DNA polymerase and topoisomerase II inhibitors from Psoralea corylifolia

Resveratrol induces apoptosis, influences IL-6 and exerts immunomodulatory effect on mouse lymphocytic leukemia both in vitro and in vivo

Resveratrol, a dietary polyphenol found in grapes, has been proposed to act as a chemopreventive or anti-tumor agent in numerous epidemiologic studies. In this study, we investigate the antitumor and immunomodulation effects of resveratrol on mouse lymphocytic leukemia cells L1210 both in vitro and in vivo. Our finding indicates that resveratrol inhibits proliferation, induces apoptosis, and influences cell cycle of L1210 cells in a dose- and time-dependent manner in vitro. Furthermore, resveratrol can exert a dose-related regulatory effect on both innate and specific immune function to L1210-bearing mice. A normalization of CD4/CD8 ratios is noted as well as an enhancement of lymphocyte proliferation, NK cell activity and anti-SRBC titers. Interleukin-6 cellular content and release are suppressed by resveratrol as well as mRNA expression. In conclusion, the data provide new findings with respect to resveratrol mechanism of action to mouse lymphocytic leukemia.

Bioactive constituents from Chinese natural medicines. XX. Inhibitors of antigen-induced degranulation in RBL-2H3 cells from the seeds of Psoralea corylifolia

The ethyl acetate-soluble fraction of the methanolic extract from the seeds of Psoralea corylifolia was found to inhibit the release of beta-hexosaminidase, as a marker of antigen-IgE-induced degranulation in RBL-2H3 cells. Sixteen constituents were isolated from the ethyl acetate-soluble fraction and several constituents, Delta(1),3-hydroxybakuchiol (IC(50) = 49 microM), Delta(3),2-hydroxybakuchiol (69 microM, bavachin (58 microM), and psoralidin (ca. 100 microM), showed inhibitory activities against the antigen-induced degranulation.

Resveratrol modulates mRNA transcripts of genes related to redox metabolism and cell proliferation in non-small-cell lung carcinoma cells

Resveratrol is a polyphenolic chemopreventive agent that has been shown to influence cellular redox reactions. As a systematic approach to elucidating the complex effects of resveratrol on eukaryotic cells, we studied its dose-dependent effects on the transcript levels of genes and activities of enzymes related to redox metabolism, cell cycle regulation, and apoptotic cascades in the cancer cell line A549. Glutathione peroxidase (GPx)1 mRNA levels, as well as GPx and thioredoxin reductase (TrxR) activities, were significantly increased after resveratrol treatment, whereas total glutathione concentrations decreased. Increased transcript levels were also detected for selenophosphate synthetase 2 and superoxide dismutase 2. However, mRNA levels of thioredoxin, TrxR, glutathione reductase, glutathione S-transferase, superoxide dismutase 1, and catalase were not altered. Among the 12 genes studied that are related to the cell cycle, differentiation and apoptosis, mRNA levels of six genes, including P53, FAS, and BCL2, were upregulated, while the mRNA level of survivin was reduced. The results suggest that GPx and other selenoproteins are important targets of resveratrol. Furthermore, genes supporting cell survival and differentiation, as well as genes involved in proliferation inhibition and apoptosis, are induced by resveratrol, resulting in a delicate balance that is likely to contribute to the chemopreventive effects of resveratrol.

Chasing molecules that were never there: misassigned natural products and the role of chemical synthesis in modern structure elucidation

Over the course of the past half century, the structural elucidation of unknown natural products has undergone a tremendous revolution. Before World War II, a chemist would have relied almost exclusively on the art of chemical synthesis, primarily in the form of degradation and derivatization reactions, to develop and test structural hypotheses in a process that often took years to complete when grams of material were available. Today, a battery of advanced spectroscopic methods, such as multidimensional NMR spectroscopy and high-resolution mass spectrometry, not to mention X-ray crystallography, exist for the expeditious assignment of structures to highly complex molecules isolated from nature in milligram or sub-milligram quantities. In fact, it could be argued that the characterization of natural products has become a routine task, one which no longer even requires a reaction flask! This Review makes the case that imaginative detective work and chemical synthesis still have important roles to play in the process of solving nature's most intriguing molecular puzzles.

Time- and concentration-dependent effects of resveratrol in HL-60 and HepG2 cells

Resveratrol, a phytochemical present in grapes, has been demonstrated to inhibit tumourigenesis in animal models. However, the specific mechanism by which resveratrol exerts its anticarcinogenic effect has yet to be elucidated. In the present study, the inhibitory effects of resveratrol on cell proliferation and apoptosis were evaluated in the human leukaemia cell line HL-60 and the human hepatoma derived cell line HepG2. We found that after a 2 h incubation period, resveratrol inhibited DNA synthesis in a concentration-dependent manner. The IC50 value was 15 microm in both HL-60 and HepG2 cells. When the time of treatment was extended, an increase in IC50 value was observed; for example, at 24 h the IC50 value was 30 microm for HL-60 cells and 60 microm for HepG2 cells. Flow cytometry revealed that cells accumulated in different phases of the cell cycle depending on the resveratrol concentration. Furthermore, an increase in nuclear size and granularity was observed in the G1 and S phases of HL-60 treated and HepG2-treated cells. Apoptosis was also stimulated by resveratrol in a concentration-dependent manner in HL-60 and HepG2 cells. In conclusion, resveratrol inhibits cell proliferation in a concentration- and time-dependent manner by interfering with different stages of the cell cycle. Furthermore, resveratrol treatment causes stimulation of apoptosis as well as an increase in nuclear size and granularity.

Cyclobakuchiol C, a new bakuchiol derivative from Psoralea coryllfolia

A new compound, cyclobakuchiol C (1), together with four known bakuchiol derivatives, 2-5, was isolated from the non-polar fraction of the seeds of Psoralea corylifolia, and compounds 3-5 were identified from this plant for the first time. The structure of 1 was determined by spectroscopic methods, especially 2D NMR experiments.

Inhibition of phosphatidylinositol 3-kinase-mediated glucose metabolism coincides with resveratrol-induced cell cycle arrest in human diffuse large B-cell lymphomas

An abnormally high rate of aerobic glycolysis is characteristic of many transformed cells. Here we report the polyphenolic compound, resveratrol, inhibited phosphatidylinositol 3-kinase (PI-3K) signaling and glucose metabolism, coinciding with cell-cycle arrest, in germinal center (GC)-like LY1 and LY18 human diffuse large B-cell lymphomas (DLBCLs). Specifically, resveratrol inhibited the phosphorylation of Akt, p70 S6K, and S6 ribosomal protein on activation residues. Biochemical analyses and nuclear magnetic resonance spectroscopy identified glycolysis as the primary glucose catabolic pathway in LY18 cells. Treatment with the glycolytic inhibitor 2-deoxy-D-glucose, resulted in accumulation of LY18 cells in G0/G1 -phase, underscoring the biological significance of glycolysis in growth. Glycolytic flux was inhibited by the PI-3K inhibitor LY294002, suggesting a requirement for PI-3K activity in glucose catabolism. Importantly, resveratrol treatment resulted in inhibition of glycolysis. Decreased glycolytic flux corresponded to a parallel reduction in the expression of several mRNAs encoding rate-limiting glycolytic enzymes. These results are the first to identify as a mechanism underlying resveratrol-induced growth arrest, the inhibition of glucose catabolism by the glycolytic pathway. Taken together, these results raise the possibility that inhibition of signaling and metabolic pathways that control glycolysis might be effective in therapy of DLBCLs.

