Endotoxin increases oxidative injury to proteins in guinea pig liver: protection by dietary vitamin C

The Anti-Leukemia Effect of Ascorbic Acid: From the Pro-Oxidant Potential to the Epigenetic Role in Acute Myeloid Leukemia

Data derived from high-throughput sequencing technologies have allowed a deeper understanding of the molecular landscape of Acute Myeloid Leukemia (AML), paving the way for the development of novel therapeutic options, with a higher efficacy and a lower toxicity than conventional chemotherapy. In the antileukemia drug development scenario, ascorbic acid, a natural compound also known as Vitamin C, has emerged for its potential anti-proliferative and pro-apoptotic activities on leukemic cells. However, the role of ascorbic acid (vitamin C) in the treatment of AML has been debated for decades. Mechanistic insight into its role in many biological processes and, especially, in epigenetic regulation has provided the rationale for the use of this agent as a novel anti-leukemia therapy in AML. Acting as a co-factor for 2-oxoglutarate-dependent dioxygenases (2-OGDDs), ascorbic acid is involved in the epigenetic regulations through the control of TET (ten-eleven translocation) enzymes, epigenetic master regulators with a critical role in aberrant hematopoiesis and leukemogenesis. In line with this discovery, great interest has been emerging for the clinical testing of this drug targeting leukemia epigenome. Besides its role in epigenetics, ascorbic acid is also a pivotal regulator of many physiological processes in human, particularly in the antioxidant cellular response, being able to scavenge reactive oxygen species (ROS) to prevent DNA damage and other effects involved in cancer transformation. Thus, for this wide spectrum of biological activities, ascorbic acid possesses some pharmacologic properties attractive for anti-leukemia therapy. The present review outlines the evidence and mechanism of ascorbic acid in leukemogenesis and its therapeutic potential in AML. With the growing evidence derived from the literature on situations in which the use of ascorbate may be beneficial in vitro and in vivo, we will finally discuss how these insights could be included into the rational design of future clinical trials.

Antioxidant and Anti-Inflammatory Activities of Agrimonia pilosa Ledeb. Extract

The purpose of this study is to investigate the effect of Agrimonia pilosa Ledeb. extract (APLE) on lipopolysaccharide- (LPS-) induced cell damage in hepatocytes with a focus on antioxidant and anti-inflammatory activities. Total antioxidant and anti-inflammatory activities of APLE itself were analyzed and phytochemical analysis was performed. Moreover, inhibitory effects of APLE on LPS-induced oxidative stress and inflammation were assessed in human HepG2 hepatocytes. APLE was found to exert α,α-diphenyl-β-picrylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and nitrite scavenging activities and reducing power in a dose-dependent manner. The total phenolic and flavonoid contents of APLE were 44.30 ± 1.61 mg GAE/g and 29.65 ± 1.81 mg QE/g, respectively. HPLC analysis revealed that gallic acid is the major phenolic compound in APLE, followed by rutin, genistein, taxifolin, quercetin, luteolin, and apigenin, in descending order. Treatment of 100 and 200 μg/mL APLE significantly reduced LPS-stimulated intracellular reactive oxygen species production to the basal level without any cytotoxicity. Oppositely, APLE reversed LPS-suppressed expression of glutathione peroxidase gene and protein. Consistent with this result, APLE suppressed LPS-triggered expression of proinflammatory cytokine genes in a dose-dependent manner. These results reinforce the fact that the antioxidant and anti-inflammatory activity of APLE helps protect hepatocytes from LPS. Thus, APLE may be utilized as a bioactive ingredient in functional foods.

The relationship between vitamin C status, the gut-liver axis, and metabolic syndrome

Metabolic syndrome (MetS) is a constellation of cardiometabolic risk factors, which together predict increased risk of more serious chronic diseases. We propose that one consequence of dietary overnutrition is increased abundance of Gram-negative bacteria in the gut that cause increased inflammation, impaired gut function, and endotoxemia that further dysregulate the already compromised antioxidant vitamin status in MetS. This discussion is timely because "healthy" individuals are no longer the societal norm and specialized dietary requirements are needed for the growing prevalence of MetS. Further, these lines of evidence provide the foundational basis for investigation that poor vitamin C status promotes endotoxemia, leading to metabolic dysfunction that impairs vitamin E trafficking through a mechanism involving the gut-liver axis. This report will establish a critical need for translational research aimed at validating therapeutic approaches to manage endotoxemia-an early, but inflammation-inducing phenomenon, which not only occurs in MetS, but is also prognostic of more advanced metabolic disorders including type 2 diabetes mellitus, as well as the increasing severity of nonalcoholic fatty liver diseases.

