title: Sphingosine-1-phosphate agonists increase macrophage homing, lymphocyte contacts, and endothelial junctional complex formation in murine lymph nodes.
abstract: The sphingosine-1-phosphate (S1P) receptor agonist, phosphorylated FTY720 (FTY-P), causes lymphopenia, lymphocyte sequestration in mesenteric lymph nodes (MLNs), and immunosuppression. Using multiple techniques to analyze MLN cells harvested from mice treated with S1P receptor agonists, we saw a redistribution of lymphocytes out of nodal sinuses and an expansion of follicles. Although changes in circulating monocytes were not observed with overnight exposure to FTY720, we saw a significant increase in S1P receptor 1 (S1P1)-expressing CD68+ macrophages in subcapsular sinuses of FTY-P-treated MLNs. This was confirmed by quantitative analysis of F4/80+ cells in MLN suspensions. The sinus volume and number of S1P1-positive cells within sinuses were also increased by FTY-P. High endothelial venules and lymphatic endothelium expressed high levels of S1P1, and treatment with FTY-P resulted in intense staining and colocalization of CD31, beta-catenin, and zona occludens 1 in junctions between sinus cells. Transmission electron microscopy showed that FTY-P greatly reduced lymphocyte microvilli and increased cell-cell contacts in the parenchyma. Immunoelectron microscopy revealed that intranodal lymphocytes lacked surface expression of S1P1, whereas S1P1 was evident on the surface and within the cytoplasm of macrophages, endothelial cells, and stromal cells. This subcellular pattern of intranodal receptor distribution was unchanged by treatment with FTY-P. We conclude that S1P1 agonists have profound effects on macrophages and endothelial cells, in addition to inducing lymphopenia.
authors.affiliation: Immunology and Rheumatology, Merck and Co., Inc., Merck Research Laboratories, Rahway, NJ 07065, USA. Irwin_Singer@Merck.com
authors.forename: Irwin I
authors.initials: II
authors.lastname: Singer
authors.forename: Min
authors.initials: M
authors.lastname: Tian
authors.forename: L Alexandra
authors.initials: LA
authors.lastname: Wickham
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Lin
authors.forename: Scaria S
authors.initials: SS
authors.lastname: Matheravidathu
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Forrest
authors.forename: Suzanne
authors.initials: S
authors.lastname: Mandala
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Quackenbush
mesh_terms: D000818:Animals; D002450:Cell Communication / Q000276:immunology; D042783:Endothelial Cells / Q000187:drug effects / Q000276:immunology / Q000648:ultrastructure; D004729:Endothelium, Lymphatic / Q000187:drug effects / Q000648:ultrastructure; D004730:Endothelium, Vascular / Q000187:drug effects / Q000648:ultrastructure; D005260:Female; D000068876:Fingolimod Hydrochloride; D005455:Fluorescent Antibody Technique; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D008198:Lymph Nodes / Q000187:drug effects / Q000276:immunology*; D008214:Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D008264:Macrophages / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D008643:Mesentery / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D046529:Microscopy, Electron, Transmission; D016253:Microscopy, Immunoelectron; D010766:Phosphorylation; D011409:Propylene Glycols / Q000494:pharmacology*; D049349:Receptors, Lysosphingolipid / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D013110:Sphingosine / Q000031:analogs & derivatives; D019108:Tight Junctions / Q000276:immunology / Q000648:ultrastructure
chemical_list: D007166:Immunosuppressive Agents; D011409:Propylene Glycols; D049349:Receptors, Lysosphingolipid; D000068876:Fingolimod Hydrochloride; D013110:Sphingosine