Effects of iodine on inducible nitric oxide synthase and cyclooxygenase-2 expression in sulfur mustard-induced skin

Molecular Genetics and Cytotoxic Responses to Titanium Diboride and Zinc Borate Nanoparticles on Cultured Human Primary Alveolar Epithelial Cells

Titanium diboride (TiB₂) and zinc borate (Zn₃BO₆) have been utilized in wide spectrum industrial areas because of their favorable properties such as a high melting point, good wear resistance, high hardness and thermal conductivity. On the other hand, the biomedical potentials of TiB₂ and Zn₃BO₆ are still unknown because there is no comprehensive analysis that uncovers their biocompatibility features. Thus, the toxicogenomic properties of TiB₂ and Zn₃BO₆ nanoparticles (NPs) were investigated on human primary alveolar epithelial cell cultures (HPAEpiC) by using different cell viability assays and microarray analyses. Protein-Protein Interaction Networks Functional Enrichment Analysis (STRING) was used to associate differentially expressed gene probes. According to the results, up to 10 mg/L concentration of TiB₂ and Zn₃BO₆ NPs application did not stimulate a cytotoxic effect on the HPAEpiC cell cultures. Microarray analysis revealed that TiB₂ NPs exposure enhances cellular adhesion molecules, proteases and carrier protein expression. Furthermore, Zn₃BO₆ NPs caused differential gene expressions in the cell cycle, cell division and extracellular matrix regulators. Finally, STRING analyses put forth that inflammation, cell regeneration and tissue repair-related gene interactions were affected by TiB₂ NPs application. Zn₃BO₆ NPs exposure significantly altered inflammation, lipid metabolism and infection response activator-related gene interactions. These investigations illustrated that TiB₂ and Zn₃BO₆ NPs exposure may affect different aspects of cellular machineries such as immunogenic responses, tissue regeneration and cell survival. Thus, these types of cellular mechanisms should be taken into account before the use of the related NPs in further biomedical applications.

Determination of Chemical Irritation Potential Using a Defined Gene Signature Set on Tissue-Engineered Human Skin Equivalents

There are no physical or visual manifestations that define skin sensitivity or irritation; a subjective diagnosis is made on the basis of the evaluation of clinical presentations, including burning, prickling, erythema, and itching. Adverse skin reaction in response to topically applied products is common and can limit the use of dermatological or cosmetic products. The purpose of this study was to evaluate the use of human skin equivalents based on immortalized skin keratinocytes and evaluate the potential of a 22-gene panel in combination with multivariate analysis to discriminate between chemicals known to act as irritants and those that do not. Test compounds were applied topically to full-thickness human skin equivalent or human ex vivo skin and gene signatures determined for known irritants and nonirritants. Principle component analysis showed the discriminatory potential of the 22-gene panel. Linear discrimination analysis, performed to further refine the gene set for a more high-throughput analysis, identified a putative seven-gene panel (IL-6, PTGS2, ATF3, TRPV3, MAP3K8, HMGB2, and matrix metalloproteinase gene MMP-3) that could distinguish potential irritants from nonirritants. These data offer promise as an in vitro prediction tool, although analysis of a large chemical test set is required to further evaluate the system.

Toxic blister agents: Chemistry, mode of their action and effective treatment strategies

Since their use during the First World War, Blister agents have posed a major threat to the individuals and have caused around two million casualties. Major incidents occurred not only due to their use as chemical warfare agents but also because of occupational hazards. Therefore, a clear understanding of these agents and their mode of action is essential to develop effective decontamination and therapeutic strategies. The blister agents have been categorised on the basis of their chemistry and the biological interactions that entail post contamination. These compounds have been known to majorly cause blisters/bullae along with alkylation of the contaminated DNA. However, due to the high toxicity and restricted use, very little research has been conducted and a lot remains to be clearly understood about these compounds. Various decontamination solutions and detection technologies have been developed, which have proven to be effective for their timely mitigation. But a major hurdle seems to be the lack of proper understanding of the toxicological mechanism of action of these compounds. Current review is about the detailed and updated information on physical, chemical and biological aspects of various blister agents. It also illustrates the mechanism of their action, toxicological effects, detection technologies and possible decontamination strategies.

Modulation of proinflammatory mediators by viruses-bacteria synergism in human osteoblasts-an in vitro study

BACKGROUND/PURPOSE

Viruses-bacteria synergistic interaction is associated with destructive periodontal diseases. However, the underlying mechanism for tissue destruction is not fully elucidated. In this study, lipopolysaccharide from Porphyromonas gingivalis (Pg-LPS) and polyinosinic-polycytidylic acid (poly I:C) were used to simulate bacteria and viruses, respectively. The possible combined effects of both molecular patterns on secretion of interleukin (IL)-6 and prostaglandin E₂ (PGE₂) from osteoblasts were determined. The effects of povidone-iodine (PVP-I) on the secretion of IL-6 and PGE₂ were also examined.

METHODS

Viability of treated osteoblastic cells (MG63) was examined by detection the mitochondrial dehydrogenase activity. Secretion of IL-6 and PGE₂ was detected using the enzyme-linked immunosorbent assay (ELISA). Mitogen-activated protein kinases (MAPKs) and cyclooxygenase-2 (COX-2) were determined using the Western blotting analysis.

RESULTS

Pg-LPS or poly I:C significantly enhanced the production of IL-6 and PGE₂ in MG63 cells. The additive/synergistic effects of Pg-LPS/poly I:C on production of IL-6 and PGE₂ were evident. The levels of phosphorylation of p38 MAPK and c-Jun N-terminal kinase (JNK) and expression of COX-2 protein were enhanced by Pg-LPS and/or poly I:C. On the other hand, the level of phosphorylation of extracellular signal-regulated kinase (ERK) was reduced by Pg-LPS and/or poly I:C. The stimulatory secretion of PGE₂ by poly I:C was significantly reduced by PVP-I.

CONCLUSION

Concomitant infection of viruses and bacteria may be potentially harmful to the tooth supporting tissues by production of proinflammatory mediators. The results suggest the potential anti-inflammatory effect of PVP-I on bacterial or viral infection.

