Grape seed extract upregulates p21 (Cip1) through redox-mediated activation of ERK1/2 and posttranscriptional regulation leading to cell cycle arrest in colon carcinoma HT29 cells

Grape seed proanthocyanidin extract induces apoptotic and autophagic cell death in rheumatoid arthritis fibroblast-like synoviocytes

Objectives

In this study, we aimed to evaluate the association between grape seed proanthocyanidin extract (GSPE) and rheumatoid arthritis-fibroblast-like synoviocytes (RA-FLSs) and to investigate whether GSPE induces cell death in RA-FLSs.

Materials and methods

The FLSs were isolated from RA synovial tissues. Cell viability and cell cycle staging were analyzed using a hemocytometer and flow cytometry. Caspase 3 and poly (ADP-ribose) polymerase (PARP) proteins were analyzed using Western blotting with z-VAD-fmk. Protein LC3 and polyubiquitin-binding protein p62 that were degraded by autophagy were evaluated using Western blotting with 3-methyladenine and chloroquine. Reactive oxygen species (ROS) were also evaluated.

Results

When RA-FLSs were treated with GSPE, cell viability decreased, the number of cells in sub-G1 and G2/M phases increased, and the expression of pro-PARP and pro-caspase 3 proteins decreased in a concentration-dependent manner. This result was offset, when the cells were co-treated with the pan-caspase inhibitor z-VAD-fmk. The reduced cell viability, increased expression of LC3-II protein, and reduced expression of p62 protein with GSPE treatment were offset, when RA-FLSs were co-treated with GSPE and autophagy inhibitors 3-methyladenine and chloroquine. The level of ROS in RA-FLSs treated with GSPE was significantly lower than treatment with N-acetyl-cysteine, a ROS inhibitor.

Conclusion

Our study results show that GSPE induces apoptotic and autophagic cell death and inhibites reactive oxygen species in RA-FLSs.

Phyto-polyphenols as potential inhibitors of breast cancer metastasis

Breast cancer is the most common cancer among women as metastasis is currently the main cause of mortality. Breast cancer cells undergoing metastasis acquire resistance to death signals and increase of cellular motility and invasiveness.Plants are rich in polyphenolic compounds, many of them with known medicinal effects. Various phyto-polyphenols have also been demonstrated to suppress cancer growth. Their mechanism of action is usually pleiotropic as they target multiple signaling pathways regulating key cellular processes such as proliferation, apoptosis and differentiation. Importantly, some phyto- polyphenols show low level of toxicity to untransformed cells, but selective suppressing effects on cancer cells proliferation and differentiation.In this review, we summarize the current information about the mechanism of action of some phyto-polyphenols that have demonstrated anti-carcinogenic activities in vitro and in vivo. Gained knowledge of how these natural polyphenolic compounds work can give us a clue for the development of novel anti-metastatic agents.

The comparative study among different fractions of muscadine grape 'Noble' pomace extracts regarding anti-oxidative activities, cell cycle arrest and apoptosis in breast cancer

As a by-product of wine making, pomace contains rich amounts of phenolic compounds that can be potentially utilized as raw materials to make beneficial products especially for the anti-cancer agents including the breast cancer. Muscadinia rotundifolia ‘Noble’ is a wine-making grape cultivar, and to better use ‘Noble’ pomace, the most effective phenolic fractions in cancer inhibition must be identified. In this study, anti-oxidative activities of three separated fractions of ‘Noble’ pomace (F1, F2 and F3) were compared in 2,2-diphenyl-1-picrylhydrazyl and 2,2ʹ-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) radical scavenging (DPPH and ABTS) assays as well as the ferric-reducing antioxidant power (FRAP) assay. The ability of different fractions to induce cell cycle arrest and apoptosis in MDA-MB-231 breast cancer cells was also evaluated by flow cytometry and Western blot analysis. Fraction F3, which contained a mixture of anthocyanidins and ellagic acids, exhibited the strongest anti-oxidative activity, as determined at both low and high concentrations in the DPPH and FRAP assays. F3 also demonstrated the greatest ability to induce apoptosis via caspase activation and cell cycle arrest by downregulating cyclin A and upregulating p21. F3 was thus the most effective bioactive fraction among those prepared from muscadine grape ‘Noble’ pomace.

