Helicobacter pylori and gastric malignancies

A review on the structures and biological activities of anti-Helicobacter pylori agents

Helicobacter pylori is one of the main causal risk factor in the generation of chronic gastritis, gastroduodenal ulcers and gastric carcinoma. Thus, the eradication of H. pylori infection is an important way for preventing and managing the gastric diseases. Multiple-therapy with several antibacterial agents is used for the eradication of H. pylori infections; however the increase of resistance to H. pylori strains has resulted in unsatisfactory eradication and unsuccessful treatment. Furthermore, the combination therapy with high dosing leads to the disruption of intestinal microbial flora and undesired side effects. Therefore, the search for new therapeutic agents with high selectivity against H. pylori is a field of current interest. In recent years, diverse compounds originating from natural sources or synthetic drug design programs were evaluated and tried to optimize for applying against H. pylori. In this review, we have described various classes of anti-H. pylori compounds, their structure-activity relationship studies, and mechanism of actions, which could be useful for the development of new drugs for the treatment of H. pylori infections.

Regional Estimates of Stomach Cancer Burden in Italy

Aims and background

Stomach cancer still remains one of the most frequent tumors in Italy and Europe. The aim of this paper is to present estimates for stomach cancer mortality, incidence and prevalence over the period 1970-2010 for the Italian regions and for Italy as a whole.

Methods

Estimated figures for incidence, prevalence and mortality were obtained by using the MIAMOD method. Starting from the knowledge of mortality in the period 1970-1999 and of relative survival in the period of diagnosis 1978-1994, we derived incidence and prevalence estimates and projections up to the year 2010 by means of a statistical back-calculation approach. Survival at the regional and national levels was modelled on the basis of published survival data from the Italian cancer registries.

Results

Incidence and mortality trends for both sexes decrease by about 60% during the estimation period 1970-2010. Both indicators show a 2-fold male/female ratio all over the country, and a similar gender time trend. The incidence and mortality in the North and Center of the country are estimated to be higher and to decrease more steeply than those in the South, both for men and women. A total of around 13,000 incident cases, 57,000 prevalent cases, and 8,000 deaths are estimated to have occurred in Italy in 2005.

Conclusions

The incidence and mortality trends are estimated to decline during the entire period 1970-2010, with different slopes between northern-central and southern regions. The incidence and mortality are quite similar among Italian regions, showing that the risk of developing the disease diminishes and is becoming more homogeneous than in the past decades all over the country.

Synthesis of 1,2,3-Triazolo[4,5-h]quinolone Derivatives with Novel Anti-Microbial Properties against Metronidazole Resistant Helicobacter pylori

Helicobacter pylori infection can lead to gastritis, peptic ulcer, and the development of mucosa associated lymphoid tissue (MALT) lymphoma. Treatment and eradication of H. pylori infection can prevent relapse and accelerate the healing of gastric and duodenal ulcers as well as regression of malignancy. Due to the increasing emergence of antibiotic resistance among clinical isolates of H. pylori, alternative approaches using newly discovered antimicrobial agents in combination with the standard antibiotic regimens for the treatment of H. pylori are of major importance. The purpose of the present study was to investigate the effect of newly synthesized 8-amino 7-substituted fluoroquinolone and their correspondent cyclized triazolo derivatives when either alone or combined with metronidazole against metronidazole-resistant H. pylori. Based on standard antimicrobial susceptibility testing methods and checkerboard titration assay, all of the tested compounds showed interesting antimicrobial activity against 12 clinical strains of H. pylori, with best in vitro effect for compounds 4b and 4c. Fractional inhibitory concentration (FIC) mean values showed synergistic pattern in all compounds of Group 5. In addition, additive activities of some of the tested compounds of Group 4 were observed when combined with metronidazole. In contrast, the tested compounds showed no significant urease inhibition activity. These results support the potential of new fluoroquinolone derivatives to be useful in combination with anti-H. pylori drugs in the management of H. pylori-associated diseases.

Crosstalk between the HpArsRS two-component system and HpNikR is necessary for maximal activation of urease transcription

Helicobacter pylori NikR (HpNikR) is a nickel dependent transcription factor that directly regulates a number of genes in this important gastric pathogen. One key gene that is regulated by HpNikR is ureA, which encodes for the urease enzyme. In vitro DNA binding studies of HpNikR with the ureA promoter (P_ureA) previously identified a recognition site that is required for high affinity protein/DNA binding. As a means to determine the in vivo significance of this recognition site and to identify the key DNA sequence determinants required for ureA transcription, herein, we have translated these in vitro results to analysis directly within H. pylori. Using a series of GFP reporter constructs in which the P_ureA DNA target was altered, in combination with mutant H. pylori strains deficient in key regulatory proteins, we confirmed the importance of the previously identified HpNikR recognition sequence for HpNikR-dependent ureA transcription. Moreover, we identified a second factor, the HpArsRS two-component system that was required for maximum transcription of ureA. While HpArsRS is known to regulate ureA in response to acid shock, it was previously thought to function independently of HpNikR and to have no role at neutral pH. However, our qPCR analysis of ureA expression in wildtype, ΔnikR and ΔarsS single mutants as well as a ΔarsS/nikR double mutant strain background showed reduced basal level expression of ureA when arsS was absent. Additionally, we determined that both HpNikR and HpArsRS were necessary for maximal expression of ureA under nickel, low pH and combined nickel and low pH stresses. In vitro studies of HpArsR-P with the P_ureA DNA target using florescence anisotropy confirmed a direct protein/DNA binding interaction. Together, these data support a model in which HpArsRS and HpNikR cooperatively interact to regulate ureA transcription under various environmental conditions. This is the first time that direct “cross-talk” between HpArsRS and HpNikR at neutral pH has been demonstrated.

