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Ascorbate is an important antioxidant in the brain. Astrocytes are capable of recycling ascorbate by taking up and then reducing its oxidation product dehydroascorbic acid (DHAA) using reducing equivalents derived from NAD(P)H. Astrocytes also contain NAD(P)H-dependent quinone reductases, such as NAD(P)H:quinone oxidoreductase (NQO1), which are capable of reducing coenzyme Q and its analogs. Short-chain coenzyme Q analogs have been proposed as therapeutic agents for neurodegenerative illnesses, but they may cause oxidative stress by non-enzymatic redox cycling or enzyme-dependent depletion of NAD(P)H. Therefore, we tested the hypothesis that the short-chain coenzyme Q analog coenzyme Q(1) (CoQ(1), ubiquinone-5) decreases intracellular NAD(P)H levels in astrocytes and impairs the ability of these cells to replace extracellular DHAA with ascorbate (i.e., ascorbate recycling). We observed that CoQ(1) inhibited the production of intra- and extracellular ascorbate by primary rat astrocytes incubated with DHAA in glucose-free medium. Reduction of CoQ(1) to CoQ(1)H(2) by astrocytes was partially blocked by the NQO1 inhibitor dicumarol but was not affected by DHAA. The inhibition of ascorbate recycling by CoQ(1) was attenuated by dicumarol and was abolished by glucose. CoQ(1) lowered intracellular levels of reactive oxygen species, as measured by oxidation of 2',7'-dichlorofluorescin but also produced marked decreases in the concentrations of NADH and NADPH. We conclude that in astrocytes CoQ(1) recycling depletes NAD(P)H and inhibits ascorbate recycling when glucose metabolism is limited. Because DHAA can cause cell-lethal oxidative stress in neurons and ascorbate produced by astrocytes may be neuroprotective, coenzyme Q analogs may adversely affect brain function through this novel mechanism.
Acute effects of mercury on mouse blood, kidneys, and liver were evaluated. Mice received a single dose of mercuric chloride (HgCl2, 4.6 mg/kg, subcutaneously) for three consecutive days. We investigated the possible beneficial effects of antioxidant therapy (N-acetylcysteine (NAC) and diphenyl diselenide (PhSe)2) compared with the sodium salt of 2,3-dimercapto-1-propanesulfonic acid (DMPS), an effective chelating agent in HgCl2 exposure in mice. We also verified whether metallothionein (MT) induction might be involved in a possible mechanism of protection against HgCl2 poisoning and whether different treatments would modify MT levels and other toxicological parameters. The results demonstrated that HgCl2 exposure significantly inhibited delta-aminolevulinate dehydratase (delta-ALA-D) activity in liver and only DMPS treatment prevented the inhibitory effect. Mercuric chloride caused an increase in renal non-protein thiol groups (NPSH) and none of the treatments modified renal NPSH levels. Urea concentration was increased after HgCl2 exposure. NAC plus (PhSe)2 was partially effective in protecting against the effects of mercury. DMPS and (PhSe)2 were effective in restoring the increment in urea concentration caused by mercury. Thiobarbituric acid-reactive substances (TBARS), aspartate aminotransferase (AST), and alanine aminotransferase (ALT) activities and ascorbic acid levels were not modified after mercury exposure. Mercuric chloride poisoning caused an increase in hepatic and renal MT levels and antioxidant treatments did not modify this parameter. Our data indicated a lack of therapeutic effect of the antioxidants tested.
