Application of transcriptomic profiling to investigate the toxicity mechanisms caused by dietary exposure of nanoplastics in fish

Nowadays, nanoplastics (NPs) are one of the main concerns regarding plastic pollution. The increasing presence of plastic particles, fibers and fragments in the marine environment pose an additional risk to both, wild and cultured fish. Ingestion is the main mechanism by which particles are internalized. Thus, this study evaluated the impact of a diet containing NPs in one of the most cultivated species across the Mediterranean Sea, the European sea bass (Dicentrarchus labrax). Polystyrene NPs (50 nm) were supplied in the food for a period of 21 days and the transcriptomic changes were measured in the intestine through RNA-seq. Additionally, enzymatic and bactericidal activities were measured in the liver or serum, respectively of the same fish to evaluate the organism stress. No significant changes in the enzymatic activities were observed in the liver, whilst the seric bactericidal activity decreased by NPs dietary treatments. This suggests that ingestion of NPs at low dosages might have an impact on fish health. In addition, our data suggested that NPs impact some important biological pathways related to fish morphogenesis, organ development, membrane receptors, and fish immunity. These routes are extremely important for fish development and growth and can have long-term impact, since the early stages of fish are the most sensitive to this kind of pollution. This study provides information on the impact of the ingestion of NPs in sea bass and can serve as a basis for future investigations on the prevention and treatment of such pollutants in aquaculture.

Immunotoxicological effects of perfluorooctanesulfonic acid on European seabass are reduced by polyethylene microplastics

Marine environments receive plastic waste, where it suffers a transformation process into smaller particles. Among them, microplastics (MPs; <5 mm) are ingested by aquatic organisms leading to negative effects on animal welfare. The interactions between MPs, contaminants and organisms are poorly understood. To clarify this issue, European seabass (Dicentrarchus labrax L.) were fed with diets supplemented with 0 (control), polyethylene (PE) MPs (100 mg/kg diet), perfluorooctanesulfonic acid (PFOS, 4.83 μg/kg diet) or PFOS adsorbed to MPs (MPs-PFOS; final concentrations of 4.83 μg and 100 mg of PFOS and MP per kg of feed, respectively). Samples of skin mucus, serum, head-kidney (HK), liver, muscle, brain and intestine were obtained. PFOS levels were high in the liver of fish fed with the PFOS-diet, and markedly reduced when adsorbed to MPs. Compared to the control groups, liver EROD activity did not show any significant changes, whereas brain and muscle cholinesterase activities were decreased in all the groups. The histological and morphometrical study on liver and intestine showed significant alterations in fish fed with the experimental diets. At functional level, all the experimental diets affected the humoral (peroxidase, IgM, protease and bactericidal activities) as well as cellular (phagocytosis, respiratory burst and peroxidase) activities of HK leukocytes, being more marked those effects caused by the PFOS diet. Besides, treatments produced inflammation and oxidative stress as evidenced at gene level. Principal component analysis demonstrated that seabass fed with MPs-PFOS showed more similar effects to MPs alone than to PFOS. Overall, seabass fed with MPs-PFOS diet showed similar or lower toxicological alterations than those fed with MPs or PFOS alone demonstrating the lack of additive effects or even protection against PFOS toxicity.

Molecular characterization of the T cell costimulatory receptors CD28 and CTLA4 in the European sea bass

For the activation of T cells, it is necessary the specific recognition of the peptide by the T cell receptors (TCR) in the surface of antigen-presenting cells (APCs) and additional signals delivered by costimulatory receptors. In fish, knowledge about the presence of these costimulatory signals is limited and functional evidence almost absent. Thus, in this study, we have identified the stimulatory CD28 and the inhibitory cytotoxic T-lymphocyte-associated protein 4 (CTLA4) coreceptors in the European sea bass (Dicentrarchus labrax), and evaluated their transcription. In parallel, the transcription encoding for the T cell markers CD8α and CD4 was also evaluated. Both coreceptors showed the canonical architecture including a signal peptide, an immunoglobulin domain, a transmembrane region and a cytosolic tail. Protein predictions and phylogenetic tree identify them as true mammalian orthologues of CD28 and CTLA4. We found these genes constitutively expressed in all studied organs of European sea bass with high expression in lymphoid organs (thymus, spleen and head-kidney) and liver. The molecular expression pattern of these genes was up-regulated in head-kidney leucocytes stimulated with T mitogens as concanavalin A and phytohemagglutinin (PHA), but not with the B cell mitogen lipopolysaccharide (LPS). Fish challenged with nodavirus (NNV) evidenced a differential and opposing regulation of the cd28 and ctla4 transcription levels in the brain, the target organ for viral replication, and head-kidney. While cd28 transcription tends to decrease over the infection time in both organs the expression of the ctla4 gene tends to increase. Interestingly, the coreceptor expression is highly and significantly correlated to the transcription of the T cell markers. Our results highlight the important role of CD28 and CTLA4 as costimulatory receptors of T cells in European sea bass but further studies are deserved.

Effects of BDE-47 exposure on immune-related parameters of Mytilus galloprovincialis

The persistent pollutants polybrominated diphenyl ethers (PBDEs) have been demonstrated to produce several negative effects on marine organisms. Although Mytilus galloprovincialis was extensively studied as model system, the effects of PBDEs on the innate immune system of mussels remains unclear. In this study, except for the control treatment, specimens of M. galloprovincialis were fed with microalgae treated with increasing concentrations of PBDEs (maximum level 100 ng L^-1 of BDE-47 per day). BDE-47 treatment was maintained for 15 days and then the animals were fed with the same control diet, without contaminants, for 15 days. Samples of haemolymph (HL) were obtained at T0, T15 and T30 days of the experiment to evaluate different parameters related to immunity, such as neutral red retention time, and peroxidase, protease, antiprotease, lysozyme and bactericidal activities. BDE-47 exposure for 15 days affected both the stability of haemocytes and humoral parameters. In addition, the obtained results indicated that, at 30 days, after 15 days of culture without contaminant, the immune parameters were still affected, as some of them did not return to the basal levels, and others remained stimulated. Overall the results indicate that BDE-47 exposures at environmentally realistic levels may affect various aspects of immune function in M. galloprovincialis, acting as stressor that can compromise the general welfare.

Mucosal and systemic immune responses in Senegalese sole (Solea senegalensis Kaup) bath challenged with Tenacibaculum maritimum: A time-course study

Tenacibaculosis, caused by Tenacibaculum maritimum, continues to inflict substantial losses among cultured marine species, particularly in the Senegalese sole. However, the immune mechanisms in fish involved in fighting against this disease are still poorly understood. Thus, the present study aimed to investigate the skin mucus's terminal carbohydrate composition, several immune-related enzymes (i.e. lysozyme, peroxidase, proteases and antiproteases), the haemolytic activity of complement and the bactericidal activity in the skin mucus and plasma of the Senegalese sole in a time-course study following a bath challenge with T. maritimum. The haematological profile and the kinetics of cell migration post-infection were also considered. The bath challenge induced slight variations in the terminal carbohydrate composition of Senegalese sole skin mucus. In general, results from this study showed a delay in the mucosal immune response compared to that found at the systemic level (i.e. blood and plasma). For instance, a significant increase in the skin mucus's lysozyme, complement, protease and antiprotease activities were observed at the end of the experiment (14 d post-challenge). Interestingly, the higher activity of these enzymes could be related to the skin mucus's bactericidal capacity and haemolytic complement activity, suggesting that these enzymes play an important role in the defence against Gram-negative bacteria. The haematological profile revealed a significant increase in circulating neutrophils in challenged fish after 48 and 72 h, which was positively correlated to the increments observed in peroxidase and lysozyme activities, respectively, in the plasma of challenged fish at the same time. Although the route of entry and the survival strategy of T. maritimum are still not fully elucidated, results from the present study will contribute to this endeavour through the study of the mucosal immune responses of fish against this particular pathogen.

