Acute exposure to a Mn/Zn ethylene-bis-dithiocarbamate fungicide leads to mitochondrial dysfunction and increased reactive oxygen species production in Caenorhabditis elegans

Solventless Synthesis of Zinc Sulphide Nanoparticles from Zinc Bis(diethyldithiocarbamate) as a Single Source Precursor

This study explores the synthesis of nanoparticles through the thermal decomposition of single-source precursors, a method gaining popularity due to its low cost, minimal environmental toxicity, rapidity, scalability, and the ability to form nanoparticles with few defects. Zinc ethyl carbamate was synthesized and characterized using 1H NMR and infrared spectroscopy. Its purity was confirmed through microelemental analysis and melting point determination. The melting point of the complex was determined to be 165 °C. The thermogravimetric analyses indicated a one-step decomposition of zinc ethyl carbamate with a decomposition onset of of 200 °C, yielding a stable ZnS residue. Further thermal decomposition led to the formation of wurtzite phase ZnS nanoparticles, as evidenced by XRD. SEM micrographs displayed mixed spherical, and cubic unevenly sized, polydispersed nanoparticles, while EDX revealed approximately a 1 : 1 Zn to S ratio. Estimated band gap from the Tauc's plot gave 3.93 eV and 3.42 eV for the nanoparticles synthesized at 300 and 400 °C respectively. The wide difference in the band gaps may be as a result of the larger particles observed at 400 °C and the deformations in the sample as observed in the SEM.

Mitochondria in the Spotlight: C. elegans as a Model Organism to Evaluate Xenobiotic-Induced Dysfunction

Mitochondria play a crucial role in cellular respiration, ATP production, and the regulation of various cellular processes. Mitochondrial dysfunctions have been directly linked to pathophysiological conditions, making them a significant target of interest in toxicological research. In recent years, there has been a growing need to understand the intricate effects of xenobiotics on human health, necessitating the use of effective scientific research tools. Caenorhabditis elegans (C. elegans), a nonpathogenic nematode, has emerged as a powerful tool for investigating toxic mechanisms and mitochondrial dysfunction. With remarkable genetic homology to mammals, C. elegans has been used in studies to elucidate the impact of contaminants and drugs on mitochondrial function. This review focuses on the effects of several toxic metals and metalloids, drugs of abuse and pesticides on mitochondria, highlighting the utility of C. elegans as a model organism to investigate mitochondrial dysfunction induced by xenobiotics. Mitochondrial structure, function, and dynamics are discussed, emphasizing their essential role in cellular viability and the regulation of processes such as autophagy, apoptosis, and calcium homeostasis. Additionally, specific toxins and toxicants, such as arsenic, cadmium, and manganese are examined in the context of their impact on mitochondrial function and the utility of C. elegans in elucidating the underlying mechanisms. Furthermore, we demonstrate the utilization of C. elegans as an experimental model providing a promising platform for investigating the intricate relationships between xenobiotics and mitochondrial dysfunction. This knowledge could contribute to the development of strategies to mitigate the adverse effects of contaminants and drugs of abuse, ultimately enhancing our understanding of these complex processes and promoting human health.

Synthetic biology in multicellular organisms: Opportunities in nematodes

Synthetic biology has mainly focused on introducing new or altered functionality in single cell systems: primarily bacteria, yeast, or mammalian cells. Here, we describe the extension of synthetic biology to nematodes, in particular the well-studied model organism Caenorhabditis elegans, as a convenient platform for developing applications in a multicellular setting. We review transgenesis techniques for nematodes, as well as the application of synthetic biology principles to construct nematode gene switches and genetic devices to control motility. Finally, we discuss potential applications of engineered nematodes.

Propineb induced notochord deformity, craniofacial malformation, and osteoporosis in zebrafish through dysregulated reactive oxygen species generation

Dithiocarbamate (DTC) fungicides are contaminants that are ubiquitous in the environment. Exposure to DTC fungicides has been associated with a variety of teratogenic developmental effects. Propineb, a member of DTCs, was evaluated for the toxicological effects on notochord and craniofacial development, osteogenesis in zebrafish model. Embryos at 6 hours post-fertilization (hpf) were exposed to propineb at dosages of 1 and 4 μM. Morphological parameters were evaluated at exposure times of 24, 48, 72, and 120 hpf after propineb exposure. The survival and hatching rates as well as body length decreased at 1 and 4 μmol/L groups. Besides, transgenic zebrafish exposed to propineb showed abnormal vacuole biogenesis in notochord cells at the early stage of development. The expression of collagen type 2 alpha 1a (col2a1a), sonic hedgehog (shh), and heat shock protein family B member 11 (hspb11) measured by quantitative PCR and in situ hybridization experiment of col8a1a gene have consolidated the proposal process. Besides, Alcian blue, calcein, and alizarin red staining profiles displayed craniofacial malformations and osteoporosis were induced following propineb exposure. PPB exposure induced the changes in oxidative stress and reactive oxygen species inhibitor alleviated the deformities of PPB. Collectively, our data suggested that propineb exposure triggered bone abnormalities in different phenotypes of zebrafish. Therefore, propineb is a potential toxicant of high priority concern for aquatic organisms.

