Nitrotyrosine as biomarker for reactive nitrogen species

Expression of inducible nitric oxide synthase, nitrotyrosine, eosinophilic peroxidase, eotaxin-3, and galectin-3 in patients with gastroesophageal reflux disease, eosinophilic esophagitis, and in healthy controls: a semiquantitative image analysis of 3,3'-diaminobenzidine-stained esophageal biopsies

Eosinophilic esophagitis (EoE) and gastroesophageal reflux disease (GERD) share many histopathological features; therefore, markers for differentiation are of diagnostic interest and may add to the understanding of the underlying mechanisms. The nitrergic system is upregulated in GERD and probably also in EoE. Esophageal biopsies of patients with EoE (n = 20), GERD (n = 20), and healthy volunteers (HVs) (n = 15) were exposed to antibodies against inducible nitric oxide synthase (iNOS), nitrotyrosine, eosinophilic peroxidase, eotaxin-3, and galectin-3. The stained object glasses were randomized, digitized, and blindly analyzed regarding the expression of DAB (3,3'-diaminobenzidine) by a protocol developed in QuPath software. A statistically significant overexpression of iNOS was observed in patients with any of the two inflammatory diseases compared with that in HVs. Eotaxin-3 could differentiate HVs versus inflammatory states. Gastroesophageal reflux patients displayed the highest levels of nitrotyrosine. Neither iNOS nor nitrotyrosine alone were able to differentiate between the two diseases. For that purpose, eosinophil peroxidase was a better candidate, as the mean levels increased stepwise from HVs via GERD to EoE. iNOS and nitrotyrosine are significantly overexpressed in patients with EoE and GERD compared with healthy controls, but only eosinophil peroxidase could differentiate the two types of esophagitis. The implications of the finding of the highest levels of nitrotyrosine among gastroesophageal reflux patients are discussed.

Oxidative Stress in Alzheimer's Disease: The Shortcomings of Antioxidant Therapies

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by gradual and progressive cognitive decline leading to dementia. At its core, the neuropathological features of AD include hallmark accumulations of amyloid-β and hyperphosphorylated tau proteins. Other harmful processes, such as oxidative stress and inflammation, contribute to the disease's neuropathological progression. This review evaluates the role of oxidative stress in AD, placing a spotlight on the disappointing outcomes of various antioxidant clinical trials. Several hypotheses are discussed that might elucidate the failures of these therapies in AD. Specifically: 1) The paradoxical and overlooked harmful implications of prooxidant intermediates, particularly stemming from conventional antioxidants like vitamins E and C; 2) The challenges and failure to appreciate the issue of bioavailability-epitomized by the dictum "no on-site protection, no protection"-and the preeminent, yet often ignored, role played by endogenous antioxidant enzymes in combating oxidative stress; 3) The influence of unrecognized etiologies, such as latent infectious agents and others, as foundational drivers of oxidative stress in AD; 4) The underestimation of the complexity of oxidative mechanisms and the necessity of multi-targeted therapeutic approaches, such as those provided by various diets; and 5) The limitations of clinical trial designs in fully capturing the effects of antioxidants on AD progression. This article also examines the outcomes of select clinical trials while highlighting the challenges and barriers these therapies pose, offering insights into potential mechanisms to overcome their marginal success.

Selective detection of nitrotyrosine using dual-fluorescent carbon dots

The post-translational modification of amino acid plays a critical role in normal and diseased biological states. Specifically, nitrotyrosine (nTyr) has been linked to diseases, including neurodegeneration, among others. Hence, alternative methods are required for detection and differentiation of nTyr from other structurally similar analogues, such as Tyrosine (Tyr) or phosphotyrosine (pTyr). Herein, the selective detection of nTyr, over other congeners, was achieved by using dual-fluorescent carbon dots (CDs) in buffered solution, artificial saliva, bovine serum albumin and diluted equine serum. The nTyr induced fluorescence quenching of the blue and red emissions of CDs, in the 20-105 μM linear range, and with the limit of detection (LOD) at 34 μM, which was well below the physiological concentration required for detection. The sensor was functional at biological pH values, with optimal quenching efficiency at basic pH. The sensor was highly selective for nTyr even in the presence of common biological interferences (metal cations, organic anions, amino acids, nucleosides and other biologicals). The mechanism of quenching (a combination of static and dynamic) was ascribed to the nonradiative energy transfer, due to electronic overlap between nTyr absorbance and CDs fluorescence emission, and electron transfer from excited CDs state to nTyr as an electron acceptor. The dual-fluorescent CDs represent viable sensors for key biological modifications, and their selectivity and sensitivity may be further improved through tailored chemical synthesis of CDs, such as tunable surface chemistry to promote selective recognition of analyte of interest.

Fermented Mangosteen (Garcinia mangostana L.) Supplementation in the Prevention of HPV-Induced Cervical Cancer: From Mechanisms to Clinical Outcomes

Simple Summary

Human papillomavirus (HPV) is connected with virtually all cases of cervical cancer. The viral infection-associated chronic inflammation, oxidative stress, and alterations in apoptosis have been considered as leading risk factors for carcinogenesis in humans. In an observational clinical study, we identified oxidative markers and the cervical/circulating ligands of TNF-alpha-induced apoptosis involved in HPV-associated cervical carcinogenesis. In the following clinical trial, 250 females infected with high-cancer-risk HPV16/18 (healthy and pre-cancerous) were recruited into a placebo-controlled clinical study of supplementation with fermented mangosteen (FM, 28g/day, daily) for three months. Our findings indicate that FM, and not a placebo, in combination with routine anti-viral therapy, could prevent, slow down, or even interrupt HPV-associated cervical carcinogenesis, mainly through the suppression of leukocyte recruitment into infected tissue, through anti-inflammatory effects, and through the restoration of nitric oxide metabolite-initiated TRAIL-dependent apoptosis.

Abstract

In the observational clinical study, we identified the oxidative markers of HPV-associated cervical carcinogenesis and the local/circulating ligands of TNF-alpha-induced apoptosis. Cervical biopsies of 196 females infected with low-cancer-risk HPV10/13 or high-cancer-risk HPV16/18 (healthy, pre-cancerous CIN I and CIN II, and CIN III carcinoma) were analysed for OH radical scavenging, catalase, GSH-peroxidase, myeloperoxidase (MPO), nitrate/nitrite, nitrotyrosine, and isoprostane. Ligands of TNF-alpha-dependent apoptosis (TNF-alpha, TRAIL, IL-2, and sFAS) were determined in cervical fluid, biopsies, and serum. Cervical MPO was highly enhanced, while nitrotyrosine decreased in CIN III. Local/circulating TRAIL was remarkably decreased, and higher-than-control serum TNF-alpha and IL-2 levels were found in the CIN I and CIN III groups. Then, 250 females infected with HPV16/18 (healthy and with CIN I and CIN II) were recruited into a placebo-controlled clinical study of supplementation with fermented mangosteen (FM, 28g/day, daily) for three months. Post-trial colposcopy revealed normal patterns in 100% of the FM group versus 62% of the placebo group. Inflammatory cells in cervical fluid were found in 21% of the FM group versus 40% of the placebo group. Locally, FM drastically diminished MPO and NO₂/NO₃, while it remarkably increased TRAIL. Additionally, FM supplementation normalised serum TRAIL, TNF-alpha, and IL-2.

