Detection of alphaII-spectrin and breakdown products in humans after severe traumatic brain injury.

AIM: alphaII-Spectrin is the major structural component of the cortical membrane cytoskeleton. It is a major substrate for the calpain and caspase-3 cysteine proteases there are considerable evidence that alfaII-spectrin is processed by the calpains and caspase-3 to signature cleavage products in vivo after experimental traumatic brain injury (TBI). We sought to determine whether aII-spectrin proteolysis is a potentially reliable biomarker for TBI in humans measuring the levels of spectrin and spectrin breakdown products (SBDPs) in cerebrospinal fluid (CSF) from adults with severe TBI, and studying the relationship between these levels and clinical outcome.
METHODS: This prospective case control study enrolled 8 patients with severe TBI, defined by a Glasgow Coma Score (GCS) of <8, and requiring intraventricular pressure monitoring. Patients without TBI requiring CSF drainage served as controls. Ventricular CSF was drained from each patient at 6, 12, 24, 48, 72, and 96 h following TBI and measured for spectrin and SBDPs. Outcome was assessed using the Glasgow Outcome Score (GOS) 6 months after injury.
RESULTS: CSF alphaII-spectrin and calpain and caspase-3 mediated SBDP levels were significantly increased compared to control patients at all time points examined (P<0.001). In patients with a better outcome, CSF spectrin and SBDPs significantly decreased from 6 to 96 h. Patients whose spectrin and SBDP levels remained elevated or failed to decline had a worse outcome (P<0.019).
CONCLUSIONS: The present work provides the first evidence that protein degradation of alphaII-spectrin is a reliable marker of severe TBI in humans and that both necrotic and apoptotic cell death mechanisms are activated in humans following a severe TBI. Moreover, the temporal profile of degradation may be an important indicator of clinical outcome.