The proinflammatory cytokines TNF-α and IL-6 in lumpfish (Cyclopterus lumpus L.) -identification, molecular characterization, phylogeny and gene expression analyses

Analyses of the Mx family members in lumpfish: Molecular characterization, phylogeny, and gene expression analyses

Members of the myxovirus resistance (Mx) protein family play an essential role in antiviral immunity. They are Dynamin-like GTPases, induced by interferons. In the current study, we have characterized two predicted MX genes (MX1 and MX2) from lumpfish (Cyclopterus lumpus L.), having 12 and 13 exons, respectively. Mx2 has two isoforms (Mx2-X1 and Mx2-X2) which differ in exon 1. The lumpfish Mx proteins contain an N-terminal Dynamin-like GTPase domain, the middle domain (MD) and GTPase effector domain (GED) characteristic for Mx proteins. Phylogenetic analyses grouped all the lumpfish Mx sequences in group 1, and synteny analyses showed that both genes were localized at chromosome 5 in proximity to the genes Tohc7, Atxn7 and Psmd6. In vitro stimulation experiment showed that both MX1 and MX2-X2 were highly upregulated upon exposure to poly(I:C), but not bacteria, 24 h post exposure, indicating their role in antiviral immunity.

Exploring the impact of nano-Se and nano-clay feed supplements on interleukin genes, immunity and growth rate in European Sea Bass (Dicentrarchus labrax)

This study aimed to investigate the effects of adding Nano-Selenium (NSe) and Nano-clay (NC) as feed supplements on European Sea Bass (Dicentrarchus labrax). Two separate experiments were conducted, one with NC and the other with NSe. Each experiment consisted of four sub-groups with varying concentrations of NC or NSe. The expression levels of five immune-related genes (TNF-α, TNF-β, IL-2, IL-6 and IL-12) were measured using Real-time Quantitative PCR (Rt-PCR) Assay. The results showed an increase in the expression of interleukins (IL-2, IL-6 and IL-12) and pro-inflammatory cytokines (TNF-α and TNF-β) after exposure to NC and NSe. TNF-α gene expression was significantly higher with both 1 mg and 10 mg concentrations of NC and NSe. TNF-β gene expression was highest with the 5 mg concentration of NC. The concentrations of 1 mg and 10 mg for NC, and 1 mg, 5 mg, and 10 mg for NSe, led to the highest (p < 0.05) levels of IL-2 expression compared to the control. Similar trends were observed for IL-6 and IL-12 gene expression. Understanding the impact of these concentrations on gene expression, growth rate, biochemical indices, and antioxidant status can provide valuable insights into the potential applications of NC and NSe supplements on European Sea Bass.

CRISPR/Cas9-mediated knockout of tnf-α1 in zebrafish reduces disease resistance after Edwardsiella piscicida bacterial infection

Tumor necrosis factor (TNF) is an important cytokine involved in immune responses to bacterial infections in vertebrates, including fish. Although Tnf-α is a well-studied cytokine, there are contradictory findings about Tnf-α function following bacterial infection. In this study, we analyzed the expression and function of the Tnf-α-type I isoform (Tnf-α1) in zebrafish by knockout experiments using the CRISPR/Cas9 gene-editing tool. The open reading frame of tnf-α1 encodes a 25.82 kDa protein with 234 amino acids (aa). The expression of tnf-α1 in the early stages of zebrafish was observed from the 2-cell stage. Adult zebrafish spleens showed the highest expression of tnf-α1. To evaluate the function of Tnf-α1, an 8 bp deletion in the target region, resulting in a short truncated protein of 55 aa, was used to create the tnf-α1 knockout mutant. The pattern of downstream gene expression in 7-day larvae in wild-type (WT) and tnf-α1 knockout fish was examined. We also verified the fish mortality rate after Edwardsiella piscicida challenge and found that it was much higher in tnf-α1 knockout fish than in WT fish. Additionally, downstream gene expression analyses after E. piscicida exposure revealed a distinct expression pattern in tnf-α1 knockout fish compared to that in WT fish. Overall, our study using tnf-α1 deletion in zebrafish confirmed that Tnf-α1 is critical for immune regulation during bacterial infection.

