The concern about B vitamins affecting the oxidant effect of intravenous ascorbate for malignancy.
The use of intravenous ascorbate has a long history in complementary medicine. Its efficacy against malignant cells via a prooxidant mechanism has been previously demonstrated. In some quarters, B vitamins have been included with intravenous ascorbate therapy. Because of the antioxidant effect of some B vitamins, the question arose as to whether their presence could decrease the antimalignant effect of ascorbate. The data are summarized regarding the direct ability of several B vitamins to decrease the concentration of the active agent providing the antimalignant effect. The individual case of cobalamin in this regard is more complex than other B vitamins, in that cobalamin and ascorbate generate hydrogen peroxide and kill tumor cells in vitro. The implications of this result certainly warrant in vivo studies. The overall conclusion is that data do exist demonstrating that some B vitamins do have the capacity to decrease the concentration of the antimalignant agent from ascorbate at the tissue of concern. The authors recommend that B vitamins or other antioxidant materials not be included with intravenous ascorbate intended for anticancer purposes.
There is adequate in vitro demonstration that ascorbate, at concentrations attainable in humans, can have a cytotoxic effect on malignant cells. (1,2) Intravenous ascorbate has been shown to benefit cancer patients. (3,7)
The proposed mechanism for the cytotoxic effect of ascorbate begins with the donation of an electron from ascorbate to molecular oxygen creating a superoxide radical anion, followed by conversion to hydrogen peroxide by several mechanisms. It is postulated that the initial electron transfer proceeds first to iron (III), which reduces to iron (II), which then transfers an electron to oxygen (see Figure 1, p. 98). (2)
Because of previous demonstrations of the antioxidant properties of several of the B vitamins, the question arises as to whether concurrent administration of B vitamins with intravenous ascorbate could be deleterious to the desired cytotoxic effect of ascorbate on malignant cells. Such concern was one factor leading to the Drisko-Khosh protocol for administration of intravenous ascorbate in the Program in Integrative Medicine at the University of Kansas Medical Center (ascorbate, magnesium chloride and sterile water). (See acknowledgement.)
The following sections cite data found on the interactions of certain B vitamins with superoxide or hydrogen peroxide, the intermediate agents believed chiefly responsible for the effect of ascorbate on malignant cells.
There are many publications on the antioxidant effects of thiamine under various conditions. The one most to the point at hand showed the scavenging ability of thiamine for superoxide (generated by the xanthine oxidase/hypoxanthine system) to be dose dependent and able to be driven to completion under the in vitro experimental conditions. It was suggested that thiamine was sacrificed to some extent in the course of scavenging reactive oxygen species (ROS). (8) A previous report demonstrated thiamine quenching of superoxide generated by pyrogallol autoxidation. It was also stated that no appreciable reaction of thiamine with hydrogen peroxide occurred, but no data were provided. (9)
Direct and uncomplicated effects of riboflavin on hydrogen peroxide or superoxide in vitro were not able to be located.
Nicotinamide (Nicotinic Acid)--Vitamin B3
A 2000 publication referred to a 1969 report, which stated that nicotinamide had a high rate constant for reaction with superoxide (7 x 109). (10,11) However, a 1999 publication determined that nicotinamide did not scavenge superoxide generated in vitro. (12)
A 1995 report showed that superoxide generated by autoxidation of pyrogallol was quenched by nicotinic acid only at supraphysiologic concentrations. It was further stated that there was no appreciable reaction of nicotinic acid with hydrogen peroxide, but data were not provided. (9)
Pantothenic Acid--Vitamin B5
Pantothenate was stated to have no quenching effect on superoxide generated by pyrogallol autoxidation until a supraphysiologic concentration of 3.0 mM was reached. However, the table provided in the publication showed a small effect at 1.0 and 2.0 mM, with no entry for 3.0 mM. It was further stated that pantothenate had no appreciable reaction with hydrogen peroxide. (9)
In 1995, there was a report of both pyridoxal and pyridoxine (P) quenching superoxide, "rather poorly" according to the rate constant of [10.sup.3][M-.sup.1]-[s.sup.-1,9] It was stated that no appreciable reaction with hydrogen peroxide was found. In a later 2001 study, high concentration glucose solutions were used for generation of superoxide and it was demonstrated that 1 mM P or pyridoxamine (PM) readily quenched superoxide to the range of 66% to 97%. (13) (Note: P, PM, and pyridoxal-5-phosphate [PP] are interconvertible in normal cells.)
