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Alzheimer's Disease is a devastating dementing disease involving amyloid deposits, neurofibrillary tangles, progressive and irreversible cognitive impairment. Today, only symptomatic drugs are available and therapeutic treatments, possibly acting at a multiscale level, are thus urgently needed. To that purpose, we designed multi-effects compounds by synthesizing drug candidates derived by substituting a novel N,N'-disubstituted piperazine anti-amyloid scaffold and adding acetylcholinesterase inhibition property. Two compounds were synthesized and evaluated. The most promising hybrid molecule reduces both the amyloid pathology and the Tau pathology as well as the memory impairments in a preclinical model of Alzheimer's disease. In vitro also, the compound reduces the phosphorylation of Tau and inhibits the release of Aβ peptides while preserving the processing of other metabolites of the amyloid precursor protein. We synthetized and tested the first drug capable of ameliorating both the amyloid and Tau pathology in animal models of AD as well as preventing the major brain lesions and associated memory impairments. This work paves the way for future compound medicines against both Alzheimer's-related brain lesions development and the associated cognitive impairments., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Tau pathology is encountered in many neurodegenerative disorders known as tauopathies, including Alzheimer's disease. Physical activity is a lifestyle factor affecting processes crucial for memory and synaptic plasticity. Whether long-term voluntary exercise has an impact on Tau pathology and its pathophysiological consequences is currently unknown. To address this question, we investigated the effects of long-term voluntary exercise in the THY-Tau22 transgenic model of Alzheimer's disease-like Tau pathology, characterized by the progressive development of Tau pathology, cholinergic alterations and subsequent memory impairments. Three-month-old THY-Tau22 mice and wild-type littermates were assigned to standard housing or housing supplemented with a running wheel. After 9 months of exercise, mice were evaluated for memory performance and examined for hippocampal Tau pathology, cholinergic defects, inflammation and genes related to cholesterol metabolism. Exercise prevented memory alterations in THY-Tau22 mice. This was accompanied by a decrease in hippocampal Tau pathology and a prevention of the loss of expression of choline acetyltransferase within the medial septum. Whereas the expression of most cholesterol-related genes remained unchanged in the hippocampus of running THY-Tau22 mice, we observed a significant upregulation in mRNA levels of NPC1 and NPC2, genes involved in cholesterol trafficking from the lysosomes. Our data support the view that long-term voluntary physical exercise is an effective strategy capable of mitigating Tau pathology and its pathophysiological consequences., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Neurofibrillary degeneration is often observed in the brain of patients with type 1 myotonic dystrophy (DM1). It consists principally of the aggregation of Tau isoforms that lack exon 2/3 encoded sequences, and is the consequence of the modified splicing of Tau pre-mRNA. In experimental models of DM1, the splicing of several transcripts is modified due to the loss of Muscleblind-like 1 (MBNL1) function. In the present study, we demonstrate that the MBNL1 protein is also present in the human brain, and consists of several isoforms, as shown by RT-PCR and sequencing. In comparison with controls, we show that the adult DM1 brain exhibits modifications in the splicing of MBNL1, with the preferential expression of long MBNL1 isoforms--a splicing pattern similar to that seen in the fetal human brain. In cultured HeLa cells, the presence of long CUG repeats, such as those found in the DM1 mutation, leads to similar changes in the splicing pattern of MBNL1, and the localization of MBNL1 in nuclear RNA foci. Long CUG repeats also reproduce the repression of Tau exon 2/3 inclusion, as in the human disease, suggesting that their effect on MBNL1 expression may lead to changes in Tau splicing. However, while an overall reduction in the expression of MBNL1 mimics the effect of the DM1 mutation, none of the MBNL1 isoforms tested so far modulates the endogenous splicing of Tau. The modified splicing of Tau thus results from a possibly CUG-mediated loss of function of MBNL1, but not from changes in the MBNL1 expression pattern.

