Evaluation of protease inhibitors and an antioxidant for treatment of sulfur mustard-induced toxic lung injury

Oxidative Stress: An Intersection Between Radiation and Sulfur Mustard Lung Injury

Nuclear and chemical weapons of mass destruction share both a tragic and beneficial legacy in mankind's history and health. The horrific health effects of ionizing radiation and mustard gas exposures unleashed during disasters, wars, and conflicts have been harnessed to treat human health maladies. Both agents of destruction have been transformed into therapies to treat a wide range of cancers. The discovery of therapeutic uses of radiation and sulfur mustard was largely due to observations by clinicians treating victims of radiation and sulfur mustard gas exposures. Clinicians identified vulnerability of leukocytes to these agents and repurposed their use in the treatment of leukemias and lymphomas. Given the overlap in therapeutic modalities, it goes to reason that there may be common mechanisms to target as protective strategies against their damaging effects. This commentary will highlight oxidative stress as a common mechanism shared by both radiation and sulfur mustard gas exposures and discuss potential therapies targeting oxidative stress as medical countermeasures against the devastating lung diseases wrought by these agents.

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.

Vitamin D3 protects against nitrogen mustard-induced apoptosis of the bronchial epithelial cells via activating the VDR/Nrf2/Sirt3 pathway

Respiratory system injury is the main cause of mortality for nitrogen mustard (NM)-induced damage. Previous studies indicate that reactive oxygen species (ROS) participates in NM-mediated respiratory injuries, but the detailed mechanism is not quite clear. Human bronchial epithelial cell lines 16HBE and BEAS-2B were treated with HN2, a type of NM. In detail, it was shown that HN2 treatment induced impaired cell viability, excessive mitochondrial ROS production and enhanced cellular apoptosis in bronchial epithelial cells. Moreover, impaired Sirt3/SOD2 axis was observed upon HN2 treatment, with decreased Sirt3 and increased acetylated SOD2 expression levels. Sirt3 overexpression partially ameliorated HN2-induced cell injury. Meanwhile, vitamin D3 treatment partially attenuated HN2-induced apoptosis and improved the mitochondrial functions upon HN2 intervention. In addition, HN2 exposure decreased VDR expression, thus inhibiting the Nrf2 phosphorylation and Sirt3 activation. Inhibition of Nrf2 or Sirt3 could decrease the protective effects of vitamin D3 and enhance mitochondrial ROS production via modulating mitochondrial redox balance. In conclusion, impaired VDR/Nrf2/Sirt3 axis contributed to NM-induced apoptosis, while vitamin D3 supplementation provides protective effects via the activation of VDR and the improvement of mitochondrial functions. This study provides novel mechanism and strategy for NM exposure-induced pulmonary injuries.

Mast Cells Promote Nitrogen Mustard-Mediated Toxicity in the Lung Associated With Proinflammatory Cytokine and Bioactive Lipid Mediator Production

Sulfur mustard (SM) has been widely used as a chemical warfare agent including most recently in Syria. Mice exposed to SM exhibit an increase in pro-inflammatory cytokines followed by immune cell infiltration in the lung, however, the mechanisms leading to these inflammatory responses has not been completely elucidated. Mast cells are one of the first responding innate immune cells found at the mucosal surfaces of the lung and have been reported to be activated by SM in the skin. Therefore, we hypothesized that nitrogen mustard (NM: a surrogate for SM) exposure promotes activation of mast cells causing chronic respiratory inflammation. To assess the role of mast cells in NM-mediated pulmonary toxicity, we compared the effects of NM exposure between C57BL/6 and B6.Cg-KitW-sh/HNihrJaeBsmJ (KitW-sh; mast cell deficient) mice. Lung injury was observed in C57BL/6J mice following NM exposure (0.125 mg/kg) at 72 h, which was significantly abrogated in KitW-sh mice. Although both strains exhibited damage from NM, C57BL/6J mice had higher inflammatory cell infiltration and more elevated prostaglandin D2 (PGD2) present in bronchoalveolar lavage fluid compared with KitW-sh mice. Additionally, we utilized murine bone marrow-derived mast cells to assess NM-induced early and late activation. Although NM exposure did not result in mast cell degranulation, we observed an upregulation in PGD2 and IL-6 levels following exposure to NM. Results suggest that mast cells play a prominent role in lung injury induced by NM and may contribute to the acute and potentially long-term lung injury observed caused by SM.

A novel sulfur mustard (HD) vapor inhalation exposure model of pulmonary toxicity for the efficacy evaluation of candidate medical countermeasures

OBJECTIVE

To develop a novel inhalation exposure system capable of delivering a controlled inhaled HD dose through an endotracheal tube to anesthetized rats to investigate the lung pathophysiology and evaluate potential medical countermeasures.

MATERIALS AND METHODS

Target HD vapor exposures were generated by a temperature-controlled vapor generator, while concentration was monitored near real-time by gas chromatography. Animal breathing parameters were monitored real-time by in-line EMKA/SciReq pulmonary analysis system. Individual exposures were halted when the target inhaled doses were achieved. Animals were observed daily for clinical observations and lethality with scheduled termination at 28 days post-exposure. Upon scheduled or unscheduled death, animals underwent a gross necropsy and lung and trachea were collected for histopathology.