Three publications after the 2001 report dispute the findings that P and PM inhibit superoxide radical generation. A 2006 report showed that in a system demonstrating reactions of superoxide, hydroxyl radical, and hydroperoxyl radical with organic molecules, superoxide radical did not react with P. (14) A 2008 report claimed that PM did not react with superoxide radical or hydrogen peroxide generated by albumin-Amadori intermediates. (15) A 2009 publication used an endothelial cell model to demonstrate whether preincubation with P, PM, or PP would inhibit superoxide generation from hydrogen peroxide. It was stated that only PP directly interacted with superoxide radical and that P and PM lowered superoxide by interaction with NADPH oxidase. (16)
When U937 cells (a human leukemic monocytic lymphoma cell line) were exposed to hydrogen peroxide, superoxide was produced. When the cells were preincubated with P, PM, or PP, superoxide was quenched in a dose-dependent manner. While the concentrations of P, PM, and PP were above physiologic levels, the authors concluded that vitamin B6 compounds could reduce damage due to ROS. (17)
Folic Acid--Vitamin B9
Folic acid was reported to have substantial scavenging ability against superoxide generated by the xanthine/ xanthine oxidase system, to a degree comparable to that of the superoxide dismutase mimetic tempol. (18)
In 2000, it was shown that 5-methyltetrahydrofolate (5-MTHF), the main circulating folate in the body, directly scavenged superoxide generated by the xanthine/ hypoxanthine system. (19) However, in 2006, a report disputed the 5-MTHF findings and claimed that 1 to 10 [micro]M concentrations of 5-MTHF did not scavenge superoxide generated by the xanthine/xanthine oxidase system. Concentrations of 100 [micro]M led to only modest scavenging of superoxide. (20)
Incubation of porcine aortic endothelial cells with 1 mM homocysteine and 0.5 mM folic acid or 5-MTHF for 24 hours prevented the homocysteine-mediated generation of superoxide radicals. The authors thought it unlikely that this effect was due to a reaction between homocysteine and folic acid or 5-MTHF, as it takes weeks for homocysteine levels to fall after folic acid administration. It was thought more likely that folic acid and 5-MTHF directly scavenged superoxide or prevented its generation. (21)
It was reported that cobalamin had potent superoxide scavenging ability. In a cell-free experiment, cob(ll)alamin (Cbl(ll), an intracellular form of vitamin B12) was reacted with superoxide (generated by the xanthine oxidase-acetaldehyde system). There was rapid oxidation of Cbl(ll) with generation of hydrogen peroxide. The resulting Cbl(lll) can be reduced to Cbl(ll) intracellularly. Cbl(ll) also disproportionates to Cbl(lll) and Cbl(l), the latter of which reacts rapidly with oxygen to produce hydrogen peroxide. To elucidate the intracellular effect of a commonly used form of cobalamin, human aortic endothelial cells were preincubated with 100 nM cyanocobalamin for 24 hours. Superoxide generation by paraquat was prevented by the intracellular result of cyanocobalamin to the same degree as by superoxide dismutase. (22)
Hydrogen peroxide was rapidly produced by combination of 25 [micro]M hydroxycobalamin and 500 [micro]M ascorbic acid added to cell-free culture medium (containing nutrients including an iron salt). No peroxide was produced by hydroxycobalamin alone. Ascorbic acid alone produced about one-fifth as much peroxide. (23)
A similar accumulation of hydrogen peroxide occurred when hydroxycobalamin and ascorbic acid were added to human epidermoid larynx carcinoma cells (HEp-2). (Note: No hydrogen peroxide was produced by either of the two reactants alone.) Within 24 hours after addition of 25 [micro]M hydroxycobalamin and 500 [micro]M ascorbic acid, there was 90 to 95% cell death. Each of the agents alone produced no cell death. (23)
