DNA damage induced by peroxynitrite: subsequent biological effects

Does 8-Nitroguanine Form 8-Oxoguanine? An Insight from Its Reaction with •OH Radical

8-Nitroguanine (8-nitroG) formed due to nitration of guanine base of DNA plays an important role in mutagenesis and carcinogenesis. In the present contribution, state-of-the-art quantum chemical calculations using M06-2X density functional and domain-based local pair natural orbital-coupled cluster theory with single, double, and perturbative triple excitations (DLPNO-CCSD(T)) methods have been carried out to investigate the mechanism of reaction of ^•OH radical with 8-nitroG leading to the formation of 8-oxoguanine (8-oxoG) (one of the most mutagenic and carcinogenic derivatives of guanine) in gas phase and aqueous media. Calculations of barrier energies and rate constants involved in the addition reactions of ^•OH radical at different sites of 8-nitroguanine show that C8 and C2 sites are the most and least reactive sites, respectively. Relative stability and Boltzmann populations of adducts show that the adduct formed at the C8 site occurs predominantly in equilibrium. Our calculations reveal that 8-nitroG is very reactive toward ^•OH radical and is converted readily into 8-oxoG when attacked by ^•OH radicals, in agreement with available experimental observations.

Genotoxic effect and antigen binding characteristics of SLE auto-antibodies to peroxynitrite-modified human DNA

Systemic lupus erythematosus (SLE) is an inflammatory autoimmune disease characterized by auto-antibodies against native deoxyribonucleic acid after modification and is one of the reasons for the development of SLE. Here, we have evaluated the structural perturbations in human placental DNA by peroxynitrite using spectroscopy, thermal denaturation and high-performance liquid chromatography (HPLC). Peroxynitrite is a powerful potent bi-functional oxidative/nitrative agent that is produced both endogenously and exogenously. In experimental animals, the peroxynitrite-modified DNA was found to be highly immunogenic. The induced antibodies showed cross-reactions with different types of DNA and nitrogen bases that were modified with peroxynitrite by inhibition ELISA. The antibody activity was inhibited by approximately 89% with its immunogen as the inhibitor. The antigen-antibodies interaction between induced antibodies with peroxynitrite-modified DNA showed retarded mobility as compared to the native form. Furthermore, significantly increased binding was also observed in SLE autoantibodies with peroxynitrite-modified DNA than native form. Moreover, DNA isolated from lymphocyte of SLE patients revealed significant recognition of anti-peroxynitrite-modified DNA immunoglobulin G (IgG). Our data indicates that DNA modified with peroxynitrite presents unique antigenic determinants that may induce autoantibody response in SLE.

Intramitochondrial Ascorbic Acid Enhances the Formation of Mitochondrial Superoxide Induced by Peroxynitrite via a Ca2+-Independent Mechanism

Exposure of U937 cells to peroxynitrite promotes mitochondrial superoxide formation via a mechanism dependent on both inhibition of complex III and increased mitochondrial Ca²⁺ accumulation. Otherwise inactive concentrations of the oxidant produced the same maximal effects in the presence of either complex III inhibitors or agents mobilizing Ca²⁺ from the ryanodine receptor and enforcing its mitochondrial accumulation. l-Ascorbic acid (AA) produced similar enhancing effects in terms of superoxide formation, DNA strand scission and cytotoxicity. However, AA failed to enhance the intra-mitochondrial concentration of Ca²⁺ and the effects observed in cells supplemented with peroxinitrite, while insensitive to manipulations preventing the mobilization of Ca²⁺, or the mitochondrial accumulation of the cation, were also detected in human monocytes and macrophages, which do not express the ryanodine receptor. In all these cell types, mitochondrial permeability transition-dependent toxicity was detected in cells exposed to AA/peroxynitrite and, based on the above criteria, these responses also appeared Ca²⁺-independent. The enhancing effects of AA are therefore similar to those mediated by bona fide complex III inhibitors, although the vitamin failed to directly inhibit complex III, and in fact enhanced its sensitivity to the inhibitory effects of peroxynitrite.

Genotoxicity and cytotoxicity of the plasma jet-treated medium on lymphoblastoid WIL2-NS cell line using the cytokinesis block micronucleus cytome assay

Despite growing interest in the application of atmospheric plasma jets as medical treatment strategies, there has been comparatively little research on the potential genotoxic and cytotoxic effects of plasma jet treatment. In this study, we have employed the cytokinesis block micronucleus cytome (CBMN-Cyt) assay with WIL2-NS B lymphoblastoid cells to test the potential genotoxicity, as well as the cytotoxicity, of toxic species generated in cell culture media by an argon (Ar) plasma jet. Elevated levels of cell death (necrosis) and occurrence of chromosomal damage (micronuclei MN, nculeoplasmic bridge NPBs and nuclear bus, Nbuds) were observed when cells were exposed to plasma jet-treated media. These results provide a first insight into how we might measure the genotoxic and cytotoxic effect of plasma jet treatments (both indirect and direct) in dividing human cells.

Biochemical and structural studies of Mycobacterium smegmatis MutT1, a sanitization enzyme with unusual modes of association

Mycobacterium smegmatis MutT1, which is made up of a Nudix domain (domain 1) and a histidine phosphatase domain (domain 2), efficiently hydrolyses 8-oxo-GTP and 8-oxo-dGTP to the corresponding nucleoside diphosphates and phosphate in the presence of magnesium ions. Domain 1 alone hydrolyses nucleoside triphosphates less efficiently. Under high concentrations and over long periods, the full-length enzyme as well as domain 1 catalyses the hydrolysis of the nucleoside triphosphates to the respective nucleoside monophosphates and pyrophosphate. The role of domain 2 appears to be limited to speeding up the reaction. Crystal structures of the apoenzyme and those of ligand-bound enzyme prepared in the presence of 8-oxo-GTP or 8-oxo-dGTP and different concentrations of magnesium were determined. In all of the structures except one, the molecules arrange themselves in a head-to-tail fashion in which domain 1 is brought into contact with domain 2 (trans domain 2) of a neighbouring molecule. The binding site for NTP (site A) is almost exclusively made up of residues from domain 1, while those for NDP (site B) and NMP (site C) are at the interface between domain 1 and trans domain 2 in an unusual instance of intermolecular interactions leading to binding sites. Protein-ligand interactions at site A lead to a proposal for the mechanism of hydrolysis of NTP to NDP and phosphate. A small modification in site A in the crystal which does not exhibit the head-to-tail arrangement appears to facilitate the production of NMP and pyrophosphate from NTP. The two arrangements could be in dynamic equilibrium in the cellular milieu.

