Comparative effects of the herbicides dicamba, 2,4-D and paraquat on non-green potato tuber calli

Impact of ozone therapy on mouse liver mitochondrial function and antioxidant system

Ozone therapy's efficacy might stem from the regulated and mild oxidative stress resulting from ozone's interactions with various biological elements. The present work aimed to characterize the hepatic mitochondrial response to ozone treatment and its relationship with the antioxidant system response. Two groups of mice were used: one control group and another injected intraperitoneally with an O3/O2 mixture (80 ml/kg) for 5 days. Mitochondrial respiration supported by different substrates was significantly inhibited, as well as complexes I and II/III, but not complex IV. The analysis of the electron transport chain complex activity showed significant inhibitions in complexes I and II/III but not in complex IV. These inhibitions can prevent mitochondrial reactive oxygen species (ROS) production. Additionally, there was a decline in glutathione content, unaccompanied by a rise in its oxidized form. The ozone-treated groups showed a significant increase in the activity of superoxide dismutase and glutathione peroxidase, while catalase and glutathione reductase experienced no significant alterations. Adenine nucleotides increased in the ozone group, but only the increase in adenosine diphosphate is significant, so the cell's energy charge is unaffected. This study shows that mitochondria may play a crucial role in ozone treatment. However, it also highlights the need for further studies to understand the molecular mechanism.

A Common Feature of Pesticides: Oxidative Stress-The Role of Oxidative Stress in Pesticide-Induced Toxicity

Pesticides are important chemicals or biological agents that deter or kill pests. The use of pesticides has continued to increase as it is still considered the most effective method to reduce pests and increase crop growth. However, pesticides have other consequences, including potential toxicity to humans and wildlife. Pesticides have been associated with increased risk of cardiovascular disease, cancer, and birth defects. Labels on pesticides also suggest limiting exposure to these hazardous chemicals. Based on experimental evidence, various types of pesticides all seem to have a common effect, the induction of oxidative stress in different cell types and animal models. Pesticide-induced oxidative stress is caused by both reactive oxygen species (ROS) and reactive nitrogen species (RNS), which are associated with several diseases including cancer, inflammation, and cardiovascular and neurodegenerative diseases. ROS and RNS can activate at least five independent signaling pathways including mitochondrial-induced apoptosis. Limited in vitro studies also suggest that exogenous antioxidants can reduce or prevent the deleterious effects of pesticides.

Methyl jasmonate and cyclodextrin-mediated defense mechanism and protective effect in response to paraquat-induced stress in peanut hairy root

Plant cells have a variety of defense mechanisms to alleviate the deleterious effects of oxidative stress. The present work elucidated a schematic diagram of the proposed pathway of peanut hairy root tissue treated with different elicitors; paraquat (PQ), methyl jasmonate (MeJA), and cyclodextrin (CD). The different elicitation approaches could provoke intrinsic stress in plant cells and might activate a distinct response pathway, allowing plants to overcome the deleterious effects of oxidative stress. Among all strategies, hairy root culture pretreated with PQ followed by application of MeJA plus CD showed an extensive induction of antioxidant defense mechanisms. The expression of the antioxidant enzyme genes and stilbene-synthesized enzyme genes were up-regulated in accordance with the dramatic increase in the production of stilbene compounds. The non-enzymatic antioxidant substances exhibited a highly enhanced capability. The pathogenesis-related protein (PR) genes were also highly up-regulated. In summary, we demonstrated that the interplay among MeJA plus CD and PQ may activate a complex signaling network to regulate plant defense mechanisms involving the up-regulation of detoxifying enzymes, induction of free-radical scavengers and overexpression of genes associated with plant defense pathways.

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.