Possible Inhibition of Group I Intron RNA by Resveratrol and Genistein

The increasing incidence of pathogens and drug resistance has become major threat in the current arena. Hence, there is a need for the development of alternative therapeutic target to combat increase in resistance problem other than the cell membrane. Besides DNA, recently RNA has been recognized as a central target site for drug design. Group I intron RNA is a unique class of RNA molecule that undergoes self-catalytic activity due to its unique folded structure that catalyze number of cellular reactions. Recently, in vitro studies have shown that the folded structure of group I intron RNA could be a potential target site for therapeutic agents. Its presence in human pathogen like Candida albicans and absence in humans, suggests that the intron could act as an alternative therapeutic target. Therefore, our interest has been to explore the RNA binding activity of dietary compounds resveratrol and genistein. The binding efficacy of resveratrol and genistein (P/D ratio's - 11.76, 4.71, 2.35, 1.17, 0.58) to group I intron RNA transcript and circular-intervening sequences (C-IVS) of Tetrahymena thermophila and the binding efficacy of resveratrol and genistein (P/D ratio's - 2.35, 1.17, 0.58, 0.29) to 25S rRNA of C. albicans is measured by quantification of the RNA using densitometric method. This suggests that these natural compounds might bind with intron RNA and acts as an potential target and modulates the cellular process during therapeutic intervention.

Gypenoside XLIX isolated from Gynostemma pentaphyllum inhibits nuclear factor-kappaB activation via a PPAR-alpha-dependent pathway

Nuclear factor (NF)-kappaB is important in the generation of inflammation. Besides regulating lipid metabolism, peroxisome proliferator-activated receptor (PPAR)-alpha activators also reduce NF-kappaB activation to terminate activation of inflammatory pathways. Gynostemma pentaphyllum (GP) has been used to treat various inflammatory diseases and hyperlipidemia. Here, we demonstrate that GP extract and one of its main components, Gypenoside XLIX (Gyp-XLIX) inhibited LPS-induced NF-kappaB activation in murine macrophages. Furthermore, Gyp-XLIX restored the LPS- and TNF-alpha-induced decrease in cytosolic I-kappaBalpha protein expression and inhibited the translocation of NF-kappaB(p65) to the nucleus in THP-1 monocyte and HUVEC cells. The inhibition of LPS- and TNF-alpha-induced NF-kappaB luciferase activity in macrophages was abolished by MK-886, a selective PPAR-alpha antagonist. GP extract and Gyp-XLIX (EC(50): 10.1 microM) enhanced PPAR-alpha luciferase activity in HEK293 cells transfected with the tK-PPREx3-Luc reporter plasmid and expression vectors for PPAR-alpha. Additionally, Gyp-XLIX specifically enhanced PPAR-alpha mRNA and protein expression in THP-1-derived macrophage cells. The selectivity of Gyp-XLIX for PPAR-alpha was demonstrated by the activation of only PPAR-alpha in HEK293 cells transfected with expression vectors for PPAR-alpha, PPAR-beta/delta or PPAR-gamma1 plasmids and in THP-1-derived macrophage naturally expressing all three PPAR isoforms. The present study demonstrates that Gyp-XLIX, a naturally occurring gynosaponin, inhibits NF-kappaB activation via a PPAR-alpha-dependent pathway.

Resveratrol induces apoptosis and inhibits angiogenesis in human breast cancer xenografts in vivo

Resveratrol, a polyphenol found in grapes and wine, is considered a potential cancer chemopreventive agent. Resveratrol has been shown to induce transcription via both ERalpha and ERbeta. We observed significantly lower tumor growth, decreased angiogenesis, and increased apoptotic index in ERalpha- ERbeta+ MDA-MB-231 tumors in resveratrol-treated nude mice compared with controls. In vitro we found a significant increase in apoptosis in resveratrol-treated MDA-MB-231 cells in addition to significantly reduced extracellular levels of VEGF. This study supports the potential use of resveratrol as a chemotherapeutic agent in breast cancers.

Modulation of DNA intercalation by resveratrol and genistein

Time correlated Single Photon Counting study (TCSPC) was performed for the first time to evaluate the effect of resveratrol (RES) and genistein (GEN) at 10-100 microM and 10-150 microM respectively, in modulating the DNA conformation and the variation induced due to intercalation by the dyes, ethidium bromide (EtBr) and acridine orange (AO). It is demonstrated using UV-absorption and fluorescence spectroscopy that RES and GEN, at 50 microM and 100 microM respectively can bind to DNA resulting in significant de-intercalation of the dyes, preventing their further intercalation within DNA. Hyperchromicity with red/blue shifts in DNA when bound to dyes was reduced upon addition of RES and GEN. DNA-dependent fluorescence of EtBr and AO was quenched in the presence of RES by 87.97% and 79.13% respectively, while similar quenching effect was observed for these when interacted with GEN (85.52% and 83.85%). It is found from TCSPC analysis that the higher lifetime component or constituent of intercalated dyes (tau(2), A (2)) decreased with the subsequent increase in smaller component or constituent of free dye (tau(1), A (1)) after the interaction of drugs with the intercalated DNA. Thus these findings signify that RES and GEN can play an important role in modulating DNA intercalation, leading to the reduction in DNA-directed toxicity.

Immunomodulatory effects of curcumin

Curcumin (diferuloylmethane), found in the spice turmeric, exhibits anti-inflammatory, antioxidant, and chemopreventive activities. However, the effect of curcumin on the immunological responses largely remains unknown. In this study we have investigated the effect of curcumin on mitogen (phytohaemagglutinin; PHA) stimulated T-cell proliferation, natural killer (NK) cell cytotoxicity, production of cytokines by human peripheral blood mononuclear cells (PBMCs), nitric oxide (NO) production in mouse macrophage cells, RAW-264.7. Furthermore, we have carried out an electromobility shift assay to elucidate the mechanism of action of curcumin at DNA protein interaction level. We observed that curcumin inhibits PHA-induced T-cell proliferation, interleukin-2 production, NO generation, and lipopolysachharide-induced nuclear factor-kappaB (NF-kappaB) and augments NK cell cytotoxicity. Our results suggest that curcumin most likely inhibits cell proliferation and cytokine production by inhibiting NF-kappaB target genes involved in the induction of these immune parameters.

Differential antibacterial activity of genistein arising from global inhibition of DNA, RNA and protein synthesis in some bacterial strains

Antibacterial activities of various flavonoids have been reported previously, but mechanism(s) of their action on bacterial cells remain(s) largely unknown. Here, we investigated effects of genistein, an isoflavone, and representatives of other flavonoids: daidzein (another isoflavone), apigenin (a flavone), naringenin (a flavanone) and kaempferol (a flavonol), on commonly used laboratory strains of model bacterial species: Escherichia coli, Vibrio harveyi and Bacillus subtilis. We found that E. coli was resistant to all tested flavonoids at concentrations up to 0.1 mM, while high sensitivity of V. harveyi to most of them (except daidzein, which exhibited significantly less pronounced effect) was observed. Effects of the flavonoids on B. subtilis were relatively intermediate to the two extremes, i.e., E. coli and V. harveyi. Action of genistein on bacterial cells was investigated in more detail to indicate changed cell morphology (formation of filamentous cells) of V. harveyi and drastic inhibition of global synthesis of DNA and RNA as shortly as 15 min after addition of this isoflavone to a bacterial culture to a final concentration of 0.1 mM. Protein synthesis inhibition was also apparent, but delayed. Both cell morphology and synthesis of nucleic acids and proteins were unaffected in E. coli cultures under analogous conditions. Studies on cell survival suggest that genistein is a bacteriostatic agent rather than a bactericidal compound.

