Arctigenin, a phenylpropanoid dibenzylbutyrolactone lignan, inhibits MAP kinases and AP-1 activation via potent MKK inhibition: the role in TNF-α inhibition

Mechanism of Arctigenin-Induced Specific Cytotoxicity against Human Hepatocellular Carcinoma Cell Lines: Hep G2 and SMMC7721

Arctigenin (ARG) has been previously reported to exert high biological activities including anti-inflammatory, antiviral and anticancer. In this study, the anti-tumor mechanism of ARG towards human hepatocellular carcinoma (HCC) was firstly investigated. We demonstrated that ARG could induce apoptosis in Hep G2 and SMMC7721 cells but not in normal hepatic cells, and its apoptotic effect on Hep G2 was stronger than that on SMMC7721. Furthermore, the following study showed that ARG treatment led to a loss in the mitochondrial out membrane potential, up-regulation of Bax, down-regulation of Bcl-2, a release of cytochrome c, caspase-9 and caspase-3 activation and a cleavage of poly (ADP-ribose) polymerase in both Hep G2 and SMMC7721 cells, suggesting ARG-induced apoptosis was associated with the mitochondria mediated pathway. Moreover, the activation of caspase-8 and the increased expression levels of Fas/FasL and TNF-α revealed that the Fas/FasL-related pathway was also involved in this process. Additionally, ARG induced apoptosis was accompanied by a deactivation of PI3K/p-Akt pathway, an accumulation of p53 protein and an inhibition of NF-κB nuclear translocation especially in Hep G2 cells, which might be the reason that Hep G2 was more sensitive than SMMC7721 cells to ARG treatment.

Trametinib, a novel MEK kinase inhibitor, suppresses lipopolysaccharide-induced tumor necrosis factor (TNF)-α production and endotoxin shock

Lipopolysaccharide (LPS), one of the most prominent pathogen-associated molecular patterns (PAMPs), activates macrophages, causing release of toxic cytokines (i.e. tumor necrosis factor (TNF)-α) that may provoke inflammation and endotoxin shock. Here, we tested the potential role of trametinib, a novel and highly potent MAPK/ERK kinase (MEK) inhibitor, against LPS-induced TNF-α response in monocytes, and analyzed the underlying mechanisms. We showed that trametinib, at nM concentrations, dramatically inhibited LPS-induced TNF-α mRNA expression and protein secretion in transformed (RAW 264.7 cells) and primary murine macrophages. In ex-vivo cultured human peripheral blood mononuclear cells (PBMCs), this MEK inhibitor similarly suppressed TNF-α production by LPS. For the mechanism study, we found that trametinib blocked LPS-induced MEK-ERK activation in above monocytes, which accounted for the defective TNF-α response. Macrophages or PBMCs treated with a traditional MEK inhibitor PD98059 or infected with MEK1/2-shRNA lentivirus exhibited a similar defect as trametinib, and nullified the activity of trametinib. On the other hand, introducing a constitutively-active (CA) ERK1 restored TNF-α production by LPS in the presence of trametinib. In vivo, mice administrated with trametinib produced low levels of TNF-α after LPS stimulation, and these mice were protected from LPS-induced endotoxin shock. Together, these results show that trametinib inhibits LPS-induced TNF-α expression and endotoxin shock probably through blocking MEK-ERK signaling.

Arctigenin Increases Hemeoxygenase-1 Gene Expression by Modulating PI3K/AKT Signaling Pathway in Rat Primary Astrocytes

In the present study, we found that the natural compound arctigenin inhibited hydrogen peroxide-induced reactive oxygen species (ROS) production in rat primary astrocytes. Since hemeoxygenase-1 (HO-1) plays a critical role as an antioxidant defense factor in the brain, we examined the effect of arctigenin on HO-1 expression in rat primary astrocytes. We found that arctigenin increased HO-1 mRNA and protein levels. Arctigenin also increases the nuclear translocation and DNA binding of Nrf2/c-Jun to the antioxidant response element (ARE) on HO-1 promoter. In addition, arctigenin increased ARE-mediated transcriptional activities in rat primary astrocytes. Further mechanistic studies revealed that arctigenin increased the phosphorylation of AKT, a downstream substrate of phosphatidylinositol 3-kinase (PI3K). Treatment of cells with a PI3K-specific inhibitor, LY294002, suppressed the HO-1 expression, Nrf2 DNA binding and ARE-mediated transcriptional activities in arctigenin-treated astrocyte cells. The results collectively suggest that PI3K/AKT signaling pathway is at least partly involved in HO-1 expression by arctigenin via modulation of Nrf2/ARE axis in rat primary astrocytes.

