Nitrative DNA damage in inflammation and its possible role in carcinogenesis

Increased DNA damage in hepatitis C virus-related hepatocellular carcinoma

One consequence of hepatitis C virus (HCV) infection is an elevated cancer risk. During chronic viral infection, deoxyribonucleic acid (DNA) damage is being induced by reactive oxygen and nitrogen species, which may play a pathogenic role in HCV-induced carcinogenesis. The study investigated DNA damage in peripheral blood lymphocytes from patients with hepatocellular carcinoma (HCC) and those with HCV infection with and without associated cirrhosis and normal controls. As a measure for genomic damage, the comet assay (single cell gel electrophoresis) was applied, which detects single- and double-strand breaks and alkali-labile sites through electrophoretic mobility of the resulting fragments. The levels of DNA damage were significantly higher in HCC and HCV-associated cirrhosis compared to HCV without cirrhosis and the control group. Patients presenting with DNA damage more than mean+two standard deviation of the controls had a 3.6-fold risk of having HCC more than those with undamaged DNA. HCV disease progression was the only discriminator predicting the extent of DNA damage. The accumulation of DNA damage is important in HCC evolution. DNA damage indicating intracellular oxidative and nitrative stress may lead to mutagenesis and consequently malignant transformation, which emphasizes the need to optimize the therapy for reducing the degree of genomic damage.

Nitrate and nitrite in the diet: how to assess their benefit and risk for human health

Nitrate is a natural constituent of the human diet and an approved food additive. It can be partially converted to nitrogen monoxide, which induces vasodilation and thereby decreases blood pressure. This effect is associated with a reduced risk regarding cardiovascular disease, myocardial infarction, and stroke. Moreover, dietary nitrate has been associated with beneficial effects in patients with gastric ulcer, renal failure, or metabolic syndrome. Recent studies indicate that such beneficial health effects due to dietary nitrate may be achievable at intake levels resulting from the daily consumption of nitrate-rich vegetables. N-nitroso compounds are endogenously formed in humans. However, their relevance for human health has not been adequately explored up to now. Nitrate and nitrite are per se not carcinogenic, but under conditions that result in endogenous nitrosation, it cannot be excluded that ingested nitrate and nitrite may lead to an increased cancer risk and may probably be carcinogenic to humans. In this review, the known beneficial and detrimental health effects related to dietary nitrate/nitrite intake are described and the identified gaps in knowledge as well as the research needs required to perform a reliable benefit/risk assessment in terms of long-term human health consequences due to dietary nitrate/nitrite intake are presented.

Direct observation of preferential processing of clustered abasic DNA damages with APE1 in TATA box and CpG island by reaction kinetics and fluorescence dynamics

Sequences like the core element of TATA box and CpG island are frequently encountered in the genome and related to transcription. The fate of repair of clustered abasic sites in such sequences of genomic importance is largely unknown. This prompted us to investigate the sequence dependence of cleavage efficiency of APE1 enzyme at abasic sites within the core sequences of TATA box and CpG island using fluorescence dynamics and reaction kinetics. Simultaneous molecular dynamics study through steady state and time resolved fluorescence spectroscopy using unique ethidium bromide dye release assay confirmed an elevated amount of abasic site cleavage of the TATA box sequence as compared to the core CpG island. Reaction kinetics showed that catalytic efficiency of APE1 for abasic site cleavage of core CpG island sequence was ∼4 times lower as compared to that of the TATA box. Higher value of Km was obtained from the core CpG island sequence than the TATA box sequence. This suggests a greater binding effect of APE1 enzyme on TATA sequence that signifies a prominent role of the sequence context of the DNA substrate. Evidently, a faster response from APE1 was obtained for clustered abasic damage repair of TATA box core sequences than CpG island consensus sequences. The neighboring bases of the abasic sites in the complementary DNA strand were found to have significant contribution in addition to the flanking bases in modulating APE1 activity. The repair refractivity of the bistranded clustered abasic sites arise from the slow processing of the second abasic site, consequently resulting in decreased overall production of potentially lethal double strand breaks.

The therapeutic value of targeting inflammation in gastrointestinal cancers

Inflammation has been implicated in the initiation and progression of gastrointestinal (GI) cancers. Inflammation also plays important roles in subverting immune tolerance, escape from immune surveillance, and conferring resistance to chemotherapeutic agents. Targeting key regulators and mediators of inflammation represents an attractive strategy for GI cancer prevention and treatment. However, the targeting of inflammation in GI cancer is not straightforward and sometimes inflammation may contribute to tumor regression. We discuss the origins and effects of inflammation in GI cancer and how to target it successfully.

Oxidative damage in the progression of chronic liver disease to hepatocellular carcinoma: An intricate pathway

The histo-pathologic and molecular mechanisms leading to initiation and progression of hepatocellular carcinoma (HCC) are still ill-defined; however, there is increasing evidence that the gradual accumulation of mutations, genetic and epigenetic changes which occur in preneoplastic hepatocytes results in the development of dysplastic foci, nodules, and finally, overt HCC. As well as many other neoplasias, liver cancer is considered an “inflammatory cancer”, arising from a context of inflammation, and characterized by inflammation-related mechanisms that favor tumor cell survival, proliferation, and invasion. Molecular mechanisms that link inflammation and neoplasia have been widely investigated, and it has been well established that inflammatory cells recruited at these sites with ongoing inflammatory activity release chemokines that enhance the production of reactive oxygen species. The latter, in turn, probably have a major pathogenic role in the continuum starting from hepatitis followed by chronic inflammation, and ultimately leading to cancer. The relationship amongst chronic liver injury, free radical production, and development of HCC is explored in the present review, particularly in the light of the complex network that involves oxidative DNA damage, cytokine synthesis, telomere dysfunction, and microRNA regulation.

A review of the use of melatonin in ulcerative colitis: experimental evidence and new approaches

: Ulcerative colitis (UC), an inflammatory bowel disease, affects many people across the globe, and its prevalence is increasing steadily. Inflammation and oxidative stress play a vital role in the perpetuation of inflammatory process and the subsequent DNA damage associated with the development of UC. UC induces not only local but also systemic damage, which involves the perturbation of multiple molecular pathways. Furthermore, UC leads to an increased risk of colorectal cancer, the third most common malignancy in humans. Most of the drugs used for the treatment of UC are unsatisfactory because they are generally mono-targeted, relatively ineffective and unaffordable for many people. Thus, agents that can target multiple molecular pathways and are less expensive have enormous potential to treat UC. Melatonin has beneficial effects against UC in experimental and clinical studies because of its ability to modulate several molecular pathways of inflammation, oxidative stress, fibrosis, and cellular injury. However, many novel targets are yet to be explored on which melatonin may act to exert its favorable effects in UC. It is time to explore improved intervention strategies with melatonin in UC on the basis of studies investigating different molecular targets using proteomic and genomic approaches. This review identifies various molecular targets for melatonin with the intent of providing novel strategies for combating UC and the associated extraintestinal manifestations of this debilitating disease.

