Albumin Stimulates Epithelial Na+ Transport and Barrier Integrity by Activating the PI3K/AKT/SGK1 Pathway

Albumin is a major serum protein and is frequently used as a cell culture supplement. It is crucially involved in the regulation of osmotic pressure and distribution of fluid between different compartments. Alveolar epithelial Na+ transport drives alveolar fluid clearance (AFC), enabling air breathi...

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Bibliographic Details
Published in:International journal of molecular sciences 2022-08, Vol.23 (15), p.8823
Main Authors: Laube, Mandy, Thome, Ulrich H.
Format: Article
Language:English
Subjects:
1-Phosphatidylinositol 3-kinase
AKT protein
Albumin
Albumins
Alveoli
barrier integrity
BSA
Cell culture
Chambers
Chronic effects
Edema
ENaC
Fetuses
Gene expression
Kinases
lung
Membrane permeability
Na+ transport
Na+/K+-exchanging ATPase
Osmosis
Osmotic pressure
Permeability
Phosphorylation
Physiology
Premature babies
Premature birth
protein kinase B
Proteins
Respiratory distress syndrome
Serum proteins
Western blotting
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Summary:Albumin is a major serum protein and is frequently used as a cell culture supplement. It is crucially involved in the regulation of osmotic pressure and distribution of fluid between different compartments. Alveolar epithelial Na+ transport drives alveolar fluid clearance (AFC), enabling air breathing. Whether or not albumin affects AFC and Na+ transport is yet unknown. We therefore determined the acute and chronic effects of albumin on Na+ transport in fetal distal lung epithelial (FDLE) cells and the involved kinase pathways. Chronic BSA treatment strongly increased epithelial Na+ transport and barrier integrity in Ussing chambers. BSA did not elevate mRNA expression of Na+ transporters in FDLE cells after 24 h. Moreover, acute BSA treatment for 45 min mimicked the chronic effects. The elevated Na+ transport was caused by an increased maximal ENaC activity, while Na,K-ATPase activity remained unchanged. Acute and chronic BSA treatment lowered membrane permeability, confirming the increased barrier integrity observed in Ussing chambers. Western blots demonstrated an increased phosphorylation of AKT and SGK1, and PI3K inhibition abolished the stimulating effect of BSA. BSA therefore enhanced epithelial Na+ transport and barrier integrity by activating the PI3K/AKT/SGK1 pathway.
ISSN:1422-0067
1661-6596
1422-0067
DOI:10.3390/ijms23158823