Lower esophageal microbiota species are affected by the eradication of Helicobacter pylori infection using antibiotics

Microbiome changes in esophageal cancer: implications for pathogenesis and prognosis

Esophageal cancer (EC) is an aggressive malignancy with a poor prognosis. Various factors, including dietary habits, and antacid and antibiotic use, have been shown to influence the esophageal microbiome. Conversely, enrichment and diversity of the esophageal microbiome can also impact its function. Recent studies have revealed prevalent changes in the esophageal microbiome among patients with EC, thus suggesting the potential contribution of the esophageal microbiome to EC development. Additionally, distinct microbiome compositions have been observed in patients with different responses to radiotherapy and chemotherapy, indicating the role of the esophageal microbiome in modulating treatment outcomes. In this review, we have examined previous studies on the esophageal microbiome in healthy individuals and patients with EC or other esophageal diseases, with a focus on identifying microbial communities associated with EC pathogenesis and prognosis. Understanding the role of the microbiome in EC may aid in early detection and optimized treatment strategies, ultimately leading to better outcomes for patients.

Esophageal microflora in esophageal diseases

With the development of endoscopic technology, an increasing number of patients with esophageal disease are being diagnosed, although the underlying pathogenesis of many esophageal diseases remains unclear. In recent years, a large number of studies have demonstrated that the occurrence and development of various intestinal diseases were related to intestinal flora. As a result, researchers have shifted their focus towards investigating esophageal flora to better understand the pathogenesis, early diagnosis, and treatment of esophageal diseases. This paper reviewed the normal esophageal flora and the changes of esophageal flora under different esophageal disease states. It was observed that there are distinct differences in the composition of esophageal microflora among Gastroesophageal Reflux, Barrett's esophagus, eosinophilic esophagitis and normal esophagus. The normal esophageal flora was dominated by gram-positive bacteria, particularly Streptococcus, while the esophageal flora under esophagitis was dominated by gram-negative bacteria. Furthermore, the diversity of esophageal flora is significantly decreased in patients with esophageal cancer. Several potential microbial biomarkers for esophageal cancer have been identified, among which Fusobacterium nucleatum showed a close association with esophageal squamous cell carcinoma's pathological stage and clinical stage.

Impact of Environmental and Pharmacologic Changes on the Upper Gastrointestinal Microbiome

Diseases of the upper gastrointestinal tract have become more prevalent over time. Mechanisms of disease formation are still only partially understood. Recent literature has shown that the surrounding microbiome affects the propensity for disease formation in various parts of the upper gastrointestinal tract. A review was performed of any literature to our best knowledge concerning the effects of pharmacologic agents, environmental changes, and surgical intervention on the microbiome of the upper gastrointestinal tract. Searches of the literature were performed using specific keywords related to drugs, surgical procedures, and environmental factors. Many prescription and nonprescription drugs that are commonly used have varying effects on the upper gastrointestinal tract. Proton pump inhibitors may affect the relative prevalence of some organisms in the lower esophagus and have less effect in the proximal esophagus. Changes in the esophageal microbiome correlate with some esophageal diseases. Drugs that induce weight loss have also been shown to affect the microbiomes of the esophagus and stomach. Common surgical procedures are associated with shifts in the microbial community in the gastrointestinal tract. Environmental factors have been shown to affect the microbiome in the upper gastrointestinal tract, as geographic differences correlate with alterations in the microbiome of the gastrointestinal tract. Understanding the association of environmental and pharmacologic changes on the microbiome of the upper gastrointestinal tract will facilitate treatment plans to reduce morbidity from disease.

Associations of the microbiome and esophageal disease

The incidence of esophageal diseases such as esophageal adenocarcinoma (EAC) and gastroesophageal reflux disease (GERD) have been increasing over the last 40 years. The esophageal microbiome appears to have a role in the development of some disease processes, and could also serve as markers of early diseases of the esophagus. A literature review was performed examining the role of the microbiome in the development of esophageal disease. In addition, the results of several studies and experiments were included in the review. Both EAC and GERD have increased in incidence over the last 40 years. Barrett's esophagus (BE) is a risk factor for EAC. Patients with BE appear to have a microbiome expression pattern distinct from patients without BE. The distinct pattern may be related to factors within the distal esophagus such as a more acidic environment, intraluminal stasis and other elements. It remains unclear whether the change in microflora leads to esophageal disease, or whether the disease process within the esophagus allows these particular organisms to experience overgrowth compared to other microflora. Patient factors such as body mass index (BMI), diet and geographic location also appear to affect the esophageal microbiome. There is an association with the esophageal microbiome and several esophageal diseases. Future studies should examine these correlations more closely. The distinct patterns may be able to serve as a marker of early disease, and possibly lead to a mechanism for the development of esophageal disease.

