Helicobacter pylori, Its Urease and Carbonic Anhydrases, and Macrophage Nitric Oxide Synthase

Interplay of carbon dioxide and peroxide metabolism in mammalian cells

The carbon dioxide/bicarbonate (CO₂/HCO₃^-) molecular pair is ubiquitous in mammalian cells and tissues, mainly as a result of oxidative decarboxylation reactions that occur during intermediary metabolism. CO₂ is in rapid equilibrium with HCO₃^-via the hydration reaction catalyzed by carbonic anhydrases. Far from being an inert compound in redox biology, CO₂ enhances or redirects the reactivity of peroxides, modulating the velocity, extent, and type of one- and two-electron oxidation reactions mediated by hydrogen peroxide (H₂O₂) and peroxynitrite (ONOO^-/ONOOH). Herein, we review the biochemical mechanisms by which CO₂ engages in peroxide-dependent reactions, free radical production, redox signaling, and oxidative damage. First, we cover the metabolic formation of CO₂ and its connection to peroxide formation and decomposition. Next, the reaction mechanisms, kinetics, and processes by which the CO₂/peroxide interplay modulates mammalian cell redox biology are scrutinized in-depth. Importantly, CO₂ also regulates gene expression related to redox and nitric oxide metabolism and as such influences oxidative and inflammatory processes. Accumulated biochemical evidence in vitro, in cellula, and in vivo unambiguously show that the CO₂ and peroxide metabolic pathways are intertwined and together participate in key redox events in mammalian cells.

The Effects of Vitamins and Micronutrients on Helicobacter pylori Pathogenicity, Survival, and Eradication: A Crosstalk between Micronutrients and Immune System

Helicobacter pylori as a class I carcinogen is correlated with a variety of severe gastroduodenal diseases; therefore, H. pylori eradication has become a priority to prevent gastric carcinogenesis. However, due to the emergence and spread of multidrug and single drug resistance mechanisms in H. pylori, as well as serious side effects of currently used antibiotic interventions, achieving successful H. pylori eradication has become exceedingly difficult. Recent studies expressed the intention of seeking novel strategies to improve H. pylori management and reduce the risk of H. pylori-associated intestinal and extragastrointestinal disorders. For which, vitamin supplementation has been demonstrated in many studies to have a tight interaction with H. pylori infection, either directly through the regulation of the host inflammatory pathways or indirectly by promoting the host immune response. On the other hand, H. pylori infection is reported to result in micronutrient malabsorption or deficiency. Furthermore, serum levels of particular micronutrients, especially vitamin D, are inversely correlated to the risk of H. pylori infection and eradication failure. Accordingly, vitamin supplementation might increase the efficiency of H. pylori eradication and reduce the risk of drug-related adverse effects. Therefore, this review aims at highlighting the regulatory role of micronutrients in H. pylori-induced host immune response and their potential capacity, as intrinsic antioxidants, for reducing oxidative stress and inflammation. We also discuss the uncovered mechanisms underlying the molecular and serological interactions between micronutrients and H. pylori infection to present a perspective for innovative in vitro investigations, as well as novel clinical implications.

Identification and characterization of the α-CA in the outer membrane vesicles produced by Helicobacter pylori

The genome of Helicobacter pylori encodes for carbonic anhydrases (CAs, EC 4.2.1.1) belonging to the α- and β-CA classes, which together with urease, have a pivotal role in the acid acclimation of the microorganism within the human stomach. Recently, in the exoproteome of H. pylori, a CA with no indication of the corresponding class was identified. Here, using the protonography and the mass spectrometry, a CA belonging to the α-class was detected in the outer membrane vesicles (OMVs) generated by planktonic and biofilm phenotypes of four H. pylori strains. The amount of this metalloenzyme was higher in the planktonic OMVs (pOMVs) than in the biofilm OMVs (bOMVs). Furthermore, the content of α-CA increases over time in the pOMVs. The identification of the α-CA in pOMVs and bOMVs might shed new light on the role of this enzyme in the colonization, survival, persistence, and pathogenesis of H. pylori.

Analysis of the Relationship between Helicobacter pylori Infection and Diabetic Gastroparesis

Background:

Whether Helicobacter pylori infection is associated with diabetic gastroparesis (DGP) is unclear. This study aimed to investigate the potential correlation between H. pylori infection and DGP.

Methods:

In this study, 163 patients with type 2 diabetes mellitus and 175 nondiabetic patients who were treated in our department were divided into DGP, simple diabetes, non-DGP (NDG), and normal groups based on their conditions. The H. pylori infection rate in each group was calculated. H. pylori eradication therapy was performed for patients with H. pylori infection in each group. The eradication rates were compared between the groups, and the improvements in gastroparesis-associated symptoms were compared before and after treatment in patients with DGP.

Results:

The H. pylori infection rate was 74.6% in the DGP group, which was significantly higher than that in the simple diabetes (51.1%, P < 0.01), NDG (57.7%, P < 0.05), and normal groups (48.0%, P < 0.01). With increased disease course, the incidence of DGP and the H. pylori infection rate gradually increased (P < 0.05). In the DGP group, the incidences of upper abdominal pain and distention, early satiety, and anorexia were 75.5%, 66.0%, and 67.9%, respectively, before eradication treatment; and 43.4%, 35.8%, and 39.6%, respectively, after eradication treatment, and the difference was statistically significant (P < 0.01). In patients with DGP with successful H. pylori eradication, the number of barium strips discharged after eradication was 5.9 ± 1.0, which was significantly larger than that before treatment (4.1 ± 0.7, P < 0.01). In addition, the number of barium strips discharged was significantly larger in patients with DGP with successful H. pylori eradication than those with failed H. pylori eradication (P < 0.01).

Conclusions:

DGP development might be associated with H. pylori infection. H. pylori eradication can effectively improve dyspepsia-associated symptoms and delayed gastric emptying in patients with DGP.