Nucleotide-binding oligomerization domain 1 and gastrointestinal disorders

Nucleotide-binding oligomerization domain 1 (NOD1) is an intracellular sensor that detects small peptides derived from the cell wall component of intestinal microflora. NOD1 is expressed in both non-hematopoietic cells such as epithelial cells and hematopoietic cells such as antigen-presenting cells. Detection of its ligand by NOD1 leads to innate immune responses through activation of nuclear factor kappa B and type I interferon as well as induction of autophagy. Innate immune responses through NOD1 activation play an indispensable role both in host defense against microbial infection and in the development of gastrointestinal disorders. Of particular importance, NOD1-mediated innate immune responses are associated with mucosal host defenses against Helicobacter pylori (H. pylori) infection of the stomach and with the development of pancreatitis. In this review, we discuss the molecular mechanisms by which NOD1 activation leads to the development of H. pylori-related gastric diseases and pancreatitis.

Estrogen-Dependent Nrf2 Expression Protects Against Reflux-Induced Esophagitis

BACKGROUND

Gastroesophageal reflux disease is more common in males than in females. The enhanced antioxidative capacity of estrogen in females might account for the gender difference. Nuclear factor erythroid 2-related factor 2 (Nrf2) plays a pivotal role in the host defense mechanism against oxidative stress.

AIMS

This study aimed to clarify the role of Nrf2 in reflux-induced esophageal inflammation, focusing on the gender difference and nitric oxide.

METHODS

Gastroesophageal reflux was surgically induced in male and female rats. Nitrite and ascorbic acid were administered for 1 week to provoke nitric oxide in the esophageal lumen. Male rats with gastroesophageal reflux were supplemented with 17β-estradiol or tert-butylhydroquinone, an Nrf2-inducing reagent. Esophageal squamous cell carcinoma KYSE30 cells were treated with 17β-estradiol. Nrf2 expression was examined by Western blotting and quantitative real-time PCR. Antioxidant gene expression profiles were examined by a PCR array.

RESULTS

In the presence of nitric oxide, reflux-induced esophageal damage was less evident, whereas esophageal expression of Nrf2 and its target genes such as Nqo1 was more evident in female or male rats supplemented with 17β-estradiol than in male rats. 17β-Estradiol increased nuclear Nrf2 expression in KYSE30 cells. tert-Butylhydroquinone increased tissue Nqo1 mRNA expression, leading to a reduction in reflux-induced esophageal damage.

CONCLUSIONS

Estrogen-dependent Nrf2 expression might contribute to protection against the development of gastroesophageal reflux disease in females.

Smoking history and severe atrophic gastritis assessed by pepsinogen are risk factors for the prevalence of synchronous gastric cancers in patients with gastric endoscopic submucosal dissection: a multicenter prospective cohort study

BACKGROUND

No studies have evaluated the relationship between lifestyle and synchronous gastric cancers (SGCs) in patients with endoscopic submucosal dissection (ESD) for early gastric cancers (EGCs). Using data from the Tohoku gastrointestinal (GI) study, we aimed to identify factors associated with SGCs.

METHODS

Tohoku GI study is a multicenter prospective cohort study investigating the relationship between lifestyle and metachronous gastric cancers. Patients who had a schedule to undergo ESD for primary EGCs were enrolled. We used logistic regression analysis to examine the relationship of 15 candidate factors, including lifestyle, with the prevalence of SGCs in this study.

RESULTS

Of 850 patients between 2016 and 2019, 16.0% (136 patients) had SGCs. In multivariate analysis, smoking history (odds ratio [OR], 1.93; p = 0.048) and severe atrophic gastritis assessed by pepsinogen (OR, 1.92; p = 0.004) were risk factors for the prevalence of SGCs. Regarding smoking, current smoking (OR, 2.33; p = 0.021), but not former smoking (OR, 1.76; p = 0.098), was a significant risk factor for its prevalence. In the stratified analysis, severe atrophic gastritis assessed by pepsinogen was a risk factor in patients without Helicobacter pylori (H. pylori) eradication (OR, 2.10; p = 0.002), but not a risk factor in those with H. pylori eradication (OR, 0.75; p = 0.737).

CONCLUSION

Smoking history was a risk factor for the prevalence of SGCs in patients with ESD for EGCs, and severe atrophic gastritis assessed by pepsinogen was also a risk factor when H. pylori was not eradicated.

Deficient aldehyde dehydrogenase 2 is associated with increased risk for esophageal squamous cell carcinoma in the presence of gastric hypochlorhydria

OBJECTIVE

In Orientals, deficient aldehyde dehydrogenase 2 (ALDH2) is associated with an increased risk for esophageal squamous cell carcinoma (ESCC). The local metabolism of carcinogenic acetaldehyde in the upper gastrointestinal tract could be involved in the association, but the underlying mechanism has not been fully elucidated. Since an anacidic stomach can promote bacteria-catalyzed local acetaldehyde production, the gastric acid level could also affect acetaldehyde metabolism. This study investigated whether ALDH2-related susceptibility to ESCC differs depending on the gastric secretion level.

