Immunosuppressive and anti-inflammatory mechanisms of triptolide, the principal active diterpenoid from the Chinese medicinal herb Tripterygium wilfordii Hook. f

Triptolide with potential medicinal value for diseases of the central nervous system

Tripterygium wilfordii Hook.f. (TWHF) has a long history as a Traditional Chinese Medicine (TCM) herb that aids in treating inflammatory and autoimmune diseases. The major bioactive component of TWHF is triptolide, which has been recognized to possess a broad spectrum of biological profiles including antiinflammatory, immunosuppressive, antifertility, and antitumor activities, as well as neurotrophic and neuroprotective effects. Limitation of triptolide, such as poor water solubility and severe systemic toxicity, has postponed clinical development and trials; however, the wide range of medicinal value of triptolide has been drawing intensive worldwide attention. In particular, triptolide has been shown to have significant effects on central nervous system (CNS) diseases, such as Parkinson's disease, Alzheimer's disease, spinal cord and brain injury, and multiple sclerosis. This review focuses on the potential therapeutic role of triptolide on CNS diseases, and discusses the structural features, potential modifications, and the other pharmacological activities of triptolide.

Biological activity and safety of Tripterygium extract prepared by sodium carbonate extraction

The commercial preparation named “Tripterygium glycosides” prepared by column chromatography has been used for the treatment of inflammatory and autoimmune diseases with significant efficacy but concurrent toxicity. The aim of this study was to reduce the toxicity of Tripterygium extracts, using cytotoxicity and anti-inflammatory activity of the three principal active components of Tripterygium wilfordii Hook. F. (TWHF) as guiding parameters. Column chromatography was replaced by sodium carbonate extraction for removing the acidic compounds and enriching epoxyditerpenoids and alkaloids in the extract. Results showed that the therapeutic index (IC₅₀/EC₅₀) on murine macrophage Raw 264.7 cells and rat mesangial HBZY-1 cells of the extract prepared by sodium carbonate extraction was significantly higher than that of Tripterygium glycosides (0.8 and 5.2 vs. 0.3 and 2.6, p < 0.05), while its cytotoxicity on human liver HL7702 cells was significantly lower (14.5 ± 1.4 vs. 6.8 ± 0.9, p < 0.05). Further acute oral toxicity experiments showed that the LD₅₀ value of this extract was 1,210 mg/kg compared to 257 mg/kg for Tripterygium glycosides. All the above results suggest that Tripterygium extract prepared by sodium carbonate extraction may represent a potentially optimal source of medicine with good therapeutic index.

Antagonist effect of triptolide on AKT activation by truncated retinoid X receptor-alpha

Background

Retinoid X receptor-alpha (RXRα) is a key member of the nuclear receptor superfamily. We recently demonstrated that proteolytic cleavage of RXRα resulted in production of a truncated product, tRXRα, which promotes cancer cell survival by activating phosphatidylinositol-3-OH kinase (PI3K)/AKT pathway. However, how the tRXRα-mediated signaling pathway in cancer cells is regulated remains elusive.

Methodology/Principal Findings

We screened a natural product library for tRXRα targeting leads and identified that triptolide, an active component isolated from traditional Chinese herb Trypterygium wilfordii Hook F, could modulate tRXRα-mediated cancer cell survival pathway in vitro and in animals. Our results reveal that triptolide strongly induces cancer cell apoptosis dependent on intracellular tRXRα expression levels, demonstrating that tRXRα serves as an important intracellular target of triptolide. We show that triptolide selectively induces tRXRα degradation and inhibits tRXRα-dependent AKT activity without affecting the full-length RXRα. Interestingly, such effects of triptolide are due to its activation of p38. Although triptolide also activates Erk1/2 and MAPK pathways, the effects of triptolide on tRXRα degradation and AKT activity are only reversed by p38 siRNA and p38 inhibitor. In addition, the p38 inhibitor potently inhibits tRXRα interaction with p85α leading to AKT inactivation. Our results demonstrate an interesting novel signaling interplay between p38 and AKT through tRXRα mediation. We finally show that targeting tRXRα by triptolide strongly activates TNFα death signaling and enhances the anticancer activity of other chemotherapies

Conclusions/Significance

Our results identify triptolide as a new xenobiotic regulator of the tRXRα-dependent survival pathway and provide new insight into the mechanism by which triptolide acts to induce apoptosis of cancer cells. Triptolide represents one of the most promising therapeutic leads of natural products of traditional Chinese medicine with unfortunate side-effects. Our findings will offer new strategies to develop improved triptolide analogs for cancer therapy.

Inhibitory effect of Astragalus polysaccharides on lipopolysaccharide-induced TNF-a and IL-1β production in THP-1 cells

Astragalus polysaccharides (APS), one of main bioactive components in Astragalus membranaceus Bunge, has been reported to possess anti-inflammatory activities, but the molecular mechanisms behind this activity are largely unknown. This study aimed to investigate expression of inflammatory cytokines and the MAPK/NF-κB pathway in human THP-1 macrophages induced by lipopolysaccharide (LPS). The results showed that the concentrations of TNF-α and IL-1β released from LPS stimulated THP-1 cells increased significantly compared to control (p < 0.01). After treatment with APS, the TNF-α and IL-1β levels were significantly lower than those in the LPS group (p < 0.05). The mRNA expression of TNF-α and IL-1β were also inhibited. Mechanistic studies indicated that APS strongly suppressed NF-κB activation and down-regulated the phosphorylation of ERK and JNK, which are important signaling pathways involved in the production of TNF-α and IL-1β, demonstrating that APS could suppress the production of TNF-α and IL-1β by LPS stimulated macrophages by inhibiting NF-κB activation and ERK and JNK phosphorylation.

