Acute intensive care unit management of mustard gas victims: the Turkish experience. Cutan Ocul Toxicol 2018;37:332-337. [PMID: 29648477 DOI: 10.1080/15569527.2018.1464018]

The blistering warfare agent O-mustard (agent T) generates protein-adducts with human serum albumin useful for biomedical verification of exposure and forms intramolecular cross-links

The highly blistering sulfur mustard analogue agent T (bis(2-chloroethylthioethyl) ether), also known as O-mustard or oxy-mustard, is a common impurity in military grade sulfur mustard (SM) and a component of mixtures such as "HT" that are still found in old munitions. Together with sesquimustard (Q), it is the most important SM analogue and tightly regulated as a Schedule 1 chemical under the Chemical Weapons Convention. We report the adducts of T with nucleophilic Cys34 and other residues in human serum albumin (HSA) formed in vitro. A micro liquid chromatography electrospray ionization high-resolution tandem-mass spectrometry method (µLC-ESI MS/HR MS) was developed for the detection and identification of biomarker peptides alkylated by a T-derived hydroxyethylthioethyloxyethylthioethyl (HETEOETE)-moiety (as indicated by an asterisk below). Following proteolysis of T-exposed human plasma with pronase, the dipeptide Cys34*Pro and the single amino acid residue His* were produced. The use of proteinase K yielded Cys34*ProPhe and the use of pepsin generated ValThrGlu48*Phe, AlaGlu230*ValSerLysLeu, and LeuGlyMet329*Phe. Corresponding peptide-adducts of SM and Q were detected in a common workflow that in principle allowed the estimation of the mustard or mustard composition encountered during exposure. Novel adducts of Q at the Glu230 and Met239 residues were detected and are reported accordingly. Based on molecular dynamics simulations, we identified regular interactions of the Cys34(-HETEOETE)-moiety with several glutamic acid residues in HSA including Glu86, which is not an obvious interaction partner by visual inspection of the HSA crystal structure. The existence of this and other intramolecular cross-links was experimentally proven for the first time.

Granulocyte Colony-Stimulating Factor (Neupogen®; Filgrastim) Accelerates Neutrophil Recovery in a Rodent Model of Sulfur Mustard-Induced Hematologic Toxicity

OBJECTIVE

Evidence of myelosuppression has been negatively correlated with patient outcomes following cases of high dose sulfur mustard (SM) exposure. These hematologic complications can negatively impact overall immune function and increase the risk of infection and life-threatening septicemia. Currently, there are no approved medical treatments for the myelosuppressive effects of SM exposure.

METHODS

Leveraging a recently developed rodent model of SM-induced hematologic toxicity, post-exposure efficacy testing of the granulocyte colony-stimulating factor drug Neupogen® was performed in rats intravenously challenged with SM. Before efficacy testing, pharmacokinetic/pharmacodynamic analyses were performed in naïve rats to identify the apparent human equivalent dose of Neupogen® for efficacy evaluation.

RESULTS

When administered 1 d after SM-exposure, daily subcutaneous Neupogen® treatment did not prevent the delayed onset of hematologic toxicity but significantly accelerated recovery from neutropenia. Compared with SM controls, Neupogen®-treated animals recovered body weight faster, resolved toxic clinical signs more rapidly, and did not display transient febrility at time points generally concurrent with marked pancytopenia.

CONCLUSIONS

Collectively, this work corroborates the results of a previous pilot large animal study, validates the utility of a rodent screening model, and provides further evidence for the potential clinical utility of Neupogen® as an adjunct treatment following SM exposure.

Differential gene expression and protein-protein interaction network profiling of sulfur mustard-exposed rabbit corneas employing RNA-seq data and bioinformatics tools

