Abstract
(5R)-5-Hydroxytriptolide (LLDT-8) displays strong immunosuppressive activities both in vitro and in vivo in our previous studies. This study aims to investigate whether LLDT-8 has antiarthritic potential in a murine model of type II bovine collagen (CII)-induced arthritis (CIA) and to show the mechanism(s) of LLDT-8 action. DBA/1 mice were immunized with CII to induce arthritis and administered with LLDT-8. The severity of arthritis was evaluated according to the clinical score and joint damage. The effects of LLDT-8 on immune responses were determined by measurement of serum antibody levels, lymphocyte proliferation assay, cytokine assay, nitric oxide (NO) production, arginase activity assays, fluorescence-activated cell sorting analysis of splenic Mac-1+ cells, as well as polymerase chain reaction analysis for interferon-γ (IFN-γ)-related gene expression. We showed that LLDT-8 treatment significantly reduced the incidence and severity of CIA. The preventive and therapeutic effects of LLDT-8 are associated with 1) reduction of serum anti-CII immunoglobulin (Ig) G, IgG2a, and IgG1 levels; 2) inhibition of CII-specific lymphocyte proliferation, IFN-γ and interleukin-2 production; 3) blockade of gene expressions in IFN-γ signaling, including IFN-γ production pathways [signal transducer and activator of transcription (STAT) 1, T-box transcription factor, interleukin 12Rβ2, and STAT4] and IFN-γ-induced chemokine transcription [macrophage inflammatory protein (Mip)-1α, Mip-1β, regulated on activation normally T cell expressed and secreted, and inducible protein 10]; and 4) retardation of the abnormal increase of NO via IFN-γ/STAT1/interferon regulatory factor 1/inducible nitric-oxide synthase pathway and arginase activity. Moreover, the mRNA transcription of chemokine receptors was also suppressed [including C-C chemokine receptor (CCR) 1, CCR5, and C-X-C chemokine receptor 3]. In conclusion, our data suggest that the antiarthritic effect of LLDT-8 is closely related to the blockade of IFN-γ signaling. LLDT-8 may have a therapeutic value in the treatment of rheumatoid arthritis.
Footnotes
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This work was supported by a grant from the Knowledge Innovation Program of Chinese Academy of Sciences (KSCX2-SW-202).
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.106.101113.
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ABBREVIATIONS: TWHF, T. wilfordii Hook F; LLDT-8, (5R)-5-hydroxytriptolide; CIA, collagen-induced arthritis; RA, rheumatoid arthritis; CII, type II bovine collagen; Th, T helper; IFN-γ, interferon-γ; IL, interleukin; STAT, signal transducer and activator of transcription; T-bet, T-box transcription factor; IRF, interferon regulatory factor; iNOS, inducible nitric-oxide synthase; NO, nitric oxide; Mip, macrophage inflammatory protein; RANTES, regulated on activation normally T-cell expressed and secreted; IP-10, inducible protein 10; CCR, C-C chemokine receptor; CXCR, C-X-C chemokine receptor; CFA, Freund's complete adjuvant; LDP, Leigongteng Duodai Pian is the prescription drug of the extracts from TWHF in China; LN, lymph node(s); Ig, immunoglobulin; ELISA, enzyme-linked immunosorbent assay; PCR, polymerase chain reaction; LPS, lipopolysaccharide; IL-12Rβ2, IL-12 receptor β2; SOCS, suppressor of cytokine signaling; GATA3, GATA binding factor 3.
- Received January 9, 2006.
- Accepted March 27, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
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