Mouse models of gastric carcinogenesis

Gastric cancer is one of the most common cancers in the world. Animal models have been used to elucidate the details of the molecular mechanisms of various cancers. However, most inbred strains of mice have resistance to gastric carcinogenesis. Helicobacter infection and carcinogen treatment have been used to establish mouse models that exhibit phenotypes similar to those of human gastric cancer. A large number of transgenic and knockout mouse models of gastric cancer have been developed using genetic engineering. A combination of carcinogens and gene manipulation has been applied to facilitate development of advanced gastric cancer; however, it is rare for mouse models of gastric cancer to show aggressive, metastatic phenotypes required for preclinical studies. Here, we review current mouse models of gastric carcinogenesis and provide our perspectives on future developments in this field.

Mucoadhesive microparticulate drug delivery system of curcumin against Helicobacter pylori infection: Design, development and optimization

The purpose of the present research was to develop and characterize mucoadhesive microspheres of curcumin for the potential use of treating gastric adenocarcinoma, gastric and duodenal ulcer associated with Helicobacter pylori. Curcumin mucoadhesive microspheres were prepared using ethyl cellulose as a matrix and carbopol 934P as a mucoadhesive polymer by an emulsion-solvent evaporation technique. Response surface methodology was used for optimization of formulation using central composite design (CCD) for two factors at three levels each was employed to study the effect of independent variables, drug:polymer:polymer ratio (curcumin:ethylcellulose:carbopol 934P)(X₁) and surfactant concentration (X₂) on dependent variables, namely drug entrapment efficiency (DEE), percentage mucoadhesion (PM), in vitro drug release and particle size (PS). Optimized formulation was obtained using desirability approach of numerical optimization. The experimental values of DEE, PM, % release and PS after 8 h for the optimized formulation were found to be 50.256 ± 1.38%, 66.23%±0.06, 73.564 ± 1.32%, and 139.881 ± 2.56 μm, respectively, which were in close agreement with those predicted by the mathematical models. The drug release was also found to be slow and extended more than 8 h and release rates were fitted to the Power law equation and Higuchi model to compute the diffusional parameters. The prolonged stomach residence time of curcumin mucoadhesive microspheres might make a contribution to H. pylori complete eradication in combination with other antimicrobial agents.

Synthesis and biological evaluation of novel benzyl piperazine derivatives of 5-(5-nitroaryl)-1,3,4-thiadiazoles as Anti-Helicobacter pylori agents

BACKGROUND AND THE PURPOSE OF THE STUDY

Helicobacter pylori is recognized as the main cause of gastritis and gastroduodenal ulcers and classified as class 1 carcinogen pathogen. Different 1,3,4-thiadiazole derivatives bearing 5-nitroaryl moiety have been shown considerable anti- H. pylori activity. In attempt to find new and potent derivatives of described scaffold, a new series of 1-(substituted benzyl)-4-(5-(5-nitroaryl-2-yl)-1,3,4-thiadiazol-2-yl)piperazine derivatives were synthesized and evaluated against three metronidazole-resistant isolates of H. pylori using paper disk diffusion bioassay test.

METHODS

The title compounds were prepared through the reaction of 1-(5-(5-nitroaryl-2-yl)-1,3,4-thiadiazol-2-yl) piperazine 5a-b and substituted benzyl chloride in DMF. The inhibitory activity of the new derivatives 6a-q against three metronidazole-resistant isolates of H. pylori was evaluated by the disc diffusion method and compared with the commercially available standard drug metronidazole.

RESULTS AND DISCUSSION

The results of SAR study indicated that the potency and anti-H. pylori activity profile of synthesized derivatives is mainly attributed to the substituted nitroaryl moiety at the C-5 position of 1,3,4-thiadiazole ring. Most of 1,3,4-thiadiazole derivatives bearing 5-nitrofuran moiety at C-5 position of central thiadiazole ring, demonstrated more promising anti-H. pylori than the 5-nitrothiophen counterpart.

CONCLUSION

The most potent nitrofuran derivative containing 3-methoxybenzyl piperazine pendant at the C-2 position of 1,3,4-thiadiazole ring (compound 6i), demonstrated strong anti-H. pylori potential at studied concentrations 100-25 μg/disk (IZD > 20 mm) against all studied metronidazole- resistant isolates of H. pylori.

Mouse models of gastric cancer

Animal models have greatly enriched our understanding of the molecular mechanisms of numerous types of cancers. Gastric cancer is one of the most common cancers worldwide, with a poor prognosis and high incidence of drug-resistance. However, most inbred strains of mice have proven resistant to gastric carcinogenesis. To establish useful models which mimic human gastric cancer phenotypes, investigators have utilized animals infected with Helicobacter species and treated with carcinogens. In addition, by exploiting genetic engineering, a variety of transgenic and knockout mouse models of gastric cancer have emerged, such as INS-GAS mice and TFF1 knockout mice. Investigators have used the combination of carcinogens and gene alteration to accelerate gastric cancer development, but rarely do mouse models show an aggressive and metastatic gastric cancer phenotype that could be relevant to preclinical studies, which may require more specific targeting of gastric progenitor cells. Here, we review current gastric carcinogenesis mouse models and provide our future perspectives on this field.