Herbal management of hepatocellular carcinoma through cutting the pathways of the common risk factors

Hepatocellular carcinoma (HCC) is considered the most frequent tumor that associated with high mortality rate. Several risk factors contribute to the pathogenesis of HCC, such as chronic persistent infection with hepatitis C virus or hepatitis B virus, chronic untreated inflammation of liver with different etiology, oxidative stress and fatty liver disease. Several treatment protocols are used in the treatment of HCC but they also associated with diverse side effects. Many natural products are helpful in the co-treatment and prevention of HCC. Several mechanisms are involved in the action of these herbal products and their bioactive compounds in the prevention and co-treatment of HCC. They can inhibit the liver cancer development and progression in several ways as protecting against liver carcinogens, enhancing effects of chemotherapeutic drugs, inhibiting tumor cell growth and metastasis, and suppression of oxidative stress and chronic inflammation. In this review, we will discuss the utility of diverse natural products in the prevention and co-treatment of HCC, through its capturing of the common risk factors known to lead to HCC and shed the light on their possible mechanisms of action. Our theory assumes that shutting down the risk factor to cancer development pathways is a critical strategy in cancer prevention and management. We recommend the use of these plants side by side to recent chemical medications and after stopping these chemicals, as a maintenance therapy to avoid HCC progression and decrease its global incidence.

In vitro antioxidant capacities of eight different kinds of apples and their effects on lipopolysaccharide-induced oxidative damage in mice

In the present study, the DPPH and ABTS⁺ radical scavenging activity of eight types of apples decreased (P < 0.05) during the 70-day storage at 4°C. The Fushi (F2) apples from Xin Jiang showed the highest radical scavenging activity. For in vivo study, 40 male Kunming mice (body weight 20–25 g) were selected and randomly assigned to four groups (10 mice per group). The F2 groups (F2S, F2 + sterile saline and F2L, F2 + lipopolysaccharide) were administered with 0.3 mL F2 filtrate via gastric intubation daily for 28 days. The control groups (CS, CON + sterile saline and CL, CON + lipopolysaccharide) were treated with sterile saline at the same volume. At day 29, mice of F2L and CL groups were injected with 100 μg/kg body weight of lipopolysaccharide (LPS) intraperitoneally, while those of F2S and CS groups were injected equal volume of sterile saline. In comparison to the CS group, the CL group showed a decrease (P < 0.05) in serum, liver, and hepatic mitochondrial antioxidant capacity, reduction (P < 0.05) in the expression of hepatic antioxidant-related genes, and an increase (P < 0.05) in serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), malondialdehyde (MDA), protein carbonyl (PC), and reactive oxygen species (ROS). In comparison to the CL group, the F2L group showed lower (P < 0.05) levels of serum ALT, AST, and ROS, higher (P < 0.05) level of serum, liver, and hepatic mitochondrial antioxidant capacity, increased mitochondrial membrane potential (MMP), and enhanced (P < 0.05) expression of hepatic antioxidant-related genes. These results suggest that F2 may exert protective effect against LPS-induced oxidative damage by improving the antioxidant capacity.

Assessment of Free Radical Scavenging Activity of Dimethylglycine Sodium Salt and Its Role in Providing Protection against Lipopolysaccharide-Induced Oxidative Stress in Mice

In the present study, the free radical scavenging activities (against 1,1-diphenyl-2-pierylhydrazy (DPPH), 2,2'-Azinobis-(3-ethylbenzthiazoline-6- sulphonate) (ABTS+), Hydrogen peroxide (H2O2)) of dimethylglycine sodium salt (DMG-Na) were measured and compared with those of Trolox (6-hydroxy-2, 5, 7, 8-tetramethylchroman-2-carboxylic acid), a commonly used antioxidant. The radical scavenging activities of DMG-Na were found to be the highest at 40 mg/ml. In Experiment 2, gastric intubation in mice with 12 mg DMG-Na/0.3 ml sterile saline solution significantly increased (P < 0.05) the body weight (BW) (28 d), organ proportion (liver and spleen), and antioxidant capacity in serum and the liver (Superoxide dismutase (SOD), Hydrogen peroxidase (CAT), Glutathione peroxidase (GPx), and Total antioxidant capacity (T-AOC)), and significantly decreased (P < 0.05) the activities of serum Glutamic-pyruvic transaminase (ALT) and Glutamic oxalacetic transaminase (AST) and Methane Dicarboxylic Aldehyde (MDA) contents in the serum and liver. Specifically, the effect of 12 mg DMG-Na/0.3 ml sterile saline solution, which showed the highest antioxidant capacity, was further studied using a mice model. In Experiment 3, the mice CL (CON+ lipopolysaccharide (LPS)) group showed a significant decrease (P < 0.05) in the serum ALT and AST content; hepatic mitochondrial antioxidant capacity (Manganese Superoxide dismutase (MnSOD), Glutathione reductase (GR), GPx, Glutathione (GSH)); MDA and Protein carbonyl (PC) content; Reactive oxygen species (ROS) level, Mitochondrial membrane potential (MMP) level, and expression of liver antioxidant genes (Nuclear factor erythroid 2-related factor 2 (Nrf2), Heme oxygenase 1 (HO-1), Manganese superoxide dismutase (MnSOD), Glutathione peroxidase 1 (Gpx1), Sirtuin 1 (Sirt1)) relative to the mice CS (CON+ sterile saline) group. The DL (DMG+LPS) group showed a significant decrease (P < 0.05) in serum ALT and AST content, ROS level, and expression of liver antioxidant gene MnSOD, Gpx1, Sirt1 and a significant increase (P < 0.05) in the hepatic mitochondrial antioxidant capacity (MnSOD, GSH, GPx, GR) and MMP level relative to the CL group. These results indicate that DMG-Na could protect against the LPS-induced oxidative stress by enhancing the free radical scavenging capacity, and increasing the activity of antioxidant defense system.

