CLARA CELL PROTEIN (CC-16) INDUCES A PHOSPHOLIPASE A(2)-MEDIATED INHIBITION OF FIBROBLAST MIGRATION IN-VITRO

Clara cell protein (CC-16, also designated CC-10) is synthesized by the bronchiolar epithelium and has been suggested as an inhibitor of phospholipase A(2) (PLA(2)) activity. Therefore, CC-16 is a candidate for controlling inflammatory events in the lung. Because CC-16 amounts and function may be altered in fibrosing lung diseases in which bronchiolar injury has been reported, it was measured in alveolar fluids and sera. Secretory PLA(2) activity in alveolar fluids and the influence of CC-16 on platelet-derived growth factor-induced human fibroblast chemotaxis and cytosolic PLA(2) activity were also explored. CC-16 content was decreased in alveolar fluids from idiopathic pulmonary fibrosis (IPF: 1.3 +/- 0.1 mg/L) and bleomycin lung (1.1 +/- 0.2 versus 2.1 +/- 0.2 mg/L in controls, p < 0.05), whereas there was a three- to ninefold increase in secretory PLA(2) activity (p < 0.05 versus controls). CC-16 inhibited fibroblast chemotaxis in a dose-dependent manner (90% inhibition at 30 mu g/ml CC-16). This inhibition was reversed by reducing CC-16. CC-16 was also able to lower fibroblastic cytosolic PLA(2) activity by 50% in vitro. In summary, CC-16 is able to inhibit fibroblast chemotaxis in vitro by mechanisms that may be related to a blockage of cytosolic PLA(2) activity. It can be postulated that CC-16 deficiency may contribute to fibroblast burden activity in fibrosing lung diseases.