Effect of sulphur mustard on human skin cell lines with differential agent sensitivity

Peripheral blood mononuclear cellular viability and its correlation with long-term pulmonary complications after sulfur mustard exposure

INTRODUCTION

Sulfur mustard (SM) as a chemical warfare agent has short- and long-term complications on its victims. Complications of exposure to SM depend on the level of contamination. Long-term pulmonary complications are the most serious problems. Recent evidence has shown that absorbed SM can be conducted to other tissues by the bloodstream. In this study, we evaluated the long-term effects of SM on the vital activity of peripheral blood mononuclear cells (PBMCs) in SM-exposed patients with long-term pulmonary complications.

MATERIALS AND METHODS

Our study samples were 110 patients with long-term pulmonary complications in the SM-exposed group and 109 unexposed individuals in the control group. After clinical examination and pulmonary function tests, the severity of pulmonary complications was classified. Also, the participants' peripheral blood was taken into EDTA-treated Vacutainer tubes. Then, the complete blood count (CBC) was calculated, and PBMCs was purified from whole blood using Ficol-Paque gradient method, finally, the vital activity was assessed by MTT assay.

RESULT

The vital activity of PBMCs in the SM-exposed group with the mitogen was significantly lower than that in the control group (P = 0.016). Whereas, there was no significant difference in the viability of PBMCs without the mitogen between two groups. Furthermore, hematologic findings indicated that the SM-exposed group had a significant increase in the total count of WBC, neutrophil, MCV, and HCT values but the lymphocyte count and MCHC value were significantly lower than those in the control group.

CONCLUSION

Exposure to SM even after a long time, can affect hematologic parameters and vital activity of PBMCs.

Current status of the acquired immune system of Iranian patients with long-term complications of sulfur mustard poisoning

BACKGROUND

Sulfur mustard (SM) is a powerful blistering chemical warfare agent that has genotoxic effects. Cells with excessive proliferation such as lymphocytes may inherit this cellular toxicity which can lead to their malfunctions in the long-term. This study was designed to evaluate the status of acquired immunity among SM poisoned veterans around three decades after exposure.

METHODS

Thirty five male Iranian veterans having at least 25% disability due to SM poisoning with long-term complications in the respiratory system, skin or eyes were investigated. Non-functional/functional tests including hematological parameters, immunostaining analysis, lymphocyte proliferation assay, cytokine profile, and levels of total serum IgM, IgG and IgA were performed.

RESULTS

The results showed that most of the parameters of adaptive immune system of the veterans were currently within the normal ranges. However, changes in the proliferation index (PI) of lymphocytes showed problems with the lymphocytes which cannot be proliferated appropriately. PI values for PBMCs (peripheral blood mononuclear cells) in presence of PHA (Phytohemagglutinin-A) and LPS (lipopolysaccharide) mitogens were 1.16 ± 0.14 and 1.13 ± 0.07, respectively which are less than expected.

CONCLUSIONS

Based on the results gathered in this study, most of the parameters of acquired immunity were normal. However, the observed failure of lymphocyte functions may disrupt physiological activity of whole immune system leading to long-term complications; including recurrent respiratory tract infections. Indeed, further cellular and molecular studies with regard to lymphocytes function are required to better understand the status of adaptive immunity in these patients. Graphical abstract ᅟ.

Development of the sulfur mustard resistant keratinocyte cell line HaCaT/SM

Pairs of corresponding cytotoxic drug sensitive and resistant cell lines are powerful tools to develop treatment strategies. Developing cytotoxic drug resistant cell lines is a well-established method in cancer research. In more than fifty years of sulfur mustard (SM) resistant research such a cell pair has never been produced. Hereinafter we describe the first successful approach to develop a SM resistant keratinocyte cell line. Starting with the SM sensitive keratinocyte cell line HaCaT we used a strategy of continuous exposure with gradually increased concentrations. Cells were cultured in total for more than 40 months starting with an initial concentration of 0.07μM SM twice a week up to a final concentration of 7.2μM SM. The achieved cell line HaCaT/SM had an LC50 resistance increase of 4.7-fold and an LC90 increase of 8.2-fold. Hereinafter we demonstrate the production of the first sulfur mustard (SM) resistant cell line. The new achieved cell line called HaCaT/SM is able to tolerate a continuous exposure of an SM concentration, which is associated with an inhibitory effect of 93% within the original HaCaT cells, which were used as starting point.

