Enzyme-treated red rice (Oryza sativa L.) bran extracts mitigate inflammatory markers in RAW 264.7 macrophage cells and exhibit anti-inflammatory efficacy greater/comparable to ferulic acid, catechin, γ-tocopherol, and γ-oryzanol

ETHNOPHARMACOLOGICAL RELEVANCE

Rice (Oryza sativa L.), a staple food for a significant portion of the global population, has been recognized for its traditional medicinal properties for centuries. Rice bran, a by-product of rice milling, contains many bioactive compounds with potential pharmaceutical and therapeutic benefits. In recent years, research has highlighted the anti-inflammatory potential of rice bran, contributed by the bioactive components concentrated in their bran but, unfortunately, entrapped in the bran matrix, with limited bioavailability. Previous studies have reported that the enzymatic treatment of rice bran improves the bran's bioactive compound profile but did not investigate its impact on chronic conditions such as inflammation.

AIM OF THE STUDY

This study investigates the anti-inflammatory effects of endo-1,4-β-xylanase (ERB) and Viscozyme (VRB) treated red rice bran extracts against lipopolysaccharide-induced inflammation in RAW264.7 macrophages in comparison with non-enzyme-treated bran (CRB). Further established their efficacy with known anti-inflammatory compounds-ferulic acid (FA), catechin (CAT), γ-tocopherol (GTP), and γ-oryzanol (ORZ).

MATERIALS AND METHODS

The RAW 264.7 macrophage cells were pre-treated with non-toxic concentrations (10-200 μg/mL) of FA, CAT, GTP, ORZ, CRB, ERB, and VRB, followed by inflammatory stimulation with LPS for 24 h. Further, the cell supernatant and pellets were harvested to study the anti-inflammatory effects by evaluating and measuring their efficacy in inhibiting pro-inflammatory cytokines (TNF-α, IL-6, IL-10, IL-1β) and mediators (ROS, NO, PGE2, COX2, iNOS) through biochemical, ELISA, and mRNA expression studies.

RESULTS

The findings showed that both ERB and VRB effectively inhibited the production of pro-inflammatory markers (TNF-α, IL-6) and mediators (ROS, NO, PGE2) by downregulating mRNA expressions of inflammatory genes (TNF-α, IL-1β, IL-6, IL-10, COX2, iNOS) and demonstrated anti-inflammatory efficacy higher than CRB. On comparison, ERB demonstrated exceptional efficacy by causing a reduction of 48% in ROS, 20% in TNF-α, and 23% in PGE2 at 10 μg/mL, surpassing the anti-inflammatory capabilities of all the bioactive compounds, FA and ORZ, respectively. At the same time, VRB exhibited remarkable efficacy by reducing NO production by 52% at 200 μg/mL and IL-6 by 66% at 10 μg/mL, surpassing FA, CAT, ORZ, and GTP. Further, ERB downregulated the mRNA expression of IL-10 and iNOS, while VRB downregulated TNF-α, IL-1β, and COX2 expression. Both extracts equally downregulated IL-6 expression at 10 μg/mL, demonstrating the efficacy more remarkable/on par with established anti-inflammatory compounds.

CONCLUSIONS

Overall, enzyme-treated rice bran/extract, particularly ERB, possesses excellent anti-inflammatory properties, making them promising agents for alternatives to contemporary nutraceuticals/functional food against inflammatory diseases.

Reduced infiltration of regulatory T cells in tumours from mice fed daily with gamma-tocotrienol supplementation

Gamma-tocotrienol (γT3) is an analogue of vitamin E with beneficial effects on the immune system, including immune-modulatory properties. This study reports the immune-modulatory effects of daily supplementation of γT3 on host T helper (Th) and T regulatory cell (Treg ) populations in a syngeneic mouse model of breast cancer. Female BALB/c mice were fed with either γT3 or vehicle (soy oil) for 2 weeks via oral gavage before they were inoculated with syngeneic 4T1 mouse mammary cancer cells (4T1 cells). Supplementation continued until the mice were euthanized. Mice (n = 6) were euthanized at specified time-points for various analysis (blood leucocyte, cytokine production and immunohistochemistry). Tumour volume was measured once every 7 days. Gene expression studies were carried out on tumour-specific T lymphocytes isolated from splenic cultures. Supplementation with γT3 increased CD4+ (p < 0.05), CD8+ (p < 0.05) T-cells and natural killer cells (p < 0.05) but suppressed Treg cells (p < 0.05) in peripheral blood when compared to animals fed with the vehicle. Higher interferon (IFN)-γ and lower transforming growth factor (TGF)-ꞵ levels were noted in the γT3 fed mice. Immunohistochemistry findings revealed higher infiltration of CD4+ cells, increased expression of interleukin-12 receptor-beta-2 (IL-12ꞵ2R), interleukin (IL)-24 and reduced expression of cells that express the forkhead box P3 (FoxP3) in tumours from the γT3-fed animals. Gene expression studies showed the down-regulation of seven prominent genes in splenic CD4+ T cells isolated from γT3-fed mice. Supplementation with γT3 from palm oil-induced T cell-dependent cell-mediated immune responses and suppressed T cells in the tumour microenvironment in a syngeneic mouse model of breast cancer.

Network Pharmacology Study on Morus alba L. Leaves: Pivotal Functions of Bioactives on RAS Signaling Pathway and Its Associated Target Proteins against Gout

M. alba L. is a valuable nutraceutical plant rich in potential bioactive compounds with promising anti-gouty arthritis. Here, we have explored bioactives, signaling pathways, and key proteins underlying the anti-gout activity of M. alba L. leaves for the first-time utilizing network pharmacology. Bioactives in M. alba L. leaves were detected through GC-MS (Gas Chromatography-Mass Spectrum) analysis and filtered by Lipinski's rule. Target proteins connected to the filtered compounds and gout were selected from public databases. The overlapping target proteins between bioactives-interacted target proteins and gout-targeted proteins were identified using a Venn diagram. Bioactives-Proteins interactive networking for gout was analyzed to identify potential ligand-target and visualized the rich factor on the R package via the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway on STRING. Finally, a molecular docking test (MDT) between bioactives and target proteins was analyzed via AutoDock Vina. Gene Set Enrichment Analysis (GSEA) demonstrated that mechanisms of M. alba L. leaves against gout were connected to 17 signaling pathways on 26 compounds. AKT1 (AKT Serine/Threonine Kinase 1), γ-Tocopherol, and RAS signaling pathway were selected as a hub target, a key bioactive, and a hub signaling pathway, respectively. Furthermore, three main compounds (γ-Tocopherol, 4-Dehydroxy-N-(4,5-methylenedioxy-2-nitrobenzylidene) tyramine, and Lanosterol acetate) and three key target proteins-AKT1, PRKCA, and PLA2G2A associated with the RAS signaling pathway were noted for their highest affinity on MDT. The identified three key bioactives in M. alba L. leaves might contribute to recovering gouty condition by inactivating the RAS signaling pathway.

Comparative Effects of Alpha- and Gamma-Tocopherol on Mitochondrial Functions in Alzheimer's Disease In Vitro Model

Vitamin E acts as an antioxidant and reduces the level of reactive oxygen species (ROS) in Alzheimer's disease (AD). Alpha-tocopherol (ATF) is the most widely studied form of vitamin E besides gamma-tocopherol (GTF) which also shows beneficial effects in AD. The levels of amyloid-beta (Aβ) and amyloid precursor protein (APP) increased in the brains of AD patients, and mutations in the APP gene are known to enhance the production of Aβ. Mitochondrial function was shown to be affected by the increased level of Aβ and may induce cell death. Here, we aimed to compare the effects of ATF and GTF on their ability to reduce Aβ level, modulate mitochondrial function and reduce the apoptosis marker in SH-SY5Y cells stably transfected with the wild-type or mutant form of the APP gene. The Aβ level was measured by ELISA, the mitochondrial ROS and ATP level were quantified by fluorescence and luciferase assay respectively whereas the complex V enzyme activity was measured by spectrophotometry. The expressions of genes involved in the regulation of mitochondrial membrane permeability such as voltage dependent anion channel (VDAC1), adenine nucleotide translocase (ANT), and cyclophilin D (CYPD) were determined by quantitative real-time polymerase chain reaction (qRT-PCR), while the expressions of cyclophilin D (CypD), cytochrome c, Bcl2 associated X (BAX), B cell lymphoma-2 (Bcl-2), and pro-caspase-3 were determined by western blot. Our results showed that mitochondrial ROS level was elevated accompanied by decreased ATP level and complex V enzyme activity in SH-SY5Y cells expressing the mutant APP gene (p < 0.05). Treatment with both ATF and GTF reduced the mitochondrial ROS level with maximum reduction was observed in the cells treated with high concentrations of ATF and GTF (p < 0.05). However, only GTF at 80 µM significantly increase the ATP level and complex V enzyme activity (p < 0.05). VDAC1 and CYPD were downregulated and CypD protein was significantly overexpressed in cells transfected with the wild-type (WT) and mutant APP gene (p < 0.05). Cytochrome c release, the ratio of BAX/Bcl-2, and pro-caspase-3 expression increased in cells expressing mutated APP gene (p < 0.05). The expression of CypD and pro-caspase 3 protein, and the ratio of BAX/Bcl-2 were increased in the following order; SH-SY5Y-APP-WT < SH-SY5Y-APP Swe Collapse

Key Words

• preclinical research
• translational research

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MESH Headings

• Alzheimer Disease/drug therapy
• Alzheimer Disease/metabolism
• Amyloid beta-Peptides/metabolism
• Amyloid beta-Protein Precursor/drug effects
• Amyloid beta-Protein Precursor/metabolism
• Apoptosis/drug effects
• Caspase 3/metabolism
• Cell Line, Tumor
• Cytochromes c/metabolism
• Humans
• Mitochondria/drug effects
• Proto-Oncogene Proteins c-bcl-2/metabolism
• Reactive Oxygen Species/metabolism
• Tocopherols/pharmacology
• alpha-Tocopherol/pharmacology
• gamma-Tocopherol/pharmacology

