Skin aging may occur as a result of increased free radicals in the body. Vitamin E, the major chain-breaking antioxidant, prevents propagation of oxidative stress, especially in biological membranes. In this study, the molecular mechanism of tocotrienol-rich fraction (TRF) in preventing oxidative stress-induced skin aging was evaluated by determining the rate of total collagen synthesis and its gene expression in human skin fibroblasts.
Skin Care
Clinical evaluation of photoprotective effect by a topical antioxidants combination (tocopherols and tocotrienols)
Pedrelli VF, Lauriola MM, Pigatto PD.
J Eur Acad Dermatol Venereol. 2011 Sep 14.
Background: Vitamin E is among the earliest recognized antioxidants. Recent findings suggested that tocotrienols have superior activity than tocopherols. Moreover, vitamin A is well-known in dermatology for its actions, including the ultraviolet radiation absorbing property.
Objectives: In view of experimental evidence for the photoprotective properties of these antioxidants, we evaluated in 30 patients with photosensitivity, the prophylactic efficacy of a new topical agent, containing tocopherols 10% and tocotrienols 0.3%, compared with retinol, simple vehicle and untreated areas.
Methods: After determination of the minimal UVB erythema dose (MED), two areas of 2 × 2 cm were selected on the buttocks of each subject, one of which was treated with the antioxidant formulation whereas the other field did not undergo any treatment. Therefore, both areas were irradiated with a twofold MED. As further controls, other two similar areas, selected on the forearm of 15 patients, were photo-irradiated similarly, 30 min after application of the simple vehicle to a field and of vitamin A in the same vehicle to the other. Reactions (erythema/oedema/itch/vesciculation) assessment was carried out assigning scores indicative of their intensity; then, mean values +DS of scores were calculated. Results The pre-treatment with the vitamin E formulation highly protects against photosensitivity, and all reactions to irradiation were significantly lower in the areas treated with the topical vitamin E formulation compared to those treated with the simple vehicle or vitamin A.
Conclusions: The use of a new topical formulation containing significant concentrations of tocotrienols and tocopherols represents a promising strategy to reduce the photo-induced skin damage.
d-δ-Tocotrienol-mediated cell cycle arrest and apoptosis in human melanoma cells
Fernandes NV, Guntipalli PK, Mo H.
Anticancer Res. 2010 Dec;30(12):4937-44.
Background: The rate-limiting enzyme of the mevalonate pathway, 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, provides essential intermediates for the prenylation or dolichylation of growth-related proteins. d-δ-tocotrienol, a post-transcriptional down-regulator of HMG CoA reductase, suppresses the proliferation of murine B16 melanoma cells. Dietary d-δ-tocotrienol suppresses the growth of implanted B16 melanomas without toxicity to host mice.
Materials And Methods: The proliferation of human A2058 and A375 melanoma cells following a 72 h incubation in 96-well plates was measured by CellTiter 96® Aqueous One Solution. Cell cycle distribution was determined by flow cytometry. Fluorescence microscopy following acridine orange and ethidium bromide dual staining and procaspase-3 cleavage were used to detect apoptosis. Western-blot was employed to measure protein expression.
Results: d-δ-Tocotrienol induced dose-dependent suppression of cell proliferation with 50% inhibitory concentrations (IC(50)) of 37.5 ± 1.4 (A2058) and 22.3 ± 1.8 (A375) μmol/l, respectively (data are reported as mean ± standard deviation). d-δ-Tocotrienol-mediated cell cycle arrest at the G(1) phase was accompanied by reduced expression of cyclin-dependent kinase 4. Concomitantly, d-δ-tocotrienol induced caspase-3 activation and apoptosis. The impact of d-δ-tocotrienol on A2058 cell proliferation was potentiated by lovastatin (IC(50)=3.1 ± 0.5 μmol/l), a competitive inhibitor of HMG CoA reductase.
Conclusion: d-δ-Tocotrienol may have potential application in melanoma chemoprevention and/or therapy.
Effect of δ-tocotrienol on melanin content and enzymes for melanin synthesis in mouse melanoma cells
Michihara A, Ogawa S, Kamizaki Y, Akasaki K.
Biol Pharm Bull. 2010;33(9):1471-6.
