Activation of nicotinic cholinergic receptors modifies the processing of rat hippocampal amyloid precursor protein both in vivo and in vitro

Abstract

oligomers on p75 expression in mouse hippocampus and SH-SY5Y cells. Methods: As-derived diffusible ligands (ADDLs) were prepared by incubation of As1-42 at 4 C for 24h. ADDLs were microinjected into mouse hippocampus region and 6-24 later hippocampus from ipsilateral and contra lateral sideswere analyzed. SH-SY5Ycells were treatedwithADDLs in the presence and absence of inhibitor and the effects on p75expression were determined. Results: Western blot analysis showed that ADDLs were heterogeneous mixtures, predominantly made up of As1-42 dimers and oligomers. After microinjection of ADDLs into mouse brain, p expression in ipsilateralhippocampus was increased by 1.4-fold in 24hrs compared to contra lateral hippocampus. No significant difference was observed at 6hrs. Anti-As antibody (6E10)-positive As1-42 was not detected in significant amounts in contralateralhippocampus by immunohistochemistry, suggesting that diffusion into the contralateral side from the injection site is limited. ADDLs (1 uM) increased (1.4-fold) p75 expression in SH-SY5Y cells 24hrs after incubation as previously reported. Insulin-like growth factor I receptor (IGF1R) is reported to be involved in the induction of p expression inSH-SY5Y cells. ADDL-induced p75 expression was inhibited by PPP, a selective IGF1R inhibitor. Moreover, ADDLs induced phosphorylation of IGF1R in SH-SY5Y cells in 30 min. Conclusions: The present study indicates that As1-42 oligomersinduce p75 NTR expression in mouse hippocampus and suggests that IGF1Rsignaling pathway contributes to As1-42 oligomer-mediated induction of p75 expression in neurons.