Reactive Nitrogen Species Mediate DNA Damage in Helicobacter pylori-Infected Gastric Mucosa

Background:  Reactive oxygen species (ROS) and reactive nitrogen species (RNS) can play an important role in cellular injury and carcinogenesis of gastric epithelial cells infected with Helicobacter pylori . 8-OH-deoxy guanosine (8-OHdG) and 8-nitroguanine (8-NG) are markers for ROS- and RNS-mediated DNA oxidation, respectively. In this study, RNS-mediated DNA damage in gastric mucosa was observed directly using a newly developed antibody to 8-NG to clarify how H. pylori infection causes nitrative DNA damage to gastric epithelial cells.
Methods:  Immunohistochemistry with anti-8-OHdG and anti-8-NG antibodies was performed on gastric tissue samples from 45 patients (25 men and 20 women) with H. pylori -positive gastritis and 19 patients (11 men and 8 women) exhibiting successful H. pylori eradication. Histologic factors for gastric mucosal inflammation were graded according to the guidelines of the Updated Sydney system.
Results:  In corpus mucosa, 8-OHdG and 8-NG production were significantly associated with the degree of glandular atrophy, infiltration of chronic inflammatory cells and intestinal metaplasia in the glandular epithelial cells. Successful H. pylori eradication resulted in a significant reduction of chronic inflammatory cell infiltration and neutrophilic activity. Mean 8-OHdG production was lower after H. pylori eradication in both corpus and antral mucosa ( p  = .022 and .049, respectively). However, the reduction in 8-NG exhibited was more pronounced than the reduction of 8-OhdG ( p  = .004 and .007, respectively).
Conclusions:  Helicobacter pylori infection can induce inflammatory cells infiltration, which evokes DNA damage of gastric epithelial cells through ROS and RNS production. 8-NG might be a more sensitive biomarker than 8-OHdG for H. pylori -induced DNA damage in gastric mucosa.     

Oxidative depolymerization of polysaccharides by reactive oxygen/nitrogen species

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are constantly produced and are tightly regulated to maintain a redox balance (or homeostasis) together with antioxidants (e.g. superoxide dismutase and glutathione) under normal physiological circumstances. These ROS/RNS have been shown to be critical for various biological events including signal transduction, aging, apoptosis, and development. Despite the known beneficial effects, an overproduction of ROS/RNS in the cases of receptor-mediated stimulation and disease-induced oxidative stress can inflict severe tissue damage. In particular, these ROS/RNS are capable of degrading macromolecules including proteins, lipids and nucleic acids as well as polysaccharides, and presumably lead to their dysfunction. The purpose of this review is to highlight (1) chemical mechanisms related to cell-free and cell-based depolymerization of polysaccharides initiated by individual oxidative species; (2) the effect of ROS/RNS-mediated depolymerization on the successive cleavage of the glycosidic linkage of polysaccharides by glycoside hydrolases; and (3) the potential biological outcome of ROS/RNS-mediated depolymerization of polysaccharides.     

Oxidative stress as a potential biomarker for determining disease activity in patients with Rheumatoid Arthritis

Rheumatoid arthritis is an inflammatory, autoimmune disease where oxidative stress has been proposed to contribute to the joint tissue damage. To establish whether measurement of the redox status in blood mirrors the oxidant status at sites of inflammation in patients with rheumatoid arthritis, we concomitantly examined their oxidant status by spectrophotometry and/or flow cytometry. The basal levels of total reactive oxygen species (ROS), superoxide and hydroxyl radicals were significantly raised in neutrophils sourced from peripheral blood and synovial infiltrate, as also showed a strong positive correlation; however, there was no major increase in the reactive nitrogen species RNS generated in monocytes from both sources. Furthermore, raised levels of superoxide in neutrophils of synovial infiltrate showed a positive correlation with NADPH oxidase activity in synovial fluid. Additionally, as ROS generated in both peripheral blood and synovial infiltrate correlated positively with both DAS 28 and CRP/anti-CCP levels, its measurement can serve as an indirect measure of the degree of inflammation in patients with RA.     

