Stimulation of erythrocyte ceramide formation by platelet-activating factor.
Osmotic erythrocyte shrinkage leads to activation of cation channels with subsequent Ca2+ entry and stimulates a sphingomyelinase with subsequent formation of ceramide. Ca2+ and ceramide then activate a scramblase leading to breakdown of phosphatidylserine asymmetry of the cell membrane. The mediators accounting for activation of erythrocyte sphingomyelinase and phosphatidylserine exposure remained elusive. The study demonstrates that platelet-activating factor (PAF) is released from erythrocytes upon hyperosmotic cell shrinkage. The experiments further disclose the presence of PAF receptors in erythrocytes and show that PAF stimulates the breakdown of sphingomyelin and the release of ceramide from erythrocytes at isotonic conditions. PAF further triggers cell shrinkage (decrease of forward scatter) and phosphatidylserine exposure (annexin binding) of erythrocytes. The stimulation of annexin-binding is blunted by a genetic knockout of PAF receptors, by the PAF receptor antagonist ABT491 or by inhibition of sphingomyelinase with urea. In conclusion, PAF activates an erythrocyte sphingomyelinase and the then formed ceramide leads to the activation of scramblase with subsequent phosphatidylserine exposure.
Lang
Philipp A
PA
Department of Physiology, University of Tübingen, Germany.
Kempe
Daniela S
DS
Tanneur
Valerie
V
Eisele
Kerstin
K
Klarl
Barbara A
BA
Myssina
Svetlana
S
Jendrossek
Verena
V
Ishii
Satoshi
S
Shimizu
Takao
T
Waidmann
Marc
M
Hessler
Gabriele
G
Huber
Stephan M
SM
Lang
Florian
F
Wieder
Thomas
T
D017302:Annexins / Q000378:metabolism; D017209:Apoptosis; D001792:Blood Platelets / Q000378:metabolism; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism; D002469:Cell Separation; D002518:Ceramides / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D003902:Detergents / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004910:Erythrocyte Membrane / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D007962:Leukocytes / Q000378:metabolism; D017830:Octoxynol / Q000494:pharmacology; D010718:Phosphatidylserines / Q000378:metabolism; D010972:Platelet Activating Factor / Q000378:metabolism*; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism; D013108:Sphingomyelin Phosphodiesterase / Q000378:metabolism; D013696:Temperature; D013997:Time Factors
D017302:Annexins; D002518:Ceramides; D003902:Detergents; D010718:Phosphatidylserines; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D043562:Receptors, G-Protein-Coupled; C039351:platelet activating factor receptor; D017830:Octoxynol; D013108:Sphingomyelin Phosphodiesterase; D002118:Calcium