Resveratrol-Cu(II) induced DNA breakage in human peripheral lymphocytes: implications for anticancer properties

Resveratrol (3,4',5-trihydroxy stilbene), a plant derived polyphenol found in mulberries, grapes and red wine is considered to possess chemopreventive properties against cancer. It is recognized as a naturally occurring antioxidant but also catalyzes oxidative DNA degradation in vitro in the presence of transition metal ions such as copper. Using a cellular system of lymphocytes isolated from human peripheral blood and Comet assay, we have confirmed that resveratrol-Cu(II) system is indeed capable of causing DNA degradation in cells such as lymphocytes. Also, trans-stilbene, which does not have any hydroxyl groups, is inactive in the lymphocyte system. Pre-incubation of lymphocytes with resveratrol indicates that it is capable of either traversing the cell membrane or binding to it. Our results are in partial support of our hypothesis that anticancer properties of various plant derived polyphenols may involve mobilization of endogenous copper and the consequent prooxidant action.

Association between pterostilbene and quercetin inhibits metastatic activity of B16 melanoma

Inhibition of cancer growth by resveratrol (trans-3,5,4'-trihydroxystilbene; RESV), a phytoalexin present in many plant species, is limited by its low bioavailability. Pterostilbene (3,5-dimethoxy-4'-hydroxystilbene; PTER) and quercetin (3,3',4',5,6-pentahydroxyflavone; QUER), two structurally related and naturally occurring small polyphenols, show longer half-life in vivo. In vitro growth of highly malignant B16 melanoma F10 cells (B16M-F10) is inhibited (56%) by short-time exposure (60 min/day) to PTER (40 microm) and QUER (20 microm) (approximate mean values of plasma concentrations measured within the first hour after intravenous administration of 20 mg/kg each polyphenol). Intravenous administration of PTER and QUER (20 mg/kg per day) to mice inhibits (73%) metastatic growth of B16M-F10 cell in the liver, a common site for metastasis development. The anti-metastatic mechanism involves: 1) a PTER-induced inhibition of vascular adhesion molecule 1 expression in the hepatic sinusoidal endothelium, which consequently decreases B16M-F10 cell adhesion to the endothelium through very late activation antigen 4; and 2) a QUER- and PTER-induced inhibition of Bcl-2 expression in metastatic cells, which sensitizes them to vascular endothelium-induced cytotoxicity. Our findings demonstrate that the association of PTER and QUER inhibits metastatic melanoma growth and extends host survival.

Phytoestrogen genistein as an anti-staphylococcal agent

The soybean-derived isoflavone genistein has been shown to exert beneficial effects on many disorders, including cancer and cardiovascular diseases. The effects of genistein on mammalian cells are mediated by its abilities to inhibit topoisomerase II and protein tyrosine kinase. In order to examine the potential antibacterial activities of genistein, we incubated the bacteria with various concentrations of this compound for different periods of time and assessed the viable counts. Exposure to genistein exhibited an inhibitory effect on all staphylococcal strains tested, including methicillin-resistant strains. Furthermore, the growth of Streptococcus pasteurianus, Bacillus cereus, and Helicobacter pylori was clearly inhibited by genistein, whereas Escherichia coli growth was not suppressed. Daidzein, which is structurally similar to genistein, but deficient in topoisomerase II inhibitory activity, also inhibited the growth of Staphylococcus aureus, albeit with lower potency than genistein. Our results indicate that genistein exerts potent antibacterial properties in vitro, which are possibly mediated by the stabilization of the covalent topoisomerase II-DNA cleavage complex.

Interaction of Resveratrol and Genistein with Nucleic Acids

Resveratrol (RES) and genistein (GEN) are the dietary natural products known to possess chemopreventive property and also the ability to repair DNA damage induced by mutagens/carcinogens. It is believed that the therapeutic activity of these compounds could be primarily due to their interaction with nucleic acids but detailed reports are not available. We here explore the interaction of these drugs with nucleic acids considering DNA and RNA as a potential therapeutic target. The interaction of RES and GEN has been analysed in buffered solution with DNA [saline sodium citrate (SSC)] and RNA [tris ethylene diammine tetra acetic acid (TE)] using UV-absorption and Fourier transform infrared (FTIR) spectroscopy. The UV analysis revealed lesser binding affinity with nucleic acids at lower concentration of RES (P/D = 5.00 and 10.00), while at higher drug concentration (P/D = 0.75, 1.00 and 2.50) hyperchromic effect with shift in the lambda(max) is noted for DNA and RNA. A major RES-nucleic acids complexes was observed through base pairs and phosphate backbone groups with K = 35.782 M(-1) and K = 34.25 M(-1) for DNARES and RNA-RES complexes respectively. At various concentrations of GEN (P/D = 0.25, 0.50, 0.75, 1.00 and 2.50) hyperchromicity with shift in the lambda(max) from 260-->263 nm and 260--> 270 nm is observed for DNA-GEN and RNA-GEN complexes respectively. The binding constant (from UV analysis) for GEN-nucleic acids complexes could not be obtained due to GEN absorbance overlap with that of nucleic acids at 260 nm. Nevertheless a detailed analysis with regard to the interaction of these drugs (RES/GEN) with DNA and RNA could feasibly be understood by FTIR.

Preparation and in vitro evaluation of radioiodinated bakuchiol as an anti tumor agent

Bakuchiol, extracted from the plant Psoralea corylifolia, has been proven to have anti-tumor, cytotoxic, anti-microbial and anti-inflammatory activity. In order to study if radiolabeled bakuchiol exhibits enhanced cytotoxicity, bakuchiol was radiolabeled with 125I. In-vitro uptake studies of 125I-bakuchiol were carried out using LS-A (lymphosarcoma) and barcl-95 (radiation-induced thymic lymphoma) ascitic and solid tumor cells of murine origin. In both LS-A and barcl-95, 125I-bakuchiol showed significant uptake. Viability studies showed that the radioiodinated compound showed greater cytotoxic effect than bakuchiol.

The cancer chemopreventive agent resveratrol induces tensin, a cell–matrix adhesion protein with signaling and antitumor activities

During a search to identify resveratrol (3,5,4'-trihydroxy-trans-stilbene, RV) target genes in the human erythroleukemic K562 cell line, we show here that the tensin gene and protein levels are remarkably induced by this dietary polyphenol. Tensin, a cell-matrix adhesion protein binding the integrins and cytoskeletal actin filaments also interacts with PI3-kinase and JNK signaling pathways. Tensin induction by RV is associated with increased K562 cell adhesion to fibronectin, cell spreading and actin polymerization. The same responses were observed in the tensin-deficient MCF7 human breast cancer cell line. In K562 and MCF7 cells treated by RV, tensin was found in punctate and intracytoplasmic areas. In MCF7 epithelial cells, induction of tensin is not exclusively associated with plasma membrane-bound vinculin, suggesting a dual localization of tensin in both focal and fibrillar adhesions. Pharmacological blockade of PI3-kinase and Rho GTPases/Rho-kinase resulted in selective depletion of focal adhesions, disorganization of tensin localization and disruption of stress fibers. RV increased cell motility and attachment to fibronectin in MCF7 cells submitted to mechanical laminar flow stress, and abrogated estrogen-induced MCF7 cancer cell invasion. Our data support the conclusion that induction of tensin by RV contributes to the chemopreventive and anti-invasive activity of this natural dietary compound in tensin-negative and -deficient leukemic cells or epithelioid cancers.