Evolutionary, comparative, and functional analyses of STATs and regulation of the JAK-STAT pathway in lumpfish upon bacterial and poly(I:C) exposure

Background

The Janus kinase/signal transducers and activators of transcription (JAK-STAT) system regulates several biological processes by affecting transcription of genes as a response to cytokines and growth factors. In the present study, we have characterized the STAT genes in lumpfish (Cyclopterus lumpus L.), belonging to the order Perciformes, and investigated regulation of the JAK-STAT signaling pathway upon exposure to bacteria (Vibrio anguillarum) and poly(I:C), the latter mimicking antiviral responses.

Methods

Characterization and evolutionary analyses of the STATs were performed by phylogeny, protein domain, homology similarity and synteny analyses. Antibacterial and antiviral responses were investigated by performing KEGG pathway analysis.

Results

We observed that lumpfish have stat1a, 2, 3, 4, 5a, 5b, and 6. Transcriptome-wide analyses showed that most components of the JAK-STAT pathway were present in lumpfish. il-6, il-10, il-21, iκBα and stat3 were upregulated 6 hours post exposure (hpe) against bacteria while type I interferons (IFNs), irf1, irf3, irf10, stat1 and 2 were upregulated 24 hpe against poly(I:C).

Conclusions

Our findings shed light on the diversity and evolution of the STATs and the data show that the STAT genes are highly conserved among fish, including lumpfish. The transcriptome-wide analyses lay the groundwork for future research into the functional significance of these genes in regulating critical biological processes and make an important basis for development of prophylactic measure such as vaccination, which is highly needed for lumpfish since it is vulnerable for both bacterial and viral diseases.

Transcriptome-wide analyses of early immune responses in lumpfish leukocytes upon stimulation with poly(I:C)

Background

Both bacterial and viral diseases are a major threat to farmed fish. As the antiviral immune mechanisms in lumpfish (Cyclopterus lumpus L.) are poorly understood, lumpfish leukocytes were stimulated with poly(I:C), a synthetic analog of double stranded RNA, which mimic viral infections, and RNA sequencing was performed.

Methods

To address this gap, we stimulated lumpfish leukocytes with poly(I:C) for 6 and 24 hours and did RNA sequencing with three parallels per timepoint. Genome guided mapping was performed to define differentially expressed genes (DEGs).

Results

Immune genes were identified, and transcriptome-wide analyses of early immune responses showed that 376 and 2372 transcripts were significantly differentially expressed 6 and 24 hours post exposure (hpe) to poly(I:C), respectively. The most enriched GO terms when time had been accounted for, were immune system processes (GO:0002376) and immune response (GO:0006955). Analysis of DEGs showed that among the most highly upregulated genes were TLRs and genes belonging to the RIG-I signaling pathway, including LGP2, STING and MX, as well as IRF3 and IL12A. RIG-I was not identified, but in silico analyses showed that genes encoding proteins involved in pathogen recognition, cell signaling, and cytokines of the TLR and RIG-I signaling pathway are mostly conserved in lumpfish when compared to mammals and other teleost species.

Conclusions

Our analyses unravel the innate immune pathways playing a major role in antiviral defense in lumpfish. The information gathered can be used in comparative studies and lay the groundwork for future functional analyses of immune and pathogenicity mechanisms. Such knowledge is also necessary for the development of immunoprophylactic measures for lumpfish, which is extensively cultivated for use as cleaner fish in the aquaculture for removal of sea lice from Atlantic salmon (Salmo salar L.).

