Transient effects of 2,4-dichlorophenoxyacetic acid (2,4-D) exposure on some metabolic and free radical processes in goldfish white muscle

MicroRNA-194-5p/Heparin-binding EGF-like growth factor signaling mediates dexamethasone-induced activation of pseudorabies virus in rat pheochromocytoma cells

Pseudorabies virus (PRV) is a neurotropic virus, which infects a wide range of mammals. The activity of PRV is gradually suppressed in hosts that have tolerated the primary infection. Increased glucocorticoid levels resulting from stressful stimuli overcome repression of PRV activity. However, the host cell mechanism involved in the activation processes under stressful conditions remains unclear. In this study, infection of rat PC-12 pheochromocytoma cells with neuronal properties using PRV at a multiplicity of infection (MOI) = 1 for 24 h made the activity of PRV be the relatively repressed state, and then incubation with 0.5 μM of the corticosteroid dexamethasone (DEX) for 4 h overcomes the relative repression of PRV activity. RNA-seq deep sequencing and bioinformatics analyses revealed different microRNA and mRNA profiles of PC-12 cells with/without PRV and/or DEX treatment. qRT-PCR and western blot analyses confirmed the negative regulatory relationship of miRNA-194-5p and its target heparin-binding EGF-like growth factor (Hbegf); a dual-luciferase reporter assay revealed that Hbegf is directly targeted by miRNA-194-5p. Further, miRNA-194-5p mock transfection contributed to PRV activation, Hbegf was downregulated in DEX-treated PRV infection cells, and Hbegf overexpression contributed to returning activated PRV to the repression state. Moreover, miRNA-194-5p overexpression resulted in reduced levels of HBEGF, c-JUN, and p-EGFR, whereas Hbegf overexpression suppressed the reduction caused by miRNA-194-5p overexpression. Overall, this study is the first to report that changes in the miR-194-5p-HBEGF/EGFR pathway in neurons are involved in DEX-induced activation of PRV, laying a foundation for the clinical prevention of stress-induced PRV activation.

Functional responses of Hyalella meinerti after exposure to environmentally realistic concentrations of 2,4-D, fipronil, and vinasse (individually and in mixture)

Sugarcane crops management in Brazil includes the use of pesticides, as well as alternative organic fertilizers such as vinasse obtained from waste of the ethanol industry. In order to assess the effects of the environmental contamination generated by such sugarcane practices, this study was aimed to investigate the effects of the pesticides 2,4-Dichlorophenoxyacetic acid (2,4-D) and fipronil, as well as vinasse, on the survival, behavior, and reproduction of the native epibenthic macroinvertebrate Hyalella meinerti through in situ and laboratory experiments. In situ assays were conducted in mesocosms with six treatments, i.e. untreated control, 2,4-D, fipronil, and vinasse, the mixture of the two pesticides, and both pesticides mixed with vinasse. Survival, swimming behavior, and reproduction were evaluated over time post contamination, from 0-96 h (T1) and 7-14 days (T2) through in situ experiments and 30-44 days (T3) and 75-89 days (T4) post contamination by laboratory bioassays with mesocosm water. In the T1 period, survival of H. meinerti was registered only in controls and mesocosms treated with 2,4-D. In the T2 period, treatments containing fipronil and vinasse (isolated or in both mixture treatments) still caused 100 % of mortality. Survival was recorded only in 2,4-D and control treatments, whereas reproduction only occurred in the control. In the T3 period, no survival occurred to fipronil and both mixture treatments. Vinasse and 2,4-D decreased total reproduction in comparison to control. In the T4 period, amphipods survival was detected when exposed to fipronil and its mixture with 2,4-D. However, these same treatments decreased the amplexus rates and total reproduction, with synergism denoted for the pesticide mixture. The swimming activity of males, females, and couples was decreased in surviving organisms exposed to 2,4-D, fipronil, vinasse, and the mixture of pesticides along all experimental periods. Our study showed that the application of fipronil, 2,4-D, and vinasse isolated or mixed at realistic concentrations of actual sugarcane management practices may negatively impact functional responses of indigenous amphipods in natural aquatic systems.

