The cytokines NAP-1 (IL-8), MCP-1, IL-1 beta, and GRO in rabbit inflammatory skin lesions produced by the chemical irritant sulfur mustard

Skin Models Used to Define Mechanisms of Action of Sulfur Mustard

Sulfur mustard (SM) is a threat to both civilian and military populations. Human skin is highly sensitive to SM, causing delayed erythema, edema, and inflammatory cell infiltration, followed by the appearance of large fluid-filled blisters. Skin wound repair is prolonged following blistering, which can result in impaired barrier function. Key to understanding the action of SM in the skin is the development of animal models that have a pathophysiology comparable to humans such that quantitative assessments of therapeutic drugs efficacy can be assessed. Two animal models, hairless guinea pigs and swine, are preferred to evaluate dermal products because their skin is morphologically similar to human skin. In these animal models, SM induces degradation of epidermal and dermal tissues but does not induce overt blistering, only microblistering. Mechanisms of wound healing are distinct in these animal models. Whereas a guinea pig heals by contraction, swine skin, like humans, heals by re-epithelialization. Mice, rats, and rabbits are also used for SM mechanistic studies. However, healing is also mediated by contraction; moreover, only microblistering is observed. Improvements in animal models are essential for the development of therapeutics to mitigate toxicity resulting from dermal exposure to SM.

Clinical and Instrumental Exploration of Sensitive Skin in a Pediatric Population

Studies on sensitive skin pathophysiology in infants are challenging because most assessment methods require self-reporting of signs. In this study, we aimed to identify and characterize sensitive skin in children for the first time. A newly developed parent-reported questionnaire was used to recruit children with sensitive skin. This questionnaire was also tested on an adult group. Hydration, transepidermal water loss (TEWL), and inflammatory markers (cytokines, and polyunsaturated fatty acids (PUFAs)) were quantified. A total of 77 children and 20 adults (33 and 10 with sensitive skin, respectively) were recruited. The groups with sensitive skin had more clinical signs of skin dryness. Skin hydration was lower in children in the sensitive compared with the nonsensitive skin group. TEWL levels were similar between sensitive and nonsensitive subjects in both infant and adult groups. Sensitive skin exhibited higher levels of cytokines and proinflammatory PUFAs as well as lower levels of anti-inflammatory PUFAs. Sensitive skin syndrome was associated with normal skin barrier function but lower hydration in infants and children. The higher levels of proinflammatory markers suggest that sensitive skin is associated with low-level inflammation. It is hypothesized, for the first time, that PUFAs are involved in sensitive skin syndrome in infants.

The systemic nature of mustard lung: Comparison with COPD patients

Sulphur mustard (SM) is a powerful blister-causing alkylating chemical warfare agent used by Iraqi forces against Iran. One of the known complications of mustard gas inhalation is mustard lung which is discussed as a phenotype of chronic obstructive pulmonary disease (COPD). In this complication, there are clinical symptoms close to COPD with common etiologies, such as in smokers. Based on information gradually obtained by conducting the studies on mustard lung patients, systemic symptoms along with pulmonary disorders have attracted the attention of researchers. Changes in serum levels of inflammatory markers, such as C-reactive protein (CRP), tumor necrosis factor alpha (TNF-α), nuclear factor κB (NF-κB), matrix metalloproteinases (MMPs), interleukin (IL), chemokines, selectins, immunoglobulins, and signs of imbalance in oxidant-antioxidant system at serum level, present the systemic changes in these patients. In addition to these, reports of extra-pulmonary complications, such as osteoporosis and cardiovascular disease are also presented. In this study, the chance of developing the systemic nature of this lung disease have been followed on using the comparative study of changes in the mentioned markers in mustard lung and COPD patients at stable phases and the mechanisms of pathogenesis and phenomena, such as airway remodeling in these patients.

Characterization of sulfur mustard resistant keratinocyte cell line HaCaT/SM

BACKGROUND

The cell line HaCaT/SM was derived from the human keratinocyte cell line HaCaT. HaCaT/SM cells display a high resistance against sulfur mustard (SM). Intention of the presented study was to determine the cellular and molecular differences between HaCaT/SM and HaCaT so as to evaluate which changes might be responsible for being resistant against SM.

METHODS

Both cell lines HaCaT and HaCaT/SM were analyzed with respect to their cell growth, nuclei perimeter, clonogenicity and secretion profile. Moreover DNA alkylation pattern under presence of SM was investigated.

RESULTS

In comparison to HaCaT, the HaCaT/SM showed a significant smaller nuclei perimeter. For DNA alkylation a significant difference was observed over time. The clonogenicity of HaCaT/SM was increased to 150%. The secretion profile of these cells demonstrated a strong increase of ANG, PDGF-AA, TIMP1, TIMP2, and a decrease of AREG, CCL5, CXC1, CXC2/3, CXCL6, CXCL7, CXCL8, CXCL10, MIF, Trappin-1.

CONCLUSION

The sulfur mustard (SM) resistant cell line HaCaT/SM demonstrates a wide range of significant differences to their origin cell line HaCaT. These differences might be responsible to provide resistance against SM and might also be useful to establish treatment concepts for humans after SM exposure.

Atopic dermatitis-associated protein interaction network lead to new insights in chronic sulfur mustard skin lesion mechanisms

Chronic sulfur mustard skin lesions (CSMSLs) are the most common complications of sulfur mustard exposure; however, its mechanism is not completely understood.According to clinical signs, there are similarities between CSMSL and atopic dermatitis (AD). In this study, proteomic results of AD were reviewed and the AD-associated protein-protein interaction network (PIN) was analyzed. According to centrality measurements, 16 proteins were designated as pivotal elements in AD mechanisms. Interestingly, most of these proteins had been reported in some sulfur mustard-related studies in late and acute phases separately. Based on the gene enrichment analysis, aging, cell response to stress, cancer, Toll- and NOD-like receptor and apoptosis signaling pathways have the greatest impact on the disease. By the analysis of directed protein interaction networks, it is concluded that TNF, IL-6, AKT1, NOS3 and CDKN1A are the most important proteins. It is possible that these proteins play role in the shared complications of AD and CSMSL including xerosis and itching.

