Resveratrol preferentially inhibits protein kinase C-catalyzed phosphorylation of a cofactor-independent, arginine-rich protein substrate by a novel mechanism

The Journey of Resveratrol from Vineyards to Clinics

With rising technological advancements, several factors influence the lifestyle of people and stimulate chronic inflammation that severely affects the human body. Chronic inflammation leads to a broad range of physical and pathophysiological distress. For many years, non-steroidal drugs and corticosteroids were most frequently used in treating inflammation and related ailments. However, long-term usage of these drugs aggravates the conditions of chronic diseases and is presented with morbid side effects, especially in old age. Hence, the quest for safe and less toxic anti-inflammatory compounds of high therapeutic potential with least adverse side effects has shifted researchers' attention to ancient medicinal system. Resveratrol (RSV) - 3,4,5^' trihydroxystilbene is one such naturally available polyphenolic stilbene derivative obtained from various plant sources. For over 2000 years, these plants have been used in Asian medicinal system for curing inflammation-associated disorders. There is a wealth of in vitro, in vivo and clinical evidence that shows RSV could induce anti-aging health benefits including, anti-cancer, anti-inflammatory, anti-oxidant, phytoesterogenic, and cardio protective properties. However, the issue of rapid elimination of RSV through the metabolic system and its low bio-availability is of paramount importance which is being studied extensively. Therefore, in this article, we scientifically reviewed the molecular targets, biological activities, beneficial and contradicting effects of RSV as evinced by clinical studies for the prevention and treatment of inflammation-mediated chronic disorders.

Oxidative Stress in Tauopathies: From Cause to Therapy

Oxidative stress (OS) is the result of an imbalance between the production of reactive oxygen species (ROS) and the antioxidant capacity of cells. Due to its high oxygen demand, the human brain is highly susceptible to OS and, thus, it is not a surprise that OS has emerged as an essential component of the pathophysiology of several neurodegenerative diseases, including tauopathies. Tauopathies are a heterogeneous group of age-related neurodegenerative disorders characterized by the deposition of abnormal tau protein in the affected neurons. With the worldwide population aging, the prevalence of tauopathies is increasing, but effective therapies have not yet been developed. Since OS seems to play a key role in tauopathies, it has been proposed that the use of antioxidants might be beneficial for tau-related neurodegenerative diseases. Although antioxidant therapies looked promising in preclinical studies performed in cellular and animal models, the antioxidant clinical trials performed in tauopathy patients have been disappointing. To develop effective antioxidant therapies, the molecular mechanisms underlying OS in tauopathies should be completely understood. Here, we review the link between OS and tauopathies, emphasizing the causes of OS in these diseases and the role of OS in tau pathogenesis. We also summarize the antioxidant therapies proposed as a potential treatment for tauopathies and discuss why they have not been completely translated to clinical trials. This review aims to provide an integrated perspective of the role of OS and antioxidant therapies in tauopathies. In doing so, we hope to enable a more comprehensive understanding of OS in tauopathies that will positively impact future studies.

Resveratrol and related stilbene derivatives induce stress granules with distinct clearance kinetics

Stress granules (SGs) are ribonucleoprotein functional condensates that form under stress conditions in all eukaryotic cells. Although their stress-survival function is far from clear, SGs have been implicated in the regulation of many vital cellular pathways. Consequently, SG dysfunction is thought to be a mechanistic point of origin for many neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS). Additionally, SGs are thought to play a role in pathogenic pathways as diverse as viral infection and chemotherapy resistance. There is a growing consensus on the hypothesis that understanding the mechanistic regulation of SG physical properties is essential to understanding their function. Although the internal dynamics and condensation mechanisms of SGs have been broadly investigated, there have been fewer investigations into the timing of SG formation and clearance in live cells. Because the lifetime of SG persistence can be a key factor in their function and tendency toward pathological dysregulation, SG clearance mechanisms deserve particular attention. Here we show that resveratrol and its analogues piceatannol, pterostilbene, and 3,4,5,4'-tetramethoxystilbene induce G3BP-dependent SG formation with atypically rapid clearance kinetics. Resveratrol binds to G3BP, thereby reducing its protein-protein association valency. We suggest that altering G3BP valency is a pathway for the formation of uniquely transient SGs.

Mechanisms of Aging and the Preventive Effects of Resveratrol on Age-Related Diseases

Aging gradually decreases cellular biological functions and increases the risk of age-related diseases. Cancer, type 2 diabetes mellitus, cardiovascular disease, and neurological disorders are commonly classified as age-related diseases that can affect the lifespan and health of individuals. Aging is a complicated and sophisticated biological process involving damage to biochemical macromolecules including DNA, proteins, and cellular organelles such as mitochondria. Aging causes multiple alterations in biological processes including energy metabolism and nutrient sensing, thus reducing cell proliferation and causing cellular senescence. Among the polyphenolic phytochemicals, resveratrol is believed to reduce the negative effects of the aging process through its multiple biological activities. Resveratrol increases the lifespan of several model organisms by regulating oxidative stress, energy metabolism, nutrient sensing, and epigenetics, primarily by activating sirtuin 1. This review summarizes the most important biological mechanisms of aging, and the ability of resveratrol to prevent age-related diseases.

Resveratrol binds and activates RKIP protein in colorectal cancer

Raf-1 kinase inhibitory protein (RKIP) acts as a tumor cell metastasis suppressor and prognostic indicator for survival in various cancers. Its use is predicted to improve therapy for various malignancies, including colorectal cancer (CRC). RKIP, frequently denoted as phosphatidylethanolamine-binding protein 1, is expressed in all normal mammalian tissues. RKIP functions as an inhibitor of the Raf-1, PI-3K, and MAP kinase (MAPK) pathways. In this study, we found that resveratrol induced the expression of RKIP at protein levels. To elucidate the structural basis of the interaction between resveratrol and RKIP, we performed computational studies that explore the binding affinity and ligand efficacy of resveratrol against RKIP. This study reveals the prognostic significance of RKIP metastasis suppressor activity against CRC and its structural arrangements during drug-target interactions.

