Protection against peroxynitrite by cocoa polyphenol oligomers

Flavonoids, natural plant constituents, protect against peroxynitrite and can thereby play a role in defense against this mediator of inflammation. Procyanidin oligomers of different size (monomer through nonamer), isolated from the seeds of Theobroma cacao, were examined for their ability to protect against peroxynitrite-dependent oxidation of dihydrorhodamine 123 and nitration of tyrosine. By molarity, oligomers were more effective than the monomeric epicatechin; the tetramer was particularly efficient at protecting against oxidation and nitration reactions. These results suggest that epicatechin oligomers found in cocoa powder and chocolate may be a potent dietary source for defense against peroxynitrite.     

Hesperetin: a potent antioxidant against peroxynitrite

Peroxynitrite (ONOO_-) is a reactive oxidant formed from superoxide (•O₂^-) and nitric oxide (•NO), that can oxidize several cellular components, including essential protein, non-protein thiols, DNA, low-density lipoproteins (LDL), and membrane phospholipids. ONOO_- has contributed to the pathogenesis of diseases such as stroke, heart disease, Alzheimer's disease, and atherosclerosis. Because of the lack of endogenous enzymes to thwart ONOO_- activation, developing a specific ONOO_- scavenger is remarkably important. In this study, the ability of hesperetin (3',5,7-trihydroxy-4-methoxyflavanone) to scavenge ONOO_- and to protect cells against ONOO_- and ROS was investigated. The data gained show that hesperetin can efficiently scavenge authentic ONOO_-. In spectrophotometric analysis, the data revealed that hesperetin led to declined ONOO_--mediated nitration of tyrosine through electron donation. Hesperetin exhibited significant inhibition on the nitration of bovine serum albumin (BSA) by ONOO_- in a dose-dependent manner. Hesperetin also manifested cytoprotection from cell damage induced by ONOO_- and ROS. The present study suggests that hesperetin is a powerful ONOO_- scavenger and promotes cellular defense activity in the protection against ONOO_- involved diseases.     

Polyphenols and red wine as antioxidants against peroxynitrite and other oxidants

The antioxidant capacity of polyphenols (+)-catechin, (-)-epicatechin and myricetin, and of different types of red wines (Cabernet Sauvignon, Malbec and blended wine) was evaluated by three assays. (a) NADH oxidation by peroxynitrite (ONOO-): the ONOO- scavenging activity was higher for myricetin (IC50=35 microM) than for (+)-catechin (IC50=275 microM) and (-)-epicatechin (IC50=313 microM). (b) Peroxynitrite initiated chemiluminescence in rat liver homogenate: (-)-epicatechin (IC50=7.0 microM) and (+)-catechin (IC50=13 microM) were more potent than myricetin (IC50=20 microM) in inhibiting the chemiluminescence signal. (c) Lucigenin chemiluminescence in aortic rings: (-)-epicatechin (IC50=15 microM) and (+)-catechin (IC50=18 microM) showed higher antioxidant capacity than myricetin (IC50=32 microM). All the assayed red wines were able to scavenge the oxidants and free radical species that generate the signal in each assay. Cabernet Sauvignon was the red wine with the highest antioxidant capacity in comparison with Malbec and blended wine. It is concluded that the use of sensitive biological systems (as the aortic ring chemiluminescence) provides important information in addition to the results from chemical (NADH oxidation by peroxynitrite) and biochemical (homogenate chemiluminescence) assays and offers advances in the physiological role of polyphenols.     