Alterations in nitric oxide homeostasis during traumatic brain injury

Changes in nitric oxide (NO) levels have been often associated with various forms of trauma, including secondary damage after traumatic brain injury (TBI). Several studies demonstrate the upregulation of NO synthase (NOS) enzymes, and concomitant increases in brain NO levels, which contribute to the TBI-associated glutamate cytotoxicity, including the pathogenesis of mitochondrial dysfunction. TBI is also associated with elevated NO levels in remote organs, indicating that TBI can induce systemic changes in NO regulation, which can be either beneficial or detrimental. Here we review the possible mechanisms responsible for changes in NO metabolism during TBI. Better understanding of the changes in NO homeostasis in TBI will be necessary to design rational therapeutic approaches for TBI. This article is part of a Special Issue entitled: Immune and Metabolic Alterations in Trauma and Sepsis edited by Dr. Raghavan Raju.

A fluorogenic and red-shifted diphenyl phosphinate-based probe for selective peroxynitrite detection as demonstrated in fixed cells

A new dicyanomethylene-4H-pyran-based fluorescent probe has been designed, synthesized and characterized. It shows selective “TURN-ON” fluorescence response upon reaction with ONOO⁻.

DNA catabolites in triathletes: effects of supplementation with an aronia-citrus juice (polyphenols-rich juice)

In this study we analyzed whether our aronia-citrus juice (ACJ, the composition is based on a mixture of 95% citrus juice with 5% of Aronia melanocarpa juice), rich in polyphenols, and physical exercise had an effect on seven catabolites of DNA identified in plasma and on a urine isoprostane (8-iso-PGF2α). Sixteen elite triathletes on a controlled diet for triathlon training (45 days) were used in this clinical trial. Our results show a decrease in the 8-hydroxy-2'-deoxyguanosine concentration due to chronic physical exercise. The ACJ intake and physical exercise maintained the guanosine-3',5'-cyclic monophosphate plasmatic concentrations and decreased the concentration of 8-hydroxyguanine as well as urinary values of 8-iso-PGF2α. Finally, we observed a significant increase in the 8-nitroguanosine levels in triathletes after ACJ intake, compared to the placebo stage. It is concluded that the combination of the intake of ACJ, rich in polyphenolic compounds, with adequate training was able to influence the plasmatic and urinary values of oxidative stress biomarkers. This suggests a positive effect on the oxidative damage and potential associations with DNA repair mechanisms.

The Proinflammatory Potential of Nitrogen Dioxide and Its Influence on the House Dust Mite Allergen Der p 1

Asthma and allergies are both major global health problems with an increasing prevalence, and environmental data implicate an influence of air pollutants on their development. The present study focuses on the influence of nitrogen dioxide (NO2) and the major allergen of the house dust mite Der p 1 on human nasal epithelial cells of nonallergic patients in vitro. Nasal epithelial mucosa samples of 11 donors were harvested during nasal air passage surgery and cultured as an air-liquid interface. Exposure to 0.1, 1 and 10 ppm NO2 or synthetic air as a control was performed for 1 h. Subsequently, the cells were exposed to Der p 1 for 24 h. The release of interleukin (IL)-6 and IL-8 was measured by ELISA, and the production of IL-6 mRNA and IL-8 mRNA was measured by RT-PCR. NO2 exposure resulted in a concentration-dependent release of IL-6, but not IL-8 release. The coexposure of 0.1 ppm NO2 and Der p 1, or 1 ppm NO2 and Der p 1 significantly increased both IL-6 and IL-8 release. Exposure to NO2, Der p 1, or their combination, did not significantly influence the production of IL-6 or IL-8 mRNA. In conclusion, NO2 increases the release of inflammatory cytokines in human nasal epithelial cells, especially in coexposure with Der p 1, as a mechanism of allergotoxicology.

8-Aminoguanosine and 8-Aminoguanine Exert Diuretic, Natriuretic, Glucosuric, and Antihypertensive Activity

In vivo, guanine moieties in DNA, RNA, guanine nucleotides, or guanosine or guanine per se can undergo nitration (for example, by peroxynitrite) or hydroxylation (for example, by superoxide anion) on position 8 of the purine ring. Subsequent catabolism of these modified biomolecules leads to the production of a diverse group of 8-nitro, 8-amino, and 8-hydroxy guanosine and guanine compounds. Indeed, studies suggest the in vivo existence of 8-nitroguanosine, 8-nitroguanine, 8-aminoguanosine, 8-aminoguanine, 8-hydroxyguanosine, 8-hydroxy-2'-deoxyguanosine, and 8-hydroxyguanine. Since a multitude of these compounds exist in vivo, and since the renal effects of 8-substituted guanosine and guanine compounds are entirely unknown, we examined the effects of guanosine, guanine, 8-nitroguanosine, 8-nitroguanine, 8-hydroxyguanosine, 8-hydroxyguanine, 8-hydroxy-2'-deoxyguanosine, 8-aminoguanosine, and 8-aminoguanine (33.5 µmol/kg/min; intravenous infusion for 115 minutes) on excretion of sodium, potassium, and glucose in rats. Guanosine, 8-nitroguanosine, and 8-hydroxy-2'-deoxyguanosine had minimal natriuretic activity. Guanine, 8-nitroguanine, 8-hydroxyguanosine, and 8-hydroxyguanine had moderate natriuretic activity (increased sodium excretion by 9.4-, 7.8-, 7.1-, and 8.6-fold, respectively). In comparison with all other compounds, 8-aminoguanosine and 8-aminoguanine were highly efficacious and increased sodium excretion by 26.6- and 17.2-fold, respectively, exceeding that of a matched dose of amiloride (13.6-fold increase). 8-Aminoguanosine and 8-aminoguanine also increased glucose excretion by 12.1- and 12.2-fold, respectively, and decreased potassium excretion by 69.1 and 71.0%, respectively. Long-term radiotelemetry studies demonstrated that oral 8-aminoguanosine and 8-aminoguanine (5 mg/kg/day) suppressed deoxycorticosterone/salt-induced hypertension. These experiments demonstrate that some naturally occurring 8-substitued guanosine and guanine compounds, particularly 8-aminoguanosine and 8-aminoguanine, are potent and efficacious potassium-sparing diuretics/natriuretics that may represent a novel class of antihypertensive diuretics.

