Effects of sulfur mustard on the basal cell adhesion complex

Small-interfering RNA for c-Jun attenuates cell death by preventing JNK-dependent PARP1 cleavage and DNA fragmentation in nitrogen mustard-injured immortalized human bronchial epithelial cells

Sulfur mustard (a type of vesicant) can directly damage lung bronchial epithelium via aerosol inhalation, and prevalent cell death is an early event that obstructs the respiratory tract. JNK/c-Jun is a stress response pathway, but its role in cell death of the injured cells is not clear. Here, we report that JNK/c-Jun was activated in immortalized human bronchial epithelial (HBE) cells exposed to a lethal dose (20 μM) of nitrogen mustard (NM, a sulfur mustard analog). c-Jun silencing using small-interfering RNA (siRNA) rendered the cells resistant to NM-mediated cell death by blocking poly(ADP-ribose) polymerase 1 (PARP1) cleavage and DNA fragmentation. In addition, the transduction of upstream extrinsic (Fasl-Fas-caspase-8) and intrinsic (loss of Bcl-2 and mitochondrial membrane potential, ΔΨm) apoptosis pathways, as well as phosphorylated (p)-H2AX (Ser139), an epigenetic marker contributing to DNA fragmentation and PARP1 activity, was partially suppressed. To mimic the detachment of cells by NM, HBE cells were trypsinized and seeded on culture plates that were pre-coated with poly-HEMA to prevent cell adhesion. The JNK/c-Jun pathway was found to be activated in the detached cells. In conclusion, our results indicate that JNK/c-Jun pathway activation is necessary for NM-caused HBE cell death and further suggest that c-Jun silencing may be a potential approach to protect HBE cells from vesicant damage.

Efficacy and safety of immunotherapy with interferon-gamma in the management of chronic sulfur mustard-induced cutaneous complications: comparison with topical betamethasone 1%

The present trial investigated the efficacy of immunotherapy with interferon-gamma (IFN-γ) in the treatment of sulfur mustard (SM)-induced chronic skin complications. Forty subjects who were suffering from chronic skin complications of SM and were diagnosed to have severe atopic dermatitis, were assigned to IFN-γ (50 μg/m(2)) subcutaneously three times per week (n = 20) or betamethasone valerate topical cream 0.1% (n = 20) every night for 30 days. Extent and intensity of cutaneous complications was evaluated using scoring atopic dermatitis (SCORAD) index, and quality of life using dermatology life quality index (DLQI) at baseline and at the end of trial. SCORAD-A and SCORAD-B scores were significantly decreased in both IFN-γ and betamethasone. However, SCORAD-C score was decreased only in the IFN-γ group. There were significant reductions in overall as well as objective SCORAD scores in both groups. As for the magnitude of changes, treatment with IFN-γ was associated with greater reductions in overall, objective and segmented SCORAD scores compared to betamethasone. DLQI reduction was found to be significantly greater in the IFN-γ group. Promising improvements in quality life and clinical symptoms that was observed in the present study suggest the application of IFN-γ as an effective therapy for the management of SM-induced chronic skin complications.

Attenuation of sulfur mustard toxicity by S-2(2-aminoethylamino)ethyl phenyl sulfide (DRDE-07) in mouse liver

Sulfur mustard (SM) (bis-(2-chloroethyl) sulfide) is a chemical warfare agent. Evaluation of toxicity and protective effect of DRDE-07 (S-2(2-aminoethylamino)ethyl phenyl sulfide) was studied in mouse liver after SM challenging. Female mice were given orally 0.2 LD(50) of DRDE-07 (249 mg/kg body weight) and exposed percutaneously with 1.0 LD(50) of SM (8.1 mg/kg body weight). Gene expression profiles were determined using global genome microarray analysis at 3 days post-exposure. DRDE-07 alone treated animal showed significant upregulation to metabolism of xenobiotics by cytochrome P450 pathways. Genes related to cell adhesion molecules (CAMs), were downregulated. DRDE-07 pretreated SM exposed animals showed upregulation of xenobiotic cytochrome P450 pathway genes. Antigen presenting, cell adhesion molecules, cytokine, cytokine receptor metabolism, fatty acid metabolism, glutathione metabolism, cell cycle signaling pathway genes showed downregulation. The present study showed that SM-induced toxicity in mouse liver was attenuated by the pretreatment with DRDE-07.

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.

Quantitation of epidermal and mucosal tissue injury using contrast agents and imaging techniques

BACKGROUND/PURPOSE

Epidermal injury is common but the accuracy of visual methods is significantly impacted by the inherent skin pigmentation. We examined imaging and fluorescence techniques to quantify tissue injury as a function of skin color.

