Antioxidants

Brand Names:

Clinical Names: Antioxidants

Summary

Antioxidants

forms: The key naturally occurring antioxidant substances in the body are catalase, glutathione peroxidase and superoxide dismutase (SOD).

Note: See also individual nutrients and herbs with antioxidant action, such as Vitamin A, Vitamin C, Vitamin E, Alpha Lipoic Acid, Glutathione, and Silybum marianum (Milk Thistle).

overview of interactions:
• nutrients affecting drug toxicity and performance: Chemotherapy especially Doxorubicin (Adriamycin®)

• Antioxidant nutrients (Vitamin A, Beta-Carotene and Vitamin E) affecting drug performance: Cyclophosphamide

• nutrients affecting drug toxicity: Indomethacin

• nutrients affecting drug toxicity: Metronidazole (Flagyl®)

• nutrients affecting drug toxicity: Valproic Acid

functions:
• Antioxidants reduce or reverse cellular damage due to free radicals. Free radicals are substances with one or more unpaired electrons, which are formed as a result of many physiological and pathological cellular metabolic processes. especially in mitochondria. Free radicals are highly reactive with the cell membrane and DNA and cause a cascade of oxidation and reduction reactions. The major free radicals are H2O2 (hydrogen peroxide), OH (hydroxy radical), and O2 (superoxide radical).
• The major types of antioxidants include:
Cellular enzymes: superoxide dismutase (zinc, manganese, copper), glutathione peroxidase (selenium), and catalase.
Metal ion chelators: albumin, transferrin, haptoglobin, ceruloplasmin, metalliothionein.
Other small molecules: Vitamin C, vitamin E, beta-carotene, uric acid, bilirubin, and others.
• Glutathione redox cycle: This metabolic process is one of the most important intracellular antioxidative systems.
• Glutathione is a tripeptide consisting of glutamate, cysteine and glycine. It is the predominant intracelluar non-protein sulfhydryl (thiols-SH). Glutathione protects cells against toxic electrophils (positively charged molecule) by thioether formation or by undergoing oxidation-reduction cycle.
• There are important synergistic interactions which occur between various antioxidants. Selenium plays a role in the induction of metallothionein synthesis. In this process vitamin C exerts a favorable effect. Vitamin C and glutathione peroxidase work together to reduce oxidized membrane-bound vitamin E.
• Antioxidants have been found to play a critical role in the etiology and prevention of cancer. In epidemiological studies antioxidative vitamins and trace element, such as selenium have been found to play a protective role against human carcinogenesis due to exogenous factors. Research has demonstrated a correlation between high intake or high blood levels of these micronutrient and reduced incidence of cancer. Individuals with cancer have been found to exhibit elevated blood levels of lipid peroxidative degradation products and a higher ratio of lipid peroxide to vitamin C and vitamin E as compared to healthy controls.

sources: Beta-carotene, niacin, vitamin B2, vitamin B6, vitamin C, vitamin E, coenzyme Q10, lutein, lycopene, and N-acetyl-cysteine, as well as many plant materials including Vaccinium myrtillus (bilberry), Curcuma longa (turmeric), and Ginkgo biloba. Foods containing flavonoids provide antioxidant support. The key flavonoids found in proanthocyanidins, in particular, can be obtained through food sources such as bilberry, black currant, cranberry, black tea and green tea. As supplements, proanthocyanidins are usually derived from grape seed or pine bark extracts. Glutathione (GSH) is also available as a supplement.

known or potential therapeutic uses: Antioxidants are used to promote health, to inhibit cellular degeneration, and to treat a large variety of conditions.

maintenance dose: Variable, depending on form.

therapeutic dose: Variable, depending on form.

side effects: Many antioxidants are considered to be free of side effects at commonly used dosages. However, the wide variety of substances that function as antioxidants ensures that no blanket assurances of safety can be prudently offered. In fact some antioxidants can cause side effects if used at too high of a dose, for too long, or by certain individuals. In particular, as discussed below, individuals taking certain medications should avoid use of antioxidants unless they are under the close supervision of a physician.

toxicity: Many antioxidants are considered safe at commonly used dosages. Since many, such as flavonoids, are water-soluble so any excess intake will be excreted in the urine and toxic accumulation is not a concern. However, some antioxidants, such as vitamin E, are fat soluble and do pose risks for toxicity with excessive use. Likewise, other substances with antioxidant activity, such as vitamin B6 and niacin, can create toxic reactions with extended use at higher doses. Overall, each antioxidant and each person needs to be considered individually.

contraindications: None known, except for use during some forms of chemotherapy and radiation where antioxidants are contraindicated due to their inhibition of the free radical formation which is an intentional part of the therapeutic mechanism.



Interactions

nutrients affecting drug toxicity and performance: Chemotherapy especially Doxorubicin (Adriamycin®)

• mechanism: Oxygen radicals have increasingly come under investigation as highly toxic stressors contributing to the pathological processes underlying many diseases, including many forms of cancer. Vitamin A and vitamin C are well known antioxidant agents. N-acetylcysteine (NAC) is a free radical scavenger and might access the endothelial cell thus increasing intracellular glutathione (GSH) stores. Even so, some concerns have been raised antioxidants might be contraindicated during chemotherapy because one way in which chemotherapeutic agents attack cancer cells is by causing oxidative damage.
(Weijl NI, et al. Ann Oncol 1998 Dec;9(12):1331-1337; Kong Q, Lillehei KO. Med Hypotheses 1998 Nov;51(5):405-409.)

• research: A variety of test tube-based and animal studies have found vitamin A, C and E to increase the effectiveness of chemotherapy in several kinds of cancer. NAC therapy may be useful therapy in advanced cervical cancers, especially squamous cell carcinomas. In a double-blind study Wagdi et al found that an antioxidant combination consisting of vitamin C, vitamin E, and N-acetylcysteine (NAC) provided protected against heart damage induced by chemotherapy without reducing the drug's effectiveness. Several researchers have offered the seemingly paradoxical conclusion that the appropriate administration of antioxidant inhibitors and/or free-radical-generating compounds may be a useful strategy in the treatment of solid tumors. After performing a comprehensive review of the relationship between chemotherapy and antioxidants Weijl et al rebuffed warnings that antioxidants needed to be avoided during chemotherapy but also determined that there substantive evidence was lacking to support the use of antioxidants to provide relief from the adverse side effects of chemotherapy. More recently, however, conference reports by Salignik R, and co-worker Zeisel SH, at the 1999 American Society of Cell Biology annual meeting suggest that vitamin A and vitamin E-deficient mice were less susceptible to brain tumor progression than non-vitamin-deficient control animals. Salignik suggested suppression of free radicals by the anti-oxidant vitamins may suppress apoptosis (programmed cell death). In their thorough analysis of the research literature Lamson and Brignall presented three conclusions: first, that NAD demonstrated a tendency to interfere with a variety of chemotherapeutic agents without offering consistent benefits; second, some flavonoids demonstrated interactions with some chemotherapeutic agents, with the interactions between tangeretin and tamoxifen being most problematic; and, third, beta-carotene was associated with reduction of 5-fluorouracil (5-FU) activity in such a way as to warrant avoidance of simultaneous use at this time.
(Sacks PG, et al. Int J Cancer 1995;61:409-415; Taper HS, et al. Int J Cancer 1987;40:575-579; Kurbacher CM, et al. Cancer Letters 1996:103-119; Gillissen A, Nowak D. Respir Med 1998 Apr;92(4):609-623; Fujiwaki R, et al. Anticancer Res 1997 Sep-Oct;17(5B):3751-3755; Teicher BA, et al. Cancer Chemother Pharmacol. 1994;34(3):235-41; Wagdi P, et al. Jpn Heart J 1996;37:353-359; Weijl NI, et al. Cancer Treatment Rev 1997;23:209-240; Kong Q, Lillehei KO. Med Hypotheses 1998 Nov;51(5):405-409; Domenighetti G, et al. Rev Mal Respir 1999 Feb;16(1):29-37; Kodama J, et al. Gan To Kagaku Ryoho 1999 Jan;26(1):89-92; Albini A, et al. Int J Cancer 1995 Mar 29;61(1):121-129; Weijl NI, et al. Cancer Treatment Rev 1997 Jul;23(4):209-240; Labriola D, Livingston R. Oncology (Huntingt). 1999 Jul;13(7):1003-1008; Lamson DW, Brignall MS. Altern Med Rev. 1999;4:304-329; Salignik R, et al. 39th Annual Meeting of the American Society for Cell Biology, Dec 11-15th, 1999.)