Myeloid-derived suppressor cells in murine AIDS inhibit B-cell responses in part via soluble mediators including reactive oxygen and nitrogen species, and TGF-β

Monocytic myeloid-derived suppressor cells (M-MDSCs) were increased during LP-BM5 retroviral infection, and were capable of suppressing not only T-cell, but also B-cell responses. In addition to previously demonstrating iNOS- and VISTA-dependent M-MDSC mechanisms, in this paper, we detail how M-MDSCs utilized soluble mediators, including the reactive oxygen and nitrogen species superoxide, peroxynitrite, and nitric oxide, and TGF-β, to suppress B cells in a predominantly contact-independent manner. Suppression was independent of cysteine-depletion and hydrogen peroxide production. When two major mechanisms of suppression (iNOS and VISTA) were eliminated in double knockout mice, M-MDSCs from LP-BM5-infected mice were able to compensate using other, soluble mechanisms in order to maintain suppression of B cells. The IL-10 producing regulatory B-cell compartment was among the targets of M-MDSC-mediated suppression.

Activation of NO-cGMP Signaling Rescues Age-Related Memory Impairment in Crickets

Age-related memory impairment (AMI) is a common feature and a debilitating phenotype of brain aging in many animals. However, the molecular mechanisms underlying AMI are still largely unknown. The cricket Gryllus bimaculatus is a useful experimental animal for studying age-related changes in learning and memory capability; because the cricket has relatively short life-cycle and a high capability of olfactory learning and memory. Moreover, the molecular mechanisms underlying memory formation in crickets have been examined in detail. In the present study, we trained male crickets of different ages by multiple-trial olfactory conditioning to determine whether AMI occurs in crickets. Crickets 3 weeks after the final molt (3-week-old crickets) exhibited levels of retention similar to those of 1-week-old crickets at 30 min or 2 h after training; however they showed significantly decreased levels of 1-day retention, indicating AMI in long-term memory (LTM) but not in anesthesia-resistant memory (ARM) in olfactory learning of crickets. Furthermore, 3-week-old crickets injected with a nitric oxide (NO) donor, a cyclic GMP (cGMP) analog or a cyclic AMP (cAMP) analog into the hemolymph before conditioning exhibited a normal level of LTM, the same level as that in 1-week-old crickets. The rescue effect by NO donor or cGMP analog injection was absent when the crickets were injected after the conditioning. For the first time, an NO donor and a cGMP analog were found to antagonize the age-related impairment of LTM formation, suggesting that deterioration of NO synthase (NOS) or molecules upstream of NOS activation is involved in brain-aging processes.

Blood Levels of Nitric Oxide, C-Reactive Protein, and Tumor Necrosis Factor-α Are Upregulated in Patients with Malignancy-Associated Hypercoagulable State: Pathophysiologic Implications

Endogenous generation of nitric oxide (NO) plays an important role in the regulation of cardiovascular and inflammatory responses. This mediator is synthesized by a family of enzymes collectively known as NO synthase. Several isoforms of this enzyme have been identified and can be grouped as constitutive or inducible. Increased production of NO is reported in several inflammatory disorders, such as sepsis, arthritis, thrombotic thrombocytopenic purpura (TTP), and antiphospholipid syndrome. In addition, NO upregulates cyclo-oxygenase-2 and synthesis of several other inflammatory cytokines. Inflammation and thrombotic complications are usually associated with malignancy. Earlier reports indicate the upregulation of tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), and tissue factor (TF) in patients with malignancy. To determine the relationship between inflammatory cytokines and NO in cancer patients with hypercoagulable states, baseline plasma samples from 160 patients with confirmed malignancy and hypercoagulable state were analyzed for NO levels. A chemical method based on a chemiluminescent reaction between NO and ozone using a highly sensitive gas phase NO analyzer was used. CRP, TF, and TNF-α were measured using enzyme-linked immunosorbent assay methods. Of the 160 patients who were plasma tested, the baseline NO levels ranged from 13.7 to 98.6 μM (63.1±15.9 μM, mean±SD) in contrast to age-matched control, which ranged from 9.1 to 34.6 μM (19.8±6.2 μM, mean±SD, n=138). Cancer patients also showed marked variations in the NO levels. Eighteen of 60 cancer patients exhibited greater than 60 μM NO levels. The CRP, TNF-α and TF were also significantly elevated. A correlation between CRP (r2=0.73) and NO levels was noted in cancer patients with hypercoagulable state. These data suggest that the pathogenesis associated with malignancy/hypercoagulable state is associated with an inflammatory component. In addition, the observed hemodynamic changes in some of the cancer patients may be due to increased NO production.

Oxidative-Nitrosative Stress and Myocardial Dysfunctions in Sepsis: Evidence from the Literature and Postmortem Observations

BACKGROUND

Myocardial depression in sepsis is common, and it is associated with higher mortality. In recent years, the hypothesis that the myocardial dysfunction during sepsis could be mediated by ischemia related to decreased coronary blood flow waned and a complex mechanism was invoked to explain cardiac dysfunction in sepsis. Oxidative stress unbalance is thought to play a critical role in the pathogenesis of cardiac impairment in septic patients.

AIM

In this paper, we review the current literature regarding the pathophysiology of cardiac dysfunction in sepsis, focusing on the possible role of oxidative-nitrosative stress unbalance and mitochondria dysfunction. We discuss these mechanisms within the broad scenario of cardiac involvement in sepsis.

CONCLUSIONS

Findings from the current literature broaden our understanding of the role of oxidative and nitrosative stress unbalance in the pathophysiology of cardiac dysfunction in sepsis, thus contributing to the establishment of a relationship between these settings and the occurrence of oxidative stress. The complex pathogenesis of septic cardiac failure may explain why, despite the therapeutic strategies, sepsis remains a big clinical challenge for effectively managing the disease to minimize mortality, leading to consideration of the potential therapeutic effects of antioxidant agents.

