SP-B refining of pulmonary surfactant phospholipid films

1999 ◽  
Vol 277 (6) ◽  
pp. L1179-L1189 ◽  
Author(s):  
Kaushik Nag ◽  
James G. Munro ◽  
Kevin Inchley ◽  
Samuel Schürch ◽  
Nils O. Petersen ◽  
...  
Keyword(s):  
Pulmonary Surfactant ◽  
Film Formation ◽  
Surfactant Protein ◽  
Neutral System ◽  
Area Reduction ◽  
Surfactant Protein B ◽  
Squeeze Out ◽  
Planar Films ◽  
Surfactant Phospholipids ◽  
Film Area

Pulmonary surfactant stabilizes the alveoli by lining the air-fluid interface with films that reduce surface tension to near 0 mN/m (γmin). Surfactant protein B (SP-B) enhances the surface activity of surfactant phospholipids. A captive bubble tensiometer (CBT) was used to study the properties of adsorbed films of dipalmitoylphosphatidylcholine (DPPC) with acidic 1-palmitoyl-2-oleoyl- sn-glycero-3-[phospho- rac-(1-glycerol)] (POPG) or neutral 1-palmitoyl-2-oleoyl- sn-glycerol-3-phosphocholine with (7:3) and without 1% dimeric SP-B. SP-B enhanced the adsorption rate of DPPC-containing neutral or acidic lipid suspensions (1 mg/ml) to a similar extent. Quasi-static cycling of these films revealed that SP-B significantly decreased the film area reduction required to reach γmin for the acidic but not for the neutral system. The results obtained with DPPC-phosphatidylglycerol (PG)-SP-B were consistent with selective DPPC adsorption into the surface monolayer during film formation. Film area reduction required to reach γmin with this system (with and without calcium) approached that of pure DPPC, suggesting selective DPPC insertion and PG squeeze-out. Dynamic cycling of such films showed that larger film area reductions were required to reach γmin for the neutral than for acidic system, even after 20 cycles. Fluorescence microscopy of solvent-spread DPPC-POPG-SP-B planar films revealed highly condensed structures at ∼25 mN/m, although no specific PG phase-segregated structures could be identified. The study suggests that specific interactions of SP-B with acidic phospholipids of surfactant may be involved in the generation and maintenance of DPPC-rich films in the alveoli.

The late asthmatic response is linked with increased surface tension and reduced surfactant protein B in mice

2002 ◽  
Vol 283 (4) ◽  
pp. L755-L765 ◽  
Author(s):  
Angela Haczku ◽  
Elena N. Atochina ◽  
Yaniv Tomer ◽  
Yang Cao ◽  
Colleen Campbell ◽  
...  
Keyword(s):  
Surface Tension ◽  
Pulmonary Surfactant ◽  
Late Phase ◽  
Surfactant Protein ◽  
Intratracheal Administration ◽  
Asthmatic Response ◽  
Surfactant Protein B ◽  
Airway Response ◽  
Allergen Provocation ◽  
Surfactant Dysfunction

Pulmonary surfactant dysfunction may significantly contribute to small airway obstruction during the asthmatic response, but neither its exact role nor its regulation is clear. Surfactant function and composition was studied in an Aspergillus fumigatus ( Af)-induced late-phase allergic airway response in sensitized BALB/c mice. The peak of Af-induced airway hyperresponsiveness in sensitized and challenged mice 24 h after allergen provocation coincided with a significant fall in surface activity of the pulmonary surfactant. The underlying changes included time-dependent elaboration of eotaxin and IL-5 followed by eosinophil influx into the airways. The height of airway inflammation and hyperresponsiveness was preceded by release of IL-4 and marked reductions in surfactant protein (SP)-B, a hydrophobic surfactant protein responsible for maintaining low surface tension of the lining fluid of distal air spaces. Furthermore, intratracheal administration of IL-4 significantly inhibited SP-B, indicating a regulatory role of this cytokine in the surfactant biophysical changes. Thus surfactant dysfunction induced by an IL-4-driven SP-B deficiency after allergen provocation may be an important part of the late asthmatic airway response.

