Hypoxic stress: impact on the modulation of TLR2, TLR4, NOD1 and NOD2 receptor and their down-stream signalling genes expression in catla (Catla catla)

Molecular Identification and Expression Analysis of NOD1/2 and TBK1 in Response to Viral or Bacterial Infection in the Spotted Knifejaw (Oplegnathus punctatus)

This study investigates the role of the Opnod1, Opnod2, and Optbk1 genes in antiviral and antibacterial immunity of spotted knifejaw (Oplegnathus punctatus). The expression patterns of these genes were analyzed using qRT-PCR in different tissues and at different time points. The open reading frame (ORF) of the Opnod1 gene was 2757 bp in length and encoded 918 amino acids, the ORF of the Opnod2 gene was 2970 bp in length and encoded 990 amino acids, while the Optbk1 gene was 2172 bp in length and encoded 723 amino acids. The Opnod1 and Opnod2 proteins contained three conserved domains (CARD, NOD, and LRR), and Optbk1 contained an STKc domain. The Opnod1, Opnod2, and Optbk1 genes were mainly expressed in immune-related tissues of spotted knifejaw, with the highest relative expression of the Opnod1 in the skin, the Opnod2 in the gill, and the Optbk1 in the liver. The expression of these genes changed significantly in the immune tissues following infection with SKIV-SD and Vibrio harveyi. In kidney cells, the Opnod1, Opnod2, and Optbk1 expression was up-regulated after stimulation by poly I:C and LPS in vitro. The results suggest that the NOD1/2-TBK1 signal pathway may play an important role in the resistance of the spotted knifejaw to virus and bacteria, providing valuable insights for disease-resistant breeding.

Chronic hypoxia has differential effects on constitutive and antigen-stimulated immune function in Atlantic salmon (Salmo salar)

Chronic hypoxia events are a common occurrence in Atlantic salmon (Salmo salar) sea-cages, especially during the summer, and their frequency and severity are predicted to increase with climate change. Although hypoxia is considered a very important fish health and welfare issue by the aquaculture industry, few studies have investigated the impact of chronic hypoxia on the fish immune system and its response to pathogen exposure. We exposed post-smolt Atlantic salmon to hypoxia (40% air sat.) for 6 weeks. Thereafter, we sampled fish prior to (i.e., at Time 0, to assess constitutive immune function), and after they were intraperitoneally injected with PBS (phosphate buffered saline) or formalin-killed Aeromonas salmonicida. We measured several innate immune parameters including: hematological immune responses [respiratory burst (RB), hemolytic activity of alternate complement system and plasma lysozyme concentration], and the relative percentage of circulating blood cells (erythrocytes/immature erythrocytes, monocytes, and granulocytes and lymphocytes) at Time 0 and at 24 hours post-injection (hpi); and the transcript expression levels of 8 anti-bacterial biomarkers in the head kidney [interleukin-1 beta (il1b), interleukin-8a (il8a), cyclooxygenase-2 (cox2), toll-like receptor 5, secreted (strl5), CC chemokine-like 19b (ccl19b), serum amyloid A5 (saa5), hepcidin anti-microbial peptide a (hampa) and cathelicidin anti-microbial peptide b (campb)] at Time 0 and at 6 and 24 hpi. In addition, we measured serum immunoglobulin (IgM) levels at Time 0 and at 8 weeks post-injection (4 weeks after a 'boost' injection). Fish exposed to chronic hypoxia had greater numbers of monocytes, which was consistent with the increase in RB, plasma lysozyme concentration and upregulated head kidney anti-bacterial gene expression (i.e., campb, ccl19b, hampa, il8a, stlr5). In contrast, chronic hypoxia: reduced RB and leukocyte numbers at 24 hpi in Asal compared to PBS-injected fish, and the transcript levels of campb, il1b, saa5, il8a and stlr5 at 6- and/or 24- hpi; but had no effect on constitutive or post-stimulation serum IgM titers. Overall, our results indicate that chronic hypoxia has differential effects on salmon constitutive innate immune function vs. following antigen exposure, and thus, it is still unclear how chronic hypoxia will impact the capacity of fish to defend against pathogens.

