Identification and Study of Biomarkers from Novichok-Inhibited Butyrylcholinesterase in Human Plasma

Mass spectrometry detection of organophosphorus pesticide adducts on butyrylcholinesterase and albumin

This study established a method to prepare and detect OPs adducts on butyrylcholinesterase (BChE) and human serum albumin (HSA). OPs (methyl paraoxon, ethyl paraoxon, methyl parathion, parathion) were incubated with BChE or HSA in vitro, and the adducts of OPs-BChE or OPs-HSA were prepared and qualitatively analyzed by ultra-performance liquid chromatography data-dependent high-resolution tandem mass spectrometry (UPLC-ddHRMS/MS). The amounts of BChE and HSA in the incubating systems were varied and the resulting amounts of the adducts were determined using linear regression. OPs-BChE in the blood were isolated by immunomagnetic separation (IMS), and then digested into the OPs-nonapeptide adduct by pepsin. The proteins in the remaining blood plasma were precipitated and digested by pronase to OPs-tyrosines(OPs-Tyr), which were quantified by UPLC-ddHRMS/MS. 4 OPs-nonapeptides and 4 OPs-Tyr adducts were obtained through the process above. The relative mass deviation of incubated adducts between the actual and theoretical exact masses was less than 10 ppm, and further confirmed by fragmentation mass spectra analysis. Calibration curves were linear for all adducts with a coefficient of determination value (R2) ≥0.995. The limits of detection (LOD) and limits of quantification (LOQ) for adducts detected by MS ranged from 0.05 to 1.0 ng/mL, and from 0.1 to 2.0 ng/mL, respectively. The recovery percentages for adducts ranged from 76.1 % to 107.1 %, matrix effects ranged from 83.4 % to 102.1 %. The inter-day and intra-day precision were 6.1-10.1 % and 6.9-12.9 % for adducts. This study provides a new reference method for the detection of organophosphorus pesticide poisoning. In addition, two blood samples with organophosphorus poisoning were tested by the designed method, and the corresponding adducts were detected in both samples.

Current Perspectives on the Management of Patients Poisoned With Novichok: A Scoping Review

INTRODUCTION

Nerve agents have emerged as a global threat since their discovery in the 1930s, posing severe risks due to their inhibition of acetylcholinesterase and the subsequent accumulation of acetylcholine in nerve synapses. Despite the enforcement of the Chemical Weapon Convention to control chemical weapons, including nerve agents, recent events, such as the Novichok attacks on Sergei Skripal and Alexei Navalny, have highlighted the persistent threat. Novichok, a distinct class of nerve agents, raises specific concerns regarding its management due to limited understanding. This article aims to comprehensively analyze existing literature.

MATERIALS AND METHODS

A scoping review was employed to comprehensively assess the current state of knowledge on managing patients poisoned with Novichok. Following the PRISMA-ScR guidelines, relevant literature was identified in peer-reviewed journals covering symptoms, diagnosis, treatment, decontamination, and long-term effects. Searches were conducted on February 1, 2023, across four electronic databases (PubMed, EMBASE, MEDLINE, and Web of Science) using "Novichok" as a keyword. No restrictions were applied, and additional studies were sought from the references of identified papers. Eligible papers included discussions on Novichok or its specific properties impacting management, regardless of study type, language, or publication date, while those unrelated to the study's conceptual framework were excluded.

RESULTS

A total of 170 records were identified from the initial database search, with 86 studies screened after removing duplicates. Among these, 28 publications met the eligibility criteria and were included in the analysis. An additional relevant study was identified from the citation lists of included studies, bringing the total to 29. The review encompasses studies published from 2018 onwards, indicating the growing interest in this topic. While most studies are reviews on Novichok or nerve agents in general, several theoretical and experimental investigations were also found.

CONCLUSION

This review highlights the significant uncertainties and knowledge gaps surrounding the management of patients poisoned with Novichok. While some aspects align with other nerve agents, limited research likely due to safety and ethical challenges leads to assumptions and uncertainties in patient care. The review identifies areas with ongoing research, such as decontamination and biomarker recognition, while other aspects remain understudied. The possible inefficacy of current treatment options and the need for further research on oximes, bioscavengers, and long-term effects emphasize the necessity for increased research to optimize patient outcomes. More studies are essential to clarify the actual threat and toxicity of Novichok. Moreover, raising awareness among medical staff is crucial for early diagnosis, prompt treatment, and safety. This review offers valuable insights into managing Novichok-poisoned patients and calls for increased research and awareness in this critical area.

A-agents, misleadingly known as "Novichoks": a narrative review

"Novichok" refers to a new group of nerve agents called the A-series agents. Their existence came to light in 2018 after incidents in the UK and again in 2020 in Russia. They are unique organophosphorus-based compounds developed during the Cold War in a program called Foliant in the USSR. This review is based on original chemical entities from Mirzayanov's memoirs published in 2008. Due to classified research, a considerable debate arose about their structures, and hence, various structural moieties were speculated. For this reason, the scientific literature is highly incomplete and, in some cases, contradictory. This review critically assesses the information published to date on this class of compounds. The scope of this work is to summarize all the available and relevant information, including the physicochemical properties, chemical synthesis, mechanism of action, toxicity, pharmacokinetics, and medical countermeasures used to date. The environmental stability of A-series agents, the lack of environmentally safe decontamination, their high toxicity, and the scarcity of information on post-contamination treatment pose a challenge for managing possible incidents.

