Protective Effect Of Ascorbate Research Articles

Tu1350 - Pathogenic Alteration in Endoplasmic Reticulum Homeostasis through Perk and Not IRE1-XBP1 Pathway, Impaired Autophagic Clearance, and Protective Effect of Ascorbate in Experimental Acute Pancreatitis

Tu1350 - Pathogenic Alteration in Endoplasmic Reticulum Homeostasis through Perk and Not IRE1-XBP1 Pathway, Impaired Autophagic Clearance, and Protective Effect of Ascorbate in Experimental Acute Pancreatitis

Ascorbic Acid Promotes Detoxification and Elimination of 4-Hydroxy-2(E)-nonenal in Human Monocytic THP-1 Cells

4-Hydroxy-2(E)-nonenal (HNE), a reactive aldehyde derived from oxidized lipids, has been implicated in the pathogenesis of cardiovascular and neurological diseases, in part by its ability to induce oxidative stress and by protein carbonylation in target cells. The effects of intracellular ascorbic acid (vitamin C) on HNE-induced cytotoxicity and protein carbonylation were investigated in human THP-1 monocytic leukemia cells. HNE treatment of these cells resulted in apoptosis, necrosis, and protein carbonylation. Ascorbic acid accumulated in the cells at concentrations of 6.4 or 8.9 mM after treatment with 0.1 or 1 mM ascorbate in the medium for 18 h. Pretreatment of cells with 1.0 mM ascorbate decreased HNE-induced formation of reactive oxygen species and formation of protein carbonyls. The protective effects of ascorbate were associated with an increase in the formation of GSH-HNE conjugate and its phase 1 metabolites, measured by LC-MS/MS, and with increased transport of GSH conjugates from the cells into the medium. Ascorbate pretreatment enhanced the efflux of the multidrug resistant protein (MRP) substrate, carboxy-2',7'-dichlorofluorescein (CDF), and it prevented the HNE-induced inhibition of CDF export from THP-1 cells, suggesting that the protective effect of ascorbate against HNE cytotoxicity is through modulation of MRP-mediated transport of GSH-HNE conjugate metabolites. The formation of ascorbate adducts of HNE was observed in the cell exposure experiments, but it represented a minor pathway contributing to the elimination of HNE and to the protective effects of ascorbate.

Haemostatic properties of human plasma subjected to a sterilizing dose of gamma irradiation in the presence of ascorbate

The objective was to study the effects of gamma irradiation, in the presence of sodium ascorbate, on coagulation/fibrinolytic activity of fresh frozen plasma to be applied to inactivate the transfusion-transmitted viruses in plasma-derived products. Plasma was irradiated (50 kGy total dose, on dry ice) using a 60Co source. The plasma proteins were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and western blot and the following parameters estimated: prothrombin time, functional fibrinogen concentration, thrombin-induced fibrinogen polymerization, plasminogen activity, and tissue-type plasminogen activator-induced conversion of plasminogen to plasmin. In irradiated plasma a moderate fragmentation of the most labile plasma proteins was found. The prothrombin time was prolonged (1.5-fold), functional fibrinogen was significantly reduced (60%), fibrinogen polymerization was impaired, plasminogen was predominantly maintained (90%) and tissue-type plasminogen activator-induced conversion of plasminogen to plasmin was unchanged. Ascorbate (25 mmol/l) raised the level of functional fibrinogen in irradiated plasma (to 50%; P=0.0245) and slightly accelerated its polymerization. The small protective effect of ascorbate might be due to inhibition of the radiation-induced fibrinogen oxidation and/or fragmentation but addition of other antioxidants/stabilizers would be crucial when a high irradiation dose, an effective treatment for inactivation of the most resistant viruses, is applied.

