Ozone-induced alterations of lamellar body lipid and protein during alveolar injury and repair

Abstract

Alveolar Type II cells in the rat respond to severe, acute ozone injury (3 ppm ozone for eight hours) by increasing their intracellular pool of surfactant; however, the newly stored surfactant is abnormal in composition. Lamellar bodies isolated between 24 and 96 hours after ozone exposure contained significantly more cholesterol in relation to phosphatidylcholine than did controls. By contrast, the cholesterol content of surfactant isolated from alveolar lavage remained unchanged throughout an 8-day post-ozone period. The total protein content of lamellar bodies in relation to phosphatidylcholine was significantly decreased at 24 and 48 hours post-ozone. Analysis of lamellar body proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the amount of a 14 kDa proteolipid was greatly reduced at the end of the eight-hour ozone exposure and remained low for at least 48 hours. This proteolipid appeared to be a specific lamellar body component since it was not detected in extracellular surfactant. The findings indicate that oxidative alveolar stress initiates characteristic alterations in both lipid and protein constituents of stored surfactant, without perturbation in the composition of extracellular surfactant.