Serum cytokine profiles of Khorasan veterans 23 years after sulfur mustard exposure

Sulfur mustard (SM) is an incapacitating chemical warfare agent that was used against Iranian soldiers during the period from 1983 to 1988. We have investigated serum cytokines profiles of Khorasan veterans who were exposed to SM >23 years earlier. Forty-four male Iranian veterans who had >40% disabilities due to delayed complications of SM poisoning and had disabilities were investigated. A total of 30 healthy male volunteers (relatives of the veterans) were selected as the control group. Cytokine levels were measured in the serum of case and control subjects using commercial ELISA kits. Hematologic parameters (white/red blood cell counts, hemoglobin levels, immune cell differentials) were also performed on blood samples from the study subjects. The results indicated that serum levels of ICAM-1 were significantly higher in the samples from SM-exposed veterans (772.8 [± 15.1] ng/ml [p=0.014] vs. control values of 710.2 [± 20.0] ng/ml). On the other hand, serum IL-1β, IL-8 levels and TNFα, were significantly lower for the veterans than the controls (IL-1β: 3.8 [± 0.1] vs. 4.3 [± 0.2] pg/ml, p=0.037; IL-8: 21.0 [± 6.1] vs. 84.6 [± 20.3] pg/ml, p=0.002; TNFα: 4.5 [± 0.1] vs. 5.5 [± 0.1] pg/ml, p=0.027). Levels of other assayed cytokines, e.g., IL-2, -4, -5, -6, -10, and -12, IFNγ, TNFβ, and sVCAM-1 were not significantly different between the study populations. None of the assayed hematologic parameters appeared to differ as well. It seems possible that dysfunctions could have been induced in the innate immune functions of the SM-exposed veterans as a result of these changes in cytokine expression and that these, in turn, may have contributed to the increased incidence of a myriad of diseases that have been documented in these veterans, including cancers. Future studies must focus on examining the significance of these changes in circulating cytokines and their potential contribution to the development of different diseases in veterans exposed to SM.

Mesenchymal stem cells are highly resistant to sulfur mustard

The effect of sulfur mustard (SM) to the direct injured tissues of the skin, eyes and airways is well investigated. Little is known about the effect of SM to mesenchymal stem cells (MSC). However, this is an interesting aspect. Comparing the clinical picture of SM it is known today that MSC play an important role e.g. in chronic impaired wound healing. Therefore we wanted to get an understanding about how SM affects MSC and if these findings might become useful to get a better understanding of the effect of sulfur mustard gas with respect to skin wounds. We used mesenchymal stem cells, isolated from femoral heads from healthy donors and treated them with a wide range of SM to ascertain the dose-response-curve. With the determined inhibitory concentrations IC1 (1μM), IC5 (10μM), IC10 (20μM) and IC25 (40μM) we did further investigations. We analyzed the migratory ability and the differentiation capacity under influence of SM. Already very low concentrations of SM demonstrated a strong effect to the migratory activity whereas the differentiation capacity seemed not to be affected. Putting these findings together it seems to be likely that a link between MSC and the impaired wound healing after SM exposure might exist. Same as in patients with chronic impaired wound healing MSC had shown a reduced migratory activity. The fact that MSC are able to tolerate very high concentrations of SM and still do not lose their differentiation capacity may reveal new ways of treating wounds caused by sulfur mustard.

