Acetylcholinesterase Inhibition in Rats and Humans Following Acute Fenitrothion Exposure Predicted by Physiologically Based Kinetic Modeling-Facilitated Quantitative In Vitro to In Vivo Extrapolation

Worldwide use of organophosphate pesticides as agricultural chemicals aims to maintain a stable food supply, while their toxicity remains a major public health concern. A common mechanism of acute neurotoxicity following organophosphate pesticide exposure is the inhibition of acetylcholinesterase (AChE). To support Next Generation Risk Assessment for public health upon acute neurotoxicity induced by organophosphate pesticides, physiologically based kinetic (PBK) modeling-facilitated quantitative in vitro to in vivo extrapolation (QIVIVE) approach was employed in this study, with fenitrothion (FNT) as an exemplary organophosphate pesticide. Rat and human PBK models were parametrized with data derived from in silico predictions and in vitro incubations. Then, PBK model-based QIVIVE was performed to convert species-specific concentration-dependent AChE inhibition obtained from in vitro blood assays to corresponding in vivo dose-response curves, from which points of departure (PODs) were derived. The obtained values for rats and humans were comparable with reported no-observed-adverse-effect levels (NOAELs). Humans were found to be more susceptible than rats toward erythrocyte AChE inhibition induced by acute FNT exposure due to interspecies differences in toxicokinetics and toxicodynamics. The described approach adequately predicts toxicokinetics and acute toxicity of FNT, providing a proof-of-principle for applying this approach in a 3R-based chemical risk assessment paradigm.

Assessment of organophosphate pesticide residues in environmental media of Araromi farm settlement, Osun State, Nigeria

The aim of the study was to assess the occurrence and distribution of organophosphate compounds residue in soil, surface water, sediment, and banana crops in Araromi farm settlement, Osun State, Nigeria. Organophosphate pesticide residues were determined using a gas chromatography equipped with Flame-Ionization Detection (GC-FID) in 16 soil samples from cocoa and banana farms, 6 water and sediment samples each, and 8 banana samples from 4 farms in the study site. Fourteen organophosphate compounds were detected (acephate, omethoate, dementon-s-methyl, dimethoate, tolcofos-methyl, pirimiphos-methyl, malathion, chlorpyrifos, methidathion, prothiofos, profenofos, ethion, azinphos-methyl and pyrazophos). Tolclofos-methyl, pirimiphos-methyl and prothiofos were detected in all the soil and sediment samples with concentration ranges of 1.9-12.9, 2.25-6.98 and 3.38-9.89 mg/kg respectively in soil and 8.13-9.83, 2.82-25.1 and 3.70-19.5 mg/kg respectively in sediment. Dimethoate, pirimiphos-methyl and prothiofos with concentration ranges, 0.06-0.28, 0.09-0.18 and 0.16-6.11 mg/L respectively were mostly detected in water samples while dimethoate, tolcofos-methyl, malathion, methidathion, prothiofos, ethion and azinphos-methyl compounds were detected in all the banana samples with concentration ranges, 3.40-12.0, 1.82-6.26, 5.73-9.48, 29.7-145, 8.24-20.1, 3.87-9.35 and 3.66-12.2 mg/kg respectively. The organophosphate mean residue concentrations were mostly significantly higher than the Maximum Residue Limits (MRL) at p<0.05. Across the three samples, only pirimiphos-methyl was significantly higher in water samples, omethoate in sediment; acephate, dementon-s-methyl and chlorpyrifos in banana were also not significantly higher at p<0.05. A strong positive significant correlation was observed between the organophosphate compounds in the banana and water samples (R=0.77, p=0.002) at p<0.05. The occurrence of organophosphate compounds in concentrations above MRLs may pose serious environmental and health risks.

Organophosphate pesticide exposure and biomarkers of liver injury/liver function

BACKGROUND AND AIMS

There is little epidemiological evidence linking the exposure of organophosphate pesticides (OPs) to liver function or liver injury in the general population. We used data from the National Health and Nutrition Examination Survey 1999-2012 to investigate the relationship of urinary OPs with biomarkers of liver function/liver injury.

