Mancini, G.-F. | bioRxiv Science

bioRxiv2022

Elucidation of Amyloid-Beta's Gambit in Oligomerisation:Truncated Aβ fragments of residues Aβ1-23, Aβ1-24 and Aβ1-25 rapidly seed to form SDS-stable, low molecular weight Aβ oligomers that impair synaptic plasticity.

In Alzheimers disease (AD), Amyloid-beta (A{beta}) oligomers are considered an appealing therapeutic- and diagnostic target. However, to date, the molecular mechanisms associated with the pathological accumulation or structure of A{beta} oligomers remains an enigma to the scientific community. Here we demonstrate the strong seeding properties of unique A{beta} fragment signatures and show that the truncated A{beta} peptides of residues A{beta}1-23, A{beta}1-24 and A{beta}1-25, rapidly seed to form small, SDS-PAGE stable assemblies of [~]5kDa to [~]14kDa molecular mass range. Mass spectrometry analysis of SDS-PAGE fractionated and gel extracted oligomers revealed that the truncated A{beta} isoforms of residues 1-23 to 1-25 form stable entities with low molecular weight (LMW) oligomers, which strongly resemble the regularly reported A{beta} entities of putative dimeric or trimeric assemblies found in human post-mortem AD and Tg mouse brain extracts. Furthermore, electrophysiological recordings in the mouse hippocampus indicate that LMW A{beta} assemblies formed by fragments A{beta}1-23 to A{beta}1-25 significantly impair long-term-potentiation (LTP) in the absence of full-length A{beta}1-42. Extensive antibody screening highlights the important observation, that the LMW A{beta} assemblies formed by these truncated A{beta} peptides escape immuno-detection using conventional, conformation specific antibodies but, more importantly, the clinical antibody aducanumab. Our novel findings suggest that there are new A{beta} target "loopholes" which can be exploited for the development of therapeutic antibodies with binding properties against stable target hotspots present in A{beta} oligomers. We provide here a first example of a new class of monoclonal antibody with unique binding properties against LMW A{beta} oligomers, in the absence of binding to large fibrillar A{beta} assemblies, or dense amyloid plaques. Our research supports a novel, unparalleled approach for targeting early, pathological A{beta} species during the insidious phase of AD and prior to the appearance of large oligomeric or protofibrilar assemblies.

neuroscience↗

bioRxiv2020

Rapid endothelialitis and vascular inflammation characterise SARS-CoV-2 infection in a human lung-on-chip model

Severe cases of COVID-19 present with hypercoagulopathies and systemic endothelialitis of the lung microvasculature. The dynamics of vascular damage, and whether it is a direct consequence of endothelial infection or an indirect consequence of immune cell mediated cytokine storms is unknown. This is in part because in vitro models are typically epithelial cell monocultures or fail to recapitulate vascular physiology. We use a vascularised lung-on-chip model where, consistent with monoculture reports, low numbers of SARS-CoV-2 virions are released apically from alveolar epithelial cells. However, rapid infection of the underlying endothelial layer leads to the generation of clusters of endothelial cells with low or no CD31 expression, a progressive loss of endothelial barrier integrity, and a pro-coagulatory microenvironment. These morphological changes do not occur if these cells are exposed to the virus apically. Viral RNA persists in individual cells, which generates a response that is skewed towards NF-KB mediated inflammation, is typified by IL-6 secretion even in the absence of immune cells, and is transient in epithelial cells but persistent in endothelial cells. Perfusion with Tocilizumab, an inhibitor of trans IL-6 signalling slows the loss of barrier integrity but does not prevent the formation of endothelial cell clusters with reduced CD31 expression. SARS-CoV-2 mediated endothelial cell damage occurs despite a lack of rapid viral replication, in a cell-type specific manner and independently of immune-cell mediated cytokine storms, whose effect would only exacerbate the damage.

microbiology↗