RESULTS

Controlled HD concentrations ranged from 60 to 320 mg/m³. Delivered inhaled doses range from 0.3 to 3.20 mg/kg with administered doses within 3% of the target. The 28-day inhaled LD₅₀ is 0.80 mg/kg (95% CI = 0.42-1.18 mg/kg). Post exposure respiratory abnormalities were observed across all dose levels though the higher dose levels had earlier onset and higher frequency of occurrence. Histopathologic alterations were not qualitatively altered in accordance with dose but instead showed a relationship to an animals' time of death, with early deaths demonstrating acute damage and later deaths displaying signs of repair.

DISCUSSION/CONCLUSION

This novel exposure system administers targeted HD inhaled doses to generate a small animal model that can be used to evaluate physiological toxicities of inhaled HD on the lungs and for evaluation of potential medical countermeasure treatments.

The effect of atorvastatin on inflammatory markers in sulfur mustard gas induced bronchitis: a randomized double-blinded, placebo-control clinical trial

Background

This study was performed to evaluate the anti-inflammatory effect of atorvastatin in patients with chronic bronchitis, exposed to sulfur mustard gas.

Methods

In this randomized double-blinded clinical trial we recruited patients with chronic bronchitis after exposure to sulfur mustard gas. Ninety men 45–75 years old diagnosed with chronic bronchitis after exposure to mustard gas during the Iran-Iraq war, were randomly assigned to receive either atorvastatin (40 mg) or placebo once a day for 3 months. The interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), procalcitonin, highly sensitive CRP and COPD assessment test (CAT) score was compared at baseline and after 12 weeks.

Results

After consuming atorvastatin for 12 weeks, IL-6 level (mean difference [95%CI]; 0.2 [− 0.05, 0.5]), TNF-α (mean difference [95%CI]; − 0.07 [− 0.2, 0.07]), high sensitive CRP (mean difference [95%CI] − 0.1 [− 1.2, 0.9]), and procalcitonin (mean difference [95%CI]; 0.003 [− 0.02, 0.03]) did not change significantly. However, in the placebo group, only IL-6 (mean difference [95%CI]; 0.6 [0.2, 1.05]) decreased significantly after 12 weeks, but levels of high sensitive CRP (mean difference [95%CI]; − 0.3 [− 1.4, 0.8]) TNF-α (mean difference [95%CI]; − 0.2 [− 0.34, − 0.06]) and procalcitonin (mean difference [95%CI]; 0.02 [− 0.001, 0.04]) did not change significantly. After 12 weeks, the mean differences in TNF- α, IL-6 level, high sensitive CRP, procalcitonin, and CAT score did not significantly differ between the two groups.

Conclusions

The administration of 40 mg atorvastatin for 3 months did not significantly change the inflammatory markers or the quality of life of patients exposed to mustard gas with chronic bronchitis.

Trial registration: IRCT, IRCT138904144312N1. Registered 16 August 2014, https://en.irct.ir/trial/4577.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01481-y.

A review of Sulfur Mustard-induced pulmonary immunopathology: An Alveolar Macrophage Approach

Despite many studies investigating the mechanism of Sulfur Mustard (SM) induced lung injury, the underlying mechanism is still unclear. Inflammatory and subsequent fibroproliferative stages of SM-toxicity are based upon several highly-related series of events controlled by the immune system. The inhalation of SM gas variably affects different cell populations within the lungs. Various studies have shown the critical role of macrophages in triggering a pulmonary inflammatory response as well as its maintenance, resolution, and repair. Importantly, macrophages can serve as either pro-inflammatory or anti-inflammatory populations depending on the present conditions at any pathological stage. Different characteristics of macrophages, including their differentiation, phenotypic, and functional properties, as well as interactions with other cell populations determine the outcomes of lung diseases and the extent of long- or short-term pulmonary damage induced by SM. In this paper, we summarize the current state of knowledge regarding the role of alveolar macrophages and their mediators in the pathogenesis of SM in pulmonary injury. Investigating the specific cells and mechanisms involved in SM-lung injury may be useful in finding new target opportunities for treatment of this injury.

Inhibition of metalloproteinases in therapy for severe lung injury due to COVID-19

Since its first appearance in December 2019 in the Chinese province of Wuhan, COVID-19 has spread rapidly throughout the world and poses a serious threat to public health. Acute respiratory failure due to widespread lung inflammation progress to acute respiratory distress syndrome (ARDS) with an altered pulmonary and alveolar function that can lead to disability, prolong hospitalizations, and adverse outcomes.

While there is no specific treatment for severe acute lung injury (ALI) and ARDS due to the COVID-19 and the management is mostly supportive, it is very important to better understand the pathophysiological processes activated by the inflammatory mediators such as cytokines and metalloproteinases with the aim of their subsequent inhibition in the course of the complex treatment.

Herein, we will discuss the pathophysiological mechanisms of ALI/ARDS, with a focus on the pivotal role played by matrix metalloproteinases (MMP) and the kinin-kallikrein system (KKS), and the effects of the possible pharmacological interventions.

Aprotinin is a nonspecific protease inhibitor especially of trypsin, chymotrypsin, plasmin, and kallikrein, and it is many years in clinical use. Aprotinin inhibits the release of pro-inflammatory cytokines and involved in the process of glycoprotein homeostasis. Experimental data support that the use of aprotinin to inhibit MMPs and KKS may be a new potential approach to the treatment of ALI / ARDS.

