Inflammatory responses in the Japanese pufferfish (Takifugu rubripes) head kidney cells stimulated with an inflammasome-inducing agent, nigericin

IL-18 signaling is regulated by caspase 6/8 and IL-18BP in turbot (Scophthalmus maximus)

Interleukin (IL)-18 is synthesized as a precursor that requires intracellular processing to become functionally active. In human, IL-18 is processed by caspase 1 (CASP1). In teleost, the maturation and signal transduction mechanisms of IL-18 are unknown. We identified two IL-18 variants, IL-18a and IL-18b, in turbot. IL-18a, but not IL-18b, was processed by CASP6/8 cleavage. Mature IL-18a bound specifically to IL-18 receptor (IL-18R) α-expressing cells and induced IL-18Rα-IL-18Rβ association. Bacterial infection promoted IL-18a maturation in a manner that required CASP6 activation and correlated with gasdermin E activation. The mature IL-18a induced proinflammatory cytokine expression and enhanced bacterial clearance. IL-18a-mediated immune response was suppressed by IL-18 binding protein (IL-18BP), which functioned as a decoy receptor for IL-18a. IL-18BP also functioned as a pathogen pattern recognition receptor and directly inhibited pathogen infection. Our findings revealed unique mechanism of IL-18 maturation and conserved mechanism of IL-18 signaling and regulation in turbot, and provided new insights into the regulation and function of IL-18 related immune signaling.

Regulation of NF-κB signaling by NLRC (NLRC3-like) gene in the common carp (Cyprinus carpio)

Among teleost NLRs, NLR-C subfamily is a large group of proteins that were teleost-specific and evolution analysis showed that NLR-Cs are most likely to evolve from NLRC3 gene (thus also called as NLRC3Ls). Presently, although there have been rich studies investigating teleost NLRC3 and NLRC3L, the data on the regulatory mechanism was limited. In this study, immune regulation of inflammatory signaling pathway mediated by common carp NLRC3L gene (CcNLRC) has been investigated. Confocal microscopy analysis showed that CcNLRC was located in cytoplasm, and in HEK293T cells, dual-luciferase reporter assay showed the regulation of NF-κB signaling by CcNLRC, in which CcNLRC could alter/decrease RIPK2-induced activation of NF-κB. These results indicated that CcNLRC may function as a negative NLR in the regulation of inflammatory response in common carp. Our data will allow to gain more insights into the molecular mechanism of teleost specific NLR (NLRC3L).

Copper induced intestinal inflammation response through oxidative stress induced endoplasmic reticulum stress in Takifugu fasciatus

Copper (Cu) pollution in aquaculture water has seriously threatened the healthy and sustainable development of the aquaculture industry. Recently, many researchers have studied the toxic effects of Cu exposure on fish. However, the relationship between endoplasmic reticulum stress (ERS) and the inflammatory response, as well as its possible mechanisms, remain unclear. Particularly, information related to fish intestines must be expanded. Our study initially investigated the mechanisms underlying intestinal toxicity and inflammation resulting from Cu-induced ERS in vivo and in vitro in Takifugu fasciatus. In vivo study, T. fasciatus were treated with different concentrations (control, 20, and 100 µg/L) of Cu exposure for 28 days, causing intestinal oxidative stress, ERS, inflammatory responses, and histopathological and ultrastructural damage. Transcriptomic data further showed that Cu exposure caused ERS, as well as inflammatory responses, in the intestinal tracts of T. fasciatus. In vitro experiments on the intestinal cells of T. fasciatus showed that Cu exposure treatment (7.5 µg/mL) for 24 h induced ERS and increased mitochondrial numbers and inflammatory responses. In contrast, the addition of 4-phenylbutyric acid (4-PBA) alleviated ERS and inflammatory response in the Cu-exposed group. Furthermore, the reactive oxygen species (ROS) inhibitor, N-Acetyl-l-cysteine (NAC), effectively alleviated Cu-induced ERS. In conclusion, our in vivo and in vitro studies have confirmed that oxidative stress triggers the ERS pathway, which is involved in the intestinal inflammatory response. Our study provides new insights into the relationship among Cu-induced oxidative stress, ERS, and inflammatory responses in fish, as well as for the healthy culture of fish in aqueous environments.

