Administration of COG1410 Reduces Axonal Amyloid Precursor Protein Immunoreactivity and Microglial Activation after Controlled Cortical Impact in Mice

Abstract

Traumatic axonal injury (TAI) accounts for at least 35% of the morbidity and mortality in traumatic brain injury (TBI) patients without space-occupying lesions. It is also believed to be a key determinant of adverse outcomes such as cognitive dysfunction across the spectrum of TBI severity. Previous studies have shown that COG1410, a synthetic peptide derived from the apolipoprotein E (apoE) receptor binding region, has anti-inflammatory effects after experimental TBI, with improvements in cognitive recovery. However, the effects of COG1410 on axonal injury following TBI are not known. The current study evaluated the effects of 1 mg/kg daily COG1410 versus saline administered intravenously starting 30 min after controlled cortical impact (CCI) injury on pericontusional TAI in young, wild-type C57BL6/J male mice. We found that COG1410 did not affect the number of amyloid precursor protein (APP)-immunoreactive axonal varicosities in the pericontusional corpus callosum and external capsule at 24 h, but reduced APP-immunoreactive varicosities by 31% at 3 days (p=0.0023), and 36% at 7 days (p=0.0009). COG1410 significantly reduced the number of Iba1-positive cells with activated microglial morphology at all three time points by 21-30%. There was no effect of COG1410 on pericontusional white matter volume or silver staining at any time point. This indicates a possible effect of COG1410 on delayed but not immediate TAI. Future studies are needed to investigate the underlying mechanisms, therapeutic time window, and physiological implications of this effect.