Cristacarpin promotes ER stress-mediated ROS generation leading to premature senescence by activation of p21(waf-1)

Stress-induced premature senescence (SIPS) is quite similar to replicative senescence that is committed by cells exposed to various stress conditions viz. ultraviolet radiation (DNA damage), hydrogen peroxide (oxidative stress), chemotherapeutic agents (cytotoxic threat), etc. Here, we report that cristacarpin, a natural product obtained from the stem bark of Erythrina suberosa, promotes endoplasmic reticulum (ER) stress, leading to sub-lethal reactive oxygen species (ROS) generation and which eventually terminates by triggering senescence in pancreatic and breast cancer cells through blocking the cell cycle in the G1 phase. The majority of cristacarpin-treated cells responded to conventional SA-β-gal stains; showed characteristic p21(waf1) upregulation along with enlarged and flattened morphology; and increased volume, granularity, and formation of heterochromatin foci-all of these features are the hallmarks of senescence. Inhibition of ROS generation by N-acetyl-L-cysteine (NAC) significantly reduced the expression of p21(waf1), confirming that the modulation in p21(waf1) by anti-proliferative cristacarpin was ROS dependent. Further, the elevation in p21(waf1) expression in PANC-1 and MCF-7 cells was consistent with the decrease in the expression of Cdk-2 and cyclinD1. Here, we provide evidence that cristacarpin promotes senescence in a p53-independent manner. Moreover, cristacarpin treatment induced p38MAPK, indicating the ROS-dependent activation of the MAP kinase pathway, and thus abrogates the tumor growth in mouse allograft tumor model.

Protective Role of Grape Seed Proanthocyanidins Against Ccl4 Induced Acute Liver Injury in Mice

Background

We investigated the effect of grape seed proanthocyanidins (GSPs) on carbon tetrachloride (CCl₄)-induced acute liver injury.

Material/Methods

Sixty SPF KM mice were randomly divided into 6 groups: the control group, CCl₄-model group, bifendate group (DDB group), and low-, moderate-, and high-dose GSP groups. The following parameters were measured: serum levels of alanine aminotransferase (ALT); aspartate aminotransferase (AST); tumor necrosis factor (TNF)-α; interleukin-6 (IL-6); high-mobility group box (HMGB)-1; body weight; liver, spleen, and thymus indexes; superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity; HMGB1 mRNA; malondialdehyde (MDA) content; hepatocyte proliferation; and changes in liver histology.

Results

Compared to the CCl₄-model group, decreases in liver index and increases in thymus index significantly increased SOD and GSH-Px activities and reduced MDA content, and higher hepatocyte proliferative activity was found in all GSP dose groups and the DDB group (all P<0.001). Compared with the CCl₄-model group, serum TNF-α and IL-6 levels and HMGB 1 mRNA and protein expressions decreased significantly in the high GSP dose group (all P<0.05).

Conclusions

Our results provide strong evidence that administration of GSPs might confer significant protection against CCl₄-induced acute liver injury in mice.

Functional modification of adipocytes by grape seed extract impairs their pro-tumorigenic signaling on colon cancer stem cells and the daughter cancer cells