Sulfur mustard (SM) ocular exposure severely damages the cornea and causes vision impairment. At present, no specific therapy exists to mitigate SM-induced corneal injury and vision loss. This study performed transcriptome profiling of naïve, SM-damaged, and SM-undamaged rabbit corneas using RNA-seq analysis and bioinformatic tools to gain a better mechanistic understanding and develop SM-specific medical countermeasures. The mRNA profiles of rabbit corneas 4 weeks post SM vapor exposure were generated using Illumina-NextSeq deep sequencing (Gene Expression Omnibus accession # GSE127708). The RNA sequences of naïve (n = 4), SM-damaged (n = 5), and SM-undamaged (n = 5) corneas were subjected to differential expression (DE) analysis after quality control profiling with FastQC. DE analysis was performed using HISAT2, StringTie, and DESeq2. The log2(FC)±2 and adjusted p˂0.05 were chosen to identify the most relevant genes. A total of 5930 differentially expressed genes (DEGs) (upregulated: 3196, downregulated: 2734) were found in SM-damaged corneas compared to naïve corneas, whereas SM-undamaged corneas showed 1884 DEGs (upregulated: 1029, downregulated: 855) compared to naïve corneas. DE profiling of SM-damaged corneas to SM-undamaged corneas revealed 985 genes (upregulated: 308, downregulated: 677). The DE profiles were subsequently subjected to signaling pathway enrichment, and protein‒protein interactions (PPIs) were analyzed. Pathway enrichment was performed for the genes associated with cellular apoptosis, death, adhesion, migration, differentiation, proliferation, extracellular matrix, and tumor necrosis factor production. To identify novel targets, we narrowed the pathway analysis to upregulated and downregulated genes associated with cell proliferation and differentiation, and PPI networks were developed. Furthermore, protein targets associated with cell differentiation and proliferation that may play vital roles in corneal fibrosis and wound healing post SM injury were identified.

Simultaneous Quantification of Biomarkers for Bis-(2-chloroethyl) Sulfide and 1,2-Bis(2-chloroethylthio) Ethane Exposure in Human Urine at Trace Exposure Levels by Gas Chromatography Tandem Mass Spectrometry via Simultaneous Incubation and Extraction

Sulfur mustard [HD; bis-(2-chloroethyl) sulfide] and other analogues are a kind of highly toxic vesicant and have been prohibited by the Organization for the Prohibition of Chemical Weapons (OPCW) since 1997. Exposures to HD could generate several adducts in the plasma and hydrolysis products in the urine, which are widely applied as biomarkers to identify HD exposure in forensic analysis. Several methods have been developed for the detection of related biomarkers. However, most methods are based on complex derivatization, and not enough attention is paid to HD analogues. A modified and convenient analytical method reported herein includes simultaneous incubation and organic solvent extraction. The biomarkers such as thiodiglycol and 1,2-bis (2-hydroxyethylthio) are transferred to HD and 1,2-bis(2-chloroethylthio) ethane via hydrochloric acid at the appropriate temperature. The analytes are analyzed by gas chromatography tandem mass spectrometry (GC-MS/MS) with 2-chloroethyl ethyl sulfide (2-CEES) applied as the internal standard. The interday and intraday study according to FDA rules has been achieved to evaluate the accuracy and precision of the method. The two targets are detected with a good linearity (R2 > 0.99) in the concentration ranges from 5 to 1000 ng/mL and 10 to 1000 ng/mL, with small relative standard deviations (RSD ≤6.62% and RSD ≤6.93%) and favorable recoveries between 90.3 and 107.3% and between 89.4 and 108.7%, respectively. The established method can be used for retrospective detection of sulfur mustards in biological samples and successfully applied in the biomedical proficiency testing organized by the OPCW.

Mustard Gas Exposure Actuates SMAD2/3 Signaling to Promote Myofibroblast Generation in the Cornea

Sulfur mustard gas (SM) is a vesicating and alkylating agent used as a chemical weapon in many mass-casualty incidents since World War I. Ocular injuries were reported in >90% of exposed victims. The mechanisms underlying SM-induced blindness remain elusive. This study tested the hypothesis that SM-induced corneal fibrosis occurs due to the generation of myofibroblasts from resident fibroblasts via the SMAD2/3 signaling pathway in rabbit eyes in vivo and primary human corneal fibroblasts (hCSFs) isolated from donor corneas in vitro. Fifty-four New Zealand White Rabbits were divided into three groups (Naïve, Vehicle, SM-Vapor treated). The SM-Vapor group was exposed to SM at 200 mg-min/m3 for 8 min at the MRI Global facility. Rabbit corneas were collected on day 3, day 7, and day 14 for immunohistochemistry, RNA, and protein lysates. SM caused a significant increase in SMAD2/3, pSMAD, and ɑSMA expression on day 3, day 7, and day 14 in rabbit corneas. For mechanistic studies, hCSFs were treated with nitrogen mustard (NM) or NM + SIS3 (SMAD3-specific inhibitor) and collected at 30 m, 8 h, 24 h, 48 h, and 72 h. NM significantly increased TGFβ, pSMAD3, and SMAD2/3 levels. On the contrary, inhibition of SMAD2/3 signaling by SIS3 treatment significantly reduced SMAD2/3, pSMAD3, and ɑSMA expression in hCSFs. We conclude that SMAD2/3 signaling appears to play a vital role in myofibroblast formation in the cornea following mustard gas exposure.