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Grants

• Universiti Kebangsaan Malaysia DIP/2013/003 Universiti Kebangsaan Malaysia FF-2015-025

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δ-Tocopherol promotes thermogenic gene expression via PGC-1α upregulation in 3T3-L1 cells

Activation of thermogenic adipocytes (brown and beige) has been considered an attractive target for weight loss and treatment of metabolic disease. Peroxisome proliferator-activated receptor γ co-activator-1 α (PGC1-α) is a master regulator of thermogenic gene expression in thermogenic adipocytes. We previously reported that α-tocopherol upregulated PGC-1α gene expression and promoted thermogenic adipocyte differentiation in mammalian adipocytes. In this study, we investigated the effects of the vitamin E analogs (α-, γ- and δ-tocopherol) on PGC-1α and uncoupling protein 1 (UCP1) gene expression in 3T3-L1 cells. The expression of PGC-1α and UCP1 increased significantly with the addition of δ-tocopherol. In δ-tocopherol-treated cells, nuclear translocation of PGC-1α increased, as did p38 mitogen-activated protein kinase (MAPK) expression and phosphorylation. Our results suggest that p38 MAPK activation by δ-tocopherol contributes to PGC-1α activation and UCP1 induction.

Differential Gene Regulation and Tumor-Inhibitory Activities of Alpha-, Delta-, and Gamma-Tocopherols in Estrogen-Mediated Mammary Carcinogenesis

Despite experimental evidence elucidating the antitumor activities of tocopherols, clinical trials with α-tocopherol (α-T) have failed to demonstrate its beneficial effects in cancer prevention. This study compared the chemopreventive efficacy of individual tocopherols (α-, δ-, and γ-T) and a γ-T-rich tocopherol mixture (γ-TmT) in the August-Copenhagen Irish (ACI) rat model of estrogen-mediated mammary cancer. Female ACI rats receiving 17β-estradiol (E2) implants were administered with 0.2% α-T, δ-T, γ-T, or γ-TmT for 30 weeks. Although α-T had no significant effects on mammary tumor growth in ACI rats, δ-T, γ-T, and γ-TmT reduced mammary tumor volume by 51% (P < 0.05), 60% (P < 0.01), and 59% (P < 0.01), respectively. Immunohistochemical analysis revealed that δ-T, γ-T, and γ-TmT reduced levels of the cell proliferation marker, proliferating cell nuclear antigen, in the rat mammary tumors. To gain further insight into the biological functions of different forms of tocopherols, RNA-seq analysis of the tumors was performed. Treatment with γ-T induced robust gene expression changes in the mammary tumors of ACI rats. Ingenuity Pathway Analysis identified "Cancer" as a top disease pathway and "Tumor growth" and "Metastasis" as the top signaling pathways modulated by γ-T. Although the results need further functional validation, this study presents an unbiased attempt to understand the differences between biological activities of individual forms of tocopherols at the whole transcriptome level. In conclusion, δ-T and γ-T have superior cancer preventive properties compared to α-T in the prevention of estrogen-mediated mammary carcinogenesis. Cancer Prev Res; 10(12); 694-703. ©2017 AACR.

Natural Forms of Vitamin E as Effective Agents for Cancer Prevention and Therapy

Initial research on vitamin E and cancer has focused on α-tocopherol (αT), but recent clinical studies on cancer-preventive effects of αT supplementation have shown disappointing results, which has led to doubts about the role of vitamin E, including different vitamin E forms, in cancer prevention. However, accumulating mechanistic and preclinical animal studies show that other forms of vitamin E, such as γ-tocopherol (γT), δ-tocopherol (δT), γ-tocotrienol (γTE), and δ-tocotrienol (δTE), have far superior cancer-preventive activities than does αT. These vitamin E forms are much stronger than αT in inhibiting multiple cancer-promoting pathways, including cyclo-oxygenase (COX)- and 5-lipoxygenase (5-LOX)-catalyzed eicosanoids, and transcription factors such as nuclear transcription factor κB (NF-κB) and signal transducer and activator of transcription factor 3 (STAT3). These vitamin E forms, but not αT, cause pro-death or antiproliferation effects in cancer cells via modulating various signaling pathways, including sphingolipid metabolism. Unlike αT, these vitamin E forms are quickly metabolized to various carboxychromanols including 13'-carboxychromanols, which have even stronger anti-inflammatory and anticancer effects than some vitamin precursors. Consistent with mechanistic findings, γT, δT, γTE, and δTE, but not αT, have been shown to be effective for preventing the progression of various types of cancer in preclinical animal models. This review focuses on cancer-preventive effects and mechanisms of γT, δT, γTE, and δTE in cells and preclinical models and discusses current progress in clinical trials. The existing evidence strongly indicates that these lesser-known vitamin E forms are effective agents for cancer prevention or as adjuvants for improving prevention, therapy, and control of cancer.

γ-Tocotrienol Inhibits Proliferation and Induces Apoptosis Via the Mitochondrial Pathway in Human Cervical Cancer HeLa Cells

γ-Tocotrienol, a kind of isoprenoid phytochemical, has antitumor activity. However, there is limited evidence that it has an effect on cervical cancer. In this study, the capacity to inhibit proliferation and induce apoptosis in human cervical cancer HeLa cells and the mechanism underlying these effects were examined. The results indicated that a γ-tocotrienol concentration over 30 μM inhibited the growth of HeLa cells with a 50% inhibitory concentration (IC₅₀) of 46.90 ± 3.50 μM at 24 h, and significantly down-regulated the expression of proliferative cell nuclear antigen (PCNA) and Ki-67. DNA flow cytometric analysis indicated that γ-tocotrienol arrested the cell cycle at G0/G1 phase and reduced the S phase in HeLa cells. γ-tocotrienol induced apoptosis of HeLa cells in a time- and dose-dependent manner. γ-tocotrienol-induced apoptosis in HeLa cells was accompanied by down-regulation of Bcl-2, up-regulation of Bax, release of cytochrome from mitochondria, activation of caspase-9 and caspase-3, and subsequent poly (ADP-ribose) polymerase (PARP) cleavage. These results suggested that γ-tocotrienol could significantly inhibit cell proliferation through G0/G1 cell cycle arrest, and induce apoptosis via the mitochondrial apoptotic pathway in human cervical cancer HeLa cells. Thus, our findings revealed that γ-tocotrienol may be considered as a potential agent for cervical cancer therapy.

Gamma tocopherol-enriched supplement reduces sputum eosinophilia and endotoxin-induced sputum neutrophilia in volunteers with asthma

BACKGROUND

We and others have shown that the gamma tocopherol (γT) isoform of vitamin E has multiple anti-inflammatory and antioxidant actions and that γT supplementation reduces eosinophilic and endotoxin (LPS)-induced neutrophilic airway inflammation in animal models and healthy human volunteers.

OBJECTIVE

We sought to determine whether γT supplementation reduces eosinophilic airway inflammation and acute neutrophilic response to inhaled LPS challenge in volunteers with asthma.

METHODS

Participants with mild asthma were enrolled in a double-blinded, placebo-controlled crossover study to assess the effect of 1200 mg of γT daily for 14 days on sputum eosinophils, mucins, and cytokines. We also assessed the effect on acute inflammatory response to inhaled LPS challenge following γT treatment, focusing on changes in sputum neutrophilia, mucins, and cytokines. Mucociliary clearance was measured using gamma scintigraphy.

RESULTS

Fifteen subjects with mild asthma completed both arms of the study. Compared with placebo, γT notably reduced pre-LPS challenge sputum eosinophils and mucins, including mucin 5AC and reduced LPS-induced airway neutrophil recruitment 6 and 24 hours after challenge. Mucociliary clearance was slowed 4 hours postchallenge in the placebo group but not in the γT treatment group. Total sputum mucins (but not mucin 5AC) were reduced at 24 hours postchallenge during γT treatment compared with placebo.

CONCLUSIONS

When compared with placebo, γT supplementation for 14 days reduced inflammatory features of asthma, including sputum eosinophils and mucins, as well as acute airway response to inhaled LPS challenge. Larger scale clinical trials are needed to assess the efficacy of γT supplements as a complementary or steroid-sparing treatment for asthma.

Alpha- and Gamma-Tocopherol and Telomere Length in 5768 US Men and Women: A NHANES Study

Antioxidants have a number of potential health benefits. The present investigation was designed to determine the relationship between serum alpha- and gamma-tocopherol levels (powerful antioxidants), and leukocyte telomere length (a biomarker of biological aging). A cross-sectional design was employed to study 5768 adults from the National Health and Nutrition Examination Survey (NHANES). DNA was obtained via blood samples. Telomere length was assessed using the quantitative polymerase chain reaction method. Serum concentrations of alpha- and gamma-tocopherol were measured using high performance liquid chromatography (HPLC). Results showed that for each one-year increase in age, telomeres were 15.6 base pairs shorter (F = 410.4, p < 0.0001). After adjusting for differences in the demographic covariates, for each µg/dL higher level of gamma-tocopherol, telomeres were 0.33 base pairs shorter (F = 7.1, p = 0.0126). Telomeres were approximately 1 year shorter (15.6 base pairs) for each increment of 47.3 to 55.7 µg/dL of gamma-tocopherol in the blood, depending on the variables controlled. Adults at the 75th percentile of gamma-tocopherol had 2.8–3.4 years greater cellular aging than those at the 25th percentile, depending on the covariates in the model. However, alpha-tocopherol was not related to telomere length. Evidently, gamma-tocopherol levels, but not alpha-tocopherol, account for meaningful increases in biological aging.