OBJECTIVE: Hypothermic cardiopulmonary bypass is associated with capillary fluid leakage, resulting in edema and occasionally organ dysfunction. Systemic inflammatory activation is considered responsible. In some studies methylprednisolone has reduced the weight gain during cardiopulmonary bypass. Vitamin C and alpha-trinositol have been demonstrated to reduce the microvascular fluid and protein leakage in thermal injuries. We therefore tested these three agents for the reduction of cold-induced fluid extravasation during cardiopulmonary bypass. METHODS: A total of 28 piglets were randomly assigned to four groups of 7 each: control group, high-dose vitamin C group, methylprednisolone group, and alpha-trinositol-group. After 1 hour of normothermic cardiopulmonary bypass, hypothermic cardiopulmonary bypass was initiated in all animals and continued to 90 minutes. The fluid level in the extracorporeal circuit reservoir was kept constant at the 400-mL level and used as a fluid gauge. Fluid needs, plasma volume, changes in colloid osmotic pressure in plasma and interstitial fluid, hematocrit, and total water contents in different tissues were recorded, and the protein masses and the fluid extravasation rate were calculated. RESULTS: Hemodilution was about 25% after start of normothermic cardiopulmonary bypass. Cooling did not cause any further changes in hemodilution. During steady-state normothermic cardiopulmonary bypass, the fluid need in all groups was about 0.10 mL/(kg.min), with a 9-fold increase during the first 30 minutes of cooling (P <.001). This increased fluid need was due mainly to increased fluid extravasation from the intravascular to the interstitial space at a mean rate of 0.6 mL/(kg.min) (range 0.5-0.7 mL/[kg.min]; P <.01) and was reflected by increased total water content in most tissues in all groups. The albumin and protein masses remained constant in all groups throughout the study. CONCLUSION: Pretreatment with methylprednisolone, vitamin C, or alpha-trinositol was unable to prevent the increased fluid extravasation rate during hypothermic cardiopulmonary bypass. These findings, together with the stability of the protein masses throughout the study, support the presence of a noninflammatory mechanism behind the cold-induced fluid leakage seen during cardiopulmonary bypass.
After their random -llocation to one of three treatment aroups, 622 volunteers received either vitamin C or placebo in a maintenance dose of 500 mg once weekly and a therapeutic dose of 1500 mg daily on the 1st day and 1000 mg on the next 4 days of any illness. Two forms of vitamin C were employed: a sustained-release capsule containing ascorbic acid and a regular tabet containing a mixture of sodium and calcium ascorbate. In the 448 subjects who completed an average of 15 weeks in the study of total of 635 episodes of illness were recroded. Respiratory symptoms were recorded on at least 1 day in 92 per cent of these episodes. There were no consistent or significant differences in the sickness experience of the subjects receiving the sustained-release vitamin capsules compared to those receiving the vitamin tablets, but subjects in both vitamin groups experienced less severe illness than subjects in the placebo group, with approximately 25 per cent fewer days spent indoors because of the illness (P smaller than 0.05). These results are compatible with the belief that supplementary vitamin C can reduce the burden of winter illness, but the intake need not be as high as has sometimes been claimed.
A hypothesis is advanced, according to which substances containing an amino group can compete with glucose in binding with protein groups and inhibiting in this way glycosylation. Screening in vitro experiments with nicotinic acid, nicotinamide, piracetam, panangin, ascorbic acid, bucarban, betanase, and adebit in a concentration of 10(-3) M were performed. Bucarban, betanase, and adebit were found to be capable of inhibiting glycosylation. Daily oral administration of bucarban and adebit in therapeutic doses for one month reduced the blood fructosamine level in rats with alloxan diabetes without changing the level of glycemia.
