Rhein induces apoptosis in human breast cancer cells

Pancreatic Stellate Cells and the Targeted Therapeutic Strategies in Chronic Pancreatitis

Chronic pancreatitis (CP) is a disease characterized by inflammatory recurrence that accompanies the development of pancreatic fibrosis. As the mystery of CP pathogenesis is gradually revealed, accumulating evidence suggests that the activation of pancreatic stellate cells (PSCs) and the appearance of a myofibroblast-like phenotype are the key gatekeepers in the development of CP. Targeting PSCs to prevent their activation and conversion to a myofibroblast-like phenotype, as well as increasing antioxidant capacity to counteract ongoing oxidative stress, are effective strategies for preventing or treating CP. Therefore, we reviewed the crosstalk between CP and pancreatic fibrosis, summarized the activation mechanisms of PSCs, and investigated potential CP therapeutic strategies targeting PSCs, including, but not limited to, anti-fibrosis therapy, antioxidant therapy, and gene therapy. Meanwhile, the above therapeutic strategies are selected in order to update the available phytopharmaceuticals as novel complementary or alternative approaches for the prevention and treatment of CP to clarify their potential mechanisms of action and their relevant molecular targets, aiming to provide the most comprehensive therapeutic treatment direction for CP and to bring new hope to CP patients.

Rhein promotes TRAIL-induced apoptosis in bladder cancer cells by up-regulating DR5 expression

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) combined with sensitizer is a potential method to reverse TRAIL-resistance in tumor cells. Rhein (RH) is a monomer extracted from Chinese herbs that has been reported to show anti-tumor effects in a variety of tumor cells, but the role of RH in TRAIL-induced anti-tumor effects in bladder cancer cells has not been reported. In this study, we found that the combined treatment of a non-toxic concentration of RH with TRAIL significantly inhibited the proliferation and induced apoptosis in both TRAIL sensitive and resistant bladder cancer cell lines. Furthermore, we found that RH promoted bladder cancer cell apoptosis by up-regulating DR5 expression. Our findings provide potential value in the clinical treatment of bladder cancer.

Rhein Inhibits the Progression of Chemoresistant Lung Cancer Cell Lines via the Stat3/Snail/MMP2/MMP9 Pathway

Chemotherapy is a common drug for lung cancer. Nevertheless, the development of drug resistance greatly limits their clinical efficacy. Therefore, to reduce drug resistance, we need to constantly explore new treatments. This study is aimed at determining the role of rhein in the proliferation and metastasis of lung cancer cell. Our study found that rhein significantly inhibits the proliferation and migration of lung cancer cells. Additionally, the mRNA expression and protein levels of Snail, MMP2, and MMP9 are decreasing in lung cancer cells treated by rhein. Our results showed that rhein plays a vital role in proliferation and metastasis of chemosensitive and chemoresistant lung cancer cells, and the mechanism may be related to the Stat3/Snail/MMP2/MMP9 pathway.

The Phytochemical Rhein Mediates M6A-Independent Suppression of Adipocyte Differentiation

Adipogenesis is mediated by the complex gene expression networks involving the posttranscriptional modifications. The natural compound rhein has been linked to the regulation of adipogenesis, but the underlying regulatory mechanisms remain elusive. Herein, we systematically analyzed the effects of rhein on adipogenesis at both the transcriptional and posttranscriptional levels. Rhein remarkably suppresses adipogenesis in the stage-specific and dose-dependent manners. Rhein has been identified to inhibit fat mass and obesity-associated (FTO) demethylase activity. Surprisingly, side-by-side comparison analysis revealed that the rhein treatment and Fto knockdown triggered the differential gene regulatory patterns, resulting in impaired adipocyte formation. Specifically, rhein treatment mildly altered the transcriptome with hundreds of genes dysregulated. N⁶-methyladenosine (m⁶A) methylome profile showed that, although the supply of rhein induced increased m⁶A levels on a small subset of messenger RNAs (mRNAs), few of them showed dramatic transcriptional response to this compound. Moreover, the specific rhein-responsive mRNAs, which are linked to mitotic pathway, are barely methylated or contain m⁶A peaks without dramatic response to rhein, suggesting separate regulation of global m⁶A pattern and adipogenesis mediated by rhein. Further identification of m⁶A-independent pathways revealed a positive regulator, receptor expressing-enhancing protein 3 (REEP3), in guidance of adipogenesis. Hence, this study provides the mechanistic view of the cellular actions of rhein in the modulation of adipogenesis and identifies a potential novel target for obesity therapeutic research.

