Toxicology of Blister Agents: Is Melatonin a Potential Therapeutic Option?

Study on the Reaction Kinetics of Sulfur Mustard, Nitrogen Mustard and Their Chosen Analogues with Sodium Ethoxide

The course and kinetics of the reactions of sulfur mustard, nitrogen mustard and their selected analogues with sodium ethoxide were studied using a gas chromatograph coupled with a mass spectrometer. 2-chloroethyl ethyl sulfide (CEES), a monofunctional analogue of sulfur mustard (HD), bis(2-chloroethyl) ether (BCEE), an oxygen analogue of sulfur mustard, and bis(2-chloroethyl)amine, an analogue of nitrogen mustard HN-3, in which one hydrogen atom remains unsubstituted with a chloroethyl group, were used as imitators of mustards. For the study, the last mentioned compound was given the acronym HN-0. The research included checking how the form of sodium ethoxide influences the reaction rate. Two solutions were used: sodium ethoxide solution obtained by dissolving a commercially available compound in crystalline form and ethoxide solution obtained by dissolving sodium in ethanol. Additionally, the extent to which diethylenetriamine (DETA) accelerates the reactions of the studied compounds with sodium ethoxide was checked. The decontamination reactions were carried out in an anhydrous environment at a constant temperature of 25.0 °C. The rate of the mustard decontamination reaction increased significantly in systems containing DETA. Therefore, this amine can be used as a catalyst for this reaction. DETA has the most significant effect on the rate of the reaction of sodium ethoxide with CEES. The effect of the EtONa form was tested in the decontamination reaction of HD, revealing that both forms are equally effective, with only minor differences in reaction rates. Freshly synthesised sodium ethoxide reacts with HD 1.24 times faster. The study also assessed whether selected non-CWA compounds can be successfully used in studies as mustard imitators. Nitrogen mustard and bis(2-chloroethyl)amine reactions proceed according to the same mechanism-nucleophilic substitution. Bis(2-chloroethyl)amine reacts slightly faster than HN-3, both in solution with and without the addition of a catalyst. Sulfur mustard (HD) and CEES with sodium ethoxide and DETA undergo an elimination reaction, while BCEE undergoes a substitution reaction, which proceeds much slower. The observed differences disqualify BCEE as a sulfur mustard imitator. HD and CEES react with sodium ethoxide and DETA so quickly that the exact kinetic parameters under the developed experimental conditions could not be determined.

Acute exposure to nitrogen mustard induces rapid nuclear component regulation and delayed stress to exogenous stimuli

Nitrogen mustard (NM) is a vesicant agent with potent toxic effects on various tissues. Numerous theories have been proposed to explain its toxic mechanisms, yet research on the interconnections among these theories is lacking. This study focuses on analyzing the characteristics of genes involved in NM-induced bronchial injury within the Comparative Toxicogenomics Database (CTD). Subsequently, based on the CTD, we compared and analyzed the acute exposure and delayed changes following exposure in 16HBE cells. The injury processes caused by NM to bronchial and skin tissues are similar, primarily involving metabolism and regulation of nuclear constituents and inflammatory responses within the cellular matrix. During the acute exposure phase, NM rapidly induces nuclear stress, with the JUN family at the core of regulating metabolic and nucleic acid activities, and various nuclear binding proteins exhibit abnormalities. Delayed reactions following acute exposure are primarily centered in the cytoplasmic region, with diverse reaction types, including oxidative stress and responses to exogenous stimuli. Abnormalities in the activity of multiple cellular matrix enzymes are observed, with a relatively even involvement of various stress responses. Communication between the nucleus and cytoplasm is extreme active during the injury, and the content of the communication changes over time. These results suggest a temporal sequence in which NM causes chromatin damage and mediates cytoplasmic stress responses. In prevention and first aid, rapid DNA repair should be the primary focus, while subsequent treatment after acute exposure should focus more on delayed inflammatory and oxidative stress responses.