Analysis of global trends and gaps for studies about 2,4-D herbicide toxicity: A scientometric review

2,4-dichlorophenoxyacetic acid (2,4-D) is a herbicide that is used worldwide in agricultural and urban activities to control pests, reaching natural environments directly or indirectly. The research on 2,4-D toxicology and mutagenicity has advanced rapidly, and for this reason, this review summarizes the available data in Web of Science (WoS) to provide insights into the specific characteristics of 2,4-D toxicity and mutagenicity. Contrary to traditional reviews, this study uses a new method to quantitatively visualize and summarize information about the development of this field. Among all countries, the USA was the most active contributor with the largest publication and centrality, followed by Canada and China. The WoS categories 'Toxicology' and 'Biochemical and Molecular Biology' were the areas of greatest influence. 2,4-D research was strongly related to the keywords glyphosate, atrazine, water and gene expression. The studies trended to be focused on occupational risk, neurotoxicity, resistance or tolerance to herbicides, and to non-target species (especially aquatic ones) and molecular imprinting. In general, the authors have worked collaboratively, with concentrated efforts, allowing important advances in this field. Future research on 2,4-D toxicology and mutagenicity should probably focus on molecular biology, especially gene expression, assessment of exposure in human or other vertebrate bioindicators, and pesticide degradation studies. In summary, this scientometric analysis allowed us to make inferences about global trends in 2,4-D toxicology and mutagenicity, in order to identify tendencies and gaps and thus contribute to future research efforts.

Alternative NADH dehydrogenase extends lifespan and increases resistance to xenobiotics in Drosophila

Mitochondrial alternative NADH dehydrogenase (aNDH) was found to extend lifespan when expressed in the fruit fly. We have found that fruit flies expressing aNDH from Ciona intestinalis (NDX) had 17–71% lifespan prolongation on media with different protein-tocarbohydrate ratios except NDX-expressing males that had 19% shorter lifespan than controls on a high protein diet. NDX-expressing flies were more resistant to organic xenobiotics, 2,4-dichlorophenoxyacetic acid and alloxan, and inorganic toxicant potassium iodate, and partially to sodium molybdate treatments. On the other hand, NDX-expressing flies were more sensitive to catechol and sodium chromate. Enzymatic analysis showed that NDX-expressing males had higher glucose 6-phosphate dehydrogenase activity, whilst both sexes showed increased glutathione S-transferase activity.

Auxinic herbicides induce oxidative stress on Cnesterodon decemmaculatus (Pisces: Poeciliidae)

Pesticides might increase the production of reactive oxygen species (ROS). Dicamba (DIC) and 2,4-dichlorophenoxyacetic acid (2,4-D) are auxinic herbicides commonly applied in agroecosystems to control unwanted weeds. We analysed the oxidative damage exerted on the fish Cnesterodon decemmaculatus by an acute exposure to DIC- and 2,4-D-based herbicides formulations Banvel® and DMA®, respectively. The Endo III- and Fpg-modified alkaline comet assay was employed for detecting DNA damage caused by oxidative stress, whereas enzymatic and non-enzymatic biomarkers such as the activities of catalase (CAT), glutathione-S-transferase (GST), acetylcholinesterase (AChE), and glutathione content (GSH) were used to assess antioxidant response to these two herbicides. At the DNA level, results demonstrate that both auxinic herbicides induce oxidative damage at purines level. An increase on CAT and GST activities were detected in 48 h- and 96 h-treated specimens with both auxinics. GSH content decreased in fish exposed to DIC during 48 h and to 2,4-D after 96 h of exposure. Additionally, a diminished AChE activity in specimens treated with DIC and 2,4-D was observed only after 96 h. Total protein content decreased in fish exposed to both auxinics during 96 h. These results represent the first evaluation of oxidative damage related to DIC and 2,4-D exposure on a fish species as the Neotropical freshwater teleost C. decemmaculatus.

