug-screening: zebrafish embryos as an in vivo platform for antimicrobial drug discovery and assessment

The rise of multidrug-resistant bacteria underlines the need for innovative treatments, yet the introduction of new drugs has stagnated despite numerous antimicrobial discoveries. A major hurdle is a poor correlation between promising in vitro data and in vivo efficacy in animal models, which is essential for clinical development. Early in vivo testing is hindered by the expense and complexity of existing animal models. Therefore, there is a pressing need for cost-effective, rapid preclinical models with high translational value. To overcome these challenges, zebrafish embryos have emerged as an attractive model for infectious disease studies, offering advantages such as ethical alignment, rapid development, ease of maintenance, and genetic manipulability. The zebrafish embryo infection model, involving microinjection or immersion of pathogens and potential antibiotic hit compounds, provides a promising solution for early-stage drug screening. It offers a cost-effective and rapid means of assessing the efficacy, toxicity and mechanism of action of compounds in a whole-organism context. This review discusses the experimental design of this model, but also its benefits and challenges. Additionally, it highlights recently identified compounds in the zebrafish embryo infection model and discusses the relevance of the model in predicting the compound's clinical potential.

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.

Xanthohumol, a prenylated flavonoid from hops (Humulus lupulus L.) exerts multidirectional pro-healing properties towards damaged zebrafish hair cells by regulating the innate immune response

Xanthohumol (XN) is a prominent prenylated flavonoid present in the hop plant (Humulus lupulus L.). Despite undoubted pro-healing properties of hop plant, there is still a need for clinical investigations confirming these effects as well as the underlying molecular mechanisms. The present study was designed to (1) establish the role of XN in non-invasive inflammation induced by chemical damage to zebrafish hair cells, (2) clarify if it influences cell injury severity, neutrophil migration, macrophage activation, cell regeneration, and (3) find out whether it modulates the gene expression profile of chosen immune and stress response markers. All experiments were performed on 3 dpf zebrafish larvae. After fertilization the embryos were transferred to appropriate XN solutions (0.1 μM, 0.3 μM and 0.5 μM). The 40 min 10 μM CuSO4 exposure evoked severe damage to posterior lateral line hair cells triggering a robust acute inflammatory response. Four readouts were selected as the indicators of XN role in the process of inflammation: 1) hair cell death, 2) neutrophil migration towards damaged hair cells, 3) macrophage activation and recruitment to damaged hair cells, 4) hair cell regeneration. The assessments involved in vivo confocal microscopy imaging and qPCR based molecular analysis. It was demonstrated that XN (1) influences death pathway of damaged hair cells by redirecting their severe necrotic phenotype into apoptotic one, (2) impacts the immune response via regulating neutrophil migration, macrophage recruitment and activation (3) modulates gene expression of immune system markers and (4) accelerates hair cell regeneration.

Teleost leukocyte immune-type receptors

Leukocyte immune-type receptors (LITRs) are a large family of teleost immunoregulatory receptor-types belonging to the immunoglobulin superfamily. These immune genes are phylogenetically and syntenically related to Fc receptor-like protein genes (fcrls) present in other vertebrates, including amphibians, birds, mice, and man. In vitro-based functional analyses of LITRs, using transfection approaches, have shown that LITRs have diverse immunoregulatory potentials including the activation and inhibition of several innate immune effector responses such as cell-mediated killing responses, degranulation, cytokine secretion, and phagocytosis. The purpose of this mini review is to provide an overview of fish LITR-mediated immunoregulatory potentials obtained from various teleost model systems, including channel catfish, zebrafish, and goldfish. We will also describe preliminary characterization of a new goldish LITR-specific polyclonal antibody (pAb) and discuss the significance of this tool for further investigation of the functions of fish LITRs.

Zebrafish functional xenograft vasculature platform identifies PF-502 as a durable vasculature normalization drug

Tumor vasculature often exhibits disorder and inefficiency. Vascular normalization offers potential for alleviating hypoxia and optimizing drug delivery in tumors. However, identifying effective agents is hindered by a lack of robust screening. We aimed to establish a comprehensive method using the zebrafish functional xenograft vasculature platform (zFXVP) to visualize and quantify tumor vasculature changes. Employing zFXVP, we systematically screened compounds, identifying PF-502 as a robust vascular normalization agent. Mechanistic studies showed PF-502 induces endothelial cell-cycle arrest, streamlines vasculature, and activates Notch1 signaling, enhancing stability and hemodynamics. In murine models, PF-502 exhibited pronounced vascular normalization and improved drug delivery at a sub-maximum tolerated dose. These findings highlight zFXVP's utility and suggest PF-502 as a promising adjunctive for vascular normalization in clinical settings.

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.

