Helicobacter pylori VacA induces autophagic cell death in gastric epithelial cells via the endoplasmic reticulum stress pathway

Hypoxia exacerbates the malignant transformation of gastric epithelial cells induced by long-term H. pylori infection

Helicobacter pylori is a microaerophilic Gram-negative bacterium that resides in the human stomach and is classified as a class I carcinogen for gastric cancer. Numerous studies have demonstrated that H. pylori infection plays a role in regulating the function of host cells, thereby contributing to the malignant transformation of these cells. However, H. pylori infection is a chronic process, and short-term cellular experiments may not provide a comprehensive understanding of the in vivo situation, especially when considering the lower oxygen levels in the human stomach. In this study, we aimed to investigate the mechanisms underlying gastric cell dysfunction after prolonged exposure to H. pylori under hypoxic conditions. We conducted a co-culture experiment using the gastric cell line GES-1 and H. pylori for 30 generations under intermittent hypoxic conditions. By closely monitoring cell proliferation, migration, invasion, autophagy, and apoptosis, we revealed that sustained H. pylori stimulation under hypoxic conditions significantly influences the function of GES-1 cells. This stimulation induces epithelial-mesenchymal transition and contributes to the propensity for malignant transformation of gastric cells. To confirm the in vitro results, we conducted an experiment involving Mongolian gerbils infected with H. pylori for 85 weeks. All the results strongly suggest that the Nod1 receptor signaling pathway plays a crucial role in H. pylori-related apoptosis and autophagy. In summary, continuous stimulation by H. pylori affects the functioning of gastric cells through the Nod1 receptor signaling pathway, increasing the likelihood of cell carcinogenesis. The presence of hypoxic conditions further exacerbates this process.IMPORTANCEDeciphering the collaborative effects of Helicobacter pylori infection on gastric epithelial cell function is key to unraveling the development mechanisms of gastric cancer. Prior research has solely examined the outcomes of short-term H. pylori stimulation on gastric epithelial cells under aerobic conditions, neglecting the bacterium's nature as a microaerophilic organism that leads to cancer following prolonged stomach colonization. This study mimics a more genuine in vivo infection scenario by repeatedly exposing gastric epithelial cells to H. pylori under hypoxic conditions for up to 30 generations. The results show that chronic exposure to H. pylori in hypoxia substantially increases cell migration, invasion, and epithelial-mesenchymal transition, while suppressing autophagy and apoptosis. This highlights the significance of hypoxic conditions in intensifying the carcinogenic impact of H. pylori infection. By accurately replicating the in vivo gastric environment, this study enhances our comprehension of H. pylori's pathogenic mechanisms in gastric cancer.

Phellodendron chinense C.K.Schneid: An in vitro study on its anti-Helicobacter pylori effect

ETHNOPHARMACOLOGICAL RELEVANCE

Phellodendron chinense C.K.Schneid(P. chinense Schneid) is known in TCM as Huang Bo, is traditionally used to support gastrointestinal function and alleviate stomach-related ailments, including gastric ulcer bleeding and symptoms of gastroesophageal reflux disease. Helicobacter pylori (H. pylori) is classified by the WHO as a Group 1 carcinogen. However, the specific activity and mechanism of action of P. chinense Schneid against H. pylori infection remain unclear. It has been noted that Huangjiu processing may alter the bitter and cold properties of P. chinense Schneid, but its effect on antimicrobial activity requires further investigation. Additionally, it remains uncertain whether berberine is the sole antimicrobial active component of P. chinense Schneid.

AIM OF STUDY

This study aims to elucidate the anti-H. pylori infection activity of P. chinense Schneid, along with its mechanism of action and key antimicrobial active components.

MATERIALS AND METHODS

Phytochemical analysis was carried out by UPLC-MS/MS. HPLC was employed to quantify the berberine content of the extracts. Antimicrobial activity was assessed using the micro broth dilution method. Morphology was observed using SEM. The impact on urease activity was analyzed through in vitro urease enzyme kinetics. RT-qPCR was employed to detect the expression of virulence genes, including adhesin, flagellum, urease, and cytotoxin-related genes. The adhesion effect was evaluated by immunofluorescence staining and agar culture.

RESULTS

P. chinense Schneid exhibited strong antimicrobial activity against both antibiotic-sensitive and resistant H. pylori strains, with MIC ranging from 40 to 160 μg/mL. Combination with amoxicillin, metronidazole, levofloxacin, and clarithromycin did not result in antagonistic effects. P. chinense Schneid induced alterations in bacterial morphology and structure, downregulated the expression of various virulence genes, and inhibited urease enzyme activity. In co-infection systems, P. chinense Schneid significantly attenuated H. pylori adhesion and urease relative content, thereby mitigating cellular damage caused by infection. Huangjiu processing enhanced the anti-H. pylori activity of P. chinense Schneid. Besides berberine, P. chinense Schneid contained seven other components with anti-H. pylori activity, with palmatine exhibiting the strongest activity, followed by jatrorrhizine.

CONCLUSIONS

This study sheds light on the potential therapeutic mechanisms of P. chinense Schneid against H. pylori infection, demonstrating its capacity to disrupt bacterial structure, inhibit urease activity, suppress virulence gene transcription, inhibit adhesion, and protect host cells. The anti-H. pylori activity of P. chinense Schneid was potentiated by Huangjiu processing, and additional components beyond berberine were identified as possessing strong anti-H. pylori activity. Notably, jatrorrhizine, a core component of P. chinense Schneid, exhibited significant anti-H. pylori activity, marking a groundbreaking discovery.

The modulatory effect of Lactobacillus gasseri ATCC 33323 on autophagy induced by extracellular vesicles of Helicobacter pylori in gastric epithelial cells in vitro

Helicobacter pylori has been recognized as a true pathogen, which is associated with various gastroduodenal diseases, and gastric adenocarcinoma. The crosstalk between H. pylori virulence factors and host autophagy remains challenging. H. pylori can produce extracellular vesicles (EVs) that contribute to gastric inflammation and malignancy. Some probiotic strains have been documented to modulate cell autophagy process. This study was aimed to investigate the modulatory effect of cell-free supernatant (CFS) obtained from Lactobacillus gasseri ATCC 33323 on autophagy induced by H. pylori-derived EVs. EVs were isolated from two clinical H. pylori strains (BY-1 and OC824), and characterized using transmission electron microscopy (TEM) and dynamic light scattering (DLS). The viability of AGS cells was assessed after exposure to different concentrations of H. pylori EVs, and L. gasseri CFS. Based on MTT assay and Annexin V-FITC/PI staining, 50 μg/ml of H. pylori EVs and 10 % v/v of L. gasseri CFS were used for further cell treatment experiments. Autophagy was examined using acridin orange (AO) staining, RT-qPCR analysis for autophagy mediators (LC3B, ATG5, ATG12, ATG16L1, BECN1, MTOR, and NOD1), and western blotting for LC3B expression. H. pylori EVs were detected to range in size from 50 to 200 nm. EVs of both H. pylori strains and L. gasseri CFS showed no significant effect on cell viability as compared to untreated cells. H. pylori EVs promoted the development of acidic vesicular organelles and the expression of autophagy-related genes (LC3B, ATG5, ATG12, ATG16L1, BECN1, and NOD1), and decreased the expression of MTOR in AGS cells at 12 and 24 h time periods. In addition, the production of LC3B was increased following 12 h of treatment in AGS cells. In contrast, L. gasseri CFS effectively inhibited EVs-induced autophagy, as evidenced by reduced acidic vesicular organelle formation and modulation of autophagy markers. Our study indicated that L. gasseri CFS can effectively suppress H. pylori EV-induced autophagy in AGS cells. Further investigations are required to decipher the mechanism of action L. gasseri CFS and its metabolites on autophagy inhibition induced by H. pylori.

