Toxic effects on bioaccumulation and hematological parameters of juvenile rockfish Sebastes schlegelii exposed to dietary lead (Pb) and ascorbic acid

Selenium protects against Pb-induced renal oxidative injury in weaning rats and human renal tubular epithelial cells through activating NRF2

BACKGROUND

Lead (Pb) poisoning posing a crucial health risk, especially among children, causing devastating damage not only to brain development, but also to kidney function. Thus, an urgent need persists to identify highly effective, safe, and low-toxicity drugs for the treatment of Pb poisoning. The present study focused on exploring the protective effects of Se on Pb-induced nephrotoxicity in weaning rats and human renal tubular epithelial cells, and investigated the possible mechanisms.

METHODS

Forty weaning rats were randomly divided into four groups in vivo: control, Pb-exposed, Pb+Se and Se. Serum creatinine (Cr), urea nitrogen (BUN) and hematoxylin and eosin (H&E) staining were performed to evaluate renal function. The activities of antioxidant enzymes in the kidney tissue were determined. In vitro experiments were performed using human renal tubular epithelial cells (HK-2 cells). The cytotoxicity of Pb and Se was detected by 3-(4,5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Inverted fluorescence microscope was used to investigate cell morphological changes and the fluorescence intensity of reactive oxygen species (ROS). The oxidative stress parameters were measured by a multi-detection reader. Nuclear factor-erythroid-2-related factor (NRF2) signaling pathways were measured by Western blot and reverse transcription polymerase chain reaction (RT-PCR) in HK-2 cells.

RESULTS

We found that Se alleviated Pb-induced kidney injury by relieving oxidative stress and reducing the inflammatory index. Se significantly increased the activity of the antioxidant enzymes glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT), whereas it decreased the excessive release of malondialdehyde (MDA) in the kidneys of weaning rats and HK-2 cells. Additionally, Se enhanced the antioxidant defense systems via activating the NRF2 transcription factor, thereby promoting the to downstream expression of heme oxygenase 1. Furthermore, genes encoding glutamate-cysteine ligase synthetase catalytic (GCLC), glutamate-cysteine ligase synthetase modifier (GCLM) and NADPH quinone oxidoreductase 1 (NQO1), downstream targets of NRF2, formed a positive feedback loop with NRF2 during oxidative stress responses. The MTT assay results revealed a significant decrease in cell viability with Se treatment, and the cytoprotective role of Se was blocked upon knockdown of NRF2 by small interfering RNA (siRNA). MDA activity results also showed that NRF2 knockdown inhibited the NRF2-dependent transcriptional activity of Se.

CONCLUSIONS

Our findings demonstrate that Se ameliorated Pb-induced nephrotoxicity by reducing oxidative stress both in vivo and in vitro. The molecular mechanism underlying Se's action in Pb-induced kidney injury is related to the activation of the NRF2 transcription factor and the activity of antioxidant enzymes, ultimately suppressing ROS accumulation.

Lead and cadmium in blood and tissues of Atlantic bluefin tuna (Thunnus thynnus L., 1758)

Cadmium (Cd) and lead (Pb) levels in blood and tissues of Atlantic bluefin tuna were analysed to gather information regarding their distribution, accumulation and inter-relationships, as well as to examine how sex affects them. In the whole population, the concentration range was from below the detection limit (bone) to 8.512 μg g-1 (liver) for Cd, and from below detection limit (bone and gills) to 0.063 μg g-1 (kidney) for Pb. The median concentration in the muscles (0.008 and 0.029 μg g-1 for Cd and Pb, respectively) was 10 times less than the maximum permitted for consumption. Sex was shown to be an important variable affecting concentrations of Cd in both liver and kidneys, so taking into account sex when interpreting results is highly recommended. The importance of Cd and Pb bioaccumulation in fishery by-products, increasingly important in commercial circuits, is also highlighted.

Toxic effects of microplastic (Polyethylene) on fish: Accumulation, hematological parameters and antioxidant responses in Korean Bullhead, Pseudobagrus fulvidraco

Plastic waste discharged into the aquatic environment decomposes into microplastics (MP), which have toxic effects on fish species. Korean bullhead, Pseudobagrus fulvidraco is widely distributed in freshwater ecosystems in Korea, and it is important as an ecological indicator species to evaluate MP toxicity in Korea. In this study, the accumulation and physiological effects of juvenile P. fulvidraco exposed to microplastics (Polyethylene: PE-MPs with white surface and spherical shape) at control (0 mg/L), 100, 200, 5000 and 10,000 mg/L for 96 h were confirmed. Exposure to PE-MPs showed significant bioaccumulation of P. fulvidraco, and the accumulation profile was in the order of gut > gills > liver. Hematological parameters such as the red blood cell (RBC), hemoglobin (Hb) and hematocrit (Ht) were significantly decreased over 5000 mg/L In plasma components, calcium, magnesium and total protein were significantly decreased over 5000 mg/L, whereas glucose, cholesterol, aspartate aminotransferase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) were significantly increased over 5000 mg/L or at 10,000 mg/L In antioxidant responses, superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) were significantly increased over 5000 mg/L, whereas glutathione (GSH) was significantly decreased over 5000 mg/L. The results of this study suggest that acute exposure to PE-MPs induced all physiological changes in a concentration-dependent manner, and it affects the hematological parameters, plasma components and antioxidant response of juvenile P. fulvidraco after accumulation in specific tissues.

Biofloc Technology in Fish Aquaculture: A Review

The application of biofloc to fish species has several advantages, including the enhancement of production by increasing growth performance and survival rate and the improvement of fish aquaculture physiological activity. There has been a recent increase in biofloc addition to fish culture, and this review examines changes this causes to the survival and growth rate of fish and its economic feasibility. Physiological activity and disease resistance of biofloc-fed fish is being extensively studied. The hematological parameters and antioxidant and immune responses of fish fed biofloc were reviewed in this study, as well as their disease resistance by testing them for major specific diseases. Standards for effectively applying biofloc to fish aquaculture are also suggested.

