Endogenous Antioxidant Defense Research Articles

Heme oxygenase-1-derived bilirubin protects endothelial cells against high glucose-induced damage

Hyperglycemia and diabetes are associated with endothelial cell dysfunction arising from enhanced oxidative injury, leading to the progression of diabetic vascular pathologies. The redox-sensitive transcription factor nuclear factor-E2-related factor 2 (Nrf2) is a master regulator of antioxidant genes, such as heme oxygenase-1 (HO-1), involved in cellular defenses against oxidative stress. We have investigated the pathways involved in high glucose-induced activation of HO-1 in endothelial cells and examined the molecular mechanisms underlying cytoprotection. Elevated d-glucose increased intracellular generation of reactive oxygen species (ROS), leading to nuclear translocation of Nrf2 and HO-1 expression in bovine aortic endothelial cells, with no changes in cell viability. Superoxide scavenging and inhibition of endothelial nitric oxide synthase (eNOS) abrogated upregulation of HO-1 expression by elevated glucose. Inhibition of HO-1 increased the sensitivity of endothelial cells to high glucose-mediated damage, while addition of bilirubin restored cell viability. Our findings establish that exposure of endothelial cells to high glucose leads to activation of endogenous antioxidant defense genes via the Nrf2/ARE pathway. Upregulation of HO-1 provides cytoprotection against high glucose-induced oxidative stress through the antioxidant properties of bilirubin. Modulation of the Nrf2 pathway in the early stages of diabetes may thus protect against sustained damage by hyperglycemia during progression of the disease.

A comprehensive overview of hepatoprotective natural compounds: mechanism of action and clinical perspectives.

Hepatoprotective effects of natural compounds have been frequently attributed to their antioxidant properties and the ability to mobilize endogenous antioxidant defense system. Because of involvement of oxidative stress in virtually all mechanisms of liver injury, it is a reasonable presumption that antioxidant properties of these compounds may play a key role in the mechanism of their hepatoprotective activity. Nevertheless, growing evidence suggests that other pharmacological activities of natural compounds distinct from antioxidant are responsible for their therapeutic effects. In this review, we discussed currently known molecular mechanisms of the hepatoprotective activity of 27 most intensively studied phytochemicals. These compounds have been shown to possess anti-inflammatory, antisteatotic, antiapoptotic, cell survival and antiviral activity through interference with multiple molecular targets and signaling pathways. Additionally, antifibrotic properties of phytochemicals have been closely associated with apoptosis of hepatic stellate cells and stimulation of extracellular matrix degradation. However, although these compounds exhibit a pronounced hepatoprotective effects in animal and cell culture models, the lack of clinical studies remains a bottleneck for their official acceptance by medical experts and physicians. Therefore, controlled clinical trials have an imperative in confirmation of the therapeutic activity of potentially hepatoprotective compounds. Understanding the principles of the hepatoprotective activity of phytochemicals could guide future drug development and help prevention of clinical trial failure. Also, the use of new delivery systems that enhances bioavailability of poorly water soluble compounds may improve the results already obtained. Most importantly, available data suggest that phytochemicals possess a various degree of modulation of specific signaling pathways, pointing out a need for usage of combinations of several hepatoprotective compounds in both experimental studies and clinical trials.

Anti-inflammatory Dietary Interventions and Supplements to Improve Performance during Athletic Training

Despite the numerous positive effects of physical exercise, some negative physiological changes occur in long-lasting heavy training with transient dysfunction of the immune system, increased inflammation, and oxidative stress. This is the case of elite athletes, who train intensively to compete at the highest levels. However, these athletes can counteract the negative effects of heavy training, reducing acute and chronic inflammations and supporting the immune system, with nutritional and supplementation countermeasures. For this purpose, macronutrient manipulation with an appropriate use of certain supplements can be considered as an intervention to reduce exercise-induced immune changes and inflammatory risk. For example, branched-chain amino acid (BCAA) supplementation may promote such immune responses in skeletal muscle. Furthermore, micronutrients play an important role in immune function; in particular, the antioxidant capacity of several dietary micronutrients (e.g., tocopherols, docosahexaenoate, and flavonoids) is very interesting to support the endogenous antioxidant defense systems of the athletes, counterbalancing the negative effects of oxidative damage due to free radicals. Some of these nutrients have potential anti-inflammatory properties as assessed by the attenuated levels of interleukin-6 (IL-6) and C-reactive protein (CRP).Key Teaching Points• Long-lasting heavy training plan and competition can lead to chronic immune suppression in athletes, increasing infection risk.• Chronic exercise increases mobilization of neutrophils, decreases mobilization of lymphocytes, and decreases the absolute and relative numbers of neutrophils at rest.• Nutritional deficiencies alter the immuno-system and increase infection risk.• Nutrition can influence exercise-induced immune suppression.• Elite athletes competing at the highest levels can benefit from nutritional and supplementation support to improve immunity and reduce acute and chronic inflammations.