Impact of a shift work-like lighting schedule on the functioning of the circadian system in the short-lived fish Nothobranchius furzeri

Adult Nothobranchius furzeri of the MZM-04/10 strain were individually kept and subjected to a "5 + 2" shifting lighting schedule (SHIFT) for 8 weeks in order to evaluate the desynchronizing effects of a simulated human-like shift-work schedule on the functioning of the circadian system (CS). With this aim, sixteen 21-week-old N. furzeri were placed into a Morning, Night and Evening schedule (lights on from 08:00 to 16:00, 00:00 to 08:00 and 16:00 to 00:00 h, respectively) and fed once a day in the middle of the corresponding photophase (12:00, 04:00 and 20:00 h, respectively). Then, in the weekends (2 days), fish were always returned to the Morning shift. As controls, 16 fish were maintained under a non-shifting LD cycle condition (CONTROL) throughout the whole experiment, with lights on from 08:00 to 16:00 h. Rest-activity rhythm (RAR) of fish subjected to SHIFT showed several symptoms of chronodisruption, such as a decrease in the percentage of diurnal activity and a reduction of the relative amplitude and the circadian function index with time. When a periodogram analysis was performed, RAR of N. furzeri under SHIFT conditions showed up to three separate circadian components: one longer than 24 h (26.5 h) that followed the weekly 8 h delays; a short-period component (~23 h) that was related to the weekend's phase advances, and finally, a 24 h component. The shifting LD schedule also affected fish CS at a molecular level, with several significant differences in the expression of core genes of the molecular clock (bmal1, clock, rorα, rev-erbα) between SHIFT and CONTROL animals. RAR impairment along with changes in clock gene expression could be associated with high stress and accelerated aging in these fish.

Metal detoxification in the marine teleost fish Sparus aurata L. and Dicentrarchus labrax L

Transcription of ATP-binding cassette (ABC) transporters has been evaluated in cell lines and primary cultures from gilthead seabream and European sea bass teleost fish exposed to methylmercury (MeHg), arsenic, cadmium or lead. The mRNA expression levels showed abcb1, abcc2 and abcc5 constitutive gene expression in all seabream tissues analyzed; however, we were unable to detect any constitutive transcription of abcb1 in many of the sea bass tissues. Furthermore, ABC mRNA expression levels were all affected by metal exposure, especially in the case of fish cell lines and erythrocytes, and greatly depended on cell type and fish species. Thus, while ABC transcription was up-regulated in the seabream cell line it was down-regulated in the sea bass cell line, while the opposite occurred in the primary cultures. All these data point to the importance of ABC transporters in metal detoxification and in the differential regulation in seabream and sea bass cells.

A time course study of glucose levels and innate immune response in gilthead seabream (Sparus aurata L.) after exposure to clove oil-eugenol derived anaesthetic

Clove oil is used as an anaesthetic for many species of fish worldwide; however, relatively few studies have assessed its effects on the innate immune response on these species. The present work aimed to investigate the effects of clove oil-eugenol derived anaesthetic on some humoral and cellular immune response in gilthead seabream (Sparus aurata L.). To compare with an unexposed control group, fish were exposed to 55 ppm clove oil for 5 min, before being sampled at 1, 24 and 48 h post-exposure. Serum glucose level was also measured to obtain information on the fish physiological response after clove oil anaesthesia. One hour after exposure the haemolytic complement activity of fish was lower than in the unexposed group. By contrast, the leucocyte peroxidase activity in head-kidney was significantly stimulated 24 h after exposure to clove oil-eugenol. The rest of innate immune parameters evaluated and the glucose levels not were affected by clove oil exposure at any sampling point. Overall, the use of clove oil at 55 ppm as anaesthetic did not seem to alter the innate immune response and neither did it trigger a stress response. The use of clove oil-eugenol derived had become common practice in aquaculture, and its use with gilthead seabream can be considered safe as it does not cause immunodepression in anesthetized fish.

Dietary administration effects of fenugreek seeds on skin mucosal antioxidant and immunity status of gilthead seabream (Sparus aurata L.)

Improving fish defense through the preventive administration of immunostimulants has an important role in controlling the outbreak of the disease in aquaculture. As a continuity of our previous studies, this paper describes the effects of dietary fenugreek (Trigonella foenum graecum) seeds on the skin mucosal antioxidant status and immune response of gilthead seabream (Sparus aurata L.). Fish were fed with four experimental diets: one a basal diet (control) and three diets with powdered fenugreek seeds incorporated in the fish feed at 1%, 5%, and 10%. After eight weeks of feeding, free radicals scavenging and antioxidant assays were assessed in skin mucus by measuring the peroxidation of phospholipid liposomes, hydroxyl radical and hydrogen peroxide scavenging, measurement of total antioxidant activity and the determination of antioxidant activity in a linoleic acid system. The skin mucosal immune response was evaluated by measuring the IgM levels and some enzymatic activities (peroxidase, antiprotease, protease, esterase, and ceruloplasmin). Our results demonstrated that fenugreek inclusion improved the hydroxyl radical scavenging capacity and conferred very high antioxidant activity. Besides, only the highest supplementation level (10%) was able to augment the peroxidase and protease activities confronted by a general decrement in the antiprotease activity in the experimental fed groups with 1% and 10%. These results suggest that the dietary administration of fenugreek at the higher inclusion dose enhances the skin mucosal immunity response and the antioxidant status of gilthead seabream a species with one of the highest rates of production in marine aquaculture.

Effects of dietary administration of fenugreek seeds on metabolic parameters and immune status of gilthead seabream (Sparus aurata L.)

Medical plants could be used as a prophylactic method in aquaculture because they are considered safe and so very promising alternatives to the use of chemicals. The aim of the present work was to examine the effects of dietary fenugreek (Trigonella foenum graecum) seeds administered for 8 weeks on the metabolic and immune status of gilthead seabream (Sparus aurata L.). Four experimental groups were designated: one receiving a basal diet (control) and three fed powdered fenugreek seeds incorporated in the fish feed at 1%, 5% and 10%. The results show that significant decreases in aspartate aminotransferase, creatine kinase, potassium and the albumin/globulin ratio were detected in the serum of fish fed 10% fenugreek compared with the values recorded in control fish. As regards the immune status, fish fed the 5% supplemented diet had higher haemolytic complement and peroxidase activities than the control fish whilst antiprotease activity was higher in fish fed the 1% fenugreek level respect to control fish and the fish fed the highest fenugreek supplementation rate. Interestingly, the results also revealed a significant enhancement of most of the cellular immune parameters studied, especially in fish fed the highest level of fenugreek (10%). However, the bacteriostatic activity of serum against fish pathogenic and non-pathogenic bacteria was non-affected to any significant extent in fish fed the supplemented diets. Overall, the results suggest that the high level of dietary fenugreek tested in this work (10%) did not negatively affect any of the metabolic parameters measured in serum but increased some of them. In addition, the inclusion of fenugreek seeds in the gilthead seabream diet at 5% or 10% improved the humoral and cellular immune activities, respectively. Further studies are needed to better understand the effects of this natural product, which may be suitable for use as a feed additive in fish aquaculture.

Molecular oxidative stress markers in olive ridley turtles (Lepidochelys olivacea) and their relation to metal concentrations in wild populations

Due to their longevity and extensive migration areas, marine turtles are able to accumulate diverse contaminants over many years and as a consequence they represent an interesting bioindicator species for marine ecosystem pollution. Metals provoke toxicological effects in many aquatic animal species, but marine turtles have been under-investigated in this area. Thus, we have determined the presence of certain inorganic elements (As, Cd, Cu, Ni, Pb, Se and Zn) in olive ridley turtles (Lepidochelys olivacea) and related them to metallothionein (MT), superoxide dismutase (SOD), catalase (CAT) and glutathione reductase (GR) transcription and/or enzymatic activities. Gene expression of sod, cat and gr was found to be higher in blood than liver or kidney but most of the significant relationships were found in liver, not only for gene expression but also for enzyme activities. This must be related to the role the liver has as the first filter organ. Several positive relationships of sod, cat and gr gene expression in the different tissues were found in this population, as well as very high Cd concentrations. This could mean that these turtles are adapting to the metals-production of ROS and damage through a high transcription of these antioxidants. Multiple positive relationships with GR seem to be part of its compensatory effect due to the decrease of SOD production against the high and chronic exposure to certain xenobiotics. CAT, on the other hand, seems not to be used much, and glutathione detoxification of H₂O₂ may be more important in this species. Finally, despite the very high Cd concentrations found in this population, no significant relationship was found in any tissue with metallothionein gene expression. These results, along with very high Cd concentrations and a negative relationship with Cu, lead us to consider some kind of disruption in mt gene expression in these turtles.

