title: Methotrexate and erythro-9-(2-hydroxynon-3-yl) adenine therapy for rat adjuvant arthritis and the effect of methotrexate on in vivo purine metabolism.
abstract: The objectives were: (1) to test the association of methotrexate (MTX) efficacy in rat adjuvant arthritis (rat AA) with interference of purine biosynthesis and adenosine metabolism and (2) to test the efficacy of erythro-9-(2-hydroxynon-3-yl) adenine (EHNA), an inhibitor of adenosine deaminase, and the efficacy of aminoimidazolecarboxamide (AICA) riboside plus MTX in rat AA. Radiographic and histologic examinations of the hind limbs were measures of efficacy. Urinary excretions of AICA and adenosine were markers of AICA ribotide transformylase inhibition (i.e., blockage of purine biosynthesis) and interference with adenosine metabolism, respectively. AICA and adenosine excretions increased during the day of MTX dosing (treatment day) compared to the previous baseline day in animals responding well to MTX (i.e., low radiographic and histologic scores). Based on radiographic and histologic scores, adjuvant injected rats were separated into two disease categories (i.e., no/mild and moderate/severe). Only AICA excretion was significantly elevated on the treatment day in rat AA with no/mild disease (i.e., those responding well to MTX therapy). AICA (not adenosine) excretion was significantly correlated with the above scores. EHNA was not efficacious, even at toxic levels, while AICA riboside potentiated the efficacy of MTX. The data suggests that efficacious MTX therapy in rat AA (1) blocks purine biosynthesis; (2) increases in in vivo AICA levels. Also adenosine accumulation and blockage of adenosine deaminase (i.e., by EHNA) appear to be less critical to MTX efficacy. Increased levels of AICA metabolites may suppress the immune response in rat AA.
authors.affiliation: Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, AL 35294-1270, USA.
authors.forename: Joseph E
authors.initials: JE
authors.lastname: Baggott
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Morgan
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D000241:Adenosine / Q000652:urine; D000243:Adenosine Deaminase / Q000378:metabolism; D058892:Adenosine Deaminase Inhibitors; D000620:Aminoimidazole Carboxamide / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use / Q000652:urine; D000818:Animals; D018501:Antirheumatic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001169:Arthritis, Experimental / Q000188:drug therapy* / Q000201:enzymology / Q000473:pathology / Q000652:urine; D015415:Biomarkers / Q000652:urine; D004305:Dose-Response Relationship, Drug; D004359:Drug Therapy, Combination; D004791:Enzyme Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D008727:Methotrexate / Q000494:pharmacology* / Q000627:therapeutic use; D051027:Phosphoribosylaminoimidazolecarboxamide Formyltransferase / Q000037:antagonists & inhibitors / Q000378:metabolism; D011687:Purines / Q000378:metabolism* / Q000652:urine; D051381:Rats; D012263:Ribonucleosides / Q000494:pharmacology* / Q000627:therapeutic use
chemical_list: D058892:Adenosine Deaminase Inhibitors; D018501:Antirheumatic Agents; D015415:Biomarkers; D004791:Enzyme Inhibitors; D011687:Purines; D012263:Ribonucleosides; D000620:Aminoimidazole Carboxamide; C011651:acadesine; C010192:9-(2-hydroxy-3-nonyl)adenine; D051027:Phosphoribosylaminoimidazolecarboxamide Formyltransferase; D000243:Adenosine Deaminase; D000225:Adenine; D000241:Adenosine; D008727:Methotrexate