From the Cover: Catalytic Antioxidant Rescue of Inhaled Sulfur Mustard Toxicity

Oxidative Stress: An Intersection Between Radiation and Sulfur Mustard Lung Injury

Nuclear and chemical weapons of mass destruction share both a tragic and beneficial legacy in mankind's history and health. The horrific health effects of ionizing radiation and mustard gas exposures unleashed during disasters, wars, and conflicts have been harnessed to treat human health maladies. Both agents of destruction have been transformed into therapies to treat a wide range of cancers. The discovery of therapeutic uses of radiation and sulfur mustard was largely due to observations by clinicians treating victims of radiation and sulfur mustard gas exposures. Clinicians identified vulnerability of leukocytes to these agents and repurposed their use in the treatment of leukemias and lymphomas. Given the overlap in therapeutic modalities, it goes to reason that there may be common mechanisms to target as protective strategies against their damaging effects. This commentary will highlight oxidative stress as a common mechanism shared by both radiation and sulfur mustard gas exposures and discuss potential therapies targeting oxidative stress as medical countermeasures against the devastating lung diseases wrought by these agents.

Role of macrophage bioenergetics in N-acetylcysteine-mediated mitigation of lung injury and oxidative stress induced by nitrogen mustard

Nitrogen mustard (NM) is a toxic vesicant that causes acute injury to the respiratory tract. This is accompanied by an accumulation of activated macrophages in the lung and oxidative stress which have been implicated in tissue injury. In these studies, we analyzed the effects of N-acetylcysteine (NAC), an inhibitor of oxidative stress and inflammation on NM-induced lung injury, macrophage activation and bioenergetics. Treatment of rats with NAC (150 mg/kg, i.p., daily) beginning 30 min after administration of NM (0.125 mg/kg, i.t.) reduced histopathologic alterations in the lung including alveolar interstitial thickening, blood vessel hemorrhage, fibrin deposition, alveolar inflammation, and bronchiolization of alveolar walls within 3 d of exposure; damage to the alveolar-epithelial barrier, measured by bronchoalveolar lavage fluid protein and cells, was also reduced by NAC, along with oxidative stress as measured by heme oxygenase (HO)-1 and Ym-1 expression in the lung. Treatment of rats with NAC attenuated the accumulation of macrophages in the lung expressing proinflammatory genes including Ptgs2, Nos2, Il-6 and Il-12; macrophages expressing inducible nitric oxide synthase (iNOS), cyclooxygenase (COX)-2 and tumor necrosis factor (TNF)α protein were also reduced in histologic sections. Conversely, NAC had no effect on macrophages expressing the anti-inflammatory proteins arginase-1 or mannose receptor, or on NM-induced increases in matrix metalloproteinase (MMP)-9 or proliferating cell nuclear antigen (PCNA), markers of tissue repair. Following NM exposure, lung macrophage basal and maximal glycolytic activity increased, while basal respiration decreased indicating greater reliance on glycolysis to generate ATP. NAC increased both glycolysis and oxidative phosphorylation. Additionally, in macrophages from both control and NM treated animals, NAC treatment resulted in increased S-nitrosylation of ATP synthase, protecting the enzyme from oxidative damage. Taken together, these data suggest that alterations in NM-induced macrophage activation and bioenergetics contribute to the efficacy of NAC in mitigating lung injury.

Novel Catalytic Antioxidant Formulation Decreases Oxidative Stress, Neuroinflammation and Cognitive Dysfunction in a Model of Nerve Agent Intoxication

