(5R)-5-hydroxytriptolide (LLDT-8), a novel triptolide analog mediates immunosuppressive effects in vitro and in vivo

A series of triptolide analogs have been successfully synthesized. In the present study we demonstrated one of them, (5R)-5-hydroxytriptolide (LLDT-8), showed low cytotoxicity and relative high immunosuppressive activities as compared with its parent compound triptolide in vitro. The CC50 values of triptolide and LLDT-8 were 2.1 ± 0.3 and 256.6 ± 73.8 nM, respectively. LLDT-8 significantly inhibited the proliferation of splenocytes induced by concanavalin A (ConA), lipopolysaccharide (LPS), or mixed lymphocyte reaction (MLR), and the IC50 values were 131.7 ± 32.4, 171.5 ± 17.3, and 38.8 ± 5.1 nM, respectively. LLDT-8 (25, 50, 100 nM) dose-dependently reduced the production of Th1 type cytokines (IFN-γ, IL-2) and inflammatory cytokines (TNF-α, IL-6) in vitro. Administration of LLDT-8 (at the low dose of 0.4 μg/kg, i.p.; 40 μg/kg, p.o.) intensively suppressed 2,4-dinitrofluorobenzene (DNFB)-induced delayed type hypersensitivity (DTH) reactions. Treatment with LLDT-8 (40 μg/kg, i.p. and p.o.) also markedly inhibited the sheep red blood cell (SRBC)-induced antibody production in BLAB/c mice. Most importantly, comparing with triptolide, LLDT-8 significantly reduced toxicity, with a 122-fold lower cytotoxicity in vitro and 10-fold lower acute toxicity in vivo. The results suggested that LLDT-8 had immunosuppressive activities in both cellular and humoral immune responses. LLDT-8 might be a potential therapeutic agent for immune-related diseases.