Treatment of metastatic melanoma B16F10 by the flavonoids tangeretin, rutin, and diosmin

Tangeretin enhances radiosensitivity and inhibits the radiation-induced epithelial-mesenchymal transition of gastric cancer cells

Irradiation has been reported to increase radioresistance and epithelial-mesenchymal transition (EMT) in gastric cancer (GC) cells. The Notch pathway is critically implicated in cancer EMT and radioresistance. In the present study, we investigated the use of a Notch-1 inhibiting compound as a novel therapeutic candidate to regulate radiation-induced EMT in GC cells. According to previous screening, tangeretin, a polymethoxylated flavonoid from citrus fruits was selected as a Notch-1 inhibitor. Tangeretin enhanced the radiosensitivity of GC cells as demonstrated by MTT and colony formation assays. Tangeretin also attenuated radiation-induced EMT, invasion and migration in GC cells, accompanied by a decrease in Notch-1, Jagged1/2, Hey-1 and Hes-1 expressions. Tangeretin triggered the upregulation of miR-410, a tumor-suppressive microRNA. Furthermore, re-expression of miR-410 prevented radiation-induced EMT and cell invasion. An in vivo tumor xenograft model confirmed the antimetastasis effect of tangeretin as we observed in vitro. In nude mice, tumor size was considerably diminished by radiation plus tangeretin co-treatment. Tangeretin almost completely inhibited lung metastasis induced by irradiation. Tangeretin may be a novel antimetastatic agent for radiotherapy.

Unzipped carbon nanotubes: analytical and binding applications of semisynthetic phlebotropic flavonoid, diosmin

Present study describes the utility of unzipped carbon nanotubes as electrochemical sensing platform for the determination of diosmin in pharmaceutical formulations and for the investigation of its binding to human serum albumin.

Rutin exerts antitumor effects on nude mice bearing SW480 tumor

BACKGROUND AND AIMS

We previously showed that extracts from Phoradendron serotinum and Croton lechleri exerted in vitro cytotoxic and in vivo antitumor effects and that their main component was rutin (RTN; 3-rhamnosyl-glucosylquercetin). However, it is unknown whether RTN exerts in vivo antitumoral effects on human colon cancer cells. The aim of this work was to evaluate the antitumor effects of RTN on a murine model.

METHODS

Cytotoxic effects of RTN on human cancer and non-tumorigenic cell lines were evaluated using the MTT assay. Different doses of RTN were injected intraperitoneally daily into nu/nu mice bearing tumors of SW480 colon cancer cells during 32 days. The growth and weight of tumors were measured. Serum levels of VEGF, survival time, increase in life span and toxicological effects on body weight and organ weight were also analyzed.

RESULTS

RTN showed the highest cytotoxic effects against SW480 cells (IC₅₀ = 125 μM) as compared to the other cancer cells lines and decreased, in a dose dependent manner, the tumor volume and weight of mice bearing SW480 tumor. RTN 20 mg/kg, the highest dose tested, lacked toxic effects on body weight and relative organ weight in mice, increased mean survival time by 50 days, and decreased by 55% the VEGF serum levels compared to untreated mice.

CONCLUSIONS

RTN exerts in vitro cytotoxic effects on SW480 cells, induces in vivo antitumor effects, lacks toxic effects on mice bearing SW480 tumor and exerts antiangiogenic properties.

Cloning, characterization, and activity analysis of a flavonol synthase gene FtFLS1 and its association with flavonoid content in tartary buckwheat

Evidence from in vitro and in vivo studies indicates that rutin, the main flavonoid in tartary buckwheat ( Fagopyrum tataricum ), may have high value for medicine and health. This paper reports the finding of a flavonol synthase (FLS) gene, cloned and characterized from F. tataricum and designated FtFLS1, that is involved in rutin biosynthesis. The FtFLS1 gene was expressed in Escherichia coli BL21(DE3), and the recombinant soluble FtFLS1 protein had a relative molecular mass of 40 kDa. The purified recombinant protein showed, with dihydroquercetin as substrate, total and specific activities of 36.55 × 10(-3) IU and 18.94 × 10(-3) IU/mg, respectively, whereas the total and specific activities were 10.19 × 10(-3) IU and 5.28 × 10(-3) IU/mg, respectively, with dihydrokaempferol. RT-PCR revealed that during F. tataricum florescence there was an organ-specific expression pattern by the FtFLS1 gene, with similar trends in flavonoid content. These observations suggest that FtFLS1 in F. tataricum encodes a functional protein, which might play a key role in rutin biosynthesis.