3,4',5-Trihydroxy-trans-stilbene (resveratrol) inhibits human cytomegalovirus replication and virus-induced cellular signaling

Resveratrol is a polyphenolic natural product that is present in red wine and peanuts and has inhibitory activity against inflammation, heart disease, and cancer. Here we describe its inhibition of human cytomegalovirus replication (IC50 = 1-2 microM). At least 50-fold higher concentrations of compound were required to produce cytotoxicity against growing or stationary human embryonic lung fibroblasts. Mechanism of action studies determined that resveratrol blocked virus-induced activation of the epidermal growth factor receptor (EGFR) and phosphatidylinositol-3-kinase signal transduction as well as NF-kappaB and Sp1 transcription factor activation shortly following infection. Resveratrol prevented the appearance of immediate-early, early, and late viral proteins. Human cytomegalovirus DNA replication was reduced to undetectable levels by treatment with resveratrol, as were the second (late) phases of virus-induced phosphatidylinositol-3-kinase signaling and transcription factor activation. Resveratrol lost substantial antiviral activity when its addition was delayed until 4 h postinfection. Compound reversibility and preincubation studies were inconsistent with a virucidal mechanism of action. These data indicated that this compound likely operated during attachment and entry. We hypothesize that the primary molecular target for resveratrol may be blockage of epidermal growth factor receptor activation and its downstream effectors.

Differential sensitivity to resveratrol-induced apoptosis of human chronic myeloid (K562) and acute lymphoblastic (HSB-2) leukemia cells

The in vitro effects of resveratrol (RES) on apoptotic pathway in human chronic myeloid (K562) and acute lymphoblastic (HSB-2) leukemia cells were investigated. RES treatment of both cell types significantly and irreversibly inhibited their growth, associated with extensive apoptosis and increase in hypodiploid cells. Cell cycle analysis showed accumulation in G(1) phase in HSB-2 drug exposed cells, while only K562-treated cells exhibited a marked accumulation in S phase with a concomitant decrease in G(1) and G(2)/M at 24 h. Moreover, RES caused internucleosomal DNA fragmentation, even if K562 cells were found less sensitive to the drug, as compared to HSB-2 cells, which also reacted earlier to the treatment. RES-induced apoptosis was associated with an increase of Bax expression and a marked release of cytochrome c from mitochondria. Interestingly, K562 cells exhibited a basal content of glutathione 10-fold that of HSB-2 cells, which increased after 24-48 h RES exposure, together with increment of glutathione reductase and peroxidase activities. However, the major resistance to apoptosis of K562 cells cannot be attributed to their higher pool of reducing power, since neither the inhibition of glutathione synthesis by buthionine sulphoximine nor glutathione depletion by diethylmaleate, sensitized these cells. In addition, glutathione enrichment of HSB-2 cells by N-acetylcysteine did not prevent the apoptotic effects of RES. Our data indicate that RES commitment to apoptosis in both cell lines is independent from the intracellular content of glutathione, while it is associated with either the enhanced expression of Bax and cytochrome c release.

Phytoalexin resveratrol attenuates the mutagenicity of the heterocyclic amines 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline

Resveratrol is a phytoalexin, that belongs to a family of naturally occurring stilbenes. It has been reported that resveratrol can inhibit chemical carcinogenesis in experimental animals and although the mechanisms involved are unknown, an anti-mutagen mechanism has been proposed. We have explored this hypothesis using mutagenicity assays based on bacterial (Salmonella typhimurium) and eukaryotic cells (Chinese hamster V79 cells). We found resveratrol to be potent in both systems, blocking the mutagenicity of the food-derived heterocyclic amines (HA) 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) at micromolar concentrations. Furthermore, in cells capable of activating 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine to cytotoxic derivatives, resveratrol was able to attenuate cytotoxicity. Paradoxically, in cells lacking the ability to activate PhIP, resveratrol itself was toxic and co-incubation with PhIP reduced this toxicity. Our data confirm the potent anti-mutagenic activity of resveratrol and support its potential as a chemopreventative.

Resveratrol inhibits benzo[a]pyrene-DNA adduct formation in human bronchial epithelial cells

Resveratrol (trans-3,4′,5-trihydroxystilbene), a phytoalexin present in various plants and foods, has in several in vitro and in vivo studies demonstrated cancer chemopreventive and chemotherapeutic potential. We investigated the in vitro effect of resveratrol on benzo[a]pyrene (B[a]P) -induced DNA adducts in human bronchial epithelial cells. This was compared to the effect of resveratrol on the expression of the cytochrome P450 (CYP) genes CYP1A1 and CYP1B1 and the formation of B[a]P metabolites. Exposure of BEAS-2B and BEP2D cells to B[a]P and increasing concentrations of resveratrol resulted in a dose- and time-dependent inhibition of DNA adduct formation quantified by ³²P-postlabelling. Supporting this result, resveratrol was shown to inhibit CYP1A1 and CYP1B1 gene expression, as measured by real-time reverse transcriptase—polymerase chain reaction. Also, a significant correlation was found between the number of DNA adducts and the mRNA levels of these genes. Using HPLC analysis, a concomitant decrease in the formation of B[a]P-derived metabolic products was detected. In conclusion, these data lend support to a chemopreventive role of resveratrol in polycyclic aromatic hydrocarbon-induced carcinogenesis.

Antibacterial prenylflavone derivatives from Psoralea corylifolia, and their structure–activity relationship study

Three new prenylflavonoids, namely corylifols A-C (1-3), together with 13 known ones, were isolated from the seeds of Psoralea corylifolia. Their structures were elucidated by spectral methods including 1D and 2D NMR techniques. All the isolates were tested on antibacterial assays, and nine of them showed significant antibacterial activities against two pathogenic bacteria Staphylococcus aureus and S. epidermidis. The antibacterial structure-activity relationship of these prenylflavonoids (1-16) was also briefly discussed.

β-d-Glucoside Suppresses Tumor Necrosis Factor-induced Activation of Nuclear Transcription Factor κB but Potentiates Apoptosis

Mangiferin, a natural polyphenol is known to exhibit anti-inflammatory, antioxidant, and antiviral effects. However the molecular mechanism underlying these effects has not been well characterized. Because NF-kappaB plays an important role in these processes, it is possible that mangiferin modulates NF-kappaB activation. Our results show that mangiferin blocks tumor necrosis factor (TNF)-induced NF-kappaB activation and NF-kappaB-dependent genes like ICAM1 and COX2. The effect was mediated through inhibition of IKK activation and subsequent blocking of phosphorylation and degradation of IkappaBalpha. In addition, mangiferin inhibits TNF-induced p65 phosphorylation as well as translocation to the nucleus and also inhibits NF-kappaB activation induced by other inflammatory agents like PMA, ceramide, and SA-LPS. Mangiferin, similar to the other known antioxidants, NAC and PDTC, inhibits TNF-induced reactive oxygen intermediate (ROI) generation. Since intracellular glutathione (GSH) levels are known to modulate NF-kappaB levels, we measured the levels of GSH. Mangiferin enhances glutathione level by almost 2-fold more than other anti-oxidants, and at the same time it decreases the levels of GSSG and increases the activity of catalase. Depletion of GSH by buthionine sulfoximine led to a significant reversal of mangiferin effect. Hence mangiferin with its ability to inhibit NF-kappaB and increase the intracellular GSH levels may prove to be a potent drug for anti-inflammatory and antioxidant therapy. Mangiferin-mediated down-regulation of NF-kappaB also potentiates chemotherapeutic agent-mediated cell death, suggesting a role in combination therapy for cancer.