Update on Pharmacological Activities, Security, and Pharmacokinetics of Rhein

Rhein, belonging to anthraquinone compounds, is one of the main active components of rhubarb and Polygonum multiflorum. Rhein has a variety of pharmacological effects, such as cardiocerebral protective effect, hepatoprotective effect, nephroprotective effect, anti-inflammation effect, antitumor effect, antidiabetic effect, and others. The mechanism is interrelated and complex, referring to NF-κB, PI3K/Akt/MAPK, p53, mitochondrial-mediated signaling pathway, oxidative stress signaling pathway, and so on. However, to some extent, its clinical application is limited by its poor water solubility and low bioavailability. Even more, rhein has potential liver and kidney toxicity. Therefore, in this paper, the pharmacological effects of rhein and its mechanism, pharmacokinetics, and safety studies were reviewed, in order to provide reference for the development and application of rhein.

The Complex Roles and Therapeutic Implications of m6A Modifications in Breast Cancer

Accumulating evidence indicates that N⁶-methyladenosine (m⁶A), which directly regulates mRNA, is closely related to multiple biological processes and the progression of different malignancies, including breast cancer (BC). Studies of the aberrant expression of m⁶A mediators in BC revealed that they were associated with different BC subtypes and functions, such as proliferation, apoptosis, stemness, the cell cycle, migration, and metastasis, through several factors and signaling pathways, such as Bcl-2 and the PI3K/Akt pathway, among others. Several regulators that target m⁶A have been shown to have anticancer effects. Fat mass and obesity-associated protein (FTO) was identified as the first m⁶A demethylase, and a series of inhibitors that target FTO were reported to have potential for the treatment of BC by inhibiting cell proliferation and promoting apoptosis. However, the exact mechanism by which m⁶A modifications are regulated by FTO inhibitors remains unknown. m⁶A modifications in BC have only been preliminarily studied, and their mechanisms require further investigation.

Selective phytochemicals targeting pancreatic stellate cells as new anti-fibrotic agents for chronic pancreatitis and pancreatic cancer

Activated pancreatic stellate cells (PSCs) have been widely accepted as a key precursor of excessive pancreatic fibrosis, which is a crucial hallmark of chronic pancreatitis (CP) and its formidable associated disease, pancreatic cancer (PC). Hence, anti-fibrotic therapy has been identified as a novel therapeutic strategy for treating CP and PC by targeting PSCs. Most of the anti-fibrotic agents have been limited to phase I/II clinical trials involving vitamin analogs, which are abundant in medicinal plants and have proved to be promising for clinical application. The use of phytomedicines, as new anti-fibrotic agents, has been applied to a variety of complementary and alternative approaches. The aim of this review was to present a focused update on the selective new potential anti-fibrotic agents, including curcumin, resveratrol, rhein, emodin, green tea catechin derivatives, metformin, eruberin A, and ellagic acid, in combating PSC in CP and PC models. It aimed to describe the mechanism(s) of the phytochemicals used, either alone or in combination, and the associated molecular targets. Most of them were tested in PC models with similar mechanism of actions, and curcumin was tested intensively. Future research may explore the issues of bioavailability, drug design, and nano-formulation, in order to achieve successful clinical outcomes with promising activity and tolerability.

Protein profiling of SH-SY5Y neuroblastoma cells: The effect of rhein

4,5-Dihydroxyanthraquinone-2-carboxylic acid (Rhein) has been shown to have various physiological and pharmacological properties including anticancer activity and modulatory effects on bioenergetics. In this study, we explored the impact of rhein on protein profiling of undifferentiated (UC) and differentiated (DC) SH-SY5Y cells. Besides that, the cellular morphology and expression of differentiation markers were investigated to determine the effect of rhein on retinoic acidinduced neuronal cell differentiation. Using two-dimensional gel electrophoresis and matrix-assisted laser desorption/ ionization-time-of-flight mass spectrometry we evaluated the changes in the proteome of both UC and DC SH-SY5Y cells after 24 h treatment with rhein. Validation of selected differentially expressed proteins and the assessment of neuronal differentiation markers were performed by western blotting. Proteomic analysis revealed significant changes in the abundance of 15 proteins linked to specific cellular processes such as cytoskeleton structure and regulation, mitochondrial function, energy metabolism, protein synthesis and neuronal plasticity. We also observed that the addition of rhein to the cultured cells during differentiation resulted in a significantly reduced neurite outgrowth and decreased expression of neuronal markers. These results indicate that rhein may strongly interfere with the differentiation process of SH-SY5Y neuroblastoma cells and is capable of inducing marked proteomic changes in these cells.

