Inflammatory Response In Gastric Mucosa Research Articles

Characterization, mechanism and in vivo validation of Helicobacter pylori antagonism by probiotics screened from infants' feces and oral cavity.

Helicobacter pylori (H. pylori) infection is a major cause of chronic gastritis, intestinal metaplasia, and gastric carcinoma. Antibiotics, the conventional regimen for eliminating H. pylori, cause severe bacterial resistance, gut dysbiosis and hepatic insufficiency. Here, fifty lactic acid bacteria (LAB) were initially screened out of 266 strains obtained from infants' feces and oral cavity. The antagonistic properties of these 50 strains against H. pylori were investigated. Based on eight metrics combined with principal component analysis, three LAB with probiotic function and excellent anti-H. pylori capacity were affirmed. Combining dynamics test, metabolite assays, adhesion assays, co-cultivation experiments, and SEM and TEM observations, LAB were found to antagonize H. pylori by causing coccoid conversion and intercellular adhesion. Furthermore, it was found that LAB antagonized H. pylori by four pathways, i.e., production of anti-H. pylori substances, inhibition of H. pylori colonization, enhancement of the gastric mucosal barrier, and anti-inflammatory effect. In addition, animal model experiments verified that the final screened superior strain L. salivarius NCUH062003 had anti-H. pylori activity in vivo. LAB also reduced IL-8 secretion, ultimately alleviating the inflammatory response of gastric mucosa. Whole genome sequencing (WGS) data showed that the NCUH062003 genome contained the secondary metabolite biosynthesis gene cluster T3PKS. Furthermore, NCUH062003 had a strong energy metabolism and substance transport capacity, and produced a small molecule heat stable peptide (SHSP, 4.1-6.5 kDa). Meanwhile, LAB proved to be safe through antibiotic susceptibility testing and CARD database comparisons.

An integrated network analysis, RNA-seq and in vivo validation approaches to explore the protective mechanism of Mongolian medicine formulae Ruda-6 against indomethacin-induced gastric ulcer in rats.

Gastric ulcer (GU) is one of the most prevalent digestive diseases that seriously affects people's health. Previous studies have demonstrated the anti-GU effect of Ruda-6 (RD-6), a classic formulae of traditional Mongolian medicine. However, the underlying mechanism of RD-6 against GU remains elusive. Thus, we conducted an integrative approach of network analysis, RNA-seq, and in vivo validation experiment to elucidate the therapeutic mechanisms of RD-6 in preventing GU. A network analysis was performed to predict the potential targets of RD-6. Rats were pretreated with RD-6 at different doses for 21days, followed by GU induction with indomethacin injection. The ulcer index and inhibition rates were calculated, and the levels of inflammatory related factors were determined by ELISA. The gastroprotective mechanism of RD-6 against ulceration was verified by RNA-seq and the key pathway was detected by in vivo validation. As the network analysis predicted, RD-6 exerts anti-GU effects by regulating 75 targets and 160 signaling pathways. Animal experiment results suggested that pretreatment with RD-6 significantly ameliorated the gastric mucosal injury and inflammatory response, as evidenced by a reduced ulcer index, decreased interleukin (IL)-1β, IL-6, and IL-17 levels, and increased prostaglandin E2 (PGE2) levels in the GU model rats induced by indomethacin. RNA-seq data identified four potential hub genes that were primarily involved in the IL-17 signaling pathway. Furthermore, in vivo validation experiment showed that RD-6 inhibited the IL-17 signaling pathway by down-regulating the expression of IL17RA, proto-oncogene C-Fos (FOS), IL1B and prostaglandin-endoperoxide synthase 2 (PTGS2). Taken together, the present study provides evidence that RD-6 could effectively protect against indomethacin-induced GU, which might be attributed to suppressed inflammation. The IL-17 signaling pathway may be one of the crucial mechanisms that mediates the effect of RD-6.

Helicobacter pylori regulates TIFA turnover in gastric epithelial cells.

