Identification of chronic brain protein changes and protein targets of serum auto-antibodies after blast-mediated traumatic brain injury

Abstract

In addition to needing acute emergency management, blast-mediated traumatic brain injury (TBI) is also a chronic disorder with delayed-onset symptoms that manifest and progress over time. While the immediate consequences of acute blast injuries are readily apparent, chronic sequelae are harder to recognize. Indeed, the identification of individuals with mild-TBI or TBI-induced symptoms is greatly impaired in large part due to the lack of objective and robust biomarkers. The purpose of this study was to address these need by identifying candidates for serumbased biomarkers of blast TBI, and also to identify unique or differentially regulated protein expression in the thalamus in C57BL/6J mice exposed to blast using high throughput qualitative screens of protein expression. To identify thalamic proteins differentially or uniquely associated with blast exposure, we utilized an antibody-based affinity-capture strategy (referred to as "proteomics-based analysis of depletomes"; PAD) to deplete thalamic lysates from blast-treated mice of endogenous thalamic proteins also found in control mice. Analysis of this "depletome" detected 75 unique proteins, many with associations to the myelin sheath. To identify blastassociated proteins eliciting production of circulating autoantibodies, serum antibodies of blast-treated mice were immobilized, and their immunogens subsequently identified by proteomic analysis of proteins specifically captured following incubation with thalamic lysates (a variant of a strategy referred to as "proteomics-based expression library screening"; PELS). This analysis identified 46 blast-associated immunogenic proteins, including 6 shared in common with the PAD analysis (ALDOA, PHKB, HBA-A1, DPYSL2, SYN1, and CKB). These proteins and their autoantibodies are appropriate for further consideration as biomarkers of blast-mediated TBI.

Characterization of the Jet-Flow Overpressure Model of Traumatic Brain Injury in Mice

“…Our results show that the jet-flow OPC, which has been widely used in experimental studies designed to model bTBI, [31][32][33][34][35][36][37][38][39][40][41] actually generates a powerful, collimated jet flow of very high dynamic pressure at the specimen location. Although the intensity of this jet flow decays over 18 msec as the Driver Section depressurizes, this exposure condition does not represent that of explosive blast or a traveling shockwave.…”

“…This model may be termed multi-modal TBI (mmTBI), with the caveat that this is purely a descriptive term for the experimental condition, and not a term that is currently used in clinical diagnosis of human TBI. We note, however, that this model is clearly capable of inducing neurotrauma [31][32][33][34][35][36][37][38][39][40][41] and may be considered useful for studying brain cell processes after injury and in evaluating the efficacy of putative therapeutic agents. For example, through this mmTBI model we have recently reported the unexpected ability to reverse chronic neurodegeneration in the brain and restore neurological function at a very distal time-point (over 1 year) after TBI in mice, challenging the long-held dogma that the treatment window for saving brain tissue from chronic degeneration and impaired cognitive functioning is limited to an acute time period immediately following injury.…”

“…Indeed, the majority of reported laboratory bTBI models fail to faithfully recapitulate conditions of free-field blast exposure, including the jet-flow overpressure chamber (OPC) that we and others have used. [31][32][33][34][35][36][37][38][39][40][41] We describe here a rigorous and comprehensive physical characterization of the jetflow OPC, which reveals that this apparatus instead produces a model of multi-modal TBI (mmTBI) that is useful for the field yet different in nature from what was previously assumed. We also summarize the important features of blast physics that must be incorporated into an accurate laboratory model of bTBI.…”

Gene Expression Signature of Traumatic Brain Injury

“…Ribosomal defects can lead to elevated ROS and activation of the TP53 pathway, which have important links with TBI (Sulima et al, 2019 ). The differential expression of RPL27 and RPS15A was validated in TBI mice (Harper et al, 2020 ). Recent studies have shown that RPL7 and RPL23A are differentially expressed in senile dementia and may be potential biomarkers (Shigemizu et al, 2020 ).…”

P7C3-A20 treatment one year after TBI in mice repairs the blood–brain barrier, arrests chronic neurodegeneration, and restores cognition

“…Here, we have studied this chronic condition in a murine model of multimodal TBI (mmTBI) that entails jet-flow exposure in an overpressure chamber to produce globally compressive forces along with a variable amount of acceleration–deceleration and early blast wave exposure. This laboratory model produces neurodegeneration and neurobehavioral deficits reminiscent of TBI in people ( 21 – 24 ). We treated and analyzed mice beginning 1 y after a single injury, as outlined in Fig.…”