Sungil Jang

Polymorphism in the CagA EPIYA Motif Impacts Development of Gastric Cancer

ABSTRACT Helicobacter pylori causes diseases ranging from gastritis to peptic ulcer disease to gastric cancer. Geographically, areas with high incidences of H. pylori infection often overlap with areas with high incidences of gastric cancer, which remains one of the leading causes of cancer-related deaths worldwide. Strains of H. pylori that carry the virulence factor cytotoxin-associated gene A (cagA) are much more likely to be associated with the development of gastric cancer. Moreover, particular C-terminal polymorphisms in CagA vary by geography and have been suggested to influence disease development. We conducted a large-scale molecular epidemiologic analysis of South Korean strains and herein report a statistical link between the East Asian CagA EPIYA-ABD genotype and the development of gastric cancer. Characterization of a subset of the Korean isolates showed that all strains from cancer patients expressed and delivered phosphorylatable CagA to host cells, whereas the presence of the cagA gene did not strictly correlate to expression and delivery of CagA in all noncancer strains.

Epidemiological Link between Gastric Disease and Polymorphisms in VacA and CagA

ABSTRACT Gastritis, peptic ulcer disease, and gastric cancer are a few of the diverse disease manifestations that have been shown to be associated with infection by Helicobacter pylori. Why some individuals develop more severe forms of disease remains largely unknown. In this study, 225 South Korean strains were genotyped for vacA and then analyzed to determine if particular genotypes varied across disease state, sex, or cagA allele. Of these strains, 206 strains carried an s1/i1/m1 allele, 11 strains carried an s1/i1/m2 allele, and 8 strains carried an s1/i2/m2 allele. By using Fishers exact test, a statistical association between variations in the cagA and vacA alleles was identified (P = 0.0007), and by using log linear modeling, this variation was shown to affect the severity of disease outcome (P = 0.027). Additionally, we present evidence that variation within the middle region of VacA contributes significantly to the distribution of vacA alleles across gender (P = 0.008) as well as the association with disease outcome (P = 0.011). In this South Korean population, the majority of H. pylori strains carry the vacA s1/i1/m1 allele and the CagA EPIYA-ABD allele. These facts may contribute to the high incidence of gastric maladies, including gastric cancer.

Polymorphisms in the Intermediate Region of VacA Impact Helicobacter pylori-Induced Disease Development

ABSTRACT Helicobacter pylori is the etiological agent of diseases such as gastritis, gastric and duodenal ulcers, and two types of gastric cancers. While some insight has been gained into the etiology of these diverse manifestations, by and large, the reason that some individuals develop more severe disease remains elusive. Recent studies have focused on the roles of H. pylori toxins CagA and VacA on the disease process and have suggested that both toxins are intimately involved. Moreover, CagA and VacA are polymorphic within different H. pylori strains, and particular polymorphisms seem to show a correlation with the development of particular disease states. Among VacA polymorphisms, the intermediate region has recently been proposed to play a major role in disease outcome. In this article, we describe a detailed sequence analysis of the polymorphic intermediate region of vacA from strains obtained from a large South Korean population. We show that polymorphisms found at amino acid position 196 are associated with more severe disease manifestations. Additionally, polymorphisms found at amino acid position 231 are linked to disease in strains that carry the non-EPIYA-ABD allele of CagA. Collectively, these data help explain the impact of the VacA intermediate region on disease and lead to the hypothesis that there are allele-driven interactions between VacA and CagA.

Protective effect of Korean Red Ginseng extract against Helicobacter pylori-induced gastric inflammation in Mongolian gerbils

Helicobacter pylori-induced gastric inflammation includes induction of inflammatory mediators interleukin (IL)-8 and inducible nitric oxide synthase (iNOS), which are mediated by oxidant-sensitive transcription factor NF-κB. High levels of lipid peroxide (LPO) and increased activity of myeloperoxidase (MPO), a biomarker of neutrophil infiltration, are observed in H. pylori-infected gastric mucosa. Panax ginseng Meyer, a Korean herb medicine, is widely used in Asian countries for its biological activities including anti-inflammatory efficacy. The present study aims to investigate whether Korean Red Ginseng extract (RGE) inhibits H. pylori-induced gastric inflammation in Mongolian gerbils. One wk after intragastric inoculation with H. pylori, Mongolian gerbils were fed with either the control diet or the diet containing RGE (200 mg RGE/gerbil) for 6 wk. The following were determined in gastric mucosa: the number of viable H. pylori in stomach; MPO activity; LPO level; mRNA and protein levels of keratinocyte chemoattractant factor (KC, a rodent IL-8 homolog), IL-1β, and iNOS; protein level of phospho-IκBα (which reflects the activation of NF-κB); and histology. As a result, RGE suppressed H. pylori-induced mRNA and protein levels of KC, IL-1β, and iNOS in gastric mucosa. RGE also inhibited H. pylori-induced phosphorylation of IκBα and increases in LPO level and MPO activity of gastric mucosa. RGE did not affect viable H. pylori colonization in the stomach, but improved the histological grade of infiltration of polymorphonuclear neutrophils, intestinal metaplasia, and hyperplasia. In conclusion, RGE inhibits H. pylori-induced gastric inflammation by suppressing induction of inflammatory mediators (KC, IL-1β, iNOS), MPO activity, and LPO level in H. pylori-infected gastric mucosa.

