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

Professional and patient perspectives on nutritional needs of patients with cancer

PURPOSE/OBJECTIVES

To identify and compare perceptions of RNs, registered dietitians (RDs), and patients regarding the best format and key nutrition information components that should be provided to patients during cancer treatment.

DESIGN

Cross-sectional study using an opinion-based questionnaire.

SETTING

Outpatient cancer centers.

SAMPLE

506 RNs and 367 RDs, as well as 653 patients undergoing cancer treatment.

METHODS

Two similar self-administered questionnaires were developed, one for patients and one for healthcare professionals. Face and content validity were assessed by a panel of experts. Data were analyzed using descriptive statistics, chi-square statistic, and a Spearman Correlation Coefficient to compare responses.

MAIN RESEARCH VARIABLES

Patient nutrition concerns as well as format and content of printed educational materials.

FINDINGS

Significant differences existed among groups regarding the most common nutrition concerns, the perception of importance of information frequently provided to patients with cancer, and rank order of importance for eight items typically provided to patients. The dietary information format preferred by all groups was an all-inclusive booklet; RNs (75%) were more likely than RDs (43%) or patients (50%) to prefer this format. Data also revealed that almost half of the patients (47%) received no dietary counseling, including 18% who experienced significant weight loss.

CONCLUSIONS

RNs and RDs who provide nutrition education to patients with cancer should consider the need to develop and use a variety of printed materials to meet individual needs. Because major concerns of patients and healthcare professionals were related to patients ability to consume adequate amounts of food, this should be the primary focus of any nutrition education materials.

IMPLICATIONS FOR NURSING

These findings provide information that can be applied to the development of informational materials and counseling practices.

Synergistic killing of human leukemia cells by antioxidants and trichostatin A

PURPOSE

Antioxidants and trichostatin A (TSA) are promising anticancer drugs, and are capable of enhancing the neoplastic toxicity of other chemicals that exert anticancer activity via different mechanisms. Since antioxidants and TSA (the specific inhibitor of histone deacetylase) are believed to combat cancer via different mechanisms, we sought to determine whether combining them would improve their anticancer activity in human leukemia cells (HL-60).

MATERIALS AND METHODS

HL-60 cells were treated with antioxidants (ascorbic acid, AA and N-acetyl-cysteine, NAC), TSA or their combination, and cell proliferation arrest, lactate dehydrogenase (LDH) release and cell viability were measured as indicators of cell damage. Accumulation of reactive oxygen species (ROS) and the acetylation of histones were also measured.

RESULTS

The cytotoxicity of AA, NAC and TSA increased in a time- and dose-dependent manner. AA (1, 2 and 4 mM) and NAC (0.2, 0.5 and 1 mM) were able to diminish ROS generation but showed no influence on histone acetylation in HL-60 cells. In contrast, TSA (20, 50, 100 and 200 nM) did not inhibit ROS generation but significantly increased histone acetylation, indicating a possible role for both scavenging ROS and increasing histone acetylation in the induction of cell death in HL-60 cells. This conclusion was further confirmed by the finding that the combination of antioxidant and TSA not only diminished ROS generation, but also increased histone acetylation, and hence showed greater cytotoxicity in HL-60 cells than either component alone.

CONCLUSIONS

Our findings show that combining antioxidants and TSA can enhance their neoplastic toxicity at least in human leukemia HL-60 cells, providing a new approach to the design of chemotherapy strategies and the development of anticancer drugs.

An evidence-based approach for dietitian prescription of multiple vitamins with minerals

Dietitians working in hospitals are routinely involved in assessing energy and macronutrient (ie, protein, fat, carbohydrate) requirements of patients. However, complete nutritional therapy requires a comprehensive review of vitamin and mineral requirements. Scientific evidence for vitamin and mineral supplementation is primarily based on healthy, free-living people. This raises clinical challenges for dietitians working with patients whose vitamin and mineral requirements are impacted by various diseases, conditions, and medical treatment. Dietitians are the best-positioned health professionals to lead an evidence-based approach toward recommending vitamin and mineral supplements. The dietitians at the Toronto Rehabilitation Institute were authorized through a medical directive to prescribe multiple vitamins with minerals and to discontinue orders for unnecessary vitamin supplements. This is an ongoing, advanced practice initiative that focuses on the clinical efficacy for and safety of supplementation with multiple vitamins with minerals. It involves assessing the strength of evidence as it emerges in the literature, determining its relevance to specific patient populations in the practice setting and re-evaluating clinical practices for potential applications. When dietitians assume advanced practice initiatives, they are better equipped to deliver high-quality patient care. Simultaneously, state-of-the-art dietetic practice heightens dietitian recognition as a valuable member of the health care team.

