Mechanism of Helicobacter pylori-associated gastric mucosal injury

Research methods assessing sodium hypochlorite cytotoxicity: A scoping review

Sodium hypochlorite (NaOCl) cytotoxicity has been assessed using different methodologies, which has led to arbitrary interpretations. This scoping review aimed to discuss the different methodological protocols for assessing NaOCl cytotoxicity. A literature review performed in the PubMed and Embase databases up to July 2023 identified manuscripts reporting NaOCl cytotoxicity. The dataset identified 546 publications, further screened by 2 reviewers. Ninety studies were identified and mined methodologically to collect information on cell type, cytotoxicity assay, NaOCl dilution solutions, presence of fetal bovine serum (FBS), and NaOCl exposure time. The culture medium used in cytotoxicity assays contains buffering substances that neutralize the pH of NaOCl, thus reducing its cytotoxicity, an approach that may lead to bias when solutions with different pH are compared. For short exposure periods, as in simulations to evaluate the contact between irrigant and periapical tissue cells during chemo-mechanical preparation, NaOCl dilution should be performed with saline, which does not buffer the irrigant. For long exposure periods, as in simulations of irrigant extrusions, NaOCl should be diluted in the culture medium, to reproduce the expected buffering effect occurring in extrusions. The presence of FBS in culture medium can decrease NaOCl toxicity. There is no standardization of NaOCl cytotoxicity methodologies. This poses the risk of arriving at incorrect results and, therefore, pertinent tests must be refined.

In situ quantification and evaluation of ClO−/H2S homeostasis in inflammatory gastric tissue by applying a rationally designed dual-response fluorescence probe featuring a novel H+-activated mechanism

A new dual-response probe for in situ quantification of ClO⁻/H₂S homeostasis in inflammatory gastric tissue.

Impact of cagPAI and T4SS on the inflammatory response of human neutrophils to Helicobacter pylori infection

Helicobacter pylori contains a pathogenicity island, cagPAI, with genes homologous to components of the type IV secretion system (T4SS) of Agrobacterium tumefaciens. The T4SS components assemble a structure that transfers CagA protein and peptidoglycan into host epithelial cells, causing the increased release of interleukin 8 (IL8) from the cells. The Toll-like receptors on neutrophils recognize H. pylori, initiating signaling pathways that enhance the activation of NF-κB. However, the roles of cagPAI and T4SS in the inflammatory response of neutrophils are unknown. We evaluated the participation of cagPAI and T4SS in the response of human neutrophils to H. pylori infection. Neutrophils were isolated from the blood of healthy donors and infected with H. pylori cagPAI(+), cagPAI(-), and cagPAI mutant strains virB4 (-) and virD4 (-). Whereas cagPAI(+) strain 26695 induced the greatest IL8 production, a proinflammatory response, cagPAI(-) strain 8822 induced the greatest IL10 production, an anti-inflammatory response. In contrast, the virB4 (-) and virD4 (-) mutant strains produced significantly more of the two proinflammatory cytokines IL1β and tumor necrosis factor αthan the cagPAI(+) strain 26695. We observed that H. pylori downregulated the expression of TLRs 2 and 5 but upregulated TLR9 expression in a cagPAI and T4SS-independent manner. These results show for the first time that the response of human neutrophils to H. pylori may vary from a pro-inflammatory to an anti-inflammatory response, depending on cagPAI and the integrity of T4SS.

Large scale screening of commonly used Iranian traditional medicinal plants against urease activity

Background and purpose of the study

H. pylori infection is an important etiologic impetus usually leading to gastric disease and urease enzyme is the most crucial role is to protect the bacteria in the acidic environment of the stomach. Then urease inhibitors would increase sensitivity of the bacteria in acidic medium.

Methods

137 Iranian traditional medicinal plants were examined against Jack bean urease activity by Berthelot reaction. Each herb was extracted using 50% aqueous methanol. The more effective extracts were further tested and their IC₅₀ values were determined.

Results

37 plants out of the 137 crude extracts revealed strong urease inhibitory activity (more than 70% inhibition against urease activity at 10 mg/ml concentration). Nine of the whole studied plants crude extracts were found as the most effective with IC₅₀ values less than 500 μg/ml including; Rheum ribes, Sambucus ebulus, Pistachia lentiscus, Myrtus communis, Areca catechu, Citrus aurantifolia, Myristica fragrans, Cinnamomum zeylanicum and Nicotiana tabacum.

Conclusions

The most potent urease inhibitory was observed for Sambucus ebulus and Rheum ribes extracts with IC₅₀ values of 57 and 92 μg/ml, respectively.

Differences of urease activity and expression of associated genes according to gastric topography

BACKGROUND

We hypothesize that pH difference between acid-secreting corpus and non-secreting antrum might influence the activity of H. pylori's urease and/or related genes. We therefore measured urease activity and the expression of amiE whose encoded protein that hydrolyzes short-chain amides to produce ammonia.

MATERIALS AND METHODS

Fifty-four patients were recruited into this study. Each gastroscopic biopsy specimen collected from the antrum and body of each patient was immediately used to measure urease activity using serial changes of urease activity (ammonia levels) during 60 minutes. Probe specific for amiE was labeled with a biotin nick-translation kit and was used to detect expression of these genes (mRNA) in fresh-frozen gastroscopic biopsy specimens using fluorescent in situ hybridization (FISH).

RESULTS

Urease activity at 60 minutes from the gastric antrum and body of all patients infected with H. pylori was 399.5 ± 490.5 and 837.9 ± 1038.9 μg/dL, respectively (p = .004). Urease activity in the antrum was correlated with H. pylori density. Urease activity or H. pylori density in the antrum was significantly correlated with chronic active inflammation; in contrast, this correlation was not found in the gastric body. The expression level of amiE was 1.5 times higher (p < .05) in the gastric body compared with the antrum.

CONCLUSION

Topographically, the urease activity in body was much higher than in antrum. The expression level of amiE was higher in the gastric body compared with the antrum.