In the present study, we investigated the dose-dependent effect of delta-tocotrienol long term (48, 72 h) on the melanin content of cells treated with delta-tocotrienol, and whether cells treated with delta-tocotrienol for long a time show cytotoxicity. We also examined whether other enzymes responsible for melanin biosynthesis, tyrosinase-related protein-1 (TRP-1) and -2 (TRP-2), are involved in the decrease in melanin levels. Protein levels in cells treated with 25 or 50 microM delta-tocotrienol for 48 h or 72 h were similar to those in control cells. Melanin content decreased by 44 (25 microM delta-tocotrienol) to 50% (50 microM) at 48 h, and by 14 to 21% at 72 h, compared to control levels. Tyrosinase activity, amounts of tyrosinase and TRP-1 decreased dependent on dose : by 50 (25 microM delta-tocotrienol) to 75% (50 microM), 20 to 45% and 42 to 82% at 48 h, and by 25 to 50%, 75 to 80% and 78 to 77% at 72 h, respectively. Although the amount of TRP-2 increased by 20% on treatment with 25 microM delta-tocotrienol for 48 h, it decreased by 52% on treatment with 50 microM delta-tocotrienol for 48 h. The amount of TRP-2 dose-dependently decreased by 55% and 75% on 72 h by treatment with 25 and 50 microM delta-tocotrienol, respectively. From these findings, delta-tocotrienol at up to 50 microM dose-dependently caused a reduction in melanin content by the decrease of TRP-1 and TRP-2 as well as tyrosinase, and no cytotoxicity.
Suppression of gamma-tocotrienol on UVB induced inflammation in HaCaT keratinocytes and HR-1 hairless mice via inflammatory mediators multiple signaling
Shibata A, Nakagawa K, Kawakami Y, Tsuzuki T, Miyazawa T.
J Agric Food Chem. 2010 Jun 9;58(11):7013-20.
Tocopherol (Toc) such as alpha-Toc has been expected to act as photochemopreventive agent of skin, but the effect of the other vitamin E forms [tocotrienols (T3)] has not been fully understood. We evaluated the anti-inflammatory effect of T3 on UVB-induced inflammatory reaction using immortalized human keratinocytes and hairless mice. gamma-T3 suppressed UVB-induced PGE(2) production while similar alpha-Toc doses had no effect. The anti-inflammatory actions of gamma-T3 were explained by its ability to reduce UVB-induced inflammatory gene and protein expression [cyclooxgenase-2 (COX-2), interleukin (IL)-1beta, IL-6, and monocyte chemotactic protein-1]. Western blot analysis revealed gamma-T3 inhibited p38, extracellular signal-regulated kinase, and c-Jun N-terminal kinase/stress-activated protein kinase activation. In HR-1 hairless mice, oral T3 suppressed UVB-induced changes in skin thickness, COX-2 protein expression, and hyperplasia, but alpha-Toc did not. These results suggest T3 has potential use to protect against UVB-induced skin inflammation.
Modulation of melanin synthesis and its gene expression in skin melanocytes by palm tocotrienol rich fraction
Suzana Makpol, Nur Nadia Mohd Arifin, Zahariah Ismail, Chua Kien Hui, Yasmin Anum Mohd Yusof and Wan Zurinah Wan Ngah
African Journal of Biochemistry Research Vol.3 (12), pp. 385-392, December, 2009
Melanin is the pigment that determines skin color. Melanin synthesis is catalysed by the enzyme tyrosinase and is controlled by TYR, TYRP1 and TYRP2 genes. The objective of this study was to evaluate the anti pigmentation property of palm tocotrienol rich fraction by determining melanin synthesis and expression of genes involved in its regulation in skin melanocytes. Palm tocotrienol rich fraction (TRF) which contains 75% a-tocotrienol and 25% tocopherol was used to inhibit melanin synthesis which was determined by determining melanin level and tyrosinase enzyme activity. Expression of TYR, TYRP1 and TYRP2 genes was determined by quantitative real time reverse transcriptase polymerase chain reaction (real time RT-PCR). Primary culture of skin melanocytes was divided into two groups; untreated control and cells that were treated with 500 μg/ml tocotrienol rich fraction for 24 h. Our results showed that there was a reduction in tyrosinase activity and melanin content in melanocytes treated with tocotrienol rich fraction compared to control (p < 0.05). Expression of TYRP2 gene in melanocytes treated with tocotrienol rich fraction was also decreased (p < 0.05) compared to control. In conclusion, palm tocotrienol rich fraction has an anti pigmentation property that inhibit melanin synthesis by inhibiting tyrosinase activity and down regulating TYRP2 gene expression.
Evidence of gamma-tocotrienol as an apoptosis-inducing, invasion-suppressing, and chemotherapy drug-sensitizing agent in human melanoma cells
Chang PN, Yap WN, Lee DT, Ling MT, Wong YC, Yap YL.
Nutr Cancer. 2009;61(3):357-66.
