Systemic response to ultraviolet radiation involves induction of leukocytic IL-1β and inflammation in zebrafish

Functionally similar genes exhibit comparable/similar time-course expression kinetics in the UV-induced photoaged mouse model

Skin photoaging induced by ultraviolet (UV) irradiation contributes to the formation of thick and coarse wrinkles. Humans are exposed to UV light throughout their lives. Therefore, it is crucial to determine the time-sequential effects of UV on the skin. In this study, we irradiated the mouse back skin with UV light for eight weeks and observed the changes in gene expressions via microarray analysis every week. There were more downregulated genes (514) than upregulated genes (123). The downregulated genes had more functional diversity than the upregulated genes. Additionally, the number of downregulated genes did not increase in a time-dependent manner. Instead, time-dependent kinetic patterns were observed. Interestingly, each kinetic cluster harbored functionally enriched gene sets. Since collagen changes in the dermis are considered to be a major cause of photoaging, we hypothesized that other gene sets contributing to photoaging would exhibit kinetics similar to those of the collagen-regulatory genes identified in this study. Accordingly, co-expression network analysis was conducted using 11 well-known collagen-regulatory seed genes to predict genes with similar kinetics. We ranked all downregulated genes from 1 to 504 based on their expression levels, and the top 50 genes were suggested to be involved in the photoaging process. Additionally, to validate and support our identified top 50 gene lists, we demonstrated that the genes (FN1, CCDC80, PRELP, and TGFBR3) we discovered are downregulated by UV irradiation in cultured human fibroblasts, leading to decreased collagen levels, which is indicative of photoaging processes. Overall, this study demonstrated the time-sequential genetic changes in chronically UV-irradiated skin and proposed 50 genes that are involved in the mechanisms of photoaging.

Assessing Larval Zebrafish Survival and Gene Expression Following Sodium Butyrate Exposure and Subsequent Lethal Bacterial Lipopolysaccharide (LPS) Endotoxin Challenge

As aquaculture production continues to grow, producers are looking for more sustainable methods to promote growth and increase fish health and survival. Butyrate is a short-chain fatty acid (SCFA) with considerable benefits to gut health, and in recent years, butyrate has been commonly used as an alternative to antimicrobials in livestock production. In this study, we aimed to assess the protective effects of sodium butyrate (NaB) on larval zebrafish subjected to a lethal Pseudomonas aeruginosa lipopolysaccharide (LPS) endotoxin challenge and to elucidate potential protective mechanisms of action. Larval zebrafish were pre-treated with 0, 3000, or 6000 μM NaB for 24 h at 72 h post-fertilization (hpf), then immune challenged for 24 h with 60 μg/mL of LPS at 96 hpf. Our results demonstrate that larval zebrafish pre-treated with 6000 μM of NaB prior to lethal LPS challenge experienced significantly increased survival by 40%, and this same level of NaB significantly down-regulated the expression of pro-inflammatory Tumor Necrosis Factor α (TNF-alpha). Findings from this study are consistent with the beneficial effects of NaB on other vertebrate species and support the potential use of NaB in aquaculture.

The microbiota regulates hematopoietic stem and progenitor cell development by mediating inflammatory signals in the niche

The commensal microbiota regulates the self-renewal and differentiation of hematopoietic stem and progenitor cells (HSPCs) in bone marrow. Whether and how the microbiota influences HSPC development during embryogenesis is unclear. Using gnotobiotic zebrafish, we show that the microbiota is necessary for HSPC development and differentiation. Individual bacterial strains differentially affect HSPC formation, independent of their effects on myeloid cells. Early-life dysbiosis in chd8-/- zebrafish impairs HSPC development. Wild-type microbiota promote HSPC development by controlling basal inflammatory cytokine expression in kidney niche, and chd8-/- commensals elicit elevated inflammatory cytokines that reduce HSPCs and enhance myeloid differentiation. We identify an Aeromonas veronii strain with immuno-modulatory activities that fails to induce HSPC development in wild-type fish but selectively inhibits kidney cytokine expression and rebalances HSPC development in chd8-/- zebrafish. Our studies highlight the important roles of a balanced microbiome during early HSPC development that ensure proper establishment of lineal precursor for adult hematopoietic system.