Redox biology and gastric carcinogenesis: the role of Helicobacter pylori

Almost half the world's population is infected by Helicobacter pylori (H. pylori). This bacterium increases the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in human stomach, and this has been reported to impact upon gastric inflammation and carcinogenesis. However, the precise mechanism by which H. pylori induces gastric carcinogenesis is presently unclear. Although the main source of ROS/RNS production is possibly the host neutrophil, H. pylori itself produces O???. Furthermore, its cytotoxin induces ROS production by gastric epithelial cells, which might affect intracellular signal transduction, resulting in gastric carcinogenesis. Excessive ROS production in gastric epithelial cells can cause DNA damage and thus might be involved in gastric carcinogenesis. Understanding the molecular mechanism of H. pylori-induced carcinogenesis is important for developing new strategies against gastric cancer.     

Interplay of Cu,Zn superoxide dismutase and nitric oxide synthase in neurodegenerative processes

Reactive oxygen and nitrogen species (ROS and RNS) have been extensively recognized as important signaling molecules implicated in physiological processes such as gene expression, cell differentiation and immune activation. Nevertheless, continuous production of these species may produce oxidative and/or nitrosative stress resulting in cell damage and ultimately leading to cell death. Due to the high oxygen consumption and relative poor antioxidant defense, the central nervous system is highly susceptible to ROS- and RNS-mediated toxicity. Actually, the oxidative and nitrosative stress have been implicated in the pathogenesis of neurodegeneration of a large variety of neurological disorders. This review will cover some aspects of the involvement of ROS- and RNS-mediated apoptotic processes occurring in cellular models of familial amyotrophic lateral sclerosis (FALS), in particular the cases associated with mutations in SOD1, the gene encoding Cu,Zn superoxide dismutase (Cu,Zn SOD). A possible role for proteasome in the inhibition of neurodegenerative process by balancing ROS and RNS species is envisaged on the basis of evidence provided by results obtained from studies on this experimental model.     

JNK signaling pathway is a key modulator in cell death mediated by reactive oxygen and nitrogen species

c-Jun N-terminal kinase (JNK), or stress-activated protein kinase, is an important member of the mitogen-activated protein kinase superfamily, the members of which are readily activated by many environmental stimuli. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are important groups of free radicals that are capable of eliciting direct damaging effects or acting as critical intermediate signaling molecules, leading to oxidative and nitrosative stress and a series of biological consequences. Recently there has been an increasing amount of research interest focusing on the regulatory role of JNK activation in ROS-and RNS-induced cellular responses. In this review we will first summarize and discuss some recent findings regarding the signaling mechanisms of ROS-or RNS-mediated JNK activation. Second, we will talk about the role of JNK in ROS-or RNS-mediated cell death (both apoptosis and necrosis). Finally, we will analyze the emerging evidence for the involvement of ROS and RNS as mediators in tumor necrosis factor alpha-induced apoptosis. Taken together, the accumulating knowledge about the ROS/RNS-induced JNK signaling pathway has greatly advanced our understanding of the complex processes deciding the cellular responses to environmental stress.     

Reactive oxygen species and gastric carcinogenesis: The complex interaction between Helicobacter pylori and host

Helicobacter pylori (H. pylori) is a highly successful human pathogen that colonizes stomach in around 50% of the global population. The colonization of bacterium induces an inflammatory response and a substantial rise in the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), mostly derived from host neutrophils and gastric epithelial cells, which play a crucial role in combating bacterial infections. However, H. pylori has developed various strategies to quench the deleterious effects of ROS, including the production of antioxidant enzymes, antioxidant proteins as well as blocking the generation of oxidants. The host's inability to eliminate H. pylori infection results in persistent ROS production. Notably, excessive ROS can disrupt the intracellular signal transduction and biological processes of the host, incurring chronic inflammation and cellular damage, such as DNA damage, lipid peroxidation, and protein oxidation. Markedly, the sustained inflammatory response and oxidative stress during H. pylori infection are major risk factor for gastric carcinogenesis. In this context, we summarize the literature on H. pylori infection-induced ROS production, the strategies used by H. pylori to counteract the host response, and subsequent host damage and gastric carcinogenesis.     

