Background & Purpose: Activation of signal transducer and activator of transcription 3 (STAT3) play a critical role in the survival, proliferation, angiogenesis and chemoresistance of tumour cells. Thus, agents that suppress STAT3 phosphorylation have potential as cancer therapies. In the present study, we investigated whether the apoptotic, antiproliferative and chemosensitizing effects of γ-tocotrienol are associated with its ability to suppress STAT3 activation in hepatocellular carcinoma (HCC).
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γ-Tocotrienol induces growth arrest through a novel pathway with TGFβ2 in prostate cancer
Campbell SE, Rudder B, Phillips RB, Whaley SG, Stimmel JB, Leesnitzer LM, Lightner J, Dessus-Babus S, Duffourc M, Stone WL, Menter DG, Newman RA, Yang P, Aggarwal BB, Krishnan K.
Free Radic Biol Med. 2011 May 15;50(10):1344-54. Epub 2011 Feb 16.
Regions along the Mediterranean and in southern Asia have lower prostate cancer incidence compared to the rest of the world. It has been hypothesized that one of the potential contributing factors for this low incidence includes a higher intake of tocotrienols. Here we examine the potential of γ-tocotrienol (GT3) to reduce prostate cancer proliferation and focus on elucidating pathways by which GT3 could exert a growth-inhibitory effect on prostate cancer cells. We find that the γ and δ isoforms of tocotrienol are more effective at inhibiting the growth of prostate cancer cell lines (PC-3 and LNCaP) compared with the γ and δ forms of tocopherol. Knockout of PPAR-γ and GT3 treatment show inhibition of prostate cancer cell growth, through a partially PPAR-γ-dependent mechanism. GT3 treatment increases the levels of the 15-lipoxygenase-2 enzyme, which is responsible for the conversion of arachidonic acid to the PPAR-γ-activating ligand 15-S-hydroxyeicosatrienoic acid. In addition, the latent precursor and the mature forms of TGFβ2 are down-regulated after treatment with GT3, with concomitant disruptions in TGFβ receptor I, SMAD-2, p38, and NF-κB signaling.
Tocotrienols-induced inhibition of platelet thrombus formation and platelet aggregation in stenosed canine coronary arteries
Qureshi AA, Karpen CW, Qureshi N, Papasian CJ, Morrison DC, Folts JD.
Lipids Health Dis. 2011 Apr 14;10:58.
Background: Dietary supplementation with tocotrienols has been shown to decrease the risk of coronary artery disease. Tocotrienols are plant-derived forms of vitamin E, which have potent anti-inflammatory, antioxidant, anticancer, hypocholesterolemic, and neuroprotective properties. Our objective in this study was to determine the extent to which tocotrienols inhibit platelet aggregation and reduce coronary thrombosis, a major risk factor for stroke in humans. The present study was carried out to determine the comparative effects of α-tocopherol, α-tocotrienol, or tocotrienol rich fraction (TRF; a mixture of α-+γ-+δ-tocotrienols) on in vivo platelet thrombosis and ex vivo platelet aggregation (PA) after intravenous injection in anesthetized dogs, by using a mechanically stenosed circumflex coronary artery model (Folts’ cyclic flow model).
