A Role for Mitochondrial Oxidative Stress in Sulfur Mustard Analog 2-Chloroethyl Ethyl Sulfide-Induced Lung Cell Injury and Antioxidant Protection

Abstract

Sulfur mustards (SMs) have been used as warfare agents since World War I and still pose a significant threat against civilian and military personnel. SM exposure can cause significant blistering of the skin, respiratory injury, and fibrosis. No antidote currently exists for SM exposure, but recent studies, using the SM analog 2-chloroethyl ethyl sulfide (CEES), have focused on the ability of antioxidants to prevent toxicity. Although antioxidants can prevent CEES-induced toxicity, the mechanisms by which these compounds are effective against SM agents are largely unknown. Using human bronchial epithelial (16HBE) cells and primary small airway epithelial cells, we show that CEES causes a significant increase in mitochondrial dysfunction as early as 4 h, which is followed by increases in mitochondrial reactive oxygen species (ROS), peaking 12 h after exposure. We also have identified a catalytic antioxidant metalloporphyrin that can rescue airway cells from CEES-induced toxicity when added 1 h after CEES exposure. In addition, the cytoprotective effects of the catalytic antioxidant are associated with correcting mitochondrial dysfunction ROS, DNA oxidation, and decreases in intracellular GSH. These findings suggest a role for oxidative stress in CEES toxicity and provide a rationale to investigate antioxidants as rescue agents in SM exposures.Bis(2-chloroethyl sulfide) or sulfur mustard (SM) was first synthesized in the late 1880s and since has been used as a warfare agent on a number of occasions. SM was first used in World War I and has been used in warfare as recently as the Iran-Iraq conflict of the late 1980s (Blanc, 1999). Although SM is less of a threat in warfare as it once was, it still posses a threat to military and civilian personnel because of current concerns for its deployment in a terrorist attack.Sulfur mustards are classic vesicating agents that mainly affect the skin, eyes, and respiratory system. There is no known antidote or specific treatment for SM exposure, and the current therapy is largely supportive. SM on the skin can be decontaminated with soap and water or a dilute bleach solution, but internal exposure, such as the respiratory system, is considerably more difficult to treat (Munro et al., 1990;Watson and Griffin, 1992). SM produces airway damage that includes necrosis, inflammation, and edema (Kehe and Szinicz, 2005). The exact mechanism of SM toxicity is unknown. 2-Chloroethyl ethyl sulfide (CEES; half mustard) is a monofunctional analog of SM (Fig. 1) that provides a useful model for SM injury without the need for a specialized containment facility. CEES, like SM, is an alkylating agent that can bind DNA and other macromolecules within the cell. Recent research into counteragents has focused on bolstering the endogenous antioxidant defenses by supplementation with N-acetyl-cysteine (McClintock et al

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

“…Although AEOL 10150 did not appear to improve GSH levels, this effect may be complicated by the formation of SM-GSH adducts which would not have been detected by the HPLC methods used here (Batal et al, 2015;Mol et al, 2008). Other publications investigating oxidative stress and vesicants have concluded that reductions in the measured markers of oxidative stress are linked to lowered toxicity (Gould et al, 2009;Laskin et al, 2010;O'Neill et al, 2010;Tewari-Singh et al, 2011;Ucar et al, 2007). Our results support the hypothesis that AEOL 10150 lowered oxidative stress in this model, which correlated with attenuating SM toxicity.…”

“…Catalytic antioxidants can scavenge multiple reactive oxygen and nitrogen species without being consumed in the reaction (Day, 2004). This antioxidant has shown promising effects in other studies of SM induced toxicity in both in vitro and in vivo models (Gould et al, 2009;O'Neill et al, 2010O'Neill et al, , 2011Tewari-Singh et al, 2014). This catalytic antioxidant has also displayed therapeutic benefits in other models of lung injury such as exposure to fractionated radiation and chlorine gas inhalation (McGovern et al, 2011;Rabbani et al, 2007).…”

“…AEOL 10150 is a metalloporphyrin class of catalytic antioxidants that has shown promising therapeutic potential for suppressing oxidative stress in relevant SM analog, 2-chloroethyl ethyl sulfide (CEES) models (Gould et al, 2009;O'Neill et al, 2010O'Neill et al, , 2011Tewari-Singh et al, 2014). The aim of this study is to characterize the efficacy of this catalytic antioxidant in improving survival by attenuating the progression of oxidative stress, inflammation, and injury following SM inhalation.…”

Efficacy of Glutathione in Ameliorating Sulfur Mustard Analog-Induced Toxicity in Cultured Skin Epidermal Cells and in SKH-1 Mouse Skin In Vivo

“…Apart from HD, its monofunctional analog 2-chloroethyl ethyl sulfide (CEES) also causes several skin toxic effects comparable with HD, and therefore CEES is used extensively to uncover the mechanism of action of HD and to screen effective therapeutic agents (Han et al, 2004;Paromov et al, 2007;Gould et al, 2009;Tewari-Singh et al, 2009. HD/CEES-caused oxidative stress results in the 8-oxo-2-deoxyguanosine DNA adduct as well as lipid and protein oxidation, which can cause inflammation and other toxic responses in skin Black et al, 2010).…”

Sulphur Mustard Induced Toxicity, Mechanism of Action and Current Medical Management

“…The standard mouse ear animal model for studying pathophysiology of SM-induced skin lesions have been shown to have altered reaction to injury with delayed inflammatory changes compared to mouse skin 78 . Animal models exposed with 2-chloroethyl ethyl sulphide [CEES; half mustard, used to produce SM like skin lesions] provides the initial steps for evaluation of therapies that need to be repeated using SM due to differences in the metabolism and the mechanism of action 105,106 . Thus, use of CEES as a stimulant of SM for antidote evaluation may not be appropriate.…”