Molecular characterization, expression analysis and function identification of TNFα in black rockfish (Sebastes schlegelii)

TNFα, as a pro-inflammatory cytokine, plays an important role in inflammation and immune homeostasis maintaining. However, the knowledge about the immune functions of teleost TNFα against bacterial infections is still limited. In this study, the TNFα was characterized from black rockfish (Sebastes schlegelii). The bioinformatics analyses showed the evolutionary conservations in sequence and structure. The expression levels of Ss_TNFα mRNA were significantly up-regulated in the spleen and intestine after Aeromonas salmonicides and Edwardsiella tarda infections, and dramatically down-regulated in PBLs after LPS and poly I:C stimulations. Meanwhile, the extremely up-regulated expressions of other inflammatory cytokines (especially for IL-1β and IL17C) were observed in the intestine and spleen after bacterial infection and down-regulations were obtained in PBLs. The significant regulation with expression patterns of Ss_TNFα and other inflammatory cytokine mRNAs illustrated the variations of immunity in different tissues and cells of black rockfish. The regulated functions of Ss_TNFα in the up/downstream signaling pathways were preliminarily verified on the transcription and translation levels. Subsequently, in vitro knockdown of Ss_TNFα in the intestine cells of black rockfish confirmed the important immune roles of Ss_TNFα. Finally, the apoptotic analyses were conducted in PBLs and intestine cells of black rockfish. The rapid increases of the apoptotic rates were obtained in both PBLs and intestine cells after treatment with rSs_TNFα, but distinct apoptotic rates at the early and late stages of apoptosis were observed between these two types of cells. The results of apoptotic analyses suggested that Ss_TNFα could trigger apoptosis of different cells in different strategies in black rockfish. Overall, the findings in this study indicated the important roles of Ss_TNFα in the immune system of black rockfish during pathogenic infection, as well as the potential function on biomarker for monitoring the health status.

Intestinal histopathology and immune responses following Escherichia coli lipopolysaccharide challenge in Nile tilapia fed enriched black soldier fly larval (BSF) meal supplemented with chitinase

This study aimed to determine to what extend the addition of chitinase to black soldier fly larvae (BSF) meals enriched with either PUFA or LC-PUFA could improve the gut health of Nile tilapia and increase its immune status. Two types of BSF meals enriched with either α-linolenic acid (ALA) or ALA + eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) were produced using BSF larvae cultured on vegetable substrates (VGS) or fish offal substrates (FOS), respectively. Seven diets were formulated: a control FMFO diet and two other control diets VGD0 vs FOD0 containing the meals of each type of BSF meal as total replacement for fishmeal (FM) and fish oil (FO), as well as four diets supplemented with chitinase. Two doses of commercial chitinase from Aspergillus niger (2 g/kg and 5 g/kg of feed) were supplemented to the other diets VGD0 and FOD0 to formulate VGD2, VGD5, FOD2 and FOD5. After 53 days of feeding, FOD5 diet induced a similar growth performance as the FMFO control diet, while a significant decrease of growth was observed for the other BSF larval-based diets. BSF/FOS meal led to higher SGR of fish than BSF/VGS, as for the FOD5 compared to VGD5. At day 53, lysozyme values showed an increasing trend in fish fed all the BSF-based diets, especially those fed the VGD5. After the Escherichia coli lipopolysaccharide (LPS) injection (day 54), the same increasing trend was observed in lysozyme activity, and modulation was observed only in the VGD5 fish. ACH50 activity was reduced by the BSF-based diets except for the FOD5 diet at day 53, and LPS modulation was only observed for the VGS-chitinase-based diets at day 54. Peroxidase activity and total immunoglobulin (Igs) blood level were not affected by substrate, chitinase dose or LPS injection. At day 53, the low or high dose of chitinase increased the expressions of tlr2, il-1β and il-6 genes in the head kidney of fish fed the BSF/VGS diets compared to those fed the VGD0 or FMFO control diets. At day 54 after LPS injection, the high dose of chitinase decreased the expressions of tlr5 gene in the spleen and mhcII-α gene in the head kidney of fish fed FOD5 diets compared to those fed FOD0 diets. BSF/VGS but not BSF/FOS based diets increased fish sub-epithelial mucosa (SM) and lamina propria (LP) thickness and the number of goblet cells (GC) in fish, but dietary chitinase seemed to prevent some of these effects, especially at low dose. Results showed that chitinase supplementation of 5 g/kg of chitinase to a BSF-based diet enriched with LC-PUFA improved growth, prevented histological changes in the proximal intestine and enhanced some innate immune functions of Nile tilapia without any clear booster effect after challenge with E. coli LPS.