Exposure to the herbicide 2,4-D produces different toxic effects in two different phytoplankters: A green microalga (Ankistrodesmus falcatus) and a toxigenic cyanobacterium (Microcystis aeruginosa)

The extensive use of 2,4-dichlorophenoxiacetic acid (2,4-D) in agriculture is an important source of pollution to water and soil. Toxicity of commonly used herbicides to non-target, planktonic photosynthetic organisms has not been described completely yet. Therefore, we determined the effect of subinhibitory 2,4-D concentrations on the Chlorophycean alga Ankistrodesmus falcatus and on a toxigenic strain of the cyanobacterium Microcystis aeruginosa. Population growth, photosynthetic pigments, macromolecular biomarkers (carbohydrates, lipids, and protein), and antioxidant enzymes (catalase [CAT], glutathione peroxidase [GPx], and superoxide dismutase [SOD]) were quantified, and the integrated biomarker response (IBR) was calculated. Scanning electron microscope (SEM) and transmission electron microscope (TEM) observations were also performed. The 96-h median inhibitory concentration (IC₅₀) for 2,4-D was 1353.80 and 71.20mgL^-1 for the alga and the cyanobacterium, respectively. Under 2,4-D stress, both organisms increased pigments and macromolecules concentration, modified the activity of all the evaluated enzymes, and exhibited ultrastructural alterations. M. aeruginosa also increased microcystins production, and A. falcatus showed external morphological alterations. The green alga was tolerant to high concentrations of the herbicide, whereas the cyanobacterium exhibited sensitivity comparable to other phytoplankters. Both organisms were tolerant to comparatively high concentrations of the herbicide; however, negative effects on the assessed biomarkers and cell morphology were significant. Moreover, stimulation of the production of cyanotoxins under chemical stress could increase the risk for the biota in aquatic environments, related to herbicides pollution in eutrophic freshwater ecosystems.

Sub-lethal effects of herbicides penoxsulam, imazamox, fluridone and glyphosate on Delta Smelt (Hypomesus transpacificus)

Concerns regarding non-target toxicity of new herbicides used to control invasive aquatic weeds in the San Francisco Estuary led us to compare sub-lethal toxicity of four herbicides (penoxsulam, imazamox, fluridone, and glyphosate) on an endangered fish species Delta Smelt (Hypomesus transpacificus). We measured 17β-estradiol (E2) and glutathione (GSH) concentrations in liver, and acetylcholinesterase (AChE) activity in brain of female and male fish after 6 h of exposure to each of the four herbicides. Our results indicate that fluridone and glyphosate disrupted the E2 concentration and decreased glutathione concentration in liver, whereas penoxsulam, imazamox, and fluridone inhibited brain AChE activity. E2 concentrations were significantly increased in female and male fish exposed to 0.21 μM of fluridone and in male fish exposed to 0.46, 4.2, and 5300 μM of glyphosate. GSH concentrations decreased in males exposed to fluridone at 2.8 μM and higher, and glyphosate at 4.2 μM. AChE activity was significantly inhibited in both sexes exposed to penoxsulam, imazamox, and fluridone, and more pronounced inhibition was observed in females. The present study demonstrates the potential detrimental effects of these commonly used herbicides on Delta Smelt.

Oxidative stress responses in gills of goldfish, Carassius auratus, exposed to the metribuzin-containing herbicide Sencor

