title: Inhibition of thymidine synthesis by folate analogues induces a Fas-Fas ligand-independent deletion of superantigen-reactive peripheral T cells.
abstract: Methotrexate (MTX), a folate antagonist with multiple enzymatic targets, is used in the treatment of malignancies as well as in autoimmune and chronic inflammatory diseases, and ZD1694 (tomudex), a water-soluble quinazoline specific inhibitor of thymidylate synthase (TS), is used in the treatment of adenocarcinomas. In this study, we investigated the effects of these folate analogues on superantigen (SAg)-reactive peripheral T cells in vivo. In BALB/c mice, staphylococcal enterotoxin B (SEB)-induced cytokine secretion, IL-2R (CD25) expression and early deletion of a fraction of SEB-reactive V(beta)8(+) T cells were not impaired by either MTX (7 mg/kg/day) or tomudex (5 mg/kg/day). However, both MTX and tomudex prevented V(beta)8-selective T cell expansion and accelerated their peripheral elimination. Administration of thymidine (500 mg/kg/12 h) completely abrogated this effect, indicating that inhibition of TS but not that of other folate-dependent enzymes was the main mechanism involved. Furthermore, a marked increase of apoptotic cells restricted to the V(beta)8(+) T cell subset indicated that proliferation inhibition was associated with apoptosis. In contrast with peripheral V(beta)8(+) T cell deletion, MTX and tomudex did not prevent the increase of V(beta)8(+) thymocytes triggered by SEB. Experiments in C57BL/6-lpr/lpr mice further demonstrated that deletion of V(beta)8(+) T cells induced by folate analogues was independent of Fas-Fas ligand interaction. Our results provide evidence that folate analogues may selectively delete dividing peripheral T cells through TS inhibition, but do not interfere with other events triggered by SAg.
authors.affiliation: Laboratory of Immunopharmacology, Institut National de la Santé et de la Recherche Médicale U503, Claude Bernard University, Hopital E. Herriot, 5 Place d'Arsonval, 69437 Lyon Cedex 03, France.
authors.forename: K
authors.initials: K
authors.lastname: Izeradjene
authors.forename: J P
authors.initials: JP
authors.lastname: Revillard
authors.forename: L
authors.initials: L
authors.lastname: Genestier
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology; D017637:Clonal Deletion / Q000187:drug effects*; D004768:Enterotoxins / Q000008:administration & dosage; D053222:Fas Ligand Protein; D005493:Folic Acid Antagonists / Q000494:pharmacology; D006131:Growth Inhibitors / Q000008:administration & dosage / Q000494:pharmacology; D007274:Injections, Intraperitoneal; D007275:Injections, Intravenous; D008024:Ligands; D008213:Lymphocyte Activation / Q000187:drug effects; D008212:Lymphocyte Depletion; D008562:Membrane Glycoproteins / Q000378:metabolism / Q000502:physiology*; D008727:Methotrexate / Q000494:pharmacology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D019463:Mice, Inbred MRL lpr; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology*; D011799:Quinazolines / Q000494:pharmacology; D013211:Staphylococcus aureus / Q000276:immunology; D018089:Superantigens / Q000276:immunology*; D016176:T-Lymphocyte Subsets / Q000201:enzymology / Q000276:immunology* / Q000378:metabolism; D013876:Thiophenes / Q000494:pharmacology; D013936:Thymidine / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D013940:Thymidylate Synthase / Q000037:antagonists & inhibitors; D019014:fas Receptor / Q000502:physiology*
chemical_list: D004768:Enterotoxins; D053222:Fas Ligand Protein; C505658:Fasl protein, mouse; D005493:Folic Acid Antagonists; D006131:Growth Inhibitors; D008024:Ligands; D008562:Membrane Glycoproteins; D019384:Nucleic Acid Synthesis Inhibitors; D011799:Quinazolines; D018089:Superantigens; D013876:Thiophenes; D019014:fas Receptor; C031818:enterotoxin B, staphylococcal; D013940:Thymidylate Synthase; C068874:raltitrexed; D013936:Thymidine; D008727:Methotrexate