Acute diquat poisoning with intracerebral bleeding

Microhemorrhages in diquat-induced encephalopathy identified using susceptibility-weighted imaging

INTRODUCTION

Intracerebral bleeding that predominantly affects the pons, midbrain, cerebral peduncle, basal ganglia, and thalamus may occur in severe diquat poisoning. We employed magnetic resonance-susceptibility-weighted imaging to highlight the presence of microhemorrhages in a patient with diquat poisoning.Case summary: A 15-year-old female patient presented with kidney and liver damage after ingesting diquat. Three days later, she developed coma. She received seven sessions of hemoperfusion and was discharged with residual cognitive impairment and right limb muscle weakness after 66 days of hospitalization.Images: Cranial computed tomography on day 5 and magnetic resonance imaging on day 8 revealed swelling in the pons, midbrain, and thalamus without evidence of hemorrhage. However, susceptibility-weighted imaging on day 8 demonstrated multiple punctate low signals, suggesting the presence of microhemorrhages.

CONCLUSION

Susceptibility-weighted imaging is a useful technique for detecting microhemorrhages in patients with diquat-induced encephalopathy, as microhemorrhages are often not detectable on computed tomography or conventional magnetic resonance imaging.

High expression of 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) associated with Diquat-induced damage

Diquat (DQ) is a commonly used bipyridine herbicide known for its toxic properties and adverse effects on individuals. However, the mechanism underlying DQ-induced damage remain elusive. Our research aimed to uncover the regulatory network involved in DQ-induced damage. We analyzed publicly accessible gene expression patterns and performed research using a DQ-induced damage animal model. The GSE153959 dataset from the Gene Expression Omnibus collection and the animal model of DQ-induced kidney injury were used to identify differentially expressed genes (DEGs). Pathways including the regulation of DNA-templated transcription in response to stress, RNA polymerase II transcription regulator complex and transcription coregulatory activity were shown to be enriched in 21 DEGs. We used least absolute shrinkage and selection operator (LASSO) regression analysis to find possible diagnostic biomarkers for DQ-induced damage. Then, we used an HK-2 cell model to confirm these results. Additionally, we confirmed that 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) was the major gene associated with DQ-induced damage using multi-omics screening. The sample validation strongly suggested that HMGCS2 has promise as a diagnostic marker and may provide new targets for therapy in the context of DQ-induced damage.

Interpretable machine learning for the prediction of death risk in patients with acute diquat poisoning

The aim of this study was to develop and validate predictive models for assessing the risk of death in patients with acute diquat (DQ) poisoning using innovative machine learning techniques. Additionally, predictive models were evaluated through the application of SHapley Additive ExPlanations (SHAP). A total of 201 consecutive patients from the emergency departments of the First Hospital and Shengjing Hospital of China Medical University admitted for deliberate oral intake of DQ from February 2018 to August 2023 were analysed. The initial clinical data of the patients with acute DQ poisoning were collected. Machine learning methods such as logistic regression, random forest, support vector machine (SVM), and gradient boosting were applied to build the prediction models. The whole sample was split into a training set and a test set at a ratio of 8:2. The performances of these models were assessed in terms of discrimination, calibration, and clinical decision curve analysis (DCA). We also used the SHAP interpretation tool to provide an intuitive explanation of the risk of death in patients with DQ poisoning. Logistic regression, random forest, SVM, and gradient boosting models were established, and the areas under the receiver operating characteristic curves (AUCs) were 0.91, 0.98, 0.96 and 0.94, respectively. The net benefits were similar across all four models. The four machine learning models can be reliable tools for predicting death risk in patients with acute DQ poisoning. Their combination with SHAP provides explanations for individualized risk prediction, increasing the model transparency.

