ascorbic-acid and baicalein

The antioxidant properties of flavonoids are mediated by their functional hydroxyl groups, which are capable of both chelating redox active metals such as iron, copper and scavenging free radicals. In this paper, the antioxidant vs. prooxidant and DNA protecting properties of baicalein and Cu(II)-baicalein complexes were studied under the conditions of the Copper-Fenton reaction and of the Copper-Ascorbate system. From the relevant EPR spectra, the interaction of baicalein with Cu(II) ions was confirmed, while UV-vis spectroscopy demonstrated a greater stability over time of Cu(II)-baicalein complexes in DMSO than in methanol and PBS and Phosphate buffers. An ABTS study confirmed a moderate ROS scavenging efficiency, at around 37%, for both free baicalein and Cu(II)-baicalein complexes (in the ratios 1:1 and 1:2). The results from absorption titrations are in agreement with those from viscometric studies and confirmed that the binding mode between DNA and both free baicalein and Cu-baicalein complexes, involves hydrogen bonds and van der Waals interactions. The DNA protective effect of baicalein has been investigated by means of gel electrophoresis under the conditions of the Cu-catalyzed Fenton reaction and of the Cu-Ascorbate system. In both cases, it was found that, at sufficiently high concentrations, baicalein offers some protection to cells from DNA damage caused by ROS (singlet oxygen, hydroxyl radicals and superoxide radical anions). Accordingly, baicalein may be useful as a therapeutic agent in diseases with a disturbed metabolism of redox metals such as copper, for example Alzheimer's disease, Wilson's disease and various cancers. While therapeutically sufficient concentrations of baicalein may protect neuronal cells from Cu-Fenton-induced DNA damage in regard to neurological conditions, conversely, in the case of cancers, low concentrations of baicalein do not inhibit the pro-oxidant effect of copper ions and ascorbate, which can, in turn, deliver an effective damage to DNA in tumour cells.

Topics: Antioxidants; Ascorbic Acid; Copper; DNA; DNA Damage; Flavonoids; Hydroxyl Radical; Metals; Oxidation-Reduction; Reactive Oxygen Species

6-OHDA plus ascorbic acid (AA) has long been used to induce Parkinson's disease in rodents, while only 6-OHDA is commonly used to induce cell damage in cellular PD models. AA was believed to act as an anti-oxidant to prevent the degradation of 6-OHDA; however, some studies suggested that AA dramatically enhanced the selectivity and toxicity of 6-OHDA. To understand the mechanisms by which 6-OHDA/AA induces cell death, we established a 6-OHDA/AA cell toxicity model in human dopaminergic neuroblastoma SH-SY5Y cells. We confirmed that the toxicity of 6-OHDA was dramatically increased in the presence of AA, and the toxicity can be prevented by a flavonoid, baicalein. Mechanistically, our research reveals that 6-OHDA/AA induces cell death mainly through the interruption of intracellular calcium homeostasis, which leads to calpain activation and mitochondrial damage. Baicalein prevents 6-OHDA/AA-induced intracellular calcium elevation as well as consequent mitochondria damage. Taken together, our study confirms that 6-OHDA/AA is a more sensitive model for inducing neuronal lesion in vitro and reveals the central role of intracellular calcium in 6-OHDA/AA-induced cell death. Our studies further show that baicalein prevents 6-OHDA/AA-induced cell death by inhibiting intracellular calcium elevation.

Topics: Adrenergic Agents; Ascorbic Acid; Calcium; Calcium-Regulating Hormones and Agents; Calpain; Cell Death; Cell Line; Dopaminergic Neurons; Flavanones; Homeostasis; Humans; Mitochondria; Oxidopamine

4-(Hydroxyphenyl)retinamide (4-HPR) is a synthetic retinoid with a strong apoptotic effect towards different cancer cell lines in vitro, and it is currently tested in clinical trials. Increases of reactive oxygen species (ROS) and modulation of endogenous sphingolipid levels are well-described events observed upon 4-HPR treatment, but there is still a lack of understanding of their relationship and their contribution to cell death. LC-MS analysis of sphingolipids revealed that in human leukemia CCRF-CEM and Jurkat cells, 4-HPR induced dihydroceramide but not ceramide accumulation even at sublethal concentrations. Myriocin prevented the 4-HPR-induced dihydroceramide accumulation, but it did not prevent the loss of viability and increase of intracellular ROS production. On the other hand, ascorbic acid, Trolox, and vitamin E reversed 4-HPR effects on cell death but not dihydroceramide accumulation. NDGA, described as a lipoxygenase inhibitor, exerted a significantly higher antioxidant activity than vitamin E and abrogated 4-HPR-mediated ROS. It did not however rescue cellular viability. Taken together, this study demonstrates that early changes observed upon 4-HPR treatment, i.e., sphingolipid modulation and ROS production, are mechanistically independent events. Furthermore, the results indicate that 4-HPR-driven cell death may occur even in the absence of dihydroceramide or ROS accumulation. These observations should be taken into account for an improved design of drug combinations.

