Functional heterogeneity of pulmonary surfactant protein-D in cystic fibrosis

• Published in: Biochimica et biophysica acta Vol. 1832; no. 12; pp. 2391 - 2400
• Main Authors: Kotecha, Sailesh, Doull, Iolo, Davies, Philip, McKenzie, Zofi, Madsen, Jens, Clark, Howard W., McGreal, Eamon P.
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.12.2013
• Subjects: Adolescent; Bacterial Infections - metabolism; Bacterial Infections - microbiology; Bacterial Infections - pathology; Biomarkers - metabolism; Blotting, Western; Bronchoalveolar Lavage Fluid - chemistry; Bronchoalveolar Lavage Fluid - microbiology; Case-Control Studies; Child; Child, Preschool; Chromatography, Gel; Cohort Studies; Cystic fibrosis; Cystic Fibrosis - metabolism; Cystic Fibrosis - microbiology; Cystic Fibrosis - pathology; Enzyme-Linked Immunosorbent Assay; Female; Humans; Infant; Inflammation; Inflammation - metabolism; Inflammation - microbiology; Inflammation - pathology; Innate immunity; Lectin; Lung; Male; Maltose - metabolism; Protein Multimerization; Pulmonary Surfactant-Associated Protein D - chemistry; Pulmonary Surfactant-Associated Protein D - metabolism; Sepharose - metabolism; Surfactant protein-D; Zymosan - metabolism; Lectin; Cystic fibrosis; Innate immunity; Inflammation; Surfactant protein-D; Lung
• ISSN: 0925-4439; 0006-3002; 1879-260X
• DOI: 10.1016/j.bbadis.2013.10.002

Pulmonary surfactant protein-D (SP-D) is a soluble collagenous C-type lectin with important anti-microbial and anti-inflammatory properties. Although it is subject to functionally relevant modification by common polymorphisms and unregulated inflammation, the functional status of SP-D in cystic fibrosis (CF) remains unclear. Given the importance of infection and inflammation in CF lung pathology we have undertaken the first systematic analysis of SP-D lectin activity in this population. By ELISA, we found that airway lavage fluid SP-D expression was greater in CF compared to control patients but was reduced in CF patients with infection and correlated negatively with markers of neutrophilic inflammation. In a functional assay, the percentage of SP-D capable of binding zymosan rarely exceeded 60% in CF or control patients and similarly restricted binding activity was observed towards maltose–agarose. SP-D lectin activity also correlated negatively with infection and neutrophilic inflammation but there was little evidence of major proteolytic degradation amongst the non-bound material. SP-D which failed to bind zymosan exhibited features of lower oligomeric form compared to bound material when tested by native gel electrophoresis. Furthermore, when separated by gel chromatography, high and low oligomeric populations of SP-D were observed in CF lavage fluid but only high oligomeric forms exhibited substantial lectin activity towards yeast derived mannan. Our data demonstrate that oligomeric heterogeneity underlies functional diversity amongst SP-D in health and disease and that dynamic regulation of oligomerisation is an important feature of SP-D biology. •SP-D is abundantly expressed in CF lung fluid.•SP-D in CF lung fluid is structurally and functionally heterogeneous.•SP-D expression and function correlate negatively with infection and inflammation.•Oligomeric form is a major determinant of SP-D function in CF and control patients.