Non-antioxidant properties of α-tocopherol reduce the anticancer activity of several protein kinase inhibitors in vitro

Perceiving the functions of vitamin E through neutron and X-ray scattering

Take your vitamins, or don't? Vitamin E is one of the few lipophilic vitamins in the human diet and is considered an essential nutrient. Over the years it has proven to be a powerful antioxidant and is commercially used as such, but this association is far from linear in physiology. It is increasingly more likely that vitamin E has multiple legitimate biological roles. Here, we review past and current work using neutron and X-ray scattering to elucidate the influence of vitamin E on key features of model membranes that can translate to the biological function(s) of vitamin E. Although progress is being made, the hundred year-old mystery remains unsolved.

α-Tocopherol inhibits atherogenesis and improves cardiac function in mice independently of its antioxidant properties

The impact of α-tocopherol on atherosclerosis is unclear and controversial. While some studies suggest potential benefits, such as antioxidant properties that may reduce oxidative stress, other studies indicate no significant preventive effects. The intricate interplay of various factors, including dosage, individual differences, and study methodologies, contributes to the ongoing uncertainty surrounding α-tocopherol's role in atherosclerosis. Further research is needed to clarify its impact and establish clearer guidelines. Therefore, we aimed to evaluate the impact of α-tocopherol on atherogenesis in ApoE-/- fibrillin (Fbn)1C1039G/+ mice, which is a unique mouse model of advanced atherosclerosis with typical features, such as large necrotic cores, high levels of inflammation, and intraplaque neovascularization, that resemble the unstable phenotype of human plaques. ApoE-/- Fbn1C1039G+/- mice were fed a western-type diet (WD) supplemented with a high dose of α-tocopherol (500 mg/kg diet), while control mice were fed a WD containing a low dose of α-tocopherol (50 mg/kg diet). The high dose of α-tocopherol reduced plaque thickness and necrotic core area in the right common carotid artery (RCCA) after 24 weeks WD. Moreover, α-tocopherol decreased plaque formation and intraplaque neovascularization in the RCCA. In addition to its antiatherogenic effect, chronic supplementation of α-tocopherol improved cardiac function in ApoE-/- Fbn1C1039G/+ mice. However, chronic supplementation of α-tocopherol did not decrease lipid peroxidation. On the contrary, α-tocopherol acted as a prooxidant by increasing plasma levels of oxidized LDL and plaque malondialdehyde, an end product of lipid peroxidation. Our data indicate that α-tocopherol inhibits atherogenesis and improves cardiac function independent of its antioxidant properties.

α-tocopherol as a selective modulator of toxicogenic damage induced by antineoplastic agents cyclophosphamide and doxorubicin

The aim of this study was to determine the oxidative/antioxidative effects, modulatory and selective potential of α-tocopherol (vitamin E) on antineoplastic drug-induced toxicogenetic damage. The toxicity, cytotoxicity and genotoxicity induced by antineoplastic agents cyclophosphamide (CPA) and doxorubicin (DOX) was examined utilizing as models Saccharomyces cerevisiae, Allium cepa, Artemia salina and human peripheral blood mononuclear cells (PBMCs) in the presence of α-tocopherol. For these tests, concentrations of α- tocopherol 100 IU/ml (67mg/ml), CPA 20 µg/ml, DOX 2 µg/ml were used. The selectivity of α-tocopherol was assessed by the MTT test using human mammary gland non-tumor (MCF10A) and tumor (MCF-7) cell lines. Data showed cytoplasmic and mitochondrial oxidative damage induced by CPA or DOX was significantly diminished by α-tocopherol in S. cerevisiae. In addition, the toxic effects on A. salina and cytotoxic and mutagenic effects on A. cepa were significantly reduced by α-tocopherol. In PBMCs, α-tocopherol alone did not markedly affect these cells, and when treated in conjunction with CPA or DOX, α-tocopherol reduced the toxicogenetic effects noted after antineoplastic drug administration as evidenced by decreased chromosomal alterations and lowered cell death rate. In human mammary gland non-tumor and tumor cell lines, α-tocopherol produced selective cytotoxicity with 2-fold higher effect in tumor cells. Evidence indicates that vitamin E (1) produced anti-cytotoxic and anti-mutagenic effects against CPA and DOX (2) increased higher selectivity toward tumor cells, and (3) presented chemoprotective activity in PBMCs.

