Cholinesterase-inhibiting and genotoxic effects of acute carbofuran intoxication in man: a case report

Postmortem redistribution of carbofuran and benzofuranol in rats determined using solid phase extraction by HPLC-MS/MS

Carbofuran has been implicated in many homicide and suicide cases worldwide. We investigated the postmortem redistribution of carbofuran and its main metabolite benzofuranol using the rat model. Carbofuran (50 mg/kg) was intragastric administrated, followed by euthanasia 1 h post injection. Tissues including cardiac blood, lung, liver, kidney, spleen, brain, myocardium, and thigh muscle were collected at different postmortem intervals (0, 12, 24, 48, 72, and 96 h). The samples were extracted using solid phase extraction cartridges filled with self-prepared multi-wall carbon nanotubes based molecular imprinting polymers, and analyzed using validated liquid chromatography tandem mass spectrometry method. The concentrations of carbofuran and benzofuranol were found both influenced by postmortem redistribution and postmortem degradation throughout the postmortem period. The carbofuran concentration increased in cardiac blood, liver and kidney, but decreased in lung, while benzofuranol concentration increased in cardiac blood, liver, spleen, and kidney. The benzofuranol in cardiac blood and liver is more prominent than carbofuran after 80 h after death, which implies that benzofuranol could be regarded as an alternative marker in carbofuran poisoning cases for the corpse died for a long time when carbofuran could hardly be detected. These findings provide a valuable aiding information when determining the cause of death of carbofuran poisoning.

Carbofuran pesticide toxicity to the eye

Pesticide exposure to eyes is a major source of ocular morbidities in adults and children all over the world. Carbofuran (CF), N-methyl carbamate, pesticide is most widely used as an insecticide, nematicide, and acaricide in agriculture, forestry, and gardening. Contact or ingestion of carbofuran causes high morbidity and mortality in humans and pets. Pesticides are absorbed in the eye faster than other organs of the body and damage ocular tissues very quickly. Carbofuran exposure to eye causes blurred vision, pain, loss of coordination, anti-cholinesterase activities, weakness, sweating, nausea and vomiting, abdominal pain, endocrine, reproductive, and cytotoxic effects in humans depending on amount and duration of exposure. Pesticide exposure to eye injures cornea, conjunctiva, lens, retina, and optic nerve and leads to abnormal ocular movement and vision impairment. Additionally, anticholinesterase pesticides like carbofuran are known to cause salivation, lacrimation, urination, and defecation (SLUD). Carbofuran and its two major metabolites (3-hydroxycarbofuran and 3-ketocarbofuran) are reversible inhibitors of acetylcholinesterase (AChE) which regulates acetylcholine (ACh), a neurohumoral chemical that plays an important role in corneal wound healing. The corneal epithelium contains high levels of ACh whose accumulation by AChE inhibition after CF exposure overstimulates muscarinic ACh receptors (mAChRs) and nicotinic ACh receptors (nAChRs). Hyper stimulation of mAChRs in the eye causes miosis (excessive constriction of the pupil), dacryorrhea (excessive flow of tears), or chromodacryorrhea (red tears). Recent studies reported alteration of autophagy mechanism in human cornea in vitro and ex vivo post carbofuran exposure. This review describes carbofuran toxicity to the eye with special emphasis on corneal morbidities and blindness.

Brain DNA damage analysis in pesticide exposed wistar albino rats (Rattus norvegicus): a chemometric approach

Brain the most important organ which controls most of the regulations in the body is composed of neurons and glia. As brain has a high metabolic rate and reduced cell renewal capability, the lipids, proteins and nucleic acids become the major targets of damage. In the present study carbofuran (CF) induced brain DNA damage in male wistar albino rats at sub-lethal doses (Control-A; B-1.0, C-0.5 and D-0.3 mg/kg BW) while the groups B1,C1, D1, B2, C2, D2 and B3, C3, D3 represents the exposure duration 30, 60 and 90 days each respectively. FTIR spectroscopy based chemometric analysis of functional groups in nucleic acids are reported, changes in band area and band frequencies were examined to understand the DNA damage by constructing heat map. Significant changes were observed in the band frequency, band areas, bandwidth and intensity values (p < 0.05, 0.01, 0.001). The principal component analysis was analyzed to study the alterations at the molecular level, which revealed maximum variance of 74% in groups A, B1, C1, D1 and C2 and 13.7% variance in B2, D2, B3, C3 and D3. The present study provides significant details to analyse DNA damage using non-conventional approach and can also be used for detecting DNA damage in several neural diseases and disorders and emphasizes on using FTIR spectral data through chemometric approach to analyse the DNA damage.Communicated by Ramaswamy H. Sarma.

