Pro- and anti-inflammatory cytokine expression in carp blood and head kidney leukocytes exposed to cyanotoxin stress--an in vitro study

Dietary leucine modulates growth performance, Nrf2 antioxidant signaling pathway and immune response of juvenile blunt snout bream (Megalobrama amblycephala)

The present study assessed the effects of dietary leucine on growth performance, antioxidant status and immunity in juvenile blunt snout bream. Fish were fed six practical diets of graded leucine levels ranging from 0.90% to 2.94% of dry basis for 8 weeks. Trail results showed that compared to control group (0.90%), 1.72% dietary leucine level significantly improved final weight (FW), weight gain rate (WG) and specific growth rate (SGR), and significantly lowered feed conversion ratio (FCR). Based on WG and SGR, the optimal dietary leucine level was obtained at 1.40% and 1.56%, respectively. Whole body crude lipid and protein contents were improved with increasing dietary leucine up to 2.14% and thereafter showed a downward trend, while whole body moisture content showed a converse trend. No significant change was found in whole body ash content. 1.72% dietary leucine level significantly improved the antioxidant capacity of fish by regulating the plasma superoxide dismutase (SOD) activity, glutathione peroxidase (GPx) activity, total antioxidant capacity (T-AOC) activity, catalase (CAT) activity, aspartate aminotransferase (AST) activities and malondialdehyde (MDA) content, furthermore, 1.72% dietary leucine level also significantly improved the antioxidant genes expressions of associated with Nrf2 signaling pathway by regulating heme oxygenase-1 (HO-1), GPx, copperezinc superoxide dismutase (Cu/Zn-SOD), manganese superoxide dismutase (Mn-SOD), 2.14% dietary leucine levels also significantly improved glutathione transferase (GST) mRNA level. Dietary leucine levels significantly affected plasma immunity parameters such as the contents of plasma complement component 3 (C3), immunoglobulin M (IgM) and lowered the hepatopancreas genes expressions of pro-inflammatory factor by regulating interleukin 1β (IL-1β), interleukin 8 (IL-8) and tumour necrosis factor-α (TNF-α) mRNA levels. The present study indicated that optimal dietary leucine level plays an important role in improving growth, enhancing antioxidant and immune status to maintain the health in juvenile blunt snout bream.

Dietary threonine deficiency depressed the disease resistance, immune and physical barriers in the gills of juvenile grass carp (Ctenopharyngodon idella) under infection of Flavobacterium columnare

This study was conducted to investigate the effects of dietary threonine on the disease resistance, gill immune and physical barriers function of juvenile grass carp (Ctenopharyngodon idella). A total of 1080 juveniles were fed six iso-nitrogenous diets containing graded levels of threonine (3.99-21.66 g kg^-1 diet) for 8 weeks, and then challenged with Flavobacterium columnare. Results showed that threonine deficiency (3.99 g kg^-1 diet): (1) increased the gill rot morbidity after exposure to F. columnare; (2) attenuated the gill immune barrier function by decreasing antimicrobial substances production, up-regulating the mRNA levels of pro-inflammatory cytokines (except IL-12p40), and down-regulating the anti-inflammatory cytokines partly due to the modulation of NF-κB and TOR signaling. (3) disrupt the gill tight junction complexes by down-regulating TJs (claudin-3, -b, -c, 12, occludin, ZO-1 and ZO-2) and up-regulating TJs (claudin-7a, -7b) as well as related signaling molecule myosin light chain kinase mRNA levels (P < 0.05). (4) exacerbated the gill apoptosis by up-regulating cysteinyl aspartic acid-protease-3, 8, 9, c-Jun N-terminal kinases and mediating apoptosis related factors mRNA levels (P < 0.05); (5) exacerbated oxidative injury with increased reactive oxygen species, malondialdehyde and protein carbonyl contents (P < 0.05), decreased the antioxidant related enzymes activities and corresponding mRNA levels (except glutathione peroxidase-1b and glutathione-S-transferase-omega 2) as well as glutathione contents (P < 0.05) partly ascribe to the abridgement of NF-E2-related factor 2 signaling [Nrf2/Keap1a (not Keap1b)] in fish gill. Overall, threonine deficiency depressed the disease resistance, and impaired immune and physical barriers in fish gill. Finally, based on the gill rot morbidity and biochemical indices (immune indices LA activity and antioxidant indices MDA content), threonine requirements for juvenile grass carp (9.53-53.43 g) were estimated to be 15.32 g kg^-1 diet (4.73 g 100 g^-1 protein), 15.52 g kg^-1 diet (4.79 g 100 g^-1 protein), 15.46 g kg^-1 diet (4.77 g 100 g^-1 protein), respectively.

