Pyridoxine Antagonist Research Articles

Genetic Analysis Using Vitamin B6 Antagonist 4-Deoxypyridoxine Uncovers a Connection between Pyridoxal 5'-Phosphate and Coenzyme A Metabolism in Salmonella enterica.

Pyridoxal 5'-phosphate (PLP) is an essential cofactor for organisms in all three domains of life. Despite the central role of PLP, many aspects of vitamin B6 metabolism, including its integration with other biological pathways, are not fully understood. In this study, we examined the metabolic perturbations caused by the vitamin B6 antagonist 4-deoxypyridoxine (dPN) in a ptsJ mutant of Salmonella enterica serovar Typhimurium LT2. Our data suggest that PdxK (pyridoxal/pyridoxine/pyridoxamine kinase [EC 2.7.1.35]) phosphorylates dPN to 4-deoxypyridoxine 5'-phosphate (dPNP), which in turn can compromise the de novo biosynthesis of PLP. The data are consistent with the hypothesis that accumulated dPNP inhibits GlyA (serine hydroxymethyltransferase [EC 2.1.2.1]) and/or GcvP (glycine decarboxylase [EC 1.4.4.2]), two PLP-dependent enzymes involved in the generation of one-carbon units. Our data suggest that this inhibition leads to reduced flux to coenzyme A (CoA) precursors and subsequently decreased synthesis of CoA and thiamine. This study uncovers a link between vitamin B6 metabolism and the biosynthesis of CoA and thiamine, highlighting the integration of biochemical pathways in microbes. IMPORTANCE PLP is a ubiquitous cofactor required by enzymes in diverse metabolic networks. The data presented here expand our understanding of the toxic effects of dPN, a vitamin B6 antagonist that is often used to mimic vitamin B6 deficiency and to study PLP-dependent enzyme kinetics. In addition to de novo PLP biosynthesis, we define a metabolic connection between vitamin B6 metabolism and synthesis of thiamine and CoA. This work provides a foundation for the use of dPN to study vitamin B6 metabolism in other organisms.

Flaxseed Increases Animal Lifespan and Reduces Ovarian Cancer Severity by Toxically Augmenting One-Carbon Metabolism.

We used an LC-MS/MS metabolomics approach to investigate one-carbon metabolism in the plasma of flaxseed-fed White Leghorn laying hens (aged 3.5 years). In our study, dietary flaxseed (via the activity of a vitamin B6 antagonist known as “1-amino d-proline”) induced at least 15-fold elevated plasma cystathionine. Surprisingly, plasma homocysteine (Hcy) was stable in flaxseed-fed hens despite such highly elevated cystathionine. To explain stable Hcy, our data suggest accelerated Hcy remethylation via BHMT and MS-B12. Also supporting accelerated Hcy remethylation, we observed elevated S-adenosylmethionine (SAM), an elevated SAM:SAH ratio, and elevated methylthioadenosine (MTA), in flaxseed-fed hens. These results suggest that flaxseed increases SAM biosynthesis and possibly increases polyamine biosynthesis. The following endpoint phenotypes were observed in hens consuming flaxseed: decreased physiological aging, increased empirical lifespan, 9–14% reduced body mass, and improved liver function. Overall, we suggest that flaxseed can protect women from ovarian tumor metastasis by decreasing omental adiposity. We also propose that flaxseed protects cancer patients from cancer-associated cachexia by enhancing liver function.

