Piceatannol inhibits phorbol ester-induced NF-kappa B activation and COX-2 expression in cultured human mammary epithelial cells

Exploring the therapeutic potential of naturally occurring piceatannol in non-communicable diseases

Piceatannol is a naturally occurring hydroxylated resveratrol analogue that can be found in a variety of fruits and vegetables. It has been documented to have a wide range of beneficial effects, including anti-inflammatory, antioxidant, anti-aging, anti-allergic, antidiabetic, neuroprotective, cardioprotective, and chemopreventive properties. Piceatannol has significantly higher antioxidant activity than resveratrol. Piceatannol has been shown in preclinical studies to have the ability to inhibit or reduce the growth of cancers in various organs such as the brain, breast, lung, colon, cervical, liver, prostate, and skin. However, the bioavailability of Piceatannol is comparatively lower than resveratrol and other stilbenes. Several approaches have been reported in recent years to enhance its bioavailability and biological activity, and clinical trials are required to validate these findings. This review focuses on several aspects of natural stilbene Piceatannol, its chemistry, and its mechanism of action, and its promising therapeutic potential for the prevention and treatment of a wide variety of complex human diseases.

A review on the anti-inflammatory activities of Brazilian green, brown and red propolis

Humanity has used propolis since ancient times, and its use as a food supplement has significantly increased. Several reports on propolis´ biological activity and toxicity have highlighted its anti-inflammatory properties, unlike many natural food supplements. This review addresses the anti-inflammatory roles of Brazilian green, brown, and red propolis produced by Apis mellifera, their extracts, isolated compounds, and their mode of action. Despite advances in anti-inflammatory therapies, the development of inflammatory processes in several diseases has been a concern for centuries. Demands for new anti-inflammatory drugs have led to studies on propolis products as diet components to treat and prevent inflammatory disorders. Brazilian green, brown, and red propolis are alternatives for obtaining extracts and compounds of valuable anti-inflammatory properties. PRACTICAL APPLICATIONS: Currently, propolis is a food supplement, and to the best of our knowledge, several studies have shown that despite advances in anti-inflammatory therapies, the inflammatory process continues to be a significant concern. However, due to the demand for new anti-inflammatory drugs, propolis products as dietary components can be used to treat and prevent inflammatory disorders.

Oxyresveratrol: Sources, Productions, Biological Activities, Pharmacokinetics, and Delivery Systems

Oxyresveratrol has recently attracted much research attention due to its simple chemical structure and diverse therapeutic potentials. Previous reviews describe the chemistry and biological activities of this phytoalexin, but additional coverage and greater accessibility are still needed. The current review provides a more comprehensive summary, covering research from 1955 to the present year. Oxyresveratrol occurs in both gymnosperms and angiosperms. However, it has never been reported in plants in the subclass Sympetalae, and this point might be of both chemotaxonomic and biosynthetic importance. Oxyresveratrol can be easily obtained from plant materials by conventional methods, and several systems for both qualitative and quantitative analysis of oxyresveratrol contents in plant materials and plant products are available. Oxyresveratrol possesses diverse biological and pharmacological activities such as the inhibition of tyrosinase and melanogenesis, antioxidant and anti-inflammatory activities, and protective effects against neurological disorders and digestive ailments. However, the unfavorable pharmacokinetic properties of oxyresveratrol, including low water solubility and poor oral availability and stability, have posed challenges to its development as a useful therapeutic agent. Recently, several delivery systems have emerged, with promising outcomes that may improve chances for the clinical study of oxyresveratrol.

