Effects Of Flavones Research Articles

Flavone inhibited proliferation of T-ALL by promoting c-Cbl-induced ubiquitinylation and degradation of Notch1

Aberrant activation of Notch1 signaling frequently occurs in T-cell acute lymphoblastic leukemia (T-ALL). Notch1 activation causes release of intracellular Notch1 (ICN1, the activated form of Notch1) from cell membrane to cytoplasm. As a transcription factor, ICN1 must be transferred into nucleus and bind to the promoters of its downstream target genes. E3 ubiquitin ligase induces ICN1 degradation in cytoplasm, which blocks ICN1 transfer into the nucleus. Flavone is a natural plant polyphenol, demonstrated to have anti-cancer effects in vitro and in vivo in breast and colon cancers. However, the effects of flavone on leukemia have not been reported. In this study, we demonstrated that flavone inhibited cell proliferation by down-regulating Notch1 signal pathway in CCRF-CEM and Molt-4 T-ALL cells. Flavone-mediated upregulation of c-Cbl level results in the increase in its interaction with ICN1, further caused ICN1 ubiquitinylation and degradation. Knockdown of c-Cbl reversed flavone-induced down-regulation of ICN1 and inhibition of cell proliferation in T-ALL cells. In short, this study indicated that flavone exerted resistance to T-ALL by promoting c-Cbl-induced ubiquitinylation and degradation of ICN1.

Effect of Flavone and Isoflavone in the Triphenylamine-Based Sensitizers for Dye-Sensitized Solar Cell Applications: DFT and TD-DFT Approach

Several metal-free organic sensitizers have been designed for dye-sensitized solar cell applications. The effect of flavone and isoflavone in the triphenylamine sensitizers was investigated in the present work. The dyes with different donors are analyzed by density functional theory and time-dependent density functional theory. The various parameters such as geometry, electronic structure, highest occupied molecular orbital and lowest unoccupied molecular orbital, light harvesting efficiency and electronic absorbance spectrum of the designed sensitizers were analyzed. The absorption bands in the visible and near-Ultra Violet (UV) region are correlated to photoinduced electron transfer process. The effect of flavone on the triphenylamine donor retards the photo degradation of the dye. It gives hyperchromic and bathochromic shift in the dyes and it also acts as UV filters. Free energy change for electron injection and dye regeneration was calculated. The results show that the designed dyes may be an efficient sensitizer for DSSC applications.

Theoretical Investigation on Flavones and Isoflavones-Added Triphenylamine-Based Sensitizers for DSSC Application

Twelve novel dye molecules developed from D-π-A-based triphenylamine (TPA) dyes were studied to evaluate their suitability for dye-sensitized solar cells (DSSC), using density functional theory (DFT) and time-dependent density functional theory (TDDFT). The effects of flavone and isoflavone on triphenylamine-based dyes were studied. B3LYP and CAM-B3LYP density functionals combined with 6-311G(d,p) basis set were chosen for optimization and TDDFT respectively. Optimization geometry, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy level, and absorption spectrum were calculated. The electron injection force and light-harvesting efficiency were calculated. We have found HOMO, LUMO energy levels, and electronic absorption spectrum suitable for DSSC application. Based on theoretical calculations, the usefulness of flavones and isoflavones-added triphenylamine dye molecules for DSSC application is examined.

Prevention of recognition memory loss and moderation of mitochondrial dynamic tendency toward fusion by flavone derivatives in Aβ-injected rats: a comparison between two flavonoids with different polarity

