Monochloramine-induced cell growth inhibition and apoptosis in a rat gastric mucosal cell line

Signaling pathways of oxidative stress response: the potential therapeutic targets in gastric cancer

Gastric cancer is one of the top causes of cancer-related death globally. Although novel treatment strategies have been developed, attempts to eradicate gastric cancer have been proven insufficient. Oxidative stress is continually produced and continually present in the human body. Increasing evidences show that oxidative stress contributes significantly to the development of gastric cancer, either through initiation, promotion, and progression of cancer cells or causing cell death. As a result, the purpose of this article is to review the role of oxidative stress response and the subsequent signaling pathways as well as potential oxidative stress-related therapeutic targets in gastric cancer. Understanding the pathophysiology of gastric cancer and developing new therapies for gastric cancer depends on more researches focusing on the potential contributors to oxidative stress and gastric carcinogenesis.

Infiltration by myeloperoxidase-positive neutrophils is an independent prognostic factor in breast cancer

PURPOSE

Myeloperoxidase (MPO) is an enzyme secreted by neutrophil granulocytes as a result of phagocytosis during inflammation. In colorectal cancer, tumour infiltration by MPO expressing cells has been shown to be independently associated with a favourable prognosis. In this study, we explored the role of MPO-positive cell infiltration and its prognostic significance in invasive breast cancer.

METHODS

We performed immunohistochemical staining for MPO on multiple tissue microarrays comprising a total of 928 human breast cancer samples with detailed clinical-pathological annotation and outcome data.

RESULTS

MPO-positive cell infiltration (≥ 5 cells/tissue punch) was found in 150 (16%) of the 928 evaluable breast cancer cases. In univariate survival analyses, infiltration by MPO-positive cells was associated with a significantly better overall survival (p < 0.001). In subset univariate analyses, the infiltration by MPO-positive cells was associated with significantly better overall survival in the Luminal B/HER2-negative subtype (p = 0.005), the HER2 enriched subtype (p = 0.011), and the Triple Negative subtype (p < 0.001). In multivariate analysis, MPO expression proved to be an independent prognostic factor for improved overall survival (p < 0.001).

CONCLUSIONS

This is the first study to show that infiltration of MPO-positive cells is an independent prognostic biomarker for improved overall survival in human breast cancer.

Oxidative stress: an essential factor in the pathogenesis of gastrointestinal mucosal diseases

Reactive oxygen species (ROS) are generated as by-products of normal cellular metabolic activities. Superoxide dismutase, glutathione peroxidase, and catalase are the enzymes involved in protecting cells from the damaging effects of ROS. ROS are produced in response to ultraviolet radiation, cigarette smoking, alcohol, nonsteroidal anti-inflammatory drugs, ischemia-reperfusion injury, chronic infections, and inflammatory disorders. Disruption of normal cellular homeostasis by redox signaling may result in cardiovascular, neurodegenerative diseases and cancer. ROS are produced within the gastrointestinal (GI) tract, but their roles in pathophysiology and disease pathogenesis have not been well studied. Despite the protective barrier provided by the mucosa, ingested materials and microbial pathogens can induce oxidative injury and GI inflammatory responses involving the epithelium and immune/inflammatory cells. The pathogenesis of various GI diseases including peptic ulcers, gastrointestinal cancers, and inflammatory bowel disease is in part due to oxidative stress. Unraveling the signaling events initiated at the cellular level by oxidative free radicals as well as the physiological responses to such stress is important to better understand disease pathogenesis and to develop new therapies to manage a variety of conditions for which current therapies are not always sufficient.

Helicobacter pylori promotes apoptosis, activates cyclooxygenase (COX)-2 and inhibits heat shock protein HSP70 in gastric cancer epithelial cells

OBJECTIVE

Apoptosis plays an important role in the regulation of gastric epithelial cell number and gastrointestinal disorders induced by Helicobacter pylori (Hp). Heat shock proteins (HSPs) are involved in cell integrity, cell growth and in gastric mucosa colonized by Hp. COX-2 was implicated in Hp-induced carcinogenesis but the effects of this germ and CagA cytotoxin on HSP70, COX-2, Bax and Bcl-2 in gastric cancer epithelial cells have been little studied.