Bacterial Quorum-Sensing Signal DSF Inhibits LPS-Induced Inflammations by Suppressing Toll-like Receptor Signaling and Preventing Lysosome-Mediated Apoptosis in Zebrafish

Bacteria and their eukaryotic hosts have co-evolved for millions of years, and the former can intercept eukaryotic signaling systems for the successful colonization of the host. The diffusible signal factor (DSF) family represents a type of quorum-sensing signals found in diverse Gram-negative bacterial pathogens. Recent evidence shows that the DSF is involved in interkingdom communications between the bacterial pathogen and the host plant. In this study, we explored the anti-inflammatory effect of the DSF and its underlying molecular mechanism in a zebrafish model. We found that the DSF treatment exhibited a strong protective effect on the inflammatory response of zebrafish induced by lipopolysaccharide (LPS). In the LPS-induced inflammation zebrafish model, the DSF could significantly ameliorate the intestinal pathological injury, reduce abnormal migration and the aggregation of inflammatory cells, inhibit the excessive production of inflammatory mediator reactive oxygen species (ROS) content, and prevent apoptosis. Through an RNA-Seq analysis, a total of 938 differentially expressed genes (DEGs) was screened between LPS and LPS + DSF treatment zebrafish embryos. A further bioinformatics analysis and validation revealed that the DSF might inhibit the LPS-induced zebrafish inflammatory response by preventing the activation of signaling in the Toll-like receptor pathway, attenuating the expression of pro-inflammatory cytokines and chemokines, and regulating the activation of the caspase cascade through restoring the expression of lysosomal cathepsins and apoptosis signaling. This study, for the first time, demonstrates the anti-inflammatory role and a potential pharmaceutical application of the bacterial signal DSF. These findings also suggest that the interkingdom communication between DSF-producing bacteria and zebrafish might occur in nature.

Evaluation of UV-B protective properties of leaves and seeds of Achyranthes aspera in Asian catfish Clarias batrachus (Linn.)

The ultraviolet-B (UV-B) radiation is harmful to the aquatic organisms. The UV-B protective properties of leaves and seeds of herb Achyranthes aspera were evaluated in Clarias batrachus. Fish were fed with four diets-EFL1, EFL2 containing 0.25 and 0.5% leaves, EFS containing 0.5% seeds and control, CF. After 83 days of feeding, fish were exposed to UV-B (157 µW/cm²) for 7 days at the rate of 15 min/day. One batch of fish in each treatment was kept unexposed. Significantly higher final weight was found in EFS followed by EFL2 and EFL1 treatments. It was higher in unexposed fish compared to the exposed ones. Among exposed fish, significantly higher lysozyme was found in EFS and myeloperoxidase in EFS and EFL2 compared to others. Nitric oxide synthase and superoxide dismutase levels were significantly higher in liver and head kidney of EFS diet fed fish compared to others. Thiobarbituric acid reactive substances (TBARS) and carbonyl protein levels were minimum in EFS followed by EFL2. The independent sample t-test showed that nitric oxide synthase was significantly higher and myeloperoxidase and TBARS levels were significantly lower in unexposed group compared to the exposed fish in respective treatment. There were up-regulations of TNF-α, iNOS, NF-kB, BAX, Cytochrome c, SOD-c, Caspase 3, Caspase 9, BCL2 in liver and head kidney of leaves and seeds incorporated diets fed fish compared to control. Supplementation of A. aspera seeds and leaves at 0.5% level in diets gave UV-B protection to the fish.