Growing evidence sheds light on the use of flavonoids as the promising alternatives for the treatment of chronic conditions, including cancer and neurodegenerative disorders. Accordingly, in the present study, we aimed at evaluating the effects of oral intake of two structurally different flavonoids 5-hydroxy-6,7,4ʹ-trimethoxyflavone (flavone 1) and 5,7,4ʹ-trihydroxyflavone (flavone 2) on recognition memory, hippocampal protein level of immediate early gene cFos and mitochondrial dynamic markers in Amyloid β (Aβ)-injected rats. Recognition aspect of memory and level of proteins were measured using novel object recognition test and Western blot, respectively. Our data indicated that even though flavone 1 was more effective than flavone 2 to prevent memory impairment, feeding with both flavones alleviated memory in Aβ-injected rats. Furthermore, in flavones-administered rats, mitochondrial dynamic balancing returned to the control level by the decline in Dynamin-related protein-1 protein level, a known marker for mitochondrial fission, and elevation in protein level of mitochondrial fusion factors Mitofusins 1 and 2. In parallel with behavior results, flavone 1 was more effectual on mitochondrial dynamic moderating. The more neuroprotective effects of flavone 1 could be attributed to its methylated structure leading to crossing of the blood-brain barrier with ease and metabolic stability and bioactivity.

ID3007 Mechanisms underlying the anticancer activities of the selected phytochemicals and their therapeutic implication in AGS gastric cancer cells

The cysteine-rich angiogenic inducer 61 (CYR61), an extracellular matrix-associated protein, is involved in survival, tumorigenesis, and drug resistance. There is an increasing demand for developing agents that target CYR61. Hence, we study the effects of flavones against CYR61-overexpressing human gastric adenocarcinoma AGS (AGS-cyr61) cells. Among the various flavones, quercetin had lowest IC50 value and reduced the viability of AGS-cyr61 cells even greater than that of AGS cells. Quercetin (1) down-regulates CYR61 and concomitantly decreases in the levels of MRP1 (multidrug resistance-associated protein 1) and nuclear factor NF-kappa B (κB) p65 subunit, (2) reverses multidrug resistance, and (3) inhibits colony formation in AGS-cyr61 cells. AGS-cyr61 cells treated with quercetin at sub IC50 over a range of 5-FU or ADR concentrations manifested strong synergistic effects with these two drugs. Our results demonstrate that CYR61 is a potential regulator of ABC transporters and quercetin can be the novel agent that improves the efficacy of anticancer drugs by down-regulating CYR61 and ABC transporters.
 Histone deacetylase 6 (HDAC6) is a unique cytoplasmic enzyme which contributes to malignant progression in various cancer. Such effect on cancer brings more interest on developing HDAC6 inhibitors. Here, we found that compound D inhibits HDAC6 activity, increases acetylated α-tubulin, reduces the level of β-catenin, and suppresses cell proliferation. Increase of α-tubulin acetylation by compound D resulted in tubulin polymerization, and consequently, induced aberrant mitosis. Moreover, DTBP elicits different effects depending on different concentrations.
 
 Treatment with high concentrations of compound D induces cell death by mitotic catastrophe, whereas low concentration of compound D induces senescence with upregulation of p21 and Rb, and increase in the phosphorylation of mTOR and the β-galactosidase activity. Therefore, compound D can also be considered as a promising new candidate for anti-cancer drug development.

Dietary Flavones as Dual Inhibitors of DNA Methyltransferases and Histone Methyltransferases.

Methylation of DNA and histone proteins are mutually involved in the epigenetic regulation of gene expression mediated by DNA methyltransferases (DNMTs) and histone methyltransferases (HMTs). DNMTs methylate cytosine residues within gene promoters, whereas HMTs catalyze the transfer of methyl groups to lysine and arginine residues of histone proteins, thus causing chromatin condensation and transcriptional repression, which play an important role in the pathogenesis of cancer. The potential reversibility of epigenetic alterations has encouraged the development of dual pharmacologic inhibitors of DNA and histone methylation as anticancer therapeutics. Dietary flavones can affect epigenetic modifications that accumulate over time and have shown anticancer properties, which are undefined. Through DNA binding and in silico protein-ligand docking studies with plant flavones viz. Apigenin, Chrysin and Luteolin, the effect of flavones on DNA and histone methylation was assessed. Spectroscopic analysis of flavones with calf-thymus DNA revealed intercalation as the dominant binding mode, with specific binding to a GC-rich sequence in the DNA duplex. A virtual screening approach using a model of the catalytic site of DNMT and EZH2 demonstrated that plant flavones are tethered at both ends inside the catalytic pocket of DNMT and EZH2 by means of hydrogen bonding. Epigenetic studies performed with flavones exhibited a decrease in DNMT enzyme activity and a reversal of the hypermethylation of cytosine bases in the DNA and prevented cytosine methylation in the GC-rich promoter sequence incubated with the M.SssI enzyme. Furthermore, a marked decrease in HMT activity and a decrease in EZH2 protein expression and trimethylation of H3K27 were noted in histones isolated from cancer cells treated with plant flavones. Our results suggest that dietary flavones can alter DNMT and HMT activities and the methylation of DNA and histone proteins that regulate epigenetic modifications, thus providing a significant anticancer effect by altering epigenetic processes involved in the development of cancer.

