Head Kidney Tissues Research Articles

Temporal Dynamics of Immune Response Signalling in Largemouth Bass (Micropterus salmoides) Infected With Largemouth Bass Virus.

The largemouth bass virus (LMBV) significantly impacts Chinese largemouth bass aquaculture. The molecular mechanisms regulating LMBV virulence and the gene responses stimulated in the host during infection remain unclear. This study investigates the transcriptional dynamics and signalling pathways activated during the immune response to LMBV by analysing the transcriptome of head kidney tissues at 1, 4, 7, and 28 days post-infection (dpi) using RNA sequencing. Histopathological and viral load analyses indicated early tissue disruption, followed by extensive recovery by 28 dpi. Analysis of differentially expressed genes (DEGs) and weighted gene co-expression network analysis (WGCNA), combined with Venn analysis of samples at 1, 4, and 7 dpi, identified significant and common genes. Early infection triggered robust innate immunity through activation of the RIG-I like receptor and cGAS-STING signalling pathways, which activated type I interferons (IFNs) and interferon-stimulated genes (ISGs). Later stages indicated activation of adaptive immune responses. Validation of randomly selected genes via RT-qPCR confirmed the RNA-seq results, showing consistent expression patterns. This comprehensive study offers new insights into the sustained innate and adaptive immune responses to LMBV.

Immunoglobulin M response in largemouth bass (Micropterus salmoides) following ranavirus infection

Immunoglobulin M (IgM) and IgM+ B cells are key components of the humoral immune system, providing defense against pathogen invasion. While the role of IgM in the systemic and mucosal immune responses of fish to parasites and bacteria has been partially investigated, its function in viral infections remains underexplored. This study successfully developed a largemouth bass (Micropterus salmoides) model for ranavirus immersion infection. Our findings revealed that viral infection caused significant pathological changes in the gill and head kidney tissues, along with a marked upregulation of adaptive immune gene expression. Interestingly, fish that survived an initial viral infection exhibited minimal mortality and low viral loads in the gill and head kidney tissues when exposed to a higher viral concentration. Notably, in these fish with secondary infections, there was a significant increase in IgM protein levels in both the blood and gill mucus, as well as a pronounced accumulation of IgM+ B cells in the gill and head kidney tissues. Additionally, the serum contained high levels of virus-specific IgM, which demonstrated the ability to neutralize the virus. These findings highlight the crucial role of IgM in the immune response to viral infections in largemouth bass and suggest its potential as a target for enhancing viral resistance in aquaculture.

Generation of IgM+ B cell-deficient Atlantic salmon (Salmo salar) by CRISPR/Cas9-mediated IgM knockout

Infectious diseases pose significant challenges to Norwegian Atlantic salmon aquaculture. Vaccines are critical for disease prevention; however, a deeper understanding of the immune system is essential to improve vaccine efficacy. Immunoglobulin M (IgM) is the main antibody involved in the systemic immune response of teleosts, including Atlantic salmon. In this study, we used CRISPR/Cas9 technology to knock out the two IgM genes in Atlantic salmon. High-throughput sequencing revealed an average mutagenesis efficiency of 97% across both loci, with a predominance of frameshift mutations (78%). Gene expression analyses demonstrated significantly reduced membrane-bound IgM mRNA levels in head kidney and spleen tissues. Flow cytometry revealed a 78% reduction in IgM+ B cells in peripheral blood, and Western blot analyses showed decreased IgM protein levels in serum. Notably, an upregulation of IgT mRNA was observed, suggesting a potential compensatory mechanism. This work presents the first application of CRISPR/Cas9 to disrupt an immune-related gene in the F0 generation of Atlantic salmon, and lays the foundation for generating a model completely lacking IgM+ B cells which can be used to study the role of B cells and antibodies. This study has implications for advancing immune research in teleosts and for developing strategies to improve salmon health and welfare in aquaculture.

Uncovering the chromatin-mediated transcriptional regulatory network governing cold stress responses in fish immune cells.