The human pathogen Helicobacter pylori induces a strong inflammatory response in gastric mucosa manifested by the recruitment of neutrophils and macrophages to the places of infection, and by changes in epithelial integrity and function. At the molecular level, this innate immune response is essentially dependent on the activation of NF-κB transcription factors regulating the expression of chemotactic factors, e.g., IL-8. Recently, it has been demonstrated that the NF-κB signaling pathway is triggered by the bacterial heptose metabolites, which activate the host ALPK1-TIFA axis. TIFA has been suggested to promote oligomerization and activity of the E3 ubiquitin ligase TRAF6, which further stimulates TAK1-IKK signaling. Here, we demonstrate that ALPK1-dependent TIFA activation in H. pylori-infected gastric epithelial cells is followed in time by a decline in TIFA levels, and that this process is impeded by inhibitors of the proteasomal and lysosomal degradation. According to our data, TRAF2, TRAF6, TAK1 or NEMO are not required for TIFA degradation. Additionally, H. pylori promotes the interaction of TIFA with free polyubiquitin as well as with optineurin, TAX1BP1 and LAMP1, which are known protein adaptors involved in intracellular trafficking to lysosomes.

APRIL-producing eosinophils are involved in gastric MALT lymphomagenesis induced by Helicobacter sp infection

The roles of the inflammatory response and production of a proliferation-inducing ligand (APRIL) cytokine in gastric mucosa-associated lymphoid tissue (MALT) lymphomagenesis induced by Helicobacter species infection are not clearly understood. We characterized the gastric mucosal inflammatory response associated with gastric MALT lymphoma (GML) and identified APRIL-producing cells in two model systems: an APRIL transgenic mouse model of GML induced by Helicobacter infection (Tg-hAPRIL) and human gastric biopsy samples from Helicobacter pylori-infected GML patients. In the mouse model, polarization of T helper 1 (tbet), T helper 2 (gata3), and regulatory T cell (foxp3) responses was evaluated by quantitative PCR. In humans, a significant increase in april gene expression was observed in GML compared to gastritis. APRIL-producing cells were eosinophilic polynuclear cells located within lymphoid infiltrates, and tumoral B lymphocytes were targeted by APRIL. Together, the results of this study demonstrate that the Treg-balanced inflammatory environment is important for gastric lymphomagenesis induced by Helicobacter species, and suggest the pro-tumorigenic potential of APRIL-producing eosinophils.

Changes in the severity of gastric mucosal inflammation associated with Helicobacter pylori in humans coinfected with intestinal helminths.

Though a few studiesin animal models suggest that intestinal helminths (IH) favorably affect evolution of gastritis associated with Helicobacter pylori (H. pylori) the studies supporting this conceptin humans are only a few and are based onserologicaldata. To evaluate the possible influence of IH on the human gastric mucosa, three groups of Venezuelan adults with gastropathy (endoscopically diagnosed) were studied: H. pylori-/IH- (n = 17), H. pylori+/IH- (n = 18), and H. pylori+/IH+ (n = 11). Histological analysis (hematoxylin-eosin) and immunohistochemical staining (peroxidase) for cytokines interleukin-1beta (IL-1β), tumor necrosis factor alpha (TNF-α), gamma interferon (IFN-γ), and interleukin 4 (IL-4) were undertaken in gastricantral biopsies. Expression of the four cytokines was detected in all individuals in varying degrees, but proinflammatory cytokines were expressed in a higher degree in the H. pylori+/IH- group, mainly IL-1β (Th1-dominant immune response), associated with a higher degree of both histological inflammation and gastric cancer risk index (GCRI), ascompared to the H. pylori-/IH- group. In contrast, an increased expression of IL-4 and a reduced expression of proinflammatory cytokines (Th2-dominant response), plus the tendency to a lower degree of mononuclear infiltration, mucosal atrophy in gastric corpus, and GCRI, were evidenced in the coinfected group. Thefindings of the present study is perhaps the first histological evidence ofa possible modulatory effect ofIH on the gastric mucosal inflammatory response due toH. pylori infectionin humans.

Factors associated with failure of Helicobacter pylori eradication.

