Avicins, a family of triterpenoid saponins from Acacia victoriae (Bentham), inhibit activation of nuclear factor-kappaB by inhibiting both its nuclear localization and ability to bind DNA

Avicin D: a protein reactive plant isoprenoid dephosphorylates Stat 3 by regulating both kinase and phosphatase activities

Avicins, a class of electrophilic triterpenoids with pro-apoptotic, anti-inflammatory and antioxidant properties, have been shown to induce redox-dependant post-translational modification of cysteine residues to regulate protein function. Based on (a) the cross-talk that occurs between redox and phosphorylation processes, and (b) the role of Stat3 in the process of apoptosis and carcinogenesis, we chose to study the effects of avicins on the processes of phosphorylation/dephosphorylation in Stat3. Avicins dephosphorylate Stat3 in a variety of human tumor cell lines, leading to a decrease in the transcriptional activity of Stat3. The expression of Stat3-regulated proteins such as c-myc, cyclin D1, Bcl2, survivin and VEGF were reduced in response to avicin treatment. Underlying avicin-induced dephosphorylation of Stat3 was dephosphorylation of JAKs, as well as activation of protein phosphatase-1. Downregulation of both Stat3 activity and expression of Stat 3-controlled pro-survival proteins, contributes to the induction of apoptosis in avicin treated tumor cells. Based on the role of Stat3 in inflammation and wounding, and the in vivo inhibition of VEGF by avicins in a mouse skin carcinogenesis model, it is likely that avicin-induced inhibition of Stat3 activity results in the suppression of the pro-inflammatory and pro-oxidant stromal environment of tumors. Activation of PP-1, which also acts as a cellular economizer, combined with the redox regulation by avicins, can aid in redirecting metabolism from growth promoting anabolic to energy sparing pathways.

Bioactive Complex Triterpenoid Saponins from the Leguminosae Family

Many classes of phytochemical products are finding therapeutic use, for example, complex triterpenoid saponins containing in their structures monoterpene moieties. Some of these compounds possess cytotoxic, anti-HIV and adjuvant activities. This review aims to give an overview of these complex triterpenoid saponins with biological activity from the Leguminosae.

The inhibitory effect of quercitrin gallate on iNOS expression induced by lipopolysaccharide in Balb/c mice

Quercetin 3-O-β-(2"-galloyl)-rhamnopyranoside (QGR) is a naturally occurring quercitrin gallate, which is a polyphenolic compound that was originally isolated from Persicaria lapathifolia (Polygonaceae). QGR has been shown to have an inhibitory effect on nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated macrophage RAW 264.7 cells. Therefore, this study was conducted to investigate the inhibitory effect of QGR on nitric oxide production and inducible nitric oxide synthases (iNOS) expression in LPS-stimulated Balb/c mice. To accomplish this, 10 mg/kg of QGR was administered via gavage once a day for 3 days. iNOS was then induced by intraperitoneal injection of LPS. Six hours after the LPS treatment the animals were sacrificed under ether anethesia. The serum levels of NO were then measured to determine if QGR exerted an inhibitory effect on NO production in vivo. LPS induced an approximately 6 fold increase in the expression of NO. However, oral administration of QGR reduced the LPS induced increase in NO by half. Furthermore, RT-PCR and western blot analysis revealed that the increased levels of iNOS expression that occurred in response to treatment with LPS were significantly attenuated in response to QGR pretreatment. Histologically, LPS induced the infiltration of polymorphonuclear neutrophils in portal veins and sinusoids and caused the formation of a large number of necrotic cells; however, pretreatment with QGR attenuated these LPS induced effects. Taken together, these results indicate that QGR inhibits iNOS expression in vivo as well as in vitro and has antiinflammatory potentials.

Avicin D selectively induces apoptosis and downregulates p-STAT-3, bcl-2, and survivin in cutaneous T-cell lymphoma cells

Avicin D, a natural triterpenoid saponin, inhibits cell growth and induces apoptosis in transformed tumor cell lines in vitro and mouse skin carcinogenesis models in vivo. To investigate the anti-tumor effects of avicin D in cutaneous T-cell lymphomas (CTCL), we compared three CTCL cell lines and Sézary cells from three Sézary syndrome (SS) patients with normal CD4+ and activated CD4+ T cells from three healthy donors. Avicin D at 0.5-5 mug ml(-1) induced apoptosis in a time- and dose-dependent manner in three cell lines: MJ (-0.2 to 13% and 0.6-37%), Hut78 (2-39% and 3-53%), and HH (13-83% and 44-89%) at 24 and 48 hours, respectively. Avicin D at 0.5-5 microg ml(-1) for 48 hours caused more apoptosis in patients' Sézary cells than in healthy donors' CD4+ T cells and activated CD4+ T cells. The general caspase inhibitor Z-VAD-FMK and caspase-3 inhibitor Z-DEVD-FMK decreased avicin D-induced apoptosis in CTCL cells. Caspase-3 was activated and poly (ADP-ribose) polymerase was cleaved after avicin D treatment. Avicin D did not change the expression of signal transducer and activator of transcription-3 (STAT-3) but decreased phospho-signal transducer and activator of transcription-3 (p-STAT-3) protein levels in all three cell lines and two patients' Sézary cells. Avicin D also decreased expression of the inhibitor of apoptosis protein survivin, the anti-apoptotic protein bcl-2, but not the pro-apoptotic protein bax in these CTCL cells. In summary, avicin D selectively induced apoptosis, inhibited STAT-3 activation, and decreased apoptosis inhibitors (bcl-2 and survivin) in CTCL cell lines and SS patients' Sézary cells. Our findings underlie the therapeutic potential of avicin D in patients with SS.

Anti-inflammatory activities of triterpenoid saponins from Polygala japonica

Bioassay-guided investigation was performed to identify the active constituents from a methanol extract of Polygala japonica, a folk medicinal plant widely used in China to treat inflammatory diseases. The n-BuOH and EtOAc fractions of the P. japonica methanol extract, which show significant anti-inflammatory activity in in vivo test, were further subjected to column chromatography to afford six triterpene glycosides, marked here as saponins 1-6. All compounds were evaluated for their anti-inflammatory activity in the carageenan-induced mouse paw edema test, and saponins 1, 4 and 5 showed significantly anti-inflammatory effects on both phases of carageenan-induced acute paw edema in mice. Saponin 5 was also found to significantly inhibit the production of inflammatory mediators - nitric oxide (NO) in LPS-stimulated RAW264.7 macrophages, with no obvious effects on macrophage viability.

A plant triterpenoid, avicin D, induces autophagy by activation of AMP-activated protein kinase

Avicins, a family of plant triterpene electrophiles, can trigger apoptosis-associated tumor cell death, and suppress chemical-induced carcinogenesis by its anti-inflammatory, anti-mutagenic, and antioxidant properties. Here, we show that tumor cells treated with benzyloxycarbonylvalyl-alanyl-aspartic acid (O-methyl)-fluoro-methylketone, an apoptosis inhibitor, and Bax(-/-)Bak(-/-) apoptosis-resistant cells can still undergo cell death in response to avicin D treatment. We demonstrate that this non-apoptotic cell death is mediated by autophagy, which can be suppressed by chloroquine, an autophagy inhibitor, and by specific knockdown of autophagy-related gene-5 (Atg5) and Atg7. Avicin D decreases cellular ATP levels, stimulates the activation of AMP-activated protein kinase (AMPK), and inhibits mammalian target of rapamycin (mTOR) and S6 kinase activity. Suppression of AMPK by compound C and dominant-negative AMPK decreases avicin D-induced autophagic cell death. Furthermore, avicin D-induced autophagic cell death can be abrogated by knockdown of tuberous sclerosis complex 2 (TSC2), a key mediator linking AMPK to mTOR inhibition, suggesting that AMPK activation is a crucial event targeted by avicin D. These findings indicate the therapeutic potential of avicins by triggering autophagic cell death.

