Systemic and ocular complications of sulfur mustard: A panoramic review

Nitrogen Mustard-Induced Ex Vivo Human Cornea Injury Model and Therapeutic Intervention by Dexamethasone

Sulfur mustard (SM), a vesicating agent first used during World War I, remains a potent threat as a chemical weapon to cause intentional/accidental chemical emergencies. Eyes are extremely susceptible to SM toxicity. Nitrogen mustard (NM), a bifunctional alkylating agent and potent analog of SM, is used in laboratories to study mustard vesicant-induced ocular toxicity. Previously, we showed that SM-/NM-induced injuries (in vivo and ex vivo rabbit corneas) are reversed upon treatment with dexamethasone (DEX), a US Food and Drug Administration-approved, steroidal anti-inflammatory drug. Here, we optimized NM injuries in ex vivo human corneas and assessed DEX efficacy. For injury optimization, one cornea (randomly selected from paired eyes) was exposed to NM: 100 nmoles for 2 hours or 4 hours, and 200 nmoles for 2 hours, and the other cornea served as a control. Injuries were assessed 24 hours post NM-exposure. NM 100 nmoles exposure for 2 hours was found to cause optimal corneal injury (epithelial thinning [∼69%]; epithelial-stromal separation [6-fold increase]). In protein arrays studies, 24 proteins displayed ≥40% change in their expression in NM exposed corneas compared with controls. DEX administration initiated 2 hours post NM exposure and every 8 hours thereafter until 24 hours post-exposure reversed NM-induced corneal epithelial-stromal separation [2-fold decrease]). Of the 24 proteins dysregulated upon NM exposure, six proteins (delta-like canonical Notch ligand 1, FGFbasic, CD54, CCL7, endostatin, receptor tyrosine-protein kinase erbB-4) associated with angiogenesis, immune/inflammatory responses, and cell differentiation/proliferation, showed significant reversal upon DEX treatment (Student's t test; P ≤ 0.05). Complementing our animal model studies, DEX was shown to mitigate vesicant-induced toxicities in ex vivo human corneas. SIGNIFICANCE STATEMENT: Nitrogen mustard (NM) exposure-induced injuries were optimized in an ex vivo human cornea culture model and studies were carried out at 24 h post 100 nmoles NM exposure. Dexamethasone (DEX) administration (started 2 h post NM exposure and every 8 h thereafter) reversed NM-induced corneal injuries. Molecular mediators of DEX action were associated with angiogenesis, immune/inflammatory responses, and cell differentiation/proliferation, indicating DEX aids wound healing via reversing vesicant-induced neovascularization (delta-like canonical Notch ligand 1 and FGF basic) and leukocyte infiltration (CD54 and CCL7).

Establishing a Dexamethasone Treatment Regimen To Alleviate Sulfur Mustard-Induced Corneal Injuries in a Rabbit Model

Sulfur mustard (SM) is an ominous chemical warfare agent. Eyes are extremely susceptible to SM toxicity; injuries include inflammation, fibrosis, neovascularization (NV), and vision impairment/blindness, depending on the exposure dosage. Effective countermeasures against ocular SM toxicity remain elusive and are warranted during conflicts/terrorist activities and accidental exposures. We previously determined that dexamethasone (DEX) effectively counters corneal nitrogen mustard toxicity and that the 2-hour postexposure therapeutic window is most beneficial. Here, the efficacy of two DEX dosing frequencies [i.e., every 8 or 12 hours (initiated, as previously established, 2 hours after exposure)] until 28 days after SM exposure was assessed. Furthermore, sustained effects of DEX treatments were observed up to day 56 after SM exposure. Corneal clinical assessments (thickness, opacity, ulceration, and NV) were performed at the day 14, 28, 42, and 56 post-SM exposure time points. Histopathological assessments of corneal injuries (corneal thickness, epithelial degradation, epithelial-stromal separation, inflammatory cell, and blood vessel counts) using H&E staining and molecular assessments (COX-2, MMP-9, VEGF, and SPARC expressions) were performed at days 28, 42, and 56 after SM exposure. Statistical significance was assessed using two-way ANOVA, with Holm-Sidak post hoc pairwise multiple comparisons; significance was established if P < 0.05 (data represented as the mean ± S.E.M.). DEX administration every 8 hours was more potent than every 12 hours in reversing ocular SM injury, with the most pronounced effects observed at days 28 and 42 after SM exposure. These comprehensive results are novel and provide a comprehensive DEX treatment regimen (therapeutic-window and dosing-frequency) for counteracting SM-induced corneal injuries. SIGNIFICANCE STATEMENT: The study aims to establish a dexamethasone (DEX) treatment regimen by comparing the efficacy of DEX administration at 12 versus 8 hours initiated 2 hours after exposure. DEX administration every 8 hours was more effective in reversing sulfur mustard (SM)-induced corneal injuries. SM injury reversal during DEX administration (initial 28 days after exposure) and sustained [further 28 days after cessation of DEX administration (i.e., up to 56 days after exposure)] effects were assessed using clinical, pathophysiological, and molecular biomarkers.

