McElroy CA

References (8)

Title : Treatment of Organophosphorus Poisoning with 6-Alkoxypyridin-3-ol Quinone Methide Precursors: Resurrection of Methylphosphonate-Aged Acetylcholinesterase - Clay_2024_Chem.Res.Toxicol__
Author(s) : Clay WK , Buck AK , He Y , Hernandez Sanchez DN , Ward NA , Lear JM , Nguyen KQ , Clark BH , Sapia RJ , Lalisse RF , Sriraman A , Cadieux CL , McElroy CA , Callam CS , Hadad CM
Ref : Chemical Research in Toxicology , : , 2024
Abstract : Organophosphorus (OP) nerve agents inhibit acetylcholinesterase (AChE), creating a cholinergic crisis in which death can occur. The phosphylated serine residue spontaneously dealkylates to the OP-aged form, which current therapeutics cannot reverse. Soman's aging half-life is 4.2 min, so immediate recovery (resurrection) of OP-aged AChE is needed. In 2018, we showed pyridin-3-ol-based quinone methide precursors (QMPs) can resurrect OP-aged electric eel AChE in vitro, achieving 2% resurrection after 24 h of incubation (pH 7, 4 mM). We prepared 50 unique 6-alkoxypyridin-3-ol QMPs with 10 alkoxy groups and five amine leaving groups to improve AChE resurrection. These compounds are predicted in silico to cross the blood-brain barrier and treat AChE in the central nervous system. This library resurrected 7.9% activity of OP-aged recombinant human AChE after 24 h at 250 microM, a 4-fold increase from our 2018 report. The best QMP (1b), with a 6-methoxypyridin-3-ol core and a diethylamine leaving group, recovered 20.8% (1 mM), 34% (4 mM), and 42.5% (predicted maximum) of methylphosphonate-aged AChE activity over 24 h. Seven QMPs recovered activity from AChE aged with Soman and a VX degradation product (EA-2192). We hypothesize that QMPs form the quinone methide (QM) to realkylate the phosphylated serine residue as the first step of resurrection. We calculated thermodynamic energetics for QM formation, but there was no trend with the experimental biochemical data. Molecular docking studies revealed that QMP binding to OP-aged AChE is not the determining factor for the observed biochemical trends; thus, QM formation may be enzyme-mediated.
ESTHER : Clay_2024_Chem.Res.Toxicol__
PubMedSearch : Clay_2024_Chem.Res.Toxicol__
PubMedID: 38556765

Title : 4-Amidophenol Quinone Methide Precursors: Effective and Broad-Scope Nonoxime Reactivators of Organophosphorus-Inhibited Cholinesterases and Resurrectors of Organophosphorus-Aged Acetylcholinesterase - Lovins_2024_ACS.Chem.Neurosci__
Author(s) : Lovins AR , Miller KA , Buck AK , Ensey DS , Homoelle RK , Murtha MC , Ward NA , Shanahan LA , Gutti G , Shriwas P , McElroy CA , Callam CS , Hadad CM
Ref : ACS Chem Neurosci , : , 2024
Abstract : Acetylcholinesterase (AChE) inhibition by organophosphorus (OP) compounds poses a serious health risk to humans. While many therapeutics have been tested for treatment after OP exposure, there is still a need for efficient reactivation against all kinds of OP compounds, and current oxime therapeutics have poor blood-brain barrier penetration into the central nervous system, while offering no recovery in activity from the OP-aged forms of AChE. Herein, we report a novel library of 4-amidophenol quinone methide precursors (QMP) that provide effective reactivation against multiple OP-inhibited forms of AChE in addition to resurrecting the aged form of AChE after exposure to a pesticide or some phosphoramidates. Furthermore, these QMP compounds also reactivate OP-inhibited butyrylcholinesterase (BChE) which is an in vivo, endogenous scavenger of OP compounds. The in vitro efficacies of these QMP compounds were tested for reactivation and resurrection of soluble forms of human AChE and BChE and for reactivation of cholinesterases within human blood as well as blood and brain samples from a humanized mouse model. We identify compound 10c as a lead candidate due to its broad-scope efficacy against multiple OP compounds as well as both cholinesterases. With methylphosphonates, compound 10c (250 microM, 1 h) shows >60% recovered activity from OEt-inhibited AChE in human blood as well as mouse blood and brain, thus highlighting its potential for future in vivo analysis. For 10c, the effective concentration (EC(50)) is less than 25 microM for reactivation of three different methylphosphonate-inhibited forms of AChE, with a maximum reactivation yield above 80%. Similarly, for OP-inhibited BChE, 10c has EC(50) values that are less than 150 microM for two different methylphosphonate compounds. Furthermore, an in vitro kinetic analysis show that 10c has a 2.2- and 92.1-fold superior reactivation efficiency against OEt-inhibited and O(i)Bu-inhibited AChE, respectively, when compared to an oxime control. In addition to 10c being a potent reactivator of AChE and BChE, we also show that 10c is capable of resurrecting (ethyl paraoxon)-aged AChE, which is another current limitation of oximes.
ESTHER : Lovins_2024_ACS.Chem.Neurosci__
PubMedSearch : Lovins_2024_ACS.Chem.Neurosci__
PubMedID: 38621296