Elucidation of arctigenin pharmacokinetics after intravenous and oral administrations in rats: integration of in vitro and in vivo findings via semi-mechanistic pharmacokinetic modeling

Although arctigenin (AR) has attracted substantial research interests due to its promising and diverse therapeutic effects, studies regarding its biotransformation were limited. The current study aims to provide information regarding the pharmacokinetic properties of AR via various in vitro and in vivo experiments as well as semi-mechanistic pharmacokinetic modeling. Our in vitro rat microsome incubation studies revealed that glucuronidation was the main intestinal and liver metabolic pathway of AR, which occurred with V max, K m, and Clint of 47.5 ± 3.4 nmol/min/mg, 204 ± 22 μM, and 233 ± 9 μl/min/mg with intestinal microsomes and 2.92 ± 0.07 nmol/min/mg, 22.7 ± 1.2 μM, and 129 ± 4 μl/min/mg with liver microsomes, respectively. In addition, demethylation and hydrolysis of AR occurred with liver microsomes but not with intestinal microsomes. In vitro incubation of AR and its metabolites in intestinal content demonstrated that glucuronides of AR excreted in bile could be further hydrolyzed back to the parent compound, suggesting its potential enterohepatic circulation. Furthermore, rapid formation followed by fast elimination of arctigenic acid (AA) and arctigenin-4'-O-glucuronide (AG) was observed after both intravenous (IV) and oral administrations of AR in rats. Linear pharmacokinetics was observed at three different doses for AR, AA, and AG after IV administration of AR (0.48-2.4 mg/kg, r (2) > 0.99). Finally, an integrated semi-mechanistic pharmacokinetic model using in vitro enzyme kinetic and in vivo pharmacokinetic parameters was successfully developed to describe plasma concentrations of AR, AA, and AG after both IV and oral administration of AR at all tested doses.

Increased chemopreventive effect by combining arctigenin, green tea polyphenol and curcumin in prostate and breast cancer cells

The low bioavailability of most flavonoids limits their application as anti-carcinogenic agents in humans. A novel approach of treatment with a mixture of bioactive compounds that share molecular anti-carcinogenic targets may enhance the effect on these targets at low concentrations of individual compound, thereby overcoming the limitations of reduced bioavailability. We therefore investigated whether a combination of three natural products arctigenin (Arc), a novel anti-inflammatory lignan from the seeds of Arctium lappa, green tea polyphenol (-)-epigallocatechin gallate (EGCG) and curcumin (Cur) increases the chemopreventive potency of individual compounds. LNCaP prostate cancer and MCF-7 breast cancer cells were treated with 2-4 mg/L (about 5-10μM) Cur, 1μM Arc and 40μM EGCG alone or in combination for 48h. In both cell lines treatment with the mixture of Cur, Arc and EGCG synergistically increased the antiproliferative effect. In LNCaP cells both Arc and EGCG increased the pro-apoptotic effect of Cur. Whereas in MCF-7 cells Arc increased the cell apoptosis of Cur while EGCG enhanced cell cycle arrest of Cur at G0/G1 phase. The strongest effects on cell cycle arrest and apoptosis were achieved by combining all three compounds in both cell lines. The combination treatment significantly increased the ratio of Bax to Bcl-2 proteins, decreased the activation of NFκB, PI3K/Akt and Stat3 pathways and cell migration compared to individual treatment. These results warrant in vivo studies to confirm the efficacy of this novel regimen by combining Arc and EGCG with Cur to enhance chemoprevention in both prostate and breast cancer.

Arctigenin, a dietary phytoestrogen, induces apoptosis of estrogen receptor-negative breast cancer cells through the ROS/p38 MAPK pathway and epigenetic regulation

This study investigates the anticancer effect of arctigenin (ATG), a natural lignan product of Arctium lappa L., in human breast cancer MDA-MB-231 cells. Results indicate that ATG inhibits MDA-MB-231 cell growth by inducing apoptosis in vitro and in vivo. ATG triggers the mitochondrial caspase-independent pathways, as indicated by changes in Bax/Bcl-2 ratio, resulting in AIF and EndoG nuclear translocation. ATG increased cellular reactive oxygen species (ROS) production by increasing p22(phox)/NADPH oxidase 1 interaction and decreasing glutathione level. ATG clearly increases the activation of p38 MAPK, but not JNK and ERK1/2. Antioxidant EUK-8, a synthetic catalytic superoxide and hydrogen peroxide scavenger, significantly decreases ATG-mediated p38 activation and apoptosis. Blocking p38 with a specific inhibitor suppresses ATG-mediated Bcl-2 downregulation and apoptosis. Moreover, ATG activates ATF-2, a transcription factor activated by p38, and then upregulates histone H3K9 trimethylation in the Bcl-2 gene promoter region, resulting in Bcl-2 downregulation. Taken together, the results demonstrate that ATG induces apoptosis of MDA-MB-231 cells via the ROS/p38 MAPK pathway and epigenetic regulation of Bcl-2 by upregulation of histone H3K9 trimethylation.