Helicobacter pylori (Hp) infection is closely related to chronic active gastritis, peptic ulcer, mucosa-associated lymphoid tissue (MALT) lymphoma, and gastric cancer, and is also associated with some parenteral diseases. Eradication of Hp can significantly improve gastric mucosal inflammatory response, prevent or delay gastric mucosal atrophy, intestinal metaplasia and its development, partially reverse atrophy, and reduce the risk of gastric cancer in varying degrees. In recent years, the eradication failure rate has increased. There are many reasons for the failure of Hp eradication. Previous studies have suggested that Hp resistance to antibiotics is the main cause of eradication failure, but recent studies have found that poor compliance is the main reason.

Upexpression of BHLHE40 in gastric epithelial cells increases CXCL12 production through interaction with p-STAT3 in Helicobacter pylori-associated gastritis.

BHLHE40, a member of the basic helix-loop-helix transcription factor family, has been reported to play an important role in inflammatory diseases. However, the regulation and function of BHLHE40 in Helicobacter pylori (H pylori)-associated gastritis is unknown. We observed that gastric BHLHE40 was significantly elevated in patients and mice with H pylori infection. Then, we demonstrate that H pylori-infected GECs express BHLHE40 via cagA-ERK pathway. BHLHE40 translocates to cell nucleus, and then binds to cagA protein-activated p-STAT3 (Tyr705). The complex increases chemotactic factor CXCL12 expression (production). Release of CXCL12 from GECs fosters CD4+ T cell infiltration in the gastric mucosa. Our results identify the cagA-BHLHE40-CXCL12 axis that contributes to inflammatory response in gastric mucosa during H pylori infection.

Helicobacter pylori Infection Aggravates Dysbiosis of Gut Microbiome in Children With Gastritis.

Introduction: Helicobacter pylori infection consistently leads to chronic and low degree of inflammatory response in gastric mucosa and is closely related with gastrointestinal and extra-gastric diseases. Effects of local microbiome in the stomach have been studied in adults and children with H. pylori infection. It is, however, not known whether the intestinal microbial community differs in children with varying H. pylori infection. The aim of this study is to characterize the altered composition of microbiome induced by H. pylori infection and in gastritis.Materials and Methods: This study involved 154 individuals, including 50 children affected by H. pylori-induced gastritis, 42 children with H. pylori-negative gastritis, and 62 healthy controls. Gut microbiome composition was analyzed using 16S rRNA gene-based pyrosequencing. Fecal bacterial diversity and composition were then compared.Results: On the basis of an analysis of similarities and differences, we found that children with H. pylori-induced gastritis exhibited gut bacteria dysbiosis. The ratio of Firmicutes/Bacteroidetes (F:B) at the phylum level had dramatically decreased in H. pylori-positive gastritis group (HPG) and H. pylori-negative gastritis group (HNG), compared with the healthy control group (HCG). At the family and genus levels, relative abundance of Bacteroidaceae and Enterobacteriaceae was prevalent in HPG and HNG, whereas relative abundance of Lachnospiraceae, Bifidobacteriaceae, and Lactobacillaceae was seen in HCG. Prevalence of different taxa of gut microbiome at the class, order, family, and genus levels was also observed among the three groups.Conclusions: Gastritis can cause changes in composition of fecal microbiome, which is exacerbated by H. pylori infection. These changes in gut microbiome may be related to drug resistance and development of chronic gastrointestinal diseases.

Syk: a new target for attenuation of Helicobacter pylori-induced gastric mucosal inflammatory responses.

The magnitude of gastric mucosal inflammatory response to H. pylori relies primarily on the extent of its key endotoxin, LPS, engagement of Toll-like receptor-4 (TLR4) and the initiation of signal transduction events converging on mitogen-activated protein kinase (MAPK) and IκB complex (IKK) cascades. These cascades, in turn, exert their control over the assembly of transcription factors, NFκB and AP1, implicated in the induction of the expression of iNOS and COX-2 proinflammatory genes. The LPS-induced TLR4 activation and the ensuing phosphorylation of its intracellular tyrosine domain by Src-family kinases not only leads to recruitment to the cytoplasmic domain of TLR4 of adaptor molecules directly involved in propagation of the signaling cascades converging on MAPK and IKK, but also provides a propitious docking site for a non-receptor tyrosine kinase, spleen tyrosine kinase (Syk), the activation of which apparently leads to upregulation in the expression of proinflammatory genes. Here, we review the pathways engaged by H. pylori in the recruitment and interaction of Syk with TLR4 in gastric mucosa, and discuss the cascades involved in Syk-mediated amplification in proinflammatory signaling. We focus, moreover, on the potential role of drugs targeting Syk and TLR4 in the treatment of H. pylori-related gastric disease.