Advances in treatment of acute sulfur mustard poisoning - a critical review

Sulfur mustard (SM) is a blistering chemical warfare agent that was used during the World War I and in the Iraq-Iran conflict. The aim of this paper is to discuss and critically review the published results of experiments on the treatment of SM poisoning based on our clinical and research experience. The victims must remove from the contaminated zone immediately. The best solution for decontamination is large amounts of water, using neutral soap and 0.5% sodium hypochlorite. Severely intoxicated patients should be treated according to advanced life support protocols and intensive care therapy for respiratory disorders and the chemical burn. Sodium thiosulfate infusion (100-500 mg/kg/min) should be started up to 60 min after SM exposure. However, N-acetyle cysteine (NAC) is recommended, none of them acts as specific or effective antidote. The important protective and conservative treatment of SM-induced pulmonary injuries include humidified oxygen, bronchodilators, NAC as muculytic, rehydration, mechanical ventilation, appropriate antibiotics and respiratory physiotherapy as clinically indicated. Treatment of acute SM ocular lesions start with topical antibiotics; preferably sulfacetamide eye drop, continue with lubricants, and artificial tears. Treatment for cutaneous injuries include: moist dressing; preferably with silver sulfadiazine cream, analgesic, anti-pruritic, physically debridement, debridase, Laser debridement, followed by skin autologous split-thickness therapy as clinically indicated. The new suggested medications and therapeutic approaches include: anti-inflammatory agents, Niacinamide, Silibinin, Calmodulin antagonists, Clobetasol, full-thickness skin grafting for skin injuries; Doxycycline; Bevacizumab, and Colchicine for ocular injuries. Recommended compounds based on animal studies include Niacinamide, Aprotinin, des-aspartate-angiotensin-I, Gamma-glutamyltransferase, vitamin E, and vitamin D. In vitro studies revealed that Dimethylthiourea, L-nitroarginine, Methyl-ester, Sodium pyruvate, Butylated hydroxyanisole, ethacrynic acid, and macrolide antibiotics are effective. However, none of them, except macrolide antibiotics have been proved clinically. Avoidance of inappropriate polypharmacy is advisable.

Fluoride Exposure Induces Inhibition of Sodium/Iodide Symporter (NIS) Contributing to Impaired Iodine Absorption and Iodine Deficiency: Molecular Mechanisms of Inhibition and Implications for Public Health

The sodium iodide symporter (NIS) is the plasma membrane glycoprotein that mediates active iodide transport in the thyroid and other tissues, such as the salivary, gastric mucosa, rectal mucosa, bronchial mucosa, placenta and mammary glands. In the thyroid, NIS mediates the uptake and accumulation of iodine and its activity is crucial for the development of the central nervous system and disease prevention. Since the discovery of NIS in 1996, research has further shown that NIS functionality and iodine transport is dependent on the activity of the sodium potassium activated adenosine 5'-triphosphatase pump (Na+, K+-ATPase). In this article, I review the molecular mechanisms by which F inhibits NIS expression and functionality which in turn contributes to impaired iodide absorption, diminished iodide-concentrating ability and iodine deficiency disorders. I discuss how NIS expression and activity is inhibited by thyroglobulin (Tg), tumour necrosis factor alpha (TNF-α), transforming growth factor beta 1 (TGF-β1), interleukin 6 (IL-6) and Interleukin 1 beta (IL-1β), interferon-γ (IFN-γ), insulin like growth factor 1 (IGF-1) and phosphoinositide 3-kinase (PI3K) and how fluoride upregulates expression and activity of these biomarkers. I further describe the crucial role of prolactin and megalin in regulation of NIS expression and iodine homeostasis and the effect of fluoride in down regulating prolactin and megalin expression. Among many other issues, I discuss the potential conflict between public health policies such as water fluoridation and its contribution to iodine deficiency, neurodevelopmental and pathological disorders. Further studies are warranted to examine these associations.

Iodine prevents the increase of testosterone-induced oxidative stress in a model of rat prostatic hyperplasia

Oxidative stress and inflammation are involved in the development and/or progression of benign prostatic hyperplasia (BPH). Molecular iodine (I₂) induces antiproliferative and apoptotic effects in prostate cancer cells, but it is unknown if I₂ regulates oxidative stress in the normal and/or tumoral prostate. The purpose of this study was to analyze the effects of I₂ and celecoxib (Cxb) on oxidative stress and inflammation in a model of prostatic hyperplasia. Cxb was used as positive control of cyclooxygenase-2 (COX-2) inhibition. Prostatic hyperplasia was induced in male Wistar rats (170g) with testosterone (5mg/kg/week, for three weeks). One week before hyperplasia induction, I₂ (25mg/day/rat) or Cxb (1.25mg/day/rat) was supplied for four weeks in the drinking water. Prostatic hyperplasia was evaluated by histological analysis, DNA content, and/or proliferating cell nuclear antigen (PCNA) expression. Lipoperoxidation (malondialdehyde) and nitrite (NO2^-) levels were analyzed by colorimetric methods, while nitric oxide synthase (NOS), COX, and myeloperoxidase (MPO) enzymes were analyzed using RT-PCR, immunoblotting, and/or enzymatic assays. Levels of 15-F2t-isoprostanes, prostaglandins (PGE₂), leukotrienes (LTB₄), and tumor necrosis factor alpha (TNFα) were measured by ELISA. Control testosterone-treated animals exhibited hyperplasia in the dorsolateral prostate, as well as increments in almost all oxidative parameters except for COX-1, TNFα, or MPO. I₂ and Cxb prevented epithelial hyperplasia (DNA content) and oxidative stress induction generated by testosterone in almost the same intensity, and the minimum I₂ dose required was 2.5mg/rat. The antioxidant capacity of I₂ was also analyzed in a cell-free system, showing that this element inhibited the conversion of nitrate (NO₃^-) to NO₂^-. I₂ did not modify the prostatic oxidative state in testosterone untreated rats. In summary, our data showed that antiproliferative and antioxidant effects of I₂ involve the inhibition of NOS and the COX-2 pathway. Further studies are necessary to analyze the therapeutic and/or adjuvant effects of I₂ with first-line medications used to treat BPH.