Arctigenin inhibits osteoclast differentiation and function by suppressing both calcineurin-dependent and osteoblastic cell-dependent NFATc1 pathways

Arctigenin, a lignan-derived compound, is a constituent of the seeds of Arctium lappa. Arctigenin was previously shown to inhibit osteoclastogenesis; however, this inhibitory mechanism has yet to be elucidated. Here, we showed that arctigenin inhibited the action of nuclear factor of activated T-cells, cytoplasmic 1 (NFATc1), a key transcription factor for osteoclastogenesis. NFATc1 in osteoclast precursors was activated through two distinct pathways: the calcineurin-dependent and osteoblastic cell-dependent pathways. Among the several lignan-derived compounds examined, arctigenin most strongly inhibited receptor activator of nuclear factor κB ligand (RANKL)-induced osteoclast-like cell formation in mouse bone marrow macrophage (BMM) cultures, in which the calcineurin-dependent NFATc1 pathway was activated. Arctigenin suppressed neither the activation of nuclear factor κB and mitogen-activated protein kinases nor the up-regulation of c-Fos expression in BMMs treated with RANKL. However, arctigenin suppressed RANKL-induced NFATc1 expression. Interestingly, the treatment of osteoclast-like cells with arctigenin converted NFATc1 into a lower molecular weight species, which was translocated into the nucleus even in the absence of RANKL. Nevertheless, arctigenin as well as cyclosporin A (CsA), a calcineurin inhibitor, suppressed the NFAT-luciferase reporter activity induced by ionomycin and phorbol 12-myristate 13-acetate in BMMs. Chromatin immunoprecipitation analysis confirmed that arctigenin inhibited the recruitment of NFATc1 to the promoter region of the NFATc1 target gene. Arctigenin, but not CsA suppressed osteoclast-like cell formation in co-cultures of osteoblastic cells and bone marrow cells, in which the osteoblastic cell-dependent NFATc1 pathway was activated. The forced expression of constitutively active NFATc1 rescued osteoclastogenesis in BMM cultures treated with CsA, but not that treated with arctigenin. Arctigenin also suppressed the pit-forming activity of osteoclast-like cells cultured on dentin slices. These results suggest that arctigenin induces a dominant negative species of NFATc1, which inhibits osteoclast differentiation and function by suppressing both calcineurin-dependent and osteoblastic cell-dependent NFATc1 pathways.

Cancer Prevention and Therapy: Integrating Traditional Korean Medicine Into Modern Cancer Care

In spite of billions of dollars spent on cancer research each year, overall cancer incidence and cancer survival has not changed significantly in the last half century. Instead, the recent projection from the World Health Organization suggests that global cancer incidence and death is expected to double within the next decade. This requires an "out of the box" thinking approach. While traditional medicine used for thousands of years is safe and affordable, its efficacy and mechanism of action are not fully reported. Demonstrating that traditional medicine is efficacious and how it works can provide a "bed to bench" and "bench to bed" back approach toward prevention and treatment of cancer. This current review is an attempt to describe the contributions of traditional Korean medicine (TKM) to modern medicine and, in particular, cancer treatment. TKM suggests that cancer is an outcome of an imbalance of body, mind, and spirit; thus, it requires a multimodal treatment approach that involves lifestyle modification, herbal prescription, acupuncture, moxibustion, traditional exercise, and meditation to restore the balance. Old wisdoms in combination with modern science can find a new way to deal with the "emperor of all maladies."

Arctigenin promotes cholesterol efflux from THP-1 macrophages through PPAR-γ/LXR-α signaling pathway

Cholesterol efflux from macrophages is a critical mechanism to prevent the development of atherosclerosis. Here, we sought to investigate the effects of arctigenin, a bioactive component of Arctium lappa, on the cholesterol efflux in oxidized low-density lipoprotein (oxLDL)-loaded THP-1 macrophages. Our data showed that arctigenin significantly accelerated apolipoprotein A-I- and high-density lipoprotein-induced cholesterol efflux in both dose- and time-dependent manners. Moreover, arctigenin treatment enhanced the expression of ATP binding cassette transporter A1 (ABCA1), ABCG1, and apoE, all of which are key molecules in the initial step of cholesterol efflux, at both mRNA and protein levels. Arctigenin also caused a concentration-dependent elevation in the expression of peroxisome proliferator-activated receptor-gamma (PPAR-γ) and liver X receptor-alpha (LXR-α). The arctigenin-mediated induction of ABCA1, ABCG1, and apoE was abolished by specific inhibition of PPAR-γ or LXR-α using small interfering RNA technology. Our results collectively indicate that arctigenin promotes cholesterol efflux in oxLDL-loaded THP-1 macrophages through upregulation of ABCA1, ABCG1 and apoE, which is dependent on the enhanced expression of PPAR-γ and LXR-α.

Anti-inflammatory intestinal activity of Arctium lappa L. (Asteraceae) in TNBS colitis model

ETHNOPHARMACOLOGICAL RELEVANCE

In Brazilian traditional medicine, Arctium lappa (Asteraceae), has been reported to relieve gastrointestinal symptoms.

AIM OF THE STUDY

In the present study, we investigated the effects of the lactone sesquiterpene onopordopicrin enriched fraction (ONP fraction) from Arctium lappa in an experimental colitis model induced by 2,4,6 trinitrobenzene sulfonic acid and performed experiments to elucidate the underlying action mechanisms involved in that effect.

MATERIALS AND METHODS

ONP fraction (25 and 50 mg/kg/day) was orally administered 48, 24 and 1 h prior to the induction of colitis and 24 h after. The inflammatory response was assessed by gross appearance, myeloperoxidase (MPO) activity, tumor necrosis factor alpha (TNF-α) levels and a histological study of the lesions. We determined cyclooxygenase (COX)-1 and -2 protein expressions by western blotting and immunohistochemistry assays.