Leveraging 3D-printed microfluidic micromixers for the continuous manufacture of melatonin loaded SNEDDS with enhanced antioxidant activity and skin permeability

Vesicants are chemical warfare agents (CWAs) capable of causing severe skin damage and systemic toxicity. Melatonin, known for its anti-inflammatory and antioxidant properties, can mitigate the effects of these agents. Self-nano-emulsifying drug delivery systems (SNEDDS) containing a high melatonin concentration (5 %, 50 mg/g) were optimized using a quality-by-design approach from biocompatible, non-irritant excipients with a particle size of about 100 nm. The melatonin-loaded SNEDDS showed a 43-fold greater permeability than a conventional melatonin cream. Chemical stability at ambient temperature (25 °C) was maintained for one year. The preparation of optimised melatonin-loaded SNEDDS using a simple mixing method was compared to microfluidic micromixers. Mixing was successfully achieved using a 3D-printed (fused deposition modeling or stereolithography) T-shaped toroidal microfluidic chip (with a channel geometry optimized by computational fluid dynamics), resulting in a scalable, continuous process for the first time with a substantial reduction in preparation time compared to other conventional mixing approaches. No statistically significant differences were observed in the key quality attributes, such as particle size and melatonin loading, between mixing method till kinetic equilibrium solubility is reached and mixing using the 3D-printed micromixers. This scalable, continuous, cost-effective approach improves the overall efficiency of SNEDDS production, reduces the cost of quality control for multiple batches, and demonstrates the potential of continuous microfluidic manufacture with readily customizable 3D-printed micromixers at points of care, such as military bases.

Nitrogen mustard induces dynamic nuclear protein spectrum change and DNA-protein crosslinking, with p97 mediating repair

Nitrogen mustard (NM) is a chemotherapeutic agent capable of alkylating nucleophilic proteins and DNA, causing severe cell damage. However, no reports have been on the dynamic changes in proteomics induced by NM. In this study, we established a model of acute exposure to NM for 1 h and a continuous cultured model for 24 h after NM removal (repair stage) using 16HBE cells. The nuclear protein spectrum and nuclear proteins crosslinked with DNA were analyzed, and the function of p97 during NM damage was examined. An hour of NM exposure resulted in severe changes in the nuclear protein spectrum and protein into the cell nucleus, which is mainly involved in nuclear acid-related issues. After 24 h, the return to normal process of the types and amounts of differentially expressed proteins was inhibited by si-p97. The main processes involved in si-p97 intervention were nucleocytoplasmic transport, processing in the endoplasmic reticulum, metabolic abnormalities, and DNA-response; however. An hour of exposure to NM increased DNA-protein crosslinking (DPC), total-H2AX, and p-H2AX. In contrast, si-p97 only further increased or maintained their levels at 24 h yet not at 1 h. The effect of the proteasome inhibitor, MG132, was similar to that of si-p97. The siRNA of DVC1, a partner of p97, also increased the DPC content. Both si-p97 and si-DVC1 increased the cytoplasmic levels of the proteasome (PSMD2). These results suggest acute NM exposure induces severe nuclear protein spectral changes, rapid protein influx into the nucleus, DPC formation, and DNA double-strand breaks. Furthermore, our data indicated that p97 is involved in normal protein spectrum maintenance and DPC removal after NM withdrawal, requiring the participation of DVC1 and the proteasome.

