Structural basis for DNA-cleaving activity of resveratrol in the presence of Cu(II)

Copper Imparts a New Therapeutic Property to Resveratrol by Generating ROS to Deactivate Cell-Free Chromatin

Resveratrol, a bioactive phytoalexin, has been extensively studied as a pharmaceutical and nutraceutical candidate for the treatment of various diseases. Although its therapeutic effects have been largely attributed to its anti-oxidant properties, its underlying mechanisms and dose dependency are not well understood. Recent studies have shown that cell-free chromatin particles (cfChPs), which are released daily from billions of dying cells, can enter circulation and be internalized by healthy cells, wherein they trigger various damaging effects, including double-strand DNA breaks. Notably, deactivating cfChPs using a mixture of resveratrol and copper can neutralize their harmful effects. The addition of copper imparts a novel therapeutic property to resveratrol viz. the generation of reactive oxygen species (ROS), which are capable of deactivating cfChPs without damaging the genomic DNA. This perspective article discusses how the deactivation of cfChPs via the ROS generated by combining resveratrol with copper can have multiple therapeutic effects. Exploiting the damaging effects of ROS to deactivate cfChPs and ameliorate disease conditions may be a viable therapeutic approach.

New light on chemotherapy toxicity and its prevention

Most patients with cancer receive chemotherapy. Unfortunately, chemotherapy is associated with a number of potentially life-threatening side effects. There is a need to ameliorate chemotoxicity to improve therapeutic outcomes and quality of life. Chemotoxicity arises from systemic DNA damage and inflammation in healthy cells due to chemotherapy drugs. Traditionally, these processes are believed to be caused by the direct death of normal cells by chemotherapeutic drugs. However, new research has challenged this dogma by suggesting that chemotoxicity is a secondary effect associated with the release of cell-free chromatin particles (cfChPs) from cells subjected to drug-induced death. Released cfChPs can freely enter into bystander healthy cells to inflict double-strand (dsDNA) breaks and activate inflammatory and apoptotic pathways. The drug-induced cell death and cfChPs release have cascading effects that exaggerate and prolong chemotoxicity. Furthermore, evidence has emerged from laboratory and preclinical studies, and two phase II clinical trials, indicating that chemotoxicity can be minimised by deactivating cfChPs. Three cfChPs-deactivating agents have been identified, of which the nutraceutical combination resveratrol and copper (R-Cu)-easily administered orally and with little toxicity-is the agent of choice for human therapeutic use. This article aims to provide practising medical oncologists with a perspective on this emerging research on chemotoxicity and its prevention and its potential implications for the future. Well-designed randomised clinical trials will be necessary to establish the true clinical value of these findings in day-to-day practice.

Exploiting the damaging effects of ROS for therapeutic use by deactivating cell-free chromatin: the alchemy of resveratrol and copper

Cell-free chromatin particles (cfChPs) that circulate in blood, or those that are released locally from dying cells, have myriad pathological effects. They can horizontally transfer themselves into healthy cells to induce DNA damage and activate inflammatory and apoptotic pathways. It has been proposed that repeated and lifelong assault on healthy cells by cfChPs may be the underlying cause of ageing and multiple age related disorders including cancer. The damaging effects of cfChPs can be minimized by deactivating them via the medium of ROS generated by admixing the nutraceuticals resveratrol (R) and copper (Cu). The antioxidant R acts as a pro-oxidant in the presence of Cu by its ability to catalyse the reduction of Cu(II) to Cu(I) with the generation of ROS via a Fenton-like reaction which can deactivate extra-cellular cfChPs. This perspective article explores the possibility of using the damaging potential of ROS for therapeutic purposes. It discusses the ability of ROS generating nutraceuticals R-Cu to deactivate the extracellular cfChPs without damaging effects on the genomic DNA. As cfChPs play a key role in activation of various disease associated pathways, R-Cu mediated deactivation of these pathways may open up multiple novel avenues for therapy. These findings have considerable translational implications which deserve further investigation by the way of well-designed randomised clinical trials.

Cell-free chromatin particles released from dying cells inflict mitochondrial damage and ROS production in living cells

Mitochondrial damage and the resultant oxidative stress are associated with neurodegenerative diseases, ageing, and cancer. However, the triggers of mitochondrial damage remain unclear. We previously reported that cell-free chromatin particles (cfChPs) released from the billions of cells that die in the body every day can readily enter healthy cells and damage their DNA. Here, we show that cfChPs isolated from the sera of healthy individuals, when applied to NIH3T3 mouse fibroblast cells, cause physical damage to mitochondrial DNA (mtDNA). cfChPs also induce ultrastructural changes, increase mitochondrial mass, alter mitochondrial shape, upregulate mitochondrial outer membrane protein translocase of the outer membrane 20, and change mitochondrial membrane potential. Furthermore, a marked increase was observed in mitochondrial superoxide (ROS) production, as detected by MitoSOX Red, and intracellular superoxide dismutase-1 activation. ROS production was also activated when a conditioned medium containing cfChPs released from hypoxia-induced dying NIH3T3 cells was applied to healthy NIH3T3 cells. ROS activation was significantly reduced when the conditioned medium was pre-treated with three different cfChP-deactivating agents: anti-histone antibody-complexed nanoparticles, DNase I, and the novel pro-oxidant combination of the nutraceuticals resveratrol and copper. Given that 1 × 109-1 × 1012 cells die in the body every day, we hypothesise that cfChPs from dying cells are the major physiological triggers for mtDNA damage and ROS production. Deactivation of cfChPs may provide a novel therapeutic approach to retard ageing and associated degenerative conditions linked to oxidative stress.

Resveratrol induces DNA damage-mediated cancer cell senescence through the DLC1-DYRK1A-EGFR axis

Inducing cell senescence is widely regarded as a potent tumor suppression mechanism. Resveratrol has attracted increasing attention for its capacity to prevent and suppress cancer. However, the mechanism of resveratrol on the induction of cancer cell senescence has not been well clarified. Our results showed that resveratrol inhibited cell viability and colony formation and promoted cell senescence along with augmentation of SA-β-gal activity and modulation of senescence-associated molecular markers p53, p21 and LaminB protein in breast and liver cancer cells. The underlying mechanism was that resveratrol increased ROS generation to enhance tumor suppressor gene DLC1 expression, and DLC1 further inhibited the DYRK1A-EGFR axis to trigger DNA damage accompanied by up-regulation of the DNA double strand break marker protein γH2AX and down-regulation of the DNA repair related proteins p-BRCA1 and RAD51, eventually leading to cancer cell senescence. Resveratrol also effectively inhibited the volume of transplanted tumor with increased SA-β-gal activity and DLC1 level in a chicken embryo allantoic membrane xenograft tumor model. This is the first report to investigate whether resveratrol induces DNA damage-mediated cancer cell senescence through the DLC1-DYRK1A-EGFR axis, which could provide a solid base for resveratrol's application in cancer prevention and clinical treatment as a food additive or adjuvant therapies.