A glance at the therapeutic potential of irisin against diseases involving inflammation, oxidative stress, and apoptosis: An introductory review

Irisin is a hormone-like molecule mainly released by skeletal muscles in response to exercise. Irisin induces browning of the white adipose tissue and has been shown to regulate glucose and lipid homeostasis. Keeping its energy expenditure and metabolic properties in view, numerous studies have focused on its therapeutic potential for the treatment of metabolic disorders like obesity and type 2 diabetes. Recently, the anti-inflammatory, anti-apoptotic and anti-oxidative properties of irisin have received a great deal of attention of the scientific society. These pathogenic processes are often associated with initiation, progression, and prognosis of numerous diseases like myocardial infarction, kidney diseases, cancer, lung injury, inflammatory bowel diseases, atherosclerosis, liver diseases, obesity and type 2 diabetes. In the current review, we present evidence regarding the anti-inflammatory, anti-apoptotic and anti-oxidative potential of irisin pertaining to various pathological conditions. Here, we explore multiple molecular pathways targeted by irisin therapy. Given the promising effects of irisin, many diseases with evident oxidative stress, inflammation and apoptosis can be targeted by irisin.

Redox-Dependent Calpain Signaling in Airway and Pulmonary Vascular Remodeling in COPD

The calcium-dependent cytosolic, neutral, thiol endopeptidases, calpains, perform limited cleavage of their substrates thereby irreversibly changing their functions. Calpains have been shown to be involved in several physiological processes such as cell motility, proliferation, cell cycle, signal transduction, and apoptosis. Overactivation of calpain or mutations in the calpain genes contribute to a number of pathological conditions including neurodegenerative disorders, rheumatoid arthritis, cancer, and lung diseases. High concentrations of reactive oxygen and nitrogen species (RONS) originated from cigarette smoke or released by numerous cell types such as activated inflammatory cells and other respiratory cells cause oxidative and nitrosative stress contributing to the pathogenesis of COPD. RONS and calpain play important roles in the development of airway and pulmonary vascular remodeling in COPD. Published data show that increased RONS production is associated with increased calpain activation and/or elevated calpain protein level, leading to epithelial or endothelial barrier dysfunction, neovascularization, lung inflammation, increased smooth muscle cell proliferation, and deposition of extracellular matrix protein. Further investigation of the redox-dependent calpain signaling may provide future targets for the prevention and treatment of COPD.

Antioxidant diet and sex interact to regulate NOS isoform expression and glomerular mesangium proliferation in Zucker diabetic rat kidney

Oxidative stress contributes substantially to the pathophysiology of diabetic nephropathy (DN). Consumption of an antioxidant-fortified (AO) diet from an early age prevents or delays later development of DN in the Zucker rat female with type 2 diabetes. We hypothesize this is due to effects on mesangial matrix and renal nitric oxide synthase (NOS) distribution and to sex-specific differences in NOS responses in the diabetic kidney. Total glomerular tuft area (GTA) and PAS-positive tuft area (PTA), endothelial (e), neuronal (n) and inducible (i) NOS were quantified in males and females on AO or regular (REG) diet at 6 and 20 weeks of age. eNOS was observed in glomeruli and tubules. nNOS predominantly localized to tubular epithelium in both cortex and medulla. iNOS was expressed in proximal and distal tubules and collecting ducts. Sex, diabetes duration and AO diet affected the distribution of the three isoforms. GTA and PTA increased with duration of hyperglycemia and showed a negative correlation with renal levels of all NOS isoforms. AO diet in both genders was associated with less PAS-positive staining and less mesangial expansion than the REG diet, an early increase in cortical iNOS in males, and sex-specific changes in cortical eNOS at 20 weeks. These effects of AO diet may contribute to sex-specific preservation of renal function in females.

Nitric oxide-associated chondrocyte apoptosis in trauma patients after high-energy lower extremity intra-articular fractures

BACKGROUND

The primary goal of this study was to identify nitric oxide (NO)-induced apoptosis in traumatized chondrocytes in intra-articular lower extremity fractures and the secondary goal was to identify the timeline of NO-induced apoptosis after injury.

MATERIALS AND METHODS

This is a prospective collection of samples of human cartilage harvested at the time of surgery to measure apoptotic cell death and the presence of NO by immunohistochemistry. Three patients met the criteria for control subjects and eight patients sustained high-energy intra-articular fractures and were included in the study. Subjects who sustained intra-articular acetabular, tibial, calcaneal and talus fracture had articular cartilage harvested at the time of surgical intervention. All 8 patients underwent open reduction and internal fixation of the displaced intra-articular fractures. The main outcome measures were rate of apoptosis, degree of NO-induced apoptosis in chondrocytes, and the timeline of NO-induced apoptosis after high-energy trauma.

RESULTS

The percentage of apoptotic chondrocytes was higher in impacted samples than in normal cartilage (56 vs 4 %), confirming the presence of apoptosis after intra-articular fracture. The percentage of cells with NO was greater in apoptotic cells than in normal cells (59 vs 20 %), implicating NO-induction of apoptosis. The correlation between chondrocyte apoptosis and increasing time from injury was found to be -0.615, indicating a decreasing rate of apoptosis post injury.

CONCLUSIONS

The data showed the involvement of NO-induced apoptosis of chondrocytes after high-energy trauma, which decreased with time from injury.

Kinetics of 3-nitrotyrosine modification on exposure to hypochlorous acid

The markers 3-nitrotyrosine and 3-chlorotyrosine are measured as surrogates for reactive nitrogen species and hypochlorous acid respectively, which are both elevated in inflamed human tissues. Previous studies reported a loss of 3-nitrotyrosine when exposed to hypochlorous acid, suggesting that observations of 3-nitrotyrosine underestimate the presence of reactive nitrogen species in diseased tissue (Whiteman and Halliwell, Biochemical and Biophysical Research Communications, 258, 168-172 (1999)). This report evaluates the significance of 3-nitrotyrosine loss by measuring the kinetics of the reaction between 3-nitrotyrosine and hypochlorous acid. The results demonstrate that 3-nitrotyrosine is chlorinated by hypochlorous acid or chloramines to form 3-chloro-5-nitrotyrosine. As 3-nitrotyrosine from in vivo samples is usually found within proteins rather than as free amino acid, we also examined the reaction of 3-nitrotyrosine modification in the context of peptides. The chlorination of 3-nitrotyrosine in peptides was observed to occur up to 700-fold faster than control reactions using equivalent amino acid mixtures. These results further advance our understanding of tyrosine chlorination and the use of 3-nitrotyrosine formed in vivo as a biomarker of reactive nitrogen species.