Synergistic antitumor effects of rhein and doxorubicin in hepatocellular carcinoma cells

The aim of this study was to investigate the synergistic antitumor activity of rhein and doxorubicin (DOX) and to elucidate the underlying mechanisms in hepatocellular SMMC-7721 and HepG2 cells. Cell growth curves, caspase-3 activity, and intracellular DOX accumulation were observed using an IncuCyte real-time video imaging system. Combination index was used to calculate synergistic potential of rhein and DOX. Cell apoptosis was detected by the Annexin V-FITC/PI apoptosis kit. Lactate dehydrogenase and adenosine triphosphate (ATP) levels were assessed using an assay kit. Oxygen consumption rates (OCR) and extracellular acidification rates were assessed by the Seahorse XFe96 Extracellular Flux Analyzer. Mitochondrial inner membrane potential (ΔΨm) was monitored with JC-1 fluorescence. Western blot analysis was used to detect the level of P-glycoprotein. Synergistic antiproliferative and proapoptotic effects were exerted by the combination of rhein at 10 μM and DOX at 2 μM in SMMC-7721 and HepG2 cells. Rhein could influenced the accumulation of DOX in both cells, which was associated with remarkably decreased mitochondrial energy metabolism and ATP levels. Rhein could reduce ΔΨm in both cells. mPTP, opener atractyloside (ATR) could accelerate the loss of ΔΨm, and further suppress the OCR induced by rhein. In contrast, the mPTP blocker cyclosporin A (Cs A) inhibited the loss of ΔΨm and the OCR induced by rhein. Our data indicate that a decline in mitochondrial energy metabolism was responsible for the synergistic antitumor effects of rhein and DOX in hepatocellular carcinoma cells. Reduction of ΔΨm and opening of mPTP inhibited the exchange of ATP/adenosine diphosphate between mitochondrial matrix and cytoplasm is the important mechanism.

Inhibition of MDM2 by a Rhein-Derived Compound AQ-101 Suppresses Cancer Development in SCID Mice

A novel small-molecule anthraquinone (AQ) analogue, AQ-101, which was synthesized through chemical modification of the core structures of rhein, exhibited potent anticancer activity. In the present study, we evaluated the cancer-inhibiting mechanism of AQ-101 and tested the therapeutic potential of this compound for treating cancer in mice. We found that AQ-101 was able to induce MDM2 protein degradation through a self-ubiquitination and proteasome-mediated mechanism. This AQ-101-induced MDM2 downregulation led to activation of p53, which contributed to apoptosis of acute lymphoblastic leukemia (ALL), especially those with a wild-type p53 phenotype and MDM2 expression in vitro and in vivo When given for a period of 2 weeks (20 mg/kg/day, 3×/week), AQ-101 inhibited development of ALL in nude or SCID mice with a human ALL xenograft and achieved cure by the end of the 5-month experiment. Importantly, AQ-101 showed minimal or no inhibitory effect on normal human hematopoiesis in vitro and was well tolerated in vivo in animal models. Given that MDM2-overexpressing cancers are commonly refractory to current treatment options, our study results suggest that further development of AQ-101 is warranted, as it represents a potentially new, safe anticancer drug with a novel strategy for targeting MDM2. Mol Cancer Ther; 17(2); 497-507. ©2017 AACR.

Herbal remedies for liver fibrosis: A review on the mode of action of fifty herbs

Liver fibrosis is a dynamic pathological condition which can be slowed down in its initial phases. Without proper clinical management of fibrosis, progressive liver damage may lead to cirrhosis and ultimately to liver failure or primary liver cancer, which are irreversible conditions. Therefore, in order to cure fibrotic damage to liver, its early stages should be the centre of attention. In this context, some supplements and ‘complementary and alternative medicine (CAM)’ deserve specific mention, because of their already recognized natural way of healing and long lasting curative effects. Moreover, CAM display negligible side effects and hence it is gaining worldwide importance in clinical practices. In particular, herbal medicines are now replacing synthetic pharmaceuticals and looked upon as the sources of novel bioactive substances. To develop satisfactory herbal combinations for treating liver fibrosis, phytoproducts need to be systematically evaluated for their potency as anti-fibrotic, anti-hepatotoxic and antioxidant agents. More importantly, the identified herb/agent should have the remarkable tendency to stimulate hepatocytes regeneration. The present review is a systematic account of at least fifty medicinal herbs and their products which in experimental models have demonstrated antifibrotic activity and thus, most likely candidates to offer therapeutic protection to liver. Nevertheless, much additional work is still needed to explore molecular pathways to discover potential applications of these medicines so as to open up new vistas in biomedical research.