PURPOSE: Aldose reductase (AR) has been a drug target because of its involvement in the development of secondary complications of diabetes including cataract. Although numerous synthetic AR inhibitors (ARI) have been tested and shown to inhibit the enzyme, clinically synthetic ARIs have not been very successful. Therefore, evaluating natural sources for ARI potential may lead to the development of safer and more effective agents against diabetic complications. In the present study we have assessed the inhibition of AR by constituents of Emblica officinalis both in vitro and in lens organ culture. METHODS: E. officinalis is widely used against many chronic ailments including diabetes. Aqeous extract of E. officinalis and its major constituent tannoids were tested for inhibition against both rat lens and purified recombinant human AR. ARI potential of isolated tannoids of E. officinalis were also investigated against osmotic stress in rat lens organ culture. RESULTS: E. officinalis extract inhibited rat lens and recombinant human AR with IC50 values 0.72 and 0.88 mg/ml respectively. Since E. officinalis is a rich source of ascorbic acid, we investigated whether ascorbic acid was responsible for AR inhibition by E. officinalis extract. However, ascorbic acid did not inhibit AR even at 5 mM concentration. Further, we demonstrate that the hydrolysable tannoids of E. officinalis were responsible for AR inhibition, as enriched tannoids of E. officinalis exhibited remarkable inhibition against both rat lens and human AR with IC50 of 6 and 10 microg/ml respectively. The inhibition of AR by E. officinalis tannoids is 100 times higher than its aqueous extract and comparable to or better than quercetin. Furthermore, the isolated tannoids not only prevented the AR activation in rat lens organ culture but also sugar-induced osmotic changes. CONCLUSIONS: These results indicate that tannoids of E. officinalis are potent inhibitors of AR and suggest that exploring the therapeutic value of natural ingredients that people can incorporate into everyday life may be an effective approach in the management of diabetic complications.
BACKGROUND/AIMS: Despite a proposed role of oxidative stress in the pathogenesis of nonalcoholic steatohepatitis, antioxidant approaches have not been investigated sufficiently in the therapy of nonalcoholic steatohepatitis. Our aim was to determine whether vitamin E plus C therapy is effective in normalization of liver enzymes compared to ursodeoxycholic acid treatment in patients with fatty liver disease. METHODS: This was an open-labeled, prospective, randomized study enrolling patients with histologically proven fatty liver disease who had chronically elevated alanine aminotransferase, despite a three-month reducing diet. Patients consuming alcohol (more than 20 g/day) were excluded. The patients were randomly prescribed either oral vitamin E (600 IU/day) plus vitamin C (500 mg/day) or ursodeoxycholic acid (10 mg/kg/day). Patients were randomized as two groups to receive vitamin E plus vitamin C combination (28 patients, 10 F) or ursodeoxycholic acid treatment (29 patients, 13 F). RESULTS: There was no significant change in body mass index before and after the treatment in both groups. At the end of six months of therapy, serum aspartate aminotransferase and aminotransferase levels significantly decreased in both treatment options. Vitamin E and C combination was more efficacious on serum aminotransferase levels than ursodeoxycholic acid, but the difference was not significant. Alanine aminotransferase decreased to normal levels in 17 of 27 (63%) and in 16 of 29 patients (55%), respectively, in the two groups. Gamma-glutamyl transpeptidase decreased in patients receiving ursodeoxycholic acid, but no change was obtained in the vitamin-treated patients. CONCLUSIONS: Vitamin E plus C combination treatment is a safe, inexpensive and effective treatment option in patients with fatty liver disease, with results comparable to those obtained with ursodeoxycholic acid. Since more effective new therapeutic options are lacking, patients with fatty liver disease should be encouraged to take vitamin E and C supplements, which are safe and affordable.
Free radicals and subsequent lipid peroxidation have been implicated in the pathogenesis of several degenerative and chronic diseases which are also treated frequently in spas. There are some data arising from previous studies which support an antioxidant or scavenging effect of iodide, being the essential ingredient of a therapeutically used local brine. The aim of the study was to test the antioxidant capacity of iodide in human serum. For this reason we measured the so-called Total Antioxidant Status determined by a colorimetric method, which reflects the protection against the attack of reactive oxygen species, including enzymic and non-enzymic antioxidants. Exogenous iodide applied as NaI, shows a significantly increased antioxidant capacity in comparison with NaCl at a concentration of 15 microM, which is quite comparable to the upper range of serum iodide levels achieved through balneo-therapeutical intervention. This result is in accordance with previous results from in vitro depolymerization experiments with hyaluronic acid. The antioxidant effect of 15 microM NaI has been found to be approaching the physiologically relevant concentration of ascorbic acid (50 microM).