Dissecting the role of DNA sequence in Helicobacter pylori NikR/DNA recognition

HpNikR is a prokaryotic nickel binding transcription factor found in Helicobacter pylori, where it functions as a regulator of multiple genes including those involved in nickel ion homeostasis and acid adaptation. The target operator sequences of the genes that are regulated by HpNikR do not have symmetric recognition sites, and the mechanism by which HpNikR distinguishes between the genes it regulates is not well understood. HpNikR utilizes a two-tiered mode of DNA binding in which some target sequences are bound with high affinity (K(d) of nM) and others with low affinity (K(d) of μM). An alignment of the high affinity and low affinity binder sequences identified a consensus binding sequence. The consensus sequence was conserved to a greater degree for the high affinity binder sequences compared to the low affinity binder sequences. The exact bases within the consensus sequence that are crucial for a high affinity binding interaction have not been identified. Here we sought to identify key residues from the consensus sequence that are crucial for a tight binding interaction using a competitive fluorescence anisotropy assay. Systematic mutations were made to a weak binder operator sequence, P(nikR), so that it more closely resembled the consensus sequence and the effect of these mutations on protein-DNA binding was measured. Similarly, mutations that disrupted the consensus sequence were made to a tight binder operator sequence, P(ureA), and their effects on protein-DNA binding were measured. Taken together, these studies implicate thymine 10, located on the 3' end of the palindrome, as crucial for tight binding.

Ni(II) coordination to mixed sites modulates DNA binding of HpNikR via a long-range effect

Helicobacter pylori NikR (HpNikR) is a nickel-dependent transcription factor that regulates multiple genes in the H. pylori pathogen. There are conflicting data regarding the locations of the Ni(II) sites and the role of Ni(II) coordination in DNA recognition. Herein, we report crystal structures of (i) the metal-binding domain (MBD) of HpNikR (3.08 Å) and (ii) a mutant, H74A (2.04 Å), designed to disrupt native Ni(II) coordination. In the MBD structure, four nickel ions are coordinated to two different types of nickel sites (4-coordinate, square planar, and 5/6-coordinate, square pyramidal/octahedral). In the H74A structure, all four nickel ions are coordinated to 4-coordinate square-planar sites. DNA-binding studies reveal tighter binding for target DNA sequences for holo-HpNikR compared with the affinities of Ni(II) reconstituted apo-HpNikR and H74A for these same DNA targets, supporting a role for Ni(II) coordination to 5/6 sites in DNA recognition. Small-angle X-ray scattering studies of holo-HpNikR and H74A reveal a high degree of conformational flexibility centered at the DNA-binding domains of H74A, which is consistent with disorder observed in the crystal structure of the protein. A model of DNA recognition by HpNikR is proposed in which Ni(II) coordination to specific sites in the MBD have a long-range effect on the flexibility of the DNA-binding domains and, consequently, the DNA recognition properties.

Characterisation of the genes encoding resistance to metronidazole (rdxA and frxA) and clarithromycin (the 23S-rRNA genes) in South African isolates of Helicobacter pylori

Helicobacter pylori has been incriminated in human diseases, such as peptic ulcer, gastritis and gastric malignancy. Although modern triple-drug regimens are usually highly effective in the treatment of H. pylori infection, the emergence of resistance to two of the most used antibiotics, metronidazole (Mtz) and clarithromycin (Cla), is a serious and increasing problem. Truncations in the rdxA and frxA genes of H. pylori are thought to be associated with Mtz resistance whereas mutations in the pathogen's 23S-ribosomal-RNA (23S-rRNA) genes are associated with Cla resistance. In a recent study, PCR and sequence analysis of the rdxA, frxA and 23S-rRNA genes were used to explore the genetic basis of resistance to Mtz and Cla in H. pylori. When 200 isolates of H. pylori from the Eastern Cape province of South Africa were tested for antibiotic susceptibility, almost all (95·5%) were found resistant to Mtz and 20·0% were found resistant to Cla. Only the Mtz-resistant isolates showed rdxA and frxA truncation. Two point mutations were detected in the 23S-rRNA genes of the Cla-resistant isolates. Many significant changes (resulting in 13 amino-acid substitutions in nine loci and truncated proteins in 14 loci) were observed in the rdxA genes of the Mtz-resistant isolates, and it appears that, compared with the rarer changes detected in frxA, such mutations may contribute more significantly to the high prevalence of Mtz resistance. To guide empiric treatment, the genotypes and antibiotic susceptibility of H. pylori in the Eastern Cape province of South Africa need to be monitored regularly.

Holo-Ni(II)HpNikR is an asymmetric tetramer containing two different nickel-binding sites

The metalloregulatory protein NikR from Helicobacter pylori (HpNikR) is a master regulator of gene expression which both activates and represses specific genes in response to nickel availability. Here, we report the first crystal structure (at 2.37 Å resolution) of Ni(II)HpNikR prepared directly from the holo protein. The protein contains four nickel ions located in two distinct coordination environments. Two nickel ions are bound to sites in a four-coordinate square-planar geometry as predicted on the basis of the structures of NikR from Escherichia coli and Pyrococcus horikoshii . The remaining two nickel ions are bound to sites with unexpected 5- or 6-coordination geometries which were previously thought to be involved in nickel incorporation into the protein. The nickel with 5-/6-coordination geometry utilizes three histidines from two separate monomeric HpNikR units along with two or three water molecules as ligands. The spatial location of the nickel in the 5-/6-coordinate site is within approximately 5 Å of the expected site if a 4-coordinate square-planar geometry occurred. Two of the histidines that participate as ligands in the 5-/6-coordinate site would also participate as ligands if the 4-coordinate site was occupied, making it impossible for both sites to be occupied simultaneously. DFT calculations show that the 5-/6-coordinate geometries are energetically favorable when the local protein environment is included in the calculations. The presence of two distinct coordination environments in HpNikR is suggested to be related to the specificity and binding affinity of this transcription factor for DNA.

Screening test for anti-Helicobacter pylori activity of traditional Chinese herbal medicines

AIM

To evaluate the anti-Helicobacter pylori (H. pylori) activity of 50 traditional Chinese herbal medicines in order to provide the primary evidence for their use in clinical practice.

METHODS

A susceptibility test of water extract from 50 selected traditional Chinese herbal medicines for in vitro H. pylori Sydney strain 1 was performed with broth dilution method. Anti-H. pylori activity of the selected Chinese herbal medicines was evaluated according to their minimum inhibitory concentration (MIC).