Reactive oxygen and nitrogen species in steatotic hepatocytes: a molecular perspective on the pathophysiology of ischemia-reperfusion injury in the fatty liver

SIGNIFICANCE

Hepatic ischemia-reperfusion (IR) injury results from the temporary deprivation of hepatic blood supply and is a common side effect of major liver surgery (i.e., transplantation or resection). IR injury, which in most severe cases culminates in acute liver failure, is particularly pronounced in livers that are affected by non-alcoholic fatty liver disease (NAFLD). In NAFLD, fat-laden hepatocytes are damaged by chronic oxidative/nitrosative stress (ONS), a state that is acutely exacerbated during IR, leading to extensive parenchymal damage.

RECENT ADVANCES

NAFLD triggers ONS via increased (extra)mitochondrial fatty acid oxidation and activation of the unfolded protein response. ONS is associated with widespread protein and lipid (per)oxidation, which reduces the hepatic antioxidative capacity and shifts the intracellular redox status toward an oxidized state. Moreover, activation of the transcription factor peroxisome proliferator-activated receptor α induces expression of mitochondrial uncoupling protein 2, resulting in depletion of cellular energy (ATP) reserves. The reduction in intracellular antioxidants and ATP in fatty livers consequently gives rise to severe ONS and necrotic cell death during IR.

CRITICAL ISSUES

Despite the fact that ONS mediates both NAFLD and IR injury, the interplay between the two conditions has never been described in detail. An integrative overview of the pathophysiology of NAFLD that renders steatotic hepatocytes more vulnerable to IR injury is therefore presented in the context of ONS.

FUTURE DIRECTIONS

Effective methods should be devised to alleviate ONS and the consequences thereof in NAFLD before surgery in order to improve resilience of fatty livers to IR injury.

Ten misconceptions about antioxidants

Oxidative damage is a common cellular event involved in numerous diseases and drug toxicities. Antioxidants prevent or delay oxidative damage, and therefore there has been extensive research into the discovery of natural and newly designed antioxidants. Initial excitement regarding the potential health benefits of antioxidants has diminished. Currently, it is even claimed that antioxidants increase mortality. The antioxidant pendulum appears to swing from healthy to toxic and from general panacea to insignificant ingredient. Owing to the polarity of views towards antioxidants, nutritional recommendation ranges from advice to increase antioxidant status in plasma to the notion that it is a useless measurement. Such views, lacking sufficient scientific support, lead to misconceptions, which in our opinion hinder the rational use of food supplements and impedes the design and development of new antioxidant drugs. As a result, good opportunities might easily be missed.

Initiation of nitric oxide (NO) synthesis in roots of etiolated seedlings of pea (Pisum sativum L.) under the influence of nitrogen-containing compounds

The level of nitric oxide (NO) in roots of 2-day-old etiolated pea (Pisum sativum L.) seedlings was investigated by fluorescence microscopy using the fluorescent probe 4,5-diaminofluorescein diacetate. Segments representing transversal (cross) cuts of the roots having thickness of 100 to 150 µm (a segment of the root located 10 to 15 mm from the apex) were analyzed. A substantial concentration of NO in the roots was registered when the seedlings were grown in water (control). Addition of 4 mM sodium nitroprusside, 20 mM KNO₃, 2 mM NaNO₂, 2 mM L-arginine into the growth medium increased NO concentration with respect to the control by 1.7- to 2.3-fold. Inhibitors of animal NO-synthase - 1 mM Nω-nitro-L-arginine methyl ester hydrochloride and 1 mM aminoguanidine hydrochloride - reduced the intensity of fluorescence in the root segments in the presence of all the studied compounds. In medium with KNO₃, the inhibitor of nitrate reductase -150 µM sodium tungstate - lowered the fluorescence intensity by 60%. Scavengers of nitric oxide - 100 µM 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and 4 µM hemoglobin - lowered NO concentration in all the studied variants. Potassium ferrocyanide (4 mM) as the inactive analog of sodium nitroprusside inhibited generation of NO. These results are discussed regarding possible pathways of NO synthesis in plants.

Protein damage, repair and proteolysis

Proteins are continuously affected by various intrinsic and extrinsic factors. Damaged proteins influence several intracellular pathways and result in different disorders and diseases. Aggregation of damaged proteins depends on the balance between their generation and their reversal or elimination by protein repair systems and degradation, respectively. With regard to protein repair, only few repair mechanisms have been evidenced including the reduction of methionine sulfoxide residues by the methionine sulfoxide reductases, the conversion of isoaspartyl residues to L-aspartate by L-isoaspartate methyl transferase and deglycation by phosphorylation of protein-bound fructosamine by fructosamine-3-kinase. Protein degradation is orchestrated by two major proteolytic systems, namely the lysosome and the proteasome. Alteration of the function for both systems has been involved in all aspects of cellular metabolic networks linked to either normal or pathological processes. Given the importance of protein repair and degradation, great effort has recently been made regarding the modulation of these systems in various physiological conditions such as aging, as well as in diseases. Genetic modulation has produced promising results in the area of protein repair enzymes but there are not yet any identified potent inhibitors, and, to our knowledge, only one activating compound has been reported so far. In contrast, different drugs as well as natural compounds that interfere with proteolysis have been identified and/or developed resulting in homeostatic maintenance and/or the delay of disease progression.

Iron overload-induced rat liver injury: Involvement of protein tyrosine nitration and the effect of baicalin

Baicalin has been reported to protect against liver injury in iron-overload mice, however, the mechanisms underlying the hepatoprotective properties of baicalin are poorly understood. In this study, we systematically studied the protective effect of baicalin on iron overload induced liver injury, as well as the underlying mechanism based on nitrative stress in rat model. We found that when iron overload rats (500mgiron/kg) were fed baicalin-containing diet (0.3% and 1% w/w) for 45days, baicalin dose dependently protected against iron overload induced liver injury, including alleviation of hepatic pathological damage, decrease of SOD activity, iron content, carbonyl content, and the thiobarbituric acid-reactive substances level in hepatic tissues. It also increased serum iron content, SH content and GPx activity, decreased serum ALT and AST activities. Immunohistochemistry and immunoprecipitation analysis revealed that baicalin could also inhibit iron overload induced protein tyrosine nitration in liver. Moreover, in iron overload rat liver, we found that baicalin decreased the iron overload increased level of glutathione-S-transferases (GSTs) expression, oxidation and nitration. These results suggest that not only oxidative stress, but also nitrative stress, is involved in iron overload induced liver injury, and the underlying mechanism might partially relate to the involvement of GSTs expression and post-translational modification. Baicalin can effectively prevent iron overload caused abnormality and can be a candidate medicine for iron overload diseases.