Evaluation of patients admitted to the emergency room with the claim of being exposed to chemical gas in northwest Syria

Objective: Our study, it was aimed to evaluate the patients who applied after being affected by chemical gas in northwest Syria, to examine the treatment results, and to raise awareness about chemical gas attacks. Method: The study included 43 patients who applied to the emergency department of our hospital, who felt an odor similar to the smell of onion and garlic and were sick. Our research is a retrospective study. Retrospective data were collected from the files of patients admitted after gas exposure. Statistical analyzes of the study were performed using Statistical Package for Social Sciences version 25.0 software for Windows. P-value below 0.05 in all statistical analyzes were interpreted as statistically significant. Results: All 43 patients were male. The mean age was 24.86 ∓ 8.81 years. Vital signs at the time of application; mean blood pressure 97.23 ∓ 5.61 mmHg, fever 37.2 ∓ 0.57 °C, heart rate 99.28 ∓ 9.89 / min, oxygen saturation 96.43 ∓ 1.53 %. In total, 3 patients had convulsions. 20 patients had agitation and spasm sensation, 12 patients had redness of the eyes and 42 patients had complaints of shortness of breath. Conclusion: Awareness, rapid decontamination, and symptomatic treatment are thought to be very important in minimizing the devastating effects of chemical attack agents.

Simultaneous quantification of multiple amino acid adducts from sulfur mustard-modified human serum albumin in plasma at trace exposure levels by ultra-high performance liquid chromatography-triple quadrupole mass spectrometry after propionyl derivatization

Sulfur mustard (HD) is a highly toxic vesicant and is prohibited by the Organisation for the Prohibition of Chemical Weapons (OPCW). HD can modify human serum albumin (HSA) to generate hydroxyethylthioethyl (HETE) adducts, which could be utilized as biomarkers for verifying HD exposure in forensic analysis. Here, five amino acid adducts generated from pronase digestion of HD-exposed human serum albumin (HD-HSA) in plasma were selected as biomarkers to retrospectively detect HD exposure. HD-HSA was precipitated from plasma with acetone, digested by pronase, derivatized with propionic anhydride (PA), and analysed with ultra-high performance liquid chromatography coupled with triple quadrupole mass spectrometry (UHPLC-TQ MS). The limits of detection (LODs) and limits of quantification (LOQs) of the HD exposure concentrations were evaluated as 1.00 ng/mL at S/N≥3 and 3.00 ng/mL at S/N≥10, respectively, which are approximately 60 times lower than those of the reported method. The approach shows good linearity (R²≥0.997) from 3.00 ng/mL to 10.0 µg/mL of HD-exposed human plasma with satisfactory precision and accuracy. The developed approach was applied to analysing samples from the 6^th OPCW Biomedical Proficiency Test (BioPT). The study showed that the developed approach was also suitable for analysing human plasma samples that were exposed to six of HD analogues, which were common impurities in sulfur mustard mixtures. Moreover, the method was successfully applied to plasma from other species, including rabbits, rats and cattle. This study provides a reliable and sensitive tool for the retrospective detection of vesicants exposure based on multiple biomarkers.

Cross-border strategies for access to healthcare in violent conflict – a scoping review

Background

The geographical reconfiguration of healthcare systems in times of violent conflict is increasingly being recognised in academic literature. This includes conflict-induced, cross-border travel for medical treatment. Yet the conceptual approach to this healthcare-seeking behaviour, by a population here referred to as cross-border population, remains poorly understood. This scoping review identifies academic literature on cross-border populations to map the current approach to cross-border populations and to propose a research agenda.

Methods

The study used a scoping review following the Joanna Briggs Institute Scoping Review methodology. We included articles on conflicts between 1980 and 2019.

Results

A total of 53 articles met the inclusion criteria. From these articles, we distinguished four types of studies on cross-border healthcare: Direct analysis, implicit analysis, clinical research, and identification. The 45 articles belonging to the first three categories were then searched for themes specifically relevant to healthcare for cross-border populations and linked with sub-themes such as border crossing time and the types of healthcare available. These themes were structured into three main areas: access to care; quality of care; and governance of care. Our analysis then describes the available knowledge, documented practices, and challenges of cross-border healthcare specifically in conflict settings.

