Plasminogen activator inhibitor-1 does not contribute to the pulmonary pathology induced by acute exposure to ozone

Expression of plasminogen activator inhibitor (PAI)-1, the major physiological inhibitor of fibrinolysis, is increased in the lung following inhalation of ozone (O₃), a gaseous air pollutant. PAI-1 regulates expression of interleukin (IL)-6, keratinocyte chemoattractant (KC), and macrophage inflammatory protein (MIP)-2, which are cytokines that promote lung injury, pulmonary inflammation, and/or airway hyperresponsiveness following acute exposure to O₃ Given these observations, we hypothesized that PAI-1 contributes to the severity of the aforementioned sequelae by regulating expression of IL-6, KC, and MIP-2 following acute exposure to O₃ To test our hypothesis, wild-type mice and mice genetically deficient in PAI-1 (PAI-1-deficient mice) were acutely exposed to either filtered room air or O₃ (2 ppm) for 3 h. Four and/or twenty-four hours following cessation of exposure, indices of lung injury [bronchoalveolar lavage fluid (BALF) protein and epithelial cells], pulmonary inflammation (BALF IL-6, KC, MIP-2, macrophages, and neutrophils), and airway responsiveness to aerosolized acetyl-β-methylcholine chloride (respiratory system resistance) were measured in wild-type and PAI-1-deficient mice. O₃ significantly increased indices of lung injury, pulmonary inflammation, and airway responsiveness in wild-type and PAI-1-deficient mice. With the exception of MIP-2, which was significantly lower in PAI-1-deficient as compared to wild-type mice 24 h following cessation of exposure to O₃, no other genotype-related differences occurred subsequent to O₃ exposure. Thus, following acute exposure to O₃, PAI-1 neither regulates pulmonary expression of IL-6 and KC nor functionally contributes to any of the pulmonary pathological sequelae that arise from the noxious effects of inhaled O₃.