Celastrol induces mitochondria-mediated apoptosis in hepatocellular carcinoma Bel-7402 cells

Withaferin A and Celastrol Overwhelm Proteostasis

Withaferin A (WA) and celastrol (CEL) are major bioactive components of plants that have been widely employed in traditional medicine. The pleiotropic activities of plant preparations and the isolated compounds in vitro and in vivo have been documented in hundreds of studies. Both WA and CEL were shown to have anticancer activity. Although WA and CEL belong to different chemical classes, our synthesis of the available information suggests that the compounds share basic mechanisms of action. Both WA and CEL bind covalently to numerous proteins, causing the partial unfolding of some of these proteins and of many bystander proteins. The resulting proteotoxic stress, when excessive, leads to cell death. Both WA and CEL trigger the activation of the unfolded protein response (UPR) which, if the proteotoxic stress persists, results in apoptosis mediated by the PERK/eIF-2/ATF4/CHOP pathway or another UPR-dependent pathway. Other mechanisms of cell death may play contributory or even dominant roles depending on cell type. As shown in a proteomic study with WA, the compounds appear to function largely as electrophilic reactants, indiscriminately modifying reachable nucleophilic amino acid side chains of proteins. However, a remarkable degree of target specificity is imparted by the cellular context.

The development and evaluation of hyaluronic acid coated mitochondrial targeting liposomes for celastrol delivery

In order to precisely deliver celastrol into mitochondria of tumor cells, improve antitumor efficacy of celastrol and overcome its troublesome problems in clinical application, a novel multistage-targeted celastrol delivery system (C-TL/HA) was developed via electrostatic binding of hyaluronic acid (HA) to celastrol-loaded cationic liposomes composed of natural soybean phosphatidylcholine and cholesterol modified with mitochondrial targeting molecular TPP. Study results in this article showed that C-TL/HA successfully transported celastrol into mitochondria, effectively activated apoptosis of mitochondrial pathway, exerted higher tumor inhibition efficiency and lower toxic side effects compared with free celastrol. More importantly, HA coating not only enabled this delivery system to have good stability and safety in vivo, but also increased drug uptake and facilitated tumor targeting through recognizing CD44 receptors rich on the surface of tumor cells. Conclusively, this HA-coated mitochondrial targeting liposomes may provide a prospect for the clinical application of celastrol in tumor therapy.

Mechanistic engineering of celastrol liposomes induces ferroptosis and apoptosis by directly targeting VDAC2 in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of most common and deadliest malignancies. Celastrol (Cel), a natural product derived from the Tripterygium wilfordii plant, has been extensively researched for its potential effectiveness in fighting cancer. However, its clinical application has been hindered by the unclear mechanism of action. Here, we used chemical proteomics to identify the direct targets of Cel and enhanced its targetability and anti-tumor capacity by developing a Cel-based liposomes in HCC. We demonstrated that Cel selectively targets the voltage-dependent anion channel 2 (VDAC2). Cel directly binds to the cysteine residues of VDAC2, and induces cytochrome C release via dysregulating VDAC2-mediated mitochondrial permeability transition pore (mPTP) function. We further found that Cel induces ROS-mediated ferroptosis and apoptosis in HCC cells. Moreover, coencapsulation of Cel into alkyl glucoside-modified liposomes (AGCL) improved its antitumor efficacy and minimized its side effects. AGCL has been shown to effectively suppress the proliferation of tumor cells. In a xenograft nude mice experiment, AGCL significantly inhibited tumor growth and promoted apoptosis. Our findings reveal that Cel directly targets VDAC2 to induce mitochondria-dependent cell death, while the Cel liposomes enhance its targetability and reduces side effects. Overall, Cel shows promise as a therapeutic agent for HCC.

Celastrol as an emerging anticancer agent: Current status, challenges and therapeutic strategies

Celastrol is a pentacyclic triterpenoid extracted from the traditional Chinese medicine Tripterygium wilfordii Hook F., which has multiple pharmacological activities. In particular, modern pharmacological studies have demonstrated that celastrol exhibits significant broad-spectrum anticancer activities in the treatment of a variety of cancers, including lung cancer, liver cancer, colorectal cancer, hematological malignancies, gastric cancer, prostate cancer, renal carcinoma, breast cancer, bone tumor, brain tumor, cervical cancer, and ovarian cancer. Therefore, by searching the databases of PubMed, Web of Science, ScienceDirect and CNKI, this review comprehensively summarizes the molecular mechanisms of the anticancer effects of celastrol. According to the data, the anticancer effects of celastrol can be mediated by inhibiting tumor cell proliferation, migration and invasion, inducing cell apoptosis, suppressing autophagy, hindering angiogenesis and inhibiting tumor metastasis. More importantly, PI3K/Akt/mTOR, Bcl-2/Bax-caspase 9/3, EGFR, ROS/JNK, NF-κB, STAT3, JNK/Nrf2/HO-1, VEGF, AR/miR-101, HSF1-LKB1-AMPKα-YAP, Wnt/β-catenin and CIP2A/c-MYC signaling pathways are considered as important molecular targets for the anticancer effects of celastrol. Subsequently, studies of its toxicity and pharmacokinetic properties showed that celastrol has some adverse effects, low oral bioavailability and a narrow therapeutic window. In addition, the current challenges of celastrol and the corresponding therapeutic strategies are also discussed, thus providing a theoretical basis for the development and application of celastrol in the clinic.