Biomonitoring findings for occupational lead exposure in battery and ceramic tile workers using biochemical markers, alkaline comet assay, and micronucleus test coupled with fluorescence in situ hybridisation

Manufacture of lead-containing products has long been associated with various health risks. To get an insight into the related genotoxic risks, we conducted a biomonitoring study in 50 exposed workers and 48 matched controls using a battery of endpoints that sensitively detect the extent of genome instability in peripheral blood lymphocytes. The levels of primary DNA damage were estimated with the alkaline comet assay, while cytogenetic abnormalities were determined with the cytokinesis-block micronucleus (CBMN) cytome assay. Additionally, CBMN slides of 20 exposed and 16 control participants were subjected to fluorescence in situ hybridisation (FISH), coupled with pancentromeric probes to establish the incidence of centromere-positive micronuclei, nuclear buds, and nucleoplasmic bridges. Blood lead levels (B-Pb) were measured with atomic absorption spectrometry. To further characterise cumulative effects of occupational exposure, we measured erythrocyte protoporphyrin (EP) concentrations and delta-aminolevulinic acid dehydratase (ALAD) activity in blood. We also assessed the influence of serum folate (S-folate) and vitamin B12 (S-B12) on genome stability. Compared to controls, occupationally exposed workers demonstrated significantly higher B-Pb (298.36±162.07 vs 41.58±23.02), MN frequency (18.71±11.06 vs 8.98±7.50), centromere positive MN (C+ MN) (8.15±1.8 vs 3.69±0.47), and centromere negative MN (C- MN) (14.55±1.80 vs 4.56±0.89). Exposed women had significantly higher comet tail intensity (TI) and length (TL) than control women. Furthermore, workers showed a positive correlation between age and nuclear buds and MN, between MN and years of exposure, and between S-B12 levels and TI and ALAD activity, while a negative correlation was found between TI and B-Pb. These findings suggest that occupational settings in the manufacture of lead-containing products pose significant genotoxic risks, which calls for developing more effective work safety programmes, including periodical monitoring of B-Pb and genetic endpoints.

Mitochondrial respiratory chain complex I dysfunction induced by N-methyl carbamate ex vivo can be alleviated with a cell-permeable succinate prodrug

Human exposure to carbamates and organophosphates poses a serious threat to society and current pharmacological treatment is solely targeting the compounds' inhibitory effect on acetylcholinesterase. This toxicological pathway, responsible for acute symptom presentation, can be counteracted with currently available therapies such as atropine and oximes. However, there is still significant long-term morbidity and mortality. We propose mitochondrial dysfunction as an additional cellular mechanism of carbamate toxicity and suggest pharmacological targeting of mitochondria to overcome acute metabolic decompensation. Here, we investigated the effects on mitochondrial respiratory function of N-succinimidyl N-methylcarbamate (NSNM), a surrogate for carbamate insecticides, ex vivo in human platelets. Characterization of the mitochondrial toxicity of NSNM in platelets revealed a dose-dependent decrease in mitochondral oxygen consumption linked to respiratory chain complex I while the pathway through complex II was unaffected. In intact platelets, an increase in lactate production was seen, due to a compensatory shift towards anaerobic metabolism. Treatment with a cell-permeable succinate prodrug restored the NSNM-induced (100 μM) decrease in mitochondrial oxygen consumption and normalized lactate production to the level of control. We have demonstrated that carbamate-induced mitochondrial complex I dysfunction can be alleviated with a mitochondrial targeted countermeasure: a cell-permeable prodrug of the mitochondrial complex II substrate succinate.

Prevalence of chromosomal aberrations in Argentinean agricultural workers

Little is known about biosecurity measures and toxic effects during pesticide application in the province of Jujuy, Argentina, particularly concerning the protective measures and mixture of pesticides used by rural workers. We carried out an observational study of agricultural workers from Jujuy (76 exposed subjects and 53 controls) to investigate the prevalence of chromosomal aberrations (CAs) in human lymphocytes as well as the activity level of acetylcholinesterase (AChE) in red blood cell erythrocytes. Whole blood samples (5 mL) were collected in heparinized Vacutainer tubes for cytogenetic analysis and erythrocyte cholinesterase activity determination according to Ellman's method. Cytogenetic results showed a significant CA increase in pesticide-exposed individuals as compared with controls (4.20 ± 0.15 vs. 1.00 ± 0.05, respectively; p < 0.001), suggesting that pesticides are clastogenic agents causing DNA damage. Erythrocyte cholinesterase activity was significantly lower in exposed individuals, evidencing the possible occurrence of perturbations in blood as well as neurotoxicity in pesticide sprayers. These results suggest the need for periodic biomonitoring of these biomarkers together with education and training of occupational workers for the safe application of potentially harmful pesticides.

Evaluation of genotoxic potential of commonly used organophosphate pesticides in peripheral blood lymphocytes of rats

Chlorpyrifos (CPF), methyl parathion (MPT), and malathion (MLT) are among the most extensively used organophosphate (OP) pesticides in India. DNA protein cross-links (DPC) and DNA strand breaks are toxic lesions associated with the mechanism(s) of toxicity of carcinogenic compounds. In the present study, we examined the hypothesis that individual and interactive genotoxic effects of CPF, MPT, and MLT are involved in the formation of DPC and DNA strand break. The DNA strand break was measured by comet assay and expressed as DNA damage index, while DPC estimation was carried out by fluorescence emission assay. The results showed that exposure of rat lymphocytes with CPF, MPT, and MLT caused significantly marked increase in DNA damage and DPC formation in time-dependent manner. MPT caused the highest damage, and these pesticides do not potentiate the toxicity of each other.