Behavioural antioxidant strategies to cope with high temperatures: a study in a tropical butterfly

Exposure to high temperatures can disrupt the balance between the production of reactive oxygen species (ROS) and antioxidant defences. Animals may be able to correct such an imbalance physiologically by up-regulating endogenous antioxidant defences. They may also respond behaviourally by increasing the intake of dietary antioxidants (e.g. polyphenols) and/or by reducing physical activity (thereby decreasing ROS production). The use of a given antioxidant strategy is expected to depend on its associated cost/benefit ratio relative to that of other strategies. We found that captive Bicyclus anynana butterflies almost doubled polyphenol intake under hot conditions and reduced flight activity, while temperature did not affect endogenous antioxidant defences (as measured by superoxide dismutase activity) and did not increase oxidative damage. These results suggest that butterflies primarily respond to hot conditions by adjusting their behaviour, thereby avoiding an imbalance between ROS production and antioxidant defences (i.e. oxidative stress). Interestingly, butterflies increased polyphenol intake in the morning when they also consumed energy resources (sugar). Increasing polyphenol intake on hot mornings subsequently led to decreased sugar intake in the middle of the day, which may have contributed to reducing flight activity at that time. Overall, this suggests that B. anynana butterflies prioritized polyphenol intake over energy intake (and its associated benefits) under hot conditions. This prioritization might be risky under natural conditions where energy intake is more critical than in captivity. Therefore, further studies should examine whether animals also prioritize the behavioural adjustments that we observed here under conditions where the benefits associated with high energy intake are increased.

Prohibitin protects proximal tubule epithelial cells against oxidative injury through mitochondrial pathways

Oxidative stress mediated by reactive oxygen species (ROS) contributes to renal tubular atrophy and fibrosis following renal transplantation. Studies have shown that mitochondrial chaperone prohibitin (PHB) has antioxidant effects. Here we used the human renal proximal tubule epithelial cell line, HK-2 cells as an in vitro model to assess the role of PHB in hydrogen peroxide (H2O2)-induced renal tubular oxidative injury. Our results showed that H2O2 treatment inhibited PHB expression in a time-dependent manner in HK-2 cells. PHB overexpression could protect cell from oxidative stress-induced injury by inhibiting H2O2-induced cell apoptosis and intracellular ROS generation and promoting endogenous antioxidant defense components including glutathione peroxidase, catalase, superoxide dismutase, and glutathione. Furthermore, oxidative stress-induced cell injury was suppressed in PHB-overexpressed tubule epithelial cells through mitochondria-mediated pathway, including inhibition of mitochondrial uncoupling protein 2 or UCP2 and Bax expression, mitochondrial ROS production, promotion of ATP production and Bcl-2 expression, inhibition of mitochondrial membrane potential loss and release of cytochrome c from mitochondria to cytoplasm, and followed by caspase-3 activation. Meanwhile, inhibition of PHB expression by small interference RNA resulted in less resistance of HK-2 cells to H2O2 toxicity as shown in decreased cell viability, increased apoptosis, ROS production, and mitochondrial dysfunction. These data indicated that PHB protected the tubule epithelial cells from oxidative stress-induced damage through the inhibition of oxidative damage, mitochondria dysfunction, and ultimately inhibition of cell apoptosis, and that increasing PHB content in mitochondria constituted a new therapeutic target for transient ischemic injury and chronic allograft nephropathy or CAN following renal transplantation.