Effects on Bioaccumulation, Growth Performance, Hematological Parameters, Plasma Components, and Antioxidant Responses in Starry Flounder (Platichthys stellatus) Exposed to Dietary Cadmium and Ascorbic Acid

This study evaluates the toxic effects of dietary Cd and mitigative effects of AsA supplementation by measuring the growth performance, bioaccumulation, hematological parameters, plasma components, and antioxidant responses of Starry flounder (Platichthys stellatus). Platichthys stellatus (mean weight, 69.5 ± 1.4 g; mean length, 18.2 ± 0.21 cm) was fed with dietary cadmium-ascorbic acid (Cd-AsA) composed of C₀A₀, C₀A₅₀₀, C₀A₁₀₀₀, C₄₀A₀, C₄₀A₅₀₀, C₄₀A₁₀₀₀, C₈₀A₀, C₈₀A₅₀₀, and C₈₀A₁₀₀₀ mg of Cd-AsA per kg diet for four weeks. Our results showed that Cd accumulation significantly increased in proportion to the Cd concentration, where the highest levels were observed in the intestine, followed by the kidney, liver, and gills. Dietary AsA significantly mitigated the Cd accumulation in all tissues, and the reduction in Cd accumulation was proportional to the increase in AsA concentration. Dietary Cd has adverse effects on growth performance (body weight gain, specific growth rate, feed conversion ratio, and hepatosomatic index) and can alter the hematological parameters (red blood cell count, hematocrit, and hemoglobin), plasma components (glucose, total protein, glutamic oxaloacetic transaminase, and glutamic pyruvic transaminase), and antioxidant responses (superoxide dismutase, catalase, glutathione S-transferase, and glutathione). Dietary AsA restored the decreased growth performance parameters and the altered hematological parameters, plasma components, and antioxidant responses caused by the dietary Cd exposure. The results of this study showed that dietary Cd is toxic to P. stellatus, while dietary AsA is effective in mitigating the toxic effects of Cd.

Expression of ABCA3 transporter gene in Tegillarca granosa and its association with cadmium accumulation

Exposure to cadmium (Cd), a heavy metal, can cause strong and toxic side effects. Cd can enter the body of organisms in several ways, leading to various pathological reactions in the body. Tegillarca granosa is a kind of bivalve shellfish favored by people in the coastal areas of China. Bivalve shellfish can easily absorb heavy metal pollutants from water bodies while filter feeding. T. granosa is considered a hyper-accumulator of Cd, and the TgABCA3 gene is highly expressed in individuals with a high content of Cd-exposed blood clam. However, it is unclear whether TgABCA3 is involved in Cd ion transport in blood clam and the molecular mechanism for the mechanism of the Cd-induced responses for maintaining cell homeostasis. In this study, the complete cDNA of the TgABCA3 gene was analyzed to provide insights into the roles of TgABCA3 in resistance against Cd in blood clam. The complete sequence of TgABCA3 showed high identity to that of TgABCA3 from other bivalves and contained some classical motifs of ATP-binding cassette transport proteins. TgABCA3 expression in different tissues was measured using real-time quantitative polymerase chain reaction (qRT-PCR) and western blot analysis. The tissue-specific expression showed that TgABCA3 expression was highest in the gill tissue. The TgABCA3 expression in the gill tissue was silenced using the RNA interference technique. After TgABCA3 silencing, the TgABCA3 expression decreased, the Cd content increased, the oxygen consumption and ammonia excretion rates increased, and the ingestion rate decreased. These results showing that the extents of Cd accumulation and resulting toxic effects are related to expression levels and activity of TgABCA3 indicate that TgABCA3 has a protective function against Cd in the clam. This increase in Cd accumulation results in serious damage to the body, leading to the enhancement of its physiological metabolism. Therefore, the findings of the study demonstrated that TgABCA3 can participate in the transport of Cd ions in the blood clam through active transport and play a vital role in Cd detoxification.

Toxic effects of waterborne cadmium exposure on hematological parameters, oxidative stress, neurotoxicity, and heat shock protein 70 in juvenile olive flounder, Paralichthysolivaceus

Cadmium-induced toxicity can affect fish embryo development, ion homeostasis regulation, energy metabolism, maturation and growth, stress response, and immunity. However, studies on the toxic effects of cadmium exposure to aquatic animals, particularly olive flounder (Paralichthys olivaceus), are limited. In this study, juvenile P. olivaceus (mean length, 12.9 ± 1.3 cm; mean weight, 23.1 ± 3.2 g) was exposed to waterborne cadmium (0, 50, 100, 200, and 400 μg/L) for 10 d. Hematological parameters, including hematocrit value and hemoglobin level, in P. olivaceus were significantly decreased after waterborne cadmium exposure. Plasma components such as calcium, glucose, cholesterol, glutamic-oxaloacetic transaminase, and glutamic-pyruvic transaminase were significantly altered via cadmium exposure. The activities of antioxidant enzymes, such as superoxide dismutase, catalase, and glutathione S-transferase, were significantly altered in P. olivaceus after cadmium exposure. Acetylcholinesterase activity was significantly inhibited upon waterborne cadmium exposure. Hepatic heat shock protein 70 was significantly upregulated in P. olivaceus after waterborne cadmium exposure. Therefore, waterborne cadmium at concentrations of >100 or 200 μg/L can induce physiological toxicity in P. olivaceus via changes in hematological parameters, antioxidant enzymes, neurotransmitters, and stress indicators.

Lead impaired immune function and tissue integrity in yellow catfish (Peltobargus fulvidraco) by mediating oxidative stress, inflammatory response and apoptosis

Lead (Pb) widely exists in the water environment and has severe toxic effects on aquatic organisms. The yellow catfish (Pelteobagrus fulvidraco) is one of the most important commercial species in China, and moreover, its natural populations are declining with the degradation of environmental water quality. However, little is known about the toxic effects of Pb on its immune organs. This study was performed to determine waterborne Pb exposure on bioaccumulation, histomorphology, antioxidant status, apoptotic and immune response in the head kidney and spleen of yellow catfish. Experimental fish were randomly allocated into twelve tanks (3 tanks per group), and the Pb concentrations of the four groups were 0, 5, 50, and 500 μg/L, respectively. The results reflected that the Pb bioaccumulation of the head kidney and spleen increased with increasing Pb exposure dose and time. Severe histological alterations in the head kidney and spleen were observed at concentration 500 ug/L. With increasing Pb exposure concentrations, the plasma activity of superoxide dismutase (SOD) and catalase (CAT) significantly increased after exposure 7 days and 14 days, and the levels significantly decreased after exposure 28 days. The change trend of glutathione (GSH) levels was opposite to that of SOD and CAT at corresponding exposure time. The plasma malondialdehyde (MDA) levels together with the activities of plasma alkaline phosphatase (AKP) and acid phosphatase (ACP) increased significantly with the increasing Pb concentrations. In contrast, the levels of lysozyme (LYZ), complement 3 (C3) and immunoglobulin M (IgM) decreased significantly with increasing Pb concentrations. Moreover, Pb exposure induced transcriptional upregulation of heat shock protein 70 (hsp70), metallothionein (mt), sod, cat, interleukin-10 (il-10), transforming growth factor-β (tgf-β), and tumor necrosis factor-α (tnf-α), bcl-2-associated X protein (bax), and cysteinyl aspartate specific proteinase -9 (caspase-9), genes in the head kidney and spleen tissues, while downregulating the levels of the lyz, c3, igm and B-cell lymphoma-2 (bcl-2) genes. Our data provide evidence that Pb impaired immune function and tissue integrity in yellow catfish through oxidative stress, inflammatory and apoptosis, and the results can serve as reference data to better protect water environments from Pb eco-toxicants.