Inhibitory Effects of γ- and δ-Tocopherols on Estrogen-Stimulated Breast Cancer In Vitro and In Vivo

Estrogens have been implicated as complete carcinogens for breast and other tissues through mechanisms involving increased cell proliferation, oxidative stress, and DNA damage. Because of their potent antioxidant activity and other effects, tocopherols have been shown to exert antitumor activities in various cancers. However, limited information is available on the effect of different forms of tocopherols in estrogen-mediated breast cancer. To address this, we examined the effects of α-, γ-, and δ-tocopherols as well as a natural γ-tocopherol-rich mixture of tocopherols, γ-TmT, on estrogen-stimulated MCF-7 cells in vitro and in vivo For the in vivo studies, MCF-7 cells were injected into the mammary fat pad of immunodeficient mice previously implanted with estrogen pellets. Mice were then administered diets containing 0.2% α-, γ-, δ-tocopherol, or γ-TmT for 5 weeks. Treatment with α-, γ-, δ-tocopherols, and γ-TmT reduced tumor volumes by 29% (P < 0.05), 45% (P < 0.05), 41% (P < 0.05), and 58% (P < 0.01), as well as tumor weights by 20%, 37% (P < 0.05), 39% (P < 0.05), and 52% (P < 0.05), respectively. γ- and δ-tocopherols and γ-TmT inhibited the expression of cell proliferation-related genes such as cyclin D1 and c-Myc, and estrogen-related genes such as TFF/pS2, cathepsin D, and progesterone receptor in estrogen-stimulated MCF-7 cells in vitro Further, γ- and δ-tocopherols decreased the levels of estrogen-induced oxidative stress and nitrosative stress markers, 8-hydroxy-2'-deoxyguanosine and nitrotyrosine, as well as the DNA damage marker, γ-H2AX. Our results suggest that γ- and δ-tocopherols and the γ-tocopherol-rich mixture are effective natural agents for the prevention and treatment of estrogen-mediated breast cancer. Cancer Prev Res; 10(3); 188-97. ©2017 AACR.

Comparable Function of γ-Tocopherols in Asthma Remission by Affecting Eotaxin and IL-4

BACKGROUND

Bronchial asthma is one of the world's most common chronic disorders dangerous to human health. It has been hypothesized that the increased number of asthma sufferers may be due to changing antioxidant intake or vitamin deficiency. However, the influence of vitamins on asthma has rarely been considered.

OBJECTIVES

The aim of this study was to explore the effects of γ-tocopherols, a specific form of vitamin E, on asthma remission together with the possible mechanism behind the process.

MATERIAL AND METHODS

Eosinophil counting was applied to detect the total number of cells, eosinophils and lymphocytes. Meanwhile, HE staining was used for morphological detection. In addition, the eotaxin and IL-4 levels in the serum and bronchoalveolar lavage fluid were measured using ELISA technology.

RESULTS

The cell counting results showed that γ-tocopherols possesses the capability to reduce the number of eosinophils. Moreover, the exudation of inflammatory cells together with the hyperplasia of goblet cells was also found to experience significant inhibition when treated with γ-tocopherols. Furthermore, the high levels of eotaxin and IL-4 in the asthma group were evidently reduced under the treatment of γ-tocopherols which was comparable with hexadecadrol.

CONCLUSIONS

γ-tocopherols can remit asthma by regulating the level of eotaxin and IL-4. Moreover, γ-tocopherols may be regarded as a potential candidate for asthma treatment after much deeper explorations.

Changes in the Bioactive Compounds Content of Soybean as a Function of Grain Moisture Content and Temperature during Long-Term Storage

Soybean is a rich source of bioactive compounds, such as phenolic acids, flavonoids, isoflavones, carotenoids, and tocopherols. The amount of bioactive compounds in freshly harvested soybeans and their derived products has been determined; however, when they are used in the food industry, soybeans are generally stored prior to being processed. This study aimed to evaluate the effects of soybean moisture content (12%, 15%, and 18%) and storage temperature (11, 18, 25, and 32 °C) on the free phenolic, total flavonoid, vanillic acid, total carotenoid, and δ- and γ-tocopherol content of soybeans stored for 12 mo. Moreover, the ABTS and DPPH radical scavenging activities of phenolic extracts were determined. There was an increase in free phenolics and total flavonoids in the stored grains compared with the grains on the 1st d of storage. Vanillic acid showed a decrease in soybeans stored at 15% and 18% moisture content and 25 or 32 °C, which indicated some degradation into other metabolites. Total carotenoid content decreased as a function of storage temperature and showed some temperature-dependent degradation. The δ- and γ-tocopherol content also tended to decrease in grains stored at 15% or 18% moisture content or 25 or 32 °C, regardless of the moisture content studied.

The relationship of antioxidant components and antioxidant activity of sesame seed oil

Although sesame seed oil contains high levels of unsaturated fatty acids and even a small amount of free fatty acids in its unrefined flavored form, it shows markedly greater stability than other dietary vegetable oils. The good stability of sesame seed oil against autoxidation has been ascribed not only to its inherent lignans and tocopherols but also to browning reaction products generated when sesame seeds are roasted. Also, there is a strong synergistic effect among these components. The lignans in sesame seed oil can be categorized into two types, i.e. inherent lignans (sesamin, sesamolin) and lignans mainly formed during the oil production process (sesamol, sesamolinol, etc.). The most abundant tocopherol in sesame seed oil is γ-tocopherol. This article reviews the antioxidant activities of lignans and tocopherols as well as the browning reaction and its products in sesame seed and/or its oil. It is concluded that the composition and structure of browning reaction products and their impacts on sesame ingredients need to be further studied to better explain the remaining mysteries of sesame oil.

Vitamin E: Curse or Benefit in Alzheimer's Disease? A Systematic Investigation of the Impact of α-, γ- and δ-Tocopherol on Aß Generation and Degradation in Neuroblastoma Cells

OBJECTIVES

The E vitamins are a class of lipophilic compounds including tocopherols, which have high antioxidative properties. Because of the elevated lipid peroxidation and increased reactive oxidative species in Alzheimer's disease (AD) many attempts have been made to slow down the progression of AD by utilizing the antioxidative action of vitamin E. Beside the mixed results of these studies nothing is known about the impact of vitamin E on the mechanisms leading to amyloid-β production and degradation being responsible for the plaque formation, one of the characteristic pathological hallmarks in AD. Here we systematically investigate the influence of different tocopherols on Aβ production and degradation in neuronal cell lines.

MEASUREMENTS

Beside amyloid-β level the mechanisms leading to Aβ production and degradation are examined.

RESULTS

Surprisingly, all tocopherols have shown to increase Aβ level by enhancing the Aβ production and decreasing the Aβ degradation. Aβ production is enhanced by an elevated activity of the involved enzymes, the β- and γ-secretase. These secretases are not directly affected, but tocopherols increase their protein level and expression. We could identify significant differences between the single tocopherols; whereas α-tocopherol had only minor effects on Aβ production, δ-tocopherol showed the highest potency to increase Aβ generation. Beside Aβ production, Aβ clearance was decreased by affecting IDE, one of the major Aβ degrading enzymes.

CONCLUSIONS

Our results suggest that beside the beneficial antioxidative effects of vitamin E, tocopherol has in respect to AD also a potency to increase the amyloid-β level, which differ for the analysed tocopherols. We therefore recommend that further studies are needed to clarify the potential role of these various vitamin E species in respect to AD and to identify the form which comprises an antioxidative property without having an amyloidogenic potential.

Gamma-tocopherol attenuates moderate but not severe colitis and suppresses moderate colitis-promoted colon tumorigenesis in mice

Inflammation can promote colon cancer. Mechanistic studies indicate that γ-tocopherol (γT), a major form of vitamin E in diets, has anti-inflammatory and anticancer properties. Here we investigated the effectiveness of γT and a mixture of tocopherols against colitis and colitis-promoted colon tumorigenesis in male BALB/c mice. γT or mixed tocopherols (at 0.1% diet) did not show any effect on colon tumorigenesis induced by azoxymethane (AOM, 10mg/kg) with three cycles of dextran sodium sulfate (DSS at 1.5-2.5%). γT failed to exhibit protection of severe colitis caused by three cycles of DSS at 2.5%. In contrast, when AOM-initiated carcinogenesis was promoted by relatively mild colitis induced by one-cycle DSS (1.5%), γT, but not mixed tocopherols, suppressed total multiplicity of macroscopic adenomas (P=0.06) and large adenomatous polyps (>2mm(2), P<0.05) by 60 and 85%, respectively. γT also significantly decreased tumor multiplicity (>2mm(2)) induced by AOM with two cycles of 1.5% DSS even when dietary supplementation was started after AOM injection. Consistently, γT but not mixed tocopherols attenuated DSS (1.5%)-induced colon inflammation and damage as well as formation of atypical glandular hyperplasia. Mice supplemented with tocopherols had high fecal excretion of 13'-carboxychromanol, a long-chain vitamin E metabolite shown to have potent anti-inflammatory activities. Our study demonstrates that γT is able to alleviate moderate but not severe colitis and its promoted tumorigenesis, and indicates that inflammation severity should be considered in evaluating anticancer effectiveness of chemoprevention agents.

Vitamin E isoforms as modulators of lung inflammation

Asthma and allergic diseases are complex conditions caused by a combination of genetic and environmental factors. Clinical studies suggest a number of protective dietary factors for asthma, including vitamin E. However, studies of vitamin E in allergy commonly result in seemingly conflicting outcomes. Recent work indicates that allergic inflammation is inhibited by supplementation with the purified natural vitamin E isoform α-tocopherol but elevated by the isoform γ-tocopherol when administered at physiological tissue concentrations. In this review, we discuss opposing regulatory effects of α-tocopherol and γ-tocopherol on allergic lung inflammation in clinical trials and in animal studies. A better understanding of the differential regulation of inflammation by isoforms of vitamin E provides a basis towards the design of clinical studies and diets that would effectively modulate inflammatory pathways in lung disease.

