The genetic toxicology of nitrogen and sulphur mustard

Nonclonal Chromosome Aberrations and Genome Chaos in Somatic and Germ Cells from Patients and Survivors of Hodgkin Lymphoma

Anticancer regimens for Hodgkin lymphoma (HL) patients include highly genotoxic drugs that have been very successful in killing tumor cells and providing a 90% disease-free survival at five years. However, some of these treatments do not have a specific cell target, damaging both cancerous and normal cells. Thus, HL survivors have a high risk of developing new primary cancers, both hematologic and solid tumors, which have been related to treatment. Several studies have shown that after treatment, HL patients and survivors present persistent chromosomal instability, including nonclonal chromosomal aberrations. The frequency and type of chromosomal abnormalities appear to depend on the type of therapy and the cell type examined. For example, MOPP chemotherapy affects hematopoietic and germ stem cells leading to long-term genotoxic effects and azoospermia, while ABVD chemotherapy affects transiently sperm cells, with most of the patients showing recovery of spermatogenesis. Both regimens have long-term effects in somatic cells, presenting nonclonal chromosomal aberrations and genomic chaos in a fraction of noncancerous cells. This is a source of karyotypic heterogeneity that could eventually generate a more stable population acquiring clonal chromosomal aberrations and leading towards the development of a new cancer.

Multifunctional Ag@MOF-5@chitosan non-woven cloth composites for sulfur mustard decontamination and hemostasis

Attachment of MOF-5 particles on the surface of carboxymethylated non-woven chitosan cloth (denoted MOF-5@chitosan) was achieved by a layer-by-layer technique in an alternating bath of Zn(OAc)2·2H2O and terephthalic acid solutions. Afterwards, silver nanoparticles were formed/loaded within the resulting MOF-5@chitosan by irradiating at 350 nm wavelength the composite immersed in an aqueous solution of silver nitrate of different concentrations, leading to the formation of ternary composites (denoted Ag@MOF-5@chitosan) which were thoroughly characterized by various techniques. Decontamination of HD over the composites was systematically studied and the results showed that decontamination efficacy increased with the increase of silver amount. The decontamination rate constant and half-life of HD were found to be 0.011 min-1 and 63.0 min over the optimal composite, respectively. Remarkably, attachment of the silver nanoparticles and MOF-5 on the chitosan cloth surface did not interfere with chitosan's original hemostatic capability that was confirmed through the arterial hemostasis of rats. It is expected that the multifunctional composite material can find practical applications in the fields of hemostasis, sterilization and chemical war agent decontamination.

Next-generation sequencing approaches for the study of genome and epigenome toxicity induced by sulfur mustard

Sulfur mustard (SM) is an extensive nucleophilic and alkylating agent that targets different tissues. The genotoxic property of SM is the most threatening effect, because it is associated with detrimental inflammations and susceptibility to several kinds of cancer. Moreover, SM causes a wide variety of adverse effects on DNA which result in accumulation of DNA adducts, multiple mutations, aneuploidies, and epigenetic aberrations in the genome. However, these adverse effects are still not known well, possibly because no valid biomarkers have been developed for detecting them. The advent of next-generation sequencing (NGS) has provided opportunities for the characterization of these alterations with a higher level of molecular detail and cost-effectivity. The present review introduces NGS approaches for the detection of SM-induced DNA adducts, mutations, chromosomal structural variation, and epigenetic aberrations, and also comparing and contrasting them with regard to which might be most advantageous.

Layer-by-layer assembly of Cu3(BTC)2 on chitosan non-woven fabrics: a promising haemostatic decontaminant composite material against sulfur mustard

Anchoring Cu₃(BTC)₂ on the surface of chitosan non-woven fabrics results in formation of a new haemostatic decontaminant composite materials.

Identification and validation of vesicant therapeutic targets using a high-throughput siRNA screening approach

Sulfur mustard [SM, bis-(2-chloroethyl) sulfide] is a highly reactive bifunctional alkylating agent that has been used as a vesicating agent in warfare scenarios to induce severe lung, skin, and eye injury. SM cutaneous lesions are characterized by both vesication and severe inflammation, but the molecular mechanisms that lead to these signs and symptoms are not well understood. There is a pressing need for effective therapeutics to treat this injury. An understanding of the molecular mechanisms of injury and identification of potential therapeutic targets is necessary for rational therapeutic development. We have applied a high-throughput small interfering RNA (siRNA) screening approach to the problem of SM cutaneous injury in an effort to meet these needs. Our siRNA screening efforts have initially focused on SM-induced inflammation in cutaneous injury since chronic inflammation after exposure appears to play a role in progressive clinical pathology, and intervention may improve clinical outcome. Also, targets that mitigate cellular injury should reduce the inflammatory response. Historical microarray data on this injury were mined for targets and pathways implicated in inflammation, and a siRNA library of 2,017 targets was assembled for screening. Primary screening and library deconvolution were performed using human HaCaT keratinocytes and focused on cell death and inflammatory markers as end points. Using this in vitro approach, we have identified and validated novel targets for the potential treatment of SM-induced cutaneous injury.

Sulforaphane induces phase II detoxication enzymes in mouse skin and prevents mutagenesis induced by a mustard gas analog

Mustard gas, used in chemical warfare since 1917, is a mutagenic and carcinogenic agent that produces severe dermal lesions for which there are no effective therapeutics; it is currently seen as a potential terrorist threat to civilian populations. Sulforaphane, found in cruciferous vegetables, is known to induce enzymes that detoxify compounds such as the sulfur mustards that react through electrophilic intermediates. Here, we observe that a single topical treatment with sulforaphane induces mouse epidermal levels of the regulatory subunit of glutamate-cysteine ligase, the rate-limiting enzyme in glutathione biosynthesis, and also increases epidermal levels of reduced glutathione. Furthermore, a glutathione S-transferase, GSTA4, is also induced in mouse skin by sulforaphane. In an in vivo model in which mice are given a single mutagenic application of the sulfur mustard analog 2-(chloroethyl) ethyl sulfide (CEES), we now show that therapeutic treatment with sulforaphane abolishes the CEES-induced increase in mutation frequency in the skin, measured four days after exposure. Sulforaphane, a natural product currently in clinical trials, shows promise as an effective therapeutic against mustard gas.