RESULTS

The water extract from Rhizoma Coptidis, Radix Scutellariae and Radix isatidis could significantly inhibit the H. pylori activity with their MIC less than 7.8 mg/mL, suggesting that traditional Chinese herbal medicines have anti-inflammatory and antibacterial effects and can thus be used in treatment of H. pylori infection.

CONCLUSION

Rhizoma Coptidis, Radix Scutellariae and Radix isatidis are the potential sources for the synthesis of new drugs against H. pylori.

Potent bactericidal constituents from Mallotus philippinensis against clarithromycin and metronidazole resistant strains of Japanese and Pakistani Helicobacter pylori

In the quest for potent anti-Helicobacter pylori agents, we found 70% EtOH extract of Mallotus philippinensis (LAM.) MUELL. (MPM) with strong bactericidal activity at the concentration of 15.6-31.2 mg/l against eight H. pylori strains. Further fractionation and purification of 70% EtOH extract of MPM led to the isolation of 5 compounds, namely 5,7-dihydroxy-8-methyl-6-prenylflavanone (1), 3'-prenylrubranine (2), red compound (3), isorottlerin (4), and rottlerin (5) which were elucidated on the basis of nuclear magnetic resonance and mass spectroscopy. Among the isolated compounds, rottlerin exhibited most potent bactericidal activity with minimum bactericidal concentration (MBC) value of 3.12-6.25 mg/l against several clinical H. pylori isolates including Japanese and Pakistani strains, nine clarithromycin resistant (CR), and seven metronidazole resistant (MR) strains. Minimum inhibitory concentration (MIC) values of CR (8->256 mg/l) and MR (>256 mg/l) strains were analyzed by E test. Moreover, the clarithromycin resistant strains were evaluated for A2143G and A2144G point mutations of 23s rRNA gene to correlate the MBC values with mutation type. Our results revealed the potent in vitro anti-H. pylori activity of MPM and rottlerin, specially against CR and MR strains, which could be gainfully utilized for the development of novel antimicrobials to prevent H. pylori related disorders.

Helicobacter pylori NikR's interaction with DNA: a two-tiered mode of recognition

HPNikR is a prokaryotic nickel binding transcription factor found in the virulent bacterium Helicobacter pylori. HPNikR regulates the expression of multiple genes as an activator or repressor, including those involved in nickel ion homeostasis, acid adaptation, and iron uptake. The target operator sequences of the genes regulated by HPNikR do not contain identifiable symmetrical recognition sites, and the mechanism by which HPNikR distinguishes between the genes it regulates is not understood. Using competitive fluorescence anisotropy (FA) and electrophoretic gel mobility shift (EMSA) assays, the interactions between HPNikR and the target operator sequences of the genes directly regulated (ureA, NixA, NikR, Fur OPI, Fur OPII, Frpb4, FecA3, and exbB) were characterized. These studies revealed that HPNikR utilizes a two-tiered mode of DNA recognition by binding to some genes with high affinity and others with low affinity. The genes that are tightly regulated by HPNikR encode proteins that utilize nickel, while those that are less tightly regulated encode other types of proteins. The affinities of low-affinity metal ions for a second metal binding site were determined to be in the micromolar regime, and a contribution of electrostatics to the HPNikR-DNA binding event was determined. Detailed studies of the role of sequence length and identity for the interaction between HPNikR and ureA revealed a specific length requirement for DNA binding.

Bactericidal activity of medicinal plants, employed for the treatment of gastrointestinal ailments, against Helicobacter pylori

AIM OF THE STUDY

Helicobacter pylori infection plays a crucial role in the pathogenesis of peptic ulcer, and gastric cancer. The current PPI-based triple regimens for the eradication of Helicobacter pylori faces uprising resistance problem demanding for the search of novel candidates. Medicinal plants have always been a source of lead compounds for drug discovery. In the present study, we evaluated the anti-Helicobacter pylori activity of 50 commonly used Unani (traditional) medicine plants from Pakistan that are extensively utilized for the cure of gastrointestinal disorders to explore the natural source for pilot compounds against Helicobacter pylori.

MATERIALS AND METHODS

Total seven clinical isolates and one standard strain were employed to examine the bactericidal effects of medicinal plants. Helicobacter pylori was isolated from the antral biopsy specimens and confirmed through the standard microbiology procedures. Minimum bactericidal concentration (MBC) of the active plants was determined at the concentration range from 7.8 to 500 microg/ml.

RESULTS

Among the herbs evaluated, more than 50% inhibited the growth of eight strains at the concentration of 500 microg/ml. The 70% aqueous-ethanol extracts of Curcuma amada Roxb., Mallotus phillipinesis (Lam) Muell., Myrisctica fragrans Houtt., and Psoralea corylifolia L. demonstrated strong anti-Helicobacter pylori activity with MBC value ranged from 15.6 to 62.5 microg/ml. The most potent bactericidal activity was exhibited by Mallotus phillipinesis (Lam) Muell. which completely killed the bacteria at the concentration of 15.6-31.2 microg/ml.

CONCLUSION

The results revealed significant anti-Helicobacter pylori activity of medicinal plants which could be the potential source of new bactericidal agents.

Practical approach to the pathologic diagnosis of gastritis

CONTEXT

Most types of gastritis can be diagnosed on hematoxylin-eosin stains. The most common type of chronic gastritis is Helicobacter pylori gastritis. Reactive or chemical gastropathy, which is often associated with nonsteroidal anti-inflammatory drug use or bile reflux, is common in most practices. The diagnosis of atrophic gastritis can be challenging if few biopsy samples are available and if the location of the biopsies in the stomach is not known, such as when random biopsies are sampled in one jar. If the biopsy site is not known, immunohistochemical stains, such as a combination of synaptophysin and gastrin, are useful in establishing the biopsy location.

