Emodin suppresses migration and invasion through the modulation of CXCR4 expression in an orthotopic model of human hepatocellular carcinoma

Accumulating evidence(s) indicate that CXCL12-CXCR4 signaling cascade plays an important role in the process of invasion and metastasis that accounts for more than 80% of deaths in hepatocellular carcinoma (HCC) patients. Thus, identification of novel agents that can downregulate CXCR4 expression and its associated functions have a great potential in the treatment of metastatic HCC. In the present report, we investigated an anthraquinone derivative, emodin for its ability to affect CXCR4 expression as well as function in HCC cells. We observed that emodin downregulated the expression of CXCR4 in a dose-and time-dependent manner in HCC cells. Treatment with pharmacological proteasome and lysosomal inhibitors did not have substantial effect on emodin-induced decrease in CXCR4 expression. When investigated for the molecular mechanism(s), it was observed that the suppression of CXCR4 expression was due to downregulation of mRNA expression, inhibition of NF-κB activation, and abrogation of chromatin immunoprecipitation activity. Inhibition of CXCR4 expression by emodin further correlated with the suppression of CXCL12-induced migration and invasion in HCC cell lines. In addition, emodin treatment significantly suppressed metastasis to the lungs in an orthotopic HCC mice model and CXCR4 expression in tumor tissues. Overall, our results show that emodin exerts its anti-metastatic effect through the downregulation of CXCR4 expression and thus has the potential for the treatment of HCC.

Anthraquinone-2-sulfonic acid (AQ2S) is a novel neurotherapeutic agent

Anthraquinone derivatives such as emodin have recently been shown to protect in models of beta amyloid β (Aβ) and tau aggregation-induced cell death. The mechanisms of action possibly involve preconditioning effects, anti-aggregation properties, and/or enhancing the phosphatidylinositol-3-kinase (PI3K)/AKT survival mechanism. We studied several natural (emodin, rhein, and aloin) and synthetic (AQ2S) anthraquinones, to screen for post-treatment therapeutic benefit in two models of neuronal death, namely hydrogen peroxide (H(2)O(2)) and staurosporine (STS)-induced injury. Treatment with emodin, rhein, or aloin failed to reduce H(2)O(2) injury. Moreover, consistent with emodin behaving like a mild toxin, it exacerbated oxidative injury at the highest concentration used (50 μM) in our post-treatment paradigm, and potently inhibited AKT. In contrast, AQ2S was neuroprotective. It reduced H(2)O(2) injury at 50 and 75 μM. In addition, AQ2S potently inhibited staurosporine (STS)-induced injury. The mechanisms of action involve caspase inhibition and AKT activation. However, blockade of AKT signaling with LY294002 failed to abolish AQ2S-mediated protection on the STS assay. This is the first study to report that AQ2S is a new neuroprotective compound and a novel caspase inhibitor.

[Active ingredients in rhubarb with anti-proliferative effects on scar fibroblasts]

This study is to explore the active ingredients of traditional Chinese medicine rhubarb with antiproliferative activity on hypertrophic scar fibroblasts (HSF). Rhubarb was extracted with Soxhlet extraction method by different polar solvents. MTS method was used to screen rhubarb solvent extracts (25 microg x mL(-1)) with anti-proliferative activity on HSF, and flow cytometry was used to detect their influences on cell cycle. Then, the active ingredients were analyzed by HPLC. The components with high activity were identified by UPLC-Q/TOF and verified by HE staining. The results showed that the ethyl acetate extract of rhubarb had higher anti-proliferative activity (P < 0.01), increased significantly the proportion of cells in G0/G1 phase (P < 0.01), and reduced the proliferation index (PI) (P < 0.01). The main active ingredients were anthraquinones. The results of confirming experiment showed that emodin, rhein and gallic acid could inhibit cell proliferation in a dose-dependent manner. In conclusion, the ethyl acetate extract of rhubarb showed anti-proliferative activity on HSF, and the anti-proliferative ingredients might be anthraquinones.