The potentiating and protective effects of ascorbate on oxidative stress depend upon the concentration of dietary iron fed C3H mice

Ascorbic acid (AA) is an antioxidant that, in the presence of iron and hydrogen peroxide, increases the production of hydroxyl radicals in vitro. Whether AA has similar pro-oxidant properties in vivo may depend upon the relative balance of iron and AA concentrations. In this study, C3H mice were fed diets supplemented with 100 or 300 mg/kg iron, with or without AA (15 g/kg), for 12 months. Liver AA concentrations were greater in mice fed AA-supplemented diets with either low or high iron ( P=.0001), while the high-iron diet was associated with a significantly lower liver AA concentration regardless of AA supplementation ( P=.0001). Only mice fed the high-iron diet with AA had a significantly greater liver iron concentration ( P=.05). In the high-iron group, AA reduced oxidative stress, as measured by greater activities of glutathione peroxidase, superoxide dismutase (SOD) and catalase and by significantly lower concentrations of 4-hydroxylalkenal (HAE) and malondialdehyde (MDA). In mice fed the low-iron diet, AA was associated with greater concentrations of HAE and MDA and with lower activities of SOD. However, AA did not increase the concentrations of modified DNA bases with the low-iron diet but was associated with significantly lower concentrations of modified DNA bases in mice fed the high-iron diet. In conclusion, dietary AA appears to have mild pro-oxidant properties at low-iron concentrations but has a strong antioxidant effect against oxidative stress and DNA damage induced by dietary iron in mouse liver.

Protein modification caused by a high dose of gamma irradiation in cryo-sterilized plasma: Protective effects of ascorbate

Gamma irradiation is a method of pathogen inactivation in plasma derivatives currently under development. Gamma rays inactivate all known blood-borne viruses. However, the virucidally effective dose of radiation may affect the integrity and function of plasma proteins. Biological activity recoveries of the therapeutic products were shown to be significantly improved by lowering the irradiation temperature and by the addition of antioxidants; the mechanisms responsible for this have not been elucidated yet. Here we sterilized human plasma by gamma irradiation (50 kGy), on dry ice, in the presence (or absence) of ascorbate. The subsequent protein oxidation was quantified by a ferric-xylenol orange (hydroperoxides) and by DNPH-coupled assays (carbonyls). We demonstrated for the first time that irradiation of frozen plasma (without saturation with oxygen) resulted in the generation of protein hydroperoxides, the yield of which was dramatically decreased when plasma was irradiated in the presence of either sodium azide or ascorbate. In irradiated plasma the concentration of protein carbonyls was twofold higher than in nonirradiated control. Ascorbate significantly inhibited protein carbonylation. We concluded that freezing of plasma during irradiation does not provide the complete protection against protein carbonylation and hydroperoxide generation. Addition of ascorbate and some nontoxic metabolic inhibitors might be useful as protecting stabilizers.

Protective effect of ascorbate against oxidative stress in the mouse lens.

The purpose of this study was to determine if high ascorbate of the human aqueous protects the lens against oxidative stress. Previous studies with the rat lens have been inconclusive because of its fortification with aldose reductase (AR), an important antioxidant. The human lens is deficient in this activity. These studies were hence done with the mouse lens, a species deficient in this enzyme. The reactive oxygen species (ROS)-induced physiological damage to the tissue was assessed in organ culture, by measuring its ability to actively transport 86Rb(+) ions, in the absence and presence of ascorbate. In addition, the status of tissue metabolism and its antioxidant reserve were assessed by quantitating ATP and glutathione (GSH). As expected, ROS decreased the membrane transport activity as well as the levels of ATP and GSH. Ascorbate minimized these toxic effects substantially. The presence of high ascorbate, therefore, appears highly beneficial in protecting the lens against oxidative damage and cataract formation, despite a deficiency of AR. The findings therefore appear to be significant from the point of view of using this nutrient for delaying the onset of cataract development in human beings, therapeutically as well as nutritionally.

The effects of ascorbic acid and iron co-supplementation on the proliferation of 3T3 fibroblasts.

Exposure of 3T3 fibroblasts to FeII reveals a concentration-dependent inhibition of cell proliferation compared to control cells, the apparent threshold for this iron-mediated effect being 5 microM FeII. The inhibition of cell proliferation was accompanied by an enhancement of total malondialdehyde (MDA) levels (as detected directly by hplc) in the cells at higher iron concentrations. The co-supplementation of FeII with varying concentrations of ascorbic acid over the range 5 microM to 240 microM had no significant effect on the threshold for iron toxicity or lipid peroxidation. These results show that there is neither a significant exacerbation of the pro-oxidant effect of FeII nor any protective effect of ascorbate when cultures of 3T3 mouse fibroblasts are exposed to co-supplementation regimes of iron with ascorbic acid.