OBJECTIVE

To demonstrate a practical approach to achieving a pathologic diagnosis of gastritis by evaluating a limited number of features in mucosal biopsies.

DATA SOURCE

In this article, we present several representative gastric biopsy cases from a gastrointestinal pathology practice to demonstrate the practical application of basic histopathologic methods for the diagnosis of gastritis.

CONCLUSIONS

Limited ancillary tests are usually required for a diagnosis of gastritis. In some cases, special stains, such as acid-fast stains, and immunohistochemical stains, such as for H pylori and viruses, can be useful. Helicobacter pylori immunohistochemical stains can particularly contribute (1) when moderate to severe, chronic gastritis or active gastritis is present but no Helicobacter organisms are identified upon hematoxylin-eosin stain; (2) when extensive intestinal metaplasia is present; and (3) in follow-up biopsies, after antibiotic treatment for H pylori.

In vitro anti-Helicobacter pylori activity of extracts of selected medicinal plants from North West Cameroon

ETHNOPHARMACOLOGICAL RELEVANCE

Helicobacter pylori, a gram negative microaerophilic bacterium is a major etiological agent in duodenal, peptic and gastric ulcers. The growing problem of antibiotic resistance by the organism demands the search for novel compounds from plant based sources.

AIM OF STUDY

The present study is aimed at evaluating the antimicrobial activity of some selected medicinal plants on clinical isolates of H. pylori circulating in Cameroon in a bid to identify potential sources of cheap starting materials for the synthesis of new drugs.

MATERIALS AND METHODS

Gastric biopsy samples were obtained from patients presenting with gastroduodenal complications. H. pylori was isolated from the specimens following standard microbiology procedures. The disk diffusion method was used to determine the susceptibility of 15 isolates to ten methanol plant extracts (Ageratum conyzoides, Scleria striatinux, Lycopodium cernua, Acanthus montanus, Eryngium foetidium, Aulutandria kamerunensis, Tapeinachilus ananassae, Euphorbia hirta, Emilia coccinea and Scleria verrucosa). The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) for the most active plant extracts were also determined by the agar dilution method. Results were analyzed statistically by the Fisher's exact test.

RESULTS

All the plants tested demonstrated antimicrobial activity with zone diameters of inhibition ranging from 0-30mm. Of these, A. conyzoides, S. striatinux and L. cernua showed very potent antibacterial activity on the isolates. The lowest MIC and MBC recorded were 0.032mg/mL and 0.098mg/mL respectively. However, the MIC of the extracts ranged from 0.032-1.0mg/mL for S. striatinux; 0.063-0.5mg/mL for L. cernua and 0.063-1.0mg/mL for A. conyzoides. The MBC of the extracts ranged from 0.098-15.0mg/mL for S. striatinux; 0.098-12.5mg/mL for A. conyzoides, and 0.195-12.5mg/mL for L. cernua. The extracts had a wide spectrum of activity. The three most potent extracts possessed significant (P<0.05) inhibitory activities.

CONCLUSION

The plant extracts may contain compounds with therapeutic activity.

Characterization of the Helicobacter pylori NikR-P(ureA) DNA interaction: metal ion requirements and sequence specificity

HPNikR, a prokaryotic nickel binding transcription factor, is found in Helicobacter pylori where it functions as a regulator of multiple genes, including those involved in acid adaptation and nickel ion homeostasis. Particularly important is HPNikR's role in the regulation of the nickel-dependent enzyme urease which is critical for the organism's survival in the acidic environment of the gastric epithelium. The target operator sequences of the genes regulated by HPNikR do not contain any identifiable palindromes, and the exact mechanism(s) of the HPNikR-DNA recognition event is unknown. HPNikR was expressed and purified as a soluble protein containing mixed alpha/beta secondary structure with evidence of a tertiary fold. A direct and competitive fluorescence anisotropy (FA) assay to probe both the metal ion requirements and sequence specificity of HPNikR for PureA, the operator sequence for the urease gene, was developed. FA studies revealed that apo-HPNikR did not bind to PureA while Ni(II)HPNikR bound PureA with nanomolar affinity, but only in the presence of a second metal ion [magnesium, calcium, or manganese(II)], suggesting that HPNikR contains a second, low-affinity metal binding site. Cu(II)HPNikR also exhibited a requirement for a second metal ion to accomplish PureA binding. Removal of a loosely conserved "putative" palindrome sequence in the PureA operator abrogated HPNikR binding. Together, these results support a model of HPNikR-PureA binding in which specific metal ions must be coordinated to high- and low-affinity sites to modulate binding.

Gastric-and-intestinal mixed-type intestinal metaplasia: aberrant expression of transcription factors and stem cell intestinalization

Helicobacter pylori plays a causative role in the development of chronic atrophic gastritis, intestinal metaplasia (IM), and stomach cancer. Although IM has long attracted attention as a putative preneoplastic lesion for stomach cancers, its clinicopathologic significance has yet to be clarified in detail. Using gastric and intestinal epithelial cell markers, IM was here divided into two major types: a gastric-and-intestinal (GI) mixed type and a solely intestinal (I) type. In the former, gastric and intestinal phenotypic markers appeared not only at the glandular but also at the cellular level. Furthermore, neuroendocrine cells also showed intestinalization along with their exocrine counterparts. In animal models, GI-type IM was found to appear first, followed by the solely I type. Summarizing these data, it was suggested that IM might be caused by the gradual intestinalization of stem cells from the GI to the I type. The molecular mechanisms of IM include the ectopic expression of CDX1, CDX2, OCT-1, and members of the Erk pathway. Suppression of the expression of gastric transcription factors such as SOX2, genes that are involved in the Sonic hedgehog pathway, and RUNX3, a tumor suppressor gene, could be additional relevant alterations. The expression of PDX1 may also be associated with pseudopyloric gland metaplasia and IM. Detailed analysis of gene regulation may shed light on the molecular bases of gastric lesions, leading to strategies for chemoprevention.