• nutritional concerns: Concerns have been raised by some oncologists that supplementation with antioxidants might in some way interfere with or limit the effectiveness of chemotherapeutic agents. However, no substantial research has emerged to support this speculation or to warrant considering antioxidants as contraindicated during the course of chemotherapy. Many nutritionally oriented healthcare professionals consider the oxidative damage caused by chemotherapy to be a particularly troublesome side effect given that evidence increasingly points to oxidative damage as being a contributing factor in the causation of many cancers. Individuals receiving chemotherapy should consult their treating physician and/or a nutritionally trained healthcare professional about potential value of adding antioxidants to their regime before starting such supplementation.

Antioxidant nutrients (Vitamin A, Beta-Carotene and Vitamin E) affecting drug performance: Cyclophosphamide

• research: Preliminary studies on humans undergoing chemotherapy with cyclophosphamide have indicated promise of increased survival rates when supplemented with antioxidant nutrients. While antioxidants might have many benefits as supplements, evidence as to their effectiveness in patients taking cyclophosphamide are inconclusive.
(Jaakkola K, et al. Anticancer Res 1992 May;12(3):599-606; Venugopal M, et al. Life Sci 1996;59(17):1389-1400; Vinitha R, et al. Jpn J Med Sci Biol 1995 Jun;48(3):145-156.)

• nutritional concerns: Since activation of cyclophosphamide requires oxidation in the liver there has been concern that antioxidant supplementation might interfere with its effectiveness. However, at this time such concern remains speculative as no conclusive evidence as emerged to confirm an adverse interaction of this type.
(Labriola D, Livingston R. Oncology (Huntingt). 1999 Jul;13(7):1003-1008.)

nutrient affecting drug toxicity: Indomethacin

• mechanism: Indomethacin causes gastric ulceration via free radicals.

• nutritional support: Supplementation with anti-oxidants in individuals using indomethacin may be indicated but should only be initiated after consultation with the prescribing physician and/or a nutritionally trained healthcare provider.

nutrient affecting drug toxicity: Metronidazole (Flagyl®)

• mechanism: Metronidazole can cause serious side effects, especially involving the digestion, liver and central nervous system. The mutagenicity of metronidazole has been extensively reported.

• research: Hrelia et al conducted research on antioxidants and the metronidazole-induced mutagenicity in the livers, kidneys and lungs of mice. After treating the mice with butylated hydroxyanisole (BHA) or butylated hydroxytoluene (BHT), by intraperitoneal injection and oral intubation, they found significantly reduced liver- and kidney-mediated mutagenicity of metronidazole. While they concluded that BHA and BHT themselves might produce possible adverse effects, they still suggested the potential value of prophylactic use of antioxidants in reducing the risk of cancer due to metronidazole.
(Hrelia P, et al. Drugs Exp Clin Res 1987;13(9):577-583.)

• nutritional support: While the data available is speculative, antioxidants could potentially play a role in protecting against the adverse effects of metronidazole. Individuals taking metronidazole, even for 7-10 days, should consult their prescribing physician, pharmacist, and/or a nutritionally trained healthcare professional about the possible benefits of supplementing with antioxidant nutrients.

nutrients affecting drug toxicity: Valproic Acid

• mechanism: Specific oxidative metabolites of valproic acid have been associated with the drug's toxicity.

• research: Research indicates that the valproic acid's cytotoxic activity is the result of generation of hydrogen peroxide and the production of highly reactive hydroxyl free radicals. Graf et al looked at children with serious adverse experiences with valproic acid and found that glutathione peroxidase was significantly depressed and glutathione reductase was significantly elevated relative to other subjects. In particular, they reported that selenium and zinc concentrations were lower in serious adverse experience patients than in controls and concluded that selenium dependent antioxidant activity might play a special role protecting against adverse reactions. Buchi et al found that the free-radical scavenging action of alpha-tocopherol (vitamin E) and N,N'-diphenyl-p-phenylenediamine (DPPD) protected against lipid peroxidation and hepatotoxicity caused by valproic acid (VPA) in rats.
(Nurge ME, et al. Nutr Res 1991;11:949-960; Tabatabaei AR, et al. Toxicology 1996 Aug 1;112(1):69-85; Abbott FS. Chem Res Toxicol 1999 Apr;12(4):323-330; Graf WD, et al. Neuropediatrics 1998 Aug;29(4):195-201; Buchi KN, et al. J Clin Pharmacol 1984 Apr;24(4):148-154.)

• nutritional support: While the use of valproic acid produces numerous adverse effects, especially upon the liver, no conclusive evidence has emerged to demonstrate the clinical role of vitamin E and selenium, or other antioxidants, in countering these adverse effects. Individuals taking valproic acid should consult their prescribing physician and/or a nutritionally trained healthcare professional regarding the use of antioxidants as part of a nutritional support program.

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References

[No authors listed]  MRC/BHF Heart Protection Study of cholesterol-lowering therapy and of antioxidant vitamin supplementation in a wide range of patients at increased risk of coronary heart disease death: early safety and efficacy experience. Eur Heart J. 1999 May;20(10):725-741.
Abstract: AIMS: In observational studies, prolonged lower blood total cholesterol levels - down at least to 3 mmol. l-1 - are associated with lower risks of coronary heart disease. Cholesterol-lowering therapy may, therefore, be worthwhile for individuals at high risk of coronary heart disease events irrespective of their presenting cholesterol levels. Observational studies also suggest that increased dietary intake of antioxidant vitamins may be associated with lower risks of coronary heart disease. The present randomized trial aims to assess reliably the effects on mortality and major morbidity of cholesterol-lowering therapy and of antioxidant vitamin supplementation in a wide range of different categories of high-risk patients. METHODS AND RESULTS: Men and women aged 40 to 80 years were eligible provided they were considered to be at elevated risk of coronary heart disease death because of past history of myocardial infarction or other coronary heart disease, occlusive disease of non-coronary arteries, diabetes mellitus or treated hypertension; had baseline blood total cholesterol of 3.5 mmol. l-1 or greater; and no clear indications for, or contraindications to, either of the study treatments. Eligible patients who completed a pre-randomization run-in phase on active treatment were randomly allocated to receive simvastatin (40 mg daily) or matching placebo tablets and, in a '2x2 factorial' design, antioxidant vitamins (600 mg vitamin E, 250 mg vitamin C and 20 mg beta-carotene daily) or matching placebo capsules. Follow-up visits after randomization are scheduled at 4, 8 and 12 months, and then 6-monthly, for at least 5 years.Between July 1994 and May 1997, 15 454 men and 5082 women were randomized, with 9515 aged over 65 years at entry. Diagnostic criteria overlapped, with 8510 (41%) having had myocardial infarction (most of whom were either female, or elderly or with low blood cholesterol), 4869 (24%) some other history of coronary heart disease, 3288 (16%) cerebrovascular disease, 6748 (33%) peripheral vascular disease, 5963 (29%) diabetes mellitus (of whom 3985 had no history of coronary heart disease) and 8455 (41%) treated hypertension. Baseline non-fasting total cholesterol levels were less than 5.5 mmol. l-1 in 7882 (38%) participants, and LDL (low density lipoprotein) cholesterol less than 3.0 mmol. l-1 in 6888 (34%).During a mean follow-up of 25 months (range: 13 to 47 months), no significant differences had been observed between the treatment groups in the numbers of patients with muscle symptoms, other possible side-effects leading to termination of study treatment, or elevated liver and muscle enzymes. After 30 months of follow-up, 81% of randomized patients remained compliant with taking their study simvastatin or placebo tablets, and allocation to simvastatin produced average reductions in non-fasting blood total and LDL cholesterol of about 1.5-1.6 mmol. l-1 and 1.1-1.2 mmol. l-1 respectively. Eighty-seven per cent of patients remained compliant with taking their vitamin or placebo capsules, and allocation to the vitamin supplement produced an average increase in plasma vitamin E levels of about 24 micromol. l-1. Based on this initial follow-up period, the estimated annual rate of non-fatal myocardial infarction or fatal coronary heart disease is 2.4%, annual stroke rate is 1.3%, and annual all-cause mortality rate is 2. 2%. CONCLUSION: The Heart Protection Study is large, it has included a wide range of patients at high risk of vascular events, and the treatment regimens being studied are well-tolerated and produce substantial effects on blood lipid and vitamin levels. The study should, therefore, provide reliable evidence about the effects of cholesterol-lowering therapy and of antioxidant vitamin supplements on all-cause or cause-specific mortality and major morbidity in a range of different categories of individuals for whom uncertainty remains about the balance of benefits and risks of these treatments.

