Effects of nitrite exposure on haematological parameters, oxidative stress and apoptosis in juvenile turbot (Scophthalmus maximus)

Protective effects of selenium against zearalenone-induced apoptosis in chicken spleen lymphocyte via an endoplasmic reticulum stress signaling pathway

Selenium (Se), an antioxidant agent, provides significant protection from reactive oxygen species (ROS)-induced cell damage in vivo and in vitro. However, it is unclear whether Se can protect against zearalenone (ZEN)-induced apoptosis in chicken spleen lymphocyte. In this study, we investigated the underlying mechanism of the apoptosis induced by ZEN in chicken spleen lymphocyte and further evaluated the protective mechanism of Se on ZEN-induced apoptosis. The results show that ZEN induced an increase in ROS generation and lipid peroxidation, and a decrease in levels of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), and glutathione (GSH). The results of apoptosis morphologically from acridine orange/ethidium bromide (AO/EB) fluorescent staining and flow cytometry analysis show apparent apoptosis in the ZEN-treated group, and was confirmed by the upregulation of caspase-3, -12 and downregulation of Bcl-2. Meanwhile, ZEN activated the endoplasmic reticulum (ER) stress by upregulating ER stress-related molecular sensors (GRP78, ATF6, ATF4, IRE). However, co-treatment with Se effectively blocked ROS generation, improved antioxdative capacity, and reversed apoptosis and ER stress-related genes and protein expression. Taken together, these data suggest that oxidative stress and ER stress play a vital role in ZEN-induced apoptosis, and Se had a significant preventive effect on ZEN-induced apoptosis in chicken spleen lymphocyte via ameliorating the ER stress signaling pathway.

Antioxidative, inflammatory and immune responses in hydrogen peroxide-induced liver injury of tilapia (GIFT, Oreochromis niloticus)

Oxidative stress has been implicated in the pathogenesis of many liver diseases in fish, but the molecular mechanism is still obscure. Here, we used hydrogen peroxide (H₂O₂) as a reactive oxygen species (ROS) to induce liver injury and assess underlying molecular mechanism linking oxidative stress and liver injury in fish. Tilapia were injected with various concentrations of H₂O₂ (0, 40, 120, 200, 300 and 400 mM) for 72 h. The blood and liver were collected to assay biochemical parameters and genes expression after 24, 48 and 72 h of injection. The results showed that treatments with higher H₂O₂ levels (300 and/or 400 mM) significantly increased the levels of GPT, GOT, AKP and MDA, and apparently decreased the levels of TP, ALB, SOD, GSH, CAT, GST and T-AOC throughout of the 72 h. The gene expression data showed that treatments with 200, 300 and/or 400 H₂O₂ suppressed Nrf2/keap1 pathway and its downstream genes including ho-1, nqo1 and gsta, activated inflammatory response via enhancing the mRNA levels of nf-κb, tnf-α, il-1β and il-8, and attenuating il-10 mRNA level, and caused immunotoxicity through downregulating the genes expression of c3, hep, lzm and Igm for 24, 48 and/or 72 h. Additionally, there was a mild or strong increase in levels of nrf2 and its subsequent antioxidant genes or enzymes such as ho-1, nqo1, gst, CAT and SOD in treatments with lower concentrations of H₂O₂ (40 or 120 mM) for 24 and/or 48 h. Overall results suggested that H₂O₂ hepatotoxicity was mainly concerned with lipid peroxidation, impairment antioxidant defense systems, inflammatory response and immunotoxicity, and Nrf2/Keap1 and NF-κB signaling pathways played important roles in oxidative stress-induced liver injury in fish.

