Biochemistry of Lung Surfactant: Apoprotein-Phospholipid Interaction1

2015 ◽  
pp. 84-92
Author(s):  
K. S. Z�nker ◽  
V. Breuninger ◽  
D. Hegner ◽  
G. Bl�mel ◽  
J. Probst
Keyword(s):  
Lung Surfactant ◽  
Surfactant Apoprotein

scholarly journals Altered lipid synthesis in type II pneumonocytes exposed to lung surfactant

1986 ◽  
Vol 240 (3) ◽  
pp. 679-690 ◽  
Author(s):  
N R Thakur ◽  
M Tesan ◽  
N E Tyler ◽  
J E Bleasdale
Keyword(s):  
Lung Surfactant ◽  
Specific Radioactivity ◽  
Lipid Synthesis ◽  
Molar Ratio ◽  
Dihydroxyacetone Phosphate ◽  
Type Ii Cells ◽  
Type Ii ◽  
Altered Lipid ◽  
Surfactant Apoprotein

When type II pneumonocytes were exposed to purified lung surfactant that contained 1-palmitoyl-2-[3H]palmitoyl-glycero-3-phosphocholine, radiolabelled surfactant was apparently taken up by the cells since it could not be removed by either repeated washing or exchange with non-radiolabelled surfactant, but was released when the cells were lysed. After 4 h of exposure to [3H]surfactant, more than half of the 3H within cells remained in disaturated phosphatidylcholine. Incorporation of [3H]choline, [14C]palmitate and [14C]acetate into glycerophospholipids was decreased in type II cells exposed to surfactant and this inhibition, like surfactant uptake, was half-maximal when the extracellular concentration of surfactant was approx. 0.1 mumol of lipid P/ml. Inhibition of incorporation of radiolabelled precursors by surfactant occurred rapidly and reversibly and was not due solely to dilution of the specific radioactivity of intracellular precursors. Activity of dihydroxyacetone-phosphate acyltransferase, but not glycerol-3-phosphate acyltransferase, was decreased in type II cells exposed to surfactant and this was reflected by a decrease in the 14C/3H ratio of total lipids synthesized when cells incubated with [U-14C]glycerol and [2-3H]glycerol were exposed to surfactant. Phosphatidylcholine, phosphatidylglycerol and cholesterol, either individually or mixed in the molar ratio found in surfactant, did not mimic purified surfactant in the inhibition of glycerophospholipid synthesis. In contrast, an apoprotein fraction isolated from surfactant inhibited greatly the incorporation of [3H]choline into lipids and this inhibitory activity was labile to heat and to trypsin. It is concluded that the apparent uptake of surfactant by type II cells in vitro is accompanied by an inhibition of glycerophospholipid synthesis via a mechanism that involves a surfactant apoprotein.

Biophysical inhibition of synthetic phospholipid-lung surfactant apoprotein admixtures by plasma proteins

1991 ◽  
Vol 57 (1) ◽  
pp. 49-57 ◽  
Author(s):  
Anand R. Venkitaraman ◽  
John E. Baatz ◽  
Jeffrey A. Whitsett ◽  
Stephen B. Hall ◽  
Robert H. Notter
Keyword(s):  
Plasma Proteins ◽  
Lung Surfactant ◽  
Surfactant Apoprotein

A captive bubble method reproduces the in situ behavior of lung surfactant monolayers

1989 ◽  
Vol 67 (6) ◽  
pp. 2389-2396 ◽  
Author(s):  
S. Schurch ◽  
H. Bachofen ◽  
J. Goerke ◽  
F. Possmayer
Keyword(s):  
Surface Film ◽  
Lung Surfactant ◽  
External Pressure ◽  
Bubble Surface ◽  
Rabbit Lung ◽  
Surfactant Monolayers ◽  
Pressure Surface ◽  
Surfactant Lipid ◽  
Surfactant Apoprotein

We tested a new captive bubble surface tensiometer with films adsorbed from aqueous suspensions of rabbit lung surfactant and a bovine lung surfactant lipid extract and with films of dipalmitoyl-sn-3-glycerophosphorylcholine (DPPC) spread from solvents. The lack of tubes penetrating the bubble surface eliminated potential leakage pathways for the surface film, which was compressed by increasing external pressure. Surface tensions and areas were calculated directly from bubble shapes without the need of pressure measurements. After only one to two compressions, the rabbit surfactant films exhibited the low surface tension, collapse rates, and compressibilities characteristic of the alveolar surface in situ and approached the behavior of spread DPPC films. The bubble “clicking” phenomenon described earlier by Pattle (Proc. R. Soc. Lond. B Biol. Sci. 148: 217-240, 1958) was also reproduced, but only with the bovine extract, which did not perform as well as the rabbit surfactant in surface tests. These findings suggest that surfactant apoprotein SP-A, which was probably present in the rabbit but not the bovine preparations, enhances both adsorption and stability of pulmonary surfactant monolayers.

