Assessment of the biochemical effects of percutaneous exposure of sulphur mustard in an in vitro human skin system

Myeloperoxidase deficiency attenuates nitrogen mustard-induced skin injuries

The pathologic mechanisms of skin injuries, following the acute inflammatory response induced by vesicating agents sulfur mustard (SM) and nitrogen mustard (NM) exposure, are poorly understood. Neutrophils which accumulate at the site of injury, abundantly express myeloperoxidase (MPO), a heme protein that is implicated in oxidant-related antimicrobial and cytotoxic responses. Our previous studies have shown that exposure to SM analog 2-chloroethyl ethyl sulfide (CEES) or NM results in an inflammatory response including increased neutrophilic infiltration and MPO activity. To further define the role of neutrophil-derived MPO in NM-induced skin injury, here we used a genetic approach and examined the effect of NM exposure (12h and 24h) on previously established injury endpoints in C57BL/6J wild type (WT) and B6.129X1-MPOtm1Lus/J mice (MPO KO), homozygous null for MPO gene. NM exposure caused a significant increase in skin bi-fold thickness, epidermal thickness, microvesication, DNA damage and apoptosis in WT mice compared to MPO KO mice. MPO KO mice showed relatively insignificant effect. Similarly, NM induced increases in the expression of inflammatory and proteolytic mediators, including COX-2, iNOS and MMP-9 in WT mice, while having a significantly lower effect in MPO KO mice. Collectively, these results show that MPO, which generates microbicidal oxidants, plays an important role in NM-induced skin injuries. This suggests the development of mechanism-based treatments against NM- and SM-induced skin injuries that inhibit MPO activity and attenuate MPO-derived oxidants.

Cytokine regulation by MAPK activated kinase 2 in keratinocytes exposed to sulfur mustard

Uncontrolled inflammation contributes to cutaneous damage following exposure to the warfare agent bis(2-chloroethyl) sulfide (sulfur mustard, SM). Activation of the p38 mitogen activated protein kinase (MAPK) precedes SM-induced cytokine secretion in normal human epidermal keratinocytes (NHEKs). This study examined the role of p38-regulated MAPK activated kinase 2 (MK2) during this process. Time course analysis studies using NHEK cells exposed to 200μM SM demonstrated rapid MK2 activation via phosphorylation that occurred within 15 min. p38 activation was necessary for MK2 phosphorylation as determined by studies using the p38 inhibitor SB203580. To compare the role of p38 and MK2 during SM-induced cytokine secretion, small interfering RNA (siRNA) targeting these proteins was utilized. TNF-α, IL-1β, IL-6 and IL-8 secretion was evaluated 24h postexposure, while mRNA changes were quantified after 8h. TNF-α, IL-6 and IL-8 up regulation at the protein and mRNA level was observed following SM exposure. IL-1β secretion was also elevated despite unchanged mRNA levels. p38 knockdown reduced SM-induced secretion of all the cytokines examined, whereas significant reduction in SM-induced cytokine secretion was only observed with TNF-α and IL-6 following MK2 knockdown. Our observations demonstrate potential activation of other p38 targets in addition to MK2 during SM-induced cytokine secretion.

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.

The transcriptional effects of the vesicants lewisite and sulfur mustard on human epidermal keratinocytes

Sulfur mustard (SM) injury is a complex process that begins with extensive alkylation of critical cellular components and culminates in cell death and skin vesication. The mechanism of toxicity is not well understood since SM broadly alkylates cellular nucleophiles. However, two events appear integral-the formation of DNA cross-links and the release of proteases into the extracellular matrix. To identify genes directly involved in vesication, the transcriptional profile of SM was compared to the vesicant lewisite (L). Similarly, to identify genes directly involved in DNA damage, the transcriptional profile of SM was compared to the genotoxic agent cisplatin (c-Pt). Microarrays containing 7,075 sequence-verified human cDNAs were screened with mRNA from human epidermal keratinocytes treated with 200 mu M agent for 2 h. A large number of differentially expressed genes were identified, with many similarities observed between agents. Many genes not previously associated with SM and L injury were also identified, including a large percentage of unknown function. A comparison of the differential expression profiles revealed that L had the broadest and most robustly altered expression. Apoptotic transcripts were clearly evident in L but not in SM, suggesting a late stage in L injury.

Baicalin as a potentially promising drug for the management of sulfur mustard induced cutaneous complications: a review of molecular mechanisms

Sulfur mustard (SM) is a bifunctional alkylating agent with strong blistering, irritant, mutagenic and cytotoxic properties. SM has been widely deployed as a chemical warfare agent for over a century, leading to extensive casualties. Skin is among the first and most heavily damaged organs upon SM exposure. Unfortunately, a considerable fraction of SM-intoxicated patients are still suffering from chronic cutaneous complications. While these complications adversely affect patients' quality of life, there is as yet no ideal treatment for them and therapeutic options are limited and mainly symptomatic. During recent decades, remarkable progress has been made in understanding molecular mechanisms underlying SM-induced dermatotoxicity and several intra- and extracellular targets have been identified. This review argues that baicalin, a bioactive flavonoid from the roots of Scutellaria spp., could counteract different molecular and biochemical abnormalities that mediate SM dermatotoxicity and could therefore be regarded as a promising therapeutic option for the management of SM-induced cutaneous lesions.