FKN/NR Signaling Pathway Regulates Hippocampal Inflammatory Responses: the Survival of Hippocampal Neurons in Diabetic Rats with Chronic Unpredictable Mild Stress

Aim

To investigate the mechanism via which FKN/CX3CR1 signaling abnormalities mediate N-methyl-D-aspartic acid receptor (NMDA) overexcitation-induced hippocampal neuronal injury in diabetic rats complicated with depression (DD).

Methods

Sixty rats were randomly divided into 5 groups. The depression-like behaviors of the rats were evaluated by open field test and Morris water maze. The pathological changes of hippocampus in DD rats were observed by HE staining. The blood levels of inflammatory factors (IL-1β, TNF-α, and IL-6) and neurotransmitters (D-serine and glutamic acid) were determined by enzyme-linked immunosorbent assay (ELISA). The expressions of BDNF, A1 receptor (A1R), A2 receptor (A2R), A3 receptor (A3R), calmodulin dependent kinase II (CaMKII), CX3CR1, CX3CL1 (FKN), NR2A, and NR2B proteins were detected by immunohistochemistry and Western-blotting.

Results

Compared with the normal control group, blood glucose level increased significantly and body weight decreased in T2DM group and T2DMC group. In addition, the number of spontaneous activities significantly decreased and the capability of learning and memory was attenuated in T2DMC group and Chronic Stress group. The blood levels of IL-1β, TNF-α, IL-6, glutamate (Glu), and D-serine significantly increased in each model group. After intervention with CX3CR1 antibody, the expressions of BDNF, CaMK II, A1R, and A3R increased and those of A2R, CX3CR1, FKN, NR2A, and NR2B decreased.

Conclusion

In the diabetic state, the binding of FKN to CX3CR1 increases, which regulates a variety of adenosine receptors. When it exerts its effect on neurons, the overactivation of NR results in neuronal injury and causes depression.

Structures, evolutionary relationships and expression profiles of the tumour necrosis factor superfamily and their receptors in black rockfish (Sebastes schlegelii)

Members of tumour necrosis factor superfamily (TNFSF) and TNF receptor superfamily (TNFRSF) have crucial roles in many important biological processes such as cell proliferation, cell death, development, survival, immunity, and various diseases. The human TNFSF consists of 19 ligands and 29 receptors. Compared with those in human, fish have most of the TNFSF and receptors that have been found in mammals, while some of the homologues are specific or lost in fish. Especially, no systematic report on the identification of TNFSF ligands and their receptors in S. schlegelii. Therefore, to investigate the characterization and molecular evolution of TNFSF and TNFRSF genes in Sebastes schlegelii, we performed a genome-wide survey and identified 14 TNFSFs and 24 TNFRSFs from S. schlegelii. In S. schlegelii, we found duplication events occurred in TNFSF2, TNFSF6, TNFSF10, TNFSF13, TNFSF14, TNFRSF5, TNFRSF6, TNFRSF6B, TNFRSF10B, TNFRSF16, and TNFRSF19 genes. Among which, the tandem duplications events occurred in TNFSF13 and TNFRSF6, and the whole genome duplications events occurred in the remaining TNFSF and TNFRSF genes. Based on the molecular phylogenetic analysis, 14 TNFSFs were divided into three different clusters and 24 TNFRSFs were classed as three distinct subgroups, respectively. Meanwhile, protein domains and motifs analysis revealed that TNFSF contain homology domain (THD), and TNFRSF have typical cysteine-rich domains (CRDs). Synteny results indicates that the TNFSFs and TNFRSFs neighborhood genes have taken place great changes compared to those in human, fugu and zebrafish. Meanwhile, qRT-PCR results demonstrated that most TNFSFs and TNFSRSFs were significantly differentially expressed in gill, skin and intestine after E. tarda infection with time-dependent manners. In addition, protein-protein interaction network (PPI) analysis indicated that the most related genes connecting to TNFSF and TNFRSFs were TNFSF ligands and receptors. In summary, this study provided a new understanding for characterization and evolution of the TNFSF genes and their receptors in S. schlegelii.