Integration of physiological, miRNA-mRNA interaction and functional analysis reveals the molecular mechanism underlying hypoxia stress tolerance in crucian carp (Carassius auratus)

Hypoxia has become one of the most critical factors limiting the development of aquaculture. Crucian carp (Carassius auratus) is widely consumed fish in China, with excellent tolerance to hypoxic environment. However, the molecular mechanisms underlying hypoxia adaptation and tolerance in crucian carp remain unclear. Compared with the control, increased T-SOD, CAT, GSH-Px, T-AOC, ALT, and AST activities and MDA, TCHO, and TG contents, and decreased TP and ATP contents were observed after hypoxia stress. Based on RNA-seq, 2479 differentially expressed (DE) mRNAs and 60 DE miRNAs were identified, and numerous DE mRNAs involved in HIF signaling pathway (hif-1α, epo, vegfa, and ho), anaerobic metabolism (hk1/hk2, pfk, gapdh, pk, and ldh) and immune response (nlrp12, cxcr1, cxcr4, ccr9, and cxcl12) were significantly upregulated after hypoxia exposure. Integrated analysis found that ho, igfbp1, hsp70, and hk2 were predicted to be regulated by novel_867, dre-miR-125c-3p/novel_173, dre-miR-181b-5p, and dre-miR-338-5p/dre-miR-17a-3p, respectively, and targets of DE miRNAs were significantly enriched in MAPK signaling pathway, FoxO signaling pathway, and glycolysis/gluconeogenesis. Expression analysis showed that the mRNA levels of vegfa, epo, ho, hsp70, hsp90aa.1, igfbp1, ldh, hk1, pfk, pk, and gapdh exhibited a remarkable increase, whereas sdh and mdh were downregulated in the H3h, H12h, and H24h groups compared with the control. Furthermore, research found that hk2 is a target of dre-miR-17a-3p, overexpression of dre-miR-17a-3p significantly decreased the expression level of hk2, while the opposite results were obtained after dre-miR-17a-3p silencing. These results contribute to our understanding of the molecular mechanisms of hypoxia tolerance in crucian carp.

Beneficiary Effects of Colchicine on Inflammation and Fibrosis in a Mouse Model of Kidney Injury

INTRODUCTION

Low-grade inflammation is seen in many chronic illnesses, including chronic kidney disease (CKD). We have recently reported on beneficiary effects of anti-inflammatory treatment in the interleukin (IL-) 1 pathway on anemia as well as CKD extent in a mouse model. Colchicine has been shown to have beneficiary effects in several inflammatory conditions through various mechanisms, including inhibition of tubulin polymerization as well as caspase-1-mediated IL-1 activation.

METHODS

Kidney injury (KI) was induced by administering an adenine diet to 8-week-old C57BL/6J mice treated with colchicine (Col) (30 µg/kg) or saline injections for 3 weeks, generating 4 groups: C, Ccol, KI, and KIcol.

RESULTS

KI animals had an increase in inflammation indices in the blood (neutrophils), liver, and kidneys (uromodulin, IL-6, pSTAT3). Increased kidney tubulin polymerization and caspase-1 in KI, as well as kidney Mid88 and IRAK4 (downstream of IL-1), were inhibited in KIcol. Kidney macrophage and polymorphonuclear infiltration (positive for F4/80 and MPO, respectively), the percentage of fibrotic area, and TGFβ mRNA levels were lower in KIcol versus KI.

CONCLUSIONS

Colchicine inhibited tubulin polymerization and caspase-1 activation and attenuated kidney inflammation and fibrosis in a mouse model of adenine-induced KI. Given its reported safety profile for long-term anti-inflammatory therapy without increasing infection tendency, it may serve as novel therapeutic approach in CKD.

