Publications
Combined treatment of gamma-tocotrienol with statins induce mammary tumor cell cycle arrest in G1
Wali VB, Bachawal SV, Sylvester PW.
Exp Biol Med (Maywood). 2009 Jun;234(6):639-50. Epub 2009 Apr 9.
Statins and gamma-tocotrienol (a rare isoform of vitamin E) both inhibit 3-hydroxy-3-methylglutaryl-coenzyme A (HMGCoA) reductase activity and display anticancer activity. However, clinical application of statins has been limited by high dose toxicity. Previous studies showed that combinedstatin and gamma-tocotrienol treatment synergistically inhibits growth of highly malignant +SA mammary epithelial cells in culture. To investigate the mechanism mediating this growth inhibition, studies were conducted to determine the effect of combination low dose gamma-tocotrienol and statintreatment on +SA mammary tumor cell cycle progression. Treatment with 0.25 microM simvastatin, lovastatin, mevastatin, 10 microM pravastatin or 2.0 microM gamma-tocotrienol alone had no effect, while combined treatment of individual statins with gamma-tocotrienol significantly inhibited +SAcell proliferation during the 4-day culture period. Flow cytometric analysis demonstrated that combined treatment induced cell cycle arrest in G1. Additional studies showed that treatment with 0.25 microM simvastatin or 2 microM gamma-tocotrienol alone had no effect on the relative intracellular levels of cyclin D1, CDK2, CDK4 and CDK6, but combined treatment caused a large reduction in cyclin D1 and CDK2 levels. Combined treatments also caused a relatively large increase in p27, but had no effect on p21 and p15 levels, and resulted in a large reduction in retinoblastoma (Rb) protein phosphorylation at ser780 and ser807/811. Similar effects were observed following combined treatment of gamma-tocotrienol with low doses of lovastatin, mevastatin and pravastatin. These findings demonstrate that combination low dose statin and gamma-tocotrienol treatment inducedmammary tumor cell cycle arrest at G1, resulting from an increase in p27 expression, and a corresponding decrease in cyclin D1, CDK2, and hypophosphorylation of Rb protein. These findings suggest that combined treatment of statins with gamma-tocotrienol may provide significant health benefits in the treatment of breast cancer in women, while avoiding myotoxicity associated with high dose statin monotherapy.
Is vitamin E toxic to neuron cells?
Then SM, Mazlan M, Mat Top G, Wan Ngah WZ.
Cell Mol Neurobiol. 2009 Jun;29(4):485-96. Epub 2009 Jan 27.
Besides acting as potent free radical scavengers, tocopherols and tocotrienols have been known to have non-antioxidant properties such as the involvement of alpha-tocopherol (alphaT) in PKC pathway and the anti-cancer properties of gamma-tocotrienol (gammaT3). This study aims to elucidate whether protective effects shown by alphaT and gammaT3 in H(2)O(2)-induced neuron cultures have anti-apoptotic or pro-apoptotic tendency toward the initiation of neuronal apoptosis. H(2)O(2) is used to induce apoptosis in primary cerebellar neuron cultures which is attenuated by pretreatment of alphaT or gammaT3 at concentrations < or =10 microM. Similar to our previous work, gammaT3 was found to be neurotoxic at concentrations > or =100 microM, whereas alphaT showed no neurotoxicity. Cellular uptake of gammaT3 was higher than that of alphaT. Treating cells simultaneously with either gammaT3 or alphaT and with then H(2)O(2) led to higher expression of Bax and Bcl-2 than in neurons exposed to H(2)O(2) alone. Analysis of Bcl-2/Bax ratio as ‘survival index’ showed that both pretreatment of gammaT3 and alphaT followed by H(2)O(2) increase the ‘survival index’ of Bcl-2/Bax ratio compared to H(2)O(2)-treated cells, while treatment of gammaT3 alone decrease the ratio compared to unchanged Bcl2/Bax ratio of similar treatment with alphaT alone. Similar treatment of gammaT3 decreased p53 expression and activates p38 MAPK phosphorylation, whereas alphaT did not alter its expression compared to H(2)O(2)-treated cells. Treating neurons with only gammaT3 or alphaT increased the expression of Bax, Bcl-2, p53, and p38 MAPK compared to control with gammaT3 exerting stronger expression for proteins involved than alphaT. In conclusion, low doses of gammaT3 and alphaT confer neuroprotection to H(2)O(2)-treated neurons via their antioxidant mechanism but gammaT3 has stronger pro-apoptosis tendency than alphaT by activating molecules involved in the neuronal apoptotic pathway in the absence of H(2)O(2).
