Transcriptomic Analysis Reveals the Molecular Relationship Between Common Respiratory Infections and Parkinson's Disease.

Parkinson's disease (PD) is one of the most rapidly growing neurological disorders globally. The molecular relationship between common respiratory infections (RIs) and idiopathic Parkinson's disease (iPD) remains a controversial issue. Multiple studies have linked acute respiratory infections to PD, but the molecular mechanism behind this connection is not significantly defined. Therefore, the aim of our study was to investigate potential molecular interactions between RIs and PD. We retrieved eight publicly available RNA-seq datasets from the NCBI Gene Expression Omnibus (NCBI GEO) and performed extensive bioinformatics analysis, including differential gene expression (DGE) analysis, the identification of overlapped differentially expressed genes (DEGs), weighted gene co-expression network analysis (WGCNA), pathway and functional enrichment analysis, the construction of protein-protein networks, and the identification of hub genes. Additionally, we applied a machine learning method, a Random Forest model (RF), to external RIs datasets to identify the most important genes. We found that ribosomal subunits, mitochondrial complex proteins, proteasome subunits, and proteins encoding ubiquitin are simultaneously downregulated and co-expressed in RIs and PD. Dysregulation of these proteins may disturb multiple pathways, such as those responsible for ribosome biogenesis, protein synthesis, autophagy, and apoptosis; the ubiquitin-proteasome system (UPS); and the mitochondrial respiratory chain. These processes have been implicated in PD's pathology, namely in the aggregation of α-synuclein, mitochondrial dysfunction, and the death of dopaminergic neuron cells. Our findings suggest that there are significant similarities in transcriptional responses and dysfunctional molecular mechanisms between RIs, PD, and aging. RIs may modulate PD-relevant pathways in an age- or immune-dependent manner; longitudinal studies are needed to examine the RIs risk factor. Therefore, future studies should experimentally investigate the influence of age, vaccination status, infection type, and severity to clarify the role of RIs in PD's pathogenesis.