Biochemical and morphological biomarkers of the liver damage in the Neotropical fish, Piaractus mesopotamicus, injected with crude extract of cyanobacterium Radiocystis fernandoi

A meta-analysis on the toxicity of microcystin-LR to fish and mammals

Microcystin-leucine arginine (MC-LR), the most prevalent and dangerous microcystin, poses high risks to living organisms, especially fish and mammals. Although many studies have focused on the toxic effect on fish and mammals exposed to MC-LR, works that incorporate published data into a comprehensive comparison and analysis are still limited. Here, the adverse effects of oxidative stress markers, health, functional traits, and performance traits in fish and mammals were systematically verified by collecting data from 67 studies for the first time. Notably, we first found that the activities of malondialdehyde (MDA) (p < 0.05) and lactoperoxidase (LPO) always showed increases, whereas the growth (performance traits) always had a significant decrease (p < 0.001) under all variables of MC-LR exposure, i.e., exposure time, exposure concentration, exposure route, and even life stage. Additionally, our study first verified that the activities of MDA and LPO can be employed as oxidative stress indicators of MC-LR effects in fish and mammals instead of other biomarkers of oxidative stress, such as superoxide dismutase (SOD) and catalase (CAT), considered by previous studies. Growth may be regarded as a highly sensitive indicator of MC-LR toxicity in mammals and fish. At the same time, we first found that the impact of MC-LR exposure concentration on LPO, MDA, and growth is higher than that of exposure time, exposure route, and different life stages using the random forest (RF) model. In short, this work sheds light on the potential biochemical and individual toxicity of MC-LR exposure in fish and mammals.

Toxicological differences of trifloxystrobin and kresoxim-methyl on zebrafish in various levels of exposure routes, organs, cells and biochemical indicators

Trifloxystrobin (TRI) and kresoxim-methyl (KRE), as quinone outside inhibitor fungicides (QoIs), have broad applications due to their effective activity against fungi. Excessive usages of agrochemicals trigger environmental risks, such as aquatic organisms (fish). Research performed in recent years has focused on the ecotoxicology of TRI and KRE in fish containing histologic morphology, enzyme activity, protein and gene expression under chronic toxicity conditions, whereas less is known about the underlying mechanisms of toxicity and differences between TRI and KRE in fish under acute toxicity conditions. In the present study, in comparison to different exposure routes [whole-body exposure (WBE), head exposure (HE), trunk exposure (TE), and Oral administration (OA)], the external substances TRI and KRE entered the fish body mainly via gill organs and led to fish toxicity. Furthermore, gill organs and gill cells were vulnerable to TRI and KRE exposure, which indicated that the gill is a vital impaired organ. The 96 h-LC₅₀ (sublethal concentration) value of KRE was 289.8 μg L^-1 (R² = 0.9855) with an approximate 10-fold difference in TRI toxicity. The cytotoxicity exposed to TRI was higher than that in KRE at the same concentration. The potential mechanisms of toxic differences could be various toxic effects in terms of MCIII (mitochondrial complex III) activity, ATP (Adenosine triphosphate) content, MA (mitochondrial activity), ROS (reactive oxygen species) levels, and cellular respiration. Furthermore, the disorder in MCIII activity was probably the main potential mechanisms of toxic differences. To some extent, this research provides not only new insight into the underlying toxic mechanism of TRI and KRE in fish but also a basis for the guidance of agrochemicals considering aquatic risks.

Multi-biomarkers approach to access the impact of novel metal-insecticide based on flavonoid hesperidin on fish

