Pharmacometrics of pterostilbene: preclinical pharmacokinetics and metabolism, anticancer, antiinflammatory, antioxidant and analgesic activity

α-Dihydroxychalcone-glycoside (α-DHC) isolated from the heartwood of Pterocarpus marsupium inhibits LPS induced MAPK activation and up regulates HO-1 expression in murine RAW 264.7 macrophage

Three phenolic glycosides isolated from the heartwood of Pterocarpus marsupium showed significant free radical and superoxide ion scavenging activity and antioxidant potential that were comparable to, or several folds higher than those of standard antioxidants, trolox and ascorbic acid. The effective concentrations of these compounds were far below their cytotoxic levels. Compound 3, which was characterized to be α-dihydroxychalcone-glycoside (α-DHC), was the most potent one. Subsequent studies demonstrated that α-DHC effectively reduced nitric oxide and cytokine production by the LPS stimulated RAW 264.7 mouse macrophage cell line. The compound effectively attenuated the expression of inflammation-mediating enzymes COX-2 and iNOS at the mRNA as well as protein levels in a concentration dependent manner. It prevented phosphorylation of all the three MAPKs (JNK, ERK, p38) and eventually blocked the activation of downstream elements contributing to inflammation. Phosphorylation of IκB-α and subsequent translocation of NF-κB into the nucleus were restricted, while the expression of stress responsive gene HO-1 was up-regulated. α-DHC targeted Keap-1 by modifying its cysteine thiols, dissociating it from Nrf-2 and facilitating nuclear entry of the latter; and this in turn induced HO-1 expression. Thus α-DHC exerts its anti-inflammatory activity in a dual manner: by down regulating MAPKs and restricting nuclear stabilization of NF-κB at one end, and by disrupting Nrf-2-Keap-1 complex on the other. In conclusion, the anti-inflammatory potential together with its high therapeutic index envisages α-DHC as a prospective candidate molecule for the development of therapeutic strategy against inflammatory disorders.

In vitro and in vivo activities of pterostilbene against Candida albicans biofilms

Pterostilbene (PTE) is a stilbene-derived phytoalexin that originates from several natural plant sources. In this study, we evaluated the activity of PTE against Candida albicans biofilms and explored the underlying mechanisms. In 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assays, biofilm biomass measurement, confocal laser scanning microscopy, and scanning electron microscopy, we found that ≤16 μg/ml PTE had a significant effect against C. albicans biofilms in vitro, while it had no fungicidal effect on planktonic C. albicans cells, which suggested a unique antibiofilm effect of PTE. Then we found that PTE could inhibit biofilm formation and destroy the maintenance of mature biofilms. At 4 μg/ml, PTE decreased cellular surface hydrophobicity (CSH) and suppressed hyphal formation. Gene expression microarrays and real-time reverse transcription-PCR showed that exposure of C. albicans to 16 μg/ml PTE altered the expression of genes that function in morphological transition, ergosterol biosynthesis, oxidoreductase activity, and cell surface and protein unfolding processes (heat shock proteins). Filamentation-related genes, especially those regulated by the Ras/cyclic AMP (cAMP) pathway, including ECE1, ALS3, HWP1, HGC1, and RAS1 itself, were downregulated upon PTE treatment, indicating that the antibiofilm effect of PTE was related to the Ras/cAMP pathway. Then, we found that the addition of exogenous cAMP reverted the PTE-induced filamentous growth defect. Finally, with a rat central venous catheter infection model, we confirmed the in vivo activity of PTE against C. albicans biofilms. Collectively, PTE had strong activities against C. albicans biofilms both in vitro and in vivo, and these activities were associated with the Ras/cAMP pathway.

Urokinase-type plasminogen activator expression and Rac1/WAVE-2/Arp2/3 pathway are blocked by pterostilbene to suppress cell migration and invasion in MDA-MB-231 cells

Breast cancer is the most common malignancy among females, and cancer invasion and metastasis are the leading causes of cancer death in breast cancer patients. Pterostilbene, a naturally occurring dimethylether analogue of resveratrol, has been demonstrated to possess anti-cancer effects. However, inhibitory effects of pterostilbene on cell migration and invasion and its underlying mechanisms are not fully understood. In this study, we investigated the anti-invasive mechanisms of pterostilbene in human breast cancer cell line MDA-MB-231 cells. Pterostilbene effectively inhibited serum-induced migration and invasion without affecting the viability of breast cancer cells. The mRNA expression and activity of urokinase-type plasminogen activator (uPA) were markedly reduced by pterostilbene treatment. Moreover, pterostilbene attenuated nuclear factor κB (NF-κB) transcriptional activity and DNA binding of NF-κB on uPA promoter. In addition, pterostilbene significantly impaired the activity of Rac1 and the expression of WASP-family verprolin-homologous protein-2 (WAVE-2) and actin-related protein 2/3 (Arp2/3). Overall, these results suggest that pterostilbene caused considerable suppression of cell migration and invasion through blocking NF-κB-mediated uPA expression and Rac1/WAVE/Arp2/3 pathway.

The effects of pterostilbene on neutrophil activity in experimental model of arthritis

It has been demonstrated that pterostilbene inhibits reactive oxygen species production in neutrophils in vitro. However, little is known about its effects on neutrophils during inflammation in vivo. In this study, the effect of pterostilbene on neutrophil activity was investigated in experimental arthritis model. Lewis rats were injected by a single intradermal injection of heat-killed Mycobacterium butyricum in Freund's adjuvant to develop arthritis. Another group of arthritic animals received pterostilbene 30 mg/kg, daily, p.o. The number and activity of neutrophils in blood were measured on a weekly basis during the whole experiment. Moreover, the total radical trapping potential in plasma was measured at the end of the experiment. In the pterostilbene treated arthritic group, the treatment significantly lowered the number of neutrophils in blood on days 14 and 21 without significant downregulation of neutrophil oxidative burst. Pterostilbene nonsignificantly increased total radical trapping potential in arthritic animals. These results indicate that the promising effects of pterostilbene on reactive oxygen species operate by different mechanisms in vitro and in the animal model of inflammation. In conclusion, the positive effects of pterostilbene in the model of arthritis may be attributed to regulation of neutrophil number.

Protective effect of Pterostilbene against free radical mediated oxidative damage

Background

Pterostilbene, a methoxylated analog of Resveratrol, is gradually gaining more importance as a therapeutic drug owing to its higher lipophilicity, bioavailability and biological activity than Resveratrol. This study was undertaken to characterize its ability to scavenge free radicals such as superoxide, hydroxyl and hydrogen peroxide and to protect bio-molecules within a cell against oxidative insult.