Comparison of Peroxidases in the Retina, Choroid and Red Blood Cells

Most of the peroxidase activity in the bovine retina is specific to glutathione (GSH) while the choroid contains both GSH peroxidases and ascorbate peroxidase. The GSH peroxidase was clearly separated from ascorbate peroxidase on a cation exchange column. The nonspecific peroxidase activity of hemoproteins accounts for the peroxidase activity detected by ascorbate oxidation. All choroidal hemoproteins contain subunits very similar to those of hemoglobin. The absence of ascorbate peroxidase in the retina indicates that the protective effect of ascorbate against photic injury is not due to its reaction with retinal peroxidase. Therefore removal of H2O2 by ascorbate peroxidase activity in the choroid could be a significant factor in studies where serum ascorbate concentrations are artificially raised far above the normal level concurrent to a very small rise in retinal ascorbate concentration.

Protective effect of ascorbate in adriamycin-induced cardiotoxity in cultured rat myocytes

Protective effect of ascorbate in adriamycin-induced cardiotoxity in cultured rat myocytes

Increased Susceptibility of the Sickle Cell Membrane Ca2+ + Mg2+-ATPase to t-Butylhydroperoxide: Protective Effects of Ascorbate and Desferal

Abstract Normal and sickle cell erythrocyte membranes were examined for significant differences in their ATPase activities, thiobarbituric acid reactive products formed (measured relative to malondialdehyde), membrane protein polymerization, and number of protein-free sulfhydryl groups when treated with 0.5 mmol/L t-butylhydroperoxide (tBHP) for 30 minutes. Isolated sickle cell membranes treated with tBHP produced significantly greater inhibition in both their basal and calmodulin- stimulated Ca2+ + Mg(2+)-ATPase activities (75% inhibition in both cases) compared with that of control membranes. In addition, there was significantly more malondialdehyde formed from sickle cell membranes compared with control membranes. Oxidation caused greater protein polymerization in sickle cell membranes compared with normal membranes as demonstrated by the formation of high molecular weight polymers separated on sodium dodecyl sulfate polyacrylamide gels. The number of free sulfhydryl groups present in spectrin and actin decreased more in sickle cell membranes as measured by 3H-N-ethyl maleimide autoradiography and gel scanning. To prevent enzyme inhibition, erythrocyte membranes were treated with tBHP in the presence of 1 mmol/L ascorbate, a potential antioxidant, and 1 mmol/L desferal, an iron chelator. Both ascorbate and desferal added alone with tBHP were effective in preventing inhibition of the basal and calmodulin- stimulated Ca2+ + Mg(2+)-ATPase activities in normal membranes, but in sickle cell membranes only the addition of ascorbate and desferal together offered significant protection. The enhanced oxidation observed with sickle cell membranes can be mimicked in normal white membranes by adding hemoglobin, hemin, or ferrous chloride in the presence of tBHP. In contrast to hemoglobin, ferrous chloride has the ability to enhance membrane oxidation in the presence of ascorbate with or without tBHP. Furthermore, the addition of desferal to these membranes greatly decreased the iron-ascorbate-tBHP oxidation of erythrocyte membranes as determined by the sustained ATPase activities and the reduced formation of malondialdehyde. Maximal protection was provided by 1 mmol/L desferal in the presence of 1 mmol/L ascorbate, although some protection was observed even at 10 mumol/L, the lowest concentration tested. These results are discussed in light of the pro- and anti-oxidant effects of ascorbate in the absence and presence of iron and tBHP.