Nitric oxide (NO) is considered a key molecule in the defense against intracellular pathogens, particularly Leishmania. The expression of inducible nitric oxide synthase and consequent production of NO by infected macrophages has been shown to correlate with leishmaniasis resistance in the murine model as well as in human patients. Nitric oxide donors have been used successfully in the treatment of cutaneous leishmaniasis in humans, although their mechanisms of action are not fully understood. In the present work, the dose-dependent cytotoxic effects of the NO-donors S-nitroso-N-acetyl-l-cysteine (SNAC) and S-nitrosoglutathione (GSNO) against Leishmania were evaluated. GSNO inhibited the growth of Leishmania major and Leishmania amazonensis with in vitro 50% inhibitory concentrations (IC(50)) of 68.8+/-22.86 and 68.9+/-7.9 micromol L(-1), respectively. The IC(50) for SNAC against L. major and L. amazonensis were, respectively, 54.6+/-8.3 and 181.6+/-12.5 micromol L(-1). The leishmanicidal activity of GSNO, but not of SNAC, was reversed by ascorbic acid (AA) and dithiothreitol (DTT), suggesting that the mechanism of action of GSNO is related to the transnitrosation of parasite proteins. These results demonstrate that SNAC and GSNO have leishmanicidal activity, and are thus potential therapeutic agents against cutaneous leishmaniasis.
Primary bladder stone is a common pediatric surgical problem in developing countries. Many theories are prevalent. The stone matrix theory is based on increased excretion of its precursor, the uromucoid (the urinary mucoprotein). Uromucoid, studied in urine and stones by the electroimmunodiffusion technique in 49 cases with controls, showed significantly increased excretion in stone cases. Family income and serum protein were the only important influencing factors (negative). Causal relationship between uromucoid excretion, stone matrix, and pediatric bladder stones is discussed. Methylene blue decreased uromucoid excretion but not magnesium oxide, vitamin C or B6 (four common therapeutic drugs for prevention/dissolution of urolithiasis).
OBJECTIVES: We sought to test the hypothesis that vascular endothelial function is impaired in Behçet's syndrome and reflects increased levels of oxidative stress. BACKGROUND: Behçet's syndrome is a multisystem inflammatory disorder commonly complicated by vascular thrombosis and arterial aneurysm formation. The precise mechanisms underlying vascular disease in Behçet's syndrome are not known. METHODS: We studied 19 patients with Behçet's syndrome (18 to 50 years old, 9 men) and 21 healthy volunteers (18 to 50 years old, 10 men). Brachial artery flow-mediated dilation (endothelium-dependent), and nitroglycerin (NTG)-induced dilation (endothelium-independent) were measured. To investigate oxidative stress mechanisms, vascular studies were repeated 1 h after administration of vitamin C (1 g, intravenous) in 12 patients and 12 control subjects. RESULTS: Flow-mediated dilation was reduced in patients with Behcet's syndrome as compared with control subjects (0.7 +/- 0.9% vs. 5.7 +/- 0.9%, p = 0.001). In contrast, there were no significant differences in the brachial artery diameter (4.2 +/- 0.2 vs. 4.0 +/- 0.2 mm, p = 0.47) or NTG-induced dilation (19.7 +/- 1.9% vs. 19.7 +/- 1.2%, p = 0.98). In regression analysis, Behçet's syndrome was associated with impaired flow-mediated dilation independent of age, gender, brachial artery diameter, blood pressure, cholesterol and glucose. Vitamin C increased flow-mediated dilation in Behçet's syndrome (0.2 +/- 0.7% to 3.5 +/- 1.0%, p = 0.002), but not in control subjects (4.3 +/- 0.6% to 4.7 +/- 0.4%, p = 0.51). In both groups, NTG-induced dilation and brachial artery diameter were unchanged after vitamin C treatment. CONCLUSIONS: Vascular endothelial function is impaired in Behcet's syndrome and can be rapidly improved by vitamin C treatment. Our results support a role for oxidative stress in the pathophysiology of Behçet's syndrome and provide a rationale for therapeutic studies aimed at reducing vascular complications in this disorder.