Cellular senescence implication in mustard keratopathy

Mustard agents are vesicants that were used in warfare multiple times. They are potent alkylating agents that activate cellular pathways of apoptosis, increase oxidative stress, and induce inflammation. Eyes are particularly susceptible to mustard exposure with a wide range of ocular surface damage. Three main categories of mustard-related eye injuries are acute, chronic, and delayed-onset manifestations. Mustard keratopathy (MK) is a known complication characterized by corneal opacification, ulceration, thinning, and neovascularization that can lead to severe vision loss and discomfort. Recently, a few reports demonstrated the role of senescence induction as a new pathological mechanism in mustard-related injuries that could affect wound healing. We ran the first murine model of delayed-onset MK and nitrogen mustard-induced senescence, evaluating the pathological signs of senescence in the cornea using beta-galactosidase staining. Our results suggest that nitrogen mustard exposure causes senescence in the corneal cells, which could be the underlying mechanism for chronic and late-onset ocular surface damage. We also found a significant correlation between the percentage of positive beta-galactosidase staining and the degree of fibrosis in the cornea. This provides valuable insight into the possible role of anti-senescence drugs in the near future for accelerating corneal healing and restricting fibrosis in patients with mustard keratopathy.

Mustard Gas-Induced Ocular Surface Disorders: An Update on the Pathogenesis, Clinical Manifestations, and Management

PURPOSE

Mustard gas (MG) is a potent blistering and alkylating agent that has been used for military and terrorism purposes. Ocular surface injuries are common after exposure to MG. This review provides an update on the pathophysiology, ocular surface complications, and treatment options for MG-related ocular injuries.

METHODS

Required information was obtained by reviewing various databases such as Cochrane Library, Google Scholar, and PubMed until March 2022. Data were collected by using keywords: "mustard gas" OR "sulfur mustard" AND "eye" OR "cornea" OR "ocular complication" OR "keratitis" OR "keratopathy" OR "limbal stem cell deficiency" OR "dry eye."

RESULTS

Chronic intracellular toxicity, inflammation, and ischemia have been shown to play an essential role in the pathogenesis of MG injury. Ocular surface injuries can have acute, chronic, and most distinctly a delayed-onset presentation leading to various degrees of limbal stem cell deficiency. To date, no treatment has been agreed on as the standard treatment for chronic/delayed-onset MG keratopathy. Based on the authors' experience, we propose a management algorithm for MG-related ocular surface injuries involving optimization of ocular health, anti-inflammatory therapy, and if needed surgical interventions. The management of chronic and delayed-onset presentation remains challenging.

CONCLUSIONS

MG keratopathy is a unique form of chemical injury which can lead to a range of ocular surface pathologies. Long-term anti-inflammatory therapy even in patients with seemingly mild disease may potentially reduce the likelihood of the development of more severe delayed-onset disease.

Supramolecular detoxification of nitrogen mustard via host-guest encapsulation by carboxylatopillar[5]arene

