Amphipathic alpha-helical peptides based on surfactant apoprotein SP-A

Area of Science:

• Biochemistry
• Pulmonary Medicine
• Materials Science

Background:

• Pulmonary surfactant apoprotein (SP-A) plays a crucial role in lung function.
• Synthetic peptides are explored as potential lung surfactant replacements.
• Dipalmitoylphosphatidylcholine (DPPC) is a key component of natural lung surfactant.

Purpose of the Study:

• To synthesize and evaluate peptides based on SP-A's amphipathic helical region for lung surfactant activity.
• To investigate the structure-activity relationship of synthetic SP-A peptides.
• To determine the efficacy of these peptides in restoring lung function in a model system.

Main Methods:

• Solid-phase synthesis of three SP-A derived peptides (SP-A81-102, SP-A78-101, and a hydrophobic analog Leu84,90SP-A78-101).
• In vitro testing of peptide and DPPC mixtures in an adult rat lavaged lung model.
• Assessment of quasi-static lung compliance and pressure-volume (P-V) curves.

Main Results:

• Native sequence peptides (SP-A81-102, SP-A78-101) were ineffective when mixed with DPPC.
• The Leu84,90SP-A78-101 analog, with increased hydrophobicity, significantly restored lung compliance (90% of unlavaged value) in DPPC mixtures.
• DPPC alone did not affect the P-V curve of the lavaged lung.
• The active peptide exhibited enhanced amphipathic alpha-helical potential and improved lipid-binding predictions.

Conclusions:

• Amphipathic alpha-helical potential and hydrophobic face size are critical for synthetic surfactant peptide function.
• A modified SP-A peptide (Leu84,90SP-A78-101) shows promise as a functional component of synthetic lung surfactants.
• This study supports the hypothesis that specific structural features are essential for effective peptide-based lung surfactants.