Title : Targeted Metabolomics of Organophosphate Pesticides and Chemical Warfare Nerve Agent Simulants Using High- and Low-Dose Exposure in Human Liver Microsomes - Agarwal_2023_Metabolites_13_
Author(s) : Agarwal G , Tichenor H , Roo S , Lane TR , Ekins S , McElroy CA
Ref : Metabolites , 13 : , 2023
Abstract : Our current understanding of organophosphorus agent (pesticides and chemical warfare nerve agents) metabolism in humans is limited to the general transformation by cytochrome P450 enzymes and, to some extent, by esterases and paraoxonases. The role of compound concentrations on the rate of clearance is not well established and is further explored in the current study. We discuss the metabolism of 56 diverse organophosphorus compounds (both pesticides and chemical warfare nerve agent simulants), many of which were explored at two variable dose regimens (high and low), determining their clearance rates (Cl(int)) in human liver microsomes. For compounds that were soluble at high concentrations, 1D-NMR, 31P, and MRM LC-MS/MS were used to calculate the Cl(int) and the identity of certain metabolites. The determined Cl(int) rates ranged from 0.001 to 2245.52 microL/min/mg of protein in the lower dose regimen and from 0.002 to 98.57 microL/min/mg of protein in the high dose regimen. Though direct equivalency between the two regimens was absent, we observed (1) both mono- and bi-phasic metabolism of the OPs and simulants in the microsomes. Compounds such as aspon and formothion exhibited biphasic decay at both high and low doses, suggesting either the involvement of multiple enzymes with different K(M) or substrate/metabolite effects on the metabolism. (2) A second observation was that while some compounds, such as dibrom and merphos, demonstrated a biphasic decay curve at the lower concentrations, they exhibited only monophasic metabolism at the higher concentration, likely indicative of saturation of some metabolic enzymes. (3) Isomeric differences in metabolism (between Z- and E- isomers) were also observed. (4) Lastly, structural comparisons using examples of the oxon group over the original phosphorothioate OP are also discussed, along with the identification of some metabolites. This study provides initial data for the development of in silico metabolism models for OPs with broad applications.
ESTHER : Agarwal_2023_Metabolites_13_
PubMedSearch : Agarwal_2023_Metabolites_13_
PubMedID: 37110155