Anti-inflammatory effect of neoechinulin a from the marine fungus Eurotium sp. SF-5989 through the suppression of NF-кB and p38 MAPK Pathways in lipopolysaccharide-stimulated RAW264.7 macrophages

In the course of a bioassay-guided study of metabolites from the marine fungus Eurotium sp. SF-5989, two diketopiperazine type indole alkaloids, neoechinulins A and B, were isolated. In this study, we investigated the anti-inflammatory effects of neoechinulins A (1) and B (2) on lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages. Neoechinulin A (1) markedly suppressed the production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) and the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in a dose dependent manner ranging from 12.5 µM to 100 µM without affecting the cell viability. On the other hand, neoechinulin B (2) affected the cell viability at 25 µM although the compound displayed similar inhibitory effect of NO production to neoechinulin A (1) at lower doses. Furthermore, neoechinulin A (1) decreased the secretion of pro-inflammatory cytokines, such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). We also confirmed that neoechinulin A (1) blocked the activation of nuclear factor-kappaB (NF-κB) in LPS-stimulated RAW264.7 macrophages by inhibiting the phosphorylation and degradation of inhibitor kappa B (IκB)-α. Moreover, neoechinulin A (1) decreased p38 mitogen-activated protein kinase (MAPK) phosphorylation. Therefore, these data showed that the anti-inflammatory effects of neoechinulin A (1) in LPS-stimulated RAW264.7 macrophages were due to the inhibition of the NF-κB and p38 MAPK pathways, suggesting that neoechinulin A (1) might be a potential therapeutic agent for the treatment of various inflammatory diseases.

The inhibition of JNK MAPK and NF-κB signaling by tenuifoliside A isolated from Polygala tenuifolia in lipopolysaccharide-induced macrophages is associated with its anti-inflammatory effect

The root of Polygala tenuifolia Willd. (Polygalaceae) is well known for its use in the treatment of neurasthenia, amnesia, and inflammation. In this study, we isolated phenyl propanoid type metabolite tenuifoliside A, one of the phenylpropanoids from P. tenuifolia, and investigated its anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated RAW264.7 and murine peritoneal macrophages. The results showed that tenuifoliside A inhibited the production of nitric oxide (NO), inducible nitric oxide synthase (iNOS), prostaglandin E2 (PG E2), and cyclooxygenase (COX)-2. In addition, tenuifoliside A suppressed the production of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β. We also evaluated the effects of tenuifoliside A on the activation of nuclear factor-kappaB (NF-κB). Tenuifoliside A inhibited the translocation of the NF-κB subunit p65 into the nucleus by interrupting the phosphorylation and degradation of inhibitor kappa B (IκB)-α in LPS-stimulated murine peritoneal macrophages. Moreover, we confirmed that the suppression of the inflammatory process by tenuifoliside A was mediated through the mitogen-activated protein kinases (MAPKs) pathway based on the fact that tenuifoliside A significantly decreased p-c-Jun N-terminal kinase (p-JNK) protein expression in LPS-stimulated murine peritoneal macrophages. Taken together, the anti-inflammatory effects of tenuifoliside A were mediated by the inhibition of the NF-κB and MAPK pathways. This study is the first report on the anti-inflammatory effects of tenuifoliside A, and the strong anti-inflammatory effects of tenuifoliside A provide potential compound to be developed as therapeutic for inflammatory diseases.

Protection from inflammatory bowel disease and colitis-associated carcinogenesis with 4-vinyl-2,6-dimethoxyphenol (canolol) involves suppression of oxidative stress and inflammatory cytokines

Oxidative stress is associated with various pathological processes including inflammatory bowel disease, which is a major cause of colon cancer. Here, we examined the antioxidative and anti-inflammatory effects of 4-vinyl-2,6-dimethoxyphenol (canolol), a potent antioxidant compound obtained from crude canola oil. Oral administration of 2% dextran sulfate sodium (DSS) resulted in the progression of colitis with shortening of the large bowel length. Administering a diet containing canolol significantly suppressed pathogenesis; diarrhea markedly improved and the length of large bowel returned to almost normal. Pathological examination clearly revealed improvement of colonic ulcers. Production of inflammatory cytokines, i.e. interleukin-12 and tumor necrosis factor-α, was significantly increased during this pathological process; their production was markedly inhibited by canolol. In the azoxymethane/DSS-induced colon cancer model, mice receiving canolol had a reduced occurrence of cancer, to 60%, compared with control mice, 100% of which had colon cancer. The numbers of tumors in each mouse were also significantly reduced in mice receiving the canolol-containing diet (5.6±2.0) compared with azoxymethane/DSS control mice (10.8±4.2). No apparent toxicity of canolol was observed. Moreover, inflammatory cytokines (i.e. cyclooxygenase-2, inducible nitric oxide synthase and tumor necrosis factor-α) and oxidative responding molecules, i.e. heme oxygenase-1, in colon were suppressed during this treatment. In a mouse colon 26 solid tumor model, canolol significantly suppressed cyclooxygenase-2 expression; however, no significant tumor growth inhibition was observed, suggesting that canolol preferably shows chemopreventive effects during the stages of initiation/promotion. Canolol may, thus, be considered a potential cancer preventive agent or supplement.

Chronic inflammation-derived nitric oxide causes conversion of human colonic adenoma cells into adenocarcinoma cells

It has been suggested that nitric oxide (NO) derived from chronically inflamed tissues is a cause of carcinogenesis. We herein demonstrated that administration of an inducible NO synthase inhibitor, aminoguanidine, significantly suppressed the tumorigenic conversion of human colonic adenoma (FPCK-1-1) cells into adenocarcinoma (FPCK/Inflam) cells accelerated by foreign body-induced chronic inflammation in nude mice. To determine whether NO directly promotes carcinogenesis, we exposed FPCK-1-1 cells continuously to chemically generated NO (FPCK/NO), and periodically examined their tumorigenicity. FPCK/NO cells formed tumors, whereas vehicle-treated cells (FPCK/NaOH) did not. We selected a tumorigenic population from FPCK/NO cells kept it in three-dimensional (3D) culture where in vivo-like multicellular spheroidal growth was expected. FPCK/Inflam cells developed large spheroids whereas FPCK/NO cells formed tiny but growing compact aggregates in 3D culture. Meanwhile, FPCK-1-1 and FPCK/NaOH cells underwent anoikis (apoptotic cell death consequential on insufficient cell-to-substrate interactions) through activation of caspase 3. The survived cells in the 3D culture (FPCK/NO/3D), which were derived from FPCK/NO cells, showed a similar tumor incidence to that of FPCK/Inflam cells. These results showed that NO was one of the causative factors for the acceleration of colon carcinogenesis, especially in the conversion from adenoma to adenocarcinoma in the chronic inflammatory environment.

