Pepsinogen I- and H+/K+-ATPase-immunohistochemical Positivity in Endoscopically Resected Early Gastric Neoplasia.

Gastric adenocarcinoma of the fundic gland type (GAFG) has been recently classified by the World Health Organization (WHO), however, clinicopathologic features of pepsinogen I- or H+/K+-ATPase-positive gastric tumors remain unclear. Therefore, this study evaluates the frequency and clinicopathologic features of those tumors, using a tissue microarray block to identify pepsinogen I- or H+/K+-ATPase-positive tumors from 810 endoscopically resected, early gastric epithelial tumors. The frequency of pepsinogen I-positive lesions was 2.1%, and that of H+/K+-ATPase-positive lesions was 2.0%. Pepsinogen I- or H+/K+-ATPase positivity was not observed in undifferentiated-type tumors, while gastric tumors with morphologic similarity to fundic glands were positive for pepsinogen I- or H+/K+-ATPase. We divided pepsinogen I- or H+/K+-ATPase-positive gastric tumors into group A, with fundic gland-like structure, or group B, without fundic gland-like structure. The frequency of group A was 1.6%: 46.2% were positive only for pepsinogen I and 53.8% for H+/K+-ATPase and pepsinogen I. The frequency of group B was 1.5%: 25% were positive only for pepsinogen I, 8.3% for H+/K+-ATPase and pepsinogen I, and 66.7% only for H+/K+-ATPase. The 2 tumor groups differed in location and endoscopic features. Hematoxylin and eosin staining showed that group B had more exposed tumors to the surface, larger nuclei, and more background atrophy than group A. Immunostaining showed significantly higher positivity rates for MUC5AC, CD10, CDX2, and p53 expression, and a higher Ki-67 labeling score. Our results provide novel insights into the pathology of early gastric tumors with histologic or immunohistochemical evidence of fundic gland differentiation.

In Search of Small Molecules That Selectively Inhibit MBOAT4.

Ghrelin is a 28-residue peptide hormone produced by stomach P/D1 cells located in oxyntic glands of the fundus mucosa. Post-translational octanoylation of its Ser-3 residue, catalyzed by MBOAT4 (aka ghrelin O-acyl transferase (GOAT)), is essential for the binding of the hormone to its receptor in target tissues. Physiological roles of acyl ghrelin include the regulation of food intake, growth hormone secretion from the pituitary, and inhibition of insulin secretion from the pancreas. Here, we describe a medicinal chemistry campaign that led to the identification of small lipopeptidomimetics that inhibit GOAT in vitro. These molecules compete directly for substrate binding. We further describe the synthesis of heterocyclic inhibitors that compete at the acyl coenzyme A binding site.

Gastric proton pump with two occluded K+ engineered with sodium pump-mimetic mutations.

The gastric H+,K+-ATPase mediates electroneutral exchange of 1H+/1K+ per ATP hydrolysed across the membrane. Previous structural analysis of the K+-occluded E2-P transition state of H+,K+-ATPase showed a single bound K+ at cation-binding site II, in marked contrast to the two K+ ions occluded at sites I and II of the closely-related Na+,K+-ATPase which mediates electrogenic 3Na+/2K+ translocation across the membrane. The molecular basis of the different K+ stoichiometry between these K+-counter-transporting pumps is elusive. We show a series of crystal structures and a cryo-EM structure of H+,K+-ATPase mutants with changes in the vicinity of site I, based on the structure of the sodium pump. Our step-wise and tailored construction of the mutants finally gave a two-K+ bound H+,K+-ATPase, achieved by five mutations, including amino acids directly coordinating K+ (Lys791Ser, Glu820Asp), indirectly contributing to cation-binding site formation (Tyr340Asn, Glu936Val), and allosterically stabilizing K+-occluded conformation (Tyr799Trp). This quintuple mutant in the K+-occluded E2-P state unambiguously shows two separate densities at the cation-binding site in its 2.6 Å resolution cryo-EM structure. These results offer new insights into how two closely-related cation pumps specify the number of K+ accommodated at their cation-binding site.

Isolation and characterization of flavonoid compounds from Stachytarpheta jamaicensis (L.) Vahl and its role as anti-gastro ulcerative agent in rats.

