1
|
Madsen J, Panchal MH, Mackay RMA, Echaide M, Koster G, Aquino G, Pelizzi N, Perez-Gil J, Salomone F, Clark HW, Postle AD. Metabolism of a synthetic compared with a natural therapeutic pulmonary surfactant in adult mice. J Lipid Res 2018; 59:1880-1892. [PMID: 30108154 PMCID: PMC6168297 DOI: 10.1194/jlr.m085431] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Revised: 07/09/2018] [Indexed: 11/24/2022] Open
Abstract
Secreted pulmonary surfactant phosphatidylcholine (PC) has a complex intra-alveolar metabolism that involves uptake and recycling by alveolar type II epithelial cells, catabolism by alveolar macrophages, and loss up the bronchial tree. We compared the in vivo metabolism of animal-derived poractant alfa (Curosurf) and a synthetic surfactant (CHF5633) in adult male C57BL/6 mice. The mice were dosed intranasally with either surfactant (80 mg/kg body weight) containing universally 13C-labeled dipalmitoyl PC (DPPC) as a tracer. The loss of [U13C]DPPC from bronchoalveolar lavage and lung parenchyma, together with the incorporation of 13C-hydrolysis fragments into new PC molecular species, was monitored by electrospray ionization tandem mass spectrometry. The catabolism of CHF5633 was considerably delayed compared with poractant alfa, the hydrolysis products of which were cleared more rapidly. There was no selective resynthesis of DPPC and, strikingly, acyl remodeling resulted in preferential synthesis of polyunsaturated PC species. In conclusion, both surfactants were metabolized by similar pathways, but the slower catabolism of CHF5633 resulted in longer residence time in the airways and enhanced recycling of its hydrolysis products into new PC species.
Collapse
Affiliation(s)
- Jens Madsen
- Child Health, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Madhuriben H Panchal
- Child Health, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Rose-Marie A Mackay
- Child Health, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom
| | - Mercedes Echaide
- Department of Biochemistry and Molecular Biology, Faculty of Biology, Hospital 12 de Octubre Research Institute, Complutense University, Madrid, Spain
| | - Grielof Koster
- Child Health, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom.,National Institute for Health Research, Biomedical Research Centre, University Hospital Southampton, Southampton, United Kingdom
| | | | | | - Jesus Perez-Gil
- Department of Biochemistry and Molecular Biology, Faculty of Biology, Hospital 12 de Octubre Research Institute, Complutense University, Madrid, Spain
| | | | - Howard W Clark
- Child Health, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom.,National Institute for Health Research, Biomedical Research Centre, University Hospital Southampton, Southampton, United Kingdom
| | - Anthony D Postle
- Child Health, Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton, United Kingdom .,National Institute for Health Research, Biomedical Research Centre, University Hospital Southampton, Southampton, United Kingdom
| |
Collapse
|
2
|
Abstract
Three pulmonary disease conditions result from the accumulation of phospholipids in the lung. These conditions are the human lung disease known as pulmonary alveolar proteinosis, the lipoproteinosis that arises in the lungs of rats during acute silicosis, and the phospholipidoses induced by numerous cationic amphiphilic therapeutic agents. In this paper, the status of phospholipid metabolism in the lungs during the process of each of these lung conditions has been reviewed and possible mechanisms for their establishment are discussed. Pulmonary alveolar proteinosis is characterized by the accumulation of tubular myelin-like multilamellated structures in the alveoli and distal airways of patients. These structures appear to be formed by a process of spontaneous assembly involving surfactant protein A and surfactant phospholipids. Structures similar to tubular myelin-like multilamellated structures can be seen in the alveoli of rats during acute silicosis and, as with the human condition, both surfactant protein A and surfactant phospholipids accumulate in the alveoli. Excessive accumulation of surfactant protein A and surfactant phospholipids in the alveoli could arise from their overproduction and hypersecretion by a subpopulation of Type II cells that are activated by silica, and possibly other agents. Phospholipidoses caused by cationic amphiphilic therapeutic agents arise as a result of their inhibition of phospholipid catabolism. Inhibition of phospholipases results in the accumulation of phospholipids in the cytoplasm of alveolar macrophages and other cells. While inhibition of phospholipases by these agents undoubtedly occurs, there are many anomalous features, such as the accumulation of extracellular phospholipids and surfactant protein A, that cannot be accounted for by this simplistic hypothesis.
Collapse
Affiliation(s)
- Gary E. R. Hook
- Biochemical Pathology Group, Laboratory of Pulmonary Pathobiology, National Institute of Environmental Health Sciences, P.O. Box 12233, Research Triangle Park, North Carolina 27709
| |
Collapse
|
3
|
Abstract
The surfactant components saturated phosphatidylcholine, SP-B and SP-C, are secreted together in lamellar bodies, and at least a part of the de novo synthesized SP-A is secreted independently. The surface film forms from tubular myelin and loose lipid arrays, and it generates unilamellar vesicles that lack surfactant proteins and are thought to represent catabolic forms. The half-life values for the clearance of surfactant proteins from lungs range from 6.5 to 28 h and vary with species. There is minimal information about the associations of the surfactant proteins with lipids or with each other after film formation, although all surfactant components seem to be recycled back into lamellar bodies in type II cells. The relative importance of type II cells or macrophages to the catabolism of the protein components of surfactant remains to be characterized, as do regulators of surfactant homeostasis.
Collapse
Affiliation(s)
- M Ikegami
- Division of Pulmonary Biology, Children's Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229-3039, USA.
| | | |
Collapse
|