Immunostimulating activity of polyhydric alcohol isolated from Taxus cuspidata

A polyhydric alcohol (PAL) was isolated from Taxus cuspidata and its immunostimulatory activities were assessed. The primary monosaccharide composition of the PAL was determined to be glucose, where HPAEC analysis showed no significant amount of any other sugars. However, glycerol and xylitol were identified as the main sugar alcohols. Fourier-transform infrared (FT-IR) analysis indicated that the purified PAL is a complex glycitol, which structurally contains significant amount of hydroxyl groups. MALDI-TOF mass spectroscopy also demonstrated that PAL is a complex glycitol built in hexose polymerization. Enzyme linked immunosorbent assay showed that the PAL stimulates the release of the proinflammatory cytokines TNF-α and IL-6 in a dose-dependent manner. Furthermore, treatment of RAW 264.7 cells with PAL for 24h remarkably increased the phosphorylation levels of ERK, p38 and JNK in a dose-dependent manner, whereas the total protein levels of ERK (t-ERK), p38 (t-p38) and JNK (t-JNK) remained unchanged. These results clearly demonstrate that PAL stimulates the immune response in RAW 264.7 cells through the activation of MAPKs (ERK, p38 and JNK) signaling pathway. To the best of our knowledge, this is the first study to demonstrate the primary structure and immune-stimulating activities of PAL from the fruit of T. cuspidata.

Antioxidant activity and structural features of Cinnamomum zeylanicum

The antioxidants in food materials have recently attracted researchers' attention because many reports have shown that the oxidative stress is closely related to the aging process of the cells and acts as a trigger to various diseases including cancer. Since reactive oxygen species (ROS) is involved in initiating and promoting several diseases such as cancer and cardiovascular events, this study was designed to evaluate the antioxidant capacity of pectic polysaccharides extracted from the bark of Cinnamomum zeylanicum, locally known as Daruchini. An arabinogalactan (A), one partly methyl esterified galacturonic acid (B) and a neutral glucan (C) were isolated. The glucan is made up of β-(1 → 3)-linked glucopyranosyl residues and has a molecular mass of 7 kDa. The arabinogalactan is highly branched and has an average molecular mass of 40 kDa. The in vitro antioxidant capacity of the fractions was studied by ferric reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays. The arabinogalactan (A) showed the highest potential followed by the uronic acid (B) and glucan (C). Taken together, these findings demonstrate that these polysaccharides could be used as natural antioxidants by the food industry.

Peroxynitrous acid induces structural and functional modifications to basement membranes and its key component, laminin

Basement membranes (BM) are specialized extracellular matrices underlying endothelial cells in the artery wall. Laminin, the most abundant BM glycoprotein, is a structural and biologically active component. Peroxynitrous acid (ONOOH), a potent oxidizing and nitrating agent, is formed in vivo at sites of inflammation from superoxide and nitric oxide radicals. Considerable data supports ONOOH formation in human atherosclerotic lesions, and an involvement of this oxidant in atherosclerosis development and lesion rupture. These effects may be mediated, at least in part, via extracellular matrix damage. In this study we demonstrate co-localization of 3-nitrotyrosine (a product of tyrosine damage by ONOOH) and laminin in human atherosclerotic lesions. ONOOH-induced damage to BM was characterized for isolated murine BM, and purified murine laminin-111. Exposure of laminin-111 to ONOOH resulted in dose-dependent loss of protein tyrosine and tryptophan residues, and formation of 3-nitrotyrosine, 6-nitrotryptophan and the cross-linked material di-tyrosine, as detected by amino acid analysis and Western blotting. These changes were accompanied by protein aggregation and fragmentation as detected by SDS-PAGE. Endothelial cell adhesion to isolated laminin-111 exposed to 10 μM or higher levels of ONOOH was significantly decreased (~25%) compared to untreated controls. These data indicate that laminin is oxidized by equimolar or greater concentrations of ONOOH, with this resulting in structural and functional changes. These modifications, and resulting compromised cell-matrix interactions, may contribute to endothelial cell dysfunction, a weakening of the structure of atherosclerotic lesions, and an increased propensity to rupture.

Pathophysiological Role of Peroxynitrite Induced DNA Damage in Human Diseases: A Special Focus on Poly(ADP-ribose) Polymerase (PARP)

Peroxynitrite is formed in biological systems when nitric oxide and superoxide rapidly interact at near equimolar ratio. Peroxynitrite, though not a free radical by chemical nature, is a powerful oxidant which reacts with proteins, DNA and lipids. These reactions trigger a wide array of cellular responses ranging from subtle modulations of cell signaling to overwhelming oxidative injury, committing cells to necrosis or apoptosis. The present review outlines the various peroxynitrite-induced DNA modifications with special mention to the formation of 8-nitroguanine and 8-oxoguanine as well as the induction of DNA single strand breakage. Low concentrations of peroxynitrite cause apoptotic death, whereas higher concentrations cause necrosis with cellular energetics (ATP and NAD(+)) serving as control between the two modes of cell death. DNA damage induced by peroxynitrite triggers the activation of DNA repair systems. A DNA nick sensing enzyme, poly(ADP-ribose) polymerase-1 (PARP-1) becomes activated upon detecting DNA breakage and it cleaves NAD(+) into nicotinamide and ADP-ribose and polymerizes the latter on nuclear acceptor proteins. Over-activation of PARP induced by peroxynitrite consumes NAD(+) and consequently ATP decreases, culminating in cell dysfunction, apoptosis or necrosis. This mechanism has been implicated in the pathogenesis of various diseases like diabetes, cardiovascular diseases and neurodegenerative diseases. In this review, we have discussed the cytotoxic effects (apoptosis and necrosis) of peroxynitrite in the etiology of the mentioned diseases, focusing on the role of PARP in DNA repair in presence of peroxynitrite.

Targeting oxidant-dependent mechanisms for the treatment of COPD and its comorbidities

Chronic obstructive pulmonary disease (COPD) is an incurable global health burden and is characterised by progressive airflow limitation and loss of lung function. In addition to the pulmonary impact of the disease, COPD patients often develop comorbid diseases such as cardiovascular disease, skeletal muscle wasting, lung cancer and osteoporosis. One key feature of COPD, yet often underappreciated, is the contribution of oxidative stress in the onset and development of the disease. Patients experience an increased burden of oxidative stress due to the combined effects of excess reactive oxygen species (ROS) and nitrogen species (RNS) generation, antioxidant depletion and reduced antioxidant enzyme activity. Currently, there is a lack of effective treatments for COPD, and an even greater lack of research regarding interventions that treat both COPD and its comorbidities. Due to the involvement of oxidative stress in the pathogenesis of COPD and many of its comorbidities, a unique therapeutic opportunity arises where the treatment of a multitude of diseases may be possible with only one therapeutic target. In this review, oxidative stress and the roles of ROS/RNS in the context of COPD and comorbid cardiovascular disease, skeletal muscle wasting, lung cancer, and osteoporosis are discussed and the potential for therapeutic benefit of anti-oxidative treatment in these conditions is outlined. Because of the unique interplay between oxidative stress and these diseases, oxidative stress represents a novel target for the treatment of COPD and its comorbidities.

