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.

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.

Biphasic glucocorticoid regulation of pulmonary SP-A: characterization of inhibitory process

1993 ◽  
Vol 264 (3) ◽  
pp. L236-L244 ◽  
Author(s):  
D. M. Iannuzzi ◽  
R. Ertsey ◽  
P. L. Ballard
Keyword(s):  
Gene Transcription ◽  
Hormonal Regulation ◽  
Prolonged Exposure ◽  
Protein A ◽  
Protein S ◽  
Fetal Lung ◽  
Surfactant Protein ◽  
Inhibitory Effect ◽  
Normal Lung ◽  
Dominant Response

Pulmonary surfactant, which is necessary for normal lung function, is under both developmental and hormonal regulation. Glucocorticoids induce all components of surfactant and have a unique biphasic effect on surfactant protein A (SP-A), either stimulating or inhibiting accumulation in cultured fetal lung depending on dose and time of exposure. In this study we further characterized glucocorticoid inhibition of SP-A in cultured explants of human fetal lung. Decreased content of SP-A mRNA was the dominant response to dexamethasone added either early or later during culture. Inhibition occurred at < or = 1 nM dexamethasone on prolonged exposure, was blocked by RU 486, and was observed with other glucocorticoids but not sex steroids. When cortisol was removed from the culture medium, inhibition was rapidly reversed. The immediate inhibitory effect of 100 nM dexamethasone on SP-A mRNA content was completely blocked in the presence of cycloheximide. SP-A gene transcription, measured by nuclear elongation assay, was decreased by 60% after 4- to 8-h exposure to 100 nM dexamethasone. Stability of SP-A mRNA, determined both by addition of actinomycin D and by label-chase experiments, was transiently decreased immediately after adding dexamethasone (t1/2 approximately 3 h). In tissue treated with dexamethasone for > or = 8 h the stability of SP-A mRNA in control and treated explants was not different (t1/2 approximately 8 h). Our findings indicate that inhibition of SP-A is the dominant response to glucocorticoid. This effect is receptor mediated and apparently involves induction of a labile protein(s) that decreases gene transcription and transiently reduces mRNA stability.

Signal transduction events involved in TPA downregulation of SP-A gene expression

2004 ◽  
Vol 286 (6) ◽  
pp. L1210-L1219 ◽  
Author(s):  
Olga L. Miakotina ◽  
Jeanne M. Snyder
Keyword(s):  
Gene Expression ◽  
Protein Kinase ◽  
Mapk Pathway ◽  
Surfactant Protein ◽  
Mapk Signaling ◽  
Mitogen Activated Protein Kinase ◽  
Mrna Levels ◽  
Dependent Manner ◽  
Inhibitory Effects ◽  
Novel Isoforms

Surfactant protein A (SP-A), the most abundant pulmonary surfactant protein, plays a role in innate host defense and blocks the inhibitory effects of serum proteins on surfactant surface tension-lowering properties. SP-A mRNA and protein are downregulated by phorbol esters (TPA) via inhibition of gene transcription. We evaluated the TPA signaling pathways involved in SP-A inhibition in a lung cell line, H441 cells. TPA caused sustained phosphorylation of p44/42 mitogen-activated protein kinase (MAPK), p38 MAPK, and c-Jun-NH2-terminal kinase. An inhibitor of conventional and novel isoforms of protein kinase C (PKC) and two inhibitors of p44/42 MAPK kinase partially or completely blocked the inhibitory effects of TPA on SP-A mRNA levels. In contrast, inhibitors of conventional PKC-α and -β, stress-activated protein kinases, protein phosphatases, protein kinase A, and the phosphatidylinositol 3-kinase pathway had no effect on the TPA-mediated inhibition of SP-A mRNA. TPA also stimulated the synthesis of c-Jun mRNA and protein in a time-dependent manner. Inhibitors of the p44/42 MAPK signaling pathway and PKC blocked the TPA-mediated phosphorylation of p44/42 MAPK and the increase in c-Jun mRNA. We conclude that TPA inhibits SP-A gene expression via novel isoforms of PKC, the p44/42 MAPK pathway, and the activator protein-1 complex.

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.