d-δ-Tocotrienol-mediated suppression of the proliferation of human PANC-1, MIA PaCa-2, and BxPC-3 pancreatic carcinoma cells
Hussein D, Mo H.
Pancreas. 2009 May;38(4):e124-36.
Objective: The rate-limiting activity of the mevalonate pathway, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, provides intermediates essential for growth. Competitive inhibitors of HMG CoA reductase, such as the statins, and down-regulators of reductase, such as the tocotrienols, suppress tumor growth. We evaluated the impact of d-delta-tocotrienol, the most potent vitamin E isomer, on human MIA PaCa-2 and PANC-1 pancreatic carcinoma cells and BxPC-3 pancreatic ductal adenocarcinoma cells.
Methods: Cell proliferation was measured by using CellTiter 96 Aqueous One Solution (Promega, Madison, Wis). Cell cycle distribution was determined by flow cytometry. Apoptosis was evaluated by Annexin V staining and fluorescence microscopy after dual staining with acridine orange and ethidium bromide.
Results: d-delta-Tocotrienol induced concentration-dependent suppression of cell proliferation with 50% inhibitory concentrations of 28 (6) micromol/L (MIA PaCa-2), 35 (7) micromol/L (PANC-1), and 35 (8) microL (BxPC-3), respectively. These effects are attributable to cell cycle arrest at the G1 phase and apoptosis. Mevalonate attenuated d-delta-tocotrienol-mediated growth inhibition. A physiologically attainable blend of d-delta-tocotrienol and lovastatin synergistically suppressed the proliferation of MIA PaCa-2 cells.
Conclusions: Suppression of mevalonate pathway activities, be it by modulators of HMG CoA reductase (statins, tocotrienols, and farnesol), farnesyl transferase (farnesyl transferase inhibitors), and/or mevalonate pyrophosphate decarboxylase (phenylacetate) activity, may have a potential in pancreatic cancer chemotherapy.
Gamma-tocotrienol ameliorates intestinal radiation injury and reduces vascular oxidative stress after total-body irradiation by an HMG-CoA reductase-dependent mechanism
Berbée M, Fu Q, Boerma M, Wang J, Kumar KS, Hauer-Jensen M.
Radiat Res. 2009 May;171(5):596-605.
Analogs of vitamin E (tocols) are under development as radioprophylactic agents because of their high efficacy and lack of toxicity. Gamma-tocotrienol (GT3) is of particular interest because, in addition to being an antioxidant, it also inhibits 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and accumulates to greater extent in endothelial cells than other tocols. We addressed in vivo whether HMG-CoA reductase inhibition contributes to the radioprotection conferred by GT3. Groups of mice were treated with vehicle, mevalonate (the product of the reaction catalyzed by HMG-CoA reductase), GT3 alone or GT3 in combination with mevalonate. Lethality and standard parameters of injury to the hematopoietic, intestinal and vascular/endothelial systems were assessed after exposure to total-body irradiation. GT3 improved postirradiation survival and decreased radiation-induced vascular oxidative stress, an effect that was reversible by mevalonate. GT3 also enhanced hematopoietic recovery, reduced intestinal radiation injury, and accelerated the recovery of soluble markers of endothelial function. These parameters were not reversed by mevalonate co-administration. Our data confirm GT3’s radioprophylactic properties against hematopoietic injury and, for the first time, demonstrate benefits in terms of protection against gastrointestinal and vascular injury. The radioprotective efficacy of GT3 against vascular injury is related to its properties as an HMG-CoA reductase inhibitor.
