Comparative evaluation of the antioxidant activity of alpha-tocopherol, alpha-tocopherol polyethylene glycol 1000 succinate and alpha-tocopherol succinate in isolated hepatocytes and liver microsomal suspensions

Invasive metastatic tumor-camouflaged ROS responsive nanosystem for targeting therapeutic brain injury after cardiac arrest

Drug transmission through the blood-brain barrier (BBB) is considered an arduous challenge for brain injury treatment following the return of spontaneous circulation after cardiac arrest (CA-ROSC). Inspired by the propensity of melanoma metastasis to the brain, B16F10 cell membranes are camouflaged on 2-methoxyestradiol (2ME2)-loaded reactive oxygen species (ROS)-triggered "Padlock" nanoparticles that are constructed by phenylboronic acid pinacol esters conjugated D-a-tocopheryl polyethylene glycol succinate (TPGS-PBAP). The biomimetic nanoparticles (BM@TP/2ME2) can be internalized, mainly mediated by the mutual recognition and interaction between CD44v6 expressed on B16F10 cell membranes and hyaluronic acid on cerebral vascular endothelial cells, and they responsively release 2ME2 by the oxidative stress microenvironment. Notably, BM@TP/2ME2 can scavenge excessive ROS to reestablish redox balance, reverse neuroinflammation, and restore autophagic flux in damaged neurons, eventually exerting a remarkable neuroprotective effect after CA-ROSC in vitro and in vivo. This biomimetic drug delivery system is a novel and promising strategy for the treatment of cerebral ischemia-reperfusion injury after CA-ROSC.

Rp-HPLC Determination of Quercetin in a Novel D-α-Tocopherol Polyethylene Glycol 1000 Succinate Based SNEDDS Formulation: Pharmacokinetics in Rat Plasma

Despite its proven efficacy in diverse metabolic disorders, quercetin (QU) for clinical use is still limited because of its low bioavailability. D-α-Tocopherol polyethylene glycol 1000 succinate (TPGS) is approved as a safe pharmaceutical adjuvant with marked antioxidant and anti-inflammatory activities. In the current study, several QU-loaded self-nanoemulsifying drug delivery systems (SNEDDS) were investigated to improve QU bioavailability. A reversed phase high performance liquid chromatography (RP-HPLC) method was developed, for the first time, as a simple and sensitive technique for pharmacokinetic studies of QU in the presence of TPGS SNEDDS formula in rat plasma. The analyses were performed on a Xterra C18 column (4.6 × 100 mm, 5 µm) and UV detection at 280 nm. The analytes were separated by a gradient system of methanol and phosphate buffer of pH 3. The developed RP-HPLC method showed low limit of detection (LODs) of 7.65 and 22.09 ng/mL and LOQs of 23.19 and 66.96 ng/mL for QU and TPGS, respectively, which allowed their determination in real rat plasma samples. The method was linear over a wide range, (30-10,000) and (100-10,000) ng/mL for QU and TPGS, respectively. The selected SNEDDS formula, containing 50% w/w TPGS, 30% polyethylene glycol 200 (PEG 200), and 20% w/w pumpkin seed oil (PSO), showed a globule size of 320 nm and -28.6 mV zeta potential. Results of the pharmacokinetic studies showed 149.8% improvement in bioavailability of QU in SNEDDS relative to its suspension. The developed HPLC method proved to be simple and sensitive for QU and TPGS simultaneous determination in rat plasma after oral administration of the new SNEDDS formula.

A solid lipid nanoparticle formulation of 4-(N)-docosahexaenoyl 2', 2'-difluorodeoxycytidine with increased solubility, stability, and antitumor activity

Previously, we synthesized 4-(N)-docosahexaenoyl 2', 2'-difluorodeoxycytidine (DHA-dFdC), a novel lipophilic compound with a potent, broad-spectrum antitumor activity. Herein, we report a solid lipid nanoparticle (SLN) formulation of DHA-dFdC with improved apparent aqueous solubility, chemical stability, as well as efficacy in a mouse model. The SLNs were prepared from lecithin/glycerol monostearate-in-water emulsions emulsified with D-α-tocopherol polyethylene glycol 1000 succinate (TPGS) and Tween 20. The resultant DHA-dFdC-SLNs were 102.2 ± 7.3 nm in diameter and increased the apparent solubility of DHA-dFdC in water to at least 5.2 mg/mL, more than 200-fold higher than its intrinsic water solubility. DHA-dFdC in a lyophilized powder of DHA-dFdC-SLNs was significantly more stable than the waxy solid of pure DHA-dFdC. DHA-dFdC-SLNs also showed an increased cytotoxicity against certain tumor cells than DHA-dFdC. The plasma concentration of DHA-dFdC in mice intravenously injected with DHA-dFdC-SLNs in dispersion followed a bi-exponential model, with a half-life of ~44 h. In mice bearing B16-F10 murine melanoma, DHA-dFdC-SLNs were significantly more effective than DHA-dFdC in controlling the tumor growth. In addition, histology evaluation revealed a high level of apoptosis and tumor encapsulation in tumors in mice treated with DHA-dFdC-SLNs. DHA-dFdC-SLNs represents a new DHA-dFdC formulation with improved antitumor activity.

