Tocotrienol-Rich Fraction Attenuates Blue Light-Induced Oxidative Stress and Melanogenesis in B16-F1 Melanocytes via Anti-Oxidative and Anti-Tyrosinase Properties

Our skin is constantly exposed to blue light (BL), which is abundant in sunlight and emitted by digital devices. Prolonged exposure to BL can lead to oxidative stress-induced damages and skin hyperpigmentation. For this study, we used a cell line-based model to examine the protective effects of tocotrienol-rich fraction (TRF) on BL-induced oxidative stress and hyperpigmentation in B16-F1 melanocytes. Alpha-tocopherol (αTP) was used as a comparator. Molecular assays such as cell viability assay, flow cytometry, western blotting, fluorescence imaging, melanin and tyrosinase analysis were performed. Our results showed that TRF effectively suppressed the formation of reactive oxygen species and preserved the mitochondrial membrane potential. Additionally, TRF exhibited anti-apoptotic properties by reducing the activation of the p38 mitogen-activated protein kinase molecule and downregulating the expression of cleaved caspase-3. Moreover, TRF modulated tyrosinase activity, resulting in a lowered rate of melanogenesis and reduced melanin production. In contrast, αTP did not exhibit significant protective effects against skin damages and pigmentation in BL-induced B16-F1 cells. Therefore, this study indicates that TRF may offer superior protective effects over αTP against the effects of BL on melanocytes. These findings demonstrate the potential of TRF as a protective natural ingredient that acts against BL-induced skin damages and hyperpigmentation via its anti-oxidative and anti-melanogenic properties.

Effects of tocotrienol on aging skin: A systematic review

The skin is the largest organ of the body that protects from mechanical, thermal, and physical injury. However, the function and appearance of skin visibly degenerates with age due to its frequent exposure to harmful effects of the environment, including ultraviolet irradiation and hazardous substances, in addition to the progression of oxidative stress in aging. These factors result in phenotypic changes in the skin, including wrinkling, pigmentation, reduced elasticity, and hydration during aging. Many natural antioxidant compounds have been studied extensively to reverse the signs of aging skin. Tocotrienols are a subfamily of vitamin E with potent antioxidant activity. Therefore, supplementation with vitamin E in the form of tocotrienol may efficiently protect skin from aging. In this review, the effects of tocotrienol on skin health, including pigmentation, moisture, and wrinkles during aging and UV exposure, were systematically evaluated based on a literature search of the PubMed and Scopus databases. The present data showed that tocotrienols protect the skin from inflammation, UV radiation and melanin accumulation. As the therapeutic value of tocotrienols grows, the potential of these vitamin E analogs to the skin requires further investigation.

Therapeutic effects of intranasal tocotrienol-rich fraction on rhinitis symptoms in platelet-activating factor induced allergic rhinitis

Background

Platelet-activating factor (PAF) has been suggested to be a potent inflammatory mediator in Allergic rhinitis (AR) pathogenesis. Vitamin E, an essential nutrient that comprises tocopherol and tocotrienol, is known as a potential therapeutic agent for airway allergic inflammation. This study aimed to investigate the beneficial effects of intranasal Tocotrienol-rich fraction (TRF) on PAF-induced AR in a rat model.

Methods

Sprague Dawley rats were randomly assigned into 3 groups: Control, PAF-induced AR and PAF-induced AR with TRF treatment. To induce AR, 50 μl of 16 μg/ml PAF was nasally instilled into each nostril. From day 1 to 7 after AR induction, 10 μl of 16 μg/μl TRF was delivered intranasally to the TRF treatment group. Complete upper skulls were collected for histopathological evaluation on day 8.

Results

The average severity scores of AR were significantly higher in the PAF-induced AR rats compared to both control and PAF-induced AR with TRF treatment. The histologic examination of the nasal structures showed moderate degree of inflammation and polymorphonuclear cells infiltration in the lamina propria, mucosa damage and vascular congestion in the PAF-induced AR rats. TRF was able to ameliorate the AR symptoms by restoring the nasal structures back to normal. H&E staining demonstrated a statistically significant benefit upon TRF treatment, where minimal degree of inflammation, and a reduction in the infiltration of polymorphonuclear cells, mucosa damage and vascular congestion were observed.

