ABSTRACT
Immunotherapeutic drugs that mimic sphingosine 1-phosphate (S1P) disrupt lymphocyte trafficking and cause T helper and T effector cells to be retained in secondary lymphoid tissue and away from sites of inflammation. The prototypical therapeutic agent, 2-alkyl-2-amino-1,3-propanediol (FTY720), stimulates S1P signaling pathways only after it is phosphorylated by one or more unknown kinases. We generated sphingosine kinase 2 (SPHK2) null mice to demonstrate that this kinase is responsible for FTY720 phosphorylation and thereby its subsequent actions on the immune system. Both systemic and lymphocyte-localized sources of SPHK2 contributed to FTY720 induced lymphopenia. Although FTY720 was selectively activated in vivo by SPHK2, other S1P pro-drugs can be phosphorylated to cause lymphopenia through the action of additional sphingosine kinases. Our results emphasize the importance of SPHK2 expression in both lymphocytes and other tissues for immune modulation and drug metabolism.
Subject(s)
Immunosuppressive Agents/toxicity , Lymphocytes/drug effects , Lymphocytes/enzymology , Lymphopenia , Phosphotransferases (Alcohol Group Acceptor)/physiology , Propylene Glycols/toxicity , Animals , Fingolimod Hydrochloride , Flow Cytometry , Homozygote , Immunosuppressive Agents/metabolism , Lymphopenia/chemically induced , Lymphopenia/enzymology , Lysophospholipids/metabolism , Mice , Mice, Inbred C57BL , Mice, Knockout , Phosphorylation/drug effects , Phosphotransferases (Alcohol Group Acceptor)/genetics , Prodrugs/metabolism , Prodrugs/toxicity , Propylene Glycols/metabolism , Reverse Transcriptase Polymerase Chain Reaction , Sphingosine/analogs & derivatives , Sphingosine/metabolismABSTRACT
Phosphothioates may provide metabolic stability when compared to their phosphate counterparts, while retaining the potency and efficacy as agonists at sphingosine-1-phosphate (S1P) G-protein coupled receptors. Unlike their phosphate precursors, phosphothioate compounds with S1P-receptor profiles similar to that of FTY720, an emerging immunomodulator, were shown to evoke prolonged lymphopenia in vivo. Analysis of mouse plasma concentrations for a series of related alcohol/phosphate/phosphothioate compounds showed the conversion of the phosphate to alcohol. These preliminary data highlight the importance of metabolic regulation of S1P receptor ligands.