Dietary α-lipoic acid can alleviate the bioaccumulation, oxidative stress, cell apoptosis, and inflammation induced by lead (Pb) in Channa argus

This study aims to evaluate the effects of dietary α-lipoic acid (α-LA) on bioaccumulation, oxidative stress, apoptosis, and inflammation in Channa argus after 28 d of lead (Pb) exposure. A total of 300 fish were divided into five groups: the first group was the control group and the other four groups were exposed to waterborne Pb (800 ppb) and fed α-LA diets supplemented with 0, 300, 600, and 900 mg/kg. The results demonstrated that dietary α-LA effectively reduced the Pb accumulation in the liver, kidney, gill, intestine, and muscle of C. argus after exposure to Pb. Meanwhile, dietary α-LA reversed alterations in the biochemical parameters (Alanine aminotransferase (ALT), lactate dehydrogenase (LDH), aspartate aminotransferase (AST), blood urea nitrogen (BUN), cortisol (COR), and creatinine (CRE)) and immunity parameters (myeloperoxidase (MPO), complement 3 (C3), lysozyme (LYS), complement 4 (C4), C-reactive protein (CRP), and immunoglobulin M (IgM)) in the serum of fish caused by Pb. Pb-induced reduction of antioxidant enzyme activities (Catalase (CAT), glutathione reductase (GR), superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GSH-Px)) was inhibited by dietary α-LA. And malondialdehyde (MDA) and protein carbonyl (PC) content exhibited an opposite trend. Meanwhile, dietary supplemented with α-LA was found to relieve Pb-induced oxidative stress by downregulating Keap1 mRNA expression levels and upregulating the expression levels of CAT, nuclear factor erythroid 2-related factor 2 (Nrf2), GSH-Px, and Cu/Zn SOD. Furthermore, α-LA supplementation reversed Pb-induced upregulation of pro-inflammatory genes (interleukin (IL)-6, IL-1β, tumor necrosis factor α (TNF-α), and nuclear factor kappa B (NF-κB)), Pro-apoptotic genes (Bcl-2-associated X (Bax), caspase (Cas)-3, and tumor protein p53 (p53)) and Hsp70, and downregulation of anti-inflammatory genes (IL-10, inhibitor of κBα (IκBα), and transforming growth factor β (TGF-β)) and anti-apoptosis gene (B-cell lymphoma-2 (Bcl-2)). Overall, dietary α-LA supplementation could enhance the innate immunity and antioxidant capacity of fish, attenuating the Pb accumulation, and cell apoptosis after being exposed to Pb. Furthermore, dietary α-LA could relieve Pb-induced inflammatory response and oxidative stress of fish via regulating NF-κB and Nrf2 signaling, respectively.

Effects of acute ammonia exposure and recovery on the antioxidant response and expression of genes in the Nrf2-Keap1 signaling pathway in the juvenile golden pompano (Trachinotus ovatus)

Continuous exposure to high levels of ammonia can cause oxidative damage to fish tissues and organs. To date, the mechanism by which juvenile golden pompano (Trachinotus ovatus) are poisoned by ammonia exposure has not been thoroughly elucidated. although the mechanisms of ammonia toxicity are not well described for the pompano, many other studies presented these effects to other fish species. So an overview would be given. First, an acute ammonia nitrogen toxicity experiment on juvenile golden pompano obtained a 96-h half-lethal concentration (96 h LC50) of 26.9 mg/L. In the ammonia exposure experiment, fish were sampled at 0 h, 6 h, 12 h, 24 h, 48 h, 72 h and 96 h after exposure to ammonia water (26.93 mg/L). The results showed that with the prolonged ammonia nitrogen exposure, plasma cortisol (COR), total cholesterol (TC), glutamic-pyruvic transaminase (ALT), glutamic oxalacetic transaminase (AST) and malonaldehyde (MDA) levels continued to rise, while glucose (GLU) levels first increased and later gradually decreased after 12 h. The activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) in the liver and the mRNA expression levels of antioxidant genes (SOD, CAT, and GPX) first increased and subsequently decreased with increasing exposure time. Through microscopic observation, it was found that the degree of liver damage increased with increasing stress time and was most serious at 96 h. In the post-poison recovery experiment, the fish exposed to ammonia were transferred to clean water, and samples were taken at 24 h, 48 h, 72 h and 96 h after recovery. The results showed that with the increasing recovery time, each index recovered to the initial level to varying degrees, but the recovery time of 96 h was not enough for the fish to return to the normal level. We also examined the regulation of the Nrf2-Keap1 signaling pathway by the molecular mechanism of the antioxidant defense system. The results of this analysis showed that there was a positive correlation between Nrf2 and liver antioxidant gene expression levels, while there was a negative correlation between Keap1 and liver antioxidant gene expression levels, which may be observed because Nrf2 plays a key role in inducing antioxidant genes, and Keap1 may hinder the response to Nrf2. These results may provide a deeper and more comprehensive understanding of the impact of ammonia exposure on fish and help to provide a foundation for managing the healthy reproduction of juvenile fish.