Temperature fluctuations challenge ectothermic species, particularly tropical fish dependent on external temperatures for physiological regulation. However, the molecular mechanisms through which low-temperature stress impacts immune responses in these species, especially in relation to chromatin accessibility and epigenetic regulation, remain poorly understood. In this study, we investigate chromatin and transcriptional changes in the head kidney and thymus tissues of Nile tilapia (Oreochromis niloticus), a tropical fish of significant economic importance, under cold stress. By analyzing cis-regulatory elements in open chromatin regions and their associated transcription factors (TFs), we construct a comprehensive transcriptional regulatory network (TRN) governing immune responses, including DNA damage-induced apoptosis. Our analysis identifies 119 TFs within the TRN, with Stat1 emerging as a central hub exhibiting distinct binding dynamics under cold stress, as revealed by footprint analysis. Overexpression of Stat1 in immune cells leads to apoptosis and increases the expression of apoptosis-related genes, many of which contain Stat1 binding sites in their regulatory regions, emphasizing its critical role in immune cell survival during cold stress. These results provide insights into the transcriptional and epigenetic regulation of immune responses to cold stress in tilapia and highlight Stat1 as a promising target for enhancing cold tolerance in tropical fish species.

Determination of Stable Reference Genes for Gene Expression Analysis in Black Rockfish (Sebastes schlegeli) Under Hypoxia Stress.

Hypoxia triggers stress, leading to significant alterations in gene expression patterns, which in turn affect fish's growth and development. Real-time quantitative PCR (RT-qPCR) is a pivotal technique for assessing changes in gene expression. However, its accuracy is highly contingent upon the stable expression of reference genes. Ribosomal RNA (18s), β-actin (actb), elongation factor 1-α (ef1a), α tubulin (tuba), and ribosomal protein L17 (rpl17) are the widely used reference genes, but their expression stability in the tissues of black rockfish under hypoxic conditions remains unclear. The expression of genes was detected by RT-qPCR and the stability was assessed by Delta Ct, geNorm, NormFinder, and BestKeeper algorithms. Results showed that tuba exhibited stable expression in liver, heart, gill tissues under normoxic conditions, and in the liver and head kidney under hypoxic conditions. Ef1a was identified as the most stably expressed gene in gill tissue under hypoxia. For hypoxic heart studies, rpl17 and tuba were recommended as reference genes. 18s showed high stability in spleen tissue under hypoxic conditions. Actb was the most stably expressed gene in spleen and head kidney tissues under normoxic conditions. The identified reference genes exhibited tissue-specific stability, and it was necessary to select appropriate reference genes based on the specific tissue type for gene expression studies under hypoxic conditions. These findings help in enhancing the accuracy of gene expression analysis in the mechanism of hypoxia for black rockfish.

Unravelling turbot (Scophthalmus maximus) resistance to Aeromonas salmonicida: transcriptomic insights from two full-sibling families with divergent susceptibility.

Furunculosis, caused by the gram-negative bacterium Aeromonas salmonicida subsp. salmonicida, remains a significant threat to turbot (Scophthalmus maximus) aquaculture. Identifying genetic backgrounds with enhanced disease resistance is critical for improving aquaculture health management, reducing antibiotic dependency, and mitigating economic losses. In this study, five full-sibling turbot families were challenged with A. salmonicida, which revealed one family with significantly greater resistance. Transcriptomic analyses (RNA-Seq) were performed on resistant and susceptible families, examining both naïve and 24-h postinfection (hpi) samples from head kidney and liver tissues. In the absence of infection, differentially expressed genes (DEGs) were identified predominantly in the liver. Following infection, a marked increase in DEGs was observed in the head kidney, with many genes linked to immune functions. Interestingly, the resistant family displayed a more controlled inflammatory response and upregulation of genes related to antigen presentation and T-cell activity in the head kidney at early infection stages, which may have contributed to its increased survival rate. In the liver, transcriptomic differences between the families were associated mainly with cytoskeletal organization, cell cycle regulation, and metabolic processes, including insulin signalling and lipid metabolism, regardless of infection status. Additionally, many DEGs overlapped with previously identified quantitative trait loci (QTLs) associated with resistance to A. salmonicida, providing further insights into the genetic basis of disease resistance. This study represents the first RNA-Seq analysis comparing resistant and susceptible turbot families and contributes valuable knowledge for the development of selective breeding programs targeting disease resistance in turbot and other aquaculture species susceptible to A. salmonicida.