RESULTS

TNBS group was characterized by increased colonic wall thickness, edema, diffuse inflammatory cell infiltration, increased MPO activity and TNF-α levels. On the contrary, ONP fraction (25 and 50 mg/kg) treatment significantly reduced the macroscopic inflammation scores (p<0.05 and p<0.01, respectively) and morphological alterations associated with an increase in the mucus secretion. Similarly, the degree of neutrophil infiltration and the cytokine levels were significantly ameliorated. Moreover, COX-2 expression was up regulated in TNBS-treated rats. In contrast, ONP fraction (50 mg/kg) administration reduced COX-2 overexpression.

CONCLUSIONS

We have shown that the ONP fraction obtained from Arctium lappa exert marked protective effects in acute experimental colitis, confirming and justifying, at least in part, the popular use of this plant to treat gastrointestinal diseases.

Arctigenin alleviates ER stress via activating AMPK

AIM

To investigate the protective effects of arctigenin (ATG), a phenylpropanoid dibenzylbutyrolactone lignan from Arctium lappa L (Compositae), against ER stress in vitro and the underlying mechanisms.

METHODS

A cell-based screening assay for ER stress regulators was established. Cell viability was measured using MTT assay. PCR and Western blotting were used to analyze gene and protein expression. Silencing of the CaMKKβ, LKB1, and AMPKα1 genes was achieved by RNA interference (RNAi). An ATP bioluminescent assay kit was employed to measure the intracellular ATP levels.

RESULTS

ATG (2.5, 5 and 10 μmol/L) inhibited cell death and unfolded protein response (UPR) in a concentration-dependent manner in cells treated with the ER stress inducer brefeldin A (100 nmol/L). ATG (1, 5 and 10 μmol/L) significantly attenuated protein synthesis in cells through inhibiting mTOR-p70S6K signaling and eEF2 activity, which were partially reversed by silencing AMPKα1 with RNAi. ATG (1-50 μmol/L) reduced intracellular ATP level and activated AMPK through inhibiting complex I-mediated respiration. Pretreatment of cells with the AMPK inhibitor compound C (25 μmol/L) rescued the inhibitory effects of ATG on ER stress. Furthermore, ATG (2.5 and 5 μmol/L) efficiently activated AMPK and reduced the ER stress and cell death induced by palmitate (2 mmol/L) in INS-1 β cells.

CONCLUSION

ATG is an effective ER stress alleviator, which protects cells against ER stress through activating AMPK, thus attenuating protein translation and reducing ER load.

pH and temperature dual-sensitive liposome gel based on novel cleavable mPEG-Hz-CHEMS polymeric vaginal delivery system

Background

In this study, a pH and temperature dual-sensitive liposome gel based on a novel cleavable hydrazone-based pH-sensitive methoxy polyethylene glycol 2000-hydrazone-cholesteryl hemisuccinate (mPEG-Hz-CHEMS) polymer was used for vaginal administration.

Methods

The pH-sensitive, cleavable mPEG-Hz-CHEMS was designed as a modified pH-sensitive liposome that would selectively degrade under locally acidic vaginal conditions. The novel pH-sensitive liposome was engineered to form a thermogel at body temperature and to degrade in an acidic environment.

Results

A dual-sensitive liposome gel with a high encapsulation efficiency of arctigenin was formed and improved the solubility of arctigenin characterized by Fourier transform infrared spectroscopy and differential scanning calorimetry. The dual-sensitive liposome gel with a sol-gel transition at body temperature was degraded in a pH-dependent manner, and was stable for a long period of time at neutral and basic pH, but cleavable under acidic conditions (pH 5.0). Arctigenin encapsulated in a dual-sensitive liposome gel was more stable and less toxic than arctigenin loaded into pH-sensitive liposomes. In vitro drug release results indicated that dual-sensitive liposome gels showed constant release of arctigenin over 3 days, but showed sustained release of arctigenin in buffers at pH 7.4 and pH 9.0.

Conclusion

This research has shed some light on a pH and temperature dual-sensitive liposome gel using a cleavable mPEG-Hz-CHEMS polymer for vaginal delivery.

Arctigenin anti-tumor activity in bladder cancer T24 cell line through induction of cell-cycle arrest and apoptosis