The interaction of resveratrol with ferrylmyoglobin and peroxynitrite; protection against LDL oxidation

Resveratrol (3,4',5-trihydroxystilbene) is a natural phytoalexin synthesized in response to injury or fungal attack, found in the grape skin and wine, specially red wine. A large number of studies have demonstrated that resveratrol regulates many biological activities, namely protection against atherosclerosis by a set of pharmacological properties, including the antioxidant activity. In this study, we explored the capacity of resveratrol in protecting low density lipoproteins (LDL) against either ferrylmyoglobin- or peroxynitrite-mediated oxidation and the underlying mechanisms of its antioxidant potential. Resveratrol efficiently decreases the accumulation of hydroperoxides in LDL promoted by ferrylmyoglobin, a potent oxidant formed by the reaction of metmyoglobin with hydrogen peroxide, in a concentration-dependent manner, promptly reducing the oxoferryl complex to metmyoglobin. Simultaneously, resveratrol is consumed as detected by the rapid decrease in the characteristic peak at 310 nm, in a similar way to that observed upon its reaction with peroxidase/H 2 O 2 , pointing to a mechanism of one-electron oxidation and subsequent resveratrol dimer formation. On the other hand, resveratrol inhibits LDL apoprotein modifications induced by peroxynitrite, another potent oxidant formed by the reaction between superoxide and nitric oxide, as assessed by the decrease in apo-B net charge alterations and in carbonyl groups formation mediated by that oxidant. Resveratrol also interacts with peroxynitrite in a similar way to that observed with laccases, suggesting a mechanism of resveratrol oxidation rather than a nitration one. These mechanisms are discussed. Considering that either ferrylmyoglobin or peroxynitrite are physiologically relevant oxidants implicated in several pathologies, including atherosclerosis, our results certainly contribute to the understanding of the antioxidant action of resveratrol and consequently provide a new approach for the cardiovascular benefits associated with moderate consumption of red wine.     

Protection against Recurrent Stroke with Resveratrol: Endothelial Protection

Despite increased risk of a recurrent stroke following a minor stroke, information is minimal regarding the interaction between injurious mild cerebral ischemic episodes and the possible treatments which might be effective. The aim of the current study was to investigate recurrent ischemic stroke and whether resveratrol, a nutritive polyphenol with promising cardio- and neuro- protective properties, could ameliorate the associated brain damage. Experiments in adult rats demonstrated that a mild ischemic stroke followed by a second mild cerebral ischemia exacerbated brain damage, and, daily oral resveratrol treatment after the first ischemic insult reduced ischemic cell death with the recurrent insult (P<0.002). Further investigation demonstrated reduction of both inflammatory changes and markers of oxidative stress in resveratrol treated animals. The protection observed with resveratrol treatment could not be explained by systemic effects of resveratrol treatment including effects either on blood pressure or body temperature measured telemetrically. Investigation of resveratrol effects on the blood-brain barrier in vivo demonstrated that resveratrol treatment reduced blood-brain barrier disruption and edema following recurrent stroke without affecting regional cerebral blood flow. Investigation of the mechanism in primary cell culture studies demonstrated that resveratrol treatment significantly protected endothelial cells against an in vitro ‘ischemia’ resulting in improved viability against oxygen and glucose deprivation (39.6±6.6% and 81.3±9.5% in vehicle and resveratrol treated cells, respectively). An inhibition of nitric oxide synthesis did not prevent the improved cell viability following oxygen glucose deprivation but SIRT-1 inhibition with sirtinol partially blocked the protection (P<0.001) suggesting endothelial protection is to some extent SIRT-1 dependent. Collectively, the results support that oral resveratrol treatment provides a low risk strategy to protect the brain from enhanced damage produced by recurrent stroke which is mediated in part by a protective effect of resveratrol on the endothelium of the cerebrovasculature.     

