Sulfur mustard: its continuing threat as a chemical warfare agent, the cutaneous lesions induced, progress in understanding its mechanism of action, its long-term health effects, and new developments for protection and therapy

Role of reactive oxygen and nitrogen species in olfactory epithelial injury by the sulfur mustard analogue 2-chloroethyl ethyl sulfide

The inhalation of sulfur mustard (SM) causes substantial deposition in the nasal region. However, specific injury has not been characterized. 2-chloroethyl ethyl sulfide (CEES) is an SM analogue used to model injury and screen potential therapeutics. After the inhalation of CEES, damage to the olfactory epithelium (OE) was extensive. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cells were present by 4 hours, and maximal at 18-72 hours. Cleaved caspase 3 immunohistochemistry (IHC) was maximal at 18 hours after the inhalation of 5% CEES. Olfactory marker protein (OMP)-positive olfactory neurons were markedly decreased at 18 hours. IHC-positive cells for 3-nitrotyrosine (3-NT) within epithelium were elevated by 8 hours, waning by 18 hours, and absent by 72 hours. AEOL 10150, a catalytic manganoporphyrin antioxidant, administered both subcutaneously (5 mg/kg) and intranasally (50 μM, "combined treatment"), decreased OE injury. CEES-induced increases in markers of cell death were decreased by combined treatment involving AEOL 10150. CEES-induced changes in OMP and 3-NT immunostaining were markedly improved by combined treatment involving AEOL 10150. The selective inducible nitric oxide synthase inhibitor 1400W (5 mg/kg, subcutaneous), administered 1 hour after inhalation and thereafter every 4 hours (five doses), also reduced OE damage with improved OMP and 3-NT staining. Taken together, these data indicate that reactive oxygen and nitrogen species are important mediators in CEES-induced nasal injury.

A review of the electrophilic reaction chemistry involved in covalent DNA binding

The need to assess the ability of a chemical to act as a mutagen or a genotoxic carcinogen (collectively termed genotoxicity) is one of the primary requirements in regulatory toxicology. Several pieces of legislation have led to an increased interest in the use of in silico methods, specifically the formation of chemical categories for the assessment of toxicological endpoints. A key step in the development of chemical categories for genotoxicity is defining the organic chemistry associated with the formation of a covalent bond between DNA and an exogenous chemical. This organic chemistry is typically defined as structural alerts. To this end, this article has reviewed the literature defining the structural alerts associated with covalent DNA binding. Importantly, this review article also details the mechanistic organic chemistry associated with each of the structural alerts. This information is extremely important in terms of meeting regulatory requirements for the acceptance of the chemical category approach. The structural alerts and associated mechanistic chemistry have been incorporated into the Organisation for Economic Co-operation and Development (OECD) (Q)SAR Application Toolbox.

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.

Expression of proliferative and inflammatory markers in a full-thickness human skin equivalent following exposure to the model sulfur mustard vesicant, 2-chloroethyl ethyl sulfide

Sulfur mustard is a potent vesicant that induces inflammation, edema and blistering following dermal exposure. To assess molecular mechanisms mediating these responses, we analyzed the effects of the model sulfur mustard vesicant, 2-chloroethyl ethyl sulfide, on EpiDerm-FT™, a commercially available full-thickness human skin equivalent. CEES (100-1000 μM) caused a concentration-dependent increase in pyknotic nuclei and vacuolization in basal keratinocytes; at high concentrations (300-1000 μM), CEES also disrupted keratin filament architecture in the stratum corneum. This was associated with time-dependent increases in expression of proliferating cell nuclear antigen, a marker of cell proliferation, and poly(ADP-ribose) polymerase (PARP) and phosphorylated histone H2AX, markers of DNA damage. Concentration- and time-dependent increases in mRNA and protein expression of eicosanoid biosynthetic enzymes including COX-2, 5-lipoxygenase, microsomal PGE₂ synthases, leukotriene (LT) A₄ hydrolase and LTC₄ synthase were observed in CEES-treated skin equivalents, as well as in antioxidant enzymes, glutathione S-transferases A1-2 (GSTA1-2), GSTA3 and GSTA4. These data demonstrate that CEES induces rapid cellular damage, cytotoxicity and inflammation in full-thickness skin equivalents. These effects are similar to human responses to vesicants in vivo and suggest that the full thickness skin equivalent is a useful in vitro model to characterize the biological effects of mustards and to develop potential therapeutics.

[Cutaneous and systemic toxicology of vesicants used in warfare]

Vesicants are a group of chemicals used in warfare. The most representative agent is yperite, also known as mustard gas. The blisters that appeared on those exposed to yperite during combat in the First World War are responsible for the current name--vesicants--for this group of chemicals. Their affects are produced mainly through localized action of liquid or vapor forms on the skin, eyes, and respiratory tract. However, the high absorption of the liquid form through the skin or the vapor form on inhalation may cause substantial systemic effects. Here we analyze these effects, treatment of intoxication, and long-term sequelae, drawing on our experience and a review of the literature.

Characterization of acute and long-term sulfur mustard-induced skin injuries in hairless guinea-pigs using non-invasive methods

BACKGROUND/PURPOSE

Skin exposure to sulfur mustard (HD) results in erythema, edema and severe injury, which take long time to heal and might impose a heavy burden on the health system. Despite many years of research, there is no treatment that prevents the development of the cytotoxic effects of HD causing acute and prolonged damage to the skin. Therefore, it is of great importance to develop treatments that will ameliorate the extent of injury and improve as well as shorten the healing process. The aim of the present study was to establish a small animal model for a long-term HD-induced skin injury using the hairless guinea-pig (HGP) and to further test the efficacy of anti-inflammatories in ameliorating the pathology.

