Impact on the antioxidant system, histology, and cell death of zebrafish liver after exposure to industrial sludge leachate

Tropane Alkaloid Isolated from Erythroxylum bezerrae Exhibits Neuropharmacological Potential in an Adult Zebrafish (Danio rerio) Model

This study carried out to investigate the anti-inflammatory and antinociceptive effect of tropane alkaloid (EB7) isolated from E. bezerrae. It evaluated the toxicity and possible involvement of ion channels in the antinociceptive effect of EB7, as well as its anti-inflammatory effect in adult zebrafish (Zfa). Docking studies with EB7 and COX-1 and 2 were also performed. The tested doses of EB7 (4, 20 and 40 mg/kg) did not show any toxic effect on Zfa during the 96h of analysis (LD50>40 mg/kg). They did not produce any alteration in the locomotor behavior of the animals. Furthermore, EB7 showed promising pharmacological effects as it prevented the nociceptive behavior induced by hypertonic saline, capsaicin, formalin and acid saline. EB7 had its analgesic effect blocked by amiloride involving the neuromodulation of ASICs in Zfa. In evaluating the anti-inflammatory activity, the edema induced by κ-carrageenan 3.5 % was reduced by the dose of 40 mg/kg of EB7 observed after the fourth hour of analysis, indicating an effect similar to that of ibuprofen. Molecular docking results indicated that EB7 exhibited better affinity energy when compared to ibuprofen control against the two evaluated targets binding at different sites in the cocrystallized COX-1 and 2 inhibitors.

Assessing the hepatotoxicity of phosphogypsum leachate in zebrafish (Danio rerio)

The improper disposal of large amounts of phosphogypsum generated during the production process of the phosphorus chemical industry (PCI) still exists. The leachate formed by phosphogypsum stockpiles could pose a threat to the ecological environment and human health. Nevertheless, information regarding the harmful effects of phosphogypsum leachate on organisms is still limited. Herein, the physicochemical characteristics of phosphogypsum leachate were analyzed, and its toxicity effect on zebrafish (Danio rerio), particularly in terms of hepatotoxicity and potential mechanisms, were evaluated. The results indicated that P, NH3-N, TN, F-, As, Cd, Cr, Co, Ni, Zn, Mn, and Hg of phosphogypsum leachate exceeded the V class of surface water environmental quality standards (GB 3838-2002) to varying degrees. Acute toxicity test showed that the 96 h LC50 values of phosphogypsum leachate to zebrafish was 2.08 %. Under exposure to phosphogypsum leachate, zebrafish exhibited concentration-dependent liver damage, characterized by vacuolization and infiltration of inflammatory cells. The increased in Malondialdehyde (MDA) content and altered activities of antioxidant enzymes in the liver indicated the induction of oxidative stress and oxidative damage. The expression of apoptosis-related genes (P53, PUMA, Caspase3, Bcl-2, and Bax) were up-regulated at low dosage group and down-regulated at medium and high dosage groups, suggesting the occurrence of hepatocyte apoptosis or necrosis. Additionally, phosphogypsum leachate influenced the composition of the zebrafish gut microbiota by reducing the relative abundance of Bacteroidota, Aeromonas, Flavobacterium, Vibrio, and increasing that of Rhodobacter and Pirellula. Correlation analysis revealed that gut microbiota dysbiosis was associated with phosphogypsum leachate-induced hepatotoxicity. Altogether, exposure to phosphogypsum leachate caused liver damage in zebrafish, likely through oxidative stress and apoptosis, with the intestinal flora also playing a significant role. These findings contribute to understanding the ecological toxicity of phosphogypsum leachate and promote the sustainable development of PCI.

Antioxidant system alterations, oxidative, and genotoxic effects in Danio rerio (zebrafish) exposed to leachate from a dumpsite

Water body contamination by leachate originated from dumpsites is a concern for municipal solid waste (MSW) management. In this context, this study aimed to evaluate antioxidant system alterations and oxidative and genotoxic effects in Danio rerio (zebrafish) exposed to leachate from a closed dumpsite. Groups comprising 50 fish were exposed (96 h) to different leachate concentrations (5, 15, 30, and 50%) to evaluate effects on liver and brain superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST) activities and reduced glutathione (GSH) and metallothionein (MT) concentrations, as well as malondialdehyde (MDA) and protein carbonylation (PTC) levels. Blood genotoxicity was evaluated by the comet assay. The investigated dumpsite leachate pond presented high chloride concentrations (Cl-; 2288.4 ± 69.5 mg L-1) and high electrical conductivity (EC; 8434.0 mS cm-1), indicating the presence of leachate. Concerning Danio rerio exposure, higher SOD (37%), CAT (67%), and GST (39%) activities and higher GSH (57%) concentrations were observed in liver following exposure to 50% leachate, while decreased brain GST (42%) activities and GSH (90%) levels were observed at the same leachate concentration. A significant increase in the olive tail moment (OTM; 280%) indicative of genotoxicity in blood was observed. A principal component analysis indicated that increased enzymatic activities and high levels of both GSH and MT were not sufficient to prevent the accumulation of reactive oxygen species, resulting in PTC and genotoxicity. Therefore, leachate exposure causes sublethal Danio rerio effects, altering the antioxidant system, increasing ROS production, and leading to PTC and genotoxicity. The findings demonstrate the need to further develop sublethal level assessments in zebrafish using leachate from different sources to subsidize risk assessments regarding MSW management.

Effects of heat stress on physiological parameters, biochemical parameters and expression of heat stress protein gene in Lateolabraxmaculatus

With global warming and the increasing frequency of extreme heat, we have to consider the heat tolerance of fish to sudden high temperatures. This study investigated the effects of high temperature (32 °C) on physiology and biochemistry and heat shock proteins (HSPs) gene of spotted sea bass (Lateolabrax maculatus). The spotted sea bass (14.7 ± 1.54 g) temporarily cultured at 26 °C was directly transferred to the 32 °C high temperature group, and the gill morphology, liver antioxidant activity, respiratory metabolism related enzyme activity and the expression of five HSP70 family members genes were measured at 3, 6, 9, 12, 24, 48, 72, and 96 h. The results showed that 32 °C had damage effect on gill tissue and antioxidant system, and the damage degree increased with high temperature. Respiratory rate and malondialdehyde increased gradually with the continuous heat stress. Superoxide dismutase and total antioxidant capacity increased briefly and then decreased continuously. Succinate dehydrogenase decreased to the lowest value at 24 h and then continued to increase. Lactate dehydrogenase decreased continuously; the expression of HSP70 increased rapidly and then decreased. These results indicated that the antioxidant system and HSP70 were activated under heat stress condition and provided protection to the body, but with the continuous high temperature, the protective effect was limited, and the fish body was irreversibly damaged. It is necessary to pay close attention to the temperature change in the production practice of spotted sea bass to reduce the influence caused by high temperature.