Celastrol acts as a potent antimetastatic agent targeting beta1 integrin and inhibiting cell-extracellular matrix adhesion, in part via the p38 mitogen-activated protein kinase pathway

The role of yes activated protein (YAP) in melanoma metastasis

Hippo was first identified in a genetic screen as a protein that suppressed proliferation and cell growth. Subsequently, it was shown that hippo acted in a so-called canonical cascade to suppress Yorkie, the Drosophila equivalent of Yes-activated protein (YAP), a mechanosensitive transcriptional cofactor that enhances the activity of the TEAD family of transcription factors. YAP promotes fibrosis, activation of cancer-associated fibroblasts, angiogenesis and cancer cell invasion. YAP activates the expression of the matricellular proteins CCN1 (cyr61) and CCN2 (ctgf), themselves mediators of fibrogenesis and oncogenesis, and coordination of matrix deposition and angiogenesis. This review discusses how therapeutically targeting YAP through YAP inhibitors verteporfin and celastrol and its downstream mediators CCN1 and CCN2 might be useful in treating melanoma.

Arylcyanomethylenequinone Oximes: An Overview of Synthesis, Chemical Transformations, and Biological Activity

Quinone methides are a class of biologically active compounds that can be used in medicine as antibacterial, antifungal, antiviral, antioxidant, and anti-inflammatory agents. In addition, quinone methides have the potential to be used as pesticides, dyes, and additives for rubber and plastics. In this paper, we discuss a subclass of quinone methides: methylenequinone oximes. Although the first representatives of the subgroup were synthesized in the distant past, they still need to be additionally studied, while their chemistry, biological properties, and perspective of practical applications require to be comprehensively summarised. Based on the analysis of the literature, it can be concluded that methylenequinone oximes exhibit a diversified profile of properties and outstanding potential as new drug candidates and reagents in organic synthesis, both of electrophilic and nucleophilic nature, worthy of wide-ranging further research.

Celastrol in cancer therapy: Recent developments, challenges and prospects

Cancer is one of the world's biggest healthcare burdens and despite the current advancements made in treatment plans, the outcomes for oncology patients have yet to reach their full potential. Hence, there is a pressing need to develop novel anti-cancer drugs. A popular drug class for research are natural compounds, due to their multi-targeting potential and enhanced safety profile. One such promising natural bioactive compound derived from a vine, Tripterygium wilfordii is celastrol. Pre-clinical studies revolving around the use of celastrol have revealed positive pharmacological activities in various types of cancers, thus suggesting the chemical's potential anti-cancerous effects. However, despite the numerous preclinical studies carried out over the past few decades, celastrol has not reached human trials for cancer. In this review, we summarize the mechanisms and therapeutic potentials of celastrol in treatment for different types of cancer. Subsequently, we also explore the possible reasons hindering its development for human use as cancer therapy, like its narrow therapeutic window and poor pharmacokinetic properties. Additionally, after critically analysing both in vitro and in vivo evidence, we discuss about the key pathways effected by celastrol and the suitable types of cancer that can be targeted by the natural drug, thus giving insight into future directions that can be taken, such as in-depth analysis and research of the druggability of celastrol derivatives, to aid the clinical translation of this promising anti-cancer lead compound.

Celastrol Modulates Multiple Signaling Pathways to Inhibit Proliferation of Pancreatic Cancer via DDIT3 and ATF3 Up-Regulation and RRM2 and MCM4 Down-Regulation

Background

Pancreatic cancer is one of the most serious and lethal human cancers with a snowballing incidence around the world. The natural product celastrol has also been widely documented as a potent anti-inflammatory, anti-angiogenic, and anti-oxidant.

Purpose

To elucidate the antitumor effect of celastrol on pancreatic cancer cells and its modulatory role on whole genome expression.

Methods

The antitumor activity of celastrol on a panel of pancreatic cancer cells has been evaluated by Sulforhodamine B assay. Caspase 3/7 and histone-associated DNA fragments assays were done for apoptosis measurement. Additionally, prostaglandin (PGE2) inhibition was evaluated. Moreover, a microarray gene expression profiling was carried out to detect possible key players that modulate the antitumor effects of celastrol on cells of pancreatic cancer.

Results

Our findings indicated that celastrol suppresses the cellular growth of pancreatic cancer cells, induces apoptosis, and inhibits PGE2 production. Celastrol modulated many signaling genes and its cytotoxic effect was mainly mediated via over-expression of ATF3 and DDIT3, and down-expression of RRM2 and MCM4.

Conclusion

The current study aims to be a starting point to generate a hypothesis on the most significant regulatory genes and for a full dissection of the celastrol possible effects on each single gene to prevent the pancreatic cancer growth.

22β-hydroxytingenone reduces proliferation and invasion of human melanoma cells

Melanoma is a skin cancer with high invasive potential and high lethality. Considering that quinonemethide triterpenes are described as promising anticancer agents, the aim of this study was to evaluate the effect of 22β-hydroxytingenone (22-HTG) against human melanoma cells. Alamar blue assay was performed in order to evaluate its cytotoxic effect. Thus, subtoxic concentrations (1.0, 2.0, and 2.5 μM) were used to evaluate the effect of this compound on proliferation, migration, metabolism, and invasion. IC₅₀ value against SK-MEL-28 cell line was 4.35, 3.72, and 3.29 μM after 24, 48, and 72 h of incubation, respectively. 22-HTG reduced proliferation, migration and invasion by melanoma cells, with decreased activity of metalloproteinases (MMP-2 and MMP-9). Futhermore, 22-HTG decreased expression of lactate dehydrogenase (LDHA), an enzyme associated with cell metabolism. Howerver, the small reduction in LDHA enzyme activity must have occurred by the cytotoxic effect of 22-HTG. According to the results, 22-HTG interferes with important characteristics of cancer, with anti-proliferative, and anti-invasive effect against melanoma cells. The data suggest that 22-HTG is an effective substance against melanoma cells and it should be considered as a potential anticancer agent.

Nutraceutical Compounds as Sensitizers for Cancer Treatment in Radiation Therapy

The improvement of diagnostic techniques and the efficacy of new therapies in clinical practice have allowed cancer patients to reach a higher chance to be cured together with a better quality of life. However, tumors still represent the second leading cause of death worldwide. On the contrary, chemotherapy and radiotherapy (RT) still lack treatment plans which take into account the biological features of tumors and depend on this for their response to treatment. Tumor cells' response to RT is strictly-connected to their radiosensitivity, namely, their ability to resist and to overcome cell damage induced by ionizing radiation (IR). For this reason, radiobiological research is focusing on the ability of chemical compounds to radiosensitize cancer cells so to make them more responsive to IR. In recent years, the interests of researchers have been focused on natural compounds that show antitumoral effects with limited collateral issues. Moreover, nutraceuticals are easy to recover and are thus less expensive. On these bases, several scientific projects have aimed to test also their ability to induce tumor radiosensitization both in vitro and in vivo. The goal of this review is to describe what is known about the role of nutraceuticals in radiotherapy, their use and their potential application.