Biomarkers Regulated by Lipid-Soluble Vitamins in Glioblastoma

Glioblastoma (GBM), a highly lethal form of adult malignant gliomas with little clinical advancement, raises the need for alternative therapeutic approaches. Lipid-soluble vitamins have gained attention in malignant brain tumors owing to their pleiotropic properties and their anti-cancer potential have been reported in a number of human GBM cell lines. The aim of this paper is to systematically review and describe the roles of various biomarkers regulated by lipid-soluble vitamins, such as vitamins A, D, E, and K, in the pathophysiology of GBM. Briefly, research articles published between 2005 and 2021 were systematically searched and selected from five databases (Scopus, PubMed, Ovid MEDLINE, EMBASE via Ovid, and Web of Science) based on the study’s inclusion and exclusion criteria. In addition, a number of hand-searched research articles identified from Google Scholar were also included for the analysis. A total of 40 differentially expressed biomarkers were identified from the 19 eligible studies. The results from the analysis suggest that retinoids activate cell differentiation and suppress the biomarkers responsible for stemness in human GBM cells. Vitamin D appears to preferentially modulate several cell cycle biomarkers, while vitamin E derivatives seem to predominantly modulate biomarkers related to apoptosis. However, vitamin K1 did not appear to induce any significant changes to the Raf/MEK/ERK signaling or apoptotic pathways in human GBM cell lines. From the systematic analysis, 12 biomarkers were identified that may be of interest for further studies, as these were modulated by one or two of these lipid-soluble vitamins.

Is Sunflower Cooking Oil Beneficial for Colorectal Cancer? In Vivo Studies on Azoxymethane-induced Colon Cancer in Rats

Background:

The incorporation of oils in the diet may have promoting or inhibitory effects on Colorectal Cancer (CRC). In this study, azoxymethane (AOM) was used to mimic CRC in rats, and the effect of sunflower oil on cancer progression in the colon of the rats was tested.

Objective:

This study was conducted to investigate the effect of sunflower oil on preneoplastic cancer properties of the colonic mucosal surface of tumors and the aberrant crypt foci (ACF).

Methods:

Six-week-old Sprague-Dawley male rats were randomized into 4 groups of 6 rats each, namely naïve, positive control, negative control, and sunflower oil-fed. CRC was induced by AOM by subcutaneous injection of 20 mg/kg. After CRC induction, the rats were given the respective treatment of either basal diet (naïve group), 10 mg/kg indomethacin (positive control), 0.9 % saline (negative control), or 7 % sunflower oil (experimental group) daily by oral gavage for 42 days. Rats were sacrificed by cervical dislocation; colon samples were visually observed for any tumors on the colonic mucosal surface and evaluated for ACF; histopathological examinations were also performed.

Results:

The mean body weights of the rats were similar in all groups as per one-way ANOVA. A total of 3 ACF were found in the negative group, while none were observed in other groups. The crypts appeared regular with circular luminal openings and were closely packed together in the naïve group. Crypts in the positive and treated group had a similar appearance to the naïve group.

Conclusion:

Sunflower oil inhibition of the preneoplastic cancer ACF properties were tested but were found to be insignificant when administered during CRC treatment or management. However, long-term experiments with a greater number of days will yield better development of tumor and ACF development and will be useful in identifying the molecular mechanism.

Modulatory Effects of Alpha- and Gamma-Tocopherol on the Mitochondrial Respiratory Capacity and Membrane Potential in an In Vitro Model of Alzheimer's Disease