Albini A, D'Agostini F, Giunciuglio D, Paglieri I, Balansky R, De Flora S. Inhibition of invasion, gelatinase activity, tumor take and metastasis of malignant cells by N-acetylcysteine. Int J Cancer 1995 Mar 29;61(1):121-129.
Abstract: The thiol N-acetylcysteine (NAC) is currently considered one of the most promising cancer chemopreventive agents by virtue of its multiple and coordinated mechanisms affecting the process of chemical carcinogenesis. Recent studies have shown that an unpaired cysteine residue in the propeptide plays a key role in inactivation of latent metastasis-associated metalloproteinases: the present study was designed to assess whether NAC could also affect tumor take, invasion and metastasis of malignant cells. As assessed by zymographic analysis, NAC completely inhibited the gelatinolytic activity of type-IV collagenases in the cells tested (gelatinases A and B). Moreover, NAC was efficient in inhibiting the chemotactic and invasive activities of tumor cells of human (A2058 melanoma) and murine origin (K1735 and B16-F10 melanoma cells as well as C87 Lewis lung carcinoma cells) in Boyden-chamber assays, which are predictive of the invasive and metastatic properties. Reduced glutathione (GSH) had a similar, although less effective activity. The number of lung metastases decreased sharply when B16-F10 murine melanoma cells, injected i.v. into nude mice, were pre-treated with NAC and resuspended in medium supplemented with 10 mM NAC. In other experiments NAC was given in drinking water, starting 48-72 hr before subcutaneous inoculation of either B16-F10 cells or of their highly metastatic variant B16-BL6, or intramuscular injection of LLC cells. In all experiments NAC treatment decreased the weight of the locally formed primary tumor and produced a dose-related delay in tumor formation. Spontaneous metastasis formation by B16-F10 and B16-BL6 tumors was slightly yet significantly reduced by oral administration of NAC. However, this was not observed for Lewis lung tumors. These data indicate that NAC affects the process of tumor-cell invasion and metastasis, probably due to inhibition of gelatinases by its sulfhydryl group, with the possible contribution of other mechanisms, including the potent antioxidant activity of this thiol.

Buchi KN, Gray PD, Rollins DE, Tolman KG. Protection against sodium valproate injury in isolated hepatocytes by alpha-tocopherol and N,N'-diphenyl-p-phenylenediamine. J Clin Pharmacol 1984 Apr;24(4):148-154.
The possibility that lipid peroxidation is involved in valproic acid (VPA) hepatotoxicity was explored by testing the ability of the free-radical scavengers alpha-tocopherol (vitamin E) and N,N'-diphenyl-p-phenylenediamine (DPPD) to protect against VPA toxicity. Rat hepatocyte cultures were treated with toxic doses of VPA, in conjunction with varying doses of vitamin E and DPPD. Lactate dehydrogenase (LDH) release into the culture media was used to calculate an LDH index as a measure of toxicity. Vitamin E afforded increasing protection against VPA toxicity at concentrations of 1.0 to 4.0 microM but then leveled off and did not give complete protection at concentrations up to 8.0 microM. No protection was seen at less than 1.0 microM. DPPD showed increasing protection from 0.05 to 0.50 microM, with complete protection at the highest concentration. These data indicate that VPA toxicity can be prevented by simultaneous administration of free-radical scavengers and support the concept that VPA hepatotoxicity is due to lipid peroxidation.

Chaudiere J, Ferrari-Iliou R. Intracellular antioxidants: from chemical to biochemical mechanisms. Food Chem Toxicol. 1999 Sep-Oct;37(9-10):949-962.
Abstract: Intracellular antioxidants include low molecular weight scavengers of oxidizing species, and enzymes which degrade superoxide and hydroperoxides. Such antioxidants systems prevent the uncontrolled formation of free radicals and activated oxygen species, or inhibit their reactions with biological structures. Hydrophilic scavengers are found in cytosolic, mitochondrial and nuclear compartments. Ascorbate and glutathione scavenge oxidizing free radicals in water by means of one-electron or hydrogen atom transfer. Similarly, ergothioneine scavenges hydroxyl radicals at very high rates, but it acts more specifically as a chemical scavenger of hypervalent ferryl complexes, halogenated oxidants and peroxynitrite-derived nitrating species, and as a physical quencher of singlet oxygen. Hydrophobic scavengers are found in cell membranes where they inhibit or interrupt chain reactions of lipid peroxidation. In animal cells, they include alpha-tocopherol (vitamin E) which is a primary scavenger of lipid peroxyl radicals, and carotenoids which are secondary scavengers of free radicals as well as physical quenchers of singlet oxygen. The main antioxidant enzymes include dismutases such as superoxide dismutases (SOD) and catalases, which do not consume cofactors, and peroxidases such as selenium-dependent glutathione peroxidases (GPx) in animals or ascorbate peroxidases (APx) in plants. The reducing coenzymes of peroxidases, and as a rule all reducing components of the antioxidant network, are regenerated at the expense of NAD(P)H produced in specific metabolic pathways. Synergistic and co-operative interactions of antioxidants rely on the sequential degradation of peroxides and free radicals as well as on mutual protections of enzymes. This antioxidant network can induce metabolic deviations and plays an important role in the regulation of protein expression and/or activity at the transcriptional or post-translational levels. Its biological significance is discussed in terms of environmental adaptations and functional regulations of aerobic cells.

Chen C, Mistry G, Jensen B, Heizmann P, Timm U, van Brummelen P, Rakhit AK.Pharmacokinetics of retinoids in women after meal consumption or vitamin A supplementation. J Clin Pharmacol 1996 Sep;36(9):799-808.
Abstract: These studies were conducted to evaluate the pharmacokinetics of several retinoids after meal consumption or vitamin A supplementation to establish a reference for future assessment of teratogenic risks of retinoid therapeutic agents. In the first study, 36 healthy young female volunteers consumed single meals containing vitamin A amounts ranging from 1,305 to 169,474 IU. In the second study, 24 other female volunteers took vitamin A supplements at a dose level of 5,000, 10,000, or 25,000 IU/day for 60 days. Plasma concentrations of tretinoin, isotretinoin, 4-oxo-tretinoin, and 4-oxo-isotretinoin in samples collected during the studies were analyzed using a high-performance liquid chromatography method with ultraviolet detection. Pharmacokinetic parameters for the retinoids were calculated using model-independent methods. Plasma concentrations of tretinoin were not altered by meal consumption or vitamin A supplementation. Plasma levels of 4-oxo-tretinoin were below the assay detection limit (0.3 ng/mL) in the majority of samples collected throughout the studies. Linear relationships between dose and maximum concentration (Cmax) and dose and area under the concentration-time curve (AUC) for isotretinoin and 4-oxo-isotretinoin were derived from data from the meal study. For the most bioavailable formulation used in the supplement study, daily ingestion of 5,000 IU of vitamin A caused increases of 141 +/- 53% and 171 +/- 77% from baseline in the 24-hour AUCs of isotretinoin and 4-oxo-isotretinoin, respectively. Dose-related increases in systemic exposure to retinoids were observed after ingestion of vitamin A by means of a meal or a supplement. Findings from these studies can be used as a basis for future safety evaluations of retinoid compounds.

Domenighetti G, Quattropani C, Schaller MD. [Therapeutic use of N-acetylcysteine in acute lung diseases]. Rev Mal Respir 1999 Feb;16(1):29-37. [Article in French]
Abstract: Oxidants play a key role in disease processes, particularly in the detrimental mechanisms leading to tissue damage in certain forms of acute lung injury. A number of mediators contribute to the pathologic response in ARDS, SIRS or hyperoxia-induced pulmonary damage. One of the most important detrimental factors is the generation and activation of highly reactive oxygen species which are leading factors implicated in the process of tissue damage. N-acetylcysteine (NAC) is a free radical scavenger and might access the endothelial cell thus increasing intracellular glutathione (GSH) stores. Different studies have demonstrated that NAC might be a promising compound either for the prevention or the treatment of acute lung damages such as ARDS. However, the true beneficial effect so far reported in several clinical and experimental studies contrasts with some contradictory and intriguing aspects, probably because the significance of a direct in vivo antioxidative effect of this compound remains to be established in humans. Thus, the mode of action of NAC may not be the same in different pathologies and clinical situations. More research into the mechanisms of action of this unique xenobiotic substance may offer a clue for elucidating these controversies.