Nitrogen mustard (NM), a kind of alkylating agent similar to sulfur mustard, remains a threat to public health. However, there is nearly no satisfactory antidote for nitrogen mustard. Herein, we developed a supramolecular antidote to nitrogen mustard through efficient complexation of NM by carboxylatopillar[5]arene potassium salts (CP[5]AK). The cavity of methoxy pillar[5]arene (P5A) is sufficient to encapsulate NM with an association constant of 1.27 × 10² M^-1, which was investigated by ¹H NMR titration, density functional theory studies and independent gradient model studies. NM degrades to the reactive aziridinium salt (2) in the aqueous phase which irreversibly alkylates DNA and proteins, causing severe tissue damage. Considering the size/charge matching with toxic intermediate 2, water-soluble CP[5]AK was selected to encapsulate the toxic aziridinium salt (2), resulting in a high association constant of 4.10 × 10⁴ M^-1. The results of protection experiments of guanosine 5'-monophosphate (GMP) by CP[5]AK indicated that the formation of a complex could effectively inhibit the alkylation of DNA. Besides, in vitro and in vivo experiments also indicated that the toxicity of the aziridinium salt (2) is inhibited with the formation of a stable host-guest complex, and CP[5]AK has a good therapeutic effect on the damage caused by NM. This study provides a new mechanism and strategy for the treatment of NM exposure-induced skin injuries.

Effect of dexamethasone treatment at variable therapeutic windows in reversing nitrogen mustard-induced corneal injuries in rabbit ocular in vivo model

Nitrogen mustard (NM) is an analogue of the potent vesicating agent sulfur mustard, with well-established ocular injury models in rabbit eyes to study vesicant-induced ocular toxicity. The effects of NM-exposure to eyes may include irritation, redness, inflammation, fibrosis, epithelial degradation, blurred vision, partial/complete blindness, which may be temporary or permanent, depending on the route, duration, and dosage of exposure. Effective countermeasures against vesicant exposure are presently not available and are warranted in case of any terrorist activity or accidental leakage from stockpiles. Herein, our focus was to evaluate whether dexamethasone (DEX), an FDA approved potent corticosteroid with documented anti-inflammatory activities, could be an effective treatment modality. Accordingly, utilizing NM-induced corneal injuries in rabbit ocular in vivo model, we examined and compared the efficacy of DEX treatments when administration was started at early (2 h), intermediate (4 h), and late (6 h) therapeutic windows of intervention after NM-exposure and administered every 8 h thereafter. The effects of NM-exposure and DEX treatments were evaluated on clinical (corneal opacity, ulceration, and neovascularization), biological (epithelial thickness, epithelial-stromal separation, blood vessels density, and inflammatory cell and keratocyte counts) and molecular (COX-2 and VEGF expression) parameters, at day 1, 3, 7 and 14. Results indicated that DEX treatment markedly and effectively reversed the NM-induced injury markers in rabbit corneas. Early administration of DEX at 2 h was found to be most effective in reversing NM-induced corneal injuries, followed by DEX 4 h and DEX 6 h administration initiation, indicating that DEX has best efficacy at the early therapeutic window in our study model.

Pathophysiology and inflammatory biomarkers of sulfur mustard-induced corneal injury in rabbits

Sulfur mustard (SM) is a cytotoxic, vesicating, chemical warfare agent, first used in 1917; corneas are particularly vulnerable to SM exposure. They may develop inflammation, ulceration, neovascularization (NV), impaired vision, and partial/complete blindness depending upon the concentration of SM, exposure duration, and bio-physiological conditions of the eyes. Comprehensive in vivo studies have established ocular structural alterations, opacity, NV, and inflammation upon short durations (<4 min) of SM exposure. In this study, detailed analyses of histopathological alterations in corneal structure, keratocytes, inflammatory cells, blood vessels, and expressions of cyclooxygenase (COX)-2, matrix metalloproteinase (MMP)-9, vascular endothelial growth factor (VEGF), and cytokines were performed in New Zealand white rabbits, in a time-dependent manner till 28 days, post longer durations (5 and 7 min) of ocular SM exposure to establish quantifiable endpoints of injury and healing. Results indicated that SM exposure led to duration-dependent increases in corneal thickness, opacity, ulceration, epithelial-stromal separation, and epithelial degradation. Significant increases in NV, keratocyte death, blood vessels, and inflammatory markers (COX-2, MMP-9, VEGF, and interleukin-8) were also observed for both exposure durations compared to the controls. Collectively, these findings would benefit in temporal delineation of mechanisms underlying SM-induced corneal toxicity and provide models for testing therapeutic interventions.

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.

Alteration in inflammatory mediators in seriously eye-injured war veterans, long-term after sulfur mustard exposure

BACKGROUND

Sulfur mustard (SM) exposure produces extensive systemic and ocular adverse effects on the victims. One of the most important effects is immunological insults that can lead to other organ damages, including the eyes.

