Impairment of antioxidant mechanisms in Japanese Medaka (Oryzias latipes) by acute exposure to aluminum

Effects of inorganic and organic pollution on development of Steindachneridion melanodermatum from the Iguaçu river, Brazil

The Iguaçu River basin, known for its rich endemic ichthyofauna, faces a significant threat from chemical pollution. The Jordão River, a major tributary, drains extensive agricultural and livestock areas and receives poorly treated domestic and industrial effluents before joining the Iguaçu River. This study investigated the pollution and toxic effects of water samples from the Iguaçu upstream (UI), Jordão (JR), and their confluence (DI) on Steindachneridion melanodermatum embryos and larvae. Chemical analyses of the water samples revealed that most contaminants were present at levels below detection limits or within the limits established by Brazilian legislation. However, cadmium in UI, aluminum in JR, and lead in DI exceeded the legal limits. Exposure up to 96 h post-fertilization revealed higher mortality and deformity rates in individuals exposed to water samples from UI and JR, despite JR having fewer detected pollutants. JR and DI samples induced increased superoxide dismutase activity, indicating activation of the antioxidant defense system due to xenobiotic exposure. Overall, the integrated biomarker response indexes showed that individuals exposed to JR water displayed the most significant variations in their responses compared to the control treatment, suggesting a higher level of contamination and toxicity. Although a direct link between water quality and toxicity in the Jordão and Iguaçu Rivers was inconclusive, the results confirmed pollution and risks to local wildlife. The study highlighted the harmful effects of pollutants, even at low concentrations. These findings underscore the need for conservation measures to safeguard endemic and endangered species in the Iguaçu River basin. Understanding pollutant effects on native species is crucial for effective mitigation strategies and ecological health preservation.

Impact of aluminum exposure on oxidative stress, intestinal changes and immune responses in red swamp crayfish (Procambarus clarkii)

Aluminum (Al) is an abundant metal that has been classified as a threatening pollutant due to indiscriminate use and anthropogenic activities. This study aimed to evaluate the impacts of Al on crayfish (Procambarus clarkii), including biochemical change, histological alteration, gut microbial community diversification, and immune changes. The bioaccumulation of Al was detected in the hemolymph and intestine of crayfish after Al exposure at different time points. Results showed that Al exposure significantly induced oxidative stress and caused pathohistological changes on intestinal barrier structures in crayfish. It was found that the intestinal microbiota was affected by retained Al and the intestinal community diversity was changed after Al treated in the crayfish. Furthermore, Al exposure affected the immunity in crayfish, by altering the expression of a set of immune-related genes, as well as reducing the phenoloxidase and lysozyme activities. Moreover, Al exposure promoted hemocytes apoptosis and impaired hemophagocytic capacity against Vibro parahamolyticus, resulting in higher mortality of crayfish upon bacterial infection. Taken these results together, we conclude that excessive Al exposure caused adverse effects on multiple biological processes of crayfish and Al pollution is a potential threat to crayfish culture.

Evaluation of cardiotoxicity in Amazonian fish Bryconops caudomaculatus by acute exposure to aluminium in an acidic environment

