Influence of apolipoprotein E genotype on neuronal damage and ApoE immunoreactivity in human hippocampus following global ischemia

Apolipoprotein E (apoE) influences the response to and outcome from brain i njury possibly through alterations in neuronal repair mechanisms. This stud y aimed to determine alterations in neuronal and glial apoE after brain inj ury in patients and sought to determine whether possession of an apoE-epsil on 4 allele influences the degree of apoE immunoreactivity or the degree of neuronal damage following brain injury. ApoE immunoreactivity and neuronal damage were semiquantitatively assessed in the temporal lobe of a group of controls (n = 44) and in a group of patients who had an episode of global ischemia and subsequently died (n = 58, survival ranged from 1 hour to 3 mo nths). There was a significant degree of neuronal damage in all hippocampal sectors and in the neocortex of the global ischemia group compared with co ntrols (p < 0.0001). Glial apoE immunoreactivity was significantly increase d in hippocampal sectors (CA1, CA2, CA3/CA4, dentate fascia) in the global ischemia group compared with controls (p < 0.01). Neuronal apoE immunoreact ivity was significantly increased in all hippocampal sectors (CA1, CA2, CA3 /CA4, dentate fascia) and in the neocortex of the global ischemia group com pared with controls (p < 0.0001). There was a significant and positive asso ciation between the degree of neuronal apoE immunoreactivity and the degree of neuronal damage in the global ischemia cases (r(2) = 0.691, p < 0.001) and there was not an association in the control group. Possession of an apo E-epsilon 4 allele did not influence the degree of neuronal or glial apoE i mmunoreactivity or the degree of neuronal damage in the global ischemia cas es or the controls. The data indicate apoE is markedly increased in neurons and glia following brain injury. In this study, apoE genotype did not appe ar to influence neuronal damage, glial apoE or intraneuronal apoE following injury.