Effects of phospholipid transfer protein overexpression on content of sphingosine-1-phosphate in mouse lipoprotein

AIM：To investigate the interaction and the mechanism of sphingosine-1-phosphate (S1P) and phospholipid transfer protein (PLTP) in lipoprotein. METHODS：The S1P content in the plasma and lipoprotein from 10-week-old PLTP transgenic (PLTP-Tg) mice and wild-type (WT) mice (n=8 each) was assayed. The transport of S1P by PLTP was determined by S1P transfer assay. The content of specific S1P carrier, apolipoprotein M, was detected by Western blotting. RESULTS：Plasma S1P contents were decreased by 21.1% in PLTP-Tg mice compared with WT mice. S1P content in high-density lipoprotein (HDL) fraction (HDL-S1P) from PLTP-Tg mice was decreased by 35.1% compared with WT mice, whereas the S1P in low-density lipoprotein (LDL) fraction (LDL-S1P) was increased by 127.4%. The results of S1P transfer assay indicated that PLTP facilitated S1P transport from erythrocyte to recombinant liposome at 37 ℃ in D-Hanks buffer solution. The plasma content of apolipoprotein M was not changed in PLTP-Tg mice compared with WT mice. CONCLUSION：PLTP is a key factor to maintain plasma HDL-S1P under physical condition. Overexpression of PLTP decreases the HDL-S1P but increases LDL-S1P. The mechanism might be related to the capability of PLTP on transferring S1P from erythrocyte to lipoprotein.