Design and synthesis of novel celastrol derivative and its antitumor activity in hepatoma cells and antiangiogenic activity in zebrafish

Two series of celastrol derivatives were designed and synthesized by modifying carboxylic acid at the 28th position with amino acid, and their intermediates with isobutyrate at the third position. All compounds were evaluated for their antiproliferation activity by four human cancer cell lines (SCG7901, HGC27, HepG2, and Bel7402) and one normal cell LO2. The most promising compound, compound 8, showed superior bioactivity and lower toxicity than others including celastrol. Further underlying tests illustrated that compound 8 induced apoptosis and cell arrest at G2/M and inhibited proliferation and mobility of human hepatoma cells by suppressing the signal transducer and activator of transcription-3 signaling pathway. Besides these, a highly accurate and reproducible high performance liquid chromatography protocol was established to determine celastrol and compound 8 absorption in zebrafish, and results demonstrated that their concentration increased rapidly within 4 hr in a time-dependent manner and the concentration of compound 8 was higher than that of celastrol. In addition, without detection at 12 hr, compound 8 was rapidly metabolized in vivo. These findings are very helpful for the structural modification of celastrol and other bioactive compounds to improve their bioactivity, toxicity, and absorption.

Dissecting celastrol with machine learning to unveil dark pharmacology

By coalescing bespoke machine learning and bioinformatics analyses with cell-based assays, we unveil the pharmacology of celastrol. Celastrol is a direct modulator of the progesterone and cannabinoid receptors, and its effects correlate with the antiproliferative activity. We demonstrate how in silico methods may drive systems biology studies for natural products.

Intermicrobial interaction: Aspergillus fumigatus siderophores protect against competition by Pseudomonas aeruginosa

Pseudomonas aeruginosa and Aspergillus fumigatus are pathogens frequently co-inhabiting immunocompromised patient airways, particularly in people with cystic fibrosis. Both microbes depend on the availability of iron, and compete for iron in their microenvironment. We showed previously that the P. aeruginosa siderophore pyoverdine is the main instrument in battling A. fumigatus biofilms, by iron chelation and denial of iron to the fungus. Here we show that A. fumigatus siderophores defend against anti-fungal P. aeruginosa effects. P. aeruginosa supernatants produced in the presence of wildtype A. fumigatus planktonic supernatants (Afsup) showed less activity against A. fumigatus biofilms than P. aeruginosa supernatants without Afsup, despite higher production of pyoverdine by P. aeruginosa. Supernatants of A. fumigatus cultures lacking the sidA gene (AfΔsidA), unable to produce hydroxamate siderophores, were less capable of protecting A. fumigatus biofilms from P. aeruginosa supernatants and pyoverdine. AfΔsidA biofilm was more sensitive towards inhibitory effects of pyoverdine, the iron chelator deferiprone (DFP), or amphothericin B than wildtype A. fumigatus biofilm. Supplementation of sidA-deficient A. fumigatus biofilm with A. fumigatus siderophores restored resistance to pyoverdine. The A. fumigatus siderophore production inhibitor celastrol sensitized wildtype A. fumigatus biofilms towards the anti-fungal activity of DFP. In conclusion, A. fumigatus hydroxamate siderophores play a pivotal role in A. fumigatus competition for iron against P. aeruginosa.

Celastrol, a plant-derived triterpene, induces cisplatin-resistance nasopharyngeal carcinoma cancer cell apoptosis though ERK1/2 and p38 MAPK signaling pathway

BACKGROUND

Developing resistance to chemotherapeutic drugs has become a major problem in the management of nasopharyngeal carcinoma (NPC). To overcome this issue, use of natural plant products as chemosensitizers is gaining importance at a fast pace.

HYPOTHESIS/PURPOSE

The present study was designed to evaluate the cytotoxic effect and mode of action of a natural pentacyclic triterpenoid, celastrol, on cisplatin-resistant NPC cells.

RESULTS

Study results revealed that celastrol treatment significantly reduced the viability of NPC cells in dose and time dependent manners, as compared to untreated control cells. The cytotoxic effect of celastrol was mediated by cell cycle arrest at G2/M phase and induction of intrinsic and extrinsic apoptotic pathways. With further analysis, we observed that celastrol-induced activation of caspases was accompanied by increased phosphorylation of MAPK pathway proteins, p38, ERK1/2.

CONCLUSION

Taken together, our observation provides a novel insight on use of a natural plant product, celastrol, in the management of chemoresistant NPC.

Celastrol as a pentacyclic triterpenoid with chemopreventive properties

Celastrol is a highly investigated anticancer moiety. It is a pentacyclic triterpenoid, isolated several decades ago with promising role in chemoprevention. Celastrol has been found to target multiple proinflammatory, angiogenic and metastatic proteins. Inhibition of these targets results in significant reduction of cancer growth, survival and metastasis. This review summarizes the varied molecular targets of celastrol along with insight into the various recently published clinical, preclinical and industrial patents (2011-2017).

Regulation of cell signaling pathways by dietary agents for cancer prevention and treatment

Although it is widely accepted that better food habits do play important role in cancer prevention and treatment, how dietary agents mediate their effects remains poorly understood. More than thousand different polyphenols have been identified from dietary plants. In this review, we discuss the underlying mechanism by which dietary agents can modulate a variety of cell-signaling pathways linked to cancer, including transcription factors, nuclear factor κB (NF-κB), signal transducer and activator of transcription 3 (STAT3), activator protein-1 (AP-1), β-catenin/Wnt, peroxisome proliferator activator receptor- gamma (PPAR-γ), Sonic Hedgehog, and nuclear factor erythroid 2 (Nrf2); growth factors receptors (EGFR, VEGFR, IGF1-R); protein Kinases (Ras/Raf, mTOR, PI3K, Bcr-abl and AMPK); and pro-inflammatory mediators (TNF-α, interleukins, COX-2, 5-LOX). In addition, modulation of proteasome and epigenetic changes by the dietary agents also play a major role in their ability to control cancer. Both in vitro and animal based studies support the role of dietary agents in cancer. The efficacy of dietary agents by clinical trials has also been reported. Importantly, natural agents are already in clinical trials against different kinds of cancer. Overall both in vitro and in vivo studies performed with dietary agents strongly support their role in cancer prevention. Thus, the famous quote "Let food be thy medicine and medicine be thy food" made by Hippocrates 25 centuries ago still holds good.

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.

Assessing the anticancer effects associated with food products and/or nutraceuticals using in vitro and in vivo preclinical development-related pharmacological tests

This review is part of a special issue entitled "Role of dietary pattern, foods, nutrients and nutraceuticals in supporting cancer prevention and treatment" and describes a pharmacological strategy to determine the potential contribution of food-related components as anticancer agents against established cancer. Therefore, this review does not relate to chemoprevention, which is analysed in several other reviews in the current special issue, but rather focuses on the following: i) the biological events that currently represent barriers against the treatment of certain types of cancers, primarily metastatic cancers; ii) the in vitro and in vivo pharmacological pre-clinical tests that can be used to analyse the potential anticancer effects of food-related components; and iii) several examples of food-related components with anticancer effects. This review does not represent a catalogue-based listing of food-related components with more or less anticancer activity. By contrast, this review proposes an original pharmacological strategy that researchers can use to analyse the potential anticancer activity of any food-related component-e.g., by considering the crucial characteristics of cancer biological aggressiveness. This review also highlights that cancer patients undergoing chemotherapy should restrict the use of "food complements" without supervision by a medical nutritionist. By contrast, an equilibrated diet that includes the food-related components listed herein would be beneficial for cancer patients who are not undergoing chemotherapy.