The amyloid precursor protein (APP) metabolism is central to pathogenesis of Alzheimer's disease (AD). Parenchymal amyloid deposits, a neuropathological hallmark of AD, are composed of amyloid-beta peptides (Abeta). Abeta derives from the amyloid precursor protein (APP) by sequential cleavages by beta- and gamma-secretases. Gamma-secretase cleavage releases the APP intracellular domain (AICD), suggested to mediate a nuclear signaling. Physiologically, AICD is seldom detected and thus supposed to be rapidly degraded. The mechanisms responsible of its degradation remain unknown. We used a pharmacological approach and showed that several alkalizing drugs induce the accumulation of AICD in neuroblastoma SY5Y cell lines stably expressing APP constructs. Moreover, alkalizing drugs induce AICD accumulation in naive SY5Y, HEK and COS cells. This accumulation is not mediated by the proteasome or metallopeptidases and is not the result of an increased gamma-secretase activity since the gamma-secretase cleavage of Notch1 and N-Cadherin is not affected by alkalizing drug treatments. Altogether, our data demonstrate for the first time that alkalizing drugs induce the accumulation of AICD, a mechanism likely mediated by the endosome/lysosome pathway.

Neurofibrillary degeneration is likely to be related to abnormal Tau phosphorylation and aggregation. Among abnormal Tau phosphorylation sites, pThr231 is of particular interest since it is associated with early stages of Alzheimer's disease and is a binding site of Pin1, a peptidyl-prolyl cis/trans isomerase mainly involved in cell cycle regulation. In the present work, Pin1 level was found strongly increased during neuronal differentiation and tightly correlated with Tau dephosphorylation at Thr231. Likewise, we showed in cellular model that Pin1 allowed for specific Tau dephosphorylation at Thr231, whereas other phosphorylation sites were unchanged. Moreover, cells displaying Tau phosphorylation at Thr231 did not show any Pin1 nuclear depletion. Altogether, these data indicate that Pin1 has key function(s) in neuron and is at least involved in the regulation of Tau phosphorylation at relevant sites. Hence, Pin1 dysfunction, unlikely by nuclear depletion, may have critical consequences on Tau pathological aggregation and neuronal death.

In Alzheimer's disease, the complex catabolism of amyloid precursor protein (APP) leads to the production of amyloid-beta (Abeta) peptide, the major component of amyloid deposits. APP is cleaved by beta- and alpha-secretases to generate APP carboxy-terminal fragments (CTFs). Abeta peptide and amyloid intracellular domain are resulting from the cleavage of APP-CTFs by the gamma-secretase. In the present study, we hypothesize that post-translational modification of APP-CTFs could modulate their processing by the gamma-secretase. Inhibition of the gamma-secretase was shown to increase the total amount of APP-CTFs. Moreover, we showed that this increase was more marked among the phosphorylated variants and directly related to the activity of the gamma-secretase, as shown by kinetics analyses. Phosphorylated CTFs were shown to associate to presenilin 1, a major protein of the gamma-secretase complex. The phosphorylation of CTFs at the threonine 668 resulting of the c-Jun N-terminal kinase activation was shown to enhance their degradation by the gamma-secretase. Altogether, our results demonstrated that phosphorylated CTFs can be the substrates of the gamma-secretase and that an increase in the phosphorylation of APP-CTFs facilitates their processing by gamma-secretase.

Apolipoprotein E (apoE) is associated with the two hallmarks of Alzheimer's disease: A beta deposits and neurofibrillary tangles. ApoE synthesis was detected in astrocytes by in situ hybridization but was not detected in neurons. Nevertheless, different studies on apoE immunoreactivity reported the presence of apoE in neurons of Alzheimer, control, and necrosis pontisubicular brains. In this study, we addressed the question of potential synthesis of apoE in neurons and its possible involvement in or in response to pathological conditions. To this purpose, we have studied human neuronal cell lines (SY 5Y and Kelly cells) originating from neuroblastoma. Using monoclonal and polyclonal antibodies, a 32-kDa band was detected in SY 5Y and Kelly cells, before and after NGF differentiation. Two-dimensional gel electrophoresis analysis showed a typical profile of apoE spots resolved to the exact isoelectric points. By reverse transcription-polymerase chain reaction experiments, we demonstrated the presence of apoE mRNA in these cell lines. SY 5Y cells synthesized the apoE3 variant, whereas Kelly cells expressed both apoE3 and apoE4 isoforms, corroborating the two-dimensional gel results. These results suggested that apoE synthesis could occur in human neuronal cell lines under certain conditions.