The antioxidant and anti-inflammatory activities of tocopherols are independent of Nrf2 in mice

The present study investigated the antioxidant and anti-inflammatory actions of tocopherols in mice and determined whether the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is involved in these activities. A mixture of tocopherols (γ-TmT) that is rich in γ-tocopherol was used. Nrf2 knockout (Nrf2 -/-) and wild-type mice were maintained on 0.03, 0.1, or 0.3% γ-TmT-enriched diet starting 2 weeks before the administration of dextran sulfate sodium (DSS) in drinking water (for 1 week, to induce colonic inflammation), until the termination of the experiment at 3 days after the DSS treatment. Dietary γ-TmT dose dependently lowered the levels of 8-oxo-deoxyguanosine, nitrotyrosine, inflammation index, and leukocyte infiltration in colon tissues, as well as 8-isoprostane and prostaglandin E2 in the serum, in both Nrf2 (-/-) and wild-type mice. No significant difference on the inhibitory actions of γ-TmT between the Nrf2 (-/-) and the wild-type mice was observed. The γ-TmT treatment significantly increased the serum levels of γ- and δ-tocopherols. Interestingly, the serum levels of tocopherol metabolites, specifically the γ- and δ-forms of carboxymethylbutyl hydroxychroman and carboxyethyl hydroxychroman, in Nrf2 (-/-) mice were significantly higher than those in wild-type mice. These findings suggest that the antioxidant and anti-inflammatory activities of γ-TmT in the colon are mostly due to the direct action of tocopherols in trapping reactive oxygen and nitrogen species, independent of the antioxidant enzymes and anti-inflammatory proteins that are regulated by Nrf2; however, Nrf2 knockout appears to affect the serum levels of tocopherol metabolites.

Effect of tocopherol supplementation during last trimester of pregnancy on mRNA abundances of interleukins and angiogenesis in ovine placenta and uterus

BACKGROUND

Interleukins (IL) play an important role in angiogenesis. Tocopherol possesses immunomodulating effect in addition to antioxidant property. The objective of this study was to determine whether gamma tocopherol's (gT) angiogenic activity in placental network is enhanced via promoting interleukins.

METHODS

Pregnant ewes (N=18) were supplemented, orally, with 500 mg of alpha tocopherol (aT; N=6) or 1,000 mg of gT (N=7) or placebo (CON; N=5) once daily from 107 to 137 days post breeding. Uterine and placental tissue samples were obtained at the end of supplementation to evaluate relative mRNA expressions of IL-1b, IL-6, IL-8, Tumor Necrosis Factor (TNF) alpha, Vascular Endothelial Growth Factor (VEGF), kinase insert domain receptor (KDR; VGFR2; a type III receptor tyrosine kinase), and soluble fms-like tyrosine kniase-1 (sFlt1 or sVEGFR1) in uterus, caruncle and cotyledon.

RESULTS

Oral supplementation of gT increased IL-6, IL-8, KDR and VEGF mRNA abundances whereas sFlt1 mRNA abundance was suppressed in uterus, caruncle and cotyledon, compared to aT and placebo treated ewes (P<0.05). The TNF alpha and IL-1b mRNA abundances were suppressed in uterus, caruncle and cotyledon but TNF alpha is higher in gT group compared to aT group (P<0.05), whereas IL-1b was similar between treatment groups (P>0.1).

CONCLUSIONS

Gamma tocopherol supplementation increased IL-6, IL-8, and KDR mRNA abundances and suppressed sFlt1 and TNFalpha mRNA abundances thereby increased VEGF mRNA expression and angiogenesis in placental vascular network during late gestation. It is plausible that the angiogenic effect of gamma tocopherol in placental vascular network is exerted via an alternate path by enhancing IL-6 and IL-8.

Chemopreventive activity of vitamin E in breast cancer: a focus on γ- and δ-tocopherol

Vitamin E consists of eight different variants: α-, β-, γ-, and δ-tocopherols (saturated phytyl tail) and α-, β-, γ-, and δ-tocotrienols (unsaturated phytyl tail). Cancer prevention studies with vitamin E have primarily utilized the variant α-tocopherol. To no avail, a majority of these studies focused on variant α-tocopherol with inconsistent results. However, γ-tocopherol, and more recently δ-tocopherol, have shown greater ability to reduce inflammation, cell proliferation, and tumor burden. Recent results have shown that γ-enriched mixed tocopherols inhibit the development of mammary hyperplasia and tumorigenesis in animal models. In this review, we discuss the possible differences between the variant forms, molecular targets, and cancer-preventive effects of tocopherols. We recommend that a γ-enriched mixture, γ- and δ-tocopherol, but not α-tocopherol, are promising agents for breast cancer prevention and warrant further investigation.

Antiseptic activity and phenolic constituents of the aerial parts of Vitex negundo var. cannabifolia

Four phenolics, salviaplebeiaside (1), γ-tocopherol (2), chrysosplenol-D (4), and isovitexin (5), along with α-tocoquinone (3) and β-sitosterol (6) were isolated from the aerial parts of Vitex negundo var. cannabifolia. The isolation was performed using bio-assay tracking experiments. The structures of compounds 1-5 were established by spectroscopic means. The antibacterial activities of the compounds were assessed against Escherichia coli, Bacillus subtilis, Micrococcus tetragenus and Pseudomonas fluorescens. Chrysosplenol-D (4) exhibited activities against all the four spoilage microorganisms.

Vitamin E decreases endogenous cholesterol synthesis and apo-AI-mediated cholesterol secretion in Caco-2 cells

Intestine is the gateway for newly absorbed tocopherols. This organ also plays a crucial role in cholesterol metabolism. Because tocopherols are known to impact cholesterol metabolism in the liver, we hypothesized that tocopherols could also modulate cholesterol metabolism in the intestine. This study aimed to verify this hypothesis and to unveil the mechanisms involved, using Caco-2 cells as a model of the human intestinal cell. Both α- and γ-tocopherol significantly (P<.05) decreased endogenous cholesterol synthesis and apo-AI-mediated cholesterol secretion in Caco-2 cells. Tocopherols down-regulated (P<.05) up to half of the genes involved in the cholesterol synthesis pathway, together with CYP27A1, which is involved in oxysterol production. The activity of this enzyme, as well as the levels of intracellular oxysterols, was significantly diminished by tocopherols. Finally, tocopherols significantly reduced ABCA1 mRNA levels in Caco-2 cells. We conclude that tocopherols impair the endogenous synthesis and apo-AI-mediated secretion of cholesterol in Caco-2 cells. This effect involves a down-regulation of genes involved in the cholesterol synthesis pathway, resulting in down-regulation of CYP27A1 which, in turn, diminishes oxysterol concentrations. The outcome is a decrease of LXR activity, resulting in down-regulation of ABCA1. These data reinforce the effect of α- and γ-tocopherol on cholesterol metabolism via gene expression regulation.

Anticancer actions of natural and synthetic vitamin E forms: RRR-alpha-tocopherol blocks the anticancer actions of gamma-tocopherol

Two naturally occurring dietary sources of vitamin E (i.e. RRR-alpha-tocopherol (alphaT) and RRR-gamma-tocopherol (gammaT)), the manufactured synthetic form of vitamin E, all-racemic-alpha-tocopherol (all-rac-alphaT), as well as a potent antitumor analog of vitamin E, RRR-alpha-tocopherol ether-linked acetic acid analog (alpha-TEA), were assessed for anticancer actions. Data showed that gammaT, all-rac-alphaT, and alpha-TEA but not alphaT or alphaT+gammaT significantly inhibited tumor burden of human MDA-MB-231 cells in nude mice. Immunohistochemical analyses of tumor tissue showed that all-rac-alphaT and alpha-TEA increased apoptosis and decreased proliferation in tumor cells while gammaT was associated with increased tumor cell apoptosis only. In vitro data showed alpha-TEA and gammaT but not all-rac-alphaT or alphaT to inhibit colony formation and induce apoptosis. Anticancer actions of alpha-TEA and gammaT involved death receptor 5 protein upregulation, Survivin protein downregulation and poly (ADP-ribose) polymerase cleavage, all of which were blocked by co-treatment with alphaT. In summary, both gammaT and alpha-TEA exhibited promising anticancer properties in vivo and in vitro, whereas all-rac-alphaT exhibited promising anticancer properties in vivo only. Importantly, alphaT not only failed to exhibit anticancer properties but it also reduced anticancer actions of gammaT in vivo and gammaT and alpha-TEA in vitro.