Minocycline inhibits PARP‑1 expression and decreases apoptosis in diabetic retinopathy

The present study aimed to investigate the mechanism underlying the effects of minocycline on diabetic retinopathy-associated cellular apoptosis. A total of 40 Sprague Dawley (SD) rats were used as a diabetic retinopathy model following injection with streptozotocin. Among the 34 rats in which the diabetes model was successfully established, 24 rats were divided into two experimental groups: I and II (T1 and T2, respectively), and orally administered with various doses of minocycline. The remaining 10 rats served as the diabetic retinopathy control group. An additional group of 10 healthy SD rats with comparable weight served as normal controls. The rats in T1 and T2 groups were treated daily for eight consecutive weeks with minocycline at a dose of 2.5 mg/kg and 5 mg/kg, respectively. The mRNA expression levels of poly (ADP-ribose) polymerase-1 (PARP-1) were subsequently measured by reverse transcription-quantitative polymerase chain reaction, and the protein expression levels of poly-ADP-ribose were measured by western blot analysis and immunohistochemistry. Retinal morphology was observed following hematoxylin and eosin staining, and retinal cell apoptosis was measured by terminal deoxynucleotidyl transferase dUTP nick end labeling and caspase-3 activity assays. The amplitudes of the electroretinogram (ERG) b-wave and oscillary potentials (OPs) were measured using visual electrophysiology, and compared among the four groups. The results of the present study demonstrated that in the diabetic rats, retinal PARP-1 gene expression was markedly upregulated, the number of apoptotic cells and the activity levels of caspase-3 were increased, and the amplitude of the ERG b-wave and the OPs were markedly lower as compared with the normal rats. Following treatment with minocycline, the abnormal expression of PARP-1 in the retina was inhibited, and cellular apoptosis was decreased. In conclusion, the results of the present study suggest that PARP-1 is involved in the development of diabetic retinopathy, and minocycline is able to inhibit PARP-1 expression and decrease cellular apoptosis, suggesting that minocycline may prove to be a promising drug for the treatment of diabetic retinopathy.

Cerium oxide nanoparticles alleviate oxidative stress and decreases Nrf-2/HO-1 in D-GALN/LPS induced hepatotoxicity

Translocation of the master regulator of antioxidant-response element-driven antioxidant gene, nuclear factor erythroid 2 (Nrf-2) from the cytoplasm into the nucleus and triggering the transcription of hemoxygenase-1 (HO-1) to counteract the oxidative stress is a key feature in D-galactoseamine and lipopolysaccharide (D-GALN/LPS) induced hepatotoxicity. We mainly aimed to study the effect of cerium oxide (CeO2) nanoparticles on Nrf-2/HO-1 pathway whereas; it has previously shown to have an antioxidant effect in liver models. Administration of CeO2 nanoparticles significantly decreased the translocation of the cytoplasmic Nrf-2 with a concomitant decrement in the gene expression of HO-1 as it reveals a powerful antioxidative effect as indicated by the significant increase in the levels of glutathione (GSH), glutathione peroxidase (GPX1), glutathione reductase (GR), superoxide dismutase (SOD) and catalase. In synchronization, a substantial decrement in the levels of inducible nitric oxide synthase (iNOS), TBARS and percentage of DNA fragmentation was established. These results were confirmed by histopathology examination which showed a severe degeneration, haemorrhages, widened sinusoids and focal leukocyte infiltration in D-GALN/LPS treatment and these features were alleviated with CeO2 administration. In conclusion, CeO2 is a potential antioxidant that can effectively decrease the translocation of the cytoplasmic Nrf-2 into the nucleus and decrease HO-1 in D-GALN/LPS induced hepatotoxicity.

SR-135, a peroxynitrite decomposing catalyst, enhances β-cell function and survival in B6D2F1 mice fed a high fat diet

Peroxynitrite has been implicated in β-cell dysfunction and insulin resistance in obesity. Chemical catalysts that destroy peroxynitrite, therefore, may have therapeutic value for treating type 2 diabetes. To this end, we have recently demonstrated that Mn(III) bis(hydroxyphenyl)-dipyrromethene complexes, SR-135 and its analogs, can effectively catalyze the decomposition of peroxynitrite in vitro and in vivo through a 2-electron mechanism (Rausaria et al., 2011). To study the effects of SR-135 on glucose homeostasis in obesity, B6D2F1 mice were fed with a high fat-diet (HFD) for 12 weeks and treated with vehicle, SR-135 (5mg/kg), or a control drug SRB for 2 weeks. SR-135 significantly reduced fasting blood glucose and insulin levels, and enhanced glucose tolerance as compared to HFD control, vehicle or SRB. SR-135 also enhanced glucose-stimulated insulin secretion based on ex vivo studies. Moreover, SR-135 increased insulin content, restored islet architecture, decreased islet size, and reduced tyrosine nitration and apoptosis. These results suggest that a peroxynitrite decomposing catalyst enhances β-cell function and survival under nutrient overload.

A tutorial on oxidative stress and redox signaling with application to exercise and sedentariness

Oxidative stress has been shown to play a role in the etiology of several chronic diseases, including cardiovascular disease, diabetes mellitus, and cancer. Free radicals and, most prominently, the superoxide radical, result from oxidative metabolism and several enzyme-catalyzed reactions, and endogenous cellular antioxidants dismutate many reactive oxygen species (ROS). Under certain conditions, ROS production can outpace dismutation (e.g., long-term sedentariness and positive energy balance) and the result is oxidative stress, with proteins, lipids, and DNA the most common targets of radicals. However, the molecules that contribute to oxidative stress also appear to participate in vital cell signaling activity that supports health and stimulates favorable adaptations to exercise training, such that inhibiting ROS formation prevents common adaptations to training. Furthermore, researchers have recently suggested that some proteins are not as readily formed when the redox state of the cell is insufficiently oxidative. Exercise training appears to optimize the redox environment by dramatically enhancing the capacity of the cell to neutralize ROS while regularly creating oxidative environments in which membrane and secretory proteins can be synthesized. The role that exercise plays in enhancing management of ROS likely explains many of the associated health benefits.