Pre-imaginal exposure to mancozeb induces morphological and behavioral deficits and oxidative damage in Drosophila melanogaster

Mancozeb (MZ), a manganese/zinc containing ethylene-bis-dithiocarbamate, is a broad-spectrum fungicide. Chronic exposure to MZ has been related to several organisms' neurological, hormonal, and developmental disorders. However, little is known about the post-natal effects of developmental exposure to MZ. In this study, Drosophila melanogaster was subjected to a pre-imaginal (eggs-larvae-pupae stage) model of exposure to MZ at 0.1 and 0.5 mg/mL. The emergence rate, body size, locomotor performance, sleep patterns, and molecular and biochemical parameters were evaluated in post-emerged flies. Results demonstrate that pre-imaginal exposure to MZ significantly impacted early emerged flies. Additionally, reduced progeny viability, smaller body size and delaying in emergence period, locomotor impairment, and prolonged sleep time were observed. Content of glucose, proteins, and triglycerides were altered, and the bioenergetics efficiency and oxidative phosphorylation at complex I were inhibited. mRNA stade state levels of genes responsive to stress, metabolism, and regulation of circadian cycle (Nrf2, p38, Hsp83, Akt1, GPDH, tor, per, tim, dILP2, and dILP6) were augmented, pointing out to stimulation of antioxidant defenses, insulin-dependent signaling pathway activation, and disruption of sleep regulation. These data were followed by increased lipid peroxidation and lower glutathione levels. In addition, the activity of catalase and glutathione-S-transferase were induced, whereas superoxide dismutase was inhibited. Together, these results demonstrate that developmental exposure to MZ formulation led to phenotype and behavioral alterations in young flies, possibly related to disruption of energetic metabolism, oxidative stress, and deregulation of genes implied in growth, sleep, and metabolism.

Mitochondrial dysfunction from malathion and chlorpyrifos exposure is associated with degeneration of GABAergic neurons in Caenorhabditis elegans

Toxicity resulting from off-target effects, beyond acetylcholine esterase inhibition, for the commonly used organophosphate (OP) insecticides chlorpyrifos (CPS) and malathion (MA) was investigated using Saccharomyces cerevisiae and Caenorhabditis elegans model systems. Mitochondrial damage and dysfunction were observed in yeast following exposure to CPS and MA, suggesting this organelle is a major target. In the C. elegans model, the mitochondrial unfolded protein response pathway showed the most robust induction from CPS and MA treatment among stress responses examined. GABAergic neurodegeneration was observed with CPS and MA exposure. Impaired movement observed in C. elegans exposed to CPS and MA may be the result of motor neuron damage. Our analysis suggests that stress from CPS and MA results in mitochondrial dysfunction, with GABAergic neurons sensitized to these effects. These findings may aid in the understanding of toxicity from CPS and MA from high concentration exposure leading to insecticide poisoning.

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.

Disruption of mitochondrial complexes, cytotoxicity, and apoptosis results from Mancozeb exposure in transformed human colon cells

Ethylene bisdithiocarbamate pesticides, including Mancozeb (MZ), are used as fungicides. Effects of MZ on apoptosis induction and mitochondrial activity of HT-29 colon cells were investigated. MZ exposed cells exhibited blebbing and cellular membrane disruption in scanning electron micrographs. Positive fluorescent staining with Annexin V at doses of 60-140 μM supports apoptosis as the mechanism of cell death. Activity of all electron transport chain complexes were evaluated. Mitochondrial Complex I activity was decreased in 100 μM treated cells. Mitochondrial Complex III activity was decreased in 60 and 100 μM MZ treated cells. Mitochondrial Complex II and Complex IV activities were decreased in cells treated with 60, 100, and 140 μM. Cells treated with 60 μM exhibited a decrease in Complex V enzyme activity. It is concluded that MZ exposure inhibits all mitochondrial complexes of HT-29 cells and that positive fluorescent microscopy and blebbing support previous studies of cell death via apoptosis.