Natural polyphenols in cancer therapy

Natural polyphenols are secondary metabolites of plants involved in defense against different types of stress. Extracts containing these compounds have been used for thousands of years in traditional eastern medicine. Polyphenols act on multiple targets in pathways and mechanisms related to carcinogenesis, tumor cell proliferation and death, inflammation, metastatic spread, angiogenesis, or drug and radiation resistance. Nevertheless, reported effects claimed for polyphenols are controversial, since correlations between in vitro effects and in vivo evidence are poorly established. The main discrepancy between health claims versus clinical observations is the frequent use of nonphysiologically relevant concentrations of these compounds and their metabolites in efficacy and mechanistic studies. The present review will discuss how in vivo administration correlates with polyphenol metabolism, toxicity, and bioavailability. Analysis of the general application of polyphenols in cancer therapy will be complemented by potential applications in the therapy of specific tumors, including melanoma, colorectal and lung cancers. Possible pharmaceutical formulations, structural modifications, combinations, and delivery systems aimed to increase bioavailability and/or biological effects will be discussed. Final remarks will include recommendations for future research and developments.

Enzymatic Synthesis of the Flavone Glucosides, Prunin and Isoquercetin, and the Aglycones, Naringenin and Quercetin, with Selective α-L-Rhamnosidase and β-D-Glucosidase Activities of Naringinase

The production of flavonoid glycosides by removing rhamnose from rutinosides can be accomplished through enzymatic catalysis. Naringinase is an enzyme complex, expressing both α-L-rhamnosidase and β-D-glucosidase activities, with application in glycosides hydrolysis. To produce monoglycosylated flavonoids with naringinase, the expression of β-D-glucosidase activity is not desirable leading to the need of expensive methods for α-L-rhamnosidase purification. Therefore, the main purpose of this study was the inactivation of β-D-glucosidase activity expressed by naringinase keeping α-L-rhamnosidase with a high retention activity. Response surface methodology (RSM) was used to evaluate the effects of temperature and pH on β-D-glucosidase inactivation. A selective inactivation of β-D-glucosidase activity of naringinase was achieved at 81.5°C and pH 3.9, keeping a very high residual activity of α-L-rhamnosidase (78%). This was a crucial achievement towards an easy and cheap production method of very expensive flavonoids, like prunin and isoquercetin starting from naringin and rutin, respectively.

Chemical genoprotection: reducing biological damage to as low as reasonably achievable levels

OBJECTIVES

The aim of this study was to evaluate the antioxidant substances present in the human diet with an antimutagenic protective capacity against genotoxic damage induced by exposure to X-rays in an attempt to reduce biological damage to as low a level as reasonably possible.

METHODS

Ten compounds were assessed using the lymphocyte cytokinesis-block micronucleus (MN) cytome test. The compounds studied were added to human blood at 25 μM 5 min before exposure to irradiation by 2 Gy of X-rays.

RESULTS

The protective capacity of the antioxidant substances assessed was from highest to lowest according to the frequency of the MN generated by X-ray exposure: rosmarinic acid = carnosic acid = δ-tocopherol = l-acid ascorbic = apigenin = amifostine (P < 0.001) > green tea extract = diosmine = rutin = dimetylsulfoxide (P < 0.05) > irradiated control. The reduction in genotoxic damage with the radiation doses administered reached 58%, which represents a significant reduction in X-ray-induced chromosomal damage (P < 0.001). This degree of protection is greater than that obtained with amifostine, a radioprotective compound used in radiotherapy and which is characterised by its high toxicity.

CONCLUSION

Several antioxidant substances, common components of the human diet and lacking toxicity, offer protection from the biological harm induced by ionizing radiation. Administering these protective substances to patients before radiological exploration should be considered, even in the case of small radiation doses and regardless of the biological damage expected.

Induction of G1 arrest and apoptosis in androgen-dependent human prostate cancer by Kuguacin J, a triterpenoid from Momordica charantia leaf

In this study, we focused on the effects of a bitter melon (Momordica charantia) leaf extract (BMLE) and a purified component, Kuguacin J (KuJ), on androgen-dependent LNCaP human prostate cancer cells. Both treatments exerted growth inhibition through G1 arrest and induction of apoptosis. In addition, KuJ markedly decreased the levels of cyclins (D1 and E), cyclin-dependent kinases (Cdk2 and Cdk4) and proliferating cell nuclear antigen, and caused an increase in p21 and p27 levels. Its induction of apoptosis was accompanied by an increase in cleavage of caspase-3 and poly (ADP-ribose) polymerase, attributable to augment of Bax/Bcl-2 and Bad/Bcl-xL and reduction of survivin levels. BMLE and KuJ also reduced the expression of androgen receptor (AR), prostate-specific antigen (PSA) while induced P53 protein level. Down-regulation of p53 by RNA interference indicated that BMLE and KuJ inhibited cell growth partly through p53-dependent cell cycle arrest and apoptotic pathways. Both BMLE and KuJ caused less toxicity in a normal prostate cell line, PNT1A. Our results suggest that BMLE and a purified component, KuJ, from its diethyl ether fraction could be promising candidate new antineoplastic and chemopreventive agents for androgen-dependent prostate cancer and carcinogenesis.

