Unbiased Proteomic Approach Identifies Pathobiological Profiles in the Brains of Preclinical Models of Repetitive Mild Traumatic Brain Injury, Tauopathy, and Amyloidosis

Abstract

No concerted investigation has been conducted to explore overlapping and distinct pathobiological mechanisms between repetitive mild traumatic brain injury (r-mTBI) and tau/amyloid proteinopathies considering the long history of association between TBI and Alzheimer's disease. We address this problem by using unbiased proteomic approaches to generate detailed time-dependent brain molecular profiles of response to repetitive mTBI in C57BL/6 mice and in mouse models of amyloidosis (with amyloid precursor protein KM670/671NL (Swedish) and Presenilin 1 M146L mutations [PSAPP]) and tauopathy (hTau). Brain tissues from animals were collected at different timepoints after injuries (24 hr-12 months postinjury) and at different ages for tau or amyloid transgenic models (3, 9, and 15 months old), encompassing the pre-, peri-, and post-"onset" of cognitive and pathological phenotypes. We identified 30 hippocampal and 47 cortical proteins that were significantly modulated over time in the r-mTBI compared with sham mice. These proteins identified TBI-dependent modulation of phosphatidylinositol-3-kinase/AKT signaling, protein kinase A signaling, and PPARa/RXRa activation in the hippocampus and protein kinase A signaling, gonadotropin-releasing hormone signaling, and B cell receptor signaling in the cortex. Previously published neuropathological studies of our mTBI model showed a lack of amyloid and tau pathology. In PSAPP mice, we identified 19 proteins significantly changing in the cortex and only 7 proteins in hTau mice versus wild-type littermates. When we explored the overlap between our r-mTBI model and the PSAPP/hTau models, a fairly small coincidental change was observed involving only eight significantly regulated proteins. This work suggests a very distinct TBI neurodegeneration and also that other factors are needed to drive pathologies such as amyloidosis and tauopathy postinjury.

Subacute and chronic proteomic and phosphoproteomic analyses of a mouse model of traumatic brain injury at two timepoints and comparison with chronic traumatic encephalopathy in human samples

“…So far, only a few proteomic studies have proposed potential targets in relation to timing post injury. Ojo and colleagues measured altered proteins in the cortex and hippocampus of C57BL/6J mice at 3, 6, 9 and 12 months after r-mTBI, using the same 5-hit model we utilized in our current study [ 24 ]. Among the most dysregulated processes common for all time-points were PI3K/AKT, PKA, and PPARα/RXRα signaling in the hippocampus, and PKA, GNRH, and B cell receptor signaling in the cortex.…”

Distinct brain regional proteome changes in the rTg‐DI rat model of cerebral amyloid angiopathy

“…To further investigate the functional significance of such a large number of altered proteins (547 total) in three distinct brain regions, we utilized IPA, as have many recent CNS and brain microvascular proteomic studies (Drummond et al, 2017;Gonzalez-Lozano et al, 2016;Herland et al, 2020;Ojo et al, 2020;. IPA identified multiple upstream regulators and causal networks, and disease related functions, both associating and distinguishing between the different regions.…”

APOE genotype dependent molecular abnormalities in the cerebrovasculature of Alzheimer’s disease and age-matched non-demented brains

“…Xcalibur (Thermo) software was used to control the instrument in data dependent acquisition (DDA) mode. DDA settings for these MS experiments followed our previous work [57,61], and were as follows: full-scan MS resolution = 140 000 full width at half maximum at 200 m/z, full-scan range = 380-1250 m/z, isolation width = 1.2 m/z, higher energy C-trap dissociation relative collision energy = 29, a minimum m/z setting of 100 m/z was used for all MS 2 spectra, MS 2 resolution = 35,000, dynamic exclusion = 180 s, and a Top 15 high/low duty cycle was used for precursor ion selection. Sample limitations did not allow for extensive two-dimensional (2D) fractionation of the labeled peptides, therefore we the use of a narrow isolation window and an ultra-long shotgun gradient was used to minimize the deleterious effects on quantitative accuracy that typically result from co-isolation of isobaric precursors.…”