Lactobacillus gasseri LGV03 isolated from the cervico-vagina of HPV-cleared women modulates epithelial innate immune responses and suppresses the growth of HPV-positive human cervical cancer cells

Persistent human papillomavirus (HPV) infections is necessary for the development of cervical cancers. An increasing number of retrospective studies have found the depletion of Lactobacillus microbiota in the cervico-vagina facilitate HPV infection and might be involved in viral persistence and cancer development. However, there have been no reports confirming the immunomodulatory effects of Lactobacillus microbiota isolated from cervico-vaginal samples of HPV clearance in women. Using cervico-vaginal samples from HPV persistent infection and clearance in women, this study investigated the local immune properties in cervical mucosa. As expected, type I interferons, such as IFN-α and IFN-β, and TLR3 globally downregulated in HPV+ persistence group. Luminex cytokine/chemokine panel analysis revealed that L. jannaschii LJV03, L. vaginalis LVV03, L. reuteri LRV03, and L. gasseri LGV03 isolated from cervicovaginal samples of HPV clearance in women altered the host's epithelial immune response, particularly L. gasseri LGV03. Furthermore, L. gasseri LGV03 enhanced the poly (I:C)-induced production of IFN by modulating the IRF3 pathway and attenuating poly (I:C)-induced production of proinflammatory mediators by regulating the NF-κB pathway in Ect1/E6E7 cells, indicating that L. gasseri LGV03 keeps the innate system alert to potential pathogens and reduces the inflammatory effects during persistent pathogen infection. L. gasseri LGV03 also markedly inhibited the proliferation of Ect1/E6E7 cells in a zebrafish xenograft model, which may be attributed to an increased immune response mediated by L. gasseri LGV03.

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.

Susceptibility and Permissivity of Zebrafish (Danio rerio) Larvae to Cypriniviruses

The zebrafish (Danio rerio) represents an increasingly important model organism in virology. We evaluated its utility in the study of economically important viruses from the genus Cyprinivirus (anguillid herpesvirus 1, cyprinid herpesvirus 2 and cyprinid herpesvirus 3 (CyHV-3)). This revealed that zebrafish larvae were not susceptible to these viruses after immersion in contaminated water, but that infections could be established using artificial infection models in vitro (zebrafish cell lines) and in vivo (microinjection of larvae). However, infections were transient, with rapid viral clearance associated with apoptosis-like death of infected cells. Transcriptomic analysis of CyHV-3-infected larvae revealed upregulation of interferon-stimulated genes, in particular those encoding nucleic acid sensors, mediators of programmed cell death and related genes. It was notable that uncharacterized non-coding RNA genes and retrotransposons were also among those most upregulated. CRISPR/Cas9 knockout of the zebrafish gene encoding protein kinase R (PKR) and a related gene encoding a protein kinase containing Z-DNA binding domains (PKZ) had no impact on CyHV-3 clearance in larvae. Our study strongly supports the importance of innate immunity-virus interactions in the adaptation of cypriniviruses to their natural hosts. It also highlights the potential of the CyHV-3-zebrafish model, versus the CyHV-3-carp model, for study of these interactions.

Nonmammalian models to study Clostridioides difficile infection; a systematic review

Clostridioide difficile is the leading cause of diarrhea disease worldwide and is a CDC-designated urgent threat level pathogen. Mammalian models are commonly utilized as gold standard to study the pathogenesis of C. difficile infection (CDI); however, alternatives are needed due to cost, higher throughput ability, and mammalian animal ethics. Nonmammalian models such as great wax worm, nematode, fruit fly, and zebrafish have been used as CDI models. This review provides a comprehensive summary of nonmammalian models used to study CDI. Multiple studies were identified using these models to study C. difficile infection, pathogenicity, colonization, host immunity, and therapy. Translational outcomes and strength and weakness of each nonmammalian model are discussed.

Th1-Th2 and M1-M2 interplay sculpt Aeromonas hydrophila pathogenesis in zebrafish (Danio rerio)

Aeromonas hydrophila is an important aquatic zoonotic pathogen that causes septicemia, necrotizing fasciitis and gastroenteritis in various aquatic and non-aquatic animals. However, the pathogenesis of A. hydrophila is not fully understood. Here, we examined the pathogenicity and histopathology of A. hydrophila in the zebrafish (Danio rerio) model system. We found that the intensity of symptoms and mortality is dose-dependent. Bacterial colonization studies demonstrated that A. hydrophila never cleared out from the fish body but stayed in a state of inactivity till it enters a fresh host. Reinfection studies showed that exposure to A. hydrophila provides immunity against future infection and hence improves fish survival. Gene expression studies revealed the crosstalk between T-helper cell and macrophage responses in fish immune system in response to A. hydrophila and infection memory. Histopathological studies showed that symptoms of tissue damage and inflammation lasted for less duration with less intensity in immunized fish when compared to non-immunized fish. Together, our results suggest that the zebrafish model is a useful system in studying the interplay between A. hydrophila pathogenesis, persistence and immunity.

Zebrafish—An Optimal Model in Experimental Oncology

A thorough understanding of cancer pathogenesis is a necessary step in the development of more effective and safer therapy. However, due to the complexity of the process and intricate interactions, studying tumor development is an extremely difficult and challenging task. In bringing this issue closer, different scientific models with various advancement levels are helpful. Cell cultures is a system that is too simple and does not allow for multidirectional research. On the other hand, rodent models, although commonly used, are burdened with several limitations. For this reason, new model organisms that will allow for the studying of carcinogenesis stages and factors reliably involved in them are urgently sought after. Danio rerio, an inconspicuous fish endowed with unique features, is gaining in importance in the world of scientific research. Including it in oncological research brings solutions to many challenges afflicting modern medicine. This article aims to illustrate the usefulness of Danio rerio as a model organism which turns out to be a powerful and unique tool for studying the stages of carcinogenesis and solving the hitherto incomprehensible processes that lead to the development of the disease.

