Sequential administration of delta-tocotrienol ameliorates radiation-induced myelosuppression in mice and non-human primates through inducing G-CSF production

To date only four recombinant growth factors, including Filgrastim (rhG-CSF), have been approved by FDA as radiomitigators to ameliorate hematopoietic acute radiation syndrome (H-ARS). These approved agents are not stable under room-temperature, needing to be stored at 2-8 °C, and would not be feasible in a mass casualty scenario where rapid and cost-effective intervention is crucial. Delta-tocotrienol (δ-T3H), the most potent G-CSF-inducing agent among vitamin E isoforms, exhibited efficiency and selectivity on G-CSF production in comparison with TLR and STING agonists in mice. Five-dose δ-T3H was utilized as the optimal therapeutic regimen due to long-term G-CSF production and the best peripheral blood (PB) recovery of irradiated mice. Comparable with rhG-CSF, sequential administration of δ-T3H post-irradiation improved hematologic recovery and accelerated the regeneration of hematopoietic stem cells (HSCs) and hematopoietic progenitor cells (HPCs) in the bone marrow (BM) and spleen of 6.5Gy irradiated mice; and consistently enhanced repopulation of BM-HSCs. In 4.0Gy irradiated nonhuman primates, δ-T3H exhibited comparable efficacy as rhG-CSF to promote PB recovery and colony-formation of BM-HPCs. Altogether, we demonstrated that sequential administration of delta-tocotrienol ameliorates radiation-induced myelosuppression in mice and non-human primates through inducing G-CSF production, indicated δ-T3H as a promising radiomitigator for the management of H-ARS, particularly in a mass casualty scenario.

Radioprotective effectiveness of a novel delta-tocotrienol prodrug on mouse hematopoietic system against 60Co gamma-ray irradiation through inducing granulocyte-colony stimulating factor production

Considering the increasing risk of nuclear attacks worldwide, the development of develop potent and safe radioprotective agents for nuclear emergencies is urgently needed. γ-tocotrienol (GT3) and δ-tocotrienol (DT3) have demonstrated a potent radioprotective effect by inducing the production of granulocyte-colony stimulating factor (G-CSF) in vivo. However, their application is limited because of their low bioavailability. The utilization of ester prodrugs can be an effective strategy for modifying the pharmacokinetic properties of drug molecules. In this study, we initially confirmed that DT3 exhibited the most significant potential for inducing G-CSF effects among eight natural vitamin E homologs. Consequently, we designed and synthesized a series of DT3 ester and ether derivatives, leading to improved radioprotective effects. The metabolic study conducted in vitro and in vivo has identified DT3 succinate 5b as a prodrug of DT3 with an approximately seven-fold higher bioavailability compared to DT3 alone. And DT3 ether derivative 8a were relatively stable and approximately 4 times more bioavailable than DT3 prototype. Furthermore, 5b exhibited superior ability to mitigate radiation-induced pancytopenia, enhance the recovery of bone marrow hematopoietic stem and progenitor cells, and promote splenic extramedullary hematopoiesis in sublethal irradiated mice. Similarly, 8a shown potential radiation protection, but its radiation protection is less than DT3. Based on these findings, we identified 5b as a DT3 prodrug, and providing an attractive candidate for further drug development.

Histopathological studies of nonhuman primates exposed to supralethal doses of total- or partial-body radiation: influence of a medical countermeasure, gamma-tocotrienol

Despite remarkable scientific progress over the past six decades within the medical arts and in radiobiology in general, limited radiation medical countermeasures (MCMs) have been approved by the United States Food and Drug Administration for the acute radiation syndrome (ARS). Additional effort is needed to develop large animal models for improving the prediction of clinical safety and effectiveness of MCMs for acute and delayed effects of radiation in humans. Nonhuman primates (NHPs) are considered the animal models that reproduce the most appropriate representation of human disease and are considered the gold standard for drug development and regulatory approval. The clinical and histopathological effects of supralethal, total- or partial-body irradiations (12 Gy) of NHPs were assessed, along with possible protective actions of a promising radiation MCM, gamma-tocotrienol (GT3). Results show that these supralethal radiation exposures induce severe injuries that manifest both clinically as well as pathologically, as evidenced by the noted functionally crippling lesions within various major organ systems of experimental NHPs. The MCM, GT3, has limited radioprotective efficacy against such supralethal radiation doses.

Formation of Previously Undescribed Δ7-Phytosterol Oxidation Products and Tocopherylquinone Adducts in Pumpkin Seed Oil during Roasting, Screw-Pressing, and Simulated Culinary Processing at Elevated Temperatures

The influence of pumpkin seed roasting conditions (110-140 °C) and screw-pressing on the formation of previously undescribed Δ⁷-phytosterol oxidation products and tocopherylquinone adducts with nucleophilic phosphatidylethanolamine species was investigated. The roasting process of pumpkin seed paste at a temperature above 120 °C for 30 min considerably enhanced the formation of Δ⁷-oxysterols. Targeted analysis [electron impact mass spectrometry (MS), 1D-nuclear magnetic resonance] led to the identification of five novel markers of pumpkin paste roasting, among which (3β,5α,22E,24S)-stigmasta-7,22-dien-6-one-3-ol (6-oxo-α-spinasterol), stereoisomers of (3β,5α,22E)-7,8-epoxystigmast-22-en-3-ol (7,8-epoxy-α-spinasterol), and (3β,5α)-22,23-epoxystigmast-7-en-3-ol (7,8-epoxy-α-spinasterol) were reported in edible oils for the first time. Simulated culinary processing provided novel stereoisomers of (3β,5α,22E)-stigmasta-7,22-dien-3,6-diol, unusual (3β,5α,22E)-stigmasta-7,22-dien-6,15-dione-3-ol, and (5α,22E)-stigmasta-7,22-dien-3-one accompanied by minor stereoisomers of (3β,5α)-7,8;22,23-diepoxystigmastan-3-ol. Moreover, a clear relationship between the pumpkin seed oil stability index and synergistic effect of glycerophospholipids with present tocochromanols was found. High-resolution atmospheric pressure chemical ionization-MS experiments clearly demonstrated the formation of various γ-tocopherylquinone adducts with primary amines, namely, octylamine. The mitigation strategy of potentially detrimental oxysterols from pumpkin seed oil included optimization of processing parameters while maintaining the formation of desirable sensory-active compounds.

Effects of Gamma-Tocotrienol on Intestinal Injury in a GI-Specific Acute Radiation Syndrome Model in Nonhuman Primate

The gastrointestinal (GI) system is highly susceptible to irradiation. Currently, there is no Food and Drug Administration (FDA)-approved medical countermeasures for GI radiation injury. The vitamin E analog gamma-tocotrienol (GT3) is a promising radioprotector in mice and nonhuman primates (NHP). We evaluated GT3-mediated GI recovery in total-body irradiated (TBI) NHPs. Sixteen rhesus macaques were divided into two groups; eight received vehicle and eight GT3 24 h prior to 12 Gy TBI. Proximal jejunum was assessed for structural injuries and crypt survival on day 4 and 7. Apoptotic cell death and crypt cell proliferation were assessed with TUNEL and Ki-67 immunostaining. Irradiation induced significant shortening of the villi and reduced mucosal surface area. GT3 induced an increase in crypt depth at day 7, suggesting that more stem cells survived and proliferated after irradiation. GT3 did not influence crypt survival after irradiation. GT3 treatment caused a significant decline in TUNEL-positive cells at both day 4 (p < 0.03) and 7 (p < 0.0003). Importantly, GT3 induced a significant increase in Ki-67-positive cells at day 7 (p < 0.05). These data suggest that GT3 has radioprotective function in intestinal epithelial and crypt cells. GT3 should be further explored as a prophylactic medical countermeasure for radiation-induced GI injury.

Cytotoxicity, cellular uptake, and metabolism to short-chain metabolites of 11'-α-tocomonoenol is similar to RRR-α-tocopherol in HepG2 cells

Contrary to the major vitamin E congener α-tocopherol, which carries a saturated sidechain, and α-tocotrienol, with a threefold unsaturated sidechain, little is known about the intracellular fate of α-tocomonoenol, a minor vitamin E derivative with a single double bond in C11'-position of the sidechain. We hypothesized that, due to structural similarities, the uptake and metabolism of α-tocomonoenol will resemble that of α-tocopherol. Cytotoxicity, cellular uptake of α-tocomonoenol, α-tocopherol and α-tocotrienol and conversion into the short-chain metabolites αCEHC and αCMBHC were studied in HepG2 cells. α-Tocomonoenol did not show significant effects on cell viability and its uptake was similar to that observed for α-tocopherol and significantly lower than for α-tocotrienol. α-Tocomonoenol was mainly metabolized to αCMBHC in liver cells, but to a lower extent than α-tocotrienol, while α-tocopherol was not metabolized in quantifiable amounts at all. In summary, the similarities in the cytotoxicity, uptake and metabolism of α-tocomonoenol and α-tocopherol suggest that this minor vitamin E congener deserves more attention in future research with regard to its potential vitamin E activity.