Increased amyloid-beta (Aβ) and amyloid precursor protein (APP) in the brains of Alzheimer's disease (AD) patients are common pathological hallmarks mediating the disease progression. Growing evidence also suggests that mitochondrial abnormalities are an early feature in the pathogenesis of AD. Intervention with antioxidants has received great interest as a molecular strategy for the manipulation of mitochondrial function. Our previous preliminary study using in vitro cell models expressing different types of APP demonstrated that treatment with alpha-tocopherol (ATF) or gamma-tocopherol (GTF) modulates mitochondrial function by reducing mitochondrial reactive oxygen species (ROS), increasing the production of ATP and preventing apoptosis events, especially in cells expressing the mutant APP form. Thus, we hypothesized that ATF or GTF treatment might also alter mitochondrial metabolic pathways such as oxidative phosphorylation. The present study aimed to investigate the role of ATF and GTF in modulating mitochondrial oxidative metabolism using high-resolution respirometry. Our results showed that both ATF and GTF increased the respiratory capacity and membrane potential in the ROUTINE and OXPHOS_CI-LINKED states as well as complex IV enzyme activity in wild-type and mutant APP-overexpressing SH-SY5Y cells. Although preliminary, these findings indicate that ATF and GTF modulate mitochondrial oxidative metabolism in APP-overexpressing cells and, in part, may contribute to the planning of strategies for utilizing vitamin E isomers against mitochondrial-related diseases such as AD.

Reflections on a century of vitamin E research: Looking at the past with an eye on the future

The name vitamin E, was given by Barnett and Sure who suggested that the factor proposed by Evans and Bishop as substance "X," be termed vitamin "E" as the next vitamin after the A, B, C and D vitamins had been already described. The identification of vitamin E with a-tocopherol was made in 1936 by Evans' group. One year later β-tocopherol and 11 years later δ-tocopherol were isolated. Tocotrienol (named zetatocopherol) was first described in 1957 and later isolated in 1961. The antioxidant property of tocopherols was reported by Olcott and Emerson in 1937. Inherited vitamin E deficiency, AVED, characterized by a form of neuromyopathy was first described in 1981. The disease, was localized to chromosome 8q and found to be caused by a mutation of the a-TTP gene. The subsequent paragraphs are not a comprehensive review but only critical reflections on some important aspects of vitamin E research.

Network Pharmacology-Based Study to Uncover Potential Pharmacological Mechanisms of Korean Thistle (Cirsium japonicum var. maackii (Maxim.) Matsum.) Flower against Cancer

Cirsium japonicum var. maackii (Maxim.) Matsum. or Korean thistle flower is a herbal plant used to treat tumors in Korean folk remedies, but its essential bioactives and pharmacological mechanisms against cancer have remained unexplored. This study identified the main compounds(s) and mechanism(s) of the C. maackii flower against cancer via network pharmacology. The bioactives from the C. maackii flower were revealed by gas chromatography-mass spectrum (GC-MS), and SwissADME evaluated their physicochemical properties. Next, target(s) associated with the obtained bioactives or cancer-related targets were retrieved by public databases, and the Venn diagram selected the overlapping targets. The networks between overlapping targets and bioactives were visualized, constructed, and analyzed by RPackage. Finally, we implemented a molecular docking test (MDT) to explore key target(s) and compound(s) on AutoDockVina and LigPlot+. GC-MS detected a total of 34 bioactives and all were accepted by Lipinski's rules and therefore classified as drug-like compounds (DLCs). A total of 597 bioactive-related targets and 4245 cancer-related targets were identified from public databases. The final 51 overlapping targets were selected between the bioactive targets network and cancer-related targets. With Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, a total of 20 signaling pathways were manifested, and a hub signaling pathway (PI3K-Akt signaling pathway), a key target (Akt1), and a key compound (Urs-12-en-24-oic acid, 3-oxo, methyl ester) were selected among the 20 signaling pathways via MDT. Overall, Urs-12-en-24-oic acid, 3-oxo, methyl ester from the C. maackii flower has potent anti-cancer efficacy by inactivating Akt1 on the PI3K-Akt signaling pathway.

Tocopherol biosynthesis in Leishmania (L.) amazonensis promastigotes

Leishmaniasis is a neglected disease caused by a trypanosomatid protozoan of the genus Leishmania. Most drugs used to treat leishmaniasis are highly toxic, and the emergence of drug‐resistant strains has been observed. Therefore, new therapeutic targets against leishmaniasis are required. Several isoprenoid compounds, including dolichols or ubiquinones, have been shown to be important for cell viability and proliferation in various trypanosomatid species. Here, we detected the biosynthesis of tocopherol in Leishmania (L.) amazonensis promastigotes in vitro through metabolic labelling with [1‐(n)‐3H]‐phytol. Subsequently, we confirmed the presence of vitamin E in the parasite by gas chromatography–mass spectrometry. Treatment with usnic acid or nitisinone, inhibitors of precursors of vitamin E synthesis, inhibited growth of the parasite in a concentration‐dependent manner. This study provides the first evidence of tocopherol biosynthesis in a trypanosomatid and suggests that inhibitors of the enzyme 4‐hydroxyphenylpyruvate dioxygenase may be suitable for use as antileishmanial compounds.

