Warfare Nerve Agents and Paraoxonase-1 as a Potential Prophylactic Therapy against Intoxication.

Nerve agents are a class of lethal neurotoxic chemicals used in chemical warfare. In this review, we have briefly discussed a brief history of chemical warfare, followed by an exploration of the historical context surrounding nerve agents. The article explores the classification of these agents, their contemporary uses, their toxicity mechanisms, and the disadvantages of the current treatment options for nerve agent poisoning. It then discusses the possible application of enzymes as prophylactics against nerve agent poisoning, outlining the benefits and drawbacks of paraoxonase-1. Finally, the current studies on paraoxonase-1 are reviewed, highlighting that several challenges need to be addressed in the use of paraoxonase-1 in the actual field and that its potential as a prophylactic antidote against nerve agent poisoning needs to be evaluated. The literature used in this manuscript was searched using various electronic databases, such as PubMed, Google Scholar, Web of Science, Elsevier, Springer, ACS, Google Patent, and books using the keywords chemical warfare agent, Butyrylcholinesterase, enzyme, nerve agent, prophylactic, and paraoxonase- 1, with the time scale for the analysis of articles between 1960 to 2023, respectively. The study has suggested that concerted efforts by researchers and agencies must be made to develop effective countermeasures against NA poisoning and that PON1 has suitable properties for the development of efficient prophylaxis against NA poisoning.

Is Human Paraoxonase 1 the Saviour Against the Persistent Threat of Organophosphorus Nerve Agents?

Nerve agents have been used extensively in chemical warfare in the past. However, recent use of Novichok agents have reignited the debate on the threat posed by Organophosphorus Nerve Agents (OPNAs). The currently available therapy for OPNA toxicity is only symptomatic and is potentially ineffective in neutralizing OPNAs. Hence, there is a dire need to develop a prophylactic therapy for counteracting OPNA toxicity. In this regard, human paraoxonase 1 has emerged as the enzyme of choice. In this review, we have focussed upon the recent and past events of OPNA use, their mechanism of action and toxicity. Further, we have emphasized upon the potential of enzyme based therapy and the various advances in the development of paraoxonase 1 as a countermeasure for OPNA poisoning. Finally, we have elaborated the shortcomings of paraoxonase 1 and the work that needs to be undertaken in order to develop human paraoxonase 1 as a prophylactic against OPNA poisoning.

Protein Chimerization: A New Frontier for Engineering Protein Therapeutics with Improved Pharmacokinetics.

With the advancement of medicine, the utility of protein therapeutics is increasing exponentially. However, a significant number of protein therapeutics suffer from grave limitations, which include their subpar pharmacokinetics. In this study, we have reviewed the emerging field of protein chimerization for improving the short circulatory half-life of protein therapeutics. We have discussed various aspects of protein therapeutics aiming at their mechanism of clearance and various approaches used to increase their short circulatory half-life with principal focus on the concept of chimerization. Furthermore, we have comprehensively reviewed various components of chimera, such as half-life extension partners and linkers, their shortcomings, and prospective work to be undertaken for developing effective chimeric protein therapeutics.

Organophosphate-Hydrolyzing Enzymes as First-Line of Defence Against Nerve Agent-Poisoning: Perspectives and the Road Ahead.

Nerve agents (NAs) are extremely neurotoxic synthetic organophosphate (OP) compounds exploited as weapons of mass destruction in terrorist attacks and chemical warfare. Considering the current world scenario, there is a persistent threat of NA-exposure to military personals and civilians. Various prophylactic and post-exposure treatments (such as atropine and oximes) available currently for NA-poisoning are inadequate and unsatisfactory and suffer from severe limitations. Hence, developing safe and effective treatment(s) against NA-poisoning is a critical necessity. With regards to counteracting NA-toxicity, the OP-hydrolyzing enzymes (OPHEs), which can hydrolyze and inactivate a variety of NAs, have emerged as promising candidates for the development of prophylactic therapy against NA-poisoning. However, there are many hurdles to be crossed before these enzymes can be brought to therapeutic use in humans. In this article, we have reviewed the various advancements in the field of development of OPHEs as prophylactic against NA-poisoning. The article majorly focuses on the toxic effects of NAs, various available therapies to counteract NA poisoning, the current status of OPHEs and attempts made to improve the various properties of these enzymes. Further, we have also briefly discussed about the prospective work that is needed to be undertaken for developing these OPHEs into those suitable for use in humans.

Toward Understanding the Catalytic Mechanism of Human Paraoxonase 1: Site-Specific Mutagenesis at Position 192.

Human paraoxonase 1 (h-PON1) is a serum enzyme that can hydrolyze a variety of substrates. The enzyme exhibits anti-inflammatory, anti-oxidative, anti-atherogenic, anti-diabetic, anti-microbial and organophosphate-hydrolyzing activities. Thus, h-PON1 is a strong candidate for the development of therapeutic intervention against a variety conditions in human. However, the crystal structure of h-PON1 is not solved and the molecular details of how the enzyme hydrolyzes different substrates are not clear yet. Understanding the catalytic mechanism(s) of h-PON1 is important in developing the enzyme for therapeutic use. Literature suggests that R/Q polymorphism at position 192 in h-PON1 dramatically modulates the substrate specificity of the enzyme. In order to understand the role of the amino acid residue at position 192 of h-PON1 in its various hydrolytic activities, site-specific mutagenesis at position 192 was done in this study. The mutant enzymes were produced using Escherichia coli expression system and their hydrolytic activities were compared against a panel of substrates. Molecular dynamics simulation studies were employed on selected recombinant h-PON1 (rh-PON1) mutants to understand the effect of amino acid substitutions at position 192 on the structural features of the active site of the enzyme. Our results suggest that, depending on the type of substrate, presence of a particular amino acid residue at position 192 differentially alters the micro-environment of the active site of the enzyme resulting in the engagement of different subsets of amino acid residues in the binding and the processing of substrates. The result advances our understanding of the catalytic mechanism of h-PON1.