Methods

Anti-oxidant activity of Pterostilbene was evaluated extensively by employing several in vitro radical scavenging/inhibiting assays and pulse radiolysis study. In addition, its ability to protect rat liver mitochondria against tertiary-butyl hydroperoxide (TBHP) and hydroxyl radical generated oxidative damage was determined by measuring the damage markers such as protein carbonyls, protein sulphydryls, lipid hydroperoxides, lipid peroxides and 8-hydroxy-2'-deoxyguanosine. Pterostilbene was also evaluated for its ability to inhibit •OH radical induced single strand breaks in pBR322 DNA.

Result

Pterostilbene exhibited strong anti-oxidant activity against various free radicals such as DPPH, ABTS, hydroxyl, superoxide and hydrogen peroxide in a concentration dependent manner. Pterostilbene conferred protection to proteins, lipids and DNA in isolated mitochondrial fractions against TBHP and hydroxyl radical induced oxidative damage. It also protected pBR322 DNA against oxidative assault.

Conclusions

Thus, present study provides an evidence for the strong anti-oxidant property of Pterostilbene, methoxylated analog of Resveratrol, thereby potentiating its role as an anti-oxidant.

Scavenging of hydroxyl radical by resveratrol and related natural stilbenes after hydrogen peroxide attack on DNA

Resveratrol (3,5,4'-trihydroxystilbene) is of interest due to its role in prevention and therapy of degenerative diseases as cancer and aging. However, depending on its concentration and cell type studied, resveratrol activity appears conflicting. It exerts antioxidant action, as a scavenger of free radicals and as promoter of antioxidant enzyme activity, but resveratrol acts also as a pro-oxidant. Here we present experimental and theoretical studies for resveratrol and two methoxy-derivatives found in plants, pterostilbene and 3,5,4'-trimethoxystilbene. We show that both methoxy-derivatives induce less DNA damage than resveratrol. The protective effects of the three molecules against oxidative DNA damage induced by hydrogen peroxide treatment were analyzed on mammalian cells in vitro. Our data show for the first time that methoxylated derivatives of resveratrol are very efficient in reducing DNA damage: using the same concentration of the three molecules we obtain a relative reduction of 85.5% (pterostilbene), 43.7% (trimethoxystilbene) and 21.1% (resveratrol). Analysis of the crystal structures of pterostilbene and 3,5,4'-trimethoxystilbene, compared to resveratrol, show fewer intermolecular interactions and a lack of planarity, due to packing forces, which is confirmed by density functional theory (DFT) calculations. We also describe the results of DFT calculations (including water solvent effects) in which the three stilbene species scavenge the hydroxyl radical (associated with the H2O2 insult).

BlueBerry Isolate, Pterostilbene, Functions as a Potential Anticancer Stem Cell Agent in Suppressing Irradiation-Mediated Enrichment of Hepatoma Stem Cells

For many malignancies, radiation therapy remains the second option only to surgery in terms of its curative potential. However, radiation-induced tumor cell death is limited by a number of factors, including the adverse response of the tumor microenvironment to the treatment and either intrinsic or acquired mechanisms of evasive resistance, and the existence of cancer stem cells (CSCs). In this study, we demonstrated that using different doses of irradiation led to the enrichment of CD133⁺ Mahlavu cells using flow cytometric method. Subsequently, CD133⁺ Mahlavu cells enriched by irradiation were characterized for their stemness gene expression, self-renewal, migration/invasion abilities, and radiation resistance. Having established irradiation-enriched CD133⁺ Mahlavu cells with CSC properties, we evaluated a phytochemical, pterostilbene (PT), found abundantly in blueberries, against irradiation-enriched CSCs. It was shown that PT treatment dose-dependently reduced the enrichment of CD133⁺ Mahlavu cells upon irradiation; PT treatment also prevented tumor sphere formation, reduced stemness gene expression, and suppressed invasion and migration abilities as well as increasing apoptosis of CD133⁺ Mahlavu CSCs. Based on our experimental data, pterostilbene could be used to prevent the enrichment of CD133⁺ hepatoma CSCs and should be considered for future clinical testing as a combined agent for HCC patients.

Stilbenes and anthocyanins reduce stress signaling in BV-2 mouse microglia

Blueberries contain an array of phytochemicals that may decrease both inflammatory and oxidative stress. This study determined if pterostilbene, resveratrol, and two anthocyanins commonly found in blueberries, delphinidin-3-O-glucoside and malvidin-3-O-glucoside, would be efficacious in protecting microglia from inflammatory-induced stress signaling. Microglia that were pretreated with blueberry extract (0.25, 0.5, 1, 2 mg/mL) or its components (1, 10, 20, 30 μM pterostilbene, resveratrol, delphinidin-3-O-glucoside, or malvidin-3-O-glucoside) prior to exposure to lipopolysaccharide (100 ng/mL) demonstrated concentration-dependent reductions in nitric oxide and tumor necrosis factor-alpha release and decreased expression of inducible nitric oxide synthase and cyclooxygenase-2. However, much higher concentrations of the individual components than those found in blueberries were needed to demonstrate the effects. For example, 1 mg/mL blueberry extract significantly reduced LPS-induced nitric oxide release; this concentration of blueberry extract contains 2.6 μM malvidin-3-O-glucoside, but when malvidin-3-O-glucoside was tested individually, 20 μM was necessary to observe a significant reduction in nitric oxide release. Therefore the protective effects of blueberries may not be due to any one component, but rather a synergism of the activity of the compounds tested and/or other blueberry compounds not tested here. These results lend further support that blueberry and its active components are able to combat some of the inflammatory mediators of aging at the cellular level.

Pharmacometrics of 3-methoxypterostilbene: a component of traditional chinese medicinal plants

3-Methoxypterostilbene is a naturally occurring stilbene with potential in the treatment of diabetes. The preclinical pharmacokinetics and pharmacodynamics of 3-methoxypterostilbene were evaluated in the present study. The right jugular veins of male Sprague-Dawley rats were cannulated. The rats were dosed 10 mg/kg or 100 mg/kg of 3-methoxypterostilbene intravenously (IV) or orally (PO), respectively. Serum and urine samples were analyzed using a previously validated reversed-phase HPLC method. Serum AUC, serum t 1/2, urine t 1/2, Cltotal, and Vd for IV dosing were 48.1 ± 23.8  μ g/h/mL, 18.9 ± 10.9 h, 9.54 ± 1.51 h, 47.8 ± 23.7 L/h/kg, and 5.11 ± 0.38 L/kg, respectively (mean ± SEM, n = 4) . Serum AUC, serum t 1/2, urine t 1/2, Cltotal, and Vd for PO dosing were 229 ± 44.6  μ g/h/mL, 73.3 ± 8.91 h, 20.6 ± 3.01 h, 0.48 ± 0.008 L/h/kg, and 52.0 ± 10.5 L/kg, respectively (mean ± SEM, n = 4). Bioavailability of the stilbene was determined to be 50.6%  ± 10.0%. A 3-methoxypterostilbene glucuronidated metabolite was detected in both serum and urine. 3-Methoxypterostilbene exhibited antidiabetic activity including α-glucosidase and α-amylase inhibition as well as concentration-dependent antioxidant capacity similar to resveratrol. 3-Methoxypterostilbene also exhibited anti-inflammatory activity. 3-Methoxypterostilbene appears to be a bioactive compound and may be useful in reducing postprandial hyperglycemia.