The BER necessities: the repair of DNA damage in human-adapted bacterial pathogens

During colonization and disease, bacterial pathogens must survive the onslaught of the host immune system. A key component of the innate immune response is the generation of reactive oxygen and nitrogen species by phagocytic cells, which target and disrupt pathogen molecules, particularly DNA, and the base excision repair (BER) pathway is the most important mechanism for the repair of such oxidative DNA damage. In this Review, we discuss how the human-specific pathogens Mycobacterium tuberculosis, Helicobacter pylori and Neisseria meningitidis have evolved specialized mechanisms of DNA repair, particularly their BER pathways, compared with model organisms such as Escherichia coli. This specialization in DNA repair is likely to reflect the distinct niches occupied by these important human pathogens in the host.

D-Galactosamine/Lipopolysaccharide-Induced Hepatotoxicity Downregulates Sirtuin 1 in Rat Liver: Role of Sirtuin 1 Modulation in Hepatoprotection

D-Galactosamine/Lipopolysaccharide (D-GalN/LPS) is a well known model of hepatotoxicity that closely resembles acute liver failure (ALF) seen clinically. The role of sirtuin 1 in this model has not yet been documented. However, there have been a number of studies about the cytoprotective effects of resveratrol, a SIRT1 activator, in the liver. This study was aimed at elucidating the roles of SIRT1 protein expression or catalytic activity in D-GalN/LPS model of hepatotoxicity. ALF was induced in male Wistar rats by intraperitoneal injection of D-GalN and LPS. Some groups of animals were pretreated with resveratrol and/or EX-527 (SIRT1 inhibitor). The effects of these treatments were evaluated by biochemical and Western blot studies. D-GalN/LPS treatment was able to induce hepatotoxicity and significantly increase all markers of liver damage and lipid peroxidation. A dramatic decrease of SIRT1 levels in response to D-GalN/LPS treatment was also documented. Resveratrol pretreatment attenuated D-GalN/LPS-induced hepatotoxicity. EX-527 blocked the cytoprotective effects of resveratrol. However, both resveratrol and EX-527 pretreatments did not exhibit any significant effect on SIRT1 protein expression. Collectively, these results suggest that downregulation of SIRT1 expression is involved in the cytotoxic effects of D-GalN/LPS model and SIRT1 activity contributes to the cytoprotective effects of resveratrol in the liver.

Peroxynitrite modified DNA presents better epitopes for anti-DNA autoantibodies in diabetes type 1 patients

Peroxynitrite (ONOO(-)), formed by the reaction between nitric oxide (NO) and superoxide (O2(-)), has been implicated in the etiology of numerous disease processes. Peroxynitrite interacts with DNA via direct oxidative reactions or via indirect radical-mediated mechanism. It can inflict both oxidative and nitrosative damages on DNA bases, generating abasic sites, resulting in the single strand breaks. Plasmid pUC 18 isolated from Escherichiacoli was modified with peroxynitrite, generated by quenched flow process. Modifications incurred in plasmid DNA were characterized by ultraviolet and fluorescence spectroscopy, circular dichroism, HPLC and melting temperature studies. Binding characteristics and specificity of antibodies from diabetes patients were analyzed by direct binding and inhibition ELISA. Peroxynitrite modification of pUC 18 plasmid resulted in the formation of strand breaks and base modification. The major compound formed when peroxynitrite reacted with DNA was 8-nitroguanine, a specific marker for peroxynitrite induced DNA damage in inflamed tissues. The concentration of 8-nitroguanine was found to be 3.8 μM. Sera from diabetes type 1 patients from different age groups were studied for their binding to native and peroxynitrite modified plasmid. Direct binding and competitive-inhibition ELISA results showed higher recognition of peroxynitrite modified plasmid, as compared to the native form, by auto-antibodies present in diabetes patients. The preferential recognition of modified plasmid by diabetes autoantibodies was further reiterated by gel shift assay. Experimentally induced anti-peroxynitrite-modified plasmid IgG was used as a probe to detect nitrosative lesions in the DNA isolated from diabetes patients.

Attenuation of skeletal muscle and renal injury to the lower limb following ischemia-reperfusion using mPTP inhibitor NIM-811

Introduction

Operation on the infrarenal aorta and large arteries of the lower extremities may cause rhabdomyolysis of the skeletal muscle, which in turn may induce remote kidney injury. NIM-811 (N-metyl-4-isoleucine-cyclosporine) is a mitochondria specific drug, which can prevent ischemic-reperfusion (IR) injury, by inhibiting mitochondrial permeability transition pores (mPTP).

Objectives

Our aim was to reduce damages in the skeletal muscle and the kidney after IR of the lower limb with NIM-811.

Materials and methods

Wistar rats underwent 180 minutes of bilateral lower limb ischemia and 240 minutes of reperfusion. Four animal groups were formed called Sham (receiving vehicle and sham surgery), NIM-Sham (receiving NIM-811 and sham surgery), IR (receiving vehicle and surgery), and NIM-IR (receiving NIM-811 and surgery). Serum, urine and histological samples were taken at the end of reperfusion. NADH-tetrazolium staining, muscle Wet/Dry (W/D) ratio calculations, laser Doppler-flowmetry (LDF) and mean arterial pressure (MAP) monitoring were performed. Renal peroxynitrite concentration, serum TNF-α and IL-6 levels were measured.

Results

Less significant histopathological changes were observable in the NIM-IR group as compared with the IR group. Serum K⁺ and necroenzyme levels were significantly lower in the NIM-IR group than in the IR group (LDH: p<0.001; CK: p<0.001; K⁺: p = 0.017). Muscle mitochondrial viability proved to be significantly higher (p = 0.001) and renal function parameters were significantly better (creatinine: p = 0.016; FENa: p<0.001) in the NIM-IR group in comparison to the IR group. Serum TNF-α and IL-6 levels were significantly lower (TNF-α: p = 0.003, IL-6: p = 0.040) as well as W/D ratio and peroxynitrite concentration were significantly lower (p = 0.014; p<0.001) in the NIM-IR group than in the IR group.

Conclusion

NIM-811 could have the potential of reducing rhabdomyolysis and impairment of the kidney after lower limb IR injury.

A boronate-based fluorescent probe for the selective detection of cellular peroxynitrite

A boronate-based fluorescent probe 1 for the selective monitoring of intracellular peroxynitrite has been developed. The probe takes advantage of the fast reaction of an arylboronate group with peroxynitrite, yielding a corresponding phenol that undergoes spontaneous subsequent reactions to produce a strongly fluorescent product associated with a large turn-on signal.