Celastrol and Its Role in Controlling Chronic Diseases

Celastrol, a triterpenoid derived from traditional Chinese medicinal plants, has anti-inflammatory, antioxidant, and anticancer activities. Celastrol has shown preventive/therapeutic effects in experimental models of several chronic diseases. These include, chronic inflammatory and autoimmune diseases (e.g., rheumatoid arthritis, multiple sclerosis, systemic lupus erythematosus, inflammatory bowel disease, and psoriasis), neurodegenerative disorders (e.g., Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis), atherosclerosis, obesity, Type 2 diabetes, and cancer. Celastrol modulates intricate cellular pathways and networks associated with disease pathology, and it interrupts or redirects the aberrant cellular and molecular events so as to limit disease progression and facilitate recovery, where feasible. The major cell signaling pathways modulated by celastrol include the NF-kB pathway, MAPK pathway, JAK/STAT pathway, PI3K/Akt/mTOR pathway, and antioxidant defense mechanisms. Furthermore, celastrol modulates cell proliferation, apoptosis, proteasome activity, heat-shock protein response, innate and adaptive immune responses, angiogenesis, and bone remodeling. Current understanding of the mechanisms of action of celastrol and information about its disease-modulating activities in experimental models have set the stage for testing celastrol in clinical studies as a therapeutic agent for several chronic human diseases.

Oxidative stress in cancer and fibrosis: Opportunity for therapeutic intervention with antioxidant compounds, enzymes, and nanoparticles

Oxidative stress, mainly contributed by reactive oxygen species (ROS), has been implicated in pathogenesis of several diseases. We review two primary examples; fibrosis and cancer. In fibrosis, ROS promote activation and proliferation of fibroblasts and myofibroblasts, activating TGF-β pathway in an autocrine manner. In cancer, ROS account for its genomic instability, resistance to apoptosis, proliferation, and angiogenesis. Importantly, ROS trigger cancer cell invasion through invadopodia formation as well as extravasation into a distant metastasis site. Use of antioxidant supplements, enzymes, and inhibitors for ROS-generating NADPH oxidases (NOX) is a logical therapeutic intervention for fibrosis and cancer. We review such attempts, progress, and challenges. Lastly, we review how nanoparticles with inherent antioxidant activity can also be a promising therapeutic option, considering their additional feature as a delivery platform for drugs, genes, and imaging agents.

Compounds From Celastraceae Targeting Cancer Pathways and Their Potential Application in Head and Neck Squamous Cell Carcinoma: A Review

Squamous cell carcinoma of the head and neck is one of the most common cancer types worldwide. It initiates on the epithelial lining of the upper aerodigestive tract, at most instances as a consequence of tobacco and alcohol consumption. Treatment options based on conventional therapies or targeted therapies under development have limited efficacy due to multiple genetic alterations typically found in this cancer type. Natural products derived from plants often possess biological activities that may be valuable in the development of new therapeutic agents for cancer treatment. Several genera from the family Celastraceae have been studied in this context. This review reports studies on chemical constituents isolated from species from the Celastraceae family targeting cancer mechanisms studied to date. These results are then correlated with molecular characteristics of head and neck squamous cell carcinoma in an attempt to identify constituents with potential application in the treatment of this complex disease at the molecular level.

Epicatechin isolated from Tripterygium wilfordii extract reduces tau-GFP-induced neurotoxicity in zebrafish embryo through the activation of Nrf2

Tau plays important roles in the assembly and stabilization of the microtubule structure to facilitate axonal transport in mammalian brain. The intracellular tau aggregates to form paired helical filaments leading to neurodegenerative disorders, collectively called tauopathies. In our previous report, we established a zebrafish model to express tau-GFP to induce neuronal death, which could be directly traced in vivo. Recently, we used this model to screen 400 herbal extracts and found 45 of them to be effective on reducing tau-GFP-induced neuronal death. One of the effective herbal extracts is the Tripterygium wilfordii stem extract. HPLC analysis and functional assay demonstrated that epicatechin (EC) is the major compound of Tripterygium wilfordii stem extract to decrease the neurotoxicity induced by tau-GFP. Using a luciferase reporter assay in the zebrafish, we confirmed that EC could activate Nrf2-dependent antioxidant responses to significantly increase the ARE-controlled expression of luciferase reporter gene. These data suggest that EC from the Tripterygium wilfordii stem extract could diminish tau-GFP-induced neuronal death through the activation of Nrf2.

HIV-1, methamphetamine and astrocytes at neuroinflammatory Crossroads

As a popular psychostimulant, methamphetamine (METH) use leads to long-lasting, strong euphoric effects. While METH abuse is common in the general population, between 10 and 15% of human immunodeficiency virus-1 (HIV-1) patients report having abused METH. METH exacerbates the severity and onset of HIV-1-associated neurocognitive disorders (HAND) through direct and indirect mechanisms. Repetitive METH use impedes adherence to antiretroviral drug regimens, increasing the likelihood of HIV-1 disease progression toward AIDS. METH exposure also directly affects both innate and adaptive immunity, altering lymphocyte numbers and activity, cytokine signaling, phagocytic function and infiltration through the blood brain barrier. Further, METH triggers the dopamine reward pathway and leads to impaired neuronal activity and direct toxicity. Concurrently, METH and HIV-1 alter the neuroimmune balance and induce neuroinflammation, which modulates a wide range of brain functions including neuronal signaling and activity, glial activation, viral infection, oxidative stress, and excitotoxicity. Pathologically, reactive gliosis is a hallmark of both HIV-1- and METH-associated neuroinflammation. Significant commonality exists in the neurotoxic mechanisms for both METH and HAND; however, the pathways dysregulated in astroglia during METH exposure are less clear. Thus, this review highlights alterations in astrocyte intracellular signaling pathways, gene expression and function during METH and HIV-1 comorbidity, with special emphasis on HAND-associated neuroinflammation. Importantly, this review carefully evaluates interventions targeting astrocytes in HAND and METH as potential novel therapeutic approaches. This comprehensive overview indicates, without a doubt, that during HIV-1 infection and METH abuse, a complex dialog between all neural cells is orchestrated through astrocyte regulated neuroinflammation.

Celastrol inhibits gastric cancer growth by induction of apoptosis and autophagy

Recently, the interest in natural products for the treatment of cancer is increasing because they are the pre-screened candidates. In the present study, we demonstrate the therapeutic effect of celastrol, a triterpene extracted from the root bark of Chinese medicine on gastric cancer. The proliferation of AGS and YCC-2 cells were most sensitively decreased in six kinds of gastric cancer cell lines after the treatment with celastrol. Celastrol inhibited the cell migration and increased G1 arrest in cell-cycle populations in both cell lines. The treatment with celastrol significantly induced autophagy and apoptosis and increased the expression of autophagy and apoptosis-related proteins. We also found an increase in phosphorylated AMPK following a decrease in all phosphorylated forms of AKT, mTOR and S6K after the treatment with celastrol. Moreover, gastric tumor burdens were reduced in a dose-dependent manner by celastrol administration in a xenografted mice model. Taken together, celastrol distinctly inhibits the gastric cancer cell proliferation and induces autophagy and apoptosis. [BMB Reports 2014; 47(12): 697-702]

The traditional Tibetan medicine Yukyung Karne exhibits a potent anti-metastatic activity by inhibiting the epithelial to mesenchymal transition and cell migration

BACKGROUND

In Traditional Tibetan medicine, Yukyung Karne has been used for the treatment of ovarian cancer. Though Yukyung Karne has been reported to be clinically effective, the molecular mechanism of its anti-metstatic action remains elusive.