Triptolide attenuate the oxidative stress induced by LPS/D-GalN in mice

Triptolide, a diterpene triepoxide, is one of the major components of most functional extracts of Tripterygium wilfordii Hook f, which is known to have various biological effects, including immunosuppressive, anti-inflammatory and anti-tumor functions. We studied the inhibitory effect of triptolide on endotoxemia (ETM)-induced oxidative stress, which was induced in C57BL/6 mice by lipopolysaccharide (LPS) and D-galactosamine (D-GalN). Pretreatment with triptolide decreased the reactive oxygen species (ROS) levels, mortality rate and liver injury after LPS/D-GalN injection. We utilized comprehensive proteomics to identify alterations in liver protein expression during pretreatment with triptolide or N-acetylcysteine (NAC) after LPS/D-GalN injection, 44 proteins were found to be related to oxidative stress, mitochondria, metabolism and signal transduction, and 23 proteins of them seemed to be significantly up- or down-regulated. Furthermore, both triptolide and NAC inhibited activation of c-jun NH2-terminal kinases (JNK) and mitogen-activated protein kinase p38 (p38), phosphorylation of inhibitor of nuclear factor-kappa B (IκB) and activation of nuclear factor-κB (NF-κB). These results demonstrated that triptolide inhibited the activation of JNK and p38 by decreasing ROS levels, which in turn inhibited the hepatic injury. In addition, we set and validated the phosphorylation model of extracellular signal-regulated kinase (ERK) and proposed that triptolide probably induced ERK phosphorylation through inhibiting its dephosphorylation rates. These results showed that triptolide can effectively reduce the oxidative stress and partially rescue the damage in the liver induced by LPS/D-GalN.

Inhibitive effect of triptolide on invasiveness of human fibrosarcoma cells by downregulating matrix metalloproteinase-9 expression

OBJECTIVE

To explore the molecular mechanisms of antitumor properties of triptolide, a bioactive component isolated from the Chinese herb Tripterygium wolfordii Hook F.

METHODS

Human fibrosarcoma HT-1080 cells were treated with different doses of triptolide for 72 h. Then the expression and activity of matrix metalloproteinase (MMP)-2 and -9 were measured and the invasiveness of triptolide-treated HT-1080 cells was compared with that of anti-MMP-9-treated HT-1080 cells.

RESULTS

18 nmol/L triptolide inhibited the gene expression and activity of MMP-9, but not those of MMP-2, in HT-1080 cells. In addition, both 18 nmol/L triptolide and 3 μg/mL anti-MMP-9 significantly reduced the invasive potential of HT-1080 cells, by about 50% and 35%, respectively, compared with the control. Whereas there was no significant difference between the effect of 18 nmol/L triptolide and that of anti-MMP-9 on invasive potential of HT-1080 cells.

CONCLUSIONS

These data suggest that triptolide inhibits tumor cell invasion partly by reducing MMP-9 gene expression and activity.

Triptolide: structural modifications, structure-activity relationships, bioactivities, clinical development and mechanisms

Triptolide, a principal bioactive ingredient of Tripterygium wilfordii Hook F, has attracted extensive exploration due to its unique structure of a diterpenoid triepoxide and multiple biological activities. This review will focus on the structural modifications, structure-activity relationships, pharmacology, and clinical development of triptolide in the last forty years.

Triptolide exhibits anti-inflammatory, anti-catabolic as well as anabolic effects and suppresses TLR expression and MAPK activity in IL-1β treated human intervertebral disc cells

INTRODUCTION

Increased levels of proinflammatory cytokines seem to play a pivotal role in the development of back pain in a subpopulation of patients with degenerative intervertebral disc (IVD) disease. As current treatment options are mostly limited to surgical interventions or conservative treatment, anti-inflammatory substances might offer a novel, more target-orientated therapeutic approach. Triptolide (TPL), a natural substance found in the Chinese medicinal herb Tripterygium wilfordii Hook, has been demonstrated to possess anti-inflammatory effects in various cells, but no studies exist so far for the IVD. Therefore, the aim of this study was to determine the effects of TPL on human IVD cells by analyzing changes in gene expression and underlying molecular mechanisms.

MATERIALS AND METHODS

In order to investigate the anti-inflammatory, anabolic and anti-catabolic effect of TPL, dose-dependency experiments (n = 5) and time course experiments (n = 5) were performed on IL-1β prestimulated human IVD cells and changes in gene expression of IL-6/-8, TNF-α, PGE2S, MMP1/2/3/13, aggrecan and collagen-I/-II were analyzed by real-time RT-PCR. The molecular mechanisms underlying the effects observed upon TPL treatment were investigated by analyzing involvement of Toll-like receptors TLR2/4 (real-time RT-PCR, n = 5), NF-κB, MAP kinases p38, ERK and JNK (immunoblotting and immunocytochemistry, n = 4) as well as RNA polymerase II (immunoblotting, n = 3).

RESULTS

Results showed that 50 nM TPL exhibited an anti-inflammatory, anti-catabolic and anabolic effect on the mRNA level for IL-6/-8, PGE2S, MMP1/2/3/13, aggrecan, collagen-II and TLR2/4, with most pronounced changes after 18 h for proinflammatory cytokines and MMPs or 30 h for TLRs and matrix proteins. However, we also observed an up-regulation of TNF-α at higher concentrations. The effects of TPL did not seem to be mediated via an inhibition of NF-κB or a decrease of RNA polymerase II levels, but TPL influenced activity of MAP kinases p38 and ERK (but not JNK) and expression of TLR2/4.

CONCLUSIONS

In conclusion, TPL may possess promising potential for the treatment of inflammation-related discogenic back pain in vitro, but its analgetic effect will need to be confirmed in an appropriate in vivo animal model.

Triptolide directly inhibits dCTP pyrophosphatase

Triptolide is a potent natural product, with documented antiproliferative, immunosuppressive, anti-inflammatory, antifertility, and antipolycystic kidney disease effects. Despite a wealth of knowledge about the biology of this compound, direct intracellular target proteins have remained elusive. We synthesized a biotinylated photoaffinity derivative of triptolide, and used it to identify dCTP pyrophosphatase 1 (DCTPP1) as a triptolide-interacting protein. Free triptolide interacts directly with recombinant DCTPP1, and inhibits the enzymatic activity of this protein. Triptolide is thus the first dCTP pyrophosphatase inhibitor identified, and DCTPP1 is a biophysically validated target of triptolide.