In vivo gamma-tocopherol supplementation decreases systemic oxidative stress and cytokine responses of human monocytes in normal and asthmatic subjects

We have recently reported that gamma-tocopherol (gammaT) reduces allergen- and zymosan-induced inflammation using rodent models. As an initial step in extending these observations to humans, we conducted an open-label, Phase I dosing study of two doses (one or two capsules daily for 1 week) of a gamma-tocopherol-rich preparation containing 623 mg of gamma-tocopherol, 61.1 mg of d-alpha-tocopherol, 11.1 mg of d-beta-tocopherol (11.1 mg), and 231 mg of d-sigma-tocopherol per capsule. Endpoints for this study include serum levels of 5-nitro-gamma-tocopherol, as a marker of oxidative stress, and changes in serum gamma-, alpha-, and delta-tocopherol and gamma-2'-carboxyethyl-6-hydroxychroman (CEHC) 6 and 24 h after the first dose and after 1 week of treatment. To assess the biological activity of this treatment, we obtained peripheral blood mononuclear cells at baseline and after 1 week of treatment with two capsules of a gamma-tocopherol-rich preparation/day and examined the inflammatory cytokine response of these cells in culture to ex vivo endotoxin/LPS (0.01 ng/ml) challenge. We also monitored a number of safety endpoints to examine how well this preparation is tolerated in eight normal volunteers (four allergic and four nonallergic) and eight allergic asthmatics. We further obtained human monocytes from a subset of these volunteers and treated them ex vivo with gammaT, alphaT, gamma-CEHC, and alpha-CEHC and assessed their actions on LPS-induced degradation of IkappaBalpha and JNK signaling and ROS generation. As detailed herein, this open-label study demonstrates that gamma-tocopherol-enriched supplementation decreased systemic oxidative stress, increased serum levels of gamma-tocopherol, and inhibited monocyte responses to LPS without any adverse health effects. Further, in vitro treatment of human monocytes with gamma-CEHC and alpha-CEHC inhibits ROS generation and LPS-induced degradation of IkappaB and JNK activation.

alpha- and gamma-Tocopherol prevent age-related transcriptional alterations in the heart and brain of mice

We used high-density oligonucleotide arrays to measure transcriptional alterations in the heart and brain (neocortex) of 30-mo-old B6C3F(1) mice supplemented with alpha-tocopherol (alphaT) and gamma-tocopherol (gammaT) since middle age (15 mo). Gene expression profiles were obtained from 5- and 30-mo-old control mice and 30-mo-old mice supplemented with alphaT (1 g/kg) or a mixture of alphaT and gammaT (500 mg/kg of each tocopherol) from middle age (15 mo). In the heart, both tocopherol-supplemented diets were effective in inhibiting the expression of genes previously associated with cardiomyocyte hypertrophy and increased innate immunity. In the brain, induction of genes encoding ribosomal proteins and proteins involved in ATP biosynthesis was observed with aging and was markedly prevented by the mixture of alphaT and gammaT supplementation but not by alphaT alone. These results demonstrate that middle age-onset dietary supplementation with alphaT and gammaT can partially prevent age-associated transcriptional changes and that these effects are tissue and tocopherol specific.

Gamma-tocopherol supplementation alone and in combination with alpha-tocopherol alters biomarkers of oxidative stress and inflammation in subjects with metabolic syndrome

Metabolic syndrome (MetS) is associated with increased incidence of diabetes and cardiovascular disease (CVD). Prospective clinical trials with alpha-tocopherol (AT) have not yielded positive results. Because AT supplementation decreases circulating gamma-tocopherol (GT), we evaluated supplementation with GT (800 mg/day), AT (800 mg/day), the combination or placebo for 6 weeks alone AT and GT concentrations, biomarkers of oxidative stress, and inflammation in subjects with MetS (n=20/group). Plasma AT and GT levels increased following supplementation with AT alone or GT alone or in combination. AT supplementation significantly decreased GT levels. Urinary alpha- and gamma-CEHC, metabolites of the respective Ts, also increased correspondingly, i.e., alpha-CEHC with AT and gamma-CEHC with GT supplementation, compared to placebo. HsCRP levels significantly decreased in the combined AT+GT group. LPS-activated whole blood release of IL-1 and IL-6 did not change. There was a significant decrease in TNF with AT alone or in combination with GT. Plasma MDA/HNE and lipid peroxides were significantly decreased with AT, GT, or in combination. Nitrotyrosine levels were significantly decreased only with GT or GT+AT but not with AT compared to placebo. Thus, the combination of AT and GT supplementation appears to be superior to either supplementation alone on biomarkers of oxidative stress and inflammation and needs to be tested in prospective clinical trials to elucidate its utility in CVD prevention.

Effect of apoE genotype and vitamin E on biomarkers of oxidative stress in cultured neuronal cells and the brain of targeted replacement mice

The aetiology of apoE4 genotype-Alzheimer's disease (AD) association are complex. The current study emphasizes the impact of apoE genotype and potential beneficial effects of vitamin E (VE) in relation to oxidative stress. Agonist induced neuronal cell death was examined 1) in the presence of conditioned media containing equal amounts of apoE3 or apoE4 obtained from stably transfected macrophages, and 2) after pretreatment with alpha- and gamma-tocopherol, and -tocotrienol. ApoE3 and apoE4 transgenic mice were fed a diet poor or rich in VE to study the interplay of both apoE genotype and VE status, on membrane lipid peroxidation, antioxidative enzyme activity and glutathione levels in the brain. Cytotoxicity of hydrogen peroxide and glutamate was higher in neuronal cells cultured with apoE4 than apoE3 conditioned media. VE pre-treatment of neurons counteracted the cytotoxicity of a peroxide challenge but not of nitric oxide. No significant effects of apoE genotype or VE supplementation were observed on lipid peroxidation or antioxidative status in the brain of apoE3 and apoE4 mice. VE protects against oxidative insults in vitro, however, no differences in brain oxidative status were observed in mice. Unlike in cultured cells, apoE4 may not contribute to higher neuronal oxidative stress in the brain of young targeted replacement mice.

RRR-gamma-tocopherol induces human breast cancer cells to undergo apoptosis via death receptor 5 (DR5)-mediated apoptotic signaling

Goal of this study was to investigate the pro-apoptotic properties of RRR-gamma-tocopherol (gammaT) in human breast cancer cells. gammaT was shown to induce cancer cells but not normal cells to undergo apoptosis, sensitize cancer cells to Tumor necrosis factor-Related Apoptosis-Inducing Ligand (TRAIL)-induced apoptosis, and increase death receptor 5 (DR5) mRNA, protein and cell surface expression. Knockdown of DR5 attenuated gammaT-induced apoptosis. Investigations of post-receptor signaling showed: caspase-8, Bid and Bax activation, increases in mitochondria permeability, cytochrome c release and caspase-9 activation. Thus, gammaT is a potent pro-apoptotic agent for human breast cancer cells inducing apoptosis via activation of DR5-mediated apoptotic pathway.

Isolation and identification of novel estrogenic compounds in yam tuber (Dioscorea alata Cv. Tainung No. 2)

Yam (Dioscorea spp.) is a common food in tropical areas and has been shown to improve the status of sex hormone in postmenopausal women. In this study, the estrogenic activity of yam was examined and active compounds were isolated and identified based on ligand-dependent transcriptional activation through estrogen receptors. Ethyl acetate extracts of various species/varieties of yam were found to activate estrogen receptors alpha and beta to various extents. The extract of Dioscorea alata cv. Tainung No. 2 tuber was fractionated by repeated silica gel column chromatography. The active compounds were isolated and purified by preparative HPLC. Based on NMR and mass spectrometry, two new compounds, hydro-Q(9) chromene (1) and gamma-tocopherol-9 (2), together with three known compounds, RRR-alpha-tocopherol (3), coenzyme Q(9) (4), and 1-feruloylglycerol (5), were identified and shown to activate human ERalpha and beta. These results provide basic evidence for the beneficial effect of yam for menopausal women.

Ascorbyl palmitate, gamma-tocopherol, and EDTA affect lipid oxidation in fish oil enriched salad dressing differently

The aim of the study was to investigate the ability of gamma-tocopherol, ethylenediaminetetraacetate (EDTA), and ascorbyl palmitate to protect fish oil enriched salad dressing against oxidation during a 6 week storage period at room temperature. The lipid-soluble gamma-tocopherol (220 and 880 microg g-1 of fish oil) reduced lipid oxidation during storage by partly retarding the formation of lipid hydroperoxides (PV) and by decreasing the concentrations of individual volatile oxidation products by 34-39 and 42-66%, respectively. EDTA (10 and 50 microg g-1 of dressing) was the most efficient single antioxidant, and overall peroxide values and volatiles were reduced by approximately 70 and 77-86%, respectively. Conversely, prooxidant effects were observed with a high concentration of ascorbyl palmitate (300 microg g-1 of fish oil), whereas a low concentration was slightly antioxidative (50 microg/g of fish oil). Finally, a combination of all three antioxidants completely inhibited oxidation during storage, indicating that the prooxidant effects of ascorbyl palmitate were reverted or overshadowed by EDTA and gamma-tocopherol.

Mixed tocopherols inhibit azoxymethane-induced aberrant crypt foci in rats

Gamma (gamma) tocopherol, but not alpha (alpha) tocopherol (vitamin E), has previously been reported as an effective inhibitor of cyclooxygenase (COX) enzyme activity. In a pilot study of 17 rats, mixed tocopherols containing more than 50% gamma-tocopherol, added at 0.1% to an AIN-76A diet, produced a significant inhibition (about 55%) of azoxymethane-induced aberrant crypt foci in the colon of rats. Mixed tocopherols also reduced tetradecanoyl phorbol acetate-induced ear inflammation in mice when topically applied.

Effect of the main dietary antioxidants (carotenoids, gamma-tocopherol, polyphenols, and vitamin C) on alpha-tocopherol absorption

OBJECTIVE

(R,R,R)-alpha-tocopherol is a fat-soluble antioxidant vitamin generally ingested with other dietary antioxidants. The objective of this study was to assess whether the main dietary antioxidant classes, that is carotenoids, polyphenols, vitamin C and gamma-tocopherol, affect the intestinal absorption of alpha-tocopherol. METHODS, DESIGN AND SUBJECTS: We evaluated first the effect of different combinations of antioxidants on (R,R,R)-alpha-tocopherol absorption by a human intestinal cell line (Caco-2 clone TC7). Then we compared the effect of two doses of a dietary antioxidant (lutein) on the postprandial chylomicron alpha-tocopherol responses to an alpha-tocopherol-rich meal. Eight healthy men ate two similar meals in a random order at a 1 month interval. The meals contained 24 mg alpha-tocopherol in sunflower oil plus either 18 or 36 mg lutein. Blood samples were collected during the postprandial periods to compare chylomicron alpha-tocopherol responses.