Dreizen S, McCredie KB, Keating MJ, Andersson BS. Nutritional deficiencies in patients receiving cancer chemotherapy. Postgrad Med 1990 Jan;87(1):163-167, 170.
Abstract: Cancer often causes malnutrition and specific vitamin and protein deficiencies. Chemotherapy also causes deficiencies by promoting anorexia, stomatitis, and alimentary tract disturbances. Antimetabolite drugs in particular inhibit synthesis of essential vitamins, purines, and pyrimidines. Because vitamin levels in the blood are often nondiagnostic, nutritional deficiency is identified almost exclusively on the basis of clinical signs and symptoms and the patient's response to therapy. Signs and symptoms of cachexia and hypoalbuminemia are common in patients with advanced cancer. Deficiencies of vitamins B1, B2, and K and of niacin, folic acid, and thymine also may result from chemotherapy. Nutritional deficiencies are chemically correctable; however, the tumor must be eradicated to relieve cachexia.

Fujiwaki R, Iida K, Ohnishi Y, Watanabe Y, Ryuko K, Takahashi K, Miyazaki K. Intra-arterial neoadjuvant chemotherapy followed by radical surgery and radiotherapy for stage IIb cervical carcinoma. Anticancer Res 1997 Sep-Oct;17(5B):3751-3755.
Abstract: BACKGROUND: The role of intra-arterial neoadjuvant chemotherapy (NAC) in the management of cervical carcinoma has not been established. The aim of this study was to determine whether pre-operative intra-arterial NAC is effective or not in patients with stage IIb cervical carcinoma. PATIENTS AND METHODS: A total of 28 patients with stage IIb cervical carcinoma (diameter > 4 cm) were treated with one cycle of intra-arterial NAC (cisplatin 70 mg/m2, and peplomycin sulfate 30 mg/m2 or doxorubicin 30 mg/m2) followed by radical surgery and post-operative radiotherapy. Immediate response, toxicity, survival, and prognostic factors for survival were evaluated. RESULTS: The overall clinical response rate was 79% (22/28) with a complete response in 1 patient (4%). Radical hysterectomy with pelvic lymphadenectomy was feasible in 25 patients (89%) 4 weeks after chemotherapy. Toxicity were generally mild, and there were no intraoperative complications related to intra-arterial NAC. The estimated 2- and 5-year survival rates for the entire group were 93% and 80%, respectively, with a median followup time in survivors of 62 months. Univariate analysis showed the following to be significantly related to survival: histologic type, PCNA index, clinical response to intraarterial NAC, and lymph node metastasis. Survival was not significantly related to age, grade of differentiation, serum level of squamous cell carcinoma antigen, p53 protein expression, or residual parametrial involvement. Multivariate Cox's proportional hazard analysis showed that only the histologic type significantly influenced survival (p = 0.0007). The estimated 2- and 5-year survival rates were 100% and 94% for patients with squamous cell carcinoma, and 75% and 50% for those with adenocarcinoma. CONCLUSIONS: Intra-arterial NAC followed by surgery and radiotherapy appeared to be effective in treating patients with stage IIb cervical squamous cell carcinoma, but was not as effective in patients with stage IIb cervical adenocarcinoma.

Gaedeke J, Fels LM, Bokemeyer C, Mengs U, Stolte H, Lentzen H. Cisplatin nephrotoxicity and protection by silibinin. Nephrol Dial Transplant 1996 Jan;11(1):55-62.
Abstract: BACKGROUND. The anticancer drug cisplatin is know to have toxic side-effects on different segments of the nephron. The flavonoid silibinin has previously been shown to be protective in models of hepatotoxicity. The aim of the present study was to evaluate, whether silibinin can also ameliorate alterations in renal glomerular and tubular function and tubular morphology induced by cisplatin. METHODS. In a rat model renal damage was induced by a single injection of cisplatin (5 mg/kg body weight). The protective effects of silibinin were studied in rats that received the flavonoid (200 mg/kg body weight, i.v.) 1 h prior to the administration of cisplatin. Kidney function was monitored by analysing urinary markers of glomerular and tubular function over a period of 11 days. Animals of a second group, with identical treatment, were sacrificed 4 days after drug application for an evaluation of tubular morphology at the light-microscopical level. RESULTS. Administration of cisplatin caused a decline in kidney function within a day following treatment. Symptoms observed were for example decreases in creatinine clearance and increases in proteinuria, in the urinary activity of the proximal tubular enzymes alanine aminopeptidase and N-acetyl-beta-D-glucosaminidase and in renal magnesium wasting. The effects of cisplatin on creatinine clearance and proteinuria were totally prevented by a pretreatment of the animals with silibinin. Impairment of proximal tubular function was ameliorated, that is enzymuria and magnesium wasting was less pronounced. Silibinin alone had no effect on kidney function. Treatment with silibinin distinctly diminished morphological alterations observed in the S3-segment of the proximal tubule 4 days after cisplatin administration. CONCLUSION. The effects of cisplatin on glomerular and proximal tubular function as well as proximal tubular morphology could totally or partly be ameliorated by silibinin. It is concluded the silibinin can act as a nephroprotectant and it is suggested that it could have beneficial effects on the kidney in clinical settings.

Gillissen A, Nowak D. Characterization of N-acetylcysteine and ambroxol in anti-oxidant therapy. Respir Med 1998 Apr;92(4):609-623. (Review)

Graf WD, Oleinik OE, Glauser TA, Maertens P, Eder DN, Pippenger CE. Altered antioxidant enzyme activities in children with a serious adverse experience related to valproic acid therapy. Neuropediatrics 1998 Aug;29(4):195-201.
Abstract: Specific oxidative metabolites of valproic acid (VPA) have been associated with the clinically defined toxicity of the drug. To investigate the role of enzymatic detoxification in clinical toxicity, we compared activities of five antioxidant enzymes in 15 patients with a serious adverse experience (SAE) related to VPA therapy, to enzyme activities measured in 35 patients with good clinical tolerance of VPA, and 50 healthy, age-matched subjects. These enzymes included glutathione peroxidase (GSH-Px), glutathione reductase (GSSG-R), glutathione transferase, superoxide dismutase, and catalase in erythrocytes; and GSH-Px in plasma. We also determined levels of Se, Cu, and Zn, trace elemental cofactors for these enzymes, in plasma from each individual. In patients with a VPA-associated SAE, GSH-Px was significantly depressed and GSSG-R was significantly elevated relative to values for the other groups. Selenium and zinc concentrations were lower in SAE patients than in controls. These findings may indicate a role for selenium dependent antioxidant activity in individual susceptibility to an SAE related to VPA therapy.

Halliwell B. Antioxidant defence mechanisms: from the beginning to the end. Free Radic Res. 1999 Oct;31(4):261-272.

Henquin N, Havivi E, Reshef A, Barak F, Horn Y. Nutritional monitoring and counselling for cancer patients during chemotherapy. Oncology 1989;46(3):173-177.
Abstract: The objective of the study was to try to monitor the nutritional status of cancer patients during chemotherapeutic treatment. Concomitantly with chemotherapeutic treatment administered to patients with cancer of the gastrointestinal tract and metastatic carcinoma of unknown origin, levels of carotene, retinol, thiamine, riboflavin, pyridoxine, iron, total protein and hemoglobin were measured in the blood periodically. In addition, anthropometric studies were performed and the nutritional status was established. A total of 19 patients were subject for final evaluation. These patients formed 3 groups according to their nutritional status (good, medium, poor). The effect of chemotherapy was correlated to the nutritional status at 3 different periods of chemotherapy. Most patients with good clinical status maintained the initial nutritional status. Half of the patients with medium nutritional status improved clinically during therapy, and patients initially with poor nutritional status further deteriorated. The levels of most vitamins decreased to a certain degree during therapy and returned to initial values thereafter. Our impression is that cancer patients might benefit from intensive ongoing personal nutritional monitoring and counselling. The results presented have a preliminary meaning because of the small number of patients included in this study.