Transcriptome analysis of molecular response to UVC irradiation in zebrafish embryos

Ultraviolet (UV) rays can be both harmful and beneficial to humans. This study aimed to investigate the toxicity and safety of ultraviolet C (UVC) exposure in living organisms and the corresponding biodefense molecular mechanisms. Zebrafish embryos, at an early developmental stage (5-6 h post-fertilization), were irradiated with increasing UVC dosages using high-efficiency deep-ultraviolet light-emitting diodes (278 nm). Morphological phenotypes including survival rate, hatching rate, heart rate, and malformation rate were evaluated. Compared to un-irradiated controls, all zebrafish embryos exposed to 4.5 mJ/cm² UVC survived and showed no significant difference in hatching and heart rate. However, 7.5 mJ/cm² of UVC irradiation caused a significantly decreased survival rate (37.5%) and an increased malformation rate (81.8%). Therefore, 4.5 mJ/cm² was chosen as the limit dosage that the internal biodefense system of zebrafish embryos can protect against UVC radiation. Transcriptome analysis (RNA sequencing) performed on 3 min and 3 days post-irradiation embryos (4.5 mJ/cm²) revealed the molecular mechanisms underlying the response of zebrafish embryos to irradiation. The embryos quickly responded to UVC-induced stress by activating the p53 signaling pathway. In addition, after 3 days of recuperation, the embryos showed activation of signal transducer and activator of transcription (STAT) signaling pathway. To our knowledge, this is the first study to evaluate the toxicological effects and the molecular mechanism of biodefense in zebrafish embryos upon 278 nm UVC irradiation.

Early Inflammation Dysregulates Neuronal Circuit Formation In Vivo via Upregulation of IL-1β

Neuroimmune interaction during development is strongly implicated in the pathogenesis of neurodevelopmental disorders, but the mechanisms that cause neuronal circuit dysregulation are not well understood. We performed in vivo imaging of the developing retinotectal system in the larval zebrafish to characterize the effects of immune system activation on refinement of an archetypal sensory processing circuit. Acute inflammatory insult induced hyperdynamic remodeling of developing retinal axons in larval fish and increased axon arbor elaboration over days. Using calcium imaging in GCaMP6s transgenic fish, we showed that these morphologic changes were accompanied by a shift toward decreased visual acuity in tectal cells. This finding was supported by poorer performance in a visually guided behavioral task. We further found that the pro-inflammatory cytokine, interleukin-1β (IL-1β), is upregulated by the inflammatory insult, and that downregulation of IL-1β abrogated the effects of inflammation on axonal dynamics and growth. Moreover, baseline branching of the retinal ganglion cell arbors in IL-1β morphant animals was significantly different from that in control larvae, and their performance in a predation assay was impaired, indicating a role for this cytokine in normal neuronal development. This work establishes a simple and powerful non-mammalian model of developmental immune activation and demonstrates a role for IL-1β in mediating the pathologic effects of inflammation on neuronal circuit development.SIGNIFICANCE STATEMENT Maternal immune activation can increase the risk of neurodevelopmental disorders in offspring; however, the mechanisms involved are not fully understood. Using a non-mammalian vertebrate model of developmental immune activation, we show that even brief activation of inflammatory pathways has immediate and long-term effects on the arborization of axons, and that these morphologic changes have functional and behavioral consequences. Finally, we show that the pro-inflammatory cytokine IL-1β plays an essential role in both the effects of inflammation on circuit formation and normal axonal development. Our data add to a growing body of evidence supporting epidemiological studies linking immune activation to neurodevelopmental disorders, and help shed light on the molecular and cellular processes that contribute to the etiology of these disorders.

Influence of chronic stress on the mechanism of the cytotoxic system in common carp (Cyprinus carpio)

Aquaculture conditions expose fish to internal and environmental stressors that increase their susceptibility to morbidity and mortality. The brain accumulates stress signals and processes them according to the intensity, frequency duration and type of stress, recruiting several brain functions to activate the autonomic or limbic system. Triggering the autonomic system causes the rapid release of catecholamines, such as adrenaline and noradrenaline, into circulation from chromaffin cells in the head kidney. Catecholamines trigger blood cells to release proinflammatory and regulatory cytokines to cope with acute stress. Activation of the limbic axis stimulates the dorsolateral and dorsomedial pallium to process emotions, memory, behaviour and the activation of preoptic nucleus‐pituitary gland‐interrenal cells in the head kidney, releasing glucocorticoids, such as cortisol to the bloodstream. Glucocorticoids cause downregulation of various immune system functions depending on the duration, intensity and type of chronic stress. As stress persists, most immune functions, with the exception of cytotoxic functions, overcome these effects and return to homeostasis. The deterioration of cytotoxic functions during chronic stress appears to be responsible for increased morbidity and mortality.

