Biomedical Chemistry: Research and Methods, 2018, 1(3), e00028
The 40th Anniversary of the Institute of Physiologically Active Compounds of the Russian Academy of Sciences

Investigation of the Esterase Status as a Complex Biomarker of Exposure to Organophosphorus Compounds

G.F. Makhaeva1*, E.V. Rudakova1, R.J. Richardson 2

1Institute of Physiologically Active Compounds of the Russian Academy of Sciences, 1 Severny proezd, Moscow region, Chernogolovka, 142432 Russia,*e-mail:
2Departments of Environmental Health Sciences and Neurology, University of Michigan, Ann Arbor, MI 48109 USA

Key words: acetylcholinesterase (AChE); butyrylcholinesterase (BChE); neuropathy target esterase (NTE); carboxylesterase (CaE); blood; biomarker; organophosphorus compounds (OPC)

DOI: 10.18097/BMCRM00028

The whole version of this paper is available in Russian.

Development of biomarkers of human exposures to organophosphorus compounds OPCs and their quantification is a vital component of a system of prediction and early diagnostics of OPC-induced diseases. Our study was focused on investigation of esterase status as a complex biomarker of exposure to OPCs and an aid in accurate diagnosis. We suggest that this complex biomarker should be more effective and informative than standard assays of plasma butyrylcholinesterase (BChE), erythrocyte acetylcholinesterase (RBC AChE), and lymphocyte neuropathy target esterase (NTE). It will help: 1) to assess an exposure as such and to confirm the nonexposure of individuals suspected to have been exposed; 2) to determine if the exposure was to agents expected to produce acute and/or delayed neurotoxicity; 3) to perform dosimetry of the exposure, which provides valuable information for medical treatment. To confirm this hypothesis, we have examined the changes in activity of blood AChE, NTE, BChE and carboxylesterase (CaE) 1 h after i.p. administration of increasing doses of three OPCs with different esterase profiles: the known neuropathic compound O,O-dipropyl-O-dichlorovinyl phosphate (C3H 7O)2P(O)OCH=CCl2 (diPr-DClVP) as the control compound and two model dialkylphosphates (C2H5O)2P(O)OCH(CF3)2 (diEt-PFP) and (C4H9O)2P(O)OCH(CF3)2 (diBu-PFP). The esterases assay was performed in hemolysed blood by spectrophotometric (AChE, BChE, CaE) and biosensor (NTE) methods. Analysis of the obtained dose-dependences for blood esterases inhibition showed that blood BChE and CaE were the most sensitive biomarkers, allowing detection of low doses. Inhibition of blood NTE and AChE can be used to assess the likelihood that an exposure to OPC would produce cholinergic and/or delayed neuropathic effects.

Figure 1. OPC interaction with various serine esterases (E-OH), their possible toxic effects, the role in mechanisms of toxicity and function as biomarkers.

Figure 2. Dose-dependent inhibition of blood BChE and CaE in mice 1h after i.p. administration of diEt-PFP . The results are expressed as % inhibition versus control (mean ± SEM, n = 6). Esterase activities in blood of control animals: mmol/min/ml, mean ± SEM: AChE – 1.02 ± 0.15 (N=12),
BChE – 0.63 ± 0.03 (N=12), CaE – 6.2 ± 0.14 (N=12),
NTE – 0.017 ± 0.003 (N=8).

Figure 3. Dose-dependent inhibition of blood BChE and CaE in mice 1h after i.p. administration of diBu-PFP. The results are expressed as % inhibition versus control (mean ± SEM, n = 6). Esterase activities in the control animals are shown in the legend to Figure 2.

Figure 4. Dose-dependent inhibition of blood AChE, NTE, BChE and CaE in mice 1h after i.p. administration of diPr-DClVP. The results are expressed as % inhibition versus control (mean ± SEM, n = 6). Esterase activities in the control animals are shown in the legend to Figure 2.

Table 1. In vitro inhibitor activity (ki, M-1min-1) of dialkylphosphates diEt-PFP, diBu-PFP
and diPr-DClVP against individual enzymes AChE, NTE, BChE, CaE (esterase profile of OPCs)

Table 2. Inhibitor selectivity of diEt-PFP, diBu-PFP and diPr-DClVP to individual enzymes AChE, NTE, BChE, CaE and acute toxicity of the compounds

Table 3. Median effective doses (ED50, mg/kg) for diEt-PFP, diBu-PFP and diPr-DClVP as esterases inhibitors in mouse blood 1h after i.p. compounds administrations


This work was supported by the NATO Science for Peace and Security Program (grant № SfP 984082) and by Russian State assignment № 0090-2017-0019. The authors thank to the colleagues from the Laboratory of molecular toxicology of IPAC RAS O.G. Serebryakova and T.G. Galenko for assistance in toxicological experiments and work with animals.


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