Rhein Induces Oxidative Stress and Apoptosis in Mouse Blastocysts and Has Immunotoxic Effects during Embryonic Development

Rhein, a glucoside chemical compound found in a traditional Chinese medicine derived from the roots of rhubarb, induces cell apoptosis and is considered to have high potential as an antitumor drug. Several previous studies showed that rhein can inhibit cell proliferation and trigger mitochondria-related or endoplasmic reticulum (ER) stress-dependent apoptotic processes. However, the side effects of rhein on pre- and post-implantation embryonic development remain unclear. Here, we show that rhein has cytotoxic effects on blastocyst-stage mouse embryos and induces oxidative stress and immunotoxicity in mouse fetuses. Blastocysts incubated with 5-20 μM rhein showed significant cell apoptosis, as well as decreases in their inner cell mass cell numbers and total cell numbers. An in vitro development assay showed that rhein affected the developmental potentials of both pre- and post-implantation embryos. Incubation of blastocysts with 5-20 μM rhein was associated with increased resorption of post-implantation embryos and decreased fetal weight in an embryo transfer assay. Importantly, in an in vivo model, intravenous injection of dams with rhein (1, 3, and 5 mg/kg body weight/day) for four days resulted in apoptosis of blastocyst-stage embryos, early embryonic developmental injury, and decreased fetal weight. Intravenous injection of dams with 5 mg/kg body weight/day rhein significantly increased the total reactive oxygen species (ROS) content of fetuses and the transcription levels of antioxidant proteins in fetal livers. Additional work showed that rhein induced apoptosis through ROS generation, and that prevention of apoptotic processes effectively rescued the rhein-induced injury effects on embryonic development. Finally, the transcription levels of the innate-immunity related genes, CXCL1, IL-1β and IL-8, were down-regulated in the fetuses of dams that received intravenous injections of rhein. These results collectively show that rhein has the potential to induce embryonic cytotoxicity and induce oxidative stress and immunotoxicity during the development of mouse embryos.

Affinity chromatographic methodologies based on immobilized voltage dependent anion channel isoform 1 and application in protein-ligand interaction analysis and bioactive compounds screening from traditional medicine

Voltage dependent anion channel isoform 1 (VDAC-1) serves as an attractive target of anti-cancer drugs by mediating the entry and exit of metabolites between cytoplasm and mitochondria. This work reports on the preparation of a VDAC-1-based bioaffinity chromatographic stationary phase by linking the protein on lecithin modified microspheres. An assay of chromatographic methods including frontal analysis, zonal elution, injection dependent analysis and nonlinear chromatography were utilized to investigate the bindings of ATP, NADH and NADPH to VDAC-1. Electrostatic interactions were found to be main forces during these bindings. The calculated association constants of the three ligands to VDAC-1 showed good agreements between diverse chromatographic methods. Validated application of the stationary phase was performed by screening anti-cancer compounds of Rheum officinale Baill. using high performance affinity chromatography coupled with electrospray ionization-quadrupole time of flight mass spectrometry. Chrysophanol, emodin, rhein, aloe-emodin and catechin were identified as the bioactive components of the herb. These compounds targeted VDAC-1 through Thr207 and the N-terminal region of the protein. Taken together, the current stationary phase was possible to become a promising tool for protein-ligand interaction analysis and anti-cancer drug screening from complex matrices.

Rhein exhibits antitumorigenic effects by interfering with the interaction between prolyl isomerase Pin1 and c-Jun

The Pin1 protein (or peptidyl-prolyl cis/trans isomerase) specifically catalyzes the cis/trans isomerization of phosphorylated serine/threonine-proline (Ser/Thr-Pro) bonds and plays an important role in many cellular events through the effects of conformational change in the function of c-Jun, its biological substrate. Pin1 expression is involved in essential cellular pathways that mediate cell proliferation, cell cycle progression, tumorigenesis and apoptosis by altering their stability and function, and it is overexpressed in various types of tumors. Pin1 phosphorylation has been regarded as a marker of Pin1 isomerase activity, and the phosphorylation of Ser/Thr-Pro on protein substrates is prerequisite for its binding activity with Pin1 and subsequent isomerization. Since phosphorylation of proteins on Ser/Thr-Pro is a key regulatory mechanism in the control of cell proliferation and transformation, Pin1 has become an attractive molecule in cancer research. Many inhibitors of Pin1 have been discovered, including several classes of both designed inhibitors and natural products. Anthraquinone compounds possess antitumor properties and have therefore been applied in human and veterinary therapeutics as active substances in medicinal products. Among the anthraquinones, rhein (4,5-dihydroxy-9,10-dioxoanthracene-2-carboxylic acid) is a monomeric anthraquinone derivative found mainly in plants in the Polygonaceae family, such as rhubarb and Polygonum cuspidatum. Recent studies have shown that rhein has numerous pharmacological activities, including antitumor effects. Here, we demonstrated the antitumorigenic effect of rhein using cell proliferation assay, anchorage-independent cell transformation, pull-down assay, luciferase promoter activity, fluorescence-activated cell sorting and western blot analysis. The rhein/Pin1 association was found to play a regulatory role in cell proliferation and neoplastic cell transformation and the binding of phosphorylated c-Jun (Ser73) with Pin1 was markedly decreased and inhibited activator protein 1 or NF-κB reporter activity by rhein. Overall, our findings and the accompanying biochemical data demonstrated the antitumorigenic effect of rhein through its interference in Pin1/c-Jun interaction and suggest the possible use of rhein in suppressing the tumor-promoting effects of Pin1. Therefore, rhein may have practical implications for cancer prevention or therapy.