Conclusions

A better understanding of cross-border healthcare systems is required to inform local practices and develop related regional and international policies. While the reviewed literature provides some highlights on various practices of cross-border healthcare, there are many gaps in available knowledge of this topic. To address these gaps, our study proposes a research framework outlining key themes and research questions to be investigated by signposting where major research and operational gaps remain. This facilitates well-directed future work on cross-border therapeutic geographies in the context of armed conflict and furthers understanding of a hitherto largely ignored area of the international healthcare system.

Effect of dexamethasone treatment at variable therapeutic windows in reversing nitrogen mustard-induced corneal injuries in rabbit ocular in vivo model

Nitrogen mustard (NM) is an analogue of the potent vesicating agent sulfur mustard, with well-established ocular injury models in rabbit eyes to study vesicant-induced ocular toxicity. The effects of NM-exposure to eyes may include irritation, redness, inflammation, fibrosis, epithelial degradation, blurred vision, partial/complete blindness, which may be temporary or permanent, depending on the route, duration, and dosage of exposure. Effective countermeasures against vesicant exposure are presently not available and are warranted in case of any terrorist activity or accidental leakage from stockpiles. Herein, our focus was to evaluate whether dexamethasone (DEX), an FDA approved potent corticosteroid with documented anti-inflammatory activities, could be an effective treatment modality. Accordingly, utilizing NM-induced corneal injuries in rabbit ocular in vivo model, we examined and compared the efficacy of DEX treatments when administration was started at early (2 h), intermediate (4 h), and late (6 h) therapeutic windows of intervention after NM-exposure and administered every 8 h thereafter. The effects of NM-exposure and DEX treatments were evaluated on clinical (corneal opacity, ulceration, and neovascularization), biological (epithelial thickness, epithelial-stromal separation, blood vessels density, and inflammatory cell and keratocyte counts) and molecular (COX-2 and VEGF expression) parameters, at day 1, 3, 7 and 14. Results indicated that DEX treatment markedly and effectively reversed the NM-induced injury markers in rabbit corneas. Early administration of DEX at 2 h was found to be most effective in reversing NM-induced corneal injuries, followed by DEX 4 h and DEX 6 h administration initiation, indicating that DEX has best efficacy at the early therapeutic window in our study model.

Advice on assistance and protection provided by the Scientific Advisory Board of the Organisation for the Prohibition of Chemical Weapons: Part 3. On medical care and treatment of injuries from sulfur mustard

Blister agents damage the skin, eyes, mucous membranes and subcutaneous tissues. Other toxic effects may occur after absorption. The response of the Scientific Advisory Board (SAB) of the Organisation for the Prohibition of Chemical Weapons (OPCW) to a request from the OPCW Director-General in 2013 on the status of medical countermeasures and treatments to blister agents is updated through the incorporation of the latest information. The physical and toxicological properties of sulfur mustard and clinical effects and treatments are summarised. The information should assist medics and emergency responders who may be unfamiliar with the toxidrome of sulfur mustard and its treatment.

Evidence of sulfur mustard poisoning by detection of the albumin-derived dipeptide biomarker C(-HETE)P after nicotinylation

Sulfur mustard (SM, bis[2-chloroethyl]-sulfide) is a banned chemical warfare agent that was frequently used in recent years and led to numerous poisoned victims who developed painful erythema and blisters. Post-exposure analysis of SM incorporation can be performed by the detection of human serum albumin (HSA)-derived peptides. HSA alkylated by SM contains a hydroxyethylthioethyl (HETE)-moiety bound to the cysteine residue C³⁴ yielding the dipeptide biomarker C(-HETE)P after pronase-catalyzed proteolysis. We herein present a novel procedure for the selective precolumn nicotinylation of its N-terminus using 1-nicotinoyloxy-succinimide. The reaction was carried out for 2 h at ambient temperature with a yield of 81%. The derivative NA-C(-HETE)P was analyzed by micro liquid chromatography-electrospray ionization tandem-mass spectrometry working in the selected reaction monitoring mode (μLC-ESI MS/MS SRM). The derivative was shown to be stable in the autosampler at 15°C for at least 24 h. The single protonated precursor ion (m/z 428.1) was subjected to collision-induced dissociation yielding product ions at m/z 116.1, m/z 137.0, and m/z 105.0 used for selective monitoring without any plasma-derived interferences. NA-C(-HETE)P showed a mass spectrometric response superior to the non-derivatized dipeptide thus yielding larger peak areas (factor 1.3 ± 0.2). The lower limit of identification corresponded to 80 nM SM spiked to plasma in vitro. The presented procedure was applied to real case plasma samples from 2015 collected in the Middle East confirming SM poisoning.