A pro-oxidant combination of resveratrol and copper down-regulates multiple biological hallmarks of ageing and neurodegeneration in mice

Billions of cells die in the body every day, and cell-free chromatin particles (cfChPs) which are released from them enter into the extracellular compartments of the body, including into the circulation. cfChPs are known to readily enter into healthy cells to damage their DNA and activate apoptotic and inflammatory pathways. We have hypothesized that lifelong assault on healthy cells by cfChPs is the underlying cause of ageing, and that ageing could be retarded by deactivating extra-cellular cfChPs. The latter can be effected by oxygen radicals that are generated upon admixing the nutraceuticals resveratrol and copper (R-Cu). The present study investigated whether prolonged administration of R-Cu would retard biological hallmarks of ageing. C57Bl/6 mice were divided into 3 equal groups; one group was sacrificed at age 3 months, and which acted as young controls. The remaining mice were allowed to age, and at age 10 months the experimental ageing group was given R-Cu by oral gavage twice daily for further 12 months at a dose of 1 mg/kg of R and 0.1 μg/kg of Cu. The control ageing group was given water by oral gavage twice daily for 12 months. Animals of both groups were sacrificed at age 22 months. R-Cu treatment led to reduction of several biological hallmarks of ageing in brain cells which included telomere attrition, amyloid deposition, DNA damage, apoptosis, inflammation, senescence, aneuploidy and mitochondrial dysfunction. R-Cu treatment also led to significant reduction in blood levels of glucose, cholesterol and C-reactive protein. These findings suggest that cfChPs may act as global instigators of ageing and neurodegeneration, and that therapeutic use of R-Cu may help to make healthy ageing an attainable goal.

A pro-oxidant combination of resveratrol and copper down-regulates hallmarks of cancer and immune checkpoints in patients with advanced oral cancer: Results of an exploratory study (RESCU 004)

Background

Our earlier studies have shown that cell-free chromatin particles (cfChPs) that are released from dying cancer cells are readily internalised by bystander cells leading to activation of two hallmarks of cancer viz. genome instability and inflammation. These hallmarks could be down-regulated by deactivating cfChPs via medium of oxygen radicals generated upon admixing small quantities of the nutraceuticals resveratrol (R) and copper (Cu). In this exploratory study, we investigated whether oral administration of R and Cu (R-Cu) would down-regulate the hallmarks of cancer and immune checkpoints in advanced squamous cell carcinoma of oral cavity (OSCC).

Patients and methods

The study comprised of 25 patients divided into 5 equal groups. Five patients acted as controls; the remaining 20 were given R-Cu in four escalating doses. The lowest dose of R-Cu was 5.6mg and 560ng respectively, and the highest dose was 500mg and 5mg respectively. An initial biopsy was taken from patients at first presentation, and a second biopsy was taken 2 weeks later on the operating table. R-Cu was administered orally twice daily in the intervening period. Confocal microscopy was performed on tumour sections after fluorescent immuno-staining with anti-DNA and anti-histone antibodies to detect presence of cfChPs in the tumour micro-environment (TME). Immunofluorescence analysis was performed for 23 biomarkers representing the 10 Hallmarks of cancer, including 5 immune checkpoints, defined by Hanahan and Weinberg.

Results

Confocal microscopy detected copious presence of cfChPs in TME of OSCC, which were eradicated/deactivated following two-week treatment with R-Cu. Eradication of cfChPs from TME was associated with marked down-regulation of 21/23 biomarkers, including the five immune checkpoints. The lower two doses of R-Cu were more effective than the higher doses. No adverse effects attributable to R-Cu were observed.

Conclusion

These results suggest that cfChPs released into TME from dying cancer cells are global instigators for cancer hallmarks and immune checkpoints in surviving cancer cells. The ability of R-Cu to deactivate cfChPs raises the prospect of a novel and non-toxic form of cancer treatment which sans killing of cancer cells, and instead induces healing by down-regulating cancer hallmarks and immune check-points.

Clinical Trial Registration

http://ctri.nic.in/Clinicaltrials/pmaindet2.php?trialid=19801&EncHid=&userName=CTRI/2018/03/012459.

Towards resolving the enigma of the dichotomy of resveratrol: cis- and trans-resveratrol have opposite effects on TyrRS-regulated PARP1 activation

Unlike widely perceived, resveratrol (RSV) decreased the average lifespan and extended only the replicative lifespan in yeast. Similarly, although not widely discussed, RSV is also known to evoke neurite degeneration, kidney toxicity, atherosclerosis, premature senescence, and genotoxicity through yet unknown mechanisms. Nevertheless, in vivo animal models of diseases and human clinical trials demonstrate inconsistent protective and beneficial effects. Therefore, the mechanism of action of RSV that elicits beneficial effects remains an enigma. In a previously published work, we demonstrated structural similarities between RSV and tyrosine amino acid. RSV acts as a tyrosine antagonist and competes with it to bind to human tyrosyl-tRNA synthetase (TyrRS). Interestingly, although both isomers of RSV bind to TyrRS, only the cis-isomer evokes a unique structural change at the active site to promote its interaction with poly-ADP-ribose polymerase 1 (PARP1), a major determinant of cellular NAD+-dependent stress response. However, retention of trans-RSV in the active site of TyrRS mimics its tyrosine-bound conformation that inhibits the auto-poly-ADP-ribos(PAR)ylation of PARP1. Therefore, we proposed that cis-RSV-induced TyrRS-regulated auto-PARylation of PARP1 would contribute, at least in part, to the reported health benefits of RSV through the induction of protective stress response. This observation suggested that trans-RSV would inhibit TyrRS/PARP1-mediated protective stress response and would instead elicit an opposite effect compared to cis-RSV. Interestingly, most recent studies also confirmed the conversion of trans-RSV and its metabolites to cis-RSV in the physiological context. Therefore, the finding that cis-RSV and trans-RSV induce two distinct conformations of TyrRS with opposite effects on the auto-PARylation of PARP1 provides a potential molecular basis for the observed dichotomic effects of RSV under different experimental paradigms. However, the fact that natural RSV exists as a diastereomeric mixture of its cis and trans isomers and cis-RSV is also a physiologically relevant isoform has not yet gained much scientific attention.

