We study the pathophysiological mechanisms that operate in Alzheimer’s disease under the scope of neuroinflammation, amyloidogenesis and synaptic dysfunctions. Understanding and fighting neurodegenerative diseases, in particular Alzheimer’s disease, is one of the most challenging endeavors of modern neuroscience. Alzheimer’s disease is the most devastating neurodegenerative disorder with a major socio-economic burden that is accentuated by the absence of effective treatments curing or slowing down its progression. Despite a variety of therapies currently under investigation, the discovery of a cure does not seem to be within reach at this point. Therefore, there is an urge in identifying new targets in the triggering/progression of the disease and understanding the underlying molecular mechanisms preceding irreversible cognitive decline. In this context, our global objective is to better understand some of the proteolytic pathways that operate at the crossroads of three major pathogenic processes tightly interconnected: neuroinflammation, amyloidogenesis and synaptic dysfunctions. Our original findings have placed some matrix metalloproteinases (MMPs), as new actors in Alzheimer’s pathogenesis because they promote neuroinflammation and amyloidogenesis, and alter synaptic transmission. Consequently, MMPs may become potential new therapeutic targets. The backbone of our research is therefore structured around two main objectives: i) increase our understanding of the pathophysiological mechanisms of Alzheimer’s disease, and ii) develop and validate innovative therapeutic strategies on the basis of newly discovered targets..We use techniques of molecular and cellular biology, biochemistry, cell and tissue imaging, pharmacology, electrophysiology and animal behavior, on in vivo and in cellulo models of the pathology, in collaboration with INP teams and worldwide. Our multilevel research strategy is based on 3 complementary aims.
1. Studying pathophysiological mechanisms of neurodegeneration involving neuroinflammation, amyloidosis and synaptic dysfunctions
In the wake of our previous findings, we are studying the impact of membrane-type MMPs (MT-MMPs), in particular MT1-MMP and MT5-MMP on the intracellular trafficking and processing of amyloid precursor protein (APP), in the context of their interplay with key inflammatory mediators (e.g, IL-1β, TNF-α ) and their receptors. We also use proteomic-based unbiased approaches to identify new physiological neural substrates of MT-MMPs that might be involved in their pathogenic effect. We investigate the functional consequences of these molecular interactions at the electrophysiological level, using whole-cell patch-clamp recording and calcium imaging in mixed primary cultures of neurons, astrocytes and microglia. We also study the functional impact throughout a panel of behavioral tests that evaluate learning and memory and emotional behaviors, and their correlation with pathological hallmarks in transgenic Alzheimer mice deficient for the MMPs of interest. These projects are developed in collaboration with the INP teams of Michel Khrestchatisky, François Roman.
2. Engineering tools to modulate MMP activity and/or protein-protein interactions
In order to set up targeted therapeutic strategies based on MMP modulation it is crucial to develop MMP-modifying drugs that selectively target a given MMP. Despite recent progress in the domain, this remains a challenging endeavor because the members of the MMP family share highly conserved catalytic domains. Accordingly, we implement alternative strategies in collaboration with chemists and biochemists aiming at the discovery and development of small organic molecules or neutralizing antibodies through the screening of chemical or nanobody libraries. Selected compounds are tested in vitro and in cellulo models for their ability to modulate pro-inflammatory and/or pro-amyloidogenic responses that depend on MMP catalytic activities or their interactions with substrates. Furthermore, the ability of the selected compounds to cross the blood brain barrier in in vitro models and their eventual optimization are carried out in collaboration with the biotech company VECT-HORUS, which is part of the INP. Together, these in silico, in vitro and in cellulo approaches allow selection of the hits that are further tested in in vivo models of Alzheimer’s disease.
3. Modeling Alzheimer with iPS cells for the study of pathophysiological mechanisms and target validation
Cell reprogramming has opened new avenues for the comprehensive study of neural pathophysiological mechanisms, but also for testing/validating new therapeutic targets. In collaboration with the team of Emmanuel Nivet at the INP, we implement neuronal and astrocyte cultures from iPS cells of Alzheimer’s patients that harbor familial mutations (e.g, Swedish, double APP…) or genetic risk factors (i.e, ApoE4). Using the CRISPR/Cas9 technology, we can knock out the MMPs of interest in human iPS cell lines and study the impact of such deficiency on neuron function and fate. Seemingly, human iPS-derived neural cells serve as biological platform to test MMP-modifying drugs or other relevant drugs. Also important, by working on neurone-astrocyte co-cultures, we propose a less neurocentric approach to the study of Alzheimer’s pathophysiology, which aims at deciphering the impact of astrocytes from sporadic or familial Alzheimer’s disease on neuronal function and vice versa.