Resveratrol induces dephosphorylation of Tau by interfering with the MID1-PP2A complex

The formation of paired helical filaments (PHF), which are composed of hyperphosphorylated Tau protein dissociating from microtubules, is one of the pathological hallmarks of Alzheimer's disease (AD) and other tauopathies. The most important phosphatase that is capable of dephosphorylating Tau at AD specific phospho-sites is protein phosphatase 2 A (PP2A). Here we show that resveratrol, a polyphenol, significantly induces PP2A activity and reduces Tau phosphorylation at PP2A-dependent epitopes. The increase in PP2A activity is caused by decreased expression of the MID1 ubiquitin ligase that mediates ubiquitin-specific modification and degradation of the catalytic subunit of PP2A when bound to microtubules. Interestingly, we further show that MID1 expression is elevated in AD tissue. Our data suggest a key role of MID1 in the pathology of AD and related tauopathies. Together with previous studies showing that resveratrol reduces β-amyloid toxicity they also give evidence of a promising role for resveratrol in the prophylaxis and therapy of AD.

Resveratrol Interaction with Lipid Bilayers: A Synchrotron X-ray Scattering Study

Resveratrol belongs to the large group of biologically active polyphenol compounds, with several beneficial health effects including antioxidant activity, anti-inflammatory action, cardiovascular protection, neuroprotection, and cancer chemoprevention. In the present study, the possibility that the effects of resveratrol described above are caused by resveratrol membrane interactions and structural modifications of lipid bilayers is evaluated. In this context, it is possible that resveratrol interacts selectively with lipid domains present in biological membranes, thereby modulating the localization of the anchored proteins and controlling their intracellular cascades. This study was conducted in a synchrotron particle accelerator, where the influence of resveratrol in the structural organization of lipid domains in bilayers was investigated using small- and wide-angle X-ray scattering (SAXS and WAXS) techniques. Membrane mimetic systems composed of egg l-α-phosphatidylcholine (EPC), cholesterol (CHOL), and sphingomyelin (SM), with different molar ratios, were used to access the effects of resveratrol on the order and structure of the membrane. The results revealed that resveratrol induces phase separation, promoting the formation of lipid domains in EPC, EPC:CHOL [4:1], and EPC:CHOL:SM [1:1:1] bilayers, which brings some structural organization to membranes. Therefore, resveratrol controls lipid packing of bilayers by inducing the organization of lipid rafts. Moreover, the formation of lipid domains is important for modulating the activity of many receptors, transmembrane proteins, and enzymes whose activity depends on the structural organization of the membrane and on the presence or absence of these organized domains. This evidence can thereby explain the therapeutic effects of resveratrol.

Polyphenol compounds and PKC signaling

BACKGROUND

Naturally occurring polyphenols found in food sources provide huge health benefits. Several polyphenolic compounds are implicated in the prevention of disease states, such as cancer. One of the mechanisms by which polyphenols exert their biological actions is by interfering in the protein kinase C (PKC) signaling pathways. PKC belongs to a superfamily of serine-threonine kinase and are primarily involved in phosphorylation of target proteins controlling activation and inhibition of many cellular processes directly or indirectly.

SCOPE OF REVIEW

Despite the availability of substantial literature data on polyphenols' regulation of PKC, no comprehensive review article is currently available on this subject. This article reviews PKC-polyphenol interactions and its relevance to various disease states. In particular, salient features of polyphenols, PKC, interactions of naturally occurring polyphenols with PKC, and future perspective of research on this subject are discussed.

MAJOR CONCLUSIONS

Some polyphenols exert their antioxidant properties by regulating the transcription of the antioxidant enzyme genes through PKC signaling. Regulation of PKC by polyphenols is isoform dependent. The activation or inhibition of PKC by polyphenols has been found to be dependent on the presence of membrane, Ca(2+) ion, cofactors, cell and tissue types etc. Two polyphenols, curcumin and resveratrol are in clinical trials for the treatment of colon cancer.

GENERAL SIGNIFICANCE

The fact that 74% of the cancer drugs are derived from natural sources, naturally occurring polyphenols or its simple analogs with improved bioavailability may have the potential to be cancer drugs in the future.

Resveratrol induces autophagy by directly inhibiting mTOR through ATP competition

Resveratrol (RSV) is a natural polyphenol that has a beneficial effect on health, and resveratrol-induced autophagy has been suggested to be a key process in mediating many beneficial effects of resveratrol, such as reduction of inflammation and induction of cancer cell death. Although various resveratrol targets have been suggested, the molecule that mediates resveratrol-induced autophagy remains unknown. Here, we demonstrate that resveratrol induces autophagy by directly inhibiting the mTOR-ULK1 pathway. We found that inhibition of mTOR activity and presence of ULK1 are required for autophagy induction by resveratrol. In line with this mTOR dependency, we found that resveratrol suppresses the viability of MCF7 cells but not of SW620 cells, which are mTOR inhibitor sensitive and insensitive cancer cells, respectively. We also found that resveratrol-induced cancer cell suppression occurred ULK1 dependently. For the mechanism of action of resveratrol on mTOR inhibition, we demonstrate that resveratrol directly inhibits mTOR. We found that resveratrol inhibits mTOR by docking onto the ATP-binding pocket of mTOR (i.e., it competes with ATP). We propose mTOR as a novel direct target of resveratrol, and inhibition of mTOR is necessary for autophagy induction.

Nickel-catalyzed synthesis of (E)-olefins from benzylic alcohol derivatives and arylacetonitriles via C–O activation

An efficient Ni-catalyzed synthesis of (E)-olefins using the readily available benzylic alcohol derivatives and arylacetonitriles is described. This transformation should proceed via a tandem process involving nickel-catalyzed cross coupling via C–O activation and subsequent stereoselective E2 elimination.

New Insights on the Biophysical Interaction of Resveratrol with Biomembrane Models: Relevance for Its Biological Effects

Resveratrol has been widely studied because of its pleiotropic effects in cancer therapy, neuroprotection, and cardioprotection. It is believed that the interaction of resveratrol with biological membranes may play a key role in its therapeutic activity. The capacity of resveratrol to partition into lipid bilayers, its possible location within the membrane, and the influence of this compound on the membrane fluidity were investigated using membrane mimetic systems composed of egg l-α-phosphatidylcholine (EPC), cholesterol (CHOL), and sphingomyelin (SM). The results showed that resveratrol has greater affinity for the EPC bilayers than for EPC:CHOL [4:1] and EPC:CHOL:SM [1:1:1] membrane models. The increased difficulty in penetrating tight packed membranes is also demonstrated by fluorescence quenching of probes and by fluorescence anisotropy measurements. Resveratrol may be involved in the regulation of cell membrane fluidity, thereby contributing for cell homeostasis.