Histopathological effects of short-term aqueous exposure to environmentally relevant concentration of lead (Pb) in shorthorn sculpin (Myoxocephalus scorpius) under laboratory conditions

Shorthorn sculpin (Myoxocephalus scorpius) has been used as a sentinel species for environmental monitoring, including heavy metal contamination from mining activities. Former lead-zinc (Pb-Zn) mines in Greenland resulted in elevated concentrations of metals, especially Pb, in marine biota. However, the potential accumulation of Pb and effects of the presence of Pb residues in fish on health of sculpins observed in the field have not been validated in laboratory experiments. Therefore, our aim was to validate field observation of shorthorn sculpin via controlled laboratory exposure to environmentally relevant concentrations of dissolved Pb. We evaluated the effects of a short-term (28 days) exposure to Pb on Pb residues in sculpin blood, gills, liver, and muscle and the morphology of gills and liver. The highest level of Pb was found in the gills, followed by muscle and then liver. Pb levels in liver, gills, and blood of Pb-exposed sculpins were significantly higher than those in control fish, showing that blood is suitable for assessing Pb accumulation and exposure in sculpins. Histopathological investigations showed that the severity score of liver necrosis and gill telangiectasia of Pb-exposed sculpins was significantly greater than in control fish. The number of mucous cells in gills was positively correlated with Pb concentrations in organs. Overall, the results validated field observation for the effects of Pb on wild sculpin and contributed to the improved use of the shorthorn sculpin as sentinel species for monitoring contamination from Pb mines in the Arctic.

Identification of Antimicrobial Peptide Genes in Black Rockfish Sebastes schlegelii and Their Responsive Mechanisms to Edwardsiella tarda Infection

The black rockfish, Sebastes schlegelii, is a typical viviparous teleost, which belongs to the family Scorpaenidae. Due to its high economic and ecological values, S. schlegelii has been widely cultured in East Asian countries. With the enlargement of cultivation scale, bacterial and viral diseases have become the main threats to the farming industry of S. schlegelii, which have resulted in significant economic losses. In this study, Illumina shotgun sequencing, single-molecule real-time (SMRT) sequencing, 10× genomics and high-throughput chromosome conformation capture (Hi-C) technologies were collectively applied to assemble the genome of S. schlegelii. Then, we identified the antimicrobial peptide genes (AMPs) in the S. schlegelii genome. In total, 214 AMPs were identified in the S. schlegelii genome, which can be divided into 33 classes according to the annotation and cataloging of the Antimicrobial Peptides Database (APD3). Among these AMPs, thrombin-derived C-terminal peptide (TCP) was the dominant type, followed by RegIIIgamma and chemokine. The amino acid sequences of the TCP, cgUbiquitin, RegIIIalpha, RegIIIgamma, chemokine shared 32.55%, 42.63%, 29.87%, 28.09%, and 32.15% similarities among the same type in S. schlegelii. Meanwhile, the expression patterns of these AMPs in nine healthy tissues and at different infection time points in intestine were investigated. The results showed that the numbers and types of AMPs that responded to Edwardsiella tarda infection gradually increased as the infection progressed. In addition, we analyzed the phylogenetic relationships of hepcidins in teleost. The identification of AMPs based on the whole genome could provide a comprehensive database of potential AMPs, and benefit for the understanding of the molecular mechanisms of immune responses to E. tarda infection in S. schlegelii. This would further offer insights into an accurate and effective design and development of AMP for aquaculture therapy in the future.

Sex-specific neurotoxic effects of heavy metal pollutants: Epidemiological, experimental evidence and candidate mechanisms

The heavy metals lead (Pb), mercury (Hg), and cadmium (Cd) are ubiquitous environmental pollutants and are known to exert severe adverse impacts on the nervous system even at low concentrations. In contrast, the heavy metal manganese (Mn) is first and foremost an essential nutrient, but it becomes neurotoxic at high levels. Neurotoxic metals also include the less prevalent metalloid arsenic (As) which is found in excessive concentrations in drinking water and food sources in many regions of the world. Males and females often differ in how they respond to environmental exposures and adverse effects on their nervous systems are no exception. Here, we review the different types of sex-specific neurotoxic effects, such as cognitive and motor impairments, that have been attributed to Pb, Hg, Mn, Cd, and As exposure throughout the life course in epidemiological as well as in experimental toxicological studies. We also discuss differential vulnerability to these metals such as distinctions in behaviors and occupations across the sexes. Finally, we explore the different mechanisms hypothesized to account for sex-based differential susceptibility including hormonal, genetic, metabolic, anatomical, neurochemical, and epigenetic perturbations. An understanding of the sex-specific effects of environmental heavy metal neurotoxicity can aid in the development of more efficient systematic approaches in risk assessment and better exposure mitigation strategies with regard to sex-linked susceptibilities and vulnerabilities.

Smart Adsorbents for Aquatic Environmental Remediation

A noticeable interest and steady rise in research studies reporting the design and assessment of smart adsorbents for sequestering aqueous metal ions and xenobiotics has occurred in the last decade. This motivates compiling and reviewing the characteristics, potentials, and performances of this new adsorbent generation's metal ion and xenobiotics sequestration. Herein, stimuli-responsive adsorbents that respond to its media (as internal triggers; e.g., pH and temperature) or external triggers (e.g., magnetic field and light) are highlighted. Readers are then introduced to selective adsorbents that selectively capture materials of interest. This is followed by a discussion of self-healing and self-cleaning adsorbents. Finally, the review ends with research gaps in material designs.

Effect of Encapsulated Lactobacillus bulgaricus on Innate Immune System and Hematological Parameters in Rainbow Trout (Oncorhynchus mykiss), Post-Administration of Pb

The present study was conducted to investigate the effects of probiotic and encapsulated Lactobacillus bulgaricus on hematological and immunological factors after lead toxicity in rainbow trout (Oncorhynchus mykiss). Two hundred and forty fish weighing about 16 ± 3.8 g were divided randomly in to four groups including two groups which were fed by a diet containing ~ 10⁸ CFU g^-1Lactobacillus bulgaricus and encapsulated Lactobacillus bulgaricus bacteria and also the third group diet without Lactobacillus bulgaricus. After 45 days, in addition to probiotic (~ 10⁸ CFU g^-1), 500 μg kg of lead nitrate was added to the food of the three groups for 21 days. The fourth group (control) was first fed to the normal diet for 45 days then exposed to Pb. Blood samples were collected at days 45, 52, 59, and 66, and hematological and some immunological parameters were assessed. Results showed that hemoglobin, red blood cells, white blood cells, and lysozyme activity in the two probiotics groups were increased significantly up to 45 day (P < 0.05), but followed by a decreasing trend by adding Pb. Complement and bactericidal activity were enhanced significantly in the bulgaricus group (P < 0.05). Respiratory burst activity at day 45 in group bulgaricus had significant increase (P < 0.05) and decreased in all groups particularly after Pb exposure (P < 0.05). The achieved data shows that microencapsulation of probiotics with alginate-chitosan may be a suitable method to improve the fish condition against heavy metal.