Pesticides-induced biochemical alterations in occupational North Indian suburban population

Pesticides are used in agriculture to protect crops from insects–pests. Most of the field workers of North Indian population are exposed to commonly used insecticides. In the present study, pesticides induced oxidative stress as well as alterations in the level of acetylcholinesterase (AChE) in a total of 70 male healthy agricultural sprayers, exposed to pesticides for about 5 years, were studied and the results were compared with 70 controls. The levels of antioxidant enzymes (superoxide dismutase, CAT, glutathione- S-transferase and glutathione peroxidase), AChE, lipid peroxidation and glutathione (GSH) contents were determined in their blood erythrocytes (red blood cells (RBCs)). The results indicated significant increase in the levels of malondialdehyde as well as the activities of antioxidant enzymes in pesticide-exposed individuals. The levels of GSH, RBC-AChE activity and plasma antioxidant potential were sharply decreased when compared with control subjects. The ferric-reducing ability of plasma (FRAP) assay was carried out to evaluate the antioxidant potential of pesticide in exposed as well as healthy controls. A significant positive correlation was observed between plasma FRAP value and the activity of AChE from RBCs in pesticides sprayers. Furthermore, these results were supported by enhanced messenger RNA expressions of cytochrome P450 isoform 2E1 (CYP2E1) and gutathione- S-transferase isoform pi (GST-pi) in the white blood cells of the randomly selected pesticide-exposed individuals. The decreased GSH level in human red blood cells accompanied by increase in the levels of the activities of antioxidative enzymes and over expressions of CYP2E1 and GST-pi is an indicative of oxidative stress in pesticides-exposed individuals. The reduced activity of AChE indicates possible occurrence of perturbations in blood as well as neurotoxicity in pesticide sprayers.

Small cages with insect couples provide a simple method for a preliminary assessment of mating disruption

Mating disruption by sex pheromones is a sustainable, effective and widely used pest management scheme. A drawback of this technique is its challenging assessment of effectiveness in the field (e.g., spatial scale, pest density). The aim of this work was to facilitate the evaluation of field-deployed pheromone dispensers. We tested the suitability of small insect field cages for a pre-evaluation of the impact of sex pheromones on mating using the grape moths Eupoecilia ambiguella and Lobesia botrana, two major pests in vineyards. Cages consisted of a cubic metal frame of 35 cm sides, which was covered with a mosquito net of 1500 μm mesh size. Cages were installed in the centre of pheromone-treated and untreated vineyards. In several trials, 1 to 20 couples of grape moths per cage were released for one to three nights. The proportion of mated females was between 15 to 70% lower in pheromone-treated compared to untreated vineyards. Overall, the exposure of eight couples for one night was adequate for comparing different control schemes. Small cages may therefore provide a fast and cheap method to compare the effectiveness of pheromone dispensers under standardised semi-field conditions and may help predict the value of setting-up large-scale field trials.

Prenatal carbofuran exposure inhibits hippocampal neurogenesis and causes learning and memory deficits in offspring

Neurogenesis is a process of generation of new neurons in the hippocampus and associated with learning and memory. Carbofuran, a carbamate pesticide, elicits several neurochemical, neurophysiological, and neurobehavioral deficits. We evaluated whether chronic prenatal oral exposure of carbofuran during gestational days 7-21 alters postnatal hippocampal neurogenesis at postnatal day 21. We found carbofuran treatment significantly decreased bromodeoxyuridine (BrdU) positive cell proliferation and long-term survival in the hippocampus only but not in the cerebellum. We observed a reduced number of transcription factor SOX-2 and glial fibrillary acidic protein (GFAP) colabeled cells, decreased nestin messenger RNA (mRNA) expression, and decreased histone-H3 phosphorylation following carbofuran treatment, suggesting a decreased pool of neural progenitor cells (NPC). Colocalization of BrdU with doublecortin (DCX), neuronal nuclei (NeuN), and GFAP suggested decreased neuronal differentiation and increased glial differentiation by carbofuran. The number of DCX(+) and NeuN(+) neurons, NeuN protein levels, and fibers length of DCX(+) neurons were decreased by carbofuran. Carbofuran caused a significant downregulation of mRNA expression of the neurogenic genes/transcription factors such as neuregulin, neurogenin, and neuroD1 and upregulation of the gliogenic gene Stat3. Carbofuran exposure led to increased BrdU/caspase 3 colabeled cells, an increased number of degenerative neurons and profound deficits in learning and memory processes. The number and size of primary neurospheres derived from the hippocampus of carbofuran-treated rats were decreased. These results suggest that early gestational carbofuran exposure diminishes neurogenesis, reduces the NPC pool, produces neurodegeneration in the hippocampus, and causes cognitive impairments in rat offspring.