title: The sphingosine-1-phosphate receptor-1 antagonist, W146, causes early and short-lasting peripheral blood lymphopenia in mice.
abstract: Agonists of the sphingosine-1-phosphate (S1P) receptors, like fingolimod (FTY720), are a novel class of immunomodulators. Administration of these compounds prevents the egress of lymphocytes from primary and secondary lymphoid organs causing peripheral blood lymphopenia. Although it is well established that lymphopenia is mediated by S1P receptor type 1 (S1P1), the exact mechanism is still controversial. The most favored hypothesis states that S1P1 agonists cause internalization and loss of the cell surface receptor on lymphocytes, preventing them to respond to S1P. Hence, S1P1 agonists would behave in vivo as functional antagonists of the receptor. For this hypothesis to be valid, a true S1P1 antagonist should also induce lymphopenia. However, it has been reported that S1P1 antagonists fail to show this effect, arguing against the concept. Our study demonstrates that a S1P1 antagonist, W146, induces a significant but transient blood lymphopenia in mice and a parallel increase in CD4+ and CD8+ lymphocytes in lymph nodes. Treatment with W146 also causes the accumulation of mature T cells in the medulla of the thymus and moreover, it induces lung edema. We show that both the S1P1 antagonist and a S1P1 agonist cause lymphopenia in vivo in spite of their different effects on receptor expression in vitro. Although the antagonist purely blocks the receptor and the agonist causes its disappearance from the cell surface, the response to the endogenous ligand is prevented in both cases. Our results support the hypothesis that lymphopenia evoked by S1P1 agonists is due to functional antagonism of S1P1 in lymphocytes.
authors.affiliation: Autoimmunity Department, R&D Center, Almirall laboratories S.A., Barcelona, Spain.
authors.forename: Gema
authors.initials: G
authors.lastname: Tarrasón
authors.forename: Mariona
authors.initials: M
authors.lastname: Aulí
authors.forename: Sanam
authors.initials: S
authors.lastname: Mustafa
authors.forename: Vladislav
authors.initials: V
authors.lastname: Dolgachev
authors.forename: Maria Teresa
authors.initials: MT
authors.lastname: Domènech
authors.forename: Neus
authors.initials: N
authors.lastname: Prats
authors.forename: María
authors.initials: M
authors.lastname: Domínguez
authors.forename: Rosa
authors.initials: R
authors.lastname: López
authors.forename: Nuria
authors.initials: N
authors.lastname: Aguilar
authors.forename: Marta
authors.initials: M
authors.lastname: Calbet
authors.forename: Mercè
authors.initials: M
authors.lastname: Pont
authors.forename: Graeme
authors.initials: G
authors.lastname: Milligan
authors.forename: Steven L
authors.initials: SL
authors.lastname: Kunkel
authors.forename: Nuria
authors.initials: N
authors.lastname: Godessart
mesh_terms: D000813:Anilides / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D002633:Chemotaxis / Q000187:drug effects; D005434:Flow Cytometry; D008198:Lymph Nodes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D018655:Lymphocyte Count; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000276:immunology; D008231:Lymphopenia / Q000139:chemically induced* / Q000276:immunology; D008297:Male; D051379:Mice; D063065:Organophosphonates / Q000097:blood / Q000494:pharmacology*; D049349:Receptors, Lysosphingolipid / Q000819:agonists* / Q000037:antagonists & inhibitors*; D013950:Thymus Gland / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D013997:Time Factors
chemical_list: C513113:3-amino-4-(3-hexylphenylamino)-4-oxobutylphosphonic acid; D000813:Anilides; D063065:Organophosphonates; D049349:Receptors, Lysosphingolipid