Inflammatory Molecules Associated with Ultraviolet Radiation-Mediated Skin Aging

Skin is the largest and most complex organ in the human body comprised of multiple layers with different types of cells. Different kinds of environmental stressors, for example, ultraviolet radiation (UVR), temperature, air pollutants, smoking, and diet, accelerate skin aging by stimulating inflammatory molecules. Skin aging caused by UVR is characterized by loss of elasticity, fine lines, wrinkles, reduced epidermal and dermal components, increased epidermal permeability, delayed wound healing, and approximately 90% of skin aging. These external factors can cause aging through reactive oxygen species (ROS)-mediated inflammation, as well as aged skin is a source of circulatory inflammatory molecules which accelerate skin aging and cause aging-related diseases. This review article focuses on the inflammatory pathways associated with UVR-mediated skin aging.

Exploring the effect of UV-C radiation on earthworm and understanding its genomic integrity in the context of H2AX expression

Maintaining genomic stability is inevitable for organism survival and it is challenged by mutagenic agents, which include ultraviolet (UV) radiation. Whenever DNA damage occurs, it is sensed by DNA-repairing proteins and thereby performing the DNA-repair mechanism. Specifically, in response to DNA damage, H2AX is a key protein involved in initiating the DNA-repair processes. In this present study, we investigate the effect of UV-C on earthworm, Perionyx excavatus and analyzed the DNA-damage response. Briefly, we expose the worms to different doses of UV-C and find that worms are highly sensitive to UV-C. As a primary response, earthworms produce coelomic fluid followed by autotomy. However, tissue inflammation followed by death is observed when we expose worm to increased doses of UV-C. In particular, UV-C promotes damages in skin layers and on the contrary, it mediates the chloragogen and epithelial outgrowth in intestinal tissues. Furthermore, UV-C promotes DNA damages followed by upregulation of H2AX on dose-dependent manner. Our finding confirms DNA damage caused by UV-C is directly proportional to the expression of H2AX. In short, we conclude that H2AX is present in the invertebrate earthworm, which plays an evolutionarily conserved role in DNA damage event as like that in higher animals.

Zebrafish as a model for inflammation and drug discovery

Zebrafish is a small teleost (bony) fish used in many areas of pharmacology and toxicology. This animal model has advantages for the discovery of anti-inflammatory drugs, such as the potential for real-time assessment of cell migration mechanisms. Additionally, zebrafish display a repertoire of inflammatory cells, mediators, and receptors that are similar to those in mammals, including humans. Inflammatory disease modeling in either larvae or adult zebrafish represents a promising tool for the screening of new anti-inflammatory compounds, contributing to our understanding of the mechanisms involved in chronic inflammatory conditions. In this review, we provide an overview of the characterization of inflammatory responses in zebrafish, emphasizing its relevance for drug discovery in this research area.

UVB Irradiation Induced Cell Damage and Early Onset of Junbb Expression in Zebrafish

Ultraviolet B (UVB) radiation has drawn more attention over these past few decades since it causes severe DNA damage and induces inflammatory response. Serial gene profiling and high throughput data in UVB-associated phenomenon in human cultured cells or full rack of human skin have been investigated. However, results using different tissue models lead to ambiguity in UVB-induced pathways. In order to systematically understand the UVB-associated reactions, the zebrafish model was used, and whole organism gene profiling was performed to identify a novel biomarker which can be used to generate a new mechanistic approach for further screening on a UVB-related system biology. In this study, detailed morphological assays were performed to address biological response after receiving UVB irradiation at morphological, cellular, and molecular levels. Microarray screening and whole genome profiling revealed that there is an early onset expression of junbb in zebrafish embryos after UVB irradiation. Also, the identified novel biomarker junbb is more sensitive to UVB response than mmps which have been used in mouse models. Moreover, cellular and molecular response chronology after UVB irradiation in zebrafish provide a solid and fundamental mechanism for use in a UV radiation-associated study in the future.