Alkylated epidermal creatine kinase as a biomarker for sulfur mustard exposure: comparison to adducts of albumin and DNA in an in vivo rat study

Sulfur mustard (SM) is a chemical warfare agent which use is banned under international law and that has been used recently in Northern Iraq and Syria by the so-called Islamic State. SM induces the alkylation of endogenous proteins like albumin and hemoglobin thus forming covalent adducts that are targeted by bioanalytical methods for the verification of systemic poisoning. We herein report a novel biomarker, namely creatine kinase (CK) B-type, suitable as a local biomarker for SM exposure on the skin. Human and rat skin were proven to contain CK B-type by Western blot analysis. Following exposure to SM ex vivo, the CK-adduct was extracted from homogenates by immunomagnetic separation and proteolyzed afterwards. The cysteine residue Cys²⁸² was found to be alkylated by the SM-specific hydroxyethylthioethyl (HETE)-moiety detected as the biomarker tetrapeptide TC(-HETE)PS. A selective and sensitive micro liquid chromatography-electrospray ionization high-resolution tandem-mass spectrometry (µLC-ESI MS/HRMS) method was developed to monitor local CK-adducts in an in vivo study with rats percutaneously exposed to SM. CK-adduct formation was compared to already established DNA- and systemic albumin biomarkers. CK- and DNA-adducts were successfully detected in biopsies of exposed rat skin as well as albumin-adducts in plasma. Relative biomarker concentrations make the CK-adduct highly appropriate as a local dermal biomarker. In summary, CK or rather Cys²⁸² in CK B-type was identified as a new, additional dermal target of local SM exposures. To our knowledge, it is also the first time that HETE-albumin adducts, and HETE-DNA adducts were monitored simultaneously in an in vivo animal study.

Corneal Endothelial Cell Toxicity Determines Long-Term Outcome After Ocular Exposure to Sulfur Mustard Vapor

PURPOSE

Ocular exposure to sulfur mustard (SM) vapor causes acute loss of corneal endothelial cells (CECs). Persistent corneal endothelial pathologies are observed in eyes that do not recover from SM exposure, suggesting that endothelial toxicity contributes to mustard gas keratopathy (MGK). Here, we evaluated the contributions of endothelial loss to acute and chronic corneal injuries in SM-exposed eyes.

METHODS

Rabbit eyes were exposed in vivo to equivalent doses of SM using 9-, 11-, or 14-mm vapor caps. The effects of exposure area on corneal injury progression were longitudinally evaluated over 12 weeks using clinical evaluations. The effects of exposure area on CEC morphology, endothelial and epithelial ultrastructure, and endothelial barrier function were determined from 1 day to 12 weeks.

RESULTS

SM exposure caused loss of CECs and failure of endothelial barrier integrity at 1 day, independent of exposure cap size. By 3 weeks, eyes exposed with the 14-mm vapor cap exhibited increased corneal permeability, repopulation of the endothelium by cells with fibroblastic morphology, and abnormal deposition of extracellular matrix. Eyes exposed with 9- or 11-mm vapor caps exhibited transient symptoms of injury that fully resolved, with the rate of recovery correlated with cap size.

CONCLUSIONS

The nonlinear correlation between endothelial lesion size and probability of developing MGK suggests that the CEC loss is a determinative factor for emergence of MGK. These studies illustrate the importance of endothelial repair in preventing MGK. Furthermore, they exclude chemical modification of basement membrane as a mechanistic cause of recurrent epithelial erosions in MGK eyes.

Chronic senescent human mesenchymal stem cells as possible contributor to the wound healing disorder after exposure to the alkylating agent sulfur mustard

Wound healing is a complex process, and disturbance of even a single mechanism can result in chronic ulcers developing after exposure to the alkylating agent sulfur mustard (SM). A possible contributor may be SM-induced chronic senescent mesenchymal stem cells (MSCs), unable to fulfil their regenerative role, by persisting over long time periods and creating a proinflammatory microenvironment. Here we show that senescence induction in human bone marrow derived MSCs was time- and concentration-dependent, and chronic senescence could be verified 3 weeks after exposure to between 10 and 40 µM SM. Morphological changes, reduced clonogenic and migration potential, longer scratch closure times, differences in senescence, motility and DNA damage response associated genes as well as increased levels of proinflammatory cytokines were revealed. Selective removal of these cells by senolytic drugs, in which ABT-263 showed initial potential in vitro, opens the possibility for an innovative treatment strategy for chronic wounds, but also tumors and age-related diseases.