CONTEXT: Stomach ulcer is one of the most common gastrointestinal problems in the world. OBJECTIVE: This study aimed to isolate flavonoid compounds from methanol extract of the aerial parts of Stachytarpheta jamaicensis (L.) Vahl. and evaluate its protective and therapeutic effects against gastric ulcer. MATERIALS AND METHODS: Chromatographic techniques were used for the identification of the isolated compounds. To explore the effects of the plant extract, it was administrated by oral gavage for one week either before or post-ethanol ulcer induction. Ranitidine was also evaluated as a reference drug. Stomach pH, gastric juice volume, lesions number, glutathione, superoxide dismutase, malondialdehyde, succinate dehydrogenase, lactate dehydrogenase, acid phosphatase, Interleukin-10, intracellular adhesion molecule-1, prostaglandin E2, and total protein levels were estimated in gastric tissue. Stomach histopathological features were also monitored. RESULTS: Six flavonoid compounds were isolated, where five of them were isolated for the first time (vitexin, isovitexin, apigenin 7,4'-dimethyl ether, 5,7,2'-trimethoxyflavone, and scutellarein), while apigenin was previously reported. Treatment with plant extract recorded amelioration in all the biochemical parameters. CONCLUSION: The methanol extract of plant aerial parts had prophylactic and treatment effects against gastric ulcer in rats, where its treatment effect exceeded its protective role. The extract recorded anti-inflammatory, and antioxidant effects due to the presence of flavonoid compounds.

Marked difference in efficiency of the digestive enzymes pepsin, trypsin, chymotrypsin, and pancreatic elastase to cleave tightly folded proteins.

In order for the intestinal mucosa to absorb dietary proteins they have to be digested into single amino acids or very short peptides of a length of not more than four amino acids. In order to study the efficiency of the digestive endopeptidases to digest folded proteins we have analyzed several target proteins under different conditions, native proteins, heat denatured and acid treated. The three pancreatic serine proteases, trypsin, chymotrypsin, and pancreatic elastase, were found to be remarkable inefficient in cleaving native folded proteins whereas pepsin, which acts at a very low pH (pH 1.2) was much more efficient, possibly due to the denaturing conditions and thereby better accessibility to internal cleavage sites at the low pH. Heat treatment improved the cleavage considerably by all three pancreatic enzymes, but acid treatment followed by return to neutral pH did not have any major effect. Cleavage at the low pH when the protein is in a denatured state, is apparently very efficient. This indicates that pepsin is the prime enzyme cleaving the properly folded native proteins and that the pancreatic enzymes primarily are involved in generating single amino acids or very short peptides for efficient uptake by the intestinal mucosa.

In vivo activation of pH-responsive oxidase-like graphitic nanozymes for selective killing of Helicobacter pylori.

Helicobacter pylori infection is a major etiological factor in gastric diseases. However, clinical antibiotic therapy for H. pylori is limited by continuously decreased therapeutic efficacy and side effects to symbiotic bacteria. Herein, we develop an in vivo activatable pH-responsive graphitic nanozyme, PtCo@Graphene (PtCo@G), for selective treatment of H. pylori. Such nanozymes can resist gastric acid corrosion, exhibit oxidase-like activity to stably generate reactive oxygen species only in acidic gastric milieu and demonstrate superior selective bactericidal property. C18-PEGn-Benzeneboronic acid molecules are modified on PtCo@G, improving its targeting capability. Under acidic gastric pH, graphitic nanozymes show notable bactericidal activity toward H. pylori, while no bacterial killing is observed under intestinal conditions. In mouse model, high antibacterial capability toward H. pylori and negligible side effects toward normal tissues and symbiotic bacteria are achieved. Graphitic nanozyme displays the desired enzyme-like activities at corresponding physiological sites and may address critical issues in clinical treatment of H. pylori infections.

Norepinephrine Enhances Aerobic Glycolysis and May Act as a Predictive Factor for Immunotherapy in Gastric Cancer.