METHODS

The cytotoxic property of Yukyung Karne was evaluated by crystal violet staining while its ability to induce ceramide production was analyzed by sphingomyelinase assay. The anti-metastatic property was investigated using adhesion, invasion, migration and colony formation assays. The effect of Yukyung Karne on the expression of extracellular matrix components, and epithelial and mesenchymal markers were evaluated by confocal microscopy and western blotting.

RESULTS

Yukyung Karne exhibited a strong anti-metastatic property by significantly reducing the invasion, migration and colony formation ability of ovarian cancer cells. Besides it inhibited the levels of biomarkers involved in epithelial to mesenchymal transition such as down-regulation of vimentin and N-cadherin and up-regulation of epithelial E-cadherin. Yukyung Karne also induced the neutral sphingomyelinase II (nSMNaseII) enzyme activity that is known to hydrolyze sphingomyelins into pro-apoptotic intracellular molecule ceramide.

CONCLUSIONS

The study provides some compelling evidences supporting the anti-metastatic potential of Yukyung Karne which strongly suggests its possible usage as a promising alternative medicine. Thus, Yukyung Karne may be used as an anticancer and anti-metastatic agent along with other conventional anticancer therapeutics to increase their efficacy.

Release of Ca2+ from the endoplasmic reticulum and its subsequent influx into mitochondria trigger celastrol-induced paraptosis in cancer cells

Celastrol, a triterpene extracted from the Chinese “Thunder of God Vine”, is known to have anticancer activity, but its underlying mechanism is not completely understood. In this study, we show that celastrol kills several breast and colon cancer cell lines by induction of paraptosis, a cell death mode characterized by extensive vacuolization that arises via dilation of the endoplasmic reticulum (ER) and mitochondria. Celastrol treatment markedly increased mitochondrial Ca²⁺ levels and induced ER stress via proteasome inhibition in these cells. Both MCU (mitochondrial Ca²⁺ uniporter) knockdown and pretreatment with ruthenium red, an inhibitor of MCU, inhibited celastrol-induced mitochondrial Ca²⁺ uptake, dilation of mitochondria/ER, accumulation of poly-ubiquitinated proteins, and cell death in MDA-MB 435S cells. Inhibition of the IP₃ receptor (IP₃R) with 2-aminoethoxydiphenyl borate (2-APB) also effectively blocked celastrol-induced mitochondrial Ca²⁺ accumulation and subsequent paraptotic events. Collectively, our results show that the IP₃R-mediated release of Ca²⁺ from the ER and its subsequent MCU-mediated influx into mitochondria critically contribute to celastrol-induced paraptosis in cancer cells.

Anti-metastatic effect of jolkinolide B and the mechanism of activity in breast cancer MDA-MB-231 cells

Tumor metastasis is the main cause of mortality in cancer patients. However, no effective therapies are currently available to prevent metastasis. Cell adhesion to the extracellular matrix (ECM) is crucial in cancer progression and metastasis. Thus, suppression of cell adhesion may be an effective therapeutic strategy for the prevention of metastasis. In the present study, the anti-adhesion and anti-invasion effects of jolkinolide B, a diterpenoid compound from Euphorbia fischeriana Steud, that were exerted through suppression of β₁-integrin expression and phosphorylation of focal adhesion kinase (FAK) were examined in human breast cancer MDA-MB-231 cells. Jolkinolide B inhibited the adhesion of MDA-MB-231 cells to fibronectin but not to poly-L-lysine. In addition, jolkinolide B inhibited extracellular signal-regulated kinase (ERK) phosphorylation. U0126, an ERK inhibitor, also suppressed the invasion and adhesion of MDA-MB-231 cells. Overall, the present data demonstrated that jolkinolide B is a novel inhibitor of FAK-mediated signaling pathways that is involved in decreasing cell adhesion and invasion. Mitogen-activated protein kinase/ERK kinase may play a critical role in these effects, indicating that jolkinolide B possesses therapeutic potential for the treatment of breast cancer metastasis.

Celastrol stimulates hypoxia-inducible factor-1 activity in tumor cells by initiating the ROS/Akt/p70S6K signaling pathway and enhancing hypoxia-inducible factor-1α protein synthesis

Celastrol, a tripterine derived from the traditional Chinese medicine plant Tripterygium wilfordii Hook F. (“Thunder of God Vine”), has been reported to have multiple effects, such as anti-inflammation, suppression of tumor angiogenesis, inhibition of tumor growth, induction of apoptosis and protection of cells against human neurodegenerative diseases. However, the mechanisms that underlie these functions are not well defined. In this study, we reported for the first time that Celastrol could induce HIF-1α protein accumulation in multiple cancer cell lines in an oxygen-independent manner and that the enhanced HIF-1α protein entered the nucleus and promoted the transcription of the HIF-1 target genes VEGF and Glut-1. Celastrol did not influence HIF-1α transcription. Instead, Celastrol induced the accumulation of the HIF-1α protein by inducing ROS and activating Akt/p70S6K signaling to promote HIF-1α translation. In addition, we found that the activation of Akt by Celastrol was transient. With increased exposure time, inhibition of Hsp90 chaperone function by Celastrol led to the subsequent depletion of the Akt protein and thus to the suppression of Akt activity. Moreover, in HepG2 cells, the accumulation of HIF-1α increased the expression of BNIP3, which induced autophagy. However, HIF-1α and BNIP3 did not influence the cytotoxicity of Celastrol because the main mechanism by which Celastrol kills cancer cells is through stimulating ROS-mediated JNK activation and inducing apoptosis. Furthermore, our data showed that the dose required for Celastrol to induce HIF-1α protein accumulation and enhance HIF-1α transcriptional activation was below its cytotoxic threshold. A cytotoxic dose of Celastrol for cancer cells did not display cytotoxicity in LO2 normal human liver cells, which indicated that the novel functions of Celastrol in regulating HIF-1 signaling and inducing autophagy might be used in new applications, such as in anti-inflammation and protection of cells against human neurodegenerative diseases. Future studies regarding these applications are required.

Gambogic amide selectively upregulates TrkA expression and triggers its activation

BACKGROUND

Gambogic amide is the first identified small molecular agonist for TrkA receptor. It mimics NGF functions by selectively activating TrkA receptor and preventing neuron death. However, its function different from that of NGF remains unknown.

METHODS

In the current study, we detect the effect of gambogic amide on TrkA expression using TrkA-expressing cell lines in vitro and hippocampi from mice treated with gambogic amide.

RESULTS

We have confirmed that gambogic amide displays robust neurotrophic activities in provoking neurite outgrowth in vitro. However, gambiogic amide displays a different kinetics from NGF in activating TrkA signals. NGF swiftly provokes TrkA activation and quickly induces TrkA degradation, while gambogic amid selectively upregulates TrkA protein and mRNA levels in a time-dependent manner. Administration of this compound in mice also activates TrkA receptor in hippocampus and promotes TrkA transcription and expression.

