Cellular expression of ceruloplasmin in baboon and mouse lung during development and inflammation.

Ceruloplasmin (CP) is an important extracellular antioxidant and free radical scavenger. Although CP is expressed mainly in the liver, recent studies have identified the lung as another major site of CP synthesis. The sites and cell types that are responsible for CP expression in baboon and mouse lung are described. CP mRNA is detected in primordial bronchial epithelium in baboon fetuses by 60 days of gestation. At 140 days of gestation and thereafter, CP mRNA is found in airway epithelium and in the ductal cells of the submucosal glands. In developing and mature mice, CP mRNA is present in epithelial cells throughout the airway. In endotoxin-treated mice, the amount of CP mRNA increases several-fold in large airways but increases only moderately in small airways. This suggests that the high concentration of CP in the mucus lining of the upper airway, which serves to filter harmful substances, is particularly important during stressful conditions. Endotoxin treatment in mice also results in the induction of high levels of CP mRNA in a subset of alveolar wall cells. The data suggest that the airway epithelial cells are the major source of CP in the lung fluid and support ceruloplasmin's critical role in host defense against oxidative damage and infection in the lung.