Anethole improves the in vitro development of isolated caprine secondary follicles

The aim of this study was to investigate the effect of three concentrations of anethole (30, 300, and 2000 μg/mL) on survival, antrum formation, follicular diameter, and oocyte maturation in the caprine species. The study also evaluated the effects of anethole on transcripts of ICAM-1, CAV-1, TIMP-2, and PAI-1 genes and levels of reactive oxygen species (ROS) in isolated goat preantral ovarian follicles before and after in vitro culture for 18 days. Preantral follicles were isolated from goat ovaries and individually cultured in alpha minimum essential medium modified (α-MEM⁺), defined as the control treatment, α-MEM⁺ supplemented with ascorbic acid at a concentration of 100 μg/mL (AA), or α-MEM⁺ supplemented with three different concentrations of anethole (30, 300, 2000 μg/mL) for a period of 18 days. Treatments were named as α-MEM⁺, AA, AN30, AN300, and AN2000, respectively. After culture, the follicles were opened, the cumulus oocytes complex (COCs) were removed and matured in vitro. The walls of the follicles were used for the quantitation of mRNA by quantitative real-time polymerase chain reaction. Finally, the medium collected at the end of culture was used for the measurements of ROS. After 18 days of culture, the AA treatment showed the percentage of intact follicles and follicular diameter significantly higher compared with the other treatments. However, daily growth rate, antrum formation, and also oocyte diameter were similar among the treatments. In addition, compared with AA, the rate of oocytes for in vitro maturation (diameter ≥ 110 μm) and the meiosis resumption rate were significantly higher in the treatments AN30 and AN2000, respectively. When assessing gene related to remodeling of the basement membrane, significant differences in mRNA levels for ICAM-1, CAV-1, TIMP-2, and PAI-1 were observed in comparison with Day 0, i.e., in the noncultured control. In addition, the ROS from Day 12, all treatments with the addition of anethole have significantly lower values of ROS than α-MEM⁺ and AA. In conclusion, the addition of anethole to the in vitro culture medium was able to improve the development of goat preantral follicles by reducing concentrations of ROS and increasing the percentage of oocytes able to resume meiosis.

Evaluation of antioxidant activities of ampelopsin and its protective effect in lipopolysaccharide-induced oxidative stress piglets

The aim of this study was to investigate the antioxidant potential of ampelopsin (APS) by using various methods in vitro, as well as to determine effects of APS on LPS-induced oxidative stress in piglets. The results showed that APS exhibited excellent free radical scavenging by DPPH, ABTS, O₂•⁻, H₂O₂ and ferric reducing antioxidant power. Ampelopsin also protected pig erythrocytes against AAPH-induced apoptosis and hemolysis, decreased total superoxide dismutase activity, and increased lipid peroxidation. Furthermore the results demonstrated that APS enhanced the total antioxidant capacity and decreased the malondialdehyde and protein carbonyl contents in LPS-treated piglets. The results of the present investigation suggest that APS possesses a strong antioxidant activity and alleviates LPS-induced oxidative stress, possibly due to its ability to prevent reactive oxygen species.

Vitamin C revisited

This narrative review summarizes the role of vitamin C in mitigating oxidative injury-induced microcirculatory impairment and associated organ failure in ischemia/reperfusion or sepsis. Preclinical studies show that high-dose vitamin C can prevent or restore microcirculatory flow impairment by inhibiting activation of nicotinamide adenine dinucleotide phosphate-oxidase and inducible nitric oxide synthase, augmenting tetrahydrobiopterin, preventing uncoupling of oxidative phosphorylation, and decreasing the formation of superoxide and peroxynitrite, and by directly scavenging superoxide. Vitamin C can additionally restore vascular responsiveness to vasoconstrictors, preserve endothelial barrier by maintaining cyclic guanylate phosphatase and occludin phosphorylation and preventing apoptosis. Finally, high-dose vitamin C can augment antibacterial defense. These protective effects against overwhelming oxidative stress due to ischemia/reperfusion, sepsis or burn seems to mitigate organ injury and dysfunction, and promote recovery after cardiac revascularization and in critically ill patients, in the latter partially in combination with other antioxidants. Of note, several questions remain to be solved, including optimal dose, timing and combination of vitamin C with other antioxidants. The combination obviously offers a synergistic effect and seems reasonable during sustained critical illness. High-dose vitamin C, however, provides a cheap, strong and multifaceted antioxidant, especially robust for resuscitation of the circulation. Vitamin C given as early as possible after the injurious event, or before if feasible, seems most effective. The latter could be considered at the start of cardiac surgery, organ transplant or major gastrointestinal surgery. Preoperative supplementation should consider the inhibiting effect of vitamin C on ischemic preconditioning. In critically ill patients, future research should focus on the use of short-term high-dose intravenous vitamin C as a resuscitation drug, to intervene as early as possible in the oxidant cascade in order to optimize macrocirculation and microcirculation and limit cellular injury.