Chronic HCV infection and inflammation: Clinical impact on hepatic and extra-hepatic manifestations

The liver has a central role in regulating inflammation by its capacity to secrete a number of proteins that control both local and systemic inflammatory responses. Chronic inflammation or an exaggerated inflammatory response can produce detrimental effects on target organs. Chronic hepatitis C virus (HCV) infection causes liver inflammation by complex and not yet well-understood molecular pathways, including direct viral effects and indirect mechanisms involving cytokine pathways, oxidative stress and steatosis induction. An increasing body of evidence recognizes the inflammatory response in chronic hepatitis C as pathogenically linked to the development of both liver-limited injury (fibrosis, cirrhosis and hepatocellular carcinoma) and extrahepatic HCV-related diseases (lymphoproliferative disease, atherosclerosis, cardiovascular and brain disease). Defining the complex mechanisms of HCV-induced inflammation could be crucial to determine the global impact of infection, to estimate progression of the disease, and to explore novel therapeutic approaches to avert HCV-related diseases. This review focuses on HCV-related clinical conditions as a result of chronic liver and systemic inflammatory states.

Biomarkers in Exhaled Breath Condensate and Serum of Chronic Obstructive Pulmonary Disease and Non-Small-Cell Lung Cancer

Chronic obstructive pulmonary disease (COPD) and lung cancer are leading causes of deaths worldwide which are associated with chronic inflammation and oxidative stress. Lung cancer, in particular, has a very high mortality rate due to the characteristically late diagnosis. As such, identification of novel biomarkers which allow for early diagnosis of these diseases could improve outcome and survival rate. Markers of oxidative stress in exhaled breath condensate (EBC) are examples of potential diagnostic markers for both COPD and non-small-cell lung cancer (NSCLC). They may even be useful in monitoring treatment response. In the serum, S100A8, S100A9, and S100A12 of the S100 proteins are proinflammatory markers. They have been indicated in several inflammatory diseases and cancers including secondary metastasis into the lung. It is highly likely that they not only have the potential to be diagnostic biomarkers for NSCLC but also prognostic indicators and therapeutic targets.

Physicochemical and immunological studies on mitochondrial DNA modified by peroxynitrite: implications of neo-epitopes of mitochondrial DNA in the etiopathogenesis of systemic lupus erythematosus

Background and objective

Recent evidence has demonstrated that mitochondria possess their own nitric oxide synthase (mtNOS) and can produce endogenous reactive-nitrogen-species (RNS) including peroxynitrite (ONOO–). This study was undertaken to investigate the role of mitochondrial DNA (mtDNA) damage by ONOO– in systemic lupus erythematosus (SLE) autoimmunity.

Methods

MtDNA was isolated from fresh goat liver and modified by ONOO–, generated by synergistic action of nitric oxide (NO) and superoxide (O–2) donors. Modifications occurring in mtDNA were characterized by physicochemical techniques. SLE patients ( n = 50) with varying disease activity according to the SLE Disease Activity Index (SLEDAI) and healthy controls ( n = 34) were evaluated for antibodies to native and ONOO–-modified mtDNA by immunoassays. Gel retardation assays were performed to cross-examine the immunoassay results using affinity-purified SLE immunoglobulin G (IgG). Nitrosative stress in SLE patients was studied by measuring nitrotyrosine and inducible NO synthase (iNOS).

Results

The ONOO– caused extensive damage to mtDNA as evident by ultraviolet (UV) hyperchromicity and loss of florescence intensity. Thermal melting studies, agarose gel electrophoresis and nuclease S1 digestibility clearly indicate structural perturbation in mtDNA by ONOO–. Quenching studies with specific NO or O–2 quenchers confirmed that the damaging agent was ONOO–. SLE autoantibodies exhibited enhanced binding with ONOO–-mtDNA as compared to their native analog. Interestingly, not only was there an increased number of subjects positive for ONOO–-mtDNA, but also the levels of anti-ONOO–-mtDNA antibodies were statistically significantly higher among SLE patients whose SLEDAI scores were ≥ 20 as compared with SLE patients with lower SLEDAI scores (SLEDAI < 20). Normal healthy controls showed negligible binding with either antigen. Furthermore, SLE patients had higher levels of nitrotyrosine and iNOS compared with their respective healthy controls.

Conclusions

Our novel results provide an important insight into the immunological basis of anti-DNA autoantibody generation in SLE. Our data conclude that modification of mtDNA by ONOO– causes structural perturbations, resulting in the generation of neo-epitopes, and making it a potential immunogen in SLE. The mtDNA modified by ONOO– may be useful in evaluating the progression of SLE and in elucidating the mechanisms of disease pathogenesis.

Nitrogen dioxide is genotoxic in urban concentrations

In the discussion on toxic and genotoxic thresholds of air pollutants such as nitrogen dioxide (NO2), realistically low urban concentration ranges are of major interest. For NO2, the WHO defines the annual limit value as corresponding to 0.02 ppm. In the present study, the toxicity and genotoxicity of NO2 is set at a concentration under this limit value and examined in human nasal epithelium at different exposure durations in vitro. Nasal epithelial mucosa samples of 10 donors were harvested during nasal air passage surgery and cultured as an air-liquid interface. Exposure to 0.01 ppm NO2 or synthetic air as a control was performed for 0.5, 1, 2 and 3 h. Analysis included the caspase-3 ELISA, the single cell microgel electrophoresis (comet) assay and the micronucleus assay. The caspase-3 activity was not influenced by NO2 exposure, DNA strand fragmentation correlated with exposure durations to NO2 at 0.01 ppm NO2, and no cytotoxic effects such as apoptosis, necrosis or disturbances of cell proliferation were present. However, micronucleus induction as a sign of genotoxicity at an exposure duration of 3 h could be shown. Shorter exposures did not induce micronucleus formation. In summary, genotoxicity of NO2 could be demonstrated at a common urban concentration in vitro, but a threshold of NO2 genotoxicity could not be defined based on the present experiments.

