Tocotrienols are members of the vitamin E family but, unlike tocopherols, possess an unsaturated isoprenoid side chain that confers superior anti-cancer properties. The ability of tocotrienols to selectively inhibit the HMG-CoA reductase pathway through posttranslational degradation and to suppress the activity of transcription factor NF-κB could be the basis for some of these properties. Our studies indicate that γ- and δ-tocotrienolshave potent antiproliferative activity in pancreatic cancer cells (Panc-28, MIA PaCa-2, Panc-1, and BxPC-3). Indeed both tocotrienols induced cell death (>50%) by the MTT cell viability assay in all four pancreatic cancer cell lines. We also examined the effects of the tocotrienols on the AKT and the Ras/Raf/MEK/ERK signaling pathways by Western blotting analysis. γ- and δ-tocotrienol treatment of cells reduced the activation of ERK MAP kinase and that of its downstream mediator RSK (ribosomal protein S6 kinase) in addition to suppressing the activation of protein kinase AKT. Suppression of activation of AKT by γ-tocotrienol led to downregulation of p-GSK-3β and upregulation accompanied by nuclear translocation of Foxo3. These effects were mediated by the downregulation of Her2/ErbB2 at the messenger level. Tocotrienols but not tocopherols were able to induce the observed effects. Our results suggest that the tocotrienol isoforms of vitamin E can induce apoptosis in pancreatic cancer cells through the suppression of vital cell survival and proliferative signaling pathways such as those mediated by the PI3-kinase/AKT and ERK/MAP kinases via downregulation of Her2/ErbB2 expression. The molecular components for this mechanism are not completely elucidated and need further investigation.
Publications
Clinical evaluation of photoprotective effect by a topical antioxidants combination (tocopherols and tocotrienols)
Pedrelli VF, Lauriola MM, Pigatto PD.
J Eur Acad Dermatol Venereol. 2011 Sep 14.
Background: Vitamin E is among the earliest recognized antioxidants. Recent findings suggested that tocotrienols have superior activity than tocopherols. Moreover, vitamin A is well-known in dermatology for its actions, including the ultraviolet radiation absorbing property.
Objectives: In view of experimental evidence for the photoprotective properties of these antioxidants, we evaluated in 30 patients with photosensitivity, the prophylactic efficacy of a new topical agent, containing tocopherols 10% and tocotrienols 0.3%, compared with retinol, simple vehicle and untreated areas.
Methods: After determination of the minimal UVB erythema dose (MED), two areas of 2 × 2 cm were selected on the buttocks of each subject, one of which was treated with the antioxidant formulation whereas the other field did not undergo any treatment. Therefore, both areas were irradiated with a twofold MED. As further controls, other two similar areas, selected on the forearm of 15 patients, were photo-irradiated similarly, 30 min after application of the simple vehicle to a field and of vitamin A in the same vehicle to the other. Reactions (erythema/oedema/itch/vesciculation) assessment was carried out assigning scores indicative of their intensity; then, mean values +DS of scores were calculated. Results The pre-treatment with the vitamin E formulation highly protects against photosensitivity, and all reactions to irradiation were significantly lower in the areas treated with the topical vitamin E formulation compared to those treated with the simple vehicle or vitamin A.
Conclusions: The use of a new topical formulation containing significant concentrations of tocotrienols and tocopherols represents a promising strategy to reduce the photo-induced skin damage.
Novel tocotrienol-entrapping vesicles can eradicate solid tumors after intravenous administration
Fu JY, Zhang W, Blatchford DR, Tetley L, McConnell G, Dufès C.
J Control Release. 2011 Aug 25;154(1):20-6. Epub 2011 Apr 22.