Hrelia P, Murelli L, Paolini M, Cantelli-Forti G. In vivo protective role of antioxidants against genotoxicity of metronidazole and azanidazole. Drugs Exp Clin Res 1987;13(9):577-583.
Abstract: The mutagenicity of metronidazole and azanidazole has been extensively reported. Previous experiments demonstrated, by means of the intrasanguineous host-mediated assay, that they significantly induced mutagenicity in liver, kidney and lung of mice. The treatment of mice with butylated hydroxyanisole (BHA) or butylated hydroxytoluene (BHT) by two different routes of administration (i.p. injection and oral intubation) significantly reduced liver- and kidney-mediated mutagenicity of azanidazole and metronidazole. No significant differences were observed between the routes of treatment in terms of protective effect on genotoxicity of azanidazole in the considered organs, whereas i.p. administration was the most suppressive on the mutagenicity of metronidazole. Even if BHT was the most effective agent in preventing mutation induction in mice, a detectable toxicity, in terms of increased mutagenicity, was evaluated in the liver. Evidence of lung abnormalities was also seen. The results suggest that the possible adverse effects on biological systems limit the prophylactic use of BHA and BHT in preventing the action of chemical carcinogens in man.

Iino Y, Yokoe T, Maemura M, Horiguchi J, Takei H, Ohwada S, Morishita Y. Immunochemotherapies versus chemotherapy as adjuvant treatment after curative resection of operable breast cancer. Anticancer Res 1995 Nov-Dec;15(6B):2907-2911.
Abstract: In our previous study, oral adjuvant combination chemotherapy of 5-fluorouracil, cyclophosphamide, mitomycin C, and predonisolone (FEMP) after curative resection of operable breast cancer with vascular invasion in the tumor and/or in the metastatic lymph node was found to be more effective than one course of mitomycin C or cyclic course of mitomycin C. In the present study, we have assessed the efficacy of protein-bound polysaccharide (PSK) or levamisole (LMS) in addition to FEMP. Between January 1980 and December 1990, 227 operable breast cancer patients with vascular invasion in the tumor and/or in the metastatic lymph node were randomized into FEMP, FEMP + LMS, or FEMP + PSK. The risk ratio was lower in the FEMP + PSK group compared to the FEMP group. In disease-free survival or overall survival, there was no significant difference between the three groups, however, the survival curve of the FEMP + PSK group tended to be better than that of the FEMP group(logrank, P = 0.0706; generalized Wilcoxon, P = 0.0739). Side effects were observed at a low incidence, but they were mild and tolerable. Immunochemotherapy using PSK improved the prognosis of patients with operable breast cancer with vascular invasion.

Invernizzi R, Bernuzzi S, Ciani D, Ascari E. Silymarine during maintenance therapy of acute promyelocytic leukemia. Haemotologia Haematologica 1993 Sep-Oct;78(5):340-341. (Letter)

Israel L, Hajji O, Grefft-Alami A, Desmoulins D, Succari M, Cals MJ, Miocque M, Breau JL, Morere JF. [Vitamin A augmentation of the effects of chemotherapy in metastatic breast cancers after menopause. Randomized trial in 100 patients]. Ann Med Interne (Paris) 1985;136(7):551-554. [Article in French]
Abstract: Vitamin A was administered to randomly allocated patients in a group of 100 patients with metastatic breast carcinoma treated by chemotherapy. The daily doses (given indefinitely) ranged from 350,000 to 500,000 IU according to body weight. A significant increase in the complete response rate was observed. When subgroups determined by menopausal status were considered, it was observed that serum retinol levels were only significantly increased in the post-menopausal group on high dose Vitamin A. Response rates, duration of response and projected survival were only significantly increased in this subgroup. The therapeutic and biological implications of these findings are discussed.

Jaakkola K, Lahteenmaki P, Laakso J, Harju E, Tykka H, Mahlberg K. Treatment with antioxidant and other nutrients in combination with chemotherapy and irradiation in patients with small-cell lung cancer. Anticancer Res 1992 May;12(3):599-606.
Abstract: Eighteen non-randomized patients with small cell lung cancer (4 women and 14 men, mean age 60.4, SD 7.8 years) received in addition to conservation small cell lung cancer treatment antioxidant treatment with vitamins, trace elements and fatty acids. All patients were out-patients who, except for one were also treated with chemotherapy and/or irradiation at regular intervals at a university of central hospital. Five patients (28%) were in an advanced stage of the disease. At the end of the follow-up period (31.7.90) the median survival time for the whole group was 505 days. Fourteen (77%) of the patients survived for more than 12 months and six patients (33%) for more than two years. One patient (5%) survived more than five years. Eight patients (44%) were still alive with a mean survival time of 32 months at the end of the study. Ten patients succumbed earlier from progression of the disease. Antioxidant treatment, in combination with chemotherapy and irradiation, prolonged the survival time of patients with small cell lung cancer compared to most published combination treatment regimens alone. We also noticed that the patients receiving antioxidants were able to tolerate chemotherapy and radiation treatment well. Surviving patients started antioxidant treatment ingeneral earlier than those who succumbed.

Kodama J, Ikuhashi H, Hongo A, Mizutani Y, Miyagi Y, Yoshinouchi M, Kobashi Y, Okuda H, Kudo T. [Neoadjuvant chemotherapy for advanced cervical cancer]. Gan To Kagaku Ryoho 1999 Jan;26(1):89-92. [Article in Japanese]
Abstract: Twenty-five patients with advanced cervical cancer (IIb-IVa) were treated with neoadjuvant chemotherapy followed by radical hysterectomy or radiotherapy. According to the evaluation by MRI, complete response was achieved in 2 cases and partial response in 17 cases. Eventually the response rate was 76%. The response rate was higher in squamous cell carcinomas (85%) than adenocarcinomas or adenosquamous carcinomas (67%). The histological effect is superior in squamous cell carcinomas than adenocarcinomas or adenosquamous carcinomas. Radical hysterectomy was performed in 5 cases of 11 (45%) stage III-IVa cervical cancers. There was no correlation between tumor size and response to NAC. NAC therapy may be useful therapy in advanced cervical cancers, especially squamous cell carcinomas.

Kong Q, Lillehei KO. Antioxidant inhibitors for cancer therapy. Med Hypotheses 1998 Nov;51(5):405-409.
Abstract: Built-in cellular defense mechanisms play a major role in a tumor's protection against non-surgical antineoplastic therapies. Of these, the overexpression of antioxidants such as superoxide dismutase (SOD) may be the most important. Oxygen radicals are highly toxic, and have been implicated in various diseases, including carcinogenesis and aging. They produce a variety of pathological changes through lipid peroxidation and DNA damage. Therefore, treating free-radical-induced diseases with antioxidants has been an accepted therapeutic approach. Ironically, however, the underlying mechanism that most chemotherapeutic agents and ionizing radiation exert on tumor cell kill is not increased antioxidation but rather the production of more free radicals leading to irreversible tissue injury. A small increase in reactive oxygen species (ROS) following non-surgical antineoplastic therapies induces the expression of antioxidants such as SOD, but overproduction of ROS, conversely, exhausts the production of SOD and other adaptive antioxidant defenses. Based on these considerations, we hypothesize that the appropriate administration of antioxidant inhibitors and/or free-radical-generating compounds may be a useful strategy in the treatment of solid tumors.

Krivit W. Adriamycin cardiotoxicity amelioration by alpha-tocopherol. Am J Pediatr Hematol Oncol 1979 Summer;1(2):151-153.
Abstract: Adriamycin has become a potent member of the cancer chemotherapeutic program. However, the full utilization of adriamycin is limited by its cardiotoxicity. In experimental animals, alpha-tocopherol has been shown by some to ameliorate or prevent cardiac dysfunction without impairing antitumor effectiveness. During adriamycin therapy, future clinical research should consist of biochemical measurements of vitamin E in plasma, lipoperoxidation in red cells and platelets, while cars to indicate deficiency, should be considered as one method of ameliorating toxicity.

