Heparan sulfate: In vitro and in vivo proof of efficacy of this new therapeutic strategy for halting Alzheimer disease‐related tauopathy development

Abstract

AbstractBackgroundDeposition of amyloid plaques and neurofibrillary tangles composed of abnormally phosphorylated tau are the neuropathological hallmarks of Alzheimer's disease (AD). However, years before the accumulation of protein aggregates, the abnormal intraneuronal accumulation of heparan sulfates (HS) is observed. This phenomenon breaks a dogma, since HS are classically located on the cell surface and in the extracellular matrix, leading to a new cell autonomous concept in tauopathy, which is the conceptual core of the FET‐OPEN ArrestAD 737390 project. Previously, we provide evidence that inside the cell, HS act as molecular chaperones inducing in Tau conformational changes favoring its abnormal phosphorylation and aggregation (Sepulveda‐Diaz JE. Brain 2015, 138(Pt 5):1339‐54). Thus, molecules able to act on heparan sulfate pathway could represent a new class of compounds for the treatment of AD‐related tauopathies.MethodPAPS is the universal sulfate donor involved in HS biosynthesis and structurally related to ATP. Thus, we first screened kinase inhibitor libraries in a sulfotransferase enzymatic assay (Byrne et al., Biochem. J. 2018; 475:2417‐2433). This strategy, in addition to a HS mimetic, were evaluated for their ability to prevent tauopathy in cells. The best molecules were then evaluated in two transgenic mice model of AD. Thereafter, proof‐of‐concept of the efficacy of compounds selected with this strategy, as well as HS mimetic (Barritault D. Glycoconj J. 2017; 34(3):325‐338) for halting AD‐related tauopathies development was assessed first in vitro and then in vivo.ResultsThe screening of libraries allowed the identification of 3 hit compounds that, in addition to a HS mimetic, were evaluated for their ability to prevent tauopathy in cells. Two molecules, one HSSTs inhibitor and one heparan sulfate mimetic, were able to reduce tauopathy in cells and in 3xTg‐AD and rTg4510 mouse models of tauopathy. In the in vivo assessment in males and females 3xTg‐AD, the behavioral dose‐response of these molecules on the cognitive, neuropsychiatric‐like and motor AD‐phenotypes was determined.ConclusionOur results support the FET‐OPEN RIA ArrestAD cell autonomous hypothesis of tauopathy based in altered heparan sulfate biology and place HS and their biosynthetic enzymes as a potential therapeutic target for AD.