Triptolide: progress on research in pharmacodynamics and toxicology

TRC4, an improved triptolide derivative, specifically targets to truncated form of retinoid X receptor-alpha in cancer cells

The nuclear retinoid X receptor-α (RXRα) plays critical roles in cell homeostasis and in many physiological processes mainly through its transcriptional function. However, an N-terminal truncated form of RXRα, tRXRα, was frequently described in various cancer cells and tumor tissues, thus representing a new promising drug target. We recently demonstrated that triptolide (TR01) could target to the oncogenic activity of tRXRα. To improve its tumor selectivity, we developed several TR01 derivatives by introducing different amine ester groups on C-14-hydroxyl site. Interestingly, C-14 modification could differently affect the expression of tRXRα without interfering the level of its full length RXRα. Among the derivatives, TRC4 could strongly reduce tRXRα expression, while TRC5-7 increased it. The capability of inhibiting tRXRα expression was shown to be closely associated with its inactivation of AKT and induction of apoptosis in various cancer cells. Conversely, treatment of cancer cells with the tRXRα-stabilizing compounds TRC5-7 resulted in enhanced AKT activity and apoptosis-resistance. However, although TR01 could strongly reduce tRXRα expression and AKT activity, it also strongly inhibited the expression and transcriptional activity of RXRα in normal cells. Importantly, the tRXRα-selective TRC4 that did not significantly inhibit RXRα transcriptional function retained the most potency of the anticancer effect of TR01 and had no significant effect on the viability of normal cells. In conclusion, our results demonstrated that tRXRα-selective TRC4 will have potential clinical application in terms of drug target and side effects. Our findings will offer new strategies to develop improved triptolide analogs for cancer therapy.

Inhibition of glycogen synthase kinase 3beta ameliorates triptolide-induced acute cardiac injury by desensitizing mitochondrial permeability transition

Triptolide (TP), a diterpene triepoxide, is a major active component of Tripterygium wilfordii extracts, which are prepared as tablets and has been used clinically for the treatment of inflammation and autoimmune disorders. However, TP's therapeutic potential is limited by severe adverse effects. In a previous study, we reported that TP induced mitochondria dependent apoptosis in cardiomyocytes. Glycogen synthase kinase-3β (GSK-3β) is a multifunctional serine/threonine kinase that plays important roles in the necrosis and apoptosis of cardiomyocytes. Our study aimed to investigate the role of GSK-3β in TP-induced cardiotoxicity. Inhibition of GSK-3β activity by SB 216763, a potent and selective GSK-3 inhibitor, prominently ameliorated the detrimental effects in C57BL/6J mice with TP administration, which was associated with a correction of GSK-3β overactivity. Consistently, in TP-treated H9c2 cells, SB 216763 treatment counteracted GSK-3β overactivity, improved cell viability, and prevented apoptosis by modulating the expression of Bcl-2 family proteins. Mechanistically, GSK-3β interacted with and phosphorylated cyclophilin F (Cyp-F), a key regulator of mitochondrial permeability transition pore (mPTP). GSK-3β inhibition prevented the phosphorylation and activation of Cyp-F, and desensitized mPTP. Our findings suggest that pharmacological targeting of GSK-3β could represent a promising therapeutic strategy for protecting against cardiotoxicity induced by TP.

Effect of triptolide on expression of Bax/Bcl-2 and cleaved Caspase 3 in HCT116 cells

AIM

To investigate the effect of triptolide (TP) on the expression of Bax/B cell lymphoma/leukmia-2 (Bcl-2) and cleaved Caspase 3 in HCT116 cells and the mechanism of TP induced apoptosis.

METHODS

HCT116 cells were divided into six groups and treated with 5, 10, 20, 30, 40, and 80 nmol/L TP, respectively. HCT116 cells treated with PBS were used control cells. After HCT116 cells were exposed to TP for 24 h, 48 h or 72 h, MTT assay was used for estimating the survival rates of HCT116 cells, flow cytometry (FCM) was applied to test the effects of TP on cell apoptosis, and Western blot was used for testing the expression of Bcl-2, Bax, Caspase 3, and activated Caspase 3.