Histopathological and immunohistochemical evaluation of nitrogen mustard-induced cutaneous effects in SKH-1 hairless and C57BL/6 mice

Sulfur mustard (SM) is a vesicant warfare agent which causes severe skin injuries. Currently, we lack effective antidotes against SM-induced skin injuries, in part due to lack of appropriate animal model(s) that can be used for efficacy studies in laboratory settings to identify effective therapies. Therefore, to develop a relevant mouse skin injury model, we examined the effects of nitrogen mustard (NM), a primary vesicant and a bifunctional alkylating agent that induces toxic effects comparable to SM. Specifically, we conducted histopathological and immunohistochemical evaluation of several applicable cutaneous pathological lesions following skin NM (3.2mg) exposure for 12-120h in SKH-1 and C57BL/6 mice. NM caused a significant increase in epidermal thickness, incidence of microvesication, cell proliferation, apoptotic cell death, inflammatory cells (neutrophils, macrophages and mast cells) and myleoperoxidase activity in the skin of both mouse strains. However, there was a more prominent NM-induced increase in epidermal thickness, and macrophages and mast cell infiltration, in SKH-1 mice relative to what was seen in C57BL/6 mice. NM also caused collagen degradation and edema at early time points (12-24h); however, at later time points (72 and 120h), dense collagen staining was observed, indicating either water loss or start of integument repair in both the mouse strains. This study provides quantitative measurement of NM-induced histopathological and immunohistochemical cutaneous lesions in both hairless and haired mouse strains that could serve as useful tools for screening and identification of effective therapies for treatment of skin injuries due to NM and SM.

A clinicopathological approach to sulfur mustard-induced organ complications: a major review

CONTEXT

Sulfur mustard (SM), with an old manufacturing history still remains as potential threat due to easy production and extensive effects.

OBJECTIVES

Increasing studies on SM indicates the interest of researchers to this subject. Almost all human body organs are at risk for complications of SM. This study offers organ-by-organ information on the effects of SM in animals and humans.

METHODS

The data sources were literature reviews since 1919 as well as our studies during the Iraq-Iran war. The search items were SM and its all other nomenclatures in relation to, in vivo, in vitro, humans, animals, eye, ocular, ophthalmic, lungs, pulmonary, skin, cutaneous, organs and systemic. Amongst more than 1890 SM-related articles, 257 more relevant clinicopathologic papers were selected for this review.

RESULTS

SM induces a vast range of damages in nearly all organs. Acute SM intoxication warrants immediate approach. Among chronic lesions, delayed keratitis and blindness, bronchiolitis obliterans and respiratory distress, skin pruritus, dryness and cancers are the most commonly observed clinical sequelae.

CONCLUSION

Ocular involvements in a number of patients progress toward a severe, rapid onset form of keratitis. Progressive deterioration of respiratory tract leads to "mustard lung". Skin problems continue as chronic frustrating pruritus on old scars with susceptibility to skin cancers. Due to the multiple acute and chronic morbidities created by SM exposure, uses of multiple drugs by several routes of administrations are warranted.

A randomized controlled trial on the anti-inflammatory effects of curcumin in patients with chronic sulphur mustard-induced cutaneous complications

Background

Chronic cutaneous complications such as pruritus are among the very frequent complaints of sulphur mustard (SM)-exposed patients. The present trial investigated the impact of curcumin on serum inflammatory biomarkers and their association with pruritus severity and quality of life (QoL).

Methods

This was a randomized, double-blind trial among 96 male Iranian veterans (age 37–59 y) who were suffering from chronic SM-induced pruritic skin lesions. Patients were randomly assigned to curcumin (1 g/d, n = 46) or placebo ( n = 50) for four weeks. Serum concentrations of interleukins 6 (IL-6) and 8 (IL-8) together with high-sensitivity C-reactive protein (hs-CRP) and calcitonin gene-related peptide (CGRP) were measured at baseline and at the end of the trial. Assessment of pruritus severity was performed using the pruritus score and QoL using the Dermatology Life Quality Index (DLQI).

Results

Serum IL-8 and hs-CRP were significantly reduced in both groups but the magnitude of reduction was greater in the curcumin group ( P < 0.001). Serum CGRP was only decreased in the curcumin group ( P < 0.001). No significant change was observed in serum IL-6. There were significant correlations between CGRP and IL-6 changes ( P = 0.011) and between DLQI and IL-8 changes ( P = 0.026) in the curcumin group. In the curcumin group, changes in serum IL-8 concentrations were found as the significant predictor of DLQI scores ( P = 0.026) but none of the independent variables could predict pruritus scores.

Conclusions

Curcumin supplementation effectively mitigates inflammation in patients suffering from chronic SM-induced cutaneous complications. This anti-inflammatory effect might account for the observed pruritus alleviation and QoL improvement by this phytochemical.

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.

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

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

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.

Mustard gas toxicity: the acute and chronic pathological effects

Ever since it was first used in armed conflict, mustard gas (sulfur mustard, MG) has been known to cause a wide range of acute and chronic injuries to exposure victims. The earliest descriptions of these injuries were published during and in the immediate aftermath of the First World War, and a further series of accounts followed the Second World War. More recently, MG has been deployed in warfare in the Middle East and this resulted in large numbers of victims, whose conditions have been studied in detail at hospitals in the region. In this review, we bring together the older and more recent clinical studies on MG toxicity and summarize what is now known about the acute and chronic effects of the agent on the eyes, skin, respiratory tract and other physiological systems. In the majority of patients, the most clinically serious long-term consequences of MG poisoning are on the respiratory system, but the effects on the skin and other systems also have a significant impact on quality of life. Aspects of the management of these patients are discussed.

Peaceful use of disastrous neurotoxicants

The increasing exposure to environmental neurotoxicants in the last decades caused serious health problems in the world population. Some of the neurotoxic agents are being used in agriculture and household such as insecticides and rodenticides and others are of natural origin like snake and scorpion venoms. Additional group of harmful substances is the chemical warfare agents including nerve and blistering agents that are known for their disastrous effects on neuronal tissues. The present paper presents a combination of epidemiological/clinical and molecular approaches for investigating the effect of certain groups of neurotoxicants on a variety of pathologies. The work of Finkelstein and coworkers describes epidemiological and clinical studies on acute and chronic organophosphate (OP)-induced neurotoxicity in certain populations in Israel. They mainly investigated the neurotoxic effects of low-level long-term exposure to OP in agricultural areas but also dealt with acute exposures as well. A molecular approach to OP mechanism of neuronal injury was described by Milatovic and coworkers. They demonstrated OP-induced oxidative injury in pyramidal neurons in the CA1 hippocampal area and its suppression by antioxidants. Lecht and coworkers described the novel snake venom angioneurins as important mediators of the physiological cross-talk between the cardiovascular and nervous systems. They also showed that under certain conditions these angioneurins may induce pathologies such as tumor development or disruption of the vascular barrier function during envenomation. Additional mechanistic/therapeutic approach was presented by Brodsky, Rosengarten, Proscura, Shapira and Wormser. They developed a novel anti-inflammatory peptide that reduced skin irritation induced by heat and sulfur mustard (SM) stimuli. Since SM causes neuropsychiatric symptoms and alterations in neurological functions this peptide may serve as a potential treatment of neuronal injuries caused by environmental neurotoxicants. These reviews highlight different aspects of neurotoxicity, addressing epidemiology and mechanisms of toxicity; and identifying novel potential therapies.