C(1)-Phenethyl Derivatives of [closo-1-CB11 H12 ]- and [closo-1-CB9 H10 ]- Anions: Difunctional Building Blocks for Molecular Materials

C(1)-vinylation of [closo-1-CB₉ H₁₀ ]^- (A) and [closo-1-CB₁₁ H₁₂ ]^- (B) with 4-benzyloxystyryl iodide followed by hydrogenation of the double bond and reductive deprotection of the phenol functionality led to C(1)-(4-hydroxyphenethyl) derivatives. The phenol functionality was protected as the acetate. The esters were then treated with PhI(OAc)₂ and the resulting isomers were separated kinetically (for derivatives of anion A) or by chromatography (for derivatives of anion B) giving the difunctionalized building blocks in overall yields of 9 % and 50 %, respectively. A similar series of reactions was performed starting with anions A and B and 4-methoxystyryl bromide and iodide. Significant differences in the reactivity of derivatives of the two carborane anions were rationalized with DFT computational results. Application of the difunctionalized carboranes as building blocks was demonstrated through preparation of two ionic liquid crystals. The extensive synthetic work is accompanied by single crystal XRD analysis of six derivatives.

Control of DNA structure and function by phytochemicals/DNA interaction: Resveratrol/piceatannol induces Cu2+-independent, cleavage of supercoiled plasmid DNA

Topoisomerases are enzymes that catalyze DNA unwinding and scissions to resolve topological entanglements possibly arising during DNA replication/transcription. Chemicals which disrupt or inhibit topoisomerase-mediated DNA unwinding can induce breaks that subsequently lead to programmed cell death. Herein we perform experiments guided by the following considerations. First, topoisomerase 1 initiates DNA cleavage utilizing the hydroxyl group of tyrosine 723 on its catalytic site as a nucleophile to attack the electrophilic phosphate on the DNA sugar-phosphate backbone. Secondly, the grape polyphenol resveratrol displays both topoisomerase inhibitory and Cu²⁺-dependent DNA-cutting activities, which contribute to its DNA replication/transcription inhibitory/anti-tumorigenic effects. Lastly, resveratrol contains a tyrosine-like phenolic ring; thus, upon binding to DNA whether resveratrol could act as a tyrosine mimetic to unwind and cut DNA via its hydroxyl groups warrants investigation. Polyphenol-DNA interactions (PDIs) were investigated using UV-visible spectral analysis; additionally, PDI mediated DNA changes were further analyzed by agarose gel electrophoresis using 3 supercoiled plasmid DNAs (pBR322, pSJ3, pHOT-1) as substrates. Resveratrol mediates time- and temperature-dependent, Cu²⁺-independent, non-enzymatic cleavage of supercoiled plasmid DNA into open, circular DNA products. Varying degree of unwinding of supercoiled DNA nucleolytic activity was also observed with other polyphenols including, piceatannol, quercetin, myricetin and EGCG. Interestingly, we found that piceatannol mediated Cu²⁺-independent DNA-cleavage activity was abolished by EDTA. The PDI-mediated nucleolytic cleavage of supercoiled DNA reported herein shows that polyphenolic phytochemicals display genome-active, nuclear effects by directly targeting the DNA topology which in turn could impact macromolecular processes associated with faithful replication and transmission of genetic information.

The interaction between resveratrol and two forms of copper as carbonate and nanoparticles on antioxidant mechanisms and vascular function in Wistar rats

BACKGROUND

Experimental studies have emphasized that cardiovascular alterations can be improved by the long-term use of resveratrol (trans-3,5,4'-trihydroxystilbene; RSV) as well as dietary copper (Cu) intake.

METHODS

Male Wistar rats were supplemented for 8 weeks with Cu (6.5 mg/kg diet) as either nanoparticles (40 nm, CuNPs) or carbonate (CuCO3). Half of the studied animals were supplemented with RSV (500 mg/kg diet). Vascular function and blood plasma antioxidant status, expressed as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), lipid hydroperoxides (LOOH) and malondialdehyde (MDA) were analyzed. The activity of ceruloplasmin (Cp), lipid profile, fasting glucose, and concentrations of Cu and zinc (Zn) were analyzed.

RESULTS

RSV supplementation resulted in the elevated activity of SOD and decreased CAT, GPx and LDL-cholesterol in both groups. RSV supplementation on CuNPs increased the participation of vasoconstrictor prostanoids and decreased ACh-induced vasodilation, while the participation of hyperpolarizing mechanism(s) was restored by activating KATP channels. Blood plasma glucose was decreased. RSV supplementation on CuCO3 enhanced ACh- and SNP-induced vasodilation and decreased NA-induced vasoconstriction. The lipid profile was improved, as well as Zn concentration. Meanwhile, Cu and Cp, and the markers of lipid peroxidation, reflected as LOOH and MDA, were decreased.

CONCLUSION

The use of RSV during CuCO3 intake improves vascular responses, the lipid profile and the antioxidant mechanism(s). The beneficial role of RSV was not observed in the CuNP group and decreased ACh-induced vasodilation and increased participation of vasoconstrictor prostanoids in the vascular regulation were noticed.

Antioxidant Activity and Neuroprotective Activity of Stilbenoids in Rat Primary Cortex Neurons via the PI3K/Akt Signalling Pathway

Antioxidant activity and neuroprotective activity of three stilbenoids, namely, trans-4-hydroxystilbene (THS), trans-3,5,4′-trihydroxy-stilbene (resveratrol, RES), and trans-3′,4′,3,5-tetrahydroxy-stilbene (piceatannol, PIC), against β-amyloid (Aβ)-induced neurotoxicity in rat primary cortex neurons were evaluated. THS, RES, and PIC significantly scavenged DPPH• and •OH radicals. All three stilbenoids were able to inhibit Aβ neurotoxicity by decreasing intracellular reactive oxygen species (ROS) via the PI3K/Akt signalling pathway. Specifically, stilbenoids significantly promoted Akt phosphorylation; suppressed Bcl-2/Bax expression; and inhibited caspase-9, caspase-3, and PARP cleavage. Molecular docking between stilbenoids with Akt indicated that stilbenoids could form hydrogen bond interactions with the COOH-terminal region of Akt. Additionally, the neuroprotective activity of stilbenoids correlated with the number and position of hydroxyl groups. The lack of meta-dihydroxyl groups on THS did not affect its neuroprotective activity in comparison with RES, whereas the ortho-dihydroxyl moiety on PIC significantly enhanced neuroprotective activity. These results provide new insights into the correlation between the biological activity and chemical structure of stilbenoids.

Oxyresveratrol-induced DNA cleavage triggers apoptotic response in Candida albicans

Oxyresveratrol is a naturally occurring phytoalexin produced by plants in response to infection. Biological activities of oxyresveratrol have been studied such as antioxidant, anticancer and anti-inflammation. However, further antimicrobial activity and its mechanism need to be investigated. This study exhibited growth inhibition against pathogenic fungi and investigated its mode of action. Oxyresveratrol inflicted cleavage on DNA, leading to G2/M phase arrest. DNA damage by oxyresveratrol was not the result of oxidative stress but it was triggered by direct binding to DNA. Oxyresveratrol-treated cells showed an apoptotic pathway characterized by phosphatidylserine exposure, apoptotic volume decrease and metacaspase activation. Mitochondria-associated apoptotic features also appeared. Oxyresveratrol-induced Ca²⁺ overload led to mitochondrial membrane depolarization and release of cytochrome c from mitochondria to cytosol. In conclusion, oxyresveratrol with DNA-binding affinity induces DNA cleavage, and eventually leads to mitochondria-mediated apoptosis in Candida albicans.