Effects of flavone on the contractile activity of the circular smooth muscle of the rabbit middle colon in vitro

The circular smooth muscles of the middle colon of the rabbit generate giant contractions of high amplitude and low frequency. Flavone, at various concentrations, reduces the giant contractions and the tonic contraction induced by 10µM carbachol and 80mM KCl. The contractions induced by dequalinium and tetraethylammonium are reduced by flavone (30µM). At 100µM, flavone decreases the contraction induced by 100µM methylene blue and 1mM orthovanadate. These results suggest that flavone inhibit the giant contractions by (1) inhibition of voltage-dependent Ca2+ channels, (2) activation of guanyl cyclase, (3) opening of K+ channels and (4) inhibition of tyrosines kinases.

Flavones inhibit the proliferation of human tumor cancer cell lines by inducing apoptosis

Dietary flavonoids have been shown to exert specific cytotoxicity toward some cancer cells, but the precise molecular mechanisms are still not completely understood. In this study, cytotoxic effects of flavones (apigenin and luteolin) on two different cancer cell lines, including human chronic myelogenous erythroleukaemia (K562) and bladder carcinoma (RT112), were determined, and the molecular mechanisms responsible for their cytotoxic effects were studied. The results of an MTT assay showed that luteolin and apigenin were able to induce cytotoxicity in K562 and RT112 cells in a dose- and time-dependent manner. The cytotoxic potency of luteolin was higher than that of apigenin. Flow-cytometry and DNA-fragmentation analysis indicated that the cytotoxicity induced by luteolin and apigenin was mainly due to apoptosis, with minor cell-cycle perturbations. This apoptotic response was characterized by an increase of the sub-G1 fraction of treated cells, poly(ADP-ribose) polymerase proteolysis, typical ladder of DNA fragmentation, and Annexin V–positive cells. In conclusion, luteolin and apigenin exert cytotoxic effects in different cancer cell lines in which apoptosis plays an important role. Thus, flavones could be considered as potential chemotherapeutic agents.

Effect of flavone on the ocular blood flow and formation of choroidal neovascularization.

To investigate the effect of flavone on ocular blood flow in rabbit eyes and the formation of choroidal neovascularization (CNV) in rat model of age-related macular degeneration (AMD). In in vivo studies, colored microsphere technique was used to determine the ocular blood flow in ocular hypertensive rabbit eyes. The rat eyes were treated with 0.5% flavone eye drops 3 times a day for 1 week before and 4 weeks after laser-induced injury of Bruch's membrane. The development of CNV was determined by fluorescein angiography (FA) performed on the 2nd and 4th after injury. In in vitro studies, the effect of flavone on the viability of human umbilical vein endothelial cells HUVECs was measured by MTT assay. The ocular blood flow in rabbit eyes was significantly increased after flavone instillation. Flavone significantly inhibited the formation of laser induced CNV. In vitro results showed that flavone inhibited the proliferation of HUVECs. Flavone could increase ocular blood flow and inhibit the formation of CNV.