New frontiers in gut nutrient sensor research: prophylactic effect of glutamine against Helicobacter pylori-induced gastric diseases in Mongolian gerbils

Ammonia is one of the important toxins produced by Helicobacter pylori (H. pylori), the major cause of peptic ulcer diseases. We examined whether glutamine or marzulene (a gastroprotective drug containing 1% sodium azulene and 99% glutamine) protects the gastric mucosa against H. pylori in vivo and investigated the mechanism underlying glutamine-induced mucosal protection against ammonia in gastric epithelial cells in vitro. Mongolian gerbils were fed for 3 months with a diet containing glutamine (2%-20%) or marzulene (20%) starting from 2 weeks or 2 years after H. pylori infection. Then, gastric mucosal changes were evaluated both macro- and microscopically. Cultured gastric epithelial cells were incubated in the presence of ammonia, with or without glutamine; and cell viability, ammonia accumulation, and chemokine production were determined. Gerbils exhibited edema, congestion, and erosion after 3-month infection; and after 2-year infection, they showed cancer-like changes in the gastric mucosa. Glutamine and marzulene significantly suppressed these pathological changes caused in the gastric mucosa by H. pylori infection. Ammonia was accumulated in the cells, resulting in an increase in chemokine production and a decrease in cell viability. These pathological responses were prevented by glutamine. In addition, glutamine decreased chemokine production and cell death through inhibition of cellular accumulation of ammonia, resulting in the prevention of H. pylori-induced gastric diseases in vivo. These results suggest that glutamine/marzulene would be useful for prophylactic treatment of H. pylori-induced gastric diseases in patients.

Antioxidant pre-treatment prevents omeprazole-induced toxicity in an in vitro model of infectious gastritis

Omeprazole is a mainstay of therapy for gastroesophageal reflux disease (GERD) and gastritis, and is increasingly used as an over-the-counter remedy for dyspepsia. Omeprazole acts by selectively oxidizing thiol targets in the gastric proton pump, but it also appears to be toxic to the gastric mucosa. We hypothesized that omeprazole toxicity is due to non-specific oxidation of cell structures other than the proton pump, and tested the efficacy of antioxidants to prevent omeprazole-induced toxicity in isolated rabbit gastric glands. Toxicity was measured by uptake and converstion of calcein-AM, following three hours of exposure to omeprazole and a non-selective thiol-oxidant, monochloramine. Intracellular concentration of Zn(2+) and the capacity to maintain luminal acidity were monitored using the fluorescent reporters fluozin-3 and Lysosensor DND-160, respectively. Both omeprazole and monochloramine caused marked reduction in cell viability. The toxicity of omeprazole was independent of monochloramine toxicity. The thiol reducing agent dithiothreitol protected gastric glands from injury. The oxidant scavenger Vitamin C also protected, and did not impair the anti-secretory effects of omeprazole. Thus, omeprazole toxicity appears to be oxidative and preventable with antioxidant therapy, including Vitamin C. Vitamin C may be a safe and efficacious addition to treatments requiring the use of PPIs.

Effect of the flavonoid quercetin on inflammation and lipid peroxidation induced by Helicobacter pylori in gastric mucosa of guinea pig

BACKGROUND

Helicobacter pylori infection induces an inflammatory response in the gastric mucosa. Activation of polymorphonuclear leukocytes can produce oxidative damage to gastric tissue through intermediary radicals of oxygen and nitrogen. Vegetable extracts containing polyphenols of the flavonoid family have antibacterial activity, and the flavonoid quercetin possesses anti-H. pylori activity in vitro. The aim of this study was to analyze the effect of oral administration of pure quercetin on inflammation and lipid peroxidation induced by H. pylori in the gastric mucosa of the guinea pig.

METHODS

Sixty days after oral infection with H. pylori guinea pigs received 200 mg/kg of quercetin daily by mouth for 15 days. The infiltration index of inflammatory cells and bacterial density in both the pyloric antrum and corpus were histologically determined by myeloperoxidase histochemistry, hematoxylin-eosin, and modified Giemsa stains. The lipid hydroperoxide content was assessed by the orange xylenol spectrophotometric method.

RESULTS

Quercetin significantly reduced the infiltration index of mononuclear cell and bacterial colonization in the pyloric antrum and corpus. In the antrum of infected quercetin-treated animals, a significant diminution of neutrophil leukocyte infiltration was observed compared with the infected nonquercetin-treated animals. In the antrum, the lipid hydroperoxide concentration was significantly decreased in infected animals treated with quercetin, whereas in the corpus no significant differences were observed.

CONCLUSIONS

Our results indicate that in vivo oral quercetin administration decreases H. pylori infection in the gastric mucosa and reduces both the inflammatory response and lipid peroxidation.

Monochloramine impairs caspase-3 through thiol oxidation and Zn2+ release

BACKGROUND

Caspase-3, a pro-apoptotic enzyme, represents a class of proteins in which the active site contains reduced thiol (S-H) groups and is modulated by heavy metal cations, such as Zn(2+). We explored the effects of the thiol oxidant monochloramine (NH(2)Cl) on caspase-3 activity within cells of isolated rabbit gastric glands. In addition, we tested the hypothesis that NH(2)Cl-induced alterations of caspase-3 activity are modulated by oxidant-induced accumulation of Zn(2+) within the cytoplasm.

MATERIALS AND METHODS

Isolated gastric glands were prepared from rabbit mucosa by collagenase digestion. Caspase-3 activity was measured colorimetrically in suspensions of healthy rabbit gastric glands, following exposure to various concentrations of NH(2)Cl with or without the zinc chelator TPEN [tetrakis-(2-pyridylmethyl)ethylene diamine] for 1 h, and re-equilibration in Ringer's solution for 5 h. Conversion of procaspase-3 to active caspase-3 was monitored by Western blot.

RESULTS

Monochloramine inhibited caspase-3 activity in a dose-dependent fashion. At concentrations of NH(2)Cl up to 100 microM, these effects were prevented if TPEN was given concurrently and were partly reversed if TPEN was given 1 h later. Caspase-3 activity was preserved by concurrent treatment with a thiol-reducing agent, dithiothreitol.

CONCLUSIONS

At pathologically relevant concentrations, NH(2)Cl impairs caspase-3 activity through oxidation of its thiol groups. Independently from its thiol oxidant effects on the enzyme, NH(2)Cl-induced accumulation of Zn(2+) in the cytoplasm is sufficient to restrain endogenous caspase-3 activity. Our studies suggest that some bacterially generated oxidants, such as NH(2)Cl, impair host pathways of apoptosis through release of Zn(2+) from endogenous pools.