A review of pterostilbene antioxidant activity and disease modification

Pterostilbene (trans-3,5-dimethoxy-4-hydroxystilbene) is a natural dietary compound and the primary antioxidant component of blueberries. It has increased bioavailability in comparison to other stilbene compounds, which may enhance its dietary benefit and possibly contribute to a valuable clinical effect. Multiple studies have demonstrated the antioxidant activity of pterostilbene in both in vitro and in vivo models illustrating both preventative and therapeutic benefits. The antioxidant activity of pterostilbene has been implicated in anticarcinogenesis, modulation of neurological disease, anti-inflammation, attenuation of vascular disease, and amelioration of diabetes. In this review, we explore the antioxidant properties of pterostilbene and its relationship to common disease pathways and give a summary of the clinical potential of pterostilbene in the prevention and treatment of various medical conditions.

Pterostilbene acts through metastasis-associated protein 1 to inhibit tumor growth, progression and metastasis in prostate cancer

The development of natural product agents with targeted strategies holds promise for enhanced anticancer therapy with reduced drug-associated side effects. Resveratrol found in red wine, has anticancer activity in various tumor types. We reported earlier on a new molecular target of resveratrol, the metastasis-associated protein 1 (MTA1), which is a part of nucleosome remodeling and deacetylation (NuRD) co-repressor complex that mediates gene silencing. We identified resveratrol as a regulator of MTA1/NuRD complex and re-activator of p53 acetylation in prostate cancer (PCa). In the current study, we addressed whether resveratrol analogues also possess the ability to inhibit MTA1 and to reverse p53 deacetylation. We demonstrated that pterostilbene (PTER), found in blueberries, had greater increase in MTA1-mediated p53 acetylation, confirming superior potency over resveratrol as dietary epigenetic agent. In orthotopic PCa xenografts, resveratrol and PTER significantly inhibited tumor growth, progression, local invasion and spontaneous metastasis. Furthermore, MTA1-knockdown sensitized cells to these agents resulting in additional reduction of tumor progression and metastasis. The reduction was dependent on MTA1 signaling showing increased p53 acetylation, higher apoptotic index and less angiogenesis in vivo in all xenografts treated with the compounds, and particularly with PTER. Altogether, our results indicate MTA1 as a major contributor in prostate tumor malignant progression, and support the use of strategies targeting MTA1. Our strong pre-clinical data indicate PTER as a potent, selective and pharmacologically safe natural product that may be tested in advanced PCa.

Analysis of safety from a human clinical trial with pterostilbene

Objectives. The purpose of this trial was to evaluate the safety of long-term pterostilbene administration in humans. Methodology. The trial was a prospective, randomized, double-blind placebo-controlled intervention trial enrolling patients with hypercholesterolemia (defined as a baseline total cholesterol ≥200 mg/dL and/or baseline low-density lipoprotein cholesterol ≥100 mg/dL). Eighty subjects were divided equally into one of four groups: (1) pterostilbene 125 mg twice daily, (2) pterostilbene 50 mg twice daily, (3) pterostilbene 50 mg + grape extract (GE) 100 mg twice daily, and (4) matching placebo twice daily for 6–8 weeks. Safety markers included biochemical and subjective measures. Linear mixed models were used to estimate primary safety measure treatment effects. Results. The majority of patients completed the trial (91.3%). The average age was 54 years. The majority of patients were females (71%) and Caucasians (70%). There were no adverse drug reactions (ADRs) on hepatic, renal, or glucose markers based on biochemical analysis. There were no statistically significant self-reported or major ADRs. Conclusion. Pterostilbene is generally safe for use in humans up to 250 mg/day.

Pterostilbene inhibits dimethylnitrosamine-induced liver fibrosis in rats

Pterostilbene, found in grapes and berries, exhibits pleiotropic effects, including anti-inflammatory, antioxidant, and anti-proliferative activities. This study was conducted to investigate the effect of pterostilbene on liver fibrosis and the potential underlying mechanism for such effect. Sprague-Dawley rats were intraperitoneally given dimethyl n-nitrosamine (DMN) (10mg/kg) 3 days per week for 4 weeks. Pterostilbene (10 or 20mg/kg) was administered by oral gavage daily. Liver function, morphology, histochemistry, and fibrotic parameters were examined. Pterostilbene supplementation alleviated the DMN-induced changes in the serum levels of alanine transaminase and aspartate transaminase (p<0.05). Fibrotic status and the activation of hepatic stellate cells were improved upon pterostilbene supplementation as evidenced by histopathological examination as well as the expression of α-smooth muscle actin (α-SMA), transforming growth factor-β1 (TGF-β1), and matrix metalloproteinase 2 (MMP2). These data demonstrated that pterostilbene exhibited hepatoprotective effects on experimental fibrosis, potentially by inhibiting the TGF-β1/Smad signaling.

Chemopreventive effects of pterostilbene on urethane-induced lung carcinogenesis in mice via the inhibition of EGFR-mediated pathways and the induction of apoptosis and autophagy

Lung cancer is the most commonly diagnosed cancer and the leading cause of cancer deaths globally. Due to the lack of successful chemopreventive agents for lung cancer, there is an emerging need to evaluate new and effective agents for lung cancer prevention. Pterostilbene, a naturally occurring analogue of resveratrol, has been reported to be an effective chemopreventive agent against many cancers. The aim of this study is to investigate the chemopreventive effects of pterostilbene in urethane-induced murine lung tumors. Pretreatment with pterostilbene at 50 or 250 mg/kg significantly reduced tumor multiplicity by 26 and 49%, respectively. Pterostilbene also significantly inhibited tumor volume by 25 and 34% and decreased the tumor burden per mouse by 45 and 63%, respectively. The mechanisms by which pterostilbene suppresses lung tumorigenesis have been investigated in lung tissues and homogenates. The results indicate that the pterostilbene-mediated chemopreventive effects in vivo were a result of the inhibition of epidermal growth factor receptor (EGFR) and its downstream pathways, leading to retarded cell cycle progression, and of the induction of apoptosis and autophagy during urethane-induced lung tumorigenesis.