The link between infection and cancer: tumor vasculature, free radicals, and drug delivery to tumors via the EPR effect

This review focuses primarily on my own research, including pathogenic mechanisms of microbial infection, vascular permeability in infection and tumors, and effects of nitric oxide (NO), superoxide anion radical (O₂⁻), and 8-nitroguanosine in the enhanced permeability and retention (EPR) effect for the tumor-selective delivery of macromolecular agents (nanomedicines). Infection-induced vascular permeability is mediated by activation of the kinin-generating protease cascade (kallikrein-kinin) triggered by exogenous microbial proteases. A similar mechanism operates in cancer tissues and in carcinomatosis of the pleural and peritoneal cavities. Infection also stimulates O₂⁻ generation via activation of xanthine oxidase while generating NO by inducing NO synthase. These chemicals function in mutation and carcinogenesis and promote inflammation, in which peroxynitrite (a product of O₂⁻ and NO) activates MMP, damages DNA and RNA, and regenerates 8-nitroguanosine and 8-oxoguanosine. We showed vascular permeability by using macromolecular drugs, which are not simply extravasated through the vascular wall into the tumor interstitium but remain there for prolonged periods. We thus discovered the EPR effect, which led to the rational development of tumor-selective delivery of polymer conjugates, micellar and liposomal drugs, and genes. Our styrene-maleic acid copolymer conjugated with neocarzinostatin was the first agent of its kind used to treat hepatoma. The EPR effect occurs not only because of defective vascular architecture but also through the generation of various vascular mediators such as kinin, NO, and vascular endothelial growth factor. Although most solid tumors, including human tumors, show the EPR effect, heterogeneity of tumor tissue may impede drug delivery. This review describes the barriers and countermeasures for improved drug delivery to tumors by using nanomedicines.

Formation, signaling functions, and metabolisms of nitrated cyclic nucleotide

8-Nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP) is a unique derivative of guanosine 3',5'-cyclic monophosphate (cGMP) formed in mammalian and plant cells in response to production of nitric oxide and reactive oxygen species. 8-Nitro-cGMP possesses signaling activity inherited from parental cGMP, including induction of vasorelaxation through activation of cGMP-dependent protein kinase. On the other hand, 8-nitro-cGMP mediates cellular signaling that is not observed for native cGMP, e.g., it behaves as an electrophile and reacts with protein sulfhydryls, which results in cGMP adduction to protein sulfhydryls (protein S-guanylation). Several proteins have been identified as targets for endogenous protein S-guanylation, including Kelch-like ECH-associated protein 1 (Keap1), H-Ras, and mitochondrial heat shock proteins. 8-Nitro-cGMP signaling via protein S-guanylation of those proteins may have evolved to convey adaptive cellular stress responses. 8-Nitro-cGMP may not undergo conventional cGMP metabolism because of its resistance to phosphodiesterases. Hydrogen sulfide has recently been identified as a potent regulator for metabolisms of electrophiles including 8-nitro-cGMP, through sulfhydration of electrophiles, e.g., leading to the formation of 8-SH-cGMP. Better understanding of the molecular basis for the formation, signaling functions, and metabolisms of 8-nitro-cGMP would be useful for the development of new diagnostic approaches and treatment of diseases related to oxidative stress and redox metabolisms.

Serum nitric oxide levels in patients with benign and malignant biliary disease: a prospective single center study

BACKGROUND

Despite advances in new diagnostic modalities, the differentiation of malignant from benign causes of biliary obstruction still remains difficult. The nitric oxide (NO) system is considered to be an important component in mediating cytokine activation of macrophages in inflammation. It also modulates tumorigenesis and regulates cell proliferation, angiogenesis, survival, and DNA repair. Although NO and its role in pancreatobiliary disorders has not been studied previously, the present study is designed to evaluate NO synthesis and metabolism in patients with biliary obstruction and to determine its usefulness in differentiating between benign and malignant causes of biliary obstruction.

MATERIALS AND METHODS

Seventy-nine consecutive patients (60 malignant and 19 benign) with a history of biliary obstruction either with a benign or a malignant cause and 23 age-matched and sex-matched controls were included in this prospective study. NO metabolites, and conventional inflammation and tumor markers were determined.

RESULTS

In patients with malignant biliary obstruction (MBO), serum NO metabolites were found to be significantly elevated (P<0.001). The receiver operating characteristic analysis showed that an NO level of 1.095 was the best cut-off value for predicting a malignant biliary stricture with a sensitivity of 78.3% and a specificity of 84.2% (area under the curve=0.821). Correlation analysis suggested that carbohydrate antigen 19-9 and carcinoembryonic antigen levels were correlated with NO levels for differentiating benign from malignant cause of biliary obstruction.

CONCLUSIONS

Serum NO-associated tissue injury might be associated with the development of pancreatobiliary neoplasia by creating a local environment that is enriched with reactive oxygen species, cytokines, and other growth factors that may promote endothelial cell apoptosis. Moreover, serum NO levels may be used as an adjunctive marker to identify malignant causes of the obstructive jaundice.

Determination of genotoxicity by the Comet assay applied to murine precision-cut lung slices

Precision-cut lung slices (PCLSs) are an organotypic lung model that is widely used in pharmacological, physiological, and toxicological studies. Genotoxicity testing, as a pivotal part of early risk assessment, is currently established in vivo in various organs including lung, brain, or liver, and in vitro in cell lines or primary cells. The aim of the present study was to provide the three-dimensional organ culture PCLS as a new ex vivo model for determination of genotoxicity using the Comet assay. Murine PCLS were exposed to increasing concentrations of ethyl methane sulfonate 'EMS' (0.03-0.4%) and formalin (0.5-5mM). Tissue was subsequently dissociated, and DNA single-strand breaks were quantified using the Comet assay. Number of viable dissociated lung cells was between 4×10(5) and 6.7×10(5)cells/slice. Even treatment with EMS did not induce toxicity compared to untreated tissue control. As expected, DNA single-strand breaks were increased dose-dependently and significantly after exposure to EMS. Here, tail length rose from 24μm to 75μm. In contrast, formalin resulted in a significant induction of DNA cross-links. The effects induced by EMS and formalin demonstrate the usefulness of PCLS as a new ex vivo lung model for genotoxicity testing in the early risk assessment of airborne substances in the future.

Catalpol inhibits LPS plus IFN-γ-induced inflammatory response in astrocytes primary cultures

A large body of evidence suggests that the inflammatory reaction plays an important role in the pathogenesis of neurodegenerative diseases. Our previous studies described the neuroprotective effects of catalpol in lipopolysaccharide (LPS)-induced inflammatory models, in which catalpol was shown to prevent mesencephalic neuron death and ameliorate cognitive ability animals. To further investigate the protective effect and underlying mechanism of catalpol, astrocytes were pretreated with low (0.1mM) and high dose (0.5mM) catalpol for 1h prior to LPS plus interferon-γ stimulation. Biochemical analyses showed that NO and ROS production and iNOS activity were significantly reduced by catalpol. Data at transcriptional level also demonstrated that catalpol potently attenuated gene expressions involved in inflammation, such as iNOS, COX-2 and TLR4. In addition, our exploration further revealed that the suppressive action of catalpol on inflammation was mediated via inhibiting nuclear factor-κB (NF-κB) activation. Collectively, these results suggest that catalpol can exert inhibitory effects on the inflammatory reaction in astrocytes and that inactivation of NF-κB could be the major determinant for its anti-inflammatory mechanism. Therefore, catalpol may potentially be a highly effective therapeutic agent in treating neurodegenerative diseases associated with inflammation.

