Integrating Bulk and Single-Cell Transcriptomic Data to Identify Ferroptosis-Associated Inflammatory Gene in Alzheimer’s Disease

Background: Ferroptosis is a form of programmed cell death triggered by iron-dependent lipid peroxidation, characterized by iron accumulation and elevated reactive oxygen species (ROS), leading to cell membrane damage. It is associated with a variety of diseases. However, the cellular and molecular links between ferroptosis, immune inflammation, and the brain-peripheral blood axis in Alzheimer's disease (AD) remain unclear. Methods: We integrated bulk RNA-seq data from AD brain tissue and peripheral blood and refined the screening of AD candidate genes through differential gene expression analysis, weighted gene co-expression network analysis (WGCNA), and other approaches. Additionally, we analyzed single-cell RNA-seq (scRNA-seq) data from AD patients' brain tissue and peripheral blood, combined with scRNA-seq data from experimental autoimmune encephalomyelitis (EAE) mouse brain tissue. This enabled us to explore AD-related molecular mechanisms from a cell-type-specific perspective. Finally, candidate genes were validated in ferroptosis models using reverse transcription quantitative PCR (RT-qPCR) and immunofluorescence methods. Results: Bulk RNA-seq analysis identified SLC11A1, an inflammatory gene associated with AD. Single-cell RNA-seq analysis further revealed that SLC11A1 expression was significantly elevated in the pro-inflammatory (M1-type) microglia and peripheral blood monocytes in AD. Moreover, we identified a microglial subpopulation in AD M1-type microglia that was highly associated with ferroptosis. This subpopulation simultaneously expressed characteristic markers of peripheral blood monocytes, suggesting that these cells may originate from peripheral blood monocytes, thereby triggering neuroinflammation through the ferroptosis pathway. Cell experiments confirmed that SLC11A1 was significantly upregulated in inflammatory microglia induced by ferroptosis. Conclusion: This study reveals the key role of SLC11A1 in AD, particularly in the context of ferroptosis and immune inflammation. It provides a novel molecular mechanistic perspective and offers potential targets for future therapeutic strategies.