Search for Alzheimer’s disease biomarkers in blood cells: hypotheses-driven approach

Written by Joanna Wojsiat , Katarzyna Laskowska-Kaszub , Anna Mietelska-Porowska & Urszula Wojda

Current Alzheimer’s disease (AD) diagnostics is based on cognitive testing, and detecting amyloid Aβ and τ pathology by brain imaging and assays of cerebrospinal fluid. However, biomarkers identifying complex pathways contributing to pathology are lacking, especially for early AD. Preferably, such biomarkers should be more cost-effective and present in easily available diagnostic tissues, such as blood. Here, we summarize the recent findings of potential early AD molecular diagnostic biomarkers in blood platelets, lymphocytes and erythrocytes. We review molecular alterations which refer to such main hypotheses of AD pathogenesis as amyloid cascade, oxidative and mitochondrial stress, inflammation and alterations in cell cycle regulatory molecules. The major advantage of such biomarkers is the potential ability to indicate individualized therapies in AD patients.
Alzheimer’s disease (AD) is the most prevalent age-related dementia worldwide and one of the major unmet, increasing medical and economic problems of the modern world. As of 2015, there were an estimated 46.8 million people with dementia worldwide. This number will increase to an estimated 74.7 million in 2030 [1].

Among the neuropathological hallmarks of AD are: the progressive loss of brain neurons, synaptic degeneration and the deposition of extracellular amyloid plaques and intracellular neurofibrillary tangles (NFTs) in such regions of the brain as the hippocampus, cortex and amygdala. Amyloid plaques consist mainly of 40- and 42-amino-acid Aβ peptides (Aβ40 and Aβ42). Peptides are proteolytic cleavage products of the Aβ protein precursor (APP) but with no fully elucidated biological function. NFTs are deposits of paired helical filaments composed mainly of hyperphosphorylated τ protein, a microtubule-stabilizing protein that maintains neuronal cell structure and axonal transport.

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