Gelam honey scavenges peroxynitrite during the immune response

Monocytes and macrophages are part of the first-line defense against bacterial, fungal, and viral infections during host immune responses; they express high levels of proinflammatory cytokines and cytotoxic molecules, including nitric oxide, reactive oxygen species, and their reaction product peroxynitrite. Peroxynitrite is a short-lived oxidant and a potent inducer of cell death. Honey, in addition to its well-known sweetening properties, is a natural antioxidant that has been used since ancient times in traditional medicine. We examined the ability of Gelam honey, derived from the Gelam tree (Melaleuca spp.), to scavenge peroxynitrite during immune responses mounted in the murine macrophage cell line RAW 264.7 when stimulated with lipopolysaccharide/interferon-γ (LPS/IFN-γ) and in LPS-treated rats. Gelam honey significantly improved the viability of LPS/IFN-γ-treated RAW 264.7 cells and inhibited nitric oxide production-similar to the effects observed with an inhibitor of inducible nitric oxide synthase (1400W). Furthermore, honey, but not 1400W, inhibited peroxynitrite production from the synthetic substrate 3-morpholinosydnonimine (SIN-1) and prevented the peroxynitrite-mediated conversion of dihydrorhodamine 123 to its fluorescent oxidation product rhodamine 123. Honey inhibited peroxynitrite synthesis in LPS-treated rats. Thus, honey may attenuate inflammatory responses that lead to cell damage and death, suggesting its therapeutic uses for several inflammatory disorders.

Base-pairing preferences, physicochemical properties and mutational behaviour of the DNA lesion 8-nitroguanine

8-Nitro-2'-deoxyguanosine (8-nitrodG) is a relatively unstable, mutagenic lesion of DNA that is increasingly believed to be associated with tissue inflammation. Due to the lability of the glycosidic bond, 8-nitrodG cannot be incorporated into oligodeoxynucleotides (ODNs) by chemical DNA synthesis and thus very little is known about its physicochemical properties and base-pairing preferences. Here we describe the synthesis of 8-nitro-2'-O-methylguanosine, a ribonucleoside analogue of this lesion, which is sufficiently stable to be incorporated into ODNs. Physicochemical studies demonstrated that 8-nitro-2'-O-methylguanosine adopts a syn conformation about the glycosidic bond; thermal melting studies and molecular modelling suggest a relatively stable syn-8-nitroG·anti-G base pair. Interestingly, when this lesion analogue was placed in a primer-template system, extension of the primer by either avian myeloblastosis virus reverse transcriptase (AMV-RT) or human DNA polymerase β (pol β), was significantly impaired, but where incorporation opposite 8-nitroguanine did occur, pol β showed a 2:1 preference to insert dA over dC, while AMV-RT incorporated predominantly dC. The fact that no 8-nitroG·G base pairing is seen in the primer extension products suggests that the polymerases may discriminate against this pairing system on the basis of its poor geometric match to a Watson-Crick pair.

Oxidative stress in ulcerative colitis: an old concept but a new concern

Ulcerative colitis is an idiopathic, chronic and relapsing inflammatory bowel disease, which elicits the risk of colorectal cancer, the third most common malignancy in humans. It has been known for a long time that oxidative stress is a major pathogenic factor in the inflamed tissue that can pave the way towards DNA damage and carcinogenesis. However, the DNA damage produced due to oxidative stress in the inflamed tissue is not limited to the local site but extends globally, thereby augmenting the risk of global carcinogenesis. Targeting oxidative stress may provide an exciting avenue to combat inflammation-associated local as well as global DNA damage and the subsequent carcinogenesis. The present review portrays the role of oxidative stress in the pathogenesis of ulcerative colitis and the associated local as well as global DNA damage, which may lead to carcinogenesis.

Reactions of amine and peroxynitrite: evidence for hydroxylation as predominant reaction and new insight into the modulation of CO2

Peroxynitrite is related to numerous diseases including cardiovascular diseases, inflammation, and cancer. In order to expand the understanding for the toxicology of peroxynitrite in biological system, the reactions of amine (morpholine as a probe) with peroxynitrite and the modulation of CO2 were investigated by using DFT methods. The results strongly indicate that the hydroxylation of amine by peroxynitrous acid ONOOH, which was previously overlooked by most studies, is predominant relative to the widely reported nitration and nitrosation in the absence of CO2. The product N-hydroxylamine is proposed to be mainly generated via nonradical pathway (two-electron oxidation). The modulation of CO2 exhibits two main functions: (1) inhibition of hydroxylation due to the promoted consumption of peroxynitrite via fast reaction of CO2 with ONOO¯ to form ONOOCO2¯; (2) dual effect (catalysis and inhibition) of CO2 toward nitration and nitrosation. As a new insight, amine does react with CO2 and produce inert amine carbamate R2NCOO¯. This reaction has the potential to compete with the reaction of CO2 and ONOO¯, which leads to inhibition of nitration and nitrosation. The concentration of CO2 could be a critical factor determining the final effect, catalysis or inhibition. As a new finding, HCO3¯ is probably an effective catalyst for the reaction of amine and CO2. Moreover, further studies on how the different types of the amine might affect the outcome of the reactions would be an interesting topic.

DNA damage in children exposed to secondhand cigarette smoke and its association with oxidative stress

OBJECTIVE

To compare oxidative status, total antioxidant capacity and values of DNA damage in peripheral blood lymphocytes in children exposed to secondhand cigarette smoke with healthy controls.

DESIGN

Analytical, Observational.

PARTICIPANTS

54 children without any chronic diseases, attending the healthy child monitoring polyclinic. These comprised 27 children who had been exposed to passive cigarette smoke and 27 children who had not been exposed to cigarette smoke.

MAIN OUTCOME MEASURES

Urine cotinine levels by the chemiluminescent technique; DNA damage by alkaline comet assay; and total oxidant status (TOS) using a novel automated measurement method.

RESULTS

The mean urine cotinine, TOS, Oxidative Stress Index (OSI) and DNA damage values of the group exposed to cigarette smoke were determined to be at significantly higher level compared to the group not exposed to cigarette smoke (P<0.001). No statistically significant difference was determined in the TAS level between the two groups (P=0.1)

CONCLUSIONS

The results showed that TOS levels, OSI index and DNA damage in peripheral blood lymphocytes were significantly higher in children exposed to secondhand cigarette smoke than in those not exposed to secondhand cigarette smoke.

[Obesity and gallbladder diseases]

Obesity is an important health problem in the world and related to many critical diseases, such as diabetes, cardiovascular disease, and metabolic syndrome. Obesity leads to fat infiltration of multiple organs and infiltrated adipose tissue produces many cytokines resulting in the dysfunction of organs such as the gallbladder. In the biliary diseases, obesity and overweight have been known as a major risk factor for gallstones. According to current studies, obesity, insulin resistance, hyperinsulinemia, and metabolic syndrome are related to various gallbladder diseases including gallbladder stones, cholecystitis, gallbladder polyps, and gallbladder cancers. We reviewed further literature on the obesity and gallbladder diseases, in aspects of epidemiology, mechanism, pathology and prevention.