Triptolide ameliorates Crohn's colitis is associated with inhibition of TLRs/NF-κB signaling pathway

Growing evidence suggests that TLRs/NF-κB signaling pathway plays a critical role in the pathogenesis of Crohn's disease (CD). We have reported that triptolide, an active component from Tripterygium wilfordii Hook, showed therapeutic activity in IL-10-deficeint (IL-10-/- mice, a murine CD model. However the full mechanisms of action of this agent in CD remain largely unknown. We hypothesized that triptolide would ameliorate the experimental colitis by inhibiting TLRs/NF-κB signaling pathway. We found TLR2 and TLR4 were upregulated in IL-10-)/- mice, triptolide inhibited the TLRs/NF-κB signaling pathway in vivo. In addition, triptolide in vitro was able to downregulate the TLRs/NF-κB pathway in cultured colonic explants from CD patients. Our results confirm the therapeutic effect of triptolide in experimental colitis, and suggest it as a promising compound for CD treatment. These findings also support the possibility that targeted inhibition of TLR signaling pathway is an approach deserving further investigation as a therapeutic strategy for CD.

Celastrol induces apoptosis in non-small-cell lung cancer A549 cells through activation of mitochondria- and Fas/FasL-mediated pathways

Celastrol is a natural compound extracted from the traditional Chinese medicinal herb, Tripterygium wilfordii Hook. It has attracted interests for its potential anti-inflammatory and antitumor effects. However, the molecular mechanisms of celastrol-induced apoptosis in cancer cells remain unclear. In this study, we investigated the effects of celastrol on the human non-small-cell lung cancer (NSCLC) cell line A549 in vitro. Celastrol caused a dose- and time-dependent growth inhibition of A549 cells with an IC(50) of 2.12 μM at 48 h treatment. Celastrol induced A549 cells apoptosis as confirmed by annexin V/propidium iodide staining and DNA fragmentation. Celastrol-induced apoptosis was characterized by cleavage of caspase-9, caspase-8, caspase-3, and PARP protein, increased Fas and FasL expression, and a reduction in the mitochondrial membrane potential. Furthermore, celastrol induced the release of cytochrome c. Celastrol also up-regulated the expression of pro-apoptotic Bax, down-regulated anti-apoptotic Bcl-2, and inhibited Akt phosphorylation. These results demonstrate that celastrol can induce apoptosis of human NSCLC A549 cells through activation of both mitochondria- and FasL-mediated pathways.

Triptolide downregulates human GD3 synthase (hST8Sia I) gene expression in SK-MEL-2 human melanoma cells

In this study, we have shown that gene expression of human GD3 synthase (hST8Sia I) is suppressed by triptolide (TPL) in human melanoma SK-MEL-2 cells. To elucidate the mechanism underlying the downregulation of hST8Sia I gene expression in TPL-treated SK-MEL-2 cells, we characterized the TPL-inducible promoter region within the hST8Sia I gene using luciferase constructs carrying 5'-deletions of the hST8Sia I promoter. Functional analysis of the 5'-flanking region of the hST8Sia I gene demonstrated that the -1146 to -646 region, which contains putative binding sites for transcription factors c-Ets-1, CREB, AP-1 and NF-κB, functions as the TPL-inducible promoter of hST8Sia I in SK-MEL-2 cells. Site-directed mutagenesis and ChIP analysis indicated that the NF-κB binding site at -731 to -722 is crucial for TPL-induced suppression of hST8Sia I in SK-MEL-2 cells. This suggests that TPL induces down-regulation of hST8Sia I gene expression through NF-κB activation in human melanoma cells.

Rebamipide-induced downregulation of phospholipase D inhibits inflammation and proliferation in gastric cancer cells

Rebamipide a gastroprotective drug, is clinically used for the treatment of gastric ulcers and gastritis, but its actions on gastric cancer are not clearly understood. Phospholipase D (PLD) is overexpressed in various types of cancer tissues and has been implicated as a critical factor in inflammation and carcinogenesis. However, whether rebamipide is involved in the regulation of PLD in gastric cancer cells is not known. In this study, we showed that rebamipide significantly suppressed the expression of both PLD1 and PLD2 at a transcriptional level in AGS and MKN-1 gastric cancer cells. Downregulation of PLD expression by rebamipide inhibited its enzymatic activity. In addition, rebamipide inhibited the transactivation of nuclear factor kappa B (NFkappaB), which increased PLD1 expression. Rebamipide or PLD knockdown significantly suppressed the expression of genes involved in inflammation and proliferation and inhibited the proliferation of gastric cancer cells. In conclusion, rebamipide-induced downregulation of PLD may contribute to the inhibition of inflammation and proliferation in gastric cancer.

A Chinese herb Tripterygium wilfordii Hook F in the treatment of rheumatoid arthritis: mechanism, efficacy, and safety

Tripterygium wilfordii Hook F (TwHF) is a Chinese herb with immunosuppressive effects and an established history of use in the treatment of rheumatoid arthritis (RA). Numerous preclinical studies have demonstrated that the extracts from the root of TwHF inhibit the expression of proinflammatory cytokines, proinflammatory mediators, adhesion molecules, and matrix metalloproteinases by macrophages, lymphocytes, synovial fibroblasts, and chondrocytes. TwHF also induces apoptosis in lymphocytes and synovial fibroblasts and inhibits their proliferation. Except numerous uncontrolled clinical trials, there are some prospective, double-blind, randomized, and placebo/sulfasalazine-controlled trials, also demonstrating greater improvement in RA disease activity by TwHF extract than placebo/sulfasalazine. Radiographic progression in RA may also be retarded by TwHF. Therefore, the immunosuppressive, cartilage protective, and anti-inflammatory effects of TwHF extracts are well demonstrated, and TwHF extract is an alternative disease modifying anti-rheumatic drug (DMARD) for the patients with RA refractory to conventional therapy.

