In vitro effects of active components of Polygonum Multiflorum Radix on enzymes involved in the lipid metabolism

ETHNOPHARMACOLOGY RELEVANCE

Raw and processed Polygoni Multiflori Radix (PMR and PMRP) are used in the prevention and treatment of non-alcoholic fatty liver disease (NAFLD), hyperlipidemia or related diseases. In our previous research, 2, 3, 5, 4'-tetrahydroxy-stilbene-2-O-β-D-glucoside (TSG) displayed the most important role in the total cholesterol (TC) lowering effect among all the chemical constituents of Polygonum multiflorum. Emodin and physcion displayed more favorable triglyceride (TG) reducing effects than TSG. However, there are few researches focus on the approach and mechanism of how do Polygonum multiflorum exhibit good lipid regulation activity. The targeted sites of active substances of Polygonum multiflorum are still not clearly elucidated. This research pays close attention to how major chemical components of Polygonum multiflorum affect the TC and TG contents in liver cells.

MATERIALS AND METHODS

In this research, a sensitive, accurate and rapid in vitro model, steatosis hepatic L02 cell, was used to explore target sites of active chemical substances of Polygonum multiflorum for 48h. Steatosis hepatic L02 cell was exposed to emodin, physcion and TSG, respectively. The contents of four key enzymes in the pathway of synthesis and decomposition of TC and TG were investigated after exposure. Meanwhile, the contents of lipid transfer protein were also tested. The diacylgycerol acyltransferase 1 (DGAT1) controlled the biosynthesis of TG from free fatty acids while 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMG-CoA reductase) limited the biosynthesis of TC. Hepatic triglyceride lipase (HTGL) and cholesterol 7α-hydroxylase (CYP7A) played the key role in the lipolysis procedure of TG and TC.

RESULTS

The synthesis of TC and TG in steatosis L02 cells were apparently increased in the model group compared to the control group. Intracellular contents of HMG-CoA reductase and DGAT1 increased 32.33% and 56.52%, while contents of CYP7A and HTGL decreased 21.61% and 47.37%. Emodin, physcion and TSG all showed down-regulation effects on HMG-CoA reductase, while up-regulation effects on CYP7A. The most remarkable effect on HMG-CoA reductase was found on emodin. Emodin could reduce the DGAT1 content from 438.44 ± 4.51 pg/mL in model group to 192.55 ± 9.85 pg/mL (100 μm). The content of HTGL in 300 μm physcion group was 3.15 ± 0.15 U/mL, which was more significantly effective than the control, lovastatin and fenofibrate group.

CONCLUSIONS

TSG could raise the content of CYP7A and then promote the lipolysis of cholesterol. Moreover, TSG also showed the best LDL-reducing effect. Emodin could inhibit HMG-CoA reductase and DGAT1, which were key enzymes in the synthesis of TC and TG. Physcion increased the content of HTGL, and then could boost the lipolysis of triglyceride. At the same time, physcion showed the best VLDL-reducing effect. In view of the above conclusions, we contributed the lipid regulation activity to an overall synergy of TSG, emodin and physcion.

Effects of emodin and irbesartan on ventricular fibrosis in Goldblatt hypertensive rats

Left ventricular (LV) fibrosis is one of the most prominent pathophysiological results of hypertension. We initiated this study to investigate the effects and mechanisms of emodin and its combination with irbesartan on LV fibrosis in Goldblatt (2K1C) hypertensive rats. Goldblatt hypertension rats were prepared by two kidney one clip (2K1C) operations and then treated with either emodin, irbesartan or their combination. As a result, the systolic blood pressure (SBP) and the left ventricular mass index (LVMI) increased significantly (P < or = 0.05) in all 2K1C rats. After drugs treatment, irbesartan and the drug combination remarkably decreased SBP, LVMI, contents of angiotensinII (AngII), hydroxyproline and collagen, the mRNA and protein expression levels of matrix metalloproteinase-2 (MMP-2) and tissue inhibitor of metalloproteinase-2 (TIMP-2) (P < or = 0.05). As for the emodin, LVMI, contents of hydroxyproline and collagen, and MMP-2 and TIMP-2 expression were found to decrease significantly; however, the SBP and AngII contents stayed stable within certain extent. Therefore, emodin, irbesartan or two drugs together can potentially inhibit the ventricular fibrosis in Goldblatt hypertensive rats by reducing MMP-2 and TIMP-2 expression. Furthermore, the combination of these two drugs may provide a better anti-fibrosis effect than the single application.

[Effect of emodin on rat bone marrow mesenchymal stem cell proliferation and mRNA expressions of hematopoietic growth factors]

OBJECTIVE

To study the effect of emodin on the proliferation, cell cycle distribution, apoptosis and expression of hematopoietic growth factors in bone marrow mesenchymal stem cells (BMSCs).

METHODS

The proliferation of rat BMSCs exposed to emodin was analyzed using MTT assay, and flow cytometry was used to detect the apoptosis and cell cycle changes of the exposed cells. Real-time quantitative PCR was used to determine the mRNA expression of the hematopoietic growth factors.