Poly(ADP-ribose) polymerase-1 is a key mediator of cisplatin-induced kidney inflammation and injury

Cisplatin is a commonly used chemotherapeutic drug, the clinical use of which is limited by the development of dose-dependent nephrotoxicity. Enhanced inflammatory response, oxidative stress, and cell death have been implicated in the development of cisplatin-induced nephropathy; however, the precise mechanisms are elusive. Overactivation of the nuclear enzyme poly(ADP-ribose) polymerase-1 (PARP-1) by oxidative DNA damage under various pathological conditions promotes cell death and up-regulation of key proinflammatory pathways. In this study, using a well-established model of nephropathy, we have explored the role of PARP-1 in cisplatin-induced kidney injury. Genetic deletion or pharmacological inhibition of PARP-1 markedly attenuated the cisplatin-induced histopathological damage, impaired renal function (elevated serum BUN and creatinine levels), and enhanced inflammatory response (leukocyte infiltration; TNF-α, IL-1β, F4/80, adhesion molecules ICAM-1/VCAM-1 expression) and consequent oxidative/nitrative stress (4-HNE, 8-OHdG, and nitrotyrosine content; NOX2/NOX4 expression). PARP inhibition also facilitated the cisplatin-induced death of cancer cells. Thus, PARP activation plays an important role in cisplatin-induced kidney injury, and its pharmacological inhibition may represent a promising approach to preventing the cisplatin-induced nephropathy. This is particularly exciting because several PARP inhibitors alone or in combination with DNA-damaging anticancer agents show considerable promise in clinical trials for treatment of various malignancies (e.g., triple-negative breast cancer).

A novel molecular mechanism for nitrated {alpha}-synuclein-induced cell death

Although previous studies have demonstrated the involvement of nitrated α-synuclein in neurodegenerative disorders (synucleinopathies), the effects of nitrated α-synuclein and the molecular mechanisms underlying its toxicity are still unclear. In the present study, nitrated α-synuclein with four 3-nitrotyrosines (Tyr(39), Tyr(125), Tyr(133), and Tyr(136)) was obtained non-enzymatically by incubation with nitrite. The nitrated protein existed as a mixture of monomers, dimers, and polymers in solution. The nitrated α-synuclein could induce cell death in a time- and concentration-dependent manner when SH-SY5Y cells (a human neuroblastoma cell line) were incubated with the dimers and polymers. Treatment with anti-integrin α5β1 antibody partially rescued the SH-SY5Y cells from the cell death. Dot blotting and immunoprecipitation revealed that the nitrated protein bound to integrin on the cell membranes. Level of nitric oxide (NO) and calcium-independent inducible NO synthase (iNOS) activity increased during the initial stages of the treatment. The expression of phosphorylated focal adhesion kinase (FAK) decreased in the cells. Subsequently, an increase in caspase 3 activity was observed in SH-SY5Y cells. Our results demonstrate that activation of iNOS and inhibition of FAK may both be responsible for the cell death induced by nitrated α-synuclein. These data suggest that the cytotoxicity of nitrated α-synuclein is mediated via an integrin-iNOS/-FAK signaling pathway, and that the nitration of α-synuclein plays a role in neuronal degeneration.

Effect of exposure to detergents and other chemicals on biomarkers of pulmonary response in exhaled breath from hospital cleaners: a pilot study

PURPOSE

The main aim of the study was to provide evidence whether professional cleaning was associated with biomarkers of lung damage in non-invasively collected biological fluids (exhaled air and exhaled breath condensate--EBC).

MATERIALS AND METHODS

This cross-sectional study involved 40 cleaners regularly exposed to cleaning detergents and 40 controls. The subjects completed a standard questionnaire from European Community Respiratory Health Survey (ECRHS II) and underwent a spirometry. Fractional exhaled nitric oxide (F(E)NO) was measured online, and pH, ammonium (NH(4) (+)), H(2)O(2) and 4-hydroxynonenal (4-HNE) were assayed in EBC.

RESULTS

Among the cleaners, the frequency of asthma and rhinitis was, respectively, 2.5 and 20%. The most frequently reported symptoms were sneezing (27.5%), nasal and/or pharyngeal pruritus (25%), ocular pruritus (22.5%) and cough (22.5%). There were no significant differences in comparison with the control group. Median F(E)NO levels were higher in African than in Caucasian cleaners (21.5 [16.5-30.0] ppb and 18.0 [13.5-20.5] ppb; p < 0.05). H(2)O(2)-EBC (0.26 [0.09-0.53] μM vs. 0.07 [0.04-0.15] μM; p < 0.01), NH(4) (+)-EBC (857 [493-1,305] μM vs. 541 [306-907] μM; p < 0.01) and pH-EBC (8.17 [8.09-8.24] vs. 8.06 [7.81-8.10]; p < 0.01) were higher in the cleaners than in the controls. Finally, the cleaners showed significant correlations between pH-EBC and NH(4) (+)-EBC (r = 0.33, p < 0.05) and a weak correlation between 4-HNE-EBC and H(2)O(2)-EBC (r = 0.37, p < 0.05).

CONCLUSION

The promising role of EBC analysis in biomonitoring of exposed workers was confirmed. It was also possible to identify the potential biomarkers of exposure to alkaline products (increased ammonium-EBC and pH-EBC levels) and potential biomarkers of oxidative stress (increased H(2)O(2)-EBC levels correlated with 4-HNE-EBC levels) in workers with no signs of airway diseases.

Effects of taurine on nitric oxide and 3-nitrotyrosine levels in spleen during endotoxemia

Taurine (2-aminoethanesulfonic acid) is a free sulfur-containing β-amino acid which has antioxidant, antiinflammatory and detoxificant properties. In the present study, the role of endotoxemia on peroxynitrite formation via 3-nitrotyrosine (3-NT) detection, and the possible antioxidant effect of taurine in lipopolysaccharide (LPS)-treated guinea pigs were aimed. 40 adult male guinea pigs were divided into four groups; control, endotoxemia, taurine and taurine+endotoxemia. Animals were administered taurine (300 mg/kg), LPS (4 mg/kg) or taurine plus LPS intraperitoneally. After 6 h of incubation, when highest blood levels of taurine and endotoxin were attained, the animals were sacrificed and spleen samples were collected. The amounts of 3-nitrotyrosine and taurine were measured by HPLC, and reactive nitrogen oxide species (NOx) which are stable end products of nitric oxide was measured spectrophotometrically in spleen tissues. LPS administration significantly decreased the concentration of taurine whilst increased levels of 3-NT and NOx compared with control group. It was determined that taurine treatment decreased the levels of 3-nitrotyrosine and NOx in taurine+endotoxemia group. The group in which taurine was administered alone, contradiction to well-known antioxidant effect, taurine caused elevated concentration of 3-NT and NOx. This data suggest that taurine protects spleen against oxidative damage in endotoxemic conditions. However, the effect of taurine is different when it is administered alone. In conclusion, taurine may act as an antioxidant during endotoxemia, and as a prooxidant in healthy subjects at this dose.

