Triptolide covalently binds to human XPB and inhibits its DNA-dependent ATPase activity, which leads to the inhibition of RNA polymerase II-mediated transcription and likely nucleotide excision repair.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).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-kappaB site.PG490 also inhibits PMA-stimulated activation of a chimeric transcription factor in which the C-terminal TA1 transactivation domain of NF-kappaB p65 is fused to the DNA binding domain of GAL4. In 16HBE human bronchial epithelial cells, IL-8 expression is regulated predominantly by NF-kappaB, and PG490 but not cyclosporin A can completely inhibit expression of IL-8.PG490 potently inhibited TNF-alpha-induced activation of NF-kappaB. PG490 also blocked TNF-alpha-mediated induction of c-IAP2 (hiap-1) and c-IAP1 (hiap-2), members of the inhibitor of apoptosis (IAP) family. Interestingly, PG490 did not block DNA binding of NF-kappaB, but it blocked transactivation of NF-kappaB.
|Cell lines||N2a and SKNSH cells|
|Preparation method||Cell viability determination
Cells were seeded in serum-containing media onto 96-well plates at densities of 3 × 103 cells per well for N2a and 5 × 103 cells per well for SKNSH. Following overnight incubation, cells were treated with varying concentrations of triptolide in serum-free media and re-incubated for varying time courses at 37 °C. Controls were treated with serum-free media.Cell viability was determined using an MTT assay. Reagent was prepared by dissolving thiazolyl blue tetrazolium bromide (Sigma-Aldrich) in phosphate-buffered saline (Invitrogen) at a concentration of 2 mg/mL and filtering. After cells were incubated in 96-well plates and subsequently exposed to triptolide at varying doses and time durations, 20 μL MTT reagent were added to each well. Cells were re-incubated at 37°C for 4 hours, after which all liquid was aspirated from each well and absorbances were measured at 550 and 650 nm. These experiments were performed in triplicate and repeated 4 times.
|Concentrations||31.25 to 500 nM|
|Incubation time||24 and 48 h|
|Animal models||Female A/J mice bearing Orthotopic neuroblastoma model|
|Body Surface Area (m2)||0.007||0.025||0.15||0.05||0.02||0.5|
|Animal A (mg/kg) = Animal B (mg/kg) multiplied by||Animal B Km|
|Animal A Km|
For example, to modify the dose of resveratrol used for a mouse (22.4 mg/kg) to a dose based on the BSA for a rat, multiply 22.4 mg/kg by the Km factor for a mouse and then divide by the Km factor for a rat. This calculation results in a rat equivalent dose for resveratrol of 11.2 mg/kg.
XPB, a subunit of TFIIH, is a target of the natural product triptolide.
Titov DV, et al. Nat Chem Biol. 2011 Mar;7(3):182-8. PMID: 21278739.
Triptolide therapy for neuroblastoma decreases cell viability in vitro and inhibits tumor growth in vivo.
Antonoff MB, et al. Surgery. 2009 Aug;146(2):282-90. PMID: 19628086.
PG490 (triptolide) cooperates with tumor necrosis factor-alpha to induce apoptosis in tumor cells.
Lee KY, et al. J Biol Chem. 1999 May 7;274(19):13451-5. PMID: 10224110.
Immunosuppressant PG490 (triptolide) inhibits T-cell interleukin-2 expression at the level of purine-box/nuclear factor of activated T-cells and NF-kappaB transcriptional activation.
Qiu D, et al. J Biol Chem. 1999 May 7;274(19):13443-50. PMID: 10224109.
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