METHODS: Monoamine neurotransmitters were detected in gastric cancer tissue and paired normal tissue, and The Cancer Genome Atlas was used to identify differentially expressed norepinephrine-degrading and synthetic enzymes. Quantitative real-time PCR and the Seahorse assay were used to determine the effect of norepinephrine on gastric cancer cell glycolysis. MAOA expression in cancer tissues was analyzed by immunohistochemistry and was compared with the patient SUVmax value of PET-CT and other clinicopathological characteristics. RESULTS: The norepinephrine levels were markedly high in gastric cancer tissue, while the norepinephrine-degrading enzymes MAOA and MAOB showed low expression. High norepinephrine levels were associated with activated glycolysis. The MAOA or MAOB expression levels in tumor tissue were closely correlated with the patient SUV max values of PET-CT and immunotherapy evaluation indices, such as PD-L1 and the microsatellite status. CONCLUSIONS: Norepinephrine shows relatively higher expression in gastric cancer tissue than in normal tissue, and its expression level is associated with the glycolysis levels in patients. The norepinephrine-degrading enzymes MAOA and MAOB have significant expression differences in cancer and normal tissue, and their missing or low expression may predict immune therapy outcomes for gastric cancer patients. High norepinephrine levels with metabolic abnormalities may be more suitable for metabolic targeted therapy or immunotherapy.

ß-Carotene Inhibits Expression of Matrix Metalloproteinase-10 and Invasion in Helicobacter pylori-Infected Gastric Epithelial Cells.

Matrix metalloproteinases (MMPs), key molecules of cancer invasion and metastasis, degrade the extracellular matrix and cell-cell adhesion molecules. MMP-10 plays a crucial role in Helicobacter pylori-induced cell-invasion. The mitogen-activated protein kinase (MAPK) signaling pathway, which activates activator protein-1 (AP-1), is known to mediate MMP expression. Infection with H. pylori, a Gram-negative bacterium, is associated with gastric cancer development. A toxic factor induced by H. pylori infection is reactive oxygen species (ROS), which activate MAPK signaling in gastric epithelial cells. Peroxisome proliferator-activated receptor γ (PPAR-γ) mediates the expression of antioxidant enzymes including catalase. ß-Carotene, a red-orange pigment, exerts antioxidant and anti-inflammatory properties. We aimed to investigate whether ß-carotene inhibits H. pylori-induced MMP expression and cell invasion in gastric epithelial AGS (gastric adenocarcinoma) cells. We found that H. pylori induced MMP-10 expression and increased cell invasion via the activation of MAPKs and AP-1 in gastric epithelial cells. Specific inhibitors of MAPKs suppressed H. pylori-induced MMP-10 expression, suggesting that H. pylori induces MMP-10 expression through MAPKs. ß-Carotene inhibited the H. pylori-induced activation of MAPKs and AP-1, expression of MMP-10, and cell invasion. Additionally, it promoted the expression of PPAR-γ and catalase, which reduced ROS levels in H. pylori-infected cells. In conclusion, ß-carotene exerts an inhibitory effect on MAPK-mediated MMP-10 expression and cell invasion by increasing PPAR-γ-mediated catalase expression and reducing ROS levels in H. pylori-infected gastric epithelial cells.

ZINC40099027 activates human focal adhesion kinase by accelerating the enzymatic activity of the FAK kinase domain.

Focal adhesion kinase (FAK) regulates gastrointestinal epithelial restitution and healing. ZINC40099027 (Zn27) activates cellular FAK and promotes intestinal epithelial wound closure in vitro and in mice. However, whether Zn27 activates FAK directly or indirectly remains unknown. We evaluated Zn27 potential modulation of the key phosphatases, PTP-PEST, PTP1B, and SHP2, that inactivate FAK, and performed in vitro kinase assays with purified FAK to assess direct Zn27-FAK interaction. In human Caco-2 cells, Zn27-stimulated FAK-Tyr-397 phosphorylation despite PTP-PEST inhibition and did not affect PTP1B-FAK interaction or SHP2 activity. Conversely, in vitro kinase assays demonstrated that Zn27 directly activates both full-length 125 kDa FAK and its 35 kDa kinase domain. The ATP-competitive FAK inhibitor PF573228 reduced basal and ZN27-stimulated FAK phosphorylation in Caco-2 cells, but Zn27 increased FAK phosphorylation even in cells treated with PF573228. Increasing PF573228 concentrations completely prevented activation of 35 kDa FAK in vitro by a normally effective Zn27 concentration. Conversely, increasing Zn27 concentrations dose-dependently activated kinase activity and overcame PF573228 inhibition of FAK, suggesting the direct interactions of Zn27 with FAK may be competitive. Zn27 increased the maximal activity (Vmax ) of FAK. The apparent Km of the substrate also increased under laboratory conditions less relevant to intracellular ATP concentrations. These results suggest that Zn27 is highly potent and enhances FAK activity via allosteric interaction with the FAK kinase domain to increase the Vmax of FAK for ATP. Understanding Zn27 enhancement of FAK activity will be important to redesign and develop a clinical drug that can promote mucosal wound healing.