Triptolide alleviates hepatic ischemia/reperfusion injury by attenuating oxidative stress and inhibiting NF-κB activity in mice

BACKGROUND

Hepatic I/R injury is unavoidable in liver transplantation and surgery. This remains a significant problem in surgical procedures. The purpose of this study was to investigate the effects of triptolide on liver ischemia/reperfusion (I/R) injury and related mechanisms in mice.

MATERIALS AND METHODS

Male C57BL/6 mice were randomized into four groups: (1) sham group; (2) sham-triptolide group; (3) I/R group; and (4) I-R/triptolide group. Ninety minutes of warm ischemia was induced and flow by 24 h reperfusion. Serum alanine aminotransferase and aspartate aminotransferase were assayed, pathologic alterations and (NF)-κB p65 immunohistochemistry were observed. Liver malondialdehyde (MDA) level, activity of endogenous antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities, and activity of neutrophil accumulation marker myeloperoxidase (MPO) were measured. TNF-α, IL-6, and IL-1β mRNA were detected by RT-PCR, whereas nuclear factor (NF)-κB p65 and IκBα were assessed with Western blotting.

RESULTS

Plasma aminotransferase activity was higher in the I/R group than in the I/R-triptolide group. MDA level and neutrophil infiltration were also markedly reduced, while SOD, CAT, and GSH-Px levels increased in I/R-triptolide group compared with I/R group. In group 4, histopathologic changes were significantly attenuated in triptolide-treated livers. In comparison with group 3, triptolide reduced NF-κB p65 nuclear and IκBα expression, and effectively suppressed pro-inflammatory cytokine level during the I/R.

CONCLUSIONS

These results suggest that triptolide has protective effects against hepatic I/R injury. Its mechanisms might be related to reduction of oxidative stress and neutrophil infiltration and inhibition NF-κB p65 activity.

Alternative therapies: what role do they have in the management of lupus?

Systemic lupus erythematosus (SLE) is an autoimmune disease with higher morbidity and mortality among ethnic Chinese patients than Whites. Corticosteroid and other immunosuppressive drugs, including cyclophosphamide, azathioprine, and hydroxychloroquine are traditional therapies for this disease. Since the year 2000, mycophenolate mofetil and rituximab have been widely used in refractory SLE or severe lupus nephritis. Because the high disease activity remains, even after active therapy, and serious side effects from Western medicines may develop, more than 40% of SLE patients in Western countries are pursuing complementary and alternative therapies (CATs). CAT remedies are multiplex, and include herbal medicines, diets and vitamins, acupuncture, chiropractice, folk medicine, massage, spiritual healing, etc. Many herbal formulas have been used but in general their efficacy in treating lupus is doubted because of the lack of strong evidence. Tripterygium (T2) has demonstrated good efficacy in rheumatoid arthritis (RA) and SLE, but widespread use is limited due to the side effects. Through randomized clinical trials, we hope in the future that some Chinese medicines may be found helpful as CATs for SLE.

Regulation of Th1 and Th17 cell differentiation and amelioration of experimental autoimmune encephalomyelitis by natural product compound berberine

Berberine (BBR), an isoquinoline alkaloid derived from plants, is widely used as an anti-inflammatory remedy in traditional Chinese medicine. In this study, we showed that BBR was efficacious in the amelioration of experimental autoimmune encephalomyelitis (EAE) through novel regulatory mechanisms involving pathogenic Th1 and Th17 cells. BBR inhibited differentiation of Th17 cells and, to a lesser degree, Th1 cells through direct actions on the JAK/STAT pathway, whereas it had no effect on the relative number of CD4(+)Foxp3(+) regulatory T cells. In addition, BBR indirectly influenced Th17 and Th1 cell functions through its effect on the expression and function of costimulatory molecules and the production of IL-6, which was attributable to the inhibition of NF-kappaB activity in CD11b(+) APCs. BBR treatment completely abolished the encephalitogenicity of MOG(35-55)-reactive Th17 cells in an adoptive transfer EAE model, and the same treatment significantly inhibited the ability of MOG(35-55)-reactive Th1 cells to induce EAE. This study provides new evidence that natural compounds, such as BBR, are of great value in the search for novel anti-inflammatory agents and therapeutic targets for autoimmune diseases.

Luteolin suppresses IL-1beta-induced cytokines and MMPs production via p38 MAPK, JNK, NF-kappaB and AP-1 activation in human synovial sarcoma cell line, SW982

Matrix metalloproteinases (MMPs) play an important role in tissue degradation in rheumatoid synovium and inflammatory cytokines are essential in the pathogenesis of rheumatoid arthritis (RA). This study was conducted to evaluate the efficacy of luteolin in regulating interleukin-1beta (IL-1beta)-induced production of MMPs (MMP-1 and -3) and cytokines (tumor necrosis factor (TNF)-alpha and IL-6) in human synovial cell line, SW982. Treatment with luteolin at 1 or 10 microM significantly (P<0.05) inhibited IL-1beta-induced MMPs (MMP-1 and -3) and cytokines (TNF-alpha and IL-6) production when measured by enzyme-linked immunosorbent assay (ELISA). The mitogen-activated protein kinases (MAPKs) represent an attractive target for RA because they can regulate MMP and cytokine expression. The effects of luteolin on the activation of MAPKs and transcription factors were also examined in SW982 cells by ELISA. IL-1beta-induced JNK and p38 activation were inhibited by luteolin. Moreover, IL-1beta-induced activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) activation were inhibited by luteolin. These results suggest that luteolin reduces the production of MMPs and cytokines in SW982 cells by inhibiting MAPKs (JNK and p38) and transcription factors (AP-1 and NF-kappaB).

