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Biochim Biophys Acta Biomembr. 2017 Aug;1859(8):1372-1380. doi: 10.1016/j.bbamem.2017.05.004. Epub 2017 May 10.

The role of multilayers in preventing the premature buckling of the pulmonary surfactant.

Author information

1
Department of Cardiovascular, University of Calgary, Calgary, Alberta, Canada; Department of Respiratory Sciences, University of Calgary, Calgary, Alberta, Canada; Snyder Institute of Chronic Diseases, University of Calgary, Calgary, Alberta, Canada.
2
Mechanical Engineering, University of Calgary, Calgary, Alberta, Canada, T2N 1N4. Electronic address: atarokh@ucalgary.ca.
3
Department of Cardiovascular, University of Calgary, Calgary, Alberta, Canada; Department of Respiratory Sciences, University of Calgary, Calgary, Alberta, Canada.
4
Cell Biology & Anatomy, University of Calgary, Calgary, Alberta, Canada.
5
Snyder Institute of Chronic Diseases, University of Calgary, Calgary, Alberta, Canada; Department of Pathology & Laboratory Medicine, University of Calgary, Calgary, Alberta, Canada.
6
Department of Chemistry, University of Calgary, Calgary, Alberta, Canada.
7
Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada.
8
Snyder Institute of Chronic Diseases, University of Calgary, Calgary, Alberta, Canada; Cell Biology & Anatomy, University of Calgary, Calgary, Alberta, Canada. Electronic address: mamrein@ucalgary.ca.

Abstract

The pulmonary surfactant is a protein-lipid mixture that spreads into a film at the air-lung interface. The highly-compacted molecules of the film keep the interface from shrinking under the influence of otherwise high surface tension and thus prevent atelectasis. We have previously shown that for the film to withstand a high film pressure without collapsing it needs to assume a specific architecture of a molecular monolayer with islands of stacks of molecular multilayers scattered over the area. Surface activity was assessed in a captive bubble surfactometer (CBS) and the role of cholesterol and oxidation on surfactant function examined. The surfactant film was conceptualized as a plate under pressure. Finite element analysis was used to evaluate the role of the multilayer stacks in preventing buckling of the plate during compression. The model of film topography was constructed from atomic force microscope (AFM) scans of surfactant films and known physical properties of dipalmitoylphosphatidylcholine (DPPC), a major constituent of surfactant, using ANSYS structural-analysis software. We report that multilayer structures increase film stability. In simulation studies, the critical load required to induce surfactant film buckling increased about two-fold in the presence of multilayers. Our in vitro surfactant studies showed that surface topography varied between functional and dysfunctional films. However, the critical factor for film stability was the anchoring of the multilayers. Furthermore, the anchoring of multilayers and mechanical stability of the film was dependent on the presence of hydrophobic surfactant protein-C. The current study expands our understanding of the mechanism of surfactant inactivation in disease.

KEYWORDS:

Buckling; Cholesterol; Finite element analysis; Multilayers; Oxidation; Pulmonary Surfactant; Surface tension

PMID:
28501605
DOI:
10.1016/j.bbamem.2017.05.004
[Indexed for MEDLINE]
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