Sulfur mustard-induced skin burns in weanling swine evaluated clinically and histopathologically

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.

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.

A dynamic system for delivering controlled bromine and chlorine vapor exposures to weanling swine skin

CONTEXT

Assessing the hazards of accidental exposure to toxic industrial chemical (TIC) vapors and evaluating therapeutic compounds or treatment regimens require the development of appropriate animal models.

OBJECTIVE

The objective of this project was to develop an exposure system for delivering controlled vapor concentrations of TICs to the skin of anesthetized weanling pigs. Injury levels targeted for study were superficial dermal (SD) and deep dermal (DD) skin lesions as defined histopathologically.

MATERIALS AND METHODS

The exposure system was capable of simultaneously delivering chlorine or bromine vapor to four, 3-cm diameter exposure cups placed over skin between the axillary and inguinal areas of the ventral abdomen. Vapor concentrations were generated by mixing saturated bromine or chlorine vapor with either dried dilution air or nitrogen.

RESULTS

Bromine exposure concentrations ranged from 6.5 × 10(-4) to 1.03 g/L, and exposure durations ranged from 1 to 45 min. A 7-min skin exposure to bromine vapors at 0.59 g/L was sufficient to produce SD injuries, while a 17-min exposure produced a DD injury. Chlorine exposure concentrations ranged from 1.0 to 2.9 g/L (saturated vapor concentration) for exposures ranging from 3 to 90 min. Saturated chlorine vapor challenges for up to 30 min did not induce significant dermal injuries, whereas saturated chlorine vapor with wetted material on the skin surface for 30-60 min induced SD injuries. DD chlorine injuries could not be induced with this system.

CONCLUSION

The vapor exposure system described in this study provides a means for safely regulating, quantifying and delivering TIC vapors to the skin of weanling swine as a model to evaluate therapeutic treatments.

Environmental hazard of yperite released at sea: sublethal toxic effects on fish

The aim of this study was to evaluate the potential toxicological effects on fish related to the leakage of yperite from rusted bomb shells dumped at sea. Both in vivo and field studies have been performed. As for the in vivo experiment, specimen of European eel were subcutaneously injected with 0.015, 0.15 and 1.5mg/kg of yperite and sacrificed after 24 and 48 h. In the field study, specimen of Conger eel were collected from a dumping site in the Southern Adriatic Sea. The presence/absence of yperite in tissues, genotoxicity, detoxification enzymes, histological alterations and gross abnormalities were investigated. Results of the in vivo experiment showed a significant increase of EROD activity at both 24h and 48 h. UGT activity increased significantly at 48 h post injection. An acute inflammatory response after 24h in skin layers and muscle was observed, associated to cell degeneration and necrosis after 48 h at the highest dose. On field, comet assay revealed genotoxicity in gills of fish from the dumping site. Specimen from the dumping site showed significantly higher EROD activities compared to controls, deep ulcers and papules on skin together with liver and spleen histopathological lesions.

An assessment of transcriptional changes in porcine skin exposed to bromine vapor

Bromine is an industrial chemical that can cause severe cutaneous burns. This study was a preliminary investigation into the effect of cutaneous exposure to bromine vapor using a weanling swine burn model and microarray analysis. Ventral abdominal sites were exposed to a mean calculated bromine vapor concentration of 0.69 g L(-1) for 10 or 20 min. At 48 h postexposure, total RNA from skin samples was isolated, processed, and hybridized to Affymetrix GeneChip Porcine Genome Arrays. Expression analysis revealed that bromine vapor exposure for 10 or 20 min promoted similar transcriptional changes in the number of significantly modulated probe sets. A minimum of 83% of the probe sets was similar for both exposure times. Ingenuity pathways analysis revealed eight common biological functions among the top 10 functions of each experimental group, in which 30 genes were commonly shared among 19 significantly altered signaling pathways. Transcripts encoding heme oxygenase 1, interleukin-1β, interleukin 2 receptor gamma chain, and plasminogen activator inhibitor-1 were identified as common potential therapeutic targets for Phase II/III clinical trial or FDA-approved drugs. The present study is an initial assessment of the transcriptional responses to cutaneous bromine vapor exposure identifying molecular networks and genes that could serve as targets for developing therapeutics for bromine-induced skin injury.

2-Chloroethyl ethyl sulfide causes microvesication and inflammation-related histopathological changes in male hairless mouse skin

Sulfur mustard (HD) is a vesicating agent that has been used as a chemical warfare agent in a number of conflicts, posing a major threat in both military conflict and chemical terrorism situations. Currently, we lack effective therapies to rescue skin injuries by HD, in part, due to the lack of appropriate animal models, which are required for conducting laboratory studies to evaluate the therapeutic efficacy of promising agents that could potentially be translated in to real HD-caused skin injury. To address this challenge, the present study was designed to assess whether microvesication could be achieved in mouse skin by an HD analog 2-chloroethyl ethyl sulfide (CEES) exposure; notably, microvesication is a key component of HD skin injury in humans. We found that skin exposure of male SKH-1 hairless mice to CEES caused epidermal-dermal separation indicating microvesication. In other studies, CEES exposure also caused an increase in skin bi-fold thickness, wet/dry weight ratio, epidermal thickness, apoptotic cell death, cell proliferation, and infiltration of macrophages, mast cells and neutrophils in male SKH-1 hairless mouse skin. Taken together, these results establish CEES-induced microvesication and inflammation-related histopathological changes in mouse skin, providing a potentially relevant laboratory model for developing effective countermeasures against HD skin injury in humans.

