Superoxide dismutase activity of Helicobacter pylori per se from 158 clinical isolates and the characteristics

Evidence of Helicobacter pylori heterogeneity in human stomachs by susceptibility testing and characterization of mutations in drug-resistant isolates

Heterogeneity of Helicobacter pylori communities contributes to its pathogenicity and diverse clinical outcomes. We conducted drug-susceptibility tests using four antibiotics, clarithromycin (CLR), amoxicillin (AMX), metronidazole and sitafloxacin, to examine H. pylori population diversity. We also analyzed genes associated with resistance to CLR and AMX. We examined multiple isolates from 42 Japanese patients, including 28 patients in whom primary eradication with CLR and AMX had failed, and 14 treatment-naïve patients. We identified some patients with coexistence of drug resistant- and sensitive-isolates (drug-heteroR/S-patients). More than 60% of patients were drug-heteroR/S to all four drugs, indicating extensive heterogeneity. For the four drugs except AMX, the rates of drug-heteroR/S-patients were higher in treatment-naïve patients than in primary eradication-failure patients. In primary eradication-failure patients, isolates multi-resistant to all four drugs existed among other isolates. In primary eradication-failure drug-heteroR/S-patients, CLR- and AMX-resistant isolates were preferentially distributed to the corpus and antrum with different minimum inhibitory concentrations, respectively. We found two mutations in PBP1A, G591K and A480V, and analyzed these in recombinants to directly demonstrate their association with AMX resistance. Assessment of multiple isolates from different stomach regions will improve accurate assessment of H. pylori colonization status in the stomach.

Helicobacter pylori infection-A risk factor for lipid peroxidation and superoxide dismutase over-activity: A cross-sectional study among patients with dyspepsia in Cameroon

Background and Aim

There is an intimate relationship between oxidative stress and inflammation. Helicobacter pylori (H. pylori) infection leads to gastritis in almost all the hosts. So, we hypothesize that gastritis in H. pylori infection may be described as the accumulation of continuous oxidative damage.

Methods

The study was conducted from October 2020 to October 2021 at three reference health facilities in Cameroon. A total of 266 participants (131 males and 135 females) ranging from 15 to 88 years old with 48.28 ± 17.29 years as mean age were enrolled. Each participant gave a written informed consent and ethical committees approved the protocol. Biopsies samples were collected for H. pylori detection using histological examination and rapid urease test. Malondialdehyde (MDA) and glutathione (GSH) content, and catalase (CAT) and superoxide dismutase (SOD) activities were evaluated in serum as biomarkers of oxidative stress.

Results

Helicobacter pylori was detected in 71.80% of our sample population. Low income level was associated with higher GSH level (P = 0.0249) and having family history of gastric cancer to higher SOD activity (P = 0.0156). A significant higher MDA content (P < 0.0001) and SOD activity (P = 0.0235) was recorded among infected individuals compared with noninfected ones. A significantly higher MDA content and SOD activity was recorded among smokers (P = 0.0461) and participants older than 50 years old (P = 0.0491) with H. pylori positivity.

Conclusion

Our findings showed that H. pylori infection is associated with overproduction of reactive oxygen species and oxidative stress. The presence of this pathogen in elderly individuals or in smokers increased their risk for oxidative stress.

Anti-Helicobacter pylori, anti-Inflammatory, and Antioxidant Activities of Trunk Bark of Alstonia boonei (Apocynaceae)

An ulcer is an erosion of the gastric mucosa that occurs following an imbalance between the aggression and protective factors and/or an infection with Helicobacter pylori (H. pylori). About 90-100% of duodenal ulcers and 70-80% of gastric ulcers are caused by H. pylori. The objective of this work was to evaluate in vitro the anti-H. pylori activity and then the anti-inflammatory and antioxidant properties of aqueous and methanol extracts of Alstonia boonei. The anti-H. pylori tests (CMI and antiureasic activity) were determined using the agar well diffusion method, the microbroth dilution method, and the measurement of ammonia production by the indophenol method; the anti-inflammatory properties were evaluated by inhibition of proteinases, denaturation of albumin, production of NO by macrophages, cell viability, and hemolysis of red blood cells by heat; then, the antioxidant properties were evaluated by the FRAP method (ferric reducing antioxidant power) and the DPPH (1,1-diphenyl-2-picrylhydrazyl) test. The results show that the best trapping of the DPPH radical was obtained with the methanol extract (EC₅₀ = 8.91 μg/mL) compared to the aqueous extract (EC₅₀ = 19.86 μg/mL). The methanol extract also showed greater iron-reducing activity than the aqueous extract and vitamin C. Furthermore, at the concentration of 200 μg/mL, the methanol extract showed a percentage (96.34%) strains of H. pylori higher than that of the aqueous extract (88.52%). The MIC₉₀ of the methanol extract was lower than that of the aqueous extract. The methanol extract showed a higher percentage inhibition (85%) of urease than the aqueous extract (73%). The methanol extract at a concentration of 1000 μg/mL showed the greatest ability to inhibit proteinase activity, albumin denaturation, and red blood cell hemolysis; on the other hand, maximum cell viability and greater production of nitrite oxide by macrophages were obtained with the aqueous extract. Aqueous and methanol extracts of Alstonia boonei possess anti-H. pylori which would probably be linked to their antioxidant and anti-inflammatory properties.