Glucocorticoid enhances pulmonary surfactant protein B gene transcription

1991 ◽  
Vol 260 (2) ◽  
pp. L37-L43 ◽  
Author(s):  
M. A. O'Reilly ◽  
J. C. Clark ◽  
J. A. Whitsett
Keyword(s):  
Protein Synthesis ◽  
Cell Line ◽  
Gene Transcription ◽  
Pulmonary Surfactant ◽  
Actinomycin D ◽  
Surfactant Protein ◽  
Surfactant Protein B ◽  
Pulmonary Surfactant Protein B ◽  
Pulmonary Surfactant Protein ◽  
Protein B

The effect of glucocorticoid on the regulation of pulmonary surfactant protein B (SP-B) synthesis was studied in a human pulmonary adenocarcinoma cell line. Northern blot analysis demonstrated a marked increase in SP-B mRNA expression after treatment with dexamethasone for 48 h. Actinomycin D, puromycin, or cycloheximide blocked the induction of SP-B mRNA by glucocorticoid. Nuclear run-on experiments demonstrated that the effects of dexamethasone on SP-B mRNA were due in part to increased transcription of the SP-B gene. However, during this time period, there was a discrepancy between SP-B gene transcription, which was increased only 2- to 4-fold, and SP-B mRNA, which increased 60- to 150-fold after treatment with dexamethasone. In the presence of actinomycin D, SP-B mRNA was relatively stable, decreasing slowly in the presence or absence of glucocorticoid. In contrast to the relative stability of SP-B mRNA in the presence of actinomycin D, SP-B mRNA was markedly decreased after exposure to puromycin, supporting the premise that continued protein synthesis, rather than transcription alone, is required for maintenance of SP-B mRNA levels. Induction of SP-B expression by glucocorticoids was dependent on enhanced SP-B gene transcription and was also dependent on continued protein synthesis. The discrepancy between the relative enhancement of SP-B transcription and SP-B mRNA suggests that posttranscriptional factors influence SP-B expression in this cell line.

An En Bloc Staining Protocol Improves The Preservation of Lamellar Bodies in Alveolar Type II Epithelial Cells for Transgenic Mice Expressing Modified Pulmonary Surfactant Protein B

1998 ◽  
Vol 4 (S2) ◽  
pp. 852-853
Author(s):  
C.-L. Na ◽  
D. C. Beck ◽  
J. S. Breslin ◽  
S. E. Wert ◽  
T. E. Weaver
Keyword(s):  
Pulmonary Surfactant ◽  
Surfactant Protein ◽  
Alveolar Type ◽  
Type Ii ◽  
Lamellar Bodies ◽  
En Bloc ◽  
Surfactant Protein B ◽  
Staining Protocol ◽  
Pulmonary Surfactant Protein B ◽  
Pulmonary Surfactant Protein

The extraction of lipids and phospholipids during dehydration and plastic embedding steps results in poor preservation of the phospholipid rich lamellar bodies (LB) in alveolar type II epithelial cells. To achieve better retention of phospholipids, we combined inflation fixation and an en bloc staining protocol using 4% aqueous uranyl acetate (UA), thereby improving the preservation of the LBs for both the wild type and transgenic mice expressing modified pulmonary surfactant protein B (SP-B; Akinbi et al., 1997).Lungs of 6-8 week-old mice were inflation fixed (Bunkingham and Weyder, 1981) with ice cold 2% paraformaldehye and 2% glutaraldehyde in 0.1 M sodium cacodylate buffer (SCB), pH 7.3, postfixed in fresh fixative at 4 °C overnight, incubated with 1% osmium tetroxide in 0.1 M SCB at room temperature for 2 hours, and stained en bloc with 4% aqueous UA overnight.