Multiple metabolic changes mediate the response of Caenorhabditis elegans to the complex I inhibitor rotenone

Rotenone, a mitochondrial complex I inhibitor, has been widely used to study the effects of mitochondrial dysfunction on dopaminergic neurons in the context of Parkinson's disease. Although the deleterious effects of rotenone are well documented, we found that young adult Caenorhabditis elegans showed resistance to 24 and 48 h rotenone exposures. To better understand the response to rotenone in C. elegans, we evaluated mitochondrial bioenergetic parameters after 24 and 48 h exposures to 1 μM or 5 μM rotenone. Results suggested upregulation of mitochondrial complexes II and V following rotenone exposure, without major changes in oxygen consumption or steady-state ATP levels after rotenone treatment at the tested concentrations. We found evidence that the glyoxylate pathway (an alternate pathway not present in higher metazoans) was induced by rotenone exposure; gene expression measurements showed increases in mRNA levels for two complex II subunits and for isocitrate lyase, the key glyoxylate pathway enzyme. Targeted metabolomics analyses showed alterations in the levels of organic acids, amino acids, and acylcarnitines, consistent with the metabolic restructuring of cellular bioenergetic pathways including activation of complex II, the glyoxylate pathway, glycolysis, and fatty acid oxidation. This expanded understanding of how C. elegans responds metabolically to complex I inhibition via multiple bioenergetic adaptations, including the glyoxylate pathway, will be useful in interrogating the effects of mitochondrial and bioenergetic stressors and toxicants.

Environmental neurotoxic pollutants: review

Environmental pollutants are recognized as one of the major concerns for public health and responsible for various forms of neurological disorders. Some of the common sources of environmental pollutants related to neurotoxic manifestations are industrial waste, pesticides, automobile exhaust, laboratory waste, and burning of terrestrial waste. Among various environmental pollutants, particulate matter, ultrafine particulate matter, nanoparticles, and lipophilic vaporized toxicant (acrolein) easily cross the blood-brain barrier, activate innate immune responses in the astrocytes, microglia, and neurons, and exert neurotoxicity. Growing shreds of evidence from human epidemiological studies have correlated the environmental pollutants with neuroinflammation, oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction, myelin sheath disruption, and alterations in the blood-brain barrier anatomy leading to cognitive dysfunction and poor quality of life. These environmental pollutants also considerably cause developmental neurotoxicity, exhibit teratogenic effect and mental growth retardance, and reduce IQ level. Until now, the exact mechanism of pollutant-induced neurotoxicity is not known, but studies have shown interference of pollutants with the endogenous antioxidant defense system, inflammatory pathway (Nrf2/NF-kB, MAPKs/PI3K, and Akt/GSK3β), modulation of neurotransmitters, and reduction in long-term potentiation. In the current review, various sources of pollutants and exposure to the human population, developmental neurotoxicity, and molecular mechanism of different pollutants involved in the pathogenesis of different neurological disorders have been discussed.

Toxic effects of a mancozeb-containing commercial formulation at environmental relevant concentrations on zebrafish embryonic development

The toxicological knowledge of mancozeb (MZ)-containing commercial formulations on non-target species is scarce and limited. Therefore, the objective of this work was to represent a realistic application scenario by evaluating the toxicity of environmental relevant and higher concentrations of a commercial formulation of MZ using zebrafish embryos. Following determination of the 96-h LC₅₀ value, the embryos at the blastula stage (~ 2 h post-fertilisation, hpf) were exposed to 0.5, 5, and 50 μg L^-1 of the active ingredient (~ 40× lower than the 96-h LC₅₀). During the exposure period (96 h), lethal, sublethal, and teratogenic parameters, as well as behaviour analysis, at 120 hpf, were assayed. Biochemical parameters such as oxidative stress-linked enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR)), reactive oxygen species (ROS) levels, and glutathione levels (GSH and GSSG), as well as the activity of degradation (glutathione S-transferase (GST) and carboxylesterase (CarE)), neurotransmission (acetylcholinesterase (AChE)), and anaerobic respiration (lactate dehydrogenase (LDH))-related enzymes, were analysed at the end of the exposure period. Exposed embryos showed a marked decrease in the hatching rate and many malformations (cardiac and yolk sac oedema and spinal torsions), with a higher prevalence at the highest concentration. A dose-dependent decreased locomotor activity and a response to an aversive stimulus, as well as a light-dark transition decline, were observed at environmental relevant concentrations. Furthermore, the activities of SOD and GR increased while the activity of GST, AChE, and MDA contents decreased. Taken together, the involvement of mancozeb metabolites and the generation of ROS are suggested as responsible for the developmental phenotypes. While further studies are needed to fully support the hypothesis presented, the potential cumulative effects of mancozeb-containing formulations and its metabolites could represent an environmental risk which should not be disregarded.