With global rise in obesity, it is imperative that we identify obesity-driven factors that increase growth and progression of colorectal cancer (CRC), and also discover and develop agents with anti-CRC efficacy under obese conditions. Here in, we investigated grape seed extract (GSE), a well-defined agent with both preventive and anti-CRC efficacy, for its potential to impair pro-tumorigenic signaling of adipocytes on CRC/colon cancer stem cells (CSCs) and associated molecular mechanisms, to control CRC under obese conditions. GSE treatment significantly decreased the growth and invasion promoting effects of both mouse and human adipocytes on CRC cells. Moreover, GSE exerted a direct inhibitory effect, as well as it strongly reduced the growth promoting signals of adipocytes, on colon CSCs. These GSE effects were associated with a decrease in both mRNA and protein levels of various CSC-associated molecules. Notably, GSE effects on adipocytes were not due to changes in lipid content, but by inducing the ‘browning’ of adipocytes as evidenced by an increase in UCP-1 mRNA level and mitochondriogenesis. Together, these findings, for the first time, suggest the ability of GSE to induce ‘brown remodeling’ of white adipocytes, which causes functional modification of adipocytes thus impairing their pro-tumorigenic signals on colon CSCs/CRC cells.

Target identification of grape seed extract in colorectal cancer using drug affinity responsive target stability (DARTS) technique: role of endoplasmic reticulum stress response proteins

Various natural agents, including grape seed extract (GSE), have shown considerable chemopreventive and anti-cancer efficacy against different cancers in pre-clinical studies; however, their specific protein targets are largely unknown and thus, their clinical usefulness is marred by limited scientific evidences about their direct cellular targets. Accordingly, herein, employing, for the first time, the recently developed drug affinity responsive target stability (DARTS) technique, we aimed to profile the potential protein targets of GSE in human colorectal cancer (CRC) cells. Unlike other methods, which can cause chemical alteration of the drug components to allow for detection, this approach relies on the fact that a drug bound protein may become less susceptible to proteolysis and hence the enriched proteins can be detected by Mass Spectroscopy methods. Our results, utilizing the DARTS technique followed by examination of the spectral output by LC/MS and the MASCOT data, revealed that GSE targets endoplasmic reticulum (ER) stress response proteins resulting in overall down regulation of proteins involved in translation and that GSE also causes oxidative protein modifications, specifically on methionine amino acids residues on its protein targets. Corroborating these findings, mechanistic studies revealed that GSE indeed caused ER stress and strongly inhibited PI3k-Akt-mTOR pathway for its biological effects in CRC cells. Furthermore, bioenergetics studies indicated that GSE also interferes with glycolysis and mitochondrial metabolism in CRC cells. Together, the present study identifying GSE molecular targets in CRC cells, combined with its efficacy in vast pre-clinical CRC models, further supports its usefulness for CRC prevention and treatment.

Alteration of antioxidant enzymes and associated genes induced by grape seed extracts in the primary muscle cells of goats in vitro

This study was conducted to investigate how the activity and expression of certain paramount antioxidant enzymes respond to grape seed extract (GSE) addition in primary muscle cells of goats. Gluteal primary muscle cells (PMCs) isolated from a 3-week old goat were cultivated as an unstressed cell model, or they were exposed to 100 µM H₂O₂ to establish a H₂O₂-stimulated cell model. The activities of catalase (CAT), superoxide dismutases (SOD) and glutathione peroxidases (GPx) in combination with other relevant antioxidant indexes [i.e., reduced glutathione (GSH) and total antioxidant capacity (TAOC)] in response to GSE addition were tested in the unstressed and H₂O₂-stimulated cell models, and the relative mRNA levels of the CAT, GuZu-SOD, and GPx-1 genes were measured by qPCR. In unstressed PMCs, GSE addition at the dose of 10 µg/ml strikingly attenuated the expression levels of CAT and CuZn-SOD as well as the corresponding enzyme activities. By contrast, in cells pretreated with 100 µM H₂O₂, the expression and activity levels of these two antioxidant enzymes were enhanced by GSE addition at 10 µg/ml. GSE addition promoted GPx activity in both unstressed and stressed PMCs, while the expression of the GPx 1 gene displayed partial divergence with GPx activity, which was mitigated by GSE addition at 10 µg/ml in unstressed PMCs. GSH remained comparatively stable except for GSE addition to H₂O₂-stimulated PMCs at 60 µg/ml, in which a dramatic depletion of GSH occurred. Moreover, GSE addition enhanced TAOC in unstressed (but not H₂O₂-stimulated) PMCs. GSE addition exerted a bidirectional modulating effect on the mRNA levels and activities of CAT and SOD in unstressed and stressed PMCs at a moderate dose, and it only exhibited a unidirectional effect on the promotion of GPx activity, reflecting its potential to improve antioxidant protection in ruminants.