Nigericin treatment activates endoplasmic reticulum apoptosis pathway in goldfish kidney leukocytes

Nigericin has been reported to induce apoptosis and pyroptosis in mammalian models. However, the effects and mechanism underlying the immune responses of teleost HKLs induced by nigericin remain enigmatic. To decipher the mechanism after nigericin treatment, the transcriptomic profile of goldfish HKLs was analyzed. The results demonstrated that a total of 465 differently expressed genes (DEGs) with 275 up-regulated and 190 down-regulated genes were identified between the control and nigericin treated groups. Among them, the top 20 DEG KEGG enrichment pathways were observed including apoptosis pathways. In addition, the expression level of selected genes (ADP4, ADP5, IRE1, MARCC, ALR1, DDX58) by quantitative real-time PCR showed a significant change after treatment with nigericin, which was generally identical to the expression patterns of the transcriptomic data. Furthermore, the treatment could induce cell death of HKLs, which was confirmed by LDH release and annexin V-FITC/PI assays. Taken together, our results support the idea that nigericin treatment might activate the IRE1-JNK apoptosis pathway in goldfish HKLs, which will provide insights into the mechanisms underlying HKLs immunity towards apoptosis or pyroptosis regulation in teleosts.

Nigericin Abrogates Maternal and Embryonic Oxidative Stress in the Streptozotocin-Induced Diabetic Pregnant Rats

Hyperglycemic exposure in diabetic pregnancy can lead to many developmental changes, such as delayed development, fetal malformations, and fetal/embryo death. These detrimental complications are collectively known as diabetic embryopathy or teratogenesis. The current study focuses to discover the therapeutic properties of the nigericin against the STZ-stimulated diabetic embryopathy via alleviation of maternal and embryonic oxidative stress. The male and female rats at a 1:1 ratio were permitted to mate overnight to establish the course of pregnancy. The pregnant rats were distributed into four groups control, diabetic pregnant (via administering 40 mg/kg of STZ), and diabetic + 10 and 20 mg/kg of nigericin-administered (via oral gavage from days 5 to 12) groups, respectively. The glucose level, urine output, diet intake, and body weight were determined carefully. The embryo and placenta weight and implantation rates were examined, and data were tabulated. The total protein and lipid profiles were assessed using respective kits. The oxidative stress markers and antioxidant enzymes were examined using respective assay kits. The 10 and 20 mg/kg of nigericin treatment decreased the glucose level and urine output and improved the diet intake and body weight gain in diabetic pregnant rats. The nigericin also decreased the total protein, cholesterol, triglycerides, and very-low-density lipoprotein (VLDL) and improved the high-density lipoprotein (HDL) in the serum of pregnant rats. The levels of malondialdehyde (MDA), reactive oxygen species (ROS), and protein carbonyls were decreased by the nigericin in both liver and embryos of the pregnant rats. The levels of glutathione (GSH), total thiols, and activities of catalase (CAT), glutathione reductase (GR), superoxide dismutase (SOD), glutathione peroxidase (GPX), and glutathione S-transferase (GST) were improved by the nigericin in the diabetic pregnant rats. Altogether, these results provide evidence that nigericin treatment remarkably attenuates the diabetes-stimulated embryopathy in rats. The nigericin effectively decreased embryo lethality, reduced glucose and dyslipidemia, and relieves oxidative stress via upregulating the antioxidant enzyme activities. Hence, it can be a talented therapeutic agent to treat diabetic pregnancy-associated complications.