A comprehensive review on celastrol, triptolide and triptonide: Insights on their pharmacological activity, toxicity, combination therapy, new dosage form and novel drug delivery routes

Celastrol, triptolide and triptonide are the most significant active ingredients of Tripterygium wilfordii Hook F (TWHF). In 2007, the 'Cell' journal ranked celastrol, triptolide, artemisinin, capsaicin and curcumin as the five natural drugs that can be developed into modern medicinal compounds. In this review, we collected relevant data from the Web of Science, PubMed and China Knowledge Resource Integrated databases. Some information was also acquired from government reports and conference papers. Celastrol, triptolide and triptonide have potent pharmacological activity and evident anti-cancer, anti-tumor, anti-obesity and anti-diabetes effects. Because these compounds have demonstrated unique therapeutic potential for acute and chronic inflammation, brain injury, vascular diseases, immune diseases, renal system diseases, bone diseases and cardiac diseases, they can be used as effective drugs in clinical practice in the future. However, celastrol, triptolide and triptonide have certain toxic effects on the liver, kidney, cholangiocyte heart, ear and reproductive system. These shortcomings limit their clinical application. Suitable combination therapy, new dosage forms and new routes of administration can effectively reduce toxicity and increase the effect. In recent years, the development of different targeted drug delivery formulations and administration routes of celastrol and triptolide to overcome their toxic effects and maximise their efficacy has become a major focus of research. However, in-depth investigation is required to elucidate the mechanisms of action of celastrol, triptolide and triptonide, and more clinical trials are required to assess the safety and clinical value of these compounds.

Celastrol: An Update on Its Hepatoprotective Properties and the Linked Molecular Mechanisms

The liver plays an important role in glucose and lipid homeostasis, drug metabolism, and bile synthesis. Metabolic disorder and inflammation synergistically contribute to the pathogenesis of numerous liver diseases, such as metabolic-associated fatty liver disease (MAFLD), liver injury, and liver cancer. Celastrol, a triterpene derived from Tripterygium wilfordii Hook.f., has been extensively studied in metabolic and inflammatory diseases during the last several decades. Here we comprehensively review the pharmacological activities and the underlying mechanisms of celastrol in the prevention and treatment of liver diseases including MAFLD, liver injury, and liver cancer. In addition, we also discuss the importance of novel methodologies and perspectives for the drug development of celastrol. Although celastrol has been claimed as a promising agent against several metabolic diseases, both preclinical and clinical studies are highly required to accelerate the clinical transformation of celastrol in treating different liver illness. It is foreseeable that celastrol-derived therapeutics is evolving in the field of liver ailments.

Recent Progress in Understanding the Action of Natural Compounds at Novel Therapeutic Drug Targets for the Treatment of Liver Cancer

Liver cancer is the third most common cause of cancer-related death following lung and stomach cancers. As a highly lethal disease, liver cancer is diagnosed frequently in less developed countries. Natural compounds extracted from herbs, animals and natural materials have been adopted by traditional Chinese medicine (TCM) practices and reported to be effective in the development of new medications for the treatment of diseases. It is important to focus on the mechanisms of action of natural compounds against hepatocellular carcinoma (HCC), particularly in terms of cell cycle regulation, apoptosis induction, autophagy mediation and cell migration and invasion. In this review, we characterize novel representative natural compounds according to their pharmacologic effects based on recently published studies. The aim of this review is to summarize and explore novel therapeutic drug targets of natural compounds, which could accelerate the discovery of new anticancer drugs.

Tripterygium hypoglaucum (Lévl.) Hutch and Its Main Bioactive Components: Recent Advances in Pharmacological Activity, Pharmacokinetics and Potential Toxicity