Covalent Modification of Proteins by Plant-Derived Natural Products: Proteomic Approaches and Biological Impacts

Plant-derived natural products (NPs) with electrophilic functional groups engage various subsets of the proteome via covalent modification of nucleophilic cysteine residues. This electrophile-nucleophile interaction can change protein conformation, alter protein function, and modulate their biological action. The biological significance of these covalent protein modifications in health and disease is increasingly recognized. One way to understand covalent NP-protein interactions is to utilize traditional proteomics and modern mass spectrometry (MS)-based proteomic strategies. These strategies have proven effective in uncovering specific NP protein targets and are critical first steps that allow for a much deeper understanding of the ability of NPs to modulate cellular processes. Here, plant-derived NPs that covalently modify proteins are reviewed, the biological significance of these covalent modifications, and the different proteomic strategies that have been employed to study these NP-protein interactions.

Piceatannol Inhibits P. acnes-Induced Keratinocyte Proliferation and Migration by Downregulating Oxidative Stress and the Inflammatory Response

The Cutibacterium acnes (also called Propionibacterium acnes, P. acnes)-induced proliferation and migration of keratinocytes contribute to acne vulgaris (AV), which is a common inflammatory skin disease that causes physical and psychological impairments. Piceatannol (3, 5, 3', 4'-tetrahydroxy-trans-stilbene, PCT) is naturally present in many human diets and plays antioxidant and anti-inflammatory roles that inhibit cell proliferation and migration. We aimed to analyse the functions and underlying mechanisms of PCT in P. acnes-stimulated keratinocytes. First, PCT showed no toxicity against the normal human keratinocyte cell line HaCaT but inhibited P. acnes-induced HaCaT cell proliferation. Next, PCT promoted the nuclear translocation and target gene transcription of the antioxidant transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), thereafter decreasing intracellular reactive oxygen species (ROS) levels. In addition, PCT inhibited the nuclear translocation of p65 [a subunit of nuclear factor kappa B (NF-κB)] and the secretion of pro-inflammatory cytokines, including interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α) and interleukin-8 (IL-8). Finally, a transfection assay showed that PCT inhibited P. acnes-induced HaCaT cell proliferation and migration by activating the antioxidant Nrf2 pathway and inhibiting the inflammatory NF-κB pathway. Our data suggested that PCT alleviated P. acnes-induced HaCaT cell proliferation and migration through its antioxidant and anti-inflammatory roles, suggesting the potential of PCT to treat AV.

Inhibiting NF-κB-Mediated Inflammation by Catechol-Type Diphenylbutadiene via an Intracellular Copper- and Iron-Dependent Pro-Oxidative Role

Chronic inflammation mediated by nuclear factor-κB (NF-κB) plays a crucial role in the development of cancer. As part of our continuous efforts placed on investigating anticancer mechanisms of dietary catechols, we further applied catechol-type diphenylbutadiene (3,4-DHB) as a model molecule to probe whether it inhibits inflammation by its pro-oxidative role. Employing lipopolysaccharide-stimulated RAW264.7 cells as a model of inflammation, we validated that benefiting from its catechol moiety, 3,4-DHB inhibited significantly the LPS-induced formation of NO (11.48 ± 0.39 μM) compared with the only LPS-stimulated group (31.8 ± 1.78 μM) with an inhibitory rate of 64% at 5 μM, expression of iNOS and COX-2 proteins, phosphorylation of IkB kinase and IkBα, and nuclear translocation of NF-κB. Noticeably, its inhibitory activity against the NF-κB-mediated inflammation can be obviously revised by pretreatment of the cells with dithiothreitol (a quencher of both electrophilic o-quinone and ROS), neocuproine (a specific chelating agent for copper ions), and deferoxamine (a specific chelating agent for iron ions). The above results support that depending on intracellular copper and iron ions, 3,4-DHB, a pro-electrophile, can be converted into its corresponding o-quinone electrophile together with the generation of ROS, a pro-oxidative event that mediates its inhibitory activity against NF-κB signaling and inflammation. The copper- and iron-dependent inhibition against inflammation supports that dietary catechols are probably pro-oxidative anti-inflammatory agents.

