title: Pyrimethamine (2,4-diamino-5-p-chlorophenyl-6-ethylpyrimidine) induces apoptosis of freshly isolated human T lymphocytes, bypassing CD95/Fas molecule but involving its intrinsic pathway.
abstract: Pyrimethamine (2,4-diamino-5-p-chlorophenyl-6-ethyl-pyrimidine), a folic acid antagonist, may exert, in addition to antiprotozoan effects, immunomodulating activities, including induction of peripheral blood lymphocyte apoptosis. However, the molecular mechanisms underlying this proapoptotic activity remain to be elucidated. Here we show that pyrimethamine, used at a pharmacologically relevant concentration, induced per se apoptosis of activated lymphocytes via the activation of the caspase-8- and caspase-10-dependent cascade and subsequent mitochondrial depolarization. Importantly, this seems to occur independently from CD95/Fas engagement. The proapoptotic activity of pyrimethamine was further confirmed in a patient with autoimmune lymphoproliferative syndrome, an immune disorder associated with a defect of Fas-induced apoptosis. In this patient, pyrimethamine treatment resulted in a "normalization" of lymphocyte apoptosis with a significant amelioration of laboratory parameters. Altogether, these results suggest a mechanism for pyrimethamine-mediated apoptosis that seems to bypass CD95/Fas engagement but fully overlaps CD95/Fas-induced subcellular pathway. On these bases, a reappraisal of the use of pyrimethamine in immune lymphoproliferative disorders characterized by defects in CD95/Fas-mediated apoptosis should be taken into account.
authors.affiliation: Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: Marina
authors.initials: M
authors.lastname: Pierdominici
authors.forename: Anna Maria
authors.initials: AM
authors.lastname: Giammarioli
authors.forename: Lucrezia
authors.initials: L
authors.lastname: Gambardella
authors.forename: Marco
authors.initials: M
authors.lastname: De Felice
authors.forename: Isabella
authors.initials: I
authors.lastname: Quinti
authors.forename: Metello
authors.initials: M
authors.lastname: Iacobini
authors.forename: Maurizio
authors.initials: M
authors.lastname: Carbonari
authors.forename: Walter
authors.initials: W
authors.lastname: Malorni
authors.forename: Antonello
authors.initials: A
authors.lastname: Giovannetti
mesh_terms: D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects*; D001327:Autoimmune Diseases / Q000188:drug therapy; D053455:Caspase 10; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D002648:Child; D045304:Cytochromes c / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005260:Female; D005434:Flow Cytometry; D016650:Fluorescein-5-isothiocyanate; D005456:Fluorescent Dyes; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology*; D016753:Interleukin-10 / Q000097:blood; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000502:physiology; D008954:Models, Biological; D011419:Propidium / Q000378:metabolism; D011739:Pyrimethamine / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects* / Q000648:ultrastructure; D016896:Treatment Outcome; D019014:fas Receptor / Q000378:metabolism*
chemical_list: D017304:Annexin A5; D005456:Fluorescent Dyes; D007166:Immunosuppressive Agents; D019014:fas Receptor; D016753:Interleukin-10; D011419:Propidium; D045304:Cytochromes c; C505530:CASP8 protein, human; D053455:Caspase 10; D053181:Caspase 8; D020169:Caspases; C506438:CASP10 protein, human; D016650:Fluorescein-5-isothiocyanate; D011739:Pyrimethamine