CONCLUSION

This study provides a novel mechanism of how gambogic amide regulates TrkA receptor, other than mimicking NGF in triggering TrkA activation.

Celastrol inhibits lung infiltration in differential syndrome animal models by reducing TNF-α and ICAM-1 levels while preserving differentiation in ATRA-induced acute promyelocytic leukemia cells

All-trans retinoic acid (ATRA) is a revolutionary agent for acute promyelocytic leukemia (APL) treatment via differentiation induction. However, ATRA treatment also increases cytokine, chemokine, and adhesive molecule (mainly ICAM-1) expression, which can cause clinical complications, including a severe situation known as differentiation syndrome (DS) which can cause death. Therefore, it is of clinical significance to find a strategy to specifically blunt inflammatory effects while preserving differentiation. Here we report that the natural compound, celastrol, could effectively block lung infiltrations in DS animal models created by loading ATRA-induced APL cell line NB4. In ATRA-treated NB4 cells, celastrol could potently inhibit ICAM-1 elevation and partially reduce TNF-α and IL-1β secretion, though treatment showed no effects on IL-8 and MCP-1 levels. Celastrol’s effect on ICAM-1 in ATRA-treated NB4 was related to reducing MEK1/ERK1 activation. Strikingly and encouragingly, celastrol showed no obvious effects on ATRA-induced NB4 differentiation, as determined by morphology, enzymes, and surface markers. Our results show that celastrol is a promising and unique agent for managing the side effects of ATRA application on APL, and suggest that hyper-inflammatory ability is accompanied by, but not necessary for, APL differentiation. Thus we offered an encouraging novel strategy to further improve differentiation therapy.

Peptide deformylase inhibitor actinonin reduces celastrol's HSP70 induction while synergizing proliferation inhibition in tumor cells

Background

Celastrol is a promising anti-tumor agent, yet it also elevates heat shock proteins (HSPs), especially HSP70, this effect believed to reduce its anti-tumor effects. Concurrent use of siRNA to increase celastrol’s anti-tumor effects through HSP70 interference has been reported, but because siRNA technology is difficult to clinically apply, an alternative way to curb unwanted HSP70 elevation caused by celastrol treatment is worth exploring.

Methods

In this work, we explore three alternative strategies to control HSP70 elevation: (1) Searching for cancer cell types that show no HSP70 elevation in the presence of celastrol (thus recommending themselves as suitable targets); (2) Modifying HSP70-inducing chemical groups, i.e.: the carboxyl group in celastrol; and (3) Using signaling molecule inhibitors to specifically block HSP70 elevation while protecting and/or enhancing anti-tumor effects.

Results

The first strategy was unsuccessful since celastrol treatment increased HSP70 in all 7 of the cancer cell types tested, this result related to HSF1 activation. The ubiquity of HSF1 expression in different cancer cells might explain why celastrol has no cell-type limitation for HSP70 induction. The second strategy revealed that modification of celastrol’s carboxyl group abolished its ability to elevate HSP70, but also abolished celastrol’s tumor inhibition effects. In the third strategy, 11 inhibitors for 10 signaling proteins reportedly related to celastrol action were tested, and five of these could reduce celastrol-caused HSP70 elevation. Among these, the peptide deformylase (PDF) inhibitor, actinonin, could synergize celastrol’s proliferation inhibition.

Conclusions

Concurrent use of the chemical agent actinonin could reduce celastrol’s HSP70 elevation and also enhance proliferation inhibition by celastrol. This combination presents a novel alternative to siRNA technology and is worth further investigation for its potentially effective anti-tumor action.

Celastrol prevents cadmium-induced neuronal cell death via targeting JNK and PTEN-Akt/mTOR network

Cadmium (Cd), a toxic environmental contaminant, induces neurodegenerative diseases. Celastrol, a plant-derived triterpene, has shown neuroprotective effects in various disease models. However, little is known regarding the effect of celastrol on Cd-induced neurotoxicity. Here, we show that celastrol protected against Cd-induced apoptotic cell death in neuronal cells. This is supported by the findings that celastrol strikingly attenuated Cd-induced viability reduction, morphological change, nuclear fragmentation, and condensation, as well as activation of caspase-3 in neuronal cells. Concurrently, celastrol remarkably blocked Cd-induced phosphorylation of c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinases 1/2 and p38, in neuronal cells. Inhibition of JNK by SP600125 or over-expression of dominant negative c-Jun potentiated celastrol protection against Cd-induced cell death. Furthermore, pre-treatment with celastrol prevented Cd down-regulation of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and activation of phosphoinositide 3'-kinase/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling in neuronal cells. Over-expression of wild-type PTEN enhanced celastrol inhibition of Cd-activated Akt/mTOR signaling and cell death in neuronal cells. The findings indicate that celastrol prevents Cd-induced neuronal cell death via targeting JNK and PTEN-Akt/mTOR network. Our results strongly suggest that celastrol may be exploited for the prevention of Cd-induced neurodegenerative disorders. Celastrol, a plant-derived triterpene, has shown neuroprotective effects. However, little is known regarding the effect of celastrol on cadmium (Cd) neurotoxicity. This study underscores that celastrol prevents Cd-induced neuronal apoptosis via inhibiting activation of JNK (c-Jun N-terminal kinase) and Akt/mTOR network. Celastrol suppresses Cd-activated Akt/mTOR pathway by elevating PTEN (phosphatase and tensin homolog). The findings suggest that celastrol may be exploited for the prevention of Cd-induced neurodegenerative disorders.

An open source based high content screening method for cell biology laboratories investigating cell spreading and adhesion

BACKGROUND

Adhesion dependent mechanisms are increasingly recognized to be important for a wide range of biological processes, diseases and therapeutics. This has led to a rising demand of pharmaceutical modulators. However, most currently available adhesion assays are time consuming and/or lack sensitivity and reproducibility or depend on specialized and expensive equipment often only available at screening facilities. Thus, rapid and economical high-content screening approaches are urgently needed.

RESULTS

We established a fully open source high-content screening method for identifying modulators of adhesion. We successfully used this method to detect small molecules that are able to influence cell adhesion and cell spreading of Swiss-3T3 fibroblasts in general and/or specifically counteract Nogo-A-Δ20-induced inhibition of adhesion and cell spreading. The tricyclic anti-depressant clomipramine hydrochloride was shown to not only inhibit Nogo-A-Δ20-induced cell spreading inhibition in 3T3 fibroblasts but also to promote growth and counteract neurite outgrowth inhibition in highly purified primary neurons isolated from rat cerebellum.

CONCLUSIONS

We have developed and validated a high content screening approach that can be used in any ordinarily equipped cell biology laboratory employing exclusively freely available open-source software in order to find novel modulators of adhesion and cell spreading. The versatility and adjustability of the whole screening method will enable not only centers specialized in high-throughput screens but most importantly also labs not routinely employing screens in their daily work routine to investigate the effects of a wide range of different compounds or siRNAs on adhesion and adhesion-modulating molecules.