Synergistic inactivation of anaerobic wastewater biofilm by free nitrous acid and hydrogen peroxide

Free nitrous acid (FNA) was recently revealed to be a strong biocide for microbes in anaerobic biofilm, achieving approximately 1-log (90%) inactivation at a concentration of 0.2-0.3 mgHNO2-N/L with an exposure time longer than 6h. The combined biocidal effects of FNA and hydrogen peroxide (H2O2) on anaerobic wastewater biofilm are investigated in this study. H2O2 greatly enhances the inactivation of microorganisms by FNA. About 2-log (99%) of microbial inactivation was achieved when biofilms were exposed to FNA at 0.2 mgN/L or above and H2O2 at 30 mg/L or above for 6h or longer. It was found, through response surface methodology and ridge analysis, that FNA is the primary inactivation agent and H2O2 enhances its efficiency. The loss and the subsequent slow recovery of biological activity in biofilm reactors subjected to FNA and H2O2 dosing confirmed that the chemical combination could achieve higher microbial inactivation than with FNA alone. Reaction simulation shows that intermediates of reactions between FNA and H2O2, like peroxynitrite and nitrogen dioxide, would be produced at elevated levels and are likely responsible for the synergism between FNA and H2O2. The combination of FNA and H2O2 could potentially provide an effective solution to sewer biofilm control.

Protection against peroxynitrite-induced DNA damage by mesalamine: implications for anti-inflammation and anti-cancer activity

Mesalamine (5-aminosalicylic acid, 5-ASA) is known to be the first-line medication for treatment of patients with ulcerative colitis. Studies have demonstrated that ulcerative colitis patients treated with 5-ASA have an overall decrease in the risk of developing colorectal carcinoma. However, the mechanisms underlying 5-ASA-mediated anti-inflammatory and anti-cancer effects are yet to be elucidated. Because peroxynitrite has been critically involved in inflammatory stress and carcinogenesis, this study was undertaken to investigate the effects of 5-ASA in peroxynitrite-induced DNA strand breaks, an important event leading to peroxynitrite-elicited cytotoxicity. Incubation of φX-174 plasmid DNA with the peroxynitrite generator 3-morpholinosydnonimine (SIN-1) led to the formation of both single- and double-stranded DNA breaks in a concentration-dependent manner. The presence of 5-ASA at 0.1 and 1.0 mM was found to significantly inhibit SIN-1-induced DNA strand breaks in a concentration-dependent manner. The consumption of oxygen induced by SIN-1 was found to not be affected by 5-ASA at 0.1-50 mM, indicating that 5-ASA at these concentrations is not involved in the auto-oxidation of SIN-1 to form peroxynitrite. It is observed that 5-ASA at 0.1-1 mM showed considerable inhibition of peroxynitrite-mediated luminol chemiluminescence in a dose-dependent fashion, suggesting that 5-ASA is able to directly scavenge the peroxynitrite. Electron paramagnetic resonance (EPR) spectroscopy in combination with spin-trapping experiments, using 5,5-dimethylpyrroline-N-oxide (DMPO) as spin trap resulting in the formation of DMPO-hydroxyl radical adduct from peroxynitrite, and 5-ASA only at higher concentration (1 mM) inhibited the hydroxyl radical adduct while shifting EPR spectra, indicating that 5-ASA at higher concentrations may generate a more stable free radical species rather than acting purely as a hydroxyl radical scavenger. Taken together, these studies demonstrate for the first time that 5-ASA can potently inhibit peroxynitrite-mediated DNA strand breakage, scavenge peroxynitrite, and affect peroxynitrite-mediated radical formation, which may be responsible, at least partially, for its anti-inflammatory and anti-cancer effects.

Analgesic and Anti-Inflammatory Activities of the Ethanolic Extract of Artemisia morrisonensis Hayata in Mice

The aim of this study was to investigate the possible analgesic and anti-inflammatory mechanisms of the ethanolic extract of A. morrisonensis Hayata (AM_EtOH). Two models were employed for evaluation of the analgesic effects: acetic acid-induced writhing response and formalin-induced paw licking. The results demonstrated that AM_EtOH decreased writhing response for both the acetic acid assay and the licking time in the formalin test. The anti-inflammatory effect was evaluated by paw edema of mice induced by λ-carrageenan. AM_EtOH significantly decreased induced paw edema three to four hours after λ-carrageenan injection. Additionally, the results indicated that the anti-inflammatory mechanism of AM_EtOH may be due to the declined levels of nitric oxide (NO) and malondialdehyde (MDA) in the edematous paw. Furthermore, AM_EtOH decreased the tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) levels, leading to the reduction of prostaglandins and subsequently alleviated edema. Isolation and purification of the AM_EtOH extract determined p-hydroxyacetophenone to be a major component at 130 mg/g of extract. No mortality was observed in the acute toxicity test given at the dose of 10 g/kg. This study demonstrated the possible mechanisms for the analgesic and anti-inflammatory effects of AM_EtOH for mice and provided evidence for the ethnobotanical uses of A. morrisonensis in treating inflammatory diseases.

Nitric oxide, can it be only good? Increasing the antioxidant properties of nitric oxide in hepatocytes by YC-1 compound

The aim of the study was to evaluate the effect of Nitric oxide (NO) on redox changes and fat accumulation in hepatocytes. AML-12 hepatocytes were exposed to the NO donor Diethylenetriamine-NONOate (DETA-NO). DETA-NO led to a dose- and time-dependent increase in lipid accumulation in the cells, measured by Nile red fluorescence. Exposure of the cells to 1mM DETA-NO for 24h increased reactive oxygen species production, mainly peroxides. At the same time, NO induced elevation of reduced glutathione (GSH) and a mild activation of the antioxidant transcription factors Hypoxia-inducible factor 1α (HIF1α) and NF-E2 related factor 2 (Nrf-2). We used 100 μM YC-1 to inhibit HIF1α activity and induce activation of soluble Guanylate Cyclase (sGC). YC-1 alone did not affect fat accumulation, and only moderately increased the expression of Nrf-2-targeted genes Heme oxygenase 1 (Hmox1), NAD(P)H dehydrogenase (quinone 1) (Nqo1) and Glutathione S-transferase α1 (Gstα1). However, YC-1 abolished the negative effect of NO on fat accumulation when administered together. Strikingly, YC-1 potentiated the effect of NO on Nrf-2 activation, thus increasing dramatically the antioxidant properties of NO. Moreover, YC-1 intensified the effect of NO on the expression of peroxisome-proliferator-activated receptor-gamma co-activator 1α (PGC1α) and mitochondrial biogenesis markers. This study suggests that YC-1 may shift the deleterious effects of NO into the beneficial ones, and may improve the antioxidant properties of NO.