RESULTS

Exposure to 0.1 and 1 µg/ml emodin for 48 and 72 h significantly enhanced the proliferation of BMSCs (P<0.01). The cells exposed to 0.1 µg/ml emodin showed significantly increased percentage of cells in G2/M phase (P<0.05), and 1 µg/ml emodin exposure caused increased cells in S phase (P<0.01) and decreased cells in G1/G0 phase (P<0.05). Emodin exposure for 48 h resulted in significantly decreased cell apoptosis (P<0.05). BMSCs treated with 0.1 µg/ml emodin showed a significant increase in the expression of thrombopoietin mRNA (P<0.05).

CONCLUSION

Emodin can promote the proliferation of BMSCs in vitro possibly by regulating the cell cycle distribution, cell apoptosis and thrombopoietin expression.

The effect of emodin on cytotoxicity, apoptosis and antioxidant capacity in the hepatic cells of grass carp (Ctenopharyngodon idellus)

We determined the effect of emodin on the lactate dehydrogenase (LDH) release, superoxide dismutase (SOD), glutathione (GSH), total antioxidant capacity (T-AOC), reactive oxygen species (ROS), mitochondria membrane potential (ΔΨm), and apoptosis in the hepatic cells of grass carp (Ctenopharyngodon idellus). Cultured cells were treated with different concentrations of emodin (0.04-25 μg/ml) for 24 h. We found that the cytotoxic effect of emodin was mediated by apoptosis, and that this apoptosis occurred in a dose-dependent manner. Emodin (1-25 μg/ml) significantly induced apoptosis accompanying by ΔΨm disruption and ROS generation and significantly reduced the SOD activities and T-AOC compared to the control. Thus, the oxidative effect of emodin may be attributed to the loss of the cell's ability to maintain the activity of its radical-scavenging enzymes. GSH was also significantly higher after 0.2-1 μg/ml emodin exposure, indicating that cells failed to maintain their redox balance when compensating for the increased oxidative stress. Our results suggest that emodin (1-25 μg/ml) exerts its cytotoxic effects via apoptosis by directly affecting the mitochondria.

In vitro anti-osteoporosis properties of diverse Korean Drynariae rhizoma phenolic extracts

Drynariae rhizoma has been used to prevent bone loss that occurs with increasing age. However, the chemical compounds in extracts that act on bone metabolism in herbal medicine are poorly understood. This study aimed to investigate and compare the extraction efficacy of polyphenolic compounds, antioxidant activity, and in vitro anti-osteoporosis properties of water extract (DR-DW) and ethanol extract (DR-EtOH) from D. rhizoma. Total phenolics and flavonoids were better extracted with 70% EtOH, and this extraction method also resulted in higher antioxidant activity and in vitro anti-osteoporosis properties in these extracts. In particular, the contents of phloroglucinol, protocatechuic acid ethyl ester, 2-amino-3,4-dimethyl-benzoic acid, 3-(3,5-dimethyl-pyrazol-1-yl)-benzoic acid, chlorogenic acid, syringic acid, trans-ferulic acid, (−)-epigallocatechin, epigallocatechin gallate, quercetin dehydrate, luteolin and emodin in DR-EtOH were higher than those in DR-DW. These results indicated that DR-EtOH could be a good source of natural herbs with anti-osteoporosis properties.

Effect of emodin on endoplasmic reticulum stress in rats with severe acute pancreatitis

This study aimed to investigate the protective effect of emodin on endoplasmic reticulum (ER) stress in rats with severe acute pancreatitis (SAP) and the underlying molecular mechanism. Sprague-Dawley male rats were randomly divided into sham operation group, SAP model group, and emodin treatment group. SAP was constructed through injecting sodium taurocholate into pancreatic and biliary duct in rats. Half an hour before establishing the animal model, emodin or sodium carboxymethylcellulose was intragastrically administrated to the rats in respective group. Rats were killed at 3, 6, and 12 h postdisease induction. The amylase, tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) levels in serum, pancreatic histopathology, acinar ER ultrastructure, protein expression of Bip, IRE1α,TRAF2, ASK1, p-JNK, and p-p38 MAPK in pancreas were examined. Sodium taurocholate induced pancreatic injury and ER lumen dilated in exocrine pancreas in rats at 3-, 6-, and 12-h time points. ER stress transducers Bip, IRE1α, and their downstream molecules TRAF2, ASK1 in pancreatitis were upregulated. Furthermore, phosphorylation of JNK and p38MAPK in pancreas was increased, which induced high expression level of inflammatory cytokines such as TNF-α and IL-6. Treatment with emodin obviously ameliorated pancreatic injury and decreased the release of amylase and inflammatory cytokines. Further studies showed that emodin significantly decreased the expression of Bip, IRE1α, TRAF2, and ASK1, inhibited phosphorylation of JNK and p38 MAPK in pancreas in rats at all time points. Emodin could reduce pancreatic injury and restrain inflammatory reaction in SAP rats partly via inhibiting ER stress transducers IRE1α and its downstream molecules.