Imaging Findings and Toxicological Mechanisms of Nervous System Injury Caused by Diquat

Diquat (DQ) is a nonselective bipyridine herbicide with a structure resembling paraquat (PQ). In recent years, the utilization of DQ as a substitute for PQ has grown, leading to an increase in DQ poisoning cases. While the toxicity mechanism of DQ remains unclear, it is primarily attributed to the intracellular generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) through the process of reduction oxidation. This results in oxidative stress, leading to a cascade of clinical symptoms. Notably, recent reports on DQ poisoning have highlighted a concerning trend: an upsurge in cases involving neurological damage caused by DQ poisoning. These patients often present with severe illness and a high mortality rate, with no effective treatment available thus far. Imaging findings from these cases have shown that neurological damage tends to concentrate on the brainstem. However, the specific mechanisms behind this poisoning remain unclear, and no specific antidote exists. This review summarizes the research progress on DQ poisoning and explores potential mechanisms. By shedding light on the nerve damage associated with DQ poisoning, we hope to raise awareness, propose new avenues for investigating the mechanisms of DQ poisoning, and lay the groundwork for the development of treatment strategies for DQ poisoning. Trial registration number: 2024PS174K.

[A Preliminary Study on the Plasma Metabolomic Profiles of Patients Suffering From Acute Diquat Poisoning]

Objective

To analyze the plasma metabolomic features of patients suffering from acute diquat (DQ) poisoning and to explore the molecular mechanism and potential biomarkers of DQ poisoning.

Methods

A total of 7 patients suffering from acute DQ poisoning were enrolled in the DQ poisoning group. The poisoning of these patients occurred within a 12-h window at the time of enrollment. Meanwhile, 7 healthy immediate family members of the patients were enrolled as the normal controls. Liquid chromatography-mass spectrometry (LC-MS) was used to perform non-targeted metabolomic profiling of the plasma samples and to screen and identify differential metabolites and metabolic pathways.

Results

A total of 104 metabolites were screened and identified (P<0.05 and the variable importance in the projection [VIP]>1). Compared with those of the control group, 61 metabolites, such as sorbitol and galactitol, were up-regulated, and 43 metabolites, such as myo-inositol and gamma-glutamylcysteine, were down-regulated in the DQ poisoning group. Pathway enrichment analysis revealed changes in 11 metabolic pathways, including those for galactose metabolism and linoleic acid metabolism (P<0.05).

Conclusion

Metabolomics analysis of plasma samples from DQ poisoning patients shows that DQ mainly interferes with the metabolism of energy, amino acids, and lipids, thus causing metabolic disorders. Some potential biomarkers closely associated with oxidative stress and organ damage of the liver, kidney, and nervous system have been identified.

Melatonin Ameliorates Diquat-Induced Testicular Toxicity via Reducing Oxidative Stress, Inhibiting Apoptosis, and Maintaining the Integrity of Blood-Testis Barrier in Mice

Diquat is a fast, potent, and widely used bipyridine herbicide in agriculture and it induces oxidative stress in several animal models. However, its genotoxic effects on the male reproductive system remain unclear. Melatonin is an effective free-radical scavenger, which has antioxidant and anti-apoptotic properties and can protect the testes against oxidative damage. This study aimed to investigate the therapeutic effects of melatonin on diquat-induced testicular injury in mice. The results showed melatonin treatment alleviated diquat-induced testicular injury, including inhibited spermatogenesis, increased sperm malformations, declined testosterone level and decreased fertility. Specifically, melatonin therapy countered diquat-induced oxidative stress by increasing production of the antioxidant enzymes GPX1 and SOD1. Melatonin treatment also attenuated diquat-induced spermatogonia apoptosis in vivo and in vitro by modulating the expression of apoptosis-related proteins, including P53, Cleaved-Caspase3, and Bax/Bcl2. Moreover, melatonin restored the blood-testicular barrier by promoting the expression of Sertoli cell junction proteins and maintaining the ordered distribution of ZO-1. These findings indicate that melatonin protects the testes against diquat-induced damage by reducing oxidative stress, inhibiting apoptosis, and maintaining the integrity of the blood-testis barrier in mice. This study provides a theoretical basis for further research to protect male reproductive health from agricultural pesticides.