Protective effect of liposome-encapsulated glutathione in a human epidermal model exposed to a mustard gas analog

Sulfur mustard or mustard gas (HD) and its monofunctional analog, 2-chloroethyl ethyl sulfide (CEES), or "half-mustard gas," are alkylating agents that induce DNA damage, oxidative stress, and inflammation. HD/CEES are rapidly absorbed in the skin causing extensive injury. We hypothesize that antioxidant liposomes that deliver both water-soluble and lipid-soluble antioxidants protect skin cells from immediate CEES-induced damage via attenuating oxidative stress. Liposomes containing water-soluble antioxidants and/or lipid-soluble antioxidants were evaluated using in vitro model systems. Initially, we found that liposomes containing encapsulated glutathione (GSH-liposomes) increased cell viability and attenuated production of reactive oxygen species (ROS) in HaCaT cells exposed to CEES. Next, GSH-liposomes were tested in a human epidermal model, EpiDerm. In the EpiDerm, GSH-liposomes administered simultaneously or 1 hour after CEES exposure (2.5 mM) increased cell viability, inhibited CEES-induced loss of ATP and attenuated changes in cellular morphology, but did not reduce caspase-3 activity. These findings paralleled the previously described in vivo protective effect of antioxidant liposomes in the rat lung and established the effectiveness of GSH-liposomes in a human epidermal model. This study provides a rationale for use of antioxidant liposomes against HD toxicity in the skin considering further verification in animal models exposed to HD.

Sulfur mustard vapor effects on differentiated human lung cells

CONTEXT

Sulfur mustard (SM) causes skin blistering and long-term pulmonary dysfunction. Its adverse effects have been studied in battlefield-exposed humans, but lack of knowledge regarding confounding factors makes interpretation challenging. Animal studies are critical to understanding mechanisms, but differences between animals and humans must be addressed. Studies of cultured human cells can bridge animal studies and humans.

OBJECTIVE

Evaluate effects of SM vapor on airway cells.

MATERIALS AND METHODS

We examined responses of differentiated human tracheal/bronchial epithelial cells, cultured at an air-liquid interface, to SM vapors. SM effects on metabolic activity (Water Soluble Tetrazolium (WST) assay), cytokine and metalloproteinase secretion, and cellular heme oxygenase 1 (HO-1), an oxidative stress indicator, were measured after 24 h.

RESULTS

At noncytotoxic levels of exposure, interleukin 8 and matrix metalloproteinase-13 were significantly increased in these cultures, but HO-1 was not significantly affected.

DISCUSSION AND CONCLUSION

Exposure of differentiated airway epithelial cells to sub-cytotoxic levels of SM vapor induced inflammatory and degradative responses that could contribute to the adverse health effects of inhaled SM.

Designing of mouse model: a new approach for studying sulphur mustard-induced skin lesions

This study was planned to design a mouse model for studying sulphur mustard (SM)-induced skin injury. SM was applied dermally at dose of 5 or 10 mg kg(-1) in polyethyleneglycol-300 (PEG-300) or dimethylsulphoxide (DMSO) or acetone once. The changes in body weight, organ body weight indices (OBWI) and haematological and oxidative stress parameters were investigated over a period of 3-7 days and supported by histopathological observations. Exposure to SM in PEG-300 or DMSO resulted in a significant depletion in body weight, OBWI, hepatic glutathione (GSH) and elevation in hepatic lipid peroxidation, without affecting the blood GSH and hepatic oxidised glutathione (GSSG) levels. Interestingly, no aforesaid change was observed after dermal application of SM diluted in acetone. These biochemical changes were supported by the histological observations, which revealed pronounced toxic effect and damage to liver, kidney and spleen after dermal application of SM diluted in PEG-300 or DMSO. The skin showed similar microscopic changes after dermal application of SM in all the three diluents, however; the severity of lesions was found to be time and dose dependent. It can be concluded that dermal exposure of SM diluted in acetone can be used to mimic SM-induced skin toxicity without systemic toxicity in a mouse model.