Joint toxicity on hepatic detoxication enzymes in goldfish (Carassius auratus) exposed to binary mixtures of lead and paraquat

Compared to single exposure, chemical mixtures might induce joint toxicity including additive, synergistic and antagonistic effects on both organisms and environment. Owing to the specific toxicity of oxidative stress and binding to proteins, lead (Pb) is generally recognized a non-essential and threatening heavy metal to animals and human. Paraquat (PQ) is a widely used herbicide in agriculture and can trigger oxidative stress as well as Pb. Little information was available about joint effects of the two chemicals on toxicological responses in organisms, especially in fish. In our present study, goldfish (Carassius auratus) were randomly exposed to single and combined experiments with different concentrations of Pb and PQ for 28 days. Activities of four enzyme biomarkers in liver, ethoxyresorufin-O-deethylase (EROD), 7-benzyloxy-4-trifluoromethyl-coumarin-O-debenzyloxylase (BFCOD), glutathione-S-transferase (GST) and UDP-glucuronosyltransferase (UGT) were evaluated in each experimental group on day 14 and 28. The results showed four enzyme levels were markedly reduced with the increase of concentrations in mixtures and prolonged exposure. The inhibitory EROD and BFCOD activities were not significantly changed in goldfish following PQ-treated groups with or without 0.5 mg/L Pb, which indicated PQ has more inhibitory toxicity on CYP450 enzymes than Pb in co-exposure groups. However, the reduced values of GST were observed only in the combinations containing high doses of Pb or PQ during experimental periods. Although the responses of UGT activity were similar to GST on 14th day, all combinations of Pb and PQ generated stronger inhibitions on UGT activities compared to individual Pb and PQ-treated group. These results suggested that combined exposure of Pb and PQ have more inhibitory toxicity on phase I enzymes than phase II enzymes.

Salinity reduces 2,4-D efficacy in Echinochloa crusgalli by affecting redox balance, nutrient acquisition, and hormonal regulation

Distinct salinity levels have been reported to enhance plants tolerance to different types of stresses. The aim of this research is to assess the interaction of saline stress and the use of 2,4-D as a means of controlling the growth of Echinochloa crusgalli. The resultant effect of such interaction is vital for a sustainable approach of weed management and food production. The results showed that 2,4-D alone treatment reduces the chlorophyll contents, photosynthetic capacity, enhanced MDA, electrolyte leakage, and ROS production (H₂O₂, O₂^·-) and inhibited the activities of ROS scavenging enzymes. Further analysis of the ultrastructure of chloroplasts indicated that 2,4-D induced severe damage to the ultrastructure of chloroplasts and thylakoids. Severe saline stress (8 dS m^-1) followed by mild saline stress treatments (4 dS m^-1) also reduced the E. crusgalli growth, but had the least impact as compared to the 2,4-D alone treatment. Surprisingly, under combined treatments (salinity + 2,4-D), the phytotoxic effect of 2,4-D was reduced on saline-stressed E. crusgalli plants, especially under mild saline + 2,4-D treatment. This stimulated growth of E. crusgalli is related to the higher activities of enzymatic and non-enzymatic antioxidants and dynamic regulation of IAA, ABA under mild saline + 2,4-D treatment. This shows that 2,4-D efficacy was affected by salinity in a stress intensity-dependent manner, which may result in the need for greater herbicide application rates, additional application times, or more weed control operations required for controlling salt-affected weed.

2,4-D attenuates salinity-induced toxicity by mediating anatomical changes, antioxidant capacity and cation transporters in the roots of rice cultivars

Growth regulator herbicides are widely used in paddy fields to control weeds, however their role in conferring environmental stress tolerance in the crop plants are still elusive. In this study, the effects of recommended dose of 2,4-dichlorophenoxyacetic acid (2,4-D)  on growth, oxidative damage, antioxidant defense, regulation of cation transporter genes and anatomical changes in the roots of rice cultivars XS 134 (salt resistant) and ZJ 88 (salt sensitive) were investigated under different levels of saline stress. Individual treatments of saline stress and 2,4-D application induced oxidative damage as evidenced by decreased root growth, enhanced ROS production, more membrane damage and Na⁺ accumulation in sensitive cultivar compared to the tolerant cultivar. Conversely, combined treatments of 2,4-D and saline stress significantly alleviated the growth inhibition and oxidative stress in roots of rice cultivars by modulating lignin and callose deposition, redox states of AsA, GSH, and related enzyme activities involved in the antioxidant defense system. The expression analysis of nine cation transporter genes showed altered and differential gene expression in salt-stressed roots of sensitive and resistant cultivars. Together, these results suggest that 2,4-D differentially regulates the Na⁺ and K⁺ levels, ROS production, antioxidant defense, anatomical changes and cation transporters/genes in roots of rice cultivars.