Quercetin increases stress resistance in the yeast Saccharomyces cerevisiae not only as an antioxidant

Quercetin is one of the most abundant dietary flavonoids and one of the most studied antioxidants. In this work, the effect of quercetin on stress resistance of exponentially growing Saccharomyces cerevisiae cells was estimated. Pre-treatment with low concentrations (10 μM and 100 μM) of quercetin enhanced yeast viability under exposure to hydrogen peroxide, copper ions (Cu2+), and heat shock. The stress-protective effects of quercetin were not connected with involvement of oxidative stress regulator Yap1p, or with induction of endogenous antioxidant defense. However, pre-treatment of wild type and ∆yap1 strains with quercetin prevented protein oxidation and antioxidant enzyme inactivation in yeast cells under H2O2-induced oxidative stress. Cycloheximide—an inhibitor of mRNA translation—or a deficiency in the transcriptional regulators Msn2p and Msn4p abolished the protective effects of low concentrations of quercetin against H2O2 toxicity. It was shown in vitro that quercetin can scavenge H2O2 and produce low amounts of H2O2 in a pH-dependent manner. The antioxidant-related and antioxidant-independent mechanisms of quercetin effects are discussed.

Curcumin Attenuates Iron Accumulation and Oxidative Stress in the Liver and Spleen of Chronic Iron-Overloaded Rats.

ObjectivesIron overload is now recognized as a health problem in industrialized countries, as excessive iron is highly toxic for liver and spleen. The potential use of curcumin as an iron chelator has not been clearly identified experimentally in iron overload condition. Here, we evaluate the efficacy of curcumin to alleviate iron overload-induced hepatic and splenic abnormalities and to gain insight into the underlying mechanisms.Design and MethodsThree groups of male adult rats were treated as follows: control rats, rats treated with iron in a drinking water for 2 months followed by either vehicle or curcumin treatment for 2 more months. Thereafter, we studied the effects of curcumin on iron overload-induced lipid peroxidation and anti-oxidant depletion.ResultsTreatment of iron-overloaded rats with curcumin resulted in marked decreases in iron accumulation within liver and spleen. Iron-overloaded rats had significant increases in malonyldialdehyde (MDA), a marker of lipid peroxidation and nitric oxide (NO) in liver and spleen when compared to control group. The effects of iron overload on lipid peroxidation and NO levels were significantly reduced by the intervention treatment with curcumin (P<0.05). Furthermore, the endogenous anti-oxidant activities/levels in liver and spleen were also significantly decreased in chronic iron overload and administration of curcumin restored the decrease in the hepatic and splenic antioxidant activities/levels.ConclusionOur study suggests that curcumin may represent a new horizon in managing iron overload-induced toxicity as well as in pathological diseases characterized by hepatic iron accumulation such as thalassemia, sickle cell anemia, and myelodysplastic syndromes possibly via iron chelation, reduced oxidative stress derived lipid peroxidation and improving the body endogenous antioxidant defense mechanism.

Neolignans from Aristolochia fordiana Prevent Oxidative Stress-Induced Neuronal Death through Maintaining the Nrf2/HO-1 Pathway in HT22 Cells.

Bioassay-guided fractionation of the ethanolic extract of the stems of Aristolochia fordiana led to the isolation of six new dihydrobenzofuran neolignans (1-3 and 7-9), three new 2-aryldihydrobenzofurans (4-6), a new 8-O-4' neolignan (10), and 14 known analogues (11-24). The structures of compounds 1-10 were established by spectroscopic methods, and their absolute configurations were determined by analyses of the specific rotation and electronic circular dichroism data. The neuroprotective effects of compounds 1-24 against glutamate-induced cell death were tested in hippocampal neuronal cell line HT22. Compounds 17 and 20-24 exhibited moderate neuroprotective activity by increasing the endogenous antioxidant defense system. In addition, the neolignans activated the Nrf2 (nuclear factor E2-related factor 2) pathway, resulting in the increase of the expression of endogenous antioxidant protein HO-1 (heme oxygenase-1). The active compounds also preserved the levels of antiapoptotic protein Bcl-2 (B cell lymphoma/leukemia-2), which was decreased by glutamate. Collectively, these results suggested that the active neolignans protect neurons against glutamate-induced cell death through maintaining the Nrf2/HO-1 signaling pathway as well as preserving the Bcl-2 protein and might be promising novel beneficial agents for oxidative stress-associated diseases.

