Does oxidative stress contribute to toxicity in acute organophosphorus poisoning? - a systematic review of the evidence

Dichlorvos poisoning caused chicken cerebellar autophagy and changes of Caecal microflora

In order to explore the effects of acute dichlorvos exposure on cerebellar autophagy and cecal microbes in broilers and to analyze the relationship between autophagy-related genes and cecal microbes. Broilers were randomly divided into three groups (with 16 broilers in each group)and respectively given distilled water and dichlorvos (2.48 mg / kg, 11.3 mg / kg). The cecal contents and cerebellum samples were collected after poisoning symptoms of broilers, and the antioxidant indexes such as SOD and CAT in cerebellum were detected. Hematoxylin-eosin (HE) staining of cerebellum and cecum, and immunofluorescence sections of cerebellum LC3 were made. RT-PCR and western blot were used to detect the expression of oxidative stress and autophagy-related genes in cerebellar tissue. The cecal contents were analyzed by 16S rRNA high-throughput sequencing, and then the correlation between the expression of autophagy-related genes and the abundance of intestinal microbes was analyzed. It was concluded that dichlorvos exposure destroyed the normal morphological structure of the cerebellum and cecum in broilers, which induced oxidative stress and autophagy in the cerebellum of broilers, reduced the diversity of cecal microorganisms, and destroyed the steady state of the cecal microbial structure. In addition, The changes of mRNA expression of autophagy-related genes is related to some specific bacteria. In summary, this study found that dichlorone exposure can cause cerebellar oxidative stress and autophagy, and the mechanism of cerebellar injury in broilers is linked to cecal microbiota changes, potentially offering a new direction for researching dichlorone's pathogenic mechanism.

A review on oxidative stress in organophosphate-induced neurotoxicity

Acetylcholinesterase inhibition, the principal mechanism of acute organophosphorus compound toxicity, cannot explain neuropsychiatric symptoms occurring after exposure to low organophosphate concentrations causing no cholinergic symptoms. Organophosphate-triggered oxidative stress has increasingly come into focus, occurring when the action of reactive oxygen species, generated from free radicals, is not compensated by antioxidant free radical scavengers. Being nucleophilic, organophosphates can easily accept an electron, thereby generating free radicals. Organophosphates inhibit the antioxidant paraoxonase, and reactive oxygen species are produced during organophosphate metabolism. Organophosphates disrupt the function of mitochondria, the principal source of free radicals. Organophosphates also induce neuroinflammation, which generates reactive oxygen species, and reactive oxygen species in turn stimulate neuroinflammation. Markers of reactive oxygen species are elevated in vitro and in vivo after exposure to organophosphates and in individuals professionally exposed to organophosphates. This most probably contributes to the pathogenesis of the intermediate syndrome, chronic organophosphate-induced neuropsychiatric disorders and neurodegeneration occurring in patients after organophosphate exposure. Evidence for beneficial effects of antioxidants in organophosphate poisoning is discussed.

A randomized, clinical trial of intravenous N-acetylcysteine as an antioxidant therapy in acute organophosphorus pesticide poisoning

The incidence of acute organophosphate (OP) poisoning has steadily increased in developing countries. Many studies showed that oxidative stress could have a significant role in its mechanism. The current study aimed to evaluate the role of N acetylcysteine (NAC) as an antioxidant in acute OP poisoned. A randomized, controlled, parallel-group trial was conducted in the period from the beginning of January 2022 to the end of June 2022. The study included 56 acute OP poisoned patients admitted to the intensive care unit (ICU) at the Poison Control Center of Ain Shams University Hospitals within 6 h after the exposure. The patients were randomly allocated in two equal groups; group (A): received the standard treatment plus NAC in a total dose of 300 mg/kg administered intravenously (IV) while group (B) received the standard treatment. Then both groups were compared as regards clinical parameters, laboratory investigations, ECG, and outcomes. Baseline parameters were comparable between the groups. However, NAC treatment significantly elevated concentrations of both serum catalase and glutathione peroxidase levels at 24 h, it did not significantly affect the total dose of atropine required, duration of atropine and oximes treatment or need for mechanical ventilation, and length of hospital stay. Mortality was lower in the NAC group (2 out of 28) than the standard treatment-only group (5 out of 28) but the difference was not statistically significant. This trial found that NAC improved antioxidant enzyme levels including serum CAT and GPX but did not affect clinically relevant outcomes.