An earlier study looked at the combined effect of cobalamin with ascorbic acid on three ascites tumor cell types and found a synergistic effect decreasing mitotic counts and survival of tumor cells. (24) For completeness, it should be mentioned that a 1991 publication claimed that the previous report by the same authors of growth inhibition and death of ascites tumor cells by cobalamin and ascorbic acid was due in fact to dehydroascorbic acid, not ascorbic acid. (25) This concept was not discussed in the 2007 publication. (23,24)
Thiamine quenches superoxide, but not hydrogen peroxide. Data were not available to define these possibilities with respect to riboflavin. There are conflicting reports on the ability of nicotinamide to react with superoxide. Nicotinic acid at supraphysiologic concentrations is said to quench superoxide, with no appreciable effect on hydrogen peroxide. Pantothenate at supraphysiologic concentration also quenched superoxide, without effect on hydrogen peroxide.
In the group of vitamin B6 compounds, pyridoxal and P reacted poorly with superoxide according to one publication, with no reaction with hydrogen peroxide. In a later publication, 1 mM P or PM quenched superoxide extensively. Three even later publications disputed the reaction of P and PM with superoxide and reported a lack of reaction of P with hydrogen peroxide. It was stated that only PP reacted directly with superoxide.
Folic acid was claimed to react with superoxide comparably with superoxide dismutase. One study found that 5-MTHF also reacted with superoxide, but a later report disputed the finding and stated that 1 to 10 [micro]m 5-MTHF did not scavenge superoxide, and that a concentration of 100 [micro]m 5-MTHF gave only modest scavenging. One year later, 0.5 mM folic acid or 5-MTHF was reported to scavenge superoxide. Therefore, 5-MTHF's ability to scavenge superoxide may depend on concentration.
Cobalamin, in a cell-free experiment, was shown to rapidly quench superoxide and produce hydrogen peroxide. In the presence of oxygen, this became a cyclic reaction to convert all superoxide to hydrogen peroxide. In a cell culture experiment, 100 nM cyanocobalamin prevented detection of superoxide produced by a generation system. In cell-free culture medium, 25 [micro]M hydroxycobalamin and 500 [micro]M ascorbic acid rapidly produced hydrogen peroxide. In studies on tumor cell lines, the combination of cobalamin and ascorbic acid produced hydrogen peroxide and had a synergistic effect in decreasing mitotic counts and survival of tumor cells.
It was mentioned above that the antitumor effect of high concentration ascorbate performs its function in the interstitial fluid beyond the blood circulation. Ascorbate is converted to superoxide, which proceeds to the hydrogen peroxide believed to be the active agent. Most of the B vitamins can quench superoxide under some conditions and would presumably lower the concentration of hydrogen peroxide available for antimalignant action. Therefore a caution seems appropriate against the inclusion of B vitamins with intravenous ascorbate aimed at tumor cell cytotoxicity. However, this general recommendation based on chemistry cited above needs the support of in vivo studies for certainty.
In the case of cobalamin specifically, the situation is more complex. As cobalamin and ascorbic acid can react in the intravenous reservoir bottle, it seems likely that less ascorbate would be delivered to the blood circulation when accompanied by cobalamin. It might appear a moot point as hydrogen peroxide results from the decreased ascorbic acid. However, it has been shown that almost all hydrogen peroxide in the systemic circulation is eliminated. (2) This occurs chiefly because the erythrocyte membrane is extremely porous to hydrogen peroxide and allows peroxide disposal by erythrocyte catalase. Therefore, it does appear that a reduced amount of ascorbate would reach the interstitial fluid, with relatively little hydrogen peroxide.