Bladder cancer is the most common neoplasm in the urinary system. This study assesses arctigenin anti-tumor activity in human bladder cancer T24 cells in vitro and the underlying molecular events. The flow cytometry analysis was used to detect cell-cycle distribution and apoptosis. Western blotting was used to detect changes in protein expression. The data showed that arctigenin treatment reduced viability of bladder cancer T24 cells in a dose- and time-dependent manner after treatment with arctigenin (10, 20, 40, 80, and 100 μmol/L) for 24 hr and 48 hr. Arctigenin treatment clearly arrested tumor cells in the G1 phase of the cell cycle. Apoptosis was detected by hoechst stain and flow cytometry after Annexin-V-FITC/PI double staining. Early and late apoptotic cells were accounted for 2.32-7.01% and 3.07-7.35%, respectively. At the molecular level, arctigenin treatment decreased cyclin D1 expression, whereas CDK4 and CDK6 expression levels were unaffected. Moreover, arctigenin selectively altered the phosphorylation of members of the MAPK superfamily, decreasing phosphorylation of ERK1/2 and activated phosphorylation of p38 significantly in a dose-dependent manner. These results suggest that arctigenin may inhibit cell viability and induce apoptosis by direct activation of the mitochondrial pathway, and the mitogen-activated protein kinase pathway may play an important role in the anti-tumor effect of arctigenin. The data from the current study demonstrate the usefulness of arctigenin in bladder cancer T24 cells, which should further be evaluated in vivo before translation into clinical trials for the chemoprevention of bladder cancer.

Tumor specific cytotoxicity of arctigenin isolated from herbal plant Arctium lappa L

The effectiveness of cancer chemotherapy is often limited by the toxicity to other tissues in the body. Therefore, the identification of non-toxic chemotherapeutics from herbal medicines remains to be an attractive goal to advance cancer treatments. This study evaluated the cytotoxicity profiles of 364 herbal plant extracts, using various cancer and normal cell lines. The screening found occurrence of A549 (human lung adenocarcinoma) specific cytotoxicity in nine species of herbal plants, especially in the extract of Arctium lappa L. Moreover, purification of the selective cytotoxicity in the extract of Arctium lappa L. resulted in the identification of arctigenin as tumor specific agent that showed cytotoxicity to lung cancer (A549), liver cancer (HepG2) and stomach cancer (KATO III) cells, while no cytotoxicity to several normal cell lines. Arctigenin specifically inhibited the proliferation of cancer cells, which might consequently lead to the induction of apoptosis. In conclusion, this study found that arctigenin was one of cancer specific phytochemicals, and in part responsible for the tumor selective cytotoxicity of the herbal medicine.

Evaluation of the antiproliferative activity of the leaves from Arctium lappa by a bioassay-guided fractionation

Arctium lappa L. (Asteraceae) is used in folk medicine around the World, and shows several kinds of biological activity, particularly in vitro antitumor activity in different cell lines. This study evaluated the antiproliferative activity of the crude extract, semipurified fractions, and isolated compounds from the leaves of A. lappa, through bioassay-guided testing in Caco-2 cells. The crude extract was obtained with a 50% hydroethanolic extract and then partitioned with hexane, ethyl acetate, and n-butanol. The ethyl-acetate fraction (EAF) showed antiproliferative activity. This fraction was subjected to sequential column chromatography over silica gel to afford onopordopicrin (1), mixtures of 1 with dehydromelitensin-8-(4'-hydroxymethacrylate) (2), a mixture of 2 with dehydromelitensin (3), mixture of 1 with melitensin (4), dehydrovomifoliol (5), and loliolide (6). The compounds were identified by spectroscopic methods (NMR, MS) and comparison with literature data. This is the first description of compounds 2-5 from this species. The compounds tested in Caco-2 cells showed the following CC(50) (µg/mL) values: 1: 19.7 ± 3.4, 1 with 2: 24.6 ± 1.5, 2 with 3: 27 ± 11.7, 1 with 4: 42 ± 13.1, 6 30 ± 6.2; compound 5 showed no activity.

Mono-2-ethylhexylphthalate (MEHP) induces TNF-α release and macrophage differentiation through different signalling pathways in RAW264.7 cells

Epidemiological studies have associated indoor phthalate exposure with increased incidences and severity of asthma in children and adults, and inflammatory effects have been suggested as a possible mechanism. Recent studies report that phthalates may activate mitogen-activated protein (MAP) kinase p38 and various peroxisome proliferator-activated receptor (PPAR) isoforms. Here we confirm and extend these findings by investigating possible signalling pathways activated in the murine monocyte-macrophage cell line RAW264.7, using mono-2-ethylhexylphthalate (MEHP) as a model compound. MEHP exposure (0.3-1.0 mM) for 3h increased tumour necrosis factor (TNF)-α release and changed the cellular morphology into elongated spindle-like appearance, resembling more differentiated anti-inflammatory macrophages (M2). This was accompanied by increased expression of the macrophage differentiation marker CD163. Western analysis showed phosphorylation of p38 and Akt after 30 min exposure. Experiments using specific inhibitors suggested that MEHP-induced activation of both p38 and the phosphoinositide-3 (PI3) kinase/Akt pathway were involved in the release of TNF-α; whereas only PI3kinase seemed to be involved in differentiation. In contrast, inhibitors of PPARα and γ reduced differentiation, but did not affect TNF-α release. In conclusion, MEHP induced cytokine release and triggered differentiation of RAW264.7 cells, possibly into M2-like macrophages, but different signalling pathways appear to be involved in these responses.