Immunological Responses, Expression of Immune-Related Genes, and Disease Resistance of Rainbow Trout (Oncorhynchus mykiss) Fed Diets Supplied with Capsicum (Capsicum annuum) Oleoresin.

A 45-day feeding study was carried out to assess the immune-stimulatory effects of capsicum oleoresin when added to rainbow trout diets. A total of 450 fish (mean weight: 155.20 ± 1.96 g) were distributed into 400 L tanks (30 fish/tank) across five experimental groups: control (CT, 0%), C7 (0.7%), C14 (1.4%), C21 (2.1%), and C28 (2.8%). Each group consisted of three replicate tanks. At the end of this period, hemato-biochemical parameters, innate immune responses, and immune-related gene expression levels were evaluated, and a histological examination of head kidney and liver sections was conducted. Finally, fish in all groups were challenged with Lactococcus garvieae and observed for an additional 20 days. The results revealed that oleoresin supplementation enhanced the immune responses of the treated fish, which was evidenced by the increased globulin, total protein, respiratory burst activity, and total immunoglobulin levels. The highest expression levels of the il-8, il-1β, TGF-β, and SAA genes was noticed in the C7 group, as compared with the results for the other groups. The IgT gene expression levels were higher in all experimental groups than in the CT group, and this increase was at the highest level in the C28 group. Following the bacterial challenge, all experimental groups displayed higher survival rates compared to that of the CT group. These values were 75.93, 72.22, 46.30, 33.33, and 29.63% in the C7, C14, C21, C28, and CT groups, respectively, with the C7 group displaying the highest survival rate among the groups. The histological examination of liver and head kidney tissues revealed that higher doses (in the C21 and C28 groups) showed an increase in cytoplasmic vacuolization, which causes adverse effects on fish health. However, the C7 group displayed normal histological structure in both tissues. Taken together, the most favorable immune responses were achieved in the C7 group, suggesting that 0.7% oleoresin could be applied to rainbow trout to boost immunity and protect the fish from diseases.

Functional characterization of peroxiredoxin 5 from yellowtail clownfish (Amphiprion clarkii): Immunological expression assessment, antioxidant activities, heavy metal detoxification, and nitrosative stress mitigation

Peroxiredoxin 5 (Prdx5) is the last recognized member of Prdx family. It is a unique, atypical, 2-Cys antioxidant enzyme, protecting cells from death caused by reactive oxygen species (ROS). In this study, the Prdx5 ortholog of Amphiprion clarkii (AcPrdx5) was identified and characterized to explore its specific structural features and functional properties. The open reading frame of AcPrdx5 is 573 bp long and encodes 190 amino acids containing a mitochondrial targeting sequence, thioredoxin domain, and two conserved cysteine residues responsible for antioxidant function. The predicted molecular weight and theoretical isoelectric point of AcPrdx5 are 20.3 kDa and 9.01, respectively. AcPrdx5 sequences were found to be highly conserved across the other orthologs from various organisms and it distinctively clustered within the fish Prdx5 subclade of the phylogenetic tree. The expression of AcPrdx5 was ubiquitously detected among twelve tested tissues, with the highest level in the brain. Furthermore, the mRNA levels of AcPrdx5 in the blood and head-kidney tissues were significantly (p < 0.05) upregulated following polyinosinic-polycytidylic acid (Poly I:C), lipopolysaccharide (LPS), and Vibrio harveyi immune challenge. A concentration-dependent antioxidant potential of recombinant AcPrdx5 was observed in insulin disulfide bond reduction, heavy metal detoxification, free radical and hydrogen peroxide (H2O2) scavenging assays. Additionally, AcPrdx5 overexpression in fathead minnow (FHM) cells upregulated the antioxidant-associated gene (Rrm1, MAPK, SOD2, and PRDX1) expression after H2O2 treatment, and promoted cell viability upon arsenic (As) exposure. In macrophages, AcPrdx5 overexpression effectively suppressed substantial nitric oxide production under lipopolysaccharide treatment. Collectively, our results suggest that AcPrdx5 may play roles in both antioxidant defense system and innate immune response against pathogenic invasions in A. clarkii.