METHODS

In this descriptive study, 128 SM-exposed veterans with severe eye injury were compared with 31 healthy controls. Tear levels of tumor necrosis factor (TNF)-α and serum concentrations of interleukin (IL)-1α, IL-1β, IL1Ra, IL-6, TNF-α, granulocyte-macrophage colony-stimulating factor (GM-CSF), and Fas Ligand (FasL) were compared between the two groups.

RESULTS

Meibomian gland dysfunction (MGD); tear breakup time (TBUT < 10″); and conjunctival, limbal, and corneal abnormalities were more frequent among the cases (MS-exposed veterans) than the controls. Ocular involvement was mild in 14.8%, moderate in 24.2%, and severe in 60.9% of the cases. Serum levels of IL-1α and FasL were significantly higher among the cases than among the controls (P < 0.001 and P = 0.037, respectively). Also, a significant decrease was observed in serum and tear levels of TNF-α in the cases as compared with controls (P < 0.001, P < 0.001, respectively). Serum levels of FasL were significantly higher in cases with severe ocular involvement than in the controls (P = 0.03). Nonetheless, serum levels of IL-1β, IL-1Ra, IL-1α/IL-1Ra, and IL-6 were not significantly different between the two groups.

CONCLUSION

Serum levels of IL-1α and FasL may cause different ocular surface abnormalities in SM-exposed patients. Lower tear TNF-α concentration may be due to lower serum levels of this cytokine in these patients.

Acute corneal injury in rabbits following nitrogen mustard ocular exposure

Sulfur mustard (SM), a potent vesicating chemical warfare agent, and its analog nitrogen mustard (NM), are both strong bi-functional alkylating agents. Eyes, skin, and the respiratory system are the main targets of SM and NM exposure; however, ocular tissue is most sensitive, resulting in severe ocular injury. The mechanism of ocular injury from vesicating agents' exposure is not completely understood. To understand the injury mechanism from exposure to vesicating agents, NM has been previously employed in our toxicity studies on primary human corneal epithelial cells and ex vivo rabbit cornea organ culture model. In the current study, corneal toxicity from NM ocular exposure (1%) was analyzed for up to 28 days post-exposure in New Zealand White male rabbits to develop an acute corneal injury model. NM exposure led to conjunctival and eyelid swelling within a few hours after exposure, in addition to significant corneal opacity and ulceration. An increase in total corneal thickness and epithelial degradation was observed starting at day 3 post-NM exposure, which was maximal at day 14 post-exposure and did not resolve until 28 days post-exposure. There was an NM-induced increase in the number of blood vessels and inflammatory cells, and a decrease in keratocytes in the corneal stroma. NM exposure resulted in increased expression levels of cyclooxygenase-2, Interleukin-8, vascular endothelial growth factor and Matrix Metalloproteinase 9 indicating their involvement in NM-induced corneal injury. These clinical, biological, and molecular markers could be useful for the evaluation of acute corneal injury and to screen for therapies against NM- and SM-induced ocular injury.

The transient but not resident (TBNR) microbiome: a Yin Yang model for lung immune system

The concept of microbial content of the lung is still controversial. What make this more complicated are controversial results obtaining from different methodologies about lung microbiome and the definition of "lung sterility". Lungs may have very low bacteria but are not completely germ-free. Bacteria are constantly entering from the upper respiratory tract, but are then quickly being cleared. We can find bacterial DNA in the lungs, but it is much harder to ask about living bacteria. Here, we propose that if there is any trafficking of the microorganisms in the lung, it should be a "Transient But Not Resident (TBNR)" model. So, we speculate a "Yin Yang model" for the lung immune system and TBNR. Despite beneficial roles of microbiome on the development of lung immune system, any disruption and alteration in the microbiota composition of upper and lower airways may trigger or lead to several diseases such as asthma, chronic obstructive pulmonary disease and mustard lung disease.

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.