Toxic effects on bioaccumulation, hematological parameters, oxidative stress, immune responses and neurotoxicity in fish exposed to microplastics: A review

Exposure to microplastics (MP) in aquatic environment leads to bioaccumulation in fish, with MP size being a major factor in determining the accumulation profile. MPs absorbed into the fish body enter the circulatory system and affect hematological properties, changing the blood physiology. MPs also induce an imbalance in reactive oxygen species (ROS) production and antioxidant capacity, causing oxidative damage. In addition, MPs impact immune responses due to physical and chemical toxicity, and cause neurotoxicity, altering AchE activity. Here, the toxic effects of MPs in fish through various indicators were examined, including bioaccumulation, hematological parameters, antioxidant responses, immune responses, and neurotoxicity in relation to MP exposure, facilitating the identification of biomarkers of MP toxicity following exposure of fish.

Effects on the survival rates, hematological parameters, and neurotransmitters in olive flounders, Paralichthys olivaceus, reared in bio-floc and seawater by Streptococcus iniae challenge

Bacterial infections cause huge losses to aquaculture globally, and increased antibiotic resistance means that alternative methods of reducing mortality from bacterial diseases are required. We compared the resistance of Juvenile olive flounders, Paralichthys olivaceus, to Streptococcus iniae between those reared in biofloc and seawater conditions for ten months. Experimental fish were challenged with S. iniae at concentrations of 0, 3.36 × 10⁶, 3.36 × 10⁷, 3.36 × 10⁸, and 3.36 × 10⁹ colony forming units (CFU)/g fish for 96 h to evaluate the difference in S. iniae susceptibility of flounders reared in biofloc and seawater. The 96 h lethal concentration 50% (LC₅₀) of fish injected with S. iniae was 2.41 × 10⁹ CFU/g fish in biofloc and 1.51 × 10⁸ CFU/g fish in seawater. Hematological parameters such as hemoglobin and hematocrit significantly decreased when fish were challenged by S. iniae. Plasma components such as calcium, glucose, cholesterol, total protein, GOT, GPT, and ALP were significantly altered by S. iniae infection and acetylcholinesterase activity was significantly inhibited. These results indicate that S. iniae infection affects the survival rates, hematological parameters, and neurotransmitter levels of flounders reared in biofloc and seawater, and that S. iniae susceptibility was higher in flounders reared in seawater than those reared in biofloc.

Protective effects of non-encapsulated and microencapsulated Lactobacillus delbrueckii subsp. bulgaricus in rainbow trout (Oncorhynchus mykiss) exposed to lead (Pb) via diet

The present study was designed to investigate the effects of dietary non-encapsulated and microencapsulated Lactobacillus delbrueckii subsp. bulgaricus on growth performance, intestinal enzymatic activities, antioxidant capacity and hepato-biochemical parameters of rainbow trout before or after exposure to lead via diet. Fingerling fish (16 ± 4 g) were divided into four groups: negative control (NC), positive control (PC), probiotic (PR) and encapsulated probiotic (EN-PR). During the pre-exposure period (days 0-45), fish in the NC and PC groups received the basal diet, whereas fish in the PR and EN-PR groups were fed with basal diet containing 108 CFU g−1 feed of non-encapsulated and microencapsulated probiotic, respectively. During the exposure period (days 46-66), the fish in the probiotic and PC groups were co-treated with 500 μg g−1 feed of lead nitrate. Blood, liver and gut samples were taken at days 0, 45, 52, 59 and 66. The results revealed that growth performance and intestinal enzymatic activities were significantly (p< 0.05) improved in the probiotic groups compared to the NC group (day 45). Dietary exposure to lead resulted in the highest levels of liver aspartate aminotransferase (AST), liver alkaline phosphatase (ALP) and serum malondialdehyde (MDA), and the lowest activities of serum superoxide dismutase (SOD) and catalase (CAT) in the PC group (day 66). The levels of liver ALP were significantly (p< 0.05) lower in the probiotic groups compared to the NC and PC groups prior to and after exposure to dietary lead. Serum levels of total protein, albumin, SOD, CAT and glutathione (GSH) were significantly increased in fish fed with both non-encapsulated and microencapsulated probiotics (p< 0.05). However, microencapsulated probiotic showed the greatest potential for alleviation of the disturbed activities of intestinal and hepatic enzymes, and improvement of serum biochemical and antioxidant parameters. Our findings suggest that L. delbrueckii subsp. bulgaricus, particularly in the microencapsulated form, can be used as a potential probiotic to protect rainbow trout from dietborne lead toxicity.

Salinity-mediated changes in hematological parameters, stress, antioxidant responses, and acetylcholinesterase of juvenile olive flounders (Paralichthys olivaceus)

The purpose of this study was to confirm the limit of salinity tolerance in juvenile olive flounders (Paralichthys olivaceus) by changes in blood parameters, AChE, antioxidant and stress responses. The P. olivaceus (mean weight 38.8 ± 4.2 g and mean length 16.4 ± 1.2 cm) were exposed to different concentrations of salinity (seawater, 16, 8, 4, 2, and 0 psu) for 2 weeks. Plasma osmotic pressure was significantly decreased in the P. olivaceus at 0 psu. Hematological parameters such as hematocrit and hemoglobin were significantly decreased in the P. olivaceus at low salinity. Plasma components also changed significantly in the low salinity environment. As a stress indicator, cortisol was significantly increased at low salinity. SOD and GST antioxidant responses, were significantly increased. GSH level in the liver was significantly increased, whereas a significant decrease was observed in the gill GSH level. AChE was significantly increased in P. olivaceus at low salinity. The results of this study indicate that exposure to salinities lower than 8 psu leads to changes in hematological parameters, neurotransmitter, antioxidant and stress responses of P. olivaceus.

