Low-Level Primary Blast Induces Neuroinflammation and Neurodegeneration in Rats

Abstract

Objective: Mild blast traumatic brain injury is commonly prevalent in modern combat casualty care and has been associated with the development of neurodegenerative conditions. However, whether primary lower level blast overpressure (LBOP) causes neurodegeneration and neuroinflammation remains largely unknown. The aim of our present study was to determine whether LBOP can cause neuroinflammation and neurodegeneration.

Methods: Anesthetized rats were randomly assigned to LBOP group (70 kPa, n = 5) or sham group (without blast, n = 5). Histopathological and cytokine changes in brain tissue at 5 days post-injury were evaluated by hematoxylin-eosin staining and Bioplex assay, respectively.

Results: Histopathological assessment revealed neuronal degeneration and increased density of inflammatory cells in frontal and parietal cortex, hippocampus and thalamus in rats exposed to LBOP. LBOP exposure significantly elevated levels of pro-inflammatory cytokines (EPO, IL-1β, IL-6, IL-12, IL-18, and TNF-α) and chemokines (GRO and RANTES) as well as of an anti-inflammatory cytokine (IL-13) in the frontal cortex.

Conclusions: This study reveals a role of neuroinflammation in neurodegeneration after mild blast traumatic brain injury. Therapies that target this process might in warfighters might function either by attenuating the development of post-traumatic stress disorder, chronic traumatic encephalopathy and Alzheimer's disease, or by slowing their progression.

Keywords: mild blast injury; neurodegeneration; neuroinflammation; traumatic brain injury.