Conclusion

TRF exhibited symptomatic relief action in AR potentially due to its antioxidant, anti-inflammatory and anti-allergic properties.

Vitamin E in Atopic Dermatitis: From Preclinical to Clinical Studies

BACKGROUND

Oxidative stress and inflammation are some of the proposed mechanisms involved in the pathogenesis of atopic dermatitis (AD). Current pharmacotherapeutic approaches are effective yet they are not without adverse effects. Vitamin E has great potential as an adjunctive treatment for AD owing to its antioxidant and anti-inflammatory bioactivities.

SUMMARY

This review article summarizes the current available evidence from cellular, animal and clinical studies on the relationship between vitamin E and AD. The future prospects of vitamin E are also discussed. Vitamin E in practice does not show any toxicity to humans within a range of reasonable dosage. Albeit rarely, vitamin E as a contact allergen should be considered. Collectively, this review envisaged vitamin E as an adjunctive treatment for AD patients. Future research on the distinct effects of different vitamin E isoforms as well as their delivery system in skin disorders is needed.

Tocotrienol is a cardioprotective agent against ageing-associated cardiovascular disease and its associated morbidities

Ageing is a nonmodifiable risk factor that is linked to increased likelihood of cardiovascular morbidities. Whilst many pharmacological interventions currently exist to treat many of these disorders such as statins for hypercholesterolemia or beta-blockers for hypertension, the elderly appear to present a greater likelihood of suffering non-related side effects such as increased risk of developing new onset type 2 diabetes (NODM). In some cases, lower efficacy in the elderly have also been reported. Alternative forms of treatment have been sought to address these issues, and there has been a growing interest in looking at herbal remedies or plant-based natural compounds. Oxidative stress and inflammation are implicated in the manifestation of ageing-related cardiovascular disease. Thus, it is natural that a compound that possesses both antioxidative and anti-inflammatory bioactivities would be considered. This review article examines the potential of tocotrienols, a class of Vitamin E compounds with proven superior antioxidative and anti-inflammatory activity compared to tocopherols (the other class of Vitamin E compounds), in ameliorating ageing-related cardiovascular diseases and its associated morbidities. In particular, the potential of tocotrienols in improving inflammaging, dyslipidemia and mitochondrial dysfunction in ageing-related cardiovascular diseases are discussed.

Tocotrienol-rich fraction attenuates UV-induced inflammaging: A bench to bedside study

BACKGROUND

UV radiation from the sun is the most common environmental stressor to damage the skin. It is now well established that photodamaged skin manifests signs of mild but chronic inflammation, termed as "inflammaging." Thus, there is an urgent need for anti-inflammatory regimes that can limit the damage caused by inflammation.

OBJECTIVES

This study aimed to evaluate the possible palliative effects of a new topical nanoemulsion formulation containing tocotrienol-rich fraction (TRF) on UV-induced inflammation (erythema) of human skin.

METHODS

An in vitro model was used to demonstrate the ability of TRF to alleviate photodamage via attenuation of UV-induced oxidative stress and inflammation. Two ex vivo models (skin antioxidative potential and radical sun protection factor) were used to determine the efficacy of different formulations of TRF on the skin. A UV-induced erythema protection test in 20 subjects was conducted.

RESULTS

In vitro studies involving HaCaT keratinocytes revealed that TRF possesses marked anti-inflammatory properties, as indicated by the attenuation of UV-induced upregulation of pro-inflammatory cytokines. A 1% TRF formulation was found to be more effective in enhancing the endogenous antioxidative protection of skin compared to 1% TRF in medium chain triglycerides because of its higher penetration kinetic profile. The clinical study showed that formulated TRF was effective in reducing skin redness after UV irradiation as early as after 6 hours of application. A significant depigmentation was also observed in TRF treatment subjects.

CONCLUSION

TRF may serve as an anti-inflammatory compound that is safe to be applied daily to protect the skin from UV-induced inflammaging.

Targeting the PI3K/Akt signaling pathway in gastric carcinoma: A reality for personalized medicine?

