Differential Effects of FK506 and Methotrexate on Inflammatory Cytokine Levels in Rat Adjuvant-Induced Arthritis

KATSUE MAGARI, SUSUMU MIYATA, FUSAKO NISHIGAKI, YOSHITAKA OHKUBO, SEITARO MUTOH, and TOSHIO GOTO

ABSTRACT.

Objective. To investigate the effects of prophylactic and therapeutic treatments with FK506 (tacrolimus), an immunosuppressive drug that specifically inhibits T cell activation, and methotrexate (MTX) on inflammatory cytokines, tumor necrosis factor (TNF)-a, interleukin (IL)-1ß, and IL-6 levels in rat adjuvant-induced arthritis (AIA).

Methods. AIA was induced in female Lewis rats. Arthritis was assessed by hindpaw swelling. TNF-a, IL-1ß, and IL-6 levels in paw extracts were determined by ELISA. To assess the effects on cytokine levels, rats were treated prophylactically with FK506 (3 mg/kg) or MTX (0.1 mg/kg) from day 1 to day 17, and therapeutically with FK506 (5 mg/kg) or MTX (1 mg/kg) from day 15 to day 17 (3-day treatment) or day 15 to 20 (6-day treatment) by oral administration.

Results. TNF-a, IL-1ß, and IL-6 levels in paw tissue were found to significantly increase between day 15 and day 21 after adjuvant injection, when the arthritis was in a developed stage. Prophylactic treatment with FK506 and MTX suppressed arthritis and reduced the levels of those inflammatory cytokines. FK506 caused a marked reduction of TNF-a and IL-1ß levels in paw tissue even in short-term (3-day) therapeutic treatment. It reduced all levels of TNF-a, IL-1ß, and IL-6 in paws in 6-day therapeutic treatment. In contrast, therapeutic treatment with MTX affected neither TNF-a or IL-6 levels in paws. MTX reduced IL-1ß levels only in the 6-day treatment.

Conclusion. FK506 is more effective than MTX in reducing elevated levels of inflammatory cytokines TNF-a, IL-1ß, and IL-6 in established stages of AIA. Our findings suggest that inhibition of T cell activation results in a rapid reduction of inflammatory cytokine levels even after the arthritis is established in AIA. (J Rheumatol 2003;30:2193-200)

Key Indexing Terms:

TUMOR NECROSIS FACTOR-a
INTERLEUKIN 1ß
INTERLEUKIN 6
FK506
INFLAMMATORY CYTOKINE
ADJUVANT INDUCED ARTHRITIS

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From Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co. Ltd., Osaka, Japan.

K. Magari, BS; S. Miyata, PhD; F. Nishigaki, PhD; Y. Ohkubo, PhD; S. Mutoh, PhD; T. Goto, PhD.

Address reprint requests to Dr. S. Miyata, Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co., Ltd., 2-1-6, Kashima, Yodogawa-ku, Osaka 532-8514, Japan. E-mail: susumu_miyata@po.fujisawa.co.jp

Submitted October 7, 2002; revision accepted February 3, 2003.

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