The APOA1-SNCA Axis as a Molecular Bridge Between CKD and Parkinson’s Disease: A Systems Biology Model of Kidney-to-Brain Propagation via Exosomal Pathways

Chronic kidney disease (CKD) is an established risk factor for Parkinson’s disease (PD), but the molecular mechanisms linking these two conditions remain elusive. We performed a systems biology analysis by retrieving high-confidence gene–disease associations from DisGeNET v7.0 (PD: score ≥ 0.8, EI ≥ 0.4; CKD: score ≥ 0.6, EI ≥ 0.4) and constructing a protein–protein interaction (PPI) network via STRING v11.5 (confidence ≥ 0.700). Direct “molecular bridges” between CKD and PD proteins were identified and validated using independent databases. To corroborate biological feasibility, candidate proteins were cross-referenced with ExoCarta and Vesiclepedia databases for exosomal localization. Functional enrichment, tissue expression, and pathway analyses were conducted. Despite zero gene overlap (64 PD genes, 17 CKD genes), the PPI network showed significant convergence (81 nodes, 280 edges, PPI enrichment p < 1.0 × 10−16). Fifteen high-confidence molecular bridges were identified, including the Apolipoprotein A1 (APOA1)–α-synuclein (SNCA) interaction (combined score 0.883), which was independently validated by IntAct. Functional enrichment revealed specific association of APOA1–SNCA with “amyloid fiber formation” (false discovery rate (FDR) = 0.038). Both APOA1 and SNCA are annotated as exosome components (Kyoto Encyclopedia of Genes and Genomes (KEGG) ko04147) and were confirmed as consistent cargo in plasma, urine, and platelet-derived extracellular vesicles within proteomic databases (ExoCarta IDs: 335, 6622). Global pathway analysis highlighted inflammation, oxidative stress, and the advanced glycation end product (AGE)–receptor for AGE (RAGE) pathway. We propose an integrative model wherein CKD-induced dysregulation of APOA1 promotes α-synuclein misfolding and aggregation, and the co-packaging of these proteins into exosomes provides a plausible vehicle for kidney-to-brain propagation. This framework offers testable hypotheses and potential therapeutic targets for PD-CKD comorbidity.