RESULTS

TP could inhibit the proliferation of HCT116 cells. The survival rates of HCT116 cells decreased with the increase in the concentration and treatment time of TP. The survival rates were 4.25%, 13.6%, 34.4%, 43.8% and 44.5%, respectively, for cells exposed to 5, 10, 20, 30, and 40 nmol/L TP for 48h. The expression of Bcl-2 was decreased with the increase in the concentration of TP. Additionally, the level of Bax was decreased in the cytoplasm but increased in mitochondria, indicating that TP can promote Bax translocation from the cytoplasm to mitochondria. TP reduced the level of Caspase 3 in a concentration dependent manner; however, cleaved Caspase 3 level was increased.

CONCLUSION

TP can induce apoptosis of HCT116 cells by inhibiting the expression of Bcl-2, increasing the expression of Bax, and promoting the activation of Caspase 3.

Anti-inflammatory effects of triptolide on IgA nephropathy in rats

IgA nephropathy (IgAN) is the finding of immune deposits predominantly containing polymeric IgA in the glomerular mesangium on renal biopsy. Recently studies show that inflammation may involve in the progression of renal glomerulosclerosis and tubulointerstitial scarring in IgAN. This study was designed to evaluate the renoprotective effect of triptolide on IgAN rat model. IgAN was induced in Sprague-Dawley rats by oral and intravenous immunization with BSA for 12 weeks. Rats were treated with triptolide (200 μg/kg/d intragastrically) from 12 to 28 weeks. At Week 28, the rats was sacrificed, kidneys and blood samples were collected for further analysis. Our data shown that IgAN rat model showed marked deterioration of proteinuria together with higher levels of the urine protein:creatinine ratio compared to the normal control. Animals that underwent intermittent exposure to triptolide treatment exhibited significant improvements in the functional parameters without severe side effects. Rats developing IgAN had profound mesangial proliferation and mesangial expansion, intense and diffuse glomerular IgA deposition, while triptolide treatment significantly attenuated it. We also observed that treatment with triptolide significantly decreases serum levels of IL-1β and IL-18, and may exerted anti-inflammatory effects by down-regulating NLRP3 and TLR4 expression. Our study clearly demonstrated that triptolide prevents IgAN progression via an amelioration of inflammasome-mediated proinflammatory cytokine production, thus brought a light of hope for treatment of IgAN.

The triptolide derivative MRx102 inhibits Wnt pathway activation and has potent anti-tumor effects in lung cancer

BACKGROUND

The natural compound triptolide has been shown to decrease cell proliferation and induce apoptosis and cellular senescence. We previously demonstrated that triptolide decreases tumor formation and metastasis of human non-small cell lung cancer cells (NSCLC). Due to the toxicity of triptolide, derivatives of the natural compound have been developed that show more favorable toxicity profiles and pharmacokinetics in animal models. The purpose of this study was to evaluate MRx102 as a novel therapeutic for lung cancer.

METHODS

Mice injected subcutaneously with H460 lung cancer cells were treated with MRx102 or carboplatin to determine the effect of MRx102 on tumor formation in comparison to standard treatment. Patient-derived xenografts (PDX) with different WIF1 expression levels were treated with MRx102 or cisplatin. We tested the effects of MRx102 treatment on migration and invasion of lung cancer cells using Transwell filters coated with fibronectin and Matrigel, respectively. Tail vein injections using H460 and A549 cells were performed.

RESULTS

Here we report that the triptolide derivative MRx102 significantly decreases NSCLC proliferation and stimulates apoptosis. Further, MRx102 potently inhibits NSCLC haptotactic migration and invasion through Matrigel. In vivo, NSCLC tumor formation and metastasis were greatly decreased by MRx102 treatment. The decrease in tumor formation by MRx102 in the patient-derived xenograft model was WIF1-dependent, demonstrating that MRx102 is a potent inhibitor of the Wnt pathway in low WIF1 expressing NSCLC patient tumors.

CONCLUSIONS

These results indicate that MRx102 has potent antitumor effects both in vitro and in vivo, and is a potential novel therapy for the treatment of NSCLC.