Tripterygium hypoglaucum (Lévl.) Hutch (THH) is believed to play an important role in health care and disease treatment according to traditional Chinese medicine. Moreover, it is also the representative of medicine with both significant efficacy and potential toxicity. This characteristic causes THH hard for embracing and fearing. In order to verify its prospect for clinic, a wide variety of studies were carried out in the most recent years. However, there has not been any review about THH yet. Therefore, this review summarized its characteristic of components, pharmacological effect, pharmacokinetics and toxicity to comprehensively shed light on the potential clinical application. More than 120 secondary metabolites including terpenoids, alkaloids, glycosides, sugars, organic acids, oleanolic acid, polysaccharides and other components were found in THH based on phytochemical research. All these components might be the pharmacological bases for immunosuppression, anti-inflammatory and anti-tumour effect. In addition, recent studies found that THH and its bioactive compounds also demonstrated remarkable effect on obesity, insulin resistance, fertility and infection of virus. The main mechanism seemed to be closely related to regulation the balance of immune, inflammation, apoptosis and so on in various disease. Furthermore, the study of pharmacokinetics revealed quick elimination of the main component triptolide. The feature of celastrol was also investigated by several models. Finally, the side effect of THH was thought to be the key for its limitation in clinical application. A series of reports indicated that multiple organs or systems including liver, kidney and genital system were involved in the toxicity. Its potential serious problem in liver was paid specific attention in recent years. In summary, considering the significant effect and potential toxicity of THH as well as its components, the combined medication to inhibit the toxicity, maintain effect might be a promising method for clinical conversion. Modern advanced technology such as structure optimization might be another way to reach the efficacy and safety. Thus, THH is still a crucial plant which remains for further investigation.

Recent progress in nanotechnology-based drug carriers for celastrol delivery

Celastrol (CLT) is an active ingredient that was initially discovered and extracted from the root of Tripterygium wilfordii. The potential pharmacological activities of CLT in cancer, obesity, and inflammatory, auto-immune, and neurodegenerative diseases have been demonstrated in recent years. However, CLT's clinical application is extremely restricted by its low solubility/permeability, poor bioavailability, and potential off-target toxicity. The advent of nanotechnology provides a solution to improve the oral bioavailability, therapeutic effects or tissue-targeting ability of CLT. This review focuses on the most recent advances, improvements, inventions, and updated literature of various nanocarrier systems for CLT.

Anti-Tumor Effect of Celastrol on Hepatocellular Carcinoma by the circ_SLIT3/miR-223-3p/CXCR4 Axis

Background

Celastrol is a potential anti-tumor agent in hepatocellular carcinoma (HCC). Identifying the molecular determinants of the anti-HCC effect of celastrol is still challenging. In this study, we undertook to associate circular RNAs (circRNAs) with the anti-HCC molecular determinants of celastrol.

Methods

Cell colony formation, proliferation, migration, invasion and apoptosis were determined using the colony formation, 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-2H-tetrazolium bromide (MTS), transwell and flow cytometry assays, respectively. The levels of circRNA slit guidance ligand 3 (circ_SLIT3), miR-223-3p and C-X-C motif chemokine receptor 4 (CXCR4) were gauged by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blot. Ribonuclease R (RNase R) and actinomycin D assays were performed to assess the stability of circ_SLIT3. Targeted relationships among circ_SLIT3, miR-223-3p and CXCR4 were confirmed by the dual-luciferase reporter assay. In vivo assays were performed to detect the roles of celastrol and circ_SLIT3 on tumor growth in vivo.

Results

Celastrol repressed HCC cell proliferation, migration, invasion, and enhanced apoptosis in vitro and suppressed tumor growth in vivo. Celastrol down-regulated circ_SLIT3 expression in HCC cells, and celastrol exerted an anti-tumor effect on HCC in vitro and in vivo by down-regulating circ_SLIT3. Mechanistically, circ_SLIT3 directly interacted with miR-223-3p, and circ_SLIT3 controlled CXCR4 expression by sponging miR-223-3p. Moreover, miR-223-3p was involved in the celastrol/circ_SLIT3-mediated regulation on HCC progression. Furthermore, celastrol exerted the anti-HCC effect in vitro through the miR-223-3p/CXCR4 axis.

Conclusion

Our present work first identified the circ_SLIT3/miR-223-3p/CXCR4 axis as a novel mechanism of the anti-HCC effect of celastrol, providing a new insight into the involvement of circRNAs in the anti-tumor molecular determinants of celastrol.

Biosynthesis, total synthesis, structural modifications, bioactivity, and mechanism of action of the quinone-methide triterpenoid celastrol

Celastrol, a quinone-methide triterpenoid, was extracted from Tripterygium wilfordii Hook. F. in 1936 for the first time. Almost 70 years later, it is considered one of the molecules most likely to be developed into modern drugs, as it exhibits notable bioactivity, including anticancer and anti-inflammatory activity, and exerts antiobesity effects. In addition, the molecular mechanisms underlying its bioactivity are being widely studied, which offers new avenues for its development as a pharmaceutical reagent. Owing to its potential therapeutic effects and unique chemical structure, celastrol has attracted considerable interest in the fields of organic, biosynthesis, and medicinal chemistry. As several steps in the biosynthesis of celastrol have been revealed, the mechanisms of key enzymes catalyzing the formation and postmodifications of the celastrol scaffold have been gradually elucidated, which lays a good foundation for the future heterogeneous biosynthesis of celastrol. Chemical synthesis is also an effective approach to obtain celastrol. The total synthesis of celastrol was realized for the first time in 2015, which established a new strategy to obtain celastroid natural products. However, owing to the toxic effects and suboptimal pharmacological properties of celastrol, its clinical applications remain limited. To search for drug-like derivatives, several structurally modified compounds were synthesized and tested. This review focuses primarily on the latest research progress in the biosynthesis, total synthesis, structural modifications, bioactivity, and mechanism of action of celastrol. We anticipate that this paper will facilitate a more comprehensive understanding of this promising compound and provide constructive references for future research in this field.

