(–)-Epicatechin 3-O-gallate ameliorates the damages related to peroxynitrite production by mechanisms distinct from those of other free radical inhibitors

Camellia sinensis in asymptomatic hyperuricemia: A meta-analysis of tea or tea extract effects on uric acid levels

Flavanols of Camellia sinensis exhibit uric acid (UA) lowering effect, through the modulation of both xanthine oxidase and urate excretion. In order to investigate the potential benefit of Camellia Sinenis products in asymptomatic hyperuricemia, a meta-analysis of long-term Randomized Controlled Trials (RCT) with tea or tea extract has been conducted. From 20 human intervention studies selected only 5 RCT (13 interventions) were suitable for meta-analysis (n = 472). The current "normal" range set for hyperuricemia fails to identify patients with potential metabolic disorders. Therefore on the basis of the literature data, we fixed cut-off limits for UA baseline levels of 4.5 mg/dl for women, 6.1 mg/dl for men, and 5.5 mg/dl for studies involving mixed populations. Statistically significant effects were not found, but subgroup analysis revealed that the Pooled Estimate effect was different in subjects with baseline levels under [MD (95% CI): 0.1078 (-0.0528 to 0.2684)] and over the cut-off [MD (95% CI): -0.0239 (0.3311 to 0.2833)]. However, due to the low number of RCT and to the lack of data on bioavailability, it is difficult to draw any firm conclusion and more studies are needed to establish if tea flavanols could be useful in asymptomatic hyperuricemia treatment.

Green Tea and Bone Marrow Transplantation: From Antioxidant Activity to Enzymatic and Multidrug-resistance Modulation

Epigallocatechin-3-gallate (EGCG), the main flavonoid of green tea (GT), could play an active role in the prevention of oxidative-stress-related diseases, such as hematologic malignancies. Some effects of EGCG are not imputable to antioxidant activity, but involve modulation of antioxidant enzymes and uric acid (UA) levels. The latter is the major factor responsible of the plasma non-enzymatic antioxidant capacity (NEAC). However, hyperuricemia is a frequent clinical feature caused by tumor lysis syndrome or cyclosporine side effects, both before and after bone marrow transplantation (BMT). Besides this, food-drug interactions could be associated with GT consumption and could have clinical implications. The molecular mechanisms involved in the redox and drug metabolizing/transporting pathways were discussed, with particular reference to the potential role of GT and EGCG in BMT. Moreover, on reviewing data on NEAC, isoprostanes, uric acid, and various enzymes from human studies on GT, its extract, or EGCG, an increase in NEAC, without effect on isoprostanes, and contrasting results on UA and enzymes were observed. Currently, few and contrasting available evidences suggest caution for GT consumption in BMT patients and more studies are needed to better understand the potential impact of EGCG on oxidative stress and metabolizing/transporting systems.

The Peroxidation of Leukocytes Index Ratio Reveals the Prooxidant Effect of Green Tea Extract

Despite tea increased plasma nonenzymatic antioxidant capacity, the European Food Safety Administration (EFSA) denied claims related to tea and its protection from oxidative damage. Furthermore, the Supplement Information Expert Committee (DSI EC) expressed some doubts on the safety of green tea extract (GTE). We performed a pilot study in order to evaluate the effect of a single dose of two capsules of a GTE supplement (200 mg × 2) on the peroxidation of leukocytes index ratio (PLIR) in relation to uric acid (UA) and ferric reducing antioxidant potential (FRAP), as well as the sample size to reach statistical significance. GTE induced a prooxidant effect on leukocytes, whereas FRAP did not change, in agreement with the EFSA and the DSI EC conclusions. Besides, our results confirm the primary role of UA in the antioxidant defences. The ratio based calculation of the PLIR reduced the sample size to reach statistical significance, compared to the resistance to an exogenous oxidative stress and to the functional capacity of oxidative burst. Therefore, PLIR could be a sensitive marker of redox status.