Modulatory effects of laurel-leaf cistus (Cistus laurifolius) ethanolic extract on innate immune responses and disease resistance in common carp (Cyprinus carpio)

Medicinal herbs are used for growth promotion, disease control and other health benefits in aquaculture industry. Here, we examined the effect of dietary laurel-leaf cistus (Cistus laurifolius) ethanolic extract on growth performance, digestive enzyme activity, haematological profile and nonspecific immune responses in common carp (Cyprinus carpio). In addition, resistance against Aeromonas hydrophila infection was examined. Common carp was fed diets containing 0 (Control), 0.1 (CL0.1), 0.5 (CL0.5) and 1 (CL1) g kg^-1 laurel-leaf cistus extract for 45 days. After 30 days, superoxide anion production (SAP) increased in CL0.1 and CL0.5 fish groups and at the end of the study all experimental fish groups had higher SAP compared to that of the control (P ˂ 0.05). Lysozyme activity (LA) was elevated in CL0.5 and CL1 treated groups on 30th day (P < 0.05), and this increase was only observed in C0.1 fish group at the end of study compared to control (P ˂ 0.05). Myeloperoxidase activity was significantly increased in CL0.5 and CL1 fish groups at the end of study. IL-1βgene expression was significantly increased in treated fish in a dose-depended manner. Similar results were observed for transcription of IL-6 and IL-8 (P < 0.05). Anti-inflammatory cytokines, IL-10 and TGF-β were highly up-regulated in the intestine and head kidney of CL treated fish groups compared to control (P < 0.05). At the end of experiment, significantly higher final body weight, weight gain, and specific growth rate were obtained in CL0.1 treated fish group compared to control. However, growth was negatively affected in CL1 fish group (P < 0.05). CL1 fish group had also a significantly higher FCR. Amylase activity was significantly increased in all experimental fish groups compared to control (P ˂ 0.05). Trypsin activity was decreased in CL0.1 and CL1 fish groups (P ˂ 0.05). WBC and RBC were significantly increased (P ˂ 0.05) in CL0.5 and CL1 fish groups, whereas haemoglobin, haematocrit, mean cell, mean cell haemoglobin contents were no significantly changed among control and treatment groups. Result of challenge test with A. hydrophila exhibited that survival rate in all treatment groups was significantly higher than that of control. These findings demonstrated that laurel-leaf cistus at 0.1 g kg^-1 can be a suitable candidate for growth promotion, immune system induction and infection control in fish.

In vitro and in vivo anti-inflammatory effect of Zaluzanin D isolated from Achillea acuminate

The present study was investigated to verify anti-inflammatory and immune regulation effect of Zaluzanin D on LPS-induced macrophages and acute lung injury. NR8383 macrophages were pre-treated with Zaluzanin D and stimulated by LPS. Zaluzanin D reduced the production of nitric oxide in NR8383 macrophages and decreased the secretions of inflammatory cytokines. In addition, intravenous of Zaluzanin D to LPS-induced rats reduced the infiltrations of macrophages into BALF and the histological inflammatory changes in lung tissues. Furthermore, Z.D inhibited lipid peroxidation and effectively recruit the anti-oxidative defense system, regulated the levels of tumor necrosis factor-α, interleukin-1β, and interleukin-6 in the lungs by inhibitory expression of nuclear factor-kappa B pathway. These findings suggested that Zaluzanin D attenuated pulmonary inflammatory responses by inhibiting the expression of diverse inflammatory mediators in vitro and in vivo.

Effects of dietary monocalcium phosphate supplementation on the anti-oxidative capacity, anti-bacteria function in immune organs of obscure puffer (Takifugu obscurus) after infection with Aeromonas hydrophila

The purpose of the present study was to explore the impaired anti-bacteria ability in immune organs and immune systems of obscure puffer induced by chronic dietary phosphorus (P) deficiency. Fish were fed diets supplemented with 6 g/kg P (P6) and 0 g/kg P (P0) respectively for 15 weeks, and lower final body weight, feed intake, weight gain, whole body P content and bone P content were observed in fish fed P0 diet (P < 0.05). Then the fish were continued to feed for 3 weeks and intraperitoneal injection with PBS (P6+PBS) and Aeromonas hydrophila (A.hydrophila) (P6 + A.hydrophila and P0 + A.hydrophila), and sampled at 3, 6, 12 and 24 h. The results showed that dietary P deficiency lowered survival rate, total hemocyte count, whereas enhanced ROS production and apoptosis rate of obscure puffer compared to the 6 g/kg P supplemented group after infection. Moreover, compared to the P sufficient group, puffer fish fed P deficient diet decreased the expressions of antioxidant genes catalase (cat) and glutathione reductase (gr), immune-related genes toll-like receptor 2 (tlr-2) and anti-inflammatory factors transforming growth factor β1 (tgf-β1) and interleukin 11 (il-11) while increased pro-inflammatory cytokines tumor necrosis factor α (tnf-α), interleukin 1β (il-1β) and interleukin 8 (il-8) in head kidney post-infection. In addition, dietary P deficiency decreased the hepatic gene expressions of anti-apoptotic factor B-cell lymphoma 2 (bcl-2) and bax-inhibitor 1 (bi-1), accompanied by increasing the mRNA expressions of pro-apoptotic factor caspase 3, caspase 8 and caspase 9 compared to the P sufficient group after A.hydrophila infection. In conclusion, dietary P deficiency impaired the anti-bacteria function of the immune system as well as immune organs by increasing oxidative stress and aggravating the inflammatory response and apoptosis in obscure puffer under the A.hydrophila challenge.