Advances in treatment of acute sulfur mustard poisoning - a critical review

Sulfur mustard (SM) is a blistering chemical warfare agent that was used during the World War I and in the Iraq-Iran conflict. The aim of this paper is to discuss and critically review the published results of experiments on the treatment of SM poisoning based on our clinical and research experience. The victims must remove from the contaminated zone immediately. The best solution for decontamination is large amounts of water, using neutral soap and 0.5% sodium hypochlorite. Severely intoxicated patients should be treated according to advanced life support protocols and intensive care therapy for respiratory disorders and the chemical burn. Sodium thiosulfate infusion (100-500 mg/kg/min) should be started up to 60 min after SM exposure. However, N-acetyle cysteine (NAC) is recommended, none of them acts as specific or effective antidote. The important protective and conservative treatment of SM-induced pulmonary injuries include humidified oxygen, bronchodilators, NAC as muculytic, rehydration, mechanical ventilation, appropriate antibiotics and respiratory physiotherapy as clinically indicated. Treatment of acute SM ocular lesions start with topical antibiotics; preferably sulfacetamide eye drop, continue with lubricants, and artificial tears. Treatment for cutaneous injuries include: moist dressing; preferably with silver sulfadiazine cream, analgesic, anti-pruritic, physically debridement, debridase, Laser debridement, followed by skin autologous split-thickness therapy as clinically indicated. The new suggested medications and therapeutic approaches include: anti-inflammatory agents, Niacinamide, Silibinin, Calmodulin antagonists, Clobetasol, full-thickness skin grafting for skin injuries; Doxycycline; Bevacizumab, and Colchicine for ocular injuries. Recommended compounds based on animal studies include Niacinamide, Aprotinin, des-aspartate-angiotensin-I, Gamma-glutamyltransferase, vitamin E, and vitamin D. In vitro studies revealed that Dimethylthiourea, L-nitroarginine, Methyl-ester, Sodium pyruvate, Butylated hydroxyanisole, ethacrynic acid, and macrolide antibiotics are effective. However, none of them, except macrolide antibiotics have been proved clinically. Avoidance of inappropriate polypharmacy is advisable.

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.

An off–on fluorescent probe for the detection of mitochondria-specific protein persulfidation

A fluorescent probe for the detection of mitochondrial protein persulfidation, and featuring fast reaction, good selectivity and high sensitivity, was developed.

From the Cover: Catalytic Antioxidant Rescue of Inhaled Sulfur Mustard Toxicity

Sulfur mustard (bis 2-chloroethyl ethyl sulfide, SM) is a powerful bi-functional vesicating chemical warfare agent. SM tissue injury is partially mediated by the overproduction of reactive oxygen species resulting in oxidative stress. We hypothesized that using a catalytic antioxidant (AEOL 10150) to alleviate oxidative stress and secondary inflammation following exposure to SM would attenuate the toxic effects of SM inhalation. Adult male rats were intubated and exposed to SM (1.4 mg/kg), a dose that produces an LD₅₀ at approximately 24 h. Rats were randomized and treated via subcutaneous injection with either sterile PBS or AEOL 10150 (5 mg/kg, sc, every 4 h) beginning 1 h post-SM exposure. Rats were euthanized between 6 and 48 h after exposure to SM and survival and markers of injury were determined. Catalytic antioxidant treatment improved survival after SM inhalation in a dose-dependent manner, up to 52% over SM PBS at 48 h post-exposure. This improvement was sustained for at least 72 h after SM exposure when treatments were stopped after 48 h. Non-invasive monitoring throughout the duration of the studies also revealed blood oxygen saturations were improved by 10% and clinical scores were reduced by 57% after SM exposure in the catalytic antioxidant treatment group. Tissue analysis showed catalytic antioxidant therapy was able to decrease airway cast formation by 69% at 48 h post-exposure. To investigate antioxidant induced changes at the peak of injury, several biomarkers of oxidative stress and inflammation were evaluated at 24 h post-exposure. AEOL 10150 attenuated SM-mediated lung lipid oxidation, nitrosative stress and many proinflammatory cytokines. The findings indicate that catalytic antioxidants may be useful medical countermeasure against inhaled SM exposure.

Mustard vesicant-induced lung injury: Advances in therapy

Most mortality and morbidity following exposure to vesicants such as sulfur mustard is due to pulmonary toxicity. Acute injury is characterized by epithelial detachment and necrosis in the pharynx, trachea and bronchioles, while long-term consequences include fibrosis and, in some instances, cancer. Current therapies to treat mustard poisoning are primarily palliative and do not target underlying pathophysiologic mechanisms. New knowledge about vesicant-induced pulmonary disease pathogenesis has led to the identification of potentially efficacious strategies to reduce injury by targeting inflammatory cells and mediators including reactive oxygen and nitrogen species, proteases and proinflammatory/cytotoxic cytokines. Therapeutics under investigation include corticosteroids, N-acetyl cysteine, which has both mucolytic and antioxidant properties, inducible nitric oxide synthase inhibitors, liposomes containing superoxide dismutase, catalase, and/or tocopherols, protease inhibitors, and cytokine antagonists such as anti-tumor necrosis factor (TNF)-α antibody and pentoxifylline. Antifibrotic and fibrinolytic treatments may also prove beneficial in ameliorating airway obstruction and lung remodeling. More speculative approaches include inhibitors of transient receptor potential channels, which regulate pulmonary epithelial cell membrane permeability, non-coding RNAs and mesenchymal stem cells. As mustards represent high priority chemical threat agents, identification of effective therapeutics for mitigating toxicity is highly significant.