Surfactant protein A expression is delayed in fetuses of streptozotocin-treated rats

1992 ◽  
Vol 262 (4) ◽  
pp. L489-L494 ◽  
Author(s):  
S. H. Guttentag ◽  
D. S. Phelps ◽  
W. Stenzel ◽  
J. B. Warshaw ◽  
J. Floros
Keyword(s):  
Protein A ◽  
Fetal Lung ◽  
Surfactant Protein ◽  
Female Rats ◽  
Surfactant Protein A ◽  
Mrna Levels ◽  
Sprague Dawley ◽  
Sprague Dawley Rats ◽  
Normal Expression

The content and distribution of the 26-to 38-kDa surfactant protein (SP-A) and its mRNA were determined in fetuses of control and streptozotocin (STZ)-treated Sprague-Dawley rats using immunohistochemistry, RNA blotting, and in situ hybridization. Female rats were treated with 50 mg/kg STZ before mating, and the fetuses were killed at fetal days 18-21 or on neonatal days 1 and 2 (day of birth = end of day 22). SP-A was barely detectable on fetal day 18 in controls and easily detected by fetal day 21. In the STZ group, SP-A was decreased compared with controls at fetal days 18-21. However, by neonatal days 1–2, there were no significant differences in SP-A levels between groups. SP-A mRNA was detectable at fetal day 18 in controls, but it was decreased in the STZ group at day 18-21 (P less than 0.02) and differences were no longer detected by neonatal days 1–2. SP-A and SP-A mRNA accumulated with advancing gestational age in both groups until neonatal days 1–2. The differences in SP-A and SP-A mRNA levels in the two groups diminished with advancing age but remained significant at fetal day 21. These data suggest that STZ-induced diabetes interferes with normal expression of SP-A in the developing fetal lung.

Intra-amniotic endotoxin increases pulmonary surfactant proteins and induces SP-B processing in fetal sheep

2001 ◽  
Vol 280 (2) ◽  
pp. L279-L285 ◽  
Author(s):  
Cindy J. Bachurski ◽  
Gary F. Ross ◽  
Machiko Ikegami ◽  
Boris W. Kramer ◽  
Alan H. Jobe
Keyword(s):  
Bronchoalveolar Lavage ◽  
Gestational Age ◽  
Bronchoalveolar Lavage Fluid ◽  
Fetal Lung ◽  
Lavage Fluid ◽  
Surfactant Protein ◽  
Lung Compliance ◽  
Lung Maturation ◽  
Fetal Sheep ◽  
Pulmonary Surfactant Proteins

Intra-amniotic (IA) endotoxin induces lung maturation within 6 days in fetal sheep of 125 days gestational age. To determine the early fetal lung response to IA endotoxin, the timing and characteristics of changes in surfactant components were evaluated. Fetal sheep were exposed to 20 mg of Escherichia coli 055:B5 endotoxin by IA injection from 1 to 15 days before preterm delivery at 125 days gestational age. Surfactant protein (SP) A, SP-B, and SP-C mRNAs were maximally induced at 2 days. SP-D mRNA was increased fourfold at 1 day and remained at peak levels for up to 7 days. Bronchoalveolar lavage fluid from control animals contained very little SP-B protein, 75% of which was a partially processed intermediate. The alveolar pool of SP-B was significantly increased between 4 and 7 days in conjunction with conversion to the fully processed active airway peptide. All SPs were significantly elevated in the bronchoalveolar lavage fluid by 7 days. IA endotoxin caused rapid and sustained increases in SP mRNAs that preceded the increase in alveolar saturated phosphatidylcholine processing of SP-B and improved lung compliance in prematurely delivered lambs.

Differential regulation of SP-A1 and SP-A2 genes by cAMP, glucocorticoids, and insulin

1998 ◽  
Vol 274 (2) ◽  
pp. L177-L185 ◽  
Author(s):  
A. R. Kumar ◽  
J. M. Snyder
Keyword(s):  
Cell Line ◽  
Lung Surfactant ◽  
Protein A ◽  
Fetal Lung ◽  
Surfactant Protein ◽  
Model Systems ◽  
Mrna Levels ◽  
Mrna Transcripts ◽  
Lung Surfactant Protein ◽  
Human Fetal Lung