Nutraceuticals as potential therapeutic agents for colon cancer: a review

Colon cancer is a world-wide health problem and the second-most dangerous type of cancer, affecting both men and women. The modern diet and lifestyles, with high meat consumption and excessive alcohol use, along with limited physical activity has led to an increasing mortality rate for colon cancer worldwide. As a result, there is a need to develop novel and environmentally benign drug therapies for colon cancer. Currently, nutraceuticals play an increasingly important role in the treatment of various chronic diseases such as colon cancer, diabetes and Alzheimer׳s disease. Nutraceuticals are derived from various natural sources such as medicinal plants, marine organisms, vegetables and fruits. Nutraceuticals have shown the potential to reduce the risk of colon cancer and slow its progression. These dietary substances target different molecular aspects of colon cancer development. Accordingly, this review briefly discusses the medicinal importance of nutraceuticals and their ability to reduce the risk of colorectal carcinogenesis.

Bitter melon juice activates cellular energy sensor AMP-activated protein kinase causing apoptotic death of human pancreatic carcinoma cells

Prognosis of pancreatic cancer is extremely poor, suggesting critical needs for additional drugs to improve disease outcome. In this study, we examined efficacy and associated mechanism of a novel agent bitter melon juice (BMJ) against pancreatic carcinoma cells both in culture and nude mice. BMJ anticancer efficacy was analyzed in human pancreatic carcinoma BxPC-3, MiaPaCa-2, AsPC-1 and Capan-2 cells by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyl tetrazolium bromide, cell death enzyme-linked immunosorbent assay and annexin/propidium iodide assays. BMJ effect on apoptosis regulators was assessed by immunoblotting. In vivo BMJ efficacy was evaluated against MiaPaCa-2 tumors in nude mice, and xenograft was analyzed for biomarkers by immunohistochemistry (IHC). Results showed that BMJ (2-5% v/v) decreases cell viability in all four pancreatic carcinoma cell lines by inducing strong apoptotic death. At molecular level, BMJ caused caspases activation, altered expression of Bcl-2 family members and cytochrome-c release into the cytosol. Additionally, BMJ decreased survivin and X-linked inhibitor of apoptosis protein but increased p21, CHOP and phosphorylated mitogen-activated protein kinases (extracellular signal-regulated kinase 1/2 and p38) levels. Importantly, BMJ activated adenosine monophosphate-activated protein kinase (AMPK), a biomarker for cellular energy status, and an AMPK inhibitor (Compound C) reversed BMJ-induced caspase-3 activation suggesting activated AMPK involvement in BMJ-induced apoptosis. In vivo, oral administration of lyophilized BMJ (5mg in 100 µl water/day/mouse) for 6 weeks inhibited MiaPaCa-2 tumor xenograft growth by 60% (P < 0.01) without noticeable toxicity in nude mice. IHC analyses of MiaPaCa-2 xenografts showed that BMJ also inhibits proliferation, induces apoptosis and activates AMPK in vivo. Overall, BMJ exerts strong anticancer efficacy against human pancreatic carcinoma cells, both in vitro and in vivo, suggesting its clinical usefulness.

Grape seeds: ripe for cancer chemoprevention

A wide variety of phytochemicals, mostly flavonoids or polyphenolics, have been shown to possess anticarcinogenic activities. Among these are the grape seed proanthocyanidins (GSPs), which are the active ingredients of grape seed extract (GSE). Substantial in vitro and preclinical in vivo studies have shown the chemopreventive efficacy of GSPs against various forms of cancers in different tumor models. In this issue of the journal, Derry and colleagues show that administration of GSE in the diet reduces azoxymethane-induced colon carcinogenesis in an A/J mouse model. The results of this innovative and comprehensive study indicate that inhibition of azoxymethane-induced colon cancer by dietary GSE is mediated through the induction of apoptosis that is associated with alterations in microRNA (miRNA) and cytokine expression profiles as well as β-catenin signaling. Notably, the demonstration that miRNA expression is affected by dietary GSE suggests a novel underlying mechanism for the chemopreventive action of GSE in colon cancer and, potentially, other cancers.