Chronic wounds alter the proteome profile in skin mucus of farmed gilthead seabream

Background

Skin and its mucus are known to be the first barrier of defence against any external stressors. In fish, skin wounds frequently appear as a result of intensive culture and also some diseases have skin ulcers as external clinical signs. However, there is no information about the changes produced by the wounds in the mucosae. In the present paper, we have studied the alterations in the proteome map of skin mucus of gilthead seabream during healing of experimentally produced chronic wounds by 2-DE followed by LC-MS/MS. The corresponding gene expression changes of some identified skin proteins were also investigated through qPCR.

Results

Our study has successfully identified 21 differentially expressed proteins involved in immunity and stress processes as well as other metabolic and structural proteins and revealed, for the first time, that all are downregulated in the skin mucus of wounded seabream specimens. At transcript level, we found that four of nine markers (ighm, gst3, actb and krt1) were downregulated after causing the wounds while the rest of them remained unaltered in the wounded fish. Finally, ELISA analysis revealed that IgM levels were significantly lower in wounded fish compared to the control fish.

Conclusions

Our study revealed a decreased-expression at protein and for some transcripts at mRNA levels in wounded fish, which could affect the functionality of these molecules, and therefore, delay the wound healing process and increase the susceptibility to any infection after wounds in the skin of gilthead seabream.

Local immune response of two mucosal surfaces of the European seabass, Dicentrarchus labrax, fed tryptophan- or methionine-supplemented diets

Immune responses relies on an adequate provision of multiple nutrients that sustain the synthesis of key effector molecules. These needs are depicted in the already reported increase of circulating free amino acids in fish under stressful conditions. Since aquaculture and the inherent fish welfare are an emergent call, the immunomodulatory effects of amino acids on gut- and skin-associated lymphoid tissues of the European seabass (Dicentrarchus labrax) were studied under unstressed conditions and after an inflammatory insult. To achieve this goal, fish were distributed in duplicate tanks (fifteen fish per tank) and were fed for 14 days with methionine or tryptophan-supplemented diets at 2× dietary requirement level (MET and TRP, respectively) or a control diet meeting the amino acids requirement levels (CTRL). Afterwards, samples of skin and posterior gut were collected from 6 fish per dietary treatment for the assessment of the immune status while the remaining animals were intraperitoneally-injected with inactivated Photobacterium damselae subsp. piscicida and subsequently sampled either 4 or 24 h post-injection. The immune status of both mucosal surfaces was poorly affected, although a tryptophan effect was denoted after bacterial inoculation, with several immune-related genes up-regulated in the gut at 4 h post-injection, which seems to suggest a neuroendocrine-immune systems interaction. In contrast, skin mucosal immunity was inhibited by tryptophan dietary supplementation. Regarding methionine, results were often statistically non-significant, though increasing trends were denoted in a few parameters. Overall, dietary methionine did not significantly affect neither gut nor skin immunity, whereas tryptophan supplementation seems to induce modulatory mechanisms that might be tissue-specific.

Evaluation of silver nanospheres on viability and innate cellular parameters of gilthead seabream (Sparus aurata L.) head-kidney leucocytes

The increasing use of nanomaterials, e.g. nanosilver, has lead to concerns about environmental contamination and possible toxic effects on aquatic organisms. Here, we present evidence for the impact of silver nanospheres (AgNSs) on fish innate immune cells after in vitro exposure. AgNSs of 20, 50 or 100 nm in diameter were tested with the smallest ones (20 nm) clearly having the most deleterious effects, after an exposure period of 30 min, followed by the medium-sized ones; the NSs of 100 nm had no impact. The effective concentration was determined at 10 μg ml^-1 while lower concentrations (1, 2.5 or 5 μg ml^-1) were ineffective. Head-kidney mixed leucocyte population showed significant viability reduction which was attributable to diminished viability of macrophages/monocytes and lymphocytes only whereas granulocytes' viability was not affected at the above exposure regime. Furthermore, cellular respiratory burst activity, phagocytic capacity and phagocytic ability were all reduced, with the first two parameters exhibiting the sharper reductions. Finally, transmission electron microscopy revealed that the AgNSs' internalization was brought about via phagocytosis, pinocytosis, receptor-mediated endocytosis and macropinocytosis; also, that cell death could be effected in either an apoptotic or a necrotic manner. It is concluded that AgNSs are potentially very noxious for the teleost fish immune system as they can adversely affect the function and viability of the head-kidney leucocytes.

Vitamin D3 affects innate immune status of European sea bass (Dicentrarchus labrax L.)

The effects of vitamin D₃ dietary administration on certain innate immune parameters on the expression of immune-related genes in head-kidney (HK) and gut were investigated in European sea bass Dicentrarchus labrax. Vitamin D₃ (vD₃) was orally administered to fish in a commercial pellet food supplemented with 0 (control); 3750; 18,750; or 37,500 U kg^-1. Furthermore, gut histology was considered. This study showed a modulation in the activities examined in fish fed with the addition of vD₃. After just 2 weeks of administration, diet supplementation with the vitamin resulted in increased phagocytic ability, while serum peroxidase content was increased in fish fed with all experimental diets after 4 weeks, no significant differences were observed in protease, anti-protease, natural haemolytic complement activities and total IgM level. At gene level, fbl and rbl transcripts were up-regulated in HK in fish fed with the highest concentration of vD₃-supplemented diets after 4 weeks, while in the gut, an up-regulation of hep gene was observed in fish fed with the different doses of vD₃. These results suggest that vD₃ may be of great interest for immunostimulatory purposes in fish farms.

Effects of dietary supplementation with fenugreek seeds, alone or in combination with probiotics, on gilthead seabream (Sparus aurata L.) skin mucosal immunity

Despite increasing interest in modulating the immune response of fish, providing a combination of probiotics and herbal immunostimulants in aquafeed has rarely has been studied. The effects on gilthead seabream (Sparus aurata L.) of the dietary administration of fenugreek (Trigonella foenum graecum) seeds alone (FE), or combined with one of the following probiotic strains: Bacillus licheniformis (FEBL), Lactobacillus plantarum (FELP) or Bacillus subtilis (FEBS) were evaluated. Fish were fed a control or one of the supplemented diets for 3 weeks. After 2 and 3 weeks of the feeding trial, the abundance of terminal carbohydrates, IgM levels, enzymatic activities (proteases, alkaline phosphatase, esterase and ceruloplasmin) and bactericidal activity were determined in skin mucus. Our results demonstrated that the dietary administration of FE in combination with L. plantarum, particularly, increased carbohydrate abundance, the activity of certain enzymes such as ceruloplasmin, and bactericidal activity against the pathogenic bacterium Photobacterium damselae and the non-pathogenic bacterium B. subtilis in skin mucus at the end of the trial. The carbohydrates most affected by the FELP diet were mannose/glucose, N-acetyl-d-galactosamine and N-acetyl-β-d-glucosamine. Interestingly, IgM levels were significantly higher in fish fed the FELP and FEBS diets whilst protease activity generally increased in all supplemented diets, which could suggests that the main effect in this activity was to the result of FE supplementation although that fact cannot be confirmed because the effects of probiotics addition alone were not studied. These results suggest that the combined dietary administration of fenugreek and L. plantarum will best enhance the skin mucosal immunity response of gilthead seabream.