Heterologous expression of Fusarium oxysporum tomatinase in Saccharomyces cerevisiae increases its resistance to saponins and improves ethanol production during the fermentation of Agave tequilana Weber var. azul and Agave salmiana must

This paper describes the effect of the heterologous expression of tomatinase from Fusarium oxysporum f. sp lycopersici in Saccharomyces cerevisiae. The gene FoTom1 under the control of the S. cerevisiae phosphoglycerate kinase (PGK1) promoter was cloned into pYES2. S. cerevisiae strain Y45 was transformed with this vector and URA3 transformant strains were selected for resistance to alpha-tomatine. Two transformants were randomly selected for further study (designated Y45-1 and Y45-2). Control strain Y45 was inhibited at 50 muM alpha-tomatine, in contrast, transformants Y45-1 and Y45-2 did not show inhibition at 200 muM. Tomatinase activity was detected by HPLC monitoring tomatine disappearance and tomatidine appearance in the supernatants of culture medium. Maximum tomatinase activity was observed in the transformants after 6 h, remaining constant during the following 24 h. No tomatinase activity was detected in the parental strain. Moreover, the transformants were able to grow and produce ethanol in a mix of Agave tequilana Weber var. azul and Agave salmiana must, contrary to the Y45 strain which was unable to grow and ferment under these conditions.

Triterpenoids and rexinoids as multifunctional agents for the prevention and treatment of cancer

Synthetic oleanane triterpenoids and rexinoids are two new classes of multifunctional drugs. They are neither conventional cytotoxic agents, nor are they monofunctional drugs that uniquely target single steps in signal transduction pathways. Synthetic oleanane triterpenoids have profound effects on inflammation and the redox state of cells and tissues, as well as being potent anti-proliferative and pro-apoptotic agents. Rexinoids are ligands for the nuclear receptor transcription factors known as retinoid X receptors. Both classes of agents can prevent and treat cancer in experimental animals. These drugs have unique molecular and cellular mechanisms of action and might prove to be synergistic with standard anti-cancer treatments.

Antiinflammatory effect of Japanese horse chestnut (Aesculus turbinata) seeds

The antiinflammatory effects of Japanese horse chestnut (Aesculus turbinata) seeds were examined in vivo and in vitro. The extract of this seed (HCSE) inhibited croton oil-induced swelling of the mouse concha. HCSE inhibited cyclooxygenase (COX) -1 and -2 activities, but had no effect on 15-lipoxygenase and phospholipase A2 activities. Inhibition of COX-2 occurred at a lower concentration of HCSE than for COX-1. Japanese horse chestnut seeds contain coumarins and saponins, but these chemicals did not inhibit COX activities. These results suggest that the antiinflammatory effect of Japanese horse chestnut seeds is caused, at least partly, by the inhibition of COX. The inhibitor of COX in this seed may be a chemical(s) other than coumarins and saponins.

Adjuvant effects of saponins on animal immune responses

Vaccines require optimal adjuvants including immunopotentiator and delivery systems to offer long term protection from infectious diseases in animals and man. Initially it was believed that adjuvants are responsible for promoting strong and sustainable antibody responses. Now it has been shown that adjuvants influence the isotype and avidity of antibody and also affect the properties of cell-mediated immunity. Mostly oil emulsions, lipopolysaccharides, polymers, saponins, liposomes, cytokines, ISCOMs (immunostimulating complexes), Freund's complete adjuvant, Freund's incomplete adjuvant, alums, bacterial toxins etc., are common adjuvants under investigation. Saponin based adjuvants have the ability to stimulate the cell mediated immune system as well as to enhance antibody production and have the advantage that only a low dose is needed for adjuvant activity. In the present study the importance of adjuvants, their role and the effect of saponin in immune system is reviewed.

Magnolol suppresses NF-kappaB activation and NF-kappaB regulated gene expression through inhibition of IkappaB kinase activation

The mis-regulation of nuclear factor-kappa B (NF-kappaB) signal pathway is involved in a variety of inflammatory diseases that leds to the production of inflammatory mediators. Our studies using human U937 promonocytes cells suggested that magnolol, a low molecular weight lignan isolated from the medicinal plant Magnolia officinalis, differentially down-regulated the pharmacologically induced expression of NF-kappaB-regulated inflammatory gene products MMP-9, IL-8, MCP-1, MIP-1alpha, TNF-alpha. Pre-treatment of magnolol blocked TNF-alpha-induced NF-kappaB activation in different cell types as evidenced by EMSA. Magnolol did not directly affect the binding of p65/p50 heterodimer to DNA. Immunoblot analysis demonstrated that magnolol inhibited the TNF-alpha-stimulated phosphorylation and degradation of the cytosolic NF-kappaB inhibitor IkappaBalpha and the effects were dose-dependent. Mechanistically, a non-radioactive IkappaB kinases (IKK) assay using immunoprecipitated IKKs protein demonstrated that magnolol inhibited both intrinsic and TNF-alpha-stimulated IKK activity, thus suggesting a critical role of magnolol in abrogating the phosphorylation and degradation of IkappaBalpha. The involvement of IKK was further verified in a HeLa cell NF-kappaB-dependent luciferase reporter system. In this system magnolol 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. Magnolol was also found to inhibit the nuclear translocation and phosphorylation of p65 subunit of NF-kappaB. In line with the observation that NF-kappaB activation may up-regulate anti-apoptotic genes, it was shown in U937 cells that magnolol enhanced TNF-alpha-induced apoptotic cell death. Our results suggest that magnolol or its derivatives may have potential anti-inflammatory actions through IKK inactivation.

Avicins, a novel plant-derived metabolite lowers energy metabolism in tumor cells by targeting the outer mitochondrial membrane

Avicins are pro-apoptotic, anti-inflammatory molecules with antioxidant effects both in vitro and in vivo. Based on their ability to perturb mitochondrial functions and initiate apoptosis in tumor cells, we chose to study the bioenergetic effects of avicins on tumor cell mitochondria. Avicin-treated Jurkat cells, showed a decrease in the levels of cellular ATP as well as the rate of oxygen consumption. These effects on cellular metabolism appear to be a result of avicin's actions on the outer mitochondrial membrane (OMM). We speculate that avicins might initially inhibit the exchange of metabolites across the OMM leading to its subsequent permeabilization to cytochrome c. This speculation is supported by biophysical studies using lipid bilayers, which suggest that upstream of these effects, avicins target and close the voltage dependent anion channel (VDAC). Closure of VDAC would lead to an overall lowering of the cell energy metabolism, subsequently pushing these cells towards the apoptotic pathway by permeabilization of the OMM and release of cyt-c. Avicins therefore not only represent a novel pharmacological tool for treatment of cancers, but also highlight the influence ancient plant metabolites could have on human health.

