Capsaicinoids, chloropicrin and sulfur mustard: possibilities for exposure biomarkers

A review of chemical warfare agents linked to respiratory and neurological effects experienced in Gulf War Illness

Over 40% of veterans from the Persian Gulf War (GW) (1990-1991) suffer from Gulf War Illness (GWI). Thirty years since the GW, the exposure and mechanism contributing to GWI remain unclear. One possible exposure that has been attributed to GWI are chemical warfare agents (CWAs). While there are treatments for isolated symptoms of GWI, the number of respiratory and cognitive/neurological issues continues to rise with minimum treatment options. This issue does not only affect veterans of the GW, importantly these chronic multisymptom illnesses (CMIs) are also growing amongst veterans who have served in the Afghanistan-Iraq war. What both wars have in common are their regions and inhaled exposures. In this review, we will describe the CWA exposures, such as sarin, cyclosarin, and mustard gas in both wars and discuss the various respiratory and neurocognitive issues experienced by veterans. We will bridge the respiratory and neurological symptoms experienced to the various potential mechanisms described for each CWA provided with the most up-to-date models and hypotheses.

Effect of supersaturated oxygen emulsion treatment on chloropicrin-induced chemical injury in ex vivo rabbit cornea

With a possibility for the use of chemical weapons in battlefield or in terrorist activities, effective therapies against the devastating ocular injuries, from their exposure, are needed. Oxygen plays a vital role in ocular tissue preservation and wound repair. We tested the efficacy of supersaturated oxygen emulsion (SSOE) in reducing ex vivo corneal and keratocyte injury from chloropicrin (CP). CP, currently used as a pesticide, is a chemical threat agent like the vesicating mustard agents and causes severe corneal injury. Since our previous study in human corneal epithelial cells showed the treatment potential of SSOE (55 %), we further tested its efficacy in an ex vivo CP-induced rabbit corneal injury model. Corneas were exposed to CP (700 nmol) for 2 h, washed and cultured with or without SSOE for 24 h or 96 h. At 96 h post CP exposure, SSOE treatment presented a healing tendency of the corneal epithelial layer, and abrogated the CP-induced epithelial apoptotic cell death. SSOE treatment also reduced the CP induced DNA damage (H2A.X phosphorylation) and inflammatory markers (e.g. MMP9, IL-21, MIP-1β, TNFα). Further examination of the treatment efficacy of SSOE alone or in combination with other therapies in in vivo cornea injury models for CP and vesicants, is warranted.

Toxic consequences and oxidative protein carbonylation from chloropicrin exposure in human corneal epithelial cells

Chloropicrin (CP), a warfare agent now majorly used as a soil pesticide, is a strong irritating and lacrimating compound with devastating toxic effects. To elucidate the mechanism of its ocular toxicity, toxic effects of CP (0-100 μM) were studied in primary human corneal epithelial (HCE) cells. CP exposure resulted in reduced HCE cell viability and increased apoptotic cell death with an up-regulation of cleaved caspase-3 and poly ADP ribose polymerase indicating their contribution in CP-induced apoptotic cell death. Following CP exposure, cells exhibited increased expression of heme oxygenase-1, and phosphorylation of H2A.X and p53 as well as 4-hydroxynonenal adduct formation, suggesting oxidative stress, DNA damage and lipid peroxidation. CP also caused increases in mitogen activated protein kinase-c-Jun N-terminal kinase and inflammatory mediator cyclooxygenase-2. Proteomic analysis revealed an increase in the carbonylation of 179 proteins and enrichment of pathways (including proteasome pathway and catabolic process) in HCE cells following CP exposure. CP-induced oxidative stress and lipid peroxidation can enhance protein carbonylation, prompting alterations in corneal epithelial proteins as well as perturbing signaling pathways resulting in toxic effects. Pathways and major processes identified following CP exposure could be lead-hit targets for further biochemical and molecular characterization as well as therapeutic intervention.

Development of mouse models for the study of chloropicrin and hydrogen fluoride ocular injury

The possibility of chemical terrorism within the United States is a rising concern, with the eye being one of the most sensitive tissues to toxicant exposure. We sought to develop mouse models of toxicant-induced ocular injury for the purpose of evaluating potential therapeutics. Chloropicrin (CP) and hydrogen fluoride (HF) were selected for the study owing to their reportedly high potential to induce ocular injury. Eyes of female BALB/c mice were exposed to CP or HF vapor in order to produce a moderate injury, as defined by acute corneal epithelial loss followed by progressive corneal pathology with the absence of injury to deeper eye structures. Clinical injury progression was evaluated up to 12 weeks postexposure, where a significant dose-dependent induction of corneal neovascularization was measured. Histopathology noted epithelial necrosis and stromal edema as early as 24 h after exposure but was resolved by 12 weeks. A significant increase in inflammatory cytokine concentrations was measured in the cornea 24 h after exposure and returned to baseline by day 14. The ocular injury models we developed here for CP and HF exposure should serve as a valuable tool for the future evaluation of novel therapeutics and the molecular mechanisms of injury.

Properties and reactivity of nucleic acids relevant to epigenomics, transcriptomics, and therapeutics

Developments in epigenomics, toxicology, and therapeutic nucleic acids all rely on a precise understanding of nucleic acid properties and chemical reactivity. In this review we discuss the properties and chemical reactivity of each nucleobase and attempt to provide some general principles for nucleic acid targeting or engineering. For adenine-thymine and guanine-cytosine base pairs, we review recent quantum chemical estimates of their Watson-Crick interaction energy, π-π stacking energies, as well as the nuclear quantum effects on tautomerism. Reactions that target nucleobases have been crucial in the development of new sequencing technologies and we believe further developments in nucleic acid chemistry will be required to deconstruct the enormously complex transcriptome.