Fabrication of novel vesicles of triptolide for antirheumatoid activity with reduced toxicity in vitro and in vivo

Triptolide (TP) displays a strong immunosuppression function in immune-mediated diseases, especially in the treatment of rheumatoid arthritis. However, in addition to its medical and health-related functions, TP also exhibits diverse pharmacological side effects, for instance, liver and kidney toxicity and myelosuppression. In order to reduce the side effects, a nano drug carrier system (γ-PGA-l-PAE-TP [PPT]), in which TP was loaded by a poly-γ-glutamic acid-grafted l-phenylalanine ethylester copolymer, was developed. PPT was characterized by photon scattering correlation spectroscopy and transmission electron microscopy, which demonstrated that the average diameter of the drug carrier system is 98±15 nm, the polydispersity index is 0.18, the zeta potential is −35 mV, and the TP encapsulation efficiency is 48.6% with a controlled release manner. The methylthiazolyldiphenyl-tetrazolium bromide assay and flow cytometry revealed that PPT could decrease toxicity and apoptosis induced by free TP on RAW264.7 cells, respectively. The detection of reactive oxygen species showed that PPT could decrease the cellular reactive oxygen species induced by TP. Compared with the free TP-treated group, PPT improved the survival rate of the mice (P<0.01) and had no side effects or toxic effects on the thymus index (P>0.05) and spleen index (P>0.05). The blood biochemical indexes revealed that PPT did not cause much damage to the kidney (blood urea nitrogen and creatinine), liver (serum alanine aminotransferase and aspartate aminotransferase), or blood cells (P>0.05). Meanwhile, hematoxylin and eosin staining and terminal-deoxynucleotidyl transferase dUTP nick-end labeling staining indicated that PPT reduced the damage of free TP on the liver, kidney, and spleen. Our results demonstrated that PPT reduced free TP toxicity in vitro and in vivo and that it is a promising fundamental drug delivery system for rheumatoid arthritis treatment.

Increased involvement of Panax notoginseng in the mechanism of decreased hepatotoxicity induced by Tripterygium wilfordii in rats

ETHNOPHARMACOLOGICAL RELEVANCE

The key problem with toxic Chinese herbs in clinical applications is how to find the most effective method to reduce toxicity. This study focuses on discussing the mechanism of decreased hepatotoxicity by the usage compatibility of two commonly used traditional Chinese drugs that are used clinically: Tripterygium wilfordii Hook. f. (TW) and Panax notoginseng (Burkill) F.H. Chen (PN). Additionally, based on the results from using metabonomics technology, the usage compatibility with these two herbs that was originated from clinical experience is the first to clarify the rationality of the drug combination.

MATERIALS AND METHODS

Through a fast and effective HPLC method, plasma concentration-time profiles and triptolide distribution characteristics in liver, heart, spleen, lung and kidney tissues were simultaneously determined in rats after oral administration of the aqueous extract of TW and TW-PN. The reduced hepatotoxicity data of the usage compatibility with TW and PN were also investigated, and then a UHPLC-QTOF/MS method was developed and validated for the explanation of the reduced hepatotoxicity mechanism.

RESULTS

It was indicated that nine endogenous metabolites might be potential biomarkers for hepatotoxicity induced by TW. In addition, the plasma concentration-time profiles and the distribution characteristics of TP in rats were changed after oral administration of the aqueous extract of TW-PN, and simultaneously, the hepatotoxicity was obviously decreased.

CONCLUSIONS

The results indicated that usage compatibility with TW and PN was reasonable in clinical use. To the best of our knowledge, this is the first report to describe the mechanism of reducing hepatotoxicity with the combined use of TW and PN from clinical experience.