RESULTS

A mixture of polyphenols (gallic acid, caffeic acid, (+)-catechin and naringenin) and a mixture of carotenoids (lycopene, beta-carotene and lutein) significantly impaired alpha-tocopherol absorption in Caco-2 cells (P<0.001 and P<0.0001, respectively). The inhibitory effect of gamma-tocopherol was close to significance (P=0.055). In contrast, vitamin C had no significant effect (P=0.158). Naringenin was the only polyphenol that significantly impaired alpha-tocopherol absorption. Postprandial alpha-tocopherol response was weakest at the highest dose of lutein (616+/-280 nmol/l h vs 1001+/-287 nmol/l h). The observed extent of reduction (-38%, P=0.069) supported the inhibitory effect of carotenoids observed in the Caco-2 experiments.

CONCLUSION

Naringenin, carotenoids and probably gamma-tocopherol can impair alpha-tocopherol absorption whereas vitamin C and phenolic acids have no effect.

Anti-inflammatory properties of alpha- and gamma-tocopherol

Natural vitamin E consists of four different tocopherol and four different tocotrienol homologues (alpha,beta, gamma, delta) that all have antioxidant activity. However, recent data indicate that the different vitamin E homologues also have biological activity unrelated to their antioxidant activity. In this review, we discuss the anti-inflammatory properties of the two major forms of vitamin E, alpha-tocopherol (alphaT) and gamma-tocopherol (gammaT), and discuss the potential molecular mechanisms involved in these effects. While both tocopherols exhibit anti-inflammatory activity in vitro and in vivo, supplementation with mixed (gammaT-enriched) tocopherols seems to be more potent than supplementation with alphaT alone. This may explain the mostly negative outcomes of the recent large-scale interventional chronic disease prevention trials with alphaT only and thus warrants further investigation.

Enhanced anti-proliferative effects of combinatorial treatment of delta-tocopherol and resveratrol in human HMC-1 cells

The tocopherols (alpha, beta-, gamma-, and delta-tocopherol) and resveratrol are phytochemicals with alleged beneficial effects against atherosclerosis, vascular diseases and different cancers. They both can act as antioxidants, but they also modulate signal transduction and gene expression by non-antioxidant mechanisms. Here we wanted to determine whether the combined treatment of mast cells with the two compounds inhibits cell proliferation more efficiently when compared to individual treatments. Both compounds inhibit HMC-1 mastocytoma cell proliferation and reduce the activity of Protein Kinase B (PKB/Akt) by inhibiting its Ser473-phosphorylation. The combination of 50 microM delta-tocopherol and 50 microM resveratrol inhibits proliferation of HMC-1 cells more efficiently when compared to single treatments. In line with this, PKB Ser473-phosphorylation is inhibited best by delta-tocopherol and resveratrol combinatory treatment. Resveratrol acts more efficiently as an inhibitor of PKB phosphorylation than alpha-, beta-, gamma-tocopherols, whereas delta-tocopherol shows a stronger inhibition possibly as a result of its apoptotic secondary effects. Our data suggest that delta-tocopherol and resveratrol can act additively in reducing cell proliferation and PKB phosphorylation. The combination of phytochemicals with relatively broad specificity on enzymes involved in signal transduction and gene expression may increase their activity in disease prevention by modulating several different molecular targets.

Does gamma-tocopherol play a role in the primary prevention of heart disease and cancer? A review

Vitamin E consists of a group of eight isomers, four tocopherols (alpha-, beta-, gamma-, delta-tocopherol) and four tocotrienols (alpha-, beta-, gamma-, delta-tocotrienol). While extensive literature has been published on the potential health benefits of alpha-tocopherol, little is known about gamma-tocopherol, the major form of vitamin E in food in the U.S. gamma-tocopherol has recently received more research attention based on findings from in vitro and animal studies indicating that it has potent anti-inflammatory and antioxidant properties. Based on these recent studies, it is important to investigate the possible health benefits of gamma-tocopherol in humans. In this article, we review publications on dietary gamma-tocopherol intake, plasma gamma-tocopherol levels, cardiovascular disease and cancer risk in humans.

Comparative approaches to facilitate the discovery of prolongevity interventions: effects of tocopherols on lifespan of three invertebrate species

Many compounds hold promise for pharmacologic manipulation of aging. However, such claims are difficult to investigate due to time and budget constraints. Here, we took a comparative approach, using short-lived invertebrate species, to directly test the effects of two tocopherols (Vitamin E) on longevity. gamma-Tocopherol represents the most abundant tocopherol in the Western diet, while alpha-tocopherol is selectively enriched in human plasma. Both isoforms demonstrate antioxidant activity and are proposed to have anti-aging activities. We compared the effects of alpha- and gamma-tocopherol supplementation on lifespan in three invertebrate species. gamma-Tocopherol, but not alpha-tocopherol, slightly extended lifespan in nematodes, but neither significantly affected lifespan in two fly species. This study shows that a comparative approach, utilizing multiple invertebrate species, can increase the robustness of invertebrate-based pilot screens for prolongevity interventions.

UVB-induced Skin Damage and the Protection/Treatment —Effects of a Novel, Hydrophilic γ-Tocopherol Derivative

Ultraviolet radiation is the major environmental cause of skin damage. Although only 0.5% of ultraviolet B (UVB) radiation reaches the earth, it is the main cause of sunburn and inflammation and the most carcinogenic constituent of sunlight. We investigated whether the topical application of a novel, water-soluble gamma-tocopherol (gamma-Toc) derivative, gamma-tocopherol-N,N-dimethylglycinate hydrochloride (gamma-TDMG), could protect against UV-induced skin damage. Topical pre- or postapplication of gamma-TDMG solution significantly prevented sunburn cell formation, lipid peroxidation, and edema/inflammation that were induced by exposure to a single dose of UV irradiation. Cyclooxygenase-2 (COX-2)-catalyzed synthesis of prostaglandin E(2) (PGE(2)) levels seen after UV exposure were significantly suppressed by pre- or posttreatment with gamma-TDMG. The increase in COX-2 activity was significantly inhibited by gamma-TDMG, suggesting that the reduction in PGE(2) concentration was due to the direct inhibition of COX-2 activity by gamma-TDMG. The derivative strongly inhibited inducible nitric oxide synthase mRNA expression and nitric oxide production. With the application of gamma-TDMG, the pigmentation in melanocytes was lightened and the increase melanin concentration was suppressed. Gamma-TDMG is converted to gamma-Toc in the skin and has higher bioavailability than gamma-Toc itself. These results suggest that gamma-TDMG-derived gamma-Toc acts as an antioxidant, antiinflammatory and antipigmentation agent. Our data further suggest that the topical application of gamma-TDMG may be efficacious in preventing and reducing UV-induced skin damage in humans.

A new wrinkle on topical vitamin E and photo-inflammation: Mechanistic studies of a hydrophilic gamma-tocopherol derivative compared with alpha-tocopherol

The antioxidant function of vitamin E is thought to mediate its photo-protective effects. Cyclooxygenase-2 (COX-2) is an important mediator of early photo-inflammation. Thus, the ability of gamma-tocopherol to inhibit COX-2 activity independently of its antioxidant function raises important questions regarding potential roles that this form of vitamin E plays in photo-protection and skin cancer chemoprevention.

gamma-tocopherol, but not alpha-tocopherol, potently inhibits neointimal formation induced by vascular injury in insulin resistant rats

Insulin resistance may enhance the neointima formation via increased oxidative stress. However, clinical trials investigating the benefit of antioxidant therapy with alpha-tocopherol showed negative results. Recent studies showed that chemical characteristics of gamma-tocopherol are distinct from those of alpha-tocopherol. We hypothesized that gamma-tocopherol is superior to alpha-tocopherol in preventing the neointima growth after arterial injury in insulin resistance. Male rats were fed with standard chow or a high fructose diet for induction of insulin resistance. Thereafter, the left carotid artery was injured with a balloon catheter. After 2 weeks, the carotid arteries were harvested and histomorphometrically analyzed. The neointima-media ratio of the injured artery was significantly greater in insulin resistance group (n=8, 1.33+/-0.12) than in normal group (n=10, 0.76+/-0.11, p<0.01). gamma-Tocopherol (100 mg/kg/day) reduced the ratio (n=5, 0.55+/-0.21, p<0.01 vs. insulin resistance group), while alpha-tocopherol was without effect (n=7, 1.08+/-0.14). The quantification of plasma phosphatidylcholine hydroperoxide, an indicator of systemic oxidative stress, and dihydroethidium fluorescence staining of the carotid artery, an indicator of the local superoxide production, showed that oxidative stress in the systemic circulation and local arterial tissue was increased in insulin resistance. Both tocopherols decreased plasma phosphatidylcholine hydroperoxide, but failed to suppress the superoxide production in the carotid arteries. Increased 3-nitrotyrosine in neointima by insulin resistance was greatly reduced only by gamma-tocopherol. In conclusion, gamma-tocopherol, but not alpha-tocopherol, reduces the neointima proliferation in insulin resistance, independently of its effects on superoxide production. The beneficial effect may be related with its inhibitory effects on nitrosative stress.

gamma-Tocopherol attenuates MPTP-induced dopamine loss more efficiently than alpha-tocopherol in mouse brain

Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated mouse has been widely used as a rodent model of Parkinson's disease. In this study, alpha-tocopherol (alphaT) transfer protein knockout (heteromutant type, alpha-TTP((+/-))) mice were used to evaluate the protective effects of alphaT and gamma-tocopherol (gammaT) against MPTP-induced neurotoxicity. The intraperitoneal administration of MPTP to mice induced a decrease in the striatal levels of dopamine (DA) 3 days after the administration in both alpha-TTP((+/-)) and wild-type mice; these mice were fed an alphaT-deficient diet for 3 weeks before the MPTP administration. The DA levels in the alpha-TTP((+/-)) mice, which had been fed a gammaT-fortified diet (0.10 wt.%) for 3 weeks and were administered with MPTP, were recovered to those of the control, whereas there was no significant protective effect of alphaT despite the considerably higher striatal concentration of alphaT than gammaT. The immunohistochemical study also revealed that gammaT exerted a protective effect against neurodegenerative toxicity of MPTP. Collectively, this is the first report showing that the protective effect of gammaT is stronger than that of alphaT against the MPTP-induced damage of dopaminergic neurons in the mouse.