The extract from hop cones in plasma protects against changes following exposure to peroxynitrite

Humulus lupulus (Cannabaceae) is well known throughout the world as a raw material in the brewing industry. The antioxidative action of hop cones is poorly understood, therefore the aim of our present study was to investigate in vitro changes in human plasma induced by peroxynitrite in the presence of the highly purified extract from hop cones (Humulus lupulus). The aim of our study was also to explain the effect of the extract from hop cones on coagulation activity of human plasma treated with peroxynitrite. The action of the extract from hop cones was compared with the properties of a well-characterized commercial monomeric polyphenol — resveratrol (3,4′,5-trihydroxystilbene). The tested plant extract, like resveratrol, significantly inhibited protein carbonylation and nitration in plasma treated with ONOO⁻(0.1 mM). The extract from hop cones, like resveratrol, also caused a distinct reduction of plasma lipid peroxidation induced by ONOO⁻. Moreover, the tested extract modulated the coagulation properties of plasma treated with peroxynitrite. It seems that antioxidative activities of the highly purified extract from hop cones may be responsible for its medicinal properties.     

Peroxiredoxins play a major role in protecting Trypanosoma cruzi against macrophage- and endogenously-derived peroxynitrite

There is increasing evidence that Trypanosoma cruzi antioxidant enzymes play a key immune evasion role by protecting the parasite against macrophage-derived reactive oxygen and nitrogen species. Using T. cruzi transformed to overexpress the peroxiredoxins TcCPX (T. cruzi cytosolic tryparedoxin peroxidase) and TcMPX (T. cruzi mitochondrial tryparedoxin peroxidase), we found that both cell lines readily detoxify cytotoxic and diffusible reactive oxygen and nitrogen species generated in vitro or released by activated macrophages. Parasites transformed to overexpress TcAPX (T. cruzi ascorbate-dependent haemoperoxidase) were also more resistant to H2O2 challenge, but unlike TcMPX and TcCPX overexpressing lines, the TcAPX overexpressing parasites were not resistant to peroxynitrite. Whereas isolated tryparedoxin peroxidases react rapidly (k=7.2 x 10(5) M(-1) x s(-1)) and reduce peroxynitrite to nitrite, our results demonstrate that both TcMPX and TcCPX peroxiredoxins also efficiently decompose exogenous- and endogenously-generated peroxynitrite in intact cells. The degree of protection provided by TcCPX against peroxynitrite challenge results in higher parasite proliferation rates, and is demonstrated by inhibition of intracellular redox-sensitive fluorescence probe oxidation, protein 3-nitrotyrosine and protein-DMPO (5,5-dimethylpyrroline-N-oxide) adduct formation. Additionally, peroxynitrite-mediated over-oxidation of the peroxidatic cysteine residue of peroxiredoxins was greatly decreased in TcCPX overexpressing cells. The protective effects generated by TcCPX and TcMPX after oxidant challenge were lost by mutation of the peroxidatic cysteine residue in both enzymes. We also observed that there is less peroxynitrite-dependent 3-nitrotyrosine formation in infective metacyclic trypomastigotes than in non-infective epimastigotes. Together with recent reports of up-regulation of antioxidant enzymes during metacyclogenesis, our results identify components of the antioxidant enzyme network of T. cruzi as virulence factors of emerging importance.     

Failure of selenomethionine residues in albumin and immunoglobulin G to protect against peroxynitrite.

Selenomethionine has been suggested to protect against peroxynitrite by quenching it in vivo. Selenomethionine is distributed randomly in the methionine pool. Albumin and IgG were purified from plasma of a human being before and after 28 days of supplementation with 400 microg selenium/day as selenomethionine. The albumin contained 1 selenium atom, presumably as selenomethionine, per 8000 methionine residues before supplementation and 1 per 2800 after supplementation. Although this ratio suggested that selenomethionine would not have as great an effect in quenching peroxynitrite as would methionine, direct testing of the albumin and IgG fractions was carried out to assess the ability of these proteins to prevent peroxynitrite oxidation of dihydrorhodamine 123 to rhodamine 123. The ability of the albumin preparations to resist nitration of tyrosine residues was also assessed. The high-selenomethionine preparations of the proteins had no greater effect in quenching the peroxynitrite than did the normal-selenomethionine preparations. These results do not support the proposal that selenomethionine in proteins contributes to in vivo protection against peroxynitrite.     