Tumor suppressor ATP4B serve as a promising biomarker for worsening of gastric atrophy and poor differentiation.

BACKGROUND: Hydrogen/potassium ATPase ß (ATP4B) is a proton pump acting an essential role in gastric acid secretion. This study aimed to investigate the diagnostic performance of ATP4B and its biological role in tumor progression in gastric cancer. METHODS: The correlations between ATP4B expression level and clinicopathologic parameters, as well as the relevance of ATP4B expression with overall survival were assessed. The functional roles of ATP4B in gastric cancer were verified by gain- and loss-of-function cell models and tumor xenograft models. The possible downstream effects of ATP4B were analyzed by iTRAQ-based quantitative proteomics analysis. RESULTS: A dramatic decrease in ATP4B was associated with malignant transformation in gastric mucosa lesions and correlated with poor differentiation. Restoration of ATP4B expression in gastric cancer cells significantly suppressed cell proliferation, cell viability, migration, invasion, tumorigenicity and induced apoptosis, whereas ATP4B silencing exerted the opposite effects. Mechanistically, we found a quality control on mitochondrial metabolism and functions in ATP4B-overexpression GC cells. CONCLUSIONS: Our data suggest that decreasing ATP4B is an indicator for gastric mucosa malignant transformation and GC aggressive phenotype and it plays an inhibitory role in gastric cancer as a tumor suppressor via regulating mitochondrial metabolism and apoptosis pathway.

Estrogen synthesis in the stomach of Sprague-Dawley rats: comparison to Wistar rats.

Aromatase, an estrogen synthase, exists in the gastric parietal cells of Wistar rats. The stomach synthesizes large amounts of estrogens and secretes them into the portal vein. We have been particularly studying gastric estrogen synthesis using Wistar rats. However, estrogen synthesis in the stomach of Sprague-Dawley (SD) rats, which are used as frequently as those of the Wistar strain, has not been clarified. We examined steroid synthesis in the stomach of SD rats using immunohistochemistry, in situ hybridization, Western blotting, real-time PCR, and LC-MS/MS. Aromatase also exists in the stomach of SD rats. Its distribution was not found to be different from that of Wistar rats. Results show that H+/K+-ATPase ß-subunit and aromatase colocalized in double immunofluorescence staining. Each steroid synthase downstream from progesterone was present in the gastric mucosa. These results suggest that steroid hormones are synthesized in the parietal cells in the same pathway as Wistar rats. Although mRNA expression of steroid synthases were higher in SD, no significant difference was found in the amount of protein and each steroid hormone level in the portal vein. Although differences between strains might exist in steroid hormone synthesis, results show that SD rats are as useful as Wistar rats for gastric estrogen synthesis experimentation.

MicroRNA signatures associated with lymph node metastasis in intramucosal gastric cancer.

Although a certain proportion of intramucosal carcinomas (IMCs) of the stomach does metastasize, the majority of patients are currently treated with endoscopic resection without lymph node dissection, and this potentially veils any existing metastasis and may put some patients in danger. In this regard, biological markers from the resected IMC that can predict metastasis are warranted. Here, we discovered unique miRNA expression profiles that consist of 21 distinct miRNAs that are specifically upregulated (miR-628-5p, miR-1587, miR-3175, miR-3620-5p, miR-4459, miR-4505, miR-4507, miR-4720-5p, miR-4742-5p, and miR-6779-5p) or downregulated (miR-106b-3p, miR-125a-5p, miR-151b, miR-181d-5p, miR-486-5p, miR-500a-3p, miR-502-3p, miR-1231, miR-3609, and miR-6831-5p) in metastatic (M)-IMC compared to nonmetastatic (N)-IMC, or nonneoplastic gastric mucosa. Intriguingly, most of these selected miRNAs showed stepwise increased or decreased expression from nonneoplastic tissue to N-IMC to M-IMC. This suggests that common oncogenic mechanisms are gradually intensified during the metastatic process. Using a machine-learning algorithm, we demonstrated that such miRNA signatures could distinguish M-IMC from N-IMC. Gene ontology and pathway analysis revealed that TGF-ß signaling was enriched from upregulated miRNAs, whereas E2F targets, apoptosis-related, hypoxia-related, and PI3K/AKT/mTOR signaling pathways, were enriched from downregulated miRNAs. Immunohistochemical staining of samples from multiple institutions indicated that PI3K/AKT/mTOR pathway components, MAPK1, phospho-p44/42 MAPK, and pS6 were highly expressed and the expression of SMAD7, a TGF-ß pathway component, was decreased in M-IMC, which could aid in distinguishing M-IMC from N-IMC. The miRNA signature discovered in this study is a valuable biological marker for identifying metastatic potential of IMCs, and provides novel insights regarding the metastatic progression of IMC.