METHODS

Epidermal and mucosal scratches were created in 20 light- (L(*) 68.2+/-2.3) and 20 dark-skinned (L(*) 46.4+/-5.2) females. Injured and uninjured sites were treated with toluidine blue (TB), fluorescein (FL) and a TB/FL mixture and photographed under conditions of white and fluorescent light. Area and intensity parameters were determined.

RESULTS

Injured sites with TB and TB/FL had higher areas than the control for both light and dark subjects (ANOVA, P<0.05). The intensity of the injured TB site was higher than the control for light skin only. The areas of injured sites with FL and TB/FL were higher than the control for both groups as were the intensities of the injured sites with FL. The findings were similar for the lip skin.

CONCLUSIONS

Application of TB and FL contrasts under white and fluorescent light can be used to quantify tissue injuries for L(*) values >35 and is a promising approach for the quantitation across a range of skin pigmentation.

Involvement of caspases and transmembrane metalloproteases in sulphur mustard-induced microvesication in adult human skin in organ culture: directions for therapy

While skin is a major target for sulphur mustard (HD), a therapy to limit HD-induced vesication is currently not available. Since it is supposed that apoptotic cell death and proteolytic digestion of extracellular matrix proteins by metalloproteases are initiating factors for blister formation, we have explored whether inhibition of these processes could prevent HD-induced epidermal-dermal separation using adult human skin in organ culture. Involvement of the caspase and the metalloprotease families was confirmed by the observation that their respective broad spectrum inhibitors, Z-VAD-fmk and GM6001, each suppressed HD-induced microvesication. The lowest effective concentrations were 10 and 100microM, respectively. Using specific inhibitors for caspase-8 (> or =10microM) and caspase-9 (> or =10microM) we learned that HD-induced apoptosis is initiated by the death receptor pathway as well as by the mitochondrial pathway. Remarkably, blocking caspase-8 activity resulted in morphologically better conserved cells than blocking caspase-9 activity. We zoomed in on the role of metalloproteases in HD-induced microvesication by testing the effects of two inhibitors: dec-RVKR-cmk and TAPI-2. Dec-RVKR-cmk is an inhibitor of furin, which activates transmembrane enzymes of the 'a disintegrin and metalloproteinase' (ADAM)-family as well as the membrane-type metalloproteases (MTx-MMP). TAPI-2 specifically inhibits TNFalpha-converting enzyme (TACE/ADAM17), which is involved in pericellular proteolysis. Both inhibitors prevented microvesication at concentrations of > or =500 and > or =20microM, respectively. This confirms that ADAMs and MT-MMPs play a role in HD-induced epidermal-dermal separation, with a particular role for TACE/ADAM17. Since TACE is involved not only in degradation of cell-matrix adhesion structures, but also in ectodomain shedding of ligands for epidermal growth factor receptor (EGFR) and in release of TNFalpha, these results imply TACE-mediated pathways as a new concept in HD toxicity. In conclusion, transmembrane metalloproteases probably form a main target for treatment of blisters in HD casualties. The observation that microvesication in the ex vivo human skin model still could be prevented when the metalloprotease inhibitor GM6001 was applied up to 8h after exposure to HD opens perspectives for non-urgent cure of HD casualties.

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.

Inhibition of caspase-dependent mitochondrial permeability transition protects airway epithelial cells against mustard-induced apoptosis

In the present study, the toxicity of yperite, SM, and its structural analogue mechlorethamine, HN2, was investigated in a human bronchial epithelial cell line 16HBE. Cell detachment was initiated by caspase-2 activation, down-regulation of Bcl-2 and loss of mitochondrial membrane potential. Only in detached cells, mustards induced apoptosis associated with increase in p53 expression, Bax activation, decrease in Bcl-2 expression, opening of the mitochondrial permeability transition pore, release of cytochrome c, caspase-2, -3, -8, -9 and -13 activation and DNA fragmentation. Apoptosis, occurring only in detached cells, could be recognized as anoikis and the mitochondrion, involved both in cell detachment and subsequent cell death, appears to be a crucial checkpoint. Based on our understanding of the apoptotic pathway triggered by mustards, we demonstrated that inhibition of the mitochondrial pathway by ebselen, melatonin and cyclosporine A markedly prevented mustard-induced anoikis, pointing to these drugs as interesting candidates for the treatment of mustard-induced airway epithelial lesions.