Development of a mouse model for sulfur mustard-induced ocular injury and long-term clinical analysis of injury progression

CONTEXT

Sulfur mustard (SM) is a highly reactive vesicating agent that can induce severe ocular injury. The clinical features of this injury have been well documented, but the molecular basis for this pathology is not well understood. Identification and validation of specific targets is necessary in the effort to develop effective therapeutics for this injury. Currently used rabbit models are not well suited for many molecular studies because the necessary reagents are not widely available. However, these reagents are widely available for the mouse model.

OBJECTIVE

Our objective is to develop a mouse model of SM-induced ocular injury suitable for the study of the molecular mechanisms of injury and the evaluation of therapeutics.

MATERIALS AND METHODS

Ocular exposure to sulfur mustard vapor was accomplished by using a vapor cup method. Dose response studies were conducted in female BALB/c mice. An exposure dose which produced moderate injury was selected for further study as moderate injury was determined to be amenable to studying the beneficial effects of potential therapeutics. Histopathology and inflammatory markers were evaluated for up to 28 days after exposure, while clinical injury progression was evaluated for 1 year post-exposure.

RESULTS

A biphasic ocular injury was observed in mice exposed to SM. Acute phase SM ocular injury in mice was characterized by significant corneal epithelium loss, corneal edema, limbal engorgement, and ocular inflammation. This was followed by a brief recovery phase. A delayed injury phase then ensued in the following weeks to months and was characterized by keratitis, stromal edema, infiltrates, neovascularization, and eventual corneal scarring.

DISCUSSION AND CONCLUSIONS

SM-induced ocular injury in mice is consistent with observations of SM-induced ocular injury in humans and rabbit models. However, in the mouse model, the SM ocular injury, a more rapid onset of the delayed injury phase was observed. We have developed an animal model of SM injury that is suitable for studies to elucidate molecular mechanisms of injury and identify potential therapeutic targets.

2,6-Dithiopurine, a nucleophilic scavenger, protects against mutagenesis in mouse skin treated in vivo with 2-(chloroethyl) ethyl sulfide, a mustard gas analog

Sulfur mustard [bis(2-chloroethyl)sulfide, SM] is a well-known DNA-damaging agent that has been used in chemical warfare since World War I, and is a weapon that could potentially be used in a terrorist attack on a civilian population. Dermal exposure to high concentrations of SM produces severe, long-lasting burns. Topical exposure to high concentrations of 2-(chloroethyl) ethyl sulfide (CEES), a monofunctional analog of SM, also produces severe skin lesions in mice. Utilizing a genetically engineered mouse strain, Big Blue, that allows measurement of mutation frequencies in mouse tissues, we now show that topical treatment with much lower concentrations of CEES induces significant dose- and time-dependent increases in mutation frequency in mouse skin; the mutagenic exposures produce minimal toxicity as determined by standard histopathology and immunohistochemical analysis for cytokeratin 6 and the DNA-damage induced phosphorylation of histone H2AX (γ-H2AX). We attempted to develop a therapeutic that would inhibit the CEES-induced increase in mutation frequency in the skin. We observe that multi-dose, topical treatment with 2,6-dithiopurine (DTP), a known chemical scavenger of CEES, beginning 1h post-exposure to CEES, completely abolishes the CEES-induced increase in mutation frequency. These findings suggest the possibility that DTP, previously shown to be non-toxic in mice, may be useful as a therapeutic agent in accidental or malicious human exposures to SM.

Microbiological evaluation of chronic blepharitis among Iranian veterans exposed to mustard gas: a case-controlled study

PURPOSE

To evaluate the microbiological characteristics of eyelid margin flora in chronic blepharitis in mustard gas-exposed individuals and compare the results with those in age- and sex-matched unexposed people.

METHODS

In this comparative case series, 289 patients with ocular manifestations of mustard gas exposure (case) were evaluated for signs of chronic blepharitis. Additionally, microbiological evaluation of eyelid margins was conducted in these patients and compared with results of 100 unexposed patients with chronic blepharitis (control).

RESULTS

One-hundred fifty (52.0%) of 289 mustard gas casualties had signs of chronic blepharitis. Microbiological evaluation revealed higher isolation rates of Staphylococcus epidermidis (78%) and Staphylococcus aureus (57%) in the case in comparison to control group (P < 0.01). Moreover, S. aureus isolated from the cases exhibited greater resistance to common antibiotics compared with control group. Fungi were isolated more frequent in the case compared with controls (30% vs. 4%, P < 0.01), with Cladosporium and Candida species being most common in the case group.

CONCLUSIONS

Exposure to mustard gas seems to alter the microbiological flora of the eyelid margin. Staphylococcus spp., including antibiotic-resistant strains, and fungi were more frequently isolated in these patients. The relationship between microbial culture results and the severity of ocular surface manifestations in mustard gas-injured cases warrant further investigation.

Inhibition of NADPH cytochrome P450 reductase by the model sulfur mustard vesicant 2-chloroethyl ethyl sulfide is associated with increased production of reactive oxygen species

Inhalation of vesicants including sulfur mustard can cause significant damage to the upper airways. This is the result of vesicant-induced modifications of proteins important in maintaining the integrity of the lung. Cytochrome P450s are the major enzymes in the lung mediating detoxification of sulfur mustard and its metabolites. NADPH cytochrome P450 reductase is a flavin-containing electron donor for cytochrome P450. The present studies demonstrate that the sulfur mustard analog, 2-chloroethyl ethyl sulfide (CEES), is a potent inhibitor of human recombinant cytochrome P450 reductase, as well as native cytochrome P450 reductase from liver microsomes of saline and beta-naphthoflavone-treated rats, and cytochrome P450 reductase from type II lung epithelial cells. Using rat liver microsomes from beta-naphthoflavone-treated rats, CEES was found to inhibit CYP 1A1 activity. This inhibition was overcome by microsomal cytochrome P450 reductase from saline-treated rats, which lack CYP 1A1 activity, demonstrating that the CEES inhibitory activity was selective for cytochrome P450 reductase. Cytochrome P450 reductase also generates reactive oxygen species (ROS) via oxidation of NADPH. In contrast to its inhibitory effects on the reduction of cytochrome c and CYP1A1 activity, CEES was found to stimulate ROS formation. Taken together, these data demonstrate that sulfur mustard vesicants target cytochrome P450 reductase and that this effect may be an important mechanism mediating oxidative stress and lung injury.