Antioxidative role of dietary ascorbic acid against arsenic induced haematological, biochemical and histomorphological alterations in Cyprinus carpio

The current study investigated the antioxidant potential of ascorbic acid to counteract arsenic induced toxic response in Cyprinus carpio. The 96 h LC50 of 107.05 mg L-1 was recorded through acute toxicity test and 1/5th and 1/10th LC50 of arsenic were chosen as sublethal concentrations for assessing toxicity induced through arsenic exposure in fish for a period of 28 days. There were six experimental groups for sublethal toxicity testing viz. negative control (basal feed), positive control (basal feed + 1 g kg-1 diet ascorbic acid), 1/5th LC50 Arsenic, 1/10th LC50 Arsenic, 1/5th LC50 Arsenic with ascorbic acid supplement, 1/10th LC50 Arsenic with ascorbic acid supplement. Following exposure, blood indices, antioxidant enzyme activity and histomorphology of gills, liver and kidney were examined. The results showed decreased total erythrocyte count, haemoglobin, haematocrit and an increased total leukocyte count upon arsenic exposure in fish with an improvement observed in the blood indices in arsenic with ascorbic acid supplementation. The study also analysed the antioxidant enzyme activity of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase and glutathione-S-transferase which was found to decline in response to arsenic exposure with an increase in their activity recorded in arsenic with ascorbic acid supplemented fish. Furthermore, uptake of arsenic was also found to decrease on ascorbic acid supplementation with improvement in the histoarchitecture of gills, liver and kidney of fish. Collectively, the findings of the present study suggest the effectiveness of ascorbic acid as an ameliorating agent against the deleterious effects of arsenic in fish.

Toxic effects of waterborne ammonia exposure on hematological parameters, oxidative stress and stress indicators of juvenile hybrid grouper, Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀

Juvenile hybrid grouper, Epinephelus lanceolatus ♂ × Epinephelus fuscoguttatus ♀ (mean weight: 26.5 ± 2.8 g, mean length: 11.8 ± 1.3 cm) were exposed to different, sub-lethal levels of waterborne ammonia (0, 1, 2, 4, and 8 mg NH₄⁺/L) for 2 weeks. We assessed the hematological parameters, antioxidant enzymes, and stress responses of juvenile hybrid grouper after 1 week and after 2 weeks. Hematological parameters such as hemoglobin and hematocrit levels, were significantly decreased by ammonia exposure. Plasma components such as the magnesium and total protein contents, and the glutamic oxaloacetic transaminase and glutamic pyruvic transaminase activities were significantly altered by ammonia exposure; however, no changes in the magnesium levels were detected. Antioxidant responses, such as superoxide dismutase and glutathione S-transferase activities, were also significantly affected by ammonia exposure. Stress indicator levels, i.e., plasma cholesterol and heat shock protein 70 levels, were significantly increased by ammonia exposure. The results of this study indicated that ammonia exposure has toxic effects on juvenile hybrid grouper and affects their hematological parameters, antioxidant enzymes, and stress responses.

Amelioration of Cd-Induced Oxidative Stress, MT Gene Expression, and Immune Damage by Vitamin C in Grass Carp Kidney Cells

Cadmium (Cd) is the most common heavy metal and is easily detected in aquatic environments on a global scale. Vitamin C was a widely used vitamin in aquaculture. The aim of this study was to explore the potential of vitamin C in ameliorating Cd-induced toxicity in grass carp kidney (CIK) cells. Cell viability, oxidative response, metallothionein (MT), and immune-related gene expression was analyzed in the present study. The results show that cell viability was significantly reduced following Cd exposure, but the vitamin C supplementation attenuated the increased in cell viability. In addition, vitamin C supplementation can increase the antioxidation response and MT and immune-related gene expression. These results indicate that vitamin C has the potential to alleviate the effects of Cd toxicity in CIK cells.

Cadmium exposure affects growth performance, energy metabolism, and neuropeptide expression in Carassius auratus gibelio

Cadmium (Cd) is the most abundant heavy metal in aquatic environments and is easily detected on a global scale. Carassius auratus gibelio is a common aquaculture species. The aim of this study was to explore the toxic effects of 1, 2, and 4 mg/L Cd on the energy metabolism, growth performance, and neurological responses of C. gibelio. After 30 days of exposure, Cd concentrations in the liver and brain were significantly increased in Cd-exposed groups. Low-level Cd exposure (1 mg/L) increased weight and length gains, as well as food intake, in the fish. Acetylcholinesterase activity decreased significantly in the Cd-exposed groups. Energy metabolism levels (as reflected by oxygen consumption, ammonia excretion rate, and swimming activity), as well as serum T3 and T4 levels, increased significantly in the fish exposed to 1 mg/L Cd. However, energy metabolism and serum T3/T4 levels decreased significantly in the 4-mg/L Cd group. Neuropeptide gene expression levels in brain were consistent with the observed changes in food intake. In the Cd-exposed groups, the expression levels of neuropeptide Y (NPY), apelin, and metallothionein (MT) increased significantly, while those of pro-opinmelanocortin (POMC), ghrelin, and corticotrophin-releasing factor (CRF) decreased significantly. Our data suggested that in fish, low doses of Cd might increase food intake, as well as weight and length gains, but high doses of Cd might have the opposite effect. These effects might be a result of neurohumoral regulation. Long-term exposure to low doses of Cd might cause weight gain and affect food intake.

Effects on hematological parameters, antioxidant and immune responses, AChE, and stress indicators of olive flounders, Paralichthys olivaceus, raised in bio-floc and seawater challenged by Edwardsiella tarda

Studies on the resistance of fish raised in bio-floc systems against bacterial infection are limited. We aimed to evaluate the changes in hematological parameters, antioxidant and immune responses, stress indicators, and acetylcholinesterase (AChE) in olive flounder, Paralichthys olivaceus, raised in bio-floc and seawater for 10 months and, then, infected with Edwardsiella tarda at concentrations of 0 (control), 6.61 × 10⁴, 6.61 × 10⁵, 6.61 × 10⁶, and 6.61 × 10⁷ CFU/g fish for 7 days. The lethal concentration 50% was 4.32 × 10⁷ in bio-floc and 3.11 × 10⁶ in seawater. Hematological parameters were significantly decreased by E. tarda challenge, and plasma components were significantly changed. The superoxide dismutase, catalase, and glutathione-S-transferase activities, as antioxidant responses, were significantly increased after infection, whereas the reduced glutathione level was significantly decreased. The lysozyme activity was significantly increased and the AChE level was significantly decreased after infection. Cortisol and HSP 70, as stress indicators, were also significantly increased. The results indicate that E. tarda infection affected various physiological factors in P. olivaceus. Additionally, P. olivaceus raised in seawater were more susceptible to E. tarda infection than those raised in bio-floc.