Topical Coenzyme Q10 demonstrates mitochondrial-mediated neuroprotection in a rodent model of ocular hypertension

Coenzyme Q10 (CoQ10) is a mitochondrial-targeted antioxidant with known neuroprotective activity. Its ocular effects when co-solubilised with α-tocopherol polyethylene glycol succinate (TPGS) were evaluated. In vitro studies confirmed that CoQ10 was significantly protective in different retinal ganglion cell (RGC) models. In vivo studies in Adult Dark Agouti (DA) rats with unilateral surgically-induced ocular hypertension (OHT) treated with either CoQ10/TPGS micelles or TPGS vehicle twice daily for three weeks were performed, following which retinal cell health was assessed in vivo using DARC (Detection of Apoptotic Retinal Cells) and post-mortem with Brn3a histological assessment on whole retinal mounts. CoQ10/TPGS showed a significant neuroprotective effect compared to control with DARC (p<0.05) and Brn3 (p<0.01). Topical CoQ10 appears an effective therapy preventing RGC apoptosis and loss in glaucoma-related models.

Mitochondrial substrates in cancer: drivers or passengers?

The majority of cancers demonstrate various tumor-specific metabolic aberrations, such as increased glycolysis even under aerobic conditions (Warburg effect), whereas mitochondrial metabolic activity and their contribution to cellular energy production are restrained. One of the most important mechanisms for this metabolic switch is the alteration in the abundance, utilization, and localization of various mitochondrial substrates. Numerous lines of evidence connect disturbances in mitochondrial metabolic pathways with tumorigenesis and provide an intriguing rationale for utilizing mitochondria as targets for anti-cancer therapy.

Evaluation of antibacterial, antioxidant and DNA protective capacity of Chenopodium album's ethanolic leaf extract

We have investigated the antibacterial effects of Chenopodium album's ethanolic leaf extract (CAE) on all the Gram (+) and Gram (-) microorganisms and evaluated the protective effects of CAE on both yeast and human mononuclear leukocytes' genomic DNA upon oxidative shock. Antibacterial activity was recorded on Bacillus subtilis with 13 mm of inhibition zone. Total oxidative status (TOS) and the total antioxidative status (TAS) levels were determined to evaluate the antioxidant activity of CAE. Results indicated that there was a good correlation between dose of CAE and TAS levels. We also observed that CAE protect the DNA of both yeast and mononuclear leukocytes against the damaging effect of hydrogen peroxide. The comet assay, applied on both Saccharomyces cerevisiae BY4741 (MATa his3Δ1 leu2Δ0 met15Δ0 ura3Δ0) and human leukocytes, results suggested that there was statistically significant correlation between CAE dilutions and antigenotoxic activity.

An in vitro study of osteoblast vitality influenced by the vitamins C and E

Vitamin C and vitamin E are known as important cellular antioxidants and are involved in several other non-antioxidant processes. Generally vitamin C and vitamin E are not synthesized by humans and therefore have to be applied by nutrition. The absence or deficiency of the vitamins can lead to several dysfunctions and even diseases (e.g. scurvy). The main interest in this study is that vitamin C and E are known to influence bone formation, e.g. vitamin C plays the key role in the synthesis of collagen, the major component of the extracellular bone matrix.

In the present study we evaluate the effect of ascorbic acid (vitamin C) and α-tocopherol (vitamin E) on the proliferation and differentiation of primary bovine osteoblasts in vitro. Starting from standard growth medium we minimized the foetal calf serum to reduce their stimulatory effect on proliferation.

An improved growth and an increased synthesis of the extracellular matrix proteins collagen type I, osteonectin and osteocalcin was observed while increasing the ascorbic acid concentration up to 200 μg/ml. Furthermore the effects of α-tocopherol on cell growth and cell differentiation were examined, whereby neither improved growth nor increased synthesis of the extracellular matrix proteins collagen type I, osteonectin and osteocalcin were detected.

Further investigations are necessary to target at better supportive effect of vitamins on bone regeneration, and healing.

Antioxidant micronutrient impact on hearing disorders: concept, rationale, and evidence

PURPOSE

Although auditory disorders are complex conditions, device-related modalities dominate current treatment. However, dysfunction from the central cortex to the inner ear apparatus is increasingly thought to be related to biochemical pathway abnormalities and to free radical-induced oxidative damage and chronic inflammation. Therefore, considering appropriate biologic therapy as an adjunct to standard care against these damaging factors may provide rational expansion of treatment options for otolaryngologists and audiologists.

METHODS

This review outlines the biologic concepts related to some auditory and vestibular conditions and details the current rationale for utilizing antioxidants for a spectrum of hearing disorders. The strategy is based on the authors' collective experience in antioxidant science and supported with published research, pilot animal data and preliminary clinical observations.

RESULTS

A comprehensive micronutrient approach was developed to exploit these pathways, and demonstrated safety and efficacy against oxidative damage and inflammation and clinically relevant neuroprotection. Cooperative research with Department of Defense institutions used prospective, randomized designs to show (1) reduction in oxidative damage measured in plasma and urine over six months, (2) protection against oxidative damage during 12 weeks of intense military training, (3) protection against inflammation after total body blast exposure (rodents), (4) strong neuroprotection against chemically-induced Parkinson's disease (rodents), (5) nerve VIII function improvement after concussive head injury in military personnel, and (6) tinnitus improvement in majority of patients after 90-day evaluation.

CONCLUSION

This systematic review of biologic strategies against hearing disorders combined with new animal and human observations may provide a rational basis for expanding current practice paradigms.

