Immunosuppressant PG490 (Triptolide) Inhibits T-cell Interleukin-2 Expression at the Level of Purine-box/Nuclear Factor of Activated T-cells and NF-κB Transcriptional Activation

• Published in: The Journal of biological chemistry 1999-05, Vol.274 (19), p.13443-13450
• Main Authors: Qiu, Daoming, Zhao, Guohua, Aoki, Yosuke, Shi, Lingfang, Uyei, Anne, Nazarian, Saman, Ng, James C.-H., Kao, Peter N.
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.274.19.13443

PG490 (triptolide) is a diterpene triepoxide with potent immunosuppressive and antiinflammatory properties. PG490 inhibits interleukin(IL)-2 expression by normal human peripheral blood lymphocytes stimulated with phorbol 12-myristate 13-acetate (PMA) and antibody to CD3 (IC50 of 10 ng/ml), and with PMA and ionomycin (Iono, IC50 of 40 ng/ml). In Jurkat T-cells, PG490 inhibits PMA/Iono-stimulated IL-2 transcription. PG490 inhibits the induction of DNA binding activity at the purine-box/antigen receptor response element (ARRE)/nuclear factor of activated T-cells (NF-AT) target sequence but not at the NF-κB site. PG490 can completely inhibit transcriptional activation at the purine-box/ARRE/NF-AT and NF-κB target DNA sequences triggered by all stimuli examined (PMA, PMA/Iono, tumor necrosis factor-α). PG490 also inhibits PMA-stimulated activation of a chimeric transcription factor in which the C-terminal TA1 transactivation domain of NF-κB p65 is fused to the DNA binding domain of GAL4. In 16HBE human bronchial epithelial cells, IL-8 expression is regulated predominantly by NF-κB, and PG490 but not cyclosporin A can completely inhibit expression of IL-8. The mechanism of PG490 inhibition of cytokine gene expression differs from cyclosporin A and involves nuclear inhibition of transcriptional activation of NF-κB and the purine-box regulator operating at the ARRE/NF-AT site at a step after specific DNA binding.