[Effect of emodin on expression of farnesoid X receptor in rats with acute cholestatic hepatitis]

OBJECTIVE

To investigate the expression of farnesoid X receptor (FXR) and the effect of emodin on FXR expression in a rat model of acute cholestatic hepatitis.

METHODS

Ninety adult Sprague-Dawley rats were randomly divided into normal control, model, and emodin groups (n=30 each). The model and emodin groups were given alpha-naphthylisothiocyanate (ANIT) 50 mg/kg by gavage to establish an animal model of cholestatic hepatitis, while the normal control group was given an equal volume of sesame oil. The emodin group was given emodin by gavage every day from 4 days before the model was prepared until the time of sacrifice, while the model and normal control groups were given an equal volume of sodium carboxymethyl cellulose solution. At 24, 48 and 72 hours after the model was prepared, serum level of total bilirubin (TB), direct bilirubin (DB), alanine aminotransferase (ALT), and total bile acids (TBA) were measured by Aeroset automatic biochemical analyzer, and the mRNA expression of FXR in the liver tissue was measured by real-time PCR.

RESULTS

At all time points FXR mRNA expression in the model group decreased, but serum levels of TB, DB, ALT and TBA increased significantly compared with the normal control group (P<0.05). The emodin group had significantly higher mRNA expression of FXR and significantly lower serum levels of TB, DB, ALT, and TBA compared with the model group (P<0.05).

CONCLUSIONS

Emodin can significantly reduce serum levels of TB, DB, ALT, and TBA in rats with ANIT-induced cholestatic hepatitis, probably by promoting FXR expression.

[Effects of emodin on IL-23/IL-17 inflammatory axis, Th17 cells and viral replication in mice with viral myocarditis]

OBJECTIVE

To explore the effects of emodin in myocardial protection in mice with viral myocarditis (VMC) and explore molecular mechanisms.

METHODS

Fifty-five male 4-week-old BALB/c mice were randomly divided into control group (n=15), model group (n=20), and emodin group (n=20). The mice in model and emodin groups were inoculated with 0.1 ml Eagle's solution containing coxsackievirus B3 intraperitoneally, and those in the control group were given only 0.1 ml Eagle's solution. From the day of inoculation, the mice in emodin group received intragastric administration with 0.1 ml of 3 mg/ml emodin solution once daily for 21 consecutive days, and those in the control and model groups received 0.1 ml distilled water only. On day 7 after inoculation, 5 mice from each group were sacrificed to determine the viral titers in the cardiac tissues. All the mice were sacrificed on day 22 for measurement of the heart weight and histopathological inspection of the heart with HE staining. The mRNA and protein expression levels of myocardial interleukin-23 (IL-23) and interleukin-17 (IL-17) were detected by real-time quantitative PCR and Western blotting, respectively, and serum IL-23 and IL-17 levels were examined using enzyme linked immunosorbent assay (ELISA). Th17 cell frequencies were analyzed by flow cytometry. The expression levels of myocardial nuclear factor-κB (NF-κB) p65 in the cardiomyocyte nuclei were examined using Western blotting, and myocardial interleukin (IL)-1β, IL-6 and tumor necrosis factor-α (TNF-α) contents were detected by ELISA.

RESULTS

The mortality, myocardial histopathologic scores and virus titers in emodin group were all significantly lower than those in the model group (P<0.05). The heart-to-body weight ratio, myocardial IL-23 and IL-17 expressions, serum IL-23 and IL-17 levels, Th17 cell frequencies, cardiomyocyte nuclear NF-κB p65 expression, and myocardial contents of IL-1β, IL-6 and TNF-α were all significantly increased in the model group as compared to the control group (P<0.01) but reduced significantly in emodin group as compared to model group (P<0.05).

CONCLUSION

Emodin can protect against VMC by inhibiting IL-23/IL-17 inflammatory axis, Th17 cell proliferation and viral replication in mice.

Inhibition of Epstein-Barr virus lytic cycle by an ethyl acetate subfraction separated from Polygonum cuspidatum root and its major component, emodin

Polygonum cuspidatum is widely used as a medicinal herb in Asia. In this study, we examined the ethyl acetate subfraction F3 obtained from P. cuspidatum root and its major component, emodin, for their capacity to inhibit the Epstein-Barr virus (EBV) lytic cycle. The cell viability was determined by the MTT [3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyltetrazolium bromide] method. The expression of EBV lytic proteins was analyzed by immunoblot, indirect immunofluorescence and flow cytometric assays. Real-time quantitative PCR was used to assess the EBV DNA replication and the transcription of lytic genes, including BRLF1 and BZLF1. Results showed that the F3 and its major component emodin inhibit the transcription of EBV immediate early genes, the expression of EBV lytic proteins, including Rta, Zta, and EA-D and reduces EBV DNA replication, showing that F3 and emodin are potentially useful as an anti-EBV drug.

Emodin inhibits ATP-induced IL-1β secretion, ROS production and phagocytosis attenuation in rat peritoneal macrophages via antagonizing P2X₇ receptor

CONTEXT

Previous in vitro studies have demonstrated that emodin (1,3,8-trihydroxy-6-methyl-anthraquinone), an anthraquinone derivative from the rhizome of Rheum palmatum L., can inhibit the activation of P2X₇ receptors (P2X₇R) as a potential antagonist. However, the effects of emodin on P2X₇R-related inflammatory processes remain unclear.

