Modulation of humoral immune response by ascorbic acid in Oreochromis mossambicus (Peters).

Fish were treated with sublethal doses of ascorbic acid before being immunised with different physical forms of bovine serum albumin (BSA). Ascorbic acid elevates the antibody response to all the physical forms of BSA tested. Generally, there was an inverse relationship between the dose of ascorbic acid and antibody response. In fish administered with multiple doses of ascorbic acid, no significant enhancement of antibody response was observed.     

Immobilized-metal affinity chromatography of serum proteins on gel-immobilized group III A metal ions

The potential pharmacologic use of enzymes has long been considered. Practical applications, however, have been limited by the toxicity and allergic response to administered foreign proteins. A simple in vitro modification that allows the intraperitoneal administration of large doses of L-gulonolactone oxidase to guinea pigs is described. The enzyme is precipitated by guinea pig antisera and reacted with glutaraldehyde (0.125%). The product is comparatively nontoxic in guinea pigs. Administration of this enzyme enables guinea pigs to synthesize ascorbic acid. Success of this approach may depend on reinforcement by the bifunctional reagent of the enzyme-antibody complex.     

Effect of ascorbic acid on prevention of hypercholesterolemia induced atherosclerosis

The notion that oxidation of lipids and propagation of free radicals may contribute to the pathogenesis of atherosclerosis is supported by a large body of evidence. To circumvent the damage caused by oxygen free radicals, antioxidants are needed which provide the much needed neutralization of free radical by allowing the pairing of electrons. In this study we have investigated the effect of ascorbic acid, a water soluble antioxidant on the development of hypercholesterolemia induced atherosclerosis in rabbits. Rabbits were made hypercholesterolemic and atherosclerotic by feeding 100 mg cholesterol/day. Different doses of ascorbic acid were administered to these rabbits. Low dose of ascorbic acid (0.5 mg/100 g body weight/day) did not have any significant effect on the percent of total area covered by atherosclerotic plaque. However, ascorbic acid when fed at a higher dose (15 mg/100 g body weight/day) was highly effective in reducing the atherogenecity. With this dose the percent of total surface area covered by atherosclerotic plaque was significantly less (p < 0.001). This suggests that use of ascorbic acid may have great promise in the prevention of hypercholesterolemia induced atherosclerosis.     

High-dose ascorbic acid decreases detoxification of cyanide derived from amygdalin (laetrile): studies in guinea pigs

Cysteine, a sulphur-containing amino acid, is required to metabolize ascorbic acid (as ascorbate sulphate) and detoxify cyanide (to thiocyanate). In guinea pigs, conjoint use of laetrile (a cyanogenic glycoside) and ascorbic acid (in large doses) decreases the detoxification of cyanide derived from laetrile through diminishing the availability of cysteine, but not impairing hepatic rhodanese activity, which is involved in the detoxification of cyanide to thiocyanate. These results agree with the symptoms of a sublethal dose of KCN toxicity manifested by the animals. The studies, therefore, indicate that individuals taking megadoses of ascorbic acid concurrently with laetrile may be subject to self-poisoning.     

Hemin-mediated Hemolysis in Erythrocytes： Effects of Ascorbic Acid and Glutathione

In the present work,we investigated the effect of ascorbic acid and glutathione on hemolysisinduced by hemin in erythrocytes.Ascorbic acid not only enhanced hemolysis,but also induced formationof thiobarbituric acid-reactive substances in the presence of hemin.It has been shown that glutathioneinhibits hemin-induced hemolysis by mediating hemin degradation.Erythrocytes depleted of glutathionebecame very sensitive to oxidative stress induced by hemin and ascorbic acid.H_2O_2 was involved in hemin-mediated hemolysis in the presence of ascorbic acid.However,a combination of glutathione and ascorbicacid was more effective in inhibiting hemolysis induced by hemin than glutathione alone.Extracellular andintracellular ascorbic acid exhibited a similar effect on hemin-induced hemolysis or inhibition of hemin-induced hemolysis by glutathione.The current study indicates that ascorbic acid might function as anantioxidant or prooxidant in hemin-mediated hemolysis,depending on whether glutathione is available.     