Mitochondria: a new therapeutic target in chronic kidney disease

Cellular metabolic changes during chronic kidney disease (CKD) may induce higher production of oxygen radicals that play a significant role in the progression of renal damage and in the onset of important comorbidities. This condition seems to be in part related to dysfunctional mitochondria that cause an increased electron "leakage" from the respiratory chain during oxidative phosphorylation with a consequent generation of reactive oxygen species (ROS). ROS are highly active molecules that may oxidize proteins, lipids and nucleic acids with a consequent damage of cells and tissues. To mitigate this mitochondria-related functional impairment, a variety of agents (including endogenous and food derived antioxidants, natural plants extracts, mitochondria-targeted molecules) combined with conventional therapies could be employed. However, although the anti-oxidant properties of these substances are well known, their use in clinical practice has been only partially investigated. Additionally, for their correct utilization is extremely important to understand their effects, to identify the correct target of intervention and to minimize adverse effects. Therefore, in this manuscript, we reviewed the characteristics of the available mitochondria-targeted anti-oxidant compounds that could be employed routinely in our nephrology, internal medicine and renal transplant centers. Nevertheless, large clinical trials are needed to provide more definitive information about their use and to assess their overall efficacy or toxicity.

Polychlorinated biphenyls impair blood–brain barrier integrity via disruption of tight junction proteins in cerebrum, cerebellum and hippocampus of female Wistar rats

Polychlorinated biphenyls (PCBs) comprise a ubiquitous class of toxic substances associated with carcinogenic and tumor-promoting effects as well as neurotoxic properties. Reactive oxygen species, which is produced from PCBs, alters blood–brain barrier (BBB) integrity, which is paralleled by cytoskeletal rearrangements and redistribution and disappearance of tight junction proteins (TJPs) like claudin-5 and occludin. Quercetin, a potent antioxidant present in onion and other vegetables, appears to protect brain cells against oxidative stress, a tissue-damaging process associated with Alzheimer’s and other neurodegenerative disorders. The aim of this study is to analyze the role of quercetin on oxidative stress markers and transcription of transmembrane and cytoplasmic accessory TJPs on cerebrum, cerebellum and hippocampus of female rats exposed to PCBs. Rats were divided into the following four groups. Group I: received only vehicle (corn oil) intraperitoneally (i.p.); group II: received Aroclor 1254 at a dose of 2 mg/kg body weight (bwt)/day (i.p); group III: received Aroclor 1254 (i.p.) and simultaneously quercetin 50 mg/kg bwt/day through gavage and group IV: received quercetin alone gavage. From the experiment, the levels of hydrogen peroxide, lipid peroxidation and thiobarbituric acid reactive substances were observed to increase significantly in cerebrum, cerebellum and hippocampus as 50%, 25% and 20%, respectively, after exposure to PCB, and the messenger RNA expression of TJP in rats exposed to PCBs is decreased and is retrieved to the normal level simultaneously in quercetin-treated rats. Hence, quercetin can be used as a preventive medicine to PCBs exposure and prevents neurodegenerative disorders.

Effect of Quercetin on Haematobiochemical and Histological Changes in the Liver of Polychlorined Biphenyls-Induced Adult Male Wistar Rats

Polychlorinated biphenyls exposure damages the rat liver cells. Hematological parameters such as hemoglobin, packed cell volume, red-blood cells, white-blood cells, neutrophils, platelet counts, and RBC indices were significantly decreased. Polymorphs, eosinophil counts, and erythrocyte sedimentation rate were significantly increased. Serum liver enzymes such as aspartate transaminase, alanine transaminase, alkaline phosphatase, and gamma-glutamyl transferase were increased by PCBs treatment. Serum lipid profiles such as cholesterol, triglycerides, low-density lipoproteins and very-low-density lipoproteins were increased in PCBs-treated rats. High-density lipoprotein, total protein, albumin, globulin levels, and albumin/globulin ratio were also decreased after PCB exposure. Then levels of sodium, potassium, chloride, and bicarbonate were also altered. Serum glucose levels were increased along with total bilirubin after PCBs exposure. Simultaneous quercetin supplementation significantly protected the PCBs-induced changes of hematobiochemical parameters. Thus, quercetin shows a protective role against PCBs-induced alterations in the hematological and biochemical parameters.