Sulfur mustard induces immune sensitization in hairless guinea pigs

Sulfur mustard (SM, bis-(2-chloroethyl) sulfide) is a well known chemical warfare agent that may cause long-term debilitating injury. Because of the ease of production and storage, it has a strong potential for chemical terrorism; however, the mechanism by which SM causes chronic tissue damage is essentially unknown. SM is a potent protein alkylating agent, and we tested the possibility that SM modifies cellular antigens, leading to an immunological response to "altered self" and a potential long-term injury. To that end, in this communication, we show that dermal exposure of euthymic hairless guinea pigs induced infiltration of both CD4(+) and CD8(+) T cells into the SM-exposed skin and strong upregulated expression of proinflammatory cytokines and chemokines (TNF-alpha, IFN-gamma, and IL-8) in distal tissues such as the lung and the lymph nodes. Moreover, we present evidence for the first time that SM induces a specific delayed-type hypersensitivity response that is associated with splenomegaly, lymphadenopathy, and proliferation of cells in these tissues. These results clearly suggest that dermal exposure to SM leads to immune activation, infiltration of T cells into the SM-exposed skin, delayed-type hypersensitivity response, and molecular imprints of inflammation in tissues distal from the site of SM exposure. These immunological responses may contribute to the long-term sequelae of SM toxicity.

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.

Transcriptional responses associated with sulfur mustard and thermal burns in porcine skin

In military and civilian environments, serious cutaneous damage can result from thermal burns or exposure to the blistering agent sulfur mustard [bis (2-chloroethyl) sulfide; HD]. Similar therapies have historically been used to treat cutaneous thermal and HD injuries; however, the underlying molecular mechanisms of tissue damage and wound healing may differ between the types of burns. Using microarray analysis, this study assessed the transcriptional responses to cutaneous HD and thermal injury at 48 hours post-exposure to identify molecular networks and genes associated with each type of skin injury. Ventral abdominal sites on each of 4 weanling swine were exposed to 400 mul of undiluted HD or a heated brass rod (70 degrees C) for 8 minutes and 45-60 seconds, respectively. At 48 hours post-exposure, total RNA was isolated from excised skin samples and hybridized to Affymetrix GeneChip Porcine Genome Arrays (containing 20,201 genes). Both HD and thermal exposure promoted significant transcriptional changes where 290 and 267 transcripts were increased and 197 and 707 transcripts were decreased with HD and thermal exposure, respectively. HD- and thermal-injured skin expressed 149 increased and 148 decreased common transcripts. Comparison of the 10 most significantly changed biological functions for HD and thermal exposures identified 7 overlapping functional groups. Canonical pathways analysis revealed 15 separate signaling pathways containing transcripts associated with both HD and thermal exposure. Within these pathways, 5 transcripts (CXCR4, FGFR2, HMOX1, IL1R1, and TLR4) were identified as known targets for existing phase II/III clinical trial or Food and Drug Administration (FDA)-approved drugs. This study is the first to directly assess transcriptional changes in porcine skin subjected to HD or thermal injury over the same time period.

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

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

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.

The effect of occlusive and unocclusive exposure to xylene and benzene on skin irritation and molecular responses in hairless rats

Aromatic hydrocarbons readily penetrate the skin on dermal exposure, leading to irritation, inflammation and cytotoxicity. The effects of short-term occlusive and long-term unocclusive dermal exposure to benzene and xylene on the skin irritation response (transepidermal water loss (TEWL), skin moisture content and erythema) and cytokine/chemokine expression (interleukin-1alpha (IL-1alpha), tumor necrosis factor-alpha (TNF-alpha) and monocyte chemoattractant protein-1 (MCP-1)) were investigated in hairless rats. Occlusive dermal exposure was carried out with 230 microL of the chemicals for 1 h using Hill top chambers. In unocclusive dermal exposure, 15 microL of the chemicals were applied to the skin every 2 h, for 8 h a day, for 4 days. The occlusive dermal exposure revealed a clear difference in the TEWL and erythema response of these chemicals (xylene>benzene) whereas unocclusive exposure revealed similar TEWL and erythema scores for both benzene and xylene. The expression of IL-1alpha was elevated 2.5- and 3.8-fold in response to occlusive and unocclusive exposure, respectively, vs control (P<0.01) for both the chemicals (benzene and xylene). Similarly, TNF-alpha levels were elevated about 2.4- and 6.0-fold as a result of occlusive and unocclusive exposure, respectively, vs control (P<0.01). These results show that unocclusive exposure induced significantly higher TNF-alpha expression than occlusive exposure (P<0.05). The MCP-1 expression in blood was slightly elevated compared with the control group, but this increase was not statistically significant (P>0.05). Similarly, MCP levels in skin were increased approximately 1.7- and 1.8-fold by occlusive and unocclusive exposure, respectively, compared with the control group (P<0.05). Our study demonstrates that the skin irritation profiles of benzene and xylene are similar and unocclusive long-term exposure to small amounts of these chemicals can induce more skin irritation and cytokine response than occlusive exposure.