Cis-acting polymorphisms affect complex traits through modifications of microRNA regulation pathways

Genome-wide association studies (GWAS) have become an effective tool to map genes and regions contributing to multifactorial human diseases and traits. A comparably small number of variants identified by GWAS are known to have a direct effect on protein structure whereas the majority of variants is thought to exert their moderate influences on the phenotype through regulatory changes in mRNA expression. MicroRNAs (miRNAs) have been identified as powerful posttranscriptional regulators of mRNAs. Binding to their target sites, which are mostly located within the 3'-untranslated region (3'-UTR) of mRNA transcripts, they modulate mRNA expression and stability. Until today almost all human mRNA transcripts are known to harbor at least one miRNA target site with an average of over 20 miRNA target sites per transcript. Among 5,101 GWAS-identified sentinel single nucleotide polymorphisms (SNPs) that correspond to 18,884 SNPs in linkage disequilibrium (LD) with the sentinels (r2 ≥ 0.8) we identified a significant overrepresentation of SNPs that affect the 3'-UTR of genes (OR = 2.33, 95% CI = 2.12-2.57, P < 10(-52)). This effect was even stronger considering all SNPs in one LD bin a single signal (OR = 4.27, 95% CI = 3.84-4.74, P < 10(-114)). Based on crosslinking immunoprecipitation data we identified four mechanisms affecting miRNA regulation by 3'-UTR mutations: (i) deletion or (ii) creation of miRNA recognition elements within validated RNA-induced silencing complex binding sites, (iii) alteration of 3'-UTR splicing leading to a loss of binding sites, and (iv) change of binding affinity due to modifications of 3'-UTR folding. We annotated 53 SNPs of a total of 288 trait-associated 3'-UTR SNPs as mediating at least one of these mechanisms. Using a qualitative systems biology approach, we demonstrate how our findings can be used to support biological interpretation of GWAS results as well as to provide new experimentally testable hypotheses.

Stepwise cumulation of RUNX3 methylation mediated by Helicobacter pylori infection contributes to gastric carcinoma progression

BACKGROUND

Helicobacter pylori has been recognized as a definite carcinogen for gastric cancer (GC); however, the pathogenesis of H. pylori infection remains unclear. Runt-related transcription factor 3 (RUNX3) is a candidate tumor suppressor gene whose deficiency is causally related to GC. However, in H. pylori infection-associated GC, the role of RUNX3 has not been studied.

METHODS

The authors used real-time methylation-specific polymerase chain reaction analysis to determine methylation status of the RUNX3 promoter in a spectrum of gastric lesions, including 220 samples of chronic atrophic gastritis, 196 samples of intestinal metaplasia, 134 samples of gastric adenoma, 102 samples of dysplasia, and 202 samples of GC with paired noncancerous mucosa tissues and corresponding blood specimens. The association of abnormal methylation with precancerous gastric lesions was evaluated along with the association between RUNX3 methylation and H. pylori infection, and the concordance of methylation levels was investigated between serum and tissues.

RESULTS

The results indicated that increasing RUNX3 promoter methylation was correlated with distinct stages of GC progression. GC tissues had the highest methylation proportion (75.2%) compared with precancerous gastric lesions, including chronic atrophic gastritis (15.9%), intestinal metaplasia (36.7%), gastric adenoma (41.8%), and dysplasia (54.9%). H. pylori infection, a major risk factor for GC, contributed to the inactivation of RUNX3 in gastric epithelial cells through promoter hypermethylation. The levels of RUNX3 methylation in serum were in significant concordance with the methylation levels observed in GC tissues (P = .887).

CONCLUSIONS

The current findings supported RUNX3 methylation as a risk factors for the carcinogenesis of chronic atrophic gastritis with H. pylori infection and indicated that circulating RUNX3 methylation is a valuable biomarker for the detection of early GC.

Regulation by mitochondrial superoxide and NADPH oxidase of cellular formation of nitrated cyclic GMP: potential implications for ROS signalling

8-Nitro-cGMP (8-nitroguanosine 3',5'-cyclic monophosphate) is a nitrated derivative of cGMP, which can function as a unique electrophilic second messenger involved in regulation of an antioxidant adaptive response in cells. In the present study, we investigated chemical and biochemical regulatory mechanisms involved in 8-nitro-cGMP formation, with particular focus on the roles of ROS (reactive oxygen species). Chemical analyses demonstrated that peroxynitrite-dependent oxidation and myeloperoxidase-dependent oxidation of nitrite in the presence of H2O2 were two major pathways for guanine nucleotide nitration. Among the guanine nucleotides examined, GTP was the most sensitive to peroxynitrite-mediated nitration. Immunocytochemical and tandem mass spectrometric analyses revealed that formation of 8-nitro-cGMP in rat C6 glioma cells stimulated with lipopolysaccharide plus pro-inflammatory cytokines depended on production of both superoxide and H2O2. Using the mitochondria-targeted chemical probe MitoSOX Red, we found that mitochondria-derived superoxide can act as a direct determinant of 8-nitro-cGMP formation. Furthermore, we demonstrated that Nox2 (NADPH oxidase 2)-generated H2O2 regulated mitochondria-derived superoxide production, which suggests the importance of cross-talk between Nox2-dependent H2O2 production and mitochondrial superoxide production. The results of the present study suggest that 8-nitro-cGMP can serve as a unique second messenger that may be implicated in regulating ROS signalling in the presence of NO.

Zuonin B Inhibits Lipopolysaccharide-Induced Inflammation via Downregulation of the ERK1/2 and JNK Pathways in RAW264.7 Macrophages

We investigated whether Zuonin B exerts immunological effects on RAW264.7 cells. Zuonin B, isolated from flower buds of Daphne genkwa, suppressed the levels of nitric oxide and prostaglandin E₂, as well as proinflammatory cytokines, such as tumor necrosis factor-α and interleukin-(IL-) 6, in lipopolysaccharide-stimulated macrophages. Moreover, the compound inhibited cyclooxygenase-2 and inducible nitric oxide synthase expression. Zuonin B attenuated NF-kappaB (NF-κB) activation via suppressing proteolysis of inhibitor kappa B-alpha (IκB-α) and p65 nuclear translocation as well as phosphorylation of extracellular signal-regulated kinase 1/2 and c-Jun N-terminal kinase. Additionally, IL-4 and IL-13 production in ConA-induced splenocytes was inhibited by Zuonin B. In conclusion, the anti-inflammatory effects of Zuonin B are attributable to the suppression of proinflammatory cytokines and mediators via blockage of NF-κB and AP-1 activation. Based on these findings, we propose that Zuonin B is potentially an effective functional chemical candidate for the prevention of inflammatory diseases.

Role of nitrative and oxidative DNA damage in inflammation-related carcinogenesis

Chronic inflammation induced by biological, chemical, and physical factors has been found to be associated with the increased risk of cancer in various organs. We revealed that infectious agents including liver fluke, Helicobacter pylori, and human papilloma virus and noninfectious agents such as asbestos fiber induced iNOS-dependent formation of 8-nitroguanine and 8-oxo-7, 8-dihydro-2′-deoxyguanosine (8-oxodG) in cancer tissues and precancerous regions. Our results with the colocalization of phosphorylated ATM and γ-H2AX with 8-oxodG and 8-nitroguanine in inflammation-related cancer tissues suggest that DNA base damage leads to double-stranded breaks. It is interesting from the aspect of genetic instability. We also demonstrated IL-6-modulated iNOS expression via STAT3 and EGFR in Epstein-Barr-virus-associated nasopharyngeal carcinoma and found promoter hypermethylation in several tumor suppressor genes. Such epigenetic alteration may occur by controlling the DNA methylation through IL-6-mediated JAK/STAT3 pathways. Collectively, 8-nitroguanine would be a useful biomarker for predicting the risk of inflammation-related cancers.

