The effects of subchronic exposure to terbuthylazine on early developmental stages of common carp

Variations in the Behaviour, Survival, Haematology, and Biochemistry of Ctenopharyngodon idella (Grass Carp) After Exposure to Commercial Grade Atrazine

The current study assessed the harmful effects of Atrazine (ATZ) herbicide on haematology and biochemistry of the freshwater fish Ctenopharyngodon idella, a commercially significant fish in Pakistan. C. idella (13 ± 8.4 cm; 132 ± 5.6 g) was exposed to graded levels of ATZ, and its 96-hour LC₅₀ value at 25°C was calculated to be 150.5 µl/L. After exposure to ATZ, fish displayed rapid movements, a loss of balance in position and equilibrium, anxious swimming patterns, colour changes, and increased mucous production. The MCHC, MCH, RBCs, and Hb in C. idella decreased significantly (P < 0.05), whereas the MCV, Ht, and WBCs were significantly increased (P < 0.05). At different time intervals (24, 48, 72, and 96 h) following ATZ administration (50, 100, 150, and 200 µl/L), biochemical analysis significantly decreased (P < 0.05) triglyceride, total protein, cholesterol, and albumin levels, whereas glucose levels significantly increased (P < 0.05). We concluded that ATZ is toxic to C. idella, altering their haematology and blood biochemistry even after only a brief exposure.

Chronic Effects of Diazinon® Exposures Using Integrated Biomarker Responses in Freshwater Walking Catfish, Clarias batrachus

Diazinon exposures have been linked to the onset of toxic pathways and adverse outcomes in aquatic species, but the ecological implications on model species are not widely emphasized. The objective of this study was to determine how the organophosphate pesticide diazinon affected hematological (hemoglobin, total red blood count, total white blood count, and mean corpuscular hemoglobin), growth (condition factor, hepatosomatic index, specific growth rate), biochemical (total serum glucose, total serum protein), and endocrine (growth hormone, tri-iodothyronine, and thyroxine) parameters in Clarias batrachus after chronic exposure. Diazinon was administered at predefined exposure doses (0.64 and 1.28 mg/L) and monitored at 15, 30, and 45 days into the investigation. Observation for most biomarkers revealed patterns of decreasing values with increasing toxicant concentration and exposure duration. Correlation analysis highlighted a significant inverse relationship between variables (mean corpuscular hemoglobin, condition factor, specific growth rate, tri-iodothyronine, thyroxine, and total serum protein) and elevated chronic diazinon exposure concentrations. The integrated indices (IBR and BRI) indexes were used to provide visual and understandable depictions of toxicity effects and emphasized the relativity of biomarkers in terms of sensitivity and magnitude or severity of responses under graded toxicant exposures. The significant damage reflected by evaluated parameters in diazinon exposure groups compared to control portends risks to the health of local fish populations, including Clarias batrachus in aquatic systems adjacent to agrarian landscapes.

Toxicity of 2-methyl-4-chlorophenoxy acetic acid alone and in combination with cyhalofop-butyl to Cyprinus carpio embryos

Herbicides may pose considerable danger to non-target aquatic organisms and further threaten human health. The present investigation was aimed to assess the effects of 2-methyl-4-chlorophenoxy acetic acid (MCPA-Na) on Cyprinus carpio embryos. Embryos were exposed to six concentrations of MCPA-Na (0, 52, 54, 56, 58 and 60 mg/L) for 96 h. A series of symptoms were observed in developmental embryos during MCPA-Na exposure, including increased death, hatching inhibited and morphological deformities. Further, MCPA-Na exposure leading to a series of morphological changes (pericardial edema, tail deformation, and spine deformation) in embryos, which were consistent with modifications in the associated genes. In this work, we also investigated the joint toxicity of herbicides (MCPA-Na and cyhalofop-butyl) commonly used in paddy fields on carp embryos, using the 96 h-LC₅₀ of herbicides (59.784 mg/L MCPA-Na and 1.472 mg/L cyhalofop-butyl) and confirmed that a synergistic effect existing in the binary mixtures.

Toxic effects of dechlorane plus on the common carp (Cyprinus carpio) embryonic development

Dechlorane Plus (DP) is a widely used chlorinated flame retardant, which has been extensively detected in the environment. Although DP content in the surface water is low, it can pose a continuous exposure risk to aquatic organisms due to its strong bioaccumulation. Considering that the related studies on the toxicity mechanism of DP exposure are limited, the effect of DP on carp embryo development was evaluated. In the present work, carp embryos were exposed to different concentrations (0, 30, 60, and 120 μg/L) of DP at 3 h post-fertilization (hpf). The expression levels of neural and skeletal development-associated genes, such as sox2, sox19a, Mef2c and BMP4, were detected with quantitative PCR, and the changes in different developmental toxicity endpoints were observed. Our results demonstrated that the expression levels of sox2, sox19a, Mef2c and BMP4 were significantly altered and several developmental abnormalities were found in DP-exposed carp embryos, such as DNA damage, increased mortality rate, delayed hatching time, reduced hatching rate, decreased body length, and increased morphological deformities. In addition, the activities of reactive oxygen species and malondialdehyde were remarkably higher in 60 and 120 μg/L DP exposure groups than in control group. These results suggest that DP can exhibit a unique modes of action, which lead to aberration occurrence in the early development stage of common carps, which may be related to some gene damage and oxidative stress. Besides, the parameters evaluated here can be used as tools to access the environmental risk for biota and humans exposed to DP.