OBJECTIVE

This study aimed to investigate the effects of emodin on different inflammation responses of macrophages induced by ATP, the natural ligand of P2X₇R.

MATERIALS AND METHODS

Rat peritoneal macrophages were treated with millimolar ATP and emodin (0.1, 0.3, 1, 3, 10 µM) or brilliant blue G (BBG, 0.1, 1, 10 µM). Cytosolic Ca²⁺ concentration ([Ca²⁺]c) was detected by fluorescent Ca²⁺ imaging. Interleukin-1β (IL-1β) release was measured by rat IL-1β ELISA kits. Reactive oxygen species (ROS) generation was examined by dihydroethidium (DHE) fluorescent staining. Phagocytic activity was tested by neutral red uptake assay.

RESULTS

We found that the [Ca²⁺](c) increase evoked by ATP (5 mM) was inhibited by emodin, in a dose-dependent manner with IC₅₀ of 0.5 μM. Furthermore, emodin reduced the IL-1β release induced by ATP (2 mM) in lipopolysaccharide (LPS)-activated macrophages, with an IC₅₀ of 1.6 μM. Emodin also strongly suppressed the ROS production and phagocytosis attenuation triggered by ATP (1 mM), with IC₅₀ values of 1 μM and 0.7 μM, respectively. Besides, BBG, a specific antagonist of P2X₇R, exhibited similar suppressive effects on these inflammation responses.

CONCLUSION

These results showed the inhibitory effects of emodin on ATP-induced [Ca²⁺](c) increase, IL-1β release, ROS production and phagocytosis attenuation in rat peritoneal macrophages, by inhibiting the activation of P2X₇R.

Inhibition of Tau aggregation by three Aspergillus nidulans secondary metabolites: 2,ω-dihydroxyemodin, asperthecin, and asperbenzaldehyde

The aggregation of the microtubule-associated protein tau is a significant event in many neurodegenerative diseases including Alzheimer's disease. The inhibition or reversal of tau aggregation is therefore a potential therapeutic strategy for these diseases. Fungal natural products have proven to be a rich source of useful compounds having wide varieties of biological activity. We have screened Aspergillus nidulans secondary metabolites containing aromatic ring structures for their ability to inhibit tau aggregation in vitro using an arachidonic acid polymerization protocol and the previously identified aggregation inhibitor emodin as a positive control. While several compounds showed some activity, 2,ω-dihydroxyemodin, asperthecin, and asperbenzaldehyde were potent aggregation inhibitors as determined by both a filter trap assay and electron microscopy. In this study, these three compounds were stronger inhibitors than emodin, which has been shown in a prior study to inhibit the heparin induction of tau aggregation with an IC50 of 1-5 µM. Additionally, 2,ω-dihydroxyemodin, asperthecin, and asperbenzaldehyde reduced, but did not block, tau stabilization of microtubules. 2,ω-Dihydroxyemodin and asperthecin have similar structures to previously identified tau aggregation inhibitors, while asperbenzaldehyde represents a new class of compounds with tau aggregation inhibitor activity. Asperbenzaldehyde can be readily modified into compounds with strong lipoxygenase inhibitor activity, suggesting that compounds derived from asperbenzaldehyde could have dual activity. Together, our data demonstrates the potential of 2,ω-dihydroxyemodin, asperthecin, and asperbenzaldehyde as lead compounds for further development as therapeutics to inhibit tau aggregation in Alzheimer's disease and neurodegenerative tauopathies.

[The effect of emodin on the contraction of isolated jejunum smooth muscle of rats]

OBJECTIVE

To investigate the effect of emodin on the contraction of jejunum smooth muscle and its underlying mechanisms.

METHODS

Rats were randomly divided into 7 groups (n = 6): control group, emodin group (1, 5, 10, 20 micromol/L), propranolol (PRO) plus emodin group, glibenclamide (GLI) plus emodin group, NG-Nitro-L-arginine Methyl Ester (L-NAME) plus emodin group, calcium free control group and calcium free emodin group. The rats were sacrificed by cervical dislocation and the small intestine was isolated. The jejunum segment specimens were mounted on an Organ Bath System with a tension transducer. The effect of emodin on contraction of jejunum smooth muscle was measured by BL-420E+ biological signal processing system and the amplitude (AM), tension (TE) and frequency (FR) of contraction were determined.

RESULTS

(1) Emodin inhibited the tension and amplitude of jejunum smooth muscle contraction in a dose-dependent manner (P < 0.05, P < 0.01) while the frequency was not obviously influenced. (2) PRO (P < 0.05) or GLI (P < 0.01) partly abolished the inhibitory effect of emodin on jejunum smooth muscle. (3) L-NAME had no obvious effect on the inhibitory effect of emodin. (4) Emodin attenuated the contraction of jejunum smooth muscle induced by calcium chloride application into calcium free K-H solution (P < 0.01).