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.

Evidence for a Morin type intramolecular cyclization of an alkene with a phenylsulfenic acid group in neutral aqueous solution

Sulfenic acids (RSOH) are among the most common sulfur-centered reactive intermediates generated in biological systems. Given the biological occurrence of sulfenic acids, it is important to explore the reactivity of these intermediates under physiological conditions. The Morin rearrangement is a synthetic process developed for the conversion of penicillin derivatives into cephalosporins that proceeds via nucleophilic attack of an alkene on a sulfenic acid intermediate. In its classic form, the Morin reaction involves initial elimination of a sulfenic acid from a cyclic sulfoxide, followed by intramolecular cyclization of the resulting alkene and sulfenic acid groups to generate an episulfonium ion intermediate that undergoes further reaction to yield ring-expanded products. On the basis of the existing literature, it is difficult to assess whether the reaction between an alkene and a sulfenic group can occur under mild conditions because the conditions required to generate the sulfenic acid from the sulfoxide precursor in the Morin reaction typically involve high temperatures and strong acid. In the work described here, beta-sulfinylketone precursors were used to generate a "Morin type" sulfenic acid intermediate under mild conditions. This approach made it possible to demonstrate that the intramolecular cyclization of an alkene with a phenylsulfenic acid to generate an episulfonium ion intermediate can occur in neutral aqueous solution at room temperature.

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.

Calmodulin mediates sulfur mustard toxicity in human keratinocytes

Sulfur mustard (SM) causes blisters in the skin through a series of cellular changes that we are beginning to identify. We earlier demonstrated that SM toxicity is the result of induction of both death receptor and mitochondrial pathways of apoptosis in human keratinocytes (KC). Because of its importance in apoptosis in the skin, we tested whether calmodulin (CaM) mediates the mitochondrial apoptotic pathway induced by SM. Of the three human CaM genes, the predominant form expressed in KC was CaM1. RT-PCR and immunoblot analysis revealed upregulation of CaM expression following SM treatment. To delineate the potential role of CaM1 in the regulation of SM-induced apoptosis, retroviral vectors expressing CaM1 RNA in the antisense (AS) orientation were used to transduce and derive stable CaM1 AS cells, which were then exposed to SM and subjected to immunoblot analysis for expression of apoptotic markers. Proteolytic activation of executioner caspases-3, -6, -7, and the upstream caspase-9, as well as caspase-mediated PARP cleavage were markedly inhibited by CaM1 AS expression. CaM1 AS depletion attenuated SM-induced, but not Fas-induced, proteolytic processing and activation of caspase-3. Whereas control KC exhibited a marked increase in apoptotic nuclear fragmentation after SM, CaM1 AS cells exhibited normal nuclear morphology up to 48h after SM, indicating that suppression of apoptosis in CaM1 AS cells increases survival and does not shift to a necrotic death. CaM has been shown to activate the phosphatase calcineurin, which can induce apoptosis by Bad dephosphorylation. Interestingly, whereas SM-treated CaM1-depleted KC expressed the phosphorylated non-apoptotic sequestered form of Bad, Bad was present in the hypophosphorylated apoptotic form in SM-exposed control KC. To determine if pharmacological CaM inhibitors could attenuate SM-induced apoptosis via Bad dephosphorylation, KC were pretreated with the CaM-specific antagonist W-13 or its less active structural analogue W-12. Following SM exposure, KC exhibited Bad dephosphorylation, which was inhibited in the presence of W-13, but not with W-12. Consequently, W-13 but not W-12 markedly suppressed SM-induced proteolytic processing and activation of caspase-3, as well as apoptotic nuclear fragmentation. Finally, while the CaM antagonist W-13 and the calcineurin inhibitor cyclosporin A attenuated SM-induced caspase-3 activation, inhibitors for CaM-dependent protein kinase II (KN62 and KN93) did not. These results indicate that CaM, calcineurin, and Bad also play a role in SM-induced apoptosis, and may therefore be targets for therapeutic intervention to reduce SM injury.

Development and application of acute exposure guideline levels (AEGLs) for chemical warfare nerve and sulfur mustard agents

Acute exposure guideline levels (AEGLs) have been developed for the chemical warfare agents GB, GA, GD, GF, VX, and sulfur mustard. These AEGLs were approved by the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances after Federal Register publication and comment, and judged as scientifically valid by the National Research Council Committee on Toxicology Subcommittee on AEGLs. AEGLs represent general public exposure limits for durations ranging from 10 min to 8 h, and for three levels of severity (AEGL-1, AEGL-2, AEGL-3). Mild effects are possible at concentrations greater than AEGL-1, while life-threatening effects are expected at concentrations greater than AEGL-3. AEGLs can be applied to various civilian and national defense purposes, including evacuation and shelter-in-place protocols, reentry levels, protective clothing specifications, and analytical monitoring requirements. This report documents development and derivation of AEGL values for six key chemical warfare agents, and makes recommendations for their application to various potential exposure scenarios.

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.

Detection of aqueous phase chemical warfare agent degradation products by negative mode ion mobility time-of-flight mass spectrometry [IM(tof)MS]

The use of negative ion monitoring mode with an atmospheric pressure ion mobility orthogonal reflector time-of-flight mass spectrometer [IM(tof)MS] to detect chemical warfare agent (CWA) degradation products from aqueous phase samples has been determined. Aqueous phase sampling used a traditional electrospray ionization (ESI) source for sample introduction and ionization. Certified reference materials (CRM) of CWA degradation products for the detection of Schedule 1, 2, or 3 toxic chemicals or their precursors as defined by the chemical warfare convention (CWC) treaty verification were used in this study. A mixture of six G-series nerve related CWA degradation products (EMPA, IMPA, EHEP, IHEP, CHMPA, and PMPA) and their related collision induced dissociation (CID) fragment ions (MPA and EPA) were found in each case to be clearly resolved and detected using the IM(tof)MS instrument in negative ion monitoring mode. Corresponding ions, masses, drift times, K(o) values, and signal intensities for each of the CWA degradation products are reported.