Development and application of a comprehensive lipidomic analysis to investigate Tripterygium wilfordii-induced liver injury

Lipid metabolic pathways play pivotal roles in liver function, and disturbances of these pathways are associated with various diseases. Thus, comprehensive characterization and measurement of lipid metabolites are essential to deciphering the contributions of lipid network metabolism to diseases or its responses to drug intervention. Here, we report an integrated lipidomic analysis for the comprehensive detection of lipid metabolites. To facilitate the characterization of untargeted lipids through fragmentation analysis, nine formulas were proposed to identify the fatty acid composition of lipids from complex MS (n) spectrum information. By these formulas, the co-eluted isomeric compounds could be distinguished. In total, 250 lipids were detected and characterized, including diacylglycerols, triacylglycerols, glycerophosphoethanolamines, glycerophosphocholines, glycerophosphoserines, glycerophosphoglycerols, glycerophosphoinositols, cardiolipins, ceramides, and sphingomyelins. Integrated with the targeted lipidomics, a total of 27 inflammatory oxylipins were also measured. To evaluate the aberrant lipid metabolism involved in liver injury induced by Tripterygium wilfordii, lipid network metabolism was further investigated. Results indicated that energy lipid modification, membrane remodeling, potential signaling lipid alterations, and abnormal inflammation response were associated with injury. Because of the important roles of lipids in liver metabolism, this new method is expected to be useful in analyzing other lipid metabolism diseases.

Sex-Related Differences of Lipid Metabolism Induced by Triptolide: The Possible Role of the LXRα/SREBP-1 Signaling Pathway

Triptolide, a diterpenoid isolated from the plant Tripterygium wilfordii Hook. f., exerts a unique bioactive spectrum of anti-inflammatory and anticancer activities. However, triptolide's clinical applications are limited due to its severe toxicities. Fatty liver toxicity occurs in response to triptolide, and this toxic response significantly differs between males and females. This report investigated the pathogenesis underlying the sex-related differences in the dyslipidosis induced by triptolide in rats. Wistar rats were administered 0, 150, 300, or 450 μg triptolide/kg/day by gavage for 28 days. Ultrastructural examination revealed that more lipid droplets were present in female triptolide-treated rats than in male triptolide-treated rats. Furthermore, liver triglyceride, total bile acid and free fatty acid levels were significantly increased in female rats in the 300 and 450 μg/kg dose groups. The expression of liver X receptor α (LXRα) and its target genes, cholesterol 7α-hydroxylase (CYP7A1) and Sterol regulatory element-binding transcription factor 1(SREBP-1), increased following triptolide treatment in both male and female rats; however, the female rats were more sensitive to triptolide than the male rats. In addition, the expression of acetyl-CoA carboxylase 1(ACC1), a target gene of SREBP-1, increased in the female rats treated with 450 μg triptolide/kg/day, and ACC1 expression contributed to the sex-related differences in the triptolide-induced dysfunction of lipid metabolism. Our results demonstrate that the sex-related differences in LXR/SREBP-1-mediated regulation of gene expression in rats are responsible for the sex-related differences in lipid metabolism induced by triptolide, which likely underlie the sex-related differences in triptolide hepatotoxicity. This study will be important for predicting sex-related effects on the pharmacokinetics and toxicity of triptolide and for improving its safety.

The HepaRG cell line, a superior in vitro model to L-02, HepG2 and hiHeps cell lines for assessing drug-induced liver injury

Drug-induced liver injury (DILI) is a leading cause of discontinuation of new drug approval or withdrawal of marketed medicine based on safety due to organ vulnerability. The aim of this research is to investigate the potential abilities of four different in vitro cell models (L-02, HepG2, HepaRG, and hiHeps cell lines) in assessing marketed drugs labeled with apparently different types of liver injury. A total of 17 drugs with versatile pharmacological profiles were chosen, of which, 14 drugs are recognized as DILI agents and 3 drugs are DILI irrelevant. Preliminary cellular screening assays indicated that the HepaRG cell line had an advantage over other cell lines in predicting drugs associated with DILI in vitro as it had the highest Youden's index (71.4%). A multi-parametric screening assay showed that oxidative stress, mitochondrial damage, and disorders of neutral lipid metabolism were changed notably in the HepaRG cell line after DILI-related drugs exposure, accounting for its high sensitivity in comparison with other three cell lines. In addition, aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and malate dehydrogenase (MDH) all correlated with the cytotoxic effects of diclofenac sodium (p < 0.05), buspirone hydrochloride (p < 0.01), and danazol (p < 0.01) in the HepaRG cell line. We conclude that the HepaRG cell line is a superior in vitro cell model to other three cell lines for evaluating drugs with DILI potential.