Effect on Serum Parameters and Immune Responses of Carassius auratus gibelio Exposed to Dietary Lead and Bacillus subtilis

Lead (Pb), a heavy metal and an environmental stressor, may affect many physiological processes, including the serum index and the immune response. The aim of this study was to explore the toxic effects of Pb on the serum index and the immune response of Carassius auratus gibelio (C. gibelio) fed 0, 120, or 240 mg/kg Pb, and 10⁹ cfu/g Bacillus subtilis (B. subtilis). After 15 and 30 days of dietary exposure, the serum indices and the immune responses of the fish were assessed. Dietary Pb exposure significantly affected various components of the serum index, including calcium, magnesium, glucose, cholesterol, total protein, glutamic-pyruvic transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH). However, sIgA activity in the gut increased significantly following B. subtilis supplementation. Notable changes were also observed in the expression levels of immune-related genes, including HSP70, IgM, HSP90, IL-1β, IL-6, and TNF-α. B. subtilis supplementation effectively attenuated the effects of dietary Pb exposure.

Changes in Hematological Parameters and Heat Shock Proteins in Juvenile Sablefish Depending on Water Temperature Stress

Juvenile Sablefish Anoplopoma fimbria were used to assess the effects of water temperature (8, 10, 12, 14, 16, 18, and 20°C) on hematological parameters and heat shock proteins 70 and 90 for 4 months. Hematological parameters, including red blood cell count, hematocrit, and hemoglobin, were significantly decreased at 18°C. The inorganic plasma components calcium and magnesium were not altered by water temperature. The organic plasma components glucose and cholesterol were notably elevated at 18°C, whereas total protein was reduced. The enzymatic components, including aspartate aminotransferase, alanine aminotransaminase, and alkaline phosphatase, were notably elevated at 16°C or 18°C. The results of this study indicate that a temperature higher than the proper temperature affects the hematological parameters and heat shock proteins of juvenile Sablefish.

Study of Bioaccumulation, Hematological Parameters, and Antioxidant Responses of Carassius auratus gibelio Exposed to Dietary Lead and Bacillus subtilis

Lead (Pb) is one of the most ubiquitous and toxic elements in the aquatic environment. Bacillus subtilis (B. subtilis) is a widely used probiotic in aquaculture. The aim of this study was to explore the toxic effects on bioaccumulation, hematological parameters, and antioxidant responses of Carassius auratus gibelio (C. gibelio) exposed to dietary lead at 0, 120, and 240 mg/kg and/or B. subtilis at 10⁹ cfu/g. At 15 and 30 days, the fish were sampled and bioaccumulation, hematological parameters, and antioxidant responses were assessed. The result showed that B. subtilis administration can provide a significant protection against lead toxicity by reducing lead bioaccumulation in tissues, increasing the antioxidant enzymes activity, recovering δ-aminolevulinic acid dehydratase activity and optimizing the hematological parameters. Our results suggested that administration of B. subtilis (109 cfu/g) has the potential to combat dietary lead toxicity in C. gibelio.

Toxic effects of lead exposure on bioaccumulation, oxidative stress, neurotoxicity, and immune responses in fish: A review

Lead (Pb) is a highly toxic metal in aquatic environments. Fish are at the top of the food chain in most aquatic environments, and are the most susceptible to the toxic effects of Pb exposure. In addition, fish are one of the most abundant vertebrates, and they can directly affect humans through food intake; therefore, fish can be used to assess the extent of environmental pollution in an aquatic environment. Pb-induced toxicity in fish exposed to toxicants is primarily induced by bioaccumulation in specific tissues, and the accumulation mechanisms vary depending on water habitat (freshwater or seawater) and pathway (waterborne or dietary exposure). Pb accumulation in fish tissues causes oxidative stress due to excessive ROS production. Oxidative stress by Pb exposure induces synaptic damage and neurotransmitter malfunction in fish as neurotoxicity. Moreover, Pb exposure influences immune responses in fish as an immune-toxicant. Therefore, the purpose of this review was to examine the various toxic effects of Pb exposure, including bioaccumulation, oxidative stress, neurotoxicity, and immune responses, and to identify indicators to evaluate the extent of Pb toxicity by based on the level of Pb exposure.

Evaluation of the bioaccumulation potential of selected alternative brominated flame retardants in marine fish using in vitro metabolic transformation rates

The global consumption of alternative brominated flame retardants (BFRs) has increased with the restriction of the first generation BFRs such as polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecanes (HBCDs). However, many alternative BFRs are suspected to be persistent in the environment and possibly bioaccumulative after their release into the environment because of their chemical properties, which are similar to those of the already banned BFRs. In this study, the bioaccumulation potential of selected alternative BFRs (1,2-bis(2,4,6‑tribromophenoxy)ethane (BTBPE), 1,2,3,4,5,6‑hexabromobenzene (HBB), pentabromoethylbenzene (PBEB), 2,3,4,5,6‑pentabromotoluene (PBT), 2‑ethylhexyl-2,3,4,5-tetrabromobenzoate (TBB), and 2,3,4,5‑tetrabromo-6-chlorotoluene (TBCT)) was evaluated. The in vitro depletion rate constants (k_depl) were measured for the alternative BFRs using liver S9 fractions isolated from five marine fish species (Epinephelus septemfasciatus, Konosirus punctatus, Lateolabrax japonicus, Mugil cephalus, and Sebastes schlegelii) that inhabit the oceans off the Korean coast. The measured k_depl values were converted to in vitro intrinsic clearance rate constants (CL_{in vitro}) to estimate whole-body metabolic rate constants (k_MET) using an in vitro to in vivo extrapolation (IVIVE) model. Finally, the bioconcentration factors (BCF) were determined using a one-compartment model. The transformation kinetics for obtaining k_depl agreed well with first-order chemical kinetics, regardless of initial BFR concentrations. The values of CL_{in vitro} were lower in the selected marine fish species than those in freshwater fish species, implying slower metabolic transformation. The derived BCF values based on the total concentration in water (BCF_TOT) ranged from 16 (TBB in M. cephalus) to 27,000 (HBB in K. punctatus). The BCF values for HBB and PBT were >2000 except for those in M. cephalus suggesting further investigation of BCF values of BFRs whose log K_OW is between 6 and 7.

Toxic Effects and Depuration on the Antioxidant and Neurotransmitter Responses after Dietary Lead Exposure in Starry Flounder

Starry Flounder Platichthys stellatus were exposed to dietary lead (Pb) at concentrations of 0, 30, 60, 120, and 240 mg/kg for 4 weeks. Recover period was conducted for 2 weeks after the exposure. Exposure to Pb concentrations over 60 mg/kg induced significant changes in the antioxidant responses in the liver, kidney, and gill and continued even after the depuration period in the liver (over 120 mg/kg for superoxide dismutase [SOD] activity) and kidney (at 240 mg/kg for glutathione [GSH] levels). Glutathione S-transferase (GST) activity in liver, kidney, and gill were increased by dietary Pb exposure, and recovery was observed in all groups during the recovery period. Acetylcholinesterase (AChE) activity was significantly inhibited in the brain and muscle of flounder at Pb exposure over 120 mg/kg, and no restoration was observed after the depuration period. Lysozyme activity in the plasma was significantly increased at Pb exposures greater than 60 mg kg but was restored after the depuration period. The results of this study indicate that dietary Pb exposure induces toxic effects on antioxidant responses, neurotransmitter, and immune responses of Starry Flounder.