Emodin-6-O-β-D-glucoside inhibits HMGB1-induced inflammatory responses in vitro and in vivo

High mobility group box 1 (HMGB1) protein acts as a potent proinflammatory cytokine and is involved in the pathogenesis of several vascular diseases, such as, systemic vasculitis and sepsis. Emodin-6-O-β-D-glucoside (EG) is a new active compound from Reynoutria japonica, and its biologic activities have not been previously investigated. In this study, we first investigated the antiinflammatory activities of EG on HMGB1-mediated proinflammatory responses in human umbilical vein endothelial cells (HUVECs) and in a murine cecal ligation and puncture (CLP)-model of sepsis in mice. EG was found to suppress the release of HMGB1, the production of tumor necrosis factor (TNF)-α, and the activation of nuclear factor-κB (NF-κB) by HMGB1 in HUVECs, and to inhibit HMGB1-mediated hyperpermeability and leukocyte migration in mice. In the CLP model, HMGB1 was highly released, but this release was prevented by EG. Furthermore, EG also increased the survival times of CLP administered mice. Collectively, this study shows EG can protect barrier integrity and inhibit HMGB1-mediated inflammatory responses, which suggests a potential use as a therapy for sepsis or septic shock.

Antitumor activity of emodin against pancreatic cancer depends on its dual role: promotion of apoptosis and suppression of angiogenesis

Background

Emodin has been showed to induce apoptosis of pancreatic cancer cells and inhibit tumor growth in our previous studies. This study was designed to investigate whether emodin could inhibit the angiogenesis of pancreatic cancer tissues and its mechanism.

Methodology/Principal Finding

In accordance with our previous study, emodin inhibited pancreatic cancer cell growth, induced apoptosis, and enhanced the anti-tumor effect of gemcitabine on pancreatic caner cells in vitro and in vivo by inhibiting the activity of NF-κB. Here, for the first time, we demonstrated that emodin inhibited tumor angiogenesis in vitro and in implanted pancreatic cancer tissues, decreased the expression of angiogenesis-associated factors (NF-κB and its regulated factors VEGF, MMP-2, MMP-9, and eNOS), and reduced eNOS phosphorylation, as evidenced by both immunohistochemistry and western blot analysis of implanted tumors. In addition, we found that emodin had no effect on VEGFR expression in vivo.

Conclusions/Significance

Our results suggested that emodin has potential anti-tumor effect on pancreatic cancer via its dual role in the promotion of apoptosis and suppression of angiogenesis, probably through regulating the expression of NF-κB and NF-κB-regulated angiogenesis-associated factors.

Anticancer potential of aloes: antioxidant, antiproliferative, and immunostimulatory attributes

Aloe is a genus of medicinal plants with a notable history of medical use. Basic research over the past couple of decades has begun to reveal the extent of Aloe's pharmaceutical potential, particularly against neoplastic disease. This review looks at Aloe, both the genus and the folk medicine, often being called informally "aloes", and delineates their chemistry and anticancer pharmacognosy. Structures of key compounds are provided, and their pharmacological activities reviewed. Particular attention is given to their free radical scavenging, antiproliferative, and immunostimulatory properties. This review highlights major research directions on aloes, reflecting the enormous potential of natural sources, and of the genus Aloe in particular, in preventing and treating cancer.