Sulfur mustard skin lesions: A systematic review on pathomechanisms, treatment options and future research directions

Sulfur mustard (SM) is a chemical warfare, which has been used for one hundred years. However, its exact pathomechanisms are still incompletely understood and there is no specific therapy available so far. In this systematic review, studies published between January 2000 and July 2017 involving pathomechanisms and experimental treatments of SM-induced skin lesions were analyzed to summarize current knowledge on SM pathology, to provide an overview on novel treatment options, and to identify promising targets for future research to more effectively counter SM effects. We suggest that future studies should focus on (I) systemic effects of SM intoxication due to its distribution throughout the body, (II) removal of SM depots that continuously release active compound contributing to chronic skin damage, and (III) therapeutic options that counteract the pleiotropic effects of SM.

A novel role of topical iodine in skin: Activation of the Nrf2 pathway

For a long time iodine has been used as an active dermal agent in the treatment of inflammatory, immune-mediated and infectious diseases. Moreover, topical iodine application has been reported to provide protection against sulfur-mustard-induced skin lesions, heat-induced and acid-induced skin burns in both haired guinea-pigs and mouse ear swelling models. However, the exact mechanism of action underlying these benefits of iodine has not yet been elucidated. In the current study, a novel mechanism of action by which iodine provides skin protection and relief, based on its electrophilic nature, is suggested. This study demonstrates that both iodine and iodide are capable of activating the Nrf2 pathway in human skin. As a result, skin protection against UVB-induced damage was acquired and the secretion of pro-inflammatory cytokines (IL-6, IL-8) from LPS-challenged skin was reduced. Iodide role in the enhanced activation of this pathway is demonstrated. The mode of action by which iodine and iodide activate the Nrf2 pathway is discussed.

Mitigation of nitrogen mustard mediated skin injury by a novel indomethacin bifunctional prodrug

Nitrogen mustard (NM) is a bifunctional alkylating agent that is highly reactive in the skin causing extensive tissue damage and blistering. In the present studies, a modified cutaneous murine patch model was developed to characterize NM-induced injury and to evaluate the efficacy of an indomethacin pro-drug in mitigating toxicity. NM (20μmol) or vehicle control was applied onto 6mm glass microfiber filters affixed to the shaved dorsal skin of CD-1 mice for 6min. This resulted in absorption of approximately 4μmol of NM. NM caused localized skin damage within 1 d, progressing to an eschar within 2-3 d, followed by wound healing after 4-5 d. NM-induced injury was associated with increases in skin thickness, inflammatory cell infiltration, reduced numbers of sebocytes, basal keratinocyte double stranded DNA breaks, as measured by phospho-histone 2A.X expression, mast cell degranulation and increases in inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Wound healing was characterized by epidermal hyperplasia and marked increases in basal cells expressing proliferating cell nuclear antigen. A novel indomethacin-anticholinergic prodrug (4338) designed to target cyclooxygenases and acetylcholinesterase (AChE), was found to markedly suppress NM toxicity, decreasing wound thickness and eschar formation. The prodrug also inhibited mast cell degranulation, suppressed keratinocyte expression of iNOS and COX-2, as well as markers of epidermal proliferation. These findings indicate that a novel bifunctional pro-drug is effective in limiting NM mediated dermal injury. Moreover, our newly developed cutaneous patch model is a sensitive and reproducible method to assess the mechanism of action of countermeasures.

Protective role of spleen-derived macrophages in lung inflammation, injury, and fibrosis induced by nitrogen mustard

Nitrogen mustard (NM) is a vesicant that causes lung injury and fibrosis, accompanied by a persistent macrophage inflammatory response. In these studies we analyzed the spleen as a source of these cells. Splenectomized (SPX) and sham control rats were treated intratracheally with NM (0.125 mg/kg) or PBS control. Macrophage responses were analyzed 1-7 days later. Splenectomy resulted in an increase in lung macrophages expressing CCR2, but a decrease in ATR-1α(+) cells, receptors important in bone marrow and spleen monocyte trafficking, respectively. Splenectomy was also associated with an increase in proinflammatory M1 (iNOS(+), CD11b(+)CD43(+)) macrophages in lungs of NM-treated rats, as well as greater upregulation of iNOS and COX-2 mRNA expression. Conversely, a decrease in CD11b(+)CD43(-) M2 macrophages was observed in SPX rats, with no changes in CD68(+), CD163(+), CD206(+), or YM-1(+) M2 macrophages, suggesting distinct origins of M2 subpopulations responding to NM. Macrophage expression of M2 genes including IL-10, ApoE, PTX-2, PTX-3, 5-HT2α, and 5-HT7 was also reduced in NM-treated SPX rats compared with shams, indicating impaired M2 activity. Changes in lung macrophages responding to NM as a consequence of splenectomy were correlated with exacerbated tissue injury and more rapid fibrogenesis. These data demonstrate that the spleen is a source of a subset of M2 macrophages with anti-inflammatory activity; moreover, in their absence, proinflammatory/cytotoxic M1 macrophages predominate in the lung, resulting in heightened pathology. Understanding the origin of macrophages and characterizing their phenotype after vesicant exposure may lead to more targeted therapeutics aimed at reducing toxicity and disease pathogenesis.

Nitrogen mustard exposure of murine skin induces DNA damage, oxidative stress and activation of MAPK/Akt-AP1 pathway leading to induction of inflammatory and proteolytic mediators

Our recent studies in SKH-1 hairless mice have demonstrated that topical exposure to nitrogen mustard (NM), an analog of sulfur mustard (SM), triggers the inflammatory response, microvesication and apoptotic cell death. Here, we sought to identify the mechanism/s involved in these NM-induced injury responses. Results obtained show that NM exposure of SKH-1 hairless mouse skin caused H2A.X and p53 phosphorylation and increased p53 accumulation, indicating DNA damage. In addition, NM also induced the activation of MAPKs/ERK1/2, JNK1/2 and p38 as well as that of Akt together with the activation of transcription factor AP1. Also, NM exposure induced robust expression of pro-inflammatory mediators namely cyclooxygenase 2 and inducible nitric oxide synthase and cytokine tumor necrosis factor alpha, and increased the levels of proteolytic mediator matrix metalloproteinase 9. NM exposure of skin also increased lipid peroxidation, 5,5-dimethyl-2-(8-octanoic acid)-1-pyrroline N-oxide protein adduct formation, protein and DNA oxidation indicating an elevated oxidative stress. We also found NM-induced increase in the homologous recombinant repair pathway, suggesting its involvement in the repair of NM-induced DNA damage. Collectively, these results indicate that NM induces oxidative stress, mainly a bi-phasic response in DNA damage and activation of MAPK and Akt pathways, which activate transcription factor AP1 and induce the expression of inflammatory and proteolytic mediators, contributing to the skin injury response by NM. In conclusion, this study for the first time links NM-induced mechanistic changes with our earlier reported murine skin injury lesions with NM, which could be valuable to identify potential therapeutic targets and rescue agents.