CONCLUSION

Emodin obviously inhibits the amplitude and tension, while has no influence on the frequency of jejunum smooth muscle contraction in rats. Activation of beta adrenergic receptor, open of ATP sensitive potassium channels, and inhibition of the extracellular calcium influx through calcium channels of smooth muscle cell membrane might be involved in the process.

Dual activities of emodin--DNA protectivity vs mutagenicity

OBJECTIVES

Emodin is a bioactive anthraquinone that has diverse biological effects. It is also known as a biosynthetic precursor of hypericin. The purpose of this study was to assess mechanisms of potential genotoxic and antioxidant effects of emodin. We also investigated the potential genotoxic effect of photoactivated emodin.

METHODS

Potential genotoxicity was determined by the alkaline comet assay and the Ames test. The potential DNA protectivity of emodin was determined by the DNA-topology assay. On purpose to clarify molecular mechanism of its DNA protectivity against Fe(2+)-induced DNA breaks, three different assays were used (Reducing power-, DPPH- and Fe(2+)-chelating assay).

RESULTS

Using the alkaline comet assay and the Ames test we confirmed the genotoxic effect of both non-photoactivated and photoactivated emodin in a dose-dependent manner. Genotoxicity of photoactivated emodin did not differ from that obtained with non-photoactivated one. The DNA-topology assay revealed a DNA-protective activity of emodin. In the reducing power and DPPH assays emodin exhibited weak antioxidant activities. We did not observe any chelating activity of emodin in the Fe(2+)-chelating assay.

CONCLUSIONS

We found out that emodin exhibited dual activities. On one side it was genotoxic inducing primary DNA lessions (determined by the comet assay) as well as gene mutations (determined by the Ames test). On the other side it exhibited DNA-protective activity (determined by the DNA-topology assay). Molecular mechanism underlying this DNA protective effect can be attributed to its free radicals scavenging and reducing activities.

The influence of various feeding patterns of emodin on growth, non-specific immune responses, and disease resistance to Aeromonas hydrophila in juvenile Wuchang bream (Megalobrama amblycephala)

The present study was conducted to evaluate the effect of various feeding patterns of emodin on growth, non-specific immune response, and disease resistance to Aeromonas hydrophila in juvenile Wuchang bream. Healthy Megalobrama amblycephala (initial weight: 3.47 ± 0.032) were grown in a circulating water system for 8 weeks. Five groups were studied: one control group was fed with a basal diet for eight weeks (Pattern 1, P1), and three treatment groups were fed with a trial diet of 30 mg emodin kg(-1) at one-week (Pattern 2, P2), two-week (Pattern 3, P3), four-week (Pattern 4, P4) intervals. The final treatment group maintained the trial diet for the entire eight-week study duration (Pattern 5, P5). Results indicated that different feeding patterns of emodin significantly influenced the weight gain rate of Wuchang bream (P < 0.05). Fish in the P4 treatment group had significantly higher rates of weight gain (WG) than those in other treatment groups. There were no significant differences in survival rates or feed conversion ratios (FCR) between treatment groups and the control group. White blood cell count (WBC), respiratory burst activity, superoxide dismutase (SOD) activity, myeloperoxidase (MPO) activity and tumor necrosis factor-α (TNF-α) activity were shown to increase at first and then decrease from P3 condition to P5 condition. Fish under P4 treatment showed the most significant improvement of all tested parameters compared to control. Significantly higher levels (P < 0.05) of plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activity were observed in P2 and P4 treatment groups when compared with the control group, while no significant differences were observed in the AST and ALT activity of fish in P2, P3, P4 and P5 treatment groups. In a bacterial challenge experiment with A. hydrophila, fish under P4 and P5 treatment showed lower cumulative mortality than the control group. The results of this study suggest that an initial 4-week feeding interval is recommended for the economic and practical culture of M. amblycephala.

AZT and emodin exhibit synergistic growth-inhibitory effects on K562/ADM cells by inducing S phase cell cycle arrest and suppressing MDR1 mRNA/p-gp protein expression

CONTEXT

Previous studies have demonstrated that both 3'-azido-3'-deoxythymidine (AZT) and emodin, a traditional chemotherapy agent, can inhibit the growth of many types of cancer cells.

OBJECTIVE

This study aimed to evaluate the effect of AZT and emodin on adriamycin-resistant human chronic myelogenous leukemia (K562/ADM) cells, determine the expression of multidrug resistance 1 (MDR1) mRNA/p-glycoprotein (p-gp) protein, a protein known to induce resistance to anticancer agents, and to elucidate the underlying molecular mechanisms.

MATERIALS AND METHODS

K562/ADM cells were treated with AZT (10-160 μM) or emodin (5-80 μM) for 24, 48 and 72 h and cell viability was measured using the MTT assay. The effect of AZT (16.5, 33 and 66 μM) and emodin (6.1, 17.6 and 33.2 μM) on K562/ADM cell cycle distribution was determined by flow cytometry, and MDR1 mRNA/p-gp protein expression was determined by real time RT-PCR and western blotting.