Metribuzin belongs to the family of asymmetrical triazine compounds and is an active ingredient in many commercial herbicides including Sencor. Effects on goldfish (Carassius auratus L.) of exposure for 96h to 7.14, 35.7 or 71.4mgL(-1) Sencor 70 WG (corresponding to 5, 25 and 50mgL(-1) of metribuzin) were examined by evaluating oxidative stress markers and activities of antioxidant and associated enzymes in gills. Fish exposed to the lowest Sencor concentration (7.14mgL(-1)) showed a 94% increase in levels of protein carbonyls in gills as well as 45% and 144% increases in the activities of glutathione peroxidase and glutathione-S-transferase. Exposure to the highest Sencor concentration (71.4mgL(-1)) resulted in reduced levels of protein carbonyls by 56% and lipid peroxides by 40%, as compared with controls, but enhanced levels of low and high molecular mass thiols by 71% and 36%, respectively. The activities of superoxide dismutase, glutathione peroxidase and glutathione-S-transferase were increased in gills of goldfish exposed to 71.4mgL(-1) Sencor. At any concentration tested, Sencor did not affect the activities of glutathione reductase, glucose-6-phosphate dehydrogenase, lactate dehydrogenase or acetylcholine esterase in gills. The results of this study indicate that acute exposure of goldfish to Sencor had effect on free radical processes in gills and glutathione-dependent antioxidants effectively protect proteins and lipids from oxidation.

Contaminant-induced oxidative stress in fish: a mechanistic approach

The presence of reactive oxygen species (ROS) in living organisms was described more than 60 years ago and virtually immediately it was suggested that ROS were involved in various pathological processes and aging. The state when ROS generation exceeds elimination leading to an increased steady-state ROS level has been called "oxidative stress." Although ROS association with many pathological states in animals is well established, the question of ROS responsibility for the development of these states is still open. Fish represent the largest group of vertebrates and they inhabit a broad range of ecosystems where they are subjected to many different aquatic contaminants. In many cases, the deleterious effects of contaminants have been connected to induction of oxidative stress. Therefore, deciphering of molecular mechanisms leading to such contaminant effects and organisms' response may let prevent or minimize deleterious impacts of oxidative stress. This review describes general aspects of ROS homeostasis, in particular highlighting its basic aspects, modification of cellular constituents, operation of defense systems and ROS-based signaling with an emphasis on fish systems. A brief introduction to oxidative stress theory is accompanied by the description of a recently developed classification system for oxidative stress based on its intensity and time course. Specific information on contaminant-induced oxidative stress in fish is covered in sections devoted to such pollutants as metal ions (particularly iron, copper, chromium, mercury, arsenic, nickel, etc.), pesticides (insecticides, herbicides, and fungicides) and oil with accompanying pollutants. In the last section, certain problems and perspectives in studies of oxidative stress in fish are described.

Diversity of the molecular responses to separate wastewater effluents in freshwater mussels

The environmental safety of pharmaceutical and personal care products (PPCPs) requires a crucial examination. The aim of this study was to evaluate the responses of biomarkers of stress and toxicity in freshwater mussels to the effect of commonly found PPCPs in wastewater. We treated male mussels Unio tumidus, from an undisturbed site with ibuprofen (IBU, 250 ng L(-1)), triclosan (TCS, 500 ng L(-1)), or estrone (E1, 100 ng L(-1)) for 14 days. Untreated mussels from this site (C) and mussels inhabiting a polluted area (P) were also examined after a similar time of being kept in the laboratory. The consequences of chronic exposure of the mussels in the P-group were reflected in elevated concentrations of oxyradicals (1.4 times), oxidized glutathione (4.3 times), lipofuscin (2.2 times), and DNA-strand breaks in the digestive gland (DG) in comparison to the C-group, higher levels of caspase-3 activity in the DG, and vitellogenin-like proteins in gonads among all studied groups. Exposed mussels demonstrated some common responses with mussels in the P-group: elevated levels of lactate/pyruvate ratio, lipofuscin (IBU and E1), DNA fragmentation (TCS and E1), and caspase-3 activity (TCS and E1). Exposed to PPCPs mussels also showed elevation of ethoxyresorufin-O-deethylase and/or glutathione-S-transferase activity in the DG and a decrease in lysosomal stability in hemocytes (TCS and E1). The TCS group was distinguished by having the highest level of DNA-fragmentation and the lowest concentrations of total glutathione, oxyradicals, lipofuscin, pyruvate, and lactate, reflecting total metabolic depression. These results show that selected PPCPs at low concentrations alter a variety of physiological processes in this animal model system.