Acute Paraoxon-Induced Neurotoxicity in a Mouse Survival Model: Oxidative Stress, Dopaminergic System Alterations and Memory Deficits

The secondary neurotoxicity induced by severe organophosphorus (OP) poisoning, including paraoxon (POX), is associated with cognitive impairments in survivors, who, despite receiving appropriate emergency treatments, may still experience lasting neurological deficits. Thus, the present study provides a survival mouse model of acute and severe POX poisoning to examine secondary neurotoxicity. Swiss CD-1 male mice were injected with POX (4 mg/kg, s.c.) followed by atropine (4 mg/kg, i.p.), pralidoxime (2-PAM; Pyridine-2-aldoxime methochloride) (25 mg/kg, i.p., twice, 1 h apart) and diazepam (5 mg/kg, i.p.), resulting in a survival rate >90% and Racine score of 5-6. Our results demonstrated that the model showed increased lipid peroxidation, downregulation of antioxidant enzymes and astrogliosis in the mouse hippocampus (HP) and prefrontal cortex (PFC), brain areas involved in cognitive functions. Moreover, dopamine (DA) levels were reduced in the hp, but increased in the PFC. Furthermore, the survival mouse model of acute POX intoxication did not exhibit phenotypic manifestations of depression, anxiety or motor incoordination. However, our results demonstrated long-term recognition memory impairments, which are in accordance with the molecular and neurochemical effects observed. In conclusion, this mouse model can aid in researching POX exposure's effects on memory and developing potential countermeasures against the secondary neurotoxicity induced by severe OP poisoning.

L-carnitine: A novel approach in management of acute cholinesterase inhibitor insecticide poisoning

Cholinesterase inhibitors (ChEIs) insecticide poisoning is a serious global health concern that results in hundreds of thousands of fatalities each year. Although inhibition of the cholinesterase enzyme is the main mechanism of ChEI poisoning, oxidative stress is considered the mechanism underlying the related complications. The study aimed to assess the oxidative status of the patients with ChEI insecticide poisoning and the role of L-carnitine as adjuvant therapy in their management. Human studies on the efficacy and safety of L-carnitine in treating insecticide poisoning are limited despite its growing research interest as a safe antioxidant. This prospective study was conducted on eighty patients with acute ChEIs insecticide poisoning admitted to Alexandria Poison Center, Alexandria Main University Hospital, Egypt. Patients were allocated into two equal groups randomly. The L-carnitine (LC) group received the conventional treatment (atropine & toxogonin) and LC and the standard treatment (ST) group received the standard treatment only. Outcome measures were fatality rate, the total administered dose of atropine & toxogonin, length of hospital stay, and the requirement for ICU admission or mechanical ventilation. The study results revealed that malondialdehyde (MDA) significantly decreased in the LC group. Cholinesterase enzyme levels increased significantly after treatment in the LC group than in the ST group. The LC group needed lower dosages of atropine and toxogonin than the ST group. Also, the LC group showed no need for ICU admission or mechanical ventilation. The study concluded that LC can be considered a promising adjuvant antioxidant treatment in acute ChEIs pesticide poisoning.

N-acetylcysteine as a potentially safe adjuvant in the treatment of neurotoxicity due to pirimiphos-methyl poisoning

Exogenous, well-established antioxidant N-acetylcysteine can reduce or prevent the deleterious effects of pesticides. In this study, utilizing a mouse model of daily single dose of N-acetylcysteine administration, we investigated the impact of this adjuvant on the treatment with atropine and/or obidoxime as well as oxidative stress response in pyrimiphos-methyl-induced toxicity. We found that N-acetylcysteine significantly reduces the oxidative stress generated by pyrimiphos-methyl. The therapy consisting of atropine and/or obidoxime routinely used in organophosphorous insecticide poisonings, including pyrimiphos-methyl, had no effect on the antioxidant properties of N-acetylcysteine. Adjunctive treatment offered by N-acetylcysteine fills therapeutic gap and may provide the full potential against pyrimiphos-methyl-induced toxicity.

