Chronic Upregulation of Cleaved-Caspase-3 Associated with Chronic Myelin Pathology and Microvascular Reorganization in the Thalamus after Traumatic Brain Injury in Rats

Abstract

Traumatic brain injury (TBI) is associated with long-term disabilities and devastating chronic neurological complications including problems with cognition, motor function, sensory processing, as well as behavioral deficits and mental health problems such as anxiety, depression, personality change and social unsuitability. Clinical data suggest that disruption of the thalamo-cortical system including anatomical and metabolic changes in the thalamus following TBI might be responsible for some chronic neurological deficits following brain trauma. Detailed mechanisms of these pathological processes are not completely understood. The goal of this study was to evaluate changes in the thalamus following TBI focusing on cleaved-caspase-3, a specific effector of caspase pathway activation and myelin and microvascular pathologies using immuno- and histochemistry at different time points from 24 h to 3 months after controlled cortical impact (CCI) in adult Sprague-Dawley rats. Significant increases in cleaved-caspase-3 immunoreactivity in the thalamus were observed starting one month and persisting for at least three months following experimental TBI. Further, the study demonstrated an association of cleaved-caspase-3 with the demyelination of neuronal processes and tissue degeneration in the gray matter in the thalamus, as reflected in alterations of myelinated fiber integrity (luxol fast blue) and decreases in myelin basic protein (MBP) immunoreactivity. The immunofluorescent counterstaining of cleaved-caspase-3 with endothelial barrier antigen (EBA), a marker of blood-brain barrier, revealed limited direct and indirect associations of cleaved caspase-3 with blood-brain barrier damage. These results demonstrate for the first time a significant chronic upregulation of cleaved-caspase-3 in selected thalamic regions associated with cortical regions directly affected by CCI injury. Further, our study is also the first to report that significant upregulation of cleaved-caspase-3 in selected ipsilateral thalamic regions is associated with microvascular reorganization reflected in the significant increases in the number of microvessels with blood-brain barrier alterations detected by EBA staining. These findings provide new insights into potential mechanisms of TBI cell death involving chronic activation of caspase-3 associated with disrupted cortico-thalamic and thalamo-cortical connectivity. Moreover, this study offers the initial evidence that this upregulation of activated caspase-3, delayed degeneration of myelinated nerve fibers and microvascular reorganization with impaired blood-brain barrier integrity in the thalamus might represent reciprocal pathological processes affecting neuronal networks and brain function at the chronic stages of TBI.

Nicotinamide Improves Functional Recovery via Regulation of the RAGE/JNK/NF-κB Signaling Pathway after Brain Injury

“…Oxidative stress and neuroinflammation are the major hallmarks of post-brain injury consequences and neuropsychiatric disturbances [18]. Excessive reactive oxygen species (ROS) in the brain can cause damage to the enzymes, nucleic acid, and disruption of structural protein [19,20,21]. Several lines of studies have demonstrated elevated ROS and neuroinflammation in brains after brain injuries [22,23].…”

Two hundred and forty-eight cases of visual snow: A review of potential inciting events and contributing comorbidities

“…It seems probable that TBI directly and indirectly damages cortical and subcortical structures that are associated with visual processing. Animal models of TBI have shown altered thalamic myelin integrity (27) and even mild TBI has been shown in some cases to contribute to excitotoxic injury with delayed cell death in the cortex, thalamus, and subcortical white matter tracts (28). Some authors hypothesize that disrupted thalamocortical circuits contribute to some of the symptoms of TBI (27), and in theory this might also contribute to VS symptoms.…”

Naltrexone is neuroprotective against traumatic brain injury in mu opioid receptor knockout mice

“…TBI can lead to chronic neurodegeneration and long‐term neurological deficits 28‐30 . For example, neurological severity scores, rotarod latency, impairments of cognitive function in Y or Water maze, 31,32 foot faults in motor function test, 33 and forelimb asymmetry 32 were increased and lasted up to 28‐35 days after CCI in mice.…”