Topical application of a novel, hydrophilic gamma-tocopherol derivative reduces photo-inflammation in mice skin

We previously demonstrated that a novel hydrophilic gamma-tocopherol (gamma-Toc) derivative, gamma-tocopherol-N,N-dimethylglycinate hydrochloride (gamma-TDMG) converts to gamma-Toc in the mouse skin and has a higher bioavailability than gamma-Toc itself. In the present study, we determined whether gamma-TDMG could reduce photo-inflammation in mouse skin, and compared its effectiveness to that of alpha-Toc acetate (alpha-TA). Topical pre- or post-application of 5% gamma-TDMG significantly reduced the formation of edema and tempered the increase in cyclooxygenase-2 (COX-2)-catalyzed synthesis of prostaglandin E2 (PGE2) that were induced by a single dose of UV irradiation of 2 kJ/m2 (290-380 nm, maximum 312 nm). The pre-treatment of mouse skin with 10% alpha-TA had the same anti-inflammatory effect as did gamma-TDMG. In spite of same having the ability to reduce PGE2 levels, the effect of gamma-TDMG pre-treatment on the inhibition of COX-2 mRNA/protein expression was less than that seen with 10% alpha-TA. In contrast, the increase in COX-2 activity seen after UV exposure was reduced more by gamma-TDMG than by alpha-TA, suggesting that the reduction in PGE2 levels might have been due to the direct inhibition of COX-2 activity by gamma-TDMG-derived gamma-Toc. Both Toc derivatives strongly suppressed inducible nitric oxide synthase (iNOS) mRNA expression and nitric oxide (NO) production, both of which play important roles in UV-induced inflammation. Both derivatives also significantly reduced lipid peroxidation in response to UV exposure, though gamma-TDMG's ability in this regard was less than that seen with alpha-TA, which correlated with their abilities to suppress COX-2 expression. Thus, the gamma-TDMG-derived gamma-Toc acts as an antioxidant, suppresses iNOS expression and directly inhibits COX-2 activity, all of which likely play a role in mediating its suppressive effects on photo-inflammation. Our data further suggest that the topical application of gamma-TDMG, a novel hydrophilic gamma-Toc derivative, may be efficacious in preventing and reducing UV-induced inflammation in humans.

Protective effects of vitamin E forms (alpha-tocopherol, gamma-tocopherol and d-alpha-tocopherol polyethylene glycol 1000 succinate) on retinal edema during ischemia-reperfusion injury in the guinea pig retina

PURPOSE

The purpose of this study is to provide evidence that free radical damage is a component of retinal ischemia-reperfusion (I/R) injury, and to determine whether alpha-tocopherol, gamma-tocopherol and d-alpha-tocopherol polyethylene glycol 1000 succinate (TPGS) can protect the retina from this injury.

METHODS

The right eyes of 40 male guinea pigs weighing 500-600 g were used. The animals were randomly assigned to group 1 (control), group 2 (I/R), group 3 (I/R plus alpha-tocopherol), group 4 (I/R plus gamma-tocopherol) and group 5 (I/R plus TPGS). Groups 3, 4 and 5 received four subcutaneous injections at six-hour intervals for total dosage of 800 IU/kg alpha-tocopherol, 1000 IU/kg gamma-tocopherol and 750 IU/kg TPGS, respectively. The first dose of each substance was administered 5 minutes before retinal ischemia. Retinal ischemia was induced for 90 minutes, then followed by reperfusion for 24 hours. Injections of three substances were repeated at 6, 12 and 18 hours during reperfusion. The animals were killed at 24 hours of reperfusion. Sagittal sections of 4 microm were cut and stained with hematoxylin and eosin for light microscopic evaluation. The average thickness (edema) of the inner plexiform layer for each eye was measured in sagittal sections near the optic nerve and expressed in microns.

RESULTS

All the three substances showed statistically significant protection against the formation of retinal edema during ischemia-reperfusion injury. The mean thickness of the inner plexiform layer were 15.0, 25.44, 19.81, 21.38 and 20.88 microm in control, I/R, I/R plus alpha-tocopherol, I/R plus gamma-tocopherol and I/R plus TPGS groups, respectively. The results showed that the thickness of the inner plexiform layer in group 1 (control) was significantly lower than the other groups (p<0.001). The inner plexiform layer was thicker in the I/R group than with I/R plus alpha-tocopherol (p<0.001), I/R plus gamma-tocopherol (p<0.001) and I/R plus TPGS (p<0.01). The inner plexiform layer was not thicker in the I/R plus TPGS group than in the I/R plus alpha-tocopherol and I/R plus gamma-tocopherol groups. Compared to the I/R plus alpha-tocopherol group, the inner plexiform layer was significantly thicker in the I/R plus gamma-tocopherol group (p<0.01).

CONCLUSIONS

The results from these experiments indicate that vitamin E forms have protective effects on the retina during retinal ischemia-reperfusion injury, but, the effects of alpha-tocopherol and TPGS appear to be much greater than that of gamma-tocopherol.

Comparative effects of RRR-alpha- and RRR-gamma-tocopherol on proliferation and apoptosis in human colon cancer cell lines

Background

Mediterranean societies, with diets rich in vitamin E isoforms, have a lower risk for colon cancer than those of northern Europe and the Americas. Vitamin E rich diets may neutralize free radicals generated by fecal bacteria in the gut and prevent DNA damage, but signal transduction activities can occur independent of the antioxidant function. The term vitamin E represents eight structurally related compounds, each differing in their potency and mechanisms of chemoprevention. The RRR-γ-tocopherol isoform is found primarily in the US diet, while RRR-α-tocopherol is highest in the plasma.

Methods

The effectiveness of RRR-α- and RRR-γ-tocopherol at inhibiting cell growth and inducing apoptosis in colon cancer cell lines with varying molecular characteristics (SW480, HCT-15, HCT-116 and HT-29) and primary colon cells (CCD-112CoN, nontransformed normal phenotype) was studied. Colon cells were treated with and without RRR-α- or RRR-γ-tocopherol using varying tocopherol concentrations and time intervals. Cell proliferation and apoptosis were measured using the trypan blue assay, annexin V staining, DNA laddering and caspase activation.

Results

Treatment with RRR-γ-tocopherol resulted in significant cell death for all cancer cell lines tested, while RRR-α-tocopherol did not. Further, RRR-γ-tocopherol treatment showed no cytotoxicity to normal colon cells CCD-112CoN at the highest concentration and time point tested. RRR-γ-tocopherol treatment resulted in cleavage of PARP, caspase 3, 7, and 8, but not caspase 9. Differences in the percentage cell death and apoptosis were observed in different cell lines suggesting that molecular differences in these cell lines may influence the ability of RRR-γ-tocopherol to induce cell death.

Conclusion

This is the first study to demonstrate that multiple colon cancer cell lines containing varying genetic alterations will under go growth reduction and apoptosis in the presence of RRR-γ-tocopherol without damage to normal colon cells. The amount growth reduction was dependent upon the molecular signatures of the cell lines. Since RRR-γ-tocopherol is effective at inhibition of cell proliferation at both physiological and pharmacological concentrations dietary RRR-γ-tocopherol may be chemopreventive, while pharmacological concentrations of RRR-γ-tocopherol may aid chemotherapy without toxic effects to normal cells demonstrated by most chemotherapeutic agents.

Vitamin E isoform-specific inhibition of the exercise-induced heat shock protein 72 expression in humans

Increased levels of reactive oxygen and nitrogen species, as seen in response to exercise, challenge the cellular integrity. Important protective adaptive changes include induction of heat shock proteins (HSPs). We hypothesized that supplementation with antioxidant vitamins C (ascorbic acid) and E (tocopherol) would attenuate the exercise-induced increase of HSP72 in the skeletal muscle and in the circulation. Using randomization, we allocated 21 young men into three groups receiving one of the following oral supplementations: RRR-alpha-tocopherol 400 IU/day + ascorbic acid (AA) 500 mg/day (CEalpha), RRR-alpha-tocopherol 290 IU/day + RRR-gamma-tocopherol 130 IU/day + AA 500 mg/day (CEalphagamma), or placebo (Control). After 28 days of supplementation, the subjects performed 3 h of knee extensor exercise at 50% of the maximal power output. HSP72 mRNA and protein content was determined in muscle biopsies obtained from vastus lateralis at rest (0 h), postexercise (3 h), and after a 3-h recovery (6 h). In addition, blood was sampled for measurements of HSP72, alpha-tocopherol, gamma-tocopherol, AA, and 8-iso-prostaglandin-F2alpha (8-PGF2alpha). Postsupplementation, the groups differed with respect to plasma vitamin levels. The marker of lipid peroxidation, 8-iso-PGF2alpha, increased from 0 h to 3 h in all groups, however, markedly less (P < 0.05) in CEalpha. In Control, skeletal muscle HSP72 mRNA content increased 2.5-fold (P < 0.05) and serum HSP72 protein increased 4-fold (P < 0.05) in response to exercise, whereas a significant increase of skeletal muscle HSP72 protein content was not observed (P = 0.07). In CEalpha, skeletal muscle HSP72 mRNA, HSP72 protein, and serum HSP72 were not different from Control in response to exercise. In contrast, the effect of exercise on skeletal muscle HSP72 mRNA and protein, as well as circulating HSP72, was completely blunted in CEalphagamma. The results indicate that gamma-tocopherol comprises a potent inhibitor of the exercise-induced increase of HSP72 in skeletal muscle as well as in the circulation.