RESULTS

The growth suppression of emodin was dramatically enhanced by AZT in K562/ADM cells. The IC50 of AZT and emodin was lower than that of emodin alone. All examined combinations of AZT and emodin yielded a synergetic effect (CI < 1). Furthermore, AZT and emodin altered the cell cycle distribution and led to an accumulation of cells in S phase. Meanwhile, the expression of MDR1 mRNA/p-gp protein was markedly decreased.

DISCUSSION AND CONCLUSION

These results show a synergistic growth-inhibitory effect of AZT and emodin in K562/ADM cells, which is achieved through S phase arrest. MDR1 might ultimately be responsible for these phenomena.

Emodin represses TWIST1-induced epithelial-mesenchymal transitions in head and neck squamous cell carcinoma cells by inhibiting the β-catenin and Akt pathways

Head and neck squamous cell carcinoma (HNSCC) is one of the leading causes of cancer deaths worldwide. In recent studies, a crucial link has been discovered between the acquisition of metastatic traits and tumour-initiating abilities in cancer cells during the epithelial-mesenchymal transition (EMT). Herein, we demonstrated that the ectopic expression of TWIST1, the EMT regulator, in HNSCC FaDu cells triggered EMT and resulted in the acquisition of a mesenchymal phenotype. Moreover, FaDu-pFLAG-TWIST1 cancer cell populations that were induced to EMT displayed an increased proportion of cells with the CD44 marker, which is associated with tumour initiation. Interestingly, we found that emodin treatment reduced the tumour-initiating abilities and inhibited cell migration and invasion in FaDu-pFLAG-TWIST1 cells. Emodin directly inhibited TWIST1 expression, upregulated E-cadherin mRNA and protein expression, and downregulated vimentin mRNA and protein expression. Moreover, we found that emodin inhibited TWIST1 binding to the E-cadherin promoter and repressed E-cadherin transcription activity. We also found that emodin inhibited TWIST1-induced EMT by inhibiting the β-catenin and Akt pathways. More interestingly, emodin significantly inhibited TWIST1-induced invasion in vivo. Therefore, emodin might be applicable to anticancer therapy and could be a potential new therapeutic drug for HNSCC.

In vitro and in vivo studies of the inhibitory effects of emodin isolated from Polygonum cuspidatum on Coxsakievirus B₄

The lack of effective therapeutics for Coxsackievirus B₄ (CVB₄) infection underscores the importance of finding novel antiviral compounds. Emodin (1,3,8-trihydroxy-6-methylanthraquinone) is one of the natural anthraquinone derivatives obtained from the root and rhizome of Polygonum cuspidatum. In the present study, the possibility of using emodin as a potential antiviral to treat CVB₄ infection was explored in vitro and in mice. Emodin reduced CVB₄ entry and replication on Hep-2 cells in a concentration- and time-dependent manner, with a 50% effective concentration (EC₅₀) of 12.06 μM and selectivity index (SI) of 5.08, respectively. The inhibitory effect of emodin for CVB₄ entry and replication was further confirmed by a quantitative real time PCR (qPCR) assay. The results further showed that the mice orally treated with different dosages of emodin displayed a dose dependent increase of survival rate, body weight and prolonged mean time of death (MTD), accompanied by significantly decreased myocardial virus titers and pathologic scores/lesions. Moreover, emodin could inhibit CVB₄-induced apoptosis in vitro and in vivo. Our results indicated that emodin could be used as potential antiviral in the post-exposure prophylaxis for CVB₄ infection.

Emodin induces cytotoxic effect in human breast carcinoma MCF-7 cell through modulating the expression of apoptosis-related genes

CONTEXT

The poor prognostic outcome of breast cancer is largely due to its resistance to cancer therapies. Development of therapeutic agents that can inhibit growth and induce apoptosis in breast cancer cells can help solve the problem. Emodin is an active anthraquinone that has been reported to have diverse biological effects.

OBJECTIVE

In this study, the anticancer effects of emodin on growth inhibition, apoptosis induction and the expression of apoptosis-related genes in MCF-7 cells were investigated.

MATERIALS AND METHODS

Growth inhibition induced by emodin was investigated by the MTS assay and the colony formation assay; while emodin-induced apoptosis was determined by the COMET assay and DNA fragmentation detection. Emodin (35 μM)-induced alterations in the expression of apoptotic-related genes were detected by using real-time PCR.

RESULTS

Emodin had significant growth inhibitory effects on MCF-7 cells with IC₅₀ = 7.22 µg/ml (∼30 μM). It also exerted a concentration-dependant inhibitory effect on the colony-forming ability of MCF-7 cells with IC₅₀ = 7.60 µg/ml (∼30 µM). Hallmarks of apoptosis, such as single-strand DNA breakage and DNA fragmentation, were observed in emodin-treated MCF-7 cells. The gene expression of Fas ligand (FASL) was up-regulated (p < 0.01) but those of MCL1, CCND1 and C-MYC were down-regulated (p < 0.05) in emodin-treated MCF-7 cells.

