Ecotoxicological strategies employing biochemical markers and organisms to monitor the efficacy of malathion photolysis treatment

The objective of this study was to assess the photolysis-mediated degradation of malathion in standard and commercial formulations, and to determine the toxicity of these degraded formulations. Degradation tests were carried out with 500 μg L-1 of malathion and repeated three times. The initial and residual toxicity was assessed by using Lactuca sativa seeds for phytotoxicity, Stegomyia aegypti larvae for acute toxicity, and Stegomyia aegypti mosquitoes (cultivated from the larval stage until emergence as mosquitoes) to evaluate the biochemical markers of sublethal concentrations. For the standard formulations the photolytic process efficiently reduced the initial concentration of malathion to levels below the regulatory limits however, the formation of byproducts was revealed by chromatography, which allowed for a more complete proposal of photolytic-mediated malathion degradation route. The degraded formulations inhibited the growth of L. sativa seeds, while only the untreated formulations showed larvicidal activity and mortality. Both formulations slightly inhibited acetylcholinesterase activity in S. aegypti mosquitoes, while the standard formulation decreased and the commercial formulation increased glutathione S-transferase activity. However, there were no significant differences for superoxide dismutase, esterase-α, esterase-β and lipid peroxidation. These findings indicate that in the absence of the target compound, the presence of byproducts can alter the enzymatic activity. In general, photolysis effectively degrade malathion lower than the legislation values; however, longer treatment times must be evaluated for the commercial formulation.

Overexpression of an Integument Esterase Gene LbEST-inte4 Infers the Malathion Detoxification in Liposcelis bostrychophila (Psocoptera: Liposcelididae)

Liposcelis bostrychophila, commonly known as booklouse, is an important stored-product pest worldwide. Studies have demonstrated that booklices have developed resistance to several insecticides. In this study, an integument esterase gene, LbEST-inte4, with upregulated expression, was characterized in L. bostrychophila. Knockdown of LbEST-inte4 resulted in a substantial increase in the booklice susceptibility to malathion. Overexpression of LbEST-inte4 in Drosophila melanogaster significantly enhanced its malathion tolerance. Molecular modeling and docking analysis suggested potential interactions between LbEST-inte4 and malathion. When overexpressed LbEST-inte4 in Sf9 cells, a notable elevation in esterase activity and malathion tolerance was observed. HPLC analysis indicated that the LbEST-inte4 enzyme could effectively degrade malathion. Taken together, the upregulated LbEST-inte4 appears to contribute to malathion tolerance in L. bostrychophila by facilitating the depletion of malathion. This study elucidates the molecular mechanism underlying malathion detoxification and provides the foundations for the development of effective prevention and control measures against psocids.

The stingless bee Trigona spinipes (Hymenoptera: Apidae) is at risk from a range of insecticides via direct ingestion and trophallactic exchanges

BACKGROUND

The stingless bee, Trigona spinipes, is an important pollinator of numerous native and cultivated plants. Trigona spinipes populations can be negatively impacted by insecticides commonly used for pest control in crops. However, this species has been neglected in toxicological studies. Here we observed the effects of seven insecticides on the survival of bees that had fed directly on insecticide-contaminated food sources or received insecticides via trophallactic exchanges between nestmates. The effects of insecticides on flight behavior were also determined for the compounds considered to be of low toxicity.

RESULTS

Imidacloprid, spinosad and malathion were categorized as highly toxic to T. spinipes, whereas lambda-cyhalothrin, methomyl and chlorfenapyr were of medium to low toxicity and interfered with two aspects of flight behavior evaluated here. Chlorantraniliprole was the only insecticide tested here that had no significant effect on T. spinipes survival, although it did interfere with one aspect of flight capacity. A single bee that had ingested malathion, spinosad or imidacloprid, could contaminate three, four and nineteen other bees, respectively via trophallaxis, resulting in the death of the recipients.

CONCLUSION

This is the first study to evaluate the ecotoxicology of a range of insecticides that not only negatively affected T. spinipes survival, but also interfered with flight capacity, a very important aspect of pollination behavior. The toxicity of the insecticides was observed following direct ingestion and also via trophallactic exchanges between nestmates, highlighting the possibility of lethal effects of these insecticides spreading throughout the colony, reducing the survival of non-foraging individuals. © 2023 Society of Chemical Industry.

Low doses of malathion impair ovarian, uterine, and follicular integrity by altering oxidative profile and gene expression of rats exposed during the peripubertal period

Malathion serves as a pivotal pesticide in agriculture and the management of the Aedes aegypti mosquito. Despite its widespread use, there is a notable absence of studies elucidating the mechanisms through which malathion may affect the female reproductive system. Consequently, the objective of this investigation was to assess whether exposing juvenile female rats to low doses of malathion during the juvenile and peripubertal periods could compromise pubertal onset, estradiol levels, and the integrity of the ovaries and uterus while also examining the underlying mechanisms of damage. To achieve this, thirty juvenile female rats were subjected to either a vehicle or malathion (10 mg/kg or 50 mg/kg) between postnatal days 22 and 60, with subsequent verification of pubertal onset. Upon completion of the exposure period, blood samples were collected for estradiol assessment. The ovaries and uterus were then examined to evaluate histological integrity, oxidative stress, and the expression of genes associated with cell proliferation, antiapoptotic responses, and endocrine pathways. Although estradiol levels and pubertal onset remained unaffected, exposure to malathion compromised the integrity and morphometry of the ovaries and uterus. This was evidenced by altered oxidative profiles and changes in the expression of genes regulating the cell cycle, anti-apoptotic processes, and endocrine pathways. Our findings underscore the role of malathion in inducing cell proliferation, promoting cell survival, and causing oxidative damage to the female reproductive system in rats exposed during peripubertal periods.

Alteration of haematological and biochemical biomarkers after sub-lethal chronic malathion (Elathion®) intoxication in freshwater fish, Labeo rohita (Hamilton, 1822)

The present investigation aimed to evaluate the long-term effects of malathion (Elathion®) at two sub-lethal concentrations (0.36 and 1.84 mgL-1) for 45 days after the determination of 96 h-LC50 value (18.35 mgL-1) in a commercially important aquaculture species, Labeo rohita by assaying multiple biomarker approaches. Total erythrocyte count (TEC), and haemoglobulin count (Hb) were found to be decreased while total leucocyte counts (TLC) were increased (p < 0.05) in malathion-intoxicated fish. Malathion exposure significantly reduced (p < 0.05) serum protein levels while significantly increased (p < 0.05) blood glucose levels. RNA activity in muscle was reduced (p < 0.05) while DNA activity increased (p < 0.05) in malathion-intoxicated fish. Acid phosphatase (ACP) activities in the brain; lacate dehydrogenase (LDH) activities in brain and liver were increased (p < 0.05), while alkaline phosphatase (ALP) activities in the brain; succinate dehydrogenase (SDH) activities in the brain, liver and kidney; acetylcholine esterase (AChE) activity in the brain; and ATPase activities in the brain, liver and kidney were reduced (p < 0.05) in comparison to control. Thus, the alteration in studied biomarkers was in a concentation-time dependent manner; however, it was more pronounced at the higher concentration at 45 days of exposure. The alteration in biomarker activity is probably a defensive mechanism/ adaptive response of fish to overcome the stress induced by malathion, which is a novel insight and possible impact on L.rohita. Our findings suggest malathion-induced stress, therefore, the use of malathion needs to be regulated to safeguard aquatic animals including fish and human health.

Mitochondrial coding genes mediate insecticide tolerance in the oriental fruit fly, Bactrocera dorsalis (Hendel)

The oriental fruit fly, Bactrocera dorsalis (Hendel), an invasive insect pest infesting fruits and vegetables, possesses a remarkable capacity for environmental adaptation. The investigation of behind mechanisms of the stress adaptability in B. dorsalis holds significantly practical relevance. Previous studies on the molecular mechanism underlying stress resistance in B. dorsalis have predominantly focused on nuclear-coding genes, with limited exploration on organelle-coding genes. In this study, we assessed alterations in the mitochondrial physiological parameters of B. dorsalis under exposure to malathion, avermectin, and beta-cypermethrin at LD50 dosages. The results showed that all three insecticides were capable of reducing mitochondrial complex IV activity and ATP content. Expression patterns of mitochondrial coding genes across different developmental stages, tissues and insecticide exposures were analyzed by RT-qPCR. The results revealed that these mitochondrial coding genes were expressed in various tissues and at different developmental stages. Particularly noteworthy, atp6, cox2, and cytb exhibited substantial up-regulation in response to malathion and avermectin treatment. Furthermore, RNAi-mediated knockdown of atp6 and cox2 resulted in the increased toxicity of malathion and avermectin against B. dorsalis, and cox2 silencing was also associated with the decreased complex IV activity. These findings suggest that atp6 and cox2 most likely play pivotal roles in mediating tolerance or resistance to malathion and avermectin in B. dorsalis. Our results provide novel insights into the role of mitochondrial coding genes in conferring tolerance to insecticides in B. dorsalis, with practical implications for controlling this pest in the field.