The therapeutic potential of tocotrienol, a vitamin E extract with anti-cancer properties, is hampered by its failure to specifically reach tumors after intravenous administration. In this work, we demonstrated that novel transferrin-bearing, tocopheryl-based multilamellar vesicles entrappingtocotrienol significantly improved tocotrienol uptake by cancer cells overexpressing transferrin receptors. This led to a dramatically improved therapeutic efficacy in vitro, ranging from 17-fold to 72-fold improvement depending on the cell lines, compared to the free drug. In vivo, the intravenous administration of this novel tocotrienol formulation led to complete tumor eradication for 40% of B16-F10 murine melanoma tumors and 20% of A431 human epidermoid carcinoma tumors. Animal survival was improved by more than 20 days compared to controls, for the two tumor models tested. These therapeutic effects, together with the lack of toxicity, potentially make transferrin-bearing vesicles entrapping tocotrienol a highly promising therapeutic system as part as an anti-cancer therapeutic strategy.
Natural vitamin E α-tocotrienol protects against ischemic stroke by induction of multidrug resistance-associated protein 1
Park HA, Kubicki N, Gnyawali S, Chan YC, Roy S, Khanna S, Sen CK.
Stroke. 2011 Aug;42(8):2308-14. Epub 2011 Jun 30.
Background & Purpose: α-Tocotrienol (TCT) represents the most potent neuroprotective form of natural vitamin E that is Generally Recognized As Safe certified by the U.S. Food and Drug Administration. This work addresses a novel molecular mechanism by which α-TCT may be protective against stroke in vivo. Elevation of intracellular oxidized glutathione (GSSG) triggers neural cell death. Multidrug resistance-associated protein 1 (MRP1), a key mediator of intracellular oxidized glutathione efflux from neural cells, may therefore possess neuroprotective functions.
Methods: Stroke-dependent brain tissue damage was studied in MRP1-deficient mice and α-TCT-supplemented mice.
Results: Elevated MRP1 expression was observed in glutamate-challenged primary cortical neuronal cells and in stroke-affected brain tissue. MRP1-deficient mice displayed larger stroke-induced lesions, recognizing a protective role of MRP1. In vitro, protection against glutamate-induced neurotoxicity by α-TCT was attenuated under conditions of MRP1 knockdown; this suggests the role of MRP1 in α-TCT-dependent neuroprotection. In vivo studies demonstrated that oral supplementation of α-TCT protected against murine stroke. MRP1 expression was elevated in the stroke-affected cortical tissue of α-TCT-supplemented mice. Efforts to elucidate the underlying mechanism identified MRP1 as a target of microRNA (miR)-199a-5p. In α-TCT-supplemented mice, miR-199a-5p was downregulated in stroke-affected brain tissue.
Conclusion: This work recognizes MRP1 as a protective factor against stroke. Furthermore, findings of this study add a new dimension to the current understanding of the molecular bases of α-TCT neuroprotection in 2 ways: by identifying MRP1 as a α-TCT-sensitive target and by unveiling the general prospect that oral α-TCT may regulate miR expression in stroke-affected brain tissue.
An in vivo and in silico approach to elucidate the tocotrienol-mediated fortification against infection and inflammation induced alterations in antioxidant defense system
Khan MS, Khan MK, Siddiqui MH, Arif JM.
Eur Rev Med Pharmacol Sci. 2011 Aug;15(8):916-30.
Background: Tocotrienol (Tocomin) are naturally occurring analogues of vitamin E family and has been reported to possess a potent free radical scavenging activity. In the present study we have initially investigated protective role of tocotrienol against infection and inflammation induced alterations in tissues antioxidant defense system, as well as speculated, via in silico docking studies, that tocotrienol can act by directly binding to antioxidant enzymes.
Materials And Methods: Syrian hamsters were injected with bacterial lipopolysaccharide (LPS, 200 microg), zymosan (20 mg), or turpentine (0.5 ml) to mimic acute infection, acute systemic inflammation, and acute localized inflammation, respectively, which are responsible for the generation of plenty of free radicals that causes oxidative stress. Tocomin (10 mg) was administered daily for 10 days before and 12 h after lipopolysaccharides (LPS) or 24 h after turpentine or zymosan injection. Molecular docking studies were performed using Autodock 4.0.
