title: Effect of methotrexate on blood purine and pyrimidine levels in patients with rheumatoid arthritis.
abstract: OBJECTIVE
  The mechanism of anti-inflammatory effects of methotrexate (MTX) at low dose may relate to a decrease in availability of the purine precursor or it may depend on accumulation of 5-aminoimidazole-4-carboxamide (AICAR) and the anti-inflammatory nucleoside adenosine. The aim of this study was to evaluate the possible mechanism of action by analysis of changes in blood concentrations of purine and pyrimidine metabolites during MTX treatment.
  
  
  METHODS
  Venous blood samples were collected from rheumatoid arthritis patients before and at different times for up to 7 days after the start of MTX treatment. Whole blood concentrations of adenosine, uridine, hypoxanthine, uric acid and erythrocyte nucleotides were measured by HPLC.
  
  
  RESULTS
  The initial blood adenosine concentration was 0.073 +/- 0.013 microM and no differences were observed during MTX treatment. However, a decrease in uric acid concentration was observed from 205.5+/-13.5 to 160. 9+/-13.5 microM (P<0.05) within 24 h after MTX administration. The hypoxanthine concentration decreased in parallel with uric acid, while the uridine concentration decreased 48 h after MTX administration. No accumulation of AICAR-triphosphate (ZTP) was observed in the erythrocytes.
  
  
  CONCLUSIONS
  MTX decreases circulating purine and pyrimidine concentrations, and their availability for DNA and RNA synthesis, which may affect immune cell proliferation and protein (cytokine) expression. The absence of adenosine concentration changes and lack of ZTP formation is evidence against an AICAR/adenosine mechanism, although localized adenosine concentration changes cannot be excluded.
authors.affiliation: Rheumatology Hospital, Sopot, Department of Biochemistry, Medical University, Gdańsk, Poland.
authors.forename: Z
authors.initials: Z
authors.lastname: Smoleńska
authors.forename: Z
authors.initials: Z
authors.lastname: Kaznowska
authors.forename: D
authors.initials: D
authors.lastname: Zarówny
authors.forename: H A
authors.initials: HA
authors.lastname: Simmonds
authors.forename: R T
authors.initials: RT
authors.lastname: Smoleński
mesh_terms: D000241:Adenosine / Q000097:blood*; D000255:Adenosine Triphosphate / Q000097:blood; D000328:Adult; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives / Q000097:blood; D018501:Antirheumatic Agents / Q000008:administration & dosage*; D001172:Arthritis, Rheumatoid / Q000097:blood / Q000188:drug therapy*; D002851:Chromatography, High Pressure Liquid; D002908:Chronic Disease; D003570:Cytidine Triphosphate / Q000097:blood; D004912:Erythrocytes / Q000187:drug effects; D005260:Female; D006160:Guanosine Triphosphate / Q000097:blood; D006801:Humans; D019271:Hypoxanthine / Q000097:blood; D008727:Methotrexate / Q000008:administration & dosage*; D008875:Middle Aged; D012265:Ribonucleotides / Q000097:blood; D014527:Uric Acid / Q000097:blood; D014529:Uridine / Q000097:blood*
chemical_list: D018501:Antirheumatic Agents; D012265:Ribonucleotides; D014527:Uric Acid; D019271:Hypoxanthine; D000620:Aminoimidazole Carboxamide; D003570:Cytidine Triphosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; C031143:AICA ribonucleotide; D000241:Adenosine; D014529:Uridine; D008727:Methotrexate