Antioxidants as potential medical countermeasures for chemical warfare agents and toxic industrial chemicals

The continuing horrors of military conflicts and terrorism often involve the use of chemical warfare agents (CWAs) and toxic industrial chemicals (TICs). Many CWA and TIC exposures are difficult to treat due to the danger they pose to first responders and their rapid onset that can produce death shortly after exposure. While the specific mechanism(s) of toxicity of these agents are diverse, many are associated either directly or indirectly with increased oxidative stress in affected tissues. This has led to the exploration of various antioxidants as potential medical countermeasures for CWA/TIC exposures. Studies have been performed across a wide array of agents, model organisms, exposure systems, and antioxidants, looking at an almost equally diverse set of endpoints. Attempts at treating CWAs/TICs with antioxidants have met with mixed results, ranging from no effect to nearly complete protection. The aim of this commentary is to summarize the literature in each category for evidence of oxidative stress and antioxidant efficacy against CWAs and TICs. While there is great disparity in the data concerning methods, models, and remedies, the outlook on antioxidants as medical countermeasures for CWA/TIC management appears promising.

Respiratory effects of sulfur mustard exposure, similarities and differences with asthma and COPD

CONTEXT

Previous research has found relationships between sulfur mustard (SM) toxicity and its adverse effects.

OBJECTIVE

SM is highly toxic to the respiratory system, leading to hacking cough, rhinorrheachest tightness, acute pharyngitis and laryngitis, chronic bronchitis and lung fibrosis. In this review, based on the scientific literature, we provide an updated summary of information on SM exposures and their differences with asthma and COPD.

METHOD

Information of this review was obtained by searching Medline/PubMed, ScienceDirect, Scopus, Google Scholar, ISI Web of Knowledge and Chemical Abstracts.

RESULTS

SM exposure can decrease pulmonary function tests (PFTs) values. In addition, inflammatory cell accumulation in the respiratory tract and increased expression of some pro-inflammatory cytokines including tumor necrosis factor-α (TNFα), IL-1a, IL-1β, and reactive oxygen radicals due to SM exposure have been shown. Matrix metalloproteinase (MMP) which degrade extracellular matrix proteins, contributing to inflammatory cell recruitment, tissue injury and fibrosis are also up-regulated in the lung after SM exposure. In the lung, SM exposure also can cause serious pathological changes including airway inflammation, parenchymal tissue destruction and airway obstruction which can lead to asthma or chronic obstructive pulmonary disease (COPD). Following SM poisoning, DNA damage, apoptosis and autophagy are observed in the lung along with the increased expression of activated caspases and DNA repair enzymes.

CONCLUSION

In the present article, respiratory symptoms, changes in PFTs, lung pathology and lung inflammation due to SM exposure and the similarities and differences between them and those observed in asthma and COPD were reviewed.

Inflammatory mechanisms of pulmonary injury induced by mustards

Exposure of humans and animals to vesicants, including sulfur mustard (SM) and nitrogen mustard (NM), causes severe and debilitating damage to the respiratory tract. Both acute and long term pathological consequences are observed in the lung following a single exposure to these vesicants. Evidence from our laboratories and others suggest that macrophages and the inflammatory mediators they release play an important role in mustard-induced lung injury. In this paper, the pathogenic effects of SM and NM on the lung are reviewed, along with the potential role of inflammatory macrophages and mediators they release in mustard-induced pulmonary toxicity.

A novel sulfur mustard (HD) vapor inhalation exposure system for accurate inhaled dose delivery

INTRODUCTION

A custom designed HD exposure system was used to deliver controlled inhaled doses to an animal model through an endotracheal tube.

METHODS

Target HD vapor challenges were generated by a temperature controlled bubbler/aerosol trap, while concentration was monitored near real-time by gas chromatography. Animal breathing parameters were monitored real-time by an in-line pneumotach, pressure transducer, and Buxco pulmonary analysis computer/software. For each exposure, the challenge atmosphere was allowed to stabilize at the desired concentration while the anesthetized animal was provided humidity controlled clean air. Once the target concentration was achieved and stable, a portion of the challenge atmosphere was drawn past the endotracheal tube, where the animal inhaled the exposure ad libitum. During the exposure, HD vapor concentration and animal weight were used to calculate the needed inhaled volume to achieve the target inhaled dose (μg/kg). The exposures were halted when the inhaled volume was achieved.

RESULTS

The exposure system successfully controlled HD concentrations from 22.2 to 278mg/m(3) and accurately delivered inhaled doses between 49.3 and 1120μg/kg with actual administered doses being within 4% of the target level.

DISCUSSION

This exposure system administers specific HD inhaled doses to evaluate physiological effects and for evaluation of potential medical countermeasure treatments.

