αII-Spectrin Breakdown Product Cerebrospinal Fluid Exposure Metrics Suggest Differences in Cellular Injury Mechanisms after Severe Traumatic Brain Injury

Abstract

Traumatic brain injury (TBI) produces aII-spectrin breakdown products (SBDPs) that are potential biomarkers for TBI. To further understand these biomarkers, the present study examined (1) the exposure and kinetic characteristics of SBDPs in cerebrospinal fluid (CSF) of adults with severe TBI, and (2) the relationship between these exposure and kinetic metrics and severity of injury. This clinical database study analyzed CSF concentrations of 150-, 145-, and 120-kDa SBDPs in 38 severe TBI patients. Area under the curve (AUC), mean residence time (MRT), maximum concentration (C max ), time to maximum concentration (T max ), and half-life (t 1=2 ) were determined for each SBDP. Markers of calpain proteolysis (SBDP150 and SBDP145) had a greater median AUC and C max and a shorter MRT than SBDP120, produced by caspase-3 proteolysis in the CSF in TBI patients ( p < 0.001). AUC and MRT for SBDP150 and SBDP15 were significantly greater in patients with worse Glasgow Coma Scale (GCS) scores at 24 h after injury compared to those whose GCS scores improved (AUC p ¼ 0.013, MRT p ¼ 0.001; AUC p ¼ 0.009, MRT p ¼ 0.021, respectively). A positive correlation was found between patients with longer elevations in intracranial pressure (ICP) measurements of 25 mm Hg or higher and those with a greater AUC and MRT for all three biomarkers. This is the first study to show that the biomarkers of proteolysis differentially associated with calpain and caspase-3 activity have distinct CSF exposure profiles following TBI that suggest a prominent role for calpain activity. Further studies are being conducted to determine if exposure and kinetic metrics for biofluidbased biomarkers can predict clinical outcome.

Therapy Development for Diffuse Axonal Injury

“…Among these, recent studies have suggested that aII-spectrin breakdown products SBDP150 and 145, produced by calpain cleavage, have been linked to acute neuronal necrosis, while SBDP120, produced by caspase 3, has been linked to apoptotic cell death cascades. 41,122,[125][126][127][128][129][130][131] While these aII-spectrin breakdown products have been discussed within the context of neuronal damage, it is important to note that they have been associated with both TAI/DAI and its downstream target deafferentation and synaptic loss. 38,51,[132][133][134] In addition to spectrin breakdown products, other potential markers of axonal injury include various phosphoforms of the neurofilament-H subunit as well as cleaved tau suggesting damage to the axon cytoskeleton.…”

Exploring the Role of Biomarkers for the Diagnosis and Management of Traumatic Brain Injury Patients

“…Examples of these techniques will be taken from studies conducted by our group. In two studies published in the Journal of Neurotrauma in 2007 by Pineda et al 42 and in 2009 by Brophy et al 43 an immunoblotting technique employing sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) was used to measure alpha-spectrin. Quantitative evaluation of intact II-spectrin and its breakdown products (SBDP150, SBDP145 and SBDP120) was performed via computer-assisted densitometric scanning.…”

Traumatic Brain Injury - Acute Care

“…Western blot analysis of the alpha-II spectrin breakdown products present in a given sample can therefore provide insight into the predominant mechanism of cellular loss . Preliminary studies using alpha-II spectrin breakdown products in humans have demonstrated that necrosis, mediated by calpain, is the predominant mechanism involved in acute DAI, suggesting that calpain inhibitors may be a potential therapeutic target (Brophy et al 2009). …”