Database

The amino acid sequence of a conserved hypothetical protein [Leishmania mexicana MHOM/GT/2001/U1103] has been deposited in GenBank (CBZ28005.1)

Vitamin E - The Next 100 Years

α-Tocopherol is the only tocopherol that has been shown to prevent the human deficiency disease Ataxia with Isolated Vitamin E Deficiency (AVED), and thus it is the only one that, for humans, can be called vitamin E. Vitamin E in addition to preventing AVED has documented immune boosting properties and an activity against nonalcoholic hepatosteatosis and low-grade inflammation. Epidemiological studies indicating that vitamin E could prevent cardiovascular events, neurodegenerative disease, macular degeneration, and cancer were in general not confirmed by clinical intervention studies. Vitamin E and some of its metabolites modulate cell signaling and gene transcription. Future research is needed to achieve a better understanding of the molecular events leading to gene regulation by vitamin E, especially in its phosphorylated form. Isolation and characterization of the vitamin E kinase and vitamin E phosphate phosphatase will help in the understanding of cell regulation processes modulated by vitamin E. A clarification of the pathogenesis of AVED remains an important goal to be achieved. © 2018 IUBMB Life, 71(4):411-415, 2019.

Exploring the effect of vitamin E in cancer chemotherapy-A biochemical and biophysical insight

Many oncologists contend that patient undergoing chemotherapy must avoid antioxidant supplementation as it may interfere with the activity of the drug. In the present investigation, we have explored the influence of vitamin E, a well-known antioxidant on Camptothecin (CPT), a potent anti-cancer drug induced cell apoptosis and death of cervical cancer cells. HeLa cells were treated with different concentrations of CPT in presence and absence of 100 μm vitamin E. Treated cells were subjected to cytotoxicity studies, catalase assay, DNA fragmentation assay, clonogenic assay and flow cytometry based apoptosis detection. Also, Raman spectroscopy a label free technique which provides global information, in conjunction with multivariate tools like PCA, PCLDA and FDA, was investigated to explore vitamin E supplementation induced alterations. Our data based on biochemical and biophysical experimental analysis reveals that CPT causes DNA damage along with protein and lipid alteration culminating in cell death. Importantly, Raman spectroscopic analysis could uniquely differentiate the cluster of control and vitamin E control from CPT and CPT + Vit E treated cells. We conclusively prove that presence of vitamin E at 100 μM concentration shows promising antioxidant activity and displays no modulatory role on CPT induced effect, thereby causing no possible hindrance with the efficacy of the drug. Vitamin E may prove beneficial to alleviate chemotherapy associated side effects in patients during clinical settings which may open the doors further for subsequent exploration in in vivo preclinical studies.

Corosolic Acid Induces Non-Apoptotic Cell Death through Generation of Lipid Reactive Oxygen Species Production in Human Renal Carcinoma Caki Cells

Corosolic acid is one of the pentacyclic triterpenoids isolated from Lagerstroemia speciose and has been reported to exhibit anti-cancer and anti-proliferative activities in various cancer cells. In the present study, we investigated the molecular mechanisms of corosolic acid in cancer cell death. Corosolic acid induces a decrease of cell viability and an increase of cell cytotoxicity in human renal carcinoma Caki cells. Corosolic acid-induced cell death is not inhibited by apoptosis inhibitor (z-VAD-fmk, a pan-caspase inhibitor), necroptosis inhibitor (necrostatin-1), or ferroptosis inhibitors (ferrostatin-1 and deferoxamine (DFO)). Furthermore, corosolic acid significantly induces reactive oxygen species (ROS) levels, but antioxidants (N-acetyl-l-cysteine (NAC) and trolox) do not inhibit corosolic acid-induced cell death. Interestingly, corosolic acid induces lipid oxidation, and α-tocopherol markedly prevents corosolic acid-induced lipid peroxidation and cell death. Anti-chemotherapeutic effects of α-tocopherol are dependent on inhibition of lipid oxidation rather than inhibition of ROS production. In addition, corosolic acid induces non-apoptotic cell death in other renal cancer (ACHN and A498), breast cancer (MDA-MB231), and hepatocellular carcinoma (SK-Hep1 and Huh7) cells, and α-tocopherol markedly inhibits corosolic acid-induced cell death. Therefore, our results suggest that corosolic acid induces non-apoptotic cell death in cancer cells through the increase of lipid peroxidation.