The Geographic Origin of Helicobacter pylori Influences the Association of the homB gene with Gastric Cancer

ABSTRACT We found that South Korean Helicobacter pylori isolates predominantly carry homB at locus B and that there is no association between the homB allele and the cagA allele or the development of gastric cancer within this population. Uniquely, several East Asian strains carried multiple copies of the hom genes.

Helicobacter pylori bab Paralog Distribution and Association with cagA, vacA, and homA/B Genotypes in American and South Korean Clinical Isolates

Helicobacter pylori genetic variation is a crucial component of colonization and persistence within the inhospitable niche of the gastric mucosa. As such, numerous H. pylori genes have been shown to vary in terms of presence and genomic location within this pathogen. Among the variable factors, the Bab family of outer membrane proteins (OMPs) has been shown to differ within subsets of strains. To better understand genetic variation among the bab genes and to determine whether this variation differed among isolates obtained from different geographic locations, we characterized the distribution of the Bab family members in 80 American H. pylori clinical isolates (AH) and 80 South Korean H. pylori clinical isolates (KH). Overall, we identified 23 different bab genotypes (19 in AH and 11 in KH), but only 5 occurred in greater than 5 isolates. Regardless of strain origin, a strain in which locus A and locus B were both occupied by a bab gene was the most common (85%); locus C was only occupied in those isolates that carried bab paralog at locus A and B. While the babA/babB/- genotype predominated in the KH (78.8%), no single genotype could account for greater than 40% in the AH collection. In addition to basic genotyping, we also identified associations between bab genotype and well known virulence factors cagA and vacA. Specifically, significant associations between babA at locus A and the cagA EPIYA-ABD motif (P<0.0001) and the vacA s1/i1/m1 allele (P<0.0001) were identified. Log-linear modeling further revealed a three-way association between bab carried at locus A, vacA, and number of OMPs from the HOM family (P<0.002). En masse this study provides a detailed characterization of the bab genotypes from two distinct populations. Our analysis suggests greater variability in the AH, perhaps due to adaptation to a more diverse host population. Furthermore, when considering the presence or absence of both the bab and homA/B paralogs at their given loci and the vacA genotype, an association was observed. Our results highlight the multifactorial nature of H. pylori mediated disease and the importance of considering how the specific combinations of H. pylori virulence genes and their multiple interactions with the host will collectively impact disease progression.

Wogonin inhibits osteoclast formation induced by lipopolysaccharide.

To evaluate the inhibitory activity of wogonin against lipopolysaccharide (LPS)‐induced bone resorption, we investigated the effect of wogonin on osteoclastogenesis induced by LPS. Wogonin inhibited LPS‐induced osteoclastogenesis in co‐cultures of mouse calvaria‐derived osteoblasts and bone marrow‐derived pre‐osteoclasts. Wogonin also suppressed osteoclastogenesis in LPS‐injected mouse calvaria. In osteoblasts, the upregulation of receptor activator of nuclear factor‐κB (RANKL) expression and the downregulation of osteoprotegerin (OPG) expression by LPS were inhibited by wogonin. Wogonin and NS‐398, a COX‐2 inhibitor, suppressed LPS‐stimulated PGE2 production in osteoblasts. NS‐398 inhibited the effect of LPS on RANKL and OPG expression in osteoblasts. These results suggest that wogonin acts as an inhibitor of LPS‐induced osteoclastogenesis through downregulation of RANKL and upregulation of OPG expression via blockage of PGE2 production. Based on these results, wogonin has potential for use as a therapeutic agent in bacteria‐induced bone resorption. Copyright

N-acetylcysteine prevents the development of gastritis induced by Helicobacter pylori infection