Green Tea Polyphenols for the Protection against Renal Damage Caused by Oxidative Stress

Green tea, prepared from the leaves of Camellia sinensis L., is a beverage that is popular worldwide. Polyphenols in green tea have been receiving much attention as potential compounds for the maintenance of human health due to their varied biological activity and low toxicity. In particular, the contribution of antioxidant activity to the prevention of diseases caused by oxidative stress has been focused upon. Therefore, in this study, we investigated the effects of (−)-epigallocatechin 3-O-gallate and (−)-epigallocatechin 3-O-gallate, which account for a large fraction of the components of green tea polyphenol, on oxidative stress-related renal disease. Our observations suggest that green tea polyphenols have a beneficial effect on pathological states related to oxidative stress of the kidney.

Effects of morin-5′-sulfonic acid sodium salt (NaMSA) on cyclophosphamide-induced changes in oxido-redox state in rat liver and kidney

Cyclophosphamide (CPX) is an anticancer drug with immunosuppressive properties. Its adverse effects are partly connected to the induction of oxidative stress. Some studies indicate that water-soluble derivative of morin—morin-5′-sulfonic acid sodium salt (NaMSA) exhibits strong antioxidant activity. The aim of present study was to evaluate the effect of NaMSA on CPX-induced changes in oxido-redox state in rat. Experiment was carried out on Wistar rats divided in three experimental groups ( N = 12) receiving: 0.9% saline, CPX (15 mg/kg) or CPX (15 mg/kg) + NaMSA (100 mg/kg), respectively, and were given intragastrically for 10 days. Malondialdehyde (MDA) and glutathione (GSH) concentrations and superoxide dismutase (SOD) activity were determined in liver and kidneys. Catalase (CAT) activity was assessed only in liver. Treatment with CPX resulted in significant decrease in MDA level in both tissues, which was completely reversed by NaMSA treatment only in liver. In comparison to the control group significant decrease in SOD activity were observed in both tissues of CPX receiving group. In kidneys this parameter was fully restored by NaMSA administration. CPX evoked significant decrease in GSH concentration in kidneys, which was completely reversed by NaMSA treatment. No significant changes were seen in GSH levels and CAT activity between all groups in liver. Results of our study suggest that CPX may exert significant impact on oxido-redox state in both organs. NaMSA fully reversed the CPX-induced changes, especially MDA level in liver, SOD activity and GSH concentration in kidneys and it may be done by enhancement of activity/concentration of endogenous antioxidants.

Pathophysiological roles of peroxynitrite in circulatory shock

Peroxynitrite is a reactive oxidant produced from nitric oxide and superoxide, which reacts with proteins, lipids, and DNA, and promotes cytotoxic and proinflammatory responses. Here, we overview the role of peroxynitrite in various forms of circulatory shock. Immunohistochemical and biochemical evidences demonstrate the production of peroxynitrite in various experimental models of endotoxic and hemorrhagic shock both in rodents and in large animals. In addition, biological markers of peroxynitrite have been identified in human tissues after circulatory shock. Peroxynitrite can initiate toxic oxidative reactions in vitro and in vivo. Initiation of lipid peroxidation, direct inhibition of mitochondrial respiratory chain enzymes, inactivation of glyceraldehyde-3-phosphate dehydrogenase, inhibition of membrane Na+/K+ ATPase activity, inactivation of membrane sodium channels, and other oxidative protein modifications contribute to the cytotoxic effect of peroxynitrite. In addition, peroxynitrite is a potent trigger of DNA strand breakage, with subsequent activation of the nuclear enzyme poly(ADP-ribose) polymerase, which promotes cellular energetic collapse and cellular necrosis. Additional actions of peroxynitrite that contribute to the pathogenesis of shock include inactivation of catecholamines and catecholamine receptors (leading to vascular failure) and endothelial and epithelial injury (leading to endothelial and epithelial hyperpermeability and barrier dysfunction), as well as myocyte injury (contributing to loss of cardiac contractile function). Neutralization of peroxynitrite with potent peroxynitrite decomposition catalysts provides cytoprotective and beneficial effects in rodent and large-animal models of circulatory shock.