Selective and sensitive determination of celastrol in traditional Chinese medicine based on molecularly imprinted polymers modified Mn-doped ZnS quantum dots optosensing materials

In this work, we proposed a facile strategy to prepare molecularly imprinted polymers (MIPs) modified Mn-doped ZnS quantum dots (QDs) as optosensing materials via sol-gel polymerization for specific recognition of celastrol (Cel) in traditional Chinese medicine (TCM). Firstly, L-Cysteine (L-Cys) modified Mn-doped ZnS QDs (L-Cys@Mn-ZnS) was used as imprinting substrate. The amino and carboxyl groups on the surface of Mn-ZnS QDs can provide more binding sites for imprinting polymerization. Then, the fluorescent MIPs was synthesized in the presence of L-Cys@Mn-ZnS QDs, template celastrol, 3-aminopropyl triethoxysilane (APTES) and ammonium hydroxide in the ethanol-water (9/1, v/v) solution. The morphology and structure of the products were characterized by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS). The resulting MIPs functionalized Mn-doped ZnS QDs (denoted as MIPs@L-Cys@Mn-ZnS QDs) had higher imprinting factor of 14.19 and significant selectivity. The MIPs@L-Cys@Mn-ZnS QDs as fluorescent probe exhibited sensitive response to Cel in the linear range from 0.1 μM to 3.5 μM and the limit of detection was estimated to be 35.2 nM. The probe was also applied for the detection of Cel in traditional Chinese medicine with recovery ranged from 88.0%-105.0%. The results confirmed that MIPs@L-Cys@Mn-ZnS QDs could efficiently and specifically capture Cel from actual complex traditional Chinese medicine samples.

Structural Requirements for Antimicrobial Activity of Phenolic Nor-Triterpenes from Celastraceae Species

The emergence of pathogenic bacteria-resistant strains is a major public health issue. In this regard, natural product scaffolds offer a promising source of new antimicrobial drugs. In the present study, we report the antimicrobial activity against Gram-positive and Gram-negative bacteria and the yeast Candida albicans of five phenolic nor-triterpenes (1–5) isolated from Maytenus blepharodes and Maytenus canariensis in addition to four derivatives (6–9), three of them reported for the first time. Their stereostructures have been elucidated on the basis of spectroscopic analysis, including one-dimensional (1D) and two-dimensional (2D) NMR techniques, spectrometric methods, and comparison with data reported in the literature. To understand the structural basis for the antimicrobial activity of this type of compounds, we have performed an in-depth study of the structure–activity relationship (SAR) of a series of previously reported phenolic nor-triterpenes. The SAR analysis was based on the skeleton framework, oxidation degree, functional groups, and regiosubstitution patterns, revealing that these aspects modulate the antimicrobial activity.

Celastrol improves the therapeutic efficacy of EGFR-TKIs for non-small-cell lung cancer by overcoming EGFR T790M drug resistance

The development of resistance to therapy continues to be a serious clinical problem in lung cancer management. Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) is one of the most common chemotherapy drugs to treat non-small-cell lung cancer. However, almost all treatments fail after ∼1 year of treatment because of drug tolerance, probably occurring from the threonine 790 mutation (T790M) of the EGFR, resulting in overactivation of the EGFR. Celastrol is a natural compound that exhibits antiproliferative activity. In this study, we showed that celastrol combined with EGFR-TKIs significantly suppressed cell invasion of lung cancer cells with a T790M mutation by suppressing the EGFR pathway. Combined therapy with celastrol and EGFR-TKIs inhibited tumor growth in vivo. Together, these results suggested that combined therapy with EGFR-TKIs and celastrol may be a more effective treatment of patients with non-small-cell lung cancer with T790M mutations of the EGFR.

Development and Validation of an HPLC-PDA Method for Biologically Active Quinonemethide Triterpenoids Isolated from Maytenus chiapensis

Background: Quinonemethide triterpenoids, known as celastroloids, constitute a relatively small group of biologically active compounds restricted to the Celastraceae family and, therefore, they are chemotaxonomic markers for this family. Among this particular type of metabolite, pristimerin and tingenone are considered traditional medicines in Latin America. The aim of this study was the isolation of the most abundant celastroloids from the root bark of Maytenus chiapensis, and thereafter, to develop an analytical method to identify pristimerin and tingenone in the Celastraceae species. Methods: Pristimerin and tingenone were isolated from the n-hexane-Et₂O extract of the root bark of M. chiapensis through chromatographic techniques, and were used as internal standards. Application of a validated RP HPLC-PDA method was developed for the simultaneous quantification of these two metabolites in three different extracts, n-hexane-Et₂O, methanol, and water, to determine the best extractor solvent. Results: Concentration values showed great variation between the solvents used for extraction, with the n-hexane⁻Et₂O extract being the richest in pristimerin and tingenone. Conclusions: M. chiapensis is a source of two biologically active quinonemethide triterpenoids. An analytical method was developed for the qualification and quantification of these two celastroloids in the root bark extracts of M. chiapensis. The validated method reported herein could be extended and be useful in analyzing Celastraceae species and real commercial samples.

