Alzheimer's disease diagnosis using blood platelets as a circulating mirror of neurons

Abstract:

Alzheimer's disease (AD) is a neurodegenerative pathology covering about 70% of all cases of dementia. Usually the diagnosis of AD is carried out in the dementia phase, often in the moderate stages when treatment efficacy is limited. Indeed, early diagnosis, when possible, is invasive and expensive in routine settings. Circulating platelets have been suggested as an alternate model to study neural dysfunctions and resident neurons and blood platelets both have similar subcellular structures and protein compositions. One of the most surprising findings is that a number of proteins are frequently expressed in both circulating platelets and neurons such as the neuronal protein reelin, which controls cell migration and synaptic plasticity, the amyloid precursor protein (APP), which produces amyloid Aβ peptides that accumulate in senile plaques in AD, brain-derived neurotrophic factor, and the neurotransmitter serotonin, which plays significant roles in regulating behavior and social interaction. Therefore platelets appear as an approachable peripheral biomarker to track the start and course of neurological illnesses. Adenosine, an ubiquitous nucleoside, plays a key role in neurodegeneration, through interaction with four receptor subtypes. The A2A receptor (A2AAR) is up-regulated in platelets of patients affected by AD and Huntington’s diseases, reflecting the same alteration found in brain tissues. PKCε, closely related with pathological devastation observed in AD, is highly expressed in the healthy brain while downregulated in AD neurons but its peripheral expression in this pathology is not known. It has to be remarked that PKCε activators are now under investigation in Phase II clinical trials in AD patients making PKCε a possible marker of the disease.In this research project we will verify whether the expression of A2AAR/PKCε could be exploited as a specific and sensitive double platelet biomarker for the diagnosis of AD. Finally, the effect of A2AAR and PKCε stimulation on neurotoxicity induced by Aβ-amyloid peptide in neuronal cells will be investigated. Altogether, the recognition of A2AARs/PKCε as a biomarker would improve the early detection of AD and related dementia and may represent the proof of concept to extend the use of A2AAR antagonists as new drugs for AD treatment.

Risultati attesi:

Alzheimer’s disease (AD) unfolds gradually and is often preceded by mild cognitive impairment, a transitional phase in which neuropathological changes begin well before clinical symptoms emerge. Pathological hallmarks such as amyloid-beta (Aβ) and phospho-TAU accumulate more than a decade prior to dementia onset, highlighting the urgent need for reliable peripheral biomarkers and new therapeutic targets that enable early diagnosis and influence disease progression.

Recent research indicates a significant overexpression of adenosine A2A receptors (A2AARs) in the frontal white matter of AD patients, corroborated by preclinical data in aged rodents and transgenic mice models. This overexpression is widely recognized as a contributor to synaptic dysfunction and cognitive decline. Concurrently, protein kinase C epsilon (PKCε), a key regulator of neuronal plasticity and memory via activation of BDNF, NGF, and IGF, is reported to be downregulated in the AD brain. These molecular alterations suggest that A2AARs and PKCε play pivotal roles in AD pathogenesis.

Milestone 1 will establish whether A2AARs and PKCε are differentially expressed in the platelets of AD patients versus healthy controls. Given that platelets share critical signaling features with neurons, including the presence of amyloid precursor protein and the release of Aβ peptides, this milestone is expected to validate their utility as accessible peripheral indicators of neurodegeneration. Outcomes will inform diagnostic strategies by providing non-invasive biomarkers that are unaffected by age or treatment history.

Milestone 2 will consolidate the translational relevance of these markers by correlating peripheral findings with those observed in different regions of the AD brain, derived from patient tissue samples. This step is expected to confirm whether variations in A2AARs and PKCε expression at the central level are mirrored in blood platelets, thus reinforcing the biomarker hypothesis. Particular attention will be given to gender-related differences, as women exhibit higher vulnerability to AD and the underlying biological mechanisms remain poorly understood. The milestone will expand the characterization of A2AARs and PKCε throughout different stages of the disease, including intermediate and advanced phases.

Milestone 3 will focus on in vitro cellular analyses to elucidate how Aβ-induced neurotoxicity affects signaling pathways involving A2AARs and PKCε. These studies will contribute mechanistic insights into neuroinflammatory processes and oxidative stress-linked neuronal damage. Based on existing evidence, the inhibition of Aβ-mediated effects via pharmacological modulation of A2AARs and PKCε holds therapeutic potential. The milestone will reinforce the relevance of targeting these proteins, capitalizing on compounds already in clinical use or trials—such as istradefylline (A2AAR antagonist) and bryostatin (PKCε activator).

Collectively, the outcomes of Milestones 1, 2, and 3 are expected to validate A2AARs and PKCε as a dual biomarker system, capable of signaling inflammatory and degenerative conditions related to AD. By bridging central and peripheral data, the project will offer novel diagnostic tools and actionable targets for therapeutic innovation. The multidisciplinary collaboration among the research Units of Ferrara, Parma, and Pavia will ensure a robust and comprehensive approach to sample collection, molecular analysis, and translational interpretation.