Low-dose exposure to malathion and radiation results in the dysregulation of multiple neuronal processes, inducing neurotoxicity and neurodegeneration in mouse

Neurodegenerative disorders are a debilitating and persistent threat to the global elderly population, carrying grim outcomes. Their genesis is often multifactorial, with a history of prior exposure to xenobiotics such as pesticides, heavy metals, enviornmental pollutants, ionizing radiation etc,. A holistic molecular insight into their mechanistic induction upon single or combinatorial exposure to different toxicants is still unclear. In the present study, one-month-old C57BL/6 male mice were administered orally with malathion (50 mg/kg body wt. for 14 days) and single whole-body radiation (0.5 Gy) on the 8th day. Post-treatment, behavioural assays for exploratory behaviour, memory, and learning were performed. After sacrifice, brains were collected for histology, biochemical assays, and transcriptomic analysis. Transcriptomic analysis revealed several altered processes like synaptic transmission and plasticity, neuronal survival, proliferation, and death. Signalling pathways like MAPK, PI3K-Akt, Apelin, NF-κB, cAMP, Notch etc., and pathways related to neurodegenerative diseases were altered. Increased astrogliosis was observed in the radiation and coexposure groups, with significant neuronal cell death and a reduction in the expression of NeuN. Sholl analysis, dendritic arborization and spine density studies revealed decreased total apical neuronal path length and dendritic spine density. Reduced levels of the antioxidants GST and GSH and acetylcholinesterase enzyme activity were also detected. However, no changes were seen in exploratory behaviour or learning and memory post-treatment. Thus, explicating the molecular mechanisms behind malathion and radiation can provide novel insights into external factor-driven neurotoxicity and neurodegenerative pathogenesis.

Overexpression of ABCB transporter genes confer multiple insecticide tolerances in Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

Bactrocera dorsalis is a notable invasive pest that has developed resistance to several commonly used insecticides in the field, such as avermectin, beta-cypermethrin and malathion. Investigating the mechanisms of insecticide resistance in this pest is of paramount importance for ensuring its effective control. The ATP-binding cassette transporter subfamily B (ABCB) genes, responsible for encoding transmembrane efflux transporters, represent a potential source of insecticide detoxification activity or transportation that remains largely unexplored in B. dorsalis. In this study, seven BdABCB genes were identified and comprehensive analyzed based on the latest genome and transcriptome dataset. Subsequently, we characterized the expression profiles of these genes across different development stages and tissues, as well as under different insecticide exposures. The results showed that the BdABCB genes were expressed at all stages in B. dorsalis, with BdABCB2 and BdABCB7 being highly expressed in the pupal stage, while BdABCB5 and BdABCB6 were highly expressed in the larval stage. Besides, the BdABCBs were highly expressed in the detoxification metabolic tissues. Among them, BdABCB5 and BdABCB6 were significantly overexpressed in the midgut and Malpighian tubules, respectively. Furthermore, with the exception of BdABCB6, the expression levels of the other six BdABCBs were significantly up-regulated following induction with avermectin, beta-cypermethrin and malathion. Six BdABCBs (BdABCB1-5 and BdABCB7) were knocked down by RNA interference, and the interference efficiencies were 46.58%, 39.50%, 45.60%, 33.74%, 66.37% and 63.83%, respectively. After injecting dsBdABCBs, the mortality of flies increased by 25.23% to 39.67% compared to the control upon exposure to the three insecticides. These results suggested that BdABCBs play crucial roles in the detoxification or tolerance of B. dorsalis to multiple insecticides.

Assessment of hematological indicators, histological alterations, and DNA damage in Danube sturgeon (Acipenser gueldenstaedtii) exposed to the organophosphate malathion

This study focused on organophosphate malathion toxicity in Danube sturgeon (Acipenser gueldenstaedtii) and its negative effects in sub-lethal concentration. In this context, the LC50 value of fish exposed to five different concentrations and two different sub-lethal concentrations depending on the LC50 value were considered. Accordingly, LC50 of malathion for 96 h was 3.24 mg L-1. In leukocyte (WBC) and hemoglobin (HGB) such as hematological indicators, significant differences were observed in sub-lethal concentration (One-eighth of the LC50 =0.4 mg L-1). In addition, serious histological alterations were observed in the gill and liver tissues after both acute (96 h) and chronic periods (28 days). While epithelial lifting and hyperplasia were the most prominent lesions in the gill, intense vacuolization were observed in the liver. In addition, circulatory disturbances, regressive changes, and progressive changes in the gill and circulatory disturbances and inflammation in the liver were significantly higher for the chronic period. Finally, significantly higher DNA damage was detected in fish exposed malathion in the chronic period compared to the control group. In conclusion, the present study has proven that malathion has a hematological, histological and genotoxic effect on the endangered species A. gueldenstaedtii. Thus, the current study will motivate for residue studies on A. gueldenstaedtii and trigger conservation strategies for local governments.

Short-term insecticide exposure amid co-occurring stressors reduces diversity and densities in north-east Indian experimental aquatic invertebrate communities

Globally, river pesticide concentrations are associated with regional and local stream invertebrate diversity declines. Pesticides often co-occur with elevated nutrients (e.g. nitrogen and phosphorus) and sediments related to agriculture, making their individual effects difficult to disentangle. These effects are also less well studied in Asia, than in other geographic regions. Within Asia, India is one of the largest producers and users of pesticides and has approximately 60% of total land mass used for agriculture. Here we examine the responses of Indian river invertebrate communities subjected to malathion, nutrients, and sediment additions in a semi-orthogonal design, in three sequential (through time) short-term (120 h) mesocosm experiments. Additionally, a series of single-species toxicity tests were run that used 24 h exposure and 72 h recovery to examine the sensitivity of 13 local invertebrate taxa to malathion, and 9 taxa to cypermethrin, comparing these results to those from other biogeographic regions. Mesocosm results indicate that malathion exposure had a major effect compared to other stressors on communities, with a lesser effect of nutrients and/or sediments. In mesocosms, taxa richness, total abundance and the abundance of sensitive species all declined associated with malathion concentrations. Comparisons of organism sensitivities from other geographic locations and those in the current paper suggest taxa in India are relatively tolerant to malathion and cypermethrin. Our results further reinforce that the high observed aquatic pesticide concentrations known to occur in Asian freshwater ecosystems are likely to be negatively affecting biodiversity, homogenising biota towards those most stress tolerant.

Formulation of water pollutant discharge limits for malathion based on nonsensitive aquatic organism protection

The "Integrated Wastewater Discharge Standard" was implemented for water pollutant discharge in China's pesticide industry, which has no control requirements for particular wastewater pollutants in the industry. In the standard, certain pollutants discharge limits are limited strictly or loosely, resulting in practical management implementation difficulties. In view of the highly selective targeting characteristics of organic pesticide active ingredients in fungicides, insecticides, and herbicides, a method for deriving discharge limits based on the water quality criteria for pesticides for the protection of nonsensitive species is established based on the idea of fully protecting aquatic organisms beyond sensitive objects. Through the use of malathion as an example, by screening its toxicity data in different species of aquatic organisms, the sequence point with the most significant change in the acute toxicity sensitivity of the species is taken as the variation point in the cumulative frequency of the sensitive and nonsensitive species to derive the water quality criteria, using the species sensitivity distribution method as the scientific basis for determining the discharge limits. After a comparative analysis of different simulation models, the sigmoid model, with the best fit, is selected to determine that the sensitive species hazard concentration (HCs) of malathion to aquatic organisms in China is 46.4 µg/L, and the discharge limit derived from the HCs based on the relationship between the environmental capacity and emissions is rounded to 250 µg/L. Studies showed that the relationship between the emissions limit derived from the water quality criteria for protecting nonsensitive species and malathion limit stipulated in the "Environmental Quality Standards for Surface Water" conforms to the corresponding relationship of the quality standard and discharge standard, which can be achieved by current pollution control technology, combined with water quality improvement. The discharge limit offers the advantages of technical accessibility and economic rationality.

Malathion or diazinon exposure and male reproductive toxicity: a systematic review of studies performed with rodents

Malathion and diazinon are pesticides commonly used in agriculture to avoid insects that damage crops; however, they may cause impairment to the male genital system of exposed humans. The present work carried out a systematic review of the literature concerning the primary studies that assessed the reproductive effects resulting from male rats and mice exposed to malathion or diazinon. The search for articles was performed on the databases PubMed, LILACS, Scopus, and SciELO, using different combinations of the search terms "malathion," "diazinon," "mice," "rats," "male reproduction," "fertility," and "sperm," followed by the Boolean operators AND or OR. The results obtained indicate that both pesticides act as reproductive toxicants by reducing sperm quality, diminishing hormonal concentrations, inducing increased oxidative stress, and provoking histopathological damage in reproductive organs. Then, the exposure to malathion and diazinon may provoke diminished levels of testosterone by increasing acetylcholine stimulation in the testis through muscarinic receptors, thus, providing a reduction in steroidogenic activity in Leydig cells, whose effect is related to lower levels of testosterone in rodents, and consequently, it is associated with decreased fertility. Considering the toxic effects on the male genital system of rodents and the possible male reproductive toxicity in humans, it is recommended the decreased use of these pesticides and their replacement for others that show no or few toxic effects for non-target animals.

