Methyl-beta-cyclodextrin restores the structure and function of pulmonary surfactant films impaired by cholesterol

Pulmonary surfactant, a defined mixture of lipids and proteins, imparts very low surface tension to the lung-air interface by forming an incompressible film. In acute respiratory distress syndrome and other respiratory conditions, this function is impaired by a number of factors, among which is an increase of cholesterol in surfactant. The current study shows in vitro that cholesterol can be extracted from surfactant and function subsequently restored to dysfunctional surfactant films in a dose-dependent manner by methyl-beta-cyclodextrin (MbetaCD). Bovine lipid extract surfactant was supplemented with cholesterol to serve as a model of dysfunctional surfactant. Likewise, when cholesterol in a complex with MbetaCD ("water-soluble cholesterol") was added in aqueous solution, surfactant films were rendered dysfunctional. Atomic force microscopy showed recovery of function by MbetaCD is accompanied by the re-establishment of the native film structure of a lipid monolayer with scattered areas of lipid bilayer stacks, whereas dysfunctional films lacked bilayers. The current study expands upon a recent perspective of surfactant inactivation in disease and suggests a potential treatment.