MATERIAL AND METHODS

Sixty-two patients with ESCC and sex- and age-matched normal controls were enrolled in this study. ALDH2 polymorphism was analyzed by polymerase chain-restriction fragment length polymorphism, and those with an inactive allele (ALDH2-1/2-2 or ALDH2-2/2-2) were defined as ALDH2 deficient. Gastrin-stimulated acid output was assessed by endoscopic gastrin test and hypochlorhydria was defined as 0.6 mEq/10 min or lower. Multiple logistic regression analyses were used to adjust for other potential confounders.

RESULTS

ALDH2 deficiency or hypochlorhydria was more prevalent in ESCC compared with controls and both showed increased independent associations with ESCC in multivariate analysis. Stratified analysis by the gastric acid secretion level revealed that the associations between the ALDH2 genotype and ESCC differed according to the individual gastric acid secretion levels and that ALDH2 deficiency was a significant risk factor for ESCC exclusively in individuals with hypochlorhydria with an odds ratio (95% confidence interval): 5.0 (1.2-21.2).

CONCLUSION

Microbial production of carcinogen acetaldehyde in the presence of gastric hypochlorhydria is most probably involved in the mechanism of ALDH2-related susceptibility to ESCC.

Linked-color Imaging May Help Improve the Visibility of Superficial Barrett's Esophageal Adenocarcinoma by Increasing the Color Difference

Objective Linked-color imaging (LCI), a new technology for image-enhanced endoscopy, emphasizes the color of the mucosa, and its practicality in the detection of early gastric and colon cancers has been reported. However, whether or not LCI is useful for the diagnosis of Barrett's adenocarcinoma (BA) has been unclear. In this study, we explored whether or not LCI enhances the color difference between a BA lesion and the surrounding mucosa. Methods Twenty-one lesions from 20 consecutive patients with superficial BA who underwent endoscopic submucosal dissection between November 2014 and September 2017 were retrospectively examined. The color differences (ΔE*) between the inside and outside of the lesion were evaluated retrospectively using white-light imaging (WLI), blue-light imaging (BLI), and LCI objectively, based on a Commission Internationale de l'Eclairage (CIE) lab color system. Furthermore, we compared the morphology, color, and circumferential location of the lesion. Results The median values of the color difference (ΔE*) in WLI and BLI were 9.1 and 5.8, respectively, and no difference was observed. In LCI, the median color difference was 17.6, which was higher than that of WLI and BLI. Regardless of the morphology, color, and circumferential location of BA lesions, the color difference was larger in LCI than in WLI. Conclusion LCI increases the color difference between the BA and the surrounding Barrett's mucosa.

Gene polymorphisms of NOD1 and interleukin-8 influence the susceptibility to erosive esophagitis in Helicobacter pylori infected Japanese population

Helicobacter pylori (H. pylori) infection generally protects patients from erosive esophagitis through reduction of acid production due to gastric mucosal atrophy. However, there are H. pylori infected patients who still have erosive esophagitis. The reason for this discrepancy remains unclear. We have previously reported that polymorphisms in IL-8 promoter region influence the susceptibility of H. pylori related diseases. On the other hand, nucleotide-binding oligomerization domain 1 (NOD1) is known to play an important role in H. pylori infection. Hence, we hypothesized polymorphisms of these two molecules in H. pylori infected patients may influence the susceptibility to erosive esophagitis. Genomic DNA was extracted from 312 H. pylori infected Japanese, consisting of 110 patients with erosive esophagitis and 202 healthy controls. ND1+32656 T/GG and IL-8-251 A/T polymorphisms were genotyped by direct sequencing. ND1+32656 GG allele and IL-8-251 T/T allele increased the risk of erosive esophagitis with odds ratio (OR) of 1.9 (95% confidence interval (CI) 1.1-3.0, p=0.013) and 1.7 (95% CI 1.1-2.8, p=0.036), respectively. Combination of these two alleles increased the risk with OR of 3.2(95% CI 1.6-6.5, p=0.001). In conclusion, ND1+32656 GG and IL-8-251 T/T allele may be associated with less reactivity to H. pylori infection, and may increase the risk of erosive esophagitis even in H. pylori infected Japanese population.

