Attenuation of entorhinal cortex hyperactivity reduces Aβ and tau pathology

Abstract

13High levels of the amyloid-beta (Aβ) peptide have been shown to disrupt neuronal function and 14 induce hyperexcitability, but it is unclear what effects Aβ-associated hyperexcitability may have 15 on tauopathy pathogenesis or propagation in vivo. Using a novel transgenic mouse line to 16 model the impact of hAPP/Aβ accumulation on tauopathy in the entorhinal cortex-hippocampal 17(EC-HIPP) network, we demonstrate that hAPP aggravates EC tau aggregation and accelerates 18 pathological tau spread into the hippocampus. In vivo recordings revealed a strong role for 19 hAPP/Aβ, but not tau, in the emergence of EC neuronal hyperactivity and impaired theta 20 rhythmicity. Chronic chemogenetic attenuation of Aβ-associated hyperactivity led to reduced 21 hAPP/Aβ accumulation and reduced pathological tau spread into downstream hippocampus. 22These data strongly support the hypothesis that in Alzheimer's disease (AD), Aβ-associated 23 hyperactivity accelerates the progression of pathological tau along vulnerable neuronal circuits, 24and demonstrates the utility of chronic, neuromodulatory approaches in ameliorating AD 25 pathology in vivo. 26 Results 84 Aβ-associated acceleration of tau pathology in EC-Tau/hAPP mice in vivo 85Overexpression of mutant hAPP (Swedish/Indiana) in the hAPP/J20 mouse line leads to progressive 86Aβ plaque deposition throughout the hippocampus and neocortex, contributing to aberrant 87 network activity and cognitive deficits (21, 22). To test whether Aβ pathology alters the 88 progression of tau pathology along the EC-HIPP circuit, we generated the hAPP/J20 x EC-Tau 89 mouse line, hereafter referred to as EC-Tau/hAPP (described in Methods). At 16-months, EC-90Tau/hAPP mice exhibit robust amyloid deposition throughout the EC and HIPP using 6E10 91( Figure 1B), with no change in Aβ deposition compared to age-matched hAPP mice sampled. 92Diffuse amyloid accumulation made up the majority of the pathology, though small, compact Aβ 93 plaques and large, dense-core Aβ plaques were also present (arrows, Figure 1B). Mice 94 expressing hTau alone (EC-Tau) did not exhibit 6E10 immunoreactivity ( Figure 1A). 95Immunostaining for MC1 revealed a dramatic increase in abnormal, misfolded tau within the 96 somatodendritic compartments of EC and HIPP neurons of EC-Tau/hAPP mice compared to 97 EC-Tau littermates ( Figure 1C-D). This increase was over three-fold higher in EC cells (EC-98 Tau/hAPP: 131.00 ± 19.38 vs EC-Tau: 40.52 ± 7.24) and over ten-fold higher in DG granule 99 cells (EC-Tau/hAPP: 359.20 ± 109.40 vs EC-Tau: 30.67 ± 14.88) ( Figure 1E), suggesting that 100 hAPP/Aβ expression in the EC-HIPP network accelerates tau pathology along the classical 101 perforant pathway. MC1 immunostaining in 10-month EC-Tau/hAPP mice revealed mostly 102 diffuse tau in neuropil throughout the EC and in axons terminating in the middle-and outer-103 molecular layers of the DG ( Figure 1F). No somatodendritic MC1+ staining was detected in 104HIPP subregions at this age. By 16-months, it was clear that tau aggregation had not ...

Synergy between amyloid-β and tau in Alzheimer’s disease

“…Increased tauopathy following neuronal stimulation was also found in rTauEC mice after 6 weeks of chemogenetic EC activation 105 , and stimulation of tau-expressing subiculum and EC enhanced tau spreading to distal, anatomically connected, regions 106 . In APP-J20/rTauEC crossed mice, 6 weeks of chemogenetic inhibition of EC, itself in a hyperexcitable state owing to mild A pathology, resulted in reduced propagation of tau pathology towards DG and HC 107 .…”

Disrupted structural connectivity in ArcAβ mouse model of Aβ amyloidosis

“…We reveal EC-centered connectivity deficits in the ArcAβ TG mice. The vulnerability of the entorhinal neurons has been reported in many previous studies (Adams et al, 2019, Rodriguez et al, 2019, Braak and Del Tredici, 2020. Differential gene expression in the EC is a possible explanation for PNN degradation (Santa-Maria et al, 2010).…”

Alzheimer’s disease and epilepsy: An increasingly recognized comorbidity

“…Elevated Aβ levels and non-motor seizures were also found in the cortical and hippocampal networks (Palop et al, 2007). Interestingly, stimulation of neuronal activity facilitated Aβ release from neurons in vivo (Rodriguez et al, 2020). Additionally, increased neuronal activity enhanced the production of Aβ from APP (Saito et al, 2012).…”