Identifying molecular targets of lifestyle modifications in colon cancer prevention

One in four deaths in the United States is cancer-related, and colorectal cancer (CRC) is the second leading cause of cancer-associated deaths. Screening strategies are utilized but have not reduced disease incidence or mortality. In this regard, there is an interest in cancer preventive strategies focusing on lifestyle intervention, where specific etiologic factors involved in cancer initiation, promotion, and progression could be targeted. For example, exposure to dietary carcinogens, such as nitrosamines and polycyclic aromatic hydrocarbons influences colon carcinogenesis. Furthermore, dietary deficiencies could alter sensitivity to genetic damage and influence carcinogen metabolism contributing to CRC. High alcohol consumption increases the risk of mutations including the fact that acetaldehyde, an ethanol metabolite, is classified as a group 1 carcinogen. Tobacco smoke exposure is also a risk factor for cancer development; approximately 20% of CRCs are associated with smoking. Additionally, obese patients have a higher risk of cancer development, which is further supported by the fact that physical activity decreases CRC risk by 55%. Similarly, chronic inflammatory conditions also increase the risk of CRC development. Moreover, the circadian clock alters digestion and regulates other biochemical, physiological, and behavioral processes that could influence CRC. Taken together, colon carcinogenesis involves a number of etiological factors, and therefore, to create effective preventive strategies, molecular targets need to be identified and beleaguered prior to disease progression. With this in mind, the following is a comprehensive review identifying downstream target proteins of the above lifestyle risk factors, which are modulated during colon carcinogenesis and could be targeted for CRC prevention by novel agents including phytochemicals.

Grape polyphenols inhibit Akt/mammalian target of rapamycin signaling and potentiate the effects of gefitinib in breast cancer

We recently reported that a combination of dietary grape polyphenols resveratrol, quercetin, and catechin (RQC), at low concentrations, was effective at inhibiting metastatic cancer progression. Herein, we investigate the molecular mechanisms of RQC in breast cancer and explore the potential of RQC as a potentiation agent for the epidermal growth factor receptor (EGFR) therapeutic gefitinib. Our in vitro experiments showed RQC induced apoptosis in gefitinib-resistant breast cancer cells via regulation of a myriad of proapoptotic proteins. Because the Akt/mammalian target of rapamycin (mTOR) signaling pathway is often elevated during development of anti-EGFR therapy resistance, the effect of RQC on the mTOR upstream effector Akt and the negative regulator AMP kinase (AMPK) was investigated. RQC was found to reduce Akt activity, induce the activation of AMPK, and inhibit mTOR signaling in breast cancer cells. Combined RQC and gefitinib decreased gefitinib resistant breast cancer cell viability to a greater extent than RQC or gefitinib alone. Moreover, RQC inhibited Akt and mTOR and activated AMPK even in the presence of gefitinib. Our in vivo experiments showed combined RQC and gefitinib was more effective than the individual treatments at inhibiting mammary tumor growth and metastasis in nude mice. Therefore, RQC treatment inhibits breast cancer progression and may potentiate anti-EGFR therapy by inhibition of Akt/mTOR signaling.

Differential effects of grape seed extract against human colorectal cancer cell lines: the intricate role of death receptors and mitochondria

Failure of anti-cancer therapy in colorectal cancer (CRC) cells involves resistance to death mechanisms. We investigated grape seed extract (GSE) ability to target CRC cells and delineated the mechanisms involved in GSE-induced CRC cell death. GSE selectively induced apoptotic death in human CRC cells; efficacy increased as the metastatic potential of the cancer cells increased. Oxidative stress, loss of mitochondrial membrane potential, modulation of pro- and anti-apoptotic proteins, and involvement of both caspase-dependent/independent apoptotic pathways contributed to GSE-induced CRC cell death. GSE intervention may serve as a multi-targeted CRC therapeutic capable of inducing selective cancer cell death.