In the human fetal lung, surfactant protein A (SP-A) is encoded by two highly similar genes, SP-A1 and SP-A2, which are developmentally and hormonally regulated. Using primer extension analysis, we evaluated the levels of SP-A1 and SP-A2 mRNA transcripts in human fetal lung explants and in a human adult lung adenocarcinoma cell line (H441 cells) cultured in the absence or presence of either dibutyryladenosine 3′,5′-cyclic monophosphate (DBcAMP, 1 mM), dexamethasone (10−7 M), or insulin (2.5 μg/ml). In the human fetal lung explants, the content of SP-A1 mRNA was approximately four times that of SP-A2 mRNA. DBcAMP increased SP-A1 mRNA levels by 100% and SP-A2 mRNA levels by 500%, thus reducing the ratio of SP-A1 mRNA to SP-A2 mRNA to ∼1:1. Dexamethasone inhibited all of the SP-A1 and SP-A2 mRNA transcripts to the same extent, by ∼70%, whereas insulin inhibited all SP-A mRNA transcripts by ∼60%. The ratio of SP-A1 to SP-A2 mRNA in dexamethasone- or insulin-treated explants was the same as the ratio observed in controls. In the H441 cells, SP-A1 mRNA levels were ∼1.5 times that of SP-A2 mRNA levels. DBcAMP increased both SP-A1 and SP-A2 mRNA levels by 100%. Dexamethasone inhibited SP-A1 mRNA levels in the cell line by 60%, whereas SP-A2 mRNA levels were not significantly affected. Insulin inhibited SP-A1 mRNA levels in the cell line by 40% without affecting SP-A2 mRNA levels. These findings suggest that the two human SP-A genes are regulated differently in the two model systems.

scholarly journals MON-005 Inhibition of Glucocorticoid Signaling in SRC-1/-2 Double-Deficient Mice Results in Impaired Lung Maturation and Delayed Parturition

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Ritu Mishra ◽  
Jingfei Chen ◽  
Lu Gao ◽  
Carole R Mendelson
Keyword(s):  
Glucocorticoid Receptor ◽  
Protein A ◽  
Platelet Activating Factor ◽  
Fetal Lung ◽  
Cell Types ◽  
Surfactant Protein ◽  
Rna Seq ◽  
Double Knockout ◽  
Lung Maturation ◽  
Fetal Lungs

Abstract The mechanisms that lead to the initiation of parturition are incompletely defined. Parturition timing is mediated by signals from both mother and fetus. Our previous findings using mice that were double-deficient in steroid receptor coactivators (Src)1 and 2 (Src-1/-2d/d) suggest that the fetus signals its mother when it is ready to be born through fetal lung production of surfactant components, surfactant protein A (SP-A) and platelet-activating factor (PAF). Notably, mice that are double knockout for Src-1/-2 die at birth of respiratory distress, due to decreased surfactant lipoprotein production. Intriguingly, we observed that wild-type (WT) mothers carrying Src-1/-2d/d fetuses manifested a ~38 h delay in parturition compared to WT mothers carrying WT fetuses. This was associated with decreased production of SP-A and PAF by the Src-1/-2d/d fetal lungs. Our findings suggested that these effects of Src-1/-2d/d were caused by impaired glucocorticoid receptor (GR) transcriptional activity in fetal lung cells. To identify other genes in fetal lung that were affected by Src-1/-2d/d, we conducted RNA-seq analysis of lungs from 18.5 days post-coitum Src-1/-2d/dvs. WT fetuses. We observed that one of the genes most highly downregulated in Src-1/-2d/d fetal lungs was 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1). 11β-HSD1 catalyzes the conversion of inactive cortisone or 11-dehydrocorticosterone into active cortisol or corticosterone, respectively, which are ligands for the glucocorticoid receptor (GR). We validated the RNA-seq results by RT-qPCR and immunoblotting and observed a striking reduction of 11β-HSD1 mRNA and protein in lungs of Src-1/2d/d fetuses, compared to WT. Others observed that glucocorticoids potently increased 11β-HSD1 expression in various cell types via activation of transcription factors C/EBPα and C/EBPβ, providing a potential positive feed-forward loop. Notably, we observed that C/EBPα and C/EBPβ mRNA and protein were markedly reduced in Src-1/-2d/d fetal lungs, compared to WT. Deletion of the Cebpa gene in respiratory epithelium of fetal mice caused respiratory failure at birth due to surfactant lipid and protein deficiency. This was associated with increased expression of TGF-β2, which inhibits fetal lung maturation. Notably, we observed that expression of TGF-β2 and TGF-β3 were increased in Src-1/-2d/d fetal lungs. Thus, impaired lung development, surfactant synthesis and delayed parturition in Src-1/-2d/d fetuses are likely caused by decreased 11β-HSD1 and GR signaling, resulting in decreased C/EBPα/β expression and increased TGF-β signaling.

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