Micronutrients and Cancer Therapy

The effect of micronutrient supplementation on the effectiveness of cancer chemotherapeutic agents is reviewed, and the efficacy of antioxidants, folic acid, and other vitamins and minerals is discussed. Although some micronutrients show promise in enhancing the cytotoxicity of anticancer agents in vitro, caution should be exercised in recommending micronutrient supplementation for cancer patients receiving chemotherapeutic drugs. To date, few well-controlled clinical trials have been conducted to evaluate the efficacy of micronutrients in promoting the sensitivity of tumors to chemotherapeutic agents.

Antioxidants and cancer therapy: a systematic review

PURPOSE

Many patients with cancer take antioxidant nutritional supplements during cancer treatment to alleviate treatment toxicities and to improve long-term outcomes, but little is known about the efficacy and safety of antioxidant use during cancer treatment. We reviewed English-language manuscripts published in the biomedical literature, reporting the results of observational studies of antioxidant status and cancer outcomes and of intervention trials of antioxidants among patients receiving chemotherapy with or without radiation for various malignancies.

METHODS

We searched the Medline database and the bibliographies of the retrieved manuscripts, reviews, and books on antioxidants and cancer. The retrieved studies are grouped by study design, malignancy, and end points.

RESULTS

More than 100 citations were retrieved; 52 met our criteria, 31 were observational studies, and 21 were intervention trials. The studies varied in study design, timing of observation/intervention, intervention protocol, malignancy, and anticancer regimen.

CONCLUSION

These inconsistencies preclude a definitive conclusion as to the effect of chemotherapy on antioxidant status in patients undergoing anticancer therapy. However, our review suggests that total antioxidant status (measured by total radical antioxidant parameter) declines during cancer treatment. Adequately powered trials or observational studies among patients with a specific cancer diagnosis receiving a specific treatment regimen are needed to address patients' and physicians' concerns regarding these associations.

The Role of Dietary Supplements during Cancer Therapy

This guide was compiled after recommendations by the American Institute for Cancer Research (AICR) Cancer Resource Advisory Council. It encompasses the AICR position on current issues in nutrition for cancer survivors during treatment and is intended to provide advice about dietary supplements for cancer survivors who are still being treated. Current scientific findings about the safety and effectiveness of some commonly used dietary antioxidants and nonantioxidant supplements during chemotherapy are presented and assessed. Use of dietary supplements during cancer treatment remains controversial. Patients are cautioned that vitamin and mineral supplements as therapies are not substitutes for established medicine. The current recommendation for cancer patients is to only take moderate doses of supplements because evidence from human clinical studies that confirm their safety and benefits is limited. A daily multivitamin containing supplements at the levels of the Dietary Reference Intakes can be used safely as part of a program of healthy nutrition. In addition, the AICR Cancer Resource Advisory Council concluded that further scientific research is needed to provide a set of firm guidelines for the use of vitamin and mineral supplements by cancer patients during treatment.

Protection against ionizing radiation by antioxidant nutrients and phytochemicals

The potential of antioxidants to reduce the cellular damage induced by ionizing radiation has been studied in animal models for more than 50 years. The application of antioxidant radioprotectors to various human exposure situations has not been extensive although it is generally accepted that endogenous antioxidants, such as cellular non-protein thiols and antioxidant enzymes, provide some degree of protection. This review focuses on the radioprotective efficacy of naturally occurring antioxidants, specifically antioxidant nutrients and phytochemicals, and how they might influence various endpoints of radiation damage. Results from animal experiments indicate that antioxidant nutrients, such as vitamin E and selenium compounds, are protective against lethality and other radiation effects but to a lesser degree than most synthetic protectors. Some antioxidant nutrients and phytochemicals have the advantage of low toxicity although they are generally protective when administered at pharmacological doses. Naturally occurring antioxidants also may provide an extended window of protection against low-dose, low-dose-rate irradiation, including therapeutic potential when administered after irradiation. A number of phytochemicals, including caffeine, genistein, and melatonin, have multiple physiological effects, as well as antioxidant activity, which result in radioprotection in vivo. Many antioxidant nutrients and phytochemicals have antimutagenic properties, and their modulation of long-term radiation effects, such as cancer, needs further examination. In addition, further studies are required to determine the potential value of specific antioxidant nutrients and phytochemicals during radiotherapy for cancer.