METHODS

HGPs were exposed to HD vapor on four sites for various time durations (1, 5, 10, 15 and 30 min). Clinical evaluation was conducted using reflectance colorimetry, transepidermal water loss and wound-area measurements. Biochemical [prostaglandin (PGE) content and metalloproteinase-9 (MMP-9) activity] and histopathological evaluations were conducted up to 2 weeks post-exposure.

RESULTS

Typical symptoms of HD skin injury developed including erythema and edema and the extent of injury was closely related to the exposure duration. Histological evaluation revealed severe edema, infiltration of inflammatory cells, damage to basal cells and vesication. By 2 weeks, healing was not completed, impaired basement membrane and epithelial hyperplasia were observed. PGE content and MMP-9 activity increased at 2 h post-exposure; however, while PGE returned to baseline levels within 24 h, MMP-9 remained elevated at least up to 48 h. Furthermore, a short-term, topical, anti-inflammatory post-exposure treatment was effective in reducing the extent of the acute injury.

CONCLUSION

These results indicate that the effects of HD on HGP skin are similar to previously shown effects in the pig model and in humans and therefore support the use of the HGP as an animal model for long-term effects of HD on skin injury and for studying the efficacy of anti-inflammatory treatments.

Role of MAP kinases in regulating expression of antioxidants and inflammatory mediators in mouse keratinocytes following exposure to the half mustard, 2-chloroethyl ethyl sulfide

Dermal exposure to sulfur mustard causes inflammation and tissue injury. This is associated with changes in expression of antioxidants and eicosanoids which contribute to oxidative stress and toxicity. In the present studies we analyzed mechanisms regulating expression of these mediators using an in vitro skin construct model in which mouse keratinocytes were grown at an air-liquid interface and exposed directly to 2-chloroethyl ethyl sulfide (CEES), a model sulfur mustard vesicant. CEES (100-1000 microM) was found to cause marked increases in keratinocyte protein carbonyls, a marker of oxidative stress. This was correlated with increases in expression of Cu,Zn superoxide dismutase, catalase, thioredoxin reductase and the glutathione S-transferases, GSTA1-2, GSTP1 and mGST2. CEES also upregulated several enzymes important in the synthesis of prostaglandins and leukotrienes including cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase-2 (mPGES-2), prostaglandin D synthase (PGDS), 5-lipoxygenase (5-LOX), leukotriene A(4) (LTA(4)) hydrolase and leukotriene C(4) (LTC(4)) synthase. CEES readily activated keratinocyte JNK and p38 MAP kinases, signaling pathways which are known to regulate expression of antioxidants, as well as prostaglandin and leukotriene synthases. Inhibition of p38 MAP kinase suppressed CEES-induced expression of GSTA1-2, COX-2, mPGES-2, PGDS, 5-LOX, LTA(4) hydrolase and LTC(4) synthase, while JNK inhibition blocked PGDS and GSTP1. These data indicate that CEES modulates expression of antioxidants and enzymes producing inflammatory mediators by distinct mechanisms. Increases in antioxidants may be an adaptive process to limit tissue damage. Inhibiting the capacity of keratinocytes to generate eicosanoids may be important in limiting inflammation and protecting the skin from vesicant-induced oxidative stress and injury.

Comparative evaluation of some flavonoids and tocopherol acetate against the systemic toxicity induced by sulphur mustard

OBJECTIVE

To evaluate the protective value of quercetin, gossypin, Hippophae rhamnoides (HR) flavone and tocopherol acetate against the systemic toxicity of percutaneously administered sulphur mustard (SM) in mice.

MATERIALS AND METHODS

Quercetin, gossypin, HR flavone or tocopherol acetate (200 mg/kg, i.p.) were administered just before percutaneous administration of SM and protection against the SM lethality was evaluated. In another experiment quercetin, gossypin, HR flavone or tocopherol acetate were administered against 2 LD(50) SM. The animals were sacrificed seven days post SM administration and various biochemical parameters were estimated.

RESULTS

The protection against the lethality of SM was very good with the flavonoids (quercetin = 4.7 folds; gossypin = 6.7 folds and HR flavone = 5.6 folds), compared to no protection with tocopherol acetate (0.7 fold). SM (2 LD(50)) showed decrease in reduced and oxidised glutathione (GSH and GSSG) levels, and an increase in malondialdehyde level (MDA). Oxidative stress enzymes like glutathione peroxidase, glutathione reductase and superoxide dismutase were significantly decreased. The total antioxidant status was also significantly decreased. Additionally, there was a significant increase in red blood corpuscles and hemoglobin content. All the flavonoids significantly protected the GSH, GSSG and MDA, and also the hematological variables. Tocopherol acetate failed to offer any protection in those parameters. Gossypin protected glutathione peroxidase, while HR flavone protected both glutathione reductase and glutathione peroxidase significantly. The decrease in body weight induced by SM and the histological lesions in liver and spleen were also significantly protected by the flavonoids but not by tocopherol acetate.

CONCLUSION

The present study supports that SM induces oxidative stress and flavonoids are promising cytoprotectants against this toxic effect.