Kurbacher CM, Wagner U, Kolster B, Andreotti PE, Krebs D, Bruckner HW. Ascorbic acid (vitamin C) improves the antineoplastic activity of doxorubicin, cisplatin, and paclitaxel in human breast carcinoma cells in vitro. Cancer Letters 1996 Jun 5;103(2):183-119.
Abstract: Utilizing a microplate ATP bioluminescence assay, two human breast carcinoma cell lines, MCF-7 and MDA-MB-231, were tested against doxorubicin (DOX), cisplatin (DDP), and paclitaxel (Tx) alone and in combination with ascorbic acid (Vit C). In both cell lines, Vit C exhibited cytotoxic activity at high concentrations (i.e. 10(2)-10(3) microM). Both cell lines also were resistant to DOX. MCF-7 was found to be DDP-resistant, MDA-MB-231 was moderately sensitive to DDP. Both cell lines were strongly sensitive to Tx. Vit C both at non-cytotoxic (1 microM) and moderately cytotoxic concentrations (10(2) microM) improved the cytotoxicity of DOX, DDP, and Tx significantly. Combination effects between Vit C and DDP or Tx were partly synergistic and partly additive or subadditive whereas a consistent synergism was found between Vit C and DOX. The mechanisms by which Vit C potentiates the cytostatics studied are yet unclear and should be evaluated further.

Labriola D, Livingston R. Possible interactions between dietary antioxidants and chemotherapy. Oncology (Huntingt). 1999 Jul;13(7):1003-1008; discussion 1008, 1011-1012.
Abstract: Many patients treat themselves with oral antioxidants and other alternative therapies during chemotherapy, frequently without advising their conventional health care provider. No definitive studies have demonstrated the long-term effects of combining chemotherapeutic agents and oral antioxidants in humans. However, there is sufficient understanding of the mechanisms of action of both chemotherapeutic agents and antioxidants to predict the obvious interactions and to suggest where caution should be exercised with respect to both clinical decisions and study interpretation. This article will describe these potential interactions and areas of concern, based on the available data. It will also suggest several potential courses of action that clinicians may take when patients indicate that they are taking or plan to use alternative therapies.

Lamson DW, Brignall MS. Antioxidants in cancer therapy; their actions and interactions with oncologic therapies. Altern Med Rev. 1999;4:304-329. (Review)

Lapenna D, De Gioia S, Mezzetti A, Grossi L, Festi D, Marzio L, Cuccurullo F. H2-receptor antagonists are scavengers of oxygen radicals. Eur J Clin Invest 1994 Jul;24(7):476-481.
Abstract: Potential oxygen radical scavenging properties of the H2-receptor antagonists cimetidine, ranitidine and famotidine were investigated. These drugs, although ineffective against superoxide anion and hydrogen peroxide, can scavenge hydroxyl radical (OH.) with a very high rate constant, which is about tenfold higher than that of the specific scavenger mannitol for famotidine (1.7 x 10(10) mol-1 s-1) and cimetidine (1.6 x 10(10) mol-1 s-1), ranitidine displaying a rate constant of 7.5 x 10(9) mol-1 s-1. These OH. savenging effects are significant beginning from 10, 28 and 100 mumol l-1 concentration for famotidine, cimetidine and ranitidine, respectively, thus suggesting that the drugs may effectively act as OH. scavengers in vivo especially in the gastric lumen. Only cimetidine can apparently bind and inactivate iron, which further emphasizes its antioxidant capacity. Moreover, all drugs, even at 10 mumol l-1 concentration, show powerful scavenging effects on hypochlorous acid and monochloramine, which are cytotoxic oxidants arising from inflammatory cells, such as neutrophils. These data suggest that some therapeutical effects of H2-receptor antagonists in peptic ulcer may also be related to their antiradical-antioxidant capacity, and that these drugs could potentially be used in other disease entities characterized by free radical-mediated oxidative stress in vivo.

Legha SS, Wang YM, Mackay B, Ewer M, Hortobagyi GN, Benjamin RS, Ali MK. Clinical and pharmacologic investigation of the effects of alpha-tocopherol on Adriamycin cardiotoxicity. Ann NY Acad Sci 1982;393:411-418.
Abstract: Our data indicate that alpha-tocopherol used in an oral dose of 2 g/m2 daily results in a six- to eightfold increase of the vitamin E levels in serum. The occurrence of congestive heart failure in three patients and the observation of significant pathologic changes in endomyocardial biopsies in approximately half of the patients treated with a median cumulative adriamycin dose level of 550 mg/m2 indicate that alpha-tocopherol does not offer substantial protection against adriamycin-induced cardiac toxicity. The antitumor activity of the drug, however, is not compromised by the concomitant administration of the vitamin.

Mitchell MS. Combining chemotherapy with biological response modifiers in treatment of cancer. J Natl Cancer Inst. 1988 Nov 16;80(18):1445-1450. (Review)

Nurge ME, Anderson CR, Bates E. Metabolic and nutritional implications of valproic acid. Nutr Res 1991;11:949-960.

Sacks PG, Harris D, Chou T-C. Modulation of growth and proliferation in squamous cell carcinoma by retinoic acid: A rationale for combination therapy with chemotherapeutic agents. Int J Cancer 1995 May 4;61(3):409-415.
Abstract: We have previously shown that beta-all trans retinoic acid (RA) inhibits macrocellular growth of a multicellular tumor spheroid model for squamous carcinoma, as measured by spheroid size, but allows for continuing DNA synthesis and cell cycle progression, the two being reconciled by a cell death effect. DNA synthesis in the presence of growth inhibition suggested a rationale for examining combination chemotherapy with RA-inhibited cells. To this aim, we have extended this observation to a series of 8 squamous carcinoma cell lines. Cells were treated with 1 microM RA for 7 days and cell growth parameters monitored. Although growth inhibition ranged from 0% (A431) to approx. 80% (MDA 886Ln), [3H]-thymidine incorporation (cpm/microgram protein) and percent S-phase (by flow cytometry) in 7-day RA-treated cells was equal or higher than in their control vehicle-treated cells in 7/8 SCC cell lines. Thus RA-induced growth inhibition is not just cytostasis. Combination therapy was examined with MDA 886Ln, MDA 686Ln, 1483 and A431 cells pre-treated for 7 days with 1 microM RA followed by cisplatin or 5-fluorouracil treatment. An increased effectiveness for the combination was shown using 5-day tetrazolium dye (MTT) growth assays when cells were growth-inhibited by RA. Computerized analysis of data using median-effect and isobologram techniques indicated that the interaction of RA with these chemotherapeutic agents was synergistic. With squamous carcinoma, RA treatment inhibits growth while allowing for continuing DNA synthesis, and these RA-treated, growth-inhibited cells exhibit increased sensitivity to chemotherapeutic agents.

Salignik R, et al, Avoiding vitamins A and E may improve cancer therapy. 39th Annual meeting of the American Society for Cell Biology, Dec 11-15th, 1999.
Abstract: Apoptosis, or programmed cell death, eliminates selectively precancerous and cancerous cells. Since reactive oxygen species (ROS) act as essential mediators of apoptosis, antioxidants inhibit this protective form of cell death. Most anticancer drugs kill cancer cells by apoptosis and antioxidants interfere with their anticancer effect. Since depletion of ROS decreases apoptosis, we reasoned that increasing the level of ROS might enhance apoptotic death of cancer cells and inhibit thereby tumor growth. Here, using a defined transgenic brain tumor model, we test the impact of feeding an antioxidant depleted diet, capable of increasing ROS accumulation, on apoptosis and tumor growth. Dramatically increased apoptosis occurs within tumors in antioxidant-depleted mice, but not in normal tissues. Detectably increased oxidant stress indicates that the likely mechanism of enhanced tumor apoptosis is via a rise in ROS. Tumor growth is significantly inhibited in mice fed an antioxidant-depleted diet. In clear contrast, an oxidant-enriched diet had no impact on tumor growth.