Gentiopicroside ameliorates ethanol-induced gastritis via regulating MMP-10 and pERK1/2 signaling.

BACKGROUND: Excessive ethanol consumption results in gastric mucosa damage, which could further develop into chronic gastritis, peptic ulcer, and gastric cancer in humans. Gentiopicroside (GPS), a major active component of Gentianae Macrophyllae radix, was reported to play a critical role in anti-inflammation. In the study, we aimed to investigate the functional role and underlying mechanism of GPS in ethanol-induced gastritis. METHODS: A model of gastritis was created by ethanol in C57BL/6 mice. Enzyme-linked immunosorbent assay was used to determine the concentration of TNF-α, IL-1ß, IL-8, and IL-10. RESULTS: We found that GPS treatment significantly ameliorated ethanol-induced gastritis in mice, with lower production of pro-inflammatory cytokine TNF-α, IL-1ß, and IL-8 and higher levels of anti-inflammatory cytokine IL-10. The anti-inflammatory effect of GPS was further confirmed in vitro in ethanol-treated human gastric mucosal GES cells. Mechanistically, we demonstrated that GPS regulated matrix metallopeptidase expression and pERK1/2 signaling. Knockdown of matrix metallopeptidase 10 (MMP-10) greatly improved cell survival and suppressed inflammatory response in ethanol-treated GES cells. Moreover, inhibition of pERK1/2 signaling using U0126 decreased the expression of MMP-10 in ethanol-induced gastritis. U0126 treatment also suppressed the expression of TNF-α, IL-1ß, and IL-8, and enhanced IL-10 expression in mice gastric mucosa. CONCLUSIONS: Taken together, our findings suggest that GPS ameliorates ethanol-induced gastritis via regulating MMP-10 and pERK1/2 signaling, which might provide a promising therapeutic drug for ethanol-induced gastritis.

A mechanistic model to study the effect of the cell wall on starch digestion in intact cotyledon cells.

The role of the plant matrix is recognized as the main factor restricting starch digestibility in beans. Several authors have provided insights about the mechanisms behind the reduced starch digestibility in plant matrices. In this study, by means of a mathematical model, we provide a mechanistic explanation of the role played by the cell wall. It was confirmed that starch entrapped within intact cells could only be hydrolysed after α-amylase diffusion through the cell wall. This process is limited by the pores naturally present in the cell wall and the adsorption of α-amylase to the cell wall surface. These factors restrict the concentration of α-amylase available within the cells. The model assumptions are valid under controlled laboratory conditions and were validated with in-vitro digestion data giving very accurate results. The proposed approach provides new information to understand the digestibility of starch, and possibly other macronutrients, in complex food matrices.

Structural changes in cow, goat, and sheep skim milk during dynamic in vitro gastric digestion.

Coagulation of milk in the stomach is the first crucial step in its digestion. Using a human gastric simulator, the dynamic gastric digestion of goat and sheep skim milk were compared with that of cow skim milk, focusing particularly on their physical characteristics. The gastric contents were analyzed for changes in dry matter and microstructure, and the extent of protein digestion. The study revealed that the skim milk from all species formed a curd within the first 15 min of gastric digestion, at which time the pH was ~6.1 to 6.3. Compared with cow skim milk, the dry matter contents of the clots formed from goat and sheep skim milk were lower and higher, respectively, which was due to the differences in their total solids and protein contents. Microstructural analysis showed that, as digestion progressed, the clot structure became more cohesive, along with a decrease in moisture content, which in turn affected the breakdown and hydrolysis of caseins by pepsin; this phenomenon was similar for milk from all species. However, the extent of moisture retained in the sheep skim milk clot appeared to be lower than those of the cow and goat skim milk clots. In addition, the relative firmness of the sheep milk clot was higher than those of the cow and goat milk clots at the end of gastric digestion. The pattern of protein hydrolysis by pepsin was similar for the milk of all species, despite the differences in the proportions of different proteins. The study provided insight into the coagulation kinetics of goat and sheep skim milk under in vitro gastric digestion conditions.