Thiol-oxidant monochloramine mobilizes intracellular Ca2+ in parietal cells of rabbit gastric glands

In Helicobacter pylori-induced gastritis, oxidants are generated through the interactions of bacteria in the lumen, activated granulocytes, and cells of the gastric mucosa. In this study we explored the ability of one such class of oxidants, represented by monochloramine (NH(2)Cl), to serve as agonists of Ca(2+) accumulation within the parietal cell of the gastric gland. Individual gastric glands isolated from rabbit mucosa were loaded with fluorescent reporters for Ca(2+) in the cytoplasm (fura-2 AM) or intracellular stores (mag-fura-2 AM). Conditions were adjusted to screen out contributions from metal cations such as Zn(2+), for which these reporters have affinity. Exposure to NH(2)Cl (up to 200 microM) led to dose-dependent increases in intracellular Ca(2+) concentration ([Ca(2+)](i)), in the range of 200-400 nM above baseline levels. These alterations were prevented by pretreatment with the oxidant scavenger vitamin C or a thiol-reducing agent, dithiothreitol (DTT), which shields intracellular thiol groups from oxidation by chlorinated oxidants. Introduction of vitamin C during ongoing exposure to NH(2)Cl arrested but did not reverse accumulation of Ca(2+) in the cytoplasm. In contrast, introduction of DTT or N-acetylcysteine permitted arrest and partial reversal of the effects of NH(2)Cl. Accumulation of Ca(2+) in the cytoplasm induced by NH(2)Cl is due to release from intracellular stores, entry from the extracellular fluid, and impaired extrusion. Ca(2+)-handling proteins are susceptible to oxidation by chloramines, leading to sustained increases in [Ca(2+)](i). Under certain conditions, NH(2)Cl may act not as an irritant but as an agent that activates intracellular signaling pathways. Anti-NH(2)Cl strategies should take into account different effects of oxidant scavengers and thiol-reducing agents.

Over-expression of 70-kDa heat shock protein confers protection against monochloramine-induced gastric mucosal cell injury

The major heat shock protein, HSP70, is known to be involved in cytoprotection against environmental stresses mediated by their function as a "molecular chaperone". Monochloramine (NH(2)Cl) is a potent cytotoxic oxidant generated by neutrophil-derived hypochlorous acid and Helicobacter pylori urease-induced ammonia. In this study, to evaluate the cytoprotective effect of HSP70 against NH(2)Cl-induced gastric mucosal cell injury, rat gastric mucosal cells (RGM-1) were stably transfected with pBK-CMV containing the human HSP70 gene (7018-RGM-1) or pBK-CMV alone (pBK-CMV-12) as control cells. These cells were treated with various concentrations of NH(2)Cl. Cell Viability was determined by MTT assay and the direct plasma membrane damage was analyzed by lactate dehydrogenase (LDH) release assay. Apoptosis was determined by DNA fragmentation analysis. NH(2)Cl caused injury to pBK-CMV-12 cells in a concentration-dependent manner. NH(2)Cl-induced gastric cell injury was significantly diminished in HSP70 over-expressing cell line (7018-RGM-1) both necrosis and apoptosis compared to the control cell line (pBK-CMV-12) transfected with CMV vector alone. These result suggest that overexpression of HSP70 plays an important role in protecting gastric cells against NH(2)Cl-induced injury.

Influence of vitamin E on gastric mucosal injury induced by Helicobacter pylori infection

We investigated the effect of vitamin E on gastric mucosal injury induced by Helicobacter pylori (H. pylori) infection. Male Mongolian gerbils were divided into 4 groups (normal group without H. pylori infection, vitamin E-deficient, -sufficient and -supplemented groups with H. pylori infection). Following oral inoculation with H. pylori (ATCC43504 2 x 10(8) CFU), animals were fed diets alpha-tocopherol 2 mg/100 g diet in the normal and vitamin E-sufficient groups and alpha-tocopherol 0.1 mg/100 g and 50 mg/100 g in the vitamin E-deficient and -supplemented groups, respectively, for 24 weeks. Chronic gastritis was detected in all gerbils inoculated H. pylori. Gastric ulcer was detected in 2 of 7 gerbils only in the vitamin E-deficient group. In the vitamin E-deficient group, myeloperoxidase activity and mouse keratinocyte derived chemokine (KC) in gastric mucosa was significantly higher than in the vitamin E supplemented group. Subsequently, in an in vitro study expression of CD11b/CD18 on neutrophils was enhanced by H. pylori water extract. This effect was suppressed in a dose dependent manner by the addition of alpha-tocopherol. These results suggest that vitamin E has a protective effect on gastric mucosal injury induced by H. pylori infection in gerbils, through the inhibition of accumulation of activated neutrophils.

Increased sorbitol pathway activity generates oxidative stress in tissue sites for diabetic complications

Chronic diabetic complications, in particular, nephropathy, peripheral and autonomic neuropathy, "diabetic foot," retinopathy, and cardiovascular disease, remain the major cause of morbidity and mortality in patients with diabetes mellitus. Growing evidence indicates that both increased activity of the sorbitol pathway of glucose metabolism and enhanced oxidative stress are the leading factors in the pathogenesis of diabetic complications. The relation between the two mechanisms remains the area of controversy. One group has reported that increased sorbitol pathway activity has a protective rather than detrimental role in complication-prone tissues because the pathway detoxifies toxic lipid peroxidation products. Others put forward a so-called "unifying hypothesis" suggesting that activation of several major pathways implicated in diabetic complications (e.g., sorbitol pathway) occurs due to increased production of superoxide anion radicals in mitochondria and resulting poly(ADP-ribose) polymerase activation. This review (a) presents findings supporting a key role for the sorbitol pathway in oxidative stress and oxidative stress-initiated downstream mechanisms of diabetic complications, and (b) summarizes experimental evidence against a detoxifying role of the sorbitol pathway, as well as the "unifying concept."