MATERIAL AND METHODS

We determined the expression for HSP70, Bax and Bcl-2 in human gastric epithelial MKN7 cells incubated with live strain Hp (cagA + vacA+) with or without co-incubation with exogenous CagA and NS-398, the selective COX-2 inhibitor. After 3-48 h of incubation, the expression of HSP70, COX-2, Bax and Bcl-2 mRNA and proteins were determined by RT-PCR and immunoprecipitation.

RESULTS

Hp inhibited expression for HSP70 and this was significantly potentiated by exogenous CagA. Co-incubation of epithelial cells with Hp, without or with CagA increased Bax expression and simultaneously decreased expression for Bcl-2. The increase in COX-2 mRNA and Bax expression were significantly inhibited by NS-398. We conclude that Hp promotes apoptosis in adenocarcinoma gastric epithelial cells in vitro and this is associated with activation of COX-2 and inhibition of HSP70.

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 O₂•⁻. 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.

Helicobacter pylori: a ROS-inducing bacterial species in the stomach

BACKGROUND

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) have been reported to impact gastric inflammation and carcinogenesis. However, the precise mechanism by which Helicobacter pylori induces gastric carcinogenesis is presently unclear.

AIM

This review focuses on H. pylori-induced ROS/RNS production in the host stomach, and its relationship with gastric carcinogenesis.

RESULTS

Activated neutrophils are the main source of ROS/RNS production in the H. pylori-infected stomach, but H. pylori itself also produces ROS. In addition, extensive recent studies have revealed that H. pylori-induced ROS production in gastric epithelial cells might affect gastric epithelial cell signal transduction, resulting in gastric carcinogenesis. Excessive ROS/RNS production in the stomach can damage DNA in gastric epithelial cells, implying its involvement in gastric carcinogenesis.

CONCLUSION

Understanding the molecular mechanism behind H. pylori-induced ROS, and its involvement in gastric carcinogenesis, is important for developing new strategies for gastric cancer chemoprevention.

Thiol chemistry and specificity in redox signaling

Exposure of cells to sublethal oxidative stress results in the modulation of various signaling pathways. Oxidants can activate and inactivate transcription factors, membrane channels, and metabolic enzymes, and regulate calcium-dependent and phosphorylation signaling pathways. Oxidation and reduction of thiol proteins are thought to be the major mechanisms by which reactive oxidants integrate into cellular signal transduction pathways. This review focuses on mechanisms for sensing and transmitting redox signals, from the perspective of their chemical reactivity with specific oxidants. We discuss substrate preferences for different oxidants and how the kinetics of these reactions determines how each oxidant will react in a cell. This kinetic approach helps to identify initial oxidant-sensitive targets and elucidate mechanisms involved in transmission of redox signals. It indicates that only those proteins with very high reactivity, such as peroxiredoxins, are likely to be direct targets for hydrogen peroxide. Other more modestly reactive thiol proteins such as protein tyrosine phosphatases are more likely to become oxidized by an indirect mechanism. The review also examines oxidative changes observed during receptor-mediated signaling, the strengths and limitations of detection methods for reactive oxidant production, and the evidence for hydrogen peroxide acting as the second messenger. We discuss areas where observations in cell systems can be rationalized with the reactivity of specific oxidants and where further work is needed to understand the mechanisms involved.

Monochloramine potently inhibits arachidonic acid metabolism in rat platelets

In the present study, the effects of hypochlorous acid (HOCl), monochloramine (NH(2)Cl), glutamine-chloramine (Glu-Cl) and taurine-chloramine (Tau-Cl) on the formation of 12-lipoxygenase (LOX) metabolite, 12-HETE, and cyclooxygenase (COX) metabolites, TXB(2), and 12-HHT, from exogenous arachidonic acid (AA) in rat platelets were examined. Rat platelets (4x10(8)/ml) were preincubated with drugs for 5min at 37 degrees C prior to the incubation with AA (40microM) for 2min at 37 degrees C. HOCl (50-250microM) showed an inhibition on the formation of LOX metabolite (12-HETE, 5-67% inhibition) and COX metabolites (TXB(2), 33-73% inhibition; 12-HHT, 27-74% inhibition). Although Tau-Cl and Glu-Cl up to 100microM were without effect on the formation of 12-HETE, TXB(2) and 12-HTT, NH(2)Cl showed a strong inhibition on the formation of all three metabolites (10-100microM NH(2)Cl, 12-HETE, 21-92% inhibition; TXB(2), 58-94% inhibition; 12-HHT, 36-92% inhibition). Methionine reversed a reduction of formation of LOX and COX metabolites induced by NH(2)Cl, and taurine restoring that induced by both NH(2)Cl and HOCl. These results suggest that NH(2)Cl is a more potent inhibitor of COX and LOX pathways in platelets than HOCl, and taurine and methionine can be modulators of NH(2)Cl-induced alterations in the COX and LOX pathways in vivo.