The balance between 4-hydroxynonenal and intrinsic glutathione/glutathione S-transferase A4 system may be critical for the epidermal growth factor receptor phosphorylation of human esophageal squamous cell carcinomas

Oxidative stress might participate in the carcinogenesis of human esophageal squamous cell carcinomas (hESCC). 4-Hydroxynonenal (HNE) is a major product of membrane lipid peroxidation with short life. It might act as an important mediator through the generation of adducts and activate epidermal growth factor receptor (EGFR) signaling. It is mainly trapped with glutathione (GSH) and catalyzed by glutathione S-transferases (GSTs). This study aimed to elucidate the possible participation of HNE, GSH/GST system, and EGFR signaling in hESCC development. Immunohistochemistry of HNE adducts, EGFR, and phosphorylated EGFR (pEGFR) was performed with hESCC specimens. The effect of HNE on the phosphorylation of EGFR and its downstream PhospholipaseCγ1 (PLCγ1) was investigated with KYSE30 cell-line. Pretreatment with GSH inducer N-acetylcysteine (NAC) or GSH inhibitor Buthionine sulfoximine (BSO) and mandatory transfection of hGSTA4 gene in KYSE30 were conducted to investigate the relationship between HNE and GSH/GST system. Immunoreactants of HNE adducts, EGFR, and pEGFR were increased in hESCC compared to non-cancerous epithelium with positive correlations. The treatment of HNE ligand-independently induced the phosphorylation of EGFR and PLCγ1 accompanying the diminishment of intracellular GSH level. NAC increased GSH contents but BSO decreased in dose-dependent manners. Reflecting changes in GSH, HNE-induced EGFR phosphorylation was suppressed by NAC, whereas it was promoted by BSO. Mandatory expression of hGSTA4 suppressed HNE-induced events. We first demonstrated that the ligand-independent activation of EGFR by the balance between the stimulation of HNE and the prevention of intrinsic GSH/GST system might participate in the development of hESCC.

The role of nitric oxide in the induction of caudal-type homeobox 2 through epidermal growth factor receptor in the development of Barrett's esophagus

OBJECTIVE

The high concentration of nitric oxide (NO) around the gastro-esophageal junction (GEJ) might play an important role in the development of Barrett's esophagus (BE), a precursor of Barrett's adenocarcimona. Although previous studies revealed that the expression of caudal-type homeobox 2 (CDX2), an important marker of BE, might be induced through Epidermal Growth Factor Receptor (EGFR), the roles of NO in this signal transduction remain unclear.

MATERIAL AND METHODS

First, we investigated the expressions of EGFR, CDX2 and nitrotyrosine by immunohistochemical study for BE and squamous epithelium of human specimens. Second, we studied the effect of peroxynitrite, peroxynitrite stimulator, SIN-1, or NO donor, NOC7, on the expression of phosphorylated EGFR and CDX2 in KYSE30, an EGFR-rich human esophageal squamous cell carcinoma cell-line. Specific inhibitors for EGFR, AG1478 and small interfering RNA for EGFR (EGFR-siRNA) were employed to elucidate the role of EGFR in the induction of CDX2.

RESULTS

The immunohistochemical study revealed that the expressions of EGFR, CDX2 and nitrotyrosine in BE were stronger than those in squamous epithelium with positive correlations. Exposure to peroxynitrite, SIN-1 or NOC7 induced EGFR phosphorylation and CDX2 expression in dose- and time-dependent manners. Both EGFR phosphorylation and CDX2 induction were significantly diminished by AG 1478 and EGFR-siRNA.

CONCLUSIONS

We revealed for the first time that extrinsic NO might directly induce CDX2 expression through EGFR phosphorylation. We suggested that NO had an important role in the development of BE from squamous epithelium around GEJ.

The Use of Higher Dose Steroids Increases the Risk of Rebleeding After Endoscopic Hemostasis for Peptic Ulcer Bleeding

BACKGROUND

Previous studies have shown that several factors such as hemodynamic instability at admission are risk factors for rebleeding of peptic ulcer bleeding. However, whether steroid use increases the risk of rebleeding remains elusive.

AIMS

This study aimed to clarify the risk factors for rebleeding after endoscopic hemostasis for peptic ulcer bleeding.

METHODS

A total of 185 patients who underwent endoscopic hemostasis for peptic ulcer bleeding at our institution between 2005 and 2017 were retrospectively analyzed. We evaluated factors, including comorbid conditions, in-hospital onset, and steroid use, associated with rebleeding by logistic regression analysis. In addition, we investigated the association between the dose of steroids and rebleeding.

RESULTS

The rebleeding rate after endoscopic hemostasis for peptic ulcer bleeding was 14.6%. In the multivariate analysis, the independent risk factors for rebleeding were steroid use (odds ratio 4.56, p = 0.015), multiple ulcers (4.43, p = 0.005), number of comorbidities ≥ 3 3.18, p = 0.026), hemodynamic instability (3.06, p = 0.039), and number of comorbidities ≥ 3 (2.93, p = 0.047). Furthermore, the use of higher dose steroids (≥ 20 mg per day in prednisolone; 10.55, p = 0.002), but not lower dose (< 20 mg per day in prednisolone), was an independent risk factor for rebleeding in the multivariate analysis. The relationship between steroid use and rebleeding was observed in a dose-dependent manner (p for trend = 0.002).