Using zebrafish to understand reciprocal interactions between the nervous and immune systems and the microbial world

Animals rely heavily on their nervous and immune systems to perceive and survive within their environment. Despite the traditional view of the brain as an immunologically privileged organ, these two systems interact with major consequences. Furthermore, microorganisms within their environment are major sources of stimuli and can establish relationships with animal hosts that range from pathogenic to mutualistic. Research from a variety of human and experimental animal systems are revealing that reciprocal interactions between microbiota and the nervous and immune systems contribute significantly to normal development, homeostasis, and disease. The zebrafish has emerged as an outstanding model within which to interrogate these interactions due to facile genetic and microbial manipulation and optical transparency facilitating in vivo imaging. This review summarizes recent studies that have used the zebrafish for analysis of bidirectional control between the immune and nervous systems, the nervous system and the microbiota, and the microbiota and immune system in zebrafish during development that promotes homeostasis between these systems. We also describe how the zebrafish have contributed to our understanding of the interconnections between these systems during infection in fish and how perturbations may result in pathology.

Heat inactivated mycobacteria, alpha-gal and zebra fish: insights gained from experiences with two promising trained immunity inductors and a validated animal model

Trained immunity (TRAIM) may be defined as a form of memory where innate immune cells such as monocytes, macrophages, dendritic and natural killer (NK) cells undergo an epigenetic reprogramming that enhances their primary defensive capabilities. Cross-pathogen protective TRAIM can be triggered in different hosts by exposure to live microbes or microbe-derived products such as heat-inactivated Mycobacterium bovis or with the glycan α-Gal to elicit protective responses against several pathogens. We review the TRAIM paradigm using two models representing distinct scales of immune sensitization: the whole bacterial cell and one of its building blocks, the polysaccharides or glycans. Observations point out to macrophage lytic capabilities and cytokine regulation as two key components in nonspecific innate immune responses against infections. The study of the TRAIM response deserves attention to better characterize the evolution of host-pathogen cooperation both for identifying the etiology of some diseases and for finding new therapeutic strategies. In this field, the zebrafish provides a convenient and complete biological system that could help to deepen in the knowledge of TRAIM-mediated mechanisms in pathogen-host interactions. This article is protected by copyright. All rights reserved.

An assessment of vaping-induced inflammation and toxicity: A feasibility study using a 2-stage zebrafish and mouse platform

It is currently understood that tobacco smoking is a major cause of pulmonary disease due to pulmonary/lung inflammation. However, due to a highly dynamic market place and an abundance of diverse products, less is known about the effects of e-cigarette (E-cig) use on the lung. In addition, varieties of E-cig liquids (e-liquids), which deliver nicotine and numerous flavor chemicals into the lungs, now number in the 1000s. Thus, a critical need exists for safety evaluations of these E-cig products. Herein, we employed a "2-stage in vivo screening platform" (zebrafish to mouse) to assess the safety profiles of e-liquids. Using the zebrafish, we collected embryo survival data after e-liquid exposure as well as neutrophil migration data, a key hallmark for a pro-inflammatory response. Our data indicate that certain e-liquids induce an inflammatory response in our zebrafish model and that e-liquid exposure alone results in pro-inflammatory lung responses in our C57BL/6J model, data collected from lung staining and ELISA analysis, respectively, in the mouse. Thus, our platform can be used as an initial assessment to ascertain the safety profiles of e-liquid using acute inflammatory responses (zebrafish, Stage 1) as our initial metric followed by chronic studies (C57BL/6J, Stage 2).

Novel Insights into Aspergillus fumigatus Pathogenesis and Host Response from State-of-the-Art Imaging of Host-Pathogen Interactions during Infection

Aspergillus fumigatus spores initiate more than 3,000,000 chronic and 300,000 invasive diseases annually, worldwide. Depending on the immune status of the host, inhalation of these spores can lead to a broad spectrum of disease, including invasive aspergillosis, which carries a 50% mortality rate overall; however, this mortality rate increases substantially if the infection is caused by azole-resistant strains or diagnosis is delayed or missed. Increasing resistance to existing antifungal treatments is becoming a major concern; for example, resistance to azoles (the first-line available oral drug against Aspergillus species) has risen by 40% since 2006. Despite high morbidity and mortality, the lack of an in-depth understanding of A. fumigatus pathogenesis and host response has hampered the development of novel therapeutic strategies for the clinical management of fungal infections. Recent advances in sample preparation, infection models and imaging techniques applied in vivo have addressed important gaps in fungal research, whilst questioning existing paradigms. This review highlights the successes and further potential of these recent technologies in understanding the host-pathogen interactions that lead to aspergillosis.