Reactive oxygen species have an emerging role in the pathologic consequences of status epilepticus. We have previously demonstrated the efficacy of a water-for-injection formulation of the meso-porphyrin catalytic antioxidant, manganese (III) meso-tetrakis (N-N-diethylimidazole) porphyrin (AEOL10150) against oxidative stress, neuroinflammation, and neuronal death initiated by kainic acid, pilocarpine, diisopropylflurophosphate (DFP), and soman. This previous dose and dosing strategy of AEOL10150 required smaller multiple daily injections, precluding our ability to test its efficacy against delayed consequences of nerve agent exposure such as neurodegeneration and cognitive dysfunction. Therefore, we developed formulations of AEOL10150 designed to deliver a larger dose once daily with improved brain pharmacodynamics. We examined four new formulations of AEOL10150 that resulted in 8 times higher subcutaneous dose with lower acute toxicity, slower absorption, longer half-life, and higher maximal plasma concentrations compared with our previous strategy. AEOL10150 brain levels exhibited improved pharmacodynamics over 24 hours with all four formulations. We tested a subcutaneous dose of 40 mg/kg AEOL10150 in two formulations (2% carboxymethyl cellulose and 4% polyethylene glycol-4000) in the DFP rat model, and both formulations exhibited significant protection against DFP-induced oxidative stress. Additionally, and in one formulation (4% polyethylene glycol-4000), AEOL10150 significantly protected against DFP-induced neuronal death, microglial activation, delayed memory impairment, and mortality. These results suggest that reformulation of AEOL10150 can attenuate acute and delayed outcomes of organophosphate neurotoxicity. SIGNIFICANCE STATEMENT: Reformulation of manganese (III) meso-tetrakis (N-N-diethylimidazole) porphyrin allowed higher tolerated doses of the compound with improved pharmacodynamics. Specifically, one new formulation allowed fewer daily doses and improvement in acute and delayed outcomes of organophosphate toxicity.

Overlapping Science in Radiation and Sulfur Mustard Exposures of Skin and Lung: Consideration of Models, Mechanisms, Organ Systems, and Medical Countermeasures: Overlapping science in radiation and sulfur mustard injuries to lung and skin

PURPOSE

To summarize presentations and discussions from the 2022 trans-agency workshop titled "Overlapping science in radiation and sulfur mustard (SM) exposures of skin and lung: Consideration of models, mechanisms, organ systems, and medical countermeasures."

METHODS

Summary on topics includes: (1) an overview of the radiation and chemical countermeasure development programs and missions; (2) regulatory and industry perspectives for drugs and devices; 3) pathophysiology of skin and lung following radiation or SM exposure; 4) mechanisms of action/targets, biomarkers of injury; and 5) animal models that simulate anticipated clinical responses.

RESULTS

There are striking similarities between injuries caused by radiation and SM exposures. Primary outcomes from both types of exposure include acute injuries, while late complications comprise chronic inflammation, oxidative stress, and vascular dysfunction, which can culminate in fibrosis in both skin and lung organ systems. This workshop brought together academic and industrial researchers, medical practitioners, US Government program officials, and regulators to discuss lung-, and skin- specific animal models and biomarkers, novel pathways of injury and recovery, and paths to licensure for products to address radiation or SM injuries.

CONCLUSIONS

Regular communications between the radiological and chemical injury research communities can enhance the state-of-the-science, provide a unique perspective on novel therapeutic strategies, and improve overall US Government emergency preparedness.

Targeting Tumor Necrosis Factor Alpha to Mitigate Lung Injury Induced by Mustard Vesicants and Radiation

Pulmonary injury induced by mustard vesicants and radiation is characterized by DNA damage, oxidative stress, and inflammation. This is associated with increases in levels of inflammatory mediators, including tumor necrosis factor (TNF)α in the lung and upregulation of its receptor TNFR1. Dysregulated production of TNFα and TNFα signaling has been implicated in lung injury, oxidative and nitrosative stress, apoptosis, and necrosis, which contribute to tissue damage, chronic inflammation, airway hyperresponsiveness, and tissue remodeling. These findings suggest that targeting production of TNFα or TNFα activity may represent an efficacious approach to mitigating lung toxicity induced by both mustards and radiation. This review summarizes current knowledge on the role of TNFα in pathologies associated with exposure to mustard vesicants and radiation, with a focus on the therapeutic potential of TNFα-targeting agents in reducing acute injury and chronic disease pathogenesis.