Celastrol induces vincristine multidrug resistance oral cancer cell apoptosis by targeting JNK1/2 signaling pathway

BACKGROUND

Oral cancers are one of the most aggressive malignancies, with high mortality rates globally. Patients with these cancers are treated using combination therapies including surgery, chemotherapy, and radiotherapy.

HYPOTHESIS/PURPOSE

Traditional Chinese medicines and other herbal medicines have been used to treat various diseases in Asia. Celastrol is a pentacyclic triterpenoid isolated from the Chinese herbal medicine Trypterygium wilfordii, which has therapeutic potential in multiple diseases. The present study was to determine the effect of celastrol on vincristine-resistant cancer cell line and to illuminate the mechanism of celastrol-induced cell apoptosis.

STUDY DESIGN

Celastrol was added to vincristine-resistant cancer cell and immunoreactive proteins were detected.

METHODS AND RESULTS

Our study demonstrated that celastrol leads to apoptosis of head and neck cancer cells through mitochondria- and Fas-mediated pathways. However, whether this herbal medicine exhibits beneficial effects on vincristine-resistant oral cancer patients remains uncertain. Therefore, our study examined the apoptotic effect exerted by celastrol and the mechanism by this drug acts on a vincristine-resistant cancer cell line. The present study demonstrated that celastrol triggered apoptotic cell death by inducing cell cycle arrest at the G2/M phase via the intrinsic and extrinsic pathways (increased cleaved caspase-3, caspase-8, caspase-9, and PARP). Increased expression of tBid also indicated the presence of crosstalk between the two pathways. Celastrol mediated cell apoptosis through the downregulation of the expression of Bcl-2, not Bcl-xL. Moreover, JNK1/2 signaling was the main pathway of celastrol-induced apoptosis.

CONCLUSION

Celastrol could become a useful agent for treating oral cancers with MDR.

Efficacy of celastrol combined with cisplatin in enhancing the apoptosis of U-2OS osteosarcoma cells via the mitochondrial and endoplasmic reticulum pathways of apoptosis

Osteosarcoma is a common primary malignant tumor of bone, and the poor prognosis and low 5-year survival rate have not improved for three decades. The present study aimed to study the effect a combination of celastrol and cisplatin on the human osteosarcoma cell line U-2OS, and to investigate the mechanism by which celastrol/cisplatin induces the apoptosis of osteosarcoma cells. MTT and Annexin V-FITC/PI assays were used to evaluate the effects of combined celastrol/cisplatin on growth and apoptosis, respectively, in U-2OS cells. Morphological changes accompanying cell growth inhibition were observed using a fluorescence microscope. Combination index (CI) analysis was used to evaluate the combinatorial effects of celastrol/cisplatin treatment. Western blotting was used to quantify the expression of apoptosis-associated proteins. It was identified that celastrol/cisplatin inhibited the growth of U-2OS cells in a dose-dependent manner. CI analysis revealed that combined celastrol/cisplatin demonstrated a synergistic effect in U-2OS cells, with CIs ranging from 0.80 to 0.97 at effect levels from IC₁₀ to IC₇₀. In addition, it was observed that celastrol/cisplatin upregulated the expression of Bcl-associated X protein, cytochrome c, caspase-3 and C/EBP homologous protein, and downregulated the expression of Bcl-2, poly(ADP-ribose) polymerase, 78 kDa glucose-regulated protein and caspase-9, whereas the expression of caspase-8 remained unchanged. To conclude, celastrol/cisplatin induced apoptosis in U-2OS cells via the mitochondrial and endoplasmic reticulum pathways, particularly in the former. Celastrol/cisplatin therefore exhibits potential as a novel therapeutic combination for the treatment of osteosarcoma.

Effects of diclofenac on the pharmacokinetics of celastrol in rats and its transport

CONTEXT

Diclofenac and celastrol are always used together for the treatment of rheumatoid arthritis; the herb-drug interaction potential between diclofenac and celastrol is still unknown.

OBJECTIVE

This study investigates the effects of diclofenac on the pharmacokinetics of celastrol in rats.

MATERIALS AND METHODS

Twelve male Sprague-Dawley rats were divided into two groups and received celastrol (1 mg/kg) or both celastrol (1 mg/kg) and diclofenac (10 mg/kg) by oral gavage, and blood samples were collected via the oculi chorioideae vein and determined using the LC-MS method developed in this study. Additionally, the effects of diclofenac on the transport of celastrol were investigated using a Caco-2 cell transwell model.