Therapeutic measures for sulfur mustard-induced ocular injury

The use of sulfur mustard (SM) in global terrorism is still a relevant threat to both civilian population and military personnel. Casualties exposed to SM may present mild, moderate or severe acute ocular lesions followed by a complete ocular resolution, chronic lesions or re-emerged ocular pathologies after a latent period. Current treatment for SM-induced ocular injury is based mainly on the clinical manifestation at the different stages of the injury and includes pharmaceutical and surgical interventions. These therapeutic measures are beneficial but not sufficient, and the ocular injury remains a continuous challenge for medical professionals. This review focuses on treatment experience carried out in humans and studied in animal models, for both SM-induced ocular acute injury and late pathology. In general, therapeutic measures are based on clinical features of the ocular injury or on the involvement of specific factors during the ocular injury that point out towards potential treatments. Anti-inflammatory treatments and limbal stem cell transplantation techniques were developed based on the clinical manifestation of the ocular injury. Optional therapies for impaired corneal innervation and endothelium are suggested for future research. Additionally, studies on potential treatments with anti-matrix metalloproteinase (MMP), anti-vascular endothelial growth factor (VEGF) and anti-IL-6 agents are discussed. Consequently, future studies may reveal the potential of additional pharmacological and biological treatments or advanced cellular and molecular biology methods to serve as novel therapeutic measures and techniques for this complicated ocular injury.

N-Acetylcysteine as a treatment for sulphur mustard poisoning

In the long and intensive search for effective treatments to counteract the toxicity of the chemical warfare (CW) agent sulphur mustard (H; bis(2-chloroethyl) sulphide), the most auspicious and consistent results have been obtained with the drug N-acetylcysteine (NAC), particularly with respect to its therapeutic use against the effects of inhaled H. It is a synthetic cysteine derivative that has been used in a wide variety of clinical applications for decades and a wealth of information exists on its safety and protective properties against a broad range of toxicants and disease states. Its primary mechanism of action is as a pro-drug for the synthesis of the antioxidant glutathione (GSH), particularly in those circumstances where oxidative stress has exhausted intracellular GSH stores. It impacts a number of pathways either directly or through its GSH-related antioxidant and anti-inflammatory properties, which make it a prime candidate as a potential treatment for the wide range of deleterious cellular effects that H is acknowledged to cause in exposed individuals. This report reviews the available literature on the protection afforded by NAC against the toxicity of H in a variety of model systems, including its efficacy in treating the long-term chronic lung effects of H that have been demonstrated in Iranian veterans exposed during the Iran-Iraq War (1980-1988). Although there is overwhelming evidence supporting this drug as a potential medical countermeasure against this CW agent, there is a requirement for carefully controlled clinical trials to determine the safety, efficacy and optimal NAC dosage regimens for the treatment of inhaled H.

A Novel Topical Ophthalmic Formulation to Mitigate Acute Mustard Gas Keratopathy In Vivo: A Pilot Study

Purpose

This pilot study investigated the in vivo therapeutic potential and tolerability of a multimodal ophthalmic formulation, topical eye drops (TED), for acute mustard gas keratopathy (MGK) using a rabbit model.

Methods

Twenty New Zealand White rabbits were used. Only right eyes of 18 rabbits (oculus dexter [OD]) received single sulfur mustard gas (SM) vapor injury, whereas contralateral eyes were left untreated or received TED for tolerabilty evaluation. Two rabbit eyes received no treatment and served as age-matched naive control. The four groups were: Naive (oculus sinister [OS] untreated eyes; n = 9); TED (OS treated only with TED BID for 3 days; n = 9); SM (OD exposed to SM vapor; n = 9); and SM+TED (OD exposed to SM+TED BID for 3 days; n = 9). Ocular examination in live rabbits were performed utilizing slit-lamp biomicroscopy, Fantes grading system, fluorescein staining, Schirmer's tests, pachymetry, and applanation tonometry. Cellular and molecular changes in rabbit corneas were assessed after humane euthanasia on day-3 and day-7 with histopathological and real-time polymerase chain reaction PCR techniques.

