Inhibition of cadmium- induced genotoxicity and histopathological changes in Nile tilapia fish by Egyptian and Tunisian montmorillonite clay

Can Lemna minor mitigate the effects of cadmium and nickel exposure in a Neotropical fish?

We aimed to evaluate if Lemna minor can mitigate the observed effects of cadmium (Cd) and nickel (Ni) exposure in Prochilodus lineatus. Fish were exposed for 96 h to 20 µg L^-1 of Cd, 1.5 mg L^-1 of Ni, or to a mixture of these two metals. In all tests, one group was exposed to the metals with duckweed on the water surface, and other group was exposed only to the metals, without plants. After each exposure, samples of P. lineatus tissues were collected to evaluate multiple biomarkers. Duckweed prevented bioaccumulation in some fish tissues and attenuated changes in acetylcholinesterase activity, increases in erythrocytic nuclear abnormality frequency, and hyperglycemia. However, the changes in plasma ion concentrations, reduction in activity of ion transport enzymes, and histological damage were not mitigated. Therefore, we concluded that L. minor partially attenuates the effects caused by Cd and Ni exposure.

Combined effects of polystyrene microplastics and copper on antioxidant capacity, immune response and intestinal microbiota of Nile tilapia (Oreochromis niloticus)

Microplastics (MPs) coexist with other pollutants (such as heavy metals) in water, adversely impacting aquatic organisms, which might cause unpredictable ecological risks. This study aims to evaluate the effect of copper (Cu²⁺) and polystyrene microplastics (PS-MPs) on antioxidant capacity, immune response and intestinal microbiota of Nile tilapia. Cu²⁺ and PS-MPs co-exposure enhanced Cu²⁺ bioaccumulation in the liver of fish compared with Cu²⁺-alone exposure. Fish exposed to PS-MPs and Cu²⁺ displayed histopathologic alterations in the liver, intestine and gill. Exposure at low concentrations of Cu²⁺ in the C0 and CP0 groups can improve antioxidant capacity and immune response, while oxidative damage and inflammation existed in the high concentration of Cu²⁺ groups. Intestinal microbiota results showed that the diversity and structure were changed by Cu²⁺ and PS-MPs exposure, and harmful bacterium even increased at high concentration of Cu²⁺ and PS-MPs exposure groups. All in all, PS-MPs aggravate the accumulation of Cu²⁺ and lead to perturbations in biological systems of Nile tilapia.

Impact of water-sediment regulation on the concentration and transport of dissolved heavy metals in the middle and lower reaches of the Yellow River

Anthropogenic activities in river basins, especially large-scale water conservancy projects, have notably impacted the physical, chemical and ecological environments of estuaries and coastal areas. In this paper, the effects of water and sediment regulation (WSR) on the concentration and transport of heavy metals in the Yellow River were studied based on a continuous daily heavy metal survey in both the middle reaches (Xiaolangdi station) and lower reaches (Lijin station) of the Yellow River during the WSR period in 2019. The results indicated that the variation in the water oxidation-reduction environment of the Xiaolangdi reservoir during the WSR process exerted an important impact on the concentrations of dissolved Cu, Cd, Pb, Cr and As at the Xiaolangdi station but exerted almost no influence on the concentration of dissolved Ni. At Lijin station, the dissolved heavy metal content first increased and then decreased in the first stage, which mainly depended on the release of heavy metals from resuspended sediments. In the second stage, the heavy metal content gradually decreased due to adsorption onto fine particles discharged from the reservoir. The dissolved heavy metal flux during the water-sediment regulation scheme (WSRS) period accounted for 16.9-33.4% of the annual total dissolved heavy metal flux. WSRS changed transport of water and sediment. The dissolved heavy metal concentrations at the Xiaolangdi station were mainly controlled by the discharge of water and sediments from the Xiaolangdi reservoir, while the dissolved heavy metal concentration at the Lijin station was largely affected by the sediments resuspended from downstream riverbeds and the water and sediment scheduling mode of the Xiaolangdi reservoir. Dissolved heavy metal transportation was highly influenced by the WSR process within a short time. Human intervention, especially WSRS operation, apparently alters the natural states of both the mainstream and estuarine environments of the Yellow River.