Nrf2 activators modulate oxidative stress responses and bioenergetic profiles of human retinal epithelial cells cultured in normal or high glucose conditions

Retinal pigment epithelial cells exert an important supporting role in the eye and develop adaptive responses to oxidative stress or high glucose levels, as observed during diabetes. Endogenous antioxidant defences are mainly regulated by Nrf2, a transcription factor that is activated by naturally-derived and electrophilic compounds. Here we investigated the effect of the Nrf2 activators dimethylfumarate (DMF) and carnosol on antioxidant pathways, oxygen consumption rate and wound healing in human retinal pigment epithelial cells (ARPE-19) cultured in medium containing normal (NG, 5mM) or high (HG, 25mM) glucose levels. We also assessed wound healing using an in vivo corneal epithelial injury model. We found that Nrf2 nuclear translocation and heme oxygenase activity increased in ARPE cells treated with 10μM DMF or carnosol irrespective of glucose culture conditions. However, HG rendered retinal cells more sensitive to regulators of glutathione synthesis or inhibition and caused a decrease of both cellular and mitochondrial reactive oxygen species. Culture in HG also reduced ATP production and mitochondrial function as measured with the Seahorse XF analyzer and electron microscopy analysis revealed morphologically damaged mitochondria. Acute treatment with DMF or carnosol did not restore mitochondrial function in HG cells; conversely, the compounds reduced cellular maximal respiratory and reserve capacity, which were completely prevented by N-acetylcysteine thus suggesting the involvement of thiols in this effect. Interestingly, the scratch assay showed that wound closure was faster in cells cultured in HG than NG and was accelerated by carnosol. This effect was reversed by an inhibitor of heme oxygenase activity. Moreover, topical application of carnosol to the cornea of diabetic rats significantly accelerated wound healing. In summary, these data indicate that culture of retinal epithelial cells in HG does not affect the activation of the Nrf2/heme oxygenase axis but influences other crucial oxidative and mitochondrial-dependent cellular functions. The additional effect on wound closure suggests that results obtained in in vitro experimental settings need to be carefully evaluated in the context of the glucose concentrations used in cell culture.

Role of oxidant–antioxidant imbalance in the pathogenesis of chronic obstructive pulmonary disease

BackgroundChronic obstructive pulmonary disease (COPD) is a common respiratory condition involving the airways and characterized by airflow limitation. Antioxidants are substances that may protect cells from the damage caused by unstable molecules known as free radicals. Antioxidants interact with and stabilize free radicals and may prevent some of the damage free radicals might otherwise cause. Under physiological conditions a balance exists between the amount of reactive oxygen species (ROS) produced in normal cellular metabolism and the endogenous antioxidant defense. An imbalance between the antioxidant capacity and the production of reactive oxygen species leads to oxidative stress, which is associated with the pathogenesis of several human diseases. An oxidant/antioxidant imbalance has been proposed as having a key role in the pathogenesis of COPD. The lung is directly exposed to high levels of oxygen, and therefore has to have efficient antioxidant mechanisms. Aim of the studyTo examine the role of altered levels of oxidant–antioxidants in disease severity of COPD and correlate it with the degree of airflow obstruction in the Egyptian population. Subjects and methodsEighty subjects with COPD, 20 healthy smokers, and 20 healthy nonsmokers participated in this study. The investigation included determination of the lung function and the measurements of plasma superoxide dismutase activity (SOD), glutathione content (GSH) reduced form, glutathione peroxidase activity (GSH-Px), catalase activity (CAT), lipid peroxidase (LP), and nitric oxide (NO). ResultsThe mean concentration of nitric oxide (NO) was significantly higher in the control subjects (smokers and nonsmokers) compared with the COPD group (p=0.001, 0.0001) respectively. Also the mean concentration of nitric oxide (NO) was significantly higher in control nonsmoker group compared to control smoker group (p=0.002). The mean concentration of lipid peroxidase (LP) was significantly higher in COPD patients compared with control subjects (smokers and nonsmokers), (p=0.0001, 0.0001) respectively. The mean concentration of glutathione (GSH) was significantly higher in the control subjects (smokers and nonsmokers) compared with COPD patients (p=0.001, 0.001) respectively. There is no significant difference in the concentration of glutathione-peroxidase (GSH-Px) in all study participants (COPD patients, control smokers, control nonsmokers). The mean concentration of catalase (CAT) was significantly higher in control nonsmokers, compared to COPD patients and control smokers (p=0.001, 0.018) respectively. The mean concentration of superoxide dismutase (SOD) was significantly higher in the control subjects (smokers and nonsmokers) compared with COPD patients (p=0.012, 0.001) respectively. Also the mean concentration of superoxide dismutase (SOD) was significantly higher in control nonsmoker group compared to control smoker group (p=0.001). ConclusionThese results support the hypothesis that an oxidant–antioxidant imbalance, associated with oxidative stress in COPD patients, plays an important role in the progression of disease severity, also these results revealed the presence of an oxidative presence in smokers and in subjects with COPD and that the imbalance may be important in the pathogenesis of this disease. The use of cigarette increased oxidative stress by causing plasma lipid peroxidation and imbalance in erythrocyte antioxidant. Nitric oxide (NO) metabolism was not increased in patients with chronic obstructive pulmonary disease compared to healthy subjects. It has been reported that GSH plays a major role in pulmonary antioxidant protection.

