We propose to develop a previously unexplored approach in therapy of nerve agent and pesticide OP exposure based on efficient reactivation of endogenous BChE directly in human circulation and tissues. This approach is largely based on accelerated OP degradation of OPs directly in tissues where OPs enter and/or accumulate first during an exposure. Oxime assisted OP hydrolysis by BChE naturally present in lungs, intestine and plasma, thus provides a barrier to subsequent distribution of OPs to target sites in skeletal muscle and CNS. We recently demonstrated as a proof of principle, the functioning of oxime assisted, BChE based, catalytic OP bioscavenger in vitro, ex vivo and in vivo (Radic et al., Biochem J 450, 2013,231-242). We demonstrated that TAB2OH, a newly developed oxime reactivator of human BChE had sufficient capacity to rapidly reactivate inactive, covalent OP- BChE conjugates in vitro, and enhance both protection and therapy of OP exposed mice when administered in combination with purified BChE. We now propose to utilize endogenous human BChE naturally present in lungs, intestine and plasma at nM concentrations instead of administering purified BChE, and to administer only highly efficient BChE reactivator to assist endogenous BChE in OP degradation. We assume that this will be possible since we recently developed a series of tertiary and quaternary imidazole based hBChE reactivators that are several fold more efficient in vitro than TAB2OH. The tertiary amines have the additional potential for blood-brain barrier and alveolar membrane permeation and oral bioavailability. We propose to investigate in vivo efficacy of new BChE reactivators in OP exposed mice and further refine their structure to improve their reactivation properties. This R21 proposed research, through accumulating in vitro kinetic parameters of reactivation and turnover of hBChE in the presence of an OP and taking the optimal compounds to an in vivo analysis in mouse, should uncover the potential of endogenous BChE reactivation in antidotal therapy. It should also lead to ascertaining the most efficacious dosage regimen and to assessing the limits of capitalizing on enhancing the potential of endogenous BChE through oxime-assisted catalysis. In short, is there an OP exposure level where oral or parenteral oximes directed to reactivating BChE are efficacious without having to resort to the cumbersome and risk- associated BChE fortification of activity in field and non-sterile conditions?

Public Health Relevance

Efficient recovery from nerve agent and pesticide organophosphate (OP) intoxication depends on removal of offending OP from circulation and tissue of exposed individuals. We describe a previously unexplored approach in therapy of OP exposure based on accelerated degradation of OPs directly in tissue where OPs enter and/or accumulate first during an exposure. We developed highly efficient oxime reactivators to assist OP hydrolysis by naturally present BChE in lungs, intestine and plasma, and provide a barrier to subsequent distribution of OPs to target sites in skeletal muscle and CNS.

Agency
National Institute of Health (NIH)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21NS084904-02
Application #
8738731
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Yeung, David
Project Start
Project End
Budget Start
Budget End
Support Year
2
Fiscal Year
2014
Total Cost
Indirect Cost
Name
University of California San Diego
Department
Pharmacology
Type
Schools of Pharmacy
DUNS #
City
La Jolla
State
CA
Country
United States
Zip Code
92093