Library-based discovery of DYRK1A/CLK1 inhibitors from natural product extracts

The dual specificity tyrosine-phosphorylation-regulated kinase DYRK1A possesses diverse roles in neuronal development and adult brain physiology, and increased activity has been linked to neurodegenerative diseases. Very few inhibitors of this kinase have been reported up to now. Screening of a library of > 900 plant and fungal extracts afforded 25 extracts with IC₅₀s < 10 µg/mL against DYRK1A. To identify the active constituents, the extracts were submitted to a process integrating physicochemical data with biological information, referred to as HPLC-based activity profiling. Follow-up investigation of four extracts led to the targeted isolation of harmine (1, IC₅₀ 0.022 µM) from Peganum harmala, emodin (3, IC₅₀ 4.2 µM) from Cassia nigricans, kaempferol (4, IC₅₀ 0.91 µM) from Cuscuta chinensis, and 3,8-di-O-methylherbacetin (11, IC₅₀ 8.6 µM), 3,3',4'-tri-O-methylmyricetin (12, IC₅₀ 7.1 µM) and ombuin (15, IC₅₀ 1.7 µM) from Larrea tridentata as the active constituents. Active extracts and compounds were also tested on the closely related cdc2-like kinase CLK1. Finally, the selectivity profile of compounds was evaluated by including other members of the DYRKs and CLKs families. While the flavonoids and emodin did not show significant differences in the potency of their activities, harmine (1) was most active against DYRK1A, CLK1, and CLK4, and less potent against the other kinases, with selectivity ranging from 2- to 20-fold.

Emodin protects against high-fat diet-induced obesity via regulation of AMP-activated protein kinase pathways in white adipose tissue

Emodin is an active herbal component traditionally used in China for treating a variety of diseases. The aim of this study was to examine the effect of emodin on the reducing lipid accumulation in white adipose tissue of high-fat diet-fed rats, and on the regulation of the expression of the genes involved in lipid metabolism to elucidate the mechanisms. After being fed a high-fat diet for two weeks, rats were dosed orally with emodin (20, 40, 80 mg/kg/day) or pioglitazone (20 mg/kg/day), once daily for eight weeks. Changes in body weight, feeding pattern, serum lipids, coronary artery risk index, and atherogenic index were investigated. Subcutaneous white adipose tissues were isolated for pathology histology and Western blot analyses. Changes of triglyceride accumulation in differentiated 3 T3-L1 adipocytes were also investigated. Emodin exhibited a significant concentration-dependent decrease in the intracellular accumulation of triglyceride in 3 T3-L1 adipocytes. Emodin (80 mg/kg/day) displayed similar characteristics to pioglitazone (20 mg/kg/day) in reducing body weight gain and plasma lipid levels as well as the coronary artery risk and atherogenic indices of high-fat diet-fed rats. Emodin also caused dose related reductions in epididymal white adipose tissue sizes in high-fat diet-fed rats. Emodin and pioglitazone enhanced the phosphorylation of AMP-activated protein kinase and its primary downstream targeting enzyme, acetyl-CoA carboxylase, upregulated gene expression of carnitine palmitoyl transferase 1, and downregulated sterol regulatory element binding protein 1 and fatty acid synthase protein levels in the epididymal white adipose tissue of high-fat diet-fed rats. Our findings suggest that emodin could attenuate lipid accumulation in white adipose tissue through AMP-activated protein kinase activation.

Emodin regulates apoptotic pathway in human liver cancer cells

Emodin, a natural anthraquinone, has been reported to possess antiproliferative effects in many cancer cell lines. However, anticancer mechanism against human liver cancer remains unclear. In this study, we observed that emodin induced apoptosis in HepG2 cells and caused a significant accumulation of cells in the G1 phase. Western blot data showed that emodin treatment caused the increasing of release of cytochrome c into cytosol from mitochondria and the activation of caspase-8 and caspase-9, which suggest that the intrinsic and extrinsic pathways could be involved. Emodin treatment also resulted in a dose-dependent accumulation of intracellular reactive oxygen species. Furthermore, emodin increased the protein level of p53 and decreased the protein level of NF-κB/p65 in HepG2 cells, which indicated these two regulators might play a role in emodin-induced apoptosis. Computational modeling showed that emodin could directly bind to the BH3 domain of Bcl-2 through forming one hydrogen bond with Ala146 residue in Bcl-2. From these examinations, emodin not only significantly downregulated expression of Bcl-2 but also inhibited the heterodimerization of Bcl-2 with Bax because of strong interaction between emodin and Bcl-2. These suggest that emodin induces apoptosis in liver cancer cell line through a multifaceted complex cascade of events.