Identification of bioactive ingredients from Babaodan using UPLC-QTOF-MS analysis combined with network pharmacology guided bioassays

Babaodan (BBD) is a traditional Chinese medicine (TCM) prescribed for various inflammatory diseases, including viral hepatitis and acute genitourinary tract infection. Like other TCMs, BBD is a multi-component formula whose chemical composition and mode of action are largely unknown. The current study identified the bioactive ingredients of BBD using ultrahigh-performance liquid chromatography combined with quadrupole time-of-flight mass spectrometry (UPLC-QTOF-MS) followed by mass spectrometry molecular networking analysis. Subsequently, network pharmacology analysis was performed to predict the potential targets and pathways regulated by BBD. Eventually, a panel of compounds was selected and examined for their anti-inflammatory effects using lipopolysaccharide-stimulated RAW264.7 cells. Eighty-six compounds, including saponins, bile acids, and fatty acids, were identified. Tumor necrosis factor-alpha was identified as a key molecule. Pathways in cancer, inflammatory bowel disease, and hepatitis were predicted to be the major regulatory pathways. The results from bioassays validated ginsenoside Rb1, ginsenoside Rd, deoxycholic acid, chenodeoxycholic acid, and taurochenodeoxycholic acid as novel bioactive ingredients in BBD with anti-inflammatory effects. In conclusion, our study explains the anti-inflammatory efficacy of BBD from both chemical and biological aspects, which provides a scientific basis for the clinical application of BBD in inflammation-related diseases.

Dietary plant pigment on blood-digestive physiology, antioxidant-immune response, and inflammatory gene transcriptional regulation in spotted snakehead (Channa punctata) infected with Pseudomonas aeruginosa

The current study addressed to investigate the effect of lycopene (LYC) on blood physiology, digestive-antioxidant enzyme activity, specific-nonspecific immune response, and inflammatory gene transcriptional regulation (cytokines, heat shock proteins, vitellogenins) in spotted snakehead (Channa punctata) against Pseudomonas aeruginosa. In unchallenged and challenged fish treated with 200 mg LYC enriched diet the growth performance and digestive-antioxidant enzymes increased after 30 days, whereas with inclusion of 100 or 400 mg LYC in the diets, the increase manifested on or after 45 days. No mortality in fish treated with any LYC diet against P. aeruginosa was revealed. In the unchallenged and challenged fish the phagocytic (PC) activity in head kidney (HK) and spleen were significantly enhanced when fed the control diet or other LYC diets, whereas the respiratory burst (RB) activity and nitric oxide (NO) production significantly increased when fed the 200 mg diet for 45 and 60 days. Similarly, the lysozyme (Lyz) activity in the HK and spleen, and total Ig content in serum were significantly higher in both groups fed the 200 mg LYC diet for 15, 45, and 60 days. Heat shock protein (Hsp 70) was significantly improved in the uninfected group fed the 200 mg LYC diet for 45 and 60 days, but Hsp27 did not significantly change among the experimental groups at any time points. TNF-α and IL-6 mRNA pro-inflammatory cytokine expression significantly increased in both groups fed the 200 mg LYC diet after 45 and 60 days, while the IL-12 mRNA expression was moderate in both groups fed the same diet for 60 days. The IL-10 did not significant mRNA expression between groups at any sampling. The iNOS and NF-κB mRNA expression was pointedly high in both groups fed the 200 mg LYC diet on day 45 and 60. Vitellogenin A (VgA) mRNA was significantly higher in the uninfected fish fed the 100 and 200 mg LYC diets for 45 and 60 days, but VgB did not reveal significant difference between the treatment groups at any time points. The present results suggest that supplementation of LYC at 200 mg significantly modulate the blood physiology, digestive-antioxidant enzymes, specific-nonspecific immune parameters, and cytokines, Hsp, and vitellogenins in spotted snakehead against P. aeruginosa.

