Exploring the causal relationship and molecular mechanisms between Methyl-4-hydroxybenzoic acid (MEP) and Alzheimer's disease: a mendelian randomization, multi-omics, and network toxicology approach.

The pathogenesis of Alzheimer's disease remains incompletely understood. Methyl-4-hydroxybenzoic acid, a common chemical additive, may play a role, though its mechanisms are unclear. This research investigated the potential causal link between Methyl-4-hydroxybenzoic acid and Alzheimer's disease and examined underlying molecular mechanisms. Mendelian randomization analysis evaluated causality, using Cochran's Q test, the Mendelian Randomization-Egger intercept test, and Mendelian Randomization Pleiotropy RESidual Sum and Outlier to assess heterogeneity and sensitivity. Methyl-4-hydroxybenzoic acid targets were identified through multiple databases, and a related target library was constructed using Weighted Gene Co-expression Network Analysis, differential gene expression analysis, and the Genecards database. A Protein-Protein Interaction network identified core genes, validated by molecular docking. Transcriptomic analysis and single-cell expression data explored cell-type-specific expression patterns. Results showed a significant positive causal association between Methyl-4-hydroxybenzoic acid and Alzheimer's disease. We identified 198 Methyl-4-hydroxybenzoic acid targets, with 99 genes associated with both Methyl-4-hydroxybenzoic acid and Alzheimer's disease. Six core genes (EGFR, ESR1, MAPK3, MMP9, PTGS2, TP53) were pinpointed. Functional enrichment implicated neuronal signaling, inflammation, and metabolism. Multi-omics and single-cell analyses revealed differential expression of core genes in key brain regions. Molecular docking confirmed stable interactions between Methyl-4-hydroxybenzoic acid and these proteins. This research confirms a causal relationship between Methyl-4-hydroxybenzoic acid and Alzheimer's disease, revealing potential molecular mechanisms and core gene functions, offering insights into pathogenesis and therapeutic targets.