Amphotericin B methyl ester (AME) has been reported to possess in vitro antifungal activity similar to that of amphotericin B and to have less intrinsic toxicity in mice and dogs. For these reasons AME has been porposed as an alternative to amphotericin B in the therapy of deep mycoses. For comparison of the therapeutic efficacy of the two polyenes in laboratory animals before initiation of studies in humans, groups of mice were infected with Candida albicans, Cryptococcus neoformans, and Blastomyces dermatitidis. Treatment consisted of two or more doses of each drug given by the intravenous route. Concurrently, studies of subacute toxicity were conducted in the same species to permit calculation of therapeutic indices. These studies have shown that AME, as the ascorbate salt, is substantially less efficacious than amphotericin B (in colloidal dispersion with sodium deoxycholate) for treatment of the fungal infections and that amphotericin B had a higher therapeutic ratio for all infections studied than did AME.
Impaired endothelial cell proliferation has been proposed to be an early, critical defect contributing to the development of atherosclerosis. Recent studies show that high plasma tumor necrosis factor (TNF)-alpha levels and low serum ascorbic acid (AA) levels correlate with atherosclerosis severity. Additionally, AA has been reported to have potential beneficial effects in preventing atherosclerosis. Based on these studies, we investigated the role of AA (< or =1mM) on TNF-alpha-mediated vascular endothelial cell growth inhibition in vitro. In accordance with previous reports, we found that TNF-alpha alone inhibited endothelial cell proliferation. Further studies revealed that AA alone enhanced endothelial cell proliferation and that AA blocked endothelial cell growth inhibition induced by TNF-alpha. By contrast, we observed no effect of AA on endothelial cell activation or nuclear entry of nuclear factor-kappaB in response to TNF-alpha. The protective effect of AA on endothelial cell proliferation was not simply the result of its antioxidant activity but did correlate with collagen IV expression by endothelial cells. AA pre-treatment of proliferating endothelial cells promoted retinoblastoma protein (Rb) phosphorylation and decreased p53 levels when compared to untreated cells. Furthermore, the addition of AA to TNF-alpha-treated proliferating endothelial cells blocked both the inhibition of retinoblastoma protein phosphorylation and enhanced p53 expression induced by TNF-alpha. Consistent with these results, we found that AA protects endothelial cells against TNF-alpha-induced apoptosis. These studies highlight the potential therapeutic role of AA in promoting endothelial cell proliferation during inflammatory conditions, such as atherosclerosis and cardiovascular disease.
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It has been proposed that beta-blockers and agents affecting Ca2+ metabolism might exert cardioprotective actions because of their ability to act as antioxidants in vivo. The feasibility of this proposal was tested by examining the reaction of a series of such compounds with various oxygen-derived species. None of the compounds tested was sufficiently reactive with superoxide radical, hydrogen peroxide or hypochlorous acid for scavenging of these species to be feasible in vivo at the drug concentrations present in patients given the usual therapeutic doses. All the drugs tested were powerful scavengers of hydroxyl radical except for flunarizine, which stimulated iron ion-dependent hydroxyl radical generation from hydrogen peroxide. However, none of the drugs significantly inhibited production of hydroxyl radicals in this system. Propranolol, verapamil and flunarizine had significant inhibitory effects on the peroxidation of rat liver microsomes in the presence of iron ions and ascorbic acid. All three compounds exerted weaker inhibitory effects on peroxidation of arachidonic acid caused by a mixture of myoglobin and H2O2: pindolol stimulated peroxidation in this system. It is concluded that the ability of beta-blockers and "Ca(2+)-blockers" to inhibit lipid peroxidation varies with the lipid substrate used and the mechanism by which peroxidation is induced. We conclude that suggestions that beta-blockers and "Ca(2+)-blockers" exert antioxidant effects in vivo are not well founded, although there is a possibility that verapamil and propranolol might have some inhibitory effects against peroxidation if they accumulate in membranes to a sufficiently-high concentration in vivo. We could not confirm the reported ability of propranolol to inhibit the enzyme xanthine oxidase.