Effects of sublethal and realistic concentrations of the commercial herbicide atrazine in Pacu (Piaractus mesopotamicus): Long-term exposure and recovery assays

Background and Aim:

The commercial formulations of the herbicide atrazine (cATZ) are widely employed in Brazilian agriculture, and, as a consequence, ATZ has been found at levels above that established by law in the river basins in Brazil. Although the toxicity of ATZ in fish is well documented, there are few studies on the recovery capacity after cATZ exposure. This work aimed to evaluate, using several biomarkers, the toxic effects of long-term exposure to the sublethal (3.57 mg/L) and nonlethal realistic (3.00 µg/L) cATZ concentrations followed by a recovery assay, in fingerlings of a Brazilian teleost, the Piaractus mesopotamicus (pacu).

Materials and Methods:

Pacu fingerlings were housed in glass tanks and divided into the following experimental groups (two tanks/group): Exposure control = EC, recovery control = RC, the sublethal groups exposed to 3.57 mg/L of cATZ, (sublethal exposure group = SLE and sublethal recovery group = SLR) and the nonlethal groups treated with 3.00 µg/L of cATZ (nonlethal exposure group = NLE and nonlethal recovery group = NLR). The exposure assay was semi-static with a duration of 30 days and the recovery assay (after cATZ withdrawal) lasted 14 days. Several biomarkers were evaluated in fingerlings from all groups: The swimming behavior, the body weight gain, the micronucleus formation and nuclear alterations in erythrocytes, and the hepatic and renal histopathology analyzed by qualitative and semi-quantitative morphological methods (using light and electron microscopy).

Results:

No significant difference in weight gain was observed among the groups after the exposure and recovery assays. The sublethal exposure induced impaired swimming movements, significant histopathological alterations, including necrosis in the liver and kidney, and a significant increase in the frequency of micronuclei in erythrocytes. The nonlethal exposure induced only subtle histopathological changes in the liver and kidney. After recovery assay, no genotoxic alteration was noted in pacu exposed to sublethal concentration, while the cATZ-induced kidney damage was partially reversed but not the hepatic injury.

Conclusion:

cATZ exhibits long-term toxic effects on pacu, even at relatively low concentrations, affecting mainly the liver and the kidney, and the effects of sublethal concentration are only partially reversed after cATZ withdrawal.

Effects of the chloro-s-triazine herbicide terbuthylazine on DNA integrity in human and mouse cells

Terbuthylazine belongs to the chloro-s-triazine group of herbicides and acts primarily as a photosynthesis inhibitor. The mechanisms of action related to its exposure, relevant both in animals and humans, are still insufficiently investigated. This comprehensive study focused on the outcomes of terbuthylazine exposure at cell level in vitro, and a mice model in vivo. Experiments in vitro were conducted on whole human peripheral blood, isolated lymphocytes, and HepG2 cells exposed for 4 h to terbuthylazine at 8.00, 0.80, and 0.58 ng/mL, which is comparable with current reference values set by the European Commission in 2011. Terbuthylazine cytotoxicity was evaluated using dual fluorescent staining with ethidium bromide and acridine orange on lymphocytes, and CCK-8 colorimetric assay on HepG2 cells. The levels of DNA damage were measured using alkaline and hOGG1-modified comet assays. The potency of terbuthlyazine regarding induction of oxidative stress in vitro was studied using a battery of standard oxidative stress biomarkers. The in vivo experiment was conducted on Swiss albino mice exposed to terbuthlyazine in the form of an active substance and its formulated commercial product Radazin TZ-50 at a daily dose of 0.0035 mg/kg bw for 14 days. Following exposure, the DNA damage levels in leukocytes, bone marrow, liver, and kidney cells of the treated mice were measured using an alkaline comet assay. In vitro results suggested low terbuthylazine cytotoxicity in non-target cells. The highest tested concentration (8.00 ng/mL) reduced lymphocyte viability by 15%, mostly due to apoptosis, while cytotoxic effects in HepG2 cells at the same concentration were negligible. Acute in vitro exposure of human lymphocytes and HepG2 cells to terbuthylazine resulted in low-level DNA instability, as detected by the alkaline comet assay. Further characterization of the mechanisms behind the DNA damage obtained using the hOGG1-modified comet assay indicated that oxidative DNA damage did not prevail in the overall damage. This was further confirmed by the measured levels of oxidative stress markers, which were mostly comparable to control. Results obtained in mice indicate that both the active substance and formulated commercial product of terbuthylazine produced DNA instability in all of the studied cell types. We found that DNA in liver and kidney cells was more prone to direct toxic effects of the parent compound and its metabolites than DNA in leukocytes and bone marrow cells. The overall findings suggest the formation of reactive terbuthylazine metabolites capable of inducing DNA cross-links, which hinder DNA migration. These effects were most pronounced in liver cells in vivo and HepG2 cells in vitro. To provide a more accurate explanation of the observed effects, additional research is needed. Nevertheless, the present study provides evidence that terbuthylazine at concentrations comparable with current reference values possesses toxicological risk because it caused low-level DNA instability, both at cellular and animal organism level, which should be further established in forthcoming studies.