Nausea and vomiting of pregnant women: pathogenesis-based management

Background. According to WHO, 70-80 % of women experience symptoms of toxicosis during the first 16 weeks of pregnancy. 10-15 % of them need inpatient treatment. Vomiting occurs in 50-80 % of pregnant women, in 2 % there is hyperemesis gravidarum.
 Objective. To describe the features of pathogenesis of nausea and vomiting in pregnant women (NVPW) and the management of women with these conditions.
 Materials and methods. Analysis of literature sources on this issue.
 Results and discussion. Risk factors for NVPW are the history of migraine and sea sickness, a family history of hyperemesis gravidarum, multiple pregnancy. Metabolic and hormonal factors, motility disorders of the digestive system, psychosocial factors and evolutionary protection of the fetus during embryogenesis are involved in the pathogenesis of NVPW. In NVPW there is a lack of energy, which leads to lipolysis with the formation of ketone bodies. Progression of hyperemesis gravidarum leads to the disruptions of water, carbohydrates, proteins and lipids metabolism, to ketoacidosis, and to vitamin and mineral deficiency. Laboratory tests show an increase in hematocrit, leukocytosis, increased urea and bilirubin, decreased total protein and albumin, proteinuria, cylindruria, erythrocyturia, and a positive acetone reaction of urine. Complications of this condition for the mother include exhaustion, micronutrient deficiencies, neurological disorders, multiple organ dysfunction and even coma, and for the child – the risk of miscarriage and premature birth. The goals of NVPW treatment include the elimination of the symptoms and reduction of the risks to the mother and fetus. The aggressiveness of treatment is determined by the severity of symptoms and the degree of weight loss. In mild cases, drinking a lot of fluids, diet, rest, acupressure, and ginger extract are recommended, in moderate cases it is advisable to add pyridoxine, antihistamines, and dopamine antagonists. If vomiting does not disappear after such treatment, it is advisable to prescribe infusions of 0.9 % NaCl and Xylate (“Yuria-Pharm”), parenteral nutrition, ondansetron. In the absence of effect, methylprednisolone (intravenously) is prescribed. Reo water for medical purposes (“Yuria-Pharm”), which quickly eliminates the deficiency of fluid and electrolytes, contains an alkalizing component, and has detoxifying properties, can be prescribed as in addition. The purpose of infusion therapy for vomiting in pregnant women is to restore the volume of circulating blood, to stop ketogenesis, to restore fluid and electrolyte and acid-base balance, and detoxification. For this purpose, it is advisable to use Xylate, as far as glucose exacerbates acidosis and is poorly absorbed under stress. Xylate has an extremely powerful antiketogenic effect. Abortion in hyperemesis gravidarum is indicated in case of continuous vomiting for 3 days in the intensive care unit, reduction of diuresis to 300 ml per day, progressive acetonuria for 3-4 days, progressive weight loss, severe tachycardia (100-120 beats/min), dysfunction of the central nervous system, jaundice of skin and sclerae, hyperbilirubinemia (80-100 μmol/L).
 Conclusions. 1. NVPW is a common pathological condition among pregnant women. 2. In NVPW there is a lack of energy, which leads to lipolysis with the formation of ketone bodies. 3. Complications of this condition include exhaustion, micronutrient deficiencies, neurological disorders, multiple organ dysfunction, coma, risk of miscarriage and premature birth. 4. In the absence of the effect of conservative measures, it is advisable to prescribe infusions of 0.9 % NaCl and Xylate, parenteral nutrition, ondansetron, methylprednisolone. 5. The purpose of infusion therapy for vomiting of pregnant women is to restore the volume of circulating blood, to stop ketogenesis, to restore fluid and electrolyte and acid-base balance, and to detoxify. For this purpose, it is advisable to use Xylate.

Sugar and Chromosome Stability: Clastogenic Effects of Sugars in Vitamin B6-Deficient Cells

Pyridoxal 5′-phosphate (PLP), the active form of vitamin B6, has been implicated in preventing human pathologies, such as diabetes and cancer. However, the mechanisms underlying the beneficial effects of PLP are still unclear. Using Drosophila as a model system, we show that PLP deficiency, caused either by mutations in the pyridoxal kinase-coding gene (dPdxk) or by vitamin B6 antagonists, results in chromosome aberrations (CABs). The CAB frequency in PLP-depleted cells was strongly enhanced by sucrose, glucose or fructose treatments, and dPdxk mutant cells consistently displayed higher glucose contents than their wild type counterparts, an effect that is at least in part a consequence of an acquired insulin resistance. Together, our results indicate that a high intracellular level of glucose has a dramatic clastogenic effect if combined with PLP deficiency. This is likely due to an elevated level of Advanced Glycation End-products (AGE) formation. Treatment of dPdxk mutant cells with α-lipoic acid (ALA) lowered both AGE formation and CAB frequency, suggesting a possible AGE-CAB cause-effect relationship. The clastogenic effect of glucose in PLP-depleted cells is evolutionarily conserved. RNAi-mediated silencing of PDXK in human cells or treatments with PLP inhibitors resulted in chromosome breakage, which was potentiated by glucose and reduced by ALA. These results suggest that patients with concomitant hyperglycemia and vitamin B6 deficiency may suffer chromosome damage. This might impact cancer risk, as CABs are a well-known tumorigenic factor.