Role of nitric oxide synthases in Parkinson's disease: a review on the antioxidant and anti-inflammatory activity of polyphenols

Natural polyphenols can exert protective action on a number of pathological conditions including neurodegenerative disorders. The neuroprotective effects of many polyphenols rely on their ability to permeate brain barrier and here directly scavenge pathological concentration of reactive oxygen and nitrogen species and chelate transition metal ions. Importantly, polyphenols modulate neuroinflammation by inhibiting the expression of inflammatory genes and the level of intracellular antioxidants. Parkinson's disease (PD) is a neurodegenerative disorder characterized by several abnormalities including inflammation, mitochondrial dysfunction, iron accumulation and oxidative stress. There is considerable evidence showing that cellular oxidative damage occurring in PD might result also from the actions of altered production of nitric oxide (NO). Indeed, high levels of neuronal and inducible NO synthase (NOS) were found in substantia nigra of patients and animal models of PD. Here, we evaluate the involvement of NOS/NO in PD and explore the neuroprotective activity of natural polyphenol compounds in terms of anti-inflammatory and antioxidant action.

Scavenging of peroxynitrite-derived radicals by flavonoids may support endothelial NO synthase activity, contributing to the vascular protection associated with high fruit and vegetable intakes

Ample intakes of fruit and vegetables have been linked epidemiologically with reduced risk for coronary disease, stroke, hypertension, obesity, many types of cancer, chronic pulmonary disease, osteoporosis, and various ocular disorders. The favorable impact of diets rich in fruit and vegetables on coronary risk has been confirmed in meta-analyses, and is thought to be largely attributable to the folk acid and potassium supplied by these foods. Although high intakes of vitamin C appear to confer some cardiovascular protection, the amounts supplied by typical diets may be too low to be of much benefit in this regard. High flavonoid intakes emerge as protective in some epidemiological studies, albeit the dose-response pattern observed is often L-shaped - seemingly more consistent with low intakes being harmful, than with high intakes being protective. Nonetheless, flavonoids have shown anti-atherogenic activity in rodent models, and both clinical and rodent supplementation studies with foods and food extracts rich in flavonoids demonstrate improvements in endothelium-dependent vasodilation traceable to increased endothelial nitric oxide synthesis. However, flavonoids do not appear to increase the expression of endothelial NO synthase, nor do they modify endothelial superoxide production. A likely explanation is that, even in nanomolar concentrations achievable in vivo, flavonoids can act as efficient scavengers of peroxynitrite-derived radicals, thereby protecting the cofactor tetrahydrobiopterin, crucial for NO synthase activity. Studies with cultured endothelial cells should be useful for evaluating this possibility. It would also be appropriate to assess the effects of flavonoids on prostacylin synthetase activity, on endothelial catabolism of asymmetric dimethylarginine, and on signaling mechanisms that activate NO synthase. Since peroxynitrite can induce mutagenic damage to DNA, it is conceivable that scavenging of peroxynitrite-derived radicals contributes to the reduction in mutagenesis associated with high intakes of fruits and vegetables. Carotenoids also have the potential to prevent peroxynitrite-mediated damage, although, as contrasted with flavonoids, there is comparatively little evidence that these compounds are anti-atherogenic or beneficial for endothelial function; a recent meta-analysis of epidemiological studies suggests that high lutein intakes may modestly reduce coronary risk.