An Antioxidant Dietary Supplement Improves Brain-Derived Neurotrophic Factor Levels in Serum of Aged Dogs: Preliminary Results.

Biological aging is characterized by a progressive accumulation of oxidative damage and decreased endogenous antioxidant defense mechanisms. The production of oxidants by normal metabolism damages proteins, lipids, and nucleotides, which may contribute to cognitive impairment. In this study 36 dogs were randomly divided into four groups and fed croquettes of different compositions for 6 months. We monitored derivatives of reactive oxygen metabolites (dROMs) and biological antioxidant potential (BAP) levels in dogs' plasma samples as well as brain-derived neurotrophic factor (BDNF) serum levels at the beginning and at the end of the dietary regime. Our results showed that a dietary regime, enriched with antioxidants, induced a significant decrease of plasma levels of dROMs (p < 0.005) and a significant increase in BDNF serum levels (p < 0.005) after six months. Thus, we hypothesized a possible role of the diet in modulating pro- and antioxidant species as well as BDNF levels in plasma and serum, respectively. In conclusion the proposed diet enriched with antioxidants might be considered a valid alternative and a valuable strategy to counteract aging-related cognitive decline in elderly dogs.

Cell type-specific Nrf2 expression in multiple sclerosis lesions.

Oxidative injury appears to play a major role in the propagation of demyelination and neurodegeneration in multiple sclerosis (MS). It has been suggested that endogenous anti-oxidant defense mechanisms within MS lesions are insufficient to prevent spreading of damage. Thus, current therapeutic approaches (e.g., fumarate treatment) target to up-regulate the expression of a key regulator of anti-oxidative defense, the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). In this study, we show that Nrf2 is already strongly up-regulated in active MS lesions. Nuclear Nrf2 expression was particularly observed in oligodendrocytes and its functional activity is indicated by the expression of one of its downstream targets (heme oxygenase 1) in the same cells. In contrast, only a minor number of Nrf2-positive neurons were detected, even in highly inflammatory cortical lesions presenting with extensive oxidative injury. Overall, the most pronounced Nrf2 expression was found in degenerating cells, which showed signs of apoptotic or necrotic cell death. Via whole-genome microarray analyses of MS lesions, we observed a differential expression of numerous Nrf2-responsive genes, also involved in the defense against oxidative stress, predominantly in areas of initial myelin destruction within actively demyelinating white matter lesions. Furthermore, the expression patterns of Nrf2-induced genes differed between the white matter and cortical gray matter. Our study shows that in the MS brain, Nrf2 expression varies in different cell types and is associated with active demyelination in the lesions.Electronic supplementary materialThe online version of this article (doi:10.1007/s00401-015-1452-x) contains supplementary material, which is available to authorized users.