Quality and antioxidant response of gilthead seabream (Sparus aurata L.) to dietary supplements of fenugreek (Trigonella foenum graecum) alone or combined with probiotic strains

The present study was conducted to determine the potential effect of the dietary intake of fenugreek (Trigonella foenum graecum) seeds alone or in combination with Bacillus licheniformis, Lactobacillus plantarum or B. subtilis on gilthead seabream quality and antioxidant response after 2 and 3 weeks of experimental feeding. The results showed that the supplements did not affect the percentage of the fatty acid profiles of muscle, demonstrating that all the additives tested can be administrated without any negative effect on biochemical composition and quality of gilthead seabream. The quantification of thiobarbituric acid reactive substances in muscle demonstrated the significant beneficial effect of the experimental diets compared with the control one. Besides, an increase in superoxide dismutase and catalase in liver was recorded after 3 weeks of administration of experimental diets. Furthermore, real time qPCR revealed that dietary supplementation with FEBS significantly enhances the expression of scavenging enzymes, such as cat and gr genes in the liver after 3 weeks. The findings suggest that the administration of fenugreek supplement alone or combined with probiotic strains could be considered as a good source of natural antioxidants and as a functional aquafeed ingredient for gilthead seabream.

The short-term effects of farmed fish food consumed by wild fish congregating outside the farms

We simulated in the laboratory the possible effects on fatty acids and immune status of wild fish arriving for the first time in the vicinity of a sea-cage fish farm, shifting their natural diet to commercial feed consumption, rich in fatty acids of vegetable origin. The flesh fatty acid profile of golden mullet specimens was altered after 2weeks of commercial feed consumption, showing an increase in fatty acids of vegetable origin. The serum peroxidase and bactericidal activities, and head-kidney leucocyte phagocytic capacity, increased after eight weeks of the new diet, while the respiratory burst activity decreased. The extent of these changes cannot be considered large enough to regard them as compromising the health status of fish. More research is needed in order to elucidate whether the rapid assimilation of the dietary fatty acids could harm the immune status of fish when feeding for longer periods than two months.

Effects of dietary administration of fenugreek seeds, alone or in combination with probiotics, on growth performance parameters, humoral immune response and gene expression of gilthead seabream (Sparus aurata L.)

The use of immunostimulants is considered a promising preventive practice that may help to maintain animal welfare and a healthy environment, while increasing production and providing higher profits. The purpose of this study was to evaluate the effects on gilthead seabream (Sparus aurata L.) of the dietary administration of fenugreek (Trigonella foenum graecum) seeds, alone or combined with one of the following probiotic strains: Bacillus licheniformis (TSB27), Lactobacillus plantarum or Bacillus subtilis (B46). Gilthead seabream were fed a control or one of the supplemented diets for 3 weeks. The effects of these supplemented diets on growth performance parameters and the humoral immune response (natural haemolytic complement, peroxidase, total IgM levels, proteases and antiproteases activities) were evaluated after 2 and 3 weeks of feeding. Simultaneously, the expression levels of some immune-relevant genes (igm, tcr-β, csfr1 and bd) were measured in the head-kidney. Interestingly, all probiotic supplemented diets increased seabream growth rates, especially the B. licheniformis supplemented diet. Generally, humoral immune parameters were enhanced by the dietary supplementation at the different time points measured. The results showed a significant increases in the immune parameters, principally in fish fed only fenugreek or fenugreek combined with B. subtilis. Furthermore, real time qPCR revealed that dietary supplementation significantly enhances the expression of immune-associated genes in the head-kidney, particularly igm gene expression. These results suggest that fenugreek alone or combined with one of the probiotic strains mentioned enhances the immune response of gilthead seabream, a species with one of the highest rates of production in marine aquaculture.

Comparative ontogenetic development of two marine teleosts, gilthead seabream and European sea bass: New insights into nutrition and immunity

Gilthead seabream and European sea bass are two of the most commonly farmed fish species. Larval development is critical to ensure high survival rates and thus avoid unacceptable economic losses, while nutrition and immunity are also important factors. For this reason this paper evaluates the ontogenetic development of seabream and sea bass digestive and immune systems from eggs to 73 days post-fertilisation (dpf) by assessing the expression levels of some nutrition-relevant (tryp, amya, alp and pept1) and immune-relevant (il1b, il6, il8, tnfa, cox2, casp1, tf, nccrp1, ighm and ight) genes. The results point to similar ontogenetic development trends for both species as regard nutrition and differences in some immunity related genes.

Characterization of the gilthead seabream (Sparus aurata L.) immune response under a natural lymphocystis disease virus outbreak

Lymphocystis or lymphocystis disease virus (LCDV) is distributed worldwide and affects many fresh and marine water fish species. LCDV is commonly found in aquaria fish species but also in farmed fish species, among them the gilthead seabream (Sparus aurata L.). The immune status of gilthead seabream (S. aurata) specimens under a natural outbreak of LCDV was studied. The replication of the virus was demonstrated in infected fish, but not in control fish. The results showed decreased total serum IgM levels and increased innate cellular immune response (peroxidase and respiratory burst activities) of head kidney leucocytes in LCDV-infected fish, compared to the values obtained in uninfected specimens. In addition, transcription of antiviral genes (ifn and irf3) was down-regulated in the skin of LCDV-positive fish as well as genes involved in cellular immunity (csf1r, mhc2a, tcra and ighm) that were down-regulated in skin and head kidney of infected fish. By contrast, the transcription of nccrp1 was up-regulated in head kidney after LCDV infection. These present results show that head kidney leucocytes are activated to encounter the virus at the sites of replication.

Interactions between candidate probiotics and the immune and antioxidative responses of European sea bass (Dicentrarchus labrax) larvae

The use of lactic acid bacteria (LAB) as probiotics in aquaculture may improve the quality of seed production and limit the use of antibiotics in fish hatcheries. This study attempted to further characterize the candidate probiotic Lactobacillus casei X2, and the immune and physiological responses of the sea bass larvae. L. casei X2 was confirmed as a good candidate, due to its wide antibacterial spectrum against both Gram-positive and Gram-negative bacteria, and its free radical scavenging activity. In addition, if the strain did not seem able to form biofilm on abiotic surfaces, it adhered strongly to Hep-2 cells. However, these characteristics did not seem efficient in vivo. At 20 days post-hatch (dph), the expression level of CAT gene was significantly different between group fed without probiotic and the two groups treated with either Pediococcus acidilactici or L. casei. This gene was upregulated in the group treated with strain X2 and downregulated in the group with a commercial probiotic strain P. acidilactici, suggesting a better antioxidant activity with the later strain. At the same sampling date, the IL-1β gene was upregulated in the group treated with P. acidilactici, and the HSP70 gene was overexpressed at 41 dph. As the stimulation of these two last genes, such transcriptomic indicators must be cautiously interpreted.

Mercury Accumulation, Structural Damages, and Antioxidant and Immune Status Changes in the Gilthead Seabream (Sparus aurata L.) Exposed to Methylmercury

In aquatic systems, mercury (Hg) is an environmental contaminant that causes acute and chronic damage to multiple organs. In fish, practically all of the organic Hg found is in the form of methylmercury (MeHg), which has been associated with animal and human health problems. This study evaluates the impact of waterborne-exposure to sublethal concentrations of MeHg (10 μg L(-1)) in gilthead seabream (Sparus aurata). Hg was seen to accumulate in liver and muscle, and histopathological damage to skin and liver was detected. Fish exposed to MeHg showed a decreased biological antioxidant potential and increased levels of the reactive oxygen molecules compared with the values found in control fish (nonexposed). Increased liver antioxidant enzyme activities (superoxide dismutase and catalase) were detected in 2 day-exposed fish with respect to the values of control fish. However, fish exposed to MeHg for 10 days showed liver antioxidant enzyme levels similar to those of the control fish but had increased hepato-somatic index and histopathological alterations in liver and skin. Serum complement levels were higher in fish exposed to MeHg for 30 days than in control fish. Moreover, head-kidney leukocyte activities increased, although only phagocytosis and peroxidase activities showed a significant increase after 10 and 30 days, respectively. The data show that 30 days of exposure to waterborne MeHg provokes more significant changes in fish than a short-term exposure of 2 or 10 days.

