title: Inhibition of paraquat-induced autophagy accelerates the apoptotic cell death in neuroblastoma SH-SY5Y cells.
abstract: Autophagy is a degradative mechanism involved in the recycling and turnover of cytoplasmic constituents from eukaryotic cells. This phenomenon of autophagy has been observed in neurons from patients with Parkinson's disease (PD), suggesting a functional role for autophagy in neuronal cell death. On the other hand, it has been demonstrated that exposure to pesticides can be a risk factor in the incidence of PD. In this sense, paraquat (PQ) (1,1'-dimethyl-4,4'-bipyridinium dichloride), a widely used herbicide that is structurally similar to the known dopaminergic neurotoxicant MPP(+) (1-methyl-4-phenyl-pyridine), has been suggested as a potential etiologic factor for the development of PD. The current study shows, for the first time, that low concentrations of PQ induce several characteristics of autophagy in human neuroblastoma SH-SY5Y cells. In this way, PQ induced the accumulation of autophagic vacuoles (AVs) in the cytoplasm and the recruitment of a LC3-GFP fusion protein to AVs. Furthermore, the cells treated with PQ showed an increase of the long-lived protein degradation which is blocked in the presence of the autophagy inhibitor 3-methyladenine and regulated by the mammalian target of rapamycin (mTOR) signaling. Finally, the cells succumbed to cell death with hallmarks of apoptosis such as phosphatidylserine exposure, caspase activation, and chromatin condensation. While caspase inhibition retarded cell death, autophagy inhibition accelerated the apoptotic cell death induced by PQ. Altogether, these findings show the relationship between autophagy and apoptotic cell death in human neuroblastoma cells treated with PQ.
authors.affiliation: CIBER de Enfermedades Neurodegenerativas, Departamento de Bioquímica y Biología Molecular y Genética, EU Enfermería y TO, Universidad de Extremadura, Avda Universidad s/n 10071 Cáceres, Spain. rosapolo@unex.es
authors.forename: Rosa A
authors.initials: RA
authors.lastname: González-Polo
authors.forename: Mireia
authors.initials: M
authors.lastname: Niso-Santano
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Ortíz-Ortíz
authors.forename: Ana
authors.initials: A
authors.lastname: Gómez-Martín
authors.forename: José M
authors.initials: JM
authors.lastname: Morán
authors.forename: Lourdes
authors.initials: L
authors.lastname: García-Rubio
authors.forename: Javier
authors.initials: J
authors.lastname: Francisco-Morcillo
authors.forename: Concepción
authors.initials: C
authors.lastname: Zaragoza
authors.forename: Germán
authors.initials: G
authors.lastname: Soler
authors.forename: José M
authors.initials: JM
authors.lastname: Fuentes
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001343:Autophagy / Q000187:drug effects*; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000473:pathology*; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D006540:Herbicides / Q000633:toxicity*; D006801:Humans; D007202:Indicators and Reagents; D008854:Microscopy, Electron; D009363:Neoplasm Proteins / Q000378:metabolism; D009447:Neuroblastoma / Q000473:pathology*; D010269:Paraquat / Q000633:toxicity*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014162:Transfection
chemical_list: D006540:Herbicides; D007202:Indicators and Reagents; D009363:Neoplasm Proteins; D017382:Reactive Oxygen Species; D010269:Paraquat