Antioxidant activities of oleanolic acid in vitro: possible role of Nrf2 and MAP kinases

Oleanolic acid (OA) is a natural triterpenoid, which has been used in Chinese medicine for the treatment of liver disorders for many years. Its pharmacological activities have been the focus of intense research in recent years. However, there is little research on the antioxidant activities of OA. In the present study, we aim to investigate whether OA produces its protective effects mainly through antioxidant mechanisms and whether OA plays as an antioxidant through quenching reactive oxygen species (ROS), inhibiting lipid peroxidation or stimulating cellular antioxidant defenses. In the in vitro antioxidant activity-assessing models, OA acted as not only a free radical-scavenger through direct chemical reactions but also a biological molecule, which may enhance the antioxidant defenses. tert-Butyl hydroperoxide (tBHP) induced ROS generation, damaged plasma membrane and decreased cell viability and the expression of key antioxidant enzymes and MAP kinases in QZG cells. OA ameliorated the oxidative injury induced by tBHP through increasing the generation of antioxidant (glutathione) and the expression of key antioxidant enzymes mediated by nuclear factorerythroid 2 p45-related factor 2 (Nrf2), in which process, activation of JNK and ERK, but not p38, was involved. The present study, for the first time, investigated the antioxidant activities of OA systematically. OA probably functions mainly through indirect biological effect and protects QZG cells against cytotoxicity induced by tBHP through increasing the generation of antioxidant and the expression of oxidative stress sensitive transcription factor-Nrf2, and MAP kinases, mainly JNK and ERK. These findings may significantly better the understanding of OA and advance therapeutic approaches to the diseases which are associated with oxidative stress.

Chemotherapy alone vs. chemotherapy plus high dose multiple antioxidants in patients with advanced non small cell lung cancer

OBJECTIVE

In vitro and animal studies suggest that antitumor effect of chemotherapeutic agents may be enhanced by antioxidants. Therefore, we initiated a clinical study to test the efficacy of high-dose multiple antioxidants (vitamins C, E and beta carotene) as an adjunct to chemotherapy (paclitaxel and carboplatin) in non-small-cell lung cancer.

METHODS

136 patients of stage IIIb and stage IV NSCLC were randomized to receive chemotherapy (paclitaxel and carboplatin) alone (chemotherapy arm, n = 72) or chemotherapy in combination with ascorbic acid 6100 mg/day, dl-alpha-tocopherol (vitamin E) 1050 mg/day and beta-carotene 60 mg/day (combination arm, n = 64). Survival were calculated by the Kaplan-Meier method and compared using the log-rank test.

RESULTS

An overall response rate (RR) of 33% was observed in chemotherapy arm with 24 patients showing a partial response (PR) and none showing a complete response (CR). In combination arm the overall RR was 37% with 24 patients showing PR and two showing CR. The median survival times in chemotherapy arm and combination arm were nine and 11 months respectively. The overall survival (OS) rates in chemotherapy arm and combination arm at one year were 32.9% and 39.1%, and at two years, 11.1% and 15.6% respectively. None of these differences were statistically significant (p = 0.20). Toxicity profiles were similar in both arms.

CONCLUSIONS

These results do not support the concern that antioxidants might protect cancer cells from the free radical damage induced by chemotherapy. Larger trials are needed to demonstrate whether high-dose multiple antioxidants in conjunction with chemotherapy increase the response rates and/or survival time in advanced lung cancer.

Differential response of human ovarian cancer cells to induction of apoptosis by vitamin E Succinate and vitamin E analogue, alpha-TEA

A vitamin E derivative, vitamin E succinate (VES; RRR-alpha-tocopheryl succinate), and a vitamin E analogue, 2,5,7,8-tetramethyl-2R-(4R,8R,12-trimethyltridecyl)chroman-6-yloxy acetic acid (alpha-TEA), induce human breast, prostate, colon, lung, cervical, and endometrial tumor cells in culture to undergo apoptosis but not normal human mammary epithelial cells, immortalized, nontumorigenic breast cells, or normal human prostate epithelial cells. Human ovarian and cervical cancer cell lines are exceptions, with alpha-TEA exhibiting greater proapoptotic effects. Although both VES and alpha-TEA can induce A2780 and subline A2780/cp70 ovarian cancer cells to undergo DNA synthesis arrest within 24 h of treatment, only alpha-TEA is an effective inducer of apoptosis. VES or alpha-TEA treatment of cp70 cells with 5, 10, or 20 microg/ml for 3 days induced 5, 6, and 19% versus 9, 36, and 71% apoptosis, respectively. Colony formation data provide additional evidence that cp70 cells are more sensitive to growth inhibition by alpha-TEA than VES. Differences in stability of the ester-linked succinate moiety of VES versus the ether-linked acetic acid moiety of alpha-TEA were demonstrated by high-performance liquid chromatography analyses that showed alpha-TEA to remain intact, whereas VES was hydrolyzed to the free phenol, RRR-alpha-tocopherol. Pretreatment of cp70 cells with bis-(p-nitrophenyl) phosphate, an esterase inhibitor, before VES treatment, resulted in increased levels of intact VES and apoptosis. Taken together, these data show alpha-TEA to be a potent and stable proapoptotic agent for human ovarian tumor cells and suggest that endogenous ovarian esterases can hydrolyze the succinate moiety of VES, yielding RRR-alpha-tocopherol, an ineffective apoptotic-inducing agent.