Pentoxifylline attenuates nitrogen mustard-induced acute lung injury, oxidative stress and inflammation

Nitrogen mustard (NM) is a toxic alkylating agent that causes damage to the respiratory tract. Evidence suggests that macrophages and inflammatory mediators including tumor necrosis factor (TNF)α contribute to pulmonary injury. Pentoxifylline is a TNFα inhibitor known to suppress inflammation. In these studies, we analyzed the ability of pentoxifylline to mitigate NM-induced lung injury and inflammation. Exposure of male Wistar rats (150-174 g; 8-10 weeks) to NM (0.125 mg/kg, i.t.) resulted in severe histopathological changes in the lung within 3d of exposure, along with increases in bronchoalveolar lavage (BAL) cell number and protein, indicating inflammation and alveolar-epithelial barrier dysfunction. This was associated with increases in oxidative stress proteins including lipocalin (Lcn)2 and heme oxygenase (HO)-1 in the lung, along with pro-inflammatory/cytotoxic (COX-2(+) and MMP-9(+)), and anti-inflammatory/wound repair (CD163+ and Gal-3(+)) macrophages. Treatment of rats with pentoxifylline (46.7 mg/kg, i.p.) daily for 3d beginning 15 min after NM significantly reduced NM-induced lung injury, inflammation, and oxidative stress, as measured histologically and by decreases in BAL cell and protein content, and levels of HO-1 and Lcn2. Macrophages expressing COX-2 and MMP-9 also decreased after pentoxifylline, while CD163+ and Gal-3(+) macrophages increased. This was correlated with persistent upregulation of markers of wound repair including pro-surfactant protein-C and proliferating nuclear cell antigen by Type II cells. NM-induced lung injury and inflammation were associated with alterations in the elastic properties of the lung, however these were largely unaltered by pentoxifylline. These data suggest that pentoxifylline may be useful in treating acute lung injury, inflammation and oxidative stress induced by vesicants.

Mustard Gas Inhalation Injury

Mustard gas (sulfur mustard [SM], bis-[2-chloroethyl] sulfide) is a vesicating chemical warfare agent and a potential chemical terrorism agent. Exposure of SM causes debilitating skin blisters (vesication) and injury to the eyes and the respiratory tract; of these, the respiratory injury, if severe, may even be fatal. Therefore, developing an effective therapeutic strategy to protect against SM-induced respiratory injury is an urgent priority of not only the US military but also the civilian antiterrorism agencies, for example, the Homeland Security. Toward developing a respiratory medical countermeasure for SM, four different classes of therapeutic compounds have been evaluated in the past: anti-inflammatory compounds, antioxidants, protease inhibitors and antiapoptotic compounds. This review examines all of these different options; however, it suggests that preventing cell death by inhibiting apoptosis seems to be a compelling strategy but possibly dependent on adjunct therapies using the other drugs, that is, anti-inflammatory, antioxidant, and protease inhibitor compounds.

A clinicopathological approach to sulfur mustard-induced organ complications: a major review

CONTEXT

Sulfur mustard (SM), with an old manufacturing history still remains as potential threat due to easy production and extensive effects.

OBJECTIVES

Increasing studies on SM indicates the interest of researchers to this subject. Almost all human body organs are at risk for complications of SM. This study offers organ-by-organ information on the effects of SM in animals and humans.

METHODS

The data sources were literature reviews since 1919 as well as our studies during the Iraq-Iran war. The search items were SM and its all other nomenclatures in relation to, in vivo, in vitro, humans, animals, eye, ocular, ophthalmic, lungs, pulmonary, skin, cutaneous, organs and systemic. Amongst more than 1890 SM-related articles, 257 more relevant clinicopathologic papers were selected for this review.

RESULTS

SM induces a vast range of damages in nearly all organs. Acute SM intoxication warrants immediate approach. Among chronic lesions, delayed keratitis and blindness, bronchiolitis obliterans and respiratory distress, skin pruritus, dryness and cancers are the most commonly observed clinical sequelae.

CONCLUSION

Ocular involvements in a number of patients progress toward a severe, rapid onset form of keratitis. Progressive deterioration of respiratory tract leads to "mustard lung". Skin problems continue as chronic frustrating pruritus on old scars with susceptibility to skin cancers. Due to the multiple acute and chronic morbidities created by SM exposure, uses of multiple drugs by several routes of administrations are warranted.

N-acetyl-L-cysteine protects against inhaled sulfur mustard poisoning in the large swine

CONTEXT

Sulfur mustard is a blister agent that can cause death by pulmonary damage. There is currently no effective treatment. N-acetyl-L-cysteine (NAC) has mucolytic and antioxidant actions and is an important pre-cursor of cellular glutathione synthesis. These actions may have potential to reduce mustard-induced lung injury.

OBJECTIVE

Evaluate the effect of nebulised NAC as a post-exposure treatment for inhaled sulfur mustard in a large animal model.

MATERIALS AND METHODS

Fourteen anesthetized, surgically prepared pigs were exposed to sulfur mustard vapor (100 μg.kg⁻¹), 10 min) and monitored, spontaneously breathing, to 12 h. Control animals had no further intervention (n = 6). Animals in the treatment group were administered multiple inhaled doses of NAC (1 ml of 200 mg.ml⁻¹ Mucomyst™ at + 30 min, 2, 4, 6, 8, and 10 h post-exposure, n = 8). Cardiovascular and respiratory parameters were recorded. Arterial blood was collected for blood gas analysis while blood and bronchoalveolar lavage fluid were collected for hematology and inflammatory cell analysis. Urine was collected to detect a sulfur mustard breakdown product. Lung tissue samples were taken for histopathological and post-experimental analyses.