METHODS

The exposures were the concentrations of urinary OP metabolites (dimethyl phosphate [DMP], dimethyl thiophosphate [DMTP], diethyl phosphate [DEP] and diethyl thiophosphate [DETP]). The health outcomes were biomarkers of liver function/liver injury. The multivariable linear regression model, restricted cubic splines (RCSs) analysis and weighted quantile sum (WQS) regression were used to evaluate the relationship between individual or overall exposure of OPs and outcomes.

RESULTS

Regressions of RCSs suggested linear and positive associations of OP metabolites with aspartate aminotransferase/alanine aminotransferase (AST/ALT) ratio (DMP and DEP) and fibrosis-4 (FIB-4) index (DMP, DEP and DMTP) (all p-non-linear values >.05). However, L-shaped relationships were found between OP metabolites (DMTP and DETP) and blood albumin and total protein (TP) concentrations (both p and non-linear values <.05). The positive associations of urinary DMP, DEP and DMTP with AST/ALT ratio, and with FIB-4 score were more pronounced among non-smokers than smokers, among alcohol drinkers than non-drinkers and among those with a body mass index (BMI) of ≥25 than participants with a BMI of <25. However, most of the interaction p values were more than .05, indicating no significant interactions between covariates and OPs on outcomes mainly including AST/ALT, FIB-4, ALB and TP levels. Finally, the WQS indices were positively associated with AST/ALT ratio (p = .014) and FIB-4 score (p = .002).

CONCLUSIONS

Our study added novel evidence that exposures to OPs might be adversely associated with the biomarkers of liver function/liver injury. These findings indicated the potential toxic effect of OP exposures on the human liver.

The ChpR transcriptional regulator of Sinorhizobium meliloti senses 3,5,6-trichloropyridinol, a degradation product of the organophosphate pesticide chlorpyrifos

The global use of organophosphate insecticides (OPPs) and the growing concern of off-target side effects due to OPP exposure has prompted the need for sensitive and economical detection methods. Here we set out to engineer a previously identified OPP responsive transcription factor, ChpR, from Sinorhizobium melilotii to respond to alternative OPPs and generate a repertoire of whole-cell biosensors for OPPs. The ChpR transcription factor and cognate promoter P _chpA, have been shown to activate transcription in the presence of the OPP chlorpyrifos (CPF). Utilizing a GFP reporter regulated by ChpR in a whole-cell biosensor we found that the system responds significantly better to 3,5,6-trichloro-2-pyridinol (TCP), the main degradation product of CPF, compared to CPF itself. This biosensor was able to respond to TCP at 390 nM within 4 h compared to 50 µM of CPF in 7 h. The ChpR-P _chpA , and the activating ligand TCP, were able to regulate expression of a kanamycin resistance/sucrose sensitivity (kan/sacB) selection/counterselection module suitable for high throughput mutagenesis screening studies. The ability to control both GFP and the kan/sacB module demonstrates the utility of this reporter for the detection of CPF affected areas. The ChpR-P _chpA system serves as an additional positive regulator switch to add to the growing repertoire of controllers available within synthetic biology.

Exposure to glyphosate and tetrachlorvinphos induces cytotoxicity and global DNA methylation in human cells

Two organophosphate pesticides-glyphosate and tetrachlorvinphos-have been announced as carcinogens to humans by various authorities, including the European Chemical Agency and the Environmental Protection Agency. We aimed to investigate molecular mechanisms associated with carcinogenicity and to examine changes in global m5C DNA methylation and cytotoxic potential in A549 lung epithelial cells in response to glyphosate and tetrachlorvinphos, and differential gene expression of m5C DNA methyltransferase genes in Sprague Dawley rats to Roundup (commercial formulation of glyphosate). Global m5C level significantly increased after 1500 μM glyphosate exposure for 24 h. We determined that exposure to tetrachlorvinphos did not significantly increase the m5C level in A549 cells for 24 h. Additionally, we did not observe significant DNA methylation alteration for both pesticides after 12 h exposure. In the animal study, we observed that DNA methyltransferase genes (DNMT3b and DNMT3a) showed significantly higher expression in Roundup-exposed rats than the control group in the liver and kidney. We also observed that a significant cytotoxic effect was determined after the treatment of the cells with higher concentrations of glyphosate and tetrachlorvinphos. Our results revealed that DNA methylation could be modified by exposure to glyphosate and that exposure to Roundup was associated with the differential expression level of m5C DNA methylation methyltransferase. Finally, exposure to both pesticides increased cytotoxicity.