The bibenzyl derivatives of Dendrobium officinale prevent UV-B irradiation induced photoaging via SIRT3

Dendrobium officinale is a valuable medicinal herb that is widely used in traditional Chinese medicine. The chemical constituents of D. officinale have attracted much attention and a large number of compounds have been reported including many bibenzyl derivatives. 13 bibenzyl derivatives from D. officinale were sent for molecular docking, surface plasmon resonance (SPR) assay and after detection of Mn-SOD and SIRT3 activities in or not in HaCaT cells, it was concluded that bibenzyl derivatives did not directly activate Mn-SOD but promoted SIRT3 proteins. In addition, HaCaT cells were irradiated with UV-B to induce an oxidative stress model in vitro to further verify the effect of bibenzyl derivatives. The results show that bibenzyl derivatives could directly bind to SIRT3, enhance the deacetylation and then activate Mn-SOD, so as to protect UV-B induced skin photoaging.

Transcriptome profiling reveals differential expression of immune-related genes in gills of hybrid yellow catfish (Tachysurus fulvidraco ♀ × Pseudobagrus vachellii ♂) under hypoxic stress: Potential NLR-mediated immune response

Fish gills are the primary organ that respond to sudden changes in the dissolved oxygen (DO) level in the aquatic environment. Hypoxic stress impairs the normal function of gill tissues. However, little is known about the mechanisms of the response of yellow catfish gills to hypoxic stress. In this study, we compared transcriptomic and physiological changes in gill tissues of hybrid yellow catfish (Tachysurus fulvidraco ♀ × Pseudobagrus vachellii ♂) between a hypoxia-treated group (DO: 1.5 mg/L) and a control group (DO: 6.5 mg/L). In fish in the hypoxia-treated group, gill filaments underwent adaptive changes, and the number of vacuoles in gill tissues increased. Exposure to hypoxic conditions for 96 h resulted in increased anaerobic metabolism and decreased antioxidant and immune capacity in gill tissues. Transcriptome analyses revealed 1556 differentially expressed genes, including 316 up-regulated and 1240 down-regulated genes, between fish in the hypoxia-treated and control groups. Functional analyses indicated that the main pathway enriched with differentially expressed genes was immune response, followed by energy metabolism and signal transduction. Under hypoxic stress, the transcript levels of genes involved in the NOD-like receptor signaling pathway initially increased rapidly but then decreased over time, suggesting that the NOD-like receptor-mediated immune response plays an essential role in hypoxia tolerance and resistance in hybrid yellow catfish. Our results provide novel insights into which immune-related genes and pathways are activated under hypoxic stress, and reveal details of early adaptation of the immune response and defense mechanisms under hypoxic stress.

Blood Will Tell: What Hematological Analyses Can Reveal About Fish Welfare

Blood analyses provide substantial information about the physiological aspects of animal welfare assessment, including the activation status of the neuroendocrine and immune system, acute and long-term impacts due to adverse husbandry conditions, potential diseases, and genetic predispositions. However, fish blood is still not routinely analyzed in research or aquaculture for the assessment of health and/or welfare. Over the years, the investigative techniques have evolved from antibody-based or PCR-based single-parameter analyses to now include transcriptomic, metabolomic, and proteomic approaches and from hematological observations to fluorescence-activated blood cell sorting in high-throughput modes. The range of testing techniques established for blood is now broader than for any other biogenic test material. Evaluation of the particular characteristics of fish blood, such as its cell composition, the nucleation of distinct blood cells, or the multiple isoforms of certain immune factors, requires adapted protocols and careful attention to the experimental designs and interpretation of the data. Analyses of fish blood can provide an integrated picture of the endocrine, immunological, reproductive, and genetic functions under defined environmental conditions and treatments. Therefore, the scarcity of high-throughput approaches using fish blood as a test material for fish physiology studies is surprising. This review summarizes the wide range of techniques that allow monitoring of informative fish blood parameters that are modulated by different stressors, conditions, and/or treatments. We provide a compact overview of several simple plasma tests and of multiparametric analyses of fish blood, and we discuss their potential use in the assessment of fish welfare and pathologies.