Mustard Gas: Imminent Danger or Eminent Threat?

Objective:

To increase awareness of the widespread environmental prevalence of the chemical warfare agent mustard gas, examine the acute and chronic toxic effects to exposed humans, and discuss medical treatment guidelines for mustard gas exposures.

Data Sources:

Literature retrieval of medical case reports and clinical studies was accomplished using PubMed and the Cochrane Database (1919–March 2007). Search terms included mustard, mustard gas, sulfur mustard, chemical warfare, blister agents, vesicants, and war gas. Historical information and current events were accessed through military field manuals and Internet searches.

Study Selection and Data Extraction:

All articles in English identified from the data sources were evaluated. Adult and pediatric populations were included in the review.

Data Synthesis:

Mustard gas and other chemical weapons are feared for their use as weapons of terror; however, the major threat of mustard gas lies elsewhere. Tons of this chemical agent were produced for war, then subsequently buried in landfills, disposed of at sea, or teft to decay in storage lacrlities. There are documented and anecdotal reports of chemical weapon buriat sites and ocean dumps across the globe spanning from the Arctic Circle to Australia. Numerous accidental exposures have occurred over the past decade. Mustard gas is corrosive to the skin, eyes, and respiratory tract. Extensive exposures can also affect other organ systems. Its ability to cause harm to multiple organ systems at extremely low doses in virtually any environmental condition makes it an extremely dangerous agent. Immediate decontamination of people exposed to mustard gas liquids and vapors is paramount. Supportive care and long-term followup is necessary for exposed persons. Research is under way to find antidotes or treatment methods for mustard gas exposure, but currently there are no definitive treatment guidelines.

Conclusions:

Mustard gas is a weapon, but also a prevalent environmental threat. Recognizing the immense environmental presence of mustard gas disposal sites and the signs and symptoms of exposure will help speed treatment to those accidentally or purposefully exposed.

Molecular determination of laminin-5 degradation: a biomarker for mustard gas exposure diagnosis and its mechanism of action

Laminin-5, a heterotrimer of laminin alpha3, beta3 and gamma2 subunits, is a component of epithelial cell basement membranes. Laminin-5 functions as a ligand of the alpha3beta1 and alpha6beta4 integrins to regulate cell adhesion, migration and morphogenesis. In the skin, laminin-5 facilitates the assembly of basement membranes; thus it is essential for a stable attachment of the epidermis to the dermis and recovery of damaged skin. Sulphur mustard (SM), also known as mustard gas, is a vesicant that has been employed as a chemical weapon in various conflicts during the twentieth century. Skin exposure to SM results in fluid-filled blisters; proposed mechanisms are inflammation, protease stimulation, basal cell death and separation of the epidermis from the dermis apparently because of the degradation of attachment proteins like laminin-5. Therefore, we investigated the effects of SM exposure on the degradation of laminin-5 and its three subunits, alpha3, beta3 and gamma2 by exposing normal human epidermal keratinocytes (NHEK) to SM (0-300 microM, 1-24 h). We found that SM degraded laminin-5 and its two subunits beta3 and gamma2, but not alpha3. Preincubation of cells with a serine protease inhibitor (PMSF), or a metalloprotease inhibitor (1,10-phenanthroline) prior to SM exposure partially prevented SM-induced degradation of laminin-5 subunits, beta3 and gamma2. Specificity studies showed that the degradation of laminin-5 gamma2 was due to a bifunctional mustard compound such as SM, but not due to the other alkylating agents tested. Our results support that laminin-5 degradation is an important mechanism of SM injury as well as a useful biomarker of SM exposure. The knowledge of the mechanisms of laminin-5 degradation in SM-exposed NHEK has potential application in developing cutaneous therapeutics against SM.

A dorsal model for cutaneous vesicant injury by 2-chloroethyl ethyl sulfide using C57BL/6 mice

To evaluate stem cell-derived therapeutics for cutaneous vesicant injuries, we developed a dorsal exposure model using C57BL/6 black mice and half-mustard, 2-chloroethyl ethyl sulfide (CEES). The dorsal side of a mouse was exposed to 1-5 microl of CEES for 10 minutes and then decontaminated. The data demonstrate that 3 microl of CEES induced edema and erythema that peaked 24 h post exposure. Histopathology showed a central area of deep injury characterized by severe necrosis of epidermis and dermis. The C57BL/6 is a unique model that can be used to unravel the molecular mechanism of injury, identify the effects of black skin pigmentation, and evaluate the efficacy of stem cell therapeutics for cutaneous vesicant exposure.

Chemical Warfare Agents Chemical Warfare Agents: Their Past and Continuing Threat and Evolving Therapies Part II of II

Chemical warfare agents are ideal weapons for terrorists and for use in military operations against both civilian populations and troops. Thus, there have been efforts by the United States in cooperation with other concerned nations to develop animal models to understand the pathophysiology of the injuries induced by these agents, and to develop suitable animal models for testing of pre-and post-exposure protectants and therapies. Sulfur mustard remains the most significant chemical warfare agent that produces cutaneous injuries. Institution of standard recommendations prior to threatened exposure or after exposure are something that we need to be aware of in the world we live in. In addition, pre-and post-exposure therapies now being studied offer hope for moderating the mortality and morbidity that can result from chemical exposure.