Effects of chlorobromoisocyanuric acid on embryonic development and immunotoxicity of zebrafish

Although chlorobromoisocyanuric acid has been widely used in agriculture, its deleterious toxicity on aquatic organisms remains rare. In this study, zebrafish were exposed to chlorobromoisocyanuric acid (0, 30, 40, and 50 mg/L) from 10 to 96 h post-fertilization (hpf). We found a significant reduction in immune cell numbers (neutrophils and macrophages) and the area of thymus at 96 hpf. The expression of immune-related genes and pro-inflammatory cytokines genes were upregulated. Besides, chlorobromoisocyanuric acid triggered neutrophils cell apoptosis. The mRNA and protein levels of pro-apoptotic p53 pathway and the Bax/Bcl-2 ratio further indicated the underlying mechanism. Furthermore, the oxidative stress was observed that the accumulation of reactive oxygen species and malondialdehyde significantly increased. Subsequently, the antioxidant agent astaxanthin significantly attenuated the level of oxidative stress and the dysregulation of inflammatory response. In summary, our results showed that chlorobromoisocyanuric acid induced developmental defects and immunotoxicity of zebrafish, partly owing to oxidative stress and cell apoptosis.

NF-κB Signaling and Inflammation-Drug Repurposing to Treat Inflammatory Disorders?

NF-κB is a central mediator of inflammation, response to DNA damage and oxidative stress. As a result of its central role in so many important cellular processes, NF-κB dysregulation has been implicated in the pathology of important human diseases. NF-κB activation causes inappropriate inflammatory responses in diseases including rheumatoid arthritis (RA) and multiple sclerosis (MS). Thus, modulation of NF-κB signaling is being widely investigated as an approach to treat chronic inflammatory diseases, autoimmunity and cancer. The emergence of COVID-19 in late 2019, the subsequent pandemic and the huge clinical burden of patients with life-threatening SARS-CoV-2 pneumonia led to a massive scramble to repurpose existing medicines to treat lung inflammation in a wide range of healthcare systems. These efforts continue and have proven to be controversial. Drug repurposing strategies are a promising alternative to de novo drug development, as they minimize drug development timelines and reduce the risk of failure due to unexpected side effects. Different experimental approaches have been applied to identify existing medicines which inhibit NF-κB that could be repurposed as anti-inflammatory drugs.

Hematopoietic stem cell and immunotoxicity in zebrafish embryos induced by exposure to Metalaxyl-M

Metalaxyl-M (MM), a protective and therapeutic fungicide, has been shown to be a promising candidate, but its toxicity toward aquatic organisms is unknown. In this study, we evaluated for the first time the immunotoxicity of MM in zebrafish embryos. Phenotypes (heart rate, body length, and yolk area) and the number of neutrophils, macrophages, and T cells in the thymus were analyzed in zebrafish embryo after exposure to MM. Our results showed that zebrafish embryos exposed to MM showed a concentration-dependent increase in the yolk area and a significant decrease in the number of neutrophils, macrophages, and thymus T cells. We detected upregulated expression of related immune signaling genes, such as tnfa, nfkb3, cxcl-c1c, il6, mmp9, and tgfb1. Additionally, we observed a significant decrease in HSCs in zebrafish larvae after exposure to MM. IWR-1 could restore the number of neutrophils and macrophages after exposure to MM. The results indicated that MM exerted developmental toxicity and immunotoxicity to zebrafish embryos, and these phenomena may be caused by MM's regulation of WNT signaling pathway.

Manipulating Galectin Expression in Zebrafish (Danio rerio)

Techniques for disrupting gene expression are invaluable tools for the analysis of the biological role of a gene product. Because of its genetic tractability and multiple advantages over conventional mammalian models, the zebrafish (Danio rerio) is recognized as a powerful system for gaining new insight into diverse aspects of human health and disease. Among the multiple mammalian gene families for which the zebrafish has shown promise as an invaluable model for functional studies, the galectins have attracted great interest due to their participation in early development, regulation of immune homeostasis, and recognition of microbial pathogens. Galectins are β-galactosyl-binding lectins with a characteristic sequence motif in their carbohydrate recognition domains (CRDs), that constitute an evolutionary conserved family ubiquitous in eukaryotic taxa. Galectins are emerging as key players in the modulation of many important pathological processes, which include acute and chronic inflammatory diseases, autoimmunity and cancer, thus making them potential molecular targets for innovative drug discovery. Here, we provide a review of the current methods available for the manipulation of gene expression in the zebrafish, with a focus on gene knockdown [morpholino (MO)-derived antisense oligonucleotides] and knockout (CRISPR-Cas) technologies.

Knowledge gaps in late-onset neonatal sepsis in preterm neonates: a roadmap for future research

Late-onset neonatal sepsis (LONS) remains an important threat to the health of preterm neonates in the neonatal intensive care unit. Strategies to optimize care for preterm neonates with LONS are likely to improve survival and long-term neurocognitive outcomes. However, many important questions on how to improve the prevention, early detection, and therapy for LONS in preterm neonates remain unanswered. This review identifies important knowledge gaps in the management of LONS and describe possible methods and technologies that can be used to resolve these knowledge gaps. The availability of computational medicine and hypothesis-free-omics approaches give way to building bedside feedback tools to guide clinicians in personalized management of LONS. Despite advances in technology, implementation in clinical practice is largely lacking although such tools would help clinicians to optimize many aspects of the management of LONS. We outline which steps are needed to get possible research findings implemented on the neonatal intensive care unit and provide a roadmap for future research initiatives. IMPACT: This review identifies knowledge gaps in prevention, early detection, antibiotic, and additional therapy of late-onset neonatal sepsis in preterm neonates and provides a roadmap for future research efforts. Research opportunities are addressed, which could provide the means to fill knowledge gaps and the steps that need to be made before possible clinical use. Methods to personalize medicine and technologies feasible for bedside clinical use are described.

