The rs662 polymorphism of paraoxonase 1 affects the difference in the inhibition of butyrylcholinesterase activity by organophosphorus pesticides in human blood

Objectives: Organophosphorus pesticides (OPs) are a human health hazard. OPs inhibit acetylcholinesterase (AChE) at nerve endings and accumulate acetylcholine (ACh) at these sites. High levels of ACh and long exposure promote cholinergic crisis. The hydrolysis of OPs by serum paraoxonase 1 (PON1) plays a role in cholinergic crisis in humans. Human serum PON1 can break down organophosphate before binding to ChE. We investigated the effect of PON1 polymorphisms on AChE activity after OP treatment. Methods: 50 healthy volunteers were randomly recruited with informed consent. We investigated butyrylcholinesterase (BuChE) activity changes in plasma as a biomarker of AChE after OP treatment in human blood samples immediately following blood sampling. After the standardization of BuChE activity in human blood, we correlated changes in BuChE activity with changes in blood pH. We analyzed the PON1 polymorphisms (rs854560 and rs662) of 50 participants to retrospectively investigate the inter individual variability of changes in BuChE activity. Results: Changes in BuChE activity are strongly correlated with pH changes after OP treatment (R-2 = 0.913). We used changes in pH as a surrogate marker for BuChE inhibition after OP treatment. OP treatment significantly decreased BuChE activity by 56.4 +/- 5.1% (p < 0.001). The degree of BuChE inhibition was significantly different in the PON1 rs662 genotype (56.10 +/- 4.74% vs. 57.96 +/- 5.67% vs. 52.34 +/- 1.51%; GG vs. GA vs. AA, respectively). Conclusion: Changes in pH can be used as a surrogate marker for the detection of BuChE inhibition after OP exposure. The rs662 polymorphism of PON1 may explain the inter-individual variability in BuChE inhibition.