To date, the most effective cure for metastatic melanoma remains the surgical resection of the primary tumor. Recently, tocotrienol-rich-fraction has shown antiproliferative effect on cancer cells. To elucidate this anticancer property in malignant melanoma, this study aimed, first, to identify the most potent isomer for eliminating melanoma cells and second to decipher the molecular pathway responsible for its activity. Results showed that the inhibitory effect of gamma-tocotrienol was most potent, which resulted in induction of apoptosis as evidenced by activation of procaspases and the accumulation of sub-G1 cell population. Examination of the prosurvival genes revealed that the gamma-tocotrienol-induced cell death was associated with suppression of NF-kappaB, EGF-R, and Id family proteins. Meanwhile, gamma-tocotrienol treatment also resulted in induction of JNK signaling pathway, and inhibition of JNK activity by selective inhibitor was able to partially block the effect of gamma-tocotrienol. Interestingly, gamma-tocotrienol treatment led to suppression of mesenchymal markers and the restoration of E-cadherin and gamma-catenin expression, which was associated with suppression of cell invasion capability. Furthermore, synergistic effect was observed when cells were cotreated with gamma-tocotrienol and chemotherapy drugs. Together, our results demonstrated for the first time the anti-invasion and chemonsensitization effect of gamma-tocotrienol against human malignant melanoma cells.
A redox-silent analogue of tocotrienol acts as a potential cytotoxic agent against human mesothelioma cells
Kashiwagi K, Virgona N, Harada K, Kido W, Yano Y, Ando A, Hagiwara K, Yano T.
Life Sci. 2009 May 8;84(19-20):650-6.
Aims: Malignant mesothelioma is an aggressive cancer with no effective treatment options. A redox-silent analogue of alpha-tocotrienol, 6-O-carboxypropyl-alpha-tocotrienol (T3E) is a new potential anti-carcinogenic agent with less toxic effect on non-tumorigenic cells. Here, we evaluated the effect of T3E on killing of chemoresistant mesothelioma cell (H28). MAIN
Methods: The cytotoxic effect of T3E was evaluated by a WST-1 assay, and cell cycle and apoptosis analysis were done by FACS. Each signal molecule’s activity was determined by protein array and immunoblot analysis.
Key Findings: T3E effectively inhibited H28 cell growth at practical pharmacological concentrations (10-20 muM) without any effect on non-tumorigenic mesothelial cell (Met-5A). Inhibition of H28 cell growth by T3E mediated through G2/M arrest in cell cycle and induction of apoptosis. Protein array and immunoblot analyses revealed that T3E inhibited the activation of epidermal growth factor receptor (EGFR) via the inactivation of the Src family of protein tyrosine kinases (Src). However, the blockade of the EGFR signaling was not associated with the T3E-dependent H28 cell growth control. In addition to Src inactivation, T3E inhibited signal transduction and activation of transcription Stat3. A combination of an Src inhibitor, PP2, and a Stat3 inhibitor, AG490, induced G2/M arrest and enhanced apoptosis compared with PP2 alone. These results suggest that T3E suppresses H28 cell growth via the inhibition of Src activation and Src-independent Stat3 activation.
Significance: T3E can be a new effective therapeutic agent against chemoresistant mesothelioma cells.
Delta-tocotrienol causes decrease of melanin content in mouse melanoma cells
Akihiro Michihara, Sachiyo Morita, Yae Hirokawa, Saya Ago, Kenji Akasaki and Hiroshi Tsuji
Journal of Health Science, 55(2) 314-318 (2009)
We examined the effect of –tocotrienol on melanin content in mouse melanoma B16 cells. Melanin content was significantly reduced in cells reated with 50 and 100µM δ–tocotrienol, but not 10µM δ–tocotrienol. The activity and amount of tyrosinase also significantly decreased in cells treated with 10, 50 and 100µM δ –tocotrienol. Furthermore, the mRNA level of tyrosinase as measured using real-time PCR was significantly decreased compared to controls in cells treated with 100µM δ–tocotrienol, but not 10 or 50µM δ–tocotrienol. These results indicated that at first δ-tocotrienol caused tyrosinase degradation, and then caused further decrease in the tyrosinase protein level via both tyrosinase degradation and a decrease in the mRNA level of tyrosinase. We conclude that the decrease of melanin content in the cells by δ–tocotrienol was the result of the decrease of the protein level of tyrosinase (tyrosinase degradation is more important than the decrease of mRNA).
The effect of vitamin E on basic fibroblast growth factor level in human fibroblast cell culture
Rashid SA, Halim AS, Muhammad NA.
Med J Malaysia. 2008 Jul;63 Suppl A:69-70.
Basic fibroblast growth factor (bFGF) is angiogenic and effective in down-regulating excess collagen production. The aim of this study is to evaluate the effectiveness of vitamin E (Tocotrienol Rich Fraction) in altering the level of bFGF, a cytokine involved in the scar formation process. In this model, normal human fibroblasts were treated with various concentrations of vitamin E at different time frames. The levels of bFGF were determined by Enzyme-Linked Immunosorbant Assay (ELISA). This study demonstrated that Tocotrienol Rich Fraction (TRF) stimulated bFGF production by fibroblast and postulate that vitamin E may decrease aberrant scar formation.