CCT020312 exerts anti-prostate cancer effect by inducing G1 cell cycle arrest, apoptosis and autophagy through activation of PERK/eIF2α/ATF4/CHOP signaling

PERK/eIF2α/ATF4/CHOP signaling pathway is one of three major branches of unfolded protein response (UPR) and has been implicated in tumor progression. CCT020312 is a selective PERK activator and may have a potential anti-tumor effect. Here we investigated the anti-prostate cancer effect and its underlying mechanism of CCT020312. Our results showed that CCT020312 inhibited prostate cancer cell viability by inducing cell cycle arrest, apoptosis and autophagy through activation of PERK/eIF2α/ATF4/CHOP signaling. CCT020312 treatment caused cell cycle arrest at G1 phase and increased the levels of cleaved-Caspase3, cleaved-PARP and Bax in prostate cancer C4-2 and LNCaP cells. Moreover, CCT020312 increased LC3II/I, Atg12-Atg5 and Beclin1 levels and induced autophagosome formation. Furthermore, knockdown of CHOP reversed CCT020312-induced cell viability decrease, apoptosis and autophagy. Bafilomycin A1 reversed CCT020312-induced cell viability decrease but had no effect on CCT020312-induced CHOP activation in C4-2 and LNCaP cells. In vivo, CCT020312 suppressed tumor growth in C4-2 cells-derived xenograft mouse model, activated PERK pathway, and induced autophagy and apoptosis. Our study illustrates that CCT020312 exerts an anti-tumor effect in prostate cancer via activating the PERK pathway, thus indicating that CCT020312 may be a potential drug for prostate cancer.

The dual effect of endoplasmic reticulum stress in digestive system tumors and intervention of Chinese botanical drug extracts: a review

Endoplasmic reticulum (ER) homeostasis is essential for maintaining human health, and once imbalanced, it will trigger endoplasmic reticulum stress (ERS), which participates in the development of digestive system tumors and other diseases. ERS has dual effect on tumor cells, activating adaptive responses to promote survival or inducing apoptotic pathways to accelerate cell death of the tumor. Recent studies have demonstrated that Chinese botanical drug extracts can affect the tumor process of the digestive system by regulating ERS and exert anticancer effects. This article summarizes the dual effect of ERS in the process of digestive system tumors and the intervention of Chinese botanical drug extracts in recent years, as reference for the combined treatment of digestive system tumors with Chinese and modern medicine.

A nanoparticle-based sonodynamic therapy reduces Helicobacter pylori infection in mouse without disrupting gut microbiota

Infection by Helicobacter pylori, a prevalent global pathogen, currently requires antibiotic-based treatments, which often lead to antimicrobial resistance and gut microbiota dysbiosis. Here, we develop a non-antibiotic approach using sonodynamic therapy mediated by a lecithin bilayer-coated poly(lactic-co-glycolic) nanoparticle preloaded with verteporfin, Ver-PLGA@Lecithin, in conjunction with localized ultrasound exposure of a dosage permissible for ultrasound medical devices. This study reveals dual functionality of Ver-PLGA@Lecithin. It effectively neutralizes vacuolating cytotoxin A, a key virulence factor secreted by H. pylori, even in the absence of ultrasound. When coupled with ultrasound exposure, it inactivates H. pylori by generating reactive oxygen species, offering a potential solution to overcome antimicrobial resistance. In female mouse models bearing H. pylori infection, this sonodynamic therapy performs comparably to the standard triple therapy in reducing gastric infection. Significantly, unlike the antibiotic treatments, the sonodynamic therapy does not negatively disrupt gut microbiota, with the only major impact being upregulation of Lactobacillus, which is a bacterium widely used in yogurt products and probiotics. This study presents a promising alternative to the current antibiotic-based therapies for H. pylori infection, offering a reduced risk of antimicrobial resistance and minimal disturbance to the gut microbiota.

Autophagy induced by Helicobacter Pylori infection can lead to gastric cancer dormancy, metastasis, and recurrence: new insights

According to the findings of recent research, Helicobacter Pylori (H. pylori) infection is not only the primary cause of gastric cancer (GC), but it is also linked to the spread and invasion of GC through a number of processes and factors that contribute to virulence. In this study, we discussed that H. pylori infection can increase autophagy in GC tumor cells, leading to poor prognosis in such patients. Until now, the main concerns have been focused on H. pylori's role in GC development. According to our hypothesis, however, H. pylori infection may also lead to GC dormancy, metastasis, and recurrence by stimulating autophagy. Therefore, understanding how H. pylori possess these processes through its virulence factors and various microRNAs can open new windows for providing new prevention and/or therapeutic approaches to combat GC dormancy, metastasis, and recurrence which can occur in GC patients with H. pylori infection with targeting autophagy and eradicating H. pylori infection.

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.

Diabetes Mellitus and Gastric Cancer: Correlation and Potential Mechanisms

This review summarizes the correlation between diabetes mellitus (DM) and gastric cancer (GC) from the perspectives of epidemiology, drug use, and potential mechanisms. The association between DM and GC is inconclusive, and the positive direction of the association reported in most published meta-analyses suggests that DM may be an independent risk factor for GC. Many clinical investigations have shown that people with DM and GC who undergo gastrectomy may have better glycemic control. The potential link between DM and GC may involve the interaction of multiple common risk factors, such as obesity, hyperglycemia and hyperinsulinemia, H. pylori infection, and the use of metformin. Although in vitro and in vivo data support that H. pylori infection status and metformin can influence GC risk in DM patients, there are conflicting results. Patient survival outcomes are influenced by multiple factors, so further research is needed to identify the patients who may benefit.

TLR2 mediates autophagy through ERK signaling pathway in Chlamydia psittaci CPSIT_p7 protein-stimulated RAW264.7 cells

Chlamydia psittaci is a zoonotic pathogen found in birds and humans. Macrophages, major components of the innate immune system, can resist chlamydial infections and trigger adaptive immune responses. However, the molecular mechanisms underlying the action of macrophages against C. psittaci infection are not well understood. This study investigated the roles and mechanisms of plasmid-encoded protein CPSIT_p7 of C. psittaci in regulating autophagy in RAW264.7 cells. The results demonstrated that stimulation of RAW264.7 with C. psittaci plasmid protein CPSIT_p7 induced the expressions of the autophagy signaling primary regulators LC3 and Beclin1, which could also significantly induce the phosphorylation levels of ERK, JNK, p38, and Akt. Next, siRNA knockdown of TLR2 resulted in significant downregulation of CPSIT_p7-triggered autophagy in RAW264.7 cells. Moreover, the extracellular regulated protein kinase (ERK) inhibitor PD98059 markedly reduced autophagy in CPSIT_p7-stimulated macrophages. In summary, these results indicated that TLR2 plays an essential role in the induction of autophagy through the ERK signaling pathway in CPSIT_p7-stimulated RAW264.7 cells.

Host cell sensing and restoration of mitochondrial function and metabolism within Helicobacter pylori VacA intoxicated cells

IMPORTANCE

Persistent human gastric infection with Helicobacter pylori is the single most important risk factor for development of gastric malignancy, which is one of the leading causes of cancer-related deaths worldwide. An important virulence factor for Hp colonization and severity of gastric disease is the protein exotoxin VacA, which is secreted by the bacterium and modulates functional properties of gastric cells. VacA acts by damaging mitochondria, which impairs host cell metabolism through impairment of energy production. Here, we demonstrate that intoxicated cells have the capacity to detect VacA-mediated damage, and orchestrate the repair of mitochondrial function, thereby restoring cellular health and vitality. This study provides new insights into cellular recognition and responses to intracellular-acting toxin modulation of host cell function, which could be relevant for the growing list of pathogenic microbes and viruses identified that target mitochondria as part of their virulence strategies.

Advancements and Obstacles of PARP Inhibitors in Gastric Cancer

Gastric cancer (GC) is a common and aggressive cancer of the digestive system, exhibiting high aggressiveness and significant heterogeneity. Despite advancements in improving survival rates over the past few decades, GC continues to carry a worrisome prognosis and notable mortality. As a result, there is an urgent need for novel therapeutic approaches to address GC. Recent targeted sequencing studies have revealed frequent mutations in DNA damage repair (DDR) pathway genes in many GC patients. These mutations lead to an increased reliance on poly (adenosine diphosphate-ribose) polymerase (PARP) for DNA repair, making PARP inhibitors (PARPi) a promising treatment option for GC. This article presents a comprehensive overview of the rationale and development of PARPi, highlighting its progress and challenges in both preclinical and clinical research for treating GC.