Modulatory role of L-carnitine against microcystin-LR-induced immunotoxicity and oxidative stress in common carp

Microcystin-LR (MCLR), one of the most popular microcystins (MCs) found in many field water bodies around the world, poses great health risks to animals and humans. In the present study, healthy common carp (initial weight 24.8 ± 2.3 g) were randomly assigned to five groups. Group I was fed on normal diet as control. Group II was maintained on normal diet and received MCLR intraperitoneal injection (150 μg kg^-1 BW). Common carp in groups III, IV, and V were daily pretreated with L-carnitine (LC) at doses of 0.5, 1.0, and 2.0 g kg^-1 of the diet for 4 weeks prior to MCLR intraperitoneal injection. The results showed that MCLR alone led to a significant downregulation in immune response, including serum complement C3, lysozyme, and bactericidal activity. However, oxidative stress response: catalase (CAT), superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GPx), and lipid peroxidation (LPO) levels were significantly increased. Similarly, gene expressions of inflammatory IL-1β, TNF-α, IFN I, and heat shock proteins (HSP70 and HSP90) were also upregulated after challenged with MCLR. However, LC pretreated group caused a significant elevation in immune response (C3, lysozyme, and bactericidal activity) and gene expressions of inflammatory IL-1β, TNF-α, IFN I, and heat shock proteins (HSP70 and HSP90) after MCLR stress. Antioxidant activities (CAT, SOD, GSH, GPx, and LPO) were returned to background levels at 96 h after MCLR challenge. Strikingly, LC supplementation at 2.0 g kg^-1 has been considered the optimum for common carp since it exhibited enhancement of immune response and antioxidant activity over the level 0.5 and 1.0 g kg^-1, and even better than that of control level. It was concluded that LC as a functional feed additive significantly inhibited the progression of MCLR-induced immunotoxicity and oxidative stress in common carp.

20 Years of fish immunotoxicology - what we know and where we are

Despite frequent field observations of impaired immune response and increased disease incidence in contaminant-exposed wildlife populations, immunotoxic effects are rarely considered in ecotoxicological risk assessment. The aim of this study was to review the literature on immunotoxic effects of chemicals in fish to quantitatively evaluate (i) which experimental approaches were used to assess immunotoxic effects, (ii) whether immune markers exist to screen for potential immunotoxic activities of chemicals, and (iii) how predictive those parameters are for adverse alterations of fish immunocompetence and disease resistance. A total of 241 publications on fish immunotoxicity were quantitatively analyzed. The main conclusions included: (i) To date, fish immunotoxicology focused mainly on innate immune responses and immunosuppressive effects. (ii) In numerous studies, the experimental conditions are poorly documented, as for instance age or sex of the fish or the rationale for the selected exposure conditions is often missing. (iii) Although a broad variety of parameters were used to assess immunotoxicity, the rationale for the choice of measured parameters was often not given, remaining unclear how they link to the suspected immunotoxic mode of action of the chemicals. (iv) At the current state of knowledge, it is impossible to identify a set of immune parameters that could reliably screen for immunotoxic potentials of chemicals. (v) Similarly, in fish immunotoxicology there is insufficient understanding of how and when chemical-induced modulations of molecular/cellular immune changes relate to adverse alterations of fish immunocompetence, although this would be crucial to include immunotoxicity in ecotoxicological risk assessment.