RESULTS

Five of six sulfur mustard-exposed animals survived to 12 h. Arterial blood oxygenation (PaO₂) and saturation levels were significantly decreased at 12 h. Arterial blood carbon dioxide (PaCO₂) significantly increased, and arterial blood pH and bicarbonate (HCO₃⁻) significantly decreased at 12 h. Shunt fraction was significantly increased at 12 h. In the NAC-treated group all animals survived to 12 h (n = 8). There was significantly improved arterial blood oxygen saturation, HCO₃⁻ levels, and shunt fraction compared to those of the sulfur mustard controls. There were significantly fewer neutrophils and lower concentrations of protein in lavage compared to sulfur mustard controls.

DISCUSSION

NAC's mucolytic and antioxidant properties may be responsible for the beneficial effects seen, improving clinically relevant physiological indices affected by sulfur mustard exposure.

CONCLUSION

Beneficial effects of nebulized NAC were apparent following inhaled sulfur mustard exposure. Further therapeutic benefit may result from a combination therapy approach.

Treatment for sulfur mustard lung injuries; new therapeutic approaches from acute to chronic phase

Objective

Sulfur mustard (SM) is one of the major potent chemical warfare and attractive weapons for terrorists. It has caused deaths to hundreds of thousands of victims in World War I and more recently during the Iran-Iraq war (1980–1988). It has ability to develop severe acute and chronic damage to the respiratory tract, eyes and skin. Understanding the acute and chronic biologic consequences of SM exposure may be quite essential for developing efficient prophylactic/therapeutic measures. One of the systems majorly affected by SM is the respiratory tract that numerous clinical studies have detailed processes of injury, diagnosis and treatments of lung. The low mortality rate has been contributed to high prevalence of victims and high lifetime morbidity burden. However, there are no curative modalities available in such patients. In this review, we collected and discussed the related articles on the preventive and therapeutic approaches to SM-induced respiratory injury and summarized what is currently known about the management and therapeutic strategies of acute and long-term consequences of SM lung injuries.

Method

This review was done by reviewing all papers found by searching following key words sulfur mustard; lung; chronic; acute; COPD; treatment.

Results

Mustard lung has an ongoing pathological process and is active disorder even years after exposure to SM. Different drug classes have been studied, nevertheless there are no curative modalities for mustard lung.

Conclusion

Complementary studies on one hand regarding pharmacokinetic of drugs and molecular investigations are mandatory to obtain more effective treatments.

Attenuation of acute nitrogen mustard-induced lung injury, inflammation and fibrogenesis by a nitric oxide synthase inhibitor

Nitrogen mustard (NM) is a toxic vesicant known to cause damage to the respiratory tract. Injury is associated with increased expression of inducible nitric oxide synthase (iNOS). In these studies we analyzed the effects of transient inhibition of iNOS using aminoguanidine (AG) on NM-induced pulmonary toxicity. Rats were treated intratracheally with 0.125 mg/kg NM or control. Bronchoalveolar lavage fluid (BAL) and lung tissue were collected 1 d-28 d later and lung injury, oxidative stress and fibrosis assessed. NM exposure resulted in progressive histopathological changes in the lung including multifocal lesions, perivascular and peribronchial edema, inflammatory cell accumulation, alveolar fibrin deposition, bronchiolization of alveolar septal walls, and fibrosis. This was correlated with trichrome staining and expression of proliferating cell nuclear antigen (PCNA). Expression of heme oxygenase (HO)-1 and manganese superoxide dismutase (Mn-SOD) was also increased in the lung following NM exposure, along with levels of protein and inflammatory cells in BAL, consistent with oxidative stress and alveolar-epithelial injury. Both classically activated proinflammatory (iNOS⁺ and cyclooxygenase-2⁺) and alternatively activated profibrotic (YM-1⁺ and galectin-3⁺) macrophages appeared in the lung following NM administration; this was evident within 1d, and persisted for 28 d. AG administration (50 mg/kg, 2×/day, 1d-3 d) abrogated NM-induced injury, oxidative stress and inflammation at 1d and 3d post exposure, with no effects at 7 d or 28 d. These findings indicate that nitric oxide generated via iNOS contributes to acute NM-induced lung toxicity, however, transient inhibition of iNOS is not sufficient to protect against pulmonary fibrosis.

CCAAT/enhancer binding protein-α regulates the protease/antiprotease balance required for bronchiolar epithelium regeneration

Many transcription factors that regulate lung morphogenesis during development are reactivated to mediate repairs of the injured adult lung. We hypothesized that CCAAT/enhancer binding protein-α (C/EBPα), a transcription factor critical for perinatal lung maturation, regulates genes required for the normal repair of the bronchiolar epithelium after injury. Transgenic Cebpα(Δ/Δ) mice, in which Cebpa was conditionally deleted from Clara cells and Type II cells after birth, were used in this study. Airway injury was induced in mice by the intraperitoneal administration of naphthalene to ablate bronchiolar epithelial cells. Although the deletion of C/EBPα did not influence lung structure and function under unstressed conditions, C/EBPα was required for the normal repair of terminal bronchiolar epithelium after naphthalene injury. To identify cellular processes that are influenced by C/EBPα during repair, mRNA microarray was performed on terminal bronchiolar epithelial cells isolated by laser-capture microdissection. Normal repair of the terminal bronchiolar epithelium was highly associated with the mRNAs regulating antiprotease activities, and their induction required C/EBPα. The defective deposition of fibronectin in Cebpα(Δ/Δ) mice was associated with increased protease activity and delayed differentiation of FoxJ1-expressing ciliated cells. The fibronectin and ciliated cells were restored by the intratracheal treatment of Cebpα(Δ/Δ) mice with the serine protease inhibitor. In conclusion, C/EBPα regulates the expression of serine protease inhibitors that are required for the normal increase of fibronectin and the restoration of ciliated cells after injury. Treatment with serine protease inhibitor may aid in the recovery of injured bronchiolar epithelial cells, and prevent common chronic lung diseases.