Parallel in vitro and in silico investigations into anti-inflammatory effects of non-prenylated stilbenoids

Stilbenoids represent a large group of bioactive compounds, which occur in food and medicinal plants. Twenty-five stilbenoids were screened in vitro for their ability to inhibit COX-1, COX-2 and 5-LOX. Piceatannol and pinostilbene showed activity comparable to the zileuton and ibuprofen, respectively. The anti-inflammatory potential of stilbenoids was further evaluated using THP-1 human monocytic leukemia cell line. Tests of the cytotoxicity on the THP-1 and HCT116 cell lines showed very low toxic effects. The tested stilbenoids were evaluated for their ability to attenuate the LPS-stimulated activation of NF-κB/AP-1. Most of the tested substances reduced the activity of NF-κB/AP-1 and later attenuated the expression of TNF-α. The effects of selected stilbenoids were further investigated on inflammatory signaling pathways. Non-prenylated stilbenoids regulated attenuation of NF-ĸB/AP-1 activity upstream by inhibiting the phosphorylation of MAPKs. A docking study used to in silico analyze the tested compounds confirmed their interaction with NF-ĸB, COX-2 and 5-LOX.

Piceatannol inhibits the IL-1β-induced inflammatory response in human osteoarthritic chondrocytes and ameliorates osteoarthritis in mice by activating Nrf2

Osteoarthritis (OA) is a complex process, to which an inflammatory environment contributes markedly. Piceatannol exerts anti-inflammatory effects on several diseases. In the current study, we explored the protective effects of piceatannol on the progression of OA and investigated its molecular target. In vitro, piceatannol not only attenuated the over-production of inflammatory mediators and cytokines-such as nitric oxide (NO), prostaglandin E2 (PGE₂), tumor necrosis factor alpha (TNF-α), and interleukin-6 (IL-6)-but also suppressed the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) at both the mRNA and protein levels. Piceatannol also decreased the expression of metalloproteinase 13 (MMP13) and thrombospondin motifs 5 (ADAMTS5), which mediate extracellular matrix degradation. Mechanistically, we found that piceatannol inhibited IL-1β-induced nuclear factor kappa B (NF-κB) activation by activating the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/heme oxygenase 1 (HO-1) pathway. Furthermore, piceatannol exerted protective effects in a mouse model of OA. Taken together, these findings indicate that piceatannol may be a potential therapeutic agent for OA.

Discovery of novel potent nuclear factor kappa-B inhibitors (IKK-β) via extensive ligand-based modeling and virtual screening

Inhibitor kappa-B kinase-beta (IKK-β) controls the activation of nuclear transcription factor kappa-B and has been linked to inflammation and cancer. Therefore, inhibitors of this kinase should have potent anti-inflammatory and anticancer properties. Accordingly, we explored the pharmacophoric space of 218 IKK-β inhibitors to identify high-quality binding models. Subsequently, genetic algorithm-based quantitative structure activity relationship (QSAR) analysis was employed to select the best possible combination of pharmacophoric models and physicochemical descriptors that explain bioactivity variation among training compounds. Three successful pharmacophores emerged in 2 optimal QSAR equations (r₁²₁₇₅  = 0.733, r₁²_LOO  = 0.52, F1 = 65.62, r₁²_PRESS against 43 test inhibitors = 0.63 and r₂²₁₇₅  = 0.683, r₂²_LOO  = 0.52, F2 = 72.66, r₂²_PRESS against 43 test inhibitors = 0.65). Two pharmacophores were merged in a single binding model. Receiver operating characteristic curve validation proved the excellent qualities of this model. The merged pharmacophore and the associated QSAR equations were applied to screen the National Cancer Institute list of compounds. Ten hits were found to exhibit potent anti-IKK-β bioactivity, out of which, one illustrates IC50 of 11.0nM.