Herbal compounds and toxins modulating TRP channels

Although the benefits are sometimes obvious, traditional or herbal medicine is regarded with skepticism, because the mechanism through which plant compounds exert their powers are largely elusive. Recent studies have shown however that many of these plant compounds interact with specific ion channels and thereby modulate the sensing mechanism of the human body. Especially members of the Transient Receptor Potential (TRP) channels have drawn large attention lately as the receptors for plant-derived compounds such as capsaicin and menthol. TRP channels constitute a large and diverse family of channel proteins that can serve as versatile sensors that allow individual cells and entire organisms to detect changes in their environment. For this family, a striking number of empirical views have turned into mechanism-based actions of natural compounds. In this review we will give an overview of herbal compounds and toxins, which modulate TRP channels.

Novel target genes responsive to the anti-growth activity of triptolide in endometrial and ovarian cancer cells

Triptolide (TPL), a bioactive component of the Chinese medicinal herb Tripterygium wilfordii Hook F, induces apoptosis in some lines of human tumor cells. However, the effect of TPL on gynecologic cancer cells has not yet been well-described. We investigated the effects of TPL on cell growth, cell cycle, and apoptosis in endometrial and ovarian cancer cell lines. Furthermore, we examined global changes in gene expression after treatment with TPL. By using a list of 20 differentially expressed genes, Western blot analyses were performed on five endometrial and ovarian cancer cell lines. All cell lines were sensitive to the growth-inhibitory effect of TPL. TPL increased the proportion of cells in the S-phase of the cell cycle and induced apoptosis. cDNA microarray assay demonstrated that the treatment with TPL changed the expression of cell cycle regulators, apoptosis-related factors and cell proliferation markers. Of the gene expression changes induced by TPL treatment, up-regulation of LRAP, CDH4, and SFRP1 and down-regulation of cystatin, TNNT 1, and L1-CAM were confirmed using Western blot analysis in all the cell lines examined. We found a strong anticancer activity of TPL and identified some potential target genes of this drug, raising hopes that TPL may become a useful therapy for endometrial and ovarian cancers.

Triptolide downregulates Rac1 and the JAK/STAT3 pathway and inhibits colitis-related colon cancer progression

Triptolide, a diterpenoid triepoxide from the traditional Chinese medicinal herb Tripterygium wilfordii Hook. f., is a potential treatment for autoimmune diseases as well a possible anti-tumor agent. It inhibits proliferation of colorectal cancer cells in vitro and in vivo. In this study, its ability to block progress of colitis to colon cancer, and its molecular mechanism of action are investigated. A mouse model for colitis-induced colorectal cancer was used to test the effect of triptolide on cancer progression. Treatment of mice with triptolide decreased the incidence of colon cancer formation, and increased survival rate. Moreover, triptolide decreased the incidence of tumors in nude mice inoculated with cultured colon cancer cells dose-dependently. In vitro, triptolide inhibited the proliferation, migration and colony formation of colon cancer cells. Secretion of IL6 and levels of JAK1, IL6R and phosphorylated STAT3 were all reduced by triptolide treatment. Triptolide prohibited Rac1 activity and blocked cyclin D1 and CDK4 expression, leading to G1 arrest. Triptolide interrupted the IL6R-JAK/STAT pathway that is crucial for cell proliferation, survival, and inflammation. This suggests that triptolide might be a candidate for prevention of colitis induced colon cancer because it reduces inflammation and prevents tumor formation and development.

Triptolide inhibits IL-12/IL-23 expression in APCs via CCAAT/enhancer-binding protein alpha

Triptolide is a biologically active component purified from Chinese herbal plant Tripterygium wilfordii Hook F. It is widely used in East Asia for treatment of systemic lupus erythematosus, rheumatoid arthritis, nephritis, Bechect's disease, psoriasis, atopic dermatitis, and asthma. However, its immunological mechanisms are poorly understood. IL-12 and IL-23 are closely related heterodimeric cytokines that share the common subunit p40. They are produced by APCs and are key factors in the generation and effector functions of Th1 and Th17 cells, respectively. They have been strongly implicated in the pathogenesis of several autoimmune disorders. In this study, we investigated the molecular mechanism whereby triptolide inhibits the expression of the p40 gene in APCs. We demonstrate that triptolide does so at the transcriptional level in part through targeting CCAAT/enhancer-binding protein-alpha (C/EBPalpha), which directly interacts with the p40 promoter and inhibits its transcription in inflammatory macrophages. Triptolide can activate the transcription of C/EBPalpha, and phosphorylation of Ser21 and Thr222/226 critical for C/EBPalpha inhibition of p40. Further, activation of C/EBPalpha by triptolide is dependent on upstream kinases ERK1/2 and Akt-GSK3beta. This study provides mechanistic insights into the immunomodulatory capacity of triptolide and has strong implications for its therapeutic applications in autoimmune diseases.

How useful is traditional herbal medicine for pulmonary fibrosis?

IPF, despite considerable advances in clinical management and understanding of its complex pathophysiology, is still a fatal disease without effective treatment. Herbal medicine has been used for more than 5000 years and is the central component of medical practice in many parts of Asia. Not surprisingly, traditional and herbal medicine is also widely applied for treatment of IPF. This review describes the most important herbal medicines that are used for IPF treatment. The relevant experimental studies investigating potential mechanisms of these drugs are discussed. The best conducted clinical studies which have reported beneficial effects of some herbal medications in the management of IPF are also evaluated. Overall, there is considerable experimental support from preclinical studies for some of these herbal medicines, but the translation into clinical practice appears difficult. The clinical trials evaluating their anti-fibrotic potential are not fulfilling the standards expected from 'Western' medicines. Systematic clinical research in this field is still in its infancy, and as such, the routine use of traditional and herbal medicine cannot be recommended for patients suffering from IPF.