Increased susceptibility of the sickle cell membrane Ca2+ + Mg(2+)- ATPase to t-butylhydroperoxide: protective effects of ascorbate and desferal

Normal and sickle cell erythrocyte membranes were examined for significant differences in their ATPase activities, thiobarbituric acid reactive products formed (measured relative to malondialdehyde), membrane protein polymerization, and number of protein-free sulfhydryl groups when treated with 0.5 mmol/L t-butylhydroperoxide (tBHP) for 30 minutes. Isolated sickle cell membranes treated with tBHP produced significantly greater inhibition in both their basal and calmodulin-stimulated Ca2+ + Mg(2+)-ATPase activities (75% inhibition in both cases) compared with that of control membranes. In addition, there was significantly more malondialdehyde formed from sickle cell membranes compared with control membranes. Oxidation caused greater protein polymerization in sickle cell membranes compared with normal membranes as demonstrated by the formation of high molecular weight polymers separated on sodium dodecyl sulfate polyacrylamide gels. The number of free sulfhydryl groups present in spectrin and actin decreased more in sickle cell membranes as measured by 3H-N-ethyl maleimide autoradiography and gel scanning. To prevent enzyme inhibition, erythrocyte membranes were treated with tBHP in the presence of 1 mmol/L ascorbate, a potential antioxidant, and 1 mmol/L desferal, an iron chelator. Both ascorbate and desferal added alone with tBHP were effective in preventing inhibition of the basal and calmodulin-stimulated Ca2+ + Mg(2+)-ATPase activities in normal membranes, but in sickle cell membranes only the addition of ascorbate and desferal together offered significant protection. The enhanced oxidation observed with sickle cell membranes can be mimicked in normal white membranes by adding hemoglobin, hemin, or ferrous chloride in the presence of tBHP. In contrast to hemoglobin, ferrous chloride has the ability to enhance membrane oxidation in the presence of ascorbate with or without tBHP. Furthermore, the addition of desferal to these membranes greatly decreased the iron-ascorbate-tBHP oxidation of erythrocyte membranes as determined by the sustained ATPase activities and the reduced formation of malondialdehyde. Maximal protection was provided by 1 mmol/L desferal in the presence of 1 mmol/L ascorbate, although some protection was observed even at 10 mumol/L, the lowest concentration tested. These results are discussed in light of the pro- and anti-oxidant effects of ascorbate in the absence and presence of iron and tBHP.

The protective effect of ascorbate on the inhibition of growth, RNA and protein synthesis by tamoxifen in yeast is time dependent

The protective effect of ascorbate on the inhibition of growth, RNA and protein synthesis by tamoxifen in yeast is time dependent

Blood and urinary measures of oxidant damage in healthy human subjects

similarity suggests that loss of protection follows the same time course in each case and indeed the onset of inhibition by tamoxifen of both RNA and protein synthesis has been shown to be simultaneous [3]. These results indicate that the protection of these cellular processes by ascorbate is time dependent and, furthermore, they show that inhibition by tamoxifen becomes irreversible with time. It is possible that cytochrome P-450 enzymes could be the intracellular target site(s) for tamoxifen in yeast [4]. The cytochrome I’-450-dependent lanosterol 14-a-demethylase enzyme on the ergosterol biosynthetic pathway is such an enzyme and is of great importance to yeast growth. Tamoxifen has been shown to inhibit this enzyme, on the analogous cholesterol biosynthetic pathway, in the breast cancer cell line MCF-7 IS]. The binding of tamoxifen to this proposed target site may thus be partially prevented by the simultaneous addition of ascorbate. This time-dependent protective effect of ascorbate could be via the maintenance of essential thiol groups in cytochrome P-450-dependent enzymes such as lanosterol 14-a-demethylase, which are deleteriously affected by the oxyradicals that might be generated by the action of cytochrome P-450 during tamoxifen metabolism 16-91. The award of a Leverhulme Emeritus Fellowship to H.K.V.A. i s gratefully acknowledged. We also thank the Charities Aid Foundation for financial help.

Protective Effect of Ascorbate on Radiation‐Sensitive Thymidine Uptake by Lymphocytes

Protective Effect of Ascorbate on Radiation‐Sensitive Thymidine Uptake by Lymphocytes

The Free and Total Folate Activity in Foods Available on the Canadian Market

The free and total folate activities of 162 foods were determined microbiologically using L. casei. A comparison with published values showed that the protective effect of ascorbate during analysis was reflected in both the free and total folate activity values reported herein. The approximate intake of folate activity from an average daily total diet, based on food disappearance data, was estimated at 140μg of free folate and 240μg of total folate activity per person per day.