Development of a strategic approach for comprehensive detection of organophosphate pesticide metabolites in urine: Extrapolation of cadusafos and prothiofos metabolomics data of mice to humans

Objectives

The comprehensive detection of environmental chemicals in biospecimens, an indispensable task in exposome research, is advancing. This study aimed to develop an exposomic approach to identify urinary metabolites of organophosphate (OP) pesticides, specifically cadusafos and prothiofos metabolites, as an example chemical group, using an original metabolome dataset generated from animal experiments.

Methods

Urine samples from 73 university students were analyzed using liquid chromatography–high‐resolution mass spectrometry. The metabolome data, including the exact masses, retention time (t_R), and tandem mass spectra obtained from the human samples, were compared with the existing reference databases and with our original metabolome dataset for cadusafos and prothiofos, which was produced from mice to whom two doses of these OPs were orally administered.

Results

Using the existing databases, one chromatographic peak was annotated as 2,4‐dichlorophenol, which could be a prothiofos metabolite. Using our original dataset, one peak was annotated as a putative cadusafos metabolite and three peaks as putative prothiofos metabolites. Of these, all three peaks suggestive of prothiofos metabolites, 2,4‐dichlorophenol, 3,4,5‐trihydroxy‐6‐(2,4‐dichlorophenoxy) oxane‐2‐carboxylic acid, and (2,4‐dichlorophenyl) hydrogen sulfate were confirmed as authentic compounds by comparing their peak data with both the original dataset and peak data of the standard reagents. The putative cadusafos metabolite was identified as a level C compound (metabolite candidate with limited plausibility).

Conclusions

Our developed method successfully identified prothiofos metabolites that are usually not a target of biomonitoring studies. Our approach is extensively applicable to various environmental contaminants beyond OP pesticides.

Organophosphate-pesticides induced survival mechanisms and APE1-mediated Nrf2 regulation in non-small-cell lung cancer cells

Epidemiological and molecular studies have indicated that environmental exposure to organophosphate pesticides (OPPs) is associated with increased cancer risk; however, the underlying molecular mechanisms still need to be explained. Increasing cancer incidence is linked to OPPs-induced oxidative stress (OS). Our study evaluates monocrotophos (MCP) and chlorpyrifos (CP)-induced OS responses and apurinic/apyrimidinic endonuclease 1 (APE1) role in human non-small-cell lung cancer (NSCLC) cells. Our prior study has implicated OPPs-induced base excision repair (BER)-pathway dysregulation and APE1-mediated regulation of transcription factor (TF) c-jun in A549 cells. We further investigated the effects of MCP and CP on apoptosis, proliferation, and APE1's redox-regulation of nuclear factor-like 2 (Nrf2). Data demonstrates that MCP and CP at subtoxic concentrations induced reactive oxygen species generation and oxidative DNA base damage 8-oxo-dG lesions in NCI-H1299 cells. CP moderately upregulated the apoptosis-inducing factor (AIF) in A549 cells, however, it did not trigger other pro-apoptotic factors viz. caspase-9 and caspase-3, suggesting early caspase-independent apoptosis. However, dose-dependent AIF-downregulation was observed for MCP treatment. Furthermore, CP and MCP treatments upregulated proliferating cell nuclear antigen levels. Immunofluorescent confocal imaging showed the colocalization of APE1 with Nrf2 in 10 µM CP- and MCP-treated NCI-H1299 cells. Immunoprecipitation confirmed that APE1 and Nrf2 physically interacted, indicating the role of APE1-mediated Nrf2 activation following OPPs treatment. This study suggests that low concentration MCP and CP exposure generates OS along with DNA damage, and modulates apoptosis, and APE1-mediated Nrf2 activation, which might be considered as the possible mechanism promoting lung cancer cell survival, suggesting that APE1 may have the potential to become a therapeutic target for the treatment of NSCLC.