CONCLUSIONS

This study first revealed that using higher dose steroids was an independent risk factor for rebleeding after endoscopic hemostasis for peptic ulcer bleeding, with a dose-response relation.

Prevention of delayed bleeding with vonoprazan in upper gastrointestinal endoscopic treatment

BACKGROUND

Delayed bleeding is the major adverse event in upper gastrointestinal endoscopic treatment (UGET). We aimed to investigate the efficacy of vonoprazan, which is the novel strong antisecretory agent, to reduce the risk for delayed bleeding in comparison with proton pump inhibitors (PPIs) in UGET.

METHODS

This retrospective population-based cohort study used the Diagnosis Procedure Combination database in Japan. We included patients on vonoprazan or PPI in UGET between 2014 and 2019. The primary outcome was delayed bleeding. We conducted propensity score matching to balance the comparison groups, and logistic regression analyses to compare the bleeding outcomes.

RESULTS

We enrolled 124,422 patients, in which 34,822 and 89,600 were prescribed with vonoprazan and PPI, respectively. After propensity score matching, the risk for delayed bleeding was lower in vonoprazan than in PPI (odds ratio [OR], 0.75; 95% confidence interval [CI], 0.71-0.80), consistent with sensitivity analysis results. In the subgroup analyses of seven UGET procedures, vonoprazan was significantly advantageous in esophageal endoscopic submucosal dissection (E-ESD) (OR, 0.71; 95% CI, 0.54-0.94) and gastroduodenal endoscopic submucosal dissection (GD-ESD) (OR, 0.70; 95% CI, 0.65-0.75), although correction for multiple testing of the outcome data removed the significance in E-ESD. These results were also consistent with sensitivity analysis results. In the five other procedures, no significant advantage was found.

CONCLUSIONS

This nationwide study found that, compared with PPI, vonoprazan can reduce delayed bleeding with approximately 30% in GD-ESD. Vonoprazan has the possibility to become a new treatment method for preventing delayed bleeding in this procedure.

Nitric oxide could promote development of Barrett's esophagus by S-nitrosylation-induced inhibition of Rho-ROCK signaling in esophageal fibroblasts

Barrett's esophagus arises in the process of wound healing in distal esophageal epithelium damaged by gastroesophageal reflux disease. Differentiation of fibroblast into myofibroblasts, a smooth muscle cell-like phenotype and tissue contraction are crucial processes in wound healing. No study has evaluated mechanism by which luminal esophageal nitric oxide (NO) affect Rho-associated coiled coil-forming protein kinase (Rho-ROCK) signaling pathway, a key factor of tissue contraction, in stromal fibroblasts to develop Barrett's esophagus. Using esophageal fibroblasts, we performed collagen-based cell contraction assays and evaluated influence of Rho-ROCK signaling in the exposure to acidic bile salts and NOC-9, which is an NO donor. We found that enhanced cell contraction induced by acidic bile salts was inhibited by NO, accompanied by decrease in phosphorylated myosin light chain expression and stress fiber formation. NO directly S-nitrosylated GTP-RhoA and consequently blocked Rho-ROCK signaling. Moreover, exposure to NO and Y27632, a Rho-ROCK signaling inhibitor, decreased α-SMA expression and increased bone morphogenetic protein-4 (BMP4) expression and secretion. These findings could account for the increased expression of BMP4 in the columnar epithelial cells and stromal fibroblasts in human Barrett's esophagus. NO could impair wound contraction by blocking the Rho-ROCK signaling pathway and promote the development of Barrett's esophagus.NEW & NOTEWORTHY Barrett's esophagus is the condition where esophageal epithelium damaged by gastroesophageal reflux disease (GERD) is abnormally healed via replacing of metaplastic columnar epithelium, but very few studies have conducted focusing wound healing in the development of Barrett's esophagus. Esophageal luminal nitric oxide inhibits Rho-ROCK signaling pathway in esophageal fibroblasts, which leads to delay tissue contraction, a pivotal step in proper wound healing. Moreover, this inhibition increases tissue BMP4 expression. Impaired wound healing could be related to Barrett's esophagus.

A Japanese case of lymphocytic esophagitis

We report the case of a 68-year-old Japanese man diagnosed with lymphocytic esophagitis (LE), a rare disease associated with refractory dysphagia. He has had severe dysphagia and heartburn since 2007. Findings of esophagogastroduodenoscopy (EGD) carried out by a local physician in 2010 showed pale mucosa with white exudate and lateral furrows in the esophagus. He was referred to Tohoku University Hospital in 2012, because the symptoms did not improve, despite regular use of a proton pump inhibitor (PPI). At that time, EGD revealed the coexistence of a slight stricture in the upper esophagus, the histopathological findings of which included a predominantly peri-papillary distribution of abundant, infiltrating CD3+ /CD4+ /CD8+ /CD20- lymphocytes without any granulocytes (CD4+  : CD8+  = 3.3:1). These were consistent with a diagnostic criteria of LE. Thereafter, severe dysphagia with food impaction occurred twice a month, despite the long-term use of a PPI, and EGD showed worsened strictures, where endoscopic ultrasonography findings showed marked circumferential thickness of the mucosal and submucosal layers. Then, one session of endoscopic balloon dilatation dramatically improved the dysphagia. Accordingly, LE should be considered an important differential diagnosis of refractory dysphagia based on the characteristic features of endoscopic and pathological findings.