Tangeretin reduces ultraviolet B (UVB)-induced cyclooxygenase-2 expression in mouse epidermal cells by blocking mitogen-activated protein kinase (MAPK) activation and reactive oxygen species (ROS) generation

The present study examined the effects of tangeretin, a polymethoxylated flavonone present in citrus fruits, on ultraviolet B (UVB)-induced cyclooxygenase-2 (COX-2) expression in JB6 P+ mouse skin epidermal cells. Tangeretin suppressed UVB-induced COX-2 expression and transactivation of nuclear factor-κB and activator protein-1 in JB6 P+ cells. Moreover, tangeretin blocked UVB-induced phosphorylation of Akt and mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated protein kinase, c-Jun N-terminal kinase, and p38, and attenuated the phosphorylation of MAPK kinases 1/2, 3/6, and 4. Tangeretin also limited the endogenous generation of reactive oxygen species (ROS), thereby protecting the cells against oxidative stress. However, tangeretin did not scavenge the stable 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and influence the nicotinamide adenine dinucleotide phosphate oxidase activity. These results suggest that the anti-inflammatory effects of tangeretin stem from its modulation of cell signaling and suppression of intracellular ROS generation. Tangeretin may have a potent chemopreventive effect in skin cancer.

Momordica charantia leaf extract suppresses rat prostate cancer progression in vitro and in vivo

Cancer metastasis is a major cause of death in cancer patients, with invasion as a first step greatly contributing to the failure of clinical treatments. Any compounds with an inhibitory influence on this process are therefore of prime interest. Momordica charantia (bitter melon) is widely consumed as a vegetable and especially as a folk medicine in Asia. Here, we investigated the anti-invasive effects of bitter melon leaf extract (BMLE) on a rat prostate cancer cell line (PLS10) in vitro and in vivo. The results indicated that non-toxic concentrations of BMLE significantly inhibited the migration and invasion of cells in vitro. The results of zymography showed that BMLE inhibited the secretion of MMP-2, MMP-9 and urokinase plasminogen activator (uPA) from PLS10. Real-time RT-PCR revealed that BMLE not only significantly decreased gene expression of MMP-2 and MMP-9, but also markedly increased the mRNA level of TIMP-2, known to have inhibitory effects on the activity of MMP-2. An EnzChek gelatinase/collagenase assay showed that collagenase type IV activity was partially inhibited by BMLE. In the in vivo study, intravenous inoculation of PLS10 to nude mice resulted in a 100% survival rate in the mice given a BMLE-diet as compared with 80% in the controls. The incidence of lung metastasis did not show any difference, but the percentage lung area occupied by metastatic lesions was slightly decreased in the 0.1% BMLE treatment group and significantly decreased with 1% BMLE treatment as compared with the control. Thus, the results indicate for the first time an anti-metastatic effect of BMLE both in vitro and in vivo.

Liposoluble antioxidants provide an effective radioprotective barrier

Ionising radiation causes the massive generation of reactive oxygen species and induces cellular DNA damage. The antioxidant, protective effects of several compounds against gamma-ray-induced chromosomal damage were determined by the micronucleus test, evaluating the reduction in the frequency of micronuclei in cytokinesis-blocked human lymphocytes. The compounds studied were added to human blood at 25 microM, 5 min before or after irradiation with 2 Gy of caesium-137. The results suggest that different protective mechanisms are operating in each case. When the phenolic compounds are added before gamma-irradiation, their protective antimutagenic activity is based on their scavenging capacity against superoxide anion (O(2)(.-)) and, especially, hydroxyl radical ((.)OH), regardless of whether they are oil- or water-soluble compounds. When the phenolic compounds are added after gamma-irradiation treatment, the protective effect relies on activity against reactive oxygen species present in cells, i.e. lipoperoxy radicals (R(-)OO(.)), which are mainly responsible for continuous chromosomal oxidative damage. In addition, ionising radiation enhances lysosomal enzyme secretion and arachidonate release from membranes through lipo-oxygenase, cyclo-oxygenase and phospholipase activities, thus increasing the inflammatory cell response. Only oil-soluble compounds, such as carnosic acid, carnosol and delta-tocopherol, provide a significant protective antimutagenic activity. The most powerful water-soluble antioxidants lack the capacity to protect against gamma-ray-induced damage. The difference between anti-radical and anti-lipoperoxidant activities could explain the different behaviour of the compounds tested in terms of protecting against the lipid peroxidative processes. This anti-lipoperoxidant activity depends on several factors, but it is clear that only the lipo-antioxidants are effective in protecting human cells against oxidative damage, even when administered after exposure to ionising radiation.