Immunomodulatory activity of curcumin: suppression of lymphocyte proliferation, development of cell-mediated cytotoxicity, and cytokine production in vitro

Curcumin (diferuloylmethane), a major curcumanoid found in the spice turmeric, exhibits anti-inflammatory, anti-oxidant, and chemopreventive activities. However, the effect of curcumin on the development of T cell-mediated immunological responses largely remains unknown. In this study we have investigated the effect of curcumin on mitogen/antigen induced proliferation of splenic lymphocytes, induction of cytotoxic T lymphocytes (CTLs), lymphokine activated killer (LAK) cells, and the production of cytokines by T lymphocytes and macrophages. We found that mitogen, interleukin-2 (IL-2) or alloantigen induced proliferation of splenic lymphocytes, and development of cytotoxic T lymphocytes is significantly suppressed at 12.5-30 micromol/L curcumin. The generation of LAK cells at similar concentrations was less sensitive to the suppressive effect of curcumin compared to the generation of antigen specific CTLs. Curcumin irreversibly impaired the production of these immune functions, since lymphoid cells failed to respond to the activation signals following 8h pretreatment with curcumin. Curcumin also inhibited the expression/production of IL-2 and interferon-gamma (IFN-gamma) by splenic T lymphocytes and IL-12 and tumor necrosis factor-alpha (TNF-alpha) by peritoneal macrophages irreversibly. Curcumin inhibited the activation of the transcription factor nuclear factor kappaB (NF-kappaB) without affecting the levels of constitutively expressed NF-kappaB. The latter result suggests that curcumin most likely inhibits cell proliferation, cell-mediated cytotoxicity (CMC), and cytokine production by inhibiting NF-kappaB target genes involved in induction of these immune responses.

Resveratrol-induced cellular apoptosis and cell cycle arrest in neuroblastoma cells and antitumor effects on neuroblastoma in mice

BACKGROUND

The prognosis of neuroblastoma patients remains unsatisfactory. Therefore, developing an effective treatment strategy is important. Resveratrol, a natural polyphenol, possesses chemopreventive and antitumor effects. We investigated the effects of resveratrol on the proliferation, apoptosis, and cell cycle alteration of neuroblastoma cells and determined its effects on neuroblastoma tumors in mice.

METHODS

Cytotoxic effects, cellular apoptosis, and alterations in the cell cycle were determined in neuro-2a neuroblastoma cells exposed for varying lengths of time to a series of resveratrol concentrations. Expression of associated cell cycle regulatory proteins, cyclin E and p21, was detected by Western blot analysis, and the antitumor effects of resveratrol were investigated by treating subcutaneous neuroblastoma tumors with intraperitoneal injections of 40 mg/kg resveratrol daily for 28 days.

RESULTS

Resveratrol exerted cytotoxic effects on neuroblastoma cells. After resveratrol treatment, the apoptosis rate of the neuroblastoma cells significantly increased, a significant accumulation of cells occurred at the S phase of the cell cycle, p21 was downregulated, and cyclin E was upregulated. In addition, resveratrol treatment suppressed the growth rate of subcutaneous neuroblastomas, resulting in 70% long-term survival.

CONCLUSION

Resveratrol caused significant cytotoxicity and increased apoptosis and S-phase accumulation of neuroblastoma cells. S-phase accumulation was related to the down-regulation of p21 and up-regulation of cyclin E. In addition, resveratrol exerted antitumor effects on neuroblastomas in mice. Thus, resveratrol shows promise for the treatment of neuroblastoma.

In vitro antitumour activity of resveratrol in human melanoma cells sensitive or resistant to temozolomide

Resveratrol, a polyphenol present in many plant species, exhibits a wide range of biological and pharmacological activities both in vitro and in vivo. It has been shown to exert a potent chemopreventive effect in carcinogenesis models and to induce cell growth inhibition and apoptosis in human tumour cells, including melanoma cells. Malignant melanoma is considered to be a chemotherapy-refractory tumour, and the commonly used anticancer drugs do not seem to modify the prognosis of metastatic disease. To further evaluate the therapeutic potential of resveratrol in the treatment of melanoma, we selected three human melanoma cell lines with different levels of resistance to temozolomide (TMZ), an antitumour triazene compound. The cell lines were subjected to resveratrol treatment and analysed for cell growth inhibition, cell cycle perturbation and apoptosis induction. We found that resveratrol markedly impaired proliferation of both the TMZ-sensitive M14 and the TMZ-resistant SK-Mel-28 and PR-Mel cell lines. The latter cell line was two-fold more resistant to the drug than M14 and SK-Mel-28 cells. The sensitivity of normal human keratinocytes to resveratrol was found to be significantly higher than that of M14 and SK-Mel-28 cells and similar to that of the PR-Mel cell line. This suggests a possible good in vivo therapeutic index for resveratrol. Our results also show that the growth-inhibitory effect of resveratrol on melanoma cells is mainly due to its ability to induce S-phase arrest and apoptosis. Taken together, our data indicate that resveratrol is an interesting candidate for the treatment of advanced melanoma.

The traditional diet of Greece and cancer

The term 'Mediterranean diet', implying that all Mediterranean people have the same diet, is a misnomer. The countries around the Mediterranean basin have different diets, religions and cultures. Their diets differ in the amount of total fat, olive oil, type of meat, wine, milk, cheese, fruits and vegetables; and the rates of coronary heart disease and cancer, with the lower death rates and longer life expectancy occurring in Greece. The diet of Crete represents the traditional diet of Greece prior to 1960. Analyses of the dietary pattern of the diet of Crete shows a number of protective substances, such as selenium, glutathione, a balanced ratio of n-6/n-3 essential fatty acids (EFA), high amounts of fibre, antioxidants (especially resveratrol from wine and polyphenols from olive oil), vitamins E and C, some of which have been shown to be associated with lower risk of cancer, including cancer of the breast. Epidemiological studies and animal experiments indicate that n-3 fatty acids exert protective effects against some common cancers, especially cancers of the breast, colon and prostate. Many mechanisms are involved, including suppression of neoplastic transformation, cell growth inhibition, and enhanced apoptosis and anti-angiogenicity, through the inhibition of eicosanoid production from n-6 fatty acids; and suppression of cyclooxygenase 2 (COX-2), interleukin 1 (IL-1) and IL-6 gene expression by n-3 fatty acids. Recent intervention studies in breast cancer patients indicate that n-3 fatty acids, and docosahexaenoic acid (DHA) in particular, increase the response to chemopreventive agents. In patients with colorectal cancer, eicosapentaenoic acid (EPA) and DHA decrease cell proliferation, and modulate favourably the balance between colonic cell proliferation and apoptosis. These findings should serve as a strong incentive for the initiation of intervention trials that will test the effect of specific dietary patterns in the prevention and management of patients with cancer.

Resveratrol Suppresses the Angiogenesis and Tumor Growth of Gliomas in Rats

PURPOSE

We wanted to investigate the antitumor effects and effect on angiogenesis of resveratrol in rat RT-2 gliomas.

EXPERIMENTAL DESIGN

RT-2 glioma cells were treated with resveratrol, and then cytotoxicity was assayed, apoptosis was measured by flow-activated cell sorter flow cytometry, and expression of vascular endothelial growth factor was measured by reverse transcription-PCR. Tumor size, animal survival time, and survival rate were followed in resveratrol-treated rats with s.c. or intracerebral gliomas. Furthermore, in vitro proliferation was assayed to explore the effect of resveratrol on the proliferation of ECV304 human umbilical vein endothelial cells. Expression of CD31 in resveratrol-treated gliomas was followed immunohistochemically to study the effect of resveratrol on the glioma-induced angiogenesis.

RESULTS

Resveratrol was demonstrated to exert cytotoxic effects and induce glioma cell apoptosis in a concentration- and time-dependent manner (P < 0.05). Resveratrol (40 mg/kg/day) exerted significant antitumor effects on s.c. tumors, including slower tumor growth rate, longer animal survival time, and higher animal survival rate (P < 0.05). In contrast, resveratrol affected intracerebral tumors at only an increased dose (100 mg/kg/day), prolonging animal survival (P < 0.05) without affecting survival rate. The expression of vascular endothelial growth factor in the glioma cells and the proliferation of ECV304 cells were inhibited by resveratrol in a concentration-dependent manner. Immunohistochemical analyses showed that the s.c. gliomas from resveratrol-treated rats had fewer microvessel densities than did control rats (P < 0.01).