Methylated dialkylphosphate metabolites of the organophosphate pesticide malathion modify actin cytoskeleton arrangement and cell migration via activation of Rho GTPases Rac1 and Cdc42

The non-cholinergic molecular targets of organophosphate (OP) compounds have recently been investigated to explain their role in the generation of non-neurological diseases, such as immunotoxicity and cancer. Here, we evaluated the effects of malathion and its dialkylphosphate (DAP) metabolites on the cytoskeleton components and organization of RAW264.7 murine macrophages as non-cholinergic targets of OP and DAPs toxicity. All OP compounds affected actin and tubulin polymerization. Malathion, dimethyldithiophosphate (DMDTP) dimethylthiophosphate (DMTP), and dimethylphosphate (DMP) induced elongated morphologies and the formation of pseudopods rich in microtubule structures, and increased filopodia formation and general actin disorganization in RAW264.7 cells and slightly reduced stress fibers in the human fibroblasts GM03440, without significantly disrupting the tubulin or vimentin cytoskeleton. Exposure to DMTP and DMP increased cell migration in the wound healing assay but did not affect phagocytosis, indicating a very specific modification in the organization of the cytoskeleton. The induction of actin cytoskeleton rearrangement and cell migration suggested the activation of cytoskeletal regulators such as small GTPases. We found that DMP slightly reduced Ras homolog family member A activity but increased the activities of Ras-related C3 botulinum toxin substrate 1 (Rac1) and cell division control protein 42 (Cdc42) from 5 min to 2 h of exposure. Chemical inhibition of Rac1 with NSC23766 reduced cell polarization and treatment with DMP enhanced cell migration, but Cdc42 inhibition by ML-141 completely inhibited the effects of DMP. These results suggest that methylated OP compounds, especially DMP, can modify macrophage cytoskeleton function and configuration via activation of Cdc42, which may represent a potential non-cholinergic molecular target for OP compounds.

Vitamin B12 alleviates malathion-induced toxicity in zebra fish by regulating cytochrome P450 and PgP expressions

The indiscriminate and rampant use of pesticides has raised serious concerns regarding their toxic impact on non-target organisms which underlines need for the development of an effective antidote. Metabolic activation of organophosphate pesticides by the phase I enzyme, cytochrome P450 plays a key role in influencing pesticide-toxicity. In this study, we have investigated the effect of environmentally relevant malathion concentration (100 μg/L) alone and in combination with vitamin B12 on the expression of genes related to xenobiotic metabolism such as CYP enzymes, PgP and the key oxidative stress responsive transcription factor, Nrf2 in zebra fish liver and brain. Expressions of Nrf2-trasncribed antioxidant genes and their activities were also measured. Administration of vitamin B12 successfully revived motor functions by modulation of AchE activity. Mechanistically, vitamin B12 was demonstrated to alleviate oxidative stress which was accompanied by decreased phase-I enzyme cyp3c1 and increased pgp expressions.

Ecological threat caused by malathion and its chiral metabolite in a honey bee-rape system: Stereoselective exposure risk and the mechanism revealed by proteome

Honey bees play an important role in the ecological environment. Regrettably, a decline in honey bee colonies caused by chemical insecticides has occurred throughout the world. Potential stereoselective toxicity of chiral insecticides may be a hidden source of danger to bee colonies. In this study, the stereoselective exposure risk and mechanism of malathion and its chiral metabolite malaoxon were investigated. The absolute configurations were identified using an electron circular dichroism (ECD) model. Ultrahigh-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was used for chiral separation. In pollen, the initial residues of malathion and malaoxon enantiomers were 3571-3619 and 397-402 μg/kg, respectively, and R-malathion degraded relatively slowly. The oral LD₅₀ values of R-malathion and S-malathion were 0.187 and 0.912 μg/bee with 5 times difference, respectively, and the malaoxon values were 0.633 and 0.766 μg/bee. The Pollen Hazard Quotient (PHQ) was used to evaluate exposure risk. R-malathion showed a higher risk. An analysis of the proteome, including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and subcellular localization, indicated that energy metabolism and neurotransmitter transport were the main affected pathways. Our results provide a new scheme for the evaluation of the stereoselective exposure risk of chiral pesticides to honey bees.

Exposure to Insecticides Modifies Gene Expression and DNA Methylation in Hematopoietic Tissues In Vitro

The evidence supporting the biological plausibility of the association of permethrin and malathion with hematological cancer is limited and contradictory; thus, further studies are needed. This study aimed to investigate whether in vitro exposure to 0.1 μM permethrin and malathion at 0, 24, 48 and 72 h after cell culture initiation induced changes in the gene expression and DNA methylation in mononuclear cells from bone marrow and peripheral blood (BMMCs, PBMCs). Both pesticides induced several gene expression modifications in both tissues. Through gene ontology analysis, we found that permethrin deregulates ion channels in PBMCs and BMMCs and that malathion alters genes coding proteins with nucleic acid binding capacity, which was also observed in PBMCs exposed to permethrin. Additionally, we found that both insecticides deregulate genes coding proteins with chemotaxis functions, ion channels, and cytokines. Several genes deregulated in this study are potentially associated with cancer onset and development, and some of them have been reported to be deregulated in hematological cancer. We found that permethrin does not induce DNA hypermethylation but can induce hypomethylation, and that malathion generated both types of events. Our results suggest that these pesticides have the potential to modify gene expression through changes in promoter DNA methylation and potentially through other mechanisms that should be investigated.

Dissecting the Enantioselective Neurotoxicity of Isocarbophos: Chiral Insight from Cellular, Molecular, and Computational Investigations

Chiral organophosphorus pollutants are found abundantly in the environment, but the neurotoxicity risks of these asymmetric chemicals to human health have not been fully assessed. Using cellular, molecular, and computational toxicology methods, this story is to explore the static and dynamic toxic actions and its stereoselective differences of chiral isocarbophos toward SH-SY5Y nerve cells mediated by acetylcholinesterase (AChE) and further dissect the microscopic basis of enantioselective neurotoxicity. Cell-based assays indicate that chiral isocarbophos exhibits strong enantioselectivity in the inhibition of the survival rates of SH-SY5Y cells and the intracellular AChE activity, and the cytotoxicity of (S)-isocarbophos is significantly greater than that of (R)-isocarbophos. The inhibitory effects of isocarbophos enantiomers on the intracellular AChE activity are dose-dependent, and the half-maximal inhibitory concentrations (IC₅₀) of (R)-/(S)-isocarbophos are 6.179/1.753 μM, respectively. Molecular experiments explain the results of cellular assays, namely, the stereoselective toxic actions of isocarbophos enantiomers on SH-SY5Y cells are stemmed from the differences in bioaffinities between isocarbophos enantiomers and neuronal AChE. In the meantime, the modes of neurotoxic actions display that the key amino acid residues formed strong noncovalent interactions are obviously different, which are related closely to the molecular structural rigidity of chiral isocarbophos and the conformational dynamics and flexibility of the substrate binding domain in neuronal AChE. Still, we observed that the stable "sandwich-type π-π stacking" fashioned between isocarbophos enantiomers and aromatic Trp-86 and Tyr-337 residues is crucial, which notably reduces the van der Waals' contribution (ΔG_vdW) in the AChE-(S)-isocarbophos complexes and induces the disparities in free energies during the enantioselective neurotoxic conjugations and thus elucidating that (S)-isocarbophos mediated by synaptic AChE has a strong toxic effect on SH-SY5Y neuronal cells. Clearly, this effort can provide experimental insights for evaluating the neurotoxicity risks of human exposure to chiral organophosphates from macroscopic to microscopic levels.

Molecular and biochemical investigation of the protective effects of rutin against liver and kidney toxicity caused by malathion administration in a rat model

Widely used malathion (MLT) causes environmental pollution, leading to toxicity in many living things, including humans. Rutin (RUT) is a flavonoid with various biological properties. In the present study, the protective effects of rutin against liver and kidney toxicity caused by malathion were investigated. In the study, MLT (100 mg/kg) and RUT (50 or 100 mg/kg) were administered to rats alone or in combination for 28 days. Then, oxidative stress, inflammation, endoplasmic reticulum stress (ERS), apoptosis, and autophagy markers in liver and kidney tissues were analyzed by biochemical and molecular methods. The results showed that MLT caused oxidative stress in both tissues, while RUT showed antioxidant properties and protected these tissues from oxidative damage. Moreover, MLT upregulated the expressions of ATF-6, PERK, IRE1, GRP78, and CHOP, leading to ERS. However, RUT alleviated ER stress and suppressed these markers. The study also found that MLT increased inflammatory, apoptotic, and autophagic markers. All these factors affected liver and kidney functions and caused an increase in plasma ALT, AST, urea, and creatinine levels. On the other hand, it has been observed that RUT may protect liver and kidney tissues from the destructive effect of MLT by showing anti-inflammatory, anti-apoptotic, and anti-autophagic properties. Thus, it was determined that ALT, AST, urea, and creatinine levels decreased after RUT treatment. As a result, it was observed that MLT had a toxic effect on the liver and kidney tissues of rats, and it was determined that this toxicity could be alleviated by RUT treatment.