Treatment of keratin intermediate filaments with sulfur mustard analogs

Sulfur mustard (SM) is an alkylating agent with a history of use as a chemical weapon. The chemical reactivity of sulfur mustard toward both proteins and nucleic acids coupled with the hours long delay between exposure and appearance of blisters has prevented the determination of the mechanism of blister formation. We have treated assembled keratin intermediate filaments with analogs of sulfur mustard to simulate exposure to SM. We find that treatment of intact filaments with chloroethyl ethyl sulfide (CEES) or mechlorethamine (MEC) produces aggregates of keratin filaments with little native appearing structure. Treatment of a mix of epidermal keratins 1/10 (keratin pair 1 and 10) and keratins 5/14 with a sulfhydryl-specific modification reagent also results in filament abnormalities. Our results are consistent with the hypothesis that modification of keratins by SM would result in keratin filament destruction, leading to lysis of epidermal basal cells and skin blistering.

Myocardial perfusion abnormalities in chemical warfare patients intoxicated with mustard gas

BACKGROUND

Mustard agents are of the major chemical agents used during Iran-Iraq war. There are no reports concerning long-term cardiac effects. The aim was to assess the scintigraphic pattern of myocardial perfusion in patients intoxicated with blistering gases.

METHOD

We analyzed myocardial perfusion scans of 22 consecutive intoxicated patients (21 male and 1 female, all < 44 years) and compared results with 14 controls. Only those patients and controls were entered whose 10-year risk of coronary artery disease (Framingham criteria) was <5%. Also only those patients were experimented upon that had currently other confirmed complications of intoxication (respiratory, cutaneous and ocular complications). All patients underwent a 1-day stress and rest protocol using (99m)Tc-MIBI. Images were assessed visually and quantitatively using Cedars Sinai program.

RESULTS

The prevalence of nonhomogeneity of uptake and left and right ventricular enlargement in both visual and quantitative analyses were higher in the mustard exposed patients than unexposed controls. The prevalence of ischemia was higher in the exposed patients (P < 0.05). Cavity to myocardium ratio, as an established and validated measure of ejection fraction, was also significantly lower in the warfare patients than the controls.

CONCLUSION

In so far it lies in our knowledge, this is the first report concerning the scintigraphic pattern of myocardial perfusion in mustard intoxicated patients. Based on the results, the pattern of myocardial perfusion in these patients is significantly different from normal controls, which could resemble either coronary artery disease or mild cardiomyopathic changes.

Delayed complications of sulfur mustard poisoning in the skin and the immune system of Iranian veterans 16?20�years after exposure

BACKGROUND

Extensive cutaneous burns caused by alkylating chemical warfare agent sulfur mustard (SM) have been associated with the severe suppression of the immune system in humans. We aimed to study the association between late cutaneous and immunological complications of SM poisoning.

METHODS

Skin examination was performed on all SM-poisoned Iranian veterans in the province of Khorasan, Iran, who had significant clinical complications, and their SM intoxication was confirmed by toxicological analysis. Light microscopy was performed on eight skin biopsies. Blood cell counts, serum immunoglobulin and complement factor, as well as flow cytometric, analyses were performed on all the patients. The severity of cutaneous complications were classified into four grades and compared with hematological and immunological parameters, using Spearman's rank correlation test.

RESULTS

Forty male subjects, confirmed with SM poisoning 16-20 years earlier, were studied. The main objective findings were hyperpigmentation (55%), dry skin (40%), multiple cherry angiomas (37.5%), atrophy (27.5%), and hypopigmentation (25%). Histopathologic findings were nonspecific and compatible with hyperpigmented old atrophic scars. Except for the hematocrit and C4 levels, hematological and immunological parameters revealed no significant correlation with the severity grades of cutaneous complications.

CONCLUSION

Sulfur mustard is an alkylating agent with prolonged adverse effects on both the skin and the immune system. Although skin is a major transporting system for SM's systemic absorption, there is probably no correlation between the severity of late cutaneous and immunological complications of SM poisoning.

Evaluation of analogues of DRDE-07 as prophylactic agents against the lethality and toxicity of sulfur mustard administered through percutaneous route

Sulfur mustard (SM), chemically bis (2-chloroethyl) sulfide is a bifunctional alkylating agent that causes serious blisters on contact with human skin. Although several antidotes have been reported for the systemic toxicity of SM in experimental animals none of them are approved so far and decontamination of SM immediately by physical or chemical means is recommended as the best protection. Two compounds amifostine [S-2(3-aminopropylamino) ethyl phosphorothioate] and DRDE-07 [S-2(2-aminoethylamino) ethyl phenyl sulfide] gave very good protection as an oral prophylactic agent against SM the in mouse model, but in the rat model the protection was only moderate. In the search for more effective and less toxic compounds, a number of analogues of DRDE-07 were synthesised and their protective efficacy was evaluated in mouse and rat models. The LD50 of S-aryl substitution was between 1 and 2 g kg(-1) and S-alkyl substitution was more than 2 g kg(-1). In the mouse model, DRDE-07, DRDE-10, DRDE-21, DRDE-30 and DRDE-35 gave about 20 fold protection, and DRDE-23 and DRDE-38 gave less protection of 4.8 and 9.0 fold respectively, against percutaneously administered SM. In the rat model, DRDE-07, DRDE-09, DRDE-10 and DRDE-21 gave about two fold protection. Percutaneously administered SM (19.33 mg kg(-1)) significantly depleted the hepatic GSH content in mice. Pretreatment with DRDE-21 significantly elevated the levels. A 4.4 fold increase in % DNA fragmentation was observed 7 days after SM administration (19.33 mg kg(-1)) in mice. Pretreatment with DRDE-07, DRDE-09, DRDE-10, DRDE-21, DRDE-30 and DRDE-35 significantly protected the mice from SM induced DNA damage. The histopathological lesions in liver and spleen induced by percutaneously administered SM was reduced by pretreatment with DRDE-07, DRDE-09, DRDE-10 and DRDE-21. These analogues may prove as prototypes for the designing of more effective prophylactic drug for SM.