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.

Effect of sub-chronic exposure to lead (Pb) and Bacillus subtilis on Carassius auratus gibelio: Bioaccumulation, antioxidant responses and immune responses

Lead (Pb) poisoning in humans and fish represents a significant global problem. Bacillus subtilis (B. subtilis) is a widely used probiotic in aquaculture. Carassius auratus gibelio (C. gibelio) is one of the most important aquaculture species with great commercial value. The objective of this study was to evaluate the potential of B. subtilis in ameliorating lead-induced toxicity in C. gibelio. The fish were exposed for 60 days to waterborne Pb at 0, 0.05, 0.5 and 1 mg/L and/or dietary B. subtilis at 10⁹ cfu/g. After 30 and 60 days, the fish were sampled and bioaccumulation, antioxidant activity and immune responses were assessed. The results revealed that B. subtilis confers significant protective effects against lead toxicity by preventing alterations in the levels of bioaccumulation, superoxide dismutase, catalase and glutathione. B. subtilis also assists in the recovery of blood δ-aminolevulinic acid dehydratase, lysozyme, and IgM levels while regulating the expression of immune-related genes including IL-10, lysozyme, TNF-α, IgM and Hsp70 after 60 days of lead exposure. Our results suggest that administration of B. subtilis (10⁹ cfu/g) has the potential to combat lead toxicity in C. gibelio.

Therapeutic Effect of Intestinal Autochthonous Lactobacillus reuteri P16 Against Waterborne Lead Toxicity in Cyprinus carpio

Harmful effects of heavy metals are myriad. Lead (Pb) from soil and atmosphere contaminates water bodies and affects the aquatic animals. Our previous study confirmed the in vitro probiotic potential of Lactobacillus reuteri against Pb toxicity, but further investigation is necessary for gaining insights into the related protection mode. Therefore, in this study, we investigated the protective effects of the potential probiotic L. reuteri P16 against waterborne Pb exposure-induced toxicity in the freshwater fish Cyprinus carpio. Fish (average weight: 23.16 ± 0.73 g) were allocated to four groups (control, Pb only, Pb + L. reuteri P16, and L. reuteri P16 only) and Pb groups were exposed to waterborne Pb (1 mg L⁻¹) for 6 weeks. L. reuteri P16 (10⁸ CFU g⁻¹) supplemented diet was provided twice daily. Growth performances, hemato-biochemical parameters, innate immune responses, intestinal microbiota, and Pb accumulation in tissues were measured at the end of the trial. When the fish were exposed to Pb, dietary supplementation of L. reuteri P16 effectively decreased mortality and accumulation of Pb in tissues, and improved the growth performance. Co-treatment with Pb and L. reuteri P16 alleviated Pb exposure-induced oxidative stress, reversed alterations in hemato-biochemical parameters, improved innate immune parameters, and restored intestinal enzymatic activities. Moreover, L. reuteri P16 supplementation reversed the changes in intestinal microbiota in Pb-exposed fish. Furthermore, Pb exposure decreased the expressions of pro-inflammatory cytokines (TNF-α, IL-1β). However, the expression of heat shock proteins (HSP70 and HSP90) increased, which might have increased the cellular stress. Interestingly, the Pb-induced alterations of gene expressions were reversed by L. reuteri P16 supplementation. Thus, dietary administration of the potential probiotic L. reuteri P16 had several beneficial effects on growth performance and immune responses, decreased Pb accumulation in tissues, and reversed alterations in hematological responses of C. carpio. Furthermore, it offered direct protection against Pb-induced oxidative stress. Therefore, L. reuteri P16 may be a novel dietary supplement for enhancing growth performance and preventing Pb-exposure-induced toxicity in fish in aquaculture and aquatic products.

Alterations in growth performance and stress responses in juvenile rockfish, Sebastes schlegelii, exposed to dietary chromium with varying levels of dietary ascorbic acid supplementation

Juvenile rockfish Sebastes schlegelii (mean length 10.8 ± 1.4 cm, and mean weight 31.7 ± 3.6 g) were exposed for 4 weeks to different levels of dietary chromium (Cr⁶⁺) at 0, 120, and 240 mg/L and ascorbic acid (AsA) at 100, 200, and 400 mg/L. Growth performance of S. schlegelii was significantly decreased due to dietary Cr exposure, whereas lysozyme activity was notably increased. Exposure to dietary Cr resulted in substantial accumulation of Cr in the blood. Levels of two stress indicators, plasma cortisol and heat shock protein 70, of S. schlegelii were increased due to dietary Cr exposure. The results indicated that dietary Cr exposure affected growth performance, lysozyme activity, and stress responses of S. schlegelii, and high levels of AsA supplementation significantly attenuated dietary Cr-induced toxicity.

Metals in Fishes from Yongshu Island, Southern South China Sea: Human Health Risk Assessment

In order to assess the bioaccumulation of metals associated with gender, tissues, and their potential ecological risk, four species of fish were collected from the Yongshu Island in the Southern South China Sea. Metals and stable Pb isotopes in their tissues (muscle, gill, liver, intestine, and ovary) were determined. The concentrations of metals (mg/kg, dry weight) in these species were ND-21.60 (Cd), 1.21-4.87 (Cr), 0.42-22.4 (Cu), 1.01-51.8 (Mn), 0.30-3.28 (Ni), 6.04-1.29 × 103 (Zn), 14.89-1.40 × 103 (Fe), and 0.22-3.36 (Pb). In general, the liver and intestine absorbed more metals than the other tissues. Metals accumulation can be influenced by gender and feeding behavior and in fact, female fish and dietary exposure are more prone to accumulate metals. In addition, Pb isotopic ratios indicated that all species had significant biological fractionation, which may not make them good tracers for source identification. The metal concentrations of most samples were lower than the national standard values of the FAO (USA), which suggested that human consumption of these species may not cause health risks. However, since the surrounding areas are developing rapidly, the potential environmental risk of metals will intensify and should receive more attention.