The extraordinary antioxidant activity of vitamin E phosphate

The antioxidant activities of RRR-vitamin E (VE), all-rac-vitamin E (all-rac-VE), trolox, RRR-vitamin E acetate (VEA), all-rac-vitamin E phosphate (VEP) and RRR-vitamin E succinate (VES) were compared. In this study, the rank order in the inhibition of lipid peroxidation (LPO) of VE and its derivatives was trolox>VE approximately all-rac-VE>VEA>VES. VE and trolox inhibited LPO in non-heated and heated rat liver microsomes. It has generally been accepted that this is due to scavenging of free radicals by these antioxidants, and during this protection the antioxidants are oxidized. VEA and VES have to be converted into VE by esterases to obtain antioxidant activity against LPO. VEP, however, had a potent antioxidant effect of its own without conversion to VE. In contrast to VE, VEP is not consumed during this protection. Of the compounds tested, VEP is the most potent in induction of hemolysis of erythrocytes. EPR experiments using the spin label 16-doxylstearic acid showed that VEP reduces membrane fluidity, in contrast to VE. This indicates that VEP acts as a detergent and forms a barrier that might inhibit the transfer of radicals from one polyunsaturated fatty acid to another. This new mechanism may form the basis for a new class of antioxidants.

Flavonol glycosides from the aerial parts ofAceriphyllum rossii and their antioxidant activities

The methanol extract obtained from the aerial parts of Aceriphyllum rossii (Saxifragaceae) was fractionated into ethyl acetate (EtOAc), n-BuOH and H2O layers through solvent fractionation. Repeated silica gel column chromatography of EtOAc and n-BuOH layers afforded six flavonol glycosides. They were identified as kaempferol 3-O-beta-D-glucopyranoside (astragalin, 1), quercetin 3-O-beta-D-glucopyranoside (isoquercitrin, 2), kaempferol 3-O-alpha-L-rhamnopyranosyl (1-->6)-beta-D-glucopyranoside (3), quercetin 3-O-alpha-L-rhamnopyranosyl (1-->6)-beta-D-glucopyranoside (rutin, 4), kaempferol 3-O-[alpha-L-rhamnopyranosyl (1-->4)-alpha-L-rhamnopyranosyl (1-->6)-beta-D-glucopyranoside] (5) and quercetin 3-O-[alpha-L-rhamnopyranosyl (1-->4)-alpha-L-rhamnopyranosyl (1-->6)-beta-D-glucopyranoside] (6) on the basis of several spectral data. The antioxidant activity of the six compounds was investigated using two free radicals such as the ABTS free radical and superoxide anion radical. Compound 1 exhibited the highest antioxidant activity in the ABTS [2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid)] radical scavenging method. 100 mg/L of compound 1 was equivalent to 72.1+/-1.4 mg/L of vitamin C, and those of compounds 3 and 5 were equivalent to 62.7+/-0.5 mg/L and 54.3+/-1.3 mg/L of vitamin C, respectively. And in the superoxide anion radical scavenging method, compound 5 exhibited the highest activity with an IC50 value of 17.6+/-0.3 microM. In addition, some physical and spectral data of the flavonoids were confirmed.

An argument for Vitamin E supplementation in the management of systemic inflammatory response syndrome

The systemic inflammatory response syndrome results from an uncontrolled, overexpression of the normal host inflammatory response, leading to destruction of host tissue and subsequent organ failure. Oxidant stress has been implicated in this process both as a mechanism for direct cellular injury, as well as activation of intracellular signaling cascades within inflammatory cells resulting in progression of the inflammatory response. Vitamin E is an inexpensive, nontoxic, chain-breaking antioxidant that has therapeutic potential in regulating this process. This review seeks to evaluate the current literature regarding the use of Vitamin E in controlling the excessive inflammation seen in systemic inflammatory response syndrome and argues for further study of its therapeutic potential for these critically ill patients.

Free radical scavenging and skin penetration of troxerutin and vitamin derivatives

BACKGROUND

By its 'protective function', human skin is a potential target for the production of free radicals. The role played by topically applied antioxidants as inhibitors of oxidative stress damage was felt to be worth investigation.

OBJECTIVE

To investigate the free radical scavenging (superoxide, hydroxyl and peroxyl radicals) and skin penetration of troxerutin in association with ascorbyl palmitate and alpha-tocopheryl succinate, esters of two vitamins commonly used in skin care products.

METHODS

The compounds' scavenging activities, in a concentration-dependent manner, were as follows: hydroxyl radicals in a Fenton-based assay; superoxide radicals in a hypoxanthine/xanthine oxidase system; and lipid peroxidation inhibition of liver microsomes was induced by 2,2'-azobis-(2-amidinopropane) dihydrochloride (ABAP).

RESULTS

A synergic action was observed between alpha-tocopheryl succinate and troxerutin for hydroxyl radical scavenging, between the three compounds for superoxide scavenging and between troxerutin and ascorbyl palmitate in lipid peroxidation inhibition.

CONCLUSION

Using a stripping method, it was shown that the three substances, incorporated in a pharmaceutical preparation, permeated through human epidermis. Thus, this association can improve skin care products for preventing free radical-mediated damage.

Scientific rationale for using high-dose multiple micronutrients as an adjunct to standard and experimental cancer therapies

We have hypothesized that high-dose multiple micronutrients, including antioxidants, as an adjunct to standard (radiation therapy and chemotherapy) or experimental therapy (hyperthermia and immunotherapy), may improve the efficacy of cancer therapy by increasing tumor response and decreasing toxicity. Several in vitro studies and some in vivo investigations support this hypothesis. A second hypothesis is that antioxidants may interfere with the efficacy of radiation therapy and chemotherapy. This hypothesis is based on the concept that antioxidants will destroy free radicals that are generated during therapy, thereby protecting cancer cells against death. None of the published data on the effect of antioxidants in combination with radiation or chemotherapeutic agents on tumor cells supports the second hypothesis. Scientific rationale in support of a micronutrient protocol to be used as an adjunct to standard or experimental cancer therapy is presented.