Lipopolysaccharide-induced hepatic oxidative injury is not potentiated by knockout of GPX1 and SOD1 in mice

Knockout of copper, zinc-superoxide dismutase (SOD1) and (or) cellular glutathione peroxidase (GPX1) has been reported to have dual impacts on coping with free radical-induced oxidative injury. Because bacterial endotoxin lipopolysaccharide (LPS) triggers inflammatory responses involving the release of cytokines, nitric oxide and superoxide in targeted organs such as liver, in this study we used SOD1 knockout (SOD1-/-), GPX1 knockout (GPX1-/-), GPX1 and SOD1 double-knockout (DKO) and their wild-type (WT) mice to investigate the role of these two antioxidant enzymes in LPS-induced oxidative injury in liver. Mice of the four genotypes (2 month old) were killed at 0, 3, 6 or 12 h after an i.p. injection of saline or 5 mg LPS/kg body weight. The LPS injection caused similar increase in plasma alanine aminotransferase among the four genotypes. Hepatic total glutathione (GSH) was decreased (P<0.05) compared with the initial values by the LPS injection at all time points in the WT mice, but only at 6 and 12 h in the other three genotypes. The GSH level in the DKO mice was higher (P<0.05) than in the WT at 6 h. Although the LPS injection resulted in substantial increases in plasma NO in a time-dependent manner in all genotypes, the NO level in the DKO mice was lower (P<0.05) at 3, 6 and 12 h than in the WT. The level in the GPX1-/- and SOD1-/- mice was also lower (P<0.05) than in the WT at 3 h. The LPS-mediated hepatic protein nitration was detected in the WT and GPX1-/- mice at 3, 6 or 12 h, but not in the SOD1-/-. In conclusion, knockout of SOD1 and (or) GPX1 did not potentiate the LPS-induced liver injury, but delayed the induced hepatic GSH depletion and plasma NO production.

Resveratrol, a red wine polyphenol, attenuates lipopolysaccharide-induced oxidative stress in rat liver

Lipopolysaccharide (LPS) is a glycolipid component of the cell wall of gram-negative bacteria inducing deleterious effects on several organs including the liver and eventually leading to septic shock and death. Endotoxemia-induced hepatotoxicity is characterized by disturbed intracellular redox balance, excessive reactive oxygen species (ROS) accumulation inducing DNA, proteins and membrane lipid damages. Resveratrol (trans-3,5,4' trihydroxystilbene) is a phytoalexin polyphenol exhibiting antioxidant and anti-inflammatory properties. In this study, we investigated the effect of subacute pre-treatment with this natural compound on LPS-induced hepatotoxicity in rat. Resveratrol counteracted LPS-induced lipoperoxidation and depletion of antioxidant enzyme activities as superoxide dismutase (SOD) and catalase (CAT) but slightly glutathione peroxidase (GPx) activity. The polyphenol also abrogated LPS-induced liver and plasma nitric oxide (NO) elevation and attenuated endotoxemia-induced hepatic tissue injury. Importantly resveratrol treatment abolished LPS-induced iron sequestration from plasma to liver compartment. Our data suggest that resveratrol is capable of alleviating LPS-induced hepatotoxicity and that its mode of action may involve differential iron compartmentalization via iron shuttling proteins.

Interaction between ascorbic acid and follicle-stimulating hormone maintains follicular viability after long-term in vitro culture of caprine preantral follicles

This study evaluates the effects of ascorbic acid and its interaction with follicle-stimulating hormone (FSH) on the morphology, activation, and in vitro growth of caprine preantral follicles. Ovarian fragments were cultured for 1, 7, or 14 d in minimum essential medium (MEM) containing ascorbic acid (50 or 100microg/mL), FSH (50ng/mL), or both of these substances. Ovarian tissue that was either fresh (control) or cultured for 1, 7, or 14 d was processed for histological and ultrastructural evaluation. The results showed that after 14 d of culture, medium supplemented with 50microg/mL of ascorbic acid alone or combined with FSH showed higher rates of follicular survival compared with MEM. After 7 d of culture, FSH, ascorbic acid at 50microg/mL with or without FSH, and ascorbic acid at 100microg/mL increased the percentage of follicular activation compared to fresh control. In addition, FSH alone significantly increased the percentage of growing follicles after 14 d. The combination of 50microg/mL of ascorbic acid and FSH promoted a significant increase in oocyte and follicular diameter after 7 d of culture. Ultrastructural and fluorescent analysis confirmed the integrity of follicles cultured with 50microg/mL of ascorbic acid and FSH after 14 d. In conclusion, the combination of 50microg/mL of ascorbic acid and FSH maintained follicular integrity and promoted follicular activation and growth after long-term in vitro culture of caprine preantral follicles.