Nitration activates tyrosine toward reaction with the hydrated electron

3-Nitrotyrosine has been reported as an important biomarker of oxidative stress that may play a role in a variety of diseases. In this work, transient UV-visible absorption spectra and kinetics observed during the reaction of the hydrated electron, e(aq)(-), with 3-nitrotyrosine and derivatives thereof were investigated. The absorption spectra show characteristics of aromatic nitro anion radicals. The absorptivity of radical anion product at 300 nm is estimated to be (1.0 ± 0.2) × 10(4) M(-1) cm(-1) at pH 7.3. The rate constants determined for the reaction of e(aq)(-) with 3-nitrotyrosine, N-acetyl-3-nitrotyrosine ethyl ester and glycylnitrotyrosylglycine at neutral pH (3.0 ± 0.3) × 10(10) M(-1) s(-1), (2.9 ± 0.2) × 10(10) M(-1) s(-1) and (1.9 ± 0.2) × 10(10) M(-1) s(-1), respectively, approach the diffusion-control limit and are almost two orders of magnitude higher than those for the reactions with tyrosine and tyrosine-containing peptides. The magnitude of the rate constants supports reaction of e(aq)(-) at the nitro group, and the product absorbance at 300 nm is consistent with formation of the nitro anion radical. The pH dependence of the second-order rate constant for e(aq)(-) decay (720 nm) in the presence of 3-nitrotyrosine shows a decrease with increasing pH, consistent with unfavorable electrostatic interactions. The pH dependence of the second-order rate constant for formation of radical anion (300 nm) product suggests that deprotonation of the amino group slows the rate, which indicates that deamination to form the 1-carboxy-2-(4-hydroxy-3-nitrophenyl)ethyl radical occurs. We conclude that the presence of the nitro group activates tyrosine and derivatives toward reaction with e(aq)(-) and can affect the redox chemistry of biomolecules exposed to oxidative stress.

Kaempferol protects MC3T3-E1 cells through antioxidant effect and regulation of mitochondrial function

Kaempferol, a natural flavonoid present in fruits, vegetables, and teas, provides beneficial effects for human health. In this study, we investigated the protective effects of kaempferol on antimycin A (AMA)-induced toxicity in osteoblast-like MC3T3-E1 cells. Exposure of MC3T3-E1 cells to AMA caused significant cell viability loss, as well as mitochondrial membrane potential dissipation, complex IV inactivation, intracellular calcium ([Ca²⁺](i)) elevation, and reactive oxygen species (ROS) production. Pretreatment with kaempferol prior to AMA exposure significantly reduced AMA-induced cell damage by preventing mitochondrial membrane potential dissipation, complex IV inactivation, [Ca²⁺](i) elevation, and ROS production. Kaempferol also induced the activation of PI3K (phosphoinositide 3-kinase), Akt (protein kinase B), and CREB (cAMP-response element-binding protein) inhibited by AMA, which result demonstrates that kaempferol utilizes the PI3K/Akt/CREB pathway to augment metabolic activity inhibited by AMA. All these data indicate that kaempferol may reduce or prevent osteoblasts degeneration in osteoporosis or other degenerative disorders.

Protein nitration, lipid peroxidation and DNA damage at high altitude in acclimatized lowlanders and native highlanders: relation with oxygen consumption

Reactive oxygen and nitrogen species have been reported to be increased due to hypobaric hypoxia. It was hypothesized that lowlanders are more susceptible to protein nitration, lipid peroxidation and DNA damage at high altitude than highlanders and formation of these biomarkers may have strong correlation with oxygen consumption. Male volunteers were randomly selected and categorized into 3 groups, i.e. lowlanders at sea level (LL-SL, n=10), lowlanders at an altitude of 4560 m (LL-HA, n=10) and highlanders (HAN, n=10). Volunteers performed maximal aerobic exercise. Resting and post-exercise blood samples were taken at sea level and high altitude. Both resting and maximum oxygen consumption showed positive correlation with stress markers. LL-HA showed increased 3-nitrotyrosine and lipid hydroperoxide than LL-SL at rest. 3-Nitrotyrosine and lipid hydroperoxide increased after exercise in 3 groups, but percentage increase was higher in HAN than LL-SL and LL-HA. LL-SL and HAN showed significant DNA damage after exercise. Results indicate that resting oxygen consumption is positively correlated with nitrosative and oxidative stress markers irrespective of environmental condition and adaptation levels. Lowlanders have shown higher susceptibility to hypoxic insult than highlanders at rest, but when subjected to exercise test, they showed better tolerance to hypoxia than highlanders.

Lipoprotein lipase is nitrated in vivo after lipopolysaccharide challenge

Lipopolysaccharide (LPS) administration down-regulates lipoprotein lipase (LPL) activity at the posttranscriptional level. Hypertriglyceridemia is the main metabolic consequence of this fall in LPL activity and is presumably involved in the innate immune response to infection. Nitric oxide (NO) has been implicated in LPS-induced down-regulation of LPL activity, but whether its effects are direct or indirect remains unclear. Here we examined the potential nitration of LPL in vivo in response to LPS challenge in rats. We found hypertriglyceridemia, iNOS expression, NO overproduction, and a generalized decrease in LPL activity in tissues 6 h after LPS administration. LPL sensitivity to nitration was first explored by in vitro exposure of bovine LPL to peroxynitrite, a reactive nitrogen species (RNS). Nitration was confirmed by anti-nitrotyrosine Western blot and subsequent identification of specific nitrotyrosine-containing LPL sequences by tandem mass spectrometry. Further analysis by targeted mass spectrometry revealed three in vivo-nitrated tyrosine residues in heart LPL from LPS-challenged rats. This is the first study to identify nitrated tyrosine residues in LPL, both in vitro and in vivo, and it demonstrates that LPL is a target for RNS in endotoxemia. These results indicate that LPL nitration may be a new mechanism of LPL activity regulation in vivo.

Myeloperoxidase: molecular mechanisms of action and their relevance to human health and disease

Myeloperoxidase (MPO) is a heme-containing peroxidase abundantly expressed in neutrophils and to a lesser extent in monocytes. Enzymatically active MPO, together with hydrogen peroxide and chloride, produces the powerful oxidant hypochlorous acid and is a key contributor to the oxygen-dependent microbicidal activity of phagocytes. In addition, excessive generation of MPO-derived oxidants has been linked to tissue damage in many diseases, especially those characterized by acute or chronic inflammation. It has become increasingly clear that MPO exerts effects that are beyond its oxidative properties. These properties of MPO are, in many cases, independent of its catalytic activity and affect various processes involved in cell signaling and cell-cell interactions and are, as such, capable of modulating inflammatory responses. Given these diverse effects, an increased interest has emerged in the role of MPO and its downstream products in a wide range of inflammatory diseases. In this article, our knowledge pertaining to the biologic role of MPO and its downstream effects and mechanisms of action in health and disease is reviewed and discussed.

