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

Authors

Darryl Johnson, Centers for Disease Control and Prevention
Melissa D. Carter, Centers for Disease Control and PreventionFollow
Brian S. Crow, Centers for Disease Control and Prevention
Samantha L. Isenberg, Centers for Disease Control and Prevention
Leigh Ann Graham, Centers for Disease Control and Prevention
H. Akin Erol, Centers for Disease Control and Prevention
Caroline M. Watson, Centers for Disease Control and Prevention
Brooke G. Pantazides, Centers for Disease Control and Prevention
Marcel J. van der Schans, The Netherlands Organization for Applied Scientific Research
Jan P. Langenberg, The Netherlands Organization for Applied Scientific Research
Daan Noort, The Netherlands Organization for Applied Scientific Research
Thomas A. Blake, Centers for Disease Control and Prevention
Jerry D. Thomas, Centers for Disease Control and Prevention
Rudolph C. Johnson, Centers for Disease Control and Prevention

Date of this Version

1-2015

Citation

J. Mass Spectrom. (2015), 50, pp. 683–692. DOI 10.1002/jms.3576

Comments

U.S. government work.

Abstract

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 fromthe liver-activatedmetabolite 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 formthe 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/MSmethod for the quantitation of unadducted BChE and the long-term CBDP biomarker, oCP-BChE, in human serum. Themethod has a reportable range from 2.0ng/ml to 150 ng/ml,which is consistent with the sensitivity ofmethods 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 72h 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.