The interaction between autophagy, Helicobacter pylori, and gut microbiota in gastric carcinogenesis

Chronic infection with Helicobacter pylori is the primary risk factor for the development of gastric cancer. Hindering our ability to comprehend the precise role of autophagy during H. pylori infection is the complexity of context-dependent autophagy signaling pathways. Recent and ongoing progress in understanding H. pylori virulence allows new frontiers of research for the crosstalk between autophagy and H. pylori. Novel approaches toward discovering autophagy signaling networks have further revealed their critical influence on the structure of gut microbiota and the metabolome. Here we intend to present a holistic view of the perplexing role of autophagy in H. pylori pathogenesis and carcinogenesis. We also discuss the intermediate role of autophagy in H. pylori-mediated modification of gut inflammatory responses and microbiota structure.

The role of microbiota in the development and treatment of gastric cancer

The stomach was once considered a sterile organ until the discovery of Helicobacter pylori (HP). With the application of high-throughput sequencing technology and macrogenomics, researchers have identified fungi and fivemajor bacterial phyla within the stomachs of healthy individuals. These microbial communities exert regulatory influence over various physiological functions, including energy metabolism and immune responses. HP is a well-recognized risk factor for gastric cancer, significantly altering the stomach's native microecology. Currently, numerous studies are centered on the mechanisms by which HP contributes to gastric cancer development, primarily involving the CagA oncoprotein. However, aside from exogenous infections such as HP and EBV, certain endogenous dysbiosis can also lead to gastric cancer through multiple mechanisms. Additionally, gut microbiota and its metabolites significantly impact the development of gastric cancer. The role of microbial therapies, including diet, phages, probiotics and fecal microbiota transplantation, in treating gastric cancer should not be underestimated. This review aims to study the mechanisms involved in the roles of exogenous pathogen infection and endogenous microbiota dysbiosis in the development of gastric cancer. Also, we describe the application of microbiota therapy in the treatment and prognosis of gastric cancer.

Reactive Oxygen Species and H. pylori Infection: A Comprehensive Review of Their Roles in Gastric Cancer Development

Gastric cancer (GC) is the fifth most common cancer worldwide and makes up a significant component of the global cancer burden. Helicobacter pylori (H. pylori) is the most influential risk factor for GC, with the International Agency for Research on Cancer classifying it as a Class I carcinogen for GC. H. pylori has been shown to persist in stomach acid for decades, causing damage to the stomach's mucosal lining, altering gastric hormone release patterns, and potentially altering gastric function. Epidemiological studies have shown that eliminating H. pylori reduces metachronous cancer. Evidence shows that various molecular alterations are present in gastric cancer and precancerous lesions associated with an H. pylori infection. However, although H. pylori can cause oxidative stress-induced gastric cancer, with antioxidants potentially being a treatment for GC, the exact mechanism underlying GC etiology is not fully understood. This review provides an overview of recent research exploring the pathophysiology of H. pylori-induced oxidative stress that can cause cancer and the antioxidant supplements that can reduce or even eliminate GC occurrence.

Restoration of mitochondrial structure and function within Helicobacter pylori VacA intoxicated cells

The Helicobacter pylori vacuolating cytotoxin (VacA) is an intracellular, mitochondrial-targeting exotoxin that rapidly causes mitochondrial dysfunction and fragmentation. Although VacA targeting of mitochondria has been reported to alter overall cellular metabolism, there is little known about the consequences of extended exposure to the toxin. Here, we describe studies to address this gap in knowledge, which have revealed that mitochondrial dysfunction and fragmentation are followed by a time-dependent recovery of mitochondrial structure, mitochondrial transmembrane potential, and cellular ATP levels. Cells exposed to VacA also initially demonstrated a reduction in oxidative phosphorylation, as well as increase in compensatory aerobic glycolysis. These metabolic alterations were reversed in cells with limited toxin exposure, congruent with the recovery of mitochondrial transmembrane potential and the absence of cytochrome c release from the mitochondria. Taken together, these results are consistent with a model that mitochondrial structure and function are restored in VacA-intoxicated cells.

The conundrum of Helicobacter pylori-associated apoptosis in gastric cancer

Helicobacter pylori is a human microbial pathogen that colonizes the gastric epithelium and causes type B gastritis with varying degrees of active inflammatory infiltrates. The underlying chronic inflammation induced by H. pylori and other environmental factors may promote the development of neoplasms and adenocarcinoma of the stomach. Dysregulation of various cellular processes in the gastric epithelium and in different cells of the microenvironment is a hallmark of H. pylori infection. We address the conundrum of H. pylori-associated apoptosis and review distinct mechanisms induced in host cells that either promote or suppress apoptosis in gastric epithelial cells, often simultaneously. We highlight key processes in the microenvironment that contribute to apoptosis and gastric carcinogenesis.

Helicobacter pylori and Gastric Cancer: Pathogenetic Mechanisms

Gastric cancer is the sixth most commonly diagnosed cancer and the fourth leading cause of cancer death worldwide. Helicobacter pylori (H. pylori) is one of the main risk factors for this type of neoplasia. Carcinogenetic mechanisms associated with H. pylori are based, on the one hand, on the onset of chronic inflammation and, on the other hand, on bacterial-specific virulence factors that can damage the DNA of gastric epithelial cells and promote genomic instability. Here, we review and discuss the major pathogenetic mechanisms by which H. pylori infection contributes to the onset and development of gastric cancer.

Gastric Epithelial Barrier Disruption, Inflammation and Oncogenic Signal Transduction by Helicobacter pylori

Helicobacter pylori exemplifies one of the most favourable bacterial pathogens worldwide. The bacterium colonizes the gastric mucosa in about half of the human population and constitutes a major risk factor for triggering gastric diseases such as stomach cancer. H. pylori infection represents a prime example of chronic inflammation and cancer-inducing bacterial pathogens. The microbe utilizes a remarkable set of virulence factors and strategies to control cellular checkpoints of inflammation and oncogenic signal transduction. This chapter emphasizes on the pathogenicity determinants of H. pylori such as the cytotoxin-associated genes pathogenicity island (cagPAI)-encoded type-IV secretion system (T4SS), effector protein CagA, lipopolysaccharide (LPS) metabolite ADP-glycero-β-D-manno-heptose (ADP-heptose), cytotoxin VacA, serine protease HtrA, and urease, and how they manipulate various key host cell signaling networks in the gastric epithelium. In particular, we highlight the H. pylori-induced disruption of cell-to-cell junctions, pro-inflammatory activities, as well as proliferative, pro-apoptotic and anti-apoptotic responses. Here we review these hijacked signal transduction events and their impact on gastric disease development.

Helicobacter pylori Infection, Its Laboratory Diagnosis, and Antimicrobial Resistance: a Perspective of Clinical Relevance

Despite the recent decrease in overall prevalence of Helicobacter pylori infection, morbidity and mortality rates associated with gastric cancer remain high. The antimicrobial resistance developments and treatment failure are fueling the global burden of H. pylori-associated gastric complications. Accurate diagnosis remains the opening move for treatment and eradication of infections caused by microorganisms. Although several reports have been published on diagnostic approaches for H. pylori infection, most lack the data regarding diagnosis from a clinical perspective. Therefore, we provide an intensive, comprehensive, and updated description of the currently available diagnostic methods that can help clinicians, infection diagnosis professionals, and H. pylori researchers working on infection epidemiology to broaden their understanding and to select appropriate diagnostic methods. We also emphasize appropriate diagnostic approaches based on clinical settings (either clinical diagnosis or mass screening), patient factors (either age or other predisposing factors), and clinical factors (either upper gastrointestinal bleeding or partial gastrectomy) and appropriate methods to be considered for evaluating eradication efficacy. Furthermore, to cope with the increasing trend of antimicrobial resistance, a better understanding of its emergence and current diagnostic approaches for resistance detection remain inevitable.