Resveratrol suppresses the proliferation of breast cancer cells by inhibiting fatty acid synthase signaling pathway

In breast cancer cells, overexpression of human epidermal growth factor receptor 2 (HER2) increases the translation of fatty acid synthase (FASN) by altering the activity of PI3K/Akt signaling pathways. Cancer chemotherapy causes major side effects and is not effective enough in slowing down the progression of the disease. Earlier studies showed a role for resveratrol in the inhibition of FASN, but the molecular mechanisms of resveratrol-induced inhibition are not known. In the present study, we examined the novel mechanism of resveratrol on Her2-overexpressed breast cancer cells. The effect of resveratrol on the growth of breast cancer cells was assessed as percent cell viability by cytotoxicity-based MTT assay and the induction of apoptosis was determined by cell-death detection ELISA and flow cytometric analysis of Annexin-V-PI binding. Western immunobloting was used to detect signaling events in human breast cancer (SKBR-3) cells. Data showed that resveratrol-mediated down-regulation of FASN and HER2 genes synergistically induced apoptotic death in SKBR-3 cells. This concurrently caused a prominent up-regulation of PEA3, leads to down-regulation of HER2 genes. Resveratrol also alleviated the PI3K/Akt/mTOR signaling by down-regulation of Akt phosphorylation and up-regulation of PTEN expression. These findings suggest that resveratrol alters the cell cycle progression and induce cell death via FASN inhibition in HER2 positive breast cancer.

Resveratrol in peanuts

Peanuts are important dietary food source of resveratrol with potent antioxidant properties implicated in reducing risk of cancer, cardiovascular and Alzheimer's disease, and delaying aging. Resveratrol is a naturally occurring stilbene phytoalexin phenolic compound produced in response to a variety of biotic and abiotic stresses. This paper is a review of trans-resveratrol and related stilbenes from peanuts--their chemical structures, mechanisms for their biosynthesis, and concentrations in comparison with other major food sources. It will also discuss trans-resveratrol's absorption, bioavailability, and major health benefits; processes to enhance their biosynthesis in peanuts by biotic and abiotic stresses; process optimization for enhanced levels in peanuts and their potential food applications; and methods used for its extraction and analysis.

[Effect of resveratrol on the fundus oculi. An overview]

Resveratrol is a polyphenol with various properties. Oncological studies have shown an excellent anti-carcinogenic effect. Due to many overlaps between tumor-mediating signaling pathways and those which mediate neovascularization and proliferation in retinal diseases, this review intends to focus on studies about the application of resveratrol in diseases of the eye fundus in vitro and in vivo. Resveratrol has been well investigated in cell culture studies and animal models. Ophthalmological in vitro and in vivo investigations have shown a large variety of possible effects without toxic side effects and antiproliferative and immune modulatory effects in particular were observed. There is general consensus that the target protein of resveratrol is NF-κB. Clinical studies are needed to confirm these effects observed in cell culture and animal models. The exact mechanism of resveratrol remains unknown and seems to vary between cell types, tissues and the pathophysiological environment.

Regulation of PKC autophosphorylation by calponin in contractile vascular smooth muscle tissue

Protein kinase C (PKC) is a key enzyme involved in agonist-induced smooth muscle contraction. In some cases, regulatory phosphorylation of PKC is required for full activation of the enzyme. However, this issue has largely been ignored with respect to PKC-dependent regulation of contractile vascular smooth muscle (VSM) contractility. The first event in PKC regulation is a transphosphorylation by PDK at a conserved threonine in the activation loop of PKC, followed by the subsequent autophosphorylation at the turn motif and hydrophobic motif sites. In the present study, we determined whether phosphorylation of PKC is a regulated process in VSM and also investigated a potential role of calponin in the regulation of PKC. We found that calponin increases the level of in vitro PKCα phosphorylation at the PDK and hydrophobic sites, but not the turn motif site. In vascular tissues, phosphorylation of the PKC hydrophobic site, but not turn motif site, as well as phosphorylation of PDK at S241 increased in response to phenylephrine. Calponin knockdown inhibits autophosphorylation of cellular PKC in response to phenylephrine, confirming results with recombinant PKC. Thus these results show that autophosphorylation of PKC is regulated in dVSM and calponin is necessary for autophosphorylation of PKC in VSM.

Inhibition of STIM1 phosphorylation underlies resveratrol-induced inhibition of store-operated calcium entry

Resveratrol, a natural phytoalexin that shows health-promoting benefits, is an inhibitor of store-operated calcium entry (SOCE). Knowledge of the molecular mechanism underlying this inhibition is required for the proper design of therapies that include resveratrol or related stilbenoids, but remains largely unknown. To unravel this mechanism, using HEK293 cells as a model, we found that resveratrol inhibited the ERK1/2 activation triggered by Ca²⁺ store depletion. As a consequence, resveratrol inhibited STIM1 phosphorylation at residues Ser575, Ser608, and Ser621. Because this phosphorylation regulates the dissociation of STIM1 from the microtubule plus-end binding protein EB1 under store depletion conditions, resveratrol inhibited STIM1-EB1 dissociation. This inhibition had downstream effects such as inhibition of STIM1 multimerization in response to store depletion, and a significant impairment in the binding of STIM1 to ORAI1. Although additional targets for resveratrol in the molecular mechanism that governs SOCE cannot be discarded, the present results demonstrate that ERK1/2 pathway is a major target for resveratrol, and that the impairment of its activation produces a significant inhibition of SOCE.

PKC activation by resveratrol derivatives with unsaturated aliphatic chain

Resveratrol (1) is a naturally occurring phytoalexin that affects a variety of human disease models, including cardio- and neuroprotection, immune regulation, and cancer chemoprevention. One of the possible mechanisms by which resveratrol affects these disease states is by affecting the cellular signaling network involving protein kinase C (PKC). PKC is the family of serine/threonine kinases, whose activity is inhibited by resveratrol. To develop PKC isotype selective molecules on the resveratrol scaffold, several analogs (2–5) of resveratrol with a long aliphatic chain varying with number of unsaturated doubled bonds have been synthesized, their cytotoxic effects on CHO-K1 cells are measured and their effects on the membrane translocation properties of PKCα and PKCε have been determined. The analogs showed less cytotoxic effects on CHO-K1 cells. Analog 4 with three unsaturated double bonds in its aliphatic chain activated PKCα, but not PKCε. Analog 4 also activated ERK1/2, the downstream proteins in the PKC signaling pathway. Resveratrol analogs 2–5, however, did not show any inhibition of the phorbol ester-induced membrane translocation for either PKCα or PKCε. Molecular docking of 4 into the activator binding site of PKCα revealed that the resveratrol moiety formed hydrogen bonds with the activator binding residues and the aliphatic chain capped the activator binding loops making its surface hydrophobic to facilitate its interaction with the plasma membrane. The present study shows that subtle changes in the resveratrol structure can have profound impact on the translocation properties of PKCs. Therefore, resveratrol scaffold can be used to develop PKC selective modulators for regulating associated disease states.