CONCLUSIONS

Resveratrol caused significant glioma cell cytotoxicity and apoptosis, exerted antitumor effects on the s.c. and intracerebral gliomas, and inhibited angiogenesis in s.c. gliomas. Thus, resveratrol might be considered a possible treatment strategy for gliomas.

Immunomodulatory activity of resveratrol: discrepant in vitro and in vivo immunological effects

trans-Resveratrol is a dietary polyphenolic compound present in grapes, which has been shown to exhibit strong anti-inflammatory, antioxidant, and chemopreventive activities. In this study we have compared the in vitro and in vivo effects of resveratrol on the development of various cell-mediated immune responses, including mitogen/antigen-induced T cell proliferation, induction of cytotoxic T lymphocytes (CTLs), interleukin-2 (IL-2) induced lymphokine activated killer cells, and cytokine production. We found significant suppression (>90%) of the mitogen/antigen-induced T cell proliferation and development of allo-antigen specific CTLs in vitro with resveratrol at a concentration of 25 microM. Intragastric administration of resveratrol (2 mg daily) to mice for 4 weeks showed no effect on age-related gain in body weight, peripheral blood cell counts (WBC, RBC, or platelets), or the cellularity of bone marrow or spleen. The CD4(+) and CD8(+) T cells in spleen or colony-forming units-total in the marrow also remained unaffected by treatment with resveratrol. Spleen cells, which were stimulated in vitro after being removed from mice which had been administered resveratrol for 2 or 4 weeks, showed no significant change in IL-2 or concanavalin A induced proliferation of T cells or production of IL-2 induced lymphokine activated killer cells. Further, the production of in interferon-gamma and IL-12 was not affected by administration of resveratrol, but production of tumor necrosis factor-alpha was reduced. Even when conducted entirely in vivo, treatment with resveratrol was found to only marginally reduce allo-antigen induced T cell proliferation and the generation of CTLs in the draining lymph nodes. Thus, even though resveratrol strongly inhibits T cell proliferation and production of cytolytic cells in vitro, oral administration of resveratrol for 4 weeks does not induce hematologic or hematopoietic toxicity, and only marginally reduces the T cell-mediated immune responses.

Synergistic protection of PC12 cells from β-amyloid toxicity by resveratrol and catechin

beta-Amyloid peptide (beta-AP) elicits a toxic effect on neurons in vitro and in vivo. Many environmental factors including antioxidants, metal ions and proteoglycans modify beta-AP toxicity. We have investigated on PC12 cells, the protective effect from beta-AP (1-41) of two plant polyphenols, resveratrol and catechin. PC12 cells treated with 10(-6)M beta-AP (1-41) for 16h decrease the cell viability at 24% of the control with an IC(50) value of 1.1+/-0.14 x 10(-8)M. Twenty-five micromolar resveratrol and 50 microM catechin protect PC12 cells from beta-AP (1-41) toxicity with the IC(50) value increased at 2.2+/-0.19 x 10(-7)M and at 8.9+/-0.7 x 10(-8)M, respectively. While the protective effect is concentration dependent for catechin, resveratrol shows a concentration-dependent biphasic effect. Up to 50 microM concentration, resveratrol protects PC12 cells from beta-AP (1-41) toxicity. At concentration higher than 50 microM, an inhibitory activity on cell proliferation appears. This antiproliferative effect is shown also in the absence of beta-AP (1-41). Resveratrol and catechin have a synergistic protective action. In the presence of 50 microM catechin and 10 microM resveratrol or 25 microM resveratrol and 10 microM catechin, the toxicity determined by 10(-7)M beta-AP (1-41) is almost completely abolished. Catechin is more effective than resveratrol in protecting PC12 cells from the toxicity of hydrogen peroxide. The protection from Oxygen Reactive Species (ROS) toxicity is concentration dependent for both resveratrol and catechin. In this case the protection is merely additive and the synergistic effect is not observed. These results demonstrate that resveratrol and catechin protect PC12 cells from beta-AP (1-41) toxicity and that their protective effect is synergistic. Such a protective effect probably is not due only to their antioxidant activity. The different chemical and biological activity shown by these compounds on several cell types and the complexity of the beta-AP (1-41) toxicity may explain the synergistic protective effect and suggest that the utilization of different compounds with synergistic activity may protect more effectively from complex mechanisms of toxicity.

Resveratrol blocks interleukin-1beta-induced activation of the nuclear transcription factor NF-kappaB, inhibits proliferation, causes S-phase arrest, and induces apoptosis of acute myeloid leukemia cells

Resveratrol, an edible polyphenolic stilbene, has been reported to possess substantial antileukemic activities in different leukemia cell lines. We investigated whether resveratrol is active against fresh acute myeloid leukemia (AML) cells and its mechanism of action. Because interleukin 1beta(IL-1beta) plays a key role in proliferation of AML cells, we first tested the effect of resveratrol on the AML cell lines OCIM2 and OCI/AML3, both of which produce IL-1beta and proliferate in response to it. Resveratrol inhibited proliferation of both cell lines in a dose-dependent fashion (5-75 microM) by arresting the cells at S phase, thus preventing their progression through the cell cycle; IL-1beta partially reversed this inhibitory effect. Resveratrol significantly reduced production of IL-1beta in OCIM2 cells. It also suppressed the IL-1beta-induced activation of transcription factor nuclear factor kappaB (NF-kappaB), which modulates an array of signals controlling cellular survival, proliferation, and cytokine production. Indeed, incubation of OCIM2 cells with resveratrol resulted in apoptotic cell death. Because caspase inhibitors Ac-DEVD-CHO or z-DEVD-FMK partially reversed the antiproliferative effect of resveratrol, we tested its effect on the caspase pathway and found that resveratrol induced the activation of the cysteine protease caspase 3 and subsequent cleavage of the DNA repair enzyme poly (adenosine diphosphate [ADP]-ribose) polymerase. Finally, resveratrol suppressed colony-forming cell proliferation of fresh AML marrow cells from 5 patients with newly diagnosed AML in a dose-dependent fashion. Taken together, our data showing that resveratrol is an effective in vitro inhibitor of AML cells suggest that this compound may have a role in future therapies for AML.

Resveratrol increases BRCA1 and BRCA2 mRNA expression in breast tumour cell lines

The phytochemical resveratrol, found in grapes, berries and peanuts, has been found to possess cancer chemopreventive effects by inhibiting diverse cellular events associated with tumour initiation, promotion and progression. Resveratrol is also a phyto-oestrogen, binds to and activates oestrogen receptors that regulate the transcription of oestrogen-responsive target genes such as the breast cancer susceptibility genes BRCA1 and BRCA2. We investigated the effects of resveratrol on BRCA1 and BRCA2 expression in human breast cancer cell lines (MCF7, HBL 100 and MDA-MB 231) using quantitative real-time RT-PCR, and by perfusion chromatography of the proteins. All cell lines were treated with 30 microM resveratrol. The expressions of BRCA1 and BRCA2 mRNAs were increased although no change in the expression of the proteins were found. These data indicate that resveratrol at 30 micro M can increase expression of genes involved in the aggressiveness of human breast tumour cell lines.

p21Cip1 gene expression is modulated by Egr1: a novel regulatory mechanism involved in the resveratrol antiproliferative effect

Epidemiological observations indicate that resveratrol, a natural antioxidant stilbene, exerts cardioprotective and chemopreventive effects. Moreover, the molecule induces in vitro cell growth inhibition and differentiation. Using human erythroleukemic K562 cells as model system, we demonstrated that resveratrol induces a remarkable gamma-globin synthesis, the erythroid differentiation being linked to impairment of cell proliferation, increased p21Cip1 expression and inhibition of cdk2 activity. The up-regulation of p21Cip1 transcription is prevented by cycloheximide, indicating the requirement of intermediate protein(s), which, in turn, regulate gene expression. The quantitative analysis of some transcription factors involved in the erythroid lineage, namely GATA-1, GATA-2, and Egr1, indicated that resveratrol selectively up-regulates Egr1 by an Erk1/2-dependent mechanism. The presence of an Egr1 consensus sequence in the p21Cip1 promoter suggested the hypothesis that this transcription factor directly regulates the expression of the cdk inhibitor. Transfection studies with deleted gene promoter constructs, as well as EMSA, pull-down, and chromatin immunoprecipitation experiments substantiated this view, demonstrating that Egr1 binds in vitro and in vivo to the identified consensus sequence of the p21Cip1 promoter. Moreover, an Egr1 phosphorothioate antisense hinders p21Cip1 accumulation and the antiproliferative effects of resveratrol. In conclusion, this is the first demonstration that Egr1 controls p21Cip1 expression by directly interacting with a specific sequence on its gene promoter. The identified regulatory mechanism also contributes to the clarification of the complex chemopreventive and antiproliferative properties of resveratrol.