Immune Response and Transcriptome Analysis of the Head Kidney to Different Concentrations of Aeromonas veronii in Common Carp (Cyprinus carpio).

The common carp (Cyprinus carpio), a major economic freshwater fish, is suffering from a variety of bacterial infectious diseases because of its high-density, factory and intensive farming patterns. Aeromonas veronii is the causative agent of high mortality in common carp, causing severe economic losses in aquaculture. However, the regulatory mechanisms involved in the response of common carp to this bacterial infection remain poorly understood. In this study, we compared mortality, blood serum LZM (Lysozyme) and IgM (Immunoglobulin M) levels and transcriptome patterns of head kidney tissues after infection with different concentrations of Aeromonas veronii. We observed that mortality increased progressively with an increasing pathogen concentration. The concentrations of blood serum LZM and IgM significantly increased after infection. A total of 13 and 925 differentially expressed genes (DEGs) were identified after infection with low (T4) and high (T9) concentrations of bacterial suspension, respectively. KEGG and GO analyses of the DEGs highlighted multiple immune-related signaling pathways. Weighted gene co-expression network analysis (WGCNA) revealed that 136 and 83 hub genes were related to blood serum LZM and IgM, respectively. Finally, the gene expression in the head kidney was validated via RT-qPCR to be consistent with the transcriptome. These results provide insights into the mechanisms of the immune response to infection with different concentrations of Aeromonas veronii and offer useful information for further studies on immune defense mechanisms in common carp.

Development of a Novel Stress and Immune Gene Panel for the Australasian Snapper (Chrysophrys auratus).

Snapper (Chrysophrys auratus) is a commercially, recreationally and culturally important teleost species in New Zealand and has been selected as a potential new species for aquaculture. Selective breeding to enhance stress tolerance, survival and growth are major breeding targets, yet research into snapper immune and stress responses has been limited. We explored a set of candidate genes in the fin, head kidney and liver tissues of 50 individuals by exposing 20 fish to increasing temperature (up to 31 °C) and 20 fish to decreasing temperature (down to 7 °C) for up to 37 h. Of these, we analysed 10 temperature-sensitive and 10 temperature-tolerant fish, along with 10 fish kept at 18 °C (acclimation temperature) as a control group. Expression analyses of candidate stress genes in the three tissue types via NanoString Technologies, Inc., Seattle, WA, USA. showed that 20 out of 25 genes significantly changed in each experiment, demonstrating the significant impact of temperature on stress and immune responses. We further document that 10 key gene biomarkers can be used to predict genotypes that are tolerant to extreme temperatures. Taken together, our novel NanoString method can be used to monitor stress in snapper rapidly, and applications of this tool in this and potentially closely related teleost species can provide insights into stress resilience of wild stocks and inform the selection of grow-out locations for aquaculture.

Comparison and evaluation of DNA vaccines against Nocardia seriolae infection in largemouth bass (Micropterus salmoides)

Chronic granulomatous diseases caused by Nocardia seriolae have resulted in substantial economic losses for the aquaculture industry. DNA vaccines are considered a promising approach for controlling infectious diseases. To develop effective DNA vaccines against N. seriolae, we selected Ag85L, MmaA4, HspX, Rv3407, and HtpG as candidate antigens. Among these, pcDNA-Ag85L and pcDNA-MmaA4 were the most effective against N. seriolae infection in largemouth bass (Micropterus salmoides), achieving the highest relative percentage survival (RPS) rates of 78.6 % and 92.9 %, respectively. Tissue bacterial loads and histopathological tests revealed a significant reduction in bacterial abundance in the liver, spleen, head kidney, and trunk kidney of the immunised groups compared to that in the control group. Additionally, no distinct pathological changes were observed in the spleen or head kidney tissues. The expression levels of immune-related genes including IL-1β, IL-8, MHCI, MHCII, CD4, and CD8α were significantly upregulated in the pcDNA-Ag85L and pcDNA-MmaA4 immunised groups, thus indicating that the two DNA vaccines mediated immune protection by promoting both humoral and cellular immune responses. Overall, the pcDNA-Ag85L and pcDNA-MmaA4 DNA vaccines demonstrated strong potential for protecting largemouth bass against N. seriolae infection, offering an innovative solution for controlling granulomatous diseases in fish.