Genome-wide identification of NOD-like receptors and their expression profiling in mucosal tissues of turbot (Scophthalmus maximus L.) upon bacteria challenge

The innate immune system plays an important role in host defense against pathogenic infections. In the innate immune system, several families of innate pattern recognition receptors, including Toll-like receptors, RIG-I-like receptors, NOD-like receptors (NLRs), and DNA receptors (cytosolic sensors for DNA), are known to play vital roles in detecting and responding to various pathogens. In this study, we identified 29 NLRs in turbot including 4 NLRs from subfamily A: NOD1, NOD2, CIITA, NLRC5, 1 NLR from subfamily B: NLRB1, 21 NLRs from subfamily C: NLR-C3.1∼NLRC3.21, 1 from NLRX subfamily, and two that do not fall within these subfamilies: APAF1, NWD1. Phylogenetic analysis showed that these NLR genes were clearly divided into five subfamilies. Protein-protein interaction network analysis showed that some of these NLR genes shared same interacting genes and might participate in signal transductions associated with immunity. The evolutionary pressure selection analysis showed that the Ka/Ks ratios for all detected NLR genes were much less than one, implying more synonymous changes than non-synonymous changes. In addition, tissue expression analysis showed that the relative higher expression levels were observed in gill, skin and intestine. Meanwhile, NLR genes expression after bacterial infection results showed that most NLR genes participated in the process of defense of V. anguillarum and A. salmonicida infections in mucosal tissues. Taken together, identification and expression profiling analysis of NLR genes can provide valuable information for further functional characterization of these genes in turbot.

Neutrophil Extracellular Traps (NETs) and Damage-Associated Molecular Patterns (DAMPs): Two Potential Targets for COVID-19 Treatment

COVID-19 is a pandemic disease caused by the new coronavirus SARS-CoV-2 that mostly affects the respiratory system. The consequent inflammation is not able to clear viruses. The persistent excessive inflammatory response can build up a clinical picture that is very difficult to manage and potentially fatal. Modulating the immune response plays a key role in fighting the disease. One of the main defence systems is the activation of neutrophils that release neutrophil extracellular traps (NETs) under the stimulus of autophagy. Various molecules can induce NETosis and autophagy; some potent activators are damage-associated molecular patterns (DAMPs) and, in particular, the high-mobility group box 1 (HMGB1). This molecule is released by damaged lung cells and can induce a robust innate immunity response. The increase in HMGB1 and NETosis could lead to sustained inflammation due to SARS-CoV-2 infection. Therefore, blocking these molecules might be useful in COVID-19 treatment and should be further studied in the context of targeted therapy.

Isolation and characterization of hypoxia inducible heme oxygenase 1 (HMOX1) gene in Labeo rohita

The HMOX1 gene plays role in several biological processes and is also responsive to hypoxia stress. Freshwater carp fish, Labeo rohita, is reported as hypoxia sensitive, but the information of annotated hypoxia genes in public domain is very scanty for this species. Here, an attempt was made to isolate and characterize HMOX1 gene in L. rohita using information from zebrafish. HMOX1 gene was obtained by mapping HMOX1 protein of zebrafish over assembled genome of L. rohita. Aligned region was used for designing primers for HMOX1 amplification. Eight overlapping sets of primers were designed for amplifying ~540 bp long successive overlapping fragments. Splicing of overlapping amplicons generated 3715 bp fragment that was confirmed as HMOX1 gene having full coding region with 6 exons between 184 and 2156 bp positions. HMOX1 characterization is an initiative for L. rohita genes annotation to support the characterization of new genes in the important species.

