In situ measurement of pH in the secreting canaliculus of the gastric parietal cell and adjacent structures

Structural Relationships to Efficacy for Prazole-Derived Antivirals

Here, an in vitro characterization of a family of prazole derivatives that covalently bind to the C73 site on Tsg101 and assay their ability to inhibit viral particle production is presented. Structurally, increased steric bulk on the 4-pyridyl of the prazole expands the prazole site on the UEV domain toward the β-hairpin in the Ub-binding site and is coupled to increased inhibition of virus-like particle production in HIV-1. Increased bulk also increased toxicity, which is alleviated by increasing flexibility. Further, the formation of a novel secondary Tsg101 adduct for several of the tested compounds and the commercial drug lansoprazole. The secondary adduct involved the loss of the 4-pyridyl substituent to form an irreversible species, with implications for increasing the half-life of the active species or its specificity toward Tsg101 UEV. It is also determined that sulfide derivatives display effective viral inhibition, presumably through cellular sulfoxidation, allowing for delayed conversion within the cellular environment, and identify SARS-COV-2 as a target of prazole inhibition. These results open multiple avenues for the design of prazole derivatives for antiviral applications.

Effect of Acid Suppressants on Non–Helicobacter pylori Helicobacters Within Parietal Cells

We investigated the effect of increased pH induced by acid suppressants on the viability of non–Helicobacter pylori helicobacters (NHPHs) within parietal cell intracellular canaliculi and fundic glandular lumina by immunohistochemistry, electron microscopy, quantitative PCR, urea breath tests, and using a bilayer culture system. Three months before the experiment, mice were infected with the NHPH H. suis and then treated with famotidine (2 mg/kg body weight [BW], once daily), lansoprazole (30 mg/kg BW, once daily), or vonoprazan (20 mg/kg BW, once daily) for 3 days. Immunohistochemical studies using the TUNEL method, quantitative PCR analysis, and urea breath tests were performed. PCR analysis showed a decrease in the NHPH quantity after vonoprazan treatment. Urea breath tests revealed a significant decrease in the NHPH urease activity after vonoprazan, lansoprazole, and famotidine treatments for 3 days; however, 4 days after the treatment, urease activity reversed to the pretreatment level for each treatment group. Electron microscopy revealed an increase in the damaged NHPH after vonoprazan treatment. The TUNEL method revealed apoptotic NHPH within parietal cells after vonoprazan treatment. The bilayer culture results demonstrated that NHPH moved more quickly at a pH of 4.0 than at a pH of 3.0, 5.0, and 6.5, and electron microscopy revealed a change from the spiral form to the coccoid form under near-neutral pH conditions. We thus proposed that acid suppressants, especially vonoprazan, induce NHPH damage by altering pH.

CHAC1 overexpression in human gastric parietal cells with Helicobacter pylori infection in the secretory canaliculi

BACKGROUND

Cation transport regulator 1 (CHAC1), a newly discovered enzyme that degrades glutathione, is induced in Helicobacter pylori (H. pylori)-infected gastric epithelial cells in culture. The CHAC1-induced decrease in glutathione leads to an accumulation of reactive oxygen species and somatic mutations in TP53. We evaluated the possible correlation between H. pylori infection and CHAC1 expression in human gastric mucosa.

MATERIALS AND METHODS

Both fresh-frozen and formalin-fixed paraffin-embedded tissue samples of gastric mucosa with or without H. pylori infection were obtained from 41 esophageal cancer patients that underwent esophago-gastrectomy. Fresh samples were used for real-time polymerase chain reaction for H. pylori DNA and CHAC1 mRNA, and formalin-fixed samples were used for immunohistochemistry with anti-CHAC1 and anti-H. pylori monoclonal antibodies. Double-enzyme or fluorescence immunohistochemistry and immuno-electron microscopy were used for further analysis.

RESULTS

Significant CHAC1 overexpression was detected in H. pylori-infected parietal cells that expressed the human proton pump/H,K-ATPase α subunit, whereas a constitutively low level of CHAC1 mRNA expression was observed in the other samples regardless of the H. pylori infection status, reflecting the weak CHAC1 expression detected by immunohistochemistry in the fundic-gland areas. Immuno-electron microscopy revealed intact H. pylori cells in the secretory canaliculi of infected parietal cells. Some parietal cells exhibited positive nuclear signals for Ki67 in the neck zone of the gastric fundic-gland mucosa with H. pylori infection.

CONCLUSION

Cation transport regulator 1 overexpression in H. pylori-infected parietal cells may cause the H. pylori-induced somatic mutations that contribute to the development of gastric cancer.

A hydrogel based nanosensor with an unprecedented broad sensitivity range for pH measurements in cellular compartments

This quadruple-labelled nanosensor has a broad sensitivity range from pH 1.4 to 7.0. It covers the full physiologically relevant range where especially the low pH range of some specialized cells can now be monitored.

Helicobacter pylori colonization critically depends on postprandial gastric conditions

The risk of Helicobacter pylori infection is highest in childhood, but the colonization process of the stomach mucosa is poorly understood. We used anesthetized Mongolian gerbils to study the initial stages of H. pylori colonization. Prandial and postprandial gastric conditions characteristic of humans of different ages were simulated. The fraction of bacteria that reached the deep mucus layer varied strongly with the modelled postprandial conditions. Colonization success was weak with fast gastric reacidification typical of adults. The efficiency of deep mucus entry was also low with a slow pH decrease as seen in pH profiles simulating the situation in babies. Initial colonization was most efficient under conditions simulating the postprandial reacidification and pepsin activation profiles in young children. In conclusion, initial H. pylori colonization depends on age-related gastric physiology, providing evidence from an in vivo infection model that suggests an explanation why the bacterium is predominantly acquired in early childhood.