Stabilized fermentation product of Cetobacterium somerae improves gut and liver health and antiviral immunity of zebrafish

Probiotics are widely used in aquafeeds and exhibited beneficial effects on fish by improving host health and resisting pathogens. However, probiotics applied to aquaculture are mainly from terrestrial sources instead of the host animal. The purpose of the work was to evaluate the effects of stabilized fermentation product of commensal Cetobacterium somerae XMX-1 on gut, liver health and antiviral immunity of zebrafish. A total of 240 zebrafish were assigned to the control (fed a basal diet) and XMX-1 group (fed a basal diet with 10 g XMX-1/kg diet). After four weeks feeding, growth performance, feed utilization, hepatic steatosis score, TAG, lipid metabolism related genes and serum ALT were evaluated. Furthermore, serum LPS, the expression of Hif-1α, intestinal inflammation score, antioxidant capability and gut microbiota were tested. The survival rate and the expression of antiviral genes were analyzed after challenge by spring viremia of carp virus (SVCV). Results showed that dietary XMX-1 did not affect growth of zebrafish. However, dietary XMX-1 significantly decreased the level of serum LPS, intestinal inflammation score and intestinal MDA, as well as increased T-AOC and the expression of Hif-1α in zebrafish intestine (p < 0.05). Furthermore, XMX-1 supplementation decreased the relative abundance of Proteobacteria and increased Firmicutes and Actinobacteria. Additionally, XMX-1 supplementation significantly decreased hepatic steatosis score, hepatic TAG, serum ALT and increased the expression of lipolysis genes versus control (p < 0.05). Zebrafish fed XMX-1 diet exhibited higher survival rate after SVCV challenge. Consistently, dietary XMX-1 fermentation product increased the expression of IFNφ2 and IFNφ3 after 2 days of SVCV challenge and the expression of IFNφ1, IFNφ2 and MxC after 4 days of SVCV challenge in the spleen in zebrafish versus control (p < 0.05). In conclusion, our results indicate that dietary XMX-1 can improve liver and gut health, while enhancing antiviral immunity of zebrafish.

In situ and transcriptomic identification of microglia in synapse-rich regions of the developing zebrafish brain

Microglia are brain resident macrophages that play vital roles in central nervous system (CNS) development, homeostasis, and pathology. Microglia both remodel synapses and engulf apoptotic cell corpses during development, but whether unique molecular programs regulate these distinct phagocytic functions is unknown. Here we identify a molecularly distinct microglial subset in the synapse rich regions of the zebrafish (Danio rerio) brain. We found that ramified microglia increased in synaptic regions of the midbrain and hindbrain between 7 and 28 days post fertilization. In contrast, microglia in the optic tectum were ameboid and clustered around neurogenic zones. Using single-cell mRNA sequencing combined with metadata from regional bulk sequencing, we identified synaptic-region associated microglia (SAMs) that were highly enriched in the hindbrain and expressed multiple candidate synapse modulating genes, including genes in the complement pathway. In contrast, neurogenic associated microglia (NAMs) were enriched in the optic tectum, had active cathepsin activity, and preferentially engulfed neuronal corpses. These data reveal that molecularly distinct phagocytic programs mediate synaptic remodeling and cell engulfment, and establish the zebrafish hindbrain as a model for investigating microglial-synapse interactions.

Microglia remodel synapses and engulf apoptotic cells. The molecular program underlying these distinct functions are unclear. Here, the authors identify distinct microglial subsets associated with synaptic vs. neurogenic regions of the developing zebrafish brain.

M. fortuitum-induced CNS-pathology: Deciphering the role of canonical Wnt signaling, blood brain barrier components and cytokines

Molecular underpinning of mycobacteria-induced CNS-pathology is not well understood. In the present study, zebrafish were infected with Mycobacterium fortuitum and the prognosis of CNS-pathogenesis studied. We observed M. fortuitum triggers extensive brain-pathology. Evans blue extravasation demonstrated compromised blood-brain barrier (BBB) integrity. Further, decreased expression in tight-junction (TJ) and adherens junction complex (AJC) genes were noted in infected brain. Wnt-signaling has emerged as a major player in host-mycobacterial immunity but its involvement/role in brain-infection is not well studied. Sustained expression of wnt2, wnt3a, fzd5, lrp5/6 and β-catenin, with concordant decline in degradation complex components axin, gsk3β and β-catenin regulator capn2a were observed. The surge in ifng1 and tnfa expression preceding il10 and il4 suggested cytokine-interplay critical in M. fortuitum-induced brain-pathology. Therefore, we suggest adult zebrafish as a viable model for studying CNS-pathology and using the same, conclude that M. fortuitum infection is associated with repressed TJ-AJC gene expression and compromised BBB permeability. Our results implicate Wnt/β-catenin pathway in M. fortuitum-induced CNS-pathology wherein Th1-type signals facilitate bacterial clearance and Th2-type signals prevent the disease sequel.