Results: Collagen-induced platelet aggregation (PA) in platelet rich plasma (PRP) was decreased markedly after treatment with α-tocotrienol (59%; P<0.001) and TRF (92%; P<0.001). α-Tocopherol treatment was less effective, producing only a 22% (P<0.05) decrease in PA. Adenosine diphosphate-induced (ADP) PA was also decreased after treatment with α-tocotrienol (34%; P<0.05) and TRF (42%; P<0.025). These results also indicate that intravenously administered tocotrienols were significantly better than tocopherols in inhibiting cyclic flow reductions (CFRs), a measure of the acute platelet-mediated thrombus formation. Tocotrienols (TRF) given intravenously (10 mg/kg), abolished CFRs after a mean of 68 min (range 22 -130 min), and this abolition of CFRs was sustained throughout the monitoring period (50-160 min).Next, pharmacokinetic studies were carried out and tocol levels in canine plasma and platelets were measured. As expected, α-Tocopherol treatment increased levels of total tocopherols in post- vs pre-treatment specimens (57 vs 18 μg/mL in plasma, and 42 vs 10 μg/mL in platelets). However, treatment with α-tocopherol resulted in slightly decreased levels of tocotrienols in post- vs pre-treatment samples (1.4 vs 2.9 μg/mL in plasma and 2.3 vs 2.8 μg/mL in platelets). α-Tocotrienoltreatment increased levels of both tocopherols and tocotrienols in post- vs pre-treatment samples (tocopherols, 45 vs 10 μg/mL in plasma and 28 vs 5 μg/mL in platelets; tocotrienols, 2.8 vs 0.9 μg/mL in plasma and 1.28 vs 1.02 μg/mL in platelets). Treatment with tocotrienols (TRF) also increased levels of tocopherols and tocotrienols in post- vs pre-treatment samples (tocopherols, 68 vs 20 μg/mL in plasma and 31.4 vs 7.9 μg/mL in platelets;tocotrienols, 8.6 vs 1.7 μg/mL in plasma and 3.8 vs 3.9 μg/mL in platelets).
Conclusions: The present results indicate that intravenously administered tocotrienols inhibited acute platelet-mediated thrombus formation, and collagen and ADP-induced platelet aggregation. α-Tocotrienols treatment induced increases in α-tocopherol levels of 4-fold and 6-fold in plasma and platelets, respectively. Interestingly, tocotrienols (TRF) treatment induced a less pronounced increase in the levels of tocotrienols in plasma and platelets, suggesting that intravenously administered tocotrienols may be converted to tocopherols. Tocotrienols, given intravenously, could potentially prevent pathological platelet thrombus formation and thus provide a therapeutic benefit in conditions such as stroke and myocardial infarction.
We previously found that 2,7,8-trimethyl-2(2′-carboxyethyl)-6-hydroxychroman (γCEHC), a metabolite of the vitamin E isoforms γ-tocopherol or γ-tocotrienol, accumulated in the rat small intestine. The aim of this study was to evaluate tissue distribution of vitamin E metabolites. A single dose of α-tocopherol, γ-tocopherol or a tocotrienol mixture containing α- and γ-tocotrienol was orally administered to rats. Total amounts of conjugated and unconjugated metabolites in the tissues were measured by HPLC with an electrochemical detector, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox) was used as an internal standard. Twenty-four hours later, the vitamin E isoforms were detected in most tissues and in the serum. However, 2,5,7,8-tetramethyl-2(2′-carboxyethyl)-6-hydroxychroman (αCEHC), a metabolite of α-tocopherol or α-tocotrienol, and γCEHC accumulated in the serum and in some tissues including the liver, small intestine and kidney. Administration of α-tocopherol increased the γCEHC concentration in the small intestine, suggesting that α-tocopherol enhances γ-tocopherol catabolism. In contrast, ketoconazole, an inhibitor of cytochrome P450 (CYP)-dependent vitamin E catabolism, markedly decreased the γCEHC concentration. These data indicate that vitamin E metabolite accumulates not only in the liver but also in the small intestine and kidney. We conclude that some dietary vitamin E is catabolized to carboxyethyl-hydroxychroman in the small intestine and is secreted into the circulatory system.
Gamma tocotrienols protects against radiation exposure
Lisa Hutson
A form of Vitamin E may help protect against high levels of radiation exposure. Studies show that a potent form of Vitamin E called gamma tocotrienols may counteract the harmful effects of radiation. “It is something we have been working on for about five years now,” says Dr. Martin Hauer-Jensen, director of radiation health at UAMS.
Tocotrienols have potent antifibrogenic effects in human intestinal fibroblasts
Luna J, Masamunt MC, Rickmann M, Mora R, España C, Delgado S, Llach J, Vaquero E, Sans M.