However, cobalamin and the remaining ascorbate would both arrive in the interstitial fluid. The previously mentioned reaction of cobalamin and ascorbate would generate hydrogen peroxide. So the obvious question becomes, does the presence of cobalamin in the interstitial fluid contribute more than the detriment of less ascorbate being present. This becomes a question of chemical kinetics. Will the presence or the absence of cobalamin with ascorbate provide the most positive effect against malignant cells in vivo? Existing in vitro studies show that cobalamin and ascorbate cause more tumor cell death than ascorbate alone. But no matter what measurements or calculations might be acquired to predict the interstitial concentration of hydrogen peroxide, with and without cobalamin, the bottom line is that in vivo studies are required before this question can be answered.
The authors would like to acknowledge that the idea for this investigation arose from a conversation with Jeanne Drisko, MD, director, Program in Integrative Medicine, Complementary and Alternative Therapies, University of Kansas Medical Center, Kansas City, KS. We also thank the Smiling Dog Foundation and Jileen and Richard Russell for financial support of research, Thome Research Inc. for funding the Thorne Post-Doctoral Fellowship for M.O., and the Tahoma Clinic Foundation for grant administration.
(1.) Riordan NH, Riordan HD, Meng X, et al. Intravenous ascorbate as a tumor cytotoxic chemotherapeutic agent. Med Hypotheses. 1995;44:207-213.
(2.) Chen Q, Espey MG, Krishna MC, et al. Pharmacologic ascorbic acid concentrations selectively kill cancer cells: action as a pro-drug to deliver hydrogen peroxide to tissues. Proc Nat/ AcadSci USA. 2005;102:13604-13609.
(3.) Padayatty SJ, Riordan HD, Hewitt SM, et al. Intravenously administered vitamin C as cancer therapy: three cases. CMAJ. 2006;174:937-942.
(4.) Drisko JA, Chapman J, Hunter VJ. The use of antioxidants with first-line chemotherapy in two cases of ovarian cancer. 1 Am Coll Nutr. 2003;22:118-123.
(5.) Riordan HD, Jackson |A, Riordan NH, Schultz M. High-dose intravenous vitamin C in the treatment of a patient with renal cell carcinoma of the kidney. J Orthmol Med. 1998;13:72-73.
(6.) Riordan HD, Jackson JA, Schultz M. High-dose intravenous vitamin C in the treatment of a patient with adenocarcinoma of the kidney. J Orthmol Med. 1990;5:5-7.
(7.) Riordan NH, Riordan HD, Casciari JP. Clinical and experimental experiences with intravenous vitamin C. J Orthmol Med. 2000;15:201-203.
(8.) Jung IL, Kim I. Thiamine protects against paraquat-induced damage: scavenging activity of reactive oxygen species. Environ Toxicol Pharmacol. 2003;15:19-26.
(9.) Hu ML, Chen YK, Lin YF. The antioxidant and prooxidant activity of some B vitamins and vitamin-like compounds. Chem Biol Interact. 1995;97:63-73.
(10.) Kamat JP, Devasagayam TP. Oxidative damage to mitochondria in normal and cancer tissues, and its modulation. Toxicology. 2000;155:73-82.
(11.) Beck G. Elektrishe leitfaehigkeits messungen zum nachweis geladener zwischenprodukte der pulsaradiolyse. Int J Radiat Phys Chem. 1969;1:361-371.
(12.) Bowes J, McDonald MC, Piper J, Thiemermann C. Inhibitors of poly (ADP-ribose) synthetase protect rat cardiomyocytes against oxidant stress. Cardiovasc Res. 1999;41:126-134.
(13.) Jain SK, Lim G. Pyridoxine and pyridoxamine inhibits superoxide radicals and prevents lipid peroxidation, protein glycosylation, and (Na+ + K +)-ATPase activity reduction in high glucose-treated human erythrocytes. Free Radic Biol Med. 2001;30:232-237.
