Surfactant deficiency plays an integral role in the pathogenesis of neonatal lung diseases such as RDS and acute lung injury. Although surfactant replacement therapy has made an impact in RDS, it is not totally effective. An alternative strategy to increase the alveolar surfactant pool is by stimulating biosynthesis. Surfactant synthesis is tightly controlled by the rate-limiting enzyme, cytidylyltransferase (CT). CT activity is inhibited by sphingolipids and stimulated by fatty acids. However, prior studies administering fatty acids in vivo to stimulate surfactant production have had mixed success with associated toxicity. Thus, the goal of this proposal is to develop a novel and safe approach to stimulating surfactant synthesis in fetal lung by the use of very low density lipoproteins (VLDL) and lipoprotein lipase (LPL). This revised competing renewal expands from recent advances in our laboratory made through support of the existing grant showing that 1) fatty acids carried within very low density lipoproteins (VLDL) are potent stimulators of CT activity in vitro in the presence of LPL and 2) oxidized lipoproteins inhibit surfactant synthesis, . These observations led to the hypothesis that native lipoprotein loading and oxidized lipoproteins differentially regulate the CT enzyme. We will investigate whether loading with native lipoproteins (VLDL) increases CT activity by altering fatty acids and sphingolipids associated with the enzyme (AIM 1). We will also investigate how modified (oxidized) lipoproteins acutely down-regulate surfactant synthesis by inducing CT proteolysis (AIM 2). Our hypothesis will be tested, in vivo, by maternal administration of lipoproteins in pregnant rats and with analysis conducted in primary fetal type II cells. These in vivo studies will be supplemented with use of a lipoprotein-responsive type II (MLE12) cell line. The unique contributions of this proposal impacting the field of surfactant metabolism include: 1) mechanistic studies with potential clinical application by which native lipoproteins control CT function post-translationally (AIM 1) and 2) studies investigating CT regulation at the level of protein stability (AIM 2) .

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL055584-09
Application #
6840342
Study Section
Human Embryology and Development Subcommittee 1 (HED)
Program Officer
Berberich, Mary Anne
Project Start
1996-04-01
Project End
2007-12-31
Budget Start
2005-01-01
Budget End
2007-12-31
Support Year
9
Fiscal Year
2005
Total Cost
$257,250
Indirect Cost
Name
University of Iowa
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
062761671
City
Iowa City
State
IA
Country
United States
Zip Code
52242
Ryan, Alan J; Andrews, Matthew; Zhou, Jiming et al. (2006) c-Jun N-terminal kinase regulates CTP:phosphocholine cytidylyltransferase. Arch Biochem Biophys 447:23-33
Zhou, J; Wu, Y; Henderson, F et al. (2006) Adenoviral gene transfer of a mutant surfactant enzyme ameliorates pseudomonas-induced lung injury. Gene Ther 13:974-85
Xu, Zhiwei; Zhou, Jiming; McCoy, Diann M et al. (2005) LASS5 is the predominant ceramide synthase isoform involved in de novo sphingolipid synthesis in lung epithelia. J Lipid Res 46:1229-38
Agassandian, Marianna; Zhou, Jiming; Tephly, Linda A et al. (2005) Oxysterols inhibit phosphatidylcholine synthesis via ERK docking and phosphorylation of CTP:phosphocholine cytidylyltransferase. J Biol Chem 280:21577-87
Zhou, Jiming; You, Yong; Ryan, Alan J et al. (2004) Upregulation of surfactant synthesis triggers ABCA1-mediated basolateral phospholipid efflux. J Lipid Res 45:1758-67
Zhou, Jiming; You, Yong; Zabner, Joseph et al. (2004) The CCT promoter directs high-level transgene expression in distal lung epithelial cell lines. Am J Respir Cell Mol Biol 30:61-8
Zhou, Jiming; Ryan, Alan J; Medh, Jheem et al. (2003) Oxidized lipoproteins inhibit surfactant phosphatidylcholine synthesis via calpain-mediated cleavage of CTP:phosphocholine cytidylyltransferase. J Biol Chem 278:37032-40
Ryan, Alan J; Medh, Jheem D; McCoy, Diann M et al. (2002) Maternal loading with very low-density lipoproteins stimulates fetal surfactant synthesis. Am J Physiol Lung Cell Mol Physiol 283:L310-8
Carroll Jr, James L; McCoy, Diann M; McGowan, Stephen E et al. (2002) Pulmonary-specific expression of tumor necrosis factor-alpha alters surfactant lipid metabolism. Am J Physiol Lung Cell Mol Physiol 282:L735-42
Mallampalli, Rama K; Ryan, Alan J; Carroll, James L et al. (2002) Lipid deprivation increases surfactant phosphatidylcholine synthesis via a sterol-sensitive regulatory element within the CTP:phosphocholine cytidylyltransferase promoter. Biochem J 362:81-8

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