Maladie d'Alzheimer | EPFL Graph Search

La (en allemand ) est une maladie neurodégénérative incurable à ce jour du tissu cérébral qui entraîne la perte progressive et irréversible des fonctions mentales et notamment de la mémoire. C'est la cause la plus fréquente de démence chez l'être humain. En 2015, il y a approximativement de personnes dans le monde atteintes de la maladie d'Alzheimer. Le plus souvent, la maladie débute chez les personnes ayant plus de ; seuls 4 % à 5 % des cas d'Alzheimer commencent avant cet âge. Environ 6 % des personnes de et plus sont touchées, mais ces chiffres diffèrent en fonction des pays. En 2010, la démence causée par la maladie a provoqué environ dans le monde. Dans les pays développés, c'est l'une des maladies les plus coûteuses pour la société. Face à la prévalence de la maladie, des efforts de recherche médicale visent à développer des médicaments capables de stopper le processus neurodégénératif. Les pistes principales sont de s'attaquer aux plaques amyloïdes qui se forment entr

TLR4- and TRIF-dependent stimulation of B lymphocytes by peptide liposomes enables T cell-independent isotype switch in mice

Anna Lucia Buccarello, Valérie Gafner, Andreas Muhs, Pedro Miguel Nunes Pereira de Almeida Reis, Andrea Pfeifer, Marija Vukicevic

Immunoglobulin class switching from IgM to IgG in response to peptides is generally T cell-dependent and vaccination in T cell-deficient individuals is inefficient. We show that a vaccine consisting of a dense array of peptides on liposomes induced peptide-specific IgG responses totally independent of T-cell help. Independency was confirmed in mice lacking T cells and in mice deficient for MHC class II, CD40L, and CD28. The IgG titers were high, long-lived, and comparable with titers obtained in wild-type animals, and the antibody response was associated with germinal center formation, expression of activation-induced cytidine deaminase, and affinity maturation. The T cell-independent (TI) IgG response was strictly dependent on ligation of TLR4 receptors on B cells, and concomitant TLR4 and cognate B-cell receptor stimulation was required on a single-cell level. Surprisingly, the IgG class switch was mediated by TIR-domain-containing adapter inducing interferon-beta (TRIF), but not by MyD88. This study demonstrates that peptides can induce TI isotype switching when antigen and TLR ligand are assembled and appropriately presented directly to B lymphocytes. A TI vaccine could enable efficient prophylactic and therapeutic vaccination of patients with T-cell deficiencies and find application in diseases where induction of T-cell responses contraindicates vaccination, for example, in Alzheimer disease. (Blood. 2013; 121(1): 85-94)

Amer Soc Hematology2013

Opportunities and challenges of alpha-synuclein as a potential biomarker for Parkinson's disease and other synucleinopathies

Hilal Lashuel, Pedro José Santana Ribeiro Magalhães

Parkinson's disease (PD), the second most common progressive neurodegenerative disease, develops and progresses for 10-15 years before the clinical diagnostic symptoms of the disease are manifested. Furthermore, several aspects of PD pathology overlap with other neurodegenerative diseases (NDDs) linked to alpha-synuclein (aSyn) aggregation, also called synucleinopathies. Therefore, there is an urgent need to discover and validate early diagnostic and prognostic markers that reflect disease pathophysiology, progression, severity, and potential differences in disease mechanisms between PD and other NDDs. The close association between aSyn and the development of pathology in synucleinopathies, along with the identification of aSyn species in biological fluids, has led to increasing interest in aSyn species as potential biomarkers for early diagnosis of PD and differentiate it from other synucleinopathies. In this review, we (1) provide an overview of the progress toward mapping the distribution of aSyn species in the brain, peripheral tissues, and biological fluids; (2) present comparative and critical analysis of previous studies that measured total aSyn as well as other species such as modified and aggregated forms of aSyn in different biological fluids; and (3) highlight conceptual and technical gaps and challenges that could hinder the development and validation of reliable aSyn biomarkers; and (4) outline a series of recommendations to address these challenges. Finally, we propose a combined biomarker approach based on integrating biochemical, aggregation and structure features of aSyn, in addition to other biomarkers of neurodegeneration. We believe that capturing the diversity of aSyn species is essential to develop robust assays and diagnostics for early detection, patient stratification, monitoring of disease progression, and differentiation between synucleinopathies. This could transform clinical trial design and implementation, accelerate the development of new therapies, and improve clinical decisions and treatment strategies.

NATURE PORTFOLIO2022

Capturing the heterogeneity of alpha-synuclein pathology in synucleinopathies

Melek Firat Altay

Synucleinopathies such as Parkinson's disease, dementia with Lewy bodies and multiple system atrophy (MSA) are detrimental neurodegenerative diseases. Alpha-synuclein (aSyn), the main aggregating protein found in the pathological inclusions of these ailments, exists in numerous modified forms and conformations, leading to neuropathological heterogeneity in synucleinopathies. The functional, pathological and clinical implications of this heterogeneity remain unclear. Responding this knowledge gap requires the development of novel toolsets capable of capturing the biochemical and structural diversity of aSyn pathology in the brain and peripheral tissues.To address this challenge, we describe in Chapter 2 the development and characterisation of antibodies that cover all three regions and post-translational modifications (PTMs) of aSyn. We assess these antibodies through a comprehensive validation pipeline, and select the best performing antibody subset to capture the neuropathological diversity of aSyn across Lewy body diseases (LBDs). We demonstrate that these antibodies could be used to achieve an in-depth characterization of the biochemical and morphological diversity of aSyn aggregates in the neuronal and in vivo models of aSyn seeding. Our results suggest that aSyn pathology is rich in Serine 129 phosphorylation (pS129) and in previously under-described PTMs, including nitration and phosphorylation at Tyrosine 39 (nY39, pY39) and C-terminal tyrosine phosphorylations (pY133, pY136) across neuronal and glial populations in LBDs. We also report that aSyn is hyperphosphorylated in the cellular and in vivo seeding models. In Chapter 3, we demonstrate the power of our antibodies to achieve an unprecedented analysis of astrocytic aSyn pathology in LBDs. We characterise the biochemical properties, post-translational modifications and the aggregation state of astrocytic aSyn accumulations in the limbic regions across sporadic and familial LBDs. The astrocytic aSyn is revealed distinctively by antibodies against the late amino-terminus (N-terminus) and non-amyloid-beta component (NAC) region of aSyn, but not by the extreme N-terminal or carboxy-terminal (C-terminal) antibodies, suggesting that these aSyn species are truncated at both ends. The astrocytic aSyn accumulations are negative for the key markers of Lewy bodies (aSyn pS129, Amytracker, p62- and ubiquitin-positivity and proteinase K resistance), and positive for aSyn nY39 and pY39. These findings suggest that the astrocytic accumulations may be composed of non-fibrillar, possibly oligomeric conformers of aSyn. Chapter 4 focuses on deciphering the biochemical and morphological signatures of aSyn pathology in MSA. The antibodies described in Chapter 2 are applied to high and low pathology regions of MSA brains by immunohistochemistry (IHC). We also biochemically profile the aSyn species, and report an abundance of aSyn pS129-positive glial and neuronal inclusions that correspond to insoluble high molecular weight species by Western blot. We detect an enrichment of insoluble and truncated aSyn in the MSA cerebellum. By IHC, there is an enhancement of aSyn nY39, pY136 and of other aSyn PTMs.Collectively, the new tools and findings described here may pave the way for future studies elucidating the role of these neuronal and glial aSyn proteoforms in disease pathogenesis and propagation in synucleinopathies.

EPFL2022