Embryonic exposure to low concentrations of aflatoxin B1 triggers global transcriptomic changes, defective yolk lipid mobilization, abnormal gastrointestinal tract development and inflammation in zebrafish

Aflatoxin B1-contaminated feeds and foods induce various health problems in domesticated animals and humans, including tumor development and hepatotoxicity. Aflatoxin B1 also has embryotoxic effects in different livestock species and humans. However, it is difficult to distinguish between the indirect, maternally-mediated toxic effects and the direct embryotoxicity of aflatoxin B1 in mammals. In the present study, we investigated the aflatoxin B1-induced direct embryotoxic effects in a zebrafish embryo model system combining toxicological, transcriptomic, immunological, and biochemical approaches. Embryonic exposure to aflatoxin B1 induced significant changes at the transcriptome level resulting in elevated expression of inflammatory gene network and repression of lipid metabolism and gastrointestinal tract development-related gene sets. According to the gene expression changes, massive neutrophil granulocyte influx, elevated nitric oxide production, and yolk lipid accumulation were observed in the abdominal region of aflatoxin B1-exposed larvae. In parallel, aflatoxin B1-induced defective gastrointestinal tract development and reduced L-arginine level were found in our model system. Our results revealed the complex direct embryotoxic effects of aflatoxin B1, including inhibited lipid utilization, defective intestinal development, and inflammation.

Analysis of the Oxidative Stress Regulon Identifies soxS as a Genetic Target for Resistance Reversal in Multidrug-Resistant Klebsiella pneumoniae

In bacteria, the defense system deployed to counter oxidative stress is orchestrated by three transcriptional factors, SoxS, SoxR, and OxyR. Although the regulon that these factors control is known in many bacteria, similar data are not available for Klebsiella pneumoniae. To address this data gap, oxidative stress was artificially induced in K. pneumoniae MGH78578 using paraquat and the corresponding oxidative stress regulon recorded using transcriptome sequencing (RNA-seq). The soxS gene was significantly induced during oxidative stress, and a knockout mutant was constructed to explore its functionality. The wild type and mutant were grown in the presence of paraquat and subjected to RNA-seq to elucidate the soxS regulon in K. pneumoniae MGH78578. Genes that are commonly regulated both in the oxidative stress and soxS regulons were identified and denoted as the oxidative SoxS regulon; these included a group of genes specifically regulated by SoxS. Efflux pump-encoding genes and global regulators were identified as part of this regulon. Consequently, the isogenic soxS mutant was found to exhibit a reduction in the minimum bactericidal concentration against tetracycline compared to that of the wild type. Impaired efflux activity, allowing tetracycline to be accumulated in the cytoplasm to bactericidal levels, was further evaluated using a tetraphenylphosphonium (TPP⁺) accumulation assay. The soxS mutant was also susceptible to tetracycline in vivo in a zebrafish embryo model. We conclude that the soxS gene could be considered a genetic target against which an inhibitor could be developed and used in combinatorial therapy to combat infections associated with multidrug-resistant K. pneumoniae.

Ustilaginoidin D induces hepatotoxicity and behaviour aberrations in zebrafish larvae

Ustilaginoidins, a group of bis-naphtho-γ-pyrones, are one of the major mycotoxins produced by Ustilaginoidea virens. This group of bis-naphtho-γ-pyrone mycotoxins has been demonstrated to have antibacterial and immunological inhibitory activities and strong cytotoxicity to human oral epidermoid carcinoma. However, little is yet known about the toxicity of ustilaginoidins to animals or toxicity mechanisms. In this study, toxicity assays to zebrafish larvae show that ustilaginoidin D is highly toxic to zebrafish with an LC₅₀ of ∼7.50 μM. Ustilaginoidin D causes an obvious yolk sac absorption delay and liver damage in zebrafish, which is indicated by liver atrophy and the increased alanine and aspartate transaminase activities. Interestingly, different doses of ustilaginoidin D can alter zebrafish movement behavior in a distinct manner. Transcriptome analyses show that global gene expression profiling in zebrafish is significantly changed in response to ustilaginoidin D exposure. KEGG pathway analyses reveal that differentially expressed genes are enriched in the pathways related to lipid metabolism and hyperbilirubinemia, which are indicators of severe liver injury. Consistently, the expression of the marker genes for hepatotoxic responses is significantly induced by ustilaginoidin D. The findings indicate that ustilaginoidin D induces lipid metabolism disorders and hepatotoxicity in zebrafish larvae and poses a potential risk to food safety.

Mitochondria-Anchored Molecular Thermometer Quantitatively Monitoring Cellular Inflammations

Temperature in mitochondria can be a critical indicator of cell metabolism. Given the highly dynamic and inhomogeneous nature of mitochondria, it remains a big challenge to quantitatively monitor the local temperature changes during different cellular processes. To implement this task, we extend our strategy on mitochondria-anchored thermometers from "on-off" probe Mito-TEM to a ratiometric probe Mito-TEM 2.0 based on the Förster resonance energy transfer mechanism. Mito-TEM 2.0 exhibits not only a sensitive response to temperature through the ratiometric changes of dual emissions but also the specific immobilization in mitochondria via covalent bonds. Both characters support accurate and reliable detection of local temperature for a long time, even in malfunctioning mitochondria. By applying Mito-TEM 2.0 in fluorescence ratiometric imaging of cells and zebrafishes, we make a breakthrough in the quantitative visualization of mitochondrial temperature rises in different inflammation states.