New uses of Melatonin as a Drug, a Review

Melatonin is a simple compound with a proper chemical name N-acetyl-5-methoxy tryptamine and known as a hormone controlling circadian rhythm. Humans produce melatonin at night which is the reason for sleeping in the night and awakening over the day. Melatonin interacts with melatonin receptors MT1 and MT2 but it was also revealed that melatonin is a strong antioxidant and it also has a role in regulation of cell cycle. Currently, melatonin is used as a drug for some types of sleep disorder but the recent research points to the fact that melatonin can also serve for the other purposes including prophylaxis or therapy of lifestyle diseases, cancer, neurodegenerative disorders and exposure to chemicals. This review summarizes basic facts and direction of the current research on melatonin. The actual literature was scrutinized for the purpose of this review.

Extracellular nucleic acid scavenging rescues rats from sulfur mustard analog-induced lung injury and mortality

Sulfur mustard (SM) is a highly toxic war chemical that causes significant morbidity and mortality and lacks any effective therapy. Rats exposed to aerosolized CEES (2-chloroethyl ethyl sulfide; 10% in ethanol), an analog of SM, developed acute respiratory distress syndrome (ARDS), which is characterized by increased inflammation, hypoxemia and impaired gas exchange. We observed elevated levels of extracellular nucleic acids (eNA) in the bronchoalveolar lavage fluid (BALF) of CEES-exposed animals. eNA can induce inflammation, coagulation and barrier dysfunction. Treatment with hexadimethrine bromide (HDMBr; 10 mg/kg), an eNA neutralizing agent, 2 h post-exposure, reduced lung injury, inhibited disruption of alveolar-capillary barrier, improved blood oxygenation (PaO₂/FiO₂ ratio), thus reversing ARDS symptoms. HDMBr treatment also reduced lung inflammation in the CEES-exposed animals by decreasing IL-6, IL-1A, CXCL-1 and CCL-2 mRNA levels in lung tissues and HMGB1 protein in BALF. Furthermore, HDMBr treatment also reduced levels of lung tissue factor and plasminogen activator inhibitor-1 indicating reduction in clot formation and increased fibrinolysis. Fibrin was reduced in BALF of the HDMBr-treated animals. This was further confirmed by histology that revealed diminished airway fibrin, epithelial sloughing and hyaline membrane in the lungs of HDMBr-treated animals. HDMBr completely rescued the CEES-associated mortality 12 h post-exposure when the survival rate in CEES-only group was just 50%. Experimental eNA treatment of cells caused increased inflammation that was reversed by HDMBr. These results demonstrate a role of eNA in the pathogenesis of CEES/SM-induced injury and that its neutralization can serve as a potential therapeutic approach in treating SM toxicity.

The immunomodulatory effects of mesenchymal stem cells on long term pulmonary complications in an animal model exposed to a sulfur mustard analog

INTRODUCTION

Sulfur Mustard (SM) is one of the most lethal chemicals with major complications manifested in the lungs. Although the pathogenesis behind SM-induced lung injury still remains poorly understood, prolonged activation and the imbalance of two major macrophage populations (M1 and M2) have been suggested to be involved. Here, we tried to investigate the effectiveness of adipose-derived mesenchymal stem cells (AD-MSC) on long-term lesions induced by CEES, an SM analog. The modulation of pulmonary immune cells and alveolar macrophage phenotype alteration was studied in the animal model used.

METHODS

Histopathological changes were investigated in the lungs and analysis of surface markers of alveolar macrophages as well as their cytokine expression in the BAL fluid was carried out by flow cytometry and ELISA, respectively.

RESULTS

Treatment of mice with AD-MSC after intraperitoneal administration of CEES (10 mg/kg) reduces progressive histopathologic changes in the lung. Flow cytometric analysis of isolated alveolar macrophages in the bronchoalveolar lavage showed that the accumulation of both M1 and M2 macrophages in response to CEES was reduced by MSC administration. AD-MSCs caused a marked reduction in the CD86- and CD206-expressing macrophages compared to the untreated groups. The modulating effect of AD-MSCs in the M1-subset was much more significant compared to M2. These findings suggest that AD-MSCs understand their environment and restore the balance in disorders associated with Th1 or Th2 imbalance. Our results indicate that MSCs may represent an effective approach to repair lung injury induced by mustards.