Chronic inflammation in cancer development

Chronic inflammatory mediators exert pleiotropic effects in the development of cancer. On the one hand, inflammation favors carcinogenesis, malignant transformation, tumor growth, invasion, and metastatic spread; on the other hand inflammation can stimulate immune effector mechanisms that might limit tumor growth. The link between cancer and inflammation depends on intrinsic and extrinsic pathways. Both pathways result in the activation of transcription factors such as NF-κB, STAT-3, and HIF-1 and in accumulation of tumorigenic factors in tumor and microenvironment. STAT-3 and NF-κB interact at multiple levels and thereby boost tumor-associated inflammation which can suppress anti-tumor immune responses. These factors also promote tumor growth, progression, and metastatic spread. IL-1, IL-6, TNF, and PGHS-2 are key mediators of an inflammatory milieu by modulating the expression of tumor-promoting factors. In this review we concentrate on the crucial role of pro-inflammatory mediators in inflammation-driven carcinogenesis and outline molecular mechanisms of IL-1 signaling in tumors. In addition, we elucidate the dual roles of stress proteins as danger signals in the development of anti-cancer immunity and anti-apoptotic functions.

Vascular permeability in cancer and infection as related to macromolecular drug delivery, with emphasis on the EPR effect for tumor-selective drug targeting

Tumor and inflammation have many common features. One hallmark of both is enhanced vascular permeability, which is mediated by various factors including bradykinin, nitric oxide (NO), peroxynitrite, prostaglandins etc. A unique characteristic of tumors, however, is defective vascular anatomy. The enhanced vascular permeability in tumors is also distinctive in that extravasated macromolecules are not readily cleared. We utilized the enhanced permeability and retention (EPR) effect of tumors for tumor selective delivery of macromolecular drugs. Consequently, such drugs, nanoparticles or lipid particles, when injected intravenously, selectively accumulate in tumor tissues and remain there for long periods. The EPR effect of tumor tissue is frequently inhomogeneous and the heterogeneity of the EPR effect may reduce the tumor delivery of macromolecular drugs. Therefore, we developed methods to augment the EPR effect without inducing adverse effects for instance raising the systemic blood pressure by infusing angiotensin II during arterial injection of SMANCS/Lipiodol. This method was validated in clinical setting. Further, benefits of utilization of NO-releasing agent such as nitroglycerin or angiotensin-converting enzyme (ACE) inhibitors were demonstrated. The EPR effect is thus now widely accepted as the most basic mechanism for tumor-selective targeting of macromolecular drugs, or so-called nanomedicine.

Pathogenesis and biomarkers of carcinogenesis in ulcerative colitis

One of the most serious complications of ulcerative colitis is the development of colorectal cancer. Screening patients with ulcerative colitis by standard histological examination of random intestinal biopsy samples might be inefficient as a method of cancer surveillance. This Review focuses on the current understanding of the pathogenesis of ulcerative colitis-associated colorectal cancer and how this knowledge can be transferred into patient management to assist clinicians and pathologists in identifying patients with ulcerative colitis who have an increased risk of colorectal cancer. Inflammation-driven mechanisms of DNA damage, including the generation and effects of reactive oxygen species, microsatellite instability, telomere shortening and chromosomal instability, are reviewed, as are the molecular responses to genomic stress. We also discuss how these mechanisms can be translated into usable biomarkers. Although progress has been made in the understanding of inflammation-driven carcinogenesis, markers based on these findings possess insufficient sensitivity or specificity to be usable as reliable biomarkers for risk of colorectal cancer development in patients with ulcerative colitis. However, screening for mutations in p53 could be relevant in the surveillance of patients with ulcerative colitis. Several other new biomarkers, including senescence markers and α-methylacyl-CoA-racemase, might be future candidates for preneoplastic markers in ulcerative colitis.

Reactive species and DNA damage in chronic inflammation: reconciling chemical mechanisms and biological fates

Chronic inflammation has long been recognized as a risk factor for many human cancers. One mechanistic link between inflammation and cancer involves the generation of nitric oxide, superoxide and other reactive oxygen and nitrogen species by macrophages and neutrophils that infiltrate sites of inflammation. Although pathologically high levels of these reactive species cause damage to biological molecules, including DNA, nitric oxide at lower levels plays important physiological roles in cell signaling and apoptosis. This raises the question of inflammation-induced imbalances in physiological and pathological pathways mediated by chemical mediators of inflammation. At pathological levels, the damage sustained by nucleic acids represents the full spectrum of chemistries and likely plays an important role in carcinogenesis. This suggests that DNA damage products could serve as biomarkers of inflammation and oxidative stress in clinically accessible compartments such as blood and urine. However, recent studies of the biotransformation of DNA damage products before excretion point to a weakness in our understanding of the biological fates of the DNA lesions and thus to a limitation in the use of DNA lesions as biomarkers. This review will address these and other issues surrounding inflammation-mediated DNA damage on the road to cancer.

Methodological proof of immunochemistry for specific identification of 8-nitroguanosine 3',5'-cyclic monophosphate formed in glia cells

The biological significance of nitrated guanine derivatives, especially 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP), has become evident. Therefore it is important to determine the presence and relative abundance of 8-nitro-cGMP formed in cells and tissues. In the present study, we performed immunocytochemistry with monoclonal antibodies specific for 8-nitroguanine (clone NO2-52) and 8-nitro-cGMP (clone 1G6) in rat C6 glioma cells and rat primary cultured astrocytes. Immunocytochemistry utilizing the anti-8-nitro-cGMP monoclonal antibody (1G6) indicated that immunostaining increased markedly in C6 cells expressing increased amounts of inducible nitric oxide synthase (iNOS) after treatment with lipopolysaccharide (LPS) plus cytokines. Treatment of C6 cells with inhibitors for NOS and soluble guanylate cyclase (sGC) completely nullified the elevated 1G6 immunoreactivity. These results were consistent with the liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses. Immunocytochemistry performed using NO2-52 also showed that treatment of cells with inhibitors for NOS and sGC completely nullified the elevated immunoreactivity; this indicated that 8-nitro-cGMP is a major component of 8-nitroguanine derivatives produced in cells. Similar results were obtained in the primary astrocytes stimulated with LPS plus cytokines. Because immunocytochemistry is a conventional, powerful, and fairly straightforward method for determining the presence, localization, and relative abundance of an antigen of interest in cultured cells, anti-8-nitroguanine (NO2-52) and anti-8-nitro-cGMP (1G6) antibodies could be useful tools for analyzing nitrated guanine nucleotides, especially 8-nitro-cGMP, by means of immunocytochemistry.