Flavanone silibinin treatment attenuates nitrogen mustard-induced toxic effects in mouse skin

Currently, there is no effective antidote to prevent skin injuries by sulfur mustard (SM) and nitrogen mustard (NM), which are vesicating agents with potential relevance to chemical warfare, terrorist attacks, or industrial/laboratory accidents. Our earlier report has demonstrated the therapeutic efficacy of silibinin, a natural flavanone, in reversing monofunctional alkylating SM analog 2-chloroethyl ethyl sulfide-induced toxic effects in mouse skin. To translate this effect to a bifunctional alkylating vesicant, herein, efficacy studies were carried out with NM. Topical application of silibinin (1 or 2mg) 30 min after NM exposure on the dorsal skin of male SKH-1 hairless mice significantly decreased NM-induced toxic lesions at 24, 72 or 120 h post-exposure. Specifically, silibinin treatment resulted in dose-dependent reduction of NM-induced increase in epidermal thickness, dead and denuded epidermis, parakeratosis and microvesication. Higher silibinin dose also caused a 79% and 51%reversal in NM-induced increases in myeloperoxidase activity and COX-2 levels, respectively. Furthermore, silibinin completely prevented NM-induced H2A.X phosphorylation, indicating reversal of DNA damage which could be an oxidative DNA damage as evidenced by high levels of 8-oxodG in NM-exposed mouse skin that was significantly reversed by silibinin. Together, these findings suggest that attenuation of NM-induced skin injury by silibinin is due to its effects on the pathways associated with DNA damage, inflammation, vesication and oxidative stress. In conclusion, results presented here support the optimization of silibinin as an effective treatment of skin injury by vesicants.

Time course of skin features and inflammatory biomarkers after liquid sulfur mustard exposure in SKH-1 hairless mice

Sulfur mustard (SM) is a strong bifunctional alkylating agent that produces severe tissue injuries characterized by erythema, edema, subepidermal blisters and a delayed inflammatory response after cutaneous exposure. However, despite its long history, SM remains a threat because of the lack of effective medical countermeasures as the molecular mechanisms of these events remain unclear. This limited number of therapeutic options results in part of an absence of appropriate animal models. We propose here to use SKH-1 hairless mouse as the appropriate model for the design of therapeutic strategies against SM-induced skin toxicity. In the present study particular emphasis was placed on histopathological changes associated with inflammatory responses after topical exposure of dorsal skin to three different doses of SM (0.6, 6 and 60mg/kg) corresponding to a superficial, a second-degree and a third-degree burn. Firstly, clinical evaluation of SM-induced skin lesions using non invasive bioengineering methods showed that erythema and impairment of skin barrier increased in a dose-dependent manner. Histological evaluation of skin sections exposed to SM revealed that the time to onset and the severity of symptoms including disorganization of epidermal basal cells, number of pyknotic nuclei, activation of mast cells and neutrophils dermal invasion were dose-dependent. These histopathological changes were associated with a dose- and time-dependent increase in expression of specific mRNA for inflammatory mediators such as interleukins (IL1β and IL6), tumor necrosis factor (TNF)-α, cycloxygenase-2 (COX-2), macrophage inflammatory proteins (MIP-1α, MIP-2 and MIP-1αR) and keratinocyte chemoattractant (KC also called CXCL1) as well as adhesion molecules (L-selectin and vascular cell adhesion molecule (VCAM)) and growth factor (granulocyte colony-stimulating factor (Csf3)). A dose-dependent increase was also noted after SM exposure for mRNA of matrix metalloproteinases (MMP9) and laminin-γ2 which are associated with SM-induced blisters formation. Taken together, our results show that SM-induced skin histopathological changes related to inflammation is similar in SKH-1 hairless mice and humans. SKH-1 mouse is thus a reliable animal model for investigating the SM-induced skin toxicity and to develop efficient treatment against SM-induced inflammatory skin lesions.

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

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

Uptake and antitumoral effects of iodine and 6-iodolactone in differentiated and undifferentiated human prostate cancer cell lines

BACKGROUND

Evidence indicates that iodine per se could be implicated in the physiology of several organs that can internalize it. In thyroid and breast cancer, iodine treatments inhibit cell proliferation and induce apoptosis through a direct (mitochondria) and/or indirect effect (iodolipid generation). Here, we determined the uptake of iodide (I(-) ) and iodine (I(2) ), as well as the antiproliferative and apoptotic effects of 6-iodolactone (6-IL) and both forms of iodine in human prostate cells lines.

METHODS

Non-cancerous (RWPE-1) and cancerous (LNCaP, DU-145) cells, as well as nude mice xenotransplanted with DU-145 cells were used as cancer models. Iodine uptake was analyzed with radioactive tracers, transporter expression by qRT-PCR, cell proliferation by blue trypan, apoptosis by enzyme immunoassay or fluorescence, BAX and BCL-2 by western-blot, and caspsase 3 by enzymatic assay.

RESULTS

All three cell lines take up both forms of iodine. In RWPE-1 cells, I(-) uptake depends on the Na(+) /I(-) symporter (NIS), whereas it was independent of NIS in LNCaP and DU-145 cells. Antiproliferative effects of iodine and 6-IL were dose and time dependent; RWPE-1 was most sensitive to I(-) and 6-IL, whereas LNCaP was more sensitive to I(2) . In the three cell lines both forms of iodine activated the intrinsic apoptotic pathway (increasing the BAX/BCL-2 index and caspases). Iodine supplementation impaired growth of the DU-145 tumor in nude mice.

CONCLUSION

Normal and cancerous prostate cells can take up iodine, and depending on the chemical form, it exerts antiproliferative and apoptotic effects both in vitro and in vivo.