Single-cell transcriptome analysis reveals a cellular immune response in brown trout (Salmon trutta fario) infected with Aeromonas salmonicida

Brown trout (Salmo trutta fario) is a salmon subspecies that is a popular fish worldwide that is of great economic and food value. However, brown trout is not resistant to Aeromonas salmonicida, leading to substantial losses in the fishing industry due to the widespread presence of this bacterium in fresh and saltwater environments. This study elucidated how brown trout develop resistance to A. salmonicida and identify associated resistance genes. For this purpose, individuals with partial resistance to A. salmonicida were selected during the production process. The study compared cellular heterogeneity among three groups: the resistant, susceptible, and control groups. Head kidney tissues were extracted, and single-cell transcriptome sequencing was performed. The results revealed that the number of dendritic cells (DCs) and granulocytes was significantly lower in the susceptible group compared to the resistant and control groups after being exposed to A. salmonicida. Conversely, the susceptible group had a higher number of erythrocytes and macrophages than the resistant and control groups. In addition, the resistant group had a higher number of T cells than the susceptible and control groups. These differences can be attributed to the induced signal recognition of DCs and granulocytes, leading to pathogen recognition, phagocytosis, and subsequent death. Furthermore, the resistant group activated T cells through similar pathways, such as Fc γ R-mediated phagocytosis and Fc ε RI regulation. These findings provide a reference for further exploration of resistance genes in brown trout, thereby providing an enhanced understanding of the molecular mechanisms responsible for disease resistance in brown trout. Moreover, the results provide valuable genetic resources for breeding resistant brown trout varieties.

Lactobacillus casei displaying MCP2α and FlaC delivered by PLA microspheres effectively enhances the immune protection of largemouth bass (Micropterus salmoides) against LMBV infection

Largemouth bass ranavirus (LMBV) seriously affects the development of largemouth bass (Micropterus salmoides) industry and causes huge economic losses. Oral vaccine can be a promising method for viral disease precaution. In this study, MCP2α was identified as a valuable epitope region superior to MCP and MCP2 of LMBV by neutralizing antibody experiments. Then, recombinant Lactobacillus casei expressing the fusion protein MCP2αC (MCP2α as antigen, C represents flagellin C from Aeromonas hydrophila as adjuvant) on surface was constructed and verified. Further, PLA microsphere vaccine loading recombinant MCP2αC L. casei was prepared. The PLA microspheres vaccine were observed by scanning electron microscopy and showed a smooth, regular spherical surface with a particle size distribution between 100 and 200 μm. Furthermore, we evaluated the tolerance of PLA-MCP2αC vaccine in simulated gastric fluid and simulated intestinal fluid, and the results showed that PLA-MCP2αC can effectively resist the gastrointestinal environment. Moreover, the protective effect of PLA-MCP2αC against LMBV was evaluated after oral immunization and LMBV challenge. The results showed that PLA-MCP2αC effectively up-regulated the activity of serum biochemical enzymes (T-SOD, T-AOC, LZM, complement C3) and induced the mRNA expression of representative immune genes (IL-1β, TNF-α, IFN-γ, MHC-IIα, Mx, IgM) in spleen and head kidney tissues. The survival rate of largemouth bass vaccinated with PLA-MCP2αC increased from 24 % to 68 %. Meanwhile, PLA-MCP2αC inhibited the LMBV burden in spleen, head kidney and liver tissues and attenuated tissue damage in spleen. These results suggested that PLA-MCP2αC can be used as a candidate oral vaccine against LMBV infection in aquaculture.