MiR-520h-mediated FOXC2 regulation is critical for inhibition of lung cancer progression by resveratrol

Resveratrol, a phytochemical found in various plants and Chinese herbs, is associated with multiple tumor-suppressing activities, has been tested in clinical trials. However, the molecular mechanisms involved in resveratrol-mediated tumor suppressing activities are not yet completely defined. Here, we showed that treatment with resveratrol inhibited cell mobility through induction of the mesenchymal-epithelial transition (MET) in lung cancer cells. We also found that downregulation of FOXC2 (forkhead box C2) is critical for resveratrol-mediated suppression of tumor metastasis in an in vitro and in vivo models. We also identified a signal cascade, namely, resveratrol-∣miRNA-520h-∣PP2A/C-∣Akt → NF-κB → FOXC2, in which resveratrol inhibited the expression of FOXC2 through regulation of miRNA-520h-mediated signal cascade. This study identified a new miRNA-520h-related signal cascade involved in resveratrol-mediated tumor suppression activity and provide the clinical significances of miR-520h, PP2A/C and FOXC2 in lung cancer patients. Our results indicated a functional link between resveratrol-mediated miRNA-520h regulation and tumor suppressing ability, and provide a new insight into the role of resveratrol-induced molecular and epigenetic regulations in tumor suppression.

Chemical modifications of resveratrol for improved protein kinase C alpha activity

Resveratrol (1) is a naturally occurring phytoalexin that affects a variety of human disease models, including cardio- and neuroprotection, immune regulation, and cancer chemoprevention. One of the possible mechanisms by which resveratrol affects these disease states is by affecting the cellular signaling network involving protein kinase C alpha (PKCα). PKCα is a member of the family of serine/threonine kinases, whose activity is inhibited by resveratrol. To study the structure-activity relationship, several monoalkoxy, dialkoxy and hydroxy analogs of resveratrol have been synthesized, tested for their cytotoxic effects on HEK293 cells, measured their effects on the membrane translocation properties of PKCα in the presence and absence of the PKC activator TPA, and studied their binding with the activator binding domain of PKCα. The analogs showed less cytotoxic effects on HEK293 cells and caused higher membrane translocation (activation) than that of resveratrol. Among all the analogs, 3, 16 and 25 showed significantly higher activation than resveratrol. Resveratrol analogs, however, inhibited phorbol ester-induced membrane translocation, and the inhibition was less than that of resveratrol. Binding studies using steady state fluorescence spectroscopy indicated that resveratrol and the analogs bind to the second cysteine-rich domain of PKCα. The molecular docking studies indicated that resveratrol and the analogs interact with the protein by forming hydrogen bonds through its hydroxyl groups. These results signify that molecules developed on a resveratrol scaffold can attenuate PKCα activity and this strategy can be used to regulate various disease states involving PKCα.

Effects of resveratrol on expression of vascular endothelial growth factor in human gingival fibroblasts stimulated by periodontal pathogens

OBJECTIVE

To investigate the effects of resveratrol, a naturally occurring polyphenol, on the expression of vascular endothelial growth factor (VEGF) in human gingival fibroblast culture in response to vesicles and outer membrane proteins from periodontopathic bacteria.

MATERIAL AND METHODS

Human gingival fibroblasts were stimulated with vesicles and outer membrane proteins from Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis. In human gingival fibroblast cultures treated with or without resveratrol, VEGF production was evaluated by means of enzyme-linked immunosorbent assay and VEGF mRNA expression by means of reverse transcription polymerase chain reaction analysis. Vascular permeability enhancement was measured by the leakage of intravenously injected dye at the injection site of supernatant from cultures of human gingival fibroblasts stimulated by vesicles and outer membrane proteins.

RESULTS

Resveratrol significantly inhibited the increased production of VEGF by human gingival fibroblasts in response to vesicles and outer membrane proteins from periodontopathic bacteria, as shown by the detection of these proteins and their mRNA in vitro. Moreover, resveratrol treatment significantly decreased vascular permeability enhancement induced by supernatant from human gingival fibroblast cultures stimulated by vesicles and outer membrane proteins.

CONCLUSIONS

Overall, these findings suggest that resveratrol inhibits production of VEGF by stimulated human gingival fibroblasts and can inhibit vascular permeability, suggesting a therapeutic role for it in pathogenic bacteria-induced periodontal inflammation.

Dendritic cells treated with resveratrol during differentiation from monocytes gain substantial tolerogenic properties upon activation

Resveratrol is a polyphenol that acts on multiple molecular targets important for cell differentiation and activation. Dendritic cells (DCs) are a functionally diverse cell type and represent the most potent antigen-presenting cells of the immune system. In this study, we investigated resveratrol-induced effects on DCs during their differentiation and maturation. Our results show that resveratrol induces DC-associated tolerance, particularly when applied during DC differentiation. Costimulatory molecules CD40, CD80 and CD86 were down-regulated, as was the expression of major histocompatibility complex (MHC) class II molecules. Surface expression of inhibitory immunoglobulin-like transcript 3 (ILT3) and ILT4 molecules was induced, while human leucocyte antigen (HLA)-G expression was not affected. Resveratrol-treated DCs lost the ability to produce interleukin (IL)-12p70 after activation, but had an increased ability to produce IL-10. Such DCs were poor stimulators of allogeneic T cells and had lowered ability to induce CD4(+) T-cell migration. Furthermore, treated cells were able to generate allogeneic IL-10-secreting T cells, but were not competent in inducing FoxP3 expression These tolerogenic effects are probably associated with the effect of resveratrol on multiple molecular targets through which it interferes with DC differentiation and nuclear factor (NF)-kappaB translocation. Our data provide new insights into the molecular and functional mechanisms of the tolerogenic effects that resveratrol exerts on DCs.

Natural products for chemopreventive and adjunctive therapy in oncologic disease

Nutritional supplements or complementary and alternative medicines (CAM) are currently being investigated for their use in preventing, inhibiting, and reversing the progression of cancer. Natural agents and their derivatives such as vitamin A, selenium, green tea, resveratrol, aspirin, and probiotics have potential benefits in chemoprevention. There is also growing evidence for the use of natural products as adjunctive therapy alongside conventional cancer treatments. Nutritional supplements expenditures demonstrated greater growth than pharmaceuticals, with approximately 80% of cancer patients using natural products. Current issues with nutritional supplements use in cancer treatment include insufficient or conflicting evidence, poor quality control, potential interactions with chemotherapy, and potential efficacy in relation to changes in certain biomarkers, but long-term implications remain largely unresolved. Continued research is needed to lend credibility to these potentially valuable naturally driven supplements in the prevention and potentially in the treatment of cancer in conjunction with standard pharmaceuticals.

