Triptolide

Biochem Biophys Res Commun. 2015 Jan 16;456(3):815-20.

Triptolide inhibits proliferation of Epstein-Barr virus-positive B lymphocytes by down-regulating expression of a viral protein LMP1.[Pubmed: 25511707]

Epstein-Barr virus (EBV) infects various types of cells and mainly establishes latent infection in B lymphocytes. The viral latent membrane protein 1 (LMP1) plays important roles in transformation and proliferation of B lymphocytes infected with EBV. Triptolide is a compound of Tripterygium extracts, showing anti-inflammatory, immunosuppressive, and anti-cancer activities.
METHODS AND RESULTS:
In this study, it is determined whether Triptolide inhibits proliferation of Epstein-Barr virus-positive B lymphocytes. The CCK-8 assays were performed to examine cell viabilities of EBV-positive B95-8 and P3HR-1 cells treated by Triptolide. The mRNA and protein levels of LMP1 were examined by real time-PCR and Western blotting, respectively. The activities of two LMP1 promoters (ED-L1 and TR-L1) were determined by Dual luciferase reportor assay. The results showed that Triptolide inhibited the cell viability of EBV-positive B lymphocytes, and the over-expression of LMP1 attenuated this inhibitory effect. Triptolide decreased the LMP1 expression and transcriptional levels in EBV-positive B cells. The activity of LMP1 promoter ED-L1 in type III latent infection was strongly suppressed by Triptolide treatment. In addition, Triptolide strongly reduced growth of B95-8 induced B lymphoma in BALB/c nude mice.
CONCLUSIONS:
These results suggest that Triptolide decreases proliferation of EBV-induced B lymphocytes possibly by a mechanism related to down-regulation of the LMP1 expression.

J Exp Clin Cancer Res . 2021 Jun 9;40(1):190.

Natural product triptolide induces GSDME-mediated pyroptosis in head and neck cancer through suppressing mitochondrial hexokinase-ΙΙ[Pubmed: 34108030]

Abstract Background: Pyroptosis is a lytic cell death form executed by gasdermins family proteins. Induction of tumor pyroptosis promotes anti-tumor immunity and is a potential cancer treatment strategy. Triptolide (TPL) is a natural product isolated from the traditional Chinese herb which possesses potent anti-tumor activity in human cancers. However, its role in pyroptosis remains to be elucidated. Methods: Cell survival was measured by colony formation assay. Cell apoptosis was determined by Annexin V assay. Pyroptosis was evaluated by morphological features and release of interleukin 1β and lactate dehydrogenase A (LDHA). Immunofluorescence staining was employed to measure subcellular localization of proteins. Tumorigenicity was assessed by a xenograft tumor model. Expression levels of mRNAs or proteins were determined by qPCR or western blot assay, respectively. Results: Triptolide eliminates head and neck cancer cells through inducing gasdermin E (GSDME) mediated pyroptosis. Silencing GSDME attenuates the cytotoxicity of TPL against cancer cells. TPL treatment suppresses expression of c-myc and mitochondrial hexokinase II (HK-II) in cancer cells, leading to activation of the BAD/BAX-caspase 3 cascade and cleavage of GSDME by active caspase 3. Silencing HK-II sensitizes cancer cells to TPL induced pyroptosis, whereas enforced expression of HK-II prevents TPL induced pyroptosis. Mechanistically, HK-II prevents mitochondrial translocation of BAD, BAX proteins and activation of caspase 3, thus attenuating cleavage of GSDME and pyroptosis upon TPL treatment. Furthermore, TPL treatment suppresses NRF2/SLC7A11 (also known as xCT) axis and induces reactive oxygen species (ROS) accumulation, regardless of the status of GSDME. Combination of TPL with erastin, an inhibitor of SLC7A11, exerts robust synergistic effect in suppression of tumor survival in vitro and in a nude mice model. Conclusions: This study not only provides a new paradigm of TPL in cancer therapy, but also highlights a crucial role of mitochondrial HK-II in linking glucose metabolism with pyroptosis. Keywords: Ferroptosis; Gasdermins; Head and neck squamous cell carcinoma; Nasopharyngeal carcinoma; X(c)(−) cysteine/glutamate antiporter.

Mol Cell Endocrinol. 2015 Jan 5;399:346-53.

Triptolide inhibits osteoclast formation, bone resorption, RANKL-mediated NF-қB activation and titanium particle-induced osteolysis in a mouse model.[Pubmed: 25448849]

The RANKL-induced NF-κB signaling pathway is required for osteoclast formation and function.
METHODS AND RESULTS:
By screening for compounds that inhibit RANKL-induced NF-κB activation using a luciferase reporter gene assay in RAW264.7 cells, we identified Triptolide (PG490), as a candidate compound targeting osteoclast differentiation and osteoclast-mediated osteolysis. Triptolide (PG490) is an active compound of the medicinal herb Tripterygium wilfordii Hook F (TWHF) or Lei Gong Teng with known anti-inflammatory properties. We found that Triptolide inhibited osteoclastogenesis and bone resorption, as well as RANKL-induced NF-қB activities as monitored by luciferase reporter gene assays and the nuclear translocation of p65. In vivo studies showed that Triptolide attenuates titanium-induced osteolysis and osteoclast formation in a mouse calvarial model.
CONCLUSIONS:
Considering that drugs which protect against localized bone loss are critically needed for the effective treatment of particle-induced osteolysis, our data suggest that Triptolide might have therapeutic potential for the treatment of bone lytic diseases caused by prosthetic wear particles.