Title : A Novel, Modified Human Butyrylcholinesterase Catalytically Degrades the Chemical Warfare Nerve Agent, Sarin - McGarry_2020_Toxicol.Sci_174_133
Author(s) : McGarry KG , Lalisse RF , Moyer RA , Johnson KM , Tallan AM , Winters TP , Taris JE , McElroy CA , Lemmon EE , Shafaat HS , Fan Y , Deal A , Marguet SC , Harvilchuck JA , Hadad CM , Wood DW
Ref : Toxicol Sci , 174 :133 , 2020
Abstract : Chemical warfare nerve agents (CWNAs) present a global threat to both military and civilian populations. The acute toxicity of CWNAs stems from their ability to effectively inhibit acetylcholinesterase (AChE). This inhibition can lead to uncontrolled cholinergic cellular signaling, resulting in cholinergic crisis and, ultimately, death. While the current FDA-approved standard of care is moderately effective when administered early, development of novel treatment strategies is necessary. Butyrylcholinesterase (BChE) is an enzyme which displays a high degree of structural homology to AChE. Unlike AChE, the roles of BChE are uncertain and possibilities are still being explored. However, BChE appears to primarily serve as a bioscavenger of toxic esters due to its ability to accommodate a wide variety of substrates within its active site. Like AChE, BChE is also readily inhibited by CWNAs. Due to its high affinity for binding CWNAs, and that null-BChE yields no apparent health effects, exogenous BChE has been explored as a candidate therapeutic for CWNA intoxication. Despite years of research, minimal strides have been made to develop a catalytic bioscavenger. Further, BChE is only in early clinical trials as a stoichiometric bioscavenger of CWNAs, and large quantities must be administered to treat CWNA toxicity. Here we describe previously unidentified mutations to residues within and adjacent to the acyl binding pocket (positions 282-285 were mutagenized from YGTP to NHML) of BChE that confer catalytic degradation of the CWNA, sarin. These mutations, along with corresponding future efforts, may finally lead to a novel therapeutic to combat CWNA intoxication.
ESTHER : McGarry_2020_Toxicol.Sci_174_133
PubMedSearch : McGarry_2020_Toxicol.Sci_174_133
PubMedID: 31879758

Title : Demonstration of In Vitro Resurrection of Aged Acetylcholinesterase after Exposure to Organophosphorus Chemical Nerve Agents - Zhuang_2018_J.Med.Chem_61_7034
Author(s) : Zhuang Q , Franjesevic AJ , Corrigan TS , Coldren WH , Dicken R , Sillart S , DeYong A , Yoshino N , Smith J , Fabry S , Fitzpatrick K , Blanton TG , Joseph J , Yoder RJ , McElroy CA , Ekici OD , Callam CS , Hadad CM
Ref : Journal of Medicinal Chemistry , 61 :7034 , 2018
Abstract : After the inhibition of acetylcholinesterase (AChE) by organophosphorus (OP) nerve agents, a dealkylation reaction of the phosphylated serine, referred to as aging, can occur. When aged, known reactivators of OP-inhibited AChE are no longer effective. Realkylation of aged AChE may provide a route to reversing aging. We designed and synthesized a library of quinone methide precursors (QMPs) as proposed realkylators of aged AChE. Our lead compound (C8) from an in vitro screen successfully resurrected 32.7 and 20.4% of the activity of methylphosphonate-aged and isopropyl phosphate-aged electric-eel AChE, respectively, after 4 days. C8 displays properties of both resurrection (recovery from the aged to the native state) and reactivation (recovery from the inhibited to the native state). Resurrection of methylphosphonate-aged AChE by C8 was significantly pH-dependent, recovering 21% of activity at 4 mM and pH 9 after only 1 day. C8 is also effective against isopropyl phosphate-aged human AChE.
ESTHER : Zhuang_2018_J.Med.Chem_61_7034
PubMedSearch : Zhuang_2018_J.Med.Chem_61_7034
PubMedID: 29870665