Cellular uptake and processing of surfactant lipids and apoprotein SP-A by rat lung

1989 ◽  
Vol 66 (3) ◽  
pp. 1336-1342 ◽  
Author(s):  
S. L. Young ◽  
J. R. Wright ◽  
J. A. Clements
Keyword(s):  
Pulmonary Surfactant ◽  
Secretory Granules ◽  
Lung Surfactant ◽  
Intratracheal Instillation ◽  
Lamellar Body ◽  
Subcellular Fractions ◽  
Clear Cut ◽  
Cut Time ◽  
Kinetics Of ◽  
Surfactant Apoprotein

The intracellular pathways and the kinetics of metabolism of surfactant apoprotein and lipid, which may be recycled from the alveolar space, are largely unknown. We used a lipid-apoprotein complex made from liposomes of pure lipids in a ratio found in mammalian pulmonary surfactant plus surfactant apoprotein (SP-A, Mr = 26,000–36,000) to test some possible relationships in the recycling of these major surfactant components between intrapulmonary compartments. After intratracheal instillation of 80 microliters of an apoprotein-liposome mixture with separate radiolabels in the lipid and the apoprotein, rats were killed at times from 8 min to 4 h later. The lungs were lavaged with saline, and subcellular fractions were isolated on discontinuous sucrose density gradients. Both the [14C]lipid radiolabel and the 125I-apoprotein radiolabel demonstrated a time-dependent increase in radioactivity recovered in a lamellar body-enriched fraction. Uptake of the radiolabels into other subcellular fractions did not exhibit a clear-cut time dependence; more of the protein than the lipid radiolabel was found in the Golgi-rich and microsomal fractions. We conclude that both the lipid and apoprotein portions of lung surfactant are taken up by lung cells and are incorporated into secretory granules of the cells.

Mixtures of synthetic peptides and dipalmitoylphosphatidylcholine as lung surfactants

1992 ◽  
Vol 262 (3) ◽  
pp. L292-L300
Author(s):  
L. R. McLean ◽  
J. L. Krstenansky ◽  
R. L. Jackson ◽  
K. A. Hagaman ◽  
K. A. Olsen ◽  
...  
Keyword(s):  
Synthetic Peptides ◽  
Lung Surfactant ◽  
Helical Structure ◽  
Lipid Binding ◽  
Water Soluble ◽  
Lung Model ◽  
Lung Surfactants ◽  
Surfactant Apoprotein

Synthetic peptides that differ in their lipid-peptide interactions were combined with dipalmitoylphosphatidylcholine (DPPC) and tested in an adult rat lavaged lung model in vitro for efficacy as totally synthetic lung surfactants. The putative amphipathic alpha-helical region of the major lung surfactant apoprotein (SP-A81-102), an analogue with increased amphipathic alpha-helical potential ([Lys88,97,Glu99,Trp102]-SP-A81-102]), and the hydrophobic peptide gramicidin D were all ineffective. Three water-soluble lipid-binding peptides that contain amphipathic alpha-helical regions were also tested. Of these, only a 24-residue amphipathic alpha-helical peptide (18As) based on the lipid-binding sequences of the plasma apolipoproteins was effective. Melittin and glucagon were ineffective. Mixtures of 18As and DPPC also restored gas exchange in an in vivo lavaged guinea pig lung model to 90-95% of its prelavage value and maintained it for at least 3 h. Mixtures of DPPC and 18As are also surface active (gamma min less than 4 mN/m in the pulsating bubble). These data demonstrate the efficacy of a combination of a single lipid and a small, water-soluble, nonhemolytic, synthetic peptide containing an amphipathic alpha-helical structure and a sequence unrelated to any of the reported lung surfactant apoprotein sequences.

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