Lipidomics of cellular and secreted phospholipids from differentiated human fetal type II alveolar epithelial cells

Linda W. Gonzales,Wolfgang Bernhard,Rodolfo I. Godinez,Anthony D. Postle,Marye H. Godinez,Philip L. Ballard,Graeme T. Clark

doi:10.1194/jlr.m600054-jlr200

Abstract

Maturation of fetal alveolar type II epithelial cells in utero is characterized by specific changes to lung surfactant phospholipids. Here, we quantified the effects of hormonal differentiation in vitro on the molecular specificity of cellular and secreted phospholipids from human fetal type II epithelial cells using electrospray ionization mass spectrometry. Differentiation, assessed by morphology and changes in gene expression, was accompanied by restricted and specific modifications to cell phospholipids, principally enrichments of shorter chain species of phosphatidylcholine (PC) and phosphatidylinositol, that were not observed in fetal lung fibroblasts. Treatment of differentiated epithelial cells with secretagogues stimulated the secretion of functional surfactant-containing surfactant proteins B and C (SP-B and SP-C). Secreted material was further enriched in this same set of phospholipid species but was characterized by increased contents of short-chain monounsaturated and disaturated species other than dipalmitoyl PC (PC16:0/16:0), principally palmitoylmyristoyl PC (PC16:0/14:0) and palmitoylpalmitoleoyl PC (PC16:0/16:1). Mixtures of these PC molecular species, phosphatidylglycerol, and SP-B and SP-C were functionally active and rapidly generated low surface tension on compression in a pulsating bubble surfactometer. These results suggest that hormonally differentiated human fetal type II cells do not select the molecular composition of surfactant phospholipid on the basis of saturation but, more likely, on the basis of acyl chain length.

Highlights

Maturation of fetal alveolar type II epithelial cells in utero is characterized by specific changes to lung surfactant phospholipids
Characterization of fetal alveolar epithelial cells differentiated in culture As demonstrated previously, culture of undifferentiated human fetal lung epithelial cells in the presence of dexamethasone 8-bromo-cAMP isobutylmethylxanthine (DCI) for 4 days induced an apparent phenotypic maturation [8, 9]
They demonstrate clearly that phenotypic differentiation of immature human fetal epithelial cells into functionally active type II alveolar epithelial cells is characterized by significant modulations to phospholipid compositions of both whole cells and secreted surfactant

Summary

Introduction

Maturation of fetal alveolar type II epithelial cells in utero is characterized by specific changes to lung surfactant phospholipids. We quantified the effects of hormonal differentiation in vitro on the molecular specificity of cellular and secreted phospholipids from human fetal type II epithelial cells using electrospray ionization mass spectrometry. Secreted material was further enriched in this same set of phospholipid species but was characterized by increased contents of short-chain monounsaturated and disaturated species other than dipalmitoyl PC (PC16:0/16:0), principally palmitoylmyristoyl PC (PC16:0/14:0) and palmitoylpalmitoleoyl PC (PC16:0/16:1) Mixtures of these PC molecular species, phosphatidylglycerol, and SP-B and SP-C were functionally active and rapidly generated low surface tension on compression in a pulsating bubble surfactometer. These results suggest that hormonally differentiated human fetal type II cells do not select the molecular composition of surfactant phospholipid on the basis of saturation but, more likely, on the basis of acyl chain length.—A. The molecular specificities of the associated synthetic enzymes and transport proteins are not developmentally regulated, suggesting that a combination of poorly defined physiological and nutritional factors may be major mediators of altered surfactant PC composition

Methods

Results

Conclusion