Chemical Warfare

Molecular Modeling Study of Uncharged Oximes Compared to HI-6 and 2-PAM Inside Human AChE Sarin and VX Conjugates

The deleterious effects of nerve agents over the enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) turned these compounds into the most dangerous chemical weapons known. Among the antidotes in use today against these agents, oximes in combination with other drugs are the only treatment with any action. HI-6 and 2-PAM are cationic oximes proved to be effective for the reactivation of AChE inhibited by the nerve agents VX and sarin (GB). However, when it comes to reactivation of AChE inside the central or peripheral nervous systems, charged molecules present low diffusion due to low penetration through the blood-brain barrier. Uncharged oximes appear as an interesting alternative to solve this problem, but the development and enhancement of more efficient uncharged oximes capable of reactivating human AChE is still necessary. Given the limitations for in vivo and in vitro experimental studies with nerve agents, modeling is an important tool that can contribute to a better understanding of factors that may affect the efficiency of uncharged oximes. In order to investigate the interaction and behavior of cationic and uncharged oximes, we performed here molecular docking, molecular dynamics simulations, and binding energies calculations of the known cationic oximes HI-6 and 2-PAM plus four uncharged oximes found in the literature, complexed with human AChE (HssACHE) conjugated with the nerve agents VX and GB. The uncharged oximes showed different behaviors, especially RS194B, which presented stability inside AChE-VX, but presented free binding energy lower than cationic oximes, suggesting that structural alterations could favor its interactions with these complexes. In contrast, HI-6 and 2-PAM showed higher affinities with more negative binding energy values and larger contribution of the amino acid Asp74, demonstrating the importance of the quaternary nitrogen to the affinity and interaction of oximes with AChE-GB and AChE-VX conjugates.

Nerve agents: a guide for emergency nurses. Part 1

Recent incidents in the UK and the alleged chemical attacks in Syria by the Bashar al-Assad regime have brought the subject of chemical weapons back into the public domain. To date these types of event have been relatively rare because terrorist plans to harm large numbers of people have mostly been thwarted. This is the first part of a two-part article on nerve agents. Part one gives an overview of these agents, their historical background and manufacture, and how the agents affect physiology. Part two, which will appear in the next issue, considers the pre-hospital response to the use of nerve agents, including effective triage and decontamination, and in-hospital treatment.

The intriguing biology and chemistry of fosfomycin: the only marketed phosphonate antibiotic

Recently infectious diseases caused by the increased emergence and rapid spread of drug-resistant bacterial isolates have been one of the main threats to global public health because of a marked surge in both morbidity and mortality. The only phosphonate antibiotic in the clinic, fosfomycin, is a small broad-spectrum molecule that effectively inhibits the initial step in peptidoglycan biosynthesis by blocking the enzyme, MurA in both Gram-positive and Gram-negative bacteria. As fosfomycin has a novel mechanism of action, low toxicity, a broad spectrum of antibacterial activity, excellent pharmacodynamic/pharmacokinetic properties, and good bioavailability, it has been approved for clinical use in the treatment of urinary tract bacterial infections in many countries for several decades. Furthermore, its potential use for difficult-to-treat bacterial infections has become promising, and fosfomycin has become an ideal candidate for the effective treatment of bacterial infections caused by multidrug-resistant isolates, especially in combination with other therapeutic drugs. Here we aim to present an overview of the biology and chemistry of fosfomycin including isolation and characterization, pharmacology, biosynthesis and chemical synthesis since its discovery in order to not only help scientists reassess the role of this exciting drug in fighting antibiotic resistance but also build the stage for discovering more novel phosphonate antibiotics in the future.

Blood and bronchoalveolar lavage fluid acetylcholinesterase levels following microinstillation inhalation exposure to sarin in Guinea pigs

We determined acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) inhibition in the bronchoalveolar lavage fluid (BALF) following inhalation exposure to chemical threat nerve agent (CTNA) sarin. Age- and weight-matched male guinea pigs were exposed to five different doses of sarin (169.3, 338.7, 508, 677.4, and 846.5 mg/m(3)) using a microinstillation inhalation exposure technique for 4 min. The technique involves aerosolization of the agent in the trachea using a microcatheter with a center hole that delivers the agent and multiple peripheral holes that pumps air to aerosolize the agent at the tip. Animals exposed to higher doses of sarin occasionally developed seizures and succumbed to death within 15 min after exposure. The LCt(50) for sarin using the microinstillation technique was determined to be close to 677.4 mg/m(3). Ear blood AChE activity showed a dose-dependent inhibition at 15 min postexposure. The inhibition of blood AChE remained constant over 35 and 55 min after sarin exposure indicating that there was no lung depot effect. Cardiac blood AChE and butyrylcholinesterase (BChE) activity in surviving animals euthanized at 24 h postexposure showed a dose-dependent inhibition with an inhibition of 60% at 677.4 and 846.5 mg/m(3) sarin exposure. AChE and BChE activity in bronchoalveolar lavage fluid (BALF) showed a slight increase at 338.7 to 677.4 mg/m(3) sarin exposure but a marginal inhibition at 169.3 mg/m(3). In contrast, the AChE protein levels determined by immunoblotting showed an increase at 169.3 mg/m(3) in the BALF. The BALF protein level, a biomarker of lung injury, was increased maximally at 338.7 mg/m(3) and that increase was dropped with an increase in the dose of sarin. The BALF protein levels correlated with the AChE and BChE activity. These data suggest that sarin microinstillation inhalation exposure results in respiratory toxicity and lung injury characterized by changes in lavage AChE, BChE, and protein levels.

Acute toxic effects of nerve agent VX on respiratory dynamics and functions following microinsillation inhalation exposure in guinea pigs

Exposure to a chemical warfare nerve agent (CWNA) leads to severe respiratory distress, respiratory failure, or death if not treated. We investigated the toxic effects of nerve agent VX on the respiratory dynamics of guinea pigs following exposure to 90.4 mug/m3 of VX or saline by microinstillation inhalation technology for 10 min. Respiratory parameters were monitored by whole-body barometric plethysmography at 4, 24, and 48 h, 7 d, 18 d, and 4 wk after VX exposure. VX-exposed animals showed a significant decrease in the respiratory frequency (RF) at 24 and 48 h of recovery (p value .0329 and .0142, respectively) compared to the saline control. The tidal volume (TV) slightly increased in VX exposed animals at 24 and significantly at 48 h (p = .02) postexposure. Minute ventilation (MV) increased slightly at 4 h but was reduced at 24 h and remained unchanged at 48 h. Animals exposed to VX also showed an increase in expiratory (Te) and relaxation time (RT) at 24 and 48 h and a small reduction in inspiratory time (Ti) at 24 h. A significant increase in end expiratory pause (EEP) was observed at 48 h after VX exposure (p = .049). The pseudo lung resistance (Penh) was significantly increased at 4 h after VX exposure and remained slightly high even at 48 h. Time-course studies reveal that most of the altered respiratory dynamics returned to normal at 7 d after VX exposure except for EEP, which was high at 7 d and returned to normal at 18 d postexposure. After 1 mo, all the monitored respiratory parameters were within normal ranges. Bronchoalveolar lavage (BAL) 1 mo after exposure showed virtually no difference in protein levels, cholinesterase levels, cell number, and cell death in the exposed and control animals. These results indicate that sublethal concentrations of VX induce changes in respiratory dynamics and functions that over time return to normal levels.