Mechanisms and consequences of paternally-transmitted chromosomal abnormalities

Paternally-transmitted chromosomal damage has been associated with pregnancy loss, developmental and morphological defects, infant mortality, infertility, and genetic diseases in the offspring, including cancer. There is epidemiological evidence linking paternal exposure to occupational or environmental agents with an increased risk of abnormal reproductive outcomes. There is also a large body of literature on germ cell mutagenesis in rodents showing that treatment of male germ cells with mutagens has dramatic consequences on reproduction, producing effects such as those observed in human epidemiological studies. However, we know very little about the etiology, transmission, and early embryonic consequences of paternally-derived chromosomal abnormalities. The available evidence suggests that: 1) there are distinct patterns of germ cell-stage differences in the sensitivity of induction of transmissible genetic damage, with male postmeiotic cells being the most sensitive; 2) cytogenetic abnormalities at first metaphase after fertilization are critical intermediates between paternal exposure and abnormal reproductive outcomes; and 3) there are maternal susceptibility factors that may have profound effects on the amount of sperm DNA damage that is converted into chromosomal aberrations in the zygote and that directly affect the risk for abnormal reproductive outcomes.

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

The ability of sulphur mustard (HD) to induce DNA damage places limits on the efficacy of approaches aimed at protecting human cells from the cytotoxic effects of HD using a variety of protective agents such as thiol-containing esters and protease inhibitors. In the present study, potential alternative strategies were investigated by examining the differential effects of HD on G361, SVK14, HaCaT and NCTC 2544 human skin cells. The G361 cell line was more resistant to the cytotoxic effects of HD than the NCTC, HaCaT and SVK14 cell lines at HD doses of >3 and <100 microM HD as determined by the MTT assay. At 72 h after exposure to 60 microM HD there was up to an 8.8-fold difference (P < 0.0001) between G361 and SVK14 cell culture viability. Buthionine sulphoximine (BSO) pretreatment increased the sensitivity of all four cell lines to HD. A substantial proportion of the resistance of G361 cells to HD was attributable to BSO-mediated effects on antioxidant-mediated metabolism, although G361 cultures still retained a high degree of viability at 30 microM HD following BSO pretreatment. Cell cycle analysis confirmed that SVK14 cells were relatively more sensitive to HD, as shown by the 2.1-fold reduction (P < 0.0001) in the percentage of cells in G0/G1 phase 24 h after HD exposure compared with control cultures. This compared well with a 1.2-fold increase (P < 0.05) in the percentage of G361 cells in G0/G1 phase following HD exposure, suggesting the existence of a more efficient G0/G1 checkpoint control mechanism in this cell line. Manipulation of the cell cycle using various modulating agents did not increase the resistance of cell lines to the cytotoxic effects of HD.

Differential toxicity of sulfur mustard administered through percutaneous, subcutaneous, and oral routes

Sulfur mustard (SM), chemically 2,2'-dichloro diethyl sulphide, is an incapacitating and extremely toxic chemical warfare agent. It causes serious blisters on contact with human skin. While screening various antidotes against its toxicity, we observed that SM was more toxic through percutaneous (p.c.) route compared to oral (p.o.) and subcutaneous (s.c.) routes. The LD(50) of SM in female mice was found to be 5.7, 8.1 and 23.0 mg/kg through p.c., p.o., and s.c. routes, respectively. The body weight of the animals was monitored and it was found that percentage body weight loss was more in the p.c. route. There was significant DNA fragmentation in liver in all the three routes evaluated at 19.3 mg/kg dose of SM. The depletion of hepatic GSH content was found to be more in the p.c. route of exposure compared to s.c. route. There was significant reduction in WBC count in all the three routes of exposure. Histopathological evaluation of lung, liver, and spleen also showed that the damage was more in the p.c. route and severity of lesions was dependent on the dose of exposure. The most affected organ was liver by all the three routes. LD(50) was also determined in male rats and it was found to be 2.4, 2.4, and 3.4 mg/kg through p.c., p.o. and s.c. routes respectively. Since skin contains maximum number of metabolically active and rapidly dividing cells, differential metabolism of SM cannot be ruled out. Probably, this is the first report of a chemical showing more toxicity through p.c. route compared to s.c. route.

Biochemical changes in mouse lung after subcutaneous injection of the sulfur mustard 2-chloroethyl 4-chlorobutyl sulfide

Sulfur mustard (HD) is a vesicant-type chemical warfare agent (CWA) introduced in World War I which continues to be produced, stockpiled, and occasionally deployed by some countries, and could be used potentially by terrorists. Exposure to HD can cause erythema, blisters, corneal opacity, and airway damage. We have reported previously that subcutaneous (SC) injection of immunodeficient athymic nude mice with the half mustard butyl 2-chloroethyl sulfide (BCS) causes systemic biochemical changes in several organs distal to the exposure site. In the present study, we examined the response of non-immunodeficient Swiss Webster mice to the mustard, 2-chloroethyl 4-chlorobutyl sulfide (CECBS). In a pilot study, we found that a single SC injection of 20-25 microl/mouse causes death within 24h. Consequently, we used 5 microl/mouse (approx. 0.017 mg/kg body weight) of neat CECBS or an equal volume of saline as control. We examined the lungs after 1, 24, and 48 h for biochemical changes including total and oxidized glutathione, protein, DNA, and lipid peroxidation contents in tissue homogenate, and superoxide dismutase, catalase, glucose-6-phosphate dehydrogenase, and glutathione S-transferases activities in the cytosol. After 1h and/or 24h, we found statistically significant changes that were resolved by 48 h. These changes mimicked those of HD and BCS and were generally consistent with free radical-mediated oxidative stress. The implications of these observations are two-fold. First, dermal exposure to low-dose mustard gas could elicit systemic changes impacting distal organs such as the lungs. It also suggests that antioxidants could potentially modulate the response and reduce the damage. Second, although the use of known CWAs such as HD is prohibited, analogs that are not recognized as agents are as toxic and could be dangerous if acquired and used by potential terrorists.