A Comprehensive Review on the Chemotherapeutic Potential of Piceatannol for Cancer Treatment, with Mechanistic Insights

Cancer is a diverse class of diseases characterized by uncontrolled cell growth that constitutes the greatest cause of mortality and morbidity worldwide. Despite steady progress, the treatment modalities of cancer are still insufficient. Several new concepts have emerged for therapeutic intervention in malignant diseases with the goal of identifying specific targets and overcoming resistance against current cytotoxic therapies. Many studies have reported the remarkable and significant properties of dietary plant polyphenols such as curcumin, resveratrol, flavopiridol, indirubin, magnolol, piceatannol, parthenolide, epigallocatechin gallate, and cucurbitacin as anticancer agents known for their pleiotropic effects on cancer, immune cells, and inflammation. Piceatannol, an analogue and metabolite of resveratrol, is a natural stilbene commonly found in grape skins and wine. Compared to resveratrol, this molecule exhibits superior bioactivities as an inhibitor of COX-1/2 and the CSN-associated kinase. Piceatannol is thought to be a potent natural compound with many therapeutic effects, such as the prevention of hypercholesterolemia, arrhythmia, atherosclerosis, angiogenesis, and cardiovascular diseases. It also demonstrates vasorelaxation, antioxidant, and anticancer activities. This comprehensive review summarizes the current data regarding the mechanisms of action of piceatannol, its chemopreventive properties, and its possible therapeutic potential against various types of human cancer.

Resveratrol for breast cancer prevention and therapy: Preclinical evidence and molecular mechanisms

Globally, breast cancer is the most frequently diagnosed cancer among women. The major unresolved problems with metastatic breast cancer is recurrence after receiving objective response to chemotherapy, drug-induced side effects of first line chemotherapy and delayed response to second line of treatment. Unfortunately, very few options are available as third line treatment. It is clear that under such circumstances there is an urgent need for new and effective drugs. Phytochemicals are among the most promising chemopreventive treatment options for the management of cancer. Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a non-flavonoid polyphenol present in several dietary sources, including grapes, berries, soy beans, pomegranate and peanuts, has been shown to possess a wide range of health benefits through its effect on a plethora of molecular targets.The present review encompasses the role of resveratrol and its natural/synthetic analogue in the light of their efficacy against tumor cell proliferation, metastasis, epigenetic alterations and for induction of apoptosis as well as sensitization toward chemotherapeutic drugs in various in vitro and in vivo models of breast cancer. The roles of resveratrol as a phytoestrogen, an aromatase inhibitor and in stem cell therapy as well as adjuvent treatment are also discussed. This review explores the full potential of resveratrol in breast cancer prevention and treatment with current limitations, challenges and future directions of research.

Dietary walnut suppression of colorectal cancer in mice: Mediation by miRNA patterns and fatty acid incorporation

Colorectal cancer, unlike many other malignancies, may be preventable. Recent studies have demonstrated an inverse association between nut consumption and incidence of colon cancer; however, the underlying mechanisms are not fully understood. An emerging concept suggests that microribonucleic acids (miRNAs) may help explain the relationship between walnut consumption and decreased colorectal neoplasia risk. Seven days after HT-29 colon cancer cell injection, mice were randomized to either control or walnut diets for 25 days of diet treatment. Thirty samples of tumor and of omental adipose were analyzed to determine changes in lipid composition in each dietary group. In the tumors of the walnut-containing diet, we found significant increases in α-linolenic, eicosapentaenoic, docosahexaenoic and total omega-3 acids, and a decrease in arachidonic acid, as compared to the control diet. Final tumor size measured at sacrifice was negatively associated with percentage of total omega-3 fatty acid composition (r=-0.641, P=.001). MicroRNA expression analysis of colorectal tumor tissue revealed decreased expression of miRNAs 1903, 467c and 3068 (P<.05) and increased expression of miRNA 297a* (P=.0059) in the walnut-treated group as compared to control diet. Our results indicate that changes in the miRNA expression profiles likely affect target gene transcripts involved in pathways of anti-inflammation, antivascularization, antiproliferation and apoptosis. We also demonstrate the incorporation of protective fatty acids into colonic epithelium of walnut-fed mice, which may independently alter miRNA expression profiles itself. Future studies of the mechanism of widespread miRNA regulation by walnut consumption are needed to offer potential prognostic and therapeutic targets.