Modulation of sulfur mustard induced cell death in human epidermal keratinocytes using IL-10 and TNF-α

We compared the effects of overexpressing a tightly regulated anti-inflammatory cytokine, interleukin 10 (IL-10), and the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) on sulfur mustard induced cytotoxicity in human epidermal keratinocytes. Both cytokines were overexpressed when compared with the cells transfected with the empty vector as determined by quantitative ELISA. Cells overexpressing interleukin 10 suppressed the pro-inflammatory cytokines interleukin 8 and interleukin 6 following exposure to 50-300 microM sulfur mustard. These cells exhibited delayed onset of sulfur mustard induced cell death. On the other hand, cells overexpressing tumor necrosis factor alpha induced a sustained elevation in both interleukin 6 and 8 expression following exposure to 50-300 microM sulfur mustard. These cells were sensitized to the effects of sulfur mustard that resulted in an increased sulfur mustard induced cell death. Normal human epidermal keratinocytes treated with sulfur mustard exhibited elevated levels of tumor necrosis factor alpha expression and increased activity of nuclear factor kappa B. Gene array data indicated that cells overexpressing interleukin 10 induced several genes that are involved in growth promotion and cell-fate determination. We, therefore, identify IL-10 and TNF-alpha signal transduction pathways and their components as possible candidates for early therapeutic intervention against sulfur mustard induced cell injury.

Production of chemokines in Kawasaki disease, Henoch-Schönlein purpura and acute febrile illness

We compared the production of three chemokines; interferon-gamma-inducible protein-10 (IP-10), monocyte chemoattractant protein-1 (MCP-1) and growth-related onco-gene-alpha(Gro-alpha) that attracts monocytes or neutrophils, or both, in peripheral blood at acute stage of Kawasaki disease (n=29), Henoch-Schönlein purpura (n=15) and acute febrile illnesses (n=12). The production of the chemokines was assayed by ELISA. The plasma levels of IP-10 were markedly elevated in Kawasaki disease (538.6+/-336.4 pg/mL) and acute febrile illnesses (417.1 +/-262.2 pg/mL) compared with in Henoch-Schönlein purpura (58.7 +/-95.7 pg/mL) (p<0.05). The MCP-1 levels were elevated in Kawasaki disease (443.0 +/-473.1 pg/mL) and acute febrile illnesses (328.6 +/-261.1 pg/mL) compared with in Henoch-Schönlein purpura (82.9 +/-79.0 pg/mL) (p<0.05). The Gro-alpha levels were elevated only in acute febrile illnesses (134.3 +/-153.6 pg/mL) compared with in Kawasaki disease (31.8 +/-22.1 pg/mL) or Henoch-Schönlein purpura (29.4 +/-53.3 pg/mL) (p<0.05). According to these results, monocytes may play an important role in Kawasaki disease. In acute febrile illnesses, both monocytes and neutrophils may play an important role. By contrast, Henoch-Schönlein purpura may not be associated with the role of monocytes and neutrophils. Further studies using a larger number of cases are needed.

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.

An inhibitor of p38 MAP kinase downregulates cytokine release induced by sulfur mustard exposure in human epidermal keratinocytes

Sulfur mustard (2,2'-dichlorodiethyl sulfide, SM) is a potent alkylating agent that induces skin vessication after cutaneous exposure. Previous work has revealed that SM induces the production of inflammatory cytokines, including IL-8, IL-6, TNF-alpha, and IL-1beta, in keratinocytes. The p38 MAP kinase (MAPK14) signaling pathway is activated via phosphorylation in response to cellular stress and has been implicated in the upregulation of cytokines in response to stress. We investigated the role of p38 MAP kinase in inflammatory cytokine upregulation following SM exposure. A dose response study in cultured human epidermal keratinocytes (HEK) revealed increasing phosphorylation of p38 MAP kinase in response to increasing concentrations of SM. A time course at the 200 microM exposure revealed that p38 MAP kinase phosphorylation is induced by 15 min post-exposure, peaks at 30 min and is sustained at peak levels until 8 h post-exposure. Phosphorylation of the upstream kinase MKK3/6 was also detected. Assay of the SM-exposed HEK culture media for cytokines revealed that exposure to 200 microM SM increased IL-8, IL-6, TNF-alpha, and IL-1beta. When cells exposed to 200 microM SM were treated with the p38 MAP kinase inhibitor SB203580, the levels of IL-8, IL-6, and TNF-alpha and IL-1beta were significantly decreased when compared with cells that were untreated. These results show that p38 MAP kinase plays a role in SM-induced cytokine production in HEK and suggest that inhibiting this pathway may alleviate the profound inflammatory response elicited by cutaneous SM exposure.

Prophylactic protection by N-acetylcysteine against the pulmonary injury induced by 2-chloroethyl ethyl sulfide, a mustard analogue

Mustard gas exposure causes adult respiratory distress syndrome associated with lung injury. The purpose of this study was to investigate whether an antioxidant, such as N-acetylcysteine (NAC), has any protective effect. Guinea pigs were given single exposure (0.5-6 mg/kg body weight) of 2-chloroethyl ethyl sulfide (CEES) as a mustard analogue intratracheally and maintained for various lengths of time (1 h to 21 days). Within 1 h of CEES infusion at 4 mg/kg, high levels of tumor necrosis factor alpha (TNF-alpha), ceramides, and nuclear factor kappaB accumulated in lung and alveolar macrophages. Both acid and neutral sphingomyelinases were activated within 4 h. These signal transduction events were associated with alteration in the oxygen defense system. Within 1 h of exposure to CEES (6 mg/kg body weight), there was 10-fold increase in the (125)I-BSA leakage into lung tissue, indicating severe lung injury. Although low level of CEES exposure (0.5 mg/kg body weight) produced symptoms of chemical burn in lung as early as 1 h after exposure, the severity of edema, congestion, hemorrhage, and inflammation increased progressively with time (1 h to 21 days). Feeding of single dose of NAC (0.5 g) by gavage just before the CEES infusion was ineffective to counteract these effects. However, consumption of the antioxidant in drinking water for 3 or 30 days prior to CEES exposure significantly inhibited the induction of TNF-alpha, activation of neutral and acid sphingomyelinases, production of ceramides, activation of caspases, leakage of (125)I-bovine serum albumin ((125)I-BSA) into lung tissue, and histological alterations in lung. Pretreatment with NAC for 3 and 30 days protected against 69-76% of the acute lung injury. Therefore, NAC may be an antidote for CEES-induced lung injury.