Use of the single cell gel electrophoresis/comet assay for detecting DNA damage in aquatic (marine and freshwater) animals

The comet assay is a rapid, sensitive and inexpensive method for measuring DNA strand breaks. The comet assay has advantages over other DNA damage methods, such as sister chromatid exchange, alkali elution and micronucleus assay, because of its high sensitivity and that DNA strand breaks are determined in individual cells. This review describes a number of studies that used the comet assay to determine DNA strand breaks in aquatic animals exposed to genotoxicants both in vitro and in vivo, including assessment of DNA damage in aquatic animals collected from contaminated sites. One difficulty of using the comet assay in environmental work is that of comparing results from studies that used different methods, such as empirical scoring or comet tail lengths. There seems to be a consensus in more recent studies to use both the intensity of the tail and the length of the tail, i.e. DNA tail moment, percentage of DNA in the tail. The comet assay has been used to assess DNA repair and apoptosis in aquatic animals and modifications of the comet assay have allowed the detection of specific DNA lesions. There have been some recent studies to link DNA strand breaks in aquatic animals to effects on the immune system, reproduction, growth, and population dynamics. Further work is required before the comet assay can be used as a standard bio-indicator in aquatic environments, including standardization of methods (such as ASTM method E2186-02a) and measurements.

Gene expressions in Jurkat cells poisoned by a sulphur mustard vesicant and the induction of apoptosis

1. The sulphur mustard vesicant 2-chloroethylethyl sulphide (CEES) induced apoptosis in Jurkat cells. 2. Akt (PKB), a pivotal protein kinase which can block apoptosis and promotes cell survival, was identified to be chiefly down-regulated in a dose-dependent manner following CEES treatment. Functional analysis showed that the attendant Akt activity was simultaneously reduced. 3. PDK1, an upstream effector of Akt, was also down-regulated following CEES exposure, but two other upstream effectors of Akt, PI3-K and PDK2, remained unchanged. 4. The phosphorylation of Akt at Ser(473) and Thr(308) was significantly decreased following CEES treatment, reflecting the suppressed kinase activity of both PDK1 and PDK2. 5. Concurrently, the anti-apoptotic genes, Bcl family, were down-regulated, in sharp contrast to the striking up-regulation of some death executioner genes, caspase 3, 6, and 8. 6. Based on these findings, a model of CEES-induced apoptosis was established. These results suggest that CEES attacked the Akt pathway, directly or indirectly, by inhibiting Akt transcription, translation, and post-translation modification. 7. Taken together, upon exposure to CEES, apoptosis was induced in Jurkat cells via the down-regulation of the survival factors that normally prevent the activation of the death executioner genes, the caspases.

Chemical and biological weapons. Implications for anaesthesia and intensive care

In the wake of recent atrocities there has been renewed apprehension regarding the possibility of chemical and biological weapon (CBW) deployment by terrorists. Despite various international agreements that proscribe their use, certain states continue to develop chemical and biological weapons of mass destruction. Of greater concern, recent historical examples support the prospect that state-independent organizations have the capability to produce such weapons. Indeed, the deliberate deployment of anthrax has claimed several lives in the USA since September 11, 2001. In the event of a significant CBW attack, medical services would be stretched. However, victim survival may be improved by the prompt, coordinated response of military and civil authorities, in conjunction with appropriate medical care. In comparison with most other specialties, anaesthetists have the professional academic background in physiology and pharmacology to be able to understand the nature of the injuries caused by CBWs. Anaesthetists, therefore, play a vital role both in the initial resuscitation of casualties and in their continued treatment in an intensive care setting. This article assesses the current risk of CBW deployment by terrorists, considers factors which would affect the severity of an attack, and discusses the pathophysiology of those CBWs most likely to be used. The specific roles of the anaesthetist and intensivist in treatment are highlighted.

The immunostatus of natural killer cells in people exposed to sulfur mustard

Sulfur mustard (2,2-dichloroethyl sulfide, SM) has been documented as an alkylating agent. It has been widely used as a chemical weapon during the last two decades. Despite extensive worldwide research, no effective therapy has yet been devised for the treatment of patients exposed to SM. A severe suppression of the immune system still remains as the major cause of opportunistic infections, septicemia and death in such patients. The aim of this study was to determine the possible effect of SM on natural killer (NK) cells in patients suffering from SM injuries. Patients were classified into three groups: mild, moderate and severe. Blood sample obtained from each patient was examined using flowcytometric technique. Results showed that the percentage of NK cells (CD45+/CD56+) is significantly lower in severe patients than that of the control group (P<0.05). It was also observed that the activity of NK cells (CD56+/CD25+) in severe alkylating group is noticeably higher compared with the control group (P<0.1).

The treatment of Lewisite burns with laser debridement---'lasablation'

Lewisite (dichloro (2-chlorovinyl) arsine) was first synthesised in 1918 and its potential for use in military confrontations as a vesicant agent has been widely recognised. These agents cause blistering skin reactions with resultant full thickness burns. Effective treatments to date have been delayed by the lack of suitable animal models. Porcine skin has recently been used successfully to model the development and natural history of these burn injuries. A large white pig model (n=6) was employed to investigate the effectiveness of CO(2) and Erbium-YAG lasers (EYL) in laser dermabrasion of established Lewisite burns. Burns underwent treatment at 4 days post-exposure and were assessed at 1, 2 and 3 weeks, thereafter, for the rate of epithelial healing. The re-epithelialisation rates in the laser dermabraded groups were accelerated by a factor of four compared to untreated controls by the first week (analysis of vartiance, ANOVA, P=0.006 for pulsed CO(2) and P=0.011 for Erbium-YAG). Ablation of the burn eschar was thought to accelerate the rate of healing by causing partial debridement. This method has been termed 'lasablation' and represents a significant advance in the clinical management of this type of injury.

An in vitro comparison of the cytotoxicity of sulphur mustard in melanoma and keratinocyte cell lines

In vivo, the pigment producing melanocytes are the most susceptible cell type to sulphur mustard (HD) in the epidermal region of pig skin. It has been postulated that this is due to the melanogenic pathway producing a cytotoxic, free radical cascade within the melanocyte following HD poisoning, leading to cellular necrosis and subsequent inflammation. To test this hypothesis, the cytotoxicity of HD was tested in three human melanoma cell lines and compared to SVK-14 human keratinocytes, a cell line in which the response to HD has already been characterised. The results of both neutral red (NR) and gentian violet (GV) assays showed that all three melanoma cell lines, particularly the G361 line, were less susceptible to the toxic effects of HD than the SVK-14 keratinocyte cell line. Preliminary data indicate that the expression level of the DNA repair cofactor, proliferating cell nuclear antigen (PCNA), is up to 13-fold greater in the HD-resistant cell line G361 compared to the HD-sensitive SVK-14 cell line. The data point to the importance of DNA lesions in HD-induced cell death and to potential mechanisms associated with increased resistance to HD. A dose-response study was carried out to confirm the differences between these two cell lines. It was found that the G361 line is 5-fold more resistant to HD and 5.5-fold more resistant to the cytotoxic effects of H2O2 than the SVK-14 line, as determined by the MTT assay. The results suggest that differences in the relative efficiency of DNA repair processes may underlie these responses. Whilst the study indicates the limitations of using melanoma cell lines (in vitro) to model melanocyte responses to HD, analysis of the biochemical basis of the observed differences in sensitivity to HD could assist in the identification of novel therapeutic strategies against HD.