CcPTGS2a-like gene-mediated NF-κB/ERK signaling regulation in the common carp (Cyprinus carpio)

Prostaglandin-endoperoxide synthase 2 (PTGS2), a common biological macromolecule, is pivotal for innate immunity and pathogen recognition. In this study, we identified and characterized a CcPTGS2a-like gene in the common carp (Cyprinus carpio) with an open reading frame (ORF) of 1821 bp and epidermal growth factor and peroxidase domains. Our multiple sequence analysis revealed high homology between the amino acid sequence of CcPTGS2a-like and those of its homologs in other fish. CcPTGS2a-like mRNA and protein expressions were significantly upregulated in the spleen, head kidney, liver, and gill tissues upon exposure to Aeromonas hydrophila stimulation. CcPTGS2a-like protein recognized the conserved bacterial surface components and exhibited detectable bacterial binding activity. CcPTGS2a-like overexpression before exposure to A. hydrophila notably enhanced the survival rate of common carp, concomitant with decreased bacterial burden. The NF-κB/ERK signaling pathway initiated the immune response in common carp upon infection with A. hydrophila. CcPTGS2a-like overexpression or interference in the head kidney and Epithelioma papulosum cyprinid cells could modulate the p–NF–κB (p-p-65), p-IκBα, and p-ERK1/2 levels as well as the IL-1β and IL-6 mRNA expression. These results indicated potential CcPTGS2a-like involvement in the immune response of the common carp to bacterial infections through the NF-κB/ERK signaling pathway.

Immersion immunization with recombinant Saccharomyces cerevisiae displaying ORF25 induced protective immunity against cyprinid herpesvirus 2.

Displaying antigens on yeast surface as an oral vaccine has been widely explored, while its potential as an immersion vaccine has not been evaluated. Here, an immersion vaccine was prepared by displaying ORF25 of Cyprinid herpesvirus 2 (CyHV-2) on the surface of Saccharomyces cerevisiae. Carassius auratus gibelio was immersion immunized by 2 × 107 CFU/mL yeast for 2 h, and reinforce the immunity using the same method 14 days after the first immunization. The results showed that ORF25 specific antibody in immunized crucian carp serum was detected at a high level, and the mRNA expression level of IgM, IgT, IL-1β, and IFN-1 in vaccinated head-kidney and spleen tissues were higher than the control group, indicating that innate and adaptive immunity were induced. Moreover, the immersion vaccination provided effective protection for fish against CyHV-2, leading to a relative percent survival of 50.2%. Meanwhile, immersion vaccination restrained virus replication and histological damage in CyHV-2 infected crucian carp. Our data suggested that immersion immunization of S. cerevisiae-displayed ORF25 could be served as a candidate vaccine to prevent CyHV-2 infection.

Identification and functional characterization of galectin-3 in silver pomfret (Pampus argenteus)

Galectin-3, as a unique member of the galectin family, exhibits a significant role in both extracellular and intracellular environments. In this study, the silver pomfret galectin-3 gene (SpGal-3) was cloned and functionally characterized. The open reading frame of SpGal-3 was found to be 843 base pairs in length, encoding a protein of 280 amino acids. Phylogenetic tree analysis indicated that SpGal-3 was highly conserved in fish species. The mRNA of SpGal-3 was expressed at various levels in all tested tissues, with the gill exhibiting the highest expression levels. Furthermore, infection with Photobacterium damselae subsp. damselae significantly changed the mRNA expression of SpGal-3 in liver and head kidney tissues. Subcellular localization analysis suggested that SpGal-3 was expressed in both the nucleus and cytoplasm. Purified recombinant protein of SpGal-3, designated as rSpGal-3, showed binding ability to two classic pathogen-associated molecular patterns (peptidoglycan and lipopolysaccharide) and two sugars (D-mannose and D-galactose), with the highest affinity toward lipopolysaccharide. Additionally, rSpGal-3 demonstrated the capability to interact with various bacterial species. Taken together, our findings underscore the critical role of SpGal-3 as a key pattern recognition receptor in the immune response of the silver pomfret.

