Functional disruption of peroxiredoxin by bismuth antiulcer drugs attenuates Helicobacter pylori survival

Reactive oxygen species and gastric carcinogenesis: The complex interaction between Helicobacter pylori and host

Helicobacter pylori (H. pylori) is a highly successful human pathogen that colonizes stomach in around 50% of the global population. The colonization of bacterium induces an inflammatory response and a substantial rise in the production of reactive oxygen species (ROS) and reactive nitrogen species (RNS), mostly derived from host neutrophils and gastric epithelial cells, which play a crucial role in combating bacterial infections. However, H. pylori has developed various strategies to quench the deleterious effects of ROS, including the production of antioxidant enzymes, antioxidant proteins as well as blocking the generation of oxidants. The host's inability to eliminate H. pylori infection results in persistent ROS production. Notably, excessive ROS can disrupt the intracellular signal transduction and biological processes of the host, incurring chronic inflammation and cellular damage, such as DNA damage, lipid peroxidation, and protein oxidation. Markedly, the sustained inflammatory response and oxidative stress during H. pylori infection are major risk factor for gastric carcinogenesis. In this context, we summarize the literature on H. pylori infection-induced ROS production, the strategies used by H. pylori to counteract the host response, and subsequent host damage and gastric carcinogenesis.

The effects of sodium sulfite on Helicobacter pylori by establishing a hypoxic environment

Helicobacter pylori (H. pylori) is an obligate microaerobion and does not survive in low oxygen. Sodium sulfite (SS) reacts and consume oxygen in solutions. The present study aimed to investigate the effects of SS on H. pylori. The effects of SS on oxygen concentrations in solutions and on H. pylori in vivo and in vitro were examined, and the mechanisms involved were explored. The results showed that SS decreased the oxygen concentration in water and artificial gastric juice. In Columbia blood agar and special peptone broth, SS concentration-dependently inhibited the proliferation of H. pylori ATCC43504 and Sydney strain-1 in Columbia blood agar or special peptone broth, and dose-dependently decreased the number of H. pylori in Mongolian gerbils and Kunming mouse infection models. The H. pylori was relapsed in 2 weeks withdrawal and the recurrence in the SS group was lower than that in the positive triple drug group. These effects were superior to positive triple drugs. After SS treatments, the cell membrane and cytoplasm structure of H. pylori were disrupted. SS-induced oxygen-free environment initially blocked aerobic respiration, triggered oxidative stress, disturbed energy production. In conclusion, SS consumes oxygen and creates an oxygen-free environment in which H. pylori does not survive. The present study provides a new strategy and perspective for the clinical treatment of H. pylori infectious disease.

Integrative proteomic and metabolomic analyses reveal the mechanism by which bismuth enables Helicobacter pylori eradication

BACKGROUND

Bismuth-based drugs are used to treat Helicobacter pylori infection; however, the antibacterial activity of bismuth, especially against H. pylori, has not been fully elucidated. In this study, the mechanisms by which bismuth exerts its detrimental effects on H. pylori were evaluated. Methods Six H. pylori strains isolated from different patients were cultured with or without bismuth; proteins and metabolites differentially expressed in these two sets of bacteria were detected via data independent acquisition proteomic and gas chromatography-mass spectrometry metabolic approaches, respectively. Gene ontology functional analysis and Kyoto Encyclopedia of Genes and Genomes database were used to identity pathway enrichment.

RESULTS

Bismuth inhibited H. pylori growth in vitro via the following mechanisms: downregulation of virulence proteins CagA and VacA; disruption of flagella assembly responsible for bacterial colonization; and inhibition of antioxidant enzymes, including catalase, catalase-related peroxidase, and superoxide dismutase. Diverse metabolic pathways related to growth and RNA translation in H. pylori were disrupted by bismuth. Bismuth treatment impaired many biological processes in H. pylori, including antioxidant response and purine, pyrimidine, amino acid, and carbon metabolism. Conclusions The findings of this study suggest that motility, virulence factors CagA and VacA, antioxidant defense system, and many important metabolic pathways associated with bacterial growth, including nucleotide and amino acid metabolism and translation in H. pylori, are inhibited by bismuth. This study provides novel insights into the mechanism by which bismuth eradicates H. pylori upon being incorporated into quadruple therapy.