Human surfactant protein B: structure, function, regulation, and genetic disease

1995 ◽  
Vol 75 (4) ◽  
pp. 749-757 ◽  
Author(s):  
J. A. Whitsett ◽  
L. M. Nogee ◽  
T. E. Weaver ◽  
A. D. Horowitz
Keyword(s):  
Gene Expression ◽  
Surfactant Protein ◽  
Structure And Function ◽  
Respiratory Epithelial Cell ◽  
Surfactant Protein B ◽  
Cell Gene Expression ◽  
Surfactant Phospholipids ◽  
And Function ◽  
Respiratory Epithelial ◽  
Cell Gene

Elucidation of the structure and function of the hydrophobic surfactant protein (SP-B) and the SP-B gene has provided critical insight into surfactant homeostasis and control of respiratory epithelial cell gene expression. Surfactant protein B, in concert with surfactant protein A (SP-A), surfactant protein C (SP-C), and surfactant phospholipids, contributes to the structure and function of surfactant particles, determining surface activities and pathways by which surfactant phospholipids and proteins are processed, routed, packaged, and secreted from lamellar bodies by type II epithelial cells. After secretion, SP-B plays an essential role in determining the structure of tubular myelin, the stability and rapidity of spreading, and the recycling of surfactant phospholipids. The biochemical and structural signals underlying the homeostasis of alveolar surfactant are likely mediated by interactions between the surfactant proteins and phospholipids producing discrete structural forms that vary in size, aproprotein, and phospholipid content. Distinctions in structure, protein, and size are likely to determine the function of surfactant particles, their catabolism, or recycling by alveolar macrophages and airway epithelial cells. Analysis of the genetic controls governing the SP-B gene has led to the definition of DNA-protein interactions that determine respiratory epithelial cell gene expression in general. The important role of SP-B in lung function was defined by the study of a lethal neonatal respiratory disease, hereditary SP-B deficiency, caused by mutations in the human SP-B gene.

scholarly journals Glucocorticoid regulation of human pulmonary surfactant protein-B (SP-B) mRNA stability is independent of activated glucocorticoid receptor

2011 ◽  
Vol 300 (6) ◽  
pp. L940-L950 ◽  
Author(s):  
Ceá C. Tillis ◽  
Helen W. Huang ◽  
Weizhen Bi ◽  
Su Pan ◽  
Shirley R. Bruce ◽  
...  
Keyword(s):  
Steady State ◽  
Glucocorticoid Receptor ◽  
Mrna Stability ◽  
Pulmonary Surfactant ◽  
Surfactant Protein ◽  
Airway Epithelial Cells ◽  
Mrna Levels ◽  
Airway Epithelial ◽  
Surfactant Protein B ◽  
Steady State Levels

Adequate expression of surfactant protein-B (SP-B) is critical in the function of pulmonary surfactant to reduce alveolar surface tension. Expression of SP-B mRNA is restricted to specific lung-airway epithelial cells, and human SP-B mRNA stability is increased in the presence of the synthetic glucocorticoid dexamethasone (DEX). Although the mechanism of SP-B mRNA stabilization by DEX is unknown, studies suggest involvement of the glucocorticoid receptor (GR). We developed a dual-cistronic plasmid-based expression assay in which steady-state levels of SP-B mRNA, determined by Northern analysis, reproducibly reflect changes in SP-B mRNA stability. Using this assay, we found that steady-state levels of SP-B mRNA increased greater than twofold in transfected human-airway epithelial cells (A549) incubated with DEX (10−7 M). DEX-mediated changes in SP-B mRNA levels required the presence of the SP-B mRNA 3′-untranslated region but did not require ongoing protein synthesis. The effect of DEX on SP-B mRNA levels was dose dependent, with maximal effect at 10−7 M. DEX increased levels of SP-B mRNA in cells lacking GR, and the presence of the GR antagonist RU486 did not interfere with the effect of DEX. Surprisingly, other steroid hormones (progesterone, estradiol, and vitamin D; 10−7 M) significantly increased SP-B mRNA levels, suggesting a common pathway of steroid hormone action on SP-B mRNA stability. These results indicate that the effect of DEX to increase SP-B mRNA stability is independent of activated GR and suggests that the mechanism is mediated by posttranscriptional or nongenomic effects of glucocorticoids.

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