CagA and VacA inhibit gastric mucosal epithelial cell autophagy and promote the progression of gastric precancerous lesions

Cytotoxin-associated gene A (CagA) and vacuolating cytotoxin A (VacA) are the keys to the pathogenic role of Helicobacter pylori and the high-risk factors for the progression of gastric precancerous lesions. Autophagy can stabilize the intracellular environment, resist Helicobacter pylori infection, prevent the accumulation of damaged DNA, and inhibit the proliferation of gastric precancerous variant cells. However, CagA and VacA can inhibit the activation of upstream signals of autophagy and the maturation of autophagy-lysosomes in various ways, thus inhibiting the autophagy of gastric mucosal cells in precancerous lesions of gastric cancer. This change can cause Helicobacter pylori to be unable to be effectively cleared by autophagy, so CagA and VacA can persist and promote the inflammation, oxidative stress, apoptosis of gastric mucosal tissue cells, and the glycolytic activity and proliferation of variant cells in gastric precancerous lesions and a series of malignant biological processes. In recent years, the research on drugs specifically inhibiting the activities of CagA and VacA has become a new direction for the prevention and treatment of Helicobacter pylori-related severe gastric diseases, and a variety of drugs or components that can precisely and effectively regulate the factors for the treatment of gastric precancerous lesions are emerged, which opens a new strategy for the treatment of gastric precancerous lesions in the future.

Vacuolating Cytotoxin A Triggers Mitophagy in Helicobacter pylori-Infected Human Gastric Epithelium Cells

Helicobacter pylori (H. pylori)-derived vacuolating cytotoxin A (VacA) causes damage to various organelles, including mitochondria, and induces autophagy and cell death. However, it is unknown whether VacA-induced mitochondrial damage can develop into mitophagy. In this study, we found that H. pylori, H. pylori culture filtrate (HPCF), and VacA could activate autophagy in a gastric epithelial cell line (GES-1). VacA-caused mitochondrial depolarization retards the import of PINK1 into the damaged mitochondria and evokes mitophagy. And, among mass spectrometry (LC-MS/MS) identified 25 mitochondrial proteins bound with VacA, Tom20, Tom40, and Tom70, TOM complexes responsible for PINK1 import, were further identified as having the ability to bind VacA in vitro using pull-down assay, co-immunoprecipitation, and protein–protein docking. Additionally, we found that the cell membrane protein STOM and the mitochondrial inner membrane protein PGAM5 also interacted with VacA. These findings suggest that VacA captured by STOM forms endosomes to enter cells and target mitochondria. Then, VacA is transported into the mitochondrial membrane space through the TOM complexes, and PGAM5 aids in inserting VacA into the inner mitochondrial membrane to destroy the membrane potential, which promotes PINK1 accumulation and Parkin recruitment to induce mitophagy. This study helps us understand VacA entering mitochondria to induce the mitophagy process.

Biomarker Characterization and Prediction of Virulence and Antibiotic Resistance from Helicobacter pylori Next Generation Sequencing Data

The Gram-negative bacterium Helicobacter pylori colonizes c.a. 50% of human stomachs worldwide and is the major risk factor for gastric adenocarcinoma. Its high genetic variability makes it difficult to identify biomarkers of early stages of infection that can reliably predict its outcome. Moreover, the increasing antibiotic resistance found in H. pylori defies therapy, constituting a major human health problem. Here, we review H. pylori virulence factors and genes involved in antibiotic resistance, as well as the technologies currently used for their detection. Furthermore, we show that next generation sequencing may lead to faster characterization of virulence factors and prediction of the antibiotic resistance profile, thus contributing to personalized treatment and management of H. pylori-associated infections. With this new approach, more and permanent data will be generated at a lower cost, opening the future to new applications for H. pylori biomarker identification and antibiotic resistance prediction.

Induction of Endoplasmic Reticulum Stress by CdhM Mediates Apoptosis of Macrophage During Mycobacterium tuberculosis Infection

The normal operation of the endoplasmic reticulum (ER) is critical for cells and organisms. However, ER stress, caused by imbalanced protein folding, occurs frequently, which perturbs the function of the ER and even results in cell apoptosis eventually. Many insults can induce ER stress; pathogen infection is one of them. Most of the genes involved in ER stress have been reported to be upregulated in Mycobacterium tuberculosis (Mtb) granulomas of humans and mice, implicating that infection with Mtb can induce ER stress. However, little is known about the molecular mechanism of Mtb induction of ER stress. Here, we reveal that Mycobacterium protein CDP-diglyceride hydrolase of Mycobacteriumn (CdhM) could target the ER and cause abnormal ER morphology and cell death. RNA-seq analysis suggests that most of the ER stress-involved genes were modulated by CdhM. Further assessed by biochemical experiments, the transcription and protein levels of ER stress markers BiP and CHOP, as well as the levels of XBP1 splicing and eIF2α phosphorylation, were significantly increased by CdhM, confirming that CdhM could induce ER stress alone or during infection. A single conserved amino acid mutant of CdhM, including L44A, G96A, H150A, and W175A, was incapable of inducing ER stress, which indicates that induction of ER stress by CdhM is specific and functional. Furthermore, CdhM-induced ER stress could also promote apoptosis of macrophages during Mtb infection. Overexpression of CdhM conferred a significant benefit for Mtb replication by releasing Mtb into extracellular during infection of macrophage in vitro, as presented in CFU assays. Overall, our study identified a novel Mtb effector protein CdhM which may promote Mtb dissemination and proliferation by induction of ER stress and apoptosis and provided new insight into the physiological significance of induction of ER stress in tuberculosis (TB) granulomas.

Staphylococcus aureus Induces Goat Endometrial Epithelial Cells Apoptosis via the Autophagy and Endoplasmic Reticulum Stress Pathway

Simple Summary

The toxicity mechanism of Staphylococcus aureus on goat endometrial epithelial cells (gEECs) is still unelucidated. The purpose of this experiment was to investigate the molecular mechanism of gEECs death caused by S. aureus in terms of autophagy and endoplasmic reticulum (ER) stress. We found that the accumulation of autophagosomes exacerbated S. aureus-induced gEECs apoptosis, and that ER stress was involved in the regulation of the autophagy. These findings may provide new insight into the therapeutic target of endometrial cell injury.

Abstract

Increasing evidence indicates that autophagy and endoplasmic reticulum (ER) stress are involved in the regulation of cell death; however, the role of autophagy and ER stress in Staphylococcus aureus-induced endometrial epithelial cell damage is still unelucidated. In the present study, our results showed that infection with S. aureus increased the cytotoxicity and the protein expression of Bax, caspase-3, and cleaved-PARP-1 in goat endometrial epithelial cells (gEECs). Moreover, after infection, the expression of LC3II and autophagosomes were markedly increased. The autophagosome inhibitor 3-methyladenine (3-MA) significantly decreased the cytotoxicity and the expression of caspase-3, and cleaved-PARP-1; however, the autophagosome–lysosome fusion inhibitor chloroquine (CQ) increased their expression. Additionally, the protein expression of GRP78, EIF2α, and ATF4 were also markedly increased after infection. The ER stress inhibitor 4-PBA decreased the cytotoxicity and the expression of LC3II and apoptosis-related proteins in S. aureus-infected gEECs. Collectively, our findings prove that the accumulation of autophagosomes exacerbated S. aureus-induced gEECs apoptosis, and that ER stress was involved in the regulation of the autophagy and apoptosis.

Cytotoxin-Associated Gene A-Negative Helicobacter pylori Promotes Gastric Mucosal CX3CR1+CD4+ Effector Memory T Cell Recruitment in Mice

Background

Helicobacter pylori can cause many kinds of gastric disorders, ranging from gastritis to gastric cancer. Cytotoxin-associated gene A (CagA)⁺H. pylori is more likely to cause gastric histopathologic damage than CagA^–H. pylori. However, the underlying mechanism needs to be further investigated.

Materials and methods

Mice were intragastrically administered equal amounts of CagA⁺ or CagA^–H. pylori. Four weeks later, 24 chemokines in stomachs were measured using a mouse chemokine array, and the phenotypes of the recruited gastric CD4⁺ T cells were analyzed. The migration pathway was evaluated. Finally, the correlation between each pair among the recruited CD4⁺ T cell sub-population, H. pylori colonization level, and histopathologic damage score were determined by Pearson correlation analysis.

