Woodsmoke Particulate + Prednisone

Overview

Deployment of military personnel has been associated with increased respiratory illness likely due, in part, to inhalation of unusual particulate matter (PM), such as from burn pits. Inflammation is a key initial response to inhaled particulates. The researchers have developed a protocol using inhaled wood smoke particles (WSP) as a way to study PM-induced airway inflammation. Exposure to wood smoke particles causes symptoms, even in healthy people, such as eye irritation, cough, shortness of breath, and increased mucous production. The purpose of this research study is to see if an oral steroid treatment can reduce the airway inflammation caused by the inhaled WSP. The exposure will be 500 µg/m³ of WSP for 2 hours, with intermittent exercise on a bicycle and rest. The wood is burned in a typical wood stove and piped into the chamber.

Military deployment is associated with exposure to novel particulate matter (PM), such as from burn pits, aeroallergens, and increased cigarette consumption. War fighters exposed to these inhalational exposures exhibit immediate and chronic respiratory morbidity. For example, military service personnel surveyed in both the Republic of Korea (ROK) and Kabul, Afghanistan reported a general increase in respiratory morbidity, including asthma and chronic bronchitis, associated with their deployment. Air contaminants in the ROK were characterized by elevated levels of both PM 0.5-2.5 and PM 2.5-10. Similarly, exposures in Kabul were characterized by multiple airborne PM exposures, including those from burn pits. Burn pit PM includes metals, bioaerosols, organic by-products, and biomass combustion particles. These findings indicate that inhaled PM is a likely cause of respiratory morbidity in the field. Inflammation is a key initial response to inhaled particulates. Wood smoke particles (WSP) serve as a model agent to study PM-induced bronchitis. WSP inhalation generates reactive oxidant (and nitrosative) species which cause local injury of airway epithelial cells and release of damage-associated molecular patterns (DAMPs) that activate toll-like receptors (TLR) and Interleukin (IL)-1-mediated innate immune responses by resident airway macrophages. Contamination of PM with bioaerosols, which contain lipopolysaccharide (LPS), also activates innate immune responses through toll-like receptor 4 (TLR4) activation of resident airway macrophages. These complementary processes result in recruitment of neutrophils (PMN), which mediate luminal airway inflammation with release of toxic mediators such as neutrophil elastase and myeloperoxidase that promote acute and chronic bronchitis. Therefore, mitigation of PM-induced airway neutrophilic inflammation should be a key focus in order to reduce the respiratory morbidity of military personnel. The researchers have studied a number of pro-inflammatory inhaled agents, such as nebulized LPS, ozone (O3), and WSP, as models of acute neutrophilic bronchitis against which to test a number of therapeutic agents. To this effect, the researchers have reported that inhaled fluticasone inhibits O3-induced and LPS-induced neutrophilic inflammation, and that parenteral anakinra and oral gamma-tocopherol inhibit neutrophilic responses to inhaled LPS. In this study, the researchers will evaluate the efficacy of oral prednisone, a readily available anti-inflammatory medication commonly used in airway inflammatory diseases, in mitigating WSP-induced airway inflammation.