Relationship between plasma total homocysteine level and dietary caffeine and vitamin B6 intakes in pregnant women

A high total homocysteine (tHcy) level during pregnancy is a risk factor for adverse perinatal outcomes, such as fetal growth restriction and preeclampsia. Caffeine is assumed to increase tHcy levels by acting as a vitamin B6 antagonist. The objective of this study was to examine a relationship between circulating tHcy levels and dietary caffeine and vitamin B6 intakes in pregnant Japanese women. A total of 321 healthy women with singleton pregnancies were recruited in metropolitan Tokyo, from June to December 2008, resulting in the final number included in the study as 254. Dietary caffeine intakes did not correlate with plasma tHcy levels. When we analyzed the data according to caffeinated beverages, caffeinated tea consumption was positively associated with plasma tHcy levels only among the women with a high intake of vitamin B6 , after controlling for confounding factors (P = 0.029). No correlation between coffee consumption and plasma tHcy levels was found. Pregnant Japanese women might need to cut down the consumption of caffeinated tea as well as take sufficient vitamin B6 in order to prevent the tHcy levels from increasing.

Effects of dietary pyridoxine on immune responses in abalone, Haliotis discus hannai Ino

A feeding experiment was conducted to investigate the effects of dietary pyridoxine (PN) on the immune responses of abalone, Haliotis discus hannai Ino. Purified diets supplemented with 0, 40, 800 mg PN kg −1 or 80 mg kg −1 of 4-deoxypyridoxine (PN antagonist) were fed to adult abalone (initial weight 45.77±0.25 g; initial shell length 68.02±0.78 mm) for 90 days. The air-dried brown kelp, Laminaria japonica, was used as a control diet. Each diet was fed to three replicate groups of abalone in a recirculation system using a completely randomised design. The results showed that weight gain ratio (WGR) of the abalone generally increased with the level of dietary PN supplementation though no significant differences were found among the treatments ( P>0.05). Phagocytic and phenoloxidase activities were significantly higher in abalone fed diets supplemented with 800 mg PN kg −1 than those fed the PN-free diet or the one with 4-deoxypyridoxine ( P<0.05). Agglutination titre and respiratory burst activity were significantly higher in abalone fed diets supplemented with 40 mg PN kg −1 than those fed the PN-free diet or the one with 4-deoxypyridoxine ( P<0.05). There were no significant differences in immunological characteristics between the abalone fed the diet containing 40 mg PN kg −1 and those fed the diet containing 800 mg PN kg −1 ( P>0.05). L. japonica resulted in significantly lower agglutination titre, respiratory burst and phagocytic activities than the artificial diets supplemented with 40 or 800 mg PN kg −1 ( P<0.05). Total haemocyte count (THC), serum protein concentration, and the activities of lysozyme and acid phosphatase were not significantly affected by the dietary treatments ( P>0.05). These results demonstrate that dietary deficiency of pyridoxine suppresses the immune functions in H. discus hannai, and further investigations are needed to optimise the dietary level of this vitamin for maintaining the best immune responses in abalone.

Sideroblastic anaemias.

Sideroblastic anaemias.

Vitamin B6-deficient diet plus 4-deoxypyridoxine (4-DPD) reduces the inflammatory response induced by T. spiralis in diaphragm, masseter and heart muscle tissue of mice.

Animals fed diets deficient in vitamin B6 develop microcytic anemia, alterations of growth, and other pathologies. 4-deoxypirydoxine is a potent antagonist of vitamin B6 coenzyme which depresses IL-1, TNF and IL-6 and has anti-inflammatory properties. The aim of this study was to show the anti-inflammatory effects of 4-DPD on chronic inflammation caused by the nematode parasite T. spiralis, specifically on the recruitment and the activation of inflammatory cells. Two groups of mice, 6 weeks of age, were used: one was maintained on a vitamin B6-deficient synthetic pellet diet for 15 days before injection of the nematode, and administered an intraperitoneal injection (i.p.) of 4-DPD (250 microg/mouse) for 15 days (the first, 5 days before infection), and the second group was maintained on a normal diet for the total duration of the experiment. These two groups were then injected with 150 larvae (L1-T7 spiralis) per os. Chronic inflammation was caused by infection of treated or untreated mice with T7 spiralis parasite. After 14 days post-infection all mice developed a chronic inflammatory response. Mice fed with a B6-deficient diet showed a significant decrease in the number of cysts found in the diaphragm when compared to mice treated with normal diet. In addition, in all mice treated with vitamin B6-deficient diet plus 4-DPD the average body weight was significantly lower, compared to the mice on normal diet in all weeks examined. Moreover, in sections of the diaphragm, masseter and myocardium muscles, the infiltration of inflammatory cells, such as macrophages, lymphocytes, and eosinophils were more intense in untreated mice compared to those fed a vitamin B6-deficient diet. These results show that BALB/c mice infected with T. spiralis and fed a vitamin B6-deficient diet plus the vitamin B6 antagonist, 4-DPD, prolong the time of invasion of the larvae in the muscle cells, influence the recruitment of inflammatory cells and the intensity of the inflammatory reaction compared to infected untreated mice (control).

