Bioinformatics identification of forkhead box O3 and the proto-oncogene tyrosine-protein kinase receptor RET as aging-associated biomarkers linked to immune cell infiltration in Parkinson’s disease

Objectives: Parkinson’s disease (PD), the second most prevalent neurodegenerative disease, is closely linked to aging and immune system dysfunction. This study aims to explore potential aging-related biomarkers of PD and examine their diagnostic value, in addition to their relationship with immune cell infiltration, to identify novel therapeutic targets. Methods: Gene expression profiles from the gene expression omnibus (GEO) database (GSE20163, GSE20164, and GSE8397) were analyzed. Aging-related genes associated with PD were screened using weighted gene co-expression network analysis. Subsequent functional enrichment analysis, protein‒protein interaction (PPI) network mapping, and least absolute shrinkage and selection operator regression were used to identify key biomarker candidates. A receiver operating characteristic (ROC) curve analysis was applied to evaluate diagnostic efficacy. Immune cell infiltration was assessed through Spearman correlation analysis, and the expression of key biomarkers was validated in both cellular and animal PD models. Results: Eighteen aging-related genes were identified through a PPI network analysis. Seven genes, including forkhead box O3 (FOXO3) and the proto-oncogene tyrosine-protein kinase receptor rearranged during transfection (RET), showed potential as diagnostic biomarkers for PD. Gene set enrichment analysis revealed that these biomarkers correlated with immune cell infiltration patterns in PD patients. The ROC curve analysis indicated high diagnostic accuracy for these genes across multiple datasets (area under the curve = 96.3158). In vivo and in vitro validation confirmed significant changes in the expression of RET and FOXO3 in PD samples, highlighting their relevance as biomarkers. Conclusion: Our findings suggest that RET and FOXO3 are promising aging-related biomarkers for PD, potentially providing new insights into the early diagnosis and targeted treatment of PD. These biomarkers also reflect the complex interplay between aging, immunity, and PD pathogenesis.