Endocrine disruption, oxidative stress and lipometabolic disturbance of Bufo gargarizans embryos exposed to hexavalent chromium

The aim of the current study was to determine the potential developmental and metabolic abnormalities caused by Cr (VI) exposure on Bufo gargarizans (B. gargarizans) embryos. B. gargarizans embryos were treated with different concentrations of Cr (VI) (13, 52, 104, 208, and 416 μg Cr⁶⁺ L^-1) for 6 days. Morphological abnormalities, total length, weight and developmental stage were monitored. Malformations of embryos were also examined using scanning electron microscopy (SEM). In addition, the transcript levels of several genes associated with lipid metabolism, oxidative stress, and thyroid hormones signaling pathways were also determined. Our results showed a time-dependent inhibitory effect of Cr (VI) on the growth and development of B. gargarizans embryos. On day 4, total length, weight, and developmental stage were significantly lower at 416 μg Cr⁶⁺ L^-1 relative to control embryos. On day 6, significant reductions in total length, weight, and developmental stage were observed at 104, 208, and 416 μg Cr⁶⁺ L^-1. Malformed embryos were found in all Cr (VI) treatments, which were characterized by axial flexures, yolk sac edema and rupture, surface tissue hyperplasia, stunted growth, wavy fin and fin flexure. RT-qPCR results showed that exposure to Cr (VI) down-regulated TRβ and Dio2 mRNA expression and up-regulated Dio3 mRNA level at 416 μg Cr⁶⁺ L^-1. The transcript levels of SOD and GPx were upregulated at 52, 208, and 416 μg Cr⁶⁺ L^-1, while the transcript level of HSP90 was downregulated at 52, 208, and 416 μg Cr⁶⁺ L^-1. Also, mRNA expression of lipid synthesis-related genes (FAE and ACC) were significantly downregulated in embryos treated with 208 and 416 μg Cr⁶⁺ L^-1, but mRNA expression of fatty acid β-oxidation-related genes (ACOX, CPT, and SCP) was significantly upregulated at 416 μg Cr⁶⁺ L^-1. Therefore, our results suggested that Cr (VI) could disrupt thyroid endocrine pathways and lipid synthesis, leading to the inhibition of growth and development in B. gargarizans embryos. Furthermore, the decreased ability of scavenging ROS induced by Cr (VI) might be responsible for the teratogenic effects of Cr (VI).

Nitrite Enhances MC-LR-Induced Changes on Splenic Oxidation Resistance and Innate Immunity in Male Zebrafish

Hazardous contaminants, such as nitrite and microcystin-leucine arginine (MC-LR), are released into water bodies during cyanobacterial blooms and may adversely influence the normal physiological function of hydrobiontes. The combined effects of nitrite and MC-LR on the antioxidant defense and innate immunity were evaluated through an orthogonal experimental design (nitrite: 0, 29, 290 μM; MC-LR: 0, 3, 30 nM). Remarkable increases in malondialdehyde (MDA) levels have suggested that nitrite and/or MC-LR exposures induce oxidative stress in fish spleen, which were indirectly confirmed by significant downregulations of total antioxidant capacity (T-AOC), glutathione (GSH) contents, as well as transcriptional levels of antioxidant enzyme genes cat1, sod1 and gpx1a. Simultaneously, nitrite and MC-LR significantly decreased serum complement C3 levels as well as the transcriptional levels of splenic c3b, lyz, il1β, ifnγ and tnfα, and indicated that they could jointly impact the innate immunity of fish. The severity and extent of splenic lesions were aggravated by increased concentration of nitrite or MC-LR and became more serious in combined groups. The damages of mitochondria and pseudopodia in splenic macrophages suggest that oxidative stress exerted by nitrite and MC-LR aimed at the membrane structure of immune cells and ultimately disrupted immune function. Our results clearly demonstrate that nitrite and MC-LR exert synergistic suppressive effects on fish innate immunity via interfering antioxidant responses, and their joint toxicity should not be underestimated in eutrophic lakes.

Oxidative stress and antioxidant responses in juvenile Brazilian flounder Paralichthys orbignyanus exposed to sublethal levels of nitrite