7,7'-Dihydroxy bursehernin inhibits the expression of inducible nitric oxide synthase through NF-kappaB DNA binding suppression

This study isolated a lignan, 7,7'-dihydroxy bursehernin, from Geranium thunbergii and investigated whether or not the lignan affects the induction of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in RAW264.7 macrophages stimulated with lipopolysaccharide (LPS). The gel shift analysis and luciferase reporter gene assays using the iNOS promoter and nuclear factor-kappaB (NF-kappaB) minimal promoter showed that a treatment with 7,7'-dihydroxy bursehernin reduced the reporter activities and binding of NF-kappaB to the NF-kappaB consensus sequence, while it had no effect on the nuclear translocation of p65 and the phosphorylation/degradation of I-kappaBalpha. It was reported that a few natural compounds directly suppressed the binding activity of the NF-kappaB components to DNA. The NF-kappaB binding activity was not reversed by the in vitro exposure of the nuclear extracts to 7,7'-dihydroxy bursehernin, which suggest that a metabolite(s) of 7,7'-dihydroxy bursehernin might target the binding of the NF-kappaB complex to the DNA binding domain region in the promoter region of the iNOS gene. After incubation of RAW264.7 cells with 7,7-dihydroxy bursehernin for 18h, the levels of parent compound were negligible; while a main metabolite, 4-[4-(n-hydroxy-phenyl)-2,3-dimethyl-buta-1,3-dienyl]-benzene-1,2-diol was detected in cell lysates and culture medium.

Dual effects of plant steroidal alkaloids on Saccharomyces cerevisiae

Many plant species accumulate sterols and triterpenes as antimicrobial glycosides. These secondary metabolites (saponins) provide built-in chemical protection against pest and pathogen attack and can also influence induced defense responses. In addition, they have a variety of important pharmacological properties, including anticancer activity. The biological mechanisms underpinning the varied and diverse effects of saponins on microbes, plants, and animals are only poorly understood despite the ecological and pharmaceutical importance of this major class of plant secondary metabolites. Here we have exploited budding yeast (Saccharomyces cerevisiae) to investigate the effects of saponins on eukaryotic cells. The tomato steroidal glycoalkaloid alpha-tomatine has antifungal activity towards yeast, and this activity is associated with membrane permeabilization. Removal of a single sugar from the tetrasaccharide chain of alpha-tomatine results in a substantial reduction in antimicrobial activity. Surprisingly, the complete loss of sugars leads to enhanced antifungal activity. Experiments with alpha-tomatine and its aglycone tomatidine indicate that the mode of action of tomatidine towards yeast is distinct from that of alpha-tomatine and does not involve membrane permeabilization. Investigation of the effects of tomatidine on yeast by gene expression and sterol analysis indicate that tomatidine inhibits ergosterol biosynthesis. Tomatidine-treated cells accumulate zymosterol rather than ergosterol, which is consistent with inhibition of the sterol C(24) methyltransferase Erg6p. However, erg6 and erg3 mutants (but not erg2 mutants) have enhanced resistance to tomatidine, suggesting a complex interaction of erg mutations, sterol content, and tomatidine resistance.

Melittin inhibits inflammatory target gene expression and mediator generation via interaction with IkappaB kinase

We previously found that bee venom (BV) and melittin (a major component of BV) has anti-inflammatory effect by reacting with the sulfhydryl group of p50 of NF-kappaB. Since the sulfhydryl group is present in IkappaB kinase (IKKalpha and IKKbeta), anti-inflammatory effect of melittin via interaction with IKKs was investigated. We first examined binding of melittin to IKKs using surface plasmon resonance analyzer. Melittin binds to IKKalpha (K(d) = 1.34 x 10(-9) M) and IKKbeta (K(d) = 1.01 x 10(-9) M). Consistent with the high binding affinity, melittin (5 and 10 microg/ml) and BV (0.5, 1 and 5 microg/ml) suppressed sodium nitroprusside, TNF-alpha and LPS induced-IKKbeta and IKKbeta activities, IkappaB release, and NF-kappaB activity as well as the expressions of iNOS and COX-2, and the generation of nitric oxide (NO) and prostaglandin E(2) (PGE(2)) in Raw 264.7 mouse macrophages and synoviocytes obtained from rheumatoid arthritis patients. The binding affinities of melittin to mutant IKKs, was reduced, and the inhibitory effect of melittin on IKK and NF-kappaB activities, and NO and PGE(2) generation were abrogated by the reducing agents or in Raw 264.7 transfected with mutant plasmid IKKalpha (C178A) or IKKbeta (C179A). These results suggest that melittin binding to the sulfhydryl group of IKKs resulted in reduced IKK activities, IkappaB release, NF-kappaB activity and generation of inflammatory mediators, indicating that IKKs may be also anti-inflammatory targets of BV.

Avicins, natural anticancer saponins, permeabilize mitochondrial membranes

Avicins are a class of natural saponins with selective pro-apoptotic activity in cancer cells. In this work, we studied the influence of avicins on metabolic state of rat liver mitochondria. Avicin-treated mitochondria underwent a significant decrease in oxygen consumption rate that was completely restored by addition of exogenous cytochrome c. On the other hand, avicins increased the rotenone-insensitive oxidation of external NADH in the presence of exogenous cytochrome c, long before high amplitude swelling of mitochondria was observed. The increase in external NADH oxidation was cyclosporin A-insensitive. Avicin G significantly accelerated hydroperoxide-induced oxidation of mitochondrial endogenous NAD(P)H, the drop of the inner membrane potential and the high amplitude swelling of mitochondria. The obtained data might explain selective induction of apoptosis in tumor cells by avicins. Based on other studies showing that tumor cells generate hydroperoxides with a very high rate, avicins could provide a new strategy of anticancer therapy by sensitizing cells with high levels of reactive oxygen species to apoptosis.

Mitochondria as therapeutic targets for cancer chemotherapy

Mitochondria are vital for cellular bioenergetics and play a central role in determining the point-of-no-return of the apoptotic process. As a consequence, mitochondria exert a dual function in carcinogenesis. Cancer-associated changes in cellular metabolism (the Warburg effect) influence mitochondrial function, and the invalidation of apoptosis is linked to an inhibition of mitochondrial outer membrane permeabilization (MOMP). On theoretical grounds, it is tempting to develop specific therapeutic interventions that target the mitochondrial Achilles' heel, rendering cancer cells metabolically unviable or subverting endogenous MOMP inhibitors. A variety of experimental therapeutic agents can directly target mitochondria, causing apoptosis induction. This applies to a heterogeneous collection of chemically unrelated compounds including positively charged alpha-helical peptides, agents designed to mimic the Bcl-2 homology domain 3 of Bcl-2-like proteins, ampholytic cations, metals and steroid-like compounds. Such MOMP inducers or facilitators can induce apoptosis by themselves (monotherapy) or facilitate apoptosis induction in combination therapies, bypassing chemoresistance against DNA-damaging agents. In addition, it is possible to design molecules that neutralize inhibitor of apoptosis proteins (IAPs) or heat shock protein 70 (HSP70). Such IAP or HSP70 inhibitors can mimic the action of mitochondrion-derived mediators (Smac/DIABLO, that is, second mitochondria-derived activator of caspases/direct inhibitor of apoptosis-binding protein with a low isoelectric point, in the case of IAPs; AIF, that is apoptosis-inducing factor, in the case of HSP70) and exert potent chemosensitizing effects.

Transcriptional regulation via cysteine thiol modification: a novel molecular strategy for chemoprevention and cytoprotection

Chemoprevention refers to the use of defined nontoxic chemical regimens to inhibit, reverse, or retard the process of multistage carcinogenesis that involves multiple signal transduction events. Identification of signaling molecules associated with carcinogenesis as prime targets of chemopreventive agents has become an area of great interest. Recent studies have implicated cysteine thiols present in various transcription factors, such as NF-kappaB, AP-1, and p53 as redox sensors in transcriptional regulation of many genes essential for maintaining cellular homeostasis. Some chemopreventive and cytoprotective agents have been found to target cysteine thiols present in key transcription factors or their regulators, thereby suppressing aberrant over-activation of carcinogenic signal transduction or restoring/normalizing or even potentiating cellular defense signaling. The focus of this review is the oxidation or covalent modification of thiol groups present in key representative redox-sensitive transcription factors and their regulating molecules as a unique strategy for molecular target-based chemoprevention and cytoprotection.