Results

The concentration of chemokines, CCL3 and CX3CL1, were significantly elevated in CagA^–H. pylori-infected gastric mucosa than in CagA⁺H. pylori-infected gastric mucosa. Among them, CX3CL1 secreted by gastric epithelial cells, which was elicited more effectively by CagA^–H. pylori than by the CagA⁺ strain, dramatically promoted mucosal CD4⁺ T cell migration. The expression of CX3CR1, the only known receptor of CX3CL1, was upregulated on the surface of gastric CD4⁺ T cells in CagA^–H. pylori-infected stomach. In addition, most of the CX3CR1-positive gastric CD4⁺ T cells were CD44⁺CD69^–CCR7^– effector memory T cells (Tem). Pearson correlation analysis showed that the recruited CX3CR1⁺CD4⁺ Tem cell population was negatively correlated with H. pylori colonization level and histopathologic damage score.

Conclusion

CagA^–H. pylori promotes gastric mucosal CX3CR1⁺CD4⁺ Tem recruitment in mice.

An Overview of Helicobacter pylori Survival Tactics in the Hostile Human Stomach Environment

Helicobacter pylori is well established as a causative agent for gastritis, peptic ulcer, and gastric cancer. Armed with various inimitable virulence factors, this Gram-negative bacterium is one of few microorganisms that is capable of circumventing the harsh environment of the stomach. The unique spiral structure, flagella, and outer membrane proteins accelerate H. pylori movement within the viscous gastric mucosal layers while facilitating its attachment to the epithelial cells. Furthermore, secretion of urease from H. pylori eases the acidic pH within the stomach, thus creating a niche for bacteria survival and replication. Upon gaining a foothold in the gastric epithelial lining, bacterial protein CagA is injected into host cells through a type IV secretion system (T4SS), which together with VacA, damage the gastric epithelial cells. H. pylori does not only establishes colonization in the stomach, but also manipulates the host immune system to permit long-term persistence. Prolonged H. pylori infection causes chronic inflammation that precedes gastric cancer. The current review provides a brief outlook on H. pylori survival tactics, bacterial-host interaction and their importance in therapeutic intervention as well as vaccine development.

Transcriptome profiling implicated in beneficiary actions of kimchi extracts against Helicobacter pylori infection

Dietary intervention to prevent Helicobacter pylori (H. pylori)-gastric cancer might be ideal because of no risk of bacterial resistance, safety, and rejuvenating action of atrophic gastritis. We have published data about the potential of fermented kimchi as nutritional approach for H. pylori. Hence recent advances in RNAseq analysis lead us to investigate the transcriptome analysis to explain these beneficiary actions of kimchi. gastric cells were infected with either H. pylori or H. pylori plus kimchi. 943 genes were identified as significantly increased or decreased genes according to H. pylori infection and 68 genes as significantly changed between H. pylori infection and H. pylori plus kimchi (p<0.05). Gene classification and Medline database showed DLL4, FGF18, PTPRN, SLC7A11, CHAC1, FGF21, ASAN, CTH, and CREBRF were identified as significantly increased after H. pylori, but significantly decreased with kimchi and NEO1, CLDN8, KLRG1, and IGFBP1 were identified as significantly decreased after H. pylori, but increased with kimchi. After KEGG and STRING-GO analysis, oxidative stress, ER stress, cell adhesion, and apoptosis genes were up-regulated with H. pylori infection but down-regulated with kimchi, whereas tissue regeneration, cellular anti-oxidative response, and anti-inflammation genes were reversely regulated with kimchi (p<0.01). Conclusively, transcriptomes of H. pylori plus kimchi showed significant biological actions.

Fermented kimchi rejuvenated precancerous atrophic gastritis via mitigating Helicobacter pylori-associated endoplasmic reticulum and oxidative stress

Dietary intervention to prevent Helicobacter pylori (H. pylori)-gastric cancer might be ideal by long-term intervention, rejuvenating action, and no risk of bacterial resistance. Stimulated with finding that kimchi prevented H. pylori-gastric cancer, we compared the efficacy of cancer preventive kimchi (cpkimchi) and standard recipe kimchi (skimchi) and the efficacy between fermented kimchi and non-fermented kimchi (kimuchi) in H. pylori-initiated gastric cancer model and explored novel mechanisms hinted from RNAseq transcriptome analysis. Animal models assessing gastric pathology on 24 and 36 weeks after H. pylori initiated, salt diet-promoted gastric mutagenesis model showed fermented cpkimchi afforded the best outcome of either rejuvenating atrophic gastritis or inhibiting tumorigenesis compared to skimchi and kimuchi. Highest inhibition of atrophic gastritis was achieved with cpkimchi, while significantly lower in kimuchi. Transcriptomic analysis showed ameliorated-endoplasmic reticulum (ER) stress, -oxidative stress, and -apoptosis as major rejuvenating action of cpkimchi. Homogenates from animal model showed that elevated expressions of p-PERK, IRE, ATF6, p-elf, and XBP1 in control group, while significantly decreased with dietary intake of only cpkimchi. Significantly increased expressions of HO-1 and γ-GCS were only noted with cpkimchi. Conclusively, long-term dietary intervention of fermented cpkimchi can be potential way preventing H. pylori-associated carcinogenesis via rejuvenation of atrophic gastritis.

Impact of Dietary Patterns on H. pylori Infection and the Modulation of Microbiota to Counteract Its Effect. A Narrative Review

Helicobacter pylori (H. pylori) is a Gram-negative bacterium that colonizes the stomach and can induce gastric disease and intra-gastric lesions, including chronic gastritis, peptic ulcers, gastric adenocarcinoma, and mucosa-associated lymphoid tissue lymphoma. This bacterium is responsible for long-term complications of gastric disease. The conjunction of host genetics, immune response, bacterial virulence expression, diet, micronutrient availability, and microbiome structure influence the disease outcomes related to chronic H. pylori infection. In this regard, the consumption of unhealthy and unbalanced diets can induce microbial dysbiosis, which infection with H. pylori may contribute to. However, to date, clinical trials have reported controversial results and current knowledge in this field is inconclusive. Here, we review preclinical studies concerning the changes produced in the microbiota that may be related to H. pylori infection, as well as the involvement of diet. We summarize and discuss the last approaches based on the modulation of the microbiota to improve the negative impact of H. pylori infection and their potential translation from bench to bedside.

Tissue distribution of polystyrene nanoplastics in mice and their entry, transport, and cytotoxicity to GES-1 cells

With the widespread use of plastics and nanotechnology products, nanoplastics (NPs) have become a potential threat to human health. It is of great practical significance to study and evaluate the distribution of NPs in mice as mammal models and their entry, transport, and cytotoxicity in human cell lines. In this study, we detected the tissue distribution of fluorescent polystyrene nanoplastics (PS-NPs) in mice and assessed their endocytosis, transport pathways, and cytotoxic effects in GES-1 cells. We found that PS-NPs were clearly visible in gastric, intestine, and liver tissues of mice and in GES-1 cells treated with PS-NPs. Entry of PS-NPs into GES-1 cells decreased with the inhibition of caveolae-mediated endocytosis (nystatin), clathrin-mediated endocytosis (chlorpromazine HCl), micropinocytosis (ethyl-isopropyl amiloride), RhoA (CCG-1423), and F-actin polymerization (lantrunculin A). Rac1 inhibitors (NSC 23766) had no significant effect on PS-NPs entering GES-1 cells. F-actin levels significantly decreased in CCG-1423-pretreated GES-1 cells exposed to PS-NPs. GES-1 cell ultrastructural features indicated that internalized PS-NPs can be encapsulated in vesicles, autophagosomes, lysosomes, and lysosomal residues. RhoA, F-actin, RAB7, and LAMP1 levels in PS-NPs-treated GES-1 cells were remarkably up-regulated and the Rab5 level was significantly down-regulated compared to levels in untreated cells. PS-NPs treatment decreased cell proliferation rates and increased cell apoptosis. The formation of autophagosomes and autolysosomes and levels of LC3II increased with the length of PS-NPs treatment. The results indicated that cells regulated endocytosis in response to PS-NPs through the RhoA/F-actin signaling pathway and internalized PS-NPs in the cytoplasm, autophagosomes, or lysosomes produced cytotoxicity. These results illustrate the potential threat of NPs pollution to human health.