Screening of immuno-modulatory potential of different herbal plant extracts using striped catfish (Pangasianodon hypophthalmus) leukocyte-based in vitro tests

Many medicinal plants have been shown to possess biological effects, including immuno-modulatory activities on human and other mammals. However, studies about the potential mechanisms of plant extracts on the humoral and tissular immunities in fish have received less attention. This study aimed to screen the immunestimulating properties of 20 ethanol plant extracts on striped catfish Pangasianodon hypophthalmus leukocytes. The peripheral blood mononuclear cells (PBMCs) and head kidney leukocytes (HKLs) of striped catfish (50 ± 5 g per fish) were stimulated at 10 and 100 μg of each plant extract per mL of cell culture medium. Several humoral immune parameters (lysozyme, complement and total immunoglobulin) were examined at 24-h post stimulation (hps). Furthermore, the responses of four cytokine genes, namely il1β, ifrγ 2a and b, and mhc class II were assessed by quantitative real-time PCR at 6, 12, 24, and 48 hps. The results showed that lysozyme, complement as well as total immunoglobulin levels in both PBMCs and HKLs were regulated by some of the plant extracts tested in a concentration-dependent manner; some plant extracts induced the highest immune responses at the low dose (10 μg mL^-1) while others were more efficient at high dose (100 μg mL^-1). Among the extracts, five extracts including garlic Allium sativum L. (As), neem Azadirachta indica A. Juss (Ai), asthma-plant Euphorbia hirta L. (Eh), bhumi amla Phyllanthus amarus Schum. et Thonn (Pa), and ginger Zingiber officinale Rosc (Zo) induced significant changes in the expression of pro-inflammatory cytokine (il1β), antiviral cytokines (ifrγ 2a and b) and adaptive immune cytokine (mhc class II) in striped catfish cells. Pa always modulated the strongest expression of the four cytokines in PBMCs and HKLs over the whole experimental period (p < 0.05), whereas Zo did not stimulate the mhc class II expression in striped catfish leukocytes throughout experimental periods. These in vitro results demonstrated that some plant extracts could differently modulate great potential immune response in fish, supporting their applications in further in vivo experiments.

Enhanced Production and Quantitative Evaluation of Nigericin from the Algerian Soil-Living Streptomyces youssoufiensis SF10 Strain

Nigericin, one of the main ionophoric polyethers produced by various Streptomyces strains, presents relevant biological activities including antibacterial and recently studied antitumor properties. This work describes the influence of different culture conditions on the production of this metabolite by Streptomyces sp. SF10, isolated from a semi-arid soil sample collected at Chélia Mountain, in Khenchela (Northeastern Algeria) and identified as Streptomyces youssoufiensis. The extracts from the strain, cultured in a solid state or submerged fermentation conditions, using several carbon sources at different pH values, in the presence or absence of iron (II) sulfate and in co-culture with other Streptomyces species, were analyzed using a high-performance liquid chromatography (HPLC) system equipped with an evaporative light scattering detector (ELSD). The best culture conditions provided a concentration of nigericin of 0.490 ± 0.001 mg/mL in the extract. The HPLC-ELSD method, optimized here for the quantitative detection of nigericin, can find wider applications in the analysis of several other metabolites characterized by a similar polycyclic polyether structure or, more generally, by the lack of significant chromophores in their molecular structure.

