Ovine surfactant protein cDNAs: use in studies on fetal lung growth and maturation after prolonged hypoxemia

2000 ◽  
Vol 278 (4) ◽  
pp. L754-L764 ◽  
Author(s):  
Geert A. Braems ◽  
Li-Juan Yao ◽  
Kevin Inchley ◽  
Anne Brickenden ◽  
Victor K. M. Han ◽  
...  
Keyword(s):  
Pulmonary Surfactant ◽  
Specific Binding ◽  
Fetal Lung ◽  
Surfactant Protein ◽  
Mrna Levels ◽  
Fetal Hypoxia ◽  
Lung Maturation ◽  
Igf I ◽  
Surfactant Apoprotein ◽  
Mild Hypoxia

cDNAs for ovine surfactant-associated protein (SP) A, SP-B, and SP-C have been cloned and shown to possess strong similarity to cDNAs for surfactant apoproteins in other species. These reagents were employed to examine the effect of fetal hypoxia on the induction of surfactant apoprotein expression in the fetal lamb. Postnatal lung function is dependent on adequate growth and maturation during fetal development. Insulin-like growth factor (IGF) I and IGF-II, which are present in all fetal tissues studied, possess potent mitogenic and proliferative actions, and their effects can be modulated by IGF-specific binding proteins (IGFBPs). Hypoxia can lead to increases in circulating cortisol and catecholamines that can influence lung maturation. Therefore, the effects of mild hypoxia in chronically catheterized fetal lambs at gestational days 126– 130 and 134– 136 (term 145 days) on the expression of pulmonary surfactant apoproteins and IGFBPs were examined. Mild hypoxia for 48 h resulted in an increase in plasma cortisol that was more pronounced at later gestation, and in these animals, there was a twofold increase in SP-A mRNA. SP-B mRNA levels also increased twofold, but this was not significant. SP-C mRNA was not altered. No significant changes in apoprotein mRNA were observed with the younger fetuses. However, these younger animals selectively exhibited reduced IGFBP-5 mRNA levels. IGF-I mRNA was also reduced at 126–130 days, although this conclusion is tentative due to low abundance. IGF-II levels were not affected at either gestational age. We conclude that these data suggest that mild prolonged fetal hypoxia produces alterations that could affect fetal cellular differentiation early in gestation and can induce changes consistent with lung maturation closer to term.

Developmental and hormonal regulation of SP-A gene expression in baboon fetal lung

1996 ◽  
Vol 271 (4) ◽  
pp. L609-L616 ◽  
Author(s):  
S. R. Seidner ◽  
M. E. Smith ◽  
C. R. Mendelson
Keyword(s):  
Gene Expression ◽  
Gestational Age ◽  
Hormonal Regulation ◽  
Protein A ◽  
Fetal Lung ◽  
Surfactant Protein ◽  
Inhibitory Effect ◽  
Mrna Levels ◽  
Inhibitory Effects ◽  
Lung Maturation

In the present study, we found that surfactant protein A (SP-A) mRNA levels, which are barely detectable in baboon fetal lung at midgestation (92 days), are increased approximately four fold between 125 and 140 days gestation, approximately 7-fold between 140 and 160 days, and approximately 1.5-fold between 160 and 174 days gestation. We also investigated the effects of dibutyryl-adenosine 3',5'-cyclic monophosphate (DB-cAMP) and dexamethasone (Dex) on SP-A gene expression in lung explants from fetal baboons at 92, 125, 140, 160, and 174 days of gestation (term = 184 days). SP-A mRNA levels, which were barely detectable in lung tissues from 92- and 125-day fetal baboons before culture, were induced after incubation for 5 days in serum-free medium and were markedly stimulated by DBcAMP. Dex caused a dose-dependent inhibition of SP-A mRNA levels and antagonized the stimulatory effect of DBcAMP. SP-A mRNA was detectable in lung tissues from 140-day fetal baboons before culture; the levels were further induced after culture and were increased greatly by DBcAMP. Again, Dex antagonized the induction of SP-A mRNA by DBcAMP. The stimulatory effects of DBcAMP and inhibitory effects of Dex on SP-A mRNA levels in lung tissues of 92- to 140-day gestational age fetal baboons were highly similar to those observed in studies using lung explants of midgestation human abortuses. By contrast, SP-A mRNA was present in relatively high levels in lung tissues of 160- and 174-day fetal baboons before culture and was relatively unaffected after incubation for 5 days in control medium. In lung explants from 160- and 174-day fetal baboons, the stimulatory effect of DBcAMP and inhibitory effect of Dex on SP-A mRNA levels were relatively modest compared with the effects of these agents on SP-A mRNA in fetal lung tissues from 92-, 125-, and 140-day gestational age fetuses. These findings suggest that, with increased lung maturation and the developmental induction of SP-A gene expression, there is a decrease in responsiveness of the fetal lung to the stimulatory effects of cAMP and inhibitory effects of glucocorticoids on SP-A gene expression.