Dietary application of Lactococcus lactis alleviates toxicity and regulates gut microbiota in Cyprinus carpio on exposure to heavy metals mixture

Heavy metals (HMs) contaminated fish is a threat to humans when consumed. Dietary probiotics have evolved as a successful HMs removal approach. In this study, probiotics Enterococcus (EC) sp. and Lactococcus (LC) sp. were evaluated for toxicity alleviation and gut microbiota maintenance in Cyprinus carpio (single and combined approach) on Cr, Cd, and Cu mixture (0.8 mg/L and 1.6 mg/L) exposure (28 days). HMs removal, oxidative stress, cytokines response, histology, and gut microbiota were investigated. LC alone showed remarkable HMs removal for Cr (62.28%-87.57%), Cd (89%-90.42%), and Cu (72%-88%) than LC + EC. Probiotics up-regulated superoxide dismutase and total protein levels, while decreased the activity of malondialdehyde than the control. Pro-inflammatory cytokine (TNF-α) and chemokine (IL-8) expressions were higher at 1.6 mg/L concentration, whereas anti-inflammatory cytokine (IL-10) was higher in the 0.8 mg/L group. LC mitigated the histological alterations of gills, kidneys, and intestines, particularly at the lower concentration. Sequencing results revealed that Proteobacteria (44%-61%) was the most dominant phylum in all groups, followed by Fusobacteria (34%-36%) at 0.8 mg/L and Firmicutes (19%-34%) at 1.6 mg/L. The current study presented LC and EC potential separately and in combination to countermeasure HMs mixture induced toxicity and gut microbial dysbiosis, in which the conjoint group was less effective.

Long-term exposure of high concentration heavy metals induced toxicity, fatality, and gut microbial dysbiosis in common carp, Cyprinus carpio

Heavy metals (HMs) in an aquatic environment mainly affects fish, and thus, fish are convenient pollution bio-indicators. In this study, the toxic effects of HM mixture (chromium (Cr), cadmium (Cd), copper (Cu)) in 0 mg/L to 3.2 mg/L concentration range was investigated in Cyprinus carpio (28 days). HM accumulation, histopathology, oxidative stress, and gut microbial changes were evaluated. HMs accumulated in the order of Cr > Cu > Cd, primarily in the kidneys and finally scales. Reactive oxygen species generation increased in all exposure groups up to day 14, with maximum generation at 3.2 mg/L mixture, which later decreased on day 28 in all. Malondialdehydeand and superoxide dismutase levels increased from day 7 to 28 with increased HM concentrations, while total protein showed an inverse trend. Gill histopathology showed major changes such as uplifted and disintegrated primary lamella, and secondary lamella shortening. The kidneys were characterized by glomerular necrosis, Bowman's capsule expansion, and tubular space dilatation. Proteobacteria and Firmicutes abundance increased up to 59.4% and 99.16% in 0.8 mg/L and 3.2 mg/L treatment groups, respectively. This study provided a better understanding on the physiology and gut microbiota alteration in C. carpio under multiple HM stress.

Evaluation of single and combined effects of cadmium and micro-plastic particles on biochemical and immunological parameters of common carp (Cyprinus carpio)

