title: Expression of methotrexate transporters and metabolizing enzymes in rheumatoid synovial tissue.
abstract: OBJECTIVE
  To determine whether methotrexate (MTX) affects the expression of genes involved in the transport [SLC19A1 (RFC1), ABCB1 (MDR1), ABCC1 (multidrug resistance proteins 1), ABCG2 (BCRP)], metabolism [γ-glutamyl hydrolase (GGH), folylpolyglutamate synthetase (FPGS)], and mechanism of action of MTX [thymidylate synthase, MTR, MTRR] in rheumatoid synovium.
  
  
  METHODS
  Synovial tissue samples were obtained from 20 patients with rheumatoid arthritis (RA). Gene expression was undertaken using quantitative real-time PCR.
  
  
  RESULTS
  All the genes examined were expressed in all samples. Expression of SLC19A1, GGH, FPGS, ABCC1, and MTRR was significantly higher in patients receiving MTX compared to those not receiving MTX (p < 0.05). The ratio of FPGS:GGH gene expression was 2.7 ± 0.51 ng/ml GAPDH (range 0.67-9.58).
  
  
  CONCLUSIONS
  Genes involved in the transport, metabolism, and mechanism of action of MTX are expressed in rheumatoid joint synovium. These data provide evidence that MTX has the potential to be polyglutamated within the joint. The higher expression of FPGS compared to GGH in synovial tissue might favor production of long-chain MTX polyglutamates. Thus MTX has the potential to exert its therapeutic effects at the primary site of the inflammatory process in RA.
authors.affiliation: Department of Medicine, University of Otago, Christchurch, New Zealand. lisa.stamp@cdhb.health.nz
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Stamp
authors.forename: Jody
authors.initials: J
authors.lastname: Hazlett
authors.forename: John
authors.initials: J
authors.lastname: Highton
authors.forename: Paul A
authors.initials: PA
authors.lastname: Hessian
mesh_terms: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase / Q000235:genetics / Q000378:metabolism; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000235:genetics / Q000378:metabolism; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000368:Aged; D000369:Aged, 80 and over; D018501:Antirheumatic Agents / Q000494:pharmacology / Q000627:therapeutic use; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005287:Ferredoxin-NADP Reductase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008297:Male; D008727:Methotrexate / Q000494:pharmacology / Q000627:therapeutic use; D008875:Middle Aged; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D058978:Reduced Folate Carrier Protein / Q000235:genetics / Q000378:metabolism; D013583:Synovial Membrane / Q000187:drug effects / Q000378:metabolism*; D013940:Thymidylate Synthase / Q000235:genetics / Q000378:metabolism
chemical_list: D013766:5-Methyltetrahydrofolate-Homocysteine S-Methyltransferase; D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D018501:Antirheumatic Agents; D005287:Ferredoxin-NADP Reductase; D008727:Methotrexate; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D058978:Reduced Folate Carrier Protein; D013940:Thymidylate Synthase; C513055:ABCB1 protein, human; C116614:ABCG2 protein, human; C548699:SLC19A1 protein, human; C111241:methionine synthase reductase; C585801:MTR protein, human; C421109:multidrug resistance-associated protein 1
keywords: GENES; METHOTREXATE; RHEUMATOID ARTHRITIS; SYNOVIUM