Antioxidant drug therapy as a neuroprotective countermeasure of nerve agent toxicity

The use of chemical warfare agents is an ongoing, significant threat to both civilians and military personnel worldwide. Nerve agents are by far the most formidable toxicants in terms of their lethality and toxicity. Nerve agents initiate neurotoxicity by the irreversible inhibition of acetylcholinesterase and resultant accumulation of acetylcholine in excitable tissues. The cholinergic toxidrome presents as miosis, lacrimation, diarrhea, fasciculations, seizures, respiratory arrest and coma. Current medical countermeasures can attenuate acute mortality and confer limited protection against secondary neuronal injury when given rapidly after exposure. However, there is an urgent need for the development of novel, add-on neuroprotective therapies to prevent mortality and long-term toxicity of nerve agents. Increasing evidence suggests that pathways other than direct acetylcholinesterase inhibition contribute to neurotoxicity and secondary neuronal injury. Among these, oxidative stress is emerging as a key therapeutic target for nerve agent toxicity. In this review, we discuss the rationale for targeting oxidative stress in nerve agent toxicity and highlight research investigating antioxidant therapy as a neuroprotective medical countermeasure to attenuate oxidative stress, neuroinflammation and neurodegeneration.

Improvements in SOD mimic AEOL-10150, a potent broad-spectrum antioxidant

AEOL-10150 is a broad-spectrum metalloporphyrin superoxidase dismutase (SOD) mimic specifically designed to neutralize reactive oxygen and nitrogen species. Research has shown that AEOL-10150 is a potent medical countermeasure against national security threats including sulfur mustard (SM), nerve agent exposure and radiation pneumonitis following a radiological/nuclear incident sufficient to cause acute radiation syndrome (ARS). AEOL-10150 performed well in animal safety studies, and two completed phase 1 safety studies in patients demonstrated that the drug was safe and well tolerated, indicating that AEOL-10150 has potential as a new catalytic antioxidant drug. In this article, we review improvements in AEOL-10150 in preclinical pharmacodynamic studies, especially regarding anti-SM, chlorine gas and radiation exposure studies.

Porphyrins in troubled times: a spotlight on porphyrins and their metal complexes for explosives testing and CBRN defense

A critical perspective on (metallo)porphyrins in security-related applications: the past, present and future of explosives detection, CBRN defense, and beyond.

An Official American Thoracic Society Workshop Report: Chemical Inhalational Disasters. Biology of Lung Injury, Development of Novel Therapeutics, and Medical Preparedness

This report is based on the proceedings from the Inhalational Lung Injury Workshop jointly sponsored by the American Thoracic Society (ATS) and the National Institutes of Health (NIH) Countermeasures Against Chemical Threats (CounterACT) program on May 21, 2013, in Philadelphia, Pennsylvania. The CounterACT program facilitates research leading to the development of new and improved medical countermeasures for chemical threat agents. The workshop was initiated by the Terrorism and Inhalational Disasters Section of the Environmental, Occupational, and Population Health Assembly of the ATS. Participants included both domestic and international experts in the field, as well as representatives from U.S. governmental funding agencies. The meeting objectives were to (1) provide a forum to review the evidence supporting current standard medical therapies, (2) present updates on our understanding of the epidemiology and underlying pathophysiology of inhalational lung injuries, (3) discuss innovative investigative approaches to further delineating mechanisms of lung injury and identifying new specific therapeutic targets, (4) present promising novel medical countermeasures, (5) facilitate collaborative research efforts, and (6) identify challenges and future directions in the ongoing development, manufacture, and distribution of effective and specific medical countermeasures. Specific inhalational toxins discussed included irritants/pulmonary toxicants (chlorine gas, bromine, and phosgene), vesicants (sulfur mustard), chemical asphyxiants (cyanide), particulates (World Trade Center dust), and respirable nerve agents.