δ-tocotrienol suppresses the migration and angiogenesis of trophoblasts in preeclampsia and promotes their apoptosis via miR-429/ ZEB1 axis

Preeclampsia (PE) is a severe medical disorder during pregnancy and there has been controversy about the effects of vitamin E on PE. This research intended to explore if δ-tocotrienol (δ-TT), an isomer of vitamin E, could impact PE. Preeclamptic and normal placentas were obtained and total RNA was extracted. The expression of different genes was analyzed through quantitative real-time polymerase chain reaction (qRT-PCR) and Pearson correlation analysis was conducted. After that, HTR-8/SVneo cells (human trophoblasts) were chosen and they were subjected to δ-tocotrienol treatment and then Cell Counting Kit-8 was used to test cell viability. To assess the effects of δ-TT on trophoblasts, wound healing assay and Transwell invasion assay were performed. How miR-429 interacts with ZEB1 was examined via dual luciferase reporter assay. Also, protein expression was evaluated via Western blotting. Our results have shown that δ-TT can impair the viability of trophoblasts and induce their apoptosis. Additionally, it can repress the growth, migration, epithelial-mesenchymal transition (EMT), invasion and angiogenesis in trophoblasts. Mechanistically, δ-TT exerts these effects on trophoblasts via downregulating miR-429 and upregulating ZEB1. Furthermore, miR-429 can bind ZEB1 directly. Clinical sample analysis has revealed that miR-429 expression in preeclamptic placenta is higher than that in normal placenta, but ZEB1 expression in preeclamptic placenta is downregulated. Also, there is a negative association between miR-429 and ZEB1 expression in preeclamptic placentas. These discoveries imply that δ-TT may be hazardous to pregnancy and should not be used in preeclamptic patients. In addition, targeting miR-429 might treat PE.

Tocopheryl quinone improves non-alcoholic steatohepatitis (NASH) associated dysmetabolism of glucose and lipids by upregulating the expression of glucagon-like peptide 1 (GLP-1) via restoring the balance of intestinal flora in rats

CONTEXT

Glucagon-like peptide 1 (GLP-1) and α-tocopheryl quinone can promote the growth of intestinal flora and affect the pathogenesis of non-alcoholic steatohepatitis (NASH).

OBJECTIVE

This study determines the molecular mechanism of the effect of tocopheryl quinone in the treatment of high cholesterol and cholate diet (HFCC)-induced NASH.

MATERIALS AND METHODS

Thirty-two male Sprague Dawley (SD) rats grouped as lean control (LC), LC + tocopheryl quinone (1 mL of 3 × 10⁶ dpm tocopheryl quinone via i.p. injection), HFCC (5.1 kcal/g of fat diet), and HFCC + tocopheryl quinone. Profiles of intestinal flora were assessed by 16S ribosomal ribonucleic acid-based analysis. Levels and activity of GLP-1, interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-α) in intestinal tissues were detected by immunohistochemistry (IHC), Western blot and enzyme-linked immunosorbent assay (ELISA).

RESULTS

HFCC rats presented higher levels of cholesterol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL), while tocopheryl quinone reversed the effects of HFCC. HFCC dysregulated malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), Vitamin E, 12-hydroxyeicosatetraenoic acid (12-HETE), 13-hydroxyoctadecadienoic acid (13-HODE) and nuclear factor kappa B (NF-κB), and the effects of HFCC were reversed by the treatment of tocopheryl quinone. Also, GLP-1 in the HFCC group was down-regulated while the IL-6 and TNF-α activity and endotoxins were all up-regulated. HFCC significantly decreased the number and diversity of bacteria, whereas tocopheryl quinone substantially restored the balance of intestinal flora and promoted the growth of both Bacteroides and Lactobacilli in vitro.

DISCUSSION AND CONCLUSIONS

α-Tocopheryl quinone relieves HFCC-induced NASH via regulating oxidative stress, GLP-1 expression, intestinal flora imbalance, and the metabolism of glucose and lipids.

Mitigation of late cardiovascular effects of oxygen ion radiation by γ-tocotrienol in a mouse model

PURPOSE

While there is concern about degenerative tissue effects of exposure to space radiation during deep-space missions, there are no pharmacological countermeasures against these adverse effects. γ-Tocotrienol (GT3) is a natural form of vitamin E that has anti-oxidant properties, modifies cholesterol metabolism, and has anti-inflammatory and endothelial cell protective properties. The purpose of this study was to test whether GT3 could mitigate cardiovascular effects of oxygen ion (¹⁶O) irradiation in a mouse model.

MATERIALS AND METHODS

Male C57BL/6 J mice were exposed to whole-body ¹⁶O (600 MeV/n) irradiation (0.26-0.33 Gy/min) at doses of 0 or 0.25 Gy at 6 months of age and were followed up to 9 months after irradiation. Animals were administered GT3 (50 mg/kg/day s.c.) or vehicle, on Monday - Friday starting on day 3 after irradiation for a total of 16 administrations. Ultrasonography was used to measure in vivo cardiac function and blood flow parameters. Cardiac tissue remodeling and inflammatory infiltration were assessed with histology and immunoblot analysis at 2 weeks, 3 and 9 months after radiation.

RESULTS

GT3 mitigated the effects of ¹⁶O radiation on cardiac function, the expression of a collagen type III peptide, and markers of mast cells, T-cells and monocytes/macrophages in the left ventricle.

CONCLUSIONS

GT3 may be a potential countermeasure against late degenerative tissue effects of high-linear energy transfer radiation in the heart.

Evaluating Anticancer and Immunomodulatory Effects of Spirulina (Arthrospira) platensis and Gamma-Tocotrienol Supplementation in a Syngeneic Mouse Model of Breast Cancer

Nutrition can modulate host immune responses as well as promote anticancer effects. In this study, two nutritional supplements, namely gamma-tocotrienol (γT3) and Spirulina, were evaluated for their immune-enhancing and anticancer effects in a syngeneic mouse model of breast cancer (BC). Five-week-old female BALB/c mice were fed Spirulina, γT3, or a combination of Spirulina and γT3 (Spirulina + γT3) for 56 days. The mice were inoculated with 4T1 cells into their mammary fat pad on day 28 to induce BC. The animals were culled on day 56 for various analyses. A significant reduction (p < 0.05) in tumor volume was only observed on day 37 and 49 in animals fed with the combination of γT3 + Spirulina. There was a marked increase (p < 0.05) of CD4/CD127+ T-cells and decrease (p < 0.05) of T-regulatory cells in peripheral blood from mice fed with either γT3 or Spirulina. The breast tissue of the combined group showed abundant areas of necrosis, but did not prevent metastasis to the liver. Although there was a significant increase (p < 0.05) of MIG-6 and Cadherin 13 expression in tumors from γT3-fed animals, there were no significant (p > 0.05) differences in the expression of MIG-6, Cadherin 13, BIRC5, and Serpine1 upon combined feeding. This showed that combined γT3 + Spirulina treatment did not show any synergistic anticancer effects in this study model.

γ-Tocotrienol reverses multidrug resistance of breast cancer cells through the regulation of the γ-Tocotrienol-NF-κB-P-gp axis

The problem of multidrug resistance (MDR) presents a major obstacle in the chemotherapy of cancer. The MDR phenotype is often linked to the overexpression of ATP-binding cassette (ABC) transporters, that pumps out and decreased intracellular drug accumulation. γ-Tocotrienol, an unsaturated tocopherol belonging to the vitamin E family, has been shown to reverse the MDR of MCF-7/Adr cell. To reveal the role of γ-tocotrienol-NF-κB-P-gp axis in the reversal process, the expression level of mdr1/P-gp was determined by real-time PCR and western blot, while NF-κB activity was detected by immunofluorescence and NF-κB transcriptional activity reporter assay. Besides, mdr1 promoter activity and P-gp transport capacity were measured with the effect of γ-tocotrienol and NF-κB agonist/antagonist. Results showed that γ-tocotrienol effectively inhibited the expression levels of mdr1 mRNA and P-gp protein. It is demonstrated that γ-tocotrienol also suppressed mdr1 promoter activity and the efflux activity of P-gp. In addition, the activation of NF-κB signaling pathway and the transcriptional activity of NF-κB were both reduced by γ-tocotrienol. Evidences also showed that the NF-κB pathway is really involved in the regulation of the expression and function of mdr1/P-gp. Taken together, we confirmed that γ-tocotrienol reversed the MDR of MCF-7/Adr through the signaling pathway of NF-κB and P-gp.

Achiote (Bixa orellana) Lipophilic Extract, Bixin, and δ-tocotrienol Effects on Lifespan and Stress Resistance in Caenorhabditis elegans

The onset of many degenerative diseases related to aging has been associated with a decrease in the activity of antistress systems, and pharmacological interventions increasing stress resistance could be effective to prevent the development of such diseases. Achiote is a valuable source of carotenoid and tocotrienols, which have antioxidant activity. In this work, we explore the capacity of an achiote seed extract and its main compounds to modulate the lifespan and antistress responses on Caenorhabditis elegans, as well as the mechanisms involved in these effects. Achiote lipophilic extract, bixin, and δ-tocotrienol were applied on nematodes to carry out lifespan, stress resistance, and fertility assays. The achiote seed extract increased the median and maximum lifespan up to 35% and 27% and increased resistance against oxidative and thermal stresses without adverse effects on fertility. The beneficial effects were mimicked by a bixin+δ-tocotrienol mixture. All the effects on lifespan and stress resistance were independent of caloric restriction but dependent on the insulin/insulin growth factor-1 pathway. This study could provide insights for further research on a new beneficial use of this important crop in health and nutraceutical applications beyond its use as a source of natural pigments.

