In chyloptysis, SP-A affects the clearance of serum lipoproteins entering the airways

• Published in: American journal of physiology. Lung cellular and molecular physiology 1998-05, Vol.274 (5), p.737-L749
• Main Authors: Alberti, Antonella, Ravenna, Franco, Quaglino, Daniela, Luisetti, Maurizio, Muraca, Maurizio, Previato, Lorenzo, Enzi, Goretta Baldo, Bruni, Roberta, Baritussio, Aldo
• Format: Article
• Language: English
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.1998.274.5.l737

Institute of Internal Medicine and Centro del Consiglio Nazionale delle Recherche per lo Studio dell' Invecchiamento, University of Padova, 35128 Padua; Institute of Respiratory Medicine, University of Ferrara, 44100 Ferrara; Institute of General Pathology, University of Modena, 41100 Modena; and Institute of Respiratory Diseases, Istituto di Ricovero e Cura a Carattere Scientifico Policlinico San Matteo, University of Pavia, 27100 Pavia, Italy; and Department of Pediatrics, King/Drew Medical Center, Los Angeles, California 90059 Serum lipoproteins may enter the airways and appear in sputum (chyloptysis) when the lymphatic circulation is impaired by inflammation, neoplasia, or an abnormal proliferation of smooth muscle cells. While analyzing the bronchoalveolar lavage fluid of a patient with chyloptysis, we noticed that surfactant could not be separated from contaminating serum lipoproteins and speculated that lipoproteins might interact with surfactant components. To clarify this point we immobilized surfactant protein (SP) A on microtiter wells and incubated it with 125 I-labeled very low density lipoproteins (VLDLs), low-density lipoproteins, and high-density lipoproteins. We found that SP-A binds lipoproteins. Studying in greater detail the interaction of SP-A with VLDLs, we found that the binding is time and concentration dependent; is inhibited by unlabeled lipoproteins, phospholipids, and antibodies to SP-A; is increased by Ca 2+ ; and is unaffected by methyl - D -mannopyranoside. Whole surfactant is a potent inhibitor of binding. Furthermore, we found that SP-A increases the degradation of VLDLs by alveolar macrophages and favors the association of VLDLs with alveolar surfactant. We conclude that SP-A influences the disposal of serum lipoproteins entering the airways and speculate that binding to alveolar surfactant might represent an important step in the interaction between exogenous substances and the lung. lung surfactant; surfactant protein A; alveolar macrophages; lymphangioleiomyomatosis