293: Transcriptomic analysis reveals potential roles for ERK3 in fetal lung maturation via surfactant protein B and corticotropin releasing hormone

Surfactant protein B (SP-B8), an 8-kDa hydrophobic protein essential for surfactant and normal lung function, is produced from the intracellular processing of preproSP-B. To characterize SP-B processing in human type 2 cells, we used human fetal lung in explant culture and polyclonal antibodies to human SP-B8(Phe201–Met279) and to specific epitopes within the NH2- and COOH-terminal propeptide domains (Ser145–Leu160, Gln186–Gln200, and Gly284–Ser304). Western blot analysis revealed a novel intermediate at ∼9 kDa, representing mature SP-B8, with a residual NH2-terminal peptide of ∼10 amino acids. Pulse-chase studies showed a precursor-product relationship between the 9- and 8-kDa forms. During differentiation of type 2 cells in explant culture, the rate of proSP-B conversion to 25-kDa intermediate remained constant, whereas the rate of 25-kDa intermediate conversion to SP-B8increased, resulting in a net increase in tissue SP-B8. Dexamethasone did not affect the rate of proSP-B processing but markedly enhanced the rate of SP-B8 accumulation. We conclude that NH2-terminal propeptide cleavage of proSP-B is a multistep process and that more distal processing events are rate limiting and both developmentally and hormonally regulated.

Download Full-text

Intra-amniotic injection of IL-1 induces inflammation and maturation in fetal sheep lung

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00097.2001 ◽

2002 ◽

Vol 282 (3) ◽

pp. L411-L420 ◽

Cited By ~ 73

Author(s):

Karen E. Willet ◽

Boris W. Kramer ◽

Suhas G. Kallapur ◽

Machiko Ikegami ◽

John P. Newnham ◽

...

Keyword(s):

Escherichia Coli ◽

Lung Function ◽

Lung Inflammation ◽

Fetal Lung ◽

Surfactant Protein ◽

Lung Compliance ◽

Fetal Membranes ◽

Lung Maturation ◽

Fetal Sheep ◽

Fetal Lung Maturation

Antenatal inflammation may be an important triggering event in the pathogenesis of bronchopulmonary dysplasia but may also accelerate fetal lung maturation. We examined the effects of intra-amniotic (IA) interleukin (IL)-1α and IL-1β on maturation of the fetal sheep lung. These cytokine effects were compared with IA endotoxin, a potent proinflammatory stimulus that accelerated lung maturation. Date-bred ewes received 15 or 150 μg recombinant ovine IL-1α or IL-1β or 10 mg Escherichia coli endotoxin by IA injection at 118 days gestation (term = 150 days), and fetuses were delivered at 125 days. IL-1α and IL-1β improved lung function and increased alveolar saturated phosphatidylcholine (Sat PC) and surfactant protein mRNA expression at the higher dose. The maturation response to IL-1α was greater than that to IL-1β, which was similar to endotoxin response. Inflammation was also more pronounced after IL-1α treatment. Only endotoxin animals had residual inflammation of the fetal membranes at 7 days. Lung compliance, lung volume, and alveolar Sat PC were positively correlated with residual alveolar wash leukocyte numbers 7 days after IL-1 treatment, suggesting a link between lung inflammation and maturation.

Download Full-text

Human surfactant protein B promoter in transgenic mice: temporal, spatial, and stimulus-responsive regulation

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00188.2001 ◽

2002 ◽

Vol 282 (3) ◽

pp. L394-L404 ◽

Cited By ~ 12

Author(s):

Marlene Strayer ◽

Rashmin C. Savani ◽

Linda W. Gonzales ◽

Aisha Zaman ◽

Zheng Cui ◽

...

Keyword(s):

Transgenic Mice ◽

Transforming Growth Factor ◽

Fetal Lung ◽

Surfactant Protein ◽

Explant Culture ◽

Developmental Expression ◽

Alveolar Type ◽

Similar Time ◽

Surfactant Protein B ◽

Protein B

Surfactant protein B (SP-B) is a developmentally and hormonally regulated lung protein that is required for normal surfactant function. We generated transgenic mice carrying the human SP-B promoter (−1,039/+431 bp) linked to chloramphenicol acetyltransferase (CAT). CAT activity was high in lung and immunoreactive protein localized to alveolar type II and bronchiolar epithelial cells. In addition, thyroid, trachea, and intestine demonstrated CAT activity, and each of these tissues also expressed low levels of SP-B mRNA. Developmental expression of CAT activity and SP-B mRNA in fetal lung were similar and both increased during explant culture. SP-B mRNA but not CAT activity decreased during culture of adult lung, and both were reduced by transforming growth factor (TGF)-β1. Treatment of adult mice with intratracheal bleomycin caused similar time-dependent decreases in lung SP-B mRNA and CAT activity. These findings indicate that the human SP-B promoter fragment directs tissue- and lung cell-specific transgene expression and contains cis-acting elements involved in regulated expression during development, fetal lung explant culture, and responsiveness to TGF-β and bleomycin-induced lung injury.

Download Full-text