δ-Tocopherol Slightly Accumulates in the Adipose Tissue of Mice

This study aimed to compare the distribution of vitamin E analogs, particularly α-tocopherol and δ-tocopherol, in mice fed with a normal diet and a high-fat and high-sucrose diet separately. We used male C57BL/6JJcl strain mice, which were divided into six groups (control [C], Cα, Cδ, high-fat and high-sucrose [H], Hα, and Hδ groups) and bred for 4 weeks. The additional quantity of α-tocopherol or E-mix D (containing 86.7% δ-tocopherol) into diet was 800 mg/kg diet. The final body weight was significantly higher in the H group than in the C group. However, the effects of vitamin E analog intake had no significant difference, with no synergy between vitamin E and diet. Similar results were obtained in epididymal fat weight. Moreover, α-tocopherol was mainly distributed in the liver in both the Cα group and Hα group, whereas δ-tocopherol mostly accumulated in the epididymal fat, in both the Cδ group and Hδ group. Also, δ-tocopherol was detected in all tissues in both groups. Both the α-tocopherol and δ-tocopherol levels in the epididymal fat were significantly lower in the H group than in the C group. In conclusion, our results suggest that a portion of δ-tocopherol was incorporated into the adipose tissue by chylomicron before arriving at the liver, and then it is metabolized in the liver.

A Facile Semisynthesis and Evaluation of Garcinoic Acid and Its Analogs for the Inhibition of Human DNA Polymerase β

Garcinoic acid has been identified as an inhibitor of DNA polymerase β (pol β). However, no structure-activity relationship (SAR) studies of garcinoic acid as a pol β inhibitor have been conducted, in part due to the lack of an efficient synthetic method for this natural product and its analogs. We developed an efficient semi-synthetic method for garcinoic acid and its analogs by starting from natural product δ-tocotrienol. Our preliminary SAR studies provided a valuable insight into future discovery of garcinoic acid-based pol β inhibitors.

Mitochondrial functional and structural impairment is involved in the antitumor activity of δ-tocotrienol in prostate cancer cells

The therapeutic options for castration-resistant prostate cancer (CRPC) are still limited. Natural bioactive compounds were shown to possess pro-death properties in different tumors. We previously reported that δ-tocotrienol (δ-TT) induces apoptosis, paraptosis and autophagy in CRPC cells. Here, we investigated whether δ-TT might exert its activity by impairing mitochondrial functions. We demonstrated that, in PC3 and DU145 cells, δ-TT impairs mitochondrial respiration and structural dynamics. In both cell lines, δ-TT triggers mitochondrial Ca²⁺ and ROS overload. In PC3 cells, both Ca²⁺ and ROS mediate the δ-TT-related anticancer activities (decrease of cell viability, apoptosis, paraptosis, autophagy and mitophagy). As expected, in autophagy-defective DU145 cells, Ca²⁺ overload was involved in δ-TT-induced pro-death effects but not in autophagy and mitophagy. In this cell line, we also demonstrated that ROS overload is not involved in the anticancer activities of δ-TT, supporting a low susceptibility of these cells to ROS-related oxidative stress. Taken together, these data demonstrate that, in CRPC cells, δ-TT triggers cell death by inducing mitochondrial functional and structural impairments, providing novel mechanistic insights in its antitumor activity.

Mechanisms Mediating Anti-Inflammatory Effects of Delta-Tocotrienol and Tart Cherry Anthocyanins in 3T3-L1 Adipocytes

Chronic low-grade inflammation is a primary characteristic of obesity and can lead to other metabolic complications including insulin resistance and type 2 diabetes (T2D). Several anti-inflammatory dietary bioactives decrease inflammation that accompanies metabolic diseases. We are specifically interested in delta-tocotrienol, (DT3) an isomer of vitamin E, and tart cherry anthocyanins (TCA), both of which possess individual anti-inflammatory properties. We have previously demonstrated that DT3 and TCA, individually, reduced systemic and adipose tissue inflammation in rodent models of obesity. However, whether these compounds have combinatorial effects has not been determined yet. Hence, we hypothesize that a combined treatment of DT3 and TCA will have great effects in reducing inflammation in adipocytes, and that these effects are mediated via the nuclear factor kappa-light-chain-enhancer of activated B cells (NFkB), a major inflammatory transcription factor. We used 3T3-L1 adipocytes and treated them with 1–5 µM doses of DT3 along with tart cherry containing 18–36 µg anthocyanin/mL, to assess effects on inflammation. Neither DT3 nor TCA, nor their combinations had toxic effects on adipocytes. Furthermore, pro-inflammatory markers interleukin-6 (IL-6) and p-65 (subunit of NFkB) were reduced at the protein level in media collected from adipocytes with both individual and combined treatments. Additionally, other downstream targets of NFkB including macrophage inflammatory protein 2 (Mip2), and Cyclooxygenase-2 (Cox2) were also significantly downregulated (p ≤ 0.05) when treated with individual and combined doses of DT3 and TCA with no additional combinatorial effects. In summary, DT3 and TCA individually, are beneficial in reducing inflammation with no additional combinatorial effects.

Structure-based design, semi-synthesis and anti-inflammatory activity of tocotrienolic amides as 5-lipoxygenase inhibitors

Inflammation contributes to the development of various pathologies, e.g. asthma, cardiovascular diseases, some types of cancer, and metabolic disorders. Leukotrienes (LT), biosynthesized from arachidonic acid by 5-lipoxygenase (5-LO), constitute a potent family of pro-inflammatory lipid mediators. δ-Garcinoic acid (δ-GA) (1), a natural vitamin E analogue, was chosen for further structural optimization as it selectively inhibited 5-LO activity in cell-free and cell-based assays without impairing the production of specialized pro-resolving mediators by 15-LO. A model of semi-quantitative prediction of 5-LO inhibitory potential developed during the current study allowed the design of 24 garcinamides that were semi-synthesized. In accordance with the prediction model, biological evaluations showed that eight compounds potently inhibited human recombinant 5-LO (IC50 < 100 nM). Interestingly, four compounds were substantially more potent than 1 in activated primary human neutrophils assays. Structure - activity relationships shed light on a supplementary hydrophobic pocket in the allosteric binding site that could be fitted with an aromatic ring.

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De Novo High-Titer Production of Delta-Tocotrienol in Recombinant Saccharomyces cerevisiae

Delta-tocotrienol as a vitamin E isomer has received much attention because of its diverse biomedical applications. Microbial biosynthesis of delta-tocotrienol is a promising strategy for its economic and environmental advantages. Here, we accomplished complete biosynthesis of delta-tocotrienol in Saccharomyces cerevisiae from glucose. We first constructed and incorporated a heterologous pathway into the genome of S. cerevisiae by incorporating the genes hpd (from Pseudomonas putida KT2440), hpt (from Synechocystis sp. PCC 6803), and vte1 (from Arabidopsis thaliana) for the biosynthesis of delta-tocotrienol. We further enhanced the biosynthesis of the precursor geranylgeranyl diphosphate by overexpressing the thmg1 and ggppssa (from Sulfolobus acidocaldarius) genes, leading to a production titer of delta-tocotrienol of 1.39 ± 0.01 mg/L. Finally, we optimized the fermentation medium using the response surface methodology, enabling a high-titer production of delta-tocotrienol (3.56 ± 0.25 mg/L), ∼2.6-fold of that of the initial culture medium. Fed-batch fermentation in a 2 L fermenter was further used to enhance the production titer of delta-tocotrienol (4.10 ± 0.10 mg/L). To the best of our knowledge, this is the first report on the de novo biosynthesis of delta-tocotrienol in S. cerevisiae, and the highest titer obtained for microbial production of delta-tocotrienol.

Beta-Tocotrienol Exhibits More Cytotoxic Effects than Gamma-Tocotrienol on Breast Cancer Cells by Promoting Apoptosis via a P53-Independent PI3-Kinase Dependent Pathway

Studies on tocotrienols have progressively revealed the benefits of these vitamin E isoforms on human health. Beta-tocotrienol (beta-T3) is known to be less available in nature compared to other vitamin E members, which may explain the restricted number of studies on beta-T3. In the present study, we aim to investigate the anti-proliferative effects and the pro-apoptotic mechanisms of beta-T3 on two human breast adenocarcinoma cell lines MDA-MB-231 and MCF7. To assess cell viability, both cell lines were incubated for 24 and 48 h, with different concentrations of beta-T3 and gamma-T3, the latter being a widely studied vitamin E isoform with potent anti-cancerous properties. Cell cycle progression and apoptosis induction upon treatment with various concentrations of the beta-T3 isoform were assessed. The effect of beta-T3 on the expression level of several apoptosis-related proteins p53, cytochrome C, cleaved-PARP-1, Bax, Bcl-2, and caspase-3, in addition to key cell survival proteins p-PI3K and p-GSK-3 α/β was determined using western blot analysis. Beta-tocotrienol exhibited a significantly more potent anti-proliferative effect than gamma-tocotrienol on both cell lines regardless of their hormonal receptor status. Beta-T3 induced a mild G1 arrest on both cell lines, and triggered a mitochondrial stress-mediated apoptotic response in MDA-MB-231 cells. Mechanistically, beta-T3′s anti-neoplastic activity involved the downregulation of phosphorylated PI3K and GSK-3 cell survival proteins. These findings suggest that vitamin E beta-T3 should be considered as a promising anti-cancer agent, more effective than gamma-T3 for treating human breast cancer and deserves to be further studied to investigate its effects in vitro and on other cancer types.