Vitamin E (d-alpha-tocopheryl succinate) decreases mitotic accumulation in gamma-irradiated human tumor, but not in normal, cells

Previous studies have shown that treatment of tumor cells in vitro with d-alpha-tocopheryl succinate (alpha-TS), a most effective form of vitamin E, alone or in combination with X-irradiation, reduced the growth of these cells more than that produced by individual agents. However, it is unknown whether alpha-TS, alone or in combination with gamma-irradiation, would produce similar effects on normal cells. To study this, we have compared the effects of alpha-TS on three human tumor cell lines, HeLa (cervical carcinoma), OVGI (ovarian carcinoma), and A549 (lung carcinoma), with the effects on three human normal fibroblast lines, GM2149, AG1522, and HF19. Results showed that alpha-TS treatment of HeLa cells for 20 hours caused inhibition of growth in a dose-dependent manner, but normal human fibroblasts treated similarly with alpha-TS did not show such an effect. alpha-TS treatment for 20 hours also decreased mitotic accumulation in all three tumor cell lines but did not produce such an effect in any of the normal fibroblasts. As expected, gamma-irradiation with 1 Gy decreased mitotic accumulation in human tumor cells and normal fibroblasts; however, alpha-TS treatment for 24 hours before, during, and after irradiation for the entire experimental period further decreased mitotic accumulation in human tumor cells but not in normal cells. These data suggest that effects of alpha-TS, alone or in combination with gamma-irradiation, are selective for tumor cells. Therefore, existing fear that antioxidants such as vitamin E may protect cancer cells from free radical damage during radiation therapy is not justified.

Influence of the antioxidants vitamin E and idebenone on retinal cell injury mediated by chemical ischemia, hypoglycemia, or oxidative stress

A role for the antioxidants vitamin E and idebenone in decreasing retinal cell injury, after metabolic inhibition induced by chemical ischemia and hypoglycemia, was investigated and compared with oxidative stress conditions. Preincubation of the antioxidants, vitamin E (20 microM) and idebenone (10 microM), effectively protected from retinal cell injury after oxidative stress or hypoglycemia, whereas the protection afforded after postincubation of both antioxidants was decreased. Delayed retinal cell damage, mediated by chemical ischemia, was attenuated at 10 or 12 h postischemia, only after exposure to the antioxidants during all the experimental procedure. An antagonist of the N-methyl-D-aspartate (NMDA) receptors, an inhibitor of nitric oxide synthase (NOS) or a blocker of L-type Ca2+ channels were ineffective in reducing cell injury induced by chemical ischemia, hypoglycemia or oxidative stress. Oxidative stress and hypoglycemia increased (about 1.2-fold) significantly the fluorescence of the probe DCFH2-DA, that is indicative of intracellular ROS formation. Free radical generation detected with the probe dihydrorhodamine 123 (DHR 123) was enhanced after oxidative stress, chemical ischemia or hypoglycemia (about 2-fold). Nevertheless, the antioxidants vitamin E or idebenone were ineffective against intracellular ROS generation. Cellular energy charge decreased greatly after chemical ischemia, was moderately affected after hypoglycemia, but no significant changes were observed after oxidative stress. Preincubation with vitamin E prevented the changes in energy charge upon 6 h posthypoglycemia. We can conclude that irreversible changes occurring during chemical ischemia mainly reflect the alterations taking place at the ischemic core, whereas hypoglycemia situations may reflect changes occurring at the penumbra area, whereby vitamin E or idebenone may help to increase cell survival, exerting a beneficial neuroprotective effect.

High doses of multiple antioxidant vitamins: essential ingredients in improving the efficacy of standard cancer therapy

Numerous articles and several reviews have been published on the role of antioxidants, and diet and lifestyle modifications in cancer prevention. However, the potential role of these factors in the management of human cancer have been largely ignored. Extensive in vitro studies and limited in vivo studies have revealed that individual antioxidants such as vitamin A (retinoids), vitamin E (primarily alpha-tocopheryl succinate), vitamin C (primarily sodium ascorbate) and carotenoids (primarily polar carotenoids) induce cell differentiation and growth inhibition to various degrees in rodent and human cancer cells by complex mechanisms. The proposed mechanisms for these effects include inhibition of protein kinase C activity, prostaglandin E1-stimulated adenylate cyclase activity, expression of c-myc, H-ras, and a transcription factor (E2F), and induction of transforming growth factor-beta and p21 genes. Furthermore, antioxidant vitamins individually or in combination enhance the growth-inhibitory effects of x-irradiation, chemotherapeutic agents, hyperthermia, and biological response modifiers on tumor cells, primarily in vitro. These vitamins, individually, also reduce the toxicity of several standard tumor therapeutic agents on normal cells. Low fat and high fiber diets can further enhance the efficacy of standard cancer therapeutic agents; the proposed mechanisms for these effects include the production of increased levels of butyric acid and binding of potential mutagens in the gastrointestinal tract by high fiber and reduced levels of growth promoting agents such as prostaglandins, certain fatty acids and estrogen by low fat. We propose, therefore, a working hypothesis that multiple antioxidant vitamin supplements together with diet and lifestyle modifications may improve the efficacy of standard and experimental cancer therapies.