This study evaluated the effects of short-term exposure to sublethal levels of nitrite on oxidative stress parameters and histology of juvenile Brazilian flounder Paralichthys orbignyanus. An assessment of fish recovery was also performed. Fish were exposed to 0.08 (control), 5.72, 10.43, and 15.27 NO₂-N mg L^-1 for 10 days followed by the same recovery time. Gill, liver, and muscle samples were collected after 1, 5, and 10 days of exposure and after recovery for the measurement of antioxidant capacity against peroxyl radicals (ACAP), glutathione-S-transferase (GST) activity, content of non-protein (NPSH) and protein thiols (PSH), and lipid peroxidation levels by thiobarbituric acid-reactive substances (TBARS) content. Nitrite exposure induced alterations which compromised the overall antioxidant system (reduced ACAP and GST activity) and enhanced oxidative damage in lipids and proteins. Increases in GST activity and NPSH and PSH contents were also demonstrated. The recovery period allowed for resumption of basal levels for all (treatment 5.72 NO₂-N mg L^-1) or some of the evaluated parameters (other treatments). In conclusion, exposure to nitrite concentrations from 5.72 to 15.27 NO₂-N mg L^-1 induced oxidative stress and antioxidant responses in juvenile Brazilian flounder. The 10-day recovery period was sufficient for a complete resumption of basal physiological condition of fish exposed to concentrations of up to 5.72 NO₂-N mg L^-1.

Effects of waterborne nitrite on hematological parameters and stress indicators in olive flounders, Paralichthys olivaceus, raised in bio-floc and seawater

Juvenile olive flounders, Paralichthys olivaceus (mean weight 2.69 ± 0.31 g), were raised in bio-floc and seawater for six months, these P. olivaceus (mean weight 280.1 ± 10.5 g, mean length 28.37 ± 2.3 cm) were exposed to different concentrations of waterborne nitrite (0, 25, 50, 100, and 200 mg NO₂^-/L) for 7 days. None of the P. olivaceus individuals exposed to bio-floc and seawater containing waterborne nitrite concentrations of 200 mg/L for 7 days survived. Hematological parameters (hemoglobin and hematocrit) were significantly reduced by nitrite exposure. Regarding plasma components, the concentrations of glucose, glutamic oxalate transaminase (GOT), and glutamic pyruvate transaminase (GPT) increased significantly in response to nitrite exposure, whereas cholesterol concentrations significantly decreased. Stress indicators, including concentrations of plasma glucose, cortisol, and liver and gill concentrations of heat shock protein 70 (HSP70) were significantly increased by nitrite exposure. The results of the study indicate that nitrite exposure affected the hematological parameters and stress indicators of P. olivaceus raised in bio-floc and seawater, and these changes were more prominent in the P. olivaceus raised in seawater than those raised in bio-floc.

Comparative transcriptome analysis reveals the gene expression profiling in bighead carp (Aristichthys nobilis) in response to acute nitrite toxicity

OBJECTIVE

Nitrite exposure induces growth inhibition, metabolic disturbance, oxidative stress, organic damage, and infection-mediated mortality of aquatic organism. This study aimed to investigate the mechanism in responses to acute nitrite toxicity in bighead carp (Aristichthys nobilis, A. nobilis) by RNA-seq analysis.

METHODS

Bighead carps were exposed to water with high nitrite content (48.63 mg/L) for 72 h, and fish livers and gills were separated for RNA-seq analysis. De novo assembly was performed, and differentially expressed genes (DEGs) between control and nitrite-exposed fishes were identified. Furthermore, enrichment analysis was performed for DEGs to annotate the molecular functions.

RESULTS

A total of 406,135 transcripts and 352,730 unigenes were tagged after de novo assembly. Accordingly, 4108 and 928 DEGs were respectively identified in gill and liver in responses to nitrite exposure. Most of these DEGs were up-regulated DEGs. Enrichment analysis showed these DEGs were mainly associated with immune responses and nitrogen metabolism.

CONCLUSIONS

We suggested that the nitrite toxicity-induced DEGs were probably related to dysregulation of nitrogen metabolism and immune responses in A. nobilis, particularly in gill.

