Oxidant air pollutants like ozone increase risk for exacerbation of cystic fibrosis, asthma, and COPD. Ultrafine particulates, which also can bear surface free radicals, can have such effects, alone or in synergy with ozone. Oxidant gases like supraphysiologic oxygen and ozone cause extracellular ATP release from lung cells, activating critical survival signals. Prompt, reversible ATP release due to ozone (50-200 ppb) occurs in tracheal, bronchial, small airway, and alveolar epithelial cells, appears due to calcium-, rho kinase-, and PI 3-kinase-dependent vesicular exocytosis, and, in polarized bronchial epithelium, is mainly from the apical surface. Acute ozone exposure also causes ATP release into lung epithelial lining fluid in mice within 15 min. In vitro, enzymatic removal of extracellular ATP increases cell death, while ATP, DTP, or a nonhydrolyzable ATP analog prevent ozone-induced apoptosis and necrosis. The protecting agonists, and their inhibition by P2 and P2Y receptor-specific antagonists, indicate a role for P2Y receptors. Extracellular ATP activates ERK 1/2 and Akt signaling. Besides epithelial injury, ozone causes release of cytokines like interleukin-8 (IL-8). IL-8 appears in CF airways even before bacterial infection, being the earliest identified pathologic event. We hypothesize that extracellular ATP preserves epithelial energy metabolism, airway cell survival and inhibits IL-8 release due to ozone in normals, that impaired ATP release in CF airways causes opposite effects, and that supplemental extracellular ATP or similar agonists will reverse these processes in CF and normals.
Our specific aims are: (1) measure ATP release, IL-8 release, and cell death in CF and non-CF airway human epithelium in response to ozone, (2) quantitate ozone-mediated ATP release, inflammatory cytokine release, and cell injury/death in airways of CFTR- mutant and non-mutant mice, (3) assess effects of ATP, DTP and ATP analog supplementation in CF and non-CF airway epithelium in ozone in vitro and in vivo, and determine activated signaling pathways and related metabolic effects. Polarized monolayers of primary and transformed CF-mutant and normal airway epithelium cultured on permeable supports with an air-liquid interface will be used. These studies will increase our understanding of lung oxidant injury and repair in CF and normals, and of normal defense mechanisms of airway epithelium.