The Protective Effects of Isoliquiritigenin and Glycyrrhetinic Acid against Triptolide-Induced Oxidative Stress in HepG2 Cells Involve Nrf2 Activation

Triptolide (TP), an active ingredient of Tripterygium wilfordii Hook f., possesses a wide range of biological activities. Oxidative stress likely plays a role in TP-induced hepatotoxicity. Isoliquiritigenin (ISL) and glycyrrhetinic acid (GA) are potent hepatoprotection agents. The aim of the present study was to investigate whether Nrf2 pathway is associated with the protective effects of ISL and GA against TP-induced oxidative stress or not. HepG2 cells were treated with TP (50 nM) for 24 h after pretreatment with ISL and GA (5, 10, and 20 μM) for 12 h and 24 h, respectively. The results demonstrated that TP treatment significantly increased ROS levels and decreased GSH levels. Both ISL and GA pretreatment decreased ROS and meanwhile enhanced intracellular GSH content. Additionally, TP treatment obviously decreased the protein expression of Nrf2 and its target genes including HO-1 and MRP2 except NQO1. Moreover, both ISL and GA displayed activities as inducers of Nrf2 and increased the expression of HO-1, NQO1, and MRP2. Taken together the current data confirmed that ISL and GA could activate the Nrf2 antioxidant response in HepG2 cells, increasing the expression of its target genes which may be partly associated with their protective effects in TP-induced oxidative stress.

Inhibition of P-glycoprotein Gene Expression and Function Enhances Triptolide-induced Hepatotoxicity in Mice

Triptolide (TP) is the major active principle of Tripterygium wilfordii Hook f. and very effective in treatment of autoimmune diseases. However, TP induced hepatotoxicity limited its clinical applications. Our previous study found that TP was a substrate of P-glycoprotein and its hepatobiliary clearance was markedly affected by P-gp modulation in sandwich-cultured rat hepatocytes. In this study, small interfering RNA (siRNA) and specific inhibitor tariquidar were used to investigate the impact of P-gp down regulation on TP-induced hepatotoxicity. The results showed that when the function of P-gp was inhibited by mdr1a-1 siRNA or tariquidar, the systemic and hepatic exposures of TP were significantly increased. The aggravated hepatotoxicity was evidenced with the remarkably lifted levels of serum biomarkers (ALT and AST) and pathological changes in liver. The other toxicological indicators (MDA, SOD and Bcl-2/Bax) were also significantly changed by P-gp inhibition. The data analysis showed that the increase of TP exposure in mice was quantitatively correlated to the enhanced hepatotoxicity, and the hepatic exposure was more relevant to the toxicity. P-gp mediated clearance played a significant role in TP detoxification. The risk of herb-drug interaction likely occurs when TP is concomitant with P-gp inhibitors or substrates in clinic.

Autophagy plays an important role in triptolide-induced apoptosis in cardiomyocytes

Triptolide (TP), a major bioactive component isolated from the traditional Chinese herb Tripterygium wilfordii Hook f. (TWHF), has been shown to exert various pharmacological effects. However, the severe toxicity of TP prevents wide clinical use. In a previous study, we reported that TP-induced mitochondria-dependent apoptosis in cardiomyocytes is mediated by reactive oxygen species (ROS). Autophagy is a cellular self-digestion process and is one of the first lines of defense against oxidative stress. Additionally, recent evidence suggests that autophagy can selectively eliminate damaged mitochondria. This study investigated the role of autophagy in TP-induced cardiotoxicity. We investigated the effects of autophagy in combination with TP on apoptosis, ROS and mitochondrial function. Rat cardiomyocytes were pre-treated with chloroquine or rapamycin followed by TP. The augmentation of autophagy with rapamycin in the presence of TP substantially ameliorated the detrimental effects induced by TP, while suppression of autophagy by chloroquine accelerates TP-induced cellular damage. In addition, pre-treated with rapamycin before TP administration also attenuated TP-induced damage in Balb/c mice heart tissues. Taken together, these results suggest that TP-induced cell death can be modified by autophagy. Furthermore, induction of autophagy by rapamycin may be a potential cardioprotective role against TP-induced cardiotoxicity by facilitating removal of dysfunctional mitochondria.

