Cerebrovascular miRNAs Track Early Development of Alzheimer's Disease & Target Molecular Markers of Angiogenesis and Blood Flow Regulation

Abstract

Alzheimer’s disease (AD) is the most prevalent form of dementia and currently impacts ~50 million people worldwide. AD is associated with impaired cerebrovascular function which underscores diminished delivery of blood oxygen and nutrients to and throughout the brain. Thus, we hypothesized that cerebrovascular miRNAs indicate early onset of AD pathology while corresponding to pathways of cerebrovascular growth, structure, and function. Total RNA was isolated from brain vessels of 3xTg-AD mice [Young, 1-2 mo; cognitive impairment (CI), 4-5 mo; extracellular amyloid-β plaques (Aβ), 6-8 mo; plaques + neurofibrillary tangles (AβT), 12-15 mo; n=3 males & 3 females per group]. Fifty-four cerebrovascular miRNAs detected by NanoString technology (nCounter miRNA Expression panel) were mapped to their known mRNA targets using Ingenuity Pathway Analysis. With the premise that AD is a neurovascular disorder, we sought mRNA targets along both the canonical Cardiovascular (Cardio; 15±2 targets per miRNA) and Nervous System (Neuro; 19±2 targets per miRNA) signaling strings with an overlap of 9±1 targets per miRNA among respective pathways. We found that eleven miRNAs were significantly ( p<0.05) downregulated in AD (Aβ + AβT) versus Pre-AD (Young + CI) animals. In particular, let-7d, miR-99a, miR-132, and miR-181a indicated onset of AD (Aβ group) versus Young or CI. Further, miR-133a delineated CI from Young, highlighting the ability of miRNA markers to track early cerebrovascular alterations prior to AD as well. In contrast to the stability of smooth muscle-selective miRNAs (miR-143, miR-145), endothelial miRNAs (miR-23, miR-27a, miR-126) decreased with AD pathology and they target members of the PDE, PDGF, SMAD, and VEGF families. The most prominent individual mRNA markers for distinguishing onset of AD pathology while regulated by ≥3 cerebrovascular miRNAs include Slc6a1, Grin2b, Igf1r, and Smad5. The absolute difference in target overlap among respective Cardio and Neuro pathways was significantly ( p<0.05) higher for all miRNAs that marked AD pathology (28±7%) relative to miRNAs stably expressed throughout (15±2%), suggesting a divergence in overall Cardio and Neuro signaling in AD relative to Pre-AD conditions. In conclusion, miRNAs selective for regulation of endothelial function and respective downstream mRNA/protein targets support a molecular basis for dysregulated cerebral blood flow regulation coupled with enhanced cell growth, proliferation, and inflammation. Accordingly, pathways associated with cerebrovascular miRNAs and their respective mRNA targets advance mechanistic and therapeutic insight for resolving early AD development. NIH Grants: R00AG047198, R56AG062169 & R01AG073230 (EJB). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.