The Ameliorating Effect of Switching to Vonoprazan: A Novel Potassium-Competitive Acid Blocker in Patients with Proton Pump Inhibitor Refractory Non-Erosive Reflux Disease

INTRODUCTION

Weakly acidic reflux has been reported to be the major cause of symptoms in patients with proton pump inhibitor (PPI)-refractory nonerosive reflux disease (NERD) undergoing PPI treatment. We previously reported that reflux at pH 4-5 was the main factor that induced symptoms in such patients. The present study aimed to elucidate the symptom-ameliorating effect of vonoprazan (VPZ) by evaluating the change in the pH value of the refluxate using multichannel intraluminal impedance and pH (MII-pH) monitoring.

METHODS

We retrospectively evaluated the records of MII-pH monitoring in 29 symptom index (SI) and/or symptom association probability (SAP)-positive patients with PPI-refractory NERD. After switching to VPZ 20 mg/day, we performed MII-pH monitoring again. We assessed the change in the score of the frequency scale for the symptoms of gastroesophageal reflux disease (FSSG), the pH value of the refluxate, and the percent times of intragastric pH <4 or <5 before and after switching. We divided the patients into the following 2 groups according to the FSSG score after switching: effective and noneffective groups.

RESULTS

Among of the 29 SI/SAP-positive patients, 16 underwent switching to VPZ. Furthermore, of these 16 patients, 10 underwent MII-pH monitoring again after switching. The FSSG score decreased, the pH value of the refluxate increased, and the percent times of intragastric pH <4 or <5 reduced after switching when compared with the findings before switching. In the effective group, both the proportion of reflux at pH <4 and that of reflux at pH 4-5 decreased while taking VPZ when compared with the findings while taking double-dose PPI. In the noneffective group, the proportion of reflux at pH <4 decreased but that of reflux at pH 4-5 increased and that of reflux at pH <5 did not change overall while taking VPZ. In addition, the percent times of intragastric pH <5 values were low in the effective group.

CONCLUSION

Symptom suppression appears to be inadequate in patients with persistent reflux at pH 4-5 even with VPZ 20 mg/day. Strong acid suppressive therapy with VPZ to increase the pH value of the refluxate to ≥5 is useful for symptom improvement.

Gastric cancers emerging after H. pylori eradication arise exclusively from non-acid-secreting areas

Although Helicobacter pylori (H. pylori) eradication has some inhibitory effects on the subsequent development of gastric cancer, there are sporadic cases of gastric cancer even after successful eradication. The pathogenesis of gastric cancer emerging after H. pylori eradication remains to be clarified. In this study, employing Congo-red chromoendoscopy, which is capable of visualizing the acid-secreting fundic mucosa, we investigated the topographic relationship of the acid secretion pattern to the occurrence site of gastric cancers emerging after eradication. Fourteen consecutive patients who suffered from new gastric cancer after eradication, defined as lesions that were discovered at least 2 years after the eradication, were prospectively enrolled. Whether the neoplasias arose from acid-secreting or non-acid-secreting areas was evaluated with Congo-red chromoendoscopy. Biopsy specimens taken from the two areas were subjected to histologic evaluation and immunohistochemistry for Ki-67 and p53. The mean period from the eradication to the subsequent occurrence of gastric cancer was 74 (44) months. There were two cancer lesions in 5 cases, and thus there was a total 19 lesions from 14 cases. Congo-red chromoendoscopy revealed that all 19 lesions arose exclusively from non-acid-secreting areas. Histological examination revealed sustained hyperproliferation and accumulation of p53 protein was frequently detectable in non-acid-secreting areas. Genetic alteration such as p53 mutation seems to be already present in the residual non-acid-secreting areas after eradication, areas that could be the origin of gastric carcinogenesis after eradication. Identification of such high-risk areas should be a promising approach for estimating the individual cancer risk after eradication.