Protective effect of persimmon peel polyphenol against high glucose-induced oxidative stress in LLC-PK1 cells

The effect of persimmon peel polyphenol (PPP) on high glucose-induced oxidative stress was investigated using LLC-PK(1) cells, which is susceptible to oxidative stress. High-concentration glucose (30 mM) treatment induced LLC-PK(1) cell death, but high molecular-PPP (HMPPP) and low molecular-PPP (LMPPP), at concentrations of 5 or 10 microg/ml, significantly inhibited the high glucose-induced cytotoxicity. Furthermore, treatment with HMPPP or LMPPP dose-dependently reduced the intracellular reactive oxygen species level increased by 30 mM glucose. In addition, nitric oxide, superoxide and peroxynitrite levels were increased by 30 mM glucose treatment, but they were concentration-dependently inhibited by HMPPP or LMPPP treatment. High glucose levels induced the overexpressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) proteins, but HMPPP or LMPPP treatment reduced the overexpressions of these proteins. HMPPP or LMPPP also inhibited the nuclear translocation of nuclear factor-kappa B (NF-kappaB) induced by 30 mM glucose in LLC-PK(1) cells. In particular, LMPPP exhibited stronger inhibitory activities on high glucose induced oxidative stress than HMPPP. These findings indicate the potential benefits of persimmon peel as a valuable source of antioxidants in the diabetic condition which will reduce the oxidative stress induced by hyperglycemia.

Novel pharmacological approaches to the treatment of renal ischemia-reperfusion injury: a comprehensive review

Renal ischemia-reperfusion (I-R) contributes to the development of ischemic acute renal failure (ARF). Multi-factorial processes are involved in the development and progression of renal I-R injury with the generation of reactive oxygen species, nitric oxide and peroxynitrite, and the decline of antioxidant protection playing major roles, leading to dysfunction, injury, and death of the cells of the kidney. Renal inflammation, involving cytokine/adhesion molecule cascades with recruitment, activation, and diapedesis of circulating leukocytes is also implicated. Clinically, renal I-R occurs in a variety of medical and surgical settings and is responsible for the development of acute tubular necrosis (a characteristic feature of ischemic ARF), e.g., in renal transplantation where I-R of the kidney directly influences graft and patient survival. The cellular mechanisms involved in the development of renal I-R injury have been targeted by several pharmacological interventions. However, although showing promise in experimental models of renal I-R injury and ischemic ARF, they have not proved successful in the clinical setting (e.g., atrial natriuretic peptide, low-dose dopamine). This review highlights recent pharmacological developments, which have shown particular promise against experimental renal I-R injury and ischemic ARF, including novel antioxidants and antioxidant enzyme mimetics, nitric oxide and nitric oxide synthase inhibitors, erythropoietin, peroxisome-proliferator-activated receptor agonists, inhibitors of poly(ADP-ribose) polymerase, carbon monoxide-releasing molecules, statins, and adenosine. Novel approaches such as recent research involving combination therapies and the potential of non-pharmacological strategies are also considered.

Protective effect of the Chinese prescription Kangen-karyu against high glucose-induced oxidative stress in LLC-PK1 cells

We investigated the effects of Chinese prescription Kangen-karyu on high glucose-induced oxidative stress using LLC-PK(1) cells, renal tubular cells, which are the most vulnerable renal tissue to oxidative stress. High-concentration glucose (30mM) treatment induced LLC-PK(1) cell death, but Kangen-karyu, at a concentration of 5, 10 or 50 microg/ml, significantly inhibited high glucose-induced cytotoxicity. In addition, the intracellular reactive oxygen species level was increased by 30mM glucose treatment, but it was concentration-dependently inhibited by Kangen-karyu treatment. Moreover, 30mM glucose treatment induced high levels of superoxide anion, nitric oxide and peroxynitrite. However, Kangen-karyu treatment significantly reduced the radical overproduction induced by high glucose, suggesting Kangen-karyu has radical-scavenging activity that would protect against oxidative stress induced by high glucose. Kangen-karyu also reduced the overexpression of inducible nitric oxide synthase and cyclooxygenase-2 proteins induced by high glucose. Furthermore, treatment with Kangen-karyu, at a concentration of 50mug/ml, inhibited the nuclear translocation of nuclear factor-kappa B induced by 30mM glucose in LLC-PK(1) cells. These findings indicate that Kangen-karyu is a potential therapeutic agent that will reduce the damage caused by hyperglycemia-induced oxidative stress associated with diabetes.