Impact of date palm fruits extracts and probiotic enriched diet on antioxidant status, innate immune response and immune-related gene expression of European seabass (Dicentrarchus labrax)

The application of additives in the diet as plants or extracts of plants as natural and innocuous compounds has potential in aquaculture as an alternative to antibiotics and immunoprophylactics. The aim of the current study was to evaluate the potential effects of dietary supplementation of date palm fruit extracts alone or in combination with Pdp11 probiotic on serum antioxidant status, on the humoral and cellular innate immune status, as well as, on the expression levels of some immune-related genes in head-kidney and gut of European sea bass (Dicentrarchus labrax) after 2 and 4 weeks of administration. This study showed for the first time in European sea bass an immunostimulation in several of the parameters evaluated in fish fed with date palm fruits extracts enriched diet or fed with this substance in combination with Pdp 11 probiotic, mainly after 4 weeks of treatment. In the same way, dietary supplementation of mixture diet has positive effects on the expression levels of immune-related genes, chiefly in head-kidney of Dicentrarchus labrax. Therefore, the combination of both could be considered of great interest as potential additives for farmed fish.

Exposure of the gilthead seabream (Sparus aurata) to sediments contaminated with heavy metals down-regulates the gene expression of stress biomarkers

Heavy metals incidence in the aquatic environment and its accumulation in fish are under constant review. Gilthead seabream (Sparus aurata) specimens were exposed for two weeks to sediments highly concentrated in metals, collected at the Portman Bay (Murcia, Spain). The metals bioaccumulation was tested in liver, muscle and skin. The potential of the sediment exposure to induce variation of the stress biomarkers genes was conducted in liver and skin. Results revealed that sediments were highly contaminated with metals. However, following 2 weeks exposure to the sediments, Cd accumulates only in liver. Interestingly, the expression of the genes mta, hsp 70 and hsp 90 were significantly down-regulated in skin. Nevertheless, cyp1a1 gene was up-regulated only in liver. Results uphold that the stress response magnitude was organ-dependent and the skin was the most responsive tissue to metal stress conditions. These results suggest that skin should be considered as target organ for biomarkers analysis in fishes.

Use of cinacalcet for the management of hyperparathyroidism in patients with different degrees of renal failure

BACKGROUND

The effects of cinacalcet in persistent and/or hypercalcaemia-associated secondary hyperparathyroidism (SHPT) have been described in patients on dialysis.

OBJECTIVES

To evaluate the efficacy and safety of cinacalcet in SHPT not on dialysis and its effects on bone turnover markers.

METHODS

Non-randomised, longitudinal, observational, analytical study of patients with chronic kidney disease (CKD) and SHPT (PTH> 80 pg/mL) as well as normo- or hypercalcaemia (≥8.5mg/dL), treated with cinacalcet.

RESULTS

Mean cinacalcet dose was 30mg/day in 66.7%. We studied 15 patients (10 women), aged 66.0±17.93years. The aetiology was unknown in 20% of cases. Sociodemographic variables and renal function parameters were recorded. We compared values at baseline as well as after 6 and 12 months. Calcium (10.3±0.55 vs. 9.4±1.04) and iPTH (392.4±317.65 vs. 141.8±59.26) levels decreased. Increased levels of phosphorus (3.7±1.06 vs. 3.9±0.85) and ß-CTX (884.2±797.22 vs. 1053.6±999.00) were detected, although there were no significant changes in GFR, urinary calcium or other bone markers. Two patients withdrew from the study (gastrointestinal intolerance and parathyroidectomy, respectively).

CONCLUSIONS

Cinacalcet at low doses is effective in the management of SHPT in CKD patients who are not on dialysis. Its use reduces iPTH and calcaemia, without causing serious side effects or significant changes in renal function.

Skin mucus proteome map of European sea bass (Dicentrarchus labrax)

Skin mucus is the first barrier of fish defence. Proteins from skin mucus of European sea bass (Dicentrarchus labrax) were identified by 2DE followed by LC-MS/MS. From all the identified proteins in the proteome map, we focus on the proteins associated with several immune pathways in fish. Furthermore, the real-time PCR transcript levels in skin are shown. Proteins found include apolipoprotein A1, calmodulin, complement C3, fucose-binding lectin, lysozyme and several caspases. To our knowledge, this is the first skin mucus proteome study and further transcriptional profiling of the identified proteins done on this bony fish species. This not only contributes knowledge on the routes involved in mucosal innate immunity, but also establishes a non-invasive technique based on locating immune markers with a potential use for prevention and/or diagnosis of fish diseases.

Dietary administration of the probiotic SpPdp11: Effects on the intestinal microbiota and immune-related gene expression of farmed Solea senegalensis treated with oxytetracycline

Few antimicrobials are currently authorised in the aquaculture industry to treat infectious diseases. Among them, oxytetracycline (OTC) is one of the first-choice drugs for nearly all bacterial diseases. The objective of this study was to evaluate the effect of the dietary administration of OTC both alone and jointly with the probiotic Shewanella putrefaciens Pdp11 (SpPdp11) on the intestinal microbiota and hepatic expression of genes related to immunity in Senegalese sole (Solea senegalensis) juveniles. The results demonstrated that the richness and diversity of the intestinal microbiota of fish treated with OTC decreased compared with those of the control group but that these effects were lessened by the simultaneous administration of SpPdp11. In addition, specimens that received OTC and SpPdp11 jointly showed a decreased intensity of the Denaturing Gradient Gel Electrophoresis (DGGE) bands related to Vibrio genus and the presence of DGGE bands related to Lactobacillus and Shewanella genera. The relationship among the intestinal microbiota of fish fed with control and OTC diets and the expression of the NADPH oxidase and CASPASE-6 genes was demonstrated by a Principal Components Analysis (PCA) carried out in this study. In contrast, a close relationship between the transcription of genes, such as NKEF, IGF-β, HSP70 and GP96, and the DGGE bands of fish treated jointly with OTC and SpPdp11 was observed in the PCA study. In summary, the results obtained in this study demonstrate that the administration of OTC results in the up-regulation of genes related to apoptosis but that the joint administration of OTC and S. putrefaciens Pdp11 increases the transcription of genes related to antiapoptotic effects and oxidative stress regulation. Further, a clear relationship between these changes and those detected in the intestinal microbiota is established.

Evaluation of waterborne exposure to heavy metals in innate immune defences present on skin mucus of gilthead seabream (Sparus aurata)

Aquatic animals are continuously exposed to chemical pollutants but the effects evoked in skin surfaces, which receive the most direct contact with them, are poorly investigated. Terminal carbohydrate composition and immunological components present in skin mucus of gilthead seabream (Sparus aurata L.) specimens exposed to waterborne sublethal dosages of heavy metals [arsenic (As2O3), cadmium (CdCl2) and mercury (CH3HgCl) at 5, 5 and 0.04 μM, respectively for 2, 10 and 30 days were analysed. Moreover, the presence of a fucose binding lectin (FBL) was evaluated by western blot and the protein profiles were by SDS-PAGE and HPLC. Results showed little effects of heavy metals in the presence of several terminal carbohydrates with few increments or decrements. Most of the enzyme activities related to immune responses were increased upon heavy metal exposure in the skin mucus including bactericidal activity. Methylmercury produced the most dramatic changes increasing all the activities. Moreover, the FBL was undetected in any of the control fish skin mucus but was evident in all the heavy metal exposed fish. In addition, As and Cd produced a clear change in the protein profile as evidenced by the lack of a protein band of around 12 kDa which is absent. These protein changes were more evident with the HPLC study showing the presence of different peaks and differences in intensity. The present results could be useful for better understanding the role and their behaviour of the mucosal immunity in skin as a key component of the innate immune system against pollutants.