Characterization of acute and long-term pathologies of superficial and deep dermal sulfur mustard skin lesions in the hairless guinea pig model

Sulfur mustard induces severe acute and prolonged damage to the skin and only partially effective treatments are available. We have previously validated the use of hairless guinea pigs as an experimental model for skin lesions. The present study aimed to characterize a model of a deep dermal lesion and to compare it with the previously described superficial lesion. Clinical evaluation of the lesions was conducted using reflectance colorimetry, trans-epidermal water loss and wound area measurements. Prostaglandin E(2) content, matrix metalloproteinase-2 and 9 activity, and histopathology were conducted up to 4 weeks post-exposure. Sulfur mustard skin injury, including erythema and edema, impairment of skin barrier and wounds developed in a dose-dependent manner. Prostaglandin E(2) content and matrix metalloproteinase-2 and 9 activities were elevated during the wound development and the healing process. Histological evaluation revealed severe damage to the epidermis and deep dermis and vesications. At 4 weeks postexposure, healing was not completed: significantly impaired stratum corneum, absence of hair follicles, and epidermal hyperplasia were observed. These results confirm the use of the superficial and deep dermal skin injuries in the hairless guinea pigs as suitable models that can be utilized for the investigation of the pathological processes of acute as well as long-term injuries. These models will be further used to develop treatments to improve the healing process and prevent skin damage and long-term effects.

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

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

Sulfur mustard analog, 2-chloroethyl ethyl sulfide-induced skin injury involves DNA damage and induction of inflammatory mediators, in part via oxidative stress, in SKH-1 hairless mouse skin

Bifunctional alkyalating agent, sulfur mustard (SM)-induced cutaneous injury is characterized by inflammation and delayed blistering. Our recent studies demonstrated that 2-chloroethyl ethyl sulfide (CEES), a monofunctional analog of SM that can be used in laboratory settings, induces oxidative stress. This could be the major cause of the activation of Akt/MAP kinase and AP1/NF-κB pathways that are linked to the inflammation and microvesication, and histopathological alterations in SKH-1 hairless mouse skin. To further establish a link between CEES-induced DNA damage and signaling pathways and inflammatory responses, skin samples from mice exposed to 2 mg or 4 mg CEES for 9-48 h were subjected to molecular analysis. Our results show a strong CEES-induced phosphorylation of H2A.X and an increase in cyclooxygenase-2 (COX-2), inducible NOS (iNOS), and matrix metalloproteinase-9 (MMP-9) levels, indicating the involvement of DNA damage and inflammation in CEES-induced skin injury in male and female mice. Since, our recent studies showed reduction in CEES-induced inflammatory responses by glutathione (GSH), we further assessed the role of oxidative stress in CEES-related DNA damage and the induction of inflammatory molecules. Oral GSH (300 mg/kg) administration 1h before CEES exposure attenuated the increase in both CEES-induced H2A.X phosphorylation (59%) as well as expression of COX-2 (68%), iNOS (53%) and MMP-9 (54%). Collectively, our results indicate that CEES-induced skin injury involves DNA damage and an induction of inflammatory mediators, at least in part via oxidative stress. This study could help in identifying countermeasures that alone or in combination, can target the unveiled pathways for reducing skin injury in humans by SM.

Structural changes in the skin of hairless mice following exposure to sulfur mustard correlate with inflammation and DNA damage

Sulfur mustard (SM, bis(2-chloroethyl)sulfide) is a bifunctional alkylating agent that causes dermal inflammation, edema and blistering. To investigate the pathogenesis of SM-induced injury, we used a vapor cup model which provides an occlusive environment in which SM is in constant contact with the skin. The dorsal skin of SKH-1 hairless mice was exposed to saturated SM vapor or air control. Histopathological changes, inflammatory markers and DNA damage were analyzed 1-14 days later. After 1 day, SM caused epidermal thinning, stratum corneum shedding, basal cell karyolysis, hemorrhage and macrophage and neutrophil accumulation in the dermis. Cleaved caspase-3 and phosphorylated histone 2A.X (phospho-H2A.X), markers of apoptosis and DNA damage, respectively, were increased whereas proliferating cell nuclear antigen (PCNA) was down-regulated after SM exposure. By 3 days, epithelial cell hypertrophy, edema, parakeratosis and loss of epidermal structures were noted. Enzymes generating pro-inflammatory mediators including myeloperoxidase and cyclooxygenase-2 were upregulated. After 7 days, keratin-10, a differentiation marker, was evident in the stratum corneum. This was associated with an underlying eschar, as neoepidermis began to migrate at the wound edges. Trichrome staining revealed increased collagen deposition in the dermis. PCNA expression in the epidermis was correlated with hyperplasia, hyperkeratosis, and parakeratosis. By 14 days, there was epidermal regeneration with extensive hyperplasia, and reduced expression of cleaved caspase-3, cyclooxygenase-2 and phospho-H2A.X. These findings are consistent with the pathophysiology of SM-induced skin injury in humans suggesting that the hairless mouse can be used to investigate the dermatoxicity of vesicants and the potential efficacy of countermeasures.

Sulfur mustard toxicity: history, chemistry, pharmacokinetics, and pharmacodynamics

Sulfur mustard (SM) and similar bifunctional agents have been used as chemical weapons for almost 100 years. Victims of high-dose exposure, both combatants and civilians, may die within hours or weeks, but low-dose exposure causes both acute injury to the eyes, skin, respiratory tract and other parts of the body, and chronic sequelae in these organs are often debilitating and have a serious impact on quality of life. Ever since they were first used in warfare in 1917, SM and other mustard agents have been the subjects of intensive research, and their chemistry, pharmacokinetics and mechanisms of toxic action are now fairly well understood. In the present article we review this knowledge and relate the molecular-biological basis of SM toxicity, as far as it has been elucidated, to the pathological effects on exposure victims.

