Profiling cholinesterase adduction: a high-throughput prioritization method for organophosphate exposure samples

Pesticide exposure and related health problems among family members of farmworkers in southeast Iran. A case-control study

BACKGROUND

Pesticides used in agriculture are some of the most common pollutants in the world. This study aimed to investigate the effects of Organophosphorus Pesticides (OPPs) and Organochlorine Pesticides (OCPs) on the families of farmworkers in the southeast of Iran.

METHODS

In the present case-control study, 141 family members of farmworkers (as the case group) and 59 family members of non-farmworkers (as the controls) were recruited. Serum levels of OCPs such as α-HCH, β-HCH, γ-HCH, 2,4-DDE, 4,4-DDE, 2,4-DDT, and 4,4-DDT were determined. In addition, erythrocyte acetylcholinesterase (AChE) activity, malondialdehyde (MDA), total antioxidant capacity (TAC), protein carbonyl (PC), nitric oxide (NO) serum levels, arylesterase activity of paraoxonase 1 (PON-1), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activity were determined in all participants. Furthermore, distance to farmlands, education, crops, type, and the number of consumed fruits were evaluated for each individual separately.

RESULTS

The erythrocyte AChE activity and serum activities of GPx, SOD, and PON-1 and TAC levels were significantly decreased, whereas the concentration of MDA, PC, NO, and seven OCPs were significantly increased in the farmworkers' families as compared to the controls. Spearman correlation and linear regression suggest that OCPs increase the oxidative stress in farmworkers' family members. Moreover, distance, education, farming precedence, products, and ventilation had significant effects on the OCP levels and increased the odds ratio of OCP levels in farmworkers' families.

CONCLUSION

With regards to the data obtained in this study, it was revealed that OCPs as illegal pesticides and OPPs were higher than expected in the farmworkers' family members. Furthermore, exposure to OCPs and OPPs, apart from the other effects on the body, leads to oxidative stress (OS) that may cause serious diseases in the exposed populations.

Organochlorine and organophosphorous pesticides may induce colorectal cancer; A case-control study

OBJECTIVES

Among the numerous agents, genetic factors and environmental elements such as pesticides have an important role in colorectal cancer (CRC) incidence. The present study aimed to investigate the probable-role of some organochlorine pesticides (OCPs) and organophosphorous pesticides (OPPs) in patients with CRC.

METHODS

In this case-control study, 42 patients with CRC and 30 healthy subjects were selected. The serum levels of some OCPs (α-HCH, β-HCH, γ-HCH, 2,4 DDE, 4,4 DDE, 2,4DDT and 4,4DDT) were measured by gas chromatography (GC) method. Serum levels of malondialdehyde (MDA), and total antioxidant capacity (TAC) as well as the enzyme activity of acetylcholinesterase (AChE) and arylesterase activity of Paraoxonase-1 (PON-1) were evaluated in all participants. The methylation specific PCR (MSP) assay was used for determining the methylation status of CpG island of p16 and MGMT genes in CRC patients.

RESULTS

The mean serum levels of each OCPs were significantly higher in the patient group compared to the control group (P < 0.001). The AChE and arylesterase activity of PON-1 in the patient group were significantly lower than the control group (P < 0.001). The mean serum levels of MDA and TAC in the serum of the patient group were significantly higher than the control group (P < 0.001 and P < 0.002, respectively). The current findings demonstrated significantly hypermethylation of p16 promoter in CRC patients.

CONCLUSION

Regarding the higher levels of OCPs in CRC patients, along with hypermethylation of the p16 promoter gene, diminishing in AChE and PON-1 activity and increasing in oxidative stress factors, the role of OCPs and OPPs in the CRC progression in the South-East of Iran may be assumed.

Quantitation of ortho-cresyl phosphate adducts to butyrylcholinesterase in human serum by immunomagnetic-UHPLC-MS/MS

Tri-ortho-cresyl phosphate (ToCP) is an anti-wear, flame retardant additive used in industrial lubricants, hydraulic fluids and gasoline. The neurotoxic effects of ToCP arise from the liver-activated metabolite 2-(o-cresyl)-4H-1,3,2-benzodioxaphosphoran-2-one (cresyl saligenin phosphate or CBDP), which inhibits esterase enzymes including butyrylcholinesterase (BChE). Following BChE adduction, CBDP undergoes hydrolysis to form the aged adduct ortho-cresyl phosphoserine (oCP-BChE), thus providing a biomarker of CBDP exposure. Previous studies have identified ToCP in aircraft cabin and cockpit air, but assessing human exposure has been hampered by the lack of a laboratory assay to confirm exposure. This work presents the development of an immunomagnetic-UHPLC-MS/MS method for the quantitation of unadducted BChE and the long-term CBDP biomarker, oCP-BChE, in human serum. The method has a reportable range from 2.0 ng/ml to 150 ng/ml, which is consistent with the sensitivity of methods used to detect organophosphorus nerve agent protein adducts. The assay demonstrated high intraday and interday accuracy (≥85%) and precision (RSD ≤ 15%) across the calibration range. The method was developed for future analyses of potential human exposure to CBDP. Analysis of human serum inhibited in vitro with CBDP demonstrated that the oCP-BChE adduct was stable for at least 72 h at 4, 22 and 37 °C. Compared to a previously reported assay, this method requires 75% less sample volume, reduces analysis time by a factor of 20 and demonstrates a threefold improvement in sensitivity. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.