SUMOs Mediate the Nuclear Transfer of p38 and p-p38 during Helicobacter Pylori Infection.

The p38 mitogen activated protein kinase (MAPK) signaling pathway has been suggested to play a significant role in the gastric mucosal inflammatory response to chronic Helicobacter pylori (H. pylori) infection. Nuclear translocation is thought to be important for p38 function, but no nuclear translocation signals have been found in the protein and no nuclear carrier proteins have been identified for p38. We have investigated the role of small ubiquitin-related modifier (SUMO) in the nuclear transfer of p38 in response to H. pylori infection. Exposure of human AGS cells to H. pylori induced the activation of p38 and the expression of SUMOs, especially SUMO-2. SUMO knockdown counteracted the effect of H. pylori infection by decreasing the resulting p38 mediated cellular apoptosis through a reduction in the nuclear fraction of phosphorylated p38. We identified a non-covalent interaction between SUMOs and p38 via SUMO interaction motifs (SIMs), and showed that SUMO-dependent nuclear transfer of p38 was decreased upon mutation of its SIMs. This study has identified a new pathway of p38 nuclear translocation, in response to H. pylori infection. We conclude that in the presence of H. pylori SUMO-2 has a major role in regulating nuclear levels of p38, through non-covalent SUMO-p38 interactions, independent of the p38 phosphorylation state.

Helicobacter pylori LPS-induced gastric mucosal spleen tyrosine kinase (Syk) recruitment to TLR4 and activation occurs with the involvement of protein kinase Cδ.

Spleen tyrosine kinase (Syk) has emerged recently as a major effector of proinflammatory genes expression induced by LPS-elicited TLR4 activation, and manifested by the up-amplification in the production of inflammatory mediators, including PGE2 and NO. Here, we investigated the nature of factors involved in the recruitment and interaction of Syk with TLR4 in gastric mucosa in response to H. pylori LPS. We show that stimulation of gastric mucosal cells with the LPS leads to localization of Syk with the membrane-associated TLR4 complex and its activation through phosphorylation on Tyr. Furthermore, we reveal that the membrane translocation of Syk upon the LPS stimulation occurs with the involvement of protein kinase Cδ (PKCδ)-mediated phosphorylation of Syk on Ser. Thus, our findings demonstrate that H. pylori LPS-induced up-regulation in Syk activity proceeds through the stage of PKCδ-mediated Syk phosphorylation on Ser, required for its recruitment to the membrane-anchored TLR4, followed by the kinase activation through phosphorylation on Tyr. Hence, the phase of PKCδ-mediated Syk phosphorylation on Ser affects the extent of amplification in gastric mucosal inflammatory response to H. pylori.

Role of LPS-elicited signaling in triggering gastric mucosal inflammatory responses to H. pylori: modulatory effect of ghrelin.

Infection with Helicobacter pylori is a primary culprit in the etiology of gastric disease, and its cell-wall lipopolysaccharide (LPS) is recognized as a potent endotoxin responsible for triggering a pattern of the mucosal inflammatory responses. The engagement by the LPS of gastric mucosal Toll-like receptor 4 (TLR4) leads to initiation of signal transduction events characterized by the activation of mitogen-activated protein kinase (MAPK) cascade, induction of phosphoinositide-specific phospholipase C (PLC)/protein kinase C (PKC)/phosphatidylinositol 3-kinase (PI3K) pathway, and up-regulation in Src/Akt. These signaling events in turn exert their influence over H. pylori-elicited excessive generation of NO and PGE2 caused by the disturbances in nitric oxide synthase and cyclooxygenase isozyme systems, increase in epidermal growth factor receptor transactivation, and the induction in matrix metalloproteinase-9 (MMP-9) release. Interestingly, the extent of gastric mucosal inflammatory response to H. pylori is influenced by a peptide hormone, ghrelin, the action of which relays on the growth hormone secretagogue receptor type 1a (GHS-R1a)-mediated mobilization of G-protein dependent transduction pathways. Yet, the signals triggered by TLR-4 activation as well as those arising through GHS-R1a stimulation converge at MAPK and PLC/PKC/PI3K pathways that form a key integration node for proinflammatory signals generated by H. pylori LPS as well as for those involved in modulation of inflammation by ghrelin. Hence, therapeutic targeting these signals' convergence and integration node could provide a novel and attractive opportunities for developing more effective treatments of H. pylori-related gastric disease.