Transcriptome profiling of Galaxea fascicularis and its endosymbiont Symbiodinium reveals chronic eutrophication tolerance pathways and metabolic mutualism between partners

In the South China Sea, coastal eutrophication in the Beibu Gulf has seriously threatened reef habitats by subjecting corals to chronic physiological stress. To determine how coral holobionts may tolerate such conditions, we examined the transcriptomes of healthy colonies of the galaxy coral Galaxea fascicularis and its endosymbiont Symbiodinium from two reef sites experiencing pristine or eutrophied nutrient regimes. We identified 236 and 205 genes that were differentially expressed in eutrophied hosts and symbionts, respectively. Both gene sets included pathways related to stress responses and metabolic interactions. An analysis of genes originating from each partner revealed striking metabolic integration with respect to vitamins, cofactors, amino acids, fatty acids, and secondary metabolite biosynthesis. The expression levels of these genes supported the existence of a continuum of mutualism in this coral-algal symbiosis. Additionally, large sets of transcription factors, cell signal transduction molecules, biomineralization components, and galaxin-related proteins were expanded in G. fascicularis relative to other coral species.

Pathological damage and immunomodulatory effects of zebrafish exposed to microcystin-LR

Cyanobacterial blooms caused by water eutrophication have become a worldwide problem. Microcystins (MCs), especially microcystin-LR (MC-LR), released during cyanobacterial blooms exert great toxicity on fish and even lead to massive death. The present study mainly investigated the pathological damage and immune response of spleen, gut and gill in zebrafish exposed to MC-LR. Fish were exposed to 0, 1, 5 and 20 μg/L of MC-LR for 30 d. In zebrafish exposed to 5 and 20 μg/L MC-LR, edematous mitochondria, deformation of the nucleus and compaction of chromatin were observed in lymphocyte of spleen; frayed gut villi, exfoliation of epithelial cells and widespread cell lyses were observed in intestines; hyperemia in gill lamellae, epithelial tissue edema and uplift and lamellar fusion were observed in gill. Varied changed gene expression was observed in spleen, intestine and gill of zebrafish. The transcriptional levels of IFN-1 and IL-8 in spleen significantly up-regulated in 20 μg/L group, and the transcription of IL-1β and TNFα in spleen increased in 1 μg/L MC-LR treated fish. In addition, the mRNA levels of IFN-1, IL-1β, IL-8, TGF-β and TNF-α dramatically increased in intestine and gill in all MC-LR treated groups. The present studies indicated that MC-LR exposure caused marked pathological damage, however, fish could adjust actively the expression of innate immune-related genes to resist the tissue damage. Our findings provided strong evidence of the recovery potential of fish exposed to microcystins.

Dietary alpha-linolenic acid/linoleic acid ratios modulate intestinal immunity, tight junctions, anti-oxidant status and mRNA levels of NF-κB p65, MLCK and Nrf2 in juvenile grass carp (Ctenopharyngodon idella)

