Disulphide Bridges in Surfactant Protein B Analogues Affect Their Activity in Synthetic Surfactant Preparations

Neonatology. 2019;115(2):134-141. doi: 10.1159/000494100. Epub 2018 Nov 19.

Abstract

Background: Limited supply and complicated manufacturing procedure of animal-derived surfactants make the development of synthetic surfactants warranted. The synthesis of surfactant protein (SP)-B and SP-C is complicated and several analogues have been developed. Mini-BLeu is an analogue that corresponds to the first and last helix of SP-B joined by a loop and linked by 2 disulphide bridges. SP-C33Leu is an SP-C analogue that can be cost-efficiently produced, but no such analogue has yet been described for SP-B.

Objective: To design short SP-B analogues which lack disulphide bridges, are easy to produce and are efficacious in a preterm rabbit fetus model of neonatal RDS.

Methods: Synthetic surfactants were prepared by adding 2 or 8% (w/w) of synthetic variants of Mini-B27, similar to Mini-BLeu but with a short loop, or different peptides covering helix 1 of SP-B to 2% (w/w) of SP-C33Leu in 80 mg/mL of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/egg yolk phosphatidylcholine/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol, 50: 40: 10 (by weight). Premature newborn rabbit fetuses were treated with 200 mg/kg of the surfactant preparations and ventilated with defined pressures for 30 min without positive end-expiratory pressure. Tidal volumes were registered during the experiments and lung gas volumes were measured at the end of the ventilation period.

Results: Synthetic surfactant containing the Mini-B27 analogue with 2 disulphides gives similar lung gas volumes as treatment with an animal-derived surfactant preparation, but all other SP-B analogues gave lower lung gas volumes. All synthetic surfactants studied gave no significant differences in compliances except the surfactant containing the Mini-B27 analogue without cysteines that performed somewhat better at 30 min.

Conclusion: The helix-loop-helix SP-B analogues tested in this study require the presence of 2 disulphide bridges for optimal activity in a rabbit RDS model.

Keywords: Protein drug; Respiratory distress syndrome; Surfactant protein.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Newborn
  • Disease Models, Animal
  • Humans
  • Infant, Newborn
  • Peptides / chemistry
  • Peptides / therapeutic use
  • Pulmonary Surfactant-Associated Protein B / chemistry
  • Pulmonary Surfactant-Associated Protein B / therapeutic use*
  • Pulmonary Surfactant-Associated Protein C / chemistry
  • Pulmonary Surfactant-Associated Protein C / therapeutic use*
  • Pulmonary Surfactants / chemistry
  • Pulmonary Surfactants / therapeutic use*
  • Rabbits
  • Respiration, Artificial
  • Respiratory Distress Syndrome, Newborn / drug therapy*
  • Respiratory Distress Syndrome, Newborn / therapy
  • Tidal Volume / drug effects

Substances

  • Peptides
  • Pulmonary Surfactant-Associated Protein B
  • Pulmonary Surfactant-Associated Protein C
  • Pulmonary Surfactants