Flavone-and Flavonol-Caused Apoptosis in Human Esophageal Cancer Cells by Inducing The Expression of PIG3

Two human esophageal cancer cell lines (KYSE-510 and OE33) were chosen as the tumor model to explore molecular mechanism of flavones and flavonols on induction of apoptosis. Effects of flavones (luteolin, apigenin, chrysin) and flavonols (quercetin, kaempferol, myricetin) on induction of apoptosis in KYSE-510 cells and OE33 cells were observed by DNA fragmentation, acridine orange staining and flow cytometry analysis. The results of real-time RT-PCR and Western-blot analysis showed that the treatment of KYSE-510 cells and OE33 cells with flavones and flavonols induced the expression of PIG3 at the mRNA and the protein levels. Western-blot analytical results further showed that induction of PIG3 caused apoptosis in both esophageal cancer cells through the mitochondrial pathway in a p53-independent manner, and p63 and p73 may be responsible for the induction of PIG3.

Effects of Flavones and Ascorbic Acid on Radiation Sickness

Effects of Flavones and Ascorbic Acid on Radiation Sickness

Effect of flavones on rat brain and lung matrix metalloproteinase activity measured by film in-situ zymography

We have evaluated the inhibitory activity of flavone, nobiletin, and heptamethoxyflavone on matrix metalloproteinase (MMP) activity in the rat. MMP in 9000-g supernatant fraction of lung homogenate was activated by p-aminophenyl mercuric acetate (APMA), and gelatinolytic activity was determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) followed by Coomassie staining. This activity should be related to MMP-2 and/or MMP-9 and was confirmed by gelatin zymography. Fluorescent-conjugated collagen used as a substrate for collagenolytic activity wasinvestigated by SDS-PAGE also. The film in-situ zymography method was applied to rat brain and lung tissue in the same manner. Flavone and nobiletin inhibited the APMA-stimulated gelatinolytic activity and also the collagenolytic activity by more than 75%. The film in-situ zymography method indicated that these compounds might be potent inhibitors of MMP, suggesting the specific inhibition of localized MMP in brain hippocampus and/or lung terminal bronchioles, which may contribute to the prevention of some types of brain disease or cancer invasion and metastasis.

Flavone inhibition of tumor growth via apoptosis in vitro and in vivo

Colorectal carcinoma is a human malignant tumor, which is very resistant to currently available methods of treatment. Therefore, developing an effective agent with anti-colorectal carcinoma activity is important. In the present study, 8 structurally related flavones including flavone, 3-OH flavone, 5-OH flavone, 7-OH flavone, quercetin, kaempferol, quercetin, and morin were used to study their effects on colorectal carcinoma cells (HT29, COLO205, COLO320-HSR). Results of MTT assay indicated that flavone shows the most potent cytoxic effect among them on these three cell types. The cytotoxicity induced by flavone is mediated by inducing the occurrence of apoptosis characterized by the appearance of DNA ladders, apoptotic bodies and hypodiploid cells. Activation of caspase 3 protein procession and enzyme activity with inducing cleavage of caspase 3 substrates PARP was identified in flavone-treated cells, and an inhibitory peptide Ac-DEVD-FMK for caspase 3, but not Ac-YVAD-FMK for caspase 1, attenuates the cytotoxic effect of flavone in COLO205 and HT29 cells. Elevation of p21 but no p53 protein was observed in flavone-treated cells. Increasing intracellular peroxide level was detected in flavone-treated cells by DCHF-DA assay, and antioxidants such as tiron, catalase, SOD, PDTC, but not DPI, suppress flavone-induced cytotoxic effect. In vivo anti-tumor study indicates that flavone exhibits ability to inhibit tumor formation elicited by s.c. injection of COLO205 cells in nude mice, and apoptotic cells and an increase in p21, but not p53, protein were observed in tumor tissues derived from flavone-treated group. Additionally, flavone induced apoptosis in primary colon carcinoma cells COLO205-X with appearance of DNA ladders, caspase 3 protein procession, PARP protein cleavage, and an increase in p21 (not p53) protein. These data provide evidence to suggest that flavone is an effective agent to induce apoptosis in colorectal carcinoma cells in vitro and in vivo; activation of caspase 3, ROS production, and increasing p21 protein are involved.