Cell-transforming activity and mutagenicity of 5 phytoestrogens in cultured mammalian cells

For the simultaneous assessment of in vitro carcinogenicity and mutagenicity of phytoestrogens, the abilities of 5 phytoestrogens, daidzein, genistein, biochanin A, prunetin, and coumestrol, to induce cell transformation and genetic effects were examined using the Syrian hamster embryo (SHE) cell model. Cellular growth was inhibited by all phytoestrogens in a concentration-related manner. The growth inhibitory effect of the compounds was ranked: genistein, prunetin > coumestrol > biochanin A > daidzein, which did not correspond to their apoptosis-inducing abilities. Morphological transformation in SHE cells was elicited by all phytoestrogens, except, prunetin. The transforming activities were ranked as follows: genistein > coumestrol > daidzein > biochanin A. Somatic mutations in SHE cells at the Na(+)/K(+) ATPase and hprt loci were induced only by genistein, coumestrol, or daidzein. Chromosome aberrations were induced by genistein or coumestrol, and aneuploidy in the near diploid range was occurred by genistein or biochanin A. Genistein, biochanin A or daidzein induced DNA adduct formation in SHE cells with the abilities: genistein > biochanin A > daidzein. Prunetin was negative for any of these genetic endpoints. Our results provide evidence that genistein, coumestrol, daidzein and biochanin A induce cell transformation in SHE cells and that the transforming activities of these phytoestrogens correspond to at least 2 of the mutagenic effects by each phytoestrogen, i.e., gene mutations, chromosome aberrations, aneuploidy or DNA adduct formation, suggesting the possible involvement of mutagenicity in the initiation of phytoestrogen-induced carcinogenesis.

Inhibition of DNA polymerases and DNA topoisomerase II by triterpenes produced by plant callus

We found that some triterpene compounds could not only selectively inhibit the activities of mammalian DNA polymerase alpha (pol alpha) and beta (pol beta), but could also potently inhibit DNA topoisomerase II (topo II) [Biochem. J. 350 (2000) 757]. Here, we report that natural triterpenes produced by callus from an ancient Chinese medicinal plant were also inhibitors of the enzymes, and some were more selective than others. The natural triterpenes with a carboxyl group equally inhibited the activities of pol alpha, pol beta, and topo II, while the olide-type triterpenes with a ketone group suppressed the activities of pol beta and topo II, but not pol alpha. The other triterpenes from the callus hardly influenced these enzyme activities. As also described previously [J. Biochem. 130 (2001) 657], pol beta and topo II have a three-dimensionally similar triterpene-binding region, which is a pocket in which specific compounds can insert. The newly found triterpene inhibitors might structure-dependently insert into the pocket, and the pocket structure of each enzyme might, three-dimensionally but slightly, differ among them. The triterpene frames could be used for screening new inhibitors of the enzymes, and computer-simulated drug design using the frame and pocket structure may in theory be a possible approach to develop new inhibitors.

Ethanolic extracts of Euphorbia and other ethnobotanical species as inhibitors of human tumour cell growth

Ethanolic extracts of 20 plant species, selected from the ethnobotanical literature, were analysed for their pharmacological potential as antineoplastic agents against the HEp-2 cell line. Psoralea corylifolia and E. grandidens were the most efficacious species eliciting IC50 values of 22 microg/ml and 57 microg/ml respectively. Psoralea corylifolia, additionally tested against lung carcinoma (A549) cells gave an IC50 value of 68 microg/ml. Such data would justify a search for active compounds from this species.

Resveratrol--a prostate cancer chemopreventive agent?

The incidence of prostate cancer in Western countries continues to rise. Whilst opinion remains divided on the best treatment for localized disease, intervention for metastatic, hormone-independent cancer remains extremely limited. The concept of chemoprevention is gaining popularity as an effective means of reducing the burden of prostate cancer on the population, and many compounds with putative chemopreventive activity are currently under investigation. Resveratrol is a plant-derived polyphenolic compound which has a wide spectrum of biological activity. It has anti-oxidant and anti-inflammatory properties, and may induce apoptosis as well as modulate the function of the androgen receptor in prostate cancer cell lines. Further studies to evaluate the use of this compound as a chemopreventive agent in prostate cancer are warranted.

Role of Bax in resveratrol-induced apoptosis of colorectal carcinoma cells

BACKGROUND

The natural plant polyphenol resveratrol present in some foods including grapes, wine, and peanuts, has been implicated in the inhibition, delay, and reversion of cellular events associated with heart diseases and tumorigenesis. Recent work has suggested that the cancer chemoprotective effect of the compound is primarily linked to its ability to induce cell division cycle arrest and apoptosis, the latter possibly through the activation of pro-apoptotic proteins such as Bax.

METHODS

The expression, subcellular localization, and importance of Bax for resveratrol-provoked apoptosis were assessed in human HCT116 colon carcinoma cells and derivatives with both bax alleles inactivated.

RESULTS

Low to moderate concentrations of resveratrol induced co-localization of cellular Bax protein with mitochondria, collapse of the mitochondrial membrane potential, activation of caspases 3 and 9, and finally, apoptosis. In the absence of Bax, membrane potential collapse was delayed, and apoptosis was reduced but not absent. Resveratrol inhibited the formation of colonies by both HCT116 and HCT116 bax -/- cells.

CONCLUSION

Resveratrol at physiological doses can induce a Bax-mediated and a Bax-independent mitochondrial apoptosis. Both can limit the ability of the cells to form colonies.

Potential antifilarial activity of the leaves and seeds extracts of Psoralea corylifolia on cattle filarial parasite Setaria cervi

The effect of aqueous and alcohol extracts of the leaves and seeds of Psoralea corylifolia, on the spontaneous movements of both the whole worm and the nerve muscle preparation of Setaria cervi and on the survival of microfilariae in vitro was studied. Alcohol extracts of both leaves and seeds caused the inhibition of spontaneous movements of the whole worm and the nerve muscle preparation of S. cervi, characterised by initial, short lasting small increase in tone of contractions followed by paralysis. The initial stimulatory effect was not observed by alcohol extract of leaves on nerve muscle preparation. The concentrations required to inhibit the movements of whole worm and nerve muscle preparations for alcohol extracts of leaves and seeds were 160, 30, and 150, 20 microg/ml, respectively suggesting a cuticular permeability barrier. Alcohol extracts of both leaves and seeds caused death of microfilariae in vitro, LC(50) and LC(90) being 15 and 25 ng/ml for alcohol extract of leaves and 12 and 18 ng/ml for alcohol extract of seeds, respectively.

