3-amino-4-(3-hexylphenylamino)-4-oxobutyl phosphonic acid (W146), a Selective Antagonist of Sphingosine-1-phospahte Receptor Subtype 1, Enhances AMD3100-stimulated Mobilization of Hematopoietic Stem Progenitor Cells in Animals

Sphingosine-1-phosphate (S1P), a serum-borne bioactive lipid, regulates various physiological functions. We observed that the S1P receptor subtype 1 (S1P₁), a high affinity G-protein coupled receptor of S1P, is the major S1P receptor expressed in the Kit⁺/Sca-1⁺/Lin^- (KSL) hematopoietic stem progenitor cells (HSPCs, KSL-HSPCs). In this study, we investigate function of S1P₁ receptors in the regulation of HSPC mobilization in Animals. Treatment with SEW2871, a specific agonist of S1P₁, had no effect on KSL-HSPC mobilization. In addition, mice pretreated with SEW2871 followed by AMD3100, a well-known activator of KSL-HSPC mobilization by antagonizing the stromal-derived factor-1 (SDF-1)/C-X-C Chemokine Receptor type 4 (CXCR4) signaling axis, did not enhance the AMD3100-induced KSL-HSPC mobilization. In contrast, pretreatment of (R)-3-amino-4-(3-hexylphenylamino)-4-oxobutyl phosphonic acid (W146), a selective antagonist of S1P₁, significantly augments AMD3100-induced KSL-HSPC mobilization into peripheral blood. The inactive enantiomer W140 was incapable of enhancing the AMD3100-induced KSL-HSPC mobilization. Moreover, treatment with selective antagonists for S1P₂ and S1P₃ had no effects on AMD3100-mediated KSL-HSPC mobilization. Collectively, our data suggest that S1P/S1P₁ signaling regulates the SDF-1/CXCR4-mediated retention of KSL-HSPCs in bone marrow microenvironment.