The effect of metformin on indomethacin-induced gastric ulcer: Involvement of nitric oxide/Rho kinase pathway.

Gastric ulcer is a very common disease that represent an economic burden. Non-steroidal anti-inflammatory drugs induce ulcer in old patients and in patients with comorbidities. Indomethacin is widely used to induce gastric ulcer in animal models. Diabetic patients are highly susceptible to develop gastric ulcer. Metformin, the first line medication for the treatment of type II diabetes melilites that have many off label uses in non-diabetic patients, has been recently reported to have anti-inflammatory activities. Therefore, this research was conducted to assess the possible healing effects of metformin on gastric ulcers induced by indomethacin in rats. Indomethacin (48 mg/kg) single dose increased stomach acidity, ulcer index and induced histopathological changes. Indomethacin also decreased mucin levels and increased the activity of tumor necrosis factor-α (TNF-α), nuclear factor kappa-B (NF-κB), Rho-associated protein kinas-1 (ROCK-1) and decreased the levels of the protective nitric oxide (NO). After the induction of ulcer, rats were treated by omeprazole (30 mg/kg) or metformin (50, 100 or 200 mg/kg). Omeprazole and metformin were found to decrease stomach acidity and ulcer index, restored the histological features and increased mucin levels. Both also decreased the levels of NF-κB, TNF-α, ROCK-1 and increased NO. Metformin exerted ulcer healing effects comparable to that of omeprazole. This can be attributed, at least partly, to its anti-inflammatory activity and increasing NO levels.

Design, synthesis, and biological evaluation of new pyrazoloquinazoline derivatives as dual COX-2/5-LOX inhibitors.

A new series of pyrazoloquinazoline derivatives equipped with different chalcones was designed, synthesized, and identified through 1 H nuclear magnetic resonance (NMR), 13 C NMR, and infrared spectroscopic techniques. Our design strategy of the quinazolinone-privileged scaffold as a new scaffold was based on merging pharmacophores previously reported to exhibit cyclooxygenase-2 (COX-2)/5-lipoxygenase (5-LOX) inhibitory activity. All the newly synthesized derivatives were biologically evaluated for COX and 5-LOX inhibitory activity and COX-2 selectivity, using celecoxib and zileuton as reference drugs, as they exhibited promising anti-inflammatory activity. Compound 3j was found to be the most promising derivative, with IC50 values of 667 and 47 nM against COX-1 and COX-2, respectively, which are superior to that of celecoxib (IC50 value against COX-2 = 95 nM), showing an SI of 14.2 that was much better than celecoxib. Compounds 3f and 3h exhibited COX-1 inhibition, with IC50 values of 1,485 and 684 nM, respectively. The synthesized compounds showed a significant inhibitory activity against 5-LOX, with IC50 values ranging from 0.6 to 4.3 µM, where compounds 3f and 3h were found to be the most potent derivatives, with IC50 values of 0.6 and 1.0 µM, respectively, in comparison with that of zileuton (IC50 = 0.8 µM). These promising derivatives, 3f, 3h, and 3j, were further investigated in vivo for anti-inflammatory, gastric ulcerogenic effects, and prostaglandin production (PGE2) in rat serum. The molecular docking studies concerning the binding sites of COX-2 and 5-LOX revealed similar orientation, compared with reported inhibitors, which encouraged us to design new leads targeting COX-2 and 5-LOX as dual inhibitors, as a new avenue in anti-inflammatory therapy.

Helicobacter pylori infection impairs chaperone-assisted maturation of Na-K-ATPase in gastric epithelium.