Decreased activity and accelerated apoptosis of neutrophils in the presence of natural polyphenols

Prolonged or excessive formation and liberation of cytotoxic substances from neutrophils intensifies inflammation and the risk of tissue damage. From this perspective, administration of substances which are able to reduce activity of neutrophils and to enhance apoptosis of these cells may improve the therapy of pathological states connected with persistent inflammation. In this short review, neutrophil oxidative burst and apoptosis are presented as potential targets for pharmacological intervention. Effects of natural polyphenols (resveratrol, pterostilbene, pinosylvin, piceatannol, curcumin, N-feruloylserotonin) are summarised, considering the ability of these compounds to affect inflammation and particularly neutrophil activity. The intended neutrophil inhibition is introduced as a part of a new strategy for pharmacological modulation of chronic inflammatory processes, focused on supporting innate anti-inflammatory mechanisms and enhancing resolution of inflammation.

Effect of stilbene derivative on superoxide generation and enzyme release from human neutrophils in vitro

Neutrophils represent the body′s primary line of defense against invading pathogens. They most rapidly reach the site of injury or infection, liberate antimicrobial proteins, proteases and produce reactive oxygen species. Prolonged or excessive liberation of these very effective and toxic substances could intensify the inflammatory process and enhance tissue damage in many diseases, such as allergies, infections and rheumatoid arthritis. Pterostilbene belongs to stilbenoids, structural analogues of resveratrol, which act as natural protective agents in defending the plant against viral and microbial attack. It possesses anticancerous, antidiabetic and anti-inflammatory properties.

The study provides new information on the effect of pterostilbene [0.01–100 µmol/l] on superoxide generation in and myeloperoxidase (MPO) release from azurophil granules of isolated human neutrophils. PMA [1µmol/l], which activates NADPH-oxidase via protein kinase C, was used for stimulation of neutrophils Unstimulated cells showed neither superoxide generation nor myelopereoxidase release after preincubation with the drug studied. Pterostilbene dose dependently decreased superoxide generation in and MPO release from stimulated human neutrophils, however a significant decrease was recorded only in the concentration 100 µmol/l. The effect of pterostilbene was more pronounced on superoxide generation in comparison to MPO release. Our results suggest that the effect of pterostilbene may prove beneficial in controlling inflammation.

Low-dose pterostilbene, but not resveratrol, is a potent neuromodulator in aging and Alzheimer's disease

Recent studies have implicated resveratrol and pterostilbene, a resveratrol derivative, in the protection against age-related diseases including Alzheimer's disease (AD). However, the mechanism for the favorable effects of resveratrol in the brain remains unclear and information about direct cross-comparisons between these analogs is rare. As such, the purpose of this study was to compare the effectiveness of diet-achievable supplementation of resveratrol to that of pterostilbene at improving functional deficits and AD pathology in the SAMP8 mouse, a model of accelerated aging that is increasingly being validated as a model of sporadic and age-related AD. Furthermore we sought to determine the mechanism of action responsible for functional improvements observed by studying cellular stress, inflammation, and pathology markers known to be altered in AD. Two months of pterostilbene diet but not resveratrol significantly improved radial arm water maze function in SAMP8 compared with control-fed animals. Neither resveratrol nor pterostilbene increased sirtuin 1 (SIRT1) expression or downstream markers of sirtuin 1 activation. Importantly, markers of cellular stress, inflammation, and AD pathology were positively modulated by pterostilbene but not resveratrol and were associated with upregulation of peroxisome proliferator-activated receptor (PPAR) alpha expression. Taken together our findings indicate that at equivalent and diet-achievable doses pterostilbene is a more potent modulator of cognition and cellular stress than resveratrol, likely driven by increased peroxisome proliferator-activated receptor alpha expression and increased lipophilicity due to substitution of hydroxy with methoxy group in pterostilbene.

Pterostilbene, a natural small-molecular compound, promotes cytoprotective macroautophagy in vascular endothelial cells

Chemical modulators of macroautophagy (herein referred to as autophagy) have aroused widespread interest among biologists and clinical physicians because of their potential for disease therapy. Pterostilbene (PT), a natural small-molecular compound, has been demonstrated to inhibit oxidized low-density lipoprotein (oxLDL)-induced apoptosis in vascular endothelial cells (VECs). The aim of the present study was to investigate whether and how PT could induce VEC autophagy. PT at 0.5 or 1 μM could effectively induce autophagosome formation in human umbilical vein VECs (HUVECs). PT promoted autophagy via a rapid elevation in intracellular calcium ([Ca(2+)]i) concentration and subsequent AMP-activated protein kinase α1 subunit (AMPKα1) activation, which in turn inhibited mammalian target of rapamycin, a potent inhibitor of autophagy. PT-induced AMPKα1 activation and autophagy were refractory to the depletion of serine/threonine kinase 11 but depended on calcium/calmodulin-dependent protein kinase kinase-β activation. Interestingly, PT stimulated cytoprotective autophagy so as to aid in the removal of accumulated toxic oxLDL and inhibit apoptosis in HUVECs. Our study provides a potent small molecule enhancer of autophagy and a novel useful tool in exploring the molecular mechanisms for crosstalk between apoptosis and autophagy. PT could serve as a potential lead compound for developing a class of autophagy regulator as autophagy-related diseases therapy.

Inhibition of nitric oxide and inflammatory cytokines in LPS-stimulated murine macrophages by resveratrol, a potent proteasome inhibitor

BACKGROUND

Altered immune function during ageing results in increased production of nitric oxide (NO) and other inflammatory mediators. Recently, we have reported that NO production was inhibited by naturally-occurring proteasome inhibitors (quercetin, δ-tocotrienol, and riboflavin) in lipopolysaccharide (LPS)-stimulated RAW264.7 cells, and thioglycolate-elicited peritoneal macrophages from C57BL/6 mice. In a continuous effort to find more potent, non-toxic, commercially available, naturally-occurring proteasome inhibitors that suppress inflammation, the present study was carried out to describe the inhibition of NF-κB activation and NO, TNF-α, IL-6, IL-1β, and iNOS expression by trans-resveratrol, trans-pterostilbene, morin hydrate, and nicotinic acid in LPS-induced RAW 264.7 cells and thioglycolate-elicited peritoneal macrophages from C57BL/6 and BALB/c mice.

RESULTS

The present results indicate that resveratrol, pterostilbene, and morin hydrate caused significant inhibition (>70% to 90%; P < 0.02) in the activities of chymotrypsin-like, trypsin-like, and post-acidic (post-glutamase) proteasome sites in RAW 264.7 cells at a dose of only 20 μM. These compounds also inhibited the production of NO by RAW-264.7 cells stimulated with LPS alone (>40%; P < 0.05), or LPS + interferon-γ (IFN-γ; >60%; P < 0.02). Furthermore, resveratrol, pterostilbene, morin hydrate, and quercetin suppressed secretion of TNF-α (>40%; P < 0.05) in LPS-stimulated RAW 264.7 cells, and suppressed NF-κB activation (22% to 45%; P < 0.05) in LPS-stimulated HEK293T cells. These compounds also significantly suppressed LPS-induced expression of TNF-α, IL-1β, IL-6, and iNOS genes in RAW 264.7 cells, and also in thioglycolate-elicited peritoneal macrophages from C57BL/6 and BALB/c mice.