IgG, IgG1 and IgM response in Trichinella spiralis-infected mice treated with 4-deoxypirydoxine or fed a Vitamin B6-deficient diet.

The aim of this study was to investigate the effect of pyridoxine (Vitamin B6) deficiency on the immunological response of BALB/c mice infected with the parasite T. spiralis. Specific anti-parasite IgM and IgG immunoglobulins were detected by ELISA method in the serum of treated animals at different periods for 60 days post infection. Vitamin B6-deficiency was induced in two separate groups of mice by either (1) maintaining the mice on a Vitamin B6-deficient synthetic pellet diet for 40 days before infection, or (2) by daily intraperitoneal injection of 8 x 10(5) M/100 microl of 4-Deoxypyridoxine (4-DPD), a potent antagonist of Vitamin B6 for 20 days prior to infection. These two groups of mice were then injected with 100 larvae (L1-T. spiralis) per os. Parasite burdens in the mice were observed by light microscopy. Cysts were present in the diaphragms of the mice after 60 days post-infection. Parasite specific IgG, as well as IgG1 levels were determined in the sera of infected mice fed a normal diet. These levels were found to be lower in the 4-DPD-treated mice compared to the untreated mice. The inhibition started from the 10th day and continued to the 60th day, and in the 4-DPD-treated group the inhibition initiated after 24 h to 60 days. IgM level also was depressed by 4-DPD, starting from 24 h after injection of the compound. In mice fed Vitamin B6-deficient diets the levels of IgG were lower than in mice fed normal diets. These results show that BALB/c mice infected with T. spiralis and fed either a Vitamin B6-deficient diet or a diet which included the Vitamin B6-antagonist, 4-DPD, both influence the course of IgG, IgG1 and IgM production.

ChemInform Abstract: Pyrimidine Compounds as Potential Pyridoxine Antagonists: A New Synthetic Approach.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Pyridoxine supplementation of Linola ™ meal for growing pigs

An experiment was conducted to determine whether a pyridoxine (Vitamin B6) antagonist was responsible for the low growth performance of grower pigs fed diets containing Linola ™ meal. Thirty pigs (15 of each sex), of 20 kg live weight, were fed ad libitum diets containing wheat-soya-bean meal, wheat-soya-Linola or wheat-soya-Linola supplemented with 100 mg kg −1 pyridoxine. The pigs were slaughtered at 45 kg live weight and carcass quality and organ weights assessed. Feed intake was lower in females given Linola meal relative to soya-bean meal ( P < 0.05) but there were no significant differences with males ( P > 0.05). Pyridoxine supplementation tended to improve feed intake but the effects were non-significant ( P > 0.05). Killing-out proportion was affected by dietary treatments (lower in males given the Linola treatments) so the results for gain per day and feed conversion ratio are best considered on a carcass basis. Carcass gain per day was lower ( P < 0.05) and feed conversion ratio higher ( P < 0.001) for pigs given Linola, relative to soya-bean meal, and there were no effects ( P > 0.05) of pyridoxine supplementation on these parameters. The results indicate that the lower nutritional value in Linola meal was not improved by the addition of pyridoxine to the diets, suggesting that an anti-pyridoxine factor was unlikely to be responsible for the lower nutritional value.