Tripterygium glycosides induce premature ovarian failure in rats by promoting p53 phosphorylation and activating the serine/threonine kinase 11-p53-p21 signaling pathway

Premature ovarian failure (POF) is a typical pathological disease of the reproductive system in aging females. Infection, inflammation, immune abnormalities, genetic mutation, radiotherapy and chemotherapy can cause POF. Tripterygium glycosides (TGs) are a component extracted from the Chinese herb Tripterygium wilfordii Hook. f., also known as Huangteng. Although TGs have been used to treat various diseases, drug resistance and toxicity can affect patients. The aim of the present study was to investigate the mechanism of TG-induced POF in rats. The rats were treated with different concentrations of TG, and pathology assays showed that the TG-induced POF was predominantly composed of interstitial cells in a fibrous matrix with a reduced number of follicles at each stage and an increased number of collapsed oocytes. Furthermore, reverse transcription-quantitative polymerase chain reaction (PCR) and immunohistochemistry assays indicated that the expression levels of serine/threonine kinase 11 (Stk11), p53 p21 and activated caspase-3 were elevated significantly in the TG-treated groups. Serine 15 phosphorylation of p53 was also enhanced significantly in the TG-treated groups. In addition, a chromatin immunoprecipitation-PCR assay revealed that the TGs induced p53 activation and enhanced the transcription of p21. In conclusion, TGs induce apoptosis and necrosis in rat ovarian tissues, as well as POF, via p53 phosphorylation and activation of the Stk11-p53-p21 signaling pathway.

Absorption and Metabolism Characteristics of Triptolide as Determined by a Sensitive and Reliable LC-MS/MS Method

In this research, a sensitive and reliable LC-MS/MS method was developed and applied to determine the concentration of triptolide in rat plasma, microsomes, and cell incubation media. The absolute oral bioavailability of triptolide is 63.9% at a dose of 1 mg·kg⁻¹. In vitro, the bidirectional transport of triptolide across Caco-2 cells was studied. A markedly higher transport of triptolide across Caco-2 cells was observed in the basolateral-to-apical direction and was abrogated in the presence of the P-gp inhibitor, verapamil. The result indicated that P-gp might be involved in the absorption of triptolide in intestinal. The metabolic stability was also investigated using human liver microsome incubation systems in vitro. In HLMs, incubations with an initial triptolide concentration of 1 μM resulted in an 82.4% loss of substrate over 60 min, and the t_1/2 was 38 min, which indicated that triptolide was easily metabolized in human liver microsomes. In conclusion, the absolute oral bioavailability of triptolide in plasma, transport across Caco-2 cell monolayers, and metabolic stability in human liver microsomes were systematically investigated by using a sensitive and reliable LC-MS/MS method.

Triptolide improves systolic function and myocardial energy metabolism of diabetic cardiomyopathy in streptozotocin-induced diabetic rats

BACKGROUND

Triptolide treatment leads to an improvement in Diabetic Cardiomyopathy (DCM) in streptozotocin-induced diabetic rat model. DCM is characterized by abnormal cardiac energy metabolism. We hypothesized that triptolide ameliorated cardiac metabolic abnormalities in DCM. We proposed (31)P nuclear magnetic resonance ((31)P NMR) spectrometry method for assessing cardiac energy metabolism in vivo and evaluating the effect of triptolide treatment in DCM rats.

METHODS

Six weeks triptolide treatment was conducted on streptozotocin-induced diabetic rats with dose of 100, 200 or 400 μg/kg/day respectively. Sex- and age-matched non-diabetic rats were used as control group. Cardiac chamber dimension and function were determined with echocardiography. Whole heart preparations were perfused with Krebs-Henseleit buffer and (31)P NMR spectroscopy was performed. Cardiac p38 Mitogen Activating Protein Kinase (MAPK) was measured using real time PCR and western blot analysis.

RESULTS

In diabetic rats, cardiac mass index was significantly higher, where as cardiac EF was lower than control group. (31)P NMR spectroscopy showed that ATP and pCr concentrations in diabetic groups were also remarkably lower than control group. Compared to non-treated diabetic rats, triptolide-treated diabetic groups showed remarkable lower cardiac mass index and higher EF, ATP, pCr concentrations, and P38 MAPK expressions. Best improvement was seen in group treated with Triptolide with dose 200 μg/kg/day.