In situ antioxidant activity of a dermo-cosmetic product: A randomized controlled clinical study

Ultraviolet light enhances the generation of reactive oxygen species that are responsible for skin photoageing. The aim of this randomized, vehicle- and active-controlled double-blind, intra-individual monocentric study was to evaluate in situ the antioxidant activity of a dermo-cosmetic product in photoaged skin. Twenty healthy volunteers had defined skin areas randomized to receive a topical product containing 3 antioxidants (pre-tocopheryl® , retinaldehyde and glycylglycine ole-amide), its vehicle and a positive antioxidant control cream. The products were applied daily for 30-day period. The skin areas were exposed to a controlled dose of UVA rays, and the skin oxidative status was evaluated 4 and 24 hours post-UVA exposure at D0 (basal value) and after 15 and 30 days of product application. Skin layers were collected by stripping, and antioxidant capacity was measured using the ferric reducing ability of a plasma assay. Lipid peroxidation (LPO) was assessed using the malonyldialdehyde test. The tested product significantly improved the skin antioxidant capacity after 15 and 30 days and significantly decreased the basal level of the skin LPO. The skin LPO level significantly decreased 4 and 24 hours after UVA exposure at 15 and 30 days. These findings were comparable to positive control treated sites and were significantly different from the vehicle and untreated sites. This minimally invasive methodology enabled a quantitative evaluation of potent antioxidant activity in situ in the stratum corneum reflecting real-life skin conditions and confirming the benefits of the topical application of a product containing 3 antioxidants in the prevention of UVA-induced oxidative damage.

Gamma-Tocotrienol Induces Apoptosis in Prostate Cancer Cells by Targeting the Ang-1/Tie-2 Signalling Pathway

Emerging evidence suggests that gamma-tocotrienol (γ-T3), a vitamin E isomer, has potent anti-cancer properties against a wide-range of cancers. γ-T3 not only inhibited the growth and survival of cancer cells in vitro, but also suppressed angiogenesis and tumour metastasis under in vivo conditions. Recently, γ-T3 was found to target cancer stem cells (CSCs), leading to suppression of tumour formation and chemosensitisation. Despite its promising anti-cancer potential, the exact mechanisms responsible for the effects of γ-T3 are still largely unknown. Here, we report the identification of Ang-1 (Angiopoietin-1)/Tie-2 as a novel γ-T3 downstream target. In prostate cancer cells, γ-T3 treatment leads to the suppression of Ang-1 at both the mRNA transcript and protein levels. Supplementing the cells with Ang-1 was found to protect them against the anti-CSC effect of γ-T3. Intriguingly, inactivation of Tie-2, a member receptor that mediates the effect of Ang-1, was found to significantly enhance the cytotoxic effect of γ-T3 through activation of AMP-activated protein kinase (AMPK) and subsequent interruption of autophagy. Our results highlighted the therapeutic potential of using γ-T3 in combination with a Tie-2 inhibitor to treat advanced prostate cancer.

Increased plasma levels of the lipoperoxyl radical-derived vitamin E metabolite α-tocopheryl quinone are an early indicator of lipotoxicity in fatty liver subjects

Lipid peroxidation is one of the earliest pathogenic events of non-alcoholic fatty liver disease (NAFLD). In this context, an increased oxidation of the lipoperoxyl radical scavenger α-tocopherol (α-TOH) should occur already in the subclinical phases of the disease to compensate for the increase oxidation of the lipid excess of liver and possibly of other tissues. However, this assumption remains unsupported by direct analytical evidence. In this study, GC-MS/MS and LC-MS/MS procedures have been developed and applied for the first time to measure the vitamin E oxidation metabolite α-tocopheryl quinone (α-TQ) in plasma of fatty liver (FL) subjects that were compared in a pilot cross-sectional study with healthy controls. The protein adducts of 4-hydroxynonenal (4-HNE) and the free form of polyunsaturated free fatty acids (PUFA) were measured as surrogate indicators of lipid peroxidation. α-TQ formation was also investigated in human liver cells after supplementation with α-TOH and/or fatty acids (to induce steatosis). Compared with controls, FL subjects showed increased (absolute and α-TOH-corrected) levels of plasma α-TQ and 4-HNE, and decreased concentrations of PUFA. α-TQ levels positively correlated with indices of liver damage and metabolic dysfunction, such as alanine aminotransferase, bilirubin and triglycerides, and negatively correlated with HDL cholesterol. Fatty acid supplementation in human hepatocytes stimulated the generation of cellular oxidants and α-TOH uptake leading to increased α-TQ formation and secretion in the extracellular medium - both were markedly stimulated by α-TOH supplementation. In conclusion, plasma α-TQ represents an early biomarker of the lipoperoxyl radical-induced oxidation of vitamin E and lipotoxicity of the fatty liver.

Annatto (Bixa orellana) δ-TCT Supplementation Protection against Embryonic Malformations through Alterations in PI3K/Akt-Cyclin D1 Pathway

Protective action by annatto-derived delta-tocotrienol (δ-TCT) and soy-derived alpha-tocopherol (α-TOC) through the regulation of the PI3K/Akt-cyclin D1 pathway against nicotine-induced DNA damage is the focus of the present study. Nicotine, which has been widely reported to have numerous adverse effects on the reproductive system, was used as a reproductive toxicant. 48 female balb/c mice (6⁻8 weeks) (23⁻25 g) were randomly divided into eight groups (Grp.1⁻Grp.8; n = 6) and treated with either nicotine or/and annatto δ-TCT/soy α-TOC for seven consecutive days. On Day 8, the females were superovulated and mated before euthanization for embryo collection (46 h post-coitum). Fifty 2-cell embryos from each group were used in gene expression analysis using Affymetrix QuantiGene Plex2.0 assay. Findings indicated that nicotine (Grp.2) significantly decreased (p < 0.05) the number of produced 2-cell embryos compared to the control (Grp.1). Intervention with mixed annatto δ-TCT (Grp.3) and pure annatto δ-TCT (Grp.4) significantly increased the number of produced 2-cell embryos by 127% and 79%, respectively compared to Grp.2, but these were lower than Grp.1. Concurrent treatment with soy α-TOC (Grp.5) decreased embryo production by 7%. Supplementations with δ-TCT and α-TOC alone (Grp.6-Grp.8) significantly increased (p < 0.05) the number of produced 2-cell embryos by 50%, 36%, and 41%, respectively, compared to control (Grp.1). These results were found to be associated with alterations in the PI3K/Akt-Cyclin D1 genes expressions, indicating the inhibitory effects of annatto δ-TCT and soy α-TOC against nicotinic embryonic damage. To our knowledge, this is the first attempt in studying the benefits of annatto δ-TCT on murine preimplantation 2-cell embryos.

A Metabolomic Serum Signature from Nonhuman Primates Treated with a Radiation Countermeasure, Gamma-tocotrienol, and Exposed to Ionizing Radiation

The search for and development of radiation countermeasures to treat acute lethal radiation injury has been underway for the past six decades, resulting in the identification of multiple classes of radiation countermeasures. However, to date only granulocyte colony-stimulating factor (Neupogen) and PEGylated granulocyte colony-stimulating factor (Neulasta) have been approved by the U.S. Food and Drug Administration for the treatment of hematopoietic acute radiation syndrome. Gamma-tocotrienol has demonstrated radioprotective efficacy in murine and nonhuman primate models. Currently, this agent is under advanced development as a radioprotector, and the authors are trying to identify its efficacy biomarkers. In this study, global metabolomic changes were analyzed using ultraperformance liquid chromatography quadrupole time-of-flight mass spectrometry. The pilot study using 16 nonhuman primates (8 nonhuman primates each in gamma-tocotrienol- and vehicle-treated groups), with samples obtained from gamma-tocotrienol-treated and irradiated nonhuman primates, demonstrates several metabolites that are altered after irradiation, including compounds involved in fatty acid beta-oxidation, purine catabolism, and amino acid metabolism. The machine-learning algorithm, Random Forest, separated control, irradiated gamma-tocotrienol-treated, and irradiated vehicle-treated nonhuman primates at 12 h and 24 h as evident in a multidimensional scaling plot. Primary metabolites validated included carnitine/acylcarnitines, amino acids, creatine, and xanthine. Overall, gamma-tocotrienol administration reduced high fluctuations in serum metabolite levels, suggesting an overall beneficial effect on animals exposed to radiation. This initial assessment also highlights the utility of metabolomics in determining underlying physiological mechanisms responsible for the radioprotective efficacy of gamma-tocotrienol.

Genotype × environment interaction on tocochromanol and plastochromanol-8 content in seeds of doubled haploids obtained from F1 hybrid black × yellow seeds of winter oilseed rape (Brassica napus L.)