Rhein suppresses matrix metalloproteinase production by regulating the Rac1/ROS/MAPK/AP-1 pathway in human ovarian carcinoma cells

Matrix metalloproteinases (MMPs) are a family of calcium-dependent zinc-containing endopeptidases, which play an integral role in migration and invasion of ovarian cancer. Rac1 proteins might mostly influence cell migration and invasion by generating endogenous reactive oxygen species. Therefore, inhibiting MMPs and regulating the Rac1/ROS/MAPK/AP-1 pathway may be a new therapeutic strategy for ovarian cancer. In this study, we found that rhein could suppress the invasion and migration of SKOV3-PM4 cells with characteristics of directional highly lymphatic metastasis. Phorbol 12-myristate 13-acetate (PMA), which is a Rac1 activator, significantly enhanced the expression levels of MMP-2, -3, -9 and -19 proteins, whereas the results of rhein and Rac1 inhibitor NSC23766 were just the opposite. The inhibitory effects of rhein were associated with the upregulation of tissue inhibitors of metalloproteinase (TIMP)-1, TIMP-2 and NM23-H1. Subsequent mechanism studies revealed that rhein reduce the production of reactive oxygen species (ROS) and lower NADPH oxidase activity. Furthermore, rhein significantly inhibited JNK, AP-1 phosphorylation in the cells treated with PMA. The results obtained from the cells treated with NSC23766 alone or NSC23766 combined with rhein, were consistent with rhein treatment alone. Taken together, these results indicate that rhein may be a potential inhibitor of Rac1 and can inhibit the migration and invasion of SKOV3-PM4 cells through modulating matrix metalloproteinases and RAC1/ROS/MAPK/AP-1 signaling pathway-associated proteins.

A Comprehensive and System Review for the Pharmacological Mechanism of Action of Rhein, an Active Anthraquinone Ingredient

Rhein is a major medicinal ingredient isolated from several traditional Chinese medicines, including Rheum palmatum L., Aloe barbadensis Miller, Cassia angustifolia Vahl., and Polygonum multiflorum Thunb. Rhein has various pharmacological activities, such as anti-inflammatory, antitumor, antioxidant, antifibrosis, hepatoprotective, and nephroprotective activities. Although more than 100 articles in PubMed are involved in the pharmacological mechanism of action of rhein, only a few focus on the relationship of crosstalk among multiple pharmacological mechanisms. The mechanism of rhein involves multiple pathways which contain close interactions. From the overall perspective, the pathways which are related to the targets of rhein, are initiated by the membrane receptor. Then, MAPK and PI3K-AKT parallel signaling pathways are activated, and several downstream pathways are affected, thereby eventually regulating cell cycle and apoptosis. The therapeutic effect of rhein, as a multitarget molecule, is the synergistic and comprehensive result of the involvement of multiple pathways rather than the blocking or activation of a single signaling pathway. We review the pharmacological mechanisms of action of rhein by consulting literature published in the last 100 years in PubMed. We then summarize these pharmacological mechanisms from a comprehensive, interactive, and crosstalk perspective. In general, the molecular mechanism of action of drug must be understood from a systematic and holistic perspective, which can provide a theoretical basis for precise treatment and rational drug use.