Role of TLR2-dependent inflammation in metastatic progression

Inflammation is a part of the host defense system, which provides protection against invading pathogens. However, it has become increasingly clear that inflammation can be evoked by endogenous mediators through Toll-like receptors (TLRs) to enhance tumor progression and metastasis. Here, we discuss the roles of TLR-mediated inflammation in tumor progression and the mechanisms through which it accomplishes this pathogenic function.

Biochemical and neurochemical sequelae following mild traumatic brain injury: summary of experimental data and clinical implications

Although numerous studies have been carried out to investigate the pathophysiology of mild traumatic brain injury (mTBI), there are still no standard criteria for the diagnosis and treatment of this peculiar condition. The dominant theory that diffuse axonal injury is the main neuropathological process behind mTBI is being revealed as weak at best or inconclusive, given the current literature and the fact that neuronal injury inherent to mTBI improves, with few lasting clinical sequelae in the vast majority of patients. Clinical and experimental evidence suggests that such a course, rather than being due to cell death, is based on temporal neuronal dysfunction, the inevitable consequence of complex biochemical and neurochemical cascade mechanisms directly and immediately triggered by the traumatic insult. This report is an attempt to summarize data from a long series of experiments conducted in the authors' laboratories and published during the past 12 years, together with an extensive analysis of the available literature, focused on understanding the biochemical damage produced by an mTBI. The overall clinical implications, as well as the metabolic nature of the post-mTBI brain vulnerability, are discussed. Finally, the application of proton MR spectroscopy as a possible tool to monitor the full recovery of brain metabolic functions is emphasized.

Nucleotides function as endogenous chemical sensors for oxidative stress signaling

Oxidized and nitrated nucleotides including 8-oxogunanine and 8-nitroguanine derivatives such as 8-nitroguanosine 3',5'-cyclic monophosphate were generated by reactive nitrogen oxides and reactive oxygen species in cultured cells and in tissues. 8-oxoguanine and 8-nitroguanine in DNA and RNA are potentially mutagenic, and the former also induces cell death. Some derivative, 8-nitroguanosine 3',5'-cyclic monophosphate a major nitrated guanine nucleotide, was identified as a novel second messenger. Surprisingly, the amount of 8-nitroguanosine 3',5'-cyclic monophosphate generated was found to be higher than that of guanosine 3',5'-cyclic monophosphate in cells expressing inducible nitric oxide synthase. More important, 8-nitroguanosine 3',5'-cyclic monophosphate is electrophilic and reacted efficiently with sulfhydryls of proteins to produce a novel posttranslational modification (named S-guanylation) via guanosine 3',5'-cyclic monophosphate adduction. For example, 8-nitroguanosine 3',5'-cyclic monophosphate-induced S-guanylation of Kelch-like ECH-associated protein 1 led to NF-E2-related factor activation and induction of antioxidant enzymes. 8-nitroguanosine 3',5'-cyclic monophosphate may thus protect cells against oxidative stress-related cytotoxicity. Therefore, although chemically modified nucleotides produced via oxidative and nitrative stress are regarded simply as endogenous mutagens, the endogenous nucleotides stored in cells per se may serve functionally as a sensing mechanism for reactive nitrogen oxides and oxygen species to induce cellular adaptive responses to oxidative stress.

When bacteria become mutagenic and carcinogenic: lessons from H. pylori

More and more convincing data link bacteria to the development of cancers. How bacteria act as mutagens by altering host genomes, what are the different strategies they develop and what consequences do they have on infection-associated pathogenesis are the main questions addressed in this review, which focuses in particular on Helicobacter pylori infection. H. pylori is a major risk factor for gastric cancer development. Its oncogenic role is mediated by the chronic active inflammation it elicits in the gastric mucosa, associated with its capacity to persistently colonize the human stomach. However, direct genotoxicity of H. pylori through the action of bacterial cytotoxin or resulting from a DNA damaging effect of its metabolic derivatives as nitroso compounds cannot be excluded. Numerous studies have investigated inflammation-associated DNA damaging activity and mutagenic response due to H. pylori infection in both human and animal models. Recent findings on its mutagenic effects at the nuclear and mitochondrial genome and related DNA damage are reviewed. This genotoxic activity associated with oxidative species produced during inflammation is linked to the decreased efficiency of DNA repair systems. DNA methylation, which plays an important role in the regulation of the host response to H. pylori infection, is also documented. Furthermore, H. pylori affects genome integrity by increasing activation-induced cytidine deaminase (AID), a DNA/RNA editing cytidine deaminase linking mutagenesis and tumorigenesis. These different strategies occurring during bacteria-host cell interaction, lead to nucleotide modifications and genome instabilities recognized as early events in the carcinogenesis process and contribute to the oncogenic properties of H. pylori infection.

Peroxynitrite-An ugly biofactor?

Cellular damage occurring under oxidative conditions has been ascribed mainly to the formation of peroxynitrite (ONOOH/ONOO(-)) that originates from the reaction of NO(*) with O(2) (*-). The detrimental effects of peroxynitrite are exacerbated by the reaction with CO(2) that leads to ONOOC(O)O(-), which further decays to the strong oxidant radicals NO(2) (*) and CO(3) (*-). The reaction with CO(2), however, may redirect peroxynitrite specificity. An excessive formation of peroxynitrite represents an important mechanism contributing to the DNA damage, the inactivation of metabolic enzymes, ionic pumps, and structural proteins, and the disruption of cell membranes. Because of its ability to oxidize biomolecules, peroxynitrite is implicated in an increasing list of diseases, including neurodegenerative and cardiovascular disorders, inflammation, pain, autoimmunity, cancer, and aging. However, peroxynitrite displays also protective activities: (i) at high concentrations, it shows anti-viral, anti-microbial, and anti-parasitic actions; and (ii) at low concentrations, it stimulates protective mechanisms in the cardiovascular, nervous, and respiratory systems. The detrimental effects of peroxynitrite and related reactive species are impaired by (pseudo-) enzymatic systems, mainly represented by heme-proteins (e.g., hemoglobin and myoglobin). Here, we report biochemical aspects of peroxynitrite actions being at the root of its biomedical effects.

Gastric cancer is associated with NOS2 -954G/C polymorphism and environmental factors in a Brazilian population

BACKGROUND

Gastric cancer can progress from a chronic inflammation of the gastric mucosa resulting from Helicobacter pylori infection that activates the inflammatory response of the host. Therefore, polymorphisms in genes involved in the inflammatory response, such as inducible nitric oxide synthase (NOS2), have been implicated in gastric carcinogenesis. The aim of this study was to evaluate the association of NOS2 polymorphisms Ser608Leu (rs2297518) in exon 16, -954G/C and -1173C/T, both in the promoter region, with gastric cancer and chronic gastritis and the association of cancer with risk factors such as smoking, alcohol intake and H. pylori infection.

METHODS

We conducted a population-based case-control study in 474 Southeast Brazilian individuals (150 with gastric cancer, 160 with chronic gastritis, and 164 healthy individuals), in which we performed NOS2 genotyping by PCR-RFLP.