BACKGROUND

The aim of the study was to determine the effect of genotype × environment interaction on the levels of α-, β-, γ- and δ-tocopherol (α-T, β-T, γ-T and δ-T, respectively) and plastochromanol-8 (PC-8) in seeds of 17 doubled haploids (DHs) obtained from the F1 hybrid derived from crossing black (DH H₂ -26) × yellow (DH Z-114) seeds of winter oilseed rape.

RESULTS

The content of tocopherols in the tested DH lines ranged from 415.6 to 540.1 mg kg^-1 seeds, while PC-8 content ranged from 56.3 to 89.0 mg kg^-1 seeds. The α-T/γ-T ratio reached a level of 0.78-1.29. Studies have shown that heritability for α-T, β-T, γ-T, total-T and PC-8 is mainly due to genotypic variation. For the δ-T homologue the level was dependent on environmental effect.

CONCLUSION

The obtained DH lines population of oilseed rape is characterized by high heritability coefficients for α-T, β-T, γ-T, total-T and PC-8 levels, which indicates a greater influence of genotype than the environment on the content of these compounds. Among all studied doubled haploids, seven DHs were selected which were characterized by stable contents of α-T, β-T, γ-T, δ-T and total-T with the simultaneous stable content of PC-8. © 2017 Society of Chemical Industry.

Behaviour of Trolox with macromolecule-bound antioxidants in aqueous medium: Inhibition of auto-regeneration mechanism

This work aimed at investigating the behaviour of Trolox, vitamin E analogue, in presence of macromolecule-bound antioxidants in aqueous radical medium. Three main groups of macromolecule-bound antioxidants were assayed: dietary fiber (DF), protein and lipid-bound antioxidants, represented by whole wheat, soybean and olive oil products, respectively. Experimental studies were carried out in aqueous ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)) radical medium. Trolox and macromolecule-bound antioxidants were added to radical separately and together in different concentrations. Antioxidant capacities were determined using QUENCHER procedure. pH of radical media was altered for DF and protein-bound antioxidant studies to examine its effect. Chemometric tools were used for experimental design and multivariate data analysis. Results revealed antagonistic interactions for Trolox with all macromolecule-bound antioxidants. The reason behind this antagonism was investigated through oxidation reactions of Trolox via mass spectrometry analysis. Consequently, a proof was obtained for inhibitory effect of bound-antioxidants on auto-regeneration reactions of Trolox.

Targeting melanoma stem cells with the Vitamin E derivative δ-tocotrienol

The prognosis of metastatic melanoma is very poor, due to the development of drug resistance. Cancer stem cells (CSCs) may play a crucial role in this mechanism, contributing to disease relapse. We first characterized CSCs in melanoma cell lines. We observed that A375 (but not BLM) cells are able to form melanospheres and show CSCs traits: expression of the pluripotency markers SOX2 and KLF4, higher invasiveness and tumor formation capability in vivo with respect to parental adherent cells. We also showed that a subpopulation of autofluorescent cells expressing the ABCG2 stem cell marker is present in the A375 spheroid culture. Based on these data, we investigated whether δ-TT might target melanoma CSCs. We demonstrated that melanoma cells escaping the antitumor activity of δ-TT are completely devoid of the ability to form melanospheres. In contrast, cells that escaped vemurafenib treatment show a higher ability to form melanospheres than control cells. δ-TT also induced disaggregation of A375 melanospheres and reduced the spheroidogenic ability of sphere-derived cells, reducing the expression of the ABCG2 marker. These data demonstrate that δ-TT exerts its antitumor activity by targeting the CSC subpopulation of A375 melanoma cells and might represent a novel chemopreventive/therapeutic strategy against melanoma.

WRINKLED1 and ACYL-COA:DIACYLGLYCEROL ACYLTRANSFERASE1 regulate tocochromanol metabolism in Arabidopsis

Photosynthetic organisms such as plants, algae and some cyanobacteria synthesize tocochromanols, a group of compounds that encompasses tocopherols and tocotrienols and that exhibits vitamin E activity in animals. While most vitamin E biosynthetic genes have been identified in plant genomes, regulatory genes controlling tocopherol accumulation are currently unknown. We isolated by forward genetics Arabidopsis enhanced vitamin E (eve) mutants that overaccumulate the classic tocopherols and plastochromanol-8, and a tocochromanol unknown in this species. We mapped eve1 and eve4, and identified the unknown Arabidopsis tocochromanol by using a combination of analytical tools. In addition, we determined its biosynthetic pathway with a series of tocochromanol biosynthetic mutants and transgenic lines. eve1 and eve4 are two seed lipid mutants affecting the WRINKLED1 (WRI1) and ACYL-COA:DIACYLGLYCEROL ACYLTRANSFERASE1 (DGAT1) genes, respectively. The unknown tocochromanol is 11'-12' γ-tocomonoenol, whose biosynthesis is VITAMIN E 1 (VTE1) - and VTE2-dependent and is initiated by the condensation of homogentisate (HGA) and tetrahydrogeranylgeranyl pyrophosphate. This study identifies the first two regulatory genes, WRI1 and DGAT1, that control the synthesis of all tocochromanol forms in seeds, and shows the existence of a metabolic trade-off between lipid and tocochromanol metabolisms. Moreover, it shows that Arabidopsis possesses a tocomonoenol biosynthetic pathway that competes with tocopherol synthesis.

A Metabolomic and Lipidomic Serum Signature from Nonhuman Primates Administered with a Promising Radiation Countermeasure, Gamma-Tocotrienol

The development of radiation countermeasures for acute radiation syndrome (ARS) has been underway for the past six decades, leading to the identification of multiple classes of radiation countermeasures. However, to date, only two growth factors (Neupogen and Neulasta) have been approved by the United States Food and Drug Administration (US FDA) for the mitigation of hematopoietic acute radiation syndrome (H-ARS). No radioprotector for ARS has been approved by the FDA yet. Gamma-tocotrienol (GT3) has been demonstrated to have radioprotective efficacy in murine as well as nonhuman primate (NHP) models. Currently, GT3 is under advanced development as a radioprotector that can be administered prior to radiation exposure. We are studying this agent for its safety profile and efficacy using the NHP model. In this study, we analyzed global metabolomic and lipidomic changes using ultra-performance liquid chromatography (UPLC) quadrupole time-of-flight mass spectrometry (QTOF-MS) in serum samples of NHPs administered GT3. Our study, using 12 NHPs, demonstrates that alterations in metabolites manifest only 24 h after GT3 administration. Furthermore, metabolic changes are associated with transient increase in the bioavailability of antioxidants, including lactic acid and cholic acid and anti-inflammatory metabolites 3 deoxyvitamin D3, and docosahexaenoic acid. Taken together, our results show that the administration of GT3 to NHPs causes metabolic shifts that would provide an overall advantage to combat radiation injury. This initial assessment also highlights the utility of metabolomics and lipidomics to determine the underlying physiological mechanisms involved in the radioprotective efficacy of GT3.

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.

Enhancement of apoptotic activities on brain cancer cells via the combination of γ-tocotrienol and jerantinine A

BACKGROUND

γ-Tocotrienol, a vitamin E isomer possesses pronounced in vitro anticancer activities. However, the in vivo potency has been limited by hardly achievable therapeutic levels owing to inefficient high-dose oral delivery which leads to subsequent metabolic degradation. Jerantinine A, an Aspidosperma alkaloid, originally isolated from Tabernaemontana corymbosa, has proved to possess interesting anticancer activities. However, jerantinine A also induces toxicity to non-cancerous cells.

PURPOSE

We adopted a combinatorial approach with the joint application of γ-tocotrienol and jerantinine A at lower concentrations in order to minimize toxicity towards non-cancerous cells while improving the potency on brain cancer cells.

METHODS

The antiproliferative potency of individual γ-tocotrienol and jerantinine A as well as combined in low-concentration was firstly evaluated on U87MG cancer and MRC5 normal cells. Morphological changes, DNA damage patterns, cell cycle arrests and the effects of individual and combined low-concentration compounds on microtubules were then investigated. Finally, the potential roles of caspase enzymes and apoptosis-related proteins in mediating the apoptotic mechanisms were investigated using apoptosis antibody array, ELISA and Western blotting analysis.

RESULTS

Combinatorial study between γ-tocotrienol at a concentration range (0-24µg/ml) and fixed IC₂₀ concentration of jerantinine A (0.16µg/ml) induced a potent antiproliferative effect on U87MG cells and led to a reduction on the new half maximal inhibitory concentration of γ-tocotrienol (i.e._tIC₅₀=1.29µg/ml) as compared to that of individual γ-tocotrienol (i.e. IC₅₀=3.17µg/ml). A reduction on undesirable toxicity to MRC5 normal cells was also observed. G0/G1 cell cycle arrest was evident on U87MG cells receiving IC₅₀ of individual γ-tocotrienol and combined low-concentration compounds (1.29µg/ml γ-tocotrienol + 0.16µg/ml jerantinine A), whereas, a profound G2/M arrest was evident on cells treated with IC₅₀ of individual jerantinine A. Additionally, individual jerantinine A and combined compounds (except individual γ-tocotrienol) caused a disruption of microtubule networks triggering Fas- and p53-induced apoptosis mediated via the death receptor and mitochondrial pathways.