Comparison of cell size in sulfur mustard-induced death of keratinocytes and lymphocytes

Sulfur mustard (HD) is a vesicant chemical warfare agent that directly alkylates cellular DNA and produces DNA strand breaks. To identify cellular models for in vitro screening of antivesicant compounds in DNA repair assays, we compared the mechanism of HD-induced cell death in cultured adult normal human epidermal keratinocytes (NHEK) and peripheral blood lymphocytes (PBL). One parameter that we used to distinguish apoptotic from necrotic cell death was the change in cell size due to HD. In the presence or absence of a poly(ADP-ribose) polymerase inhibitor (PARPI), cell preparations were exposed to various concentrations of HD (0.01-1.0 mM) and harvested at selected times after exposure (up to 24 h). Results from these experiments suggest that, with increasing HD concentration and time, NHEK will fragment irrespective of the presence or absence of PARPI, with cell fragmentation presumably preceded by necrosis. In the absence of PARPI, PBL size initially decreases and then remains constant over time. Previous DNA fragmentation studies indicate that both apoptosis and necrosis occur in HD-exposed PBL in a time-dependent manner. In the presence of PARPI, there is a HD concentration- and time-dependent decrease in PBL size that is characteristic of apoptosis. The shift in the mechanism of HD-induced PBL death from apoptosis followed by necrosis to exclusively apoptosis in the absence and presence of PARPI, respectively, is in agreement with previous findings on HD-induced changes in membrane integrity, energy levels and DNA fragmentation. Considering that NHEK fragment early after exposure to HD concentrations that produce vesication in human skin, PBL may be a more appropriate model for use in DNA repair assays.

Sulphur mustard induced DNA damage in mice after dermal and inhalation exposure

Sulphur mustard (SM) is a chemical warfare agent of the blistering agent category for which there is still no effective therapy. SM, being a strong electrophile, readily reacts with a wide range of cellular macromolecules including DNA, RNA and protein. Since the main intoxication routes for SM are inhalation and dermal penetration, in the present study we have exposed female mice to different concentrations of SM by dermal and inhalation exposures and estimated the DNA damage in different organs viz., liver, lung, spleen and thymus. SM was applied at 38.7, 77.4, 154.7 mg/kg body weight, on the hair-clipped skin (dermal exposure) equivalent to 0.25, 0.5 and 1.0 of the LD50. Inhalation exposure was carried out at 10.6, 21.2 and 42.3 mg/m3 for 1 h duration equivalent to 0.25, 0.5 and 1.0 LC50. SM induced a dose-dependent DNA damage in all the organs except the lung in dermal exposure. Similarly the inhalation exposure resulted in dose- and time-dependent effect in all the organs including lung. By both routes of exposure liver was the most affected organ followed by spleen, thymus and lung in decreasing order. The quantitative data were corroborated by qualitative analysis of DNA on agarose gel electrophoresis. The genomic DNA analysis of the organs had revealed random nuclear DNA fragmentation resulting in a 'smear' typical of necrotic form of cell death. Since DNA damage is not reversible especially in liver, this can be used as a marker for SM exposure through either the dermal or inhalation route.

The development of Lewisite vapour induced lesions in the domestic, white pig

Studies performed in the past in our laboratory have detailed the development of sulphur mustard lesions in the domestic, white pig using small glass chambers to achieve saturated vapour exposure under occluded conditions. We have now used this experimental model to produce cutaneous lesions for detailed histopathological studies following challenge with lewisite. Histological examination of resulting lesions have revealed that although the overall pattern of lesion development is similar to that seen following mustard challenge, the time-course of cellular events is very much compressed. The epidermis showed focal basal cell vacuolation with associated acute inflammation as early as one hour postexposure. Coagulative necrosis of the epidermis and papillary dermis was complete by 24 hours and followed the appearance of multiple coalescent blisters between six and 12 hours post-exposure. At 48 hours, the lesions were full thickness burns with necrosis extending into the deep subcutaneous connective and adipose tissues. The study of lesions beyond 24 hours revealed early epithelial regeneration at the wound edge. The overall spontaneous healing rate of these biologically severe lesions was significantly faster than comparable sulphur mustard injuries and probably reflected a lack of alkylation of DNA and RNA.

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.

Alterations in human lymphocyte DNA caused by sulfur mustard can be mitigated by selective inhibitors of poly(ADP-ribose) polymerase

Changes in genomic DNA caused by exposure to the cytotoxic alkylating agent, 2,2'-dichlorodiethyl sulfide (sulfur mustard; HD), alone or in combination with selective inhibitors of poly(ADP-ribose) polymerase (PARP), were analyzed as a function of HD concentration and post-exposure time. Preparations of human peripheral blood lymphocytes were exposed to HD (1x10(-8) M-1x10(-3) M), and incubated at 37 degrees C for 0-24 h. Total genomic DNA was extracted from these cells and compared with DNA from control cells of the same donor using agarose gel electrophoresis. The effects of HD on genomic DNA depended on the HD concentration and the length of the post-exposure time interval. DNA fragmentation was detected as early as 2 h after exposure to 3x10(-4) M HD, or at 24 h after exposure to 6x10(-6) M HD. The qualitative DNA pattern, as well as the extent of DNA fragmentation, changed with post-exposure time. Exposure to HD caused a time-dependent shift in the DNA cleavage pattern from an oligonucleosome-sized 'DNA ladder' characteristic of apoptotic cell death, to a 'broad band' pattern characteristic of necrotic cell death. DNA fragmentation was not observed if cells were killed with heat or with Lewisite. Treatment of cells with selective PARP inhibitors consistently altered the DNA fragmentation caused by HD exposure. The inhibitors arrested DNA fragmentation at the DNA ladder stage. This effect only was observed if the PARP inhibitors were applied within 8 h of HD exposure. We conclude that early inhibition of PARP activity can induce a switch in the mechanism of cell death caused by HD. Such a switch may be useful therapeutically to convert a lytic, pro-inflammatory cell death that includes the disintegration of dying cells (necrosis), into a slower, programmed cell death that includes absorption of dying cells (apoptosis).