Ethyl caffeate suppresses NF-kappaB activation and its downstream inflammatory mediators, iNOS, COX-2, and PGE2 in vitro or in mouse skin

Ethyl caffeate, a natural phenolic compound, was isolated from Bidens pilosa, a medicinal plant popularly used for treating certain inflammatory syndromes. The purpose of this study was to investigate the structural activity, and the anti-inflammatory functions and mechanism(s) of ethyl caffeate. Ethyl caffeate was found to markedly suppress the lipopolysaccharide (LPS)-induced nitric oxide (NO) production (IC(50) = 5.5 microg ml(-1)), mRNA and protein expressions of inducible nitric oxide synthase (iNOS), and prostaglandin E(2) (PGE(2)) production in RAW 264.7 macrophages. Transient gene expression assays using human cox-2 promoter construct revealed that ethyl caffeate exerted an inhibitory effect on cox-2 transcriptional activity in 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated MCF-7 cells. Immunohistochemical studies of mouse skin demonstrated that TPA-induced COX-2 expression was significantly inhibited by ethyl caffeate with a superior effect to that of celecoxib, a nonsteroidal anti-inflammatory drug. The phosphorylation and degradation of inhibitor kappaB (IkappaB) and the translocation of nuclear transcription factor-kappaB (NF-kappaB) into the nucleus, as well as the activation of mitogen-activated protein kinases (MAPKs) induced by LPS in macrophages, were not affected by ethyl caffeate. Ethyl caffeate, however, could inhibit NF-kappaB activation by impairing the binding of NF-kappaB to its cis-acting element. These results suggest that ethyl caffeate suppresses iNOS and COX-2 expressions partly through the inhibition of the NF-kappaB.DNA complex formation. Structure-activity relationship analyses suggested that the catechol moiety and alpha,beta-unsaturated ester group in ethyl caffeate are important and essential structural features for preventing NF-kappaB.DNA complex formation. This study provides an insight into the probable mechanism(s) underlying the anti-inflammatory and therapeutic properties of ethyl caffeate.

1-Cinnamoyl-3,11-dihydroxymeliacarpin is a natural bioactive compound with antiviral and nuclear factor-kappaB modulating properties

We have reported the isolation of the tetranortriterpenoid 1-cinnamoyl-3,11-dihydroxymeliacarpin (CDM) from partially purified leaf extracts of Melia azedarach L. (MA) that reduced both, vesicular stomatitis virus (VSV) and Herpes simplex virus type 1 (HSV-1) multiplication. CDM blocks VSV entry and the intracellular transport of VSV-G protein, confining it to the Golgi apparatus, by pre- or post-treatment, respectively. Here, we report that HSV-1 glycoproteins were also confined to the Golgi apparatus independently of the nature of the host cell. Considering that MA could be acting as an immunomodulator preventing the development of herpetic stromal keratitis in mice, we also examined an eventual effect of CDM on NF-kappaB signaling pathway. CDM is able to impede NF-kappaB activation in HSV-1-infected conjunctival cells and leads to the accumulation of p65 NF-kappaB subunit in the cytoplasm of uninfected treated Vero cells. In conclusion, CDM is a pleiotropic agent that not only inhibits the multiplication of DNA and RNA viruses by the same mechanism of action but also modulates the NF-kappaB signaling pathway.

A Cytotoxic Saponin from Albizia julibrissin

A new triterpenoidal saponin (1: Julibroside J(21)) with a xylopyranosyl moiety located at its C-21 side chain was isolated from Albizia julibrissin DURAZZ. (Leguminosae), and its structure was determined on the basis of comprehensive spectroscopic analyses. Compound 1 showed marked inhibitory action against Bel-7402 cancer cell line at 10 microg/ml.

Inhibition of transcription factor NF-kappaB signaling proteins IKKbeta and p65 through specific cysteine residues by epoxyquinone A monomer: correlation with its anti-cancer cell growth activity

Transcription factor NF-kappaB is constitutively active in many human chronic inflammatory diseases and cancers. Epoxyquinone A monomer (EqM), a synthetic derivative of the natural product epoxyquinol A, has previously been shown to be a potent inhibitor of tumor necrosis factor-alpha (TNF-alpha)-induced activation of NF-kappaB, but the mechanism by which EqM inhibits NF-kappaB activation was not known. In this report, we show that EqM blocks activation of NF-kappaB by inhibiting two molecular targets: IkappaB kinase IKKbeta and NF-kappaB subunit p65. EqM inhibits TNF-alpha-induced IkappaBalpha phosphorylation and degradation by targeting IKKbeta, and an alanine substitution for Cys179 in the activation loop of IKKbeta makes it resistant to EqM-mediated inhibition. EqM also directly inhibits DNA binding by p65, but not p50; moreover, replacement of Cys38 in p65 with Ser abolishes EqM-mediated inhibition of DNA binding. Pretreatment of cells with reducing agent dithiothreitol dose-dependently reduces EqM-mediated inhibition of NF-kappaB, further suggesting that EqM directly modifies the thiol group of Cys residues in protein targets. Modifications of the exocyclic alkene of EqM substantially reduce EqM's ability to inhibit NF-kappaB activation. In the human SUDHL-4 lymphoma cell line, EqM inhibits both proliferation and NF-kappaB DNA binding, and activates caspase-3 activity. EqM also effectively inhibits the growth of human leukemia, kidney, and colon cancer cell lines in the NCI's tumor cell panel. Among six colon cancer cell lines, those with low amounts of constitutive NF-kappaB DNA-binding activity are generally more sensitive to growth inhibition by EqM. Taken together, these results suggest that EqM inhibits growth and induces cell death in tumor cells through a mechanism that involves inhibition of NF-kappaB activity at multiple steps in the signaling pathway.

A pair of isomeric saponins with cytotoxicity from Albizzia julibrissin

Two new saponins have been isolated from the stem barks of Albizzia julibrissin Durazz, and their structures identified as 3-O-[beta-D-xylopyranosyl-(1 --> 2)-beta-D-fucopyranosyl-(1 --> 6)-beta-D-2-deoxy-2-acetoamidoglucopyranosyl]-21-O-{(6S)-2-trans-2-hydroxymethyl-6-methyl-6-O-[4-O-((6S)-2-trans-2-hydroxymethyl-6-hydroxy-6-methyl-2,7-octadienoyl)-beta-D-quinovopyranosyl]-2,7-octadienoyl}-acacic acid-28-O-beta-D-glucopyranosyl-(1 --> 3)-[alpha-L-arabinofuranosyl-(1 --> 4)]-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl ester (1) and 3-O-[beta-D-xylopyranosyl-(1 --> 2)-beta-D-fucopyranosyl-(1 --> 6)-beta-D-2-deoxy-2-acetoamidoglucopyranosyl]-21-O-{(6S)-2-trans-2-hydroxymethyl-6-methyl-6-O-[3-O-((6S)-2-trans-2-hydroxymethyl-6-hydroxy-6-methyl-2,7-octadienoyl)-beta-D-quinovopyranosyl]-2,7-octadienoyl}acacic acid 28-O-beta-D-glucopyranosyl-(1 --> 3)-[alpha-L-arabinofuranosyl-(1 --> 4)]-alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl ester (2), based on chemical and spectral evidences, named as julibroside J19 and julibroside J18, respectively. Both compounds show significant inhibition action against HeLa, Bel-7402 and MDA-MB-435 cancer cell lines in vitro.

