Association between IgM Anti-Herpes Simplex Virus and Plasma Amyloid-Beta Levels

OBJECTIVE: Herpes simplex virus (HSV) reactivation has been identified as a possible risk factor for Alzheimer's disease (AD) and plasma amyloid-beta (Aβ) levels might be considered as possible biomarkers of the risk of AD. The aim of our study was to investigate the association between anti-HSV antibodies and plasma Aβ levels. METHODS: The study sample consisted of 1222 subjects (73.9 y in mean) from the Three-City cohort. IgM and IgG anti-HSV antibodies were quantified using an ELISA kit, and plasma levels of Aβ(1-40) and Aβ(1-42) were measured using an xMAP-based assay technology. Cross-sectional analyses of the associations between anti-HSV antibodies and plasma Aβ levels were performed by multi-linear regression. RESULTS: After adjustment for study center, age, sex, education, and apolipoprotein E-e4 polymorphism, plasma Aβ(1-42) and Aβ(1-40) levels were specifically inversely associated with anti-HSV IgM levels (β = -20.7, P=0.001 and β = -92.4, P=0.007, respectively). In a sub-sample with information on CLU- and CR1-linked SNPs genotyping (n=754), additional adjustment for CR1 or CLU markers did not modify these associations (adjustment for CR1 rs6656401, β = -25.6, P=0.002 for Aβ(1-42) and β = -132.7, P=0.002 for Aβ(1-40;) adjustment for CLU rs2279590, β = -25.6, P=0.002 for Aβ(1-42) and β = -134.8, P=0.002 for Aβ(1-40)). No association between the plasma Aβ(1-42)-to-Aβ(1-40) ratio and anti-HSV IgM or IgG were evidenced. CONCLUSION: High anti-HSV IgM levels, markers of HSV reactivation, are associated with lower plasma Aβ(1-40) and Aβ(1-42) levels, which suggest a possible involvement of the virus in the alterations of the APP processing and potentially in the pathogenesis of AD in human

Alternative splicing of exon 10 in the tau gene as a target for treatment of tauopathies

Tau aggregation is one of the major features in Alzheimer's disease and in several other tauopathies, including frontotemporal dementia with Parkinsonism linked to chromosome 17 (FTDP-17), and progressive supranuclear palsy (PSP). More than 35 mutations in the tau gene have been identified from FTDP-17 patients. A group of these mutations alters splicing of exon 10, resulting in an increase in exon 10 inclusion into tau mRNA. Abnormal splicing with inclusion of exon 10 into tau mRNA has also been observed in PSP and AD patients. These results indicate that abnormal splicing of exon 10, leading to the production of tau with exon 10, is probably one of the mechanisms by which tau accumulates and aggregates in tauopathic brains. Therefore, modulation of exon 10 splicing in the tau gene could potentially be targeted to prevent tauopathies. To identify small molecules or compounds that could potentially be developed into drugs to treat tauopathies, we established a cell-based high-throughput screening assay. In this review, we will discuss how realistic, specific biological molecules can be found to regulate exon 10 splicing in the tau gene for potential treatment of tauopathies

Mannose-binding lectin (MBL) genetic susceptibility for Alzheimer's disease

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Extracellular vesicles: Major actors of heterogeneity in tau spreading among human tauopathies.

Tauopathies are neurodegenerative diseases characterized by tau inclusions in brain cells. Seed-competent tau species have been suggested to spread from cell to cell in a stereotypical manner, indicating that this may involve a prion-like mechanism. Although the intercellular mechanisms of transfer are unclear, extracellular vesicles (EVs) could be potential shuttles. We assessed this in humans by preparing vesicles from fluids (brain-derived enriched EVs [BD-EVs]). These latter were isolated from different brain regions in various tauopathies, and their seeding potential was assessed in vitro and in vivo. We observed considerable heterogeneity among tauopathies and brain regions. The most striking evidence was coming mainly from Alzheimer's disease where the BD-EVs clearly contain pathological species that can induce tau lesions in vivo. The results support the hypothesis that BD-EVs participate in the prion-like propagation of tau pathology among tauopathies, and there may be implications for diagnostic and therapeutic strategies

Mis-splicing of Tau exon 10 in myotonic dystrophy type I is reproduced by overexpression of CELF2 but not by MBNL1 silencing

International audienceTau is the proteinaceous component of intraneuronal aggregates common to neurodegenerative diseases called Tauopathies, including myotonic dystrophy type I (DM1). In DM1, the presence of microtubule-associated protein Tau aggregates is associated with a mis-splicing of Tau. A toxic gain-of-function at the RNA level is a major etiological factor responsible for the mis-splicing of several transcripts in DM1. These are probably the consequence of a loss of MBNL1 function or gain of CELF1 splicing function. Whether these two dysfunctions occur together or separately, and whether all mis-splicing events in DM1 brain result from one or both of these dysfunctions remains unknown. Here, we analyzed the splicing of Tau exons 2 and 10 in the brain of DM1 patients. Two DM1 patients showed a mis-splicing of exon 10 whereas exon 2-inclusion was reduced in all DM1 patients. In order to determine the potential factors responsible for exon 10 mis-splicing, we studied the effect of the splicing factors MBNL1, CELF1, CELF2 and CELF4 or a dominant-negative CELF factor on Tau exon 10 splicing by ectopic expression or siRNA. Interestingly, the inclusion of Tau exon 10 is reduced by CELF2 whereas it is insensitive to the loss-of-function of MBNL1, CELF1 gain-of-function or a dominant-negative of CELF factor. Moreover, we observed an increased expression of CELF2 only in the brain of DM1 patients with a mis-splicing of exon 10. Taken together, our results indicate the occurrence of a mis-splicing event in DM1 that is neither induced by a loss of MBNL1 function nor a gain of CELF1 function, but is rather associated to CELF2 gain-of-function