Asiatic acid, a triterpene, inhibits cell proliferation through regulating the expression of focal adhesion kinase in multiple myeloma cells

The aim of the present study was to investigate whether asiatic acid (AA), a pentacyclic triterpene derived from Centella asiatica, exerts anti-proliferative effects on multiple myeloma RPMI 8226 cells and to determine the molecular mechanism underlying the anticancer action of AA. The study sought to analyze the potential role of AA on the proliferation of the RPMI 8226 cells using a 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium assay. Cell cycle arrest was detected by flow cytometry, and the expression levels of focal adhesion kinase (FAK) in the myeloma cells induced by AA were analyzed using the western blotting and immunoprecipitation methods. The results indicated that AA significantly inhibited cell proliferation in a time- and dose-dependent manner and led to G₂/M phase arrest at concentrations of 35 and 40 μmol/l in the RPMI 8226 cells. The expression levels of FAK and p-FAK were distinctly decreased following AA treatment (at the concentration of 40 μmol/l) for 24 h compared with that of the control groups. Taken together, these results demonstrated that AA was able to regulate cell cycle progression in RPMI 8226 cells, thereby significantly inhibiting cell growth. Furthermore, AA decreased the expression levels of FAK, indicating that the antitumor mechanism of AA may be associated with the inhibition of signal transduction mediated by FAK.

AFM studied the effect of celastrol on β1 integrin-mediated HUVEC adhesion and migration

Integrin-mediated human umbilical vein endothelial cells (HUVECs) adhesion to the extracellular matrix plays a fundamental role in tumor-induced angiogenesis. Celastrol, a traditional Chinese medicine plant, has possessed anticancer and suppressed angiogenesis activities. Here, the mechanism underling the antiangiogenesis capacity of celastrol was investigated by exploring the effect of celastrol on β1(CD29) integrin-mediated cell adhesion and migration. Flow cytometry results showed that the HUVECs highly expressed CD29 and cell adhesion assay indicated that celastrol specifically inhibited the adhesion of HUVECs to fibronectin (FN) without affecting nonspecific adhesion to poly-L-lysine (PLL). After cell FN adhesion being inhibited, the cell surface nanoscale structure and adhesion force were detected by atomic force microscope (AFM). High-resolution imaging revealed that cell morphology and ultrastructure changed a lot after being treated with celastrol. The membrane average roughness (Ra) and the major forces were decreased from 31.34 ± 4.56 nm, 519.60 ± 82.86 pN of 0 μg/ml celastrol to 18.47 ± 6.53 nm, 417.79 ± 53.35 pN of 4.0 μg/ml celastrol, 10.54 ± 2.85 nm, 258.95 ± 38.98 pN of 8.0 μg/ml celastrol, respectively. Accompanying with the decrease of adhesion force, the actin cytoskeleton in the cells was obviously disturbed by the celastrol. All of these changes influenced the migration of HUVECs from the wound-healing migration assay. Taken together, our results suggest that celastrol can be as an inhibitor of HUVEC adhesion to FN. This work provides a novel approach to inhibition of tumor angiogenesis and tumor growth.

Celastrol suppresses tumor cell growth through targeting an AR-ERG-NF-κB pathway in TMPRSS2/ERG fusion gene expressing prostate cancer

The TMPRSS2/ERG (T/E) fusion gene is present in the majority of all prostate cancers (PCa). We have shown previously that NF-kB signaling is highly activated in these T/E fusion expressing cells via phosphorylation of NF-kB p65 Ser536 (p536). We therefore hypothesize that targeting NF-kB signaling may be an efficacious approach for the subgroup of PCas that carry T/E fusions. Celastrol is a well known NF-kB inhibitor, and thus may inhibit T/E fusion expressing PCa cell growth. We therefore evaluated Celastrol's effects in vitro and in vivo in VCaP cells, which express the T/E fusion gene. VCaP cells were treated with different concentrations of Celastrol and growth inhibition and target expression were evaluated. To test its ability to inhibit growth in vivo, 0.5 mg/kg Celastrol was used to treat mice bearing subcutaneous VCaP xenograft tumors. Our results show Celastrol can significantly inhibit the growth of T/E fusion expressing PCa cells both in vitro and in vivo through targeting three critical signaling pathways: AR, ERG and NF-kB in these cells. When mice received 0.5 mg/kg Celastrol for 4 times/week, significant growth inhibition was seen with no obvious toxicity or significant weight loss. Therefore, Celastrol is a promising candidate drug for T/E fusion expressing PCa. Our findings provide a novel strategy for the targeted therapy which may benefit the more than half of PCa patients who have T/E fusion expressing PCas.

The tumor suppressor gene ARHI (DIRAS3) inhibits ovarian cancer cell migration through multiple mechanisms

ARHI is an imprinted tumor suppressor gene that is downregulated in > 60% of ovarian cancers, associated with decreased progression-free survival. ARHI encodes a 26 kDa GTPase with homology to Ras. Re-expression of ARHI inhibits ovarian cancer growth, initiates autophagy and induces tumor dormancy. Recent studies have demonstrated that ARHI also plays a particularly important role in ovarian cancer cell migration. Re-expression of ARHI decreases motility of IL-6- and EGF-stimulated SKOv3 and Hey ovarian cancer cells, inhibiting both chemotaxis and haptotaxis. ARHI inhibits cell migration by binding and sequestering STAT3 in the cytoplasm, and preventing STAT3 translocation to the nucleus and localization in focal adhesion complexes. Re-expression of ARHI inhibits FAK (Y397) phosphorylation, disrupts focal adhesions and blocks FAK-mediated RhoA signaling, resulting in decreased levels of GTP-RhoA. Re-expression of ARHI disrupts formation of actin stress fibers in a FAK- and RhoA-dependent manner. Recent studies indicate that re-expression of ARHI inhibits expression of β-1 integrin which may also contribute to inhibition of migration, adhesion and invasion.

Up-regulation of TIMP-1 by genipin inhibits MMP-2 activities and suppresses the metastatic potential of human hepatocellular carcinoma

Aim of the Study

Hepatocellular carcinoma is one of the most malignant human cancers with high metastatic potential. The aim of this study is to investigate the anti-metastatic effect of genipin and its underlying mechanism.

Experimental Approach

The anti-metastatic potential of genipin was evaluated by both cell and animal model. Wound healing and invasion chamber assays were introduced to examine the anti-migration and anti-invasion action of genipin in human hepatocellular carcinoma cell HepG2 and MHCC97L; orthotopical implantation model was used for in vivo evaluation. Gelatin Zymography, Immunoblotting, quantitative real-time polymerase chain reaction and ELISA assays were used to study the mechanisms underlying genipin’s anti-metastatic effect.

Key Results

Genipin suppresses the motility and invasiveness of HepG2 and MHCC97L at non-toxic doses, which may be correlated to the inhibition of genipin on MMP-2 activities in the cells. No significant reduced expression of MMP-2 was observed either at mRNA or at protein level. Furthermore, genipin could specifically up-regulate the expression of TIMP-1, the endogenous inhibitor of MMP-2 activities. Silencing of TIMP-1 by RNA interference abolishes genipin’s anti-metastaic effect. Activation of p38 MAPK signaling was observed in genipin-treated cells, which is responsible for the TIMP-1 overexpression and MMP-2 inhibition. Presence of SB202190, the p38 MAPK inhibitor, attenuates the anti-metastatic potential of genipin in hepatocellular carcinoma. Orthotopical implantation model showed that genipin could suppress the intrahepatic metastatic as well as tumor expansion in liver without exhibiting potent toxicity.