Depletion of neutrophils in IL-10(-/-) mice delays clearance of gastric Helicobacter infection and decreases the Th1 immune response to Helicobacter

Gastric infection with Helicobacter induces a lymphocyte-rich mucosal inflammation that contains a minor population of neutrophilic granulocytes. The function of neutrophils in the local immune response to gastric Helicobacter infection remains unknown. To investigate this issue, we conducted experiments in neutrophil-depleted control wild-type (wt) and IL-10(-/-) mice infected with Helicobacter felis by gastric lavage. Infection of wt mice elicited a mild, focal gastritis and a Helicobacter-specific Th1 immune response. In wt mice Helicobacter colonization of the stomach was persistent and progressively increased during the 29 days of observation. Infection of IL-10(-/-) mice with H. felis elicited a severe chronic gastritis and a greatly enhanced Helicobacter-specific Th1 immune response, as compared with wt mice. After initial colonization, the IL-0(-/-) mice completely cleared Helicobacter from the stomach by day 8. The gastric inflammation in wt and IL-10(-/-) mice contained modest numbers of neutrophils. The intensity of gastric inflammation and the extent of Helicobacter colonization were similar in control and in neutrophil-depleted wt mice. In contrast, neutrophil depletion of Helicobacter-infected IL-10(-/-) mice decreased the severity of gastritis, modulated the Helicobacter-specific Th1 immune response, and delayed the clearance of bacteria from the stomach. These studies identify a role for neutrophils in the local and systemic immune response to gastric Helicobacter in IL-10(-/-) mice.

How does glucose generate oxidative stress in peripheral nerve?

Diabetes-associated oxidative stress is clearly manifest in peripheral nerve, dorsal root, and sympathetic ganglia of the peripheral nervous system and endothelial cells and is implicated in nerve blood flow and conduction deficits, impaired neurotrophic support, changes in signal transduction and metabolism, and morphological abnormalities characteristic of peripheral diabetic neuropathy (diabetic peripheral neuropathy). Hyperglycemia has a key role in oxidative stress in diabetic nerve, whereas the contribution of other factors, such as endoneurial hypoxia, transition metal imbalance, and hyperlipidemia, has not been rigorously proven. It has been suggested that oxidative stress, particularly mitochondrial superoxide production, is responsible for sorbitol pathway hyperactivity, nonenzymatic glycation/glycooxidation, and activation of protein kinase C. However, this concept is not supported by in vivo studies demonstrating the lack of any inhibition of the sorbitol pathway activity in peripheral nerve, retina, and lens by antioxidants, including potent superoxide scavengers. Its has been also hypothesized that aldose reductase (AR) detoxifies lipid peroxidation products, and therefore, the enzyme inhibition in diabetes is detrimental rather than benefical. However, the role for AR in lipid peroxdation product metabolism has never been demonstrated in vivo, and the effects of aldose reductase inhibitors and antioxidants on diabetic peripheral neuropathy are unidirectional, i.e., both classes of agents prevent and correct functional, metabolic, neurotrophic, and morphological changes in diabetic nerve. Growing evidence indicates that AR has a key role in oxidative stress in the peripheral nerve and contributes to superoxide production by the vascular endothelium. The potential mechanisms of this phenonmenon are discussed.

Suppression of Helicobacter pylori-induced interleukin-8 production in gastric cancer cell lines by an anti-ulcer drug, geranylgeranylacetone

BACKGROUND

Geranylgeranylacetone (GGA) is an antigastritis and anti-ulcer agent, with as yet an unknown mechanism of action. In this study, we investigated the effect of GGA on Helicobacter pylori-induced interleukin (IL)-8 production and IL-8 mRNA expression in KATOIII cells, an established gastric cell line.

METHODS

Interleukin-8 production in H. pylori-infected KATOIII cells was measured by using enzyme-linked immunoassay. The cytotoxicity of H. pylori on KATOIII cells was measured by a 51Cr release assay. The effect of GGA on H. pylori-induced IL-8 mRNA expression was measured by using northern blotting.

RESULTS

Interleukin-8 production increased with time and H. pylori dose; the most significant increase was seen within 6-24 h of coculture with H. pylori. A dose of 0.1 mmol GGA suppressed IL-8 production (P = 0.0077) and inhibited H. pylori-induced IL-8 mRNA expression (P = 0.0019). Furthermore, H. pylori-induced gastric mucosal cell injury associated with IL-8 and neutrophil activation was enhanced by NH3, and this enhancement was suppressed by GGA (P = 0.0043).

CONCLUSIONS

Helicobacter pylori-infected gastric mucosal cells produce IL-8, which can promote neutrophil activation, thus contributing to mucosal tissue injury associated with H. pylori infection. Agents like GGA, which can suppress IL-8 production may have a protective role in the treatment of mucosal tissue damage seen in H. pylori infection.

Effect of taurine on ulcerogenic response and impaired ulcer healing induced by monochloramine in rat stomachs

BACKGROUND

It is well known that neutrophil-derived hypochlorous acid interacts with ammonia (NH4OH) to generate monochloramine (NH2Cl) and that NH2Cl irritates the gastric mucosa and impairs ulcer healing.

AIM

To examine the effect of taurine, a hypochlorous acid scavenger, on the mucosal ulcerogenic and the impaired healing response induced by NH2Cl in rat stomachs, in comparison with those of methionine and glycine.

METHODS AND RESULTS

Under anaesthesia, oral administration of NH2Cl (120 mmol/L) produced severe lesions in male Sprague-Dawley rat stomachs. Taurine (10-100 mg/kg) given p.o. 30 min prior to NH2Cl dose-dependently prevented these lesions in response to NH2Cl. This action was mimicked by methionine (3-30 mg/kg) but not by glycine (10-100 mg/kg). Under urethane anaesthesia, mucosal exposure to NH4OH (120 mmol/L) caused a marked reduction of potential difference (PD) in the ex vivo chambered stomachs after induction of ischaemia, resulting in severe lesions. These ulcerogenic and PD responses by NH4OH plus ischaemia were also mitigated by taurine and methionine, but not glycine, applied to the chamber 20 min before the onset of NH4OH plus ischaemia. Moreover, oral administration of 100% ethanol produced severe haemorrhagic lesions in rat stomachs, all of which rapidly healed within 7 days after lesion induction. Daily administration of NH2Cl (20 mmol/L) significantly delayed the healing of these lesions, but recovery of this impaired healing response was obtained by concurrent administration of taurine. Both taurine and methionine showed a potent scavenging effect against NH2Cl in vitro.