Frequent activation of phosphatidylinositol-3 kinases (PI3K)/Akt/mTOR signaling pathway in gastric cancer (GC) is gaining immense popularity with identification of mutations and/or amplifications of PIK3CA gene or loss of function of PTEN, a tumor suppressor protein, to name a few; both playing a crucial role in regulating this pathway. These aberrations result in dysregulation of this pathway eventually leading to gastric oncogenesis, hence, there is a need for targeted therapy for more effective anticancer treatment. Several inhibitors are currently in either preclinical or clinical stages for treatment of solid tumors like GC. With so many inhibitors under development, further studies on predictive biomarkers are needed to measure the specificity of any therapeutic intervention. Herein, we review the common dysregulation of PI3K/Akt/mTOR pathway in GC and the various types of single or dual pathway inhibitors under development that might have a superior role in GC treatment. We also summarize the recent developments in identification of predictive biomarkers and propose use of predictive biomarkers to facilitate more personalized cancer therapy with effective PI3K/Akt/mTOR pathway inhibition.

Anti-inflammatory γ- and δ-tocotrienols improve cardiovascular, liver and metabolic function in diet-induced obese rats

PURPOSE

This study tested the hypothesis that γ- and δ-tocotrienols are more effective than α-tocotrienol and α-tocopherol in attenuating the signs of diet-induced metabolic syndrome in rats.

METHODS

Five groups of rats were fed a corn starch-rich (C) diet containing 68 % carbohydrates as polysaccharides, while the other five groups were fed a diet (H) high in simple carbohydrates (fructose and sucrose in food, 25 % fructose in drinking water, total 68 %) and fats (beef tallow, total 24 %) for 16 weeks. Separate groups from each diet were supplemented with either α-, γ-, δ-tocotrienol or α-tocopherol (85 mg/kg/day) for the final 8 of the 16 weeks.

RESULTS

H rats developed visceral obesity, hypertension, insulin resistance, cardiovascular remodelling and fatty liver. α-Tocopherol, α-, γ- and δ-tocotrienols reduced collagen deposition and inflammatory cell infiltration in the heart. Only γ- and δ-tocotrienols improved cardiovascular function and normalised systolic blood pressure compared to H rats. Further, δ-tocotrienol improved glucose tolerance, insulin sensitivity, lipid profile and abdominal adiposity. In the liver, these interventions reduced lipid accumulation, inflammatory infiltrates and plasma liver enzyme activities. Tocotrienols were measured in heart, liver and adipose tissue showing that chronic oral dosage delivered tocotrienols to these organs despite low or no detection of tocotrienols in plasma.

CONCLUSION

In rats, δ-tocotrienol improved inflammation, heart structure and function, and liver structure and function, while γ-tocotrienol produced more modest improvements, with minimal changes with α-tocotrienol and α-tocopherol. The most important mechanism of action is likely to be reduction in organ inflammation.

Y-tocotrienol inhibits angiogenesis-dependent growth of human hepatocellular carcinoma through abrogation of AKT/mTOR pathway in an orthotopic mouse model

Angiogenesis is one of the key hallmarks of cancer. In this study, we investigated whether γ-tocotrienol can abrogate angiogenesis-mediated tumor growth in hepatocellular carcinoma (HCC) and if so, through what molecular mechanisms. We observed that γ-tocotrienol inhibited vascular endothelial growth factor (VEGF)-induced migration, invasion, tube formation and viability of HUVECs in vitro. Moreover, γ-tocotrienol reduced the number of capillary sprouts from matrigel embedded rat thoracic aortic ring in a dose-dependent manner. Also, in chick chorioallantoic membrane assay, γ-tocotrienol significantly reduced the blood vessels formation. We further noticed that γ-tocotrienol blocked angiogenesis in an in vivo matrigel plug assay. Furthermore, γ-tocotrienol inhibited VEGF-induced autophosphorylation of VEGFR2 in HUVECs and also suppressed the constitutive activation of AKT/mammalian target of rapamycin (mTOR) signal transduction cascades in HUVECs as well as in HCC cells. Interestingly, γ-tocotrienol was also found to significantly reduce the tumor growth in an orthotopic HCC mouse model and inhibit tumor-induced angiogenesis in HCC patient xenografts through the suppression of various biomarkers of proliferation and angiogenesis. Taken together, our findings strongly suggest that γ-tocotrienol might be a promising anti-angiogenic drug with significant antitumor activity in HCC.

