Byron J. Richards
Encouraging results from several studies show vitamin E tocotrienol’s anti-tumour properties in various cancer types. Breast Cancer – A study showed that gamma tocotrienol, at levels of dietary supplement intake, reduced the spreading of breast cancer cells by 58%.
A recent study from our laboratory indicated the cardioprotective ability of the tocotrienol-rich fraction (TRF) from red palm oil. The present study compared cardioprotective abilities of different isomers of tocotrienol against TRF as recently tocotrienol has been found to function as a potent neuroprotective agent against stroke. Rats were randomly assigned to one of the following groups: animals were given, by gavage, either 0.35%, 1%, or 3.5% TRF for two different periods of time (2 or 4 wk) or 0.03, 0.3, and 3 mg/kg body wt of one of the isomers of tocotrienol (alpha, gamma, or delta) for 4 wk; control animals were given, by gavage, vehicle only. After 2 or 4 wk, rats were killed, and their hearts were then subjected to 30 min of global ischemia followed by 2 h of reperfusion. Dose-response and time-response experiments revealed that the optimal concentration for TRF was 3.5% TRF and 0.3 mg/kg body wt of tocotrienol given for 4 wk. TRF as well as all the isomers of tocotrienol used in our study providedcardioprotection, as evidenced by their ability to improve postischemic ventricular function and reduce myocardial infarct size. The gamma-isoform of tocotrienol was the most cardioprotective of all the isomers followed by the alpha- and delta-isoforms. The molecular mechanisms of cardioprotectionafforded by tocotrienol isoforms were probed by evaluating their respective abilities to stabilize the proteasome, allowing it to maintain a balance between prodeath and prosurvival signals. Our results demonstrated that tocotrienol isoforms reduced c-Src but increased the phosphorylation of Akt, thus generating a survival signal.
Taxanes, including docetaxel, are widely used for the treatment of squamous cell carcinoma of the head and neck. However, the gastrointestinal toxicity of docetaxel has limited its high-dose clinical use. In this study, we examined the synergistic anticancer effects of combined low-dose docetaxel and γ-tocotrienol treatment on human oral cancer (B88) cells. We treated B88 cells with docetaxel and γ-tocotrienol at concentrations of 0.5 nM and 50 µM, respectively. When cells were treated with either agent alone at a low dose, no significant cytotoxic effect was observed. However, the simultaneous treatment of cells with both agents almost completely suppressed cell growth. Whereas docetaxel stimulated the expression of nuclear factor-κB (NF-κB) p65 protein in B88 cells, γ-tocotrienol slightly inhibited the expression of constitutive nuclear p65 protein. Of note, the combined treatment with both agents inhibited docetaxel-induced nuclear p65 protein expression. Electrophoretic mobility shift assay (EMSA) revealed that the simultaneous treatment with these agents suppressed the NF-κB DNA binding activity in B88 cells. In addition, γ-tocotrienol downregulated the docetaxel-induced expression of NF-κB-regulated gene products associated with the inhibition of apoptosis. Furthermore, the activation of initiator caspases, caspases-8 and -9, and the effector caspase, caspase-3, was detected following treatment with both agents. Finally, apoptosis was also clearly observed as demonstrated by the cleavage of poly(ADP-ribose) polymerase (PARP) and nuclear fragmentation through the activation of caspase-3 by combined treatment with docetaxel and γ-tocotrienol. These findings suggest that the combination treatment with these agents may provide enhanced therapeutic response in oral cancer patients, while avoiding the toxicity associated with high-dose β-tubulin stabilization monotherapy.
Vitamin E tocotrienol synthesis in monocots requires homogentisate geranylgeranyl transferase (HGGT), which catalyzes condensation of homogentisate and the unsaturated C20 isoprenoid geranylgeranyl diphosphate (GGDP). By contrast, vitamin E tocopherol synthesis is mediated by homogentisate phytyltransferase (HPT), which condenses homogentisate and the saturated C20 isoprenoid phytyl diphosphate (PDP). An HGGT-independent pathway for tocotrienol synthesis has also been shown to occur by deregulation of homogentisate synthesis. In this report, the basis for this pathway and its impact on vitamin E ion when combined with HGGT were explored. An Arabidopsis line was initially developed that accumulates tocotrienols and homogentisate by co-expression of Arabidopsis hydroxyphenylpyruvate dioxygenase (HPPD) and Escherichia coli bifunctional chorismate mutase/prephenate dehydrogenase (TyrA). When crossed into the vte2-1 HPT null mutant, tocotrienol ion was lost, indicating that HPT catalyzes tocotrienol synthesis in HPPD/TyrA-expressing plants by atypical use of GGDP as a substrate. Consistent with this, recombinant Arabidopsis HPT preferentially catalyzed in vitro production of the tocotrienol precursor geranylgeranyl benzoquinol only when presented with high molar ratios of GGDP:PDP. In addition, tocotrienol levels were highest in early growth stages in HPPD/TyrA lines, but decreased strongly relative to tocopherols during later growth stages when PDP is known to accumulate. Collectively, these results indicate that HPPD/TyrA-induced tocotrienol production requires HPT and occurs upon enrichment of GGDP relative to PDP in prenyl-DP pools. Finally, combined expression of HPPD/TyrA and HGGT in Arabidopsis leaves and seeds resulted in large additive increases in vitamin E production indicating that homogentisate concentrations limit HGGT-catalyzed tocotrienol synthesis.