This study was conducted to investigate the effects of dietary alpha-linolenic acid/linoleic acid (ALA/LNA) ratios on the immune response, tight junctions, antioxidant status and immune-related signaling molecules mRNA levels in the intestine of juvenile grass carp (Ctenopharyngodon idella). A total of 1260 juvenile grass carp with an average initial weight of 8.78 ± 0.03 g were fed diets with different ALA/LNA ratios (0.01, 0.34, 0.68, 1.03, 1.41, 1.76 and 2.15) for 60 days. Results indicated that ALA/LNA ratio of 1.03 significantly increased acid phosphatase, lysozyme activities and complement C3 contents, promoted interleukin 10, transforming growth factor β1 and κB inhibitor α mRNA abundance, whereas suppressed pro-inflammatory cytokines (interleukin 1β, interleukin 8, tumor necrosis factor α and interferon γ2) and signal molecules (IκB kinase β, IκB kinase γ and nuclear factor κB p65) mRNA levels in the intestine (P < 0.05), suggesting that optimal dietary ALA/LNA ratio improved intestinal immune response of juvenile fish. Additionally, ALA/LNA ratio of 1.03 significantly promoted Claudin-3, Claudin-b, Claudin-c, Occludin and ZO-1 gene transcription, whereas reduced Claudin-15a and myosin light-chain kinase mRNA levels in the intestine, suggesting that appropriate dietary ALA/LNA ratio strengthened tight junctions in the intestine of juvenile fish. Meanwhile, ALA/LNA ratio of 1.03 noticeably elevated glutathione contents, copper/zinc superoxide dismutase, glutathione peroxidase, glutathione S-transferase and glutathione reductase activities and mRNA levels, as well as signaling molecule nuclear factor erythoid 2-related factor 2 gene transcriptional abundance in the intestine, suggesting that proper ratio of dietary ALA/LNA ameliorate the intestinal antioxidant status of juvenile fish. Based on the quadratic regression analysis of the complement C3 content in the distal intestine and malondialdehyde content in the whole intestine, optimal ALA/LNA ratio for maximum growth of juvenile grass carp (8.78-72.00 g) were estimated to be 1.13 and 1.12, respectively.

Chronic exposure to microcystin-LR affected mitochondrial DNA maintenance and caused pathological changes of lung tissue in mice

Microcystin-LR (MC-LR), an important variant of cyanotoxin family, was frequently encountered in the contaminated aquatic environment and taken as a potent hepatotoxin. However, a little was known on the association between the long-term MC-LR exposure and lung damage. In this study, we investigated the changes of the pulmonary histopathology, mitochondrial DNA (mtDNA) integrity and the expression of mtDNA encoded genes in the mice with chronic exposed to MC-LR at different concentrations (1, 5, 10, 20 and 40 μg/L) for 12 months. Our results showed that the long-term and persistent exposure to MC-LR disturbed the balance of redox system, influenced mtDNA stability, changed the expression of mitochondrial genes in the lung cells. Notably, MC-LR exposure influenced the level of inflammatory cytokines and resulted in thickening of the alveolar septa. In conclusion, chronic exposure to MC-LR affected mtDNA maintenance, and caused lung impairment in mice.

Deficiency of dietary niacin impaired intestinal mucosal immune function via regulating intestinal NF-κB, Nrf2 and MLCK signaling pathways in young grass carp (Ctenopharyngodon idella)

This study investigated the effects of dietary niacin on intestinal mucosal immune and physical barrier, and relative mRNA levels of signaling molecules in the intestine of young grass carp (Ctenopharyngodon idella). A total of 540 young grass carp (255.63 ± 0.41 g) were fed six diets containing graded levels of niacin (3.95, 14.92, 24.98, 35.03, 44.97 and 55.01 mg/kg diet) for 8 weeks. Results observed that niacin deficiency decreased lysozyme (LA) and acid phosphatase (ACP) activities, and complement 3 (C3) content in the intestine (P < 0.05), down-regulated mRNA levels of liver expressed antimicrobial peptide 2 (LEAP-2), hepcidin, interleukin 10, transforming growth factor β1 and inhibitor of κBα (IκBα) (P < 0.05), up-regulated tumor necrosis factor α, interleukin 1β, interferon γ2, interleukin 8, nuclear factor kappa B P65 (NF-κB P65), IκB kinase α (IKKα), IκB kinase β (IKKβ) and IκB kinase γ (IKKγ) in all intestinal segments of young grass carp (P < 0.05). In addition, niacin deficiency increased reactive oxygen species (ROS), malondialdehyde (MDA) and protein carbonyl (PC) contents, decreased glutathione content, and copper/zinc superoxide dismutase (CuZnSOD), manganese superoxide dismutase (MnSOD), catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferases (GST) and glutathione reductase (GR) activities in the intestine of young grass carp (P < 0.05). Additionally, niacin deficiency decreased mRNA levels of CuZnSOD, MnSOD, GPx, CAT, GST, GR, Claudin b, Claudin 3, Claudin c, Occludin, ZO-1, Claudin 15 and NF-E2-related factor 2 (Nrf2) (P < 0.05), and increased Claudin 12, Kelch-like ECH-associating protein 1a (Keap1a), myosin light-chain kinase (MLCK) and p38 mitogen-activated protein kinase (p38 MAPK) mRNA expression levels in the intestine of young grass carp (P < 0.05), while the mRNA level of Kelch-like ECH-associating protein 1b (Keap1b) did not change (P > 0.05). In conclusion, niacin deficiency decreased intestinal mucosal immune and intestinal physical function, as well as regulated mRNA levels of NF-κB P65, IκBα, IKKα, IKKβ, IKKγ, Nrf2, Keap1a, p38 MAPK and MLCK in the intestine of young grass carp. Based on the broken-line model analysis of intestinal lysozyme activity, the requirement of niacin for young grass carp (255.63 ± 0.41 g) were estimated to be 39.80 mg/kg diet.