[Emodin combined gemcitabine inhibited the growth of pancreatic cancer in vitro and in vivo and its mechanisms study]

OBJECTIVE

To study the effect of emodin combined gemcitabine on the growth of pancreatic cancer in vivo and in vitro as well as its mechanisms.

METHODS

After human pancreatic cancer cell line SW1990 was treated with emodin (40 micromol/L), gemcitabine (20 micromol/L), and emodin combined gemcitabine, the cell proliferation was detected by cell counting kit-8 (CCK-8) assay. The apoptosis of pancreatic cancer cells was detected using the flow cytometry (FCM). The protein expressions of Bax and Bcl-2 were detected using Western blot. SW1990 cells were injected subcutaneously into nude mice to establish pancreatic xenograft tumors. The mice were then treated by emodin, gemcitabine, and emodin combined gemcitabine, respectively. The changes of tumor volume were monitored. The positive expressions of Ki-67, Bax, and Bcl-2 in the xenograft tumors were detected using immunohistochemical method.

RESULTS

Emodin combined with gemcitabine induced a higher percentage of growth inhibition and apoptosis in pancreatic cancer cell line SW1990 than that of gemcitabine or emodin alone (P < 0.05). The protein expression of Bax was up-regulated and that of Bcl-2 down-regulated in the emodin group and the emodin combined gemcitabine group when compared with the control group (P < 0.05). Emodin combined with gemcitabine could significantly inhibit the growth of pancreatic xenograft tumors, increase the positive expression of Bax in tumor tissues, obviously decrease the positive expressions of Ki-67 and Bcl-2 (P < 0.05). The optimal effects were obtained in the emodin combined gemcitabine group (P < 0.05).

CONCLUSION

Emodin could potentiate the inhibition of pancreatic cancer growth induced by gemcitabine both in vitro and in vivo, which might be achieved by up-regulating the expression of Bax and down-regulating the expression of Bcl-2.

On the novel action of melanolysis by a leaf extract of Aloe vera and its active ingredient aloin, potent skin depigmenting agents

The present study was carried out to investigate the effects of an Aloe vera leaf extract, along with its standard active ingredient aloin, on the isolated tail melanophores of Bufo melanostictus tadpoles, which are a type of disguised smooth muscle cells offering excellent in vitro opportunities for studying the effects of pharmacological and pharmaceutical agents. It was found that the leaf extract of A. vera and its active ingredient aloin induced powerful, dose-dependent, physiologically significant melanin aggregating effects in the isolated tail melanophores of B. melanostictus similar to those of adrenaline per se. These preliminary findings clearly demonstrate that the extract of A. vera and its active ingredient aloin cause melanin aggregation leading to skin lightening via alpha adrenergic receptor stimulation. The present study opens new vistas for the use of A. vera regarding its clinical application as a new nontoxic melanolytic agent for the treatment of hyperpigmentation.

Screening of anti-cancer agent using zebrafish: comparison with the MTT assay

The MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyltetrazolium bromide) assay is a classical method for screening cytotoxic anti-cancer agents. Candidate drugs from the MTT assay need in vivo models to test their efficiency and to assess the absorption, distribution, metabolism, excretion, and toxicity of the drugs. An in vivo screening model could increase the rate of development of anti-cancer drugs. Here, we used zebrafish to screen a library of 502 natural compounds and compared the results with those from an MTT assay of the MCF7 breast cancer cell line. We identified 59 toxic compounds in the zebrafish screen, 21 of which were also identified by the MTT assay, and 28 of which were already known for their anti-cancer and apoptosis-inducing effects. These compounds induced apoptosis and activated the p53 pathway in zebrafish within 3h treatment. Our results indicate that zebrafish is a simple, reliable and highly efficient in vivo tool for cancer drug screening, and could complement the MTT assay.