Impaired intestinal immune barrier and physical barrier function by phosphorus deficiency: Regulation of TOR, NF-κB, MLCK, JNK and Nrf2 signalling in grass carp (Ctenopharyngodon idella) after infection with Aeromonas hydrophila

In aquaculture, the occurrence of enteritis has increased and dietary nutrition is considered as one of the major strategies to solve this problem. In the present study, we assume that dietary phosphorus might enhance intestinal immune barrier and physical barrier function to reduce the occurrence of enteritis in fish. To test this assumption, a total of 540 grass carp (Ctenopharyngodon idella) were investigated by feeding graded levels of available phosphorus (0.95-8.75 g/kg diet) and then infection with Aeromonas hydrophila. The results firstly showed that phosphorus deficiency decreased the ability to combat enteritis, which might be related to the impairment of intestinal immune barrier and physical barrier function. Compared with optimal phosphorus level, phosphorus deficiency decreased fish intestinal antimicrobial substances activities or contents and down-regulated antimicrobial peptides mRNA levels leading to the impairment of intestinal immune response. Phosphorus deficiency down-regulated fish intestinal anti-inflammatory cytokines mRNA levels and up-regulated the mRNA levels of pro-inflammatory cytokines [except IL-1β and IL-12p35 in distal intestine (DI) and IL-12p40] causing aggravated of intestinal inflammatory responses, which might be related to the signalling molecules target of rapamycin and nuclear factor kappa B. In addition, phosphorus deficiency disturbed fish intestinal tight junction function and induced cell apoptosis as well as oxidative damage leading to impaired of fish intestinal physical barrier function, which might be partially associated with the signalling molecules myosin light chain kinase, c-Jun N-terminal protein kinase and NF-E2-related factor 2, respectively. Finally, based on the ability to combat enteritis, dietary available phosphorus requirement for grass carp (254.56-898.23 g) was estimated to be 4.68 g/kg diet.

Immunomodulatory Effects of a Bioactive Compound Isolated from Dryopteris crassirhizoma on the Grass Carp Ctenopharyngodon idella

In the present study, we investigated effects of compound kaempferol 3-a-L-(4-O-acetyl)rhamnopyranoside-7-a-L-rhamnopyranoside (SA) isolated from Dryopteris crassirhizoma during immune-related gene expression in Ctenopharyngodon idella head kidney macrophages (CIHKM). The expression of immune-related genes (IL-1β, TNF-α, MyD88, and Mx1) were investigated using real-time PCR at 2 h, 8 h, 12 h, and 24 h after incubation with 1, 10, and 50 μg mL⁻¹ of SA. Furthermore, fish were injected intraperitoneally with 100 μL of SA, and immune parameters such as lysozyme activity, complement C3, SOD, phagocytic activity, and IgM level were examined at 1, 2, and 3 weeks after injection. The differential expression of cytokines was observed after exposure to SA. IL-1β genes displayed significant expression at 2 and 8 h after exposure to 1–10 μg mL⁻¹ of SA. SA also induced gene expression of cytokines such as MyD88, Mx1, and TNF-α. Furthermore, enhanced immune parameters in grass carp confirmed the immunomodulatory activity of SA. Interestingly, this compound has no toxic effect on CIHKM cells as tested by MTT assay. In addition, fish immunised with 10 μg mL⁻¹ of SA exhibited maximum resistance against Aeromonas hydrophila infection. These results suggest that SA has the potential to stimulate immune responses in grass carp.

Heat-killed whole-cell products of the probiotic Pseudomonas aeruginosa VSG2 strain affect in vitro cytokine expression in head kidney macrophages of Labeo rohita