Mustard: a potential agent of chemical warfare and terrorism

As one of the most important vesicant agents, the destructive properties of mustards on the skin, eyes and respiratory system, combined with a lack of antidote, makes them effective weapons. Such weapons are inexpensive, easily obtainable and frequently stockpiled. Sulphur mustard (mustard gas) has been used as a chemical warfare agent in at least 10 conflicts. In this article, the use of mustard as a potential agent of chemical warfare and terrorism is outlined. The dose-dependent effects of acute sulphur mustard exposure on the skin, eyes, and respiratory system are described, as well as the possible extents of injuries, the mechanisms of action and the long-term complications. Prevention and management of mustard exposure are briefly discussed. The need for awareness and preparedness in the dermatological community regarding mustard exposure is emphasized.

Medical aspects of sulphur mustard poisoning

Sulphur mustard is one of the major chemical warfare agents developed and used during World War I. Large stockpiles are still present in several countries. It is relatively easy to produce and might be used as a terroristic weapon. Sulphur mustard is a vesicant agent and causes cutaneous blisters, respiratory tract damage, eye lesions and bone marrow depression. The clinical picture of poisoning is well known from the thousands of victims during World War I and the Iran-Iraq war. In the latter conflict, sulphur mustard was heavily used and until now about 30,000 victims still suffer from late effects of the agent like chronic obstructive lung disease, lung fibrosis, recurrent corneal ulcer disease, chronic conjunctivitis, abnormal pigmentation of the skin, and several forms of cancer. Despite enormous research efforts during the last 90 years, no specific sulphur mustard antidote has been found. The prospering knowledge and developments of modern medicine created nowadays new chances to minimize sulphur mustard-induced organ damage and late effects.

Vesicants

Vesicants (or blister agents) are cytotoxic alkylating compounds, which are chemical agents sometimes collectively known as mustard gas or simply as mustard. Other blister agents are nitrogen mustard; sulfur mustard; lewisite, a vesicant that contains arsenic; and phosgene oxime, a halogenated oxime that possesses different properties and toxicity from the other agents. This article discusses history, toxicity, clinical presentation, and common treatment for vesicants.

Medical management of incidents with chemical warfare agents

Successful management of incidents with chemical warfare agents strongly depends on the speed of medical help and the ability of helpers to react properly. Though the general principles of clinical toxicology, such as decontamination, stabilization, patient evaluation and symptomatic treatment are similar for many toxicants, chemical warfare agents deserve special attention because of their very high inhalative and cutaneous toxicity, rapid onset of the disease and multiple organ failures. This article describes the medical management of mass casualties with blister agents, nerve agents and blood agents from the viewpoint of a clinical toxicologist. Characteristic diagnostic signs, decontamination procedures and therapeutic schemes for these agents are described. Treatment options are discussed. The importance of planning (e.g. antidote availability) and preparedness is emphasized.

Chemical warfare agents: their past and continuing threat and evolving therapies. Part I of II

Chemical warfare agents are potentially accessible to even underdeveloped nations because they are easily and inexpensively produced. This means that they are ideal for use by terrorists and in military operations against civilian populations and troops. In terms of cutaneous injury, vesicants-mainly sulfur mustard-are the most significant chemical warfare agents. Advances in understanding the pathophysiology of the lesions produced by sulfur mustard have led to the research and development of barrier creams as well as pre- and post-exposure therapies to moderate the damage and accelerate healing. Part I of this paper will discuss the history and classification of chemical agents; Part II, which will appear in the September/October 2003 issue of SKINmed, will discuss characteristic manifestations of exposure to chemical agents, as well as prevention and therapy.

Incidence of Lung, Eye, and Skin Lesions as Late Complications in 34,000 Iranians With Wartime Exposure to Mustard Agent

Approximately 34,000 Iranians known to have sustained mustard agent exposure during the Iran-Iraq war of 1980-1988 and survived over a decade afterwards were screened for distribution of the most commonly occurring medical problems. In order of greatest incidence, these include lesions of the lungs (42.5%), eyes (39.3%), and skin (24.5%). Within each subpopulation, patients were ranked according to severity of lesions. Twenty-three percent to 37% of patients exhibited at least mild coverage, with 1.5% to 4.5% classed as moderate, and a much smaller population (0.023-1.0%) of the 34,000 patients exhibiting extensive (severe) lesional coverage. These results provide a comprehensive overview of the medical problem most common among mustard victims and could serve as a predictor of the likely impact of these weapons on health status of populations exposed to them during ongoing military conflicts.