Characterization of the IFN pathway in the teleost fish gonad against vertically transmitted viral nervous necrosis virus

One of the most powerful innate immune responses against viruses is mediated by type I IFN. In teleost fish, it is known that virus infection triggers the expression of ifn and many IFN-stimulated genes, but the viral RNA sensors and mediators leading to IFN production are scarcely known. Thus, we have searched for the presence of these genes in gilt-head sea bream (Sparus aurata) and European sea bass (Dicentrarchus labrax), and evaluated their expression after infection with viral nervous necrosis virus (VNNV) in the brain, the main viral target tissue, and the gonad, used to transmit the virus vertically. In sea bream, a fish species resistant to the VNNV strain used, we found an upregulation of the genes encoding MDA5 (melanoma differentiation-associated gene 5), TBK1 (TANK-binding kinase 1), IRF3 (IFN regulatory factor 3), IFN, Mx [myxovirus (influenza) resistance protein] and PKR (dsRNA-dependent protein kinase receptor) proteins in the brain, which were unaltered in the gonad and could favour the dissemination by gonad fluids or gametes. Strikingly, in European sea bass, a very susceptible species, we also identified, transcripts coding for LGP2 (Laboratory of Genetics and Physiology 2), MAVS (mitochondrial antiviral signalling), TRAF3 (TNF receptor-associated factor 3), TANK (TRAF family member-associated NFκB activator) and IRF7 (IFN regulatory factor 7), and found that all the genes analysed were upregulated in the gonad, but only mda5, lgp2, irf3, mx and pkr were upregulated in the brain. These findings supported the notion that the European sea bass brain innate immune response is unable to clear the virus and pointed to the importance of gonad immunity to control the dissemination of VNNV to the progeny--an aspect that is worth investigating in aquatic animals.

The treatment with the probiotic Shewanella putrefaciens Pdp11 of specimens of Solea senegalensis exposed to high stocking densities to enhance their resistance to disease

Aquaculture industry exposes fish to acute stress events, such as high stocking density, and a link between stress and higher susceptibility to diseases has been concluded. Several studies have demonstrated increased stress tolerance of fish treated with probiotics, but the mechanisms involved have not been elucidated. Shewanella putrefaciens Pdp11 is a strain isolated from healthy gilthead seabream (Sparus aurata L.) and it is considered as probiotics. The aim of this study was to evaluate the effect of the dietary administration of this probiotics on the stress tolerance of Solea senegalensis specimens farmed under high stocking density (PHD) compared to a group fed a commercial diet and farmed under the same conditions (CHD). In addition, during the experiment, a natural infectious outbreak due to Vibrio species affected fish farmed under crowding conditions. Changes in the microbiota and histology of intestine and in the transcription of immune response genes were evaluated at 19 and 30 days of the experiment. Mortality was observed after 9 days of the beginning of the experiment in CHD and PHD groups, it being higher in the CHD group. Fish farmed under crowding stress showed reduced expression of genes at 19 day probiotic feeding. On the contrary, a significant increase in immune related gene expression was detected in CHD fish at 30 day, whereas the gene expression in fish from PHD group was very similar to that showed in specimens fed and farmed with the conventional conditions. In addition, the dietary administration of S. putrefaciens Pdp11 produced an important modulation of the intestinal microbiota, which was significantly correlated with the high number of goblet cells detected in fish fed the probiotic diet.

Molecular mechanisms by which white tea prevents oxidative stress

The flavonoid content of tea (Camellia sinensis) has beneficial properties in the prevention of diseases. However, the mechanisms by which white tea can protect against oxidative stress remain unclear. To shed light on this issue, rats were given distilled water (controls), 0.15 mg/day (dose 1) or 0.45 mg/day (dose 2) of solid tea extract/kg body weight for 12 months. All the animals received an injection of adriamycin (ADR; 10 mg/kg body weight), except half of the control group, which were given an injection of saline solution. The expression of the nuclear factor, E2-related factor 2 (Nrf2), NAD(P)H:quinone oxidoreductase 1 (Nqo1), glutathione S-transferase (Gst), haem oxygenase-1 (Ho1), catalase (Cat), superoxide dismutase (Sod) and glutathione reductase (Gr) in liver was analysed by real-time PCR, and the activity of catalase (CAT), superoxide dismutase (SOD) and glutathione reductase (GR) was measured spectrophotometrically. ADR significantly increased the expression of Nrf2, Gst, Nqo1, Ho1, Cat, Sod and Gr with respect to the control levels and also increased the activity of CAT, SOD and GR. The intake of white tea increased in a higher degree the expression of Nrf2, Gst, Nqo1 and Ho1 in the tea + ADR group compared with the control group and C + ADR group. In addition, tea + ADR groups decreased the expression and activity of CAT, SOD and GR in a dose-dependent manner.

Comparative analysis of the humoral immunity of skin mucus from several marine teleost fish

Fish skin mucus contains several immune substances that provide the first line of defence against a broad spectrum of pathogens although they are poorly studied to date. Terminal carbohydrate composition and levels of total IgM antibodies, several immune-related enzymes (lysozyme, peroxidase, alkaline phosphatase, esterases, proteases and antiproteases) as well as the bactericidal activity (against fish pathogenic Vibrio harveyi, Vibrio angillarum, Photobacterium damselae and non-pathogenic bacteria Escherichia coli, Bacillus subtilis, Shewanella putrefaciens) were identified and measured in the skin mucus of five marine teleosts: gilthead seabream (Sparus aurata), European sea bass (Dicentrarchus labrax), shi drum (Umbrina cirrosa), common dentex (Dentex dentex) and dusky grouper (Epinephelus marginatus). First, lectin binding results suggests that skin mucus contain, in order of abundance, N-acetylneuraminic acid, glucose, N-acetyl-glucosamine, N-acetyl-galactosamine, galactose and fucose residues. Second, results showed that while some immune activities were very similar in the studied fish (e.g. IgM and lysozyme activity) other such as protease, antiprotease, alkaline phosphatase, esterase and peroxidase activities varied depending on the fish species. High levels of peroxidase and protease activity were found in U. cirrosa respect to the values obtained in the other species while E. marginatus and S. aurata showed the highest levels of alkaline phosphatase and esterase activities, respectively. Moreover, skin mucus of S. aurata revealed higher bactericidal activity against pathogenic bacteria, contrarily, to what happened with non-pathogenic bacteria (E. coli, B. subtilis). Thus, study of the variations in the carbohydrate profile and immune-related components of the fish skin mucus could help to understand the fish resistance as well as the presence and distribution of pathogens and magnitude of infections, aspects that are of major importance for the aquaculture industry.

Effect of dietary supplementation of probiotics and palm fruits extracts on the antioxidant enzyme gene expression in the mucosae of gilthead seabream (Sparus aurata L.)

Antioxidant activity is particularly important, since oxidation is an unavoidable reaction in all living bodies. At present, natural antioxidants to be used on food as an alternative to synthetic ones are being sought. Gilthead seabream (Sparus aurata L.) specimens were fed for 4 weeks with diets enriched with bacterial probiotics (Shewanella putrefaciens Pdp11 and Bacillus sp), single or in combination with Tunisian dates palm fruit extracts. The expression of the main antioxidant enzyme genes (superoxide dismutase, catalase and glutathione reductase) in the mucosae (gut, skin and gill) was evaluated after 2 and 4 weeks. Previously, free radical scavenging and several antioxidant assays were developed to know the antioxidant properties present on the palm fruits extracts. The results demonstrated that experimental diets alter the expression of the studied antioxidant genes, primarily in the gill and skin. Furthermore, the tested probiotics and mainly, the aqueous date palm fruits extracts had significant antioxidant properties based on their protective effect against the levels of intracellular reactive oxygen species, especially when administering during 4 weeks. For this reason, probiotics and date palm fruit extracts may serve as good natural antioxidants and could potentially be considered as a functional food ingredient for fish in farms.

