Effect of SP-B peptides on the uptake of liposomes by alveolar cells.
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.


OBJECTIVE
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.
Poelma
D L
DL
Department of Anesthesiology, Erasmus MC-Faculty, Rotterdam, The Netherlands.
Walther
F J
FJ
Waring
A J
AJ
Haitsma
J J
JJ
Zimmermann
L J
LJ
Lachmann
B
B
van Iwaarden
J F
JF
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D007700:Kinetics; D008081:Liposomes / Q000493:pharmacokinetics*; D016676:Macrophages, Alveolar / Q000187:drug effects / Q000502:physiology; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000494:pharmacology*; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000378:metabolism*; D037701:Pulmonary Surfactant-Associated Protein B / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D013552:Swine
D008081:Liposomes; D010446:Peptide Fragments; D037701:Pulmonary Surfactant-Associated Protein B