Bioaccumulation, metabolism and toxicological effects of chiral insecticide malathion and its metabolites in zebrafish (Danio rerio)

The bioaccumulation, metabolism, tissue-specific distribution and toxicity of the widely used organophosphorous pesticide malathion to zebrafish were investigated on an enantiomeric level for evaluating the environmental risks. The metabolites were also monitored and evaluated. Malathion was metabolized by zebrafish very fast with the half-life of 0.12 d and showed a middle accumulation capacity in zebrafish with bioaccumulation factor (BCF) of 12.9 after a 15-d exposure. Brain could enrich higher concentration of malathion than other tissues. The metabolites malaoxon, malathion/malaoxon monocarboxylic acid (DMA), malathion/malaoxon dicarboxylic acid (DCA), dimethylthiophosphate (DMTP) and dimethyldithiophosphate (DMDTP) were found, in which DMTP and DCA were in higher level, indicating the metabolism was mainly induced by carboxylesterase degradation. The accumulation of malathion and malaoxon was stereoselective in zebrafish tissues, exhibiting S-enantiomer preferentially enriched. The acute toxicity test showed rac-malathion was low toxic to zebrafish, which was 1.2 and 1.6 folds more toxic than S-malathion and R-malathion respectively. Malaoxon was highly toxic to zebrafish and approximately 32 times more toxic than malathion. The toxicity of other metabolites was lower than malathion. Malathion could cause an apparent developmental toxicity to zebrafish embryo, including bradycardia, hatchability reduction and deformity, and abnormal movement patterns in zebrafish larva. Chronic toxicity indicated that malathion and malaoxon induced oxidative damage and neurotoxicity in the liver, brain and gill of zebrafish, and malaoxon exhibited a relatively high injury to the zebrafish brain. The results can provide information for the comprehensive assessment of the potential risk of malathion to aquatic organisms and highlight the necessity of consideration of stereoselectivity and metabolites when systemically evaluating pesticides.

Theoretical evaluation of the malathion and its chemical derivatives interaction with cytosolic phospholipase A2 from zebrafish

Cytosolic phospholipase A2 (cPLA2) belongs to a large family of proteins and plays a crucial role in the regulation of arachidonic acid metabolism and inflammation cascade in zebrafish (Danio rerio). This enzyme with a molecular weight of 85 kDa, has two distinct domains. One is the regulatory and calcium-dependent (Ca²⁺) domain called C2, the other is the catalytic α/β hydrolase Ca²⁺-independent domain, where serine and aspartic acid catalytic dyad residues are present. We investigated the interaction of malathion and their organophosphate metabolites in the cPLA2 using in silico tools. Molecular docking results showed hydrophobic interactions with the paraoxon and catalytic site residue (Ser 223). Malathion increases intracellular Ca²⁺ due to endoplasmic reticulum influx which in turn activities phospholipase A2 and arachidonic acid release. Molecular docking and homology modelling of proteins and ligands could be a complementary tool for ecotoxicology and environment pollution assessment.

Preconception exposure to malathion and glucose homeostasis in rats: Effects on dams during pregnancy and post-term periods, and on their progeny

Understanding the individual and global impact of pesticides on human physiology and the different stages of life is still a challenge in environmental health. We analyzed here whether administration of the organophosphate insecticide malathion before pregnancy could affect glucose homeostasis during pregnancy and, in addition, generate possible later consequences in mothers and offspring. For this, adult Wistar rats were allocated into two groups and were treated daily (intragastric) with malathion (14 or 140 mg/kg, body mass (bm)) for 21-25 days. Corn oil was used as vehicle in the Control group. Subgroups were defined based on the absence (nulliparous) or presence (pregnant) of a copulatory plug. Pregnant rats were followed by an additional period of 2 months after the term (post-term), without continuing malathion treatment. Fetuses and adult offspring of males and females were also evaluated. We ran an additional experimental design with rats exposed to malathion before pregnancy at a dose of 0.1 mg/kg bm. Malathion exposure resulted in glucose intolerance in the mothers during pregnancy and post-term period, regardless of the exposure dose. This was accompanied by increased visceral adipose tissue mass, dyslipidemia, unchanged pancreatic β-cell mass, and varying insulin responses to glucose in vivo. The number of total newborns and birthweight was not affected by malathion exposure. Adult offspring from both sexes also became glucose-intolerant, regardless of the pesticide dose their dams were exposed to. This alteration could be associated with changes at the epigenomic level, as reduced hepatic mRNA content of DNA methylases and demethylases was found. We demonstrated that periconceptional exposure to malathion with doses aiming to mimic from work environment to indirect contamination predisposes progenitors and offspring rats to glucose intolerance. Thus, we conclude that subchronic exposure to malathion is a risk factor for gestational diabetes and prediabetes later in life.

Effect of probiotics on glucose levels and weight gain in mice exposed to low doses of malathion

INTRODUCTION

Owing to its ability to reduce the toxicity of environmental pollutants that are risk factors for diabetes and obesity, the use of probiotic bacteria might aid the treatment of these diseases.

OBJECTIVE

To determine the effects of chronic exposure to low-dose malathion on weight and glucose levels in mice, as well as to evaluate the protective role of a probiotic supplement.

METHODS

Weight and serum glucose levels of four groups of mice (control, malathion-exposed [10 ppm], probiotics and malathion + probiotics) were determined every 10 days for 180 days.

RESULTS

Malathion administration induced an increase in weight and glucose levels in the malathion group mice in comparison with the other groups.

CONCLUSIONS

Consumption of food contaminated with malathion residues increases glucose levels and favors weight gain, while consumption of probiotics reduces the effects generated by residues in food.

Physiological selectivity and tolerance of social wasps exposed to Malathion

Insect pest infestations are a worldwide problem as a result of human actions. Among them, Aedes aegypti stands out as vector of several diseases. Like other pests, A. aegypti has become resistant to the insecticide used for its control, thus harming the local fauna of non-target insects. Therefore, the aim of this study was to study the physiological selectivity of social wasps exposed to Malathion, as well as to investigate possible resistance to this insecticide. Adults of the swarming species Polybia platycephala and Protopolybia sedula and the independent species Polistes versicolor were exposed to four Malathion concentrations. Overall, Malathion was more selective to P. versicolor and more toxic to P. platycephala, and despite the decrease in the concentration of the product recommended by the manufacturer, which in theory would be sublethal doses, social wasps still exhibited high mortality rates. In comparing the mortalities of species collected in an area where there is no application of the insecticide with an area where there is regular application, the data showed an indication that populations of non-target insects are also becoming resistant to insecticides, especially in urban environments.

Photocatalytic activity of graphene oxide-TiO2 nanocomposite on dichlorvos and malathion and assessment of toxicity changes due to photodegradation

Heterogeneous photocatalysis was used for the removal of two widely used organophosphorus pesticides, dichlorvos, and malathion from water. Graphene oxide-TiO₂ nanocomposite (GOT) was synthesized and used as a photocatalyst for the removal of these pesticides. Batch studies for optimizing photocatalytic degradation and mineralization of pesticides over 80 min were conducted by varying the pH (2-10), catalyst dose (20 mg/L-200 mg/L), and initial pesticide concentration (0.5 mg/L-20 mg/L), and the irradiation source (125 W UV and visible lamp). Degradation kinetics for the pesticides were evaluated. Ellman assay was used to estimate the toxic effect of pesticides and evaluate toxicity reduction due to treatment. The highest degradation and mineralization of dichlorvos and malathion was observed at pH 6 and the optimum catalyst dose was 60 mg/L. Under UV irradiation, 80% and 90% degradation were observed for dichlorvos and malathion, respectively for 0.5 mg/L initial pesticide concentration. The photocatalytic degradation reaction followed Langmuir-Hinshelwood kinetics. A high degree of mineralization was achieved for both the pesticides. Analysis of the results revealed that the residual toxic effect after photocatalysis was primarily due to the residual parent compound. A comparative study revealed that GOT yielded better pesticide degradation compared to commercially available TiO₂ under both UV and visible irradiation.

Discovery of malathion resistance QTL in Drosophila melanogaster using a bulked phenotyping approach

Drosophila melanogaster has proved an effective system with which to understand the evolutionary genetics and molecular mechanisms of insecticide resistance. Insecticide use has left signatures of selection in the fly genome, and both functional and quantitative genetic studies in the system have identified genes and variants associated with resistance. Here, we use D. melanogaster and leverage a bulk phenotyping and pooled sequencing "extreme quantitative trait loci" approach to genetically dissect variation in resistance to malathion, an organophosphate insecticide. We resolve 2 quantitative trait loci, one of which implicates allelic variation at the cytochrome P450 gene Cyp6g1, a strong candidate based on previous work. The second shows no overlap with hits from a previous genome-wide association study for malathion resistance, recapitulating other studies showing that different strategies for complex trait dissection in flies can yield apparently different architectures. Notably, we see no genetic signal at the Ace gene. Ace encodes the target of organophosphate insecticide inhibition, and genome-wide association studies have identified strong Ace-linked associations with resistance in flies. The absence of quantitative trait locus implicating Ace here is most likely because our mapping population does not segregate for several of the known functional polymorphisms impacting resistance at Ace, perhaps because our population is derived from flies collected prior to the widespread use of organophosphate insecticides. Our fundamental approach can be an efficient, powerful strategy to dissect genetic variation in resistance traits. Nonetheless, studies seeking to interrogate contemporary insecticide resistance variation may benefit from deriving mapping populations from more recently collected strains.

