RBAD: the first database dedicated alterations of blood RNA in individuals with Alzheimer's disease and their clinical relevance.

Alzheimer's disease-associated transcriptomic landscapes have been defined in brain tissue. However, changes in blood RNA and their clinical relevance remain poorly understood. In this study, we developed an RNA profile based on 1468 blood samples from both human and mouse studies, which include bulk RNA sequencing (RNA-seq), microRNA-seq, and single-cell RNA-seq data. We developed a comprehensive analysis pipeline that conducted over 11 million comparisons and correlations to identify more than 20,000 blood features. With these findings, we established a blood RNA database related to Alzheimer's disease, RNAs in Blood of AD (RBAD, http://www.bioinform.cn/RBAD/). Using RBAD, we initially validated well-established Alzheimer's disease-related pathways, including olfactory transduction. We then observed a decrease in both the proportion and functionality of erythroid cells, likely attributed to their elevated CD45 levels and interactions with GZMK+CD8+ T cells. Furthermore, we identified 449 blood RNAs linked to patients' overall survival, along with two mRNAs (H4C3 and CTU1) associated with cognitive decline. In summary, RBAD is the first web-based analysis platform dedicated to investigating blood RNA changes in Alzheimer's disease, and provides valuable insights into potential peripheral biomarkers and pathogenic mechanisms related to Alzheimer's disease.