Neuronally-derived tau is increased in experienced breachers and is associated with neurobehavioral symptoms

Katie A Edwards,Christina Devoto,Kisha Greer,Carina Martin,Eric M Wassermann,Matthew L Lopresti,Jacqueline Leete,Angela M Yarnell,Peter Walker,Jessica M Gill,Kristine C Dell,James R Stone,Bao-Xi Qu,Rany Vorn,Elena Polejaeva,Chen Lai,Stephen T Ahlers,Walter Carr

doi:10.1038/s41598-021-97913-0

Abstract

Military and law enforcement breachers are exposed to many low-level blasts during their training and occupational experiences in which they detonate explosives to force entry into secured structures. There is a concern that exposure to these repetitive blast events in career breachers could result in cumulative neurological effects. This study aimed to determine concentrations of neurofilament light (NF-L), tau, and amyloid-beta 42 (Aβ42) in serum and in neuronal-derived extracellular vesicles (EVs) in an experienced breacher population, and to examine biomarker associations with neurobehavioral symptoms. Thirty-four participants enrolled in the study: 20 experienced breachers and 14 matched military or civilian law enforcement controls. EV tau concentrations were significantly elevated in experienced breachers (0.3301 ± 0.5225) compared to controls (−0.4279 ± 0.7557; F = 10.43, p = 0.003). No statistically significant changes were observed in EV levels of NF-L or Aβ42 or in serum levels of NF-L, tau, or Aβ42 (p’s > 0.05). Elevated EV tau concentrations correlated with increased Neurobehavioral Symptom Inventory (NSI) score in experienced breachers (r = 0.596, p = 0.015) and predicted higher NSI score (F(1,14) = 7.702, p = 0.015, R2 = 0.355). These findings show that neuronal-derived EV concentrations of tau are significantly elevated and associated with neurobehavioral symptoms in this sample of experienced breachers who have a history of many low-level blast exposures.

Highlights

Military and law enforcement breachers are exposed to many low-level blasts during their training and occupational experiences in which they detonate explosives to force entry into secured structures
Thirty-four males were recruited into the study (20 breachers and 14 matched military or civilian law enforcement controls)
There were higher reported Post-Traumatic Stress Disorder Checklist-Military (PCL-M) scores in experienced breachers when compared with controls, indicating increased PTSD-related symptoms, these levels do not meet clinical criteria for PTSD diagnosis

Summary

Introduction

Military and law enforcement breachers are exposed to many low-level blasts during their training and occupational experiences in which they detonate explosives to force entry into secured structures. Elevated EV tau concentrations correlated with increased Neurobehavioral Symptom Inventory (NSI) score in experienced breachers (r = 0.596, p = 0.015) and predicted higher NSI score (F(1,14) = 7.702, p = 0.015, R2 = 0.355). Breachers construct and detonate explosives, often while at a close distance, to create a breach in a locked door or wall to force entry into a secured structure While these subconcussive blast exposures do not result in medically diagnosed injuries, there may be neurological sequelae due to the chronic, repetitive nature of these exposures. Repeated exposure to low-level blasts has been associated with a reduction in neurocognitive performance that correlated with elevations in serum levels of NF-L, tau, and Aβ4213

Objectives

Methods

Results

Conclusion