Mutations induced by monofunctional and bifunctional phosphoramide mustards in supF tRNA gene

The relative mutagenicity, nature of the mutations and the sequence specificity of mutations induced by the bifunctional alkylating agent, phosphoramide mustard (PM) and a monofunctional derivative, dechloroethyl phosphoramide mustard (dePM), were analyzed by the Ames test and by an in vitro shuttle vector mutagenesis assay. Both PM and dePM increased the mutation frequency above background in either assay. However, on an equimolar basis, dePM was less mutagenic than PM. In the in vitro shuttle vector mutagenesis assay, sequencing demonstrated that about 40% of the mutant plasmids contained more than one mutation in the supF tRNA gene segment of the plasmid. About 70% of the mutations observed in dePM-treated plasmids were single base substitutions with A:T and G:C base pairs being mutated at equivalent rates. In contrast, only about 50% of the mutations observed in PM-treated plasmids were single base substitutions, 80% of which involved G:C base pairs. Single base deletions and insertions were found in approximately equal proportions with both compounds; however, these lesions were in greater abundance in PM-treated plasmids. Putative hot-spots for mutation in the supF tRNA gene included base pairs at position 102 and 110 for PM and positions 170 and 171 for dePM.

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

1. The A549 cell line was used to assess the toxicity of sulphur mustard (HD), using gentian violet (GV) and neutral red (NR) dyes as indicators of cell viability. It was found that exposure to concentrations in excess of 40 microM HD resulted in a rapid onset of toxicity. 2. The ability of monoisopropylglutathione ester (MIPE) to protect A549 cells against the effects of a 100 microM challenge dose of HD was determined using the NR and GV assays. It was found that MIPE (8 mM) could protect cells against the effects of HD though MIPE had to be present at the time of HD challenge. Cultures protected with MIPE were two times more viable than HD exposed cells 48 h after HD challenge when using the GV and NR assays to assess viability. Observations by phase contrast microscopy of NR and GV stained cultures confirmed these findings. Addition of MIPE after previously exposing the A549 cultures to HD (for up to 5 min) maintained cell viability at 72% compared to 37% for unprotected cultures, after which time viability fell significantly so that at 10 min there was no difference in viability between the MIPE treated and untreated cultures. 3. Pretreating A549 cultures with MIPE for 1 h followed by its removal prior to HD challenge did not maintain cell viability. Treatment of cultures with HD for 1 h followed by addition of MIPE did not maintain the viability of the cultures, thus the window within which it was possible for MIPE to rescue cell cultures from the effects of HD was of short duration. 4. High performance liquid chromatography was used to determine the biochemical basis of the actions of MIPE. It was found that whilst intracellular levels of cysteine were increased up to 40-fold following treatment of A549 cell cultures with MIPE, levels of reduced glutathione did not rise. The lack of protection seen in cultures pretreated with MIPE for 1 h prior to HD exposure suggests that raising intracellular cysteine levels was not an effective strategy for protecting cells from the effects of HD. The protection observed is probably due to extracellular inactivation of HD by MIPE.

Presence of methenamine/glutathione mixtures reduces the cytotoxic effect of sulphur mustard on cultured SVK-14 human keratinocytes in vitro

The basal epidermal keratinocytes of the skin are a main target for the vesicating agent, sulphur mustard (SM). A human keratinocyte cell line (SVK-14) has been used to model the effects of SM on the basal epidermal keratinocytes and subsequently to test the efficacy of potential prophylactic compounds in reducing the SM-induced cytotoxicity. The cultures were pretreated with mixtures of methenamine (HMT) and glutathione (GSH) for 1 h prior to exposure to 10 microM SM. The viability of the cultures was then assessed using neutral red (NR) dye uptake and crystal violet DNA staining assays at 24 h intervals post exposure. Pretreatment led to a 1.9 fold increase in culture viability (NR assay) compared to those exposed to SM only, and a 2.3 fold increase in cell number (crystal violet assay). Photomicrography showed that pretreatment preserved the morphology of the cultured cells and maintained their mitotic activity whereas those exposed to SM only show non-proliterative cultures with extensive cellular damage. The results of this study show that it is possible to protect mitotically active cultures from the effects of SM, however the measures must be in place prior to SM exposure.

Ultrastructural characterization of sulfur mustard-induced vesication in isolated perfused porcine skin

The isolated perfused porcine skin flap (IPPSF) is a novel alternative, humane in vitro model consisting of a viable epidermis and dermis with a functional microvasculature. For this study, 200 microliters of either 10.0, 5.0, 2.5, 1.25, 0.50, or 0.20 mg/ml of bis (2-chloroethyl) sulfide (HD) in ethanol or ethanol control was topically applied to a 5.0 cm2 dosing area of the IPPSF and perfused for 8 h with recirculating media. HD dermatotoxicity was assessed in the flap by cumulative glucose utilization (CGU), vascular resistance (VR), light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). HD produced a statistically significant dose relationship for gross blisters and microvesicles. The HD-treated IPPSFs were also characterized by a decrease in CGU and an increase in VR. Light microscopic changes included mild intracellular and slight intracellular epidermal edema, multifocal epidermal-dermal separation, and dark basal cells. Ultrastructural alterations consisted of cytoplasmic vacuoles, pyknotic basal cells, nucleolar segregation, and epidermal-dermal separation occurring between the lamina lucida and lamina densa of the basement membrane. The severity of these changes increased in a dose-dependent manner. Morphologically, the IPPSF appeared similar to human skin exposed to HD with the formation of macroscopic blisters and microscopic vesicles. In conclusion, the IPPSF appears to be an appropriate in vitro model with which to study the pathogenesis of vesicant-induced toxicity.