Low-dose sulfur mustard primes oxidative function and induces apoptosis in human polymorphonuclear leukocytes

Although considerable work has focused on understanding the processes of direct tissue injury mediated by the chemical warfare vesicant, sulfur mustard (2,2'-bis-chloroethyl sulfide; SM), relatively little is known regarding the mechanisms of secondary injury caused potentially by the acute inflammatory response that follows SM exposure. Polymorphonuclear leukocytes (PMNs) play a central role in the initiation and propagation of inflammatory responses that, in some cases, result in autoimmune tissue damage. The potential for PMN-derived tissue damage following SM exposure may, in part, account for the protracted progression of the injury before it resolves. The current study was undertaken to evaluate the priming, oxidative function, and viability of PMN following exposure to low doses of SM such as those that might remain in tissues as a result of topical exposure. Our results demonstrate that doses of SM ranging from 25 to 100 microM primed PMN for oxidative burst in response to activation by fMLP, and that doses of SM ranging from 50 to 100 microM induced PMN apoptosis. Understanding the mechanisms through which SM directly affects PMN activation and apoptosis will be of critical value in developing novel treatments for inflammatory tissue injury following SM exposure.

[Acute poisoning by chemical warfare agent: sulfur mustard]

OBJECTIVE

To review story, mechanism of action, clinical and therapeutic bases of a sulfur mustard poisoning, by accidental, terrorism or war exposure.

DATA SOURCES

References were obtained from computerised bibliographic research (Medline), from personnel data (academic memoir, documents under approbation of the National Defense Office) and from the Library of Military Medical Service.

DATA SYNTHESIS

Sulfur mustard is a chemical warfare agent with peace time results: leak, accidental handling, acts of terrorism. Sulfur mustard is a vesicant agent, an organochlorine agent, who alkylate DNA. Under liquid or gas form its main target are skin and lungs. Clinical effects are like burns with loss of immunity, with respiratory failure, ophthalmic, gastrointestinal and haematological signs. The last studies have improved knowledge about the mechanism of action, detection, protection and treatment. Methods for determination of sulfur mustard are based on gas chromatographic method and mass spectrometry. During sulfur mustard contamination the first priorities of treatment are to remove victims from the contaminated place and to initiate decontamination. Emergency workers and materials must take protection to avoid secondary contamination of emergency unit. With treatment of vital functions and respiratory failure, the new ways of treatment are about N-acetyl cysteine for lung injury, poly (ADP-ribose) polymerase inhibitors, calmodulin antagonists and Ca(++) chelators. Interactions between sulfur mustard and anaesthetic agents are not well known and are based on clinical observations.

CONCLUSION

Emergency care unit can be confronted with sulfur mustard during accidental contamination or acts of terrorism. First and most efficacy priorities of treatment are to remove and to decontaminate victims. New means of detection and treatment are studied since several years but are not still appropriate to human victims or mass treatment.

Microbiological, biological, and chemical weapons of warfare and terrorism

Microbiological, biological, and chemical toxins have been employed in warfare and in terrorist attacks. In this era, it is imperative that health care providers are familiar with illnesses caused by these agents. Botulinum toxin produces a descending flaccid paralysis. Staphylococcal enterotoxin B produces a syndrome of fever, nausea, and diarrhea and may produce a pulmonary syndrome if aerosolized. Clostridium perfringens epsilon-toxin could possibly be aerosolized to produce acute pulmonary edema. Ricin intoxication can manifest as gastrointestinal hemorrhage after ingestion, severe muscle necrosis after intramuscular injection, and acute pulmonary disease after inhalation. Nerve agents inhibit acetylcholinesterase and thus produce symptoms of increased cholinergic activity. Ammonia, chlorine, vinyl chloride, phosgene, sulfur dioxide, and nitrogen dioxide, tear gas, and zinc chloride primarily injure the upper respiratory tract and the lungs. Sulfur mustard (and nitrogen mustard) are vesicant and alkylating agents. Cyanide poisoning ranges from sudden-onset headache and drowsiness to severe hypoxemia, cardiovascular collapse, and death. Health care providers should be familiar with the medical consequences of toxin exposure, and understand the pathophysiology and management of resulting illness.

Potential anti-inflammatory treatments against cutaneous sulfur mustard injury using the mouse ear vesicant model

In spite of several decades of research, no effective treatment to skin injuries following exposure to sulfur mustard (HD) has yet been found. In the present study, the mouse ear vesicant model was applied to awake mice in order to evaluate the efficiency of potential anti-inflammatory treatments in preventing HD-induced skin damages. Clinical follow-up and histological evaluation were used to characterize the injuries to the skin and to evaluate the efficiency of the drugs that were applied. Thus, the extent of mouse ear oedema and the histopathological changes following a single application of 0.2 or 1 microL of neat HD for 10 min (representing moderate and severe lesions, respectively), were monitored. Typical HD skin lesions were observed including epithelial and dermal damage. The development of the injury in mouse ears was found to be very similar to that reported in human skin. Screening of post-exposure topical steroids and non-steroidal antiinflammatory drugs (NSAIDs) proved that HD-induced inflammation could be diminished significantly as long as the treatment was applied during the early stages following exposure. A combined application of these drugs approved to be particularly effective in reducing inflammation.