scholarly journals Igf2 Deficiency Results in Delayed Lung Development at the End of Gestation

Endocrinology ◽  
2006 ◽  
Vol 147 (12) ◽  
pp. 5584-5591 ◽  
Author(s):  
Delia Silva ◽  
Maria Venihaki ◽  
Wei-Hui Guo ◽  
Mary Frances Lopez
Keyword(s):  
Fetal Lung ◽  
Plasma Corticosterone ◽  
Mrna Levels ◽  
Wild Type ◽  
Lung Maturation ◽  
Morphological Alterations ◽  
Lung Histology ◽  
Igf I ◽  
Fetal Lung Maturation

IGF-II is a polypeptide hormone with structural homology to insulin and IGF-I. IGF-II plays an important role in fetal growth as mice with targeted disruption of the IGF-II gene (Igf2) exhibit severe growth retardation. The role of IGFs in the fetal lung has been suggested by several studies, including those that have identified IGF mRNA expression, and that of their receptors and binding proteins in the lungs at different stages of development. In this study, we used mice carrying a null mutation of Igf2 (Igf2−/− mice) to determine whether the absence of IGF-II had any effect in fetal lung maturation. Our results showed that the lungs of Igf2−/− fetuses had thicker alveolar septae and poorly organized alveoli when compared with those of Igf2+/+ on d 17.5 and 18.5 of gestation. These morphological alterations may be the result of exposure to lower levels of glucocorticoids because plasma corticosterone levels were significantly lower in Igf2−/− mothers compared with wild-type controls. In support of this, fetuses from homozygous knockout matings, where mothers were treated with 15 μg/ml corticosterone, and Igf2−/− fetuses obtained from heterozygous matings had similar lung histology to those of wild-type fetuses. Finally, we found that IGF-I and SP-B mRNA levels were up-regulated in the lungs of Igf2−/− fetuses at the end of gestation. This study suggests that Igf2 plays an important role in the development of the fetal lung and may affect fetal lung maturation by regulating maternal factors, such as corticosterone levels, during pregnancy.

Effect of tyrosine kinase inhibition on surfactant protein A gene expression during human lung development

1998 ◽  
Vol 274 (4) ◽  
pp. L542-L551 ◽  
Author(s):  
Jonathan M. Klein ◽  
Louis J. Dewild ◽  
Troy A. McCarthy
Keyword(s):  
Tyrosine Kinase ◽  
Tyrosine Phosphorylation ◽  
Lung Tissue ◽  
Receptor Tyrosine Kinase ◽  
Lung Development ◽  
Egf Receptor ◽  
Fetal Lung ◽  
Surfactant Protein ◽  
Mrna Levels ◽  
Human Fetal Lung

Epidermal growth factor (EGF) stimulates surfactant protein (SP) A synthesis in human fetal lung explants. Ligand binding to the EGF receptor stimulates an intrinsic receptor tyrosine kinase with subsequent activation of second messengers. We hypothesized that inhibition of EGF-receptor tyrosine kinase activity would block SP-A expression in spontaneously differentiating cultured human fetal lung tissue. Midtrimester fetal lung explants were exposed for 4 days to genistein (a broad-range inhibitor of tyrosine kinases) and tyrphostin AG-1478 (a specific inhibitor of EGF-receptor tyrosine kinase). Genistein significantly decreased SP-A and SP-A mRNA levels without affecting either tissue viability or the morphological differentiation of alveolar type II cells. Tyrphostin AG-1478 also decreased SP-A content and SP-A mRNA levels in cultured fetal lung explants. Treatment with EGF could not overcome the inhibitory effects of either genistein or tyrphostin on SP-A; however, only tyrphostin inhibited EGF-receptor tyrosine phosphorylation. We conclude that specific inhibition of EGF-receptor tyrosine kinase with tyrphostin AG-1478 blocks the expression of SP-A during spontaneous differentiation of cultured human fetal lung tissue. Furthermore, exposure to genistein also decreases SP-A expression and blocks the effects of EGF in human fetal lung tissue without inhibiting EGF-receptor tyrosine phosphorylation. These findings support the importance of tyrosine kinase-dependent signal transduction pathways in the regulation of SP-A during human fetal lung development.