Transcriptome-Based Analysis in Lactobacillus plantarum WCFS1 Reveals New Insights into Resveratrol Effects at System Level

SCOPE

This study was undertaken to expand our insights into the mechanisms involved in the tolerance to resveratrol (RSV) that operate at system-level in gut microorganisms and advance knowledge on new RSV-responsive gene circuits.

METHODS AND RESULTS

Whole genome transcriptional profiling was used to characterize the molecular response of Lactobacillus plantarum WCFS1 to RSV. DNA repair mechanisms were induced by RSV and responses were triggered to decrease the load of copper, a metal required for RSV-mediated DNA cleavage, and H₂ S, a genotoxic gas. To counter the effects of RSV, L. plantarum strongly up- or downregulated efflux systems and ABC transporters pointing to transport control of RSV across the membrane as a key mechanism for RSV tolerance. L. plantarum also downregulated tRNAs, induced chaperones, and reprogrammed its transcriptome to tightly control ammonia levels. RSV induced a probiotic effector gene and a likely deoxycholate transporter, two functions that improve the host health status.

CONCLUSION

Our data identify novel protective mechanisms involved in RSV tolerance operating at system level in a gut microbe. These insights could influence the way RSV is used for a better management of gut microbial ecosystems to obtain associated health benefits.

Antioxidant activity of resveratrol ester derivatives in food and biological model systems

Resveratrol (R) was lipophilized by esterification in order to facilitate its application in a wide range of products and to possibly enhance its bioactivity. Twelve resveratrol derivatives were prepared using acyl chlorides of different chain length (C3:0-C22:6) and their antioxidant activities assessed. While resveratrol showed the highest antioxidant activity in oil-in-water emulsion, its derivatives (RC6:0, RC8:0, RC10:0, RC12:0, RC16:0) showed better antioxidant activity in a bulk oil system. Resveratrol esters RC20:5n-3 (REPA) and RC22:6n-3 (RDHA) showed the highest antioxidant activity when added to ground meat. Meanwhile, resveratrol derivatives (RC3:0-RC14:0) had better hydrogen peroxide scavenging activity than resveratrol. All test compounds except resveratrol and REPA inhibited copper-induced LDL oxidation. Moreover, test compounds effectively inhibited hydroxyl radical induced DNA scission. These results suggest that resveratrol derivatives could potentially serve as functional food ingredients and supplements for health promotion and disease risk reduction.

HPLC Identification of Copper (II)-Trans-Resveratrol Complexes in Ethanolic Aqueous Solution

Reversed-phase high-performance liquid chromatography assay with the diode array detector was applied for detection of trans-resveratrol complexes with copper (II). Two complexes with copper to resveratrol ratio 3:2 and 1:1 were identified in ethanolic-aqueous solutions in neutral and acidic conditions. The matrix-assisted laser desorption ionization-time of flight mass spectrometry was used for evaluation of complexes in eluate liquid fraction. The structures of complexes were modeled by Titan, Spartan and HyperChem software. The findings obtained satisfactorily explain the chromatographic data and could provide useful an additional data about these forms in which is present trans-resveratrol in wine (free and/or forming complex with copper).

Resveratrol-Potential Antibacterial Agent against Foodborne Pathogens

Bacterial foodborne pathogens are a significant health burden and the recent emergence of pathogenic resistant strains due to the excessive use of antibiotics makes it more difficult to effectively treat infections as a result of contaminated food. Awareness of this impending health crisis has spurred the search for alternative antimicrobials with natural plant antimicrobials being among the more promising candidates as these substances have good acceptability and likely low toxicity levels as they have long been used in traditional medicines. Resveratrol (3,5,4′-trihydroxystilbene) is a naturally occurring stilbenoid which has been gaining considerable attention in medical field due to its diverse biological activities - it has been reported to exhibit antioxidant, cardioprotective, anti-diabetic, anticancer, and antiaging properties. Given that resveratrol is phytoalexin, with increased synthesis in response to infection by phytopathogens, there has been interest in exploring its antimicrobial activity. This review aims to provide an overview of the published data on the antibacterial activity of resveratrol against foodborne pathogens, its mechanisms of action as well as its possible applications in food packing and processing; in addition we also summarize the current data on its potential synergism with known antibacterials and future research and applications.

Resveratrol stimulates the metabolic reprogramming of human CD4+ T cells to enhance effector function

The polyphenol resveratrol activates the deacetylase Sirt1, resulting in various antioxidant, chemoprotectant, neuroprotective, cardioprotective, and anti-inflammatory properties. We found that at high concentrations of resveratrol, human CD4⁺ T cells showed defective antigen receptor signaling and arrest at the G₁ stage of the cell cycle, whereas at low concentrations, cells were readily activated and exhibited enhanced Sirt1 deacetylase activity. Nevertheless, low-dose resveratrol rapidly stimulated genotoxic stress in the T cells, which resulted in engagement of a DNA damage response pathway that depended on the kinase ATR [ataxia telangiectasia-mutated (ATM) and Rad3-related], but not ATM, and subsequently in premitotic cell cycle arrest. The concomitant activation of p53 was coupled to the expression of gene products that regulate cell metabolism, leading to a metabolic reprogramming that was characterized by decreased glycolysis, increased glutamine consumption, and a shift to oxidative phosphorylation. These alterations in the bioenergetic homeostasis of CD4⁺ T cells resulted in enhanced effector function, with both naïve and memory CD4⁺ T cells secreting increased amounts of the inflammatory cytokine interferon-γ. Thus, our data highlight the wide range of metabolic adaptations that CD4⁺ T lymphocytes undergo in response to genomic stress.