Grape seed proanthocyanidins inhibit colon cancer-induced angiogenesis through suppressing the expression of VEGF and Ang1

Tumor cells trigger angiogenesis through overexpression of various angiogenic factors including vascular endothelial growth factor (VEGF) and angiopoietin 1 (Ang1). Therefore, inhibition of the expression of both VEGF and Ang1, the initial step of tumor angiogenesis, is a promising strategy for cancer chemoprevention and therapy. Grape seed proanthocyanidins (GSPs) are widely consumed dietary supplements that have antitumor activity. Due to their polymeric structure, GSPs are poorly absorbed along the gastrointestinal tract and can reach the colon at high concentrations, allowing these chemicals to act as chemopreventive agents for colon cancer. In the present study, we found that GSPs inhibited colon tumor-induced angiogenesis and, thus, the growth of colon tumor xenografts on the chick chorioallantoic membranes. The mechanisms of their action were related to inhibiting the expression of both VEGF and Ang1 through scavenging reactive oxygen species. Previous studies have demonstrated that the chemopreventive effects of GSPs on colon cancer are associated with their growth inhibitory and apoptosis-inducing effects. Our results demonstrate another mechanism by which GSPs inhibit colon tumor growth, which will be helpful for developing GSPs as a pharmacologically safe angiopreventive agent against colorectal cancer.

Potential anticancer properties of grape antioxidants

Dietary intake of foods rich in antioxidant properties is suggested to be cancer protective. Foods rich in antioxidant properties include grape (Vitis vinifera), one of the world's largest fruit crops and most commonly consumed fruits in the world. The composition and cancer-protective effects of major phenolic antioxidants in grape skin and seed extracts are discussed in this review. Grape skin and seed extracts exert strong free radical scavenging and chelating activities and inhibit lipid oxidation in various food and cell models in vitro. The use of grape antioxidants are promising against a broad range of cancer cells by targeting epidermal growth factor receptor (EGFR) and its downstream pathways, inhibiting over-expression of COX-2 and prostaglandin E2 receptors, or modifying estrogen receptor pathways, resulting in cell cycle arrest and apoptosis. Interestingly, some of these activities were also demonstrated in animal models. However, in vivo studies have demonstrated inconsistent antioxidant efficacy. Nonetheless, a growing body of evidence from human clinical trials has demonstrated that consumption of grape, wine and grape juice exerts many health-promoting and possible anti-cancer effects. Thus, grape skin and seed extracts have great potential in cancer prevention and further investigation into this exciting field is warranted.

Homeostatic imbalance and colon cancer: the dynamic epigenetic interplay of inflammation, environmental toxins, and chemopreventive plant compounds

The advent of modern medicine has allowed for significant advances within the fields of emergency care, surgery, and infectious disease control. Health threats that were historically responsible for immeasurable tolls on human life are now all but eradicated within certain populations, specifically those that enjoy higher degrees of socio-economic status and access to healthcare. However, modernization and its resulting lifestyle trends have ushered in a new era of chronic illness; one in which an unprecedented number of people are estimated to contract cancer and other inflammatory diseases. Here, we explore the idea that homeostasis has been redefined within just a few generations, and that diseases such as colorectal cancer are the result of fluctuating physiological and molecular imbalances. Phytochemical-deprived, pro-inflammatory diets combined with low-dose exposures to environmental toxins, including bisphenol-A (BPA) and other endocrine disruptors, are now linked to increasing incidences of cancer in westernized societies and developing countries. There is recent evidence that disease determinants are likely set in utero and further perpetuated into adulthood dependent upon the innate and environmentally-acquired phenotype unique to each individual. In order to address a disease as multi-factorial, case-specific, and remarkably adaptive as cancer, research must focus on its root causes in order to elucidate the molecular mechanisms by which they can be prevented or counteracted via plant-derived compounds such as epigallocatechin-3-gallate (EGCG) and resveratrol. The significant role of epigenetics in the regulation of these complex processes is emphasized here to form a comprehensive view of the dynamic interactions that influence modern-day carcinogenesis, and how sensibly restoring homeostatic balance may be the key to the cancer riddle.