Title : Study of para-Quinone Methide Precursors toward the Realkylation of Aged Acetylcholinesterase - Yoder_2017_ACS.Med.Chem.Lett_8_622
Author(s) : Yoder RJ , Zhuang Q , Beck JM , Franjesevic AJ , Blanton TG , Sillart S , Secor T , Guerra L , Brown JD , Reid C , McElroy CA , Dogan Ekici O , Callam CS , Hadad CM
Ref : ACS Med Chem Lett , 8 :622 , 2017
Abstract : Acetylcholinesterase (AChE) is an essential enzyme that can be targeted by organophosphorus (OP) compounds, including nerve agents. Following exposure to OPs, AChE becomes phosphylated (inhibited) and undergoes a subsequent aging process where the OP-AChE adduct is dealkylated. The aged AChE is unable to hydrolyze acetylcholine, resulting in accumulation of the neurotransmitter in the central nervous system (CNS) and elsewhere. Current therapeutics are only capable of reactivating inhibited AChE. There are no known therapeutic agents to reverse the aging process or treat aged AChE. Quinone methides (QMs) have been shown to alkylate phosphates under physiological conditions. In this study, a small library of novel quinone methide precursors (QMPs) has been synthesized and examined as potential alkylating agents against model nucleophiles, including a model phosphonate. Computational studies have been performed to evaluate the affinity of QMPs for the aged AChE active site, and preliminary testing with electric eel AChE has been performed.
ESTHER : Yoder_2017_ACS.Med.Chem.Lett_8_622
PubMedSearch : Yoder_2017_ACS.Med.Chem.Lett_8_622
PubMedID: 28626522

Title : Efforts toward treatments against aging of organophosphorus-inhibited acetylcholinesterase - Zhuang_2016_Ann.N.Y.Acad.Sci_1374_94
Author(s) : Zhuang Q , Young A , Callam CS , McElroy CA , Ekici OD , Yoder RJ , Hadad CM
Ref : Annals of the New York Academy of Sciences , 1374 :94 , 2016
Abstract : Aging is a dealkylation reaction of organophosphorus (OP)-inhibited acetylcholinesterase (AChE). Despite many studies to date, aged AChE cannot be reactivated directly by traditional pyridinium oximes. This review summarizes strategies that are potentially valuable in the treatment against aging in OP poisoning. Among them, retardation of aging seeks to lower the rate of aging through the use of AChE effectors. These drugs should be administered before AChE is completely aged. For postaging treatment, realkylation of aged AChE by appropriate alkylators may pave the way for oxime treatment by neutralizing the oxyanion at the active site of aged AChE. The other two strategies, upregulation of AChE expression and introduction of exogenous AChE, cannot resurrect aged AChE but may compensate for lowered active AChE levels by in situ production or external introduction of active AChE. Upregulation of AChE expression can be triggered by some peptides. Sources of exogenous AChE can be whole blood or purified AChE, either from human or nonhuman species.
ESTHER : Zhuang_2016_Ann.N.Y.Acad.Sci_1374_94
PubMedSearch : Zhuang_2016_Ann.N.Y.Acad.Sci_1374_94
PubMedID: 27327269

Title : High-Throughput Screening for Positive Allosteric Modulators Identified Potential Therapeutics against Acetylcholinesterase Inhibition - Chapleau_2015_J.Biomol.Screen_20_1142
Author(s) : Chapleau RR , McElroy CA , Ruark CD , Fleming EJ , Ghering AB , Schlager JJ , Poeppelman LD , Gearhart JM
Ref : J Biomol Screen , 20 :1142 , 2015
Abstract : The current standard of care for treatment of organophosphate (OP) poisoning includes pretreatment with the weak reversible acetylcholinesterase (AChE) inhibitor pyridostigmine bromide. Because this drug is an AChE inhibitor, similar side effects exist as with OP poisoning. In an attempt to provide a therapeutic capable of mitigating AChE inhibition without such side effects, high-throughput screening was performed to identify a compound capable of increasing the catalytic activity of AChE. Herein, two such novel positive allosteric modulators (PAMs) of AChE are presented. These PAMs increase AChE activity threefold, but they fail to upshift the apparent IC50 of a variety of OPs. Further development and optimization of these compounds may lead to pre- and/or postexposure therapeutics with broad-spectrum efficacy against pesticide and nerve agent poisoning. In addition, they could be used to complement the current therapeutic standard of care to increase the activity of uninhibited AChE, potentially increasing the efficacy of current therapeutics in addition to altering the therapeutic window.
ESTHER : Chapleau_2015_J.Biomol.Screen_20_1142
PubMedSearch : Chapleau_2015_J.Biomol.Screen_20_1142
PubMedID: 26078409