Effect of nitrite exposure on the antioxidant enzymes and glutathione system in the liver of bighead carp, Aristichthys nobilis

Nitrite (NO₂^-) can cause oxidative stress in aquatic animal when it accumulates in the organism, resulting in different toxic effects on fish. In the present study, we investigated the effects of nitrite exposure on the antioxidant enzymes and glutathione system in the liver of Bighead carp (Aristichthys nobilis). Fish [Initial average weight: (180.05 ± 0.092) g] were exposed to 48.634 mg/L nitrite for 96 h, and a subsequent 96 h for the recovery test. Fish livers were collected to assay antioxidant enzymes activity, hepatic structure and expression of genes after 0 h, 6 h, 12 h, 24 h, 48 h, 72 h, 96 h of exposure and12 h, 24 h, 48 h, 72 h, 96 h of recovery. The results showed that the activity of glutathione peroxidase (GSH-Px), glutathione S-transferase (GST), and glutathione reductase (GR) increased significantly in the early stages of nitrite exposure. The study also showed that nitrite significantly up-regulated the mRNA levels of glutathione peroxidase (GSH-Px), glutathione S-transferase (GST), and glutathione reductase (GR) after 6, 48, and 72 h of exposure respectively. Nitrite also increased the formation of malondialdehyde (MDA), oxidized glutathione (GSSG), and the activity of catalase (CAT). Nitrite was observed to reduce the activity of superoxide dismutase (SOD) and the level of glutathione (GSH). In the recovery test, GSH and the GSSG recovered but did not return to pre-stress levels. The results suggested that the glutathione system played important roles in nitrite-induced oxidative stress in fish. The bighead carp responds to oxidative stress by enhancing the activity of GSH-Px, GST, GR and up-regulating the expression level of GSH-Px, GST, GR, a whilst simultaneously maintaining the dynamic balance of GSH/GSSG. CAT was also indispensable. They could reduce the degree of lipid peroxidation, and ultimately protect the body from oxidative damage.

The synergistic effects of waterborne microcystin-LR and nitrite on hepatic pathological damage, lipid peroxidation and antioxidant responses of male zebrafish

Hazardous materials from decaying cyanobacterial blooms, such as microcystin-LR (MC-LR) and nitrite pose serious challenges to aquatic organisms. To assess combined toxic effects of MC-LR and nitrite on hepatic pathology, lipid peroxidation and antioxidant responses of fish, adult male zebrafish (Danio rerio) were exposed to solutions with different combined concentrations of MC-LR (0, 3, 30 μg/L) and nitrite (0, 2, 20 mg/L) for 30 d. The results showed that hepatic pathological lesions progressed in severity and extent with increasing concentration of single factor MC-LR or nitrite and became more severe in co-exposure groups. Concurrently, significant increases in malondialdehyde (MDA) revealed the occurrence of oxidative stress caused by MC-LR, nitrite and both of them, which was indirectly verified by remarkable decreases in the total antioxidant capacity (T-AOC) as well as the transcription and activity of antioxidant enzymes (CAT and GPx). Hepatic mitochondria were damaged as the common action site of MC-LR and nitrite, suggesting that oxidative stress played a significant role in the mechanisms of the hepatotoxicity of MC-LR and nitrite. The depletion of hepatic glutathione (GSH) indicated the importance of GSH/glutathione-S-transferases (GST) system in these two chemicals detoxification. These results clearly illustrated that MC-LR and nitrite have synergistic effects on the histostructure, antioxidant capacity and detoxification capability in the liver of zebrafish. Therefore, the combined pollution of MC-LR and nitrite in eutrophic lakes can reduce the defense mechanism of the fish and accelerate the consumption of GSH, which compromise the survival of the fish during prolonged cyanobacterial blooms episodes.

Acute oral dose of sodium nitrite causes redox imbalance and DNA damage in rat kidney

Sodium nitrite (NaNO₂ ) is widely used as a food additive and preservative in fish and meat products. We have evaluated the effect of a single acute oral dose of NaNO₂ on oxidative stress parameters, antioxidant capacity, and DNA in rat kidney. Male Wistar rats were divided into four groups and given single oral dose of NaNO₂ at 20, 40, 60, and 75 mg/kg body weight; untreated rats served as the control group. All animals in NaNO₂ -treated groups showed marked alterations in various parameters of oxidative stress as compared to the control group. This included increase in lipid peroxidation, protein oxidation, hydrogen peroxide levels, and decrease in reduced glutathione content and antioxidant capacity. Administration of NaNO₂ also increased DNA damage as evident from release of free nucleotides and confirmed by comet assay. It also led to greater cross-linking of DNA to proteins. Histological analysis showed marked morphological changes in the kidney of NaNO₂ -treated animals. These alterations could be due to increased free radical generation or direct chemical modification by reaction intermediates. Our results suggest that nitrite-induced nephrotoxicity is mediated through redox imbalance and results in DNA damage.

