INSULIN AND HUMAN FETAL LUNG DEVELOPMENT

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DESCRIPTION: This revised application proposes to study effects and mechanisms of insulin action on surfactant protein A of human fetal lung. The fetus of the diabetic mother is at increased risk for newborn lung disease and it has been proposed that high levels of insulin delay human lung maturation. The previous studies by the applicant indicated that insulin treatment of human fetal lung explants did not affect surfactant phospholipid synthesis or composition but did decrease accumulation of surfactant protein A and its mRNA. Also, concentrations of SP-A in amniotic fluid were found to be lower in diabetic vs. non-diabetic women. In this proposal it is hypothesized that hyperinsulinemia may predispose infants of diabetic mothers to develop respiratory distress by inhibiting the synthesis of surfactant associated proteins, in particular SP-A, thereby altering the composition and function of surfactant. Experiments are proposed using cultured human fetal lung and the H-441 adenocarcinoma cell line to explore the mechanism of insulin effects. The first aim will determine insulin regulation of the two human SP-A genes in cultured tissue and use in situ hybridization to localize the two SP-A transcripts in human lung tissue. The second Specific Aim will examine molecular mechanisms for insulin regulation of SP-A using nuclear run-on assays, studies of SP-A mRNA stability, and inhibitors. The third specific aim will investigate the role of 3' untranslated portion of SP-A mRNA which is predicted to mediate the inhibitory effects of insulin. Transient transfection studies with chimeric genes will identify sequences involved in the proposed destabilizing effect of insulin. In the fourth specific aim, mechanisms involved in the interaction between insulin and glucocorticoid in gene expression will be examined including transcription rate, transcript stability and possible induction of new gene products using differential PCR. These studies will provide new information on the role and mechanism of insulin effects and interaction with glucocorticoids in human fetal lung development.