Piceatannol inhibits phorbol ester-induced expression of COX-2 and iNOS in HR-1 hairless mouse skin by blocking the activation of NF-κB and AP-1

OBJECTIVES

The present study was aimed at elucidating the molecular mechanisms of anti-inflammatory activity of piceatannol (trans-3,4,3',5'-tetrahydroxystilbene) in mouse skin in vivo.

METHODS

Female HR-1 hairless mice were topically treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) with or without piceatannol pretreatment. Epidermal protein expression was assessed by Western blot analysis. The cyclooxygenase-2 (COX-2) expression was detected by immunohistochemistry. The DNA binding of nuclear factor-kappaB (NF-κB) and activator protein-1 (AP-1) was examined by the electrophoretic mobility gel shift assay. The catalytic activity of IκBα kinase-β (IKKβ) was measured by in vitro kinase assay.

RESULTS

Pretreatment with piceatannol attenuated TPA-induced expression of COX-2 and inducible nitric oxide synthase (iNOS) in mouse skin. Piceatannol diminished nuclear translocation and the DNA binding of NF-κB through the blockade of phosphorylation and subsequent degradation of IκBα. Piceatannol attenuated the catalytic activity of IKKβ and inhibited the phosphorylation of mitogen-activated protein (MAP) kinases in TPA-treated mouse skin. In addition, piceatannol decreased TPA-induced expression of c-Fos and the DNA binding of AP-1.

CONCLUSION

Piceatannol inhibits TPA-induced COX-2 and iNOS expression by blocking the activation of NF-κB and AP-1 via suppression of the IKKβ activity and phosphorylation of MAP kinases, which provides a mechanistic basis of its anti-inflammatory effects in mouse skin.

The spleen tyrosine kinase (Syk) regulates Alzheimer amyloid-β production and Tau hyperphosphorylation

We have previously shown that the L-type calcium channel (LCC) antagonist nilvadipine reduces brain amyloid-β (Aβ) accumulation by affecting both Aβ production and Aβ clearance across the blood-brain barrier (BBB). Nilvadipine consists of a mixture of two enantiomers, (+)-nilvadipine and (-)-nilvadipine, in equal proportion. (+)-Nilvadipine is the active enantiomer responsible for the inhibition of LCC, whereas (-)-nilvadipine is considered inactive. Both nilvadipine enantiomers inhibit Aβ production and improve the clearance of Aβ across the BBB showing that these effects are not related to LCC inhibition. In addition, treatment of P301S mutant human Tau transgenic mice (transgenic Tau P301S) with (-)-nilvadipine reduces Tau hyperphosphorylation at several Alzheimer disease (AD) pertinent epitopes. A search for the mechanism of action of (-)-nilvadipine revealed that this compound inhibits the spleen tyrosine kinase (Syk). We further validated Syk as a target-regulating Aβ by showing that pharmacological inhibition of Syk or down-regulation of Syk expression reduces Aβ production and increases the clearance of Aβ across the BBB mimicking (-)-nilvadipine effects. Moreover, treatment of transgenic mice overexpressing Aβ and transgenic Tau P301S mice with a selective Syk inhibitor respectively decreased brain Aβ accumulation and Tau hyperphosphorylation at multiple AD relevant epitopes. We show that Syk inhibition induces an increased phosphorylation of the inhibitory Ser-9 residue of glycogen synthase kinase-3β, a primary Tau kinase involved in Tau phosphorylation, by activating protein kinase A, providing a mechanism explaining the reduction of Tau phosphorylation at GSK3β-dependent epitopes following Syk inhibition. Altogether our data highlight Syk as a promising target for preventing both Aβ accumulation and Tau hyperphosphorylation in AD.