Many tocopherols, one vitamin E

Four tocopherols are available in nature and are absorbed with the diet, but only one RRR-α-tocopherol satisfies the criteria of being a vitamin. The biological activity of the different tocopherols studied in the rat by the resorption-gestation test has been inconsistently extrapolated to human beings where the tocopherols have no influence on a successful pregnancy. Diminution of RRR-α-tocopherol intake results in diseases characterized by ataxia, whose pathogenetic mechanism, despite vigorous claims, has not been clarified. The calculation of the Daily Reference Intake (DRI), necessary to prevent disease, is based on an obsolete test, the peroxide-induced erythrocyte hemolysis, called the gold standard, but of highly questioned validity. If many epidemiological studies have given positive results, showing prevention by high vitamin E containing diets of cardiovascular events, neurodegenerative disease, macular degeneration and cancer, the clinical confirmatory intervention studies were mostly negative. On the positive side, besides preventing vitamin E deficiency diseases, vitamin E has shown efficacy as anti-inflammatory and immune boosting compound. It has also shown some efficacy in protecting against nonalcoholic hepato-steatosis. At a molecular level, vitamin E and some of its metabolites have shown capacity of regulating cell signaling and modulating gene transcription.

Vitamin E supplementation in chemical colorectal carcinogenesis: a two-edged knife

This work investigated the effects of Vitamin E (VE) on aberrant crypt foci (ACF) incidence, oxidative stress parameters (serum and hepatic VE concentration, and homocysteine, glutathione (GSH), and malondialdehyde (MDA) levels), and expression of both cyclooxygenase-2 (COX2) and proliferating cellular nuclear antigen (PCNA) in experimental colorectal carcinogenesis. Male Wistar rats received subcutaneous injections of 1,2-dimethylhydrazine (DMH) twice a week, for two weeks (40 mg/kg), except for the Control group. Animals were separated into groups that received different amounts of VE in the diet: 0 IU (0×), 75 IU (recommended daily intake, RDI), 225 IU (3× RDI), or 1500 IU (20× RDI), during (dDMH) or after (aDMH) administration of carcinogen. The 0×dDMH and 3×dDMH groups showed decreased serum VE levels. Hepatic VE concentration was higher in 3×aDMH as compared with the other groups. All the groups, except the Control and the 0×aDMH groups, had reduced GSH levels. The 0×dDMH, 0×aDMH, and 20×aDMH groups exhibited increased MDA levels. The aDMH groups had higher ACF incidence and PCNA expression. The 0×aDMH group presented higher ACF rate, followed by 20×aDMH. Moreover, the 3×aDMH group displayed reduced ACF incidence and COX2 expression. Multivariate analysis revealed that GSH modulated homocysteine levels and COX2. These results suggested that 1500 IU of VE is hazardous, whereas 225 IU of VE has beneficial effects on chemical colorectal carcinogenesis.

Polyphenol compounds in the chicken/animal diet: from the past to the future

Animal feed provides a range of antioxidants that help the body building an integrated antioxidant system responsible for a prevention of damaging effects of free radicals and products of their metabolism. Vitamin E is considered to be the main chain-breaking antioxidant located in the membranes and effectively protecting them against lipid peroxidation. Recently, various polyphenol compounds, especially flavonoids, have received substantial attention because of their antioxidant activities in various in vitro systems. However, it was shown that flavonoid compounds are poorly absorbed in the gut and their concentrations in target tissues are too low to perform an effective antioxidant defences. The aim of the present paper is to review existing evidence about possible roles of various plant extracts provided with the diet in animal/poultry nutrition with a specific emphasis to their antioxidant activities.