Results: Our results show a significant decrease in the activities of antiperoxidative enzymes, glutathione reductase (GR), glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), glutathione-s-transferase (GST), as well as reduced glutathione (GSH), in liver and kidney of LPS, turpentine or zymosan stressed hamsters. Feeding of 10 mg Tocomin to stressed hamsters was quite effective in reversing/normalizing the altered levels of enzymatic and nonenzymatic antioxidants in liver and kidney. In order to explore the interaction between tocotrienol and antioxidant enzymes a molecular docking study was performed. The results showed good interaction in term of binding energy and inhibition constant in the following order GR > CAT > SOD > GST > GPx.
Conclusion: Our in vivo and in silico results for the first time indicate that tocotrienol significantly alleviate the condition of oxidative stress not only by its potent free radical scavenging properties but also may be by interacting directly and strongly with antioxidant enzymes as proved by molecular docking simulations.
A paraptosis-like cell death induced by δ-tocotrienol in human colon carcinoma SW620 cells is associated with the suppression of the Wnt signaling pathway
Zhang JS, Li DM, He N, Liu YH, Wang CH, Jiang SQ, Chen BQ, Liu JR.
Toxicology. 2011 Jul 11;285(1-2):8-17. Epub 2011 Mar 29.
Tocotrienol is considered a beneficial effect agent on inhibition of tumor development. In this study, we focused on the effects of δ-tocotrienol and its possible mechanism on induction of death in human colon cancer SW620 cells. δ-Tocotrienol inhibited proliferation of SW620 cell in a dose-dependent manner. Our findings showed that δ-tocotrienol effectively induced paraptosis-like death in SW620 cells, correlated with the vacuolation that may be from welling and fusion of mitochondria and/or the endoplasmic reticulum (ER) as well as caspase-3 nonactivated. However, there were no changes in apoptosis based on flow cytometry analysis. Of being noted, δ-tocotrienol reduced the expression of β-catenin and wnt-1 proteins by about 50% at the highest dose (20μmol/L). δ-Tocotrienol also decreased cyclin D1, c-jun and MMP-7 protein levels in SW620 cells. Altogether, these data indicate that δ-tocotrienol induces paraptosis-like cell death, which is associated with the suppression of the Wnt signaling pathway. Thus, our findings may provide a novel application in treatment of human colon carcinoma.
Role of immunoregulatory transcription factors in differential immunomodulatory effects of tocotrienols
Wilankar C, Sharma D, Checker R, Khan NM, Patwardhan R, Patil A, Sandur SK, Devasagayam TP.
Free Radic Biol Med. 2011 Jul 1;51(1):129-43. Epub 2011 Apr 8.
Tocotrienols have been shown to possess antioxidant, antitumor, cardioprotective, and antiproliferative effects. This report describes novel immunomodulatory effects of tocotrienols in murine lymphocytes. γ-Tocotrienol (GT) was more effective in suppressing concanavalin A (Con A)-induced T cell proliferation and cytokine production compared to α-tocotrienol (AT) when present continuously in the culture. GT inhibited T cell activation markers and costimulatory molecule. GT modulated intracellular glutathione in lymphocytes, and the suppressive effects of GT could not be abrogated by thiol or nonthiol antioxidants, indicating a poor link between anti-inflammatory properties of tocotrienols and cellular redox status. It was also observed that GT suppressed Con A-induced activation of NF-κB, AP-1, and NF-κB-dependent gene expression. Cellular uptake studies with tocotrienols showed higher accumulation of GT compared to AT. Similar immunosuppressive effects of GT were also observed when administered to mice. In contrast, transient exposure of lymphocytes to GT (4 h) resulted in higher survival and proliferation of lymphocytes in vitro and in vivo in syngeneic and allogeneic hosts. This was attributed to the ability of GT to induce NF-κB, AP-1, and mTOR activation in lymphocytes upon transient exposure. Our results demonstrated that antioxidants such as tocotrienols may exhibit pleiotropic effects by activating multiple mechanisms in cells.
The impact of dietary changes and dietary supplements on lipid profile
Huang J, Frohlich J, Ignaszewski AP.
Can J Cardiol. 2011 Jul-Aug;27(4):488-505.