Methimazole, an Effective Neutralizing Agent of the Sulfur Mustard Derivative 2-Chloroethyl Ethyl Sulfide

Sulfur mustard (SM), designated by the military as HD, is a highly toxic and dangerous vesicant that has been utilized as a chemical warfare agent since World War I. Despite SM's extensive history, an effective antidote does not exist. The effects of SM are predominantly based on its ability to alkylate important biomolecules. Also, with the potential for a fraction of SM to remain unreacted up to days after initial contact, a window of opportunity exists for direct neutralization of unreacted SM over the days following exposure. In this study, we evaluated the structure-activity relationship of multiple nucleophilic molecules to neutralize the toxic effects of 2-chloroethyl ethyl sulfide (CEES), a monofunctional analogue of SM, on human keratinocyte (HaCaT) cells. Cell viability, relative loss of extracellular matrix adhesions, and apoptosis caused by CEES were measured via MTT, cell-matrix adhesion (CMA), and apoptosis protein marker assays, respectively. A set of five two-carbon compounds with various functional groups served as a preliminary group of first-generation neutralizing agents to survey the correlation between mitigation of CEES's toxic effects and functional group nucleophilicity. Apart from thioacids, which produced additive toxicity, we generally observed the trend of increasing protection from cytotoxicity with increasing nucleophilicity. We extended this treatment strategy to second-generation agents which contained advantageous structural features identified from the first-generation molecules. Our results show that methimazole (MIZ), a currently FDA-approved drug used to treat hyperthyroidism, effectively reduced cytotoxicity, increased CMA, and decreased apoptosis resulting from CEES toxicity. MIZ selectively reacts with CEES to produce 2-(2-(ethylthio)ethylthio)-1-methyl-1H-imidazole (EEMI) in media and cell lysate treatments resulting in the reduction of toxicity. Based on these results, future development of MIZ as an SM therapeutic may provide a viable approach to reduce both the immediate and long-term toxicity of SM and may also help mitigate slower developing SM toxicity due to residual intact SM.

Melatonin as Modulator for Sulfur and Nitrogen Mustard-Induced Inflammation, Oxidative Stress and DNA Damage: Molecular Therapeutics

Sulfur and nitrogen mustards, bis(2-chloroethyl)sulfide and tertiary bis(2-chloroethyl) amines, respectively, are vesicant warfare agents with alkylating activity. Moreover, oxidative/nitrosative stress, inflammatory response induction, metalloproteinases activation, DNA damage or calcium disruption are some of the toxicological mechanisms of sulfur and nitrogen mustard-induced injury that affects the cell integrity and function. In this review, we not only propose melatonin as a therapeutic option in order to counteract and modulate several pathways involved in physiopathological mechanisms activated after exposure to mustards, but also for the first time, we predict whether metabolites of melatonin, cyclic-3-hydroxymelatonin, N1-acetyl-N2-formyl-5-methoxykynuramine, and N1-acetyl-5-methoxykynuramine could be capable of exerting a scavenger action and neutralize the toxic damage induced by these blister agents. NLRP3 inflammasome is activated in response to a wide variety of infectious stimuli or cellular stressors, however, although the precise mechanisms leading to activation are not known, mustards are postulated as activators. In this regard, melatonin, through its anti-inflammatory action and NLRP3 inflammasome modulation could exert a protective effect in the pathophysiology and management of sulfur and nitrogen mustard-induced injury. The ability of melatonin to attenuate sulfur and nitrogen mustard-induced toxicity and its high safety profile make melatonin a suitable molecule to be a part of medical countermeasures against blister agents poisoning in the near future.

The Multiple Functions of Melatonin: Applications in the Military Setting

The aim of this review is to provide the reader with a general overview on the rationale for the use of melatonin by military personnel. This is a technique that is being increasingly employed to manage growing psycho-physical loads. In this context, melatonin, a pleotropic and regulatory molecule, has a potential preventive and therapeutic role in maintaining the operational efficiency of military personnel. In battlefield conditions in particular, the time to treatment after an injury is often a major issue since the injured may not have immediate access to medical care. Any drug that would help to stabilize a wounded individual, especially if it can be immediately administered (e.g., per os) and has a very high safety profile over a large range of doses (as melatonin does) would be an important asset to reduce morbidity and mortality. Melatonin may also play a role in the oscillatory synchronization of the neuro-cardio-respiratory systems and, through its epigenetic action, poses the possibility of restoring the main oscillatory waves of the cardiovascular system, such as the Mayer wave and RSA (respiratory sinus arrhythmia), which, in physiological conditions, result in the oscillation of the heartbeat in synchrony with the breath. In the future, this could be a very promising field of investigation.