Recent Advances in Anthocyanin Analysis and Characterization

Anthocyanins are a class of polyphenols responsible for the orange, red, purple and blue colors of many fruits, vegetables, grains, flowers and other plants. Consumption of anthocyanins has been linked as protective agents against many chronic diseases and possesses strong antioxidant properties leading to a variety of health benefits. In this review, we examine the advances in the chemical profiling of natural anthocyanins in plant and biological matrices using various chromatographic separations (HPLC and CE) coupled with different detection systems (UV, MS and NMR). An overview of anthocyanin chemistry, prevalence in plants, biosynthesis and metabolism, bioactivities and health properties, sample preparation and phytochemical investigations are discussed while the major focus examines the comparative advantages and disadvantages of each analytical technique.

Phytochemical regulation of UDP-glucuronosyltransferases: implications for cancer prevention

Uridine 5'-diphospho-glucuronosyltransferases (UGTs) are Phase II biotransformation enzymes that metabolize endogenous and exogenous compounds, some of which have been associated with cancer risk. Many phytochemicals have been shown to induce UGTs in humans, rodents, and cell culture systems. Because UGTs maintain hormone balance and facilitate excretion of potentially carcinogenic compounds, regulation of their expression and activity may affect cancer risk. Phytochemicals regulate transcription factors such as the nuclear factor-erythroid 2-related factor 2 (Nrf2), aryl hydrocarbon, and pregnane X receptors as well as proteins in several signal transduction cascades that converge on Nrf2 to stimulate UGT expression. This induction can be modified by several factors, including phytochemical dose and bioavailability and interindividual variation in enzyme expression. In this review, we summarize the knowledge of dietary modulation of UGTs, particularly by phytochemicals, and discuss the potential mechanisms by which phytochemicals regulate UGT transcription.

Resveratrol and its analogs: defense against cancer, coronary disease and neurodegenerative maladies or just a fad?

Resveratrol (3,5,4'-trihydroxy-trans-stilbene; RV), a dietary constituent found in grapes and wine, exerts a wide variety of pharmacological activities. Because the grape skins are not fermented in the production process of white wines, only red wines contain considerable amounts of this compound. RV is metabolized into sulfated and glucuronidated forms within approximately 15min of entering the bloodstream, and moderate consumption of red wine results in serum levels of RV that barely reach the micromolar concentrations. In contrast, its metabolites, which may be the active principle, circulate in serum for up to 9h. RV has been identified as an effective candidate for cancer chemoprevention due its ability to block each step in the carcinogenesis process by inhibiting several molecular targets such as kinases, cyclooxygenases, ribonucleotide reductase, and DNA polymerases. In addition, RV protects the cardiovascular system by a large number of mechanisms, including defense against ischemic-reperfusion injury, promotion of vasorelaxation, protection and maintenance of intact endothelium, anti-atherosclerotic properties, inhibition of low-density lipoprotein oxidation, and suppression of platelet aggregation, thereby strongly supporting its role in the prevention of coronary disease. Promising data within the use of RV have also been obtained regarding progressive neurodegenerative maladies such as Alzheimer's, Huntington's, and Parkinson's diseases. Because neurotoxicity is often related to mitochondrial dysfunction and may be ameliorated through the inclusion of metabolic modifiers and/or antioxidants, RV may provide an alternative (and early) intervention approach that could prevent further damage. RV induces a multitude of effects that depend on the cell type (e.g., NF-kappaB modulation in cancer cells vs. neural cells), cellular condition (normal, stressed, or malignant), and concentration (proliferative vs. growth arrest), and it can have opposing activities. RV affects whole pathways and sets of intracellular events rather than a single enzyme and, therefore, may be an effective therapy to restore homoestasis. Nonetheless, the question of whether RV or its metabolites can accumulate to bioactive levels in target organs remains to be addressed.

Real-time protein kinase assay

We report a novel, real-time fluorogenic kinase assay. The peptide substrates are synthesized with a fluorescent dye and a hydrocarbon tail. The substrate self-assembles into micelles, increasing the local concentration of the dye and quenching its fluorescence. Upon phosphorylation, the fluorescence intensity increases 4-6-fold due to micelle reorganization. Both dynamic light scattering data and cryoelectron microscope images show that the size and the shape of the phosphopeptide micelles are significantly different from micelles of substrate peptide. The system provides a robust fluorescence increase in a real-time protein kinase assay. Unlike other fluorogenic systems, the fluorophore may be distant from the serine, threonine, or tyrosine that is phosphorylated. Assays for several kinases, including PKA, PKC, p38, MAPKAP K2, akt, Erk1, and src-family kinases, have been developed. IC(50) values of inhibitors for PKC betaII determined with this technology are consistent with published values. The utility of this assay to high-throughput screening was demonstrated with Sigma's LOPAC library, a collection of 640 compounds with known biological activities, and satisfactory results were obtained.

Antiangiogenic activity of brown algae fucoxanthin and its deacetylated product, fucoxanthinol

The antiangiogenic effects of fucoxanthin and a deacetylated product, fucoxanthinol, were examined. Fucoxanthin significantly suppressed HUVEC proliferation and tube formation at more than 10 microM, but it had no significant effect on HUVEC chemotaxis. The formation of blood vessel-like structures from CD31-positive cells was evaluated using embryonic stem cell-derived embryoid bodies. Fucoxanthin effectively suppressed the development of these structures at 10-20 microM, suggesting that it could suppress differentiation of endothelial progenitor cells into endothelial cells involving new blood vessel formation. Fucoxanthin and fucoxanthinol suppressed microvessel outgrowth in an ex vivo angiogenesis assay using a rat aortic ring, in a dose-dependent manner. These results imply that fucoxanthin having antiangiogenic activity might be useful in preventing angiogenesis-related diseases.

Therapeutic potential of resveratrol: the in vivo evidence

Resveratrol, a constituent of red wine, has long been suspected to have cardioprotective effects. Interest in this compound has been renewed in recent years, first from its identification as a chemopreventive agent for skin cancer, and subsequently from reports that it activates sirtuin deacetylases and extends the lifespans of lower organisms. Despite scepticism concerning its bioavailability, a growing body of in vivo evidence indicates that resveratrol has protective effects in rodent models of stress and disease. Here, we provide a comprehensive and critical review of the in vivo data on resveratrol, and consider its potential as a therapeutic for humans.