New developments and novel therapeutic perspectives for vitamin C

Vitamin C is required for collagen synthesis and biosynthesis of certain hormones and recommended dietary intake levels are largely based these requirements. However, to function effectively as an antioxidant (or a pro-oxidant), relatively high levels of this vitamin must be maintained in the body. The instability of vitamin C combined with its relatively poor intestinal absorption and ready excretion from the body reduce physiological availability of this vitamin. This inability to maintain high serum levels of vitamin C may have serious health implications and is particularly relevant in the onset and progression of degenerative disease, such as cancer and cardiovascular disease (CVD), which have a strong contributing oxidative damage factor. In this review, we examine recent studies on the regulation of transport mechanisms for vitamin C, related clinical ramifications, and potential implications in high-dose vitamin C therapy. We also evaluate recent clinical and scientific evidence on the effects of this vitamin on cancer and CVD, with focus on the key mechanisms of action that may contribute to the therapeutic potential of this vitamin in these diseases. Several animal models that could be utilized to address unresolved questions regarding the feasibility of vitamin C therapy are also discussed.

Immunomodulatory effect of vitamin C on intracytoplasmic cytokine production in neonatal cord blood cells

BACKGROUND

Vitamin C (ascorbic acid) is an essential water-soluble antioxidant in cells and plasma. Besides metabolic functions, vitamin C is also known to contribute to immune homeostasis. Recently, it has been demonstrated that vitamin C has an inhibitory effect on the expression of pro-inflammatory cytokines such as interleukin (IL)-6 and tumor necrosis factor alpha (TNF-alpha) in adult whole blood cells in vitro. It has been postulated that vitamin C might be an interesting compound for modulation of an over-exuberant immune response, e.g., in patient cohorts susceptible for the development of systemic inflammatory response syndrome such as neonates. It was the aim of this study to investigate the modulatory effects of vitamin C on the production of inflammatory mediators in neonatal cord blood cells.

METHODS

The intracytoplasmic production of pro-inflammatory cytokines in neonatal cord blood cells stimulated with lipopolysaccharide or phorbol 12-myristate 13-acetate/ionomycin was assessed by flow-cytometry.

RESULTS

In contrast to our previous observations from adult whole blood cells, 20 mM vitamin C mildly stimulated the percentage of neonatal monocytes producing IL-6 after lipopolysaccharide stimulation (e.g., 11.3% increase compared to control, p = 0.005). In the presence of 20 mM vitamin C, even a stronger stimulatory effect was noted for the percentage of IL-8 (e.g., 46.7% increase, p < 0.001) and TNF-alpha producing neonatal monocytes (e.g., 69.2% increase, p = 0.004; n = 20). In accordance with adult data, the percentage of neonatal lymphocytes producing IL-2 after phorbol 12-myristate 13-acetate/ionomycin stimulation was dose-dependently reduced (e.g., 41.3% inhibition, p = 0.001, 20 mM vitamin C), while the percentage of TNF-alpha producing lymphocytes was mildly stimulated (e.g., 20.8% increase, p = 0.003, 20 mM vitamin C).

CONCLUSIONS

Interestingly, vitamin C was demonstrated to enhance pro-inflammatory responses in CD14(+) cord blood cells while only intracellular IL-2 production in CD3(+) cells was diminished. These data suggest that vitamin C differentially influences intracytoplasmic cytokine production in adults and neonates, and further studies are needed to elucidate the underlying mechanisms of this selective immunomodulation.

The effect of taurine or betaine pretreatment on hepatotoxicity and prooxidant status induced by lipopolysaccharide treatment in the liver of rats

BACKGROUND

Taurine or betaine have been reported to have antioxidative potential and inhibit Kupffer cell activation. These effects may play an important role in their hepatoprotective effects. Therefore, they may also have protective effects in lipopolysaccharide hepatotoxicity by both inhibiting Kupffer cell activation and behaving as antioxidants.

DESIGN

The prophylactic efficiency of taurine or betaine pretreatment for the prevention of peroxidative changes induced by lipopolysaccharide treatment in the rat liver was investigated.

METHODS

Lipopolysaccharide (10 mg/kg intraperitoneally) was given to rats pretreated with taurine (1.5%, w/v) or betaine (1.5%, w/v) in drinking water for 4 weeks and plasma transaminase activities as well as hepatic malondialdehyde, diene conjugate (DC), glutathione, alpha-tocopherol and ascorbic acid levels, and superoxide dismutase (SOD) and glutathione peroxidase activities were determined.

RESULTS

Significant increases in plasma transaminase activities and hepatic malondialdehyde and DC levels and decreases in hepatic glutathione and alpha-tocopherol levels and SOD and glutathione peroxidase activities were observed 6 h after lipopolysaccharide treatment. This treatment did not alter ascorbic acid levels in the liver compared with controls. Taurine or betaine pretreatment in lipopolysaccharide-injected rats caused significant decreases in plasma transaminase activities and hepatic malondialdehyde and DC levels, and significant increases in glutathione and alpha-tocopherol (not betaine) levels without changing ascorbic acid levels and SOD and glutathione peroxidase activities in the liver.