Sulfur mustard primes phagocytosis and degranulation in human polymorphonuclear leukocytes

Sulfur mustard (2,2'-bis-chloroethyl-sulfide; SM) is a chemical warfare vesicant that causes debilitating skin lesions. Although a great deal of work has focused on the direct effects of SM exposure on the epithelium, it is unclear how much the inflammatory response, induced by exposure, contributes to lesion pathogenesis. Keratinocytes exposed to SM express a number of inflammatory mediators and elicit a cellular infiltrate consisting largely of polymorphonuclear leukocytes (PMN). PMN infiltration into SM lesions occurs as early as 30 min and peaks after several hours postexposure, and, despite the relatively short half-life of SM, PMN infiltrating a lesion could be exposed to micromolar concentrations of the agent. Previously, we have shown that exposure to low doses of sulfur mustard prime oxidative function in human PMN. The current study was undertaken to evaluate the effects of low-dose SM exposure on PMN phagocytosis, degranualtion and chemotaxis. PMN exposed to low doses of SM (50-200 microM) showed a dose-dependent enhancement of phagocytic function. Exocytosis of PMN azurophilic and specific granules [determined by analysis of granule-specific intravesicular receptors, Interleukin 10 receptor (IL-10R) and CD63] was also enhanced by SM exposure. Finally, we examined the effect of SM as a chemoattractant for PMN and show that SM is not itself a chemotaxin. These results suggest that SM injury may, in part, be caused by normal inflammatory function, and that therapeutic strategies aimed at down-regulating PMN activation could lessen the severity of SM injury and the time required for its resolution.

Evidence of hair loss after subacute exposure to 2-chloroethyl ethyl sulfide, a mustard analog, and beneficial effects ofN-acetyl cysteine

Mustard gas has been used as a vesicant chemical warfare agent. However, a suitable biomarker for monitoring mustard gas exposure is not known. We observed that the hairs of the guinea pigs exposed intratracheally to subacute doses of 2-chloroethyl ethyl sulfide (CEES), a mustard analog, came out very easily though there was no sign of skin lesions or skin damage. Also the hairs looked rough and dry and lost the shiny glaze. There was no recovery from this hair loss, though the animals never became hairless, following CEES exposure. Hairs were observed in this study both visually and with light microscopy. Treatment with N-acetylcysteine (NAC) prior to CEES exposure could prevent the hair loss completely. Hence, sudden hair loss might be a good biomarker for subacute exposure of mustard gas to subjects at risks when the victims might have no other visible symptom of toxicity.

Cytokine, chemokine, and matrix metalloproteinase response after sulfur mustard injury to weanling pig skin

Cutaneous exposure to sulfur mustard [bis(2-chloroethyl) sulfide; SM] produces a delayed inflammatory skin response and severe tissue injury. Pig skin has organ similarities to human skin that is characterized by the content and types of epidermal lipids, the density of hair follicles and presence of sweat glands, which together afford penetration of topically applied compounds, complex inflammatory responses, and subsequent wound healing. The goal of this study was to identify in vivo proinflammatory biomarkers of the SM porcine skin injury within 72 h after SM challenge, using the weanling pig model. Changes in gene expression of inflammatory mediators were examined at 3, 6, 24, 48, and 72 h, using subtraction library analyses and by quantitation of selected transcripts by reverse transcription-polymerase chain reaction (RT-PCR). Sequence analysis of subtraction libraries identified up-regulation of IL-8 at 24, 48, and 72 h. No other specific proinflammatory gene transcripts were isolated from the libraries. Specific transcript RT-PCR analysis showed increased production of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interleukin-8 (IL-8), and matrix metalloproteinase-9 (MMP-9, gelatinase B) mRNA levels in response to SM exposure. Tumor necrosis factor-alpha (TNF-alpha) expression was only slightly increased and no change in the levels of expression was observed for monocyte chemoattractant protein-1 and MMP-2. This study identifies the main proinflammatory mediators involved in SM-induced skin injury in a weanling pig model. The results suggest transcriptional activity in the inflammatory response proteins IL-8, IL-6, IL-1beta, and MMP-9 and modest changes in TNF-alpha that together produce inflammation and contribute to the pathogenesis of SM dermatotoxicity. Therefore, drugs preventing SM-induced inflammation should be prime candidates for medical intervention to lessen collateral inflammation associated with tissue destruction.

Low-dose sulfur mustard primes oxidative function and induces apoptosis in human polymorphonuclear leukocytes

Although considerable work has focused on understanding the processes of direct tissue injury mediated by the chemical warfare vesicant, sulfur mustard (2,2'-bis-chloroethyl sulfide; SM), relatively little is known regarding the mechanisms of secondary injury caused potentially by the acute inflammatory response that follows SM exposure. Polymorphonuclear leukocytes (PMNs) play a central role in the initiation and propagation of inflammatory responses that, in some cases, result in autoimmune tissue damage. The potential for PMN-derived tissue damage following SM exposure may, in part, account for the protracted progression of the injury before it resolves. The current study was undertaken to evaluate the priming, oxidative function, and viability of PMN following exposure to low doses of SM such as those that might remain in tissues as a result of topical exposure. Our results demonstrate that doses of SM ranging from 25 to 100 microM primed PMN for oxidative burst in response to activation by fMLP, and that doses of SM ranging from 50 to 100 microM induced PMN apoptosis. Understanding the mechanisms through which SM directly affects PMN activation and apoptosis will be of critical value in developing novel treatments for inflammatory tissue injury following SM exposure.

Mitochondrial and nuclear DNA damage induced by sulphur mustard in keratinocytes

The extent and role of mitochondrial DNA damage in the mechanism of action of sulphur mustard (SM) is poorly understood. In this study, a combination of quantitative polymerase chain reaction and Southern hybridization was used to determine the levels of both total DNA adducts and DNA interstrand crosslinks in genomic and mitochondrial DNA isolated from normal human epidermal keratinocytes exposed to SM. The formation of both types of lesions occurred simultaneously in nuclear and mitochondrial DNA, however, SM produced significantly higher levels of both total adducts and crosslinks in genomic DNA than mitochondrial DNA. The total lesion frequency was 0.45 lesions/kb per 100 microM SM in the DHFR gene and 0.12 lesions/kb per 100 microM SM in the mitochondrial segment. Interstrand crosslinks occurred at a frequency of 0.28 crosslinks/10 kb per 100 microM SM in the DHFR gene and 0.05 crosslinks/10 kb per 100 microM SM in the mitochondrial segment. DNA interstrand crosslinks are thought to be the critical lesion produced by similar bi-functional alkylating agents. However, the levels of DNA cross-linking revealed in this study show that even at vesicating doses of SM mitochondrial DNA is still largely free of cross-links and the predominant form of DNA damage contributing to cell death occurs in the nucleus.