Conclusion

Our findings demonstrated the potential of genipin in suppressing hepatocellular carcinoma metastasis, and p38/TIMP-1/MMP-2 pathway may be involved as the key mechanism of its anti-metastasis effect.

Preparation, characterization, and assessment of the antiglioma effects of liposomal celastrol

The role of celastrol in the treatment of cancer has been an area of growing interest. To circumvent the issues of low solubility, poor bioavailability, and systemic toxicity of celastrol, we prepared liposomal celastrol using the thin-film dispersion method. We characterized particle size, encapsulation efficiency, and pharmacological parameters of liposomal celastrol. The drug concentration in plasma and tissues was measured using LC-MS/MS. In addition, the sulforhodamine B assay was used to determine the 50% inhibiting concentration. We assessed the effects of the compound in SHG-44 glioma subcutaneous xenografts in BALB/c nude mice. To compare the toxic effects of liposomal and free celastrol, the weight as well as hematologic, heart, liver, and kidney parameters were measured weekly and the morphology of organ tissues was observed pathologically. We found that liposomal celastrol had high encapsulation efficiency (71.67%) and liposomal celastrol had a higher C(max) and area under the curve, longer t(1/2), and better biodistribution than free celastrol. A cytotoxicity assay indicated that free celastrol had lower 50% inhibiting concentration values than the liposomal celastrol; however, treatment of subcutaneous xenografts with 1 mg/kg of liposomal celastrol induced greater antitumor activity than free celastrol at an equimolar concentration. In addition, a 4 mg/kg dose of liposomal celastrol had fewer severe side effects than free celastrol at the same dose. In this study, we found that the use of liposomes as a carrier of celastrol increased the bioavailability and reduced the side effects of the compound. Our findings suggest that liposomal celastrol should be further investigated in the clinical setting.

Furanodiene induces endoplasmic reticulum stress and presents antiproliferative activities in lung cancer cells

Furanodiene (FUR) is a natural terpenoid isolated from Curcumae Rhizoma, a well-known Chinese medicinal herb that presents antiproliferation activities in several cancer cell lines. In this study, we demonstrated that FUR concentration dependently inhibits the cell proliferation of A549, NIH-H1299, and 95-D lung cancer cells. β-elemene, another terpenoid isolated from Curcumae Rhizoma, exhibited weaker antiproliferative effects in A549 and NIH-H1299 cells and activities similar to FUR in 95-D cells. FUR significantly inhibited colony formation in A549 and 95-D cells and upregulated both the mRNA and protein expression levels of binding immunoglobulin protein (BIP) and C/EBP homologous protein (CHOP), indicating that endoplasmic reticulum (ER) stress is induced. FUR treatment led to the accumulation of CHOP in the nucleus, which further confirms induction of ER stress. Furthermore, combined treatment of FUR with paclitaxel showed significant synergetic activities in NIH-H1299 and 95-D cells, suggesting its potential roles in combination therapy. These findings provide a basis for the further study of the anticancer effects in vivo and the internal mechanisms of FUR.

Modulation of inflammatory signaling and cytokine release from microglia by celastrol incorporated into dendrimer nanocarriers

Aim: This study investigates the capacity of a potent anti-inflammatory nanomedicine, celastrol, incorporated into poly(amidoamine) dendrimers, to inhibit endotoxin-mediated signaling in microglia. Materials & methods: Celastrol was incorporated into amino (Cel/G4-NH2) and hydroxyl (Cel/G4-OH) terminus poly(amidoamine) (G4) dendrimers. Cell viability, release of nitric oxide, IL-6, TNF-α and activation of MAPK (e.g., p38 and JNK) and NF-κB were assessed in endotoxin (i.e., lipopolysaccharide) stimulated microglial cells. Results: G4-OH and G4-NH2 increased celastrol aqueous solubility by seven- and 12-fold, respectively. G4-OH and Cel/G4-OH suppressed lipopolysaccharide-mediated release of proinflammatory mediators, such as nitric oxide and IL-6, but not TNF-α, without reducing microglial cell viability, while Cel/G4-NH2 potentiated cytotoxicity and cytokine release. Blockade of proinflammatory signaling was accompanied by attenuation of p38 MAPK activation. Conclusion: This study supports the potential use of poly(amidoamine) dendrimers for effective anti-inflammatory therapy in the chronically inflamed CNS.

Original submitted 22 July 2011; Revised submitted 8 December 2011; Published online 4 April 2012

Alkaloids from Pachysandra terminalis inhibit breast cancer invasion and have potential for development as antimetastasis therapeutic agents

The aim of the present study was to identify potentially useful natural compounds for the development of novel therapeutic agents to inhibit metastasis. A phytochemical investigation of Pachysandra terminalis resulted in the isolation of seven new pregnane alkaloids, terminamines A-G (1-7), and seven known alkaloids (8-14). The structures of 1-7 were elucidated by 1D- and 2D-NMR spectroscopic and mass spectrometric methods. Compounds 1-5 and 8-14 inhibited the migration of MB-MDA-231 breast cancer cells induced by the chemokine epithelial growth factor. In addition, compound 1 inhibited phosphorylation of integrin β(1), which plays an important role in MB-MDA-231 cell adhesion and metastasis.

Strong inhibition of celastrol towards UDP-glucuronosyl transferase (UGT) 1A6 and 2B7 indicating potential risk of UGT-based herb-drug interaction

Celastrol, a quinone methide triterpene isolated from Tripterygium wilfordii Hook F., has various biochemical and pharmacological activities, and is now being developed as a promising anti-tumor agent. Inhibitory activity of compounds towards UDP-glucuronosyltransferase (UGT) is an important cause of clinical drug-drug interactions and herb-drug interactions. The aim of the present study is to investigate the inhibition of celastrol towards two important UDP-glucuronosyltransferase (UGT) isoforms UGT1A6 and UGT2B7. Recombinant UGT isoforms and non-specific substrate 4-methylumbelliferone (4-MU) were used. The results showed that celastrol strongly inhibited the UGT1A6 and 2B7-mediated 4-MU glucuronidation reaction, with 0.9 ± 0.1% and 1.8 ± 0.2% residual 4-MU glucuronidation activity at 100 μM of celastrol, respectively. Furthermore, inhibition kinetic study (Dixon plot and Lineweaver-Burk plot) demonstrated that celastrol noncompetitively inhibited the UGT1A1-mediated 4-MU glucuronidation, and competitively inhibited UGT2B7-catalyzed 4-MU glucuronidation. The inhibition kinetic parameters (Ki) were calculated to be 0.49 μM and 0.045 μM for UGT1A6 and UGT2B7, respectively. At the therapeutic concentration of celastrol for anti-tumor utilization, the possibility of celastrol-drug interaction and celastrol-containing herbs-drug interaction were strongly indicated. However, given the complicated nature of herbs, these results should be viewed with more caution.

Histamine modulates microglia function

BACKGROUND

Histamine is commonly acknowledged as an inflammatory mediator in peripheral tissues, leaving its role in brain immune responses scarcely studied. Therefore, our aim was to uncover the cellular and molecular mechanisms elicited by this molecule and its receptors in microglia-induced inflammation by evaluating cell migration and inflammatory mediator release.