Antisense inhibition of surfactant protein A decreases tubular myelin formation in human fetal lung in vitro

2002 ◽  
Vol 282 (3) ◽  
pp. L386-L393 ◽  
Author(s):  
Jonathan M. Klein ◽  
Troy A. McCarthy ◽  
John M. Dagle ◽  
Jeanne M. Snyder
Keyword(s):  
Gene Expression ◽  
Protein A ◽  
Fetal Lung ◽  
Surfactant Protein ◽  
Surfactant Protein A ◽  
Mrna Levels ◽  
Phosphorothioate Oligonucleotide ◽  
Myelin Formation ◽  
Surfactant Phospholipids ◽  
Human Fetal Lung

Surfactant protein A (SP-A) is the most abundant of the surfactant-associated proteins. SP-A is involved in the formation of tubular myelin, the modulation of the surface tension-reducing properties of surfactant phospholipids, the metabolism of surfactant phospholipids, and local pulmonary host defense. We hypothesized that elimination of SP-A would alter the regulation of SP-B gene expression and the formation of tubular myelin. Midtrimester human fetal lung explants were cultured for 3–5 days in the presence or absence of an antisense 18-mer phosphorothioate oligonucleotide (ON) complementary to SP-A mRNA. After 3 days in culture, SP-A mRNA was undetectable in antisense ON-treated explants. After 5 days in culture, levels of SP-A protein were also decreased by antisense treatment. SP-B mRNA levels were not affected by the antisense SP-A ON treatment. However, there was decreased tubular myelin formation in the antisense SP-A ON-treated tissue. We conclude that selective elimination of SP-A mRNA and protein results in a decrease in tubular myelin formation in human fetal lung without affecting SP-B mRNA. We speculate that SP-A is critical to the formation of tubular myelin during human lung development and that the regulation of SP-B gene expression is independent of SP-A gene expression.

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.

Intrafetal glucose infusion alters glucocorticoid signaling and reduces surfactant protein mRNA expression in the lung of the late-gestation sheep fetus

2014 ◽  
Vol 307 (5) ◽  
pp. R538-R545 ◽  
Author(s):  
Erin V. McGillick ◽  
Janna L. Morrison ◽  
I. Caroline McMillen ◽  
Sandra Orgeig
Keyword(s):  
Mrna Expression ◽  
Fetal Lung ◽  
Glucose Transporters ◽  
Surfactant Protein ◽  
Glucose Infusion ◽  
Late Gestation ◽  
Lung Maturation ◽  
Increased Risk ◽  
Sheep Fetus ◽  
Diabetic Mothers

Increased circulating fetal glucose and insulin concentrations are potential inhibitors of fetal lung maturation and may contribute to the pathogenesis of respiratory distress syndrome (RDS) in infants of diabetic mothers. In this study, we examined the effect of intrafetal glucose infusion on mRNA expression of glucose transporters, insulin-like growth factor signaling, glucocorticoid regulatory genes, and surfactant proteins in the lung of the late-gestation sheep fetus. The numerical density of the cells responsible for producing surfactant was determined using immunohistochemistry. Glucose infusion for 10 days did not affect mRNA expression of glucose transporters or IGFs but did decrease IGF-1R expression. There was reduced mRNA expression of the glucocorticoid-converting enzyme HSD11B-1 and the glucocorticoid receptor, potentially reducing glucocorticoid responsiveness in the fetal lung. Furthermore, surfactant protein ( SFTP) mRNA expression was reduced in the lung following glucose infusion, while the number of SFTP-B-positive cells remained unchanged. These findings suggest the presence of a glucocorticoid-mediated mechanism regulating delayed maturation of the surfactant system in the sheep fetus following glucose infusion and provide evidence for the link between abnormal glycemic control during pregnancy and the increased risk of RDS in infants of uncontrolled diabetic mothers.

Oxygen modulates surfactant protein mRNA expression and phospholipid production in human fetal lung in vitro

1995 ◽  
Vol 268 (5) ◽  
pp. L818-L825 ◽  
Author(s):  
M. J. Acarregui ◽  
J. J. Brown ◽  
R. K. Mallampalli
Keyword(s):  
Mrna Expression ◽  
Fetal Lung ◽  
Surfactant Protein ◽  
Mrna Levels ◽  
Choline Incorporation ◽  
Associated Proteins ◽  
Dependent Protein ◽  
Surfactant Composition ◽  
Human Fetal Lung

We studied the effect of 20-95% O2 on mRNA levels for the surfactant-associated proteins (SP)-A, SP-B, and SP-C and [3H]choline incorporation into total phosphatidylcholine and type II cell-specific disaturated phosphatidylcholine (DPPC) in human fetal lung in culture. SP-A mRNA levels were increased by 25 and 39% in lung explants incubated in 70 and 95% O2, respectively, compared with levels in tissues incubated in 20% O2. SP-B mRNA levels were unaffected by O2, whereas SP-C mRNA levels were increased by 85, 102, and 115% in atmospheres of 35, 50, and 70% O2, respectively. [3H]choline incorporation into total phosphatidylcholine and DPPC were both increased in human fetal lung explants incubated in increased O2 concentrations compared with tissues incubated in 20% O2. Tissue levels of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase (PKA) activity were not affected by O2 concentration, implying that the changes observed in SP mRNA levels and [3H]choline incorporation may not be mediated through alterations in PKA enzyme activity. These findings demonstrate that O2 regulates SP mRNA expression and phospholipid production in human fetal lung in vitro. We speculate that surfactant composition and possibly function may be regulated by O2 in human lung.