Results

TED to rabbit eyes was found tolerable in vivo. SM-exposed eyes showed significant increase in Fantes scores, central corneal thickness (CCT), Schirmer's test, epithelium-stroma separation, and corneal edema. TED mitigated clinical symptoms by reducing corneal edema, Fantes scores, CCT, and Schirmer's test. Further, TED decreased SM-induced corneal haze, inflammatory and profibrotic markers, transforming growth factor-TGF-β1 and cyclooxygenase-2COX-2, and damage to corneal structure, including epithelial-stromal integrity.

Conclusions

The developed multimodal eyedrop formulation, TED, has potential to mitigate acute MGK effectively in vivo.

Translational Relevance

TED is effective against MGK.

Progressive Lung Injury, Inflammation, and Fibrosis in Rats Following Inhalation of Sulfur Mustard

Sulfur mustard (SM) inhalation causes debilitating pulmonary injury in humans which progresses to fibrosis. Herein, we developed a rat model of SM toxicity which parallels pathological changes in the respiratory tract observed in humans. SM vapor inhalation caused dose (0.2-0.6 mg/kg)-related damage to the respiratory tract within 3 days of exposure. At 0.4-0.6 mg/kg, ulceration of the proximal bronchioles, edema and inflammation were observed, along with a proteinaceous exudate containing inflammatory cells in alveolar regions. Time course studies revealed that the pathologic response was biphasic. Thus, changes observed at 3 days post-SM were reduced at 7-16 days; this was followed by more robust aberrations at 28 days, including epithelial necrosis and hyperplasia in the distal bronchioles, thickened alveolar walls, enlarged vacuolated macrophages, and interstitial fibrosis. Histopathologic changes were correlated with biphasic increases in bronchoalveolar lavage (BAL) cell and protein content and proliferating cell nuclear antigen expression. Proinflammatory proteins receptor for advanced glycation end product (RAGE), high-mobility group box protein (HMGB)-1, and matrix metalloproteinase (MMP)-9 also increased in a biphasic manner following SM inhalation, along with surfactant protein-D (SP-D). Tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS), inflammatory proteins implicated in mustard lung toxicity, and the proinflammatory/profibrotic protein, galectin (Gal)-3, were upregulated in alveolar macrophages and in bronchiolar regions at 3 and 28 days post-SM. Inflammatory changes in the lung were associated with oxidative stress, as reflected by increased expression of heme oxygenase (HO)-1. These data demonstrate a similar pathologic response to inhaled SM in rats and humans suggesting that this rodent model can be used for mechanistic studies and for the identification of efficacious therapeutics for mitigating toxicity.

Long-term Respiratory Effects of Mustard Vesicants

Sulfur mustard and related vesicants are cytotoxic alkylating agents that cause severe damage to the respiratory tract. Injury is progressive leading, over time, to asthma, bronchitis, bronchiectasis, airway stenosis, and pulmonary fibrosis. As there are no specific therapeutics available for victims of mustard gas poisoning, current clinical treatments mostly provide only symptomatic relief. In this article, the long-term effects of mustards on the respiratory tract are described in humans and experimental animal models in an effort to define cellular and molecular mechanisms contributing to lung injury and disease pathogenesis. A better understanding of mechanisms underlying pulmonary toxicity induced by mustards may help in identifying potential targets for the development of effective clinical therapeutics aimed at mitigating their adverse effects.

NAD+ in sulfur mustard toxicity

Sulfur mustard (SM) is a toxicant and chemical warfare agent with strong vesicant properties. The mechanisms behind SM-induced toxicity are not fully understood and no antidote or effective therapy against SM exists. Both, the risk of SM release in asymmetric conflicts or terrorist attacks and the usage of SM-derived nitrogen mustards as cancer chemotherapeutics, render the mechanisms of mustard-induced toxicity a highly relevant research subject. Herein, we review a central role of the abundant cellular molecule nicotinamide adenine dinucleotide (NAD⁺) in molecular mechanisms underlying SM toxicity. We also discuss the potential beneficial effects of NAD⁺ precursors in counteracting SM-induced damage.

