title: In vitro detoxification of cyclosarin in human blood pre-incubated ex vivo with recombinant serum paraoxonases.
abstract: An ex vivo protocol was developed to assay the antidotal capacity of rePON1 variants to protect endogenous acetylcholinesterase and butyrylcholinesterase in human whole blood against OP nerve agents. This protocol permitted us to address the relationship between blood rePON1 concentrations, their kinetic parameters, and the level of protection conferred by rePON1 on the cholinesterases in human blood, following a challenge with cyclosarin (GF). The experimental data thus obtained were in good agreement with the predicted percent residual activities of blood cholinesterases calculated on the basis of the rate constants for inhibition of human acetylcholinesterase and butyrylcholinesterase by GF, the concentration of the particular rePON1 variant, and its k(cat)/K(m) value for GF. This protocol thus provides a rapid and reliable ex vivo screening tool for identification of rePON1 bioscavenger candidates suitable for protection of humans against organophosphorus-based toxicants. The results also permitted the refinement of a mathematical model for estimating the efficacious dose of rePON1s variants required for prophylaxis in humans.
authors.affiliation: Department of Structural Biology, The Weizmann Institute of Science, Rehovot 76100, Israel.
authors.forename: Yacov
authors.initials: Y
authors.lastname: Ashani
authors.forename: Moshe
authors.initials: M
authors.lastname: Goldsmith
authors.forename: Haim
authors.initials: H
authors.lastname: Leader
authors.forename: Israel
authors.initials: I
authors.lastname: Silman
authors.forename: Joel L
authors.initials: JL
authors.lastname: Sussman
authors.forename: Dan S
authors.initials: DS
authors.lastname: Tawfik
mesh_terms: D000110:Acetylcholinesterase / Q000097:blood / Q000378:metabolism; D000931:Antidotes / Q000494:pharmacology*; D043303:Aryldialkylphosphatase / Q000235:genetics / Q000494:pharmacology*; D055162:Biocatalysis; D002091:Butyrylcholinesterase / Q000097:blood / Q000378:metabolism; D002619:Chemical Warfare Agents / Q000633:toxicity; D004912:Erythrocytes / Q000187:drug effects / Q000201:enzymology; D006801:Humans; D006868:Hydrolysis; D066298:In Vitro Techniques; D008658:Inactivation, Metabolic; D020258:Neurotoxicity Syndromes / Q000097:blood / Q000517:prevention & control; D009943:Organophosphorus Compounds / Q000097:blood* / Q000633:toxicity; D011994:Recombinant Proteins / Q000235:genetics / Q000494:pharmacology
chemical_list: D000931:Antidotes; D002619:Chemical Warfare Agents; D009943:Organophosphorus Compounds; D011994:Recombinant Proteins; D000110:Acetylcholinesterase; D002091:Butyrylcholinesterase; D043303:Aryldialkylphosphatase; C468406:PON1 protein, human; C053914:cyclohexyl methylphosphonofluoridate