Lipopolysaccharide induced protection against sulfur mustard cytotoxicity in RAW264.7 cells through generation of TNF-alpha

Sulfur mustard (HD), a very potent alkylating agent and lipopolysacchride (LPS), are both well characterized inflammatory factors. We have found that concomitant exposure of murine macrophage cells (RAW264.7) to LPS and HD induced protection against HD induced cytotoxicity. Both HD and LPS induce release of inflammatory markers in RAW264.7 cells. However, there are marked differences in the repertoire of inflammatory factors released by the two toxins: While exposure to HD, induced a dose-dependant death of these cells, no significant change in survival rate was observed following LPS (1-100 ng/ml) exposure. Additionally, LPS elicited a robust nitric oxide (NO) and TNF-alpha secretion whereas HD was practically ineffective. Both toxins increased PGE(2) secretion in a concentration dependent manner. Treatment of HD-exposed RAW264.7 cells with anti-inflammatory drugs such as dexamethazone (5 muM), voltaren (diclofenac) (8 muM) or doxycycline (5 muM), decreased the release of cytokines but had no effect on cell viability. Simultaneous application of LPS (100 ng/ml) and HD (20-100 muM) resulted in an amelioration of HD cytotoxicity. Adding the NO generator S-nitrosoglutathione (GSNO) or inhibiting NO production using L-N(G)-monomethyl Arginine, had no effect on cell viability. Moreover, addition of PGE(2) (20 ng/ml) failed to induce any changes in cell viability under basal or HD-induced toxicity. In contrast, TNF-alpha (20 ng/ml) provided remarkable protection against HD-induced cell death. These findings strongly suggest that LPS exerts its protective action against HD toxicity through the generation of TNF-alpha and may provide better understanding of the mechanism of cytoprotection.

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.

Oxidants and antioxidants in sulfur mustard-induced injury

Sulfur mustard (SM) is a chemical weapon that targets the skin, eyes, and lung. It was first employed during World War I and it remains a significant military and civilian threat. As a bifunctional alkylating agent, SM reacts with a variety of macromolecules in target tissues including nucleic acids, proteins and lipids, as well as small molecular weight metabolites such as glutathione. By alkylating subcellular components, SM disrupts metabolism, a process that can lead to oxidative stress. Evidence for oxidative stress in tissues exposed to SM or its analogs include increased formation of reactive oxygen species, the presence of lipid peroxidation products and oxidized proteins, and increases in antioxidant enzymes such as superoxide dismutase, catalase, and glutathione-S-transferase. Inhibition of antioxidant enzymes including thioredoxin reductase by SM can also disrupt cellular redox homeostasis. Consistent with these findings, SM-induced toxicity has been shown to be reduced by antioxidants in both in vitro and in vivo models. These data indicate that drugs that target oxidative stress pathways may represent important candidates for reducing SM-induced tissue injury.

Inflammatory effects of inhaled sulfur mustard in rat lung

Inhalation of sulfur mustard (SM), a bifunctional alkylating agent that causes severe lung damage, is a significant threat to both military and civilian populations. The mechanisms mediating its cytotoxic effects are unknown and were investigated in the present studies. Male rats Crl:CD(SD) were anesthetized, and then intratracheally intubated and exposed to 0.7-1.4mg/kg SM by vapor inhalation. Animals were euthanized 6, 24, 48h or 7days post-exposure and bronchoalveolar lavage fluid (BAL) and lung tissue collected. Exposure of rats to SM resulted in rapid pulmonary toxicity, including focal ulceration and detachment of the trachea and bronchial epithelia from underlying mucosa, thickening of alveolar septal walls and increased numbers of inflammatory cells in the tissue. There was also evidence of autophagy and apoptosis in the tissue. This was correlated with increased BAL protein content, a marker of injury to the alveolar epithelial lining. SM exposure also resulted in increased expression of markers of inflammation including cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNFα), inducible nitric oxide synthase (iNOS), and matrix metalloproteinase-9 (MMP-9), each of which has been implicated in pulmonary toxicity. Whereas COX-2, TNFα and iNOS were mainly localized in alveolar regions, MMP-9 was prominent in bronchial epithelium. In contrast, expression of the anti-oxidant hemeoxygenase, and the anti-inflammatory collectin, surfactant protein-D, decreased in the lung after SM exposure. These data demonstrate that SM-induced oxidative stress and injury are associated with the generation of cytotoxic inflammatory proteins which may contribute to the pathogenic response to this vesicant.

Role of MAP kinases in regulating expression of antioxidants and inflammatory mediators in mouse keratinocytes following exposure to the half mustard, 2-chloroethyl ethyl sulfide

Dermal exposure to sulfur mustard causes inflammation and tissue injury. This is associated with changes in expression of antioxidants and eicosanoids which contribute to oxidative stress and toxicity. In the present studies we analyzed mechanisms regulating expression of these mediators using an in vitro skin construct model in which mouse keratinocytes were grown at an air-liquid interface and exposed directly to 2-chloroethyl ethyl sulfide (CEES), a model sulfur mustard vesicant. CEES (100-1000 microM) was found to cause marked increases in keratinocyte protein carbonyls, a marker of oxidative stress. This was correlated with increases in expression of Cu,Zn superoxide dismutase, catalase, thioredoxin reductase and the glutathione S-transferases, GSTA1-2, GSTP1 and mGST2. CEES also upregulated several enzymes important in the synthesis of prostaglandins and leukotrienes including cyclooxygenase-2 (COX-2), microsomal prostaglandin E synthase-2 (mPGES-2), prostaglandin D synthase (PGDS), 5-lipoxygenase (5-LOX), leukotriene A(4) (LTA(4)) hydrolase and leukotriene C(4) (LTC(4)) synthase. CEES readily activated keratinocyte JNK and p38 MAP kinases, signaling pathways which are known to regulate expression of antioxidants, as well as prostaglandin and leukotriene synthases. Inhibition of p38 MAP kinase suppressed CEES-induced expression of GSTA1-2, COX-2, mPGES-2, PGDS, 5-LOX, LTA(4) hydrolase and LTC(4) synthase, while JNK inhibition blocked PGDS and GSTP1. These data indicate that CEES modulates expression of antioxidants and enzymes producing inflammatory mediators by distinct mechanisms. Increases in antioxidants may be an adaptive process to limit tissue damage. Inhibiting the capacity of keratinocytes to generate eicosanoids may be important in limiting inflammation and protecting the skin from vesicant-induced oxidative stress and 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.

Sulfur mustard downregulates iNOS expression to inhibit wound healing in a human keratinocyte model

BACKGROUND

Increased nitric oxide (NO) synthesized by inducible NO synthase (iNOS) is involved in inflammatory and pathological conditions. iNOS also regulates several biomarkers that accelerate normal wound healing. Effects of exposure to sulfur mustard (SM) on the skin include formation of blisters and slow-healing injuries. Promoting re-epithelialization is a challenging issue in the treatment of the delayed healing of SM-induced skin injuries.