Effect of antioxidant supplementation on the adaptive response of human skin fibroblasts to UV-induced oxidative stress

The effect of supplementation with substances having antioxidant properties on the adaptive responses of human skin fibroblasts to UV-induced oxidative stress was studied in vitro. UVR was found to induce a substantial oxidative stress in fibroblasts, resulting in an increased release of superoxide anions and an increase in lipid peroxidation (shown by an elevated malonaldehyde content). Sub-lethal doses of UVR were also found to induce adaptive responses in the fibroblast antioxidant defences, with a transient rise in catalase and superoxide dismutase activities followed by a slower, large increase in cellular glutathione content. Supplementation of the fibroblasts with the antioxidants, Trolox (a water soluble analogue of alpha-tocopherol), ascorbic acid or beta-carotene, had differential effects on these responses. Trolox supplementation reduced the UVR-induced cellular oxidative stress and adaptive response in a predictable concentration-dependent manner. This was in contrast to ascorbic acid which increased superoxide release from fibroblasts. At low doses, ascorbate supplements also reduced the magnitude of the adaptive increases in catalase and superoxide dismutase activities and increase in glutathione content. Beta-carotene had a similar effect to ascorbic acid, reducing the extent of the adaptations to UVR at lower doses while simultaneously increasing superoxide release and malonaldehyde content. These in vitro data indicate that only the vitamin E analogue suppressed UVR-induced oxidative stress in a predictable manner and suggest that common dietary antioxidants may not be equally effective in reducing the potential deleterious effects of UVR-induced oxidative stress in skin.     

Effect of antioxidant supplementation on the adaptive response of human skin fibroblasts to UV-induced oxidative stress

Abstract

The effect of supplementation with substances having antioxidant properties on the adaptive responses of human skin fibroblasts to UV-induced oxidative stress was studied in vitro. UVR was found to induce a substantial oxidative stress in fibroblasts, resulting in an increased release of superoxide anions and an increase in lipid peroxidation (shown by an elevated malonaldehyde content). Sub-lethal doses of UVR were also found to induce adaptive responses in the fibroblast antioxidant defences, with a transient rise in catalase and superoxide dismutase activities followed by a slower, large increase in cellular glutathione content. Supplementation of the fibroblasts with the antioxidants, Trolox (a water soluble analogue of α-tocopherol), ascorbic acid or β-carotene, had differential effects on these responses. Trolox supplementation reduced the UVR-induced cellular oxidative stress and adaptive response in a predictable concentration-dependant manner. This was in contrast to ascorbic acid which increased superoxide release from fibroblasts. At low doses, ascorbate supplements also reduced the magnitude of the adaptive increases in catalase and superoxide dismutase activities and increase in glutathione content. β-Carotene had a similar effect to ascorbic acid, reducing the extent of the adaptations to UVR at lower doses while simultaneously increasing superoxide release and malonaldehyde content. These in vitro data indicate that only the vitamin E analogue suppressed UVR-induced oxidative stress in a predictable manner and suggest that common dietary antioxidants may not be equally effective in reducing the potential deleterious effects of UVR-induced oxidative stress in skin.     

The orthomolecular treatment of cancer. II. Clinical trial of high-dose ascorbic acid supplements in advanced human cancer

This communication reports the clinical response of fifty consecutive advanced cancer patients to the continuous administration of large doses of ascorbic acid. It concludes that this simple and safe form of medication is of definite value in the palliation of terminal cancer. The findings suggest that it should be employed as a standard supportive measure to reinforce established methods of treatment in the general management of earlier and more favorable cases.     

High dose of ascorbic acid induces cell death in mesothelioma cells

Malignant mesothelioma is an asbestos-related fatal disease with no effective cure. Recently, high dose of ascorbate in cancer treatment has been reexamined. We studied whether high dose of ascorbic acid induced cell death of four human mesothelioma cell lines. High dose of ascorbic acid induced cell death of all mesothelioma cell lines in a dose-dependent manner. We further clarified the cell killing mechanism that ascorbic acid induced reactive oxygen species and impaired mitochondrial membrane potential. In vivo experiment, intravenous administration of ascorbic acid significantly decreased the growth rate of mesothelioma tumor inoculated in mice. These data suggest that ascorbic acid may have benefits for patients with mesothelioma.     