Mitigation of nitrite toxicity by increased salinity is associated with multiple physiological responses: A case study using an economically important model species, the juvenile obscure puffer (Takifugu obscurus)

Nitrite is a common pollutant in water and is highly toxic to aquatic animals. To reveal the mechanism of salinity in attenuating nitrite toxicity to fish, we measured the physiological responses of juvenile Takifugu obscurus exposed to nitrite concentrations (0, 10, 20, 50, and 100 mg/L) under different salinity levels (0, 10, and 20 ppt) for 96 h. Salinity increased the survival rates of juvenile T. obscurus exposed to nitrite. Changes in key hematological parameters, antioxidant system, malondialdehyde, Na⁺/K⁺-ATPase, and HSP70 indicated that nitrite induced considerable damage to juveniles; salinity mitigated the harmful effects. This finding reflects similar changing trends in both antioxidants and their gene expressions among different tissues. We applied an overall index, an integrated biomarker response (IBR), that increased under high-nitrite condition but recovered to the normal levels under salinity treatment. Analysis of the selected detection indices and IBR values showed that the overall mitigating effect of salinity on nitrite toxicity seems to be at sub-cellular level and associated with complicated physiological responses.

Analysis of 28 trace elements in the blood and serum antioxidant status in chickens under arsenic and/or copper exposure

This study aimed to evaluate the 28 trace elements in the blood and serum antioxidant status in chickens under arsenic (As) and/or copper (Cu) exposure. A total of 200 1-day-old male Hy-Line chickens were fed either a commercial diet (C-group) or arsenic trioxide (30 mg/kg) and/or cupric sulfate (300 mg/kg) for 90 days. The 28 trace element levels in the blood were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of As in the blood of chickens were elevated approximately 17.15-fold, 2.30-fold, and 13.37-fold in the As-group, Cu-group, and As + Cu-group, respectively, at 90 days. The concentrations of Cu did not change in the As-group and increased approximately 29.53 and 23.37% in the Cu-group and As + Cu-group, respectively, at 90 days. Moreover, As exposure caused ion profile disorders in the blood, including increased concentrations of Na, Mg, Si, K, Cr, Fe, and Se and reduced B, Ca, Ti, V, Mn, Co, Ni, Zn, Sr, and Mo. Cu exposure increased the contents of Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Zn, and Se and decreased the content of B, Ca, Al, Ni, and Mo. As + Cu exposure increased the contents of Mg, Si, Cr, Fe, Zn, and Se and decreased the content of B, Ca, Ti, Co, Ni, Sr, and Mo. Moreover, As and/or Cu exposure induced oxidative stress in the blood of chickens. In conclusion, the results indicated that the mixture of As and Cu caused a synergistic effect via disturbing homeostasis of trace elements and oxidative stress in the blood of chickens.

Histopathological changes and lipid metabolism in the liver of Bufo gargarizans tadpoles exposed to Triclosan

In the current study, the adverse effects of TCS on liver health of B. gargarizans tadpoles were assessed. B. gargarizans larvae were exposed to TCS at 0, 10, 30, 60, and 150 μg L^-1 from Gosner stage 3 until metamorphic climax. The hepatosomatic index (HSI), hepatic histological and ultrastructural features, and transcript levels of genes associated with detoxification and oxidative stress as well as lipid metabolism in the livers were determined. Exposure to 150 μg L^-1 TCS resulted in increased HSI of tadpoles at metamorphic climax. Histological changes characterized by an increase in the number of melanomacrophage, nucleus pyknosis, and deposition of collagen fibers were observed in liver at 60 and 150 μg L^-1 TCS. Moreover, marked ultrastructural alterations including high electron dense in mitochondrial matrix and lipid accumulation were also observed. In addition, abundances of transcripts of Cu/Zn superoxide dismutase (SOD), phospholipid hydroperoxide glutathione peroxidase (PHGPx), and heat shock protein 90 (HSP₉₀) were decreased in larvae exposed to 60 and 150 μg L^-1 TCS, while transcript level of HSP₉₀ was increased at 30 μg L^-1 TCS. Also, abundances of transcripts of acetyl-CoA carboxylase (ACC), carnitine palmitoyltransferase 2 (CPT2), peroxisome proliferator-activated receptor alpha (PPARa), fatty acid elongase 1 (FAE), sterol carrier protein 2 (SCP) were significantly lesser in larvae exposed to 60 and 150 μg L^-1 TCS. Overall, TCS at high levels induced histopathological changes in the liver of B. gargarizans tadpoles. This might have been due to the alteration of oxidative stress-related genes and lipid metabolism-related genes expression levels.

