Aggregated Amyloid-β Protein Induces Cortical Neuronal Apoptosis and Concomitant “Apoptotic” Pattern of Gene Induction

Abstract

To gain a molecular understanding of neuronal responses to amyloid-β peptide (Aβ), we have analyzed the effects of Aβ treatment on neuronal gene expressionin vitroby quantitative reverse transcription-PCR andin situhybridization. Treatment of cultured rat cortical neurons with Aβ1–40results in a widespread apoptotic neuronal death. Associated with death is an induction of several members of the immediate early gene family. Specifically, we (1) report the time-dependent and robust induction ofc-jun,junB,c-fos, andfosB, as well astransin, which is induced by c-Jun/c-Fos heterodimers and encodes an extracellular matrix protease; these gene inductions appear to be selective because other Jun and Fos family members, i.e.,junDandfra-1, are induced only marginally; (2) show that thec-juninduction is widespread, whereasc-fosexpression is restricted to a subset of neurons, typically those with condensed chromatin, which is a hallmark of apoptosis; (3) correlate gene induction and neuronal death by showing that each has a similar dose–response to Aβ; and (4) demonstrate that both cell death and immediate early gene induction are dependent on Aβ aggregation state. This overall gene expression pattern during this “physiologically inappropriate” apoptotic stimulus is markedly similar to the pattern we previously identified after a “physiologically appropriate” stimulus, i.e., the NGF deprivation-induced death of sympathetic neurons. Hence, the parallels identified here further our understanding of the genetic alterations that may lead neurons to apoptosis in response to markedly different insults.

The role of seladin-1/DHCR24 in cholesterol biosynthesis, APP processing and Aβ generation in vivo

“…Cholesterol reduction was monitored by the Ecoline 25 kit as described above. Cell viability after these treatments was not affected (Estus et al, 1997).…”

Soluble Oligomers of Amyloid-β Peptide Disrupt Membrane Trafficking of α-Amino-3-hydroxy-5-methylisoxazole-4-propionic Acid Receptor Contributing to Early Synapse Dysfunction

“…Cells were seeded at a density of 5 ϫ 10 4 cells/cm 2 in Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum (FBS, heat inactivated), 50 units/ml penicillin, 50 g/ml streptomycin, 2 mM glutamine, and 30 mM glucose. Three hours after seeding, medium was replaced with serum-free Neurobasal medium supplemented with 2% B27 (Invitrogen), 50 units/ml penicillin, 50 g/ml streptomycin, 2 mM glutamine, 30 mM glucose, which yielded nearly pure neuronal cultures (21). Culture medium was partially replaced every 3-4 days with fresh Neurobasal supplemented with B27.…”

Unconventional ligands and modulators of nicotinic receptors

“…Aggregated, but not soluble forms of A␤ are highly neurotoxic (Estus et al, 1997;Ferreira et al, 1997;Troy et al, 2000). However, it has been reported that there does not seem to be a direct, simple correlation between levels of insoluble (i.e., aggregated) A␤ and cognitive deficits observed in transgenic mice that express a mutant form of human APP.…”