Involvement of pachybasin and emodin in self-regulation of Trichoderma harzianum mycoparasitic coiling

Our aim was to determine the effects of two secondary metabolites secreted by Trichoderma harzianum, pachybasin and emodin, on the mycoparasitic coiling behavior and cAMP content of T. harzianum. The number of T. harzianum coils around Nylon 66 fiber was increased in the presence of R. solani. The number of T. harzianum coils around R. solani hyphae and Nylon 66 fiber were significantly increased in the presence of pachybasin and emodin. The cAMP level in T. harzianum was significantly increased by close contact with R. solani and much higer cAMP level in the presence of exogenous pachybasin and emodin. A cAMP inhibitor diminished the effect of pachybasin and emodin on T. harzianum coiling around Nylon 66 fiber. The results suggest that pachybasin and emodin mediate the increase in the number of Trichoderma mycoparasitic coils via cAMP signaling. This is the first report to suggest that pachybasin and emodin play roles in the biocontrol mechanism of Trichoderma.

Hepatoprotection of emodin and Polygonum multiflorum against CCl(4)-induced liver injury

CONTEXT

Polygonum multiflorum is known as a medicinal plant. It has been used as a folk medicine which showed antioxidative property.

OBJECTIVE

Protective effects of the water extracts (w/v:1/10) from fresh P. multiflorum (WEP) on carbon tetrachloride (CCl(4))-induced liver damage in rats were investigated.

MATERIALS AND METHODS

CCl(4) was used for inducing liver damage of SD rats, and WEP and emodin were fed for eight consecutive weeks.

RESULTS

We found that emodin levels in fresh WEP was higher than that in ripening WEP. Rats were administered WEP and emodin, the main active compound, for 56 consecutive days. WEP significantly lowered the serum levels of hepatic enzyme markers, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) and reduced the generation of malonaldehyde. Treatment with WEP recovered glutathione S-transferase and catalase activity in rats as compared to treatment with CCl(4) alone. In addition, serum tumor necrosis factor-α, an inflammatory marker, was found to decrease in rats treated with WEP. In histopathological evaluation, fatty degeneration and necrosis were found to be significantly decreased in the CCl(4) plus WEP treatment group.

DISCUSSION AND CONCLUSION

WEP may be effective in attenuating liver damage by reducing lipid peroxidation as well as by positively modulating inflammation.

Emodin prevents intrahepatic fat accumulation, inflammation and redox status imbalance during diet-induced hepatosteatosis in rats

High-fat and/or high-carbohydrate diets may predispose to several metabolic disturbances including liver fatty infiltration (hepatosteatosis) or be associated with necro-inflammation and fibrosis (steatohepatitis). Several studies have emphasized the hepatoprotective effect of some natural agents. In this study, we investigated the potential therapeutic effects of the treatment with emodin, an anthraquinone derivative with anti-oxidant and anti-cancer abilities, in rats developing diet-induced hepatosteatosis and steatohepatitis. Sprague-Dawley rats were fed a standard diet (SD) for 15 weeks, or a high-fat/high-fructose diet (HFD/HF). After 5 weeks, emodin was added to the drinking water of some of the SD and HFD/HF rats. The experiment ended after an additional 10 weeks. Emodin-treated HFD/HF rats were protected from hepatosteatosis and metabolic derangements usually observed in HFD/HF animals. Furthermore, emodin exerted anti-inflammatory activity by inhibiting the HFD/HF-induced increase of tumor necrosis factor (TNF)-α. Emodin also affected the hepatocytes glutathione homeostasis and levels of the HFD/HF-induced increase of glutathionylated/phosphorylated phosphatase and tensin homolog (PTEN). In conclusion, we demonstrated that a natural agent such as emodin can prevent hepatosteatosis, preserving liver from pro-inflammatory and pro-oxidant damage caused by HFD/HF diet. These findings are promising, proposing emodin as a possible hindrance to progression of hepatosteatosis into steatohepatitis.

[Research progress of the anti-proliferation effect of emodin on VSMCs]

Emodin has such pharmacological effects as ant-inflammatory, anti-tumor, immunoregulation. Meanwhile, emodin could be used for inhibiting the proliferation of vascular smooth muscle cells (VSMC). Many foreign studies demonstrated that emodin had an effect on inhibiting proliferation of VSMCs and cell migration and promoting cell apoptosis, and probed into molecular mechanisms in all aspects. Besides, clinical translational researches and application explorations were also carried out. This article summarizes the research progress of the anti-proliferation effect of emodin on VSMCs.

