An effector-reduced anti-ß-amyloid (Aß) antibody with unique aß binding properties promotes neuroprotection and glial engulfment of Aß.

Passive immunization against ß-amyloid (Aß) has become an increasingly desirable strategy as a therapeutic treatment for Alzheimer's disease (AD). However, traditional passive immunization approaches carry the risk of Fcγ receptor-mediated overactivation of microglial cells, which may contribute to an inappropriate proinflammatory response leading to vasogenic edema and cerebral microhemorrhage. Here, we describe the generation of a humanized anti-Aß monoclonal antibody of an IgG4 isotype, known as MABT5102A (MABT). An IgG4 subclass was selected to reduce the risk of Fcγ receptor-mediated overactivation of microglia. MABT bound with high affinity to multiple forms of Aß, protected against Aß1-42 oligomer-induced cytotoxicity, and increased uptake of neurotoxic Aß oligomers by microglia. Furthermore, MABT-mediated amyloid plaque removal was demonstrated using in vivo live imaging in hAPP((V717I))/PS1 transgenic mice. When compared with a human IgG1 wild-type subclass, containing the same antigen-binding variable domains and with equal binding to Aß, MABT showed reduced activation of stress-activated p38MAPK (p38 mitogen-activated protein kinase) in microglia and induced less release of the proinflammatory cytokine TNFα. We propose that a humanized IgG4 anti-Aß antibody that takes advantage of a unique Aß binding profile, while also possessing reduced effector function, may provide a safer therapeutic alternative for passive immunotherapy for AD. Data from a phase I clinical trial testing MABT is consistent with this hypothesis, showing no signs of vasogenic edema, even in ApoE4 carriers.

BACE-1 is expressed in the blood-brain barrier endothelium and is upregulated in a murine model of Alzheimer's disease.

Endothelial cells of the blood-brain barrier form a structural and functional barrier maintaining brain homeostasis via paracellular tight junctions and specific transporters such as P-glycoprotein. The blood-brain barrier is responsible for negligible bioavailability of many neuroprotective drugs. In Alzheimer's disease, current treatment approaches include inhibitors of BACE-1 (ß-site of amyloid precursor protein cleaving enzyme), a proteinase generating neurotoxic ß-amyloid. It is known that BACE-1 is highly expressed in endosomes and membranes of neurons and glia. We now provide evidence that BACE-1 is expressed in blood-brain barrier endothelial cells of human, mouse, and bovine origin. We further show its predominant membrane localization by 3D-dSTORM super-resolution microscopy, and by biochemical fractionation that further shows an abluminal distribution of BACE-1 in brain microvessels. We confirm its functionality in processing APP in primary mouse brain endothelial cells. In an Alzheimer's disease mouse model we show that BACE-1 is upregulated at the blood-brain barrier compared to healthy controls. We therefore suggest a critical role for BACE-1 at the blood-brain barrier in ß-amyloid generation and in vascular aspects of Alzheimer's disease, particularly in the development of cerebral amyloid angiopathy.

Increased efflux of amyloid-ß peptides through the blood-brain barrier by muscarinic acetylcholine receptor inhibition reduces pathological phenotypes in mouse models of brain amyloidosis.

The formation and accumulation of toxic amyloid-ß peptides (Aß) in the brain may drive the pathogenesis of Alzheimer's disease. Accordingly, disease-modifying therapies for Alzheimer's disease and related disorders could result from treatments regulating Aß homeostasis. Examples are the inhibition of production, misfolding, and accumulation of Aß or the enhancement of its clearance. Here we show that oral treatment with ACI-91 (Pirenzepine) dose-dependently reduced brain Aß burden in AßPPPS1, hAßPPSL, and AßPP/PS1 transgenic mice. A possible mechanism of action of ACI-91 may occur through selective inhibition of muscarinic acetylcholine receptors (AChR) on endothelial cells of brain microvessels and enhanced Aß peptide clearance across the blood-brain barrier. One month treatment with ACI-91 increased the clearance of intrathecally-injected Aß in plaque-bearing mice. ACI-91 also accelerated the clearance of brain-injected Aß in blood and peripheral tissues by favoring its urinal excretion. A single oral dose of ACI-91 reduced the half-life of interstitial Aß peptide in pre-plaque mhAßPP/PS1d mice. By extending our studies to an in vitro model, we showed that muscarinic AChR inhibition by ACI-91 and Darifenacin augmented the capacity of differentiated endothelial monolayers for active transport of Aß peptide. Finally, ACI-91 was found to consistently affect, in vitro and in vivo, the expression of endothelial cell genes involved in Aß transport across the Blood Brain Brain (BBB). Thus increased Aß clearance through the BBB may contribute to reduced Aß burden and associated phenotypes. Inhibition of muscarinic AChR restricted to the periphery may present a therapeutic advantage as it avoids adverse central cholinergic effects.

Elevated NMDA receptor levels and enhanced postsynaptic long-term potentiation induced by prenatal exposure to valproic acid.

Valproic acid (VPA) is a powerful teratogen causing birth defects in humans, including autism spectrum disorder (ASD), if exposure occurs during the first trimester of embryogenesis. Learning and memory alterations are common symptoms of ASD, but underlying molecular and synaptic alterations remain unknown. We therefore studied plasticity-related mechanisms in the neocortex of 2-week-old rats prenatally exposed to VPA and tested for changes in glutamate-mediated transmission and plasticity in the neocortex. We found a selective overexpression of NR2A and NR2B subunits of NMDA receptors, as well as the commonly linked kinase calcium/calmodulin-dependent protein kinase II. Synaptic plasticity experiments between pairs of pyramidal neurons revealed an augmented postsynaptic form of long-term potentiation. These results indicate that VPA significantly enhances NMDA receptor-mediated transmission and causes increased plasticity in the neocortex. Enhanced plasticity introduces a surprising perspective to the potential molecular and synaptic mechanisms involved in children prenatally exposed to VPA.