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.
Monthly Archives: June 2009
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).
As rice bran tocotrienol (T3) has been known to have a wide range of physiological functions (e.g., antiangiogenesis), we aimed at developing a T3-rich rice variety for nutraceutical purposes. T3 content in more than 250 kinds of rice bran samples were investigated, and Milyang23 was found as the best variety rich in T3. The variety was therefore chosen for cross-fertilization with Koshihikari. Among obtained F(2) progenies, some of them became improved in T3 content (up to 2-fold of reference Koshihikari). QTL analysis of the F(2) progenies revealed five putative loci corresponding to T3 biosynthesis, in which the main loci were located near a marker RM3827 on chromosome 6. The results show that cross-breeding is effective in improving rice bran T3 and provides more genetic understanding on T3 biosynthesis in rice plants
The subtropical plant species Cyphostemma digitatum, Vitaceae, is used in central Yemen in traditional medicine, as a culinary herb, and as a source of food flavoring. The contents of vitamin C, vitamin E, and carotenoids and changes caused by common processing were investigated. Carotenoids were determined by reversed phase C30-high-performance liquid chromatography (HPLC) with diode array detection at 470 nm, while tocopherols and tocotrienols were analyzed by using normal phase HPLC with fluorescence detection (excitation, 292 nm; emission, 330 nm). Ascorbic acid was determined spectrophotometrically after reaction with DNP by measuring the absorbance at 520 nm. For the raw material and for the processed commercial food product, both in dried form, reasonable quantities of carotenoids were found in the raw material as follows: lutein, 18.89 +/- 0.73 mg/100 g; zeaxanthin, 9.46 +/- 0.30 mg/100 g; canthaxanthin, 0.21 +/- 0.01 mg/100 g; beta-cryptoxanthin, 0.67 +/- 0.03 mg/100 g; and beta-carotene, 14.60 +/- 0.46 mg/100 g. Household processing reduced the carotenoid contents dramatically; only beta-carotene sustained the processing. Likewise, vitamin C, 49.50 +/- 0.01 mg/100 g in the raw material and 20.30 +/- 0.02 mg/100 g in the processed material, was affected negatively by processing; only 41% was retained after processing. In contrast, the outstanding high content of vitamin E, 82.74 +/- 0.63 mg/100 g in the raw material, was increased by processing to 101.20 +/- 1.38 mg/100 g; it was found in different forms, some of which were rare in other sources.