Neuroprotective Effects of Quercetin and Rutin on Spatial Memory Impairment in an 8-Arm Radial Maze Task and Neuronal Death Induced by Repeated Cerebral Ischemia in Rats

In order to determine the differential effects of flavonoids on cerebral ischemia, we investigated the effects of (-)-epigallocatechin gallate (EGCG), catechin, rutin, and quercetin on spatial memory impairment and neuronal death induced by repeated cerebral ischemia in rats. Both rutin and quercetin (50 mg/kg x 2) improved spatial memory impairment in the 8-arm radial maze task and neuronal death in the hippocampal CA1 area; however, catechin (200 mg/kg x 2) and EGCG (50 mg/kg x 1) did not. Administration of EGCG (50 mg/kg x 2) resulted in a high mortality rate. These results suggest that in this repeated cerebral ischemia model, the 4-oxo group and the 2,3-double bond in the C ring of rutin and quercetin are related to their neuroprotective action.

Nitric oxide and peroxynitrite in health and disease

The discovery that mammalian cells have the ability to synthesize the free radical nitric oxide (NO) has stimulated an extraordinary impetus for scientific research in all the fields of biology and medicine. Since its early description as an endothelial-derived relaxing factor, NO has emerged as a fundamental signaling device regulating virtually every critical cellular function, as well as a potent mediator of cellular damage in a wide range of conditions. Recent evidence indicates that most of the cytotoxicity attributed to NO is rather due to peroxynitrite, produced from the diffusion-controlled reaction between NO and another free radical, the superoxide anion. Peroxynitrite interacts with lipids, DNA, and proteins via direct oxidative reactions or via indirect, radical-mediated mechanisms. These reactions trigger cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. In vivo, peroxynitrite generation represents a crucial pathogenic mechanism in conditions such as stroke, myocardial infarction, chronic heart failure, diabetes, circulatory shock, chronic inflammatory diseases, cancer, and neurodegenerative disorders. Hence, novel pharmacological strategies aimed at removing peroxynitrite might represent powerful therapeutic tools in the future. Evidence supporting these novel roles of NO and peroxynitrite is presented in detail in this review.

Contribution of flavonoid antioxidants to the preventive effect of mesna in cyclophosphamide-induced cystitis in rats

Cyclophosphamide (CP) is widely used, alone or in combination with other chemotherapeutic agents, for treatment of neoplastic diseases. Its urotoxicity may cause dose-limiting side-effects, for example hemorrhagic cystitis. The agent most often used to prevent this side-effect is mesna (2-mercaptoethane sulfonate). Overproduction of reactive oxygen species during inflammation is one reason for possible urothelial injury. The aim of this study was to evaluate whether combinations of quercetin and epigallocatechin 3-gallate (EGCG), flavonoid antioxidants and mesna could prevent cystitis induced by cyclophosphamide, better than mesna alone. A total of 38 male Sprague-Dawley rats were divided into five groups. Four groups received single dose of CP (100 mg kg(-1)) intraperitoneally at the same time. Group 2 received CP only, group 3 received mesna (3 x 21.5 mg kg(-1)), group 4 received a single dose of mesna+EGCG (2 x 20 mg kg(-1)), and group 5 received a single dose of mesna+quercetin (2 x 20 mg kg(-1)), before and after CP injection. Group 1 (not treated) served as control. CP injection alone resulted in severe cystitis. Mesna resulted in some, but not full, protection against CP toxicity. Quercetin and catechine, together with mesna, resulted in full protection against CP toxicity, on the basis of histopathology of the urinary bladder. It was concluded that oxidants might be important in the pathogenesis of CP-induced cystitis, and that flavonoid antioxidants, used in addition to mesna, may help to ameliorate bladder damage.