The effect of trimethylamine N-oxide on Helicobacter pylori-induced changes of immunoinflammatory genes expression in gastric epithelial cells

Colonization of Helicobacter pylori (H. pylori) induces immune and inflammatory response in gastric mucosa. Trimethylamine N-oxide (TMAO), from diet and metabolite through the action of gut microbiota, has been linked to inflammatory diseases. To investigate the effects of TMAO and H. pylori infection on gene expression in gastric epithelial cells, Human gene chip Affymetrix HTA 2.0 was used in this study. 1312 genes were identified as differentially expressed genes in GES-1 cells with H. pylori and TMAO co-treatment compared to the control. GO and KEGG analyses indicated that the functions of these differentially expressed genes were related closely with immune inflammation. GO-network showed that Toll-like receptor signaling pathway was the most important biological processes and 49 up-regulated genes related to immune inflammation were obtained. The synergistic effects of H. pylori and TMAO enhanced the genes expression of IL-6, CXCL1, CXCL2, FOS and C3 related to immune inflammation in comparison with those of non-infected control cells, H. pylori-infected cells, and TMAO-stimulated cells. RT-PCR verified the expression levels of IL-6, CXCL1. Additionally, expression levels of 2053 genes were altered and 52 immunoinflammatory genes were upregulated in comparison with H. pylori-infected cells. This study suggested that TMAO altered the expression levels of immunoinflammatory genes induced by H. pylori infection, and the synergistic effects of H. pylori and TMAO provided novel insights into the development of chronic gastritis, gastric ulcer and gastric cancer.

Increased Proliferative Activity Accompanies the Local Inflammatory Response of Gastric Mucosa After Intragastric Balloon Insertion

The use of BioEnterics intragastric balloon (BIB) is progressively increasing, owing to the fact that morbid obesity becomes a global epidemic together with risks of bariatric surgery. Yet, the possible local BIB effect on gastric mucosa is not clearly elucidated. The aim of the current study was to assess the histological changes occurring in the gastric mucosa post-BIB insertion. Gastric mucosa biopsy was obtained from 87 cases of morbid obesity both pre-BIB and 6months post-BIB insertion to compare the local changes by histological and immunohistochemical analysis. An inflammatory reaction was detected in the post-BIB mucosa which displayed a positive CD20, CD3 (p<0.05), and the proliferation index (Ki67) increased significantly compared with that of the pre-BIB cases. The Ki67 index showed a significant positive correlation with CD20 and CD3 immunoexpression in the post-BIB gastric mucosae. Our results demonstrated a possible increase in the gastric proliferative activity after BIB insertion accompanied with a remarkable local inflammatory reaction. Although these findings may be reactive and transient, endoscopic follow-up is recommended for early detection of further pathological changes.

Role of protein kinase D2 phosphorylation on Tyr in modulation by ghrelin of Helicobacter pylori-induced up-regulation in gastric mucosal matrix metalloproteinase-9 (MMP-9) secretion.