Efficacy of glutathione in ameliorating sulfur mustard analog-induced toxicity in cultured skin epidermal cells and in SKH-1 mouse skin in vivo

Exposure to chemical warfare agent sulfur mustard (HD) is reported to cause GSH depletion, which plays an important role in HD-linked oxidative stress and skin injury. Using the HD analog 2-chloroethyl ethyl sulfide (CEES), we evaluated the role of GSH and its efficacy in ameliorating CEES-caused skin injury. Using mouse JB6 and human HaCaT epidermal keratinocytes, we observed both protective and therapeutic effects of exogenous GSH (1 or 10 mM) in attenuating a CEES-caused decrease in cell viability and DNA synthesis, as well as S and G(2)M phase arrest in cell cycle progression. However, the protective effect of GSH was stronger than its ability to reverse CEES-induced cytotoxic effect. The observed effect of GSH could be associated with an increase in intracellular GSH levels after its treatment before or after CEES exposure, which strongly depleted cellular GSH levels. N-Acetyl cysteine, a GSH precursor, also showed both protective and therapeutic effects against CEES-caused cytotoxicity. Buthionine sulfoximine, which reduces cellular GSH levels, caused an increased CEES cytotoxicity in both JB6 and HaCaT cells. In further studies translating GSH effects in cell culture, pretreatment of mice with 300 mg/kg GSH via oral gavage 1 h before topical application of CEES resulted in significant protection against CEES-caused increase in skin bifold and epidermal thickness, apoptotic cell death, and myeloperoxidase activity, which could be associated with increased skin GSH levels. Together, these results highlight GSH efficacy in ameliorating CEES-caused skin injury and further support the need for effective antioxidant countermeasures against skin injury by HD exposure.

Biological and molecular mechanisms of sulfur mustard analogue-induced toxicity in JB6 and HaCaT cells: possible role of ataxia telangiectasia-mutated/ataxia telangiectasia-Rad3-related cell cycle checkpoint pathway

Effective medical treatment and preventive measures for chemical warfare agent sulfur mustard (HD)-caused incapacitating skin toxicity are lacking, because of limited knowledge of its mechanism of action. The proliferating basal epidermal cells are primary major sites of attack during HD-caused skin injury. Therefore, employing mouse JB6 and human HaCaT epidermal cells, here, we investigated the molecular mechanism of HD analogue 2-chloroethyl ethyl sulfide (CEES)-induced skin cytotoxicity. As compared to the control, up to 1 mM CEES treatment of these cells for 2, 4, and 24 h caused dose-dependent decreases in cell viability and proliferation as measured by DNA synthesis, together with S and G2-M phase arrest in cell cycle progression. Mechanistic studies showed phosphorylation of DNA damage sensors and checkpoint kinases, ataxia telangiectasia-mutated (ATM) at ser1981 and ataxia telangiectasia-Rad3-related (ATR) at ser428 within 30 min of CEES exposure, and modulation of S and G2-M phase-associated cell cycle regulatory proteins, which are downstream targets of ATM and ATR kinases. Hoechst-propidium iodide staining demonstrated that CEES-induced cell death was both necrotic and apoptotic in nature, and the latter was induced at 4 and 24 h of CEES treatment in HaCaT and JB6 cells, respectively. An increase in caspase-3 activity and both caspase-3 and poly(ADP-ribose)polymerase (PARP) cleavage coinciding with CEES-caused apoptosis in both cell lines suggested the involvement of the caspase pathway. Together, our findings suggest a DNA-damaging effect of CEES that activates ATM/ATR cell cycle checkpoint signaling as well as caspase-PARP pathways, leading to cell cycle arrest and apoptosis/necrosis in both JB6 and HaCaT cells. The identified molecular targets, quantitative biomarkers, and epidermal cell models in this study have the potential and usefulness in rapid development of effective prophylactic and therapeutic interventions against HD-induced skin toxicity.