Rebamipide, a gastro-protective drug, inhibits indomethacin-induced apoptosis in cultured rat gastric mucosal cells: association with the inhibition of growth arrest and DNA damage-induced 45 alpha expression

Rebamipide, a gastromucosal protective drug, suppresses indomethacin-induced gastropathy in humans and rodents. Effects of rebamipide on gene expression in indomethacin-treated gastric mucosal cells (RGM1) were investigated using high-density oligonucleotide arrays. Indomethacin induced apoptosis in RGM1 cells in a dose-dependent manner. Rebamipide pretreatment significantly reduced indomethacin-induced apoptosis. We used gene expression profiling on high-density oligonucleotide probe arrays to characterize the transcriptional response of RGM1 cells to indomethacin treatment for 6 hr. Of the 8,799 probes examined, 717 (8.1%) were induced (400 probes) or repressed (317 probes) at least 1.5-fold. Among the 158 genes that were induced by indomethacin at least 2.0-fold, four genes that were down-regulated by rebamipide at least 2.0-fold are listed: growth arrest and DNA-damage-inducible 45 alpha (GADD 45 alpha), golgi SNAP receptor complex member 1, iodothyronine deiodinases, and transcription factor 8. Real time-PCR confirmed GADD 45 alpha expression and its inhibition by rebamipide. Inhibition of apoptosis-related genes is possibly important for the cytoprotective effect of rebamipide against indomethacin-induced gastric mucosal cell injury.

Characterization of monochloramine toxicity on PC12 cells and protective effect of tocopherol via antioxidative function

Monochloramine (NH(2)Cl) is a physiological oxidant produced by activated neutrophils. In the present work, we studied the underlying mechanism of cytotoxic effects of NH(2)Cl on an undifferentiated rat pheochromocytoma PC12 cell line and the protective effects of antioxidants. The cells treated with 100 microM NH(2)Cl exhibited signs of apoptotic cell death such as phosphatidylserine exposure and caspase activation. To understand the mechanism of NH(2)Cl cytotoxicity, we examined the effect of various kinds of antioxidants including alpha-tocopherol (alpha-Toc) and beta-tocopherol (beta-Toc). These antioxidants exerted a protective effect against NH(2)Cl-induced cell death, and alpha-Toc exhibited the most potent inhibitory effect among the antioxidants used. A loss of cellular glutathione was observed in the cells treated with 100 microM NH(2)Cl. The formation of reactive oxygen species (ROS) was also measured using the fluorescent probe dichlorofluorescin diacetate. The fluorescence intensity increased prior to cell death and an antioxidant, such as alpha-Toc, suppressed the increase in ROS. Interestingly, beta-Toc also exerted similar inhibitory effects on cytotoxicity and caspase activation. These results suggest that free radical mediated process is involved in NH(2)Cl-induced PC12 cell death and that tocopherols inhibit this cell death via antioxidative function.

Extracellular Oxidation by Taurine Chloramine Activates ERK via the Epidermal Growth Factor Receptor