Tannic acid down-regulates the angiotensin type 1 receptor through a MAPK-dependent mechanism

In the present study, we investigated the effects of tannic acid (TA), a hydrolysable polyphenol, on angiotensin type 1 receptor (AT1R) expression in continuously passaged rat liver epithelial cells. Under normal conditions, exposure of cells to TA resulted in the down-regulation of AT1R-specific binding in concentrations ranging from 12.5-100 μg/ml (7.34-58.78 μm) over a time period of 2-24 h with no change in receptor affinity to angiotensin II (AngII). The inhibitory effect of TA on AT1R was specific and reversible. In TA-treated cells, we observed a significant reduction in AngII-mediated intracellular calcium signaling, a finding consistent with receptor down-regulation. Under similar conditions, TA down-regulated AT1R mRNA expression without changing the rate of mRNA degradation, suggesting that TA's effect is mediated through transcriptional inhibition. Cells expressing recombinant AT1R without the native promoter show no change in receptor expression, whereas a pCAT reporter construct possessing the rat AT1R promoter was significantly reduced in activity. Furthermore, TA induced the phosphorylation of MAPK p42/p44. Pretreatment of the cells with a MAPK kinase (MEK)-specific inhibitor PD98059 prevented TA-induced MAPK phosphorylation and down-regulation of the AT1R. Moreover, there was no reduction in AngII-mediated intracellular calcium release upon MEK inhibition, suggesting that TA's observed inhibitory effect is mediated through MEK/MAPK signaling. Our findings demonstrate, for the first time, that TA inhibits AT1R gene expression and cellular response, suggesting the observed protective effects of dietary polyphenols on cardiovascular conditions may be, in part, through inhibition of AT1R expression.

Generation of reactive oxygen species by grape seed extract causes irreparable DNA damage leading to G2/M arrest and apoptosis selectively in head and neck squamous cell carcinoma cells

Head and neck squamous cell carcinoma (HNSCC) accounts for 6% of all malignancies in USA and unfortunately the recurrence of secondary primary tumors and resistance against conventional treatments decrease the overall 5 year survival rate in HNSCC patients. Thus, additional approaches are needed to control HNSCC. Here, for the first time, employing human HNSCC Detroit 562 and FaDu cells as well as normal human epidermal keratinocytes, we investigate grape seed extract (GSE) efficacy and associated mechanism in both cell culture and nude mice xenografts. GSE selectively inhibited the growth and caused cell cycle arrest and apoptotic death in both Detroit 562 and FaDu cells by activating DNA damage checkpoint cascade, including ataxia telangiectasia mutated/ataxia telangiectasia-Rad3-related-checkpoint kinase 1/2-cell division cycle 25C as well as caspases 8, 9 and 3. Consistent with these results, GSE treatment resulted in a strong DNA damage and a decrease in the levels of DNA repair molecules breast cancer gene 1 and Rad51 and DNA repair foci. GSE-caused accumulation of intracellular reactive oxygen species was identified as a major mechanism of its effect for growth inhibition, DNA damage and apoptosis, which was remarkably reversed by antioxidant N-acetylcysteine. GSE feeding to nude mice decreased Detroit 562 and FaDu xenograft tumor growth by 67 and 65% (P < 0.001), respectively. In immunohistochemical analysis, xenografts from GSE-fed groups showed decreased proliferation but increased DNA damage and apoptosis. Together, these findings show that GSE targets both DNA damage and repair and provide mechanistic insights for its efficacy selectively against HNSCC both in cell culture and mouse xenograft, supporting its translational potential against HNSCC.