CONCLUSIONS

These findings demonstrated that the combined use of lower concentrations of γ-tocotrienol and jerantinine A induced potent cytotoxic effects on U87MG cancer cells resulting in a reduction on the required individual concentrations and thereby minimizing toxicity of jerantinine A towards non-cancerous MRC5 cells as well as probably overcoming the high-dose limiting application of γ-tocotrienol. The multi-targeted mechanisms of action of the combination approach have shown a therapeutic potential against brain cancer in vitro and therefore, further in vivo investigations using a suitable animal model should be the way forward.

α-Tocopheryl Phosphate Induces VEGF Expression via CD36/PI3Kγ in THP-1 Monocytes

The CD36 scavenger receptor binds several ligands and mediates ligand uptake and ligand-dependent signal transduction and gene expression, events that may involve CD36 internalization. Here we show that CD36 internalization in THP-1 monocytes is triggered by α-tocopherol (αT) and more strongly by α-tocopheryl phosphate (αTP) and EPC-K1, a phosphate diester of αTP and L-ascorbic acid. αTP-triggered CD36 internalization is prevented by the specific covalent inhibitor of selective lipid transport by CD36, sulfo-N-succinimidyl oleate (SSO). Moreover, SSO inhibited the CD36-mediated uptake of 14C-labelled αTP suggesting that αTP binding and internalization of CD36 is involved in cellular αTP uptake, whereas the uptake of αT was less affected. Similar to that, inhibition of selective lipid transport of the SR-BI scavenger receptor resulted mainly in reduction of αTP and not αT uptake. In contrast, uptake of αT was mainly inhibited by Dynasore, an inhibitor of clathrin-mediated endocytosis, suggesting that the differential regulatory effects of αTP and αT on signaling may be influenced by their different routes of uptake. Interestingly, αTP and EPC-K1 also reduced the neutral lipid content of THP-1 cells and the phagocytosis of fluorescent Staphylococcus aureus bioparticles. Moreover, induction of the vascular endothelial growth factor (VEGF) promoter activity by αTP occurred via CD36/PI3Kγ/Akt, as it could be inhibited by specific inhibitors of this pathway (SSO, Wortmannin, AS-605240). These results suggest that αTP activates PI3Kγ/Akt signaling leading to VEGF expression in monocytes after binding to and/or transport by CD36, a receptor known to modulate angiogenesis in response to amyloid beta, oxLDL, and thrombospondin. J. Cell. Biochem. 118: 1855-1867, 2017. © 2017 Wiley Periodicals, Inc.

Gamma-tocotrienol reverses multidrug resistance of breast cancer cells with a mechanism distinct from that of atorvastatin

In addition to its antioxidant properties, γ-tocotrienol also has the ability to inhibit HMG-CoA reductase, which is the key enzyme in the mevalonate pathway for cholesterol biosynthesis. Statins, the competitive inhibitors of HMG-CoA reductase, display potent anticancer activity and reversal ability of multidrug resistance in a variety of tumor cells, which is believed to be due to their inhibition of HMG-CoA reductase. Here, we determined the role of the mevalonate pathway in γ-tocotrienol-mediated reversal of multidrug resistance in cancer cells. We found both γ-tocotrienol and atorvastatin effectively reversed multidrug resistance of MCF-7/Adr and markedly inhibited the intracellular levels of FPP and GGPP. Exogenous addition of mevalonate or FPP and GGPP almost completely prevented the reversal ability of atorvastatin but only partly attenuated the reversal effect of γ-tocotrienol on doxorubicin resistance. In addition, γ-tocotrienol actively inhibited the expression of P-gp and increased the accumulation of doxorubicin in cells, which led to the enhanced G2/M arrest and cell apoptosis. Taken together, γ-tocotrienol reversed the multidrug resistance of MCF-7/Adr with a mechanism distinct from that of atorvastatin. Instead of the mevalonate pathway, the inhibition of P-gp expression is a potential mechanism by which γ-tocotrienol reverses multidrug resistance in MCF-7/Adr.

Enhanced plastochromanol-8 accumulation during reiterated drought in maize (Zea mays L.)

Plastochromanol-8 (PC-8) belongs to the group of tocochromanols, and together with tocopherols and carotenoids, might help protect photosystem II from photoinhibition during environmental stresses. Here, we aimed to unravel the time course evolution of PC-8 together with that of vitamin E compounds, in maize (Zea mays L.) plants exposed to reiterated drought. Measurements were performed in plants grown in a greenhouse subjected to two consecutive cycles of drought-recovery. PC-8 contents, which accounted for more than 25% of tocochromanols in maize leaves, increased progressively in response to reiterated drought stress. PC-8 contents paralleled with those of vitamin E, particularly α-tocopherol. Profiling of the stress-related phytohormones (ABA, jasmonic acid and salicylic acid) was consistent with a role of ABA in the regulation of PC-8 and vitamin E biosynthesis during drought stress. Results also suggest that PC-8 may help tocopherols prevent damage to the photosynthetic apparatus. A better knowledge of the ABA-dependent regulation of PC-8 may help us manipulate the contents of this important antioxidant in crops.

Development of Orally Administered γ-Tocotrienol (GT3) Nanoemulsion for Radioprotection

The purpose of this study was two-fold: (1) to formulate γ-tocotrienol (GT3) in a nanoemulsion formulation as a prophylactic orally administered radioprotective agent; and (2) to optimize the storage conditions to preserve the structural integrity of both the formulation and the compound. γ-tocotrienol was incorporated into a nanoemulsion and lyophilized with lactose. Ultra performance liquid chromatography–mass spectroscopy (UPLC–MS) was used to monitor the chemical stability of GT3 over time, the particle size and ζ potential, and scanning electron microscopy (SEM) were used to study the physical stability of the nanoemulsion. Radioprotective and toxicity studies were performed in mice. The liquid formulation exhibited GT3 degradation at all storage temperatures. Lyophilization, in the presence of lactose, significantly reduced GT3 degradation. Both the liquid and lyophilized nanoemulsions had stable particle size and ζ potential when stored at 4 °C. Toxicity studies of the nanoemulsion resulted in no observable toxicity in mice at an oral dose of 600 mg/kg GT3. The nano-formulated GT3 (300 mg/kg) demonstrated enhanced survival efficacy compared to GT3 alone (200 and 400 mg/kg) in CD2F1 mice exposed to total body gamma radiation. The optimal long-term storage of formulated GT3 is as a powder at −20 °C to preserve drug and formulation integrity. Formulation of GT3 as a nanoemulsion for oral delivery as a prophylactic radioprotectant shows promise and warrants further investigation.

THE POTENTIATION OF THE RADIOPROTECTIVE EFFICACY OF TWO MEDICAL COUNTERMEASURES, GAMMA-TOCOTRIENOL AND AMIFOSTINE, BY A COMBINATION PROPHYLACTIC MODALITY

This study was designed to evaluate the possible potentiation of survival protection afforded by relatively low-dose amifostine prophylaxis against total body irradiation in combination with a protective, less toxic agent, gamma-tocotrienol (GT3). Mice were administered amifostine and/or GT3, then exposed to 9.2 Gy ⁶⁰Co γ-irradiation and monitored for survival for 30 days. To investigate cytokine stimulation, mice were administered amifostine or GT3; serum samples were collected and analyzed for cytokines. Survival studies show single treatments of GT3 or amifostine significantly improved survival, compared to the vehicle, and combination treatments resulted in significantly higher survival compared to single treatments. In vivo studies with GT3 confirmed prior work indicating GT3 induces granulocyte colony-stimulating factor (G-CSF). This approach, the prophylactic combination of amifostine and GT3, which act through different mechanisms, shows promise and should be investigated further as a potential countermeasure for acute radiation syndrome.

The long chain α-tocopherol metabolite α-13'-COOH and γ-tocotrienol induce P-glycoprotein expression and activity by activation of the pregnane X receptor in the intestinal cell line LS 180

SCOPE

Members of the vitamin E family or their metabolites may induce the xenobiotic transporter P-glycoprotein (P-gp), which can limit the bioavailability of drugs and phytochemicals. This study aimed to investigate if α- and γ-tocopherol, α- and γ-tocotrienol, the long chain metabolite α-tocopherol-13'-COOH, the short chain metabolites α- and γ-carboxyethylhydroxychromanol and plastochromanol-8 activate the pregnane X receptor (PXR) and thereby modulate P-gp expression and/or activity.

METHODS AND RESULTS

P-gp protein expression and activity were studied in LS 180 cells incubated with the respective test compound for 48 h. Furthermore, we determined if the compounds activate PXR in LS 180 cells, as PXR regulates P-gp expression. Neither P-gp protein expression and activity, nor PXR activity were influenced by α-tocopherol, γ-tocopherol and plastochromanol-8. α-Tocotrienol activated PXR in the reporter gene assay but did not induce protein expression or activity of P-gp. γ-Tocotrienol and α-13'-COOH activated PXR and induced protein expression and transporter activity of P-gp.

CONCLUSION

Because the induction of P-gp in the intestine may limit the systemic bioavailability of its substrates, the concurrent intake of drugs and γ-tocotrienol and, if ever applicable, α-13'-COOH should be avoided.