Exposure to pesticide components causes recurrent pregnancy loss by increasing placental oxidative stress and apoptosis: a case-control study

We investigated the plasma levels of pesticides components namely polychlorinated biphenyls (PCBs), dieldrin, dichlorodiphenyldichloroethylene (DDE), ethion, malathion, and chlorpyrifos in recurrent pregnancy loss (RPL) cases, and tested their associations with placental oxidative stress (OS) biomarkers [nitric oxide (NO.), thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH), and superoxide dismutase (SOD)] and with placental apoptotic/antiapoptotic indices (Bcl-2 and caspase-3), and evaluated their possible cut-off points to distinguish RPL cases. The study recruited 101 pregnant women divided into; G1 [n = 49, control, normal 1st-trimester pregnancy, normal obstetric history with at least one previous normal live birth], G2 [n = 26, cases with missed abortion (< 3 abortions) before 24 weeks of gestation], and G3 [n = 26, cases with missed abortion (≥ 3 abortions) before 24 weeks of gestation]. The plasma pesticide levels were analyzed by gas chromatography-mass spectrometry. Plasma human chorionic gonadotrophin (HCG), placental OS, Bcl-2, and caspase-3, were analyzed by their corresponding methods and kits. Plasma PCBs, DDE, dieldrin, and ethion levels were significantly higher in RPL cases than in normal pregnancies (p ≤ 0.001). These levels correlated positively with placental OS and apoptosis and negatively with plasma HCG levels. Also, these levels were reliable markers of risk to RPL. Malathion and chlorpyrifos were not detected in any of the study's participants. Pesticides may be risk factors in cases of spontaneous RPL cases. They are associated with an increasing placental OS and placental apoptosis. Specific measures should be taken to decrease maternal exposure to these pollutants' sources, especially in underdeveloped and developing countries.

Perigestational exposure of a combination of a high-fat diet and pesticide impacts the metabolic and microbiotic status of dams and pups; a preventive strategy based on prebiotics

PURPOSE

Metabolic changes during the perinatal period are known to promote obesity and type-2 diabetes in adulthood via perturbation of the microbiota. The risk factors for metabolic disorders include a high-fat diet (HFD) and exposure to pesticide residues. The objective of the present study was to evaluate the effects of perigestational exposure to a HFD and chlorpyrifos (CPF) on glycemia, lipid profiles, and microbial populations in Wistar dams and their female offspring. We also tested a preventive strategy based on treatment with the prebiotic inulin.

METHODS

From 4 months before gestation to the end of the lactation period, six groups of dams were exposed to either a standard diet, a HFD alone, CPF alone, a combination of a HFD and CPF, and/or inulin supplementation. All female offspring were fed a standard diet from weaning to adulthood. We measured the impacts of these exposures on glycemia, the lipid profile, and the microbiota (composition, metabolite production, and translocation into tissues).

RESULTS

HFD exposure and CPF + HFD co-exposure induced dysmetabolism and an imbalance in the gut flora in both the dams and the female offspring. Inulin mitigated the impact of exposure to a HFD alone but not that of CPF + HFD co-exposure.

CONCLUSION

Our results provide a better understanding of the complex interactions between environmental pollutants and diet in early life, including in the context of metabolic diseases.

The role of a combination of N-acetylcysteine and magnesium sulfate as adjuvants to standard therapy in acute organophosphate poisoning: A randomized controlled trial

Background

Mortality in acute organophosphate (OP) poisoning remains high despite current standard therapy with atropine and oximes. Due to dose-limiting side effects of atropine, novel therapies are targeting other putative mechanisms of injury, including oxidative damage, to reduce atropine dosage.

Objectives

N-acetylcysteine (NAC) and magnesium sulfate (MgSO₄) have different mechanisms of actions and should act synergistically in OP poisoning. In this study, we wanted to evaluate whether this novel combination, used as an adjuvant to standard care, could improve clinical outcomes.

Methods

The study was conducted in the Emergency Department and ICU of AIIMS Bhubaneswar (a tertiary care center and government teaching institute) between July 2019 and July 2021. Eighty-eight adult patients with history and clinical features of acute OP poisoning were randomly allocated (1:1) into two groups. The Study group received 600 mg NAC via nasogastric tube thrice daily for 3 days plus a single dose of 4 g Inj. MgSO₄ IV on first day and the Control group received suitably matched placebo (double-blinding) - in addition to standard care in both the groups. The primary outcome measure was to compare the total dose of Inj. Atropine required (cumulative over the entire treatment duration) between the control group and the study group receiving NAC and MgSO₄. The secondary outcome measures were lengths of ICU and hospital stays, need and duration of mechanical ventilation, the differences in BuChE activity, oxidative stress biomarkers - MDA and GSH levels, the incidences of adverse effects including delayed sequalae like intermediate syndrome and OPIDN, and comparison of mortality between the two groups.