The role of interleukin-6 (IL-6) in human sulfur mustard (HD) toxicology

The authors applied in vitro models of controlled damage to human epidermal keratinocytes (HEKs), human skin fibroblasts (HSFs), and human breast skin tissue (HBST) to examine the mechanism responsible for sulfur mustard (HD)-induced interleukin-6 (IL-6) alterations. Treatment with 100 microM HD for 24 hours resulted in a significant increased amount of IL-6 being secreted by HEKs (HD-exposed to control ratio [E/C] = 4.15 +/- 0.07) and by HSFs (E/C = 7.66 +/- 0.04). Furthermore, the HD-induced secretion of IL-6 in HEKs was neutralized with monoclonal human IL-6 antibodies. The secretion of IL-6 in HBST supernatant exposed to HD produced conflicting results. Although an increase of IL-6 was observed in control superfusion media from HBST, IL-6 levels were observed to decrease as the concentration of HD increased. Time course of IL-6 mRNA levels were performed using a competitive polymerase chain reaction (PCR) and human IL-6 mRNA assay detection kit in control and HD (100 microM)-treated HEKs cells. IL-6 mRNA transcripts in HD-exposed HEKs were first observed within 2 hours, dropped at 5 to 6 hours, and increased by approximately 2.2-fold and 8.5-fold at 24 to 48 hours after HD exposure, respectively, as detected by the Xplore mRNA Quantification System. Surface-enhanced laser desorption ionization (SELDI) mass spectrometry was also applied to study the secretion pattern of IL-6 on lysate preparations of HBST. A peak in the area of 23,194 to 23,226 Da was detected using antibody coupled to the chip. This peak was assigned to correspond to the mass of the IL-6 glycoprotein. Recombinant human IL-6 (rhIL-6) exposed to HD lacked the second disulfide bridge and was partially unfolded, as determined by nuclear magnetic resonance-nuclear Overhauser enhancement and exchange spectroscopy (NMR-NOESY). The disappearance of the resonance peak at 3.54 ppm and the appearance of a new chemical shift at 1.85 ppm suggested that a change in structure had occurred in the presence of HD. From the data, the possibility cannot be excluded that IL-6 might be involved in the early event of structural changes of the signal transducer glycoprotein that indirectly initiates the cascade of events such as skin irritation and blister formation observed in the pathophysiology of HD injury.

Contact sensitivity reactions in the oral mucosa

Although the role of T cells in skin contact sensitivity (CS) immune reactions has been intensely studied, much less is known about the regulatory properties of T cells in the oral mucosa. Animal experiments have shown that hapten sensitization of the ectodermal oral mucosa leads to antigen-specific hypersensitivity reactions in the skin. Furthermore, oral mucosa or skin hapten sensitization resulted in CS inflammatory reactions in the oral mucosa on challenge. The oral mucosa CS responses were similar to those found skin with regard to cell phenotypes and cytokines. CS-like reactions were also found in the oral mucosa after exposure to an irritant detergent, sodium lauryl sulfate (SLS). The oral mucosa reacted at smaller SLS doses than did skin. Ions and molecules released fron dental restorative materials (together with saliva and food and/or beverages) expose the gastrointestinal mucosa continuously over long time periods. From animal experiments we have learned that mice given antigen by gastric feeding, subsequently antigen-sensitized on skin, and finally elicited in the oral mucosa and in ear skin, showed tolerance in skin but gave simultaneous CS inflammatory reactions in the oral mucosa. Moreover, exposure of colon mucosa to antigen produced CS reactions in oral mucosa after challenge. Are there CS reactions in the oral mucosa? Clinical and experimental studies indicate that the oral mucosa can function both as induction and expression site of CS. The GI tract may be an important modifier of the CS inflammatory reactions seen in the oral mucosa.

Role of chemokines and formyl peptides in pneumococcal pneumonia-induced monocyte/macrophage recruitment

Host-derived chemoattractant factors are suggested to play crucial roles in leukocyte recruitment elicited by inflammatory stimuli in vitro and in vivo. However, in the case of acute bacterial infections, pathogen-derived chemoattractant factors are also present, and it has not yet been clarified how cross-talk between chemoattractant receptors orchestrates diapedesis of leukocytes in this context of complex chemoattractant arrays. To investigate the role of chemokine (host-derived) and formyl peptide (pathogen-derived) chemoattractants in leukocyte extravasation in life-threatening infectious diseases, we used a mouse model of pneumococcal pneumonia. We found an increase in mRNA expression of eight chemokines (RANTES, macrophage-inflammatory protein (MIP)-1alpha, MIP-1beta, MIP-2, IP-10, monocyte chemoattractant protein (MCP)-1, T cell activation 3, and KC) within the lungs during the course of infection. KC and MIP-2 protein expression closely preceded pulmonary neutrophil recruitment, whereas MCP-1 protein production coincided more closely than MIP-1alpha with the kinetics of macrophage infiltration. In situ hybridization of MCP-1 mRNA suggested that MCP-1 expression started at peribronchovascular regions and expanded to alveoli-facing epithelial cells and infiltrated macrophages. Interestingly, administration of a neutralizing Ab against MCP-1, RANTES, or MIP-1alpha alone did not prevent macrophage infiltration into infected alveoli, whereas combination of the three Abs significantly reduced macrophage infiltration without affecting neutrophil recruitment. The use of an antagonist to N-formyl peptides, N-t-Boc-Phe-D-Leu-Phe-D-Leu-Phe, reduced both macrophages and neutrophils significantly. These data demonstrate that a complex chemokine network is activated in response to pulmonary pneumococcal infection, and also suggest an important role for fMLP receptor in monocyte/macrophage recruitment in that model.