Medicinal chemistry and biomedical applications of bismuth-based compounds and nanoparticles

Bismuth as a relatively non-toxic and inexpensive metal with exceptional properties has numerous biomedical applications. Bismuth-based compounds are used extensively as medicines for the treatment of gastrointestinal disorders including dyspepsia, gastric ulcers and H. pylori infections. Recently, its medicinal application was further extended to potential treatments of viral infection, multidrug resistant microbial infections, cancer and also imaging, drug delivery and biosensing. In this review we have highlighted the unique chemistry and biological chemistry of bismuth-209 as a prelude to sections covering the unique antibacterial activity of bismuth including a description of research undertaken to date to elucidate key molecular mechanisms of action against H. pylori, the development of novel compounds to treat infection from microbes beyond H. pylori and the significant role bismuth compounds can play as resistance breakers. Furthermore we have provided an account of the potential therapeutic application of bismuth-213 in targeted alpha therapy as well as a summary of the biomedical applications of bismuth-based nanoparticles and composites. Ultimately this review aims to provide the state of the art, highlight the untapped biomedical potential of bismuth and encourage original contributions to this exciting and important field.

Hydrogen Peroxide-Mediated Oxygen Enrichment Eradicates Helicobacter pylori In Vitro and In Vivo

Helicobacter pylori is an important risk factor for gastric ulcers. However, antibacterial therapies increase the resistance rate and decrease the eradication rate of H. pylori Inspired by the microaerophilic characteristics of H. pylori, we aimed at effectively establishing an oxygen-enriched environment to eradicate and prevent the recurrence of H. pylori The effect and the mechanism of an oxygen-enriched environment in eradicating H. pylori and preventing the recurrence were explored in vitro and in vivo During oral administration and after drug withdrawal, H. pylori counts were evaluated by Giemsa staining in animal cohorts. An oxygen-enriched environment in which H. pylori could not survive was successfully established by adding hydrogen peroxide into several solutions and rabbit gastric juice. Hydrogen peroxide effectively killed H. pylori in Columbia blood agar and special peptone broth. Minimum inhibition concentrations and minimum bactericidal concentrations of hydrogen peroxide were both relatively stable after promotion of resistance for 30 generations, indicating that hydrogen peroxide did not easily promote resistance in H. pylori In models of Mongolian gerbils and Kunming mice, hydrogen peroxide has been shown to significantly eradicate and effectively prevent the recurrence of H. pylori without toxicity and damage to the gastric mucosa. The mechanism of hydrogen peroxide causing H. pylori death was related to the disruption of bacterial cell membranes. The oxygen-enriched environment achieved by hydrogen peroxide eradicates and prevents the recurrence of H. pylori by damaging bacterial cell membranes. Hydrogen peroxide thus provides an attractive candidate for anti-H. pylori treatment.

The synergy of resveratrol and alcohol against Helicobacter pylori and underlying anti-Helicobacter pylori mechanism of resveratrol

AIMS

To determine individual antibacterial and synergistic antibacterial effects of resveratrol and alcohol against Helicobacter pylori 26695 in vitro, and to elucidate the underlying mechanism of action of resveratrol against H. pylori.

METHODS AND RESULTS

The minimum inhibitory concentrations (MICs) and time-killing curve of resveratrol and alcohol were determined. Transcriptome analysis by RNA sequencing was used to elucidate the underlying mechanism of action of resveratrol against H. pylori. Our results showed that the MICs of resveratrol and alcohol against H. pylori 26695 are about 64 μg ml^-1 and 4% (v/v) respectively. The synergy was found: resveratrol at concentration of 64 μg ml^-1 in combination with alcohol at concentration of 4% (v/v) showed >10 000-fold decrease in the mount of viable bacteria compared with resveratrol and alcohol used alone. Transcriptome analysis showed 152 genes were downregulated and 111 genes were upregulated in the presence of resveratrol. Genes involved in protein translation (17·1%), outer membrane proteins (OMPs) (9·9%) and transports (11·2%) comprise 38·2% of the downregulated genes. In comparison, genes involved in redox (13·5%), pathogenesis and motility (9·9%) and iron homeostasis (4·5%) comprise 27·9% of the upregulated genes.