For many decades, the use of synthetic chemicals as drugs has been effective in the treatment of most diseases. Moreover, from ancient to modern history, many traditional plant based medicines are playing an important role in health care. Phytochemicals are natural bioactive compounds found in vegetables, fruits, medicinal plants, aromatic plants, leaves, flowers and roots which act as a defense system to combat against diseases. The phytochemicals from natural products cover a diverse range of chemical entities such as polyphenols, flavonoids, steroidal saponins, organosulphur compounds and vitamins. A number of bioactive compounds generally obtained from terrestrial plants such as isoflavones, diosgenin, resveratrol, quercetin, catechin, sulforaphane, tocotrienols and carotenoids are proven to reduce the risk of cardiovascular diseases and aid in cardioprotection which is the leading cause of death globally. The cardioprotective effects of the various phytochemicals are perhaps due to their antioxidative, antihypercholesteroemic, antiangiogenic, anti-ischemic, inhibition of platelet aggregation and anti inflammatory activities that reduce the risk of cardiovascular disorders. The multi-faceted role of the phytochemicals is mediated by its structure-function relationship and can be considered as leads for cardiovascular drug design in future. This review summarizes the findings of recent studies on selected phytochemicals as prophylactic and therapeutic agents in cardioprotection.
Systemic chemotherapy is the only current method of treatment that provides some chance for long-term survival in patients with advanced or metastatic cancer. gamma-Tocotrienol is a natural form of vitamin E found in high concentrations in palm oil and displays potent anticancer effects, but limited absorption and transport of by the body has made it difficult to obtain and sustain therapeutic levels in the blood and target tissues. Statins are inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMGCoA) reductase and are an example of a promising cancer chemotherapeutic agent whose clinical usefulness has been limited due to high-dose toxicity. Similarly, erlotinib and gefitinib are anticancer agents that inhibit the activation of individual HER/ErbB receptor subtypes, but have shown limited clinical success because of heterodimerization between different EGF receptor family members that can rescue cancer cells from agents directed against a single receptor subtype. Recent studies have investigated the anticancer effectiveness of low-dose treatment of various statins or EGF receptor inhibitors alone and in combination with gamma-tocotrienol on highly malignant +SA mouse mammary epithelial cells in vitro. Combined treatment with subeffective doses of gamma-tocotrienol with these other chemotherapeutic agents resulted in a synergistic inhibition of +SA cell growth and viability. These findings strongly suggest that combined treatment of gamma-tocotrienol with other anticancer agents may not only provide an enhanced therapeutic response but also provide a means to avoid the toxicity, low bioavailability, or limited therapeutic action associated with high-dose monotherapy.
Vitamin E comprises 8 functionally unique isoforms and may be a suitable candidate for the adjuvant treatment of prostate cancer. In this study, we examined the ability of 2 vitamin E isoforms [α-tocotrienol (γ-TT) and δ-tocotrienol (δ-TT)] and 4 synthetic derivatives [γ- and δ-tocotrienol succinate (γ-TS, δ-TS), α-tocopheryl polyethylene glycol succinate (TPGS), and α-tocopheryl polyethylene glycol ether (TPGS-e)] of vitamin E to induce cell death in AR- (DU145 and PC-3) and AR+ (LNCaP) prostate cancer cell lines. Our results show that δ-TT and TPGS-e are the most effective isoform and synthetic derivative, respectively, of all compounds examined. Overall, the results of our study suggest that isoforms and synthetic derivatives of vitamin E have the potency to trigger both caspase-dependent and -independent DNA damage and dominant caspase-independent programmed cell death. The capacity of vitamin E to trigger caspase-independent programmed cell death suggests that it may be useful in the chemotherapy of prostate cancer since it may prevent the tumor resistance commonly associated with the use of classical chemotherapeutic agents that trigger caspase-dependent programmed cell death.
Small-fiber painful peripheral neuropathy is one of the long-term complications of alcohol for which there is no reliable successful therapy available. The precise mechanisms by which chronic alcohol consumption produces peripheral nerve fiber damage and loss remain unclear. Emerging data from clinical and preclinical studies suggest that increased oxidative-nitrodative stress mediated release of proinflammatory cytokines from damaged neural tissues may play a central role in the pathogenesis of alcoholic neuropathy. The present study investigated the effect of both the isoforms of vitamin E (α-tocopherol and tocotrienol) against chronic alcohol-induced peripheral neuropathy in rats. Ethanol treated rats showed a significant decrease in paw-withdrawal threshold in both Randall-Selitto and von-Frey hair tests along with a significant reduction in tail flick latency in the tail-immersion test. A decreased pain threshold was associated with significant alterations in oxidative-nitrodative stress markers and an increase in proinflammatory cytokines (TNF-α and IL-1β). The 4-week treatment with tocotrienol significantly ameliorated behavioral, biochemical and molecular alterations in alcohol treated rats. However, α-tocopherol failed to produce any protective effect. The results of the present study suggest that oxidative-nitrodative stress mediated cytokine signaling may be responsible for alcohol-induced peripheral neurotoxicity and tocotrienol treatment might be beneficial in chronic alcoholics exhibiting neuropathy
Published
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.
Subjects: Patients with photosensitivity
Intervention: Tocotrienol and tocopherol containing formulation
Primary outcome: Photosensitivity (erythema/oedema/itch/vesciculation) scores
Methodology: 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.
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.