Antitumor activity of resveratrol is independent of Cu(II) complex formation in MCF-7 cell line

Resveratrol (Rsv) is widely reported to possess anticarcinogenic properties in a plethora of cellular and animal models having limited toxicity toward normal cells. In the molecular level, Rsv can act as a suppressive agent for several impaired signaling pathways on cancer cells. However, Fukuhara and Miyata have shown a non-proteic reaction of Rsv, which can act as a prooxidant agent in the presence of copper (Cu), causing cellular oxidative stress accompanied of DNA damage. After this discovery, the complex Rsv-Cu was broadly explored as an antitumor mechanism in multiples tumor cell lines. The aim of the study is to explore the anticarcinogenic behavior of resveratrol-Cu(II) complex in MCF-7 cell line. Selectivity of Rsv binding to Cu ions was analyzed by HPLC and UV-VIS. The cells were enriched with concentrations of 10 and 50µM CuSO₄ solution and treated with 25µM of Rsv. Copper uptake after enrichment of cells, as its intracellular distribution in MCF-7 line, was scanned by ICP-MS and TEM-EDS. Cell death and intracellular ROS production were determined by flow cytometry. Different from the extracellular model, no relationship of synergy between Rsv-Cu(II) and reactive oxidative species (ROS) production was detected in vitro. ICP-MS revealed intracellular copper accumulation to both chosen concentrations (0.33±0.09 and 1.18±0.13ppb) but there is no promotion of cell death by Rsv-Cu(II) complex. In addition, significant attenuation of ROS production was detected when cells were exposed to CuSO₄ after Rsv treatment, falling from 7.54% of ROS production when treated only with Rsv to 3.07 and 2.72% with CuSO₄. Based on these findings antitumor activity of resveratrol when in copper ions presence, is not mediated by Rsv-Cu complex formation in MCF-7 human cell line, suggesting that the antitumoral reaction is dependent of a cancer cellular model.

Involvement of NADPH oxidase in high-dose phenolic acid-induced pro-oxidant activity on rat mesenteric venules

In the present study, we investigated the potential role of phenolic acids in initiating oxidative damage to microvascular endothelial cells and the underlying mechanism mediating the pro-oxidant action. Male Wistar rats received high doses of phenolic acid [caffeic acid (CA), salvianolic acid B (SAB), chlorogenic acid (ChA) or ferulic acid (FA)]. The creation of reactive oxygen species in mesenteric microcirculation endothelial cells and adherent leukocytes along with venules were assessed using intravital microscopy. The expression levels of NADPH oxidase subunits (Nox4 and p22^phox) in terminal ileum tissues were determined by western blot analysis. Intravenous injection of high-dose ChA or CA (7 mg/kg) markedly increased the peroxide production in the venular walls and upregulated the protein expression levels of Nox4 and p22^phox in the ileum tissues, while the same dose of CA and SAB made no difference within the observation period. No changes were observed in the number of leukocytes adhering to the venular walls. High-dose ChA and FA led to an imbalance between the oxidant and antioxidant mechanism by boosting the expression levels of NADPH oxidase. Thus, we clarified the rationale behind the adverse effects of a herbal injection containing high levels of phenolic acid compounds.

A comparative assessment of the cytotoxicity and nitric oxide reducing ability of resveratrol, pterostilbene and piceatannol in transformed and normal mouse macrophages

The present study investigated the pharmacological effects of three stilbenoids, resveratrol (RES), pterostilbene (PTR) and piceatannol (PIC), in transformed and normal macrophages. Our first aim was to comparatively assess the cytotoxicity of RES, PTR and PIC in unstimulated transformed mouse macrophages (RAW 264.7 cells) and primary peritoneal macrophages (PMs) harvested from both wild type and Nrf2 (nuclear factor erythroid 2-related factor 2)-deficient female mice. Our second aim was to investigate whether the inhibitory effect of RES, PTR and PIC on nitric oxide (NO) release from stimulated PMs depends on the status of the transcription factor Nrf2. The rationale for investigating Nrf2 status was based upon recent reports showing that certain compounds (sulforaphane and linalool) suppress LPS-induced inflammation in an Nrf2-dependent manner. Cell viability studies confirmed our prior work in unstimulated RAW 264.7 cells, with cytotoxic potency decreasing in the order of PTR > PIC > RES. Unstimulated PMs, regardless of Nrf2 status, were less sensitive to stilbenes, requiring at least a threefold higher stilbene concentration to inhibit cell viability, with cytotoxic potency again decreasing in the order of PTR > PIC > RES. In studies focused on our second aim, IC₅₀ values for NO inhibition (measured as [Formula: see text]) in wild type PMs were similar for all three stilbenes (∼10 μM). In Nrf2-deficient PMs, the IC₅₀ for NO inhibition by PIC did not change; however, a rightward shift in the concentration effect curve was observed for both RES and PTR, indicating a role for Nrf2 in the suppression of LPS-induced [Formula: see text] accumulation by these particular stilbenes.

Resveratrol Directly Binds to Mitochondrial Complex I and Increases Oxidative Stress in Brain Mitochondria of Aged Mice

Resveratrol is often described as a promising therapeutic molecule for numerous diseases, especially in metabolic and neurodegenerative disorders. While the mechanism of action is still debated, an increasing literature reports that resveratrol regulates the mitochondrial respiratory chain function. In a recent study we have identified mitochondrial complex I as a direct target of this molecule. Nevertheless, the mechanisms and consequences of such an interaction still require further investigation. In this study, we identified in silico by docking study a binding site for resveratrol at the nucleotide pocket of complex I. In vitro, using solubilized complex I, we demonstrated a competition between NAD+ and resveratrol. At low doses (<5μM), resveratrol stimulated complex I activity, whereas at high dose (50 μM) it rather decreased it. In vivo, in brain mitochondria from resveratrol treated young mice, we showed that complex I activity was increased, whereas the respiration rate was not improved. Moreover, in old mice with low antioxidant defenses, we demonstrated that complex I activation by resveratrol led to oxidative stress. These results bring new insights into the mechanism of action of resveratrol on mitochondria and highlight the importance of the balance between pro- and antioxidant effects of resveratrol depending on its dose and age. These parameters should be taken into account when clinical trials using resveratrol or analogues have to be designed.

A paradoxical relationship between Resveratrol and copper (II) with respect to degradation of DNA and RNA

Resveratrol (R), a plant polyphenol, is known to reduce Cu (II) to Cu (I) generating reactive oxygen species that can cleave plasmid DNA. Here we report a surprising observation of a paradoxical relationship between R and Cu whereby plasmid DNA cleaving / degrading activity of R-Cu increased progressively as the ratio of R to Cu was increased i.e., the concentration of Cu was successively reduced with respect to a fixed concentration R. Whereas cleavage of plasmid DNA occurred at low molar ratios of R to Cu, at higher ratios, complete degradation of DNA was achieved. By further increasing the ratio, whereby the concentration of Cu was reduced to very low levels, the DNA degrading activity of R-Cu was lost. This paradoxical relationship is also seen with respect to eukaryotic genomic DNA and RNA. Since R-Cu may have anti-cancer and anti-viral activities, our findings may not only help to improve the therapeutic efficacy of R-Cu but also reduce its toxic side effects with the use of low concentration of Cu.