In Vitro and In Vivo Characteristics of Olive Oil as Excipient for Topical Administration

Oily excipients are vital components of dermatological products. In this study, the in vitro and in vivo characteristics of Wild Olive Oil (WOO) were compared with two other types of olive oils: Extra Virgin Olive Oil (EVOO) and Virgin Olive Oil (VOO). This work has also included Liquid Paraffin (LP) and Rosehip Oil (RO) as reference oils. Melatonin was used in the study as a model drug to demonstrate the antioxidant capacity of the oils. The melatonin carrier capacity and antioxidant performance was related to the degree of unsaturation of the oils and was highest for RO and WOO and lowest for LP. However, the most stable oil to oxidation was LP. The in vivo performance of the oils in the skin of eight healthy volunteers was investigated with a dermoanalyser. The highest increment of oil and hydration in the skin was obtained with RO. The lowest perception of oiliness was described for WOO, which produced the highest increase in elasticity of the skin area where it was applied. An in vitro-in vivo correlation was therefore performed through multivariable analysis (MVA).

Role of hair follicles in the pathogenesis of arsenical-induced cutaneous damage

Arsenical vesicants cause skin inflammation, blistering, and pain. The lack of appropriate animal models causes difficulty in defining their molecular pathogenesis. Here, Ptch1+/- /C57BL/6 mice were employed to investigate the pathobiology of the arsenicals lewisite and phenylarsine oxide (PAO). Following lewisite or PAO challenge (24 h), the skin of animals becomes grayish-white, thick, leathery, and wrinkled with increased bi-fold thickness, Draize score, and necrotic patches. In histopathology, infiltrating leukocytes (macrophages and neutrophils), epidermal-dermal separation, edema, apoptotic cells, and disruption of tight and adherens junction proteins can be visualized. PCR arrays and nanoString analyses showed significant increases in cytokines/chemokines and other proinflammatory mediators. As hair follicles (HFs), which provide an immune-privileged environment, may affect immune cell trafficking and consequent inflammatory responses, we compared the pathogenesis of these chemicals in this model to that in Ptch1+/- /SKH-1 hairless mice. Ptch1+/- /SKH-1 mice have rudimentary, whereas Ptch1+/- /C57BL/6 mice have well-developed HFs. Although no significant differences were observed in qualitative inflammatory responses between the two strains, levels of cytokines/chemokines differed. Importantly, the mechanism of inflammation was identical; both reactive oxygen species induction and consequent activation of unfolded protein response signaling were similar. These data reveal that the acute molecular pathogenesis of arsenicals in these two murine models is similar.

Toxic blister agents: Chemistry, mode of their action and effective treatment strategies

Since their use during the First World War, Blister agents have posed a major threat to the individuals and have caused around two million casualties. Major incidents occurred not only due to their use as chemical warfare agents but also because of occupational hazards. Therefore, a clear understanding of these agents and their mode of action is essential to develop effective decontamination and therapeutic strategies. The blister agents have been categorised on the basis of their chemistry and the biological interactions that entail post contamination. These compounds have been known to majorly cause blisters/bullae along with alkylation of the contaminated DNA. However, due to the high toxicity and restricted use, very little research has been conducted and a lot remains to be clearly understood about these compounds. Various decontamination solutions and detection technologies have been developed, which have proven to be effective for their timely mitigation. But a major hurdle seems to be the lack of proper understanding of the toxicological mechanism of action of these compounds. Current review is about the detailed and updated information on physical, chemical and biological aspects of various blister agents. It also illustrates the mechanism of their action, toxicological effects, detection technologies and possible decontamination strategies.