Genome-wide analysis of DNA methylation in testis of male rat exposed to chlorpyrifos

In our previous study, we found that subchronic exposure of chlorpyrifos (CPF) can cause reproductive damage in male rats. However, the mechanisms underlying the reproductive effects of CPF are not well understood. DNA methylation is essential for epigenetic gene regulation in development and disease. Therefore, we aim to compare DNA methylation profiles between controls and CPF-treated rats in order to identify the epigenetic mechanism of male reproductive toxicity induced by CPF. Methylated DNA immunoprecipitation with high-throughput sequencing (MeDIP-seq) was used to investigate the genome-wide DNA methylation pattern in testes of control and CPF-treated rats for 90 days. We identified 27 019 differentially methylated regions (DMRs) (14 150 upmethylated and 12 869 downmethylated) between CPF-exposed and control groups. The DMR-related genes are mainly involved in 113 pathways predicted by Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis. The result showed that high methylation gene PIK3CD may play a key role in epigenetic regulation of multiple pathways, such as Ras signaling pathway, AGE-RAGE signaling pathway in diabetic complications, HIF-1 signaling pathway, VEGF signaling pathway, and glioma and Fc epsilon RI signaling pathway in rats exposed to CPF. Our study provides significant explanations for the epigenetic mechanism of male reproductive toxicology induced by CPF.

Effects of long-term chlorpyrifos exposure on mortality and reproductive tissues of Banded Gourami (Trichogaster fasciata)

This study assessed the long-term toxicity of chlorpyrifos on survival and reproduction of Banded Gourami by using mortality, gonado-somatic index (GSI) and histopathological observations as endpoints. Adult fish were exposed to five different concentrations of chlorpyrifos (0, 15, 50, 150, 500 µg/L) in 15 PVC tanks for 15, 30, 45, 60 and 75 days. Results showed that all male and female fish died after 15 days of 500 µg/L chlorpyrifos exposure. No consistent significant effect was observed for both male and female GSI. Furthermore, results showed dose- and time-dependent histopathological alterations for both ovary and testes. The 60-d No Observed Effect Concentration (NOEC) for most histopathological alterations of Banded Gourami ovary and testes was 50 μg/L, while 60-d NOEC for mortality of both male and female fish was < 15 μg/L. The results show that the long-term exposure to chlorpyrifos not only affect the reproductive tissues of Banded Gourami at exposure concentrations but also cause their mortality. Future studies should evaluate effects at lower concentrations.

Oxidative stress, cholinesterase activity, and DNA damage in the liver, whole blood, and plasma of Wistar rats following a 28-day exposure to glyphosate

In this 28 day-study, we evaluated the effects of herbicide glyphosate administered by gavage to Wistar rats at daily doses equivalent to 0.1 of the acceptable operator exposure level (AOEL), 0.5 of the consumer acceptable daily intake (ADI), 1.75 (corresponding to the chronic population-adjusted dose, cPAD), and 10 mg kg-1 body weight (bw) (corresponding to 100 times the AOEL). At the end of each treatment, the body and liver weights were measured and compared with their baseline values. DNA damage in leukocytes and liver tissue was estimated with the alkaline comet assay. Oxidative stress was evaluated using a battery of endpoints to establish lipid peroxidation via thiobarbituric reactive substances (TBARS) level, level of reactive oxygen species (ROS), glutathione (GSH) level, and the activity of glutathione peroxidase (GSH-Px). Total cholinesterase activity and the activities of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) were also measured. The exposed animals gained less weight than control. Treatment resulted in significantly higher primary DNA damage in the liver cells and leukocytes. Glyphosate exposure significantly lowered TBARS in the liver of the AOEL, ADI, and cPAD groups, and in plasma in the AOEL and cPAD group. AChE was inhibited with all treatments, but the AOEL and ADI groups significantly differed from control. Total ChE and plasma/liver ROS/GSH levels did not significantly differ from control, except for the 35 % decrease in ChE in the AOEL and ADI groups and a significant drop in liver GSH in the cPAD and 100xAOEL groups. AOEL and ADI blood GSH-Px activity dropped significantly, but in the liver it significantly increased in the ADI, cPAD, and 100xAOEL groups vs. control. All these findings show that even exposure to low glyphosate levels can have serious adverse effects and points to a need to change the approach to risk assessment of low-level chronic/sub-chronic glyphosate exposure, where oxidative stress is not necessarily related to the genetic damage and AChE inhibition.

