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Published on: June 8, 2012
Effect of SP-B peptides on the uptake of liposomes by alveolar cells
D L Poelma1, F J Walther, A J Waring
1Department of Anesthesiology, Erasmus MC-Faculty, Rotterdam, The Netherlands.
Insights
Synthetic SP-B peptides, used in artificial surfactant therapy for respiratory distress syndrome, do not affect surfactant uptake by alveolar type II cells. However, some peptides influenced uptake by alveolar macrophages in vivo.
Area of Science:
- Pulmonary medicine
- Biochemistry
- Cell biology
Background:
- Exogenous surfactant therapy is standard for respiratory distress syndrome (RDS) in infants.
- Current therapies use lung extracts; synthetic surfactant preparations with SP-B and SP-C peptides are under development.
- The impact of synthetic SP-B peptides on endogenous surfactant metabolism is unknown.
Purpose of the Study:
- To investigate the effect of synthetic SP-B peptides on the uptake of surfactant-like liposomes by alveolar cells.
- To evaluate both in vitro and in vivo cellular interactions with SP-B peptides.
Main Methods:
- Alveolar macrophages (AM) and alveolar type II cells (ATII) were incubated with liposomes containing SP-B or its peptides in vitro.
- Rats received intratracheal instillation of fluorescent liposomes with SP-B peptides in vivo.
- Cell-associated fluorescence was quantified using flow cytometry and confocal microscopy.
Main Results:
- In vitro, SP-B peptides did not alter liposome uptake by AM or ATII.
- In vivo, SP-B(1-25) and Ser-SP-B(1-25) enhanced AM uptake, while dSP-B(1-25) decreased it.
- No significant effect on ATII uptake was observed with SP-B(1-25) or dSP-B(1-25).
Conclusions:
- Surface-active synthetic SP-B peptides do not impede the normal surfactant uptake mechanism in alveolar type II cells.
- The findings suggest synthetic peptides may have differential effects on various alveolar cell types in vivo.
Background:
Exogenous surfactant has been accepted worldwide as a therapy of RDS in premature and term infants. Exogenous surfactant is usually derived from lung extracts containing phospholipids and the surfactant proteins SP-B and SP-C. Synthetic peptides of SP-B and SP-C are being tested with the aim to develop a completely synthetic surfactant preparation. Nevertheless, the effects of these peptides on the endogenous surfactant metabolism remain unknown.
Objectives:
The effect of synthetic SP-B peptides on uptake of surfactant-like liposomes was investigated in alveolar cells. Native SP-B and seven SP-B peptides were included: monomeric and dimeric SP-B(1-25) (Cys-11 --> Ala-11), SP-B(63-78)and Ala-SP-B(63-78) (Cys-71 --> Ala-71;Cys-77 --> Ala-77)and their serine mutants.
Methods:
In vitro, alveolar macrophages (AM) and alveolar type II cells (ATII) were incubated with liposomes containing SP-B or one of its peptides. In vivo, rats received intratracheally various SP-B peptides (SP-B/lipid ratio 1:33 w/w) incorporated in fluorescent surfactant-like liposomes. One hour after instillation, AM and ATII were isolated and cell-associated fluorescence was determined using flow cytometry. Confocal laser microscopy was performed to ensure internalization of the liposomes.
Results:
In vitro uptake by AM or ATII was not influenced by the SP-B peptides. In vivo, SP-B(1-25) and Ser-SP-B(1-25) increased the uptake by AM whereas dSP-B(1-25) decreased the uptake. Neither SP-B(1-25) nor dSP-B(1-25 )affected total uptake by ATII. The overall uptake by SP-B(63-78) variants was not changed.
Conclusions:
Surface-active synthetic SP-B peptides do not interfere with the normal uptake of surfactant by ATII.