Zinc alleviates maneb-induced kidney injury in adult mice through modulation of oxidative stress, genotoxicity, and histopathological changes

Zinc is one of the important essential trace minerals to human health due to its antioxidant properties. The present study was conducted to elucidate its potential protective role against maneb-induced nephrotoxicity. For this purpose, animals were randomly divided into four groups of six each. Mice of group I (negative controls) have received daily 0.5 ml of distilled water, a solvent of maneb. Mice of group II (MB) have received 30 mg/kg bw of maneb daily by intraperitoneal way. Mice of group III (MB + Zn) have received the same dose of maneb as group II, along with ZnSO4 (30 mg/kg bw) daily. Mice of group IV (Zn), considered as positive controls, have received the same dose of ZnSO4 as group III daily. Our results revealed that ZnSO4 co-administration to maneb-treated mice decreased kidney levels of malondialdehyde, hydrogen peroxide, protein carbonyls, and advanced oxidation protein products; the levels of non-enzymatic antioxidants like vitamin C, glutathione, and metallothionein. It recovered the alteration of antioxidant enzyme activities (catalase, superoxide dismutase, and glutathione peroxidase) and attenuated DNA fragmentation. Furthermore, this essential trace element was also able to alleviate kidney biomarkers' alterations by lowering plasma levels of creatinine, urea, uric acid, and lactate dehydrogenase. In addition, the histopathological changes induced by maneb were improved following zinc administration. Our results indicated that zinc might be beneficial against maneb-induced renal oxidative damage in mice.

Caenorhabditis elegans as a tool for environmental risk assessment: emerging and promising applications for a "nobelized worm"

Caenorhabditis elegans has been an invaluable model organism in research fields such as developmental biology and neurobiology. Neurotoxicity is one of the subfields greatly profiting from the C. elegans model within biomedical context, while the corresponding potential of the organism applied to environmental studies is relevant but has been largely underexplored. Within the biomedical scope, the implication of metals and organic chemicals with pesticide activity (hereinafter designated as pesticides) in the etiology of several neurodegenerative diseases has been extensively investigated using this nematode as a primary model organism. Additionally, as a well-known experimental model bearing high sensitivity to different contaminants and representing important functional levels in soil and aquatic ecosystems, C. elegans has high potential to be extensively integrated within Environmental Risk Assessment (ERA) routines. In spite of the recognition of some regulatory agencies, this actual step has yet to be made. The purpose of this review is to discuss the major advantages supporting the inclusion of C. elegans in lower tiers of ERA. Special emphasis was given to its sensitivity to metals and pesticides, which is similar to that of other model organisms commonly used in ERA (e.g. Daphnia magna and Eisenia sp.), and to the large array of endpoints that can be tested with the species, both concerning the aquatic and the soil compartments. The inclusion of C. elegans testing may hence represent a relevant advance in ERA, providing ecologically relevant insights toward improvement of the regulatory capacity for establishing appropriate environmental protection benchmarks.

Developmental exposure to mancozeb induced neurochemical and morphological alterations in adult male mouse hypothalamus

Mancozeb, a dithiocarbamate widely used in agriculture, is considered a developmental hazard in humans; however, more evidences are still needed concerning the consequences of chronic exposure to this pesticide. Mancozeb neurotoxicity in developing mouse hypothalamus was evaluated by subchronic exposure of male Mus musculus mice to low and high doses of mancozeb (30 and 90 mg/kg body weight, respectively) from late neonatal until adolescence. Variations in hypothalamic amino acid neurotransmitter levels and changes in histological as well as cytological characteristics were analyzed in young adult experimental mice and compared with control. A dose-dependent increase in excitation/ inhibition ratio was observed in mancozeb-exposed hypothalamus, indicating an overall state of excitoxicity. Histopathological and ultrastructural studies showed increased apoptosis, neuroinflammation and demyelination, demonstrating mancozeb-induced cytotoxicity in hypothalamic neurosecretory cells. In summary, both neurochemical and morphological data revealed mancozeb-induced alterations during development of hypothalamic circuitry that are critical for maturation of the neuroendocrine system.

