Ozone-induced Inflammation in the Lower Airways of Human Subjects

Abstract Although ozone (O3) has been shown to induce inflammation in the lungs of animals, very little is known about its inflammatory effects on humans. In this study, 11 healthy nonsmoking men, 18 to 35 yr of age (mean, 25.4 ± 3.5), were exposed once to 0.4 ppm O3 and once to filtered air for 2 h with intermittent exercise. Eighteen hours later, bronchoalveolar lavage (BAL) was performed and the cells and fluid were analyzed for various indicators of inflammation. There was an 8.2-fold increase in the percentage of polymorphonuclear leukocytes (PMN) in the total cell population, and a small but significant decrease in the percentage of macrophages after exposure to O3. Immunoreactive neutrophil elastase often associated with inflammation and lung damage increased by 3.8-fold in the fluid while its activity increased 20.6-fold in the lavaged cells. A 2-fold increase in the levels of protein, albumin, and IgG suggested increased vascular permeability of the lung. Several biochemical markers that could act as chemotactic or regulatory factors in an inflammatory response were examined in the BAL fluid (BALF). The level of complement fragment C3α was increased by 1.7-fold. The chemotactic leukotriene B4 was unchanged while prostaglandin E2 increased 2-fold. In contrast, three enzyme systems of phagocytes with potentially damaging effects on tissues and microbes, namely, NADPH-oxidase and the lysosomal enzymes acid phosphatase and β-glucuronidase, were increased neither in the lavaged fluid nor cells. In addition, the amounts of f ibrogenic-related molecules were assessed in BALF. Fibronectin was elevated 6.4-fold while tissue factor and factor VII, two initiating proteins of the extrinsic coagulation pathway, increased by 2.1- and 1.8-fold, respectively. Urokinase plasminogen activator (U-PA), a neutral protease with fibrinolytic activity, increased by 3.6-fold. The findings show that an acute exposure to 0.4 ppm O3 results in increased levels of inflammatory cells and soluble factors potentially capable of producing damage in the lower airways of humans.