Abstract 1656: Id1, inhibitor of differentiation, is a key protein mediating anti-tumor responses of gamma-tocotrienol in breast cancer cells

Background: Gamma-tocotrienol has demonstrated anti-proliferative effect on breast cancer (BCa) cells, but mechanisms involved are largely unknown. This study aimed at deciphering the molecular pathways responsible for its activity. Methods: MTT cell proliferation, DNA fragmentation, TUNEL assay and flow cytometry were performed to investigate gamma-tocotrienol induced cell cytotoxicity and cell cycle arrest. Western blotting was used to characterize multiple signaling pathways associated with gamma-tocotrienol in BCa. Docetaxel, a chemotherapeutic drug that is able to provide significant survival advantage in metastatic BCa, was used in the chemosensitization studies. Results: Our results showed that treatment of BCa cells with gamma-tocotrienol resulted in induction of apoptosis as evidenced by activation of pro-caspases (cleaved caspase-3, −7, −8, −9 and cleaved PARP), accumulation of sub-G1 cells and DNA fragmentations. Examination of the pro-survival genes revealed that the gamma-tocotrienol-induced cell death was associated with suppression of Id1 and NF-κB through modulation of their upstream regulators (Src, Smad1/5/8, Fak and LOX). Meanwhile, gamma-tocotrienol treatment also resulted in the induction of JNK signaling pathway and inhibition of JNK activity by specific inhibitor partially blocked the effect of gamma-tocotrienol. Furthermore, synergistic effect was observed when cells were co-treated with gamma-tocotrienol and Docetaxel. Interestingly, in cells that treated with gamma-tocotrienol, alpha-tocopherol or ß-aminoproprionitrile were found to partially restore Id1 expression. Meanwhile, this restoration of Id1 was found to protect the cells from gamma-tocotrienol induced apoptosis. Consistent outcome was observed in cells ectopically transfected with the Id-1 gene. Conclusion: Our results suggested that the anti-proliferative and chemosensitization effect of gamma-tocotrienol on BCa cells may be mediated through downregulation of Id1 protein.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1656.

In vivo evidence of gamma-tocotrienol as a chemosensitizer in the treatment of hormone-refractory prostate cancer

gamma-Tocotrienol (gammaT3) is known to selectively kill prostate cancer (PCa) cells and to sensitize the cells to docetaxel (DTX)-induced apoptosis. In the present study, the pharmacokinetics of gammaT3 and the in vivo cytotoxic response of androgen-independent prostate cancer (AIPCa) tumor following gammaT3 treatment were investigated. Here, we investigated these antitumor effects for PCa tumors in vivo. The pharmacokinetic and tissue distribution of gammaT3 after exogenous gammaT3 supplementation were examined. Meanwhile, the response of the tumor to gammaT3 alone or in combination with DTX were studied by real-time in vivo bioluminescent imaging and by examination of biomarkers associated with cell proliferation and apoptosis. After intraperitoneal injection, gammaT3 rapidly disappeared from the serum and was selectively deposited in the AIPCa tumor cells. Administration of gammaT3 alone for 2 weeks resulted in a significant shrinkage of the AIPCa tumors. Meanwhile, further inhibition of the AIPCa tumor growth was achieved by combined treatment of gammaT3 and DTX (p < 0.002). The in vivo cytotoxic antitumor effects induced by gammaT3 seem to be associated with a decrease in expression of cell proliferation markers (proliferating cell nuclear antigen, Ki-67 and Id1) and an increase in the rate of cancer cell apoptosis [cleaved caspase 3 and poly(ADP-ribose) polymerase]. Additionally, the combined agents may be more effective at suppressing the invasiveness of AIPCa. Overall, our results indicate that gammaT3, either alone or in combination with DTX, may provide a treatment strategy that can improve therapeutic efficacy against AIPCa while reducing the toxicity often seen in patients treated with DTX.

Evidence of gamma-tocotrienol as an apoptosis-inducing, invasion-suppressing, and chemotherapy drug-sensitizing agent in human melanoma cells

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.