Three MOF-Templated Carbon Nanocomposites for Potential Platforms of Enzyme Immobilization with Improved Electrochemical Performance

An efficient and facile metal-organic framework (MOF)-template strategy for preparing carbon nanocomposites has been developed. First of all, a series of metal ions, including Fe³⁺, Zr⁴⁺, and La³⁺, were respectively connected with 2-aminoterephthalate (H₂ATA) to form three metal-organic frameworks (MOFs) and then three novel MOF-derived materials were obtained by annealing them at 550 °C under N₂ atmosphere. The morphologies and microstructure results showed that they still retained the original structure of MOFs and formed carbon-supported metal oxide hybrid nanomaterials. Interestingly, it was found that La-MOF-NH₂ and its derived materials were first reported, which had wool-ball-like structure formed by many streaky-shaped particles intertwining each other. Furthermore, these MOF-derived materials were all successfully used as effective immobilization matrixes of acetylcholinesterase (AChE) to construct biosensors for the detection of methyl parathion. Especially, [La-MOF-NH₂]_N2 with wool-ball-like structure not only provided more active sites of multicontents to increase AChE immobilization amount but also facilitated the accessibility of electron transfer and shorten their diffusion length on the surface of electrode. Under optimal conditions, the biosensor based on [La-MOF-NH₂]_N2 displayed the widest linear range of 1.0 × 10^-13-5.0 × 10^-9 g mL^-1 and the lowest detection limit of 5.8 × 10^-14 g mL^-1 in three biosensors. This study illustrates the feasibility and the potential of a series of MOF-derived materials for biosensors with improved electrochemical performance.

Hierarchical Porous Magnesium Oxide (Hr-MgO) Microspheres for Adsorption of an Organophosphate Pesticide: Kinetics, Isotherm, Thermodynamics, and DFT Studies

In this study, hierarchical porous magnesium oxide (Hr-MgO) microspheres have been fabricated from a hydromagnesite precursor via a facile precipitation method followed by calcination. The Hr-MgO microspheres consist of several nanosheet building blocks that generate a flowerlike architecture. Chlorpyrifos (CPF), a persistent organic pollutant, has been chosen as a model organophosphate pesticide to determine the adsorptive capacities of the fabricated Hr-MgO. The equilibrium adsorption data fits well with the Langmuir isotherm model, showing a maximum adsorption capacity of 3974 mg g^-1, which is the highest value to date. Both kinetic as well as thermodynamic parameters reveal the spontaneous, exothermic, and pseudo-second-order nature of the adsorption process due to chemisorption between the pesticide and the adsorbent. Density functional theory studies suggest the importance of hydroxylation on the MgO surface for the successful destructive adsorption, which takes place via the cleavage of S═P and Cl-C bonds resulting in the fragmentation of CPF, which is in good agreement with Fourier transform infrared and mass spectrometric studies. The present study shows the potential use of hierarchically structured porous MgO microspheres as an efficient adsorbent for the removal of CPF pollutant.

Two-Dimensional 1T-Phase Transition Metal Dichalcogenides as Nanocarriers To Enhance and Stabilize Enzyme Activity for Electrochemical Pesticide Detection

Single or few layers lithium-exfoliated transition metal dichalcogenides (TMDs) are found to exist predominantly in the conducting metallic 1T-polymorph, which makes it desirable for numerous applications due to its large surface area, good electrical conductivity, and enhanced electrocatalytic capabilities. We demonstrated the use of tert-butyllithium exfoliated TMDs (MoS₂, MoSe₂, WS₂, WSe₂) as a platform for the indirect electrochemical detection of an organophosphate pesticide, fenitrothion, via enzymatic inhibition pathway. All four reported materials enhanced the response of the enzymatic biosensor in comparison to the corresponding biosensor in the absence of TMDs. 1T-Phase WS₂ outperforms all other TMD materials, and we proved that it serves as an excellent transducer for enhancing electron transfer in a robust model enzyme-based inhibition assay system using cross-linking immobilization with glutaraldehyde. The reported system showed a broad fenitrothion concentration range (1-1000 nM) with an excellent linearity (r = 0.987). Moreover, the system displayed high sensitivity with low limit of detection (2.86 nM) obtained, which far exceeds the required limit set by Food and Agriculture Organisation (FAO) of the United Nations (UN). The feasibility of the proposed system in real samples was demonstrated in apple juice samples with good recoveries of 80.2% and 80.3% obtained at 10 and 1000 nM fenitrothion, respectively.