Tyrosinase inhibitory effects and inhibition mechanisms of nobiletin and hesperidin from citrus peel crude extracts

The inhibitory effects of nobiletin and hesperidin from citrus peel crude extracts on tyrosinase diphenolase activity have been evaluated. IC50 of nobiletin and hesperidin were 1.49 mM and 16.08 mM, respectively and their inhibition mechanisms are competitive type with inhibition constant (Ki) 2.82 mM and noncompetitive type with Ki 9.16 mM, respectively. Crude extracts from citrus peel (C. unshiu Marc.) were extracted with 95% ethanol and fractionated by petroleum ether (PCPE). The ethanol phase (ECPE) was further desorbed from macroporous adsorption resin (FGRE). Their IC50 values were 8.09 mg/mL, 7.53 mg/mL and 4.80 mg/mL, respectively. Their inhibition of melanogenesis in B16 mouse melanoma cells was also evaluated. FGRE showed a significant inhibition (42.48% at 31.25 microg/mL, p < 0.01) while hesperidin showed almost no inhibition. Nobiletin and PCPE gave efficacious antiproliferation effects on the B16 mouse melanoma cell with IC50 values 88.6 microM and 62.96 microg/mL, respectively, through the MTT test. Hesperidin and other crude extracts showed very low cytotoxity to the B16 cell.

Tyrosinase inhibitory effects and inhibition mechanisms of nobiletin and hesperidin from citrus peel crude extracts

The inhibitory effects of nobiletin and hesperidin from citrus peel crude extracts on tyrosinase diphenolase activity are evaluated. IC50 of nobiletin and hesperidin is 1.49 mM and 16.08mM, respectively and their inhibition mechanism is competitive type with Ki = 2.82 mM and noncompetitive with Ki = 9.16 mM, respectively. Crude extracts from citrus peel (C. unshiu Marc.) were extracted with 95% ethanol and fractionated by petroleum ether (PCPE). The ethanol phase (ECPE) was further desorbed from macroporous adsorption resin (FGRE). Their IC50 values were 8.09 mg/mL, 7.53 mg/mL and 4.80 mg/mL, respectively. Their inhibition on melanogenesis in B16 mouse melanoma cells was also evaluated. FGRE showed a significant inhibition (42.5% at 31.25 microg/mL, p < 0.01) while hesperidin showed almost no inhibition. Nobiletin and PCPE give efficacious antiproliferation effects on B16 mouse melanoma cell with IC50 values 88.6 microM and 62.96 microg/mL, respectively, by the MTT test. Hesperidin and other crude extracts showed very low cytotoxity to the B16 cell.

Methoxyflavones protect cells against endoplasmic reticulum stress and neurotoxin

Enhanced endoplasmic reticulum (ER) stress leads to cell death in various pathophysiological situations. During a search for compounds that regulate ER stress, we identified methoxyflavones, a group of flavonoids, as strong protective agents against ER stress. Analysis in mouse insulinoma MIN6 cells revealed that methoxyflavones mildly activated the eukaryotic initiation factor 2alpha and nuclear factor erythroid 2-related factor pathways, but not the XBP1 pathway, and induced downstream genes, including glucose-regulated protein (GRP) 78, a molecular chaperone in the ER. The protective effect of methoxyflavones was enhanced by agents that increase intracellular cAMP levels such as forskolin, dibutyryl-cAMP and IBMX, but suppressed by the protein kinase A (PKA) inhibitor H-89, suggesting involvement of the PKA pathway in the regulation of ER stress by methoxyflavones. Consistent with the results in cultured cells, pretreatment of mice with tangeretin, a methoxyflavone, enhanced expression of GRP78 and HO-1 without causing ER stress in renal tubular epithelium and prevented tunicamycin-induced cell death. Furthermore, preadministration of tangeretin in mice enhanced expression of GRP78 in the substantia nigra pars compacta and protected dopaminergic neurons against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, a neurotoxin that induces both oxidative and ER stress. These results suggest that methoxyflavones play an important role in the regulation of ER stress and could be a therapeutic target for the ER stress-related diseases.