With a growing number of dietary interventions that claim to improve lipid profile, it is important to ensure that these claims are evidence based. The objective of this study was to make recommendations for dietary regimens by analyzing their effectiveness and the level of evidence. We searched MEDLINE as well as the Cochrane Database of Systematic Reviews for nutritional studies. Meta-analyses and randomized controlled trials published in English and including data on the effect on blood lipid levels were used. Randomized controlled trials were included if they were at least 4 weeks in duration and had a minimum of 50 participants. We identified 22 different dietary interventions and reviewed 136 studies published between January 1990 and December 2009 that met our inclusion criteria. Our literature review showed that to improve lipid profile, the following regimens can be recommended fully: Mediterranean and Portfolio diets; low-fat diet; diet high in soy protein, fibre, or phytosterols; whole grain foods, and omega-3 fatty acid supplementation. The consumption of nuts, a diet high in carbohydrates and protein, green tea, and red wine, as well as the supplementation with policosanol and red yeast rice extract, can be considered for improvement of the lipid profile, while the supplements of guggulipid, garlic, chromium, vitamin C, magnesium-pyridoxal-phosphate-glutamate, tocotrienols, and absorbitol cannot be recommended.
Nutrapharmacology of tocotrienols for metabolic syndrome
Weng-Yew W, Brown L.
Curr Pharm Des. Volume 17, Number 21, July 2011
Metabolic syndrome is defined as a set of health risk factors that are associated with an increased chance of cardiovascular diseases and type 2 diabetes. These include abdominal obesity, hyperglycemia, impaired glucose tolerance, dyslipidemia, and hypertension. Interventions in metabolic syndrome include lifestyle interventions such as a healthy diet using functional foods together with increased physical activity to induce weight loss as the first aim of treatment. Nutraceuticals such as tocotrienols and tocopherols as members of the vitamin E family may be more targeted interventions. This review evaluates the effects of tocotrienols on the risk factors of metabolic syndrome using data from human, animal and in vitro studies. Tocotrienols improved lipid profiles and reduced atherosclerotic lesions, decreased blood glucose and glycated hemoglobin concentrations, normalized blood pressure, and inhibited adipogenesis. The differences in responses between tocopherols and tocotrienols in preventing obesity, diabetes, hypertension, artherosclerosis, ischemia, and inflammation suggest that different receptors or signaling mechanisms may be involved.
γ-tocotrienol induces apoptosis in human T cell lymphoma through activation of both intrinsic and extrinsic pathways.
Wilankar C, Khan NM, Checker R, Sharma D, Patwardhan R, Gota V, Sandur SK, Devasagayam TP.
Curr Pharm Des. 2011;17(21):2176-89.
Tocotrienols are members of vitamin E family and possess broad biological activities including antioxidant, anti-inflammatory and antitumor effects. In the present study, we examine the potential of α-tocotrienol (AT) and γ-tocotrienol (GT) in inhibiting the proliferation of human T cell lymphoma Jurkat cells and elucidate the pathways involved in anti tumor effects of GT. Only GT but not AT inhibited proliferation and induced apoptosis in Jurkat cells in a dose dependent manner. GT treatment resulted in elevated mitochondrial ROS production, activation of JNK and suppression of ERK and p38 MAPK. GT also induced calcium release, loss of mitochondrial membrane potential and cytochrome c release from the mitochondria. These changes were accompanied by increase in Bax expression with a concomitant decrease in Bcl-xl expression suggesting activation of mitochondrial apoptotic pathway. GT induced increase in mitochondrial ROS was abrogated by catalase. Besides, GT also up-regulated surface expression of Fas and FasL on Jurkat cells. Further, caspase activation and PARP degradation was also seen in cells treated with GT. Inhibitors of caspase-8 and caspase-9 significantly abrogated GT mediated apoptosis. In contrast GT was not toxic to normal human peripheral blood mononuclear cells suggesting differential cytotoxicity towards normal lymphocytes and transformed lymphoma cells. Cellular uptake studies with tocotrienols showed higher intracellular accumulation of GT as compared to AT which may be responsible for its better antitumor activity. Our results show antitumor effects of GT in human lymphoma cells via increased mitochondrial ROS generation and activation of both intrinsic and extrinsic apoptotic pathways.