CONCLUSIONS

The synergy of resveratrol and alcohol against H. pylori was found in this study. The underlying mechanism of action of resveratrol against H. pylori may be mainly attributed to its inhibitory effect on translation, OMPs, transports, ATP synthase and possible oxidative damage.

SIGNIFICANCE AND IMPACT OF THIS STUDY

Our study provides a global insight into the anti-H. pylori mechanism of resveratrol. Both resveratrol and alcohol can contribute to inhibition of ribosomes, changes in OMPs and oxidative damage, which may be the explanations of synergistic effect against H. pylori elicited by resveratrol and alcohol.

Inactivation of NikR from Helicobacter pylori by a bismuth drug

The NikR protein is an essential DNA regulator of Helicobacter pylori, a human pathogen, which infects almost half of the world's population. Herein, we comprehensively characterized the interaction of a bismuth drug with Helicobacter pylori NikR. We show that Bi(III) can occupy the high-affinity Ni(II) site of NikR. The highly-conserved residue Cys107 at this site is critical for Bi(III) binding. Importantly, such a binding disassembles physiologically functional NikR tetramer into inactive dimer, leading to abrogation of the DNA-binding capability of NikR. Bi(III)-binding also significantly disturbs regulatory function of Helicobacter pylori NikR in vivo. Therefore, NikR might serve as a potential intracellular target of a bismuth drug.

Systems Approaches for Unveiling the Mechanism of Action of Bismuth Drugs: New Medicinal Applications beyond Helicobacter Pylori Infection

Metallodrugs have been widely used as diagnostic and therapeutic agents. Understanding their mechanisms of action may lead to advances in rational drug design. However, to achieve this, diversified approaches are required because of the complexity of metal-biomolecule interactions. Bismuth drugs in combination with antibiotics as a quadruple therapy show excellent success rates in the eradication of Helicobacter pylori, even for antibiotic-resistant strains, and in fact, they have been used in the clinic for decades for the treatment of infection. Understanding the mechanism of action of bismuth drugs may extend their medicinal application beyond the treatment of H. pylori infection. This Account describes several general strategies for mechanistic studies of metallodrugs, including system pharmacology and metalloproteomics approaches. The application of these approaches is exemplified using bismuth drugs. Through a system pharmacology approach, we showed that glutathione- and multidrug-resistance-associated protein 1-mediated self-propelled disposal of bismuth in human cells might explain the selective toxicity of bismuth drugs to H. pylori but not the human host. The development of metalloproteomics has enabled extensive studies of the putative protein targets of metallodrugs with a dynamic range of affinity. Continuous-flow GE-ICP-MS allows simultaneous monitoring of metals and their associated proteins with relatively high affinity on a proteome-wide scale. The fluorescence approach relies on unique M ⁿ⁺-NTA-based fluorescence probes and is particularly applicable for mining those proteins that bind to metals/metallodrugs weakly or transiently. Integration of these methods with quantitative proteomics makes it possible to maximum coverage of bismuth-associated proteins, and the sustained efficacy of bismuth drugs lies in their ability to disrupt multiple biological pathways through binding and functional perturbation of key enzymes. The knowledge acquired by mechanistic studies of bismuth drugs led to the discovery of UreG as a new target for the development of urease inhibitors. The ability of Bi(III) to inhibit metallo-β-lactamase (MBL) activity through displacement of the Zn(II) cofactor renders bismuth drugs new potential as broad-spectrum inhibitors of MBLs. Therefore, bismuth drugs could be repurposed together with clinically used antibiotics as a cotherapy to cope with the current antimicrobial resistance crisis. We anticipate that the methodologies described in this Account are generally applicable for understanding the (patho)physiological roles of metals/metallodrugs. Our mechanism-guided discovery of new druggable targets as well as new medicinal applications of bismuth drugs will inspire researchers in relevant fields to engage in the rational design of drugs and reuse of existing drugs, eventually leading to the development of new effective therapeutics.