Preparation and in vivo/in vitro evaluation of formononetin phospholipid/vitamin E TPGS micelles

To enhance the formononetin (FN) antitumor effect, we developed a passive targeting FN-contained formulation. FN-contained Vitamin E d-α-tocopheryl polyethylene glycol 1000 succinate (vitamin E TPGS or TPGS)/phospholipid micelles were prepared by the solvent injection method. Particle size, polydispersity, zeta potential, encapsulation efficiency, drug release profile, and micelles morphology were evaluated and characterized by various methods including high-performance liquid chromatography, dynamic light scattering, and transmission electron microscopy. Cellular uptake of micelles was evaluated with fluorescence imaging coupled with HPLC method. Cytotoxicity of FN micelles and free FN was compared using MTT method. In vivo imaging was employed to assess the accumulation of DiR micelles and free DiR at tumor site. The antitumor effect of FN micelles was examined in tumor-bearing mice. The results showed that prepared FN micelles had an average particle diameter of 111.91 ± 5.82 nm with good stability. FN micelles enhanced the cellular uptake and improved cell cytotoxicity than free FN. Furthermore, DiR micelles quickly accumulated at the tumor site than free DiR. FN micelles significantly improved tumor inhibition rate compared to that observed with free FN in tumor-bearing mice with great biosafety. Thus, FN micelles demonstrated a clear treatment advantage and provided an ideal drug administration system to improve the antitumor effect of FN.

Progenitor Cell Mobilization by Gamma-tocotrienol: A Promising Radiation Countermeasure

This article reviews studies of progenitor mobilization with gamma-tocotrienol (GT3), a tocol under advanced development as a radiation countermeasure for acute radiation syndrome (ARS). GT3 protects mice against high doses of ionizing radiation and induces high levels of granulocyte colony-stimulating factor (G-CSF). GT3-induced G-CSF in conjunction with AMD3100 (a chemokine receptor antagonist clinically used to improve the yield of mobilized progenitors) mobilizes progenitors; these mobilized progenitors mitigate injury when infused to mice exposed to acute, high-dose ionizing radiation. The administration of a G-CSF antibody to GT3-injected donor mice abrogated the radiomitigative efficacy of blood or peripheral blood mononuclear cells (PBMC) in irradiated recipient mice. The efficacy of GT3-injected donor mice blood or PBMC was comparable to a recently published article involving blood or mononuclear cells obtained from mice injected with G-CSF. The injected progenitors were found to localize in various tissues of irradiated hosts. The authors demonstrate the efficacy of a bridging therapy in a preclinical animal model that allows the lymphohematopoietic system of severely immunocompromised mice to recover. This suggests that GT3 is a highly effective agent for radioprotection and mobilizing progenitors with significant therapeutic potential. Therefore, GT3 may be considered for further translational development and ultimately for use in humans.

Vitamin E δ-tocotrienol triggers endoplasmic reticulum stress-mediated apoptosis in human melanoma cells

Malignant melanoma is the leading cause of death from skin cancer. Drug toxicity and resistance represent a serious challange for melanoma treatments. Evidence demonstrates that natural compounds may play a crucial role in cancer prevention, growth and progression. Vitamin E tocotrienols (TT) were shown to possess antitumor activity. Here, we analyzed the effects of δ-TT on melanoma cell growth and the involvement of the endoplasmic reticulum (ER) stress in this activity. The experiments were performed on human melanoma cell lines, BLM and A375. δ-TT exerted a significant proapoptotic effect on both cell lines, involving the intrinsic apoptosis pathway; importantly, this compound did not affect the viability of normal human melanocytes. In melanoma cells, δ-TT exerted its antitumor effect through activation of the PERK/p-eIF2α/ATF4/CHOP, IRE1α and caspase-4 ER stress-related branches. Salubrinal, an inhibitor of the ER stress, counteracted the cytotoxic activity of δ-TT. In vivo experiments performed in nude mice bearing A375 xenografts evidenced that δ-TT reduces tumor volume and tumor mass; importantly, tumor progression was significantly delayed by δ-TT treatment. In conclusion, δ-TT exerts a proapoptotic activity on melanoma cells, through activation of the ER stress-related pathways. δ-TT might represent an effective option for novel chemopreventive/therapeutic strategies for melanoma.

The Effect of Surfactant on Paclitaxel Nanocrystals: An In Vitro and In Vivo Study

In this study, we first investigated the change of the morphology of paclitaxel (PTX) nanocrystals by varying the type of stabilizer and increasing the amount of D-a-tocopheryl polyethylene glycol 1000 succinate (TPGS) in PTX/TPGS nanocrystals. Rod-shaped nanocrystals changed into relatively thermally stable spherical micelles as the amount of TPGS increased to 1/20 (PTX/TPGS). With these increasing amounts of TPGS, higher cytotoxicity and cellular uptake were observed in P-glycoprotein-overexpressing PTX-resistant (H460/TaxR) cancer cells. Compared to Taxol, PTX/Pluronic F127 (F127) (1/5) nanocrystals, PTX/TPGS (1/5) nanocrystals and PTX/TPGS (1/40) micelles showed significantly sustained in vitro release profiles. Pharmacokinetic studies showed that PTX from these nanoformulations was cleared more rapidly than PTX from Taxol after intravenous administration. However, although presenting an unfavorable pharmacokinetic profile, the biodistribution study showed that PTX/TPGS (1/40) micelles were more effective in promoting accumulation of PTX in drug resistant tumors than Taxol, due to the P-gp inhibition effect of TPGS.

Synergistic cytotoxic effects of combined δ-tocotrienol and jerantinine B on human brain and colon cancers

ETHNOPHARMACOLOGICAL RELEVANCE

The genus Tabernaemontana has widespread distribution throughout tropical and subtropical parts of the world, i.e. Africa, Asia and America which has long been used for treatments of different disease conditions including tumours, wounds, syphilis, stomach ache and headache. Some Tabernaemontana species are used for treatment of piles, spleen and abdominal tumours in India. In particular, the leaf of Tabernaemontana corymbosa is used for treatment of tumours in Bangladesh. Parts of the plant or whole plants are used as decoctions, steam bath, powder and ointments.

AIM OF STUDY

The present study was undertaken to study the mechanism of apoptosis induction in human glioblastoma (U87MG) and colorectal adenocarcinoma (HT-29) cancer cells by a novel indole alkaloid, jerantinine B isolated from T. corymbosa, δ-tocotrienol and the combined low-dose treatments of δ-tocotrienol with IC20 dose of jerantinine B.

MATERIALS AND METHODS

Cell viability, isobologram and combinational index (CI) analyses were used to determine the pharmacological interaction between combined treatments based on the IC50 values obtained. Fluorescence and histochemical staining techniques as well as comet assay were used for evaluating the morphological changes and DNA damage pattern, respectively. The effects of treatments on microtubules, caspase activity and cell death were determined using immunofluorescence technique, caspase colorimetric and neutral red uptake assays, respectively.

RESULTS

Jerantinine B, δ-tocotrienol and combined low-dose treatments induced a dose-dependent growth inhibition against U87MG and HT-29 cells selectively with less toxicity acted towards the normal MRC5 cells. Synergistic growth inhibition observed with CI values of 0.85 and 0.77 for U87MG and HT-29 cells, resulting in up to 2-fold and 3.8-fold dose reduction of δ-tocotrienol and jerantinine B, respectively. U87MG and HT-29 cells exhibited morphological features of apoptosis and double stranded DNA breaks. Individual and combined treatments induced caspase 8 and 3 activities and cell death independent of caspase activation on U87MG and HT-29 cells. An increased caspase 9 activity was also evident on U87MG and HT-29 treated with combined treatments and HT-29 cells treated with jerantinine B. Jerantinine B and combined low-dose treatments with δ-tocotrienol undoubtedly disrupted the microtubule networks.

CONCLUSION

The present study demonstrated the mechanism for cytotoxic potency of δ-tocotrienol and jerantinine B against U87MG and HT-29 cells. Furthermore, combined low-dose treatments induced concurrent synergistic inhibition of cancer cell growth with concomitant dose reduction thus minimizing toxicity to normal cells and improving potency of δ-tocotrienol and jerantinine B.

γ-Tocotrienol as a Promising Countermeasure for Acute Radiation Syndrome: Current Status

The hazard of ionizing radiation exposure due to nuclear accidents or terrorist attacks is ever increasing. Despite decades of research, still, there is a shortage of non-toxic, safe and effective medical countermeasures for radiological and nuclear emergency. To date, the U.S. Food and Drug Administration (U.S. FDA) has approved only two growth factors, Neupogen (granulocyte colony-stimulating factor (G-CSF), filgrastim) and Neulasta (PEGylated G-CSF, pegfilgrastim) for the treatment of hematopoietic acute radiation syndrome (H-ARS) following the Animal Efficacy Rule. Promising radioprotective efficacy results of γ-tocotrienol (GT3; a member of the vitamin E family) in the mouse model encouraged its further evaluation in the nonhuman primate (NHP) model. These studies demonstrated that GT3 significantly aided the recovery of radiation-induced neutropenia and thrombocytopenia compared to the vehicle controls; these results particularly significant after exposure to 5.8 or 6.5 Gray (Gy) whole body γ-irradiation. The stimulatory effect of GT3 on neutrophils and thrombocytes (platelets) was directly and positively correlated with dose; a 75 mg/kg dose was more effective compared to 37.5 mg/kg. GT3 was also effective against 6.5 Gy whole body γ-irradiation for improving neutrophils and thrombocytes. Moreover, a single administration of GT3 without any supportive care was equivalent, in terms of improving hematopoietic recovery, to multiple doses of Neupogen and two doses of Neulasta with full supportive care (including blood products) in the NHP model. GT3 may serve as an ultimate radioprotector for use in humans, particularly for military personnel and first responders. In brief, GT3 is a promising radiation countermeasure that ought to be further developed for U.S. FDA approval for the ARS indication.

