Stabilization of lung surfactant particles against conversion by a cycling interface

Area of Science:

• Pulmonary medicine
• Biochemistry
• Cellular biology

Background:

• Large active particles of pulmonary surfactant are depleted in acute respiratory distress syndrome (ARDS).
• Understanding factors affecting surfactant particle conversion is crucial for ARDS research.

Purpose of the Study:

• To investigate how factors lavaged from oleic acid-injured rabbits affect in vitro conversion of large to small pulmonary surfactant particles.
• To determine the role of proteins and proteinase inhibitors in surfactant particle stabilization.

Main Methods:

• Pulmonary surfactant particles were separated by differential sedimentation.
• In vitro conversion of large to small particles was studied using samples from control and injured rabbits.
• The effect of hemoglobin, neutrophil elastase, and oxidized alpha1-antiproteinase (alpha1-PI) on particle conversion was assessed.

Main Results:

• Factors from injured animals increased large particle recovery from 40% to 62% during cycling.
• Hemoglobin, neutrophil elastase, and oxidized alpha1-PI stabilized large surfactant particles.
• Hemoglobin was highly effective, increasing large particle recovery to 86% at 0.4 mg/ml.

Conclusions:

• Accelerated surfactant particle conversion is unlikely to explain large particle depletion in injured lungs.
• Surfactant particle conversion via differential sedimentation does not require proteinase susceptible to alpha1-PI inhibition.
• Interfacial effects, rather than proteinase inhibition, may explain the previously reported effects of alpha1-PI on surfactant particle conversion.