Sphingosine 1-phosphate, a bioactive sphingolipid abundantly stored in platelets, is a normal constituent of human plasma and serum.
Although sphingosine 1-phosphate (Sph-1-P) is reportedly involved in diverse cellular processes and the physiological roles of this bioactive sphingolipid have been strongly suggested, few studies have revealed the presence of Sph-1-P in human samples, including body fluids and cells, under physiological conditions. In this study, we identified Sph-1-P as a normal constituent of human plasma and serum. The Sph-1-P levels in plasma and serum were 191+/-79 and 484+/-82 pmol/ml (mean+/-SD, n=8), respectively. Furthermore, when Sph-1-P was measured in paired plasma and serum samples obtained from 6 healthy adults, the serum Sph-1-P/plasma Sph-1-P ratio was found to be 2.65+/-1.26 (mean+/-SD). It is most likely that the source of discharged Sph-1-P during blood clotting is platelets, because platelets abundantly store Sph-1-P compared with other blood cells, and release part of their stored Sph-1-P extracellularly upon stimulation. We also studied Sph-1-P-related metabolism in plasma. [3H]Sph was stable and not metabolized at all in plasma, but was rapidly incorporated into platelets and metabolized mainly to Sph-1-P in platelet-rich plasma. [3H]Sph-1-P was found to be unchanged in plasma, revealing that plasma does not contain the enzymes needed for Sph-1-P degradation. In summary, platelets can convert Sph into Sph-1-P, and are storage sites for the latter in the blood. In view of the diverse biological effects of Sph-1-P, the release of Sph-1-P from activated platelets may be involved in a variety of physiological and pathophysiological processes, including thrombosis, hemostasis, atherosclerosis and wound healing.
Yatomi
Y
Y
Department of Laboratory Medicine, Yamanashi Medical University, Nakakoma-gun. yatomiy@res.yamanashi-med.ac.jp
Igarashi
Y
Y
Yang
L
L
Hisano
N
N
Qi
R
R
Asazuma
N
N
Satoh
K
K
Ozaki
Y
Y
Kume
S
S
D001773:Blood Cells / Q000737:chemistry; D001792:Blood Platelets / Q000737:chemistry* / Q000378:metabolism*; D001826:Body Fluids / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008246:Lysophospholipids; D010949:Plasma / Q000737:chemistry*; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000097:blood; D014316:Tritium
D008246:Lysophospholipids; D014316:Tritium; C060506:sphingosine 1-phosphate; D013110:Sphingosine