title: The active metabolite of leflunomide, A77 1726, attenuates inflammatory arthritis in mice with spontaneous arthritis via induction of heme oxygenase-1.
abstract: Leflunomide is a low-molecular-weight compound that is widely used in the treatment of rheumatoid arthritis. Although leflunomide is thought to act through the inhibition of the de novo pyrimidine synthesis, the molecular mechanism of the drug remains largely unknown. We investigated the antiarthritis effects and mechanisms of action of the active metabolite of leflunomide, A77 1726, in interleukin-1 receptor antagonist-knockout (IL-1Ra-KO) mice.
  
  
  
  14- to 15-week-old male IL-1Ra-KO mice were treated with 10 or 30 mg/kg A77 1726 via intraperitoneal injection three times per week for 6 weeks. The effects of A77 1726 on arthritis severities were assessed by clinical scoring and histological analysis. The serum concentrations of IL-1β, tumor necrosis factor-α (TNF-α), and malondialdehyde were measured by enzyme-linked immunosorbent assay. Histologic analysis of the joints was performed using Safranin O, and immunohistochemical staining. The frequencies of interleukin-17-producing CD4+T (Th17) cells were analyzed by flow cytometry. Heme oxygenase-1 (HO-1) expression in splenic CD4+T cells isolated from A77 1726-treated arthritis mice were assessed by western blotting.
  
  
  
  A77 1726 treatment induced heme oxygenase-1 (HO-1) in Jurkat cells and primary mouse T cells. Interestingly, A77 1726 inhibited Th17 cell differentiation. In vivo, A77 1726 reduced the clinical arthritis severity of histological inflammation and cartilage destruction. The joints isolated from A77 1726-treated mice showed decreased expression of inducible nitric oxide synthase, nitrotyrosine, TNF-α, and IL-1β. The serum levels of TNF-α, IL-1β, and malondialdehyde were also decreased in A77 1726-treated mice. Whereas the number of Th17 cells in spleens was decreased in A77 1726-treated arthritis mice, a significant increase in the number of Treg cells in spleens was observed. Interestingly, HO-1 expression was significantly higher in splenic CD4+T cells isolated from A77 1726-treated mice compared with those from vehicle-treated mice, whereas HO-1 expression of splenic non-CD4+T cells did not differ between groups.
  
  
  
  The inhibitory effects of A77 1726 on joint inflammation and oxidative stress in autoimmune arthritis may be associated with HO-1 induction in CD4+T cells.
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Su-Jin
authors.initials: SJ
authors.lastname: Moon
authors.affiliation: The Rheumatism Research Center, Catholic Research Institute of Medical Science, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Eun-Kyung
authors.initials: EK
authors.lastname: Kim
authors.affiliation: The Rheumatism Research Center, Catholic Research Institute of Medical Science, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Joo Yeon
authors.initials: JY
authors.lastname: Jhun
authors.affiliation: Clinical Medicine Research Institute of Bucheon St. Mary's Hospital, The Catholic University of Korea, Bucheon-si, Gyeonggi-do, South Korea.
authors.forename: Hee Jin
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Clinical Medicine Research Institute of Bucheon St. Mary's Hospital, The Catholic University of Korea, Bucheon-si, Gyeonggi-do, South Korea.
authors.forename: Weon Sun
authors.initials: WS
authors.lastname: Lee
authors.affiliation: Clinical Medicine Research Institute of Bucheon St. Mary's Hospital, The Catholic University of Korea, Bucheon-si, Gyeonggi-do, South Korea.
authors.forename: Sang-Hi
authors.initials: SH
authors.lastname: Park
authors.affiliation: The Rheumatism Research Center, Catholic Research Institute of Medical Science, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Mi-La
authors.initials: ML
authors.lastname: Cho
authors.affiliation: Division of Rheumatology, Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, South Korea. min6403@catholic.ac.kr.
authors.forename: Jun-Ki
authors.initials: JK
authors.lastname: Min
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology / Q000627:therapeutic use*; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology / Q000627:therapeutic use; D001169:Arthritis, Experimental / Q000150:complications* / Q000188:drug therapy* / Q000201:enzymology; D001172:Arthritis, Rheumatoid / Q000188:drug therapy / Q000473:pathology; D002454:Cell Differentiation / Q000187:drug effects; D003437:Crotonates; D051858:Forkhead Transcription Factors / Q000378:metabolism; D051547:Heme Oxygenase-1 / Q000378:metabolism*; D006801:Humans; D006885:Hydroxybutyrates / Q000494:pharmacology / Q000627:therapeutic use*; D007249:Inflammation / Q000150:complications* / Q000188:drug therapy* / Q000201:enzymology; D007555:Isoxazoles / Q000378:metabolism*; D019169:Jurkat Cells; D000077339:Leflunomide; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D051267:NF-E2-Related Factor 2 / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D009570:Nitriles; D018384:Oxidative Stress / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013154:Spleen / Q000473:pathology; D058504:Th17 Cells / Q000166:cytology; D014052:Toluidines; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
chemical_list: D000814:Aniline Compounds; D000893:Anti-Inflammatory Agents; D003437:Crotonates; D051858:Forkhead Transcription Factors; C498833:Foxp3 protein, mouse; D006885:Hydroxybutyrates; D007555:Isoxazoles; D051267:NF-E2-Related Factor 2; D009570:Nitriles; D014052:Toluidines; C527525:teriflunomide; C002744:3-nitrotyrosine; D014443:Tyrosine; D052247:Nitric Oxide Synthase Type II; D051547:Heme Oxygenase-1; D000077339:Leflunomide
keywords: Heme oxygenase-1; Leflunomide; Rheumatoid arthritis