The synthetic epoxyquinoids jesterone dimer and epoxyquinone A monomer induce apoptosis and inhibit REL (human c-Rel) DNA binding in an IkappaBalpha-deficient diffuse large B-cell lymphoma cell line

The NF-kappaB transcription factor signaling pathway is constitutively active in many human cancers, and inhibition of this pathway can often kill cancer cells by inducing apoptosis. In this study, we show that two synthetic epoxyquinoids, jesterone dimer (JD) and epoxyquinone A monomer (EqM), are equally effective at inhibiting the growth of two human lymphoma cell lines that have constitutively nuclear REL (human c-Rel) DNA-binding complexes, but either express (SUDHL-4 cells) or do not express (RC-K8 cells) the NF-kappaB inhibitor IkappaBalpha. Furthermore, in these cells, both JD and EqM dose-dependently induced apoptosis, inhibited REL DNA-binding activity, and converted REL to a high molecular weight form. In A293 cells, JD and EqM inhibited the DNA-binding activity of overexpressed REL, but not p50. Replacement of Cys-27 with Ser in REL reduced JD- and EqM-mediated inhibition of REL DNA-binding activity. These results suggest that JD and EqM can induce apoptosis in IkappaBalpha-deficient lymphoma cells through a mechanism involving direct inhibition of transcription factor REL.

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.

Avicinylation (thioesterification): a protein modification that can regulate the response to oxidative and nitrosative stress

Avicins are a recently discovered family of plant-derived terpenoid molecules that possess proapoptotic, antiinflammatory, and cytoprotective properties in mammalian cells. Previous work demonstrating that avicins can exert their effects by suppressing or activating the redox-sensitive transcription factors NF-kappaB and nuclear factor-erythroid 2 p45-related factor (Nrf2), respectively, has raised the idea that they may react with critical cysteine residues. To understand the molecular mechanism through which avicins regulate protein function, we examined their effects on the paradigmatic redox-responsive transcriptional activator, OxyR of Escherichia coli, which protects bacterial cells against oxidative and nitrosative stresses. In vitro transcription assays demonstrated that avicins activate OxyR and its target genes katG and oxyS in a DTT-reversible manner. In addition, katG-dependent hydroperoxidase I activity was enhanced in avicin-treated bacteria. Mass spectrometric analysis of activated OxyR revealed thioesterification of the critical regulatory cysteine, Cys-199, to an avicin fragment comprising the outer monoterpene side chain. Our results indicate that avicinylation can induce adaptive responses that protect cells against oxidative or nitrosative stress. More generally, transesterification may represent a previously undescribed thiol-directed posttranslational modification, which extends the code for redox regulation of protein function.

Oridonin, a diterpenoid purified from Rabdosia rubescens, inhibits the proliferation of cells from lymphoid malignancies in association with blockade of the NF-kappa B signal pathways

This study found that oridonin, a natural diterpenoid purified from Rabdosia rubescens, inhibited growth of multiple myeloma (MM; U266, RPMI8226), acute lymphoblastic T-cell leukemia (Jurkat), and adult T-cell leukemia (MT-1) cells with an effective dose that inhibited 50% of target cells (ED50) ranging from 0.75 to 2.7 microg/mL. Terminal deoxynucleotidyltransferase-mediated dUTP nick end labeling staining showed that oridonin caused apoptosis of MT-1 cells in a time-dependent manner. We explored effects of oridonin on antiapoptotic Bcl-2 family members and found that it down-regulated levels of Mcl-1 and BCL-x(L), but not Bcl-2 protein, in both MT-1 and RPMI8226 cells. Further studies found that oridonin inhibited nuclear factor-kappa B (NF-kappa B) DNA-binding activity in these cells as measured by luciferase reporter gene, ELISA-based, and electrophoretic mobility shift assays. Oridonin also blocked tumor necrosis factor-alpha- and lipopolysaccharide-stimulated NF-kappa B activity in Jurkat cells as well as RAW264.7 murine macrophages. Of note, oridonin decreased survival of freshly isolated adult T-cell leukemia (three samples), acute lymphoblastic leukemia (one sample), chronic lymphocytic leukemia (one sample), non-Hodgkin's lymphoma (three samples), and MM (four samples) cells from patients in association with inhibition of NF-kappa B DNA-binding activity. On the other hand, oridonin did not affect survival of normal lymphoid cells from healthy volunteers. Taken together, oridonin might be useful as adjunctive therapy for individuals with lymphoid malignancies, including the lethal disease adult T-cell leukemia.

Effects of the tumor inhibitory triterpenoid avicin G on cell integrity, cytokinesis, and protein ubiquitination in fission yeast

Avicins comprise a class of triterpenoid compounds that exhibit tumor inhibitory activity. Here we show that avicin G is inhibitory to growth of the fission yeast Schizosaccharomyces pombe. S. pombe cells treated with a lethal concentration of avicin G (20 microM) exhibited a shrunken morphology, indicating that avicin G adversely affects cell integrity. Cells treated with a sublethal concentration of avicin G (6.5 microM) exhibited a strong cytokinesis-defective phenotype (multiseptated cells), as well as cell morphology defects. These phenotypes bear resemblance to those resulting from loss of Rho1 GTPase function in S. pombe. Indeed, Rho1-deficient S. pombe cells were strongly hypersensitive to avicin G, suggesting that the compound may perturb Rho1-dependent processes. Consistent with previously observed effects in human Jurkat T cells, avicin G treatment resulted in hyperaccumulation of ubiquitinated proteins in S. pombe cells. Interestingly, proteasome-defective S. pombe mutants were not markedly hypersensitive to avicin G, whereas an anaphase-promoting complex (mitotic ubiquitin ligase) mutant exhibited avicin G resistance, suggesting that the increase in levels of ubiquitinated proteins resulting from avicin G treatment may be due to increased protein ubiquitination, rather than inhibition of 26S proteasome activity. Mutants defective in the cAMP/PKA pathway also exhibited resistance to avicin G. Our results suggest that S. pombe will be a useful model organism for elucidating molecular targets of avicin G and serve as a guide to clinical application where dysfunctional aspects of Rho and/or ubiquitination function have been demonstrated as in cancer, fibrosis, and inflammation.

Triterpenoid electrophiles (avicins) suppress heat shock protein-70 and x-linked inhibitor of apoptosis proteins in malignant cells by activation of ubiquitin machinery: implications for proapoptotic activity

Avicins are plant-derived triterpenoid stress metabolites that have both proapoptotic and cytoprotective properties. Avicins induce apoptosis in Jurkat T leukemia cells by targeting mitochondria and release of cytochrome c that occurs in a p53-independent manner. However, postmitochondrial antiapoptotic barriers, such as increased expression of heat shock proteins (Hsp) and X-linked inhibitor of apoptosis proteins (XIAP), frequently exist in cancer cells and often account for resistance to chemotherapy and a poor prognosis. In this article, we show the role of avicins in the activation of stress-regulated ubiquitination and degradation of Hsp70 and XIAP. This is the first report showing the regulation of Hsp70 via the ubiquitin/proteasome pathway. We also show the induction of E3alpha ubiquitin ligase in avicin-treated Jurkat T leukemia cells, and its involvement in the degradation of XIAP. Avicin-mediated suppression of Hsp70 and XIAP was further confirmed in other leukemic/lymphoma cell lines and freshly isolated peripheral blood lymphocytes from Sezary syndrome patients. No change in the Hsp70 and XIAP proteins was observed in peripheral blood lymphocytes from normal donors. We propose that the ability of avicins to induce ubiquitination and regulate the degradation of Hsp70 and XIAP in leukemia cells could have important implications in the treatment of drug-resistant neoplasia and inflammatory disorders.