Alterations in inflammatory cytokine gene expression in sulfur mustard-exposed mouse skin

Cutaneous exposure to sulfur mustard (bis(2-chloroethyl) sulfide, HD), a chemical warfare agent, produces a delayed inflammatory skin response and severe tissue injury. Despite defined roles of inflammatory cytokines produced or released in response to skin-damaging chemicals, in vivo cytokine responses associated with HD-induced skin pathogenesis are not well understood. Additionally, there is little information on the in vivo temporal sequence of gene expression of cytokines postexposure to HD. The goal of these studies was to identify in vivo molecular biomarkers of HD skin injury within 24 hours after HD challenge. Gene expression of interleukin 1beta (IL-1beta), granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin 6 (IL-6), and interleukin 1alpha (IL-1alpha) in the mouse ear vesicant model was examined by quantitative reverse transcription-polymerase chain reaction (RT-PCR). An increase in IL-1beta mRNA levels was first observed at 3 hours. IL-1beta, GM-CSF, and IL-6 mRNA levels were dramatically increased at 6-24 hours postexposure. IL-1alpha mRNA levels were not increased following HD exposure. Immunohistochemical studies demonstrated that IL-1beta and IL-6 protein was produced at multiple sites within the ear, including epithelial cells, inflammatory cells, hair follicles, sebaceous glands, the dermal microvasculature, smooth muscle, and the dermal connective tissue. An increase in the intensity of staining for IL-1beta, and IL-6 was observed in localized areas at 6 hours and was evident in multiple areas at 24 hours. Positive staining for GM-CSF immunoreactive protein was localized to the inflammatory cells within the dermis. The number of immunostaining cells was increased as early as 1 hour following HD exposure. These studies document an early increase in the in vivo expression of inflammatory cytokines following cutaneous HD exposure. An understanding of the in vivo cytokine patterns following HD skin exposure may lead to defining the pathogenic mechanisms of HD injury and the development of pharmacological countermeasures.

Immune responses in tuberculosis: antibodies and CD4-CD8 lymphocytes with vascular adhesion molecules and cytokines (chemokines) cause a rapid antigen-specific cell infiltration at sites of bacillus Calmette-Guérin reinfection

Rabbit primary dermal bacillus Calmette-Guérin (BCG) lesions were compared with reinfection BCG lesions in order to gain insight into how immune responses protect against clinical tuberculosis. As early as 3 hr, a marked infiltration of macrophages and lymphocytes occurred in the reinfection group, while very little cell infiltration occurred in the primary group. It seems that only an antigen-antibody reaction could produce such an immediate pronounced antigen-specific chemotactic effect, because very few lymphocytes are normally present in the skin. Therefore, antibodies hasten the accumulation of an expanded antigen-specific T-lymphocyte population (memory cells) at sites of bacillary lodgement. By 1-2 days, the primary and reinfection BCG lesions differed 400- to 500-fold in size. By 4-5 days, the size of the reinfection lesions had declined, while the size of the primary lesions had increased, so that, grossly, both types of lesion were similar. At 8 days in reinfection lesions and at 12 days in primary lesions, small secondary peaks in size occurred, which were probably caused by cell-mediated immune responses. In rabbits with primary BCG lesions, skin tests with Old Tuberculin were positive at 9 days, accompanied by a rise in the levels of antibodies to the secreted antigen, phosphate-specific transport protein 1, but the levels of antibodies to the constitutive antigens, purified protein derivative and heat-shock protein 65, did not increase appreciably until some time after 23 days. In tissue sections of reinfection BCG lesions, the percentage of mononuclear cells labelled, by in situ hybridization techniques, for the mRNA of monocyte chemoattractant protein 1 (MCP-1), a chemokine, peaked at 3 hr and then was down-regulated, whereas in primary lesions, this percentage was down-regulated only after 2 days. [The percentage in the tissue sections for the mRNAs of interleukins 1beta and 8, as well as the proteins of MCP-1 and tumor necrosis factor alpha (TNF-alpha), followed a somewhat similar time-course to that of MCP-1 mRNA.] A high percentage of mononuclear cells containing the MCP-1 mRNA 'factory' would favour enlargement of the lesions and a low percentage would favour their regression. At 5 days, the percentage of CD4 and CD8 lymphocytes, stained by immunohistochemical techniques, and the amount of microvasculature stained similarly for vascular cell adhesion molecule 1 were higher in the reinfection group, indicating that prior immunization caused a more rapid (antigen-dependent) up-regulation of these factors. Tuberculin reactions resembled early reinfection BCG lesions in almost every factor evaluated herein. In brief, the production of chemokines began soon after BCG reinfection, peaked within a few hours and was markedly down-regulated by 24 hr, a time at which the lesions of reinfection were of maximal size. Therefore, the amount of cell infiltration was tightly controlled, probably by the variety of mechanisms listed herein.

Redox-modulated pathways in inflammatory skin diseases

Inflammatory skin diseases account for a large proportion of all skin disorders and constitute a major health problem worldwide. Contact dermatitis, atopic dermatitis, and psoriasis represent the most prevalent inflammatory skin disorders and share a common efferent T-lymphocyte mediated response. Oxidative stress and inflammation have recently been linked to cutaneous damage in T-lymphocyte mediated skin diseases, particularly in contact dermatitis. Insights into the pathophysiology responsible for contact dermatitis can be used to better understand the mechanism of other T-lymphocyte mediated inflammatory skin diseases, and may help to develop novel therapeutic approaches. This review focuses on redox sensitive events in the inflammatory scenario of contact dermatitis, which comprise for example, several kinases, transcription factors, cytokines, adhesion molecules, dendritic cell surface markers, the T-lymphocyte receptor, and the cutaneous lymphocyte-associated antigen (CLA). In vitro and animal studies clearly point to a central role of several distinct but interconnected redox-sensitive pathways in the pathogenesis of contact dermatitis. However, clinical evidence that modulation of the skin's redox state can be used therapeutically to modulate the inflammatory response in contact dermatitis is presently not convincing. The rational for this discrepancy seems to be multi-faceted and complex and will be discussed.

Interleukin-1beta augments in vitro alveolar epithelial repair

Biologically active interleukin (IL)-1beta is present in the pulmonary edema fluid obtained from patients with acute lung injury and has been implicated as an important early mediator of nonpulmonary epithelial wound repair. Therefore, we tested the hypothesis that IL-1beta would enhance wound repair in cultured monolayers from rat alveolar epithelial type II cells. IL-1beta (20 ng/ml) increased the rate of in vitro alveolar epithelial repair by 118 +/- 11% compared with that in serum-free medium control cells (P < 0.01). IL-1beta induced cell spreading and migration at the edge of the wound but not proliferation. Neutralizing antibodies to epidermal growth factor (EGF) and transforming growth factor-alpha or inhibition of the EGF receptor by tyrphostin AG-1478 or genistein inhibited IL-1beta-induced alveolar epithelial repair, indicating that IL-1beta enhances in vitro alveolar epithelial repair by an EGF- or transforming growth factor-alpha-dependent mechanism. Moreover, the mitogen-activated protein kinase pathway is involved in IL-1beta-induced alveolar epithelial repair because inhibition of extracellular signal-regulated kinase activation by PD-98059 inhibited IL-1beta-induced alveolar epithelial repair. In conclusion, IL-1beta augments in vitro alveolar epithelial repair, indicating a possible novel role for IL-1beta in the early repair process of the alveolar epithelium in acute lung injury.