Influence of Spirulina platensis exudates on the endocrine and nervous systems of a mammalian model

ObjectiveTo investigate the effect of intra-peritoneal injection of purified exudates of axenic Spirulina platensis on the mammalian endocrine and nervous systems. MethodsThe intra-peritoneal injection of the cyanobacterial exudates in mice was applied. Sex hormonal levels of testosterone and progesterone were measured using radioimmunoassay while the follicular stimulating hormone and luteinizing hormone were evaluated by direct chemiluminescence. In addition, superoxide dismutase, catalase and glutathione peroxidase were monitored in the hippocampus region using spectrophotometric method. The levels of the hippocampal monoamines, dopamine, noradrenaline and serotonin were analyzed by high performance liquid chromatography while the acetyl choline neurotransmitter was measured by colorimetric method using choline/acetylcholine assay kit. ResultsA sharp disruption in the sex hormones levels of testosterone, progesterone, follicular stimulating hormone and luteinizing hormone was demonstrated in the serum of the treated mice. At the same time, a significant reduction in the endogenous antioxidant defense enzymes, superoxide dismutase, catalase and glutathione peroxidase was observed in the hippocampus region of the injected mice. Moreover, levels of dopamine, noradrenaline, serotonin and acetyl choline neurotransmitter in the same region were significantly affected as a result of the treatment with Spirulina filtrate. The gas chromatography–mass spectrometer and liquid chromatography mass spectrometry/mass spectrometry analysis showed the presence of some sterol-like compounds in the cyanobacterial filtrate. ConclusionsThis study demonstrated the capability of Spirulina to release detrimental bioactive metabolites into their surrounding that can disrupt the mammalian endocrine and nervous systems.

Selective induction of oxidative stress in cancer cells via synergistic combinations of agents targeting redox homeostasis

Cancer cell resistance to chemotherapy is still a heavy burden that impairs the response of many cancer patients to conventional chemotherapy. Using drug combinations is one therapeutic approach to overcome the developing resistance to any one drug. Oxidative stress is now a generally regarded hallmark of cancer that can be one approach to selectively target cancer cells while sparing normal cells. With the aim of increasing oxidative stress in cancer cells to a lethal set point, we have generated and combined several series of redox active compounds that act at different points of the cellular oxidative cascade. The premise of such combinations is to deplete of endogenous antioxidant defence proteins (e.g., Glutathione) while concomitantly increasing the generation of ROS via metal redox recycling and Fenton chemistry which eventually leads to the disruption of cellular redox homeostasis and induction of cell death. Through this approach, we have identified highly synergistic combinations of two distinctive classes of compounds (Azines and Copper(II) complexes of 2-pyridyl ketone thiosemicarbazones) which are capable of eliminating cancer cells without concomitant increase in toxicity toward normal cells. In one of our most potent combinations, a combination index (CI) value of 0.056 was observed, representing a 17 fold enhancement in activity beyond additive effects. Such new combination regimen of redox active compounds can be one step closer to potentially safer low dose chemotherapy.

Glutaredoxin 1 (Grx1) Protects Human Retinal Pigment Epithelial Cells From Oxidative Damage by Preventing AKT Glutathionylation.

Glutaredoxin 1 (Grx1) belongs to the oxidoreductase family and is a component of the endogenous antioxidant defense system. However, its physiological function remains largely unknown. In this study, we investigated whether and how Grx1 overexpression protects the retinal pigment epithelial (RPE) cells against H2O2-induced apoptosis. Human retinal pigment epithelial (ARPE-19) cells were transfected with either a Grx1-containing plasmid or an empty vector. Primary human RPE cells were transfected with Grx1 small interfering RNA (siRNA) or scrambled siRNA. Cell viability was measured with the WST8 assay. Apoptosis was quantitatively measured by annexin V/propidium iodide (PI) double staining. The level of protein glutathionylation (PSSG) was measured by immunoblotting using anti-PSSG antibody. Protein kinase B (AKT) activation was examined by Western blot. Protein kinase B glutathionylation was detected by immunoprecipitation followed by immunoblotting with anti-PSSG antibody. Glutaredoxin 1 overexpression protected ARPE-19 cells from H2O2-induced cell viability loss. Conversely, Grx1 gene knockdown sensitized primary human RPE cells to H2O2. Assessment of apoptosis indicated that cells transfected with the Grx1-containing plasmid were more resistant to H2O2 with fewer cells undergoing apoptosis as compared to empty vector-transfected cells. Hydrogen peroxide-induced PSSG accumulation was also attenuated by Grx1 enrichment. Furthermore, Grx1 overexpression prevented H2O2-induced AKT glutathionylation, resulting in a sustained phospho-AKT elevation in RPE cells. Glutaredoxin 1 can protect RPE cells against oxidative stress-induced apoptosis. The mechanism of this protection is associated with its ability to stimulate the phosphorylation of AKT by preventing AKT glutathionylation. Considering Grx1's protective abilities in RPE cells, Grx1 could be a potential pharmacological target for retinal degenerative diseases.