Results

Data from 43 patients in Control and 42 patients in Study group was finally analyzed. The baseline parameters were comparable. Total atropine requirements were lower in the Study group [175.33 ± 81.25 mg (150.01-200.65)] compared to the Control [210.63 ± 102.29 mg (179.15-242.11)] [Mean ± SD (95% CI)], but was not statistically significant. No significant differences in any of the other clinical or biochemical parameters were noted.

Conclusion

The N-acetylcysteine and MgSO₄ combination as adjuvants failed to significantly reduce atropine requirements, ICU/hospital stay, mechanical ventilatory requirements, mortality and did not offer protection against oxidative damage.

Prediction of acute organophosphate poisoning severity using machine learning techniques

Poisoning with organophosphate compounds is a significant public health risk, especially in developing countries. Considering the importance of early and accurate prediction of organophosphate poisoning prognosis, the aim of this study was to develop a machine learning-based prediction model to predict the severity of organophosphate poisoning. The data of patients with organophosphate poisoning were retrospectively extracted and split into training and test sets in a ratio of 70:30. The feature selection was done by least absolute shrinkage and selection operator method. Selected features were fed into five machine learning techniques, including Histogram Boosting Gradient, eXtreme Gradient Boosting, K-Nearest Neighborhood, Support Vector Machine (SVM) (kernel = linear), and Random Forest. The Scikit-learn library in Python programming language was used to implement the models. Finally, the performance of developed models was measured using ten-fold cross-validation methods and some evaluation criteria with 95 % confidence intervals. A total of 1237 patients were used to train and test the machine learning models. According to the criteria determining severe organophosphate poisoning, 732 patients were assigned to group 1 (patients with mild to moderate poisoning) and 505 patients were assigned to group 2 (patients with severe poisoning). With an AUC value of 0.907 (95 % CI 0.89-0.92), the model developed using XGBoost outperformed other models. Feature importance evaluation found that venous blood gas-pH, white blood cells, and plasma cholinesterase activity were the top three variables that contribute the most to the prediction performance of the prognosis in patients with organophosphate poisoning. XGBoost model yield an accuracy of 90.1 % (95 % CI 0.891-0.918), specificity of 91.4 % (95 % CI 0.90-0.92), a sensitivity of 89.5 % (95 % CI 0.87-0.91), F-measure of 91.2 % (95 % CI 0.90-0.921), and Kappa statistic of 91.2 % (95 % CI 0.90-0.92). The machine learning-based prediction models can accurately predict the severity of organophosphate poisoning. Based on feature selection techniques, the most important predictors of organophosphate poisoning were VBG-pH, white blood cell count, plasma cholinesterase activity, VBG-BE, and age. The best algorithm with the highest predictive performance was the XGBoost classifier.

Neurotoxicity evoked by organophosphates and available countermeasures

Organophosphorus compounds (OP) are a constant problem, both in the military and in the civilian field, not only in the form of acute poisoning but also for their long-lasting consequences. No antidote has been found that satisfactorily protects against the toxic effects of organophosphates. Likewise, there is no universal cure to avert damage after poisoning. The key mechanism of organophosphate toxicity is the inhibition of acetylcholinesterase. The overstimulation of nicotinic or muscarinic receptors by accumulated acetylcholine on a synaptic cleft leads to activation of the glutamatergic system and the development of seizures. Further consequences include generation of reactive oxygen species (ROS), neuroinflammation, and the formation of various other neuropathologists. In this review, we present neuroprotection strategies which can slow down the secondary nerve cell damage and alleviate neurological and neuropsychiatric disturbance. In our opinion, there is no unequivocal approach to ensure neuroprotection, however, sooner the neurotoxicity pathway is targeted, the better the results which can be expected. It seems crucial to target the key propagation pathways, i.e., to block cholinergic and, foremostly, glutamatergic cascades. Currently, the privileged approach oriented to stimulating GABA_AR by benzodiazepines is of limited efficacy, so that antagonizing the hyperactivity of the glutamatergic system could provide an even more efficacious approach for terminating OP-induced seizures and protecting the brain from permanent damage. Encouraging results have been reported for tezampanel, an antagonist of GluK1 kainate and AMPA receptors, especially in combination with caramiphen, an anticholinergic and anti-glutamatergic agent. On the other hand, targeting ROS by antioxidants cannot or already developed neuroinflammation does not seem to be very productive as other processes are also involved.