CONCLUSIONS

(31)P NMR spectroscopy enables assessment of cardiac energy metabolism in whole heart preparations. It detects energy metabolic abnormalities in DCM hearts. Triptolide therapy improves cardiac function and increases cardiac energy metabolism at least partly through upregulation of MAPK signaling transduction.

Triptolide ameliorates colonic fibrosis in an experimental rat model

Triptolide is known to exert anti-inflammatory and immunomodulatory activities; however, its impact on intestinal fibrosis has not been previously examined. Based on our previous studies of the suppressive activity of triptolide on human colonic subepithelial myofibroblasts and the therapeutic efficacy of triptolide in Crohn's disease, it was hypothesized that triptolide may have beneficial effects on intestinal fibrosis. In the present study, colonic fibrosis was induced in rats by 6 weekly repeated administration with a low-dose of 2,4,6-trinitrobenzene sulfonic acid (TNBS) and was then treated with triptolide or PBS daily (control) simultaneously. Extracellular matrix (ECM) deposition in the colon was examined with image analysis of Masson Trichrome staining. Total collagen levels in colonic homogenates were measured by a Sircol assay. Collagen Iα1 transcripts and collagen I protein were measured ex vivo in the isolated colonic subepithelial myofibroblasts by reverse transcription-quantitative polymerase chain reaction and immunoblot analysis, respectively. The results indicated that triptolide decreased ECM deposition and collagen production in the colon, and inhibited collagen Iα1 transcripts and collagen I protein expression in the isolated subepithelial myofibroblasts of the rats with colonic fibrosis. In conclusion, triptolide ameliorates colonic fibrosis in the experimental rat model, suggesting triptolide may be a promising compound for inflammatory bowel disease treatment.

Investigation of the active components in Tripterygium wilfordii leading to its acute hepatotoxicty and nephrotoxicity

ETHNOPHARMACOLOGICAL RELEVANCE

The traditional herbal medicine Tripterygium wilfordii Hook. f. (TW) has been widely used for the treatment of rheumatoid arthritis and autoimmune disease in the clinic. However, adverse reactions of TW including hepatotoxicity and nephrotoxicity have been frequently reported. Terpenes and alkaloids are among the most important active components in TW. Triptolide (TP), a major terpene in TW, has been found to induce toxicity, and metabolic pathways could lead to detoxification of TP. In this study, whether other major terpenes or alkaloids in TW contribute to its toxicity was investigated. The role of metabolic eliminations in their potential detoxification process was also evaluated.

MATERIALS AND METHODS

The toxicity of TW and its five major active components (one terpene and four alkaloids) in mice was evaluated in terms of mortality and blood biochemical levels (ALT, AST, BUN and CREA). TP was used as a positive control. Metabolic pathways leading to potential detoxification of TW or its two representative components (triptonide and wilforgine) were evaluated in glutathione (GSH)-depleted (treated with L-buthionine-S,R-sulfoxinine, BSO) and aminobenzotriazole (ABT; a nonspecific inhibitor for P450s)-treated mice.

RESULTS

In normal mice, the major metabolic pathways for the terpene compounds TP and triptonide (TN) were hydroxylation and cysteine conjugation, and the alkaloid wilforgine (WG) mainly underwent oxidative metabolism and hydrolysis. In ABT/BSO-treated mice, the hydroxylated metabolites of TP, TN and WG were found at a lower level than normal mice, and the level of cysteine conjugates of TN increased probably due to the stress response. Compared with normal mice, mortality and levels of ALT (but not BUN) were significantly higher (P<0.01) in TW (or TP)-treated mice (1.2 mg kg(-1)), indicating the acute toxicity (may not nephrotoxicity) of TW and its active component TP. Pretreatment with ABT and/or BSO increased the acute toxicity (including hepatotoxicity and nephrotoxicity) caused by TW or TP. No significant toxicity was found for TN or four alkaloids in normal mice or ABT/BSO-treated mice.