RESULTS

Diclofenac could significantly (p < 0.05) decrease the C_max (from 66.93 ± 10.28 to 41.25 ± 8.06 ng/mL) and AUC_0-t (from 765.84 ± 163.61 to 451.33 ± 110.88 μg × h/L) of celastrol in rats. The efflux ratio of celastrol increased significantly (p < 0.05) from 3.12 to 4.55 with the treatment of diclofenac.

DISCUSSION AND CONCLUSION

These results indicated that diclofenac could decrease the system exposure of celastrol in rats when they are co-administered, and these effects might be exerted via decreasing its absorption in intestine.

Celastrol downregulates E2F1 to induce growth inhibitory effects in hepatocellular carcinoma HepG2 cells

Celastrol, a natural compound extracted from Tripterygium wilfordii, is known to exhibit potential anticancer activities in various types of tumor cells. E2F1 is reported to be overexpressed in several types of human tumors and its inactivation may be a valuable novel potential therapeutic strategy for cancer treatment. However, the molecular mechanism underlying the pro-apoptotic effects of celastrol on hepatocellular carcinoma (HCC) cells remains unclear, and E2F1-targeted compounds have been rarely identified. In the present study, we demonstrated that celastrol inhibited the proliferation of human HCC cells and triggered apoptosis of HepG2 cells in a caspase-dependent manner. E2F1 was potently downregulated by celastrol in a dose- and time-dependent manner at both the mRNA and protein levels. Moreover, siRNA-mediated E2F1 silencing enhanced celastrol-induced apoptosis and inhibition of proliferation. Our data imply that downregulation of E2F1 may be a key factor in the celastrol-mediated inhibitory effects in HepG2 cells, and celastrol can serve as a leading compound for the development of compounds designed to inactivate E2F1 for HCC therapy.

Celastrol: A Spectrum of Treatment Opportunities in Chronic Diseases

The identification of new bioactive compounds derived from medicinal plants with significant therapeutic properties has attracted considerable interest in recent years. Such is the case of the Tripterygium wilfordii (TW), an herb used in Chinese medicine. Clinical trials performed so far using its root extracts have shown impressive therapeutic properties but also revealed substantial gastrointestinal side effects. The most promising bioactive compound obtained from TW is celastrol. During the last decade, an increasing number of studies were published highlighting the medicinal usefulness of celastrol in diverse clinical areas. Here we systematically review the mechanism of action and the therapeutic properties of celastrol in inflammatory diseases, namely, rheumatoid arthritis, systemic lupus erythematosus, inflammatory bowel diseases, osteoarthritis and allergy, as well as in cancer, neurodegenerative disorders and other diseases, such as diabetes, obesity, atherosclerosis, and hearing loss. We will also focus in the toxicological profile and limitations of celastrol formulation, namely, solubility, bioavailability, and dosage issues that still limit its further clinical application and usefulness.

Celastrol inhibits migration and invasion through blocking the NF-κB pathway in ovarian cancer cells

Metastatic ovarian cancer is a major clinical challenge with poor prognosis and high mortality. Celastrol is a natural compound that has exhibits antiproliferative activity; however, its effects on metastasis-related phenotypes in ovarian cancer models are unclear. In the current study, the anti-invasive activities and associated signaling pathways of celastrol were determined in ovarian cancer cells. Cell proliferation was tested by MTT assay. Cell migration was detected by wound healing and Transwell assays, while cell invasion was detected by a Matrigel-coated Transwell method. In addition, nuclear factor (NF)-κB and matrix metalloproteinase (MMP) expression was examined by western blotting, and MMP-2/-9 activities were determined by gelatin zymography. At sub-toxic concentrations (<0.5 µM), celastrol inhibited migration and invasion in a concentration-dependent manner in SKOV-3 and OVCAR-3 cells. At the molecular level, celastrol blocked the canonical NF-κB pathway by inhibiting IκBα phosphorylation, and preventing IκBα degradation and p65 accumulation. Furthermore, the expression and activity of the NF-κB target protein MMP-9, but not MMP-2, were inhibited by celastrol. Furthermore, celastrol showed no synergistic effect with MG132, an NF-κB inhibitor. In conclusion, celastrol exhibited significant anti-invasive activities in ovarian cancer cells. Such functions may be mediated via NF-κB pathway blockade. The results of this in vitro study strengthen the value of applying celastrol as a potential clinical intervention modality for delaying ovarian cancer metastasis. This, celastrol warrants further preclinical investigation.