A redox-silent analogue of tocotrienol acts as a potential cytotoxic agent against human mesothelioma cells
Kashiwagi K, Virgona N, Harada K, Kido W, Yano Y, Ando A, Hagiwara K, Yano T.
Life Sci. 2009 May 8;84(19-20):650-6.
Aims: Malignant mesothelioma is an aggressive cancer with no effective treatment options. A redox-silent analogue of alpha-tocotrienol, 6-O-carboxypropyl-alpha-tocotrienol (T3E) is a new potential anti-carcinogenic agent with less toxic effect on non-tumorigenic cells. Here, we evaluated the effect of T3E on killing of chemoresistant mesothelioma cell (H28). MAIN
Methods: The cytotoxic effect of T3E was evaluated by a WST-1 assay, and cell cycle and apoptosis analysis were done by FACS. Each signal molecule’s activity was determined by protein array and immunoblot analysis.
Key Findings: T3E effectively inhibited H28 cell growth at practical pharmacological concentrations (10-20 muM) without any effect on non-tumorigenic mesothelial cell (Met-5A). Inhibition of H28 cell growth by T3E mediated through G2/M arrest in cell cycle and induction of apoptosis. Protein array and immunoblot analyses revealed that T3E inhibited the activation of epidermal growth factor receptor (EGFR) via the inactivation of the Src family of protein tyrosine kinases (Src). However, the blockade of the EGFR signaling was not associated with the T3E-dependent H28 cell growth control. In addition to Src inactivation, T3E inhibited signal transduction and activation of transcription Stat3. A combination of an Src inhibitor, PP2, and a Stat3 inhibitor, AG490, induced G2/M arrest and enhanced apoptosis compared with PP2 alone. These results suggest that T3E suppresses H28 cell growth via the inhibition of Src activation and Src-independent Stat3 activation.
Significance: T3E can be a new effective therapeutic agent against chemoresistant mesothelioma cells.
Design and QSAR study of analogs of gamma-tocotrienol with enhanced antiproliferative activity against human breast cancer cells
Nikolic K, Agababa D.
J Mol Graph Model. 2009 Apr;27(7):777-83. Epub 2008 Nov 27.
Quantitative structure-activity relationships (QSAR) study has been performed for two sets of the antitumor drugs against human breast cancer MCF-7 cell lines, alpha-tocopherol and cholesterol derivatives. Constitutional, geometrical, physico-chemical and electronic descriptors (using the density functional theory, B3LYP/6-31G (d,p) basis set) were computed and analyzed. The most relevant of these descriptors were grouped and multiple linear regressions have been carried out. Optimal QSAR models with three and four variables, R(2)>0.95 and cross-validation parameter q(pre)(2)>0.88, were selected. Based on the QSAR study, novel vitamin-E derivatives (compounds D-1 and D-2) were designed and their antiproliferative activities were evaluated using the proposed regression models. Calculated antiproliferative activities of the designed compounds, IC(50) (D-1): 3.09 microM and IC(50) (D-2): 3.54 microM, were significantly stronger than anticancer effect of the other analyzed compounds IC(50): 4-1461 microM.
Suppression of NF-kappa beta signaling pathway by tocotrienol can prevent diabetes associated cognitive deficits
Kuhad A, Bishnoi M, Tiwari V, Chopra K.
Pharmacol Biochem Behav. 2009 Apr;92(2):251-9. Epub 2008 Dec 24.
Abstract
Objective: The etiology of diabetes associated cognitive decline is multifactorial and involves insulin receptor down regulation, neuronal apoptosis and glutamatergic neurotransmission. The study was designed to evaluate the impact of tocotrienol on cognitive function and neuroinflammatory cascade in streptozotocin-induced diabetes.
