Surfactant metabolism

Stable Identifier
Homo sapiens
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The alveolar region of the lung creates an extensive epithelial surface that mediates the transfer of oxygen and carbon dioxide required for respiration after birth. Type I epithelial cells form the alveolar surface and mediate gaseous exchange. Type II epithelial cells secrete pulmonary surfactant, a lipoprotein complex that forms a thin interfacial film, lowering surface tension at the air-liquid interface in alveoli and maintaining the structural integrity of alveoli, preventing their collapse at low volumes (Agassandian & Mallampalli 2013). Surfactant production is increased prior to birth, in preparation for air breathing at birth (Hallman 2013). Pre-term infants, where type II epithelial cells are not fully differentiated yet, can produce insufficient surfactant and result in respiratory distress syndrome. Surfactant is composed primarily of phospholipids enriched in phosphatidylcholine (PC) and phosphatidylglycerol (PG) (Agassandian & Mallampalli 2013) and the pulmonary collectins, termed surfactant proteins A, B, C and D (SFTPA-D). They influence surfactant homeostasis, contributing to the physical structures of lipids in the alveoli and to the regulation of surfactant function and metabolism. They are directly secreted from alveolar type II cells into the airway to function as part of the surfactant. SFTPA and D are large, hydrophilic proteins while SFTPB and C are small, very hydrophobic proteins (Johansson et al. 1994). In addition to their surfactant functions, SFTPA and D play important roles in innate host defense by binding and clearing invading microbes from the lung (Kingma & Whitsett 2006). Nuclear regulation, transport, metabolism, reutilisation and degradation of surfactant are described here (Ikegami 2006, Boggaram 2009, Whitsett et al. 2010). Mutations in genes involved in these processes can result in respiratory distress syndrome, lung proteinosis, interstitial lung diseases and chronic lung diseases (Perez-Gil & Weaver 2010, Whitsett et al. 2010, Akella & Deshpande 2013, Jo 2014).
Literature References
PubMed ID Title Journal Year
23441475 Pulmonary surfactants and their role in pathophysiology of lung disorders

Akella, A, Deshpande, SB

Indian J. Exp. Biol. 2013
23026158 Surfactant phospholipid metabolism

Agassandian, M, Mallampalli, RK

Biochim. Biophys. Acta 2013
20551227 Pulmonary surfactant pathophysiology: current models and open questions

Weaver, TE, Perez-Gil, J

Physiology (Bethesda) 2010
8162991 The proteins of the surfactant system

Johansson, J, Robertson, B, Curstedt, T

Eur. Respir. J. 1994
19824815 Alveolar surfactant homeostasis and the pathogenesis of pulmonary disease

Whitsett, JA, Weaver, TE, Wert, SE

Annu. Rev. Med. 2010
24868212 Genetic risk factors associated with respiratory distress syndrome

Jo, HS

Korean J Pediatr 2014
23736009 The surfactant system protects both fetus and newborn

Hallman, M

Neonatology 2013
19037882 Thyroid transcription factor-1 (TTF-1/Nkx2.1/TITF1) gene regulation in the lung

Boggaram, V

Clin. Sci. 2009
16580255 In defense of the lung: surfactant protein A and surfactant protein D

Whitsett, JA, Kingma, PS

Curr Opin Pharmacol 2006
16423266 Surfactant catabolism

Ikegami, M

Respirology 2006
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