CONCLUSIONS

TP was probably the main contributor to the toxicity of TW, and the terpene TN and alkaloids in TW may be of no toxicological concern at dosage levels up to 20-fold of the therapeutic dose. Metabolic eliminations to less reactive metabolites implied a high potential for detoxification of TW, and caution should be taken for TW clinical use during co-administration with other CYP inhibitors or GSH-depleting agents.

Combination treatment with triptolide and hydroxycamptothecin synergistically enhances apoptosis in A549 lung adenocarcinoma cells through PP2A-regulated ERK, p38 MAPKs and Akt signaling pathways

Lung cancer is the leading cause of cancer death worldwide. Recently, two plant-derived drugs triptolide (TP) and hydroxycamptothecin (HCPT) both have shown broad-spectrum anticancer activities. Our previous study documented that combination treatment with these two drugs acted more effectively than mono-therapy, however, the molecular basis underlying the synergistic cytotoxicity remains poorly understood. In this study, we aimed to clarify the molecular mechanism of TP/HCPT anticancer effect in A549 lung adenocarcinoma cells, by investigating the involvement of phosphatase 2A (PP2A) and PP2A-regulated mitogen-activated protein kinases (MAPKs) and Akt signaling pathways. The results showed that TP and HCPT synergistically exerted cytotoxicity in the growth of A549 cells. Combinatorial TP/HCPT treatment significantly enhanced the activation of caspase-3 and -9, Bax/Bcl-2 ratio, release of cytochrome c from mitochondrial and subsequent apoptosis. While the Akt survival pathway was inhibited, ERK and p38 MAPKs were dramatically activated. Furthermore, the activity of PP2A was significantly augmented. Regulation of p38, ERK and Akt by PP2A was demonstrated, by using a specific PP2A inhibitor okadaic acid (OA). Finally, pharmacological inhibitors OA, SB203580, SP600125 and PD98059 confirm the role of PP2A and its substrates ERK, p38 MAPK and Akt in mediating TP/HCPT-induced apoptosis. Taken together, this study provides the first evidence for a synergistic TP/HCPT anti-cancer activity in A549 cells and also supports a critical role of PP2A and PP2A-regulated signaling pathways, providing new insight into the mode of action of TP/HCPT in cancer therapy.

Aromatic abietane diterpenoids: their biological activity and synthesis

In this study, the biological properties of abietane-type diterpenoids with an aromatic C ring are reviewed. The review contains about 160 references.

Triptolide suppresses airway goblet cell hyperplasia and Muc5ac expression via NF-κB in a murine model of asthma

BACKGROUND

We have reported that triptolide inhibited pulmonary inflammation in patients with steroid-resistant asthma. In the present study, we investigated whether suppresses airway remodeling and goblet cell hyperplasia, studied the mechanism of triptolide on mucin5ac (Muc5ac) expression in a murine model of asthma.

METHODS

BALB/c mice were sensitized to intraperitoneal ovalbumin (OVA) followed by repetitive ovalbumin challenge for 6 weeks. Treatments included triptolide (40 μg/kg) and dexamethasone (2mg/kg). The area of bronchial airway (WAt/Pbm), smooth muscle (WAm/Pbm) and mucus index were assessed 24h after the final OVA challenge. Levels of Muc5ac were assessed by ELISA, immunohistology and real-time PCR. Western blot was performed to analyze the phosphorylation of NF-κB p65.

RESULTS

Triptolide and dexamethasone significantly reduced allergen-induced increases in the thickness of bronchial airway, smooth muscle and goblet cell hyperplasia. Levels of lung Muc5ac and Muc5ac mRNA were significantly reduced in mice treated with triptolide and dexamethasone. Phosphorylation of NF-κB p65 was significantly reduced in mice treated with triptolide and dexamethasone.

CONCLUSION

Triptolide may inhibit airway goblet cell hyperplasia and Muc5ac expression in asthmatic mice via NF-κB. It may be a potential drug for the treatment of patients with severe asthma.

Triptolide inhibits TGF-β1-induced cell proliferation in rat airway smooth muscle cells by suppressing Smad signaling

BACKGROUND

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

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.

RESULTS

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.