CONCLUSIONS

(1) NH2Cl generated either exogenously or endogenously damages the gastric mucosa and impairs the healing response; (2) taurine exerts a prophylactic effect against the deleterious effects of NH2Cl, mainly due to its scavenging action against NH2Cl; and (3) this effect of taurine may be useful for treatment of gastritis associated with Helicobacter pylori infection.

Phospholipase C activity of Helicobacter pylori is not associated with the presence of the cagA gene

BACKGROUND

Knowledge about the possible role of phospholipase C (PLC) activity of microbial pathogens in the development of disease is increasing. Recently attention has focused on investigating PLC activity elaborated by Helicobacter pylori, but the role of this enzyme in H. pylori pathogenesis is still unknown. The aim of this study was to correlate PLC-activity of H. pylori on the basis of the cagA status with the clinical diagnosis of the patients.

MATERIALS AND METHODS

Helicobacter pylori was isolated from patients with gastritis (G; n = 38), duodenal ulcer (DU; n = 15), gastric ulcer (GU; n = 11) and gastric cancer (GC; n = 12). Polymerase chain reaction primers DZ3/R009 which amplified a 1350-bp fragment were used to detect the cagA gene. PLC activity was determined using p-nitrophenylphosphorylcholine as substrate.

RESULTS

Of the strains, 60% were cagA(+) and 40% were cagA(-). All strains showed PLC activity (2.20 +/- 0.91 U mg(-1) protein). PLC activity showed no association with the cagA status: cagA(+) (2.21 +/- 1.03 U mg(-1) protein), cagA(-) (2.18 +/- 0.79 U mg(-1) protein). Patients with GU had the highest PLC activity (2.77 +/- 1.26 U mg(-1) protein) and patients with GC had the lowest activity (1.8 +/- 0.57 U mg(-1) protein).

CONCLUSIONS

Although PLC activity was present in all strains tested, it may only have pathological importance in patients with GU. However, the extent of PLC activity was independent of the presence of the cagA gene.

Monochloramine impairs mucosal blood flow response and healing of gastric lesions in rats: relation to capsaicin-sensitive sensory neurons

AIMS

We examined the effects of monochloramine (NH2Cl) on the gastric mucosal blood flow (GMBF) response and the healing of ethanol-induced gastric lesions in rats.

METHODS

Rats fasted for 18 h were given the 99% ethanol p.o. for induction of gastric lesions, and were fed normally from 1 h later onwards. Monochloramine, at non-ulcerogenic doses (5 to approximately 20 mmol/L), was given p.o. twice daily for 7 days, starting 2 h after ethanol treatment.

RESULTS

Gastric lesions caused by ethanol healed almost completely within 7 days with re-epithelialization. The repeated administration of NH2Cl significantly delayed the healing of ethanol-induced gastric lesions in a dose-dependent manner. The damaged mucosa showed a marked rise in H+ permeability, resulting in luminal acid loss, but this process was accompanied by an increase of mucosal blood flow. Monochloramine did not affect the increased mucosal H+ permeability observed in the stomach after damage by ethanol, but significantly inhibited the mucosal hyperemic response associated with luminal acid loss. Prior exposure of the mucosa to NH2Cl (20 mmol/L) did not affect the gastric hyperemic response caused by mucosal application of misoprostol (a prostaglandin E1 derivative) or NOR-3 (a nitric oxide donor), but totally attenuated the increase of GMBF in response to intragastric capsaicin. Impaired healing and GMBF responses were also observed in rats following chemical ablation of capsaicin-sensitive sensory neurons.

CONCLUSIONS

These results suggest that NH2Cl impaired the healing of acute gastric mucosal lesions at low concentrations, and this action may be attributable, at least partly, to the impairment of gastric hyperemic response caused by the dysfunction of capsaicin-sensitive sensory neurons.

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.

Luminal ammonia retards restitution of guinea pig injured gastric mucosa in vitro

The present study was conducted to elucidate the mechanisms by which Helicobacter pylori (HP)-derived ammonia causes gastric mucosal injury. Intact sheets of guinea pig gastric fundic mucosae were incubated in Ussing chambers. Both the luminal and the serosal pH were kept at 7.4. Transmucosal potential difference (PD) and electrical resistance (R) were monitored as indices of mucosal integrity. Restitution was evaluated by recovery of PD, R, and transmucosal [(3)H]mannitol flux after Triton X-100-induced mucosal injury. The effects of luminal or serosal NH(4)Cl on function and morphology of uninjured or injured mucosae were examined. In uninjured mucosae, serosal NH(4)Cl induced more profound decreases in PD and R and more prominent vacuolation in gastric epithelial cells than did luminal NH(4)Cl. In contrast, luminal NH(4)Cl markedly inhibited restitution in injured mucosae and caused an extensive vacuolation in gastric epithelial cells, as did serosal NH(4)Cl. Transmucosal ammonia flux was greater in the injured than in the uninjured mucosae. These results suggest that 1) basolateral membrane of gastric epithelial cells is more permeable to ammonia than apical membrane and 2) luminal ammonia, at concentrations detected in HP-infected gastric lumen, retards restitution in injured mucosae.

Protective effect of Irsogladine on monochloramine induced gastric mucosal lesions in rats: a comparative study with rebamipide

AIM: To examine the effect of irsogladine, a novel antiulcer drug, on the mucosal ulcerogenic response to monochloramine ( NH₂Cl ) in rat stom ach, in comparison with rebamipide, another antiulcer drug with cytoprotective activity.

METHODS AND RESULTS: Oral administration of NH₂Cl (120 mM) produced severe hemorrhagic lesions in unanesthetized rat stomachs. Both irso gladine (1 mg/kg-10 mg/kg, po) and rebamipide (30 mg/kg-100 mg/kg, po) dose-dependently prevented the development of these lesions in response to NH₂Cl, the effect of irsogladine was significant at 3 mg/kg or greater, and that of rebamipide only at 100 mg/kg. The protective effect of irsogladine on NH₂Cl-induced gastric lesions was significantly reduced by N^G-nitro-L-arginine methyl ester (L-NAME) but not by indomethacin, while that of rebamipide was significantly mitigated by indom ethacin but not by L-NAME. Topical application of NH₂Cl (20mM) caused a marked reduction of potential difference (PD) in ex-vivo stomachs. This PD reduction was not affected by mucosal application of irsogladine, but significa ntly prevented by rebamipide. The mucosal exposure to NH₄OH (120 mM) also caused a marked PD reduction in the ischemic stomach (bleeding from the carotid artery), resulting in gastric lesions. These ulcerogenic and PD responses caused by NH₄OH plus ischemia were also significantly mitigated by rebamipide, in an indomethacin-sensitive manner, while irsogladine potently prevented such lesions without affecting the PD response, in a L-NAME-sensitive manner.