Micropropagation and validation of genetic and biochemical fidelity amongst regenerants of Cassia angustifolia Vahl employing RAPD marker and HPLC

In vitro protocol has been established for clonal propagation of Cassia angustifolia Vahl which is an important source of anticancerous bioactive compounds, sennoside A and B. Nodal explants excised from field raised elite plant (showing optimum level of sennoside A and B) of C. angustifolia when reared on Murashige and Skoog's medium augmented with different cytokinins, viz. N(6)-benzyladenine (BA), N(6)-(2-isopentenyl) adenine (2iP) and 6-furfuryl aminopurine (Kn) differentiated multiple shoots in their axils. Of the three cytokinins, BA at 5 μM proved optimum for differentiating multiple shoots in 95 % cultures with an average of 9.14 shoots per explant within 8 weeks of culture. Nearly, 95 % of the excised in vitro shoots rooted on half strength MS medium supplemented with 10 μM indole-3-butyric acid (IBA). The phenotypically similar micropropagated plants were evaluated for their genetic fidelity employing random amplified polymorphic DNA (RAPD) markers. Eleven individuals, randomly chosen amongst a population of 120 regenerants were compared with the donor plant. A total of 36 scorable bands, ranging in size from 100 to 1,000 bp were generated amongst them by the RAPD primers. All banding profiles from micropropagated plants were monomorphic and similar to those of mother plant proving their true to the type nature. Besides, high performance liquid chromatography evaluation of the sennoside A and B content amongst leaves of the mature regenerants and the elite mother plant too revealed consistency in their content.

Inhibition of glioma progression by a newly discovered CD38 inhibitor

Glioma, the most common cancer of the central nervous system, has very poor prognosis and no effective treatment. It has been shown that activated microglia/macrophages in the glioma tumor microenvironment support progression. Hence, inhibition of the supporting effect of these cells may constitute a useful therapeutic approach. Recently, using a syngeneic mouse glioma progression model, we showed that the ectoenzyme CD38 regulated microglia activation and, in addition, that the loss of CD38 from the tumor microenvironment attenuated glioma progression and prolonged the life span of the tumor-bearing mice. These studies, which employed wild-type (WT) and Cd38(-/-) C57BL/6J mice, suggest that inhibition of CD38 in glioma microenvironment may be used as a new therapeutic approach to treat glioma. Our study tested this hypothesis. Initially, we found that the natural anthranoid, 4,5-dihydroxyanthraquinone-2-carboxylic acid (rhein), and its highly water-soluble tri-potassium salt form (K-rhein) are inhibitors of CD38 enzymatic (nicotinamide adenine dinucleotide glycohydrolase) activity (IC50 = 1.24 and 0.84 μM, respectively, for recombinant mouse CD38). Treatment of WT, but not Cd38(-/-) microglia with rhein and K-rhein inhibited microglia activation features known to be regulated by CD38 (lipopolysaccharide/IFN-γ-induced activation, induced cell death and NO production). Furthermore, nasal administration of K-rhein into WT, but not Cd38(-/-) C57BL/6J, mice intracranially injected with GL261 cells substantially and significantly inhibited glioma progression. Hence, these results serve as a proof of concept, demonstrating that targeting CD38 at the tumor microenvironment by small-molecule inhibitors of CD38, for example, K-rhein, may serve as a useful therapeutic approach to treat glioma.

Rhein induces a necrosis-apoptosis switch in pancreatic acinar cells

Objectives. The Chinese herbal medicine Da-Cheng-Qi decoction can regulate a necrosis-apoptosis switch in injured pancreatic acinar cells. This study investigated the effects of rhein, a component of this medicine, on a necrosis-apoptosis switch in pancreatic rat AR42J cells. Methods. Cerulein-treated AR42J cells were used. After pretreatment with 479, 119.8, or 29.9  μ g/L rhein, cells were cocultured with rhein and cerulein (10(-8) M) for 4, 8, or 16 h. Apoptosis and necrosis were examined using annexin V and propidium iodide costaining. Mitochondria-dependent apoptosis-associated proteins were examined using enzyme-linked immunosorbent assays and western blotting. Results. Few cells died in untreated samples. The number was significantly higher in 16-h-cerulein-treated samples and treatment with 479  μ g/L rhein most effectively increased the apoptotic-to-necrotic cell ratio (P < 0.05). In cerulein-treated cells, rhein increased the concentrations of p53, cytochrome C, and caspase-3, and increased the Bax/Bcl-2 ratio in a time- and dose-dependent manner, with the maximum effect in cells treated with 479  μ g/L rhein for 16 h (P < 0.05). Conclusions. Rhein induces the necrosis-apoptosis switch in injured pancreatic acinar cells in a time- and dose-dependent manner. Mitochondria-dependent apoptosis signaling pathways might play an important role in this effect.