The use of antioxidants with first-line chemotherapy in two cases of ovarian cancer

OBJECTIVE

Because of poor overall survival in advanced ovarian malignancies, patients often turn to alternative therapies despite controversy surrounding their use. Currently, the majority of cancer patients combine some form of complementary and alternative medicine with conventional therapies. Of these therapies, antioxidants, added to chemotherapy, are a frequent choice.

METHODS

For this preliminary report, two patients with advanced epithelial ovarian cancer were studied. One patient had Stage IIIC papillary serous adenocarcinoma, and the other had Stage IIIC mixed papillary serous and seromucinous adenocarcinoma. Both patients were optimally cytoreduced prior to first-line carboplatinum/paclitaxel chemotherapy. Patient 2 had a delay in initiation of chemotherapy secondary to co-morbid conditions and had evidence for progression of disease prior to institution of therapy. Patient 1 began oral high-dose antioxidant therapy during her first month of therapy. This consisted of oral vitamin C, vitamin E, beta-carotene, coenzyme Q-10 and a multivitamin/mineral complex. In addition to the oral antioxidant therapy, patient 1 added parenteral ascorbic acid at a total dose of 60 grams given twice weekly at the end of her chemotherapy and prior to consolidation paclitaxel chemotherapy. Patient 2 added oral antioxidants just prior to beginning chemotherapy, including vitamin C, beta-carotene, vitamin E, coenzyme Q-10 and a multivitamin/mineral complex. Patient 2 received six cycles of paclitaxel/carboplatinum chemotherapy and refused consolidation chemotherapy despite radiographic evidence of persistent disease. Instead, she elected to add intravenous ascorbic acid at 60 grams twice weekly. Both patients gave written consent for the use of their records in this report.

RESULTS

Patient 1 had normalization of her CA-125 after the first cycle of chemotherapy and has remained normal, almost 3(1/2) years after diagnosis. CT scans of the abdomen and pelvis remain without evidence of recurrence. Patient 2 had normalization of her CA-125 after the first cycle of chemotherapy. After her first round of chemotherapy, the patient was noted to have residual disease in the pelvis. She declined further chemotherapy and added intravenous ascorbic acid. There is no evidence for recurrent disease by physical examination, and her CA-125 has remained normal three years after diagnosis.

CONCLUSION

Antioxidants, when added adjunctively, to first-line chemotherapy, may improve the efficacy of chemotherapy and may prove to be safe. A review of four common antioxidants follows. Because of the positive results found in these two patients, a randomized controlled trial is now underway at the University of Kansas Medical Center evaluating safety and efficacy of antioxidants when added to chemotherapy in newly diagnosed ovarian cancer.

The use of antioxidant therapies during chemotherapy

OBJECTIVE

At the present time, many cancer patients combine some form of complementary and alternative medicine therapies with their conventional therapies. The most common choice of these therapies is the use of antioxidants.

RESULTS

A review of four common antioxidants is undertaken, which includes vitamin E (mixed tocopherols and tocotrienols), beta-carotene (natural mixed carotenoids), vitamin C (ascorbic acid), and vitamin A (retinoic acid). Antioxidants act as electron acceptors as well as therapeutic biologic response modifiers. Despite the fact that chemotherapy-induced formation of free radicals is well-demonstrated, chemotherapy-induced cytotoxicity in general does not seem to depend on formation of reactive oxygen species.

CONCLUSIONS

Currently, evidence is growing that antioxidants may provide some benefit when combined with certain types of chemotherapy. Because of the potential for positive benefits, a randomized controlled trial evaluating the safety and efficacy of adding antioxidants to chemotherapy in newly diagnosed ovarian cancer is underway at the University of Kansas Medical Center.