CONCLUSION: These results suggest that (1) NH₂Cl generated either exogenously or endogenously damages the gastric mucosa, (2) both irsogladine and rebamipide protect the stomach against injury caused by NH₂Cl, and (3) the mechanism underlying the protective action of irsogladine is partly mediated by endogenous nitric oxide, while that of rebamipide is in part mediated by endogenous prostaglandins.

Effect of monochloramine on recovery of gastric mucosal integrity and blood flow response in rat stomachs--relations to capsaicin-sensitive sensory neurons

Gastric mucosal blood flow (GMBF) response and the recovery of gastric mucosal integrity were investigated in anesthetized rat stomachs after damage by monochloramine (NH2Cl), in comparison with 20 mM taurocholate Na (TC). A rat stomach was mounted in an ex-vivo chamber, and the mucosa was exposed to 50 mM HCl during a test period. Mucosal application of 20 mM TC for 10 min caused a marked reduction of transmucosal potential difference (PD), but the PD recovered rapidly without development of gross lesions 90 min later. In contrast, the exposure of the mucosa to NH2Cl (5 to approximately 20 mM) produced a concentration-dependent decrease in gastric PD, and the values remained lowered even 90 min after removal of the agent, resulting in severe hemorrhagic damage in the stomach. TC caused a considerable H+ back-diffusion, followed by an increase in the GMBF. In the mucosa damaged by NH2Cl, such GMBF responses were not observed, except for the temporal increase during the exposure, although similar degrees of H+ back-diffusion were observed following NH2Cl treatment. In addition, the prior exposure of the mucosa to NH2Cl significantly attenuated gastric hyperemic response induced by capsaicin but not by misoprostol (a PGE1 derivative) or NOR-3 (a NO donor). Chemical ablation of capsaicin-sensitive sensory neurons had no effect on the PD reduction caused by TC but totally attenuated the GMBF response, resulting in hemorrhagic damage in the stomach. These results suggest that NH2Cl delayed the recovery of the mucosal integrity in the stomach after damage, and this effect may be attributable, at least partly, to the impairment of gastric hyperemic response associated with H+ back-diffusion, probably due to dysfunction of capsaicin-sensitive sensory neurons.

Effect of lafutidine, a novel histamine H2-receptor antagonist, on monochloramine-induced gastric lesions in rats: role of capsaicin-sensitive sensory neurons

BACKGROUND

Lafutidine ((+/-)-2-(furfurylsulfinyl)-N-(4-(4-(piperidinomethyl)-2-pyr idyl)oxy-(Z)-2-butenyl)acetamide) is a novel histamine H2-receptor antagonist and has been shown to exhibit a potent gastroprotective activity in addition to its antisecretory action. In the present study, we examined the effects of lafutidine on the mucosal ulcerogenic and potential difference (PD) responses induced by monochloramine (NH2Cl) in rat stomachs.

METHODS

Oral administration of NH2Cl at 120 mmol/L produced haemorrhagic lesions in the stomach in unanaesthetized rats.

RESULTS

Lafutidine (3-30mg/kg), given p.o., showed a dose-dependent and significant inhibition against damage caused by NH2Cl: the effect was significant at 10 mg/kg or greater but disappeared almost totally in the sensory deafferented animals following capsaicin pretreatment. Likewise, capsaicin (10 mg/kg, p.o.), but not cimetidine (100 mg/kg, p.o.) exhibited a potent protection against NH2Cl-induced gastric lesions. Topical application of NH2Cl (10 mmol/L) reduced transmucosal PD in ex-vivo stomachs of anaesthetized rats, but this PD response was also prevented by pre-exposure to lafutidine, in a dose-dependent and sensory neuron-sensitive manner. Mucosal exposure to NH4OH (60 mmol/L) also caused PD reduction in ex-vivo stomachs made ischaemic by bleeding from the carotid artery (1 mL/100 g bodyweight), resulting in severe gastric lesions. These ulcerogenic and PD responses caused by NH4OH plus ischaemia were attenuated by prior application of lafutidine as well as taurine, a scavenger of NH2Cl. The former effect was, again, dependent on the sensory neurons. Intraluminal capsaicin but not cimetidine was also effective in preventing a PD response to NH2Cl.

CONCLUSIONS

These results suggest that lafutidine, but not cimetidine, protects the stomach against NH2Cl, whether occurring endogenously or administered exogenously and that this action may be mediated by capsaicin-sensitive sensory neurons.

Gastritis in the alcoholic: relationship to gastric alcohol metabolism and Helicobacter pylori

Chronic gastritis is common in the alcoholic. It is characterized by histological inflammation of the gastric mucosa and is associated with variable symptomatology. Its etiology is still the subject of debate. Recently, a new alcohol dehydrogenase isoenzyme, called sigma ADH, absent from the liver but predominant in the upper GI tract, has been fully characterized, its gene cloned, and it appears to play a major role in gastric ethanol metabolism. Indeed, it has now been established, both in vivo in experimental animals and in vitro in cultured human gastric cells, that alcohol is metabolized in the gastric mucosa, resulting in the production of acetaldehyde, a toxic metabolite. In addition, Helicobacter pylori infection is common in the alcoholic, resulting in the breakdown of urea to ammonia, another toxic product. A number of studies carried out over the last 40 years revealed that antibiotic treatment eradicates ammonia production and results in histological and symptomatic improvement in the majority of patients with alcoholic gastritis. Non-invasive tests for the detection of H. pylori are now available which will facilitate the large scale studies needed to confirm whether, in H. pylori -positive patients, antibiotics should become routine treatment for alcoholic gastritis.