Aluminium (Al) is soluble in acidic waters and may become toxic to organisms. In this study, the acute effects of two Al concentrations were evaluated in the Amazonian fish Bryconops caudomaculatus. Antioxidant responses and lipid damage were assessed in gills, liver and muscle, along with the electrocardiography (ECG) and characterization of cardiac complex and wave intervals. Fish were essayed as follows: two control groups at neutral and acidic pH and two exposure groups at acidic pH (0.3 mg/L and 3.0 mg/L Al). Water samples were collected at 0h, 24h and 48h, for chloride (Cl^-), fluoride (F^-) and sulphate (SO₄^2-) ion analyses, while total Al was quantified in muscle. Concentrations of Cl^- and SO₄^2- were constant over time whereas F^- was not detected. Total Al concentrations in water and muscle were concentration-dependent. Antioxidant responses, total antioxidant capacity against peroxyl radicals (ACAP) and glutathione S-transferase were not triggered in fish tissues exposed to 0.3 mg/L Al; however, fish exposed to 3.0 mg/L Al presented increased and reduced ACAP in gills and liver, respectively. No changes in lipoperoxidation levels occurred among groups. Fish exposed to 0.3 mg/L Al showed prolonged intervals in ECG as a reflection of low heart rate (HR), with sinus bradycardia. Moreover, there was a marked prolongation of the PQ interval (time between the atrial activity and the start of ventricular activity), indicating interference on the cardiac cell automaticity. Fish exposed to the highest concentration of Al showed reduced wave intervals as a consequence of increased HR, with sinus arrhythmia, while ECG tracings did not present P waves (atrial contraction), indicating an atrioventricular blockade. In conclusion, 48h exposure sufficed to cause cardiotoxicity in B. caudomaculatus at either Al concentration. However, as oxidative stress was not observed, such cardiac alterations seem to be reversible under the experimental conditions established herein.

Aluminum bioconcentration in female Nile tilapia Oreochromis niloticus (Perciformes: Cichlidae) and the effects on pituitary gonadotropins

In this study, we measured aluminum (Al) bioconcentration in the brain, ovaries, and liver of Oreochromis niloticus females, and analyzed the effects of exposure to Al and acidic pH on the gene expression of follicle-stimulating hormone (βfsh) and luteinizing hormone (βlh) in these animals. Mature females were divided into 4 groups, thus being maintained for 96 h in one of the following conditions: control at neutral pH (Ctr); Al at neutral pH (Al); acidic pH (Ac), and Al at acidic pH (Al-Ac). pH alone did not influence Al bioconcentration in the brain. The animals from the Al-Ac group bioconcentrated more Al in the ovaries than those from the Al group, while no differences were observed in the liver. Aluminum bioconcentration was higher in the brain than in the liver and ovaries in Al-exposed animals (Al and Al-Ac), and higher in the brain than in the ovaries in the Ctr and Ac groups. The liver bioconcentrates more Al than the ovaries in the females from the Ctr and Ac groups. Aluminum and/or acidic pH did not alter βfsh gene expression, while βlh gene expression decreased in females from the Al group. Aluminum acted as an endocrine disruptor, suggesting deleterious effects in reproduction that could result in ovulation failure. Aluminum can act directly and/or indirectly in the pituitary, affecting ovarian steroidogenesis and altering the reproductive endocrine axis of mature O. niloticus females in an acute period of exposure.

Paternal exposure to aluminum, acidity, and temperature affect fatty acid seminal profile, embryonic and larval development of Astyanax altiparanae

We investigated the effects of water acidity, temperature, and aluminum (Al) on the fatty acid (FA) seminal profile, reproductive parameters (fertilization and hatching) and embryonic development of Astyanax altiparanae. We treated males with different experimental treatments, corresponding to the combination of water temperature (20 °C; 25 °C), pH (neutral - 7.0; acidic - 5.5), and the absence or presence of Al (0.5 mg L^-1). After 96 h, we analyzed the FA profile of semen and performed artificial fertilization in activating medium with neutral pH or activating medium in the same experimental conditions of the males (neutral pH, acidic pH, and Al) to evaluate fertilization and hatching rates and to monitor embryonic development. Polyunsaturated FA percentage decreased in semen of fish from the neutral group, while monounsaturated FA increased in all groups maintained at 20 °C compared to 25 °C. Aluminum exposure decreased the percentage of C20:4n6 and increased the percentage of C22:5n3 at 20 °C. Males exposed to acidic pH and Al showed lower fertilization and hatching rates, as well as increased mortality of embryos and larvae. Moreover, Al favoured a higher percentage of abnormal larvae. Fertilization in Al activating medium harmed the embryos and larvae since fertilization and hatching rates decreased. Finally, temperature influenced fertilization time, hatching rate, and the morphology of embryos and larvae. Males exposed to Al had lower fertilizing capacity, which negatively affected the embryonic development of the species. Furthermore, Al activating medium reduced the number of fertilized oocytes, hatched embryos, and normal larvae. All events were temperature dependent.

