title: Dysfunction of the unfolded protein response increases neurodegeneration in aged rat hippocampus following proteasome inhibition.
abstract: Dysfunctions of the ubiquitin proteasome system (UPS) have been proposed to be involved in the aetiology and/or progression of several age-related neurodegenerative disorders. However, the mechanisms linking proteasome dysfunction to cell degeneration are poorly understood. We examined in young and aged rat hippocampus the activation of the unfolded protein response (UPR) under cellular stress induced by proteasome inhibition. Lactacystin injection blocked proteasome activity in young and aged animals in a similar extent and increased the amount of ubiquitinated proteins. Young animals activated the three UPR arms, IRE1alpha, ATF6alpha and PERK, whereas aged rats failed to induce the IRE1alpha and ATF6alpha pathways. In consequence, aged animals did not induce the expression of pro-survival factors (chaperones, Bcl-XL and Bcl-2), displayed a more sustained expression of pro-apoptotic markers (CHOP, Bax, Bak and JKN), an increased caspase-3 processing. At the cellular level, proteasome inhibition induced neuronal damage in young and aged animals as assayed using Fluorojade-B staining. However, degenerating neurons were evident as soon as 24 h postinjection in aged rats, but it was delayed up to 3 days in young animals. Our findings show evidence supporting age-related dysfunctions in the UPR activation as a potential mechanism linking protein accumulation to cell degeneration. An imbalance between pro-survival and pro-apoptotic proteins, because of noncanonical activation of the UPR in aged rats, would increase the susceptibility to cell degeneration. These findings add a new molecular vision that might be relevant in the aetiology of several age-related neurodegenerative disorders.
authors.affiliation: Departamento de Bioquímica, Bromatología, Toxicología y Medicina Legal, Facultad de Farmacia, Universidad de Sevilla, Seville, Spain.
authors.forename: María Paz
authors.initials: MP
authors.lastname: Gavilán
authors.forename: Cristina
authors.initials: C
authors.lastname: Pintado
authors.forename: Elena
authors.initials: E
authors.lastname: Gavilán
authors.forename: Sebastián
authors.initials: S
authors.lastname: Jiménez
authors.forename: Rosa M
authors.initials: RM
authors.lastname: Ríos
authors.forename: Javier
authors.initials: J
authors.lastname: Vitorica
authors.forename: Angélica
authors.initials: A
authors.lastname: Castaño
authors.forename: Diego
authors.initials: D
authors.lastname: Ruano
mesh_terms: D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000375:Aging; D000818:Animals; D015415:Biomarkers; D053148:Caspase 3 / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D009410:Nerve Degeneration / Q000139:chemically induced / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D056811:Unfolded Protein Response / Q000187:drug effects*
chemical_list: D015415:Biomarkers; D004791:Enzyme Inhibitors; D061988:Proteasome Inhibitors; D019253:Proto-Oncogene Proteins c-bcl-2; C067713:lactacystin; D053148:Caspase 3; D046988:Proteasome Endopeptidase Complex; D000111:Acetylcysteine