Resveratrol inhibits Src and Stat3 signaling and induces the apoptosis of malignant cells containing activated Stat3 protein

Resveratrol is a naturally occurring phytoalexin with antioxidant and antiinflammatory properties. Recent studies suggest that resveratrol possesses anticancer effects, although its mechanism of action is not well understood. We now show that resveratrol inhibits Src tyrosine kinase activity and thereby blocks constitutive signal transducer and activator of transcription 3 (Stat3) protein activation in malignant cells. Analyses of resveratrol-treated malignant cells harboring constitutively-active Stat3 reveal irreversible cell cycle arrest of v-Src-transformed mouse fibroblasts (NIH3T3/v-Src), human breast (MDA-MB-231), pancreatic (Panc-1), and prostate carcinoma (DU145) cell lines at the G0-G1 phase or at the S phase of human breast cancer (MDA-MB-468) and pancreatic cancer (Colo-357) cells, and loss of viability due to apoptosis. By contrast, cells treated with resveratrol, but lacking aberrant Stat3 activity, show reversible growth arrest and minimal loss of viability. Moreover, in malignant cells harboring constitutively-active Stat3, including human prostate cancer DU145 cells and v-Src-transformed mouse fibroblasts (NIH3T3/v-Src), resveratrol treatment represses Stat3-regulated cyclin D1 as well as Bcl-xL and Mcl-1 genes, suggesting that the antitumor cell activity of resveratrol is in part due to the blockade of Stat3-mediated dysregulation of growth and survival pathways. Our study is among the first to identify Src-Stat3 signaling as a target of resveratrol, further defining the mechanism of antitumor cell activity of resveratrol and raising its potential application in tumors with an activated Stat3 profile.

Antiangiogenic activity of nasunin, an antioxidant anthocyanin, in eggplant peels

Nasunin, delphinidin-3-(p-coumaroylrutinoside)-5-glucoside, an antioxidant anthocyanin isolated from eggplant peels, was demonstrated as an angiogenesis inhibitor. Nasunin at higher 10 microM suppressed microvessel outgrowth in an ex vivo angiogenesis assay using a rat aortic ring. The effect of nasunin was examined in various in vitro angiogenesis models using human umbilical vein endothelial cells (HUVECs). Nasunin suppressed HUVEC proliferation in a dose-dependent manner (50-200 microM); however, it had no significant effect on HUVEC chemotaxis in a Boyden chamber assay and HUVEC tube formation on a reconstituted basement membrane. These results imply that nasunin with both antioxidant and antiangiogenic activities might be useful to prevent angiogenesis-related diseases.

Resveratrol and breast cancer risk

Resveratrol is a non-flavonoid polyphenol that has attracted attention as a potential anticancer agent in vitro and in vivo, but scanty epidemiological data are available. We have therefore analysed the relation between dietary intake of resveratrol and breast cancer risk using data from a case-control study conducted between 1993 and 2003 in the Swiss Canton of Vaud on 369 cases and 602 controls. Compared with the lowest tertile of total resveratrol intake, the multivariate odds ratios (OR) were 0.50 for the intermediate and 0.39 for the highest tertile, and the trend in risk was significant. A significant inverse association was observed for resveratrol from grapes (OR = 0.64 and 0.55), but not for wine. The inverse relation between resveratrol and breast cancer risk was not explained by several potential confounding factors, including detailed allowance for alcohol intake, nor attributable to a non-specific favourable effect of fruit on breast cancer risk.

Resveratrol regulates cellular PKC alpha and delta to inhibit growth and induce apoptosis in gastric cancer cells

Resveratrol, a dietary phytoalexin, has emerged as a promising chemopreventive agent due to its antiproliferative and pro-apoptotic action toward cancer cells and its ability to inhibit tumor growth in animals. Gastric adenocarcinoma cells respond to resveratrol treatment with suppression of DNA synthesis, activation of nitric oxide synthase, induction of apoptosis and inhibition of total PKC and PKC alpha activity. Here we demonstrate that treatment of gastric adenocarcinoma SNU-1 cells with resveratrol results in time and concentration dependent accumulation of tumor suppressors p21(cip1/WAF-1) and p53 and is preceded by loss of membrane-associated PKC delta protein and a concomitant increase in cytosolic PKC alpha. Arrest of the cell cycle at transition of S to G(2)/M phases correlates with the profile of (3)H-thymidine incorporation and accumulation of p21(cip1/WAF-1) and was temporally dependent on increase of p53. SNU-1 cells respond to resveratrol treatment with up-regulation of both Fas and Fas-L proteins, whereas in KATO-III cells, with deleted p53, only Fas-L is increased after resveratrol treatment. Although Fas and Fas-L proteins in SNU-1 cells and Fas-L in KATO-III cells were elevated within 24 h of cell treatment with low concentrations of resveratrol, significant apoptotic response at these concentrations was observed only after 48 h. Altogether, our findings indicate that resveratrol engages PKC alpha and delta signals in gastric adenocarcinoma SNU-1 cells prior to up-regulation of antiproliferative and pro-apoptotic signals. The specific cell death signals engaged by resveratrol appear to be cell type dependent and suggest that resveratrol has chemopreventive potential even after mutational changes have occurred.

Association between pterostilbene and quercetin inhibits metastatic activity of B16 melanoma

Inhibition of cancer growth by resveratrol (trans-3,5,4'-trihydroxystilbene; RESV), a phytoalexin present in many plant species, is limited by its low bioavailability. Pterostilbene (3,5-dimethoxy-4'-hydroxystilbene; PTER) and quercetin (3,3',4',5,6-pentahydroxyflavone; QUER), two structurally related and naturally occurring small polyphenols, show longer half-life in vivo. In vitro growth of highly malignant B16 melanoma F10 cells (B16M-F10) is inhibited (56%) by short-time exposure (60 min/day) to PTER (40 microm) and QUER (20 microm) (approximate mean values of plasma concentrations measured within the first hour after intravenous administration of 20 mg/kg each polyphenol). Intravenous administration of PTER and QUER (20 mg/kg per day) to mice inhibits (73%) metastatic growth of B16M-F10 cell in the liver, a common site for metastasis development. The anti-metastatic mechanism involves: 1) a PTER-induced inhibition of vascular adhesion molecule 1 expression in the hepatic sinusoidal endothelium, which consequently decreases B16M-F10 cell adhesion to the endothelium through very late activation antigen 4; and 2) a QUER- and PTER-induced inhibition of Bcl-2 expression in metastatic cells, which sensitizes them to vascular endothelium-induced cytotoxicity. Our findings demonstrate that the association of PTER and QUER inhibits metastatic melanoma growth and extends host survival.

