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Hypoxia promotes tau hyperphosphorylation with associated neuropathology in vascular dysfunction.

ABSTRACT: BACKGROUND:Hypertension-induced microvascular brain injury is a major vascular contributor to cognitive impairment and dementia. We hypothesized that chronic hypoxia promotes the hyperphosphorylation of tau and cell death in an accelerated spontaneously hypertensive stroke prone rat model of vascular cognitive impairment. METHODS:Hypertensive male rats (n?=?13) were fed a high salt, low protein Japanese permissive diet and were compared to Wistar Kyoto control rats (n?=?5). RESULTS:Using electron paramagnetic resonance oximetry to measure in vivo tissue oxygen levels and magnetic resonance imaging to assess structural brain damage, we found compromised gray (dorsolateral cortex: p?=?.018) and white matter (corpus callosum: p?=?.016; external capsule: p?=?.049) structural integrity, reduced cerebral blood flow (dorsolateral cortex: p?=?.005; hippocampus: p?

SUBMITTER: Raz L

PROVIDER: S-EPMC6347559 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Hypoxia promotes tau hyperphosphorylation with associated neuropathology in vascular dysfunction.

Raz Limor L Bhaskar Kiran K Weaver John J Marini Sandro S Zhang Quanguang Q Thompson Jeffery F JF Espinoza Candice C Iqbal Sulaiman S Maphis Nicole M NM Weston Lea L Sillerud Laurel O LO Caprihan Arvind A Pesko John C JC Erhardt Erik B EB Rosenberg Gary A GA

Neurobiology of disease 20180725

<h4>Background</h4>Hypertension-induced microvascular brain injury is a major vascular contributor to cognitive impairment and dementia. We hypothesized that chronic hypoxia promotes the hyperphosphorylation of tau and cell death in an accelerated spontaneously hypertensive stroke prone rat model of vascular cognitive impairment.<h4>Methods</h4>Hypertensive male rats (n = 13) were fed a high salt, low protein Japanese permissive diet and were compared to Wistar Kyoto control rats (n = 5).<h4>Res ...[more]

PMID: 30010004

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Project description:The unfolded protein response (UPR) in the endoplasmic reticulum (ER) and the cytoplasmic heat stress response are two major stress response systems necessary for maintaining proteostasis for cellular health. Failure of either of these systems, such as in sustained UPR activation or in insufficient heat shock response activation, can lead to the development of neurodegeneration. Alleviation of ER stress and enhancement of heat shock response through heat shock factor 1 (HSF1) activation have previously been considered as attractive potential therapeutic targets for Alzheimer's disease (AD)-a prevalent and devastating tauopathy. Understanding the interplay of the two aforementioned systems and their cooperative role in AD remain elusive. Here we report studies in human brain and tau pathogenic mouse models (rTg4510, PS19, and rTg21221), identifying HSF1 degradation and UPR activation as precursors of aberrant tau pathogenesis. We demonstrate that chemical ER stress inducers caused autophagy-lysosomal HSF1 degradation, resulting in tau hyperphosphorylation in rat primary neurons. In addition, permanent HSF1 loss reversely causes chronic UPR activation, leading to aberrant tau phosphorylation and aggregation in the hippocampus of aged HSF1 heterozygous knock-out mice. The deleterious interplay of UPR activation and HSF1 loss is exacerbated in N2a cells stably overexpressing a pro-aggregation mutant TauRD ΔK280 (N2a-TauRD ΔK280). We provide evidence of how these two stress response systems are intrinsically interweaved by showing that the gene encoding C/EBP-homologous protein (CHOP) activation in the UPR apoptotic pathway facilitates HSF1 degradation, which likely further contributes to prolonged UPR via ER chaperone HSP70 a5 (BiP/GRP78) suppression. Upregulating HSF1 relieves the tau toxicity in N2a-TauRD ΔK280 by reducing CHOP and increasing HSP70 a5 (BiP/GRP78). Our work reveals how the bidirectional crosstalk between the two stress response systems promotes early tau pathology and identifies HSF1 being one likely key player in both systems.

Dataset Information

Hypoxia promotes tau hyperphosphorylation with associated neuropathology in vascular dysfunction.

Publications

Hypoxia promotes tau hyperphosphorylation with associated neuropathology in vascular dysfunction.

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