Lysozyme is an ozone-sensitive component of alveolar type II cell lamellar bodies

Abstract

Exposure of rats to 3 ppm ozone for up to 8 h results in significant changes in lamellar bodies, the surfactant storing organelles of type II cells. We have previously shown that a 14 kDa lamellar body protein is decreased as early as 4 h after the onset of ozone exposure. We have isolated this ozone-sensitive protein from rat lung lamellar bodies and identified it as lysozyme by immunochemical methods, as well as by its amino acid composition, N-terminal amino acid sequence and bacteriolytic activity. Reduced lysozyme activity in isolated lamellar bodies is detected as early as 4 h after the start of ozone exposure. Following an 8 h ozone exposure, the activity does not return to control levels for at least 48 h. Lamellar body lysozyme is expected to be secreted with surfactant phospholipids, thereby contributing to the antimicrobial defense of the alveolar lining layer. The acute lysozyme deficiency seen in ozone-induced oxidant injury may reduce the resistance of the lung to infection.