Taurine is present in high concentrations in neutrophils, and when the cells are stimulated taurine can react with hypochlorous acid (HOCl) to form taurine-chloramine (Tau-Cl). This compound retains oxidant activity and can affect the neutrophil itself or surrounding tissue cells. We have investigated the effects of Tau-Cl on MAPK signaling in human umbilical vein endothelial cells (HUVEC). Tau-Cl caused no loss in intracellular glutathione or inactivation of the thiol-sensitive enzyme glyceraldehyde-3-phosphate dehydrogenase, indicating that it had not entered the cells. However, stimulation of HUVEC with Tau-Cl (20-100 microM) induced the rapid activation of ERK within 10 min. This activation was abolished by inhibition of MEK by U0126, indicating that it was not because of direct oxidation of ERK. No activation of p38 was detected. These results suggest that Tau-Cl reacts with a cell membrane target that results in intracellular ERK activation. Tau-Cl over the same concentration range and time scale stimulated epidermal growth factor (EGF) receptor tyrosine phosphorylation in A431 cells and HUVEC. The EGF receptor inhibitor PD158780 significantly attenuated Tau-Cl-induced phosphorylation of both the EGF receptor and ERK. This implicates the EGF receptor in the upstream activation of ERK. The Src tyrosine kinase inhibitor 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolol[3,4-d]pyrimidine had no effect on Tau-Cl-induced EGF receptor or ERK activation. We propose that Tau-Cl acts on an oxidant-sensitive target on the cell surface, this being either the EGF receptor itself or another target that can interact with the EGF receptor, with consequential activation of ERK.

The physiology and pharmacology of singlet oxygen

Reactive oxygen species (ROS) are generated by many different cells. Singlet oxygen (1O(2)) and a reaction product of it, excited carbonyls (C=O*), are important ROS. 1O(2) and C=O* are nonradicalic and emit light (one photon/molecule) when returning to ground state oxygen. Especially activated polymorphonuclear neutrophil granulocytes (PMN) produce large amounts of 1O(2). Via activation of the respiratory burst (NADPH oxidase and myeloperoxidase) they synthesize hypochlorite (NaOCl) and chloramines (in particular N-chlorotaurine). Chloramines are selective and stable chemical generators of 1O(2). In the human organism, 1O(2) is both a signal and a weapon with therapeutic potency against very different pathogens, such as microbes, virus, cancer cells and thrombi. Chloramines at blood concentrations between 1 and 2 mmol/L inactivate lipid enveloped virus and chloramines at blood concentrations below 0.5 mmol/L, i.e. at oxidant concentrations that do not affect thrombocytes or hemostasis factors, act antithrombotically by activation of the physiologic PMN mediated fibrinolysis; this thrombolysis is of selective nature, i.e. it does not impair the hemostasis system of the patient allowing the antithrombotic treatment in patients where the current risky thrombolytic treatment is contraindicated. The action of 1O(2) might be compared to the signaling and destroying gunfire of soldiers directed against bandits at night, resulting in an autorecruitment of the physiological inflammatory response. Chloramines (such as the mild and untoxic oxidant chloramine T (N-chloro-p-toluene-sulfonamide)) and their signaling and destroying reaction product 1O(2) might be promising new therapeutic agents against a multitude of up to now refractory diseases.

Association of the myeloperoxidase -463G-->A polymorphism with development of atrophy in Helicobacter pylori-infected gastritis

OBJECTIVES

Although the host factors governing clinical outcomes subsequent to Helicobacter pylori infection have not yet been defined, it has been generally perceived that the development of the atrophic gastritis is determined more by host-related factors than by bacterial factors. It is very important to define the host factors controlling the pathway to atrophic gastritis, which is the precursor of gastric cancer. H. pylori infection is characterized by extensive infiltration of neutrophils. Myeloperoxidase in neutrophils amplifies the oxidative potential of hydrogen peroxides that induce gastric mucosal damage, and thus myeloperoxidase is suspected to play a role in H. pylori-induced gastric injury. The aim of this study was to elucidate the association of host myeloperoxidase genetic polymorphism with atrophic gastritis upon H. pylori infection.

METHODS

Biopsy specimens taken from the gastric mucosa were examined histologically using the updated Sydney System in 127 Korean patients. The polymerase chain reaction-restriction fragment length polymorphism assay was used to characterize myeloperoxidase genotypes.

RESULTS

The distributions of myeloperoxidase genotypes in Korea were 81.9% for myeloperoxidase (G/G) and 18.1% for myeloperoxidase (G/A). No myeloperoxidase (A/A) genotype was observed in 127 patients studied. The degree of active inflammation increased with the increase in H. pylori colonization. A strong positive correlation between the levels of neutrophil infiltration and gastric atrophy was found in the myeloperoxidase (G/G) genotype but not in myeloperoxidase (G/A).

CONCLUSIONS

These results suggest that myeloperoxidase genotype is a critical determinant in the pathogenesis of atrophic gastritis subsequent to H. pylori infection. More work is needed to clarify the functional relevance of myeloperoxidase genetic polymorphisms to gastric cell injury.