Resveratrol: Preventing properties against vascular alterations and ageing

Cardiovascular diseases are the leading cause of death in developed countries where the common pathological substrate underlying this process is atherosclerosis. Several new concepts have emerged in relation to mechanisms that contribute to the regulation of the vascular diseases and associated inflammatory effects. Recently, potential antioxidants (vitamin E, polyphenols) have received much attention as potential anti-atherosclerotic agents. Among the polyphenols with health benefic properties, resveratrol, a phytoalexin of grape, seem to be a good candidate protecting the vascular walls from oxidation, inflammation, platelet aggregation, and thrombus formation. In this review, we focus on the mechanism of resveratrol cardiovascular benefic effects. We analyze, in relation with the different steps of atherosclerotic process, the resveratrol properties at multiple levels, such as cellular signaling, enzymatic pathways, apoptosis, and gene expression. We show and discuss the relationship with reactive oxygen species, regulation of pro-inflammatory genes including cycloxygenases and cytokines in molecular inflammatory and aging processes, and how the regulation of these activites by resveratrol can lead to a prevention of vascular diseases.

3,4',5-Trihydroxy-trans-stilbene (resveratrol) inhibits human cytomegalovirus replication and virus-induced cellular signaling

Resveratrol is a polyphenolic natural product that is present in red wine and peanuts and has inhibitory activity against inflammation, heart disease, and cancer. Here we describe its inhibition of human cytomegalovirus replication (IC50 = 1-2 microM). At least 50-fold higher concentrations of compound were required to produce cytotoxicity against growing or stationary human embryonic lung fibroblasts. Mechanism of action studies determined that resveratrol blocked virus-induced activation of the epidermal growth factor receptor (EGFR) and phosphatidylinositol-3-kinase signal transduction as well as NF-kappaB and Sp1 transcription factor activation shortly following infection. Resveratrol prevented the appearance of immediate-early, early, and late viral proteins. Human cytomegalovirus DNA replication was reduced to undetectable levels by treatment with resveratrol, as were the second (late) phases of virus-induced phosphatidylinositol-3-kinase signaling and transcription factor activation. Resveratrol lost substantial antiviral activity when its addition was delayed until 4 h postinfection. Compound reversibility and preincubation studies were inconsistent with a virucidal mechanism of action. These data indicated that this compound likely operated during attachment and entry. We hypothesize that the primary molecular target for resveratrol may be blockage of epidermal growth factor receptor activation and its downstream effectors.

Differential sensitivity to resveratrol-induced apoptosis of human chronic myeloid (K562) and acute lymphoblastic (HSB-2) leukemia cells

The in vitro effects of resveratrol (RES) on apoptotic pathway in human chronic myeloid (K562) and acute lymphoblastic (HSB-2) leukemia cells were investigated. RES treatment of both cell types significantly and irreversibly inhibited their growth, associated with extensive apoptosis and increase in hypodiploid cells. Cell cycle analysis showed accumulation in G(1) phase in HSB-2 drug exposed cells, while only K562-treated cells exhibited a marked accumulation in S phase with a concomitant decrease in G(1) and G(2)/M at 24 h. Moreover, RES caused internucleosomal DNA fragmentation, even if K562 cells were found less sensitive to the drug, as compared to HSB-2 cells, which also reacted earlier to the treatment. RES-induced apoptosis was associated with an increase of Bax expression and a marked release of cytochrome c from mitochondria. Interestingly, K562 cells exhibited a basal content of glutathione 10-fold that of HSB-2 cells, which increased after 24-48 h RES exposure, together with increment of glutathione reductase and peroxidase activities. However, the major resistance to apoptosis of K562 cells cannot be attributed to their higher pool of reducing power, since neither the inhibition of glutathione synthesis by buthionine sulphoximine nor glutathione depletion by diethylmaleate, sensitized these cells. In addition, glutathione enrichment of HSB-2 cells by N-acetylcysteine did not prevent the apoptotic effects of RES. Our data indicate that RES commitment to apoptosis in both cell lines is independent from the intracellular content of glutathione, while it is associated with either the enhanced expression of Bax and cytochrome c release.

Resveratrol inhibits phenotypic and functional maturation of murine bone marrow-derived dendritic cells

This study investigated the effects of resveratrol, a natural polyphenol found in grapes and grape products such as wine and having a wide range of biological and pharmacological activities effecting on the phenotypic and functional maturation of bone marrow (BM)-derived dendritic cells (DC). Resveratrol inhibited the expression of costimulatory molecules (CD80 and CD86), and major histocompatibility complex (MHC) classes I and II significantly, and had the same effect dose-dependently on DC. Resveratrol also significantly suppressed the ability of BM-DC to produce intracellular IL-12 p40/p70 and secretory IL-12 p70 in response to lipopolysaccharides (LPS) stimulation. Resveratrol-treated DC were highly efficient in antigen capture via mannose receptor-mediated endocytosis. Also, they were poor stimulators of naïve allogeneic T-cell proliferation and induced lower levels of IL-2 in responding T cells. These results indicate the immunosuppressive properties of resveratrol, which may be therapeutically useful in controlling chronic immune and/or inflammatory diseases through the down-regulation of DC differentiation and maturation.

Resveratrol antagonizes EGFR-dependent Erk1/2 activation in human androgen-independent prostate cancer cells with associated isozyme-selective PKC alpha inhibition

The development of androgen-independent prostate cancer (AI PrCa) involves constitutive Erk1/2 activation sustained by the epidermal growth factor/transforming growth factor-alpha/EGF receptor (EGF/TGFalpha/EGFR) axis and other trophic signaling mechanisms in neoplastic human prostate epithelial cells in vivo. In this report, we show that growth-inhibitory concentrations of the dietary phytochemical resveratrol suppress EGFR-dependent Erk1/2 activation pathways stimulated by EGF and phorbol ester (12- O -tetradecanoyl phorbol 13-acetate, TPA) in human AI PrCa PC-3 cells in vitro. Because protein kinase C (PKC) is the major cellular receptor for phorbol esters and taking into consideration that resveratrol is PKC-inhibitory, we investigated resveratrol effects on cellular PKC isozymes associated with the suppression of TPA-induced Erk1/2 activation. The PKC isozyme composition of PC-3 cells was defined by Western analysis of the cell lysate with a comprehensive set of isozyme-selective PKC Ab's. PC-3 cells expressed PKCalpha, epsilon, zeta, iota, and PKD (PKCmicro), as did another human AI PrCa cell line of distinct genetic origin, DU145. The effects of resveratrol on TPA-induced PKC isozyme activation were defined by monitoring PKC isozyme translocation and autophosphorylation. Under conditions where resveratrol suppressed TPA-induced Erk1/2 activation, the phytochemical produced isozyme-selective interference with TPA-induced translocation of cytosolic PKCalpha to the membrane/cytoskeleton and selectively diminished the amount of autophosphorylated PKCalpha in the membrane/cytoskeleton of the TPA-treated cells. These results demonstrate that resveratrol abrogation of a PKC-mediated Erk1/2 activation response in PC-3 cells correlates with isozyme-selective PKCalpha inhibition. The results provide evidence that resveratrol may have value as an adjuvant cancer therapeutic in advanced prostate cancer.