Rhein, a natural anthraquinone derivative, attenuates the activation of pancreatic stellate cells and ameliorates pancreatic fibrosis in mice with experimental chronic pancreatitis

Pancreatic fibrosis, a prominent histopathological feature of chronic pancreatitis (CP) and pancreatic ductal adenocarcinoma, is essentially a dynamic process that leads to irreversible scarring of parenchymal tissues of the pancreas. Though the exact mechanisms of its initiation and development are poorly understood, recent studies suggested that the activation of pancreatic stellate cells (PSCs) plays a critical role in eliciting such active course of fibrogenesis. Anthraquinone compounds possess anti-inflammatory bioactivities whereas its natural derivative rhein has been shown to effectively reduce tissue edema and free-radical production in rat models of inflammatory conditions. Apart from its anti-inflammatory properties, rhein actually exerts strong anti-fibrotic effects in our current in-vivo and in-vitro experiments. In the mouse model of cerulein-induced CP, prolonged administration of rhein at 50 mg/kg/day significantly decreased immunoreactivities of the principal fibrotic activators alpha-smooth muscle actin (α-SMA) and transforming growth factor-beta (TGF-β) on pancreatic sections implicating the activation of PSCs, which is the central tread to fibrogenesis, was attenuated. Consequently, the overwhelmed deposition of extracellular matrix proteins fibronectin 1 (FN1) and type I collagen (COL I-α1) in exocrine parenchyma was found accordingly reduced. In addition, the expression levels of sonic hedgehog (SHH), which plays important roles in molecular modulation of various fibrotic processes, and its immediate effector GLI1 in pancreatic tissues were positively correlated to the degree of cerulein-induced fibrosis. Such up-regulation of SHH signaling was restrained in rhein-treated CP mice. In cultured PSCs, we demonstrated that the expression levels of TGF-β-stimulated fibrogenic markers including α-SMA, FN1 and COL I-α1 as well as SHH were all notably suppressed by the application of rhein at 10 μM. The present study firstly reported that rhein attenuates PSC activation and suppresses SHH/GLI1 signaling in pancreatic fibrosis. With strong anti-fibrotic effects provided, rhein can be a potential remedy for fibrotic and/or PSC-related pathologies in the pancreas.

Role of mitochondrial permeability transition in human hepatocellular carcinoma Hep-G2 cell death induced by rhein

Rhein, a compound found as a glucoside in the root of rhubarb, is currently a subject of interest for its antitumor properties. The apoptosis of tumor cell lines induced by rhein was observed, and the involvement of mitochondria was established; however, the role of mitochondrial permeability transition (MPT) remains unknown. Here we report that MPT plays an important role in the apoptosis of human hepatocellular carcinoma Hep-G2 cells induced by rhein. After adding rhein to the isolated hepatic mitochondria, swelling effects and the leakage of Ca(2+) were observed. These alterations were suppressed by cyclosporin A (CsA), an MPT inhibitor. Furthermore, in Hep-G2 cells, the decrease of ATP production, the loss of mitochondrial transmembrane potential (MTP), the release of cytochrome c (Cyto c), and the activation of caspase 3 were also observed. These toxic effects of rhein can also be attenuated by CsA as well. Moreover, TUNEL assay confirmed that in the presence of CsA, rhein-induced apoptosis was largely inhibited. These results suggest that MPT plays a critical role in the pathogenesis of Hep-G2 cell injury induced by rhein, and imply that MPT may contribute to the anti-cancer activity of rhein.

Acceleration of pro-caspase-3 maturation and cell migration inhibition in human breast cancer cells by phytoconstituents of Rheum emodi rhizome extracts

The aggressive nature of estrogen receptor (ER)-negative breast cancer subtype obligates for innovative targeted therapies. The present study aimed to investigate the phytoconstituents and specific anticancer activities of Rheum emodi rhizome, a known food source used locally to treat various ailments. Petroleum ether extracts (hot [PHR] and cold [PCR]) of R. emodi, exhibited significant free radical scavenging potentials through DPPH and reducing power assays, rendering them as good sources of antioxidants. The extracts, PHR and PCR had shown significant (P < 0.05) cancer-cell-specific cytotoxicity in the assayed cells (MDA-MB-231 [breast carcinoma] and WRL-68 [non-tumoral]) at 100 μg/ml, and 50 and 100 μg/ml concentrations respectively. Extracts also induced fervent apoptosis in ER-negative cells (MDA-MB-231) compared to ER-positive subtype (MCF-7), and found to involve CPP32/caspase-3 in its apoptosis induction mechanism. Moreover, extracts had an inevitable potential to inhibit the migration of metastatic breast cancer cells (MDA-MB-231) in vitro. Further, the active principles of extracts were identified through HPLC and GC-MS analysis to reveal major polyphenolics, 4,7-Dimethyl-(octahydro)indolo[4,3-fg]quinolin-10-one, 5-Oxo-isolongifolene, Valencene-2, and other quinone, quinoline and anthraquinone derivatives. The extracts are thus good candidates to target malignant ER-negative breast cancer, and the identified phytoconstituents could be eluted in further exploratory studies for use in dietary-based anti-breast cancer therapies.