DISCUSSION AND CONCLUSION

This study indicated that emodin could induce growth inhibition and apoptosis in MCF-7 cells through the modulation of the expression of apoptosis-related genes. The growth inhibitory effects of emodin might involve both the intrinsic and the extrinsic apoptotic pathways and cell cycle arrest.

[Effect of PML(NLS-) gene mediated by recobinant adenovirus vector on emodin-induced apoptosis of HL-60 cells]

OBJECTIVE

To determine the effect and mechanism of action of PML(NLS-) gene on emodin-induced apoptosis of human HL-60 cells.

METHODS

HL-60 cells were infected with recombinant adenovirus Ad-PML (NLS-) and Ad-KZ, respectively. The PML(NLS-) gene was detected by Real-time PCR(RT-PCR) and Western blot. The proliferation level of the HL-60 cells was determined by MTT method. The HL-60 cells were treated with 60 micromol/L emodin for 72 h and then analyzed by flow cytometry for their cell cycle and apoptosis rate. The transcription levels of apoptosis-related BCL-2, BAX and C-MYC genes were determined by RT-PCR. The translation levels of those genes were determined by Western blot.

RESULTS

Compared with normal controls and the HL-60 cells infected with Ad-KZ, the mRNA and protein expression levels of PML(NLS-) gene increased significantly in the HL-60 cells infected with Ad-PML( NLS-). Increased proliferation levels of the Ad-PML (NLS-) infected HL-60 cells were observed in those treated with 60 pmol/L emodin, which showed decreased percentage of cells at Gx phase, increased percentage of cells at S phase, and decreased emodin-induced apoptosis. The levels of mRNA transcription and protein expression of BAX gene decreased, while those of BCL-2 and C-MYC genes increased significantly.

CONCLUSION

The over-expression of PML(NLS-) gene might promote the proliferation and arrest the apoptosis of HL-60 cells by up-regulating the expressions of BCL-2 and C-MYC genes and down-regulating the expression of BAX gene.

Synergistic effects of curcumin with emodin against the proliferation and invasion of breast cancer cells through upregulation of miR-34a

Curcumin, a biphenyl compound derived from rhizome, is a powerful anti-cancer agent. Emodin is an active component isolated from the root and rhizome of Rheum palmatum that has been widely used in traditional Chinese medicine for the treatment of various diseases. Currently, there are no studies examining the effect of curcumin in combination with emodin on tumor cell growth. In this study, we report for the first time that combined curcumin and emodin administration synergistically inhibits proliferation (MTT assay), survival (flow cytometry), and invasion (transwell migration assay) of breast cancer cells. Synergism is determined by the Chou-Talalay method. Moreover, we demonstrate that miR-34a is upregulated by curcumin and emodin. This microRNA helps mediate the anti-tumor effects of curcumin and emodin by downregulating Bcl-2 and Bmi-1. Our results not only provide insight into the mechanism of synergy between curcumin and emodin in breast cancer cells, but also suggest a new and potentially useful approach for breast cancer therapy.

[Effect of emodin lipid nano-microbubble on MAPK signal pathway and inflammation cytokine in AT-II cells by mechanical stretch]

OBJECTIVE

To investigate the effect of emodin lipid nano-microbubble on MAPK signaling pathway and the level of inflammation cytokine in AT-II cells induced by mechanical stretch and its mechanism.

METHODS

Emodin nanofibers, prepared by electrospinning with lecithin and PVP as carrier, were put into a seal bottle full of perfluoropropane, after they mixed with water and turned into self-assembled nano-microbubble. AT-II cells, separated and purified from primary rat AT-II cells, suffered 20% mechanical stretch for 4, 8, 16, 24, 48 h, and its protein expressions of p-P38/P38, p-ERK/ERK, p-JNK/JNK and the inflammation cytokine release levels of TNF-alpha, IL-1beta, IL-6 were detected by Western-Blot and ELISA. And further oberved the intervention effect of emodin lipid nano-microbubble on VILI.

RESULTS

The protein expressions of p-P38, p-ERK, p-JNK were significantly increased in AT-II cells induced by mechanical stretch, and continuously evaluated from the 4-16 h, but the protein expressions of p38, ERK, JNK had no significant difference. The release levels of TNF-alpha, IL-1beta, IL-6 in AT-II cells had no change during 8 h, and they were gradually increased significantly in followed 16 h. In AT-II cells induced by mechanical stretch, due to intervention effect of emodin lipid nano-microbubble, the the protein expressions of p-P38, p-ERK, p-JNK and the inflammation cytokine release levels of TNF-alpha, IL-1beta, IL-6 were significantly decreased.

CONCLUSION

Emodin lipid nano-microbubble shows protective effect on AT-II cells induced by mechanical stretch (VILI), and its mechanism may be related to down-regulation of protein expression of MAPK signaling pathway to regulate the release levels of inflammatory cytokine.

Emodin regulating excision repair cross-complementation group 1 through fibroblast growth factor receptor 2 signaling

AIM: To investigate the molecular mechanisms underlying the reversal effect of emodin on platinum resistance in hepatocellular carcinoma.