RESULTS

SNP Ser608Leu was not associated with risk of chronic gastritis or gastric cancer. The polymorphic allele -1173T was not found in the studied population. However, the frequency of -954GC+CC genotypes was significantly higher (p < 0.01) in the cancer group (48.7%) than in both the gastritis (28.1%) and the control (29.9%) groups. Multivariate logistic regression showed that the NOS2 SNP -954G/C was associated with higher risk of gastric cancer (OR = 1.87; 95% CI = 1.12-3.13). We also observed an association with risk factors such as smoking and alcohol intake in both the gastric cancer (OR = 2.68; 95% CI = 1.58-4.53; OR = 3.60; 95% CI = 2.05-6.32, respectively) and the chronic gastritis (OR = 1.93; 95% CI = 1.19-3.13; OR = 2.79; 95% CI = 1.55-5.02, respectively) groups. This is the first report of increased risk of gastric cancer in association with the -954G/C polymorphism. These findings show that several polymorphisms in the promoter region of the NOS2 gene may contribute to the susceptibility to gastric cancer.

CONCLUSIONS

Polymorphism NOS2 -954 G/C, along with alcohol intake and tobacco smoking, is associated with gastric cancer. However, the NOS2 Ser608Leu polymorphism was not associated with gastric carcinogenesis. The NOS2 -1173C/T polymorphism was absent in the studied population.

Semi-micro flow injection analysis method for evaluation of quenching effect of health foods or food additive antioxidants on peroxynitrite

A semi-micro flow injection analysis (SMFIA) method for evaluation of quenching effect of food additive antioxidants or health foods on peroxynitrite (ONOO(-)) is described. The injected sample was carried with phosphate buffer containing NaNO(2), mixed with a trigger solution to generate ONOO(-) and then detected CL generated after mixing with luminol solution. Selective chemiluminescence caused by ONOO(-) in this generation system was confirmed by catalase treatment. Ascorbic acid (ASA), Trolox and ascorbyl palmitate (ASP) were used as food additive antioxidants. EC(50) values of ASA, Trolox and ASP were 2.6, 6.4 and 43 µg/mL, respectively. The amount of reagents required for an assay by this SMFIA system could reduce the time by a third compared with the conventional method previously reported. Furthermore, as an application of the proposed method, the quenching effect of commercially available Noni (Morinda citrifolia) juices was evaluated.

High urinary excretion of lipid peroxidation-derived DNA damage in patients with cancer-prone liver diseases

Chronic inflammatory processes induce oxidative and nitrative stress that trigger lipid peroxidation (LPO), whereby DNA-reactive aldehydes such as trans-4-hydroxy-2-nonenal (HNE) are generated. Miscoding etheno-modified DNA adducts including 1,N(6)-etheno-2'-deoxyadenosine (epsilondA) are formed by reaction of HNE with DNA-bases which are excreted in urine, following elimination from tissue DNA. An ultrasensitive and specific immunoprecipitation/HPLC-fluorescence detection method was developed for quantifying epsilondA excreted in urine. Levels in urine of Thai and European liver disease-free subjects were in the range of 3-6 fmol epsilondA/micromol creatinine. Subjects with inflammatory cancer-prone liver diseases caused by viral infection or alcohol abuse excreted massively increased and highly variable epsilondA-levels. Groups of Thai subjects (N=21) with chronic hepatitis, liver cirrhosis, or hepatocellular carcinoma (HCC) due to HBV infection had 20, 73 and 39 times higher urinary epsilondA levels, respectively when compared to asymptomatic HBsAg carriers. In over two thirds of European patients (N=38) with HBV-, HCV- and alcohol-related liver disease, urinary epsilondA levels were increased 7-10-fold compared to healthy controls. Based on this pilot study we conclude: (i) high urinary epsilondA-levels, reflecting massive LPO-derived DNA damage in vivo may contribute to the development of HCC; (ii) epsilondA-measurements in urine and target tissues should thus be further explored as a putative risk marker to follow malignant progression of inflammatory liver diseases in affected patients; (iii) etheno adducts may serve as biomarkers to assess the efficacy of (chemo-)preventive and therapeutic interventions.

Chronic inflammation and mutagenesis

Inflammation is a necessary part of the immune response. However, when inflammation persists, the resultant state of chronic inflammation may have a number of secondary consequences associated with increased risk of chronic disease. Among these is an increased rate of mutation. There is evidence to suggest that the accumulation of reactive oxygen and nitrogen species may be a causal factor in chronic inflammation. These reactive species are also produced through the oxidative burst associated with the inflammatory process, and may interact with various cellular components including proteins, lipids and, most important for mutagenesis, nucleic acids. DNA strand breaks are commonly produced, leading to chromosomal mutation. Oxidized bases, abasic sites, DNA-DNA intrastrand adducts, and DNA-protein cross-links also occur. Not only do the nucleic acid products act directly as pro-mutagenic lesions, lipid peroxidation products may also lead to secondary DNA damage, including pro-mutagenic exocyclic DNA adducts. While frameshift and chromosomal mutations have been associated with chronic inflammation, much of the evidence reveals base pair substitution mutations associated with polymerase stalling near the lesions, and base pair mis-incorporation. There are also indirect effects of ROS/RNS through inhibition of DNA repair enzymes and/or effects on metabolic activation of known carcinogens. Certain disease states, including the Inflammatory bowel diseases, Crohn's disease and ulcerative colitis are associated with enhanced levels of chronic inflammation, and show evidence of enhanced levels of genetic damage in the colonic mucosa. Mutations may provide at least part of the cause of enhanced susceptibility to chronic diseases associated with chronic inflammation.

Protein cysteine S-guanylation and electrophilic signal transduction by endogenous nitro-nucleotides

Nitric oxide (NO), a gaseous free radical that is synthesized in organisms by nitric oxide synthases, participates in a critical fashion in the regulation of diverse physiological functions such as vascular and neuronal signal transduction, host defense, and cell death regulation. Two major pathways of NO signaling involve production of the second messenger guanosine 3',5'-cyclic monophosphate (cGMP) and posttranslational modification (PTM) of redox-sensitive cysteine thiols of proteins. We recently clarified the physiological formation of 8-nitroguanosine 3',5'-cyclic monophosphate (8-nitro-cGMP) as the first demonstration, since the discovery of cGMP more than 40 years ago, of a new second messenger derived from cGMP in mammals. 8-Nitro-cGMP is electrophilic and reacts efficiently with sulfhydryls of proteins to produce a novel PTM via cGMP adduction, a process that we named protein S-guanylation. 8-Nitro-cGMP may regulate electrophilic signaling on the basis of its electrophilicity through induction of S-guanylation of redox sensor proteins. Examples include S-guanylation of the redox sensor protein Kelch-like ECH-associated protein 1 (Keap1), which leads to activation of NF-E2-related factor 2 (Nrf2)-dependent expression of antioxidant and cytoprotective genes. This S-guanylation-mediated activation of an antioxidant adaptive response may play an important role in cytoprotection during bacterial infections and oxidative stress. Identification of new redox-sensitive proteins as targets for S-guanylation may help development of novel therapeutics for oxidative stress- and inflammation-related disorders and vascular diseases as well as understanding of cellular protection against oxidative stress.