A paradoxical relationship between Resveratrol and copper (II) with respect to degradation of DNA and RNA

Resveratrol (R), a plant polyphenol, is known to reduce Cu (II) to Cu (I) generating reactive oxygen species that can cleave plasmid DNA. Here we report a surprising observation of a paradoxical relationship between R and Cu whereby plasmid DNA cleaving / degrading activity of R-Cu increased progressively as the ratio of R to Cu was increased i.e., the concentration of Cu was successively reduced with respect to a fixed concentration R. Whereas cleavage of plasmid DNA occurred at low molar ratios of R to Cu, at higher ratios, complete degradation of DNA was achieved. By further increasing the ratio, whereby the concentration of Cu was reduced to very low levels, the DNA degrading activity of R-Cu was lost. This paradoxical relationship is also seen with respect to eukaryotic genomic DNA and RNA. Since R-Cu may have anti-cancer and anti-viral activities, our findings may not only help to improve the therapeutic efficacy of R-Cu but also reduce its toxic side effects with the use of low concentration of Cu.

Modulation of copper accumulation and copper-induced toxicity by antioxidants and copper chelators in cultured primary brain astrocytes

Copper is essential for several important cellular processes, but an excess of copper can also lead to oxidative damage. In brain, astrocytes are considered to play a pivotal role in the copper homeostasis and antioxidative defence. To investigate whether antioxidants and copper chelators can modulate the uptake and the toxicity of copper ions in brain astrocytes, we used primary astrocytes as cell culture model. These cells accumulated substantial amounts of copper during exposure to copper chloride. Copper accumulation was accompanied by a time- and concentration-dependent loss in cell viability, as demonstrated by a lowering in cellular MTT reduction capacity and by an increase in membrane permeability for propidium iodide. During incubations in the presence of the antioxidants ascorbate, trolox or ebselen, the specific cellular copper content and the toxicity in copper chloride-treated astrocyte cultures were strongly increased. In contrast, the presence of the copper chelators bathocuproine disulfonate or tetrathiomolybdate lowered the cellular copper accumulation and the copper-induced as well as the ascorbate-accelerated copper toxicity was fully prevented. These data suggest that predominantly the cellular content of copper determines copper-induced toxicity in brain astrocytes.

Toward an understanding of the role of a catechol moiety in cancer chemoprevention: The case of copper- and o-quinone-dependent Nrf2 activation by a catechol-type resveratrol analog

SCOPE

Catechol moieties are commonly present in dietary natural products that exert cancer chemopreventive activity. While the oxidative conversion of catechols into their corresponding o-quinones is generally considered to contribute to their cancer chemopreventive effects, the mechanism of the intracellular conversion has not been fully elucidated.

METHODS AND RESULTS

Among resveratrol and its hydroxylated analogs examined, only 3,4-dihydroxy-trans-stilbene exerted cytoprotective effects against t-butylhydroperoxide-induced death of HepG2 cells. This resveratrol analog activated the nuclear factor erythroid-2-related factor 2 (Nrf2) pathway through stimulating phosphorylation of Akt and inducing keap1 modification, thereby resulting in its nuclear translocation and subsequent transcriptional induction of phase II detoxifying enzymes. Its cytoprotective effect through Nrf2 activation was largely abrogated by pretreatment of cells with DTT, a sulfhydryl-containing nucleophile, and neocuproine, a specific chelating agent for copper ions.

CONCLUSION

We identified 3,4-dihydroxy-trans-stilbene as a novel Nrf2 activator that is converted intracellularly into its corresponding o-quinone electrophile by copper ions. The copper-mediated oxidation was required for the Nrf2 activation, subsequent transcriptional induction of phase II detoxifying enzymes and ultimately for cytoprotection. The findings demonstrate a previously underrecognized role for intracellular copper ions in the cancer chemopreventive effects of catechol-containing dietary natural products.

Resveratrol induces DNA damage in colon cancer cells by poisoning topoisomerase II and activates the ATM kinase to trigger p53-dependent apoptosis

Resveratrol (trans-3,4',5-trihydroxystilbene) is a natural polyphenol synthesized by various plants such as grape vine. Resveratrol (RSV) is a widely studied molecule, largely for its chemopreventive effect in different mouse cancer models. We propose a mechanism underlying the cytotoxic activity of RSV on colon cancer cells. Our data show that resveratrol induces apoptosis, as observed by the cleavage of PARP-1 and chromatin condensation. We show that the tumor suppressor p53 is activated in response to RSV and participates to the apoptotic process. Additionally, we show that HCT-116 p53 wt colon carcinoma cells are significantly more sensitive than HCT-116 p53-/- cells to RSV. RSV induces DNA damage including double strand breaks, as evidenced by the presence of multiple γ-H2AX foci in 50% of cells after a 24 h treatment with 25 μM RSV. The formation of DNA damage does not appear to rely on a pro-oxidant effect of the molecule, inhibition of topoisomerase I, or DNA intercalation. Rather, we show that DNA damage is the consequence of type II topoisomerase poisoning. Exposure of HCT-116 cells to RSV leads to activation of the Ataxia Telangiectasia Mutated (ATM) kinase, and ATM is required to activate p53.

Inhibition of cancer derived cell lines proliferation by synthesized hydroxylated stilbenes and new ferrocenyl-stilbene analogs. Comparison with resveratrol

Further advances in understanding the mechanism of action of resveratrol and its application require new analogs to identify the structural determinants for the cell proliferation inhibition potency. Therefore, we synthesized new trans-resveratrol derivatives by using the Wittig and Heck methods, thus modifying the hydroxylation and methoxylation patterns of the parent molecule. Moreover, we also synthesized new ferrocenylstilbene analogs by using an original protective group in the Wittig procedure. By performing cell proliferation assays we observed that the resveratrol derivatives show inhibition on the human colorectal tumor SW480 cell line. On the other hand, cell viability/cytotoxicity assays showed a weaker effects on the human hepatoblastoma HepG2 cell line. Importantly, the lack of effect on non-tumor cells (IEC18 intestinal epithelium cells) demonstrates the selectivity of these molecules for cancer cells. Here, we show that the numbers and positions of hydroxy and methoxy groups are crucial for the inhibition efficacy. In addition, the presence of at least one phenolic group is essential for the antitumoral activity. Moreover, in the series of ferrocenylstilbene analogs, the presence of a hidden phenolic function allows for a better solubilization in the cellular environment and significantly increases the antitumoral activity.

High-dose chlorogenic acid induces inflammation reactions and oxidative stress injury in rats without implication of mast cell degranulation

ETHNOPHARMACOLOGICAL RELEVANCE

Chlorogenic acid (CA) exits widely in those Chinese herbal injections that have antibacterial and antiphlogistic effects and belongs to the ethnopharmacological family of medicines. Chinese herbal injections containing high levels of CA have been reported to increase the adverse drug reactions, but the mechanism for which is still unclear. In this study, we investigated the mechanism of the CA derived adverse drug reactions.

AIM OF THE STUDY

The present study was to explore the potential role of CA in initiating inflammatory reaction and the underlying mechanism.