Intestinal immune function, antioxidant status and tight junction proteins mRNA expression in young grass carp (Ctenopharyngodon idella) fed riboflavin deficient diet

This study investigated the effects of riboflavin on intestinal immunity, tight junctions and antioxidant status of young grass carp (Ctenopharyngodon idella). Fish were fed diets containing graded levels of riboflavin (0.63-10.04 mg/kg diet) for 8 weeks. The study indicated that riboflavin deficiency decreased lysozyme, acid phosphatase, copper/zinc superoxide dismutase, glutathione reductase and glutathione peroxidase activities, and contents of complement component 3 and reduced glutathione in the intestine of fish (P < 0.05). Meanwhile, riboflavin deficiency increased reactive oxygen species, malondialdehyde and protein carbonyl contents and catalase activity (P < 0.05) in the intestine of fish. Furthermore, real-time polymerase chain reaction analysis was used to investigate mRNA expression patterns and found that the mRNA levels of interleukin 10 and transforming growth factor β1, Occludin, zonula occludens 1, Claudin-b and Claudin-c, inhibitor protein κBα, target of rapamycin, ribosomal S6 protein kinase 1 and NF-E2-related factor 2, copper/zinc superoxide dismutase, glutathione peroxidase and glutathione reductase were decreased (P < 0.05) in the intestine of fish fed riboflavin-deficient diet. Conversely, the mRNA levels of tumor necrosis factor α, interleukin 1β, interleukin 8, nuclear factor kappa B p65, Ikappa B kinase β, Ikappa B kinase γ, Kelch-like-ECH-associated protein 1b, p38 mitogen-activated protein kinase, myosin light chain kinase and Claudin-12 were increased (P < 0.05) in the intestine of fish fed riboflavin-deficient diet. In conclusion, riboflavin deficiency decreased immunity and structural integrity of fish intestine. The optimum riboflavin level for intestinal acid phosphatase activity of young grass carp was estimated to be 6.65 mg/kg diet.

Effects of cylindrospermopsin on the phagocytic cells of the common carp (Cyprinus carpio L.)

Cylindrospermopsin is a cyanotoxin with cytotoxic activity. It is released into water during and after cyanobacterial water blooms and thus poses a threat to the health of fish. There is very little information available concerning the effects of the toxin on fish immune cells. In this study, we assessed the potential impact of cylindrospermopsin on the basic functions of phagocytic cells from common carp (Cyprinus carpio L.), including phagocytosis, reactive oxygen and nitrogen species production, and the structure of microfilaments and selected cytokine expression. Phagocytic cells, isolated from fish head kidneys, were exposed to the toxin at concentrations of 0.05, 0.1, 0.5 or 1 µg ml(-1), for up to 24 h. Cytotoxicity, detected by lactate dehydrogenase release, was observed at the highest studied concentration. A decrease in phagocytic activity and changes in actin cytoskeletal structures were observed after the cell exposure to the toxin at 0.5 and 1 µg ml(-1). Moreover, at all tested concentrations, cylindrospermopsin increased the production of reactive oxygen and nitrogen species. It also evidently influenced the expression of genes of proinflammatory cytokines interleukin-1β and tumour necrosis factor-α and, to a minor extent, anti-inflammatory transforming growth factor-β, but had no effects on interleukin-10. The results indicated that the cyanotoxin cylindrospermopsin is able to modify basic features of carp phagocytic cells, which might result in adverse consequences for fish health.