Innate humoral immune parameters in Tilapia zillii under acute stress by low temperature and crowding

Redbelly tilapia (Tilapia zillii; Gervais, 1848) is one of the most valuable freshwater species in North Africa representing an important part of the continental production, especially in brackish lakes. In Algeria, T. zillii is distributed in several lakes and tributaries of some rivers in the south. Though some attempts are in progress to culture this species, many investigations covering its biology and farm management are still needed. In this sense, this is the first study attempting to evaluate some of the T. zillii immune parameters and valuable data to assess their health and well-being status. Thus, we have determined the levels of serum peroxidases as well as the alternative complement, antiprotease and bactericidal activities. Furthermore, we have also evaluated the potential impact of two acute stress factors, commonly found in fish farms, in these parameters. Although it was assessed that fish exposed to low temperatures or crowding were stressed, as indicated by their increased serum levels of cortisol and glucose, both acute stressors failed to significantly affect serum peroxidases as well as antiprotease and complement activities. However, the bactericidal activity was reduced in general but only in those exposed to crowding reached statistical significance. Further studies are needed to characterise the immune response in T. zillii as well as the effects that farming stresses may produce.

Comparative skin mucus and serum humoral defence mechanisms in the teleost gilthead seabream (Sparus aurata)

Mucosal surfaces of fish, including skin, gill and gut, contain numerous immune substances poorly studied that act as the first line of defence against a broad spectrum of pathogens. This study aimed to identify and characterize for the first time different constitutive humoral defence mechanisms of the skin mucus of gilthead seabream (Sparus aurata). To do this, the levels of total immunoglobulin M, several enzymes and proteins (peroxidase, lysozyme, alkaline phosphatase, esterases, proteases and antiproteases), as well as the bactericidal activity against opportunist fish pathogens (Vibrio harveyi, Vibrio angillarum, Photobacterium damselae) and non-pathogenic bacteria (Escherichia coli, Bacillus subtilis) were measured in the skin mucus and compared with those found in the serum. This study demonstrates that gilthead seabream skin mucus contains lower levels of IgM, similar levels of lysozyme, alkaline phosphatase and proteases, and higher esterase, peroxidase and antiprotease activities than serum. In addition, skin mucus revealed stronger bactericidal activity against tested fish pathogen bacteria compared to the serum activity, while human bacteria can even grow more in the presence of mucus. The results could be useful for better understanding the role of the skin mucus as a key component of the innate immune system with potential application for the aquaculture.

Modulatory effects of deltamethrin-exposure on the immune status, metabolism and oxidative stress in gilthead seabream (Sparus aurata L.)

Deltamethrin, a sintetic pyrethroid, is the insecticide that has been replacing recently to others like organochlorines, organophosphates and carbamates which are less toxic for birds and mammals, although, unfortunately, all of them are highly toxic to various non-targeted aquatic organisms including fish. In the present study, the consequences of the exposition of gilthead seabream (Sparus aurata L.) specimens to sublethal bath dose of deltamethrin (0.1 ppb) on organo-somatic indexes, immunity, seric metabolic parameters, oxidative stress and liver histology were determined after 1, 3, 7 and 14 days of exposure. Deltamethrin alters gilthead seabream immune status, the hepato-somatic index and various seric metabolic parameters since the first exposure day while important progressive deleterious morphological changes in liver were also observed. However, no statistically significant deviation was detected in the expression of oxidative stress-related genes whilst the expression of cytochrome P450 gene was up-regulated in head-kidney and liver of exposed fish. Overall, the present results indicate severe immunotoxicological and metabolic effects of deltamethrin in gilthead seabream, the species with the highest rate of production in Mediterranean aquaculture. In general, the values obtained for the tested parameters during the trial seem to indicate that specimens try to adapt to this adverse situation although the continuous presence of the toxic impede the hypothetic recovery of homoeostasis. The use of deltamethrin in the proximities of seabream farms should be carefully considered.

Accumulation, histopathology and immunotoxicological effects of waterborne cadmium on gilthead seabream (Sparus aurata)

Studies in fish have demonstrated that Cd-exposure produce skeletal deformities and alterations in tissue morphology, enzyme activities, stress response, ion regulation and immune response. In the present work, gilthead seabream (Sparus aurata) specimens were exposed to waterborne Cd (5 μM CdCl2 or 1 mg L(-1)) for 2, 10 or 30 days. Organo-somatic changes, Cd accumulation, liver histology and humoral and cellular immune responses were determined. Results showed that exposure of seabream specimens to Cd induced no alterations on spleen and liver organo-somatic indexes whilst produced progressive deleterious morphological alterations in liver and exocrine pancreas that correlated with the hepatic Cd-accumulation. Regarding the immunotoxicological potential, strikingly, Cd-exposure produced a reduction in the serum complement activity and leucocyte respiratory burst to a significant extent after 10 and 30 days whilst the serum peroxidase activity and leucocyte phagocytosis were increased at different sampling times. On the other hand, serum IgM levels and leucocyte peroxidase activity resulted unaltered. The present results seem to indicate that seabream exposed to Cd in the present conditions suffer toxicity.

Immunotoxicological effects of inorganic arsenic on gilthead seabream (Sparus aurata L.)

Arsenic (As) has been associated with multitude of animal and human health problems; however, its impact on host immune system has not been extensively investigated. In fish, there are very few works on the potential risks or problems associated to the presence of arsenic. In the present study we have evaluated the effects of exposure (30 days) to sub-lethal concentrations of arsenic (5 μM As₂O₃) in the teleost fish gilthead seabream (Sparus aurata), with special emphasis in the innate immune response. The arsenic concentration was determined using atomic fluorescence spectrometry (AFS) in liver and muscle of exposed fish showing As accumulation in the liver after 30 days of exposure. The hepatosomatic index was increased at significant extent after 10 days but returned to control values after 30 days of exposure. Histological alterations in the liver were observed including hypertrophy, vacuolization and cell-death processes. Focusing on the immunological response, the humoral immune parameters (seric IgM, complement and peroxidase activities) were no affected to a statistically significant extent. Regarding the cellular innate parameters, head-kidney leucocyte peroxidase, respiratory burst and phagocytic activities were significantly increased after 10 days of exposition compared to the control fish. Overall, As-exposure in the seabream affects the immune system. How this might interfere with fish biology, aquaculture management or human consumers warrants further investigations. This paper describes, for the first time, the immunotoxicological effects of arsenic exposure in the gilthead seabream, which is a species with the largest production in Mediterranean aquaculture.

Nodavirus infection induces a great innate cell-mediated cytotoxic activity in resistant, gilthead seabream, and susceptible, European sea bass, teleost fish

Viral nervous necrosis (VNN) virus produces great mortalities in fish having susceptible and reservoir species between the most important marine aquaculture species. Cell-mediated cytotoxicity (CMC) is considered, towards the interferon (IFN), the most important mechanism of the immune response to fight against viral infections but it has been very scarcely evaluated. We aimed to evaluate the effects of VNNV infection in the reservoir gilthead seabream (Sparus aurata) and susceptible European sea bass (Dicentrarchus labrax). Firstly, after experimental infection we found mortalities in the sea bass (55%) but no in the seabream. Moreover, VNN virus replicates in the brain of both species as it was reflected by the high up-regulation of the Mx gene expression. Interestingly, the head-kidney leucocyte cell-mediated cytotoxic activity was significantly increased in both species reaching highest activity at 7 days: 3.65- and 2.7-fold increase in seabream and sea bass, respectively. This is supported by the significant up-regulation of the non-specific cytotoxic cell receptor (NCCRP-1) in the two fish species. By contrast, phagocytosis was unaffected in both species. The respiratory burst was increased in seabream 7 days post-infection whilst in sea bass this activity was significantly decreased at days 7 and 15. Our results demonstrate the significance of the CMC activity in both gilthead seabream and European sea bass against nodavirus infections but further studies are still needed to understand the role of cytotoxic cells in the antiviral immune response and the mechanisms involved in either reservoir or susceptible fish species.