Triptolide-induced suppression of phospholipase D expression inhibits proliferation of MDA-MB-231 breast cancer cells

In spite of the importance of phospholipase D (PLD) in cell proliferation and tumorigenesis, little is known about the molecules regulating PLD expression. Thus, identification of small molecules inhibiting PLD expression would be an important advance for PLD- mediated physiology. We examined one such here, denoted Triptolide, which was identified in a chemical screen for inhibitors of PLD expression using cell assay system based on measurement of PLD promoter activity. Triptolide significantly suppressed the expression of both PLD1 and PLD2 with sub-mM potency in MDA-MB-231 breast cancer cells as analyzed by promoter assay and RT-PCR. Moreover, triptolide abolished the protein level of PLD in a time and dose-dependent manner. Triptolide-induced PLD1 downregulation was also observed in all the cancer cells examined, suggesting a general phenomenon detected in various cancer cells. Decrease of PLD expression by triptolide suppressed both basal and PMA-induced PLD activity. In addition, triptolide inhibited activation of NFkB which increased PLD1 expression. Ultimately, downregulation of PLD by triptolide inhibited proliferation of breast cancer cells. Taken together, we demonstrate that triptolide suppresses the expression of PLD via inhibition of NFkappaB activation and then decreases cell proliferation.

Meta-analysis of Tripterygium wilfordii Hook F in the immunosuppressive treatment of IgA nephropathy

OBJECTIVE

Numerous Chinese patients with IgA nephropathy (IgAN) have benefited from Tripterygium wilfordii Hook F (TwHF) from two decades ago. However, to date there is no systematic evaluation of this remedy for IgAN.

METHODS

We conducted a meta-analysis of all eligible randomized clinical trials (RCTs) to assess the effect of TwHF on IgAN for the first time. In August 2009 a systematic search was performed among eight electronic databases. Review Manager (RevMan) version 5.0 was used.

RESULTS

(i) Four eligible RCTs with 188 participants were included; (ii) The validities of included RCTs were generally acceptable; (iii) TwHF brought about a favorable increase in complete remission (CR) (RR 1.53, 95%CI 1.09 to 2.16, I(2)=12%) and total remission (TR) (RR 1.27, 95%CI 1.08 to 1.48, I(2)=0%) compared with non-TwHF treatment; and this result was further confirmed by intention-to-treat analysis; (iv) Exploiting subgroup meta-analysis, TwHF led to significantly greater improvements of IgAN with non-nephrotic proteinuria with regard to the increase of CR (RR 1.80, 95%CI 1.21 to 2.68, I(2)=0%) and TR (RR 1.32, 95%CI 1.11 to 1.57, I(2)=0%), and decrease of urinary proteinuria excretion (UPE) (MD -467.41 mg/24h, 95%CI -633.99 to -300.82, I(2)=0%). Meanwhile, the renal function was well preserved (MD -2.66 µmol/L, 95%CI -9.26 to 3.94, I(2)=0%). Conclusion Although the results of this meta-analysis should be interpreted with caution and warrant further investigation, TwHF was certainly a valuable and promising immunosuppressive remedy for IgAN, which was in accordance with the accruing evidence from numerous large clinical and experimental studies.

Effects of triptolide from Tripterygium wilfordii on ERalpha and p53 expression in two human breast cancer cell lines

The aim of the study was to discover possible differential cytotoxicity of triptolide towards estrogen-sensitive MCF-7 versus estrogen-insensitive MDA-MB-231 human breast cancer cells. Considering that MCF-7 cells express functional Estrogen receptor alpha (ERalpha) and wild-type p53, whereas MDA-MB-231 cells which are ERalpha-negative express mutant p53, the anti-proliferation effect of triptolide on MCF-7 and MDA-MB-231 cells were examined, the apoptotic effect and cell cycle arrest caused by triptolide were investigated, ERalpha and p53 expression were also observed in this paper. The results showed that the anti-proliferation effects were induced by triptolide in both cell lines. But the value of IC(50) in MCF-7 cells for its anti-proliferation effect was about one tenth of that in MDA-MB-231 cells, which indicated that the effect is more potent in MCF-7 cells. Condensed chromatin or fragmented nuclei could be found in MCF-7 cells treated with only 40nM triptolide but in MDA-MB-231 cells they couldn't be observed until the concentration reached to 400nM. Triptolide induced significant S cell cycle arrest along with the presence of sub-G0/G1 peak in MDA-MB-231 cells, whereas there was only slightly S cell cycle arrest on cell cycle distribution in MCF-7 cells. The role of p53 in two breast cancer cells was examined, the results showed that the mutant p53 in MDA-MB-231 cells was suppressed and the wild-type p53 in MCF-7 was increased. Moreover, triptolide could down regulate the expression of ERalpha in MCF-7 cells. The results showed that triptolide is much more sensitive to ERalpha-positive MCF-7 cells than to ERalpha-negative MDA-MB-231 cells, and the sensitivity is significantly associated with the ERalpha and p53 status.

Triptolide is an inhibitor of RNA polymerase I and II-dependent transcription leading predominantly to down-regulation of short-lived mRNA

Triptolide, a natural product extracted from the Chinese plant Tripterygium wilfordii, possesses antitumor properties. Despite numerous reports showing the proapoptotic capacity and the inhibition of NF-kappaB-mediated transcription by triptolide, the identity of its cellular target is still unknown. To clarify its mechanism of action, we further investigated the effect of triptolide on RNA synthesis in the human non-small cell lung cancer cell line A549. Triptolide inhibited both total RNA and mRNA de novo synthesis, with the primary action being on the latter pool. We used 44K human pan-genomic DNA microarrays and identified the genes primarily affected by a short treatment with triptolide. Among the modulated genes, up to 98% are down-regulated, encompassing a large array of oncogenes including transcription factors and cell cycle regulators. We next observed that triptolide induced a rapid depletion of RPB1, the RNA polymerase II main subunit that is considered a hallmark of a transcription elongation blockage. However, we also show that triptolide does not directly interact with the RNA polymerase II complex nor does it damage DNA. We thus conclude that triptolide is an original pharmacologic inhibitor of RNA polymerase activity, affecting indirectly the transcription machinery, leading to a rapid depletion of short-lived mRNA, including transcription factors, cell cycle regulators such as CDC25A, and the oncogenes MYC and Src. Overall, the data shed light on the effect of triptolide on transcription, along with its novel potential applications in cancers, including acute myeloid leukemia, which is in part driven by the aforementioned oncogenic factors.