Celastrol-induced apoptosis in human nasopharyngeal carcinoma is associated with the activation of the death receptor and the mitochondrial pathway

Nasopharyngeal carcinoma (NPC) is a cancer that arises from the epithelium of the nasopharynx. Celastrol is a triterpene from traditional Chinese medicine, which demonstrates anti-proliferative activity in several cancer cell lines. However, the effect of celastrol on human NPC and the underlying mechanisms are not yet elucidated. The present study investigated whether celastrol induced apoptosis in human NPC cells, and the underlying molecular mechanisms were explored. Celastrol decreased the viability of HONE-1 and NPC-039 cells in a dose-dependent manner, and induced G1 and G2/M phase cell cycle arrest. The level of cleaved caspases-3, -8, and -9 and poly (ADP-ribose) polymerase 1 increased in cells treated with celastrol. There was an increase in active Bcl-2-like 11 isoform S, Bcl-2-associated X, Bcl-2 antagonist/killer and truncated BH3-interacting death antagonist, and the levels of the anti-apoptotic Bcl-2 and Bcl-2-like 1 decreased. Celastrol induced an increase in Fas, Fas-associated via death domain, TNF receptor superfamily members (TNRSF) 1A and 10B, and TNFRSF1A associated via death domain, and induced a dose-dependent reduction in mitochondrial membrane potential. Celastrol inhibited activation of mitogen-activated protein kinase (MAPK) 1/3 and 14, and induced MAPK 8/9 activation. The results indicated that celastrol induced apoptosis through the death receptor and the mitochondrial pathway in human NPC cells, and is a promising candidate in the development of drugs against NPC.

Celastrol protects TGF-β1-induced endothelial-mesenchymal transition

The endothelial-to-mesenchymal transition (EndMT) in endothelial cells contributes to the development of cardiac fibrosis, ultimately leading to cardiac remodeling. In this study, the effects and molecular mechanisms of celastrol (CEL) on transforming growth factor-β1 (TGF-β1)-induced EndMT in human umbilical vein endothelial (HUVEC-12) cells were investigated. The presented data demonstrated that CEL significantly blocked the morphology change of HUVEC-12 cells induced by TGF-β1 without cell cytotoxicity. In accordance with these findings, CEL blocked TGF-β1-induced EndMT as evidenced by the inhibition of the mesenchymal markers, including collagen I, III, α-SMA, fibronectin mRNA expression, and the increase in the mRNA expression of endothelial cell marker CD31. These changes were also confirmed by double immunofluorescence staining of CD31 and vimentin. The in vitro scratch assay showed that CEL inhibited the migration capacity of the transitioned endothelial cells induced by TGF-β1. Further experiments showed that the beneficial effect of CEL on blocking the EndMT in HUVEC-12 cells was associated with the suppression of the TGF-β1/Smads signalling pathway, which was also confirmed by the inhibition of its downstream transcription factor snail1, twist1, twist2, ZEB1 and ZEB2. These results indicate that CEL blocks TGF-β1-induced EndMT through TGF-β1/Smads signalling pathway and suggest that it may be a feasible therapy for cardiac fibrosis diseases.

Celastrol negatively regulates cell invasion and migration ability of human osteosarcoma via downregulation of the PI3K/Akt/NF-κB signaling pathway in vitro

Osteosarcoma (OS) is a primary malignant tumor of the bone, with a tendency to metastasize early. Despite the advances in treatment options, more than 30% of patients develop distant metastases, and the prognosis of these patients with metastases is extremely poor. Celastrol has been demonstrated to manifest multiple pharmacological activities, including induction of apoptosis in numerous types of cancer cell lines. Our previous studies have also suggested that Celastrol is capable of inducing apoptosis of human osteosarcoma cells via the mitochondrial-dependent pathway. The purpose of this study was to investigate the effects of Celastrol on the migration and invasion of human osteosarcoma U-2OS cells in vitro. Cell migration and invasion were investigated using wound healing and Boyden chamber Transwell assays. We observed that Celastrol suppressed cell invasion and migration in human osteosarcoma U-2OS cells. Furthermore, protein expression levels of phosphorylated phosphatidylinositol 3-kinase (PI3K), Akt, inhibitor of κB kinase α/β, inhibitor of κB α, nuclear factor-κB (NF-κB subunit p65) and matrix metalloproteinase (MMP)-2 and -9 were measured by western blot analysis. We observed that the PI3K/Akt/NF-κB signaling pathway was inhibited following Celastrol treatment. In addition, the expression levels of MMP-2 and -9 proteins were also reduced significantly following Celastrol treatment. Therefore, we confirmed that Celastrol suppressed osteosarcoma U-2OS cell metastasis via downregulation of the PI3K/Akt/NF-κB signaling pathway in vitro.

Protective effects of Celastrol on diethylnitrosamine-induced hepatocellular carcinoma in rats and its mechanisms