Preparation and characterization of diethoxy- and monoethoxy phosphylated ('aged') serine haptens and use in the production of monoclonal antibodies

In this study, the first mechanism-based monoclonal antibodies have been produced that recognize and differentiate diethoxy- and monoethoxyphosphorylated serine residues. Haptens were synthesized as the stable phosphonate form of phosphoserine esters to improve the immunoresponse. Following condensation with a glutaric anhydride to link the phosphoserine moieties to carrier protein, the hapten densities attached to bovine serum albumin and keyhole limpet henocyanin were determined by partial trypsin digestion and MALDI mass spectrometry, and confirmed using a fluorescent assay (FITC) to quantify unmodified lysine residues. The conjugation reactions were pH optimized to improve hapten density. Screening of subclones led to the identification of two monoclonal antibodies: (a) N257/25.11 that specifically recognizes (EtO)2P(O)-Ser as the phosphylated or inhibited form, and (b) N262/16 that recognizes (EtO)(HO)P(O)-Ser as the 'aged' form. Analysis of blood samples treated with paraoxon (EtO)2P(O)-OPhNO2 showed a concentration dependent recognition of the phosphylated form.

An enhanced butyrylcholinesterase method to measure organophosphorus nerve agent exposure in humans

Organophosphorus nerve agent (OPNA) adducts to butyrylcholinesterase (BChE) can be used to confirm exposure in humans. A highly accurate method to detect G- and V-series OPNA adducts to BChE in 75 μL of filtered blood, serum, or plasma has been developed using immunomagnetic separation (IMS) coupled with liquid chromatography tandem mass spectrometry (LC-MS/MS). The reported IMS method captures > 88 % of the BChE in a specimen and corrects for matrix effects on peptide calibrators. The optimized method has been used to quantify baseline BChE levels (unadducted and OPNA-adducted) in a matched-set of serum, plasma, and whole blood (later processed in-house for plasma content) from 192 unexposed individuals to determine the interchangeability of the tested matrices. The results of these measurements demonstrate the ability to accurately measure BChE regardless of the format of the blood specimen received. Criteria for accepting or denying specimens were established through a series of sample stability and processing experiments. The results of these efforts are an optimized and rugged method that is transferrable to other laboratories and an increased understanding of the BChE biomarker in matrix.

Direct quantitation of methyl phosphonate adducts to human serum butyrylcholinesterase by immunomagnetic-UHPLC-MS/MS

Hydrolysis of G- and V-series organophosphorus nerve agents (OPNAs) containing a phosphorus-methyl bond yields a methylphosphonic acid (MeP) product when adducted to human butyrylcholinesterase (BChE). The MeP adduct is considered a sign of "aging" and results in loss of the o-alkyl identifier specific to each nerve agent. After aging has occurred, common therapeutics such as oximes cannot reactivate the cholinesterase enzyme and relieve cholinergic inhibition. Until now, a direct, quantitative method for determination of the MeP adduct to BChE was unavailable. Aged adducts in serum samples were processed by immunomagnetic separation of BChE by antibody conjugated bead, isotope-dilution, pepsin digestion, followed by UHPLC separation and detection by conventional electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Ions were detected in selected reaction monitoring (SRM) mode, and transition m/z 874.3 → 778.3 was used for quantitation. The analytical response ratio was linearly proportional to the serum concentration of MeP-adducted peptide (MeP-P) over the nominal concentration range of 2.0-250 ng/mL, with a coefficient of determination of R(2) ≥ 0.997. Intrarun accuracy, expressed as %Relative Error (%RE), was ≤13.5%, 16.3%, and 3.20% at 2.0, 16, and 250 ng/mL, respectively; the corresponding precision expressed as %RSD was ≤11.9%, 6.15%, and 3.39%. Interday %RSD was ≤7.13%, 5.69%, and 1.91%. Recovery of MeP-P from serum was ≥68% across the validated concentration range, and contributions from matrix effects were minimal. The method provides a direct, quantitative measurement of MeP-P found in clinical samples suspected of nerve agent exposure and subjected to such post-sampling stresses as elevated temperature and extended shipping.