Effects of CEES on inflammatory mediators, heat shock protein 70A, histology and ultrastructure in two skin models

Chemical warfare threats require the development of diverse models for the assessment of countermeasures. Human skin products, Skin2 (differentiating keratinocytes on a fibroblast-collagen matrix) and EpiDerm (differentiating keratinocytes) were exposed (2 h) to the sulfur mustard 2-chloroethyl ethyl sulfide (CEES, 1-2 mg l(-1) min(-1)) in humidified air or to humidified air alone. Tissues were evaluated histologically, ultrastructurally and for viability 22 h later; media and tissues were also analyzed for inflammatory mediators. Histology showed that CEES induced the separation of dermal and epidermal regions in Skin2 with severe damage to basal keratinocytes. Histology and electron microscopy of both products revealed condensation of nuclear chromatin, retraction of spinous processes, collapse of the tonofibrillar network and cytoplasmic vacuolization and blebbing in those cells with loss of pseudobasement membrane integrity. Exposure of Skin2 to CEES increased extracellular interleukin-1alpha (IL-1alpha), prostaglandin-E2 (PGE2) and especially IL-1 receptor antagonist (IL-1Ra) release (56,334 vs 84,614 pg ml(-1)), but decreased interleukin-6 (IL-6, 4,755 vs 351 pg ml(-1)). Exposure of EpiDerm to CEES led to unaffected extracellular and reduced intracelluar IL-1alpha (371 vs 92 pg ml(-1)). Extracellular IL-1Ra greatly increased (2,375 vs 24,875 pg ml(-1)), whereas cellular levels decreased (16,5425 vs 96,625 pg ml(-1)). Extracellular (224 vs 68 pg ml(-1)) and intracellular (485 vs 233 pg ml(-1)) soluble interleukin-1 receptor H (sIL-1RII) decreased. Prostanglandin E2 increased (1,835 vs 2,582 pg ml(-1)), whereas heat shock protein 70A (Hsp70A) remained statistically unchanged (57,000 vs 96,000 pg ml(-1)). Failure to obtain a heat shock response to CEES may contribute to the susceptibility of tissue to the alkylating agent. Consistent and marked responses of cellular and extracellular IL-1Ra to CEES suggest a potential for use as a tissue status marker and primary antiinflammatory regulator in skin.

Sulfur mustard upregulates the expression of interleukin-8 in cultured human keratinocytes

Although the morphological description of sulfur mustard (SM) injury is well characterised, little is known of the molecular mediators involved in cutaneous toxicity. Since infiltration by lymphocytes and PMNs represents one of the very first events observed in vivo upon exposure to SM, this study examined whether SM exposure can modify the expression by cultured human keratinocytes of interleukin-8, one of the most important chemoattractants for polymorphonuclear leukocytes (PMNs) in humans. Conditioned medium harvested from control keratinocyte cultures showed a gradual accumulation of this cytokine over time followed by a levelling off after 12 hours. Upon treatment with 10(-6) and 10(-5) M SM, no significant difference compared to the control situation was observed. After 6 h, a significantly higher amount of IL-8 was secreted by human keratinocytes treated with 10(-4) M SM and the accumulation of the cytokine persisted up to 24 h after exposure. The expression of IL-8 mRNA was assessed semi-quantitatively (RT-PCR) at the same time points in control and SM-treated (10(-4) M) human keratinocytes. When compared to control cultures, a clear upregulation of IL-8 mRNA levels was observed 6 and 12 h after SM exposure, which is consistent with the secretion pattern of the protein. The present observation indicates that increased secretion of IL-8 by human keratinocytes represents an early event of the inflammatory reaction following SM which is coherent with the reported delay in the recruitment of lymphocytes and PMNs observed in vivo.

Cytokines and irritant contact dermatitis

Skin irritation is a complex phenomenon that involves resident epidermal cells, fibroblasts of dermis, and endothelial cells as well as invading leukocytes interacting with each other under the control of a network of cytokines and lipid mediators. Keratinocytes play an important role in the initiation and perpetuation of skin inflammatory reactions through the release of, and responses to cytokines. While resting keratinocytes produce some cytokines constitutively, a variety of environmental stimuli, such as tumor promoters, ultraviolet light and chemical agents, can induce epidermal keratinocytes to release inflammatory cytokines (IL-1, TNF-alpha), chemotactic cytokines (IL-8, IP-10), growth promoting cytokines (IL-6, IL-7, IL-15, GM-CSF, TGF-alpha) and cytokines regulating humoral vs. cellular immunity (IL-10, IL-12, IL-18). The role of cytokines in xenobiotics-induced skin irritation and the early molecular events that follow the treatment with irritant compounds will be discussed.

Chemotactic factors released in culture by intact developing and healing skin lesions produced in rabbits by the irritant sulfur mustard

Development, peak and healing lesions were induced in the skin of rabbits by topical applications (on different days) of the chemical irritant sulfur mustard (SM). Immediately after the rabbits were euthanized, the intact lesions were excised and organ-cultured for 17 to 20 hours. The culture fluids from early, peak and healing SM lesions all showed high chemotactic activity for both PMN and MN. This finding suggests that the PMN and MN, seen microscopically in tissue sections of the lesions, were entering continuously, even during the healing process. The chemotaxins identified were the eicosanoid LTB4, the chemokine IL-8, and proteases producing the complement fragment C5a. Other studies from our laboratory showed that the number of cells containing IL-1, IL-8, MCP-1, and GRO mRNAs was increased in SM lesions. Chemotactic activity was released by both live and dead (frozen and thawed) cell suspensions of PMN, MN, and fibroblasts, suggesting that these cells were major sources of the chemotaxins produced by the SM lesion explants. Explants of normal skin produced considerable chemotactic activity for MN, but not for PMN. Chemotactic activity for PMN, and the release of LTB4, IL-8 and proteases cleaving C5 to C5a, occurred only in explants infiltrated by leukocytes.