Research design and method: Streptozotocin-induced diabetic rats were treated with tocotrienol for 10 weeks. Morris water maze was used for behavioral assessment of memory. Cytoplasmic and nuclear fractions of cerebral cortex and hippocampus were prepared for the quantification of acetylcholinesterase activity, oxidative-nitrosative stress, tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), NFkappabeta and caspase-3.
Results: After 10 weeks of streptozotocin injection, the rats produced significant increase in transfer latency which was coupled with enhanced acetylcholinesterase activity, increased oxidative-nitrosative stress, TNF-alpha, IL-1beta, caspase-3 activity and active p65 subunit of NFkappabeta in different regions of diabetic rat brain. Interestingly, co-administration of tocotrienol significantly and dose-dependently prevented behavioral, biochemical and molecular changes associated with diabetes. Moreover, diabetic rats treated with insulin-tocotrienol combination produced more pronounced effect on molecular parameters as compared to their per se groups.
Conclusions: Collectively, the data reveal that activation of NFkappabeta signaling pathway is associated with diabetes induced cognitive impairment and point towards the therapeutic potential of tocotrienol in diabetic encephalopathy.
Chemoprevention of tocotrienols: The mechanism of antiproliferative effects
Wada S.
Forum Nutr. 2009;61:204-16. Epub 2009 Apr 7.
Tocotrienols have been reported as antitumor agents and widely commercialized as an antioxidant dietary supplement. Tocotrienols have more significant biological activity than tocopherols, although serum level of tocotrienols is much lower than that of tocopherols. This may be because intracellular concentration of tocotrienols was revealed to be significantly higher compared with tocopherols, and tocotrienol accumulation is observed in tumor. Previous reports have suggested antiproliferative effect, induction of apoptosis, modulation of cell cycle, antioxidant activity, inhibition of angiogenesis, and suppression of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase activity as anticarcinogenesis mechanisms of tocotrienols both in vivo and in vitro. Extension of the duration of host survival was observed in tumor-implanted mice treated with tocotrienol. Tocotrienols induce apoptosis mainly via mitochondria-mediated pathway. Cell cycle arrest is due to suppression of cyclin D bytocotrienols. Tocotrienols also inhibit vascularization-reducing proliferation, migration and tube formation. Malignant proliferation demands elevation of HMG CoA reductase activity, and tocotrienols suppress its activity. Tocotrienol treatment decreases oncogene expression and increases the level of tumor suppressors. Only a few clinical trials to determine the effects of tocotrienol on cancer prevention or treatment have been carried out. There is no convincing or probable evidence of the role of tocotrienols in cancer prevention, while alpha-tocopherol has been suggested to have a limited anti-prostate cancer potential. Neither beneficial activity nor adverse effect of tocotrienol has sufficiently been explored so far. The above-mentioned mechanisms of tocotrienols seem to be promising for cancer prevention; however, further clinical studies are warranted to assess the efficacy and safety of tocotrienol.
Towards the interaction mechanism of tocopherols and tocotrienols (Vitamin E) with selected metabolizing enzymes
Upadhyay J, Misra K. Source
Bioinformation. 2009 Apr 21;3(8):326-31.
Vitamin E is a mixture of eight compounds alpha, beta, gamma, delta- tocopherols and alpha, beta, gamma, delta- tocotrienols. Their individual role in cellular transport as antioxidants and in metabolic pathways has been highlighted in the present work. All the eight compounds have been docked with the respective metabolizing enzymes (alpha-tocopherol transfer protein (ATTP), alpha-tocopherol associated protein (TAP), P-glycoprotein (P-gly) and human serum albumin (HSA)) to understand molecular interactions for pharmacokinetics. These have been structurally aligned against the four human phospholipids in order to reveal their individual role in chylomicron formation and hence the mechanism of cellular transport. The study of their binding with their metabolizing enzymes provides insight to the comparative antioxidant activity of each of these isomers.