CONCLUSIONS

The present results clearly demonstrate that resveratrol and pterostilbene are particularly potent proteasome inhibitors that suppress expression of genes, and production of inflammatory products in LPS-stimulated RAW 264.7 cells, and macrophages from C57BL/6 and BALB/c mice. Resveratrol and pterostilbene which are present in grapes, blueberries, and red wine, have been implicated as contributing factors to the lower incidence of cardiovascular disease in the French population, despite their relatively high dietary fat intake. Consequently, it appears likely that the beneficial nutritional effects of resveratrol and pterostilbene are due at least in part, to their ability to inhibit NF-κB activation by the proteasome, thereby suppressing activation of pro-inflammatory cytokines and iNOS genes, resulting in decreased secretion of TNF-α, IL-1β, IL-6, and NO levels, in response to inflammatory stimuli. This is the first report demonstrating that resveratrol and pterostilbene act as proteasome inhibitors, thus providing a mechanism for their anti-inflammatory effects.

Co-expression of VpROMT gene from Chinese wild Vitis pseudoreticulata with VpSTS in tobacco plants and its effects on the accumulation of pterostilbene

Plant secondary metabolites, such as stilbenes, have fungicidal potential and have been found in several plant species. Stilbenes in grapevine, such as resveratrol and pterostilbene, have recently attracted much attention, they are not only helping the plant to fight against pathogen attack, but they are also being widely used as ingredients of fungicide, anti-inflammatory drugs, antioxidant, and anti-infective agents. However, resveratrol O-methyltransferase gene, related with the synthesis of pterostilbene from resveratrol, has not been characterized effectively from Chinese wild Vitis pseudoreticulata. In this study, a candidate of resveratrol O-methyltransferase gene designated as VpROMT was isolated from a powdery mildew-resistant Chinese wild V. pseudoreticulata 'Baihe-35-1', and characterization studies were performed. Expression studies showed that VpROMT was predominantly expressed in developing roots yet not found in the leaves, stems, nor tendrils when the plants are not challenged. Results of qRT-PCR showed that VpROMT was rapidly induced by Erysiphe necator in V. pseudoreticulata and by methyl-jasmonate, UV-irradiation in suspension culture cells of Vitis romanetii. The expression level varies in different tissues of grapevine, which MeJA and UV-C treatment significantly upregulated the expression of VpROMT gene while UV-B treatment failed to. Co-expression of VpROMT and grapevine stilbene synthase (VpSTS) gene leads to the accumulation of pterostilbene in leaves of tobacco (Nicotiana tabacum) indicating that VpROMT was able to catalyze the biosynthesis of pterostilbene from resveratrol in over-expression transgenic tobacco plants.

Activation of AMPK by pterostilbene suppresses lipogenesis and cell-cycle progression in p53 positive and negative human prostate cancer cells

Prostate cancer is one of the leading causes of cancer death in men in Western countries. Epidemiological studies have linked the consumption of fruits and vegetables to a reduced risk of prostate cancer, and small fruits are particularly rich sources of many active phytochemical stilbenes, such as pterostilbene. As a constituent of small fruits such as grapes, berries, and their products, pterostilbene is under intense investigation as a cancer chemopreventive agent. Using the p53 wild type LNCaP and p53 null PC3 cells, we found that treatment with pterostilbene resulted in dose-dependent inhibition of cellular proliferation, which suggested that the interaction of pterostilbene with the p53 might not fully explain its inhibitory effect on proliferation. In this study, we found that pterostilbene activated AMPK in both p53 positive and negative human prostate cancer cells. Pterostilbene-activated AMPK decreased the activity and/or expression of lipogenic enzymes, such as fatty acid synthase (FASN) and acetyl-CoA carboxylase (ACC). Interestingly, the resolution between apoptosis and growth arrest following AMPK activation is greatly influenced by p53 status. In p53 positive LNCaP cells, pterostilbene blocked the progression of cell cycle at G1 phase by inducing p53 expression and further up-regulating p21 expression. However, pterostilbene induced apoptosis in p53 negative PC3 cells. Our results suggest that pterostilbene may be a functional chemopreventive agent and that dietary exposure to pterostilbene would be helpful for antiprostate cancer activity.

In planta production of the highly potent resveratrol analogue pterostilbene via stilbene synthase and O-methyltransferase co-expression

Resveratrol and related stilbenes are thought to play important roles in defence responses in several plant species and have also generated considerable interest as nutraceuticals owing to their diverse health-promoting properties. Pterostilbene, a 3,5-dimethylether derivative of resveratrol, possesses properties similar to its parent compound and, additionally, exhibits significantly higher fungicidal activity in vitro and superior pharmacokinetic properties in vivo. Recombinant enzyme studies carried out using a previously characterized O-methyltransferase sequence from Sorghum bicolor (SbOMT3) demonstrated its ability to catalyse the A ring-specific 3,5-bis-O-methylation of resveratrol, yielding pterostilbene. A binary vector was constructed for the constitutive co-expression of SbOMT3 with a stilbene synthase sequence from peanut (AhSTS3) and used for the generation of stably transformed tobacco and Arabidopsis plants, resulting in the accumulation of pterostilbene in both species. A reduced floral pigmentation phenotype observed in multiple tobacco transformants was further investigated by reversed-phase HPLC analysis, revealing substantial decreases in both dihydroquercetin-derived flavonoids and phenylpropanoid-conjugated polyamines in pterostilbene-producing SbOMT3/AhSTS3 events. These results demonstrate the potential utility of this strategy for the generation of pterostilbene-producing crops and also underscore the need for the development of additional approaches for minimizing concomitant reductions in key phenylpropanoid-derived metabolites.

Suppression of Nitric Oxide Production and Cardiovascular Risk Factors in Healthy Seniors and Hypercholesterolemic Subjects by a Combination of Polyphenols and Vitamins