Protein tyrosine nitration: selectivity, physicochemical and biological consequences, denitration, and proteomics methods for the identification of tyrosine-nitrated proteins

Protein tyrosine nitration (PTN) is a post-translational modification occurring under the action of a nitrating agent. Tyrosine is modified in the 3-position of the phenolic ring through the addition of a nitro group (NO2). In the present article, we review the main nitration reactions and elucidate why nitration is not a random chemical process. The particular physical and chemical properties of 3-nitrotyrosine (e.g., pKa, spectrophotometric properties, reduction to aminotyrosine) will be discussed, and the biological consequences of PTN (e.g., modification of enzymatic activity, sensitivity to proteolytic degradation, impact on protein phosphorylation, immunogenicity and implication in disease) will be reviewed. Recent data indicate the possibility of an in vivo denitration process, which will be discussed with respect to the different reaction mechanisms that have been proposed. The second part of this review article focuses on analytical methods to determine this post-translational modification in complex proteomes, which remains a major challenge.

Tyrosine phosphorylation/dephosphorylation regulates peroxynitrite-mediated peptide nitration

Proteins are targets of reactive nitrogen species such as peroxynitrite and nitrogen dioxide. Among the various amino acids in proteins, tyrosine and tryptophan residues are especially susceptible to attack by reactive nitrogen species. On the other hand, protein tyrosine phosphorylation has gained much attention in respect to cellular regulatory events and signal transduction. Peroxynitrite-mediated nitration of peptide YPPPPPW and phosphopeptide pYPPPPPW were studied at pH 7.4. The predominant nitrated products were separated and identified by reverse phase high performance liquid chromatography coupled with electrospray ionization mass spectrometry (LC-MS). The nitration sites were established by tandem electrospray ionization-mass spectrometry (LC-MS/MS). A regulatory effect of tyrosine phosphorylation/dephosphorylation on peptide nitration was observed. YPPPPPW was predominantly nitrated at tyrosine residue while pYPPPPPW was nitrated at tryptophan one. Our results can help in understanding the biochemical significance of the relationship of tyrosine phosphorylation and nitration in proteins.

iNOS-mediated generation of reactive oxygen and nitrogen species by biomaterial-adherent neutrophils

Infection due to implanted cardiovascular biomaterials is a serious complication initiated by bacterial adhesion to the surface of the implant. The release of reactive oxygen species by neutrophils, particularly superoxide anion, is a well-known bactericidal mechanism. Additionally, nitric oxide (NO) has also been identified as an important cytotoxic mediator in acute and chronic inflammatory responses with enhanced NO production by upregulation of inducible nitric oxide synthase (iNOS). The interaction of NO and superoxide anion will result in the formation of peroxynitrite (OONO-), a potent cytotoxic oxidant. In this study, we have shown that biomaterial-induced neutrophil activation does not cause upregulation of iNOS and activation of iNOS-mediated pathways. However, NO and O2- production does occur over time upon adhesion to a biomaterial and is modulated by biomaterial surface chemistry. With no stimulus, the polyethylene oxide-modified polyurethane induced greater neutrophil activation than did the control as indicated by the increased production of NO and O2- over time. Adherent-stimulated neutrophils generally produced lower amounts of NO over time in comparison with unstimulated cells. Furthermore, there is no evidence of peroxynitrite activity in unstimulated neutrophils adherent to the Elasthane 80A. However, upon stimulation with adherent Staphylococcus epidermidis, peroxynitrite formation did occur. Our results suggest that bactericidal mechanisms in neutrophils involving NO generation (NOS pathway) are further compromised than O2- producing pathways (NADPH oxidase) upon exposure to biomaterials, resulting in a diminished microbial killing capacity, which can increase the probability of device-centered infections.

Peroxynitrite formation in radiation-induced salivary gland dysfunction in mice

Xerostomia frequently arises in patients with head and neck malignancies that are treated by radiation. However, the mechanisms responsible for the destruction of the salivary gland remain unknown. We previously established a xerostomia model of mice and identified the pathway through which nitric oxide (NO) affects the pathogenesis of radiation-induced salivary gland dysfunction. Although the toxicity of NO alone is modest, NO with superoxide anion (O2(*-)) rapidly forms peroxynitrite (ONOO), a more powerful toxic oxidant. In this study, we used the experimental model to examine: 1) when NO and O2(*-) production is maximum in the salivary gland after irradiation;2) whether peroxynitrite, as assessed by nitrotyrosine production, is responsible for salivary gland dysfunction; and 3) the effect of the iNOS selective inhibitor, aminoguanidine (AG), on nitrotyrosine formation. The increases in production of NO and O2(*-) in the salivary gland peaked on day 7 after irradiation. Nitrotyrosine detected immunohistochemically was significantly reduced by AG in the salivary gland. On the basis of these results, we concluded that NO together with O2(*-) forms the more reactive ONOO, which might be an important pathogenic factor in radiation-induced salivary gland dysfunction.

Modulation of astroglial energy metabolism by nitric oxide

Activated astroglial cells produce large amounts of nitric oxide (NO) which, through the binding to soluble guanylyl cyclase, rapidly increases cyclic GMP concentrations. In addition, through the binding with the a-a (3) binuclear center of cytochrome c oxidase, NO rapidly decreases the affinity of this complex for O(2), hence reversibly inhibiting the mitochondrial electron flux and ATP synthesis. Despite promoting a profound degree of mitochondrial inhibition, astrocytes show remarkable resistance to NO and peroxynitrite, whereas neurons are highly vulnerable. Recent evidence suggests that the inhibition of mitochondrial respiration by these nitrogen-derived reactive species leads to the modulation of key regulatory steps of glucose metabolism. Thus, upregulation of glucose uptake, the stimulation of glycolysis and the activation of pentose-phosphate pathway appear to be important sites of action. The stimulation of these glucose-metabolizing pathways by NO would represent a transient attempt by the glial cells to compensate for energy impairment and oxidative stress, and thus to emerge from an otherwise pathological outcome.

Evidence for the participation of nitric oxide in pemphigus

Pemphigus is an inflammatory autoimmune disorder of the skin. Nitric oxide (NO) is an inflammatory mediator linked to a variety of physiological and pathophysiological phenomena that include skin tumors, psoriasis, urticaria, and atopic dermatitis. Inflammatory cells present in pemphigus lesions are important sources of NO production. We investigated whether NO is involved in pemphigus. A prospective cohort study was conducted at the Dermatology Service of the Hospital Universitário Walter Cantídio of the Federal University of Ceará. All patients seen at the outpatient clinic between August 2000 and July 2001, with a clinically and histologically confirmed diagnosis of pemphigus were included. The median age was 42.5 years (range: 12-69 years) with a male to female ratio of 3:2. Total serum nitrite levels, used as a marker for NO production, were determined by the Griess reaction. Skin biopsies from pemphigus and breast surgery (control) patients were used for the detection of the inducible NO synthase (iNOS) by immunohistochemistry. Twenty-two (22) patients with pemphigus and eight (8) controls who did not differ in demographic characteristics were included. Total serum nitrite levels were significantly higher (>7 micromol/L) in pemphigus patients compared to controls (<6 micromol/L), regardless of the severity of the clinical activity of pemphigus (P < 0.0001). All pemphigus biopsies presented increased immunostaining for iNOS that was not detected in normal skin samples. These data are the first to demonstrate that pemphigus patients display increased serum NO levels that are associated with increased iNOS expression in the affected skin.