Lethal diquat poisoning manifests as acute central nervous system injury and circulatory failure: A retrospective cohort study of 50 cases

BACKGROUND

The mortality rate of patients with diquat (DQ) poisoning is extremely high due to insufficient understanding of DQ-induced injury. This study aimed to summarize the characteristics of DQ poisoning as well as analyse the correlation between plasma DQ concentration and patient outcomes, thus providing a new strategy for diagnosis and treatment.

METHODS

This single-centre retrospective cohort study was conducted at the Emergency Department of the First Affiliated Hospital, Zhejiang University School of Medicine, China, between Oct 9, 2019 and March 10, 2022. 50 patients, whose plasma or urine samples tested positive for diquat and negative for paraquat by high performance liquid chromatography-tandem mass spectrometry, were included in the study.

FINDINGS

The mortality rate of acute DQ poisoning was 25 (50%) of 50. Compared with the survival group, the death group presented significantly higher initial plasma DQ concentration (Cp₁), aspartate aminotransferase, alanine aminotransferase, serum creatinine, and creatine kinase-MB (P < 0.05). We found that six (24.0%) patients died of central nervous system injury, six (24.0%) patients died of refractory circulatory failure, and 13 (52.0%) patients died of central nervous system injury combined with circulatory failure. Receiver operator characteristic curve analysis showed that the area under the curve of Cp₁ was 0.967 (95% CI: 0.911, 1.000), and the cut-off value was 3516.885 ng/mL (sensitivity, 90.9%; specificity, 96.0%).

INTERPRETATION

Lethal DQ poisoning is primarily associated with serious brain and vascular injury, as well as a high rate of mortality. Further research into the mechanisms of refractory circulatory failure and central nerve system damage could help reduce mortality.

FUNDING

There are no funding sources to declare.

Acute diquat poisoning causes rhabdomyolysis

We studied the case of a 36-year-old female patient who self-administered about 30 ml of diquat solution (200 g/L) during a suicide attempt. She developed nausea, vomiting, dizziness, and weakness in her limbs and was admitted to the emergency department of our hospital 4 h later. The patient developed progressive swelling and pain in both calves 12 h after admission. Based on symptoms, lower limb color Doppler ultrasound, and elevated levels of myoglobin and creatine kinase, the patient was diagnosed with rhabdomyolysis caused by diquat poisoning. The patient recovered and was discharged after treatment with hemoperfusion, continuous venovenous hemodialysis, acid suppression, liver protection, low-dose glucocorticoids, etc. Rhabdomyolysis caused by diquat poisoning has not been previously reported. We attempted to analyze the mechanism of this symptom through a literature review. We recommend the routine monitoring of creatine phosphokinase (CK) and myoglobin (MYO) in patients with diquat poisoning to avoid missed diagnosis. Further, the mechanism of this poisoning symptom was discussed through the literature review.

A Case of a Lethal Diquat Ingestion in a Toddler

BACKGROUND

Diquat is an herbicide that may cause rapid and profound systemic toxicity. It can cause multisystem organ failure, primarily via its effects on the gastrointestinal, renal, cardiovascular, and central nervous systems. Case fatality rates as high as 43% have been reported. There is a paucity of pediatric literature on diquat poisoning, and in this article, we will discuss an unfortunate pediatric case that highlights the severity of diquat toxicity.

CASE REPORT

We present the case of a child who ingested diquat, which led to multisystem organ failure and death. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Clinicians should be aware of this herbicide's potential for significant morbidity and mortality, especially in children, in whom small quantities can be lethal. It is important that emergency physicians are aware of the significant toxicity of diquat and provide early gastric decontamination, as it is the only proven therapeutic strategy.