BACKGROUND: Dysregulated immune function associated with ageing has been implicated in a variety of human diseases. We have demonstrated the anti-inflammatory properties of resveratrol, pterostilbene, morin hydrate, quercetin, δ-tocotrienol, riboflavinin a variety of experimental animal models, and determined that these compounds act by inhibiting proteasome activity. AIMS: To determine whether serum nitric oxide (NO) levels increase with age in humans, and whether the combined cholesterol-lowering and inflammation-reducing properties of resveratrol, pterostilbene, Morin hydrate, quercetin, δ-tocotrienol, riboflavin, and nicotinic acid would reduce cardiovascular risk factors in humans when used as nutritional supplements with, or without, other dietary changes. METHODS: Elderly human subjects were stratified into two groups based on total serum cholesterol levels. Initial total serum cholesterol levels were normal and elevated in Group 1 and 2 subjects, respectively. Baseline serum NO, C-reactive protein (CRP), γ-glutamyltransferase (γ-GT) activity, uric acid, total antioxidant status (TAS), total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides levels were established over a four week period. Group 1 subjects subsequently received nutritional supplementation with one of two different combinations (NS-7 = 25 mg of each, resveratrol, pterostilbene, quercetin, δ-tocotrienol, nicotinic acid, morin hydrate or NS-6 = morin hydrate replaced with quercetin, 50 mg/capsule). Group 2 subjects also received these nutritional supplements (two capsules/d), but an AHA Step-1 diet was also implemented. After these interventions were administered for four weeks, the above parameters were re-measured and changes from baseline levels determined. Nitric acid (NO) levels in children, young adults, and seniors were also compared. RESULTS: The key results of the current study were: 1) that serum NO levels were significantly increased in seniors compared to both children (~80%) and young adults (~65%); 2) that the intake of two capsules/d of NS-7 or NS-6 for four weeks significantly (P < 0.05) decreased serum NO (39%, 24%), CRP (19%, 21%), uric acid (6%, 12%) levels, and γ-GT activity (8%, 6%), respectively in free-living healthy seniors; 3) that serum NO (36%, 29%), CRP (29%, 20%), uric acid (6%, 9%) γ-GT activity (9%, 18%), total cholesterol (8%, 11%), LDL-cholesterol (10%, 13%), and triglycerides (16%, 23%) levels were significantly (P < 0.02) decreased in hypercholesterolemic subjects restricted to AHA Step-1 diet plus intake of SN-7 or SN-6 (two capsules/d), respectively; 4) that TAS was increased (3%, 9%; P < 0.05) in free-living healthy seniors receiving NS-7 or NS-6 alone, and in hypercholesterolemic subjects plus AHA Step-1 diet (20%, 12%; P < 0.02) with either of the combinations tested. CONCLUSIONS: Serum NO levels are elevated in elderly humans compared to children or young adults. Diet supplementation with combinations of resveratrol, pterostilbene, morin hydrate, quercetin, δ-tocotrienol, riboflavin, and nicotinic acid reduce cardiovascular risk factors in humans when used as nutritional supplements with, or without, other dietary changes.

Resveratrol modulates MED28 (Magicin/EG-1) expression and inhibits epidermal growth factor (EGF)-induced migration in MDA-MB-231 human breast cancer cells

Resveratrol and pterostilbene exhibit diverse biological activities. MED28, a subunit of the mammalian Mediator complex for transcription, was also identified as magicin, an actin cytoskeleton Grb2-associated protein, and as endothelial-derived gene (EG-1). Several tumors exhibit aberrant MED28 expression, whereas the underlying mechanism is unclear. Triple-negative breast cancers, often expressing epidermal growth factor (EGF) receptor (EGFR), are associated with metastasis and poor survival. The objective of this study is to compare the effect of resveratrol and pterostilbene and to investigate the role of MED28 in EGFR-overexpressing MDA-MB-231 breast cancer cells. Pretreatment of resveratrol, but not pterostlbene, suppressed EGF-mediated migration and expression of MED28 and matrix metalloproteinase (MMP)-9 in MDA-MB-231 cells. Moreover, overexpression of MED28 increased migration, and the addition of EGF further enhanced migration. Our data indicate that resveratrol modulates the effect of MED28 on cellular migration, presumably through the EGFR/phosphatidylinositol 3-kinase (PI3K) signaling pathway, in breast cancer cells.

Pterostilbene and cancer: current review

Pterostilbene (trans-3,5-dimethoxy-4-hydroxystilbene) is an antioxidant that is primarily found in blueberries. Studies suggest that pterostilbene exhibits the hallmark characteristics of an effective anticancer agent based on its antineoplastic properties in several common malignancies. In vitro models have shown that pterostilbene inhibits cancer growth through alteration of the cell cycle, induction of apoptosis, and inhibition of metastasis. In vivo, pterostilbene inhibits tumorigenesis and metastasis with negligible toxicity. Pterostilbene has also been shown to be effective as an inducer of antioxidant capacity in multiple cancer cell lines that may facilitate its function as an anticarcinogenic compound. Additionally, preliminary studies show that pterostilbene exhibits much greater bioavailability compared with other stilbene compounds; however the exact pharmacologic mechanism of pterostilbene and its effects in humans are still under investigation. In this review, we present a comprehensive summary of the antineoplastic mechanisms of pterostilbene based on the results of preclinical studies and highlight recent advances in the study of this dietary compound.

Pterostilbene induces autophagy and apoptosis in sensitive and chemoresistant human bladder cancer cells

SCOPE

Bladder cancer is one of the most common malignancies in the world. The majority of bladder cancer deaths are due to unresectable lesions that are resistant to chemotherapy. Pterostilbene (PT), a naturally occurring phytoalexin, possesses a variety of pharmacologic activities, including antioxidant, cancer prevention activity and cytotoxicity to many cancers. We found that PT effectively inhibits the growth of sensitive and chemoresistant human bladder cancer cells by inducing cell cycle arrest, autophagy and apoptosis. Down-regulations of Cyclin A, B and D1 and pRB are the results of PT-induced cell cycle arrest.

METHODS AND RESULTS

Autophagy occurred at an early stage and was observed through the formation of acidic vesicular organelles (the marker for autophagy) and microtubule-associated protein 1 light chain 3-II production. Apoptosis occurred at a later stage and was detected by Annexin V and 4',6-diamidino-2-phenylindole staining. PT-induced autophagy was triggered by the inhibition of active human protein kinase/the mammalian TOR/p70S6K pathway and activation of extracellular signal-regulated kinase pathway. Inhibition of autophagy by pretreatment with 3-methyladenine, bafilomycin A1, Beclin 1 or extracellular signal-regulated kinase short hairpin RNA enhanced PT-triggered apoptosis.

CONCLUSION

This is the first study to demonstrate that PT causes autophagy in cancer cells and suggests that PT could serve as a new and promising agent for the treatment of sensitive and chemoresistant bladder cancer cells.

Evaluation of antinociceptive effect of Aegiceras corniculatum stems extracts and its possible mechanism of action in rodents

ETHNOPHARMACOLOGICAL RELEVANCE

Aegiceras corniculatum (Linn.) Blanco is used in various traditional medicinal system(s) for the treatment of rheumatism, painful arthritis and inflammation. Therefore, the pharmacological studies of its antinociceptive effect was undertaken to validate its traditional use.

MATERIALS AND METHODS

n-Hexane, ethyl acetate and methanol extract(s) derived from Aegiceras corniculatum (stems) were studied using various nociceptive model(s) induced chemically or thermally in mice including acetic acid-induced writhing, formalin-induced paw licking and hot plate test.