METHODS

Firstly, we detected the expression of all known histamine receptor subtypes (H1R, H2R, H3R and H4R), using a murine microglial cell line and primary microglia cell cultures from rat cortex, by real-time PCR analysis, immunocytochemistry and Western blotting. Then, we evaluated the role of histamine in microglial cell motility by performing scratch wound assays. Results were further confirmed using murine cortex explants. Finally, interleukin-1beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) levels were evaluated by ELISA measurements to determine the role of histamine on the release of these inflammatory mediators.

RESULTS

After 12 h of treatment, 100 μM histamine and 10 μg/ml histamine-loaded poly (lactic-co-glycolic acid) microparticles significantly stimulated microglia motility via H4R activation. In addition, migration involves α5β1 integrins, and p38 and Akt signaling pathways. Migration of microglial cells was also enhanced in the presence of lipopolysaccharide (LPS, 100 ng/ml), used as a positive control. Importantly, histamine inhibited LPS-stimulated migration via H4R activation. Histamine or H4R agonist also inhibited LPS-induced IL-1β release in both N9 microglia cell line and hippocampal organotypic slice cultures.

CONCLUSIONS

To our knowledge, we are the first to show a dual role of histamine in the modulation of microglial inflammatory responses. Altogether, our data suggest that histamine per se triggers microglia motility, whereas histamine impedes LPS-induced microglia migration and IL-1β release. This last datum assigns a new putative anti-inflammatory role for histamine, acting via H4R to restrain exacerbated microglial responses under inflammatory challenge, which could have strong repercussions in the treatment of CNS disorders accompanied by microglia-derived inflammation.

Targeted inhibition of tumor proliferation, survival, and metastasis by pentacyclic triterpenoids: potential role in prevention and therapy of cancer

Over the last two decades, extensive research on plant-based medicinal compounds has revealed exciting and important pharmacological properties and activities of triterpenoids. Fruits, vegetables, cereals, pulses, herbs and medicinal plants are all considered to be biological sources of these triterpenoids, which have attracted great attention especially for their potent anti-inflammatory and anti-cancer activities. Published reports in the past have described the molecular mechanism(s) underlying the various biological activities of triterpenoids which range from inhibition of acute and chronic inflammation, inhibition of tumor cell proliferation, induction of apoptosis, suppression of angiogenesis and metastasis. However systematic analysis of various pharmacological properties of these important classes of compounds has not been done. In this review, we describe in detail the pre-clinical chemopreventive and therapeutic properties of selected triterpenoids that inhibit multiple intracellular signaling molecules and transcription factors involved in the initiation, progression and promotion of various cancers. Molecular targets modulated by these triterpenoids comprise, cytokines, chemokines, reactive oxygen intermediates, oncogenes, inflammatory enzymes such as COX-2, 5-LOX and MMPs, anti-apoptotic proteins, transcription factors such as NF-κB, STAT3, AP-1, CREB, and Nrf2 (nuclear factor erythroid 2-related factor) that regulate tumor cell proliferation, transformation, survival, invasion, angiogenesis, metastasis, chemoresistance and radioresistance. Finally, this review also analyzes the potential role of novel synthetic triterpenoids identified recently which mimic natural triterpenoids in physical and chemical properties and are moving rapidly from bench to bedside research.

Celastrol decreases specificity proteins (Sp) and fibroblast growth factor receptor-3 (FGFR3) in bladder cancer cells

Celastrol (CSL) is a naturally occurring triterpenoid acid that exhibits anticancer activity, and in KU7 and 253JB-V bladder cells, CSL induced apoptosis, inhibited growth, colony formation and migration and CSL decreased bladder tumor growth in vivo. CSL also decreased expression of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and several Sp-regulated genes/proteins including vascular endothelial growth factor, survivin and cyclin D1 and fibroblast growth factor receptor-3, a potential drug target for bladder cancer therapy, has now been characterized as an Sp-regulated gene downregulated by CSL. The mechanism of Sp downregulation by CSL was cell context-dependent due to activation of proteosome-dependent (KU7) and -independent (253JB-V) pathways. In 253JB-V cells, CSL induced reactive oxygen species (ROS) and inhibitors of ROS blocked CSL-induced growth inhibition and repression of Sp1, Sp3 and Sp4. This response was due to induction of the Sp repressors ZBTB10 and ZBTB4 and downregulation of miR-27a and miR-20a/17-5p, respectively, which regulate expression of these transcriptional repressors. Thus, the anticancer activity of CSL in 253JB-V cells is due to induction of ROS and ROS-mediated induction of Sp repressors (ZBTB4/ZBTB10) through downregulation of miR-27a and miR-20a/17-5p.

Resveratrol suppresses human colon cancer cell proliferation and induces apoptosis via targeting the pentose phosphate and the talin-FAK signaling pathways-A proteomic approach

Background

We and others have previously reported that resveratrol (RSV) suppresses colon cancer cell proliferation and elevates apoptosis in vitro and/or in vivo, however molecular mechanisms are not fully elucidated. Particularly, little information is available on RSV's effects on metabolic pathways and the cell-extra cellular matrix (ECM) communication that are critical for cancer cell growth. To identify important targets of RSV, we analyzed whole protein fractions from HT-29 advanced human colon cancer cell line treated with solvent control, IGF-1 (10 nM) and RSV (150 μM) using LC/MS/MS-Mud PIT (Multidimensional Protein Identification Technology).

Results

Pentose phosphate pathway (PPP), a vital metabolic pathway for cell cycle progression, was elevated and suppressed by IGF-1 and RSV, respectively in the HT-29 cell line. Enzymatic assays confirmed RSV suppression of glucose-6 phosphate dehydrogenase (rate limiting) and transketolase, key enzymes of the PPP. RSV (150 μM) suppressed, whereas IGF-1 (10 nM) elevated focal adhesion complex (FAC) proteins, talin and pFAK, critical for the cell-ECM communication. Western blotting analyses confirmed the suppression or elevation of these proteins in HT-29 cancer cells treated with RSV or IGF-1, respectively.

Conclusions

Proteomic analysis enabled us to establish PPP and the talin-pFAK as targets of RSV which suppress cancer cell proliferation and induce apoptosis in the colon cancer cell line HT-29. RSV (150 μM) suppressed these pathways in the presence and absence of IGF-1, suggesting its role as a chemo-preventive agent even in obese condition.

The main anticancer bullets of the Chinese medicinal herb, thunder god vine

The thunder god vine or Tripterygium wilfordii Hook. F. is a representative Chinese medicinal herb which has been used widely and successfully for centuries in treating inflammatory diseases. More than 100 components have been isolated from this plant, and most of them have potent therapeutic efficacy for a variety of autoimmune and inflammatory diseases. In the past four decades, the anticancer activities of the extracts from this medicinal herb have attracted intensive attention by researchers worldwide. The diterpenoid epoxide triptolide and the quinone triterpene celastrol are two important bioactive ingredients that show a divergent therapeutic profile and can perturb multiple signal pathways. Both compounds promise to turn traditional medicines into modern drugs. In this review, we will mainly address the anticancer activities and mechanisms of action of these two agents and briefly describe some other antitumor components of the thunder god vine.