Hydrogen peroxide-induced apoptosis of HL-60 human leukemia cells is mediated by the oxidants hypochlorous acid and chloramines

We set out to identify whether HOCl, which is generated from H(2)O(2) /MPO/Cl(-), is a proximal mediator of H(2)O(2) programmed cell death in the HL-60 human leukemia cell. We found that authentic HOCl induces apoptosis in the HL-60 cell. Both the addition of methionine, an HOCl scavenger, and the removal of Cl(-) from the medium to prevent the formation of HOCl inhibited H(2)O(2)-induced apoptosis. HL-60 cells underwent apoptosis when exposed to HOCl in full medium, which gives rise to chloramines by the reaction of HOCl with amine groups, but not by HOCl in the amine-free HBSS, in which HOCl but not chloramines can be detected. Authentic chloramines induced apoptosis in this cell line in a concentration-dependent manner and at concentrations lower than HOCl. Full medium exposed to HOCl for 24 h would support methionine noninhibitable apoptosis, but did not react with 2-nitro-5-thiobenzoic acid (TNB), raising the possibility that the final inducer is a nonoxidant formed from HOCl and chloramines. We conclude that the signal for apoptosis induced by H(2)O(2) in the MPO-containing HL-60 cell involves the reaction of the diffusible oxidant HOCl with amines producing chloramines and a subsequent non-TNB-reactive product.

Ubiquitin-proteasome inhibitor enhances tumour necrosis factor-alpha-induced apoptosis in rat gastric epithelial cells

BACKGROUND

Tumour necrosis factor (TNF-alpha) is a candidate factor for involvement in inflammation-mediated gastric mucosal injury. However, the effect of this cytokine on gastric epithelial cells has been poorly investigated. In the present study, we examined whether gastric epithelial cells are resistant to TNF-alpha-induced apoptosis, and whether this resistance is related to ubiquitin-proteasome-associated nuclear factor-kappaB (NF-kappaB) activation.

METHODS

The rat gastric mucosal cell line RGM-1 was grown in DMEM/F12 medium supplemented with 10% FCS. Confluent monolayers of cells were pretreated or not for 60 min with PSI, a peptide aldehyde known to specifically inhibit the chymotrypsin-like activity of 26S proteasome. Cells were subsequently stimulated with recombinant rat TNF-alpha and their viability was determined by WST-1 assay. Apoptosis was confirmed by fluorescence microscopy after staining with Hoechst 33342 and propidium iodide, and DNA fragmentation was determined by flow cytometry using an APO-BRDU kit. IkappaB-alpha and the p65 binding subunit of NF-kappaB were detected by Western blots.

RESULTS

Twenty-four-hour incubation with TNF-alpha alone or PSI alone did not affect the cell viability of RGM-1 cells. Pretreatment with PSI significantly enhanced the level of apoptosis induced by TNF-alpha. In RGM-1 cells treated with TNF-alpha, cytoplasmic IkappaB-alpha decreased and p65 in nuclear extracts increased markedly 30 min after cytokine stimulation. Pretreatment with PSI at 12.5 micromol/L blocked these TNF-alpha-induced changes.

CONCLUSION

PSI enhances TNF-alpha-induced apoptosis through inhibition of NF-kappaB activation in RGM-1 cells.

Apoptosis in gastric epithelium induced by Helicobacter pylori infection: implications in gastric carcinogenesis

OBJECTIVES

Helicobacter pylori is an identified carcinogen for gastric cancer, however, the underlying mechanisms remain to be defined. In this review, we sought to elucidate the role of apoptosis in gastric carcinogenesis, to determine the influence of H. pylori infection on apoptosis, and finally to provide insights into the mechanisms by which H. pylori may lead to gastric carcinogenesis.

METHODS

A broad-based MEDLINE and Current Contents literature search was performed to identify relevant publications between 1966 and March 2000 addressing H. pylori infection, apoptosis, cell proliferation, gastric carcinoma, oncogenes, and tumor suppressor genes, as well as the products of these genes. Abstracts from recent major conferences that provided adequate additional data were also included.