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.

Identification of two ABCC transporters involved in malathion detoxification in the red flour beetle, Tribolium castaneum

ABC transporters have been suggested to be involved in insecticide detoxification in different insect species mainly based on the indirect observation of transcriptional upregulation of ABC gene expression in response to insecticide exposure. Previous studies performed by us and others in the red flour beetle, Tribolium castaneum, have analyzed the function of TcABCA-C and TcABCG-H genes using RNA interference (RNAi) and demonstrated that specific TcABCA and TcABCC genes are involved in the elimination of the pyrethroid tefluthrin and the benzoylurea diflubenzuron, because gene silencing increased the beetle's susceptibility to the insecticides. In this study, we focused on the potential functions of TcABCA-C genes in detoxification of the pyrethroid cyfluthrin (CF), the organophosphate malathion (MAL) and the diacylhdyazine tebufenozide (TBF). Analysis of transcript levels of selected TcABCA-C genes in response to treatment with these three chemically unrelated insecticides revealed that some genes were particularly upregulated after insecticide treatment. In addition, the ABC inhibitor verapamil synergized significantly the toxicity of MAL but only negligibly CF and TBF toxicities. Finally, silencing of two TcABCC genes by RNAi revealed a significant increase in susceptibility to MAL. In contrast, we did not observe a significant increase in insecticide-induced mortalities when knocking down TcABC genes in larvae treated with CF or TBF, although they were upregulated in response to insecticide treatment. Our results suggest that two pleiotropic ABCC transporters expressed in metabolic and excretory tissues contribute to the elimination of MAL.

Rifaximin Protects against Malathion-Induced Rat Testicular Toxicity: A Possible Clue on Modulating Gut Microbiome and Inhibition of Oxidative Stress by Mitophagy

Testicular dysfunction is caused by chronic exposure to environmental pollution, such as malathion, which causes oxidative stress, promoting cell damage. Autophagy is a key cellular process for eliminating malfunctioning organelles, such as the mitochondria (mitophagy), an eminent source of reactive oxygen species (ROS). Autophagy is crucial for protection against testicular damage. Rifaximin (RFX) is a non-absorbable antibiotic that can reshape the gut microbiome, making it effective in different gastrointestinal disorders. Interestingly, the gut microbiome produces short chain fatty acids (SCFAs) in the circulation, which act as signal molecules to regulate the autophagy. In this study, we investigated the regulatory effects of RFX on gut microbiota and its circulating metabolites SCFA and linked them with the autophagy in testicular tissues in response to malathion administration. Moreover, we divided the groups of rats that used malathion and RFX into a two-week group to investigate the mitophagy process and a four-week group to study mitochondriogenesis. The current study revealed that after two weeks of cotreatment with RFX, apoptosis was inhibited, oxidative stress was improved, and autophagy was induced. More specifically, PINK1 was overexpressed, identifying mitophagy activation. After four weeks of cotreatment with RFX, there was an increase in acetate and propionate-producing microflora, as well as the circulating levels of SCFAs. In accordance with this, the expression of PGC-1α, a downstream to SCFAs action on their receptors, was activated. PGC-1α is an upstream activator of mitophagy and mitochondriogenesis. In this sense, the protein expression of TFAM, which regulates the mitochondrial genome, was upregulated along with a significant decrease in apoptosis and oxidative stress. Conclusion: we found that RFX has a positive regulatory effect on mitophagy and mitochondria biogenesis, which could explain the novel role played by RFX in preventing the adverse effects of malathion on testicular tissue.

Risk assessment of glyphosate and malathion pollution and their potential impact on Oreochromis niloticus: role of organic selenium supplementation

A field survey was conducted on five fish farms to trace glyphosate and malathion pollution with some physicochemical parameters. A precise half-life time, LC50-96h, of these agrochemicals on Oreochromis niloticus, as well as chronic exposure with organic selenium (OS) supplementation, were experimentally investigated. Oreochromis niloticus was subjected to the following: (negative control); (2 mg L-1 glyphosate); (0.5 mg L-1 malathion); (glyphosate 1.6 mg L-1 and 0.3 mg L-1 malathion); (glyphosate 2 mg L-1 and OS 0.8 g kg-1 diet); (malathion 0.5 mg L-1 and OS 0.8 g kg-1 diet) and (glyphosate 1.6 mg L-1; malathion 0.3 mg L-1 and OS 0.8 g kg-1 diet). Furthermore, data from the analyzed pond revealed a medium risk quotient (RQ) for both agrochemicals. The detected agrochemicals were related to their application, and vegetation type surrounding the farms, also their biodegradation was correlated to water pH, temperature, and salinity. Glyphosate and malathion had half-lives of 2.8 and 2.3 days and LC50-96h of 2.331 and 0.738 mg L-1, respectively. The severest nervous symptoms; increased oxidative stress markers, as well as high bacterial count in the livers and kidneys of fish challenged with Aeromonas hydrophila, were observed in the combined exposure, followed by a single exposure to malathion and then glyphosate. Organic selenium mitigated these impacts.

Inhibition of Oocyte Maturation by Malathion and Structurally Related Chemicals in Zebrafish (Danio rerio) After In Vitro and In Vivo Exposure

Oogenesis is the process by which a primary oocyte develops into a fertilizable oocyte, making it critical to successful reproduction in fish. In zebrafish (Danio rerio), there are five stages of oogenesis. During the final step (oocyte maturation), the maturation-inducing hormone 17α,20β-dihydroxy-4-pregnen-3-one (MIH) activates the membrane progestin receptor, inducing germinal vesicle breakdown. Using in vitro assays, it has been shown that anthropogenic stressors can dysregulate MIH-induced oocyte maturation. However, it is unknown whether the in vitro assay is predictive of reproductive performance after in vivo exposure. We demonstrate that a known inhibitor of oocyte maturation, malathion, and a structurally related chemical, dimethoate, inhibit oocyte maturation. However, malaoxon and omethoate, which are metabolites of malathion and dimethoate, did not inhibit oocyte maturation. Malathion and dimethoate inhibited maturation to a similar magnitude when oocytes were exposed for 4 h in vitro or 10 days in vivo, suggesting that the in vitro zebrafish oocyte maturation assay might be predictive of alterations to reproductive performance. However, when adult zebrafish were exposed to malathion for 21 days, there was no alteration in fecundity or fertility in comparison with control fish. Our study supports the oocyte maturation assay as being predictive of the success of in vitro oocyte maturation after in vivo exposure, but it remains unclear whether inhibition of MIH-induced oocyte maturation in vitro correlates to decreases in reproductive performance. Environ Toxicol Chem 2022;41:1381-1389. © 2022 SETAC.

Effect of Malathion on the Development of Megaselia scalaris (Loew, 1866) (Diptera: Phoridae), a Forensically Important Fly

Malathion is a widely used organophosphorus pesticide; it is also a molecule of forensic interest due to its moderate to high toxicity in nontarget organisms, humans included. This compound is present in some fatal intoxications, accidental or intentional; its presence in the tissues on which the cadaveric entomofauna feeds may affect its growth rate and life cycle duration leading to an error in the estimation of the minimum postmortem interval (PMImin). Since the toxic effect of malathion on the cadaveric entomofauna could affect the estimation of the PMImin, the aim of this work was to study the toxic effect of malathion on the growth and development of the scuttle fly, Megaselia scalaris, a fly of forensic interest which plays an important role in forensics cases related to human remains found indoors or in concealed environments. The study was complemented with some morphological observations; no morphological changes were observed in the larvae, nor the adult flies exposed to malathion. Malathion affects the viability of the egg and pupa, it also reduces the larval growth rate and increases the duration of the larval stage; therefore, the estimation of the PMImin, with this species when malathion is present in tissues, could be affected.

Ameliorative effect of selenium yeast supplementation on the physio-pathological impacts of chronic exposure to glyphosate and or malathion in Oreochromis niloticus

BACKGROUND

Pesticide exposure is thought to be a major contributor to living organism health deterioration, as evidenced by its impact on both cultured fish species and human health. Commercial fish diets are typically deficient in selenium (Se); hence, supplementation may be necessary to meet requirements during stress. Therefore, this study was conducted to investigate the protective role of selenium yeast (SY) supplementation for 60 days against the deleterious effects of glyphosate and or malathion chronic toxicity at sublethal concentrations in Oreochromis niloticus .

METHODS

Two hundred and ten fish were divided into seven groups (n = 30/group) as follows: G1 (negative control); G2 (2 mg L- 1 glyphosate); G3 (0.5 mg L- 1 malathion); G4 (glyphosate 1.6 mg L- 1 and malathion 0.3 mg L- 1); G5 (glyphosate 2 mg L- 1 and SY 3.3 mg kg- 1); G6 (malathion 0.5 mg L- 1 and SY 3.3 mg kg- 1); and G7 (glyphosate 1.6 mg L- 1; malathion 0.3 mg L- 1 and SY 3.3 mg kg- 1).