OBJECTIVES

To clarify the role(s) of iNOS in wound healing and the effect of SM on iNOS expression in an in vitro wound assay to eventually develop therapies for SM skin injuries.

METHODS

A wound was created by scratching normal human epidermal keratinocytes grown in vitro. iNOS expression was monitored by Western blotting, fluorescence microscopy, and real-time RT-PCR. Wound healing was analyzed using digitalized image analysis software.

RESULTS

The level of iNOS peaked 24-48h after wounding. SM exposure strongly reduced iNOS protein and mRNA levels. Fluorescence microscopy revealed that induction of iNOS expression by wounding and inhibition of iNOS expression by SM occurred not only in the cells at the wound edge but also in cells in the surrounding area, suggesting that wounding may induce and SM may inhibit release of cytokines that stimulate iNOS expression. iNOS-specific small interfering RNAs caused a marked decrease of iNOS expression irrespective of wounding. Gene silencing also completely inhibited wound healing.

CONCLUSION

These results suggest that preventing SM-induced inhibition of iNOS may be a prospective strategy to promote wound healing in SM-exposed skin.

Early effects of iodine on DNA synthesis in sulfur mustard-induced skin lesions

Sulfur mustard (SM) is powerful alkylator and highly cytotoxic blisterogen in both humans and animals. This study in male guinea pigs shows that, at an early stage (5 h) after SM exposure, a marked increase occurred in epithelial nuclear vacuolation, epidermal thickening, and dermal acute inflammation. Topical iodine treatment reduced the severity of these parameters. The rate of DNA synthesis expressed by incorporation of bromodeoxyuridine was reduced upon topical treatment with iodine only or SM only by 46 and 72%, respectively. Iodine treatment following SM exposure exerted an effect similar to that of SM only, indicating that DNA synthesis is not directly involved in the mechanism of action of iodine-induced protection.

Molecular targets against mustard toxicity: implication of cell surface receptors, peroxynitrite production, and PARP activation

Despite many years of research into chemical warfare agents, cytotoxic mechanisms induced by mustards are not well understood. Reactive oxygen and nitrogen species (ROS and RNS) are likely to be involved in chemical warfare agents induced toxicity. These species lead to lipid peroxidation, protein oxidation, and DNA injury, and trigger many pathophysiological processes that harm the organism. In this article, several steps of pathophysiological mechanisms and possible ways of protection against chemical warfare agents have been discussed. In summary, pathogenesis of mustard toxicity is explained by three steps: (1) mustard binds target cell surface receptor, (2) activates intracellular ROS and RNS leading to peroxynitrite (ONOO(-)) production, and (3) the increased ONOO(-) level damages organic molecules (lipids, proteins, and DNA) leading to poly(adenosine diphosphate-ribose) polymerase (PARP) activation. Therefore, protection against mustard toxicity could also be performed in these ways: (1) blocking of cell surface receptor, (2) inhibiting the ONOO(-) production or scavenging the ONOO(-) produced, and (3) inhibiting the PARP, activated by ONOO(-) and hydroxyl radical (OH(*)) induced DNA damage. As conclusion, to be really effective, treatment against mustards must take all molecular mechanisms of cytotoxicity into account. Combination of several individual potent agents, each blocking one of the toxic mechanisms induced by mustards, would be interesting. Therefore, variations of combination of cell membrane receptor blockers, antioxidants, nitric oxide synthase inhibitors, ONOO(-) scavengers, and PARP inhibitors should be investigated.

Involvement of tumor necrosis factor-alpha in sulfur mustard-induced skin lesion; effect of topical iodine

Sulfur mustard (SM), also termed mustard gas, is a potent vesicant that elicits an inflammatory response upon exposure of the skin. Evaluation of mouse ear 3 h after SM exposure revealed acute inflammatory-cell aggregates in the vascular beds accompanied by strongly TNF-alpha-positive neutrophils. Eight hours after SM exposure, this phenomenon became intensified and associated with infiltration into the adjacent dermis. In ear skin topically treated with iodine, however, no inflammatory cells were observed 3 h after SM exposure; 8 h postexposure, blood vessels contained very few TNF-alpha-positive inflammatory cells. Since TNF-alpha induction was shown to be associated with reactive oxygen species production, we studied the effect of iodine on activated peritoneal mouse neutrophils. Iodine elicited a concentration-dependent reduction in the oxidative burst of activated neutrophils. Iodine also scavenged hydroxyl radicals generated by glucose oxidase in a concentration-dependent manner. The involvement of TNF-alpha in SM-induced skin toxicity was confirmed by reduction of 49 and 30% in ear edema following administration of 1 and 2 mug anti-TNF-alpha antibodies, respectively. These findings were corroborated by quantitative analysis of the histological findings showing 46% reduction in acute inflammation and no signs of subacute inflammation in the treated group, in contrast to the control group treated with SM only. Other epidermal (microblister formation, ulceration, and necrosis) and dermal (neutrophilia, hemorrhage, and necrosis) parameters also showed marked reductions in the antibodies-treated group in comparison to controls. The combination of iodine and antiTNF-alpha antibodies might constitute a new approach for treatment of SM-exposed individuals.

Effect of doxycycline on sulfur mustard-induced respiratory lesions in guinea pigs

Respiratory tract lesions induced by the chemical warfare agent sulfur mustard (SM) are characterized by epithelial damages associated with inflammatory cell infiltration. Here we evaluated the imbalance between gelatinase and tissue inhibitors of metalloproteinases (TIMPs), and we tested pretreatment with the protease inhibitor doxycycline. Guinea pigs were intoxicated intratracheally with SM and evaluated 24 h after exposure. Matrix metalloproteinase (MMP) gelatinase activity of bronchial lavage (BL) fluid from SM-exposed guinea pigs was high compared with controls, as shown by both zymography and biotinylated substrate degradation, whereas TIMP-1 and -2 levels by immunoblotting were similar. Extensive areas of lysis were evidenced by in situ zymography, indicating imbalance between gelatinases and inhibitors towards net proteolytic activity. Doxycycline pretreatment resulted in 1) decreased gelatinase activity (zymography, free gelatinase activity assay, and in situ zymography); 2) decreased inflammation (BL fluid cellularity and protein level); and 3) dramatic decrease in histological epithelial lesions. Our results suggest inadequate levels of TIMP to counteract increased gelatinase activity and further support a role for MMP gelatinases in SM-induced respiratory lesions. They also suggest that doxycycline may hold promise as a therapeutic tool.