Organic parasite control for poultry and rabbits in British Columbia, Canada

Plants used for treating endo- and ectoparasites of rabbits and poultry in British Columbia included Arctium lappa (burdock), Artemisia sp. (wormwood), Chenopodium album (lambsquarters) and C. ambrosioides (epazote), Cirsium arvense (Canada thistle), Juniperus spp. (juniper), Mentha piperita (peppermint), Nicotiana sp. (tobacco), Papaver somniferum (opium poppy), Rubus spp. (blackberry and raspberry relatives), Symphytum officinale (comfrey), Taraxacum officinale (common dandelion), Thuja plicata (western redcedar) and Urtica dioica (stinging nettle).

Arctigenin from Arctium lappa inhibits interleukin-2 and interferon gene expression in primary human T lymphocytes

BACKGROUND

Arctium lappa (Niubang), a Chinese herbal medicine, is used to treat tissue inflammation. This study investigates the effects of arctigenin (AC), isolated from A. lappa, on anti-CD3/CD28 Ab-stimulated cell proliferation and cytokine gene expression in primary human T lymphocytes.

METHODS

Cell proliferation was determined with enzyme immunoassays and the tritiated thymidine uptake method. Cytokine production and gene expression were analyzed with reverse transcription-polymerase chain reaction.

RESULTS

AC inhibited primary human T lymphocytes proliferation activated by anti-CD3/CD28 Ab. Cell viability test indicated that the inhibitory effects of AC on primary human T lymphocyte proliferation were not due to direct cytotoxicity. AC suppressed interleukin-2 (IL-2) and interferon-γ (IFN-γ) production in a concentration-dependent manner. Furthermore, AC decreased the IL-2 and IFN-γ gene expression in primary human T lymphocytes induced by anti-CD3/CD28 Ab. Reporter gene analyses revealed that AC decreased NF-AT-mediated reporter gene expression.

CONCLUSION

AC inhibited T lymphocyte proliferation and decreased the gene expression of IL-2, IFN-γ and NF-AT.

Biological activities of Fructus arctii fermented with the basidiomycete Grifola frondosa

Fructus arctii extract containing phenolic glycosides was cultured with Grifola frondosa mycelia to produce β-glucosidase and its biological activities were studied. This β-glucosidase converted the glycosides (arctiin and caffeic acid derivatives) into aglycones (arctigenin and caffeic acid). Fermented Fructus arctii extract (G-FAE) with G. frondosa had antioxidant and 5-lipoxygenase inhibitory activities. The photoprotective potential of G-FAE was tested in human dermal fibroblasts (HDF) exposed to ultra-violet A (UVA). It was revealed that G-FAE had an inhibitory effect on human interstitial collagenase (matrix metalloproteinase, MMP-1) expression in UVA-irradiated HDF. The treatment of UVA-irradiated HDF with G-FAE resulted in a dose-dependent decrease in the expression level of MMP-1 mRNA. G-FAE also showed notable stimulation of collagen biosynthetic activity for fibroblasts. These diverse functionalities suggest that G-FAE could be a promising cosmetic ingredient.

A review of the pharmacological effects of Arctium lappa (burdock)

Arctium lappa, commonly known as burdock, is being promoted/recommended as a healthy and nutritive food in Chinese societies. Burdock has been used therapeutically in Europe, North America and Asia for hundreds of years. The roots, seeds and leaves of burdock have been investigated in view of its popular uses in traditional Chinese medicine (TCM). In this review, the reported therapeutic effects of the active compounds present in the different botanical parts of burdock are summarized. In the root, the active ingredients have been found to "detoxify" blood in terms of TCM and promote blood circulation to the skin surface, improving the skin quality/texture and curing skin diseases like eczema. Antioxidants and antidiabetic compounds have also been found in the root. In the seeds, some active compounds possess anti-inflammatory effects and potent inhibitory effects on the growth of tumors such as pancreatic carcinoma. In the leaf extract, the active compounds isolated can inhibit the growth of micro-organisms in the oral cavity. The medicinal uses of burdock in treating chronic diseases such as cancers, diabetes and AIDS have been reported. However, it is also essential to be aware of the side effects of burdock including contact dermatitis and other allergic/inflammatory responses that might be evoked by burdock.

Arctigenin blocks the unfolded protein response and shows therapeutic antitumor activity

Cancer cells in poorly vascularized solid tumors are constantly or intermittently exposed to stressful microenvironments, including glucose deprivation, hypoxia, and other forms of nutrient starvation. These tumor-specific conditions, especially glucose deprivation, activate a signaling pathway called the unfolded protein response (UPR), which enhances cell survival by induction of the stress proteins. We have established a screening method to discover anticancer agents that could preferentially inhibit tumor cell viability under glucose-deprived conditions. Here we identify arctigenin (ARC-G) as an active compound that shows selective cytotoxicity and inhibits the UPR during glucose deprivation. Indeed, ARC-G blocked expression of UPR target genes such as phosphorylated-PERK, ATF4, CHOP, and GRP78, which was accompanied by enhanced phosphorylation of eIF2 alpha during glucose deprivation. The UPR inhibition led to apoptosis involving a mitochondrial pathway by activation of caspase-9 and -3. Furthermore, ARC-G suppressed tumor growth of colon cancer HT-29 xenografts. Our results demonstrate that ARC-G can be served as a novel type of antitumor agent targeting the UPR in glucose-deprived solid tumors.