Scambia G, De Vincenzo R, Ranelletti FO, Panici PB, Ferrandina G, D'Agostino G, Fattorossi A, Bombardelli E, Mancuso S. Antiproliferative effect of silybin on gynaecological malignancies: synergism with cisplatin and doxorubicin. Eur J Cancer 1996 May;32A(5):877-882.
Abstract: The aim of this study was to test the antiproliferative activity of silybin, a flavonoid, on human ovarian and breast cancer cell lines. Since flavonoids are thought to act through Type II oestrogen binding sites (Type II EBS), silybin binding to Type II EBS was also examined. Silybin, used in concentrations from 0.1 to 20 microM, exerted a dose-dependent growth inhibitory effect on OVCA 433, A2780 parental and drug-resistant ovarian cancer cells, and MCF-7 doxorubicin (DOX)-resistant breast cancer cells (IC50 = 4.8-24 microM). Both L and D diastereoisomers of silybin were effective in inhibiting A2780 WT cell growth (IC50 = 14 and 20 microM, respectively). Flow cytometry revealed that silybin decreased the percentage of cells in the S and G2-M phases of the cell cycle with a concomitant increase in cells in the G0-G1 phase. Silybin was able to compete with [3H]E2 for nuclear but not cytosolic Type II EBS. Its affinity parallels its efficacy in inhibiting cell proliferation. Furthermore, silybin (0.1 and 1 microM) potentiates the effect of cisplatin (CDDP) (0.1-1 micrograms/ml) in inhibiting A2780 WT and CDDP-resistant cell growth. Similar results were obtained on MCF-7 DOX-resistant cells when silybin (0.1 microM) was associated with doxorubicin (0.1-10 micrograms/ml). As assessed by the Berembaum isobole method, the effect of silybin-CDDP and silybin-DOX combinations results in a synergistic action. Using the 'stem cell assay' described by Hamburger and Salmon [Science 1977, 197, 461-463], we found that silybin exerted a dose-dependent inhibition of clonogenic efficiency of cells derived from three ovarian tumours (IC50 = 7.4, 4 and 6.4 microM, respectively). Since CDDP and DOX are the two most commonly used drugs for gynaecological tumours, the clinical application of silybin is currently under investigation in our institute.

Shi X, Ding M, Dong Z, Chen F, Ye J, Wang S, Leonard SS, Castranova V, Vallyathan V. Antioxidant properties of aspirin: characterization of the ability of aspirin to inhibit silica-induced lipid peroxidation, DNA damage, NF-kappaB activation, and TNF-alpha production. Mol Cell Biochem. 1999 Sep;199(1-2):93-102.
Abstract: Electron spin resonance (ESR) was used to investigate the reaction of aspirin toward reactive oxygen species, such as hydroxyl radicals (*OH), superoxide radicals (O2-) and H2O2. The Fenton reaction (Fe(II) + H2O2 ---> FE(III) + *OH + OR) was used as a source of *OH radicals. The results show that aspirin is an efficient *OH radical scavenger with a reaction rate constant of k = 3.6 x 10(10) M(-1) sec(-1), which is faster than several well established antioxidants, such as ascorbate, glutathione and cysteine. However, aspirin is not a good scavenger for O2- or H2O2. Through its antioxidant property, aspirin exhibited a protective effect against silica-induced lipid peroxidation and DNA strand breakage. Aspirin also inhibited the activation of nuclear transcription factor-kappaB induced by silica, lipopolysaccharide or the transition metal, Fe(II), as demonstrated by electrophoretic mobility shift assay. The results show that aspirin functions as an antioxidant via its ability to scavenge *OH radicals. This antioxidant property may explain some of its various physiological and pharmacological actions.

Sznol M, et al. Chemotherapy drug interactions with biological agents. Semin Oncol. 1993 Feb;20(1):80-93. (Review)

Tabatabaei AR, Abbott FS. Assessing the mechanism of metabolism-dependent valproic acid-induced in vitro cytotoxicity. Chem Res Toxicol 1999 Apr;12(4):323-330.
Abstract: This study was designed to distinguish and evaluate the contribution of reactive metabolite and reactive oxygen species as the mechanism of metabolism-dependent valproic acid-induced in vitro cytotoxicity. The involvement of reactive oxygen species in the mechanism of in vitro cytotoxicity was examined by the addition of a series of antioxidant enzymes and iron chelators to the reaction mixture. Addition of catalase to the reaction mixture resulted in a complete prevention of valproic acid-induced cytotoxicity. Co-incubation of a cell impermeable iron chelator deferoxamine did not effect cytotoxicity, whereas 1,10-phenanthroline, a chelator with the ability to traverse cell membranes at low concentrations, afforded significant protection against valproic acid-induced cytotoxicity. A possible inhibitory effect of catalase and 1,10-phenanthroline on the microsomal metabolism of valproic acid was disproved by the quantification of valproic acid metabolites in the presence and absence of these compounds. To assess the specificity of the mechanism of in vitro valproic acid-induced cytotoxicity, prevention of in vitro acetaminophen-induced cytotoxicity by antioxidant enzymes and iron chelators was also evaluated. Addition of catalase to the reaction mixture in the presence of acetaminophen resulted in a moderate reduction in the level of but a lack of complete protection of cytotoxicity. Addition of 1,10-phenanthroline to the reaction mixture in the presence of acetaminophen did not result in a detectable change in acetaminophen-induced cytotoxicity. These data suggest the involvement of reactive oxygen species in the mechanism of toxicity of valproic acid and perhaps reactive metabolites as the major cause of cytotoxicity in the case of acetaminophen in the in vitro model investigated. Inhibition of poly(ADP-ribose) polymerase activity by various antagonists resulted in complete prevention of valproic acid-induced in vitro cytotoxicity. The cytoprotective effects of known poly(ADP-ribose) polymerase antagonists implicate poly(ADP-ribose) polymerase in the mechanism of in vitro metabolism-dependent valproic acid-induced cytotoxicity under these conditions. These results further point to nuclear DNA as the intracellular site of insult by the generated oxygen radicals. Overall, the data obtained support the hypothesis that the metabolism-dependent valproic acid-induced in vitro cytotoxicity is the result of generation of hydrogen peroxide in the medium that can readily cross cell membranes and subsequently interact intracellularly with iron to produce the highly reactive hydroxyl free radicals.

Taper HS, de Gerlache J, Lans M, Roberfroid M. Non-toxic potentiation of cancer chemotherapy by combined C and K3 vitamin pre-treatment. Int J Cancer 1987 Oct 15;40(4):575-579.
Abstract: The influence on the survival of ascitic liver tumor (TLT)-bearing mice of combined vitamins C and K3 administered before or after a single i.p. dose of 6 different cytotoxic drugs, all commonly used in human cancer therapy, was investigated. Combined i.p. administration of these vitamins produced a distinct chemotherapy-potentiating effect for all drugs examined, especially when injected before chemotherapy. This potentiating treatment did not increase the general and organ toxicity that accompanies cancer chemotherapy. The possible generation of peroxides followed by membrane lipid alteration, DNase activation and DNA destruction by combined vitamin C and K3 in catalase-deficient cancer cells might be involved in the mechanisms of this selective potentiation.

Taper HS, Keyeux A, Roberfroid M. Potentiation of radiotherapy by nontoxic pretreatment with combined vitamins C and K3 in mice bearing solid transplantable tumor. Anticancer Res 1996 Jan;16(1):499-503.
Abstract: BACKGROUND: The effect of intraperitoneal and oral pretreatment with combined vitamins C and K3 on the single dose radiotherapy of a transplantable solid mouse tumor have been investigated. MATERIALS AND METHODS: Groups of mice bearing intramuscularly transplanted liver tumors, were orally and parenterally pretreated with combined vitamins C and K3 and locally irradiated with single doses of 20, 30, or 40 Gy of X-rays. After this treatment tumor dimensions were measured twice weekly and the approximate tumor volume in groups of pretreated vitamins and irradiated mice was compared to the groups of mice only irradiated and to the absolute control groups without any therapy. RESULTS: This nontoxic pretreatment produced statistically significant potentiation of radiotherapy induced by 20 to 40 Gy of X-rays doses in groups of 11 to 20 mice. Combined vitamins C with K3 most probably constitute a redox-cycling system producing hydrogen peroxide and other active oxygen species to which cancer cells are selectively sensitive due to their frequent deficiency in enzymatic defense system against free oxyradicals agression. CONCLUSIONS: A possible introduction of such nontoxic and selective potentiation procedure into classical protocols of human cancer therapy appears to be generally accessible and without any additional risk for patients.

Taylor RT, Huskisson EC, Whitehouse GH, Hart FD, Trapnell DH. Gastric ulceration occurring during indomethacin therapy. Br Med J 1968 Dec 21;4(633):734-737.

