The Crosstalk Between Sepsis-Associated Encephalopathy and Alzheimer's Disease: Identifying Potential Biomarkers and Therapeutic Targets for Cognition

Patients with sepsis are at a heightened risk of long-term cognitive impairment, including neurodegenerative diseases; however, the underlying pathophysiological mechanisms remain incompletely understood. This study examines key genes associated with sepsis and Alzheimer's disease (AD), as well as their potential molecular mechanisms. We downloaded the GSE135838 dataset from the Gene Expression Omnibus (GEO) database and performed comparative analysis of differentially expressed genes (DEGs) using the AlzData database to identify co-expressed DEGs. Functional and protein-protein interaction (PPI) network analyses were used to identify hub genes and their associated molecular mechanisms. Animal experiments were conducted to validate the role of the central gene C5aR1 in the pathological processes of sepsis-related cognitive impairment, blood-brain barrier (BBB) disruption, and microglial activation. Co-culture experiments were performed to assess the protective effect of C5aR1 against inflammation-induced neuronal damage. In GSE135838, 25 DEGs exhibited consistent expression changes in the brain tissue of AD patients. Notably, LYZ, C5AR1, ZFP36, MPZL2, APOL4, CD163, SERPINA3, and CCL2 showed significant differential expression in the cortex and hippocampus of AD patients. KEGG pathway enrichment analysis revealed that among the 14 pathways meeting the criteria, the TNF signaling pathway demonstrated the highest significance. Key intersections of multiple GO enrichment terms included IL-6, ICAM1, CLEC4E, and PCK1. The top ten hub genes identified from the PPI network analysis included IL6, CCL2, ICAM1, CXCL1, CD163, C5AR1, SOCS3, CLEC4E, HSPB1, and HSPA1A. Pharmacological inhibition of the hub gene product C5aR1 using PMX205 improved cognitive and emotional dysfunction in CLP-induced septic mice and reduced BBB damage and microglial activation. Inhibition of C5aR1 also alleviated microglia-induced neuronal injury. In summary, the neuroimmune dysregulation caused by sepsis is correlated with potential pathological mechanisms in AD. This study provides additional molecular evidence for potential biomarkers and therapeutic targets for drug intervention in the risk of AD among sepsis survivors.

Alzheimer’s Disease; C5aR1; Neuroinflammation; Sepsis-Associated Encephalopathy.