Using cells devoid of RAS proteins as tools for drug discovery

Mutational activation of RAS proteins occurs in nearly 30% of all human tumors. To date direct pharmacological inhibition of RAS oncoproteins has not been possible. As a consequence, current strategies are focusing on the development of inhibitors that target those kinases acting downstream of RAS proteins, including those of the RAF/MEK/ERK and PI3K/AKT pathways. Most of these inhibitors have undesired off-target effects that mask the potential therapeutic effect of blocking their targeted kinases. To facilitate the screening of selective inhibitors, we have generated lines of mouse embryonic fibroblasts that lack endogenous Ras proteins. These cells proliferate due to ectopic expression of either Ras oncoproteins that selectively activate the Raf/Mek/Erk pathway such as H-Ras(G12V/D38E) or constitutively active kinases such as B-Raf and Mek1. These cell lines were exposed to inhibitors against the RAF, MEK, and AKT kinases as well as inhibitors of other kinases known to crosstalk with RAS signaling such as JNK and p38. Amongst all compounds tested, only the MEK inhibitors U0126 and PD0325901, showed the expected specificity pattern. Yet, PD0325901, but not U0126, was able to inhibit a cell line lacking Ras proteins that owed its proliferative properties to loss of p53. Thus, suggesting unexpected off-target activities for this compound. The use of cell lines whose proliferative properties exclusively depend on selective targets provide a novel strategy to analyze the specificity of selective inhibitors designed against molecular targets implicated in human cancer.

Ameliorative effects of arctiin from Arctium lappa on experimental glomerulonephritis in rats

Membranous glomerulonephritis (MGN) remains the most common cause of adult-onset nephrotic syndrome in the world and up to 40% of untreated patients will progress to end-stage renal disease. Although the treatment of MGN with immunosuppressants or steroid hormones can attenuate the deterioration of renal function, numerous treatment-related complications have also been established. In this study, the ameliorative effects of arctiin, a natural compound isolated from the fruits of Arctium lappa, on rat glomerulonephritis induced by cationic bovine serum albumin (cBSA) were determined. After oral administration of arctiin (30, 60, 120 mg/kgd) for three weeks, the levels of serum creatinine (Scr) and blood urea nitrogen (BUN) and 24-h urine protein content markedly decreased, while endogenous creatinine clearance rate (ECcr) significantly increased. The parameters of renal lesion, hypercellularity, infiltration of polymorphonuclear leukocyte (PMN), fibrinoid necrosis, focal and segmental proliferation and interstitial infiltration, were reversed. In addition, we observed that arctiin evidently reduced the levels of malondialdehyde (MDA) and pro-inflammatory cytokines including interleukin-6 (IL-6) and tumor necrosis factor (TNF-alpha), suppressed nuclear factor-kappaB p65 (NF-kappaB) DNA binding activity, and enhanced superoxide dismutase (SOD) activity. These findings suggest that the ameliorative effects of arctiin on glomerulonephritis is carried out mainly by suppression of NF-kappaB activation and nuclear translocation and the decreases in the levels of these pro-inflammatory cytokines, while SOD is involved in the inhibitory pathway of NF-kappaB activation. Arctiin has favorable potency for the development of an inhibitory agent of NF-kappaB and further application to clinical treatment of glomerulonephritis, though clinical studies are required.

In vitro anti-inflammatory effects of arctigenin, a lignan from Arctium lappa L., through inhibition on iNOS pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Arctigenin, a bioactive constituent from dried seeds of Arctium lappa L. (Compositae) which has been widely used as a Traditional Chinese Medicine for dispelling wind and heat included in Chinese Pharmacophere, was found to exhibit anti-inflammatory activities but its molecular mechanism remains unknown yet.

AIM OF THE STUDY

To investigate the anti-inflammatory mechanism of arctigenin.

MATERIALS AND METHODS

Cultured macrophage RAW 264.7 cells and THP-1 cells were used for the experiments. Griess assay was used to evaluate the inhibitory effect of arctigenin on the overproduction of nitric oxide (NO). ELISA was used to determine the level of pro-inflammatory cytokines including tumor necrosis factor alpha (TNF-alpha) and interleukin-6 (IL-6). The inhibitory effect on the enzymatic activity of cyclooxygenase-2 (COX-2) was tested by colorimetric method. Western blot was used to detect the expression of inducible nitric oxide synthase (iNOS) and COX-2.

RESULTS

Arctigenin suppressed lipopolysaccharide (LPS)-stimulated NO production and pro-inflammatory cytokines secretion, including TNF-alpha and IL-6 in a dose-dependent manner. Arctigenin also strongly inhibited the expression of iNOS and iNOS enzymatic activity, whereas the expression of COX-2 and COX-2 enzymatic activity were not affected by arctigenin.

CONCLUSIONS

These results indicated that potent inhibition on NO, TNF-alpha and IL-6, but not COX-2 expression and COX-2 activity, might constitute the anti-inflammatory mechanism of arctigenin. Arctigenin suppressed the overproduction of NO through down-regulation of iNOS expression and iNOS enzymatic activity in LPS-stimulated macrophage.

