Amyloid β-protein potentiates tunicamycin-induced neuronal death in organotypic hippocampal slice cultures

• Published in: Neuroscience 2007-07, Vol.147 (3), p.639-651
• Main Authors: Imai, T, Kosuge, Y, Ishige, K, Ito, Y
• Format: Article
• Language: English
• Subjects: Allium sativum; Alzheimer’s disease; Amyloid beta-Peptides - pharmacology; amyloid β-protein; Animals; Animals, Newborn; Antiviral Agents - pharmacology; Biological and medical sciences; caspase-12; Cell Count; Cell Death - drug effects; Degenerative and inherited degenerative diseases of the nervous system. Leukodystrophies. Prion diseases; Dose-Response Relationship, Drug; Drug Synergism; ER stress; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - drug effects; Hippocampus - cytology; Medical sciences; Molecular Chaperones - metabolism; Neurology; neuronal death; Neurons - drug effects; Organ Culture Techniques; Peptide Fragments - pharmacology; Rats; Rats, Wistar; S-allyl- l-cysteine; Tunicamycin - pharmacology; Vertebrates: nervous system and sense organs
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2007.04.057

Abstract We have assessed amyloid β protein (Aβ)–induced neurotoxicity, with and without added tunicamycin (TM), an inhibitor of N-glycosylation in the endoplasmic reticulum (ER), in rat organotypic hippocampal slice cultures (OHCs). In the rat OHCs cultured for 3 weeks, there was little neurotoxicity after treatment with Aβ25-35 (25 μM) alone for 48 h. However, with TM alone, concentration-dependent neuronal death was observed at concentrations between 20 and 80 μg/mL. When amyloid-β protein was combined with tunicamycin (Aβ+TM), cell death was more acute than with TM alone. Western blot analysis revealed that calpain activity and the active forms of caspase-12 and caspase-3 was increased after exposure to Aβ+TM as compared with exposure to TM alone. In contrast, the levels of glucose regulated protein (GRP)94, GRP78 and C/EBP homologous protein (CHOP) were not changed in the presence of Aβ. Aβ potentiation of TM neurotoxicity was reversibly blocked by S-allyl- l -cysteine (SAC), an organosulfur compound purified from aged garlic extract, and the L-type calcium channel blocker, nifedipine, in a restricted neuronal area of the OHCs. Simultaneously applied SAC also reversed the increases in calpain activity and the active forms of caspase-12 and caspase-3 by Aβ+TM with no change in the increased levels of GRP94, GRP78 and CHOP. These data indicate that Aβ facilitates the calpain–caspase-12–caspase-3 pathway, thus potentiating TM-induced neuronal death in the hippocampus.