Development of a PCR-restriction fragment length polymorphism assay using the nucleotide sequence of the Helicobacter hepaticus urease structural genes ureAB

Infection with Helicobacter hepaticus causes chronic active hepatitis in certain strains of mice and is associated with hepatocellular carcinoma in A/JCr mice. Like the gastric helicobacters, H. pylori and H. mustelae, H. hepaticus possesses a high level of urease activity. However, the H. hepaticus urease structural gene sequences have not been previously determined, and the role of the urease enzyme in colonization and in pathogenesis is not known. PCR was used to amplify a portion of the urease structural genes from H. hepaticus genomic DNA. Amplified DNA fragments were cloned, and the nucleotide sequence was determined. The deduced amino acid sequence of the partial H. hepaticus ureA gene product was found to exhibit 60% identity and 75% similarity to the predicted H. pylori UreA. The deduced amino acid sequence of a partial H. hepaticus ureB gene product exhibited 75% identity and 87% similarity to the predicted H. pylori UreB. Diversity among H. hepaticus isolates was evaluated by means of a restriction fragment length polymorphism (RFLP) assay. The 1.6-kb fragments within the ureAB open reading frames, amplified from 11 independent isolates, were digested with the restriction endonuclease HhaI. Three distinct RFLP patterns were observed. Identical RFLP profiles were noted in sequential isolates of one strain of H. hepaticus during an 18 month in vivo colonization study, suggesting that the urease genes of H. hepaticus are stable. The urease genes among H. hepaticus strains were also well conserved, showing 98.8 to 99% nucleotide sequence identity among three isolates analyzed. These findings indicate that H. hepaticus has urease structural genes which are homologous to those of the gastric Helicobacter species and that these gene sequences can be used in a PCR and RFLP assay for diagnosis of this important murine pathogen.

Delayed healing of chronic gastric ulcer after Helicobacter pylori infection in mice

It has been suggested that there is a close relationship between Helicobacter pylori and the onset or recurrence of gastroduodenal disease. The aim of this study was to examine the effect of H. pylori on the healing of chronic gastric ulcers induced in mice. H. pylori administered to nude mice delayed the healing of experimental acetic acid-induced gastric ulcers. Histological examination showed the occurrence of high densities of H. pylori on the surface of epithelial cells and in the ulcerated area. Repeated administration of amoxicillin (10 mgkg(-1) daily for 5 days) eradicated H. pylori and increased the rate of healing of gastric ulcers in H. pylori-infected mice, but metronidazole, which also eradicated the organisms, did not significantly affect the rate of healing. In conclusion, H. pylori-infection delayed the healing of gastric ulcers induced by the serosal application of acetic acid in mice, possibly by aggravation or prolongation of the mucosal inflammation. Amoxicillin eradicated H. pylori and promoted gastric ulcer healing in mice infected with H. pylori.

Helicobacter pylori-dependent intragastric urea biodegradation in children: diagnostic and pathogenetic importance

The objective of the present work was to study the relationship between intragastric urea hydrolysis generated by Helicobacter pylori urease and acid-peptic disease in childhood. Intragastric urease activity was examined by urea and ammonia concentration measurement in gastric juice in 91 children with upper abdominal complaints. Helicobacter pylori infection was detected from 70 (76.9%) of 91 patients, including all of the 15 subjects with peptic ulcer disease. Helicobacter pylori-related gastritis in children was associated with a decrease of urea and an increase of ammonia in gastric juice (P < 0.001) in comparison with H. pylori-negative children. The gastritis score was correlated with the concentrations of urea and ammonia in the gastric juice of patients infected with H. pylori. There was a significant correlation between the histologically detected dissemination of organisms and gastric ammonia levels. Similar results were obtained concerning correlation between gastric juice ammonia and anti-H. pylori specific immunoglobulin G versus highly purified antigen of H. pylori containing urease. Present findings prove that H. pylori plays an essential role in the pathogenesis of gastritis and that ammonia is one of the main pathogenic factors of acid-peptic disease.

Attenuation by methionine of monochloramine-enhanced gastric carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine in Wistar rats

Helicobacter pylori appears to play a major role in the development of gastric cancer in humans. The mechanism behind the carcinogenic or co-carcinogenic effects of H. pylori has not been established. Ammonia, generated by urea from H. pylori, has been studied as a possible cause. However, the ammonia-monochloramine system has been shown to play a more important role in H. pylori-associated mucosal injury. Therefore, the effects of combined administration of monochloramine and methionine, singly or together, on the development of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) were investigated in inbred Wistar rats. After receiving oral MNNG and regular chow pellet for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without a subcutaneous injection of methionine, until the end of the experiment (week 52). Treatment with both ammonium acetate and sodium hypochlorite, which produce monochloramine, significantly increased the incidence of gastric cancers in week 52, whereas the concomitant administration of methionine with ammonium acetate and sodium hypochlorite significantly attenuated such enhanced gastric carcinogenesis. Spectrophotometric examination revealed that methionine scavenged monochloramine. Our findings suggest that H. pylori-associated gastric carcinogenesis may be mediated by monochloramine.

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

Recent studies have indicated that monochloramine (NH2Cl), a reaction product of NH3 and hypochlorous acid, is involved in the pathogenesis of Helicobacter pylori-associated gastric mucosal damage, but how NH2Cl contributes to lesions is unclear. In the present study, the effects of NH2Cl on mucosal cell growth and the cell cycle were evaluated in vitro using a normal rat gastric mucosal cell line RGM-1. Cell viability was assessed by the Trypan Blue dye exclusion test and cell cycle patterns were determined by DNA labeling with propidium iodide and flow cytometric quantification. NH2Cl inhibited the growth of RGM-1 cells in a concentration-dependent manner. Exposure of cells to NH2Cl caused a time- and dose-dependent loss of G1-phase cells with accumulation of G2/M-phase cells, and produced a fraction of subdiploid cells with oligonucleosomal DNA degradation characteristic of apoptosis. NH2Cl-induced apoptosis was confirmed by fluorescent microscopy with Hoechst 33342 and propidium iodide. These results suggest that NH2Cl inhibits gastric mucosal cell growth and induces apoptosis in RGM-1 cells, events that may be important in gastric mucosal damage or atrophy induced by H. pylori infection.