Early habituation of maize (Zea mays) suspension-cultured cells to 2,6-dichlorobenzonitrile is associated with the enhancement of antioxidant status

The cellulose biosynthesis inhibitor 2,6-dichlorobenzonitrile (DCB) has been widely used to gain insights into cell wall composition and architecture. Studies of changes during early habituation to DCB can provide information on mechanisms that allow tolerance/habituation to DCB. In this context, maize-cultured cells with a reduced amount of cellulose (∼20%) were obtained by stepwise habituation to low DCB concentrations. The results reported here attempt to elucidate the putative role of an antioxidant strategy during incipient habituation. The short-term exposure to DCB of non-habituated maize-cultured cells induced a substantial increase in oxidative damage. Concomitantly, short-term treated cells presented an increase in class III peroxidase and glutathione S-transferase activities and total glutathione content. Maize cells habituated to 0.3-1 µM DCB (incipient habituation) were characterized by a reduction in the relative cell growth rate, an enhancement of ascorbate peroxidase and class III peroxidase activities, and a net increment in total glutathione content. Moreover, these cell lines showed increased levels of glutathione S-transferase activity. Changes in antioxidant/conjugation status enabled 0.3 and 0.5 µM DCB-habituated cells to control lipid peroxidation levels, but this was not the case of maize cells habituated to 1 μM DCB, which despite showing an increased antioxidant capacity were not capable of reducing the oxidative damage to control levels. The results reported here confirm that exposure and incipient habituation of maize cells to DCB are associated with an enhancement in antioxidant/conjugation activities which could play a role in incipient DCB habituation of maize-cultured cells.

2,4-D resistance in wild radish: reduced herbicide translocation via inhibition of cellular transport

Resistance to auxinic herbicides is increasing in a range of dicotyledonous weed species, but in most cases the biochemical mechanism of resistance is unknown. Using (14)C-labelled herbicide, the mechanism of resistance to 2,4-dichlorophenoxyacetic acid (2,4-D) in two wild radish (Raphanus raphanistrum L.) populations was identified as an inability to translocate 2,4-D out of the treated leaf. Although 2,4-D was metabolized in wild radish, and in a different manner to the well-characterized crop species wheat and bean, there was no difference in metabolism between the susceptible and resistant populations. Reduced translocation of 2,4-D in the latter was also not due to sequestration of the herbicide, or to reduced uptake by the leaf epidermis or mesophyll cells. Application of auxin efflux or ABCB transporter inhibitors to 2,4-D-susceptible plants caused a mimicking of the reduced-translocation resistance phenotype, suggesting that 2,4-D resistance in the populations under investigation could be due to an alteration in the activity of a plasma membrane ABCB-type auxin transporter responsible for facilitating long-distance transport of 2,4-D.

Clinical characteristics of patients after dicamba herbicide ingestion

OBJECTIVE

Despite a widespread use of dicamba herbicide and numerous animal model studies, there had not been studies on acute toxicity of this chemical compound in human subjects following ingestion. Therefore, this study was conducted to investigate clinical characteristics of dicamba poisoning and to guide physicians treating patients intoxicated with dicamba herbicide.

MATERIAL AND METHOD

A retrospective observational case series was conducted for 14 patients with history of dicamba herbicide ingestion. Data were collected for clinical manifestation, patient management, and final outcome.

RESULT

The most common symptom was altered mental state (Glasgow Coma Scale ≤ 14). Laboratory abnormalities were elevations in lactate, and creatine kinase, metabolic acidosis (pH < 7.35, and HCO3(-) < 20 mmol/L), and elevated lipase. QTc prolongation was commonly observed. These abnormal clinical findings had normalized within two days of supportive treatment after dicamba ingestion. One patient did demonstrate corrosive esophagitis.

DISCUSSION AND CONCLUSION

Acute toxicity of dicamba herbicide in human following oral exposure was manageable with supportive treatment. However, physician should take into account for corrosive effect on GI tract, rhabdomyolysis, or acute pancreatitis.