Sulfur mustard primes human neutrophils for increased degranulation and stimulates cytokine release via TRPM2/p38 MAPK signaling

Sulfur mustard (2,2'-bis-chloroethyl-sulfide; SM) has been a military threat since the World War I. The emerging threat of bioterrorism makes SM a major threat not only to military but also to civilian world. SM injury elicits an inflammatory response characterized by infiltration of neutrophils. Although SM was reported to prime neutrophils, the mechanism has not been identified yet. In the present study, we investigated the mechanism of SM-induced priming in human neutrophils. SM increased [Ca(2+)](i) in human neutrophils in a concentration-dependent fashion. Transient receptor potential melastatin (TRPM) 2 inhibitors (clotrimazole, econazole and flufenamic acid) and silencing of TRPM2 by shRNA attenuated SM-induced [Ca(2+)](i) increase. SM primed degranulation of azurophil and specific granules in response to activation by fMLP as previously reported. SB203580, an inhibitor of p38 MAPK, inhibited SM-induced priming. Neither PD98057, an ERK inhibitor, nor SP600215, a JNK inhibitor, inhibited SM-induced priming. In addition, SM enhanced phosphorylation of NF-kB p65 and release of TNF-α, interleukin (IL)-6 and IL-8. SB203580 inhibited SM-induced NF-kB phosphorylation and cytokine release. These results suggest the involvement of TRPM2/p38 MAPK pathway in SM-induced priming and cytokines release in neutrophils.

Macrophages and tissue injury: agents of defense or destruction?

The past several years have seen the accumulation of evidence demonstrating that tissue injury induced by diverse toxicants is due not only to their direct effects on target tissues but also indirectly to the actions of resident and infiltrating macrophages. These cells release an array of mediators with cytotoxic, pro- and anti-inflammatory, angiogenic, fibrogenic, and mitogenic activity, which function to fight infections, limit tissue injury, and promote wound healing. However, following exposure to toxicants, macrophages can become hyperresponsive, resulting in uncontrolled or dysregulated release of mediators that exacerbate acute tissue injury and/or promote the development of chronic diseases such as fibrosis and cancer. Evidence suggests that the diverse activity of macrophages is mediated by distinct subpopulations that develop in response to signals within their microenvironment. Understanding the precise roles of these different macrophage populations in the pathogenic response to toxicants is key to designing effective treatments for minimizing tissue damage and chronic disease and for facilitating wound repair.

The injured lung: clinical issues and experimental models

Exposure of military and civilian populations to inhaled toxic chemicals can take place as a result of deliberate release (warfare, terrorism) or following accidental releases from industrial concerns or transported chemicals. Exposure to inhaled toxic chemicals can result in an acute lung injury, and in severe cases acute respiratory distress syndrome, for which there is currently no specific medical therapy, treatment remaining largely supportive. This treatment often requires intensive care facilities that may become overwhelmed in mass casualty events and may be of limited benefit in severe cases. There remains, therefore, a need for evidence-based treatment to inform both military and civilian medical response teams on the most appropriate treatment for chemically induced lung injury. This article reviews data used to derive potential clinical management strategies for chemically induced lung injury.

Functional and inflammatory alterations in the lung following exposure of rats to nitrogen mustard

Nitrogen mustard is a vesicant that causes damage to the respiratory tract. In these studies, we characterized the acute effects of nitrogen mustard on lung structure, inflammatory mediator expression, and pulmonary function, with the goal of identifying mediators potentially involved in toxicity. Treatment of rats (male Wistar, 200-225 g) with nitrogen mustard (mechlorethamine hydrochloride, i.t., 0.25mg/kg) resulted in marked histological changes in the respiratory tract, including necrotizing bronchiolitis, thickening of alveolar septa, and inflammation which was evident within 24h. This was associated with increases in bronchoalveolar lavage protein and cells, confirming injury to alveolar epithelial regions of the lung. Nitrogen mustard administration also resulted in increased expression of inducible nitric oxide synthase and cyclooxygenase-2, pro-inflammatory proteins implicated in lung injury, in alveolar macrophages and alveolar and bronchial epithelial cells. Expression of connective tissue growth factor and matrix metalloproteinase-9, mediators regulating extracellular matrix turnover was also increased, suggesting that pathways leading to chronic lung disease are initiated early in the pathogenic process. Following nitrogen mustard exposure, alterations in lung mechanics and function were also observed. These included decreases in baseline static compliance, end-tidal volume and airway resistance, and a pronounced loss of methacholine responsiveness in resistance, tissue damping and elastance. Taken together, these data demonstrate that nitrogen mustard induces rapid structural and inflammatory changes in the lung which are associated with altered lung functioning. Understanding the nature of the injury induced by nitrogen mustard and related analogs may aid in the development of efficacious therapies for treatment of pulmonary injury resulting from exposure to vesicants.