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.

DNA damage, severe organ lesions and high muscle levels of As and Hg in two benthic fish species from a chemical warfare agent dumping site in the Mediterranean Sea

The aim of the present study was to evaluate the environmental threat to benthic species from chemical weapons dumped in the southern Adriatic Sea. An ecotoxicological approach using chemical analysis and biological responses was applied, in two sentinel species: the Blackbelly rosefish Helicolenus dactylopterus and European conger Conger conger. Specimen were collected in a stretch of sea, where had been dumped war materials and from a reference site free of ordnance. Residues of yperite, Hg and As were measured in fish fillets. Skin, liver, kidney and spleen were examined for histopathological and macroscopical lesions. Liver detoxifying capacities (EROD and UDPGT) and genotoxicity (comet assay) were also investigated. As and Hg levels were three-four times higher than those from the reference site in both species (p<0.001). Both species captured in dumping site showed clear signs of chronic illness according to the health assessment index (HAI). Deep ulcers and nodules were observed on skin and external organs. Histological lesions such as periportal and bile duct fibrosis, pericholangitis, steatosis, granuloma and elevated splenic MMCs were detected in liver and spleen. Significantly higher EROD activities were also found in both species from dumping site (p<0.01). Comet assay revealed genotoxicty in gills of C. conger from dumping site, indicating uptake of chemical warfare agents through fish gills. European conger was found to be a more sensitive bioindicator of this type of contamination than the Blackbelly rosefish.

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.

Biomechanical monitoring of cutaneous sulfur mustard-induced lesions in the weanling pig model for depth of injury

BACKGROUND/PURPOSE

A sulfur mustard (SM)-induced cutaneous injury model was developed in weanling swine to evaluate the efficacy of candidate treatment regimens. Lesions were assessed clinically and histopathologically. Histopathologic evaluation of lesions was a subjective and invasive assessment. Biomechanical engineering methods offer an objective and less invasive method to evaluate lesions. The purpose of this study was to use biomechanical engineering instruments to assess SM-induced lesions for depth of injury and to correlate those assessments with histopathology.

METHODS

Two groups of six animals each were exposed to 400 microL undiluted SM applied at each of six abdominal sites for either 2 or 30 min. An additional seven animals received a sham treatment (control; 400 microL deionized water applied to each of six sites for 30 min). Each site was evaluated before exposure and 2 days after exposure. Biomechanical engineering techniques used to assess each lesion were reflectance colorimetry, evaporimetry [transepidermal water loss (TEWL)], laser Doppler perfusion imaging, and high-frequency (20 MHz) two-dimensional ultrasound. Injury depth and lesion severity were assessed and correlated to biomechanical methods using special histopathologic staining techniques.

RESULTS

Two- and 30-min cutaneous lesions were significantly different from controls at the 0.05 probability level for redness (chroma meter) and TEWL (evaporimeter), but were not significantly different from each other. The 2-min lesions had a significant increase (2.11 AU, SE=0.06) and the 30-min lesions had a decrease (0.96 AU, SE=0.04) from controls (1.31 AU, SE=0.03) in microcirculatory blood flux (laser Doppler). The 2-min lesions and controls were significantly different at the 0.05 level from 30-min lesions in skin thickness (ultrasound). The 2- and 30-min groups were significantly different from controls and from each other at the 0.05 level in histopathologic assessment of injury depth, basal cell necrosis, depth of necrosis, and vascular necrosis, with the 30-min injuries being most severe.

CONCLUSION

There was mixed evidence that the bioengineering techniques tested could differentiate between controls, 2-min (partial-thickness) cutaneous injuries and 30-min (full-thickness) cutaneous injuries at day 2. Both biomechanical and histopathologic assessments are useful methods of characterizing SM lesions in the weanling pig model. Biomechanical methods are non-invasive and quantitative, and multiple readings over shorter and longer periods of time may improve differentiation in depth of injury. Histopathologic assessments are important for confirmation of lesion depth and severity, and for assisting interpretation when a single assessment using bioengineering methods is used.

Efficacy of laser debridement with autologous split-thickness skin grafting in promoting improved healing of deep cutaneous sulfur mustard burns

The consequences of receiving a cutaneous sulfur mustard (SM) burn are prolonged wound healing and secondary infection. This study was undertaken to find a treatment that promotes quick healing with few complications and minimal disfigurement. Multiple deep SM burns (4 cm diameter) were generated on the ventrum of weanling pigs and treated at 48 h. Four treatments were compared: (1) full-thickness CO(2) laser debridement followed by skin grafting; (2) full-thickness sharp surgical tangential excision followed by skin grafting, the "Gold Standard" used in deep thermal burns management; (3) partial-thickness laser ablation with no grafting; and (4) partial-thickness sharp excision with no grafting. A computer controlled, raster scanned, high-powered continuous wave (cw) CO(2) laser was utilized. Ulceration, wound geometry, and wound contraction were evaluated during a 36-day healing period. Histopathological evaluations were conducted at the end of the healing period. Engraftment rates were similar between both methods of debridement. Laser debridement followed by skin grafting was as efficacious in improving the wound healing of deep SM burns as the "Gold Standard." Full-thickness laser debridement of these small total body surface area (TBSA) burns was time efficient and provided adequate beds for split-thickness skin grafting. Laser debridement offered additional benefits that included hemostatic control during surgery and minimal debridement of normal perilesional skin. Mid-dermal debridement by sharp excision or laser ablation without grafting produced less desirable results but was better than no treatment.