Endothelial potentiation of relaxation response to ascorbic acid in rat and guinea pog thoracic aorta

The role of the endothelium was evaluated in the relaxation of rat and guinea pig aortic rings induced by ascorbic acid. Ascorbic acid relaxed rat and guinea pig aortic rings that were previously contracted with submaximal dose of phenylephrine (PE), in a concentration dependent manner. Removal of the endothelium significantly reduced the sensitivity but not the magnitude of the response to ascorbic acid. Methylene blue, but not propranolol, blocked the endothelial augmentation of vascular relaxation to ascorbic acid. Vessels precontracted with potassium chloride (high K⁺ were also relaxed by ascorbic acid. Methylene blue also inhibited the response to ascorbic acid in the intact vessels precontracted with high K⁺. A23187 and acetylcholine, but not ADP, variably caused endothelium dependent component relaxation in guinea pigs, whereas all of these three probes constantly caused it. In Ca²⁺-free medium, Ca²⁺-induced contraction of high K⁺-depolarized rat aorta was inhibited by the presence of ascorbate, which was more pronounced in endothelium intact rings than in endothelium denuded ones. PE-induced contraction in the presenced of different concentrations of ascorabte reduced both the sensitivity and the maximal contractile force in rat aorta. Ascorbic acid (0.125-32 mM) did not change the pH in the medium. From these findings, it is speculated that 1) receptor- and potential-operated Ca²⁺ channeld may be modulated by ascorbate, 2) endothelium has a significant role in promoting relaxation induced by ascorbic acid.     

Characterization of osteoblastic differentiation of stromal cell line ST2 that is induced by ascorbic acid

The stromal cell line ST2, derived from mouse bone marrow,differentiated into osteoblast-like cells in response to ascorbic acid.Ascorbic acid induced alkaline phosphatase (ALPase) activity, theexpression of mRNAs for proteins that are markers of osteoblastic differentiation, the deposition of calcium, and the formation ofmineralized nodules by ST2 cells. We investigated the mechanism wherebyascorbic acid induced the differentiation of ST2 cells. Inhibitors ofthe formation of collagen triple helices completely blocked the effectsof ascorbic acid on ST2 cells, an indication that matrix formation bytype I collagen is essential for the induction of osteoblasticdifferentiation of ST2 cells by ascorbic acid. We furthermore examinedthe effects of bone morphogenetic proteins (BMPs) on thedifferentiation of ST2 cells induced by ascorbic acid. Ascorbic acidhad no effect on the expression of mRNAs for BMP-4 and the BMPreceptors. However, a soluble form of BMP receptor IAinhibited the induction of ALPase activity by ascorbic acid. Theseresults suggest that ascorbic acid might promote the differentiation ofST2 cells into osteoblast-like cells by inducing the formation of amatrix of type I collagen, with subsequent activation of the signalingpathways that involve BMPs.

     

Effect of ferrous sulphate and ascorbic acid on motility, viability and lipid peroxidation of crossbred cattle bull spermatozoa

Numerous factors influence male fertility, one of these being the oxidative stress, which has elicited enormous interest recently. In sperm, induction of oxidation decreases motility and viability but increases lipid peroxidation (LPO). The optimum dose of ferrous ascorbate (FeAA: FeSO4 + ascorbic acid) for inducing oxidative stress by affecting motility, viability and LPO has been ascertained in local crossbred cattle bull spermatozoa. The fractions of spermatozoa suspended in 2.9% sodium citrate were subjected to three doses of FeAA (100 : 500, 150 : 750, 200 : 1000; μmol/l FeSO4 : μmol/l ascorbic acid). These fractions were assessed for various parameters. Increase in the incubation period and promoter concentration induced a decrease in motility and viability, but an increase in LPO. Among three doses of FeAA, 150 : 750 μmol/l ascorbic acid is suggested to be the optimum/best dose as it induces the oxidative stress/LPO to a significant extent and also maintains better motility and viability as compared with the other two doses, and such conditions may enhance the fertilising potential of bull spermatozoa.     

Correction of biochemical and immunological indices in colonic cancer using optimal doses of retinyl acetate and ascorbic acid

Blood plasma retinol level in normal donors and patients with colonic carcinoma was measured by high-pressure liquid chromatography and the concentration of p-hydroxyphenyl lactic and homogentizine acids by Gas Chromatograph Mass Spectrometer MAT-311A using 2H4-p-hydroxyphenylacetic acid as internal reference. The functional activity of lymphocytes was estimated from the proliferative response to alloantigens in a one-way mixed lymphocyte culture and in blast transformation reaction to Con A and pokeweed mitogen. After systematic intake of retinyl acetate and ascorbic acid in optimally high doses, the patients manifested an increase in vitamin C level in plasma and lymphocytes and a lowering of p-hydroxyphenyl lactic acid excretion. Blood plasma retinol remained unchanged. Daily intake of retinyl acetate and ascorbic acid for 8-12 days produced a significant increase of lymphocyte proliferation in response to alloantigens in mixed lymphocyte culture and blast transformation reaction to suboptimal mitogen doses.     