CONCLUSIONS

Our findings clearly indicate that taurine or betaine pretreatment was effective in the prevention of lipopolysaccharide-induced hepatotoxicity and prooxidant status.

Protection of endotoxin-induced oxidative renal tissue damage of rats by vitamin E or/and EGb 761 treatment

The aim of the present study was to evaluate the possible protective effects of vitamin E and EGb 761 treatments, alone or in combination, against oxidative renal tissue damage in experimentally induced endotoxaemic rats. Fifty healthy male Wistar albino rats, weighing 150-250 g and averaging 12 weeks old, were allotted randomly into one of five experimental groups: A (untreated), B (endotoxaemic), C (endotoxaemic + vitamin E treated), D (endotoaxemic + EGb 761 treated) and E (endotoxaemic + vitamin E and EGb 761 treated), each containing ten animals. Group A received only an intraperitoneal (i.p.) injection of 2 ml of normal saline solution and served as the control. Groups B, C, D and E were administrated a single i.p. injection of 0.5 ml of endotoxin solution. In addition, groups C, D and E received i.p. injections of 600 mg kg(-1) body mt. of vitamin E and oral extract of 50 mg kg(-1) body wt. of EGb 761, alone or in combination, immediately after the endotoxin injection. The experiment lasted for 24 h. At the end of the experiment blood and tissue samples were obtained for biochemical and histopathological investigation. Endotoxin injection produced renal damage, increased lipid peroxidation and decreased antioxidant enzyme activity. Vitamin E or/and EGb 761 treatment decreased lipid peroxidation, increased antioxidant enzyme activity and also prevented renal tissue damage in experimentally induced endotoxaemic rats. In conclusion, vitamin E and EGb 761 treatment, alone or in combination, appears to be beneficial in preventing endotoxin-induced oxidative renal tissue damage and therefore shows potential for clinical use.

Protective Effects of Vitamin C, Alone or in Combination with Vitamin A, on Endotoxin-Induced Oxidative Renal Tissue Damage in Rats

This study was designed to investigate the protective effects of vitamin C and vitamin A on oxidative renal tissue damage. Male Wistar rats were given an intraperitoneal injection of 0.5 ml saline (control) or 0.5 ml solution of lipopolysaccharide (10 mg/kg), which caused endotoxemia. Immediately (within 5 min) after the endotoxin injection, the endotoxemic rats were untreated or treated with intraperitoneal injection of vitamin A (195 mg/kg bw), vitamin C (500 mg/kg bw) or their combination. After 24 hours, tissue and blood samples were obtained for histopathological and biochemical investigation. Endotoxin injection caused renal tissue damage and increased erythrocyte and tissue malondialdehyde (MDA) and serum nitric oxide (NO), urea and creatinine concentrations, but decreased the superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) activities compared to the parameters of control animals. Treatment with vitamin C or with vitamins C and A significantly decreased the MDA levels and serum NO, urea and creatinine levels, recovered the antioxidant enzyme activities (SOD, GSH-Px and CAT), and prevented the renal tissue damage in endotoxemic rats. In contrast, vitamin A alone did not change the altered parameters except for creatinine levels. Notably, the better effects were observed when vitamins A and C given together. It is concluded that vitamin C treatment, alone or its combination with vitamin A, may be beneficial in preventing endotoxin-induced oxidative renal tissue damage and shows potential for clinical use.

Progress in clinical neurosciences: sepsis-associated encephalopathy: evolving concepts

Systemic sepsis commonly produces brain dysfunction, sepsis-associated encephalopathy, which can vary from a transient, reversible encephalopathy to irreversible brain damage. The encephalopathy in the acute phase clinically resembles many metabolic encephalopathies: a diffuse disturbance in cerebral function with sparing of the brain stem. The severity of the encephalopathy, as reflected in progressive EEG abnormalities, often precedes then parallels dysfunction in other organs. Recent research has revealed a number of potentially important, non-mutually exclusive, mechanisms that have therapeutic implications.

Vitamin C as an antioxidant: evaluation of its role in disease prevention

Vitamin C in humans must be ingested for survival. Vitamin C is an electron donor, and this property accounts for all its known functions. As an electron donor, vitamin C is a potent water-soluble antioxidant in humans. Antioxidant effects of vitamin C have been demonstrated in many experiments in vitro. Human diseases such as atherosclerosis and cancer might occur in part from oxidant damage to tissues. Oxidation of lipids, proteins and DNA results in specific oxidation products that can be measured in the laboratory. While these biomarkers of oxidation have been measured in humans, such assays have not yet been validated or standardized, and the relationship of oxidant markers to human disease conditions is not clear. Epidemiological studies show that diets high in fruits and vegetables are associated with lower risk of cardiovascular disease, stroke and cancer, and with increased longevity. Whether these protective effects are directly attributable to vitamin C is not known. Intervention studies with vitamin C have shown no change in markers of oxidation or clinical benefit. Dose concentration studies of vitamin C in healthy people showed a sigmoidal relationship between oral dose and plasma and tissue vitamin C concentrations. Hence, optimal dosing is critical to intervention studies using vitamin C. Ideally, future studies of antioxidant actions of vitamin C should target selected patient groups. These groups should be known to have increased oxidative damage as assessed by a reliable biomarker or should have high morbidity and mortality due to diseases thought to be caused or exacerbated by oxidant damage.