Salivary levels of secretary IgA, C5a and alpha 1-antitrypsin in sulfur mustard exposed patients 20 years after the exposure, Sardasht-Iran Cohort Study (SICS)

Sulfur mustard (SM) is a strong toxic agent that causes acute and chronic health effects on a myriad of organs following exposure. Although the primary targets of inhaled mustard gas are the epithelia of the upper respiratory tract, the lower respiratory tract is the focus of the current study, and upper tract complications remain obscure. To our knowledge there is no study addressing the secretory IgA (S-IgA), C5a, alpha 1 antitrypsin (A1AT) in the saliva of SM-exposed victims. In this study, as many as 500 volunteers, including 372 SM-exposed cases and 128 control volunteers were recruited. A 3 ml sample of saliva was collected from each volunteer, and the level of secretory IgA, C5a, and alpha 1 antitrypsin in the samples were compared between the two groups. The SM-exposed group showed a significantly higher amount of salivary alpha 1 antitrypsin and secretary IgA compared to the control group (p<.006 and p<.018 respectively). The two groups showed no significant difference (p=0.192) in the level of C5a. The results also showed that the level of salivary A1AT is more than that of IgA in severely injured cases. The findings presented here provide valuable insight for both researchers and practitioners dealing with victims of the chemical warfare agent, sulfur mustard. This research indicates that certain branches of the inflammatory processes mandate serious attention in therapeutic interventions.

Conjunctival microbial florae in patients with seriously sulfur mustard induced eye injuries

INTRODUCTION

Ocular surface disorders and infections in sulfur mustard (SM) exposed patients are of particular clinical importance. The aim of the present study is to detect the conjunctival bacterial florae in patients with seriously SM induced eye injuries.

MATERIALS AND METHODS

Conjunctival bacterial florae of 143 seriously eye injured subjects as the study group was detected. The results were compared with 26 normal participants. Both groups were matched in age and sex. The samples were taken by sterile swab from interior fornixes of conjunctiva in both groups and were transported to microbiology laboratory by Stuart's Transport Medium. All samples were inoculated onto Blood agar, Mac Conkey agar and Chocolate agar and isolated microorganisms were identified by biochemical tests. The data were analyzed by SPSS and Man Whitney tests.

RESULTS

Nineteen cases (13.39%) and none of the controls (0%) had positive culture results (p = .043). Isolated microorganisms from patients included coagulase-negative staphylococci 10 cases (52.6%), Staphylococcus aureus 5 cases (26.3%), non enterobacteriaceae gram negative bacilli 2 cases (10.5%), Penicillium spp. 2 cases (10.5%), Citrobacter sp. 1 case (5.2%), non-spore forming Gram positive bacillus 1 case (5.2%) and α hemolytic streptococcus 1 case (5.2%). Two patients had mixed microorganisms and other patients had just one microorganism. Most of the S. aureus isolates were sensitive to usual antibiotics.

CONCLUSIONS

The results of this study showed that the prevalence rate of conjunctival bacterial isolates in patients with seriously SM induced ocular injuries are higher and potentially more dangerous than normal controls.

Evaluation of relationship between the serum levels of inflammatory mediators and ocular injuries induced by sulfur mustard: Sardasht-Iran Cohort Study

Ocular damages induced by sulfur mustard (SM) are the important problems in exposed patients. The damaging mechanisms are not clearly understood. In the present study the relationship between the serum levels of inflammatory mediators and ocular injuries induced by SM was evaluated. Bulbar conjunctiva and limbal tissue abnormalities were significantly more frequent in the expose versus control group (P=0.004 and 0.048 respectively). The serum levels of IL-1alpha and TNF-alpha in the exposed group with and without Slit lamp findings were significantly lower than their counterpart in the control group. The serum levels of IL-1beta in the exposed group with Slit lamp findings were significantly lower than their counterpart in the control group. The serum levels of IL-1beta in the controls with Slit lamp findings were significantly higher than the controls without Slit lamp findings. The serum levels of IL-1Ra and MMP-9 in the exposed group with and without Slit lamp findings do not display any significant differences as compared to the similar controls. The serum levels of IL-6 in the exposed group with or without Slit lamp findings were significantly lower than their counterpart in the control group (P=0.048 and 0.008 respectively). The serum titers of the CRP and RF in the exposed group without Slit lamp findings were significantly elevated versus their counterpart in the control group (P=0.004 and 0.011 respectively). The serum levels of these inflammatory cytokines except for IL-1Ra and MMP-9, decreased in SM exposed subject independent of ocular problems. More local studies on the eyes are needed to clarify the exact role of this cytokines in ocular problems of chemical.