Emodin induces chloride secretion in rat distal colon through activation of mast cells and enteric neurons

BACKGROUND AND PURPOSE

Emodin (1,3,8-trihydroxy-6-methylanthraquinone) is an active component of many herb-based laxatives. However, its mechanism of action is unclear. The aim of the present study was to investigate the role of mast cells and enteric neurons in emodin-induced ion secretion in the rat colon.

EXPERIMENTAL APPROACH

Short-circuit current (I(SC)) recording was used to measure epithelial ion transport. A scanning ion-selective electrode technique was used to directly measure Cl(-) flux (J(Cl)-) across the epithelium. RIA was used to measure emodin-induced histamine release.

KEY RESULTS

Basolateral addition of emodin induced a concentration-dependent increase in I(SC) in colonic mucosa/submucosa preparations, EC(50) 75 µM. The effect of emodin was blocked by apically applied glibenclamide, a Cl(-) channel blocker, and by basolateral application of bumetanide, an inhibitor of the Na(+) -K(+) -2Cl(-) cotransporter. Emodin-evoked J(Cl)- in mucosa/submucosa preparations was measured by scanning ion-selective electrode technique, which correlated to the increase in I(SC) and was significantly suppressed by glibenclamide and bumetanide. Pretreatment with tetrodotoxin and the muscarinic receptor antagonist atropine had no effect on emodin-induced ΔI(SC) in mucosa-only preparations, but significantly reduced emodin-induced ΔI(SC) and J(Cl)- in mucosa/submucosa preparations. The COX inhibitor indomethacin, the mast cell stabilizer ketotifen and H(1) receptor antagonist pyrilamine significantly reduced emodin-induced ΔI(SC) in mucosa and mucosa/submucosa preparations. The H(2) receptor antagonist cimetidine inhibited emodin-induced ΔI(SC) and J(Cl)- only in the mucosa/submucosa preparations. Furthermore, emodin increased histamine release from the colonic mucosa/submucosa tissues.

CONCLUSIONS AND IMPLICATIONS

The results suggest that emodin-induced colonic Cl(-) secretion involves mast cell degranulation and activation of cholinergic and non-cholinergic submucosal neurons.

[Experimental study on anti-metastasis effect of emodin on human pancreatic cancer]

OBJECTIVE

To investigate the anti-metastasis effect of emodin on the pancreatic cancer in vitro and in vivo.

METHOD

Human pancreatic cancer cell line SW1990 was treated with different concentrations of emodin (10, 20, 40 micromol x L(-1)) for 2 h, the effects of emodin on the migration and invasion of SW1990 cells were examined by using wound assay and matrigel counting. Western blot was used to detect the protein expression of NF-kappaB and MMP-9 in SW1990 cells after various concentrations of emodin (10, 20, 40 micromol x L(-1)) treatment for 48 h. Metastatic model simulating human pancreatic cancer was established by orthotropic implantation of histologically intact human tumor tissue into pancreatic wall of nude mice, and then divided into three groups: control group, low-dose emodin group (L-EMO) and high-dose emodin group (H-EMO). Eight weeks after implantation, the presences of metastasis were evaluated respectively after the mice were sacrificed. Immunohistochemistry was used to detect the positive expression of CD34, NF-kappaB and MMP-9 in the tumors.

RESULT

Emodin suppressed the migration and invasion of SW1990 cells in a dose-dependent manner. Western bolt assay indicated that emodin down-regulated the expression of NF-kappaB and MMP-9 proteins in SW1990 cells. The incidences of metastasis were decreased significantly in L-EMO group and H-EMO group as compared with that in control group. The percentage of CD34, NF-kappaB and MMP-9-positive cells in the tumors were significantly reduced by the administration of emodin.

CONCLUSION

Emodin exerts anti-metastatic activity in pancreatic cancer both in vitro and in vivo, which may be related to down-regulation of NF-kappaB and MMP-9.

