Release of sphingosine-1-phosphate from human platelets is dependent on thromboxane formation.
BACKGROUND
Platelets release the immune-modulating lipid sphingosine-1-phosphate (S1P). However, the mechanisms of platelet S1P secretion are not fully understood.


OBJECTIVE
The present study investigates the function of thromboxane (TX) for platelet S1P secretion during platelet activation and the consequences for monocyte chemotaxis.


METHODS
S1P was detected using thin-layer chromatography in [(3)H]sphingosine-labeled platelets and by mass spectrometry. Monocyte migration was measured in modified Boyden chamber chemotaxis assays.


RESULTS
Release of S1P from platelets was stimulated with protease-activated receptor-1-activating peptide (PAR-1-AP, 100 μM). Acetylsalicylic acid (ASA) and two structurally unrelated reversible cyclooxygenase inhibitors diclofenac and ibuprofen suppressed S1P release. Oral ASA (500-mg single dose or 100 mg over 3 days) attenuated S1P release from platelets in healthy human volunteers ex vivo. This was paralleled by inhibition of TX formation. S1P release was increased by the TX receptor (TP) agonist U-46619, and inhibited by the TP antagonist ramatroban and by inhibitors of ABC-transport. Furthermore, thrombin-induced release of S1P was attenuated in platelets from TP-deficient mice. Supernatants from PAR-1-AP-stimulated human platelets increased the chemotactic capacity of human peripheral monocytes in a S1P-dependent manner via S1P receptors-1 and -3. These effects were inhibited by ASA-pretreatment of platelets.


CONCLUSIONS
TX synthesis and TP activation mediate S1P release after thrombin receptor activation. Inhibition of this pathway may contribute to the anti-inflammatory actions of ASA, for example by affecting activity of monocytes at sites of vascular injury.
Institut für Pharmakologie und Klinische Pharmakologie, Universitätsklinikum Düsseldorf, Düsseldorf, Germany.
T
T
Ulrych
A
A
Böhm
A
A
Polzin
G
G
Daum
R M
RM
Nüsing
G
G
Geisslinger
T
T
Hohlfeld
K
K
Schrör
B H
BH
Rauch
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D002855:Chromatography, Thin Layer; D006801:Humans; D008246:Lysophospholipids / Q000097:blood*; D017482:Receptors, Thromboxane / Q000819:agonists; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000097:blood; D013917:Thrombin / Q000494:pharmacology; D013931:Thromboxanes / Q000096:biosynthesis*
D008246:Lysophospholipids; D017482:Receptors, Thromboxane; D013931:Thromboxanes; C060506:sphingosine 1-phosphate; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D013917:Thrombin; D013110:Sphingosine; D001241:Aspirin