Comparison of the toxicity of sulfur mustard and its oxidation products in vitro

The molecular toxicology of the chemical warfare agent sulfur mustard (SM) is still not completely understood. It has been suggested that in addition to SM itself also biotransformation products thereof mediate cytotoxicity. In the current study, we assessed this aspect by exposing a human hepatocyte cell line (HepG2) to SM or to its oxidation products sulfur mustard sulfoxide (SMO), sulfur mustard sulfone (SMO₂), and divinyl sulfone (DVS). Cytotoxicity, determined with the XTT assay, revealed a significant higher toxicity of SMO₂ and DVS compared to SM while SMO had no effect at any concentration. The exact biotransformation of SM leading to SMO, SMO₂ and finally DVS is unknown so far. Involvement of the CYP450 system is discussed and was also investigated in the presented study. Modulation of CYP1A2 activity, taken as a model enzyme for CYP450, affected cytotoxicity of SM, SMO₂ or DVS significantly. Induction of CYP1A2 with omeprazole led to decreased cytotoxicity for all compounds whereas inhibition with cimetidine resulted in an increased cytotoxicity for SM, but not for SMO₂ and DVS. Our results indicate a distinctive role of the CYP450 system in SM poisoning. Future studies should address the metabolic conversion of SM in more detail. Our data may suggest the well-tolerated drug omeprazole as a potential co-treatment after contact to SM.

Skin sensitizing effects of sulfur mustard and other alkylating agents in accordance to OECD guidelines

Vesicants cause a multitude of cutaneous reactions like erythema, blisters and ulcerations. After exposure to sulfur mustard (SM) and related compounds, patients present dermal symptoms typically known for chemicals categorized as skin sensitizer (e.g. hypersensitivity and flare-up phenomena). However, although some case reports led to the assumption that SM and other alkylating compounds represent sensitizers, a comprehensive investigation of SM-triggered immunological responses has not been conducted so far. Based on a well-structured system of in chemico and in vitro test methods, the Organization for Economic Co-operation and Development (OECD) established procedures to categorize agents on their skin sensitizing abilities. In this study, the skin sensitizing potential of SM and three related alkylating agents (AAs) was assessed following the OECD test guidelines. Besides SM, investigated AAs were chlorambucil (CHL), nitrogen mustard (HN3) and 2-chloroethyl ethyl sulfide (CEES). The methods are described in detail in the EURL ECVAM DataBase service on ALternative Methods to animal experimentation (DB-ALM). In accordance to OECD recommendations, skin sensitization is a pathophysiological process starting with a molecular initiating step and ending with the in vivo outcome of an allergic contact dermatitis. This concept is called adverse outcome pathway (AOP). An AOP links an adverse outcome to various key events which can be assayed by established in chemico and in vitro test methods. Positive outcome in two out of three key events indicates that the chemical can be categorized as a skin sensitizer. In this study, key event 1 "haptenation" (covalent modification of epidermal proteins), key event 2 "activation of epidermal keratinocytes" and key event 3 "activation of dendritic cells" were investigated. Covalent modification of epidermal proteins measured by using the DPRA-assay provided distinct positive results for all tested substances. Same outcome was seen in the KeratinoSens assay, investigating the activation of epidermal keratinocytes. The h-CLAT assay performed to determine the activation of dendritic cells provided positive results for SM and CEES but not for CHL and HN3. Altogether, following OECD requirements, our results suggest the classification of all investigated substances as skin sensitizers. Finally, a tentative AOP for SM-induced skin sensitization is suggested.

Surgical Evaluation of Flame Burn Injuries in Syrian Civilians

The aim of the current study was to evaluate the severity and location of flame burns and the mortality rate of civilians affected by these in the Syrian Civil War and to present the surgical treatment outcomes of the injured civilians to be able to provide recommendations. This was a prospective hospital-based observational cohort study involving 573 patients with data collected from 2011 to 2018. All of these patients were Syrian civilians, and their flame burn injuries were related to the Syrian conflict. All burns were divided into four subgroups according to TBSA and compared. The groups of TBSA were compared as 0 to 25% (n = 97), 25 to 50% (n = 257), 50 to 75% (n = 135), and >75% (n = 84) (P = .413). Almost all had a second (n = 331; 57.7%) and third (n = 189; 32.9%) degree deep burns. The median burn size was 47% TBSA in the patients. The burn mechanism was mostly the flame type of burn (n = 467; 81.5%) as a result of fuel oil explosions, followed by bomb-related burns (n = 106; 18.5%) (P < .001). Mortality was seen in 223 (39%) due to the high surface area and reaching hospital too late at 1 to 8 days (P = .187). The findings of this study indicate that war-related flame burns result in an extremely high mortality rate and time is lost, which could protect against life-threatening outcomes.