ABSTRACT
The present study examined the relationship between amyloid beta (Aß)-peptide aggregation state and neurotoxicity in vivo using the rat retinal-vitreal model. Following single unilateral intravitreal injection of either soluble Aß1-42 or Aß1-42 preaggregated for different periods, retinal pathology was evaluated at 24 hours, 48 hours, and 1-month postinjection. Injection of either soluble Aß (sAß) or preaggregated Aß induced a rapid reduction in immunoreactivity (IR) for synaptophysin, suggesting that direct contact with neurons is not necessary to disrupt synapses. Acute neuronal ionic and metabolic dysfunction was demonstrated by widespread loss of IR to the calcium buffering protein parvalbumin (PV) and protein gene product 9.5, a component of the ubiquitin-proteosome system. Injection of sAß appeared to have a more rapid impact on PV than the preaggregated treatments, producing a marked reduction in PV cell diameters at 48 hours, an effect that was only observed for preaggregated Aß after 1-month survival. Extending the preaggregation period from 4 to 8 days to obtain highly fibrillar Aß species significantly increased the loss of choline acteyltransferase IR, but had no effect on PV-IR. These findings prompt the conclusion that Aß assembly state has a significant impact on in vivo neurotoxicity by triggering distinct molecular changes within the cell.