2,6-Dithiopurine blocks toxicity and mutagenesis in human skin cells exposed to sulfur mustard analogues, 2-chloroethyl ethyl sulfide and 2-chloroethyl methyl sulfide

Sulfur mustard (bis-(2-chloroethyl)sulfide) is a well-known chemical warfare agent that induces debilitating cutaneous toxicity in exposed individuals. It is also known to be carcinogenic and mutagenic because of its ability to damage DNA via electrophilic attack. We previously showed that a nucleophilic scavenger, 2,6-dithiopurine (DTP), reacts chemically with several electrophilic carcinogens, blocking DNA damage in vitro and in vivo and abolishing tumor formation in a two-stage mouse skin carcinogenesis model. To assess the potential of DTP as an antagonist of sulfur mustard, we have utilized monofunctional chemical analogues of sulfur mustard, 2-chloroethyl ethyl sulfide (CEES) and 2-chloroethyl methyl sulfide (CEMS), to induce toxicity and mutagenesis in a cell line, NCTC2544, derived from a human skin tumor. We show that DTP blocks cytotoxicity in CEMS- and CEES-treated cells when present at approximately equimolar concentration. A related thiopurine, 9-methyl-6-mercaptopurine, is similarly effective. Correlated with this, we find that DTP is transported into these cells and that adducts between DTP and CEES are found intracellularly. Using a shuttle vector-based mutagenesis system, which allows enumeration of mutations induced in the skin cells by a blue/white colony screen, we find that DTP completely abolishes the mutagenesis induced by CEMS and CEES in human cells.

Dermal toxicity and environmental contamination: electron transfer, reactive oxygen species, oxidative stress, cell signaling, and protection by antioxidants

Large numbers of chemicals are known to produce diverse types of skin injury, and these substances fit into a wide variety of both organic and inorganic chemical classes. Skin contact with toxins is difficult to avoid, because they are widely distributed, e.g., in industrial substances, agricultural chemicals, household products, and plants. Although various hypotheses have been advanced, there is no universal agreement as to how dermal toxins act to produce their effects. In this review, we provide evidence and numerous literature citations to support the view that oxidative stress (OS) and electron transfer (ET) comprise a portion of a key mechanism, and perhaps unifying theme that underlie the action of dermatotoxins. We apply the concept that ET and OS are key elements in the induction of dermatotoxic effects to all of the main classes of toxins, and to other toxins, as well. We believe it is not coincidental that the vast majority of dermatotoxic substances incorporate recurrent ET chemical functionalities (i.e., quinone, metal complexes, ArNO2, or conjugated iminium), either per se or as metabolites; such entities potentially give rise to reactive oxygen species (ROS) by redox cycling. However, in some categories, wherein agents cause dermal damage, e.g., peroxides and radiation, it appears that ROS are generated by non-ET routes. As expected, if ET and oxidative process do constitute the mechanistic framework by which most dermal toxins act, then antioxidants (AOs), if present, should prevent or mitigate effects. This is exactly what has been discovered to occur. Because ET and OS either cause or contribute to dermal toxicity, and AOs may offer protection therefrom, policy makers and researchers may be better positioned to prevent human dermatotoxicity.

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.

Inflammatory biomarkers of sulfur mustard analog 2-chloroethyl ethyl sulfide-induced skin injury in SKH-1 hairless mice