Helicobacter pylori-Mediated Oxidative Stress and Gastric Diseases: A Review

Gastric cancer is considered to be a type of gastrointestinal tumor and is mostly accompanied by Helicobacter pylori (HP) infection at the early stage. Hence, the long-term colonization of the gastric mucosa by HP as a causative factor for gastrointestinal diseases cannot be ignored. The virulence factors secreted by the bacterium activate the signaling pathway of oxidative stress and mediate chronic inflammatory response in the host cells. The virulence factors also thwart the antibacterial effect of neutrophils. Subsequently, DNA methylation is induced, which causes continuous cell proliferation and evolution toward low-grade-differentiated gastric cells. This process provides the pathological basis for the occurrence of progressive gastric cancer. Therefore, this review aims to summarize the oxidative stress response triggered by HP in the gastric mucosa and the subsequent signaling pathways. The findings are expected to help in the formulation of new targeted drugs for preventing the occurrence of early gastric cancer and its progression to middle and advanced cancer.

Helicobacter pylori: an up-to-date overview on the virulence and pathogenesis mechanisms

Helicobacter pylori is an organism associated with ulcer disease and gastric cancer. The latter is one of the most prevalent malignancies and currently the fourth major cause of cancer-related deaths globally. The pathogen infects about 50% of the world population, and currently, no treatment ensures its total elimination. There has been an increase in our understanding of the pathophysiology and pathogenesis mechanisms of H. pylori over the years. H. pylori can induce several genetic alterations, express numerous virulence factors, and trigger diverse adaptive mechanisms during its adherence and colonization. For successful colonization and infection establishment, several effector proteins/toxins are released by the organism. Evidence is also available reporting spiral to coccoid transition as a unique tactic H. pylori uses to survive in the host’s gastrointestinal tract (GIT). Thus, the virulence and pathogenicity of H. pylori are under the control of complex interplay between the virulence factors, host, and environmental factors. Expounding the role of the various virulence factors in H. pylori pathogenesis and clinical outcomes is crucial for vaccine development and in providing and developing a more effective therapeutic intervention. Here we critically reflect on H. pylori infection and delineate what is currently known about the virulence and pathogenesis mechanisms of H. pylori.

Helicobacter pylori Virulence Factors-Mechanisms of Bacterial Pathogenicity in the Gastric Microenvironment

Gastric cancer constitutes one of the most prevalent malignancies in both sexes; it is currently the fourth major cause of cancer-related deaths worldwide. The pathogenesis of gastric cancer is associated with the interaction between genetic and environmental factors, among which infection by Helicobacter pylori (H. pylori) is of major importance. The invasion, survival, colonization, and stimulation of further inflammation within the gastric mucosa are possible due to several evasive mechanisms induced by the virulence factors that are expressed by the bacterium. The knowledge concerning the mechanisms of H. pylori pathogenicity is crucial to ameliorate eradication strategies preventing the possible induction of carcinogenesis. This review highlights the current state of knowledge and the most recent findings regarding H. pylori virulence factors and their relationship with gastric premalignant lesions and further carcinogenesis.

Polyamine- and NADPH-dependent generation of ROS during Helicobacter pylori infection: A blessing in disguise

Helicobacter pylori is a Gram-negative bacterium that specifically colonizes the gastric ecological niche. During the infectious process, which results in diseases ranging from chronic gastritis to gastric cancer, the host response is characterized by the activation of the innate immunity of gastric epithelial cells and macrophages. These cells thus produce effector molecules such as reactive oxygen species (ROS) to counteract the infection. The generation of ROS in response to H. pylori involves two canonical pathways: 1) the NADPH-dependent reduction of molecular oxygen to generate O₂^•-, which can dismute to generate ROS; and 2) the back-conversion of the polyamine spermine into spermidine through the enzyme spermine oxidase, leading to H₂O₂ production. Although these products have the potential to affect the survival of bacteria, H. pylori has acquired numerous strategies to counteract their deleterious effects. Nonetheless, ROS-mediated oxidative DNA damage and mutations may participate in the adaptation of H. pylori to its ecological niche. Lastly, ROS have been shown to play a major role in the development of the inflammation and carcinogenesis. It is the purpose of this review to summarize the literature about the production of ROS during H. pylori infection and their role in this infectious gastric disease.