Do foodborne polyethylene microparticles affect the health of rainbow trout (Oncorhynchus mykiss)?

Due to the fact that plastic pollution is a global environmental problem of modern age, studies on the impact of these synthetic materials on aquatic, and especially fish organisms, are an important part of the ecosystem and human nutrition. In our study, the toxicity of pristine polyethylene (PE) microparticles (approx. 50 μm) on rainbow trout (Oncorhynchus mykiss) was tested in three different dietary concentrations - 0.5%, 2% and 5%. After six weeks of exposure, various health indices were evaluated. Electron microscopy of the intestine revealed the disintegration of PE particles to <5 μm in size, and thus we concluded that microplastics are able to reach tissues. The haematological profile revealed changes in total red blood cells count and haematocrit (5% PE) which could be associated with spleen congestion observed histologically. The marker of lipid peroxidation was increased in gills suggesting the disruption of balance in antioxidant enzymes capacity and histopathological imaging revealed inflammation in higher PE concentrations. In addition, ammonia was decreased and calcium elevated in biochemical profile, confirming the gill damage. Electron microscopy of the gills showed lesions of lamellae and visible rings around the mucinous cell opening indicating their higher activity. Another injured was the liver tissue, as confirmed by hepatodystrophies and increased expression of pro-inflammatory genes in 2% PE. Impaired innate immunity was confirmed by an increased presence of mucinous cells and a decrease in leukocytes. Kidney damage manifested itself by higher expression of pro-inflammatory cytokines and histopathology. The damage in gills, liver and kidney together correlated with the increased antioxidant capacity of plasma. In conclusion, PE microparticles are able to affect health indices of O. mykiss. The potential problem for aquatic ecosystems and even human consumption should be considered.

Functional characterization of TNF-α in pufferfish (Takifugu obscurus) in immune response and apoptosis against Aeromonas hydrophila

Tumour necrosis factor-α (TNF-α) is a multifunctional cytokine involved in immune system homeostasis, antimicrobial defence, regulation of apoptosis, cell proliferation and differentiation. Although the pro-inflammatory property of TNF-α has been made new progress, detailed research on host defence against bacterial infection and inducing apoptosis remains to be revealed in early vertebrates. Here, we reported the TNF-α homologue (ToTNF-α) from pufferfish (Takifugu obscurus). The open reading frame (ORF) of ToTNF-α was 753 bp, encoding a protein of 250 aa contained the TNF family signature and conserved cysteine residues. The mRNA expression of ToTNF-α had a wide range of tested tissues, with the highest expression in the skin. After Aeromonas hydrophila infection, the mRNA expression of ToTNF-α was significantly up-regulated both in vivo and in vitro experiments. After stimulation by recombinant protein of ToTNF-α ((r)ToTNF-α), the relative expressions of endogenous TNF-α, caspase 8, caspase 3, p53, and Bax inhibitor-1 in head kidney leucocytes were all notably up-regulated. These results showed that ToTNF-α might induce apoptosis depend on pro- and anti-apoptotic proteins at mRNA level. Moreover, flow cytometry analysis indicated that the (r)ToTNF-α can induce apoptosis of head kidney leucocytes. Taken together, these characteristics suggest that ToTNF-α can participate in immune response against A. hydrophila and induce apoptosis at mRNA and cellular level, which will help to understand the mechanism of apoptosis and immune response in teleost fish.