Acute and subacute dermal toxicity of Break-Free CLP®: a weapons cleaning and maintenance compound

Break-Free CLP((R)) is a commercial cleaning, lubricating and preserving compound used in both the military and civilian sectors for maintenance of small- and large-caliber weapons. Like many commercial mixtures, there is very little information available on the toxicity of Break-Free CLP. Studies were conducted to characterize the biological effects of single or repeat dermal application of Break-Free CLP to the clipped backs of CD-1 mice. Break-Free CLP was applied neat, 50 microl three times of week for up to 2 weeks. Foci of epithelial ulceration were observed in skin sections from 22% of Break-Free CLP-treated animals in conjunction with markedly thickened epithelium suggesting that robust epithelial regeneration was occurring in these animals. Skin histopathology of Break-Free CLP-treated animals closely matched the histopathology from mice treated repeatedly with 2% croton oil in acetone (dermal irritation positive control). Serum alkaline phosphatase activity was significantly (P < 0.05) lower for mice treated with Break-Free CLP, 2% croton oil or 7,12-dimethylbenz[a]anthracene (DMBA) compared with negative and vehicle control mice. Skin nitric oxide (NO) levels were not significantly elevated for mice treated with Break-Free CLP but were significantly elevated for mice treated with dermal irritation positive control compound DMBA. The cumulative skin changes in Break-Free CLP-treated animals support conducting a subchronic dermal application study. The observed decreases in serum alkaline phosphatase activity suggest that future studies should include the liver and bone as possible target organs. Additionally, dermal penetration studies could provide key health risk assessment information for characterizing the potential health risks associated with chronic dermal exposure to Break-Free CLP.

Reduced sulfur mustard-induced skin toxicity in cyclooxygenase-2 knockout and celecoxib-treated mice

Sulfur mustard (SM), a potent vesicant and chemical warfare agent, induces tissue damage involving an inflammatory response, including vasodilatation, polymorphonuclear infiltration, production of inflammatory mediators, and cyclooxygenase activity. To evaluate the role of cyclooxygenase-1 and -2 (COX-1, COX-2) in sulfur mustard-induced skin toxicity, we applied the agent to the ears of wildtype (WT) and COX-1- and COX-2-deficient mice. In the latter, ear swelling 24 and 48 h after exposure was significantly reduced (P < 0.05) by 55% and 30%, respectively, compared to WT. Quantitative histopathology revealed no epidermal ulceration in COX-2-deficient mice but some degree of severity in WT. COX-2-deficient mice showed significant reductions (P < 0.05) in severity of epidermal necrosis (29%), acute inflammation (42%), and hemorrhage (25%), compared to the WT mice. COX-1 deficiency resulted in significant exacerbation (P < 0.05) in severity of some parameters, including increases of 4.6- and 1.2-fold in epidermal ulceration and epidermal necrosis, respectively, compared to WT. Postexposure treatment of normal male ICR mice with the selective COX-2 inhibitor celecoxib resulted in significant reductions of 27% (P < 0.05) and 28% (P < 0.01) in ear swelling at intervals of 40 and 60 min between exposure and treatment, respectively. Histopathological evaluation revealed significant reductions (P < 0.05) in subepidermal microblister formation (73%) and dermal necrosis (32%), compared to the control group. These findings may indicate that COX-2 participates in the early stages of sulfur mustard-induced acute skin toxicity and that COX-1 might exert some protective function against this chemical insult.

Degradation of VX and sulfur mustard by enzymatic haloperoxidation

Chloroperoxidase (CPO) isolated from Caldariomyces fumago (20 U ml(-1)) together with urea hydrogenperoxide (UPER, 0.5 mM) and sodium chloride as co-substrate (NaCl, 0.5 M) caused rapid breakdown of VX (10 microM) (t((1/2)) = 8 s, 25 C, 50 mM tartarate, pH 2.75). Glucose oxidase (GOX, Aspergillus niger) and glucose were used as an alternative source for H(2)O(2). A mixture of GOX (20 U ml(-1)), glucose (GLU 0.45 M), CPO (20 U ml(-1)) and NaCl (0.5 M) caused a 3.8-fold slower degradation of VX (10 microM) (t((1/2)) = 30 s, 25 C, 50 mM tartarate, pH 2.75). The concentrations of H(2)O(2) and chlorine produced by this enzyme/substrate mixture depended mainly on the GLU concentration. Horseradish peroxidase (HRP) together with UPER (1 mM) and sodium iodide (NaI, 0.05 M) caused progressive degradation of VX that was more than 400-fold slower than with CPO (20 U ml(-1)), UPER (0.5 mM) and NaCl (0.5 M) (t((1/2)) = 55 min, 25 C, pH 8). Skin decontamination of VX by CPO was tested in pig-ear skin in vitro. The chemical agent VX (0.01 M, 100 microl) was degraded by 98% within 3 h of skin diffusion when a mixture of UPER/NaCl/CPO was applied 60 min prior to VX application. A mixture of UPER/NaCl without CPO also caused significant VX degradation (94%) during skin diffusion whereas it did not cause any VX degradation in solution. Degradation of VX in skin, obtained without exogenous CPO, may indicate involvement of endogenous intradermal haloperoxidase-like enzyme. Reagent UPER (1 mM) did not cause any degradation of VX in solution or during its skin diffusion. Furthermore, a mixture of CPO, UPER and NaCl caused rapid degradation of sulfur mustard (HD). Sulfur mustard (50 microM) incubated in the presence of CPO (4 U ml(-1)), UPER (0.05 M) and NaCl (0.5 M) at pH 2.75 and 30 C was oxidized by 97% and 99% within 5 and 10 min, respectively. The oxidation products HD sulfoxide, HD sulfone and HD sulfoxidevinyl were identified by GC/MS in the enzymatic chloroperoxidation mixture.