A comparative study on the interference of two herbicides in wheat and italian ryegrass and on their antioxidant activities and detoxification rates

A study was carried out to compare the effects of treating wheat (Triticum aestivum) and Italian ryegrass (Lolium multiflorum) with atrazine and fluorodifen. The herbicides interfered with photosynthesis and dark respiration, depending on the species. Atrazine decreased photosynthesis in both species and dark respiration in wheat, while fluorodifen caused decrements of photosynthetic activity of wheat. Antioxidant enzymes, such as ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and glutathione reductase (GR), were generally more active in untreated and treated wheat with respect to Italian ryegrass, which explains why oxidative damage, expressed as malondialdehyde (MDA) content, was only found in ryegrass. Investigations on the activity of herbicide-detoxifying enzyme, glutathione S-transferase (GST), and on the accumulation and persistence of the herbicides in the plants showed higher detoxification rates in wheat than in the grass.

Differential response of young and adult leaves to herbicide 2,4-dichlorophenoxyacetic acid in pea plants: role of reactive oxygen species

In this work the differential response of adult and young leaves from pea (Pisum sativum L.) plants to the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) (23 mm) applied by foliar spraying was investigated. The concentration of 2,4-D (23 mm) and the time of treatment (72 h) were previously optimized in order to visualize its toxic effects on pea plants. Under these conditions, the herbicide induced severe disturbances in mesophyll cells structure and proliferation of vascular tissue in young leaves and increased acyl-CoA oxidase (ACX), xanthine oxidase (XOD) and lipoxygenase (LOX) activities in young leaves, and only ACX and LOX in adult leaves. This situation produced reactive oxygen species (ROS) over-accumulation favoured by the absence of significant changes in the enzymatic antioxidants, giving rise to oxidative damages to proteins and membrane lipids. An increase of ethylene took place in both young and adult leaves and the induction of genes encoding the stress proteins, PRP4A and HSP 71,2, was observed mainly in young leaves. These results suggest that ROS overproduction is a key factor in the effect of high concentrations of 2,4-D, and ROS can trigger a differential response in young and adult leaves, either epinasty development in young leaves or senescence processes in adult tissues.

Evaluation of 2,4-D and Dicamba genotoxicity in bean seedlings using comet and RAPD assays

The present study was undertaken to evaluate genotoxic potential of two auxinic herbicides [2,4-dicholorophenoxy acetic acid (2,4-D) and 3,6-dichloro-2-methoxybenzoic acid (Dicamba)] in the roots of common bean (Phaseolus vulgaris L.) seedlings. Two-day-old etiolated seedlings were treated with 10 ppm methyl methanesulfonate (MMS, positive control) or 0.1, 0.2, or 0.3 ppm of either 2,4-D or Dicamba. At the end of a 96 h growth period, root growth, total soluble protein content, DNA damage in individual cells (comet assay scores) and randomly amplified polymorphic DNA (RAPD) profiles were used as endpoints of genotoxicity. 2,4-D and Dicamba were clearly dose-dependent root growth inhibitors. Total soluble protein content was significantly decreased in the positive control and at high concentrations (0.2 and 0.3 ppm) of Dicamba. Soluble protein content increased significantly only at 0.3 ppm 2,4-D (P<0.05). In the comet assay, DNA fragmentation increased in a dose-dependent manner. The diagnostic and phenetic analyzes of appeared and/or disappeared RAPD bands indicated that dose-dependent DNA polymorphism was induced by both herbicides. Genomic template stability was significantly affected at all 2,4-D and Dicamba doses tested. Overall 2,4-D and Dicamba have similar effects on DNA damage detected by comet and RAPD assays.

Inhibitory effects of paraquat on photosynthesis and the response to oxidative stress in Chlorella vulgaris

This study investigated the effects of paraquat, a widely used herbicide, on the aquatic unicellular alga Chlorella vulgaris through short-term toxicity tests at the physiological and gene transcriptional levels. Exposure to 0.5 microM paraquat increased the activities of the antioxidant enzymes superoxide dismutase, peroxidase, and catalase to levels 4.93, 3.19, and 3.09 times higher, respectively, than those of the control. Furthermore, exposure to 0.75 microM paraquat increased the activities of these antioxidant enzymes to even higher levels. The decrease in chlorophyll content and the increases in reactive oxygen species (ROS) and malondialdehyde content following exposure to paraquat suggest that the alga was severely damaged and cell growth was greatly inhibited. Real-time PCR showed that paraquat reduced the transcript abundance of psaB and rbcL to 7.09 and 29.83% of the control, respectively. Our results demonstrate that paraquat inhibited electron transport and CO2 assimilation, and also triggered the synthesis of ROS that disrupt cellular structure and inhibit cell growth.