Celastrol, an active ingredient of Tripterygium Wilfordii, is a traditional Chinese medicinal herb, which has attracted interests for its potential anti-inflammatory and anti-cancer activities. The aim of this study was to evaluate the anti-tumor effect of Celastrol against diethylnitrosamine (DEN)-induced hepatocellular carcinoma (HCC) in rats and furthermore, to explore the underlying mechanism. Sprague-Dawley rats were intragastrically administered with DEN (10mg/kg) for 6 days every week and persisting 16 weeks. The number of nodules was calculated. Hematoxylin-Eosin (HE) staining was used to evaluate the hepatic pathological lesions. The levels of serum alanine aminotransferase (ALT), glutamic oxalacetic transaminase (AST), alkaline phosphatase (ALP) and alpha fetoprotein (AFP) were analyzed by Elisa kits, and the protein levels of p53, Murine double minute (MDM) 2, Bax, Bcl-2, Bcl-xl, cytochrome C, Caspase-3, Caspase-9 and Poly (ADP-ribose) polymerase (PARP) were analyzed by western blot. The results showed that Celastrol could significantly decrease the mortality, the number of tumor nodules and the index of liver in the Celastrol groups compared with DEN-treated group. Moreover, Celastrol obviously improved the hepatic pathological lesions and decreased the elevated levels of ALT, AST, ALP and AFP. Meanwhile, Celastrol suppressed the expression of the protein MDM2, activated the intrinsic mitochondrial apoptosis pathway induced by p53, inhibited anti-apoptotic Bcl-2 and Bcl-xl, induced the pro-apoptotic Bax, cytochrome C, PARP and caspases. These results suggested that Celastrol had a good therapeutic action in reversing DEN-induced HCC rats, which may be associated with the apoptosis of hepatoma cells induced by Celastrol.

An Ethnopharmacological, Phytochemical and Pharmacological Review of the Genus Meconopsis

The Meconopsis plants (Chinese: 绿绒篙), belonging to the family Papaveraceae, have been used as traditional Tibetan medicine (TTM) for thousands of years. Meconopsis has the effects of clearing heat, reducing swelling, and easing pain, and is mainly prescribed for heat syndromes, hepatitis, pneumonia, and pain in joints. Phytochemical studies have revealed the presence of major isoquinoline alkaloids and flavonoids. Modern pharmacological research has demonstrated its antitumor, hepatoprotective, analgestic, antimicrobial, anti-oxidant, antitussive, and anti-inflammatory activities. However, resource availability, in-depth in vivo pharmacological study and qualitative and quantitative analysis are still insufficient and deserve further efforts. This paper provides a comprehensive advance on the ethnopharmacological, phytochemical, and pharmacological studies of the genus, in hopes of promoting a better understanding of their medicinal values.

Protective Effects of Celastrol on Diabetic Liver Injury via TLR4/MyD88/NF-κB Signaling Pathway in Type 2 Diabetic Rats

Immune and inflammatory pathways play a central role in the pathogenesis of diabetic liver injury. Celastrol is a potent immunosuppressive and anti-inflammatory agent. So far, there is no evidence regarding the mechanism of innate immune alterations of celastrol on diabetic liver injury in type 2 diabetic animal models. The present study was aimed at investigating protective effects of celastrol on the liver injury in diabetic rats and at elucidating the possible involved mechanisms. We analyzed the liver histopathological and biochemical changes and the expressions of TLR4 mediated signaling pathway. Compared to the normal control group, diabetic rats were found to have obvious steatohepatitis and proinflammatory cytokine activities were significantly upregulated. Celastrol-treated diabetic rats show reduced hepatic inflammation and macrophages infiltration. The expressions of TLR4, MyD88, NF-κB, and downstream inflammatory factors IL-1β and TNFα in the hepatic tissue of treated rats were downregulated in a dose-dependent manner. We firstly found that celastrol treatment could delay the progression of diabetic liver disease in type 2 diabetic rats via inhibition of TLR4/MyD88/NF-κB signaling cascade pathways and its downstream inflammatory effectors.

Celastrol induces apoptosis of human osteosarcoma cells via the mitochondrial apoptotic pathway

Celastrol is an active compound extracted from the root bark of Triptergium wilfordii Hook F., also known as 'Thunder of God Vine'. It is a well-known Chinese medicinal herb that was found to inhibit tumor cell growth and promote apoptosis in several tumor cell lines. However, research into its effects on osteosarcoma cell apoptosis is still extremely limited. The present study was undertaken to determine the effect of celastrol on viability and apoptosis of osteosarcoma cells and furthermore, to illuminate the molecular mechanism of celastrol-induced osteosarcoma cell apoptosis. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay was used to evaluate the viability of the cells following treatment with celastrol. The effect of celastrol on the apoptotic rate of the cells was evaluated by flow cytometry using Annexin V-PE/7-AAD staining assay. Fluorescence microscopy was used to detect the morphological changes in the human osteosarcoma U-2OS cell lines. The expression of Bcl-2 family proteins, caspase-3, caspase-8, caspase-9, cytochrome c and PARP was measured by western blotting. We found that celastrol significantly inhibited the growth of osteosarcoma cells in a dose-dependent manner, particularly U-2OS cells. Furthermore, we observed that celastrol upregulated the expression of the pro-apoptotic proteins Bax and cytochrome c and altered the ratio of Bax/Bcl-2, and triggered the mitochondrial apoptotic pathway, resulting in caspase-3 and -9 activation and PARP cleavage. To conclude, the results indicate that celastrol inhibits the proliferation of human osteosarcoma cancer cells by inducing apoptosis via the mitochondrial-dependent pathway.