Methamidophos induces cytotoxicity and oxidative stress in human peripheral blood mononuclear cells

Previous studies have shown that organophosphate pesticide (OP) exposure is associated with oxidative stress. Methamidophos (MET) is an OP widely used in agriculture, which is regarded as a highly toxic pesticide and it is a potent inhibitor of acetylcholinesterase. The aim of this study was to evaluate whether MET can induce oxidative stress at low concentrations in primary cultures of human peripheral blood mononuclear cells (PBMCs). PBMCs from healthy individuals were exposed to MET (0-80 mg/L) for 0-72 h. We performed the MTT and neutral-red assays to assess the cytotoxicity. As indicators of oxidative stress, the levels of reactive oxygen species (ROS) were assessed using flow cytometry, and the malondialdehyde (MDA) and reduced glutathione (GSH) levels were determined. MET decreased the viability of PBMCs in a dose-dependent manner. At concentrations of 3, 10, or 20 mg/L for 24 h, MET increased the ROS production significantly compared with the vehicle control. Similarly, MET increased the levels of MDA at the same concentrations that increased ROS (10 and 20 mg/L); however, no changes in GSH levels were observed. These results suggest that MET increased the generation of oxidative stress in PBMCs. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 147-155, 2017.

Organophosphate Hydrolase in Conductometric Biosensor for the Detection of Organophosphate Pesticides

The research has developed an enzyme biosensor for the detection organophosphate pesticide residues. The biosensor consists of a pair of screen-printed carbon electrode (SPCEs). One of electrodes contains immobilized organophosphate hydrolase (OPH) on a chitosan membrane by cross-linking it with glutaraldehyde. The area of the electrodes was optimized to 3, 5, and 7 mm(2). The OPH was isolated from Pseudomonas putida, and was purified by the ammonium sulfate precipitation method, with 6444 ppm (A) and 7865 ppm (B). The organophosphate pesticide samples were 0-100 ppb in tris-acetate buffer 0.05 M, pH 8.5. The results showed that the best performance of the biosensor was achieved by the enzyme A with an electrode area of 5 mm(2). The sensitivity of the biosensor was between 3 and 32 µS/ppb, and the detection limit for the organophosphate pesticides was 40 ppb (diazinon), 30 ppb (malathion), 20 ppb (chlorpyrifos), and 40 ppm (profenofos).

Detection of genotoxicity and mutagenicity of chlorthiophos using micronucleus, chromosome aberration, sister chromatid exchange, and Ames tests

Potential mutagenic and genotoxic effects of Chlorthiophos, an organophosphate pesticide, were evaluated using four standard assays. Five different concentrations of the pesticide were tested by an Ames test using Salmonella typhimurium strains TA97, TA98, TA100, and TA102, with and without S9 metabolic activation. No concentrations of Chlorthiophos showed mutagenic activity on the TA97, TA100, and TA102 strains, with and without S9 fraction, but were all mutagenic to the TA98 strain without S9. Sister chromatid exchange (SCE), chromosome aberration (CA), and micronucleus (MN) tests were used to investigate the genotoxic effects of Chlorthiophos in human peripheral lymphocytes treated with 25, 50, 100, and 200 µg/mL concentrations of Chlorthiophos for 24 and 48 h. The nuclear division index (NDI), replication index (RI), and mitotic index (MI) were also calculated to determine the cytotoxicity of Chlorthiophos. No increase in SCE frequency was seen for any treatment period or concentration, but Chlorthiophos at 200 µg/mL increased the frequency of CAs. Increases in MN formation were only observed at Chlorthiophos concentrations of 200 µg/mL following 24 and 48 h treatments. Chlorthiophos treatment reduced the MI and NDI significantly, but had no effect on the RI.

Suicide in India: a systematic review

BACKGROUND

Suicide is an important cause of death in India but estimated suicide rates based on data from India's National Crime Records Bureau are unreliable.

AIM

Systematically review existing literature on suicide and the factors associated with suicide in India.

METHODS

PubMed, PsycINFO, EMBASE, Global Health, Google Scholar and IndMED were searched using appropriate search terms. The abstracts of relevant papers were independently examined by both authors for possible inclusion. A standardized set of data items were abstracted from the full text of the selected papers.