Teicher BA, Schwartz JL, Holden SA, Ara G, Northey D. In vivo modulation of several anticancer agents by beta-carotene. Cancer Chemother Pharmacol. 1994;34(3):235-241.
Abstract: The ability of the collagenase inhibitor minocycline and of beta-carotene to act as positive modulators of cytotoxic anticancer agents was assessed in vitro and in vivo. Cell-culture studies were conducted using the human SCC-25 squamous carcinoma cell line. Simultaneous exposure of the cells to minocycline and beta-carotene or 13-cis-retinoic acid along with cisplatin (CDDP) resulted in a small decrease in the cytotoxicity of the CDDP. The addition of each of the modulator combinations for 1 h or 24 h to treatment with melphalan (L-PAM) or carmustine (BCNU) resulted in greater-than-additive cytotoxicity with each of four regimens. The modulator combinations of minocycline and beta-carotene applied for 1 h or 24 h and the modulator combination of minocycline and 13-cis-retinoic acid produced greater-than-additive cytotoxicity at 50 microM 4-hydroperoxycyclophosphamide (4-HC), whereas minocycline and 13-cis-retinoic acid applied for 1 h was antagonistic with 4-HC and the other modulator treatments at low concentrations of 4-HC resulted in subadditive cytotoxicity. The effect of treatment with beta-carotene alone and in combination with several different anticancer agents was examined in two murine solid tumors, the FSaII fibrosarcoma and the SCC VII carcinoma. Administration of the modulators alone or in combination did not alter the growth of either tumor. Whereas increases in tumor growth delay occurred with the antitumor alkylating agents and beta-carotene and with minocycline and beta-carotene, a diminution in tumor growth delay was produced by 5-fluorouracil in the presence of these modulators. The modulator combination also resulted in increased tumor growth delay with adriamycin and etoposide. Tumor-cell survival assay showed increased killing of FSaII tumor cells with the modulator combination and melphalan or cyclophosphamide as compared with the drugs alone. These results indicate that further investigation of this modulator strategy is warranted.

Vaananen PM, Meddings JB, Wallace JL. Role of oxygen-derived free radicals in indomethacin-induced gastric injury. Am J Physiol 1991 Sep;261(3 Pt 1):G470-G475.
Abstract: The role of oxygen-derived free radicals in the pathogenesis of acute gastric ulceration induced by indomethacin (Indo) was investigated in rats. Gastric damage was assessed by blood-to-lumen leakage of 51Cr-EDTA, as well as by measuring the extent of macroscopically visible hemorrhagic lesions. The stomach was perfused with isotonic saline for 30 min, followed by Indo (10 mg/ml for 30 min) and HCl (100 mM for 60 min). Rats were given a continuous intravenous infusion of the antioxidant enzymes superoxide dismutase (SOD) or catalase or the iron-chelating agent deferoxamine. Additional rats received an intravenous infusion of the vehicle (control group) or were pretreated with prostaglandin E2 (100 micrograms/kg ip) or allopurinol (50 mg/kg po). Exposure of the stomach to Indo caused a fourfold increase in 51Cr-EDTA leakage compared with that observed in rats receiving only the vehicle for Indo. Subsequent exposure of the stomach to HCl resulted in a further twofold increase in 51Cr-EDTA leakage. Treatment with SOD, catalase, or deferoxamine significantly (P less than 0.05) reduced 51Cr-EDTA leakage during the intragastric perfusion with Indo and during the subsequent exposure to HCl. Pretreatment with PGE2 reduced 51Cr-EDTA leakage during perfusion with HCl only. Pretreatment with allopurinol did not significantly affect 51Cr-EDTA leakage at any time during the experiment. In addition to reducing the leakage of 51Cr-EDTA into the gastric lumen, SOD, catalase, and PGE2 significantly reduced the extent of macroscopically visible mucosal damage (P less than 0.05). These results support the hypothesis that oxygen-derived free radicals, probably derived from neutrophils, contribute to the pathogenesis of Indo-induced ulceration.

van Zyl JM, Kriegler A, van der Walt BJ. Anti-oxidant properties of H2-receptor antagonists. Effects on myeloperoxidase-catalysed reactions and hydroxyl radical generation in a ferrous-hydrogen peroxide system. Biochem Pharmacol 1993 Jun 22;45(12):2389-2397.

Venugopal M, Jamison JM, Gilloteaux J, Koch JA, Summers M, Giammar D, Sowick C, Summers JL. Synergistic antitumor activity of vitamins C and K3 on human urologic tumor cell lines. Life Sci 1996;59(17):1389-1400.

Vinitha R, Thangaraju M, Sachdanandam P. Effect of administering cyclophosphamide and vitamin E on the levels of tumor-marker enzymes in rats with experimentally induced fibrosarcoma. Jpn J Med Sci Biol 1995 Jun;48(3):145-156.

Weijl NI, Hopman GD, Wipkink-Bakker A, Lentjes EG, Berger HM, Cleton FJ, Osanto S. Cisplatin combination chemotherapy induces a fall in plasma antioxidants of cancer patients. Ann Oncol 1998 Dec;9(12):1331-1337.
Abstract: BACKGROUND: Antioxidants protect the body against cellular oxidative damage and thus some of the adverse effects induced by cisplatin and other cytostatic drugs. PATIENTS AND METHODS: The effect of cisplatin-combination chemotherapy on concentrations of plasma antioxidants was studied in 36 cancer patients, including osteosarcoma and testicular carcinoma patients. RESULTS: Eight to 15 days after the start of each cytostatic drug infusion concentrations of various plasma antioxidants were measured and compared to pretreatment values: vitamin C and E, uric acid and ceruloplasmin levels fell significantly (P < 0.01-0.005) and returned to baseline levels before the start of the next chemotherapy cycle. Levels of the antioxidants bilirubin albumin and the ratio vitamin E/cholesterol + triglycerides measured three weeks after the start of chemotherapy significantly decreased compared to pretreatment levels and remained low thereafter (P < 0.001-0.002). Dietary intake of antioxidants and anthropometric measurements, evaluated in 14 patients did not change during the whole treatment period. CONCLUSIONS: Cisplatin-combination chemotherapy induces a fall in plasma antioxidant levels, that may reflect a failure of the antioxidant defense mechanism against oxidative damage induced by commonly used anticancer drugs. This probably results from consumption of antioxidants caused by chemotherapy induced-oxidative stress as well as renal loss of water-soluble, small molecular weight antioxidants such as uric acid.

Weijl NI, Cleton FJ, Osanto S. Free radicals and antioxidants in chemotherapy-induced toxicity. Cancer Treatment Rev 1997 Jul;23(4):209-240 (Review)

Werbach MR. Foundations of Nutritional Medicine. Tarzana, CA: Third Line Press, 1997. (Review).

Wiegand UW, Hartmann S, Hummler H. Safety of vitamin A: recent results. Int J Vitam Nutr Res 1998;68(6):411-416. (Review)
Abstract: A still unresolved public health concern is that excessive vitamin A intake, like vitamin A deficiency, possibly causes birth defects not only in animals but also in man. Due to the low incidence of possibly vitamin A-related malformations in man, available data cannot convincingly define the upper safe limit of periconceptional vitamin A intake. Direct human intervention studies are not feasible for ethical reasons. Therefore, a novel approach in addressing this issue was chosen by combining teratogenicity data from a validated animal model with data on systemic exposure to vitamin A and its major metabolites in female volunteers. In a study in pregnant women endogenous plasma concentrations of vitamin A metabolites during early pregnancy ranged from 0.26 to 7.72 ng/ml. Since they did not cause any foetal malformations, retinoid plasma levels in this range can be considered non-teratogenic. Results of a trial in non-pregnant women document that daily oral vitamin A supplements of 4000, 10,000 and 30,000 IU given for 3 weeks were in the range or slightly above the range of endogenous plasma levels seen in early pregnancy. Even after a 3-week treatment with 30,000 IU/day, peak plasma levels of retinoic acid and isotretinoin were within or just slightly above the range of their physiological levels. In cynomolgus monkeys (average weight: 3-4 kg), a NOAEL (no observed adverse effect level) of 7500 IU per kg body weight and a LOAEL (lowest observed adverse effect level) for developmental toxicity of 20,000 IU/kg was found. Considering these results in the cynomolgus monkey, a dose of 30,000 IU/day should also be considered as non-teratogenic in man.