A phase I radioimmunolocalization trial of humanized monoclonal antibody huA33 in patients with gastric carcinoma

In order to determine the in vivo characteristics of huA33, an open label dose escalation biopsy-based phase I clinical trial and radioimmunolocalization study were conducted with a complement determinant region-grafted humanized monoclonal antibody against the A33 antigen in patients with gastric carcinoma. Thirteen patients were entered onto one of four dose levels (1.0, 2.0, 5.0 or 10.0 mg/m(2)). Patients with locally advanced (UICC-TNM [International Union Against Cancer-tumor, node, metastasis] stage over 2 but resectable at clinical diagnosis) gastric carcinoma received a single infusion of (131)I-huA33 1 week prior to surgery. Adverse events were monitored, and imaging studies with gamma camera plus ex vivo scintigraphy of the resected specimen, biodistribution study by dosimetry analysis of the biopsied and resected tissues, and immunohistochemical analysis were carried out and evaluated. No dose-limiting toxicity was observed during the trial. Therefore, the maximum tolerated dose was not reached. Although cancer tissues with + intensity and <25% extent by immunostaining in biopsied frozen sections did not show positive imaging or postoperative dosimetry findings, cancers with ++ or +++ intensity or wide (>25%) extent by frozen and paraffin sections in the biopsied specimen showed positive ex vivo tumor images and positive antigen expression in resected gastric cancer specimens, and the biodistribution analysis showed tumor uptake of (131)I-huA33. In conclusion, humanized monoclonal antibody huA33 demonstrated selective localization to gastric cancer that expressed A33 antigen strongly. These excellent targeting characteristics of huA33 indicate potential for targeted therapy of advanced gastric cancer that is refractory to cytotoxic therapy, and could also be exploitable for curatively resected early gastric cancer in an adjuvant setting.

Association of T-cell regulatory gene polymorphisms with susceptibility to gastric mucosa-associated lymphoid tissue lymphoma

PURPOSE

Helicobacter pylori infection and host susceptibility interact to develop gastric mucosa-associated lymphoid tissue (MALT) lymphoma, and activation of specific T cells might play a crucial role in this process. Recent investigations show that the CTLA4, CD28, and ICOS genes are located on chromosome 2q33 and their polymorphisms confer susceptibility to infectious and immune diseases through deregulation of T-cell stimulation. We aimed to determine the role of CTLA4, CD28, and ICOS polymorphisms in gastric MALT lymphoma.

PATIENTS AND METHODS

Genotyping for CTLA4 (49 A/G, -318 C/T, and CT60 A/G), CD28 (IVS3+ 17T/C), and ICOS (c.602 A/C and c.1624C/T) was performed for 62 patients with gastric MALT lymphoma and compared with 250 unrelated healthy controls.

RESULTS

H pylori infection was significantly higher in patients with gastric MALT lymphoma (90.3%) compared with controls (66.4%; P < .001). The CTLA4 -318 C/T genotype was associated with a lower risk of developing gastric MALT lymphoma (odds ratio [OR] = 0.3; P = .022), whereas CTLA4 49 G/G genotype was linked to a higher risk (OR = 4.1; P = .044). In patients with H pylori infection, CTLA4 49 G/G genotype was associated with an even higher risk (OR = 6.4; P = .047). Carriage of the tightly linked -318C -49G haplotype conferred a four-fold higher susceptibility to MALT lymphoma (OR = 4.2; P = .042). Complete remission after H pylori eradication was related to tumor stage but not to genotypes or haplotypes.

CONCLUSION

These results indicate a genetic link of CTLA4 gene polymorphisms to development of gastric MALT lymphoma and indirectly support the crucial role of host activated T cells in the MALT lymphomagenesis.

Prevalence of Helicobacter pylori infection and intestinal metaplasia in subjects who had undergone surgery for gastric adenocarcinoma in Northwest Italy

AIM

To investigate the seroprevalence of Helicobacter pylori (H pylori) infection and its more virulent strains as well as the correlation with the histologic features among patients who had undergone surgery for gastric cancer (GC).

METHODS

Samples from 317 (184 males, 133 females, mean age 69+/-3.4 years) consecutive patients who had undergone surgery for gastric non-cardia adenocarcinoma were included in the study. Five hundred and fifty-five (294 males, 261 females, mean age 57.3+/-4.1 years) patients consecutively admitted to the Emergency Care Unit served as control. Histological examination of tumor, lymph nodes and other tissues obtained at the time of surgery represented the diagnostic "gold standard". An enzyme immunosorbent assay was used to detect serum anti-H pylori (IgG) antibodies and Western blotting technique was utilized to search for anti-CagA protein (IgG).

RESULTS

Two hundred and sixty-one of three hundred and seventeen (82.3%) GC patients and 314/555 (56.5%) controls were seropositive for anti-H pylori (P<0.0001; OR, 3.58; 95%CI, 2.53-5.07). Out of the 317 cases, 267 (84.2%) were seropositive for anti-CagA antibody vs 100 out of 555 (18%) controls (P<0.0001; OR, 24.30; 95%CI, 16.5-35.9). There was no difference between the frequency of H pylori in intestinal type carcinoma (76.2%) and diffuse type cancer (78.8%). Intestinal metaplasia (IM) was more frequent but not significant in the intestinal type cancer (83.4% vs 75.2% in diffuse type and 72.5% in mixed type). Among the patients examined for IM, 39.8% had IM type I, 8.3% type II and 51.9% type III(type III vs others, P = 0.4).

CONCLUSION

This study confirms a high seroprevalence of H pylori infection in patients suffering from gastric adenocarcinoma and provides further evidence that searching for CagA status over H pylori infection might confer additional benefit in identifying populations at greater risk for this tumor.