Clearance of ascorbic acid in plasma in patients before major maxillofacial surgery compared with that in volunteers

Reduced concentration of ascorbic acid (AA) in plasma is often observed in tumor patients. Besides malnutrition, an increased AA consumption in tumor patients is discussed as a main reason for reduced AA concentration in plasma. A reduced AA concentration caused by malnutrition would not influence the total clearance (Cltot) of AA in plasma; however, a change in AA consumption would alter the Cltot. To investigate this further, a study was carried out on 20 patients hospitalized for major maxillofacial surgery and 20 volunteers. The Cltot of AA in plasma after bolus injection of AA (4 mg/kg body wt) in tumor patients was compared with that in volunteers. AA concentration in plasma (P < 0.05) was significantly lower in tumor patients (median and 25th and 75th percentiles: 23.7, 14.6, and 32.7 mumol/l) than in volunteers (median and 25th and 75th percentiles: 66.5, 59.6, and 78.6 mumol/l). No significant change in Cltot was observed for tumor patients (median and 25th and 75th percentiles: 11.5, 8.0, and 14.0 l/h) compared with volunteers (median and 25th and 75th percentiles: 11.3, 9.9, and 13.2 l/h). No indication of an increased consumption of AA in tumor patients could be detected. The lowered concentration of AA in plasma observed in our patients might be the result of a reduced AA intake.

Potentiation of the effect of paclitaxel and carboplatin by antioxidant mixture on human lung cancer h520 cells

OBJECTIVE

Antioxidants have been shown to enhance the effect of certain chemotherapeutic agents on tumor cells in culture. However, this effect differs depending upon the type of tumor and the drugs. In this study, the objective was to see whether pretreatment with antioxidant mixture could enhance the cytotoxic and apoptotic effect of commonly used chemotherapeutic agents, paclitaxel and carboplatin for the treatment of NSCLC.

METHODS

Human lung squamous cell carcinoma cell line, H520, was treated with antioxidant mixture (vitamin C, vitamin E and beta carotene), paclitaxel and carboplatin, individually and in combination of different doses in different sequences. Growth inhibition and induction of apoptosis was studied by morphological changes, MTT assay and flow-cytometric analysis.

RESULTS

The antioxidant mixture by itself led to 15% apoptosis in H520 cells. Paclitaxel treatment 24 hours prior to carboplatin caused 54% apoptosis, more than that produced by simultaneous treatment with both agents (40%). A statistically significant improvement in the degree of apoptosis, induced by paclitaxel and carboplatin combination, was seen when the cells were pretreated with antioxidant mixture immediately before paclitaxel exposure (70%) or 24 hours before paclitaxel exposure (89%).

CONCLUSION

The data suggests that the apoptotic effects of paclitaxel and carboplatin are enhanced by pretreatment with the antioxidant mixture. Thus, the most promising sequence of these agents, which emerged in this study, was pretreatment with antioxidant mixture for 24 hours followed by paclitaxel treatment for 24 hours followed by carboplatin exposure for 24 hours.

D-alpha-tocopheryl succinate (vitamin E) enhances radiation-induced chromosomal damage levels in human cancer cells, but reduces it in normal cells

OBJECTIVE

The purpose of this study was to measure and compare the effect of d-alpha-tocopheryl succinate (alpha-TS) in modifying radiation-induced chromosomal damage in human normal cells and cancer cells in culture.

METHODS

Three human normal fibroblast cell lines (GM2149, AG1522 and HF19) and three human cancer cell lines, cervical cancer (HeLa) and ovarian carcinoma cells (OVGI and SKOV3) were treated with alpha-TS (37.6 microM) 20 hours before 100 cGy gamma-irradiation. After 30 minutes of irradiation, colcemid was added and cells were fixed. One hundred randomly selected metaphase cells were scored for the presence of chromatid gaps and breaks. To study the cellular accumulation of alpha-TS. cells were incubated in the presence of alpha-TS (18.8 and 37.6 microM) for 24 hours, and alpha-TS was extracted with hexane using a-tocopheryl acetate as an internal standard. The levels of alpha-TS were determined by HPLC.