To wall off neoplasms with more viscous extracellular matrix

Normal inflammatory and immune mechansims would destroy most neoplasms if the neoplasm did not alter its immediate environment to weaken the host defenses. Based on factors that seem to increase extracellular matrix viscosity, methods of enhancing host resistance in the vicinity of the tumor are suggested by the author. This includes adjuvant therapy, pyridoxine antagonist, cytokines, beta carotene, retinoids, vitamin C, iodides, bromides, and pellagragenic substances. Hyperthermia may also have an effect.

Vitamin B6 in Clinical Neurology

Many conditions in clinical neurology may be responsive to pyridoxine as a therapeutic agent. The current difficulty is in trying to isolate the conditions that are most likely to respond. Treating seizures is a major part of a neurologic practice. Our current therapeutic agents are only partially successful and limited by multiple side effects. One problem is that patients often have to take these agents for an entire lifetime, further raising the risk of toxicity. If pyridoxine supplementation can improve the efficacy of currently used medications, it will be gladly accepted into our therapeutic arsenal. Headache, chronic pain, and depression all appear to run together in many of our patients. The observations that serotonin deficiency is a common thread between them and that pyridoxine can raise serotonin levels open a wide range of therapeutic options. Small studies have been carried out with mixed success. Comparison with amitriptyline in the treatment of headache appears to show about equal efficacy, although side effects would be expected to be more of a problem with the amitriptyline. Behavioral disorders are relatively common and continue to be a major problem, disrupting the lives of the patients and their families. Current treatments are not acceptable to most people because of the risk of side effects with long-term usage. If, as Dr. Feingold suggests, many of these problems are caused by "toxic" exposures to chemicals that are pyridoxine antagonists, supplementation at early ages may reduce the incidence of hyperactivity and aggressive behavior. This raises the question of safety. Is pyridoxine safe for long-term use in large segments of the population, including children? The studies on children with Down's syndrome and autism, utilizing much higher doses than are used for other therapeutic purposes, seem to indicate relative safety if carefully monitored. Studies involving large population groups with carpal tunnel syndrome, all adults, using 100-150 mg/day have shown minimal or no toxicity in five- to 10-year studies. Women self-medicating for PMS taking 500 to 5000 mg/day have shown peripheral neuropathy within one to three years. It would appear from this retrospective analysis that pyridoxine is safe at doses of 100 mg/day or less in adults. In children there is not enough data to make any sort of suggestion. Because the major neurologic complication is a peripheral neuropathy and the causes of this condition are myriad, pyridoxine may cause neuropathy only in patients with a pre-existing susceptibility to this condition.

Inhibitory effect of deoxypyridoxine on the action of certain mitogenic factors.

We studied the effect of pyridoxine deficiency state on the responses of human lymphocytes to certain mitogenic factors. Deoxypyridoxine (DB6), a potent pyridoxine antagonist, considerably inhibited Bromodeoxyuridine (BrdU) incorporation into the newly synthesized DNA of lymphocytes cultured with Phytohemagglutinin (PHA) and Concanavalin A (Con A) in separate sets of experiments. The addition of deoxypyridoxine simultaneously with or few hours prior to initiation of cell cultures did not significantly alter the inhibitory action of deoxypyridoxine. Titration studies of deoxypyridoxine showed the direct relation between the concentration of deoxypyridoxine and the degree of DNA synthesis' inhibition with subsequent lymphocyte proliferation. The results obtained with monoclonal antibody (anti-BrdU) studies were further confirmed with tritiated thymidine incorporation (3H Thymidine) studies. Addition of pyridoxine concurrently with the addition of DB- or 8 hours later than initiation of lymphocyte incubation period was capable of effectively reversing the inhibition caused by its antagonist, the level of DNA synthesis reaching that of the control cultures where only PHA or Con A were present. Our results confirm part of previously reported findings concerning the involvement of vitamin B- in immune processes.

The effect of pyridoxine on the number of lymphocytes in the blood of rats fed caramel colour (III)

The effect of vitamin E, folic acid, pyridoxine (vitamin B 6) and choline on the reduction in circulating lymphocytes in the blood of rats fed Caramel Colour (III) also known as ammonia caramel colour (beer type; AC) has been examined. It was found that the reduction in the number of circulating lymphocytes in rats fed AC could be prevented by the addition of pyridoxine to the diet. The activity of AC in reducing the number of circulating lymphocytes also closely resembled that of the pyridoxine antagonist 4′-deoxypyridoxine. After the isolation and identification of 2-acetyl-4(5)-tetrahydroxybutylimidazole (THI), comparative studies indicated that THI was the component of AC responsible for reducing the number of circulating lymphocytes. Although the effect of AC was reduced or prevented by increasing dietary pyridoxine, the lymphocyte reduction associated with the administration of THI was not materially affected by the dietary level of pyridoxine.