Helicobacter pylori infection, but not low-dose aspirin, results in a local reduction of the secretory leukocyte protease inhibitor in gastroduodenal mucosa

BACKGROUND

The secretory leukocyte protease inhibitor (SLPI) represents a multifunctional protein with mucosa-protective features. Helicobacter pylori and the usage of low-dose aspirin are two independent risk factors for the development of gastrointestinal diseases. Therefore, the effect of low-dose aspirin on gastrointestinal SLPI expression was analyzed in the context of H. pylori infection.

MATERIAL AND METHODS

The study included 20 volunteers (H. pylori positive and negative: n = 10) who received 2 x 50 mg aspirin/day for 7 days. H. pylori-positive subjects underwent eradication therapy and repeated the protocol. Gastroduodenoscopy was performed at day 0, 1, 3, and 7, and biopsies were obtained each from antrum, corpus, and duodenal bulb. SLPI expression was determined by quantitative reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA).

RESULTS

A reduction of antral SLPI levels, ranging between 582 (day 0) and 941 pg/10 microg protein (day 7), was determined in H. pylori-positive compared to H. pylori-negative and -eradicated subjects (1600-2050 pg/10 microg protein, ANOVA: p = .001-.045). No differences concerning aspirin were observed within the groups. SLPI levels in corpus and duodenal mucosa were neither affected by H. pylori nor low-dose aspirin. There was an inverse correlation between SLPI and H. pylori-induced inflammation (activity: r = -0.575, -0.69 to -0.43, p < .0001; chronicity: r = -0.54, -0.66 to -0.39, p < .0001) in antral mucosa only, whereas other locations as well as the usage of low-dose aspirin did not show an association between SLPI and inflammation.

CONCLUSIONS

H. pylori infection, but not the usage of low-dose aspirin, has a role in the down-regulation of antral SLPI levels.

Chronic inflammatory disorders of the gastrointestinal tract of companion animals

In the inflammatory bowel diseases (IBD) that affect dogs and cats there appears to be dysregulation of normal mucosal immunity, characterised by polyclonal lymphocytic infiltrates which are presumably specific for luminal antigens. There is an absence of a classical polarisation of either T-helper (Th) 1 or Th2 cytokine responses, although increased expression of mRNA for interleukin (IL) 2 and IL-12p40 and a shift towards mucosal immunoglobulin (Ig) G production are consistent findings, whilst variable responses are seen in tumour necrosis factor-alpha (TNF-alpha), IL-1, IL-4, IL-6, and interferon-gamma (IFN-gamma). Increased mucosal permeability and deranged intestinal motility are common sequelae. Despite obvious similarities with Crohn's disease and ulcerative colitis in humans, important differences exist. Of these, the diffuse superficial nature but with no Th1 or Th2 bias, and the prevalence of proximal small intestinal disease are notable. Potential hypotheses for these disparities include specific differences in the types or locations of agonistic gut flora, diffuse abnormalities in microbial-host interactions, a greater importance of diet, or anatomical or cellular differences in mucosal immune responses. Although specific pathogens and genetic susceptibilities may be involved, quantitative or qualitative changes in the normal flora or abnormal responses to a normal flora are more likely to be involved in the immunopathogenesis. Dietary influences include a large source of antigen, promotion of abnormal microbial growth through Maillard compounds within canned diets, and specific macro- and micronutrient deficiencies. Although dependent on a histopathological diagnosis, limitations of biopsies procured endoscopically, lack of histopathological standardisation and difficulty distinguishing inflammation from neoplasia remain significant problems. Clinician-pathologist dialogue, immunohistochemistry, cytokine profiling and lymphocyte clonality assessment may lead to more accurate diagnoses, a deeper understanding of the immunopathogenesis, and ultimately to new therapies or prevention of disease induction.

Novel therapeutic targets in Helicobacter pylori

The failure of current regimens to treat the gastric pathogen Helicobacter pylori is a growing problem. Responsible for gastritis and peptic ulcer disease, and designated as a Class 1 carcinogen, its presence in up to 90% of the population of the developing world makes its treatment a primary concern. The use of genomic, proteomic and transcriptomic data to determine essential gene products as targets for novel therapeutic agents is of key interest in this research. This review describes how such data can be obtained, evaluated and eventually used as a basis for the development of both vaccine and novel anti-helicobacter agents. It indicates both past successes and possible new avenues to exploit the increased availability of such data, whilst also examining the limitations of such approaches.

Helicobacter felis eradication restores normal architecture and inhibits gastric cancer progression in C57BL/6 mice

BACKGROUND & AIMS

The impact of Helicobacter eradication therapy on the progression or regression of gastric lesions is poorly defined. This study examined the effects of eradication therapy on inflammation, atrophy, metaplasia, dysplasia, and cancer progression.

METHODS

C57BL/6 mice were infected with Helicobacter felis and received bacterial eradication therapy after 2, 6, or 12 months of infection. The gastric mucosa was examined at early, mid, and late intervals after eradication and graded for histology, expression pattern of alpha-catenin and beta-catenin, and IQGAP1.

RESULTS

Eradication of Helicobacter infection after 2 or 6 months of infection led to a regression of inflammation, restoration of parietal cell mass, and reestablishment of normal architecture. Progression to adenocarcinoma was prevented. Bacterial eradication at 1 year was associated with the reappearance of parietal cells, partial regression of inflammation, and restoration of architecture. Hyperplasia scores significantly improved, and dysplasia did not progress. Infected mice developed antral adenocarcinoma and gastric outlet obstruction by 24 months. Only 30% of the mice receiving bacterial eradication therapy at 12 months developed antral carcinoma. Bacterial eradication at any time during the first year of infection prevented death due to gastric outlet obstruction. The expression pattern of alpha-catenin, beta-catenin, and IQGAP1 varied with cell type and paralleled histologic changes.