Inhibition of cancer growth by resveratrol is related to its low bioavailability

The relationship between resveratrol (RES) bioavalability and its effect on tumor growth was investigated. Tissue levels of RES were studied after i.v. and oral administration of trans-resveratrol (t-RES) to rabbits, rats, and mice. Half-life of RES in plasma, after i.v. administration of 20 mg t-RES/kg b.wt., was very short (e.g., 14.4 min in rabbits). The highest concentration of RES in plasma, either after i.v. or oral administration (e.g., 2.6 +/- 1.0 microM in mice 2.5 min after receiving 20 mg t-RES/kg orally), was reached within the first 5 min in all animals studied. Extravascular levels (brain, lung, liver, and kidney) of RES, which paralleled those in plasma, were always < 1 nmol/g fresh tissue. RES measured in plasma or tissues was in the trans form (at least 99%). Hepatocytes metabolized t-RES in a dose-dependent fashion (e.g., 43 nmol of t-RES/g x min in the presence of 20 microM tRES), which means that the liver can remove circulating RES very rapidly. In vitro B16 melanoma (B16M) cell proliferation and generation of reactive oxygen species (ROS) was inhibited by t-RES in a concentration-dependent fashion (100% inhibition of tumor growth was found in the presence of 5 microM t-RES). Addition of 10 microM H(2)O(2) to B16M cells, cultured in the presence of 5 microM t-RES, reactivated cell growth. Oral administration of t-RES (20 mg/kg twice per day; or included in the drinking water at 23 mg/l) did not inhibit growth of B16M inoculated into the footpad of mice (solid growth). However, oral administration of t-RES (as above) decreased hepatic metastatic invasion of B16M cells inoculated intrasplenically. The antimetastatic mechanism involves a t-RES (1 microM)-induced inhibition of vascular adhesion molecule 1 (VCAM-1) expression in the hepatic sinusoidal endothelium (HSE), which consequently decreased in vitro B16M cell adhesion to the endothelium via very late activation antigen 4 (VLA-4).

Resveratrol enhances the differentiation induced by butyrate in caco-2 colon cancer cells

Butyrate, a short-chain fatty acid produced in the colon by microbial fermentation of fiber, inhibits growth of colonic carcinoma cells while inducing differentiation. Resveratrol, a plant polyphenol found in red wine and peanuts, has been shown to exert chemopreventive properties on colon cancer cells. The aim of this study was to determine whether resveratrol modulates the effects of butyrate on Caco-2, a colonic adenocarcinoma cell line. The growth inhibitory effect of resveratrol (50 micromol/L) was more powerful than that of butyrate (2 mmol/L). Butyrate did not intensify the inhibition of proliferation exerted by resveratrol. Although the polyphenol enhanced the differentiation-inducing effect of butyrate, it did not elevate alkaline phosphatase activity or E-cadherin protein expression, markers of epithelial differentiation, when applied alone. Butyrate-induced transforming growth factor-beta1 secretion was inhibited by resveratrol. Treatment with the combination of resveratrol and butyrate attenuated levels of p27(Kip1), whereas resveratrol enhanced butyrate's effect on the induction of p21(Waf1/Cip1) expression. These data demonstrate a possible combined chemopreventive effect of two substances naturally occurring in the colonic lumen after ingestion of fibers and resveratrol-containing food.

Disparate in vitro and in vivo antileukemic effects of resveratrol, a natural polyphenolic compound found in grapes

Resveratrol (trans-3,4',5-trihydroxystilbene), a polyphenol found in grapes and grape wine, has been reported to exhibit cardioprotective and chemopreventive activity against chemical carcinogenesis. It has also been shown to have growth inhibitory activity toward solid tumors in vivo. However, the antitumor activity of resveratrol against hematologic tumors in vivo has not been examined. In this study, the antileukemic activity of resveratrol in vitro and in vivo was examined using a mouse myeloid leukemia cell line (32Dp210). Treatment of 32Dp210 leukemia cells with resveratrol at micromolar concentrations (25-50 micromol/L) significantly and irreversibly inhibited their clonal growth in vitro. The clonal growth inhibition by resveratrol was associated with extensive cell death and an increase in hypodiploid (sub-G1) cells. Resveratol caused internucleosomal DNA fragmentation, suggesting apoptosis as the mode of cell death in 32Dp210 cells. DNA fragmentation was associated with activation of caspase-3, because cleavage of procaspase-3 was detected in resveratrol-treated cells. Although 32Dp210 cells treated with resveratrol in vitro did not produce leukemia in vivo, only a weak antileukemic effect of resveratrol was observed when administered orally. At doses of 8 mg or 40 mg/kg body daily, five times/wk, resveratrol did not affect the survival of mice injected with leukemia cells. Weak potential antileukemic activity of resveratrol was suggested only at a dose of 80 mg/kg body (2 survivors of 14 mice treated). Thus, despite strong antiproliferative and proapoptotic activities of resveratrol against 32Dp210 cells in vitro, a potential antileukemia effect in vivo, if present, occurs only in a small fraction of mice.

Gonadal toxicity of an ethanol extract of Psoralea corylifolia in a rat 90-day repeated dose study

Ethanol extracts of seeds of Psoralea corylifolia are proposed as food additives for processed food preservation. An extract was administered by admixing into diet at concentrations of 0, 0.375, 0.75, 1.5 or 3.0% to 10 male and 10 female F344 rats each for 90 days to evaluate its toxicity. Body weight gain, food consumption and food conversion efficiency (body weight gain per food consumption) were lower in the extract-treated animals, except for the 0.375% males, as compared to the control animals. Absolute and/or relative testes weights in the 1.5 and 3.0% groups and those of ovaries in the 3.0% group were significantly (p < 0.01) lower than in the control group. On histopathological examination, seminiferous tubular atrophy and Leydig cell atrophy in the testes, and epithelial cell atrophy in the seminal vesicles and prostate were observed in the 1.5 and 3.0% males. Decrease in the number of corpora lutea associated with frequent necrotic follicles in the ovaries in the 1.5 and 3.0% females and less frequent endometrial glands in the uterus in the 3.0% females were also detected. These results might suggest disruption of the hypothalamus-pituitary-gonadal axis in Psoralea corylifolia-treated rats as possible mechanisms underlying this gonadal toxicity.

Cancer chemopreventive activity of resveratrol

Cancer chemopreventive agents are designed to reduce the incidence of tumorigenesis by intervening at one or more stages of carcinogenesis. Recently, resveratrol, a natural product found in the diet of humans, has been shown to function as a cancer chemopreventive agent. Resveratrol was first shown to act as an antioxidant and antimutagenic agent, thus acting as an anti-initiation agent. Further evidence indicated that resveratrol selectively suppresses the transcriptional activation of cytochrome P-450 1A1 and inhibits the formation of carcinogen-induced preneoplastic lesions in a mouse mammary organ culture model. Resveratrol also inhibits the formation of 12-O-tetradecanoylphorbol-13-acetate (TPA)-promoted mouse skin tumors in the two-stage model. The enzymatic activities of COX-1 and -2 are inhibited by resveratrol in cell-free models, and COX-2 mRNA and TPA-induced activation of protein kinase C and AP-1-mediated gene expression are suppressed by resveratrol in mammary epithelial cells. In addition, resveratrol strongly inhibits nitric oxide generation and inducible nitric oxide synthase protein expression. NF kappa B is strongly linked to inflammatory and immune responses and is associated with oncogenesis in certain models of cancer, and resveratrol suppresses the induction of this transcription factor by a number of agents. The mechanism may involve decreasing the phosphorylation and degradation of I kappa B alpha. At the cellular level, resveratrol also induces apoptosis, cell cycle delay or a block in the G(1) --> S transition phase in a number of cell lines. Thus, resveratrol holds great promise for future development as a chemopreventive agent that may be useful for several disorders. Preclinical toxicity studies are underway that should be followed by human clinical trials.