[Elucidation of the functional roles of lysophospholipid mediators and its application in laboratory medicine]

Sphingosine 1-phosphate (Sph-1-P) is a sphingolipid, while lysophosphatidic acid (LPA) is a glycerophospholipid. Both lipids are classified as lysophospholipid mediators and are attracting great attention since it has been established that these bioactive lipids act as multifunctional extracellular mediators through interaction with G protein-coupled cell surface receptors. Blood platelets are unique in that they store Sph-1-P abundantly (possibly due to the existence of highly active Sph kinase and a lack of Sph-1-P lyase) and release this bioactive lipid extracellularly upon stimulation. It is likely that platelets are an important source of extracellular Sph-1-P, especially of plasma and serum Sph-1-P. Platelet-derived Sph-1-P seems to play an important role in vascular biology. On the other hand, LPA has been recently shown to be produced by plasma lysophospholipase D, which is identical to autotaxin, originally identified as a potent tumor cell motility-stimulating factor. We have examined the functional roles of these lysophospholipid mediators and attempted to apply their measurements in the laboratory testing, as described in this article.