A review on the biological effects of nanomaterials on silkworm (Bombyx mori)

The production of high-quality silkworm silk is of importance in sericulture in addition to the production of biomass, silk proteins, and animal feed. The distinctive properties of nanomaterials have the potential to improve the development of various sectors including medicine, cosmetics, and agriculture. The application of nanotechnology in sericulture not only improves the survival rate of the silkworm, promotes the growth and development of silkworm, but also improves the quality of silk fiber. Despite the positive contributions of nanomaterials, there are a few concerns regarding the safety of their application to the environment, in humans, and in experimental models. Some studies have shown that some nanomaterials exhibit toxicity to tissues and organs of the silkworm, while other nanomaterials exhibit therapeutic properties. This review summarizes some reports on the biological effects of nanomaterials on silkworm and how the application of nanomaterials improves sericulture.

Anti-inflammatory effect of rosmarinic acid isolated from Blechnum brasiliense in adult zebrafish brain

Neuroinflammation has been associated to neurodegenerative disease development, with evidence suggesting that high levels of proinflammatory cytokines promote neuronal dysfunction and death. Therefore, it is necessary to study new compounds that may be used as adjuvant treatments of neurodegenerative diseases by attenuating the inflammatory response in the central nervous system (CNS). The aim of this study was to utilize the lipopolysaccharide (LPS) induction model of neuroinflammation to evaluate the modulation of inflammation by rosmarinic acid (RA) isolated from Blechnum brasiliense in adult zebrafish. First, we investigated the toxicity and antioxidant properties of fractionated B. brasiliense extract (ethyl acetate fraction- EAF) and the isolated RA in zebrafish embryos. Next, we developed a model of neuroinflammation induction by intraperitoneal (i.p.) injection of LPS to observe the RA modulation of proinflammatory cytokines. The median lethal concentration (LC50) calculated was 185.2 ± 1.24 μg/mL for the ethyl acetate fraction (EAF) and 296.0 ± 1.27 μM for RA. The EAF showed free radical inhibition ranging from 23.09% to 63.44% at concentrations of 10-250 μg/mL. The RA presented a concentration-dependent response ranging from 18.24% to 47.63% at 10-250 μM. Furthermore, the RA reduced LPS induction of TNF-α and IL-1β levels, with the greatest effect observed 6 h after LPS administration. Thus, the data suggested an anti-inflammatory effect of RA isolated from B. brasiliense and reinforced the utility of the new model of neuroinflammation to test the possible neuroprotective effects of novel drugs or compounds.

Effect of fomesafen on the embryonic development of zebrafish

Fomesafen is widely used in agriculture and can be detected in the environment and agricultural products. Research on the developmental toxicity of fomesafen in animals is currently very limited. Here, we used zebrafish as an animal model to evaluate the toxicity of fomesafen in developing aquatic vertebrates and higher animals. From 6h to 72h following fertilization, exposure of zebrafish embryos to 5, 10 and 20 mg/L of fomesafen resulted in pericardial edema, a reduction in heart rate, shortening of body length, and yolk sac edema. Fomesafen reduced the number of immune cells such as neutrophils and macrophages, increased the expression of a number of inflammatory factors, induced the up-regulation of the oxidative stress response and apoptosis, and disrupted the activity of enzymes related to nerve development, which affected the motility of the embryos. In conclusion, the results provide new evidence for the comprehensive assessment of fomesafen toxicity in aquatic vertebrates.

Transcriptome sequencing supports a conservation of macrophage polarization in fish

Mammalian macrophages can adopt polarization states that, depending on the exact stimuli present in their extracellular environment, can lead to very different functions. Although these different polarization states have been shown primarily for macrophages of humans and mice, it is likely that polarized macrophages with corresponding phenotypes exist across mammals. Evidence of functional conservation in macrophages from teleost fish suggests that the same, or at least comparable polarization states should also be present in teleosts. However, corresponding transcriptional profiles of marker genes have not been reported thus far. In this study we confirm that macrophages from common carp can polarize into M1- and M2 phenotypes with conserved functions and corresponding transcriptional profiles compared to mammalian macrophages. Carp M1 macrophages show increased production of nitric oxide and a transcriptional profile with increased pro-inflammatory cytokines and mediators, including il6, il12 and saa. Carp M2 macrophages show increased arginase activity and a transcriptional profile with increased anti-inflammatory mediators, including cyr61, timp2b and tgm2b. Our RNA sequencing approach allowed us to list, in an unbiased manner, markers discriminating between M1 and M2 macrophages of teleost fish. We discuss the importance of our findings for the evaluation of immunostimulants for aquaculture and for the identification of gene targets to generate transgenic zebrafish for detailed studies on M1 and M2 macrophages. Above all, we discuss the striking degree of evolutionary conservation of macrophage polarization in a lower vertebrate.

Exploration of anti-inflammatory mechanism of forsythiaside A and forsythiaside B in CuSO4-induced inflammation in zebrafish by metabolomic and proteomic analyses

BACKGROUND

Inflammation is a general pathological phenomenon during severe disturbances to the homeostasis. Forsythiaside A (FA) and forsythiaside B (FB), isolated from the dried fruit of Forsythia suspensa (Thunb.) Vahl, are phenylethanoid compounds that show a significant anti-inflammatory effect. However, the properties and therapeutic mechanisms of this effect have not yet been systematically elucidated.