Inflamm Bowel Dis. 2011 Mar;17(3):732-41
Background: Excessive fibroblast expansion and extracellular matrix (ECM) deposition are key events for the development of bowel stenosis in Crohn’s disease (CD) patients. Tocotrienols are vitamin E compounds with proven in vitro antifibrogenic effects on rat pancreatic fibroblasts. We aimed at investigating the effects of tocotrienols on human intestinal fibroblast (HIF) proliferation, apoptosis, autophagy, and synthesis of ECM.
Methods: HIF isolated from CD, ulcerative colitis (UC), and normal intestine were treated with tocotrienol-rich fraction (TRF) from palm oil. HIF proliferation was quantified by (3) H-thymidine incorporation, apoptosis was studied by DNA fragmentation, propidium iodide staining, caspase activation, and poly(ADP-ribose) polymerase cleavage, autophagy was analyzed by quantification of LC3 protein and identification of autophagic vesicles by immunofluorescence and production of ECM components was measured by Western blot.
Results: TRF significantly reduced HIF proliferation and prevented basic fibroblast growth factor-induced proliferation in CD and UC, but not control HIF. TRF enhanced HIF death by promoting apoptosis and autophagy. HIF apoptosis, but not autophagy, was prevented by the pan-caspase inhibitor zVAD-fmk, whereas both types of cell death were prevented when the mitochondrial permeability transition pore was blocked by cyclosporin A, demonstrating a key role of the mitochondria in these processes. TRF diminished procollagen type I and laminin γ-1 production by HIF.
Conclusions: Tocotrienols exert multiple effects on HIF, reducing cell proliferation, enhancing programmed cell death through apoptosis and autophagy, and decreasing ECM production. Considering their in vitro antifibrogenic properties, tocotrienols could be useful to treat or prevent bowel fibrosis in CD patients.
Tocotrienol-rich fraction prevents cell cycle arrest and elongates telomere length in senescent human diploid fibroblasts
Makpol S, Durani LW, Chua KH, Mohd Yusof YA, Ngah WZ.
J Biomed Biotechnol. 2011;2011:506171. Epub 2011 Mar 30.
This study determined the molecular mechanisms of tocotrienol-rich fraction (TRF) in preventing cellular senescence of human diploid fibroblasts (HDFs). Primary culture of HDFs at various passages were incubated with 0.5 mg/mL TRF for 24 h. Telomere shortening with decreased telomerase activity was observed in senescent HDFs while the levels of damaged DNA and number of cells in G(0)/G(1) phase were increased and S phase cells were decreased. Incubation with TRF reversed the morphology of senescent HDFs to resemble that of young cells with decreased activity of SA-β-gal, damaged DNA, and cells in G(0)/G(1) phase while cells in the S phase were increased. Elongated telomere length and restoration of telomerase activity were observed in TRF-treated senescent HDFs. These findings confirmed the ability of tocotrienol-rich fraction in preventing HDFs cellular ageing by restoring telomere length and telomerase activity, reducing damaged DNA, and reversing cell cycle arrest associated with senescence.
Vitamin E, an essential nutrient with powerful antioxidant activity, is the mixture of two classes of compounds, tocopherols (TPs) and tocotrienols (TTs). Although TTs exhibit better bone protective activity than α-TP, the underlying mechanism is poorly understood. In this study, we investigated whether α-TT and α-TP can modulate osteoclastic bone resorption. We found that α-TT but not α-TP inhibits osteoclastogenesis in coculture of osteoblasts and bone marrow cells induced by either IL-1 or combined treatment with 1α,25(OH)(2) vitamin D(3) and prostaglandin E(2). In accordance with this, only α-TT inhibited receptor activator of NF-κB ligand (RANKL) expression in osteoblasts. In addition, α-TT but not α-TP inhibited RANKL-induced osteoclast differentiation from precursors by suppression of c-Fos expression, possibly through inhibiting ERK and NF-κB activation. This anti-osteoclastogenic effect was reversed when c-Fos or an active form of NFATc1, a critical downstream of c-Fos during osteoclastogenesis, was overexpressed. Furthermore, only α-TT reduced bone resorbing activity of mature osteoclasts without affecting their survival. Overall, our results demonstrate that α-TT but not α-TP has anti-bone resorptive properties by inhibiting osteoclast differentiation and activation, suggesting that α-TT may have therapeutic value for treating and preventing bone diseases characterized by excessive bone destruction.