The flavones luteolin and apigenin inhibit in vitro antigen-specific proliferation and interferon-gamma production by murine and human autoimmune T cells

Plant-derived flavonoids are inhibitors of various intracellular processes, notably phosphorylation pathways, and potential inhibitors of cellular autoimmunity. In this study, the inhibiting effects of various flavonoids on antigen-specific proliferation and interferon-gamma (IFN-γ) production by human and murine autoreactive T cells were evaluated in vitro. T-cell responses were evaluated for the human autoantigen alpha B-crystallin, a candidate autoantigen in multiple sclerosis, and for the murine encephalitogen proteolipid protein peptide PLP (139–151). The flavones apigenin and luteolin were found to be strong inhibitors of both murine and human T-cell responses while fisitin, quercitin, morin and hesperitin, members of the subclasses of flavonoles and flavanones, were ineffective. Antigen-specific IFN-γ production was reduced more effectively by flavones than T-cell proliferation, suggesting that the intracellular pathway for IFN-γ production in T cells is particularly sensitive to flavone inhibition. These results indicate that flavones but not flavanoles or flavanones are effective inhibitors of the potentially pathogenic function of autoreactive T cells. The effects of flavones were the same for human and murine autoreactive T cells, stressing the usefulness of animal models of autoimmunity for further studies on the effects of flavonones on autoimmune diseases.

Inhibition of nitric oxide (NO •) production in murine macrophages by flavones

The effect of flavone (2-phenylbenzopyran-4-one) and three amino-substituted flavones on the production of nitrite by murine activated peritoneal macrophages was studied in vitro. Activated peritoneal macrophages obtained from mice pre-treated with concanavalin A (Con A) ( in vivo), after exposure in vitro to lipopolysaccharide (LPS) at a concentration of 100 ng/ml, produced nitrite (20.3 ± 2.5 nmol/10 6 cells), as measured after 24 hr by the Griess reaction. Stimulation of production of nitrite was inhibited by N G-mono-methyl-L-arginine, suggesting that nitrite was formed via nitric oxide (NO •) as a product of metabolism of arginine. Stimulation was inhibited by flavone and the aminoflavones (20–100 μM). 3′-amino-4′-hydroxyflavone was the most potent inhibitor of nitrite production. Genistein (5,7-dihydroxy-3-(4-hydroxy-phenyl)-4H-1-ben-zopyran-4-one) also inhibited production of nitrite, by a mechanism that appears not to involve protein tyrosine kinases. These results suggest that the flavones can modulate the immune responses and the inflammatory reactions by controlling production of nitric oxide.

Flavone improves functional recovery after ischemia in isolated reperfused rabbit hearts

The effects of flavone (2-phenyl-1,4-benzopyrone), a modulator of the cytochrome P-450 monooxygenase system, on myocardial postischemic reperfusion recovery were examined in the present study. Left ventricular functional recovery was evaluated in isolated, crystalloid-perfused rabbit hearts after 2 hours of modestly hypothermic (34 degrees C) global ischemia. Four groups (n = 8 in each group) were studied and compared: a vehicle control group, a second group pretreated with flavone (8 x 10(-6) mol/L) before ischemia, a third group pretreated with flavone followed by SKF 525-A (1.7 x 10(-5) mol/L), an inhibitor of cytochrome P-450, and a fourth group pretreated with flavone followed by indomethacin (1 x 10(-6) mol/L), an inhibitor of cyclooxygenase. At 15, 30, and 45 minutes after reperfusion, recovery of left ventricular developed pressure in the control group averaged (mean +/- standard deviation) only 2.60% +/- 12.7%, 35.5% +/- 15.0%, and 42.9% +/- 13.5% of baseline, respectively. In the flavone-treated group, recovery was significantly better, averaging 67.7% +/- 10.7%, 73.9% +/- 9.3%, and 73.6% +/- 7.6% of baseline at the same time periods. Recovery of peak positive rate of pressure rise in the control group averaged 27.4% +/- 15.2%, 38.6% +/- 19.2%, and 45.4% +/- 18.6% of baseline at 15, 30, and 45 minutes of reperfusion, respectively. In the flavone-treated group recovery values were significantly higher, averaging 67.8% +/- 9.6%, 77.3% +/- 8.5%, and 77.0% +/- 9.0% of baseline. End-diastolic pressures were significantly lower in the flavone-treated group compared with the control group at all reperfusion time points. Myocardial oxygen consumption was significantly higher in the flavone-treated group at 30 and 45 minutes of reperfusion, as well. The improvement resulting from flavone infusion was abolished completely by SKF 525-A, providing support for the interpretation that the effects of flavone were mediated through the cytochrome P-450 system. The cyclooxygenase inhibitor indomethacin midly attenuated the effects of flavone pretreatment, suggesting that the effects of flavone were only minimally related to metabolites of cyclooxygenase. We conclude that pretreatment with flavone represents a promising approach to myocardial protection that may be due to modulation of the myocardial cytochrome P-450 system.