Present study was undertaken to investigate the efficiency of heat-killed whole-cell products (HKWCPs) of probiotic Pseudomonas aeruginosa VSG2 strain in stimulating the cytokine responses in the head kidney (HK) macrophages of Labeo rohita. The HK macrophages were incubated with HKWCPs or lipopolysaccharide (LPS), and the responses of cytokine genes, namely interleukin-10 (IL-10), IL-1β, IL-p35, IL-12p40, tumour necrosis factor-α (TNF-α), nuclear factor kappa B (NF-κB), cyclooxygenase-2 (COX-2), interferon-alpha (IFN-α), and interferon-gamma (IFN-γ) were assessed by quantitative real-time PCR (qRT-PCR) at 2, 8, 16, 24, 48, 72 h post-stimulation (hps). Among proinflammatory cytokines, significantly higher expression of IL-1β and TNF-α was observed at 8-24 hps, and 2-16 hps with HKWCPs, respectively, as compared to controls. However, COX-2 and NF-κB displayed strong expression (P < 0.05) at 2-8 hps, and 8, 16 and 72 hps with HKWCPs, respectively. Antiviral cytokines IFN-α and IFN-γ displayed strong expression (P < 0.05) at 8-24 hps, and 2, 24 and 48 hps with HKWCPs, respectively. Expressions of cell-mediated immune factor genes (IL-12p35 and IL-12p40) were also significantly upregulated at various time points, except IL-12p40 at 72 hps, in HK macrophages stimulated with HKWCPs. Expression of the anti-inflammatory cytokine IL-10 was upregulated (P < 0.05) at 2-24 hps HKWCPs, compared to controls. Enhanced cellular (phagocytic activity and superoxide anion production) and humoral (lysozyme) immune parameters of treated HK macrophages confirmed the induction of inflammatory response. Thus, our results indicated that HKWCPs of probiotic P. aeruginosa VSG2 had greater potential for stimulating the in vitro expression of cytokines in fish and that these HKWCPs may be used as vaccine adjuvants in aquaculture.

Immune responses in the Japanese pufferfish (Takifugu rubripes) head kidney cells stimulated with particulate silica

Studies on immune response to crystal silica in mammals indicate immune stimulation effect of environmental parameters including silica or asbestos, but there is no information on this aspect in lower vertebrates. Therefore, we examined expression of cytokine genes related to innate immunity in the Japanese pufferfish, Fugu (Takifugu rubripes) head kidney (HK) cells stimulated with particulate silica at 10 and 50 μg mL(-1). Expression of eleven cytokine genes was analyzed by the multiplex RT-PCR method (GenomeLab Genetic Analysis System, GeXPS; Beckman Coulter Inc.). Additionally, to confirm functionality of activated inflammatory immunity, we assessed phagocytic activity. Expression of NLR family genes as potential sensor molecules of inflammasome and inflammasome-associated genes (ASC and caspase-1) was also confirmed in HK cells by quantitative real-time PCR (qRT-PCR). As a result, an increased gene expression of pro-inflammatory cytokines (IL-6, IL-17A/F3, TNF-α, TNF-β and IFN-γ) and other cytokines (IL-4/13A, IL-4/13B, Type I-IFN) was recorded in particulate silica stimulated HK cells. Moreover, phagocytic activity showed a tendency to significantly increase in stimulated monocyte of HK cells after 6 h. Expression of NLR-C9 and NLR-C12 genes significantly increased in silica-stimulated HK cells. The particulate silica also significantly induced expression of inflammosome-associated genes, which may relate to the induced NLR-Cs.

Inflammatory immune response by lipopolysaccharide-responsive nucleotide binding oligomerization domain (NOD)-like receptors in the Japanese pufferfish (Takifugu rubripes)