Multi-omics and temporal dynamics profiling reveal disruption of central metabolism in Helicobacter pylori on bismuth treatment

Integration of multi-omics enables uncovering cellular responses to stimuli or the mechanism of action of a drug at a system level. Bismuth drugs have long been used for the treatment of Helicobacter pylori infection and their antimicrobial activity was attributed to dysfunction of multiple proteins based on previous proteome-wide studies. Herein, we investigated the response of H. pylori to a bismuth drug at transcriptome and metabolome levels. Our multi-omics data together with bioassays comprehensively reveal the impact of bismuth on a diverse array of intracellular pathways, in particular, disruption of central carbon metabolism is systematically evaluated as a primary bismuth-targeting system in H. pylori. Through temporal dynamics profiling, we demonstrate that bismuth initially perturbs the TCA cycle and then urease activity, followed by the induction of oxidative stress and inhibition of energy production, and in the meantime, induces extensive down-regulation in H. pylori metabolome. The present study thus expands our knowledge on the inhibitory actions of bismuth and provides a novel systematic perspective of H. pylori in response to a clinical drug that sheds light on enhanced therapeutic methodologies.

Gastroprotective effect of oral kefir on indomethacin-induced acute gastric lesions in mice: Impact on oxidative stress

AIMS

This study investigated the gastroprotective effects and the systemic oxidative status of oral kefir pretreatment in albino mice submitted to acute gastric ulcer induced by indomethacin.

MAIN METHODS

Male Swiss mice were divided into three groups (n = 7): Vehicle (0.3 mL of whole milk/100 g body weight, pH adjusted to 5.0), Kefir (0.3 mL of kefir/100 g body weight) and Proton Pump Inhibitor (PPI, 30 mg/kg of lansoprazole), via gavage for 14 days. Animals were fasted for 16 h and treated orally with indomethacin (40 mg/kg). After 6 h the animals were euthanized, the blood samples were obtained and used for the determination of ROS production, oxidation of macromolecules and apoptosis. The stomachs were removed, opened by the greater curvature, and a macroscopic analysis of the gastric lesions was performed.

KEY FINDINGS

Our findings demonstrated that the symbiotic kefir significantly alleviated blood oxidative stress by reducing superoxide anion, hydrogen peroxide and hydroxyl/peroxynitrite radicals, thereby leading to reduced oxidative damage to macromolecules due to a decreased oxidative stress status in induced gastric lesions. These anti-oxidative properties might contribute favorably to the ulcer attenuation in the kefir group.

SIGNIFICANCE

Taken together, these findings support a significant role played by the antioxidant actions of kefir in counteracting the gastric damage induced by this cyclooxygenase inhibitor. It is also worthy to mention that, kefir also exerted the gastroprotective property partly by inhibiting oxidative systemic damage. Based on these considerations, it was implied that kefir might be a contributor for the ROS-scavenging effect.

Cytotoxicity of biologically synthesised bismuth nanoparticles against HT-29 cell line

This study was purposed to examine the cytotoxicity and functions of biologically synthesised bismuth nanoparticles (Bi NPs) produced by Delftia sp. SFG on human colon adenocarcinoma cell line of HT-29. The structural properties of Bi NPs were investigated using transmission electron microscopy, energy dispersive X-ray, and X-ray diffraction techniques. The cytotoxic effects of Bi NPs were analysed using flow cytometry cell apoptosis while western blot analyses were applied to analyse the cleaved caspase-3 expression. Oxidative stress (OS) damage was determined using the measurement of the glutathione (GSH) and malondialdehyde (MDA) levels and antioxidant activity of superoxide dismutase (SOD) and catalase (CAT) levels. The half maximal inhibitory concentration (IC50) value of Bi NPs was measured to be 28.7 ± 1.4 µg/ml on HT-29 cell line. The viability of HT-29 represented a concentration-dependent pattern (5-80 µg/ml). The mode of Bi NPs induced apoptosis was found to be mainly related to late apoptosis or necrosis at IC50 concentration, without the effect on caspase-3 activities. Furthermore, Bi NPs reduced the GSH and increased the MDA levels and decreased the SOD and CAT activities. Taken together, biogenic Bi NPs induced cytotoxicity on HT-29 cell line through the activation of late apoptosis independent of caspase pathway and may enhance the OS biomarkers.