Lethal diquat poisoning manifesting as central pontine myelinolysis and acute kidney injury: A case report and literature review

Diquat is a nonselective herbicide that is used as a contact and preharvest desiccant to control terrestrial and aquatic vegetation. Increasing numbers of cases of diquat poisoning have recently been reported. Organs commonly affected by diquat poisoning include the kidney, liver, and lung. Neurological involvement of diquat poisoning is relatively rare. A 21-year-old man ingested 100 mL of diquat (20 g/100 mL) 5 hours before admission. Fifteen minutes after ingestion, he developed nausea and vomiting. The patient was sent to the emergency intensive care unit, and gastric lavage was performed. Continuous renal replacement therapy and continuous venovenous hemodiafiltration with hemoperfusion were performed, and methylprednisolone was administered. Five days after admission, the patient developed disturbance of consciousness and positive bilateral Babinski signs. Head computed tomography demonstrated hypodensity in the pons. At 11 days after admission, brain magnetic resonance imaging showed acute pontine demyelination. At 15 days after admission, the patient died of multiple organ dysfunction syndrome. We encountered a case of diquat poisoning with central pontine myelinolysis and acute kidney injury. This case highlights the clinical value of neuroimaging examination for early diagnosis of central pontine myelinolysis.

Association between liberal oxygen therapy and mortality in patients with paraquat poisoning: A multi-center retrospective cohort study

Paraquat (N, N'-dimethyl-4, 4'-bipyridinium dichloride, PQ) intoxication is a common cause of lethal poisoning. This study aimed to identify the risk of using liberal oxygen therapy in patients with PQ poisoning. This was a multi-center retrospective cohort study involving four medical institutions in Taiwan. Data were extracted from the Chang Gung Research Database (CGRD) from January 2004 to December 2016. Patients confirmed to have PQ intoxication with a urine PQ concentration ≥ 5 ppm were analyzed. Patients who received oxygen therapy before marked hypoxia (SpO2 ≥ 90%) were defined as receiving liberal oxygen therapy. The association between mortality and patient demographics, blood paraquat concentration (ppm), and liberal oxygen therapy were analyzed. A total of 416 patients were enrolled. The mortality rate was higher in the liberal oxygen therapy group (87.8% vs. 73.7%, P = 0.007), especially in 28-day mortality (adjusted odds ratio [aOR]: 4.71, 95% confidence interval [CI]: 1.533–14.471) and overall mortality (aOR: 5.97, 95% CI: 1.692–21.049) groups. Mortality in patients with PQ poisoning was also associated with age (aOR: 1.04, 95% CI: 1.015–1.073), blood creatinine level (aOR: 1.49, 95% CI: 1.124–1.978), and blood paraquat concentration (ppm) (aOR, 1.51; 95% CI: 1.298–1.766). Unless the evidence of hypoxia (SpO2 < 90%) is clear, oxygen therapy should be avoided because it is associated with increased mortality.

Simultaneous determination of paraquat and diquat in human plasma by HPLC-DAD: Its application in acute poisoning patients induced by these two herbicides

Background

Paraquat and diquat are widely used in agricultural production in many countries, which are very toxic to human beings. Paraquat can be detected in some diquat solution sold in the market. The blood concentration of paraquat or diquat is an important indicator for clinical diagnosis of paraquat or diquat poisoning. So, it is very meaningful to develop a method for simultaneous determination of paraquat and diquat in human plasma.

Objective

To develop and validate a HPLC‐DAD method for simultaneous determination of paraquat and diquat in human plasma and to apply it in the acute poisoning patients by these two herbicides.

Methods

Paraquat and diquat were simultaneously determined by HPLC‐DAD. The plasma was treated using Waters OASIS^® Column and then separated on a Thermo Hypersil GOLD (250 × 4.6 mm, 5 μm) Column with the mobile phase consisted of 75 mmol/L sodium heptane sulfonate (containing 0.1 mol/L phosphoric acid, pH 3.0) and acetonitrile (87:13, v:v) at a flow rate of 1.0 mL/min. The full‐wavelength scanning was 200‐400 nm, and the detection wavelength of paraquat and diquat was 257nm and 310nm, respectively. 120 and 30 plasma samples from patients with paraquat and diquat poisoning were collected and analyzed by the established method.