Cancer prevention studies: past, present, and future directions

In spite of extensive research on vitamins and diet, a consistent beneficial role of vitamin supplements, together with diet modification in human cancer prevention, has not been demonstrated. Published results of human intervention trials with vitamin supplements have been contradictory. This review critically, but briefly, evaluates (a) current concepts of human carcinogenesis, (b) effects of vitamins on biochemical parameters that are pertinent to cancer prevention, and (c) whether past or current protocols for intervention trials among high-risk populations adopt specific scientific rationales that are based on laboratory and human epidemiology studies. In addition, we propose a novel experimental design for intervention trials among high-risk human populations that is based on sound scientific principles derived from laboratory and human epidemiologic data on vitamins, diet, lifestyle, and cancer prevention. Such trials would answer a fundamental public health issue of today: Does supplementation with multiple vitamins, together with diet and lifestyle modifications, reduce the risk of cancer?

Role of cellular thiol status in tocopheryl hemisuccinate cytoprotection against ethyl methanesulfonate-induced toxicity

Suspensions of rat hepatocytes treated with the alkylating agent ethyl methanesulfonate (EMS) exhibited extensive lipid peroxidation as well as rapid and near complete depletion of cellular reduced glutathione (GSH) levels prior to cell death. Pretreatment of hepatocytes with medium deficient in sulfur amino acids accelerated cell death induced by EMS, confirming the previously reported cytoprotective role for GSH in this toxic event. Nearly all of the cellular GSH lost following 50 mM EMS treatment was accounted for as S-ethyl glutathione (GS-Et). No significant formation of glutathione disulfide was observed. The GS-Et formed was not exported from the cell but remained at high intracellular concentrations throughout the course of the experiment. In addition, EMS treatment inhibited the efflux of intracellular GSH and inhibited the cellular accumulation of glutamate (Glu). Supplementation of hepatocytes with 25 microM d-alpha-tocopheryl hemisuccinate (TS) protected these cells against EMS-induced lipid peroxidation and cell death. Cytoprotection with TS had no effect on EMS-induced depletion of intracellular GSH or intracellular levels of GS-Et or Glu. However, TS supplementation did prevent EMS-induced depletion of cellular protein thiols. Interestingly, the pretreatment of hepatocytes with 1 mM dithiothreitol promoted EMS toxicity. The results of this study suggest that the cytoprotective abilities of TS are related to the prevention of both EMS-induced lipid peroxidation and protein thiol depletion. Thus, the onset of lipid peroxidation and the loss of protein thiols in hepatocytes appear to be critical cellular events leading to EMS-induced cell death.

RRR-alpha-tocopheryl succinate inhibits EL4 thymic lymphoma cell growth by inducing apoptosis and DNA synthesis arrest

RRR-alpha-tocopheryl succinate (vitamin E succinate, VES) treatment of murine EL4 T lymphoma cells induced the cells to undergo apoptosis. After 48 hours of VES treatment at 20 micrograms/ml, 95% of cells were apoptotic. Evidence for the induction of apoptosis by VES treatments is based on staining of DNA for detection of chromatin condensation/fragmentation, two-color flow-cytometric analyses of DNA content, and end-labeled DNA and electrophoretic analyses for detection of DNA ladder formation. VES-treated EL4 cells were blocked in the G1 cell cycle phase; however, apoptotic cells came from all cell cycle phases. Analyses of mRNA expression of genes involved in apoptosis revealed decreased c-myc and increased bcl-2, c-fos, and c-jun mRNAs within three to six hours after treatment. Western analyses showed increased c-Jun, c-Fos, and Bcl-2 protein levels. Electrophoretic mobility shift assays showed increased AP-1 binding at 6, 12, and 24 hours after treatment and decreased c-Myc binding after 12 and 24 hours of VES treatment. Treatments of EL4 cells with VES+RRR-alpha-to-copherol reduced apoptosis without effecting DNA synthesis arrest. Treatments of EL4 cells with VES+rac-6-hydroxyl-2, 5,7,8-tetramethyl-chroman-2-carboxylic acid, butylated hydroxytoluene, or butylated hydroxyanisole had no effect on apoptosis or DNA synthesis arrest caused by VES treatments. Analyses of bcl-2, c-myc, c-jun, and c-fos mRNA levels in cells receiving VES + RRR-alpha-tocopherol treatments showed no change from cells receiving VES treatments alone, implying that these changes are correlated with VES treatments but are not causal for apoptosis. However, treatments with VES + RRR-alpha-tocopherol decreased AP-1 binding to consensus DNA oligomer, suggesting AP-1 involvement in apoptosis induced by VES treatments.

Conversion of gamma-glutamylcysteinylethyl ester to glutathione in rat hepatocytes

The conversion of gamma-glutamylcysteinylethyl ester (gamma-GCE) to glutathione in a reduced form (GSH) was examined using isolated rat hepatocytes pretreated with diethylmaleate, a GSH-depletor. Incubation of hepatocytes with 0.1 and 5.0 mM gamma-GCE (gamma-GCE-hepatocytes) over a 30-min period resulted in time-dependent increases in intracellular GSH and nonprotein-SH (NP-SH) concentrations. Hepatocytes incubated with 5.0 mM but not 0.1 mM GSH over a period of 30 min showed a time-dependent increase in intracellular GSH concentration. In the gamma-GCE-hepatocytes pretreated with bis-(p-nitrophenyl)phosphate (BNPP), a non-specific esterase inhibitor, an enhancement of intracellular GSH concentration was markedly reduced. gamma-GCE concentration in the gamma-GCE-hepatocytes with BNPP pretreatment was significantly higher than that in the cells without BNPP pretreatment, although there was no difference in the total amount of intracellular NP-SH, i.e., gamma-GCE, GSH, gamma-glutamylcysteine, cysteine ethyl ester, and cysteine between both gamma-GCE-hepatocytes. The present results indicate that gamma-GCE is transported into liver cells more easily than GSH itself, resulting in its conversion to GSH via esterase and glutathione synthetase within the cells.