Microcystin-LR exposure to adult zebrafish (Danio rerio) leads to growth inhibition and immune dysfunction in F1 offspring, a parental transmission effect of toxicity

Microcystins (MCs) are algal toxins produced intracellularly within the cyanobacteria cells. MCs exposure exerts great harm to the reproductive system of fish and deteriorates the quality of eggs and sperms, and has further adverse effects on early developmental stages of fish. Whether the MC toxicity can be parentally transmitted to offspring, even though the embryos and larvae are free of MC exposure? In the present study, adult zebrafish were continuously exposed to MC-LR (with dose of 1, 5 and 20 μg/L) for 30 days. After MC-LR exposure, fertilized eggs were collected and the following F1 generation was reared in water containing no MC-LR until 60 days post fertilization (dpf). In F1 offspring, both body weight and body length were evidently dropped. Some growth and immune related genes were detected using the real-time PCR. The transcriptional levels of these genes significantly decreased in F1 offspring of zebrafish whose parents were treated with 5 and 20 μg/L MC-LR. The activities of some antioxidant enzymes, including superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) significantly dropped in 5 and 20 μg/L MC-LR groups, and the malondialdehyde (MDA) levels markedly increased in all the three treatment groups. Furthermore, distinct pathological changes in liver were observed in F1 zebrafish. Our findings show that the MC-LR exposure to parental zebrafish results in liver damage and evidently influences the growth and immune function in F1 offspring. We consider this damage as a parental transmission effect of microcystin toxicity. Further mechanism studies are necessary to elucidate this transmission effect.

Dietary tryptophan modulates intestinal immune response, barrier function, antioxidant status and gene expression of TOR and Nrf2 in young grass carp (Ctenopharyngodon idella)

The present research evaluated the effects of dietary tryptophan (Trp) on growth performance, intestinal mucosal immune, barrier function and antioxidant capacity and gene expression of young grass carp (Ctenopharyngodon idella). Fish were fed six different experimental diets containing graded levels of Trp at 0.7(control), 1.7, 3.1, 4.0, 5.2 and 6.1 g kg(-1) diet for 8 weeks. The results showed that Trp supplementation significantly enhanced the percent weight gain (PWG), feed intake and feed efficiency (P < 0.05), and decreased the plasma ammonia content (PAC) (P < 0.05). After the 8-week feeding trail, an environmental copper exposure trail was conducted for 4 days. Results from the copper exposure trail showed that dietary Trp enhanced the lysozyme, acid phosphatase activities and complement 3 contents in the intestine of young grass carp (P < 0.05). In addition, Trp supplementation increased the copper/zinc superoxide dismutase (SOD1), glutathione peroxidase (GPx) activities and glutathione contents (P < 0.05), and decreased the protein carbonyl and malondialdehyde contents (P < 0.05). Furthermore, the relative gene expression levels of interleukin 10, transforming growth factor-β1, occludin, zonula occludens 1, claudin-b, -c, and -3, SOD1, GPx and NF-E2-related factor 2 in the intestine were significantly up-regulated with increasing of dietary Trp up to a certain level (P < 0.05). Conversely, the mRNA levels of tumor necrosis factor α, interleukin 8, target of rapamycin, Kelch-like-ECH-associated protein 1, claudin-12 and -15a in the intestine were significantly down-regulated by Trp (P < 0.05). Collectively, appropriate dietary Trp level improves fish growth, intestinal immune response, barrier function and antioxidant status, and regulated the mRNA levels of related signal molecules of young grass carp. Based on the quadratic regression analysis of the PWG and PAC, the dietary Trp requirement of young grass carp (287-699 g) was estimated to be 3.81 g kg(-1) diet (12.7 g kg(-1) protein) and 3.89 g kg(-1) diet (13.0 g kg(-1) protein), respectively.