Differential effects of resveratrol and its natural analogs, piceatannol and 3,5,4'-trans-trimethoxystilbene, on anti-inflammatory heme oxigenase-1 expression in RAW264.7 macrophages

Resveratrol (Res) and its two natural analogs that are also related to Res metabolism, piceatannol (Pic) and 3,5,4'-trans-trimethoxystilbene (TMS), were compared in their ability to suppress lipopolysaccharide (LPS)-induced production of proinflammatory tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) and to induce anti-inflammatory heme oxygenase-1 (HO-1) expression in RAW264.7 macrophages. At non-cytotoxic concentrations, they differentially suppressed LPS-induced production of TNF-α and IL-1β; the relative potency for suppression of TNF-α and IL-1β production was Pic > Res > TMS. Res and Pic differentially induced HO-1 expression; Pic, which possesses four hydroxyl groups, was more active in inducing HO-1 expression than Res that contains three hydroxyl groups. TMS, which has none of hydroxyl groups, failed to induce HO-1 expression. These findings suggest that the hydroxyl groups of Res analogs are important for suppression of TNF-α and IL-1β production and HO-1 expression. Interestingly, protoporphyrin-IX, a competitive inhibitor of HO-1 activity, partly attenuated the inhibitory effects of Res and Pic (but not TMS) on TNF-α and IL-1β production, suggesting that suppression of TNF-α and IL-1β production correlates at least in part with HO-1 expression. Overall, the ability of Res analogs to induce HO-1 expression may provide one of possible mechanisms of their anti-inflammatory action.

Piceatannol suppresses endotoxin-induced ocular inflammation in rats

Anti-inflammatory effect of piceatannol, a naturally occurring polyphenol and a potent free radical scavenger, on ocular inflammation is not known. We examined the anti-inflammatory role of piceatannol in ocular inflammatory response due to endotoxin-induced uveitis (EIU) in rats. EIU was induced in Lewis rats by subcutaneous injection of lipopolysaccharide (LPS; 150 ug/rat). Piceatannol (30mg/kg body wt, i.p) was injected either 2h prior to or 1h post LPS induction. A significant increase in the number of infiltrating cells, total protein, and various cytokines and chemokines in AqH were observed in the EIU rat eyes as compared to control groups. However, pre- or post-treatment of piceatannol significantly blocked the LPS-induced changes. Further, piceatannol also suppressed the expression of cyclooxygenase-2 (Cox-2), inducible nitric oxide synthase (iNOS) and activation of NF-κB in the ciliary bodies as well as retina. Further, piceatannol also inhibited the expression of Cox-2, iNOS, and phosphorylation of NF-κB in primary human non-pigmented ciliary epithelial cells (HNPECs) treated with LPS. Similarly, piceatannol also diminished LPS-induced level of NO and prostaglandin E2 in HNPECs. Thus our results demonstrate an anti-inflammatory role of piceatannol in suppressing ocular inflammation induced by endotoxin in rats.

Prevention of colitis-associated cancer: natural compounds that target the IL-6 soluble receptor

The risk of developing colorectal cancer increases in patients with inflammatory bowel disease (IBD) and a growing body of evidence shows the critical role of interleukin (IL-6) in this process. IL-6 is both a pro- and anti-inflammatory cytokine whose effects are mediated through activation of STAT3. Recent studies have also demonstrated that IL-6 trans-signaling through its soluble receptor occurs in IBD and cancer. IL-6 trans-signaling therefore is emerging as an attractive approach to diminish the inflammatory signals in conditions of chronic inflammation. The purpose of cancer chemoprevention is to either delay the onset or progression from precancerous lesions. Natural compounds because of their low toxicity render themselves excellent candidates that can be administered over the lifetime of an individual. With the focus of managing IBD over a long time and preventing onset of colitis-associated cancer, we believe that there should be increased research focus on identifying chemopreventive compounds that can render themselves to long term use possibly for the lifetime of predisposed individuals. Here, we review the role of IL-6 signaling in IBD and colitis-associated cancer and underscore the importance of searching for natural compounds that would target the IL-6 trans-signaling pathway as a way to diminish chronic inflammatory conditions in the gastrointestinal tract and possibly hamper the progression to colon cancer. We propose that effective screening and identification of natural chemopreventive compounds that target IL-6 trans-signaling has important implications for the development of optimal strategies against cancer development triggered by inflammation.