Activation loop phosphorylation controls protein kinase D-dependent activation of nuclear factor kappaB

Activation of the inducible transcription factor nuclear factor kappaB (NF-kappaB) occurs in cells exposed to oxidative stress, and the serine/threonine kinase protein kinase D (PKD) is critical for signal relay to NF-kappaB. We have recently delineated two coordinated events that control PKD activation in response to oxidative stress: phosphorylation at Tyr463 by the tyrosine kinase Abl, and phosphorylation at the activation loop Ser738/Ser742 by the protein kinase C (PKC) isoform PKCdelta. The result is fully active PKD that controls NF-kappaB activation through the IkappaB kinase (IKK) complex. Here, we investigate the mechanism by which PKD controls IKK/NF-kappaB activation. Resveratrol, a potent antioxidant, blocks both PKD activation and NF-kappaB induction. In particular, resveratrol blocked PKD activation loop phosphorylation and activity, and this was caused by a specific inhibition of the Ser738/Ser742 kinase PKCdelta. On the other hand, resveratrol did not affect Abl kinase activity and had no effect on Tyr463 phosphorylation. Moreover, we show that the mechanism by which resveratrol inhibits NF-kappaB is by blocking the translocation of PKD to the IKK complex, specifically by inhibiting Ser738/Ser742 phosphorylation. We therefore propose that rather than acting as an antioxidant, resveratrol specifically blocks oxidative stress-dependent NF-kappaB activation by interfering with PKD phosphorylation and association with the IKK complex.

Resveratrol induces growth inhibition and apoptosis in metastatic breast cancer cells via de novo ceramide signaling

Resveratrol (3,4',5-trans-trihydroxystilbene), a phytoalexin present in grapes and red wine, is emerging as a natural compound with potential anticancer properties. Here we show that resveratrol can induce growth inhibition and apoptosis in MDA-MB-231, a highly invasive and metastatic breast cancer cell line, in concomitance with a dramatic endogenous increase of growth inhibitory/proapoptotic ceramide. We found that accumulation of ceramide derives from both de novo ceramide synthesis and sphingomyelin hydrolysis. More specifically we demonstrated that ceramide accumulation induced by resveratrol can be traced to the activation of serine palmitoyltransferase (SPT), the key enzyme of de novo ceramide biosynthetic pathway, and neutral sphingomyelinase (nSMase), a main enzyme involved in the sphingomyelin/ceramide pathway. However, by using specific inhibitors of SPT, myriocin and L-cycloserine, and nSMase, gluthatione and manumycin, we found that only the SPT inhibitors could counteract the biological effects induced by resveratrol. Thus, resveratrol seems to exert its growth inhibitory/apoptotic effect on the metastatic breast cancer cell line MDA-MB-231 by activating the de novo ceramide synthesis pathway.

Resveratrol: a candidate nutritional substance for prostate cancer prevention

The dietary stilbene resveratrol is a major constituent of a variety of edible plant products, including grapes and peanuts. Resveratrol has been identified as an excellent candidate cancer chemopreventive, based on its safety and efficacy in animal models of carcinogenesis. Resveratrol is a prototype of a plethora of bioactive polyphenols in the food supply that has just begun to be mined for cancer preventive agents. For example, polyphenolic grapeseed fractions were shown recently to potently antagonize chemical carcinogenesis. Taking into consideration that the identification of resveratrol as a cancer preventive agent is largely owed to its high abundance in nature (e.g., it accounts for 5-10% of the grapeskin biomass), it is logical to expect that naturally occurring stilbenes that are superior to resveratrol in their cancer preventive properties await identification. Thus, resveratrol may represent the tip of the iceberg of a broad class of stilbene and related polyphenolic natural products that include safe and highly effective agents for cancer prevention. We hypothesize that resveratrol may be especially suitable as a lead agent for prostate cancer prevention given its ability to: 1) inhibit each stage of multistage carcinogenesis, 2) scavenge incipient populations of androgen-dependent prostate cancer cells through androgen receptor antagonism, and 3) scavenge incipient populations of androgen-independent prostate cancer cells by short-circuiting the epidermal growth factor-receptor (EGFR)-dependent autocrine loops in the cancer cells.

Inhibition of protein kinase C by resveratrol

Evidence is emerging that resveratrol (RV), a polyphenolic phytoaxelin present in dietary sources including red wine, may protect against atherosclerosis and cardiovascular disease by enhancing the integrity of the endothelium. In this study, the possibility that such beneficial effects of RV may arise from a modulation of protein kinase C (PKC)-mediated signaling was investigated by determining the effects of RV on the in vitro activities of PKC isozymes. It was found that the Ca(2+)-dependent activities of membrane-associated PKCalpha induced by either phorbol ester or diacylglycerol were potently inhibited by RV, each with an IC(50) of approximately 2 microM. The inhibitory effect of RV was also observed for conventional PKCbetaI, whereas the activities of novel PKC epsilon and atypical PKCzeta were each unaffected. The inhibition of PKCalpha activity was found to be competitive with respect to phorbol ester concentration but noncompetitive with respect to Ca(2+) and phosphatidylserine concentrations, suggesting that the RV may compete for phorbol ester-binding to the C1 domains. Supporting this, it was found that RV bound to a fusion peptide containing the C1A and C1B domains of PKCalpha. Similar to the effects of diacylglycerol and phorbol ester, the interaction of RV with the C1 domains induced the association of PKCalpha with membrane lipid vesicles, although this did not result in activation. Overall, the results suggest that the inhibitory effect of RV on PKC activity, and therefore on the associated signaling networks, may, in part, underlie the mechanism(s) by which this agent exerts its beneficial effects on endothelial and cardiovascular function. Furthermore, the effects of RV on these signaling networks are predicted to differ according to the cellular localization and the regulating PKC isozyme.