In vivo systemic chlorogenic acid therapy under diabetic conditions: Wound healing effects and cytotoxicity/genotoxicity profile

Oxidative stress occurs following the impairment of pro-oxidant/antioxidant balance in chronic wounds and leads to harmful delays in healing progress. A fine balance between oxidative stress and endogenous antioxidant defense system may be beneficial for wound healing under redox control. This study tested the hypothesis that oxidative stress in wound area can be controlled with systemic antioxidant therapy and therefore wound healing can be accelerated. We used chlorogenic acid (CGA), a dietary antioxidant, in experimental diabetic wounds that are characterized by delayed healing. Additionally, we aimed to understand possible side effects of CGA on pivotal organs and bone marrow during therapy. Wounds were created on backs of streptozotocin-induced diabetic rats. CGA (50 mg/kg/day) was injected intraperitoneally. Animals were sacrificed on different days. Biochemical and histopathological examinations were performed. Side effects of chronic antioxidant treatment were tested. CGA accelerated wound healing, enhanced hydroxyproline content, decreased malondialdehyde/nitric oxide levels, elevated reduced-glutathione, and did not affect superoxide dismutase/catalase levels in wound bed. While CGA induced side effects such as cyto/genotoxicity, 15 days of treatment attenuated blood glucose levels. CGA decreased lipid peroxidation levels of main organs. This study provides a better understanding for antioxidant intake on diabetic wound repair and possible pro-oxidative effects.

Incretins Increase the Tissue Level of Endogenous Antioxidants in Experimental Diabetes Mellitus

Diabetes‐induced angiopathy is caused by chronic hyperglycemia via increased tissue level of free radicals. A decrease in the tissue levels of free radicals or elevation of the tissue concentration of endogenous antioxidant defense system can prevent or delay diabetes‐induced complications. The aim of the study was to examine the effect of incretins on selected markers of the antioxidant system (catalase, dismutase and glutathione reductase) in streptozotocin‐induced diabetic rats using immunohistochemical techniques. The extent of glutathione peroxidase gene expression was also determined in the pancreas of control and GLP‐1 or exenatide‐treated rats. The administration of GLP‐1 and exenatide caused large and significant (p&lt;0.05) increases in the number of catalase‐immunopositive cells in incretin‐treated rats when compared to untreated diabetic controls. The percentage number of glutathione reductase‐ and dismutase‐immunoreactive cells was significantly increased (p&lt;0.05) in diabetic animals treated with either GLP‐1 or exenatide compared to those of untreated diabetic rats. Morphological studies showed that catalase, dismutase and glutathione reductase co‐localized with insulin in pancreatic beta cells. GLP‐1 and exenatide caused marked (p&lt;0.05) elevations in the tissue level of glutathione peroxidase gene expression when compared to that of untreated control. In conclusion, incretin‐induced increase in the tissue level of endogenous antioxidants may play an important role in the protection of the pancreatic beta cell.