RESULTS

Apoptotic cells are rare in the glandular neck region (the generative cell zone) of normal gastric mucosa. With progression of atrophic gastritis, the generative cell zone shifts downward and a relatively large number of apoptotic cells occur. In intestinalized glands, both apoptotic cells and proliferative cells are present in deeper portions of the glands, corresponding to the generative zone. A higher frequency of apoptosis has been observed in gastric dysplasia than in coexisting gastric carcinomas, whereas the number of proliferative cells is significantly higher in gastric carcinoma than in dysplasia. Upregulation of oncogene bcl-2 in premalignant lesions and "downregulation" of the gene after malignant change is probably a common event. Accumulation of p53 protein is first detected in dysplasia, although mutation of the pS3 gene may occur in intestinal metaplasia. H. pylori infection induces apoptosis in gastric epithelial cells, which returns to normal after eradication of the infection. Numerous molecules produced by H. pylori including cytotoxin (VacA), lipopolysaccharide, monochloramine, and nitric oxide may directly induce apoptosis. Moreover, H. pylori-stimulated host inflammatory/immune responses lead to release of a large amount of cytokines. Cytokines produced by type 1 T helper cells, such as TNF-alpha and IFN-gamma, markedly potentiate apoptosis. Gastric cell proliferation is significantly higher in patients with H. pylori infection than in normal controls, and eradication of the infection leads to a reduction in cell proliferation. Apoptosis and cell proliferation are also increased in precancerous lesions such as gastric atrophy, intestinal metaplasia, and dysplasia in the presence of H. pylori infection. However, H. pylori-induced apoptosis may no longer be cell cycle-dependent in these lesions because of the occurrence of alterations and mutations of apoptosis-regulating genes, resulting in a loss of balance between apoptosis and cell proliferation.

CONCLUSIONS

It is hypothesized that H. pylori-induced apoptosis may play a key role in gastric carcinogenesis by increasing cell proliferation and/or resulting in gastric atrophy.

The role of neutrophils and inflammation in gastric mucosal injury

Gastric inflammation is a highly complex biochemical protective response to cellular/tissue injury. When this process occurs in an uncontrolled manner, the result is excessive cellular/tissue damage that results chronic inflammation and destruction of normal tissue. Current evidence suggests that Helicobacter pylori (H. pylori) infection and nonsteroidal anti-inflammatory drug (NSAID) ingestion are major causative factors in the pathogenesis of gastric mucosal injury in humans. In response to H. pylori infection or NSAID, neutrophils are recruited to the site of inflammation and generate reactive oxygen and nitrogen species and proteases. However, neutrophils are not able to kill the bacteria that live in the gastric mucus, and compounds produced by activated neutrophils themselves may be potentially harmful for normal tissue. It has been shown that leukocyte-vascular endothelial cell interaction is regulated by various cell adhesion molecules, and that this interaction is directly or indirectly modified by many factors, the origin of which is H. pylori and NSAIDs. This review describes the potential role of neutrophils and neutrophil-associated inflammation for gastric oxidative stress and injury induced by H. pylori and/or NSAID.

Rat CXC chemokine GRO/CINC-1 paradoxically stimulates the growth of gastric epithelial cells

BACKGROUND

CXC chemokines such as interleukin (IL)-8 are neutrophil chemoattractants, the levels of which increase in Helicobacter pylori-infected gastric mucosa. Many investigators have focused on the chemotactic aspects of IL-8: however, CXC chemokines are also reported to have angiogenic activity and to serve as remodelling factors. Rat GRO/CINC-1 is a rodent counterpart of human GROalpha, a member of the family of CXC chemokines. Gastric mucosa infected with H. pylori is in a state of hyperproliferation, with increases in the amounts of growth factors such as hepatocyte growth factor (HGF).

AIM

To investigate whether rat GRO/CINC-1 had growth-stimulating activity for gastric epithelial cells.

METHODS

The rat gastric epithelial cell line RGM-1 was incubated in serum-free medium for 12 h to adjust the cell cycle to the G0 phase, and GRO/CINC-1 was then added for 24 h. The total cell number was determined by fluorogenic analysis after propidium iodide staining, and cell proliferation was assessed by measuring 5-bromo-2'-deoxyuridine (BrdU) incorporation. The activity of p42/p44 mitogen-activated protein kinase (MAPK) was measured 5-20 min after the start of GRO/CINC-1 exposure.