Free radical mediated oxidative stress and toxic side effects in brain induced by the anti cancer drug adriamycin: insight into chemobrain

Adriamycin (ADR) is a chemotherapeutic agent useful in treating various cancers. ADR is a quinone-containing anthracycline chemotherapeutic and is known to produce reactive oxygen species (ROS) in heart. Application of this drug can have serious side effects in various tissues, including brain, apart from the known cardiotoxic side effects, which limit the successful use of this drug in treatment of cancer. Neurons treated with ADR demonstrate significant protein oxidation and lipid peroxidation. Patients under treatment with this drug often complain of forgetfulness, lack of concentration, dizziness (collectively called somnolence or sometimes called chemobrain). In this study, we tested the hypothesis that ADR induces oxidative stress in brain. Accordingly, we examined the in vivo levels of brain protein oxidation and lipid peroxidation induced by i.p. injection of ADR. We also measured levels of the multidrug resistance-associated protein (MRP1) in brain isolated from ADR- or saline-injected mice. MRP1 mediates ATP-dependent export of cytotoxic organic anions, glutathione S-conjugates and sulphates. The current results demonstrated a significant increase in levels of protein oxidation and lipid peroxidation and increased expression of MRP1 in brain isolated from mice, 72 h post i.p injection of ADR. These results are discussed with reference to potential use of this redox cycling chemotheraputic agent in the treatement of cancer and its chemobrain side effect in brain.

Plasma levels of nitrites, PGF1α and nitrotyrosine in LPS-treated rats: functional and histochemical implications in aorta

We investigated the effects of lipopolysaccharide (LPS) administration on plasma nitrite, nitrotyrosine and 6-keto prostaglandin F1alpha, (PGF1alpha) levels and the related resultant changes in function and histochemistry of aorta in rats. Plasma nitrite and PGF1alpha nitrotyrosine levels were analysed after 5 mg/kg intravenous LPS was administered to rats compared with those in non-treated rats. The distribution of nitrotyrosine in the aorta was studied immunohistochemically. The contractile responses of aortic rings to phenylephrine (PE) from both the LPS-treated and control rats were studied in the organ baths. There were increases in plasma nitrite, PGF1alpha, and nitrotyrosine concentrations of LPS-treated rats compared to non-treated rats. Immunoreactivity of nitrotyrosine residues were detected in the endothelial and smooth muscle cells in LPS-treated but not in control rat aorta. The contractile responses to PE of the LPS-treated rat aortic rings were significantly reduced as compared with those of control rat's. Incubation of the aortic rings from LPS-treated rats with cyclooxygenase inhibitor indomethacine or with a combination of indomethacine and nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) increased the contractile responses to the levels observed in control rats suggesting that both prostanoids and particularly nitric oxide (NO) are involved in the reduced contractile responses in LPS-treated rats. These results supported the view that LPS might cause an increment in both NO and PGI2 levels. This increase in the NO and PGI2 levels may be responsible from the reduction in responses of aorta to contractile agents in LPS-treated rats. Increased peroxynitrite formation in LPS-treated rats may lead to nitration of the tyrosil residues of the proteins in the aorta.

Nitrative and oxidative DNA damage in oral lichen planus in relation to human oral carcinogenesis

Oral lichen planus (OLP) is a chronic inflammatory disease, which has been clinically associated with development to oral cancer. A double immunofluorescence labeling study found that 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) accumulated in oral epithelium in OLP and oral squamous cell carcinoma (OSCC) biopsy specimens, whereas little or no immunoreactivity was observed in normal oral mucosa. Colocalization of 8-nitroguanine and inducible nitric oxide synthase (iNOS) was found in oral epithelium of OLP and OSCC. Immunoreactivity of 3-nitrotyrosine, which is formed by protein tyrosine nitration and is considered to be a biochemical marker for inflammation, was also observed in oral epithelial cells and colocalized with 8-nitroguanine. Accumulation of p53 was more strongly observed in oral epithelium in OSCC than OLP, whereas there was no p53 accumulation in normal oral mucosa. Our findings demonstrate that iNOS-dependent DNA damage in OLP may lead to p53 accumulation in not only OLP but also OSCC. We conclude that the formation of potentially mutagenic DNA lesions including 8-nitroguanine and 8-oxodG may contribute to the development of oral cancer from OLP.

Trace analysis of oxidized, nitrated, and chlorinated aromatic amino acids by capillary electrophoresis with electroosmotic flow modification allowing large-volume sample stacking

A capillary electrophoresis method has been developed for the simultaneous analysis of the oxidized, nitrated, and chlorinated aromatic amino acids, as well as their parent compounds. These modifications of the aromatic amino acids in proteins or free form are induced by the attack of reactive, mainly free radical species generated during cell stress, and these stable products may serve as biomarkers of cell damage. The analytes tyrosine, phenylalanine, dihydroxyphenylalanine, tryptophan, 3-nitrotyrosine, 3-chlorotyrosine, ortho-tyrosine, meta-tyrosine, 3-hydroxyphenylacetic acid (internal standard 1), and alpha-methyltyrosine (internal standard 2) were separated in their anionic forms in alkaline borate buffer. The polyamine spermine was used as electroosmotic flow (EOF) modifier. Adsorbing to the capillary wall, spermine can either suppress or even reverse the EOF depending on its concentration and the pH. The effects of the pH of the separation buffer, the spermine concentration, the temperature, and the applied field strength on the separation were examined. The modified aromatic amino acids are present in biological fluids in a much lower concentration than their parent compounds, thus high detection sensitivity of the analytical method is required. To achieve good detection sensitivity, field-amplified sample stacking of large injection volumes was applied. Omitting polyamine from the sample buffer allowed local reversal of the EOF, thus removal of the low conductivity sample buffer at the capillary inlet. In this way, 100% of the capillary to the detection window could be filled with the sample, and the detection limits achieved for the modified aromatic amino acids were in the range of 2.5-10 nM.

Cigarette smoke alters human vitamin E requirements

Vitamin E is a lipophilic chain-breaking antioxidant that prevents lipid peroxidation. Although cigarette smoke is a potent source of oxidative stress that depletes vitamin E in vitro, it is unclear whether it has a similar effect in vivo, particularly in humans. Therefore, this review will discuss the role of cigarette smoke on gamma-tocopherol (gamma-T) nitration, its effect on alpha-tocopherol (alpha-T) biokinetics in smokers, and the changes in the synthesis, plasma concentrations, and urinary excretion of the vitamin E metabolite (CEHC; carboxy-ethyl-hydroxy-chroman). Last, the possibility of CEHC as a biomarker of vitamin E status will be assessed as will the question whether smokers have increased dietary requirements of vitamin E.

