Surfactant proteins A and D increase in response to intratracheal lipopolysaccharide.
Surfactant proteins A (SP-A) and D (SP-D) are "collectins": proteins with collagen-like region and lectin domain that bind carbohydrates in a calcium-dependent manner. Mannose-binding protein, a serum collectin, is an acute-phase protein. We hypothesized that SP-A and SP-D would respond to an acute stress, such as lung inflammation, in the same manner as does mannose-binding protein, with increased messenger ribonucleic acid (mRNA) and protein production. Rats received intratracheal lipopolysaccharide (LPS; 0.5 mg/kg) or vehicle and were killed 1, 6, 24, and 72 h later. Their lungs were lavaged and the lung tissue homogenized and analyzed for SP-A, SP-D, and phospholipids. Tissue levels of SP-A were increased by 6 h, peaked at 24 h, and were still elevated at 72 h in LPS-treated animals as compared with those given vehicle. SP-A and SP-D levels in lavage fluid were significantly elevated at 72 h. Message levels for SP-A and SP-D, but not SP-B, were significantly increased at 24 h. Lavage phospholipid levels first increased, then decreased in both the control and LPS-treated animals, and significantly less phospholipid was recovered in the lavage fluid of the LPS-treated animals than in that of controls at 72 h. Although other mechanisms, including altered surfactant metabolism, may be involved, these data are consistent with our hypothesis that SP-A and SP-D are upregulated by an acute inflammatory stress in a manner analogous to that of the structurally and functionally related serum acute-phase reactant, mannose-binding protein. We speculate that this upregulation may be a protective response for the lungs.
McIntosh
J C
JC
Department of Pediatrics, Duke University Medical Center, Durham, North Carolina 27710, USA.
Swyers
A H
AH
Fisher
J H
JH
Wright
J R
JR
D000280:Administration, Inhalation; D000818:Animals; D006023:Glycoproteins / Q000096:biosynthesis*; D008070:Lipopolysaccharides / Q000008:administration & dosage*; D008168:Lung / Q000378:metabolism*; D008297:Male; D011510:Proteolipids / Q000096:biosynthesis*; D037662:Pulmonary Surfactant-Associated Protein A; D037663:Pulmonary Surfactant-Associated Protein D; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants / Q000096:biosynthesis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D007507:Therapeutic Irrigation; D015854:Up-Regulation
D006023:Glycoproteins; D008070:Lipopolysaccharides; D011510:Proteolipids; D037662:Pulmonary Surfactant-Associated Protein A; D037663:Pulmonary Surfactant-Associated Protein D; D037661:Pulmonary Surfactant-Associated Proteins; D011663:Pulmonary Surfactants