Ascorbate inhibits iNOS expression in endotoxin- and IFN gamma-stimulated rat skeletal muscle endothelial cells

Lipopolysaccharide endotoxin and interferon-gamma induced inducible nitric oxide synthase (iNOS) protein expression and nitrite/nitrate formation in microvascular endothelial cell cultures (ECs) derived from rat skeletal muscle. Pretreatment of ECs with ascorbate accumulated a large amount of ascorbate inside the cells and consequently decreased both intracellular oxidant level and iNOS induction. These effects of ascorbate were abolished in the presence of exogenous superoxide generated by xanthine oxidase/xanthine plus catalase but were not altered when N-nitro-L-arginine methyl ester was applied to inhibit nitric oxide synthesis. Ascorbate also attenuated the activation of transcription factor IRF-1 but not NF kappa B. These results indicate that ascorbate inhibits iNOS expression in ECs by an antioxidant mechanism independent of both NF kappa B activation and the reported negative feedback effect of nitric oxide.

Sepsis inhibits reduction of dehydroascorbic acid and accumulation of ascorbate in astroglial cultures: intracellular ascorbate depletion increases nitric oxide synthase induction and glutamate uptake inhibition

Sepsis is associated with oxidative stress and impaired glutamatergic transmission in brain. We investigated whether sepsis impairs accumulation of the antioxidant, ascorbate, and uptake of glutamate by astrocytes. Bacterial endotoxin (Escherichia coli lipopolysaccharide, LPS) and the inflammatory cytokine, interferon-gamma (IFNgamma), were applied to primary astrocyte cultures to model sepsis. In the absence of ascorbate, the combination of LPS and IFNgamma (LPS + IFNgammay) up-regulated inducible nitric oxide synthase (iNOS) and decreased the initial rate of glutamate uptake by 50% within 24 h. Cell viability and facilitated glucose transport activity were not affected at 24 h. Pre-treatment with ascorbate-2-O-phosphate increased intracellular ascorbate concentration and attenuated the induction of iNOS and inhibition of glutamate uptake caused by LPS + IFNgamma. Subsequent experiments examined the mechanisms by which cells accumulate ascorbate. LPS + IFNy decreased slightly the initial rate of uptake of ascorbate and inhibited markedly the rate with which intracellular dehydroascorbic acid (DHAA) was reduced to ascorbate. We conclude that septic insult impairs astrocytic clearance of DHAA from the extracellular fluid and decreases intracellular ascorbate concentration. Furthermore, sepsis induces iNOS and inhibits glutamate uptake by astrocytes through mechanisms that can be modulated by intracellular ascorbate. These results indicate treatments that increase intracellular ascorbate concentration may be beneficial for patients at risk for neurologic complication in sepsis.

Ascorbate prevents microvascular dysfunction in the skeletal muscle of the septic rat

Septic patients have low plasma ascorbate concentrations and compromised microvascular perfusion. The purpose of the present experiments was to determine whether ascorbate improves capillary function in volume-resuscitated sepsis. Cecal ligation and perforation (CLP) was performed on male Sprague-Dawley rats. The concentration of ascorbate in plasma and urine, mean arterial blood pressure, and density of continuously perfused capillaries in the extensor digitorum longus muscle were measured 24 h after surgery. CLP caused a 50% decrease (from 56 +/- 4 to 29 +/- 2 microM) in plasma ascorbate concentration, 1,000% increase (from 46 +/- 13 to 450 +/- 93 microM) in urine ascorbate concentration, 20% decrease (from 115 +/- 2 to 91 +/- 2 mmHg) in mean arterial pressure, and 30% decrease (from 24 +/- 1 to 17 +/- 1 capillaries/mm) in the density of perfused capillaries, compared with time-matched controls. A bolus of intravenous ascorbate (7.6 mg/100 g body wt) administered immediately after the CLP procedure increased plasma ascorbate concentration and restored both blood pressure and density of perfused capillaries to control levels. In vitro experiments showed that ascorbate (100 microM) inhibited replication of bacteria and prevented hydrogen peroxide injury to cultured microvascular endothelial cells. These results indicate that ascorbate is lost in the urine during sepsis and that a bolus of ascorbate can prevent microvascular dysfunction in the skeletal muscle of septic animals. Our study supports the view that ascorbate may be beneficial for patients with septic syndrome.