A Regenerative Antioxidant Protocol of Vitamin E and α-Lipoic Acid Ameliorates Cardiovascular and Metabolic Changes in Fructose-Fed Rats
Patel J, Matnor NA, Iyer A, Brown L.
Evid Based Complement Alternat Med. 2011;2011:120801
Type 2 diabetes is a major cause of cardiovascular disease. We have determined whether the metabolic and cardiovascular changes induced by a diet high in fructose in young adult male Wistar rats could be prevented or reversed by chronic intervention with natural antioxidants. We administered a regenerative antioxidant protocol using two natural compounds: α-lipoic acid together with vitamin E (α-tocopherol alone or a tocotrienol-rich fraction), given as either a prevention or reversal protocol in the food. These rats developed glucose intolerance, hypertension, and increased collagen deposition in the heart together with an increased ventricular stiffness. Treatment with a fixed combination of vitamin E (either α-tocopherol or tocotrienol-rich fraction, 0.84 g/kg food) and α-lipoic acid (1.6 g/kg food) normalized glucose tolerance, blood pressure, cardiac collagen deposition, and ventricular stiffness in both prevention and reversal protocols in these fructose-fed rats. These results suggest that adequate antioxidant therapy can both prevent and reverse the metabolic and cardiovascular damage in type 2 diabetes.
Pentoxifylline enhances the radioprotective properties of γ-tocotrienol: Differential effects on the hematopoietic, gastrointestinal and vascular systems
Berbée M, Fu Q, Garg S, Kulkarni S, Kumar KS, Hauer-Jensen M.
Radiat Res. 2011 Mar;175(3):297-306.
The vitamin E analog γ-tocotrienol (GT3) is a potent radioprotector and mitigator. This study was performed to (a) determine whether the efficacy of GT3 can be enhanced by the addition of the phosphodiesterase inhibitor pentoxifylline (PTX) and (b) to obtain information about the mechanism of action. Mice were injected subcutaneously with vehicle, GT3 [400 mg/kg 24 h before total-body irradiation (TBI)], PTX (200 mg/kg 30 min before TBI), or GT3+PTX before being exposed to 8.5-13 Gy TBI. Overall lethality, survival time and intestinal, hematopoietic and vascular injury were assessed. Cytokine levels in the bone marrow microenvironment were measured, and the requirement for endothelial nitric oxide synthase (eNOS) was studied in eNOS-deficient mice. GT3+PTX significantly improved survival compared to GT3 alone and provided full protection against lethality even after exposure to 12.5 Gy. GT3+PTX improved bone marrow CFUs, spleen colony counts and platelet recovery compared to GT3 alone. GT3 and GT3+PTX increased bone marrow plasma G-CSF levels as well as the availability of IL-1α, IL-6 and IL-9 in the early postirradiation phase. GT3 and GT3+PTX were equally effective in ameliorating intestinal injury and vascular peroxynitrite production. Survival studies in eNOS-deficient mice and appropriate controls revealed that eNOS was not required for protection against lethality after TBI. Combined treatment with GT3 and PTX increased postirradiation survival over that with GT3 alone by a mechanism that may depend on induction of hematopoietic stimuli. GT3+PTX did not reduce GI toxicity or vascular oxidative stress compared to GT3 alone. The radioprotective effect of either drug alone or both drugs in combination does not require the presence of eNOS.