A comparative study on the tissue distributions of rhubarb anthraquinones in normal and CCl4-injured rats orally administered rhubarb extract

AIM OF THE STUDY

The present study comparatively investigated the tissue distributions of rhubarb anthraquinone derivatives (AQs) to examine whether they undergo different uptakes in normal or CCl(4)-induced liver-damaged rats, to explore possible reasons for the different toxicities of AQs in pathological model rats and normal rats at the tissue distribution level.

MATERIALS AND METHODS

The total rhubarb extract (14.49 g kg(-1) of body weight per day based on the quantity of crude material) was administrated orally to normal and model rats for 12 weeks. The concentrations of free AQs in tissues were quantitated by liquid chromatography-tandem mass spectrometry (LC-MS). After drug withdrawal for 4 weeks, tissue distributions were again determined.

RESULTS

The five free AQs-aloe-emodin, rhein, emodin, chrysophanol and physcion--were detected in the liver, kidney and spleen, while only rhein, aloe-emodin and emodin reached the quantitative limit. The tissue distributions of rhein (p < 0.001), aloe-emodin (p < 0.001) and emodin (p < 0.05) in normal rats were higher than those in model rats with rhein>aloe-emodin>emodin in kidney and spleen tissues and aloe-emodin > rhein > emodin in liver tissues. Free AQs were not detected in the tissues after drug withdrawal for 4 weeks.

CONCLUSIONS

These results suggest that the tissue toxicity of AQs in normal animals is higher than that in pathological model animals with little accumulative toxicity of rhubarb. The results are concordant with the traditional Chinese theory of You Gu Wu Yun recorded first in Su Wen, a classical Chinese medical treatise.

[Effects of emodin on human erythroleukemia cell line HEL]

This study was aimed to investigate the inhibitory effect of emodin on the proliferation of HEL cells, the inducing apoptosis effect of HEL cells and their mechanisms. The proliferation inhibition was detected by MTT method; the change of morphology was observed by AO/EB stains; the cell cycle and apoptosis was analyzed by flow cytometry; the expressions of Akt, P-Akt, P-GSK3β and HSP70 proteins were determined by Western blot. The results indicated that emodin displayed significant anti-proliferative effect on HEL cells in a dose dependent manner(r = 0.99), with IC(50) value of 4.19 µmol/L; AO/EB stains showed that the morphology of HEL cells obviously changed after emodin treatment for 24 hours, and at 24 and 48 hours the apoptosis rates of HEL cells treated by emodin were (27.35 ± 1.68)% and (58.49 ± 1.55)% respectively. Compared with blank control group, the cell ratio in G(0)/G(1) phase increased while that in S phase decreased (p < 0.01); the expression of Akt protein was not changed (p > 0.05), and that of P-Akt, P-GSK3β and HSP70 proteins were down-regulated (p < 0.05). It is concluded that emodin efficiently inhibits the HEL cell proliferation and induces apoptosis of HEL cells, which may be related to the down-regulation of P-Akt, P-GSK3β and HSP70 proteins expression.

Emodin, a naturally occurring anthraquinone derivative, suppresses IgE-mediated anaphylactic reaction and mast cell activation

The high-affinity receptor for IgE (FcɛRI)-mediated activation of mast cells plays an important role in allergic diseases such as asthma, allergic rhinitis and atopic dermatitis. Emodin, a naturally occurring anthraquinone derivative in oriental herbal medicines, has several beneficial pharmacologic effects, such as anti-cancer and anti-diabetic activities. However, the anti-allergic effect of emodin has not yet been investigated. To assess the anti-allergic activity of emodin, in vivo passive anaphylaxis animal model and in vitro mouse bone marrow-derived mast cells were used to investigate the mechanism of its action on mast cells. Our results showed that emodin inhibited degranulation, generation of eicosanoids (prostaglandin D(2) and leukotriene C(4)), and secretion of cytokines (TNF-α and IL-6) in a dose-dependent manner in IgE/Ag-stimulated mast cells. Biochemical analysis of the FcɛRI-mediated signaling pathways demonstrated that emodin inhibited the phosphorylation of Syk and multiple downstream signaling processes including mobilization of intracellular Ca(2+) and activation of the mitogen-activated protein kinase, phosphatidylinositol 3-kinase, and NF-κB pathways. When administered orally, emodin attenuated the mast cell-dependent passive anaphylactic reaction in IgE-sensitized mice. Thus, emodin inhibits mast cell activation and thereby the anaphylactic reaction through suppression of the receptor-proximal Syk-dependent signaling pathways. Therefore, emodin might provide a basis for development of a novel anti-allergic drug.

