Post-Exposure Antioxidant Treatment in Rats Decreases Airway Hyperplasia and Hyperreactivity Due to Chlorine Inhalation

Abstract

We assessed the safety and efficacy of combined intravenous and aerosolized antioxidant administration to attenuate chlorine gasinduced airway alterations when administered after exposure. Adult male Sprague-Dawley rats were exposed to air or 400 parts per million (ppm) chlorine (a concentration likely to be encountered in the vicinity of industrial accidents) in environmental chambers for 30 minutes, and returned to room air, and they then received a single intravenous injection of ascorbic acid and deferoxamine or saline. At 1 hour and 15 hours after chlorine exposure, the rats were treated with aerosolized ascorbate and deferoxamine or vehicle. Lung antioxidant profiles, plasma ascorbate concentrations, airway morphology, and airway reactivity were evaluated at 24 hours and 7 days after chlorine exposure. At 24 hours after exposure, chlorine-exposed rats had significantly lower pulmonary ascorbate and reduced glutathione concentrations. Treatment with antioxidants restored depleted ascorbate in lungs and plasma. At 7 days after exposure, in chlorineexposed, vehicle-treated rats, the thickness of the proximal airways was 60% greater than in control rats, with twice the amount of mucosubstances. Airway resistance in response to methacholine challenge was also significantly elevated. Combined treatment with intravenous and aerosolized antioxidants restored airway morphology, the amount of airway mucosubstances, and airway reactivity to control levels by 7 days after chlorine exposure. Our results demonstrate for the first time, to the best of our knowledge, that severe injury to major airways in rats exposed to chlorine, as characterized by epithelial hyperplasia, mucus accumulation, and airway hyperreactivity, can be reversed in a safe and efficacious manner by the postexposure administration of ascorbate and deferoxamine.Keywords: epithelial injury; epithelial repair; mucosubstances; ascorbate; deferoxamine; aerosol Chlorine is essential to global industry and to global public health. According to the World Chlorine Council (http://www. worldchlorine.org), 14.4 million metric tons were produced in North America in 2008, and 62.8 million metric tons were produced globally. Water treatment makes up only 5% of the world's use of chlorine. The majority of chlorine is used in the production of plastics such as polyvinyl chloride (1). It is also used as a bleaching agent for pulp and paper production, as feedstock in the production of chlorinated solvents used in metalworking, in dry cleaning, in electronics, and in pharmaceutical production (1-6).Only 20 American states contain facilities that produce chlorine, but every American state has facilities that use chlorine. This results in the shipping of chlorine by railcar, and increases the potential for large-scale accidents. According to the Environmental Protection Agency, chlorine gas was related to 518 serious accidents over a 5-year period during the 1990s (1). Multiple-casualty exposures to chlorine have resulted from industrial accidents involving chlorine ta...

Hyaluronan mediates airway hyperresponsiveness in oxidative lung injury

“…There are of course significant differences between Cl 2 and ozone gas toxicity, with respect to acute symptoms, airway penetration, and sequelae (70,73). Nevertheless, both agents cause significant oxidative injury to airway epithelium and increase airway resistance and hyperresponsiveness to methacholine, which last for days postexposure (2,15,21,23,30,60,65,67); furthermore, workers exposed to ozone or chlorine both report a significant increase in acute wheezing episodes (27). In both cases there is increased generation of reactive intermediates, which lasts after the cessation of exposure.…”

“…Increased levels of reactive intermediates were also documented in the lungs of mice and rats exposed to Cl 2 and returned to room air by measuring levels of isoprostanes (75) and products of lipid peroxidation (77). Postexposure administration of antioxidant decreased mortality (77) and decreased airway hypersensitivity (15). Ozone also generates a variety of reactive intermediates and lipid ozonation products (61,62); both Cl 2 and ozone lead to intense inflammatory response and migration of activated inflammatory cells into the lung vascular and alveolar spaces (23,32) and subsequent generation of reactive intermediates, which may fracture H-HA.…”

Formation of chlorinated lipids post-chlorine gas exposure

“…Whole body exposures of male mice or male rats to Cl 2 gas were performed as previously described (31)(32)(33). Exposures were performed with either two mice or rats in the same chamber at any one time, and all exposures were performed between 8:00 AM and 12:00 PM.…”

The role of glucose-6-phosphate dehydrogenase in adipose tissue inflammation in obesity

“…21 Multiple lines of evidence suggest that G6PD-derived NADPH has a contradictory impact on ROS level in different cell types (Table 1). 12,[30][31][32][33][34][35][36][37][38][39][40] Previous reports highlight that cells with intrinsic susceptibility to ROS predominantly use G6PD-derived NADPH for antioxidant defense in response to oxidative stress. In the case of red blood cells (RBCs), there is constant production of ROS by spontaneous reaction and oxygen oxidation of ferrous iron (Fe 2C ) to ferric iron (Fe 3C ).…”

“…32 Neurons are another cell type that is intrinsically vulnerable to oxidative stress and their antioxidant system is significantly alleviated in response to G6PD deficiency. 33 Given that neurons express antioxidant scavengers and enzymes at a very low concentration/activity, reduction of NADPH level by G6PD deficiency appears to affect ROS scavenging system more than ROS production that is mediated by both NADPH-dependent and independent pathways. [34][35][36] Moreover, several neurodegenerative diseases are characterized by downregulation of both expression and activity of G6PD in parallel with a decrement of neuronal antioxidant response.…”