Neutrophils, eosinophils, and intraepithelial lymphocytes in the squamous esophagus in subjects with and without gastroesophageal reflux symptoms

Untangling immune cell contributions in the progression from GERD to Barrett's esophagus and esophageal cancer: Insights from genetic causal analysis

BACKGROUND

Esophageal adenocarcinoma (EAC) is a rapidly increasing malignancy with significant morbidity and mortality. The progression from gastroesophageal reflux disease (GERD) to Barrett's esophagus (BE) and ultimately to EAC is thought to be influenced by chronic inflammation and immune cell dynamics. Despite the observed correlations in observational studies, the causal relationships between immune cell phenotypes and this disease continuum remain unclear.

METHODS

This study utilized a two-sample Mendelian Randomization (MR) approach to investigate the causal roles of 731 distinct immune cell phenotypes in the GERD-BE-EAC continuum. The analysis leveraged genome-wide association study (GWAS) data for immune phenotypes from a Sardinian cohort and data for GERD, BE, and EAC from the FinnGen and Open GWAS databases. A comprehensive set of MR methods, including inverse variance weighted (IVW), MR-Egger, and weighted median estimators, was employed to assess causality. Sensitivity analyses were conducted to evaluate heterogeneity and pleiotropy, ensuring the robustness of the findings.

RESULTS

The study revealed complex and multifaceted roles of immune cells across the GERD-BE-EAC continuum. In GERD, 34 immune phenotypes were found to be causally associated with either increased or decreased risk. Protective effects were observed in phenotypes such as Unswitched Memory B cells, while others like CD45RA- CD4+ T cells were linked to an elevated risk. In the context of BE, 28 immune phenotypes demonstrated significant causal associations, with the majority being protective, including Unswitched Memory B cells and CD62L on Granulocytes. Conversely, certain phenotypes, such as CD24 on Transitional B cells, were identified as risk factors for BE. For EAC, 34 immune phenotypes were implicated, with various B cell subsets, particularly those expressing BAFF-R and CD24, associated with an increased risk, while Switched Memory B cells and specific myeloid cell phenotypes showed protective effects.

CONCLUSIONS

This study provides novel insights into the complex role of immune cells in the pathogenesis of EAC, revealing a dynamic interplay where certain immune phenotypes may be protective in early stages but become risk-enhancing in later stages of disease progression. These findings highlight the potential of immune cell phenotypes to serve as biomarkers for early detection and targeted therapeutic interventions across the GERD-BE-EAC continuum. Further research is warranted to validate these findings in diverse populations and to explore the underlying mechanisms driving these immune-mediated effects.

Mucosal neuroimmune mechanisms in gastro-oesophageal reflux disease (GORD) pathogenesis

Gastro-oesophageal reflux disease (GORD) is a chronic condition characterised by visceral pain in the distal oesophagus. The current first-line treatment for GORD is proton pump inhibitors (PPIs), however, PPIs are ineffective in a large cohort of patients and long-term use may have adverse effects. Emerging evidence suggests that nerve fibre number and location are likely to play interrelated roles in nociception in the oesophagus of GORD patients. Simultaneously, alterations in cells of the oesophageal mucosa, namely epithelial cells, mast cells, dendritic cells, and T lymphocytes, have been a focus of GORD research for several years. The oesophagus of GORD patients exhibits both macro- and micro-inflammation as a response to chronic acidic reflux at the epithelium. In other conditions of the GI tract, such as IBS and IBD, well-characterised bidirectional processes between immune cells and mucosal nerve fibres contribute to pathogenesis and symptom generation. Sensory alterations in these conditions such as nerve fibre outgrowth and hypersensitivity can be driven by inflammatory processes, which promote visceral pain signalling. This review will examine what is currently known of the molecular pathways linking inflammation and sensory perception leading to the development of GORD symptoms and explore potentially relevant mechanisms in other GI regions which may indicate new areas in GORD research.

Selective Elimination of NRF2-Activated Cells by Competition With Neighboring Cells in the Esophageal Epithelium

BACKGROUND & AIMS

NF-E2-related factor 2 (NRF2) is a transcription factor that regulates cytoprotective gene expression in response to oxidative and electrophilic stresses. NRF2 activity is mainly controlled by Kelch-like ECH-associated protein 1 (KEAP1). Constitutive NRF2 activation by NRF2 mutations or KEAP1 dysfunction results in a poor prognosis for esophageal squamous cell carcinoma (ESCC) through the activation of cytoprotective functions. However, the detailed contributions of NRF2 to ESCC initiation or promotion have not been clarified. Here, we investigated the fate of NRF2-activated cells in the esophageal epithelium.

METHODS

We generated tamoxifen-inducible, squamous epithelium-specific Keap1 conditional knockout (Keap1-cKO) mice in which NRF2 was inducibly activated in a subset of cells at the adult stage. Histologic, quantitative reverse-transcription polymerase chain reaction, single-cell RNA-sequencing, and carcinogen experiments were conducted to analyze the Keap1-cKO esophagus.

RESULTS

KEAP1-deleted/NRF2-activated cells and cells with normal NRF2 expression (KEAP1-normal cells) coexisted in the Keap1-cKO esophageal epithelium in approximately equal numbers, and NRF2-activated cells formed dysplastic lesions. NRF2-activated cells exhibited weaker attachment to the basement membrane and gradually disappeared from the epithelium. In contrast, neighboring KEAP1-normal cells exhibited accelerated proliferation and started dominating the epithelium but accumulated DNA damage that triggered carcinogenesis upon carcinogen exposure.

CONCLUSIONS

Constitutive NRF2 activation promotes the selective elimination of epithelial cells via cell competition, but this competition induces DNA damage in neighboring KEAP1-normal cells, which predisposes them to chemical-induced ESCC.