Propyl gallate inhibits TPA-induced inflammation via the nuclear factor-κB pathway in human THP-1 monocytes

Propyl gallate (PG) is an antioxidant that has been used as an additive in several foods to protect against oxidation. The present study examined the anti-inflammatory effect of PG on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation in human THP-1 monocytes. Pretreatment with PG markedly inhibited the TPA-induced expression levels of cyclooxygenase-2 and prostaglandin E2. The application of PG significantly inhibited the nuclear translocation of p65, a subunit of nuclear factor-κB (NF-κB) and phosphorylation of p65 (Ser536) in TPA-treated THP-1 cells. PG also inhibited the phosphorylation of IκB and IκB kinase. These results indicate that PG inhibits the inflammatory response by blocking the NF-κB signaling pathway in TPA-induced THP-1 monocytes. Therefore, PG may be useful as a therapeutic agent in inflammatory diseases.

Oxyresveratrol from Mulberry as a dihydrate

The title compound {systematic name: 4-[(E)-2-(3,5-dihy­droxy­phen­yl)ethen­yl]benzene-1,3-diol dihydrate}, C₁₄H₁₂O₄·2H₂O, a derivative of resveratrol, was isolated from mulberry. The linking C=C double bond has a trans conformation and allows the formation of a conjugated system throughout the mol­ecule. The dihedral angle between the benzene rings is 9.39 (9)°. In the crystal, mol­ecules are connected into a three-dimensional architecture through O—H⋯O hydrogen bonds between hy­droxy groups of oxyresveratrol and solvent water mol­ecules.

AKT/mTOR as Novel Targets of Polyphenol Piceatannol Possibly Contributing to Inhibition of Proliferation of Cultured Prostate Cancer Cells

The polyphenol piceatannol has shown inhibition against tyrosine and serine/threonine kinases. Whether piceatannol also exerts activity on the mammalian target of rapamycin (mTOR), a kinase involved in growth control of eukaryotic cells, is not known. In this study, we tested the effects of piceatannol on proliferation of androgen-dependent (AD) LNCaP and androgen-independent (AI) DU145 and PC-3 prostate cancer (CaP) cells. Suppression of AD and AI CaP cell growth by piceatannol was accompanied by cell cycle blockade in G(1)/S and S phases for LNCaP and PC-3 and induction of apoptosis in DU145 cells. Induction of apoptosis by piceatannol in DU145 cells was evident by reduced expression of poly(ADP-ribose) polymerase (PARP), cleavage of caspase 3 and apoptosis inducing factor AIF, and an increase in cytochrome c. The apoptotic changes occurred in concordance with DNA damage, supported by increased phosphorylated histone H2AX. Immunoblot analyses showed that exposure of different-stage CaP cells to piceatannol also resulted in cell-type-specific downregulation of mTOR and its upstream and downstream effector proteins, AKT and eIF-4E-BP1. We propose that the observed AKT and mTOR changes are new targets of piceatannol possibly contributing to its inhibitory activities on proliferation of CaP cells.

p65-Dependent production of interleukin-1β by osteolytic prostate cancer cells causes an induction of chemokine expression in osteoblasts