Cadmium exposure induces inflammation through the canonical NF-κΒ pathway in monocytes/macrophages of Channa punctatus Bloch

A vast range of research related to the toxicity of the heavy metal cadmium (Cd) has been carried out in a wide variety of fish species. However, Cd induced immunomodulation in monocytes/macrophages of Channa punctatus Bloch. has rarely been explored. The present study was designed to determine Cd induced immune response, role of NF-κB (nuclear factor kappa B) pathway and the subsequent downstream molecular responses in monocytes/macrophages of C. punctatus. Fish were sampled and acclimatized, with one group treated with cadmium chloride (CdCl₂) (1.96 mg/L) and another kept as untreated control group, both under observation for 7 days. Exposure to CdCl₂ was found to alter hematological profile of C. punctatus in addition to incurring histo-architectural damages in the HK (head kidney) and ultrastructural changes in the monocytes/macrophages. The innate immune potential was found to be significantly compromised as evident from decreased phagocytosis, intracellular killing, cell adhesion and reduced release of nitric oxide (NO) and myeloperoxidase (MPO) in Cd intoxicated group. Also Cd triggered ROS generation, reduced cellular NO levels by forming peroxynitrite along with the upregulated expression of the inflammatory marker iNOS (inducible nitric oxide synthase) in monocytes/macrophages, both at mRNA and protein levels, indicating inflammation. Inflammation is further verified from the upregulated expression of proinflammatory cytokines viz. TNF-α, IL-1β, IL-6, IL-12 along with a central inflammatory mediator NF-κΒ and downregulation of the anti-inflammatory cytokine IL-10, both at mRNA and protein levels. It can be concluded that, a sub-lethal exposure of Cd in C. punctatus for 7 days caused significant alterations in the hematological, histological and ultrastructural profile in monocytes/macrophages; impaired innate immune parameters, triggers ROS generation and inflammation as validated from the upregulated expression of NF-κΒ, iNOS, TNF-α, IL-1β, IL-6, IL-12 and IL-10 downregulation.

Interleukin-1 Ligands and Receptors in Lumpfish (Cyclopterus lumpus L.): Molecular Characterization, Phylogeny, Gene Expression, and Transcriptome Analyses

The interleukin (IL)-1 family play a fundamental role as immune system modulators. Our previous transcriptome-analyses of leukocytes from lumpfish (Cyclopterus lumpus L.) showed that IL-1β was among the most highly upregulated genes following bacterial exposure. In the present study, we characterized IL-1 signaling pathways, identified and characterized four ligands of the IL-1 family in lumpfish; IL-1β type I and type II, IL-18, and the novel IL-1 family members (nIL-1F), both at mRNA and gene levels. The two IL-1β in lumpfish is termed IL-1β1 (type II) and IL-1β2 (type I). Furthermore, a comprehensive phylogenetic analysis of 277 IL-1 ligands showed that nIL-1F, in common with IL-1β, likely represents an ancestral gene, as representatives for nIL-1F were found in cartilaginous and lobe-finned fish, in addition to teleosts. This shows that nIL-1F is not exclusively present in teleosts as previously suggested. Our analyses of exon-intron structures, intron phases, phylogeny and synteny clearly show the separation of IL-1β into groups; type I and type II, which likely is a result of the third whole genome duplication (3R WGD). The phylogenetic analysis shows that most teleosts have both type I and type II. Furthermore, we have determined transcription levels of the IL-1 ligands in leukocytes and 16 different tissues, and their responses upon in vitro stimulation with seven different ligands. In addition, we have identified the IL-1 receptors IL-1R1, IL-1R2, IL-1R4 (ST2/IL-33 receptor/IL-1RL), IL-1R5 (IL-18R1), and partial sequences of DIGIRR and IL-1R3 (IL-RAcP). Identification of immune molecules and description of innate responses in lumpfish is interesting for comparative and evolutionary studies and our study constitutes a solid basis for further functional analyses of IL-1 ligands and receptors in lumpfish. Furthermore, since lumpfish are now farmed in large numbers to be used as cleaner fish for removal of sea lice on farmed salmon, in-depth knowledge of key immune molecules, signaling pathways and innate immune responses is needed, as the basis for design of efficient immune prophylactic measures such as vaccination.