Pro- and anti-inflammatory cytokine expression in immune organs of the common carp exposed to atrazine and chlorpyrifos

Atrazine (ATR) and chlorpyrifos (CPF) are toxic and subject to long-term in vivo accumulation in different aquatic species throughout the world. The purpose of the present study was to examine the effect of ATR, CPF and combined ATR/CPF exposure on cytokines in the head kidney and spleen of common carp (Cyprinus carpio L.). The carp were sampled after a 40-d exposure to CPF and ATR, individually or in combination, followed by a 40-d recovery to measure the mRNA expression of IL-6fam (IL-6), IL-8, TNF-α, IL-10 and TGF-β1 (TGF-β) in the head kidney and spleen tissues. These results showed that the expression of cytokines IL-6, IL-8 and TNF-α in the head kidney and spleen was upregulated following ATR, CPF and mixed ATR/CPF exposure compared with the control group. The expression of IL-10 and TGF-β mRNA was significantly inhibited in both head kidney and spleen of carp exposed to ATR, CPF and the ATR/CPF mixture. The results suggested that long-term exposure of ATR, CPF and the ATR/CPF mixture in aquatic environments can induce the dysregulation of pro-/anti-inflammatory cytokine expression. The information regarding the effects of ATR and CPF on cytokine mRNA expression generated in this study will be important information for pesticides toxicology evaluation.

Effects of subchronic exposure to N,N-diethyl-m-toluamide on selected biomarkers in common carp (Cyprinus carpio L.)

DEET (N,N-diethyl-m-toluamide) is the most common active ingredient in the insect repellents commonly detected in European groundwater. The aim of this study was to investigate the effect of subchronic DEET exposure on biochemical and haematological parameters, antioxidant enzymes, including catalase, glutathione peroxidase, glutathione reductase, and glutathione S-transferase, and the amount of thiobarbituric acid reactive substances (TBARS) in common carp (Cyprinus carpio L.). Two specific proinflammatory and anti-inflammatory cytokine genes were selected to assess an immunological status of the fish. Fish were exposed for 28 days to three concentrations of DEET (1.0 µg/L, 0.1 mg/L, and 1.0 mg/L) where 1 µg/L is corresponding to the concentration found in the environment. DEET had a significant (P < 0.05) effect on increased RBC, decreased mean corpuscular volume (MCV), and mean corpuscular haemoglobin value (MCH) compared to control groups in the concentration of 1 mg/L. A significant decline (P < 0.05) in triacylglycerols (TAG) in plasma was found in the concentration of 1 mg/L compared to the control groups. The parameters of oxidative stress in tissues of common carp were weekly affected and immunological parameters were not affected.

Cytotoxic effects and changes in cytokine gene expression induced by microcystin-containing extract in fish immune cells--an in vitro and in vivo study

Blooms of cyanobacteria producing very toxic secondary metabolites (especially microcystins) are potent environmental stressors, hazardous not only to aquatic animals but also to public health. The purpose of this study was to investigate the effects of an extract containing microcystins on immune cells isolated from the common carp (Cyprinus carpio L.). In the present study it has been found that the extract induced apoptosis and inhibited in vitro lymphocyte proliferation. In addition, the results indicated the possible role of oxidative stress in this cytotoxicity and apoptosis. The in vivo investigations showed that the extract containing microcystins had greater suppressive effects on the essential functions of immune cells (intracellular reactive oxygen species production and lymphocyte proliferation) than the pure toxin alone. Moreover, immersion of fish in the toxic extract caused changes in the mRNA levels of various pro- and anti-inflammatory cytokines in carp leukocytes, while after exposure to the pure toxin, only IL1-β expression was markedly up-regulated. The observed modulatory effects on immune cells could have important implications for the health of planktivorous fish, which feed more frequently on toxic cyanobacteria.