Autophagy in Gastric Mucosa: The Dual Role and Potential Therapeutic Target

The incidence of stomach diseases is very high, which has a significant impact on human health. Damaged gastric mucosa is more vulnerable to injury, leading to bleeding and perforation, which eventually aggravates the primary disease. Therefore, the protection of gastric mucosa is crucial. However, existing drugs that protect gastric mucosa can cause nonnegligible side effects, such as hepatic inflammation, nephritis, hypoacidity, impotence, osteoporotic bone fracture, and hypergastrinemia. Autophagy, as a major intracellular lysosome-dependent degradation process, plays a key role in maintaining intracellular homeostasis and resisting environmental pressure, which may be a potential therapeutic target for protecting gastric mucosa. Recent studies have demonstrated that autophagy played a dual role when gastric mucosa exposed to biological and chemical factors. More indepth studies are needed on the protective effect of autophagy in gastric mucosa. In this review, we focus on the mechanisms and the dual role of various biological and chemical factors regulating autophagy, such as Helicobacter pylori, virus, and nonsteroidal anti-inflammatory drugs. And we summarize the pathophysiological properties and pharmacological strategies for the protection of gastric mucosa through autophagy.

Clinical Strains of Helicobacter pylori With Strong Cell Invasiveness and the Protective Effect of Patchouli Alcohol by Improving miR-30b/C Mediated Xenophagy

Helicobacter pylori was classified by the World Health Organization as a class 1 carcinogen. The development of drug-resistant strains of this pathogen poses a serious threat to human health worldwide. The cell invasion of H. pylori activates xenophagy in gastric epithelial cells by mediating miR-30b/c, and the emergence of autophagosomes provides a niche that enables the survival of intracellular H. pylori and promotes its drug resistance. This study revealed that some clinical drug-resistant H. pylori strains present much stronger invasive ability than standard strains. Patchouli alcohol (PA), a tricyclic sesquiterpene from Pogostemon cablin (Blanco) Benth (Labiatae), showed reliable activity against intracellular H. pylori. The mechanisms appeared to involve the downregulation of miR-30c-3p/5p and miR-30b-5p, thereby upregulating xenophagy-related gene expression (ULK1, ATG5, ATG12, and ATG14) and enhancing xenophagy. PA also inhibited the nuclear transfection of miR-30b-5p induced by H. pylori, thereby enhancing transcription factor EB function and increasing lysosome activity. The finding of strongly invasive intracellular H. pylori has great implications for clinical treatment, and PA can act against invasive H. pylori based on the improvement of miR-30b/c mediated xenophagy. Taken together, the results demonstrate that PA have potential use as a candidate medication for intracellular drug-resistant H. pylori.

In vitro characterization of subventricular zone isolated neural stem cells, from adult monkey and rat brain

Neural stem cells (NSCs) are multipotent, self-renewable cells who are capable of differentiating into neurons, astrocytes, and oligodendrocytes. NSCs reside at the subventricular zone (SVZ) of the adult brain permanently to guarantee a lifelong neurogenesis during neural network plasticity or undesirable injuries. Although the specious inaccessibility of adult NSCs niche hampers their in vivo identification, researchers have been seeking ways to optimize adult NSCs isolation, expansion, and differentiation, in vitro. NSCs were isolated from rhesus monkey SVZ, expanded in vitro and then characterized for NSCs-specific markers expression by immunostaining, real-time PCR, flow cytometry, and cell differentiation assessments. Moreover, cell survival as well as self-renewal capacity were evaluated by TUNEL, Live/Dead and colony assays, respectively. In the next step, to validate SVZ-NSCs identity in other species, a similar protocol was applied to isolate NSCs from adult rat's SVZ as well. Our findings revealed that isolated SVZ-NSCs from both monkey and rat preserve proliferation capacity in at least nine passages as confirmed by Ki67 expression. Additionally, both SVZ-NSCs sources are capable of self-renewal in addition to NESTIN, SOX2, and GFAP expression. The mortality was measured meager with over 95% viability according to TUNEL and Live/Dead assay results. Eventually, the multipotency of SVZ-NSCs appraised authentic after their differentiation into neurons, astrocytes, and oligodendrocytes. In this study, we proposed a reliable method for SVZ-NSCs in vitro maintenance and identification, which, we believe is a promising cell source for therapeutic approach to recover neurological disorders and injuries condition.

The relationship between endoplasmic reticulum stress and autophagy in apoptosis of BEAS-2B cells induced by cigarette smoke condensate

Cigarette smoke (CS) is one of the severe risk factors for the development of the pulmonary disease. However, the underlying mechanisms, especially the CS-induced the human bronchial epithelial cells (BEAS-2B) apoptosis related to endoplasmic reticulum stress (ERS) and autophagy, remains to be studied. This study aims to investigate the relationship between ERS and autophagy in apoptosis induced by CS condensate (CSC). BEAS-2B cells were stimulated with 0.02, 0.04 and 0.08 mg/ml CSC for 24 h to detect the ERS, autophagy and apoptosis. Then, ERS and autophagy of BEAS-2B cells were inhibited, respectively, by using 4-PBA and 3-MA, and followed by CSC treatment. The results showed that CSC decreased cell viability, increased cell apoptosis, elevated cleaved-caspase 3/pro-caspase 3 ratio and Bax expressions, but decreased Bcl-2 expressions. The GRP78 and CHOP expressions and LC3-II/LC3-I ratio were dose-dependently increased. The structure of the endoplasmic reticulum was abnormal and the number of autolysosomes was increased in BEAS-2B cells after CSC stimulation. The LC3-II/LC3-I ratio was decreased after ERS inhibition with 4-PBA, but GRP78 and CHOP expressions were enhanced after autophagy inhibition with 3-MA. CSC-induced apoptosis was further increased, Bax expressions and cleaved-caspase 3/pro-caspase 3 ratio were improved, but Bcl-2 expressions were decreased after 3-MA or 4-PBA treatment. In conclusion, the study indicates that ERS may repress apoptosis of BEAS-2B cells induced by CSC via activating autophagy, but autophagy relieves ERS in a negative feedback. This study provides better understanding and experimental support on the underlying mechanisms of pulmonary disease stimulated by CS.

Organelle-specific mechanisms of drug-induced autophagy-dependent cell death

The conserved catabolic process of autophagy is an important control mechanism that degrades cellular organelles, debris and pathogens in autolysosomes. Although autophagy primarily protects against cellular insults, nutrient starvation or oxidative stress, hyper-activation of autophagy is also believed to cause autophagy-dependent cell death (ADCD). ADCD is a caspase-independent form of programmed cell death (PCD), characterized by an over-activation of autophagy, leading to prominent self-digestion of cellular material in autolysosomes beyond the point of cell survival. ADCD plays important roles in the development of lower organisms, but also in the response of cancer cells upon exposure of specific drugs or natural compounds. Importantly, the induction of ADCD as an alternative cell death pathway is of special interest in apoptosis-resistant cancer types and serves as an attractive and potential therapeutic option. Although the mechanisms of ADCD are diverse and not yet fully understood, both non-selective (bulk) autophagy and organelle-specific types of autophagy are believed to be involved in this type of cell death. Accordingly, several ADCD-inducing drugs are known to trigger severe mitochondrial damage and endoplasmic reticulum (ER) stress, whereas the contribution of other cell organelles, like ribosomes or peroxisomes, to the control of ADCD is not well understood. In this review, we highlight the general mechanisms of ADCD and discuss the current evidence for mitochondria- and ER-specific killing mechanisms of ADCD-inducing drugs.

Inhibition of autophagy aggravates DNA damage response and gastric tumorigenesis via Rad51 ubiquitination in response to H. pylori infection

Helicobacter pylori (H. pylori) infection is the strongest known risk factor for the development of gastric cancer. DNA damage response (DDR) and autophagy play key roles in tumorigenic transformation. However, it remains unclear how H. pylori modulate DDR and autophagy in gastric carcinogenesis. Here we report that H. pylori infection promotes DNA damage via suppression of Rad51 expression through inhibition of autophagy and accumulation of p62 in gastric carcinogenesis. We find that H. pylori activated DNA damage pathway in concert with downregulation of repair protein Rad51 in gastric cells, C57BL/6 mice and Mongolian gerbils. In addition, autophagy was increased early and then decreased gradually during the duration of H. pylori infection in vitro in a CagA-dependent manner. Moreover, loss of autophagy led to promotion of DNA damage in H. pylori-infected cells. Furthermore, knockdown of autophagic substrate p62 upregulated Rad51 expression, and p62 promoted Rad51 ubiquitination via the direct interaction of its UBA domain. Finally, H. pylori infection was associated with elevated levels of p62 in gastric intestinal metaplasia and decreased levels of Rad51 in dysplasia compared to their H. pylori- counterparts. Our findings provide a novel mechanism into the linkage of H. pylori infection, autophagy, DNA damage and gastric tumorigenesis.

