Induction of apolipoprotein E after traumatic brain injury in forensic autopsy cases

We investigated the dynamics of the induction of apolipoprotein E (apoE) in the human brain after death caused by traumatic brain injury (TBI). A striking difference in apoE immunoreactivity in the traumatised cortical hemisphere compared with the contralateral non-traumatised hemisphere was observed. ApoE was detected within the neurons of the traumatised cortical hemisphere in cases surviving only about 2 h, as well as in those surviving for extended periods. In contrast, no apoE staining within the neurons was seen in the contralateral cortical hemisphere. ApoE staining within astrocytes was faint in both traumatised and contralateral hemispheres of cases surviving only 2 h. However, staining was intense in the traumatised hemispheres in short as well as long surviving cases, even those surviving more than 1 month. ApoE immunoreactivity was also observed in areas adjacent to capillaries and surrounding the neuropil of the injured hemisphere. These observations corroborated the idea of a prolonged induction of apoE within the neurons and also in the extracellular matrix after TBI. Furthermore, the possibility is suggested that the alteration of apoE distribution may contribute to a cerebroprotective mechanism immediately after TBI.