Genetically modified macrophages accelerate myelin repair

[EN] Preventing neurodegeneration-associated disability progression in patients with multiple sclerosis (MS) remains an unmet therapeutic need. As remyelination prevents axonal degeneration, promoting this process in patients might enhance neuroprotection. In demyelinating mouse lesions, local overexpression of semaphorin 3F (Sema3F), an oligodendrocyte progenitor cell (OPC) attractant, increases remyelination. However, molecular targeting to MS lesions is a challenge. A clinically relevant paradigm for delivering Sema3F to demyelinating lesions could be to use blood-derived macrophages as vehicles. Thus, we chose transplantation of genetically modified hematopoietic stem cells (HSCs) as means of obtaining chimeric mice with circulating Sema3F-overexpressing monocytes. We demonstrated that Sema3F-transduced HSCs stimulate OPC migration in a neuropilin 2 (Nrp2, Sema3F receptor)-dependent fashion, which was conserved in middle-aged OPCs. While demyelinating lesions induced in mice with Sema3F-expressing blood cells showed no changes in inflammation and OPC survival, OPC recruitment was enhanced which accelerated the onset of remyelination. Our results provide a proof of concept that blood cells, particularly monocytes/macrophages, can be used to deliver pro-remyelinating agents "at the right time and place," suggesting novel means for remyelination-promoting strategies in MS.This work was supported by the French National Institute of Health and Medical Research (INSERM), French National Research Agency (ANR, project Stemimus ANR-12-BSV4-0002-02), the European Leukodystrophy Association (ELA, project 2016-004C5B), NeurATRIS, the program "Investissements d'avenir" (ANR-10-IAIHU-06), CIBERNED (CB06/0005/0076), and Gobierno Vasco (IT1203-19). VT was a recipient of the Spanish Ministry of Economy Young Investigator Grant (SAF2015-74332-JIN)

Alzheimer's disease-like APP processing in wild-type mice identifies synaptic defects as initial steps of disease progression.

International audienceAlzheimer's disease (AD) is the most frequent form of dementia in the elderly and no effective treatment is currently available. The mechanisms triggering AD onset and progression are still imperfectly dissected. We aimed at deciphering the modifications occurring in vivo during the very early stages of AD, before the development of amyloid deposits, neurofibrillary tangles, neuronal death and inflammation. Most current AD models based on Amyloid Precursor Protein (APP) overproduction beginning from in utero, to rapidly reproduce the histological and behavioral features of the disease within a few months, are not appropriate to study the early steps of AD development. As a means to mimic in vivo amyloid APP processing closer to the human situation in AD, we used an adeno-associated virus (AAV)-based transfer of human mutant APP and Presenilin 1 (PS1) genes to the hippocampi of two-month-old C57Bl/6 J mice to express human APP, without significant overexpression and to specifically induce its amyloid processing. The human APP, βCTF and Aβ42/40 ratio were similar to those in hippocampal tissues from AD patients. Three months after injection the murine Tau protein was hyperphosphorylated and rapid synaptic failure occurred characterized by decreased levels of both PSD-95 and metabolites related to neuromodulation, on proton magnetic resonance spectroscopy ((1)H-MRS). Astrocytic GLT-1 transporter levels were lower and the tonic glutamatergic current was stronger on electrophysiological recordings of CA1 hippocampal region, revealing the overstimulation of extrasynaptic N-methyl D-aspartate receptor (NMDAR) which precedes the loss of long-term potentiation (LTP). These modifications were associated with early behavioral impairments in the Open-field, Y-maze and Morris Mater Maze tasks. Altogether, this demonstrates that an AD-like APP processing, yielding to levels of APP, βCTF and Aβ42/Aβ40 ratio similar to those observed in AD patients, are sufficient to rapidly trigger early steps of the amyloidogenic and Tau pathways in vivo. With this strategy, we identified a sequence of early events likely to account for disease onset and described a model that may facilitate efforts to decipher the factors triggering AD and to evaluate early neuroprotective strategies

Inhibition of DYRK1A proteolysis modifies its kinase specificity and rescues Alzheimer phenotype in APP/PS1 mice

Abstract Recent evidences suggest the involvement of DYRK1A (dual specificity tyrosine phosphorylation-regulated kinase 1 A) in Alzheimer’s disease (AD). Here we showed that DYRK1A undergoes a proteolytic processing in AD patients hippocampus without consequences on its kinase activity. Resulting truncated forms accumulate in astrocytes and exhibit increased affinity towards STAT3ɑ, a regulator of inflammatory process. These findings were confirmed in APP/PS1 mice, an amyloid model of AD, suggesting that this DYRK1A cleavage is a consequence of the amyloid pathology. We identified in vitro the Leucettine L41 as a compound able to prevent DYRK1A proteolysis in both human and mouse protein extracts. We then showed that intraperitoneal injections of L41 in aged APP/PS1 mice inhibit STAT3ɑ phosphorylation and reduce pro-inflammatory cytokines levels (IL1- β, TNF-ɑ and IL-12) associated to an increased microglial recruitment around amyloid plaques and decreased amyloid-β plaque burden. Importantly, L41 treatment improved synaptic plasticity and rescued memory functions in APP/PS1 mice. Collectively, our results suggest that DYRK1A may contribute to AD pathology through its proteolytic process, reducing its kinase specificity. Further evaluation of inhibitors of DYRK1A truncation promises a new therapeutic approach for AD

Additional file 2: Figure S2. of Alzheimer’s disease-like APP processing in wild-type mice identifies synaptic defects as initial steps of disease progression

AAV-PS1 and AAV-APP mice do not exhibit neuronal defects in terms of PSD-95, GLT-1 and tonic glutamatergic current. C57Bl/6 J mice (all males) were injected at 8 weeks of age either with AAV-CAG-PS1M146L (AAV-PS1 mice) or AAV-CAG-APPSL (AAV-APP mice). Mice were killed three months later for analyses. (A) Western blot of PSD-95 and GLT-1 (n = 3-4 per group). (B) Densitometric analyses of the antibody immunoreactivities shown in panel A. (C) Tonic glutamatergic current recorded at a holding potential of +40 mV by the whole-cell patch-clamping of CA1 pyramidal cells. No significant difference in tonic glutamatergic current intensity was observed between the AAV-PS1 and AAV-APP groups (whole cell patch-clamp of CA1 pyramidal cells, n = 11/group from n = 10 mice per group). (PNG 447 kb

Additional file 1: Figure S1. of Alzheimer’s disease-like APP processing in wild-type mice identifies synaptic defects as initial steps of disease progression

APP is processed in sporadic AD cases. Human samples were obtained from late-onset AD cases (Braak 6, Thal 5) and age-matched controls (n = 5 per group). The hippocampus was the studied structure. (A) Western blot analysis of NeuN. (B) Densitometric analyses of western blots showing the expression of human APP in the hippocampus of human controls and AD cases (n = 5 per group). Bars represent means ± SEM, and data were normalized with respect to GAPDH. Statistical analyses were performed with Student’s t-test: **p < 0.01. (C) Densitometric analyses of A, showing the expression of NeuN in the hippocampus of human controls and AD cases (n = 5 per group). Bars represent means ± SEM, and data were normalized with respect to GAPDH. Statistical analyses were performed with Student’s t-test: *p < 0.05. (D) Representation of the APP/NeuN ratio following densitometric analyses of the corresponding western blots (n = 5 per group). Note that APP seems to be processed in sporadic AD cases. Bars represent means ± SEM and data were normalized with respect to GAPDH. Statistical analyses were performed with Student’s t-test: *p < 0.05. (PNG 325 kb