Topics: Antineoplastic Agents; Antioxidants; Apoptosis; Ascorbic Acid; Cell Line, Tumor; Cell Survival; Ceramides; Fenretinide; Flavanones; Humans; Leukemia; Lipid Peroxidation; Lipoxygenase Inhibitors; Masoprocol; Mitochondria; Oxidative Stress; Oxidoreductases; Reactive Oxygen Species; Sphingolipids; Vitamin E

Aggregation of alpha-synuclein (αS) into oligomers is critically involved in the pathogenesis of Parkinson's disease (PD). Using confocal single-molecule fluorescence spectroscopy, we have studied the effects of 14 naturally-occurring polyphenolic compounds and black tea extract on αS oligomer formation. We found that a selected group of polyphenols exhibited potent dose-dependent inhibitory activity on αS aggregation. Moreover, they were also capable of robustly disaggregating pre-formed αS oligomers. Based upon structure-activity analysis, we propose that the key molecular scaffold most effective in inhibiting and destabilizing self-assembly by αS requires: (i) aromatic elements for binding to the αS monomer/oligomer and (ii) vicinal hydroxyl groups present on a single phenyl ring. These findings may guide the design of novel therapeutic drugs in PD.

Topics: Acetylcysteine; alpha-Synuclein; Antioxidants; Apigenin; Ascorbic Acid; Deferoxamine; Dose-Response Relationship, Drug; Flavanones; Flavonoids; Humans; Iron Chelating Agents; Microscopy, Confocal; Microscopy, Fluorescence; Molecular Structure; Mutation; Parkinson Disease; Phenols; Polyphenols; Protein Multimerization; Protein Structure, Quaternary; Recombinant Proteins; Spectrometry, Fluorescence; Structure-Activity Relationship

All-trans-N-(4-hydroxyphenyl)retinamide (4HPR) is a synthetic retinoid that can induce apoptosis in many cancer cell lines. The cytotoxicity of 4HPR is dependent on the production of ROS but the underlying reasons are not entirely certain. We have investigated the role of 4HPR-induced production of ROS in mediating the expression of the recently identified 4HPR-responsive gene Gadd153. In 4HPR-treated cells, the elevation of Gadd153 protein level was prevented by vitamin C, which had no effect on the activation of the Gadd153 gene promoter. The 4HPR-induced elevation of Gadd153 mRNA level persisted even after transcription was blocked with actinomycin D, but declined rapidly upon the addition of antioxidants to the transcription-arrested cells. The mRNA expressed from the full-length Gadd153 cDNA was degraded constitutively in cells in the absence but not in the presence of 4HPR. Such an inhibitory effect of 4HPR was abolished by antioxidants and by inhibitors of 12-lipoxygenase, baicalein (specific) and esculetin (panspecific). The inhibition of 4HPR-induced expression of Gadd153 protein by vitamin C was independent of intracellular proteasome activity and vitamin C had no effect on the intracellular decay of Gadd153 protein. Our data provide the first evidence that the posttranscriptional expression of the Gadd153 gene can be regulated by ROS produced by 4HPR.

Topics: Antioxidants; Ascorbic Acid; CCAAT-Enhancer-Binding Proteins; Dactinomycin; Fenretinide; Flavanones; HeLa Cells; HT29 Cells; Humans; Lipoxygenase Inhibitors; Promoter Regions, Genetic; Reactive Oxygen Species; RNA, Messenger; Transcription Factor CHOP; Transcription Factors; Transcription, Genetic; Umbelliferones

The effect of baicalein (5,6,7-trihydroxy-2-phenyl-4H-1-benzopyran-4-one), a flavonoid isolated from Scutellaria baicalensis Georgi, on lipid peroxidation in rat liver microsomes was studied. Ascorbic acid-induced lipid peroxidation in microsomes obtained from baicalein-treated rats was inhibited by treatment on different days and at different doses. Iron release induced by ascorbic acid from microsomes of baicalein-treated rats was markedly lower than from microsomes of control rats. However, no statistical differences in total, nonheme and nonprotein-bound (free iron) iron contents could be detected in the two microsomes. The degradation of calf thymus DNA, an indicator of free iron existence, was observed in the reactions of microsomes obtained from control and baicalein-treated rats with ascorbic acid in the presence of bleomycin. These results suggest that baicalein can inhibit lipid peroxidation in microsomes induced by ascorbic acid by forming an inert complex of iron.

Topics: Animals; Ascorbic Acid; Astringents; Bleomycin; Flavanones; Flavonoids; In Vitro Techniques; Iron; Lipid Peroxidation; Male; Microsomes, Liver; Plant Roots; Plants, Medicinal; Quercetin; Rats; Rats, Wistar; Reactive Oxygen Species; Rutin