In vivo imaging of reactive oxygen and nitrogen species in inflammation using the luminescent probe L-012

Production of reactive oxygen and nitrogen species (ROS/RNS) is an important part of the inflammatory response, but prolonged elevated levels of ROS/RNS as under chronic inflammation can contribute to the development of disease. Monitoring ROS/RNS in living animals is challenging due to the rapid turnover of ROS/RNS and the limited sensitivity and specificity of ROS/RNS probes. We have explored the use of the chemiluminescent probe L-012 for noninvasive imaging of ROS/RNS production during inflammation in living mice. Various inflammatory conditions were induced, and L-012-dependent luminescence was recorded with an ultrasensitive CCD camera. Strong luminescent signals were observed from different regions of the body corresponding to inflammation. The signal was reduced by administration of the SOD mimetic tempol, the NADPH oxidase inhibitor apocynin, and the inhibitor of nitric oxide synthesis L-NAME, signifying the requirement for the presence of ROS/RNS. Additionally, the L-012 signal was abolished in mice with a mutation in the Ncf1 gene, encoding a protein in the NADPH oxidase complex 2, which generates ROS/RNS during inflammation. In conclusion, L-012 is well distributed in the mouse body and mediates a strong ROS/RNS-dependent luminescent signal in vivo and is useful for monitoring the development and regulation of inflammation in living organisms.     

Nitrosative damage to free and zinc-bound cysteine thiols underlies nitric oxide toxicity in wild-type Borrelia burgdorferi

Borrelia burgdorferi encounters potentially harmful reactive nitrogen species (RNS) throughout its infective cycle. In this study, diethylamine NONOate (DEA/NO) was used to characterize the lethal effects of RNS on B. burgdorferi. RNS produce a variety of DNA lesions in a broad spectrum of microbial pathogens; however, levels of the DNA deamination product, deoxyinosine, and the numbers of apurinic/apyrimidinic (AP) sites were identical in DNA isolated from untreated and DEA/NO-treated B. burgdorferi cells. Strains with mutations in the nucleotide excision repair (NER) pathway genes uvrC or uvrB treated with DEA/NO had significantly higher spontaneous mutation frequencies, increased numbers of AP sites in DNA and reduced survival compared with wild-type controls. Polyunsaturated fatty acids in B. burgdorferi cell membranes, which are susceptible to peroxidation by reactive oxygen species (ROS), were not sensitive to RNS-mediated lipid peroxidation. However, treatment of B. burgdorferi cells with DEA/NO resulted in nitrosative damage to several proteins, including the zinc-dependent glycolytic enzyme fructose-1,6-bisphosphate aldolase (BB0445), the Borrelia oxidative stress regulator (BosR) and neutrophil-activating protein (NapA). Collectively, these data suggested that nitrosative damage to proteins harbouring free or zinc-bound cysteine thiols, rather than DNA or membrane lipids underlies RNS toxicity in wild-type B. burgdorferi.     

Reactive oxygen and nitrogen species induce cell apoptosis via a mitochondria-dependent pathway in hyperoxia lung injury

Hyperoxia-induced lung injury limits the application of mechanical ventilation on rescuing the lives of premature infants and seriously ill and respiratory failure patients, and its mechanisms are not completely understood. In this article, we focused on the relationship between hyperoxia-induced lung injury and reactive oxygen species (ROS), reactive nitrogen species (RNS), mitochondria damage, as well as apoptosis in the pulmonary epithelial II cell line RLE-6TN. After exposure to hyperoxia, the cell viability was significantly decreased, accompanied by the increase in ROS, nitric oxide (NO), inflammatory cytokines, and cell death. Furthermore, hyperoxia triggered the loss of mitochondrial membrane potential (▵Ψm), thereby promoting cytochrome c to release from mitochondria to cytoplasm. Further studies conclusively showed that the Bax/Bcl-2 ratio was enlarged to activate the mitochondria-dependent apoptotic pathway after hyperoxia treatment. Intriguingly, the effects of hyperoxia on the level of ROS, NO and inflammation, mitochondrial damage, as well as cell death were reversed by free radical scavengers N-acetylcysteine and hemoglobin. In addition, a hyperoxia model of neonatal Sprague-Dawley (SD) rats presented the obvious characteristics of lung injury, such as a decrease in alveolar numbers, alveolar mass edema, and disorganized pulmonary structure. The effects of hyperoxia on ROS, RNS, inflammatory cytokines, and apoptosis-related proteins in lung injury tissues of neonatal SD rats were similar to that in RLE-6TN cells. In conclusion, mitochondria are a primary target of hyperoxia-induced free radical, whereas ROS and RNS are the key mediators of hyperoxia-induced cell apoptosis via the mitochondria-dependent pathway in RLE-6TN cells.     