Matrix metalloproteinas-9 (MMP-9) is a glycosylated endopeptidase associated with host reaction to microbial endotoxins and also characterizes gastric mucosal inflammatory response to H. pylori infection. Here, we report on the factors involved in gastric mucosal MMP-9 secretion in response to H. pylori LPS, and the effect of hormone, ghrelin. We show that both the LPS-elicited induction in MMP-9 secretion and also the modulatory influence of ghrelin occur at the level of MMP-9 processing between the endoplasmic reticulum (ER) and Golgi. Further, we demonstrate that the LPS effect is associated with up-regulation in the activation of Arf1, a small GTPase of the ADP-ribosylation factor family, and the recruitment and phosphorylation of protein kinase D2 (PKD2), involved in the secretory cargo processing in the Golgi. Moreover, we reveal that the LPS-induced up-regulation in MMP-9 secretion is reflected in a marked increase in PKCδ-mediated PKD2 phosphorylation on Ser, while the modulatory effect of ghrelin is manifested by the SFK-PTKs-dependent phosphorylation of PKD2 on Tyr. Thus, our findings demonstrate the role of Arf1/PKD2 in mediation of H. pylori LPS-induced up-regulation in gastric mucosal MMP-9 secretion and suggest the modulatory mechanism of ghrelin action.

Helicobacter pylori-elicited induction in gastric mucosal matrix metalloproteinase-9 (MMP-9) release involves ERK-dependent cPLA2 activation and its recruitment to the membrane-localized Rac1/p38 complex.

Matrix metalloproteinases (MMPs) are a family of endopeptidases implicated in a wide rage of degenerative and inflammatory diseases, including Helicobacter pylori-associated gastritis, and gastric and duodenal ulcer. As gastric mucosal inflammatory responses to H. pylori are characterized by the rise in MMP-9 production, as well as the induction in mitogen-activated protein kinase (MAPK) and Rac1 activation, we investigated the role of Rac1/MAPK in the processes associated with the release of MMP-9. We show that H. pylori LPS-elicited induction in gastric mucosal MMP-9 release is associated with MAPK, ERK and p38 activation, and occurs with the involvement of Rac1 and cytosolic phospholipase A2 (cPLA2). Further, we demonstrate that the LPS-induced MMP-9 release requires ERK-mediated phosphorylation of cPLA2 on Ser(505) that is essential for its membrane localization with Rac1, and that this process necessitates p38 participation. Moreover, we reveal that the activation and membrane translocation of p38 to the Rac1-GTP complex plays a pivotal role in cPLA2-dependent enhancement in MMP-9 release. Hence, our findings provide a strong evidence for the role of ERK/cPLA2 and Rac1/p38/cPLA2 cascade in H. pylori LPS-induced up-regulation in gastric mucosal MMP-9 release.

Lack of association among TNF-α gene expression, -308 polymorphism (G > A) and virulence markers of Helicobacter pylori.

BackgroundTumor necrosis factor plays a critical role in the pathogenesis of gastric diseases such as gastric cancer, and an abnormal inflammatory response has frequently been observed in dyspeptic patients. Helicobacter pylori infection can induce a gastric mucosal inflammatory response that may be influenced by -308 (G > A) polymorphisms and gene expression of the TNF-α gene.MethodsOne hundred and thirty-four gastric biopsy samples were collected from patients of both genders (61♂ and 73♀, mean age 40.3 ± 24.2 years) with gastric symptoms. The -308 (G > A) polymorphism of TNF-α was characterized using polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The expression level was measured using real-time PCR, and relative quantification (RQ) was calculated using the comparative CT method (2-ΔΔCT).ResultsThe analysis revealed an increase in TNF-α gene expression in patients with gastritis; on the other hand, no statistical differences were observed in patients with gastric cancer. In addition, no association was found among -308 polymorphism genotypes, virulence markers, or TNF-α gene expression.ConclusionsHelicobacter pylori induces a large increase in TNF-α expression in patients with gastritis, regardless of tissue inflammation, but after the tissue becomes neoplastic, the presence of bacteria did not influence expression. These results suggest that the TNF-α pathway may play an important role in the progression from gastritis to gastric cancer

Regulatory role of guanine nucleotide exchange factor (GEF) Dock180 phosphorylation on Tyr/Ser in mediation of gastric mucosal Rac1 activation in response to Helicobacter pylori and ghrelin.