Molecular Mechanisms of Acute Organophosphate Nephrotoxicity

Organophosphates (OPs) are toxic chemicals produced by an esterification process and some other routes. They are the main components of herbicides, pesticides, and insecticides and are also widely used in the production of plastics and solvents. Acute or chronic exposure to OPs can manifest in various levels of toxicity to humans, animals, plants, and insects. OPs containing insecticides were widely used in many countries during the 20th century, and some of them continue to be used today. In particular, 36 OPs have been registered in the USA, and all of them have the potential to cause acute and sub-acute toxicity. Renal damage and impairment of kidney function after exposure to OPs, accompanied by the development of clinical manifestations of poisoning back in the early 1990s of the last century, was considered a rare manifestation of their toxicity. However, since the beginning of the 21st century, nephrotoxicity of OPs as a manifestation of delayed toxicity is the subject of greater attention of researchers. In this article, we present a modern view on the molecular pathophysiological mechanisms of acute nephrotoxicity of organophosphate compounds.

Clinical Analysis of Acute Organophosphorus Pesticide Poisoning and Successful Cardiopulmonary Resuscitation: A Case Series

Acute organophosphorus pesticide poisoning (AOPP) with cardiac arrest has an extremely high mortality rate, and corresponding therapeutic strategies have rarely been reported. Therefore, this study aimed to explore the prognostic factors and effective treatments of AOPP-related cardiac arrest. This retrospective study was conducted in our department in the years 2018–2021. We conducted a descriptive analysis of the clinical manifestations, rescue strategies, and prognosis of patients with AOPP who had experienced cardiac arrest and successful cardiopulmonary resuscitation. This study included six cases of patients with AOPP in addition to cardiac arrest; in four cases, cardiac arrest occurred <12 h after ingestion, and in two, cardiac arrest occurred more than 48 h after ingestion. Five patients had not undergone hemoperfusion therapy before cardiac arrest, and all six were treated with atropine during cardiopulmonary resuscitation and subsequent pralidoxine. Four patients recovered and were discharged from the hospital, one died in our department, and one was transferred to a local hospital and died there 2 h later. The last two patients had severe pancreatic injuries and disseminated intravascular coagulation. This, along with their death, might have been related to their prognosis. Cardiac arrest can occur in patients with severe AOPP for whom antidote administration was insufficient or not timely. Application of atropine and pralidoxine in a timely manner after cardiac arrest following AOPP is the key to successful treatment. This study provides useful guidelines for the treatment of similar cases in the future.

Protective effects of antioxidants on striatal dopamine release induced by organophosphorus pesticides

Although the toxic effects of organophosphorus (OP) pesticides have been classically attributed to inhibition of the acetylcholinesterase, other neurotoxic mechanisms, as oxidative stress can also occur. Here we evaluated if antioxidants prevent the excessive dopamine release induced by OP pesticides in conscious and freely moving rats, using cerebral microdialysis technique. Intrastriatal infusion of paraoxon (5 mM), glufosinate (10 mM) or glyphosate (5 mM) significantly increased the dopamine release (1006 ± 106%, 991 ± 142%, and 1164 ± 128%, relative to baseline, respectively). To evaluate if these increased dopamine release could be related to oxidative stress, we pretreated animals with antioxidants glutathione (GSH, 400 or 800 μM), dithiothreitol (DTT, 5 or 10 μM), trolox (1 or 3 mM), and α-lipoic acid (ALA, 400 or 800 μM) before administration of OP pesticides. Intrastriatal administration of the antioxidants GSH, DTT, trolox, and ALA was highly effective in preventing the glyphosate and glufosinate-induced dopamine overflow. However, only GSH (800 μM) significantly decreased the effect of paraoxon on dopamine levels. The high toxicity of this pesticide and the low concentrations used could explain this lack of effect in our experimental conditions. The fact that ROS scavengers prevent the excessive dopamine release induced by OP pesticides, further supports the view that dopamine overflow can cause neuronal damage mediated, at least in part, by oxidative stress.