Some of NOD-like receptors (NLRs), the cytosolic pattern recognition receptors form a multi-protein complex, inflammasome consisting of one or more NLRs, the adaptor protein ASC and inflammatory caspase to generate mature inflammatory cytokines, interleukin (IL)-1β and IL-18. However, inflammasome-mediated inflammatory cascade involving any NLR member is unknown in a lower vertebrate like fish. Also, inflammatory cytokine induction pathway in response to a specific ligand, namely bacterial lipopolysaccharide (LPS) has not yet been clarified. Therefore, 13 predicted NLR sequences of the Japanese pufferfish, Fugu (Takifugu rubripes) were retrieved in silico and categorized as NLR-C1∼13. Expression analysis of these genes in Fugu head kidney (HK) cells stimulated with a heat-killed Lactobacillus paracasei spp. paracasei (Lpp), LPS, nigericin and a combination of nigericin + LPS showed consistent up-regulations of NLR-C1, 5, 7, 10 and 12 genes in both Lpp and LPS stimulations and NLR-C9 gene in LPS stimulation only. However, nigericin and nigericin + LPS caused an increased expression of NLR-C10 and 12 in HK cells and leukocytes. Fugu treated with Lpp and LPS (in vivo), and infected with Vibrio harveyi had an elevated expression of NLR-C10 and 12. Increased transcription of caspase-1, ASC, IL-1β and IL-18 was recorded in nigericin-stimulated HK cells and leukocytes. Results suggested activation of probable inflammasome-mediated inflammatory cytokine response in Fugu. Moreover, LPS may be a key ligand that induces some of the Fugu NLR-Cs (NLR-C9, 10 and 12). Further characterization and functional analysis of Fugu NLR-C10 and 12 for ligand sensing, and processing of pro-inflammatory cytokine, IL-1β would elucidate the inflammasome evolution in fish.

Effects of intracellular products of Bacillus subtilis VSG1 and Lactobacillus plantarum VSG3 on cytokine responses in the head kidney macrophages of Labeo rohita

The efficiency of intracellular products (ICPs) of the probiotics Bacillus subtilis VSG1 and Lactobacillus plantarum VSG3 in stimulating cytokine responses in the head kidney (HK) macrophages of Labeo rohita was investigated. The HK macrophages were incubated with ICPs and lipopolysaccharide (LPS), and the responses of cytokine genes, namely interleukin-10 (IL-10), IL-1β, IL-12p35, IL-12p40, IL-18, tumour necrosis factor-α (TNF-α), nuclear factor kappa B (NF-κB), cyclo-oxygenase-2 (COX-2), interferon-1 (IFN-1), and IFN-γ were assessed by quantitative real-time PCR (qRT-PCR) at 2, 6, 12, 24, and 48 h post-stimulation (hps). Among the proinflammatory cytokines, a strong increase in the gene expression of IL-1β and TNF-α was displayed mainly at 2-6 hps with ICPs, as compared to that of the positive control (LPS) or the negative control (PBS) (P < 0.05). However, COX-2 and NF-κB showed higher expression at 2 and 24 hps, and 6-24 hps with ICPs, respectively. Antiviral cytokines IFN-1 and IFN-γ displayed strong expressions (P < 0.05) at 6-12 hps, and 12-24 hps with ICPs, respectively. Upregulation of the anti-inflammatory cytokine, IL-10, was recorded at 6-24 hps with ICPs, as compared to that controls. Expressions of cell-mediated immune factor genes (IL-12p35, IL-12p40, and IL-18) were also significantly upregulated at different time points, except 48 hps, in HK macrophages stimulated with ICPs. Furthermore, enhanced cellular (phagocytic activity and nitroblue tetrazolium assay) and humoral (lysozyme) immune parameters in stimulated cells confirmed the induction of the inflammatory response. Therefore, the results of this in vitro study indicate that the ICPs of B. subtilis VSG1 or L. plantarum VSG3 have great potential for stimulating the cytokine responses in fish, and are thereby potential immunostimulants to fish. Further studies could be conducted to explore its suitability as an adjuvant vaccine in aquaculture.

Toxicological Effect of Manganese on NF-κB/iNOS-COX-2 Signaling Pathway in Chicken Testes

Manganese (Mn) pollution can cause tissue and organ dysfunction and structural damage. The toxicity of Mn in poultry was reported, but inflammatory damage that Mn induced in the testicular tissue has not been reported. The aim of this study was to investigate the effect of Mn poisoning on NF-κB/iNOS-COX-2 signaling pathway in chicken testes. One hundred eighty Hyline male chickens at 7 days of age were fed either commercial diet or MnCl2-added commercial diet containing 600, 900, and 1800 mg/kg Mn for 30, 60, and 90 days, respectively. The messenger RNA (mRNA) expression of nuclear factor-κB (NF-κB), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS), nitric oxide (NO) content, iNOS activity, and histopathology were examined in chicken testes. The results showed that excess Mn upregulated mRNA expression of NF-κB, COX-2, TNF-α, and iNOS, NO content, and iNOS activity at 60th and 90th day. Mn had a time-dependent effect on NF-κB and TNF-α mRNA expression. Mn had a dose- and time-dependent effect on NO content and iNOS activity. Mn exposure induced chicken testis histological changes in dose- and time-dependent manner. It indicated that Mn exposure resulted in inflammatory injury of chicken testis tissue through NF-κB/iNOS-COX-2 signaling pathway.