Selective targeting of selenocysteine in thioredoxin reductase by the half mustard 2-chloroethyl ethyl sulfide in lung epithelial cells

Thioredoxin reductase (TrxR) is a selenocysteine-containing flavoprotein that catalyzes the NADPH-dependent reduction of oxidized thioredoxin and plays a key role in regulating cellular redox homeostasis. In the present studies, we examined the effects of 2-chloroethyl ethyl sulfide (CEES), a model sulfur mustard vesicant, on TrxR in lung epithelial cells. We speculated that vesicant-induced alterations in TrxR contribute to oxidative stress and toxicity. The treatment of human lung A549 epithelial cells with CEES resulted in a time- and concentration-dependent inhibition of TrxR. Using purified rat liver TrxR, we demonstrated that only the reduced enzyme was inhibited and that this inhibition was irreversible. The reaction of TrxR with iodoacetamide, which selectively modifies free thiol or selenol on proteins, was also markedly reduced by CEES, suggesting that CEES induces covalent modification of the reduced selenocysteine-containing active site in the enzyme. This was supported by our findings that recombinant mutant TrxR, in which selenocysteine was replaced by cysteine, was markedly less sensitive to inhibition by CEES and that the vesicant preferentially alkylated selenocysteine in the C-terminal redox motif of TrxR. TrxR also catalyzes quinone redox cycling, a process that generates reactive oxygen species. In contrast to its inhibitory effects on TrxR activity, CEES was found to stimulate redox cycling. Taken together, these data suggest that sulfur mustard vesicants target TrxR and that this may be an important mechanism mediating oxidative stress and tissue injury.

Sulfur mustard-induced pulmonary injury: therapeutic approaches to mitigating toxicity

Sulfur mustard (SM) is highly toxic to the lung inducing both acute and chronic effects including upper and lower obstructive disease, airway inflammation, and acute respiratory distress syndrome, and with time, tracheobronchial stenosis, bronchitis, and bronchiolitis obliterans. Thus it is essential to identify effective strategies to mitigate the toxicity of SM and related vesicants. Studies in animals and in cell culture models have identified key mechanistic pathways mediating their toxicity, which may be relevant targets for the development of countermeasures. For example, following SM poisoning, DNA damage, apoptosis, and autophagy are observed in the lung, along with increased expression of activated caspases and DNA repair enzymes, biochemical markers of these activities. This is associated with inflammatory cell accumulation in the respiratory tract and increased expression of tumor necrosis factor-α and other proinflammatory cytokines, as well as reactive oxygen and nitrogen species. Matrix metalloproteinases are also upregulated in the lung after SM exposure, which are thought to contribute to the detachment of epithelial cells from basement membranes and disruption of the pulmonary epithelial barrier. Findings that production of inflammatory mediators correlates directly with altered lung function suggests that they play a key role in toxicity. In this regard, specific therapeutic interventions currently under investigation include anti-inflammatory agents (e.g., steroids), antioxidants (e.g., tocopherols, melatonin, N-acetylcysteine, nitric oxide synthase inhibitors), protease inhibitors (e.g., doxycycline, aprotinin, ilomastat), surfactant replacement, and bronchodilators. Effective treatments may depend on the extent of lung injury and require a multi-faceted pharmacological approach.

Mustard gas toxicity: the acute and chronic pathological effects

Ever since it was first used in armed conflict, mustard gas (sulfur mustard, MG) has been known to cause a wide range of acute and chronic injuries to exposure victims. The earliest descriptions of these injuries were published during and in the immediate aftermath of the First World War, and a further series of accounts followed the Second World War. More recently, MG has been deployed in warfare in the Middle East and this resulted in large numbers of victims, whose conditions have been studied in detail at hospitals in the region. In this review, we bring together the older and more recent clinical studies on MG toxicity and summarize what is now known about the acute and chronic effects of the agent on the eyes, skin, respiratory tract and other physiological systems. In the majority of patients, the most clinically serious long-term consequences of MG poisoning are on the respiratory system, but the effects on the skin and other systems also have a significant impact on quality of life. Aspects of the management of these patients are discussed.

Inflammatory effects of inhaled sulfur mustard in rat lung

Inhalation of sulfur mustard (SM), a bifunctional alkylating agent that causes severe lung damage, is a significant threat to both military and civilian populations. The mechanisms mediating its cytotoxic effects are unknown and were investigated in the present studies. Male rats Crl:CD(SD) were anesthetized, and then intratracheally intubated and exposed to 0.7-1.4mg/kg SM by vapor inhalation. Animals were euthanized 6, 24, 48h or 7days post-exposure and bronchoalveolar lavage fluid (BAL) and lung tissue collected. Exposure of rats to SM resulted in rapid pulmonary toxicity, including focal ulceration and detachment of the trachea and bronchial epithelia from underlying mucosa, thickening of alveolar septal walls and increased numbers of inflammatory cells in the tissue. There was also evidence of autophagy and apoptosis in the tissue. This was correlated with increased BAL protein content, a marker of injury to the alveolar epithelial lining. SM exposure also resulted in increased expression of markers of inflammation including cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNFα), inducible nitric oxide synthase (iNOS), and matrix metalloproteinase-9 (MMP-9), each of which has been implicated in pulmonary toxicity. Whereas COX-2, TNFα and iNOS were mainly localized in alveolar regions, MMP-9 was prominent in bronchial epithelium. In contrast, expression of the anti-oxidant hemeoxygenase, and the anti-inflammatory collectin, surfactant protein-D, decreased in the lung after SM exposure. These data demonstrate that SM-induced oxidative stress and injury are associated with the generation of cytotoxic inflammatory proteins which may contribute to the pathogenic response to this vesicant.