Comparison of spectrophotometric, HPLC and chemilumines-cence methods for 3-nitrotyrosine and peroxynitrite interaction

We have studied the interaction of 3-nitrotyrosine with peroxynitrite using three different methods; chemiluminescence, spectrophotometry and HPLC. Peroxynitrite-induced luminol or lucigenin chemiluminescence were significantly decreased by 3-nitrotyrosine, in concentration-dependent manners. The intensity of the peroxynitrite spectrum was also markedly reduced in the presence of 3-nitrotyrosine in the spectrophometric assay. However, there was no attenuation of the 3-nitrotyrosine signal in the HPLC assay after mixing with peroxynitrite. The interaction of 3-nitrotyrosine and hypochlorous acid (HOCl) was also studied via the chemiluminescence assay, where the HOCl-induced responses were markedly inhibited by 3-nitrotyrosine. These results suggest that caution should be taken when studying the levels or interactions of 3-nitrotyrosine.

High sensitivity analysis of nitrite and nitrate in biological samples by capillary zone electrophoresis with transient isotachophoretic sample stacking

Tissue level of nitrate and nitrite are established indicators of altered nitric oxide metabolism under various pathological conditions. Determination of these anions in biological samples, in the presence of high chloride concentration, using capillary zone electrophoresis suffers from poor detection sensitivity. Separation conditions providing excellent resolution and submicromolar detection sensitivity of nitrate and nitrite have been developed and validated. Simple sample preparation was applied that maintains nitrite stability in tissue extracts and at the same time allows transient isotachophoresis stacking of the analytes. Nitrate and nitrite concentrations in rat brain and liver tissue samples were determined in control and lipopolysaccharide treated animals.

Accumulation of 8-nitroguanine in human gastric epithelium induced by Helicobacter pylori infection

Helicobacter pylori infection causes chronic inflammation, which can lead to gastric carcinoma. A double immunofluorescence labeling study demonstrated that the level of 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) apparent in gastric gland epithelium was significantly higher in gastritis patients with H. pylori infection than in those without infection. A significant accumulation of proliferating cell nuclear antigen, a prognostic factor for gastric cancer, was observed in gastric gland epithelial cells in patients with H. pylori infection as compared to those without infection, and its accumulation was closely correlated with the formation of 8-nitroguanine and 8-oxodG. These results suggest that nitrosative and oxidative DNA damage in gastric epithelial cells and their proliferation by H. pylori infection may lead to gastric carcinoma. 8-Nitroguanine could be not only a promising biomarker for inflammation but also a useful indicator of the risk of gastric cancer development in response to chronic H. pylori infection.

Oxidative DNA damage induced by nitrotyrosine, a biomarker of inflammation

Inflammation has been postulated as a risk factor for several cancers. 3-Nitrotyrosine is a biochemical marker for inflammation. We investigated the ability of nitrotyrosine and nitrotyrosine-containing peptides (nitroY-peptide) to induce DNA damage by the experiments using 32P-labeled DNA fragments obtained from the human p53 tumor suppressor gene and an HPLC-electrochemical detector. Nitrotyrosine and nitroY-peptide caused Cu(II)-dependent DNA damage in the presence of P450 reductase, which is considered to yield nitroreduction. Catalase inhibited DNA damage, suggesting the involvement of H2O2. Nitrotyrosine and nitroY-peptide increased 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) formation, an indicator of oxidative DNA damage. Nitrotyrosine-containing peptides of histone induced 8-oxodG formation more efficiently than free nitrotyrosine. We propose the possibility that nitrotyrosine-induced H2O2 formation and DNA damage contribute to inflammation-associated carcinogenesis.

Reactive nitrogen species scavenging, rather than nitric oxide inhibition, protects from articular cartilage damage in rat zymosan-induced arthritis

1. The contribution of nitric oxide (NO) and peroxynitrite (PN) to inflammation in a zymosan-induced (1 mg, intra-articular, i.art.) rat model of arthritis was assessed by histopathology and by measuring the glycosaminoglycan (GAG) content of the articular cartilage. 2. Progression of the chronic synovitis in zymosan-induced arthritis (ZYA) was associated with increased nitrite and nitrotyrosine (3-NT) levels in the joint exudates that paralleled a progressive loss of the GAG content. An increase in 3-NT was also observed after i.art. PN. 3. The nonselective nitric oxide synthase (NOS) inhibitor l-N(G)-nitroarginine methyl ester (25-75 mg x kg(-1)day(-1)) or the selective inducible NOS inhibitor aminoguanidine (50-100 mg x kg(-1)day(-1)) given 1 h before (prophylactic) or 3 days after (therapeutic) injection of the zymosan ameliorated the synovitis, but worsened the GAG loss, as measured at the end of the experiment (day 7). 4. The PN scavenger uric acid (100-250 mg x kg(-1) i.p. four times daily) given prophylactically until the end of the experiment (day 14), in a dose compatible with its PN scavenging activity, significantly decreased both the synovitis and the GAG loss. 5. In conclusion, PN formation is associated with cartilage damage in addition to proinflammatory activity in ZYA. NOS inhibitors and a PN scavenger were able to reduce the cellular infiltration, while displaying opposite effects on cartilage homeostasis either by enhancing or ameliorating the damage, respectively.

The induction and detection in vitro of iNOS in the porcine basilar artery

The expression of iNOS in vascular tissues has an adverse effect on vascular responses to vasoconstrictors and NO-mediated vasodilators. The development of a simple method for detecting the iNOS expression by functional means would be extremely useful. Here we describe a method for inducing iNOS in the porcine basilar artery followed by the detection of iNOS protein by immunocytochemical means and the characterisation of functional responses to U46619 and L-arginine. Porcine basilar arteries were treated with LPS (1, 10 and 100 microg/ml) for between 5 and 18 h at 37 degrees C. Inducible NOS protein was expressed in a concentration-dependent manner in the endothelial and smooth muscle cells after 5 h and persisted for 18 h. Vessels treated with LPS showed a time-dependent reduction in contractile function in response to U46619 (10 nM) reaching significance at the 18-h time point. Moreover, a similar time-dependent increase in the vasodilator response to exogenously applied L-arginine (30 microM) was observed at both 5- and 18-h time points. These effects of LPS at the 18-h time point were prevented by the incubation of vessels with dexamethasone (100 microM) in addition to LPS. The vasodilator response to L-arginine was prevented with the incubation with and in the presence of the inhibitor of inducible NOS, 1400W (10 microM) in addition to LPS. These results show that iNOS protein can be expressed in porcine cerebral arteries and that the iNOS is functional. The assessment of contractile function and responses to L-arginine using single concentrations is a rapid and effective method for establishing whether functional iNOS is present in porcine cerebral arteries.