Results

The standard curve for paraquat and diquat ranged from 0.05 to 20 μg/mL, and the precision of LLOQ for paraquat was 16.49%, which was required to be less than 20%. The precision of other concentrations was less than 14.14%. The recovery of paraquat and diquat was 95.38%‐103.97% and 94.79%‐98.40%, respectively. The results showed that paraquat and diquat were stable under various storage conditions. 120 plasma samples of paraquat poisoning patients and 30 plasma samples of diquat poisoning patients were determined by the established method. The blood concentration of paraquat ranged from 0.10 to 20.62 μg/mL, with an average of 3.61 μg/mL, while for diquat, the concentration ranged from 0 to 26.59 μg/mL, with an average of 2.00 μg/mL. Among the diquat suspected poisoning samples, 5 samples were detected not only diquat but also paraquat, and 2 samples were detected only paraquat, no diquat.

Conclusion

The HPLC‐DAD method established in this study was high throughput, high sensitivity, simple operation, and wide linear ranges. It can be used for the screening analysis and quantitative detection of paraquat and diquat in acute poisoning patients, which can provide basis for the treatment and prognosis of these two herbicides poisoning patients.

Anhydroecgonine methyl ester (AEME), a cocaine pyrolysis product, impairs glutathione-related enzymes response and increases lipid peroxidation in the hippocampal cell culture

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AEME and cocaine decreased GPx, GR and GST activities after 3 and 6 h of exposure.

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AEME and cocaine increased MDA after 48 h of exposure.

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AEME-cocaine combination decreased GPx, GR and GST activities after 3 and 6 h.

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AEME-cocaine combination showed an additive effect on MDA after 48 h of exposure.

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A higher neurotoxic effect after crack cocaine use is suggested.

Crack cocaine smokers inhale, alongside with cocaine, its pyrolysis product, anhydroecgonine methyl ester (AEME). We have previously described AEME neurotoxic effect and its additive effect when co-incubated with cocaine. Our aim was to evaluate, the effect of AEME, cocaine and AEME-cocaine combination on glutathione peroxidase (GPx), glutathione reductase (GR) and glutathione S-transferase (GST) activities after 3 and 6 h of exposure, periods previous to neuronal death. Lipid peroxidation was evaluated through malonaldehyde (MDA) levels at 3, 6, 24 and 48 h of exposure. All treated groups reduced neuronal viability after 24 h of exposure. AEME and cocaine decreased GPx, GR and GST activities after 3 and 6 h, with an increase in MDA levels after 48 h. AEME-cocaine combination decreased the enzymes activities after 3 and 6 h, showing an additive effect in MDA levels after 48 h. These data show that the glutathione-related enzymes imbalance caused by AEME, cocaine or AEME-cocaine combination exposure preceded neuronal death and lipid peroxidation. Moreover, the additive effect on lipid peroxidation observed with AEME-cocaine exposure after 48 h, suggest a higher neurotoxic effect after crack cocaine use when compared to cocaine alone.

Successful extracorporeal membrane oxygenation support for severe acute diquat and glyphosate poisoning: A case report

RATIONALE

Because of the lack of an antidote or effective treatment, patients with severe acute diquat and glyphosate poisoning always died within a few hours. Extracorporeal membrane pulmonary oxygenation (ECMO), as an artificial heart-lung supporting system, can be applied to support lung that is expected to recover from reversible pathological damage. However, to our knowledge, the application of ECMO for patients with diquat and glyphosate poisoning has not been reported.

PATIENT CONCERNS

A 40-year-old man ingested in 100 ml of diquat (20 g/100 ml) and 400 ml glyphosate (41 g/100 ml) was admitted to the intensive care unit (ICU), immediately complicated by the development of ventricular fibrillation, respiratory failure, renal failure, and multi-organ failure.

DIAGNOSIS

Diquat and glyphosate poisoning were diagnosed by stated ingestion history, and the diagnostic criteria for acute respiratory distress syndrome (ARDS) and multi-organ dysfunction syndrome were also met.

INTERVENTIONS

He was treated with veno-venous ECMO.