Mitochondria as integrators of information in an early-evolving animal: insights from a triterpenoid metabolite

Mitochondria have the capacity to integrate environmental signals and, in animals with active stem cell populations, trigger responses in terms of growth and growth form. Colonial hydroids, which consists of feeding polyps connected by tube-like stolons, were treated with avicis, triterpenoid electrophiles whose anti-cancer properties in human cells are mediated in part by mitochondria. In treated hydroids, both oxygen uptake and mitochondrial reactive oxygen species were diminished relative to controls, similar to that observed in human cells exposed to avicins. While untreated colonies exhibit more stolon branches and connections in the centre of the colony than at the periphery, treated colonies exhibit the opposite: fewer stolon branches in the centre of the colony than at the periphery. The resulting growth form suggest an inversion of the normal pattern of colony development mediated by mitochondrial and redox-related perturbations. An as-yet-uncharacterized gradient within the colony may determine the ultimate phenotypic effects of avicin perturbation.

Proapoptotic triterpene electrophiles (avicins) form channels in membranes: cholesterol dependence

Avicins, a family of triterpenoid saponins from Acacia victoriae, can regulate the innate stress response in human cells. Their ability to induce apoptosis in transformed cells makes them potential anticancer agents. We report that avicins can form channels in membranes. The conductance reached a steady state after each addition, indicating a dynamic equilibrium between avicin in solution and in the membrane. The high power dependence (up to 10) of the membrane conductance on the avicin concentration indicates the formation of multimeric channels, consistent with the estimated pore radius of 1.1 nm. This radius is too small to allow protein flux across the mitochondrial outer membrane, a process known to initiate apoptosis. Channel formation is lost when avicin's amphipathic side chain is removed, implicating this as the channel-forming region. A small difference in this side chain results in strong cholesterol dependence of channel formation in avicin G that is not found in avicin D. In neutral membranes, avicin channels are nonselective, but negatively-charged lipids confer cation selectivity (5:1, K(+):Cl(-)), indicating that phospholipids form part of the permeation pathway. Avicin channels in the mitochondrial outer membrane may favor apoptosis by altering the potential across this membrane and the intermembrane space pH.

Metabolic profiling of Medicago truncatula cell cultures reveals the effects of biotic and abiotic elicitors on metabolism

GC-MS-based metabolite profiling was used to analyse the response of Medicago truncatula cell cultures to elicitation with methyl jasmonate (MeJa), yeast elicitor (YE), or ultraviolet light (UV). Marked changes in the levels of primary metabolites, including several amino acids, organic acids, and carbohydrates, were observed following elicitation with MeJa. A similar, but attenuated response was observed following YE elicitation, whereas little response was observed following UV elicitation. MeJa induced the accumulation of the triterpene beta-amyrin, a precursor to the triterpene saponins, and LC-MS analysis confirmed the accumulation of triterpene saponins in MeJa-elicited samples. In addition, YE induced a slight, but significant accumulation of shikimic acid, an early precursor to the phenylpropanoid pathway, which was also demonstrated to be YE-inducible by LC-MS analyses. Correlation analyses of metabolite relationships revealed perturbation of the glycine, serine, and threonine biosynthetic pathway, and suggested the induction of threonine aldolase activity, an enzyme as yet uncharacterized from plants. Members of the branched chain amino acid pathway accumulated in a concerted fashion, with the strongest correlation being that between leucine and isoleucine (r2=0.941). While UV exposure itself had little effect on primary metabolites, the experimental procedure, as revealed by control treatments, induced changes in several metabolites which were similar to those following MeJa elicitation. Sucrose levels were lower in MJ- and YE-elicited samples compared with control samples, suggesting that a portion of the effects observed on the primary metabolic pool are a consequence of fundamental metabolic repartitioning of carbon resources rather than elicitor-specific induction. In addition, beta-alanine levels were elevated in all elicited samples, which, when viewed in the context of other elicitation responses, suggests the altered metabolism of coenzyme A and its esters, which are essential in secondary metabolism.

Antiarthritic effect of bee venom: Inhibition of inflammation mediator generation by suppression of NF-?B through interaction with the p50 subunit

OBJECTIVE

To investigate the molecular mechanisms of the antiarthritic effects of bee venom (BV) and melittin (a major component of BV) in a murine macrophage cell line (Raw 264.7) and in synoviocytes obtained from patients with rheumatoid arthritis.

METHODS

We evaluated the antiarthritic effects of BV in a rat model of carrageenan-induced acute edema in the paw and in a rat model of chronic adjuvant-induced arthritis. The inhibitory effects of BV and melittin on inflammatory gene expression were measured by Western blotting, and the generation of prostaglandin E(2) (PGE(2)) and nitric oxide (NO) and the intracellular calcium level were assayed. NF-kappaB DNA binding and transcriptional activity were determined by gel mobility shift assay or by luciferase assay. Direct binding of BV and melittin to the p50 subunit of NF-kappaB was determined with a surface plasmon resonance analyzer.

RESULTS

BV (0.8 and 1.6 mug/kg) reduced the effects of carrageenan- and adjuvant-induced arthritis. This reducing effect was consistent with the inhibitory effects of BV (0.5, 1, and 5 mug/ml) and melittin (5 and 10 mug/ml) on lipopolysaccharide (LPS; 1 mug/ml)-induced expression of cyclooxygenase 2, cytosolic phospholipase A(2), inducible NO synthase, generation of PGE(2) and NO, and the intracellular calcium level. BV and melittin prevented LPS-induced transcriptional and DNA binding activity of NF-kappaB via the inhibition of IkappaB release and p50 translocation. BV (affinity [K(d)] = 4.6 x 10(-6)M) and melittin (K(d) = 1.2 x 10(-8)M) bound directly to p50.

CONCLUSION

Target inactivation of NF-kappaB by directly binding to the p50 subunit is an important mechanism of the antiarthritic effects of BV.

Inhibition of lipopolysaccharide-induced inducible nitric oxide synthase expression by a novel compound, mercaptopyrazine, through suppression of nuclear factor-kappaB binding to DNA

Macrophage cells in response to cytokines and endotoxins produced a large amount of nitric oxide (NO) by expression of inducible nitric oxide synthase (iNOS), resulting in acute or chronic inflammatory disorders including septic hypotension and atherosclerosis. In the present study, we investigated the effect and the mechanism of mercaptopyrazine (MP) in the induction of iNOS and NO production as a culminating factor for several inflammatory disorders. Pretreatment of MP alleviated the mortality of endotoxemic mice receiving a lethal bolus of lipopolysaccharide (LPS), which was associated with the reduced levels of serum nitrite/nitrate and IL-1beta. In RAW264.7 mouse macrophage cells, MP (300microM) inhibited both protein and mRNA levels of iNOS stimulated by LPS/interferon-gamma (IFNgamma) up to 50%. The nuclear factor-kappa B (NF-kappaB)-driven transactivation was also suppressed by MP to the same degree. Treatment of MP reduced the binding of NF-kappaB to the oligonucleotides containing NF-kappaB consensus sequence, while it did not affect the translocation of NF-kappaB to nuclear. Suppression of NF-kappaB activity by MP was completely reversed by a reducing agent, dithiothreitol, implying that MP might oxidize the sulfhydryl group(s) of DNA binding domain of NF-kappaB. In conclusion, MP would be one of interesting candidates or chemical moieties of iNOS expression inhibitor via specific suppression of NF-kappaB binding to DNA, and be useful as a chemopreventive agent or a therapeutic against iNOS-associated inflammatory diseases.