Oxidative mechanism of arsenic toxicity and carcinogenesis

Arsenic is a known toxin and carcinogen that is present in industrial settings and in the environment. The mechanisms of disease initiation and progression are not fully understood. In the last a few years, there has been increasing evidence of the correlation between the generation of reactive oxygen species (ROS), DNA damage, tumor promotion, and arsenic exposure. This article summarizes the current literature on the arsenic mediated generation of ROS and reactive nitrogen species (RNS) in various biological systems. This article also discusses the role of ROS and RNS in arsenic-induced DNA damage and activation of oxidative sensitive gene expression.     

Reactive sulfur species: an emerging concept in oxidative stress

The ingredients of oxidative stress include a variety of reactive species such as reactive oxygen and reactive nitrogen species (ROS, RNS). While sulfur is usually considered as part of cellular antioxidant systems there is mounting evidence that reactive sulfur species (RSS) with stressor properties similar to the ones found in ROS are formed under conditions of oxidative stress. Thiols as well as disulfides are easily oxidised to sulfur species with sulfur in higher oxidation states. Such agents include thiyl radicals, disulfides, sulfenic acids and disulfide-S-oxides. They rapidly oxidise and subsequently inhibit thiol-proteins and enzymes and can be considered as a separate class of oxidative stressors providing new antioxidant drug targets.     

Photoprotective Potential of Penta-O-Galloyl-β-DGlucose by Targeting NF-κB and MAPK Signaling in UVB Radiation-Induced Human Dermal Fibroblasts and Mouse Skin

Exposure of the skin to ultraviolet radiation can cause skin damage with various pathological changes including inflammation. In the present study, we identified the skin-protective activity of 1,2,3,4,6-penta-O-galloyl-β-D-glucose (pentagalloyl glucose, PGG) in ultraviolet B (UVB) radiation-induced human dermal fibroblasts and mouse skin. PGG exhibited antioxidant activity with regard to intracellular reactive oxygen species (ROS) generation as well as ROS and reactive nitrogen species (RNS) scavenging. Furthermore, PGG exhibited anti-inflammatory activity, inhibiting the activation of nuclear factor-kappaB (NF-κB) and mitogen-activated protein kinase (MAPK) signaling, resulting in inhibition of the expression of pro-inflammatory mediators. Topical application of PGG followed by chronic exposure to UVB radiation in the dorsal skin of hairless mice resulted in a significant decrease in the progression of inflammatory skin damages, leading to inhibited activation of NF-κB signaling and expression of pro-inflammatory mediators. The present study demonstrated that PGG protected from skin damage induced by UVB radiation, and thus, may be a potential candidate for the prevention of environmental stimuli-induced inflammatory skin damage.     

Role of oxidative damage in the pathogenesis of viral infections of the nervous system

Oxidative stress, primarily due to increased generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS), is a feature of many viral infections. ROS and RNS modulate the permissiveness of cells to viral replication, regulate host inflammatory and immune responses, and cause oxidative damage to both host tissue and progeny virus. The lipid-rich nervous system is particularly susceptible to lipid peroxidation, an autocatalytic process that damages lipid-containing structures and yields reactive by-products, which can covalently modify and damage cellular macromolecules. Oxidative injury is a component of acute encephalitis caused by herpes simplex virus type 1 and reovirus, neurodegenerative disease caused by human immunodeficiency virus and murine leukemia virus, and subacute sclerosing panencephalitis caused by measles virus. The extent to which oxidative damage plays a beneficial role for the host by limiting viral replication is largely unknown. An enhanced understanding of the role of oxidative damage in viral infections of the nervous system may lead to therapeutic strategies to reduce tissue damage during viral infection without impeding the host antiviral response.     

