Polymorphism of the APOE Gene and Markers of Brain Damage in the Outcomes of Severe Traumatic Brain Injury in Children

Objective. To compare the genotypes at the apolipoprotein E (APOE) gene with outcomes and level of neural markers in children with severe traumatic brain injury (TBI). Materials and methods. A total of 69 children with severe TBI underwent typing of APOE polymorphisms and estimation of the contents of the following markers of brain damage/repair: neuron-specific enolase (NSE), S100b protein, autoantibodies (aAB) to glutamate receptors (NR2 subunits of glutamate receptors), aAB to S100b, and brain-derived neurotrophic factor (BDNF). Results and conclusions. The study cohort of children with severe TBI showed no link between the characteristics of the APOE 3/3, 3/4, or 3/2 genotypes and outcomes assessed on the Glasgow scale. The largest number of favorable outcomes was seen with the APOE genotype 3/3 (60%). Among children with the other two genotypes – APOE 3/4 and 3/2 – favorable and unfavorable outcomes were distributed 50:50. A significant link with genotype was seen for BDNF: a normal level was seen for APOE 3/3, while the level was reduced for APOE 3/2. Correlational links between neural marker contents and assessments on the Glasgow scale were seen for BDNF and aAB to S100b. BDNF levels were normal and aAB to S100b levels were low for favorable TBI outcomes. All APOE genotypes were combined by the observation that in the longer term, 95% of children with severe TBI showed significant increases in aAB to glutamate receptors and most showed increases in blood aAB to S100b. We link this observation with cerebral hypoxia, activation of autoimmune processes, and increases in the permeability of the blood:brain barrier, which may promote increases in NO content and intensification of oxidative processes in children with severe TBI.