Goldfish can recover after short-term exposure to 2,4-dichlorophenoxyacetate: use of blood parameters as vital biomarkers

Meta-analytical review of antioxidant mechanisms responses in animals exposed to herbicide 2,4-D herbicide

The 2,4-Dichlorophenoxyacetic acid (2,4-D) is a low-cost herbicide to eradicate broadleaf weeds. Since the development of 2,4-D resistant transgenic crops, it has been described as one of the most widely distributed pollutants in the world, increasing concern about its environmental impacts. This study aimed to elucidate the antioxidant system response in animals exposed to 2,4-D by different routes of exposure. It focused on determining if tissue, phylogenetic group, and herbicide formulation would influence the antioxidant mechanisms. A careful literature search of Scopus, WoS, and Science Direct retrieved 6983, 24,098, and 20,616 articles, respectively. The dataset comprised 390 control-treatment comparisons and included three routes of exposure: transgenerational, oral, and topical. The data set for transgenerational and oral exposure revealed oxidative stress through a decrease in enzymatic activities and the level of molecules of the antioxidant system. In contrast, topical exposure increased the oxidative stress. Tissue-specific analyses revealed that the transgenerational effects reduced hepatic catalase (CAT) activity. Oral exposure caused a variety of effects, including increased CAT activity in the prostate and decreased activity in various tissues. Mammals predominate in the transgenerational and oral groups, showing a significantly reduced activity of the antioxidant system. In contrast, in the topical exposure, an increased activity of oxidative stress biomarkers was observed in fish, earthworms, and mollusks. The effects of the 2,4-D formulation on oxidative stress responses showed significant differences between pure and commercial formulations, with oral exposure resulting in decreased activity and topical exposure increasing responses. In summary, orally exposed animals exhibited a clear decrease in enzyme activities, transgenerational exposure elicited tissue-specific prompted biochemical reductions, and topical exposure induced increased responses, emphasizing the need for unbiased exploration of the effects of 2,4-D on biomarkers of oxidative stress while addressing publication bias in oral and topical datasets.

Acute Exposure to the Penconazole-Containing Fungicide Topas Induces Metabolic Stress in Goldfish

Triazole fungicides are widely used in agriculture that leads to pollution of freshwater ecosystems. The mechanisms of toxicity to fish by the triazole fungicide Topas that contains penconazole (1-[2-(2,4-dichlorophenyl)pentyl]-1H-1,2,4-triazole) have not been studied. The present study aimed to evaluate the effect of goldfish exposure for 96 h to the fungicide Topas at concentrations of 1.5, 15, or 25 mg/L on the plasma and liver biochemical parameters and blood hematological profile. Goldfish exposure to Topas decreased alanine and aspartate transaminase activity and increased lactate dehydrogenase activity in the liver. Plasma lactate dehydrogenase and alanine transaminase activities were elevated in fungicide-treated fish. Topas exposure also enhanced plasma glucose and triacylglycerol concentrations. In the liver, fungicide treatment decreased levels of glucose but elevated triacylglycerols, glycogen, and protein. The results indicate that acute exposure of goldfish to Topas induced strong metabolic perturbations and disruptions of metabolic parameters, suggesting that these could be used to assess sublethal or acute toxic effects of pesticides on aquatic species.

Impact of copper and zinc mixture on haematological parameters of rainbow trout (Oncorhynchus mykiss): acute exposure and recovery

Significant changes in composition of rainbow trout Oncorhynchus mykiss blood cells types were induced after 4-days exposure with mixture of Cu²⁺ and Zn²⁺ at 0.25, 0.125 and 0.06 parts of LC₅₀ in comparison to control group. The highest concentration of metal mixture (0.25 of LC₅₀) significantly induced elevation of the number of monocytes and poly-segmented neutrophils. Treatment with 0.125 parts of LC₅₀ concentration increased the number of thrombocytes, monocytes and non-segmented neutrophils. The most diluted mixture resulted in significant induction of thrombocytes, monocytes, non- and poly segmented neutrophils. Analysis of leucocyte cell types in the O. mykiss blood samples after 4-days of exposure at all applied mixture parts showed signs of monocytosis and neutrophilia. Comparison of different types of leucocytes' percentages (leukogram) in fish after 4-days exposure to metal mixture and after 4, 8, and 12-days recovery periods showed that, values of neutrophils even after the 12-days recovery period at all tested parts of LC₅₀, and monocytes after exposure with the highest (0.25) used part of LC₅₀ were not restored to control group levels. Depuration and recovery processes in treated fish are concentration and recovery period dependent.