Dietary resveratrol supplementation inhibits heat stress-induced high-activated innate immunity and inflammatory response in spleen of yellow-feather broilers

The aim of this study was to investigate the effect of dietary resveratrol supplementation on innate immunity and inflammatory responses in the spleen of yellow-feather broilers under heat stress. A total of 288 yellow-feather broilers of 28-day-old were randomly assigned to 3 treatment groups with 6 replicates. A thermo-neutral group (TN) (24 ± 2°C) received a basal diet and another 2 heat-stressed groups (37 ± 2°C for 8 h/D and 24 ± 2°C for the remaining time) were fed the basal diet (HT) or basal diet with 500 mg/kg resveratrol (HT+Res) for 14 consecutive days. The results showed that heat stress decreased (P < 0.05) the growth index of thymus, spleen, and bursa of Fabricius, reduced (P < 0.05) the levels of complement C3 and C4 in serum. Heat stress also caused activation of inflammatory immune responses evidenced by increased (P < 0.05) the mRNA abundance of HSP (heat shock protein) 70, toll-like receptor (TLR)1, TLR4, TLR5, myeloid differentiation factor-88 (MyD88), nucleotide-binding oligomerization domain 1 (NOD1), Dectin-1, transforming growth factor-β-activated kinase 1 (TAK1), interleukin (IL)-1, IL-4, IL-6, and tumor necrosis factor (TNF)-α, but decreased the mRNA abundance of interferon (IFN)-γ, activated nuclear factor kappa B (NF-κB), mitogen-activated protein kinases (MAPK), and phosphoinositide-3 kinases-protein kinase B (PI3K/AKT) signaling pathways. Dietary supplementation with resveratrol improved (P < 0.05) the growth index of thymus, spleen and bursa Fabricius, and increased (P < 0.05) the serum level of complement C3 under heat stress. In addition, resveratrol reduced (P < 0.05) the mRNA abundance of HSP70, TLR4, TLR5, NOD1, Dectin-1, and TAK1, and inhibited the NF-κB, MAPK and PI3K/AKT signaling pathway via down-regulated the phosphorylation of p65, extracellular signal-regulated kinases 1/2, c-Jun N-terminal protein kinase and AKT, as well as decreased the inflammatory cytokines expression, including IL-1, IL-4, IL-6, and TNF-α in the spleen under heat stress. Collectively, dietary resveratrol could have beneficial effects to regulate innate immunity and inflammatory response, via inhibiting the activation of NF-κB, MAPK, and PI3K/AKT signaling pathways induced by heat stress in the spleen.

Stocking density induces differential expression of immune-related genes in skeletal muscle and head kidney of fine flounder (Paralichthys adspersus)

Immunity can be modulated by different internal and external factors, being stress one of the most important. However, the stress effects on the immunocompetence of the skeletal muscle has not been studied in detail in earlier vertebrates. Here, we examine the effect of chronic (4 and 7 weeks) crowding stress on the immunocompetence of skeletal muscle and head kidney in the fine flounder (Paralichthys adspersus). Corticosteroid receptor transcript levels and their target genes; pro-inflammatory cytokines, and Toll-, NOD-, and RIG-like receptors were quantified by qPCR. The results indicate that chronic stress down-regulates the expression of these genes in muscle, compromising skeletal muscle immunocompetence, while the expression of these genes is upregulated in head kidney after seven weeks of crowding stress. The data suggests that chronic stress modulates the expression of these immune-related genes in a tissue-specific manner.

Isolation and characterization of hypoxia inducible gene connective tissue growth factor (CTGF) in Labeo rohita

The connective tissue growth factor gene plays important role in several biological processes and also responsive to hypoxia stress in fishes. The freshwater fish, Labeo rohita, highly cultured in Indian subcontinent for food, is reported as hypoxia sensitive but annotation and sequences of nuclear genes were not available for this species so far in the public domain, except some transcripts. In this study, an attempt was made for isolation and annotation of the CTGF gene in L. rohita using information of zebrafish from the same family. The CTGF gene sequence was obtained by aligning assembled genome of L. rohita, (NCBI BioProject ID: PRJNA437789), with the CTGF protein of zebrafish. Eight overlapping sets of forward and reverse primers from aligned region were designed for amplification of around 600 bp long successive overlapping fragments of CTGF gene in L. rohita. Assembly and annotation of overlapping fragments confirmed a complete 2421 bp long CTGF gene sequence with a full coding region that comprised of five exons between 308 and 1921 positions. This annotated CTGF gene sequence was submitted to GenBank (Acc. No. KY940466). Characterization of CTGF will be an initiative in identification of hypoxia response genes in L. rohita which may further help in understanding the mechanism of hypoxia tolerability in this species.