OUTCOMES

He was successfully transferred out of the ICU on day 46 and discharged on day 67. The computed tomography scan showed no obvious pulmonary fibrosis 2 months after poisoning.

LESSONS

ECMO may be effective in the treatment of patients with severe ARDS caused by diquat and glyphosate poisoning when conventional management does not work.

Human and experimental toxicology of diquat poisoning: Toxicokinetics, mechanisms of toxicity, clinical features, and treatment

Diquat (1,1'-ethylene-2,2'-bipyridinium ion; DQ) is a nonselective quick-acting herbicide, which is used as contact and preharvest desiccant to control terrestrial and aquatic vegetation. Several cases of human poisoning were reported worldwide mainly due to intentional ingestion of the liquid formulations. Its toxic potential results from its ability to produce reactive oxygen and nitrogen species through redox cycling processes that can lead to oxidative stress and potentially cell death. Kidney is the main target organ due to DQ toxicokinetics and redox cycling. There is no antidote against DQ intoxications, and the efficacy of treatments currently applied is still unsatisfactory. The aim of this work was to review the most relevant human and experimental findings related to DQ, characterizing its chemistry, activity as herbicide, mechanisms of toxicity, consequences of poisoning, and potential therapeutic approaches taking into account previous experience in developing antidotes for paraquat, a more toxic bipyridinium herbicide.

Oxidative stress affects sperm performance and ejaculate redox status in subordinate House Sparrows

Oxidative stress (OS) is the result of random cellular damage caused by reactive oxygen species that leads to cell death, ageing, or illness. Most physiological processes can result in OS, which in turn has been identified as a major cause of infertility. In promiscuous species, the fertilizing ability of the ejaculate partly determines the male reproductive success. When dominance determines access to fertile females, theory predicts that lower ranking males should increase resource investment into enhancing ejaculate quality. We hypothesized that subordinate males should thus prioritize antioxidant protection of their ejaculates to protect them from OS. We put this hypothesis to the test, by chronically dosing wild House Sparrows with diquat (∼1mg/kg), an herbicide that increases pro-oxidant generation. We found that, although they increased their antioxidant levels in the ejaculate, diquat-treated males produced sperm with reduced velocity. Importantly, and contrary to our hypothesis, males at the bottom of the hierarchy suffered the largest reduction in sperm velocity. We suggest that resource access hinders individuals' ability to cope with environmental hazards. Our results point at OS as a likely physiological mechanism mediating ejaculate quality, while individual ability to access resources may play a role in constraining the extent to which such resources can be allocated into the ejaculate.

Diquat causes caspase-independent cell death in SH-SY5Y cells by production of ROS independently of mitochondria

Evidence indicates that Parkinson's disease (PD), in addition to having a genetic aetiology, has an environmental component that contributes to disease onset and progression. The exact nature of any environmental agent contributing to PD is unknown in most cases. Given its similarity to paraquat, an agrochemical removed from registration in the EU for its suspected potential to cause PD, we have investigated the in vitro capacity of the related herbicide Diquat to cause PD-like cell death. Diquat showed greater toxicity towards SH-SY5Y neuroblastoma cells and human midbrain neural cells than paraquat and also MPTP, which was independent of dopamine transporter-mediated uptake. Diquat caused cell death independently of caspase activation, potentially via RIP1 kinase, with only a minor contribution from apoptosis, which was accompanied by enhanced reactive oxygen species production in the absence of major inhibition of complex I of the mitochondrial respiratory chain. No changes in α-synuclein expression were observed following 24-h or 4-week exposure. Diquat may, therefore, kill neural tissue by programmed necrosis rather than apoptosis, reflecting the pathological changes seen following high-level exposure, although its ability to promote PD is unclear.