RESULTS

Results revealed significant alteration in growth performance parameters including feed intake (FI), body weight (BW), body weight gain (BWG), specific growth rate (SGR), feed conversion ratio (FCR), and protein efficiency ratio (PER). G4 has the highest documented cumulative mortalities (40%), followed by G3 (30%). Additionally, the greatest impact was documented in G4, followed by G3 and then G2 as severe anemia with significant thrombocytopenia; leukocytosis; hypoproteinemia; increased Alanine aminotransferase (ALT) and Aspartate aminotransferase (AST), urea, and creatinine, as well as malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GPx). Considering the previously mentioned parameters, selenium yeast (Saccharomyces cerevisiae) (3.3 mg kg- 1 available selenium) mitigated the negative impact of both the agrochemicals, whether exposed singly or in combination, in addition to their antioxidative action.

CONCLUSIONS

In conclusion, our study found that organophosphorus agrochemicals, single or combined, had negative impacts on Oreochromis niloticus regarding growth performance, biochemical and hematological changes in the serum, as well as induced oxidative damage in liver and kidney tissues. Supplementation of SY at the rate of 3.3 mg kg- 1 diet (2.36 mg kg- 1 selenomethionine and 0.94 mg organic selenium) ameliorated the fish performance and health status adversely affected by organophosphorus agrochemical intoxication.

A global systematic review of the concentrations of Malathion in water matrices: Meta-analysis, and probabilistic risk assessment

Pesticide applications and the proximity of land use to water matrices have resulted in discharges of pollutants including Malathion -one of the most widely used organophosphorus pesticides- to water resources such as marine, freshwater, and under groundwater. Exposure to malathion through consumption of contaminated water may cause deleterious health effects on consumers. Determining the amount of pesticides used on farms can play an important role in preventing potential toxicity and pollution of nearby aquatic ecosystems. Therefore, this systematic review and meta-analysis is focused on evaluating the concentrations of Malathion in water resources while considering probabilistic health risk assessment. The international databases of Scopus, Embase, and PubMed were investigated to evaluate the related articles from January 01, 1968 to March 25, 2021. Thirty-four articles containing 206 samples from 15 countries were included. A meta-analysis of carcinogenic and non-carcinogenic risk assessments for Malathion was also performed. To determine uncertainty intervals, a Monte-Carlo simulation was conducted. The results of the meta-analysis showed that the rankings of Malathion pollution (from the most to the least) were: drinking water > surface waters > groundwaters. Moreover, the results of the risk assessments confirm that there is no non-carcinogenic risk for any of the study areas. The carcinogenic risk assessment was within the limit for the countries under this study, except for Ethiopia that was slightly over the limit as well as Iran, and Mexico had high carcinogenic risk.

Decontamination of toxic Malathion pesticide in aqueous solutions by Fenton-based processes: Degradation pathway, toxicity assessment and health risk assessment

This study evaluates the degradation efficiency of Malathion using Fenton (Fe²⁺/H₂O₂: F), photo-Fenton (UV/Fe²⁺/H₂O₂: PF), and sono-photo Fenton (US/UV/Fe²⁺/H₂O₂: SPF) processes as well as determines the toxicity of the byproducts of degradation. The effect of various operational parameters on the Malathion degradation rate, including pH, Fe²⁺ concentration, Malathion concentration, and H₂O₂ were studied. The removal efficiency was determined to be 98.79% for the SPF, > 70.92% for the PF, and > 55.94% for the F processes under the following optimal conditions: pH = 3, [H₂O₂]₀ = 700 mg/L, [Fe²⁺]₀ = 20 mg/L, and [Malathion]₀ = 20 mg/L. The operating costs (USD/kg_{Malathion-removed}) were acquired as SPF > PF > F. Moreover, Malaoxon, diethyl maleate, diethyl malate, ethyl 2-hydroxysuccinate, and D-malate were among the detected byproducts from the Malathion degradation in the SPF process. Both the non-carcinogenic risk and the carcinogenic risk were assessed to establish the quality of the effluent from all three processes. The toxicity of the treated effluents, determined by Vibrio fischeri luminescence, indicated that the toxicity depends on the selected treatment process. The high degradation efficiency of the Fenton-based processes is not equivalent to achieving detoxification of the effluents. As such, the SPF process was determined to be the most effective for the Malathion degradation, total organic carbon (TOC) removal, and health risk assessment.

The synergistic effect of microplastic and malathion exposure on fiddler crab Minuca ecuadoriensis microplastic bioaccumulation and survival

We assessed the combined effects of polyethylene microplastic (MP) and malathion (MLT) on the survival of the fiddler crab Minuca ecuadoriensis, and MP tissue bioaccumulation in four treatments following 120 h exposure: T1) Control; T2) MLT 50 mg L^-1; T3) MP 200 mg L^-1; and T4) MLT (50 mg L^-1) + MP (200 mg L^-1). The highest mortality (80%) was in T4, followed by T2 (28%) and no mortality was in T3. Higher MP bioaccumulation was observed in T4 (572 items g tissue^-1) followed by T3 (70 items g tissue^-1). Our findings indicate that the synergistic effect of MLT and MP increased M. ecuadoriensis bioaccumulative capacity and decreases survival. Thus, as MP contamination in aquatic environments is ubiquitous, our study raises a warning on the synergistic effects of MP with other environmental contaminants and serves as a baseline for further studies.

Vitamin B6 prevents Isocarbophos-induced posterior cerebral artery injury in offspring rats through up-regulating S1P receptor expression

We have previously reported that the long-term exposure of Isocarbophos, a kind of organophosphorus compounds, induces vascular dementia (VD) in rats. Studies have also shown that organophosphorus compounds have adverse effects on offsprings. Vitamin B6 is a coenzyme mainly involved in the regulation of metabolism and has been demonstrated to ameliorate VD. Sphingosine-1-phosphate (S1P), a biologically active lipid, plays a vital role in the cardiovascular system. However, whether S1P is involved in the therapeutic effects of Vitamin B6 on posterior cerebral artery injury has yet to be further answered. In the present study, we aimed to explore the potential influence of Vitamin B6 on Isocarbophos-induced posterior cerebral artery injury in offspring rats and the role of the S1P receptor in this process. We found that Vitamin B6 significantly improves the vasoconstriction function of the posterior cerebral artery in rats induced by Isocarbophos by the blood gas analysis and endothelium-dependent relaxation function assay. We further demonstrated that Vitamin B6 alleviates the Isocarbophos-induced elevation of ICAM-1, VCAM-1, IL-1, and IL-6 by using the enzyme-linked immunosorbent assay kits. By performing immunofluorescence and the western blot assay, we revealed that Vitamin B6 prevents the down-regulation of S1P in posterior cerebral artery injury. It is worth noting that Fingolimod, the S1P inhibitor, significantly inhibits the Vitamin B6-induced up-regulation of S1P in posterior cerebral artery injury. Collectively, our data indicate that Vitamin B6 may be a novel drug for the treatment of posterior cerebral artery injury and that S1P may be a drug target for its treatment.

Temporal exposure to malathion: Biochemical changes in the Amazonian fish tambaqui, Colossoma macropomum

The main toxicity mechanism of organophosphate insecticides such as malathion is the acetylcholinesterase enzyme inhibition. However, fish responses to organophosphates may vary depending on the activation of different defense mechanisms as well as the length of exposure. As such, the evaluation of acetylcholinesterase activity, in combination with the evaluation of biotransformation and antioxidants enzymes levels, is useful for indicating damage in fish exposed to this insecticide. Moreover, evaluating mitochondrial activity might evidence how the hierarchic responses occur in relation to the length of time that the fish is exposed. Therefore, the aim of our study is to evaluate whether the length of exposure to malathion differentially affects the biochemical responses of tambaqui. Our hypothesis is that the physiological alterations due to exposure are time dependent. Fish were exposed to sublethal concentrations of the insecticide during 6, 12, 24, 36, and 48 h. Contrary to expectations, there was no acetylcholinesterase activity inhibition during the experiment, which indicates an absence of neurotoxicity. Phase II biotransformation mechanism was activated early, especially in the liver. Oxidative damage was evident in the first hours of exposure and was concurrent with the activation of antioxidant enzymes. Mitochondrial bioenergetics were differentially affected by the length of exposure. The data suggest that the tambaqui regulates mitochondrial respiration differently over time, seeking to maintain homeostasis and ATP demand, and ensures the activation of response mechanisms, thus minimizing oxidative damage and avoiding the neurotoxicity of malathion.

Investigating the Effects of Pesticides on Ramshorn Snails (Planorbella [Helisoma] trivolvis) Infected with Echinostoma spp

Globally, parasite-induced diseases in humans and wildlife are on the rise, and pesticide pollution may be a contributing factor. Echinostoma spp. trematode parasites are prominent in North America, and they use ramshorn snails (Planorbella [Helisoma] trivolvis) as intermediate hosts. We investigated the impact of chronic exposure to 1 of 5 pesticide treatments (control, or 50 μg/L of atrazine, glyphosate, carbaryl, or malathion) on uninfected and Echinostoma-infected snails for 41 d in the laboratory. We recorded snail mortality, the number of egg masses laid, change in mass, and behavior. Chronic exposure to atrazine, carbaryl, and malathion significantly decreased snail survival, whereas parasite infection status or exposure to glyphosate did not. Pesticide and parasite treatments did not influence growth or behavior, but parasite infection caused complete reproductive failure in snail hosts. Our results indicated that the direct effects of pesticides could threaten snail populations in natural environments and disrupt host-parasite dynamics.  Environ Toxicol Chem 2021;40:2755-2763. © 2021 SETAC.