METHODS: After the addition of 10 μmol/L emodin to HepG2/oxaliplatin (OXA) cells, the inhibition rate (IR), 50% inhibitory concentration (IC₅₀) and reversal index (IC₅₀ in experimental group/IC₅₀ in control group) were calculated. For HepG2, HepG2/OXA, HepG2/OXA/T, each cell line was divided into a control group, OXA group, OXA + fibroblast growth factor 7 (FGF7) group and OXA + emodin group, and the final concentrations of FGF7, emodin and OXA in each group were 5 ng/mL, 10 μg/mL and 10 μmol/L, respectively. Single-cell gel electrophoresis was conducted to detect DNA damage, and the fibroblast growth factor receptor 2 (FGFR2), phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2) and excision repair cross-complementing gene 1 (ERCC1) protein expression levels in each group were examined by Western blotting.

RESULTS: Compared with the IC₅₀ of 120.78 μmol/L in HepG2/OXA cells, the IC₅₀ decreased to 39.65 μmol/L after treatment with 10 μmol/L emodin; thus, the reversal index was 3.05. Compared with the control group, the tail length and Olive tail length in the OXA group, OXA + FGF7 group and OXA + emodin group were significantly increased, and the differences were statistically significant (P < 0.01). The tail length and Olive tail length were lower in the OXA + FGF7 group than in the OXA group, and this difference was also statistically significant. Compared with the OXA + FGF7 group, the tail extent, the Olive tail moment and the percentage of tail DNA were significantly increased in the OXA + emodin group, and these differences were statistically significant (P < 0.01). In comparison with its parental cell line HepG2, the HepG2/OXA cells demonstrated significantly increased FGFR2, p-ERK1/2 and ERCC1 expression levels, whereas the expression of all three molecules was significantly inhibited in HepG2/OXA/T cells, in which FGFR2 was silenced by FGFR2 shRNA. In the examined HepG2 cells, the FGFR2, p-ERK1/2 and ERCC1 expression levels demonstrated increasing trends in the OXA group and OXA + FGF7 group. Compared with the OXA group and OXA + FGF7 group, the FGFR2, p-ERK1/2, and ERCC1 expression levels were significantly lower in the OXA + emodin group, and these differences were statistically significant. In the HepG2/OXA/T cell line that was transfected with FGFR2 shRNA, the FGFR2, p-ERK1/2 and ERCC1 expression levels were significantly inhibited, but there were no significant differences in these expression levels among the OXA, OXA + FGF7 and OXA + emodin groups.

CONCLUSION: Emodin markedly reversed OXA resistance by enhancing OXA DNA damage in HepG2/OXA cells, and the molecular mechanism was related to the inhibitory effect on ERCC1 expression being mediated by the FGFR2/ERK1/2 signaling pathway.

Evaluation of natural anthracene-derived compounds as antimitotic agents

Plants that contain anthracene-derived compounds such as anthraquinones have been reported to act as anticancer besides their use for millennia to treat constipation, but the mechanism of action is still unfolding. Therefore we pursue this study to explore a new horizon in the anticancer property of these agents with relevance to mitotic arrest. To achieve this goal, the antimitotic activity of a series of naturally occurring anthracene-derived anthraquinones including anthrone, alizarin (1,2-dihydroxyanthraquinone), quinizarin (1,4-dihydroxyanthraquinone), rhein (4,5-dihydroxyanthraquinone-2-carboxylic acid), emodin (1,6,8-trihydroxy-3-methylanthraquinone), and aloe emodin (1,8-dihydroxy-3-hydroxymethylanthraquinone) were evaluated using Allium cepa root tips. Initial results revealed that the mitosis was inhibited after 3, 6, and 24 h, respectively, of incubation with 500, 250, and 125 ppm of each compound in a dose-dependent manner. Furthermore, alizarin at 500 ppm was proved to be the most active compound to arrest the mitosis after 24 h followed by emodin, aloe emodin, rhein, and finally quinizarin. Interestingly, this inhibition of mitosis was irreversible in root tips incubated with each compound at concentration of 500 ppm but not with 250 ppm or 125 ppm, where the roots regained their normal mitotic activity after 96 h post-incubation in water. This re-evaluation of an old remedy suggests that several bioactive anthraquinones possess promising anti-mitotic activity that may have the potential to be lead compounds for the development of a new class of multifaceted natural anticancer/antimitotic agents.

Is it possible to increase the aloin content of Aloe vera by the use of ultraviolet light?

In this paper, the effects of ultraviolet (UV) treatments on the aloin content of Aloe vera L. gel have been analyzed. UV-A treatment to A. vera plants for 36 days led to an increase in the aloin concentration in gel, rind tissue, and latex, while a decrease in chlorophylls a and b occurred in the photosynthetic tissue as a consequence of UV treatment. The growth of Penicillium digitatum and Botrytis cinerea (artificially inoculated on the leaf surface) was drastically decreased in UV-A-treated leaves, which could be attributed to the increase in the aloin concentration by the UV-A treatment. In addition, UV-C treatment to detached leaves also led to an increase in the gel aloin concentration, at higher levels than occurred with UV-A treatment, although leaves showed severe lesions after 48 h of treatment.