Il-1-related cytokine responses of nonimmune skin cells subjected to CEES exposure with and without potential vesicant antagonists

Sulfur mustard provokes an acute inflammatory response in skin. To determine if keratinocytes regulate this response and whether three potential vesicant antagonists can counteract adverse changes, specimens of EpiDerm (MatTek Corp., Ashland, MA), a human skin model of differentiating keratinocytes, were exposed 2 h to humidified air with or without 2-chloroethyl ethyl sulfide (CEES, 1.72-1.73 mg/L/min) with or without 10 mM niacinamide, a poly (ADP-ribose) polymerase (PARP) inhibitor, 25 microM CGS9343B (calmodulin antagonist), or 8.4 mM leupeptin (cysteine protease inhibitor). After a 22-h incubation, levels of interleukin-1 alpha (IL-1alpha), its receptor antagonist (IL-1Ra), soluble type II receptor (sIL-1RII) and prostaglandin-E(2) (PGE(2)) were determined. Methylthiazole tetrazolium (MTT) viability tests and histological observations were also conducted. PGE(2) levels were abundant but unaffected by CEES regardless of antagonist presence. Total amounts (media plus lysate) of IL-1alpha, IL-1Ra, and sIL-1RII were reduced with CEES irrespective of antagonist. CEES promoted the release of IL-1Ra. Exposure of EpiDerm to CEES in the presence of the vesicant antagonists did not improve viability or counteract histological damage. We conclude CEES depresses total IL-1alpha and related cytokines, does not affect PGE(2) release, and adverse changes associated with CEES-exposed EpiDerm are not ameliorated by these particular antagonists. Dramatically increased (5- to 10-fold) release of IL-1Ra may provide a useful marker for cytotoxicity. The high level of IL-1Ra and increased release with injury suggest a primary function in down-regulating IL-1 inflammatory responses in skin.

In vitro neurotoxic and DNA-damaging properties of nitrogen mustard

Sulfur mustard and nitrogen mustard (HN2) are reported to produce neurobehavioral and neuropathological changes in animals and humans, but the mechanisms are unknown. We examined the cytotoxic properties of HN2 in cultures of dividing and post-mitotic neurons and astrocytes, which comprise the majority of cells in the central nervous system. Cultures of rat cerebellar astrocytes, post-mitotic granule cell neurons or dividing and terminally differentiated human SY5Y neuroblastoma cell cultures were treated with various concentrations of HN2 for 24 h. After treatment, culture medium was removed, the cell monolayer was incubated for 30 min with calcein-AM (green, live cells) and propidium iodide (red, dead cells) in control medium, the fluorochrome-containing medium was removed and replaced with control medium and cell density and viability were examined by fluorescence and light microscopy. Extensive cell loss (>90%) was observed in rat neuronal and SY5Y neuroblastoma cell cultures treated with 10 microM HN2, whereas cell loss was similar to controls in comparably treated astrocyte cultures. The DNA from HN2-treated cultures of rat neurons and SY5Y neuroblastoma cells was examined by high-performance liquid chromatography with electrochemical detection for the major HN2 DNA adduct N-(2-hydroxyethyl)-N[2-(7-guaninyl)ethyl]methylamine (GMOH). GMOH was detected in rat neuronal (85 fmol microg(-1) DNA) and SY5Y neuroblastoma cell cultures (46 fmol microg(-1) DNA) treated with 10 microM HN2 for 24 h, but was not detected in comparably treated astrocyte cell cultures. These findings are consistent with HN2 preferentially targeting neurons in vivo, possibly through a mechanism involving DNA damage.

Sulfur mustard induces apoptosis and necrosis in SCL II cells in vitro

Sulfur mustard (bis(2-chloroethyl) sulfide, HD) is an alkylating agent causing erythema and blistering with a latency of several hours after skin exposure. In the present in vitro study the influence of HD (1 microM-1 mM for 30 min or 4 h) on the viability and growth of SCL II cells was investigated. No significant differences in cytotoxicity were observed as assessed by formazan formation from XTT tetrazolium salt at 24, 48 and 72 h after exposure. Sulfur mustard concentrations of >500 microM were associated with an increasing portion of apoptotic cells without change in necrosis rate as assessed by nuclear morphology and gel electrophoresis of the DNA. The ATP levels were not affected up to 6 h after HD exposure (< or =1 mM). Twelve hours later, ATP depletion was observed at HD concentrations of >500 microM. Colony-forming ability was impaired at concentrations of <1 microM. Cell growth studies in comparison with nuclear morphology indicated late apoptotic death predominating at lower concentrations of HD. In summary, the data show that HD may inhibit cell growth already at concentrations where viability parameters and cell metabolism are not yet affected.

Protective effect of povidone iodine ointment against skin lesions induced by chemical and thermal stimuli

Mustard gas (sulfur mustard, HD) is a powerful vesicant employed as a chemical weapon. The present study demonstrates the effect of povidone iodine (PI) ointment against skin toxicity caused by HD. Gross and histopathological examinations showed that application of PI 20 min or less following exposure to the vesicant resulted in marked skin protection. The shorter, interval between exposure and treatment, the better was the protection achieved. Povidone iodine was also effective against other mustards, such as carboxybutylchloroethyl sulfide (CBCS) and mechlorethamine. The fact that PI protected the skin against agents that cannot be oxidized, such as iodoacetic acid, divinylsulfone and cantharidine, indicated that the antidotal effect of PI was unrelated to oxidation of the nitrogen and sulfur atoms of the mustards. Furthermore, NMR spectroscopy of CBCS treated with iodine did not show oxidation of the sulfur atom. Clinical experience with patients after accidential heat burns (mostly of grade I) has shown that topical application of PI ointment immediately after the stimulus significantly reduced, and often prevented, skin lesions. Apart from being a safe and widely used disinfectant, PI ointment is recommended as an efficient protective agent against skin toxicity caused by hazardous chemicals and by heat stimuli.