Toxicity of malathion during Senegalese sole, Solea senegalensis larval development and metamorphosis: Histopathological disorders and effects on type B esterases and CYP1A enzymatic systems

The toxicity of malathion to Solea senegalensis was studied in a static renewal bioassay during its first month of larval life (between 4 and 30 dph). Through the use of different biomarkers and biochemical, cellular and molecular approaches (inhibition of cholinesterases [ChEs], changes in cytochrome P450-1A [CYP1A] and the study of histopathological alterations), the effects of three concentrations of malathion (1.56, 3.12, and 6.25 μg/L) have been analyzed. In subacute exposure, malathion inhibited cholinesterase activities (AChE, BChE, CbE) in a dose- and time-dependent manner, ranging the inhibition percentage from 20% to 90%. However, the expression levels of CYP1A and AChE transcripts or proteins were not modified. Additionally, exposure to malathion provoked histopathological alterations in several organ systems of Senegalese sole in a time- and dose dependent way, namely disruption of parenchymal architecture in the liver, epithelial desquamation, pyknotic nuclei and steatosis in the intestine, disorganization of supporting cartilage, and sings of hyperplasia and hypertrophy in the gills and degeneration of the epithelial cells from the renal tubules. Malathion exposure also provoked strong disorganization of cardiac fibers from the heart. The findings provide evidence that exposure to sublethal concentrations of malathion that provoked serious injury to the fish S. senegalensis, were below the expected environmental concentrations reported in many other ecosystems and different fish species,revealing a higher sensitivity for Solea senegalensis to malathion exposure, thus reinforcing its use as sentinel species for environmental pollution in coastal and estuarine environments.

Sub-organism (acetylcholinesterase activity), population (survival) and chemical concentration responses reinforce mechanisms of antagonism associated with malathion toxicity

Within human modified ecosystems the effects of individual stressors are difficult to establish amid co-occurring biological processes, environmental gradients and other stressors. Coupled examination of several endpoints across different levels of organisation may help elucidate the individual and combined effects of stressors and interactions. Malathion is a commonly used organophosphate pesticide that contaminates freshwaters and has strong negative effects on aquatic biota. However, both other stressors (e.g. increased sediment) and common ecosystem components (e.g. macrophytes and variable pH) can reduce the aqueous concentrations of malathion, reducing its toxic effects. We conducted a fully orthogonal bioassay to examine how pH (at 7 and 7.8) and sorptive processes (across two levels of kaoline clay 0 and 24 g L^-1) affected aqueous malathion concentrations and toxicity in an aquatic invertebrate genus. Survival and acetylcholinesterase activity as a sub-organism response were examined in the mayfly Coloburiscoides spp. (Ephemeroptera; Coluburiscidae). Measured aqueous malathion concentrations decreased with increased pH and in the presence of kaolin clay. Survival declined with increasing malathion concentrations and exposure period. Results further identify that antagonism of malathion toxicity was associated with both pH (alkaline hydrolysis) and effects associated with sediment independent of pH (driven by sorptive processes). However, model predictions varied associated with target and measured concentrations and concentrations examined. Antagonistic effects were most apparent using subset target malathion concentrations because of the dominant effect of malathion at high concentrations. Acetylcholinesterase activity, identified repression occurred across all treatments and did not identify antagonistic interactions, but these results were similar to survival responses at the time points examined (i.e. 120 h). Examination of chemistry, acetylcholinesterase, and survival, affords greater understanding of stressor effects and their interactions. Measured malathion concentrations may underestimate effects on aquatic biota; not because of synergism among stressors, but because of strong effects despite antagonism.

Molecular and biochemical evaluation of effects of malathion, phenanthrene and cadmium on Chironomus sancticaroli (Diptera: Chironomidae) larvae

In-vitro effects of sub-lethal concentrations of malathion, phenanthrene (Phe) and cadmium (Cd) were tested on Chironomus sancticaroli larvae in acute bioassays by measuring biochemical and molecular parameters. Malathion was evaluated at 0.001, 0.0564 and 0.1006 mg L^-1; Phe at 0.0025, 1.25 and 2.44 mg L^-1; and Cd at 0.001, 3.2 and 7.4 mg L^-1. The recovery test carried out at the highest concentration of each compound showed that survival of larvae exposed to Phe ranged from 4% to 5%, while the effects of malathion and Cd were irreversible, not allowing the emergence of adults. Results showed that malathion and Cd inhibited AChE, EST-α and ES-β activities at the two highest concentrations. Phe at 0.0025, 1.25 and 2.44 mg L^-1; and Cd at 3.2 and 7.4 mg L^-1 inhibited glutathione S-transferase activity. Oxidative stress was exclusively induced by the lowest concentration of malathion considering SOD activity once CAT was unaffected by the stressors. Lipid peroxidation was registered exclusively by malathion at the two highest concentrations, and total hemoglobin content was only reduced by Cd at the two highest concentrations. The relationship among biochemical results, examined using the PCA, evidenced that malathion and Cd concentrations were clustered into two groups, while Phe only formed one group. Four hemoglobin genes of C. sancticaroli were tested for the first time in this species, with Hemoglobin-C being upregulated by malathion. The toxicity ranking was malathion > Phe > Cd, while biochemical and molecular results showed the order malathion > Cd > Phe. Our results highlight the importance of combining different markers to understand the effects of the diverse compounds in aquatic organisms.

Biochemical changes and antioxidant capacity of naringin and naringenin against malathion toxicity in Saccharomyces cerevisiae

Flavonoids are rich in seeds, citrus fruits, olive oil, tea and red wine. Citrus flavonoids constitute an important type of flavonoids. Naringin and naringenin belong to flavonoids with known antioxidant and were found to display antioxidant activities. Malathion is an organophosphorus pesticide that has been broadly used throughout the world to control weeds and pests. It has also been used in public health for mosquito control and fruit fly eradication programs. Malathion, naringin, and naringenin were added to be in 40, 80, and 160 mg doses in Saccharomyces cerevisiae cultures mainly used to determine the antioxidant capacity, it is known that they have shown similar results to man. At the end of the experiment, total protein, malondialdehyde (MDA), reduced glutathione (GSH), oxidized glutathione (GSSG), vitamin K, vitamin E, vitamin D, ergosterol, stigmasterol, β-Sitosterol, and fatty acids were analyzed by HPLC (high performance liquid chromatography) and GC (gas chromatography) devices in the tested S. cerevisiae samples. The contents of the yeast cell of octanoic acid (C8:0), lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), palmitoleic acid (C16:1n-7), heptadecanoic acid (C17:0), stearic acid (C18:0), oleic acid (C18:1n-9), and linoleic acid (C18:2n-6) were identified. There were statistically significant changes in total protein, MDA, GSH, GSSG, vitamin K, vitamin E, vitamin D, phytosterol and fatty acid levels. It was determined that naringin and naringenin showed statistically significant decreases against malathion toxicity on these parameters. From this study it is found that, the mitigating effect of naringin against DPPH stable free radical was higher than that of naringenin. Citrus flavonoid, naringin showed promising antioxidant activity which can be used as effective protecting agents against oxidative stress.

Combined endocrine disruptive toxicity of malathion and cypermethrin to gene transcription and hormones of the HPG axis of male zebrafish (Danio rerio)

Cypermethrin (CYP) and malathion (MAT) have been widely used and are frequently detected in surface waters. The purpose of the present study was to investigate the endocrine disrupting toxicity of CYP, MAT, and CYP + MAT to 5-month-old male zebrafish (Danio rerio). After exposure, the hepatosomatic index (HSI) and gonadosomatic index (GSI) did not change significantly. Following exposure to the combination of 0.1 μg/L CYP +25 μg/L MAT, the E2 and VTG levels of male zebrafish were significantly increased compared to those after individual pesticide treatments. The molecular level of the hypothalamic-pituitary-gonadal (HPG) axis in zebrafish was studied; it was found that the expression of the estrogen-related genes, especially the vtg1 gene, was significantly altered in 0.1 μg/L CYP + 25 μg/L MAT. Overall, our observation indicated that CYP or MAT could disturb the hormonal balance, and their combination of 0.1 μg/L CYP +25 μg/L MAT could significantly enhance the estrogenic effect.