Aquatic ecosystem health is the main concern to increasing pesticides application to control agricultural pests as it is the ultimate receptor of such materials. This study evaluated the impact of new metal-insecticide, the [Mg(hesp)₂(phen)], referred as MgHP, on fish using physiological, genetic, biochemical, and morphological biomarkers. The fish, Prochilodus lineatus, was exposed to 0 (control), 1, 10, 100, 1000 μg L^-1 MgHP, for 24 and 96 h. MgHP was not lethal but caused genotoxicity, altered hematological variables and, the activity of antioxidant and biotransformation enzymes and histology of liver, depending on concentration and time exposure. Hematocrit and erythrocyte number (RBC) increased without change hemoglobin content resulting in changes in hematimetric indexes after 24 h; after 96 h, only RBC was changed. Erythrocyte nuclear abnormalities and crenate cells increased after 24 h but, not after 96 h. Erythrocytes and hepatocytes indicated instability in DNA integrity however, the absence of micronuclei suggested DNA damage repairment. After 24 h, the antioxidant defense system and the phase II biotransformation enzyme was responsiveness and catalase activity decreased at high MgHP concentrations; the antioxidant response was triggered after 96 h. Hepatocyte hypertrophy, intracellular cytoplasmic substances, cytoplasm degeneration, melanomacrophage and hyperemia increased in fish exposed from 10 μg L^-1 to higher MgHP concentrations; the organ alteration index increased as MgHP concentration increased showing dose-dependence. Most of hematological and genotoxic effects occurred after 24 h exposure evidencing potential recover capability of organism by activation of the antioxidant defense system and DNA repairment mechanisms. Nevertheless, the histopathological changes in the liver was maintained over time at high MgHP concentrations, a concentration usually no environmental relevant. In conclusion, this data reinforced the importance of continuing research on MgHP effects in other organisms considering the promising use of such compound to control the leaf-cutter ants and other insects.

Biotransformations, Antioxidant System Responses, and Histopathological Indexes in the Liver of Fish Exposed to Cyanobacterial Extract

Radiocystis fernandoi, a microcystin (MC) producer, has been common in cyanobacterial blooms in tropical regions. Microcystin is a hepatotoxin that causes tissue damage and even death in animals, including humans; its detoxification process may involve biotransformation and activation of the antioxidant defense system. We evaluated the detoxification pathway, examined the antioxidant defense system responses, and determined the alterations and the organ histopathological indexes in the liver of the tropical fish Hoplias malabaricus after acute and subchronic intraperitoneal exposure to microcystin. The crude microcystin extract of R. fernandoi had predominantly MC-RR and MC-YR. The detoxification process was activated by increasing ethoxyresorufin-O-deethylase activity, whereas glutathione S-transferase was inhibited. The activity of the antioxidant defense enzymes superoxide dismutase (SOD) and glutathione peroxidase decreased after acute exposure; the SOD-catalase system and the glutathione level increased after subchronic exposure. The carbonyl protein level, lipid peroxidation (LPO), and DNA damage were unchanged after acute exposure, whereas protein carbonyl was unchanged, LPO decreased, and DNA damage increased after subchronic exposure. Histopathological alteration indexes differed between acute and subchronic exposure, but the histopathological organ indexes indicate liver dysfunction in both exposure periods. We conclude that MC-RR and MC-YR induce different liver responses depending on the time of exposure, and the antioxidant defense responses after subchronic exposure may help to partially restore the liver function. Environ Toxicol Chem 2020;39:1041-1051. © 2020 SETAC.

Uso de biomarcadores en la evaluación ambiental de ecosistemas marinos en América

The use of biomarkers in the assessment of the marine environmental status offers an integrated approach to the effects caused by diverse pollutants. This article compiles and analyzes the original research on the study of possible biomarkers in wild coastal-marine organisms from America. One of the outcomes of this review research is the need for a continuous evaluation of organisms in conjunction with the assessment of environmental vari-ables and the levels of pollutants that may be found in any ecosystem. It is well stated that the use of biomarkers is a practical tool for the environmental management; however, some limitations apply and there are several questions in regards to specificity, sensibility, usability, replicability, and interpretation to be solved, yet. Along the American continent, multiple biomarkers have been used to evaluate specific pollutants or highly impacted zones at marine-coastal environments. The most commonly used organisms are fishes and bivalves and they have been also extensively used in marine turtles. In regards of the type of biomarkers, plenty of authors integrate biomarkers from different groups, sorted in this review as biometric biomarkers (morphologic and corporal in-dexes), histological biomarkers (for tissues), molecular biomarkers (genetic) and biochemical and physiological biomarkers (both at the cellular and molecular levels). Following this classification, the most used biomarkers were biochemical and physiological biomarkers, due to the great advantages and information that they provide. It is of utmost importance to set guidelines and referenced threshold values for each biomarker to allow the early environmental diagnosis and integrated evaluation of harmful pollutants effects. Keywords: Biomarkers, environmental assessment, America.