METHODS

In this study, the anti-inflammatory effects of FA and FB were investigated in CuSO₄-induced inflammation in zebrafish larvae. Intracellular generation of reactive oxygen species (ROS) and nitric oxide (NO) was investigated using fluorescence probes. Metabolomic and proteomic analyses using liquid chromatography-mass spectrometry were carried out to identify the expressions of metabolites and proteins associated with the anti-inflammatory mechanism of FA and FB. Quantitative polymerase chain reaction (PCR) was performed to detect the progressive changes in gene expression.

RESULTS

FA and FB inhibited neutrophils migration to the damaged neuromasts and remarkably reduced CuSO₄-induced ROS and NO generation in zebrafish larvae. Metabolomic analysis pointed to the involvement of nicotinate and nicotinamide metabolism, energy metabolism, pyrimidine metabolism, and purine metabolism. Proteomic analysis identified 146 differentially expressed proteins between the control and model groups. These included collagen [collagen type II alpha 1b precursor (col2a1b), collagen alpha-2(IX) chain precursor (col9a2), collagen type IX alpha I precursor (col9a1b)], nucleoside diphosphate kinase 3 isoform X1 (Nme3), WD repeat-containing protein 3 (Wdr3), and 28S ribosomal protein S7 mitochondrial precursor (Mrps7). FA and FB were shown to reverse the abnormal expressions of potential metabolite and protein biomarkers and alleviate CuSO₄-induced damage to the neuromasts in the zebrafish lateral line.

CONCLUSIONS

Our results indicate that FA and FB possess remarkable anti-inflammatory properties, protecting against CuSO₄-induced neuromasts damage in zebrafish larvae. The results also suggest a multi-component and multi-regulatory therapeutic mechanism for FA and FB.

The immunotoxicity and neurobehavioral toxicity of zebrafish induced by famoxadone-cymoxanil

As a new protective and therapeutic fungicide, studies on famoxadone-cymoxanil are rare, and its toxicity to aquatic organisms has not been reported. In the present study, zabrafish embryos were exposed to several concentrations of famoxadone-cymoxanil at 10 hpf. Then, the changes of their shape, heart rate, development and function of innate and adaptive immune cells, oxidative stress, apoptosis, the expression of apoptosis-related genes and immune-related genes, the locomotor behavior were observed and detected in acute toxicity of famoxadone-cymoxanil. Our studies showed that, after exposure to famoxadone-cymoxanil, zebrafish embryos had decreased heart rate, shortened body length, swollen yolk sac. Secondly, the number of innate and adaptive immune cells was significantly reduced; and neutrophil migration and retention at the injury area were inhibited, indicating the developmental toxicity and immunotoxicity of famoxadone-cymoxanil on the zebrafish. We also found that the oxidative stress related indicators of embryos were changed significantly, and apoptosis were substantially increased. Further investigation of changes of some key genes in TLR signaling including TLR4, MYD88 and NF-κB p65 revealed that the mRNA expression of these genes was up-regulated. Meanwhile, the mRNA expression of some proinflammatory cytokines such as TNF-α, IFN-γ, IL6 and IL-1β was also up-regulated. In addition, the activity, the total distance, time and average speed were decreased along with the increase of exposure concentration. The absolute turn angle, sinuosity and the enzymatic activity of acetylcholinesterase (AChE) were also increased. These results suggested that famoxadone-cymoxanil can induce developmental toxicity, immunotoxicity and neurobehavioral toxicity in zebrafish larvae.

Inflammatory Responses during Tumour Initiation: From Zebrafish Transgenic Models of Cancer to Evidence from Mouse and Man

The zebrafish is now an important model organism for cancer biology studies and provides unique and complementary opportunities in comparison to the mammalian equivalent. The translucency of zebrafish has allowed in vivo live imaging studies of tumour initiation and progression at the cellular level, providing novel insights into our understanding of cancer. Here we summarise the available transgenic zebrafish tumour models and discuss what we have gleaned from them with respect to cancer inflammation. In particular, we focus on the host inflammatory response towards transformed cells during the pre-neoplastic stage of tumour development. We discuss features of tumour-associated macrophages and neutrophils in mammalian models and present evidence that supports the idea that these inflammatory cells promote early stage tumour development and progression. Direct live imaging of tumour initiation in zebrafish models has shown that the intrinsic inflammation induced by pre-neoplastic cells is tumour promoting. Signals mediating leukocyte recruitment to pre-neoplastic cells in zebrafish correspond to the signals that mediate leukocyte recruitment in mammalian tumours. The activation state of macrophages and neutrophils recruited to pre-neoplastic cells in zebrafish appears to be heterogenous, as seen in mammalian models, which provides an opportunity to study the plasticity of innate immune cells during tumour initiation. Although several potential mechanisms are described that might mediate the trophic function of innate immune cells during tumour initiation in zebrafish, there are several unknowns that are yet to be resolved. Rapid advancement of genetic tools and imaging technologies for zebrafish will facilitate research into the mechanisms that modulate leukocyte function during tumour initiation and identify targets for cancer prevention.