Pesticide toxicity: a mechanistic approach

Pesticides are known for their high persistence and pervasiveness in the environment, and along with products of their biotransformation, they may remain in and interact with the environment and living organisms in multiple ways, according to their nature and chemical structure, dose and targets. In this review, the classifications of pesticides based on their nature, use, physical state, pathophysiological effects, and sources are discussed. The effects of these xenobiotics on the environment, their biotransformation in terms of bioaccumulation are highlighted with special focus on the molecular mechanisms deciphered to date. Basing on targeted organisms, most pesticides are classified as herbicides, fungicides, and insecticides. Herbicides are known as growth regulators, seedling growth inhibitors, photosynthesis inhibitors, inhibitors of amino acid and lipid biosynthesis, cell membrane disrupters, and pigment biosynthesis inhibitors, whereas fungicides include inhibitors of ergosterol biosynthesis, protein biosynthesis, and mitochondrial respiration. Insecticides mainly affect nerves and muscle, growth and development, and energy production. Studying the impact of pesticides and other related chemicals is of great interest to animal and human health risk assessment processes since potentially everyone can be exposed to these compounds which may cause many diseases, including metabolic syndrome, malnutrition, atherosclerosis, inflammation, pathogen invasion, nerve injury, and susceptibility to infectious diseases. Future studies should be directed to investigate influence of long term effects of low pesticide doses and to minimize or eliminate influence of pesticides on non-target living organisms, produce more specific pesticides and using modern technologies to decrease contamination of food and other goods by pesticides.

Endoplasmic reticulum stress is involved in 2,4-dichlorophenol-induced hepatotoxicity

2,4-Dichlorophenol (2,4-DCP) is an environmental pollutant exhibiting a wide spectrum of toxic effects. We investigated the toxic effects and potential mechanisms underlying 2,4-DCP-induced hepatotoxicity. In vitro, 2,4-DCP caused hepatotoxicity manifested by a decrease in cell viability and inhibition of colony formation. Bip and CHOP expression was up-regulated at the mRNA and protein levels. Moreover, 2,4-DCP induced eIF2α phosphorylation and Xbp1 mRNA splicing, indicating that endoplasmic reticulum (ER) stress was activated after exposure of HL7702 cells to 2,4-DCP for 12 hr. Furthermore, the mitochondrial membrane potential collapsed and apoptosis was triggered after exposure to 2,4-DCP for 24 hr. In vivo, 2,4-DCP caused histological changes in the liver, and dramatically elevated the serum alanine transaminase (ALT) and aspartate aminotransferase (AST) levels of mice. ER stress was also triggered in the liver of mice on days 1 and 3. The ER stress inhibitor TUDCA could partly relieve the liver damage, as indicated by the restoration of serum ALT and AST levels. Taken together, our results demonstrated that ER stress may serve as an early warning mechanism against 2,4-DCP-induced hepatotoxicity, and severe ER stress may lead to apoptosis.

2,4-Dichlorophenol induces global DNA hypermethylation through the increase of S-adenosylmethionine and the upregulation of DNMTs mRNA in the liver of goldfish Carassius auratus

Altered DNA methylation is associated with changes in gene expression, signal transduction and stress response after exposure to a wide range of exogenous compounds, and abnormal methylation is a major toxic effect induced by chemicals such as benzene and phenols. 2,4-Dichlorophenol (2,4-DCP), a derivative of phenol, has been classified as a priority pollutant by the US EPA due to its toxic effects on aquatic organisms. However, the effect of 2,4-DCP on DNA methylation and its potential mechanism in fish are rarely understood. The present study aims to figure out whether 2,4-DCP could impact DNA methylation and explore its potential mechanisms by measuring the global DNA methylation levels, S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) contents, the mRNA expression of DNA methyltransferase1 (DNMT1) and DNA methyltransferase3 (DNMT3) in the liver of goldfish Carassius auratus. DNA methylation levels were analyzed using high performance liquid chromatography (HPLC) and MspI/HpaII ethidium bromide assay, SAM and SAH contents were determined by HPLC, the mRNA expression of DNMT1 and DNMT3 was measured by quantitative-PCR (qPCR). The results showed that 2,4-DCP caused global DNA hypermethylation, elevated the methylation levels of CpG islands, increased the SAM and SAH contents, decreased the SAM/SAH ratio, and upregulated the mRNA expression of DNMT1 and DNMT3, while depletion of SAM with Na2SeO3 and inhibition of DNMTs activity with 5-aza-2'-deoxycytidine (5AdC) impaired 2,4-DCP-induced global DNA hypermethylation, suggesting that the increase of SAM contents and upregulation of the mRNA expression of DNMT1 and DNMT3 may play important roles in 2,4-DCP-induced global DNA hypermethylation process. Our report is the first one to show that short-term 2,4-DCP exposure caused the global DNA hypermethylation via altered SAM level and DNMTs expression in fish.