A Siglec3-like lectin from Nile tilapia (Oreochromis niloticus): Transcriptional profiling upon Streptococcus agalactiae infection and its potential role in immune escape

Siglec-3, also known as CD33, is a type of sialic acid binding immunoglobulin-like lectin that plays a role in regulating cellular activation in the innate immune system and subsequent inflammatory responses. In this study, we cloned the cDNA encoding OnSiglec3-like ORF sequence (1170 bp) in Nile tilapia, contained two Ig-like domains in the extracellular region and one inhibitory ITIM-like motif in the intracellular region. Through qRT-PCR analysis, we found that the mRNA of OnSiglec3-like lectin was highly expressed in the brain and head kidney. When challenged with Streptococcus agalactiae both in vivo and in vitro, we observed a significant up-regulation in the expression of OnSiglec3-like lectin in the head kidney tissues and leukocytes, respectively. Additionally, we investigated the interaction between a recombinant extracellular region protein (referred to as (r)exSiglec3-like protein) and three different phenotypes of S. agalactiae: WT (wild type), ∆cps (cps-deficient mutant), and ∆neuA (sia-deficient mutant) using ELISA. We found that the exOnSiglec3-like protein, when combined with RNA interference and bacterial infection, significantly enhanced the phagocytic ability against S. agalactiae. Furthermore, the expression of four common inflammatory factors (OnIL-6, OnIL-10, OnTNF-α, and OnTGF-β) showed a significant up-regulation. Overall, this study suggests that OnSigelc3-like lectin may play a role in host defence against bacterial infection and mediate immune escape in Nile tilapia.

Chlorella vulgaris algae ameliorates chlorpyrifos toxicity in Nile tilapia with special reference to antioxidant enzymes and Streptococcus agalactiae infection

BackgroundChlorpyrifos (CPF) is a widely used pesticide in the production of plant crops. Despite rapid CPF biodegradation, fish were exposed to wastewater containing detectable residues. Recently, medicinal plants and algae were intensively used in aquaculture to replace antibiotics and ameliorate stress impacts.Methods and resultsAn indoor experiment was conducted to evaluate the deleterious impacts of CPF pollution on Nile tilapia health and the potential mitigation role of Chlorella vulgaris algae. Firstly, the median lethal concentration LC50 − 72 h of CPF was determined to be 85.8 µg /L in Nile tilapia (35.6 ± 0.5 g body weight) at a water temperature of 27.5 °C. Secondly, fish were exposed to 10% of LC50 − 72 h for six weeks, and tissue samples were collected and examined every two weeks. Also, Nile tilapia were experimentally infected with Streptococcus agalactiae. Exposed fish were immunosuppressed expressed with a decrease in gene expressions of interleukin (IL) 1β, IL-10, and tumor necrosis factor (TNF)-α. Also, a decline was recorded in glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT) gene expression in the head kidney tissue. A high mortality rate (MR) of 100% was recorded in fish exposed to CPF for six weeks and challenged with S. agalactiae. Fish that received dietary C. vulgaris could restore gene expression cytokines and antioxidants compared to the control. After six weeks of CPF exposure, fish suffered from anemia as red blood cell count (RBCs), hemoglobin (Hb), and packed cell volume (PCV) significantly declined along with downregulation of serum total protein (TP), globulin (GLO), and albumin (ALB). Liver enzymes were significantly upregulated in fish exposed to CPF pollution, alanine aminotransferase (ALT) (42.5, 53.3, and 61.7 IU/L) and aspartate aminotransferase (AST) (30.1, 31.2, and 22.8) after 2, 4, and 6 weeks, respectively. On S. agalactiae challenge, high MR was recorded in Nile tilapia exposed to CPF (G3) 60%, 60%, and 100% in week 2, week 4, and week 6, and C. vulgaris provided a relative protection level (RPL) of 0, 14.29, and 20%, respectively.ConclusionsIt was concluded that CPF pollution induces immunosuppressed status, oxidative stress, and anemic signs in Nile tilapia. In contrast, C. vulgaris at a 50 g/kg fish feed dose could partially ameliorate such withdrawals, restoring normal physiological parameters.