Potential of Skin Microbiome, Pro- and/or Pre-Biotics to Affect Local Cutaneous Responses to UV Exposure

The human skin hosts innumerable microorganisms and maintains homeostasis with the local immune system despite the challenges offered by environmental factors such as ultraviolet radiation (UVR). UVR causes cutaneous alterations such as acute (i.e., sunburn) and chronic inflammation, tanning, photoaging, skin cancer, and immune modulation. Phototherapy on the other hand is widely used to treat inflammatory skin diseases such as psoriasis, atopic dermatitis, polymorphic light eruption and graft-versus-host disease (GvHD), as well as neoplastic skin diseases such as cutaneous T cell lymphoma, among others. Previous work has addressed the use of pro- and pre-biotics to protect against UVR through anti-oxidative, anti-inflammatory, anti-aging, anti-carcinogenic and/or pro-and contra-melanogenic properties. Herein, we discuss and share perspectives of the potential benefits of novel treatment strategies using microbes and pro- and pre-biotics as modulators of the skin response to UVR, and how they could act both for protection against UVR-induced skin damage and as enhancers of the UVR-driven therapeutic effects on the skin.

P2X7R and PANX-1 channel relevance in a zebrafish larvae copper-induced inflammation model

Copper is a metal that participates in several essential reactions in living organisms, and it has been used as an inflammatory inducing agent in zebrafish larvae. In this study, we evaluated the effect P2X7 receptor and/or pannexin channel 1 (PANX-1) blockage in this inflammation model. To perform the experiments, 7 dpf larvae were exposed to 10 μM of copper and treated with 100 μM probenecid, PANX-1 inhibitor, and/or 300 nM A740003, a P2X7R selective antagonist. Larvae survival was assessed up to 24 h after treatments. The evaluation of larvae behavior was evaluated after acute (4 h) and chronic (24 h) exposure. The parameters of locomotor activity measured were: mobile time, average speed, distance and turn angle. We analyzed the gene expression of the P2X7 receptor, PANX1a and PANX1b channels and interleukins IL-10 and IL-1b after 24 h of treatment. Treatments did not decrease larval survival in the time interval studied. Changes in larvae locomotion were observed after the longest time of exposure to copper and the treatment with probenecid was able to reverse part of the effects caused by copper. No significant difference was observed in the oxidative stress assays and probenecid and copper treatment decrease partially PANX1a gene expression groups. The data presented herein shows the relevance of the blockage of P2X7-PANX-1 in copper-induced inflammation.

Sub-lethal UV radiation during early life stages alters the behaviour, heart rate and oxidative stress parameters in zebrafish (Danio rerio)

Environmental UV radiation in sufficient doses, as a possible consequence of climate change, is potent enough to affect living organisms with different outcomes, depending on the exposure life stage. The aim of this project was to evaluate the potentially toxic effects of exposure to sub-lethal and environmentally relevant doses of UVA (9.4, 18. 7, 37.7 J/cm²) and UVB radiation (0.013, 0.025, 0.076 J/cm²) on the development and behaviour in early life stages (4.5-5.5 h post fertilization, hpf) of the zebrafish (Danio rerio). The used doses were all below the median lethal dose (LD₅₀) and caused no significant difference in survival, deformities, or hatching between exposed and control groups. Compared to controls, there were transient UVA and UVB exposure effects on heart rate, with dose dependent reductions at 50 hpf, and at 60 hpf for UVA only. The UVB exposure caused an increasing trend in reactive oxygen species (ROS) formation at the two highest doses, even though only significant at 120 hpf for the second highest dose. Both UVA and UVB caused an increasing trend in lipid peroxidation (LPO) at the highest doses tested at 72 hpf. Furthermore, UVA exposure led to significant reductions in larval movement following exposure to the two highest doses of UVA, i.e., reduction in the time spent active and the total distance moved compared to control at 100 hpf, while no effect on the swimming speed was observed. The lowest dose of UVA had no effect on behaviour. In contrast, the highest dose of UVB led to a possible increase in the time spent active and a slower average swimming speed although these effects were not significant (p = 0.07). The obtained results show that UV doses below LD₅₀ levels are able to cause changes in the behaviour and physiological parameters of zebrafish larvae, as well as oxidative stress in the form of ROS formation and LPO. Further testing is necessary to assess how this type of radiation and the effects observed could affect fish population dynamics.