RESULTS

In acetic acid-induced writhing test, plant extracts dose dependently decreased the writhing numbers. The methanolic extract (1-10mg/kg, i.p. in mice) of the plant was more potent than acetaminophen and acetyl salicylic acid, with an IC(50) of 4.2 ± 0.99 mg/kg. Moreover, the time of nociceptive behaviors induced by intraplantar formalin injection was also suppressed during 1st and 2nd phases in the presence of ethyl acetate extract whereas, n-hexane and methanolic extracts inhibited the paw licking in mice during the 1st (IC(50) 12 ± 0.76 mg/kg) and 2nd phases (IC(50) 3.8 ± 0.55 mg/kg). Naloxone, β-funaltrexamine, and naltrindole antagonized the n-hexane extract-induced antinociception in the first phase of formalin test indicating its non-selective analgesic response via opioid receptor(s). However, ethyl acetate extract was devoid of any opioid action. Additionally, these extracts significantly inhibited the pain stimulation in hot plate test. Withdrawal syndrome of morphine dependence was also diminished in the presence of plant extracts via potentiation of GABAergic system.

CONCLUSION

These results suggested that Aegiceras corniculatum extract(s) possesses analgesic properties and acts on the central nervous system, thereby suppressing the inflammatory pain justifying its folklore use.

Preclinical pharmacokinetic evaluation of resveratrol trimethyl ether in sprague-dawley rats: the impacts of aqueous solubility, dose escalation, food and repeated dosing on oral bioavailability

Resveratrol trimethyl ether (trans-3,5,4'-trimethoxystilbene, RTE) is a naturally occurring and pharmacologically active resveratrol derivative. To evaluate its suitability as a drug candidate, a pharmacokinetic study was carried out in Sprague-Dawley rats with the emphasis to identify the impact of aqueous solubility, dose escalation, food, and repeated dosing on its oral bioavailability. Upon single intravenous administration (5 mg/kg), RTE displayed moderate clearance (35.5 ± 5.3 mL/min/kg) and a fairly long terminal elimination half-life (511 ± 136 min); dose escalation (5-20 mg/kg) did not cause nonlinear pharmacokinetics. When given orally in suspension (60 mg/kg), RTE was poorly absorbed with negligible bioavailability (< 1.5%), fasting further decreased its bioavailability (<1%). However, when administered in a solution formulated with randomly methylated-β-cyclodextrin (15 mg/kg), RTE was rapidly absorbed with good bioavailability (46.5 ± 4.8%). Dose escalation resulted in increased bioavailability (64.6 ± 8.0%) at the dose of 60 mg/kg. Repeated RTE dosing (7 daily oral doses) did not alter the clearance, terminal elimination half-life and bioavailability. In summary, the aqueous solubility of RTE was a barrier to oral absorption; repeated RTE administrations did not alter its pharmacokinetic profiles; as RTE possessed appropriate pharmacokinetic profiles, further investigation on RTE as a drug candidate is warranted.

Kinetic mechanism and product characterization of the enzymatic peroxidation of pterostilbene as model of the detoxification process of stilbene-type phytoalexins

The enzymatic peroxidation of pterostilbene, a strong antifungal belonging to the stilbene family, by peroxidase (POX), is reported for the first time as a model of phytoalexin detoxification carried out by the enzymatic pool of pathogens. Kinetic characterization of the pterostilbene oxidation reaction pointed to an optimum pH of 7.0, at which value the thermal stability of POX was studied. Moreover, the data showed that pterostilbene inhibits POX activity at high concentrations of substrate. Several kinetic parameters, including V(max), K(m) and K(I), were calculated and values of 0.16ΔAbs min(-1), 14.61 μM, and 31.41 μM were reported. To understand the possible physiological role of this reaction in the phytoalexin detoxification process, the products of pterostilbene oxidation were identified using HPLC-MS and a radical-radical coupling reaction mechanism was proposed. Three main products with a high molecular weight and pronounced hydrophobicity were identified: pterostilbene cis dehydromer, pterostilbene trans dehydromer and pterostilbene open dimer. The dimeric structures of these molecules indicate that the pterostilbene oxidation reaction took place at the 4'-OH position of the hydroxystilbenic moieties and the three above mentioned dimeric products were found, due to the ability of electron-delocalized radicals to couple at various sites. Finally, the capacity of cyclodextrins (CDs) as starch model molecules in plants to complex both the substrate and the products of the oxidation reaction was evaluated. The inhibition process of POX activity was modified at high pterostilbene concentrations due to sequestering of the substrate reaction and to the different affinity of the reaction products for CDs.

Stereospecific pharmacokinetics of racemic homoeriodictyol, isosakuranetin, and taxifolin in rats and their disposition in fruit

The chirality of flavonoids has been overlooked in the majority of pharmacokinetic studies of homoeriodictyol, isosakuranetin, and taxifolin. The stereospecific pharmacokinetic disposition of these xenobiotics in male Sprague-Dawley rats is described for the first time. Validated HPLC methods were used to analyze serum and urine samples of rats following intravenous administration of each flavonoid via jugular vein cannulation and to determine their content in selected fruits. The characterization and interpretation of the pharmacokinetic disposition profiles of homoeriodictyol, isosakuranetin, and taxifolin are described. A discrepancy exists between half-lives in serum and urine which may be attributed to low assay sensitivity in serum for the three compounds; thus, a more accurate estimation of the pharmacokinetic parameters was obtained from urine. The pharmacokinetics of homoeriodictyol, isosakuranetin, and taxifolin revealed distribution, metabolism, and elimination that were dependent on the stereochemistry of the stereoisomers. The (-)-(S)-enantiomers of homoeriodictyol and isosakuranetin and the (+)-(2S; 3R)-stereoisomer of taxifolin were predominant in lemon, grapefruit, and tomato. These findings were achieved using chiral methods of analysis; the utility and necessity of developing chiral methods of analysis for chiral xenobiotics are discussed.

Pterostilbene inhibits colorectal aberrant crypt foci (ACF) and colon carcinogenesis via suppression of multiple signal transduction pathways in azoxymethane-treated mice

Pterostilbene (PS), a natural dimethylated analogue of resveratrol, is known to have diverse pharmacologic activities including anticancer, anti-inflammation, antioxidant, apoptosis, antiproliferation, and analgesic potential. This paper reports the inhibitory effect of dietary administration of pterostilbene against the formation of azoxymethane (AOM)-induced colonic aberrant crypt foci (ACF) preneoplastic lesions and adenomas in male ICR mice and delineates its possible molecular mechanisms. ICR mice were given two AOM injections intraperitoneal and continuously fed a 50 or 250 ppm pterostilbene diet for 6 or 23 weeks. It was found that the dietary administration of pterostilbene effectively reduced AOM-induced formation of ACF and adenomas and inhibited the transcriptional activation of iNOS and COX-2 mRNA and proteins in mouse colon stimulated by AOM. Treatment with pterostilbene resulted in the induction of apoptosis in mouse colon. Moreover, administration of pterostilbene for 23 weeks significantly suppressed AOM-induced GSK3beta phosphorylation and Wnt/beta-catenin signaling. It was also found that pterostilbene significantly inhibited AOM-induced expression of VEGF, cyclin D1, and MMPs in mouse colon. Furthermore, pterostilbene markedly inhibited AOM-induced activation of Ras, phosphatidylinositol 3 kinase/Akt, and EGFR signaling pathways. All of these results revealed that pterostilbene is an effective antitumor agent as well as its inhibitory effect through the down-regulation of inflammatory iNOS and COX-2 gene expression and up-regulation of apoptosis in mouse colon, suggesting that pterostilbene is a novel functional agent capable of preventing inflammation-associated colon tumorigenesis.