Identification of Potent and Selective Acetylcholinesterase/Butyrylcholinesterase Inhibitors by Virtual Screening

Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) play important roles in human neurodegenerative disorders such as Alzheimer's disease. In this study, machine learning methods were applied to develop quantitative structure-activity relationship models for the prediction of novel AChE and BChE inhibitors based on data from quantitative high-throughput screening assays. The models were used to virtually screen an in-house collection of ∼360K compounds. The optimal models achieved good performance with area under the receiver operating characteristic curve values ranging from 0.83 ± 0.03 to 0.87 ± 0.01 for the prediction of AChE/BChE inhibition activity and selectivity. Experimental validation showed that the best-performing models increased the assay hit rate by several folds. We identified 88 novel AChE and 126 novel BChE inhibitors, 25% (AChE) and 53% (BChE) of which showed potent inhibitory effects (IC50 < 5 μM). In addition, structure-activity relationship analysis of the BChE inhibitors revealed scaffolds for chemistry design and optimization. In conclusion, machine learning models were shown to efficiently identify potent and selective inhibitors against AChE and BChE and novel structural series for further design and development of potential therapeutics against neurodegenerative disorders.

Precisely predicting the 1H and 13C NMR chemical shifts in new types of nerve agents and building spectra database

Following the recent terrorist attacks using Novichok agents and the subsequent decomposition operations, understanding the chemical structures of nerve agents has become important. To mitigate the ever-evolving threat of new variants, the Organization for the Prohibition of Chemical Weapons has updated the list of Schedule 1 substances defined by the Chemical Weapons Convention. However, owing to the several possible structures for each listed substance, obtaining an exhaustive dataset is almost impossible. Therefore, we propose a nuclear magnetic resonance-based prediction method for ¹H and ¹³C NMR chemical shifts of Novichok agents based on conformational and density functional study calculations. Four organophosphorus compounds and five G- and V-type nerve agents were used to evaluate the accuracy of the proposed procedure. Moreover, ¹H and ¹³C NMR prediction results for an additional 83 Novichok candidates were compiled as a database to aid future research and identification. Further, this is the first study to successfully predict the NMR chemical shifts of Novichok agents, with an exceptional agreement between predicted and experimental data. The conclusions enable the prediction of all possible structures of Novichok agents and can serve as a firm foundation for preparation against future terrorist attacks using new variants of nerve agents.

Design and production strategies for developing a recombinant butyrylcholinesterase medical countermeasure for Organophosphorus poisoning

Organophosphorus nerve agents represent a serious chemical threat due to their ease of production and scale of impact. The recent use of the nerve agent Novichok has re-emphasised the need for broad-spectrum medical countermeasures (MCMs) to these agents. However, current MCMs are limited. Plasma derived human butyrylcholinesterase (huBChE) is a promising novel bioscavenger MCM strategy, but is prohibitively expensive to isolate from human plasma at scale. Efforts to produce recombinant huBChE (rBChE) in various protein expression platforms have failed to achieve key critical attributes of huBChE such as circulatory half-life. These proteins often lack critical features such as tetrameric structure and requisite post-translational modifications. This review evaluates previous attempts to generate rBChE and assesses recent advances in mammalian cell expression and protein engineering strategies that could be deployed to achieve the required half-life and yield for a viable rBChE MCM. This includes the addition of a proline-rich attachment domain, fusion proteins, post translational modifications, expression system selection and optimised downstream processes. Whilst challenges remain, a combinatorial approach of these strategies demonstrates potential as a technically feasible approach to achieving a bioactive and cost effective bioscavenger MCM.

Unambiguous identification and determination of A234-Novichok nerve agent biomarkers in biological fluids using GC-MS/MS and LC-MS/MS

The present study was intended to develop suitable methods for unambiguous identification and determination of ethyl (1-(diethylamino)ethylidene) phosphoramidofluoridate (known as A234-Novichok) biomarkers in urine and plasma samples. Multiple biomarkers were investigated for the first time, to verify intoxication by the A234-Novichok agent, using sensitive and accurate techniques including gas and liquid chromatography-tandem mass spectrometry (GC-MS/MS and LC-MS/MS). Like other nerve agents, in biological matrices, the A234-Novichok agent reacts with several proteins to form related adducts. Considering this, two different protein adduct biomarkers in blood samples were analyzed, and the regenerated A234 was determined. Two-dimensional chromatography and solid-phase extraction techniques were employed for blood sample preparation. Limits of detection for butyrylcholinesterase (BChE) adduct, the regenerated A234, and albumin covalent adduct were determined and reported as 1, 1, and 10 ng mL^-1, while the related calibration curves were linear within the range of 2-100, 2-100, and 15-100 ng mL^-1, respectively. The detection limit and linear range for the intact agent in the urine sample were determined as 0.1 and 1-100 ng mL^-1, respectively. Since A234 and some other Novichok chemicals have been added to the Schedule 1 of the Chemical Weapons Convention (CWC), Annex on Chemicals, after UK incidents, the analytical methods developed in this work might be used for verification purposes, as well as OPCW Biomedical Proficiency Tests.