Abstract
Organophosphate (OP) intoxications from nerve agent and OP pesticide exposures are managed with pyridinium aldoxime- based therapies whose success rates are currently limited. The pyridinium cation hampers uptake of OPs into the central nervous system (CNS). Furthermore, it frequently binds to aromatic residues of OP-inhibited acetylcholinesterase (AChE) in orientations that are nonproductive for AChE reactivation, and the structural diversity of OPs impedes efficient reactivation. Improvements of OP antidotes need to include much better access of AChE reactivators to the CNS and optimized orientation of the antidotes' nucleophile within the AChE active-center gorge. On the basis of X-ray structures of a CNS-penetrating reactivator, monoxime RS194B, reversibly bound to native and venomous agent X (VX)-inhibited human AChE, here we created seven uncharged acetamido bis-oximes as candidate antidotes. Both oxime groups in these bis-oximes were attached to the same central, saturated heterocyclic core. Diverse protonation of the heterocyclic amines and oxime groups of the bis-oximes resulted in equilibration among up to 16 distinct ionization forms, including uncharged forms capable of diffusing into the CNS and multiple zwitterionic forms optimal for reactivation reactions. Conformationally diverse zwitterions that could act as structural antidote variants significantly improved in vitro reactivation of diverse OP-human AChE conjugates. Oxime group reorientation of one of the bis-oximes, forcing it to point into the active center for reactivation, was confirmed by X-ray structural analysis. Our findings provide detailed structure-activity properties of several CNS-directed, uncharged aliphatic bis-oximes holding promise for use as protonation-dependent, conformationally adaptive, “smart” accelerated antidotes against OP toxicity.
| Original language | English |
|---|---|
| Pages (from-to) | 4079-4092 |
| Number of pages | 14 |
| Journal | Journal of Biological Chemistry |
| Volume | 295 |
| Issue number | 13 |
| DOIs | |
| State | Published - Mar 27 2020 |
Funding
This work was supported by CounterACT Program (National Institutes of Health (NIH) Office of the Director and NINDS, NIH) Grants U01 NS083451 and R21 NS098998 and by University of California San Diego, Academic Senate Grant BG084144. The authors declare that they have no conflicts of interest with the contents of this article. The content is solely the respon-sibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Acknowledgments—X-ray crystallographic data presented in this report are derived from work performed at Argonne National Laboratory, Structural Biology Center at the Advanced Photon Source, beamline ID19. Use of the Advanced Photon Source, an Office of Science User Facility operated for the United States Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the United States DOE under Contract DE-AC02-06CH11357. The Office of Biological and Environmental Research supported research at the Center for Structural Molecular Biology at Oak Ridge National Laboratory using facilities supported by the Scientific User Facilities Division, Office of Basic Energy Sciences, United States DOE. The assistance of Kwok-Yiu Ho and University of California San Diego undergraduate students Stephanie Luedtke, Yun-shen Li, Celine Bojo, and Bianca Pomar in completion of oxime reactivation and oximolysis experiments is greatly appreciated.