Protective effect of Zataria multiflora Boiss. and its main compound, rosmarinic acid, against malathion induced oxidative stress and apoptosis in HepG2 cells

Malathion (MT) is one of the most widely used organophosphorus insecticides which induces toxicity through oxidative stress induction, free radical production and acetylcholinesterase inhibition. In this work, HepG2 cells were used to determine the effect of Zataria multiflora methanolic extract (MEZM) and rosmarinic acid (RA) on MT-induced cytotoxicity, oxidative stress, and apoptosis. Total phenolic content (TPC) and total flavonoid content (TFC) were determined and plant was further standardized based on RA content using HPLC method. The cultured HepG2 cells were pretreated with MEZM (1 μg/ml) and RA (0.1 μg/ml) for 4 h and exposed to MT (100 μM). Cell viability, oxidative stress biomarkers, ROS production, and cell death were examined after 24 h. The amount of RA was determined 73.48 mg/g dried extract. IC50 values of MEZM and MT were 368.56 μg/ml and 99.43 μM, respectively. Pretreatment with MEZM and RA decreased the cytotoxicity, oxidative stress, and cell percentage in the late apoptosis and necrosis stages induced by MT. There was no significant difference between MEZM and RA effects. The present study showed the significant protective effects of MEZM against toxicity induced by MT in hepatocytes which can be attributed to the plant antioxidant constituents including RA.

Carvacrol loaded beta cyclodextrin-alginate-chitosan based nanoflowers attenuates renal toxicity induced by malathion and parathion: A comparative toxicity

Most of approximately 1.8 billion people involved in agriculture protect their food products using pesticides especially insecticides which may remain in foods as pesticide residues. Among insecticides organophosphates such as malathion have been widely used around the world and others such as parathion has been restricted because of their toxicity. Carvacrol (CAR) is the main component of Satureja khuzestanica. Since chemical composition of foods can alter toxicity of pesticides, in this work, the effect of coadministration of CAR and organophosphates on renal function has been studied and compared with the effect of coadministration of carvacrol loaded beta cyclodextrin-alginate-chitosan (BAC) based nanoflowers. Serum levels of urea and creatinine and histological examination were analyzed after 10 days of administration of chemicals. Malathion and parathion significantly increased urea and creatinine and induced renal inflammation. However, coadministration of CAR or BAC-CAR modified urea and creatinine and improved renal inflammation. BAC-CAR modified serum levels of urea more efficient than CAR (P < 0.05). It is concluded that BAC could be considered as a carrier for drugs used to treat renal disorders. Carvacrol can be used in the formulation of organophosphate pesticides, which may control pests more efficiently than conventional organophosphate pesticides.

A fuzzy cognitive map approach to predict the hazardous effects of malathion to environment (air, water and soil)

Malathion is an organophosphorus insecticide and pesticide commonly used in crops and residential applications. The negative effects of Malathion on human health and ecosystems are of great concern. In this work, a mathematical model pivot on Fuzzy Cognitive Map (FCM) is used to analyse the causes and hazardous effects of Malathion to the environmental components (air, water and soil). Based on expert's opinion the possible factors that cause damage to health and ecosystems due to Malathion is identified, which serve as the input to the FCM. The FCM mathematically establishes the causal relation between these factors. The mathematical simulation is done by Python Programming. This approach can be used to study the interdependencies between the adverse effects of any pesticide in human health and environment due to prolonged exposure.

Severe damages caused by Malathion exposure in Colossoma macropomum

The increase in pesticide use in response to agricultural demands poses a risk to non-target organisms, including fish. Integrated analysis of biochemical, histopathological and genetic parameters in fish exposed to Malathion insecticide provide information on the toxicity mechanisms of this pesticide, which is classified as a probable carcinogen for humans. The present study assessed the biological responses of Colossoma macropomum after exposure to Malathion. We started determining the lethal concentration, which is the concentration capable of killing 50% of the subjects in an acute toxicity test (LC₅₀-96 h), which was 15.77 ± 3.30 mgL^-1. The fish were, then, exposed to Malathion during 96 h at a sublethal concentration, 7.30 mgL^-1. Overall, we observed an increased activity of biotransformation and antioxidant enzymes, which reduced production of mitochondrial reactive oxygen species after 96 h exposure, as well as kept constant the mitochondrial respiration, Acetylcholinesterase activity and DNA damage. However, fish exposed to insecticide presented severe gill histopathological damage and increased expression of proto-oncogene ras. Taken together, the results suggest that, after four days of exposure to the Malathion, C. macropomum efficiently activates its defense mechanisms, suggesting that the basal response mechanisms are responsive. On the other hand, histopathologic damages evidenced the adverse effects of Malathion on fish, since it promoted gill necrosis and increased the expression of ras oncogene that is directly related to tumorigenesis events.

Reduction of Pesticide Toxicity Under Field-Relevant Conditions? The Interaction of Titanium Dioxide Nanoparticles, Ultraviolet, and Natural Organic Matter

In surface waters, the illumination of photoactive engineered nanomaterials (ENMs) with ultraviolet (UV) light triggers the formation of reactive intermediates, consequently altering the ecotoxicological potential of co-occurring organic micropollutants including pesticides due to catalytic degradation. Simultaneously, omnipresent natural organic matter (NOM) adsorbs onto ENM surfaces, altering the ENM surface properties. Also, NOM absorbs light, reducing the photo(cata)lytic transformation of pesticides. Interactions between these environmental factors impact 1) directly the ecotoxicity of photoactive ENMs, and 2) indirectly the degradation of pesticides. We assessed the impact of field-relevant UV radiation (up to 2.6 W UVA/m²), NOM (4 mg TOC/L), and photoactive ENM (nTiO₂, 50 µg/L) on the acute toxicity of 6 pesticides in Daphnia magna. We selected azoxystrobin, dimethoate, malathion, parathion, permethrin, and pirimicarb because of their varying photo- and hydrolytic stabilities. Increasing UVA alone partially reduced pesticide toxicity, seemingly due to enhanced degradation. Even at 50 µg/L, nano-sized titanium dioxide (nTiO₂) reduced but also increased pesticide toxicity (depending on the applied pesticide), which is attributable to 1) more efficient degradation and potentially 2) photocatalytically induced formation of toxic by-products. Natural organic matter 1) partially reduced pesticide toxicity, not evidently accompanied by enhanced pesticide degradation, but also 2) inhibited pesticide degradation, effectively increasing the pesticide toxicity. Predicting the ecotoxicological potential of pesticides based on their interaction with UV light or interaction with NOM was hardly possible, which was even more difficult in the presence of nTiO₂. Environ Toxicol Chem 2020;39:2237-2246. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

miR-96-5p attenuates malathion-induced apoptosis of human kidney cells by targeting the ER stress marker DDIT3

Micro RNAs (miRNAs) are major players in cellular responses to xenobiotic compounds and toxins. However, their functions in organophosphate-induced cytotoxicity remain unclear. This study investigated the involvement of miR-96-5p in the non-cholinergic toxicity of malathion in normal human kidney cells (HK-2 cells). Malathion decreased HK-2 cell viability and the expression of miR-96-5p in a dose- and time-dependent manner. In addition, transfection with miR-96-5p mimics attenuated malathion-induced HK-2 cell apoptosis, whereas transfection with a miR-96-5p inhibitor increased HK-2 cell apoptosis. Luciferase assays indicated that miR-96-5p could bind directly to the 3'-untranslated region of DDIT3, a well-known marker of endoplasmic reticulum stress. Further analyses of the expression of apoptosis-related genes and proteins indicated that miR-96-5p may function to reduce malathion-induced HK-2 cell apoptosis via regulation of the DDIT3/B-cell lymphoma (BCL)-2/caspase-3 signaling pathway. In summary, the results of the present study indicate that miR-96-5p protects HK-2 cells from malathion-induced ER stress-dependent apoptosis by targeting DDIT3.

Insecticide residue longevity for on-site screening of Drosophila suzukii (Matsumura) resistance

BACKGROUND

Preventative application of insecticides reduces marketable yield losses caused by Drosophila suzukii females that selectively lay eggs into ripe and ripening fruits. However, repeated applications of insecticides increase the risk of resistance development. It is therefore critical to test field-collected flies on-site to assess the level of sensitivity of D. suzukii to insecticides to monitor resistance, before it becomes a widespread issue. This requires that insecticide-treated vials be readily available to conduct bioassays. Thus, bioassays were conducted using malathion-, methomyl-, zeta-cypermethrin-, phosmet-, spinetoram- and spinosad-treated scintillation vials at 1 to 28 days after treatment to assess how residue age affects insecticide toxicity in scintillation vials. The impact of temperature on residue longevity was also assessed.

RESULTS

Insecticide-treated vials stored for 28 days provided reliable estimates of susceptibility of D. suzukii to some of the tested insecticides. The toxicity of malathion remained consistently high throughout the experiment followed by methomyl. However, toxicities of zeta-cypermethrin, phosmet were variable whereas those of the spinosyns declined relatively quickly. Overall, storage temperature did not affect the residual toxicity of most of the tested insecticides except zeta-cypermethrin.

CONCLUSION

These findings suggest that the toxicity of insecticide residues in treated vials remains active for ≤28 d for malathion and ≤21 and 28 days in methomyl-treated vials stored at 4 °C in Georgia and Michigan, respectively. However, the toxicities of spinosad, zeta-cypermethrin and phosmet were less consistent. Hence, vials treated with these insecticides should be freshly made to be effective for screening D. suzukii field populations for resistance. © 2020 Society of Chemical Industry.