Peripheral inflammatory processes in Alzheimer disease: from biomarker profiling to pathophysiological studies; – CytokALZ

The experimental technologies performed for this study rely on multiplex systems: protein antibody arrays, microfluidic and biochips multiplex assays. This approach is innovative in the field of blood biomarkers as it combines detection and identification of pro-inflammatory factors in human samples with dementia, and in transgenic animal models. These allow several tests to be performed simultaneously without dividing the original patient sample, on the contrary to classical methods that necessitate multiple divisions of the original sample for each test. Modification of putative blood biomarkers will be evaluated in both human samples (AD patients, other forms of dementia and inflammatory peripheral and central nervous system diseases without dementia) and murine samples (murine model of AD: THY-Tau22). Concerning the murine model, serum samples will be collected at three different periods of time: between 2 and 3 month, between 6 and 7 and at 12 months of age, corresponding to early-pre symptomatic, medium state and late phase of the disease, respectively. Samples from the wild-type and heterozygote THY-Tau 22 mice will be collected at matching ages as controls.
The all study is expected to last 36 months and is organized in 5 tasks (see illustration for the plan).

In human, our results confirm the potential diagnosis interest of previously published blood biomarkers and propose two new ones: IL-8 and sTNFR-1. Further studies will be needed to validate these biomarkers which could be used alone, combined or in association with the classical amyloid and tau biomarkers.
In mice, our results show an increase in 2 pro-inflammatory proteins LIX/CXCL5 et VCAM-1 in the plasma of ThyTau22 compared to WT mice. We have shown that this overexpression is also observed in the brain and occur after development of the first DNF lesions in the model, and concomitantly with mnesic alterations. The interest of these proteins as potential biomarkers or therapeutic targets in AD must be further studied by overexpression or inhibition experiments in the ThyTau22 model.

The impact of the identification of biomarkers favoring an early diagnosis of AD is very promising, because of the ageing of the population and the frequency of the disease among the ageing subjects in the general population. Furthermore, the identification of serum biomarkers is particularly attractive because of the less invasive character of a sampling of blood with regard to the lumbar puncture necessary for the dosage of peptides and proteins of the LCR for the current biochemical diagnosis of AD.
Finally, the identification of potential therapeutic targets for the treatment of AD thanks to the mice is particularly attractive, because of the absence of curative treatment and the contribution to the palliative care for the current care of the AD.

This project led to the presentation of a poster at the AAIC of Copenhague, 2014: “Peripheral inflammatory processes in alzheimer disease: biomarkers profiling approach”.

A first OPEN ACESS scientific publication was published in journal Frontiers in Neurology :
Constance Delaby, Audrey Gabelle, David Blum, Susanna Schraen-Maschke, Amandine Moulinier, Justine Boulanghien, Dany Séverac, Luc Buée, Thierry Rème and Sylvain Lehmann
Central nervous system and peripheral inflammatory processes in Alzheimer’s disease: biomarker profiling approach
Front. Neurol., 24 August 2015 | dx.doi.org/10.3389/fneur.2015.00181

Alzheimer disease (AD) is a neurodegenerative disorder characterized by significant cognitive deficits, behavioral changes, sleep disorders and loss of functional autonomy. The number of patients suffering from AD is growing rapidly as the population ages worldwide. AD represents major cause of dementia in occidental countries. New revised AD diagnosis criteria were proposed. They highlighted the reduction of hippocampic volumetry by MRI, the reduction of glucidic metabolism in specific brain regions as well as alteration of CSF biomarkers: decrease of Aß1-42 peptides, increase of Tau and P-tau proteins. All these biomarkers help the clinical diagnosis with a sensitivity and specificity around 80% but the challenge of AD requires biomarkers beyond these probability and detectable in the blood. The use of news biomarkers in the field of the early diagnosis becomes a requirement because of the current development of therapeutic strategies aiming at slowing down, to even block the neurodegenerative process. Moreover, research in the field of biomarkers leads to relevant data to help elucidate Alzheimer pathophysiological mechanisms. One of the most interesting approaches is the analysis of inflammatory processes involved in AD. Incidentally, recent data suggested that AD pathological processes would produce disease-specific molecular changes in the blood, specifically on secreted signalling proteins, including cytokines, chemokines, and growth factors, as these are the primary means of communication between cells. Genomic investigation in human, as well as in AD animal models, also pointed out the implication of inflammatory molecules such as TNFs in the disease.
We propose here further investigations on the involvement of inflammatory processes in AD. This approach is innovative in the field of blood biomarkers as it combines detection and identification of pro-inflammatory factors in human samples with dementia, and in transgenic animal models. A first part our project is based on the targeted and multiplex exploration and validation of inflammatory factors eventually identified in previous proteomic and genomic works. Both microfluidic and biochip multiplex technologies will be utilized. This will be done in patients (AD, prodromal AD, other dementia and inflammatory peripheral and central nervous system) and in a relevant AD transgenic mouse model: THY-Tau22. Data generated will be analysed with state-of-the art bioinformatics. We will then come full circle by cross-validating mouse and human models. In a second phase, putative biomarker candidates will be explored using immuno-histological approaches in mice, and will be measured in the CSF of patients. Our work program will therefore rationalize the identification and characterization of peripheral biomarkers of AD and help decipher the exact function of inflammation in neurodegeneration eventually leading to new therapeutic targets.