CONCLUSIONS

Inflammation, metaplasia, and dysplasia are reversible with early eradication therapy; progression of dysplasia was arrested with eradication therapy given as late as 1 year and prevented gastric cancer-related deaths.

Universal high-level primary metronidazole resistance in Helicobacter pylori isolated from children in Egypt

Antimicrobial susceptibility testing was performed on 48 isolates of Helicobacter pylori recovered from Egyptian children undergoing routine endoscopies. The isolates were universally highly resistant to metronidazole, but resistance to other tested antimicrobial agents was rare (4% for clarithromycin, erythromycin, and azithromycin resistance versus 2% for ciprofloxacin and ampicillin resistance). Use of metronidazole for the treatment of H. pylori in Egypt should be avoided.

Promoter polymorphisms of tumor necrosis factor-alpha are associated with risk of gastric mucosa-associated lymphoid tissue lymphoma

Genes involved in regulating antimicrobial immunity and inflammation may modulate the risk of Helicobacter pylori-associated diseases. IL-1 and TNF-alpha are major cytokines detected in H. pylori-infected tissues. We aimed to determine the role of gene polymorphisms for these cytokines and their receptors in 2 distinct H. pylori-related gastric malignancies, adenocarcinoma (GAC) and maltoma. Genotyping for IL-1beta (-31 C/T, -511 C/T), TNF-alpha (-238 G/A, -308 G/A, -857 C/T, -863 C/A, -1031 T/C), TNFR1 (-383 A/C) and TNFR2 (196 G/T) was undertaken for 70 patients with maltoma and 204 patients with noncardia GAC and compared to 210 unrelated healthy controls. Genotype frequencies showed no differences among patients with GAC or maltoma and controls for IL-1beta, TNFR1 or TNFR2. The TNF-alpha -857 T variant was significantly underrepresented in maltoma compared to controls (6.4% vs. 14.3%, p = 0.018), conferring a 3-fold decrease in risk (OR = 0.33, 95% CI 0.15-0.75). Comparison of allele frequencies between GAC and controls failed to show any statistical significance for TNF-alpha polymorphisms. We concluded that TNF-alpha -857 T itself or a neighboring gene may modify the risk of maltoma. The differences in genetic background as well as divergent clinicopathologic features between GAC and maltoma support the notion that fundamental mechanistic differences exist in these 2 well-defined H. pylori-related malignancies.

Anti-CagA and anti-VacA antibodies in Helicobacter pylori-infected patients with and without peptic ulcer disease in Serbia and Montenegro

BACKGROUND

The expression of two Helicobacter pylori proteins, CagA and VacA, is associated with more severe pathogenesis and clinical outcomes of the infection. However, this association varies among geographical regions and ethnic groups. We therefore evaluated CagA and VacA seroprevalence in H. pylori-positive dyspeptic patients in Serbia and Montenegro.

METHODS

In 173 consecutive dyspeptic patients referred to endoscopy (67M, mean age 49 +/- 15, 76 smokers), immunoblot assay was used to detect serum antibodies against CagA and VacA. Presence of H. pylori infection was assessed using a rapid urease test (RUT), routine histology and serology (anti-IgG ELISA). Duodenal ulcer (DU) was diagnosed in 28, gastric ulcer (GU) in 3 and non-ulcer dyspepsia (NUD) in the remaining 142 patients.

RESULTS

129 (74.6%) patients were H. pylori-positive, 27 (96.4%) with DU, 3 (100%) with GU and 99 (69.7%) with NUD (P < 0.01); 121 (93.8%) patients carried anti-CagA antibodies and there was no difference between the DU and NUD groups. VacA antibodies were detected in sera of 50 (38.75%) and were more prevalent in patients with DU compared to the NUD group (P < 0.05).

CONCLUSIONS

In Serbia and Montenegro there is high seroprevalence of CagA-positive H. pylori strains in dyspeptic patients with and without peptic ulcer, while VacA-positive strains are more closely related to peptic ulcer disease.

Down-regulation of secretory leukocyte protease inhibitor expression in gastric mucosa is a general phenomenon in Helicobacter pylori-related gastroduodenal diseases

BACKGROUND

Secretory leukocyte protease inhibitor (SLPI) represents a multifunctional protein of the gastric mucosa exerting anti-microbial and anti-inflammatory effects. Recently, a local down-regulation of antral SLPI expression in Helicobacter pylori (Hp)-infected healthy volunteers was demonstrated.

AIM

To analyze mucosal SLPI expression in patients with various gastroduodenal disorders.

METHODS

The prospective study included 90 patients with following gastroduodenal disorders diagnosed: gastric cancer (GC, n=22), duodenal ulcer (DU, n=17), Hp-positive dyspeptic patients (NUD, n=31) and Hp-negative NUD (n=20). During esophagogastroduodenoscopy, biopsies were taken each from antrum, corpus and tumor. SLPI expression was analyzed by quantitative RT-PCR and ELISA.

RESULTS

Antral SLPI levels were reduced in all Hp-infected patients (NUD, DU, GC) by about 75% (1,494-1,826 pg/50 microg protein) compared to Hp-negative NUD (6,563 pg/50 microg protein, p<0.001, ANOVA). Tumor tissue had twofold higher SLPI levels than surrounding tumor-free gastric mucosa (3,900 vs. 1,826 pg/50 microg protein, p=0.013), but revealed reduced SLPI levels compared to Hp-negative NUD patients (p=0.067). No differences were found between SLPI expression of intestinal and diffuse GC. SLPI transcript levels were unchanged throughout all groups and locations implying that transcriptional regulation of SLPI is not involved.

CONCLUSION

Local down-regulation of SLPI in antral mucosa is a general phenomenon of Hp-related diseases.