A small GTPase, Rac1, is recognized as an important modulator of the inflammatory responses to bacterial lipopolysaccharide (LPS) by affecting the processes of phospholipase C activation. The activation of Rac1 involves the exchange of GDP for GTP and is catalyzed by the guanine nucleotide exchange factors (GEFs). Here, we report on the gastric mucosal GEF, Dock180, activation in response to H. pylori PS, and the hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to up-regulation in Dock180 phosphorylation on Tyr and Ser that is accompanied by a massive rise in Rac1-GTP level, while the effect of ghrelin, manifested by a drop in Dock180 phosphorylation on Ser, is associated with a decrease in Rac1-GTP formation. Furthermore, we demonstrate that phosphorylation on Tyr remains under the control of the Src family protein tyrosine kinases (SFK-PTKs), and is accompanied by Dock180 membrane translocation, while phosphorylation of the membrane-localized Dock180 on Ser represents the stimulatory contribution of protein kinase Cδ (PKCδ) to Dock180 activation. Moreover, we reveal that the interaction between Dock180 and PKCδ is dependent on Dock180 Tyr phosphorylation as well as the activity of PKCδ. Thus, our findings point to the involvement of PKCδ in the LPS-induced up-regulation of Dock180 activation, and suggest the modulatory mechanism of ghrelin influence on the gastric mucosal inflammatory responses to H. pylori.

Mechanism of Rac1-induced amplification in gastric mucosal phospholipase Cγ2 activation in response to Helicobacter pylori: modulatory effect of ghrelin.

Membrane recruitment followed by targeted phosphorylation of specific Tyr and Ser residues and the interaction with Rac GTPases are the crucial parts of an elaborate mechanism of PLCγ2 activation essential for its role in linking the specific receptor responses to a variety of hormones and bacterial endotoxins with the intended intracellular targets. Here, we explored the involvement of Rac in mediation of PLCγ2 activation associated with gastric mucosal inflammatory responses to H. pylori LPS and the hormone, ghrelin. We show that stimulation of gastric mucosal cells with the LPS leads to the membrane translocation of Rac1 as well as PLCγ2, while the effect of ghrelin is manifested by elevation in the membrane PLCγ2 activation and suppression in Rac1 translocation. However, blocking the LPS-induced Rac1 translocation, while detrimental to the PLCγ2 activation, has no effect on its membrane translocation. We reveal further that PLCγ2, localized in the membrane in association with Rac1 following the LPS stimulation, exhibits a marked increase in phosphorylation on Ser, while the modulatory effect of ghrelin, manifested by a drop in Rac1 translocation, is associated with a distinct decrease in PLCγ2 phosphorylation on Ser. Thus, the results suggest that H. pylori-elicited increase in gastric mucosal PLCγ2 phosphorylation on Ser serves as an essential platform for Rac1 colocalization and amplification in PLCγ2 activation.

Repressed TGF-β signaling through CagA-Smad3 interaction as pathogenic mechanisms of &lt;i&gt;Helicobacter pylori&lt;/i&gt;-associated gastritis

Helicobacter pylori (H. pylori) infection causes chronic gastric inflammation, peptic ulceration, and gastric carcinogenesis, in which H. pylori cytotoxin-associated gene A (CagA) plays major pathogenic action. Since transforming growth factor-β (TGF-β) and its signaling also are principally implicated in either modulating gastric mucosal inflammatory responses or causing carcinogenesis and are attenuated after H. pylori infection, we hypothesized that dysregulated Smad signaling and repressed TGF-β might be core pathogenic mechanism for H. pylori-associated gastritis or carcinogenesis. Until now, no precise underlying mechanism how deranged TGF-β signaling developed after H. pylori infection relevant to various clinical manifestations remains unclear. In this study, we examined the molecular mechanism about the inhibition of TGF-β signaling by H. pylori CagA protein. H. pylori CagA significantly suppressed TGF-β/Smad transcriptional responses through critical inhibition of Smad3, though CagA interacted constitutively with Smad2, Smad3, and Smad4. CagA inhibited TGF-β-induced suppression of proinflammatory chemokines, such as IL-8, CXCL1 and CXCL3, as well as TGF-β-induced transcription of target genes. In conclusion, repressed TGF-β signaling associated with CagA-positive H. pylori infection could be an important determinant for the outcome of H. pylori infection. Therefore, TGF-β signaling is one of the important determinants to avoid from H. pylori CagA pathogenicity.