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.

Mechanisms mediating the vesicant actions of sulfur mustard after cutaneous exposure

Sulfur mustard (SM), a chemical weapon first employed during World War I, targets the skin, eyes, and lung. It remains a significant military and civilian threat. The characteristic response of human skin to SM involves erythema of delayed onset, followed by edema with inflammatory cell infiltration, the appearance of large blisters in the affected area, and a prolonged healing period. Several in vivo and in vitro models have been established to understand the pathology and investigate the mechanism of action of this vesicating agent in the skin. SM is a bifunctional alkylating agent which reacts with many targets including lipids, proteins, and DNA, forming both intra- and intermolecular cross-links. Despite the relatively nonselective chemical reactivity of this agent, basal keratinocytes are more sensitive, and blistering involves detachment of these cells from their basement membrane adherence zones. The sequence and manner in which these cells die and detach is still unresolved. Much has been discovered over the past two decades with respect to the mechanisms of SM-induced cytotoxicity and the intracellular and extracellular targets of this vesicant. In this review, the effects of SM exposure on the skin are described, as well as potential mechanisms mediating its actions. Successful therapy for SM poisoning will depend on following new mechanistic leads to develop drugs that target one or more of its sites of action.

The use of doxycycline as a protectant against sulphur mustard in HaCaT cells

As part of an ongoing programme on medical countermeasures against the chemical warfare agent sulphur mustard (HD) and set against the background of the involvement of matrix metalloproteinases (MMPs) in the pathology of HD-induced vesication processes, the potentially beneficial effects of doxycycline on cell attachment was determined in confluent HaCaT cell cultures exposed to HD. Doxycycline was found to inhibit to a significant extent the tendency of HD-exposed cells to detach from the growth substrate, however, analysis of the metabolic activity of the adherent cells indicated that doxycycline treatment did not maintain cell viability. It was confirmed that apoptosis was the predominant mode of HD-induced cell death. The results suggested that doxycycline and other MMP inhibitors may have a role to play in therapeutic intervention against HD exposure, but only as part of a combination therapy. The specific value of protease inhibitors in this capacity remains to be determined.

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.

Localization of substance P gene expression for evaluating protective countermeasures against sulfur mustard

Sulfur mustard [bis(2-chloroethyl)sulfide; SM] is a chemical warfare agent that produces edema and blister formation with a severe inflammatory reaction. The mouse ear vesicant model for SM injury has been used to evaluate pharmacological agents for countering SM dermal injury. The vanilloid olvanil reduces SM-induced edema and mRNA expression of cytokines and chemokines, suggesting that blocking the inflammatory effects of neuropeptides, such as substance P (SP), may provide protection against SM-induced dermal injury. This study examined SP expression in mice exposed to SM (0.16 mg) on the inner surface of the right ear, with or without olvanil pretreatment at 1, 10, 30, 60, and 360 min following exposure. In naïve skin, SP mRNA localization was associated with blood vessels and sebaceous glands. In SM-exposed skin, SP mRNA was also detected in perivascular dermal cells. Immunohistochemical localization of SP protein was observed in the ear skin of naïve, SM-, olvanil/SM-, and vehicle-treated mice. Quantification of SP+ perivascular dermal cells revealed that SM exposure led to a significant increase (P < or = 0.05) in SP+ cells over the observed time period. Olvanil pretreatment significantly reduced (P < or = 0.05) the mean number of SP+ cells at 60 and 360 min. This study demonstrates that SP expression could provide an additional endpoint for evaluating the effectiveness of vanilloid drugs on SM-induced skin inflammation.

Diisopropylglutathione ester protects A549 cells from the cytotoxic effects of sulphur mustard

The A549 cell line was used to assess the ability of diisopropylglutathione (DIPE) to protect against a 100 microM challenge dose of sulphur mustard (HD) using gentian violet (GV), thiazolyl blue (MTT) and neutral red (NR) assays as indicators of cell culture viability. As part of a continuing study of the efficacy of protective nucleophiles as candidate treatments for HD poisoning, several different combinations of protectant and HD were used to determine the optimal means of protecting A549 cells from the effects of HD. It was found that DIPE (4 mM) could protect cells against the effects of HD though for optimal effect, DIPE had to be present at the time of HD challenge. Cultures protected with DIPE were up to 2.9-fold more viable than HD exposed cells 48 h after HD challenge when using the GV, MTT and NR assays to assess viability. Observations by phase contrast microscopy of GV stained cultures confirmed these findings. Pretreating A549 cultures with DIPE for 1 h followed by its removal prior to HD challenge did maintain cell viability, though at a relatively low level (only up to 1.4-fold more viable than HD only exposed cells). DIPE was also able to protect HD exposed A549 cultures when added to cell cultures at intervals of up to 12 to 15 min after the initial HD exposure, though viability tended to decrease over this period, so that at 1 h, addition of DIPE did not maintain the viability of the cultures. This is the first such report of the anti-HD protectant properties of DIPE in A549 cells. It is concluded that the protection observed against HD is probably largely due to extracellular inactivation of HD by DIPE.