Phenolic Extracts of Cranberry Positively Modulate Endogenous Antioxidant Defenses and Signalling Pathways Against Oxidative Challenge

Oxidative stress and reactive oxygen species (ROS)‐mediated cell damage are implicated in various chronic pathologies. Emerging studies show polyphenols may act by increasing endogenous antioxidant defense potential. Cranberry has one of the highest polyphenols content among commonly consumed fruits. In this study, hepato‐protective activity of two cranberry extracts (CP1 and CP2) against oxidative challenge were screened using HepG2 cells, looking at ROS production, intracellular non‐enzymatic and enzymatic defenses by reduced glutathione concentration (GSH), glutathione peroxidase (GPx) and glutathione reductase (GR) activity and lipid peroxidation biomarker malondialdehyde (MDA). Both extracts in basal conditions did not affect cell viability but decreased ROS production and increased GPx activity, conditions that may place the cells in favorable conditions against oxidative stress. Extracts pre‐treatment of HepG2 cells for 20h significantly reduced (tert‐butylhydroperoxide (t‐BOOH)‐induced cell damage compared to untreated cells. Both extracts (5‐50ug/ml) reduced t‐BOOH‐induced increase of MDA by 20 % (CP1) and 25 % (CP2), and significantly reduced increase in GPx and GR. CP2 prevented a reduction in GSH and significantly reduced ROS production. CP1 reverted the t‐BOOH‐induced increase in p‐JNK. This study demonstrates that cranberry polyphenols may help protect liver cells against oxidative insult by modulating GSH concentration, ROS and MDA generation, antioxidant enzymes activity and cell signaling pathways. Funded by Ocean Spray Cranberries.

Chicory (Cichorium intybus L.) root extract regulates the oxidative status and antioxidant gene transcripts in CCl4-induced hepatotoxicity.

The ability of Cichorium intybus root extract (chicory extract) to protect against carbon tetrachloride (CCl4)-induced oxidative stress and hepatotoxicity was evaluated in male rats. The rats were divided into four groups according to treatment: saline (control); chicory extract (100 mg/kg body weight daily, given orally for 2 weeks); CCl4 (1 ml/kg body weight by intraperitoneal injection for 2 consecutive days only); or chicory extract (100 mg/kg body weight daily for 2 weeks) + CCl4 injection on days 16 and 17. The levels of hepatic lipid peroxidation, antioxidants, and molecular biomarkers were estimated twenty-four hours after the last CCl4 injection. Pretreatment with chicory extract significantly reduced CCl4-induced elevation of malondialdehyde levels and nearly normalized levels of glutathione and activity of glutathione S-transferase, glutathione peroxidase (GPx), glutathione reductase, catalase (CAT), paraoxonase-1 (PON1), and arylesterase in the liver. Chicory extract also attenuated CCl4-induced downregulation of hepatic mRNA expression levels of GPx1, CAT and PON1 genes. Results of DNA fragmentation support the ability of chicory extract to ameliorate CCl4-induced liver toxicity. Taken together, our results demonstrate that chicory extract is rich in natural antioxidants and able to attenuate CCl4-induced hepatocellular injury, likely by scavenging reactive free radicals, boosting the endogenous antioxidant defense system, and overexpressing genes encoding antioxidant enzymes.

NRF2 promotes neuronal survival in neurodegeneration and acute nerve damage.

Oxidative stress contributes to the loss of neurons in many disease conditions as well as during normal aging; however, small-molecule agents that reduce oxidation have not been successful in preventing neurodegeneration. Moreover, even if an efficacious systemic reduction of reactive oxygen and/or nitrogen species (ROS/NOS) could be achieved, detrimental side effects are likely, as these molecules regulate normal physiological processes. A more effective and targeted approach might be to augment the endogenous antioxidant defense mechanism only in the cells that suffer from oxidation. Here, we created several adeno-associated virus (AAV) vectors to deliver genes that combat oxidation. These vectors encode the transcription factors NRF2 and/or PGC1a, which regulate hundreds of genes that combat oxidation and other forms of stress, or enzymes such as superoxide dismutase 2 (SOD2) and catalase, which directly detoxify ROS. We tested the effectiveness of this approach in 3 models of photoreceptor degeneration and in a nerve crush model. AAV-mediated delivery of NRF2 was more effective than SOD2 and catalase, while expression of PGC1a accelerated photoreceptor death. Since the NRF2-mediated neuroprotective effects extended to photoreceptors and retinal ganglion cells, which are 2 very different types of neurons, these results suggest that this targeted approach may be broadly applicable to many diseases in which cells suffer from oxidative damage.