Helicobacter pylori factors involved in the development of gastroduodenal mucosal damage and ulceration

Many putative virulence determinants of Helicobacter pylori are believed to trigger and worsen the gastroduodenal mucosa damage observed in infected patients. H. pylori urease reacts with the gastric urea and generates ammonia; ammonia combines with water and yields ammonium hydroxide, which is cytotoxic. Ammonia may also inhibit cell proliferation and cause indirect mucosal injury by stimulating neutrophils. Phospholipases may damage the gastric mucosa by degrading phospholipids and generating precursors of ulcerogenic components. Other enzymes, such as protease, neuraminidase, fucosidase, and alcohol dehydrogenase, can contribute to damage of the gastric epithelium by destroying the integrity of mucus or by inducing lipid peroxidation. Infection by vacuolating cytotoxic (VacA+) H. pylori strains is considered to constitute increased risk for development of peptic ulcer and gastric cancer. Exploration of the vacA gene structure has shown the existence of strongly toxigenic strains, and has confirmed at the molecular level the increased ulcerogenic potential of VacA+ H. pylori strains. A pathogenicity island called cag has been recently described in Type 1 H. pylori strains (VacA+/CagA+).cag contains the cagA gene (whose expression is associated with toxigenicity) and many genes, some of which are highly homologous to virulence genes of other virulent bacteria, that account for the enhanced pathogenic potential of CagA+ organisms.

Gastric ethanol metabolism and gastritis: interactions with other drugs, Helicobacter pylori, and antibiotic therapy (1957-1997)--a review

The stomach provides some protection against the penetration of ethanol into the body by contributing to the metabolism of ethanol. The latter is attenuated by various drugs and, although the magnitude of this effect is still the subject of debate, patients should be warned of the corresponding possible increase in blood alcohol levels. Furthermore, oxidation of ethanol generates acetaldehyde, a toxic metabolite. In addition, chronic alcohol abuse seems to favor colonization by Helicobacter pylori, which produces ammonia that also contributes to the commonly associated chronic gastritis. Because antibiotics were shown over the last 4 decades to effectively eliminate gastric ammonia, they should be considered for the routine treatment of such chronic gastritis in the way they are now being used for ulcer therapy.

Enhancement by monochloramine of the development of gastric cancers in rats: a possible mechanism of Helicobacter pylori-associated gastric carcinogenesis

The effects of cytotoxic monochloramine on the development of gastric cancers induced by N-methyl-N'-nitro-N-nitrosoguanidine were investigated in Wistar rats. After oral administration of drinking water containing the carcinogen and regular chow pellets for 25 weeks, rats received regular chow pellets or chow pellets containing 20% ammonium acetate, and normal tap water or water containing 30 mM sodium hypochlorite, with or without s.c. injection of taurine, until the end of the experiment in week 52. Treatment with both ammonium acetate and sodium hypochlorite significantly increased the incidence of gastric cancers in week 52, while the concomitant use of taurine with ammonium acetate and sodium hypochlorite significantly attenuated the enhanced gastric carcinogenesis. Spectrophotometric examinations revealed that taurine scavenged monochloramine. These findings suggest that Helicobacter pylori-associated gastric carcinogenesis may be mediated by monochloramine.

Identifiable Helicobacter pylori strains or factors important in the development of duodenal ulcer disease

BACKGROUND

Helicobacter pylori is a primary pathogen as its presence in the stomach almost always is associated with a strong mucosal and systemic immune response. Putative virulence factors of H. pylori are numerous. In this article, we evaluate whether currently available evidence supports the existence of factors important in the development of duodenal ulcer disease.

METHODS

The evaluation is conducted by a review of the literature on H. pylori toxins and virulence factors.

RESULTS

Most putative H. pylori virulence factors are present in all isolates examined, though some are present only in, or are expressed more intensively by, determined strains. Urease is the main virulence determinant of H. pylori. It generates ammonia from the gastric urea, which in turn injures the gastric mucosa either directly by forming ammonium hydroxide or indirectly by stimulating polymorphonuclear leukocytes and inhibiting cell proliferation. Other enzymes (e.g., mucinase, phospholipases, alcohol dehydrogenase, neuraminidase) could promote tissue erosion and ulceration by destroying the integrity of mucus, by inducing lipid peroxidation, and the like. H. pylori strains that express the vacuolating toxin vacA and the associated protein cagA are called type I and are considered to be endowed with increased ulcerogenic and inflammatory potential. Exploration of the structure of the vacA gene has shown that the degree of toxicity is regulated at the molecular level. Type I H. pylori strains carry a 40-kb genomic fragment called cag that is absent from type II strains (vacA- and cagA-negative). cag is considered a pathogenicity island because it contains numerous genes that are highly homologous to virulence genes of classic bacterial pathogens and because it has been suggested that it is acquired through recombination events. CagA is part of the pathogenicity island. CagA-positive strains are more likely to be isolated from patients with duodenal ulcer and other severe digestive pathological processes.

CONCLUSIONS

The use of simple serological tests to identify patients infected with type I H. pylori strains could help to calculate the risk of development of severe gastroduodenal diseases and, possibly, to prevent such severe diseases.

Helicobacter pylori and atrophic gastritis

Infection with Helicobacter pylori plays a crucial role in the etiology of atrophic gastritis and gastric cancer. Studies suggest a nine-fold increased risk for both conditions in the presence of infection. The risk of atrophic gastritis in the presence of infection is dependent upon the severity of the gastritis. Gastritis is increased in subjects infected with a cytotoxic H pylori strain and in those with a decreased acid production. The development of atrophy may be related to the induction of cross-reacting antibodies recognizing Lewis epitopes on H pylori lipopolysaccharide and gastric mucosa. Future studies have to demonstrate whether atrophic gastritis and gastric cancer can be prevented by early H pylori eradication.

Hypochlorous acid and its pharmacological antagonism: an update picture

1. Some biochemical and pathophysiological aspects of hypochlorous acid (as major oxidant species produced by activated white blood cells) are discussed. 2. Moreover, we have discussed the problem of the pharmacological scavenging of hypochlorous acid, focusing attention on the biochemical tests able to study therapeutically relevant scavenging properties of various drugs against hypochlorous acid itself.