Effect of cellular products of potential probiotic bacteria on the immune response of Labeo rohita and susceptibility to Aeromonas hydrophila infection

In the present study, the immunological efficacy of cellular components from the potential probiotic bacteria Bacillus subtilis VSG1, Pseudomonas aeruginosa VSG2, and Lactobacillus plantarum VSG3 was evaluated in Labeo rohita fingerlings. Fish were immunized intraperitoneally with 0.1 mL phosphate-buffer solution (PBS) containing 0.1 mg of any of the following cellular components: intercellular products (ICPs) of VSG1 (BS-ICPs), heat-killed whole cell products of VSG2 (PA-HKWCPs), or ICPs of VSG3 (LP-ICPs). Fish injected with 0.1 mL PBS served as the control. Various immunological parameters, including the expression of immune-related genes, were measured 14 and 21 days post-immunization. The fish were challenged with Aeromonas hydrophila and mortality was recorded up to 21 days post-infection. The results revealed that administration of cellular components significantly increased the activity of serum lysozyme and the alternative complement pathway, phagocytosis, and respiratory bursts throughout the experimental period. Total serum protein, albumin, and globulin levels were significantly higher in experimental groups than in the control up to 14 days post-immunization, and decreased thereafter. With respect to immune-related genes, IL-1β, COX-2, iNOS, and IL-10 were highly (P < 0.05) up-regulated in fish immunized with cellular components, compared to the control. The expression of TNF-α and NF-κB was up-regulated in immunized fish up to 14 days post-immunization. Interestingly, fish immunized with LP-ICPs exhibited a significantly higher post-challenge relative percent survival (83.32%), followed by PA-HKWCPs (66.66%), and BS-ICPs (50%). These results indicate that cellular components of probiotic bacteria can influence immune responses, enhance disease protection, and stimulate immune-related gene expression in rohu. Hence, these cellular components may be useful as adjuvants for vaccines in aquaculture.

Sensors of Infection: Viral Nucleic Acid PRRs in Fish

Viruses produce nucleic acids during their replication, either during genomic replication or transcription. These nucleic acids are present in the cytoplasm or endosome of an infected cell, or in the extracellular space to be sensed by neighboring cells during lytic infections. Cells have mechanisms of sensing virus-generated nucleic acids; these nucleic acids act as flags to the cell, indicating an infection requiring defense mechanisms. The viral nucleic acids are called pathogen-associated molecular patterns (PAMPs) and the sensors that bind them are called pattern recognition receptors (PRRs). This review article focuses on the most recent findings regarding nucleic acids PRRs in fish, including: Toll-like receptors (TLRs), RIG-I-like receptors (RLRs), cytoplasmic DNA sensors (CDSs) and class A scavenger receptors (SR-As). It also discusses what is currently known of the downstream signaling molecules for each PRR family and the resulting antiviral response, either type I interferons (IFNs) or pro-inflammatory cytokine production. The review highlights what is known but also defines what still requires elucidation in this economically important animal. Understanding innate immune systems to virus infections will aid in the development of better antiviral therapies and vaccines for the future.

Analysis and characterization of the head kidney transcriptome from the Antarctic fish Trematomus bernacchii (Teleostea, Notothenioidea): a source for immune relevant genes

In this study we describe the de novo assembled head kidney transcriptome of the Antarctic notothenioid fish Trematomus bernacchii, an important model species for biochemical, environmental and immunological studies. RNA-seq data was generated using Illumina paired-end sequencing, obtaining ~7 Gbp of sequence data, which were assembled into 96,641 contigs and annotated with the Trinotate pipeline. Since this sequence collection is expected to contain a relevant number of immunity-related transcripts, it will be used as a reference for future immunological studies in this species.