Epigenetic regulation of HIF-1α in renal cancer cells involves HIF-1α/2α binding to a reverse hypoxia-response element

Inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene underlies the majority of sporadic clear cell renal cell carcinomas (CCRCCs) and is also responsible for the hereditary VHL cancer syndrome. VHL loss of function results in constitutive stabilization of hypoxia-inducible factors (HIF-1α and HIF-2α) due to insufficient proteolysis in the presence of oxygen. This activates multiple genes relevant to tumorigenesis, allowing cells to acquire further mutations and undergo malignant transformation. However, the specific role of each HIF-α subunit in CCRCC tumorigenesis is not yet well understood. The current paradigm supports that in the first stages of CCRCC formation the stabilization of HIF-1α is dominant and this limits proliferation, but later on HIF-2α increases and this induces a more aggressive cell behavior. Understanding how this transition happens is highly relevant, as it may provide novel ways to treat these cancers. Here, we show that VHL inactivation in CCRCC cells results in HIF-1α/2α-dependent downregulation of HIF-1α mRNA through direct binding of either subunit to a reverse hypoxia-response element in the HIF-1α proximal promoter. This binding activates a series of repressive histone modification marks including histone 3 lysine 27 trimethylation (H3K27me3) to make the changes stable, and if overturned reduces CCRCC cell proliferation due to excessive HIF-1α expression level. Our findings thus help understand how HIF-α subunits influence each other and also reinforce the idea that epigenetic mechanisms are a key step of CCRCC progression.

Effects of 2-deoxy-D-glucose on the immune system of seabream (Sparus aurata L.)

Stressful situations are a major problem in aquaculture because they affect the immune system. 2-Deoxy-D-glucose (2-DG) is a derivative of a glucose analogue that reduces the availability of energy, thereby inhibiting cell metabolism so that it is unable to enter the glycolysis pathway. In this paper, 2-DG has been administered in order to study if the immune function is compromised during metabolic stress. Blood glucose level was measured as an indicator of the inhibition of glycolysis, and the effects of intraperitoneal administration of 2-DG on the main parameters of the humoral (complement, IgM levels and peroxidase activity in blood plasma) and cellular (respiratory burst, intracellular peroxidase level and phagocytosis activity) immune parameters of gilthead seabream (Sparus aurata, L) were evaluated. Furthermore, the expression levels of immune-associated genes (CSF-1R, NCCRP-1, Hep, TCR-β, IgM(H), MHC-IIα, C3 and IL-1β) were analyzed by real-time PCR in head-kidney. A total of 5 intraperitoneal injections were performed at 48 h intervals. Three experimental groups were established: a control group injected with phosphate buffer saline, group 2-DG 500 and group 2-DG 750 injected with 500 mg kg⁻¹ and 750 mg kg⁻¹ 2-DG, respectively (N=15). After the third and fourth injection, some specimens of both DG-treated groups died. Following the first and third injection, the blood glucose levels of both 2-DG treated groups increased to a statistically significant extent with respect to the control group. While the humoral immune parameters were not significantly affected as a consequence of 2-DG administration, the cellular activities of leucocytes were. The injection of 500 mg kg⁻¹ 2-DG provoked up- or down-regulation of the immune-relevant genes analyzed, while the injection of 750 mg kg⁻¹ always caused down-regulation of these genes. The results suggest that 2-DG provokes metabolic stress, which reduces the activities carried out by immune cells (leucocytes) and induces down-regulation of the immune-relevant genes analyzed when the energy available to the cell decreases.

The expression profile of TLR9 mRNA and CpG ODNs immunostimulatory actions in the teleost gilthead seabream points to a major role of lymphocytes

The potential effects of synthetic unmethylated oligodeoxynucleotides (ODN) containing CpG motifs, mimicking bacterial DNA, has never been evaluated on the immune response in the teleost fish gilthead seabream (Sparus aurata), the most important fish species in Mediterranean aquaculture. First, binding and competition studies have demonstrated that binding is saturated and promiscuous, suggesting the participation of several receptors. Moreover, leucocyte cytotoxic (NCC) activity, production of ROIs (reactive oxygen intermediates), and expression of immune-relevant genes was greatly primed by ODNs. Focusing on the mechanism, the TLR9 gene is widely distributed in seabream tissues and differently regulated in vitro by several stimuli. Moreover, and for the first time in fish, TLR9 mRNA has been detected in lymphocytes as the main cell-source. To conclude, ODNs containing GACGTT, GTCGTT (optimal for mouse and human, respectively) or AACGTT motifs are the most potent inducers of seabream immunity, whilst the involvement of TLR9 is under debate.

Effect of sex-steroid hormones, testosterone and estradiol, on humoral immune parameters of gilthead seabream

The role of sex-steroid hormones, testosterone (T) and 17beta-estradiol (E2), on the humoral immune parameters of the teleost gilthead seabream Sparus aurata was studied attempting to deepen on the knowledge of the immune-reproductive system interactions. Fish were injected intraperitoneally with coconut oil containing different dosages of T (0, 2, or 5 microg g(-1) body weight [bw]) or E2 (0, 1, or 2 microg g(-1) bw) and sampled 1, 3, and 7 days later. Hormonal levels and immune parameters (complement, peroxidase and antiprotease activities and IgM levels) were determined in plasma. Plasma hormone levels peaked at 1 day post-injection decreasing thereafter. Treatment with T significantly increased both complement and peroxidase activities after 3 days of injection but antiprotease activity and IgM levels remained unchanged. Treatment with E2 enhanced complement activity 1 day post-injection while decreased it after 3 and 7 days. However, peroxidase activity increased at 3 and 7 days post-injection while total IgM levels decreased. Implications of T and E2 in the immune-reproductive system interactions were discussed.

Sharpsnout sea bream (Diplodus puntazzo) humoral immune response against the parasite Enteromyxum leei (Myxozoa)

The humoral innate immune response of sharpsnout seabream Diplodus puntazzo against the myxozoan Enteromyxum leei was studied. Enteromyxosis was transmitted by cohabitation and a group of uninfected fish served as control. At 5, 12, 19, 26, 40 and 55 days post-exposure (p.e.), control and recipient fish were sampled to determine the prevalence of infection and some humoral innate immune parameters (antiprotease, antitumoral and peroxidase activities). Prevalence of infection was high from day 12 p.e. and reached 100% at days 40 and 55, when intensity of infection was medium to severe. The antiprotease activity was significantly increased in E. leei-exposed fish with respect to control fish at days 12 and 19 p.e. The serum antitumoral activity was slightly lower in recipient than in control fish at all sampling times, except at 40 days p.e., though no statistically significant differences were observed. Serum peroxidases were higher in all recipient fish than in control ones, with the highest stimulation index at 40 days p.e. Within recipient fish, no differences were detected between sampling times in any of the measured activities. The possible implication of these immune factors in the high susceptibility of D. puntazzo to this enteromyxosis is discussed.

Cell-mediated cytotoxicity is the main innate immune mechanism involved in the cellular defence of gilthead seabream (Teleostei: Sparidae) against Enteromyxum leei (Myxozoa)

The cellular innate immune response of gilthead seabream (Sparus aurata L.) against the myxozoan Enteromyxum leei was studied. Enteromyxosis was transmitted by maintaining uninfected fish (recipients) together with infected animals. A group of fish not exposed to the infection served as controls. After 10, 22, 38, 52 and 108 days, control and recipient fish were sampled and leucocyte subpopulations and cellular immune responses (leucocyte peroxidases, phagocytosis, respiratory burst and cytotoxicity) of the head-kidney leucocytes were determined. The percentage of acidophilic granulocytes was significantly lower in non-parasitized and parasitized recipient fish than in control fish after 22 days but no significant differences were seen between non-parasitized and parasitized recipient animals. The leucocyte peroxidase content, phagocytosis and respiratory burst activity were seen to have decreased significantly at different sampling times in both non-parasitized and parasitized recipient fish with respect to the controls, whereas cytotoxic activity was up to 2.3 times higher than in control fish. Within the recipient group, little difference was observed in the studied parameters between non-parasitized and parasitized fish. These data demonstrate that cytotoxic activity may have an important role in the defence of gilthead seabream against the myxosporean E. leei. Immunological implications of E. leei infections are discussed.