Signet Ring Cell Gastric Cancer Occurring after Radiation Therapy for Helicobacter pylori-Uninfected Mucosa-Associated Lymphoid Tissue Lymphoma

Helicobacter pylori infection is the major cause for mucosa-associated lymphoid tissue (MALT) lymphoma and gastric cancers. On the other hand, gastric cancers are known to arise from gastric mucosal atrophy. We here report a case of signet ring cell gastric cancer that developed after radiation therapy for MALT lymphoma in H. pylori-uninfected patient whose stomach did not show gastric mucosal atrophy. A 58-year-old female was referred to our hospital for treatment of gastric MALT lymphoma. This patient was not infected with H. pylori, and upper gastrointestinal endoscopy revealed that she did not have gastric mucosal atrophy but had submucosal tumor-like MALT lymphoma lesion in the anterior wall of the upper gastric body. Since conventional eradication therapy was ineffective, her whole stomach was irradiated as a second-line therapy. The MALT lymphoma lesion turned into complete remission state after the therapy. The patient was followed every 6 months by upper gastrointestinal endoscopy for 4 years as complete remission until a newly developed decolorized depressed lesion was detected in the greater curvature of the proximal antrum, a completely different location from the MALT lymphoma lesion. A biopsy specimen from the lesion contained signet ring cell carcinoma, and she was successfully treated by endoscopic submucosal dissection. No signs of recurrence have been detected so far. The radiation therapy for MALT lymphoma might be associated with the occurrence of this signet ring cell gastric cancer, and since MALT lymphoma is indolent in nature, this case suggests that careful consideration is required when choosing the second-line therapy for MALT lymphoma patients.

The Impact of Tobacco Smoking and Alcohol Consumption on the Development of Gastric Cancers

Chronic infection of Helicobacter pylori is considered the principal cause of gastric cancers, but evidence has accumulated regarding the impact of tobacco smoking and alcohol consumption on the development of gastric cancers. Several possible mechanisms, including the activation of nicotinic acetylcholine receptors, have been proposed for smoking-induced gastric carcinogenesis. On the other hand, local acetaldehyde exposure and ethanol-induced mucosal inflammation have been proposed as the mechanisms involved in the development of gastric cancers in heavy alcohol drinkers. In addition, genetic polymorphisms are also considered to play a pivotal role in smoking-related and alcohol-related gastric carcinogenesis. In this review, we will discuss the molecular mechanisms involved in the development of gastric cancers in relation to tobacco smoking and alcohol consumption.

Influence of the pH Value of Refluxate and Proximal Extent on Heartburn Perception in Patients with Proton Pump Inhibitor-Refractory Non-Erosive Reflux Disease

BACKGROUND AND OBJECTIVES

Weakly acidic reflux has been reported as the major cause of symptom occurrence in patients with proton pump inhibitor (PPI)-refractory non-erosive reflux disease (NERD). This study is aimed at clarifying whether the pH value of weakly acidic reflux affects the induction of symptoms.

METHODS

We retrospectively evaluated the records of combined multichannel intraluminal impedance and pH monitoring in 57 patients with PPI-refractory NERD. Weakly acidic refluxes were divided into 3 categories based on the pH value of the refluxate: pH 4-5, 5-6, and 6-7.

RESULTS

A total of 29 patients were positive in the symptom index. The symptom provocation rate in reflux of pH 4-5 (19%) was much higher than in that of pH 5-6 (11%) and pH 6-7 (12%). In the reflux at pH 4-5, the symptom provocation rate in the proximal reflux was higher than that in the distal reflux (p < 0.05), whereas the reflux at pH 5-6 and pH 6-7 was not significantly different in the symptom provocation rate between the proximal and distal refluxes.

CONCLUSION

Reflux at pH <5 reaching the proximal esophagus was the main factor in the induced symptoms of patients with PPI-refractory NERD.

Impaired Mucosal Integrity in Proximal Esophagus Is Involved in Development of Proton Pump Inhibitor-Refractory Nonerosive Reflux Disease

BACKGROUND AND OBJECTIVE

Weakly acidic reflux reaching to the proximal esophagus is closely related to the perception of gastroesophageal reflux in patients with nonerosive reflux disease despite treatment with a proton pump inhibitor (PPI). However, little is known about the involvement of the patients' mucosal integrity of the proximal esophagus.

METHODS

We recruited 15 symptomatic nonerosive gastroesophageal reflux disease (GERD) patients with a positive symptom index despite PPI treatment and 11 healthy asymptomatic volunteers as controls. The biopsy specimens obtained from the proximal and distal esophagus were applied to a mini-Ussing chamber system to measure transepithelial electrical resistance (TEER) against a pH 4 weak acid. The esophageal biopsy samples were subjected to quantitative real-time PCR and immunohistochemical analysis.

RESULTS

In the proximal esophagus, the weak acid exposure reduced the TEER in the PPI-refractory patients compared to that in the controls. The frequency of the reflux extending to the proximal esophagus had a significant correlation with the reduction in the proximal esophageal TEER in the patients. The reduced TEER in the proximal esophagus was accompanied by an increase in IL-8 and IL-1β mRNA and a decrease in occludin mRNA levels. The proximal esophageal mucosa in the patients presented infiltration of CD3-positive lymphocytes and an increased expression of solute carrier organic anion transporter family member 2A1 (SLCO2A1), a passage gate of reflux symptom-evoking molecules.