Correlation between acute brain injury and brain metabonomics in dichlorvos-poisoned broilers

Dichlorvos (DDVP) is an insecticide with neurotoxicity that is widely used in agricultural production and life. However, the effects of acute DDVP poisoning on brain tissue remain underinvestigated. The purpose of this study was to evaluate the differences within 15 min-6 h in plasma biochemical indexes, brain histology and metabolites among three groups of commercial broilers orally administered different dosages of DDVP one time: (1) high-dose group (11.3 mg/kg), (2) low-dose group (2.48 mg/kg) and (3) control group (0 mg/kg). The results of biochemical indexes showed that acute DDVP poisoning could cause hyperglycemia and oxidative stress in poisoned broilers. Histological examination showed that DDVP could induce brain edema, abnormal expression of glial fibrillary acidic protein (GFAP) and neuronal mitochondrial damage in broilers. Whole-brain metabolism showed that DDVP could significantly change the secretion of neurotransmitters, energy metabolism, amino acid metabolism and nucleotide metabolism. Correlation analysis showed that metabolites such as hypoxanthine, acetylcarnitine and glucose 6-phosphate were significantly correlated with blood glucose, biomarkers of oxidative stress and brain injury pathology. The results of this study provide new insights into the molecular mechanism of brain tissue responses to acute DDVP exposure in broilers and deliver important information for clinical research on neurodegenerative diseases caused by acute DDVP poisoning.

Effects of chlorpyrifos exposure on liver inflammation and intestinal flora structure in mice

Chlorpyrifos (CPF) is an organophosphate insecticide commonly used to treat fruit and vegetable crops. CPF can cause severe adverse effects on body organs including the liver and central nervous system. This study investigated the CPF-induced inflammation in mice and explored the role of intestinal flora changes in liver inflammation. Adult C57BL/6 male mice were exposed to a CPF of 0.01-, 0.1-, 1- and 10-mg/kg bodyweight for 12 weeks. The mice in experimental group given CPF solution dissolved in corn oil vehicle by gavage, was administered by intraoral gavage for 5 days per week for 12 weeks. Histopathological examination and inflammatory factor detection were performed on mice liver tissue. Faeces were used for 16S ribosomal RNA high-throughput sequencing to explore the impact of CPF on intestinal flora structure and diversity. The results showed that 1- and 10-mg/kg CPF caused different degrees of liver focal inflammation. The structure of intestinal flora changed significantly in mice including the decreased beneficial bacteria (Akkermansia, Prevotella and Butyricimonas) and increased pathogenic bacteria (Helicobacter and Desulfovibrio). Meanwhile, the results of Q-RT-PCR showed that there was more total bacterial DNA in the liver tissue of the mice treated with 10-mg/kg groups. In conclusion, the imbalance of intestinal flora, the decreased abundance of beneficial bacteria and the increased abundance of pathogenic bacteria, as well as the increase of total bacterial DNA in the liver tissues, maybe associated with the liver focal inflammation induced by CPF.

Neuropathological Mechanisms Associated with Pesticides in Alzheimer's Disease

Environmental toxicants have been implicated in neurodegenerative diseases, and pesticide exposure is a suspected environmental risk factor for Alzheimer’s disease (AD). Several epidemiological analyses have affirmed a link between pesticides and incidence of sporadic AD. Meanwhile, in vitro and animal models of AD have shed light on potential neuropathological mechanisms. In this paper, a perspective on neuropathological mechanisms underlying pesticides’ induction of AD is provided. Proposed mechanisms range from generic oxidative stress induction in neurons to more AD-specific processes involving amyloid-beta (Aβ) and hyperphosphorylated tau (p-tau). Mechanisms that are more speculative or indirect in nature, including somatic mutation, epigenetic modulation, impairment of adult neurogenesis, and microbiota dysbiosis, are also discussed. Chronic toxicity mechanisms of environmental pesticide exposure crosstalks in complex ways and could potentially be mutually enhancing, thus making the deciphering of simplistic causal relationships difficult.