Comparison of Tripterygium wilfordii Hook F versus sulfasalazine in the treatment of rheumatoid arthritis: a randomized trial

BACKGROUND

Extracts of the medicinal plant Tripterygium wilfordii Hook F (TwHF) have been used in China for centuries to treat a spectrum of inflammatory diseases.

OBJECTIVE

To compare the benefits and side effects of TwHF extract with those of sulfasalazine for the treatment of active rheumatoid arthritis.

DESIGN

Randomized, controlled trial. A computer-generated code with random, permuted blocks was used to assign treatment.

SETTING

2 U.S. academic centers (National Institutes of Health, Bethesda, Maryland, and University of Texas, Dallas, Texas) and 9 rheumatology subspecialty clinics (in Dallas and Austin, Texas; Tampa and Fort Lauderdale, Florida; Arlington, Virginia; Duncanville, Pennsylvania; Wheaton and Greenbelt, Maryland; and Lansing, Michigan).

PATIENTS

121 patients with active rheumatoid arthritis and 6 or more painful and swollen joints.

INTERVENTION

TwHF extract, 60 mg 3 times daily, or sulfasalazine, 1 g twice daily. Patients could continue stable doses of oral prednisone or nonsteroidal anti-inflammatory drugs but had to stop taking disease-modifying antirheumatic drugs at least 28 days before randomization.

MEASUREMENTS

The primary outcome was the rate of achievement of 20% improvement in the American College of Rheumatology criteria (ACR 20) at 24 weeks. Secondary end points were safety; radiographic scores of joint damage; and serum levels of interleukin-6, cholesterol, cortisol, and adrenocorticotropic hormone.

RESULTS

Outcome data were available for only 62 patients at 24 weeks. In a mixed-model analysis that imputed data for patients who dropped out, 65.0% (95% CI, 51.6% to 76.9%) of the TwHF group and 32.8% (CI, 21.3% to 46.0%) of the sulfasalazine group met the ACR 20 response criteria (P=0.001). Patients receiving TwHF also had significantly higher response rates for ACR 50 and ACR 70 in mixed-model analyses. Analyses of only completers showed similar significant differences between the treatment groups. Significant improvement was demonstrated in all individual components of the ACR response, including the Health Assessment Questionnaire disability score. Interleukin-6 levels rapidly and significantly decreased in the TwHF group. Although not statistically significant, radiographic progression was lower in the TwHF group. The frequency of adverse events was similar in both groups.

LIMITATIONS

Only 62% and 41% of patients continued receiving TwHF extract and sulfasalazine, respectively, during the 24 weeks of the study. Long-term outcome data were not collected on participants who discontinued treatment.

CONCLUSION

In patients who continued treatment for 24 weeks and could also use stable oral prednisone and nonsteroidal anti-inflammatory drugs, attainment of the ACR 20 response criteria was significantly greater with TwHF extract than with sulfasalazine.

Triptolide promotes generation of FoxP3+ T regulatory cells in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Triptolide (TPT), a component of the Chinese herb Triptergium wilfordii, has potent immunosuppressive and anti-inflammatory activity and is used clinically in recipients of kidney transplantation.

AIM OF THE STUDY

This work aimed to investigate the effect of TPT on the differentiation of regulatory T lymphocytes (Tregs) from CD4+ cells in rats.

MATERIALS AND METHODS

MACS-purified rat CD4+ cells were costimulated with anti-CD3 and anti-CD28 in the presence of TGF-beta to induce the expression of FoxP3, which was detected by flow cytometry. TPT and cyclosporine A (CsA) were separately added into the cultures to observe the effect on the expression of FoxP3. Kidney transplantation was performed in rats that either received no treatment or were treated with TPT after transplantation.

RESULTS

TPT treatment enhanced the expression of FoxP3 in CD4+ cells, whereas CsA inhibited the FoxP3 expression. In the rat kidney transplantation model, the recipient rats treated with TPT survived longer than the control rats (18-19.83 vs 6.83 days, P<0.05). Meanwhile, the FoxP3+ T cells in the spleens of treated rats were higher than those from the untreated rats (12.4% vs 4.7%, P<0.05).

CONCLUSIONS

These data suggest that TPT may promote the differentiation of CD4+ cells to FoxP3+ Tregs. This would be at least one of the pathways responsible for the immunosuppressive activity of TPT.

Geranylated flavonoids from the roots of Campylotropis hirtella and their immunosuppressive activities