Alteration of the esophageal microbiota in Barrett's esophagus and esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma (EAC) has increased in recent decades, and its 5-year survival rate is less than 20%. As a well-established precursor, patients with Barrett's esophagus (BE) have a persistent risk of progression to EAC. Many researchers have already identified some factors that may contribute to the development of BE and EAC, and the identified risks include gastroesophageal reflux (GER), male sex, older age, central obesity, tobacco smoking, Helicobacter pylori (H. pylori) eradication, and the administration of proton pump inhibitors (PPIs) and antibiotics. The human gut harbors trillions of microorganisms, the majority of which are bacteria. These microorganisms benefit the human host in many ways, such as helping in digestion, assisting in the synthesis of certain vitamins, promoting the development of the gastrointestinal immune system, regulating metabolism and preventing invasion by specific pathogens. In contrast, microbial dysbiosis may play important roles in various diseases, such as inflammation and cancers. The composition of the microbiota located in the normal esophagus is relatively conserved without distinct microbial preferences in the upper, middle and lower esophagus. Six major phyla constitute the esophageal microbiota, including Firmicutes, Bacteroides, Actinobacteria, Proteobacteria, Fusobacteria and TM7, similar to the oral microbiota. Streptococcus dominates the esophageal microbiota. However, the microbiota varies in different esophageal diseases compared to that in the healthy esophagus. The type I microbiota, which is primarily composed of gram-positive bacteria, is closely associated with the normal esophagus, while type II microbiota has enriched gram-negative bacteria and is mainly associated with the abnormal esophagus. These increased gram-negative anaerobes/microaerophiles include Veillonella, Prevotella, Haemophilus, Neisseria, Granulicatella and Fusobacterium, many of which are associated with BE. The microbial diversity in the esophagus is decreased in EAC patients, and Lactobacillus fermentum is enriched compared to that in controls and BE patients. Furthermore, the microbiota may be associated with BE and EAC by interacting with their risk factors, including central obesity, GER, H. pylori, administration of PPIs and antibiotics. Therefore, a large gap in research must be bridged to elucidate the associations among these factors. Some studies have already proposed several potential mechanisms by which the microbiota participates in human carcinogenesis by complicated interactions with the human host immune system and signaling pathways. The activation of the LPS-TLR4-NF-κB pathway may contribute to inflammation and malignant transformation. This exciting field of gastrointestinal microbiota allows us to unravel the mystery of carcinogenesis from another perspective. Further studies are needed to explore whether the microbiota changes before or after disease onset, to improve our understanding of the pathogenesis, and to find novel targets for prevention, diagnosis and therapy, which could offer more cost-effective and relatively safe choices.

Potential Role of the Microbiome in Barrett's Esophagus and Esophageal Adenocarcinoma

Esophageal adenocarcinoma and its precursor Barrett's esophagus have been rapidly increasing in incidence for half a century, for reasons not adequately explained by currently identified risk factors such as gastroesophageal reflux disease and obesity. The upper gastrointestinal microbiome may represent another potential cofactor. The distal esophagus has a distinct microbiome of predominantly oral-derived flora, which is altered in Barrett's esophagus and reflux esophagitis. Chronic low-grade inflammation or direct carcinogenesis from this altered microbiome may combine with known risk factors to promote Barrett's metaplasia and progression to adenocarcinoma.

Pathogenesis of Helicobacter pylori Infection

Three decades have passed since Warren and Marshall described the successful isolation and culture of Helicobacter pylori, the Gram-negative bacterium that colonizes the stomach of half the human population worldwide. Although it is documented that H. pylori infection is implicated in a range of disorders of the upper gastrointestinal tract, as well as associated organs, many aspects relating to host colonization, successful persistence, and the pathophysiological mechanisms of this bacteria still remain controversial and are constantly being explored. Unceasing efforts to decipher the pathophysiology of H. pylori infection have illuminated the crucially important contribution of multifarious bacterial factors for H. pylori pathogenesis, in particular the cag pathogenicity island (PAI), the effector protein CagA, and the vacuolating cytotoxin VacA. In addition, recent studies have provided insight into the importance of the gastrointestinal microbiota on the cumulative pathophysiology associated with H. pylori infection. This review focuses on the key findings of publications related to the pathogenesis of H. pylori infection published during the last year, with an emphasis on factors affecting colonization efficiency, cagPAI, CagA, VacA, and gastrointestinal microbiota.

Gastric Microbiota

After the discovery of Helicobacter pylori in 1983, the stomach was no longer considered a sterile environment. In 2015, evolving data shows that H. pylori is not the only inhabitant of the gastric mucosa. Using culture-independent methods of analysis, a non-H. pylori microbial community has been recently observed in the human stomach, the so-called human gastric microbiota, along with H. pylori itself. Increasing evidence supports the hypothesis that although H. pylori may be the most relevant, it is not the only local bacterial culprit leading to gastric diseases. Further studies are warranted to offer a better picture of the role and functions of gastric microbiota and to identify the best therapeutic modulators of gut microbiota for the management of gastric diseases.

Inhibition of autophagy using 3-methyladenine increases cisplatin-induced apoptosis by increasing endoplasmic reticulum stress in U251 human glioma cells

Cisplatin is one of the most widely used chemotherapeutic drugs; however, the side effects and drug resistance limit its usage. Previous findings have demonstrated that cisplatin kills tumor cells through endoplasmic reticulum (ER) stress, which provides a novel method to minimize cisplatin toxicity and circumvent cisplatin resistance. ER stress induces cell autophagy, cell apoptosis and the complicated regulatory network between them. The role of autophagy in cisplatin chemotherapy remains to be elucidated. 3-Methyladenine (3-MA) is normally used as an inhibitor of autophagy. The present study reveals a significant role of the inhibition of autophagy by treatment with 3-MA and cisplatin in combination in U251 human glioma cells. It was demonstrated that cisplatin induced the ER stress associated with apoptosis and autophagy in U251 cells. Inhibition of autophagy by 3-MA increased the expression levels of protein disulfide isomerase, ubiquitinated proteins, glucose regulated protein 78 and CCAAT-enhancer-binding protein homologous protein, and induced the activation of caspase-4 and caspase-3. Treatment with 3-MA combined with cisplatin increased cisplatin-induced apoptosis by increasing ER stress. Therefore, the inhibition of autophagy has the potential to improve cisplatin chemotherapy.