Taurine mitigates nitrite-induced methemoglobin formation and oxidative damage in human erythrocytes

Nitrite is present as a noxious contaminant in drinking water and causes oxidative damage in various tissues of humans and animals. It is a well-known methemoglobin-forming agent that has been shown to damage blood cells. The protective effect of taurine, a semi-essential sulfur-containing amino acid, was studied on sodium nitrite (NaNO₂)-induced oxidative damage in human erythrocytes. Erythrocytes were incubated with NaNO₂, in the presence and absence of taurine, and changes in oxidative stress parameters determined. Pretreatment with taurine significantly ameliorated NaNO₂-induced oxidative damage to lipids, proteins, and plasma membrane. It also reduced the NaNO₂-induced increase in methemoglobin levels and ROS production. Taurine improved the antioxidant capacity of cells, restored the alterations in the activities of various metabolic enzymes, and prevented morphological changes in erythrocytes. Thus, taurine can be potentially used as a protective agent against the damaging effects of nitrite.

Modulation of the stress response in wild fish is associated with variation in dissolved nitrate and nitrite

Disruption of non-reproductive endocrine systems in wildlife by chemicals has received little attention but represents a potentially significant problem. Nitrate is a major anthropogenic contaminant in the freshwater aquatic environment and has been identified as a potential disrupter of endocrine function in aquatic animals. This study was conducted to investigate the relationship between the function of the neuroendocrine stress axis in fish and inorganic N loading along reaches of rivers receiving cumulative point source and diffuse chemical inputs. To accomplish this, the responsiveness of the stress axis, quantified as the rate of release of cortisol to water across the gills during exposure to a standardised stressor, was measured in three-spined sticklebacks (Gasterosteus aculeatus L.) resident at three sites on each of four rivers in north-west England. The magnitude of the stress response in fish captured at the sites furthest downstream on all rivers was more than twice that of fish captured at upstream sites. Site-specific variation in stress axis reactivity was better explained by between-site variation in concentrations of dissolved nitrate, nitrite, and ammonia than by the concentration of wastewater treatment works effluent. An increase in the magnitude of the stress response was seen among sticklebacks at sites where long-term averaged concentrations of NH₃-N, NO₃-N and NO₂-N exceeded 0.6, 4.0 and 0.1 mg/L respectively. These data suggest that either (i) inorganic N is a better surrogate than wastewater effluent concentration for an unknown factor or factors affecting stress axis function in fish, or (ii) dissolved inorganic N directly exerts a disruptive influence on the function of the neuroendocrine stress axis in fish, supporting concerns that nitrate is an endocrine-modulating chemical.

Mitochondria-rich cells changes induced by nitrite exposure in tambaqui (Colossoma macropomum Cuvier, 1818)

The gill mitochondria-rich cells of the juvenile Amazonian fish Colossoma macropomum were analyzed using light and scanning and transmission electron microscopy after 96 h exposure to 0.04 and 0.2 mM nitrite. Although the number of mitochondria-rich cells decreased significantly in the lamellar epithelium, no decrease was found in the interlamellar region of the gill filament. Nitrite exposure caused significant reduction on the apical surface area of individual mitochondria-rich cells (p < 0.05), with a resulting reduction of the fractional area of these cells in both the lamellar and filament epithelium. Swelling of endoplasmic reticulum cisternae, nuclear envelope and mitochondria were the main changes found in the mitochondria-rich cells. Cristae lysis and matrix vacuolization characterized the mitochondrial changes. The overall ultrastructural changes indicated cellular functional disruption caused by exposure to nitrite. The changes observed in the gill indicate that the cellular structures involved in the process of energy production become severely damaged by exposure to nitrite indicating irreversible damage conducting to cell death.