RESULTS

Thirty-six papers met inclusion criteria for the analysis. The heterogeneity of sampling procedures and methods of the studies made meta-analysis of the results infeasible. Verbal autopsy studies in several rural locations in India report high suicide rates, from 82 to 95 per 100,000 population - up to 8-fold higher than the official national suicide rates. Suicide rates are highest in persons 20 to 29 years of age. Female suicide rates are higher than male rates in persons under 30 years of age but the opposite is true in those 30 years of age or older. Hanging and ingestion of organophosphate pesticides are the most common methods of suicide. Among women, self-immolation is also a relatively common method of suicide. Low socioeconomic status, mental illness (especially alcohol misuse) and inter-personal difficulties are the factors that are most closely associated with suicide.

CONCLUSION

The quality of the information about suicide in India is quite limited, but it is clearly an important and growing public health problem. Compared to suicides in high-income countries, suicide in India is more prevalent in women (particularly young women), is much more likely to involve ingestion of pesticides, is more closely associated with poverty, and is less closely associated with mental illness.

Functional paraoxonase 1 variants modify the risk of Parkinson's disease due to organophosphate exposure

BACKGROUND

We previously demonstrated that carriers of the "slower metabolizer" MM genotype of paraoxonase (PON1) who were also exposed to ambient organophosphate (OP) pesticides at their residences were at increased risk of developing Parkinson's disease (PD). Here, with a larger sample size, we extend our previous investigation to consider additional sources of ambient exposure and examined two additional functional PON1 variants.

METHODS

From 2001 to 2011, we enrolled incident cases of idiopathic PD and population controls living in central California. We genotyped three well-known functional PON1 SNPs: two exonic polymorphisms (PON1L55M and PON1Q192R) and the promoter region variant (PON1C-108T). Ambient exposures to diazinon, chlorpyrifos, and parathion at residential and workplace addresses were assessed using a validated geographic information system-based model incorporating records of agricultural pesticide applications in California.

RESULTS

The odds ratio (OR) for Caucasians exposed to OPs at either residential or workplace addresses varied by PON1 genotype; for exposed carriers of the "faster" metabolizer genotypes, ML or LL, we estimated lower odds ratios (range, 1.20-1.39) than for exposed carriers of the "slower" metabolizer genotype MM (range, 1.78-2.45) relative to unexposed carriers of the faster genotypes. We observed similarly increased ORs for exposure across PON1Q192R genotypes, but no differences across PON1C-108T genotypes. The largest ORs were estimated for exposed carriers of both PON1192QQ and PON155MM (OR range, 2.84-3.57).

CONCLUSIONS

Several functional PON1 variants may act together to modify PD risk for ambient OP exposures. While either PON1L55M or PON1Q192R may be sufficient to identify increased susceptibility, carriers of both slow metabolizer variants seem most susceptible to OP exposures.

Transcriptional impact of organophosphate and metal mixtures on olfaction: copper dominates the chlorpyrifos-induced response in adult zebrafish

Chemical exposures in fish have been linked to loss of olfaction leading to an inability to detect predators and prey and decreased survival. However, the mechanisms underlying olfactory neurotoxicity are not well characterized, especially in environmental exposures which involve chemical mixtures. We used zebrafish to characterize olfactory transcriptional responses by two model olfactory inhibitors, the pesticide chlorpyrifos (CPF) and mixtures of CPF with the neurotoxic metal copper (Cu). Microarray analysis was performed on RNA from olfactory tissues of zebrafish exposed to CPF alone or to a mixture of CPF and Cu. Gene expression profiles were analyzed using principal component analysis and hierarchical clustering, whereas gene set analysis was used to identify biological themes in the microarray data. Microarray results were confirmed by real-time PCR on genes serving as potential biomarkers of olfactory injury. In addition, we mined our previously published Cu-induced zebrafish olfactory transcriptional response database (Tilton et al., 2008) for the purposes of discriminating pathways of olfaction impacted by either the individual agents or the CPF-Cu mixture transcriptional signatures. CPF exposure altered the expression of gene pathways associated with cellular morphogenesis and odorant binding, but not olfactory signal transduction, a known olfactory pathway for Cu. The mixture profiles shared genes from the Cu and CPF datasets, whereas some genes were altered only by the mixtures. The transcriptional signature of the mixtures was more similar to that in zebrafish exposed to Cu alone than for CPF. In conclusion, exposure to a mixture containing a common environmental metal and pesticide causes a unique transcriptional signature that is heavily influenced by the metal, even when organophosphate predominates.