Mutagenicity of anticancer drugs in mammalian germ cells

The evidence for mammalian germ cell mutagenicity induced by anticancer drugs is summarized. Primary attention is paid to the three major mouse germ cell mutagenicity tests- the dominant lethal, heritable translocation, and morphological specific locus tests- from which most germ cell mutagenicity data historically have been obtained. Of the 21 anticancer drugs reviewed, 16 have been tested in one or more of these three tests; with all 16 tested in the most common germ cell test, the male dominant lethal test, and 9 of the 16 also tested in the female dominant lethal test. The patterns of germ cell stage specificity for most of the anticancer drugs are similar, and generally resemble the patterns seen with other types of chemicals; however, some of the patterns are unique. For example, 2 of the 8 chemicals shown to induce dominant lethal mutations in female oocytes, do not induce dominant lethal mutations in male germ cells (adriamycin and platinol). Ten of the 16 chemicals tested in the dominant lethal test were positive in post-meiotic stages (spermatids through mature sperm), and seven also induced reciprocal translocations and/or specific locus mutations in post-meiotic stages. This propensity to induce mutations in post-meiotic stages has been observed with most mutagens. However, 5 of the anticancer drugs also induced dominant lethal mutations in spermatocytes (meiotic prophase cells) and one of them, 6-mercaptopurine, uniquely induced dominant lethal mutations exclusively in preleptotene spermatocytes. Finally, three of the anticancer drugs (melphalan, mitomycin C, procarbazine) are members of a very select group of chemicals shown to induce specific locus mutations in spermatogonial stem cells of mice. The implications for human risk are discussed.

The time-dependent effect of 2,2'-dichlorodiethyl sulfide (sulfur mustard, HD, 1,1'-thiobis [2-chloroethane]) on the lymphocyte viability and the kinetics of protection by poly(ADP-ribose) polymerase inhibitors

2,2'-Dichlorodiethyl sulfide (sulfur mustard, HD, 1,1'-thiobis [2-chloroethane]) is a potent vesicant which can cause severe lesions to skin, lung, and eyes. Due to the high number of debilitating exposures during the Iran-Iraq war to the alkylating agent, HD, there is an increased interest in its mechanism of action and in the development of therapeutic interventions to prevent HD-induced lesions. Recently we reported an in vitro assay using human mononuclear leukocytes for studying HD-induced pathology. To study the time dependence of HD-induced mononuclear leukocyte cell death and to determine the parameters of any potential therapeutic intervention, an assay was developed and automated using a flow cytometer to measure propidium iodide exclusion by mononuclear cells. This assay demonstrated that HD-initiated cell death did not begin before 4 h post-exposure, but after 4 h proceeded in a concentration-dependent manner. In this assay, both niacinamide and 3-aminobenzamide, poly(ADP-ribose) polymerase inhibitors, were shown to be effective in blocking HD-induced cell death when added to the cultures during the first 4 h post-exposure. They offered partial protection when added between 6 and 12 h and were of no benefit when added after 12 h post-exposure.

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

1. Sulphur mustard (HD) is a potent chemical warfare agent which causes incapacitating blisters on human skin. There is no specific pretreatment nor therapy against this agent and the mechanism of dermo-epidermal cleavage is unclear. The aim of this study was to use a human skin explant system to determine the consequences of percutaneous exposure to HD. 2. Increased activities of serine proteases associated with blistering disorders in humans were detected from human skin explants after exposure to HD. The most consistent response and the highest protease activities measured were found for trypsin. This class of enzyme is therefore implicated in the dermo-epidermal separation which is associated with blistering in humans following exposure to HD. 3. An inflammatory response was observed in the skin explants exposed to HD. At low doses of HD it was characterised by the presence of neutrophils in the papillary dermis, culminating in the infiltration of the epidermis by these inflammatory cells at higher concentrations of HD. A variety of other histopathological changes in the explants was found such as focal dermo-epidermal separation, nuclear pyknosis and perinuclear vacuolation. 4. The study indicates that full thickness human skin explants can be used to investigate various aspects of the possible pathogenesis of HD-induced skin damage, including the associated inflammatory response.

Appearance of interleukin 1 alpha relates DNA interstrand cross-links and cytotoxicity in cultured human keratinocytes exposed to bis-(2-chloroethyl) sulfide

The utility of an increase in the level of interleukin 1 alpha (IL-1 alpha) as an indicator of cytotoxicity from exposure to bis-(2-chloroethyl) sulfide (BCES) was evaluated in submerged monolayer cultures of human cutaneous keratinocytes. Four-day-old cultures were exposed to 1-100 microM BCES at 37 degrees for 30 min. The amounts of IL-1 alpha in the medium at and in cells 72 h after exposure were measured immunologically with an enzyme-linked immunosorbent assay using monoclonal antibody to human IL-1 alpha. The antibody was conjugated with peroxidase for visualization. Cell viability was measured concomitantly using the trypan blue exclusion technique. The degree of interstrand cross-linking as a measure of damage in the cellular DNA was determined by measuring the fluorescence resulting from the intercalation of ethidium bromide into double-stranded molecules that remained in heat-denatured DNA isolated from cells that had been exposed to BCES. A high correlation was observed between the dose-responsive increase in the level of IL-1 alpha in the medium and in the cells, and the dose-responsive decrease that took place in the fraction of viable cells in exposed cultures. The dose-responsive increase in the interstrand cross-linking found in the DNA of cells immediately after exposure to BCES also correlated with the increase in IL-1 alpha 72 h after exposure. These data suggest that the appearance of IL-1 alpha can be used to quantify the cytotoxicity resulting from BCES-medicated damage to cellular DNA and that degree of cross-linking in the DNA immediately after exposure to BCES is predictive of the level of cytotoxicity in an exposed culture 3 days later.

The release of lysosomal arylsulfatase from liver lysosomes exposed to 2-chloroethylethyl sulfide

Treatment of a lysosome-rich fraction from liver with 2-chloroethylethyl sulfide resulted in a dose-dependent release of arylsulfatase. The inclusion of Ca2+ enhanced the enzyme release by approximately 2.3-fold. The enhancing effect of Ca2+, showing an EC50 value of 30 mM, was mimicked by neither Mg2+ nor Mn2+. Studies on a structural requirement and a time-dependent release suggest that the Ca(2+)-dependent release proceeds via a specific process involving the alkylation of lysosomal membranes by 2-chloroethylethyl sulfide. Furthermore, the Ca(2+)-dependent process was prevented partially by either leupeptin or gentamycin, but neither pepstatin nor PMSF, implying that the enzyme release may be partially mediated by lysosomal cysteine-protease or phospholipase. Meanwhile, the Ca(2+)-independent release seems to be expressed non-specifically by various compounds.