Relationship between injury severity and serum tau protein levels in traumatic brain injured rats

Although serum tau protein levels increase following TBI, the time course is unknown. The aim of the present study was to determine whether serum tau protein levels increased in both a severity-dependent and time-dependent manner in an experimental model of rat traumatic brain injury (TBI).A total of 24 Sprague-Dawley rats were subjected to varying grades of TBI using a contusion injury model on the right parietal cortex. Enzyme-linked Immunoabsorbent Assay (ELISA) analysis for serum was performed at 15 min pre-injury, 1, 6, 24, 48, and 168 h post-injury. Immunoblotting for serum tau protein, neurological evaluation and histological observation were also performed.Tau protein levels rapidly increased after 1 h in both mild and severe TBI groups (p0.001), and declined after 6 h. In the sham-operated group, tau protein levels did not change significantly after TBI. Tau protein levels were severity-dependent at 1 and 6 h after TBI. The levels were higher in the severe TBI group than in the mild TBI group at 1 h (p0.001) and 6 h (p0.001).Serum tau protein levels were severity-dependent and time-dependent at 1 and 6 h after TBI. However, the serum tau protein may not be a useful marker 24 h after TBI.