Antioxidants Abrogate Alpha-Tocopherylquinone-Mediated Down-Regulation of the Androgen Receptor in Androgen-Responsive Prostate Cancer Cells

Tocopherylquinone (TQ), the oxidation product of alpha-tocopherol (AT), is a bioactive molecule with distinct properties from AT. In this study, AT and TQ are investigated for their comparative effects on growth and androgenic activity in prostate cancer cells. TQ potently inhibited the growth of androgen-responsive prostate cancer cell lines (e.g., LAPC4 and LNCaP cells), whereas the growth of androgen-independent prostate cancer cells (e.g., DU145 cells) was not affected by TQ. Due to the growth inhibitory effects induced by TQ on androgen-responsive cells, the anti-androgenic properties of TQ were examined. TQ inhibited the androgen-induced activation of an androgen-responsive reporter and inhibited the release of prostate specific antigen from LNCaP cells. TQ pretreatment was also found to inhibit AR activation as measured using the Multifunctional Androgen Receptor Screening assay. Furthermore, TQ decreased androgen-responsive gene expression, including TM4SF1, KLK2, and PSA over 5-fold, whereas AT did not affect the expression of androgen-responsive genes. Of importance, the antiandrogenic effects of TQ on prostate cancer cells were found to result from androgen receptor protein down-regulation produced by TQ that was not observed with AT treatment. Moreover, none of the androgenic endpoints assessed were affected by AT. The down-regulation of androgen receptor protein by TQ was abrogated by co-treatment with antioxidants. Overall, the biological actions of TQ were found to be distinct from AT, where TQ was found to be a potent inhibitor of cell growth and androgenic activity in androgen-responsive prostate cancer cells.

Fluoridated hydroxyapatite: Eu(3+) nanorods-loaded folate-conjugated D-α-tocopheryl polyethylene glycol succinate (vitamin E TPGS) micelles for targeted imaging of cancer cells

In this study, fluoridated hydroxyapatite: Eu(3+) nanorod-loaded folate-conjugated TPGS micelles were prepared by thin-film hydration. The findings in this study demonstrate that micelles show improved dispersion, high stability, and excellent fluorescent property in aqueous solutions, suitable for targeted imaging of cancer cells with over-expressing folate receptors on their surface. The micelles designed in this study will be a promising tool for early detection of cancer.

Regulation of Obesity and Metabolic Complications by Gamma and Delta Tocotrienols

Tocotrienols (T3s) are a subclass of unsaturated vitamin E that have been extensively studied for their anti-proliferative, anti-oxidative and anti-inflammatory properties in numerous cancer studies. Recently, T3s have received increasing attention due to their previously unrecognized property to attenuate obesity and its associated metabolic complications. In this review, we comprehensively evaluated the recent published scientific literature about the influence of T3s on obesity, with a particular emphasis on the signaling pathways involved. T3s have been demonstrated in animal models or human subjects to reduce fat mass, body weight, plasma concentrations of free fatty acid, triglycerides and cholesterol, as well as to improve glucose and insulin tolerance. Their mechanisms of action in adipose tissue mainly include (1) modulation of fat cell adipogenesis and differentiation; (2) modulation of energy sensing; (3) induction of apoptosis in preadipocytes and (4) modulation of inflammation. Studies have also been conducted to investigate the effects of T3s on other targets, e.g., the immune system, liver, muscle, pancreas and bone. Since δT3 and γT3 are regarded as the most active isomers among T3s, their clinical relevance to reduce obesity should be investigated in human trials.

pH-Sensitive self-assembling nanoparticles for tumor near-infrared fluorescence imaging and chemo-photodynamic combination therapy

The development of visual tumor theranostic nanoparticles has become a great challenge. In this study, d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS) was conjugated to acid-sensitive cis-aconitic anhydride-modified doxorubicin (CAD) to obtain pH-sensitive anti-tumor prodrug nanoparticles (TCAD NPs) via self-assembling. Subsequently, the photosensitizer chlorin e6 (Ce6) was loaded into the resulting prodrug nanoparticles to prepare a novel tumor near-infrared fluorescence imaging and chemo-photodynamic combination therapy system (TCAD@Ce6 NPs). An accelerated release of doxorubicin (DOX) and chlorin e6 (Ce6) from the TCAD@Ce6 NPs could be achieved due to the hydrolysis of the acid-sensitive amide linker under mild acidic conditions (pH = 5.5). An in vitro experiment showed that A549 lung cancer cells exhibited a significantly higher uptake of DOX and Ce6 by using our delivery system than the free form of DOX and Ce6. An in vivo experiment showed that TCAD@Ce6 NPs displayed better tumor targeting gathering through the enhanced permeability and retention (EPR) effect than free Ce6, thus improving fluorescence imaging. Moreover, the chemo-photodynamic combination therapy of TCAD@Ce6 NPs combined with near-infrared laser irradiation was confirmed to be capable of inducing high apoptosis and necrosis of tumor cells (A549) in vitro and to display a significantly higher tumor growth suppression in the A549 lung cancer-bearing mice model. Furthermore, compared with exclusive chemotreatment (DOX) or photodynamic treatment (Ce6), our system showed enhanced therapeutic effects both in vitro and in vivo. In conclusion, the high performance TCAD@Ce6 NPs can be used as a promising NIR fluorescence imaging and highly effective chemo-photodynamic system for theranostics of lung cancer, etc. in the near future.

Docetaxel (DTX)-loaded polydopamine-modified TPGS-PLA nanoparticles as a targeted drug delivery system for the treatment of liver cancer

Polydopamine-based surface modification is a simple way to functionalize polymeric nanoparticle (NP) surfaces with ligands and/or additional polymeric layers. In this work, we developed DTX-loaded formulations using polydopamine-modified NPs synthesized using D-α-tocopherol polyethylene glycol 1000 succinate-poly(lactide) (pD-TPGS-PLA/NPs). To target liver cancer cells, galactosamine was conjugated on the prepared NPs (Gal-pD-TPGS-PLA/NPs) to enhance the delivery of DTX via ligand-mediated endocytosis. The size and morphology of pD-TPGS-PLA/NPs and Gal-pD-TPGS-PLA/NPs changed obviously compared with TPGS-PLA/NPs. In vitro studies showed that TPGS-PLA/NPs, pD-TPGS-PLA/NPs and Gal-pD-TPGS-PLA/NPs had similar release profiles of DTX. Both confocal laser scanning microscopy and flow cytometric results showed that coumarin 6-loaded Gal-pD-TPGS-PLA/NPs had the highest cellular uptake efficiency in liver cancer cell line HepG2. Moreover, DTX-loaded Gal-pD-TPGS-PLA/NPs inhibited the growth of HepG2 cells more potently than TPGS-PLA/NPs, pD-TPGS-PLA/NPs, and a clinically available DTX formulation (Taxotere®). The in vivo biodistribution experiments show that the Gal-pD-TPGS-PLA/NPs are specifically targeted to the tumor. Furthermore, the in vivo anti-tumor effects study showed that injecting DTX-loaded Gal-pD-TPGS-PLA/NPs reduced the tumor size most significantly on hepatoma-bearing nude mice. These results suggest that Gal-pD-TPGS-PLA/NPs prepared in the study specifically interacted with the hepatocellular carcinoma cells through ligand-receptor recognition and they may be used as a potentially eligible drug delivery system targeting liver cancers.

STATEMENT OF SIGNIFICANCE

Polydopamine-based surface modification is a simple way to functionalize polymeric nanoparticle surfaces with ligands and/or additional polymeric layers. In this work, we developed docetaxel (DTX)-loaded formulations using polydopamine-modified NPs synthesized from D-α-tocopherol polyethylene glycol 1000 succinate-poly(lactide) (pD-TPGS-PLA/NPs). To target liver cancer cells, galactosamine was conjugated on the prepared NPs (Gal-pD-TPGS-PLA/NPs) to enhance the delivery of DTX via ligand-mediated endocytosis. Both confocal laser scanning microscopy and flow cytometric results showed that coumarin 6-loaded Gal-pD-TPGS-PLA/NPs had the highest cellular uptake efficiency for liver cancer cell line HepG2. The in vivo biodistribution experiments show that the Gal-pD-TPGS-PLA/NPs are specifically targeted to the tumor. Furthermore, the in vivo anti-tumor effects study showed that injecting DTX-loaded Gal-pD-TPGS-PLA/NPs reduced the tumor size most significantly on hepatoma-bearing nude mice. These results suggest that Gal-pD-TPGS-PLA/NPs prepared in the study specifically interacted with the hepatocellular carcinoma cells through ligand-receptor recognition and they could be used as a potentially eligible drug delivery system targeting liver cancers.