MATERIALS AND METHODS

Male Wistar rats were treated with different dosages of CA for different time period. The variables examined included microcirculation by intravital microscopy, histology of ileum tissue, expression of adhesion molecules CD11b and CD18 on leukocytes by flow cytometry, myeloperoxidase activity and maleic dialdehyde content in ileum tissue by spectrophotometry, activity of superoxide dismutase and catalase in serum by ELISA, and expression of NADPH oxidase subunits by PCR and Western blot.

RESULTS

High-dose CA increased the number of adherent leukocytes, generation of peroxides in the venular walls and induced albumin leakage from mesentery venules. High-dose CA induced changes also included an increase in maleic dialdehyde, myeloperoxidase, inflammatory cytokines and NADPH oxidase activities, and a decline in activity of superoxide dismutase and catalase.

CONCLUSION

High-dose, but not Low-dose CA induced inflammation reaction, and in this process an imbalance between oxidant and antioxidant mechanism may be involved, providing more information for better understanding the rationale behind the adverse effects of CA.

Resveratrol induces premature senescence in lung cancer cells via ROS-mediated DNA damage

Resveratrol (RV) is a natural component of red wine and grapes that has been shown to be a potential chemopreventive and anticancer agent. However, the molecular mechanisms underlying RV's anticancer and chemopreventive effects are incompletely understood. Here we show that RV treatment inhibits the clonogenic growth of non-small cell lung cancer (NSCLC) cells in a dose-dependent manner. Interestingly, the tumor-suppressive effect of low dose RV was not associated with any significant changes in the expression of cleaved PARP and activated caspase-3, suggesting that low dose RV treatment may suppress tumor cell growth via an apoptosis-independent mechanism. Subsequent studies reveal that low dose RV treatment induces a significant increase in senescence-associated β-galactosidase (SA-β-gal) staining and elevated expression of p53 and p21 in NSCLC cells. Furthermore, we show that RV-induced suppression of lung cancer cell growth is associated with a decrease in the expression of EF1A. These results suggest that RV may exert its anticancer and chemopreventive effects through the induction of premature senescence. Mechanistically, RV-induced premature senescence correlates with increased DNA double strand breaks (DSBs) and reactive oxygen species (ROS) production in lung cancer cells. Inhibition of ROS production by N-acetylcysteine (NAC) attenuates RV-induced DNA DSBs and premature senescence. Furthermore, we show that RV treatment markedly induces NAPDH oxidase-5 (Nox5) expression in both A549 and H460 cells, suggesting that RV may increase ROS generation in lung cancer cells through upregulating Nox5 expression. Together, these findings demonstrate that low dose RV treatment inhibits lung cancer cell growth via a previously unappreciated mechanism, namely the induction of premature senescence through ROS-mediated DNA damage.

DNA breakage induced by piceatannol and copper(II): Mechanism and anticancer properties

Piceatannol (3,3',4,5'-tetrahydroxy-trans-stilbene; Pice), found in a variety of plant sources including grapes, red wine, peanuts and rhubarb, is known as a metabolite and analog of Resveratrol (3,5,4'-trihydroxy-trans-stilbene; Res) and has higher bioactivity than Res. To explore the mechanism of DNA damage induced by Pice in the presence of copper (Cu)(II), gel electrophoresis, UV-visible spectroscopy, fluorescence spectroscopy and Fourier transform infrared spectroscopy were used. The results of gel electrophoresis demonstrated that the hydroxyl radical played a critical role in DNA cleavage. Spectroscopy confirmed that the mechanism of DNA cleavage induced by Pice-Cu(II) involves the Haber Weiss and Fenton reactions. Pice chelates with Cu(II) as a bidentate ligand, and the Pice-Cu(II) complex undergoes intramolecular electron transfer to form the semiquinone radical anion and Cu(I), which may be reoxidated by O(2) to form Cu(II) with hydroxyl radical generation. In brief, the formation of the hydroxyl radical and the Cu(II)/Cu(I) redox cycle play a key role in inducing DNA damage. In this process, Pice demonstrated pro-oxidant properties. Oxidative product(s) of Pice, semiquinone, was formed and Cu(I) was reoxidized to Cu(II). The redox cycling of copper generated reactive oxygen species, which induced DNA cleavage, the hallmark of cell apoptosis. The mechanism of DNA breakage induced by Pice-Cu(II) may be a significant pathway through which cancer cells are killed.

Safety of resveratrol with examples for high purity, trans-resveratrol, resVida(®)

Studies with resVida(®) (a high purity trans-resveratrol) show that trans-resveratrol is a substance of low oral toxicity. An acceptable daily intake (ADI) in food of 450 mg/day has been defined, a level well beyond natural dietary intake of trans-resveratrol. The ADI was based on no-observed-adverse-effect-levels (NOAELs) of 750 mg/kg bw/day in 13-week developmental toxicity studies by the dietary route and a standard safety margin of 100. In studies by gavage, the kidney and bladder are target organs at very high dosages (2,000-3,000 mg/kg bw/day). Six-month studies in rat and rabbit models show no significant increase in toxicity in comparison to 4-week studies. Lower quoted NOAELs in gavage studies (ca. 300 mg/kg bw/day) potentially reflect more rapid bioavailability, but different dosage regimes complicate comparisons. Short-term studies show no genotoxicity in vivo. A 6-month mouse carcinogenicity model showed no increase in tumors. Clinical data support an ADI of at least 450 mg/day, and kinetic data from the DSM 13-week toxicity study also support the expectation of no increase in toxicity with longer term intake.

A study of resveratrol-copper complexes by electrospray ionization mass spectrometry and density functional theory calculations

Resveratrol is a polyphenolic compound found in plants and human foods which has shown biological activities including chemoprevention, acting through a mechanism which involves the reduction of Cu(II) species. By electrospray ionization (ESI) mass spectrometry we have produced and detected the resveratrol-copper complexes [Resv+Cu](+), [Resv+Cu+H(2)O](+) and [2Resv+Cu](+) by using a resveratrol/CuSO(4) solution in CH(3)CN/H(2)O. The most stable structures of the detected complexes have been calculated at the B3LYP/6-311G(d) level of theory. Resveratrol interacts with the copper ion through nucleophilic carbon atoms on the aromatic ring and the alkenyl group. The fact that only singly charged ions were observed implies that Cu(II) is reduced to Cu(I) in the ESI process. For investigating the structure-reactivity correlation, we have carried out a similar study on the synthetic analogue dihydroresveratrol (DHResv). For the latter only the [DHResv+Cu](+) complex has been detected.