Exp Cell Res. 2015 Feb 15;331(2):362-8.

Triptolide inhibits TGF-β1-induced cell proliferation in rat airway smooth muscle cells by suppressing Smad signaling.[Pubmed: 25447441]

We have reported that Triptolide can inhibit airway remodeling in a murine model of asthma via TGF-β1/Smad signaling. In the present study, we aimed to investigate the effect of Triptolide on airway smooth muscle cells (ASMCs) proliferation and the possible mechanism.
METHODS AND RESULTS:
Rat airway smooth muscle cells were cultured and made synchronized, then pretreated with different concentration of Triptolide before stimulated by TGF-β1. Cell proliferation was evaluated by MTT assay. Flow cytometry was used to study the influence of Triptolide on cell cycle and apoptosis. Signal proteins (Smad2, Smad3 and Smad7) were detected by western blotting analysis. Triptolide significantly inhibited TGF-β1-induced ASMC proliferation (P<0.05). The cell cycle was blocked at G1/S-interphase by Triptolide dose dependently. No pro-apoptotic effects were detected under the concentration of Triptolide we used. Western blotting analysis showed TGF-β1 induced Smad2 and Smad3 phosphorylation was inhibited by Triptolide pretreatment, and the level of Smad7 was increased by Triptolide pretreatment.
CONCLUSIONS:
Triptolide may function as an inhibitor of asthma airway remodeling by suppressing ASMCs proliferation via negative regulation of Smad signaling pathway.

Mol Med Rep. 2015 Feb;11(2):791-6.

Triptolide inhibits cell proliferation and tumorigenicity of human neuroblastoma cells.[Pubmed: 25354591]

Triptolide is a diterpene triepoxide, extracted from the Chinese herb Tripterygium wilfordii Hook F, which has been shown to have antitumor activity in a number of cancers. Neuroblastoma is an aggressive extracranial pediatric solid tumor, with significant chemotherapeutic resistance.
METHODS AND RESULTS:
In this study, Triptolide was hypothesized to be a potential therapeutic agent for neuroblastoma. The effects of Triptolide on neuroblastoma cell growth and tumor development were investigated. Cell growth and proliferation were evaluated using a cell counting kit‑8 assay and a 5-bromo-2-deoxyuridine staining assay. Cell cycle and apoptosis were detected by flow cytometry. Reverse transcription‑quantitative polymerase chain reaction was conducted to detect the expression levels of the apoptosis‑associated proteins, caspase‑3 and caspase‑9. The tumorigenicity of neuroblastoma cells was assessed by a soft agar clonogenic assay and an in vivo tumorigenic assay. The results demonstrated that exposure of BE(2)‑C human neuroblastoma cells to Triptolide resulted in a reduction in cell growth and proliferation, and the induction of cell death and apoptosis, together with cell cycle arrest in the S phase. A soft agar assay indicated that Triptolide inhibited the colony‑forming ability of BE(2)‑C neuroblastoma cells. The xenograft experiment showed that Triptolide significantly reduced tumor growth and development in vivo.
CONCLUSIONS:
The data suggested that this Chinese herb may be a potential novel chemotherapeutic agent for neuroblastoma.

Immunology. 2014 Sep 29.

Triptolide inhibits TGF-β1 induced proliferation and migration of rat airway smooth muscle cells by suppressing NF-κB but not ERK1/2.[Pubmed: 25267491]

Airway remodeling contributes to increased mortality in asthma. We have reported that Triptolide can inhibit airway remodeling in a mouse asthma model. In this study, we aimed to investigate the effect of Triptolide on airway smooth muscle cells (ASMCs) proliferation, migration and the possible mechanism.
METHODS AND RESULTS:
Rat airway smooth muscle cells were cultured and made synchronized, then pretreated with different concentrations of Triptolide before stimulated by TGF-β1. Cell proliferation was evaluated by cell counting and MTT assay. Flow cytometry was used to study the influence of Triptolide on cell cycle. Migration was measured by Transwell analysis. Signal proteins (NF-κB p65 and ERK1/2) were detected by western blotting analysis. LDH releasing test and flow cytometry analysis of apoptosis were also performed to explore the potential cytotoxic or pro-apoptotic effects of Triptolide. Triptolide significantly inhibited TGF-β1 induced ASMC proliferation and migration (p<0.05). The cell cycle was blocked at G1/S-interphase by Triptolide dose dependently. Western blotting analysis showed TGF-β1 induced NF-κB p65 phosphorylation was inhibited by Triptolide pretreatment, but ERK1/2 was not affected. No cytotoxic or pro-apoptotic effects were detected under the concentration of Triptolide we used.
CONCLUSIONS:
Triptolide may function as an inhibitor of asthma airway remodeling by suppressing ASMCs proliferation and migration through inactivation of NF-κB pathway.