Sustained Exposure to Helicobacter pylori Lysate Inhibits Apoptosis and Autophagy of Gastric Epithelial Cells

Helicobacter pylori is designated as a class I carcinogen of human gastric cancer following long-term infection. During this process, H. pylori bacteria persist in proliferation and death, and release bacterial components that come into contact with gastric epithelial cells and regulate host cell function. However, the impact of long-term exposure to H. pylori lysate on the pathological changes of gastric cells is not clear. In this study, we aimed to investigate the regulation and mechanisms involved in gastric cell dysfunction following continuous exposure to H. pylori lysate. We co-cultured gastric cell lines GES-1 and MKN-45 with H. pylori lysate for 30 generations, and we found that sustained exposure to H. pylori lysate inhibited GES-1 cell invasion, migration, autophagy, and apoptosis, while it did not inhibit MKN-45 cell invasion or migration. Furthermore, Mongolian gerbils infected with H. pylori ATCC 43504 strains for 90 weeks confirmed the in vitro results. The clinical and in vitro data indicated that sustained exposure to H. pylori lysate inhibited cell apoptosis and autophagy through the Nod1-NF-κB/MAPK-ERK/FOXO4 signaling pathway. In conclusion, sustained exposure to H. pylori lysate promoted proliferation of gastric epithelial cells and inhibited autophagy and apoptosis via Nod1-NF-κB/MAPK-ERK/FOXO4 signaling pathway. In the process of H. pylori-induced gastric lesions, H. pylori lysate plays as an “accomplice” to carcinogenesis.

ATF4 links ER stress with reticulophagy in glioblastoma cells

Selective degradation of the endoplasmic reticulum (ER; reticulophagy) is a type of autophagy involved in the removal of ER fragments. So far, amino acid starvation as well as ER stress have been described as inducers of reticulophagy, which in turn restores cellular energy levels and ER homeostasis. Here, we explored the autophagy-inducing mechanisms that underlie the autophagic cell death (ACD)-triggering compound loperamide (LOP) in glioblastoma cells. Interestingly, LOP triggers upregulation of the transcription factor ATF4, which is accompanied by the induction of additional ER stress markers. Notably, knockout of ATF4 significantly attenuated LOP-induced autophagy and ACD. Functionally, LOP also specifically induces the engulfment of large ER fragments within autophagosomes and lysosomes as determined by electron and fluorescence microscopy. LOP-induced reticulophagy and cell death are predominantly mediated through the reticulophagy receptor RETREG1/FAM134B and, to a lesser extent, TEX264, confirming that reticulophagy receptors can promote ACD. Strikingly, apart from triggering LOP-induced autophagy and ACD, ATF4 is also required for LOP-induced reticulophagy. These observations highlight a key role for ATF4, RETREG1 and TEX264 in response to LOP-induced ER stress, reticulophagy and ACD, and establish a novel mechanistic link between ER stress and reticulophagy, with possible implications for additional models of drug-induced ER stress.Abbreviations: ACD: autophagic cell death; ATF6: activating transcription factor 6; ATL3: atlastin 3; BafA₁: bafilomycin A₁; CCPG1: cell cycle progression gene 1; co-IP: co-immunoprecipitation; DDIT3/CHOP: DNA damage inducible transcript 3; ER: endoplasmic reticulum; EIF2A/eIF2α: eukaryotic translation initiation factor 2A; EIF2AK3/PERK: eukaryotic translation initiation factor 2 alpha kinase 3; ERN1/IRE1α: endoplasmic reticulum to nucleus signaling 1; GABARAP: GABA type A receptor-associated protein; GBM: glioblastoma multiforme; HSPA5/BiP: heat shock protein family (Hsp70) member 5; LOP: loperamide; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; RETREG1/FAM134B: reticulophagy regulator 1; RTN3L: reticulon 3 long; SEC62: SEC62 homolog, protein translocation factor; TEX264: testis-expressed 264, reticulophagy receptor; UPR: unfolded protein response.

The role of non-H. pylori bacteria in the development of gastric cancer

There is a complex ecosystem of bacteria and other microorganisms inside and outside the human body, which play an intricate role in maintaining health. In recent years, many researches focused on the relationship between microorganisms and cancer. Studies have identified that numerous microbes are presented in human stomach, which are closely linked to the development of gastric cancer (GC). Helicobacter pylori (H. pylori) is the mostly well-studied bacterial pathogen in the stomach, which account for the vast majority of GC. However, recent studies have found that microflora dysbiosis was occurred in mucosa of GC patients, and evidences have potentially proved that microbes other than H. pylori are also contribute to the development of GC, while the overall knowledge is still limited. In this review, we summarized the role of gastric flora in GC, especially the possible role of non-H. pylori bacteria in the development of GC. These knowledges and awareness may open doors for new therapeutic strategies of GC.

Role of vacuolating cytotoxin A in Helicobacter pylori infection and its impact on gastric pathogenesis

Introduction Helicobacter pylori causes, via the influence of several virulence factors, persistent infection of the stomach, which leads to severe complications. Vacuolating cytotoxin A (VacA) is observed in almost all clinical strains of H. pylori; however, only some strains produce the toxigenic and pathogenic VacA, which is influenced by the gene sequence variations. VacA exerts its action by causing cell vacuolation and apoptosis. We performed a PubMed search to review the latest literatures published in English language. Areas covered Articles regarding H. pylori VacA and its genotypes, architecture, internalization, and role in gastric infection and pathogenicity are reviewed. We included the search for recently published literature until January 2020. Expert opinion H. pylori VacA plays a crucial role in severe gastric pathogenicity. In addition, VacA mediated in vivo bacterial survival leads to persistent infection and an enhanced bacterial evasion from the action of antibiotics and the innate host defense system, which leads to drug evasion. VacA as a co-stimulator for the CagA phosphorylation may exert a synergistic effect playing an important role in the CagA-mediated pathogenicity.

NOD1 and NOD2 Activation by Diverse Stimuli: a Possible Role for Sensing Pathogen-Induced Endoplasmic Reticulum Stress

Prompt recognition of microbes by cells is critical to eliminate invading pathogens. Some cell-associated pattern recognition receptors (PRRs) recognize and respond to microbial ligands. However, others can respond to cellular perturbations, such as damage-associated molecular patterns (DAMPs). Nucleotide oligomerization domains 1 and 2 (NOD1/2) are PRRs that recognize and respond to multiple stimuli of microbial and cellular origin, such as bacterial peptidoglycan, viral infections, parasitic infections, activated Rho GTPases, and endoplasmic reticulum (ER) stress. How NOD1/2 are stimulated by such diverse stimuli is not fully understood but may partly rely on cellular changes during infection that result in ER stress. NOD1/2 are ER stress sensors that facilitate proinflammatory responses for pathogen clearance; thus, NOD1/2 may help mount broad antimicrobial responses through detection of ER stress, which is often induced during a variety of infections. Some pathogens may subvert this response to promote infection through manipulation of NOD1/2 responses to ER stress that lead to apoptosis. Here, we review NOD1/2 stimuli and cellular responses. Furthermore, we discuss pathogen-induced ER stress and how it might potentiate NOD1/2 signaling.

Chronic in vivo exposure to Helicobacter pylori VacA: Assessing the efficacy of automated and long-term intragastric toxin infusion

Helicobacter pylori (Hp) secrete VacA, a diffusible pore-forming exotoxin that is epidemiologically linked to gastric disease in humans. In vitro studies indicate that VacA modulates gastric epithelial and immune cells, but the in vivo contributions of VacA as an important determinant of Hp colonization and chronic infection remain poorly understood. To identify perturbations in the stomachs of C57BL/6 or BALB/C mice that result specifically from extended VacA exposure, we evaluated the efficacy of administering purified toxin using automated infusion via surgically-implanted, intragastric catheters. At 3 and 30 days of interrupted infusion, VacA was detected in association with gastric glands. In contrast to previously-reported tissue damage resulting from short term exposure to Hp extracts administered by oral gavage, extended infusion of VacA did not damage stomach, esophageal, intestinal, or liver tissue. However, several alterations previously reported during Hp infection were detected in animals infused with VacA, including reduction of the gastric mucus layer, and increased vacuolation of parietal cells. VacA infusion invoked an immune response, as indicated by the detection of circulating VacA antibodies. These foundational studies support the use of VacA infusion for identifying gastric alterations that are unambiguously attributable to long-term exposure to toxin.