Reversion of p-glycoprotein-mediated multidrug resistance in human leukemic cell line by diallyl trisulfide

Multidrug resistance (MDR) is the major obstacle in chemotherapy, which involves multiple signaling pathways. Diallyl trisulfide (DATS) is the main sulfuric compound in garlic. In the present study, we aimed to explore whether DATS could overcome P-glycoprotein-(P-gp-)mediated MDR in K562/A02 cells, and to investigate whether NF-κB suppression is involved in DATS-induced reversal of MDR. MTT assay revealed that cotreatment with DATS increased the response of K562/A02 cells to adriamycin (the resistance reversal fold was 3.79) without toxic side effects. DATS could enhance the intracellular concentration of adriamycin by inhibiting the function and expression of P-gp, as shown by flow cytometry, RT-PCR, and western blot. In addition, DATS resulted in more K562/A02 cell apoptosis, accompanied by increased expression of caspase-3. The expression of NF-κB/p65 (downregulation) was significantly linked to the drug-resistance mechanism of DATS, whereas the expression of IκBα was not affected by DATS. Our findings demonstrated that DATS can serve as a novel, nontoxic modulator of MDR, and can reverse the MDR of K562/A02 cells in vitro by increasing intracellular adriamycin concentration and inducing apoptosis. More importantly, we proved for the first time that the suppression of NF-κB possibly involves the molecular mechanism in the course of reversion by DATS.

Acute and Chronic Administrations of Rheum palmatum Reduced the Bioavailability of Phenytoin in Rats: A New Herb-Drug Interaction

The rhizome of Rheum palmatum (RP) is a commonly used herb in clinical Chinese medicine. Phenytoin (PHT) is an antiepileptic with narrow therapeutic window. This study investigated the acute and chronic effects of RP on the pharmacokinetics of PHT in rat. Rats were orally administered with PHT (200 mg/kg) with and without RP decoction (single dose and seven doses of 2 g/kg) in a crossover design. The serum concentrations of PHT, PHT glucuronide (PHT-G), 4-hydroxyphenytoin (HPPH), and HPPH glucuronide (HPPH-G) were determined by HPLC method. Cell line models were used to identify the underlying mechanisms. The results showed that coadministration of single dose or multiple doses of RP significantly decreased the C_max and AUC_0-t as well as the K₁₀ of PHT, PHT-G, HPPH, and HPPH-G. Cell line studies revealed that RP significantly induced the P-gp-mediated efflux of PHT and inhibited the MRP-2-medicated transport of PHT and HPPH. In conclusion, acute and chronic coadministrations of RP markedly decreased the oral bioavailability of PHT via activation of P-gp, although the MRP-2-mediated excretion of PHT was inhibited. It is recommended that caution should be exercised during concurrent use of RP and PHT.

Predicting new molecular targets for rhein using network pharmacology

Background

Drugs can influence the whole biological system by targeting interaction reactions. The existence of interactions between drugs and network reactions suggests a potential way to discover targets. The in silico prediction of potential interactions between drugs and target proteins is of core importance for the identification of new drugs or novel targets for existing drugs. However, only a tiny portion of drug-targets in current datasets are validated interactions. This motivates the need for developing computational methods that predict true interaction pairs with high accuracy. Currently, network pharmacology has used in identifying potential drug targets to predicting the spread of drug activity and greatly contributed toward the analysis of biological systems on a much larger scale than ever before.

Methods

In this article, we present a computational method to predict targets for rhein by exploring drug-reaction interactions. We have implemented a computational platform that integrates pathway, protein-protein interaction, differentially expressed genome and literature mining data to result in comprehensive networks for drug-target interaction. We used Cytoscape software for prediction rhein-target interactions, to facilitate the drug discovery pipeline.

Results

Results showed that 3 differentially expressed genes confirmed by Cytoscape as the central nodes of the complicated interaction network (99 nodes, 153 edges). Of note, we further observed that the identified targets were found to encompass a variety of biological processes related to immunity, cellular apoptosis, transport, signal transduction, cell growth and proliferation and metabolism.

Conclusions

Our findings demonstrate that network pharmacology can not only speed the wide identification of drug targets but also find new applications for the existing drugs. It also implies the significant contribution of network pharmacology to predict drug targets.