100 years of peroxynitrite chemistry and 11 years of peroxynitrite biochemistry

The paper on the unusual properties of a mixture of hydrogen peroxide and nitrous acid by Baeyer and Villiger from 1901 can be regarded as the first report on peroxynitrite. In 1990, Beckman and co-workers suggested that peroxynitrite, formed from the reaction of superoxide with nitrogen monoxide, could be a transient oxidizing species in vivo, a report that revolutionized investigations in the field of oxidative stress.     

100 Years of peroxynitrite chemistry and 11 years of peroxynitrite biochemistry

Abstract

The paper on the unusual properties of a mixture of hydrogen peroxide and nitrous acid by Baeyer and Villiger from 1901 can be regarded as the first report on peroxynitrite. In 1990, Beckman and co-workers suggested that peroxynitrite, formed from the reaction of superoxide with nitrogen monoxide, could be a transient oxidizing species in vivo, a report that revolutionized investigations in the field of oxidative stress.     

Protection against pertussis by immunisation.

Review of all 126 children admitted to the communicable diseases unit with whooping cough during the epidemic in 1978 showed that two had received two doses of triple vaccine and only one had had full primary immunisation against the disease. None of these three children suffered complications of the disease. Of the 123 children who had not been immunised against pertussis, however, 66 had had one or more complications. In Birmingham the dramatic decline in immunisation against pertussis has been accompanied by a fall in acceptance rates for diphtheria and tetanus immunization. Nevertheless, of the 62 children aged over 1 year in this series, 41 had been so immunised. These findings suggest that the apparently positive decision by parents to omit pertussis immunisation was misplaced, since immunisation does protect against the more serious complications of the disease. Furthermore, there is no firm evidence that pertussis immunisation of children without specific contraindications is associated with serious adverse reactions.     

Protection by metallothionein against cadmium toxicity

1. The protective effect against Cd toxicity of prior exposure to Cd or Zn solutions at low concentration was studied. 2. Carp were bred in tap water (A), 1 ppm Cd solution (B) and 5 ppm Zn solution (C) for 14 days and then transferred into 15 ppm Cd solution. The survival ratio of carp decreased in the order: (C):(B):(A). 3. Binding capacity of Cd to high molecular and metallothionein fractions in the cytoplasmic solutions of the hepato-pancreas was studied and the binding capacity to the metallothionein fraction was stronger than that to the high molecular fraction. The authors recognized that Zn in the metallothionein fraction is substituted by Cd.     

Protection against progressive leishmaniasis by IFN-beta

Type I IFNs (IFN-alphabeta) exert potent antiviral and immunoregulatory activities during viral infections, but their role in bacterial or protozoan infections is poorly understood. In this study, we demonstrate that the application of low, but not of high doses of IFN-beta protects 60 or 100% of BALB/c mice from progressive cutaneous and fatal visceral disease after infection with a high (10(6)) or low (10(4)) number of Leishmania major parasites, respectively. IFN-beta treatment of BALB/c mice restored the NK cell cytotoxic activity, increased the lymphocyte proliferation, and augmented the production of IFN-gamma and IL-12 in the draining lymph node. Low, but not high doses of IFN-beta caused enhanced tyrosine phosphorylation of STAT1 and STAT4, suppressed the levels of suppressor of cytokine signaling-1, and up-regulated the expression of inducible NO synthase in vivo. The IFN-beta-induced increase of IFN-gamma production was dependent on STAT4. Protection by IFN-beta strictly required the presence of inducible NO synthase. In the absence of STAT4 or IL-12, IFN-beta led to an amelioration of the cutaneous and visceral disease, but was unable to prevent its progression. These results identify IFN-beta as a novel cytokine with a strong, dose-dependent protective effect against progressive cutaneous leishmaniasis that results from IL-12- and STAT4-dependent as well as -independent events.