The growing accumulation of microplastics (MPs) in aquatic environments is a global concern. MPs are capable to interact with other environmental contaminants, including heavy metals, altering their toxicity. The aim of the study was to investigate the sub-lethal effects of cadmium chloride (Cd) alone and in combination with MPs on common carp (Cyprinus carpio). Multi-biomarkers, including plasma biochemical parameters and intrinsic immunological factors, were measured after 30 days of exposure. Exposure to Cd or NPs reduced the plasma activities of acetylcholinesterase (AChE) and gamma-glutamyl-transferase (GGT) and increased aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) and alkaline phosphatase (ALP). Exposure to both compounds enhanced the observed effects except for AST activity and ALP at the highest concentrations, whereas evidenced an antagonistic interaction in ALT. Plasma total protein, albumin, and globulin levels were decreased, and the levels of glucose, triglyceride, and cholesterol levels increased mainly in the Cd groups with no additional effects derived from the co-exposure to both stressors. Lysozyme and alternative complement (ACH50) activities and the levels of total immunoglobulins, and complement C3 and C4 in fish exposed to Cd and MPs were lower than those in the control group and this decrease was more significant by the mixture of both compounds. These findings showed that the exposure to Cd or MPs alone is toxic to fish altering the biochemical and immunological parameters. Moreover, these alterations are even greater when the Cd and the MPS are combined suggesting synergistic effects in increasing Cd toxicity and vice versa.

Toxicological Potential of Cadmium Impact on Rainbow Trout (Oncorhynchus mykiss) in Early Development

Cadmium (Cd) is a toxic element widely distributed in the aquatic environment and producing a wide variety of harmful effects. In this study, the acute toxicity (96 h LC50) of Cd to rainbow trout Oncorhynchus mykiss embryos and larvae was determined. The obtained results showed that hatched larvae were the most sensitive to Cd exposure. After 4 days of exposure, embryos were found to have accumulated greater concentrations of Cd than larvae. Exposure to Cd at sublethal concentrations produced deleterious, exposure duration-related effects on biological parameters (mortality, heart rate and gill ventilation frequency) of larvae. Cd induced a significant elevation of all the studied geno- and cytotoxicity endpoints in larval erythroblasts.

Filed studies on some probiotics to minimize hazard effects of prevailing heavy metals contamination for improving immunity and growth performance of Oreochromis niloticus

AIM

The objective of the present study was to determine the effect of some types of probiotics to minimize the hazard effect of cadmium on Oreochromis niloticus (O. niloticus) and to determine the influence of probiotics on the growth performance and immune status of O. niloticus.

METHODS

Fish were divided into four groups, the first one was fed on a diet without any additives (control group), and the second group was fed on diet with the addition of 0.1 from (LC₅₀) of cadmium 32 ppm in water. The third group was fed on a diet containing 1 gm/kg of Lactobacillus acidophilus. The fourth group was fed on a diet containing 1 gm/kg of L. acidophilus with 0.1 addition from (LC₅₀) of cadmium 32 ppm.

RESULTS

The experiment lasted about 60 days which resulted in an improvement in growth performance, with a decrease in the number of micronucleus formation in the group which received the probiotic. The group which was affected with cadmium showed decrease in the growth performance with increase in the number of micronucleus formation while the group which received probiotics and treated with cadmium had significant improvement in growth performance and decreased in the number of micronucleus formation.

CONCLUSIONS

Probiotics decrease cadmium pollution.

Liver alterations in Oreochromis niloticus (Pisces) induced by insecticide imidacloprid: Histopathology and heat shock protein in situ localization

Liver is very sensitive to environmental contaminants such as pesticides, it being the first target of toxicity of a substance. The objective of this study was to investigate the possible effects of the insecticide imidacloprid (IMI) on the liver of Oreochromis niloticus according concentrations used for growing sugarcane. A semi-quantitative analysis of histopathological alterations of IMI on liver was performed by light microscopy and cellular labeling of heat shock proteins (HSP70) by immunohistochemistry. The most common changes in liver at all concentrations of IMI were hydropic degeneration, pyknotic nuclei, and loss of cell limits. Steatosis and increased levels of HSP70 were detected in hepatocytes with the highest concentration of IMI. In conclusion, the tested concentrations of IMI induced histopathological changes in the liver of O. niloticus and active defence mechanisms to maintain the morphophysiological integrity of the liver. This insecticide has a toxicity potential for these fish, which is a non-target organism of its action.