RESULTS

Cultures treated with GRO/CINC-1 showed a significant increase in cell number and BrdU incorporation in a concentration-dependent fashion. The MAPK activity increased within 5 min after GRO/CINC-1 application and returned to the control level at 20 min.

CONCLUSION

The growth-stimulatory effect of GRO/CINC-1 on rat gastric epithelial cells suggests a dual function of this chemokine: proinflammatory action and induction of epithelial proliferation.

Effects of subchronic exposure of rats to dichloramine and trichloramine in drinking water

The subchronic toxicity of 0.2-200 ppm dichloramine and 0.2-90 ppm trichloramine in the drinking water of rats was investigated using biochemical, hematological, and histopathological parameters. Animals in the highest dose groups consumed 5-15% less fluid than controls with no significant decrease in body weight gain. No clinical signs of toxicity were observed in either case. Both males and females dosed with 90 ppm trichloramine had significantly increased relative kidney/body weights and the females had increased hepatic glutathione S-transferase and UPD-glucuronosyltransferase activities. No significant changes were detected in other xenobiotic metabolizing enzymes or in serum biochemistry, urine biochemistry, or hematology. Both dichloramine and trichloramine induced minimal to mild adaptive histopathological changes in thyroids and kidneys of animals of both sexes. Dichloramine, but not trichloramine, was associated with histological changes in the gastric cardia characterized by epithelial hyperplasia at concentrations of 2 ppm and above in the males and 200 ppm in the females. This study indicates that dichloramine produced mild histological effects at drinking water concentrations of >0.2 ppm in males (0.019 mg/kg/day) and >2 ppm in females (0.26 mg/kg/day) while trichloramine produced biochemical and mild histological effects at levels of >2 ppm both in males (0.23 mg/kg/day) and in females (0.29 mg/kg/day).

Role of apoptosis in Helicobacter pylori-associated gastric mucosal injury

Apoptosis, a programmed cell death, was ignored, just like Helicobacter pylori, only to reappear recently. However, the number of current publications dealing with apoptosis or H. pylori has increased exponentially. Although gastric epithelial apoptosis is a programmed physiological event in the superficial aspect of the mucosa and is important for healthy cell turnover, H. pylori infection reportedly promotes such a cell death sequence. Because apoptosis regulates the cycle of cell turnover in balance with proliferation, dysregulation of apoptosis or proliferation evoked by H. pylori colonization would be linked to the gastric carcinogenesis. In other words, a reduced level of apoptosis could contribute to the generation of gastric cancer. Herein, we review apoptosis as well as its associated pathological events, such as hyperproliferation, in H. pylori-colonized gastric mucosa.

Myeloperoxidase

This review covers recent advances in the biology of myeloperoxidase. Mechanisms of posttranslational processing and how these fail in some of the common deficiency mutants are discussed. We also review the enzymology that points to myeloperoxidase having a number of physiologic substrates in addition to chloride and the evidence that it produces hypochlorous acid in the neutrophil phagosome in sufficient quantities to be bactericidal. Evidence is accumulating that myeloperoxidase-derived oxidants modify biologic macromolecules and cell-regulatory pathways and that they play a role in atherosclerosis. Investigation of disease incidence in relation to a polymorphism in the promoter region of the gene has produced interesting associations. These links with inflammatory diseases can now be pursued further using specific biomarkers of myeloperoxidase activity.

Detection of Helicobacter pylori in oral aphthous ulcers

A causative role for Helicobacter pylori (H. pylori) in the pathogenesis of oral mucosal ulcerations has been suggested previously. We have adopted the polymerase chain reaction (PCR) as a rapid and sensitive means to detect H. pylori in swabs of recurrent oral aphthous ulcers and in samples of other oral sites. Of the oral aphthous ulcer samples, 32 (71.8%) were found to be positive, while the saliva and plaque samples (most of them taken from the patients with aphthous ulcers) were consistently negative for H. pylori DNA, as detected by the PCR assay. Only two of the swab samples from the tongue (collected at the time of concurrent, H. pylori-positive oral aphthous ulcers) were found to be positive. The data suggest that H. pylori may be associated frequently with recurrent oral aphthous ulcers, and are consistent with previous studies indicating that saliva and plaque are not likely sources of contamination with this microorganism. There was no apparent correlation with HIV status (infection with human immunodeficiency virus). The possible pathogenic significance of Helicobacter pylori in oral ulcerations is discussed.