In vivo evidence of sea buckthorn relieving oxidative stress and improving immune performance of common carp (Cyprinus carpio L.).

Sea buckthorn has the functions of antioxidation, antitumor, anti-inflammation and regulating energy metabolism. In order to investigate the effects of sea buckthorn powder and sea buckthorn flavonoids on the antioxidant properties, immune function and muscle fatty acid composition of common carp, an oral feeding experiment was carried out. The administration of glucose significantly reduced the levels of glutathione and the activity of total antioxidant capacity enzyme in serum and hepatopancreas, while concurrently upregulating the level of malondialdehyde (MDA)(P < 0.05). Conversely, oral intake of sea buckthorn powder and flavonoids increased antioxidant enzyme activity and decreased MDA levels. In terms of antioxidant molecular indicators, sea buckthorn powder and sea buckthorn flavonoids significantly increased the mRNA levels of nuclear factor NF-E2-related factor (nrf2) in the hepatopancreas and muscle. Meanwhile, mRNA expression levels of downstream antioxidant-related genes (gr, cat, gpx, and sod) regulated by Nrf2 were also upregulated. In the immune aspects, the mRNA expression levels of proinflammatory cytokines, such as interleukin-6 (il-6), interleukin-1β (il-1β) and nuclear factor-κB (nf-κb), were reduced but the expressions of anti-inflammatory cytokines, such as growth factor-β (tgf-β) and interleukin-10 (il-10), were enhanced in the head kidney and spleen tissues after oral administration with sea buckthorn. In terms of muscle fatty acid composition, the ratio of n-3 polyunsaturated fatty acid (PUFA)/n-6 PUFA was notably higher after administering sea buckthorn flavonoids than that of the glucose group (P < 0.05). This study demonstrated that oral administration of sea buckthorn powder and sea buckthorn flavonoids significantly enhanced the antioxidant capacity and immune response and improved the muscle fatty acid compositions in common carp, and also mitigated the adverse effects of glucose treatment to a certain extent. © 2024 Society of Chemical Industry.

Metabolic, neurotoxic and immunotoxic effects of PFAAs and their mixtures on the proteome of the head kidney and plasma from rainbow trout (Oncorhynchus mykiss)

PFAAs (Perfluoroalkyl acids) are a class of bioaccumulative, persistent and ubiquitous environmental contaminants which primarily occupy the hydrosphere and its sediments. Currently, a paucity of toxicological information exists for short chain PFAAs and complex mixtures. In order to address these knowledge gaps, we performed a 3-week, aqueous exposure of rainbow trout to 3 different concentrations of a PFAA mixture (50, 100 and 500 ng/L) modeled after the composition determined in Lake Ontario. We conducted an additional set of exposures to individual PFAAs (25 nM each of PFOS (12,500 ng/L), PFOA (10,300 ng/L), PFBS (7500 ng/L) or PFBA (5300 ng/L) to evaluate differences in biological response across PFAA congeners. Untargeted proteomics and phosphorylated metabolomics were conducted on the blood plasma and head kidney tissue to evaluate biological response. Plasma proteomic responses to the mixtures revealed several unexpected outcomes including Similar proteomic profiles and biological processes as the PFOS exposure regime while being orders of magnitude lower in concentration and an atypical dose response in terms of the number of significantly altered proteins (FDR < 0.1). Biological pathway analysis revealed the low mixture, medium mixture and PFOS to significantly alter (FDR < 0.05) a number of processes including those involved in lipid metabolism, oxidative stress and the nervous system. We implicate plasma increases in PPARD and PPARG as being directly related to these biological processes as they are known to be important regulators in all 3 processes. In contrast to the blood plasma, the high mixture and PFOA exposure regimes caused the greatest change to the head kidney proteome, altering many proteins being involved in lipid metabolism, oxidative stress and inflammation. Our findings support the pleiotropic effect PFAAs have on aquatic organisms at environmentally relevant doses including those on PPAR signaling, metabolic dysregulation, immunotoxicity and neurotoxicity.