Skeletal metastases are a frequent complication of prostate, breast and lung cancer, and the interactions of tumor cells with bone-forming osteoblasts and bone-resorbing osteoclasts have been suggested to play critical roles in disease progression. We have previously shown that treatment of primary murine osteoblasts with conditioned medium of the human osteolytic prostate cancer cell line PC-3 results in a rapid induction of chemokine expression, thereby providing further evidence for a molecular crosstalk between bone and tumor cells. The aim of our current study was to identify PC-3-derived molecules mediating this effect. Using Affymetrix Gene Chip hybridization followed by qRT-PCR we were able to confirm that the expression of chemokine-encoding genes is markedly induced in human primary osteoblasts following incubation with PC-3-conditioned medium. Since this induction was significantly affected upon alteration of p65-levels in PC-3 cells, we performed a second genome-wide expression analysis to identify p65-regulated cytokines, which were then tested for their ability to induce chemokine expression. Here we observed that interleukin-1β (IL-1B) did not only increase the expression of chemokines in osteoblasts, but also the phosphorylation of p65 and thereby its own expression. Since immunohistochemistry on bone biopsy sections from prostate cancer metastases demonstrated IL-1B expression in both, tumor cells and osteoblasts, our data suggest that IL-1B is one of the relevant cytokines involved in the skeletal complications of cancer metastases.

Dietary walnut suppressed mammary gland tumorigenesis in the C(3)1 TAg mouse

Walnuts contain multiple ingredients that, individually, have been shown to slow cancer growth, including omega-3 fatty acids, antioxidants, and phytosterols. In previous research, consumption of walnuts has slowed the growth of implanted breast cancers. We wanted to determine whether regular walnut consumption might reduce the risk for developing cancer. Homozygous male C(3)1 TAg mice were bred with female SV129 mice consuming either the control AIN-76 diet or the walnut-containing diet. At weaning, the female hemizygous pups were randomized to control or walnut-containing diets and followed for tumor development. Compared to a diet without walnuts, consumption of walnuts significantly reduced tumor incidence (fraction of mice with at least one tumor), multiplicity (number of glands with tumor/mouse), and size. Gene expression analyses indicated that consumption of the walnut diet altered expression of multiple genes associated with proliferation and differentiation of mammary epithelial cells. A comparison with another dietary intervention indicated that the omega 3 content alone did not account for the extent of tumor suppression due to the walnut. The results of this study indicate that walnut consumption could contribute to a healthy diet to reduce risk for breast cancer.

Piceatannol, a catechol-type polyphenol, inhibits phorbol ester-induced NF-{kappa}B activation and cyclooxygenase-2 expression in human breast epithelial cells: cysteine 179 of IKK{beta} as a potential target

There are multiple lines of evidence supporting that chronic inflammation is linked to carcinogenesis. Nuclear factor-kappaB (NF-kappaB), a major redox-sensitive transcription factor responsible for the induction of a wide array of pro-inflammatory genes, is frequently overactivated in many tumors. Moreover, constitutive activation of IkappaB kinase (IKK), a key regulator of NF-kappaB signaling, has been implicated in inflammation-associated tumorigenesis. Piceatannol (trans-3,4,3',5'-tetrahydroxystilbene; PIC) derived from grapes, rhubarb and sugarcane exhibits immunosuppressive and antitumorigenic activities in several cell lines, but the underlying mechanisms are poorly understood. In the present study, we found that PIC inhibited migration and anchorage-independent growth of human mammary epithelial cells (MCF-10A) treated with the prototypic tumor promoter, 12-O-tetradecanoylphorbol-13-aceate (TPA). PIC treatment suppressed the TPA-induced activation of NF-kappaB and expression of cyclooxygenase-2 (COX-2) in MCF-10A cells. We speculate that an electrophilic quinone formed as a consequence of oxidation of PIC bearing the catechol moiety may directly interact with critical cysteine thiols of IKKbeta, thereby inhibiting its catalytic activity. In support of this speculation, the reducing agent dithiothreitol abrogated the inhibitory effects of PIC on TPA-induced activation of NF-kappaB signaling and expression of COX-2. In addition, the inhibitory effects of PIC on NF-kappaB activation and COX-2 induction were blunted in cells expressing mutant IKKbeta (C179A) in which cysteine 179 was replaced by alanine. In conclusion, our results show that direct modification of IKKbeta by PIC, presumably at the cysteine 179 residue, blocks NF-kappaB activation signaling and COX-2 induction in TPA-treated MCF-10A cells and also migration and transformation of these cells.