Antiproliferative activity of derivatives of trans-bis(salicylaldoximato)copper(II) in vitro. Some in vivo properties of the parent compound.

Several derivatives and analogs of the recently reported antiproliferative and antitumor agent trans-bis(salicylaldoximato)copper(II) (CuSAO2) have been prepared and tested for antiproliferative activity against L1210 leukemia cells in vitro. The salicylaldimine analog of CuSAO2 had a very strong antiproliferative activity, the 2-day IC50 value being lower than 3 micrograms/ml. The 2,3-dihydroxybenzaldoxime analog was equally active with CuSAO2, while the corresponding 2,5-dihydroxy derivative had a slightly lower activity. The 2,3,4-trihydroxybenzaldoxime derivative had a much lower activity than had the dihydroxybenzaldoxime derivatives. The zinc(II) analog of CuSAO2 had only a low antiproliferative activity. The ligand of CuSAO2, salicylaldoxime, resembles pyridoxal oxime, a vitamin B6 antagonist and a powerful inhibitor of pyridoxal kinase. An attempt to reduce the toxicity of CuSAO2 in vivo with pyridoxal hydrochloride led to increased toxicity.

Nutritional requirements of Plasmodium falciparum in culture. III. Further observations on essential nutrients and antimetabolites.

In a semi-defined minimal medium for cultivation of Plasmodium falciparum, ribose, mannose, fructose, galactose, and maltose could not replace glucose. Hypoxanthine was the preferred purine source for the parasite over adenine, guanine, inosine, adenosine and guanosine although all supported growth equally. Inhibitors of nucleoside uptake had low potency in killing the parasites but depressed incorporation of [3H]adenosine more than [3H]hypoxanthine. Glutamate could not be replaced by 5-oxoproline, indicating that the gamma-glutamyl transferase pathway for amino acid uptake is probably not found in this organism. Adenine, nicotinamide, and orotic acid could not supplement glutamine-deficient medium. The pyridoxine antagonists isoniazid and 4-deoxypyridoxine were reversed by amino acid supplementation, suggesting that transaminases may be targets of these drugs. Orotic acid, but not glutathione or its amino acid components, partially reversed the effects of 8-methylamino-8-desmethyl riboflavin. Thus, the flavin enzyme, dihydroorotic acid dehydrogenase, but not glutathione reductase, appears to be a target of this riboflavin antagonist. Five biotin antagonists had no significant activity. The choline antagonist 2-(tert-butylamino)ethanol and thiamin uptake inhibitors had nonspecific inhibitory effects, which were not reversed by the respective target vitamin. Buthionine sulfoximine and methionine sulfoximine, inhibitors of glutathione synthesis, had significant oxygen-dependent toxicity. Six sulfonamides showed marked variation in potency and efficacy. Sulfathiazole and sulfadoxine were reversed differentially by p-aminobenzoic acid, folic acid, and folinic acid. Folinic acid was more effective than folic acid at reversing the toxicity of the dihydrofolate reductase inhibitors aminopterin and pyrimethamine; p-amino-benzoic acid had no effect.