CONCLUSIONS

The reflux perception is related to an impairment of the proximal esophageal mucosal integrity in patients with nonerosive reflux disease despite PPI.

Continuous liquid-suction catheter attachment for endoscope reduces volume of liquid reflux to the mouth in esophageal endoscopic submucosal dissection

BACKGROUND AND AIM

Pooling of liquid in the esophageal lumen can worsen the field of vision and cause liquid reflux to the mouth, which leads to aspiration pneumonia, in esophageal endoscopic submucosal dissection (ESD). We developed a continuous liquid-suction catheter attachment for the endoscope (CLCA) that has multiple tiny holes and can suction the liquid without causing mucosal injury. Thus, we aim to show the efficacy of CLCA in esophageal ESD.

METHODS

This was a single-blinded, randomized controlled trial involving patients with superficial esophageal cancer. The enrolled patients were randomly assigned to the conventional ESD (C-ESD) or ESD with CLCA (CLCA-ESD) groups. Primary endpoint was volume of liquid reflux to the mouth during the ESD procedure. Secondary endpoints were incidence of aspiration pneumonia and procedure time.

RESULTS

Fifty patients were enrolled in this trial. Volume of liquid reflux to the mouth was significantly lower in the CLCA-ESD group than in the C-ESD group (mean: 10 vs 73 mL, P = 0.010). Furthermore, the incidence of aspiration pneumonia on computed tomography (CT) scan between the two groups was also significantly different (4.0% vs 32.0%, P = 0.023), although no significant difference was observed through chest radiography. In addition, procedure time tended to be shorter in the CLCA-ESD group (P = 0.054).

CONCLUSION

This study first showed that use of CLCA in esophageal ESD reduced the volume of liquid reflux to the mouth and contributed to decreased incidence of aspiration pneumonia on CT scan (UMIN000018167).

Wnt Signaling and Aging of the Gastrointestinal Tract

Aging is considered a risk factor for various diseases including cancers. In this aging society, there is an urgent need to clarify the molecular mechanisms involved in aging. Wnt signaling has been shown to play a crucial role in the maintenance and differentiation of tissue stem cells, and intensive studies have elucidated its pivotal role in the aging of neural and muscle stem cells. However, until recently, such studies on the gastrointestinal tract have been limited. In this review, we discuss recent advances in the study of the role of Wnt signaling in the aging of the gastrointestinal tract and aging-related carcinogenesis.

Calcium carbonate breath test for non-invasive estimation of gastric acid secretion

Gastric acid measurement is useful in assessing the effectiveness of antisecretory drugs, however, the conventional tests involve invasive nasogastric intubation. Orally administered ¹³C-labeled calcium carbonate (Ca¹³CO₃) reacts with gastric acid to produce ¹³C-labeled carbon dioxide (¹³CO₂), which is then excreted in the breath. The objective of this study was to evaluate the suitability of Ca¹³CO3 breath test for estimating gastric acid secretion in human noninvasively. First, the Ca¹³CO₃ breath test and the measurement of pooled gastric acid under a fasting condition were performed in 6 healthy volunteers to evaluate the correlation between the two parameters. Next, endoscopic gastric acid collection and the Ca¹³CO₃ breath test were performed on different days after pentagastrin injection in 20 subjects to evaluate the correlation between the tests and the reproducibility. Finally, the same studies were repeated in 4 subjects before and after 1-week rabeprazole, a proton pump inhibitor, administration. The maximum CO₂ concentration (Cmax) correlated very well with the amount of pooled gastric acid (r = 0.95), suggesting that Ca¹³CO₃ breath test values well reflected the fasting intragastric acidity. The ¹³CO₂ concentration after pentagastrin injection correlated well with pentagastrin-stimulated maximal acid output (r = 0.79 at 20 min). The reproducibility of the Ca¹³CO₃ breath test under pentagastrin-stimulation was good (coefficient of variation = 0.11). Rabeprazole administration markedly reduced the values of the Ca¹³CO₃ breath test, suggesting that it can sensitively assess the efficacy of rabeprazole. The Ca¹³CO₃ breath test can potentially be a useful method for non-invasive estimation for gastric acid secretion in human.

Characteristics of symptomatic reflux episodes in Japanese proton pump inhibitor-refractory non-erosive reflux disease patients

AIM

To clarify the pathogenesis of gastroesophageal reflux disease symptoms in non-erosive reflux disease (NERD) patients.

METHODS

Thirty-five NERD patients with persistent symptoms, despite taking rabeprazole 10 mg twice daily for at least 8 wk, were included in this study. All patients underwent 24 h combined impedance - pH on rabeprazole. The symptom index (SI) was considered to be positive if ≥ 50%, and proximal reflux episodes were determined when reflux reached 15 cm above the proximal margin of the lower esophageal sphincter.