The impact of ultraviolet B (UV-B) radiation in combination with different temperatures in the early life stage of zebrafish (Danio rerio)

Ultraviolet B (UV-B) radiation is an environmental stressor with detrimental effects on many aquatic organisms including fish.

A high-sensitivity bi-directional reporter to monitor NF-κB activity in cell culture and zebrafish in real time

Nuclear factor (NF)-κB transcription factors play major roles in numerous biological processes including development and immunity. Here, we engineered a novel bi-directional NF-κB-responsive reporter, pSGNluc, in which a high-affinity NF-κB promoter fragment simultaneously drives expression of luciferase and GFP. Treatment with TNFα (also known as TNF) induced a strong, dose-dependent luciferase signal in cell culture. The degree of induction over background was comparable to that of other NF-κB-driven luciferase reporters, but the absolute level of expression was at least 20-fold higher. This extends the sensitivity range of otherwise difficult assays mediated exclusively by endogenously expressed receptors, as we show for Nod1 signaling in HEK293 cells. To measure NF-κB activity in the living organism, we established a transgenic zebrafish line carrying the pSGNluc construct. Live in toto imaging of transgenic embryos revealed the activation patterns of NF-κB signaling during embryonic development and as responses to inflammatory stimuli. Taken together, by integrating qualitative and quantitative NF-κB reporter activity, pSGNluc is a valuable tool for studying NF-κB signaling at high spatiotemporal resolution in cultured cells and living animals that goes beyond the possibilities provided by currently available reporters.

The notochord curvature in medaka (Oryzias latipes) embryos as a response to ultraviolet A irradiation

In the present work, the destructive effects of ultraviolet A (UVA; 366nm) irradiation on the developmental stages of Japanese medaka (Oryzias latipes) are revealed in terms of hatching success, mortality rate, and morphological malformations (yolk sac edema, body curvature, fin blistering, and dwarfism). Fertilized eggs in stage 4 were exposed to 15, 30, and 60min/day UVA for 3days in replicates. Fish were staged and aged following the stages established by Iwamatsu [1]. We observed and recorded the hatching time and deformed and dead embryos continuously. The hatching time was prolonged and the deformed and dead embryos numbers were increased by UVA dose increase. At stage 40, samples from each group were fixed to investigate their morphology and histopathology. Some morphological malformations were recorded after UVA exposure in both strains. Histopathological changes were represented as different shapes of curvature in notochord with collapse. The degree of collapsation was depended on the dose and time of UVA exposure. Our findings show that exposure to UVA irradiation caused less vertebral column curvature in medaka fry. Moreover, p53-deficient embryos were more tolerant than those of wild-type (Hd-rR) Japanese medaka. This study indicated the dangerous effects of the UVA on medaka.

Administration of a Polyphenol-Enriched Feed to Farmed Sea Bass (Dicentrarchus labrax L.) Modulates Intestinal and Spleen Immune Responses

Farmed fish are exposed to a continuous antigenic pressure by microbial and environmental agents, which may lead to a condition of chronic inflammation. In view of the notion that polyphenols, largely contained in fruits and vegetables, are endowed with antioxidant and anti-inflammatory activities, farmed sea bass (Dicentrarchus labrax L.) have been administered with red grape polyphenol-enriched feed. Polyphenols were extracted from the seeds of Canosina Nero di Troia Vitis vinifera and mixed with conventional feed at two different concentrations (100 and 200 mg/kg, resp.). Fish samples collected at days 223 and 273, respectively, were evaluated for intestinal and spleen cytokine release as well as for spleen macrophage (MØ) and melanomacrophage center (MMC) areas and distribution. Data will show that in treated fish decrease of intestinal interleukin- (IL-) 1β and IL-6 and increase of splenic interferon- (IFN-) γ occur. On the other hand, in the spleen reduction of MØ number seems to parallel increase in MMCs. Collectively, these data suggest that polyphenol-administered sea bass generate lower levels of intestinal proinflammatory cytokines, while producing larger amounts of spleen IFN-γ, as an expression of a robust and protective adaptive immune response. Increase of MMCs corroborates the evidence for a protective spleen response induced by feed enriched with polyphenols.