Interference by flavone and flavonols with chloroplast-mediated electron transport and phosphorylation

The effects of flavone and seven flavonols on the light-induced electron transport and phosphorylation of isolated spinach ( Spinacia oleracea L.) chloroplasts were investigated. With the exception of flavonol (3-hydroxyflavone), all of the compounds interacted with components of both the ATP-generating and electron transport pathways. Flavonol only interacted with the phosphorylation pathway. Interference with the phosphorylation pathway was evidenced by the greater sensitivity of the phosphorylation reaction than coupled whole-chain electron transport, inhibition of cyclic phosphorylation, inhibition of the light-activated Mg 2+-ATPase, and inhibition of the heat-activated Ca 2+ -ATPase associated with CF 1. The overall decreasing order of effectiveness for inhibition of cyclic phosphorylation was: galangin > quercetin = kaempferol = myricetin = flavonol > fisetin > flavone > morin. On the electron transport pathway, all of the compounds, except flavonol, interacted with the Q B-protein complex as, evidenced by inhibition of uncoupled electron transport, alteration of chlorophyll fluorescence transients, and competitive displacement of previously bound radiolabeled atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)- s-triazine]. The decreasing order of effectiveness for inhibition of uncoupled electron transport was: fisetin > quercetir = galangin > kaempferol > flavone > morin.

Inhibition in vitro of platelet aggregation and arachidonic acid metabolism by flavone

The effects of flavone on platelet aggregation and arachidonic acid (AA) metabolism were tested in vitro. When incubated at a concentration of 50 μM, flavone completely suppressed platelet aggregation induced by 150 μM AA in thirty-six out of forty-three subjects tested. A lower concentration (10 μM) was effective in about 50% of the donors. Flavone also inhibited the second wave of aggregation induced by epinephrine and ADP. Platelet thromboxane formation, estimated both by radioimmuno-assay measurements and by studies of 14C-labeled AA metabolism, was depressed by flavone. Flavone-treated platelets preferentially utilized [ 14C]AA for the lipoxygenase pathway while cyclo-oxygenase activity was depressed. Adenosine 3':5'-cyclic monophosphate (cAMP) was measured in flavone-treated and control platelets. While their baseline levels were similar, flavone-treated platelets showed a lower stimulation of cAMP induced by prostacyclin (PGI 2) than did controls. Phosphodiesterase activity was not affected by flavone as judged from the decay rates of PGI 2-stimulated cAMP levels. From these findings we conclude that the antiaggregating activity of flavone is not a consequence of changes in platelet cAMP but is due to inhibition of cyclo-oxygenase.

Effects of flavone on the oxidative properties of intact plant mitochondria

The effects of flavone on the oxidative and phosphorylative properties of plant mitochondria from potato tubers and etiolated mung bean hypocotyls were investigated. Flavone inhibited the state 3 oxidation rates of malate, NADH and, to a lesser extent, succinate but was without effect on the ascorbate-TMPD oxidation rate. The inhibition was the same whether the mitochondria were in state 3 or in an uncoupled state 3. When 100 μM flavone was added during the state 4, the tight coupling of succinate or NADH oxidation was not released. In the electron transfer chain, flavone inhibition appeared to be located in the flavoprotein region. All forms of NADH dehydrogenases seemed to be affected but the greatest inhibition appeared when exogenous NADH was used.