Effects of mechanical factors on growth and maturation of the lung in fetal sheep

1997 ◽  
Vol 272 (1) ◽  
pp. L95-L105 ◽  
Author(s):  
P. Joe ◽  
L. D. Wallen ◽  
C. J. Chapin ◽  
C. H. Lee ◽  
L. Allen ◽  
...  
Keyword(s):  
Cervical Spinal Cord ◽  
Fetal Lung ◽  
Surfactant Protein ◽  
Lung Hypoplasia ◽  
Alveolar Type ◽  
Sham Operation ◽  
Mechanical Forces ◽  
Lung Growth ◽  
Fetal Sheep ◽  
Igf I

Previous fetal studies indicated that endocrine factors control surfactant maturation, whereas mechanical forces affect lung growth, but not surfactant. We altered mechanical forces in fetal sheep lungs at 100-108 days gestation by tracheal ligation (TL, n = 15, 7 successful studies) to accelerate lung growth, transection of cervical spinal cord (TCSC, n = 17, 6 successful studies) to produce lung hypoplasia, or sham operation (n = 11, 6 successful studies). The reasons for the high mortality rates are not known. At delivery (130-142 days), groups were similar in gestational age, weight, and cortisol. Effects on lung growth were similar to, but effects on surfactant differed from, previous reports. TL increased lung growth but decreased saturated phosphatidylcholine (SatPC) and surfactant protein (SP)A and apparently decreased SP-B and relative numbers of alveolar type II cells (based on immunohistochemical studies of 1 animal in each group); TCSC had opposite effects. In contrast to a previous study (J. A. Kitterman, G. C. Liggins, G. A. Campos, J. A. Clements, C. S. Forster, C. H. Lee, and R. K. Creasy, J. Appl. Physiol, 51: 384-390, 1981), SatPC did not correlate with cortisol. We conclude that altering mechanical forces in fetal lung affects not only lung growth but also surfactant maturation and possibly alveolar epithelial differentiation and disturbs the normal correlation between cortisol and surfactant. Associated changes in insulin-like growth factor I (IGF-I; increased by TL, P = 0.003) suggest a possible role for IGF-I in these effects.

scholarly journals Sequences of a hairpin structure in the 3′-untranslated region mediate regulation of human pulmonary surfactant protein B mRNA stability

2012 ◽  
Vol 302 (10) ◽  
pp. L1107-L1117 ◽  
Author(s):  
Helen W. Huang ◽  
David E. Payne ◽  
Weizhen Bi ◽  
Su Pan ◽  
Shirley R. Bruce ◽  
...  
Keyword(s):  
Mrna Stability ◽  
Hormonal Regulation ◽  
Untranslated Region ◽  
Pulmonary Surfactant ◽  
Specific Binding ◽  
Surfactant Protein ◽  
Hairpin Structure ◽  
Cytosolic Proteins ◽  
Surfactant Protein B ◽  
Protein B

The ability of pulmonary surfactant to reduce alveolar surface tension requires adequate expression of surfactant protein B (SP-B). Dexamethasone (DEX, 10−7 M) increases human SP-B mRNA stability by a mechanism that requires a 126-nt-long segment (the 7.6S region) of the 3′-untranslated region (3′-UTR). The objective of this study was to identify sequences in the 7.6S region that mediate regulation of SP-B mRNA stability. The 7.6S region was found to be sufficient for DEX-mediated stabilization of mRNA. Sequential substitution mutagenesis of the 7.6S region indicates that a 90-nt region is required for DEX-mediated stabilization and maintenance of intrinsic stability. In this region, one 30-nt-long element (002), predicted to form a stem-loop structure, is sufficient for DEX-mediated stabilization of mRNA and intrinsic mRNA stability. Cytosolic proteins specifically bind element 002, and binding activity is unaffected whether proteins are isolated from cells incubated in the absence or presence of DEX. While loop sequences of element 002 have no role in regulation of SP-B mRNA stability, the proximal stem sequences are required for DEX-mediated stabilization and specific binding of proteins. Mutation of the sequences that comprise the proximal or distal arm of the stem negates the destabilizing activity of element 002 on intrinsic SP-B mRNA stability. These results indicate that cytosolic proteins bind a single hairpin structure that mediates intrinsic and hormonal regulation of SP-B mRNA stability via mechanisms that involve sequences of the stems of the hairpin structure.

Sign in / Sign up

Export Citation Format

Share Document