4-Hydroxykobusin Inhibits the Induction of Nitric Oxide Synthase by Inhibiting NF-.KAPPA.B and AP-1 Activation

We recently isolated a novel lignan, 4-hydroxykobusin from Geranium thunbergii (Liu et al., Arch. Pharm. Res., 29, 1109-1113, 2006). Here, we studied its effect on the expression of inducible nitric oxide synthase (iNOS) gene in RAW264.7 cells. 4-Hydroxykobusin inhibited nitric oxide (NO) production in a concentration-dependent manner and blocked the lipopolysaccharide (LPS)-induced expression of inducible nitric oxide synthase (iNOS). To identify the mechanistic basis for its inhibition of iNOS induction, we examined the effect of 4-hydroxykobusin on the transactivation of iNOS gene by luciferase reporter activity using -1.59 kb flanking region. The lignan suppressed the reporter gene activity and the LPS-induced reporter activations of nuclear factor-kappaB (NF-kappaB) and activator protein-1 (AP-1) were also significantly blocked by 4-hydroxykobusin. These findings suggest that the inhibition of LPS-induced NO formation by 4-hydroxykobusin is due to its inhibition of NF-kappaB and AP-1 activation.

Antinociceptive effect from Ipomoea cairica extract

Ipomoea cairica L. Sweet (Convolvulaceae) is used in Brazilian folk medicine for the treatment of rheumatism and inflammations. Ipomoea cairica ethanolic extract (100, 300, 1000 and 3000 mg/kg; per os) induced dose-dependent reduction of response in the formalin test inflammatory phase in mice. The same dose range did not modify neurogenic pain in formalin test, tail-flick reflex latency, carrageenan-induced paw edema, and Rota-Rod test motor performance. From the bio-active fraction 3,5-di-O-caffeoylquinic acid and 4,5-di-O-caffeoylquinic acid were obtained. These compounds have been previously reported to have analgesic and antioxidative effects. A possible explanation for the antinociception is that somehow the compounds present in the extract reduced the release of pro-nociceptive mediators unrelated to carrageenan-induced edema, such as histamine. Interestingly, caffeoylquinic acid derivatives have been reported to inhibit histamine release on in vitro models. The isolated caffeoylquinic acids could explain, at least in part, the antinociceptive effect of Ipomoea cairica polar extract.

Honokiol inhibits TNF-α-stimulated NF-κB activation and NF-κB-regulated gene expression through suppression of IKK activation

Honokiol, a small molecular weight lignan originally isolated from Magnolia officinalis, shows anti-angiogenic, anti-invasive and anti-proliferative activities in a variety of cancers. In this study, we investigated whether honokiol affects the transcription factor nuclear factor-kappa B (NF-kappaB) which controls a large number of genes involved in angiogenesis, metastasis and cell survival. We observed that the tumor necrosis factor-alpha (TNF-alpha)-induced NF-kappaB activation was blocked by honokiol in four different cancer cell lines as evidenced by EMSA. Honokiol did not directly affect the NF-kappaB-DNA binding. Immunoblot experiments demonstrated that honokiol inhibited the TNF-alpha-stimulated phosphorylation and degradation of the cytosolic NF-kappaB inhibitor IkappaBalpha. Furthermore, honokiol suppressed the intrinsic and TNF-alpha-stimulated upstream IkappaB kinases (IKKs) activities measured by a non-radioactive kinase assay using immunoprecipitated IKKs, suggesting a critical role of honokiol in abrogating the phosphorylation and degradation of IkappaBalpha. In a HeLa cell NF-kappaB-dependent luciferase reporter system, honokiol suppressed luciferase expression stimulated by TNF-alpha and by the transient transfection and expression of NIK (NF-kappaB-inducing kinase), wild type IKKbeta, constitutively active IKKalpha and IKKbeta, or the p65 subunit. Honokiol was also found to inhibit the nuclear translocation and phosphorylation of p65 subunit of NF-kappaB. RT-PCR results showed that honokiol suppressed NF-kappaB-regulated inflammatory and carcinogenic gene products including MMP-9, TNF-alpha, IL-8, ICAM-1 and MCP-1. In line with the observation that NF-kappaB activation may up-regulate anti-apoptotic genes, it was shown that honokiol enhanced TNF-alpha-induced apoptotic cell death. In summary, our results demonstrate that honokiol suppresses NF-kappaB activation and NF-kappaB-regulated gene expression through the inhibition of IKKs, which provides a possible mechanism for its anti-tumor actions.

An update on bioactive plant lignans

Lignans are a class of secondary plant metabolites produced by oxidative dimerization of two phenylpropanoid units. Although their molecular backbone consists only of two phenylpropane (C6-C3) units, lignans show an enormous structural diversity. There is a growing interest in lignans and their synthetic derivatives due to applications in cancer chemotherapy and various other pharmacological effects. This review deals with lignans possessing anticancer, antioxidant, antimicrobial, anti-inflammatory and immunosuppressive activities, and comprises the data reported in more than 100 peer-reviewed articles, so as to highlight the recently reported bioactive lignans that could be a first step towards the development of potential new therapeutic agents.