Involvement of ayu NOD2 in NF-κB and MAPK signaling pathways: Insights into functional conservation of NOD2 in antibacterial innate immunity

Nucleotide oligomerization domain 2 (NOD2) is a major cytoplasmic sensor for pathogens and is critical for the clearance of cytosolic bacteria in mammals. However, studies regarding NOD2, especially the initiated signaling pathways, are scarce in teleost species. In this study, we identified a NOD2 molecule (PaNOD2) from ayu (Plecoglossus altivelis). Bioinformatics analysis showed the structure of NOD2 to be highly conserved during vertebrate evolution. Dual-luciferase reporter assays examined the activation of NF-κB signaling and Western blotting analysis detected the phosphorylation of three MAP kinases (p-38, Erk1/2, and JNK1/2). Functional study revealed that, like its mammalian counterparts, PaNOD2 was the receptor of the bacterial cell wall component muramyl dipeptide (MDP), and the leucine-rich repeat motif was responsible for the recognition and binding of PaNOD2 with the ligand. Overexpression of PaNOD2 activated the NF-κB signaling pathway, leading to the upregulation of inflammatory cytokines, including TNF-α and IL-1β in HEK293T cells and ayu head kidney-derived monocytes/macrophages (MO/MΦ). Particularly, we found that PaNOD2 activated the MAPK signaling pathways, as indicated by the increased phosphorylation of p-38, Erk1/2, and JNK1/2, which have not been characterized in any teleost species previously. Our findings proved that the NOD2 molecule and initiated pathways are conserved between mammals and ayu. Therefore, ayu could be used as an animal model to investigate NOD2-based diseases and therapeutic applications.

Mutual Regulation of NOD2 and RIG-I in Zebrafish Provides Insights into the Coordination between Innate Antibacterial and Antiviral Signaling Pathways

Nucleotide-binding oligomerization domain-containing protein 2 (NOD2) and retinoic acid-inducible gene I (RIG-I) are two important cytosolic pattern recognition receptors (PRRs) in the recognition of pathogen-associated molecular patterns (PAMPs), initiating innate antibacterial and antiviral signaling pathways. However, the relationship between these PRRs, especially in teleost fish models, is rarely reported. In this article, we describe the mutual regulation of zebrafish NOD2 (DrNOD2) and RIG-I (DrRIG-I) in innate immune responses. Luciferase assays were conducted to determine the activation of NF-κB and interferon signaling. Morpholino-mediated knockdown and mRNA-mediated rescue were performed to further confirm the regulatory roles between DrNOD2 and DrRIG-I. Results showed that DrNOD2 and DrRIG-I shared conserved structural hallmarks with their mammalian counterparts, and activated DrRIG-I signaling can induce DrNOD2 production. Surprisingly, DrNOD2-initiated signaling can also induce DrRIG-I expression, indicating that a mutual regulatory mechanism may exist between them. Studies conducted using HEK293T cells and zebrafish embryos showed that DrRIG-I could negatively regulate DrNOD2-activated NF-κB signaling, and DrNOD2 could inhibit DrRIG-I-induced IFN signaling. Moreover, knocking down DrRIG-I expression by morpholino could enhance DrNOD2-initiated NF-κB activation, and vice versa, which could be rescued by their corresponding mRNAs. Results revealed a mutual feedback regulatory mechanism underlying NOD2 and RIG-I signaling pathways in teleosts. This mechanism reflects the coordination between cytosolic antibacterial and antiviral PRRs in the complex network of innate immunity.