Quantitative structure-antioxidant activity relationship of trans-resveratrol oligomers, trans-4,4'-dihydroxystilbene dimer, trans-resveratrol-3-O-glucuronide, glucosides: trans-piceid, cis-piceid, trans-astringin and trans-resveratrol-4'-O-beta-D-glucopyranoside

By means of the accurate computations based on the density functional theory, the relationships between the molecular structure and free radical scavenging activity have been studied for dimer of trans-4,4'-dihydroxystilbene, trans-resveratrol-3-O-glucuronide, glucosides: geometric stereoisomers of piceid, trans-astringin, trans-resveratrol-4'-O-beta-D-glucopyranoside and trans-resveratrol dimers: pallidol, geometric stereoisomers of epsilon-viniferin, stereoisomers of trans-delta-viniferin and trans-resveratrol trimer-gnetin H. Our results have shown that all oligomers, glucosides and trans-resveratrol-3-O-glucuronide exhibit stronger antioxidant activity than trans-resveratrol and that dimer of trans-4,4'-dihydroxystilbene is a stronger antioxidant than its monomer as well as that cis stereoisomers of piceid and epsilon-viniferin are weaker antioxidant than their trans stereoisomers. The homolytic bond dissociation enthalpy values calculated reveal the predominant H-transfer capacity of the OH groups in the trans-stilbene moiety. The hydrogen atom transfer mechanism of free radicals scavenging by the compounds studied is proved more preferable than the single-electron transfer mechanism in the mediums investigated. All the above-mentioned compounds have been proved to have significantly higher ability to electron donation in water medium than in the gas phase. The experimental observations are satisfactorily explained by the results obtained.

Resveratrol: its biologic targets and functional activity

The polyphenolic phytoalexin resveratrol (RSV) and its analogues have received tremendous attention over the past couple of decades because of a number of reports highlighting their benefits in vitro and in vivo in a variety of human disease models, including cardio- and neuroprotection, immune regulation, and cancer chemoprevention. These studies have underscored the high degree of diversity in terms of the signaling networks and cellular effector mechanisms that are affected by RSV. The activity of RSV has been linked to cell-surface receptors, membrane signaling pathways, intracellular signal-transduction machinery, nuclear receptors, gene transcription, and metabolic pathways. The promise shown by RSV has prompted heightened interest in studies aimed at translating these observations to clinical settings. In this review, we present a comprehensive account of the basic chemistry of RSV, its bioavailability, and its multiple intracellular target proteins and signaling pathways.

Radical-scavenging activity and mechanism of resveratrol-oriented analogues: influence of the solvent, radical, and substitution

Resveratrol (3,5,4'-trihydroxy-trans-stilbene, 3,5,4'-THS) is a well-known natural antioxidant and cancer chemopreventive agent that has attracted much interest in the past decade. To find a more active antioxidant and investigate the antioxidative mechanism with resveratrol as the lead compound, we synthesized 3,5-dihydroxy-trans-stilbene (3,5-DHS), 4-hydroxy-trans-stilbene (4-HS) 3,4-dihydroxy-trans-stilbene (3,4-DHS), 4,4'-dihydroxy-trans-stilbene (4,4'-DHS), 4-hydroxy-3-methoxy-trans-stilbene (3-MeO-4-HS), 4-hydroxy-4'-methoxy-trans-stilbene (4'-MeO-4-HS), 4-hydroxy-4'-methyl-trans-stilbene (4'-Me-4-HS), 4-hydroxy-4'-nitro-trans-stilbene (4'-NO(2)-4-HS), and 4-hydroxy-4'-trifluoromethyl-trans-stilbene (4'-CF(3)-4-HS). The radical-scavenging activity and detailed mechanism of resveratrol and its analogues (ArOHs) were investigated by the reaction kinetics with galvinoxyl (GO(*)) and 2,2-diphenyl-1-picrylhydrazyl (DPPH(*)) radicals in ethanol and ethyl acetate at 25 degrees C, using UV-vis spectroscopy. It was found that the reaction rates increase with increasing the electron-rich environment in the molecules, and the compound bearing o-dihydroxyl groups (3,4-DHS) is the most reactive one among the examined resveratrol analogues. The effect of added acetic acid on the measured rate constant for GO(*)-scavenging reaction reveals that in ethanol that supports ionization solvent besides hydrogen atom transfer (HAT), the kinetics of the process is partially governed by sequential proton loss electron transfer (SPLET). In contrast to GO(*), DPPH(*) has a relatively high reduction potential and therefore enhances the proportion of SPLET in ethanol. The relatively low rate constants for the reactions of ArOHs with GO(*) or DPPH(*) in ethyl acetate compared with the rate constants in ethanol prove that in ethyl acetate these reactions occur primarily by the HAT mechanism. The contribution of SPLET and HAT mechanism depends on the ability of the solvent to ionize ArOH and the reduction potential of the free radical involved. Furthermore, the fate of the ArOH-derived radicals, i.e., the phenoxyl radicals, was investigated by the oxidative product analysis of ArOHs and GO(*) in ethanol. The major products were dihydrofuran dimers in the case of resveratrol, 4,4'-DHS, and 4-HS and a dioxane-like dimer in the case of 3,4-DHS. It is suggested from the oxidative products of these ArOHs that the hydroxyl group at the 4-position is much easier to subject to oxidation than other hydroxyl groups, and the dioxane-like dimer is formed via an o-quinone intermediate.

Monitoring of long-term effects of resveratrol on cell cycle progression of human HeLa cells after administration of a single dose

Expression of the human papillomavirus-encoded oncoproteins E6 and E7 in human HeLa cervical carcinoma cells results in their escape from the proper control of the cell cycle progression. Therefore, their susceptibility to agents modulating cell cycle differs from that in cells in which the control of cell cycle regulation is intact. Recently, a number of experimental studies revealed that polyphenols, especially resveratrol, could exert a strong antiproliferative effect. Polyphenols (e.g., resveratrol or epicatechins), potent antioxidant agents, are abundant components of our diet and, therefore, may not only affect the proliferation of healthy cells in the organism but also modulate the action of distinct anticancer drugs. Indeed, it has been shown that resveratrol enhances the antimitotic effect exerted by roscovitine (ROSC), a potent cyclin-dependent kinase inhibitor, on human MCF-7 breast cancer cells. In the present contribution the action of resveratrol alone and in combination with ROSC on human HeLa cells was determined. Resveratrol inhibited proliferation of exponentially growing HeLa cells. Exposure of HeLa cells to 50 micromol/L resveratrol blocked cells in the S phase in a time-dependent manner. After 12 h the population of G(2)/M-phase cells completely disappeared, and during a further 12 h the frequency of S-phase cells markedly increased and reached approximately 90%. Thus, resveratrol synchronized HeLa cells in the S phase. After removal of resveratrol, synchronized HeLa cells rapidly progressed through the cell cycle. Four hours after medium change, more than 70% of cells moved into the G(2)/M phase. Moreover, resveratrol combined with ROSC enhanced the antiproliferative action of resveratrol.