Sulfur mustard (HD) is an alkylating and cytotoxic chemical warfare agent, which inflicts severe skin toxicity and an inflammatory response. Effective medical countermeasures against HD-caused skin toxicity are lacking due to limited knowledge of related mechanisms, which is mainly attributed to the requirement of more applicable and efficient animal skin toxicity models. Using a less toxic analog of HD, chloroethyl ethyl sulfide (CEES), we identified quantifiable inflammatory biomarkers of CEES-induced skin injury in dose- (0.05-2 mg) and time- (3-168 h) response experiments, and developed a CEES-induced skin toxicity SKH-1 hairless mouse model. Topical CEES treatment at high doses caused a significant dose-dependent increase in skin bi-fold thickness indicating edema. Histopathological evaluation of CEES-treated skin sections revealed increases in epidermal and dermal thickness, number of pyknotic basal keratinocytes, dermal capillaries, neutrophils, macrophages, mast cells, and desquamation of epidermis. CEES-induced dose-dependent increases in epidermal cell apoptosis and basal cell proliferation were demonstrated by the terminal deoxynucleotidyl transferase (tdt)-mediated dUTP-biotin nick end labeling and proliferative cell nuclear antigen stainings, respectively. Following an increase in the mast cells, myeloperoxidase activity in the inflamed skin peaked at 24 h after CEES exposure coinciding with neutrophil infiltration. F4/80 staining of skin integuments revealed an increase in the number of macrophages after 24 h of CEES exposure. In conclusion, these results establish CEES-induced quantifiable inflammatory biomarkers in a more applicable and efficient SKH-1 hairless mouse model, which could be valuable for agent efficacy studies to develop potential prophylactic and therapeutic interventions for HD-induced skin toxicity.

Cetirizine, Doxepine, and Hydroxyzine in the Treatment of Pruritus due to Sulfur Mustard: A Randomized Clinical Trial

A 4-week randomized, double-blind safety and efficacy study was conducted to compare the safety and efficacy of cetirizine, doxepine, and hydroxyzine 5 in the treatment of chronic pruritus due to sulfur mustard. Patients were treated in the Dermatology Clinic of Baqiyatallah Hospital. The study population consisted of 75 patients with chronic pruritus due to sulfur mustard exposure. Patients were given either cetirizine 10 mg, doxepine 10 mg, or hydroxyzine 25 mg/day, for 4 weeks. A calculated pruritic score for each patient was taken before and 1 month after treatment. Mean before-treatment pruritic scores were 38.2 +/- 4.8, 37.2 +/- 4.9, and 37.3 +/- 5.1 in the cetirizine, doxepine, and hydroxyzine groups, respectively. After treatment, the mean pruritic scores were 24.8 +/- 3.1, 17.8 +/- 2.5, and 16.7 +/- 2.3 in the cetirizine, doxepine, and hydroxyzine groups, respectively. In addition, 65%, 75%, and 80% of patients in the cetirizine, doxepine, and hydroxyzine groups were downgraded in the severity of pruritus (P 1/4 0.465). Sedation effects were reported in 6, 14, and 18 patients in the cetirizine, doxepine, and hydroxyzine groups, respectively. Hydroxyzine 25 mg/day has equal results compared to doxepine 10 mg once daily; but greater than cetirizine 10 mg once a day in controlling the symptoms of patients with chronic pruritus.

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.

Comparison of hydroxyzine and doxepin in treatment of pruritus due to sulfur mustard

OBJECTIVE

To compare the safety and efficacy of doxepin and hydroxyzine in the treatment of chronic pruritus due to exposure to sulfur mustard.

METHODS

In a randomized, double-blind safety and efficacy study, 50 patients with chronic pruritus were given either doxepin 10 mg/d or hydroxyzine 25 mg/d for 4 weeks. Pruritic score was calculated for each patient before treatment and 1 month after.

RESULTS

After treatment, the mean pruritic scores +/- SD of the hydroxyzine and doxepin groups were 16.7+/-2.3 and 17.8+/-2.5, respectively. The severity of pruritus was decreased in 80% of patients in the hydroxyzine group and 75% in the doxepin group (P=.786). Eighteen patients in the hydroxyzine group and 14 patients in the doxepin group reported sedation.

CONCLUSIONS

Both hydroxyzine and doxepin are effective and have equivalent results in controlling the symptoms of patients with chronic pruritus due to exposure to sulfur mustard.