Mass Spectrometric Analyses of Organophosphate Insecticide Oxon Protein Adducts

Abstract

ObjectiveOrganophosphate (OP) insecticides continue to be used to control insect pests. Acute and chronic exposures to OP insecticides have been documented to cause adverse health effects, but few OP-adducted proteins have been correlated with these illnesses at the molecular level. Our aim was to review the literature covering the current state of the art in mass spectrometry (MS) used to identify OP protein biomarkers.Data sources and extractionWe identified general and specific research reports related to OP insecticides, OP toxicity, OP structure, and protein MS by searching PubMed and Chemical Abstracts for articles published before December 2008.Data synthesisA number of OP-based insecticides share common structural elements that result in predictable OP–protein adducts. The resultant OP–protein adducts show an increase in molecular mass that can be identified by MS and correlated with the OP agent. Customized OP-containing probes have also been used to tag and identify protein targets that can be identified by MS.ConclusionsMS is a useful and emerging tool for the identification of proteins that are modified by activated organophosphate insecticides. MS can characterize the structure of the OP adduct and also the specific amino acid residue that forms the key bond with the OP. Each protein that is modified in a unique way by an OP represents a unique molecular biomarker that with further research can lead to new correlations with exposure.

Immunodetection of Serum Albumin Adducts as Biomarkers for Organophosphorus Exposure

“…Currently available approaches for the detection of OP exposure including functional enzyme assays and MS-based approaches have certain advantages and drawbacks (Worek et al, 2005;Thompson et al, 2010). For example, assays of Western blot using mAb-HSA-VX of plasma samples from rats treated with VX (0.8 Â LD 50 ) for 72 hours.…”

“…Generally, the approach to detect protein-OP adducts has relied on MS (Thompson et al, 2010), although one report showed that antibodies could be raised against phosphorylated AChE (George et al, 2003). However, in that report, the antibodies reported to recognize the inhibited form of AChE did not distinguish OP-AChE adducts arising from different OPs (George et al, 2003).…”

“…AChE inhibition results in accumulation of excess acetylcholine that leads to stimulation of acetylcholine receptors, which can produce convulsions and other central nervous system toxicity (Marrs et al, 2007). In addition to AChE inhibition, OPs also covalently modify other proteins Wieseler et al, 2006;Thompson et al, 2010), including butyrylcholinesterase (BChE) and serum albumin.…”

“…Numerous approaches have been used in the detection of OP exposure (Worek et al, 2005;Thompson et al, 2010), including determination of inhibition of serum AChE and BChE functional activities with biochemical assays and detection of unbound OPs in plasma or their decomposition products with mass spectrometry (MS) methods, including gas chromatography-MS (GC-MS) or liquid chromatography-tandem MS (LC-MS/MS). Other approaches include GC-MS detection of fluoride-induced reactivated AChE or BChE and detection of AChE-, BChE-, or albumin-OP adducts with capillary electrophoresis-MS or LC-MS-MS after proteolytic digestion of those proteins.…”

“…Detection of protein-OP adducts (i.e., AChE, BChE, or serum albumin) as biomarkers for OP exposure has provided insight into the structural biology of OP action (Read et al, 2010;Thompson et al, 2010). Generally, the approach to detect protein-OP adducts has relied on MS (Thompson et al, 2010), although one report showed that antibodies could be raised against phosphorylated AChE (George et al, 2003).…”