Effects of CEES on inflammatory mediators, heat shock protein 70A, histology and ultrastructure in two skin models

Chemical warfare threats require the development of diverse models for the assessment of countermeasures. Human skin products, Skin2 (differentiating keratinocytes on a fibroblast-collagen matrix) and EpiDerm (differentiating keratinocytes) were exposed (2 h) to the sulfur mustard 2-chloroethyl ethyl sulfide (CEES, 1-2 mg l(-1) min(-1)) in humidified air or to humidified air alone. Tissues were evaluated histologically, ultrastructurally and for viability 22 h later; media and tissues were also analyzed for inflammatory mediators. Histology showed that CEES induced the separation of dermal and epidermal regions in Skin2 with severe damage to basal keratinocytes. Histology and electron microscopy of both products revealed condensation of nuclear chromatin, retraction of spinous processes, collapse of the tonofibrillar network and cytoplasmic vacuolization and blebbing in those cells with loss of pseudobasement membrane integrity. Exposure of Skin2 to CEES increased extracellular interleukin-1alpha (IL-1alpha), prostaglandin-E2 (PGE2) and especially IL-1 receptor antagonist (IL-1Ra) release (56,334 vs 84,614 pg ml(-1)), but decreased interleukin-6 (IL-6, 4,755 vs 351 pg ml(-1)). Exposure of EpiDerm to CEES led to unaffected extracellular and reduced intracelluar IL-1alpha (371 vs 92 pg ml(-1)). Extracellular IL-1Ra greatly increased (2,375 vs 24,875 pg ml(-1)), whereas cellular levels decreased (16,5425 vs 96,625 pg ml(-1)). Extracellular (224 vs 68 pg ml(-1)) and intracellular (485 vs 233 pg ml(-1)) soluble interleukin-1 receptor H (sIL-1RII) decreased. Prostanglandin E2 increased (1,835 vs 2,582 pg ml(-1)), whereas heat shock protein 70A (Hsp70A) remained statistically unchanged (57,000 vs 96,000 pg ml(-1)). Failure to obtain a heat shock response to CEES may contribute to the susceptibility of tissue to the alkylating agent. Consistent and marked responses of cellular and extracellular IL-1Ra to CEES suggest a potential for use as a tissue status marker and primary antiinflammatory regulator in skin.

Topical iodine preparation as therapy against sulfur mustard-induced skin lesions

Sulfur mustard (SM) is a powerful vesicant employed as an agent of chemical warfare. This study demonstrates the therapeutic effect of a novel topical iodine preparation as a postexposure treatment against SM-induced lesions in the fur-covered guinea-pig skin model. Iodine treatment 15 min after SM exposure resulted in statistically significant reductions of 48, 50, and 55% in dermal acute inflammation, hemorrhage, and necrosis, respectively, whereas, the epidermal healing markers, hyperkerathosis and acanthosis, were significantly elevated by 72 and 67%, respectively, 2 days after treatment. At the interval of 30 min between SM exposure and iodine treatment, there was a significant degree of healing or recovery, albeit to a lesser extent than that observed in the shorter interval. Although the epidermal healing markers were not elevated, the parameters indicative of active tissue damage, such as subepidermal microblisters, epidermal ulceration, dermal acute inflammation, hemorrhage, and necrosis, were significantly reduced by 35, 67, 43, 39, and 45%, respectively. At the 45-min interval between exposure and treatment, there was also a certain degree of healing or recovery expressed as significant reductions in dermal subacute inflammation, subepidermal microblister formation, and epidermal ulceration, whereas, acanthosis was statistically elevated, indicating an increased healing potential. At the 60-min interval, iodine was less efficacious; nevertheless, a significant reduction in the incidence of subepidermal microblisters and an expansion of the acanthotic area were observed. Gross ulceration was significantly decreased at intervals of 15 and 30 min between exposure and treatment. The local anesthetic, lidocaine, did not alter the therapeutic effect of iodine. SM was not affected chemically by iodine as measured by gas chromatography-mass spectrometry (GC-MS) analysis. These findings suggest that the iodine preparation functions as an antidote against skin lesions induced by SM.

DNA fragmentation pattern induced in thymocytes by sulphur mustard

Sulphur mustard (HD) is a blister agent for which no specific therapy exists. The mechanism of cell injury caused by HD is not well understood. This study examined DNA damage in thymocytes exposed to a range of HD concentrations over a time course of 1-24 h. Thymocytes incubated with HD showed an increase in the production of DNA fragments of the type frequently associated with apoptosis, namely, initial formation of large fragments of 30-50, 200-300 and > 700 kilobase pairs (kbp), followed by further degradation to produce an internucleosomal 'ladder' of oligomers of approximately 180 base pairs (bp). Pulsed field electrophoresis analysis of thymocytes incubated with HD detected breakdown of the chromatin up to 3 h before a corresponding increase in the low molecular weight (MW) oligonucleosomal fragments could be seen on conventional agarose gels. These results suggest that cells damaged by HD poisoning may be irretrievably committed to cell death sooner after exposure than previous studies suggested. The nature of the DNA fragments produced suggested that apoptosis may represent a component of the pathway of cell death induced by HD. These aspects may have implications for the search for specific therapeutic reagents effective in the prevention or treatment of HD poisoning.