RESULTS

Results showed that alpha-TS induced chromosomal damage in both human cervical cancer cells and ovarian cancer cells, but not in human normal fibroblasts in culture. In addition, alpha-TS enhanced the level of radiation-induced chromosomal damage in cancer cells, but it protected normal cells against such damage. Both cancer cells and normal cells accumulated similar levels of alpha-TS, suggesting that increased sensitivity of cancer cells to alpha-TS is acquired during transformation.

CONCLUSION

The use of alpha-TS during radiation therapy may improve the efficacy of radiation therapy by enhancing tumor response and decreasing some of the toxicities on normal cells.

Pros and cons of antioxidant use during radiation therapy

Radiation therapy is one of the major treatment modalities in the management of human cancer. While impressive progress like more accurate dosimetry and more precise methods of radiation targeting to tumor tissue has been made, the value of radiation therapy in tumor control may have reached a plateau. At present, two opposing hypotheses regarding the use of antioxidants during radiation therapy have been proposed. One hypothesis states that supplementation with high doses of multiple micronutrients including high dose dietary antioxidants (vitamins C and E, and carotenoids) may improve the efficacy of radiation therapy by increasing tumor response and decreasing some of its toxicity on normal cells. The other hypothesis suggests that antioxidants (dietary or endogenously made) should not be used during radiation therapy, because they would protect cancer cells against radiation damage. Each of these hypotheses is based on different conceptual frameworks that are derived from results obtained from specific experimental designs, and thus, each may be correct within its parameters. The question arises whether any of these concepts and experimental designs can be used during radiation therapy to improve the management of human cancer by this modality. This review has analyzed published data that are used in support of each hypothesis, and has revealed that the current controversies can be resolved, if the results obtained from one experimental design are not extrapolated to the other. This review has also discussed the scientific rationale for a micronutrient protocol that includes high doses of dietary antioxidants (vitamin C, vitamin E succinate and natural beta-carotene) which can be used adjunctively with radiation therapy.

A simple assay for the measurement of plasma antioxidant status using spontaneous autoxidation of homovanillic acid

INTRODUCTION

Reactive oxygen species (ROS) contribute to the development of pathophysiological processes, hence the increasing interest in modulating the antioxidant status of patient by nutritional or pharmacological intervention. Antioxidants act by preventing the formation of ROS (inhibitory effect) and/or by trapping these species (scavenger effect). We have developed a simple, sensitive, and reliable test to measure the total antioxidative efficiency of plasma or other biological fluids using microliter samples.

METHODS

Autoxidation of homovanillic acid (HVA) gives rise to fluorescent dimers. Antioxidants contained in the plasma (or free aqueous solutions) scavenge the ROS involved in this process and transiently stop the linear increase in fluorescence intensity during a time (delay) proportional to the total concentration of antioxidants and their scavenging efficiency. In addition to this scavenging effect, the kinetics of HVA autoxidation, restarting after the delay, reflects the ability of the plasma antioxidants to inhibit the ROS-triggered autoxidation.

RESULTS

The rate of the HVA autoxidation depended on the temperature, the protonation of the phenolic group, and on the presence of peroxide, peroxyl radicals, and peroxidase as well as metal ions. This Fenton-like reaction was transiently stopped by various ROS scavengers including quercetin, ascorbic acid, and thiol derivatives (glutathione and N-acetylcystein) while metal chelating agents such as desferrioxamine, ethylene diamine tetracetic acid (EDTA), and polyamine only reduced its rate.

DISCUSSION

The main advantages of this new assay are its versatility to investigate in a single run both the scavenging and inhibitory components of the antioxidant capacity, and its relevance to the reactive hydroxyl radical. As shown in this study, the increase in the antioxidant capacity of human plasma during pharmacological supplementation with antioxidant illustrates one of the various fields of application of this assay.

