Inhibition of interleukin-13 gene expression by triptolide in activated T lymphocytes.

Background And Objective: Triptolide, a type of diterpenoid, is the active compound of Tripterygium wilfordii; it plays roles in anti-inflammatory and immune response regulation. Our objective was to investigate the mechanism of the inhibitory effect of triptolide on interleukin-13 (IL-13) gene expression in activated T lymphocytes. Understanding the molecular mechanism by which triptolide exerts a therapeutic function may be useful in developing a pharmaceutical treatment for asthma.

Methods: Peripheral blood mononuclear cells (PBMC) and Hut-78 cells were stimulated with anti-CD3/CD28 with or without co-incubation with triptolide. The alteration of IL-13 messenger RNA (mRNA), expression and protein level were analysed using real-time reverse transcription polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay, respectively. The intracellular distribution profile of transcription factor GATA3 and nuclear factor of activated T cells (NFAT1) were analysed by Western blotting. The binding rates of GATA3 and NFAT1 to the promoter sequence of IL-13 were analysed by chromatin immunoprecipitation (ChIP) PCR.

Results: In PBMC, the release of IL-13 was dependent on anti-CD3/CD28 stimulation. Its release could be inhibited by triptolide at the concentration of 500 nmol. In Hut-78 cells, IL-13 mRNA and protein expression were increased with anti-CD3/CD28 stimulation and significantly inhibited by incubation with 28 nmol triptolide. This concentration of triptolide also significantly inhibited the nuclear translocation of GATA3 and NFAT1 reducing the binding rate to the IL-13 gene promoter.

Conclusions: Triptolide inhibits IL-13 gene transcription and protein expression by inhibiting GATA3 and NFAT1 nuclear translocation and their binding rates to the IL-13 gene promoter region.