ウシ胎児大動脈培養細胞に対するビタミンB&lt;sub&gt;6&lt;/sub&gt;阻害剤の影響について

For more than 30 years, we reported that experimental atherosclerosis similar to that of human beings was produced in monkeys by Vitamin B6 deprived diet. However, as the effect of Vitamin B6 on forming atherosclerotic lesion was not obvious, we examined the effect of Vitamin B6 and its antagonists on the cultured endothelial cells from fetal bovine aorta. The patients with homocystinuria, who lack the activity of cystathione synthetase which needs Vitamin B6 as a cofactor, have the tendency to suffer from atherosclerosis in their early life. So it was considered that the impairment of sulfurcontaining amino acid metabolism might play a role in the formation of atherosclerosis in monkeys fed on Vitamin B6 deprived diet. Because the patients with cystathionine synthetase deficiency had homocysteine in their blood at higher concentrations, we also studied the effect of homocysteine and its precursor, S-adenosyl-1-homocysteine.We evaluated the effect of the above substances on the cultured endothelial cells with cell detachment assay by modifying the method of Harker et al. When seeded endothelial cells became confluent in 24 multiwell plate (Corning 25820), test media were added. After 24-hour incubation, each well was washed with PBS and still-adherent cells were counted. Results were expressed as percent detachment compared to control: % Detachment =(Control—Test)/Control×100.We used isoniazid and deoxypyridoxine as Vitamin B6 antagonists. When isoniazid was added, the results were 27.2±1.7%, 49.4±5.7%, 52.8±3.5% at concentration 1mM, 2.5mM, 5mM, respectively. When deoxypyridoxine was added, the results were 12.3±8.3%, 25.4±7.0%, 41.9±2.7% at concentration 0.5mM, 1mM, 2.5mM, respectively. On the other hand, we used pyriodoxal phosphate, active form of Vitamin B6, and pyridoxal HCl as Vitamin B6. When pyridoxal phosphate was added, the results were 0.9±3.6%, 4.4±2.5%, 8.1±2.2% at concentration 0.01mM, 0.1mM, 1mM, respectively. When pyridoxal HCl was added, the results were 7.5±1.5%, 11.7±4.1%, 18.9±2.6% at concentration 0.01mM, 0.1mM, 1mM, respectively. Also sulfur containing amino acids, DL-homocysteine and S-adenosyl-1-homocysteine was tested. When DL-homocysteine was added, the results were 2.8±6.4%, 19.0±6.3%, 16.5±6.3% at concentration 0.5mM, 1mM, 2mM, respectively. When S-adenosyl-1-homo-cysteine was added, the results were 24.2±9.1%, 32.9±7.3%, 33.2±8.1% at concentration 0.5mM, 1mM, 2mM, respectively.The role of Vitamin B6 deficiency in the formation of atherosclerosis is not clear in this study, which uses endothelial cells alone in vitro. However, it was interesting that Vitamin B6 itself, as well as its antagonists, had endothelial detaching potential, although tested drug concentrations had to be taken into consideration. It was supposed that the atherosclerosis may be caused by the impairment of multiple factors, for example, not only endothelial cells but also smooth muscle cells, platelets, coagulants and their interactions in vivo. Vitamin B6 depletion may also take part in the formation of atherosclerosis by influencing many factors but many problems regarding these mechanisms still remain to be clarified.

Alteration of convulsive threshold and conditioned avoidance response in mice fed diets containing contraceptive steroids.

Female CD1 mice given the contraceptive steroids mestranol and norethynodrel (1:10) in the diet (0.0033%) for 4 months had a growth reduction of 20% when compared with mice fed a normal diet, and had lower convulsive thresholds when tested with the vitamin B6 antagonists 2,4-dimethyl-5-methyl-hydroxypyrimidine and thiosemicarbazide. In conditioned avoidance response (CAR) tests, mice fed the steroid-containing diets showed a decreased acquisition performance during all six sessions; however, mice fed the same diet supplemented with vitamin B6 (0.04%) performed as well during the last three sessions of the CAR tests as mice fed the normal diet.

High-dose pyridoxal supplemented culture medium inhibits the growth of a human malignant melanoma cell line.

The in vitro growth characteristics of a human malignant melanoma cell line cultured in 0.5 mM pyridoxal supplemented medium were studied. Experimentation revealed that the high-dose pyridoxal supplemented medium severely inhibited the growth of melanoma cells over a 72-hour growth period. Additional experimentation showed that cells cultured for 6 hours in the pyridoxal supplemented medium took up 25% less and incorporated 20% less [3H]uridine than control cultures. [3H]Glucose uptake was reduced by 23% at this time point. [3H]Thymidine uptake was inhibited by 12%, but no inhibition was detected in [3H]thymidine incorporation. When the vitamin B6 antagonist 4-deoxypyridoxine (which competes with pyridoxal for pyridoxal kinase) was added to the pyridoxal supplemented medium, the inhibition in [3H]uridine incorporation was reduced from 19% to 6%. However, 4-deoxypyridoxine did not reverse the inhibition of [3H]uridine uptake. These results indicate that pyridoxal and its metabolite, pyridoxal 5'-phosphate, may be involved in the growth regulation of a human malignant melanoma cell line.