Effect of vitamin E on human glutathione peroxidase (GSH-PX1) expression in cardiomyocytes

To determine the effect of vitamin E on cellular antioxidant enzymes, human ventricular cardiomyocytes were incubated with 200 microM all-racemic-alpha-tocopheryl acetate for 14 d at pO2s of 150 and 40 mm Hg. Cellular Cu, Zn superoxide dismutase, catalase, and GSH-Px1 activities were measured. Although SOD and catalase activities were unaffected by alpha-tocopherol, GSH-Px1 activities increased (p < .0001) as much as twofold. This increase was independent of oxygen tension and selenium. The increase in GSH-Px1 activity became significant (p < .01) by day 4. A nonantioxidant analog of alpha-tocopherol, 200 microM RRR-alpha-tocopherol methyl ether, did not affect GSH-Px1 activities. Although GSH-Px1 mRNA levels mirrored the changes in enzyme activities, the de novo nuclear GSH-Px1 transcript synthesis was unaffected by alpha-tocopherol. Because the increase in GSH-Px1 activities also occurred after cellular alpha-tocopherol levels had plateaued, the above results were most consistent with posttranscriptional stabilization of GSH-Px1 mRNA by alpha-tocopherol or an alpha-tocopherol-related metabolic product.

Importance of the form of topical vitamin E for prevention of photocarcinogenesis

With increasing solar ultraviolet (UV)-B radiation reaching the Earth's surface and the incidence of skin cancer rising steadily, there is an ever-increasing need to determine agents that modulate photocarcinogenesis and to understand the mechanisms underlying this modulation. Our laboratory has demonstrated that topical application of the dl-alpha-tocopherol form of vitamin E to mice prevents skin cancer and the immunosuppression induced by UVB irradiation. However, dl-alpha-tocopherol has limited stability at room temperature. The current study was designed to ask whether the thermostable esters of vitamin E, alpha-tocopheryl acetate, or alpha-tocopheryl succinate prevent skin cancer and immunosuppression induced in mice by UV radiation. In the alpha-tocopheryl acetate study, skin cancers developed in 70% of UVB-irradiated control mice and in 90%, 73%, and 90% of mice receiving topical applications of 12.5, 25, and 50 mg of dl-alpha-tocopheryl acetate, respectively. In the alpha-tocopheryl succinate study, skin cancer developed in 59.3% of control UVB-irradiated mice and in 82%, 100%, and 81.5% of mice treated with 2.5, 12.5, and 25 mg d-alpha-tocopheryl succinate, respectively. Thus neither alpha-tocopheryl acetate nor alpha-tocopheryl succinate prevented photocarcinogenesis. At 12.5 and 25 mg/treatment, alpha-tocopheryl acetate and alpha-tocopheryl succinate, respectively, enhanced photocarcinogenesis (p = 0.0114 and 0.0262, respectively, log rank test). On the basis of high-performance liquid chromatography analysis at 16-17 weeks after the first vitamin E treatment, the esterified forms of vitamin E applied epicutaneously accumulated in the skin, but the levels of free alpha-tocopherol remained low. Neither alpha-tocopheryl acetate nor alpha-tocopheryl succinate prevented the induction by UV radiation of immunosusceptibility to implanted syngeneic antigenic UV-induced tumor cells. Thus alpha-tocopheryl acetate or alpha-tocopheryl succinate not only failed to prevent photocarcinogenesis, but may have enhanced to process. Considering that alpha-tocopherol esters are included in many skin lotions, cosmetics, and sunscreens, further studies are needed to determine the conditions under which topical alpha-tocopheryl acetate and alpha-tocopheryl succinate enhance photocarcinogenesis.

Modification of the aerobic cytotoxicity of etanidazole

PURPOSE

To determine the feasibility of modifying the aerobic cytotoxicity of etanidazole without interfering with the tumoricidal action of radiation plus etanidazole.

METHODS AND MATERIALS

The aerobic cytotoxicity of etanidazole was studied using two different models: (1) Induction of apoptosis in EL4 cells: apoptotic DNA fragmentation was analyzed by agarose gel electrophoresis following 24 h treatment with etanidazole alone or in combination with various modifiers. (2) Spinal cord neuronal loss in organotypic roller tube cultures: Survival of acetylcholinesterase positive ventral horn neurons was analyzed morphometrically following 72 h treatment with etanidazole alone or in combination with vitamin E succinate.

RESULTS

Etanidazole (10 mM) induced apoptosis in EL4 cells. This effect was suppressed by 24 h treatment with TPA, IBMX, the free radical scavenger TEMPOL or vitamin E succinate. Vitamin E succinate also protected spinal cord cultures from etanidazole-induced neuronal loss.

CONCLUSION

These results suggest that it might be possible to modify the neurotoxicity of etanidazole with agents that would not be expected to interfere with the tumoricidal action of radiation plus etanidazole.

Cytoprotective effect of tocopherols in hepatocytes cultured with polyunsaturated fatty acids

When highly unsaturated fatty acids are added to cell cultures, it can become important to include antioxidants in the culture medium to prevent cytotoxic peroxidation. To find an optimal antioxidant for this purpose, the effect of 50 microM alpha-tocopherol, gamma-tocopherol, alpha-tocopheryl acetate, alpha-tocopheryl acid succinate, or alpha-tocopheryl phosphate, or of 1 microM N,N'-diphenyl-1,4-phenylenediamine, was investigated with respect to the agent's ability to prevent lactate dehydrogenase leakage in long-term rat hepatocyte cultures supplemented with 0.5 mM highly unsaturated fatty acids. Formation of thiobarbituric acid reactive substances in the cultures was also measured. alpha-Tocopheryl acid succinate was found to be the most effective cytoprotective compound, followed by N,N'-diphenyl-1,4-phenylenediamine, alpha-tocopherol, gamma-tocopherol and alpha-tocopheryl acetate, and alpha-tocopheryl phosphate was without effect.