Helicobacter pylori infection always induces gastritis, which may progress to ulcer disease or cancer. The mechanisms underlying mucosal injury by the bacteria are incompletely understood. Here, we identify a novel pathway for H. pylori-induced gastric injury, the impairment of maturation of the essential transport enzyme and cell adhesion molecule, Na-K-ATPase. Na-K-ATPase comprises α- and ß-subunits that assemble in the endoplasmic reticulum (ER) before trafficking to the plasma membrane. Attachment of H. pylori to gastric epithelial cells increased Na-K-ATPase ubiquitylation, decreased its surface and total levels, and impaired ion balance. H. pylori did not alter degradation of plasmalemma-resident Na-K-ATPase subunits or their mRNA levels. Infection decreased association of α- and ß-subunits with ER chaperone BiP and impaired assembly of α/ß-heterodimers, as was revealed by quantitative mass spectrometry and immunoblotting of immunoprecipitated complexes. The total level of BiP was not altered, and the decrease in interaction with BiP was not observed for other BiP client proteins. The H. pylori-induced decrease in Na-K-ATPase was prevented by BiP overexpression, stopping protein synthesis, or inhibiting proteasomal, but not lysosomal, protein degradation. The results indicate that H. pylori impairs chaperone-assisted maturation of newly made Na-K-ATPase subunits in the ER independently of a generalized ER stress and induces their ubiquitylation and proteasomal degradation. The decrease in Na-K-ATPase levels is also seen in vivo in the stomachs of gerbils and chronically infected children. Further understanding of H. pylori-induced Na-K-ATPase degradation will provide insights for protection against advanced disease.NEW & NOTEWORTHY This work provides evidence that Helicobacter pylori decreases levels of Na-K-ATPase, a vital transport enzyme, in gastric epithelia, both in acutely infected cultured cells and in chronically infected patients and animals. The bacteria interfere with BiP-assisted folding of newly-made Na-K-ATPase subunits in the endoplasmic reticulum, accelerating their ubiquitylation and proteasomal degradation and decreasing efficiency of the assembly of native enzyme. Decreased Na-K-ATPase expression contributes to H. pylori-induced gastric injury.

Hydrogen molecules can modulate enzymatic activity and structural properties of pepsin in vitro.

Hydrogen gas therapy has been recognized as the promising application merit. However, the underlying mechanism on the biological effects remains far from being understood. In this work, pepsin used as a research model, the effects of hydrogen-rich water on the protein activities and structural properties were investigated by enzymatic assay, atomic force microscopy-based peakforce quantitative nanomechanical mapping (PF-QNM) and terahertz time-domain spectroscopy (THz-TDS). We found that hydrogen-rich water can increase the protein activity and its apparent height while alter the mechanical properties (Young's modulus) and the terahertz dynamics. These results suggest a possible mode of hydrogen molecules acting with pepsin through the local changes of hydrophobic interfaces in the protein molecules, thus provide the first evidence for the direct interaction between hydrogen with proteins and a biophysical insight into the mechanism of hydrogen as well as other gases on the biological effects.

Helicobacter Pylori Targets the EPHA2 Receptor Tyrosine Kinase in Gastric Cells Modulating Key Cellular Functions.

Helicobacter pylori, a stomach-colonizing Gram-negative bacterium, is the main etiological factor of various gastroduodenal diseases, including gastric adenocarcinoma. By establishing a life-long infection of the gastric mucosa, H. pylori continuously activates host-signaling pathways, in particular those associated with receptor tyrosine kinases. Using two different gastric epithelial cell lines, we show that H. pylori targets the receptor tyrosine kinase EPHA2. For long periods of time post-infection, H. pylori induces EPHA2 protein downregulation without affecting its mRNA levels, an effect preceded by receptor activation via phosphorylation. EPHA2 receptor downregulation occurs via the lysosomal degradation pathway and is independent of the H.pylori virulence factors CagA, VacA, and T4SS. Using small interfering RNA, we show that EPHA2 knockdown affects cell-cell and cell-matrix adhesion, invasion, and angiogenesis, which are critical cellular processes in early gastric lesions and carcinogenesis mediated by the bacteria. This work contributes to the unraveling of the underlying mechanisms of H. pylori-host interactions and associated diseases. Additionally, it raises awareness for potential interference between H. pylori infection and the efficacy of gastric cancer therapies targeting receptors tyrosine kinases, given that infection affects the steady-state levels and dynamics of some receptor tyrosine kinases (RTKs) and their signaling pathways.