Session Title: Apolipoprotein-E
Presentation Date: Thursday, March 12 – Friday, March 13 ,2009
DEVELOPMENT OF AN IN-VITRO SYSTEM FOR STUDYING THE MECHANISMS UNDERLYING THE PATHOLOGICAL SYNERGY BETWEEN APOE4 AND Aβ
O. Liraz, D.M. Michaelson
The George S. Wise Faculty of Life Sciences, Tel Aviv University, Department of Neurobiology, Tel Aviv, Israel
Activation of the amyloid cascade by inhibition of the Aβ-degrading enzyme neprilysin in brains of apoE3 and apoE4 mice results in the isoform specific degeneration in apoE4 mice, of hippocampal CA1 neurons. This is accompanied by the accumulation of intracellular Aβ and apoE and by cognitive deficits in the ApoE4 mice. We presently describe a novel in vitro system which utilized brain slices from apoE4 and apoE3 mice and which reproduces the neuron specific synergistic pathological effects of apoE4 and Aβ.
Brain slices from ApoE3 and ApoE4 target replacement mice were incubated with the neprilysin inhibitor Thiorphan (100µM for up to 8 hours) after which the resulting effects on the levels of intracellular Ab were determined immunohistochemically. This revealed time dependent and neuron specific accumulation of oligomerised Aβ42 in CA1 neurons of the apoE4 mice and that Aβ40 did not accumulate in these neurons. In contrast neither Aβ42 nor Aβ40 accumulated in the CA1 neurons of the corresponding slices of apoE3 mice. Further experiments revealed that the accumulation of Aβ42 in CA1 neurons of the apoE4 mice was associated with lysosomal activation and subsequent neuronal apoptotic cell death. These effects were apoE4 dependent and were not observed in the corresponding brain slices of the apoE3 mice.
These finding provide a new in vitro system for studying the cellular and molecular mechanisms underlying the neuron specific pathological effects of ApoE4 and Aβ.