Acute oral dose of sodium nitrite induces redox imbalance, DNA damage, metabolic and histological changes in rat intestine

Industrialization and unchecked use of nitrate/nitrite salts for various purposes has increased human exposure to high levels of sodium nitrite (NaNO₂) which can act as a pro-oxidant and pro-carcinogen. Oral exposure makes the gastrointestinal tract particularly susceptible to nitrite toxicity. In this work, the effect of administration of a single acute oral dose of NaNO₂ on rat intestine was studied. Animals were randomly divided into four groups and given single doses of 20, 40, 60 and 75 mg NaNO₂/kg body weight. Untreated animals served as the control group. An NaNO₂ dose-dependent decline in the activities of brush border membrane enzymes, increase in lipid peroxidation, protein oxidation, hydrogen peroxide levels and decreased thiol content was observed in all treated groups. The activities of various metabolic and antioxidant defense enzymes were also altered. NaNO₂ induced a dose-dependent increase in DNA damage and DNA-protein crosslinking. Histopathological studies showed marked morphological damage in intestinal cells. The intestinal damage might be due to nitrite-induced oxidative stress, direct action of nitrite anion or chemical modification by reaction intermediates.

Response of AMP-activated protein kinase and energy metabolism to acute nitrite exposure in the Nile tilapia Oreochromis niloticus

Adenosine monophosphate-activated protein kinase (AMPK) is a prevalent mammalian energy metabolism sensor, but little is known about its role as an energy sensor in fish experiencing stress. We aimed to study AMPK in Oreochromis niloticus on both the molecular and the physical level. We found that the cDNAs encoding the AMPKα1 and AMPKα2 variants of the O. niloticus catalytic α subunit were 1753bp and 2563 bp long and encoded 571 and 557 amino acids, respectively. Both the AMPKα1 and the AMPKα2 isoform possess structural features similar to mammalian AMPKα, including a phosphorylation site at Thr172 in the N-terminus, and exhibit high homology with other fish and vertebrate AMPKα sequences (81.3%-98.1%). mRNA encoding the AMPKα isoforms was widely expressed in various tissues with distinctive patterns. AMPKα1 and AMPKα2 were primarily expressed in the intestines and brain, respectively. Under acute nitrite challenge, the mRNA encoding the AMPKα isoforms, as well as AMPK activity, changed over time. Its recovery period in freshwater, combined with the fact that it is highly conserved, suggests that fish AMPK, like its mammalian orthologues, acts as an energy metabolism sensor. Furthermore, subsequent decreases in AMPK mRNA levels and activity suggested that its action was transient but efficient. Physically, glucose, lactic acid and TGs in plasma, as well as energy materials in the hepatopancreas and muscle, were significantly altered over time, indicating changes in energy metabolism during the experimental period. These data have enabled us to characterize energy utilization in O. niloticus and further illustrate the role of fish AMPK as an energy sensor. This study provides new insight into energy metabolism and sensing by AMPK in teleost and necessitates further study of the multiple physiologic roles of AMPK in fish.

Effects of berberine on the growth and immune performance in response to ammonia stress and high-fat dietary in blunt snout bream Megalobrama amblycephala