Immunomodulating activity of p-hydroxyphenyllactic and ascorbic acids

p-Hydroxyphenyl lactic acid (PHA) in a concentration of 5 . 10(-5) M produced a significant inhibition of cell proliferation in response to alloantigens in a one-way mixed lymphocyte culture (MLC) in colonic cancer patients and in blast transformation in response to suboptimal doses of Con A. Multiple administration of ascorbic acid in an optimal concentration to the culture increased the proliferative response of lymphocytes to alloantigens and Con A. PHA and ascorbic acid did not exhibit any immunomodulating action during the use of healthy donors' lymphocytes or lymphocytes from colonic cancer patients, transformed with optimal mitogen doses. PHA did not affect the production of cytotoxic T lymphocytes in the MLC of the spleens of allogeneic mice but inhibited lymphocyte proliferation in response to alloantigens in the MLC of the spleens obtained from B6 and vitamin A deficient animals.     

Ascorbic acid absorption in man: influence of divided dose and food

The urinary recovery of ascorbic acid (AA) was examined in 3 subjects when the vitamin was given as a single 1 g dose in solution (control), as divided doses in solution (0.125 g every 15 min. for 8 doses) and as a 1 g solution after eating a meal high in fat content. The divided dose and after-meal treatments produced a significant increase in AA absorption compared to the corresponding control experiment, 72% and 69% increase, respectively. Absorption appears to be delayed and prolonged under the latter conditions. These results are consistent with the suggestion that the vitamin is absorbed by a specialized process at sites high in the small intestine.     

Vitamin C (ascorbic acid) induced hydroxyl radical formation in copper contaminated household drinking water: role of bicarbonate concentration

We have previously shown that Vitamin C (ascorbic acid) can trigger hydroxyl radical formation in copper contaminated household drinking water. We report here that the capacity of ascorbic acid to catalyze hydroxyl radical generation in the drinking water samples is strongly dependent on the bicarbonate concentration (buffer capacity and pH) of the samples. We found that at least 50 mg/l bicarbonate was required in the water samples to maintain the pH over 5.0 after ascorbic acid addition. At this pH, that is higher than the pKa

1

4.25 of ascorbic acid, a hydroxyl radical generating redox cycling reaction involving the mono-anion of vitamin C and copper could take place. The ascorbic acid induced hydroxyl radical generating reaction could easily be mimicked in Milli-Q water by supplementing the water with copper and bicarbonate. Our results demonstrate that ascorbic acid can induce a pH dependent hydroxyl radical generating reaction in copper contaminated household tap water that is buffered with bicarbonate. The impact of consuming ascorbic acid together with copper and bicarbonate containing drinking water on human health is discussed.     

Acute liver damage induced by 2-nitropropane in rats: effect of diphenyl diselenide on antioxidant defenses

The effect of post-treatment with diphenyl diselenide on liver damage induced by 2-nitropropane (2-NP) was examined in male rats. Rats were pre-treated with a single dose of 2-NP (100 mg/kg body weight dissolved in canola oil). Afterward, the animals were post-treated with a dose of diphenyl diselenide (10, 50 or 100 micromol/kg). The parameters that indicate tissue damage such as liver histopathology, plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT), urea and creatinine were determined. Since the liver damage induced by 2-NP is related to oxidative damage, lipid peroxidation, superoxide dismutase (SOD), catalase (CAT) and ascorbic acid level were also evaluated. Diphenyl diselenide (50 and 100 micromol/kg) effectively restored the increase of ALT and AST activities and urea level when compared to the 2-NP group. At the higher dose, diphenyl diselenide decreased GGT activity. Treatment with diphenyl diselenide, at all doses, effectively ameliorated the increase of hepatic and renal lipid peroxidation when compared to 2-NP group. 2-NP reduced CAT activity and neither alter SOD activity nor ascorbic acid level. This study points out the involvement of CAT activity in 2-NP-induced acute liver damage and suggests that the post-treatment with diphenyl diselenide was effective in restoring the hepatic damage induced by 2-NP.