Detection of Adduct on Tyrosine 411 of Albumin in Humans Poisoned by Dichlorvos

Abstract

Studies in mice and guinea pigs have shown that albumin is a new biomarker of organophosphorus toxicant (OP) and nerve agent exposure. Our goal was to determine whether OP-labeled albumin could be detected in the blood of humans exposed to OP. Blood from four OP-exposed patients was prepared for mass spectrometry analysis by digesting 0.010 ml of serum with pepsin and purifying the labeled albumin peptide by offline high performance liquid chromatography. Dimethoxyphosphate-labeled tyrosine 411 was identified in albumin peptides VRY(411)TKKVPQVSTPTL and LVRY(411)TKKVPQVSTPTL from two patients who had attempted suicide with dichlorvos. The butyrylcholinesterase activity in these serum samples was inhibited 80%. A third patient whose serum BChE activity was inhibited 8% by accidental inhalation of dichlorvos had undetectable levels of adduct on albumin. A fourth patient whose BChE activity was inhibited 60% by exposure to chlorpyrifos had no detectable adduct on albumin. This is the first report to demonstrate the presence of OP-labeled albumin in human patients. It is concluded that tyrosine 411 of human albumin is covalently modified in the serum of humans poisoned by dichlorvos and that the modification is detectable by mass spectrometry. The special reactivity of tyrosine 411 with OP suggests that other proteins may also be modified on tyrosine. Identification of other OP-modified proteins may lead to an understanding of neurotoxic symptoms that appear long after the initial OP exposure.

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

“…Other approaches for detecting OPNA exposure include the measurement of OPNA hydrolysis products in urine [12], OPNA fluoride reactivation in blood [11] and OPNA adduction to albumin in blood [18]. OPNA metabolites including GB, soman, cyclosarin, VX and Russian-VX phosphonic acids are rapidly detected in urine using liquid chromatography tandem mass spectrometry (LC-MS/MS) [12, 13].…”

Spectroscopic Methods for the Detection of Organophosphate Pesticides – A Preview

“…In another study, albumin was studied; peptide fragments of human serum albumin were analyzed in response to chlorpyrifos oxon, dichlorvos, diisopropylfluorophosphate, and sarin. [50][51][52][53] Complexes of Ni, Co, and Fe, were evaluated for the OPs sensing, but Cu 2+ gave the best response indicating that the ligand had to accommodate enough vacancy. Thus, at this early point it was concluded that "copper complexes may adsorb and desorb phosphorus esters in air."…”

Pesticide Biomarkers

“…Similarly, Noort et al (2009) suggested that the affinity of OP for albumin could provide a mechanism for a more complete assessment of OP pesticide exposure. In addition, a mass spectrometry method to identify exposure to several pesticides (dichlorvos, chlorpyrifos oxon and aldicarb) based on the identification of pesticide adducts on the active site (i.e., serine) of human BChE has been proposed by Li et al (2010a).…”

“…Measurements are performed on blood, urine or homogenates of tissues that are obtained from biopsies. Specifically, adducts have been detected on tyrosine 411 of human albumin exposed to dichlorvos (Li et al, 2010a), and adducts have also been identified at Ser 198 of human BChE upon exposure to carbofuran (Li et al, 2009) and on the DNA-adduct 8-hydroxy-2-deoxyguanosine (8-OHdG) in the plasma of farm workers (Tope & Panemangalore, 2007), among others. Pesticides have been considered as potential mutagens because they contain ingredients capable of causing changes in DNA.…”