This study aimed to figure out the effects of berberine on growth performance, immunity, oxidative stress and hepatocyte apoptosis of blunt snout bream (Megalobrama amblycephala) fed with high-fat diet. 320 fish (80.00 ± 0.90 g) were divided randomly into four trial groups (each with four replicates) and fed with 4 diets (normal diet, normal diet with 50 mg/kg berberine, high-fat diet, high-fat diet with 50 mg/kg berberine), respectively. At the end of the feeding trial, ammonia stress test was carried out for 5 days. The result showed the growth performance, immune parameters including plasm acid phosphatase (ACP) activities, lysozyme (LYZ) activities and alternative complement C3 and C4 contents were suppressed in fish fed with high-fat diets but improved in berberine diets compared with control (normal diet). Hepatopancreas oxidative status, the malondialdehyde (MDA), protein carbonyl (PC) and lipid peroxide (LPO) were increased significantly (P < 0.05) when fish were fed with high-fat diets. Berberine could slow the progression of the oxidative stress induced by high-fat through increasing superoxide dismutase (SOD) activities and total sulfydryl (T-SH) levels of fish. And the hepatocyte apoptosis in the high-fat group could also be alleviated by berberine. After the ammonia stress test, the accumulative mortality was extremely (P < 0.05) low in fish fed high-fat diet with berberine compared to other groups. It was concluded berberine as a functional feed additive significantly inhibited the progression of oxidative stress, reduced the apoptosis and enhanced the immunity of fish fed with high-fat diet.

Effects of different light wavelengths from LEDs on oxidative stress and apoptosis in olive flounder (Paralichthys olivaceus) at high water temperatures

We investigated how different light spectra affect thermal stress in olive flounder (Paralichthys olivaceus), using light emitting diodes (LEDs; blue, 450 nm; green, 530 nm; red, 630 nm) at two intensities (0.3 and 0.5 W/m(2)) at relatively high water temperatures (25 and 30 °C, compared to a control condition of 20 °C). We measured the expression and activity of antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT), and the levels of plasma hydrogen peroxide (H2O2) and lipid peroxidation (LPO). Furthermore, the levels and mRNA expression of caspase-3 were measured, and terminal transferase dUTP nick end labeling (TUNEL) assays of liver and comet assays were performed. The expression and activity of antioxidant enzymes, as well as plasma H2O2 and LPO levels were significantly higher after exposure to high temperatures, and significantly lower after exposure to green and blue light. Caspase-3 levels and mRNA expression showed a similar pattern. The TUNEL assay showed that apoptosis markedly increased at higher water temperatures, compared with the 20 °C control. In contrast, green light irradiation decreased apoptosis rate. Furthermore, the comet assays showed that nuclear DNA damage was caused by thermal stress, and that green light irradiation played a role in partially preventing this damage. Overall, these results suggest that light with green and blue wavelengths can reduce both high temperature-induced oxidative stress and apoptosis, and that particularly green light is efficient for this. Therefore, green light can play a role in protecting in olive flounder from thermal stress damage.

Effects of various LED light spectra on antioxidant and immune response in juvenile rock bream, Oplegnathus fasciatus exposed to bisphenol A

Bisphenol A (BPA) is a monomer used in plastics and plasticizers. As an environmental toxin included in industrial wastewater, it contaminates the aquatic environment and is known to cause endocrine disruption in fish. Particular wavelengths of light-emitting diodes (LEDs) are known to affect the endocrine regulation of fish. The present study aimed to investigate the effects of green and red LED light on the antioxidant and immune systems in juvenile rock bream (Oplegnathus fasciatus) exposed to BPA. We used green and red LED exposure at two intensities (0.3 and 0.5W/m(2)) for 1, 3, and 5 days. We measured liver mRNA expression and plasma levels of antioxidant enzyme superoxide dismutase (SOD) and caspase-3. Furthermore, we measured plasma levels of hydrogen peroxide (H2O2), lipid peroxidation (LPO), melatonin, and immunoglobulin M (IgM). DNA damage and apoptotic activity were measured using comet and terminal transferase dUTP nick end labeling (TUNEL) assays, respectively. We found that SOD, H2O2, and LPO increased significantly, whereas melatonin and IgM decreased significantly, suggesting that BPA induces oxidative stress and reduces immune function. Likewise, both DNA damage and apoptotic activity increased following BPA exposure. However, we found that exposure to green LED light effectively reduced the detrimental effects induced by BPA, including decreasing DNA damage, apoptotic activity, SOD mRNA expression, and plasma levels of SOD, H2O2, and LPO. Likewise, the plasma levels of melatonin and IgM increased. Thus, our results indicate that green light conditions effectively reduces oxidative stress and promotes the immune function in juvenile rock bream.