High-performance liquid chromatographic analysis: applications to nutraceutical content and urinary disposition of oxyresveratrol in rats

A high-performance liquid chromatographic (HPLC) method was developed for the analysis of the stilbene, oxyresveratrol. This method involves the use of a Luna C(18) column with ultraviolet detection at 320 nm. The mobile phase consisted of acetonitrile, water and formic acid (30 : 70 : 0.04 v/v) with a flow rate of 0.6 mL/min. The calibration curves were linear over the range of 0.5-100.0 microg/mL. The mean extraction efficiency was between 98.9 and 109%. The precision of the assay was 0.069-18.4% (RSD%), and within 20% at the limit of quantitation (0.5 microg/mL). The bias of the assay was <15% and within 15% at the limit of quantitation. This assay was successfully applied to pre-clinical pharmacokinetic samples from rat urine and to nutraceutical product analysis.

Structural identification of mouse urinary metabolites of pterostilbene using liquid chromatography/tandem mass spectrometry

Pterostilbene, the dimethoxy derivative of resveratrol, has drawn much attention recently due to its potential beneficial health effects. The metabolic fate of pterostilbene, however, is not well understood. In the present study, we identified nine novel mouse urinary pterostilbene metabolites, pterostilbene glucuronide, pterostilbene sulfate, mono-demethylated pterostilbene glucuronide, mono-demethylated pterostilbene sulfate, mono-hydroxylated pterostilbene, mono-hydroxylated pterostilbene glucuronide, mono-hydroxylated pterostilbene sulfate, and mono-hydroxylated pterostilbene glucuronide sulfate, using liquid chromatography/atmospheric pressure chemical ionization and electrospray ionization tandem mass spectrometry. The structures of these metabolites were confirmed by analyzing the MS(n) (n = 1-3) spectra. To our knowledge, this is the first report of the identification of urinary metabolites of pterostilbene in mice.

Pterostilbene inhibits pancreatic cancer in vitro

INTRODUCTION

Stilbenes are phenolic compounds present in grapes and blueberries. Resveratrol, a naturally occurring compound present in grapes, has been shown to have potent antioxidant properties as well as an ability to induce apoptosis. Resveratrol has also been reported to have significant inhibitory effects against a variety of primary tumors including breast, colon, and prostate. Pterostilbene, a naturally occurring analogue of resveratrol found in blueberries, also has antioxidant and antiproliferative properties. It is also substantially more bioavailable orally than resveratrol. These effects have not been studied in pancreatic cancer. We hypothesized that pterostilbene would inhibit pancreatic cancer cell growth in vitro.

MATERIALS AND METHODS

Two pancreatic cancer cell lines (MIA PaCa and PANC-1) were cultured using standard techniques. Cells were treated with graduated doses of pterostilbene ranging from 10 to 100 microM. Cell viability was measured by MTT at 24, 48, and 72 h.

RESULTS

Pterostilbene decreases cell viability in both cancer cell lines in a concentration- and time-dependent manner. Higher doses (75-100 microM) caused a significant reduction in cell viability at 24 and 48 h. However, by 72 h, all tested concentrations of pterostilbene (10 to 100 microM) resulted in significantly reduced cell viability in both pancreatic cancer cell lines in a dose-dependent fashion. Pterostilbene caused a dose-dependent 10-63% inhibition in MIA PaCa-2 cells and 10-75% inhibition in PANC-1 cells.

DISCUSSION

Treatment of pancreatic cancer cells in vitro with Pterostilbene leads to inhibition of cell proliferation and/or cell death, cell cycle arrrest, mitochondrial membrane depolarization, and activation of effector caspases. This naturally occurring agent may have a role in treating pancreatic cancer.

CONCLUSIONS

Pterostilbene inhibits the growth of pancreatic cancer in vitro. Further, in vitro mechanistic studies and in vivo experiments are warranted to determine its potential for the treatment of pancreatic cancer.

Pterostilbene, a natural dimethylated analog of resveratrol, inhibits rat aortic vascular smooth muscle cell proliferation by blocking Akt-dependent pathway

Vascular smooth muscle cells (VSMCs) are the main cellular component in the arterial wall, and abnormal proliferation of VSMCs plays a central role in the pathogenesis of atherosclerosis and restenosis after angioplasty, and possibly in the development of hypertension. Pterostilbene, a natural dimethylated analog of resveratrol, is known to have diverse pharmacological activities including anti-cancer, anti-inflammation and anti-oxidant activities. The present study was designed to investigate the effects of pterostilbene on platelet-derived growth factor (PDGF)-BB-induced VSMCs proliferation as well as the molecular mechanisms of the antiproliferative effects. The cell growth of VSMCs was determined by cell counting and [(3)H]thymidine incorporation assays. Pterostilbene significantly inhibited the DNA synthesis and proliferation of PDGF-BB-stimulated VSMCs in a concentration-dependent manner. The inhibition percentages of pterostilbene at 1, 3 and 5microM to VSMCs proliferation were 68.5, 80.7 and 94.6%, respectively. The DNA synthesis of pterostilbene at 1, 3 and 5microM in VSMCs was inhibited by 47.4, 76.7 and 100%, respectively. Pterostilbene inhibited the PDGF-BB-stimulated phosphorylation of Akt kinase. However, pterostilbene did not change the expression of extracellular signal-related kinase (ERK) 1/2, PLCgamma1, phosphatidylinositol (PI)3 kinase and PDGF-Rbeta phosphorylation. In addition, pterostilbene down-regulated the cell cycle-related proteins including the expression of cyclin-dependent kinase (CDK) 2, cyclin E, CDK4, cyclin D1, retinoblastoma (Rb) proteins and proliferative cell nuclear antigen (PCNA). These findings suggest that the inhibition of pterostilbene to the cell proliferation and DNA synthesis of PDGF-BB-stimulated VSMCs may be mediated by the suppression of Akt kinase. Furthermore, pterostilbene may be a potential anti-proliferative agent for the treatment of atherosclerosis and angioplasty restenosis.