CXCL16 Promotes the Development of Chronic Atrophic Gastritis by Regulating M1 Macrophage Polarisation

Objective: The objective of this study was to investigate the regulatory effect of CXCL16 on macrophage polarization within the microenvironment of chronic atrophic gastritis (CAG), thereby providing a theoretical foundation for understanding the pathogenesis of CAG and developing effective therapeutic strategies. Methods: We employed a bioinformatics approach to explore the immune-related biological mechanisms associated with CAG, identifying key markers in the process. Initially, we examined differential expression and correlation of these key markers between patients with CAG and those with chronic non-atrophic gastritis (CNAG) using data from relevant databases. This was further validated through multiplex immunohistochemistry (mIHC). Finally, we verified the impact of CXCL16 on macrophage polarization through in vitro experiments. Results: The bioinformatics analysis identified 24 immune-related genes associated with CAG, primarily involved in immune cell activation and differentiation, cellular chemotaxis, and intrinsic immunity. These genes were notably enriched in cytokine-cytokine receptor interactions and chemokine signaling pathways. Additionally, a protein interaction analysis was conducted to pinpoint core proteins such as the macrophage-related markers CD86 and CD163, along with their candidate effector CXCL16. Analysis of the GEO database indicated that the expression levels of these core proteins exhibited significant differences between the CAG and CNAG groups. Conversely, multiplex immunohistochemistry (mIHC) staining demonstrated that CD86 protein expression was markedly elevated in patients with CAG and CAG-E compared to the control group (CNAG), while CD163 expression was downregulated. Furthermore, CXCL16 expression showed an upregulation in both CAG cases but decreased in those classified as CAG-E; this difference reached statistical significance when comparing these two groups ( P < 0.05). Co-localization and correlation analyses further revealed that CXCL16 was predominantly co-expressed with the M1 macrophage marker CD86 in patients diagnosed with CAG, exhibiting a strong correlation between their expressions. Ultimately, in vitro experiments confirmed significant expressions of CXCL16 and its receptor CXCR6 within macrophages. Moreover, upon stimulation with varying concentrations of CXCL16, these macrophages displayed an M1 phenotype characterized by a substantial increase in mRNA levels of CD86—providing additional evidence that CXCL16 facilitates macrophage polarization towards an M1 state. Conclusion: In this study, by analyzing the presence, phenotype and influencing factors of macrophages in patients with different pathological types of gastritis, we concluded that macrophage polarisation is crucially involved in CAG pathogenesis, and that CXCL16 could promote macrophage polarisation towards the M1 phenotype in the CAG microenvironment.This provides some reference for future CAG diagnosis and treatment. Keywords: chronic atrophic gastriti, bioinformatics, macrophage polarization, CXCL16, multiple fluorescence immunohistochemistry