Flavonoids have been reported to be potent antioxidants and beneficial in oxidative stress related diseases. Quercetin, a major flavonoid in food, deserves much attention because of its antioxidative activity. However, the actions of flavonoids including quercetin are complex and paradoxical. Quercetin caused apoptosis and/or cell death in various cells including cancer cells and normal cells. In this study, we investigated the effects of quercetin with or without hydrogen peroxide (H2O2) on cell death of PC12 cells, a neuronal cell line. We showed that quercetin at 10-30 microM alone caused cell death accompanied by caspase-mediated DNA fragmentation in undifferentiated PC12 cells. Quercetin did not inhibit and rather enhanced 0.1 mM H2O2-induced cell death. The toxic effect of quercetin was not inhibited by antioxidants such as N-acetylcysteine and GSH, although H2O2-induced cell death was inhibited by the antioxidants. Quercetin-induced cell death was reduced by 2 h treatment with nerve growth factor and serum. In addition, quercetin caused cell death in differentiated PC12 cells that were cultured with nerve growth factor for 6 d. Genistein, a soy isoflavone that has the pro-apoptotic activity, also caused cell death with DNA fragmentation. Further evaluation of the potential of dietary flavonoids as neuroprotective reagents is needed.
"In contrast to our present findings, it has been reported that genistein at a high concentration (165 μM) produces pro-apoptotic activity and causes cell death by DNA fragmentation in PC12 cells (Sasaki et al., 2007). It is conceivable that high concentrations of flavonoids can induce cytotoxicity, as it is known that flavonoids are prone to oxidation in culture media where oxygen tension is high and metal ion contamination is common, a condition known as " culture shock " (Halliwell, 2003). "
[Show abstract][Hide abstract] ABSTRACT: We investigated the mechanism of D-galactose (DG)-induced oxidative damage and the neuroprotective action of genistein in PC12 cells.
PC12 cells were treated with 40mM DG dissolved in medium containing 85% RPMI1640, 10% HBS and 5% FBS with or without genistein. We measured the protein expression of β-amyloid (Aβ), advanced glycation end products (AGEs), IκB-α and manganese-superoxide dismutase (MnSOD) by western blotting, intracellular reactive oxygen species (ROS) by 2, 7-dichlorofluorescin-diacetate, and the binding activity of nuclear factor kappa B (NF-κB) by electrophortic mobility shift assay.
DG (40mM) completely retarded cell growth after incubation for 72h, and this effect was not due to osmotic changes, as 40mM mannitol had no effect. Mechanistically, we found that DG increased intracellular ROS starting at 4h and increased Aβ and AGEs at 24h. DG treatment for 24h also increased the binding activity of NF-κB but strongly decreased the expression of IκB-α protein. Furthermore, DG treatment for 48h increased MnSOD protein expression. All these effects of DG were effectively inhibited by genistein (0.5-10μM).
The present study indicates that the protection of genistein against DG-induced oxidative stress in PC12 cells, and the effect is likely mediated by decreased intracellular ROS and binding activity of NF-κB.
Life sciences 11/2010; 88(1-2):82-8. DOI:10.1016/j.lfs.2010.10.021 · 2.70 Impact Factor
"Oxidative stress describes a cellular imbalance of oxidants over antioxidants that is suggested to play an important role in the pathogenesis of cancer, cardiovascular disease, inflammation , and neurodegenerative diseases such as Parkinson's and Alzheimer's (Sasaki et al. 2007). Previous studies have identified ROS and RNS, including superoxide anion, hydroxyl radical, NO, and H 2 O 2 , as key ROS modulators in intracellular signaling, host defence, and redox regulation (Silva et al. 2008). "
[Show abstract][Hide abstract] ABSTRACT: To investigate the beneficial properties associated with polyphenols, we screened 12 polyphenols for their ability to increase the viability of PC12 cells subjected to oxidative stress via CoCl2 and H2O2. Cell viability data demonstrate that 50 micromol/L methyl gallate and 50 micromol/L fisetin significantly increase viability of H2O2-stressed cells. Further, viability data suggest that 100 micromol/L epigallocatechin gallate (EGCG) increases basal viability, but has no rescue effect on cells stressed with CoCl2 or H2O2. Analysis of intracellular reactive oxygen species (ROS) shows that EGCG, methyl gallate, and gallic acid are effective in reducing CoCl2-derived ROS, and that methyl gallate is effective in attenuating H2O2-derived ROS. Examination of nitric oxide concentrations shows that methyl gallate significantly increases nitric oxide, both in nonstressed and H2O2-stressed cells, whereas EGCG results are consistent with the scavenging of nitric oxide under nonstressed and stressed conditions. Furthermore, analysis of total glutathione levels reveals that EGCG, methyl gallate, and gallic acid pretreatments with and without H2O2 stress have the ability to significantly alter glutathione metabolism. These findings suggest that EGCG, methyl gallate, and gallic acid may have potential therapeutic properties.
Canadian Journal of Physiology and Pharmacology 04/2010; 88(4):429-38. DOI:10.1139/y09-137 · 1.77 Impact Factor
"In recent years, it has been reported that the herbal drugs play a significant role in the therapy of hepatic disorders.[16–18] Quercetin, a flavonoid constituent [Figure 1], is found in many herbal drugs and foods, demonstrating broad biopharmacological properties. Quercetin demonstrates antioxidant defense by scavenging free radicals and inhibiting various molecules oxidation, being an useful agent for protecting various neuronal cells against oxidative stress. "
[Show abstract][Hide abstract] ABSTRACT: Quercetin, a natural compound of multiple origins, has broad biopharmacological effects, such as antioxidant, directly scavenging free radical, and hepatoprotectivity effects. This study is designed to investigate the interveneous effect of quercetin on liver injury induced by ethanol in rats. The rats that were orally treated with 50% ethanol for continuous ten days, which resulted in cell necrosis, fibrosis and inflammatory infiltration, were included in this study. Higher contents of AST, ALT ADH, gamma-GT, TG in plasma and MDA in liver tissue, and lower content of GSH in liver tissue were highlighted in ethanol-treated rats when compared with healthy ones. The levels of cytokines such as IL-1beta, IL-1, IL-6, IL-8, and TNF-alpha in rats plasma were also significantly enhanced, and level of IL-10 was obviously lowered through ethanol treatment. By preventive and synchronism treatment with quercetin for fourteen days, the contents of AST, ALT ADH, gamma-GT, TG and MDA, and levels of IL-1beta, IL-1, IL-6, IL-8, and TNF-alpha were significantly reduced, whereas GSH and level of IL-10 were obviously increased. It may be deduced that quercetin, by multiple mechanisms interplay, demonstrated somewhat protective effect on liver injury induced by ethanol in rats.
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