Helicobacter pylori (H. pylori) is a human gastric pathogen, causing various gastric diseases ranging from gastritis to gastric adenocarcinoma. It has been reported that combining N-acetylcysteine (NAC) with conventional antibiotic therapy increases the success rate of H. pylori eradication. We evaluated the effect of NAC itself on the growth and colonization of H. pylori, and development of gastritis, using in vitro liquid culture system and in vivo animal models. H. pylori growth was evaluated in broth culture containing NAC. The H. pylori load and histopathological scores of stomachs were measured in Mongolian gerbils infected with H. pylori strain 7.13, and fed with NAC-containing diet. In liquid culture, NAC inhibited H. pylori growth in a concentration-dependent manner. In the animal model, 3-day administration of NAC after 1 week from infection reduced the H. pylori load; 6-week administration of NAC after 1 week from infection prevented the development of gastritis and reduced H. pylori colonization. However, no reduction in the bacterial load or degree of gastritis was observed with a 6-week administration of NAC following 6-week infection period. Our results indicate that NAC may exert a beneficial effect on reduction of bacterial colonization, and prevents the development of severe inflammation, in people with initial asymptomatic or mild H. pylori infection.

Role of bacterial γ-glutamyltranspeptidase as a novel virulence factor in bone-resorbing pathogenesis.

Mammalian γ-glutamyltranspeptidase (GGT) has been identified as a bone-resorbing factor. Since GGT of Bacillus subtilis exhibits similarity in their primary structure and enzymatic characteristics with mammalian GGTs, the bone-resorbing activity of bacterial GGT was examined in this study. Osteoclastogenesis was performed in a co-culture system of mouse calvaria-derived osteoblasts and bone marrow cells. A conditioned medium from GGT-overproducing B. subtilis culture showed significantly higher activity of osteoclast formation than a conditioned medium from wild-type B. subtilis culture. Recombinant GGT (rGGT) of wild-type B. subtilis and an enzymatic activity-defected rGGT of B. subtilis 2288 mutant were expressed in Escherichia coli and purified using His tag. Both purified rGGTs induced similar levels of osteoclastogenesis, suggesting that B. subtilis GGT possesses virulent bone-resorbing activity and its activity is probably independent of its enzymatic activity. Furthermore, a recombinant protein of B. subtilis GGT heavy subunit (Bs rGGT/H) showed strong activity of osteoclastogenesis while the light subunit failed to show strong activity, suggesting that the bone-resorbing activity is mainly located at the heavy subunit. More importantly, the GGT enzymatic activity may not be required for this virulence activity since the light subunit contains the catalytic pocket. In addition, B. subtilis rGGT stimulated mRNA expressions of receptor activator of nuclear factor kappa-B ligand (RANKL) and cyclooxygenase-2 (COX-2), while an osteoprotegerin inhibited the osteoclast formation induced by Bs rGGT/H. This is the first demonstration that bacterial GGT itself is sufficient to act as a bone-resorbing virulence factor via RANKL-dependent pathway. Therefore, it can be hypothesized that GGT of periodontopathic bacteria may play an important role as a virulence factor in bone destruction.

Complementation System for Helicobacter pylori

Previously Langford et al. (2006) developed the pIR203C04 complementation system for Helicobacter pylori, which can be used to complement and restore phenotypic effects in H. pylori mutant, and furthermore they used the complementation system in vivo experiments to animals without altering the ability of strain SSI to colonize mice. In their previous study, the pIR203C04 was able to transform 26695, SSI, J99, and 43504 H. pylori strains by an electroporation method. However, in the present study using a natural transformation the pIR203C04 transformed only 26695 H. pylori but not SSI, J99, 7.13, and G27 H. pylori strains. Since the useful complementation system has a limitation of narrow selection among H. pylori strains, we redesigned the complementation system for the improvement. The same intergenic chromosomal site between hp0203 and hp0204 was utilized for the new complementation system because the insertion at the intergenic site didn’t show any polar effects and disruption of other H. pylori genes. The genome sequence analysis showed that the intergenic regions among H. pylori strains may have too low homology to each others to do a homologous recombination. Thus, in addition to the short intergenic region, the fragments of the new complementation system included 3′ conserved parts of hp0203 and hp0204 coding regions. Between the fragments there are a chloramphenicol acetyltransferase cassette and multicloning sites, resulting in pKJMSH. DNA fragment of the interest can be cloned into the multicloning sites of pKJMSH and the fragment can be integrated at the intergenic region of H. pylori chromosome by the homologous recombination. Indeed, by the natural transformation, pKJMSH was able to transform all five H. pylori strains of 26695, SSI, J99, 7.13, and G27, which are common for the investigation of molecular pathogenesis. Thus, the new pKJMSH complementation system is applicable to most H. pylori wild-type stains.