Dermal absorption of fumigant gases during HAZMAT incident exposure scenarios—Methyl bromide, sulfuryl fluoride, and chloropicrin

Accidental or intentional releases of toxic gases or vapors are the most common occurrence in hazardous material (HAZMAT) incidents that result in human injuries. The most serious hazard from exposure to gases or vapors is via the respiratory system. Dermal uptake, as a secondary route, is still a concern, most acutely for the unprotected public. There is a limited evidence base describing skin absorption of toxic gases and vapors in HAZMAT exposure scenarios, which are relatively brief compared with traditional test periods for skin absorption studies. We describe research designed to provide experimental data to support decision-making by first responders regarding skin decontamination in HAZMAT-focused exposure scenarios involving toxic gases. We present findings for three common fumigants, methyl bromide, sulfuryl fluoride, and chloropicrin assessed using an Organization for Economic Co-operation and Development in vitro toxicology protocol utilizing human skin and gas/vapor exposures. Results indicate that for atmospheric concentrations that would be lethal via inhalation (LCLo), intact skin provides an excellent barrier to exposures up to 30 min, with little influence of common clothing fabric and high temperature and humidity conditions. The findings may challenge the current HAZMAT dogma requiring mass personal decontamination by strip and shower for short-term exposures to sulfuryl fluoride and chloropicrin gas/vapor.

Accumulation of intact sulfur mustard in adipose tissue and toxicokinetics by chemical conversion and isotope-dilution liquid chromatography-tandem mass spectrometry

Sulfur mustard (SM) is a powerful vesicant and one of the most harmful chemical warfare agents. Although having been studied for a long time, it is still difficult to fully elucidate the mechanisms of SM poisoning, and there is no effective antidote or specific treatment for SM injury. The investigations on toxicokinetics and tissue distribution of SM will help to understand its toxicity and provide a theoretical basis for pretreatment and therapy of SM poisoning. But the metabolic trajectory or fate of intact SM in vivo remains unclear, and there are insufficient experimental data to elucidate, due to its high reactivity and difficulty in biomedical sample analysis. In this paper, a sensitive method for the detection and quantification of intact SM in blood or tissues using isotope-dilution LC-MS/MS coupled with chemical conversion was developed. By transforming highly reactive SM into stable derivative product, the real concentration of intact SM in biological samples was obtained accurately. The toxicokinetics and tissue distribution studies of intact SM in rats were successfully profiled by the novel method after intravenous (10 mg/kg) or cutaneous administration (1, 3 and 10 mg/kg). The SM level in blood with peak time at 30-60 min determined in cutaneous exposure experiment was found much higher than previously reported, and the mean residence time in blood extended to 1-1.5 h. A significant accumulation of intact SM was observed in adipose tissues, including the perirenal fat, epididymal fat, subcutaneous fat and brown fat, in which the concentrations of SM were at least 15 times greater than those in non-adipose tissues in cutaneous exposed rats. The recovery of SM in body fat was calculated as 3.3 % of bioavailable SM (the bioavailability after cutaneous exposure was evaluated as 16 %). Thus, the adipose tissue was important for SM distribution and toxicity, which may pioneer a new model for both the prevention and treatment of SM exposure.

Antioxidants as potential medical countermeasures for chemical warfare agents and toxic industrial chemicals

The continuing horrors of military conflicts and terrorism often involve the use of chemical warfare agents (CWAs) and toxic industrial chemicals (TICs). Many CWA and TIC exposures are difficult to treat due to the danger they pose to first responders and their rapid onset that can produce death shortly after exposure. While the specific mechanism(s) of toxicity of these agents are diverse, many are associated either directly or indirectly with increased oxidative stress in affected tissues. This has led to the exploration of various antioxidants as potential medical countermeasures for CWA/TIC exposures. Studies have been performed across a wide array of agents, model organisms, exposure systems, and antioxidants, looking at an almost equally diverse set of endpoints. Attempts at treating CWAs/TICs with antioxidants have met with mixed results, ranging from no effect to nearly complete protection. The aim of this commentary is to summarize the literature in each category for evidence of oxidative stress and antioxidant efficacy against CWAs and TICs. While there is great disparity in the data concerning methods, models, and remedies, the outlook on antioxidants as medical countermeasures for CWA/TIC management appears promising.

Organochlorine pesticide levels and risk of Alzheimer’s disease in north Indian population

Alzheimer’s disease (AD) could result from a multifactorial process involving both genetic predisposition and exposure to environmental factors like pesticides. A case control study of 70 patients of AD and 75 controls was done to examine the association between organochlorine pesticides (OCPs) and risk of AD. OCPs (hexachlorocyclohexane (HCH), aldrin, dieldrin, endosulfan, pp′-dichlorodiphenyldichloroethylene ( pp′-DDE), op′-DDE, pp′-dichlorodiphenyltrichloroethane ( pp′-DDT), op′-DDT, pp′-dichlorodiphenyldichloroethane ( pp′ -DDD) and op′-DDD) were extracted from blood and quantitatively estimated using gas chromatography. A Mann–Whitney U test revealed significant difference in β-HCH levels ( U = 1237.00, W = 4087.00, z = −6.296, p = 0.000, r = −0.71), dieldrin levels ( U = 1449.00, W = 4299.00, z = −5.809, p = 0.000, r = −0.68) and pp′-DDE levels ( U = 2062.00, W = 4912.00, z = −2.698, p = 0.007, r = −0.59) between AD patients and controls. In conclusion, this study supports epidemiological studies that associate exposure to pesticides with increased risk of AD, and we identified the specific pesticides β-HCH, dieldrin and pp′-DDE that are associated with the risk of AD in the north Indian population. However, further research is needed to establish the potential role of these OCPs as an etiologic agent for AD case.