RESULTS

In 14 (40%) SI-positive patients, with liquid weakly acid reflux, the occurrence rate of reflux symptoms was significantly more frequent in proximal reflux episodes (46.7%) than in distal ones (5.7%) (P < 0.001). With liquid acid reflux, there were no significant differences in the occurrence rate of reflux symptoms between proximal reflux episodes (38.5%) and distal ones (20.5%) (NS). With mixed liquid-gas weakly acid reflux, the occurrence rate of reflux symptoms in proximal reflux episodes was significantly more frequent (31.0%) than in distal reflux ones (3.3%) (P < 0.001). With mixed liquid-gas acid reflux, there were no significant differences in the occurrence rate of reflux symptoms between proximal reflux episodes (29.4%) and distal ones (14.3%) (NS).

CONCLUSION

The proximal extent of weakly acidic liquid and mixed liquid-gas reflux is a major factor associated with reflux perception in SI-positive patients on proton pump inhibitor therapy.

Acidic bile salts induces mucosal barrier dysfunction through let-7a reduction during gastric carcinogenesis after Helicobacter pylori eradication

Gastric cancer (GC) after eradication for Helicobacter pylori (H.pylori) increases, but its carcinogenesis is not elucidated. It is mainly found in acid non-secretion areas (ANA), as mucosal regeneration in acid secretory areas (AA) after eradication changes the acidity and bile toxicity of gastric juice. We aimed to clarify the role of barrier dysfunction of ANA by the stimulation of pH3 bile acid cocktail (ABC) during carcinogenesis. We collected 18 patients after curative endoscopic resection for GC, identified later than 24 months after eradication, and took biopsies by Congo-red chromoendoscopy to distinguish AA and ANA (UMIN00018967). The mucosal barrier function was investigated using a mini-Ussing chamber system and molecular biological methods. The reduction in mucosal impedance in ANA after stimulation was significantly larger than that in AA, 79.6% vs. 87.9%, respectively. The decrease of zonula occludens-1 (ZO-1) and let-7a and the increase of snail in ANA were significant compared to those in AA. In an in vitro study, the restoration of ZO-1 and let-7a as well as the induction of snail were observed after stimulation. High mobility group A2 (HMGA2)-snail activation, MTT proliferation, and cellular infiltration capacity were significantly increased in AGS transfected with let-7a inhibitor, and vice versa. Accordingly, using a mini-Ussing chamber system for human biopsy specimens followed by an in vitro study, we demonstrated for the first time that the exposure of acidic bile salts to ANA might cause serious barrier dysfunction through the let-7a reduction, promoting epithelial-mesenchymal transition during inflammation-associated carcinogenesis even after eradication.

Parietal Cell Dysfunction: A Rare Cause of Gastric Neuroendocrine Neoplasm with Achlorhydria and Extreme Hypergastrinemia

A 69-year-old woman with multiple neuroendocrine neoplasms (NENs) was referred to our hospital. Although she had extreme hypergastrinemia (11,675 pg/mL), no findings that indicated types I to III gastric NENs were found. Although gastric corpus atrophy was suspected on conventional white-light imaging, findings on magnifying endoscopy with narrow-band imaging indicated no severe atrophy. A biopsy from the background fundic gland mucosa revealed no atrophic changes, parietal cells with vacuolated cytoplasm and negative findings for H+K+-ATPase. Thus, this case was diagnosed as multiple NENs with parietal cell dysfunction. Neither progression nor metastasis has been confirmed during two-year follow-up.

Interactive training with a novel simulation model for upper gastrointestinal endoscopic hemostasis improves trainee technique and confidence

Background and study aims Endoscopic hemostasis is a life-saving procedure for gastrointestinal bleeding; however, training for it is often performed on real patients and during urgent situations that put patients at risk. Reports of simulation-based training models for endoscopic hemostasis are scarce. Herein, we developed a novel simulator called "Medical Rising STAR-Ulcer type" to practice endoscopic hemostasis with hemoclips and coagulation graspers. This study aimed to evaluate the reproducibility of the clinical difficulty of this model and the effectiveness of simulation-based training for clipping hemostasis. Patients and methods This was a prospective educational study. Fifty gastroenterology residents from Japan and Canada were recruited to participate in a simulation-based training program. The primary outcome was the success rate for clipping hemostasis. We measured differences in trainee subjective assessment scores and evaluated the co-occurrence network based on comments after training. Results The hemostasis success rate of the trainees significantly increased after instruction (64% vs. 86%, P < 0.05). The success rate for ulcers in the upper body of the stomach (59%), a high-difficulty site, was significantly lower than that for ulcers in the antrum, even after feedback and instruction. Trainee self-perceived proficiency and confidence significantly improved after simulation-based training ( P < 0.05). Co-occurrence network analysis showed that trainees valued a structured learning approach, acknowledged simulator limitations, and recognized the need for continuous skill refinement. Conclusions Our study demonstrates the potential of our simulation-based training model as a valuable tool for improving technical skills and confidence in trainees learning to perform endoscopic hemostasis.