In an effort to identify new immunosuppressive agents from natural sources, 12 new geranylated flavonoids, 5,7,4'-trihydroxy-3'-[7-hydroxy-3,7-dimethyl-2(E)-octenyl]isoflavone (1), a racemate of 5,7,2',4'-tetrahydroxy-3'-[7-hydroxy-3,7-dimethyl-2(E)-octenyl]isoflavanone (2), 2''(S)-5,7-dihydroxy-[2''-methyl-2''-(4-methyl-3-pentenyl)pyrano]-5'',6'':3',4'-isoflavone (3), (2''S,3''R,4''S)-5,7,3'',4''-tetrahydroxy[2''-methyl-2''-(4-methyl-3-pentenyl)pyrano]-5'',6'':3',4'-isoflavone (4), a racemate of 3'-geranyl-5,7,2',4'-tetrahydroxyisoflavanone (5), a racemate of 3'-geranyl-4'-methoxy-5,7,2'-trihydroxyisoflavanone (6), 3'-geranyl-5,7,4',5'-tetrahydroxyisoflavone (8), 3'-geranyl-5,7,2',5'-tetrahydroxyisoflavone (9), 3'-geranyl-4'-methoxy-5,7,2'-trihydroxyisoflavone (10), 2(R),3(R)-3'-geranyl-2,3-trans-5,7,4'-trihydroxyflavonol (12), (2R,3R)-6-methyl-3'-geranyl-2,3-trans-5,7,4'-trihydroxyflavonol (13), and 5,7-dihydroxy-4'-O-geranylisoflavone (14), were isolated from the roots of Campylotropis hirtella (Franch.) Schindl. together with three previously described flavonoids. Their structures were elucidated by spectroscopic measurements, including two-dimensional nuclear magnetic resonance (NMR) techniques. The immunosuppressive effects of these compounds were assessed using mitogen-induced splenocyte proliferation, and the cytotoxicity of the compounds was also examined. The IC50 values of the compounds were found to be in the range of 1.49-61.23 microM for T lymphocyte suppression and 1.16-73.07 microM for B lymphocyte suppression. An analysis of their structure-activity relationships revealed that an isoflavonoid carbon skeleton with a C10 substituent at the C3' position was necessary for the activity. As many of the compounds exhibited good immunosuppressive activities, they may be promising as novel immunosuppressive agents.

Triptolide inhibits proliferation and migration of colon cancer cells by inhibition of cell cycle regulators and cytokine receptors

BACKGROUND

Phytochemicals are an important source of emerging preventive and therapeutic agents for cancer. Triptolide/PG490, an extract of the Chinese herb Tripterygium wilfordii Hook F, is a potent anti-inflammatory agent that also possesses anticancer activity. While its antiproliferative effects are well-established, the potential antimigratory effects of triptolide have not been characterized.

MATERIAL AND METHODS

Effects of triptolide on the proliferation and invasion of colon cancer cells and expression of cancer-related genes and proteins were assessed.

RESULTS

Triptolide potently inhibited HT29 and HCT116 colon cancer cell growth and reduced basal and stimulated HCT116 migration through collagen by 65% to 80%. Triptolide inhibited mRNA expression of the positive cell cycle regulatory genes c-myc, and A, B, C, and D-type cyclins in multiple colon cancer cell lines. Additionally, we show that triptolide treatment decreased expression of VEGF and COX-2, which promote cancer progression and invasion, and inhibited the expression of multiple cytokine receptors potentially involved in cell migration and cancer metastasis, including the thrombin receptor, CXCR4, TNF receptors, and TGF-β receptors.

CONCLUSIONS

Triptolide is a potent inhibitor of colon cancer proliferation and migration in vitro. The down-regulation of multiple cytokine receptors, in combination with inhibition of COX-2 and VEGF and positive cell cycle regulators, may contribute to the antimetastatic action of this herbal extract.

A system for screening agonists targeting beta2-adrenoceptor from Chinese medicinal herbs

In order to develop a model for screening the agonists of human beta(2)-adrenoceptor from Chinese medicinal herbs extracts, we used a cell-based functional assay based on a common G protein-coupled receptor (GPCR) regulation mechanism and destabilized enhanced green fluorescent protein (d(2)EGFP) reporter gene technique. The positive cell clone was confirmed by real-time polymerase chain reaction (PCR) and imaging analysis. To assess the value of this model, we screened over 2000 high performance liquid chromatography (HPLC)-fractionated samples from the ethanol extracts of Chinese medicinal herbs. Six fractions (isolated from Panax japonicus, Veratrum nigrum, Phellodendron amurense, Fructus Aurantii Immaturus, Chaenomeles speciosa, and Dictamnus dasycarpus) showed significant effects on active reporter gene expression, three of which (isolated from Phellodendron amurense, Fructus Aurantii Immaturus, and Chaenomeles speciosa) were selected for further concentration response analysis and the half maximal effective concentration (EC(1/2 max)) values were 4.2, 2.7, and 4.8 microg/ml, respectively. Therefore, this reporter gene assay was suitable for screening beta(2)-adrenoceptor agonists. The results suggest that the six herbal extracts are the possible agonists of beta(2)-adrenoceptor.

Activity of triptolide against human mast cells harboring the kinase domain mutant KIT

Gain-of-function mutations of the receptor tyrosine kinase KIT can cause systemic mastocytosis (SM) and gastrointestinal stromal tumors. Most of the constitutively active KIT can be inhibited by imatinib; D816V KIT cannot. In this study, we investigated the activity of triptolide, a diterpenoid isolated from the Chinese herb Tripterygium wilfordii Hook. f., in cells expressing mutant KIT, including D816V KIT. Imatinib-sensitive HMC-1.1 cells harboring the mutation V560G in the juxtamembrane domain of KIT, imatinib-resistant HMC-1.2 cells harboring both V560G and D816V mutations, and murine P815 cells, were treated with triptolide, and analyzed in terms of growth, apoptosis, and signal transduction. The in vivo antitumor activity was evaluated by using the nude mouse xenograft model. Our results demonstrated that triptolide potently inhibits the growth of both human and murine mast cells harboring not only imatinib-sensitive KIT mutation but also imatinib-resistant D816V KIT. Triptolide markedly inhibited KIT mRNA levels and strikingly reduced the levels of phosphorylated and total Stat3, Akt, and Erk1/2, downstream targets of KIT. Triptolide triggered apoptosis by inducing depolarization of mitochondrial potential and release of cytochrome c, downregulation of Mcl-1 and XIAP. Furthermore, triptolide significantly abrogated the growth of imatinib-resistant HMC-1.2 cell xenografts in nude mice and decreased KIT expression in xenografts. Our data demonstrate that triptolide inhibits imatinib-resistant mast cells harboring D816V KIT. Further investigation of triptolide for treatment of human neoplasms driven by gain-of-function KIT mutations is warranted.