Submitted on November 25, 2003
Accepted on July 16, 2004
Disparate Effects of Two Phosphatidylcholine Binding Proteins, C-Reactive Protein (CRP) and Surfactant Protein A (SP-A) on Pulmonary Surfactant Structure and Function
Kaushik Nag1, Karina Rodriguez-Capote2, Amiya Kumar Panda3, Laura Frederick4, Stephen A. Hearn5, Nils O. Petersen6, Samuel Schurch7, and Fred Possmayer1*
1 Department of Obstetrics and Gynaecology, University of Western Ontario, London, Ontario, Canada; Department of Chemistry, University of Western Ontario, London, Ontario, Canada
2 Department of Obstetrics and Gynaecology, University of Western Ontario, London, Ontario, Canada; Canadian Institutes of Health Research Group in Fetal and Neonatal Health and Development, University of Western Ontario, London, Ontario, Canada; Departamento de Bioquimica, Instituto Superior de Ciencias Medicas, Habana, Cuba
3 Department of Obstetrics and Gynaecology, University of Western Ontario, London, Ontario, Canada; Department of Chemistry, University of Western Ontario, London, Ontario, Canada; Department of Chemistry, Behala College, Kolkata, India
4 Department of Obstetrics and Gynaecology, University of Western Ontario, London, Ontario, Canada; Canadian Institutes of Health Research Group in Fetal and Neonatal Health and Development, University of Western Ontario, London, Ontario, Canada
5 Department of Pathology, St. Joseph's Health Centre, London, Ontario, Canada
6 Department of Chemistry, University of Western Ontario, London, Ontario, Canada
7 Department of Physiology and Biophysics, University of Calgary, Calgary, Alberta, Canada
* To whom correspondence should be addressed. E-mail: schurch{at}ucalgary.ca.
C-reactive protein (CRP) and surfactant protein-A (SP-A) are phosphatidylcholine (PC) binding proteins that function in the innate host defense system. We examined the effects of CRP and SP-A on the surface activity of bovine lipid extract surfactant (BLES), a clinically applied modified natural surfactant. CRP inhibited BLES adsorption to form a surface-active film and the film's ability to lower surface tension (
) to low values near 0 mN/m during surface
area reduction. The inhibitory effects of CRP were reversed by phosphatidylcholine, a water soluble CRP ligand. SP-A enhanced BLES adsorption and its ability to lower to low values. Small amounts of SP-A block the inhibitory effects of CRP. Electron microscopy showed CRP has little effect on the lipid structure of BLES. SP-A altered BLES multilamellar vesicular structure by generating large, loose bilayer structures which were separated by a fuzzy
amorphous material, likely SP-A. These studies indicate that while SP-A and CRP both bind PC, there is a difference in the manner in which they interact with surface films.