Fatal diquat intoxication

Background. Since the introduction of diquat in agriculture practice in 1960's, about 40 cases of poisoning have been described in detail in medical literature. Case report. We presented two cases. A case one, a 35-year-old, previously healthy, woman ingested 14% diquat solution. The poisoning had fulminant course, consisted of severe stomachache, vomiting, cardiocirculatory shock, respiratory failure and cardiac arrest 20 hours post-ingestion. Autopsy revealed myocardial infarction, bronchopneumonia and incipient renal damage. A case two, a 64-year-old man developed severe gastroenteritis, corrosive lesions of mucosal surfaces, acute renal injury, arrhythmias, brain stem infarction and bronchopneumonia. The diagnosis of diquat poisoning was made retrospectively upon the clinical picture and identification of pesticides he had been exposed to. The patient died 18 days post-exposure. The most prominent findings on autopsy were pontine hemorrhage and infarction, bronchopneumonia, left ventricle papillary muscle infarction and renal tubular damage. Conclusion. Cardiocirculatory disturbances led to fatal complications, the heart and brain infarction. We pointed out the heart as one of the most severely affected organs in diquat poisoning.

Potential developmental neurotoxicity of pesticides used in Europe

Pesticides used in agriculture are designed to protect crops against unwanted species, such as weeds, insects, and fungus. Many compounds target the nervous system of insect pests. Because of the similarity in brain biochemistry, such pesticides may also be neurotoxic to humans. Concerns have been raised that the developing brain may be particularly vulnerable to adverse effects of neurotoxic pesticides. Current requirements for safety testing do not include developmental neurotoxicity. We therefore undertook a systematic evaluation of published evidence on neurotoxicity of pesticides in current use, with specific emphasis on risks during early development. Epidemiologic studies show associations with neurodevelopmental deficits, but mainly deal with mixed exposures to pesticides. Laboratory experimental studies using model compounds suggest that many pesticides currently used in Europe--including organophosphates, carbamates, pyrethroids, ethylenebisdithiocarbamates, and chlorophenoxy herbicides--can cause neurodevelopmental toxicity. Adverse effects on brain development can be severe and irreversible. Prevention should therefore be a public health priority. The occurrence of residues in food and other types of human exposures should be prevented with regard to the pesticide groups that are known to be neurotoxic. For other substances, given their widespread use and the unique vulnerability of the developing brain, the general lack of data on developmental neurotoxicity calls for investment in targeted research. While awaiting more definite evidence, existing uncertainties should be considered in light of the need for precautionary action to protect brain development.

Diquat induces renal proximal tubule injury in glutathione reductase-deficient mice

Reactive oxygen species (ROS) have been associated with many human diseases, and glutathione (GSH)-dependent processes are pivotal in limiting tissue damage. To test the hypothesis that Gr1(a1Neu) (Neu) mice, which do not express glutathione reductase (GR), would be more susceptible than are wild-type mice to ROS-mediated injury, we studied the effects of diquat, a redox cycling toxicant. Neu mice exhibited modest, dose- and time-dependent elevations in plasma alanine aminotransferase (ALT) activities, 126+/-36 U/l at 2 h after 5 micromol/kg of diquat, but no ALT elevations were observed in diquat-treated C3H/HeN mice for up to 6 h after 50 micromol/kg of diquat. Histology indicated little or no hepatic necrosis in diquat-treated mice of either strain, but substantial renal injury was observed in diquat-treated Neu mice, characterized by brush border sloughing in the proximal tubules by 1 h and tubular necrosis by 2 h after doses of 7.5 micromol/kg. Decreases in renal GSH levels were observed in the Neu mice by 2 h post dose (3.4+/-0.4 vs 0.2+/-0.0 micromol/g tissue at 0 and 50 micromol/kg, respectively), and increases in renal GSSG levels were observed in the Neu mice as early as 0.5 h after 7.5 micromol/kg (105.5+/-44.1 vs 27.9+/-4.8 nmol/g tissue). Blood urea nitrogen levels were elevated by 2 h in Neu mice after doses of 7.5 micromol/kg (Neu vs C3H, 32.8+/-4.1 vs 17.9+/-0.3 mg/dl). Diquat-induced renal injury in the GR-deficient Neu mice offers a useful model for studies of ROS-induced renal necrosis and of the contributions of GR in defense against oxidant-mediated injuries in vivo.