Suppression of nitric oxide production in mouse macrophages by soybean flavonoids accumulated in response to nitroprusside and fungal elicitation

BACKGROUND

The anti-inflammatory properties of some flavonoids have been attributed to their ability to inhibit the production of NO by activated macrophages. Soybean cotyledons accumulate certain flavonoids following elicitation with an extract of the fungal pathogen Diaporthe phaseolorum f. sp. meridionalis (Dpm). Sodium nitroprusside (SNP), a nitric oxide donor, can substitute for Dpm in inducing flavonoid production. In this study, we investigated the effect of flavonoid-containing diffusates obtained from Dpm- and SNP-elicited soybean cotyledons on NO production by lipopolysaccharide (LPS)- and LPS plus interferon-gamma (IFNgamma)-activated murine macrophages.

RESULTS

Significant inhibition of NO production, measured as nitrite formation, was observed when macrophages were activated in the presence of soybean diffusates from Dpm- or SNP-elicited cotyledons. This inhibition was dependent on the duration of exposure to the elicitor. Daidzein, genistein, luteolin and apigenin, the main flavonoids present in diffusates of elicited cotyledons, suppressed the NO production by LPS + IFNgamma activated macrophages in a concentration-dependent manner, with IC50 values of 81.4 microM, 34.5 microM, 38.6 microM and 10.4 microM respectively. For macrophages activated with LPS alone, the IC50 values were 40.0 microM, 16.6 microM, 10.4 microM and 2.8 microM, respectively. Western blot analysis showed that iNOS expression was not affected by daidzein, was reduced by genistein, and was abolished by apigenin, luteolin and Dpm- and SNP-soybean diffusates at concentrations that significantly inhibited NO production by activated macrophages.

CONCLUSIONS

These results suggest that the suppressive effect of flavonoids on iNOS expression could account for the potent inhibitory effect of Dpm- and SNP-diffusates on NO production by activated macrophages. Since the physiological concentration of flavonoids in plants is normally low, the treatment of soybean tissues with SNP may provide a simple method for substantially increasing the concentration of metabolites that are beneficial for the treatment of chronic inflammatory diseases associated with NO production.

In addition to membrane injury, an affinity for melanin might be involved in the high sensitivity of human melanoma cells to hederacolchiside A1

We previously reported that hederacolchiside A1 (Hcol A1), a new oleanene saponin isolated from Hedera colchica Koch (Araliaceae) exhibits a preferential cytotoxicity on a pigmented melanoma cell line. The present study confirms the high susceptibility of melanoma cell lines to this drug and shows concentrations producing a 50% decrease in cell content (IC50 values) inversely proportional to the melanin content of each cell line. At cytotoxic concentrations, Hcol A1 induces membrane-damaging effects within 6 h, cytoplasmic vacuolization within 24 h, and non-apoptotic cell death within 48 h. Using a new high-resolution magic-angle spinning nuclear magnetic resonance method, we have shown for the first time that this hederasaponin specifically interacts with melanin. The dissociation constant (2.7 mM) is comparable to those observed with drugs known to interact with melanin. Taking into consideration that the IC50 values were inversely proportional to the melanin in each cell line, our data suggest that, in addition to the delayed membrane injury induced by this drug, the ability of Hcol A1 to bind melanin could contribute to the higher toxicity of Hcol A1 in pigmented melanoma cells.

Triterpenoid electrophiles (avicins) activate the innate stress response by redox regulation of a gene battery

Avicins are proapoptotic and anti-inflammatory triterpene electrophiles isolated from an Australian desert tree, Acacia victoriae. The presence of two alpha,beta unsaturated carbonyl groups (Michael reaction sites) in the side chain of the avicin molecule prompted us to study its effects on NF-E2-related factor 2 (Nrf2), a redox-regulated transcription factor that controls the expression of a battery of detoxification and antioxidant proteins via its binding to antioxidant response element (ARE). Avicin D-treated Hep G2 cells showed translocation of Nrf2 into the nucleus and a time-dependent increase in ARE activity. These properties were sensitive to DTT, suggesting that avicins affect one or more critical cysteine residues, probably on the Keap1 molecule. Downstream of ARE, an activation of a battery of stress-induced proteins occurred. The implications of these findings were evaluated in vivo in mouse skin exposed to an ancient stressor, UV light. Avicins inhibited epidermal hyperplasia, reduced p53 mutation, enhanced apoptosis, decreased generation of 8-hydroxy-2'-deoxyguanosine, and enhanced expression of NADPH:quinone oxidoreductase 1 and heme oxygenase-1. These data, combined with our earlier published work, demonstrate that avicins represent a new class of plant stress metabolites capable of activating stress adaptation and suppressing proinflammatory components of the innate immune system in human cells by redox regulation. The relevance for treatment of clinical diseases in which stress responses are dysfunctional or deficient is discussed.

PC-SPES: A Potent Inhibitor of Nuclear Factor-κB Rescues Mice from Lipopolysaccharide-Induced Septic Shock

Septic shock is the most common cause of death in intensive care units, and no effective treatment is available at present. Lipopolysaccharide (LPS) is the primary mediator of Gram-negative sepsis by inducing the production of macrophage-derived proinflammatory cytokines, in which activation of nuclear factor-kappaB (NF-kappaB) plays an important role. PC-SPES is an eight-herb mixture active against a variety of malignancies, including prostate cancer and leukemia. In this study, we demonstrated that PC-SPES inhibited the LPS-induced NF-kappaB reporter activity in RAW264.7 macrophages. Electrophoretic mobility shift assay showed that PC-SPES inhibited the binding of NF-kappaB to specific DNA sequences; however, it did not affect either degradation of inhibitory kappaBalpha or nuclear translocation of NF-kappaB. Also, we explored the effect of PCSPES on LPS-induced mitogen-activated protein (MAP) kinase signaling; PC-SPES did not affect LPS-induced phosphorylation of MAP kinases, including c-Jun NH2-terminal kinase, p38, and extracellular signal-regulated kinase 1/2. Moreover, PC-SPES decreased the production of proinflammatory cytokines and inducible enzymes, such as tumor necrosis factor (TNF) alpha, interleukin (IL)-1beta, IL-6, cyclooxygenase-2, as well as inducible nitric-oxide synthase in RAW264.7 macrophages and peritoneal macrophages from C57BL/6 mice after the cells were stimulated by either LPS or LPS and interferon-gamma. Furthermore, PC-SPES rescued C57BL/6 mice from death caused by LPS-induced septic shock in conjunction with decreased serum levels of TNFalpha and IL-1beta. Together, PC-SPES is a potent inhibitor of NF-kappaB and might be useful for the treatment of sepsis and inflammatory diseases.

Gypenosides derived from Gynostemma pentaphyllum suppress NO synthesis in murine macrophages by inhibiting iNOS enzymatic activity and attenuating NF-kappaB-mediated iNOS protein expression

Gypenosides isolated from Gynostemma pentaphyllum are widely used in traditional Chinese medicine, with beneficial effects reported in numerous diseases, including inflammation and atherosclerosis, although the mechanism underlying these therapeutic effects is unknown. Because increased nitric oxide (NO) plays a role in these pathological conditions, we investigated whether the pharmacological activity of gypenosides is due to suppression of NO synthesis. The markedly increased production of nitrite by stimulation of RAW 264.7 murine macrophages with 1 microg/mL lipopolysaccharide (LPS) for 20 h (unstimulated: 0.3+/-0.3 microM vs. LPS: 32.5+/-1.2 microM) was dose-dependently inhibited by gypenosides (0.1-100 microg/mL). When cells were pretreated with gypenosides (for 1h) prior to LPS stimulation, subsequent NO production was significantly attenuated (IC(50) of 3.1+/-0.4 microg/mL) (P<0.05). Gypenosides (25 microg/mL) produced the same maximum inhibition of LPS-induced NO production as aminoguanidine, a standard inhibitor of NOS enzymes. Suppression of NO production occurred both by direct inhibition of the activity and expression of iNOS. Inhibition of iNOS protein expression appears to be at the transcriptional level, since gypenosides decreased LPS-induced NF-kappaB activity in a dose-dependent manner (P<0.05), with significant inhibition achieved following pretreatment with 10 microg/mL gypenoside. Taken together, these results suggest that gypenosides derived from G. pentaphyllum suppress NO synthesis in murine macrophages by inhibiting iNOS enzymatic activity and attenuating NF-kappaB-mediated iNOS protein expression, thereby implicating a mechanism by which gypenosides may exert their therapeutic effects.