The study of H. pylori putative candidate factors for single- and multi-component vaccine development

Helicobacter pylori has grown to colonize inside the stomach of nearly half of the world's population, turning into the most prevalent infections in the universe. Medical care failures noticeably confirm the need for a vaccine to hinder or deal with H. pylori. This review is planned to discuss the most known factors as a vaccine candidate, including single (AhpC, BG, CagA, KatA, Fla, Hsp, HWC, Lpp, LPS, NAP, OMP, OMV, SOD, Tpx, Urease, VacA) and multi-component vaccines. Many promising results in the field of single and multivalent vaccine can be seen, but there is no satisfactory outcome and neither a prophylactic nor a therapeutic vaccine to treat or eradicate the infection in human has been acquired. Hence, selecting suitable antigen is an important factor as an appropriate adjuvant. Taken all together, the development of efficient anti-H. pylori vaccines relies on the fully understanding of the interactions between H. pylori and its host immune system. Therefore, more work should be done on epitope mapping, analysis of molecular structure, and determination of the antigen determinant region as well due to design a vaccine, preferably a multi-component vaccine to elicit specific CD4 T-cell responses that are required for H. pylori vaccine efficacy.

Diphenyleneiodonium Inhibits Apoptotic Cell Death of Gastric Epithelial Cells Infected with Helicobacter pylori in a Korean Isolate

NADPH oxidase produces a large amount of reactive oxygen species (ROS) in Helicobacter pylori (H. pylori)-induced gastric epithelial cells. Even though ROS mediate apoptotic cell death, direct involvement of NADPH oxidase on H. pylori-induced apoptosis remains unclear. Besides, H. pylori isolates show a high degree of genetic variability. The predominant genotype of H. pylori in Korea has been reported as cagA⁺, vacA s1b, m2, iceA genotype. Present study aims to investigate whether NADPH oxidase-generated ROS mediate apoptosis in human gastric epithelial AGS cells infected with H. pylori in a Korean isolate. AGS cells were pretreated with or without an NADPH oxidase inhibitor diphenyleneiodonium (DPI) and cultured in the presence of H. pylori at a bacterium/cell ratio of 300:1. Cell viability, hydrogen peroxide level, DNA fragmentation, and protein levels of p53, Bcl-2, and Bax were determined. Results showed that H. pylori inhibited cell viability with the density of H. pylori added to the cells. Inhibition of NADPH oxidase by DPI suppressed H. pylori-induced cell death, increased hydrogen peroxide, DNA fragmentation, and the ratio of Bax/Bcl-2, and p53 induction in AGS cells dose-dependently. The results suggest that targeting NADPH oxidase may prevent the development of gastric inflammation associated with H. pylori infection by suppressing abnormal apoptotic cell death of gastric epithelial cells.

Response to metronidazole and oxidative stress is mediated through homeostatic regulator HsrA (HP1043) in Helicobacter pylori

Metronidazole (MTZ) is often used in combination therapies to treat infections caused by the gastric pathogen Helicobacter pylori. Resistance to MTZ results from loss-of-function mutations in genes encoding RdxA and FrxA nitroreductases. MTZ-resistant strains, when cultured at sub-MICs of MTZ (5 to 20 μg/ml), show dose-dependent defects in bacterial growth; depressed activities of many Krebs cycle enzymes, including pyruvate:ferredoxin oxidoreductase (PFOR); and low transcript levels of porGDAB (primer extension), phenotypes consistent with an involvement of a transcriptional regulator. Using a combination of protein purification steps, electrophoretic mobility shift assays (EMSAs), and mass spectrometry analyses of proteins bound to porG promoter sequences, we identified HP1043, an essential homeostatic global regulator (HsrA [for homeostatic stress regulator]). Competition EMSAs and supershift analyses with HsrA-enriched protein fractions confirmed specific binding to porGDAB and hsrA promoter sequences. Exposure to MTZ resulted in >10-fold decreases in levels of HsrA and in levels of the HsrA-regulated gene products PFOR and TlpB. Exposure to paraquat (PQ), hydrogen peroxide, or organic peroxides showed near equivalence with MTZ, revealing a common oxidative stress response pathway. Finally, direct superoxide dismutase (SOD) assays showed an inverse relationship between HsrA levels and SOD activity, suggesting that HsrA may serve as a repressor of sodB. As a homeostatic sentinel, HsrA appears to be ideally positioned to enable rapid shutdown of genes associated with metabolism and growth while activating (directly or indirectly) oxidative defense genes in response to low levels of toxic metabolites (MTZ or oxygen) before they reach DNA-damaging levels.

Pathogenesis of Helicobacter pylori infection

Helicobacter pylori infection and disease outcome are mediated by a complex interplay between bacterial, host, and environmental factors. Over the past year, our understanding of this complex interplay has been improved by a variety of studies focusing on both host and bacterial factors. These include studies assessing novel virulence factors as well as those most frequently associated with severity of disease outcome including cagA and the cag pathogenicity island, and the vacuolating cytotoxin. Several studies have focused on regulation of virulence factors by environmental factors. In addition, mechanisms by which bacterial virulence factors influence the host response and disease, by inducing epigenetic changes, autophagy and altered oxidative stress have also been elucidated. This review highlights key findings in the pathogenesis of H. pylori infection reported over the past year.