Alpha tocopheryl succinate, retinoic acid and polar carotenoids enhanced the growth-inhibitory effect of a cholesterol-lowering drug on immortalized and transformed nerve cells in culture

OBJECTIVE

Statins (cholesterol lowering drugs) with a closed-ring structure (lovastatin, simvastatin and mevastatin) and an open-ring structure (pravastatin and fluvastatin) are currently used in the management of cardiac disease. Lovastatin and simvastatin inhibit the growth of tumor cells; however, the studies on the effect of a statin in combination with micronutrients such as alpha-tocopheryl succinate (alpha-TS), 13-cis retinoic acid (RA) and polar carotenoids (PC) have never been performed. The primary objective of this study was to investigate the effect of mevastatin alone and in combination with the above micronutrients on the growth of mouse neuroblastoma (NB) cells and rat immortalized dopamine (DA) neurons in culture. In addition, a comparative efficacy of mevastatin and pravastatin on the growth of NB cells was studied.

METHODS

Cells were treated with mevastatin in combination with individual antioxidants, alpha-TS, RA and polar carotenoids, 24 hours after plating. Fresh growth medium and agents were changed at two days after treatment, and the viability in control and experimental groups was determined at three days after treatment by MTT assay. Each experiment was repeated three times with triplicate samples per treatment. Growth in experimental groups was expressed as % of untreated cells.

RESULTS

Mevastatin inhibited the growth of neuroblastoma (NB) cells and immortalized, non-tumorigenic dopamine (DA) neurons in culture in a dose-dependent manner. Immortalized DA neurons were more sensitive to mevastatin than NB cells. Pravastatin at similar concentrations was ineffective in inhibiting the growth of NB cells. Mevastatin in combination with alpha-TS, RA or PC was more effective in reducing the growth of NB and DA neurons than the individual agents.

CONCLUSIONS

Statins with a closed-ring structure can inhibit the growth of established cancer cells as well as immortalized cells (equivalent to pre-malignant lesion), whereas statins with an open-ring structure may be ineffective. A combination of a statin having a closed-ring structure with alpha-TS, RA and PC may be one of the potentially useful anti-cancer agents for prevention and treatment strategies.

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.

Influence of antioxidative vitamins A, C and E on lipid peroxidation in BOP-induced pancreatic cancer in Syrian hamsters

Persistent oxidative stress is thought to play an important role in carcinogenesis. Vitamins may influence oxygen radical metabolism and thus inhibit tumor growth. In the present trial the effects of Vitamins (Vit.) A, C and E on neoplastic growth and lipid peroxidation in pancreatic tissue were evaluated on chemically-induced pancreatic adenocarcinoma in the Syrian hamster. The incidence of pancreatic cancer was decreased by Vit. A (64.3%) and Vit. C (71.4%) as compared to the control group (100%, P<0.05). All vitamins increased the activity of superoxidedismutase (SOD) in pancreatic carcinomas. Accumulation of vitamins in tumor cells seems to be responsible for high levels of SOD and consecutive intracellular increase of hydrogen peroxide levels. Since this effect is selectively toxic for tumor cells it might be one of the mechanisms decreasing the incidence of pancreatic cancer in our trial.

Vitamins C and E improve rat embryonic antioxidant defense mechanism in diabetic culture medium

BACKGROUND

Diabetes teratogenicity seems to be related to embryonic oxidative stress and the extent of the embryonic damage can apparently be reduced by antioxidants. We have studied the mechanism by which antioxidants, such as vitamins C and E, reduce diabetes-induced embryonic damage. We therefore compared the antioxidant capacity of 10.5-day-old rat embryos and their yolk sacs cultured for 28h in diabetic culture medium with or without vitamins C and E.

METHODS

The embryos were cultured in 90% rat serum to which 2mg/ml glucose, 2mg/ml beta hydroxy butyrate (BHOB) and 10 microg/ml of acetoacetate were added. Rat embryos were also cultured in a diabetic medium with 25 microg/ml of vitamin E and 50 microg/ml of vitamin C. Control embryos were cultured in normal rat serum with or without vitamins C and E.

RESULTS

Decreased activity of Cu/Zn superoxide dismutase (SOD) and of catalase (CAT) in the "diabetic" embryos and their yolk sacs, and reduced concentrations of low molecular weight antioxidant (LMWA) were found. Under these conditions we also found a decrease in vitamin C and vitamin E concentrations in the embryos, as measured by HPLC. In situ hybridization for SOD mRNA showed a marked reduction of SOD mRNA in the brain, spinal cord, heart and liver of embryos cultured in diabetic medium in comparison to controls. Following the addition of vitamins C and E to the diabetic culture medium, SOD and CAT activity, the concentrations of LMWA, the levels of vitamin C and E and the expression of SOD mRNA in the embryos and yolk sacs returned to normal.