Inhibition of free radical generation by biotin

To assess the inhibitory effect of biotin on free radical generation, we used a spectrophotometric assay of cytochrome c reduction and determined the 2-methyl-6-phenyl-3,7-dihydroimidazo[1,3-a]-pyrazin-3-one (CLA)-dependent chemiluminescence response of human neutrophils or a hypoxanthine-xanthine oxidase (XOD) system. In the spectrophotometric assay of cytochrome c reduction, superoxide (O2-) generation by neutrophils stimulated with N-formyl-methionyl-leucyl-phenylalanine (f-MLP) was reduced significantly when biotin was added. In the CLA-dependent chemiluminescence test of neutrophils stimulated by f-MLP, biotin significantly reduced the generation of free radical species, including O2-, in a concentration-dependent manner, the concentration corresponding to 50% inhibition (IC50) of biotin for free radical generation was 1.12 x 10(-7) mol. However, biotin did not exert an inhibitory effect on oxidative metabolism by directly scavenging superoxide anion, as shown by the study using the hypoxanthine-XOD system.

Inhibition of fatty acid synthesis in rat hepatocytes by exogenous polyunsaturated fatty acids is caused by lipid peroxidation

Rat hepatocyte long-term cultures were utilized to investigate the impact of different polyunsaturated fatty acids (PUFA) on the insulin-induced de novo fatty acid synthesis in vitro. The addition of 0.5 mM albumin-complexed oleic, linoleic, columbinic, arachidonic, eicosapentaenoic or docosahexaenoic acid resulted in a marked suppression of fatty acid synthesis. By evaluation of cell viability (determined as the leakage of lactate dehydrogenase (LDH) it turned out, that the antioxidant used (50 microM alpha-tocopherol phosphate) had a low antioxidant activity, resulting in cytotoxic effects by the peroxidized PUFA. Arachidonic acid and eicosapentaenoic acid showed a dose- and time-dependent cytotoxicity. Two other antioxidants: 50 microM alpha-tocopherol acid succinate and 1 microM N,N'-diphenyl-1,4-phenylenediamine, both proved more efficient than alpha-tocopherol phosphate. There was a significant correlation between LDH-leakage and inhibition of fatty acid synthesis. Lipid peroxidation, measured as thiobarbituric acid-reactive substances, also showed a significant correlation with the degree of inhibition of fatty acid synthesis. Furthermore, PUFA had no inhibitory effect on fatty acid synthesis when peroxidation was minimized by the use of proper antioxidants. These data indicate that PUFA in vitro inhibit the insulin-induced de novo fatty acid synthesis in hepatocytes from starved rats, due to cytotoxic effects caused by lipid peroxidation.

The role of metabolism in the antioxidant function of vitamin E

Vitamin E (alpha-tocopherol), the principal chain-breaking antioxidant in biological membranes, prevents toxicant- and carcinogen-induced oxidative damage by trapping reactive oxyradicals. Although alpha-tocopherol antioxidant reactions appear to be not under direct metabolic control, alpha-tocopherol may function through redox cycles, which deliver reducing equivalents for antioxidant reactions and link antioxidant function to cellular metabolism. This review describes the antioxidant chemistry of alpha-tocopherol and evaluates the experimental evidence for the linkage of alpha-tocopherol turnover to cellular metabolism through redox cycles. Numerous in vitro experiments demonstrate antioxidant synergism between alpha-tocopherol and ascorbate, reduced glutathione, NADPH, and cellular electron transport proteins. Nevertheless, evidence that a one-electron redox cycle regenerates alpha-tocopherol from the tocopheroxyl radical is inconclusive. The difficulty of separating tocopheroxyl recycling from direct antioxidant actions of other antioxidants has complicated interpretation of the available data. A two-electron redox cycle involving alpha-tocopherol oxidation to 8a-substituted tocopherones followed by tocopherone reduction to alpha-tocopherol may occur, but would require enzymatic catalysis in vivo. Metabolism of antioxidant-inactive alpha-tocopheryl esters releases alpha-tocopherol, whereas reductive metabolism of alpha-tocopherylquinone, an alpha-tocopherol oxidation product, yields alpha-tocopherylhydroquinone, which also may provide antioxidant protection.

RRR-alpha-tocopheryl succinate inhibits proliferation and enhances secretion of transforming growth factor-beta (TGF-beta) by human breast cancer cells

The RRR-alpha-tocopheryl succinate form of vitamin E inhibits the proliferation of estrogen receptor-positive and estrogen receptor-negative human breast cancer cell lines in a dose-dependent manner in vitro. Analyses of cell-conditioned medium from RRR-alpha-tocopheryl succinate growth-inhibited cells revealed the presence of a potent antiproliferative activity. Characterization of the antiproliferative activity as transforming growth factor-beta (TGF-beta) was established by 1) growth inhibition of the TGF-beta-responsive Mv1Lu-CCL-64 mink lung and murine CTLL-2 cell lines, 2) combination of physical characteristics including heat stability, acid stability, and Bio-Gel P-60 column chromatography elution profile, and 3) neutralization of the antiproliferative activity in the conditioned media by antibodies specific for TGF-beta.