Effect of natural antioxidants and apocynin on LPS-induced endotoxemia in rabbit

The objective of this study was to compare the prophylactic effects of the natural antioxidant from spinach (NAO) and apocynin, on the hepatic oxidative stress and liver damage induced by lipopolysaccharide (LPS). Male New Zealand rabbits were challenged with LPS with or without 8 days of antioxidant pretreatment. Pretreatment with NAO, but not apocynin, significantly (p < 0.05) decreased the levels of hydroperoxides and malondialdehyde (MDA) in the liver cytosolic fraction and the activity of NADPH oxidase-generated superoxide in the microsomal fraction, compared to LPS alone. The activity of glutathione peroxidase (G-POX) was significantly (p < 0.05) increased in the LPS-treated group, whereas treatment with NAO, but not apocynin, significantly (p < 0.05) decreased G-POX activity. Pretreatment with the same antioxidants had no significant effects on superoxide dismutase (SOD) activity, whereas an increased level of catalase (CAT) was obtained in all LPS-treated groups. TUNEL immunohistochemical staining in the LPS-treated animals indicated that there was no increase in apoptosis outside of necrotic foci. However, apoptotic hepatocytes were observed within areas of focal necrosis in animals exposed to LPS alone or LPS plus apocynin. Hepatocyte cell proliferation was tested by the proliferating-cell nuclear antigen (PCNA) tool, which indicated a proliferative effect in the LPS group, whereas the effect disappeared in the antioxidant-treated groups. The prophylactic effect of NAO on liver pathology and the significant decreases in lipid peroxidation products and NADPH oxidase activity suggest the use of NAO as an efficient strategy for treatment of endotoxemia.

Effects of antioxidants apocynin and the natural water-soluble antioxidant from spinach on cellular damage induced by lipopolysaccaride in the rat

Oxidative damage plays a key role in septic shock induced by the endotoxin lipopolysaccaride (LPS) by enhancing the formation of reactive oxygen species such as superoxide anion radicals, peroxides, and their secondary product, malondialdehyde, especially in the liver. In this study, histopathologic changes in several organs were compared among groups of male Wistar rats that had been injected with LPS following prophylactic pretreatment with either of 2 antioxidants, a group that had been injected with LPS without pretreatment with antioxidants, an untreated control group, and groups that had been injected with either of the 2 antioxidants only. The antioxidants used were a water-soluble natural antioxidant from spinach (NAO) and the NADPH oxidase inhibitor apocynin. Hematoxylin-and-eosin-stained slides were prepared, and lesions were semiquantitatively scored. Exposure to LPS alone was associated with multifocal hepatocellular necrosis and acute inflammation, thymic and splenic lymphoid necrosis, ocular retinal hemorrhage and acute endophthalmitis, adrenal medullary vacuolation and necrosis and acute inflammation, and decreased adrenal cortical cytoplasmic vacuolation (consistent with depletion of steroidal hormone contents). Results indicated that pretreatment with both antioxidants for 8 days reduced, in some organs, the necrotic and inflammatory changes associated with the LPS challenge. These findings suggest a potential therapeutic application for these antioxidants in clinical sepsis.

Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans

The current recommended dietary allowance (RDA) for vitamin C for adult nonsmoking men and women is 60 mg/d, which is based on a mean requirement of 46 mg/d to prevent the deficiency disease scurvy. However, recent scientific evidence indicates that an increased intake of vitamin C is associated with a reduced risk of chronic diseases such as cancer, cardiovascular disease, and cataract, probably through antioxidant mechanisms. It is likely that the amount of vitamin C required to prevent scurvy is not sufficient to optimally protect against these diseases. Because the RDA is defined as "the average daily dietary intake level that is sufficient to meet the nutrient requirement of nearly all healthy individuals in a group," it is appropriate to reevaluate the RDA for vitamin C. Therefore, we reviewed the biochemical, clinical, and epidemiologic evidence to date for a role of vitamin C in chronic disease prevention. The totality of the reviewed data suggests that an intake of 90-100 mg vitamin C/d is required for optimum reduction of chronic disease risk in nonsmoking men and women. This amount is about twice the amount on which the current RDA for vitamin C is based, suggesting a new RDA of 120 mg vitamin C/d.

Does vitamin C act as a pro-oxidant under physiological conditions?

Vitamin C readily scavenges reactive oxygen and nitrogen species and may thereby prevent oxidative damage to important biological macromolecules such as DNA, lipids, and proteins. Vitamin C also reduces redox active transition metal ions in the active sites of specific biosynthetic enzymes. The interaction of vitamin C with 'free', catalytically active metal ions could contribute to oxidative damage through the production of hydroxyl and alkoxyl radicals; whether these mechanisms occur in vivo, however, is uncertain. To examine this issue, we reviewed studies that investigated the role of vitamin C, both in the presence and absence of metal ions, in oxidative DNA, lipid, and protein damage. We found compelling evidence for antioxidant protection of lipids by vitamin C in biological fluids, animals, and humans, both with and without iron cosupplementation. Although the data on protein oxidation in humans are sparse and inconclusive, the available data in animals consistently show an antioxidant role of vitamin C. The data on vitamin C and DNA oxidation in vivo are inconsistent and conflicting, but some of the discrepancies can be explained by flaws in experimental design and methodology. These and other important issues discussed here need to be addressed in future studies of the role of vitamin C in oxidative damage.