(14.) Matxain JM, Ristila M, Strid A, Eriksson LA. Theoretical study of the antioxidant properties of pyridoxine. J Phys Chem A. 2006;110:13068-13072.
(15.) Chetyrkin SV, Mathis ME, Ham AJ, et al. Propagation of protein glycation damage involves modification of tryptophan residues via reactive oxygen species: inhibition by pyridoxamine. Free Radic Biol Med. 2008;44:12761285.
(16.) Mahfouz MM, Zhou SQ, Kummerow FA. Vitamin B6 compounds are capable of reducing the superoxide radical and lipid peroxide levels induced by H202 in vascular endothelial cells in culture. Int J Vitam Nutr Res. 2009;79:218-229.
(17.) Kannan K, Jain SK. Effect of vitamin B6 on oxygen radicals, mitochondrial membrane potential, and lipid peroxidation in H202-treated U937 monocytes. Free Radic Biol Med. 2004;36:423-428.
(18.) Moens AL, Champion HC, Claeys MJ, et al. Highdose folic acid pretreatment blunts cardiac dysfunction during ischemia coupled to maintenance of high-energy phosphates and reduces postreperfusion injury. Circulation. 2008;117:1810-1819.
(19.) Stroes ES, van Faassen EE, Yo M, et al. Folic acid reverts dysfunction of endothelial nitric oxide synthase. Circ Res. 2000;86:1129-1134.
(20.) Antoniades C, Shirodaria C, Warrick N, et al. 5-methyltetrahydrofolate rapidly improves endothelial function and decreases superoxide production in human vessels: effects on vascular tetrahydrobiopterin availability and endothelial nitric oxide synthase coupling. Circulation. 2006;114:1193-1201.
(21.) Doshi SN, McDowell IF, Moat SJ, et al. Folate improves endothelial function in coronary artery disease: an effect mediated by reduction of intracellular superoxide? Arterioscler Thromb Vase Biol. 2001;21:1196-1202.
(22.) Suarez-Moreira E, Yun J, Birch CS, et al. Vitamin B(12) and redox homeostasis: cobdDalamin reacts with superoxide at rates approaching superoxide dismutase (SOD). J Am Chem Soc. 2009;131:15078-15079.
(23.) Solovieva ME, Soloviev W, Akatov VS. Vitamin B12b increases the cytotoxicity of short-time exposure to ascorbic acid, inducing oxidative burst and iron-dependent DNA damage. Eur J Pharmacol. 2007;566:206-214.
(24.) Poydock ME, Fardon JC, Callina D, et al. Inhibiting effect of vitamins C and B12 on the mitotic activity of ascites tumors. Exp Cell Biol. 1979;47:210-217.
(25.) Poydock ME. Effect of combined ascorbic acid and B-12 on survival of mice with implanted Ehrlich carcinoma and LI 210 leukemia. Am J Clin Nutr. 1991 ;54:1261 S-1265S.
Maiko Ochi, ND, is in private practice and held the 2010-2011 Thorne Postdoctoral Research Fellowship.
James Hetherington, ND, is in private practice at Anderson Medical Specialty Associates in Seattle.
Davis W. Lamson, MS, ND, was previously adjunct faculty in oncology, School of Medicine, Bastyr University, for 17 years and continues in private practice at Tahoma Clinic, Tukwila, Washington. Correspondence: firstname.lastname@example.org.
|Printer friendly Cite/link Email Feedback|
|Author:||Ochi, Maiko; Hetherington, James; Lamson, Davis W.|
|Date:||Aug 1, 2015|
|Previous Article:||Let's talk about sex: the effects of prostate cancer on sex, men, and their relationships.|
|Next Article:||Inositol modulation of essential metabolic pathways of insulin resistance in metabolic syndrome, polycystic ovarian syndrome, and type 2 diabetes.|