Metabolomics of plant saponins: bioprospecting triterpene glycoside diversity with respect to mammalian cell targets

One of the goals of cancer chemotherapy and prevention is the discovery of compounds that are relatively selective to tumor cells and, therefore, have reduced effects on normal cell growth. In previously published studies, it was shown that certain triterpene saponins (called avicins) from a desert tree, Acacia victoriae, are selectively toxic to tumor cells at very low doses (IC(50): 0.2 microg/mL for Jurkat cells). To extend this research to human clinical studies, we needed to find a reliable supply of avicins and have developed a transformed "hairy root" culture as a means of biomass production. Protocols were optimized for A. victoriae micropropagation; after a boiling water treatment, A. victoriae seeds were maintained under in vitro conditions on defined media. Embryo-axis explants from shoot tips were removed and infected with Agrobacterium rhizogenes Conn (R 1000) for hairy root induction. Plasmid integration was confirmed by PCR analysis with a primer set for a segment of the rol B gene. Culture conditions have been optimized for root biomass production, and various inducers have been investigated for enhancement of avicin production. Hairy root cultures were compared with intact pod tissue from field-grown sources for avicin content following partial purification of triterpene glycosides and HPLC separation of the secondary metabolites. From bioassays of the collected HPLC fractions, we have identified putative triterpene "metabolic clusters" with enhanced activity against tumor cells. This now provides a system for both production of clinical trial lots of active samples, but also a means to correlate structure of individual triterpene glycosides with specific cellular target activity in mammalian cells.

Chemotherapy: targeting the mitochondrial cell death pathway

One of the mechanisms by which chemotherapeutics destroy cancer cells is by inducing apoptosis. Apoptosis can be activated through several different signalling pathways, but these all appear to converge at a single event - mitochondrial membrane permeabilization (MMP). This 'point-of-no-return' in the cell death program is a complex process that is regulated by the composition of the mitochondrial membrane and pre-mitochondrial signal-transduction events. MMP is subject to a complex regulation, and local alterations in the composition of mitochondrial membranes, as well as alterations in pre-mitochondrial signal-transducing events, can determine chemotherapy resistance in cancer cells. Detecting MMP might thus be useful for detecting chemotherapy responses in vivo. Several cytotoxic drugs induce MMP by a direct action on mitochondria. This type of agents can enforce death in cells in which upstream signals normally leading to apoptosis have been disabled. Cytotoxic components acting on mitochondria can specifically target proteins from the Bcl-2 family, the peripheral benzodiazepin receptor, or the adenine nucleotide translocase, and/or act by virtue of their physicochemical properties as steroid analogues, cationic ampholytes, redox-active compounds or photosensitizers. Some compounds acting on mitochondria can overcome the cytoprotective effect of Bcl-2-like proteins. Several agents which are already used in anti-cancer chemotherapy can induce MMP, and new drugs specifically designed to target mitochondria are being developed.

The biological action of saponins in animal systems: a review

Saponins are steroid or triterpenoid glycosides, common in a large number of plants and plant products that are important in human and animal nutrition. Several biological effects have been ascribed to saponins. Extensive research has been carried out into the membrane-permeabilising, immunostimulant, hypocholesterolaemic and anticarcinogenic properties of saponins and they have also been found to significantly affect growth, feed intake and reproduction in animals. These structurally diverse compounds have also been observed to kill protozoans and molluscs, to be antioxidants, to impair the digestion of protein and the uptake of vitamins and minerals in the gut, to cause hypoglycaemia, and to act as antifungal and antiviral agents. These compounds can thus affect animals in a host of different ways both positive and negative.

The genetics and molecular genetics of terpene and sterol origami

Terpenes and sterols are complex molecules synthesized by equally complex biosynthetic pathways. Recent progress in using the tools of genetics, molecular genetics and genetic engineering to dissect triterpene metabolism in the cytosol, and terpene metabolism in the plastids, has opened up new strategies and avenues of investigation. Most importantly, these studies have enhanced our appreciation of the biological significance of these compounds for plants, and have revealed new secrets of this intriguing biochemistry for practical applications in agriculture and medicine.

Natural products as targeted modulators of the nuclear factor-kappaB pathway

The use of plant extracts to alleviate inflammatory diseases is centuries old and continues to this day. This review assesses the current understanding of the use of such plants and natural products isolated from them in terms of their action against the ubiquitous transcription factor, nuclear factor kappa B (NF-kappaB). As an activator of many pro-inflammatory cytokines and inflammatory processes the modulation of the NF-kappaB transduction pathway is a principal target to alleviate the symptoms of such diseases as arthritis, inflammatory bowel disease and asthma. Two pathways of NF-kappaB activation will first be summarised, leading to the IKK (IkappaB kinase) complex, that subsequently initiates phosphorylation of the NF-kappaB inhibitory protein (IKB). Natural products and some extracts are reviewed and assessed for their activity and potency as NF-kappaB inhibitors. A large number of compounds are currently known as NF-kappaB modulators and include the isoprenoids, most notably kaurene diterpenoids and members of the sesquiterpene lactones class, several phenolics including curcumin and flavonoids such as silybin. Additional data on cellular toxicity are also highlighted as an exclusion principle for pursuing such compounds in clinical development. In addition, where enough data exists some conclusions on structure-activity relationship are provided.

Avicins, a family of triterpenoid saponins from Acacia victoriae (Bentham), suppress H-ras mutations and aneuploidy in a murine skin carcinogenesis model

We tested the ability of avicins, a family of triterpenoid saponins obtained from Acacia victoriae (Bentham) (Leguminosae: Mimosoideae), to inhibit chemically induced mouse skin carcinogenesis. Varying doses of avicins were applied to shaved dorsal skin of SENCAR mice 15 min before application of 100 nmol of 7,12-dimethylbenz[a]anthracene (DMBA) twice a week for 4 weeks (complete carcinogenesis model). The dorsal skin of a second group of mice was treated with one dose of 10 nmol of DMBA. Avicins were then applied 15 min before repetitive doses of 2 microg of phorbol 12-tetradecanoate 13-acetate (TPA) twice a week for 8 weeks (initiation/promotion model). At 12 weeks, avicins produced a 70% decrease in the number of mice with papillomas and a greater than 90% reduction in the number of papillomas per mouse in both protocols. We also observed a 62% and 74% reduction by avicins in H-ras mutations at codon 61 in the DMBA and DMBA/TPA models, respectively, as well as a significant inhibition of the modified DNA base formation (8-OH-dG) in both protocols. Marked suppression of aneuploidy occurred with treatment at 16 weeks in the initiation/promotion experiment. These findings, when combined with the proapoptotic property of these compounds and their ability to inhibit hydrogen peroxide (H(2)O(2)) generation, nuclear factor-kappaB (NF-kappaB) activation, and inducible nitric oxide synthase (iNOS) induction reported elsewhere, suggest that avicins could prove exciting in reducing oxidative and nitrosative stress and thereby suppressing the development of human skin cancer and other epithelial malignancies.