Microarray Analysis of Mouse Ear Tissue Exposed to Bis-(2-chloroethyl) Sulfide: Gene Expression Profiles Correlate with Treatment Efficacy and An Established Clinical Endpoint

Bis-(2-chloroethyl) sulfide (sulfur mustard; SM) is a potent alkylating agent. Three treatment compounds have been shown to limit SM damage in the mouse ear vesicant model: dimercaprol, octyl homovanillamide, and indomethacin. Microarrays were used to determine gene expression profiles of biopsies taken from mouse ears after exposure to SM in the presence or absence of treatment compounds. Mouse ears were topically exposed to SM alone or were pretreated for 15 min with a treatment compound and then exposed to SM. Ear tissue was harvested 24 h after exposure for ear weight determination, the endpoint used to evaluate treatment compound efficacy. RNA extracted from the tissues was used to generate microarray probes for gene expression profiling of therapeutic responses. Principal component analysis of the gene expression data revealed partitioning of the samples based on treatment compound and SM exposure. Patterns of gene responses to the treatment compounds were indicative of exposure condition and were phenotypically anchored to ear weight. Pretreatment with indomethacin, the least effective treatment compound, produced ear weights close to those treated with SM alone. Ear weights from animals pretreated with dimercaprol or octyl homovanillamide were more closely associated with exposure to vehicle alone. Correlation coefficients between gene expression level and ear weight revealed genes involved in mediating responses to both SM exposure and treatment compounds. These data provide a basis for elucidating the mechanisms of response to SM and drug treatment and also provide a basis for developing strategies to accelerate development of effective SM medical countermeasures.

Sulfur mustard induces the formation of keratin aggregates in human epidermal keratinocytes☆1Current address: University of Texas at Austin, Cell & Molecular Biology, 1 University Station C0930, Austin, TX 78712-0253, USA

The vesicant sulfur mustard is an alkylating agent that has the capacity to cross-link biological molecules. We are interested in identifying specific proteins that are altered upon sulfur mustard exposure. Keratins are particularly important for the structural integrity of skin, and several genetically inherited blistering diseases have been linked to mutations in keratin 5 and keratin 14. We examined whether sulfur mustard exposure alters keratin biochemistry in cultured human epidermal keratinocytes. Western blotting with specific monoclonal antibodies revealed the formation of stable high-molecular-weight "aggregates" containing keratin 14 and/or keratin 5. These aggregates begin to form within 15 min after sulfur mustard exposure. These aggregates display a complex gel electrophoresis pattern between approximately 100 and approximately 200 kDa. Purification and analysis of these aggregates by one- and two-dimensional gel electrophoresis and mass spectrometry confirmed the presence of keratin 14 and keratin 5 and indicate that at least some of the aggregates are composed of keratin 14-keratin 14, keratin 14-keratin 5, or keratin 5-keratin 5 dimers. These studies demonstrate that sulfur mustard induces keratin aggregation in keratinocytes and support further investigation into the role of keratin aggregation in sulfur mustard-induced vesication.

Effects of sulfur mustard on transcription in human epidermal keratinocytes: analysis by mRNA differential display

This study examines the transcriptional response of human epidermal keratinocytes (HEK) to sulfur mustard (HD) in order to gain a better understanding of the intracellular events that result in cytotoxicity. Differential display polymerase chain reaction technology was used to examine the relative transcriptional activity of healthy cells to those exposed to subvesicating or vesicating concentrations of HD for 4 h. Approximately 2% of the HEK transcriptome had altered expression. Sixty of the most prominently altered transcripts were characterized. Important upregulated genes include NADH dehydrogenase III, GADD45 and ubiquitin. Key downregulated genes include type I keratin 14, alpha-enolase and caltractin. Many of the identified transcripts protein products presently do not have an assigned function and eleven transcripts were unidentifiable. These transcriptional alterations provide one of the first molecular insights into the intracellular events induced by HD.

Multiphoton microscopy: an optical approach to understanding and resolving sulfur mustard lesions

Sulfur mustard (SM; 2,2(')-dichloroethyl sulfide) is a percutaneous alkylating agent first used as a chemical weapon at Ypres, Belgium, in World War I. Despite its well-documented history, the primary lesions effecting dermal-epidermal separation and latent onset of incapacitating blisters remain poorly understood. By immunofluorescent imaging of human epidermal keratinocytes (HEK) and epidermal tissues exposed to SM (400 microM for 5 min), we have amassed unequivocal evidence that SM disrupts adhesion complex molecules, which are also disrupted by epidermolysis bullosa-type blistering diseases of the skin. Images of keratin 14 (K14) in control cells showed tentlike filament networks linking the HEK's basolateral anchoring sites to the dorsal surface of its nuclei. Images from 6-h postexposure profiles revealed early disruption (</=1 h) and progressive collapse of the K14 cytoskeleton. Collapse involved focal erosions, loss of functional asymmetry, and displacement of nuclei beneath a mat of jumbled filaments. In complementary studies, 1-h images showed statistically significant (p<0.01) decreases of 25 to 30% in emissions from labeled alpha(6)beta(4) integrin and laminin 5, plus disruption of their receptor-ligand organization. Results indicate that SM alkylation destabilizes dermal-epidermal attachments and potentiates vesication by disrupting adhesion complex molecules and associated signaling mechanisms required for their maintenance and repair.