Geno-cytotoxicity and congenital malformations produced by relevant environmental concentrations of aluminum, diclofenac and their mixture on Cyprinus carpio. An interactions study

Several studies highlight the presence of aluminum and diclofenac in water bodies around the world and their ability to induce oxidative stress and a negative effect on biomolecules in several aquatic species. However, studies evaluating the toxic effect of mixtures of these contaminants are scarce. The objective of this work was to determine the genotoxic, cytotoxic and embryotoxic effect of the mixture of aluminum and diclofenac at environmentally relevant concentrations on Cyprinus carpio. Juveniles of Cyprinus carpio were exposed to 0.31 μg L^-1 of diclofenac, 24.45 mg L^-1 of aluminum, and a mixture of both contaminants at the same concentrations for 12, 24, 48, 72 and 96 h. After the exposure time the liver, gills and blood were extracted and the following biomarkers were evaluated: micronucleus frequency, comet assay, caspase activity and TUNEL test. On the other hand, Cyprinus carpio embryos were exposed to diclofenac (0.31 μg L^-1), aluminum (0.06 mg L^-1) and their mixture at the same concentrations and exposure time. Microscopic observation was performed to evaluate embryonic development at 12, 24, 48, 72 and 96 h. Diclofenac (0.31 μg L^-1) induces significant increases in micronucleus frequency with respect to control (p < 0.05), in all tissues. Aluminum (24.45 mg L^-1) significantly increases DNA damage index in liver and blood cells with respect to control (p < 0.05). All treatments increase caspases activity in all tissues with respect to control (p < 0.05). Diclofenac increases the percentage of TUNEL-positive cells in liver and blood; while aluminum and the mixture increases it significantly in gills and blood with respect to the control (p < 0.05). The mixture significantly delays embryonic development, while aluminum and the mixture significantly increase teratogenic index with respect to control (p < 0.05). In conclusion, exposure to environmental concentrations of aluminium, diclofenac and their mixture induces genotoxic damage, cell death by apoptosis and negative effects on the development of Cyprinus carpio and the toxic response is modified by the interaction of the xenobiotics.

Experimental evidence of masculinization by continuous illumination in a temperature sex determination teleost (Atherinopsidae) model: is oxidative stress involved?

The present study evaluates the influence of continuous light on phenotypic sex ratios in Chirostoma estor, a temperature sex determination animal model. Relative gene expression levels of 5 day old larvae were performed on two early gonad differentiation genes (sox9 and foxl2), two stress axis activation genes (gcr1 and crf) and four reactive oxygen species (ROS) antagonist effector genes (sod2, ucp2, gsr and cat). Two light treatments were applied from fertilization; control (12L:12D) simulated natural photoperiod and a continuous illumination photoperiod. By the end of the trial (12 weeks after hatching), differentiated and normal gonads were clearly identifiable in both treatments by histological observations. Regarding sex ratio, 73% of phenotypic males were found in continuous illumination compared with 40% in controls. Consistently, the sox9 gene (involved in early testis differentiation) showed an over expression in 64% of the individual larvae analysed compared with foxl2 (ovarian differentiation) suggesting a masculinization tendency in continuous illumination. On the other hand, only 36% of individuals showed the same tendency in the control treatment consistent with phenotypic sex ratios found under normal culture conditions. Relative gene expression results did not show significant difference in sod2, ucp2 and gcr1 levels, but cat, gsr and crf showed significantly higher expression levels in the continuous illumination treatment suggesting that both, the stress axis and ROS response mechanisms were activated at this time. This study suggests, a link between continuous light, oxidative stress and environmental sex determination in vertebrates. However, further research is necessary to describe this possible upstream mechanism that may drive some aspects of sexual plasticity in vertebrates.