CONCLUSIONS

Diabetic metabolic factors seem to have a direct effect on embryonic SOD gene and perhaps genes of other antioxidant enzymes, reducing embryonic endogenous antioxidant defense mechanism. This in turn may cause a depletion of the LMWA, such as vitamins C and E. The addition of these vitamins normalizes the embryonic antioxidant defense mechanism, reducing the damage caused by the diabetic environment.

Ligand-protein inverse docking and its potential use in the computer search of protein targets of a small molecule

Ligand-protein docking has been developed and used in facilitating new drug discoveries. In this approach, docking single or multiple small molecules to a receptor site is attempted to find putative ligands. A number of studies have shown that docking algorithms are capable of finding ligands and binding conformations at a receptor site close to experimentally determined structures. These algorithms are expected to be equally applicable to the identification of multiple proteins to which a small molecule can bind or weakly bind. We introduce a ligand-protein inverse-docking approach for finding potential protein targets of a small molecule by the computer-automated docking search of a protein cavity database. This database is developed from protein structures in the Protein Data Bank (PDB). Docking is conducted with a procedure involving multiple-conformer shape-matching alignment of a molecule to a cavity followed by molecular-mechanics torsion optimization and energy minimization on both the molecule and the protein residues at the binding region. Scoring is conducted by the evaluation of molecular-mechanics energy and, when applicable, by the further analysis of binding competitiveness against other ligands that bind to the same receptor site in at least one PDB entry. Testing results on two therapeutic agents, 4H-tamoxifen and vitamin E, showed that 50% of the computer-identified potential protein targets were implicated or confirmed by experiments. The application of this approach may facilitate the prediction of unknown and secondary therapeutic target proteins and those related to the side effects and toxicity of a drug or drug candidate. Proteins 2001;43:217-226.

Ligand-protein inverse docking and its potential use in the computer search of protein targets of a small molecule

Ligand-protein docking has been developed and used in facilitating new drug discoveries. In this approach, docking single or multiple small molecules to a receptor site is attempted to find putative ligands. A number of studies have shown that docking algorithms are capable of finding ligands and binding conformations at a receptor site close to experimentally determined structures. These algorithms are expected to be equally applicable to the identification of multiple proteins to which a small molecule can bind or weakly bind. We introduce a ligand-protein inverse-docking approach for finding potential protein targets of a small molecule by the computer-automated docking search of a protein cavity database. This database is developed from protein structures in the Protein Data Bank (PDB). Docking is conducted with a procedure involving multiple-conformer shape-matching alignment of a molecule to a cavity followed by molecular-mechanics torsion optimization and energy minimization on both the molecule and the protein residues at the binding region. Scoring is conducted by the evaluation of molecular-mechanics energy and, when applicable, by the further analysis of binding competitiveness against other ligands that bind to the same receptor site in at least one PDB entry. Testing results on two therapeutic agents, 4H-tamoxifen and vitamin E, showed that 50% of the computer-identified potential protein targets were implicated or confirmed by experiments. The application of this approach may facilitate the prediction of unknown and secondary therapeutic target proteins and those related to the side effects and toxicity of a drug or drug candidate. Proteins 2001;43:217-226.

Interfacial properties of phosphatidylcholine bilayers containing vitamin E derivatives

alpha-Tocopherol and alpha-tocopheryl succinate are biologically active lipids. The activity of these lipids may be related to how they affect membrane physical-chemical properties. Utilizing fluorescence methods, we have investigated the effect of alpha-tocopherol, alpha-tocopheryl succinate, and alpha-tocopheryl acetate on the properties of model membranes consisting of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine. In liquid-crystalline phase phospholipid bilayers, alpha-tocopherol decreased acyl chain mobility and decreased the interfacial polarity, but had no effect on the interfacial surface charge. In contrast, alpha-tocopheryl succinate had little effect on acyl chain motion or interfacial hydration, but increased the interfacial surface charge. alpha-Tocopheryl acetate had very little effect on any of the measurements of these bilayer properties. In a gel phase bilayer, alpha-tocopherol decreased acyl chain order, whereas alpha-tocopheryl succinate and alpha-tocopheryl acetate did not. Each alpha-tocopheryl derivative had a different effect on interfacial polarity, however, only alpha-tocopheryl succinate increased the interfacial surface charge. The acylation of alpha-tocopherol abolishes its antioxidant activity and generates molecules with different membrane physical properties. The non-polar acetate group of alpha-tocopheryl acetate locates this compound in a region of the bilayer where it has little effect on bilayer interfacial properties. The free carboxyl group of alpha-tocopheryl succinate is located in the interfacial region of the bilayer where it increases the membrane surface charge.