Gamma-tocopherol induces apoptosis in androgen-responsive LNCaP prostate cancer cells via caspase-dependent and independent mechanisms

We found that gamma-tocopherol, the predominant vitamin E form in diets, but not alpha-tocopherol, which is the exclusive form of vitamin E in most supplements, exhibited antiproliferation effect on prostate (PC-3, LNCaP) and lung (A549) cancer cells. gamma-Tocopherol induced apoptosis in androgen-sensitive LNCaP but not androgen-resistant PC-3 cells. Consequently, gamma-tocopherol treatment caused cytochrome c release and caspase-9, -3 and -7 activation. However, the apoptosis could not be completely reversed by an irreversible pancaspase inhibitor, indicating that an alternative caspase-independent pathway may also be involved. Our study suggests that gamma-tocopherol may be valuable in the prevention and therapy for certain types of cancer.

Suppression of murine cerebral F2-isoprostanes and F4-neuroprostanes from excitotoxicity and innate immune response in vivo by alpha- or gamma-tocopherol

Oxidative damage to brain is a featured shared by several destructive and degenerative diseases and is thought to contribute to disease pathogenesis. Two commonly proposed sources of the increased free radical stress that leads to oxidative damage in several of these diseases are excitotoxicity and activation of innate immunity, both of which are proposed pharmacologic targets. Here we used models of excitotoxicity, intracerebroventricular (ICV) kainate (KA), and innate immune activation, ICV lipopolysaccharide (LPS), to test the effectiveness of peripherally administered alpha-tocopherol (AT) and gamma-tocopherol (GT) as neuroprotectants. We quantified murine cerebral oxidative damage by measuring F(2)-isoprostanes (IsoPs) and F(4)-neuroprostanes (NeuroPs) using stable isotope dilution methods followed by gas chromatography-mass spectrometry with selective ion monitoring. Our data showed that peripherally administered AT and GT were equally effective at suppressing acute oxidative damage from direct excitotoxicity caused by KA. In contrast, peripherally administered AT, but not GT, was effective at suppressing delayed neuronal oxidative damage from activated glial innate immune response. These data imply that AT may be more broadly protective of cerebrum from oxidative damage in different disease contexts.

Alpha-tocopherol modulates Cyp3a expression, increases gamma-CEHC production, and limits tissue gamma-tocopherol accumulation in mice fed high gamma-tocopherol diets

Although all forms of vitamin E are absorbed, the liver preferentially secretes alpha-, but not gamma-tocopherol, into plasma. Liver alpha-tocopherol secretion is under the control of the alpha-tocopherol transfer protein (TTP). Therefore, to assess gamma-tocopherol bioactivities Ttpa-/-, +/- and +/+ mice were fed for 5 weeks diets containing gamma-tocopherol 550 (gamma-T550), gamma-tocopherol 60 (gamma-T60) mg/kg that also contained trace amounts of alpha-tocopherol, a vitamin E-deficient diet, or a control diet. Plasma and tissues from mice fed gamma-T550 diets were found to contain similar gamma- and alpha-tocopherol concentrations despite the high dietary gamma-tocopherol content; nervous tissues contained almost no gamma-tocopherol. Liver vitamin E metabolites (carboxyethyl hydroxychromans, CEHCs) were also measured. In mice with widely ranging liver alpha- (from 0.7 to 16 nmol/g) and gamma-tocopherol concentrations (0 to 13 nmol/g), hepatic alpha-CEHC was undetectable, but gamma-CEHC concentrations (0.1 to 0.8 nmol/g) were correlated with both alpha- and gamma-tocopherol concentrations (P < 0.004). Hepatic cytochrome P450s (CYPs) involved in vitamin E metabolism, Cyp4f and Cyp3a, were also measured. There were no variations in Cyp4f protein expression as related to diet or mouse genotype. However, Cyp3a was correlated (P < 0.0001) with liver alpha-, but not gamma-tocopherol concentrations. These data support the hypothesis that alpha-tocopherol modulates xenobiotic metabolism by increasing Cyp3a expression, gamma-CEHC formation, and the excretion of both gamma-tocopherol and gamma-CEHC.

Topical application of a novel, water-soluble gamma-tocopherol derivative prevents UV-induced skin damage in mice

We investigated whether the topical application of a novel, water-soluble gamma-tocopherol (gamma-Toc) derivative, gamma-tocopherol-N,N-dimethylglycinate hydrochloride (gamma-TDMG), could protect against UV-induced skin damage in hairless mice. Topical pre- or post-application of a 5% (93 mM) gamma-TDMG solution in water/propylene glycol/ethanol (2:1:2) significantly prevented sunburn cell formation, lipid peroxidation and edema/inflammation that were induced by exposure to a single dose of UV irradiation of 5 kJ/m2 (290-380 nm, maximum 312 nm). This effect was greater than that seen with two alpha-Toc derivatives, alpha-tocopherol acetate (alpha-TA) and alpha-tocopherol-N,N-dimethylglycinate (alpha-TDMG). When a 5% solution of gamma-TDMG was applied to mouse skin for 1 h, cutaneous gamma-Toc increased by 25-fold after 24 h; levels of cutaneous alpha-Toc increased by only two- and eight-fold in alpha-TDMG and alpha-TA treated skins, respectively. These findings indicated that gamma-TDMG immediately converted to gamma-Toc in the skin and suggest that ability of gamma-TDMG to protect the skin from the damaging effects of irradiation was due to its conversion to gamma-Toc. When a 5% solution of gamma-Toc was applied to mouse skin for 1 h, cutaneous gamma-Toc rapidly increased by 25-fold, but fell to baseline levels by 24 h. In contrast, the concentration of gamma-Toc in skin that was treated with gamma-TDMG similarly increased, but these high levels were maintained after 24 h. These results suggest that gamma-TDMG may be a more effective source of gamma-Toc in skin. Thus, the topical application of gamma-TDMG may be efficacious for the prevention of UV-B-induced skin damage.

Modulation of Cyp3a11 mRNA expression by alpha-tocopherol but not gamma-tocotrienol in mice

Metabolism of vitamin E is initiated by cytochrome P450 (CYP) enzymes usually involved in the metabolism of xenobiotics. Like other CYP substrates, vitamin E induced a reporter gene under the control of the pregnane X receptor (PXR) which regulates the expression of CYPs including CYP3A4. gamma-Tocotrienol, the most effective PXR activator, also induced endogenous CYP3A4 mRNA in HepG2 cells. Since these findings imply an interference of vitamin E with drug metabolism it was deemed necessary to investigate their in vivo relevance. Therefore, mice were grown for 3 months with alpha-tocopherol-deficient, -adequate, and -supranutritional diet, i.e. 2, 20 and 200 mg RRR-alpha-tocopheryl acetate/kg diet, respectively. Half of them received 250 microg gamma-tocotrienol/day for the last 7 days. After 3 months, hepatic levels of Cyp3a11 mRNA, the murine homolog to human CYP3A4, were about 2.5-fold higher in the 20 and 200 mg alpha-tocopherol groups than in the 2 mg group. After feeding 200 mg alpha-tocopherol for 9 months, Cyp3a11 mRNA was 1.7-fold higher than after 3 months. In contrast, gamma-tocotrienol did not induce Cyp3a11 mRNA. This could be explained by its high metabolism as demonstrated by the 20- to 25-fold increase in the urinary excretion of gamma-CEHC, the final metabolite of gamma-tocotrienol degradation. In conclusion, alpha-tocopherol maintains an adequate level of xenobiotic-metabolizing enzymes. If fed in supranutritional dosages, especially for longer times, alpha-tocopherol induces Cyp3a11 to levels which might interfere with drug metabolism.

gamma-Tocopherol or combinations of vitamin E forms induce cell death in human prostate cancer cells by interrupting sphingolipid synthesis

gamma-Tocopherol (gammaT), the predominant form of vitamin E in diets, but not alpha-tocopherol, the major vitamin E form in tissues and supplements, inhibits proliferation of prostate cancer cells (LNCaP and PC-3) and lung cancer cells (A549). In contrast, at similar concentrations, gammaT has no effect on normal prostate epithelial cells. Combinations of some vitamin E forms, such as gammaT and delta-tocopherol, exhibit additive or synergistic inhibitory effects. In this study, gammaT or its combination with delta-tocopherol induced apoptosis in androgen-sensitive prostate LNCaP, but not in androgen-resistant PC-3 cells, by the induction of cytochrome c release, activation of caspase 9 and caspase 3, cleavage of poly-ADP-ribose polymerase (PARP), and involvement of caspase-independent pathways. Myriocin and fumonisin B1, specific inhibitors of key enzymes (serine palmitoyltransferase and dihydroceramide synthase, respectively) in de novo synthesis of sphingolipids, significantly protected cells from gammaT-induced DNA fragmentation, cytochrome c release, PARP cleavage, and the formation of active caspase 3. Compared with vehicle-treated controls, gammaT treatment led to pronounced dihydroceramide and dihydrosphingosine accumulation, which preceded morphological and biochemical manifestations of apoptosis. In contrast, ceramide and shpingosine levels did not increase until day 3, when substantial cell death took place. Our study demonstrates that gammaT and mixed vitamin E forms induce cell death by interrupting the de novo sphingolipid pathway in a prostate cancer cell line. Thus, certain vitamin E forms may be valuable as anticancer agents.