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P1‐221: TBI‐ACTIVATED AEP IS A NOVEL PROTEASE THAT CONTRIBUTES TO AD ONSET THROUGH C/EBPβ ACTIVATION
Author(s) -
Wu Zhourui,
Liu Xia,
Yu Shan-Ping,
Cheng Liming,
Ye Keqiang
Publication year - 2018
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2018.06.226
Subject(s) - traumatic brain injury , downregulation and upregulation , neuroinflammation , tauopathy , tau protein , in vivo , neuroscience , medicine , chemistry , biology , alzheimer's disease , inflammation , biochemistry , disease , neurodegeneration , microbiology and biotechnology , psychiatry , gene
contributes to neurodegenerative progression. Specifically, hyperactivation of calpain-1 (CAPN1), a modulary cysteine protease, has been implicated in the early pathogenesis of Alzheimer’s Disease (AD), traumatic brain injury (TBI), and ischemic stroke. Prolonged CAPN1 over-activation indirectly permeabilizes lysosomes, leading to release of cathepsin B (CTSB), a lysosomal cysteine-protease implicated in neurodegeneration. Several reports propose CAPN1 and CTSB as therapeutic targets in AD and TBI, but do not unambiguously provide evidence for a desired strategy, and selectivity for inhibition of CAPN1 over CTSB has been the goal of the most developed program in pharma. We hypothesize that dual CAPN1/CTSB inhibition will afford superior efficacy in AD and TBI over selective inhibition. Methods: Inhibition profiles (potency, selectivity, reversibility) of small molecules were characterized through enzyme kinetic assays. Subsequently, neuroprotection was characterized in neuronal cells using Oxygen Glucose Deprivation (OGD), an in vitro model simulating ischemia-reperfusion injury in stroke. Additional in vitro models using chemical insults were utilized to monitor CAPN1/CTSB substrates with roles in neuroplasticity/neurodegeneration via immunoblots. Finally, selective and dual inhibitors were tested in a mild TBI (mTBI) mouse model. Results: We have identified selective and dual inhibitors and established enzyme inhibition and neuroprotective profiles. All inhibitors were differentially neuroprotective against OGDinduced cell death, depending on the treatment paradigm (pretreatment, ischemia, and reperfusion). Monitoring spectrin breakdown products (CAPN1-specific) identified different pathways of neuronal death with varying neuro-insults. After establishing the selectivity of inhibitors for CAPN1 and CTSB, monitoring of peptide substrate proteolysis confirmed inhibitory effects in neuronal cultures, and allowed selection of inhibitors for further study in vivo. Conclusions: Neuroprotective profiles of selective versus dual CAPN1/CTSB inhibitors in vitro varied, depending on timing of treatment and neuronal insult. In a mouse model of mTBI manifesting cognitive deficit and cytokine surge, benefit was seen in behavioral and biochemical analysis. Further drug development for selective and dual inhibitor strategies will need to overcome limitations in brain bioavailability.