Sonodynamic effect of an anti-inflammatory agent--emodin on macrophages

Emodin has been used as an anti-inflammatory agent and inflammation is a crucial feature of atherosclerosis. Here, we investigated the sonodynamic effect of emodin on macrophages, the pivotal inflammatory cells in atherosclerotic plaque. THP-1 derived macrophages were cultured with emodin and exposed to ultrasound. Six hours later, unlike the cells treated for 5 and 10 min, the viability of cells treated for 15 min decreased significantly and the cells showed typical apoptotic chromatin fragmentation. The percentage of apoptotic and necrotic cells in the sonodynamic therapy (SDT) group was higher than that in the ultrasound group. Two hours after treatment for 15 min, the cytoskeleton lost its original features as the filaments dispersed and the cytoskeletal proteins aggregated. The percentage of cells with disturbed cytoskeletal filaments in the SDT group was higher than that in the ultrasound group. These results suggest emodin has a sonodynamic effect on macrophages and might be used as a novel sonosensitizer for SDT for atherosclerosis.

Screening for novel quorum-sensing inhibitors to interfere with the formation of Pseudomonas aeruginosa biofilm

The objective of this study was to screen for novel quorum-sensing inhibitors (QSIs) from traditional Chinese medicines (TCMs) that inhibit bacterial biofilm formation. Six of 46 active components found in TCMs were identified as putative QSIs based on molecular docking studies. Of these, three compounds inhibited biofilm formation by Pseudomonas aeruginosa and Stenotrophomonas maltophilia at a concentration of 200 µM. A fourth compound (emodin) significantly inhibited biofilm formation at 20 µM and induced proteolysis of the quorum-sensing signal receptor TraR in Escherichia coli at a concentration of 3-30 mM. Emodin also increased the activity of ampicillin against P. aeruginosa. Therefore, emodin might be suitable for development into an antivirulence and antibacterial agent.

Cryptic Aspergillus nidulans antimicrobials

Secondary metabolite (SM) production by fungi is hypothesized to provide some fitness attribute for the producing organisms. However, most SM clusters are "silent" when fungi are grown in traditional laboratory settings, and it is difficult to ascertain any function or activity of these SM cluster products. Recently, the creation of a chromatin remodeling mutant in Aspergillus nidulans induced activation of several cryptic SM gene clusters. Systematic testing of nine purified metabolites from this mutant identified an emodin derivate with efficacy against both human fungal pathogens (inhibiting both spore germination and hyphal growth) and several bacteria. The ability of catalase to diminish this antimicrobial activity implicates reactive oxygen species generation, specifically, the generation of hydrogen peroxide, as the mechanism of emodin hydroxyl activity.

Emodin inhibits current through SARS-associated coronavirus 3a protein

The open-reading-frame 3a of SARS coronavirus (SARS-CoV) had been demonstrated previously to form a cation-selective channel that may become expressed in the infected cell and is then involved in virus release. Drugs that inhibit the ion channel formed by the 3a protein can be expected to inhibit virus release, and would be a source for the development of novel therapeutic agents. Here we demonstrate that emodin can inhibit the 3a ion channel of coronavirus SARS-CoV and HCoV-OC43 as well as virus release from HCoV-OC43 with a K1/2 value of about 20 μM. We suggest that viral ion channels, in general, may be a good target for the development of antiviral agents.