Exposure of Drosophila melanogaster to Mancozeb Induces Oxidative Damage and Modulates Nrf2 and HSP70/83

Mancozeb (MZ), a manganese- and zinc-containing ethylene-bis-dithiocarbamate, is a broad-spectrum fungicide. Harmful effects of this fungicide have been reported in nontarget organisms via a not fully understood mechanism. Drosophila melanogaster has provided remarkable contributions for toxicological studies. This work was aimed at evaluating the biochemical targets and implication of oxidative stress in MZ-mediated toxicity in drosophilas. Exposure of flies for fifteen days to MZ at 5 and 10 mg/mL through the diet impaired locomotor performance and induced fly mortality. In parallel, it caused lipid peroxidation and reactive oxygen species (ROS) formation and Mn overload. MZ inhibited superoxide dismutase and inducted catalase and glutathione S-transferase activities. Nitric oxide and reduced glutathione levels were significantly decreased by MZ. Heat shock proteins (HSP70 and HSP83) and Nrf2 mRNA levels were significantly augmented in MZ-exposed flies. Our study reinforced the use of Drosophila melanogaster as a reliable model for the study of biochemical targets of pesticides, and based on our data, MZ induced oxidative damage and Mn accumulation in a concentration-dependent manner. An adaptative cellular state was inducted by the lower concentration of pesticide, possibly contributing to the slighter damage observed.

Transport of a manganese/zinc ethylene-bis-dithiocarbamate fungicide may involve pre-synaptic dopaminergic transporters

Mancozeb (MZ), an organic-metal fungicide used predominantly on vegetables and fruits, has been linked to neurodegeneration and behavioral disruptions in a variety of organisms, including humans. Both γ-aminobutyric acid and dopamine neurons appear to be more vulnerable to MZ exposure than other neuronal populations. Based on these observations, we hypothesized that MZ may be differentially transported into these cells through their presynaptic neurotransmitter transporters. To test this, we pretreated Caenorhabditis elegans with transporter antagonists followed by exposure to various concentrations of MZ. Potential neuroprotection was monitored via green fluorescence associated with various neuron populations in transgenic worm strains. Neurodegeneration associated with subacute MZ treatment (30 min) was not altered by transporter antagonist pretreatment. On the other hand, pretreatment with a dopamine transporter antagonist (GBR12909) appeared to protect dopaminergic neurons from chronic (24 h) MZ treatment. These results are consistent with other reports that dopamine transporter levels or activity may modulate toxicity for neurotoxicants.

Chronic exposure to a glyphosate-containing pesticide leads to mitochondrial dysfunction and increased reactive oxygen species production in Caenorhabditis elegans

Glyphosate-containing herbicides are among the most widely-used in the world. Although glyphosate itself is relatively non-toxic, growing evidence suggests that commercial herbicide formulations may lead to increased oxidative stress and mitochondrial inhibition. In order to assess these mechanisms in vivo, we chronically (24h) exposed Caenorhabditis elegans to various concentrations of the glyphosate-containing herbicide TouchDown (TD). Following TD exposure, we evaluated the function of specific mitochondrial electron transport chain complexes. Initial oxygen consumption studies demonstrated inhibition in mid- and high-TD concentration treatment groups compared to controls. Results from tetramethylrhodamine ethyl ester and ATP assays indicated reductions in the proton gradient and ATP levels, respectively. Additional studies were designed to determine whether TD exposure resulted in increased reactive oxygen species (ROS) production. Data from hydrogen peroxide, but not superoxide or hydroxyl radical, assays showed statistically significant increases in this specific ROS. Taken together, these data indicate that exposure of Caenorhabditis elegans to TD leads to mitochondrial inhibition and hydrogen peroxide production.

Cell Biology of the Mitochondrion

Mitochondria are best known for harboring pathways involved in ATP synthesis through the tricarboxylic acid cycle and oxidative phosphorylation. Major advances in understanding these roles were made with Caenorhabditiselegans mutants affecting key components of the metabolic pathways. These mutants have not only helped elucidate some of the intricacies of metabolism pathways, but they have also served as jumping off points for pharmacology, toxicology, and aging studies. The field of mitochondria research has also undergone a renaissance, with the increased appreciation of the role of mitochondria in cell processes other than energy production. Here, we focus on discoveries that were made using C. elegans, with a few excursions into areas that were studied more thoroughly in other organisms, like mitochondrial protein import in yeast. Advances in mitochondrial biogenesis and membrane dynamics were made through the discoveries of novel functions in mitochondrial fission and fusion proteins. Some of these functions were only apparent through the use of diverse model systems, such as C. elegans Studies of stress responses, exemplified by mitophagy and the mitochondrial unfolded protein response, have also benefitted greatly from the use of model organisms. Recent developments include the discoveries in C. elegans of cell autonomous and nonautonomous pathways controlling the mitochondrial unfolded protein response, as well as mechanisms for degradation of paternal mitochondria after fertilization. The evolutionary conservation of many, if not all, of these pathways ensures that results obtained with C. elegans are equally applicable to studies of human mitochondria in health and disease.