Endometrial autophagy is essential for embryo implantation during early pregnancy

Embryo implantation is an essential and complex process in mammalian reproduction. However, little evidence has indicated the involvement of autophagy during embryo implantation. To determine the possible role of autophagy in uterine of pregnant mice during the peri-implantation stage, we first examined the expression of autophagy-related markers ATG5 and LC3 on day 4, 5, and 6 of pregnancy (D4, D5, and D6, respectively). Compared with expression on D4, downregulation of the autophagy-related markers was observed on D5 and D6, the days after the embryo attached to the receptivity endometrium. Further examination showed that autophagy-related markers ATG5, ATG12, LC3, cathepsin B, and P62 at the implantation site were significantly decreased when comparing with the inter-implantation site. Fewer number of autophagosomes at the implantation site were also observed by transmission electron microscopy. To confirm the functional role of autophagy during embryo implantation in mice, we administered the autophagy inhibitor 3-methyladenine and chloroquine to mice. After treated with 3-methyladenine, the expression of decidual markers HOXA10 and progesterone receptor were significantly reduced. Furthermore, a reduction in implantation sites and increase in the HOXA10 and PR protein levels were observed in response to chloroquine treatment. In addition, impaired uterine decidualization and dysregulation of the PR and HOXA10 protein levels was observed after autophagy inhibited by 3-methyladenine and chloroquine in in vivo artificial decidualization mouse model. In the last, LC3 and P62 were also observed in normal human proliferative, secretory, and decidua tissues. In conclusion, endometrial autophagy may be essential for embryo implantation, and it may be associated with endometrial decidualization during early pregnancy. KEY MESSAGE: • Autophagy-related markers were significantly decreased at implantation site. • Autophagy inhibition results in abnormal decidualization. • Autophagy is essential for embryo implantation.

Risk factors associated with gastric malignancy during chronic Helicobacter pylori Infection

Chronic Helicobacter pylori (Hp) infection is considered to be the single most important risk factor for the development of gastric adenocarcinoma in humans, which is a leading cause of cancer-related death worldwide. Nonetheless, Hp infection does not always progress to malignancy, and, gastric adenocarcinoma can occur in the absence of detectable Hp carriage, highlighting the complex and multifactorial nature of gastric cancer. Here we review known contributors to gastric malignancy, including Hp virulence factors, host genetic variation, and multiple environmental variables. In addition, we assess emerging evidence that resident gastric microflora in humans might impact disease progression in Hp-infected individuals. Molecular approaches for microbe identification have revealed differences in the gastric microbiota composition between cancer and non-cancerous patients, as well as infected and uninfected individuals. Although the reasons underlying differences in microbial community structures are not entirely understood, gastric atrophy and hypochlorhydria that accompany chronic Hp infection may be a critical driver of gastric dysbiosis that promote colonization of microbes that contribute to increased risk of malignancy. Defining the importance and role of the gastric microbiota as a potential risk factor for Hp-associated gastric cancer is a vital and exciting area of current research.

Methylomic Changes of Autophagy-Related Genes by Legionella Effector Lpg2936 in Infected Macrophages

Legionella pneumophila (L. pneumophila) is a Gram-negative bacterium that infects the human respiratory tract causing Legionnaires’ disease, a severe form of pneumonia. Recently, rising evidence indicated the ability of Legionella to regulate host defense via its type 4 secretion system including hundreds of effectors that promote intracellular bacterial replication. The host defense against such invaders includes autophagic machinery that is responsible for degradation events of invading pathogens and recycling of cell components. The interplay between host autophagy and Legionella infection has been reported, indicating the role of bacterial effectors in the regulation of autophagy during intracellular replication. Here, we investigated the potential impact of Legionella effector Lpg2936 in the regulation of host autophagy and its role in bacterial replication using mice-derived macrophages and human lung epithelial cells (A549 cells). First, monitoring of autophagic flux following infection revealed a marked reduction of Atg7 and LC3B expression profile and low accumulation levels of autophagy-related LC3-I, LC3-II, and the Atg12–Atg5 protein complex. A novel methyladenine alteration was observed due to irreversible changes of GATC motif to G(6 mA) TC in the promoter region of Atg7 and LC3B indicated by cleaved genomic-DNA using the N6 methyladenine-sensitive restriction enzyme DpnI. Interestingly, RNA interference (RNAi) of Lpg2936 in infected macrophages showed dramatic inhibition of bacterial replication by restoring the expression of autophagy-related proteins. This is accompanied by low production levels of bacterial-associated pro-inflammatory cytokines. Furthermore, a constructed Lpg2936 segment in the GFP expression vector was translocated in the host nucleus and successfully induced methyladenine changes in Atg7 and LC3B promoter region and subsequently regulated autophagy in A549 cells independent of infection. Finally, treatment with methylation inhibitors 5-AZA and (2)-Epigallocatechin-3-gallate (EGCG) was able to restore autophagy-related gene expression and to disrupt bacterial replication in infected macrophages. This cumulative evidence indicates the methylation effect of Legionella effector Lpg2936 on the host autophagy-related molecules Atg7 and LC3B and subsequent reduction in the expression levels of autophagy effectors during intracellular replication of L. pneumophila.

Intracellular proliferation of Anaplasma phagocytophilum is promoted via modulation of endoplasmic reticulum stress signaling in host cells

Anaplasma phagocytophilum, an obligate intracellular bacterium that propagates within host granulocytes, is considered to modify the host intracellular environment for pathogenesis. However, the mechanism(s) underlying such host modifications remain unclear. Here, we aimed to investigate the relation between A. phagocytophilum and endoplasmic reticulum (ER) stress in THP-1 cells. A. phagocytophilum activated the three ER stress sensors: inositol-requiring enzyme-1 (IRE1), protein kinase RNA-like endoplasmic reticulum kinase (PERK), and activating transcription factor-6 (ATF6). IRE1 activation occurred immediately after host cell invasion by A. phagocytophilum; however, the activated IRE1-induced splicing of X-box-binding protein 1 was not promoted during A. phagocytophilum infection. This suppression was sustained even after the doxycycline-mediated elimination of intracellular A. phagocytophilum. IRE1 knockdown accelerated A. phagocytophilum-induced apoptosis and decreased intracellular A. phagocytophilum. These data suggest that A. phagocytophilum utilizes IRE1 activation to promote its own intracellular proliferation. Moreover, PERK and ATF6 partially mediated A. phagocytophilum-induced apoptosis by promoting the expression of CCAAT/enhancer-binding protein homologous protein, which induces the transcription of several proapoptotic genes. Thus, A. phagocytophilum possibly manipulates the host ER stress signals to facilitate intracellular proliferation and infection of surrounding cells before/after host cell apoptosis.

Helicobacter pylori Virulence Factors Exploiting Gastric Colonization and its Pathogenicity

Helicobacter pylori colonizes the gastric epithelial cells of at least half of the world's population, and it is the strongest risk factor for developing gastric complications like chronic gastritis, ulcer diseases, and gastric cancer. To successfully colonize and establish a persistent infection, the bacteria must overcome harsh gastric conditions. H. pylori has a well-developed mechanism by which it can survive in a very acidic niche. Despite bacterial factors, gastric environmental factors and host genetic constituents together play a co-operative role for gastric pathogenicity. The virulence factors include bacterial colonization factors BabA, SabA, OipA, and HopQ, and the virulence factors necessary for gastric pathogenicity include the effector proteins like CagA, VacA, HtrA, and the outer membrane vesicles. Bacterial factors are considered more important. Here, we summarize the recent information to better understand several bacterial virulence factors and their role in the pathogenic mechanism.