Hypoxia-induced modifications in plasma membranes and lipid microdomains in A549 cells and primary human alveolar cells.
We evaluated the response to mild hypoxia exposure of A549 alveolar human cells and of a continuous alveolar cell line from human excised lungs (A30) exposed to 5% O(2) for 5 and 24 h. No signs of increased peroxidation and of early apoptosis were detected. After 24 h of hypoxia total cell proteins/DNA ratio decreased significantly by about 20%. Similarly, we found a decrease in membrane phospholipid and cholesterol content. The membrane fluidity assessed by fluorescence anisotropy measurements was unchanged. We also prepared the detergent resistant membrane fraction (DRM) to analyze the distribution of the two types of lipid microdomains, caveolae and lipid rafts. The DRM content of Cav-1, marker of caveolae, was decreased, while CD55, marker of lipid rafts, increased in both cell lines. Total content of these markers in the membranes was unchanged indicating remodelling of their distribution between detergent-resistant and detergent-soluble fraction of the cellular membrane. The changes in protein markers distribution did not imply changes in the corresponding mRNA, except in the case of Cav-1 for A30 line. In the latter case we found a parallel decrease in Cav-1 and in the corresponding mRNA. We conclude that an exposure to a mild degree of hypoxia triggers a significant remodelling of the lipid microdomains expression, confirming that they are highly dynamic structures providing a prompt signalling platform to changes of the pericellular microenvironment.
Botto
Laura
L
Department of Experimental Medicine (DIMS), University of Milano-Bicocca, Via Cadore 48, 20052 Monza, Italy.
Laura
Botto
B
Beretta
Egidio
E
Egidio
Beretta
B
Bulbarelli
Alessandra
A
Alessandra
Bulbarelli
B
Rivolta
Ilaria
I
Ilaria
Rivolta
R
Lettiero
Barbara
B
Barbara
Lettiero
L
Leone
Biagio Eugenio
BE
Eugenio
Leone Biagio
LB
Miserocchi
Giuseppe
G
Giuseppe
Miserocchi
M
Palestini
Paola
P
Paola
Palestini
P
D021941:Caveolae / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry*; D002478:Cells, Cultured; D002784:Cholesterol / Q000032:analysis; D003902:Detergents / Q000494:pharmacology; D006801:Humans; D000860:Hypoxia / Q000378:metabolism*; D008563:Membrane Lipids / Q000032:analysis; D021962:Membrane Microdomains / Q000737:chemistry*; D010100:Oxygen; D011650:Pulmonary Alveoli / Q000166:cytology*; D012333:RNA, Messenger / Q000032:analysis; D013997:Time Factors
D003902:Detergents; D008563:Membrane Lipids; D012333:RNA, Messenger; D002784:Cholesterol; D010100:Oxygen