Antioxidant nutrients: current dietary recommendations and research update

OBJECTIVE

To review the importance of antioxidant nutrients in the maintenance of health and the prevention and treatment of disease, with a focus on data pertaining to vitamin C, vitamin E, selenium, and carotenoids. A secondary objective was to discuss the new Dietary Reference Intakes released by the Institute of Medicine (IOM) for these nutrients.

DATA SOURCES

IOM reports on the use of antioxidant vitamins were reviewed for nutrient recommendations. In addition, a MEDLINE search was performed to identify recent research and review articles on the topic, which were analyzed to identify key research findings in the area.

DATA SYNTHESIS

The review discusses the biologic processes of oxidation reactions and antioxidants in biologic systems, provides an overview of information on selected antioxidant nutrients, and explores their role in the prevention and treatment of cancer, cardiovascular disease, ocular disorders, and respiratory disorders.

CONCLUSION

There appear to be significant health benefits from dietary antioxidants, as can be found in fruits and vegetables. Some prospective assessment of the effect of supplemental antioxidants also suggests benefit, especially for vitamin E; however, there are conflicting results in this area. Overall, it appears that antioxidant nutrients, especially those from food sources, have important roles in preventing pathogenic processes related to cancer, cardiovascular disease, macular degeneration, cataracts, and asthma, and may enhance immune function.

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.

Vitamin E reduces chromosomal damage and inhibits hepatic tumor formation in a transgenic mouse model

We have previously shown that chronic activation of mitogenic signaling induced by over-expression of c-myc and transforming growth factor-alpha (TGFalpha) transgenes in mouse liver induces a state of oxidative stress. We therefore proposed that increased reactive oxygen species (ROS) generation might be responsible for the extensive chromosomal damage and acceleration of hepatocarcinogenesis characteristic for TGFalpha/c-myc mice. In this study, we show that vitamin E (VE), a potent free radical scavenging antioxidant, is able to protect liver tissue against oxidative stress and suppress tumorigenic potential of c-myc oncogene. Dietary supplementation with VE, starting from weaning, decreased ROS generation coincident with a marked inhibition of hepatocyte proliferation while increasing the chromosomal as well as mtDNA stability in the liver. Similarly, dietary VE reduced liver dysplasia and increased viability of hepatocytes. At 6 mo of age, VE treatment decreased the incidence of adenomas by 65% and prevented malignant conversion. These results indicate that ROS generated by over-expression of c-myc and TGFalpha in the liver are the primary carcinogenic agents in this animal model. Furthermore, the data demonstrate that dietary supplementation of VE can effectively inhibit liver cancer development.

Multiple antioxidants in the prevention and treatment of neurodegenerative disease: analysis of biologic rationale

Parkinson's disease and Alzheimer's disease are major progressive neurologic disorders, the risk of which increases with advancing age (65 years and over). In familial cases, however, early onset of disease (35-65 years) is observed. In spite of extensive basic and chemical research on Parkinson's disease and Alzheimer's disease, no preventive or long-term effective treatment strategies are available. The analysis of existing literature suggests that oxidative stress is a major intermediary risk factor for the action of diverse groups of neurotoxins that are involved in these neurodegenerative diseases. In this review, it is proposed that the epigenetic components (mitochondria, other organelles, membranes, protein modification) rather than nuclear genes of neurons are the primary targets for the action of neurotoxins, including free radicals. In addition, a scientific rationale for using multiple antioxidants in clinical trials for the prevention of Parkinson's disease and Alzheimer's disease among high-risk populations, and as an adjunct to standard therapy in the treatment of these diseases is presented.