Oxidative stress: Normal pregnancy versus preeclampsia

The role of oxidative stress in the physiopathology of human pregnancy is of particular interest. Pregnancy is well-known to increase the oxidative stress, mainly produced by a normal systemic inflammatory response, which results in high amounts of circulating reactive oxygen species (ROS) and reactive nitrogen species (RNS). Both ROS and RNS play an important role as secondary messengers in many intracellular signalling cascades. However, they can also exert critical effects on pathological processes involving the pregnant woman. ROS, RNS and antioxidants establish a balance that determines the oxidation status of animals and humans. This review focuses on the mechanism of oxidative stress in pregnancy as well as its involvement and consequences on the human pregnancy-specific clinical syndrome preeclampsia.     

诱导型一氧化氮合酶抑制剂研发现状

一氧化氮(NO)对炎症性疾病的治疗作用近来引起了广泛的重视。诱导型一氧化合成酶(iNOS)被发现广泛地参与趋炎因子表达和反应性氧化产物(ROS)/反应性氮化产物(RNS)的产生,从而进一步证明了一氧化氮在炎症病理发生发展中的关键作用。由于传统的抗炎药物环氧合酶-2(COX-2)抑制剂被报导有较多副作用,新型抑制炎症药物的研究开发势在必行。本文分别介绍了化学来源、生物来源、植物来原性iNOS抑制剂阻的开发、研究现状,阐述了其在断炎症信息传递通道中的作用。表明了iNOS抑制剂防止炎症损害的相关机理,提出iNOs不仅能在初始阶段影响炎症的发生,也对抑制和终结炎症有作用。最后进一步介绍了用中草药研发iNOs抑制剂的可能性,展望了于中药在该领域内的巨大前景。     

Antioxidant responses to oxidant-mediated lung diseases

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are generated throughout the human body. Enzymatic and nonenzymatic antioxidants detoxify ROS and RNS and minimize damage to biomolecules. An imbalance between the production of ROS and RNS and antioxidant capacity leads to a state of "oxidative stress" that contributes to the pathogenesis of a number of human diseases by damaging lipids, protein, and DNA. In general, lung diseases are related to inflammatory processes that generate increased ROS and RNS. The susceptibility of the lung to oxidative injury depends largely on its ability to upregulate protective ROS and RNS scavenging systems. Unfortunately, the primary intracellular antioxidants are expressed at low levels in the human lung and are not acutely induced when exposed to oxidative stresses such as cigarette smoke and hyperoxia. However, the response of extracellular antioxidant enzymes, the critical primary defense against exogenous oxidative stress, increases rapidly and in proportion to oxidative stress. In this paper, we review how antioxidants in the lung respond to oxidative stress in several lung diseases and focus on the mechanisms that upregulate extracellular glutathione peroxidase.     

The effects of reactive nitrogen and oxygen species on the regeneration and growth of cucumber cells from isolated protoplasts

The present study investigated changes in the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in isolated mesophyll protoplasts and cell cultures of the cucumber Cucumis sativus cv. Marketer. Although only a minor increase in the level of nitrogen oxide (NO) was observed during the first 7 days of culture following protoplast isolation, a substantial accumulation of ROS was detected. Compounds known to modulate endogenous ROS and RNS levels were employed to study their role in cucumber protoplast regeneration and growth. Supplementing the culture medium with the NO donors S-nitrosoglutathione and sodium nitroprusside and the ROS scavenger ascorbate significantly increased protoplast viability and cell density. In contrast, cell density was significantly decreased following the addition of catalase to the medium. Scavenging of ROS and RNS induced the formation of cucumber microcalli, thus suggesting a differential role of NO in the maintenance of cell viability and in the control of cell division. Our findings confirm the crucial role of controlled ROS and RNS production in both protoplast regeneration and cellular growth and differentiation.