Vitamin C modulates cadmium-induced hepatic antioxidants' gene transcripts and toxicopathic changes in Nile tilapia, Oreochromis niloticus

Cadmium (Cd) is one of the naturally occurring heavy metals having adverse effects, while vitamin C (L-ascorbic acid) is an essential micronutrient for fish, which can attenuate tissue damage owing to its chain-breaking antioxidant and free radical scavenger properties. The adult Nile tilapia fish were exposed to Cd at 5 mg/l with and without vitamin C (500 mg/kg diet) for 45 days in addition to negative and positive controls fed with the basal diet and basal diet supplemented with vitamin C, respectively. Hepatic relative mRNA expression of genes involved in antioxidant function, metallothionein (MT), glutathione S-transferase (GST-α1), and glutathione peroxidase (GPx1), was assessed using real-time reverse transcription polymerase chain reaction (RT-PCR). Hepatic architecture was also histopathologically examined. Tilapia exposed to Cd exhibited upregulated antioxidants' gene transcript levels, GST-⍺1, GPx1, and MT by 6.10-, 4.60-, and 4.29-fold, respectively. Histopathologically, Cd caused severe hepatic changes of multifocal hepatocellular and pancreatic acinar necrosis, and lytic hepatocytes infiltrated with eosinophilic granular cells. Co-treatment of Cd-exposed fish with vitamin C overexpressed antioxidant enzyme-related genes, GST-⍺1 (16.26-fold) and GPx1 (18.68-fold), and maintained the expression of MT gene close to control (1.07-fold), averting the toxicopathic lesions induced by Cd. These results suggested that vitamin C has the potential to protect Nile tilapia from Cd hepatotoxicity via sustaining hepatic antioxidants' genes transcripts and normal histoarchitecture.

The role of vitamin E or clay in growing Japanese quail fed diets polluted by cadmium at various levels

This study was conducted to verify whether vitamin (Vit) E or natural clay as feed additives has the potential to modulate the deleterious effects resulting from exposure to cadmium (Cd) in growing Japanese quail. 648 Japanese quail chicks (1 week old) were used to evaluate the effects of dietary Cd (0, 40, 80 and 120 mg/kg diet) and two levels of Vit E (0, 250 mg/kg diet) or two levels of natural clay (0 and 100 mg/kg diet) to study the influences of Cd, Vit E, clay or their different combinations on growth performance, carcass traits, some blood biochemical components and Cd residues in muscles and liver. Live BW and weight gain of quails were linearly decreased with increasing dietary Cd levels. Moreover, feed conversion was significantly worsened with increasing Cd level. Mortality percentage was linearly increased as dietary Cd level increased up to 120 mg/kg diet. Carcass percentage was linearly decreased as dietary Cd level increased. While, giblets percentage were linearly and quadratically differed as dietary Cd level increased. Cd caused significant changes in total plasma protein, albumin, globulin, A/G ratio, creatinine, urea-N and uric acid concentrations as well as ALT, AST and ALP activities. Increasing dietary Cd level was associated with its increase in the muscles and liver. Dietary supplementation with 250 mg of Vit E/kg diet or 100 mg clay/kg improved live BW, BW gain and feed conversion when compared with the un-supplemented diet. Quails fed diet contained 250 mg Vit E/kg and those fed 100 mg clay/kg had the highest percentages of carcass and dressing than those fed the un-supplemented diet. Blood plasma biochemical components studied were better when birds received 250 mg of Vit E/kg diet and those received 100 mg clay/kg. Cd residues in the muscles and liver were significantly less in the birds had 250 mg of Vit E/kg or those received 100 mg clay/kg diet than those un-supplemented with Vit E. Growth performance traits and blood plasma biochemical components studied were significantly affected linearly by the interactions among Cd and each of Vit E and clay levels. In conclusion, the present results indicate that the deleterious effects induced by Cd plays a role in decreasing the performance of Japanese quail and that dietary supplementation with natural clay or Vit E may be useful in partly alleviating the adverse effects of Cd.